Quantum interference between three two-spin states in a double quantum dot - Studenikin, S.A.; Aers, G.C.; Granger, G.; Gaudreau, L.; Kam, A.; Zawadzki, P.; Wasilewski, Z.R.; Sachrajda, A.S. (Physical Review Letters, 2012)
Qubits based on the singlet (S) and the triplet (T 0, T +) states in double quantum dots have been demonstrated in separate experiments. It has been recently proposed theoretically that under certain conditions a quantum interference could occur from the interplay between these two qubit species. Here we report experiments and modeling that confirm these theoretical predictions and identify the conditions under which this interference occurs. Density matrix calculations show that the interference pattern manifests primarily via the occupation of the common singlet state. The S/T 0 qubit is found to have a much longer coherence time as compared to the S/T + qubit. © 2012 American Physical Society.
Keywords: Coherence time; Density matrix; Double quantum dots; Interference patterns; Quantum interference; Singlet state; Theoretical prediction; Two-qubit; Experiments; Quantum computers; Quantum interference devices; Semiconductor quantum dots; Current voltage characteristics

Silicon nanowire based optical XOR logic gate at 40Gb/s for DPSK data - Li, F.; Vo, T.D.; Husko, C.; Pelusi, M.; Xu, D.-X.; Ma, R.; Janz, S.; Eggleton, B.J.; Moss, D.J. (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
We demonstrate all-optical XOR logic function for 40Gb/s DPSK signals in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. Error-free operation with a system penalty of ∼ 4.3dB at 10-9 BER has been achieved. © 2012 OSA.
Keywords: DPSK signals; Error free operations; Logic functions; Optical XOR; Silicon nanowires; System penalty; Lasers; Nanowires; Silicon; Four wave mixing

Transcriptional and metabolomic analysis of Ascophyllum nodosum mediated freezing tolerance in Arabidopsis thaliana - Nair, P.; Kandasamy, S.; Zhang, J.; Ji, X.; Kirby, C.; Benkel, B.; Hodges, M.D.; Critchley, A.T.; Hiltz, D.; Prithiviraj, B. (BMC Genomics, 2012)
Background: We have previously shown that lipophilic components (LPC) of the brown seaweed Ascophyllum nodosum (ANE) improved freezing tolerance in Arabidopsis thaliana. However, the mechanism(s) of this induced freezing stress tolerance is largely unknown. Here, we investigated LPC induced changes in the transcriptome and metabolome of A. thaliana undergoing freezing stress.Results: Gene expression studies revealed that the accumulation of proline was mediated by an increase in the expression of the proline synthesis genes P5CS1 and P5CS2 and a marginal reduction in the expression of the proline dehydrogenase (ProDH) gene. Moreover, LPC application significantly increased the concentration of total soluble sugars in the cytosol in response to freezing stress. Arabidopsis sfr4 mutant plants, defective in the accumulation of free sugars, treated with LPC, exhibited freezing sensitivity similar to that of untreated controls. The 1H NMR metabolite profile of LPC-treated Arabidopsis plants exposed to freezing stress revealed a spectrum dominated by chemical shifts (δ) representing soluble sugars, sugar alcohols, organic acids and lipophilic components like fatty acids, as compared to control plants. Additionally, 2D NMR spectra suggested an increase in the degree of unsaturation of fatty acids in LPC treated plants under freezing stress. These results were supported by global transcriptome analysis. Transcriptome analysis revealed that LPC treatment altered the expression of 1113 genes (5%) in comparison with untreated plants. A total of 463 genes (2%) were up regulated while 650 genes (3%) were down regulated.Conclusion: Taken together, the results of the experiments presented in this paper provide evidence to support LPC mediated freezing tolerance enhancement through a combination of the priming of plants for the increased accumulation of osmoprotectants and alteration of cellular fatty acid composition. © 2012 Nair et al.; licensee BioMed Central Ltd.
Keywords: carboxylic acid; fatty acid; proline; proline dehydrogenase; pyrroline 5 carboxylate reductase; sugar; sugar alcohol; Arabidopsis; article; Ascophyllum; ascophyllum nodosum; controlled study; cytosol; down regulation; freezing; freezing tolerance; gene expression; genetic transcription; heteronuclear multiple bond correlation; heteronuclear single quantum coherence; lipid composition; lipophilicity; metabolomics; nonhuman; nuclear magnetic resonance spectroscopy; osmotic stress; P5CS1 gene; P5CS2 gene; plant gene; ProDH gene; proton nuclear magnetic resonance; sfr4 gene; transcriptomics; upregulation; Arabidopsis; Ascophyllum; Carbohydrate Metabolism; Freezing; Gene Expression Profiling; Hot Temperature; Hydrophobic and Hydrophilic Interactions; Metabolomics; Mutation; Proline; Solubility; Transcription, Genetic; Arabidopsis; Arabidopsis thaliana; Ascophyllum nodosum

The comparison of bitumens from oil sands with different recovery profiles - Woods, J.R.; Kung, J.; Kingston, D.; McCracken, T.; Kotlyar, L.S.; Sparks, B.D.; Mercier, P.H.J.; Ng, S.; Moran, K. (Petroleum Science and Technology, 2012)
It has been proposed that, regardless of origin, the recovery of bitumen from oil sands is related to its viscosity. Asphaltene and resin contents are known to affect the viscosity of bitumen. In this article we compare the composition of solvent-extracted bitumens from several Athabasca oil sands with very different recovery profiles. After careful removal of any associated mineral matter by ultra-centrifugation, each bitumen sample was separated into saturate, aromatic, resin, and asphaltene (SARA) fractions by an enhanced SARA technique. The individual components were then characterized by several complementary analytical techniques, including carbon, nitrogen, nitrogen, sulfur, size exclusion chromatography molecular weight (MW n) plus proton and 13C nuclear magnetic resonance spectroscopy. Based on this comparison, we see no correlation between the recovery of bitumen and its composition. © Crown Copyright.
Keywords: Analytical techniques; Athabasca oil sands; Bitumen recovery; Individual components; Mineral matters; Recovery profiles; Resin content; SARA; Asphaltenes; Centrifugation; Nuclear magnetic resonance spectroscopy; Oil sands; Resins; Sulfur; Viscosity; Bituminous materials

Double pendulum dynamic impact test set-up for ice-grillage collision - Alam, Md.S.; Daley, C.; Colbourne, B.; Hermanski, G.; Gagnon, B.; Bruneau, S.; Clarke, G.; Quinton, B. (International Conference and Exhibition on Performance of Ships and Structures in Ice 2012, ICETECH 2012, 2012)
This paper details the development of a double pendulum dynamic impact test apparatus to study the behavior of collisions between ice and structural grillages, typical of those used in ship structures. Direct collisions between ice and ships involve high impact energy and can cause substantial damage to the ship structure. In order to apply this type of impact energy in a controlled and repeatable way, a double pendulum dynamic impact test frame has been developed. The frame consists of two pendulums: one to cany an ice sample and the other to carry a test grillage structure. The overall size of the apparatus is 4m x 5m x 8m. The live weight of each pendulum is approximately 3000 kg. In operation, the pendulums will be lifted and then released simultaneously to impact each other in a vertical position. The frame is instrumented to measure the impact force and deflection of the grillage. Copynght ©2012 ICETECH 12. All rights reserved.
Keywords: Double pendulum; Dynamic impacts; Grillage; High impact energy; Impact loads; Ship structure; Test apparatus; Vertical positions; Exhibitions; Pendulums; Ships; Vehicle performance; Ice

Polymer micromolds with near optical quality surface finishes - Shiu, P.-P.; Knopf, G.K.; Nikumb, S. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
Disposable microfluidic systems are used to avoid sample contamination in a variety of medical and environmental monitoring applications. A contactless hot intrusion (HI) process for fabricating reusable polymer micromolds with near "optical quality" surface finishes is described in this paper. A metallic hot intrusion mask with the desired microchannels and related passive components is first machined using a tightly focused beam from a diode-pumped solid-state (DPSS) laser. The polymer mold master is then created by pressing the 2D metallic mask onto a polymethylmethacrylate (PMMA) substrate. Since it is a contactless fabrication process the resultant 3D micro-reliefs have near optical quality surface finishes. Unfortunately, the desired micro-relief dimensions (height and width) are not easily related to the hot intrusion process parameters of pressure, temperature, and time exposure profile. A finite element model is introduced to assist the manufacturing engineer in predicting the behavior of the PMMA substrate material as it deforms under heat and pressure during micromold manufacture. The FEM model assumes that thermo-plastics like PMMA become "rubber like" when heated to a temperature slightly above the glass transition temperature. By controlling the material temperature and maintaining its malleable state, it is possible to use the stress-strain relationship to predict the profile dimensions of the imprinted microfeature. Examples of curved microchannels fabricated using PMMA mold masters are presented to illustrate the proposed methodology and verify the finite element model. In addition, the non-contact formation of the micro-reliefs simplifies the demolding process and helps to preserve the high quality surface finishes. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Keywords: Contact less; Curved microchannel; Demolding; Diode-pumped solid-state laser; Environmental Monitoring; Fabrication process; FEM models; Finite element models; Focused beams; High quality surface; Intrusion process; Manufacturing engineers; Material temperature; Metallic masks; Micro fluidic system; Micro-feature; Micro-molds; Microfeatures; micromold; Mold-Masters; Non-contact; Optical qualities; Optical quality surfaces; Passive components; Polymer molds; Stress-strain relationships; Substrate material; Surface finishes; BioMEMS; Finishing; Manufacture; Microchannels; Microfluidics; Microsystems; Molds; Pumping (laser); Stress-strain curves; Substrates; Surface properties; Functional polymers

Gemini high-resolution optical spectrograph conceptual optical design - Pazder, J.; Desaulniers, P.; Spanò, P.; Szeto, K.; Thibault, S.; Zhang, H. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
The instrument group of the Herzberg Institute of Astrophysics has been commissioned by the Gemini Observatory as one of the three competing organizations to conduct a conceptual design study for a new Gemini High-Resolution Optical Spectrograph (GHOS). This paper outlines the main features of the optical design, including the Cassegrain-mounted science input unit, the bench-mounted spectrograph and the fibre relay system. The predicted imaging performance and efficiency are presented with the design trade offs explored in the study. © 2012 SPIE.
Keywords: Echelle spectrograph; Gemini telescopes; High resolution; Volume phase holographic gratings; VPH; VPHG; White pupil relay; Astrophysics; Conceptual design; Fibers; Instruments; Optical design; Optical resolving power; Spectrographs

Role of Rydberg states in the photochemical dynamics of ethylene - Mori, T.; Glover, W.J.; Schuurman, M.S.; Martinez, T.J. (The Journal of Physical Chemistry A, 2012)
We use the ab initio multiple spawning method with potential energy surfaces and nonadiabatic coupling vectors computed from multistate multireference perturbation theory (MSPT2) to follow the dynamics of ethylene after photoexcitation. We introduce an analytic formulation for the nonadiabatic coupling vector in the context of MSPT2 calculations. We explicitly include the low-lying 3s Rydberg state which has been neglected in previous ab initio molecular dynamics studies of this process. We find that although the 3s Rydberg state lies below the optically bright ππ* state, little population gets trapped on this state. Instead, the 3s Rydberg state is largely a spectator in the photodynamics, with little effect on the quenching mechanism or excited state lifetime. We predict the time-resolved photoelectron spectrum for ethylene and point out the signature of Rydberg state involvement that should be easily observed. © 2011 American Chemical Society.

Identification of genes and gene markers by genomics, genome mapping and comparative proteomics and their relationship to potato tuber qualities - Wang-Pruski, G.; Babin, S.; Murphy, P.; Kong, F.; Wu, Y.; Douglass, K.; Murphy, A.; De Koeyer, D.; Pinto, D. (Acta Horticulturae, 2012)
The potato crop is one of the four most important food crops. Since it is a cross-fertilizing, highly heterozygous, and vegetatively-propagated tetraploid species, genetic improvements through traditional breeding are slow, expensive and relatively imprecise. Also, the genetic base in existing cultivars is narrow, making them difficult to use for genetic and genomic analyses. After-cooking darkening (ACD) and enzymatic browning are the major tuber quality defects for both tablestock and processing. This study examined two candidate genes encoding cinnamic acid 4-hydroxylase (C4H) and polyphenol oxidase (PPO), and their functions in relation to ACD. The gene encoding C4H was first cloned from the processing cultivar 'Russet Burbank'. Its gene expression level was shown to be positively related to ACD in a variety of diploid and tetraploid samples tested. Through QTL mapping analysis, we confirmed that the c4h gene, located on chromosome 6, was in one of four QTL regions identified for ACD. PPO is well-known for its involvement in enzymatic browning. This protein was identified through our comparative proteomics study, based on its significant correlation to ACD in a diploid population. This relationship was further examined by real-time qRT-PCR in a larger genetic mapping population. A SNP marker was designed in the coding region of the ppo gene and the association mapping was successfully completed. We believe these two genes are effective candidate markers for breeding for both low ACD and enzymatic browning varieties in potatoes.
Keywords: Solanum tuberosum

Evaluation of mitral valve replacement anchoring in a phantom - McLeod, A.J.; Moore, J.; Lang, P.; Bainbridge, D.; Campbell, G.; Jones, D.L.; Guiraudon, G.M.; Peters, T.M. (Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2012)
Conventional mitral valve replacement requires a median sternotomy and cardio-pulmonary bypass with aortic crossclamping and is associated with significant mortality and morbidity which could be reduced by performing the procedure off-pump. Replacing the mitral valve in the closed, off-pump, beating heart requires extensive development and validation of surgical and imaging techniques. Image guidance systems and surgical access for off-pump mitral valve replacement have been previously developed, allowing the prosthetic valve to be safely introduced into the left atrium and inserted into the mitral annulus. The major remaining challenge is to design a method of securely anchoring the prosthetic valve inside the beating heart. The development of anchoring techniques has been hampered by the expense and difficulty in conducting large animal studies. In this paper, we demonstrate how prosthetic valve anchoring may be evaluated in a dynamic phantom. The phantom provides a consistent testing environment where pressure measurements and Doppler ultrasound can be used to monitor and assess the valve anchoring procedures, detecting pararvalvular leak when valve anchoring is inadequate. Minimally invasive anchoring techniques may be directly compared to the current gold standard of valves sutured under direct vision, providing a useful tool for the validation of new surgical instruments. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Keywords: Anchoring technique; Animal studies; Beating heart; Cardiac surgery; Consistent testing; Doppler ultrasound; Gold standards; Image guidance systems; Image guided surgery; Left atriums; Median sternotomy; Minimally invasive; Mitral annulus; Mitral valves; Surgical instrument; surgical phantom; Cardiovascular surgery; Medical imaging; Prosthetics; Robotics; Surgical equipment; Pumps

Identification of genes involved in the acetamidino group modification of the flagellin N-Linked glycan of Methanococcus maripaludis - Jones, G.M.; Wu, J.; Ding, Y.; Uchid, K.; Aizaw, S.-I.; Robotham, A.; Logan, S.M.; Kelly, J.; Jarrell, K.F. (Journal of Bacteriology, 2012)
N-linked glycosylation of protein is a posttranslational modification found in all three domains of life. The flagellin proteins of the archaeon Methanococcus maripaludis are known to be modified with an N-linked tetrasaccharide consisting of N-acetylgalactosamine (GalNAc), a diacetylated glucuronic acid (GlcNAc3NAc), an acetylated and acetamidino-modified mannuronic acid with a substituted threonine group (ManNAc3NAmA6Thr), and a novel terminal sugar residue [(5S)-2-acetamido-2,4-dideoxy-5-O-methyl-α-L-erythro-hexos-5-ulo-1,5-pyranose]. To identify genes involved in biosynthesis of the component sugars of this glycan, three genes, mmp1081, mmp1082, and mmp1083, were targeted for in-frame deletion, based on their annotation and proximity to glycosyltransferase genes known to be involved in assembly of the glycan. Mutants carrying a deletion in any of these three genes remained flagellated and motile. A strain with a deletion of mmp1081 had lower-molecular-mass flagellins in Western blots. Mass spectrometry of purified flagella revealed a truncated glycan with the terminal sugar absent and the threonine residue and the acetamidino group missing from the third sugar. No glycan modification was seen in either the Δmmp1082 or Δmmp1083 mutant grown in complex Balch III medium. However, a glycan identical to the Δmmp1081 glycan was observed when the Δmmp1082 or Δmmp1083 mutant was grown under ammonia-limited conditions. We hypothesize that MMP1082 generates ammonia and tunnels it through MMP1083 to MMP1081, which acts as the amidotransferase, modifying the third sugar residue of the M. maripaludis glycan with the acetamidino group. © 2012, American Society for Microbiology.
Keywords: ammonia; flagellin; glycan; glycosyltransferase; threonine; article; bacterial gene; bacterial growth; bacterium mutant; carbohydrate synthesis; controlled study; flagellum; gene deletion; gene identification; gene targeting; mass spectrometry; Methanococcus maripaludis; mmp1081 gene; mmp1082 gene; mmp1083 gene; nonhuman; operon; priority journal; Western blotting; Amino Acid Sequence; Blotting, Western; Carbohydrate Conformation; Flagellin; Gene Deletion; Gene Expression Regulation, Archaeal; Methanococcus; Mutation; Polysaccharides; Reverse Transcriptase Polymerase Chain Reaction; Archaea; Methanococcus maripaludis

Sound transmission loss of orthotropic sandwich panels with soft core and noise control treatment - Ghinet, S.; Osman, H.A. (41st International Congress and Exposition on Noise Control Engineering 2012, INTER-NOISE 2012, 2012)
A new improved model of diffuse field acoustic transmission in symmetrical sandwich panels with thin skins and a soft core is presented in this paper. Generally, asymmetric motion is the only dynamic behaviour which is considered in the modeling of sandwich panels. Bending and membrane behaviour are considered in the skins while the core is assumed to be incompressible over the thickness and experiences only shearing deformations. This set of assumptions is suitable for structures with relatively stiff and thin cores. However, the symmetric mode of motion becomes important for panels with thick and soft cores which exhibit significant compression deformations over the thickness. In this paper, both symmetric and asymmetric modes of motion are considered numerically. Their impact on the transmission loss is addressed in the configuration of a sandwich panel with attached multilayer Noise Control Treatment (NCT). Experimental and literature results are compared with the numerical simulations using the present theoretical approach in order to prove the validity and effectiveness of this approach. Copyright © (2012) by the Institute of Noise Control Engineering (INCE).
Keywords: Compression deformation; Control treatments; Dynamic behaviours; Membrane behaviours; Shearing deformation; Sound transmission loss; Theoretical approach; Transmission loss; Acoustic variables control; Deformation; Sandwich structures; Honeycomb structures

Identification of a general O-linked protein glycosylation system in Acinetobacter baumannii and its role in virulence and biofilm formation - Iwashkiw, J.A.; Seper, A.; Weber, B.S.; Scott, N.E.; Vinogradov, E.; Stratilo, C.; Reiz, B.; Cordwell, S.J.; Whittal, R.; Schild, S.; Feldman, M.F. (PLoS Pathogens, 2012)
Acinetobacter baumannii is an emerging cause of nosocomial infections. The isolation of strains resistant to multiple antibiotics is increasing at alarming rates. Although A. baumannii is considered as one of the more threatening "superbugs" for our healthcare system, little is known about the factors contributing to its pathogenesis. In this work we show that A. baumannii ATCC 17978 possesses an O-glycosylation system responsible for the glycosylation of multiple proteins. 2D-DIGE and mass spectrometry methods identified seven A. baumannii glycoproteins, of yet unknown function. The glycan structure was determined using a combination of MS and NMR techniques and consists of a branched pentasaccharide containing N-acetylgalactosamine, glucose, galactose, N-acetylglucosamine, and a derivative of glucuronic acid. A glycosylation deficient strain was generated by homologous recombination. This strain did not show any growth defects, but exhibited a severely diminished capacity to generate biofilms. Disruption of the glycosylation machinery also resulted in reduced virulence in two infection models, the amoebae Dictyostelium discoideum and the larvae of the insect Galleria mellonella, and reduced in vivo fitness in a mouse model of peritoneal sepsis. Despite A. baumannii genome plasticity, the O-glycosylation machinery appears to be present in all clinical isolates tested as well as in all of the genomes sequenced. This suggests the existence of a strong evolutionary pressure to retain this system. These results together indicate that O-glycosylation in A. baumannii is required for full virulence and therefore represents a novel target for the development of new antibiotics. © 2012 Iwashkiw et al.
Keywords: galactose; glucose; glucuronic acid; glycan; glycoprotein; n acetylglucosamine; pentasaccharide; bacterial protein; glycoprotein; membrane protein; polysaccharide; Acinetobacter baumannii; analytic method; animal experiment; animal model; article; bacterial genome; bacterial growth; bacterial strain; bacterial virulence; bacterium isolate; bacterium isolation; biofilm; carbon nuclear magnetic resonance; chromatography; controlled study; Dictyostelium discoideum; galleria mellonella; gene sequence; heteronuclear single quantum coherence; homologous recombination; hospital infection; in vivo study; insect; mass spectrometry; matrix assisted laser desorption ionization time of flight mass spectrometry; nonhuman; protein glycosylation; proton nuclear magnetic resonance; sepsis; tandem mass spectrometry; two dimensional difference gel electrophoresis; zwitterionic hydrophilic interaction chromatography; Acinetobacter infection; animal; Bagg albino mouse; confocal microscopy; gene inactivation; glycosylation; metabolism; mouse; nuclear magnetic resonance spectroscopy; pathogenicity; virulence; Western blotting; Acinetobacter baumannii; Dictyostelium discoideum; Galleria mellonella; Hexapoda; Acinetobacter baumannii; Acinetobacter Infections; Animals; Bacterial Proteins; Biofilms; Blotting, Western; Gene Knockout Techniques; Glycoproteins; Glycosylation; Magnetic Resonance Spectroscopy; Mass Spectrometry; Membrane Proteins; Mice; Mice, Inbred BALB C; Microscopy, Confocal; Polysaccharides; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Virulence

Hippocampal membrane-associated p75 ntr levels are increased in alzheimer's Disease - Chakravarthy, B.; Ménard, M.; Ito, S.; Gaudet, C.; Dal Prà, I.; Armato, U.; Whitfield, J. (Journal of Alzheimer's Disease, 2012)
The pan-specific p75 neurotrophin receptor (p75 NTR) is believed to play an important role in the pathogenesis of Alzheimer's disease (AD). It is involved in mediating amyloid-β (Aβ) toxicity and stimulating amyloidogenesis. In addition, we have recently shown that stimulating cultured SH-SY5Y human neuroblastoma cells with Aβ 42 increases the level of membrane-associated p75 NTR and that Aβ 42- accumation in two strains of transgenic AD model mice is accompanied by an increased level of hippocampal membrane-associated p75 NTR (Chakravarthy et al. J Alzheimers Dis 19, 915-925, 2010). This raised an important question whether accumulating Aβ 42 in human AD is also accompanied by an increased hippocampal membrane-associated p75 NTR. In this study, using polyclonal and monoclonal antibodies against the p75 NTR receptor's intra-and extracellular domains, we show that indeed the mean level of membrane-associated p75 NTR in the hippocampal formation is significantly higher (~two-fold, p < 0.03) in human AD brains than in identical samples of hippocampal formation in age-matched non-AD human brains. The possible relation of this elevated hippocampal p75 NTR to AD cognitive decline is discussed. © 2012 -IOS Press and the authors.
Keywords: amyloid beta protein[1-42]; neurotrophin receptor p75; adult; aged; Alzheimer disease; article; autopsy; brain tissue; clinical article; cognition; controlled study; female; frontal cortex; hippocampus; human; human cell; human cell culture; human tissue; male; mouse; neuroblastoma cell; nonhuman; priority journal; Aged; Aged, 80 and over; Alzheimer Disease; Cell Line, Tumor; Cell Membrane; Female; Frontal Lobe; Hippocampus; Humans; Male; Middle Aged; Neurons; Receptor, Nerve Growth Factor; Tumor Cells, Cultured

Microchip-Based Flow Cytometry in Photonic Sensing: Principles and Applications for Safety and Security Monitoring - Watts, B.R.; Zhang, Z.; Xu, C.-Q. (Photonic Sensing: Principles and Applications for Safety and Security Monitoring, 2012)

Theory of electronic properties and quantum spin blockade in a gated linear triple quantum dot with one electron spin each - Hsieh, C.-Y.; Shim, Y.-P.; Hawrylak, P. (Physical Review B - Condensed Matter and Materials Physics, 2012)
We present a theory of electronic properties and the spin-blockade phenomena in a gated linear triple quantum dot. Quadruple points where four different charge configurations are on resonance, particularly involving (1,1,1) configuration, are considered. In the symmetric case, the central dot is biased to higher energy and a single electron tunnels through the device when the (1,1,1) configuration is resonant with (1,0,1), (2,0,1), (1,0,2) configurations. The electronic properties of a triple quantum dot are described by a Hubbard model containing two orbitals in the two unbiased dots and a single orbital in the biased dot. The transport through the triple-quantum-dot molecule involves both singly and doubly occupied configurations and necessitates the description of the (1,1,1) configuration beyond the Heisenberg model. Exact eigenstates of the triple-quantum-dot molecule with up to three electrons are used to compute current assuming weak coupling to the leads and nonequilibrium occupation of quantum molecule states obtained from the rate equation. The intramolecular relaxation processes due to acoustic phonons and cotunneling with the leads are included, and are shown to play a crucial role in the spin-blockade effect. We find a quantum-interference-based spin-blockade phenomenon at low source-drain bias and a distinct spin blockade due to a trap state at higher bias. We also show that, for an asymmetric quadruple point with (0,1,1), (1,1,1,), (0,2,1), (0,1,2) configurations on resonance, the spin blockade is analogous to the spin blockade in a double quantum dot. ©2012 American Physical Society.

An integrated approach for the predictions of the workpiece vibrations during machining of aerospace structure-numerical and experimental validation - Meshreki, M.; Kövecses, J.; Attia, H. (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 2012)
Accurate predictions of the workpiece vibrations during high speed machining of aerospace structural components is a critical issue since it affects the accuracy of the final part. For fixture design purposes, and for force predictions, the computational efficiency of the dynamic models predicting the workpiece vibrations is a crucial factor since it affects the cycle time for the design and optimization of the fixtures. Most of the available dynamic models are based on computationally prohibitive techniques, such as finite element analysis. In this work, an integrated approach, based on recently developed semi-analytical models, is presented for the analysis of the effect of the fixture layout on the dynamics of thin-walled structures while taking into account the continuous change of thickness of the workpiece, and the effect of rigid and deformable fixture supports. The developed approach is based on plate models with holonomic constraints and finite stiffness springs. This approach, together with all the developed models and formulations are validated numerically for different workpiece geometries and various types of loading. An experimental study has been performed to validate this approach through the machining of thin-walled components. It was found that this approach led to prediction errors within 10% and more than 20 times reduction in the computation time. The challenge of filtering the effect of the dynamics of the force measurement system from the measured signals was overcome by developing a new hybrid semi-analytical methodology for accurate measurement of the machining forces. Copyright © 2012 by ASME.
Keywords: Accurate measurement; Aerospace structural components; Design and optimization; Experimental validations; High speed machining; Holonomic constraints; Semi-analytical model; Thin walled components; Dynamic models; Fixtures (tooling); Forecasting; Integrated control; Thin walled structures; Machining

Strain induced martensite formation in PM nickel steels - Tougas, B.; Blais, C.; Chagnon, F.; Pelletier, S. (Powder Metallurgy, 2012)
Powder metallurgy (PM) nickel steels are often selected because they have high strength, high impact resistance and good abrasion resistance. The microstructure of slowly cooled PM nickel steels typically contains pearlite, bainite, martensite and a fair volume fraction of retained austenite. Since volume diffusion is really low at conventional sintering temperatures [1120- 1150uC (2050-2100uF)], nickel rich areas are usually found where prior admixed nickel particles were located, i.e. at the surface of iron particles and in sintering necks. Therefore, there is a discrepancy between the rather low mechanical properties of austenite and the high strength of PM nickel steel. Hence, the hypotheses that stress induced or strain induced martensite formation takes place during mechanical testing have been investigated. Results show that martensite forms during mechanical testing, and its final volume fraction is proportional to nickel content. © 2013 Institute of Materials, Minerals and Mining.
Keywords: Conventional sintering; High impact resistance; Iron Particles; Nickel particles; Strain-induced martensite; Stress-induced; Volume diffusion; Volume fraction of retained austenite; Martensite; Mechanical properties; Mechanical testing; Nickel; Optical microscopy; Phase transitions; Sintering; Steel; Powder metallurgy

Detection of atherosclerotic vascular tissue from optical coherence tomography images - Prakash, A.; Hewko, M.; Sowa, M.; Sherif, S. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
Atherosclerotic coronary artery disease continues to be one of the major causes of mortality. Prevention, diagnosis and treatment of atherosclerotic coronary artery disease are dependent on the detection of high risk atherosclerotic plaque. As age is one of the most important risk factors, atherosclerosis worsens steadily with increasing age. Automatic characterization of atherosclerotic plaque using the optical coherence tomography (OCT) images provides a powerful tool to classify patients with high risk plaque. In this study we develop an automatic classifier to detect atherosclerotic plaque in young and old Watanabe heritable hyperlipidemic (WHHL) rabbits, using OCT images without reliance on visual inspection. Our classifier based on texture analysis technique may provide an efficient tool for detecting invisible changes in tissue structure. We extracted a set of 22 statistical textural features for each image using the spatial gray level dependence matrix (SGLDM) method. An optimal scalar feature selection process was carried to select the best discriminating features that employ the Fisher discriminant ratio (FDR) criterion, and cross correlation measure between the pairs of features. Using these optimal features, we formed a combination of 5 best classification features using an exhaustive search method. A combined feature set was finally employed for the classification of plaque. We obtained correct classification rate and validation of 76.67% and 75% respectively. © 2012 SPIE.
Keywords: Atherosclerosis; Atherosclerotic plaque; Automatic classification; Automatic classifiers; Classification features; Coronary artery disease; Plaque; Spatial gray level dependence matrixes; Diseases; Feature extraction; Tissue; Optical tomography

Durability of acrylic sealants applied to joints of autoclaved lightweight concrete walls: evaluation of exposure testing - Miyauchi, H.; Lacasse, Michael A.; Enomoto, N.; Murata, S.; Tanaka, K. (ASTM Special Technical Publication, 2012)
In Japan acrylic sealants are traditionally the sealant products of choice when specified for use between autoclaved lightweight concrete (ALC) panels. Although, in general terms, the mechanisms of the deterioration of acrylic sealants are well known its long-term durability to outdoor exposure has not, however, been fully investigated. The research described in this paper focuses on the change in the properties and deterioration of acrylic sealant products when exposed to outdoor testing. The two stage project consisted of (i) on-site investigations of deteriorated acrylic sealants that had been placed in external joints of ALC-clad buildings; and (ii) outdoor exposure testing of different types of acrylic sealant in three climate regions located in Japan. The results of the work from the first stage of the study revealed the following. Two-sided adhesion joint configurations installed in deep panel ALC cladding were more reliable than three-sided adhesion joints used for thin panel ALC cladding from the viewpoint of the durability of the sealed joint installed in actual buildings. Most fractures of the sealed joint could be characterized as failure in peel (or thin layer cohesive failures), in which the sealant ruptured at the interface with the ALC substrate to which it was applied. Additionally, in 47 of 62 locations surveyed, surface cracks were apparent on the coating that had been applied to protect the sealant. The second stage of the project focused on the degree of deterioration of coated and non-coated acrylic sealants subjected to outdoor exposure testing in a cold, a warm, and a subtropical climate. Results from this stage showed that aging of the sealant, as determined by the degree of surface cracking, expectedly depended on the local temperature and the respective degree of exposure to solar radiation. It was determined that the longer the exposure period, the lower the tensile performance of the acrylic sealants. The elongation of three-sided adhesive joint configurations after 5 years exposure testing decreased remarkably and their maximum elongation was less than 50%. A significant number of sealed joints after 5 years ofexposure had ALC substrate failure
Keywords: Adhesion joints; Climate regions; Cohesive failures; Exposure period; Exposure testing; Joint configuration; Local temperature; Outdoor exposure; Outdoor testing; Sealant products; Subtropical climates; Surface cracking; Surface cracks; Tensile performance; Thin layers; Wall panels; Adhesion; Adhesive joints; Adhesives; Concrete products; Concrete testing; Construction; Deterioration; Durability; Interfaces (materials); Sun; Surface defects; Walls (structural partitions); Sealants

A fuzzy logic based approach to expressing and reasoning with uncertain knowledge on the semantic web - Zhao, J.; Boley, H.; Du, W. (Studies in Computational Intelligence, 2012)
The necessity of dealing with uncertain knowledge has arisen from Semantic Web applications in different areas. Handling uncertainty thus becomes one of the key research directions in the Semantic Web community. This paper introduces a fuzzy logic based approach which extends the classic Description Logic with Zadeh semantics to deal with uncertain knowledge about concepts and roles as well as instances of concepts and roles. Uncertain knowledge representation and the reasoning algorithm for consistency checking of a fuzzy knowledge base are addressed in detail. This paper also discusses complexity issues of the reasoning problem. © 2012 Springer-Verlag GmbH Berlin Heidelberg.

