Density-functional theory, finite-temperature classical maps, and their implications for foundational studies of quantum systems - Dharma-Wardana, M. W. C. (Journal of Physics: Conference Series, 2013)
The advent of the Hohenberg-Kohn theorem in 1964, its extension to finite-T, Kohn-Sham theory, and relativistic extensions provide the well-established formalism of density-functional theory (DFT). This theory enables the calculation of all static properties of quantum systems without the need for an n-body wavefunction ψ. DFT uses the one-body density distribution instead of ψ. The more recent time-dependent formulations of DFT attempt to describe the time evolution of quantum systems without using the time-dependent wavefunction. Although DFT has become the standard tool of condensed-matter computational quantum mechanics, its foundational implications have remained largely unexplored. While all systems require quantum mechanics (QM) at T=0, the pair-distribution functions (PDFs) of such quantum systems have been accurately mapped into classical models at effective finite-T, and using suitable non-local quantum potentials (e.g., to mimic Pauli exclusion effects). These approaches shed light on the quantum → hybrid → classical models, and provide a new way of looking at the existence of non- local correlations without appealing to Bell's theorem. They also provide insights regarding Bohmian mechanics. Furthermore, macroscopic systems even at 1 Kelvin have de Broglie wavelengths in the micro-femtometer range, thereby eliminating macroscopic cat states, and avoiding the need for ad hoc decoherence models.
Keywords: De Broglie wavelength; Decoherence models; Density distributions; Hohenberg-Kohn theorem; Local correlations; Macroscopic systems; Pair distribution functions; Pauli exclusion effects; Density functional theory; Quantum electronics; Quantum optics

Effect of an in-plane magnetic field on microwave photoresistance and Shubnikov-de Haas effect in high-mobility GaAs/AlGaAs quantum wells - Bogan, A.; Hatke, A. T.; Studenikin, S. A.; Sachrajda, A.; Zudov, M. A.; Pfeiffer, L. N.; West, K. W. (Journal of Physics: Conference Series, 2013)
A recent study of the decay of microwave-induced resistance oscillations (MIRO) in GaAs/AlGaAs quantum wells due to an in-plane magnetic field B ∥ has revealed the dominant role of a quadratic-in-B ∥ correction to the quantum scattering rate. In the present study, we examine the evolution of Shubnikov-de Haas oscillations (SdHO) with increasing tilt angle in the same sample. Even though we find that the SdHO also diminish at high tilt angles, this decay is qualitatively different from that of MIRO, possibly indicating a different physical origin.
Keywords: GaAs/AlGaAs quantum well; High mobility; High tilt angle; In-plane magnetic fields; Microwave-induced resistance oscillations; Photoresistance; Quantum scattering; Shubnikov-de Haas oscillations; Electric resistance; Magnetic fields; Semiconductor quantum wells; Shubnikov-de Haas effect; Microwave oscillators

Phase diagram and magnetic structures of the Co-bearing dugganites Pb3TeCo3A2O14 (A = V, P) - Silverstein, H. J.; Sharma, A. Z.; Stoller, A. J.; Cruz-Kan, K.; Flacau, R.; Donaberger, R. L.; Zhou, H. D.; Manuel, P.; Huq, A.; Kolesnikov, A. I.; Wiebe, C. R. (Journal of Physics Condensed Matter, 2013)
Exhibiting rich magnetic behaviour and potentially multiferroic properties, the dugganites, a Te6+ containing subgroup of the langasite series, are an attractive family of compounds for future study. It was recently shown that Pb-bearing members of the dugganite series undergo distortions away from the P321 symmetry that is characteristic of the langasites. Here, we detail the consequences these distortions have on the magnetism exhibited by Pb 3TeCo3V2O14 and Pb 3TeCo3P2O14, solving the magnetic structures of both compounds with respect to a new supercell. Using neutron scattering and magnetic susceptibility measurements, we show that small applied magnetic fields can seriously perturb the delicate magnetic states in both of these systems. This is further demonstrated by presenting how doping P 5+ onto the nonmagnetic V5+ site completely changes the magnetic structure from either of the end series members. Finally, it is shown using inelastic neutron scattering and magnetic susceptibility measurements that Pb3TeCo3V2O14 can be characterized using a model for isosceles trimers, which do not exist in the previously reported P321 subcell.
Keywords: Applied magnetic fields; Langasites; Magnetic behaviour; Magnetic state; Magnetic susceptibility measurements; Multiferroic properties; Nonmagnetics; Super cell; Magnetic structure; Magnetic susceptibility; Oligomers; Phase diagrams; Lead compounds

Vector space model for adaptation in statistical machine translation - Chen, Boxing; Kuhn, Roland; Foster, George (Proceedings of the 51st Annual Meeting of the Association for Computational Linguistics, 2013)
This paper proposes a new approach to domain adaptation in statistical machine translation (SMT) based on a vector space model (VSM). The general idea is first to create a vector profile for the in-domain development (“dev”) set. This profile might, for instance, be a vector with a dimensionality equal to the number of training subcorpora; each entry in the vector reflects the contribution of a particular subcorpus to all the phrase pairs that can be extracted from the dev set. Then, for each phrase pair extracted from the training data, we create a vector with features defined in the same way, and calculate its similarity score with the vector representing the dev set. Thus, we obtain a decoding feature whose value represents the phrase pair’s closeness to the dev. This is a simple, computationally cheap form of instance weighting for phrase pairs. Experiments on large scale NIST evaluation data show improvements over strong baselines: +1.8 BLEU on Arabic to English and +1.4 BLEU on Chinese to English over a non-adapted baseline, and significant improvements in most circumstances over baselines with linear mixture model adaptation. An informal analysis suggests that VSM adaptation may help in making a good choice among words with the same meaning, on the basis of style and genre.

Core/shell metal/heterogeneous oxide nanocapsules: the empirical formation law and tunable electromagnetic losses - Zhang, X. F.; Huang, H.; Dong, X. L. (The Journal of Physical Chemistry C, 2013)
We report an empirical thermodynamic law for the synthesis of core/shell metal/heterogeneous oxide nanocapsules, such as Fe/SiO2, Ni/SiO 2, Fe/B2O3, Ni/B2O3, Fe/Al2O3, Fe/MnO2, Fe/Y2O 3, Fe/CeO2, and Fe/La2O3, by arc-discharge evaporating a compressed mixture of Fe (or Ni) powders and the oxide powders of shell components. By integrating such dielectric oxide shells and magnetic metal cores in each particle, the electromagnetic losses can be artificially manipulated at the whole S-band, C-band, X-band, and Ku frequency ranges. The microscopic origins of the controllability of electromagnetic losses are ascribed to the specific matching and interfacial coupling between the magnetic cores and dielectric shells.
Keywords: Arc discharge; Dielectric oxides; Dielectric shells; Electromagnetic loss; Frequency ranges; Interfacial couplings; Magnetic metals; Oxide powder; Electromagnetism; Nanocapsules; Powder metals; Electric discharges

Water-halogen interactions in chlorine and bromine clathrate hydrates: An example of multidirectional halogen bonding - Udachin, Konstantin A.; Alavi, Saman; Ripmeester, John A. (The Journal of Physical Chemistry C, 2013)
There are unresolved questions in our understanding of the clathrate hydrates with halogen molecule guests. In this work, we describe the synthesis and single crystal X-ray structural determination of cubic structure I (sI) Cl2, tetragonal structure III (sIII) Br2, and mixed cubic sI Cl2-Br2 clathrate hydrate phases. Unlike the previous X-ray structural determination of the pure chlorine clathrate hydrate by Pauling and Marsh (Proc. Nat. Acad. Sci. USA1952, 38, 112), we report that 32.5% of the clathrate small cages are occupied by Cl2 molecules. Pure Br 2 produces the unique tetragonal sIII clathrate hydrate whose structure is refined from single-crystal measurements, identifying disordered Br2 guest positions in cages and giving structural details not previously identified. In mixed sI clathrate hydrate of Cl2 and Br2, we observed that Br2 guests fit into the large sI cages. The introduction of Br2 in the Cl2 hydrate lattice causes severe distortions because of strong Br⋯OH2 interactions. In these three hydrate structures, based on accepted van der Waals radii, the effective diameters of the clathrate hydrate cages are smaller than the size of the Cl2 and Br2 guest molecules. The accommodation of these guests in the cages and the short O⋯Cl and O⋯Br contact distances reveal halogen bonding between the water oxygen atoms and the dihalogen guests. The X-ray structural determinations of the length of the Cl-Cl and Br-Br bonds of the Cl2 and Br2 guests show significant librational shortening compared to free Cl2 and Br2 molecules.
Keywords: Effective diameter; Hydrate structures; Multi-directional; Structural details; Tetragonal structure; Van der Waals radius; Water oxygen atoms; X-ray structural determination; Chlorine; Crystal structure; Hydration; Molecules; X rays; Hydrates

Identification of nonequivalent framework oxygen species in metal-organic frameworks by 17O solid-state NMR - He, Peng; Xu, Jun; Terskikh, Victor V.; Sutrisno, Andre; Nie, Heng-Yong; Huang, Yining (The Journal of Physical Chemistry C, 2013)
Metal-organic frameworks (MOFs) are a class of novel nanoporous materials with many potential applications. Structural characterization is important because understanding the relationship between the properties of these industrially relevant materials and their structures allows one to develop new applications and improve current performance. Oxygen is one of the most important elements in many MOFs and exists in various forms. Ideally, 17O solid-state NMR (SSNMR) should be an excellent tool for characterizing various oxygen species. However, the major obstacles that prevent applying 17O SSNMR to MOF characterization are the synthetic effort needed for 17O isotopic enrichment and the associated high cost. In this work, we successfully prepared several prototypical 17O-enriched MOFs, including Zr-UiO-66, MIL-53(Al), CPO-27-Mg (or Mg-MOF-74), and microporous α-Mg3(HCOO)6. Depending on the target MOF, different isotopic enrichment methods were used to effectively incorporate 17O from 17O-enriched H2O. Using these 17O-enriched MOFs, we were able to acquire 17O SSNMR spectra at a magnetic field of 21.1 T. They provide distinct spectral signatures of various key oxygen species commonly seen in representative MOFs. We demonstrate that 17O SSNMR can be used to differentiate chemically and, under favorite circumstances, crystallographically nonequivalent oxygens and to follow the phase transitions. The synthetic approaches for preparation of 17O-enriched sample described in this paper are fairly simple and cost-effective.
Keywords: Current performance; Isotopic enrichment; Metal organic framework; Metalorganic frameworks (MOFs); Nano-porous materials; Spectral signature; Structural characterization; Synthetic approach; Crystalline materials; Isotopes; Java programming language; Nuclear magnetic resonance spectroscopy; Porous materials; Solid state physics; Oxygen

Initial processes of proton transfer in salicylideneaniline studied by time-resolved photoelectron spectroscopy - Sekikawa, Taro; Schalk, Oliver; Wu, Guorong; Boguslavskiy, Andrey E.; Stolow, Albert (The Journal of Physical Chemistry A, 2013)
Excited-state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in the para position of the anilino group have been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). SA has a twisted structure at the energetic minimum of the ground state, but ESIPT is assumed to take place through a planar structure, although this has not been fully established. The TRPES studies revealed that the excited-state dynamics within the S1 band varied significantly with excitation wavelength. At finite temperatures, the ground state was found to sample a broad range of torsional angles, from planar to twisted. At lower photon energies (370 nm), only the planar ground-state molecules were excited, and the excited-state reaction took place within 50 fs. At higher energies (350 and 330 nm), predominantly twisted ground-state molecules were excited: they had to planarize before ESIPT could occur. This process was found to be slower in methylated SA but did not change significantly in the brominated and nitrated SAs. These substitution effects on the decay dynamics can be explained by modifications of the potential barriers, as predicted by the TDDFT calculations, and support the mechanism of a twisting motion of the anilino ring prior to ESIPT. The contribution of another pathway leading to internal conversion within the enol form was found to be minor at the excitation wavelengths considered here.
Keywords: Excitation wavelength; Excited state reactions; Excited-state dynamics; Excited-state intramolecular proton transfer; Femtosecond time-resolved; Ground-state molecules; Time dependent density functional theory; Time-resolved photoelectron spectroscopy; Density functional theory; Excited states; Photoelectron spectroscopy; Proton transfer; Ground state; aniline derivative; salicylideneaniline; X ray photoelectron spectroscopy; Aniline Compounds; Quantum Theory; Schiff Bases

On the condensed phase ring-closure of vinylheptafulvalene and ring-opening of gaseous dihydroazulene - Schalk, Oliver; Broman, Søren L.; Petersen, Michael Å.; Khakhulin, Dmitry V.; Brogaard, Rasmus Y.; Nielsen, Mogens Brøndsted; Boguslavskiy, Andrey E.; Stolow, Albert; Sølling, Theis I. (The Journal of Physical Chemistry A, 2013)
Dihydroazulenes are interesting because of their photoswitching behavior. While the ring-opening to vinylheptafulvalene (VHF) is light induced, the back reaction is known to proceed thermally. In the present paper, we show the first gas phase study of the ring-opening reaction of 2-phenyl-1,8a-dihydroazulene-1, 1-dicarbonitrile (Ph-DHA) by means of time-resolved photoelectron spectroscopy which permits us to follow the ring-opening process. Moreover, we investigated s-trans-Ph-VHF in a series of transient absorption experiments, supported by ab initio computations, to understand the origin of the absence of light-induced ring-closure. The transient absorption results show a biexponential decay governed by a hitherto unknown state. This state is accessed within 1-2 ps and return to the ground state is probably driven through a cis-trans isomerization about the exocyclic C1=C2 double bond. The rapid decrease in potential energy disfavors internal rotation to s-cis-Ph-VHF, the structure that would precede the ring-closure reaction.
Keywords: Ab initio computations; Biexponential decay; Cis-trans Isomerization; Condensed phase; Internal rotations; Ring opening reaction; Time-resolved photoelectron spectroscopy; Transient absorption; Photoelectron spectroscopy; cyclopentane derivative; dihydroazulene; X ray photoelectron spectroscopy; Azulenes; Cyclopentanes; Photoelectron Spectroscopy

CO dimer: the infrared spectrum revisited - Rezaei, Mojtaba; Sheybani-Deloui, S.; Moazzen-Ahmadi, N.; Michaelian, K. H.; McKellar, A. R. W. (The Journal of Physical Chemistry A, 2013)
A broad-band (2135-2200 cm-¹) infrared spectrum of the CO dimer is recorded using a tunable quantum cascade laser to probe a supersonic jet expansion with an effective rotational temperature of about 2.5 K. Analysis of the spectrum reveals the first known levels of the excited state (vCO = 1) with A+ symmetry and establishes that resonant vibrational splittings are small (<0.2 cm-¹) for both the C-bonded and O-bonded dimer isomers. The spectrum extends over a surprisingly large range, with somewhat reduced intensity above 2150 cm-¹. A total of 28 new "stacks" of rotational levels having A- symmetry are assigned for vCO = 1 on the basis of combination differences, adding to the 8 stacks previously known, and extending up to 51 cm-¹ above the vCO = 1 origin. Assignments are given for the first 13 stacks of vCO = 1 in terms of the very low frequency geared bending intermolecular vibration.
Keywords: Broad bands; Infrared spectrum; Intermolecular vibrations; Rotational levels; Rotational temperature; Splittings; Supersonic jet expansion; Very low frequency; Isomers; Quantum cascade lasers; Supersonic aerodynamics; Spectroscopy

Substituent effects on dynamics at conical intersections: Cycloheptatrienes - Schalk, Oliver; Boguslavskiy, Andrey E.; Schuurman, Michael S.; Brogaard, Rasmus Y.; Unterreiner, Andreas N.; Wrona-Piotrowicz, Anna; Werstiuk, Nick H.; Stolow, Albert (The Journal of Physical Chemistry A, 2013)
Using selective methyl substitution, we study the effects of vibrational dynamics at conical intersections in unsaturated hydrocarbons. Here, we investigate the excited state nonadiabatic dynamics of cycloheptatriene (CHT) and its relation to dynamics in other polyenes by comparing CHT with 7-methyl CHT, 7-ethyl CHT, and perdeuterated CHT using time-resolved photoelectron spectroscopy and photoelectron anisotropy. Our results suggest that, upon ππ-excitation to the bright 2A″ state, we observe an early intersection with the dark 2A′ state close to the Franck-Condon region with evidence of wavepacket bifurcation. This indicates that the wavepacket evolves on both states, likely along a planarization coordinate, with the majority of the flux undergoing nonadiabatic transition via conical intersections within 100 fs following light absorption. In CHT, large amplitude motion along the planarization coordinate improves the intra-ring π-overlap, yielding a delocalized electronic density. However, substitutions in 7 position, chosen to modify the inertia of the planarization motion, did not markedly alter the first step in the sequential kinetic scheme. This suggests that there is a crossing of potential energy surfaces before planarization is achieved and, thus, nonadiabatic transition likely takes place far away from a local minimum.
Keywords: Conical intersection; Large-amplitude motion; Non-adiabatic dynamics; Non-adiabatic transitions; Photoelectron anisotropy; Time-resolved photoelectron spectroscopy; Unsaturated hydrocarbons; Vibrational dynamics; Dynamics; Photoelectron spectroscopy; Quantum chemistry; Wave packets; Excited states

Zero-point tunneling splittings in compounds with multiple hydrogen bonds calculated by the rainbow instanton method - Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio (The Journal of Physical Chemistry A, 2013)
Zero-point tunneling splittings are calculated, and the values are compared with the experimentally observed values for four compounds in which the splittings are due to multiple-proton transfer along hydrogen bonds. These compounds are three binary complexes, namely, the formic acid and benzoic acid dimer and the 2-pyridone-2-hydroxypyridine complex, in which the protons move in pairs, and the calix[4]arene molecule, in which they move as a quartet. The calculations make use of and provide a test for the newly developed rainbow approximation for the zero-temperature instanton action which governs the tunneling splitting (as well as the transfer rate). This approximation proved to be much less drastic than the conventional adiabatic and sudden approximations, leading to a new general approach to approximate the instanton action directly. As input parameters the method requires standard electronic-structure data and the Hessians of the molecule or complex at the stationary configurations only; the same parameters also yield isotope effects. Compared to our earlier approximate instanton method, the rainbow approximation offers an improved treatment of the coupling of the tunneling mode to the other vibrations. Contrary to the conventional instanton approach based on explicit evaluation of the instanton trajectory, both methods bypass this laborious procedure, which renders them very efficient and capable of handling systems that thus far have not been handled by other theoretical methods. Past results for model systems have shown that the method should be valid for a wide range of couplings. The present results for real compounds show that it gives a satisfactory account of tunneling splittings and isotope effects in systems with strong coupling that enhances tunneling, thus demonstrating its applicability to low-temperature proton dynamics in systems with multiple hydrogen bonds.
Keywords: Binary complexes; Handling systems; Low temperatures; Stationary configurations; Sudden approximation; Theoretical methods; Tunneling splittings; Zero temperatures; Carrier mobility; Hydrogen bonds; Isotopes; Molecules; Complexation

Identity verification based on haptic handwritten signature : novel fitness functions for GP framework - Alsulaiman, Fawaz A.; Valdes, Julio J.; El Saddik, Abdulmotaleb (IEEE, 2013)
Fitness functions are the evaluation measures driving evolutionary processes towards solutions. In this paper, three fitness functions are proposed for solving the unbalanced dataset problem in Haptic-based handwritten signatures using genetic programming (GP). The use of these specifically designed fitness functions produced simpler analytical expressions than those obtained with currently available fitness measures, while keeping comparable classification accuracy. The functions introduced in this paper capture explicitly the nature of unbalanced data, exhibit better dimensionality reduction and have better False Rejection Rate.

¹H NMR metabolomics analysis of the effect of dichloroacetate and allopurinol on breast cancers - Lefort, Natalie; Brown, Amy; Lloyd, Vett; Ouellette, Rodney; Touaibia, Mohamed; Culf, Adrian S.; Cuperlovic-Culf, Miroslava (Journal of Pharmaceutical and Biomedical Analysis, 2013)
Metabolomics analysis was used to determine the effect of two well known, non-proprietary metabolic modulators, dichloroacetate and allopurinol on breast cancer cell lines. Dichloroacetate, a pyruvate dehydrogenase kinase inhibitor and allopurinol, a xanthine oxidase/dehydrogenase inhibitor, have been previously explored as chemotherapeutics showing potential in some cancer subtypes while at the same time leading to unexpected increase in proliferation in others. In this work, metabolic effects of these drugs, applied singly and in combination, were explored in three different breast cell lines including cancer cells, MDA-MB-231 and MCF-7 and normal control cell line, MCF-10A. The metabolic changes induced by these drugs were monitored by ¹H NMR metabolic profiling. Analyses were performed on complete spectral data as well as quantified metabolic data in intracellular fractions and extracellular media leading to the determination of the most significantly affected metabolites. The effect of dichloroacetate and allopurinol is the most apparent in the metabolic profile of extracellular media. In MCF-7 cells, dichloroacetate treatment is dominant with only a minor observed influence of allopurinol in combined treatment. In MDA-MB-231 cells, both allopurinol and DCA lead to a metabolic shift with the allopurinol change dominating the effect of combined treatment. Results show the power of metabolomics as a tool for fast molecular profiling of drug effects in cells. In summary, treatments of breast cancer cells with DCA and allopurinol result in larger changes in metabolites found in extracellular medium than intracellular pools.

Effect of reverse polarity on space charge evolution in polypropylene with different concentration of natural and synthetic nano clay - Abou-Dakka, Mahmoud; Chen, Yaoren (2013 Annual Report: Conference on Electrical Insulation and Dielectric Phenomena, 2013)
The space charge evolution in the Polypropylene (PP) loaded with two types of nanoparticles, synthetic and natural clay with weekly reversing polarity was studied. The sapce charge in these two polymer nanocomposites (PNCs) were measured with the PEA technique after he each period of poling. The charge distribution in the host materials was substantially smaller after reverse polarity compared to dc negative polarity. This could be related to the mitigation of charge bay the compatibilizers added to the host materials. The charge accumulation measured after the negative periods were lower than the positive periods. The PNC with 2-wt& of synthtic clay stocks lots of charges after the end of the positive periods. Then, it will not be optimal concentration as it was for dc poling. It is found out that the two optimal concentrations for reverse polarity were 4-wt% (PPI-S4%) for the synthetic PNC and the 2-wt% (PPI-N2%) for the natural PNC. With reverse polarity and before the 12th week of poling all filled and unfilled materials stock charges of the same order. The unfilled materials show increasing of charges that crosses the values of filled materials, except the PPA-S3%, after the 12 weeks of poling with reverse polarity. More poling time is necessary to investigate the effect of long term poling on the charge evolution and investigate the continuous increase of charge in the unfilled materials.

Reinforced plastics and aerogels by nanocrystalline cellulose - Leung, Alfred C. W.; Lam, Edmond; Chong, Jonathan; Hrapovic, Sabahudin; Luong, John H. T. (Journal of Nanoparticle Research, 2013)
Nanocrystalline cellulose (NCC), a rigid rod-like nanoscale material, can be produced from cellulosic biomass in powder, liquid, or gel forms by acid and chemical hydrolysis. Owing to its unique and exceptional physicochemical properties, the incorporation of a small amount of NCC into plastic enhances the mechanical strength of the latter by several orders of magnitudes. Carbohydrate-based NCC poses no serious environmental concerns, providing further impetus for the development and applications of this green and renewable biomaterial to fabricate lightweight and biodegradable composites and aerogels. Surface functionalization of NCC remains the main focus of NCC research to tailor its properties for dispersion in hydrophilic or hydrophobic media. It is of uttermost importance to develop tools and protocols for imaging of NCC in a complex matrix and quantify its reinforcement effect.
Keywords: Nanocrystalline cellulose; Nanoﬁller; Nanocomposite; Nanomaterials; Nanoparticles; Renewable biomass; Cellulose

Infrared spectra of the Ne-C2D4 and Ar-C2D4 complexes - Rezaei, M.; Michaelian, K. H.; McKellar, A. R. W.; Moazzen-Ahmadi, N. (Journal of Molecular Spectroscopy, 2013)
Spectra of Ne-C2D4 and Ar-C2D4 are studied in the ν11 fundamental band region of C 2D4 (≈2200 cm-¹) using a tuneable quantum cascade laser to probe a pulsed supersonic slit jet expansion. The spectra are those of perpendicular bands of near-prolate asymmetric rotors, but with a doubling of transitions due to tunneling. These tunneling splittings are due to hindered internal rotation of C2D4 around its C-C axis, and are more prominent for Ne-C2D4 than for Ar-C2D4. The analysis yields the first direct measurement of the A rotational constants for these complexes, and shows that the vibrational shifts are very small (<0.3 cm-¹). Attempts to observe the spectrum of He-C2D4 were not successful.
Keywords: Direct measurement; Fundamental bands; Hindered internal rotations; Infrared spectrum; Rotational constants; Supersonic jets; Tunneling splittings; Vibrational shift; Argon; Ethylene; Neon; Quantum cascade lasers; Spectroscopy; Supersonic aerodynamics; van der Waals

Probing ultrafast dynamics with time-resolved multi-dimensional coincidence imaging: butadiene - Hockett, Paul; Ripani, Enrico; Rytwinski, Andrew; Stolow, Albert (Journal of Modern Optics, 2013)
Time-resolved coincidence imaging of photoelectrons and photoions represents the most complete experimental measurement of ultrafast excited state dynamics, a multi-dimensional measurement for a multi-dimensional problem. Here we present the experimental data from recent coincidence imaging experiments, undertaken with the aim of gaining insight into the complex ultrafast excited-state dynamics of 1,3-butadiene initiated by absorption of 200 nm light. We discuss photoion and photoelectron mappings of increasing dimensionality, and focus particularly on the time-resolved photoelectron angular distributions (TRPADs), expected to be a sensitive probe of the electronic evolution of the excited state and to provide significant information beyond the time-resolved photoelectron spectrum (TRPES). Complex temporal behaviour is observed in the TRPADs, revealing their sensitivity to the dynamics while also emphasising the difficulty of interpretation of these complex observables. From the experimental data some details of the wavepacket dynamics are discerned relatively directly, and we make some tentative comparisons with existing ab initio calculations in order to gain deeper insight into the experimental measurements; finally, we sketch out some considerations for taking this comparison further in order to bridge the gap between experiment and theory. © 2013 Copyright Crown Copyright 2013. Reproduced with the permission of the National Research Council of Canada.
Keywords: ultrafast dynamics, coincidence imaging, butadiene, photoionization, time-resolved photoelectron spectroscopy (TRPES), time-resolved photoelectron angular distributions (TRPADs)

Photometry, colorimetry and radiometry: Issues and applications - Bullough, John D.; Zwinkels, Joanne C. (Journal of Modern Optics, 2013)

Near-infrared photoluminescence of orange color standards: then and now - Zwinkels, Joanne C.; Noël, Mario; Hillman, Sean (Journal of Modern Optics, 2013)
The presence of near-infrared (NIR) photoluminescence has been recently reported in some of the second series of Ceramic Color Standards (CCSII) that are widely used in the calibration and performance evaluation of color measuring instruments. The impact of this photoluminescence effect can cause significant colorimetric errors particularly for broadband measurements using a detector with high spectral responsivity in the NIR region. The magnitude of this effect has been demonstrated for specific color standards and specific instrument systems but has not been unambiguously quantified to allow general predictions or absolute comparisons of different instrument designs or different ceramic tiles. Here we present absolute NIR photoluminescence measurements on three different formulations of the CCSII orange ceramic color standard using the National Research Council of Canada (NRC) Reference Spectrofluorimeter whose spectral range has been recently extended to 1000 nm. The validation for this extended spectral range is shown by comparison of an independent method of instrument calibration using a different combination of physical standards. It is convincingly shown that the two different leaded formulations of this ceramic orange standard issued in 2000 and 2011 have no significant photoluminescence and thus can be used for calibration with any type of spectrophotometer design whereas the unleaded formulation issued in 2011 has significant NIR photoluminescence and should not be used for instrument calibration and validation over an extended range into the NIR for certain spectrophotometers with relatively high throughput in the NIR region, such as a spectrophotometer with polychromatic illumination mode using a xenon source or with monochromatic illumination mode using a Si detector. It is shown that for colorimetric applications, the impact of this NIR fluorescence is only significant for the latter spectrophotometer design with broadband detection with a Si or spectrally flat detector and is negligible with a narrowband PMT detector. These calculated colorimetric results are also consistent with previously estimated colorimetric errors for this type of orange CCSII ceramic tile used to transfer calibration between these two types of detector systems. © 2013 Crown copyright © National Research Council Canada.

Coincidence and covariance data acquisition in photoelectron and -ion spectroscopy. I. Formal theory - Mikosch, Jochen; Patchkovskii, Serguei (Journal of Modern Optics, 2013)
We derive a formal theory of noisy Poisson processes with multiple outcomes. We obtain simple, compact expressions for the probability distribution function of arbitrarily complex composite events and its moments. We illustrate the utility of the theory by analyzing properties of coincidence and covariance photoelectron-photoion detection involving single-ionization events. The results and techniques introduced in this work are directly applicable to more general coincidence and covariance experiments, including multiple ionization and multiple-ion fragmentation pathways.

Towards a sustainable smart e-marketplace: a stable, efficient and responsive smart exchange with strategic conduct - Ghonaim, Wafa; Ghenniwa, Hamada; Shen, Weiming (ICAART 2013 - Proceedings of the 5th International Conference on Agents and Artificial Intelligence, 2013)
The landscapes of e-marketplaces are changing profoundly, evident in the phenomenal growth and potential of online services, consumers, and enabling mobile technologies. However, it is unleashing grave concerns about sustainability due to the fierce competitions, fuzzy dynamics and rapidly shifting powers. While it is attributed to the game-theoretic economics and computation complexities of the decentralized combinatorial allocation problem, this work establishes, denying e-traders expressing fair strategic choice is unfounded of adverse strategic risk. In fact, free market dynamics realize impact of smart learning on strategic conduct. The fact strategic rules enable faster consumer-to-market bidding lifecycle is another compelling factor. Hence, the work introduces the novel rule-based bidding language and GSPM double auction for the smart exchange that facilitates expressions of strategic rules, while uniquely exploits forward and reverse GSP auctions for efficient, tractable, stable, and budget balanced e-marketplace. The e-marketplace deliberates on rules for effective preference elicitation, while bringing self-prosperity in socially efficient ecosystem.
Keywords: Bidding languages; Double auction; GSP auction; GSP matching; Preference elicitation; Preference formulation; Reverse GSP auction; Strategic rules; Winner determination; Artificial intelligence; Game theory; Commerce

Coincidence and covariance data acquisition in photoelectron and -ion spectroscopy. II. Analysis and applications - Mikosch, Jochen; Patchkovskii, Serguei (Journal of Modern Optics, 2013)
We use an analytical theory of noisy Poisson processes, developed in the preceding companion publication, to compare coincidence and covariance measurement approaches in photoelectron and -ion spectroscopy. For non-unit detection efficiencies, coincidence data acquisition (DAQ) suffers from false coincidences. The rate of false coincidences grows quadratically with the rate of elementary ionization events. To minimize false coincidences for rare event outcomes, very low event rates may hence be required. Coincidence measurements exhibit high tolerance to noise introduced by unstable experimental conditions. Covariance DAQ on the other hand is free of systematic errors as long as stable experimental conditions are maintained. In the presence of noise, all channels in a covariance measurement become correlated. Under favourable conditions, covariance DAQ may allow orders of magnitude reduction in measurement times. Finally, we use experimental data for strong-field ionization of 1,3-butadiene to illustrate how fluctuations in experimental conditions can contaminate a covariance measurement, and how such contamination can be detected.

The effect of oxygen, nitrogen and carbon on the microstructure and compression properties of titanium foams - Lefebvre, Louis-Philippe; Baril, Eric; De Camaret, Laurent (Journal of Materials Research, 2013)
This paper presents the effect of oxygen, nitrogen, and carbon concentration on the microstructure and properties of titanium foams produced with a powder metallurgy process. Oxygen and nitrogen reduce the ductility and increase the compression yield strength of CpTi foams. The effect of nitrogen appears to be similar to the effect of oxygen, a trend different from the ones reported in the literature for dense titanium in tension, where the effect of nitrogen is recognized to be significantly more important than the effect of oxygen. For carbon, the levels investigated were above the room temperature solubility limit of carbon in α-Ti and titanium carbides were observed in the microstructure. The volume fraction of carbides observed in the microstructure increased with carbon content. The effect of the carbides on the compression properties and ductility of the titanium foams is, however, small compared to the effect of oxygen and nitrogen. © Crown Copyright, Published by the Materials Research Society 2013.

