Transition state analysis of Vibrio cholerae sialidase-catalyzed hydrolyses of natural substrate analogues - Chan, Jefferson; Lewis, Andrew R.; Indurugalla, Deepani; Schur, Melissa; Wakarchuk, Warren; Bennet, Andrew J. (Journal of the American Chemical Society, 2012)
A series of isotopically labeled natural substrate analogues (phenyl 5-N-acetyl-α-d-neuraminyl-(2→3)-β-d-galactopyranosyl-(1→4)-1-thio-β-d-glucopyranoside; Neu5Acα2,3LacβSPh, and the corresponding 2→6 isomer) were prepared chemoenzymatically in order to characterize, by use of multiple kinetic isotope effect (KIE) measurements, the glycosylation transition states for Vibrio cholerae sialidase-catalyzed hydrolysis reactions. The derived KIEs for Neu5Acα2,3LacβSPh for the ring oxygen (18V/K), leaving group oxygen (°⁶V/K), C3-S deuterium (DV/KS) and C3-R deuterium (DV/KR) are 1.029 ± 0.002, 0.983 ± 0.001, 1.034 ± 0.002, and 1.043 ± 0.002, respectively. In addition, the KIEs for Neu5Acα2,6βSPh for C3-S deuterium (DV/KS) and C3-R deuterium (DV/KR) are 1.021 ± 0.001 and 1.049 ± 0.001, respectively. The glycosylation transition state structures for both Neu5Acα2,3LacβSPh and Neu5Acα2,6LacβSPh were modeled computationally using the experimental KIE values as goodness of fit criteria. Both transition states are late with largely cleaved glycosidic bonds coupled to pyranosyl ring flattening (4H5 half-chair conformation) with little or no nucleophilic involvement of the enzymatic tyrosine residue. Notably, the transition state for the catalyzed hydrolysis of Neu5Acα2,6βSPh appears to incorporate a lesser degree of general-acid catalysis, relative to the 2,3-isomer.

Continuous synthesis and in situ monitoring of biodiesel production in different microfluidic devices - Martínez Arias, Edgar L.; Fazzio Martins, Patricia; Jardini Munhoz, André L.; Gutierrez-Rivera, Luis; Maciel Filho, Rubens (Industrial & Engineering Chemistry Research, 2012)
Currently, there is great interest in developing new processes for continuous biodiesel synthesis in order to overcome problems imposed by biphasic reaction and thermodynamic equilibrium, as well as to reduce production costs related to the conventional batch reaction processes. The use of microreactors can significantly improve the mixing between reactants and phases, enhancing the transfer rates, and, consequently, increasing biodiesel yields. Therefore, in this work, microreactors with different internal geometries have been fabricated and used for continuous production of biodiesel from castor oil and ethanol. The influences of the microchannel geometry (Tesla-, omega-, and T-shaped) on the performance of the biodiesel synthesis were experimentally studied. Higher biodiesel yields were reached using the Tesla- and omega-shaped microchannels than during the T-shaped microchannels due to better mixture mechanism efficiency. Using a catalyst loading of 1.0 wt % NaOH and a reaction temperature of 50 °C, ethyl ester conversions of 96.7, 95.3, and 93.5% were achieved using Tesla-, omega-, and T-shaped microreactors, respectively. In addition, transesterification reaction in situ monitoring by near-infrared spectroscopy using a fiber-optic probe was evaluated, showing that more studies must be performed in order to allow its use in online monitoring of continuous processes.

The International Deep Planet Survey I. The frequency of wide-orbit massive planets around A-stars - Vigan, A.; Patience, J.; Marois, C.; Bonavita, M.; De Rosa, R. J.; Macintosh, B.; Song, I.; Doyon, R.; Zuckerman, B.; Lafrenière, D.; Barman, T. (Astronomy & Astrophysics, 2012)
Breakthrough direct detections of planetary companions orbiting A-type stars confirm the existence of massive planets at relatively large separations, but dedicated surveys are required to estimate the frequency of similar planetary systems. To measure the first estimation of the giant exoplanetary systems frequency at large orbital separation around A-stars, we have conducted a deep-imaging survey of young (8−400 Myr), nearby (19−84 pc) A- and F-stars to search for substellar companions in the ~10−300 AU range. The sample of 42 stars combines all A-stars observed in previous AO planet search surveys reported in the literature with new AO observations from VLT/NaCo and Gemini/NIRI. It represents an initial subset of the International Deep Planet Survey (IDPS) sample of stars covering M- to B-stars. The data were obtained with diffraction-limited observations in H- and Ks-band combined with angular differential imaging to suppress the speckle noise of the central stars, resulting in typical 5σ detection limits in magnitude difference of 12 mag at 1′′, 14 mag at 2′′ and 16 mag at 5′′ which is sufficient to detect massive planets. A detailed statistical analysis of the survey results is performed using Monte Carlo simulations. Considering the planet detections, we estimate the fraction of A-stars having at least one massive planet (3−14 MJup) in the range 5−320 AU to be inside 5.9−18.8% at 68% confidence, assuming a flat distribution for the mass of the planets. By comparison, the brown dwarf (15−75 MJup) frequency for the sample is 2.0−8.9% at 68% confidence in the range 5−320 AU. Assuming power law distributions for the mass and semimajor axis of the planet population, the AO data are consistent with a declining number of massive planets with increasing orbital radius which is distinct from the rising slope inferred from radial velocity (RV) surveys around evolved A-stars and suggests that the peak of the massive planet population around A-stars may occur atseparations between the ranges probed by existing RV and AO observations. Finally, we report the discovery of three new close M-star companions to HIP 104365 and HIP 42334.

Solvent free generation of open and skinless foam in poly(l-lactic acid)/Poly(d,l-lactic acid) blends using carbon dioxide - Liao, Xia; Nawaby, Arghavan V. (Industrial & Engineering Chemistry Research, 2012)
Foams generated via carbon dioxide (CO2) processing typically exhibit a solid skin layer on the exterior surface and a closed-pore structure with limited interconnectivity in the core section thus limiting its application for biomedical intent. By controlling the properties of poly(l-lactic acid)/poly(d,l-lactic acid) (PLLA/PDLLA) blends and using CO2 with specific processing parameters, skinless foams with interconnected porous structure were prepared in this work using only CO2 as a physical foaming agent, which overcome the necessity to use organic solvents and solid porogens. The crystallization behaviors and sorption kinetics of PLLA and its blends were studied. Addition of PDLLA reduces the crystallinity of PLLA/PDLLA blends while treated with CO2 as compared to neat PLLA. The solubility and diffusion coefficients of CO2 in PLLA and its blends were found to be similar. Furthermore, the effect of PLLA/PDLLA blend ratio and CO2 treatment conditions on the foam morphologies was investigated. Through fine parameter control, well interconnected pore structures with a porous surface were generated. Results indicated that by controlling the physical properties of samples combined with optimizing CO2 foaming process, it is indeed possible to create biodegradable interconnected porous structures for potential biomedical applications.

HD 96446: a puzzle for current models of magnetospheres? - Neiner, C.; Landstreet, J. D.; Alecian, E.; Owocki, S.; Kochukhov, O.; Bohlender, D.; MiMes Collaboration (Astronomy & Astrophysics, 2012)
Context. Oblique magnetic dipole fields have been detected in Bp stars for several decades, and more recently also in normal massive stars. In the past decade, it has been established that stellar magnetospheres form through the channelling and confinement of an outflowing stellar wind by the stellar magnetic field. This explains specific properties of magnetic massive stars, such as their rotationally modulated photometric light curve, Hα emission, UV spectra, and X-ray emission. Aims. In the framework of the MiMeS (Magnetism in Massive Stars) project, four HARPSpol observations of the magnetic Bp star HD 96446 have been obtained. HD 96446 is very similar to σ Ori E, the prototype of centrifugally supported rigidly rotating magnetospheres (CM) and is therefore a perfect target to study the validity of this model. Methods. We first updated the basic parameters of HD 96446 and studied its spectral variability. We then analysed the HARPSpol spectropolarimetric observations using the LSD (Least-Squares Deconvolution) technique to derive the longitudinal magnetic field and Zeeman signatures in various types of lines. With LTE spectrum modelling, we derived constraints on the field modulus, the rotational velocity, and the inclination angle, and measured non-solar abundances of several elements which we checked with NLTE modelling. Finally, we calculated the magnetic confinement and Alfvén and Kepler radii from the stellar magnetic field and rotation properties, and we examined the various types of magnetospheres that may be present around HD 96446. Results. We find radial velocity variations with a period around 2.23 h, that we attribute to β Cep-type p-mode pulsations. We detect clear direct magnetic Stokes V signatures with slightly varying values of the longitudinal magnetic field, typical of an oblique dipole rotator, and show that these signatures are not much perturbed by the radial velocity variations. The magnetic confinement parameter and Alfvén radius in the centrifugally supported, rigidly-rotating magnetosphere (CM) model points towards the presence of confined material in the magnetosphere. However, HD 96446 does not present signatures of the presence of such confined material, such as Hα emission. Conclusions. We conclude that, even though HD 96446 fulfills all criteria to host a CM with confined material, it does not. The rotation period must be significantly revised, or another model of magnetosphere with a leakage mechanism will need to be developed to explain the magnetic environment of this star.

Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope - Maire, A.-L.; Galicher, R.; Boccaletti, A.; Baudoz, P.; Schneider, J.; Cahoy, K. L.; Stam, D. M.; Traub, W. A. (Astronomy & Astrophysics, 2012)
Context. High-contrast imaging is currently the only available technique for the study of the thermodynamical and compositional properties of exoplanets in long-period orbits, comparable to the range from Venus to Jupiter. The SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) project is a coronagraphic space telescope dedicated to the spectro-polarimetric analysis of gaseous and icy giant planets as well as super-Earths at visible wavelengths. So far, studies for high-contrast imaging instruments have mainly focused on technical feasibility because of the challenging planet/star flux ratio of 10-8−10-10 required at short separations (200 mas or so) to image cold exoplanets. However, the main interest of such instruments, namely the analysis of planet atmospheric/surface properties, has remained largely unexplored. Aims. The aim of this paper is to determine which planetary properties SPICES or an equivalent direct imaging mission can measure, considering realistic reflected planet spectra and instrument limitation. Methods. We use numerical simulations of the SPICES instrument concept and theoretical planet spectra to carry out this performance study. We also define a criterion on the signal-to-noise ratio of the measured spectrum to determine under which conditions SPICES can retrieve planetary physical properties. Results. We find that the characterization of the main planetary properties (identification of molecules, effect of metallicity, presence of clouds and type of surfaces) would require a median signal-to-noise ratio of at least 30. In the case of a solar-type star ≤10 pc, SPICES will be able to study Jupiters and Neptunes up to ~5 and ~2 AU respectively, because of the drastic flux decrease with separation. It would also analyze cloud and surface coverage of super-Earths of radius 2.5 Earth radii at 1 AU. Finally, we determine the potential targets in terms of planet separation, radius and distance for several stellar types. For a Sun analog, we show that SPICES could characterize Jupiters (M ≥ 30 Earth masses) as small as 0.5 Jupiter radii at ≲2 AU up to 10 pc, and super-Earths at 1−2 AU for the handful of stars that exist within 4−5 pc. Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around α Cen A and B. However, these results depend on the planetary spectra we use, which are derived for a few planet parameters assuming a solar-type host star. Grids of model spectra are needed for a further performance analysis. Our results obtained for SPICES are also applicable to other small (1−2 m) coronagraphic space telescopes.

Stripped gas as fuel for newly formed H ii regions in the encounter between VCC 1249 and M 49: a unified picture from NGVS and GUViCS - Arrigoni Battaia, F.; Gavazzi, G.; Fumagalli, M.; Boselli, A.; Boissier, S.; Cortese, L.; Heinis, S.; Ferrarese, L.; Côté, P.; Mihos, J. C.; Cuillandre, J. C.; Duc, P.-A.; et al. (Astronomy & Astrophysics, 2012)
Context. We study the peculiar interacting galaxy system of VCC 1249/M 49 located in the core of the Virgo B subcluster. Owing to a recent interaction between the dwarf galaxy VCC 1249 and the halo gas of the elliptical galaxy M 49, neutral hydrogen has been displaced from the interstellar medium of this dwarf into the Virgo intracluster medium. Observations also reveal multiple compact star-forming regions (aka H ii regions) that are embedded in this H i cloud, with a projected separation up to 13 kpc from VCC 1249 in the northwest direction. Aims. Motivated by recent near-ultraviolet imaging from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) of the VCC 1249/M 49 system that shows significant ongoing/recent star formation in the compact regions, we aim to constrain the origin of these outlying H ii regions with a multi-wavelength approach. Methods. Using deep optical (u,g,i,z) imaging from the Next Generation Virgo Cluster Survey (NGVS) and new Hα imaging obtained at the San Pedro Martir observatory together with Keck long-slit spectroscopy, we characterize the star formation rates, ages, and metallicity of VCC 1249 and its outlying compact regions. Moreover, we analyze the color and luminosity profile of the galaxy to investigate its recent interaction with M 49. Results. Our new observations indicate that VCC 1249 underwent a recent interaction with M 49 in which both ram-pressure stripping and tidal interaction occured. The joint action of the two mechanisms led to the removal of the H i gas from the interstellar medium of VCC 1249, while the gravitational tides triggered the stellar tail and counter-tail of VCC 1249. Our stellar population synthesis analysis reveals that the star formation in this galaxy was truncated around 200 Myr ago and that the outlying H ii regions were born in situ ≈10 Myr ago out of pre-enriched gas removed from the dwarf galaxy. These observations also reveal that interactions between central and satellite galaxies similar to those between VCC 1249/M 49 may be an effective way of dispersing metals into the halos of massive galaxies.

A background galaxy in the field of the β Pictoris debris disk - Regibo, S.; Vandenbussche, B.; Waelkens, C.; Acke, B.; Sibthorpe, B.; Nottebaere, M.; Voet, K.; Di Francesco, J.; Fridlund, M.; Gear, W. K.; Ivison, R. J.; Olofsson, G. (Astronomy & Astrophysics, 2012)
Herschel images in six photometric bands show the thermal emission of the debris disk surrounding β Pic. In the three PACS bands at 70 μm, 100 μm and 160 μm and in the 250 μm SPIRE band, the disk is well-resolved, and additional photometry is available in the SPIRE bands at 350 μm and 500 μm, where the disk is only marginally resolved. The SPIRE maps reveal a blob to the southwest of β Pic, coinciding with submillimetre detection of excess emission in the disk. We investigated the nature of this blob. Our comparison of the colours, spectral energy distribution and size of the blob, the disk and the background sources shows that the blob is most likely a background source with a redshift between z = 1.0 and z = 1.6.

The JCMT 12CO(3–2) survey of the Cygnus X region I. A pathfinder - Gottschalk, M.; Kothes, R.; Matthews, H. E.; Landecker, T. L.; Dent, W. R. F. (Astronomy & Astrophysics, 2012)
Context. Cygnus X is one of the most complex areas in the sky, rich in massive stars; Cyg OB2 (2600 stars, 120 O stars) and other OB associations lie within its boundaries. This complicates interpretation, but also creates the opportunity to investigate accretion into molecular clouds and many subsequent stages of star formation, all within one small field of view. Understanding large complexes like Cygnus X is the key to understanding the dominant role that massive star complexes play in galaxies across the Universe. Aims. The main goal of this study is to establish feasibility of a high-resolution CO survey of the entire Cygnus X region by observing part of it as a pathfinder, and to evaluate the survey as a tool for investigating the star-formation process. We can investigate the mass accretion history of outflows, study interaction between star-forming regions and their cold environment, and examine triggered star formation around massive stars. Methods. A 2° × 4° area of the Cygnus X region has been mapped in the 12CO(3–2) line at an angular resolution of 15′′ and a velocity resolution of ~0.4 km s-¹ using HARP-B and ACSIS on the James Clerk Maxwell Telescope. The star formation process is heavily connected to the life-cycle of the molecular material in the interstellar medium. The high critical density of the 12CO(3–2) transition reveals clouds in key stages of molecule formation, and shows processes that turn a molecular cloud into a star. Results. We observed ~15% of Cygnus X, and demonstrated that a full survey would be feasible and rewarding. We detected three distinct layers of 12CO(3–2) emission, related to the Cygnus Rift (500–800 pc), to W75N (1–1.8 kpc), and to DR 21 (1.5–2.5 kpc). Within the Cygnus Rift, H i self-absorption features are tightly correlated with faint diffuse CO emission, while HISA features in the DR 21 layer are mostly unrelated to any CO emission. 47 molecular outflows were detected in the pathfinder, 27 of them previously unknown. Sequentially triggered star formation is a widespread phenomenon.

Herschel images of Fomalhaut - Acke, B.; Min, M.; Dominik, C.; Vandenbussche, B.; Sibthorpe, B.; Waelkens, C.; Olofsson, G.; Degroote, P.; Smolders, K.; Pantin, E.; Barlow, M. J.; Blommaert, J. A. D. L.; et al. (Astronomy & Astrophysics, 2012)
Context. Fomalhaut is a young (2 ± 1 × 10^8 years), nearby (7.7 pc), 2 M⊙ star that is suspected to harbor an infant planetary system, interspersed with one or more belts of dusty debris. Aims. We present far-infrared images obtained with the Herschel Space Observatory with an angular resolution between 5.7′′ and 36.7′′ at wavelengths between 70 μm and 500 μm. The images show the main debris belt in great detail. Even at high spatial resolution, the belt appears smooth. The region in between the belt and the central star is not devoid of material; thermal emission is observed here as well. Also at the location of the star, excess emission is detected. We aim to construct a consistent image of the Fomalhaut system. Methods. We use a dynamical model together with radiative-transfer tools to derive the parameters of the debris disk. We include detailed models of the interaction of the dust grains with radiation, for both the radiation pressure and the temperature determination. Comparing these models to the spatially resolved temperature information contained in the images allows us to place strong constraints on the presence of grains that will be blown out of the system by radiation pressure. We use this to derive the dynamical parameters of the system. Results. The appearance of the belt points toward a remarkably active system in which dust grains are produced at a very high rate by a collisional cascade in a narrow region filled with dynamically excited planetesimals. Dust particles with sizes below the blow-out size are abundantly present. The equivalent of 2000 one-km-sized comets are destroyed every day, out of a cometary reservoir amounting to 110 Earth masses. From comparison of their scattering and thermal properties, we find evidence that the dust grains are fluffy aggregates, which indicates a cometary origin. The excess emission at the location of the star may be produced by hot dust with a range of temperatures, but may also be due to gaseous free-free emission from a stellar wind.

Cluster-formation in the Rosette molecular cloud at the junctions of filaments - Schneider, N.; Csengeri, T.; Hennemann, M.; Motte, F.; Didelon, P.; Federrath, C.; Bontemps, S.; Di Francesco, J.; Arzoumanian, D.; Minier, V.; André, Ph.; Hill, T.; et al. (Astronomy & Astrophysics, 2012)
Aims. For many years feedback processes generated by OB-stars in molecular clouds, including expanding ionization fronts, stellar winds, or UV-radiation, have been proposed to trigger subsequent star formation. However, hydrodynamic models including radiation and gravity show that UV-illumination has little or no impact on the global dynamical evolution of the cloud. Instead, gravitational collapse of filaments and/or merging of filamentary structures can lead to building up dense high-mass star-forming clumps. However, the overall density structure of the cloud has a large influence on this process, and requires a better understanding. Methods. The Rosette molecular cloud, irradiated by the NGC 2244 cluster, is a template region for triggered star-formation, and we investigated its spatial and density structure by applying a curvelet analysis, a filament-tracing algorithm (DisPerSE), and probability density functions (PDFs) on Herschel column density maps, obtained within the HOBYS key program. Results. The analysis reveals not only the filamentary structure of the cloud but also that all known infrared clusters except one lie at junctions of filaments, as predicted by turbulence simulations. The PDFs of sub-regions in the cloud show systematic differences. The two UV-exposed regions have a double-peaked PDF we interprete as caused by shock compression, while the PDFs of the center and other cloud parts are more complex, partly with a power-law tail. A deviation of the log-normal PDF form occurs at AV ≈ 9m for the center, and around 4m for the other regions. Only the part of the cloud farthest from the Rosette nebula shows a log-normal PDF. Conclusions. The deviations of the PDF from the log-normal shape typically associated with low- and high-mass star-forming regions at AV ≈ 3–4^m and 8–10^m, respectively, are found here within the very same cloud. This shows that there is no fundamental difference in the density structure of low- and high-mass star-forming regions. We conclude that star-formation in Rosette – and probably in high-mass star-forming clouds in general – is not globally triggered by the impact of UV-radiation. Moreover, star formation takes place in filaments that arose from the primordial turbulent structure built up during the formation of the cloud. Clusters form at filament mergers, but star formation can be locally induced in the direct interaction zone between an expanding H II-region and the molecular cloud.
Erratum published in volume 551, article C1, March 2013. DOI: 10.1051/0004-6361/201118566e

The WIRCam Deep Survey - Bielby, R.; Hudelot, P.; McCracken, H. J.; Ilbert, O.; Daddi, E.; Le Fèvre, O.; Gonzalez-Perez, V.; Kneib, J.-P.; Marmo, C.; Mellier, Y.; Salvato, M.; Sanders, D. B.; et al. (Astronomy & Astrophysics, 2012)
We present a new near-infrared imaging survey in the four CFHTLS deep fields: the WIRCam Deep Survey or “WIRDS”. WIRDS comprises extremely deep, high quality (FWHM ~ 0.6″) J, H, and Ks imaging covering a total effective area of 2.1 deg2 and reaching AB 50% completeness limits of ≈ 24.5. We combine our images with the CFHTLS to create a unique eight-band ugrizJHKS photometric catalogues in the four CFHTLS deep fields; these four separate fields allow us to make a robust estimate of the effect of cosmic variance for all our measurements. We use these catalogues in combination with ≈ 9800 spectroscopic redshifts to estimate precise photometric redshifts (σΔz/(1 + z) ≲ 0.03 at i < 25), galaxy types, star-formation rates and stellar masses for a unique sample of ≈ 1.8 million galaxies. Our JHKs number counts are consistent with previous studies. We apply the “BzK” selection to our gzK filter set and find that the star forming BzK selection successfully selects 76% of star-forming galaxies in the redshift range 1.4 < z < 2.5 in our photometric catalogue, based on our photometric redshift measurement. Similarly the passive BzK selection returns 52% of the passive 1.4 < z < 2.5 population identified in the photometric catalogue. We present the mass functions of the total galaxy population as a function of redshift up to z = 2 and present fits using double Schechter functions. A mass-dependent evolution of the mass function is seen with the numbers of galaxies with masses of M ≲ 1010.75 still evolving at z ≲ 1, but galaxies of higher mass reaching their present day numbers by z ~ 0.8−1. This is consistent with the present picture of downsizing in galaxy evolution. We compare our results with the predictions of the GALFORM semi-analytical galaxy formation model and find that the simulations provide a relatively successful fit to the observed mass functions at intermediate masses (i.e. 10 ≲ log    (M/M⊙) ≲ 11). However, as is common with semi-analytical predictions of the mass function, the GALFORM results under-predict the mass function at low masses (i.e. log    (M/M⊙) ≲ 10), whilst the fit as a whole degrades beyondredshifts of z ~ 1.2. All photometric catalogues and images are made publicly available from TERAPIX and CADC.

An improved map of the Galactic Faraday sky - Oppermann, N.; Junklewitz, H.; Robbers, G.; Bell, M. R.; Enßlin, T. A.; Bonafede, A.; Braun, R.; Brown, J. C.; Clarke, T. E.; Feain, I. J.; Gaensler, B. M.; Hammond, A.; et al. (Astronomy & Astrophysics, 2012)
We aim to summarize the current state of knowledge regarding Galactic Faraday rotation in an all-sky map of the Galactic Faraday depth. For this we have assembled the most extensive catalog of Faraday rotation data of compact extragalactic polarized radio sources to date. In the map-making procedure we used a recently developed algorithm that reconstructs the map and the power spectrum of a statistically isotropic and homogeneous field while taking into account uncertainties in the noise statistics. This procedure is able to identify some rotation angles that are offset by an integer multiple of π. The resulting map can be seen as an improved version of earlier such maps and is made publicly available, along with a map of its uncertainty. For the angular power spectrum we find a power law behavior Cℓ ∝ ℓ^-2.17 for a Faraday sky where an overall variance profile as a function of Galactic latitude has been removed, in agreement with earlier work. We show that this is in accordance with a 3D Fourier power spectrum P(k) ∝ k^-2.17 of the underlying field neBr under simplifying geometrical and statistical assumptions.

The abundance of C¹⁸8O and HDO in the envelope and hot core of the intermediate mass protostar NGC 7129 FIRS 2 - Fuente, A.; Caselli, P.; Mccoey, C.; Cernicharo, J.; Johnstone, D.; Fich, M.; Van Kempen, T.; Van Dishoeck, E.; Yıldız, U.; Visser, R.; Kristensen, L.; Alonso-Albi, T.; et al. (Astronomy & Astrophysics, 2012)
Context. NGC 7129 FIRS 2 is a young intermediate-mass (IM) protostar, which is associated with two energetic bipolar outflows and displays clear signs of the presence of a hot core. It has been extensively observed with ground based telescopes and within the WISH guaranteed time Herschel key program. Aims. This paper is dedicated to the modeling of the C18O and HDO lines in NGC 7129 FIRS 2. Our goal is to investigate the chemistry in the envelope and hot core of this IM protostar. Conclusions.Herschel data combined with ground based observations have allowed us to estimate the C18O and HDO abundance in the protostellar envelope and hot core of an IM protostar. The HDO abundance in the hot core is ~0.4−1 × 10^-7, similar to that found in the hot corinos NGC 1333 IRAS 2A and IRAS 16293−2422. The C18O abundance, at ≈ 1.6 × 10^-8, is a factor of 10 lower than the reference value.

The double sub-giant branch of NGC 6656 (M 22): a chemical characterization - Marino, A. F.; Milone, A. P.; Sneden, C.; Bergemann, M.; Kraft, R. P.; Wallerstein, G.; Cassisi, S.; Aparicio, A.; Asplund, M.; Bedin, R. L.; Hilker, M.; Lind, K.; et al. (Astronomy & Astrophysics, 2012)
We present an abundance analysis of 101 subgiant branch (SGB) stars in the globular cluster M 22. Using low-resolution FLAMES/GIRAFFE spectra we have determined abundances of the neutron-capture strontium and barium and the light element carbon. With these data we explore relationships between the observed SGB photometric split in this cluster and two stellar groups characterized by different contents of iron, slow neutron-capture process (s-process) elements, and the α element calcium, which we previously discovered in M 22’s red-giant stars. We show that the SGB stars correlate in chemical composition and the color–magnitude diagram position. The stars with higher metallicity and relative s-process abundances define a fainter SGB, while stars with lower metallicity and s-process content reside on a relatively brighter SGB. This result has implications for the relative ages of the two stellar groups of M 22. In particular, it is inconsistent with a broad spread in ages of the two SGBs. By accounting for the chemical content of the two stellar groups, isochrone fitting of the double SGB suggests that their agesare not different by more than ~300 Myr.

A tidal disruption-like X-ray flare from the quiescent galaxy SDSS J120136.02+300305.5 - Saxton, R. D.; Read, A. M.; Esquej, P.; Komossa, S.; Dougherty, S.; Rodriguez-Pascual, P.; Barrado, D. (Astronomy & Astrophysics, 2012)
Aims. The study of tidal disruption flares from galactic nuclei has historically been hampered by a lack of high quality spectral observations taken around the peak of the outburst. Here we introduce the first results from a program designed to identify tidal disruption events at their peak by making near-real-time comparisons of the flux seen in XMM-Newton slew sources with that seen in ROSAT. Methods. Flaring extragalactic sources, which do not appear to be AGN, are monitored with Swift and XMM-Newton to track their temporal and spectral evolution. Timely optical observations are made to monitor the reaction of circumnuclear material to the X-ray flare. Results. SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to LX ~ 3 × 1044 erg s-¹. It has the optical spectrum of a quiescent galaxy (z = 0.146). Overall the X-ray flux has evolved consistently with the canonical t^−5/3 model, expected for returning stellar debris, fading by a factor ~300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event.

Herschel observations of a potential core-forming clump: Perseus B1-E - Sadavoy, S. I.; Di Francesco, J.; André, Ph.; Pezzuto, S.; Bernard, J.-P.; Bontemps, S.; Bressert, E.; Chitsazzadeh, S.; Fallscheer, C.; Hennemann, M.; Hill, T.; Martin, P.; et al. (Astronomy & Astrophysics, 2012)
We present continuum observations of the Perseus B1-E region from the Herschel Gould Belt Survey. These Herschel data reveal a loose grouping of substructures at 160−500 μm not seen in previous submillimetre observations. We measure temperature and column density from these data and select the nine densest and coolest substructures for follow-up spectral line observations with the Green Bank Telescope. We find that the B1-E clump has a mass of ~100 M⊙ and appears to be gravitationally bound. Furthermore, of the nine substructures examined here, one substructure (B1-E2) appears to be itself bound. The substructures are typically less than a Jeans length from their nearest neighbour and thus, may interact on a timescale of ~1 Myr. We propose that B1-E may be forming a first generation of dense cores, which could provide important constraints on the initial conditions of prestellar core formation. Our results suggest that B1-E may be influenced by a strong, localized magnetic field, but further observations are still required.
Keywords: stars; formation; dust; extinction; Perseus B1-E

A Vacancy-Disordered, Oxygen-Deficient Perovskite with Long-Range Magnetic Ordering: Local and Average Structures and Magnetic Properties of Sr 2 Fe 1.5 Cr 0.5 O 5 - Ramezanipour, Farshid; Greedan, John E.; Siewenie, Joan; Donaberger, Ronald L.; Turner, Stuart; Botton, Gianluigi A. (Inorganic Chemistry, 2012)
The local and average crystal structures and magnetic properties of the oxygen-deficient perovskite Sr2Fe1.5Cr0.5O5+y were studied using powder X-ray and neutron diffraction, neutron-pair distribution function analysis, and electron energy-loss spectroscopy. This material crystallizes in the cubic Pm3̅m space group, with a = 3.94491(14) Å. The oxygen vacancies are distributed randomly throughout the perovskite-type structure, and the average coordination number of the Fe(Cr) sites is 5. Refinement of the neutron diffraction data indicates y 0.05. This is in discordance with an earlier report on a material with the same nominal composition and cell constant. Electron energy-loss Cr L2,3-edge spectroscopy shows that Cr³⁺ is present, which is also contrary to previous speculation. Neutron-pair distribution function studies show that a brownmillerite-like model involving ordered vacancies and alternating octahedral and tetrahedral coordination at the metal sites, gives a better description of the local structure out to 5 Å. A remarkable phenomenon determined by neutron diffraction in Sr2Fe1.5Cr0.5O5 is the occurrence of a long-range G-type antiferromagnetic ordering with Tc ≈ 565 K because cubic oxygen-deficient perovskites with B-site disorder usually do not undergo transitions to magnetically ordered states. The observation of long-range antiferromagnetic order and the Tc value are in accordance with previous Mössbauer spectroscopic studies.

Tip-tilt estimation and correction using FQPM coronagraphic images - Mas, M.; Baudoz, P.; Rousset, G.; Galicher, R. (Astronomy & Astrophysics, 2012)
Context. Direct imaging of exoplanets located a few AU from their hosting star requires angular resolution at the diffraction limit of large telescopes and a contrast level in the image of 10^5 to 10^10. Simultaneous use of adaptive optics and coronagraphy is mandatory to fulfil these requirements. Aims. Coronagraphs are usually very sensitive to pointing errors upstream of their focal plane mask. Approaches to measuring these errors in conventional adaptive optics systems consist in setting a wavefront sensor in an additional channel. Differential aberrations between the coronagraphic channel and the additional one induce a loss in performance. To tackle this limitation, we propose a new technique for measuring the tip-tilt errors directly from the coronagraphic image. Methods. Our method uses the relations between the intensity distribution in the coronagraphic image and upstream tip-tilt errors. We also propose a method of estimating the tip-tilt errors downstream of the focal plane mask. We validate at visible wavelength our upstream and downstream tip-tilt estimation and compensation techniques with numerical simulation images and on laboratory images. Results. Numerical simulations predict that our techniques correct for the tip-tilt errors to a 1.3 × 10-² λ/D level when considering a λ/40 wavefront error upstream of the coronagraph. In laboratory, where the coronagraph is mostly limited by wavefront errors, we correct for the tip-tilt errors with an accuracy better than 6.5 × 10-² λ/D. Conclusions. We demonstrate in numerical simulations and in laboratory that our technique can efficiently estimate the tip-tilt errors directly from the coronagraphic image with no additional channel. It is robust and can be used with small wavefront errors. It should be applicable to planet imager systems currently in preparation, such as SPHERE and MIRI/JWST.
Keywords: adaptive optics; high angular resolution; image processing

Nuclear resonance vibrational spectra of five-coordinate imidazole-ligated iron(II) porphyrinates - Hu, Chuanjiang; Barabanschikov, Alexander; Ellison, Mary K.; Zhao, Jiyong; Alp, E. Ercan; Sturhahn, Wolfgang; Zgierski, Marek Z.; Sage, J. Timothy; Scheidt, W. Robert (Inorganic Chemistry, 2012)
Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate, or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200–300 cm–1. Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with density functional theory (DFT) calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe–NIm vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape).