Terahertz quantum cascade lasers based on phonon scattering assisted injection and extraction - Fathololoumi, S.; Dupont, E.; Wasilewski, Z.R.; Aers, G.; Laframboise, S.R.; Lindskog, M.; Wacker, A.; Ban, D.; Liu, H.C. (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
A novel terahertz quantum cascade laser, based on consecutive phonon-photon-phonon emissions, is proposed. The design procedure used a density matrix based figure-of-merit and a generic algorithm approach; the fabricated device lased up to 138 K. © 2012 OSA.
Keywords: Density matrix; Design procedure; Fabricated device; Generic algorithm; Terahertz quantum-cascade lasers; Computer programming; Phonons; Quantum cascade lasers; Lasers

The ACS Fornax Cluster Survey. VI. the nuclei of early-type galaxies in the Fornax Cluster - Turner, M.L.; Côté, P.; Ferrarese, L.; Jordán, A.; Blakeslee, J.P.; Mei, S.; Peng, E.W.; West, M.J. (Astrophysical Journal, Supplement Series, 2012)
The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both one-dimensional and two-dimensional techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central "luminosity excesses", relative to a Sersic model fitted to the underlying host. We find 72% ± 13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 05 from their galaxy photocenter, and with the majority of nuclei having colors bluer than their hosts. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters and to follow different structural scaling relations. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We briefly review a variety of proposed formation models and conclude that, for the low-mass galaxies in our sample, the most important mechanism for nucleus growth is probably infall of star clusters through dynamical friction, while for higher mass galaxies, gas accretion triggered by mergers, accretions, and tidal torques is likely to dominate, with the relative importance of these two processes varying smoothly as a function of galaxy mass. Some intermediate-mass galaxies in our sample show a complexity in their inner structure that may be the signature of the "hybrid nuclei" that arose through parallel formation channels. © 2012. The American Astronomical Society. All rights reserved.

Corrosion sensor development for condition-based maintenance of aircraft - Rinaldi, G.; Huber, T.; McIntosh, H.; Lebrun, L.; Ding, H.; Weber, J. (International Journal of Aerospace Engineering, 2012)
Aircraft routinely operate in atmospheric environments that, over time, will impact their structural integrity. Material protection and selection schemes notwithstanding, recurrent exposure to chlorides, pollution, temperature gradients, and moisture provide the necessary electrochemical conditions for the development and profusion of corrosion in aircraft structures. For aircraft operators, this becomes an important safety matter as corrosion found in a given aircraft must be assumed to be present in all of that type of aircraft. This safety protocol and its associated unscheduled maintenance requirement drive up the operational costs of the fleet and limit the availability of the aircraft. Hence, there is an opportunity at present for developing novel sensing technologies and schemes to aid in shifting time-based maintenance schedules towards condition-based maintenance procedures. In this work, part of the ongoing development of a multiparameter integrated corrosion sensor is presented. It consists of carbon nanotube/polyaniline polymer sensors and commercial-off-the-shelf sensors. It is being developed primarily for monitoring environmental and material factors for the purpose of providing a means to more accurately assess the structural integrity of aerospace aluminium alloys through fusion of multiparameter sensor data. Preliminary experimental test results are presented for chloride ion concentration, hydrogen gas evolution, humidity variations, and material degradation. Copyright © 2012 Gino Rinaldi et al.

Disulfide linkage engineering for improving biophysical properties of human VH domains - Kim, D.Y.; Kandalaft, H.; Ding, W.; Ryan, S.; Van Faassen, H.; Hirama, T.; Foote, S.J.; MacKenzie, R.; Tanha, J. (Protein Engineering, Design and Selection, 2012)
To enhance their therapeutic potential, human antibody heavy chain variable domains (VHs) would benefit from increased thermostability. The highly conserved disulfide linkage that connects Cys23 and Cys104 residues in the core of VH domains is crucial to their stability and function. It has previously been shown that the introduction of a second disulfide linkage can increase the thermostability of camelid heavy-chain antibody variable domains (VHHs). Using four model domains we demonstrate that this strategy is also applicable to human VH domains. The introduced disulfide linkage, formed between Cys54 and Cys78 residues, increased the thermostability of VHs by 1418°C. In addition, using a novel hexa-histidine capture technology, circular dichroism, turbidity, size exclusion chromatography and multiangle light scattering measurements, we demonstrate reduced VH aggregation in domains with the Cys54Cys78 disulfide linkage. However, we also found that the engineered disulfide linkage caused conformational changes, as indicated by reduced binding of the VHs to protein A. This indicates that it may be prudent to use the synthetic VH libraries harboring the engineered disulfide linkage before screening for affinity reagents. Such strategies may increase the number of thermostable binders. © 2012 The Author.
Keywords: Affinity reagents; Biophysical properties; Conformational change; Disulfide linkages; Heavy chain; Heavy-chain antibodies; Human antibodies; Model domains; Multi-angle light scatterings; Therapeutic potentials; thermostability; Variable domain; Agglomeration; Amino acids; Antibodies; Libraries; Turbidity; Sulfur compounds; antibody; cysteine; disulfide; heavy chain antibody variable domain; protein A; unclassified drug; amino acid substitution; article; Artiodactyla; binding affinity; biophysics; circular dichroism; covalent bond; disulfide linkage; gel permeation chromatography; human; mass spectrometry; molecular cloning; priority journal; protein engineering; protein expression; thermostability; turbidity; Amino Acid Sequence; Amino Acid Substitution; Disulfides; Humans; Immunoglobulin Heavy Chains; Immunoglobulin Variable Region; Molecular Sequence Data; Protein Conformation; Protein Engineering; Protein Stability; Sequence Alignment; Temperature; Camelidae

Complex Faraday depth structure of active galactic nuclei as revealed by broad-band radio polarimetry - O'Sullivan, S.P.; Brown, S.; Robishaw, T.; Schnitzeler, D.H.F.M.; Mcclure-Griffiths, N.M.; Feain, I.J.; Taylor, A.R.; Gaensler, B.M.; Landecker, T.L.; Harvey-Smith, L.; Carretti, E. (Monthly Notices of the Royal Astronomical Society, 2012)
We present a detailed study of the Faraday depth structure of four bright (>1 Jy), strongly polarized, unresolved radio-loud quasars. The Australia Telescope Compact Array (ATCA) was used to observe these sources with 2 GHz of instantaneous bandwidth from 1.1 to 3.1 GHz. This allowed us to spectrally resolve the polarization structure of spatially unresolved radio sources, and by fitting various Faraday rotation models to the data, we conclusively demonstrate that two of the sources cannot be described by a simple rotation measure (RM) component modified by depolarization from a foreground Faraday screen. Our results have important implications for using background extragalactic radio sources as probes of the Galactic and intergalactic magneto-ionic media as we show how RM estimations from narrow-bandwidth observations can give erroneous results in the presence of multiple interfering Faraday components. We postulate that the additional RM components arise from polarized structure in the compact inner regions of the radio source itself and not from polarized emission from galactic or intergalactic foreground regions. We further suggest that this may contribute significantly to any RM time variability seen in RM studies on these angular scales. Follow-up, high-sensitivity very long baseline interferometry (VLBI) observations of these sources will directly test our predictions. © 2012 CSIRO. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Multivalent display of single-domain antibodies - Zhang, J.; MacKenzie, C.R. (Methods in Molecular Biology, 2012)
Antigen-binding fragments, such as single-domain antibodies (sdAbs), can now be readily isolated by in vitro technologies. Antibody fragment libraries derived from immune or nonimmune sources are presented in a molecular display format, typically phage display, and binders to individual antigens are selected from the libraries by a so-called panning process. Nonimmune libraries can serve as sources of binders to a wide range of targets but yield antigen-binding fragments that generally have much lower affinities than those obtained from immune sources. Here we describe a strategy for constructing pentameric sdAbs termed pentabodies. Pentamerization introduces avidity which can greatly enhance the binding of low affinity sdAbs to antigens presented on surfaces. © 2012 Springer Science+Business Media, LLC.
Keywords: carcinoembryonic antigen related cell adhesion molecule 1; nanobody; pentabody ES1; plasmid vector; unclassified drug; nanobody; antigen binding; antigen recognition; article; carcinoma cell; controlled study; drug purification; drug synthesis; gene expression; human; human cell; nucleotide sequence; phage display; priority journal; amino acid sequence; animal; Artiodactyla; cell surface display; chemistry; gene expression; gene library; gene order; genetics; immunoglobulin variable region; immunology; methodology; molecular genetics; protein binding; tumor cell line; Amino Acid Sequence; Animals; Camelids, New World; Cell Line, Tumor; Cell Surface Display Techniques; Gene Expression; Gene Library; Gene Order; Humans; Immunoglobulin Variable Region; Molecular Sequence Data; Protein Binding; Single-Domain Antibodies

Invasive potential of nonencapsulated disease isolates of neisseria: Meningitidis - Johswich, K.O.; Zhou, J.; Law, D.K.S.; St. Michael, S.F.; McCaw, S.E.; Jamieson, F.B.; Cox, A.D.; Tsang, R.S.W.; Gray-Owen, S.D. (Infection and Immunity, 2012)
The capsule of Neisseria meningitidis is the major virulence factor that enables this bacterium to overcome host immunity elicited by complement and phagocytes, rendering it capable of surviving in blood. As such, nonencapsulated N. meningitidis isolates are generally considered nonpathogenic. Here, we consider the inherent virulence of two nonencapsulated N. meningitidis isolates obtained from our national surveillance of infected blood cultures in Canada. Capsule deficiency of both strains was confirmed by serology and PCR for the ctrA to ctrD genes and siaA to siaC genes, as well as siaD genes specific to serogroups B, C, Y, and W135. In both strains, the capsule synthesis genes were replaced by the capsule null locus, cnl-2. In accordance with a lack of capsule, both strains were fully susceptible to killing by both human and baby rabbit complement. However, in the presence of cytidine-5' monophospho-N-acetylneuraminic acid (CMP-NANA), allowing for lipooligosaccharide (LOS) sialylation, a significant increase of resistance to complement killing was observed. Mass spectrometry of purified LOS did not reveal any uncommon modifications that would explain their invasive phenotype. Finally, in a mouse intraperitoneal challenge model, these nonencapsulated isolates displayed enhanced virulence relative to an isogenic mutant of serogroup B strain MC58 lacking capsule (MC58ΔsiaD). Virulence of all nonencapsulated isolates tested was below that of encapsulated serogroup B strains MC58 and B16B6. However, whereas no mortality was observed with MC58ΔsiaD, 5/10 mice succumbed to infection with strain 2275 and 2/11 mice succumbed to strain 2274. Our results suggest the acquisition of a new virulence phenotype by these nonencapsulated strains. © 2012, American Society for Microbiology.
Keywords: cytidine phosphate n acetylneuraminic acid; lipooligosaccharide; animal experiment; animal model; article; bacterial gene; bacterial membrane; bacterial strain; bacterial virulence; bacterium isolate; blood culture; Canada; controlled study; gene locus; mass spectrometry; meningococcosis; mortality; mouse; Neisseria meningitidis; nonhuman; phenotype; polymerase chain reaction; priority journal; serology; sialylation; Animals; Bacterial Capsules; Canada; Complement System Proteins; Disease Models, Animal; Female; Genes, Bacterial; Humans; Male; Meningococcal Infections; Mice; Mice, Inbred C57BL; Neisseria meningitidis; Peritonitis; Polymerase Chain Reaction; Rabbits; Serotyping; Survival Analysis; Virulence Factors

Cyclic Dwell Fatigue Behaviour of Single Crystal Ni-Base Superalloys with/without Rhenium - Yandt, S.; Wu, X.-J.; Tsuno, N.; Sato, A. (Superalloys 2012, 2012)
In this study, compressive dwell (C-D) and no-dwell (N-D) lowcycle fatigue (LCF) behaviours of several single crystal Ni-base superalloys, including CMSX-4, LSC-11 and LSC-15, were studied under strain-controlled zero-compression (R, = -co) loading at 1100°C. LSC-11 and LSC-15 are new alloys developed by IHI Corporation, Japan with 0.8 wt% Re and without Re addition, respectively, as reduced-cost alternatives to the second generation single crystal Ni-base superalloys. The fatigue experiments were conducted with or without a two-minute dwell (hold) in compression and total strain ranges of 0.7%, 0.6% and 0.5% on uncoated specimens in the [001] orientation. Examination of the cyclic stress-strain behavior revealed that the initially compressive mean stress relaxed to approximately zero stress in N-D tests, while compressive hold resulted in the development of a tensile mean stress during C-D fatigue. Cyclic stress softening was observed under all test conditions. Microstructural analysis of tested specimens showed that N-D fatigue promoted isotropic coarsening of the γ' precipitates, while C-D loading resulted in the formation of discontinuous γ' rafting parallel to the loading direction. Fatigue cracks initiated from the specimen surface from regions of localized oxide attack. All alloys were compressive dwell sensitive. C-D fatigue lives were 4-15x shorter than N-D when the same alloys were considered. CMSX-4 exhibited 1.5-3* N-D fatigue life advantage over alloys LSC-11 and LSC-15. Under C-D fatigue the life advantage of CMSX-4 was 20-50% greater than alloys LSC-11 and LSC-15. The differences in these behaviours could be attributed to Re content and oxidation. © 2012 The Minerals, Metals, & Materials Society. All rights reserved.

MAGMO: Coherent magnetic fields in the star-Forming regions of the Carina-Sagittarius spiral arm tangent - Green, J.A.; McClure-Griffiths, N.M.; Caswell, J.L.; Robishaw, T.; Harvey-Smith, L. (Monthly Notices of the Royal Astronomical Society, 2012)
We present the pilot results of the 'MAGMO' project, targeted observations of ground-state hydroxyl masers towards sites of 6.7-GHz methanol maser emission in the Carina-Sagittarius spiral arm tangent, Galactic longitudes 280° to 295°. The 'MAGMO' project aims to determine if Galactic magnetic fields can be traced with Zeeman splitting of masers associated with star formation. Pilot observations of 23 sites of methanol maser emission were made, with the detection of ground-state hydroxyl masers towards 11 of these and six additional offset sites. Of these 17 sites, nine are new detections of sites of 1665-MHz maser emission, three of them accompanied by 1667-MHz emission. More than 70 per centof the maser features have significant circular polarization, whilst only ~10 per cent have significant linear polarization (although some features with up to 100 per cent linear polarization are found). We find 11 Zeeman pairs across six sites of high-mass star formation with implied magnetic field strengths between -1.5 and +3.8 mG and a median field strength of +1.6 mG. Our measurements of Zeeman splitting imply that a coherent field orientation is experienced by the maser sites across a distanc of 5.3 ± 2.0 kpc within the Carina-Sagittarius spiral arm tangent. © 2012 CSIRO.

Isolation and characterization of clostridium difficile toxin-specific single-domain antibodies - Hussack, G.; Arbabi-Ghahroudi, M.; MacKenzie, C.R.; Tanha, J. (Methods in Molecular Biology, 2012)
Camelidae single-domain antibodies (VHHs) are a unique class of small binding proteins that are promising inhibitors of targets relevant to infection and immunity. With VHH selection from hyperimmunized phage display libraries now routine and the fact that VHHs possess long, extended complementarity- determining region (CDR3) loop structures that can access traditionally immunosilent epitopes, VHH-based inhibition of targets such as bacterial toxins are being explored. Toxin A and toxin B are high molecular weight exotoxins (308 kDa and 269 kDa, respectively) secreted by Clostridium difficile that are the causative agents of C. difficile-associated diseases in humans and in animals. Here, we provide protocols for the rapid generation of C. difficile toxin A-and toxin B-specific VHHs by llama immunization and recombinant antibody/phage display technology approaches and for further characterization of the VHHs with respect to toxin-binding affinity and specificity and the conformational nature of their epitopes. © 2012 Springer Science+Business Media, LLC.
Keywords: Clostridium difficile toxin A; Clostridium difficile toxin B; epitope; nanobody; recombinant antibody; bacterial toxin; epitope; immunoglobulin G; immunoglobulin heavy chain; immunoglobulin M; animal experiment; antibody affinity; antibody production; antibody specificity; article; binding affinity; camel; Clostridium difficile; complementarity determining region; human; immunization; male; molecular weight; nonhuman; priority journal; animal; Artiodactyla; blood; cell surface display; immunology; isolation and purification; peptide library; Animals; Antibody Affinity; Antibody Specificity; Bacterial Toxins; Camelids, New World; Cell Surface Display Techniques; Clostridium difficile; Epitopes; Immunoglobulin G; Immunoglobulin Heavy Chains; Immunoglobulin M; Male; Peptide Library; Single-Domain Antibodies

Mechanisms of two-color laser-induced field-free molecular orientation - Spanner, Michael; Patchkovskii, Serguei; Frumker, Eugene; Corkum, Paul (Physical Review Letters, 2012)
Two mechanisms of two-color (ω+2ω) laser-induced field-free molecular orientation, based on the hyperpolarizability and ionization depletion, are explored and compared. The CO molecule is used as a computational example. While the hyperpolarizability mechanism generates small amounts of orientation at intensities below the ionization threshold, ionization depletion quickly becomes the dominant mechanism as soon as ionizing intensities are reached. Only the ionization mechanism leads to substantial orientation (e.g., on the order of cosθ0.1). For intensities typical of laser-induced molecular alignment and orientation experiments, the two mechanisms lead to robust, characteristic timings of the field-free orientation wave-packet revivals relative to the alignment revivals and the revival time. The revival timings can be used to detect the active orientation mechanism experimentally.
Keywords: CO molecule; Dominant mechanism; Field-free orientation; Hyper-polarizability; Ionization mechanisms; Ionization thresholds; Laser induced; Orientation mechanism; Two-color; Ionization; Molecular orientation

VLBI for Gravity Probe B. VI. the orbit of im Pegasi and the location of the source of radio emission - Ransom, R.R.; Bartel, N.; Bietenholz, M.F.; Lebach, D.E.; Lestrade, J.-F.; Ratner, M.I.; Shapiro, I.I. (Astrophysical Journal, Supplement Series, 2012)
We present a physical interpretation for the locations of the sources of radio emission in IM Pegasi (IMPeg, HR8703), the guide star for the NASA/Stanford relativity mission Gravity Probe B. This emission is seen in each of our 35 epochs of 8.4 GHz very long baseline interferometry observations taken from 1997 to 2005. We found that the mean position of the radio emission is at or near the projected center of the primary to within about 27% of its radius, identifying this active star as the radio emitter. The positions of the radio brightness peaks are scattered across the disk of the primary and slightly beyond, preferentially along an axis with position angle, P.A.= -38° ± 8°, which is closely aligned with the sky projections of the orbit normal (P.A.= -495 ± 86) and the expected spin axis of the primary. Comparison with simulations suggests that brightness peaks are 3.6 +0.4 - 0.7 times more likely to occur (per unit surface area) near the pole regions of the primary (latitude, |λ| ≥ 70°) than near the equator (|λ| ≤ 20°), and to also occur close to the surface with 2/3 of them at altitudes not higher than 25% of the radius of the primary. © 2012. The American Astronomical Society. All rights reserved..

Advanced vibration suppression algorithms in adaptive optics systems - Correia, C.; Véran, J.-P.; Herriot, G. (Journal of the Optical Society of America A: Optics and Image Science, and Vision, 2012)
Vibration suppression in astronomical adaptive optics (AO) systems has gathered great attention in the context of next-generation instrumentation for current telescopes and future Extremely Large Telescopes. Laser tomographic AO systems require natural guide stars to measure the low-order modes such as tip-tilt (TT) and TT-anisoplanatism. To increase the sky coverage, the guide stars are often faint, thus requiring lower temporal sampling frequencies to work on a more favorable signal-to-noise regime. Such sampling frequencies can be of the order of, or even lower than, the range of frequencies where vibrations are likely to appear. Ideally, vibrations affecting the loworder modes could be corrected at the higher laser loop frame rate using an upsampling procedure. This paper compares the most relevant solutions proposed hitherto to a novel multirate algorithm using the linear-quadratic-Gaussian (LQG) approach capable of upsampling the correction to further reduce the impact of vibrations. Results from numerical Monte Carlo simulations span a large range of parameters from pure sinusoids to relatively broad peak vibrations, covering the likely-to-be signals in a realistic AO system. The improvement is shown at sampling frequencies from 20 to 800 Hz, including below the vibration itself, in the example of 29.5 Hz on a Thirty Meter Telescope-like scenario. The multirate LQG ensures the least residual for both faint and bright stars for all the peak widths considered based on telemetry from the Keck Observatory. © 2012 Optical Society of America.
Keywords: Adaptive optics systems; Extremely Large Telescopes; Frame rate; Guide star; Keck observatory; Linear quadratic Gaussian; Monte Carlo Simulation; Multi rate; Multi-rate algorithm; Natural guide star; Peak vibrations; Peak widths; Sampling frequencies; Signal to noise; Sky coverage; Temporal sampling; Tip-tilt; Tomographic; Upsampling; Vibration suppression; Algorithms; Monte Carlo methods; Stars; Telescopes; Optical telescopes

VLBI for Gravity Probe B. IV. A new astrometric analysis technique and a comparison with results from other techniques - Lebach, D.E.; Bartel, N.; Bietenholz, M.F.; Campbell, R.M.; Gordon, D.; Lederman, J.I.; Lestrade, J.-F.; Ransom, R.R.; Ratner, M.I.; Shapiro, I.I. (Astrophysical Journal, Supplement Series, 2012)
When very long baseline interferometry (VLBI) observations are used to determine the position or motion of a radio source relative to reference sources nearby on the sky, the astrometric information is usually obtained via (1) phase-referenced maps or (2) parametric model fits to measured fringe phases or multiband delays. In this paper, we describe a "merged" analysis technique which combines some of the most important advantages of these other two approaches. In particular, our merged technique combines the superior model-correction capabilities of parametric model fits with the ability of phase-referenced maps to yield astrometric measurements of sources that are too weak to be used in parametric model fits. We compare the results from this merged technique with the results from phase-referenced maps and from parametric model fits in the analysis of astrometric VLBI observations of the radio-bright star IMPegasi (HR8703) and the radio source B2252+172 nearby on the sky. In these studies we use central-core components of radio sources 3C454.3 and B2250+194 as our positional references. We obtain astrometric results for IMPeg with our merged technique even when the source is too weak to be used in parametric model fits, and we find that our merged technique yields astrometric results superior to the phase-referenced mapping technique. We used our merged technique to estimate the proper motion and other astrometric parameters of IMPeg in support of the NASA/Stanford Gravity Probe B mission. © 2012. The American Astronomical Society. All rights reserved..

Thermodynamic stability of structure H hydrates based on the molecular properties of large guest molecules - Tezuka, K.; Taguchi, T.; Alavi, S.; Sum, A.K.; Ohmura, R. (Energies, 2012)
This paper report analyses of thermodynamic stability of structure-H clathrate hydrates formed with methane and large guest molecules in terms of their gas phase molecular sizes and molar masses for the selection of a large guest molecule providing better hydrate stability. We investigated the correlation among the gas phase molecular sizes, the molar masses of large molecule guest substances, and the equilibrium pressures. The results suggest that there exists a molecular-size value for the best stability. Also, at a given molecule size, better stability may be available when the large molecule guest substance has a larger molar mass. © 2012 by the authors; licensee MDPI, Basel, Switzerland.
Keywords: Clathrate hydrate; Equilibrium pressure; Gasphase; Guest molecules; Hydrate stabilities; Large molecule guest substance; Molecular properties; Molecular size; Molecule sizes; Structure H-hydrate; Gas hydrates; Gases; Hydration; Methane; Phase equilibria; Thermodynamic stability; Molecules

Strong-field ionization and high-order-harmonic generation during polyatomic molecular dynamics of N 2O 4 - Spanner, M.; Mikosch, J.; Boguslavskiy, A.E.; Murnane, M.M.; Stolow, A.; Patchkovskii, S. (Physical Review A - Atomic, Molecular, and Optical Physics, 2012)
We present state-of-the-art ab initio-type computations of strong-field ionization (SFI) and the single-molecule response contribution to high-order-harmonic generation (HHG) in the polyatomic molecule N 2O 4. The numerical method uses a mixed orbital- and grid-based approach to model the multielectron bound states and single-electron continuum. The effects of ionic-core attraction and Coulomb-mediated interchannel coupling are rigorously included. We show that full-dimensionality time-dependent multielectron computations of SFI and HHG in polyatomic molecules are now feasible. The computational results indicate that (a) SFI yields in N 2O 4 are dominated by a single ionic state (the A g state), and are strongly modulated by the N-N stretch coordinate; and (b) the HHG radiating dipole as a function of the N 2O 4 N-N stretch is dominated by the same, single state. The molecular-beam coincidence measurements presented here support the computational results. Due to the differences in the estimated vibrational amplitude, however, the computations are not in full agreement with previous HHG data. ©2012 American Physical Society.
Keywords: Bound state; Coincidence measurement; Computational results; Grid-based approach; Interchannel coupling; Ionic state; Multi-electron; Polyatomic molecular dynamics; Polyatomic molecules; Radiating dipole; Single electron; Single state; Single-molecule; Strong field ionization; Time-dependent; Vibrational amplitudes; Harmonic generation; Ionization; Molecular dynamics

Crystal structure of a human single domain antibody dimer formed through V H-V H non-covalent interactions - Baral, T.N.; Chao, S.-Y.; Li, S.; Tanha, J.; Arbabi-Ghahroudi, M.; Zhang, J.; Wang, S. (PLoS ONE, 2012)
Single-domain antibodies (sdAbs) derived from human V H are considered to be less soluble and prone to aggregate which makes it difficult to determine the crystal structures. In this study, we isolated and characterized two anti-human epidermal growth factor receptor-2 (HER2) sdAbs, Gr3 and Gr6, from a synthetic human V H phage display library. Size exclusion chromatography and surface plasmon resonance analyses demonstrated that Gr3 is a monomer, but that Gr6 is a strict dimer. To understand this different molecular behavior, we solved the crystal structure of Gr6 to 1.6 Å resolution. The crystal structure revealed that the homodimer assembly of Gr6 closely mimics the V H-V L heterodimer of immunoglobulin variable domains and the dimerization interface is dominated by hydrophobic interactions. © 2012 Baral et al.
Keywords: epidermal growth factor receptor 2 single domain antibody Gr3; epidermal growth factor receptor 2 single domain antibody Gr6; epidermal growth factor receptor antibody; homodimer; unclassified drug; antibody; epidermal growth factor receptor 2; HER2 protein, human; article; controlled study; covalent bond; crystal structure; dimerization; gel permeation chromatography; hydrophobicity; immunoglobulin variable region; molecular cloning; molecular interaction; molecular library; phage display; protein analysis; protein assembly; protein isolation; surface plasmon resonance; thermostability; amino acid sequence; antibody specificity; chemical phenomena; chemical structure; chemistry; human; immunology; metabolism; molecular genetics; protein binding; protein multimerization; protein secondary structure; protein tertiary structure; solution and solubility; transition temperature; X ray crystallography; Amino Acid Sequence; Antibodies; Antibody Specificity; Crystallography, X-Ray; Humans; Hydrophobic and Hydrophilic Interactions; Immunoglobulin Variable Region; Models, Molecular; Molecular Sequence Data; Protein Binding; Protein Multimerization; Protein Structure, Secondary; Protein Structure, Tertiary; Receptor, erbB-2; Solutions; Transition Temperature

Mathematical modelling of flow and heat/mass transfer during reactive spraying deposition technology (RSDT) process for high temperature fuel cells - Hu, G.; Neagu, R.; Wang, Q.; Zhang, Z.; Li, G.; Zheng, Y. (Engineering Applications of Computational Fluid Mechanics, 2012)
A three-dimensional mathematical model of flow and heat/mass transfer coupling with chemical reactions for fuel gas and droplet combustion during reactive spraying deposition technology (RSDT) is presented in this paper. The RNG k- ε model is employed in the numerical simulation of turbulent combustion gas flow. The droplet particle is tracked and analyzed in a Lagrangian frame. The heating and vaporization histories of the injected droplet are also calculated during its movement. The three-dimensional distributions of velocity, species concentration and temperature are numerically obtained. The results indicate that the droplet will disappear over a very short distance and the vaporized fuel gas will burn immediately. Both the methods and the results described in this paper will help in the control of the final catalyst particle size and the optimization of the microstructure of the catalyst layer.