A high capacity silicon-graphite composite as anode for lithium-ion batteries using low content amorphous silicon and compatible binders - Yim, Chae-Ho; Courtel, Fabrice M.; Abu-Lebdeh, Yaser (Journal of Materials Chemistry A, 2013)
In this study, silicon-graphite composites were prepared and investigated as anode materials for Li-ion batteries with small amounts of silicon and different binders. The silicon powders were prepared by ball-milling crystalline silicon for 100 h and 200 h. After 200 h, an average silicon particle size of 0.73 μm was obtained and XRD measurements confirmed the formation of an amorphous powder embedded within nanocrystalline regions. XPS analysis of the silicon samples showed that silicon particles were covered with a native silicon oxide layer that grows during ball-milling. Battery cycling of the silicon powders in half cells showed that the powder ball milled for 200 h gave the lowest first-cycle irreversible capacity and the highest reversible capacity reaching over 500 mA h g-1 after 50 cycles at C/12. Composites were made using graphite and only 5 wt% silicon powders. The silicon was found to be uniformly dispersed into the composites as evidenced by X-ray mapping and SEM. When tested in half cells using different binders, it was found that the polyetherimide binder showed the highest capacity reaching 514 mA h g -1 after 350 cycles at C/12, which is 1.6 times greater than commercial graphite anode. High rate cycling showed good capacity retention reaching half the capacity at 5 C.
Keywords: Amorphous powders; Crystalline silicons; Different binders; Good capacity retentions; Irreversible capacity; Lithium-ion battery; Reversible capacity; Silicon oxide layers; Anodes; Ball milling; Binders; Graphite; Lithium batteries; Lithium compounds; Milling (machining); Nanocrystalline silicon; Powders; Silicon oxides; Amorphous silicon

Echelle diffractive grating based wavelength interrogator for potential aerospace applications - Guo, Honglei; Xiao, Gaozhi; Mrad, Nezih; Yao, Jianping (Journal of Lightwave Technology, 2013)
Operational load monitoring and impact damage detection are the two critical aspects of aerospace structural health monitoring (SHM). Fiber Bragg grating (FBG) sensors have demonstrated great potential in both. But the currently available interrogation systems can only handle one of the two types of SHM capabilities offered by FBG sensors. In addition, the practical implementation of FBG sensor systems in aerospace vehicles requires the interrogator to be small size, light weight, and low-power consuming. In this paper, we present an Echelle diffractive grating (EDG) based interrogation system for FBG sensors, which possesses two operation modes, i.e., the sweeping mode for operational load monitoring and the parked mode for impact damage detection. Experimental results show that this interrogator offers better than 1-pm measurement resolution and 10-pm repeatability. In addition, the interrogation system is very compact and weighs less than 60 g (excluding the electronic controller). It also has the potential to achieve a measurement speed of 300 kHz and be powered by a battery.
Keywords: Echelle diffractive gratings; Fiber Bragg Grating Sensors; Impact damage detection; interrogator; Measurement resolution; Practical implementation; Structural health monitoring (SHM); Wavelength interrogator; Aerospace applications; Damage detection; Electric sensing devices; Fiber Bragg gratings; Fiber optic sensors; Structural health monitoring; Diffraction gratings

Bacillus anthracis cell wall peptidoglycan but not lethal or edema toxins produces changes consistent with disseminated intravascular coagulation in a rat model - Qiu, Ping; Li, Yan; Shiloach, Joseph; Cui, Xizhong; Sun, Junfeng; Trinh, Loc; Kubler-Kielb, Joanna; Vinogradov, Evgeny; Mani, Haresh; Al-Hamad, Mariam; Fitz, Yvonne; Eichacker, Peter Q. (Journal of Infectious Diseases, 2013)
Background. Disseminated intravascular coagulation (DIC) appears to be important in the pathogenesis of Bacillus anthracis infection, but its causes are unclear. Although lethal toxin (LT) and edema toxin (ET) could contribute, B. anthracis cell wall peptidoglycan (PGN), not the toxins, stimulates inflammatory responses associated with DIC.Methods and Results. To better understand the pathogenesis of DIC during anthrax, we compared the effects of 24-hour infusions of PGN, LT, ET, or diluent (control) on coagulation measures 6, 24, or 48 hours after infusion initiation in 135 rats. No control recipient died. Lethality rates (approximately 30%) did not differ among PGN, LT, and ET recipients (P =. 78). Thirty-three of 35 deaths (94%) occurred between 6 and 24 hours after the start of challenge. Among challenge components, PGN most consistently altered coagulation measures. Compared with control at 6 hours, PGN decreased platelet and fibrinogen levels and increased prothrombin and activated partial thromboplastin times and tissue factor, tissue factor pathway inhibitor, protein C, plasminogen activator inhibitor (PAI), and thrombin-antithrombin complex levels, whereas LT and ET only decreased the fibrinogen level or increased the PAI level (P ≤. 05). Nearly all effects associated with PGN infusion significantly differed from changes associated with toxin infusion (P ≤. 05 for all comparisons except for PAI level).Conclusion. DIC during B. anthracis infection may be related more to components such as PGN than to LT or ET. © 2013 The Author.
Keywords: anthrax infection; sepsis; coagulopathy; thrombocytopenia; Bacillus anthracis; disseminated intravascular coagulation; peptidoglycan; lethal toxin; edema toxin

A typology of clean technology commercialization accelerators - Malek, Kourosh; Maine, Elicia; McCarthy, Ian P. (Journal of Engineering and Technology Management, 2013)
Accelerators are a type of incubation program that are concerned with attracting, supporting and developing new ventures. Although there is significant enthusiasm for accelerators and their potential benefits, there is limited research on how their core capabilities can vary. In response, we develop a typology of accelerator capabilities taking into account their strategy, governance, business model, operations and finance. To develop the typology we carried out a benchmark analysis of six clean energy commercialization accelerators (CECAs). From this we verified and illustrated the dimensions of our typology and identified four types of accelerator capabilities: R&D focused, technology enabled, market enabled, and network enabled. We then use a seventh accelerator case to illustrate how our typology can be used to describe, understand and prescribe appropriate capabilities for a CECA. We conclude our paper by explaining the research and practice implications of our research. Crown Copyright © 2013.

Ordered gold nanoparticle arrays on glass and their characterization - Yuan, Jie; Hajebifard, Akram; George, Christeen; Berini, Pierre; Zou, Shan (Journal of Colloid and Interface Science, 2013)
Using self-assembly of block copolymer micelle loaded metal precursors, combined with a seeding growth route, we have developed a novel approach to create ordered metal nanoparticle (NP) arrays of controllable size over large areas (~80mm2) on solid substrates. Atomic force microscopy (AFM), UV-Vis extinction spectrophotometry, and theoretical simulations were systematically carried out to determine the size and pattern of NP arrays, and locate the localized surface plasmon resonance (LSPR) peak. By tuning the molar ratios of precursors, hexagonal arrays of AuNPs of mean heights of 5.2±0.6nm, 8.3±1.7nm, and 10.0±2.1nm were obtained by self-assembly of poly(styrene-b-2-vinyl pyridine) micelle-loaded gold salt on glass. Further seeding growth was then used to enlarge the AuNPs to heights of 25.7 and 33nm and decrease the edge-to-edge inter-particle spacing. The optical response of AuNP arrays was determined by measuring and computing their absorbance spectra as a function of the cover medium refractive index over the range from 1 to 1.55; the measured spectra agree very well with the computations. The resonance wavelength red-shifts as the medium refractive index increases and the bulk sensitivity of the arrays increases with increasing AuNP size. When the edge-to-edge inter-particle spacing decreased to ~50nm, coupling of adjacent AuNPs became apparent, as a shoulder which developed in the spectra. Also, the AuNPs were found to be embedded in the substrate glass by about ~20-30%, as determined by comparing the experimental and computed bulk sensitivities. The fabrication technique devised is suitable for low-cost mass-manufacturing of large area arrays of ordered high-quality AuNPs on a substrate for biosensor or other applications. © 2013 .
Keywords: Gold nanoparticles (AuNPs); Localized surface plasmon resonance (LSPR); Self-assembly; Diblock copolymer; Seeding growth

Communication: Spectroscopic evidence for a planar cyclic CO trimer - Rezaei, Mojtaba; Sheybani-Deloui, S.; Moazzen-Ahmadi, N.; Michaelian, K. H.; McKellar, A. R. W. (Journal of Chemical Physics, 2013)
A high-resolution spectrum in the region of 2144 cm-1 is assigned to the previously elusive CO trimer. In spite of interference from the CO dimer and some remaining unexplained details, there is strong evidence for a planar, cyclic, C-bonded trimer structure, with C3h symmetry and 4.42 Å intermolecular separation, in agreement with theoretical calculations. A modest vibrational blueshift of +0.85 cm-1 is observed for the CO trimer, as compared to +0.71 cm-1 for the C-bonded form of the dimer.
Keywords: Blue shift; Cyclic CO; High-resolution spectra; Intermolecular separations; Spectroscopic evidence; Theoretical calculations; Trimer structure; Dimers

A comprehensive experimental and theoretical study of H2-CO spectra - Jankowski, Piotr; Surin, L. A.; Potapov, A.; Schlemmer, S.; McKellar, A. R. W.; Szalewicz, Krzysztof (Journal of Chemical Physics, 2013)
A detailed description of a new ab initio interaction potential energy surfaces for the H2-CO complex computed on a six-dimensional grid (i.e., including the dependence on the H-H and C-O separations) is presented. The interaction energies were first calculated using the coupled-cluster method with single, double, and noniterative triple excitations and large basis sets, followed by an extrapolation procedure. Next, a contribution from iterative triple and noniterative quadruple excitations was added from calculations in smaller basis sets. The resulting interaction energies were then averaged over the ground-state and both ground- and first-excited-states vibrational wave functions of H2 and CO, respectively. The two resulting four-dimensional potential energy surfaces were fitted by analytic expressions. Theoretical infrared spectra calculated from these surfaces have already been shown [P. Jankowski, A. R. W. McKellar, and K. Szalewicz, Science 336, 1147 (2012)] to agree extremely well, to within a few hundredth of wavenumber, with the experimental spectra of the para and orthoH2-CO complex. In the latter case, this agreement enabled an assignment of the experimental spectrum, ten years after it had been measured. In the present paper, we provide details concerning the development of the surfaces and the process of spectral line assignment. Furthermore, we assign some transitions for paraH2-CO that have not been assigned earlier. A completely new element of the present work are experimental investigations of the orthoH2-CO complex using microwave spectroscopy. Vast parts of the measured spectrum have been interpreted by comparisons with the infrared experiments, including new low-temperature ones, and theoretical spectrum. Better understanding of the spectra of both para and orthoH2-CO complexes provides a solid foundation for a new search of the bound H2-CO complex in space.
Keywords: Analytic expressions; Coupled-cluster methods; Experimental investigations; Experimental spectra; Extrapolation procedure; Interaction energies; Quadruple excitations; Vibrational wave functions; Calculations; Microwave spectroscopy; Potential energy surfaces; Quantum chemistry; Spectroscopy; Iterative methods

Pressure induced dimer to ionic insulator and metallic structural changes in Al2Br6 - Yao, Yansun; Klug, Dennis D. (Journal of Chemical Physics, 2013)
High-pressure phase transitions in Al2Br6 were theoretically investigated using first principles density functional methods. A structural transformation from the initial molecular solid phase to a planar polymeric phase is predicted near 0.4 GPa that is accompanied with a substantial volume drop. A unique feature of this phase transition is that the hcp lattice of Br atoms remains unchanged during the transition, whereas the Al atoms are displaced from the original tetrahedral sites to the octahedral sites. The calculated phonon spectra indicate that the predicted phase is mechanically stable at 1 atm, and therefore it may be quench-recovered to ambient conditions and exist as a metastable form. A second structural transformation is predicted to occur at around 80 GPa, and also at this point, the AlBr3 reaches a metallic state. The electronic structure of the metallic phase features soft phonon modes and Fermi surface nesting in the Brillouin zone, which leads to localized electron-phonon coupling. By comparing with the experimental data available for high-pressure BI3, the superconducting critical temperature Tc for the metallic phase of AlBr3 is estimated to be at 0.5 K or above.
Keywords: Electron phonon couplings; Experimental datum; Fermi surface nesting; First-principles density-functional method; High-pressure phase transitions; Mechanically stable; Structural transformation; Superconducting critical temperatures; Dimers; Electronic structure; Phonons; Aluminum

Communication: selection rules for tunneling splitting of vibrationally excited levels - Siebrand, Willem; Smedarchina, Zorka; Fernández-Ramos, Antonio (Journal of Chemical Physics, 2013)
Five symmetry-based selection rules are formulated that relate the tunneling splitting of a vibrationally excited level to that of the ground level in molecules with a symmetric double-minimum potential. The rules, which explain why excited levels frequently have smaller splittings than zero-point levels, are used to interpret the observed and calculated splittings in malonaldehyde.
Keywords: Excited levels; Ground level; Malonaldehyde; Selection Rules; Splittings; Tunneling splittings; Vibrationally excited; Zero-point; Excited states

The quantitative determination of laser-induced molecular axis alignment - Mikosch, Jochen; Bisgaard, Christer Z.; Boguslavskiy, Andrey E.; Wilkinson, Iain; Stolow, Albert (Journal of Chemical Physics, 2013)
Experiments in the gas phase usually involve averaging observables over a random molecular axis alignment distribution. This deleterious averaging limits insights gained by probes of molecular dynamics, but can be overcome by prealigning molecular axes using laser-alignment methods. However, the transformation from the laboratory frame to the molecular frame of reference requires quantitative knowledge of the axis alignment distribution. The latter is often hard to obtain directly from experimental data, particularly for polyatomic molecules. Here we describe a general maximum-likelihood classification procedure for non-adiabatic numerical alignment simulations with free parameters that employs experimental data from an alignment-dependent probe. This method delivers (i) the most probable molecular frame angular dependence of the probe, and (ii) the most likely laboratory frame axis alignment distribution of the sample, each with a confidence interval. This procedure was recently used for studies of angle- and channel-resolved strong field ionization of 1,3-butadiene in the molecular frame [Mikosch, Phys. Rev. Lett. 110, 023004 (2013)], used here as an illustrative example. © 2013 Crown.
Keywords: Angular dependence; Confidence interval; Experimental datum; Maximum-likelihood classification; Polyatomic molecules; Quantitative determinations; Quantitative knowledge; Strong field ionization; Alignment; Molecular dynamics; Probes; Angular distribution

Posttranslational modification of flagellin flaB in Shewanella oneidensis - Sun, Linlin; Jin, Miao; Ding, Wen; Yuan, Jie; Kelly, John; Gao, Haichun (Journal of Bacteriology, 2013)
Shewanella oneidensis is a highly motile organism by virtue of a polar, glycosylated flagellum composed of flagellins FlaA and FlaB. In this study, the functional flagellin FlaB was isolated and analyzed with nano-liquid chromatography-mass spectrometry (MS) and tandem MS. In combination with the mutational analysis, we propose that the FlaB flagellin protein from S. oneidensis is modified at five serine residues with a series of novel O-linked posttranslational modifications (PTMs) that differ from each other by 14 Da. These PTMs are composed in part of a 274-Da sugar residue that bears a resemblance to the nonulosonic acids. The remainder appears to be composed of a second residue whose mass varies by 14 Da depending on the PTM. Further investigation revealed that synthesis of the glycans initiates with PseB and PseC, the first two enzymes of the Pse pathway. In addition, a number of lysine residues are found to be methylated by SO4160, an analogue of the lysine methyltransferase of Salmonella enterica serovar Typhimurium.
Keywords: cysteine; flagellin; lysine; protein FlaB; protein PseB; protein PseC; serine; bacterial strain; bacterium mutant; controlled study; glycosylation; liquid chromatography; methylation; protein isolation; protein processing; Salmonella enterica; Shewanella oneidensis; Amino Acid Sequence; Amino Acid Substitution; Bacterial Proteins; Chromatography, Liquid; Flagella; Genetic Complementation Test; Glycosylation; Mass Spectrometry; Mutagenesis, Site-Directed; Mutation; Polysaccharides; Protein Processing, Post-Translational; Recombinant Fusion Proteins; Tandem Mass Spectrometry

Generating extractive summaries of scientific paradigms - Qazvinian, Vahed; Radev, Dragomir R.; Mohammad, Saif M.; Dorr, Bonnie; Zajic, David; Whidby, Michael; Moon, Taesun (Journal of Artificial Intelligence Research, 2013)
Researchers and scientists increasingly find themselves in the position of having to quickly understand large amounts of technical material. Our goal is to effectively serve this need by using bibliometric text mining and summarization techniques to generate summaries of scientific literature. We show how we can use citations to produce automatically generated, readily consumable, technical extractive summaries. We first propose C-LexRank, a model for summarizing single scientific articles based on citations, which employs community detection and extracts salient information-rich sentences. Next, we further extend our experiments to summarize a set of papers, which cover the same scientific topic. We generate extractive summaries of a set of Question Answering (QA) and Dependency Parsing (DP) papers, their abstracts, and their citation sentences and show that citations have unique information amenable to creating a summary.
Keywords: Automatically generated; Community detection; Dependency parsing; Large amounts; Scientific articles; Scientific literature; Scientific paradigm; Set of questions; Data mining; Dynamic positioning; Natural language processing systems

Photopolymerizable organically modified holographic glass with enhanced thickness for spectral filters - Velasco, A. V.; Calvo, M. L.; Cheben, P. (Journal of Applied Physics, 2013)
A novel formulation and synthesis method to overcome the thickness limitations in samples of photopolymerizable glasses with high refractive index species is presented. The reported method allows the recording of volume holographic diffraction gratings in samples of ∼500 μm thickness with a high optical quality and low scattering. Holographic grating recording is performed in a single coherent light exposure step, resulting in volume gratings of high optical quality. A holographic notch filter implemented in a 500 μm thick photopolymerizable glass with a spectral bandwidth below 0.3 nm and an excellent filter extinction ratio of <-27 dB is also demonstrated.
Keywords: Extinction ratios; High refractive index; Holographic grating recording; Holographic notch filters; Optical qualities; Spectral bandwidth; Spectral filters; Synthesis method; Volume gratings; Volume holographic; Diffraction gratings; Glass; Refractive index; Holography

Manipulated electromagnetic losses by integrating chemically heterogeneous components in Fe-based core/shell architecture - Huang, Hao; Zhang, Xue-Feng; Lv, Bo; Xue, Fang-Hong; Shah, Asif; Su, Lei; Yan, Jing-Guo; Yao, Man; Dong, Xing-Long (Journal of Applied Physics, 2013)
Existing techniques for stabilizing and functionalizing metal nanostructures required precise control of complex procedures and probably introduce undesirable impurities. We herein report an arc-discharge chemical vapor deposition strategy for the synthesis of chemically heterogeneous core/shell metal/oxide nanocapsules Fe/TiFe2O4, Fe/MnFe2O4, and Fe/Al2O3. A universal formation mechanism based on the co-effect of oxygen potential and surface energy is further proposed, derived from fundamental thermodynamics. Such core/shell nanocapsules, integrated with tunable components, present an effective manipulability of microwave absorption at expected frequency, originating from the various dielectric behaviors of the heterogeneous oxide shells.
Keywords: Dielectric behavior; Electromagnetic loss; Formation mechanism; Heterogeneous component; Heterogeneous cores; Metal nanostructure; Microwave absorption; Tunable components; Chemical vapor deposition; Nanocapsules; Thermodynamics; Electric discharges

Effect of oscillator strength and intermediate resonance on the performance of resonant phonon-based terahertz quantum cascade lasers - Fathololoumi, S.; Dupont, E.; Wasilewski, Z. R.; Chan, C. W. I.; Razavipour, S. G.; Laframboise, S. R.; Huang, S.; Hu, Q.; Ban, D.; Liu, H. C. (Journal of Applied Physics, 2013)
We experimentally investigated the effect of oscillator strength (radiative transition diagonality) on the performance of resonant phonon-based terahertz quantum cascade lasers that have been optimized using a simplified density matrix formalism. Our results show that the maximum lasing temperature (T max) is roughly independent of laser transition diagonality within the lasing frequency range of the devices under test (3.2-3.7 THz) when cavity loss is kept low. Furthermore, the threshold current can be lowered by employing more diagonal transition designs, which can effectively suppress parasitic leakage caused by intermediate resonance between the injection and the downstream extraction levels. Nevertheless, the current carrying capacity through the designed lasing channel in more diagonal designs may sacrifice even more, leading to electrical instability and, potentially, complete inhibition of the devices lasing operation. We propose a hypothesis based on electric-field domain formation and competition/switching of different current-carrying channels to explain observed electrical instability in devices with lower oscillator strengths. The study indicates that not only should designers maximize Tmax during device optimization but also they should always consider the risk of electrical instability in device operation.
Keywords: Density matrix formalism; Device optimization; Devices under tests; Electric field domain; Electrical instability; Oscillator strengths; Radiative transitions; Terahertz quantum-cascade lasers; Optimization; Design

An indirectly pumped terahertz quantum cascade laser with low injection coupling strength operating above 150 K - Razavipour, S. G.; Dupont, E.; Fathololoumi, S.; Chan, C. W. I.; Lindskog, M.; Wasilewski, Z. R.; Aers, G.; Laframboise, S. R.; Wacker, A.; Hu, Q.; Ban, D.; Liu, H. C. (Journal of Applied Physics, 2013)
We designed and demonstrated a terahertz quantum cascade laser based on indirect pump injection to the upper lasing state and phonon scattering extraction from the lower lasing state. By employing a rate equation formalism and a genetic algorithm, an optimized active region design with four-well GaAs / Al0.25 Ga0.75 As cascade module was obtained and epitaxially grown. A figure of merit which is defined as the ratio of modal gain versus injection current was maximized at 150 K. A fabricated device with a Au metal-metal waveguide and a top n+ GaAs contact layer lased at 2.4 THz up to 128.5 K, while another one without the top n+ GaAs lased up to 152.5 K (1.3ω/kB). The experimental results have been analyzed with rate equation and nonequilibrium Green's function models. A high population inversion is achieved at high temperature using a small oscillator strength of 0.28, while its combination with the low injection coupling strength of 0.85 meV results in a low current. The carefully engineered wavefunctions enhance the quantum efficiency of the device and therefore improve the output optical power even with an unusually low injection coupling strength.
Keywords: Coupling strengths; Fabricated device; Injection currents; Metal-metal waveguides; Non-equilibrium Green's function; Oscillator strengths; Population inversions; Terahertz quantum-cascade lasers; Gallium arsenide; Gold; Semiconducting gallium; Quantum cascade lasers

Microbial communities in low permeability, high pH uranium mine tailings: characterization and potential effects - Bondici, V. F.; Lawrence, J. R.; Khan, N. H.; Hill, J. E.; Yergeau, E.; Wolfaardt, G. M.; Warner, J.; Korber, D. R. (Journal of Applied Microbiology, 2013)
Aims: To describe the diversity and metabolic potential of microbial communities in uranium mine tailings characterized by high pH, high metal concentration and low permeability. Methods and Results: To assess microbial diversity and their potential to influence the geochemistry of uranium mine tailings using aerobic and anaerobic culture-based methods, in conjunction with next generation sequencing and clone library sequencing targeting two universal bacterial markers (the 16S rRNA and cpn60 genes). Growth assays revealed that 69% of the 59 distinct culturable isolates evaluated were multiple-metal resistant, with 15% exhibiting dual-metal hypertolerance. There was a moderately positive correlation coefficient (R = 0·43, P < 0·05) between multiple-metal resistance of the isolates and their enzyme expression profile. Of the isolates tested, 17 reduced amorphous iron, 22 reduced molybdate and seven oxidized arsenite. Based on next generation sequencing, tailings depth was shown to influence bacterial community composition, with the difference in the microbial diversity of the upper (0-20 m) and middle (20-40 m) tailings zones being highly significant (P < 0·01) from the lower zone (40-60 m) and the difference in diversity of the upper and middle tailings zone being significant (P < 0·05). Phylotypes closely related to well-known sulfate-reducing and iron-reducing bacteria were identified with low abundance, yet relatively high diversity. Conclusions: The presence of a population of metabolically-diverse, metal-resistant micro-organisms within the tailings environment, along with their demonstrated capacity for transforming metal elements, suggests that these organisms have the potential to influence the long-term geochemistry of the tailings. Significance and Impact of the study: This study is the first investigation of the diversity and functional potential of micro-organisms present in low permeability, high pH uranium mine tailings.
Keywords: biotransformation, ecology, microbial diversity, uranium tailings

Selective hydride generation-cryotrapping-ICP-MS for arsenic speciation analysis at picogram levels: analysis of river and sea water reference materials and human bladder epithelial cells - Matoušek, Tomáš; Currier, Jenna M.; Trojánková, Nikola; Saunders, R. Jesse; Ishida, María C.; González-Horta, Carmen; Musil, Stanislav; Mester, Zoltán; Stýblo, Miroslav; Dědina, Jiří (Journal of Analytical Atomic Spectrometry, 2013)
An ultra-sensitive method for arsenic (As) speciation analysis based on selective hydride generation (HG) with preconcentration by cryotrapping (CT) and inductively coupled plasma-mass spectrometry (ICP-MS) detection is presented. Determination of the valency of the As species is performed by selective HG without prereduction (trivalent species only) or with l-cysteine prereduction (sum of tri- and pentavalent species). Methylated species are resolved on the basis of thermal desorption of the formed methyl substituted arsines after collection at -196 °C. Limits of detection of 3.4, 0.06, 0.14 and 0.10 pg mL-¹ (ppt) were achieved for inorganic As, mono-, di- and trimethylated species, respectively, from a 500 μL sample. Speciation analysis of river water (NRC SLRS-4 and SLRS-5) and sea water (NRC CASS-4, CASS-5 and NASS-5) reference materials certified to contain 0.4 to 1.3 ng mL-¹ total As was performed. The concentrations of methylated As species in tens of pg mL-¹ range obtained by HG-CT-ICP-MS systems in three laboratories were in excellent agreement and compared well with results of HG-CT-atomic absorption spectrometry and anion exchange liquid chromatography-ICP-MS; sums of detected species agreed well with the certified total As content. The HG-CT-ICP-MS method was successfully used for analysis of microsamples of exfoliated bladder epithelial cells isolated from human urine. Here, samples of lysates of 25 to 550 thousand cells contained typically tens of pg up to ng of iAs species and from single to hundreds of pg of methylated species, well within detection power of the presented method. A significant portion of As in the cells was found in the form of the highly toxic trivalent species.
Keywords: Absorption spectrometry; Arsenic speciation analysis; Epithelial cells; Hydride generations; Limits of detection; Pre-concentration; Speciation analysis; Amino acids; Atomic absorption spectrometry; Hydrides; Inductively coupled plasma; Liquid chromatography; Mass spectrometers; Seawater; Inductively coupled plasma mass spectrometry

Effects of precursor treatment on the structure and electrochemical properties of spinel LiMn2O4 cathode - Tang, Hongwei; Chang, Zhaorong; Zhao, Haili; Yuan, Xiao-Zi; Wang, Haijiang; Gao, Shuyan (Journal of Alloys and Compounds, 2013)
As a precursor of spinel LiMn2O4 cathode, manganese oxide is prepared by co-precipitation via a two-step drying method. The effects of precursor treatment on the structure, morphology, and electrochemical performance of the synthesized spinel LiMn2O4 are studied using contrasting experiments involving the addition of hydrazine, N 2, and H2O2. The tests show that different treatments have a great effect on the crystal structure, morphology, tap density, and electrochemical performance of LiMn2O4. When the precursor is treated by adding hydrazine and pure N2, the synthesized LiMn2O4 shows an integral lattice, uniform particle size, a pure spinel phase with an ordered octahedral crystal structure, and high tap density (2.23 g cm-3). The electrochemical results show that spinel LiMn2O4 exhibits higher specific capacity and better cyclic stability than other samples, especially at an elevated temperature and high discharge current. The initial discharge capacity of the electrode is 110.8 mAh g-1 at a rate of 3 C, and exhibits a good capacity retention of 96.4% after 30 cycles; at a rate of 5 C, the initial discharge capacity is 107.5 mAh g-1, with a capacity retention of 87.3% after 50 cycles.
Keywords: Cathode materials; Different treatments; Discharge rates; Electrochemical performance; Good capacity retentions; Initial discharge capacities; Lithium manganates; Two-step drying method; Electric discharges; Hydrazine; Lithium compounds; Morphology; Lithium alloys

Spectroscopy of dimers, trimers and larger clusters of linear molecules - Moazzen-Ahmadi, N.; McKellar, A. R. W. (International Reviews in Physical Chemistry, 2013)
Rotationally resolved spectra of van der Waals clusters provide the most direct, precise and unambiguous experimental probe of intermolecular potential energy surfaces, particularly in the lower energy range of attractive forces. The spectroscopy of such weakly bound complexes is reviewed with a focus on those containing only the following five small linear molecules: N2O, CO2, OCS, CS2 and C2H2. Even with this limitation, there are over 30 such complexes for which high-resolution spectroscopic results are now available in the microwave, millimetre wave and infrared regions. Dimers formed from these five species tend to be planar with slipped parallel structures, though there are some exceptions. Trimers tend to be barrel-shaped, that is, non-planar with approximately parallel monomers. Larger clusters are almost invariably non-planar and sometimes highly symmetric. Three significant themes emerge here. First, the possibility of determining low-frequency intermolecular vibrational modes by means of mid-infrared combination bands. Second, the increasing number of complexes for which more than one structural form, or isomer, is observed. And finally, the growing amenability of even 'large' clusters (say, tetramers and larger) to spectroscopic study. All three factors help to probe potential energy surfaces more completely in regions away from the global minimum.
Keywords: Cluster, dimer, trimer, van der Waals, intermolecular forces, infrared, high resolution

Review of confederation bridge ice forces: Winter 2008-2010 - Frederking, Robert; Li, Lian-Feng; Kubat, Ivana (International Journal of Offshore and Polar Engineering, 2013)
Ice interactions with the Confederation Bridge for the winters 2008, 2009 and 2010 have been studied. Ice conditions for these winters were characterized as two average winters and one very mild winter. Tilt data from piers P23 and P24 in response to ice and wind actions were recorded by a data acquisition system. Video records of ice interactions with pier P23 and overall ice conditions adjacent to piers P23 and P24 allowed ice conditions and interaction processes to be related to tilt measurements. Wind data were analyzed to correct for the tilt caused by wind actions on the bridge. Limit stress and limit force events were identified. An ice loading scenario that transitioned from limit force to limit stress resulted in the highest ice forces over the three years of monitoring, with forces of 3.1 MN and 4.3 MN at P23 and P24, respectively. ISO 19906 Arctic offshore structures can provide reasonable predictions of ice forces for ice actively failing on a conical structure.
Keywords: Conical structures; Data acquisition system; Ice interactions; Interaction process; Measurement system; Tilt measurement; Bridge piers; Loading; Meteorological problems; Offshore structures; Standards; Data set; Ice core; Ice-structure interaction; Videography; Wind forcing

Assessment of hydrodynamic impacts from tidal power lagoons in the Bay of Fundy - Cornett, Andrew; Cousineau, Julien; Nistor, Ioan (International Journal of Marine Energy, 2013)
The Bay of Fundy located in eastern Canada is home to some of the world's largest tides. Currently there is renewed interest in harnessing these very large tides for power generation in ways that avoid upsetting ecosystems, infrastructure and human activities that are presently well adapted to existing conditions. This paper investigates the hydrodynamic impacts due to tidal power lagoons, an approach to power generation that involves temporarily storing seawater behind a circular engineered dyke and generating power by gradually releasing the impounded seawater through conventional low-head hydroelectric turbines. This paper describes a study in which a two-dimensional, depth-averaged hydrodynamic model based on the TELEMAC modelling system was developed, calibrated, and applied to analyze, predict, and quantify the potential changes in tidal hydrodynamics (water levels, tide range, circulation patterns and tidal currents) throughout the Bay of Fundy and Gulf of Maine due to the presence of a single tidal lagoon and multiple lagoons operating at various locations in the upper Bay of Fundy. The sensitivity of the hydrodynamic impacts to changes in lagoon type, size, location, the number of lagoons, and their operating mode have also been investigated. The methods employed in this study and the main findings are presented and discussed herein. These results will help inform future decisions concerning development of the vast tidal energy resources in the Bay of Fundy. © 2013 Elsevier Ltd. All rights reserved.
Keywords: Circulation patterns; Human activities; Hydrodynamic impacts; Hydrodynamic model; Modelling systems; Potential change; Tidal lagoon; Energy resources; Hydrodynamics; Numerical models; Ocean currents; Tidal power; Tides; Water levels; Lakes; Electricity generation; Energy resource; Hydrodynamics; Hydroelectric power; Resource management

Sodium tungstate as electrolyte additive to improve high-temperature performance of nickel-metal hydride batteries - Shangguan, Enbo; Li, Jing; Chang, Zhaorong; Tang, Hongwei; Li, Bao; Yuan, Xiao-Zi; Wang, Haijiang (International Journal of Hydrogen Energy, 2013)
Sodium tungstate (Na2WO4) used as new electrolyte additive to enhance the high-temperature performance of Nickel-metal hydride (Ni-MH) battery is investigated in this paper. The effects of Na 2WO4 on nickel hydroxide electrodes are investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and a charge/discharge test. It is found that the Ni-MH cell with the conventional KOH electrolyte containing 1 wt.% Na2WO4 additive exhibits higher discharge retention and better cycling performance than the cell without Na2WO4 additive at both 25 °C and 70 °C. These performance improvements are ascribed to the enhancement of oxygen evolution overvoltage and lower electrochemical impedance, as indicated by CV and EIS. The results suggest that the proposed approach be an effective way to improve the high temperature performance of Ni-MH batteries.
Keywords: Charge/discharge test; Cycle stability; Electrochemical impedance; High temperature performance; Nickel hydroxide electrode; Performance improvements; Sodium tungstate; Cyclic voltammetry; Electrochemical impedance spectroscopy; Electrolytes; Nickel cadmium batteries; Tungsten compounds; Sodium

Enhancement of the high-temperature performance of advanced nickel-metal hydride batteries with NaOH electrolyte containing NaBO2 - Shangguan, Enbo; Wang, Jianling; Li, Jing; Dan, Guo; Chang, Zhaorong; Yuan, Xiao-Zi; Wang, Haijiang (International Journal of Hydrogen Energy, 2013)
In this paper, an alternative approach to improve the high-temperature performance of nickel-metal hydride (Ni-MH) batteries is proposed by introducing NaOH electrolyte with sodium metaborate (NaBO2) additives. Compared with conventional batteries using KOH electrolyte, the in-house prepared batteries with proposed electrolytes exhibit an enhanced discharge capacity, improved high-rate discharge ability, increased cycle stability and reduced self-discharge rate at an elevated temperature (70 °C). The charge acceptance of these Ni-MH batteries at 70 °C is over 96% at a charge/discharge rate of 1 C. These performance improvements are ascribed to the increased oxygen evolution overpotential, slower oxygen evolution rate and lower electrochemical impedance, as indicated by CV, steady-state polarization measurements and EIS. The results suggest that the proposed approach be an effective way to improve the high-temperature performance of Ni-MH batteries.
Keywords: Conventional batteries; Cycle stability; Electrochemical impedance; Nickel metal hydride battery; Oxygen evolution overpotential; Sodium metaborate; Steady state polarization; Nickel cadmium batteries; Oxygen; Sodium; Electrolytes

Effect of KOH concentration on the oxygen reduction kinetics catalyzed by heat-treated co-pyridine/C electrocatalysts - Qiao, Jinli; Xu, Li; Ding, Lei; Shi, Penghui; Zhang, Lei; Baker, Ryan; Zhang, Jiujun (International Journal of Electrochemical Science, 2013)
Using a simple thermal method, a non-noble metal electrocatalyst (Co-N-S/C) is successfully synthesized and its' composition is analyzed using EDX. The electrochemical activity of such a catalyst is also tested using surface electrochemical methods. Three one-electron transfer redox processes in the studied potential range are identified, where only one such a process is associated with the catalyst's ORR activity. The effect of KOH on the Co-N-S/C catalyzed ORR kinetics is investigated using the rotating disk electrode technique in a concentration range of 0.05 to 6.0M. Several ORR kinetic parameters such as overall electron transfer number (n), the product of electron transfer number and coefficient in ORR rate determining step (αnα), and the exchange current density (iO2/H2O°) are estimated. The results show that values of n at different KOH concentrations are close to 4.0, suggesting that Co-N-S/C catalyzed ORR is a 4-electron transfer process from O2 to H2O. KOH concentration has an insignificant effect on the value of n, however, a significant effect is observed on both values of αnα and iO2/H2O°. (αnα decreases while that of iO2/H2O° increases with increasing KOH concentration).