Topotactic oxidation pathway of ScTiO3 and high-temperature structure evolution of ScTiO3.5 and Sc4Ti3O12-type phases - Shafi, Shahid P.; Hernden, Bradley C.; Cranswick, Lachlan M. D.; Hansen, Thomas C.; Bieringer, Mario (Inorganic Chemistry, 2012)
The novel oxide defect fluorite phase ScTiO3.5 is formed during the topotactic oxidation of ScTiO3 bixbyite. We report the oxidation pathway of ScTiO3 and structure evolution of ScTiO3.5, Sc4Ti3O12, and related scandium-deficient phases as well as high-temperature phase transitions between room temperature and 1300 °Cusing in-situ X-ray diffraction. We provide the first detailed powder neutron diffraction study for ScTiO3. ScTiO3 crystallizes in the cubic bixbyite structure in space group Ia3̅ (206) with a = 9.7099(4) Å. The topotactic oxidation product ScTiO3.5 crystallizes in an oxide defect fluorite structure in space group Fm3̅m (225) with a = 4.89199(5) Å. Thermogravimetric and differential thermal analysis experiments combined with in-situ X-ray powder diffraction studies illustrate a complex sequence of a topotactic oxidation pathway, phase segregation, and ion ordering at high temperatures. The optimized bulk synthesis for phase pure ScTiO3.5 is presented. In contrast to the vanadium-based defect fluorite phases AVO3.5+x (A = Sc, In) the novel titanium analogue ScTiO3.5 is stable over a wide temperature range. Above 950 °C ScTiO3.5 undergoes decomposition with the final products being Sc4Ti3O12 and TiO2. Simultaneous Rietveld refinements against powder X-ray and neutron diffraction data showed that Sc4Ti3O12 also exists in the defect fluorite structure in space group Fm3̅m (225) with a = 4.90077(4) Å. Sc4Ti3O12 undergoes partial reduction in CO/Ar atmosphere to form Sc4Ti3O11.69(2).

The Herschel view of the on-going star formation in the Vela-C molecular cloud - Giannini, T.; Elia, D.; Lorenzetti, D.; Molinari, S.; Motte, F.; Schisano, E.; Pezzuto, S.; Pestalozzi, M.; Di Giorgio, A. M.; André, P.; Hill, T.; Benedettini, M.; et al. (Astronomy & Astrophysics, 2012)
Aims. As part of the Herschel guaranteed time key programme “HOBYS”, we present the PACS and SPIRE photometric survey of the star-forming region Vela-C, one of the nearest sites of low-to-high-mass star formation in the Galactic plane. Our main objectives are to take a census of the cold sources and to derive their mass distribution down to a few solar masses. Methods. Vela-C was observed with PACS and SPIRE in parallel mode at ﬁve wavelengths between 70μm and 500μm over an area of about 3 square degrees. A photometric catalogue was extracted from the detections in each of the ﬁve bands, using a threshold of 5σ over the local background. Out of this catalogue we selected a robust sub-sample of 268 sources, of which ∼75% are cloud clumps (diameter between 0.05 pc and 0.13 pc) and 25% are cores (diameter between 0.025 pc and 0.05 pc). Their spectral energy distributions (SEDs) were ﬁtted with a modiﬁed black body function. We classify 48 sources as protostellar, based on their detection at 70μm or at shorther wavelengths, and 218 as starless, because of non-detections at 70μm. For two other sources, we do not provide a secure classiﬁcation, but suggest they are Class 0 protostars. Results. From the SED ﬁtting we derived key physical parameters (i.e. mass, temperature, bolometric luminosity). Protostellar sources are in general warmer (T=12.8 K) and more compact (diameter=0.040 pc) than starless sources (T=10.3 K, diameter=0.067 pc). Both these ﬁndings can be ascribed to the presence of an internal source(s) of moderate heating, which also causes a temperature gradient and hence a more peaked intensity distribution. Moreover, the reduced dimensions of protostellar sources may indicate that they will not fragment further. A virial analysis of the starless sources gives an upper limit of 90% probability for the sources to be gravitationally bound and therefore prestellar in nature. A luminosity vs. mass diagram of the two populations shows that protostellar sources are in the early accretion phase, while prestellar sources populate a region of the diagram where mass accretion has not started yet. We ﬁtted a power law N(log M) ∝ M−1.1±0.2 to the linear portion of the mass distribution of prestellar sources. This is in between that typical of CO clumps and those of cores in nearby star-forming regions. We i
Keywords: individual objects; Vela-C; clouds; stars; formation; submillimeter; circumstellar matter

Bacterial inhibition of methane clathrate hydrates formed in a stirred autoclave - Townson, Iwan; Walker, Virginia K.; Ripmeester, John A.; Englezos, Peter (Energy & Fuels, 2012)
The potential for hydrate inhibition in a stirred autoclave at a subcooling of 2.3 K has been tested on two bacterial isolates. Chryseobacterium sp. C14 survives multiple freeze–thaw events and inhibits ice recrystallization, and Escherichia coli has neither of these properties but is a biofilm producer. Both strains showed methane hydrate inhibition, with a significant reduction in total hydrate formed. Chryseobacterium delayed hydrate nucleating time, to a similar level found for the commercial kinetic inhibitor, polyvinylpyrrolidone (PVP; 0.2 wt %). However, in the presence of E. coli, in comparison to PVP, the time to nucleation was almost tripled and the hydrate growth rate was reduced by half. Because of the variation inherent with the microbial samples, likely a result of the complexities associated with varying cell numbers and metabolic activity, numerous experiments were required. Analysis of the distinct hydrate growth profiles shown by the two bacterial strains indicated that different molecular sources were likely responsible for the observed inhibition. As a working hypothesis, it is suggested that the inhibition observed by Chryseobacterium cultures was partially due to ice recrystallization inhibition properties, while that of E. coli may be due to secreted macromolecules and the effect of biofilm.

Density functional theory investigation of the contributions of π–π stacking and hydrogen-bonding interactions to the aggregation of model asphaltene compounds - Da costa, Leonardo M.; Stoyanov, Stanislav R.; Gusarov, Sergey; Tan, Xiaoli; Gray, Murray R.; Stryker, Jeffrey M.; Tykwinski, Rik; de M. Carneiro, J. Walkimar; Seidl, Peter R.; Kovalenko, Andriy (Energy & Fuels, 2012)
We performed density functional theory (DFT) calculations using the WB97Xd functional with a dispersion correction term and the 6-31G(d,p) basis set to study the contributions of π–π stacking and hydrogen-bonding interactions to the aggregation of asphaltene model compounds containing a 2,2′-bipyridine moiety covalently bonded to one (monosubstituted) and two (disubstituted) aromatic hydrocarbon moieties (phenyl, naphthyl, anthracyl, phenanthryl, and pyrenyl) through ethylene tethers. In these compounds, the N atoms of the 2,2′-bipyridine moiety provide lone pairs for hydrogen bonding to water molecules present in solution. The aggregation strength of the homodimers of these model compounds is evaluated in terms of the aggregation energies, enthalpies, and ΔG²⁹⁸, as well as the π–π interaction distances. Geometry optimization and thermochemistry analysis results show that the homodimers of both mono- and disubstituted compounds are stable and have a negative ΔG²⁹⁸ of aggregation because of π–π stacking interactions. Two water bridges containing one, two, or three water molecules per bridge span between two monomers and provide additional stabilization of the homodimers because of hydrogen bonding. The stabilization of the monosubstituted homodimers is the largest with two water molecules per bridge, whereas the stabilization of the disubstituted homodimers is the largest with three water molecules per bridge. The calculated ¹H nuclear magnetic resonance chemical shifts for the monomers and dimers of the three model compounds of this series synthesized to date are in excellent agreement with experimental results for dilute and concentrated solutions in chloroform, respectively (Tan, X.; Fenniri, H.; Gray, M. R.Water enhances the aggregation of model asphaltenes in solution via hydrogen bonding. Energy Fuels 2009, 23, 3687). The ΔH and ΔG²⁹⁸ results show that hydrogen bonding is as important as π–π interactions for asphaltene aggregation.

3D-RISM-Dock: a new fragment-based drug design protocol - Nikolić, Dragan; Blinov, Nikolay; Wishart, David; Kovalenko, Andriy (Journal of Chemical Theory and Computation, 2012)
We explore a new approach in the rational design of specificity in molecular recognition of small molecules based on statistical-mechanical integral equation theory of molecular liquids in the form of the three-dimensional reference interaction site model with the Kovalenko–Hirata closure (3D-RISM-KH). The numerically stable iterative solution of conventional 3D-RISM equations includes the fragmental decomposition of flexible ligands, which are treated as distinct species in solvent mixtures of arbitrary complexity. The computed density functions for solution (including ligand) molecules are obtained as a set of discrete spatial grids that uniquely describe the continuous solvent-site distribution around the protein solute. Potentials of mean force derived from these distributions define the scoring function interfaced with the AutoDock program for an automated ranking of docked conformations. As a case study in terms of solvent composition, we analyze cooperative interactions encountered in the binding of a flexible thiamine molecule to the prion protein at near-physiological conditions. The predicted location and residency times of computed binding modes are in excellent agreement with the available experimental data.

Overcoming the barrier on time step size in multiscale molecular dynamics simulation of molecular liquids - Omelyan, Igor P.; Kovalenko, Andriy (Journal of Chemical Theory and Computation, 2012)
We propose and validate a new multiscale technique, the extrapolative isokinetic Nóse–Hoover chain orientational (EINO) motion multiple time step algorithm for rigid interaction site models of molecular liquids. It nontrivially combines the multiple time step decomposition operator method with a specific extrapolation of intermolecular interactions, complemented by an extended isokinetic Nosé–Hoover chain approach in the presence of translational and orientational degrees of freedom. The EINO algorithm obviates the limitations on time step size in molecular dynamics simulations. While the best existing multistep algorithms can advance from a 5 fs single step to a maximum 100 fs outer step, we show on the basis of molecular dynamics simulations of the TIP4P water that our EINO technique overcomes this barrier. Specifically, we have achieved giant time steps on the order of 500 fs up to 5 ps, which now become available in the study of equilibrium and conformational properties of molecular liquids without a loss of stability and accuracy.

Bandpass filter implemented with blazed waveguide sidewall gratings in silicon-on-insulator - Velasco, A. V.; Bock, P. J.; Cheben, P.; Calvo, M. L.; Schmid, J. H.; Lapointe, J.; Xu, D.-X.; Janz, S.; Delâge, A. (Electronics Letters, 2012)
The fabrication and experimental characterisation of a two-stage band-pass filter based on curved waveguide sidewall gratings is reported for the silicon-on-insulator platform. At each cascaded filtering stage, the spectral components of the input signal are dispersed by the diffraction grating formed in the sidewall of a silicon strip waveguide. Different wavelengths are focused onto different positions along the Rowland circle and the filter central wavelength is selected by a specific receiver waveguide. By using two consecutive filtering stages, both the filter passband profile and the stopband rejection ratio are substantially increased. The grating is apodised and chirped to ensure a constant effective index along the grating length to minimise phase distortions. Blazed geometry is used to maximise the diffraction efficiency to the −1st order. The device was fabricated with electron beam lithography and reactive ion etching using a single etch step. A bandwidth of 6.2 nm was measured near 1590 nm for the fabricated filter, with a roll-off of 4 dB/nm at the passband edge, and a stopband rejection of 40 dB.

Temperature dependence of gas-detection sensitivity of InGaAsSb/AlGaAsSb distributed feedback lasers at 2396 nm - Ventrudo, B. F.; Storey, C.; Gupta, J. A.; Bezinger, A. (Electronics Letters, 2012)
The HF gas detection sensitivity of GaSb-based distributed feedback lasers was studied in order to evaluate the potential use of operating temperature to control the laser output power in field applications. Measurements were made in the 2f wavelength modulation spectroscopy mode to monitor a prominent HF absorption feature at 2396 nm. An Allan variance analysis indicates that the best sensitivity is obtained when a larger thermoelectric current is applied to maintain temperature control by actively heating or cooling the laser. The reduced detection sensitivity for a setpoint near the ambient laser operating temperature is similar to that obtained without active temperature control.

Partitioning of ethanol into lipid membranes and its effect on fluidity and permeability as seen by X-ray and neutron scattering - Toppozini, Laura; Armstrong, Clare L.; Barrett, Matthew A.; Zheng, Songbo; Luo, Lindy; Nanda, Hirsh; García Sakai, Victoria; Rheinstädter, Maikel C. (Soft Matter, 2012)
We present a combined neutron and X-ray scattering investigation to study the effect of ethanol on the molecular structure and dynamics of lipid membranes. 1,2-Dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) powder hydrated with a 5 wt% ethanol solution (corresponding to 2 mol% of ethanol) was used in this study. From high-resolution X-ray experiments the position and partitioning of the ethanol molecules in the phospholipid bilayers was determined in their gel and fluid phases. We find that the ethanol molecules reside in the head group region of the bilayers, with 1.6 ethanol molecules per lipid molecule in the gel phase and 1.2 ethanol molecules per lipid molecule in the fluid phase. We find evidence for enhanced permeability in both fluid and gel phases of the phospholipid bilayers in the presence of ethanol molecules. Elastic and quasi-elastic neutron scattering data, obtained using a neutron backscattering spectrometer, was used to study slow, nanosecond molecular dynamics on length scales corresponding to lipid diffusion, acyl chain dynamics and solvent dynamics. While the presence of ethanol molecules had no observable effect on these types of dynamics in the fluid (Lα) phase, the membranes appeared to have a higher degree of order in gel (Lβ) and ripple (Pβ′) phases. In particular, lipid diffusion was found to be slower by a factor of two in the more rigid gel phase when ethanol was present.

Synthesis and enzymatic evaluation of ketose phosphonates: the interplay between mutarotation, monofluorination and acidity - Forget, Stephanie M.; Bhattasali, Debabrata; Hart, V. Catherine; Cameron, T. Stanley; Syvitski, Ray T.; Jakeman, David L. (Chemical Science, 2012)
Ketose-phosphonates may adopt open chain, or α- or β-furanosyl, or α- or β-pyranosyl configurational isomers in aqueous solution. An HPLC and NMR analysis of a series of ketose-phosphonates with a thymidylyltransferase (dTDP-glucose pyrophosphorylase) implied a rapid dynamic equilibrium between the pyranosyl forms of gluco-ketose phosphonate leading to efficient production of unique sugar nucleotide analogues. The preparation of diastereomerically pure gluco-configured monofluoromethylenephosphonates enabled the determination of the thymidylyltransferase preference for CHF stereochemistry. The effects of acidity upon thymidylyltransferase substrate specificity were determined using a series of monofluoro- and difluoro- ketose-phosphonates. WaterLOGSY NMR spectroscopy demonstrated a switching of the ordered Bi-Bi mechanism with ketose-phosphonate substrates. Ketose-phosphonates are presented as a unique class of sugar 1-phosphate analogues with potential applications as glycosyltransferase probes.

Perturbation induced formation of a 3D-network of microcrystals producing soft materials - Bardelang, David; Giorgi, Michel; Hornebecq, Virginie; Stepanov, Anatoli; Rizzato, Egon; Zaman, Md. Badruz; Chan, Gordon; Ouari, Olivier; Tordo, Paul (RSC Advances, 2012)
Toluene and 1-chloronaphthalene immobilization was observed when perturbing stimuli such as agitation or ultrasound are applied during the cooling of a hot supersaturated solution of the rigid dinitroxide bTbk. X-Ray diffraction and cryo-SEM on gels and solid samples (crystal, powder) confirmed the pivotal role of clathrate type microcrystals in the solvent immobilization process.

Supercapacitive carbon nanotube-cobalt molybdate nanocomposites prepared via solvent-free microwave synthesis - Xu, Zhanwei; Li, Zhi; Tan, Xuehai; Holt, Chris M. B.; Zhang, Li; Amirkhiz, Babak Shalchi; Mitlin, David (RSC Advances, 2012)
Cobalt molybdate (CoMoO4) nanoplatelets with a crystalline-amorphous core-shell structure anchored via multi-walled carbon nanotubes were prepared by a solvent-free microwave synthesis method. The entire procedure took only 15 min. The nanocomposite shows a promising capacitance of 170 F g−¹ with a potential window of 0.8 V, degrading by only 6.8% after 1000 cycles.

Kinetics studies of rapid strain-promoted [3 + 2]-cycloadditions of nitrones with biaryl-aza-cyclooctynone - McKay, Craig S.; Chigrinova, Mariya; Blake, Jessie A.; Pezacki, John Paul (Organic & Biomolecular Chemistry, 2012)
Strain-promoted cycloadditions of cyclic nitrones with biaryl-aza-cyclooctynone (BARAC) proceed with rate constants up to 47.3 M−¹ s−¹, this corresponds to a 47-fold rate enhancement relative to reaction of BARAC with benzyl azide and a 14-fold enhancement over previously reported strain promoted alkyne–nitrone cycloadditions (SPANC). Studies of the SPANC reaction using the linear free energy relationship defined by the Hammett equation demonstrated that the cycloaddition reaction has a rho value of 0.25 ± 0.04, indicating that reaction is not sensitive to substituents and thus should have broad applicability.

Structure, ordering, and surfaces of Pt–Fe alloy catalytic nanoparticles from quantitative electron microscopy and X-ray diffraction - Chan, Mickey C. Y.; Chen, Liang; Nan, Feihong; Britten, James F.; Bock, Christina; Botton, Gianluigi A. (Nanoscale, 2012)
The current challenge in catalyst development is to produce highly active and economical catalysts. This challenge cannot be overcome without an accurate understanding of catalyst structure, surfaces and morphology as the catalytic reactions occur on the surface active sites. Transmission Electron Microscopy (TEM) is an excellent tool for understanding the structures of the nanoparticles down to the atomic level in determining the relationship with the catalyst's performance in fuel cell applications. This paper describes a detailed structural characterization of Pt–Fe nanoparticles using aberration corrected TEM. Detailed analysis regarding the morphology, structural ordering, facets, nature of the surfaces, atomic displacements and compositions was carried out and presented in the context of their electrochemical performances. In addition, the effects of electrochemical cycling in terms of morphology and composition evolution of the nanoparticles were analyzed. Lastly, along with data from X-ray diffractometry, two different crystallographic models of the unknown Pt3Fe2 nanoparticle phase are proposed. The detailed characterization by TEM provides useful insights into the nanoparticle chemistry and structure that contributes to catalyst development for next generation fuel cells.

An upstream interacting context based framework for the computational inference of microRNA functions - Qiu, Chengxiang; Wang, Dong; Wang, Edwin; Cui, Qinghua (Molecular BioSystems, 2012)
With the rapid accumulation of microRNA (miRNAs), a class of newly identified small noncoding RNAs, in silico inference of miRNA functions has become one of the central tasks in miRNA bioinformatics. Traditional methods have helped in the understanding of miRNAs, but they also have limitations. In this paper, we first gave a brief review for the progress of bioinformatic methods in miRNA function inference and next presented a new framework (miRUPnet) for inferring the functions of miRNAs by functional analysis of a novel dimension of miRNA network, the context of its transcription factors (TFs) in a protein-protein interaction network. This dimension represents specific biological processes initiated by TF combinations and therefore differs from traditional methods in concept. To validate the accuracy of our method, we first comprehensively mined literature-reported miRNA functions and then made a comparison with the prediction result. The results show that even using the stringent TFBS rule, our method has independently predicted 68.2% of the literature reported miRNA functions, suggesting that miRUPnet has a high accuracy. Moreover, our approach successfully predicted specific functions that could not be inferred for given miRNAs using traditional methods. More importantly, it can distinguish miRNAs from the same family, as well as those present in multiple copies that cannot be differentiated through traditional methods. This study presents a new concept and dimension for miRNA function inference. miRUPnet represents an important and novel method for inferring the function of miRNAs. miRUPnet is available at http://cmbi.bjmu.edu.cn/mirupnet.

Growth and positioning of adipose-derived stem cells in microfluidic devices - Wadhawan, Nitin; Kalkat, Harmandeep; Natarajan, Kanmani; Ma, Xiuli; Gajjeraman, Sivakumar; Nandagopal, Saravanan; Hao, Ning; Li, Jing; Zhang, Michael; Deng, Jixian; Xiang, Bo; Mzengeza, Shadreck; et al. (Lab on a Chip, 2012)
Stem cells hold great promise for treatment of various degenerative diseases. However, clinical studies have only shown very moderate benefits of cell therapy. We believe that insufficiency of therapeutic benefits is due to limited homing of implanted stem cells to targeted organs. Microfluidic devices are a very useful research tool for quantitative characterizations of stem cells. The present study therefore was to assess the effects of epidermal growth factor (EGF) and direct current electric field (dcEF) on the growth and trafficking of adipose-derived stem cells (ASC). It was found that EGF did not affect cell proliferation in cell-culture flasks. However, ASC proliferated at a higher rate in microfluidic devices with continuous infusion of EGF. Furthermore, we found that ASC migrated toward an EGF gradient in microfluidic devices. Moreover, we found that ASC tended to position perpendicularly to dcEF. The results suggest that EGF and dcEF may be effective in guiding homing and trafficking of implanted ASC.

Microfluidic designs and techniques using lab-on-a-chip devices for pathogen detection for point-of-care diagnostics - Foudeh, Amir M.; Fatanat Didar, Tohid; Veres, Teodor; Tabrizian, Maryam (Lab on a Chip, 2012)
Effective pathogen detection is an essential prerequisite for the prevention and treatment of infectious diseases. Despite recent advances in biosensors, infectious diseases remain a major cause of illnesses and mortality throughout the world. For instance in developing countries, infectious diseases account for over half of the mortality rate. Pathogen detection platforms provide a fundamental tool in different fields including clinical diagnostics, pathology, drug discovery, clinical research, disease outbreaks, and food safety. Microfluidic lab-on-a-chip (LOC) devices offer many advantages for pathogen detection such as miniaturization, small sample volume, portability, rapid detection time and point-of-care diagnosis. This review paper outlines recent microfluidic based devices and LOC design strategies for pathogen detection with the main focus on the integration of different techniques that led to the development of sample-to-result devices. Several examples of recently developed devices are presented along with respective advantages and limitations of each design. Progresses made in biomarkers, sample preparation, amplification and fluid handling techniques using microfluidic platforms are also covered and strategies for multiplexing and high-throughput analysis, as well as point-of-care diagnosis, are discussed.

Fe3O4–silica core–shell nanoporous particles for high-capacity pH-triggered drug delivery - Zhang, X. F.; Mansouri, S.; Clime, L.; Ly, H. Q.; Yahia, L. 'H.; Veres, T. (Journal of Materials Chemistry, 2012)
We demonstrate a one-step procedure for the synthesis of Fe3O4–silica core–shell nanoparticles with hierarchically ultra-large pores independent of any post-treatment such as annealing and template-molecule removal. The nanoporous silica shells with available amine groups were functionalized by clickable linkers to produce pH-sensitive amides for regulating the release of an anti-cancer drug, doxorubicin (DOX). The loading amount of DOX reached up to 13.2 mg per 100 mg nanoparticles, 74.2% of which can be effectively released after 63 h at body temperature and pH 5 with decreased side effects. Such excellent features of these nanoparticles appear to arise from the integrated hierarchically ultra-large open-porosities and a homogeneous dispersibility in aqueous solution that has a great potential for their use as drug delivery systems.

Self-assembly of carboxylated polythiophene nanowires for improved bulk heterojunction morphology in polymer solar cells - Li, Weiwei; Worfolk, Brian J.; Li, Peng; Hauger, Tate C.; Harris, Kenneth D.; Buriak, Jillian M. (Journal of Materials Chemistry, 2012)
Conjugated regioregular poly[3-(5-carboxypentyl) thiophene-2,5-diyl] (P3CPenT), a derivative of poly(3-hexylthiophene) (P3HT), is introduced as a hole transport layer (HTL) for P3HT:PCBM plastic solar cells (PSCs). P3CPenT, a carboxyl-functionalized polythiophene, is insoluble in solvents typically used in the preparation of photoactive layers such as chloroform, chlorobenzene and dichlorobenzene, allowing successive processing of the photoactive layer without dissolution of the HTL. P3CPenT self-assembles into nanowires in DMSO solution and when cast as a film, reduces concentration gradients of P3HT:PCBM photoactive layers. P3HT:PCBM PSCs incorporating P3CPenT nanowires as the HTL have a higher fill factor (FF, 0.67) and power conversion efficiency (PCE, 3.7%) than devices with conventional PEDOT:PSS HTLs.

Bacteriophage based probes for pathogen detection - Singh, Amit; Arutyunov, Denis; Szymanski, Christine M.; Evoy, Stephane (The Analyst, 2012)
Rapid and specific detection of pathogenic bacteria is important for the proper treatment, containment and prevention of human, animal and plant diseases. Identifying unique biological probes to achieve a high degree of specificity and minimize false positives has therefore garnered much interest in recent years. Bacteriophages are obligate intracellular parasites that subvert bacterial cell resources for their own multiplication and production of disseminative new virions, which repeat the cycle by binding specifically to the host surface receptors and injecting genetic material into the bacterial cells. The precision of host recognition in phages is imparted by the receptor binding proteins (RBPs) that are often located in the tail-spike or tail fiber protein assemblies of the virions. Phage host recognition specificity has been traditionally exploited for bacterial typing using laborious and time consuming bacterial growth assays. At the same time this feature makes phage virions or RBPs an excellent choice for the development of probes capable of selectively capturing bacteria on solid surfaces with subsequent quick and automatic detection of the binding event. This review focuses on the description of pathogen detection approaches based on immobilized phage virions as well as pure recombinant RBPs. Specific advantages of RBP-based molecular probes are also discussed.

Highly corrosion resistant platinum–niobium oxide–carbon nanotube electrodes for the oxygen reduction in PEM fuel cells - Zhang, Li; Wang, Liya; Holt, Chris M. B.; Zahiri, Beniamin; Li, Zhi; Malek, Kourosh; Navessin, Titichai; Eikerling, Michael H.; Mitlin, David (Energy & Environmental Science, 2012)
Nanocomposite materials consisting of platinum deposited on carbon nanotubes are emerging electrocatalysts for the oxygen reduction reaction in PEM fuel cells. However, these materials albeit showing promising electrocatalytic activities suffer from unacceptable rates of corrosion during service. This study demonstrates an effective strategy for creating highly corrosion-resistant electrocatalysts utilizing metal oxide coated carbon nanotubes as a support for Pt. The electrode geometry consisted of a three-dimensional array of multi-walled carbon nanotubes grown directly on Inconel and conformally covered by a bilayer of Pt/niobium oxide. The activities of these hybrid carbon-metal oxide materials are on par with commercially available carbon-supported Pt catalysts. We show that a sub-nanometre interlayer of NbO2 provides effective protection from electrode corrosion. After 10,000 cyclic voltammetry cycles from 0.5 V to 1.4 V, the loss of electrochemical surface area, reduction of the half-wave potential, and the loss of specific activity of the NbO2 supported Pt were 10.8%, 8 mV and 10.3%, respectively. Under the same conditions, the catalytic layers with Pt directly deposited onto carbon nanotubes had a loss of electrochemical area, reduction of half-wave potential and loss of specific activity of 47.3%, 65 mV and 65.8%, respectively. The improved corrosion resistance is supported by microstructural observations of both electrodes in their post-cycled state. First principles calculations at the density functional theory level were performed to gain further insight into changes in wetting properties, stability and electronic structure introduced by the insertion of the thin NbO2 film.

American cranberry (Vaccinium macrocarpon) extract affects human prostate cancer cell growth via cell cycle arrest by modulating expression of cell cycle regulators - Déziel, Bob; MacPhee, James; Patel, Kunal; Catalli, Adriana; Kulka, Marianna; Neto, Catherine; Gottschall-Pass, Katherine; Hurta, Robert (Food & Function, 2012)
Prostate cancer is one of the most common cancers in the world, and its prevalence is expected to increase appreciably in the coming decades. As such, more research is necessary to understand the etiology, progression and possible preventative measures to delay or to stop the development of this disease. Recently, there has been interest in examining the effects of whole extracts from commonly harvested crops on the behaviour and progression of cancer. Here, we describe the effects of whole cranberry extract (WCE) on the behaviour of DU145 human prostate cancer cells in vitro. Following treatment of DU145 human prostate cancer cells with 10, 25 and 50 μg ml−¹ of WCE, respectively for 6 h, WCE significantly decreased the cellular viability of DU145 cells. WCE also decreased the proportion of cells in the G2-M phase of the cell cycle and increased the proportion of cells in the G1 phase of the cell cycle following treatment of cells with 25 and 50 μg ml−¹ treatment of WCE for 6 h. These alterations in cell cycle were associated with changes in cell cycle regulatory proteins and other cell cycle associated proteins. WCE decreased the expression of CDK4, cyclin A, cyclin B1, cyclin D1 and cyclin E, and increased the expression of p27. Changes in p16INK4a and pRBp107 protein expression levels also were evident, however, the changes noted in p16INK4a and pRBp107 protein expression levels were not statistically significant. These findings demonstrate that phytochemical extracts from the American cranberry (Vaccinium macrocarpon) can affect the behaviour of human prostate cancer cells in vitro and further support the potential health benefits associated with cranberries.

Improved in situ Hf isotope ratio analysis of zircon using newly designed X skimmer cone and jet sample cone in combination with the addition of nitrogen by laser ablation multiple collector ICP-MS - Hu, Zhaochu; Liu, Yongsheng; Gao, Shan; Liu, Wengui; Zhang, Wen; Tong, Xirun; Lin, Lin; Zong, Keqing; Li, Ming; Chen, Haihong; Zhou, Lian; Yang, Lu (Journal of Analytical Atomic Spectrometry, 2012)
The effect of three different cone combinations on the performance of laser ablation MC-ICP-MS (Neptune plus) for the in situ Hf isotope analysis of zircon were investigated. The signal sensitivities of Hf, Yb and Lu were improved by a factor of 1.4 and 2.5, respectively, with using the X skimmer cone + standard sampler cone and the X skimmer cone + Jet sample cone compared to the standard arrangement (H skimmer cone + standard sample cone). However, when using the high-sensitivity Jet sample cone, the instrumental mass fractionation for hafnium displayed a large non-linear component that could not be corrected using the normal mass fractionation laws. The magnitude of this non-linear mass fractionation was strongly related to the central gas flow rate. The in situ Hf isotope analysis of zircon standards 91500 and Mud Tank using the Jet cone displayed large deviations (410–470 ppm) at the optimum central gas flow rate for Hf, which seriously deteriorated the performance of the Jet cone. The addition of 4 ml min−¹ nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to not only increase the sensitivity of Hf by a factor of 2.1, but also suppress this non-linear mass fractionation. The determined Yb/Hf and Lu/Hf ratios at their corresponding optimum makeup gas flow rates for Hf intensity were found to be reduced by factors of 2 and 1.3 in the presence of nitrogen, respectively, which would benefit the accurate in situ determination of Hf isotopes in high-content Yb and Lu samples. Compared to the standard arrangement, the corresponding precision (2σ) of 176Hf/177Hf for single spot analysis of zircon standard 91500 was improved from 224 ppm to 50 ppm by using the newly designed X-skimmer cone and Jet sample cone in combination with the nitrogen addition technique. The determined 176Hf/177Hf ratios are in excellent agreement with published values in five reference zircon standards (91500, GJ-1, Mud Tank, Penglai and Plešovice). Our first Hf isotopic results from zircon standard M257 (0.281544 ± 0.000018; 2SD, n = 151) showed that it was fairly homogeneous in Hf isotopes. These results clearly demonstrate that the present analytical method has the potential to become an important tool for the pursuit of high-quality in situ Hf isotope data for zircons.