Specific synthesis of neurostatin and gangliosides O-acetylated in the outer sialic acids using a sialate transferase - Romero-Ramírez, L.; García-Álvarez, I.; Campos-Olivas, R.; Gilbert, M.; Goneau, M.-F.; Fernández-Mayoralas, A.; Nieto-Sampedro, M. (PLoS ONE, 2012)
Gangliosides are sialic acid containing glycosphingolipids, commonly found on the outer leaflet of the plasma membrane. O-acetylation of sialic acid hydroxyl groups is one of the most common modifications in gangliosides. Studies on the biological activity of O-acetylated gangliosides have been limited by their scarcity in nature. This comparatively small change in ganglioside structure causes major changes in their physiological properties. When the ganglioside GD1b was O-acetylated in the outer sialic acid, it became the potent inhibitor of astroblast and astrocytoma proliferation called Neurostatin. Although various chemical and enzymatic methods to O-acetylate commercial gangliosides have been described, O-acetylation was nonspecific and produced many side-products that reduced the yield. An enzyme with O-acetyltransferase activity (SOAT) has been previously cloned from the bacteria Campylobacter jejuni. This enzyme catalyzed the acetylation of oligosaccharide-bound sialic acid, with high specificity for terminal alpha-2,8-linked residues. Using this enzyme and commercial gangliosides as starting material, we have specifically O-acetylated the gangliosides' outer sialic acids, to produce the corresponding gangliosides specifically O-acetylated in the sialic acid bound in alpha-2,3 and alpha-2,8 residues. We demonstrate here that O-acetylation occurred specifically in the C-9 position of the sialic acid. In summary, we present a new method of specific O-acetylation of ganglioside sialic acids that permits the large scale preparation of these modified glycosphingolipids, facilitating both, the study of their mechanism of antitumoral action and their use as therapeutic drugs for treating glioblastoma multiform (GBM) patients. © 2012 Romero-Ramírez et al.
Keywords: acyltransferase; antineoplastic agent; cholic acid; ganglioside; ganglioside GD 1b; glycosphingolipid; neurostatin; sialate transferase; sialic acid; transferase; unclassified drug; acetylation; antineoplastic activity; article; concentration (parameters); drug determination; drug structure; drug synthesis; hydrolysis; intermethod comparison; matrix assisted laser desorption ionization time of flight mass spectrometry; molecular interaction; molecular weight; proton nuclear magnetic resonance; Acetylation; Acetyltransferases; Campylobacter jejuni; Carbohydrate Sequence; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Gangliosides; Glycosphingolipids; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Recombinant Proteins; Sialic Acids; Spectrometry, Mass, Electrospray Ionization; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Campylobacter jejuni

Awaveguide-coupled on-chip single-photon source - Laucht, A.; Pütz, S.; Günthner, T.; Hauke, N.; Saive, R.; Frédérick, S.; Bichler, M.; Amann, M.-C.; Holleitner, A.W.; Kaniber, M.; Finley, J.J. (Physical Review X, 2012)
We investigate single-photon generation from individual self-assembled InGaAs quantum dots coupled to the guided optical mode of a GaAs photonic crystal waveguide. By performing confocal microscopy measurements on single dots positioned within the waveguide, we locate their positions with a precision better than 0:5 μm. Time-resolved photoluminescence and photon autocorrelation measurements are used to prove the single-photon character of the emission into the propagating waveguide mode. The results obtained demonstrate that such nanostructures can be used to realize an on-chip, highly directed singlephoton source with single-mode spontaneous emission coupling efficiencies in excess of βΓ ~ 85% and the potential to reach maximum emission rates >1 GHz.
Keywords: Autocorrelation measurement; Coupling efficiency; Emission rates; GaAs; InGaAs quantum dots; On chips; Optical modes; Photonic crystal waveguide; Self-assembled; Single mode; Single photon generation; Single-photon source; Time-resolved photoluminescence; Waveguide mode; Confocal microscopy; Optical waveguides; Waveguides; Particle beams

Robust force controller for industrial robots: Optimal design and real-time implementation on a KUKA robot - Bigras, P.; Lambert, M.; Perron, C. (IEEE Transactions on Control Systems Technology, 2012)
In this brief, a new formulation is proposed for the design of a robust force controller for industrial robots with closed architecture controller. A recent model, which takes into account the complete kinematics of the system and the position response of the industrial robot controller, allows this formulation. The proposed design is based on a set of nonlinear matrix inequalities, and solved by the dual iteration algorithm. The robust controller is implemented on a KUKA robot. Good results are obtained with the proposed approach. © 2011 IEEE.
Keywords: Dual iteration algorithm; KUKA robot; Linear matrix inequality (LMI); Non-linear matrix inequality; Optimal design; Position response; Real-time implementations; Robust controllers; Robust force; Algorithms; Controllers; Force control; Industrial robots; Industry; Linear matrix inequalities; Real time control; Stiffness matrix; Machine design

VLBI for Gravity Probe B. II. Monitoring of the structure of the reference sources 3C 454.3, B2250+194, and B2252+172 - Ransom, R.R.; Bartel, N.; Bietenholz, M.F.; Lebach, D.E.; Lederman, J.I.; Luca, P.; Ratner, M.I.; Shapiro, I.I. (Astrophysical Journal, Supplement Series, 2012)
We used 8.4GHz very long baseline interferometry images obtained at up to 35 epochs between 1997 and 2005 to examine the radio structures of the main reference source, 3C 454.3, and two secondary reference sources, B2250+194 and B2252+172, for the guide star for the NASA/Stanford relativity mission Gravity Probe B (GP-B). For one epoch in 2004 May, we also obtained images at 5.0 and 15.4GHz. The 35 8.4GHz images for quasar 3C 454.3 confirm a complex, evolving, core-jet structure. We identified at each epoch a component, C1, near the easternmost edge of the core region. Simulations of the core region showed that C1 is located, on average, 0.18 ± 0.06mas west of the unresolved "core" identified in 43GHz images. We also identified in 3C 454.3 at 8.4GHz several additional components that moved away from C1 with proper motions ranging in magnitude between 0.9 c and 5 c. The detailed motions of the components exhibit two distinct bends in the jet axis located 3 and 5.5mas west of C1. The spectra between 5.0 and 15.4GHz for the "moving" components are steeper than those for C1. The 8.4GHz images of B2250+194 and B2252+172, in contrast to those of 3C 454.3, reveal compact structures. The spectrum between 5.0 and 15.4GHz for B2250+194 is inverted while that for B2252+172 is flat. Based on its position near the easternmost edge of the 8.4GHz radio structure, close spatial association with the 43GHz core, and relatively flat spectrum, we believe 3C 454.3 component C1 to be the best choice for the ultimate reference point for the GP-B guide star. The compact structures and inverted-to-flat spectra of B2250+194 and B2252+172 make these objects valuable secondary reference sources. © 2012. The American Astronomical Society. All rights reserved..

Determination of optimum process conditions for processing AS4/APC-2 thermoplastic composites by automated fiber placement - Cai, X.; Shadmehri, F.; Hojjati, M.; Chen, J.; Van Hoa, S. (International SAMPE Technical Conference, 2012)
In this study, thermoplastic composite (AS4/APC-2) rings were fabricated using automated fiber placement technique. To compare the quality of the rings under different process conditions, differential scanning calorimetry (DSC) test was conducted to investigate the crystallinity level in the samples. Short-beam shear test was performed to demine the interlaminar shear strength. Digital Image Correlation (DIC) technique was used to measure ultimate through-the-thickness strain. Microscopic photos were used to determine the failure mode. Based on the short-beam strength results, Taguchi method was employed to identify the significance of each process parameters and to obtain the optimum process conditions.
Keywords: Crystallinities; Digital image correlations; Fiber placement; Interlaminar shear strength; Microscopic photos; Optimum process conditions; Process condition; Process parameters; Shear tests; Thermoplastic composite; Differential scanning calorimetry; Exhibitions; Taguchi methods; Thermoplastics; Composite materials; Assembly; Calorimetry; Composites; Failure; Tensile Strength; Thermoplastics

Conformational modes in biomolecules: Dynamics and approximate invariance - Potapov, A.; Stepanova, M. (Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 2012)
Understanding the physical mechanisms behind the folding and conformational dynamics of biomolecules is one of the major unsolved challenges of soft matter theory. In this contribution, a theoretical framework for biomolecular dynamics is introduced, employing selected aspects of statistical mechanics, dimensionality reduction, the perturbation theory, and the theory of matrices. Biomolecular dynamics is represented by time-dependent orthogonal conformational modes, the dynamics of the modes is investigated, and invariant properties that persist are identified. As an example, the dynamics of a human prion protein is considered. The theory provides a rigorous background for assessing the stable dynamical properties of biomolecules, such as their coarse-grained structure, through a multiscale approach using short subnanosecond segments of molecular dynamics trajectories. Furthermore, the paper offers a theoretical platform for models of conformational changes in macromolecules, which may allow complementing molecular dynamics simulations. ©2012 American Physical Society.
Keywords: Biomolecular dynamics; Coarse-grained structure; Conformational change; Conformational dynamics; Dimensionality reduction; Dynamical properties; Human prion protein; Invariant properties; Molecular dynamics simulations; Molecular dynamics trajectories; Multi-scale approaches; Perturbation theory; Physical mechanism; Soft matter; Subnanosecond; Theoretical framework; Time-dependent; Biomolecules; Molecular dynamics; Statistical mechanics; Dynamics

Structural bonding of the next generation large canadarm (NGLC) ground test bed - Djokic, D.; Krimbalis, P.P.; Hay, G.; Cole, R.; Rogers, J.; Brunet, S. (International SAMPE Technical Conference, 2012)
The Next Generation Large Canadarm (NGLC) ground test bed is constrained by the physical stowage volume available on future exploration vehicles. NGLC demonstrates a reduction in the launch package of a large manipulator system while maintaining reach capability through deployment and retraction. NGLC is comprised of two telescoping segments, connected by three pitch joints. The segments consist of an inner and outer boom with a lock mechanism for either position. A rail network allows relative translation of the booms. NGLC bending and torsional stiffness requirements were met through the use of composite materials and adhesive bonding. Each boom features a centre composite section bonded to two aluminum sections using a stepped-lap joint. The elimination of mechanical fasteners maximized NGLC stiffness through a reduction of the clearance required between the telescoping assemblies and an increase of the inner segment diameter. Progressive damage finite element (FE) models optimized the lay-up and predicted positive margins of safety for combined bending and torsion load cases. Continuum mechanics analysis of the bonded joint was used to predict adhesive and adherend stresses due to the applied loads. A modular bonding apparatus with constrained relative adherend translation accommodated customized bonding processes for each operation. Steel rail segments were simultaneously bonded to the composite section inner surfaces, while the composite and aluminum sections were sequentially bonded. The joint and the bonding processes were optimized for bondline thickness control and minimum void entrapment. Key challenges included maintaining dimensional tolerances over the large structure, excess adhesive management and fouling of inaccessible critical surfaces.
Keywords: Bondline thickness; Dimensional tolerance; Finite element models; Manipulator systems; Mechanical fastener; Progressive damage; Telescoping segments; Torsional stiffness; Adhesive joints; Aluminum; Cargo handling; Continuum mechanics; Equipment testing; Exhibitions; Finite element method; Optimization; Robotic arms; Stiffness; Translation (languages); Reduction

State-related changes in MEG functional connectivity reveal the task-positive sensorimotor network - Bardouille, T.; Boe, S. (PLoS ONE, 2012)
Functional connectivity measures applied to magnetoencephalography (MEG) data have the capacity to elucidate neuronal networks. However, the task-related modulation of these measures is essential to identifying the functional relevance of the identified network. In this study, we provide evidence for the efficacy of measuring "state-related" (i.e., task vs. rest) changes in MEG functional connectivity for revealing a sensorimotor network. We investigate changes in functional connectivity, measured as cortico-cortical coherence (CCC), between rest blocks and the performance of a visually directed motor task in a healthy cohort. Task-positive changes in CCC were interpreted in the context of any concomitant modulations in spectral power. Task-related increases in whole-head CCC relative to the resting state were identified between areas established as part of the sensorimotor network as well as frontal eye fields and prefrontal cortices, predominantly in the beta and gamma frequency bands. This study provides evidence for the use of MEG to identify task-specific functionally connected sensorimotor networks in a non-invasive, patient friendly manner. © 2012 Bardouille, Boe.
Keywords: adult; anatomical variation; article; beta rhythm; brain function; electroencephalogram; female; frontal eye field; functional assessment; gamma rhythm; human; human experiment; image analysis; image display; magnetoencephalography; male; motor performance; neuroimaging; normal human; prefrontal cortex; rest; sensorimotor function; task performance; visual feedback; Adult; Brain; Brain Mapping; Cues; Female; Humans; Magnetoencephalography; Male; Nerve Net; Psychomotor Performance; Reproducibility of Results; Rest; Visual Perception; Young Adult

Influence of speciation on the response from selenium to UV-photochemical vapor generation - Suzuki, Toshihiro; Sturgeon, Ralph E.; Zheng, Chengbin; Hioki, Akiharu; Nakazato, Tetsuya; Tao, Hiroaki (Analytical Sciences, 2012)
By exposure to appropriate UV intensities, rapid and quantitative oxidation/reduction of inorganic selenite, selenate and several organoselenium compounds representative of those of biochemical/metabolic interest, including selenomethionine, selenobetaine, L-selenocystine, selenomethylselenocysteine, γ-glutamyl-seleno-methylselenocysteine and selenocystamine, is achieved. In the presence of acetic acid, quantitative conversion to volatile SeH₂ and SeCO occurs using a flow-through system comprising a highly efficient 40 W UV lamp for oxidation in tandem with a lower power 8 W UV photocatalytic reactor utilizing a thin-film coating of titania. The volatile reduced species are detected by atomic absorption spectrometry using a heated quartz tube atomizer. Direct photochemical conversion of selenite, selenomethionine, L-selenocystine, γ-glutamyl-Se-methylselenocysteine and selenocystamine occurs in the presence of 5% acetic acid, following exposure to an 8 W UV field, to yield volatile detectable species, whereas selenobetaine and selenate are unresponsive unless the latter is first subjected to oxidation by exposure to a highly efficient 40 W UV lamp and the selenate reduced in the presence of titania. © The Japan Society for Analytical Chemistry.

Experimental modeling of extreme hydrodynamic forces on structural models - Al-Faesly, Taofiq; Palermo, Dan; Nistor, Ioan; Cornett, Andrew (International Journal of Protective Structures, 2012)
This paper presents the results of a comprehensive experimental program focused on the impact of extreme hydrodynamic forces on structural models generated by a turbulent hydraulic bore. The parameters investigated include: (1) bore depth-time history; (2) initial flume-bed conditions (dry bed versus wet); and (3) damping effect of mitigation walls on the hydrodynamic forces. At impact, the maximum inundation (bore) depths varied between 250 mm and 450 mm and the bore front velocity ranged from 2.6 m/s to 5.0 m/s. High-speed video recordings of the bore-structural model interaction were captured simultaneously with the base shear force-, pressure-, base overturning moment-, and top lateral displacement-time histories experienced by the structural models. Three force components were identified in the bore-induced force-time histories: impulsive, run-up (transient hydrodynamic force), and quasi-steady hydrodynamic. The impulsive or run-up force was the maximum force component experienced by the structural models under initial dry-bed flume conditions; while for the initial wet-bed flume condition, the run-up force component was the maximum force. The effect of 100 mm and 150 mm low-height mitigation walls inclined at angles of 45° or 90°, which were installed at distances of 305 mm or 915 mm upstream from the structural model, was also investigated. The angle of inclination of the mitigation walls, its location relative to the structural model, and its cross-sectional shape all influence the base shear force- and base overturning moment-time histories. The base shear forces in the direction of the flow measured during experimental testing were greater than those estimated using the Federal Emergency Management Agency (FEMA) document P646, while the Structural Design Method of Buildings for Tsunami Resistance (SMBTR) overestimated the base shear forces.
Keywords: Cross-sectional shape; Displacement-time history; Experimental modeling; Experimental program; Experimental testing; Federal Emergency Management Agency; FEMA P646; Hydrodynamic forces; Flow velocity; Hydrodynamics; Model structures; Structural design; Tsunamis; Video recording; Walls (structural partitions); Shear flow

Micromachined edge illuminated optically transparent automotive light guide panels - Ronny, R.A.; Knopf, G.K.; Bordatchev, E.; Tauhiduzzaman, M.; Nikumb, S. (Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2012)
Edge-lit backlighting has been used extensively for a variety of small and medium-sized liquid crystal displays (LCDs). The shape, density and spatial distribution pattern of the micro-optical elements imprinted on the surface of the flat light-guide panel (LGP) are often "optimized" to improve the overall brightness and luminance uniformity. A similar concept can be used to develop interior convenience lighting panels and exterior tail lamps for automotive applications. However, costly diffusive sheeting and brightness enhancement films are not be considered for these applications because absolute luminance uniformity and the minimization of Moiré fringe effects are not significant factors in assessing quality of automotive lighting. A new design concept that involves micromilling cylindrical micro-optical elements on optically transparent plastic substrates is described in this paper. The variable parameter that controls illumination over the active regions of the panel is the depth of the individual cylindrical micro-optical elements. LightToolsTM is the optical simulation tool used to explore how changing the micro-optical element depth can alter the local and global luminance. Numerical simulation and microfabrication experiments are performed on several (100mmx100mmx6mm) polymethylmethacrylate (PMMA) test samples in order to verify the illumination behavior. © 2012 SPIE.
Keywords: Active regions; Automotive applications; Automotive light panels; Automotive lighting; Edge lighting; Fringe-effects; Light guide panels; Lighting panels; Luminance uniformity; Micro milling; Micro-optical elements; Micromachined; New design; Optical light; Optical simulation; Spatial distribution patterns; Test samples; Transparent plastics; Variable parameters; Composite micromechanics; Diffractive optics; Lighting; Liquid crystal displays; Microanalysis; Microfabrication; Microoptics; Milling (machining); Optical fibers; Micromachining

The genome of flax (Linum usitatissimum) assembled de novo from short shotgun sequence reads - Wang, Z.; Hobson, N.; Galindo, L.; Zhu, S.; Shi, D.; McDill, J.; Yang, L.; Hawkins, S.; Neutelings, G.; Datla, R.; Lambert, G.; Galbraith, D.W.; et al. (Plant Journal, 2012)
Flax (Linum usitatissimum) is an ancient crop that is widely cultivated as a source of fiber, oil and medicinally relevant compounds. To accelerate crop improvement, we performed whole-genome shotgun sequencing of the nuclear genome of flax. Seven paired-end libraries ranging in size from 300 bp to 10 kb were sequenced using an Illumina genome analyzer. A de novo assembly, comprised exclusively of deep-coverage (approximately 94× raw, approximately 69× filtered) short-sequence reads (44-100 bp), produced a set of scaffolds with N50 = 694 kb, including contigs with N50 = 20.1 kb. The contig assembly contained 302 Mb of non-redundant sequence representing an estimated 81% genome coverage. Up to 96% of published flax ESTs aligned to the whole-genome shotgun scaffolds. However, comparisons with independently sequenced BACs and fosmids showed some mis-assembly of regions at the genome scale. A total of 43 384 protein-coding genes were predicted in the whole-genome shotgun assembly, and up to 93% of published flax ESTs, and 86% of A. thaliana genes aligned to these predicted genes, indicating excellent coverage and accuracy at the gene level. Analysis of the synonymous substitution rates (Ks) observed within duplicate gene pairs was consistent with a recent (5-9 MYA) whole-genome duplication in flax. Within the predicted proteome, we observed enrichment of many conserved domains (Pfam-A) that may contribute to the unique properties of this crop, including agglutinin proteins. Together these results show that de novo assembly, based solely on whole-genome shotgun short-sequence reads, is an efficient means of obtaining nearly complete genome sequence information for some plant species. © 2012 Blackwell Publishing Ltd.
Keywords: DNA Sequencing; Illumina; Industrial crops; Malpighiales; Whole-genome shotgun; Crops; DNA sequences; Flax; Linen; Proteins; Yarn; Genes; plant DNA; article; bacterial artificial chromosome; chemistry; chromosome map; contig mapping; DNA sequence; expressed sequence tag; flax; gene library; genetics; high throughput sequencing; methodology; molecular genetics; nucleotide sequence; plant genome; protein tertiary structure; Base Sequence; Chromosome Mapping; Chromosomes, Artificial, Bacterial; Contig Mapping; DNA, Plant; Expressed Sequence Tags; Flax; Gene Library; Genome, Plant; High-Throughput Nucleotide Sequencing; Molecular Sequence Annotation; Molecular Sequence Data; Protein Structure, Tertiary; Sequence Analysis, DNA; Arabidopsis thaliana; Linum usitatissimum; Malpighiales

Magnetic Resonance Technology - Tomanek, B.; Sharp, J.C. (Biomedical Imaging: Principles and Applications, 2012)

Star formation in the outer disk of spiral galaxies - Barnes, K.L.; Van Zee, L.; Côté, S.; Schade, D. (The Astrophysical Journal, 2012)
We combine new deep and wide field of view Hα imaging of a sample of eight nearby (d 17Mpc) spiral galaxies with new and archival H I and CO imaging to study the star formation and the star formation regulation in the outer disk. We find that, in agreement with previous studies, star formation in the outer disk has low covering fractions, and star formation is typically organized into spiral arms. The star formation in the outer disk is at extremely low levels, with typical star formation rate surface densities of ∼10 -5 to 10 -6 M Oyr -1kpc -2. We find that the ratio of the radial extent of detected H II regions to the radius of the H I disk is typically ≳85%. This implies that in order to further our understanding of the implications of extended star formation, we must further our understanding of the formation of extended H I disks. We measure the gravitational stability of the gas disk, and find that the outer gaseous disk is typically a factor of ∼2times more stable than the inner star-forming disk. We measure the surface density of outer disk H I arms, and find that the disk is closer to gravitational instability along these arms. Therefore, it seems that spiral arms are a necessary, but not sufficient, requirement for star formation in the outer disk. We use an estimation of the flaring of the outer gas disk to illustrate the effect of flaring on the Schmidt power-law index; we find that including flaring increases the agreement between the power-law indices of the inner and outer disks. © 2012. The American Astronomical Society. All rights reserved.

Quantum random bit generation by stimulated Raman scattering - Bustard, P.J.; Moffatt, D.; Lausten, R.; Wu, G.; Walmsley, I.A.; Sussman, B.J. (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
We introduce a quantum random number generator based on the phase measurement of Stokes light generated by amplification of zero-point vacuum fluctuations using stimulated Raman scattering in bulk diamond. © 2012 OSA.
Keywords: Random number generators; Vacuum fluctuations; Zero-point; Lasers; Random number generation; Stimulated Raman scattering

The spectroscopic orbits OF HD 23052 and HD 90512 - Scarfe, C.D.; Griffin, R.F. (Revista Mexicana de Astronomia y Astrofisica, 2012)
We present radial-velocity observations from DAO and Cambridge, from which we derive orbital elements. HD 23052 is a G-type main-sequence object which has been regarded as a solar analogue, in an orbit of period nearly three years. HD 90512 is a G-type giant in a nearly circular orbit with a period just over 100 days.

Rapid and simple preparation of a reagentless glucose electrochemical biosensor - Zheng, D.; Vashist, S.K.; Al-Rubeaan, K.; Luong, J.H.T.; Sheu, F.-S. (Analyst, 2012)
A rapid and simple procedure was developed for the preparation of a highly stable and leach-proof glucose oxidase (GOx)-bound glassy carbon electrode (GCE). Crosslinked GOx via glutaraldehyde was drop-cast on a KOH-pretreated GCE followed by drop-casting of 3-aminopropyltriethoxysilane (APTES) to form a stable bioactive layer. At -0.45 V, the biosensor exhibited a wide dynamic detection range of 0.5-48 mM for commercial glucose and 1.3-28.2 mM for Sugar-Chex blood glucose linearity standards. Several endogenous electroactive substances and drug metabolites commonly found in blood were tested and provoked no signal response. To our knowledge, the developed procedure is the most rapid method for preparing a glucose biosensor. The biosensor suffered no biofouling after 7 days of immersion in Sugar-Chex blood glucose. With excellent production reproducibility, GOx-bound electrodes stored dry at room temperature retained their initial activity after several weeks. © 2012 The Royal Society of Chemistry.
Keywords: carbon; glass; glucose; glucose oxidase; immobilized enzyme; article; Aspergillus niger; chemistry; electrochemistry; electrode; enzymology; genetic procedures; metabolism; methodology; time; Aspergillus niger; Biosensing Techniques; Carbon; Electrochemistry; Electrodes; Enzymes, Immobilized; Glass; Glucose; Glucose Oxidase; Time Factors

The velocity dispersion and mass function of the outer halo globular cluster Palomar 4 - Frank, M.J.; Hilker, M.; Baumgardt, H.; Côté, P.; Grebel, E.K.; Haghi, H.; Küpper, A.H.W.; Djorgovski, S.G. (Monthly Notices of the Royal Astronomical Society, 2012)
We obtained precise line-of-sight radial velocities of 23 member stars of the remote halo globular cluster Palomar4 (Pal4) using the High Resolution Echelle Spectrograph at the Keck I telescope. We also measured the mass function of the cluster down to a limiting magnitude of V~ 28mag using archival Hubble Space Telescope/Wide Field Planetary Camera 2 (WFPC2) imaging. We derived the cluster's surface brightness profile based on the WFPC2 data and on broad-band imaging with the Low Resolution Imaging Spectrometer at the Keck II telescope. We find a mean cluster velocity of 72.55 ± 0.22kms -1 and a velocity dispersion of 0.87 ± 0.18kms -1. The global mass function of the cluster, the mass range 0.55 ≤M≤ 0.85M ⊙, is shallower than a Kroupa mass function and the cluster is significantly depleted low-mass stars its centre compared to its outskirts. Since the relaxation time of Pal4 is of the order of a Hubble time, this points to primordial mass segregation this cluster. Extrapolating the measured mass function towards lower mass stars and including the contribution of compact remnants, we derive a total cluster mass of 29800M ⊙. For this mass, the measured velocity dispersion is consistent with the expectations of Newtonian dynamics and below the prediction of modified Newtonian dynamics (MOND). Pal4 adds to the growing body of evidence that the dynamics of star clusters the outer Galactic halo can hardly be explained by MOND. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Spatial control of electronic wave packets with attosecond precision - Zhang, Li; Xie, Xinhua; Roither, Stefan; Kartashov, Daniil; Schöffler, Markus; Shafir, Dror; Corkum, Paul; Baltuka, Andrius; Staudte, André; Kitzler, Markus (Journal of Physics: Conference Series, 2012)
Atomic single- and double- ionization using orthogonally polarized two-color laser fields was investigated via COLTRILMS technique. We prove that the electronic wave packets can be spatially controlled with attosecond precision.
Keywords: Attoseconds; Electronic wave packets; Spatial control; Two-color laser fields; Atoms; Wave packets

Magnetic Milky Way - Vallée, J.P. (EAS Publications Series, 2012)
Spiral arm shapes, locations, and velocities can be well determined, when model pitfalls are avoided (Vallée 2008a). Similarly, circularly orbiting gas and magnetic field lines can cross the spiral arms, when observational pitfalls are avoided (Vallée 2008b). © EAS, EDP Sciences 2012.
Keywords: Magnetic field line; Milky ways; Spiral arms; Publishing; Galaxies

The spectral energy distributions of white dwarfs in 47 Tucanae: The distance to the cluster - Woodley, K.A.; Goldsbury, R.; Kalirai, J.S.; Richer, H.B.; Tremblay, P.-E.; Anderson, J.; Bergeron, P.; Dotter, A.; Esteves, L.; Fahlman, G.G.; Hansen, B.M.S.; Heyl, J.; et al. (Astronomical Journal, 2012)
We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting the spectral energy distributions of its white dwarfs (WDs) to pure hydrogen atmosphere WD models. Our photometric data set is obtained from a 121-orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 arcmin 2 and extend over a radial range of 5-13.7 arcmin (6.5-17.9pc) within the globular cluster. Using a likelihood analysis, we obtain a best-fitting unreddened distance modulus of (m - M) o = 13.36 0.02 0.06 corresponding to a distance of 4.69 0.04 0.13kpc, where the first error is random and the second is systematic. We also search the WD photometry for infrared excess in the F160W filter, indicative of low-mass companions, and find no convincing cases within our sample. © 2012. The American Astronomical Society. All rights reserved.

Woofer-tweeter temporal correction split in atmospheric adaptive optics - Correia, C.; Véran, J.-P. (Optics Letters, 2012)
Many adaptive optics applications require wavefront correctors with a high stroke, and at a high bandwidth. Often, these two requirements cannot be met by a single wavefront corrector, and, instead, the combination of a lowbandwidth, high-stroke woofer and a high-bandwidth low-stroke tweeter is used in a so-called woofer-tweeter architecture. The optimal (minimum residual phase variance) way to split the correction between the woofer and the tweeter in the context of a linear-quadratic-Gaussian (LQG) controller has been addressed previously. However, the necessity to fold the temporal characteristics of the woofer and tweeter into the LQG controller significantly increases its complexity. In this Letter, this optimal strategy is compared to a simpler, ad hoc approach, which consists in optimizing the LQG controller as if it were controlling a high-bandwidth, high-stroke corrector and splitting the correction using first-order high- and low-pass temporal filters. In the case of tilt correction for NFIRAOS on the Thirty Meter Telescope, it is found that the ad hoc approach, which is already used or planned for several systems, holds the same overall correction performance compared to the optimal strategy. © 2012 Optical Society of America.
Keywords: Ad hoc approach; Correction performance; First-order; High bandwidth; Linear Quadratic Gaussian controllers; Low-bandwidth; Low-pass; LQG controller; Optics application; Optimal strategies; Residual phase; Temporal characteristics; Temporal filters; Thirty Meter Telescope; Tilt correction; Wavefront corrector; Low pass filters; Optimal systems; Optimization; Vision aids; Loudspeakers

Weak lensing measurement of galaxy clusters in the CFHTLS-wide survey - Shan, H.; Kneib, J.-P.; Tao, C.; Fan, Z.; Jauzac, M.; Limousin, M.; Massey, R.; Rhodes, J.; Thanjavur, K.; McCracken, H.J. (The Astrophysical Journal, 2012)
We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We study the 64 deg 2 W1 field, the largest of the CFHTLS-Wide survey fields, and present the largest contiguous weak lensing convergence "mass map" yet made. 2.66 million galaxy shapes are measured, using the Kaiser Squires and Broadhurst Method (KSB) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS. Our i′-band measurements are also consistent with an analysis of independent r′-band imaging. The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio ν > 3.5, consistent with predictions of a ΛCDM model. Of these peaks, 126 lie within 30 of a brightest central galaxy identified from multicolor optical imaging in an independent, red sequence survey. We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 deg 2 XMM-LSS survey. With photometric redshift estimates for the source galaxies, we use a tomographic lensing method to fit the redshift and mass of each convergence peak. Matching these to the optical observations, we confirm 85 groups/clusters with χ 2 reduced < 3.0, at a mean redshift 〈z c 〉 = 0.36 and velocity dispersion 〈σ c〉 = 658.8 km s -1. Future surveys, such as DES, LSST, KDUST, and EUCLID, will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models. © 2012 The American Astronomical Society. All rights reserved.