Assessing performance in brain tumor resection using a novel virtual reality simulator - Gélinas-Phaneuf, Nicholas; Choudhury, Nusrat; Al-Habib, Ahmed R.; Cabral, Anne; Nadeau, Etienne; Mora, Vincent; Pazos, Valerie; Debergue, Patricia; DiRaddo, Robert; Del Maestro, Rolando F. (International Journal of Computer Assisted Radiology and Surgery, 2013)
Purpose: NeuroTouch is a virtual reality (VR) simulator developed for neurosurgical skill training. Validation demonstrating that the system is useful and reliable is required for formal adoption into training curriculums. Face and content validity have been demonstrated for some neurosurgical simulators, but construct validity remains difficult to establish. A pilot validation study was conducted for a NeuroTouch training exercise. Methods: Participants completed the internal resection of a simulated convexity meningioma and filled out questionnaires to provide feedback on the experience. Performance metrics included volume of tissues removed, tool path lengths, duration of excessive forces applied and efficient use of the aspirator. Results were analyzed according to participants' level of training, gender, handedness, surgical experience in meningioma removal and hours/week playing musical instruments or video games. Results: Seventy-two participants (10 medical students, 18 junior residents and 44 senior residents) were enrolled. Analyses demonstrated statistically significant increase in tumor removed and efficiency of ultrasonic aspirator use between medical students and residents, but not between junior and senior residents. After covariate adjustment for the number of meningioma cases operated on, multivariate analysis of the level of training became nonsignificant. Participants judged the exercise appropriate and realistic, desiring use of the system in current training programs. Conclusion: We have conducted a pilot validation study for the NeuroTouch tumor resection scenario and demonstrated for the first time, face, content and construct validity of a VR neurosurgical simulation exercise. Future full-scale studies will be conducted in noncompetitive settings and incorporate expert participants.
Keywords: NeuroTouch; virtual reality simulation; Haptic feedback; Brain tumor resection; Neurosurgical oncology; performance metrics

High resolution Fourier-transform microspectroscopy based on spiral silicon waveguides - Velasco, Aitor V.; Cheben, Pavel; Calvo, Maria L.; Florjańczyk, Miroslaw; Bock, Przemek J.; Delâge, André; Schmid, Jens H.; Lapointe, Jean; Janz, Siegfried; Xu, Dan-Xia; Vachon, Martin (ICTON 2013: 15th International Conference on Transparent Optical Networks, June 23-27, 2013, Cartagena, Spain : conference proceedings, 2013)
We report a spatial heterodyne Fourier-transform spectrometer consisting of an array of Mach-Zehnder interferometers (MZI) implemented in silicon microphotonics. Optical path differences between the MZI arms increase linearly along the array, generating a wavelength-dependent interferogram which enables the retrieval of the source spectrum with a single measurement. Optical delays were implemented with Si-wire waveguides arranged in tightly coiled spirals to achieve a high resolution in a reduced footprint. Our spectral retrieval algorithm compensates phase and amplitude errors arising from fabrication imperfections by using a transformation matrix based on the calibration data. A wavelength resolution of 40 pm within a free spectral range of 0.75 nm is demonstrated.
Keywords: Fabrication imperfections; Fourier transform spectrometers; Machzehnder interferometers (MZI); Optical path difference; Silicon microphotonics; spectral retrieval; Transformation matrices; Fourier transform infrared spectroscopy; Linear transformations; Transparent optical networks

Quantitative vibrational dynamics of the metal site in a tin porphyrin: an IR, NRVS, and DFT study - Leu, Bogdan M.; Zgierski, Marek Z.; Bischoff, Christian; Li, Ming; Hu, Michael Y.; Zhao, Jiyong; Martin, Steve W.; Alp, Esen Ercan; Scheidt, W. Robert (Inorganic Chemistry, 2013)
We used a newer, synchrotron-based, spectroscopic technique (nuclear resonance vibrational spectroscopy, NRVS) in combination with a more traditional one (infrared absorption, IR) to obtain a complete, quantitative picture of the metal center vibrational dynamics in a six-coordinated tin porphyrin. From the NRVS 119Sn site-selectivity and the sensitivity of the IR signal to 112Sn/119Sn isotope substitution, we identified the frequency of the antisymmetric stretching of the axial bonds (290 cm -1) and all the other vibrations involving Sn. Experimentally authenticated density functional theory (DFT) calculations aid the data interpretation by providing detailed normal mode descriptions for each observed vibration. These results may represent a starting point toward the characterization of the local vibrational dynamics of the metallic site in tin porphyrins and compounds with related structures. The quantitative complementariness between IR, NRVS, and DFT is emphasized.

Elimination of mass-exchange errors in the NRC watt balance - Sanchez, Carlos A.; Wood, Barry M.; Inglis, Dave; Robinson, Ian A. (IEEE Transactions on Instrumentation and Measurement, 2013)
We report on the evaluation, correction, and subsequent elimination of the mass-exchange errors in the National Research Council (NRC) of Canada watt balance. Two effects arising from mass exchanges during the weighing phase initially produced significant systematic errors in the measurements of the Planck constant (h). These effects were estimated, and corresponding corrections were applied to measurements of h made at NRC between August and September of 2011. The effect due to the tilting of the beam required an estimated correction of (0.238 ± 0.018) μJ/s(J s) , and the effect due to the tilting of the flat, which supports the beam, required an estimated correction of (-0.636 ± 0.056) μJsJs). After the initial measurements were completed, we made several modifications to the balance which achieved a reduction of the two errors to negligible levels. A second set of measurements, made with the modified apparatus in May and June of 2012, shows very good agreement with the first measurements.
Keywords: Electromagnetic forces; Electronic kilogram; Measurements of; National Research Council Canada; Planck constants; Electrical engineering; Instruments; Errors

Low-frequency quantum-based AC power standard at NRC Canada - Djokić, Branislav V. (IEEE Transactions on Instrumentation and Measurement, 2013)
A low-frequency AC power standard based on the programmable Josephson voltage standard (PJVS) has been developed at the National Research Council of Canada. At the step voltages, PJVS provides quantum accuracy. Differential digital sampling is used to extend the quantum accuracy to the AC power standard output voltage and current, nominally 120 V and 5 A. The paper describes the power standard and its evaluation.
Keywords: Digital sampling; Inductive voltage divider; ITS evaluation; National Research Council of Canada; Output voltages; Programmable Josephson voltage standard; Calibration; Electric instrument transformers; Electric transformers; Voltage dividers; Josephson junction devices

High-current CT calibration using a sampling current ratio bridge - Rietveld, Gert; Jol, Leendert; van den Brom, Helko E.; So, Eddy (IEEE Transactions on Instrumentation and Measurement, 2013)
A measurement setup is developed for the accurate ratio measurement of ac current transformers (CTs) for primary currents up to 5 kA. A unique property of the system is the use of high-quality digitizers for sampling of the secondary current signals and step-down transformers with different current ratios. This allows for accurate comparison of CTs even when their nominal ratios are not equal. The calibration results of the key components in the setup show that the sampling current ratio bridge has a ratio uncertainty of better than 2 μ A/A in magnitude and 0.8 μrad in phase for CT-under-test current ratios that do not differ by more than a factor of 5 from one of the ratios in the reference CT. The linearity of the bridge for input currents changing between 1% and 120% of nominal input current is better than 4 μ A/A in magnitude and 0.5 μ rad in phase.
Keywords: Alternating current; Current ratios; Digital sampling; Phase displacement; Phase error; Ratio error; Electric current measurement; Electric instrument transformers

Effect of additives on the performance of cross-linked polyethylene subjected to long term single and periodically reversed polarity DC voltage - Abou-Dakka, M.; Bulinski, A.; Bamji, S. S. (IEEE Transactions on Dielectrics and Electrical Insulation, 2013)
The performance of cross-linked polyethylene with and without tree-retarding additives, aged with single and reversed polarity DC voltage was investigated. Under single polarity field of a 50 kV/mm, cross-linked polyethylene without the tree retardant (XLPE) showed significantly longer time to breakdown than the material with a tree retardant (TR-XLPE). This is attributed to the difference in how the two materials accumulate and retain space charge. In the case of polarity reversals, TR-XLPE showed better performance than XLPE. This seeming contradiction was studied by measuring the dynamics of space charge evolution with time. The Thermal Step Method (TSM) of space charge measurements was used. It showed that after the polarity reversal the TSM current rapidly inversed in the TR-XLPE but not in the XLPE. This implies more rapid charge dissipation in TR-XLPE. The retained charges cause the electric field enhancement in the material when the polarity is reversed. Thus, after each polarity reversal XLPE was subjected to higher local electric stress for a longer time and thus broke down sooner than TR-XLPE. For both materials the space charge decreased faster when the polarity was changed from negative to positive than vice versa. This could be explained by more efficient electron than holes injection. Since the control of the power flow in DC networks requires reversals of voltage polarity, their detrimental effect on XLPE-insulated equipment, such as cables, cannot be avoided. The effect could be mitigated by the application of carefully designed additives. However, as the present study indicates, additives that improve insulation performance under polarity reversals can be harmful under single polarity voltage.
Keywords: Crosslinked polyethylene; Electric field enhancement; Electric insulation performance; Polarity reversal; Space charge measurements; Thermal step method; XLPE; Electric space charge; Forestry

Three-dimensional spine model reconstruction using one-class SVM regularization - Lecron, Fabian; Boisvert, Jonathan; Mahmoudi, Saïd; Labelle, Hubert; Benjelloun, Mohammed (IEEE Transactions on Biomedical Engineering, 2013)
Statistical shape models have become essential for medical image registration or segmentation and are used in many biomedical applications. These models are often based on Gaussian distributions learned from a training set. We propose in this paper a shape model which does not rely on the estimation of a Gaussian distribution, but on similarities computed with a kernel function. Our model takes advantage of the one-class support vector machine (OCSVM) to do so. In this context, we propose in this paper a method for reconstructing the spine of scoliotic patients using OCSVM regularization. Current state-of-the-art methods use conventional statistical shape models, and the reconstruction is commonly processed by minimizing a Mahalanobis distance. Nevertheless, when a shape differs significantly from the statistical model, the associated Mahalanobis distance often overstates the need for statistical regularization. We show that OCSVM regularization is more robust and is less sensitive to weak landmarks definition and is hardly influenced by the presence of outliers in the training data. The proposed OCSVM model applied to 3-D spine reconstruction was evaluated on real patient data, and results showed that our approach allows precise reconstruction.
Keywords: 3D reconstruction; Biomedical applications; One-class support vector machines (OCSVM); scoliosis; State-of-the-art methods; Statistical shape model; Gaussian distribution; Hospital data processing; Medical applications; Support vector machines; accuracy; algorithm; anatomic model; image reconstruction; sensitivity analysis; statistical shape model; validity

Validation of strain gauges for structural health monitoring with bayesian belief networks - Liu, Zheng; Mrad, Nezih (IEEE Sensors Journal, 2013)
The application of structural health monitoring (SHM) often employs multiple sensors to monitor the state of health and usage of the structures. The fault of any sensor may lead to an inaccurate or even incorrect inference with the collected sensor data, which will accordingly create a negative impact on higher-level decisions for maintenance and services. Thus, sensor validation becomes a critical process to the performance of the whole SHM system. This paper presents the use of Bayesian belief network to validate the reading of strain gauges on an aluminum plate for loading monitoring. The Bayesian belief network is constructed with the training data. The factors investigated in this paper, which may affect the validation process, include sensor configuration, sensor redundancy, and sensor data range for the discretization. The feasibility of using a Bayesian belief network for SHM sensor validation is demonstrated with the experimental results.
Keywords: Aluminum plates; Discretizations; Multiple sensors; Sensor configurations; Sensor data; Sensor redundancy; Sensor validation; State of health; Training data; Validation process; Virtual sensor; Decision theory; Loading; Strain gages

Direct and sensitive phase readout for integrated waveguide sensors - Halir, R.; Vivien, L.; Le Roux, X.; Xu, D.-X.; Cheben, P. (IEEE Photonics Journal, 2013)
Integrated optical affinity sensors based on Mach-Zehnder interferometers (MZIs) enable sensitive and label-free detection of chemical and biological molecules. However, since MZIs transduce optical phase changes into sinusoidal intensity variations, they exhibit a variable sensitivity that vanishes at the extrema of the transmittance function. Moreover, the direction of phase change cannot be unambiguously determined with these sensors. Here, we present a coherent detection scheme based on integrated optics that enables unambiguous readout of the optical phase with a constant sensitivity. Our approach furthermore cancels the effect of imperfections in the sensor hardware using a blind calibration scheme. We experimentally show completely linear readout of the optical phase, with a fourfold enhancement of average sensitivity compared to conventional detection.
Keywords: Average sensitivities; Conventional detection; Integrated optical sensors; Integrated waveguides; Intensity variations; Optical phase changes; Phase detection; Transmittance function; Chemical detection; Sensitivity analysis

Optimal relay selection for physical-layer security in cooperative wireless networks - Zou, Yulong; Wang, Xianbin; Shen, Weiming (IEEE Journal on Selected Areas in Communications, 2013)
In this paper, we explore the physical-layer security in cooperative wireless networks with multiple relays where both amplify-and-forward (AF) and decode-and-forward (DF) protocols are considered. We propose the AF and DF based optimal relay selection (i.e., AFbORS and DFbORS) schemes to improve the wireless security against eavesdropping attack. For the purpose of comparison, we examine the traditional AFbORS and DFbORS schemes, denoted by T-AFbORS and T-DFbORS, respectively. We also investigate a so-called multiple relay combining (MRC) framework and present the traditional AF and DF based MRC schemes, called T-AFbMRC and T-DFbMRC, where multiple relays participate in forwarding the source signal to destination which then combines its received signals from the multiple relays. We derive closed-form intercept probability expressions of the proposed AFbORS and DFbORS (i.e., P-AFbORS and P-DFbORS) as well as the T-AFbORS, T-DFbORS, T-AFbMRC and T-DFbMRC schemes in the presence of eavesdropping attack. We further conduct an asymptotic intercept probability analysis to evaluate the diversity order performance of relay selection schemes and show that no matter which relaying protocol is considered (i.e., AF and DF), the traditional and proposed optimal relay selection approaches both achieve the diversity order M where M represents the number of relays. In addition, numerical results show that for both AF and DF protocols, the intercept probability performance of proposed optimal relay selection is strictly better than that of the traditional relay selection and multiple relay combining methods. © 2013 IEEE.
Keywords: Cooperative wireless networks; Decode-and-forward protocols; Diversity order; Eavesdropping attacks; Physical-layer securities; Probability expressions; Probability performance; Relay selection; Numerical methods; Security systems; Optimization

Modeling of single-section quantum dot mode-locked lasers: impact of group velocity dispersion and self phase modulation - Jiao, Zhejing; Zhang, Rong; Zhang, Xiupu; Liu, Jiaren; Lu, Zhenguo (IEEE Journal of Quantum Electronics, 2013)
A short pulse train with pulsewidth < 1 ps was generated in a quantum dot mode-locked laser (QD MLL). Due to the short dispersion length, it is required to include group-velocity dispersion (GVD) in modeling pulse train generation and evolution from QD MLLs. On the other hand, Kerr effect is also required to consider due to high peak power density in the laser cavity, and its induced self-phase modulation (SPM) also contributes to the pulse evolution. In this paper, a time domain traveling wave model, including the effect of GVD and SPM, combined with rate equations, is established to model the pulse evolution in a single-section QD MLL. It is shown that the pulse evolution calculated by this model is in reasonable agreement with the experiments. The contribution to the pulse evolution by the GVD and SPM impact is discussed.
Keywords: Dispersion length; High peak power; Kerr-lens effect; Mode-locked laser; Pulse evolution; Pulse-train generation; Traveling wave; Traveling wave model; Group velocity dispersion; Laser accessories; Quantum dot lasers; Self phase modulation; Locks (fasteners)

Hepatitis C virus induced up-regulation of microRNA-27: a novel mechanism for hepatic steatosis - Singaravelu, Ragunath; Chen, Ran; Lyn, Rodney K.; Jones, Daniel M.; O'Hara, Shifawn; Rouleau, Yanouchka; Cheng, Jenny; Srinivasan, Prashanth; Nasheri, Neda; Russell, Rodney S.; Tyrrell, D. Lorne; Pezacki, John Paul (Hepatology, 2013)
MicroRNAs (miRNAs) are small RNAs that posttranscriptionally regulate gene expression. Their aberrant expression is commonly linked with diseased states, including hepatitis C virus (HCV) infection. Herein, we demonstrate that HCV replication induces the expression of miR-27 in cell culture and in vivo HCV infectious models. Overexpression of the HCV proteins core and NS4B independently activates miR-27 expression. Furthermore, we establish that miR-27 overexpression in hepatocytes results in larger and more abundant lipid droplets, as observed by coherent anti-Stokes Raman scattering (CARS) microscopy. This hepatic lipid droplet accumulation coincides with miR-27b's repression of peroxisome proliferator-activated receptor (PPAR)-α and angiopoietin-like protein 3 (ANGPTL3), known regulators of triglyceride homeostasis. We further demonstrate that treatment with a PPAR-α agonist, bezafibrate, is able to reverse the miR-27b-induced lipid accumulation in Huh7 cells. This miR-27b-mediated repression of PPAR-α signaling represents a novel mechanism of HCV-induced hepatic steatosis. This link was further demonstrated in vivo through the correlation between miR-27b expression levels and hepatic lipid accumulation in HCV-infected SCID-beige/Alb-uPa mice. Conclusion: Collectively, our results highlight HCV's up-regulation of miR-27 expression as a novel mechanism contributing to the development of hepatic steatosis.

The antigen-binding site of an N-propionylated polysialic acid-specific antibody protective against group B meningococci is consistent with extended epitopes - Johal, Asha R.; Jarrell, Harold C.; Letts, James A.; Khieu, Nam Huan; Landry, Roxanne C.; Jachymek, Wojciech; Yang, Qingling; Jennings, Harold J.; Brisson, Jean-Robert; Evans, Stephen V. (Glycobiology, 2013)
Monoclonal antibodies 13D9 and 6B9 are both specific for N-propionylated polysialic acid (NPrPSA); however, while 13D9 is protective against meningitis caused by group B meningococci and Escherichia coli capsular type K1 infection, 6B9 is not. The crystal structures of the Fabs from the two antibodies determined at 2.06 and 2.45 Å resolutions, respectively, reveal markedly different combining sites, where only the surface of 13D9 is consistent with the recognition of extended helical epitopes known to exist in the capsular polysaccharides of etiological agents of meningitis. Interestingly, complementarity determining region H2 on 13D9 lies in a non-canonical conformation that docking studies show is a critical feature in the generation of negative free energy of binding. Finally, the model of extended NPrPSA decasaccharide bound to 13D9 derived from docking studies is consistent with saturation transfer difference nuclear magnetic resonance experiments. Together, these results provide further evidence that extended epitopes have the ability to break immune tolerance associated with the polysialic acid capsule of these pathogens.
Keywords: epitope; polysaccharide; polysialic acid; conformational transition; crystal structure; Escherichia coli; immunological tolerance; molecular docking; molecular recognition; Neisseria meningitidis

Leveraging metabolomics to assess the next generation of temozolomide-based therapeutic approaches for glioblastomas - St-Coeur, Patrick-Denis; Touaibia, Mohamed; Cuperlovic-Culf, Miroslava; Morin, Pier Jr (Genomics, Proteomics and Bioinformatics, 2013)
Glioblastoma multiforme (GBM) is the most common adult primary tumor of the central nervous system. The current standard of care for glioblastoma patients involves a combination of surgery, radiotherapy and chemotherapy with the alkylating agent temozolomide. Several mechanisms underlying the inherent and acquired temozolomide resistance have been identified and contribute to treatment failure. Early identification of temozolomide-resistant GBM patients and improvement of the therapeutic strategies available to treat this malignancy are of uttermost importance. This review initially looks at the molecular pathways underlying GBM formation and development with a particular emphasis placed on recent therapeutic advances made in the field. Our focus will next be directed toward the molecular mechanisms modulating temozolomide resistance in GBM patients and the strategies envisioned to circumvent this resistance. Finally, we highlight the diagnostic and prognostic value of metabolomics in cancers and assess its potential usefulness in improving the current standard of care for GBM patients.
Keywords: Glioblastoma multiforme; Temozolomide; Signaling cascades; Cancer therapeutics; Cancer diagnosis

Model-based ex situ diagnostics of water fluxes in catalyst layers of polymer electrolyte fuel cells - Liu, J.; Gazzarri, J.; Eikerling, M. (Fuel Cells, 2013)
The ability to predict the electrochemical performance of the cathode catalyst layer in a polymer electrolyte fuel cell hinges on a precise knowledge of water distribution and fluxes. Water transport mechanisms that must be accounted for include vapor diffusion, liquid water permeation and vaporization exchange. In order to facilitate experimental efforts to this effect, we propose an ex situ model of water fluxes in catalyst layers. The model formulation is similar to transmission line models that are widely used in the analysis of electrochemical impedance spectra of porous composite electrodes. Focusing in this article on steady state and isothermal conditions, we rationalize the response function between defined environmental conditions, i.e. gas pressures, partial vapor pressures and temperature, which are defined at the boundaries of the catalyst layer, and the net water flux. This response function provides diagnostic capabilities to isolate and extract water transport parameters of catalyst layers from measurements of water fluxes through membrane electrode assemblies or half cell systems. An important asset of the model is the ability to analyze catalyst layer transport properties under partial saturation.
Keywords: Catalyst Layer Modeling; Extraction of Effective Transport Properties; Partial Liquid Saturation; Polymer Electrolyte Fuel Cell; Water Flux Response Function

Distribution of colonization and antimicrobial resistance genes in campylobacter jejuni isolated from chicken - Thibodeau, Alexandre; Fravalo, Philippe; Garneau, Philippe; Masson, Luke; Laurent-Lewandowski, Sylvette; Quessy, Sylvain; Harel, Josée; Letellier, Ann (Foodborne Pathogens and Disease, 2013)
Campylobacter jejuni is an important worldwide foodborne pathogen commonly found as a commensal organism in poultry that can reach high numbers within the gut after colonization. Although information regarding some genes involved in colonization is available, little is known about their distribution in strains isolated specifically from chickens and whether there is a linkage between antimicrobial resistance (AMR) and colonization genes. To assess the distribution and relevance of genes associated with chicken colonization and AMR, a C. jejuni microarray was created to detect 254 genes of interest in colonization and AMR including variants. DNA derived from chicken-specific Campylobacter isolates collected in 2003 (n=29) and 2008 (n=28) was hybridized to the microarray and compared. Hybridization results showed variable colonization-associated gene presence. Acquired AMR genes were low in prevalence whereas chemotaxis receptors, arsenic resistance genes, as well as genes from the cell envelope and flagella functional groups were highly variable in their presence. Strains clustered into two groups, each linked to different control strains, 81116 and NCTC11168. Clustering was found to be independent of collection time. We also show that AMR weakly associated with the CJ0628 and arsR genes. Although other studies have implicated numerous genes associated with C. jejuni chicken colonization, our data on chicken-specific isolates suggest the opposite. The enormous variability in presumed colonization gene prevalence in our chicken isolates suggests that many are of lesser importance than previously thought. Alternatively, this also suggests that combinations of genes may be required for natural colonization of chicken intestines.

Evolution of methane during gas hydrate dissociation - Bagherzadeh, S. Alireza; Alavi, Saman; Ripmeester, John A.; Englezos, Peter (Fluid Phase Equilibria, 2013)
We simulated decomposition of structure I methane hydrate (H) with all cages filled in contact with two reservoirs (pools) of liquid water (W) which in turn are in contact with either two methane gas reservoirs (G), or with vacuum (V), under constant volume-constant energy conditions. By adding gas or empty spaces to the simulation box we allow the released methane to diffuse out of the liquid phase and into the gas phase similar to what happens during methane hydrate dissociation. The evolution of the released methane molecules during the hydrate dissociation process was carefully monitored. We found that some of the released methane gas reaches the gas phase and contributes to the increase of gas pressure on the hydrate phase. As the hydrate dissociates, liquid water phase becomes supersaturated with methane, methane molecules aggregate, and spherical regions of high concentration of methane form which we identify as "nano-bubbles". These nano-bubbles grew to a specific size range which depends on simulation conditions and remained stable in the liquid phase for the duration of the simulations (5. ns).
Keywords: Methane hydrate; Dissociation process; Nano-bubble formation; Molecular dynamics

Studying the RNA silencing pathway with the p19 protein - Danielson, Dana C.; Pezacki, John Paul (FEBS Letters, 2013)
The origins of the RNA silencing pathway are in defense against invading viruses and in response, viruses have evolved counter-measures to interfere with the host pathway. The p19 protein is expressed by tombusviruses as a suppressor of RNA silencing and functions to sequester small RNA duplexes, thereby preventing induction of the pathway. p19 exhibits size-specific and sequence-independent binding of its small RNA ligands, binding with high affinity to duplexes 20-22 nucleotides long. p19's binding specificity and its ability to sequester small RNAs has made it a unique protein-based tool for probing the molecular mechanisms of the highly complex RNA silencing pathway in a variety of systems. Furthermore, protein engineering of this 'molecular caliper' promises novel applications in biotechnology and medicine where small RNA molecules are of remarkable interest given their potent gene regulatory abilities.
Keywords: p19 protein; Viral suppressors of RNA silencing; Small RNA detection; miRNA-122; Protein engineering; Heterologous expression

Expression of a type 2 diacylglycerol acyltransferase from Thalassiosira pseudonana in yeast leads to incorporation of docosahexaenoic acid B-oxidation intermediates into triacylglycerol - Xu, Jingyu; Kazachkov, Michael; Jia, Yunhua; Zheng, Zhifu; Zou, Jitao (FEBS Journal, 2013)
Glycerolipids of the marine diatom Thalassiosira pseudonana are enriched particularly with eicosapentaenoic acid (EPA), and also with an appreciable level of docosahexaenoic acid (DHA). The present study describes the functional characterization of a type 2 diacylglycerol acyltransferase (DGAT2, EC 2.3.1.20) from T. pseudonana, designated TpDGAT2, which catalyzes the final step of triacylglycerol (TAG) synthesis. Heterologous expression of this gene restored TAG formation in a yeast mutant devoid of TAG biosynthesis. TpDGAT2 was also shown to exert a large impact on the fatty acid profile of TAG. Its expression caused a 10-12% increase of 18:1 and a concomitant decrease of 16:0 relative to that of AtDGAT1(Arabidopsis thaliana). Furthermore, in the presence of the very-long-chain polyunsaturated fatty acids (VLCPUFA) EPA and DHA, TAG formed by TpDGAT2 displayed three- to six-fold increases in the percentage of VLCPUFA relative to that of AtDGAT1 even though TpDGAT2 conferred much lower TAG-synthetic activities than Arabidopsis DGAT1. Strikingly, when fed DHA, the yeast mutant expressing TpDGAT2 incorporated high levels of EPA and DHA isomers derived from DHA β-oxidation. In contrast, no such phenomenon occurred in the cells expressing AtDGAT1. These results suggested that, in addition to the role in breaking down storage lipids, yeast peroxisomes also contribute to lipid synthesis by recycling acyl-CoAs when a fatty acyl assembly system is available to capture and utilize the fatty acyl pools generated via β-oxidation. Our study hence illustrated a case where the efficiency and substrate preference of an acyltransferase can elicit far reaching metabolic adjustments that affect TAG composition.
Keywords: docosahexaenoic acid; eicosapentaenoic acid; triacylglycerol; type 2 diacylglycerol acyltransferase; β-oxidation

The three pillars of photo-initiated quantum molecular dynamics - Stolow, Albert (Faraday Discussions, 2013)
Studies of the interaction of light with matter, based on spectroscopy and diffraction, yielded a microscopic view of nature. The detailed structure of molecules and solids emerged from this effort and led to many of the advances of the 20th century, with the 'structure-function' paradigm being perhaps paramount. This static view of Nature is a necessary but insufficient advance and, in the 21st century, we will need to develop microscopic yet dynamical views of Nature. We consider here issues in Photo-initiated Quantum Molecular Dynamics raised by Faraday Discussions 163, in the context of three main categories or 'pillars' of light-matter interaction: energy/time, phase/coherence, intensity.

Influence of lipoplex surface charge on siRNA delivery: application to the in vitro downregulation of CXCR4 HIV-1 co-receptor - Lavigne, Carole; Slater, Kathryn; Gajanayaka, Niranjala; Duguay, Christian; Arnau Peyrotte, Erika; Fortier, Germaine; Simard, Martin; Kell, Arnold J.; Barnes, Michael L.; Thierry, Alain R. (Expert Opinion on Biological Therapy, 2013)
Objective: Cationic lipidic formulations have been successfully used to deliver small interfering RNA (siRNA) into cells but they show limitations for in vivo application due to their cytotoxicity and instability in the presence of serum. To overcome these limitations, the authors developed an anionic lipid-based carrier named Neutraplex (Nx). Here, they wanted to investigate the influence of the lipoplex (Lx) surface charge on cytotoxicity, delivery and silencing activity of siRNAs. Methods: The efficiency of three Nx formulations (cationic, close to neutrality and anionic) to deliver anti-CXCR4 siRNAs in MAGI cells was investigated and compared with the cationic commercial transfection reagent Lipofectamine RNAiMAX. Cellular uptake and intracellular localization of a fluorescent siRNA was monitored in live cells using fluorescence microscopy and silencing activity was measured by flow cytometry and RT-PCR analysis. Results: The authors found that the Lx surface charge influenced cellular uptake and silencing activity of siRNA in cell cultures. Although cationic Lx formulations were the most efficient carriers to deliver active silencing siRNAs, negatively charged lipoplexes were taken up by cells, delivered active siRNAs and presented low cytotoxicity. Conclusions: Altogether, the findings support further investigation for in vivo delivery of therapeutic siRNAs using Nx. Furthermore, this study indicates that anionic delivery systems may have potential for in vivo RNAi therapeutics.
Keywords: anti-HIV therapy, CXCR4, lipoplex charge, nanodelivery system, Neutraplex, siRNA delivery

The dynamophore : localization of excited state dynamics studied by time-resolved photoelectron spectroscopy - Schalk, O.; Boguslavskiy, A. E.; Schuurman, M. S.; Stolow, A. (XVIIIth International Conference on Ultrafast Phenomena, 2013)
Photoinduced dynamics tend to localize at a confined region of a molecule, called dynamophore. Here, we show examples from time-resolved photoelectron spectroscopy

Initial processes of proton transfer in salicylideneaniline studied by time-resolved photoelectron spectroscopy - Sekikawa, Taro; Schalk, Oliver; Wu, Guorong; Boguslavskiy, Andrey E.; Stolow, Albert (EPJ Web of Conferences; 41, 2013)
Excited state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in para-position of the anilino group has been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). The planarity of the molecule was found to be a key parameter to describe ESIPT. © Owned by the authors, published by EDP Sciences, 2013.

Internal conversion vs. intersystem crossing: what drives the dynamics of cyclic α,β-Enones? - Schalk, O.; Lang, P.; Schuurman, M.S.; Wu, G.; Bradler, M.; Riedle, E.; Stolow, A. (XVIIIth International Conference on Ultrafast Phenomena, 2013)
The origin of ultrafast intersystem crossing and its competitiveness with singlet pathways was studied in cyclic α,β-enones by transient absorption, time-resolved photoelectron spectroscopy and ab initio calculations. © Owned by the authors, published by EDP Sciences, 2013.

When does an electron exit a tunneling barrier? - Shafir, D.; Soifer, H.; Bruner, B. D.; Dagan, M.; Mairesse, Y.; Patchkovskii, S.; Ivanov, M. Y.; Smirnova, O.; Dudovich, N. (EPJ Web of Conferences, 2013)
We probe the dynamics of tunnel ionization via high harmonic generation. We characterize the ionization dynamics in helium atoms, and apply our approach to resolve subtle differences in ionization from different orbitals of a CO 2 molecule. © Owned by the authors, published by EDP Sciences, 2013.