Cation exchange: A facile method to make NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles with a thin, tunable, and uniform shell - Dong, Cunhai; Korinek, Andreas; Blasiak, Barbara; Tomanek, Boguslaw; Van veggel, Frank C. J. M. (Chemistry of Materials, 2012)
Cation exchange was performed on up-conversion NaYF4:Yb,Tm nanoparticles, resulting in NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles as indicated by electron energy-loss spectroscopy 2D mapping. Results show that core–shell nanoparticles with a thin, tunable, and uniform shell of subnanometer thickness can be made via this cation exchange process. The resulting NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles have an enhanced up-conversion intensity relative to the initial core nanoparticles. As potential magnetic resonance imaging (MRI) contrast agents, they were tested for their proton relaxivities. The r1 relaxivity per Gd³⁺ ion of the nanoparticles with a thin NaGdF4 shell (ca. 0.6 nm thick) measured at 9.4 T was found to be 2.33 mM–1·s–1. This r1 relaxivity is among the highest in all the reported NaYF4–NaGdF4 core–shell nanoparticles. The r1 relaxivity per nanoparticle is 1.56 × 104 mM–1·s–1, which is over 4000 times higher than commercial Gd³⁺-complexes. The very high proton relaxivity per nanoparticle is critical for targeted MRI as such nanoparticles provide strong contrast even in low concentrations. The presented cation exchange method is a promising way to manufacture core–shell nanoparticles with up-conversion NaYF4:Yb,Tm core and paramagnetic NaGdF4 shell for bimodal imaging, i.e. MR and optical imaging.
Keywords: cation exchange; sodium lanthanide fluoride nanoparticles; core−shell nanoparticles; magnetic resonance imaging; up-conversion optical imaging

Pb3TeCo3V2O14: A potential multiferroic Co bearing member of the dugganite series - Silverstein, H. J.; Cruz-kan, K.; Hallas, A. M.; Zhou, H. D.; Donaberger, R. L.; Hernden, B. C.; Bieringer, M.; Choi, E. S.; Hwang, J. M.; Wills, A. S.; Wiebe, C. R. (Chemistry of Materials, 2012)
Polycrystalline Pb3TeCo3V2O14, a structural analogue of the multiferroic Ba3NbFe3Si2O14, was synthesized and characterized using X-ray diffraction, magnetic susceptibility, specific heat, dielectric constant, and neutron diffraction. Magnetic susceptibility, specific heat capacity measurements, and bond valence analysis confirmed that the V5+ ion is nonmagnetic, while Co2+ is in its high spin state (S = 3/2). Two magnetic transitions were seen at TN1 = 8.6 K and TN2 = 6.0 K where the spins first adopt a magnetic structure with propagation vector k = (0.752,0,1/2) and reorder into a commensurate structure with propagation vector k = (5/6,5/6,1/2). Changes in the dielectric constant at both magnetic phase transitions suggest that magnetoelectric coupling exists in Pb3TeCo3V2O14.

Nano-architecture and material designs for water splitting photoelectrodes - Chen, Hao Ming; Chen, Chih Kai; Liu, Ru-Shi; Zhang, Lei; Zhang, Jiujun; Wilkinson, David P. (Chemical Society Reviews, 2012)
This review concerns the efficient conversion of sunlight into chemical fuels through the photoelectrochemical splitting of water, which has the potential to generate sustainable hydrogen fuel. In this review, we discuss various photoelectrode materials and relative design strategies with their associated fabrication for solar water splitting. Factors affecting photoelectrochemical performance of these materials and designs are also described. The most recent progress in the research and development of new materials as well as their corresponding photoelectrodes is also summarized in this review. Finally, the research strategies and future directions for water splitting are discussed with recommendations to facilitate the further exploration of new photoelectrode materials and their associated technologies.

Body centered cubic magnesium niobium hydride with facile room temperature absorption and four weight percent reversible capacity - Tan, Xuehai; Wang, Liya; Holt, Chris M. B.; Zahiri, Beniamin; Eikerling, Michael H.; Mitlin, David (Physical Chemistry Chemical Physics, 2012)
We have synthesized a new metastable metal hydride with promising hydrogen storage properties. Body centered cubic (bcc) magnesium niobium hydride (Mg0.75Nb0.25)H2 possesses 4.5 wt% hydrogen gravimetric density, with 4 wt% being reversible. Volumetric hydrogen absorption measurements yield an enthalpy of hydride formation of −53 kJ mol−¹ H2, which indicates a significant thermodynamic destabilization relative to the baseline −77 kJ mol−¹ H2 for rutile MgH2. The hydrogenation cycling kinetics are remarkable. At room temperature and 1 bar hydrogen it takes 30 minutes to absorb a 1.5 μm thick film at sorption cycle 1, and 1 minute at cycle 5. Reversible desorption is achieved in about 60 minutes at 175 °C. Using ab initio calculations we have examined the thermodynamic stability of metallic alloys with hexagonal close packed (hcp) versus bcc crystal structure. Moreover we have analyzed the formation energies of the alloy hydrides that are bcc, rutile or fluorite.

Flux engineering to control in-plane crystal and morphological orientation - Laforge, Joshua M.; Ingram, Grayson L.; Taschuk, Michael T.; Brett, Michael J. (Crystal Growth & Design, 2012)
We tailored nanostructured morphology and crystal texture of iron nanocolumns by engineering the inclination and azimuthal directions of the collimated flux characteristic of glancing angle deposition (GLAD). Under continuous substrate rotation, the flux is azimuthally isotropic within one rotation. With large substrate rotation speeds, we can deposit vertical nanocolumns with a faceted, tetrahedral apex, BCC crystal structure and 111 fiber texture. Designing the flux to have an azimuthal 3-fold symmetry, which reflects the symmetry of the tetrahedral apex, allows us to induce both an in-plane and out-of-plane texture (biaxial texture) by evolutionary selection. In-plane crystal orientation is accompanied by a preferential azimuthal nanocolumn orientation, where the sides of tetrahedral apex are directed toward the flux direction. This work demonstrates the flux engineering technique, which can orient in-plane crystal texture and morphology of crystalline nanocolumns on amorphous substrates. This control is a useful addition to vapor–solid, physical self-assembly with the potential to improve the performance of porous thin film architectures as biaxial buffer layers, and in a variety of device applications such as photovoltaics and energy storage.

The Paternò–Büchi reaction: importance of triplet states in the excited-state reaction pathway - Brogaard, Rasmus Y.; Schalk, Oliver; Boguslavskiy, Andrey E.; Enright, Gary D.; Hopf, Henning; Raev, Vitaly; Tarcoveanu, Eliza; Sølling, Theis I.; Stolow, Albert (Physical Chemistry Chemical Physics, 2012)
The Paternò–Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction. We studied the excited-state dynamics of the isolated molecule in a molecular beam using femtosecond time-resolved photoelectron spectroscopy and ab initio calculations. The results show that inter-system crossing within two picoseconds competes efficiently with the reaction in the singlet manifold. Thus, the PB reaction in this model system takes place in the triplet state on a time scale of nanoseconds. This result stresses the importance of triplet states in the excited-state pathway of the PB reaction involving aromatic carbonyl compounds, even in situations in which the reacting moieties are in immediate vicinity.

Activity-Based Protein Profiling of the Escherichia coli GlpG Rhomboid Protein Delineates the Catalytic Core - Sherratt, Allison R.; Blais, David R.; Ghasriani, Houman; Pezacki, John Paul; Goto, Natalie K. (Biochemistry, 2012)
Rhomboid proteins comprise the largest class of intramembrane protease known, being conserved from bacteria to humans. The functional status of these proteases is typically assessed through direct or indirect detection of peptide cleavage products. Although these assays can report on the ability of a rhomboid to catalyze peptide bond cleavage, differences in measured hydrolysis rates can reflect changes in the structure and activity of catalytic residues, as well as the ability of the substrate to access the active site. Here we show that a highly reactive and sterically unencumbered fluorophosphonate activity-based protein profiling probe can be used to report on the catalytic integrity of active site residues in the Escherichia coli GlpG protein. We used results obtained with this probe on GlpG in proteomic samples, in combination with a conventional assay of proteolytic function on purified samples, to identify residues that are located on the cytoplasmic side of the lipid bilayer that are required for maximal proteolytic activity. Regions tested include the 90-residue aqueous-exposed N-terminus that encompasses a globular structure that we have determined by solution nuclear magnetic resonance, along with residues on the cytoplasmic side of the transmembrane domain core. While in most cases mutation or elimination of these residues did not significantly alter the catalytic status of the GlpG active site, the lipid-facing residue Arg227 was found to be important for maintaining a catalytically competent active site. In addition, we found a functionally critical region outside the transmembrane domain (TMD) core that is required for maximal protease activity. This region encompasses an additional 8–10 residues on the N-terminal side of the TMD core that precedes the first transmembrane segment and was not previously known to play a role in rhomboid function. These findings highlight the utility of the activity-based protein profiling approach for the characterization of rhomboid function.

Infrared spectra of ethylene clusters: (C2D4)2 and (C2D4)3 - Rezaei, M.; Michaelian, K. H.; McKellar, A. R. W.; Moazzen-Ahmadi, N. (Physical Chemistry Chemical Physics, 2012)
Spectra of ethylene dimers and trimers are studied in the ν11 fundamental band region of C2D4 (≈2200 cm−¹) using a tuneable quantum cascade laser to probe a pulsed supersonic slit jet expansion. The dimer spectrum is that of a prolate symmetric top perpendicular band, with a distinctive appearance because the A rotational constant is almost exactly equal to six times the B constant. The analysis supports the previously determined cross-shaped dimer structure with D2d symmetry. An ethylene trimer has not previously been observed with rotational resolution. The spectrum is that of an oblate symmetric top parallel band. It leads to a proposed trimer structure which is barrel shaped and has C3h or C3 symmetry, with the ethylene monomer C–C axes approximately aligned along the trimer symmetry axis.

Pressure amorphized ices – an atomistic perspective - Tse, John S.; Klug, Dennis D. (Physical Chemistry Chemical Physics, 2012)
We offer our viewpoint on the nature of amorphous ices produced by pressurization of crystalline ice Ih and the inter-relationship between them from an atomistic perspective. We argue that the transformation of high density amorphous (HDA) ice from crystalline ice is due to a mechanical process arising from the instability of the ice Ih structure. The densification of HDA upon thermal annealing under pressure is a relaxation process. The conversion of the densified amorphous ice to a lower density form (LDA) upon the release of pressure can be attributed to a similar process. It is speculated that amorphous ices are metastable frustrated structures due to the large activation barriers associated with proton reorientation in the formation of the underlying stable crystalline ice polymorphs.

Nonlinear optics: high harmonics with a twist - Patchkovskii, Serguei; Spanner, Michael (Nature Physics, 2012)
Optical vortices usually break up when they propagate through nonlinear media. Now, however, experiments show the helical structure of an infrared beam can survive a high-harmonic-generation process. This could lead to a table-top source of attosecond helical light pulses.

Quantum interference and phonon-mediated back-action in lateral quantum-dot circuits - Granger, G.; Taubert, D.; Young, C. E.; Gaudreau, L.; Kam, A.; Studenikin, S. A.; Zawadzki, P.; Harbusch, D.; Schuh, D.; Wegscheider, W.; Wasilewski, Z. R.; Clerk, A. A.; et al. (Nature Physics, 2012)
Spin qubits have been successfully realized in electrostatically defined, lateral few-electron quantum-dot circuits. Qubit readout typically involves spin to charge information conversion, followed by a charge measurement made using a nearby biased quantum point contact (QPC). It is critical to understand the back-action disturbances resulting from such a measurement approach. Previous studies have indicated that QPC detectors emit phonons which are then absorbed by nearby qubits. We report here the observation of a pronounced back-action effect in multiple dot circuits, where the absorption of detector-generated phonons is strongly modified by a quantum interference effect, and show that the phenomenon is well described by a theory incorporating both the QPC and coherent phonon absorption. Our combined experimental and theoretical results suggest strategies to suppress back-action during the qubit readout procedure.

Spintronics: all-optical spin-wave control - Freeman, Mark R.; Diao, Zhu (Nature Photonics, 2012)
Spin waves show promise as a means of transporting information in integrated magnetic devices, but convenient ways to control their properties are required. Now directional control of spin-wave emission using photonics has been demonstrated in an all-optical pump–probe experiment.

Mapping coherence in measurement via full quantum tomography of a hybrid optical detector - Zhang, Lijian; Coldenstrodt-Ronge, Hendrik B.; Datta, Animesh; Puentes, Graciana; Lundeen, Jeff S.; Jin, Xian-Min; Smith, Brian J.; Plenio, Martin B.; Walmsley, Ian A. (2012)
Quantum states and measurements exhibit wave-like (continuous) or particle-like (discrete) character. Hybrid discrete–continuous photonic systems are key to investigating fundamental quantum phenomena, generating superpositions of macroscopic states, and form essential resources for quantum-enhanced applications such as entanglement distillation and quantum computation, as well as highly efficient optical telecommunications. Realizing the full potential of these hybrid systems requires quantum-optical measurements sensitive to non-commuting observables such as field quadrature amplitude and photon number. However, a thorough understanding of the practical performance of an optical detector interpolating between these two regions is absent. Here, we report the implementation of full quantum detector tomography, enabling the characterization of the simultaneous wave and photon-number sensitivities of quantum-optical detectors. This yields the largest parameterization to date in quantum tomography experiments, requiring the development of novel theoretical tools. Our results reveal the role of coherence in quantum measurements and demonstrate the tunability of hybrid quantum-optical detectors.
Keywords: Quantum optics; Optoelectronic devices and components

New magnetic phase diagram of (Sr,Ca)₂RuO₄ - Carlo, J. P.; Goko, T.; Gat-Malureanu, I. M.; Russo, P. L.; Savici, A. T.; Aczel, A. A.; MacDougall, G. J.; Rodriguez, J. A.; Williams, T. J.; Luke, G. M.; Wiebe, C. R.; Yoshida, Y.; et al. (Nature Materials, 2012)
High- Tc cuprates, iron pnictides, organic BEDT and TMTSF, alkali-doped C60, and heavy-fermion systems have superconducting states adjacent to competing states exhibiting static antiferromagnetic or spin density wave order. This feature has promoted pictures for their superconducting pairing mediated by spin fluctuations. Sr2RuO4 is another unconventional superconductor which almost certainly has a p-wave pairing. The absence of known signatures of static magnetism in the Sr-rich side of the (Ca, Sr) substitution space, however, has led to a prevailing view that the superconducting state in Sr2RuO4 emerges from a surrounding Fermi-liquid metallic state. Using muon spin relaxation and magnetic susceptibility measurements, we demonstrate here that (Sr,Ca)2RuO4 has a ground state with static magnetic order over nearly the entire range of (Ca, Sr) substitution, with spin-glass behaviour in Sr1.5Ca0.5RuO4 and Ca1.5Sr0.5RuO4. The resulting new magnetic phase diagram establishes the proximity of superconductivity in Sr2RuO4 to competing static magnetic order.
Keywords: Superconductors; Magnetic materials

Type I interferon induces necroptosis in macrophages during infection with Salmonella enterica serovar Typhimurium - Robinson, Nirmal; McComb, Scott; Mulligan, Rebecca; Dudani, Renu; Krishnan, Lakshmi; Sad, Subash (Nature Immunology, 2012)
Salmonella enterica serovar Typhimurium (S. Typhimurium) is a virulent pathogen that induces rapid host death. Here we observed that host survival after infection with S. Typhimurium was enhanced in the absence of type I interferon signaling, with improved survival of mice deficient in the receptor for type I interferons (Ifnar1−/− mice) that was attributed to macrophages. Although there was no impairment in cytokine expression or inflammasome activation in Ifnar1−/− macrophages, they were highly resistant to S. Typhimurium–induced cell death. Specific inhibition of the kinase RIP1 or knockdown of the gene encoding the kinase RIP3 prevented the death of wild-type macrophages, which indicated that necroptosis was a mechanism of cell death. Finally, RIP3-deficient macrophages, which cannot undergo necroptosis, had similarly less death and enhanced control of S. Typhimurium in vivo. Thus, we propose that S. Typhimurium induces the production of type I interferon, which drives necroptosis of macrophages and allows them to evade the immune response.

Localizing internal friction along the reaction coordinate of protein folding by combining ensemble and single-molecule fluorescence spectroscopy - Borgia, Alessandro; Wensley, Beth G.; Soranno, Andrea; Nettels, Daniel; Borgia, Madeleine B.; Hoffmann, Armin; Pfeil, Shawn H.; Lipman, Everett A.; Clarke, Jane; Schuler, Benjamin (Nature Communications, 2012)
Theory, simulations and experimental results have suggested an important role of internal friction in the kinetics of protein folding. Recent experiments on spectrin domains provided the first evidence for a pronounced contribution of internal friction in proteins that fold on the millisecond timescale. However, it has remained unclear how this contribution is distributed along the reaction and what influence it has on the folding dynamics. Here we use a combination of single-molecule Förster resonance energy transfer, nanosecond fluorescence correlation spectroscopy, microfluidic mixing and denaturant- and viscosity-dependent protein-folding kinetics to probe internal friction in the unfolded state and at the early and late transition states of slow- and fast-folding spectrin domains. We find that the internal friction affecting the folding rates of spectrin domains is highly localized to the early transition state, suggesting an important role of rather specific interactions in the rate-limiting conformational changes.

Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt - De Vries, B. L.; Acke, B.; Blommaert, J. A. D. L.; Waelkens, C.; Waters, L. B. F. M.; Vandenbussche, B.; Min, M.; Olofsson, G.; Dominik, C.; Decin, L.; Barlow, M. J.; Brandeker, A.; et al. (2012)
Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2−2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x ≈ 0.29). In the cold outskirts of the β Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of β Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15–45 astronomical units from the star (one astronomical unit is the Sun–Earth distance), determine their magnesium-rich composition (x = 0.01 ± 0.001) and show that they make up 3.6 ± 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though β Pictoris is more massive and more luminous and has a different planetary system architecture.

Resolving the time when an electron exits a tunnelling barrier - Shafir, Dror; Soifer, Hadas; Bruner, Barry D.; Dagan, Michal; Mairesse, Yann; Patchkovskii, Serguei; Ivanov, Misha Yu.; Smirnova, Olga; Dudovich, Nirit (2012)
The tunnelling of a particle through a barrier is one of the most fundamental and ubiquitous quantum processes. When induced by an intense laser field, electron tunnelling from atoms and molecules initiates a broad range of phenomena such as the generation of attosecond pulses, laser-induced electron diffraction and holography. These processes evolve on the attosecond timescale (1 attosecond ≡ 1 as = 10−^18 seconds) and are well suited to the investigation of a general issue much debated since the early days of quantum mechanics5, 6, 7—the link between the tunnelling of an electron through a barrier and its dynamics outside the barrier. Previous experiments have measured tunnelling rates with attosecond time resolution and tunnelling delay times. Here we study laser-induced tunnelling by using a weak probe field to steer the tunnelled electron in the lateral direction and then monitor the effect on the attosecond light bursts emitted when the liberated electron re-encounters the parent ion. We show that this approach allows us to measure the time at which the electron exits from the tunnelling barrier. We demonstrate the high sensitivity of the measurement by detecting subtle delays in ionization times from two orbitals of a carbon dioxide molecule. Measurement of the tunnelling process is essential for all attosecond experiments where strong-field ionization initiates ultrafast dynamics. Our approach provides a general tool for time-resolving multi-electron rearrangements in atoms and molecules—one of the key challenges in ultrafast science.

Pathophysiology of the neurovascular unit: disease cause or consequence? - Stanimirovic, Danica b; Friedman, Alon (Journal of Cerebral Blood Flow & Metabolism, 2012)
Pathophysiology of the neurovascular unit (NVU) is commonly seen in neurological diseases. The typical features of NVU pathophysiology include tissue hypoxia, inflammatory and angiogenic activation, as well as initiation of complex molecular interactions between cellular (brain endothelial cells, astroctyes, pericytes, inflammatory cells, and neurons) and acellular (basal lamina) components of the NVU, jointly resulting in increased blood–brain barrier permeability, brain edema, neurovascular uncoupling, and neuronal dysfunction and damage. The evidence of important role of the brain vascular compartment in disease pathogenesis has elicited the debate whether the primary vascular events may be a cause of the neurological disease, as opposed to a mere participant recruited by a primary neuronal origin of pathology? Whereas some hereditary and acquired cerebral angiopathies could be considered a primary cause of neurological symptoms of the disease, the epidemiological studies showing a high degree of comorbidity among vascular disease and dementias, including Alzheimer's disease, as well as migraine and epilepsy, suggested that primary vascular pathology may be etiological factor causing neuronal dysfunction or degeneration in these diseases. This review focuses on recent hypotheses and evidence, suggesting that pathophysiology of the NVU may be initiating trigger for neuronal pathology and subsequent neurological manifestations of the disease.
Keywords: Alzheimer's disease; blood–brain barrier; genetic vasculopathies; migraine; neurovascular unit; seizures

cIAP1 and cIAP2 limit macrophage necroptosis by inhibiting Rip1 and Rip3 activation - McComb, S.; Cheung, H. H.; Korneluk, R. G.; Wang, S.; Krishnan, L.; Sad, S. (Cell Death & Differentiation, 2012)
Cellular inhibitor of apoptosis proteins (cIAPs) have emerged as important anti-cell death mediators, particularly in cancer. Although they are known to be expressed in immune tissue, their specific immune function remains unclear. We observed that degradation of cIAPs with SMAC mimetic (SM) results in death of primary bone-marrow-derived macrophages. SM-induced death of macrophages occurred by programmed necrosis (necroptosis), which was dependent on TNF receptor expression. Consistent with necroptosis, SM-induced death of macrophages was abrogated by inhibition of receptor interacting protein 1 (Rip1) kinase signaling or by receptor interacting protein 3 (Rip3) knockdown. SM-induced necroptosis was also dependent on inhibition of SM-induced apoptosis due to the expression of the endogenous caspase inhibitor, xIAP. We found that cIAPs limit Rip3, and to a lesser extent Rip1, expression via post-transcriptional mechanisms, leading to inhibition of the Rip1–Rip3 death complex (necrosome). Reduced cIAP activity in vivo, via SM treatment or specific knockout of either cIAP, resulted in elevated macrophage cell death and compromised control of an intracellular bacterium, Listeria monocytogenes. These results show that cIAPs have an important role in limiting programmed necrosis of macrophages, which facilitates effective control of a pathogen.
Keywords: innate immunity; macrophage; inflammation; host–pathogen interactions

The dependence of ice microphysics on aerosol concentration in arctic mixed-phase stratus clouds during ISDAC and M-PACE - Jackson, Robert C.; Mcfarquhar, Greg M.; Korolev, Alexei V.; Earle, Michael E.; Liu, Peter S. K.; Lawson, R. Paul; Brooks, Sarah; Wolde, Mengistu; Laskin, Alexander; Freer, Matt (Journal of Geophysical Research, 2012)
Cloud and aerosol data acquired by the National Research Council of Canada (NRC) Convair-580 aircraft in, above, and below single-layer arctic stratocumulus cloud during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 were used to test three aerosol indirect effects hypothesized to act in mixed-phase clouds: the riming indirect effect, the glaciation indirect effect, and the thermodynamic indirect effect. The data showed a correlation of R = 0.78 between liquid drop number concentration, Nliq inside cloud and ambient aerosol number concentration NPCASP below cloud. This, combined with increasing liquid water content LWC with height above cloud base and the nearly constant vertical profile of Nliq, suggested that liquid drops nucleated from aerosol at cloud base. No evidence of a riming indirect effect was observed, but a strong correlation of R = 0.69 between ice crystal number concentration Ni and NPCASP above cloud was noted. Increases in ice nuclei (IN) concentration with NPCASP above cloud for 2 flight dates combined with the subadiabatic LWC profiles suggest possible mixing of IN from cloud top consistent with the glaciation indirect effect. The lower Nice and lower effective radius rel for the more polluted ISDAC cases compared to data collected in cleaner single-layer stratocumulus conditions during the Mixed-Phase Arctic Cloud Experiment is consistent with the operation of the thermodynamic indirect effect. However, more data in a wider variety of meteorological and surface conditions, with greater variations in aerosol forcing, are required to identify the dominant aerosol forcing mechanisms in mixed-phase arctic clouds.
Keywords: arctic clouds; cloud aerosol interactions; mixed phase clouds

Protein profiling in potato (Solanum tuberosum L.) leaf tissues by differential centrifugation - Lim, Sanghyun; Chisholm, Kenneth; Coffin, Robert H.; Peters, Rick D.; Al-Mughrabi, Khalil I.; Wang-Pruski, Gefu; Pinto, Devanand M. (Journal of Proteome Research, 2012)
Foliar diseases, such as late blight, result in serious threats to potato production. As such, potato leaf tissue becomes an important substrate to study biological processes, such as plant defense responses to infection. Nonetheless, the potato leaf proteome remains poorly characterized. Here, we report protein profiling of potato leaf tissues using a modified differential centrifugation approach to separate the leaf tissues into cell wall and cytoplasmic fractions. This method helps to increase the number of identified proteins, including targeted putative cell wall proteins. The method allowed for the identification of 1484 nonredundant potato leaf proteins, of which 364 and 447 were reproducibly identified proteins in the cell wall and cytoplasmic fractions, respectively. Reproducibly identified proteins corresponded to over 70% of proteins identified in each replicate. A diverse range of proteins was identified based on their theoretical pI values, molecular masses, functional classification, and biological processes. Such a protein extraction method is effective for the establishment of a highly qualified proteome profile.
Keywords: potato leaf; protein profiling; differential centrifugation; reproducibility; cell wall and cytoplasmic fractions

Isolation of steroidal glycosides from the Caribbean sponge Pandaros acanthifolium - Berrué, Fabrice; Mcculloch, Malcolm W. B.; Boland, Patricia; Hart, Saskia; Harper, Mary Kay; Johnston, James; Kerr, Russell (Journal of Natural Products, 2012)
Four new steroidal glycosides, acanthifoliosides G–J (1–4), were isolated as minor constituents from the Caribbean marine sponge Pandaros acanthifolium. These metabolites are characterized by a highly oxygenated D ring and the presence of a disaccharide rhamnose-glucose residue and a rhamnose at positions C-3 and C-15, respectively. Their structures were established on the basis of extensive interpretation of 1D and 2D NMR data and HRESIMS analyses. The absolute configurations of the glucose and rhamnose sugars were determined by preparing aldose o-tolylthiocarbamate derivatives and comparison to authentic standards by LC/HRESIMS. Acanthifolioside G (1) exhibited antioxidant and cytoprotective activities.

Ultraclean emission from InAsP quantum dots in defect-free wurtzite InP nanowires - Dalacu, Dan; Mnaymneh, Khaled; Lapointe, Jean; Wu, Xiaohua; Poole, Philip J.; Bulgarini, Gabriele; Zwiller, Val; Reimer, Michael E. (Nano Letters, 2012)
We report on the ultraclean emission from single quantum dots embedded in pure wurtzite nanowires. Using a two-step growth process combining selective-area and vapor–liquid–solid epitaxy, we grow defect-free wurtzite InP nanowires with embedded InAsP quantum dots, which are clad to diameters sufficient for waveguiding at λ 950 nm. The absence of nearby traps, at both the nanowire surface and along its length in the vicinity of the quantum dot, manifests in excitonic transitions of high spectral purity. Narrow emission line widths (30 μeV) and very-pure single photon emission with a probability of multiphoton emission below 1% are achieved, both of which were not possible in previous work where stacking fault densities were significantly higher.
Keywords: Nanowire; Qauntum dot; InAs/InP; Single photon source; Chemical beam epitaxy; Selective-area VLS growth

UV-initiated hydrosilylation on hydrogen-terminated silicon (111): rate coefficient increase of two orders of magnitude in the presence of aromatic electron acceptors - Huck, Lawrence A.; Buriak, Jillian M. (Langmuir, 2012)
UV-initiated (254 nm) hydrosilylation of hexadecene on Si(111)-H has been studied in the presence of various aliphatic and aromatic molecules (additives). Many of these additives cause an enhancement in the pseudo-first-order rate coefficient (kobs) of hydrosilylation, some up to 200× faster than observed in neat hexadecene. It is proposed that these additives capture the photoejected electron from the surface, thereby increasing the probability of reaction of the alkene with the surface hole (h+), leading to Si–C bond formation. While the ability of these additives to increase kobs is related to their reduction potential, aromatic additives are particularly efficient; we suspect this is due to the relatively strong physisorption of the aromatic molecules leading to a favorable geometry for electron transfer. The presence of these additives permits the use of a much lower intensity of UV light (30 μW/cm²), reducing the probability of photodegradation of the monolayer, and maximum coverage can be reached within minutes.

Nonfouling hydrophilic poly(ethylene glycol) engraftment strategy for PDMS/SU-8 heterogeneous microfluidic devices - Yeh, Po Ying; Zhang, Zhiyi; Lin, Min; Cao, Xudong (Langmuir, 2012)
We report a novel nonfouling passivation method using poly(ethylene glycol) (PEG) engraftment on the surfaces of poly(dimethylsiloxane) (PDMS) microfluidic devices sealed with SU-8. To achieve bonding between the PDMS and SU-8 surfaces, the PDMS surface was first functionalized with amines by treatment with 3-aminopropyltrimethoxysilane (APTMS) for subsequent reaction with epoxide functional groups on SU-8 surfaces. To modify the heterogeneous surfaces of the resulting PDMS/SU-8 microfluidic device further, the remaining SU-8 surfaces were amino functionalized using ethylene diamine (EDA), followed by treating both amino-functionalized PDMS and SU-8 surfaces with mPEG-NHS (N-hydroxysuccinimide) through an amine-NHS reaction for facile PEG immobilizations, thus simultaneously modifying both PDMS and SU-8 surfaces in one reaction. Detailed surface analyses such as the water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were conducted to confirm the chemical reactions and characterize the resulting surface properties. To test the efficacy of this surface-modification strategy, we conducted nonspecific protein and particle binding tests using microfluidic devices with and without modifications. The PEG-modified PDMS/SU-8 device surfaces showed a 64.5% reduction in nonspecific bovine serum albumin (BSA) adsorption in comparison to that of the unmodified surfaces and 92.0 and 95.8% reductions in microbead adhesion under both stagnant and flowing conditions, respectively.

Spectroelectrochemical characterization of small hemoproteins adsorbed within nanostructured mesoporous ITO electrodes - Schaming, Delphine; Renault, Christophe; Tucker, Ryan T.; Lau-Truong, Stéphanie; Aubard, Jean; Brett, Michael J.; Balland, Véronique; Limoges, Benoît (Langmuir, 2012)
3D nanostructured transparent indium tin oxide (ITO) electrodes prepared by glancing angle deposition (GLAD) were used for the spectroelectrochemical characterization of cytochrome c (Cyt c) and neuroglobin (Nb). These small hemoproteins, involved as electron-transfer partners in the prevention of apoptosis, are oppositely charged at physiological pH and can each be adsorbed within the ITO network under different pH conditions. The resulting modified electrodes were investigated by UV–visible absorption spectroscopy coupled with cyclic voltammetry. By using nondenaturating adsorption conditions, we demonstrate that both proteins are capable of direct electron transfer to the conductive ITO surface, sharing apparent standard potentials similar to those reported in solution. Preservation of the 3D protein structure upon adsorption was confirmed by resonance Raman (rR) spectroscopy. Analysis of the derivative cyclic voltabsorptograms (DCVA) monitored either in the Soret or the Q bands at scan rates up to 1 V s–¹ allowed us to investigate direct interfacial electron transfer kinetics. From the DCVA shape and scan rate dependences, we conclude that the interaction of Cyt c with the ITO surface is more specific than Nb, suggesting an oriented adsorption of Cyt c and a random adsorption of Nb on the ITO surface. At the same time, Cyt c appears more sensitive to the experimental adsorption conditions, and complete denaturation of Cyt c may occur as evidenced from cross-correlation of rR spectroscopy and spectroelectrochemistry.

Nitric oxide delivery by core/shell superparamagnetic nanoparticle vehicles with enhanced biocompatibility - Zhang, X. F.; Mansouri, S.; Mbeh, D. A.; Yahia, L’H.; Sacher, E.; Veres, T. (Langmuir, 2012)
We report the synthesis of Fe3O4/silica core/shell nanoparticles and their functionalization with S-nitrosothiols. These nanoparticles are of immense interest because of their nitric oxide (NO) release capabilities in human alveolar epithelial cells. Moreover, they act as large storage reservoirs of NO that can be targeted magnetically to the specific site with a sustainable release of NO for up to 50 h. Such nanoparticles provide an enhancement of the biocompatibility with released NO while allowing intracellular accumulation ascribed to their small size.

A combined vibrational sum frequency generation spectroscopy and atomic force microscopy study of sphingomyelin–cholesterol monolayers - Weeraman, Champika; Chen, Maohui; Moffatt, Douglas J.; Lausten, Rune; Stolow, Albert; Johnston, Linda J. (Langmuir, 2012)
A combination of vibrational sum frequency generation spectroscopy and atomic force microscopy is used to study the changes in morphology and conformational order in monolayers prepared from three natural sphingomyelin (SM) mixtures as a function of surface pressure and cholesterol concentration. The most homogeneous SM gave monolayers with well-ordered acyl chains and few gauche defects with relatively small effects of either increasing surface pressure or cholesterol addition. Heterogeneous SM mixtures with a mixture of acyl chain lengths or with significant fractions of unsaturated acyl chains had much larger contributions from gauche defects at low surface pressure and gave increasingly well-ordered monolayers as the surface pressure increased. They also showed substantial increases in lipid chain order after cholesterol addition. Overall, these results are consistent with the strong hydrogen bonding capacity of SM leading to well-ordered monolayers over a range of surface pressures. The changes in acyl chain order for natural SMs as a function of cholesterol are relevant to formation of sphingolipid–cholesterol enriched domains in cell membranes.