V881 Persei: a spotted, detached eclipsing binary - Nelson, R. H. (Information Bulletin on Variable Stars, 2012)

Performance of the vapor fed direct alcohol phosphoric acid fuel cell - Fan, S.; Wilkinson, D.P.; Wang, H. (Journal of the Electrochemical Society, 2012)
Due to improved kinetics and reduced CO poisoning effects, higher temperature alcohol fuel cells have been shown to have higher activity and increased performance output when compared to lower temperature alcohol fuel cells. In this work, the Direct Alcohol Phosphoric Acid Fuel Cell (DAPAFC) with methanol and ethanol as reactant fuels, and Pt and PtRu as catalysts is studied. The electrolyteseparator consists of Phosphoric Acid in a Silicon Carbide (SiC) matrix and replaces conventional polymer electrolyte or PBI membranes. Comprehensive studies are conducted to demonstrate the performance effects of the Gas Diffusion Layer (GDL), Micro-porous Layer (MPL) and such parameters as the stream pressures, higher temperature operation (120-180°C), and the thickness of the SiC separator, etc. Results show that at the same operating conditions, the cell performance is comparable to that of a vapour fed Nafion membrane based fuel cell. Structure improvement of the Phosphoric Acid Electrode Assembly (PAEA) and reactant vapor composition can significantly improve durability. This type of fuel cell demonstrates performance improvement and stability in a higher temperature range than is possible with the conventional PEMFC. © 2012 The Electrochemical Society.
Keywords: Cell performance; CO poisoning; Comprehensive studies; Conventional polymers; Electrode assemblies; Gas diffusion layers; Higher temperatures; Microporous layers; Nafion membrane; Operating condition; Performance effect; Performance improvements; Stream pressure; Structure improvement; Vapor composition; Electrolytes; Ethanol; Ethanol fuels; Methanol; Methanol fuels; Phosphoric acid; Phosphoric acid fuel cells (PAFC); Platinum; Proton exchange membrane fuel cells (PEMFC); Silicon carbide; Vapors

Wing-in-ground effect oscillating foil turbine from concept to innovation - Liu, P. (Proceedings of the IASTED Asian Conference on Power and Energy Systems, AsiaPES 2012, 2012)
This paper presents recent turbine research and development work on renewable energy technology development and innovation at the Institute for Ocean Technology, National Research Council Canada. The advantages of the oscillating foil turbines as opposed to horizontal axis turbines are identified and discussed. A wing-in-ground effect (WIG) application for oscillating turbine is introduced and the systematic development of a novel WIG oscillating foil turbine is briefly presented with conceptual design example. In-house simulation tool development, numerical and experimental capability development and testing facilities for turbine energy research are also briefly introduced.
Keywords: Energy research; Horizontal axis; National Research Council; Ocean technology; Oscillating foils; Panel methods; Renewable energy technologies; Research and development; Testing facility; Tool development; Wing in ground effect; Conceptual design; Innovation; Research; Turbines

Morphological zones in micro injection molding of poly(oxymethylene) - El Otmani, R.; Kamal, M.R.; Derdouri, A. (Annual Technical Conference - ANTEC, Conference Proceedings, 2012)
A Battenfeld System 50 micro injection molding machine was used to produce micro moldings of polyoxymethylene (POM), using a stepwise reduced thickness (0.8 mm, 0.45 mm, 0.2 mm) mold. Polarized light microscopy (PLM) was employed to investigate the morphology of the POM micro moldings. Morphology was examined in both the flow and transverse planes. A variety of morphological zones (oriented skin, shish kebab, cylindrulite, twisted lamellae, oblate, spherulite, etc.) are obtained, depending on the location. The morphology depends strongly on the thickness of the molding and thickness changes. The oriented skin layer tends to diminish away from the gate and near the vent end.
Keywords: Battenfeld; Micro molding; Micro-injection molding; Microstr8ucture; Poly(oxymethylene); Shish-kebabs; Skin layer; Skin-core; Transverse planes; Acetal resins; Morphology; Plastic products; Injection molding

Simulations of airfoil limit-cycle oscillations at transitional Reynolds numbers - Yuan, W.; Poirel, D.; Wang, B.; Khalid, M. (50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2012)
Structural response models addressing one-degree-of-freedom (1DOF) and two-degree-of-freedom (2DOF) aeroelastic oscillations were coupled with an in-house incompressible CFD code to perform large-eddy-based simulations (LES) for flows past rigid airfoils in free-to-rotate and free-to-rotate-and-heave conditions at low Reynolds numbers. As observed in experiments, the numerical simulations confirmed the presence of the self-sustained low-amplitude limit-cycle oscillations (LCOs) of the airfoils. It is understood that this behavior in the transitional Reynolds number regime results from the unsteadiness of the laminar boundary layer separation and its delayed recovery when compared to the corresponding static conditions. © 2012 by NRC and RMC.
Keywords: Aeroelastic oscillations; Boundary-layer separation; Incompressible CFD; Limit cycle oscillations; Low Reynolds number; Low-amplitude; Static conditions; Structural response; Two-degree-of-freedom; Aeroelasticity; Aerospace engineering; Computer simulation; Exhibitions; Reynolds number; Airfoils

Optofluidic Techniques for the Manipulation of Micro Particles: Principles and Applications to Bioanalyses - Guo, H.; Xiao, G.; Yao, J. (Photonic Sensing: Principles and Applications for Safety and Security Monitoring, 2012)

Tolerancing the fabrication errors of static optical elements for ELT-size wide-field AO systems - Véran, J.-P.; Pazder, J.; Herriot, G.; Andersen, D. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
Advanced wide-field AO systems, such as Multi-Conjugate AO (MCAO) systems often require many static optical elements (mirror and lenses) in addition to the active ones (deformable mirrors). These static elements induce additional wave-front errors due to random fabrication errors such as polishing errors. For ELT-size AO systems, these optical elements can be very large, and thus their cost and availability critically depends on how of much fabrication error can be tolerated. Therefore, a rigorous tolerance analysis is absolutely critical. Requirements can, in principle be relaxed, on account that fabrication errors with spatial scales larger than the inter-actuator spacing of the deformable mirrors (DMs) can be corrected. However, this process is significantly complicated by the fact that these optical elements are often conjugated far away from the DMs, and therefore DM correction cannot be achieved over a wide field of view (FOV). In this paper, we present our tolerance analysis in the context of NFIRAOS, the first-light MCAO system for the Thirty Meter Telescope. We start from two top-level error budgets: the "on-axis error budget, which specifies the acceptable residual wave-front error in the narrow 17''x17'' science FOV; and the "off-axis" error budget, which specifies the acceptable residual wave-front error at the edge of the 2' diameter technical FOV. The former directly relates to science image quality, whereas the latter directly relates to sky coverage. For different assumptions on the spatial power spectrum of the polishing errors, we derive the requirements on each optical element in NFIRAOS using a Monte-Carlo analysis of the predicted off-axis performance of the system with on axis AO correction. © 2012 SPIE.
Keywords: Deformable mirrors; Error budgets; Fabrication errors; Monte carlo analysis; Off-axis; Optical fabrication; Optical tolerancing; Sky coverage; Spatial scale; Thirty Meter Telescope; Tolerance analysis; Tolerancing; Wavefront errors; Wide field of view; Wide-field; Adaptive optics; Automobile manufacture; Budget control; Fabrication; Fits and tolerances; Polishing; Random errors; Wavefronts; Optics

New developments in nanoparticle-liquid crystal composites: From magic-sized semiconductor nanoclusters to alignment pattern formation via nanoparticle stenciling - Mirzaei, J.; Sawatzky, R.; Sharma, A.; Urbanski, M.; Yu, K.; Kitzerow, H.-S.; Hegmann, T. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
We here report on the alignment and electro-optic properties of nematic liquid crystals (LCs) either containing nanoscale particles as additives or featuring particles patterned on substrates. The investigated nematic LCs or LC dispersions are doped or in contact with magic-sized semiconductor CdSe nanocrystals (MSNCs) or silane- and alkylthiol monolayercapped gold nanoparticles. Three single-sized CdSe quantum dots capped with myristic acid exhibiting bright bandgap photoluminescence (PL) at λ max ∼ 463 nm were tested as additives. Two of the quantum dots only vary in the amount of defects as indicated by different bandgap and deep trap PL. The third MSNC sample is compositionally different, doped with Zn. These MSNCs with almost identical sizes were doped at different concentrations (1-5 wt%) into the nematic phase of the 2-phenylpyrimidine-based LC1. Only the Zn-doped MSNCs showed the formation of birefringent stripes surrounded by areas of homeotropic alignment between plain glass slides at all concentrations as observed for many other nanoparticle-doped nematic LCs reported earlier by our group. In polyimide-coated glass slides favoring planar orientation of the nematic director, planar alignment was observed. Similarly, siloxane-coated gold nanoparticle additives with narrow size distribution, but larger size, show homeotropic alignment between plain glass and planar alignment in rubbed polyimide-coated cells. Surprisingly then, we succeeded in creating alignment patterns using smaller, ∼2 nm alkylthiol-capped gold nanoparticles using a process called stenciling that allowed us to generate patterns of homeotropic alignment in a continuum of planar alignment of the nematic LC. Finally, electro-optic investigations on some of these samples revealed that only the Zn-doped magic-sized MSNCs significantly lower the dielectric anisotropy as well as the splay elastic constant of the nematic host, despite identical size and surface functionality of the three used MSNCs, which highlights the tremendous effect of the nanocrystal core composition on the electro-optic properties of the nematic host. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Keywords: liquid crystal alignment; nematic; Pattern formation; Quantum Dot; stenciling; Cadmium alloys; Cadmium compounds; Defects; Doping (additives); Electrooptical devices; Energy gap; Glass; Gold; Liquid crystals; Nanocrystals; Nanoparticles; Nematic liquid crystals; Polyimides; Semiconductor doping; Semiconductor quantum dots; Zinc; Alignment

The HIA MCAO laboratory bench - Véran, J.-P.; McWeigh, E.; Andersen, D.; Correia, C.; Herriot, G.; Pazder, J. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
This paper presents an update on the design and deployment of the HIA MCAO laboratory bench. This bench directly supports the development of NFIRAOS, the first light MCAO facility for the Thirty Meter Telescope. The bench implements a closed-loop MCAO system, with two magnetic DMs, four LGS Shack-Hartmann WFSs, two NGS T/T WFS, one NGS T/T/F WFS and one higher order Truth WFS, making up a scaled down version of NFIRAOS. The bench includes several artificial turbulence screens and reproduces realistic LGS spot elongations. It is driven by software in Matlab, frame-rates ranging from 1Hz to 15Hz. The goals of this bench are to anchor the NFIRAOS end-to-end simulation tools; to exercise real-time LGS tomographic AO in a variety of well controlled conditions, such as faint and poorly corrected NGSs, non-uniformities in the sodium layer and field dependant Non-Common-Path Aberrations (NCPAs); develop and demonstrate calibration procedures, such as PSF reconstruction and tomographic reconstruction and correction of field dependant NCPAs; and to validate optimization methods that operate at 10+ second time scales, which is not tractable in a numerical simulation, such as matched filter update and Cn2 estimation using a SLODAR method. © 2012 SPIE.
Keywords: Calibration procedure; Closed-loop; Controlled conditions; End-to-end simulation; Laboratory experiments; Multiconjugate adaptive optics; Non-uniformities; Optimization method; Scaled-down versions; Second time scale; Shack-Hartmann; Sodium layer; Thirty Meter Telescope; Tomographic; Tomographic reconstruction; MATLAB; Sodium; Tomography; Adaptive optics

Preface - Xiao, G.; Bock, W.J. (Photonic Sensing: Principles and Applications for Safety and Security Monitoring, 2012)

The optical alignment of the Gemini planet imager adaptive optics bench - Pazder, J.; Bauman, B.; Dillon, D.; Fletcher, M.; Lacoursièred, J.; Reshetova, V. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
The Gemini Planet Imager (GPI) is a facility instrument under construction for the 8-m Gemini South telescope. This paper describes the methods used for optical alignment of the adaptive optics (AO) bench. The optical alignment of the off-axis paraboloid mirrors was done using a pre-alignment method utilizing a HeNe laser and alignment telescopes followed by a fine-tuning using a Shack-Hartmann wavefront sensor and a shear plate. A FARO arm measuring system was used to place the fiducials for the alignment. Using these methods the AO bench was aligned to 13nm RMS of wavefront error. © 2012 SPIE.
Keywords: Astronomical instrumentation; FaroArm; Gemini telescopes; Off-axis; Optical alignments; Shack-Hartmann wavefront sensors; Helium neon lasers; Mirrors; Optical telescopes; Telescopes; Wavefronts; Alignment

GRACES, the gemini remote access CFHT ESPaDOnS spectrograph; initial design and testing - Tollestrup, E.V.; Pazder, J.; Barrick, G.; Martioli, E.; Schiavon, R.P.; Anthony, A.; Halman, M.; Veillet, C. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
The Gemini Remote Access CFHT ESPaDOnS Spectrograph (GRACES) is an innovative instrumentation experiment that will demonstrate if ESPaDOnS, a bench-mounted high-resolution optical spectrograph at CFHT, can be fed by a 270-m long fiber from the Gemini-North telescope with low enough losses to remain competitive with conventional spectrographs on other 8 to 10-m telescopes. Detailed simulations have shown that GRACES should be more sensitive than the HIRES spectrograph at Keck Observatory at wavelengths longer than about 600-700 nm. This result is possible by using FPB-type of optical fibers made by Polymicro Technologies and by keeping the critical focal ratio degradation (FRD) losses to less than 10%. Laboratory tests on these FPB optical fibers are underway and show that for 36-m lengths that the FRD losses are as low as 0.8% with a repeatability of 1%. Tests are currently underway on 280-m lengths. © 2012 SPIE.
Keywords: Focal ratio degradation; High resolution; Initial design; Keck observatory; Laboratory test; Long fiber; Optical spectrograph; Remote access; Transmission loss; Astronomy; Optical fibers; Optical telescopes; Telescopes; Spectrographs

Vibrations in AO control: A short analysis of on-sky data around the world - Kulcsár, C.; Sivo, G.; Raynaud, H.-F.; Neichel, B.; Rigaut, F.; Christou, J.; Guesalaga, A.; Correia, C.; Véran, J.-P.; Gendron, É.; Vidal, F.; Rousset, G.; et al. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
We present in this paper an analysis of several tip-tilt on-sky data registered on adaptive optics systems installed on different telescopes (Gemini South, William Herschel Telescope, Large Binocular Telescope, Very Large Telescope, Subaru). Vibration peaks can be detected, and it is shown that their presence and location may vary, and that their origin is not always easy to determine. Mechanical solution that have been realized to mitigate vibrations are presented. Nevertheless, residual vibrations may still affect the instruments' performance, ranging from narrow high frequency vibration peaks to wide low frequency windshake-type perturbations. Power Spectral Densities (PSDs) of on-sky data are presented to evidence these features. When possible, indications are given regarding the gain in performance that could be achieved with adequate controllers accounting for vibration mitigation. Two examples of controller identification and design illustrate their ability to compensate for various types of disturbances (turbulence, windshake, vibration peaks, ...), showing a significant gain in performance. © 2012 SPIE.
Keywords: Adaptive optics systems; Disturbance identification; H2 control; High frequency vibration; Large binocular telescope; LQG control; Residual vibrations; Tip-tilt; Very large telescope; Vibration mitigation; Vibration peak; William herschel telescopes; Adaptive optics; Atmospheric turbulence; Controllers; Identification (control systems); Optical telescopes; Power spectral density; Spectrum analysis; Telescopes; Vibrations (mechanical); Discrete time control systems

Improved stress intensity factor solution for cracks in panels with arbitrarily located stringers - Bombardier, Yan; Liao, Min; Renaud, Guillaume (53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2012)
This paper presents a stress intensity factor solution for cracks located in panels reinforced with arbitrarily located stringers. The new solution was developed by modifying the constituting equations of a solution for symmetrically and periodically spaced stringers with riveted rigid fasteners. The new solution supports arbitrary stringer locations with respect to the crack location, includes the capability to model compliant fasteners, improves the accuracy of the equivalent stringer compliance by considering Poisson's effect, and allows the fasteners to be arbitrarily located within each stringer. The stress intensity factors calculated using the new closed-form solution were compared to linear static finite element analysis results and very good agreement was obtained for the tested cases. Through two examples for the CC-130 aircraft, it was shown that the closed-form solution developed for a center crack in an infinite sheet could also be used to model an edge crack growing in a relatively large panel.
Keywords: A-center; Closed form solutions; Crack location; Edge cracks; Linear statics; Poisson's effects; Cracks; Locks (fasteners); Stress intensity factors; Structural dynamics; Stringers

Identification of aeroelastic parameters for cormorant tail rotor structures based on vibration measurement in the stationary frame - Chen, Y.; Wickramasinghe, V.; Zimcik, D.G. (Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2012)
The teetering tail rotor of the Canadian CH-149 Cormorant helicopter fleet experienced limit cycle oscillation (LCO) phenomenon in certain adverse flight conditions in which the transient high amplitude vibration resulted in significant increase of dynamic strain to the tail rotor structures. This could contribute to pre-mature damage of the composite half hub among other causes. Therefore it is required to evaluate the integrity of the tail rotor structure using realistic aeroelastic parameters of the tail rotor in the rotating frame. This paper presents a novel center frequency scaling factor theory and related parameter identification methodologies in order to estimate and track the variation of the critical aeroelastic parameters in the rotating frame during LCO events based on vibration information measured exclusively in the stationary frame. This information would enable update of the tail rotor stability diagram in order to confidently evaluate the impact of LCO events to the structural integrity of the Cormorant tail rotor structures. Based on the developed procedures and identified parameters, recommendations are provided for data analysis and techniques to improve the fidelity of results from aeroelastic simulation analysis for the Cormorant tail rotor structures without the need to install sensors in the rotating frame. © 2012 AIAA.
Keywords: Aero-elastic simulations; Center frequency; Flight conditions; Helicopter fleets; High-amplitude vibrations; Identified parameter; Limit Cycle Oscillation (LCO); Stationary frame; Aeroelasticity; Structural dynamics; Helicopter rotors

Microfluidic control of adipose-derived stem cell growth and positioning - Lin, F.; Wadhawan, N.; Kalkat, H.; Ma, X.; Gajjeraman, S.; Nandagopal, S.; Hao, N.; Deng, J.; Xiang, B.; Zhang, M.; Tian, G. (Nanotechnology 2012: Technical Proceedings of the 2012 NSTI Nanotechnology Conference and Expo. Volume 2: Electronics, devices, fabrication, MEMS, fluidics and computational., 2012)
Microfluidic devices provide powerful new tools for quantitative stem cell research owing to its advantages in cellular microenvironmental control and experiment throughput over conventional methods. Particularly, microfluidics is playing a growing role in studying stem cell growth, differentiation and trafficking mediated by chemical factors such as different growth and differentiation factors and physical parameters such as direct current electric fields (dcEF). In the present study, we focused on adipose-derived stem cells (ADSCs) and we quantitatively characterized ADSCs growth and positioning mediated by epidermal growth factor (EGF) and dcEF using microfluidic devices. Our results revealed mat ADSCs preferentially grow toward the EGF gradient. In addition, we showed that ADSCs tend to orient perpendicularly to the dcEF. These microfluidics-based results demonstrated the interesting roles of EGF and dcEF in controlling ADSCs growth and trafficking.
Keywords: Adipose derived stem cells; Cell migration; Chemical factors; Conventional methods; Direct current electric fields; EGF; Epidermal growth factors; Micro-fluidic devices; Microfluidic control; Physical parameters; Stem cell research; Cell growth; Electric fields; Exhibitions; Fabrication; Fluidic devices; Growth kinetics; Nanotechnology; Stem cells; Microfluidics

Dynamical thermal effects in InGaAsP microtubes at telecom wavelengths - Tian, Z.; Bianucci, P.; Roche, P.J.R.; Dastjerdi, M.H.T.; Mi, Z.; Poole, P.J.; Kirk, A.G.; Plant, D.V. (Optics Letters, 2012)
We report on the observation of a dynamical thermal effect in InGaAsP microtubes at telecom wavelengths. The microtubes are fabricated by releasing a strained semiconductor bilayer and are picked up by abruptly tapered optical fibers for subsequent coupling with adiabatically tapered optical fibers. As a result of absorption by InAs quantum dots embedded in the tube structure, these microtubes show dynamical thermal effects at wavelengths around 1525 nm and 1578 nm, while they are passive at longer wavelengths near 1634 nm. The photon absorption induced thermal effect is visualized by generating a pair of microbottles. The dynamical thermal effect can be avoided or exploited for passive or active applications by utilizing appropriate resonance wavelengths. © 2012 Optical Society of America.
Keywords: Active application; Bi-layer; InAs quantum dots; Induced thermal effects; InGaAsP; Micro-tubes; Photon absorptions; Resonance wavelengths; Tapered optical fibers; Telecom wavelengths; Tube structures; Indium arsenide; Optical fiber coupling; Optical fiber fabrication; Wavelength

Carrier dynamics in type-II GaAsSb/GaAs quantum wells - Baranowski, M.; Syperek, M.; Kudrawiec, R.; Misiewicz, J.; Gupta, J.A.; Wu, X.; Wang, R. (Journal of Physics Condensed Matter, 2012)
Time-resolved photoluminescence (PL) characteristics of type-II GaAsSb/GaAs quantum wells are presented. The PL kinetics are determined by the dynamic band bending effect and the distribution of localized centers below the quantum well band gap. The dynamic band bending results from the spatially separated electron and hole distribution functions evolving in time. It strongly depends on the optical pump power density and causes temporal renormalization of the quantum well ground-state energy occurring a few nanoseconds after the optical pulse excitation. Moreover, it alters the optical transition oscillator strength. The measured PL lifetime is 4.5ns. We point out the critical role of the charge transfer processes between the quantum well and localized centers, which accelerate the quantum well photoluminescence decay at low temperature. However, at elevated temperatures the thermally activated back transfer process slows down the quantum well photoluminescence kinetics. A three-level rate equation model is proposed to explain these observations.

Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins - Liao, D.; Pajak, A.; Karcz, S.R.; Patrick Chapman, B.; Sharpe, A.G.; Austin, R.S.; Datla, R.; Dhaubhadel, S.; Marsolais, F. (Journal of Experimental Botany, 2012)
The lack of phaseolin and phytohaemagglutinin in common bean (dry bean, Phaseolus vulgaris) is associated with an increase in total cysteine and methionine concentrations by 70% and 10%, respectively, mainly at the expense of an abundant non-protein amino acid, S-methyl-cysteine. Transcripts were profiled between two genetically related lines differing for this trait at four stages of seed development using a high density microarray designed for common bean. Transcripts of multiple sulphur-rich proteins were elevated, several previously identified by proteomics, including legumin, basic 7S globulin, albumin-2, defensin, albumin-1, the Bowman-Birk type proteinase inhibitor, the double-headed trypsin inhibitor, and the Kunitz trypsin inhibitor. A co-ordinated regulation of transcripts coding for sulphate transporters, sulphate assimilatory enzymes, serine acetyltransferases, cystathionine β-lyase, homocysteine S-methyltransferase and methionine gamma-lyase was associated with changes in cysteine and methionine concentrations. Differential gene expression of sulphur-rich proteins preceded that of sulphur metabolic enzymes, suggesting a regulation by demand from the protein sink. Up-regulation of SERAT1;1 and-1;2 expression revealed an activation of cytosolic O-acetylserine biosynthesis. Down-regulation of SERAT2;1 suggested that cysteine and S-methyl-cysteine biosynthesis may be spatially separated in different subcellular compartments. Analysis of free amino acid profiles indicated that enhanced cysteine biosynthesis was correlated with a depletion of O-acetylserine. These results contribute to our understanding of the regulation of sulphur metabolism in developing seed in response to a change in the composition of endogenous proteins. © 2012 The Author.
Keywords: amino acid; cysteine; drug derivative; lectin; messenger RNA; methionine; o acetylserine; O-acetylserine; phaseolin protein, Phaseolus vulgaris; plant RNA; s methylcysteine; S-methylcysteine; seed storage protein; serine; sulfur; vegetable protein; article; cluster analysis; DNA microarray; gene expression profiling; gene expression regulation; genetics; growth, development and aging; metabolism; Phaseolus; plant seed; Amino Acids; Cluster Analysis; Cysteine; Gene Expression Profiling; Gene Expression Regulation, Plant; Lectins; Methionine; Oligonucleotide Array Sequence Analysis; Phaseolus; Plant Proteins; RNA, Messenger; RNA, Plant; Seed Storage Proteins; Seeds; Serine; Sulfur; Phaseolus vulgaris

Evolution of microstructure, microtexture and mechanical properties of linear friction welded IMI 834 - Dalgaard, E.; Wanjara, P.; Gholipour, J.; Jonas, J.J. (Canadian Metallurgical Quarterly, 2012)
Titanium alloys have been of great interest in the aerospace industry for many years. Recently, linear friction welding has also been making strides in conquering a part of the aerospace manufacturing market, with its clear advantages over fusion welding and mechanical fastening methods for integrated bladed rotors. High tech near-α alloy IMI834 (Ti-5·8Al-4Sn- 3·5Zr-0·7Nb- 0·5Mo-0·35Si) was designed to have improved creep resistance and retains its mechanical properties at temperatures up to 600°C. It balances creep resistance and fatigue strength, making it an excellent material for compressor discs and blades. IMI834 with an initial bimodal αzb microstructure was welded using varying axial pressures during welding and then characterised using both microstructural examination and mechanical testing. Electron backscatter diffraction (EBSD) was used to characterise the texture and phase fraction of the welded IMI834 samples in the weld zone (WZ) and thermomechanically affected zones. The EBSD analysis revealed fine recrystallised grains at the weld centres. The microhardness evaluation of the weldments showed that the recrystallised WZ was slightly harder than the parent material (PM). The local and global tensile properties of the welds, investigated using a tensile testing rig with integrated digital image correlation, revealed higher strength in the WZ and failure in the PM. © 2012 Crown in Right of Canada.
Keywords: Aerospace; Aerospace manufacturing; Axial pressures; Bladed rotors; Compressor discs; Digital image correlations; EBSD analysis; Electron back scatter diffraction; Fatigue strength; Fusion welding; High tech; IMI834; Linear friction; Linear friction welding; Mechanical fastening; Micro-texture; Microstructural examination; Parent materials; Phase fractions; Thermomechanically affected zones; Weld zone; Weldments; Aerospace industry; Friction welding; Microstructural evolution; Molybdenum; Niobium; Recrystallization (metallurgy); Tensile testing; Textures; Tin; Titanium alloys; Welding; Welds; Zirconium; Creep resistance

Effect of circular tool path on cutting force profile in micro-end-milling - Banerjee, A.; Bordatchev, E.V. (Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2012)
Micro-end-milling requires high spindle rotational speed to achieve effective material removal. This results in the requirement of tool stoppage or slowdown during a micro-end-milling operation, a deterrent to productivity and to part acceptability. A circular tool path geometry can avoid discontinuities in the tool movements leading to a more consistent and smooth material removal. However, optimal process planning for such a tool path will require detailed understanding of the chip-formation mechanism in circular end-milling. The cut geometry during end-milling along a circular tool path is often approximated as that of a linear tool path. Although this assumption works well for circular tool paths with higher tool path radius, this is not the case for lower tool path radius often used in micro-milling. In this study, the effect of circular tool path on the cutting force for varying tool path rotation angle, tool path radius, and feed rate is experimentally investigated. Systematic signal processing was applied to analyse the measured cutting force signal along linear and several circular tool paths. Qualitative as well as quantitative differences were observed in the cutting force profiles obtained using different tool path radii, tool path orientations, and feed rates. This implies the need for an improved chip thickness formulation dedicated to micro-end-milling with circular tool path rather than approximating it with formulations derived for linear tool path. © Authors 2011.
Keywords: Chip thickness; Cutting force measurements; Cutting force signals; Cutting forces; End-milling; Feed-rates; Material removal; Micro milling; Micro-end-milling; Rotation angles; Rotational speed; Toolpaths; Cutting; Micromachining; Milling (machining); Signal processing; Scanning

A Novel Role for the Transcription Factor Cwt1p as a Negative Regulator of Nitrosative Stress in Candida albicans - Sellam, A.; Tebbji, F.; Whiteway, M.; Nantel, A. (PLoS ONE, 2012)
The ability of Candida albicans to survive in the presence of nitrosative stress during the initial contact with the host immune system is crucial for its ability to colonize mammalian hosts. Thus, this fungus must activate robust mechanisms to neutralize and repair nitrosative-induced damage. Until now, very little was known regarding the regulatory circuits associated with reactive nitrogen species detoxification in fungi. To gain insight into the transcriptional regulatory networks controlling nitrosative stress response (NRS) in C. albicans a compilation of transcriptional regulator-defective mutants were screened. This led to the identification of Cwt1p as a negative regulator of NSR. By combining genome-wide location and expression analyses, we have characterized the Cwt1p regulon and demonstrated that Cwt1p is directly required for proper repression of the flavohemoglobin Yhb1p, a key NO-detoxification enzyme. Furthermore, Cwt1p operates both by activating and repressing genes of specific functions solicited upon NSR. Additionally, we used Gene Set Enrichment Analysis to reinvestigate the C. albicans NSR-transcriptome and demonstrate a significant similarity with the transcriptional profiles of C. albicans interacting with phagocytic host-cells. In summary, we have characterized a novel negative regulator of NSR and bring new insights into the transcriptional regulatory network governing fungal NSR. © 2012 Sellam et al.
Keywords: transcription factor; transcription factor Cwt1p; unclassified drug; article; Candida albicans; controlled study; fungal genome; fungus mutant; gene activation; gene expression; gene expression profiling; gene location; gene regulatory network; gene repression; genetic analysis; host cell; nitrosative stress; nonhuman; phagocyte; regulon; transcription regulation; Candida albicans; Fungal Proteins; Gene Expression Profiling; Gene Expression Regulation, Fungal; Genomics; Oxygenases; Promoter Regions, Genetic; Reactive Nitrogen Species; Stress, Physiological; Transcription Factors; Transcription, Genetic; Candida albicans; Fungi; Mammalia

Flight test evaluation of a prototype optical instrument for airborne sense-and-avoid applications - Minwalla, C.; Thomas, P.; Ellis, K.; Hornsey, R.; Jennings, S. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
A prototype, wide-field, optical sense-and-avoid instrument was constructed from low-cost commercial off-the-shelf components, and configured as a network of smart camera nodes. To detect small, general-aviation aircraft in a timely manner, such a sensor must detect targets at a range of 5-10 km at an update rate of a few Hz. This paper evaluates the flight test performance of the "DragonflEYE" sensor as installed on a Bell 205 helicopter. Both the Bell 205 and the Bell 206 (intruder aircraft) were fully instrumented to record position and orientation. Emphasis was given to the critical case of head-on collisions at typical general aviation altitudes and airspeeds. Imagery from the DragonflEYE was stored for the offline assessment of performance. Methodologies for assessing the key figures of merit, such as the signal-to-noise ratio, the range at first detection (R0) and angular target size were developed. Preliminary analysis indicated an airborne detection range of 6:7 km under typical visual meteorological conditions, which significantly exceeded typical visual acquisition ranges under the same conditions. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Keywords: COTS; Flight test; MTF; sense-and-avoid; Smart nodes; SNR; UAS; Accident prevention; Aircraft accidents; Bells; Helicopters; Sensors; Instruments

Preface - Liu, R.; Zhang, L.; Sun, X.; Liu, H.; Zhang, J. (Electrochemical Technologies for Energy Storage and Conversion: volume 1 & 2, 2012)