Fractographic examination of coupons representing aircraft structural joints with and without hole cold expansion - Yanishevsky, Marko; Li, Gang; Shi, Guoqin; Backman, David (Engineering Failure Analysis, 2013)
In an effort to establish the potential benefits of hole cold expansion and interference fit fasteners for long term fatigue performance, coupons representing three types of aircraft structural joints were designed, manufactured and assembled. These joints, manufactured using 7075-T6 aluminium alloys for main members and 7075-T73 for doublers or spacers, were representative of: No Load Transfer joints, simulating " non-structural" joints, such as brackets, supports for conduits, fuel lines, and wire bundles. Medium Load Transfer joints, simulating symmetrical doubler, stiffener and rib joints; and High Load Transfer joints, simulating symmetrical splices in major load carrying members. The joints were assembled using Hi-Lok™ interference fit fasteners, with and without hole cold expansion, and were fatigue tested to complete failure using a representative mission mix service load spectrum for a coastal patrol aircraft wing fatigue sensitive location. The failure surfaces were examined with the aid of an optical microscope at various magnifications. The fractographic descriptions for the three types of joints examined document the crack nucleation sites, mechanisms of crack formation, and extent of damage at catastrophic failure, including the effects of manufacturing, such as direction of hole cold expansion and direction of interference fit fastener insertion. Examination of fracture surfaces for fractographic evidence provides researchers and engineers with valuable insights into the failure process, which will enable them to perform more accurate and representative life predictions of joint performance. © 2013 Elsevier Ltd.
Keywords: Aircraft structural joints; Failure analysis; Hole cold expansion; Interference fit fasteners; Spectrum fatigue testing

Cracks formation and residual stress in chromium carbide overlays - Ma, Liang; Huang, Cheng; Jiang, Jiaren; Hui, Rob; Xie, Yongsong; Liu, Zhong-Sheng (Engineering Failure Analysis, 2013)
A chromium carbide overlay is often welded on the surfaces that are subject to severe wear attack, of mining equipment in order to prolong its service time. The welding causes unequal and unsynchronized thermal expansion/shrinkage between the overlay and its substrate, leading to a significant level of thermal strain/stress in the overlay. When the stress level at any location becomes higher than material strength, at that location a crack will start to form and propagate, resulting in partial release of stress. The residual stress varying by location can lead to delamination and spalling of chunks of the overlay. This paper tries to give better understanding of cracks-formation and residual stress, covering the driving force for cracks formation and residual stress, the locations where cracks initiate, the directions towards to which the cracks propagate, the resulting patterns of the cracks and the residual stress at the interfaces between the overlay and its substrate. The approach to realize this is through mechanics modeling and simulation plus experimental observations. The practical significance of this work lies in its values to improvement of welding processes and the basis for evaluating overlay quality.
Keywords: Chromium carbide overlays; Solidification cracks; Welding process; Finite element method; Thermal expansion and shrinkage

Photoluminescence efficiency of germanium dots self-assembled on oxides - Lockwood, David J.; Rowell, Nelson L.; Barbagiovanni, Eric G.; Goncharova, Lyudmila V.; Simpson, Peter J.; Berbezier, Isabelle; Amiard, Guillaume; Favre, Luc; Ronda, Antoine; Faustini, Marco; Grosso, David (Graphene, Ge/III-V, and Emerging Materials for Post CMOS Applications 5, 2013)
Self-assembled Ge quantum dots were formed by in-situ thermal annealing of a thin amorphous Ge layer deposited by molecular beam epitaxy either on a thin porous TiO2 layer grown on SiO2 on Si(001) or directly on the SiO2 layer itself. For samples with dot diameters ranging from 10 to 35 nm, the dot photoluminescence (PL) appeared primarily as a wide near-infrared band peaked near 800 meV. The peak energy of the PL band reflects the average dot size and its shape depends on the dot size distribution. Using tight binding and effective mass theoretical models, we have analyzed the PL spectrum in terms of the dot size distribution. The observed size distribution determined from transmission electron and atomic force microscopy allowed the determination of the nonlinear increase in the PL efficiency with decreasing dot diameter. Although the absolute intensities of the PL from the samples vary, the calculated efficiency curves are all well fitted by straight lines on a log-log plot, with essentially the same slope for all samples, thereby demonstrating that under the weak confinement regime investigated here there is a universal power-law increase in PL efficiency with decreasing dot size. Knowing this generic PL efficiency, we show that it is possible to evaluate the size distribution of Ge dots from their PL energy dependence.
Keywords: Absolute intensity; Efficiency curves; Energy dependence; Near-infrared bands; Photoluminescence efficiency; Self-assembled Ge quantum dots; Thermal-annealing; Transmission electron; Atomic force microscopy; Germanium; Graphene; Molecular beam epitaxy; Photoluminescence; Size distribution

(Invited) Fast and slow light-emitting silicon-germanium nanostructures - Lockwood, David J.; Wu, Xiaohua; Baribeau, Jean-Marc; Mala, Selina A.; Modi, Nikhil; Tsybeskov, Leonid (Nanocrystal Embedded Dielectrics for Electronic and Photonic Devices, 2013)
Epitaxially-grown three-dimensional Si/SiGe nanostructures (NSs) produce photoluminescence (PL) and electroluminescence in the desired spectral range of 1.3-1.6 μm. We show that by controlling and modifying such Ge-rich SiGe nanoclusters during growth it is possible to fabricate very fast (PL lifetime <20 ns) and hence more efficient SiGe light-emitting devices. The results presented here demonstrate that in such Si/SiGe 3D NSs with a nominal Ge concentration approaching ∼35% the PL peaked near 0.78 eV strongly depends on the Si/SiGe heterointerface abruptness. In other Si/SiGe NS/quantum-well samples with a Ge concentration approaching ∼40%, we find two PL bands peaked at ∼0.8 eV and ∼0.9 eV at low temperatures. The PL peaked at 0.8 eV rises and decays slowly, and it quickly saturates as the excitation intensity increases. In contrast, the PL peaked at 0.9 eV shows a much shorter lifetime and exhibits a linear dependence versus excitation intensity. The slow/delayed PL at 0.8 eV is attributed to carrier recombination at the SiGe NS/Si transition layer while the faster and more efficient PL at 0.9 eV is associated with SiGe quantum wells. More complicated and similarly fast (∼10-7 s) decays are observed at very high excitation intensities due to electron-hole droplet formation. The physics of carrier recombination in these Si/SiGe NSs is discussed.
Keywords: Carrier recombination; Electron-hole droplets; Excitation intensity; Ge concentrations; Hetero interfaces; Light emitting devices; Linear dependence; SiGe quantum wells; Nanocrystals; Photonic devices; Semiconductor quantum wells; Silicon alloys; Three dimensional; Germanium

Spinel NixCo2-xO4 as a bifunctional air electrode for zinc-air batteries - Yuan, Xiao Zi; Qu, Wei; Zhang, Xinge; Yao, Peter; Fahlman, Jason (Batteries and Energy Technology (General) – 221st ECS Meeting, 2013)
Spinel NixCo2-xO4 powder was prepared through a sol-gel method and characterized by X-ray diffraction (XRD). The electrocatalytic properties of NixCo2-xO4/C composites towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were studied using rotating ring-disk electrode (RDE) technique and Koutecky-Levich theory in 1 M, 3M, and 6 M KOH electrolytes. The results show that the synthesized spinel NixCo2- xO4 exhibits activities for both ORR and OER. The OER Tafel slope is around 60mVdec -1 at a low overpotential, and the ORR process is dominated by a 4-electron transfer pathway. Cell test demonstrates that the ORR activity of non-carbon NixCo2-xO4 air electrode reached 56mA cm -2 at a potential of 0.9V and the OER activity reached 62mA cm -2 at a potential of 2.2V for the first cycle However, the ORR cycling property is not satisfying due to flooding issues. This can probably be solved by an advanced air electrode design. Copyright 2013 by The Electrochemical Society.
Keywords: Air electrodes; Cycling properties; Electrocatalytic properties; Oxygen evolution reaction; Oxygen reduction reaction; Rotating ring-disk electrode; Transfer pathway; Zinc-air battery; Design; Electrolytic reduction; Sol-gel process; X ray diffraction; Electrodes

Galvanic corrosion associated with Al-B4C composites/SS304 and Al-B4C composites/AA6061 couples in NaCl and H3BO 3 solutions - Han, Yu-Mei; Gallant, Danick; Chen, X.-Grant (Electrochimica Acta, 2013)
Al-B4C composites are neutron absorber materials utilized in the nuclear industry that are often assembled to structural materials AA6061 or SS304, which increases the likelihood of galvanic corrosion, especially under wet storage conditions. This study investigates the galvanic corrosion behavior that may occur between Al-B4C composites and AA6061 or SS304 in NaCl and H3BO3 solutions using a zero resistance ammeter (ZRA). The effects of dissimilar materials (e.g., B4C content), immersion solution, and ratio of the coupled material areas are reported. In the NaCl solution, depending on the nature of the coupling agent (SS304 or AA6061), the composite or base alloy always acts as an anode and the measured galvanic currents are directly proportional to the cathode area. In contrast, in the H3BO3 solution, the composites preferentially dissolve in the presence of SS304, while AA6061 protects the metal matrix composites from dissolution. Although galvanic corrosion is controlled by oxygen diffusion at the cathode in both NaCl and H3BO3 solutions, its intensity is appreciably lower in the H3BO3 solution than in the NaCl solution. The B4C content is also found to play a key role in galvanic corrosion; its influence is modulated by the solution composition and the materials to which the composite is galvanically coupled.
Keywords: Neutron absorber material; Solution composition; Zero resistance ammeter; Boric acid; Cathodes; Coupling agents; Dissimilar materials; Metallic matrix composites; Nuclear industry; Aluminum

Graphene-TiO2 composite supported Pt electrocatalyst for oxygen reduction reaction - Tiido, Kristiina; Alexeyeva, Nadezda; Couillard, Martin; Bock, Christina; MacDougall, Barry R.; Tammeveski, Kaido (Electrochimica Acta, 2013)
A nano-sized Pt catalyst supported onto titanium dioxide functionalized graphene nanosheets (TiO2-FGSs) was prepared using the polyol method and utilized for a catalyst activity investigation toward the oxygen reduction reaction (ORR). The electrochemical and microscopic studies were carried out using a 40 wt.% Pt/TiO2-FGS catalyst. Cyclic voltammetry and the rotating disk electrode experiments were performed in 0.5 M H2 SO4 and 0.1 M KOH solutions in order to investigate the electrocatalytic behavior of the prepared catalysts. The composite catalyst samples were characterized by scanning electron microscopy and transmission electron microscopy showing a good dispersion of the Pt particles on the surface of the graphene supported TiO2 particles. The average Pt particle size was 11 ± 2 nm. The values of specific activity and other kinetic parameters were determined from the Tafel plots taking into account the real electroactive area of each electrode. The electrodes exhibited a relatively high electrocatalytic activity for the four-electron reduction of oxygen to water.
Keywords: Electrocatalytic activity; Electrocatalytic behavior; Functionalized graphene; Oxygen Reduction; Oxygen reduction reaction; Pt nanoparticles; Pt-based catalyst; Rotating disk electrodes; Catalyst activity; Cyclic voltammetry; Electrolytic reduction; Graphene; Oxides; Rotating disks; Scanning electron microscopy; Titanium dioxide; Transmission electron microscopy; Platinum

Synthesis of highly active SnO2-CNTs supported Pt-on-Au composite catalysts through site-selective electrodeposition for HCOOH electrooxidation - Wang, Jianshe; Xi, Jingyu; Zhang, Lei; Zhang, Jiujun; Guo, Xun; Zhao, Jianhong; Song, Chengying; Wang, Liucheng (Electrochimica Acta, 2013)
In this paper, site-selective electrodeposition method is developed to prepare Pt-on-Au composite catalysts for HCOOH electrooxidation. In the synthesis, Au nanoparticles are prepared through reduction of NaAuCl4 by Sn(OH)2 supported on carbon nanotubes and after thermal transformation of Sn(OH)2 to SnO2, composite supports (Au/SnO2-CNTs) were obtained. By adjusting the potential of Au/SnO2-CNTs coated glassy carbon electrode, Pt entities are selectively deposited on Au particles to form SnO2-CNTs supported Pt-on-Au composite catalysts. The morphology and composition of the formed composite catalysts are characterized by instrument techniques such as X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The site-selectivity of Pt electrodeposition on Au is confirmed by electrochemical measurements. The composite catalysts are tested to have high Pt mass activity toward HCOOH oxidation reaction, demonstrating that the synthesis method developed in this paper has promising potential for developing high performance composite catalysts. The Pt content effect on the catalytic activity is also tested for catalyst performance optimization.
Keywords: Electrochemical measurements; Glassy carbon electrodes; High performance composites; Morphology and composition; Site selective; Thermal transformations; Excitons; Formic acid; Glass membrane electrodes; Gold deposits; High resolution transmission electron microscopy; Synthesis (chemical); Tin; X ray diffraction; Platinum

Assessment of three techniques for delivering stem cells to the heart using PET and MR imaging - Elhami, Esmat; Dietz, Bryson; Xiang, Bo; Deng, Jixian; Wang, Fei; Chi, Chao; Goertzen, Andrew L.; Mzengeza, Shadreck; Freed, Darren; Arora, Rakesh C.; Tian, Ganghong (EJNMMI Research, 2013)
Background: Stem cell therapy has a promising potential for the curing of various degenerative diseases, including congestive heart failure (CHF). In this study, we determined the efficacy of different delivery methods for stem cell administration to the heart for the treatment of CHF. Both positron emission tomography (PET) and magnetic resonance imaging (MRI) were utilized to assess the distribution of delivered stem cells. Methods: Adipose-derived stem cells of male rats were labeled with super-paramagnetic iron oxide (SPIO) and 18 F-fluorodeoxyglucose (FDG). The left anterior descending coronary artery (LAD) of the female rats was occluded to induce acute ischemic myocardial injury. Immediately after the LAD occlusion, the double-labeled stem cells were injected into the ischemic myocardium (n = 5), left ventricle (n = 5), or tail vein (n = 4). In another group of animals (n = 3), the stem cells were injected directly into the infarct rim 1 week after the LAD occlusion. Whole-body PET images and MR images were acquired to determine biodistribution of the stem cells. After the imaging, the animals were euthanized and retention of the stem cells in the vital organs was determined by measuring the cDNA specific to the Y chromosome. Results: PET images showed that retention of the stem cells in the ischemic myocardium was dependent on the cell delivery method. The tail vein injection resulted in the least cell retention in the heart (1.2% ± 0.6% of total injected cells). Left ventricle injection led to 3.5% ± 0.9% cell retention and direct myocardial injection resulted in the highest rate of cell retention (14% ± 4%) in the heart. In the animals treated 1 week after the LAD occlusion, rate of cell retention in the heart was only 4.5% ±1.1%, suggesting that tissue injury has a negative impact on cell homing. In addition, there was a good agreement between the results obtained through PET-MR imaging and histochemical measurements. Conclusion: PET-MR imaging is a reliable technique for noninvasive tracking of implanted stem cells in vivo. Direct injection of stem cells into the myocardium is the most effective way for cell transplantation to the heart in heart failure models.

Temperature effects on kinetics of paralytic shellfish toxin elimination in Atlantic surfclams, Spisula solidissima - Bricelj, V. Monica; Cembella, Allan D.; Laby, David (Deep-Sea Research Part II: Topical Studies in Oceanography, 2013)
Surfclams, Spisula solidissima, pose a particular health risk for human consumption as they are characterized by accumulation of extremely high levels of toxins associated with paralytic shellfish poisoning (PSP), slow toxin elimination and an extremely high post-ingestive capacity for toxin bioconversion. Surfclam populations experience a wide range of temperatures along the NW Atlantic continental shelf, and are undergoing range contraction that has been attributed to global warming. In this study the influence of temperature (5, 12 and 21 °C) on detoxification kinetics of individual PSP toxins in two tissue compartments of juvenile surfclams (∼35 mm shell length) was determined under controlled laboratory conditions, over prolonged (2.4 months) depuration. Clams were toxified with a representative regional Gulf of Maine isolate of the dinoflagellate Alexandrium fundyense of known toxin profile, allowing tracking of changes in toxin composition and calculated toxicity in surfclam tissues. The visceral mass detoxified at all temperatures, although toxin loss rate increased with increasing temperature. In contrast, total toxin content and calculated toxicities in other tissues remained constant or even increased during depuration, suggesting a physiological or biochemical toxin-retention mechanism in this tissue pool and temperature-independent detoxification. In vivo toxin compositional changes in surfclam tissues found in this study provide evidence of specific toxin conversion pathways, involving both reductive and decarbamoylation pathways. We conclude that such toxin biotransformations, especially in non-visceral tissues, may introduce a discrepancy in describing kinetics of total toxicity (in saxitoxin equivalents [STXeq]) of S. solidissima over prolonged detoxification. Nevertheless, use of total toxicity values generated by routine regulatory monitoring based upon mouse bioassays or calculated from chemical analytical determination of molar toxin concentrations is adequate for first-order modeling of toxin kinetics in this species. Furthermore, the differential detoxification response of viscera and other tissues in relation to temperature emphasizes the need for two-compartment modeling to describe the fate of PSP toxins in this species. Finally, key parameters were identified that may prove useful in hindcasting the timing of toxic blooms or new toxin input in deep offshore waters where routine monitoring of toxic phytoplankton is impractical.

Macromolecular structure comparison and docking: an algorithmic review - Paquet, Eric; Viktor, Herna L. (Current Pharmaceutical Design, 2013)
The comparison of macromolecular structures, in terms of functionalities, is a crucial step when aiming to identify potential docking sites. Drug designers require the identification of such docking sites for the binding of two proteins, in order to form a stable complex. This paper presents a review of current approaches to macromolecular structure comparison and docking, following an algorithmic approach. We describe techniques based on the Bayesian framework, kernel-based methods, projection-based techniques and spectral approaches. We introduce the use of quantum particle swarm optimization, in order to aid us to find the most appropriate docking sites. We discuss the importance of the heat and Schrödinger equations to address the non-rigid nature of proteins and highlight the strengths and limitations of the various methods.
Keywords: Macromolecular structures, docking, protein-protein interaction, alignment, algorithms, drug designers, comparison, Bayesian framework, kernel-based methods, projection-based techniques

Structural assessment of anhydrous sulfates with high field 33S solid state NMR and first principles calculations - Pallister, Peter J.; Moudrakovski, Igor L.; Enright, Gary D.; Ripmeester, John A. (CrystEngComm, 2013)
A combination of solid state NMR, first principles calculations and single crystal XRD was applied to relate solid state 33S NMR parameters obtained from a series of anhydrous sulfates of the elements of groups I-III. Operating at high magnetic field of 21.14 T provides a dramatic improvement in the quality of spectra due to significantly enhanced sensitivity and a reduction of second order quadrupolar effects. Experimental 33S NMR spectra for most studied sulfates are dominated by quadrupolar interactions with the quadrupolar parameters unique for each compound. Magnetic shielding constants and quadrupolar parameters for sulfur were calculated using plane wave pseudo-potential density functional theory as implemented in the CASTEP computational package. The calculated NMR parameters are in very good agreement with the experimental results and help in assignment of the stationary spectra. The results demonstrate that such a combined computational-experimental solid state NMR approach can aid in an assessment and improved interpretation of the crystallographic data.

USNCCM-11: computational fluid mechanics for free and moving boundary problems - Rao, Rekha R.; Roberts, S. A.; Noble, David R.; Anderson, Patrick D.; Hétu, Jean-François (Computers and Fluids, 2013)

An immersed boundary-body conformal enrichment method for thermal flow problems - Ilinca, F.; Hétu, J.-F. (Computers and Fluids, 2013)
Solving the flow around objects with complex shapes may involve extensive meshing work that has to be repeated each time a change in the geometry is needed. The same problem arises if one need to solve the heat transfer involving multiple materials whose interface is complex or changes with time. Time consuming meshing can be avoided when the solution algorithm can tackle grids that do not fit the shape of the interface between different materials. This work presents the extension of a recently proposed immersed boundary-body conformal enrichment (IB-BCE) method to the solution of the heat transfer. The method produces solutions of the temperature field satisfying accurately the continuity of the normal heat flux at interfaces between materials with different thermal properties. As for the isothermal flow problems, the fluid/solid interface is defined using a level-set function and the finite element discretization of interface elements is enriched with additional degrees of freedom which are eliminated at element level. The method is first validated in the case of heat conduction in two solids with different thermal properties. Then, solutions are shown for the more complex conjugate heat transfer between water and aluminum for two configurations: steady state flow inside a channel obstructed by a heated cylinder and transient flow around a heated cylinder. For each problem the solutions obtained using the proposed immersed boundary method are compared with solutions on body-conformal meshes having comparable mesh size distribution. The proposed approach is very accurate and effective in capturing the sharp discontinuity in the normal temperature gradient at the interface.
Keywords: Body conformal enrichments; Complex conjugates; Finite-element discretization; Immersed boundary methods; Interface elements; Level-set function; Multiple materials; Solution algorithms; Cylinder configurations; Cylinders (shapes); Finite element method; Heat flux; Heat transfer; Thermodynamic properties; Turbulent flow; Interfaces (materials)

B-spline surface based concept design module for applications in virtual reality environment - Pungotra, Harish; Knopf, George K.; Canas, Roberto (Computer-Aided Design and Applications, 2013)
Over the past decade, B-spline modeling has become the standard mathematical model for representing freeform or organic objects in CAD/CAM systems. Using a Bspline surface to represent the virtual model in a haptic concept design module helps to streamline the exchange of the information with existing CAD/CAM systems. Bspline surfaces also help increase visual realism because these represent continuous surface. At the same time, physically based virtual deformable models provide a sense of realism to the user. However, the algorithms used for interaction with the virtual model should be efficient to maintain acceptable level of virtual realism and perceive the simulation as continuous with no time lag. This paper presents a B-spline surface based concept design framework, which can be used to generate various concepts, evaluate these concepts, and provide user training. The proposed framework assumes that all deformable models are represented as B-spline surfaces. The tools used to interact with the deformable models can be implicit surface, tessellated surface, Bspline surface, or point-based. The technique exploits blending matrices for the Bspline surface that are independent of the control point positions and, hence, can be pre-calculated prior to haptic interaction. Once determined, the pre-calculated blending matrices are used to generate discrete points on the B-spline surface. Mass spring system is used to incorporate material properties to the virtual objects. Practical illustrations of the concept design framework are presented for modeling and evaluation of concepts and provide training to the intended user segment.
Keywords: concept design, deformable model, virtual reality, blending matrices

An alternative methodology to represent B-spline surface for applications in virtual reality environment - Pungotra, Harish; Knopf, George K.; Canas, Roberto (Computer-Aided Design and Applications, 2013)
B-spline representation is one of the main methods for free-form surface modeling and has become the standard for CAD systems. However, in Virtual Reality (VR) environment, when a B-spline surface deforms, the blending functions need to be continuously computed. The high computational cost of continuously calculating the blending functions for merging, collision detection and physics-based deformation system, while the model is deforming, restricts the use of B-spline representation in a VR environment. This paper presents an alternative methodology to represent B-spline surface patches for an interactive VR environment. A uniformly discretized B-spline surface patch can be represented by a set of control points and two precalculated B-spline blending matrices. The proposed technique exploits the fact that these B-spline blending matrices are independent of the position of control points and therefore can be pre-calculated. The blending matrices enable the algorithm to merge B-spline surface patches, accurately check the collision, and generate nodes for the mass spring system to determine deformation using the physics-based model. This technique does away with the need to calculate computationally intensive blending functions for the Bspline surfaces, and inverse of large matrices during the run-time.
Keywords: B-spline representation; Collision detection; Computational costs; Deformable object; Mass spring systems; Physics-based modeling; Physics-based models; Virtual-reality environment; Blending; Deformation; Matrix algebra; Virtual reality; Interpolation

Computing lexical contrast - Mohammad, Saif M.; Dorr, Bonnie J.; Hirst, Graeme; Turney, Peter D. (Computational Linguistics, 2013)
Knowing the degree of semantic contrast between words has widespread application in natural language processing, including machine translation, information retrieval, and dialogue systems. Manually created lexicons focus on opposites, such as hot and cold. Opposites are of many kinds such as antipodals, complementaries, and gradable. Existing lexicons often do not classify opposites into the different kinds, however. They also do not explicitly list word pairs that are not opposites but yet have some degree of contrast in meaning, such as warm and cold or tropical and freezing. We propose an automatic method to identify contrasting word pairs that is based on the hypothesis that if a pair of words, A and B, are contrasting, then there is a pair of opposites, C and D, such that A and C are strongly related and B and D are strongly related. (For example, there exists the pair of opposites hot and cold such that tropical is related to hot, and freezing is related to cold.) We will call this the contrast hypothesis. We begin with a large crowdsourcing experiment to determine the amount of human agreement on the concept of oppositeness and its different kinds. In the process, we flesh out key features of different kinds of opposites. We then present an automatic and empirical measure of lexical contrast that relies on the contrast hypothesis, corpus statistics, and the structure of a Roget-like thesaurus. We show how, using four different data sets, we evaluated our approach on two different tasks, solving "most contrasting word" questions and distinguishing synonyms from opposites. The results are analyzed across four parts of speech and across five different kinds of opposites. We show that the proposed measure of lexical contrast obtains high precision and large coverage, outperforming existing methods.

Thermal, oxygen barrier and mechanical properties of polylactide-organoclay nanocomposites - Yourdkhani, Mostafa; Mousavand, Tahereh; Chapleau, Nathalie; Hubert, Pascal (Composites Science and Technology, 2013)
Polylactide (PLA) nanocomposites reinforced with commercially available organoclays, Nanomer I.28E and Nanomer I.34TCN, were prepared using a melt intercalation technique. In this work, two different clay concentrations (2 and 4. wt.%) were considered. The morphology of the resulting nanocomposites was observed by TEM micrographs while the interaction between polymer and clay was measured by FTIR analysis and contact angle measurements. Better dispersion quality and interaction with the polymer matrix was observed for I.34TCN organoclay. The effect of clay dispersion and its interaction with PLA was investigated by measuring the thermal, oxygen barrier and mechanical properties of the prepared nanocomposites; consequently, higher improvements were observed in the properties of nanocomposites containing I.34TCN compared to the I.28E counterpart. Besides, 2. wt.% clay content was found as an optimum concentration for enhancing the different properties of the resulting nanocomposites with respect to neat PLA. However, higher improvements in oxygen permeability and tensile modulus were achieved by embedding 4. wt.% organoclay into the PLA matrix.
Keywords: Clay concentration; Clay dispersion; Dispersion quality; Melt intercalation; Optimum concentration; Oxygen permeability; Poly lactide; Contact angle; Dispersions; Organoclay; Oxygen permeable membranes; Polyesters; Transmission electron microscopy; Nanocomposites

Polyphenylene sulfide (PPS) composites reinforced with recycled carbon fiber - Stoeffler, Karen; Andjelic, Stefan; Legros, Nathalie; Roberge, Judith; Schougaard, Steen B. (Composites Science and Technology, 2013)
Recycled carbon fibers were reclaimed by commercial scale pyrolysis from carbon fiber reinforced thermoset composite waste generated by the aerospace industry. The mechanical and physical properties of the reclaimed carbon fibers were shown to be comparable to those of aerospace grade virgin carbon fibers. The recycled carbon fibers were integrated into a polyphenylene sulfide (PPS) thermoplastic resin by twin screw compounding followed by injection molding. Composites containing 20. wt.% and 40. wt.% recycled carbon fibers were produced. Overall, the fibers were found to be uniformly dispersed in the polymeric matrix. The tensile, flexural and impact properties of the composites were evaluated. The recycled carbon fiber reinforced PPS composites exhibited comparable mechanical properties to equivalent compounds produced using industrial grades of short virgin carbon fiber. In addition, thermogravimetric analysis showed that the introduction of recycled carbon fibers was not detrimental to the inherent thermal stability of PPS.
Keywords: Carbon fiber reinforced; E. Extrusion; Impact property; Mechanical and physical properties; Polymer Matrix Composites (PMCs); Polymeric matrices; Polyphenylene sulfides; Thermoset composites; Aerospace industry; Mechanical properties; Polypropylenes; Thermogravimetric analysis; Thermosets; Recycling

Multidisciplinary characterization of new shield with metallic nanoparticles for composite aircrafts - Jalali, M.; Molière, T.; Michaud, A.; Wuthrich, R. (Composites Part B: Engineering, 2013)
Because of major advantages (e.g. weight saving, maintenance advantages), the airframe manufacturers use more and more Polymer Matrix Composites (PMCs) in different parts of aircraft structures. But PMCs have a substantial disadvantage of low conductivity and therefore low Electromagnetic (EM) Shielding. Electromagnetic Interference (EMI) sources are all around and inside aircraft and can potentially threat the immunity of aircraft. Metallic meshes have been used to overcome this shortage. However in high frequencies most of the mentioned methods loose their performances. Regrettably on one side most of the present and upcoming systems onboard of aircraft are functional in mentioned range of frequencies. On the other side, passengers use more and more Personal Electronic Devices (PEDs) onboard of aircraft. Interferences caused by PEDs are also in the same range of frequencies. Measured susceptibility caused by PEDs is higher in composite aircrafts comparing to metallic ones. To overcome this back door lack of composite aircrafts, design of a new light weight shield particularly for aeronautic application is needed. Metallic nanoparticles have a great potential to be used as new EM shields for aerospace applications, particularly in high frequencies. Without multidisciplinary characterization of new shield, the application onboard would be suspended. Here the encouraging results of EM characterization are presented. Thermal, microscopy and mechanical tests are also performed. Based on acquired results in this work, thermal and mechanical behaviors as well as distribution of particles are all acceptable. The promising results obtained in this work can assure the designers on using metallic nanoparticles as a new shield for protection of composite aircrafts.
Keywords: Aeronautic applications; Aircraft structure; High frequency HF; Mechanical behavior; Personal electronic devices; Polymer Matrix Composites (PMCs); Aerodynamics; Aerospace applications; Aircraft manufacture; Airframes; Electromagnetic pulse; Electromagnetic shielding; Electron microscopy; Mechanical testing; Optical microscopy; Polymer matrix composites; Thermoanalysis

Effects of dietary cholesterol on astaxanthin transport in plasma of Atlantic salmon (Salmo salar) - Chimsung, N.; Lall, S. P.; Tantikitti, C.; Verlhac-Trichet, V.; Milley, J. E. (Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology, 2013)
The effect of dietary cholesterol on astaxanthin (Ax) absorption and transport in the plasma of Atlantic salmon was investigated. Under controlled conditions, three experimental diets, non-pigmented diet (NPD), NPD with 40mg Axkg-1, and NPD with 40mg Axkg-1 and 2% cholesterol, were fed to juvenile salmon reared in sea water. After 12weeks, blood was collected and plasma separated for analysis of plasma Ax and cholesterol content. In addition, plasma samples from each group of fish were fractionated into lipoproteins using a sucrose density gradient and ultracentrifugation. The apolipoprotein components of VLDL, LDL and HDL from each sample fraction were separated using SDS-PAGE. The addition of 2% cholesterol to the Ax-containing diet significantly increased the concentration of Ax and cholesterol in fish plasma. The protein-rich fraction was found to be the major carrier of Ax in salmon plasma. Cholesterol supplementation significantly increased Ax in plasma and VLDL as well as increasing plasma cholesterol. The VLDL fraction showed the most significant change in fish fed diet supplemented with cholesterol resulting in higher levels of Ax in this lipoprotein. The results clearly show that dietary cholesterol had a significant effect on the Ax transport process in the blood.
Keywords: high density lipoprotein cholesterol; low density lipoprotein cholesterol; very low density lipoprotein; absorption; blood sampling; density gradient centrifugation; dietary intake; fish; nonhuman; polyacrylamide gel electrophoresis; separation technique; sucrose density gradient centrifugation; Animals; Cholesterol, Dietary; Cholesterol, VLDL; Lipoproteins; Lipoproteins, HDL; Xanthophylls

Bacterial community evidence for anaerobic degradation of petroleum hydrocarbons in cold climate groundwater - Yeung, C. William; Van Stempvoort, Dale R.; Spoelstra, John; Bickerton, Greg; Voralek, John; Greer, Charles W. (Cold Regions Science and Technology, 2013)
There is currently limited scientific data to assess whether groundwater bacterial communities in fractured rock environments can degrade petroleum hydrocarbon plumes in cold regions. The former Colomac Mine is located in the Canadian Shield in the Northwest Territories (mean annual air temperature of -. 5°C) and is currently listed on the Federal Contaminated Sites inventory. Groundwater in fractured rock beneath the former fuel tank-farm at the mine site is contaminated by petroleum hydrocarbons. The objectives of this study were to investigate the bacterial community structure in the groundwater associated with hydrocarbon contamination, and to probe for potential anaerobic microbial processes involved in intrinsic bioremediation. Groundwater monitoring wells previously installed at the site were used to collect samples for chemical, isotopic and microbial analyses. Denaturing gradient gel electrophoresis (DGGE) analysis identified a relatively high bacterial diversity in the least contaminated locations, but as the hydrocarbon contamination increased, bacterial diversity decreased. Sequence analysis of the 16S rRNA gene demonstrated that the bacteria belonged to a wide range of genera, such as Pseudomonas, Thiobacillus, and Geobacter, all of which have been associated with the anaerobic degradation of hydrocarbons. Two putative nitrate-reducing genes were detected in samples with high nitrate reducing activity. Both chemical and microbiological results indicated the presence of microbial anaerobic processes by using nitrate, manganese(IV), ferric iron and sulfate as electron acceptors and suggest that these anaerobic processes play an important role in the biodegradation of dissolved petroleum hydrocarbons in the groundwater at the Colomac site. Our results also revealed that more than one biogeochemical process linked to hydrocarbon degradation could be present in a single borehole and these processes could vary spatially at this site.
Erratum published in volume 89, page 48, May 2013. DOI: 10.1016/j.coldregions.2013.01.007
Keywords: DGGE; Hydrocarbon contamination; Hydrocarbon degradation; Microbial diversity; Nitrate reduction; Biodegradation; Bioremediation; Chemical analysis; Electrophoresis; Fuel tanks; Genes; Groundwater pollution; Hydrocarbons; Manganese; Nitrates; Petroleum chemistry; RNA; Hydrochemistry; Anoxic conditions; Bacterium; Biodegradation; Community structure; Fractured medium; Microbial community; Reduction; Sulfate; Canada; Canadian Shield; Northwest Territories; Bacteria (microorganisms); Geobacter; Pseudomonas; Thiobacillus

Revisiting the Sanderson pressure-area curve: Defining parameters that influence ice pressure - Timco, G. W.; Sudom, D. (Cold Regions Science and Technology, 2013)
There is a strong perception in the ice mechanics community that during ice-structure interaction, the ice pressure always decreases as the area of contact increases. This understanding is often based on the pressure-area plot published by Sanderson (1988), which combines a large number of data sources and ice interaction situations on a single plot and shows a definite decrease in pressure with increasing area. This paper examines the data sources in the Sanderson plot as well as some more recent data, and discusses the definitions of global, local, spatial and process pressure-area. It is found that the pressure over a defined local geometric area or over the full global ice contact area can either show no dependence on area or a decrease with increasing area, depending on the interaction scenario. Factors other than area are examined to determine their influence on pressure including the loading rate, aspect ratio, ice failure mode, and ice properties. It is shown that in many cases, these factors are more important than the area in predicting ice pressure. The theory of Palmer et al. (2009) provides a reasonable explanation for some of the observed trends in pressure-area behavior. Examples from field data are provided to illustrate the application of pressure-area relationships for offshore structures in icy waters.
Keywords: Contact areas; Geometric area; Ice interactions; Ice properties; Ice-structure interaction; Number of datum; Offshore; Pressure area; Aspect ratio; Design; Offshore structures; Pressure; Sea ice; Structure (composition); Loading

Modulation of fatty acid synthase enzyme activity and expression during hepatitis C virus replication - Nasheri, Neda; Joyce, Michael; Rouleau, Yanouchka; Yang, Pengyu; Yao, Shao; Tyrrell, D. Lorne; Pezacki, John Paul (Chemistry and Biology, 2013)
The hepatitis C virus (HCV) induces alterations of host cells to facilitate its life cycle. Fatty acid synthase (FASN) is a multidomain enzyme that plays a key role in the biosynthesis of fatty acids and is upregulated during HCV infection. Herein, we applied activity-based protein profiling (ABPP) that allows for the identification of differentially active enzymes in complex proteomic samples, to study the changes in activity of FASN during HCV replication. For this purpose, we used an activity-based probe based on the FASN inhibitor Orlistat, and observed an increase in the activity of FASN in the presence of a subgenomic and a genomic HCV replicon as well as in chimeric SCID/Alb-uPA mice infected with HCV genotype 1a. To study the molecular basis for this increase in FASN activity, we overexpressed individual HCV proteins in Huh7 cells and observed increased expression and activity of FASN in the presence of core and NS4B, as measured by western blots and ABPP, respectively. Triglyceride levels were also elevated in accordance with FASN expression and activity. Lastly, immunofluorescence and ABPP imaging analyses demonstrated that while the abundance and activity of FASN increases significantly in the presence of HCV, its localization does not change. Together these data suggest that the HCV-induced production of fatty acids and neutral lipids is provided by an increase in FASN abundance and activity that is sufficient to allow HCV propagation without transporting FASN to the replication complexes.