Dispersions of nanocrystalline cellulose in aqueous polymer solutions: structure formation of colloidal rods - Boluk, Yaman; Zhao, Liyan; Incani, Vanessa (Langmuir, 2012)
The steady-state shear and linear viscoelastic deformations of semidilute suspensions of rod-shaped nanocrystalline cellulose (NCC) particles in 1.0% hydroxyethyl cellulose and carboxymethyl cellulose solutions were investigated. Addition of NCC at the onset of semidilute suspension concentration significantly altered the rheological and linear viscoelastic properties of semidilute polymer solutions. The low-shear viscosity values of polymers solutions were increased 20–490 times (depending on polymer molecular weight and functional groups) by the presence of NCC. NCC suspensions in polymer solutions exhibited yield stresses up to 7.12 Pa. Viscoelasticity measurements also showed that NCC suspended polymer solutions had higher linear elastic moduli than the loss moduli. All of those results revealed the gel formation of NCC particles and presence of internal structures. The formation of a weak gel structure was due to the nonadsorbing macromolecules which caused the depletion-induced interaction among NCC particles. A simple interaction energy model was used to show successfully the flocculation of NCC particles in the presence of nonadsorbing polymers. The model is based on the incorporation of the depletion interaction term between two parallel plates into the DLVO theory for cubic prismatic rod shaped NCC particles.

Superparamagnetic microspheres with controlled macroporosity generated in microfluidic devices - Paquet, Chantal; Jakubek, Zygmunt J.; Simard, Benoit (ACS Applied Materials & Interfaces, 2012)
A microfluidic approach to preparing superparamagnetic microspheres with tunable porosity is described. In this method, droplets consisting of iron oxide nanoparticles, a functional polymer and solvent are formed in a microfluidic channel. The droplets are subsequently collected in solutions of sodium dodecyl sulfate (SDS) where the solvent is left to diffuse out of the droplet phase. By adjusting the concentration of the SDS and the polarity of the solvent of the dispersed phase, the porosity of the microparticles is controlled from non porous to porous structure. The formation of the pores is shown to depend on the rate at which solvent diffuses out of the droplet phase and the availability of SDS to adsorb at the droplet interface.
Keywords: microfluidic; superparamagnetic; porous; microparticles; assembly; magnetic separation

Electrochemical supercapacitor electrodes from sponge-like graphene nanoarchitectures with ultrahigh power density - Xu, Zhanwei; Li, Zhi; Holt, Chris M. B.; Tan, Xuehai; Wang, Huanlei; Amirkhiz, Babak Shalchi; Stephenson, Tyler; Mitlin, David (The Journal of Physical Chemistry Letters, 2012)
We employed a microwave synthesis process of cobalt phthalocyanine molecules templated by acid-functionalized multiwalled carbon nanotubes to create three-dimensional sponge-like graphene nanoarchitectures suited for ionic liquid-based electrochemical capacitor electrodes that operate at very high scan rates. The sequential “bottom-up” molecular synthesis and subsequent carbonization process took less than 20 min to complete. The 3D nanoarchitectures are able to deliver an energy density of 7.1 W·h kg–¹ even at an extra high power density of 48 000 W kg–¹. In addition, the ionic liquid supercapacitor based on this material works very well at room temperature due to its fully opened structures, which is ideal for the high-power energy application requiring more tolerance to temperature variation. Moreover, the structures are stable in both ionic liquids and 1 M H2SO4, retaining 90 and 98% capacitance after 10 000 cycles, respectively.
Keywords: electrochemical capacitor; three-dimensional; graphene; carbon nanotube; microwave

Multifunctional resistive-heating and color-changing monofilaments produced by a single-step coaxial melt-spinning process - Laforgue, Alexis; Rouget, Geoffroy; Dubost, Sylvain; Champagne, Michel F.; Robitaille, Lucie (ACS Applied Materials & Interfaces, 2012)
Multifunctional coaxial monofilaments were successfully produced by melt-spinning several polymer composites in a single-step. The external layer of the monofilaments was a thermochromic composite having a color-transition at 40 °C (above the ambient temperature) in order to avoid control interferences by the external temperature. The core layer of the monofilaments was a conductive polymer nanocomposite whose resistive heating properties were used to control the monofilament’s temperature and therefore its color using electrical current. The careful selection of the materials and adequate formulation allowed to obtain a trilayer structure with enhanced compatibility between the layers. The mechanical properties of the monofilaments were improved by a solid-state stretching step while also decreasing their diameter. A 64 cm ³ prototype fabric was woven to characterize the resistive-heating and color-changing properties of the monofilaments. Exceptional thermal output levels were reached, with a temperature rising up to over 100 °C at voltages above 110 V. The reversible color change properties were also successfully demonstrated.
Keywords: monofilament; melt-spinning; multifunctional; electrochromic; color change; resistive heating; coaxial monofilament; smart textile

A (nearly) universally applicable method for modeling noncovalent interactions using B3LYP - Torres, Edmanuel; DiLabio, Gino A. (The Journal of Physical Chemistry Letters, 2012)
B3LYP is the most widely used density-functional theory (DFT) approach because it is capable of accurately predicting molecular structures and other properties. However, B3LYP is not able to reliably model systems in which noncovalent interactions are important. Here we present a method that corrects this deficiency in B3LYP by using dispersion-correcting potentials (DCPs). DCPs are utilized by simple modifications to input files and can be used in any computational package that can read effective-core potentials. Therefore, the technique requires no programming. DCPs (developed for H, C, N, and O) produce the best results when used in conjunction with 6-31+G(2d,2p) basis sets. The B3LYP-DCP approach was tested on the S66, S22, and HSG-A benchmark sets of noncovalently interacting dimers and trimers and was found to, on average, significantly outperform almost all other DFT-based methods that were designed to treat van der Waals interactions. Users of B3LYP who wish to model systems in which noncovalent interactions (viz., steric repulsion, hydrogen bonding, π-stacking) are present, should consider B3LYP-DCP.
Keywords: dispersion-corrected density-functional theory; B3LYP; dispersion-correcting potentials; B3LYP-DCP; accurate noncovalent binding energies

NaDyF4 nanoparticles as T2 contrast agents for ultrahigh field magnetic resonance imaging - Das, Gautom Kumar; Johnson, Noah J. J.; Cramen, Jordan; Blasiak, Barbara; Latta, Peter; Tomanek, Boguslaw; van Veggel, Frank C. J. M. (The Journal of Physical Chemistry Letters, 2012)
A major limitation of the commonly used clinical MRI contrast agents (CAs) suitable at lower magnetic field strengths (<3.0 T) is their inefficiency at higher fields (>7 T), where next-generation MRI scanners are going. We present dysprosium nanoparticles (β-NaDyF4 NPs) as T2 CAs suitable at ultrahigh fields (9.4 T). These NPs effectively enhance T2 contrast at 9.4 T, which is 10-fold higher than the clinically used T2 CA (Resovist). Evaluation of the relaxivities at 3 and 9.4 T show that the T2 contrast enhances with an increase in NP size and field strength. Specifically, the transverse relaxivity (r2) values at 9.4 T were 64 times higher per NP (20.3 nm) and 6 times higher per Dy3+ ion compared to that at 3 T, which is attributed to the Curie spin relaxation mechanism. These results and confirming phantom MR images demonstrate their effectiveness as T2 CAs in ultrahigh field MRIs.

Influence of hydrated silica surfaces on interfacial water in the presence of clathrate hydrate forming gases - Bagherzadeh, S. Alireza; Englezos, Peter; Alavi, Saman; Ripmeester, John A. (The Journal of Physical Chemistry C, 2012)
We study the hydrated silica–water interface in the presence of methane or carbon dioxide gas with molecular dynamics simulations. The simulations are performed with a limited amount of water, which forms a meniscus between two hydroxylated silica surfaces separated by 40 to 60 Å. Simulations were performed with the remaining space of the simulation cell left empty or filled with different numbers of methane or carbon dioxide gas molecules. The meniscus is used to determine the contact angle between water and silica in the absence and presence of the gases. The distribution profiles of the water and gas phases are determined over the duration of the simulation. The water number density in the layers adjacent to the silica is higher, and these layers are more structured and less mobile compared with water layers far from the surface. Additionally, the concentrations of the gases are significantly higher at the liquid and silica interfaces than in other locations in the gas phase. We speculate that the enhanced concentration of gases at the interface along with the extended contact area (curved meniscus compared with flat interface in the absence of silica surfaces) between water and guest molecules at the meniscus as well as lesser mobility of water molecules near the silica surface may provide a mechanism for the heterogeneous nucleation of the clathrate hydrate in water-wetting porous medium.

Molecular simulation of gas transport in hydrated nafion membranes: influence of aqueous nanostructure - Ban, Shuai; Huang, Cheng; Yuan, Xiao-Zi; Wang, Haijiang (The Journal of Physical Chemistry C, 2012)
Molecular simulation was used to investigate the nanoporous structure of hydrated Nafion membrane and its impact on gas transport. The structural changes of Nafion induced by water uptakes were characterized in terms of the density and the pore size distribution. It was found that membrane hydration leads to a growth of separated water domains, which are gradually interconnected via newly formed water channels. The sorption and diffusion of H2 and O2 were studied at different temperatures and water contents of Nafion. Simulation results show that the water loading reduces gas solubilities as the adsorption site of gas molecules transforms from small cavities to large surfaces due to the enlargement of aqueous domains. However, such an opening of Nafion porous nanostructure effectively reduces gas diffusion barriers, and results in a 2-fold increase of O2 diffusivities. Molecular configurations of gases inside Nafion nanoporous frameworks were examined on the basis of calculated radial distribution functions.

Effect of clathrate hydrate formation and decomposition on NMR parameters in THF–D2O Solution - Rousina-Webb, Alexander; Leek, Donald M.; Ripmeester, John (The Journal of Physical Chemistry B, 2012)
The NMR spin–lattice relaxation time (T1), spin–spin relaxation time (T2) and the diffusion coefficient D were measured for 1H in a 1:17 mol % solution of tetrahydrofuran (THF) in D2O. The aim of the work was to clarify some earlier points raised regarding the utility of these measurements to convey structural information on hydrate formation and reformation. A number of irregularities in T1 and T2 measurements during hydrate processes reported earlier are explained in terms of the presence of interfaces and possible temperature gradients. We observe that T1 and T2 in solution are exactly the same before and after hydrate formation, thus confirming that the solution is isotropic. This is inconsistent with the presence of memory effects, at least those that may affect the dynamics to which T1 and T2 are sensitive. The measurement of the diffusion coefficient for a number of hours in the subcooled solution before nucleation proved invariant with time, again suggesting that the solution remains isotropic without affecting the guest dynamics and diffusion.

Multinuclear solid-state nuclear magnetic resonance and density functional theory characterization of interaction tensors in taurine - O’Dell, Luke A.; Ratcliffe, Christopher I.; Kong, Xianqi; Wu, Gang (The Journal of Physical Chemistry A, 2012)
A variety of experimental solid-state nuclear magnetic resonance (NMR) techniques has been used to characterize each of the elements in 2-aminoethane sulfonic acid (taurine). A combination of 15N cross-polarization magic angle spinning (CPMAS), 14N ultrawideline, and 14N overtone experiments enabled a determination of the relative orientation of the nitrogen electric field gradient and chemical shift tensors. 17O spectra recorded from an isotopically enriched taurine sample at multiple magnetic fields allowed the three nonequivalent oxygen sites to be distinguished, and NMR parameters calculated from a neutron diffraction structure using density functional theory allowed the assignment of the 17O parameters to the correct crystallographic sites. This is the first time that a complete set of 17O NMR tensors are reported for a sulfonate group. In combination with 1H and 13C MAS spectra, as well as a previously reported 33S NMR study, this provides a very broad set of NMR data for this relatively simple organic molecule, making it a potentially useful structure on which to test DFT calculation methods (particularly for the quadrupolar nuclei 14N, 17O, and 33S) or NMR crystallography approaches.

Molecular modeling of the dissociation of methane hydrate in contact with a silica surface - Bagherzadeh, S. Alireza; Englezos, Peter; Alavi, Saman; Ripmeester, John A. (The Journal of Physical Chemistry B, 2012)
We use constant energy, constant volume (NVE) molecular dynamics simulations to study the dissociation of the fully occupied structure I methane hydrate in a confined geometry between two hydroxylated silica surfaces between 36 and 41 Å apart, at initial temperatures of 283, 293, and 303 K. Simulations of the two-phase hydrate/water system are performed in the presence of silica, with and without a 3 Å thick buffering water layer between the hydrate phase and silica surfaces. Faster decomposition is observed in the presence of silica, where the hydrate phase is prone to decomposition from four surfaces, as compared to only two sides in the case of the hydrate/water simulations. The existence of the water layer between the hydrate phase and the silica surface stabilizes the hydrate phase relative to the case where the hydrate is in direct contact with silica. Hydrates bound between the silica surfaces dissociate layer-by-layer in a shrinking core manner with a curved decomposition front which extends over a 5–8 Å thickness. Labeling water molecules shows that there is exchange of water molecules between the surrounding liquid and intact cages in the methane hydrate phase. In all cases, decomposition of the methane hydrate phase led to the formation of methane nanobubbles in the liquid water phase.

Reactions of the cumyloxyl and benzyloxyl radicals with strong hydrogen bond acceptors. Large enhancements in hydrogen abstraction reactivity determined by substrate/radical hydrogen bonding - Salamone, Michela; DiLabio, Gino A.; Bietti, Massimo (The Journal of Organic Chemistry, 2012)
A kinetic study on hydrogen abstraction from strong hydrogen bond acceptors such as DMSO, HMPA, and tributylphosphine oxide (TBPO) by the cumyloxyl (CumO•) and benzyloxyl (BnO•) radicals was carried out in acetonitrile. The reactions with CumO• were described in terms of a direct hydrogen abstraction mechanism, in line with the kinetic deuterium isotope effects, kH/kD, of 2.0 and 3.1 measured for reaction of this radical with DMSO/DMSO-d6 and HMPA/HMPA-d18. Very large increases in reactivity were observed on going from CumO• to BnO•, as evidenced by kH(BnO•)/kH(CumO•) ratios of 86, 4.8 × 10³, and 1.6 × 10^4 for the reactions with HMPA, TBPO, and DMSO, respectively. The kH/kD of 0.91 and 1.0 measured for the reactions of BnO• with DMSO/DMSO-d6 and HMPA/HMPA-d18, together with the kH(BnO•)/kH(CumO•) ratios, were explained on the basis of the formation of a hydrogen-bonded prereaction complex between the benzyloxyl α-C–H and the oxygen atom of the substrates followed by hydrogen abstraction. This is supported by theoretical calculations that show the formation of relatively strong prereaction complexes. These observations confirm that in alkoxyl radical reactions specific hydrogen bond interactions can dramatically influence the hydrogen abstraction reactivity, pointing toward the important role played by structural and electronic effects.

High-efficiency inverted solar cells based on a low bandgap polymer with excellent air stability - Chu, Ta-Ya; Tsang, Sai-Wing; Zhou, Jiayun; Verly, Pierre G.; Lu, Jianping; Beaupré, Serge; Leclerc, Mario; Tao, Ye (Solar Energy Materials and Solar Cells, 2012)
A high-efficiency inverted bulk heterojunction (BHJ) solar cell with good air stability is fabricated using annealing-free ZnO nanocrystals as an electron-transport layer and a blend of a low bandgap polymer PDTSTPD and PC71BM as an active layer. A power conversion efficiency as high as 6.7% has been achieved on the inverted devices with an active area of 1.0 cm² using nitrobenzene as a processing additive. The device is highly stable, retaining 85% of its original efficiency after being stored in air for 32 days even without encapsulation.
Keywords: Inverted organic solar cells; Alternating dithienosilole and thienopyrrole-4,6-dione copolymer; ZnO nanocrystals; Processing additives; Air stability

Community patterns of soil bacteria and nematodes in relation to geographic distance - Monroy, Fernando; van der Putten, Wim H.; Yergeau, Étienne; Mortimer, Simon R.; Duyts, Henk; Bezemer, T. Martijn (Soil Biology and Biochemistry, 2012)
Ecosystems consist of aboveground and belowground subsystems and the structure of their communities is known to change with distance. However, most of this knowledge originates from visible, aboveground components, whereas relatively little is known about how soil community structure varies with distance and if this variability depends on the group of organisms considered. In the present study, we analyzed 30 grasslands from three neighboring chalk hill ridges in southern UK to determine the effect of geographic distance (1–198 km) on the similarity of bacterial communities and of nematode communities in the soil. We found that for both groups, community similarity decayed with distance and that this spatial pattern was not related to changes either in plant community composition or soil chemistry. Site history may have contributed to the observed pattern in the case of nematodes, since the distance effect depended on the presence of different nematode taxa at one of the hill ridges. On the other hand, site-related differences in bacterial community composition alone could not explain the spatial turnover, suggesting that other factors, such as biotic gradients and local dispersal processes that we did not include in our analysis, may be involved in the observed pattern. We conclude that, independently of the variety of causal factors that may be involved, the decay in similarity with geographic distance is a characteristic feature of both communities of soil bacteria and nematodes.
Keywords: Geographic distance; Taxa turnover; Spatial distribution; PCR-DGGE; Grasslands; Microbial biogeography; Community similarity

Decoupling sensor morphology and material: atomic layer deposition onto nanocolumn scaffolds - Taschuk, M. T.; Harris, K. D.; Smetaniuk, D. P.; Brett, M. J. (Sensors and Actuators B: Chemical, 2012)
We have demonstrated direct surface modification of nanocolumn relative humidity sensors with conformal coatings deposited by atomic layer deposition (ALD). TiO2 and Si nanocolumn films were fabricated using glancing-angle deposition (GLAD). Both film types were subsequently coated with ≈0.3–4 nm thick ALD TiO2. The impact of the addition of subnanometer TiO2 layers on water contact angle, sensor responsivity, and the utility of an ultraviolet regeneration procedure has been tested. We have found that TiO2 coatings as thin as 0.5 nm provide much of the humidity sensing and regeneration functionality of a photocatalytic TiO2 film. In principle, any GLAD film architecture may be used as a scaffold for an active sensing layer, decoupling surface functionality and nanoscale morphology. Such capability offers an additional degree of freedom for designers of nanostructured gas sensors.
Keywords: Glancing angle deposition; Atomic layer deposition; TiO2; Si; SiO2; Relative humidity; Sensors

Thermal spray 2012 : proceedings from the international spray conference and exposition - Lima, R. S.; Agarwal, A.; Hyland, M. M.; Lau, Y.-C.; Li, C.-J.; McDonald, A.; Toma, F.-L. (ASM International, 2012)
Complete proceedings, 156 papers, from ITSC 2012: Proceedings from the International Thermal Spray Conference and Exposition, May 21-24, 2012, Houston, Texas, USA.

Poly(lactic acid) crystallization - Saeidlou, Sajjad; Huneault, Michel A.; Li, Hongbo; Park, Chul B. (Progress in Polymer Science, 2012)
Poly(lactic acid) is a biobased and compostable thermoplastic polyester that has rapidly evolved into a competitive commodity material over the last decade. One key bottleneck in extending the use of PLA is the control of its crystallinity. Understanding the crystallization behavior is particularly crucial to control PLA's degradation rate, thermal resistance as well as optical, mechanical and barrier properties. PLA crystallization has also been a particularly rich topic from a fundamental point of view because of the existence of the two enantiomeric forms of lactic acid that can be used to control the crystallization rate but also to form high melting point stereocomplex structures. This article presents an overview of the current understanding on the fundamentals of PLA crystallization in quiescent conditions and on the practical means to enhance its rate. Data from the abundant literature on PLA crystallization were compiled and analyzed to provide comprehensive relationships between crystallization kinetics and the main molecular structure characteristics of PLA. In addition, the most promising efforts in enhancing PLA crystallization kinetics through plasticization or heterogeneous nucleation were reviewed.
Keywords: Poly(lactic acid); Polylactide; PLA; Crystallization; Kinetics; Review

Degradation mechanism of benzodithiophene-based conjugated polymers when exposed to light in air - Alem, Salima; Wakim, Salem; Lu, Jianping; Robertson, Gilles; Ding, Jianfu; Tao, Ye (ACS Applied Materials & Interfaces, 2012)
We report the investigation of the air photostability of benzo[1,2-b:4,5-b′]dithiophene (BDT) based conjugated polymers using UV–visible spectroscopy, X-ray photoelectron spectroscopy, gel permeation chromatography, and nuclear magnetic resonance spectroscopy. Three low band gap alternating D–A copolymers consisting of 3-fluoro-2-heptylcarbonylthieno[3,4-b]thiophene and alkyl-substituted BDT, alkoxy-substituted BDT, or dithienosilole, respectively, were prepared for investigating their photovoltaic performance and photostability. After only two hours of simultaneous exposure to light and air, the main absorption peak of the polymer films containing BDT units blue-shifted and its intensity dramatically decreased. We demonstrated that the BDT unit underwent dramatic structural change under illumination in air by reacting with the oxygen molecules at the excited state, leading to the disruption of the main-chain conjugation of the polymer. As a result, the color of the alkyl-BDT based polymer film permanently changed from deep blue to light yellow. In contrast, the dithienosilole based polymer was quite stable when treated under the same condition with negligible change in the absorption spectrum.
Keywords: benzodithiophene; low band gap polymers; solar cell; bulk heterojunction; photostability

Size reduction of CdSe/ZnS quantum dots by a peptidic amyloid supergelator - Zaman, Md. Badruz; Bardelang, David; Prakesch, Michaël; Leek, Donald M.; Naubron, Jean-Valère; Chan, Gordon; Wu, Xiaohua; Ripmeester, John A.; Ratcliffe, Christopher I.; Yu, Kui (ACS Applied Materials and Interfaces, 2012)
Anchoring of a self-assembling dipeptide on the surface of core/shell CdSe/ZnS quantum dots resulted in a competition between coordination of the surface atoms of the QDs and the strong tendency for the dipeptide to self-assemble in toluene. This resulted in a mild QD etching and in a corresponding increase in the band gap of the nanocrystals whose photoluminescent emission gradually turns blue with time. The FmocLeuLeuOH dipeptide supergelator self-assembles in fibrils in which the Fmoc groups are surrounded by the pendant isobutyl side chains of the leucine residues with vibrational circular dichroism (VCD) and liquid- and solid-state NMR attributes of twist anti-parallel β-sheets.
Keywords: nanoparticles; etching; peptide; gelator; self-assembly; quantum dots

Large-Scale Production of PMMA/SWCNT Composites Based on SWCNT Modified with PMMA - Fraser, Robin Anderson; Stoeffler, Karen; Ashrafi, Behnam; Zhang, Yunfa; Simard, Benoit (ACS Applied Materials & Interfaces, 2012)
In this work, a two-step method consisting of in situ polymerization of polymethyl methacrylate (PMMA) in the presence of single-walled carbon nanotubes (SWCNT), followed by the redispersion of the resulting compound in dimethylformamide (DMF), was used to fabricate SWCNT modified with PMMA (SWCNT–PMMA). Raman spectroscopy revealed that PMMA was merely wrapped around the SWCNT when raw SWCNT or purified SWCNT were used as the starting material. However, PMMA was covalently bonded to SWCNT when acid treated SWCNT (SWCNT-COOH) was used as the starting material. SWCNT–PMMA compounds were further diluted in pure PMMA by conventional melt compounding at large scale (several kilograms) to obtain transparent composites containing 0.09 wt % SWCNT. The micro- and nano-dispersion of the SWCNT in the composites were analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal and mechanical properties of the composites were determined by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, and Charpy impact testing. At the the low SWCNT loading studied, the tensile properties remain unchanged, whereas the impact strength improves by 20%.
Keywords: single-walled carbon nanotubes (SWCNT); polymethyl methacrylate (PMMA); covalent functionalization; dispersion

Capillary electrophoresis mass spectrometry for the characterization of O-acetylated N-glycans from fish serum - Jayo, Roxana G.; Li, Jianjun; Chen, David D. Y. (Analytical Chemistry, 2012)
O-Acetylated N-glycans from fish serum of Atlantic salmon (Salmo salar) are characterized by capillary electrophoresis (CE) in conjunction with both laser-induced fluorescence (LIF) and mass spectrometry (MS) detection methods. Glycans derivatized with negatively charged fluorescent label 8-aminopyrene-1,2,6-trisulfonate (APTS) were separated to obtain a CE-LIF profile of the complex glycan mixture, and the profile concurs with that obtained by using electrospray mass spectrometry. The identity of the APTS-labeled glycans was confirmed by CE–MS. The same glycans can be identified also in their native state by CE–MS without derivatization. The structural variations of O-acetylated sialic acid isomers in fish serum glycans are investigated by CE–MS/MS. Selected ion monitoring provided useful structural information of the underivatized glycans from fragmentation spectra. New complex fish serum glycans that are not reported previously were observed and characterized. These methods may be useful not only for the characterization of acetylation of complex glycans but also to study other types of glycan modifications, as well as to allow determination of overall glycan composition in glycoproteins.

Protein quantitation using Ru-NHS ester tagging and isotope dilution high-pressure liquid chromatography–inductively coupled plasma mass spectrometry determination - Liu, Rui; Lv, Yi; Hou, Xiandeng; Yang, Lu; Mester, Zoltan (Analytical Chemistry, 2012)
An accurate, simple, and sensitive method for the direct determination of proteins by nonspecies specific isotope dilution and external calibration high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICPMS) is described. The labeling of myoglobin (17 kDa), transferrin (77 kDa), and thyroglobulin (670 kDa) proteins was accomplished in a single-step reaction with a commercially available bis(2,2′-bipyridine)-4′-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester-bis(hexafluorophosphate) (Ru-NHS ester). Using excess amounts of Ru-NHS ester compared to the protein concentration at optimized labeling conditions, constant ratios for Ru to proteins were obtained. Bioconjugate solutions containing both labeled and unlabeled proteins as well as excess Ru-NHS ester reagent were injected onto a size exclusion HPLC column for separation and ICPMS detection without any further treatment. A 99Ru enriched spike was used for nonspecies specific ID calibration. The accuracy of the method was confirmed at various concentration levels. An average recovery of 100% ± 3% (1 standard deviation (SD), n = 9) was obtained with a typical precision of better than 5% RSD at 100 μg mL–1 for nonspecies specific ID. Detection limits (3SD) of 1.6, 3.2, and 7.0 fmol estimated from three procedure blanks were obtained for myoglobin, transferrin, and thyroglobulin, respectively. These detection limits are suitable for the direct determination of intact proteins at trace levels. For simplicity, external calibration was also tested. Good linear correlation coefficients, 0.9901, 0.9921, and 0.9980 for myoglobin, transferrin, and thyroglobulin, respectively, were obtained. The measured concentrations of proteins in a solution were in good agreement with their volumetrically prepared values. To the best of our knowledge, this is the first application of nonspecies specific ID for the accurate and direct determination of proteins using a Ru-NHS ester labeling reagent.

Nonlinear signal response in electrospray mass spectrometry: implications for quantitation of arsenobetaine using stable isotope labeling by liquid chromatography and electrospray orbitrap mass spectrometry - Ouerdane, Laurent; Meija, Juris; Bakirdere, Sezgin; Yang, Lu; Mester, Zoltán (Analytical Chemistry, 2012)
Isotope amount ratio measurements by electrospray ionization mass spectrometry show large systematic biases. Moreover, the signal ratio response can vary nonlinearly with respect to the amount ratio depending on the concentration of the analyte or coeluting matrix components, among other things. Since isotope dilution relies inherently on the linearity of response, accurate quantitation is then more difficult to achieve. In this study, we outline a method to eliminate the quantitation errors due to the effects of the nonlinear signal response. The proposed approach is a hybrid of the method of standard additions and isotope dilution allowing correction for nonlinear trend. As a proof of concept, determination of arsenobetaine content in fish tissue was performed using liquid chromatography coupled with a linear quadrupole ion trap (LTQ) Orbitrap mass spectrometer. The nonlinear isotope dilution method could, in principle, be applied to correct isotope ratio measurement biases in popular relative quantitation methods of biomolecules such as stable isotope labeling by amino acids in cell culture (SILAC), isotope-coded affinity tag (ICAT), or isobaric tags for relative and absolute quantification (iTRAQ).

Porous graphitized carbon monolith as an electrode material for probing direct bioelectrochemistry and selective detection of hydrogen peroxide - He, Xiaoyun; Zhou, Lin; Nesterenko, Ekaterina P.; Nesterenko, Pavel N.; Paull, Brett; Omamogho, Jesse O.; Glennon, Jeremy D.; Luong, John H. T. (Analytical Chemistry, 2012)
For the first time, graphitized carbon particles with a high surface area have been prepared and evaluated as a new material for probing direct electrochemistry of hemoglobin (Hb). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging revealed that the carbon monolithic skeleton was constructed by a series of mesopores with irregular shapes and an average pore diameter of 5.6 nm. With a surface area of 239.6 m2/g, carbon particles exhibited three major Raman peaks as commonly observed for carbon nanotubes and other carbon materials, i.e., the sp3 and sp2 carbon phases coexisted in the sample. A glassy carbon electrode modified with carbon monoliths and didodecyldimethylammonium bromide exhibited direct electron transfer between Hb molecules and the underlying electrode with a transfer rate constant of 6.87 s–1. The enzyme electrode displayed a pair of quasi-reversible reduction–oxidation peaks at −0.128 and −0.180 V, reflecting the well-known feature of the heme [Fe3+/Fe2+] redox couple: a surface-controlled electrochemical process with one electron transfer. This reagentless biosensing approach was capable of detecting H2O2, a simple molecule but plays an important role in analytical and biological chemistry, as low as 0.1 μM with linearity of 0.1–60 μM and a response time of <0.8 s, comparing favorably with other carbon based electrodes (5 s).

Negative chemical ionization GC/MS determination of nitrite and nitrate in seawater using exact matching double spike isotope dilution and derivatization with triethyloxonium tetrafluoroborate - Pagliano, Enea; Meija, Juris; Sturgeon, Ralph E.; Mester, Zoltan; D’Ulivo, Alessandro (Analytical Chemistry, 2012)
The alkylation of nitrite and nitrate by triethyloxonium tetrafluoroborate allows determination of their ethyl esters by headspace GC–MS. In the present study, significant improvement in analytical performance are achieved by using negative chemical ionization (CI–). Detection limits are improved for at least an order of magnitude than those achieved using electron impact ionization (EI). The derivatization procedure has been optimized and alkaline conditions are adopted to minimize the conversion of nitrite to nitrate (determined to be 0.07% at 100 mg/L NO2–) and to avoid the exchange of oxygen between the analytes and the solvent (water). Quantitation entails the use of isotopically enriched standards (N18O2– and 15NO3–), which also permits monitoring of potential conversion from nitrite to nitrate during the analysis (double spike isotope dilution).

Determination of the atomic weight of ²⁸Si-enriched silicon for a revised estimate of the Avogadro Constant - Yang, Lu; Mester, Zoltán; Sturgeon, Ralph E.; Meija, Juris (Analytical Chemistry, 2012)
The much anticipated overhaul of the International System of Units (SI) will result in new definitions of base units in terms of fundamental constants. However, redefinition of the kilogram in terms of the Planck constant (h) cannot proceed without consistency between the Avogadro and Planck constants, which are both related through the Rydberg constant. In this work, an independent assessment of the atomic weight of silicon in a highly enriched ²⁸Si crystal supplied by the International Avogadro Coordination (IAC) was performed. This recent analytical approach, based on dissolution with NaOH and its isotopic characterization by multicollector inductively coupled plasma mass spectrometry, is critically evaluated. The resultant atomic weight Ar(Si) = 27.976 968 39(24)k=1 differs significantly from the most recent value of Ar(Si) = 27.976 970 27(23)k=1. Using the results generated herein for Ar(Si) along with other IAC measurement results for mass, volume, and the lattice spacing, the estimate of the Avogadro constant becomes NA = 6.022 140 40(19) × 10²³ mol⁻¹.