Advanced control of low order modes in laser guide star multi-conjugate adaptive optics systems - Correia, C.; Véran, J.-P.; Herriot, G.; Ellerbroek, B.; Wang, L.; Gilles, L. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
Laser-guide-star-based multi-conjugate adaptive optics (MCAO) systems require natural guide-stars to measure tilt and tilt-anisoplanatism modes. This paper focuses on the parameter optimisation of sub-optimal integrator-based controllers using a single and a double integrator (baseline option) to drive the low-order loop of NFIRAOS, the 1st light MCAO system for the Thirty-Meter Telescope. The minimum-variance (MV) controller is outlined, against which integrators are compared. Simulations using ∼500 asterisms considered in sky-coverage simulations for the TMT show that the double integrator gives competitive results thoughout the range of asterisms and magnitudes considered. It is shown that using an optimal modal gain integrator can further improve the performance with respect to using an averaged gain for all of part of the modes. However, it is outperformed by the MV controller, in particular for asterisms with relatively dim stars (lower bound is magnitude 22 in H-band) requiring low temporal frame-rates (as low as 16Hz) to integrate more flux. Over all the cases tested, an average of ∼100 nm rms (23 nm rms median) improvement can be achieved with the MV. The MV further increases by 15% the probability of working below the 50th-percentile residual of the double integrator. © 2012 SPIE.
Keywords: Advanced control; Anisoplanatism; Atmospheric tomography; Double integrator; Kalman-filtering; Laser guide star; Low order; Lower bounds; Modal gain; Multi-conjugate adaptive optics systems; Parameter optimisation; Thirty Meter Telescope; Lasers; Mineralogy; Optimization; Stars

Evaluation of sealed joint performance for the selection of sealants suitable for use in autoclaved lightweight concrete panels - Miyauchi, H.; Lacasse, M. A.; Murata, S.; Enomoto, N.; Tanaka, K. (Journal of ASTM International, 2012)
The strength of autoclaved lightweight concrete (ALC) is evidently lower than that of normal concrete. Therefore, when movement occurs at a sealed joint between ALC panels, the sealant is required to deform and remain intact without damaging the ALC substrate. However, there is currently not sufficient information to permit evaluation of the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out in order to obtain an index that could be used to select the modulus of a sealant that can be expected to provide long-term performance when applied to an ALC substrate. To develop this index, an initial study was carried out in order to clarify actual joint movement between ALC panels of buildings; the expansion and contraction at the joint were measured, and shear joint movement was calculated based on the expected story-to-story drift of an external wall due to earthquake loads. Thereafter, in a subsequent stage of the study, five types of two-component polyurethane sealant products, of different elastic modulus, were subjected to tensile and shear tests from which the relationship between stress and the type of joint fracture was determined. The results from these tests revealed that when the stress is greater than 0.6 to 0.7 N/mm 2, the ALC substrate is more easily fractured than the sealant. In a final stage of the study, the cyclic fatigue resistance of the same two-component sealants was evaluated using tensile and shear fatigue tests. Results from the fatigue tests indicated that the high modulus sealants lost adhesion from the ALC substrate at an early stage in the test. As well, the fatigue resistance of test specimens with joints having three-sided adhesion was lower than that of specimens having normally configured joints with adhesion on two sides of the sealant. Therefore, on the basis of results derived from all the studies, it was determined that a suitable sealant for use on ALC substrates is a sealant having a low modulus that is applied in the normal fashion as a two-sided joint
Keywords: Cyclic fatigue; Earthquake load; Expansion and contraction; External walls; Fatigue tests; Joint fracture; Joint movement; Joint performance; Lightweight concrete panel; Long term performance; Low modulus; Modulus; Normal concretes; Sealant products; Shear joints; Shear tests; Static and dynamic; Test specimens; Two-component; Wall panels; Adhesion; Concrete slabs; Fatigue of materials; Fatigue testing; Fracture; Precast concrete; Substrates; Testing; Walls (structural partitions); Sealants

Ecotoxicity of canola and tallow biodiesel blends to selected soil organisms - Rocheleau, S.; Sarrazin, M.; Dodard, S.; Beaulieu, C.; Hawari, J.; Hollebone, B.P.; Yang, Z.; Sunahara., G. (Proceedings of the 35th AMOP Technical Seminar on Environmental Contamination and Response, 2012)
In view of depleting fossil fuel resources and environmental concern, biodiesel couldpotentially replace petroleum-derived diesel. Aquatic toxicity of diesel and biodiesel has beenextensively studied over the past decades but little is still known about their toxicity in soilenvironment. The scope of this study was to evaluate the environmental impact of biodiesel,biodiesel blends and petroleum diesel in soil using direct contact toxicity assays. The selectedbiodiesels included canola-source biodiesel (B100 and B20). and tallow-source biodiesel (B100and B20), which were compared to petroleum ultra-low-sulfur based diesel (ULSD). Selectedstandard terrestrial toxicity tests included ryegrass Lolium perenne seedling emergence andgrowth, earthworm Eisenia fetida survival, and soil microbial dehydrogenase activity. Soilcharacterization included the quantification of total extractable materials (corresponding to the n-alkane range of C10-C34). Preliminary results indicate that: 1) canola and tallow B20 biodieselblends were less toxic to earthworm than ULSD; 2) canola and tallow B20 blends had similartoxic effects to ryegrass as ULSD; and 3) petroleum ULSD inhibited the DHA activity at allconcentrations tested, and B20 canola biodiesel had a deleterious effect on the DHA activity atthe lowest nominal loadings tested (1 and 10 ml/kg dry soil). Therefore, this study providesuseful toxicological data for the evaluation of potential adverse impact of biodiesel in theenvironment, such as an accidental release or spill. This project was funded by EnvironmentCanada and Natural Resources Canada and is part of the Advanced Fuels and Technologies forEmissions Reduction (AFTER) Program for energy research and development (PERD).
Keywords: Accidental release; Advanced fuels; Aquatic toxicity; Biodiesel blends; Dehydrogenase activity; Deleterious effects; Direct contact; Dry soil; Earthworm Eisenia fetida; Ecotoxicity; Energy research and development; Environmental concerns; Fossil fuel resources; Lolium perenne; n-Alkanes; Petroleum diesel; Seedling emergence; Soil organisms; Toxicity assays; Toxicity test; Contamination; Fossil fuels; Paraffins; Soils; Sulfur; Technical presentations; Toxicity; Biodiesel

Spin textures in strongly coupled electron spin and magnetic or nuclear spin systems in quantum dots - Abolfath, R.M.; Korkusinski, M.; Brabec, T.; Hawrylak, P. (Physical Review Letters, 2012)
Controlling electron spins strongly coupled to magnetic and nuclear spins in solid state systems is an important challenge in the field of spintronics and quantum computation. We show here that electron droplets with no net spin in semiconductor quantum dots strongly coupled with magnetic ion or nuclear spin systems break down at low temperature and form a nontrivial antiferromagnetic spatially ordered spin texture of magnetopolarons. The spatially ordered combined electron-magnetic ion spin texture, associated with spontaneous symmetry breaking in the parity of electronic charge and spin densities and magnetization of magnetic ions, emerges from an ab initio density functional approach to the electronic system coupled with mean-field approximation for the magnetic or nuclear spin system. The predicted phase diagram determines the critical temperature as a function of coupling strength and identifies possible phases of the strongly coupled spin system. The prediction may arrest fluctuations in the spin system and open the way to control, manipulate, and prepare magnetic and nuclear spin ensembles in semiconductor nanostructures. © 2012 American Physical Society.
Keywords: Ab initio; Antiferromagnetics; Break down; Coupling strengths; Critical temperatures; Density-functional approach; Electron spins; Electronic charges; Electronic systems; Low temperatures; Magnetic ions; Magnetopolarons; Mean field approximation; Nuclear spin system; Nuclear spins; Semiconductor nanostructures; Solid-state system; Spin densities; Spin systems; Spin textures; Spontaneous symmetry breaking; Strongly coupled spin system; Antiferromagnetism; Computational linguistics; Electrospinning; Ions; Magnetic moments; Phase diagrams; Quantum computers; Semiconductor quantum dots; Temperature; Textures; Spin dynamics

Miniaturized Fiber Bragg Grating Sensor Systems for Potential Air Vehicle Structural Health Monitoring Applications - Guo, H.; Xiao, G.; Mrad, N.; Yao, J. (Photonic Sensing: Principles and Applications for Safety and Security Monitoring, 2012)

Effect of the nonresonant background medium in CARS and SRS microscopy image formation - Popov, K.I.; Pegoraro, A.F.; Stolow, A.; Ramunno, L. (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
Using mathematical modeling and numerical simulations, we examine the image formation in CARS, FM-CARS, AM-SRS and FM-SRS nonlinear Raman-based modalities. We find that in the presence of a nonresonant spatially-nonuniform background medium, only the FM-SRS modality can be considered to be both background and distortion free. © 2012 OSA.
Keywords: Background medium; Microscopy images; Nonresonant; Lasers; Coherent scattering

Ion channel screening: Advances in technologies and analysis - Martina, M. (Frontiers in Pharmacology, 2012)
Keywords: bungarotoxin receptor; G protein coupled inwardly rectifying potassium channel; G protein coupled receptor; ion channel; potassium channel blocking agent; potassium channel HERG; unclassified drug; vu 573; article; cell communication; degenerative disease; drug cost; drug research; drug safety; drug screening; drug targeting; heart muscle conduction system; heterologous expression; high throughput screening; human; laboratory automation; nerve cell membrane potential; nerve cell network; patch clamp; protein analysis

A limited role of p53 on the ability of a hexane fraction of American ginseng to suppress mouse colitis - Poudyal, D.; Cui, X.; Mai Le, P.; Davis, T.; Hofseth, A.B.; Jin, Y.; Chumanevich, A.A.; Wargovich, M.J.; Nagarkatti, M.; Nagarkatti, P.S.; Windust, A.; Hofseth, L.J. (Journal of Biomedicine and Biotechnology, 2012)
Ulcerative colitis (UC) is debilitating and carries a high colon cancer risk. Apoptosis of inflammatory cells is a key mechanism regulating UC. We have recently shown that American ginseng (AG), and to a greater extent, a Hexane fraction of AG (HAG) can cause apoptosis and suppress mouse colitis through a p53-mediated mechanism. Here, we tested the hypothesis that HAG suppresses colitis through a p53 mechanism. We found only a limited impact of p53 in the ability of HAG to induce inflammatory cell apoptosis and suppress mouse colitis in vitro and in vivo. Finally, we asked whether HAG could cause cell cycle arrest of HCT116 colon cancer cells in vitro. Interestingly, HAG caused a G1 arrest of such cells independent of p53 status. Findings are significant because HAG suppresses colitis and associated colon cancer, and mutation in p53 is observed in most colitis-driven colon cancers. Therefore, HAG might be very effective in targeting the inflammatory cells and cancer cells since it induces apoptosis of inflammatory cells and cell cycle arrest in both p53(-/-) and WT p53 colon cancer cells. © Copyright 2012 Deepak Poudyal et al.
Keywords: ginseng extract; protein p53; hexane; plant extract; protein p53; American ginseng; animal experiment; animal model; animal tissue; antiinflammatory activity; apoptosis; article; cell cycle arrest; colon cancer; controlled study; gene mutation; ginseng; human; human cell; in vitro study; in vivo study; mouse; nonhuman; ulcerative colitis; animal; cell line; chemistry; colitis; colon; disease model; drug effect; fractionation; G1 phase cell cycle checkpoint; metabolism; nick end labeling; Panax; pathology; phytotherapy; Animals; Apoptosis; Cell Line; Chemical Fractionation; Colitis; Colon; Disease Models, Animal; G1 Phase Cell Cycle Checkpoints; Hexanes; Humans; In Situ Nick-End Labeling; Mice; Panax; Phytotherapy; Plant Extracts; Tumor Suppressor Protein p53

Chemical microanalysis with cavity-enhanced optical waveguide devices - Loock, H.-P.; Barnes, J.A.; Bescherer, K.; Brzezinski, A.; Gagliardi, G.; Gribble, A.; Janz, S.; Ma, R.; Munzke, D.; Ongo, G.; Saunders, J.; Waechter, H.; et al. (SPIE - International Society for Optical Engineering. Proceedings, 2012)
Three examples of cavity-enhanced measurements of refractive index and optical absorption are discussed. Using microphotonic silicon-on-insulator ring-resonators we determine the concentration of cyclohexane and m-xylene at detection levels of 300-3000 ppm. The gases are first absorbed into a siloxane polymer and its refractive index change is detected by a characteristic wavelength shift of the cavity resonance. In a second device phase-shift cavity ring-down spectroscopy is applied to simultaneously measure the optical absorption at two wavelengths of either a dye, nucleic acids or a pharmaceutical component. Multiplexing the ring-down measurement permits dual wavelength absorption spectroscopy without the use of a dispersion element. Finally, a combination of resonance wavelength measurements and cavity ring-down spectroscopy is used to simultaneously determine the change in refractive index and the absorption induced by adsorption of ethylene diamine on a 300 μm silica sphere. A whispering gallery mode of the microsphere resonator is excited with intensity modulated light and the intensity and AM modulation phase of the Rayleigh backscattered light is measured. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Keywords: Cavity enhanced spectroscopy; cavity ring-down; microphotonics; microsphere resonators; Silicon-on-insulators; waveguide cavity; Adsorption; Ethylene; Light absorption; Microspheres; Nucleic acids; Resonators; Silica; Spectroscopy; Spheres; Wavelength; Refractive index

Cyclic dwell fatigue behaviour of single crystal Ni-base superalloys with/without rhenium - Yandt, S.; Wu, X.-J.; Tsuno, N.; Sato, A. (Proceedings of the International Symposium on Superalloys, 2012)
In this study, compressive dwell (C-D) and no-dwell (N-D) low-cycle fatigue (LCF) behaviours of several single crystal Ni-base superalloys, including CMSX-4, LSC-11 and LSC-15, were studied under strain-controlled zero-compression (RE = -co) loading at 1100°C. LSC-11 and LSC-15 are new alloys developed by 1H1 Corporation, Japan with 0.8 wt% Re and without Re addition, respectively, as reduced-cost alternatives to the second generation single crystal Ni-base superalloys. The fatigue experiments were conducted with or without a two-minute dwell (hold) in compression and total strain ranges of 0.7%, 0.6% and 0.5% on uncoated specimens in the [001] orientation. Examination of the cyclic stress-strain behavior revealed that the initially compressive mean stress relaxed to approximately zero stress in N-D tests, while compressive hold resulted in the development of a tensile mean stress during C-D fatigue. Cyclic stress softening was observed under all test conditions. Microstructural analysis of tested specimens showed that N-D fatigue promoted isotropic coarsening of the γ′ precipitates, while C-D loading resulted in the formation of discontinuous γ′ rafting parallel to the loading direction. Fatigue cracks initiated from the specimen surface from regions of localized oxide attack. All alloys were compressive dwell sensitive. C-D fatigue lives were 4-15× shorter than N-D when the same alloys were considered. CMSX-4 exhibited 1.5-3× N-D fatigue life advantage over alloys LSC-11 and LSC-15. Under C-D fatigue the life advantage of CMSX-4 was 20-50% greater than alloys LSC-11 and LSC-15. The differences in these behaviours could be attributed to Re content and oxidation.
Keywords: Creep-fatigue; Cyclic stress-strain behavior; Fatigue experiments; Isotropic coarsening; Low cycle fatigues; Microstructural analysis; Ni-base superalloys; Second generation; Fatigue of materials; Nickel; Single crystals; Superalloys

Attosecond pulse trains generated with oriented molecules - Frumker, Eugene; Kajumba, Nathaniel; Bertrand, Julien; Worner, Hans; Hebeisen, Christoph; Hockett, Paul; Spanner, Michael; Patchkovskii, Serguei; Paulus, Gerhard; Villeneuve, David M.; Corkum, Paul B. (2012 Conference on Lasers and Electro-Optics. CLEO 2012, 2012)
We report the measurement of high harmonics from oriented molecules in the gas phase. We show that attosecond and re-collision science provides a detailed and sensitive probe of electronic asymmetry in polar molecules.
Keywords: Attosecond pulse trains; Attoseconds; Electronic asymmetry; Gasphase; High harmonics; Polar molecules; Sensitive probe; Lasers; Molecules

Aggregation and privacy in multi-relational databases - Jafer, Y.; Viktor, H. L.; Paquet, E. (Privacy, Security and Trust (PST), 2012 Tenth Annual International Conference on, 2012)
The aim of privacy-preserving data mining is to construct highly accurate predictive models while not disclosing privacy information. Aggregation functions, such as sum and count are often used to pre-process the data prior to applying data mining techniques to relational databases. Often, it is implicitly assumed that the aggregated (or summarized) data are less likely to lead to privacy violations during data mining. This paper investigates this claim, within the relational database domain. We introduce the PBIRD (Privacy Breach Investigation in Relational Databases) methodology. Our experimental results show that aggregation potentially introduces new privacy violations. That is, potentially harmful attributes obtained with aggregation are often different from the ones obtained from non-aggregated databases. This indicates that, even when privacy is enforced on non-aggregated data, it is not automatically enforced on the corresponding aggregated data. Consequently, special care should be taken during model building in order to fully enforce privacy when the data are aggregated. © 2012 IEEE.
Keywords: Aggregation functions; Data mining techniques; Predictive models; Privacy breaches; Privacy information; Privacy preserving data mining; Privacy violation; Relational Database; Aggregates; Data mining; Database systems; Data privacy

Photonic sensing: principles and applications for safety and security monitoring - Xiao, Gaozhi; Bock, Wojtek J. (Wiley Series in Microwave and Optical Engineering, 2012)
A cutting-edge look at safety and security applications of photonic sensors. With its many superior qualities, photonic sensing technology is increasingly used in early-detection and early-warning systems for biological hazards, structural flaws, and security threats. Photonic Sensing provides for the first time a comprehensive review of this exciting and rapidly evolving field, focusing on the development of cutting-edge applications in diverse areas of safety and security, from biodetection to biometrics. The book brings together contributions from leading experts in the field, fostering effective solutions for the development of specialized materials, novel optical devices, and networking algorithms and platforms. A number of specific areas of safety and security monitoring are covered, including background information, operation principles, analytical techniques, and applications. Topics include: Document security and structural integrity monitoring, as well as the detection of food pathogens and bacteria Surface plasmon sensors, micro-based cytometry, optofluidic techniques, and optical coherence tomography Optic fiber sensors for explosive detection and photonic liquid crystal fiber sensors for security monitoring Photonics-assisted frequency measurement with promising electronic warfare applications An invaluable, multidisciplinary resource for researchers and professionals in photonic sensing, as well as safety and security monitoring, this book will help readers jump-start their own research and development in areas of physics, chemistry, biology, medicine, mechanics, electronics, and defense.

Electrochemical Technologies for Energy Storage and Conversion: volume 1 & 2 - Liu, Ru-Shi; Zhang, Lei; Sun, Xueliang; Liu, Hansan; Zhang, Jiujun (Wiley, 2012)
In this handbook and ready reference, editors and authors from academia and industry share their in-depth knowledge of known and novel materials, devices and technologies with the reader. The result is a comprehensive overview of electrochemical energy and conversion methods, including batteries, fuel cells, supercapacitors, hydrogen generation and storage as well as solar energy conversion. Each chapter addresses electrochemical processes, materials, components, degradation mechanisms, device assembly and manufacturing, while also discussing the challenges and perspectives for each energy storage device in question. In addition, two introductory chapters acquaint readers with the fundamentals of energy storage and conversion, and with the general engineering aspects of electrochemical devices. With its uniformly structured, self-contained chapters, this is ideal reading for entrants to the field as well as experienced researchers. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

Low-cost and high-efficient W-band substrate integrated waveguide antenna array made of printed circuit board process - Ghassemi, Nasser; Wu, Ke; Claude, Stephane; Zhang, Xiupu; Bornemann, Jens (Transactions on Antennas and Propagation, 2012)
A novel class of low-cost, small-footprint and high-gain antenna arrays is presented for W-band applications. A 4 × 4 antenna array is proposed and demonstrated using substrate-integrated waveguide (SIW) technology for the design of its feed network and longitudinal slots in the SIW top metallic surface to drive the array antenna elements. Dielectric cubes of low-permittivity material are placed on top of each 1 × 4 antenna array to increase the gain of the circular patch antenna elements. This new design is compared to a second 4 × 4 antenna array which, instead of dielectric cubes, uses vertically stacked Yagi-like parasitic director elements to increase the gain. Measured impedance bandwidths of the two 4 × 4 antenna arrays are about 7.5 GHz (94.2-101.8 GHz) at 18 ± 1 dB gain level, with radiation patterns and gains of the two arrays remaining nearly constant over this bandwidth. While the fabrication effort of the new array involving dielectric cubes is significantly reduced, its measured radiation efficiency of 81 percent is slightly lower compared to 90 percent of the Yagi-like design.
Keywords: Antenna array; W-band antenna; Yagi-like antenna; substrate integrated waveguide (SIW)

Assessment of scavenge efficiency for a helicopter particle separation system - Jiang, L. Y.; Benner, M.; Bird, J. (Journal of the American Helicopter Society, 2012)
The effectiveness of a helicopter particle separation system has been numerically assessed at practical operating conditions and sand environments for various scenarios. The particle separation mechanism and its limitations are revealed by the predicted flow field characteristics and particle trajectories. The separation-by-inertia concept is effective for removing large particles, but problematic for small particles of diameter ≤36 μm for the configuration and operating conditions considered in the present study. It is also found that particle size, shape factor, and rebound characteristics exert substantial effects on particle scavenge efficiency. However, the effects of gravity, particle inlet velocity, inlet mass distribution, and engine-operating conditions on scavenge efficiency are minor or limited. Finally, a few suggestions for further investigation on engine particle separation systems are included.

Screening of pancreatic lipase and α-glucosidase inhibitors from Chinese dietary herbs - Xiaoli, Sun; Zhang, Kaibin; Ji, Xiuhong; Wang, Yanwen; Zidichouski, Jeffrey; Tong, Yan; Gao, Huimin; Zhang, Junzeng; Wang, Zhimin (China Journal of Chinese Materia Medica, 2012)
The present study was conducted to develop new inhibitors of pancreatic lipase and α-glucosidase from Chinese dietary herbs. Sixty-three dietary herbs from 39 taxonomic families were selected and extracted with aqueous ethanol or water. The extracts were then tested with in vitro enzyme assays for their ability to inhibit pancreatic lipase and α-glucosidase activities. Orlistat and acarbose were used as two positive controls. The extracts of Nelumbo nucifera, Curcuma longa, Piper longum and Morus alba showed strong pancreatic lipase inhibitory effects with IC50 at (28.00±5.51), (5.24±0.51), (14.76±2.58), (4.78±0.58), (3.41±0.67) mg·L-1, respectively. These extracts also showed potent α-glucosidase inhibitory activities with IC50 at (1.98±0.13), (0.18±0.007), (0.71±0.08), (0.077±0.005), (0.089±0.006) g·L-1, respectively. The results provide useful information for developing new drugs or natural health products for hyperlipidemia and hypoglycemia from Chinese dietary herbs.
Keywords: lipase inhibitor; α-glucosidase inhibitor; Chinese dietary herbs; screening

Wind tunnel and track tests of class 8 tractors pulling single and tandem trailers fitted with side skirts and boat-tails - Cooper, Kevin R. (SAE International Journal of Commercial Vehicles, 2012)
A 1:10-scale wind tunnel development program was undertaken by the National Research Council of Canada and Airshield Inc. in 1994 to develop trailer side skirts that would reduce the aerodynamic drag of single and tandem trailers. Additionally, a second wind tunnel program was performed by the NRC to evaluate the fuel-saving performance of boat-tail panels when used in conjunction with the skirt-equipped single and tandem trailers. Side skirts on tandem, 8.2-m-long trailers (all model dimensions converted to full scale) were found to reduce the wind-averaged drag coefficient at 105 km/h (65 mi/h) by 0.0758. The front pair of skirts alone produced 75% of the total drag reduction from both sets of skirts and the rear pair alone produced 40% of that from both pairs. The sum of the drag reductions from front and rear skirts separately was 115% of that when both sets were fitted, suggesting an interaction between both. The reductions in wind-averaged drag coefficient for single trailers with skirts only were 0.0524 for the 14.6-m trailer and 0.0406 for the 16.2-m single trailer. The data are quoted for skirt ground clearances of 305 mm (12 in.). The 0.50-m-long boat-tail panels combined with the tandem-trailer skirts to increase the wind-averaged drag coefficient reduction to a total of 0.1177. Boat-tails combined with skirts on the single trailers also increased the wind-averaged drag coefficient reductions to totals of 0.1051 and 0.0979 for the 14.6 m and 16.2 m trailers, respectively. Each boat-tail assembly consisted of angled panels attached to the top and the side rear edges of a trailer. The boat-tail panels on the single trailers and the rear trailer of the tandem pair were set at the optimum angle of 15°. The boat-tail panels on the front trailer of the tandem pair were set at 0°. Skirts were predicted to provide fuel savings for the tandem trailers at 105 km/h of 3.79 liters per hundred kilometers (L/(100 km)) (1.61 US gallons per 100 miles - US gal/(100 mi)) and 2.18 L/(100 km) (0.93 US gal/(100 mi)) and of 1.95 L/(100 km) (0.83 US gal/(100 mi)) for the 14.6-m and 16.2-m single trailers, respectively. It is not known why the longer trailer had the smaller fuel saving. The addition of boat-tail panels increased the predicted fuel savings for the skirt-equipped tandem trailers to 5.88 L/(100 km) (2.50 US gal/(100 mi)) and increased the fuel savings of the 14.6 m and 16.2 m single, skirt-equipped trailers to 5.25 L/(100 km) (2.23 US gal/(100 mi)) and to 4.89 L/(100 km) (2.08 US gal/(100 mi)), respectively. Track tests were undertaken using 8.2-m-long, skirt-equipped tandem trailers to verify the fuel-saving predictions based on the wind tunnel drag data. The boat-tails were not track tested. The track tests were performed by the staff at the Goodyear Proving Grounds in San Angelo, Texas. They demonstrated that skirts provided fuel savings of from 0.86 L/(100 km) to 3.54 L/(100 km), with the largest savings in the strongest side winds. The average track-test fuel saving measured over all runs was 2.29 L/(100 km) at an average road speed of 88 km/h. The average wind-tunnel-based prediction for these track runs was 2.25 L/(100 km), using a wind-averaged drag coefficient calculated for the wind conditions of each run. This was within one percent of the average of the track measurements. The wind speeds during the track tests were generally lower than the national average 11.3 km/h wind at truck mid height, averaging only 8 km/h. This indicated that the average fuel saving on the track was less than would be expected annually in North America. The track-test results confirmed the fuel-saving potential of skirts and demonstrated the reliability of fuel-saving predictions made from high-quality wind tunnel data. This correlation was only possible because the track-side winds were measured during each run.
Keywords: Fuel Consumption; Aerodynamics; Heavy trucks

Hot forming of 7075 aluminium alloy tubes to produce complex and strong components - Béland, Jean-François; D'Amours, Guillaume (SAE Technical Papers; no. 2012-01-0539, 2012)
Lightweight tubular products offering enhanced stiffness and strength have always been of major concern for transportation and recreational applications. Hence, industries have turned to complex-shaped tubes to increase product performance and reduce energy costs. High-performance aluminum alloys, like 7075 for instance, have good mechanical properties such as high strength, but low formability at ambient temperature. Fortunately, hot tensile tests on 7075 samples have yielded an increase in formability with temperature. Therefore, testing has recently been launched at the Aluminum Technology Center to develop a new product application. More precisely, a 1,000-ton hydraulic press was equipped with +600°C heating plates and fitted with a bicycle handlebar mold. The plates provide 10 separate heating zones that can be adjusted independently. A thermo-mechanical model was also developed using LS-DYNA to determine tube temperatures around the heating zones. Hot tensile test results were also utilized to model tube behavior using an elastic viscoplastic temperature-dependent material constitutive law to predict tube wall stresses and strains. The finite element model can predict tube temperatures and gas pressures relative to time. Hot-forming process parameters were rapidly adjusted to successfully produce perfect handlebars. Conclusions not only include successful application where high formability is required, but also lead to a significant decrease in forming loads and lower tooling and mechanical energy costs.

Examination of the Maskell III blockage correction technique for full scale testing in the NRC 9-meter wind tunnel - Leuschen, Jason; Mébarki, Youssef (SAE International Journal of Commercial Vehicles, 2012)
The objective of this study was to assess the antimicrobial resistance and virulence genotypes of Enterococcus faecalis isolated from samples obtained from a commercial pork processing plant. A total of 200 samples were randomly obtained from carcasses after bleeding (BC; 50 samples) and pasteurization (PC; 100 samples) and from retail pork products (RP; 50 samples). One isolate from each E. faecalis –positive sample was analyzed for antimicrobial susceptibility and characterized using a enterococcal microarray for analysis of resistance and virulence genes. E. faecalis was isolated from 79.5% of BC samples, 2% of PC samples, and 72.7% of RP samples. Resistance to the clinically important drugs ciprofloxacin (one isolate each from BC and RP samples) and daptomycin (one isolate each from PC and RP samples) was found. Multiresistance (to five or more antimicrobials) was more common in E. faecalis isolates from BC (77.4% of isolates) samples than those from PC (25%) and RP (37.6%) samples. Resistance to kanamycin (43.5%) and streptomycin (69.2%) was noted mostly in E. faecalis from BC samples. The most common resistance genes (>5% prevalence) found in E. faecalis were those for aminoglycosides (aac(6), aphA3, and aadE), macrolides-lincosamide (ermB, ermA, sat(4), and linB), and tetracyclines (tetL, tetM, and tetO ). The virulence genes expressing adhesion (ace, efaAfs, and agrBfs), gelatinase (gelE), and pheromone (cAM, ccF10, cob, and cpd1) factors were found in the majority of isolates. Significant associations were found between resistance and virulence genes, suggesting their possible relationship. These data suggest that carcasses entering the final product processing area are mostly free of E. faecalis but are recontaminated with antimicrobial-resistant strains during processing. The source of these contaminants remains to be identified; however, these results underscore the importance of E. faecalis as a reservoir of resistance and virulence genes.