A combined ultra-wideline solid-state NMR and DFT study of 137Ba electric field gradient tensors in barium compounds - O'Dell, Luke A.; Moudrakovski, Igor L. (Chemical Physics Letters, 2013)
Ultra-wideline 137Ba solid-state (SS) NMR spectra have been obtained from a series of five barium compounds (BaSO4, BaMoO 4, Ba(CH3COO)2, Ba(OH)2· 8H2O and α-Ba2P2O7), using the broadband WURST-QCPMG pulse sequence and magnetic field of 21.1 T. The signals from the two distinct crystallographic sites in α-Ba2P 2O7 are resolved, with one of them demonstrating a C Q of 42.3 ± 0.3 MHz, the largest obtained for 137Ba in a powder. The quadrupolar parameters reported in this work are in excellent agreement with the DFT calculations and correlate well with those previously reported by Hamaed et al. (2010) [24].
Keywords: Crystallographic sites; DFT calculation; DFT study; Electric field gradient tensors; NMR spectrum; Pulse sequence; Solid state NMR; Density functional theory; Electric fields; Nuclear magnetic resonance spectroscopy; Barium compounds

Infrared spectrum of the CS2 tetramer: observation of a structure with D2d symmetry - Rezaei, M.; Norooz Oliaee, J.; Moazzen-Ahmadi, N.; McKellar, A. R. W. (Chemical Physics Letters, 2013)
Infrared spectra of carbon disulfide clusters are studied in the region of the CS2 ν3 fundamental band (≈1535 cm-1), using a tuneable diode laser to probe a pulsed supersonic slit jet expansion. A symmetric rotor parallel band at 1551.438 cm-1 is assigned to CS2 tetramer. The likely structure is a staggered and tilted barrel with D2d symmetry, similar to the previously observed oblate tetramer of nitrous oxide, and in reasonable agreement with that calculated from an empirical CS2 intermolecular potential function. This is the first high-resolution spectroscopic detection of CS2 tetramer, and the calculations suggest that there could be other low energy isomers of (CS2)4 which are not yet observed.
Keywords: Energy isomers; Fundamental bands; High resolution; Infrared spectrum; Intermolecular potentials; Jet expansion; Spectroscopic detection; Symmetric rotors; Isomers; Nitrogen oxides; Spectroscopy; Supersonic aerodynamics; Oligomers

The structure and optical absorption of single source precursors for II-VI quantum dots - Wang, Xinqin; Zeng, Qun; Shi, Jing; Jiang, Gang; Yang, Mingli; Liu, Xiangyang; Enright, Gary; Yu, Kui (Chemical Physics Letters, 2013)
Starting from its measured structure, the electronic structures and optical absorptions of CdSe single source precursor, cadmium bis(diselenophosphinate) (CSP), have been studied by means of density functional theory calculations. In contrast to covalent bonding in ligand-free cadmium selenide, the Cd-Se bonds in CSP are featured by the coordination of the 4p electrons of Se atoms, resulting in low net charge on Cd and blue shifted electron transitions. The ligands not only stabilize the CdSe core but also affect the HOMO-LUMO transition. Computations were extended to the corresponding ZnSe and CdS complexes and came to similar conclusions.
Keywords: Blue-shifted; Cadmium selenides; Covalent bonding; Density functional theory calculations; HOMO-LUMO transitions; II-VI quantum dots; Ligand-free; Single-source precursor; Cadmium compounds; Cadmium sulfide; Chemical bonds; Density functional theory; Electron transitions; Electronic structure; Semiconducting selenium compounds; Light absorption

Reprint of: Neon interatomic potentials from scattering data and crystalline properties - Farrar, J. M.; Lee, Y. T.; Goldman, V. V.; Klein, M. L. (Chemical Physics Letters, 2013)
Interatomic potentials for Ne2 derived from recent differential elastic scattering cross section measurements and properties of solid neon are presented. Cross sections and second virial coefficients are calculated with the proposed potentials and comparisons with experiment are made. The Ne2 potential derived from scattering data only is shown to provide a good fit to the solid state data.

Electronic spectra and excited-state dynamics of 4-fluoro-N,N- dimethylaniline - Fujiwara, Takashige; Reichardt, Christian; Vogt, R. Aaron; Crespo-Hernández, Carlos E.; Zgierski, Marek Z.; Lim, Edward C. (Chemical Physics Letters, 2013)
Concerted ultrafast time-resolved spectroscopic experiments and ab initio computational (TDDFT) studies of the electronic transitions of 4-fluoro-N,N-dimethylaniline (FDMA) have been performed to investigate the mechanism of photo-induced intramolecular charge transfer (ICT). The compound FDMA shows dual fluorescence from a ππ state and a closely-lying twisted intramolecular charge transfer (TICT) state in both n-hexane and acetonitrile. The very similar lifetimes observed for the two emission bands indicate that the ππ* and the TICT states are effectively in thermal equilibrium at room temperature.
Keywords: Dual fluorescence; Electronic spectrum; Electronic transition; Excited-state dynamics; Intramolecular charge transfers; Room temperature; Thermal equilibriums; Twisted intra-molecular charge transfers; Physical chemistry; Charge transfer

New interpretation of proton and deuteron tunneling in 2′- methylacetophenone - Fernández-Ramos, Antonio; Siebrand, Willem; Smedarchina, Zorka (Chemical Physics Letters, 2013)
The enol-keto transition rate constants in 2′-methylacetophenone observed by Grellmann et al. [3] are calculated from first principles. The results reinterpret the proposed mechanism and show that proton tunneling is preceded by dissociation of a substrate-solvent complex rather than by rotamer interconversion.
Keywords: First principles; Interconversions; Proton tunneling; Rotamers; Transition rates; Rate constants; Protons

Effect of ammonia gas addition to the synthesis environment of single-walled carbon nanotubes on their surface chemistry - Shahverdi, Ali; Soucy, Gervais; Simard, Benoit; Mostaghimi, Javad (Chemical Engineering Journal, 2013)
This study evaluates the effect of ammonia gas addition on synthesis environment and surface chemistry of single-walled carbon nanotubes (SWCNTs) produced by induction thermal plasma system (ITP). The experiments were carried out based on the opposed-flow injection of ammonia into the ITP reactor used for mass production of SWCNTs containing soot. The influence of in situ ammonia injection on the SWCNT final products was closely examined by Raman spectroscopy at three wavelengths, coupled thermogravimetry-infrared spectroscopy (TG-FTIR) and solid-phase infrared spectroscopy. The results clearly indicated the surface modification of SWCNTs where the metallic tubes had a greater tendency than the semiconducting tubes to react with ammonia at high temperature. To better understand the reaction system and predict the concentration profile of the intermediates and the product species from thermal decomposition of ammonia in the ITP reactor, a numerical simulation was developed including both the detailed kinetic of ammonia decomposition and turbulent mixing in the reaction system. By comparing the experimental and simulation results, a two-step reaction mechanism is suggested for this in situ SWCNTs chemistry in which the reaction of atomic hydrogen and amidogen radicals with SWCNTs, is followed by the ammonia chemisorption.
Keywords: Ammonia chemisorption; Ammonia decomposition; Concentration profiles; Induction thermal plasma; Semiconducting tubes; Single-walled carbon nanotubes (SWCNTs); Singlewalled carbon nanotube (SWCNT); Two-step reaction mechanisms; Chemical modification; Computer simulation; Infrared spectroscopy; Kinetics; Numerical models; Reaction intermediates; Surface chemistry; Synthesis (chemical); Thermogravimetric analysis

Misalignment of magnetic fields and outflows in protostellar cores - Hull, Charles L. H.; Plambeck, Richard L.; Bolatto, Alberto D.; Bower, Geoffrey C.; Carpenter, John M.; Crutcher, Richard M.; Fiege, Jason D.; Franzmann, Erica; Hakobian, Nicholas S.; Heiles, Carl; Houde, Martin; Hughes, A. Meredith; et al. (The Astrophysical Journal, 2013)
We present results of λ1.3 mm dust-polarization observations toward 16 nearby, low-mass protostars, mapped with ∼2.″5 resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of ∼1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotation axes of circumstellar disks, and that the outflows have not disrupted the fields in the surrounding material, then our results imply that the disks are not aligned with the fields in the cores from which they formed.

Most observations of σ Ori E: challenging the centrifugal breakout narrative - Townsend, R. H. D.; Rivinius, Th.; Rowe, J. F.; Moffat, A. F. J.; Matthews, J. M.; Bohlender, D.; Neiner, C.; Telting, J. H.; Guenther, D. B.; Kallinger, T.; Kuschnig, R.; Rucinski, S. M.; et al. (The Astrophysical Journal, 2013)
We present results from three weeks' photometric monitoring of the magnetic helium-strong star σ Ori E using the Microvariability and Oscillations of Stars microsatellite. The star's light curve is dominated by twice-per-rotation eclipse-like dimmings arising when magnetospheric clouds transit across and occult the stellar disk. However, no evidence is found for any abrupt centrifugal breakout of plasma from the magnetosphere, either in the residual flux or in the depths of the light minima. Motivated by this finding we compare the observationally inferred magnetospheric mass against that predicted by a breakout analysis. The large discrepancy between the values leads us to argue that centrifugal breakout does not play a significant role in establishing the magnetospheric mass budget of σ Ori E.

Herschel reveals massive cold clumps in NGC 7538 - Fallscheer, C.; Reid, M. A.; Di Francesco, J.; Martin, P. G.; Hill, T.; Hennemann, M.; Nguyen-Luong, Q.; Motte, F.; Men'Shchikov, A.; André, Ph.; Ward-Thompson, D.; Griffin, M.; et al. (The Astrophysical Journal, 2013)
We present the first overview of the Herschel observations of the nearby high-mass star-forming region NGC 7538, taken as part of the Herschel imaging study of OB young stellar objects (HOBYS) Key Programme. These PACS and SPIRE maps cover an approximate area of one square degree at five submillimeter and far-infrared wavebands. We have identified 780 dense sources and classified 224 of those. With the intention of investigating the existence of cold massive starless or class 0-like clumps that would have the potential to form intermediate- to high-mass stars, we further isolate 13 clumps as the most likely candidates for follow-up studies. These 13 clumps have masses in excess of 40 M ⊙and temperatures below 15 K. They range in size from 0.4 pc to 2.5 pc and have densities between 3 × 103 cm -3 and 4 × 104 cm-3. Spectral energy distributions are then used to characterize their energetics and evolutionary state through a luminosity-mass diagram. NGC 7538 has a highly filamentary structure, previously unseen in the dust continuum of existing submillimeter surveys. We report the most complete imaging to date of a large, evacuated ring of material in NGC 7538 which is bordered by many cool sources.

Ionisation impact of high-mass stars on interstellar filaments: a Herschel study of the RCW 36 bipolar nebula in Vela C - Minier, V.; Tremblin, P.; Hill, T.; Motte, F.; André, Ph.; Lo, N.; Schneider, N.; Audit, E.; White, G. J.; Hennemann, M.; Cunningham, M.; Deharveng, L.; et al. (Astronomy and Astrophysics, 2013)
Context. Ionising stars reshape their original molecular cloud and impact star formation, leading to spectacular morphologies such as bipolar nebulae around H ii regions. Molecular clouds are structured in filaments where stars principally form, as revealed by the Herschel space observatory. The prominent southern hemisphere H ii region, RCW 36, is one of these bipolar nebulae. Aims. We study the physical connection between the filamentary structures of the Vela C molecular cloud and the bipolar morphology of RCW 36, providing an in-depth view of the interplay occurring between ionisation and interstellar structures (bright-rims and pillars) around an H ii region. Methods. We have compared Herschel observations in five far-infrared and submillimetre filters with the PACS and SPIRE imagers, to dedicated numerical simulations and molecular line mapping. Results. Our results suggest that the RCW 36 bipolar morphology is a natural evolution of its filamentary beginnings under the impact of ionisation. Conclusions. Such results demonstrate that, filamentary structures can be the location of very dynamical phenomena inducing the formation of dense clumps at the edge of H ii regions. Moreover, these results could apply to better understanding the bipolar nebulae as a consequence of the expansion of an H ii region within a molecular ridge or an interstellar filament.
Keywords: Dynamical phenomena; Far-infrared; Filamentary structures; H II regions; HERSCHEL; Herschel space observatories; High-mass stars; ISM: individual objects; ISM: structure; Molecular clouds; Molecular lines; Natural evolution; Southern Hemisphere; Star formations; Stars: massive; Submillimetre; Galaxies; Hydrodynamics; Ionization; Morphology

2011 HM102: discovery of a high-inclination L5 Neptune Trojan in the search for a post-Pluto New Horizons target - Parker, Alex H.; Buie, Marc W.; Osip, David J.; Gwyn, Stephen D. J.; Holman, Matthew J.; Borncamp, David M.; Spencer, John R.; Benecchi, Susan D.; Binzel, Richard P.; DeMeo, Francesca E.; Fabbro, Sébastien; Fuentes, Cesar I.; et al. (The Astronomical Journal, 2013)
We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission. This Neptune Trojan, 2011 HM102, has the highest inclination (29.°4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at HV 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ103 and 2007 VL305), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM102, and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM102 from the New Horizons spacecraft during its close approach in mid- to late-2013.
Keywords: astronomy; Pluto; New Horizons; minor planets; asteroids

The Herschel view of the massive star-forming region NGC 6334 - Russeil, D.; Schneider, N.; Anderson, L. D.; Zavagno, A.; Molinari, S.; Persi, P.; Bontemps, S.; Motte, F.; Ossenkopf, V.; André, Ph.; Arzoumanian, D.; Bernard, J.-Ph.; et al. (Astronomy and Astrophysics, 2013)
Aims. Fundamental to any theory of high-mass star formation are gravity and turbulence. Their relative importance, which probably changes during cloud evolution, is not known. By investigating the spatial and density structure of the high-mass star-forming complex NGC 6334 we aim to disentangle the contributions of turbulence and gravity. Methods. We used Herschel PACS and SPIRE imaging observations from the HOBYS key programme at wavelengths of 160, 250, 350, and 500 μm to construct dust temperature and column density maps. Using probability distribution functions (PDFs) of the column density determined for the whole complex and for four distinct sub-regions (distinguished on the basis of differences in the column density, temperature, and radiation field), we characterize the density structure of the complex. We investigate the spatial structure using the Δ-variance, which probes the relative amount of structure on different size scales and traces possible energy injection mechanisms into the molecular cloud. Results. The Δ-variance analysis suggests that the significant scales of a few parsec that were found are caused by energy injection due to expanding H ii regions, which are numerous, and by the lengths of filaments seen everywhere in the complex. The column density PDFs have a lognormal shape at low densities and a clearly defined power law at high densities for all sub-regions whose slope is linked to the exponent α of an equivalent spherical density distribution. In particular with α = 2.37, the central sub-region is largly dominated by gravity, caused by individual collapsing dense cores and global collapse of a larger region. The collapse is faster than free-fall (which would lead only to α = 2) and thus requires a more dynamic scenario (external compression, flows). The column density PDFs suggest that the different sub-regions are at different evolutionary stages, especially the central sub-region, which seems to be in a more evolved stage.
Keywords: Density distributions; Density structures; ISM : clouds; ISM: individual objects; Star-forming complexes; Star-forming region; Stars: formation; Using probabilities; Distribution functions; Gravitation; Probability distributions; Space applications; Turbulence

Calcium-sensing receptor antagonist (calcilytic) NPS 2143 specifically blocks the increased secretion of endogenous Aβ42 prompted by exogenous fibrillary or soluble Aβ25-35 in human cortical astrocytes and neurons: therapeutic relevance to Alzheimer's disease - Armato, Ubaldo; Chiarini, Anna; Chakravarthy, Balu; Chioffi, Franco; Pacchiana, Raffaelia; Colarusso, Enzo; Whitfield, James F.; Dal Prà, Ilaria (Biochimica et Biophysica Acta - Molecular Basis of Disease, 2013)
The "amyloid-β (Aβ) hypothesis" posits that accumulating Aβ peptides (Aβs) produced by neurons cause Alzheimer's disease (AD). However, the Aβs contribution by the more numerous astrocytes remains undetermined. Previously we showed that fibrillar (f)Aβ25-35, an Aβ42 proxy, evokes a surplus endogenous Aβ42 production/accumulation in cortical adult human astrocytes. Here, by using immunocytochemistry, immunoblotting, enzymatic assays, and highly sensitive sandwich ELISA kits, we investigated the effects of fAβ25-35 and soluble (s)Aβ25-35 on Aβ42 and Aβ40 accumulation/secretion by human cortical astrocytes and HCN-1A neurons and, since the calcium-sensing receptor (CaSR) binds Aβs, their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fAβ25-35-exposed astrocytes and surviving neurons produced, accumulated, and secreted increased amounts of Aβ42, while Aβ40 also accrued but its secretion was unchanged. Accordingly, secreted Aβ42/Aβ40 ratio values rose for astrocytes and neurons. While slightly enhancing Aβ40 secretion by fAβ25-35-treated astrocytes, NPS 2143 specifically suppressed the fAβ25-35-elicited surges of endogenous Aβ42 secretion by astrocytes and neurons. Therefore, NPS 2143 addition always kept Aβ42/Aβ40 values to baseline or lower levels. Mechanistically, NPS 2143 decreased total CaSR protein complement, transiently raised proteasomal chymotrypsin activity, and blocked excess NO production without affecting the ongoing increases in BACE1/β-secretase and γ-secretase activity in fAβ25-35-treated astrocytes. Compared to fAβ25-35, sAβ25-35 also stimulated Aβ42 secretion by astrocytes and neurons and NPS 2143 specifically and wholly suppressed this effect. Therefore, since NPS 2143 thwarts any Aβ/CaSR-induced surplus secretion of endogenous Aβ42 and hence further vicious cycles of Aβ self-induction/secretion/spreading, calcilytics might effectively prevent/stop the progression to full-blown AD.
Keywords: Amyloid-β; Human astrocyte; Human neuron; NPS 2143; NPS R-568; Calcium-sensing receptor

Fomalhaut b: independent analysis of the hubble space telescope public archive data - Galicher, Raphaël; Marois, Christian; Zuckerman, B.; MacIntosh, Bruce (The Astrophysical Journal, 2013)
The nature and even the existence of a putative planet-mass companion ("Fomalhaut b") to Fomalhaut has been debated since 2008. In the present paper, we reanalyze the multi-epoch ACS/STIS/WFC3 Hubble Space Telescope (HST) optical/near-infrared images on which the discovery and some other claims were based. We confirm that the HST images do reveal an object in orbit around Fomalhaut, but the detailed results from our analysis differ in some ways from previous discussions. In particular, we do not confirm flux variability over a two-year interval at 0.6 μm wavelength and we detect Fomalhaut b for the first time at the short wavelength of 0.43 μm. We find that the HST image of Fomalhaut b at 0.8 μm may be extended beyond the point-spread function. We cannot determine from our astrometry if Fomalhaut b will cross or not the dust ring. The optical through mid-infrared spectral energy distribution (SED) of Fomalhaut b cannot be explained as due to direct or scattered radiation from a massive planet. We consider two models to explain the SED: (1) a large circumplanetary disk around an unseen planet and (2) the aftermath of a collision during the past 50-150 yr of two Kuiper-Belt-like objects of radii ∼50 km.

X-ray observations of the supernova remnant CTB 87 (G74.9+1.2): an evolved pulsar wind nebula - Matheson, H.; Safi-Harb, S.; Kothes, R. (The Astrophysical Journal, 2013)
Pulsar wind nebulae (PWNe) studies with the Chandra X-Ray Observatory have opened a new window to address the physics of pulsar winds, zoom on their interaction with their hosting supernova remnant (SNR) and interstellar medium, and identify their powering engines. We here present a new 70 ks, plus an archived 18 ks, Chandra ACIS observation of the SNR CTB 87 (G74.9+1.2), classified as a PWN with unusual radio properties and poorly studied in X-rays. We find that the peak of the X-ray emission is clearly offset from the peak of the radio emission by ∼100″ and located at the southeastern edge of the radio nebula. We detect a point source - the putative pulsar - at the peak of the X-ray emission and study its spectrum separately from the PWN. This new point source, CXOU J201609.2+371110, is surrounded by a compact nebula displaying a torus-like structure and possibly a jet. A more extended diffuse nebula is offset from the radio nebula, extending from the point source to the northwest for ∼250″. The spectra of the point source, compact nebula, and extended diffuse nebula are all well described by a power-law model with a photon index of 1.1 (0.7-1.6), 1.2 (0.9-1.4), and 1.7 (1.5-1.8), respectively, for a column density NH=1.38(1.21-1.57)×10²² cm⁻² (90% confidence). The total X-ray luminosity of the source is ∼1.6 × 10³⁴ erg s⁻¹ at an assumed distance of 6.1 kpc, with ∼2% and 6% contribution from the point source and compact nebula, respectively. The observed properties suggest that CTB 87 is an evolved (∼5-28 kyr) PWN, with the extended radio emission likely a "relic" PWN, as in Vela-X and G327.1-1.1. To date, however, there is no evidence for thermal X-ray emission from this SNR, and the SNR shell is still missing, suggesting expansion into a low-density medium ( n0<0.2D[sub 6.1][super -1/2] cm⁻³), likely caused by a stellar wind bubble blown by the progenitor star.

Particle-physics constraints from the globular cluster M5: neutrino dipole moments - Viaux, N.; Catelan, M.; Stetson, P. B.; Raffelt, G. G.; Redondo, J.; Valcarce, A. A. R.; Weiss, A. (Astronomy and Astrophysics, 2013)
Stellar evolution is modified if energy is lost in a "dark channel" similar to neutrino emission. Comparing modified stellar evolution sequences with observations provides some of the most restrictive limits on axions and other hypothetical low-mass particles and on non-standard neutrino properties. In particular, a putative neutrino magnetic dipole moment μν enhances the plasmon decay process, postpones helium ignition in low-mass stars, and therefore extends the red giant branch (RGB) in globular clusters (GCs). The brightness of the tip of the RGB (TRGB) remains the most sensitive probe for μν and we revisit this argument from a modern perspective. Based on a large set of archival observations, we provide high-precision photometry for the Galactic GC M5 (NGC 5904) and carefully determine its TRGB position. On the theoretical side, we add the extra plasmon decay rate brought about by μν to the Princeton-Goddard-PUC (PGPUC) stellar evolution code. Different sources of uncertainty are critically examined. The main source of systematic uncertainty is the bolometric correction and the main statistical uncertainty derives from the distance modulus based on main-sequence fitting. (Other measures of distance, e.g., the brightness of RR Lyrae stars, are influenced by the energy loss that we wish to constrain.) The statistical uncertainty of the TRGB position relative to the brightest RGB star is less important because the RGB is well populated. We infer an absolute I-band brightness of MI = -4.17 ± 0.13 mag for the TRGB compared with the theoretical prediction of - 3.99 ± 0.07 mag, in reasonable agreement with each other. A significant brightness increase caused by neutrino dipole moments is constrained such that μν < 2.6 × 10-12 μB (68% CL), where μB ≡ e/2me is the Bohr magneton, and μν < 4.5 × 10-12 μB (95% CL). In these results, statistical and systematic errors have been combined in quadrature.
Keywords: Globular clusters: general; Globular clusters: individual; Hertzsprung-Russell and C-M diagrams; Neutrinos; Stars: evolution; Stars: Interiors; Dipole moment; Energy dissipation; Luminance; Neutrons; Plasmons

High-resolution radio emission from RCW 49/Westerlund 2 - Benaglia, P.; Koribalski, B.; Peri, C. S.; Martí, J.; Sánchez-Sutil, J. R.; Dougherty, S. M.; Noriega-Crespo, A. (Astronomy and Astrophysics, 2013)
Aims. The HII region RCW49 and its ionizing cluster form an extensive, complex region that has been widely studied at infrared (IR) and optical wavelengths. The Molonglo 843 MHz and Australia Telescope Compact Array data at 1.4 and 2.4 GHz showed two shells. Recent high-resolution IR imaging revealed a complex dust structure and ongoing star formation. New high-bandwidth and high-resolution data of the RCW 49 field have been obtained to survey the radio emission at arcsec scale and investigate the smallscale features and nature of the HII region. Methods. Radio observations were collected with the new 2-GHz bandwidth receivers and the CABB correlator of the Australia Telescope Compact Array [ATCA], at 5.5 and 9.0 GHz. In addition, archival observations at 1.4 and 2.4 GHz have been re-reduced and re-analyzed in conjunction with observations in the optical, IR, X-ray, and gamma-ray regimes. Results. The new 2-GHz bandwidth data result in the most detailed radio continuum images of RCW 49 to date. The radio emission closely mimics the near-IR emission observed by Spitzer, showing pillars and filaments. The brightest continuum emission comes from the region known as the bridge. The overall flattish spectral index is typically consistent with a free-free emission mechanism. However, hints of nonthermal components are also present in the bridge. An interesting jet-like structure surrounded by a bubble feature whose nature is still unclear has been discovered close to the Westerlund 2 core. Two apparent bow shocks and a number of discrete sources have been detected as well in the surroundings of RCW 49. In addition, we also report on and discuss the possible detection of a hydrogen recombination line. Conclusions. The radio results support an association between the cm continuum and molecular emission. The detection of the radio recombination line kinematically favors a RCW49 distance of 6-7 kpc. If the negative spectral indices measured at the bridge should be confirmed to be caused by synchrotron emission, we propose a scenario where high-energy emission could be produced. Finally, the newly discovered jet-like structure appears to be an intriguing source that deserves a detailed study by itself.
Keywords: Gamma rays: stars; ISM: individual objects; Open clusters and associations; Radio continuum: ISM; Stars: winds, outflows; Bandwidth; Infrared imaging; Optical waveguides; Telescopes

The luminosities of protostars in the Spitzer c2d and Gould Belt legacy clouds - Dunham, Michael M.; Arce, Héctor G.; Allen, Lori E.; Evans Ii, Neal J.; Broekhoven-Fiene, Hannah; Chapman, Nicholas L.; Cieza, Lucas A.; Gutermuth, Robert A.; Harvey, Paul M.; Hatchell, Jennifer; Huard, Tracy L.; Kirk, Jason M.; et al. (The Astronomical Journal, 2013)
Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate Lbol for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 L☉ to 69 L☉, and has a mean and median of 4.3 L☉ and 1.3 L☉, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (Lbol ≲ 0.5 L☉) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 μm <λ < 850 μm) and have Lbol underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35%-40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased data set should aid such future work.

On a possible size/color relationship in the Kuiper Belt - Pike, R. E.; Kavelaars, J. J. (Astronomical Journal, 2013)
Color measurements and albedo distributions introduce non-intuitive observational biases in size-color relationships among Kuiper Belt Objects (KBOs) that cannot be disentangled without a well characterized sample population with systematic photometry. Peixinho et al. report that the form of the KBO color distribution varies with absolute magnitude, H. However, Tegler et al. find that KBO color distributions are a property of object classification. We construct synthetic models of observed KBO colors based on two B-R color distribution scenarios: color distribution dependent on H magnitude (H-Model) and color distribution based on object classification (Class-Model). These synthetic B-R color distributions were modified to account for observational flux biases. We compare our synthetic B-R distributions to the observed "Hot" and "Cold" detected objects from the Canada-France Ecliptic Plane Survey and the Meudon Multicolor Survey. For both surveys, the Hot population color distribution rejects the H-Model, but is well described by the Class-Model. The Cold objects reject the H-Model, but the Class-Model (while not statistically rejected) also does not provide a compelling match for data. Although we formally reject models where the structure of the color distribution is a strong function of H magnitude, we also do not find that a simple dependence of color distribution on orbit classification is sufficient to describe the color distribution of classical KBOs.

The RR Lyrae variables and horizontal branch of NGC 6656 (m22) - Kunder, Andrea; Stetson, Peter B.; Cassisi, Santi; Layden, Andrew; Bono, Giuseppe; Catelan, Márcio; Walker, Alistair R.; Paredes Alvarez, Leonardo; Clem, James L.; Matsunaga, Noriyuki; Salaris, Maurizio; Lee, Jae-Woo; et al. (Astronomical Journal, 2013)
The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC 6656 (M22), with observations spanning a range of 22 years. We have also redetermined the variability types and periods for the RR Lyrae stars identified previously by photographic observations, revising the number of fundamental-mode RR Lyrae variables (RR0) to 10 and the number of first-overtone variables (RR1) to 16. The mean periods of the RR0 and RR1 variables are 〈P〉RR0 = 0.66 ± 0.02 days and 〈P〉RR1 = 0.33 ± 0.01 days, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1-type to all RR-type variables is N 1/NRR = 0.61, also consistent with an Oosterhoff II designation. Both the RR Lyrae stars' minimum light colors and the blue edge of the RR Lyrae instability strip suggest E( B - V) = 0.36 ± 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R) = +0.97 ± 0.1 and at least one "gap" located in an unusual part of the blue HB, in the middle of the so-called hot HB stars. © 2013. The American Astronomical Society. All rights reserved.

Atmospheric pressure plasma oxidation of AA6061-T6 aluminum alloy surface for strong and durable adhesive bonding applications - Saleema, N.; Gallant, D. (Applied Surface Science, 2013)
AA 6061-T6 aluminum alloy surface has been treated using atmospheric pressure helium-oxygen plasma at room temperature prior to bonding with a bi-component epoxy resin. The adhesive joint strengths were evaluated via single lap shear tests as prepared (pristine conditions) as well as following degradation by exposure to extreme temperature and humidity conditions (cataplasma conditions). Very high adhesion strength of 24 ± 1 MPa was achieved on surfaces after a very short exposure of the He/O2 plasma of only 15 s under pristine conditions resulting in cohesive failure of the adhesive itself. Best results were obtained under cataplasma conditions with adhesion strength of 22.6 ± 1 MPa by introducing a very simple pretreatment with scotch brite® prior to plasma exposure. With many different surface treatment methods being predominantly tested and evaluated, the adhesive bonding community may highly benefit from the present work as the treatment method uses very simple, economical and safe procedures in obtaining results comparable to benchmark methods such as Forest Products Laboratory (FPL) etch, anodization and so on.
Keywords: Adhesive bonding; Atmospheric pressure plasmas; IRRAS; Plasma oxidation; SEM/EDX; Adhesion; Adhesive joints; Aluminum; Atmospheric pressure; Bond strength (materials); Epoxy resins; Wetting

Fast and intense photoluminescence in a SiGe nano-layer embedded in multilayers of Si/SiGe clusters - Mala, S. A.; Tsybeskov, L.; Lockwood, D. J.; Wu, X.; Baribeau, J.-M. (Applied Physics Letters, 2013)
An intense photoluminescence (PL) peaking near 0.9 eV is emitted by a single Si1-xGex nanometer-thick layer (NL) with x ≈ 8% incorporated into Si/Si0.6Ge0.4 cluster multilayers (CMs). The SiGe NL PL does not saturate in output intensity with up to 50 mJ/cm^2 of excitation energy density, and it has nearly a 1000 times shorter lifetime compared to CM PL, which peaks at ∼0.8 eV. These dramatic differences in observed PL properties are attributed to different compositions and structures of the Si/SiGe NL and CM hetero-interfaces.
Keywords: Excitation energy density; Hetero-interfaces; Output intensity; PL property; Si/SiGe; Germanium; Multilayers; Silicon alloys; Photoluminescence

Strain analysis of highly scalable single InAs/InP quantum dots in a stress-sensitive environment - Mnaymneh, K.; Dalacu, D.; Poole, P. J.; Williams, R. L. (Applied Physics Letters, 2013)
We perform an experimental and computational study of the effects of external stress and intermixing on single site-selected InAs/InP quantum dots in a highly scalable stress-sensitive environment. While such effects are well known for their ability to tune emission spectra, little is known on how they influence emission shell spacing, electron-hole effective mass renormalization, and the physical size of the embedded quantum dot, which are all important parameters affecting the intended functionality. We show excellent agreement between experiment and finite-element solutions of the coupled Navier and Schrödinger equations, including recent atomistic pseudopotential calculations in the literature. These results indicate that using single self-assembled quantum dots in highly scalable, stress-sensitive settings as active elements in future bottom-up nanosystems offers greater versatility to not only quantum information systems where they serve as scalable single-photon sources but also to ultra-sensing capabilities in future nano-electro-mechanical architectures.
Keywords: Computational studies; Emission spectrums; InAs/InP quantum dots; Pseudopotential calculation; Quantum information systems; Self assembled quantum dots; Single-photon source; Stress sensitive; Emission spectroscopy; Quantum optics; Semiconductor quantum dots

Highly polarized emission from electrical spin injection into an InGaAs quantum well with free carriers - Li, C. H.; Kioseoglou, G.; Petrou, A.; Korkusinski, M.; Hawrylak, P.; Jonker, B. T. (Applied Physics Letters, 2013)
We report on a highly polarized emission from InGaAs/GaAs-quantum well light-emitting diodes in which we inject spin-polarized electrons from an Fe/Schottky contact. The emission spectra consist of the e1h 1 free exciton (FX) and a feature 12 meV below FX attributed to band-to-band (BB) recombination. The FX exhibits a maximum circular polarization of 22%, with a magnetic-field dependence characteristic of spin injection from Fe. The BB emission on the other hand exhibits a polarization that is strongly bias and temperature dependent, with intriguing magnetic-field dependence: The polarization exhibits a maximum of 78% at 2.5 T and 2 K, then decreases linearly with field and reaches -78% at 7 T, attributed to magnetic-field dependent spin relaxation in the presence of excess electrons.