Star-forming substructure within molecular clouds - Di Francesco, James (Molecular Gas, Dust, and Star Formation in Galaxies, 2012)
Wide-field far-infrared/submillimeter continuum maps of molecular clouds by the Herschel Space Observatory GBS and HOBYS surveys are revealing the star-forming substructures that lead to star formation in dense gas. In particular, these maps have revealed the central role in clouds of filaments, likely formed through turbulent motions. These filaments appear to be non-isothermal and fragment into cores only when their column densities exceed a stability threshold. Organizations of filament networks suggest the relative role of turbulence and gravity can be traced in different parts of a cloud, and filament intersections may lead to larger amounts of mass flow that form the precursors of high-mass stars or clusters.
Keywords: ISM: dust; extinction — ISM: structure — ISM: evolution — submillimeter

Neglected infectious diseases in Aboriginal communities: Haemophilus influenzae serotype a and Helicobacter pylori - Ulanova, Marina; Tsang, Raymond; Altman, Eleonora (Vaccine, 2012)
This report describes proceedings of a workshop entitled “Neglected Infectious Diseases in Aboriginal Communities” which took place in Thunder Bay, Ontario, Canada, on October 12, 2011. This workshop was jointly organized by the National Research Council of Canada (NRC), the National Microbiology Laboratory (Public Health Agency of Canada) and Northern Ontario School of Medicine (NOSM) with participants from the Medical Sciences Division and Clinical Sciences Division of NOSM, NRC, National Microbiology Laboratory (NML), Public Health Laboratory (Thunder Bay), Thunder Bay District Health Unit, and Regional Health Survey at Chiefs of Ontario. The main purpose of the workshop was to summarize the current state of knowledge on two less publicized infectious disease agents afflicting Canadian Aboriginal communities: Haemophilus influenzae serotype a (Hia) and Helicobacter pylori. Another highlight of this workshop was the discussion on novel approaches for vaccination strategies in the control and prevention of such disease agents. In conclusion, a long-term collaborative research framework was established between NRC, NML and NOSM to develop carbohydrate-based vaccines against these pathogens that may benefit the health of Canadian Aboriginal peoples and other population groups at risk.
Keywords: Infectious diseases; Haemophilus influenzae serotype a (Hia); Helicobacter pylori; Vaccine development; Aboriginal communities

The SCAR astronomy & astrophysics from Antarctica scientific research programme - Storey, John W. V.; Abe, Lyu; Andersen, Michael; Anderson, Philip; Burton, Michael; Cui, Xiangqun; Ichikawa, Takashi; Karle, Albrecht; Lloyd, James; Masi, Silvia; Steinbring, Eric; Travouillon, Tony; et al. (Astrophysics from Antarctica, 2012)
SCAR, the Scientific Committee on Antarctic Research, is, like the IAU, a committee of ICSU, the International Council for Science. For over 30 years, SCAR has provided scientific advice to the Antarctic Treaty System and made numerous recommendations on a variety of matters. In 2010, Astronomy and Astrophysics from Antarctica was recognized as one of SCAR's five Scientific Research Programs. Broadly stated, the objectives of Astronomy & Astrophysics from Antarctica are to coordinate astronomical activities in Antarctica in a way that ensures the best possible outcomes from international investment in Antarctic astronomy, and maximizes the opportunities for productive interaction with other disciplines. There are four Working Groups, dealing with site testing, Arctic astronomy, science goals, and major new facilities. Membership of the Working Groups is open to any professional working in astronomy or a related field.
Keywords: Telescopes; Atmospheric Effects; Instrumentation; Site Testing; Antarctica

225 GHz atmospheric opacity measurements from two Arctic sites - Matsushita, S.; Chen, Ming-tang; Martin-Cocher, P.; Asada, K.; Chen, C.-P.; Inoue, M.; Paine, S.; Turner, D.; Steinbring, E. (Astrophysics from Antarctica, 2012)
We report the latest results of 225 GHz atmospheric opacity measurements from two Arctic sites; one on high coastal terrain near the Eureka weather station, on Ellesmere Island, Canada, and the other at the Summit Station near the peak of the Greenland icecap. This is a campaign to search for a site to deploy a new telescope for submillimeter Very Long Baseline Interferometry and THz astronomy in the northern hemisphere. Since 2011, we have obtained 3 months of winter data near Eureka, and about one year of data at Summit Station. The results indicate that these sites offer a highly transparent atmosphere for observations in submillimeter wavelengths. Summit Station is particularly excellent, and its zenith opacity at 225 GHz is statistically similar to the Atacama Large Milllimeter/submillimeter Array site in Chile. In winter, the opacity at Summit Station is even comparable to that observed at the South Pole.
Keywords: Arctic sites; 225 GHz opacity; site testing

Disassembling glancing angle deposited films for high-throughput, single-post growth scaling measurements - Siewert, Joshua Morgan Arthur; Laforge, Joshua Michael; Taschuk, Michael Thomas; Brett, Michael Julian (Microscopy and Microanalysis, 2012)
With growing interest in nanostructured thin films produced by glancing angle deposition (GLAD), it becomes increasingly important to understand their overall growth mechanics and nanocolumn structure. We present a new method of isolating the individual nanocolumns of GLAD films, facilitating automated measurement of their broadening profiles. Data collected for α = 81° TiO2 vertical nanocolumns deposited across a range of substrate rotation rates demonstrates that these rates influence growth scaling parameters. Further, individual posts were found in each case that violate predicted Kardar-Parisi-Zhang growth scaling limits. The technique's current iteration is comparable to existing techniques in speed: though data were studied from 10,756 individual objects, the majority could not be confidently used in subsequent analysis. Further refinement may allow high-throughput automated film characterization and permit close examination of subtle growth trends, potentially enhancing control over GLAD film broadening and morphology.
Keywords: GLAD; growth; broadening; disassembling; isolating; scaling; single post

Evidence of a dual network/spherulitic crystalline morphology in PLA stereocomplexes - Saeidlou, Sajjad; Huneault, Michel A.; Li, Hongbo; Sammut, Pierre; Park, Chul B. (Polymer, 2012)
Stereocomplex formation between poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) in the melt state was investigated. Blends with up to 5% PDLA were prepared via melt-blending and characterized by rheological, calorimetric, X-ray diffraction (XRD) and optical microscopy techniques. Kinetic studies suggest that the stereocomplex formation half-time (t1/2) is in the range of 5–7 min. The nucleating role of the stereocomplex for PLA homocrystallization was demonstrated in XRD experiment and in optical microscopy observations through an increase in the spherulite density as well as the growth of a transcrystalline layer on stereocomplex spherulites. More interestingly, a dual crystalline morphology for PLA stereocomplex comprising a spherulitic and a network structure was revealed by optical microscopy observations. This complex morphology was associated to a double stereocomplex melting peak behavior observed after isothermal crystallization in DSC as well as to a huge viscosity increase observed in the presence of a small concentration of stereocomplex in a PLLA melt.
Keywords: PLA; Stereocomplex; Crystallization

Characterization of nanometer-scale porosity in reservoir carbonate rock by focused ion beam–scanning electron microscopy - Bera, Bijoyendra; Gunda, Naga Siva Kumar; Mitra, Sushanta K.; Vick, Douglas (Microscopy and Microanalysis, 2012)
Sedimentary carbonate rocks are one of the principal porous structures in natural reservoirs of hydrocarbons such as crude oil and natural gas. Efficient hydrocarbon recovery requires an understanding of the carbonate pore structure, but the nature of sedimentary carbonate rock formation and the toughness of the material make proper analysis difficult. In this study, a novel preparation method was used on a dolomitic carbonate sample, and selected regions were then serially sectioned and imaged by focused ion beam–scanning electron microscopy. The resulting series of images were used to construct detailed three-dimensional representations of the microscopic pore spaces and analyze them quantitatively. We show for the first time the presence of nanometer-scale pores (50–300 nm) inside the solid dolomite matrix. We also show the degree of connectivity of these pores with micron-scale pores (2–5 μm) that were observed to further link with bulk pores outside the matrix.
Keywords: reservoir rock; carbonate; dolomite core; FIB-SEM; serial sectioning; microstructure

Prolonged survival and serial magnetic resonance imaging/magnetic resonance spectroscopy changes in infantile Krabbe disease - Udow, Sean; Bunge, Martin; Ryner, Lawrence; Mhanni, Aizeddin A.; Salman, Michael S. (Pediatric Neurology, 2012)
Krabbe disease may present during infancy, late infancy, or adulthood. Earlier-onset disease is associated with shorter survival times. We present a case of infantile onset Krabbe disease with prolonged survival, initial intracranial optic nerves and optic chiasm hypertrophy, and serial changes on cranial magnetic resonance imaging and magnetic resonance spectroscopy.

Hole transfer from PbS nanocrystal quantum dots to polymers and efficient hybrid solar cells utilizing infrared photons - Zhang, Yanguang; Li, Zhao; Ouyang, Jianying; Tsang, Sai-Wing; Lu, Jianping; Yu, Kui; Ding, Jianfu; Tao, Ye (Organic Electronics, 2012)
Polymer/inorganic-nanocrystals bulk heterojunction solar cells, where inorganic semiconductor nanocrystals such as CdSe, CdS, CdTe, ZnO, TiO2, and silicon, replace the fullerene molecules as the electron acceptors, typically exhibit a power conversion efficiency (PCE) below 3% even after tremendous engineering efforts to optimize the nanocrystal size, shape, and nanoscale morphology. One promising feature of polymer hybrid solar cells is the ability to sensitize conjugated polymers, which on their own absorb only in the visible part of solar spectrum, into the infrared spectral range using infrared-active lead salt nanocrystal quantum dots (NQDs). Here we observed for the first time hole transfer from PbS NQDs to polymers as evidenced by the quenching of the PbS photoluminescence (PL), a sign of the presence of charge separating type II heterojunction. The type II band-offset at the NQD/polymer heterojunction enables efficient hole extraction from NQDs and leads to a record PCE of 3.80%, realized in a planar junction configuration under simulated air mass 1.5 global (AM 1.5G) irradiation of 100 mW/cm2. The photocurrent has an extended spectral range spanning from the ultraviolet (UV) to the infrared (IR). Contributions from the polymer and PbS to the photocurrent were identified. Infrared photons (>700 nm) contribute about 30% of the photocurrent and yield a high external quantum efficiency (EQE) of 20% at 1050 nm.
Keywords: Conjugated polymers; PbS nanocrystals; Solar cells; Heterojunction; Charge transfer; Infrared photovoltaics

Development of a turbojet engine gearbox test rig for prognostics and health management - Rezaei, Aida; Dadouche, Azzedine (Mechanical Systems and Signal Processing, 2012)
Aircraft engine gearboxes represent one of the many critical systems/elements that require special attention for longer and safer operation. Reactive maintenance strategies are unsuitable as they usually imply higher repair costs when compared to condition based maintenance. This paper discusses the main prognostics and health management (PHM) approaches, describes a newly designed gearbox experimental facility and analyses preliminary data for gear prognosis. The test rig is designed to provide full capabilities of performing controlled experiments suitable for developing a reliable diagnostic and prognostic system. The rig is based on the accessory gearbox of the GE J85 turbojet engine, which has been slightly modified and reconfigured to replicate real operating conditions such as speeds and loads. Defect to failure tests (DTFT) have been run to evaluate the performance of the rig as well as to assess prognostic metrics extracted from sensors installed on the gearbox casing (vibration and acoustic). The paper also details the main components of the rig and describes the various challenges encountered. Successful DTFT results were obtained during an idle engine performance test and prognostic metrics associated with the sensor suite were evaluated and discussed.
Keywords: Accessory gearbox; Defect to failure tests; Signal processing; Prognostics and health management; Vibration; Acoustics

Inverted photovoltaic cells of nanocolumnar C60 filled with solution processed small molecule 3-Q - Thomas, M.; Li, W.; Bo, Z. S.; Brett, M. J. (Organic Electronics, 2012)
Nanocolumnar C60 films for inverted organic photovoltaic cells (OPVs) were fabricated by glancing angle deposition (GLAD), and morphologies depending on variation in deposition angle were studied. To complete the OPV devices, small molecules of the donor material 3-Q were spin coated into the C60 films. In order to avoid the difficulties of solvent stability of the C60 films, acetone was used as the process solvent for spin coating. The nanocolumnar morphology improves exciton harvesting by increasing absorbance while providing an effective conductive path for charge carriers. The resulting GLAD C60/3-Q devices outperformed both planar devices and PC61BM:3-Q bulk heterojunctions with threefold and twofold short-circuit current increases, respectively.
Keywords: Glancing angle deposition; Small molecule thin films; Organic solar cells; C60 fullerene; Nanostructure; Inverted architecture

The use of laser range finder on a robotic platform for pipe inspection - Liu, Zheng; Krys, Dennis (Mechanical Systems and Signal Processing, 2012)
In this paper, we investigate the use of a laser range finder on a robotic platform for buried water pipe inspection. A robotic platform carrying and manipulating multiple nondestructive inspection sensors may require accurately locating robot's body in the pipe. The laser range finder provides an accurate distance measurement, which can generate a profile of the pipe inner surface. This profile, on one hand, can be used to identify the location of the laser source and thus the robot's body. Such information can further help the navigation of the robot. On the other hand, the anomalies presented in the profile can be detected and characterized in terms of the range measurement. The simulated and real data tests presented in this paper demonstrate the feasibility and effectiveness of incorporating the laser range finder into a robotic platform for the underground pipe inspection.
Keywords: Laser range finder; Underwater vehicle; Nondestructive inspection; Water pipe

Control of the active layer nanomorphology by using co-additives towards high-performance bulk heterojunction solar cells - Aïch, Badrou Réda; Lu, Jianping; Beaupré, Serge; Leclerc, Mario; Tao, Ye (Organic Electronics, 2012)
In this work, two high boiling-point solvents (1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO)) were utilized as co-additives in ortho-dichlorobenzene (ODCB) and chlorobenzene (CB) solutions to fine tune the donor and acceptor domains in the bulk heterojunction (BHJ) of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) and fullerene derivatives. A power conversion efficiency of 7.1% and a fill factor up to 70% were obtained for solar cells with active area of 1 cm2 when using [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) as acceptor, suggesting that an optimized morphology was achieved.
Keywords: Conjugated polymers; Co-additives; Solar cells; Bulk heterojunction; Nanomorphology; PCBM

Estimation of impact forces between small bodies in waves - Raman-Nair, W.; Chin, S. N. (Ocean Engineering, 2012)
Impact forces between small bodies colliding in a regular wave are estimated using the contact theory of Hertz and an elastoplastic model due to Lankarani and Nikravesh (1994). To determine the relative impact speed, the equations of motion for the bodies on a surface wave are formulated in two dimensions using the methods of Kane and Levinson (1985) and solved numerically. It is assumed that the motion normal to the wave surface is small and can be neglected, i.e. the bodies move along the propagating wave profile. A Stokes second order wave is used and the wave forces are applied using Morison's equation for a body in accelerated flow. Wind loads are similarly modeled using drag coefficients.
Keywords: Hertz contact; Plastic deformation; Small bodies; Waves

Effect of arginine vasopressin on the behavioral activity in the behavior despair depression rat model - Yang, Jun; Pan, Yan-Juan; Yin, Zhi-Kui; Hai, Guang-Fan; Lu, Lu; Zhao, Ying; Wang, Da-Xin; Wang, Huan; Wang, Gen (Neuropeptides, 2012)
Arginine vasopressin (AVP), a nonapeptide posterior hormone of the pituitary, is mainly synthesized and secreted in the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON). Large numbers of studies have reported that AVP plays a role in depression. The present study was to investigate by which level, brain or periphery, AVP affects the behavioral activity in the behavior despair depression rat model. The results showed that (1) either forced swimming or tail suspension significantly increased AVP concentration not only in the brain (PVN, SON, frontal of cortex, hippocampus, amygdala, lumber spinal cord) but also in the periphery (posterior pituitary and serum); (2) intraventricular injection (icv) of AVP decreased the animal immobility time, whereas V1 receptor antagonist d(CH2)5Tyr(Me)AVP (icv) increased the animal immobility time in a dose-dependent manner not only in FST but also in TST, but the V2 receptor antagonist d(CH2)5[D-Ile, Ile, Ala-NH9]AVP did not change the animal immobility time in FST or TST; (3) V1, not V2 receptor antagonist could inhibit the animal immobility time decrease induced by AVP (icv); (4) neither AVP nor its receptor antagonist (including V1 and V2 receptor antagonist) influenced the animal immobility time in both FST and TST. The data suggested that AVP in the brain rather than the periphery played a role in the behavior despair depression by V1, not V2 receptors, which behavior despair might have a positive feedback effect on central AVP and blood AVP might have a negative feedback on central AVP in the depressive process.
Keywords: Arginine vasopressin; Depression; Behavior despair; V1 receptor; V2 receptor; Brain; Periphery

First demonstration of a Compton gamma imager based on silicon photomultipliers - Saull, P. R. B.; Sinclair, L. E.; Seywerd, H. C. J.; Hanna, D. S.; Boyle, P. J.; Macleod, A. M. L. (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012)
We are developing a rugged and person-transportable Compton gamma imager for use in security investigations of radioactive materials, and for radiological incident remediation. The imager is composed of layers of scintillator with light collection for the forward layers provided by silicon photomultipliers and for the rear layer by photomultiplier tubes. As a first step, we have developed a 1/5th-scale demonstration unit of the final imager. We present the imaging performance of this demonstration unit for 137Cs at angles of up to 30° off-axis. Results are also presented for 113Sn and 22Na. This represents the first demonstration of the use of silicon photomultipliers as an embedded component for light collection in a Compton gamma imager.
Keywords: SiPM; Silicon photomultiplier; Compton; Gamma; Imager

Spectroscopic and photometric study of the contact binary BO CVn - Zola, S.; Nelson, R. H.; Şenavcı, H. V.; Szymanski, T.; Kuźmicz, A.; Winiarski, M.; Jableka, D. (New Astronomy, 2012)
We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88%. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20–24%, while the absolute parameters of components are: M1 = 1.16, M2 = 0.39, R1 = 1.62 and R2 = 1.00 (in solar units). The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt = 6.3 × 10−8M⊙/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility).
Keywords: Binaries; Eclipsing binaries; Close binaries – fundamental parameters

Cocaine sensitization does not alter SP effects on locomotion or excitatory synaptic transmission in the NAc of rats - Kombian, Samuel B.; Ananthalakshmi, Kethireddy V. V.; Zidichouski, Jeffrey A.; Saleh, Tarek M. (Neuropharmacology, 2012)
Substance P (SP) and cocaine employ similar mechanisms to modify excitatory synaptic transmission in the nucleus accumbens (NAc), a region implicated in substance abuse. Here we explored, using NAc slices, whether SP effects on these synaptic responses were altered in rats that have been sensitized to cocaine and whether SP could mimic cocaine in triggering increased locomotion in sensitized rats. Intraperitoneal (IP) injection of naïve rats with cocaine (15 mg/kg) caused increased locomotion by 408.5 ± 85.9% (n = 5) which further increased by 733.1 ± 157.8% (n = 5) following a week of cocaine sensitization. A similar challenge with 10 mg/kg of SP after cocaine sensitization did not produce significant changes in locomotion (170.6 ± 61.0%; n = 4). In contrast to cocaine, IP injection of rats with SP or SP5–11 (10–100 mg/kg) with or without phosphoramidon did not elicit changes in locomotion. In electrophysiological studies, both cocaine and SP depressed evoked NMDA and non-NMDA receptor-mediated excitatory synaptic currents (EPSCs) in slices obtained from naïve rats. In slices derived from cocaine-sensitized rats, cocaine but not SP produced a more profound decrease in non-NMDA compared to NMDA responses. Similar to that in naïve rats, cocaine’s effect on the EPSCs in these sensitized rats occluded those of SP. Thus, although SP and cocaine may employ similar mechanisms to depress EPSCs in the NAc, IP injection of SP does not mimic cocaine-induced hyperlocomotion indicating that not all of cocaine’s effects are mimicked by SP.
Keywords: Substance abuse; Cocaine; Substance P; Excitatory postsynaptic currents; Synaptic plasticity; Neuropeptides

Processing thermography images for pitting corrosion quantification on small diameter ductile iron pipe - Liu, Zheng; Genest, Marc; Krys, Dennis (NDT & E International, 2012)
The condition of a metallic pipe is determined mainly by the extent to which it is corroded. Thus, the quantification of pitting corrosion in terms of metal loss is required for the understanding of pipe condition. There are different ways to quantify corrosion pit geometry. Direct methods measure the pit depth of pipe samples, which are sand/grit blasted to remove corrosion products, and are often adopted in laboratory. Indirect methods employ non-destructive inspection techniques to detect and quantify the corrosion without sandblasting, which is preferred for field test. In this study, the pulsed thermography is considered for fast quantification of pitting corrosion in a ductile iron pipe, which is sandblasted. The thermography testing generates a sequence of infrared images, which reflect the diffusion process of heat through pipe wall. This paper proposes a processing procedure to extract the corrosion information from the thermography images with phase congruency measurement and local binary fitting. The extracted feature is further related to the corrosion damage. Among all the features, the second principal component demonstrates a reasonably good linear relationship with metal loss of the pipe. The application potential is demonstrated by the experimental results.
Keywords: Thermography; Image feature extraction; Corrosion quantification; Pipe condition assessment

Lap shear strength and fatigue life of friction stir spot welded AZ31 magnesium and 5754 aluminum alloys - Chowdhury, S. H.; Chen, D. L.; Bhole, S. D.; Cao, X.; Wanjara, P. (Materials Science and Engineering: A, 2012)
Lightweighting is today considered as one of the key strategies in reducing fuel consumption and anthropogenic greenhouse gas emissions. The structural applications of lightweight magnesium and aluminum alloys in the transportation industry inevitably involve welding and joining while guaranteeing the safety and reliability of motor vehicles. This study was aimed at evaluating lap shear strength and fatigue properties of friction stir spot welded (FSSWed) AZ31B-H24 Mg and 5754-O Al alloys in three combinations, i.e., similar Mg-to-Mg, Al-to-Al, and dissimilar Al-to-Mg joints. The Mg/Mg similar weld had a nugget-shaped stir zone (SZ) around the keyhole where fine recrytallized equiaxed grains were observed. While the hardness profile of the Mg/Mg similar weld exhibited a W-shaped appearance, the lower hardness values appeared in the TMAZ and HAZ of both Mg/Mg and Al/Al similar welds. In the Al/Mg dissimilar weld, a characteristic interfacial layer consisting of intermetallic compounds (IMC) Al12Mg17 and Al3Mg2 was observed. Both Mg/Mg and Al/Al similar welds had significantly higher lap shear strength, failure energy and fatigue life than the Al/Mg dissimilar weld. While the Al/Al weld displayed a slightly lower lap shear strength than the Mg/Mg weld, the Al/Al weld had higher failure energy and fatigue life. Three types of failure modes were observed. In the Mg/Mg and Al/Al similar welds, at higher cyclic loads nugget pullout failure occurred due to fatigue crack propagation circumferentially around the nugget, while at lower cyclic loads fatigue failure occurred perpendicular to the loading direction caused by the opening of keyhole through crack initiation in the TMAZ and HAZ. In the Al/Mg dissimilar weld nugget debonding failure mode was observed because of the presence of an interfacial IMC layer.
Keywords: Magnesium alloy; Aluminum alloy; Friction stir spot welding; Microstructure; Lap shear strength; Fatigue properties

Maximizing the integrity of linear friction welded Waspaloy - Chamanfar, A.; Jahazi, M.; Gholipour, J.; Wanjara, P.; Yue, S. (Materials Science and Engineering: A, 2012)
The Ni-base superalloy, Waspaloy, was linear friction welded (LFWed) under various processing parameters and then subjected to a post weld heat treatment (PWHT). Tensile testing integrated with the optical image correlation Aramis® system indicated that there is a critical axial shortening value (2 mm) below which LFWed and post weld heat treated (PWHTed) Waspaloy exhibited weak integrity. At and above this critical shortening, the yield strength and ultimate tensile stress (UTS) values were more or less the same as for the parent material. However, total elongation continued to increase with axial shortening even above the critical value due to decrease in width of thermo-mechanically affected zone (TMAZ). The sample with the highest axial shortening (4.9 mm) exhibited an elongation 91% of the parent material elongation. According to Aramis® data, the mixture rule can be used reliably to determine the contribution of TMAZ to the tensile elongation of PWHTed Waspaloy. Microstructure characterization across the weld in the as-LFWed and PWHTed conditions was carried out to correlate the process parameters and microstructural changes that affect the tensile properties. Weak integrity at axial shortening below 2 mm was mainly due to lack of bonding and/or presence of oxides at the weld interface. In the as-welded condition, a loss in hardness was observed, and related to the extensive dissolution of strengthening phase (γ′) in the weld area. The applied PWHT restored the hardness in the weld region.
Keywords: Waspaloy; Linear friction welding; Weld integrity; Tensile properties; Microstructure

Microstructure evolution and mechanical properties of dissimilar friction stir welded joints between AA1100-B4C MMC and AA6063 alloy - Guo, J.; Gougeon, P.; Chen, X.-G. (Materials Science and Engineering: A, 2012)
The feasibility of dissimilar friction stir welding (FSW) between the AA1100-16 vol.% B4C metal matrix composite and the AA6063 alloy has been evaluated. The effect of the welding parameters on the interface bonding, joint microstructure and mechanical properties was investigated. The results revealed that all dissimilar joints produced under welding conditions investigated were stronger than the base materials of the Al-B4C composite. Analysis of the Mg concentration and the B4C particle distribution indicates that good material mixing and seamless bonding was achieved around the interface between the Al-B4C composite and the Al 6063 alloy during FSW. The electron backscatter diffraction analysis (EBSD) shows that during dissimilar FSW, there was a gradual microstructural evolution on both material sides, resulting in a variety of grain structures in the different weld zones. In the weld zones of FSW joints, the materials underwent dynamic recovery and recrystallization to different extents depending on their thermal mechanical history. The grain refinement of both materials in the nugget zone was observed. It is recommended that the 6063 aluminum alloy should be fixed on the advancing side and the use of an appropriate offset to the 6063 aluminum side is preferred.
Keywords: Friction stir welding; Dissimilar joints; Al-B4C metal matrix composites; AA6063 alloy; Microstructure; Mechanical properties

Short echo time in vivo prostate 1H-MRSI - Venugopal, Niranjan; Mccurdy, Boyd; Al Mehairi, Salem; Alamri, Aziz; Sandhu, Gurdarshan S.; Sivalingam, Sri; Drachenberg, Darrel; Ryner, Lawrence (Magnetic Resonance Imaging, 2012)
Visualization of short echo time (TE) metabolites in prostate magnetic resonance spectroscopic imaging is difficult due to lipid contamination and pulse timing constraints. In this work, we present a modified pulse sequence to permit short echo time (TE=40ms) acquisitions with reduced lipid contamination for the detection of short TE metabolites. The modified pulse sequence employs the conformal voxel MRS (CV-MRS) technique, which automatically optimizes the placement of spatial saturation planes to adapt the excitation volume to the shape of the prostate, thus reducing lipid contamination in prostate magnetic resonance spectroscopic imaging (MRSI). Metabolites were measured and assessed using a modified version of LCModel for analysis of in vivo prostate spectra. We demonstrate the feasibility of acquiring high quality spectra at short TEs, and show the measurement of short TE metabolites, myo-inositol, scyllo-inositol, taurine and glutamine/glutamate for both single and multi-voxel acquisitions. In single voxels experiments, the reduction in TE resulted in 57% improvement in the signal-to-noise ratio (SNR). Additional 3D MRSI experiments comparing short (TE=40 ms), and long (TE=130 ms) TE acquisitions revealed a 35% improvement in the number of adequately fitted metabolite peaks (775 voxels over all subjects). This resulted in a 42±24% relative improvement in the number of voxels with detectable citrate that were well-fitted using LCmodel. In this study, we demonstrate that high quality prostate spectra can be obtained by reducing the TE to 40 ms to detect short T2 metabolites, while maintaining positive signal intensity of the spin-coupled citrate multiplet and managing lipid suppression.
Keywords: Short TE; Conformal voxel; Magnetic resonance spectroscopic imaging; LCModel; Prostate cancer; Lipid contamination; Lipid suppression

A volume microstrip RF coil for MRI microscopy - Jasiński, Krzysztof; Młynarczyk, Anna; Latta, Peter; Volotovskyy, Vyacheslav; Węglarz, Władyslaw P.; Tomanek, Bogusław (Magnetic Resonance Imaging, 2012)
Quantitative magnetic resonance imaging (MRI) studies of small samples such as a single cell or cell clusters require application of radiofrequency (RF) coils that provide homogenous B1 field distribution and high signal-to-noise ratio (SNR). We present a novel design of an MRI RF volume microcoil based on a microstrip structure. The coil consists of two parallel microstrip elements conducting RF currents in the opposite directions, thus creating homogenous RF field within the space between the microstrips. The construction of the microcoil is simple, efficient and cost-effective. Theoretical calculations and finite element method simulations were used to optimize the coil geometry to achieve optimal B1 and SNR distributions within the sample and predict parameters of the coil. The theoretical calculations were confirmed with MR images of a 1-mm-diameter capillary and a plant obtained with the double microstrip RF microcoil at 11.7 T. The in-plane resolution of MR images was 24 μm×24 μm.
Keywords: MRI microcoil; RF coil; Micro MRI; SNR; FEM

The role of WlaRG, WlaTB and WlaTC in lipooligosaccharide synthesis by Campylobacter jejuni strain 81116 - Holden, Karen M.; Gilbert, Michel; Coloe, Peter J.; Li, Jianjun; Fry, Benjamin N. (Microbial Pathogenesis, 2012)
Campylobacter jejuni is a major bacterial cause of gastroenteritis world-wide. C. jejuni produces a range of glycans including lipooligosaccharide (LOS), an important virulence factor. The genetic content of the LOS synthesis locus varies between C. jejuni strains and 19 classes have been described. Three LOS synthesis genes of C. jejuni strain 81116 (NCTC 11828), wlaRG, wlaTB and wlaTC were the focus of this study. WlaRG and the remaining two proteins of interest share sequence similarity to aminotransferases and glycosyltransferases, respectively. These genes were insertionally inactivated and phenotypically characterised. Each mutant produced truncated LOS. Mutants lacking WlaRG, WlaTB and WlaTC produced LOS with reduced immunogenicity. Both the wlaRG and wlaTC mutants were non-motile and aflagellate. In vitro invasion and adhesion assays revealed that the wlaRG, wlaTB and wlaTC mutants displayed reduced adherence to chicken embryo fibroblasts. All mutants were less invasive of human cells than 81116 confirming the role of intact LOS during invasion of human cells in vitro. Here we propose the general composition for the 81116 LOS core backbone based on capillary electrophoresis-mass spectrometry.
Keywords: Campylobacter jejuni; Lipooligosaccharide; Mutagenesis; Glycosyltransferase; Aminotransferase

Molecular simulation of CO2/N2 separation using vertically-aligned carbon nanotube membranes - Ban, Shuai; Huang, Cheng (Journal of Membrane Science, 2012)
The CO2/N2 permeation through carbon nanotube (CNT) membrane was studied using molecular simulations to explore its potential for flue gas separation. The theory of gas permeation was derived on the basis of the Maxwell–Stefan formulas. Adsorption isotherms calculated using grand-canonical Monte Carlo methods show a higher loading of pure CO2 than that of N2, while an approximately identical loading was found for CO2/N2 mixture with a feed pressure ratio of 1:9. The molecular snapshot indicates a concentrically layered structure inside the cylindrical channel of CNT. Results of molecular dynamics simulations show that the diffusion of N2 is a few times faster than that of CO2. For binary mixtures, the diffusion coefficients of CO2/N2 mixtures become identical at high concentrations due to the correlation effect that causes a slowing-down of the mobile species, and a speed-up of the other tardy component. The calculated N2 permeance agrees with the experimental measurement. The computed CO2 flux through CNT membranes is higher than N2 for single components, while they become nearly equal under flue gas conditions.
Keywords: Computer modeling; Molecular transport; Gas separation; Nanomaterials

Biomechanically constrained groupwise ultrasound to CT registration of the lumbar spine - Gill, Sean; Abolmaesumi, Purang; Fichtinger, Gabor; Boisvert, Jonathan; Pichora, David; Borshneck, Dan; Mousavi, Parvin (Medical Image Analysis, 2012)
We present a groupwise US to CT registration algorithm for guiding percutaneous spinal interventions. In addition, we introduce a comprehensive validation scheme that accounts for changes in the curvature of the spine between preoperative and intraoperative imaging. In our registration methodology, each vertebra in CT is treated as a sub-volume and transformed individually. A biomechanical model is used to constrain the displacement of the vertebrae relative to one another. The sub-volumes are then reconstructed into a single volume. During each iteration of registration, an US image is simulated from the reconstructed CT volume and an intensity-based similarity metric is calculated with the real US image. Validation studies are performed on CT and US images from a sheep cadaver, five patient-based phantoms designed to preserve realistic curvatures of the spine and a sixth patient-based phantom where the curvature of the spine is changed between preoperative and intraoperative imaging. For datasets where the spine curve between two imaging modalities was artificially perturbed, the proposed methodology was able to register initial misalignments of up to 20 mm with a success rate of 95%. For the phantom with a physical change in the curvature of the spine introduced between the US and CT datasets, the registration success rate was 98.5%. Finally, the registration success rate for the sheep cadaver with soft-tissue information was 87%. The results demonstrate that our algorithm allows for robust registration of US and CT datasets, regardless of a change in the patients pose between preoperative and intraoperative image acquisitions.
Keywords: Ultrasound; Spine; Multimodal registration; Biomechanical model