Characterization of antimicrobial resistance and virulence genotypes of Enterococcus faecalis recovered from a pork processing plant - Aslam, Mueen; Diarra, Moussa S.; Masson, Luke (Journal of Food Protection, 2012)
The objective of this study was to assess the antimicrobial resistance and virulence genotypes of Enterococcus faecalis isolated from samples obtained from a commercial pork processing plant. A total of 200 samples were randomly obtained from carcasses after bleeding (BC; 50 samples) and pasteurization (PC; 100 samples) and from retail pork products (RP; 50 samples). One isolate from each E. faecalis –positive sample was analyzed for antimicrobial susceptibility and characterized using a enterococcal microarray for analysis of resistance and virulence genes. E. faecalis was isolated from 79.5% of BC samples, 2% of PC samples, and 72.7% of RP samples. Resistance to the clinically important drugs ciprofloxacin (one isolate each from BC and RP samples) and daptomycin (one isolate each from PC and RP samples) was found. Multiresistance (to five or more antimicrobials) was more common in E. faecalis isolates from BC (77.4% of isolates) samples than those from PC (25%) and RP (37.6%) samples. Resistance to kanamycin (43.5%) and streptomycin (69.2%) was noted mostly in E. faecalis from BC samples. The most common resistance genes (>5% prevalence) found in E. faecalis were those for aminoglycosides (aac(6), aphA3, and aadE), macrolides-lincosamide (ermB, ermA, sat(4), and linB), and tetracyclines (tetL, tetM, and tetO ). The virulence genes expressing adhesion (ace, efaAfs, and agrBfs), gelatinase (gelE), and pheromone (cAM, ccF10, cob, and cpd1) factors were found in the majority of isolates. Significant associations were found between resistance and virulence genes, suggesting their possible relationship. These data suggest that carcasses entering the final product processing area are mostly free of E. faecalis but are recontaminated with antimicrobial-resistant strains during processing. The source of these contaminants remains to be identified; however, these results underscore the importance of E. faecalis as a reservoir of resistance and virulence genes.

Immunomagnetic capture of Bacillus anthracis spores from food - Shields, Michael J.; Hahn, Kristen R.; Janzen, Timothy W.; Goji, Noriko; Thomas, Matthew C.; Kingombe, Cesar Bin I.; Paquet, Chantal; Kell, Arnold J.; Amoako, Kingsley K. (Journal of Food Protection, 2012)
Food is a vulnerable target for potential bioterrorist attacks; therefore, a critical mitigation strategy is needed for the rapid concentration and detection of biothreat agents from food matrices. Magnetic beads offer a unique advantage in that they have a large surface area for efficient capture of bacteria. We have demonstrated the efficient capture and concentration of Bacillus anthracis (Sterne) spores using immunomagnetic beads for a potential food application. Magnetic beads from three different sources, with varying sizes and surface chemistries, were functionalized with monoclonal antibodies and polyclonal antibodies from commercial sources and used to capture and concentrate anthrax spores from spiked food matrices, including milk, apple juice, bagged salad, processed meat, and bottled water. The results indicated that the Pathatrix beads were more effective in the binding and capture of anthrax spores than the other two bead types investigated. Furthermore, it was observed that the use of polyclonal antibodies resulted in a more efficient recovery of anthrax spores than the use of monoclonal antibodies. Three different magnetic capture methods, inversion, the Pathatrix Auto system, and the new i CropTheBug system, were investigated. The i CropTheBug system yielded a much higher recovery of spores than the Pathatrix Auto system. Spore recoveries ranged from 80 to 100% for the i CropTheBug system when using pure spore preparations, whereas the Pathatrix Auto system had recoveries from 20 to 30%. Spore capture from food samples inoculated at a level of 1 CFU/ml resulted in 80 to 100% capture for milk, bottled water, and juice samples and 60 to 80% for processed meat and bagged salad when using the i CropTheBug system. This efficient capture of anthrax spores at very low concentrations without enrichment has the potential to enhance the sensitivity of downstream detection technologies and will be a useful method in a foodborne bioterrorism response.

Metallic under-layer coating as third line of protection of underground oil and gas pipelines from external corrosion - Papavinasam, S.; Arsenault, B.; Attard, M.; Revie, R. W. (Corrosion, 2012)
This paper presents the concept of introducing a third line of defense in the form of a metallic under-layer coating—in addition to the traditional polymeric coating and applied cathodic protection (CP)—to protect the external surface of oil and gas pipelines. The three levels of protection would be the metallic under-layer coating, the polymeric top-layer coating, and the applied CP. This three-level system would be beneficial when the applied CP current is shielded from the pipeline by a dis-bonded polymeric coating, thermal insulator, or highly resistive soil. Two different combinations of metallic under-layer and polymeric top-layer coatings are presented to demonstrate this concept: 48%Zn and 52%Al under-layer with four different top-layer coatings: fusion-bonded epoxy (FBE), composite, urethane, and coal tar epoxy. Urethane top-layer coating with four different metallic under-layers: 48%Zn-52%Al, 85%Zn-15%Al, Al, and Zn. The criteria for the successful application of this concept also have been described.
Keywords: cathodic protection, external corrosion, metallic under-layer coating, oil and gas pipelines, polymeric coating

Economic-based modelling for resource scheduling in grid computing - Aburukba, Raafat; Ghenniwa, Hamada; Shen, Weiming (Proceedings of the 2012 IEEE 16th International Conference on Computer Supported Cooperative Work in Design (CSCWD): May 23-25, 2012, Wuhan, China, 2012)
In decentralized computational environments applications or services belong to different organizations with different objectives. Grid computing model is appropriate for such environments, in particular for large scale computations. In this paper, decentralization is modeled in terms self-interested, economically inspired agents that attempt to achieve their goals. The objective of this work is to model the Grid scheduling problem based on the nature of the Grid environment and the characteristics of the Grid entities focusing on the resource utilization and completion time objectives. We create a mapping between the Grid scheduling problem and the combinatorial allocation problem and propose an adequate economic-based optimization model and a bidding language for the Grid scheduling problem. The proposed approach is being validated through a prototype implementation using the Coordinated Intelligent Rational Agent (CIR-Agent) model.
Keywords: Agent oriented; Grid bidding language; Grid computing; decentralized scheduling; economic-based approach

On the molar mass of silicon for a new Avogadro constant - Meija, J.; Mester, Z.; Pramann, A.; Rabb, S.; Rienitz, O.; Schiel, D.; Sturgeon, R.; Turk, G.; Vocke, R.; Yang, L. (2012 Conference on Precision Electromagnetic Measurements (CPEM 2012), 2012)
An overview of the present results and status of the molar mass of a silicon crystal highly enriched in ²⁸Si used for a new determination of the Avogadro constant is given with special emphasis on the cooperation between NIST, NRC, and PTB currently working on this topic. Using an experimental combination of multicollector ICP and isotope dilution mass spectrometry, a new approach developed by PTB for the measurement of the isotopic composition has been applied. It focuses on the isotope ratio treatment of ³°Si/²⁹Si mainly, avoiding the more uncertain measurement of ratios related to the main isotope ²⁸Si.
Keywords: Avogadro constant; isotope dilution mass spectrometry; molar mass; multicollector ICP-mass spectrometry; silicon; uncertainty

Membrane raft disruption results in neuritic retraction prior to neuronal death in cortical neurons - Whitehead, S. N.; Gangaraju, S.; Aylsworth, A.; Hou, S. T. (BioScience Trends, 2012)
Membrane rafts, rich in sphingolipids and cholesterol, play an important role in neuronal membrane domain-specific signaling events, maintaining synapses and dendritic spines. The purpose of this study is to examine the neuronal response to membrane raft disruption. Membrane rafts of 8 DIV primary neuronal cultures were isolated based on the resistance to Triton X-100 and ability to float in sucrose gradients. Membrane rafts from primary cortical neurons were also imaged using the membrane raft marker, cholera toxin subunit-B (CTxB), and were co-immunolabelled with the dendritic microtubule associated protein marker, MAP-2, the dendritic and axonal microtubule protein, β-III-Tubulin, and the axonal microtubule protein, Tau. Exposure of cortical neurons to either the cholesterol depleting compound, methyl-beta-cyclodextrin (MBC), or to the glycosphingolipid metabolism inhibiting agent D-threo-1-phenyl-2-decanoylamino-3- morpholino-1-propanol (D-PDMP), resulted in neuritic retraction prior to the appearance of neuronal death. Further investigation into the effects of MBC revealed a pronounced perturbation of microtubule protein association with membrane rafts during neuritic retraction. Interestingly, stabilizing microtubules with Paclitaxel did not prevent MBC induced neuritic retraction, suggesting that neuritic retraction occurred independently of microtubule disassembly and that microtubule association with membrane rafts is critical for maintaining neuritic stability. Overall, the data indicated that membrane rafts play an important role in neurite stability and neuronal viability.

In-flight icing of UAVs: the influence of flight speed coupled with chord size - Szilder, Krzysztof; McIlwain, Stuart (Canadian Aeronautics Space Journal, 2012)
The intensive deployment of unmanned aerial vehicles (UAVs) for surveillance and reconnaissance missions during the last couple of decades has revealed their vulnerability to icing conditions. At present, a common icing avoidance strategy is simply not to fly when icing is forecast. Consequently, UAV missions in cold seasons and cold regions can be delayed for days when icing conditions persist. While this approach limits substantially the failure of UAV missions as a result of icing, there is obviously a need to develop all-weather capabilities. A key step in accomplishing this objective is to understand better the influence of a smaller geometry and a lower speed on the ice accretion process, relative to the extensively researched area of in-flight icing for traditional aircraft configurations characterized by high Reynolds number. Our analysis of the influence of Reynolds number on the ice accretion process is performed for the NACA0012 airfoil. Analytical analysis of the integrated mass and energy balance equations along the airfoil surface allows the identification of regimes of rime and glaze formation, as well as the ice accretion extent as a function of static air temperature and liquid water content. For each Reynolds number, a Computational Fluid Dynamics solver computes the airflow field and the distributions of Stanton number and static air pressure along the airfoil surface. Next, a drop trajectory solver computes the distribution of collection efficiency along the airfoil for a given drop size. Finally, a morphogenetic model is used to predict the ice accretion shape and its extent over the entire Reynolds number range under consideration. Our analysis highlights the differences between ice accretions on components of traditional aircraft and UAVs, arising from their differences in cruising speed and airfoil dimensions.

Development of the shock simulation methodology for spacecraft components - Nejad Ensan, M.; Zimcik, D. G. (Canadian Aeronautics Space Journal, 2012)
Spacecraft components encounter mechanical shock from a variety of sources. Components must withstand a series of flight shock pulses and must be designed and tested accordingly to ensure reliability. This paper presents a “Design for Shock” methodology to accurately analyze the response to shock for components under the short duration dynamic loading to assess component structural integrity and demonstrate design robustness. This methodology uses a more realistic simulation of the response of the component to shock loading using a wave propagation solution based on explicit time integration of the transient shock event rather than a stationary random and (or) quasi-static approach which has been traditionally used for this analysis. This approach was applied to a sensitive scientific instrument to demonstrate its effectiveness. The method is shown to provide a more accurate simulation of the shock event thereby reducing the unknown conservatism of the stationary random and (or) quasi-static approach while providing accurate simulation of the transient dynamic response of the structure.

Erosion-corrosion assessment of tungsten carbide-based plasma-tranferred arc-welded overlays - Jones, M.; Llewellyn, R. J. (Corrosion, 2012)
Two commercially available tungsten carbide-based, Ni alloy binder plasma-transferred arc-welded (PTAW) overlays, which had both previously exhibited excellent resistance to slurry erosion (in substantially non-corrosive conditions) and abrasion, were assessed in a more corrosive slurry erosion environment. One overlay consisted of a 50 vol% mixture of crushed eutectic (WC/W2C), spherical eutectic, and tungsten monocarbide (WC) particles in a NiBSi matrix, while the other contained 50 vol% WC in a NiCrBSi matrix. Initial microstructural examination of the mixed carbide/NiBSi overlay confirmed that substantial dissolution/degradation of the spherical eutectic and crushed eutectic carbides had occurred as a consequence of interaction with its matrix alloy constituent at the high temperatures encountered during arc deposition. Conversely, the WC-based overlay exhibited very limited carbide dissolution or degradation. The total erosion-corrosion (E-C) rate, as well as its separate components, namely, erosion, corrosion, and synergy, was established using a novel slurry pot erosion-corrosion (SPEC) tester. The E-C rate for the WC/NiCrBSi overlay was approximately four times less than the E-C rate for the mixed carbide/NiBSi overlay, which performed comparatively poorly. The mixed carbide/NiBSi overlay displayed a very large synergistic value, which accounted for 90% of the total erosion-corrosion rate, with the WC/NiCrBSi showing a synergy level accounting for 50% of the total E-C rate. To establish and compare the damage mechanisms affecting both overlays, a novel technique was implemented where specific regions were examined using scanning electron microscopy (SEM) before and after SPEC testing. This procedure was applied to identify any preferential attack that was occurring and to elucidate the reasons for the significantly different E-C performance of the two products. The main reasons for the inferior performance of the mixed carbide/NiBSi overlay were found to be caused by the attack of the non-Cr bearing matrix and preferential removal of the W/Ni-rich boundary layer and eta-carbides, formed around the eutectic carbides during deposition.

Isolation, identification and characterization of a antidementia acetylcholinesterase inhibitor-producing Yarrowia lipolytica S-3 - Kang, Min-Gu; Yoon, Min-Ho; Choi, Young-Jun; Lee, Jong-Soo (Mycobiology, 2012)
This report describes the isolation and identification of a potent acetylcholinesterase (AChE) inhibitor-producing yeasts. Of 731 species of yeast strain, the S-3 strain was selected as a potent producer of AChE inhibitor. The selected S-3 strain was investigated for its microbiological characteristics. The S-3 strain was found to be short-oval yeast that did not form an ascospore. The strain formed a pseudomycelium and grew in yeast malt medium containing 50% glucose and 10% ethanol. Finally, the S-3 strain was identified by its physiological characteristics and 26S ribosomal DNA sequences as Yarrowia lipolytica S-3.
Keywords: Antidementia acetylcholinesterase inhibitor, Yarrowia lipolytica S-3, 26S rDNA sequences

Nonlinear effects of carbon nanotube coated single mode optical fiber gratings - Villanueva, Guillermo E.; Jakubinek, Michael B.; Simard, Benoit; Otón, Claudio J.; Shao, Li-Yang; Pérez-Millán, Pere; Albert, Jacques (Óptica Pura y Aplicada, 2012)
Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump- probe pulses experiment.
Keywords: Fiber Bragg Grating, Non-Linear Materials, Fiber Devices

In-storage psychrophilic anaerobic digestion: acclimated microbial kinetics - King, Susan; Courvoisier, Pierre; Guiot, Serge; Barrington, Suzelle (Environmental Technology, 2012)
In-storage psychrophilic anaerobic digestion develops by microbial acclimation in covered swine-manure storage tanks, producing CH4 and stabilizing organic matter. To optimize the system's performance, the process kinetics must be understood. The objective of this study was to evaluate kinetic parameters describing the major stages in the digestion process, and to investigate the effect of temperature acclimation on these parameters. Specific activity tests were performed using manure inocula and five substrates at three incubation temperatures. Extant substrate activities were determined analytically for each case, and intrinsic kinetic parameters for glucose uptake were estimated by grid search fitting to the Monod model. The results demonstrate that this acclimated microbial community exhibits different kinetic parameters to those of the mesophilic communities currently modelled in the literature, with increased activity at low temperatures, varying with substrate and temperature. For glucose, the higher uptake is accompanied by lower microbial yield and half-saturation constant. Decomposing these values suggests that active psychrophilic and mesophilic microbial populations co-exist within the community. This work also confirms that a new method of assessing microbial substrate kinetics must be developed for manure microbial communities, separating microbial mass from other suspended organics.
Keywords: psychrophilic anaerobic digestion, specific substrate uptake, manure treatment, microbial kinetics, swine manure

Shaping polarization of attosecond pulses via laser control of electron and hole dynamics - Morales, Felipe; Barth, Ingo; Serbinenko, Valeria; Patchkovskii, Serguei; Smirnova, Olga (Journal of Modern Optics, 2012)
We show how laser control over both electronic and hole dynamics in aligned molecules can be used to shape polarization of attosecond pulses produced via high harmonic generation driven by two-color, linearly polarized laser fields.
Keywords: attosecond science, high harmonic generation, attosecond pulses, polarization, nonlinear and ultrafast optics (inc. harmonic generation, multiphoton spectroscopy)

Towards an understanding of the helium–acetylene van der Waals complex - Rezaei, Mojtaba; Moazzen-Ahmadi, N.; McKellar, A. R. W.; Fernández, Berta; Farrelly, David (Molecular Physics, 2012)
The weakly bound complex He–C2D2 is studied in the ν 3 fundamental band of C2D2 (≈2440 cm−¹) using a tuneable infrared diode laser to probe a pulsed supersonic slit jet expansion. This is the first published spectrum for helium–acetylene. Transitions observed in the region of the C2D2 R(0) line are assigned with the help of theoretical results based on an ab initio intermolecular potential, and fitted using a simple Coriolis model. The results indicate that the complex is rather close to the free rotor limit, helping to explain the absence of previous data. Scaled parameters from the model are used to predict a spectrum for He–C2H2.
Keywords: helium, acetylene, dimer, spectroscopy, infrared, van der Waals

On the assignment problem of arbitrary processing time operations in partially overlapping manufacturing resources - Ghonaim, W.; Ghenniwa, H.; Shen, W. (IEEE International Conference on Automation Science and Engineering (CASE), 2012 20-24 Aug. 2012, Seoul, Korea, 2012)
The frequent transfers' challenge of workpieces between multiple resources is quite evident in the production process of customized parts. In fact, special jobs' transfers and processing, often, require workpiece unloading, transport and loading with, rather, idling and reconfiguration of resources that impact much job completion time and resource utilization. The overlapping capabilities of machine tools, otherwise, are common with, typically, few special tooling. In such settings, the overlapping and special tooling capabilities intensify the complexity of the assignment problem, mainly, when allocating the operations of arbitrary processing times. This work targets the efficient assignment of unrelated jobs of operations with arbitrary processing time to multiple resources of partially overlapping capabilities. The work introduces a formal model and a more efficient solution approach for minimizing jobs' transfer and balancing workloads. The sequencing problem of the assigned unrelated jobs would be, then, an orthogonal problem, of less significance, that can be tackled separately.
Keywords: job shop scheduling; machine tools; manufacturing resources planning; resource allocation

New spectroscopic results on acetylene dimers and trimers - Oliaee, J. Norooz; Moazzen-Ahmadi, N.; McKellar, A. R. W. (Molecular Physics, 2012)
Spectra of acetylene dimers and trimers containing one or more C2D2 monomer are studied in the ν3 fundamental band region of C2D2 (≈2440 cm−¹) using a tuneable infrared diode laser to probe a pulsed supersonic slit jet expansion. Four new subbands are observed in the perpendicular band of (C2D2)2, and this enables the first direct determination of the A rotational constant for an acetylene dimer. The value found for A is significantly larger than the previous indirect value based on microwave spectra. The dimer parallel band is observed and found to be highly perturbed, and observations are extended for the mixed dimer C2D2 – C2H2. The trimers (C2D2)3, (C2D2)2 – C2H2, and C2D2 – (C2H2)2 are observed spectroscopically for the first time. Establishment of a precise band origin is difficult for (C2D2)3 because of the inherent nature of the spectrum, but this is possible for two out of three of the bands of the mixed trimers.
Keywords: acetylene, dimer, trimer, cluster, spectroscopy, infrared, van der Waals

Diversity in the protein N-glycosylation pathways within the Campylobacter genus - Nothaft, Harald; Scott, Nichollas E.; Vinogradov, Evgeny; Liu, Xin; Hu, Rui; Beadle, Bernadette; Fodor, Christopher; Miller, Willian G.; Li, Jianjun; Cordwell, Stuart J.; Szymanski, Christine M. (Molecular & Cellular Proteomics, 2012)
The foodborne bacterial pathogen, Campylobacter jejuni, possesses an N-linked protein glycosylation (pgl) pathway involved in adding conserved heptasaccharides to asparagine-containing motifs of >60 proteins, and releasing the same glycan into its periplasm as free oligosaccharides. In this study, comparative genomics of all 30 fully sequenced Campylobacter taxa revealed conserved pgl gene clusters in all but one species. Structural, phylogenetic and immunological studies showed that the N-glycosylation systems can be divided into two major groups. Group I includes all thermotolerant taxa, capable of growth at the higher body temperatures of birds, and produce the C. jejuni-like glycans. Within group I, the niche-adapted C. lari subgroup contain the smallest genomes among the epsilonproteobacteria, and are unable to glucosylate their pgl pathway glycans potentially reminiscent of the glucosyltransferase regression observed in the O-glycosylation system of Neisseria species. The nonthermotolerant Campylobacters, which inhabit a variety of hosts and niches, comprise group II and produce an unexpected diversity of N-glycan structures varying in length and composition. This includes the human gut commensal, C. hominis, which produces at least four different N-glycan structures, akin to the surface carbohydrate diversity observed in the well-studied commensal, Bacteroides. Both group I and II glycans are immunogenic and cell surface exposed, making these structures attractive targets for vaccine design and diagnostics.

Domain organization of the polymerizing mannosyltransferases involved in synthesis of the Escherichia coli O8 and O9a lipopolysaccharide O-antigens - Greenfield, Laura K.; Richards, Michele R.; Vinogradov, Evgeny; Wakarchuk, Warren W.; Lowary, Todd L.; Whitfield, Chris (Journal of Biological Chemistry, 2012)
The Escherichia coli O9a and O8 polymannose O-polysaccharides (O-PSs) serve as model systems for the biosynthesis of bacterial polysaccharides by ATP-binding cassette transporter-dependent pathways. Both O-PSs contain a conserved primer-adaptor domain at the reducing terminus and a serotype-specific repeat unit domain. The repeat unit domain is polymerized by the serotype-specific WbdA mannosyltransferase. In serotype O9a, WbdA is a bifunctional α-(1→2)-, α-(1→3)-mannosyltransferase, and its counterpart in serotype O8 is trifunctional (α-(1→2), α-(1→3), and β-(1→2)). Little is known about the detailed structures or mechanisms of action of the WbdA polymerases, and here we establish that they are multidomain enzymes. WbdA^O9a contains two separable and functionally active domains, whereas WbdA^O8 possesses three. In WbdC^O9a and WbdB^O9a, substitution of the first Glu of the EX7E motif had detrimental effects on the enzyme activity, whereas substitution of the second had no significant effect on activity in vivo. Mutation of the Glu residues in the EX7E motif of the N-terminal WbdA^O9a domain resulted in WbdA variants unable to synthesize O-PS. In contrast, mutation of the Glu residues in the motif of the C-terminal WbdA^O9a domain generated an enzyme capable of synthesizing an altered O-PS repeat unit consisting of only α-(1→2) linkages. In vitro assays with synthetic acceptors unequivocally confirmed that the N-terminal domain of WbdA^O9a possesses α-(1→2)-mannosyltransferase activity. Together, these studies form a framework for detailed structure-function studies on individual domains and a strategy applicable for dissection and analysis of other multidomain glycosyltransferases.
Keywords: Bacteria; Biosynthesis; Glycoconjugate; Glycosyltransferases; Lipopolysaccharide (LPS); E. coli; O-polysaccharide; Mannosyltransferase; Modular Enzyme; Polymerase

Biosynthesis of the polymannose lipopolysaccharide O-antigens from Escherichia coli serotypes O8 and O9a requires a unique combination of single- and multiple-active site mannosyltransferases - Greenfield, Laura K.; Richards, Michele R.; Li, Jianjun; Wakarchuk, Warren W.; Lowary, Todd L.; Whitfield, Chris (Journal of Biological Chemistry, 2012)
The Escherichia coli O9a and O8 O-antigen serotypes represent model systems for the ABC transporter-dependent synthesis of bacterial polysaccharides. The O9a and O8 antigens are linear mannose homopolymers containing conserved reducing termini (the primer-adaptor), a serotype-specific repeat unit domain, and a terminator. Synthesis of these glycans occurs on the polyisoprenoid lipid-linked primer, undecaprenol pyrophosphoryl-GlcpNAc, by two conserved mannosyltransferases, WbdC and WbdB, and a serotype-specific mannosyltransferase, WbdA. The glycan structure and pattern of conservation in the O9a and O8 mannosyltransferases are not consistent with the existing model of O9a biosynthesis. Here we establish a revised pathway using a combination of in vivo (mutant complementation) experiments and in vitro strategies with purified enzymes and synthetic acceptors. WbdC and WbdB synthesize the adaptor region, where they transfer one and two α-(1→3)-linked mannose residues, respectively. The WbdA enzymes are solely responsible for forming the repeat unit domains of these O-antigens. WbdA^O9a has two predicted active sites and polymerizes a tetrasaccharide repeat unit containing two α-(1→3)- and two α-(1→2)-linked mannopyranose residues. In contrast, WbdA^O8 polymerizes trisaccharide repeat units containing single α-(1→3)-, α-(1→2)-, and β-(1→2)-mannopyranoses. These studies illustrate assembly systems exploiting several mannosyltransferases with flexible active sites, arranged in single- and multiple-domain formats.
Keywords: Cell Wall; Escherichia coli; Glycobiology' Glycoconjugate; Glycosyltransferases; Lipopolysaccharide (LPS); O-antigen; Bacterial Cell Envelope; Mannosyltransferases; Polysaccharides; O-polysaccharide; Glycan Synthesis

Enzymatic engineering of polysialic acid on cells in vitro and in vivo using a purified bacterial polysialyltransferase - El Maarouf, Abderrahman; Moyo-Lee Yaw, Damali; Lindhout, Theresa; Pearse, Damien D.; Wakarchuk, Warren; Rutishauser, Urs (Journal of Biological Chemistry, 2012)
In vertebrates, polysialic acid (PSA) is typically added to the neural cell adhesion molecule (NCAM) in the Golgi by PST or STX polysialyltransferase. PSA promotes plasticity, and its enhanced expression by viral delivery of the PST or STX gene has been shown to promote cellular processes that are useful for repair of the injured adult nervous system. Here we demonstrate a new strategy for PSA induction on cells involving addition of a purified polysialyltransferase from Neisseria meningitidis (PSTNm) to the extracellular environment. In the presence of its donor substrate (CMP-Neu5Ac), PSTNm synthesized PSA directly on surfaces of various cell types in culture, including Chinese hamster ovary cells, chicken DF1 fibroblasts, primary rat Schwann cells, and mouse embryonic stem cells. Similarly, injection of PSTNm and donor in vivo was able to produce PSA in different adult brain regions, including the cerebral cortex, striatum, and spinal cord. PSA synthesis by PSTNm requires the presence of the donor CMP-Neu5Ac, and the product could be degraded by the PSA-specific endoneuraminidase-N. Although PSTNm was able to add PSA to NCAM, most of its product was attached to other cell surface proteins. Nevertheless, the PSTNm-induced PSA displayed the ability to attenuate cell adhesion, promote neurite outgrowth, and enhance cell migration as has been reported for endogenous PSA-NCAM. Polysialylation by PSTNm occurred in vivo in less than 2.5 h, persisted in tissues, and then decreased within a few weeks. Together these characteristics suggest that a PSTNm-based approach may provide a valuable alternative to PST gene therapy.
Keywords: Adhesion; Bioengineering; Glycobiology; Glycoprotein Biosynthesis; Glycosyltransferases; Cell Surface; Neuroplasticity; Polysialic Acid; Polysialyltransferase; Tissue Repair

Differential glycosylation of polar and lateral flagellins in Aeromonas hydrophila AH-3 - Wilhelms, Markus; Fulton, Kelly M.; Twine, Susan M.; Tomas, Juan M.; Merino, Susana (Journal of Biological Chemistry, 2012)
Polar and lateral flagellin proteins from Aeromonas hydrophila strain AH-3 (serotype O34) were found to be glycosylated with different carbohydrate moieties. The lateral flagellin was modified at three sites in O-linkage, with a single monosaccharide of 376 Da, which we show to be a pseudaminic acid derivative. The polar flagellin was modified with a heterogeneous glycan, comprised of a heptasaccharide, linked through the same 376-Da sugar to the protein backbone, also in O-linkage. In-frame deletion mutants of pseudaminic acid biosynthetic genes pseB and pseF homologues resulted in abolition of polar and lateral flagellar formation by posttranscriptional regulation of the flagellins, which was restored by complementation with wild type pseB or F homologues or Campylobacter pseB and F.
Keywords: Bacteria; Genetics; Glycoprotein; Molecular Biology; Mutagenesis; Flagellin; Mass Spectrometry; Pseudaminic Acid

Secondary cell wall polymers of Enterococcus faecalis are critical for resistance to complement activation via mannose-binding lectin - Geiss-liebisch, Stefan; Rooijakkers, Suzan H. M.; Beczala, Agnieszka; Sanchez-Carballo, Patricia; Kruszynska, Karolina; Repp, Christian; Sakinc, Tuerkan; Vinogradov, Evgeny; Holst, Otto; Huebner, Johannes; Theilacker, Christian (Journal of Biological Chemistry, 2012)
The complement system is part of our first line of defense against invading pathogens. The strategies used by Enterococcus faecalis to evade recognition by human complement are incompletely understood. In this study, we identified an insertional mutant of the wall teichoic acid (WTA) synthesis gene tagB in E. faecalis V583 that exhibited an increased susceptibility to complement-mediated killing by neutrophils. Further analysis revealed that increased killing of the mutant was due to a higher rate of phagocytosis by neutrophils, which correlated with higher C3b deposition on the bacterial surface. Our studies indicated that complement activation via the lectin pathway was much stronger on the tagB mutant compared with wild type. In concordance, we found an increased binding of the key lectin pathway components mannose-binding lectin and mannose-binding lectin-associated serine protease-2 (MASP-2) on the mutant. To understand the mechanism of lectin pathway inhibition by E. faecalis, we purified and characterized cell wall carbohydrates of E. faecalis wild type and V583ΔtagB. NMR analysis revealed that the mutant strain lacked two WTAs with a repeating unit of →6)[α-L-Rhap-(1→3)]β-D-GalpNAc-(1→5)-Rbo-1-P and →6) β-D-Glcp-(1→3) [α-D-Glcp-(1→4)]-β-D-GalpNAc-(1→5)-Rbo-1-P→, respectively (Rbo, ribitol). In addition, compositional changes in the enterococcal rhamnopolysaccharide were noticed. Our study indicates that in E. faecalis, modification of peptidoglycan by secondary cell wall polymers is critical to evade recognition by the complement system.
Keywords: Bacterial Pathogenesis; Cell Wall; Immunology; Innate Immunity; Polysaccharide; Enterococcus faecalis; Complement System; Mannose-binding Lectin; Teichoic Acid

¹H NMR metabolomics analysis of glioblastoma subtypes: correlation between metabolomics and gene expression characteristics - Cuperlovic-Culf, Miroslava; Ferguson, Dean; Culf, Adrian; Morin Jr, Pier; Touaibia, Mohamed (Journal of Biological Chemistry, 2012)
Glioblastoma multiforme (GBM) is the most common form of malignant glioma, characterized by unpredictable clinical behaviors that suggest distinct molecular subtypes. With the tumor metabolic phenotype being one of the hallmarks of cancer, we have set upon to investigate whether GBMs show differences in their metabolic profiles. ¹H NMR analysis was performed on metabolite extracts from a selection of nine glioblastoma cell lines. Analysis was performed directly on spectral data and on relative concentrations of metabolites obtained from spectra using a multivariate regression method developed in this work. Both qualitative and quantitative sample clustering have shown that cell lines can be divided into four groups for which the most significantly different metabolites have been determined. Analysis shows that some of the major cancer metabolic markers (such as choline, lactate, and glutamine) have significantly dissimilar concentrations in different GBM groups. The obtained lists of metabolic markers for subgroups were correlated with gene expression data for the same cell lines. Metabolic analysis generally agrees with gene expression measurements, and in several cases, we have shown in detail how the metabolic results can be correlated with the analysis of gene expression. Combined gene expression and metabolomics analysis have shown differential expression of transporters of metabolic markers in these cells as well as some of the major metabolic pathways leading to accumulation of metabolites. Obtained lists of marker metabolites can be leveraged for subtype determination in glioblastomas.
Keywords: bioinformatics; glioblastoma; metabolomics; transcriptomics; tumor metabolism