Substrate profiling of cyclohexylamine oxidase and its mutants reveals new biocatalytic potential in deracemization of racemic amines - Li, Guangyue; Ren, Jie; Iwaki, Hiroaki; Zhang, Dalong; Hasegawa, Yoshie; Wu, Qiaqing; Feng, Jinhui; Lau, Peter C. K.; Zhu, Dunming (Applied Microbiology and Biotechnology, 2013)
A cyclohexylamine oxidase (CHAO) of bacterial origin was previously shown to be a potentially useful catalyst in the deracemization of racemic primary amines. To further explore the properties and application of this enzyme, five single-amino acid substitution mutants (L199A, M226A, Y321A, Y321F, and L353M) were created based on superimposition of the tertiary structure of CHAO and the monoamine oxidase (MAO) B homolog. The substrate specificity of the purified wild-type and five mutant enzymes were examined towards 38 structurally diverse amines. All the enzymes exhibited better activity for primary amines than secondary and tertiary amines and in general exhibited high stereoselectivity. Among the mutant enzymes, M226A displayed an enhanced activity (5-400 %) towards most substrates, and L353M showed 7-445 % higher activity towards primary aliphatic amines with cycloalkane or aromatic moieties. Kinetic parameters revealed that both Y321 mutants showed higher catalytic efficiency towards cyclooctanamine, whereas the wild-type CHAO (wt CHAO) was most efficient towards cyclohexylamine. The wt CHAO or variant L353M in combination with a borane-ammonia complex as reducing agent was applied to the deracemization of 1-aminotetraline to give the (R)-enantiomer, a precursor of an antidepressant drug Norsertraline, in good yield (73-76 %), demonstrating their application potential in chiral amine synthesis.

Camphor pathway redux: functional recombinant expression of 2,5-and 3,6-diketocamphane monooxygenases of Pseudomonas putida ATCC 17453 with their cognate flavin reductase catalyzing Baeyer-Villiger reactions - Iwaki, Hiroaki; Grosse, Stephan; Bergeron, Hélène; Leisch, Hannes; Morley, Krista; Hasegawa, Yoshie; Lau, Peter C. K. (Applied and Environmental Microbiology, 2013)
Whereas the biochemical properties of the monooxygenase components that catalyze the oxidation of 2,5-diketocamphane and 3,6-diketocamphane (2,5-DKCMO and 3,6-DKCMO, respectively) in the initial catabolic steps of (+) and (-) isomeric forms of camphor (CAM) metabolism in Pseudomonas putida ATCC 17453 are relatively well characterized, the actual identity of the flavin reductase (Fred) component that provides the reduced flavin to the oxygenases has hitherto been ill defined. In this study, a 37-kDa Fred was purified from a camphor-induced culture of P. putida ATCC 17453 and this facilitated cloning and characterization of the requisite protein. The active Fred is a homodimer with a subunit molecular weight of 18,000 that uses NADH as an electron donor (Km(32 μM), and it catalyzes the reduction of flavin mononucleotide (FMN) (Km=3.6 μM; kcat=283 s-¹) in preference to flavin adenine dinucleotide (FAD) (Km(19 μM; kcat(128 s-¹). Sequence determination of~40 kb of the CAM degradation plasmid revealed the locations of two isofunctional 2,5-DKCMO genes (camE25-1 for 2,5-DKCMO-1 and camE25-2 for 2,5-DKCMO-2) as well as that of a 3,6-DKCMO-encoding gene (camE36). In addition, by pulsed-field gel electrophoresis, the CAM plasmid was established to be linear and~533 kb in length. To enable functional assessment of the two-component monooxygenase system in Baeyer-Villiger oxidations, recombinant plasmids expressing Fred in tandem with the respective 2,5-DKCMO- and 3,6-DKCMO-encoding genes in Escherichia coli were constructed. Comparative substrate profiling of the isofunctional 2,5-DCKMOs did not yield obvious differences in Baeyer-Villiger biooxidations, but they are distinct from 3,6-DKCMO in the stereoselective oxygenations with various mono- and bicyclic ketone substrates.
Keywords: Baeyer Villiger oxidation; Baeyer-Villiger reaction; Biochemical properties; Flavin adenine dinucleotide; Flavin mono nucleotides (FMN); Pulsed field gel electrophoresis; Recombinant expression; Recombinant plasmid; Cams; DNA; Electrophoresis; Escherichia coli; Genes; Genetic engineering; Ketones; Oxygenation; Substrates; Camphor; bacteriology; bacterium; catalysis; electrokinesis; enzyme activity; gene expression; ketone; oxidation; plasmid; recombination; terpene

Potentiation of azole antifungals by 2-adamantanamine - LaFleur, Michael D.; Sun, Lingmei; Lister, Ida; Keating, John; Nantel, Andre; Long, Lisa; Ghannoum, Mahmoud; North, Jeffrey; Lee, Richard E.; Coleman, Ken; Dahl, Thomas; Lewis, Kim (Antimicrobial Agents and Chemotherapy, 2013)
Azoles are among the most successful classes of antifungals. They act by inhibiting 14 lanosterol demethylase in the ergosterol biosynthesis pathway. Oropharyngeal candidiasis (OPC) occurs in about 90% of HIV-infected individuals, and 4 to 5%are refractory to current therapies, including azoles, due to the formation of resistant biofilms produced in the course of OPC. We reasoned that compounds affecting a different target may potentiate azoles to produce increased killing and an antibiofilm therapeutic. 2-Adamantanamine (AC17) was identified in a screen for compounds potentiating the action of miconazole against biofilms of Candida albicans. AC17, a close structural analog to the antiviral amantadine, did not affect the viability of C. albicans but caused the normally fungistatic azoles to become fungicidal. Transcriptome analysis of cells treated with AC17 revealed that the ergosterol and filamentation pathways were affected. Indeed, cells exposed to AC17 had decreased ergosterol contents and were unable to invade agar. In vivo, the combination of AC17 and fluconazole produced a significant reduction in fungal tissue burden in a guinea pig model of cutaneous candidiasis, while each treatment alone did not have a significant effect. The combination of fluconazole and AC17 also showed improved efficacy (P value of 0.018) compared to fluconazole alone when fungal lesions were evaluated. AC17 is a promising lead in the search for more effective antifungal therapeutics.
Keywords: 2 adamantanamine; amantadine derivative; antifungal agent; ergosterol; fluconazole; miconazole; rimantadine; transcriptome; unclassified drug; voriconazole; biofilm; Candida albicans; controlled study; drug efficacy; drug potentiation; drug screening; fungicidal activity; fungus growth; genetic analysis; guinea pig; human cell; human tissue; IC 50; skin candidiasis

Effect of tertiary and secondary phosphines on low-temperature formation of quantum dots - Yu, Kui; Liu, Xiangyang; Zeng, Qun; Leek, Donald M.; Ouyang, Jianying; Whitmore, Kenneth Matthew; Ripmeester, John A.; Tao, Ye; Yang, Mingli (Angewandte Chemie - International Edition, 2013)
Getting to the TOP of things: The coordination of tri-n-octylphosphine (TOP) instead of diphenylphosphine (DPP) to cadmium oleate (Cd(OA)2) reveals how tertiary and secondary phosphines enhance the yield and reproducibility of the synthesis of nanocrystals by shifting the equilibrium of the reaction to the right (see picture). High Cd-to-Se and Se-to-TOP feed molar ratios facilitate the formation of Se[DOUBLE BOND]DPP by way of Se exchange from TOP to DPP.
Keywords: Diphenylphosphine; Feed molar ratio; Low temperature formation; Reproducibilities; Secondary phosphines; Semiconducting nanocrystals; Tri-n-octylphosphine; Coordination reactions; Density functional theory; Molecular modeling; Nanocrystals; Phosphorus compounds; Semiconductor quantum dots; Semiconducting selenium compounds; Phosphine derivative; Chemical structure; Cadmium; Cold Temperature; Models, Molecular; Oleic Acid; Phosphines

Structure of the benzene dimer - governed by dynamics - Schnell, Melanie; Erlekam, Undine; Bunker, P. R.; von Helden, Gert; Grabow, Jens-Uwe; Meijer, Gerard; van der Avoird, Ad (Angewandte Chemie - International Edition, 2013)
The benzene dimer, an important prototype for studying noncovalent interactions, exhibits characteristic splitting patterns in its rotational spectrum, which for a long time were not understood. A new theoretical model reveals their origin: a concerted internal motion involving sixfold hindered rotation tunneling of the molecule forming the stem of the T-shaped structure and tilt tunneling of the cap.
Keywords: Ab initio calculations; Hindered rotations; Internal rotations; Non-covalent interaction; Rotational spectra; Rotational spectroscopy; Splitting patterns; Theoretical models; Electron tunneling; Ions; Benzene

The formation mechanism of binary semiconductor nanomaterials: Shared by single-source and dual-source precursor approaches - Yu, Kui; Liu, Xiangyang; Zeng, Qun; Yang, Mingli; Ouyang, Jianying; Wang, Xinqin; Tao, Ye (Angewandte Chemie - International Edition, 2013)
One thing in common: The formation of binary colloidal semiconductor nanocrystals from single- (M(EEPPh2)n) and dual-source precursors (metal carboxylates M(OOCR)n and phosphine chalcogenides such as E=PHPh2) is found to proceed through a common mechanism. For CdSe as a model system 31Pa NMR spectroscopy and DFT calculations support a reaction mechanism which includes numerous metathesis equilibriums and Se exchange reactions.
Keywords: Binary semiconductors; Colloidal semiconductor nanocrystals; Formation mechanism; Metal-ligand interactions; Nanocrystal formation mechanism; Phosphine chalcogenides; phosphines; Reaction mechanism; Inorganic compounds; Molecular modeling; Nuclear magnetic resonance spectroscopy; Semiconductor quantum dots; Phosphorus compounds

Acid extraction for the determination of methyl mercury in biotissues by isotope dilution gas chromatography inductively coupled plasma-mass spectrometry - D'Ulivo, Lucia; Yang, Lu; Feng, Yong-Lai; Mester, Zoltán (Analytical Methods, 2013)
Methyl mercury (MeHg) is a common contaminant worldwide. Health authorities keep monitoring MeHg levels in biological and environmental samples to assess the corresponding exposure in the population. So far, a basic leaching has been mostly used for the MeHg extraction. In this study, it was demonstrated that methanesulfonic acid, commonly used for amino acid extraction, can be used for MeHg extraction. Species-specific isotope dilution was employed to achieve accurate results. The method was validated by analysis of dogfish liver certified reference material (DOLT-4). The derivatized extracts were then analyzed with gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS). Results obtained for MeHg in DOLT-4 are in agreement with the certified value (t-test, P = 0.05), confirming that methanesulfonic acid extraction is suitable for extraction of MeHg in biological tissues. This new procedure could be of particular interest in biological and toxicological studies where a simultaneous determination of MeHg and certain amino acids is sometimes required.

Absolute quantification of peptides by isotope dilution liquid chromatography-inductively coupled plasma mass spectrometry and gas chromatography/mass spectrometry - Liu, Rui; Hou, Xiandeng; Lv, Yi; McCooeye, Margaret; Yang, Lu; Mester, Zoltán (Analytical Chemistry, 2013)
Absolute quantitation of peptides/proteins in dilute calibration solutions used in various diagnostic settings is a major challenge. Here we report the absolute quantitation of peptides by non-species-specific isotope dilution liquid chromatography-inductively coupled plasma mass spectrometry (ID LC-ICPMS) based on stoichiometric Eu tagging. The method was validated by species-specific isotope dilution gas chromatography/mass spectrometry (GC/MS) analysis of constituent amino acids of the target peptide. Quantitative labeling of bradykinin peptide was accomplished with a commercially available 2′,2″-(10-(2-((2,5-dioxopyrrolidin-1-yl)oxy)-2-oxoethyl)-1,4,7, 10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (DOTA-NHS-ester) and subsequently tagged with Eu. A 151Eu-enriched spike was used for the non-species-specific ID LC-ICPMS determination of bradykinin. The non-species-specific ID LC-ICPMS method was cross-validated by a species-specific ID GC/MS approach, which is based on the determination of phenylalanine in bradykinin to derive the concentration of the peptide in the sample. The hydrolysis of the peptide into amino acids was achieved by microwave digestion with 4 M methanesulfonic acid, and derivatization of phenylalanine with methyl chloroformate (MCF) was performed prior to its detection by GC/MS based on a 13C-enriched phenylalanine spike. The accuracy of the method was confirmed at various concentration levels with a typical precision of better than 5% relative standard deviation (RSD) at 20 pmol for non-species-specific ID LC-ICPMS and 500 pmol for species-specific ID GC/MS. A detection limit (3 SD) of 7.2 fmol estimated for ID LC-ICPMS with a 10 μL injection volume from three procedure blanks was obtained for bradykinin, confirming the suitability of the method for the direct determination of peptides at trace levels. To the best of our knowledge, the proposed method is the first ICPMS peptide quantification strategy which employs an independent validation strategy using species-specific ID GC/MS for amino acid quantitation.
Keywords: Absolute quantification; Calibration solutions; Gas chromatography/Mass spectrometry; Methane sulfonic acid; Peptide quantification; Relative standard deviations; Species-specific isotope dilution; Validation strategies; Amino acids; Chromatography; Inductively coupled plasma mass spectrometry; Isotopes; Spectrometry; Trace analysis; Peptides

Reduction of measurement uncertainty by experimental design in high-order (double, triple, and quadruple) isotope dilution mass spectrometry: application to GC-MS measurement of bromide - Pagliano, Enea; Mester, Zoltán; Meija, Juris (Analytical and Bioanalytical Chemistry, 2013)
Since its introduction a century ago, isotope dilution analysis has played a central role in developments of analytical chemistry. This method has witnessed many elaborations and developments over the years. To date, we have single, double, and even triple isotope dilution methods. In this manuscript, we summarize the conceptual aspects of isotope dilution methods and introduce the quadruple dilution and the concept of exact matching triple and quadruple dilutions. The comparison of isotope dilution methods is performed by determination of bromide ions in groundwater using novel ethyl-derivatization chemistry in conjunction with GC/MS. We show that the benefits of higher-order isotope dilution methods are countered with a greater need for careful experimental design of the isotopic blends. Just as for ID2MS, ID3MS and ID4MS perform best when the isotope ratio of one sample/spike blend is matched with that of a standard/spike blend (exact matching). © 2013 Her Majesty the Queen in Right of Canada.

Papal chemistry challenge - Meija, Juris (Analytical and Bioanalytical Chemistry, 2013)
The article presents a quiz for readers to identify a certain element using a clue given in it. While searching for the sacred treasure, Robert Langdon of The Da Vinci Code encountered a cryptic clue: 'a knight whose funeral was presided over by a Pope.' Not much different from Langdon's, the clue for this challenge is: 'this element is Pope.' As with the election of a new Pope, once discovery of a new chemical element is officially recognized, a new name is adopted. The christening of an element, however, does not happen overnight as the assumption of regnal names by pontiffs. The element 114 was discovered in 1999, this discovery was confirmed a decade later in 2009, the element was officially recognized in 2011. To facilitate the scientific communications regarding elements which lack a formal name, a nomenclature of systematic naming has been established by the International Union of Pure and Applied Chemistry (IUPAC), the International body in charge of christening all new chemical elements.
Keywords: International union of pure and applied chemistries; Scientific communication; Systematic naming; Mass spectrometry; Surface analysis; Chemical elements

Strained lattice with persistent atomic order in Pt3Fe 2 intermetallic core-shell nanocatalysts - Prabhudev, Sagar; Bugnet, Matthieu; Bock, Christina; Botton, Gianluigi A. (ACS Nano, 2013)
Fine-tuning nanocatalysts to enhance their catalytic activity and durability is crucial to commercialize proton exchange membrane fuel cells. The structural ordering and time evolution of ordered Pt3Fe2 intermetallic core-shell nanocatalysts for the oxygen reduction reaction that exhibit increased mass activity (228%) and an enhanced catalytic activity (155%) compared to Pt/C has been quantified using aberration-corrected scanning transmission electron microscopy. These catalysts were found to exhibit a static core-dynamic shell regime wherein, despite treating over 10 000 cycles, there is negligible decrease (9%) in catalytic activity and the ordered Pt 3Fe2 core remained virtually intact while the Pt shell suffered a continuous enrichment. The existence of this regime was further confirmed by X-ray diffraction and the compositional analyses using energy-dispersive spectroscopy. With atomic-scale two-dimensional (2-D) surface relaxation mapping, we demonstrate that the Pt atoms on the surface are slightly relaxed with respect to bulk. The cycled nanocatalysts were found to exhibit a greater surface relaxation compared to noncycled catalysts. With 2-D lattice strain mapping, we show that the particle was about -3% strained with respect to pure Pt. While the observed enhancement in their activity is ascribed to such a strained lattice, our findings on the degradation kinetics establish that their extended catalytic durability is attributable to a sustained atomic order.
Keywords: Aberration-corrected scanning transmission electron microscopies; Compositional analysis; Enhanced catalytic activity; Lattice strain; Nanocatalysts; Oxygen reduction reaction; Scanning transmission electron microscopy; Two Dimensional (2 D); Atoms; Catalyst activity; Degradation; Durability; Electrolytic reduction; Energy dispersive spectroscopy; Proton exchange membrane fuel cells (PEMFC); Shells (structures); Surface relaxation; Transmission electron microscopy; Two dimensional; X ray diffraction; Platinum

Patient-specific scatter correction in clinical cone beam computed tomography imaging made possible by the combination of Monte Carlo simulations and a ray tracing algorithm - Thing, Rune S.; Bernchou, Uffe; Mainegra-Hing, Ernesto; Brink, Carsten (Acta Oncologica, 2013)
Purpose. Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from being fully implemented in a clinical setting. This study investigates the combination of using fast MC simulations to predict scatter distributions with a ray tracing algorithm to allow calibration between simulated and clinical CBCT images. Material and methods. An EGSnrc-based user code (egs-cbct), was used to perform MC simulations of an Elekta XVI CBCT imaging system. A 60keV x-ray source was used, and air kerma scored at the detector plane. Several variance reduction techniques (VRTs) were used to increase the scatter calculation efficiency. Three patient phantoms based on CT scans were simulated, namely a brain, a thorax and a pelvis scan. A ray tracing algorithm was used to calculate the detector signal due to primary photons. A total of 288 projections were simulated, one for each thread on the computer cluster used for the investigation. Results. Scatter distributions for the brain, thorax and pelvis scan were simulated within 2% statistical uncertainty in two hours per scan. Within the same time, the ray tracing algorithm provided the primary signal for each of the projections. Thus, all the data needed for MC-based scatter correction in clinical CBCT imaging was obtained within two hours per patient, using a full simulation of the clinical CBCT geometry. Conclusions. This study shows that use of MC-based scatter corrections in CBCT imaging has a great potential to improve CBCT image quality. By use of powerful VRTs to predict scatter distributions and a ray tracing algorithm to calculate the primary signal, it is possible to obtain the necessary data for patient specific MC scatter correction within two hours per patient.
Keywords: calibration; computed tomography scanner; cone beam computed tomography; image quality; imaging system; Monte Carlo method; phantom; radiation dose distribution; radiation scattering; simulation

Quantum memories and large-scale quantum coherence based on Raman interactions - Nunn, Josh; Sprague, Michael R.; Michelberger, Patrick S.; Champion, Tessa F. M.; Jin, Xian-Min; Langford, Nathan K.; Sussman, Benjamin J.; England, Duncan G.; Barbieri, Marco; Kolthammer, W. Steven; Walmsley, Ian A. (Photonics Society Summer Topical Meeting Series, 2013 IEEE, 2013)
Applied research into quantum technologies and fundamental research into the foundations of quantum mechanics run hand in hand, since our understanding of quantum correlations both advances, and is advanced by, our ability to control large quantum systems. The off-resonant Raman interaction of light with material systems provides a powerful tool both for quantum information processing, and for accessing macroscopic non-classical states of matter. We describe a recent demonstration of entanglement between the motion of separated diamond crystals at room temperature, and the implementation of quantum memories in cesium vapour that can store and retrieve photons on demand with a time-bandwidth product exceeding 2000, both based on Raman scattering. © 2013 IEEE.
Keywords: Foundations of quantum mechanics; Fundamental research; Quantum coherence; Quantum correlations; Quantum technologies; Quantum-information processing; Raman interactions; Time-bandwidth products; Quantum electronics; Quantum optics; Quantum entanglement

Femtosecond laser nanomachining initiated by ultraviolet multiphoton ionization - Yu, Xiaming; Bian, Qiumei; Chang, Zenghu; Corkum, P. B.; Lei, Shuting (Optics Express, 2013)
We report on the experimental results of 300 nm features generated on fused silica using a near-infrared (IR) femtosecond laser pulse initiated by an ultraviolet (UV) pulse. With both pulses at a short (~60 fs) delay, the damage threshold of the UV pulse is only 10% of its normal value. Considerable reduction of UV damage threshold is observed when two pulses are at ± 1.3 ps delay. The damage feature size of the combined pulses is similar to that of a single UV pulse. A modified rate equation model with the consideration of defect states is used to help explain these results. This concept can be applied to shorter wavelengths, e.g. XUV and X-ray, with the required fluence below their normal threshold.
Keywords: Combined pulse; Damage features; Damage threshold; Multiphoton ionization; Nanomachining; Near-infrared; Rate-equation models; Shorter wavelength; Fused silica; Photoionization; Ultrafast lasers; Ultrashort pulses

Near-infrared femtosecond laser machining initiated by ultraviolet multiphoton ionization - Yu, X.; Bian, Q.; Zhao, B.; Chang, Z.; Corkum, P. B.; Lei, S. (Applied Physics Letters, 2013)
We report on the experimental study of microstructures fabricated on the surface of fused silica by two femtosecond laser pulses, a tightly focused 266 nm beam followed by a loosely focused 800 nm beam. By setting the fluence of each pulse below the damage threshold, visible microstructures are fabricated using the combined beams. Our results suggest that the ultraviolet pulse generates seed electrons through multiphoton absorption, and the near-infrared pulse utilizes these electrons to cause damage by avalanche ionization.

Molecular alignment using circularly polarized laser pulses - Smeenk, C. T. L.; Corkum, P. B. (Journal of Physics B: Atomic, Molecular and Optical Physics, 2013)
We show that circularly polarized femtosecond laser pulses produce field-free alignment in linear and planar molecules. We study the rotational wavepacket evolution of O2 and benzene created by circularly polarized light. For benzene, we align the molecular plane to the plane of polarization. For O2, we demonstrate that circular polarization yields a net alignment along the laser propagation axis at certain phases of the evolution. Circular polarization gives us the ability to control alignment of linear molecules outside the plane of polarization, providing new capabilities for molecular imaging.

High harmonic cutoff energy scaling and laser intensity measurement with a 1.8 μm laser source - Shiner, A. D.; Trallero-Herrero, C.; Kajumba, N.; Schmidt, B. E.; Bertrand, J. B.; Kim, Kyung Taec; Bandulet, H.-C.; Comtois, D.; Kieffer, J.-C.; Rayner, D. M.; Corkum, P. B.; Légaré, F.; et al. (Journal of Modern Optics, 2013)
High harmonic generation in gas targets leads to the production of attosecond pulses. The process of high harmonic generation requires that the gas be ionized by an intense femtosecond laser field. The highest photon energy produced is related to the laser intensity times the wavelength squared. This cutoff is reached only if good phase matching is achieved. Using a laser with a wavelength of 1800 nm, we estimate the laser intensity in the gas jet by recording the ion yield, and simultaneously record the high harmonic spectrum. We show that the cutoff energy matches the measured intensity, confirming that good phase matching is achieved to 100 eV. We also use the ion collector to characterize the spatial size of the gas jet and to measure the confocal parameter of the laser beam, parameters that are useful for numerical modelling.
Keywords: high harmonic generation; phase matching

Trajectory-resolved Coulomb focusing in tunnel ionization of atoms with intense, elliptically polarized laser pulses - Shafir, D.; Soifer, H.; Vozzi, C.; Johnson, A. S.; Hartung, A.; Dube, Z.; Villeneuve, D. M.; Corkum, P. B.; Dudovich, N.; Staudte, A. (Physical Review Letters, 2013)
In strong-field light-matter interactions, the strong laser field dominates the dynamics. However, recent experiments indicate that the Coulomb force can play an important role as well. In this Letter, we have studied the photoelectron momentum distributions produced from noble gases in elliptically polarized, 800 nm laser light. By performing a complete mapping of the three-dimensional electron momentum, we find that Coulomb focusing significantly narrows the lateral momentum spread. We find a surprisingly sensitive dependence of Coulomb focusing on the initial transverse momentum distribution, i.e., the momentum at the moment of birth of the photoelectron. We also observe a strong signature of the low-energy structure in the above threshold ionization spectrum.

Control of energy deposition in femtosecond laser dielectric interactions - Peng, Jiahui; Grojo, David; Rayner, David M.; Corkum, Paul B. (Applied Physics Letters, 2013)
There are natural limits to the spatial resolution and the deposited energy densities that can be achieved in femtosecond laser dielectric modification. These arise because of the threshold-like nature of nonlinear absorption. We use two-pulse experiments to show that both limits can be exceeded by taking advantage of absorption seeded by free electrons or self-trapped excitons, depending on the pulse separation.

Femtosecond laser desorption of ultrathin polymer films from a dielectric surface - Mercadier, Laurent; Peng, Jiahui; Sultan, Yasir; Davis, Thomas A.; Rayner, David M.; Corkum, Paul B. (Applied Physics Letters, 2013)
By focusing femtosecond pulses on the front and rear surface of a fused silica coverslip, we desorb 8-nm thick polymer films at submicron scale. To determine the role of the substrate in the desorption process, we measure the threshold for nonlinear absorption in fused silica and compare it to the threshold for desorption, taking into account the enhancement of the field at the dielectric-air interface. The results indicate that absorption of energy only occurs in the film. We then measure the beam radius in situ by the knife-edge technique and characterize the desorption by atomic force microscopy. The radius of the laser desorbed area is determined by the desorption threshold intensity and can be a factor of 5 smaller than the beam waist

Petahertz optical oscilloscope - Kim, Kyung Taec; Zhang, Chunmei; Shiner, Andrew D.; Schmidt, Bruno E.; Légaré, François; Villeneuve, D. M.; Corkum, P. B. (Nature Photonics, 2013)
The time-dependent field of an electromagnetic pulse can be measured if there is a fast enough gate. For terahertz radiation, femtosecond photoinjection of free carriers into a semiconductor in the presence of the terahertz radiation can serve as the gate1. For visible or infrared radiation, attosecond photoionization of a gas target in the presence of the optical field is a direct analogue2–8. Here, we show that nonlinear optical mixing9–13 in a medium in which attosecond pulses are being generated can also be used to measure the time-dependent field of an optical pulse. The gate is the phase accumulated by the recollision electron during the subcycle time interval between ionization and recombination. We show that the instantaneous field of an unknown pulse is imprinted onto the deflection of the attosecond extreme ultraviolet pulse using an all-optical set-up with a bandwidth up to 1 PHz.

Photonic streaking of attosecond pulse trains - Kim, Kyung Taec; Zhang, Chunmei; Ruchon, Thierry; Hergott, Jean-François; Auguste, Thierry; Villeneuve, D. M.; Corkum, P. B.; Quéré, F. (Nature Photonics, 2013)
High harmonic radiation, produced when intense laser pulses interact with matter, is composed of a train of attosecond pulses. Individual pulses in this train carry information on ultrafast dynamics that vary from one half-optical-cycle to the next. Here, we demonstrate an all-optical photonic streaking measurement that provides direct experimental access to each attosecond pulse by mapping emission time onto propagation angle. This is achieved by inducing an ultrafast rotation of the instantaneous laser wavefront at the focus. We thus time-resolve attosecond pulse train generation, and hence the dynamics in the nonlinear medium itself. We apply photonic streaking to harmonic generation in gases and directly observe, for the first time, the influence of non-adiabatic electron dynamics and plasma formation on the generated attosecond pulse train. These experimental and numerical results also provide the first evidence of the generation of attosecond lighthouses in gases, which constitute ideal sources for attosecond pump–probe spectroscopy.

Not so loosely bound rare gas atoms : finite-temperature vibrational fingerprints of neutral gold-cluster complexes - Ghiringhelli, Luca M.; Gruene, Philipp; Lyon, Jonathan T.; Rayner, David M.; Meijer, Gerard; Fielicke, André; Scheffler, Matthias (New Journal of Physics, 2013)
We present an experimental and theoretical study of the structure of small, neutral gold clusters—Au3, Au4 and Au7—'tagged' by krypton atoms. Infrared (IR) spectra of AuNcenterdotKrM complexes formed at 100 K are obtained via far-IR multiple photon dissociation in a molecular beam. The theoretical study is based on a statistical (canonical) sampling of the AuNcenterdotKrM complexes through ab initio molecular dynamics using density-functional theory in the generalized gradient approximation, explicitly corrected for long-range van-der-Waals (vdW) interactions. The choice of the functional is validated against higher-level first-principle methods. Thereby finite-temperature theoretical vibrational spectra are obtained that are compared with the experimental spectra. This enables us to identify which structures are present in the experimental molecular beam for a given cluster size. For Au2, Au3 and Au4, the predicted vibrational spectra of the Kr-complexed and pristine species differ. For Au7, the presence of Kr influences the vibrational spectra only marginally. This behavior is explained in terms of the formation of a weak chemical bond between Kr and small gold clusters that localizes the Kr atom at a defined adsorption site, whereas for bigger clusters the vdW interactions prevail and the Kr adatom is delocalized and orbits the gold cluster. In all cases, at temperatures as low as T = 100 K, vibrational spectra already display a notable anharmonicity and show, in comparison with harmonic spectra, different position of the peaks, different intensities and broadenings, and even the appearance of new peaks.

Laser-induced orbital projection and diffraction of O-2 with velocity map imaging - Comtois, D.; Bandulet, H.-C.; Spanner, M.; Pavičić, D.; Meckel, M.; Zeidler, D.; Pépin, H.; Dörner, R.; Kieffer, J.-C.; Villeneuve, D. M.; Corkum, P. B.; Staudte, A. (Journal of Modern Optics, 2013)
In a velocity map imaging spectrometer, we measured the electron momentum distributions from the ionization of O molecules with 800 nm wavelength, 40 fs laser pulses at a peak intensity of W cm. The molecules were aligned at 0, 45 and 90 relative to the laser polarization prior to ionization. We show that for all alignments the low momentum region – populated by direct electrons which do not recollide with the parent ion – is consistent with the ionized orbital being filtered and projected onto the continuum electron wave packet. In the high momentum region – populated by rescattered electrons – we observe that the pattern created by diffraction of the recolliding wave packet by the ion core disappears as the alignment gets closer to the laser field axis. We find that a two-slit diffraction model agrees well with the results for molecules aligned at 90, but only partially predicts the decrease in the diffraction signature for smaller alignment angles.
Keywords: velocity map imaging; laser induced electron diffraction; orbital imaging

Performance evaluation of 3D imaging systems based on GD&T - Carrier, Benjamin; Mackinnon, David K.; Cournoyer, Luc (Manufacturing Letters, 2013)
We present a method for evaluating the performance of short-range non-contact 3D imaging systems. This method is intended to address the lack of internationally-recognized standards for the characterization of these systems. We begin by presenting characterization-speciﬁc terminology before introducing a geometrical and dimensional tolerancing-based approach for the characterization of these systems. This approach focuses on what these systems are typically used for rather than being designed speciﬁcally for speciﬁc classes of 3D imaging systems. A Portable Characterization Target (PCT) is then presented as an artifact that provides a simple way to perform the characterization of short-range non-contact 3D imaging systems.
Keywords: 3D imaging systems; performance; characterization; geometrical and dimensional tolerancing; 3D metrology

Linked attosecond phase interferometry for molecular frame measurements - Bertrand, J. B.; Wörner, H. J.; Salières, P.; Villeneuve, D. M.; Corkum, P. B. (Nature Physics, 2013)
High-harmonic spectroscopy uses attosecond techniques to measure single-atom or molecule photorecombination cross-sections. Whereas the amplitude of the extreme-ultraviolet light is easily measurable, the phase is more challenging to access. However, the phase contains information necessary for tomographic imaging of the molecular orbital wavefunction with attosecond–ångström resolution. Present techniques cannot simultaneously measure the phase as a function of molecular angle and photon frequency, which is necessary for a full reconstruction of the wavefunction. We overcome this limitation with an all-optical method that does not require any ad hoc assumptions about the phase. We apply it to record the full phase map of aligned bromine molecules relative to reference xenon atoms. It allows us to resolve, both spectrally and angularly, the participation of multiple molecular orbitals, and infer a phase of ionization. This method opens a path to time-resolved molecular orbital tomography.

Manipulation of quantum paths for space–time characterization of attosecond pulses - Kim, Kyung Taec; Zhang, Chunmei; Shiner, Andrew D.; Kirkwood, Sean E.; Frumker, Eugene; Gariepy, Genevieve; Naumov, Andrei; Villeneuve, D. M.; Corkum, P. B. (Nature Physics, 2013)
Attosecond extreme-ultraviolet pulses have a complex space–time structure. However, at present, there is no method to observe this intricate detail; all measurements of the duration of attosecond pulses are, to some extent, spatially averaged. A technique for determining the full space–time structure would enable a detailed study of the highly nonlinear processes that generate these pulses as a function of intensity without averaging. Here, we introduce and demonstrate an all-optical method to measure the space–time characteristics of an isolated attosecond pulse. Our measurements show that intensity-dependent phase and quantum-path interference both play a key role in determining the pulse structure. In the generating medium, the attosecond pulse is strongly modulated in space and time. Propagation modifies but does not erase this modulation. Quantum-path interference of the single-atom response, previously obscured by spatial and temporal averaging, may enable measuring the laser-field-driven ion dynamics with sub-cycle resolution.

Small platinum cluster hydrides in the gas phase - Kerpal, Christian; Harding, Dan J.; Rayner, David M.; Fielicke, André (The Journal of Physical Chemistry A, 2013)
The reactions of small cationic platinum clusters (Pt2+–Pt7+) with molecular hydrogen were investigated, and the structures of the hydride complexes were analyzed using IR spectroscopy. We determined the relative reaction rates for the addition of the first H2 molecule to the platinum clusters, and we report the hydrogen saturation coverages observed at high H2 concentration. High H atom per Pt atom ratios were observed, similar to earlier measurements on other group-10 transition metals. The structures of the fully saturated complexes of Pt2+–Pt5+ were investigated using a combination of infrared multiple-photon dissociation (IR-MPD) spectroscopy in the frequency range of 550–2050 cm–1 and density functional theory-based calculations. We found molecularly bound hydrogen alongside bridge and often atop binding of hydrogen atoms for all of the low-energy structures, in contrast to earlier theoretical predictions.