International comparison of quantum AC voltage standards for frequencies up to 100kHz - Filipski, Piotr S.; van den Brom, Helko E.; Houtzager, Ernest (Measurement, 2012)
This paper presents results of an international comparison of two quantum AC voltage standards based on pulse-driven Josephson arrays. The two systems differ in several hardware and software characteristics as well as in the level of automation, features which can influence the accuracy of transferring the quantum-standard voltage value to a calibrated instrument. The comparison was performed at 100 mV, 20 mV and 12 mV, at frequencies between 2.5 kHz and 100 kHz. An electronically-aided thermal transfer standard was used as a travelling standard. At the most accurate voltage and frequency point, 100 mV at 2.5 kHz, both laboratories agreed to better than 1 part in 10^6.
Keywords: Josephson arrays; Signal synthesis; Standards; AC voltage standard

Discovery of Al2O3 particles incorporation mechanism in plasma electrolytic oxidation of AM60B magnesium alloy - Li, Xijin; Luan, Ben Li (Materials Letters, 2012)
Al2O3 particles were suspended in the aluminate electrolyte to form a ceramic coating on an AM60B magnesium alloy by plasma electrolytic oxidation (PEO), and a new mechanism for the Al2O3 particle incorporation in the coating was discovered. Energy Dispersive Spectroscopy (EDS) results showed that Al2O3 addition increased the Al content in the coating. The absence of Al2O3 particles combined with the increased MgAl2O4/MgO phase ratio in the coatings with the addition of Al2O3 indicated that the Al2O3 particles participated in chemical reactions during the coating formation, as opposed to a previously reported understanding of simple mechanical incorporation.
Keywords: Particle incorporation; Al2O3; Magnesium; Plasma electrolytic oxidation

Suppressed liquation and microcracking in linear friction welded WASPALOY - Chamanfar, A.; Jahazi, M.; Gholipour, J.; Wanjara, P.; Yue, S. (Materials & Design, 2012)
Fusion welding of nickel-base superalloys is often associated with fusion zone solidification cracking and/or liquation induced heat affected zone (HAZ) cracking. As an alternative joining technology, linear friction welding (LFW) was used in the current study to join the nickel-base superalloy, WASPALOY. Under the experimental conditions used in the present investigation, the temperature data recorded by inserting thermocouples at different locations from the weld interface indicated that the temperature in the weld area reached up to 1280 °C, which is at least 50 °C below the melting point of the bulk alloy. However, this temperature is well above the liquation temperature of the low melting point components in the alloy (1245 °C). As a result, liquation may occur in linear friction welded (LFWed) WASPALOY. The occurrence of liquation and/or microcracking was investigated using optical microscopy (OM), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) X-ray mapping. The high pressure applied during the oscillation and forge phases of the LFW process and the resulting γ grain refinement contributed in preventing liquation and microcracking in the weldments. Furthermore, according to the SEM and X-ray mapping results, LFW altered the chemical composition, morphology and size of the γ′ precipitates at a location of 2 mm from the weld interface. It was determined that γ′ coalescence at 2 mm from the weld interface played a role in decreasing the microhardness (by 30%) relative to the base metal.
Keywords: Non-ferrous metals and alloys; Welding; Microstructure

The characteristics of gas hydrates recovered from Shenhu area in the South China Sea - Liu, Changling; Ye, Yuguang; Meng, Qingguo; He, Xingliang; Lu, Hailong; Zhang, Jian; Liu, Jian; Yang, Shengxiong (Marine Geology, 2012)
For the first time gas hydrate samples were recovered in the South China Sea during a drilling campaign implemented in Shenhu area in June 2007. Laboratory based studies for the characteristics of gas hydrate were carried out on two hydrate-bearing sediment samples. Observations found that gas hydrates occurred in the pores of fine grained sediments. The hydrates were structure I based on the Raman spectroscopic results. The guest gas molecules in hydrate cages were predominantly methane (> 99.3%) and trace amount of ethane (0.4%) and propane (0.04%) as determined with the method of gas chromatography. As estimated from the intensities of Raman peaks, the cage occupancy rates were more than 99% in large cage, and ~ 86% in small cage, respectively, corresponding to a hydration number of 5.9.
Keywords: Gas hydrates; South China Sea; Methane; Occurrence; Hydration number; Gas composition

Wind-induced response and excitation characteristics of an inclined cable model in the critical Reynolds number range - Jakobsen, J. B.; Andersen, T. L.; Macdonald, J. H. G.; Nikitas, N.; Larose, G. L.; Savage, M. G.; McAuliffe, B. R. (Journal of Wind Engineering and Industrial Aerodynamics, 2012)
This paper focuses on wind-induced vibrations of dry inclined bridge cables in the critical Reynolds number range. The cable response and the associated wind load characteristics are studied experimentally, in the third phase of a major wind tunnel investigation on cable aerodynamics at the National Research Council Canada. The displacement (and acceleration) response of a 6.7 m long section cable model, 160 mm in diameter, was monitored simultaneously with 162 surface pressure taps, for inclinations of 60°, 77° and 90°. The data corroborate the susceptibility of dry cables to respond, primarily in the across-flow direction, to load variations associated with transitions between flow regimes throughout the drag crisis region. The most vigorous vibrations (stopped at approximately 60% diameter response amplitude) were observed at 60°, with damping ratios below 0.2%. Significant “lock-in” between the lift force and the violent sway cable response was identified in terms of the transfer function between the two during the large vibration events. The large responses were confined to a narrow Reynolds number range, often at flow conditions giving the minimum normal (drag) coefficient and a significant derivative of the lift coefficient with respect to Reynolds number. Throughout the drag crisis region, significant variation in flow characteristics along the cable aligned at 60° has been observed, in terms of both mean pressure distributions and pressure fluctuations.
Keywords: Bridge cable; Inclined circular cylinder; Surface pressures; Drag crisis; Critical Reynolds number; High reduced wind speed; Dry inclined cable galloping

Shaping of bridge box girders to avoid vortex shedding response - Larsen, Allan; Wall, Alanna (Journal of Wind Engineering and Industrial Aerodynamics, 2012)
This paper presents a wind tunnel study carried out with the objective of exploring the effect of shape on vortex induced vibrations of trapezoidal box girder bridge decks. It is demonstrated that it is possible to derive a virtually vibration free deck and that the angle between the horizontal bottom plate and the inclined side panes is an important parameter in achieving this goal.
Keywords: Vortex shedding excitation; Bridge decks; Section model tests

Sectional model investigation at high Reynolds number for a super tall building - Larose, G. L.; Wall, A.; McAuliffe, B. R.; Kelly, D.; Stone, G.; Yakymyk, W. (Journal of Wind Engineering and Industrial Aerodynamics, 2012)
This paper presents the results of an experimental study of the influence of Reynolds number on the vortex-shedding excitation of a super tall building with a quasi-circular cross-section, uniform with height. Sectional model tests were carried out on a large model in a large wind tunnel at high wind speeds to reach Reynolds number in excess of 3 million based on the model diameter. Stationary model tests and free-to-respond model tests were carried out for various azimuth angles, in smooth and turbulent flow. The study revealed that for this building cross-section, the dynamic excitation due to vortex shedding was equally important at high Reynolds numbers when compared to experiments performed in the sub-critical Reynolds number regime.
Keywords: Super tall building; Vortex-shedding induced oscillations; Reynolds number; Sectional model; Wind tunnel tests

Reynolds-number and surface-modeling sensitivities for experimental simulation of flow over complex topography - McAuliffe, Brian R.; Larose, Guy L. (Journal of Wind Engineering and Industrial Aerodynamics, 2012)
This paper documents the development of an experimental approach for determining the wind characteristics over complex topography. Using fast-response pressure probes, vertical wind profiles were measured over wind-tunnel models representing the complex topography of a wind farm currently under construction. A terraced-model approach was taken to simplify the manufacturing of the topographic models, providing the added benefit of enhanced surface roughness from the terraced steps. A preliminary study in a small wind tunnel identified restrictions on the Reynolds number and terrace step size that are required for attaining adequate high-Reynolds-number boundary-layer characteristics at a scale of 1:1500. Subsequent measurements over the entire wind-farm topography were compared to site measurements from meteorological masts, from which recommendations for improved experimental simulation techniques are identified.
Keywords: Complex terrain; Wind farm; Atmospheric boundary layer; Wind profiles; Turbulence; Wind tunnel testing

Wind turbulence in speed skating: measurement, simulation and its effect on aerodynamic drag - D'auteuil, Annick; Larose, Guy L.; Zan, Steve J. (Journal of Wind Engineering and Industrial Aerodynamics, 2012)
This paper presents the results of an investigation on the effect of wind turbulence for the reduction of drag for a speed skater. A speed skater competing in an indoor oval is subjected to turbulent flow conditions. Measurements of flow characteristics in a speed skating oval were made and a simulation of those conditions was developed in the NRC 2 m×3 m Wind Tunnel. Wind tunnel tests on mannequins of a speed skater with force measurement using an external balance have indicated that the reduction of drag coefficient with Reynolds number was strongly affected by the flow conditions. The effects were not consistent for three different positions of a speed skater.
Keywords: Wind turbulence; Drag; Speed skater; Wind simulation; Wind tunnel

Optical tomography with the discontinuous Galerkin formulation of the radiative transfer equation in frequency domain - Balima, O.; Favennec, Y.; Boulanger, J.; Charette, A. (Journal of Quantitative Spectroscopy and Radiative Transfer, 2012)
Optical tomography is an inverse method of probing semi-transparent media with the help of light sources. The reconstruction of the optical properties usually employs finite volumes or continuous finite elements formulations of light transport as a forward model for the predictions. In a previous study, we have introduced a generalization of the inversion approach with finite elements formulations by using an integral form of the objective function. The novelty is that the surfaces of the detectors are taken into account in the reconstruction and compatibility is obtained for all finite element formulations. This present paper illustrates this new approach by developing a Discontinuous Galerkin formulation as a forward model for an optical tomography application in the frequency domain framework. Numerical tests are performed to gauge the accuracy of the method in recovering optical properties distribution with a gradient-based algorithm where the adjoint method is used to fastly compute the objective function gradient. It is seen that the reconstruction is accurate and can be affected by noise on the measurements as expected. Filtering of the gradient at each iteration of the reconstruction is used to cope with the ill-posed nature of the inverse problem and to improves the quality and accuracy of the reconstruction.
Keywords: Inverse problem; Adjoint method; Limited memory BFGS; Finite element; Filtering; Radiative transfer equation

Nb-doped TiO2/carbon composite supports synthesized by ultrasonic spray pyrolysis for proton exchange membrane (PEM) fuel cell catalysts - Senevirathne, Keerthi; Neburchilov, Vladimir; Alzate, Vanesa; Baker, Ryan; Neagu, Roberto; Zhang, Jiujun; Campbell, Stephen; Ye, Siyu (Journal of Power Sources, 2012)
In this paper we report the use of both ultrasonic spray pyrolysis and microwave-assisted polyol reduction methods to synthesize Nb-doped TiO2/carbon (25 wt% Nb0.07Ti0.93O2/75 wt% carbon) composite supports and Pt0.62Pd0.38 alloy catalysts, respectively. The physicochemical properties of the synthesized supports and their Pt0.62Pd0.38 supported catalysts are evaluated using several methods including XRD, TEM, BET surface area analysis, TGA, as well as ICP-MS elemental analysis. The electronic conductivities and thermal/chemical stabilities of the supports are also evaluated with respect to their possible use as catalyst supports. Electrochemical measurements for oxygen reduction activity of the Pt0.62Pd0.38 alloy catalysts supported on oxide/carbon composites are also carried out in order to check their suitability for possible PEM fuel cell applications. The results show that 20wt%Pt0.62Pd0.38/25 wt%(Nb0.07Ti0.93O2)-75 wt%C catalysts exhibit enhanced mass activities compared to those of commercially available 48wt% Pt/C and home-made 20wt% Pt62Pd38/C catalysts.
Keywords: Ultrasonic spray pyrolysis; Microwave-assisted polyol reduction; Nb-doped TiO2; PtPd alloy catalysts; Oxygen reduction reaction; PEM fuel cells

Impacts of operating conditions on the effects of chloride contamination on PEM fuel cell performance and durability - Li, Hui; Zhang, Shengsheng; Qian, Weimin; Yu, Yi; Yuan, Xiao-Zi; Wang, Haijiang; Jiang, Max; Wessel, Silvia; Cheng, Tommy T. H. (Journal of Power Sources, 2012)
Chloride contaminated fuel and/or air streams in an operating proton exchange membrane fuel cell can cause significant adverse effects on fuel cell performance and durability. This paper reports investigations of chloride contamination effects on PEM fuel cell performance and durability under a wide range of operating conditions, using various in-situ diagnostic measurements. Increases in current density and Cl− concentration as well as decreases in fuel cell RH were found to enlarge the severity of the chloride contamination effect. Temperature was also found to have a significant influence on the contamination effect. Electrochemical impedance spectroscopy was used as a diagnostic tool during the contamination tests to explore changes in cell component resistances. The results indicated that chloride contamination causes predominantly an increase in charge transfer resistance as well as an increase in mass transfer resistance. The membrane resistance was not found to be impacted by chloride contamination. As measured by cyclic voltammetry, the presence of chloride in the air stream significantly reduced the cathode electrochemical surface area, and this reduction is believed to be due to the adsorption of chloride on the Pt surface causing active site blockage and accelerated Pt dissolution and agglomeration via the formation of Pt–Cl complexes.
Keywords: Charge transfer; Chloride contamination; Electrochemical surface area; Mass transfer; PEM fuel cells

High gravimetric capacity and long cycle life in Mn3O4/graphene platelet/LiCMC composite lithium-ion battery anodes - Lavoie, Nathalie; Malenfant, Patrick R. L.; Courtel, Fabrice M.; Abu-Lebdeh, Yaser; Davidson, Isobel J. (Journal of Power Sources, 2012)
We report the synthesis, characterization and battery performance of a novel Mn3O4/graphene composite based on graphene platelets and also an Mn3O4/reduced-graphene-oxide composite for comparison. The electrodes were cast from aqueous dispersions in which lithium carboxymethyl cellulose was used as a binder thus enabling an aqueous based process for anode fabrication. The Mn3O4/graphene-platelet and the Mn3O4/reduced-graphene-oxide composites anode system possess high gravimetric capacities (∼700 mAh g−¹) and excellent cycling stability (>100 cycles).
Keywords: Graphene; Manganese oxide; Li-ion batteries; Anode materials; Lithium carboxymethyl cellulose (LiCMC)

Application of a composite structure of carbon nanoparticles and Nb–TiO2 nanofibers as electrocatalyst support for PEM fuel cells - Bauer, Alex; Hui, Rob; Ignaszak, Anna; Zhang, Jiujun; Jones, Deborah J. (Journal of Power Sources, 2012)
Platinum catalyst nanoparticles (20 wt.%) were deposited on a mixed support, which consisted of 25 at.% Nb doped TiO2 nanofibers and carbon agglomerates. XRD analysis revealed that titania was present in the rutile phase. The catalyst was characterized electrochemically with respect to durability and oxygen reduction activity. Based on cyclic voltammetry tests, the Nb–TiO2/C supported catalyst was more stable compared to a commercially available carbon supported Pt catalyst (E-tek) over 1000 cycles. The apparent active Pt area decreased by 5% due to cycling, whereas in the case of Pt/C the decrease was 23%. The oxygen reduction performance was comparable for both cases. For example, during the anodic sweep the mass activity at 0.9 V vs. the reversible hydrogen electrode (RHE) was 19 A gPt−¹ and 20 A gPt−¹ for the freshly prepared in-house prepared and commercial catalysts, respectively. After the durability experiment both types of catalysts yielded a mass activity of 17 A gPt−¹. Fuel cell tests with a single cell configuration were also carried out with the Nb–TiO2/C supported catalyst on the cathode side (gas diffusion electrode), yielding a peak power density of 0.34 W cm−² at 75 °C when pure oxygen was supplied on the cathode side.
Keywords: Fuel cells; Conductive ceramics; Catalyst support; Nanofibers; Doped titanium oxide

Membrane electrode assembly degradation under idle conditions via unsymmetrical reactant relative humidity cycling - Vengatesan, S.; Panha, Karachakorn; Fowler, Michael W.; Yuan, Xiao-Zi; Wang, Haijiang (Journal of Power Sources, 2012)
The objective of this study is to investigate membrane electrode assembly (MEA) failure modes under accelerated test conditions via reactant relative humidity (RH) cycling. In this study, the anode and cathode underwent RH cycling in an unsymmetrical manner and the cell was run at a minimal “idle” current during endurance testing. The cell performance was monitored periodically and the degradation curve showed a difference in the anode and cathode induced RH cycling modes. Anode RH cycling had a more pronounced effect on MEA degradation than cathode RH cycling. Electrochemical diagnostic testing methods such as AC impedance and H2 crossover measurements revealed the degradation phenomena in more detail. The fluoride release data of the anode RH cycling cell showed a sudden increase in fluoride rate within a short period of endurance testing. The infrared imaging results revealed thinning and hotspot pinholes in the membrane, and ionomer delamination from the PTFE reinforcement layer was identified by scanning electron microscopy. The anode RH cycling cell had a shorter lifespan than the cell with cathode RH cycling, highlighting the significance of anode humidification for MEA durability.
Keywords: Durability; PEM failure modes; RH cycling; Idle condition; Membrane electrode assembly

Ex situ study of chloride contamination on carbon supported Pt catalyst - Lam, Alfred; Li, Hui; Zhang, Shengsheng; Wang, Haijiang; Wilkinson, David P.; Wessel, Silvia; Cheng, Tommy T. H. (Journal of Power Sources, 2012)
The effect of ppm levels of chloride ions on a carbon supported platinum catalyst was examined using an ex situ electrochemical quartz crystal microbalance (EQCM) method. The dissolution of Pt as chloride complexes and the adsorption of chloride ions resulted in a loss of electrochemical surface area (ECSA) by 4%, 7% and 13% for the respective chloride concentrations of 500 ppm, 1000 ppm and 2000 ppm. Catalyst durability was examined by cyclic voltammetry (CV) and scanning electron microscopy (SEM) in the presence of 1000 ppm chloride. The beginning of life (BOL) ECSA of 8.1 cm² cm−² was significantly reduced to an end of life (EOL) ECSA of 3.2 cm² cm−² after cycling in the presence of 1000 ppm chloride.
Keywords: Polymer electrolyte membrane; Fuel cell; Chloride contamination; Electrochemical quartz crystal microbalance

Nickel and cobalt oxide composite as a possible electrode material for electrochemical supercapacitors - Wang, Guoping; Zhang, Lei; Kim, Jenny; Zhang, Jiujun (Journal of Power Sources, 2012)
In this paper, a composite material, Ni0.37Co0.63(OH)2, is synthesized using the chemical precipitation method with the purpose to develop electrode materials for supercapacitors. Physical characterization using XRD, EDX, and SEM show that Ni0.37Co0.63(OH)2 possesses an amorphous structure, which leads to high specific capacitance of 1840 F g−¹ in the potential window of 0–1.5 V. Cyclic voltammetry methods are employed to characterize the electrochemical properties of this electrode material in a N2-saturated alkaline solution. The results demonstrate that this material could give a two-electron redox process accompanied by two OH− ions. Cyclic voltammogram curves recorded for this Ni0.37Co0.63(OH)2 material are used to measure the specific capacitances at different potential scan rates. To validate this material for supercapacitor applications, charging/discharging tests are also conducted.
Keywords: Electrochemical supercapacitor; Ni oxide; Co oxide; Composite electrode material

Pulsed laser deposition of cobalt-doped manganese oxide thin films for supercapacitor applications - Yang, Dongfang (Journal of Power Sources, 2012)
Thin films of manganese oxide doped with various percentages of cobalt oxide were grown by pulsed laser deposition on silicon wafers and stainless steel substrates. The films were characterized by X-ray diffraction and field emission scanning electron microscopy in order to identify their phases and microstructures. The pseudo-capacitance behavior of the Co-doped manganese oxide films were then evaluated using electrochemical cyclic voltammetry in an aqueous electrolyte. Their specific current and capacitance determined by electrochemical measurements were compared with undoped manganese oxide films, and the results show that Co-doped amorphous MnOx films have significantly higher specific current and capacitance than undoped amorphous MnOx films. The 3.0% Co-doped MnOx (i.e., Mn0.970Co0.030Ox) film had the highest specific capacitance of 99 F g−¹ at a 5 mV s−¹ scan rate. However, Co-doped crystalline Mn2O3 films did not show an improvement in specific current and capacitance compared with undoped Mn2O3 crystalline films. High Co doping level (20.7% doped) in the crystalline Mn2O3 films actually decreased both the specific current and capacitance values. These findings demonstrate that elemental doping is an effective way to improve the performance of pseudo-capacitive metal oxides.
Keywords: Electrochemical capacitor; Supercapacitor; Ultracapacitor; Pulsed laser deposition; Cobalt-doped manganese oxides; Thin films

The calcium-sensing receptor: a novel Alzheimer's disease crucial target? - Armato, Ubaldo; Bonafini, Clara; Chakravarthy, Balu; Pacchiana, Raffaella; Chiarini, Anna; Whitfield, James F.; Dal Prà, Ilaria (Journal of the Neurological Sciences, 2012)
Alzheimer's disease (AD) is the most common human neurodegenerative ailment, the most prevalent (> 95%) late-onset type of which has a still uncertain etiology. The progressive decline of cognitive functions, dementia, and physical disabilities of AD is caused by synaptic losses that progressively disconnect key neuronal networks in crucial brain areas, like the hippocampus and temporoparietal cortex, and critically impair language, sensory processing, memory, and conscious thought. AD's two main hallmarks are fibrillar amyloid-β (fAβ) plaques in extracellular spaces and intracellular accumulation of fAβ peptides and neurofibrillary tangles (NFTs). It is still undecided whether either or both these AD hallmarks cause or result from the disease. Recently, the dysregulation of calcium homeostasis has been advanced as a novel cause of AD. In this case, a suitable candidate of AD driver would be the Aβ peptides–binding/activated calcium-sensing receptor (CaSR), whose intracellular signalling is triggered by Aβ peptides. In this review, we briefly discuss CaSR's roles in normal adult human astrocytes (NAHAs) and their possible impacts on AD.
Keywords: Alzheimer's disease; Amyloid-β peptides; Calcium-sensing receptor; Human astrocytes

Comparing gray and white matter fMRI activation using asymmetric spin echo spiral - McWhinney, Sean R.; Mazerolle, Erin L.; Gawryluk, Jodie R.; Beyea, Steven D.; D’arcy, Ryan C. N. (Journal of Neuroscience Methods, 2012)
Recent developments have shown that it is possible to detect functional magnetic resonance imaging (fMRI) activation in white matter (WM). Enhanced sensitivity to WM fMRI signals has been associated with the asymmetric spin echo (ASE) spiral sequence. The ASE spiral sequence produces three consecutive images that have equal blood-oxygen level-dependent (BOLD) contrast but increasing T2 contrast. The current study evaluated whether ASE spiral sensitivity differed between white and gray matter in the corpus callosum, superior parietal lobes, cingulate gyrus, and inferior frontal lobes. Contrast and noise were compared across the three images for each region. Results showed increasing gains in functional contrast in both white and gray matter as a function of T2 contrast. The third image, with the most T2 contrast, showed the largest increase in contrast, while changes in noise were maintained. The results suggest that ASE spiral increases fMRI sensitivity globally through the addition of T2 weighted contrast.
Keywords: Asymmetric spin echo; fMRI; White matter; Contrast-to-noise

A comparison of MR imaging of a mouse model of glioma at 0.2T and 9.4T - Blasiak, Barbara; Volotovskyy, Vyacheslav; Deng, Charlie; Foniok, Tadeusz; Tomanek, Boguslaw (Journal of Neuroscience Methods, 2012)
Both 0.2 T and 9.4 T MRI systems were used to image a mouse model of glioma. RF coils were designed for both fields. A spin-echo, multi-echo pulse sequence was used to determine T2 relaxation times of both brain and tumor tissues. Contrast-to-noise ratio was calculated based on the selected echo time. The results showed that 0.2 T is suitable for mouse model imaging, however total scan time must be long to achieve high enough SNR. T2 relaxation times of the tumor and brain tissues can be measured at 0.2 T and are 2.1 and 1.8 times respectively longer at 0.2 T than at 9.4 T. Contrast to noise ratio for tumor and brain was better at high field than at the low field. We concluded that 0.2 T may be used to study mouse model of glioma using spin echo pulse sequence, yet the total scan time is long (about 40 min), resolution is lower (∼250 μm × 250 μm) and slice thickness (3 mm) must be large enough to obtain sufficient SNR.
Keywords: MRI; Glioma; Brain; Low field MRI; RF coil

Infrared spectra of rare gas–carbon disulfide complexes: He–CS2, Ne–CS2, and Ar–CS2 - Mivehvar, F.; Lauzin, Clément; Mckellar, A. R. W.; Moazzen-Ahmadi, N. (Journal of Molecular Spectroscopy, 2012)
Spectra of the weakly-bound van der Waals complexes Ar–CS2, Ne–CS2, and He–CS2 are studied in the region of the CS2ν3 fundamental band (≈1535 cm−¹) using a tunable diode laser to probe a pulsed supersonic expansion from a slit jet nozzle. He–CS2 is also observed in the ν1 + ν3 region (≈2185 cm−¹). These are the first reported spectra for rare gas–CS2 complexes, which are shown to have T-shaped structures similar to their CO2 analogs but with intermolecular separations which are 0.2–0.3 Å greater.
Keywords: Carbon disulfide; Spectrum; Dimer; van der Waals; Infrared; Supersonic jet

Infrared spectra of the Ne2–N2O, Ar2–N2O trimers - Rezaei, M.; Michaelian, K. H.; Mckellar, A. R. W.; Moazzen-Ahmadi, N. (Journal of Molecular Spectroscopy, 2012)
Spectra of the van der Waals trimers Ar2–N2O and Ne2–N2O are studied in the region of the N2O ν1 fundamental (≈2220 cm−¹) using a tunable quantum cascade laser to probe a pulsed supersonic expansion from a slit jet nozzle. Improved data are obtained for the dimers Ar–N2O and Ne–N2O, and the Q-branch of Ar3–N2O is tentatively assigned. The vibrational shifts for Nen–N2O are almost exactly linear for n = 0–2. However, for Arn–N2O the n = 2 band origin is slightly blue-shifted compared to the linear prediction, and the n = 3 origin (if correct) is more significantly blue-shifted (by 0.09 cm−¹).
Keywords: Argon; Neon; Nitrous oxide; Spectrum; Dimer; Trimer; van der Waals

Infrared spectra of acetylene–water complexes: C2D2–H2O, C2D2–HDO, and C2D2–D2O - Rezaei, Mojtaba; Moazzen-Ahmadi, N.; Mckellar, A. R. W. (Journal of Molecular Spectroscopy, 2012)
Infrared spectra of C2D2–water complexes are studied in the 4.1 μm region of the C2D2 ν3 fundamental band using a tunable diode laser source to probe a pulsed supersonic slit jet. Relatively large vibrational red shifts (−27.7 to −28.0 cm−¹) are observed which are more easily interpretable than for the analogous C2H2 vibration thanks to the absence of Fermi resonance effects for C2D2. Noticeable homogeneous line broadening leads to estimates of upper state predissociation lifetimes of about 0.5, 0.9 and 1.1 ns for C2D2–H2O, –HDO, and –D2O, respectively. Transitions involving Ka = 0 and 1 levels are observed for C2D2–HDO, but there is a puzzling absence of Ka = 1 for C2D2–H2O and C2D2–D2O.
Keywords: Acetylene–water complex; Infrared; Dimer; Jet spectroscopy; High resolution; Van der Waals

Influence of overlap between the laser beam tracks on surface quality in laser polishing of AISI H13 tool steel - Hafiz, Abdullah M. Khalid; Bordatchev, Evgueni V.; Tutunea-Fatan, Remus O. (Journal of Manufacturing Processes, 2012)
Polishing by laser beam radiation is a novel manufacturing process to modify the initial surface topography in order to achieve a desired level of surface finish. The performance of laser polishing (LP) is determined by an optimum combination of several key process parameters. In this regard, the overlap between two successive laser beam tracks is one of the important LP process parameters, which has a significant effect over the final surface quality. In the current study, influence of overlap between the laser beam tracks on surface quality was experimentally investigated during the laser polishing of AISI H13 tool steel. Surface areas were polished by using four different overlap percentages (e.g. 80%, 90%, 95%, and 97.5%) while applying the same energy density. The improvement of surface quality was estimated through the analysis of line profiling surface roughness Ra, areal topography surface roughness Sa, and material ratio function. Also, individual components of the surface quality, e.g. waviness and roughness, and their evolution during LP were statistically analyzed using the power spectral density and the transfer functions. Finally, as an example of the best achieved LP result, flat surface area was polished using optimum set of the process parameters improving surface quality by 86.7% through the reduction of an areal topography surface roughness Sa from 1.35 μm to 0.18 μm.
Keywords: Laser polishing; Surface quality; Material ratio function; Power spectral density; Transfer function

American ginseng inhibits vascular smooth muscle cell proliferation via suppressing Jak/Stat pathway - Wu, Qi; Wang, Wenjuan; Li, Siying; Nagarkatti, Prakash; Nagarkatti, Mitzi; Windust, Anthony; Wang, Xing li; Tang, Dongqi; Cui, Taixing (Journal of Ethnopharmacology, 2012)
Ethnopharmcological relevance - Ginseng, a folk medicine which has been used for thousands of years in Asia, has been promoted for the treatment or prevention of health problems including cardiovascular disease. However, the molecular mechanism of ginseng-induced cardiovascular protection is unclear. Thus, we investigated signaling mechanism by which American ginseng inhibits vascular smooth muscle cell (VSMC) proliferation, a key feature of diverse vascular disease. Materials and methods - A standardized crude extract of American ginseng was supplied by the National Research Council of Canada, Institute for National Measurement Standards. Rat aortic smooth muscle cells (RASMCs) were exposed to fetal bovine serum (FBS), platelet derived growth factor (PDGF), insulin, or angiotensin II (Ang II) to induce proliferation that was examined by measuring DNA synthesis and cell numbers. Western blot was applied to determine the activations of Jak, Stat, Akt, and ERK. Results - American ginseng inhibited RASMC proliferation induced by FBS, PDGF, insulin or Ang II. American ginseng slightly increased both basal and FBS-, PDGF- or Ang II-induced activities of Akt and ERK in RASMCs; however, it dramatically inhibited the activation of Jak2 and Stat3. Conclusion - These results demonstrate that American ginseng inhibits VSMC proliferation through suppressing the Jak/Stat pathway.
Keywords: Panax quinquefolius; American ginseng; Jak; Stat; Vascular smooth muscle cells; Proliferation

Molecular dynamics Gibbs free energy calculations for CO2 capture and storage in structure I clathrate hydrates in the presence of SO2, CH4, N2, and H2S impurities - Nohra, Michael; Woo, Tom K.; Alavi, Saman; Ripmeester, John A. (The Journal of Chemical Thermodynamics, 2012)
Keywords: Clathrate hydrates; Molecular dynamics; Free energy calculations; Carbon dioxide sequestration; Thermodynamic integration; Carbon capture and storage; Sulfur dioxide; Flue gas

Influence of carbon coated pBN crucible on crystal growth of Cd0.9Zn0.1Te for radiation detector applications - Crocco, J.; Carcelen, V.; Methven, B.; Gallardo, I.; Bensalah, H.; Zheng, Q.; Rivas, I.; Moreno, F.; Vela, O.; Diéguez, E. (Journal of Crystal Growth, 2012)
In the Bridgman and Vertical Gradient Freeze (VGF) techniques, it is common to use a high purity crucible for crystal growth. One disadvantage of pBN crucibles is associated with the crucible material interacting with the melt during the growth cycle. Using pBN crucibles for the growth of CZT, we have observed that the crucible does in fact interact with the CZT melt. To prevent this interaction, a vacuum carbon coating system for applying a carbon coating to pBN crucibles has been developed. The effects of crucible use with time are studied, as are the compositional and device properties of the bulk material. GDMS measurements are used to investigate on broron and nitrogen content, among other trace impurities found in the crystal. Devices harvested from ingots grown using cc-pBN exhibit high resistivity and good functionality as room temperature gamma ray detectors.
Keywords: Gradient freeze technique; Impurities; Cadmium compounds; Nitrides