Energy landscape analysis of native folding of the prion protein yields the diffusion constant, transition path time, and rates - Yu, Hao; Gupta, Amar Nath; Liu, Xia; Neupane, Krishna; Brigley, Angela M.; Sosova, Iveta; Woodside, Michael T. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Protein folding is described conceptually in terms of diffusion over a configurational free-energy landscape, typically reduced to a one-dimensional profile along a reaction coordinate. In principle, kinetic properties can be predicted directly from the landscape profile using Kramers theory for diffusive barrier crossing, including the folding rates and the transition time for crossing the barrier. Landscape theory has been widely applied to interpret the time scales for protein conformational dynamics, but protein folding rates and transition times have not been calculated directly from experimentally measured free-energy profiles. We characterized the energy landscape for native folding of the prion protein using force spectroscopy, measuring the change in extension of a single protein molecule at high resolution as it unfolded/refolded under tension. Key parameters describing the landscape profile were first recovered from the distributions of unfolding and refolding forces, allowing the diffusion constant for barrier crossing and the transition path time across the barrier to be calculated. The full landscape profile was then reconstructed from force-extension curves, revealing a double-well potential with an extended, partially unfolded transition state. The barrier height and position were consistent with the previous results. Finally, Kramers theory was used to predict the folding rates from the landscape profile, recovering the values observed experimentally both under tension and at zero force in ensemble experiments. These results demonstrate how advances in single-molecule theory and experiment are harnessing the power of landscape formalisms to describe quantitatively the mechanics of folding.
Keywords: kinetics; optical trapping; single molecule

Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems - Shin, Kyuchul; Kumar, Rajnish; Udachin, Konstantin A.; Alavi, Saman; Ripmeester, John A. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
There is interest in the role of ammonia on Saturn’s moons Titan and Enceladus as the presence of water, methane, and ammonia under temperature and pressure conditions of the surface and interior make these moons rich environments for the study of phases formed by these materials. Ammonia is known to form solid hemi-, mono-, and dihydrate crystal phases under conditions consistent with the surface of Titan and Enceladus, but has also been assigned a role as water-ice antifreeze and methane hydrate inhibitor which is thought to contribute to the outgassing of methane clathrate hydrates into these moons’ atmospheres. Here we show, through direct synthesis from solution and vapor deposition experiments under conditions consistent with extraterrestrial planetary atmospheres, that ammonia forms clathrate hydrates and participates synergistically in clathrate hydrate formation in the presence of methane gas at low temperatures. The binary structure II tetrahydrofuran + ammonia, structure I ammonia, and binary structure I ammonia + methane clathrate hydrate phases synthesized have been characterized by X-ray diffraction, molecular dynamics simulation, and Raman spectroscopy methods.
Keywords: ice; single crystal X-ray diffraction; hydrogen bonding; hydrate inhibitors; ethane

Programmed -1 frameshifting efficiency correlates with RNA pseudoknot conformational plasticity, not resistance to mechanical unfolding - Ritchie, Dustin B.; Foster, Daniel A. N.; Woodside, Michael T. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Programmed −1 frameshifting, whereby the reading frame of a ribosome on messenger RNA is shifted in order to generate an alternate gene product, is often triggered by a pseudoknot structure in the mRNA in combination with an upstream slippery sequence. The efficiency of frameshifting varies widely for different sites, but the factors that determine frameshifting efficiency are not yet fully understood. Previous work has suggested that frameshifting efficiency is related to the resistance of the pseudoknot against mechanical unfolding. We tested this hypothesis by studying the mechanical properties of a panel of pseudoknots with frameshifting efficiencies ranging from 2% to 30%: four pseudoknots from retroviruses, two from luteoviruses, one from a coronavirus, and a nonframeshifting bacteriophage pseudoknot. Using optical tweezers to apply tension across the RNA, we measured the distribution of forces required to unfold each pseudoknot. We found that neither the average unfolding force, nor the unfolding kinetics, nor the parameters describing the energy landscape for mechanical unfolding of the pseudoknot (energy barrier height and distance to the transition state) could be correlated to frameshifting efficiency. These results indicate that the resistance of pseudoknots to mechanical unfolding is not a primary determinant of frameshifting efficiency. However, increased frameshifting efficiency was correlated with an increased tendency to form alternate, incompletely folded structures, suggesting a more complex picture of the role of the pseudoknot involving the conformational dynamics.
Keywords: force spectroscopy; gene regulation; RNA folding; translation

Charge transport in molecular electronic junctions: compression of the molecular tunnel barrier in the strong coupling regime - Sayed, Sayed Y.; Fereiro, Jerry A.; Yan, Haijun; Mccreery, Richard L.; Bergren, Adam Johan (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Molecular junctions are essentially modified electrodes familiar to electrochemists where the electrolyte is replaced by a conducting “contact.” It is generally hypothesized that changing molecular structure will alter system energy levels leading to a change in the transport barrier. Here, we show the conductance of seven different aromatic molecules covalently bonded to carbon implies a modest range (< 0.5 eV) in the observed transport barrier despite widely different free molecule HOMO energies (> 2 eV range). These results are explained by considering the effect of bonding the molecule to the substrate. Upon bonding, electronic inductive effects modulate the energy levels of the system resulting in compression of the tunneling barrier. Modification of the molecule with donating or withdrawing groups modulate the molecular orbital energies and the contact energy level resulting in a leveling effect that compresses the tunneling barrier into a range much smaller than expected. Whereas the value of the tunneling barrier can be varied by using a different class of molecules (alkanes), using only aromatic structures results in a similar equilibrium value for the tunnel barrier for different structures resulting from partial charge transfer between the molecular layer and the substrate. Thus, the system does not obey the Schottky-Mott limit, and the interaction between the molecular layer and the substrate acts to influence the energy level alignment. These results indicate that the entire system must be considered to determine the impact of a variety of electronic factors that act to determine the tunnel barrier.
Keywords: energy alignment; molecular electronics; electronic coupling; charge transport; Fermi-level pinning

Direct observation of multiple misfolding pathways in a single prion protein molecule - Yu, Hao; Liu, Xia; Neupane, Krishna; Gupta, Amar Nath; Brigley, Angela M.; Solanki, Allison; Sosova, Iveta; Woodside, Michael T. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Protein misfolding is a ubiquitous phenomenon associated with a wide range of diseases. Single-molecule approaches offer a powerful tool for deciphering the mechanisms of misfolding by measuring the conformational fluctuations of a protein with high sensitivity. We applied single-molecule force spectroscopy to observe directly the misfolding of the prion protein PrP, a protein notable for having an infectious misfolded state that is able to propagate by recruiting natively folded PrP. By measuring folding trajectories of single PrP molecules held under tension in a high-resolution optical trap, we found that the native folding pathway involves only two states, without evidence for partially folded intermediates that have been proposed to mediate misfolding. Instead, frequent but fleeting transitions were observed into off-pathway intermediates. Three different misfolding pathways were detected, all starting from the unfolded state. Remarkably, the misfolding rate was even higher than the rate for native folding. A mutant PrP with higher aggregation propensity showed increased occupancy of some of the misfolded states, suggesting these states may act as intermediates during aggregation. These measurements of individual misfolding trajectories demonstrate the power of single-molecule approaches for characterizing misfolding directly by mapping out nonnative folding pathways.
Keywords: protein folding; optical tweezers

Vertebrate-like regeneration in the invertebrate chordate amphioxus - Somorjai, Ildikó M. L.; Somorjai, Rajmund L.; Garcia-fernandez, Jordi; Escriva, Hector (Proceedings of the National Academy of Sciences of the United States of America, 2012)
An important question in biology is why some animals are able to regenerate, whereas others are not. The basal chordate amphioxus is uniquely positioned to address the evolution of regeneration. We report here the high regeneration potential of the European amphioxus Branchiostoma lanceolatum. Adults regenerate both anterior and posterior structures, including neural tube, notochord, fin, and muscle. Development of a classifier based on tail regeneration profiles predicts the assignment of young and old adults to their own class with >94% accuracy. The process involves loss of differentiated characteristics, formation of an msx-expressing blastema, and neurogenesis. Moreover, regeneration is linked to the activation of satellite-like Pax3/7 progenitor cells, the extent of which declines with size and age. Our results provide a framework for understanding the evolution and diversity of regeneration mechanisms in vertebrates.
Keywords: invertebrate chordate-vertebrate transition; stem cells; cephalochordate

A network extraction tool for mineral exploration: a case study from the Wopmay Orogen, Northwest Territories, Canada - Lee, Madeline; Morris, William; Harris, Jeff; Leblanc, George (Exploration Geophysics, 2012)
Many mineral exploration initiatives target regional- and local-scale lineaments (e.g. fault systems and dyke swarms) as they may act as conduits for mineralized fluids. In this work, we apply an automatic lineament ‘network extraction’ method that draws on similar processes as the Blakely-Simpson peak detection algorithm and a stream network extraction algorithm commonly used in the mapping of drainage patterns from a topographic surface (e.g. DEM, DTM) within a Geographic Information System (GIS) environment. We apply the network extraction algorithm to a magnetic surface (grid) rather than a topographic surface. The method uses a simple quadratic surface across a 3 × 3 window to determine the degree of surface slope and if the centre cell of the window represents a localised low point in the surface. Thus this routine is particularly effective at identifying magnetic lows that may represent faults, which have undergone magnetite depletion (e.g. hematization). These lineament solutions provide insight into mineral exploration vectors through the computation of rose diagrams, fracture density plots and intersection locations. These diagrams, plots, and locations are used in conjunction with other geophysical layers (e.g. radiometrics) to help identify potential mineral exploration targets. We successfully applied this algorithm to an aeromagnetic dataset from the Wopmay Orogen in Northwestern Canada. This area is characterised by extensive regional and localised fault systems and dyke swarms, along with promising polymetallic hydrothermal mineral occurrences. Key areas for follow up exploration are identified through a combined study of geophysical grids and lineament analysis.
Keywords: geographic information system, lineament analysis, magnetics, mineral exploration, potential field.

A simple adaptable data fusion methodology for geophysical exploration - Leblanc, George; Lee, Madeline; Morris, William (Exploration Geophysics, 2012)
We present a simple and adaptive method of data fusion using grey-scale grids for general geophysical exploration. The methodology relies upon: (1) understanding the physical property variations that might be associated with the mineral exploration target, and (2) applying appropriate (forward or inverse) grey-scaling to each input dataset so that before addition of the grids the anomalous patterns all express the phenomena of interest in the same sense (i.e. all positive anomalies). If the resulting fused dataset has a Gaussian population distribution then a linear grey-scale is applied to the data within the 95% (2σ) confidence interval; if it is non-Gaussian then the linear grey scale is applied to the entire dataset. The methodology has been applied to very low frequency (VLF), aeromagnetic and radiometric data measured during the 1980s over the Hemlo disseminated lode-gold deposit. The resulting fused data derived from our methodology produces a coherent region of anomalous geophysical response that is coincident in location and geometry to the surficial extent of the known mineralized zone of the deposit. Integration of multi-sensor response has the added advantage of significantly reducing the number of false-targets. Further, this method also illustrates the continued benefits that can be obtained from re-evaluation of older data.
Keywords: electromagnetics, magnetics, mineral exploration, radiometrics, VLF

The Renner effect in triatomic molecules - Bunker, P. R.; Kraemer, W. P.; Hirano, Tsuneo; Jensen, Per (International Conference of Computational Methods in Sciences and Engineering 2009: (ICCMSE 2009), 2012)
To calculate the rovibronic energies of a triatomic molecule in an electronic state that is degenerate at linear nuclear configurations, it is necessary to allow for the breakdown of the Born-Oppenheimer approximation. This is because the electronic degeneracy is resolved at bent configurations and there is a nonnegligible coupling between the two states caused by molecular rotation. This is termed the Renner (or Renner-Teller) effect. To calculate the rovibronic term values and wavefunctions in this situation, we have developed a variational computational procedure and we have included the effect of spin-orbit coupling for nonsinglet states. The wavefunctions can be used to predict and interpret the results of Coulomb explosion imaging experiments. We can also calculate spectral line intensities so that absorption and emission spectra can be simulated. We review the work and our application to the CH+2 and FeOH molecules.

Highlighted symposium in computational spectroscopy high precision calculations of molecular energy levels and spectra - Bunker, Philip; Schwerdtfeger, Peter (International Conference of Computational Methods in Sciences and Engineering 2009: (ICCMSE 2009), 2012)

The Renner effect in triatomic molecules - Bunker, P. R.; Kraemer, W. P.; Hirano, Tsuneo; Jensen, Per (International Conference of Computational Methods in Sciences and Engineering 2009: (ICCMSE 2009), 2012)
To calculate the rovibronic energies of a triatomic molecule in an electronic state that is degenerate at linear nuclear configurations, it is necessary to allow for the breakdown of the Born-Oppenheimer approximation. This is because the electronic degeneracy is resolved at bent configurations and there is a nonnegligible coupling between the two states caused by molecular rotation. This is termed the Renner (or Renner-Teller) effect. To calculate the rovibronic term values and wavefunctions in this situation, we have developed a variational computational procedure and we have included the effect of spin-orbit coupling for nonsinglet states. The wavefunctions can be used to predict and interpret the results of Coulomb explosion imaging experiments. We can also calculate spectral line intensities so that absorption and emission spectra can be simulated. We review the work and our application to the CH+2 and FeOH molecules.

The rainbow instanton method: A new approach to tunneling splitting in polyatomics - Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio (The Journal of Chemical Physics, 2012)
A new instanton approach is reported to tunneling at zero-temperature in multidimensional (MD) systems in which a “light particle” is transferred between two equivalent “heavy” sites. The method is based on two concepts. The first is that an adequate MD potential energy surface can be generated from input of the stationary configurations only, by choosing as a basis the normal modes of the transition state. It takes the form of a double-minimum potential along the mode with imaginary frequency and coupling terms to the remaining (harmonic) oscillators. Standard integrating out of the oscillators gives rise to an effective 1D instanton problem for the adiabatic potential, but requires evaluation of a nonlocal term in the Euclidean action, governed by exponential (memory) kernels. The second concept is that this nonlocal action can be treated as a “perturbation,” for which a new approximate instanton solution is derived, termed the “rainbow” solution. Key to the approach is avoidance of approximations to the exponential kernels, which is made possible by a remarkable conversion property of the rainbow solution. This leads to a new approximation scheme for direct evaluation of the Euclidean action, which avoids the time-consuming search of the exact instanton trajectory. This “rainbow approximation” can handle coupling to modes that cover a wide range of frequencies and bridge the gap between the adiabatic and sudden approximations. It suffers far fewer restrictions than these conventional approximations and is proving particularly effective for systems with strong coupling, such as proton transfer in hydrogen bonds. Comparison with the known exact instanton action in two-dimensional models and application to zero-level tunneling splittings in two isotopomers of malonaldehyde are presented to show the accuracy and efficiency of the approach.

Time-resolved photoelectron imaging of excited state relaxation dynamics in phenol, catechol, resorcinol, and hydroquinone - Livingstone, Ruth A.; Thompson, James O. F.; Iljina, Marija; Donaldson, Ross J.; Sussman, Benjamin J.; Paterson, Martin J.; Townsend, Dave (The Journal of Chemical Physics, 2012)
Time-resolved photoelectron imaging was used to investigate the dynamical evolution of the initially prepared S1 (ππ*) excited state of phenol (hydroxybenzene), catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene) following excitation at 267 nm. Our analysis was supported by ab initio calculations at the coupled-cluster and CASSCF levels of theory. In all cases, we observe rapid (<1 ps) intramolecular vibrational redistribution on the S1potential surface. In catechol, the overall S1 state lifetime was observed to be 12.1 ps, which is 1–2 orders of magnitude shorter than in the other three molecules studied. This may be attributed to differences in the H atom tunnelling rate under the barrier formed by a conical intersection between the S1 state and the close lying S2 (πσ*) state, which is dissociative along the O–H stretching coordinate. Further evidence of this S1/S2 interaction is also seen in the time-dependent anisotropy of the photoelectron angular distributions we have observed. Our data analysis was assisted by a matrix inversion method for processing photoelectron images that is significantly faster than most other previously reported approaches and is extremely quick and easy to implement.

Sequence-dependent effects of cryoprotectants on the active sites of the human ABO(H) blood group A and B glycosyltransferases - Johal, Asha R.; Schuman, Brock; Alfaro, Javier A.; Borisova, Svetlana; Seto, Nina O. L.; Evans, Stephen V. (Acta Crystallographica Section D: Biological Crystallography, 2012)
The human ABO(H) A and B blood group glycosyltransferases GTA and GTB differ by only four amino acids, yet this small dissimilarity is responsible for significant differences in biosynthesis, kinetics and structure. Like other glycosyltransferases, these two enzymes have been shown to recognize substrates through dramatic conformational changes in mobile polypeptide loops surrounding the active site. Structures of GTA, GTB and several chimeras determined by single-crystal X-ray diffraction demonstrate a range of susceptibility to the choice of cryoprotectant, in which the mobile polypeptide loops can be induced by glycerol to form the ordered closed conformation associated with substrate recognition and by MPD [hexylene glycol, (±)-2-methyl-2,4-pentanediol] to hinder binding of substrate in the active site owing to chelation of the Mn²⁺ cofactor and thereby adopt the disordered open state. Glycerol is often avoided as a cryoprotectant when determining the structures of carbohydrate-active enzymes as it may act as a competitive inhibitor for monosaccharide ligands. Here, it is shown that the use of glycerol as a cryoprotectant can additionally induce significant changes in secondary structure, a phenomenon that could apply to any class of protein.
Keywords: cryoprotectants; glycosyltransferases; GTA; GTB

Time-of-flight Bragg scattering from aligned stacks of lipid bilayers using the Liquids Reflectometer at the Spallation Neutron Source - Pan, Jianjun; Heberle, Frederick A.; Carmichael, Justin R.; Ankner, John F.; Katsaras, John (Journal of Applied Crystallography, 2012)
Time-of-flight (TOF) neutron diffraction experiments on aligned stacks of lipid bilayers using the horizontal Liquids Reflectometer at the Spallation Neutron Source are reported. Specific details are given regarding the instrumental setup, data collection and reduction, phase determination of the structure factors, and reconstruction of the one-dimensional neutron scattering length density (NSLD) profile. The validity of using TOF measurements to determine the one-dimensional NSLD profile is demonstrated by reproducing the results of two well known lipid bilayer structures. The method is then applied to show how an antimicrobial peptide affects membranes with and without cholesterol.
Keywords: time-of-flight neutron diffraction; Spallation Neutron Source; Liquids Reflectometer; lipid bilayers

Broadband Purcell enhanced emission dynamics of quantum dots in linear photonic crystal waveguides - Laucht, A.; Günthner, T.; Pütz, S.; Saive, R.; Frédérick, S.; Hauke, N.; Bichler, M.; Amann, M.-C.; Holleitner, A. W.; Kaniber, M.; Finley, J. J. (Journal of Applied Physics, 2012)
The authors investigate the spontaneous emission dynamics of self-assembled InGaAs quantum dots embedded in GaAs photonic crystal waveguides. For an ensemble of dots coupled to guided modes in the waveguide, we report spatially, spectrally, and time-resolved photoluminescence measurements, detecting normal to the plane of the photonic crystal. For quantum dots emitting in resonance with the waveguide mode, an ∼21× enhancement of photoluminescence intensity is observed as compared to dots in the unprocessed region of the wafer. This enhancement can be traced back to the Purcell enhanced emission of quantum dots into leaky and guided modes of the waveguide with moderate Purcell factors up to ∼4×. Emission into guided modes is shown to be efficiently scattered out of the waveguide within a few microns, contributing to the out-of-plane emission and allowing the use of photonic crystal waveguides as broadband, efficiency-enhancing structures for surface-emitting diodes or single photon sources.

A little ribbing: flux starvation engineering for rippled indium tin oxide nanotree branches - Tucker, Ryan T.; Beaudry, Allan L.; LaForge, Joshua M.; Taschuk, Michael T.; Brett, Michael J. (Applied Physics Letters, 2012)
Combining vapour-liquid-solid growth with glancing angle deposition (VLS-GLAD) facilitates fabrication of branched nanowires not possible with either technique alone. Indiumtin oxide (ITO) nanostructuresgrown by VLS-GLAD produce extremely porous nanotree structures, where periodic branch diameter oscillations are sometimes observed. We explain this rippled branch growth with a simple model linking the physics governing branch growth to the process variables controlled in VLS-GLAD. The model is verified by inducing specific, aperiodic ripples onto growing ITO branches through macroscopic vapour flux control and manipulation of local shadowing.

A semiconductor under insulator technology in indium phosphide - Mnaymneh, K.; Dalacu, D.; Frédérick, S.; Lapointe, J.; Poole, P. J.; Williams, R. L. (Applied Physics Letters, 2012)
This letter introduces a semiconductor-under-insulator (SUI) technology in InP for designing strip waveguides that interfaceInPphotonic crystal membrane structures. Strip waveguides in InP-SUI are supported under an atomic layer deposited insulator layer in contrast to strip waveguides in silicon supported oninsulator. We show a substantial improvement in optical transmission when using InP-SUI strip waveguides interfaced with localized photonic crystal membrane structures when compared with extended photonic crystal waveguide membranes. Furthermore, SUI makes available various fiber-coupling techniques used in SOI, such as sub-micron coupling, for planar membrane III-V systems.

Omnidirectional reflection from nanocolumnar TiO2 films - Leontyev, Viktor; Hawkeye, Matthew; Kovalenko, Andriy; Brett, Michael J. (Journal of Applied Physics, 2012)
Anisotropic properties of columnar nanoporous thin films were utilized to design and fabricate interference mirrors with lossless omnidirectional reflection in the visible spectral range. Index graded columnar films with distributed Bragg reflector (DBR), sinusoidal, and Gaussian refractive index profiles were studied using finite-difference frequency-domain and finite-difference time-domain methods, with an emphasis on maximizing the omnidirectional reflection bandwidth. Titanium dioxide columnar films with sixteen period sinusoidal refractive index profile were fabricated using the glancing angle deposition technique and characterized by angle resolved transmittance measurements. Simulations and experimental measurements have shown the presence of the omnidirectional reflection band up to 5% wide for a film with a maximum refractive index nmax=2.3 and refractive index contrast Δn=0.8. Simulations further showed that with the optimal choice of the refractive index variation range, the omnidirectional reflection band can reach 10.5% width in TiO2films with a sinusoidal index profile, 14.5% with a DBR index profile, and 12% with a Gaussian profile. Due to the optical anisotropy of the columnar films, the reflection bandwidth exceeded the corresponding value, observed in isotropic analogs, by a factor of three to four depending on the choice of the refractive index profile.

Assembled Fe3O4 nanoparticles on graphene for enhanced electromagnetic wave losses - Guan, P. F.; Zhang, X. F.; Guo, J. J. (Applied Physics Letters, 2012)
We present an one-step procedure for the synthesis of hybrid Fe3O4 nanoparticles/graphene composite with self-assemble superlattices of Fe3O4nanoparticles. We find that the Fe3O4/graphene nanocomposite exhibits both enhanced dielectric losses and magnetic losses at 2–18 GHz, resulting from the interfacial polarizations between the Fe3O4nanoparticles and the graphene, as well as the coupling between the neighbouring Fe3O4nanoparticles. Theoretical simulations uncover the origins of the electromagnetic losses of hybrid Fe3O4/graphene nanocomposite and provide additional insight into the microscopic dielectric polarization mechanism.

Enhanced charge detection of spin qubit readout via an intermediate state - Studenikin, S. A.; Thorgrimson, J.; Aers, G. C.; Kam, A.; Zawadzki, P.; Wasilewski, Z. R.; Bogan, A.; Sachrajda, A. S. (Applied Physics Letters, 2012)
We employ an intermediate excited charge state of a lateral quantum dot device to increase the charge detection contrast during the qubit state readout procedure, allowing us to increase the visibility of coherent qubit oscillations. This approach amplifies the coherent oscillation magnitude but has no effect on the detector noise resulting in an increase in the signal to noise ratio. In this letter, we apply this scheme to demonstrate a significant enhancement of the fringe contrast of coherent Landau-Zener-Stückelberg oscillations between singlet S and triplet two-spin states.

Effect of small cage guests on hydrogen bonding of tetrahydrofuran in binary structure II clathrate hydrates - Alavi, Saman; Ripmeester, John A. (The Journal of Chemical Physics, 2012)
Molecular dynamics simulations of the pure structure II tetrahydrofuran clathrate hydrate and binary structure II tetrahydrofuran clathrate hydrate with CO2, CH4, H2S, and Xe small cage guests are performed to study the effect of the shape, size, and intermolecular forces of the small cages guests on the structure and dynamics of the hydrate. The simulations show that the number and nature of the guest in the small cage affects the probability of hydrogen bonding of the tetrahydrofuran guest with the large cage water molecules. The effect on hydrogen bonding of tetrahydrofuran occurs despite the fact that the guests in the small cage do not themselves form hydrogen bonds with water. These results indicate that nearest neighbour guest-guest interactions (mediated through the water lattice framework) can affect the clathrate structure and stability. The implications of these subtle small guest effects on clathrate hydrate stability are discussed.

New infrared bands of nonpolar OCS dimer and experimental frequencies for two intermolecular modes - Afshari, M.; Dehghany, M.; McKellar, A. R. W; Moazzen-Ahmadi, N. (The Journal of Chemical Physics, 2012)
Spectra of the nonpolar carbonyl sulfide dimer in the region of the OCS ν1 fundamental band were observed in a slit-jet supersonic expansion. The jet was probed using radiation from a tunable diode laser employed in a rapid-scan signal averaging mode. Six new bands were observed and analyzed, all of which originate from the dimer ground vibrational state. Three were vibrational fundamentals involving the (18OCS)2 and 16OCS-18OCS isotopologues. They enabled an estimate to be made of the frequency of the infrared-forbidden mode corresponding to in-phase vibration of the OCS monomers in the dimer, a value needed to obtain an intermolecular vibrational frequency from one of the observed combination bands. A relatively weak b-type dimer band centered at 2103.105 cm−¹ was assigned to the OCS 4ν2 (l = 0) bending overtone. Combination bands were observed involving the geared bend and van der Waals stretch intermolecular modes. The resulting experimental frequencies of 37.5(20) cm−¹ for the bend and 42.9727(1) cm−¹ for the stretch are in good agreement with a recent high level theoretical calculation.

Self-organized InAs/InGaAsP quantum dot tube lasers - Bianucci, Pablo; Mukherjee, Shouvik; Dastjerdi, M. Hadi Tavakoli; Poole, Philip J.; Mi, Zetian (Applied Physics Letters, 2012)
We report the achievement of a semiconductor tube laser that can operate in the optical communication wavelength range for applications in the emerging Si-photonics. Such nanoscale devices are fabricated from self-organized InAs/InGaAsP quantum dotnanomembranes through a strain-driven self-rolling mechanism using standard photolithography process. Under continuous wave optical pumping, the devices exhibit an ultralow lasing threshold of ∼1.26 μW at 82 K, with multiple emission wavelengths in the S band of optical communications. The spontaneous emission coupling factor and Purcell factor are estimated to be ∼0.30 and ∼4.8, respectively.

Magnetooptic coupling coefficients for one- and two-magnon Raman scattering in rutile-structure antiferromagnets FeF₂, MnF₂, CoF₂, and NiF₂ - Lockwood, D. J.; Cottam, M. G. (Low Temperature Physics, 2012)
Inelastic light scattering intensities in response to magnetic excitations are governed by magnetooptic coupling coefficients, which have been previously evaluated, for instance, for the ferrimagnetic Y3Fe5O12 (YIG) and the metamagnetic FeCl2 and FeBr2. However, by far the most detailed studies to date were performed on the classic rutile-structure antiferromagnets, and here we summarize the results obtained from the many experimental and theoretical investigations of these compounds for both one-magnon and two-magnon excitations. A comparison of the magnitudes of the various coupling coefficients for MnF2, FeF2, CoF2, and NiF2 reveals a surprising similarity in many coefficients. In one-magnon Raman scattering the in-phase linear magnetooptic coefficient dominates, and the main differences between MnF2, FeF2, and NiF2 lie in the relative significance of the in-phase quadratic magnetooptic coefficient. Thus, the quadratic coefficients now appear to be of particular importance in determining the strength of one-magnon scattering in a variety of magnetic insulators. In two-magnon Raman scattering one magnetooptic coefficient is dominant for all of these antiferromagnets. However, the other six coefficients are in general remarkably similar in magnitude and not negligible in most cases, indicating some similarity in the way light interacts with the pairs of magnons of opposite and equal wave vectors in rutile structure antiferromagnets.
Keywords: Antiferromagnets; Coupling coefficient; Ferrimagnets; In-phase; Inelastic light scattering; Magnetic excitations; Magnetic insulator; Magnons; Metamagnets; One-magnon Raman scattering; Quadratic coefficients; Rutile structure; Theoretical investigations; Two-magnon Raman scattering; Wave vector; Oxide minerals; Raman scattering; Antiferromagnetic materials

Nanophotonic detection of side-coupled nanomechanical cantilevers - Sauer, V. T. K.; Diao, Z.; Freeman, M. R.; Hiebert, W. K. (Applied Physics Letters, 2012)
A silicon nanophotonic Mach-Zehnder interferometer (MZI) is used to detect the mechanical resonance of a cantilever external to a nanophotonicwaveguide. Small cantilever devices, below the cut-off for waveguide supported modes, are fabricated ∼140 nm away from one MZI arm. Cantilever resonant frequencies up to 60 MHz are measured with mechanical quality factors around 20 000 and signal to noise ratios up to 1000. Phase-locked loop frequency stability measurements indicate a mass sensitivity of 2 zg in an example cantilever of 0.5 pg mass. An interferometric transduction mechanism is confirmed, and the system is shown to work effectively in all-optical operation.

Spectroscopic observation of nitrous oxide pentamers - Rezaei, Mojtaba; Oliaee, J. Norooz; Moazzen-Ahmadi, N.; McKellar, A. R. W. (The Journal of Chemical Physics, 2012)
Two new infrared bands in the ν1 fundamental region of N2O are observed in a supersonic jet expansion and assigned to nitrous oxide pentamers. Each band is measured using both 14N2 16O and 15N2 16O. Although they are similar in appearance, the bands have slightly different lower state rotational parameters, and are thus assigned to distinct structural isomers of the pentamer. Cluster calculations using two N2O intermolecular potentials give results in good agreement with the observed spectra, and indicate that the two isomers probably have the same basic structure (which is unsymmetrical), but differ in the alignment (N-N-O or O-N-N) of one or two of the constituent monomers. Calculations using a resonant dipole interaction model also support the proposed assignment and structure. These are the first reported high-resolution spectra for N2O pentamers.