Molecular motions of adsorbed CO2 on a tetrazole-functionalized PIM polymer studied with 13C NMR - Moore, Jeremy K.; Guiver, Michael D.; Du, Naiying; Hayes, Sophia E.; Conradi, Mark S. (The Journal of Physical Chemistry C, 2013)
The CO2 adsorption in a polymer of intrinsic microporosity (PIM) functionalized by tetrazole (TZPIM) has been studied with in situ 13C nuclear magnetic resonance (NMR) spectroscopy at variable temperature and loading conditions. The CO2 molecules are seen to interact with tetrazole sites through physisorption. The adsorbed system was studied from 8 K to 385 K at two loadings of CO2. The 13C NMR resonance lineshapes and relaxation times have been analyzed to give insights into the adsorption process. The CO2 molecules undergo site to site hopping with accompanying CO2 reorientations while adsorbed on TZPIM, resulting in line narrowing starting near 100 K. Correspondingly, the spin echo T2 passes through a minimum at 100 K. The analysis indicates two kinds of adsorption sites are available.
Keywords: CO2; 13C NMR; in situ NMR; adsorption; membrane separation; PIM; tetrazole-functionalized

Artery phantoms for intravascular optical coherence tomography : diseased arteries - Bisaillon, Charles-Étienne; Lamouche, Guy (Journal of Biomedical Optics, 2013)
We propose and test various strategies for the creation of artery phantoms mimicking different kinds of diseased arteries when imaged by intravascular optical coherence tomography (IVCT). We first review the method for making artery phantoms. We then describe the procedure to fabricate diseased artery phantoms with intima thickening, lipid pool, thin-capped fibroatheroma, calcification, and restenosis (homogeneous and layered) after stent apposition. For each case, a phantom is fabricated, an IVOCT image is obtained and the image is compared to that of a real artery.
Keywords: medical imaging; coherent optical systems; tissues; targets

Distributed cavity phase calculation for a rectangular Ramsey cavity in NRC-FCs1 - Marmet, Louis; Dube, Pierre; Shtin, Nicolas; Lopez, J. Maricio (2013 Joint European Frequency and Time Forum & International Frequency Control Symposium (EFTF/IFC), 2013)
A preliminary calculation of the frequency shifts resulting from the distributed phase of a rectangular cavity is used to model frequency measurements of the fountain clock NRC-FCs1. The calculation is based on a numerical evaluation of the cavity field made with a finite element EM solver. The frequency shift is obtained by solving the Bloch-equations numerically along the path of the atoms on the free-fall trajectories through the cavity. We study the frequency shifts as a function of the launch direction, the tilt of the physics package and offsets in the position of the MOT relative to the axis defined by the state-selection cavity and the Ramsey cavity.

Quantifying the calibration uncertainty attributable to thermocouple inhomogeneity - Hill, Kenneth D.; Gee, Douglas J. (Temperature : Its Measurement and Control in Science and Industry, 2013)
Inhomogeneity in the Seebeck coefficient as a function of position along a thermocouple wire frequently dominates the uncertainty budgets of thermocouple calibration and use. The calibration process itself, simply through exposure to elevated temperatures for relatively modest times, generates both reversible and irreversible changes to the thermocouple that are a complex function of time, temperature, alloy composition, sheath structure, etc. We present data acquired using a salt bath at 250 °C to provide the step-function-like gradient that is our spatial probe of thermoelectric homogeneity. We show how the finite width of the step-function limits our ability to assess the "true" inhomogeneity of the thermocouple, and explore how the inhomogeneity impacts the calibration uncertainty attainable with the various thermal sources used for the calibration of thermocouples (based on their characteristic temperature gradients).
Keywords: Inhologeneity; Seebeck; thermocouple

Fast luminescence in silicon-germanium nanostructures - Lockwood, David J.; Wu, Xiaohua; Baribeau, Jean-Marc; Modi, Nikhil; Tsybeskov, Leonid (Luminescence and Display Materials: Fundamentals and Applications, 2013)
Epitaxially-grown three-dimensional Si/SiGe nanostructures produce photoluminescence and electroluminescence in the desired spectral range of 1.3-1.6 μm. We show that by controlling and modifying such Ge-rich SiGe nanoclusters during growth it is possible to fabricate very fast and hence more efficient SiGe light-emitting devices. The physics of carrier recombination in these Si/SiGe nanostructures is discussed. The present results provide another possible route toward CMOS compatible light emitters.
Keywords: Carrier recombination; CMOS Compatible; Light emitters; Light emitting devices; Si/SiGe; Silicon Germanium; Spectral range; Germanium; Light; Silicon alloys; Nanostructures

Diagnostic technique for smart maintenance of medium voltage power cables based on Depolarization Principle - Abou-Dakka, Mahmoud; McIntyre, Douglas (Proceedings of the Fourth International Meeting on Dielectric Materials, 2013)
In this paper, after showing the evolution of the insulation condition with aging time and its link to water trees, the results obtained from performing the depolarization techniques in-field on a large number of cables will be presented. The link between age of cable and its condition will be discussed. This would make a large step toward the development of a smart maintenance strategy for planning the replacement strategy of power cables.
Keywords: Diagnostic; Polarization/depolarization; cable maintenance strategy

Water-use efficiency Code requirements reach public review stage - Green, Diane (Construction Innovation, 2013)
The fall 2013 public review provides an opportunity to comment on proposed changes to add water-use efficiency requirements to the National Plumbing Code of Canada 2015. The proposed changes are issued for public review by the Canadian Commission on Building and Fire Codes (CCBFC).

Commission reviews standards for low lead in Canadian plumbing fittings - Green, Diane (Construction Innovation, 2013)
According to Health Canada, exposure to lead can be harmful to human health, even in small amounts. Everyone is exposed to trace amounts of it in air, soil, household dust and drinking water. Although drinking water is not the most significant source of exposure in Canada, lead can leach into the water system from the corrosion of pipes and fittings, especially if those fittings touch stagnant water.

Electrochemical characterization of anodic biofilm development in a microbial fuel cell - Martin, Edith; Savadogo, Oumarou; Guiot, Serge R.; Tartakovsky, Boris (Journal of Applied Electrochemistry, 2013)
Electrochemical impedance spectroscopy, cyclic voltammetry, and polarization tests were used to monitor the progress of the anode colonization by electrode-reducing microorganisms in a single-chamber membraneless microbial fuel cell seeded with anaerobic sludge. The electrochemical methods showed that an increase in microbial fuel cell power output coincided with a progressive decrease of the anode internal resistance and a more negative open circuit potential. Two redox systems were observed in cyclic voltammograms shortly after microbial fuel cell startup, while a redox system with a peak around −330 mV (vs. Ag/AgCl) was predominant in the mature biofilm. The redox systems were also dependent on the external resistance chosen for microbial fuel cell operation. This suggests that within the diverse microbial populations several species are capable of electron transfer to the anode, and that the microorganisms with the highest electron transfer rate become predominant. Furthermore, the growth of these electrode-reducing microorganisms can be accelerated by optimizing the microbial fuel cell electrical load.
Keywords: MFC; Anodic biofilm; Cyclic voltammetry; EIS; Internal resistance

An improved current-comparator-based power standard with an uncertainty of 2.5 μw/VA (k = 1) - So, E.; Arseneau, R.; Angelo, D. (IEEE Transactions on Instrumentation and Measurement, 2013)
An improved power standard derived from a current comparator power bridge for calibrating active/reactive power and energy meters under sinusoidal conditions is described. Measurements can be made at any power factor from zero lag through unity to zero lead, at positive or negative power, at 120 V, 5 A, and 50 or 60 Hz. The improved power standard has an estimated uncertainty of not more than 2.5 μW/VA at k = 1. Special high-accuracy current and voltage range extenders have been incorporated to extend the current and voltage ranges up to 200 A and 1200 V, respectively. © 2013 IEEE.
Keywords: Current comparators; High-accuracy; Power bridges; Power factors; Power standard; Sinusoidal conditions; uncertainty; Voltage ranges; Comparators (optical); Electric power factor; Electric power measurement; Uncertainty analysis

Studies of variability in proto-planetary nebulae. II. Light and velocity curve analyses of Iras 22272+5435 and 22223+4327 - Hrivnak, B.J.; Lu, W.; Sperauskas, J.; Van Winckel, H.; Bohlender, D.; Začs, L. (The Astrophysical Journal, 2013)
We have carried out a detailed observational study of the light, color, and velocity variations of two bright, carbon-rich proto-planetary nebulae, IRAS 22223+4327 and 22272+5435. The light curves are based upon our observations from 1994 to 2011, together with published data by Arkhipova and collaborators. They each display four significant periods, with primary periods for IRAS 22223+4327 and 22272+5435 being 90 and 132 days, respectively. For each of them, the ratio of secondary to primary period is 0.95, a value much different from that found in Cepheids, but which may be characteristic of post-asymptotic giant branch (AGB) stars. Fewer significant periods are found in the smaller radial velocity data sets, but they agree with those of the light curves. The color curves generally mimic the light curves, with the objects reddest when faintest. A comparison in seasons when there exist contemporaneous light, color, and velocity curves reveals that the light and color curves are in phase, while the radial velocity curves are ∼0.25 P out of phase with the light curves. Thus they differ from what is seen in Cepheids, in which the radial velocity curve is 0.50 P out of phase with the light curve. Comparison of the observed periods and amplitudes with those of post-AGB pulsation models shows poor agreement, especially for the periods, which are much longer than predicted. These observational data, particularly the contemporaneous light, color, and velocity curves, provide an excellent benchmark for new pulsation models of cool stars in the post-AGB, proto-planetary nebula phase. © 2013. The American Astronomical Society. All rights reserved.
Erratum published in volume 777, issue 1, article 80, 2013. DOI: 10.1088/0004-637X/777/1/80

Plant and bird presence strongly influences the microbial communities in soils of Admiralty Bay, Maritime Antarctica - Teixeira, L.C.R.S.; Yeargeau, E.; Balieiro, F.C.; Piccolo, M.C.; Peixoto, R.S.; Greer, C.W.; Rosado, A.S. (PLoS ONE, 2013)
Understanding the environmental factors that shape microbial communities is crucial, especially in extreme environments, like Antarctica. Two main forces were reported to influence Antarctic soil microbes: birds and plants. Both birds and plants are currently undergoing relatively large changes in their distribution and abundance due to global warming. However, we need to clearly understand the relationship between plants, birds and soil microorganisms. We therefore collected rhizosphere and bulk soils from six different sampling sites subjected to different levels of bird influence and colonized by Colobanthus quitensis and Deschampsia antarctica in Admiralty Bay, King George Island, Maritime Antarctic. Microarray and qPCR assays targeting 16S rRNA genes of specific taxa were used to assess microbial community structure, composition and abundance and analyzed with a range of soil physico-chemical parameters. The results indicated significant rhizosphere effects in four out of the six sites, including areas with different levels of bird influence. Acidobacteria were significantly more abundant in soils with little bird influence (low nitrogen) and in bulk soil. In contrast, Actinobacteria were significantly more abundant in the rhizosphere of both plant species. At two of the sampling sites under strong bird influence (penguin colonies), Firmicutes were significantly more abundant in D. antarctica rhizosphere but not in C. quitensis rhizosphere. The Firmicutes were also positively and significantly correlated to the nitrogen concentrations in the soil. We conclude that the microbial communities in Antarctic soils are driven both by bird and plants, and that the effect is taxa-specific. © 2013 Teixeira et al.
Keywords: nitrogen; RNA 16S; Acidobacteria; Antarctica; article; Colobanthus quitensis; community structure; controlled study; Deschampsia antarctica; environmental factor; Firmicutes; greenhouse effect; microarray analysis; microbial community; nitrogen concentration; nonhuman; penguin; plant; polymerase chain reaction; population abundance; rhizosphere; sampling; soil microflora; species distribution; taxon

Correlating infall with deuterium fractionation in dense cores - Schnee, S.; Brunetti, N.; Di Francesco, J.; Caselli, P.; Friesen, R.; Johnstone, D.; Pon, A. (The Astrophysical Journal, 2013)
We present a survey of HCO+ (3-2) observations pointed toward dense cores with previous measurements of N(N2D+)/N(N 2H+). Of the 26 cores in this survey, 5 show the spectroscopic signature of outward motion, 9 exhibit neither inward nor outward motion, 11 appear to be infalling, and 1 is not detected. We compare the degree of deuterium fractionation with infall velocities calculated from the HCO + spectra and find that those cores with [D]/[H] > 0.1 are more likely to have the signature of inward motions than cores with smaller [D]/[H] ratios. Infall motions are also much more common in cores with masses exceeding their thermal Jeans masses. The fastest infall velocity measured belongs to one of the two protostellar cores in our survey, L1521F, and the observed motions are typically on the order of the sound speed. © 2013. The American Astronomical Society. All rights reserved.

Nanoscale structuring of tungsten tip yields most coherent electron point-source - Mutus, J.Y.; Livadaru, L.; Urban, R.; Pitters, J.; Peter Legg, A.; Salomons, M.H.; Cloutier, M.; Wolkow, R.A. (New Journal of Physics, 2013)
This report demonstrates the most spatially-coherent electron source ever reported. A coherence angle of 14.3 ± 0.5° was measured, indicating a virtual source size of 1.7 ± 0.6 Å using an extraction voltage of 89.5 V. The nanotips under study were crafted using a spatially-confined, field-assisted nitrogen etch which removes material from the periphery of the tip apex resulting in a sharp, tungsten-nitride stabilized, high-aspect ratio source. The coherence properties are deduced from holographic measurements in a low-energy electron point source microscope with a carbon nanotube bundle as sample. Using the virtual source size and emission current the brightness normalized to 100 kV is found to be 7.9 × 108 A sr-1 cm2. © IOP Publishing and Deutsche Physikalische Gesellschaft.
Keywords: Coherence properties; Emission current; Extraction voltage; High-aspect ratio; Holographic measurement; Low energy electrons; Point source microscopes; Virtual sources; Aspect ratio; Electrons; Optical microscopy; Tungsten

A MegaCam survey of outer halo satellites. II. Blue stragglers in the lowest stellar density systems - Santana, F.A.; Muñoz, R.R.; Geha, M.; Côté, P.; Stetson, P.; Simon, J.D.; Djorgovski, S.G. (The Astrophysical Journal, 2013)
We present a homogeneous study of blue straggler stars across 10 outer halo globular clusters, 3 classical dwarf spheroidal galaxies, and 9 ultra-faint galaxies based on deep and wide-field photometric data taken with MegaCam on the Canada-France-Hawaii Telescope. We find blue straggler stars to be ubiquitous among these Milky Way satellites. Based on these data, we can test the importance of primordial binaries or multiple systems on blue straggler star formation in low-density environments. For the outer halo globular clusters, we find an anti-correlation between the specific frequency of blue stragglers and absolute magnitude, similar to that previously observed for inner halo clusters. When plotted against density and encounter rate, the frequency of blue stragglers is well fit by a single trend with a smooth transition between dwarf galaxies and globular clusters; this result points to a common origin for these satellites' blue stragglers. The fraction of blue stragglers stays constant and high in the low encounter rate regime spanned by our dwarf galaxies, and decreases with density and encounter rate in the range spanned by our globular clusters. We find that young stars can mimic blue stragglers in dwarf galaxies only if their ages are 2.5 ± 0.5 Gyr and they represent ∼1%-7% of the total number of stars, which we deem highly unlikely. These results point to mass-transfer or mergers of primordial binaries or multiple systems as the dominant blue straggler formation mechanism in low-density systems. © 2013. The American Astronomical Society. All rights reserved.

A pixel is an artifact: On the necessity of zero-filling in Fourier imaging - Zhu, X.; Tomanek, B.; Sharp, J. (Concepts in Magnetic Resonance Part A: Bridging Education and Research, 2013)
MR imaging data is sometimes presented in a "patchwork quilt" format with individual pixels visible as squares of uniform intensity. This phenomenon often arises by default from an image space convolution (performed implicitly by the graphics system) used to convert the sparse point sampling of the spatial domain offered by the discrete Fourier transform (DFT) into a sufficiently dense sampling to allow assignment of an intensity value to each addressable point on the display device. Typical examples are fMRI maps, spectroscopic images and zoomed-in views. These square patches are image structure not present in the object, i.e., artifacts. This form of image display is studied by both an image analysis method and by Fourier analysis. Image formation by display of the 2D DFT of an acquired k-space matrix as a 2D pixel array is a poor reconstruction because it does not ensure a faithful representation of the spatial frequency content actually present in the data. By analysis of the visual appearance of 2D pixel arrays we show that there are two principal effects: (a) attenuation of higher spatial frequencies (i.e., low-pass filtering); (b) introduction of artifactual high frequency image structure. These effects can lead to very poor performance with an artifact/signal ratio of over 200% in the corners of 2D k-space. Generated k-space maps demonstrate that both detrimental effects increase radially in k-space. The simple remedy is to zero-fill (resulting in image interpolation) until individual pixels become invisible in the displayed image. Alternatively, data modeling may be used. © 2013 Wiley Periodicals, Inc.

Aerodynamic characterization of a thin, high-performance airfoil for use in ground fluids testing - Broeren, A.P.; Lee, S.; Clark, C. (5th AIAA Atmospheric and Space Environments Conference, 2013)
The FAA has worked with Transport Canada and others to develop allowance times for aircraft operating in ice-pellet precipitation. Wind-tunnel testing has been carried out to better understand the flowoff characteristics and resulting aerodynamic effects of anti-icing fluids contaminated with ice pellets using a thin, high-performance wing section at the National Research Council of Canada Propulsion and Icing Wind Tunnel. The objective of this paper is to characterize the aerodynamic behavior of this wing section in order to better understand the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination. Aerodynamic performance data, boundary-layer surveys and flow visualization were conducted at a Reynolds number of approximately 6.0×106 and a Mach number of 0.12. The clean, baseline model exhibited leading-edge stall characteristics including a leading-edge laminar separation bubble and minimal or no separation on the trailing edge of the main element or flap. These results were consistent with expected 2-D aerodynamics and showed no anomalies that could adversely affect the evaluation of anti-icing fluids and ice-pellet contamination on the wing. Tests conducted with roughness and leading-edge flow disturbances helped to explain the aerodynamic impact of the anti-icing fluids and contamination. The stalling characteristics of the wing section with fluid and contamination appear to be driven at least partially by the effects of a secondary wave of fluid that forms near the leading edge as the wing is rotated in the simulated takeoff profile. These results have provided a much more complete understanding of the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination on this wing section. This is important since these results are used, in part, to develop the ice-pellet allowance times that are applicable to many different airplanes.
Keywords: Aero-dynamic performance; Aerodynamic characterization; Aerodynamic effect; Anti-icing fluids; Flow disturbances; Laminar separation bubble; National Research Council of Canada; Wind-tunnel testing; Contamination; Data visualization; Ice; Laminar flow; Pelletizing; Reynolds number; Wind tunnels; Aerodynamics

Distortion and residual stress measurements of induction hardened AISI 4340 discs - Yi, J.; Gharghouri, M.; Bocher, P.; Medraj, M. (Materials Chemistry and Physics, 2013)
10 Induction hardened discs with two initial hardness levels were used for exploring the influences of the variation of initial hardness as well as induction hardening (IH) recipes on the heat treatment distortions and hardening depth. The results show that for the same initial hardness, the larger the energy input, the higher the distortion size as well as the hardening depth. For a given induction hardening recipe, the increase in initial hardness leads to a deeper hardening depth but a smaller distortion. One disc was selected for the residual stress investigation in three orthogonal directions by neutron diffraction (ND). The corresponding stress-free lattice spacing d0 was measured from the same material using both ND and X-ray diffraction (XRD) methods. The ND results show that the variation of d0 in the hardened layer is significant and should be taken into account for stress calculation. However, regarding the core region, the d0 value measured by XRD is more reliable. Accordingly, a combination of the ND-measured d0 profiles in the hardened layer and the XRD-measured d0 value in the core was adopted for the determination of residual stress distributions. © 2013 Elsevier B.V. All rights reserved.
Keywords: Hardened layers; Hardening depth; Hardness levels; Induction hardening; Lattice spacing; Neutron scattering and diffraction; Orthogonal directions; Stress calculations; Hardness; Heat treatment; Induction heating; Metals; Neutron diffraction; Residual stresses; Stress concentration; X ray diffraction; Hardening

Analytical technologies for influenza virus-like particle candidate vaccines: Challenges and emerging approaches - Thompson, C.M.; Petiot, E.; Lennaertz, A.; Henry, O.; Kamen, A.A. (Virology Journal, 2013)
Influenza virus-like particle vaccines are one of the most promising ways to respond to the threat of future influenza pandemics. VLPs are composed of viral antigens but lack nucleic acids making them non-infectious which limit the risk of recombination with wild-type strains. By taking advantage of the advancements in cell culture technologies, the process from strain identification to manufacturing has the potential to be completed rapidly and easily at large scales. After closely reviewing the current research done on influenza VLPs, it is evident that the development of quantification methods has been consistently overlooked. VLP quantification at all stages of the production process has been left to rely on current influenza quantification methods (i.e. Hemagglutination assay (HA), Single Radial Immunodiffusion assay (SRID), NA enzymatic activity assays, Western blot, Electron Microscopy). These are analytical methods developed decades ago for influenza virions and final bulk influenza vaccines. Although these methods are time-consuming and cumbersome they have been sufficient for the characterization of final purified material. Nevertheless, these analytical methods are impractical for in-line process monitoring because VLP concentration in crude samples generally falls out of the range of detection for these methods. This consequently impedes the development of robust influenza-VLP production and purification processes. Thus, development of functional process analytical techniques, applicable at every stage during production, that are compatible with different production platforms is in great need to assess, optimize and exploit the full potential of novel manufacturing platforms. © 2013 Thompson et al.; licensee BioMed Central Ltd.
Keywords: influenza vaccine; influenza virus like particle vaccine; unclassified drug; virus protein; cell strain HEK293; DNA vector; electron microscopy; enzyme activity; enzyme linked immunosorbent assay; HeLa cell; immunodiffusion; Influenza virus; insect cell; protein analysis; reversed phase high performance liquid chromatography; review; Vero cell; virion; virus hemagglutination; virus strain; Western blotting; Orthomyxoviridae

Impact of water quality on the bacterial populations and off-flavours in recirculating aquaculture systems - Auffret, M.; Yergeau, E.; Pilote, A.; Proulx, E.; Proulx, D.; Greer, C.W.; Vandenberg, G.; Villemur, R. (FEMS Microbiology Ecology, 2013)
A variety of factors affecting water quality in recirculating aquaculture systems (RAS) are associated with the occurrence of off-flavours. In this study, we report the impact of water quality on the bacterial diversity and the occurrence of the geosmin-synthesis gene (geoA) in two RAS units operated for 252 days. Unit 2 displayed a higher level of turbidity and phosphate, which affected the fresh water quality compared with unit 1. In the biofilter, nitrification is one of the major processes by which high water quality is maintained. The bacterial population observed in the unit 1 biofilter was more stable throughout the experiment, with a higher level of nitrifying bacteria compared with the unit 2 biofilter. Geosmin appeared in fish flesh after 84 days in unit 2, whereas it appeared in unit 1 after 168 days, but at a much lower level. The geoA gene was detected in both units, 28 days prior to the detection of geosmin in fish flesh. In addition, we detected sequences associated with Sorangium and Nannocystis (Myxococcales): members of these genera are known to produce geosmin. These sequences were observed at an earlier time in unit 2 and at a higher level than in unit 1. This study confirms the advantages of new molecular methods to understand the occurrence of geosmin production in RAS. © 2012 Federation of European Microbiological Societies.
Keywords: 2 methylisoborneol; 2-methylisoborneol; bornane derivative; fresh water; geosmin; naphthol derivative; aquaculture; bacterium; biofiltration; gene expression; nitrification; phosphate; population structure; species diversity; turbidity; water quality; animal; aquaculture; article; bacterium; chemistry; genetics; isolation and purification; metabolism; microbiology; nitrification; rainbow trout; water quality; Animals; Aquaculture; Bacteria; Bornanes; Fresh Water; Naphthols; Nitrification; Oncorhynchus mykiss; Water Quality; Bacteria (microorganisms); Myxococcales; Nannocystis; Sorangium

Dynamical magnetic and nuclear polarization in complex spin systems: Semi-magnetic II-VI quantum dots - Abolfath, R.M.; Trojnar, A.; Roostaei, B.; Brabec, T.; Hawrylak, P. (New Journal of Physics, 2013)
Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems. © 2013 IOP Publishing and Deutsche Physikalische Gesellschaft.
Keywords: Dipole interaction; Electron spin transfer; Hyperfine interactions; II-VI quantum dots; Nuclear polarization; Nuclear-spin polarization; Radiative recombination; Spin-polarized excitons; Excitons; Polarization; Semiconductor quantum dots; Spin dynamics; Magnetism

Verification of icephobic/anti-icing properties of a superhydrophobic surface - Wang, Y.; Xue, J.; Wang, Q.; Chen, Q.; Ding, J. (ACS Applied Materials and Interfaces, 2013)
Four aluminum surfaces with wettability varied from superhydrophilic to superhydrophobic were prepared by combining an etching and a coating process. The surface wettability was checked in terms of water contact angle (CA) and sliding angle (SA) under different humidity at -10 C. High-speed photography was applied to study water droplet impact dynamics on these surfaces. It was found that single and successive water droplets could rebound on the superhydrophobic surface and roll off at a tilt angle larger than 30 under an extremely condensing weather condition (-10 C and relative humidity of 85-90%). In addition, the superhydrophobic surface showed a strong icephobic property, the ice adhesion on this surface was only 13% of that on the superhydrophilic surface, though they had a similar nano/microtopological structure. Moreover, this superhydrophobic surface displayed an excellent durability of the icephobic property. The ice adhesion only increased to 20% and 16% of that on the superhydrophobic surface after the surface was undergone 20 icing/ice-breaking cycles and 40 icing/ice-melting cycles, respectively. Surface profile and XPS studies on these surfaces indicated a minor damage of the surface nano/microstructure and the coating layer upon these multiple ice-breaking and ice-melting processes. Therefore, this superhydrophobic surface could be a good candidate for icephobic applications. © 2013 American Chemical Society.
Keywords: ice-repellent; Impact dynamics; Sliding angle; Super-hydrophobic surfaces; Superhydrophilic surface; Superhydrophobic; Surface wettability; Water contact angle; Adhesion; Atmospheric humidity; Coatings; Contact angle; High speed photography; Ice; Surface properties; Temperature; Wetting; Hydrophobicity

Increased microbial activity and nitrogen mineralization coupled to changes in microbial community structure in the rhizosphere of Bt corn - Velasco, A.G.V.; Kowalchuk, G.A.; Mañero, F.J.G.; Ramos, B.; Yergeau, E.; García, J.A.L. (Applied Soil Ecology, 2013)
The interactions between plant roots and soil microorganisms are essential for the function and stability of ecosystems, primary agricultural production and plant health. Despite the importance of soil microbes the response of these microbes to large-scale cultivation of genetically modified (GM) crops is still poorly understood. This study evaluated the potential impact of two lines of transgenic Bt maize on rhizosphere microorganisms. A time-course field experiment was conducted over a period of two years in two fields in Guadalajara (Spain) with monthly sampling from April to September. Rhizosphere soil was collected from transgenic (TG) and unmodified (WT) maize plants from each field and sampling time for the analysis of several important functional and structural soil quality parameters. Total microbial activity, as determined by H3-Thymidine and C14-Leucine incorporation, was found to be higher in the rhizospheres of the transgenic plants. Similarly, differences in potential ammonification and nitrification were observed in the second year of the study. In contrast, bacterial and fungal microbial catabolic abilities, as determined by Biolog ECO and FF plate analyses, respectively, were more influenced by sampling time than the transgenic nature of the plants. Microbial community structure was also studied by bacterial and phylum-specific PCR-DGGE and PCR cloning approaches. In general, differences were again more pronounced between sampling times, as opposed to between TG versus WT plants, although marked differences were observed within the Betaproteobacteria between plant lines. For the first time it describes the presence of Iamiaceae family in soil, specifically to TG plant rhizosphere. To summarize, the study showed that some important properties of rhizopshere microbes may be impacted by Bt maize cultivation and highlighted the fact that such potential effects need to be viewed within the context of seasonal and spatial variability. © 2013 Elsevier B.V.

Morphological and rheological properties of PET/clay nanocomposites - Ghanbari, A.; Heuzey, M.-C.; Carreau, P.J.; Ton-That, M.-T. (Rheologica Acta, 2013)
This work investigates the effects of clay chemistry and concentration on the morphology and rheology of polyethylene terephthalate (PET)/clay nanocomposites. The complex viscosity of the PET nanocomposites exhibited a more solid-like behavior, in contrast to the matrix that had a frequency-independent viscosity. In addition, at high frequencies where the behavior of the matrix should be dominant, a lower complex viscosity of the nanocomposites was observed due to PET degradation in the presence of the organoclays. The high-frequency data were used to estimate the matrix degradation using the Maron-Pierce equation. The apparent molecular weight of the PET matrix was found to decrease from 65 kg/mol for the neat PET to 30 kg/mol for a PET nanocomposite containing 8 wt% Cloisite® 30B. The apparent yield stress in the nanocomposites was determined using the Herschel-Bulkley model. Yield stress increased with the level of exfoliation and clay concentration, from ~0 to 166 Pa when the clay concentration increased from 2 to 8 wt%. © 2012 Springer-Verlag Berlin Heidelberg.

Selective pharmacological modulation of pyramidal neurons and interneurons in the CA1 region of the rat hippocampus - Martina, M.; Comas, T.; Mealing, G.A.R. (Frontiers in Pharmacology, 2013)
The hippocampus is a complex network tightly regulated by interactions between excitatory and inhibitory neurons. In neurodegenerative disorders where cognitive functions such as learning and memory are impaired this excitation-inhibition balance may be altered. Interestingly, the uncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist memantine, currently in clinical use for the treatment of Alzheimer's disease, may alter the excitation-inhibition balance in the hippocampus. However, the specific mechanism by which memantine exerts this action is not clear. To better elucidate the effect of memantine on hippocampal circuitry, we studied its pharmacology on NMDAR currents in both pyramidal cells (PCs) and interneurons (Ints) in the CA1 region of the hippocampus. Applying whole-cell patch-clamp methodology to acute rat hippocampal slices, we report that memantine antagonism is more robust in PCs than in Ints. Using specific NMDAR subunit antagonists, we determined that this selective antagonism of memantine is attributable to specific differences in the molecular make-up of the NMDARs in excitatory and inhibitory neurons. These findings offer new insight into the mechanism of action and therapeutic potential of NMDA receptor pharmacology in modulating hippocampal excitability. © 2013 Martina, Comas and Mealing.
Keywords: AMPA receptor; dizocilpine; memantine; n methyl dextro aspartic acid receptor; n methyl dextro aspartic acid receptor 1; n methyl dextro aspartic acid receptor 2A; n methyl dextro aspartic acid receptor 2B; n methyl dextro aspartic acid receptor 2C; animal cell; animal tissue; article; cell structure; cellular distribution; concentration response; controlled study; dose response; drug antagonism; excitatory postsynaptic potential; hippocampal CA1 region; hyperpolarization; inhibitory postsynaptic potential; interneuron; membrane steady potential; nerve cell stimulation; neurotransmission; nonhuman; patch clamp; protein expression; pyramidal nerve cell; rat; stratum radiatum

Detecting concept relations in clinical text: Insights from a state-of-the-art model - Zhu, X.; Cherry, C.; Kiritchenko, S.; Martin, J.; de Bruijn, B. (Journal of Biomedical Informatics, 2013)
This paper addresses an information-extraction problem that aims to identify semantic relations among medical concepts (problems, tests, and treatments) in clinical text. The objectives of the paper are twofold. First, we extend an earlier one-page description (appearing as a part of [5]) of a top-ranked model in the 2010 I2B2 NLP Challenge to a necessary level of details, with the belief that feature design is the most crucial factor to the success of our system and hence deserves a more detailed discussion. We present a precise quantification of the contributions of a wide variety of knowledge sources. In addition, we show the end-to-end results obtained on the noisy output of a top-ranked concept detector, which could help construct a more complete view of the state of the art in the real-world scenario. As the second major objective, we reformulate our models into a composite-kernel framework and present the best result, according to our knowledge, on the same dataset. © 2012.
Keywords: Electronic health record; Knowledge sources; Medical concepts; NAtural language processing; Real-world scenario; Semantic relations; State of the art; Text mining; Algorithms; Artificial intelligence; Data mining; Medical problems; Semantics; Natural language processing systems; accuracy; article; data extraction; human; kernel method; priority journal; semantics

Data mining based fault isolation with FMEA rank: A case study of APU fault identification - Yang, C.; Létourneau, S.; Yang, Y.; Liu, J. (PHM 2013 - 2013 IEEE International Conference on Prognostics and Health Management, Conference Proceedings, 2013)
FMEA (Failure Mode and Effects Analysis), which was developed to enhance the reliability of complex systems, is a standard method to characterize and document product and process problems and a systematic method for fault identification/isolation in maintenance industry. Fault identification for a given failure effect or mode is a reactive process. Usually, a failure has occurred and it needs to identify which component is the root cause or to isolate the fault to a specific contributing component. Traditional method is to conduct TSM (Trouble Shooting Manuals)-based fault isolation, which is complicated, expensive, and time-consuming. To efficiently perform fault isolation, this paper proposed data mining-based framework for fault isolation by using FMEA information to rank data-driven models. In this paper, we present the proposed framework along with a case study for APU fau It identification. © 2013 IEEE.