Multiwafer zinc diffusion in an OMVPE reactor - Pitts, O. J.; Benyon, W.; Goodchild, D.; Springthorpe, A. J. (Journal of Crystal Growth, 2012)
We study diffusion of zinc into InP in a multiwafer OMVPE reactor using dimethylzinc as the diffusant source. The resulting diffusion profiles are measured by electrochemical capacitance–voltage profiling and by secondary ion mass spectrometry and compared with cleaved cross-sections imaged by scanning electron microscopy. Very good uniformity of the diffusion profile is achieved, with variation across a 3 in. wafer as little as 5%. The dependence of the diffusion depth and Zn concentration on the diffusion temperature, partial pressure of dimethylzinc, and diffusion time are reported. We observe an enhancement of the diffusion depth in area-selective diffusion of planar devices, compared to the depth obtained for blanket diffusion.
Keywords: Diffusion; Metalorganic chemical vapor deposition; Metalorganic vapor phase epitaxy; Organometallic vapor phase epitaxy; Semiconducting indium phosphide

Expression and characterization of recombinant human alpha-antitrypsin in transgenic rice seed - Zhang, Liping; Shi, Jingni; Jiang, Daiming; Stupak, Jacek; Ou, Jiquan; Qiu, Qichuan; An, Na; Li, Jianjun; Yang, Daichang (Journal of Biotechnology, 2012)
Human alpha-antitrypsin (AAT) is the most abundant circulating protease inhibitor in the human plasma. It is produced in the liver and exerts a primary physiological role as inhibitor for the neutrophil elastase in the lung. Individuals with one or several gene mutations in AAT causing reduction of the protein are related to lung, liver and pancreatic emphysema diseases and are treated lifelong with infusions of human plasma-derived AAT. Due to shortage of plasma and low expression levels of recombinant AAT in conventional gene expression systems, we explored the possibility to produce recombinant AAT in rice grains (Oryza sativa AAT, OsrAAT). An expression level of up to 2.24 g/kg brown rice and a final recovery of purified 0.366 g/kg OsrAAT has been obtained. OsrAAT has the same secondary structure and protease inhibitory activity as plasma-derived AAT (pAAT), but was highly heterogeneous with regard to glycan modifications. Thus 32.8% of OsrAAT were glycosylated and 67.2% were free of glycans as determined by MALDI-MS. Of the N-glycan structures 64.8% were vacuole-specific paucimannosidic molecules. Immune electron microscopy located OsrAAT in the endoplasmic reticulum lumen as precursor-accumulating (PAC)-like vesicle structures. The pharmacokinetic study indicated that the half-life of OsrAAT was prolonged, while the clearance rate was faster than that of pAAT in vivo. The results demonstrate that rice endosperm is a promising system to express this biopharmaceutical protein.
Keywords: Recombinant human alpha-1-antitrypsin; Rice endosperm; Plant N-glycan modification; Protein expression and processing; Protein trafficking

Studies of CoSn grains in the carbon matrix structure of nanostructured tin–cobalt–carbon - Ferguson, P. P.; Fleischauer, M. D.; Laforge, J. M.; Todd, A. D. W.; Li, P.; Dahn, J. R. (Journal of Alloys and Compounds, 2012)
Small angle neutron scattering (SANS) and transmission electron microscopy (TEM) have been used to qualitatively analyze the structure of Sn30Co30C40 alloys produced by vertical axis mechanical attriting to those produced by magnetron sputter deposition. From SANS and TEM, CoSn grains embedded in a carbon matrix structure were observed for all samples. The size of CoSn grains in the attrited samples was approximately 10 ± 3 nm by both TEM and SANS, while that of the sputtered samples was about 7 times smaller.
Keywords: Tin cobalt carbon; Small angle neutron scattering; Transmission electron microscopy; Li-ion battery negative electrode; Sputtering; Mechanical alloying

Effect of cold rolling on hydrogen sorption properties of die-cast and as-cast magnesium alloys - Amira, S.; Huot, J. (Journal of Alloys and Compounds, 2012)
The effect of cold rolling, as an activation process of materials aimed to hydrogen storage application, was applied to some cast magnesium alloys. The alloys studied in this work are AZ91D and three experimental creep resistant magnesium alloys (MRI153, AXJ530, ZAEX10430) in the as-cast and die-cast states. Experiments showed that AZ91D, MRI153 and ZAEX10430 have faster absorption/desorption kinetic than as-cast pure magnesium. On the other hand, AXJ530 showed the worst hydrogen storage properties. These results were attributed to a possible beneficial effect of aluminum and zinc as alloying elements. Segregation inside primary α-Mg grains may explain the difference of hydrogen storage properties between as-cast and die-cast alloys.
Keywords: Severe Plastic Deformation (SPD); Magnesium alloys; Hydrogen storage; Casting

Performance-based parameter tuning method of model-driven PID control systems - Zhao, Y. M.; Xie, W. F.; Tu, X. W. (ISA Transactions, 2012)
In this paper, performance-based parameter tuning method of model-driven Two-Degree-of-Freedom PID (MD TDOF PID) control system has been proposed to enhance the control performances of a process. Known for its ability of stabilizing the unstable processes, fast tracking to the change of set points and rejecting disturbance, the MD TDOF PID has gained research interest recently. The tuning methods for the reported MD TDOF PID are based on internal model control (IMC) method instead of optimizing the performance indices. In this paper, an Integral of Time Absolute Error (ITAE) zero-position-error optimal tuning and noise effect minimizing method is proposed for tuning two parameters in MD TDOF PID control system to achieve the desired regulating and disturbance rejection performance. The comparison with Two-Degree-of-Freedom control scheme by modified smith predictor (TDOF CS MSP) and the designed MD TDOF PID tuned by the IMC tuning method demonstrates the effectiveness of the proposed tuning method.
Keywords: MD TDOF PID; Modified smith predictor; PD feedback; Q filter and set-point filter

Calculations of gas radiation heat transfer in a two-dimensional rectangular enclosure using the line-by-line approach and the statistical narrow-band correlated-k model - Chu, Huaqiang; Liu, Fengshan; Zhou, Huaichun (International Journal of Thermal Sciences, 2012)
Radiation heat transfer in a two-dimensional rectangular enclosure containing CO2/H2O/N2 mixtures was calculated using the line-by-line and the statistical narrow-band correlated-k models. The radiative transfer equation was solved using the discrete ordinates method along with the T7 quadrature scheme. The updated HITEMP spectroscopic database, HITEMP2010, was employed in line-by-line calculations to obtain the most accurate line-by-line results. The statistical narrow-band model parameters of Sourfiani and Taine [IJHMT 40, 987–991, 1997] were used to obtain the statistical narrow-band correlated-k model results. Calculations were carried out for five test cases involving isothermal/non-isothermal and homogeneous/inhomogeneous CO2/N2, H2O/N2, and CO2/H2O/N2 mixtures. The present line-by-line results can serve as benchmark results for the purpose of validating other approximate models in gas radiation heat transfer calculations in two-dimensional enclosures. Results of the statistical narrow-band correlated-k model are in good agreement with those of the line-by-line method in all the test cases. The statistical narrow-band correlated-k model was found sufficiently accurate to generate benchmark solutions in multi-dimensional gas radiation transfer problems where line-by-line calculations are infeasible due to excessively long computing time.
Keywords: Non-gray gas radiation; LBL calculations; SNBCK model

Assessment of silk fibroin for the repair of buccal mucosa in a rat model - Ge, Z.; Yang, Q.; Xiang, X.; Liu, K.-Z. (International Journal of Oral and Maxillofacial Surgery, 2012)
This study evaluated the effectiveness of silk fibroin materials for wound repair confined to the buccal mucosa in a rat model by assessing several key clinical parameters and the associated local and systemic immune response. Ninety male SD rats were subjected to microscopic oral surgery to establish a full thickness wound on the buccal mucosa. Rats were randomly divided into three groups based on the treatments received: group A, covered with polyporous silk fibroin scaffold; group B, repaired with crosslinking silk fibroin film; and group C, control. Visual observation of the wounds suggests that wound shrinkage 5 days after the operation was significantly lower in both silk fibroin repaired groups (A and B) than that in the controls. The distribution of inflammatory neutrophils in group A was significantly lower than those in the control group throughout the entire study. The percentage of fibroblasts and capillary endothelia (CD34+), and the subgroups of peripheral lymphocytes (CD3+, CD4+, CD8+) were similar amongst the groups. The results revealed that placement of silk fibroin in an oral buccal defect can reduce the degree of wound shrinkage and enhance the growth of mucosal epithelial cells without any local or systemic immunological incompatibility.
Keywords: silk fibroin; buccal mucosa; tissue repair; tissue engineering

An integrated multi-level watershed-reservoir modeling system for examining hydrological and biogeochemical processes in small prairie watersheds - Zhang, Hua; Huang, Guo H.; Wang, Dunling; Zhang, Xiaodong; Li, Gongchen; An, Chunjiang; Cui, Zheng; Liao, Renfei; Nie, Xianghui (Water Research, 2012)
Eutrophication of small prairie reservoirs presents a major challenge in water quality management and has led to a need for predictive water quality modeling. Studies are lacking in effectively integrating watershed models and reservoir models to explore nutrient dynamics and eutrophication pattern. A water quality model specific to small prairie water bodies is also desired in order to highlight key biogeochemical processes with an acceptable degree of parameterization. This study presents a Multi-level Watershed-Reservoir Modeling System (MWRMS) to simulate hydrological and biogeochemical processes in small prairie watersheds. It integrated a watershed model, a hydrodynamic model and an eutrophication model into a flexible modeling framework. It can comprehensively describe hydrological and biogeochemical processes across different spatial scales and effectively deal with the special drainage structure of small prairie watersheds. As a key component of MWRMS, a three-dimensional Willows Reservoir Eutrophication Model (WREM) is developed to addresses essential biogeochemical processes in prairie reservoirs and to generate 3D distributions of various water quality constituents; with a modest degree of parameterization, WREM is able to meet the limit of data availability that often confronts the modeling practices in small watersheds. MWRMS was applied to the Assiniboia Watershed in southern Saskatchewan, Canada. Extensive efforts of field work and lab analysis were undertaken to support model calibration and validation. MWRMS demonstrated its ability to reproduce the observed watershed water yield, reservoir water levels and temperatures, and concentrations of several water constituents. Results showed that the aquatic systems in the Assiniboia Watershed were nitrogen-limited and sediment flux played a crucial role in reservoir nutrient budget and dynamics. MWRMS can provide a broad context of decision support for water resources management and water quality protection in the prairie region.
Keywords: Prairie watershed; Multi-level; Eutrophication; Reservoir; Simulation

Relative permeability for two-phase flow through corrugated tubes as model porous media - Ahmadlouydarab, Majid; Liu, Zhong-Sheng (Simon); Feng, James J. (International Journal of Multiphase Flow, 2012)
We report finite-element simulations of gas–liquid two-phase flows through a model porous medium made of corrugated tubes. By resolving the pore-scale fluid dynamics and interfacial morphology, we compute the relative permeability of the porous medium by averaging over a pore-size-distribution of a real porous medium. A constant pressure gradient is applied on both fluids to simulate a pressure-driven creeping flow, and a diffuse-interface model is used to compute the interfacial evolution and the contact line motion. We observe a number of flow regimes in the micro-pores, depending on the pore size, imposed pressure gradient, and other geometric and physical parameters. The flow rates vary nonlinearly with the pressure gradient, and the extended Darcy’s law does not hold in general. The interaction between the two phases, known as viscous coupling, is a prominent feature of the process. As a result, the relative permeability depends not only on saturation, but also on the capillary number, viscosity ratio, wettability of the solid wall, pore geometry, and the initial configuration. The effects of these factors are explored systematically and compared with previous studies.
Keywords: Interfacial flow; Viscous coupling; Pore-scale simulation; Moving contact line; Cahn–Hilliard model; Lubrication effect

Far- and mid-infrared photoacoustic spectra of tetracene, pentacene, perylene and pyrene - Michaelian, K.H.; Wen, Q.; Billinghurst, B.E.; Shaw, J.M.; Lastovka, V. (Vibrational Spectroscopy, 2012)
Far- and mid-infrared photoacoustic (PA) spectra of tetracene, pentacene, perylene and pyrene were acquired in this study. Far-infrared data were obtained at wavenumbers down to ∼80 cm−1 using large-amplitude phase modulation in a step-scan spectrometer; many previously unreported bands were observed in these spectra. For each compound, the fingerprint region of the mid-infrared spectrum (approximately 400–2000 cm−1) contained a large number of bands correlated with vibrations that are predicted to be either infrared or Raman active. In addition, numerous combination and overtone bands appeared in the mid-infrared spectra. This PA investigation provides the most detailed spectral data known for these four aromatic compounds.
Keywords: Photoacoustic infrared spectroscopy; Aromatic hydrocarbons; DFT calculations

Estimating microbial electrolysis cell (MEC) investment costs in wastewater treatment plants: case study - Escapa, A.; Gómez, X.; Tartakovsky, B.; Morán, A. (International Journal of Hydrogen Energy, 2012)
Microbial electrolysis represents a new approach for harnessing the energy contained in the organic matter of wastewater. However, before this approach can be implemented on a practical basis, a cost-effective manufacturing process for microbial electrolysis cells (MECs) must be developed. The objective of this study is to estimate an acceptable purchase cost of an MEC reactor for a domestic wastewater treatment plant. We estimate that for a full-scale MEC operating at a current density of 5 A ma−² (amperes per square meter of anode) and an energy consumption of 0.9 kWh kg-COD−¹ (kilowatt-hour per kg of removed chemical oxygen demand (COD)), a cost of €1220 ma−³ (euro per m³ of anodic chamber) can be established as a target purchase cost at which a break-even point is reached after 7 years.
Keywords: Microbial electrolysis cell; Costs estimation; Hydrogen; Domestic wastewater

Highly active electrocatalysts for oxygen reduction from carbon-supported copper-phthalocyanine synthesized by high temperature treatment - Ding, Lei; Qiao, Jinli; Dai, Xianfeng; Zhang, Jing; Zhang, Jiujun; Tian, Binglun (International Journal of Hydrogen Energy, 2012)
The active, carbon-supported copper phthalocyanine (CuPc/C) nano-catalyst, as a novel cathode catalyst for oxygen reduction reaction, is synthesized via a combined solvent-impregnation along with the high temperature treatment. The catalytic activities of both pyrolyzed and unpyrolyzed catalysts are screened by linear sweep voltammetry (LSV) employing a rotating disk electrode (RDE) technique to quantitatively obtain the oxygen reduction reaction (ORR) kinetic constants and the reaction mechanisms. The results show that heat-treatment can significantly improve the ORR activity of the catalyst, and the optimal heat-treated temperature is around 800 °C, under which, an onset potential of 0.10 V and a half-wave potential of −0.05 V are achieved in alkaline electrolyte. Besides the ORR kinetic rate is increased, the ORR electron transfer number is also increased from 2.5 to 3.6 with increasing heat-treatment temperature from 600 to 800 °C. Also, the effect of catalyst loading in the catalyst layer on the corresponding ORR activity is also studied, and finds that increasing the catalyst loading, the catalyzed ORR kinetic current density can be significantly increased. For a fully understanding of this heat-treatment temperature effect, XRD, TEM, SEM–EDX, TG and XPS are used to identify the catalyst structure and composition. TG results demonstrated that the presence of Cu prevents phthalocyanine from thermal decomposition, thus contribute to higher nitrogen content which can form more Cu–Nx activity sites for the ORR. XPS analysis indicates that both pyridinic-N and graphitic-N may be responsible for the enhanced ORR activity.
Keywords: Copper phthalocyanine; Electrocatalysts; Oxygen reduction reaction; Heat treatment; Alkaline fuel cell

Current mapping of a proton exchange membrane fuel cell with a segmented current collector during the gas starvation and shutdown processes - Yu, Yi; Yuan, Xiao-Zi; Li, Hui; Gu, Elton; Wang, Haijiang; Wang, Guangjin; Pan, Mu (International Journal of Hydrogen Energy, 2012)
Current distribution during the gas starvation and shutdown processes is investigated in a proton exchange membrane fuel cell with an active area of 184 cm². The cell features a segmented cathode current collector. The response characteristics of the segmented single cell under different degrees of hydrogen and air starvation are explored. The current responses of the segment cells at different positions under a dummy load in the shutdown process are reported for various operating conditions, such as different dummy loads, cell temperatures, and gas humidities under no back pressure. The results show that applying a dummy load during the cell shutdown process can quickly reduce the cell potential and thereby avoid the performance degradation caused by high potentials. The currents of all the segment cells decrease with time, but the rate of decrease varies with the segment cell positions. The rate for the segment cells near the gas outlet is much higher than that of the segment cells near the gas inlet. The current of the segment cells decreases much more quickly at a lower gas humidity and high temperature. This study provides insights in the development of mitigation strategies for the degradation caused by starvation and shutdown process.
Keywords: Proton exchange membrane fuel cell; Startup and shutdown processes; Reverse current; Current distribution; Current mapping; Segmented fuel cell

Phylogroup and lpfA influence epithelial invasion by mastitis associated Escherichia coli - Dogan, Belgin; Rishniw, Mark; Bruant, Guillaume; Harel, Josee; Schukken, Ynte H.; Simpson, Kenneth W. (Veterinary Microbiology, 2012)
Escherichia coli infection is one of the most common causes of bovine mastitis in well managed dairies. Although E. coli infections are usually transient, E. coli can also cause persistent intramammary infections. We sought to determine whether E. coli isolates recovered from either transient or persistent intramammary infections differed both genetically and in their ability to invade mammary epithelial cells. E. coli isolates from transient (ECtrans, n = 16) and persistent (ECpers, n = 12) mastitis cases were compared for differences in overall genotype, virulence genes, serotype, phylogroup (A, B1, B2, D), and invasion of bovine mammary epithelial cells, MAC-T by microarray analysis, suppressive subtractive hybridization, PCR and gentamicin protection assays. ECtrans and ECpers were diverse in overall genotype and serotype, and were predominantly of phylogroups A and B1. Both ECtrans and ECpers contained genes encoding type II, IV and VI secretion systems, long polar fimbriae (lpfA) and iron acquisition, and lacked genes associated with virulence in diarrheagenic E. coli. ECtrans had fewer virulence genes than ECpers (p < 0.05), but no individual virulence genes were unique to either group. In phylogroup A, ECpers were more invasive than ECtrans (p < 0.05), but no difference was observed between them in phylogroup B1. Enhanced epithelial cell invasion was associated with lpfA (p < 0.05). Our findings indicate that a genetically diverse group of E. coli is associated with transient and persistent mastitis. We did not identify a set of bacterial genes to account for phenotypic differences. However, we found that mastitis phenotype, phylogroup and presence of lpfA were associated with the ability to invade cultured bovine mammary epithelial cells.
Keywords: Escherichia coli; Mastitis; Virulence; Long polar fimbriae; Phylogroup

An atypical biotype I Actinobacillus pleuropneumoniae serotype 13 is present in North America - Perry, Malcolm B.; Angen, Øystein; Maclean, Leann L.; Lacouture, Sonia; Kokotovic, Branko; Gottschalk, Marcelo (Veterinary Microbiology, 2012)
Atypical Actinobacillus pleuropneumoniae serotype 13 strains present in North America are described here for the first time. Different from serotype 13 strains described in Europe, North America strains are biotype I and antigenically related to both, serotypes 13 and 10. Chemical and structural analysis of the capsular polysaccharide (CPS) and lipopolysaccharide (LPS) of a representative strain revealed that the CPS is almost identical to that of the reference strain of serotype 13, having a slightly higher degree of glycose O-acetylation. However, it produces an O-PS within the LPS antigenically and structurally identical with that of the reference strain of A. pleuropneumoniae serotype 10. The O-PS was characterized as a homopolymer of 1,2 linked β-d-galactofuranosyl residues, a structure unrelated to that of the O-PS produced by the reference strain of serotype 13. Strains from Canada and United States are antigenically, phenotypically and genotypically similar. Animals infected by one of these strains induced antibodies that were detected by a LPS-based ELISA diagnostic test using either the homologous antigen or that of serotype 10. Based on the LPS and toxin profile, these strains might be misidentified as A. pleuropneumoniae serotype 10.
Keywords: Actinobacillus pleuropneumoniae; Biotype 1; Serotype 13 capsular polysaccharide; Serotype 10 lipopolysaccharide

Diagnosis of contamination introduced by ammonia at the cathode in a polymer electrolyte membrane fuel cell - Yuan, Xiao-Zi; Li, Hui; Yu, Yi; Jiang, Max; Qian, Weimin; Zhang, Shengsheng; Wang, Haijiang; Wessel, Silvia; Cheng, Tommy T. H. (International Journal of Hydrogen Energy, 2012)
Contamination introduced by impurities from feed streams can impact polymer electrolyte membrane fuel cell performance dramatically. The presence of unwanted trace species, such as CO, H2S, and NH3, can adversely affect the function of a fuel cell. It has been reported that the major impact of CO and H2S contamination on fuel cell performance is kinetic, while the effect of NH3 contamination is speculated to be mainly membrane conductivity reduction. In this paper, the effect of NH3 contamination from the cathode side was investigated. The mechanisms of NH3 contamination were diagnosed based on degradation tests using electrochemical impedance spectroscopy and cyclic voltammetry. The contamination factors investigated included ammonia concentration, operating current, temperature, and relative humidity. The results show that the severity of the adverse effect caused by ammonia contamination was enhanced by increased ammonia concentration, decreased operating temperature, and decreased relative humidity. The performance decay induced by ammonia is attributable to reduced membrane/ionomer conductivity and ammonia adsorption on the catalyst surface, which blocks the active sites and hinders mass transfer.
Keywords: PEM fuel cell; Ammonia; Contamination; Diagnosis

Effects of flow field design on the performance of a PEM fuel cell with metal foam as the flow distributor - Tsai, Bin-Tsang; Tseng, Chung-Jen; Liu, Zhong-Sheng; Wang, Chih-Hao; Lee, Chun-I; Yang, Chang-Chung; Lo, Shih-Kun (International Journal of Hydrogen Energy, 2012)
In this work, we report the improvements made on the PEM fuel cell with metal foam as the flow distributor. The comparison in polarization curve is made between the PEM unit cell with different metal foam flow field designs and the PEM unit cell with graphite bipolar plate as flow distributor. The experimental results show that after using improved metal foam flow field designs, the fuel cell's performance increases. Our results show that, in the PEM unit cell with single zone metal foam, the convection is weak at side corners. Dividing the metal foam into multiple regions and using multiple inlets effectively improves gas distribution. AC impedance measurement was also performed to study impedance characteristics. The Nyquist and Bode plots confirmed that Ohmic resistance, activation resistance, and mass transfer resistance of metal foam fuel cell are all smaller than that of conventional PEM unit cell.
Keywords: Proton exchange membrane fuel cell; Metal foam; Flow distributor; AC impedance

Fine specificity and cross-reactions of monoclonal antibodies to group B streptococcal capsular polysaccharide type III - Pincus, Seth H.; Moran, Emily; Maresh, Grace; Jennings, Harold J.; Pritchard, David G.; Egan, Marianne L.; Blixt, Ola (Vaccine, 2012)
Group B streptococcus (GBS) is a major cause of neonatal sepsis and meningitis. Despite aggressive campaigns using antenatal prophylactic antibiotic therapy, infections continue. Developing an effective maternal vaccine is a public health priority. Antibody (Ab) to the capsular polysaccharide (CPS) is considered the dominant “protective” immune mediator. Here we study the fine specificity and potential host reactivity of a panel of well-characterized murine monoclonal Abs against the type III CPS by examining the binding of the Abs to intact and neuraminidase-digested GBS, purified CPS, synthetic carbohydrate structures, and cells. The results showed marked differences in the fine specificity among these mAbs to a single carbohydrate structure. Cross-reactions with synthetic GD3 and GT3 carbohydrates, representing structures found on surfaces of neural and developing cells, were demonstrated using carbohydrate array technology. The anti-CPSIII mAbs did not react with cells expressing GD3 and GT3, nor did mAbs specific for the host carbohydrates cross-react with GBS, raising questions about the physiological relevance of this cross-reaction. But in the process of these investigations, we serendipitously demonstrated cross-reactions of some anti-CPSIII mAbs with antigens, likely carbohydrates, found on human leukocytes. These studies suggest caution in the development of a maternal vaccine to prevent infection by this important human pathogen.
Keywords: CPSIII, group B streptococcal capsular polysaccharide type III; GBS, group B streptococci; GD3, glycan Neu5Ac(α2-8)Neu5Ac(α2-3)Gal (β1-4)Glc; GT3, glycan Neu5Ac(α2-8)Neu5Ac (α2-8)Neu5Ac(-α2-3)Gal(β1-4)Glc; PAA, polyacrylamide

Microstructural evolution during low temperature sorption cycling of Mg-AlTi multilayer nanocomposites - Zahiri, Ramin; Zahiri, Beniamin; Kubis, Alan; Kalisvaart, Peter; Amirkhiz, Babak Shalchi; Mitlin, David (International Journal of Hydrogen Energy, 2012)
We studied the hydrogen storage behavior of sputtered Mg-AlTi multilayers where nanometric Mg or Mg–Al–Ti layers were confined by 2 nm thick layers of AlTi. By decreasing the thickness of Mg layers, we were able to achieve 5.1 wt.% H capacity without significant degradation in over 200 cycles at 473 K. However, for the samples with pure Mg layers degradation eventually occurred at higher cycle numbers. In multilayers of 34 nm thick Mg degradation was followed by disintegration of the films into sponge-like flakes. Alloying Mg layers with Al and Ti through cosputtering improved the performance of the multilayer composites. Through cycling, Al and Ti segregated out of Mg matrix and formed a nanocrystalline/amorphous AlTi phase as observed by X-ray diffraction and electron microscopy. This improved resistance of the microstructure against coarsening while a well dispersion of AlTi particles was achieved. Moreover, the stability of multilayers enhanced to an extent that they not only preserved their physical integrity, also did they maintain their superior kinetics up to over 250 cycles. Pressure - composition isotherms showed no significance change in thermodynamics of MgH2 formation.
Keywords: Magnesium hydride; Catalyst dispersion; Z-contrast STEM; Cycling stability; Sputtering; Multilayers; Activation

Design and immunological properties of Helicobacter pylori glycoconjugates based on a truncated lipopolysaccharide lacking Lewis antigen and comprising an α-1,6-glucan chain - Altman, Eleonora; Chandan, Vandana; Harrison, Blair A.; Veloso-pita, Roberto; Li, Jianjun; Kuolee, Rhonda; Chen, Wangxue; Vérez-bencomo, Vicente (Vaccine, 2012)
To investigate the vaccine potential of H. pylori lipopolysaccharide (LPS), truncated LPS of H. pylori strain 26695 HP0826::Kan lacking O-chain polysaccharide and comprising an extended α-1,6-linked glucan chain was conjugated to tetanus toxoid (TT) or bovine serum albumin (BSA). Two approaches were used for delipidation or partial delipidation of H. pylori LPS: (1) mild hydrolysis resulting in delipidated LPS (dLPS) and (2) treatment with anhydrous hydrazine resulting in removal of O-linked fatty acids (LPS-OH). Both LPS-OH and dLPS were covalently linked through a 2-keto-3-deoxy-octulosonic acid (Kdo) residue to a diamino group-containing spacer, followed by conjugation to thiolated TT or BSA to give conjugates LPS-OH-TT, dLPS-BSA and dLPS-TT, respectively. The LPS-OH-TT, dLPS-BSA and dLPS-TT conjugates were immunogenic in both rabbits and mice, inducing strong and specific IgG responses against homologous and heterologous strains of H. pylori. Moreover, the rabbit post-immune sera showed cross-reactivity against clinical isolates of H. pylori in a whole-cell indirect ELISA, which was further confirmed by indirect immunofluorescent microscopy. A tenfold stronger IgG immune response to the immunizing antigen was generated in mice and rabbits that received dLPS-containing conjugate. The post-immune sera of rabbits immunized with LPS-OH-TT, dLPS-BSA or dLPS-TT displayed significant bactericidal activity against mutant and wild-type α-1,6-glucan-expressing strains and selected clinical isolates of H. pylori. Finally, partial protection against H. pylori challenge was demonstrated in mice vaccinated with dLPS-TT conjugate adjuvanted with cholera toxin. In summary, this study shows that glycoconjugates based on delipidated or partially delipidated LPS from H. pylori 26695 HP0826::Kan mutant induce broadly cross-reactive functional antibodies in immunized animals and should be considered for further vaccine development and testing.
Keywords: Helicobacter pylori; Conjugate vaccine; LPS; Bactericidal assay

Characterization of antimicrobial resistance and virulence genes in Enterococcus spp. isolated from retail meats in Alberta, Canada - Aslam, Mueen; Diarra, Moussa S.; Checkley, Sylvia; Bohaychuk, Valerie; Masson, Luke (International Journal of Food Microbiology, 2012)
The objective of this study was to characterize antimicrobial resistance (AMR) and virulence genotypes of Enterococcus spp. particularly Enterococcus faecalis isolated from retail meats purchased (2007–2008) in Alberta, Canada. Unconditional statistical associations between AMR pheno- and genotypes and virulence genotypes were determined. A total of 532 enterococci comprising one isolate from each positive sample were analyzed for antimicrobial susceptibility. A customized enterococcal microarray was used for species identification and the detection of AMR and virulence genes. E. faecalis was found in > 94% of poultry samples and in about 73% of beef and 86% of pork samples. Enterococcus faecium was not found in turkey meat and its prevalence was 2% in beef and pork and 4% in chicken samples. None of the enterococci isolates were resistant to the clinically important drugs ciprofloxacin, daptomycin, linezolid and vancomycin. Multiresistance (≥ 3 antimicrobials) was more common in E. faecalis (91%) isolated from chicken and turkey (91%) than those isolated from beef (14%) or pork (45%). Resistance to aminoglycosides was also noted at varying degrees. The most common resistance genes found in E. faecalis were aminoglycosides (aac, aphA3, aadE, sat4, aadA), macrolides (ermB, ermA), tetracyclines (tetM, tetL, tetO), streptogramin (vatE), bacitracin (bcrR) and lincosamide (linB). Virulence genes expressing aggregation substances (agg) and cytolysin (cylA, cylB, cylL, cylM) were found more frequently in poultry E. faecalis and were unconditionally associated with tetM, linB and bcrR resistance genes. Other virulence genes coding for adhesion (ace, efaAfs), gelatinase (gelE) were also found in the majority of E. faecalis. Significant statistical associations were found between resistance and virulence genotypes, suggesting their possible physical link on a common genetic element. This study underscores the importance of E. faecalis as a reservoir of resistance and virulence genes and their potential transfer to humans through consumption of contaminated undercooked meat.
Keywords: Antimicrobial resistance; Resistance genes; Virulence genes; Enterococcus spp. retail meats

Trophic transfer of brevetoxins to the benthic macrofaunal community during a bloom of the harmful dinoflagellate Karenia brevis in Sarasota Bay, Florida - Bricelj, V. M.; Haubois, A.-G.; Sengco, M. R.; Pierce, R. H.; Culter, J. K.; Anderson, D. M. (Harmful Algae, 2012)
Harmful algal blooms can cause mass mortalities of top predators such as fish, marine mammals and seabirds but the food web transfer from toxic phytoplankton to these organisms has not been fully elucidated. Macrobenthic invertebrates in coastal waters, including bivalve suspension- and deposit-feeders, carnivorous gastropods, deposit-feeding amphipods and polychaetes, are a major food source for a wide variety of predators and can thus play a critical role in the trophic transfer of algal toxins to higher trophic levels. The objective of this study was to investigate toxin accumulation in transplanted juvenile hard clams, Mercenaria mercenaria, a species naturally occurring in the region, and in various macrobenthic functional groups from Florida coastal waters during a natural bloom of the dinoflagellate, Karenia brevis, a producer of brevetoxins. Bloom concentrations in the water column ranged from 100 to 1200 cells ml−¹ over the course of the experiment. This study revealed that these lipophilic toxins can be rapidly accumulated by both suspension- and deposit-feeding benthos, especially bivalve molluscs [1.9–2.8 μg PbTx-3 eq (g wet weight)−¹]. Transplanted M. mercenaria rapidly accumulated toxins from the water column attaining ∼0.5 μg PbTx-3 eq (g wet tissue)−¹ after only 4 h-exposure to the K. brevis bloom and a maximum value of 1.5 ± 0.2 μg PbTx-3 eq (g wet tissue)−¹ after 72 h. Relatively high brevetoxin concentrations were also measured in co-occurring benthic carnivorous gastropods [1–2.6 μg PbTx-3 eq (g wet weight, WW)−¹]. Mean toxin concentrations in polychaetes and crustaceans varied in the range ∼0.04–0.2 μg PbTx-3 eq (g WW)−¹ over the study period, and thus were typically lower than in molluscs. This study demonstrated in situ toxin accumulation by benthic primary and secondary consumers during a natural Florida red tide. Accumulation by primary consumers may be highly variable in space and time (as shown in bivalves from the natural benthic community) and among taxonomic groups. Toxin transfer further up the food web will thus depend on the toxin level accumulated in prey, the number of pathways from which the predator may accumulate toxins and on possible biological magnification of lipophilic toxins. Overall, this study revealed qualitatively and quantitatively that benthic consumers of a number of taxa can serve as vectors for transporting brevetoxins within the food web.
Keywords: Karenia brevis; Brevetoxins; Benthic trophic transfer