Identification of the common antigenic determinant shared by Streptococcus pneumoniae serotypes 33A, 35A, and 20 capsular polysaccharides - Lin, F.L.; Vinogradov, E.; Deng, C.; Zeller, S.; Green, B.A.; Jansen, K.U.; Pavliak, V. (Carbohydrate Research, 2013)
In order to better understand cross-reactions of serogroup 33 polysaccharides and the typing sera, the structure of pneumococcal capsular polysaccharide serotype 33A was elucidated. Serotype 33A has been shown to have an identical polysaccharide backbone as that of serotype 33F, with two additional sites of O-acetylation at C5, and C6 of the 3-β-Galf residue in serotype 33A. This finding is consistent with the presence of an additional functional acetyltransferase gene (wcjE) in the cps biosynthetic locus of serotype 33A compared to 33F. The identical polysaccharide backbone with at least one common O-acetylation site (C2 of 5-β-Galf) shared by serotype 33A and 33F polysaccharides is proposed to be the epitope recognized by typing serum 33b. In addition, a 5,6-di-O-acetylated →3)-β-d-Galf5,6Ac- (1→3)-β-d-Glcp-(1→ disaccharide unit, a common structural motif present in serotypes 33A, 20, and 35A polysaccharides, is proposed to be the antigenic determinant recognized by typing serum 20b. © 2013 Published by Elsevier Ltd.
Keywords: Acetyl transferase; Antigenic determinant; Capsular polysaccharides; Serotypes; Streptococcus pneumoniae; Acetylation; Body fluids; Polysaccharides; Antigens; acyltransferase; bacterial polysaccharide; disaccharide; epitope; monosaccharide; acetylation; anion exchange chromatography; article; capillary electrophoresis; chemical structure; linkage analysis; nonhuman; nuclear magnetic resonance spectroscopy; priority journal; serotype; Streptococcus pneumoniae

A magnetic confinement versus rotation classification of massive-star magnetospheres - Petit, V.; Owocki, Department of Physics and Astronomy; Wade, Department of Physics; Cohen, D.H.; Sundqvist, J.O.; Gagne, M.; Máiz Apellaniz, J.; Oksala, M.E.; Bohlender, D.A.; Rivinius, T.; Henrichs, H.F.; Alecian, E.; et al. (Monthly Notices of the Royal Astronomical Society, 2013)
Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfv́en radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organization of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff> 16 kK. Using these parameters, we locate the stars in the magnetic confinement-rotation diagram, a log-log plot of RK versus RA. This diagram can be subdivided into regimes of centrifugal magnetospheres (CM), with RA > RK, versus dynamical magnetospheres (DM), with RK > RA. We show how key observational diagnostics, like the presence and characteristics of Ha emission, depend on a star-s position within the diagram, as well as other parameters, especially the expected wind mass-loss rates. In particular, we identify two distinct populations of magnetic stars with Ha emission: namely, slowly rotating O-type stars with narrow emission consistent with a DM, and more rapidly rotating B-type stars with broader emission associated with a CM. For O-type stars, the high mass-loss rates are sufficient to accumulate enough material for line emission even within the relatively short free-fall time-scale associated with a DM: this high mass-loss rate also leads to a rapid magnetic spindown of the stellar rotation. For the B-type stars, the longer confinement of a CMis required to accumulate sufficient emitting material from their relatively weak winds, which also lead to much longer spindown time-scales. Finally, we discuss how other observational diagnostics, e.g. variability of UV wind lines or X-ray emission, relate to the inferred magnetic properties of these stars, and summarize prospects for future developments in our understanding of massive-star magnetospheres©2012 The Authors.

Variable stars in the globular cluster NGC 2808 - Kunder, A.; Stetson, P.B.; Catelan, M.; Walker, A.R.; Amigo, P. (Astronomical Journal, 2013)
The first calibrated broadband BVI time-series photometry is presented for the variable stars in NGC 2808, with observations spanning a range of 28 years. We have also redetermined the variability types and periods for the variable stars identified previously by Corwin et al., revising the number of probable fundamental-mode RR Lyrae variables (RR0) to 11 and the number of first-overtone variables (RR1) to five. Our observations were insufficient to discern the nature of the previously identified RR1 star, V24, and the tentatively identified RR1 star, V13. These two variables are ∼0.8 mag brighter than the RR Lyrae variables, appear to have somewhat erratic period and/or luminosity changes, and lie inside the RR Lyrae instability strip. Curiously, all but one of the RR Lyrae stars studied in this relatively metal-rich cluster exhibit the Blazhko phenomenon, an effect thought to occur with higher frequency in metal-poor environments. The mean periods of the RR0 and RR1 variables are 〈P〉RR0 = 0.56 ± 0.01 d and 0.30 ± 0.02 d, respectively, supporting an Oosterhoff I classification of the cluster. On the other hand, the number ratio of RR1-to-RR0-type variables is high, though not unprecedented, for an Oosterhoff I cluster. The RR Lyrae variables have no period shifts at a given amplitude compared to the M3 variables, making it unlikely that these variables are He enhanced. Using the recent recalibration of the RR Lyrae luminosity scale by Catelan & Cortés, a mean distance modulus of (m-M)V = 15.57 ± 0.13 mag for NGC 2808 is obtained, in good agreement with that determined here from its type II Cepheid and SX Phoenicis population. Our data have also allowed the discovery of two new candidate SX Phoenicis stars and an eclipsing binary in the blue straggler region of the NGC 2808 color-magnitude diagram. © 2013. The American Astronomical Society. All rights reserved.

Microwave-enhanced dephasing time in a HgCdTe film - Wei, L.M.; Gao, K.H.; Liu, X.Z.; Yu, G.; Wang, Q.W.; Lin, T.; Guo, S.L.; Wei, Y.F.; Yang, J.R.; He, L.; Dai, N.; Chu, J.H.; et al. (Applied Physics Letters, 2013)
The antilocalization effect in a compensated HgCdTe film is observed. With an applied microwave field, both the zero-magnetic-field conductance and the dephasing time are enhanced nonlinearly with microwave power. The observation concerning the dephasing time is inconsistent with a heating mechanism. Such behavior is also in contrast to the microwave-induced suppression of weak-antilocalization and dephasing time seen for a two-dimensional electron gas of the anodic-oxidized HgCdTe. The nonlinear increase in zero-magnetic-field conductance is consistent with a microwave-assisted-hopping mechanism. The increased dephasing time can be explained qualitatively by the microwave-assisted-hopping mechanism and a microwave-induced increase in the electron density. © 2013 American Institute of Physics.
Keywords: Anti-localization effects; Dephasing; Heating mechanisms; HgCdTe; HgCdTe films; Microwave field; Microwave power; Electron gas; Mercury compounds

The effect of drying method on ordinary Portland cement surfaces during the early stages of hydration - Makar, J.M.; Sato, T. (Materials and Structures/Materiaux et Constructions, 2013)
During the early stages of ordinary Portland cement (OPC) hydration, ettringite, calcium hydroxide and C-S-H form on the OPC surface while nanoscale pits are formed in the exposed surface areas. In order to study these features using high resolution electron microscopy, samples must be appropriately dried to remove unbound water. The work reported here compares the effects of freeze-drying to drying by solvent exchange using four different solvents on the surface features of OPC after four hours of hydration in order to determine whether the solvent exchange process produces nanoscale changes in the surface features that can be detected using high resolution scanning electron microscopy (SEM). A quantitative image analysis of secondary electron SEM images was performed and the results analyzed using small sample statistics. They suggest that all of the solvent exchange methods damage the OPC surface and produce surface structures not seen in the freeze-dried samples. Caution is therefore warranted in the use of solvent exchange in the preparation of samples for the study of the dissolution of OPC surfaces. © 2012 RILEM.
Keywords: Different solvents; Drying methods; Ettringites; High-resolution scanning electron microscopies; Nano scale; Ordinary Portland cement; Quantitative image analysis; Secondary electrons; SEM image; Small sample statistics; Solvent exchanges; Surface area; Surface feature; Dissolution; Electron microscopy; High resolution electron microscopy; Hydrated lime; Hydration; Nanotechnology; Scanning electron microscopy; Solvents

Multiplexed electrokinetic sample fractionation, preconcentration and elution for proteomics - Hua, Y.; Jemere, A.B.; Dragoljic, J.; Harrison, D.J. (Lab on a Chip - Miniaturisation for Chemistry and Biology, 2013)
Both 6 and 8-channel integrated microfluidic sample pretreatment devices capable of performing "in space" sample fractionation, collection, preconcentration and elution of captured analytes via sheath flow assisted electrokinetic pumping are described. Coatings and monolithic polymer beds were developed for the glass devices to provide cationic surface charge and anodal electroosmotic flow for delivery to an electrospray emitter tip. A mixed cationic ([2-(methacryloyloxy)ethyl] trimethylammonium chloride) (META) and hydrophobic butyl methacrylate-based monolithic porous polymer, photopolymerized in the 6- or 8-fractionation channels, was used to capture and preconcentrate samples. A 0.45 wt% META loaded bed generated comparable anodic electroosmotic flow to the cationic polymer PolyE-323 coated channel segments in the device. The balanced electroosmotic flow allowed stable electrokinetic sheath flow to prevent cross contamination of separated protein fractions, while reducing protein/peptide adsorption on the channel walls. Sequential elution of analytes trapped in the SPE beds revealed that the monolithic columns could be efficiently used to provide sheath flow during elution of analytes, as demonstrated for neutral carboxy SNARF (residual signal, 0.08% RSD, n = 40) and charged fluorescein (residual signal, 2.5% n = 40). Elution from monolithic columns showed reproducible performance with peak area reproducibility of ∼8% (n = 6 columns) in a single sequential elution and the run-to-run reproducibility was 2.4-6.7% RSD (n = 4) for elution from the same bed. The demonstrated ability of this device design and operation to elute from multiple fractionation beds into a single exit channel for sample analysis by fluorescence or electrospray mass spectrometry is a crucial component of an integrated fractionation and assay system for proteomics. © 2013 The Royal Society of Chemistry.
Keywords: [2 (methacryloyloxy)ethyl] trimethylammonium chloride; fluorescein isothiocyanate; polymer; unclassified drug; article; electroosmosis; electrospray mass spectrometry; elution; fluorescence; microfluidics; polymerization; priority journal; proteomics; solid phase extraction

Investigation of corrosion behavior of wrought Co-Cr-W super alloys - Zhang, X.Z.; Liu, R.; Chen, K.Y.; Yao, M.X. (NACE - International Corrosion Conference Series, 2013)
The corrosion behavior of two wrought Co-Cr-W superalloys is studied under both polarization immersion tests. The corrosive media, Green Death solution, is used in both tests. Potentiodynamic polarization and cyclic polarization testes are performed to investigate general and localized corrosion resistance of these alloys. Immersion tests of the two alloys are conducted in Green Death solution to determine Critical Pitting Temperature (CPT), mass loss, thickness change and the Extreme Value (minimum thickness) using Extreme Value Analysis (EVA) model derived from the Gumbel Distribution. A Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDX) spectrum is utilized to analyze the chemical composition of the corrosion products (pits). The presence of carbides generates potential in the electrochemical reaction, causing corrosion of the alloys in the solution. The larger the carbide volume fraction, the more the pits are formed in the alloy. Carbide size also affects maximum pit depths; the larger the carbide size, the bigger and deeper the pits. The EDX analysis results of pits show large amount of oxygen in the carbide phase and a small amount of oxygen in the solid solution phase. The Cr-rich carbides react with oxygen forming Cr-rich carbonates which are easily brittle, loose and broken. © 2013 by NACE International.

Strongly magnetic iron nanoparticles improve the fiagnosis of small tumours in the reticuloendothelial system by magnetic resonance imaging - Ferguson, P.M.; Feindel, K.W.; Slocombe, A.; MacKay, M.; Wignall, T.; Delahunt, B.; Tilley, R.D.; Hermans, I.F. (PLoS ONE, 2013)
Despite advances in non-invasive medical imaging, accurate nodal staging of malignancy continues to rely on surgery. Superparamagnetic iron oxide nanoparticles (IONP) with lymphotropic qualities have shown some promise as contrast agents for MRI of the lymph nodes, but recent large-scale studies failed to show consistent detection of tumours below 5 mm. Herein we compare imaging of splenic and lymph node tissue using iron/iron oxide core/shell nanoparticles (Fe NP) that have superior magnetic qualities to IONP, to determine whether improved negative contrast in T2-weighted MRI can enhance the diagnosis of small tumours in the reticuloendothelial system. To provide an in vivo pre-clinical model of human lymph node micrometastases, breast cancer cells were injected into the spleens of mice, providing localised areas of tumour growth. MR images of groups of tumour-bearing and sham-treated animals were generated using a 1.5 T imaging system and analysed by two independent, blinded radiologists. Fe NP improved the sensitivity and specificity of MRI when compared to IONP, enabling accurate detection of tumours as small as 1-3 mm. The use of Fe NP as contrast agents have the potential to improve the diagnostic accuracy of MRI in cancer patients, leading to more rapid and effective treatment. © 2013 Ferguson et al.
Keywords: superparamagnetic iron oxide nanoparticle; animal cell; animal experiment; animal model; article; breast cancer; cancer cell; controlled study; diagnostic accuracy; diagnostic test accuracy study; image analysis; image display; in vivo study; lymph node metastasis; micrometastasis; mouse; nonhuman; nuclear magnetic resonance imaging; outcome assessment; reticuloendothelial neoplasm; sensitivity and specificity; spleen; tumor diagnosis; tumor localization; Animals; Breast Neoplasms; Cell Line, Tumor; Contrast Media; Female; Humans; Iron; Magnetic Resonance Imaging; Magnetite Nanoparticles; Metal Nanoparticles; Mice; Mononuclear Phagocyte System

Relating centromeric topography in fixed human chromosomes to -satellite DNA and CENP-B distribution - Khan, W.A.; Chisholm, R.; Tadayyon, S.; Subasinghe, A.; Norton, P.; Samarabandu, J.; Johnston, L.J.; Knoll, J.H.; Rogan, P.K. (Cytogenetic and Genome Research, 2013)
Despite extensive analyses on the centromere and its associated proteins, detailed studies of centromeric DNA structure have provided limited information about its topography in condensed chromatin. We have developed a method with correlative fluorescence light microscopy and atomic force microscopy that investigates the physical and structural organization of -satellite DNA sequences in the context of its associated protein, CENP-B, on human metaphase chromosome topography. Comparison of centromeric DNA and protein distribution patterns in fixed homologous chromosomes indicates that CENP-B and -satellite DNA are distributed distinctly from one another and relative to observed centromeric ridge topography. Our approach facilitates correlated studies of multiple chromatin components comprising higher-order structures of human metaphase chromosomes. © 2013 S. Karger AG, Basel.
Keywords: centromere protein B; satellite DNA; article; atomic force microscopy; centromere; comparative study; controlled study; DNA sequence; fluorescence microscopy; fluorescent lighting; human; human cell; human chromosome; metaphase chromosome; priority journal; protein localization; Cell Line, Tumor; Centromere; Centromere Protein B; Chromatin; Chromosomes, Human, Pair 17; DNA Probes; DNA, Satellite; Fluorescent Antibody Technique; Humans; In Situ Hybridization, Fluorescence; Lymphocytes; Metaphase; Microscopy, Atomic Force; Tissue Fixation

Sialyltransferase inhibitors : consideration of molecular shape and charge/hydrophobic interactions - Kumar, Rishi; Nasi, Ravindranath; Bhasin, Milan; Khieu, Nam Huan; Hsieh, Margaret; Gilbert, Michel; Jarrell, Harold; Zou, Wei; Jennings, Harold J. (Carbohydrate Research, 2013)
In order to evaluate the importance of molecular shape of inhibitor molecules and the charge/H-bond and hydrophobic interactions, we synthesized three types of molecules and tested them against a sialyltransferase. The first type of compounds were designed as substrate mimics in which the phosphate in CMP-Neu5NAc was replaced by a non-hydrolysable, uncharged 1,2,3-triazole moiety. The second type of compound contained a 2-deoxy-2,3-dehydro-acetylneuraminic moiety which was linked to cytidine through its carboxylic acid and amide linkers. In the third type of compound the sialyl phosphate was substituted by an aryl sulfonamide which was then linked to cytidine. Inhibition study of these cytidine conjugates against Campylobacter jejuni sialyltransferase Cst 06 showed that the first type of molecules are competitive inhibitors, whereas the other two could only inhibit the enzyme non-competitively. The results indicate that although the binding specificity may be guided by molecular shape and H-bond interaction, the charge and hydrophobic interactions contributed most to the binding affinity.
Keywords: 1,2,3-Triazole; 2-Deoxy-2; Click chemistry; Sialic acids; Sialyltransferase; Sialyltransferease inhibitors>; 2-Deoxy-2,3-dehydro-acetylneuraminic acid; Amino acids; Bacteria; Binding energy; Carboxylic acids; Hydrophobicity; Molecules; Nitrogen compounds; Sulfur compounds; Synthesis (chemical); Enzyme inhibition; 1,2,3 triazole derivative; benzoic acid derivative; cytidine; cytidine phosphate n acetylneuraminic acid; phosphate; sialyltransferase; sulfanilamide; sulfonamide; article; binding affinity; Campylobacter jejuni; chemical structure; click chemistry; competitive inhibition; enzyme inhibition; glycosylation; hydrogen bond; hydrophobicity; molecular docking; molecular interaction; priority journal; Campylobacter jejuni

Proximity, knowledge transfer, and innovation in technology-based M&As - Ensign, P.C.; Chreim, S.; Persaud, A.; Lin, C.-D. (Proceedings of the Annual Hawaii International Conference on System Sciences, 2013)
This paper presents the findings from a qualitative study on the extent to which three dimensions of proximity-geographic, cognitive, and organizational-impact knowledge transfer and innovation post-M&A. Findings show that the elements of proximity substantially influence both knowledge transfer and innovation although the nature of the impact varies and is influenced by the type of management interventions or lack thereof post-M&A. © 2012 IEEE.
Keywords: Knowledge transfer; Management interventions; Qualitative study; Technology-based; Three dimensions; Systems science; Knowledge management

Density functional theory investigation of the binding interactions between phosphoryl, carbonyl, imino, and thiocarbonyl ligands and the pentaaqua nickel(II) complex: Coordination affinity and associated parameters - Da Costa, L.M.; Stoyanov, S.R.; Damasceno, R.N.; De M. Carneiro, J.W. (International Journal of Quantum Chemistry, 2013)
Density Functional Theory (UB3LYP/6-311++G(d,p)) calculations of the affinity of the pentaaqua nickel(II) complex for a set of phosphoryl [Oï£P(H)(CH3)(PhR)], imino [HNï£C(CH 3)(PhR)], thiocarbonyl [Sï£C(CH3)(PhR)] and carbonyl [Oï£C(CH3)(PhR)] ligands were performed, where Rï£NH2, OCH3, OH, CH3, H, Cl, CN, and NO2 is a substituent at the para-position of a phenyl ring.The affinity of the pentaaqua nickel(II) complex for these ligands was analized and quantified in terms of interaction enthalpy (ΔH), Gibbs free energy (ΔG298), geometric and electronic parameters of the resultant octahedral complexes. The ΔH and ΔG298 results show that the ligand coordination strength increases in the following order: carbonyl < thiocarbonyl < imino < phosphoryl. This coordination strength order is also observed in the analysis of the metal-ligand distances and charges on the ligand atom that interacts with the Ni(II) cation. The electronic character of the substituent R is the main parameter that affects the strength of the metal-ligand coordination. Ligands containing electron-donating groups (NH 2, OCH3, OH) have more exothermic ΔH and ΔG298 than ligands with electron-withdrawing groups (Cl, CN, NO2). The metal-ligand interaction decomposed by means of the energy decomposition analysis (EDA) method shows that the electronic character of the ligand modulates all the components of the metal-ligand interaction. The absolute softness of the free ligands is correlated with the covalent contribution to the instantaneous interaction energy calculated using the EDA method. © 2013 Wiley Periodicals, Inc. The interactions between metal cations and biomolecules are extensively studied in bioinorganic and coordination chemistry. Transition metal ions are present in many enzymes, metalloproteins, peptide hormones, and nucleic acids and are fundamental for their biological functions. In this work, the affinity of the pentaaqua nickel(II) complex toward a set of para-substituted ligands is evaluated. The electronic nature of the ligand modulates the magnitude of the electrostatic, covalent, and repulsion components of the interaction. © 2013 Wiley Periodicals, Inc.
Keywords: DFT; EDA; Electron withdrawing group; Electron-donating group; Energy decomposition analysis; Interaction enthalpies; Metal-ligand interactions; Substituent effect; Binding energy; Chlorine compounds; Density functional theory; Metals; Nitrogen oxides; Positive ions; Ligands

Ultra-deep hubble space telescope imaging of the small magellanic cloud: The initial mass function of stars with M ≲ 1 M - Kalirai, J.S.; Anderson, J.; Dotter, A.; Richer, H.B.; Fahlman, G.G.; Hansen, B.M.S.; Hurley, J.; Reid, I.N.; Rich, R.M.; Shara, M.M. (The Astrophysical Journal, 2013)
We present a new measurement of the stellar initial mass function (IMF) based on ultra-deep, high-resolution photometry of >5000 stars in the outskirts of the Small Magellanic Cloud (SMC) galaxy. The Hubble Space Telescope (HST) Advanced Camera for Surveys observations reveal this rich, cospatial population behind the foreground globular cluster 47 Tuc, which we targeted for 121 HST orbits. The stellar main sequence of the SMC is measured in the F606W, F814W color-magnitude diagram down to 30th magnitude, and is cleanly separated from the foreground star cluster population using proper motions. We simulate the SMC population by extracting stellar masses (single and unresolved binaries) from specific IMFs and converting those masses to luminosities in our bandpasses. The corresponding photometry for these simulated stars is drawn directly from a rich cloud of 4 million artificial stars, thereby accounting for the real photometric scatter and completeness of the data. Over a continuous and well-populated mass range of M = 0.37-0.93 M(e.g., down to a 75% completeness limit at F606W = 28.7), we demonstrate that the IMF is well represented by a single power-law form with slope α = -1.90 ( +0.15 0.10) (3σ error) (e.g., dN/dM M α). This is shallower than the Salpeter slope of α = -2.35, which agrees with the observed stellar luminosity function at higher masses. Our results indicate that the IMF does not turn over to a more shallow power-law form within this mass range. We discuss implications of this result for the theory of star formation, the inferred masses of galaxies, and the (lack of a) variation of the IMF with metallicity. © 2013. The American Astronomical Society. All rights reserved..

Comparing the white dwarf cooling sequences in 47 tuc and NGC 6397 - Richer, H.B.; Goldsbury, R.; Heyl, J.; Hurley, J.; Dotter, A.; Kalirai, J.S.; Woodley, K.A.; Fahlman, G.G.; Rich, R.M.; Shara, M.M. (The Astrophysical Journal, 2013)
Using deep Hubble Space Telescope imaging, color-magnitude diagrams are constructed for the globular clusters 47 Tuc and NGC 6397. As expected, because of its lower metal abundance, the main sequence of NGC 6397 lies well to the blue of that of 47 Tuc. A comparison of the white dwarf cooling sequences of the two clusters, however, demonstrates that these sequences are indistinguishable over most of their loci - a consequence of the settling out of heavy elements in the dense white dwarf atmosphere and the near equality of their masses. Lower quality data on M4 continues this trend to a third cluster whose metallicity is intermediate between these two. While the path of the white dwarfs in the color-magnitude diagram is nearly identical in 47 Tuc and NGC 6397, the numbers of white dwarfs along the path are not. This results from the relatively rapid relaxation in NGC 6397 compared to 47 Tuc and provides a cautionary note that simply counting objects in star clusters in random locations as a method of testing stellar evolutionary theory is likely dangerous unless dynamical considerations are included. © 2013. The American Astronomical Society. All rights reserved.

R-Spondin 2 signalling mediates susceptibility to fatal infectious diarrhoea - Papapietro, O.; Teatero, S.; Thanabalasuriar, A.; Yuki, K.E.; Diez, E.; Zhu, L.; Kang, E.; Dhillon, S.; Muise, A.M.; Durocher, Y.; Marcinkiewicz, M.M.; Malo, D.; et al. (Nature Communications, 2013)
Citrobacter rodentium is a natural mouse pathogen widely used as a model for enteropathogenic and enterohemorrhagic Escherichia coli infections in humans. While C. rodentium causes self-limiting colitis in most inbred mouse strains, it induces fatal diarrhoea in susceptible strains. The physiological pathways as well as the genetic determinants leading to susceptibility have remained largely uncharacterized. Here we use a forward genetic approach to identify the R-spondin2 gene as a major determinant of susceptibility to C. rodentium infection. Robust induction of R-spondin2 expression during infection in susceptible mouse strains causes a potent Wnt-mediated proliferative response of colonic crypt cells, leading to the generation of an immature and poorly differentiated colonic epithelium with deficiencies in ion-transport components. Our data demonstrate a previously unknown role of R-spondins and Wnt signalling in susceptibility to infectious diarrhoea and identify R-spondin2 as a key molecular link between infection and intestinal homoeostasis. © 2013 Macmillan Publishers Limited. All rights reserved.
Keywords: alpha smooth muscle actin; beta actin; beta catenin; cyclin D1; matrilysin; messenger RNA; Myc protein; protein; spondin 2; unclassified drug; Wnt protein; coliform bacterium; diarrheal disease; homeostasis; infectious disease; ion; molecular analysis; pathogen; physiological response; rodent; signal; animal experiment; article; Citrobacter rodentium; colon mucosa; diarrhea; gene expression; gene locus; genetic susceptibility; infection sensitivity; ion transport; mouse; nonhuman; signal transduction; single nucleotide polymorphism

Morphological aspects of injected polypropylene/clay nanocomposite materials - Salah, H.B.H.; Daly, H.B.; Denault, J.; Perrin, F. (Polymer Engineering and Science, 2013)
Polypropylene (PP) clay nanocomposites were injection-molded using two different coupling agents based on maleic anhydride-grafted PP (MA-g-PP) and two clay loadings. The morphological aspects of these materials were studied by depth profiling. Molecular chain and clay orientations were characterized using attenuated total reflectance-infrared analysis and transmission electron microscopy (TEM). Both clay platelets and PP molecular chain orientations were found to decrease from the surface toward the core of the injection-molded specimens. Clay intercalation, characterized by both complementary X-ray diffraction and TEM, was found to be significantly influenced by both the characteristics of the coupling agent used and the type of residual stresses generated at each layer across the thickness of the injection-molded parts. The use of low-molecular weight (Mw) MA-g-PP led to a uniform intercalation but with no further exfoliation. The use of higher molecular weight MA-g-PP led to a heterogeneous intercalation with some signs of exfoliation. The crystallization behavior of PP clay nanocomposites studied by differential scanning calorimetry showed an increase in the level of crystallinity from the surface to the core of the specimens; these results were also confirmed by scanning electron microscopy. Copyright © 2012 Society of Plastics Engineers.
Keywords: Clay intercalation; Clay nanocomposites; Crystallization behavior; Injection-molded specimens; Low-molecular weight; Molecular chain orientation; Morphological aspects; Transmission electron microscopy (TEM); Coupling agents; Crystallization; Differential scanning calorimetry; Molecular weight; Nanocomposites; Polypropylenes; Scanning electron microscopy; Transmission electron microscopy; X ray diffraction; Injection molding

Genome-wide transcriptional profiling and enrichment mapping reveal divergent and conserved roles of Sko1 in the Candida albicans osmotic stress response - Marotta, D.H.; Nantel, A.; Sukala, L.; Teubl, J.R.; Rauceo, J.M. (Genomics, 2013)
Candida albicans maintains both commensal and pathogenic states in humans. Here, we have defined the genomic response to osmotic stress mediated by transcription factor Sko1. We performed microarray analysis of a sko1δ/δ mutant strain subjected to osmotic stress, and we utilized gene sequence enrichment analysis and enrichment mapping to identify Sko1-dependent osmotic stress-response genes. We found that Sko1 regulates distinct gene classes with functions in ribosomal synthesis, mitochondrial function, and vacuolar transport. Our in silico analysis suggests that Sko1 may recognize two unique DNA binding motifs. Our C. albicans genomic analyses and complementation studies in Saccharomyces cerevisiae showed that Sko1 is conserved as a regulator of carbohydrate metabolism, redox metabolism, and glycerol synthesis. Further, our real time-qPCR results showed that osmotic stress-response genes that are dependent on the kinase Hog1 also require Sko1 for full expression. Our findings reveal divergent and conserved aspects of Sko1-dependent osmotic stress signaling. © 2013 Elsevier Inc.
Keywords: phosphotransferase; protein hog1; unclassified drug; article; Candida albicans; computer model; controlled study; DNA binding motif; enzyme activity; gene; gene function; gene mapping; genetic conservation; genetic regulation; genetic transcription; genetic variability; genome analysis; microarray analysis; nonhuman; osmotic stress; priority journal; real time polymerase chain reaction; signal transduction; Sko1 gene; Candida albicans; Saccharomyces cerevisiae

Experimental characterization of contaminants in engine lubricants using surface plasmon resonance sensing - Aghayan, H.R.; Bordatchev, E.V.; Yang, J. (Industrial Lubrication and Tribology, 2013)
Purpose - The purpose of this paper is to develop new knowledge in experimental characterization of contaminants in engine lubricants, using surface plasmon resonance (SPR) sensing that can be applicable for on-line condition monitoring of lubricant quality and engine component performance. Design/methodology/approach - The effect of change in optical properties (e.g. transparency, absorption, and refractive index) of engine lubricants caused by the introduction of contaminants, such as gasoline, coolant, and water, on the surface plasmon resonance characteristics is analyzed experimentally. In SPR measurement, variations in both the refractive index and absorption cause changes in the SPR curve, which is the dependence of reflectivity vs incidence angle. The SPR characteristics (e.g. refractivity) of engine lubricant contaminated by gasoline, water and coolant at different concentration are measured as a function of resonance angle and analyzed with respect to different concentration (1%-10%) of contaminants. Also, pattern recognition analysis between fresh and used engine lubricants is performed, to show applicability of Bayesian classification methodology for on-line monitoring and predicting engine lubricant condition. Findings - It was shown experimentally that attenuation of surface plasmons due to introduction of contaminants to the engine lubricant leads to a noticeable change in resonance angle and reflectivity minimum of the SPR curve due to an increase in the dielectric permittivity. In addition, the changes in the SPR characteristics were observed between fresh and used engine lubricant, causing resonance angle and reflectivity minimum of the SPR curve to shift. Practical implications - The knowledge generated in this study lays the informational basis to further develop an on-line system for engine lubricant condition monitoring using miniaturized SPR sensors fully suitable for on board applications. Originality/value - SPR characterization is originally applied for analysis of optical properties of engine lubricants caused by the introduction of contaminants, such as gasoline, coolant, and water. © Emerald Group Publishing Limited.
Keywords: Automotive components industry; Bayesian classification; Design/methodology/approach; Dielectric permittivities; Engine components; Engine lubricants; Experimental characterization; Incidence angles; Online condition monitoring; Online monitoring; Resonance angle; SPR sensors; Surface plasmon resonance sensing; Surface plasmons; Absorption refrigeration; Characterization; Condition monitoring; Contamination; Coolants; Engines; Gasoline; Impurities; Lubricants; Pattern recognition; Permittivity; Plasmons; Reflection; Refractive index; Water; Water absorption; Surface plasmon resonance

First results of the SONS survey : submillimetre detections of debris discs - Panić, O.; Holland, W. S.; Wyatt, M. C.; Kennedy, G. M.; Matthews, B. C.; Lestrade, J. F.; Sibthorpe, B.; Greaves, J. S.; Marshall, J. P.; Phillips, N. M.; Tottle, J. (Monthly Notices of the Royal Astronomical Society, 2013)
New detections of debris discs at submillimetre wavelengths present highly valuable complementary information to prior observations of these sources at shorter wavelengths. Characterization of discs through spectral energy distribution modelling including the submillimetre fluxes is essential for our basic understanding of disc mass and temperature, and presents a starting point for further studies using millimetre interferometric observations. In the framework of the ongoing SCUBA-2 Observations of Nearby Stars, the instrument SCUBA-2 on the James Clerk Maxwell Telescope was used to provide measurements of 450 and 850 μm fluxes towards a large sample of nearby main-sequence stars with debris discs detected previously at shorter wavelengths. We present the first results from the ongoing survey, concerning 850 μm detections and 450 μm upper limits towards 10 stars, the majority of which are detected at submillimetre wavelengths for the first time. One, or possibly two, of these new detections is likely a background source. We fit the spectral energy distributions of the star+disc systems with a blackbody emission approach and derive characteristic disc temperatures. We use these temperatures to convert the observed fluxes to disc masses. We obtain a range of disc masses from 0.001 to 0.1M, values similar to the prior dust mass measurements towards debris discs. There is no evidence for evolution in dust mass with age on the main sequence, and indeed the upper envelope remains relatively flat at ~0.5M at all ages. The inferred disc masses are lower than those from disc detections around pre-main-sequence stars, which may indicate a depletion of solid mass. This may also be due to a change in disc opacity, though limited sensitivity means that it is not yet known what fraction of pre-main-sequence stars have discs with dust masses similar to debris disc levels. New, high-sensitivity detections are a path towards investigating the trends in dust mass evolution.

Ice-phobic coatings based on silicon-oil-infused polydimethylsiloxane - Zhu, L.; Xue, J.; Wang, Y.; Chen, Q.; Ding, J.; Wang, Q. (ACS Applied Materials and Interfaces, 2013)
A simple and low-cost technique for the preparation of silicon-oil-infused polydimethylsiloxane (PDMS) coatings with different silicon oil contents have been developed and studied. This material is designed for ice-phobic applications, and thus a high hydrophobic property of PDMS is maintained by avoiding any polar groups such as C=O and OH in the structure. Therefore, the polymer main chain was attached with vinyl and Si-H groups to obtain a cross-linking capability, meanwhile to ensure a nonpolar chemical structure. Its ice-phobic property has been investigated in terms of ice adhesion strength (tensile and shear), water contact angle, icing dynamics using high-speed photography and morphology using TEM, SEM and AFM. The prepared coating surface shows a low surface energy and very low ice adhesion strength of 50 kPa, only about 3% of the value on a bare aluminum (Al) surface. In the silicon oil infused PDMS coatings, the low surface energy of the silicon oil and PDMS, and the high mobility of silicon oil played an important role on the ice-phobic property. Both of these factors offer the surface a large water contact angle and hence a small contact area, leading to the formation of a loose ice layer. In addition, the oil infused polymer structure significantly reduces the contact area of the ice with solid substrate since the ice mostly contacts with the mobile oil. This leads to a very weak interaction between the substrate and ice, consequently significantly reduces the ice adhesion strength on the surface. Therefore, such material could be a good candidate for ice-phobic coatings on which the accumulated ice may be easily removed by a nature force, such as wind, gravity, and vibration. © 2013 American Chemical Society.
Keywords: hydrophobic; Hydrophobic properties; Ice adhesion strength; ice-phobic; Low surface energy; Polydimethylsiloxane PDMS; Silicon oil; Water contact angle; Adhesion; Aluminum coatings; Bond strength (materials); Contact angle; High speed photography; Hydrophobicity; Microchannels; Plastic coatings; Polydimethylsiloxane; Polymers; Silicon; Silicones; Surfaces; Ice

Special track on bioinformatics - Tulpan, D.; Lecca, P.; Palakal, M.J. (Proceedings of the ACM Symposium on Applied Computing, 2013)