A quality of service (QoS)-aware execution plan selection approach for a service composition process - Liu, Min; Wang, Mingrui; Shen, Weiming; Luo, Nan; Yan, Junwei (Future Generation Computer Systems, 2012)
The quality of service (QoS)-aware service composition (QSC) problem is to find an execution plan of a service composition process which can ensure that the quality of service meets given user requirements. This paper proposes a branch and bound for execution plan selection (BB4EPS) algorithm to solve the QSC problem. In the proposed BB4EPS algorithm, a universal QoS model is used to evaluate the QoS parameters for service composition, and the QSC problem is modeled as an extended flexible constraint satisfaction framework, in which the utility function is applied to build the objective function. Numerical simulation results show that the proposed algorithm is feasible and effective.
Keywords: QoS; Service composition; Flexible constraint; Web services

Performance in fire of FRP-strengthened and insulated reinforced concrete columns - Cree, D.; Chowdhury, E. U.; Green, M. F.; Bisby, L. A.; Bénichou, N. (Fire Safety Journal, 2012)
This research investigates the fire performance of one circular and one square reinforced concrete column strengthened with a fibre reinforced polymer (FRP) wrap and covered with a unique supplemental fire protection system. An experimental full-scale fire resistance test was conducted at the National Research Council of Canada. The insulated and strengthened FRP wrapped columns were exposed to the ULC-S101 standard fire and both columns obtained fire endurance ratings of over 4 h. Details of the fire endurance experiment on both columns are described in this paper. Additionally, numerical models developed specifically for circular and square columns are validated against the experimental results.
Keywords: Fire test; FRP; Insulation; Reinforced concrete column; High temperature; Full-scale

Trajectories of changes over twelve years in the health status of Canadians from late middle age - Mitnitski, A.; Song, X.; Rockwood, K. (Experimental Gerontology, 2012)
Aging in a given individual can be characterized by the number of deficits (symptoms, signs, laboratory abnormalities, disabilities) that they accumulate. The number of accumulated deficits, more than their nature, well characterizes health status in individuals — the proportion of deficits present in an individual to deficits considered is known as a frailty index. While on average deficits accumulate with age, individual trajectories in the number of deficits is highly dynamic. Transitions in the number of deficits over a fixed time interval can be represented by the Poisson law, with the Poisson mean dependent on the deficit numbers at baseline. Here we present an extension of the model to make possible predictions for any given time period. Using data from the Canadian National Population Health Survey of people aged 55 and over (n = 4330), followed during 7 cycles being the baseline and 6 cycles of follow-up every 2 years, we found that the transition in the number of deficits during any time period can be approximated using a time dependent Poisson distribution with the Poisson mean tending to decelerate over time, according to square-root-of-time kinetics characteristic for stochastic processes (e.g. diffusion, Brownian motion ) while the probability of death shows a pattern of time acceleration with a high degree of precision, “explaining” over 98% of variance. The model predicts a variety of changes in health status including the possibility of health improvement indicating the repair/remodeling abilities of the organism. The model is valuable for estimating how changes in health can influence mortality across the life course from late middle age.
Keywords: Health status; Deficit accumulation; Frailty index; Mortality; Stochastic process; Aging

The development of conductive carbon nanotube network in polypropylene-based composites during simultaneous biaxial stretching - Shen, Jiabin; Champagne, Michel F.; Gendron, Richard; Guo, Shaoyun (European Polymer Journal, 2012)
The development of electronic conducting networks during the simultaneous biaxial stretching of isotactic polypropylene/carbon nanotube (iPP/CNT) composites was investigated. During the stretching process, the electrical resistivity of the composites was found to be very sensitive to the draw ratios. This was especially true at CNT concentration close to the percolation threshold, ca. 2.2 vol.%. The resistivity–draw ratio dependence was divided into two stages. In the first stage, the stretching was taken by the amorphous zones and only led to the enlargement of the distance between CNT aggregates. This resulted in the breaking of the conductive network and, consequently, a sharp increase in resistivity. As the turning point was approached, individual nanotubes started to disentangle from CNT aggregates. Meanwhile, the resistivity of the stretched films was dramatically decreased by 7 orders of magnitude, indicating a rebuilding of the conducting network during the biaxial stretching process.
Keywords: Biaxial stretching; Polymer-matrix composites; Carbon nanotube; Electrical properties

BALB/c mice, but not C57BL/6 mice immunized with a ΔclpB mutant of Francisella tularensis subspecies tularensis are protected against respiratory challenge with wild-type bacteria: Association of protection with post-vaccination and post-challenge immune responses - Twine, Susan; Shen, Hua; Harris, Gregory; Chen, Wangxue; Sjostedt, Anders; Ryden, Patrik; Conlan, Wayne (Vaccine, 2012)
Francisella tularensis subspecies tularensis is highly virulent for humans especially when it is inhaled. Therefore, it has the potential to be used as a biothreat agent. Vaccines against F. tularensis will need to be approved in accordance with the FDA Animal Rule. This will require identification of robust correlates of protection in experimental animals and the demonstration that similar immune responses are generated in vaccinated humans. Towards this goal, we have developed an experimental live vaccine strain by deleting the gene, clpB, encoding a heat shock protein from virulent subsp. tularensis strain, SCHU S4. SCHU S4ΔclpB administered intradermally protects BALB/c, but not C57BL/6 mice from subsequent respiratory challenge with wildtype SCHU S4. A comparison of post-vaccination and post-challenge immune responses in these two mouse strains shows an association between several antibody and cytokine responses and protection. In particular, elevated IFNγ levels in the skin 2 days after vaccination, sero-conversion to hypothetical membrane protein FTT_1778c, and to 30S ribosomal protein S1 (FTT_0183c) of F. tularensis after 30 days of vaccination, and elevated levels of pulmonary IL-17 on day 7 after respiratory challenge with SCHU S4 were all associated with protection.
Keywords: Francisella tularensis; Vaccine; Cytokines: Immunoproteomics

Ultrasound-enhanced monoclonal antibody production - Xing, James Z.; Yang, Xiaoyan; Xu, Peng; Ang, Woon T.; Chen, Jie (Ultrasound in Medicine & Biology, 2012)
With the rapidly growing demand for monoclonal antibody (mAb)–based products, new technologies are urgently needed to increase mAb production while reducing manufacturing costs. To solve this problem, we report our research findings of using low-intensity pulsed ultrasound (LIPUS) to enhance mAb production. LIPUS with frequency of 1.5 MHz and pulse repetition frequency of 1 kHz, as well as duty cycle of 20%, was used to stimulate hybridoma cells to enhance the production of mAb, anti-CD4 (hybridoma GK1.5). The enzyme-linked immunosorbent assay results show a 60.42 ± 7.63% increase of mAb expression in hybridoma cells. The evidence of structural changes of the cellular outer membrane in both transmission electron microscopy and scanning electron microscopy images and the more than 20% lactate dehydrogenase release indicates that the increased mAb production is related to the increased cell permeability induced by LIPUS. This value-added ultrasound technology provides a potential cost-effective solution for pharmaceutical companies to manufacture mAb-based drugs. The technology, in turn, can reduce the drug manufacturing costs and decrease health care spending.
Keywords: Ultrasound-enhanced drug production; Low-intensity pulsed ultrasound; Value-added biotechnology; Monoclonal antibody production; Hybridoma

Re-assessment of resistance of cast iron pipes subjected to vertical loads and internal pressure - Rajani, Balvant; Abdel-Akher, Ahmed (Engineering Structures, 2012)
Longitudinal fracture is one predominant observed failure mode in large diameter cast iron pipes installed between 1850 and early 1960s. Some of these failures occur where there is evidence of some corrosion activity. This paper addresses three specific issues, namely, (1) review of expected loads, i.e., internal pressure, earth loads, traffic loads, (2) estimated pipe failure load (pipe resistance), and (3) estimated structural factor of safety. The second and third issues can be equally applicable to non-deteriorated and deteriorated pipes. The procedures described in this paper were motivated by the need to purposefully use the information derived from pipe inspection to assess the margin of safety of deteriorated large diameter cast iron pipes. A mechanistic model that accounts for cast iron material non-linearity is described. The model is validated using data obtained from experimental tests conducted in the mid 1930s on undamaged (new) pipes. The model is subsequently extended to permit the analysis of pipes with corrosion pits or corroded areas. Reliability analysis using Monte Carlo simulations is proposed to account for uncertainties in input data. Illustrative analyses of 16″ and 48″ diameter pipes subjected to vertical loads and internal pressure showed that significantly high margins of safety exist in cast iron pipes with no damage (due to corrosion and or casting voids) while this margin of safety is meaningfully reduced in the presence of corrosion pits or corroded areas. The methodology described should enable engineers to realistically assess the pipe resistance capacity and hence the corresponding margin of safety of undamaged or damaged cast iron pipes encountered in current operational conditions.
Keywords: Cast iron; Corrosion; Deteriorated pipe; Vertical loads; Internal water pressure; Factor of safety

Inelastic load distribution in multi-girder composite bridges - Razaqpur, A. Ghani; Shedid, Marwan; Nofal, Mostafa (Engineering Structures, 2012)
To accurately assess the ultimate load capacity of concrete slab-steel girder bridges, the effects of concrete nonlinearity and steel yielding on the truck load distribution in simply supported composite bridges are investigated using the nonlinear finite element (FE) method. In this study, fifty cases are analyzed to investigate the effect of the aforementioned parameters as well as the effects of other parameters including longitudinal and transversal truck position, number of loaded lanes (2–4), bridge length (12–20 m) and width (8–16 m), number of girders (3–6), girder spacing (2–3.75 m), and slab thickness (175–275 mm). The moment in each girder, based on the nonlinear FE analysis, is used to obtain its Load Distribution Factor (LDF) at different load levels up to failure and is compared with the corresponding elastic LDF according to AASHTO LRFD specifications. The results show from zero to 54% increase in the internal girder LDF (average 32%), and from zero to 29% decrease in the external girder LDF (average 17%) as the bridge traverses from the elastic to the ultimate state. This redistribution can be advantageously used when evaluating the load carrying capacity of existing bridges.
Keywords: Analysis; Bridge; Composite; Concrete; Finite element; Load distribution; Reinforced; Steel

A fracture toughness model for brittle coating on ductile substrate under indentation loading - Demidova, N. V.; Wu, X. J.; Liu, R. (Engineering Fracture Mechanics, 2012)
This paper presents an analytical fracture toughness model for brittle coating/ductile substrate systems. The model considers a well-developed radial/median crack of semi-elliptical shape in proximity of the coating/substrate interface. It incorporates three critical factors to correct Lawn et al.’s formalism for monolithic materials: (i) an elliptical crack shape factor introduced by adopting Borodachev’s solution for an elliptical crack under a concentrated force at the crack center, which represents the residual plastic component due to expansion of the plastic zone under indentation; (ii) an interface correction factor obtained by analyzing Noda et al.’s results for an elliptical crack near a bi-material interface, which expresses explicitly its dependence on the distance ratio, h/a, and Young’s modulus ratio, Es/Ec, and (iii) the composite system hardness incorporated in the formula to take into account the influence of the substrate material. Overall, the model shows a non-linear relationship between the radial crack length, c³/², and indentation load, P, for brittle coating on ductile substrate systems. A series of indentation experiments have been carried out on a WC/10Co/4Cr coating/1080 low carbon steel substrate system to validate the model.
Keywords: Brittle coating; Ductile substrate; Indentation; Elliptical crack; Fracture toughness; Composite hardness; Interface correction factor

Field ion microscope evaluation of tungsten nanotip shape using He and Ne imaging gases - Urban, Radovan; Wolkow, Robert A.; Pitters, Jason L. (Ultramicroscopy, 2012)
Field ion microscopy (FIM) using neon imaging gas was used to evaluate a W(111) nanotip shape during a nitrogen assisted etching and evaporation process. Using appropriate etching parameters a narrow ring of atoms centered about the tip axis appears in a helium generated image. Etching of tungsten atoms continues exclusively on the outside of this well-defined ring. By replacing helium imaging gas with neon, normally inaccessible crystal structure of a tip apex is revealed. Comparison of the original W(111) tip (before etching) and partly etched tip shows no atomic changes at the tip apex revealing extraordinarily spatially selective etching properties of the etching process. This observation is an important step towards a detailed understanding of the nitrogen assisted etching and evaporation process and will lead to better control over atomically defined tip shapes.
Keywords: Nanotip; Field ion microscopy; Gas field ion source

A data-model-fusion prognostic framework for dynamic system state forecasting - Liu, J.; Wang, W.; Ma, F.; Yang, Y. B.; Yang, C. S. (Engineering Applications of Artificial Intelligence, 2012)
A novel data-model-fusion prognostic framework is developed in this paper to improve the accuracy of system state long-horizon forecasting. This framework strategically integrates the strengths of the data-driven prognostic method and the model-based particle filtering approach in system state prediction while alleviating their limitations. In the proposed methodology, particle filtering is applied for system state estimation in parallel with parameter identification of the prediction model (with unknown parameters) based on Bayesian learning. Simultaneously, a data-driven predictor is employed to learn the system degradation pattern from history data so as to predict system evolution (or future measurements). An innovative feature of the proposed fusion prognostic framework is that the predicted measurements (with uncertainties) from the data-driven predictor will be properly managed and utilized by the particle filtering to further update the prediction model parameters, thereby enabling markedly better prognosis as well as improved forecasting transparency. As an application example, the developed fusion prognostic framework is employed to predict the remaining useful life of lithium ion batteries through electrochemical impedance spectroscopy tests. The investigation results demonstrate that the proposed fusion prognostic framework is an effective forecasting tool that can integrate the strengths of both the data-driven method and the particle filtering approach to achieve more accurate state forecasting.
Keywords: Nonlinear prediction; Fault diagnosis; Failure prognostics; Neural networks; Neural fuzzy systems; Remaining useful life prediction

Electron beam deposited Nb-doped TiO2 toward nanostructured transparent conductive thin films - Tucker, Ryan T.; Beckers, Nicole A.; Fleischauer, Michael D.; Brett, Michael J. (Thin Solid Films, 2012)
Nb-doped TiO2 (TNO) has been widely explored as an alternative transparent conductor. TNO thin films have been fabricated by various deposition methods, and here we demonstrate fabrication by evaporation of sol–gel synthesized TNO source material. A range of NbxTi1 − xO2 (x = 0, 0.03, 0.06, 0.12, 0.24) compositions were synthesized, pressed into pellets, and deposited as thin films via electron beam evaporation. The thin films were characterized for composition by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy and for crystallinity by X-ray diffraction for the different Nb contents explored. Transparency, conductivity, and Haacke transparent conductor figure of merit values are reported for the evaporated TNO films as a function of Nb content, substrate heating temperature, and post deposition annealing conditions. Glancing angle deposition (GLAD) is used to demonstrate nanostructuring of evaporated TNO based on physical shadowing. Nanostructured GLAD TNO films of increased morphological complexity can be produced using this method, and could lead to unique transparent conductor device architectures.
Keywords: Nb-doped TiO2; Transparent conducting oxides; Doped oxides; Evaporation; Glancing angle deposition; Sol–gel; Thin film

Goniocolorimetric study of aluminum oxide films deposited by atomic layer deposition - Gordon, Peter G.; Baribeau, Réjean; Barry, Seán T. (Thin Solid Films, 2012)
The interference colors resulting from thin films of Al2O3 deposited by atomic layer deposition (ALD) on silicon have been rigorously analyzed using a recently developed robotic gonioreflectometer. A series of eleven increasingly thick films was deposited, up to 1613 Å, and their reflectance values obtained for the visible spectrum. A comparison of these values with the predictions of computer simulations employing Fresnel equations has revealed that while there was generally good agreement between predicted and measured spectra, there are some spectral regions that exhibit large deviations from predicted reflectances, typically at near-normal measurement angles and shorter wavelengths. The effect of these discrepancies on color appearance was investigated in the CIE L*a*b* color space for the daylight illuminant D65. Large iridescence is both predicted and measured for most film thicknesses. Chroma and hue differences as large as 20 CIELAB units between the predicted and the measured color centers were obtained. Simulation also predicts larger iridescence than what is actually measured. A likely cause for the observed discrepancies is that the dielectric constants of the ALD films deviate from the literature values for the bulk material.
Keywords: Atomic layer deposition; Interference color; Goniocolorimetry; Chroma and hue

Activity-based protein profiling of host–virus interactions - Blais, David R.; Nasheri, Neda; Mckay, Craig S.; Legault, Marc C.B.; Pezacki, John paul (Trends in Biotechnology, 2012)
Virologists have benefited from large-scale profiling methods to discover new host–virus interactions and to learn about the mechanisms of pathogenesis. One such technique, referred to as activity-based protein profiling (ABPP), uses active site-directed probes to monitor the functional state of enzymes, taking into account post-translational interactions and modifications. ABPP gives insight into the catalytic activity of enzyme families that does not necessarily correlate with protein abundance. ABPP has been used to investigate several viruses and their interactions with their hosts. Differential enzymatic activity induced by viruses has been monitored using ABPP. In this review, we present recent advances and trends involving the use of ABPP methods in understanding host–virus interactions and in identifying novel targets for diagnostic and therapeutic applications.

Intramolecular cyclization and subsequent rearrangements of alkyne-tethered N-heterocyclic carbenes - Legault, Marc C.B.; Mckay, Craig S.; Moran, Joseph; Lafreniere, Matthew A.; Pezacki, John paul (Tetrahedron Letters, 2012)
Alkyne-tethered imidazole and 1,2,4-triazole-based N-heterocyclic carbene precursors have been prepared and studies of the intramolecular reactions of carbenes are performed. Products consistent with intramolecular cyclizations and subsequent rearrangements were observed. Mechanistic studies using crossover experiments showed that the products did arise from intramolecular carbene additions. The reactions are proposed to go through vinylogous diaminocarbene intermediates similar to vinylogous dialkoxycarbenes formed during Boger cycloaddition reactions. Imidazole substituted dienes were observed to be the major products of tandem cyclization and elimination reactions that were observed for imidazole-based N-heterocyclic carbenes.
Keywords: N-heterocyclic carbenes; Intramolecular cyclization; Diels–Alder cycloaddition

A PEM fuel cell with metal foam as flow distributor - Tseng, Chung-Jen; Tsai, Bin Tsang; Liu, Zhong-Sheng; Cheng, Tien-Chun; Chang, Wen-Chen; Lo, Shih-Kun (Energy Conversion and Management, 2012)
In this work, we report our experimental results of the PEM fuel cell with metal foam as flow distributor. These experimental results show the characteristics of the PEM fuel cell with the metal foam as flow distributor and extend our understanding of the relation between cell performance and mass transport properties into a region of parameters that the conventional PEM unit cell cannot provide. The comparison in polarization curve is made between the PEM unit cell with different metal-foam properties and the PEM unit cell with graphite flow channel plate as flow distributor. The experimental results show that the PEM fuel cell with metal foam as flow distributor possesses some unique characteristics compared with the conventional PEM unit cell with flow channel plate as flow distributor. The unique characteristics are listed in this paper with our preliminary analysis. Due to the high porosity of metal-foam (as high as 95%) plus convective flow through the metal-foam, mass transport limitation phenomenon is not as pronounced as in the case of conventional PEM unit cell with flow channel plate as flow distributor. Another interesting phenomenon is that electrical conductivity of metal-foam plays a significant role in performance, which is seldom the case in the conventional PEM unit cell with flow channel plate as flow distributor. Although there are several technical challenges to be overcome for the current form of metal-foam to replace flow channel plates, the unique mass-transport properties of metal foam plus its light weight are very attractive.
Keywords: PEM fuel cell; Metal foam; Flow distributor; Mass transport

A novel methodology for knowledge discovery through mining associations between building operational data - Yu, Zhun (Jerry); Haghighat, Fariborz; Fung, Benjamin C. M.; Zhou, Liang (Energy and Buildings, 2012)
Nowadays, vast amounts of data on building operation and management have been collected and stored. However, the data is rarely translated into useful knowledge about building energy performance improvement, due mainly to its extreme complexity and a lack of effective data analysis techniques. This paper reports the development of a new methodology for examining all associations and correlations between building operational data, thereby discovering useful knowledge about energy conservation. The method is based on a basic data mining technique (association rule mining). To take full advantage of building operational data, both daily and annual time periods should be mined. Moreover, data from two different years should be mined, and the obtained associations and correlations in the two years should be compared. In order to demonstrate the applicability of the proposed method, the method was applied to the operational data of the air-conditioning system in a building located in Montreal. The results show energy waste in the air-conditioning system as well as equipment faults. A low/no cost strategy for saving energy in the system operation was also proposed. The results obtained could help to better understand building operation and provide opportunities for energy conservation.
Keywords: Data mining; Association; Correlation; Knowledge discovery; Building operational data; Energy conservation; Influencing factors

A knife-edge measurement of the beam profile of STXM 5.3.2.2 using a focussed ion beam milled metallic glass - Burke, Kerry B.; Luber, Erik J.; Holmes, Natalie P.; Murray, Andrew J.; Belcher, Warwick J.; Zhou, Xiaojing; Mitlin, David; Dastoor, Paul C. (Journal of Electron Spectroscopy and Related Phenomena, 2012)
We present a simple knife-edge measurement of the STXM 5.3.2.2 synchrotron X-ray beam width. The knife edge was constructed by ion beam milling a metallic glass alloy consisting of 60% gold, 20% nickel and 20% hafnium and was determined to be well-defined to within 2 nm by TEM. An asymmetric beam profile of 120 nm FWHM in the vertical direction and 150 nm FWHM in the horizontal direction was determined and was observed to depart from the expected Airy function profile.
Keywords: Scanning transmission X-ray microscopy (STXM) resolution; Focussed ion beam (FIB) milling; Metallic glass

Mediatorless amperometric glucose biosensing using 3-aminopropyltriethoxysilane-functionalized graphene - Zheng, Dan; Vashist, Sandeep kumar; Al-rubeaan, Khalid; Luong, John H.T.; Sheu, Fwu-shan (Talanta, 2012)
A mediatorless glucose biosensor was developed by the immobilization of glucose oxidase (GOx) to graphene-functionalized glassy carbon electrode (GCE). The surface of GCE was functionalized with graphene by incubating it with graphene dispersed in 3-aminopropyltriethoxysilane (APTES), which acted both as a dispersion agent for graphene and as an amine surface modification agent for GCE and graphene. This was followed by the covalent binding of GOx to graphene-functionalized GCE using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) based crosslinking. Graphene provided signal enhancement by providing greater surface area for GOx binding, while APTES-functionalization led to a higher GOx immobilization density by providing free amino groups for crosslinking. The developed biosensor used a redox potential of −0.45 V (vs. Ag/AgCl) for detecting glucose in the diabetic pathophysiological range 0.5–32 mM. There was no interference from endogenous electroactive substances and drug metabolites. The developed biosensor was further validated for detecting blood glucose in commercial artificial blood glucose linearity standards in the range 1.4–27.9 mM. Therefore, it is ideal for diabetic blood glucose monitoring. The developed bioanalytical procedure for preparation of GOx-bound graphene-functionalized GCEs had high production reproducibility and high storage stability, which is appropriate for the commercial mass production of enzyme-bound electrodes.
Keywords: Graphene; Glucose biosensor; APTES; Mediatorless; Amperometric; Glucose oxidase

An investigation of new barium phosphate chemical conversion coating on AZ31 magnesium alloy - Chen, Yougui; Luan, Ben li; Song, Guang-ling; Yang, Qi; Kingston, David M.; Bensebaa, Farid (Surface and Coatings Technology, 2012)
Barium phosphate chemical conversion coating is a new research area for the corrosion protection of Mg alloys. We report a new process conducted in a simple solution with Ba(NO3)2 and NH4H2PO4 as the precursors. The influences of pH value and temperature of the coating bath, concentrations of Ba(NO3)2 and NH4H2PO4, and deposition time were evaluated. The coating obtained typically featured a two-layer structure. The chemical compositions and structures were then further characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), revealing an under layer of mixed amorphous phosphates and a top layer of crystalline BaHPO4. The corrosion resistances of bare Mg alloy and those with coatings were compared with electrochemical polarization, showing an improved corrosion resistance of samples with coating. More specifically, the two-layer coating was shown to be more effective than with the under layer coating alone. In addition, adhesion test was also conducted to evaluate the bonding strength and to identify the separation interface of the coatings.
Keywords: Chemical conversion coating; Mg alloy; Barium phosphate; Corrosion

In situ deposition behavior of SiO2 on YSZ-TBC-coated IN738LC during a burner rig test - Kim, Min tae; Jung, Yong chan; Seo, Dongyi (Surface and Coatings Technology, 2012)
This work was planned as a preliminary test to obtain an optimal condition for in situ deposition of SiO2 on zirconia-based thermal barrier coating (TBC)-coated IN738LC specimens using a burner rig. The effect of the in situ deposited SiO2 on the long-term reliability of TBCs upon cyclic burner rig operations will be tested in the next study. Tetraethylorthosilicate (TEOS), the precursor for the deposition, was fed admixed with methanol into the combustion chamber of the burner rig at an exhaust flame temperature of 1530 °C. All five coating processes were selected by varying the concentration of TEOS in the mixture and applied to hollow type pin specimens infixed to the rotating carousel to face the downstream exhaust gas vertically. A total of 1500 cc of the mixture at a given vol.% TEOS was fed evenly to the burner rig for 54 min during the coating process. After the process, TBC spallation was observed on the front side of the specimens processed with 10, 5, and 2 vol.% TEOS, while the specimen of 0.5 vol.% TEOS was coated with a ~ 5 μm thick SiO2 layer without any macroscopic damages. The surface of the coatings consisted of fractal-structured nodules at 10 vol.% TEOS, and of smooth grains at 0.5 vol.% TEOS. The spallation of SiO2-coated TBC was attributed to the thermal mismatch due to the difference in the thermal expansion coefficients of the two materials. Based on these results, the mixing ratio of TEOS to methanol was reduced to 0.3 vol.%, which produced a 1–2 μm thick, smooth and homogenous SiO2 coating without any spallation of TBC. This deposition condition was chosen for the planned test to evaluate on the effects of the in situ deposition of SiO2 on the long-term durability of TBC-coated IN738LC specimens upon cyclic burner rig operations.
Keywords: Gas turbine; Burner rig; In situ deposition; Thermal barrier coating; SiO2

Nanopillar niobium oxides as support structures for oxygen reduction electrocatalysts - Bonakdarpour, Arman; Tucker, Ryan T.; Fleischauer, Michael D.; Beckers, Nicole A.; Brett, Michael J.; Wilkinson, David P. (Electrochimica Acta, 2012)
Metal oxides such as niobium oxides have been demonstrated as alternative support materials for Pt and non-precious metal catalysts in fuel cells. High surface area and columnar niobium oxide catalyst support structures were produced by the glancing angle deposition (GLAD) technique on 5 mm diameter glassy carbon disks. The columnar structures have lengths of about 500 nm, diameters of 50 nm and an areal density of about 10^9 cm−². Annealing under different gas mixtures (Ar/H2) led to the formation of various oxides (Nb2O5, NbO2, or NbO + NbO2). Pt catalyst, with a loading of 0.1 mgPt cm−², was deposited onto these structures by magnetron sputter deposition. Rotating disk electrode characterization of the samples, performed in 0.1M HClO4 electrolyte at room temperature, revealed surface enhancement factors of up to 11 and oxygen reduction specific activities of ≥1 mA cm−²Pt at 0.9 V (vs. RHE). The impact of annealing on Nb-O phase formation, conductivity, oxygen reduction activity and stability are discussed.
Keywords: Glancing angle deposition; Niobium oxide; Oxygen reduction reaction; Catalyst support

Effects of synthesis condition on formation of desired crystal structures of doped-TiO2/carbon composite supports for ORR electrocatalysts - Bing, Yonghong; Neburchilov, Vladimir; Song, Chaojie; Baker, Ryan; Guest, Alan; Ghosh, Dave; Ye, Siyu; Campbell, Stephen; Zhang, Jiujun (Electrochimica Acta, 2012)
The composite supports, (Nb0.07Ti0.93O2)25wt%–C75wt% and (Nb0.07Ti0.93O2)70wt%–C30wt%, as well as their supported Pt–Pd alloy electrocatalysts, 20 wt%Pt0.62Pd0.38/((Nb0.07Ti0.93O2)25wt%–C75wt%)80wt% and 20 wt%Pt0.62Pd0.38/((Nb0.07Ti0.93O2)70wt%–C30wt%)80wt% for oxygen reduction reaction (ORR), are synthesized, respectively, using an acid-water based solution as solvent. The effects of three factors, namely concentration of HCl, the ratio of titanium precursor to solvent, and the ratio of metal-oxide to carbon in the composite support, on the TiO2 anatase-to-rutile transition are investigated in an effort to optimize the supports and their supported catalysts with respect to both ORR catalytic activity and durability. Based on both the high ORR activity and durability, these catalysts should be feasible if used in PEM fuel cells as cathode electrocatalysts.
Erratum published in volume 103, page 277, July 2013. DOI: 10.1016/j.electacta.2013.05.076
Keywords: Doped-TiO2; Thermal hydrolysis; Hybrid support; Oxygen reduction mass activity; Durability of supports; TiO2 anatase-to-rutile transition; PEM fuel cell

Carbon–Nb0.07Ti0.93O2 composite supported Pt–Pd electrocatalysts for PEM fuel cell oxygen reduction reaction - Ignaszak, Anna; Song, Chaojie; Zhu, Weimin; Wang, Yan-Jie; Zhang, Jiujun; Bauer, Alex; Baker, Ryan; Neburchilov, Vladimir; Ye, Siyu; Campbell, Stephen (Electrochimica Acta, 2012)
Carbon–Nb0.07Ti0.93O2 (C67 wt%–(Nb0.07Ti0.93O2)33 wt%) composite support for Pt0.55Pd0.45 alloy catalysts was prepared by hydrolysis of metal alkoxides in the presence of carbon. Physical characterization by XRD, EDX, BET, TEM and TGA showed that the Nb0.07Ti0.93O2 was well distributed on the carbon particle surface with an average particle size of 15 nm, and this support has a high surface area of 176 m2/g and a similar porosity to that of carbon used to prepare this composite support. Pt0.55Pd0.45 alloy nanoparticles were deposited on the composite support to form a Pt0.55Pd0.45/C67 wt%–(Nb0.07Ti0.93O2)33 wt% catalyst, which shows a higher catalytic activity toward ORR than those of monometallic counterpart Pt/C67 wt%–(Nb0.07Ti0.93O2)33 wt%, Pt0.55Pd0.45/C, and Pt0.55Pd0.45/Nb0.07Ti0.93O2. Pt0.55Pd0.45/C67 wt%–(Nb0.07Ti0.93O2)33 wt% showed higher stability than Pt0.55Pd0.45/C, and similar to the commercially available Pt/C catalyst.
Erratum published in volume 103, page 276, July 2013. DOI: 10.1016/j.electacta.2013.05.075
Keywords: Pt–Pd alloys; NbTiO2–carbon composite support; Oxygen reduction reaction; Fuel cell catalysts

Synthesis and characterization of Nb-TiO2 mesoporous microsphere and nanofiber supported Pt catalysts for high temperature PEM fuel cells - Bauer, Alex; Chevallier, Laure; Hui, Rob; Cavaliere, Sara; Zhang, Jiujun; Jones, Deborah; Rozière, Jacques (Electrochimica Acta, 2012)
Two differently structured Nb-doped TiO2 support materials, i.e., mesoporous microspheres and nanofibers, were synthesized and used as Pt catalyst supports for the oxygen reduction reaction (ORR), which is a critical research topic for PEM fuel cells. Compared to a commercially available Pt/C catalyst, improved electrochemical ORR stability was observed when using the novel supports in an acidic environment. XRD, SEM, TEM, and BET were used to characterize the morphologies of these supports and the attached Pt catalyst. Electrochemical methods were used to measure both the ORR mass activity and stability of these materials. Improvement in both the specific area and conductivity were identified as the area for further development.
Keywords: Niobium doped titanium oxide; Mesoporous microsphere; Nanofiber; Catalyst support; Fuel cells oxygen reduction reaction