Excitation wavelength dependent photoluminescence in structurally non-uniform Si/SiGe-island heteroepitxial multilayers - Modi, N.; Lockwood, D. J.; Wu, X.; Baribeau, J.-M.; Tsybeskov, L. (Journal of Applied Physics, 2012)
In nanometer-size Si/SiGe-island heteroepitxial multilayers grown on Si(001), low temperature photoluminescence spectra are observed that strongly depend on the excitation wavelength and show a strong correlation with structural properties revealed by transmission electron microscopy. These experimental results can be explained by assuming that the optically created carriers are strongly localized at Si/SiGe island heterointerfaces. We show that electron-hole pairs are generated and recombine within spatial regions mainly defined by the photoexcitation penetration depth, and that the estimated exciton diffusion length is notably short and comparable with the SiGe-island average size.

Gas field ion source current stability for trimer and single atom terminated W(111) tips - Urban, Radovan; Pitters, Jason L.; Wolkow, Robert A. (Applied Physics Letters, 2012)
Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.

Pulsed thermography image processing for damage growth monitoring - Genest, M. (Review of progress in quantitative nondestructive evaluation : Burlington, Vermont, USA : 17-22 July 2011, 2012)
An image processing algorithm based on a combination of the most commonly used signal processing techniques in pulsed thermography is applied to monitor the progression of impact damage sites during the full-scale testing of a composite test article. It is demonstrated that the algorithm can be used to monitor damage during a durability and damage tolerance testing. Over the first phase of the test program, although no damage growth was detected, the processed pulsed thermography images showed that the average standard deviation of the measurements was only ~0.08 inches, the equivalent of 2 infrared camera pixels.

Dynamics of localized excitons in Ga0.69In0.31N0.015As0.985/GaAs quantum well: experimental studies and Monte-Carlo simulations - Baranowski, M.; Kudrawiec, R.; Latkowska, M.; Syperek, M.; Misiewicz, J.; Gupta, J. A. (Applied Physics Letters, 2012)
Time resolved photoluminescence (PL) spectroscopy has been applied to study dynamics of localized excitons in a single Ga0.7In0.3N0.015As0.985/GaAs quantum well(QW). The decay time constant, τPL, has been determined for different PL peak energies at various temperatures. An increase in temperature produced two effects: (i) a reduction of τPL and (ii) changes in the τPLdispersion. These two experimental observations as well as the shape of PL decay curves were very well reproduced by Monte-Carlo simulations of hopping excitons with parameters derived from PL and photoreflectance measurements for this QW.

Photovoltaic infrared detection with p-type graded barrier heterostructures - Pitigala, P. K. D. D. P.; Matsik, S. G.; Perera, A. G. U.; Khanna, S. P.; Li, L. H.; Linfield, E. H.; Wasilewski, Z. R.; Buchanan, M.; Liu, H. C. (Journal of Applied Physics, 2012)
Photovoltaicinfrared detectors have significant advantages over photoconductive detectors due to zero bias operation, requiring low power and having reduced low frequency noise. They also exhibit no thermally assisted tunneling currents, leading to higher operating temperatures. p-type emitter/graded barrier GaAs/AlxGa1−xAs structures were tested as photovoltaicdetectors in the infrared region, operating under uncooled conditions and without an applied bias voltage. A photovoltaic responsivity of 450 mV/W was obtained with a detectivity (D*) of 1.2 × 10^6 Jones at a peak wavelength 1.8 μm at 300 K. Responsivity and D* increased to ∼1.2 V/W and 2.8 × 10^6 Jones, respectively, at 280 K. A non-linear improvement in responsivity was observed with increased emitter thickness.

Creation and recovery of a W(111) single atom gas field ion source - Pitters, Jason L.; Urban, Radovan; Wolkow, Robert A. (The Journal of Chemical Physics, 2012)
Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

First science results with a new, inexpensive liquid crystal polarimeter module for the DAO 1.8m telescope - Bohlender, David; Monin, Dmitry (Stellar polarimetry : from birth to death, 2012)
A new polarimeter module has been built for the Dominion Astrophysical Observatory's (DAO) 1.8m Plaskett telescope for a hardware cost, including spare components, of approximately CDN$5,000. Implemented as a plug-in addition to the telescope's existing Cassegrain spectrograph, the device is being used to obtain medium resolution (R ≈ 10;000) circular spectropolarimetry of stars in an approximately 280Å wide wavelength region centered on the Hβ line. The intermediate resolution of the spectrograph permits stellar longitudinal magnetic field measurements to be made with both single or multiple strong metallic lines as well as the Hβ line. The instrument's dual-beam design together with fast switching of the liquid crystal wave plate (up to 100 Hz) synchronized with charge shuffling on the CCD is used to significantly reduce instrumental effects and achieve high precision polarimetric measurements. In this paper we present the first new science results obtained with the instrument. These include the discovery of a strong magnetic field and co-rotating magnetosphere in the helium-weak star HD176582, the detection of several new magnetic stars, and a study of the observed (and occasionally very large) differences in stellar longitudinal magnetic fields as measured with the Hβ line and metallic lines.

Recent developments in submillimeter polarimetry archives, the polarization spectrum and the interpretation of polarization data - Matthews, Brenda C.; Vaillancourt, John E. (Stellar polarimetry : from birth to death, 2012)
Significant progress has been made in our understanding of the power of polarization maps in the submillimeter and millimeter in the past decade. This is made more remarkable by the dearth of new polarimetric facilities over the past 10 years and decommissioning of several long-standing instruments. In particular, we discuss recent work to establish the validity of the previously measured polarization spectrum in the submillimeter, and the enhanced analysis techniques presented in recent years for the interpretation of polarization position angle data without the need for models of the ordered field geometry.

Square spiral photonic crystal with visible bandgap - Krabbe, Joshua D.; Leontyev, Viktor; Taschuk, Michael T.; Kovalenko, Andriy; Brett, Michael J. (Journal of Applied Physics, 2012)
Nanoimprint lithography was combined with glancing angle deposition (GLAD) of titanium dioxide to fabricate a square spiral columnar film with a bandgap in the visible spectral range. Nanoimprint stamps were fabricated with seed spacing ranging from 80 to 400 nm, and four periods of square spiral film were deposited on top of the 320 nm array of seeds. The ratio of lattice spacing, vertical pitch and spiral arm swing was chosen as a : P : A = 1 : 1.35 : 0.7 and the deposition angle was fixed at 86° to maximize the square spiral film’s bandgap.Reflectivity measurements show that the fabricated structure exhibit a pseudo-gap centered at around 600 nm wavelength, in good agreement with finite difference electromagnetic simulations. The absence of a full 3D bandgap is due the deviation of GLAD columns’ cross-section from the optimal one, which has to be highly elongated in the deposition plane. However, simulations show that a geometry close to the fabricated one will produce a full 3D bandgap, if the structure is inverted. The material refractive index in such an inverted photonic crystal can be as low as n = 2.15.

A 3-dimensional time-resolved photothermal deflection “Mirage” method - Astrath, N. G. C.; Malacarne, L. C.; Lukasievicz, G. V. B.; Bernabe, H. S.; Rohling, J. H.; Baesso, M. L.; Shen, J.; Bialkowski, S. E. (Applied Physics Letters, 2012)
A three-dimensional time-resolved theory and experiment for photothermal deflection spectroscopy is developed. The heat conduction equations for two semi-infinite media consisting of an opaque sample and a fluid are solved considering temperature and energy flux balance conditions for a Gaussian heat source. The time dependent perpendicular deflection signal is calculated and compared to experimental measurements on glassy carbon and copper samples. Excellent agreement with literature values for thermal diffusivity of the samples is found. The transient behavior is analyzed for different coupling fluids.

Could diastereoselectivity in the presence of O-2 chiral nonparticipating groups be an indicator of glycopyranosyl oxacarbenium ions in glycosylation reactions? - Kumar, Rishi; Whitfield, Dennis M. (The Journal of Organic Chemistry, 2012)
Although long postulated, the existence of glycopyranosyl oxacarbenium ions as intermediates or transition states (TS) in chemical glycosylation reactions has not been convincingly demonstrated experimentally. It is anticipated that elucidation of such reactive species will greatly assist synthetic chemists to control the α/β stereoselectivity by rational means. Previous density functional theory (DFT) calculations from our group found that the torsion potential about C-2–O-2 in protected glycopyranosyl donors changed from a conventional 3-fold rotor to a 2-fold rotor with a strong syn (CH-2–C-2–O-2–CPg) preference once the donor was ionized to its oxacarbenium ion. This suggested to us that if CPg of the protecting group was a chiral carbon, then diastereoselectivity might be observed in glycosylation reactions that proceed through oxacarbenium ions. The hypothesis to test is as follows: if a nonparticipating O-2 racemic chiral protecting group exhibits diastereoselectivity in glycosylation reactions, then the reaction probably proceeds through an oxacarbenium ion intermediate or TS. We present data for O-2 ether-protected d-glucopyranosyl donors where the racemic protecting group 1-methyl 1′-methylcyclopropylmethyl (MCPM) provides the chirality. MCPM proves to be more activating than the O-2-benzyl ether, and in cases where the donor is otherwise deactivated, several examples of moderate diastereoselectivity are found. These results can be interpreted to indicate that a continuum of reactivity exists where some glycosyl donors form oxacarbenium ions in glycosylation reactions but more reactive donors do not. The strongly activating properties of the cyclopropylmethyl ether functionality and the ability to induce diastereoselectivity with chiral derivatives strongly suggest widespread applications.

Kinetic solvent effects on hydrogen abstraction from phenol by the cumyloxyl radical. Toward an understanding of the role of protic solvents - Bietti, Massimo; Salamone, Michela; DiLabio, Gino A.; Jockusch, Steffen; Turro, Nicholas J. (The Journal of Organic Chemistry, 2012)
A time-resolved kinetic study of the hydrogen atom abstraction reactions from phenol by the cumyloxyl radical (CumO•) was carried out in different solvents. The hydrogen atom abstraction rate constant (kH) was observed to decrease by almost 3 orders of magnitude on going from isooctane to MeOH. In TFE, MeCN/H2O 2:1, and MeOH, the measured kH values were lower than expected on the basis of the Snelgrove–Ingold (SI) equation that correlates log kH to the solvent hydrogen bond acceptor (HBA) ability parameter β2H. As these solvents also act as hydrogen bond donors (HBDs), we explored the notion that a more thorough description of solvent effects could be provided by including a solvent HBD ability term, α2H, into the SI equation via β2H(1 + α2H). The inclusion of such a term greatly improves the fitting for TFE, MeCN/H2O 2:1, and MeOH but at the expense of that for tertiary alkanols. This finding suggests that, for the reaction of CumO• with phenol, the HBA and HBD abilities of both the solvent and the substrate could be responsible for the observed KSEs. but this requires that primary and tertiary alkanols exhibit different solvation behaviors. Possible explanations for this different behavior are explored.

Inhibition of Galactosyltransferases by a Novel Class of Donor Analogues - Descroix, Karine; Pesnot, Thomas; Yoshimura, Yayoi; Gehrke, Sebastian S.; Wakarchuk, Warren; Palcic, Monica M.; Wagner, Gerd K. (Journal of Medicinal Chemistry, 2012)
Galactosyltransferases (GalT) are important molecular targets in a range of therapeutic areas, including infection, inflammation, and cancer. GalT inhibitors are therefore sought after as potential lead compounds for drug discovery. We have recently discovered a new class of GalT inhibitors with a novel mode of action. In this publication, we describe a series of analogues which provide insights, for the first time, into SAR for this new mode of GalT inhibition. We also report that a new C-glycoside, designed as a chemically stable analogue of the most potent inhibitor in this series, retains inhibitory activity against a panel of GalTs. Initial results from cellular studies suggest that despite their polarity, these sugar-nucleotides are taken up by HL-60 cells. Results from molecular modeling studies with a representative bacterial GalT provide a rationale for the differences in bioactivity observed in this series. These findings may provide a blueprint for the rational development of new GalT inhibitors with improved potency.

Oligosaccharide and peptidoglycan of Ganoderma lucidum activate the immune response in human mononuclear cells - Tsai, Chia-Che; Yang, Feng-Ling; Huang, Zih-You; Chen, Chien-Sheng; Yang, Yu-Liang; Hua, Kuo-Feng; Li, Jianjun; Chen, Shui-Tein; Wu, Shih-Hsiung (Journal of Agricultural and Food Chemistry, 2012)
The acid-hydrolyzed fragments of Ganoderma lucidum polysaccharides (GLPS) obtained by Smith degradation were separated by size-exclusion chromatography into two major water-soluble fractions: peptidoglycans (GLPS-SF1) and oligosaccharides (GLPS-SF2). Both fractions induced CD69 in human peripheral blood mononuclear cells (hPB-MNCs), and they displayed distinct immunomodulating properties. GLPS-SF1, with a molecular weight of around 20 kDa, were heterogeneous peptidoglycans composed of glucose/mannose (4:1) that exhibited biological activities with Th1 cytokines IL-12, IL-2, TNF-α, and IFN-γ in hPB-MNCs and stimulated macrophage cytokine expression via Toll-like receptor 4 (TLR4) signaling. For GLPS-SF2, with a molecular weight of around several kilodaltons, its sugar sequence was elucidated by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy as [−α-1,4-Glc–(β-1,4-GlcA)3−]n. This oligosaccharide displayed specific immune property with low monocyte induction, greatly stimulated cell activation and proliferation of NK and T cells. This oligosaccharide isolated from G. lucidum polysaccharides with internal glucuronic acids/glucose repeat unit in a 3:1 ratio may be responsible for the active stimulation of NK and T cells.
Keywords: Ganoderma lucidum; peptidoglycan; oligosaccharide; glucuronic acid; human mononuclear cells

Infrared spectra of CO2-doped hydrogen clusters, (H2)N–CO2 - McKellar, A. R. W. (The Journal of Chemical Physics, 2012)
Clusters of para-H2 and/or ortho-H2 containing a single carbon dioxide molecule are studied by high resolution infrared spectroscopy in the 2300 cm−¹ region of the CO2 ν3 fundamental band. The (H2) N –CO2 clusters are formed in a pulsed supersonic jet expansion from a cooled nozzle and probed using a rapid scan tunable diode laser. Simple symmetric rotor type spectra are observed with little or no resolved K-structure, and prominent Q-branch features for ortho-H2 but not para-H2. Observed rotational constants and vibrational shifts are reported for ortho-H2 up to N = 7 and para-H2 up to N = 15, with the N > 7 assignments only made possible with the help of theoretical simulations. The para-H2 cluster with N = 12 shows clear evidence for superfluid effects, in good agreement with theory. The presence of larger clusters with N > 15 is evident in the spectra, but specific assignments are not possible. Mixed para- + ortho-H2 cluster transitions are well predicted by linear interpolation between corresponding pure cluster line positions.

Chemical synthesis and immunological evaluation of the inner core oligosaccharide of Francisella tularensis - Boltje, Thomas J.; Zhong, Wei; Park, Jin; Wolfert, Margreet A.; Chen, Wangxue; Boons, Geert-jan (Journal of the American Chemical Society, 2012)
Francisella tularensis, which is a Gram negative bacterium that causes tularemia, has been classified by the Center for Disease Control and Prevention (CDC) as a category A bioweapon. The development of vaccines, immunotherapeutics, and diagnostics for F. tularensis requires a detailed knowledge of the saccharide structures that can be recognized by protective antibodies. We have synthesized the inner core region of the lipopolysaccharide (LPS) of F. tularensis to probe antigenic responses elicited by a live and subunit vaccine. The successful preparation of the target compound relied on the use of a disaccharide which was modified by the orthogonal protecting groups diethylisopropylsilyl (DEIPS), 2-naphthylmethyl (Nap), allyl ether (All), and levulinoyl (Lev) ester. The ability to remove the protecting groups in different orders made it possible to establish the optimal glycosylations sequence to prepare a highly crowded 1,2,3-cis configured branching point. A variety of different methods were exploited to control anomeric selectivities of the glycosylations. A comparison of the ¹H NMR spectra of isolated material and the synthetic derivative confirmed the reported structural assignment of the inner core oligosaccharide of F. tularensis. The observation that immunizations with LPS lead to antibody responses to the inner core saccharides provides an impetus to further explore this compound as a vaccine candidate.

Four-wave mixing in carbon nanotube-coated optical fiber gratings - Shao, Li-Yang; Jakubinek, Michael B.; Sun, Tingting; Simard, Benoit; Albert, Jacques (Applied Physics Letters, 2012)
The observation of four-wave mixing(FWM) in single-walled carbon nanotubes(SWCNTs) deposited around a tilted fiber Bragg grating (TFBG) has been demonstrated. A thin, floating SWCNTfilm is manually wrapped around the outer cladding of the fiber and FWM occurs between two core-guided laser signals by TFBG-induced interaction of the core mode and cladding modes. The effective nonlinear coefficient is calculated to be 1.8 × 103 W−¹ Km−¹. The wavelength of generated idlers is tunable with a range of 7.8 nm.

The effect of In-flush on the optical anisotropy of InAs/GaAs quantum dots - Molas, M.; Gołasa, K.; Kuldová, K.; Borysiuk, J.; Babiński, A.; Lapointe, J.; Wasilewski, Z. R. (Journal of Applied Physics, 2012)
The effect of the In-flush technique on the optical anisotropy of InAs/GaAs quantum dots(QDs) has been investigated. The anisotropy was deduced from low temperature microluminescence measurements of the splitting of the emission lines related to single neutral excitons confined to the QDs. It was found that the anisotropy was significantly smaller in a structure grown by the In-flush technique as compared to a structure grown without this procedure. It is proposed that this anisotropy reduction is due to the reduction in the strain generated within the GaAs barrier when using the In-flush procedure.

A Convenient Method for Preparing Alkyl-Functionalized Silicon Nanocubes - Yang, Zhenyu; Dobbie, Alexander R.; Cui, Kai; Veinot, Jonathan G. C. (Journal of the American Chemical Society, 2012)
The first solid-state synthesis of diamond structure silicon nanocube structures with edge lengths of 8–15 nm is reported. It is well-established that controlled high-temperature processing of hydrogen silsesquioxane produces exceptionally well-defined pseudospherical silicon nanocrystals. However, only a small number of accounts outlining shape-controlled synthesis have appeared. We report here that, upon prolonged annealing in an oxide matrix, nanocrystal surfaces thermodynamically self-optimize, yielding particles with cubic geometries. Surface functionalization of the resulting nanocubes is readily achieved via thermal hydrosilylation. Discussion will include description of the synthetic procedure, comprehensive material characterization, and the factors that lead to the formation of cubic structures.

Spatially resolved raman spectroelectrochemistry of solid-state polythiophene/viologen memory devices - Kumar, Rajesh; Pillai, Rajesh G.; Pekas, Nikola; Wu, Yiliang; McCreery, Richard L. (Journal of the American Chemical Society, 2012)
A three terminal molecular memory device was monitored with in situ Raman spectroscopy during bias-induced switching between two metastable states having different conductivity. The device structure is similar to that of a polythiophene field effect transistor, but ethylviologen perchlorate was added to provide a redox counter-reaction to accompany polythiophene redox reactions. The conductivity of the polythiophene layer was reversibly switched between high and low conductance states with a “write/erase” (W/E) bias, while a separate readout circuit monitored the polymer conductance. Raman spectroscopy revealed reversible polythiophene oxidation to its polaron form accompanied by a one-electron viologen reduction. “Write”, “read”, and “erase” operations were repeatable, with only minor degradation of response after 200 W/E cycles. The devices exhibited switching immediately after fabrication and did not require an “electroforming” step required in many types of memory devices. Spatially resolved Raman spectroscopy revealed polaron formation throughout the polymer layer, even away from the electrodes in the channel and drain regions, indicating that thiophene oxidation “propagates” by growth of the conducting polaron form away from the source electrode. The results definitively demonstrate concurrent redox reactions of both polythiophene and viologen in solid-state devices and correlate such reactions with device conductivity. The mechanism deduced from spectroscopic and electronic monitoring should guide significant improvements in memory performance.

Quantum confinement in Si and Ge nanostructures - Barbagiovanni, E. G.; Lockwood, D. J.; Simpson, P. J.; Goncharova, L. V. (Journal of Applied Physics, 2012)
We apply perturbative effective mass theory as a broadly applicable theoretical model for quantum confinement (QC) in all Si and Genanostructures including quantum wells(QWs), wires (Q-wires), and dots(QDs). Within the limits of strong, medium, and weak QC, valence and conduction band edge energy levels (VBM and CBM) were calculated as a function of QD diameters, QW thicknesses, and Q-wire diameters. Crystalline and amorphous quantum systems were considered separately. Calculated band edge levels with strong, medium, and weak QC models were compared with experimental VBM and CBM reported from X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS), or photoluminescence(PL). Experimentally, the dimensions of the nanostructures were determined directly, by transmission electron microscopy(TEM), or indirectly, by x-ray diffraction (XRD) or by XPS. We found that crystalline materials are best described by a medium confinement model, while amorphous materials exhibit strong confinement regardless of the dimensionality of the system. Our results indicate that spatial delocalization of the hole in amorphous versus crystalline nanostructures is the important parameter determining the magnitude of the band gap expansion, or the strength of the quantum confinement. In addition, the effective masses of the electron and hole are discussed as a function of crystallinity and spatial confinement.

3D hydraulic model studies of pipeline secondary stabilization measures - Baker, Scott; Cornett, Andrew; Knox, Paul (Coastlab 2012 : 4th International Conference on the Application of Physical Modelling to Port and Coastal Protection Book of Abstracts, 2012)
A 3D physical modelling campaign has been conducted to support the efficient and reliable design of secondary stabilization measures for subsea pipelines to be installed as part of the Browse LNG project. Many different secondary stabilization designs were assessed including static and dynamically re-shaping rock berms, gravity anchors, and V-shaped trenches. Modelled rock berm structures were constructed underwater to simulate prototype construction by fallpipe. This study generated a large amount of data and new information concerning the behaviour and reliability of pipeline stabilization measures in shallow water under extreme short-crested waves and currents.

Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study - Tulk, C. A.; Klug, D. D.; Dos Santos, A. M.; Karotis, G.; Guthrie, M.; Molaison, J. J.; Pradhan, N. (The Journal of Chemical Physics, 2012)
A neutron diffraction study was performed on the CD4 : D2O structure H clathrate hydrate to refine its CD4 fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris–Edinburgh press and in situneutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD4 molecules in the large 20-hedron (5^12 6^8) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (5^12) and 12-hedron (4^3 5^6 6^3) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD4 molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water–methane hydrophobic interaction in clathrate hydrates and related dense structures.

Thermo-mechanical sensitivity calibration of nanotorsional magnetometers - Losby, Joseph; Burgess, Jacob A. J.; Diao, Zhu; Fortin, David C.; Hiebert, Wayne K.; Freeman, Mark R. (Journal of Applied Physics, 2012)
We report on the fabrication of sensitive nanotorsional resonators, which can be utilized as magnetometers for investigating the magnetization dynamics in small magnetic elements. The thermo-mechanical noise is calibrated with the resonator displacement in order to determine the ultimate mechanical torque sensitivity of the magnetometer.

Ultraviolet ZnSe1–xSx gradient-alloyed nanocrystals via a noninjection approach - Yu, Kui; Hrdina, Amy; Ouyang, Jianying; Kingston, David; Wu, Xiaohua; Leek, Donald M.; Liu, Xiangyang; Li, Chunsheng (ACS Applied Materials and Interfaces, 2012)
Highly emissive ultraviolet ZnSeS nanocrystals (NCs), with a core–shell-like structure, were designed and synthesized via a one-step noninjection approach in 1-octadecene (ODE). These ultraviolet ZnSeS NCs exhibit bright bandgap emission with high color purity and little trap emission. With full width at half-maximum (fwhm) of 21 nm only, photoluminescent (PL) quantum yield (QY) of 60% was estimated for one ensemble dispersed in toluene exhibiting bandgap absorption peaking at 380 nm and bandgap emission at 389 nm. These alloyed ZnSeS NCs present a cubic crystal structure consisting of a Se-rich core and a S-rich shell. Such a gradiently alloyed structure was suggested by our investigation on the temporal evolution of optical properties of the growing ZnSeS NCs monitored from 80 to 300 °C, together with structural and compositional characterization performed with XRD, XPS, EDX, and TEM. This newly developed one-step noninjection approach was achieved with zinc oleate (Zn(OA)2), diphenylphosphine selenide (SeDPP), and diphenylphosphine sulfide (SDPP) as Zn, Se, and S precursors, respectively. ZnSe monomers mainly participated in nucleation at 120 °C, while both ZnSe and ZnS monomers contributed to NC formation in later growth stages (160 °C and higher). 31P NMR study demonstrates that SeDPP is more reactive than SDPP toward Zn(OA)2, and also supports such a model proposed on the combination of ZnSe and ZnS monomers leading to nucleation/growth of ZnSeS alloyed NCs. The present study offers conceptual methodology to various highly photoluminescent alloyed NCs with high quality, high particle yield, and high synthetic reproducibility.
Keywords: alloyed ZnSeS nanocrystals; colloidal quantum dots; photoluminescent; diphenylphosphine; noninjection approach

Andromeda and the Milky Way: twin sisters, distant relations, or strangers in the night? - McConnachie, A.; Richardson, J.; Mackey, D.; PAndAS collaboration (EPJ web of conferences: assembling the puzzle of the Milky Way, 2012)
I summarize some recent key results from the Pan-Andromeda Archaeological Survey (PAndAS), in particular showing how recent discoveries in and around M31 compare to the known structure of the Milky Way and its satellite population.

Multiple H 2 Occupancy of Cages of Clathrate Hydrate under Mild Conditions - Lu, Hailong; Wang, Jianwei; Liu, Changling; Ratcliffe, Christopher I.; Becker, Udo; Kumar, Rajnish; Ripmeester, John (Journal of the American Chemical Society, 2012)
Experiments were carried out by reacting H2 gas with N2 hydrate at a temperature of 243 K and a pressure of 15 MPa. The characterizations of the reaction products indicated that multiple H2 molecules can be loaded into both large and small cages of structure II clathrate hydrates. The realization of multiple H2 occupancy of hydrate cages under moderate conditions not only brings new insights into hydrogen clathrates but also refreshes the perspective of clathrate hydrates as hydrogen storage media.

Organic nanostructures on hydrogen-terminated silicon report on electric field modulation of dangling bond charge state - Ryan, Peter M.; Livadaru, Lucian; Dilabio, Gino A.; Wolkow, Robert A. (Journal of the American Chemical Society, 2012)
We pursue dynamic charge and occupancy modulation of silicon dangling bond sites on H–Si(100)-2 × 1 with a biased scanning tunneling microscope tip and demonstrate that the reactivity and mechanism of product formation of cyclobutylmethylketone (CBMK) on the surface at the active sites may be thus spatially regulated. Reactivity is observed to be dependent on the polarity between tip and surface while the area over which reactivity modulation is established scales according to the dopant concentration in the sample. We account for these observations with examination of the competition kinetics applicable to the CBMK/H–Si reaction and determine how said kinetics are affected by the charge state of DB sites associated with reaction initiation and propagation. Our experiments demonstrate a new paradigm in lithographic control of a self-assembly process on H–Si and reveal a variant to the well-known radical mediated chain reaction chemistry applicable to the H–Si surface where self-assembly is initiated with dative bond formation between the molecule and a DB site.

A DEBRIS disk around the planet hosting M-star GJ 581 spatially resolved with Herschel - Lestrade, J.-F.; Matthews, B. C.; Sibthorpe, B.; Kennedy, G. M.; Wyatt, M. C.; Bryden, G.; Greaves, J. S.; Thilliez, E.; Moro-Martín, A.; Booth, M.; Dent, W. R. F.; Duchêne, G.; et al. (Astronomy & Astrophysics, 2012)
Debris disks have been found primarily around intermediate and solar mass stars (spectral types A–K) but rarely around low mass M-type stars. We have spatially resolved a debris disk around the remarkable M3-type star GJ 581 hosting multiple planets using deep PACS images at 70, 100 and 160 μm as part of the DEBRIS Program on the Herschel Space Observatory. This is the second spatially resolved debris disk found around an M-type star, after the one surrounding the young star AU Mic (12 Myr). However, GJ 581 is much older (2–8 Gyr), and is X-ray quiet in the ROSAT data. We fit an axisymmetric model of the disk to the three PACS images and found that the best fit model is for a disk extending radially from 25 ± 12 AU to more than 60 AU. Such a cold disk is reminiscent of the Kuiper belt but it surrounds a low mass star (0.3 M⊙) and its fractional dust luminosity Ldust/L∗ of ~ 10-4 is much higher. The inclination limits of the disk found in our analysis make the masses of the planets small enough to ensure the long-term stability of the system according to some dynamical simulations. The disk is collisionally dominated down to submicron-sized grains and the dust cannot be expelled from the system by radiation or wind pressures because of the low luminosity and low X-ray luminosity of GJ 581. We suggest that the correlation between low-mass planets and debris disks recently found for G-type stars also applies to M-type stars. Finally, the known planets, of low masses and orbiting within 0.3 AU from the star, cannot dynamically perturb the disk over the age of the star, suggesting that an additional planet exists at larger distance that is stirring the disk to replenish the dust.

On the incidence of weak magnetic fields in DA white dwarfs - Landstreet, J. D.; Bagnulo, S.; Valyavin, G. G.; Fossati, L.; Jordan, S.; Monin, D.; Wade, G. A. (Astronomy & Astrophysics, 2012)
Context. About 10% of white dwarfs have magnetic fields with strength in the range between about 105 and 5 × 108 G. It is not known whether the remaining white dwarfs are not magnetic, or if they have magnetic fields too weak to be detected with the techniques adopted in the large surveys. Information is particularly lacking for the cooler (and generally fainter) white dwarfs. Aims. We describe the results of the first survey specifically devised to clarify the detection frequency of kG-level magnetic fields in cool DA white dwarfs. Methods. Using the FORS1 instrument of the ESO VLT, we have obtained Balmer line circular spectropolarimetric measurements of a small sample of cool (DA6 – DA8) white dwarfs. Using FORS and UVES archive data, we have also revised numerous white dwarf field measurements previously published in the literature. Results. We have discovered an apparently constant longitudinal magnetic field of ~9.5 kG in the DA6 white dwarf WD 2105−820. This star is the first weak-field white dwarf that has been observed sufficiently to roughly determine the characteristics of its field. The available data are consistent with a simple dipolar morphology with magnetic axis nearly parallel to the rotation axis, and a polar strength of ≃ 56 kG. Our re-evaluation of the FORS archive data for white dwarfs indicates that longitudinal magnetic fields weaker than 10 kG have previously been correctly identified in at least three white dwarfs. However, for one of these three weak-field stars (WD 2359−434), UVES archive data show a ~100 kG mean field modulus. Either at the time of the FORS observations the star’s magnetic field axis was nearly perpendicular to the line of sight, or the star’s magnetic field has rather complex structure. Conclusions. We find that the probability of detecting a field of kG strength in a DA white dwarf is of the order of 10% for each of the cool and hot DA stars. If there is a lower cutoff to field strength in white dwarfs, or a field below which all white dwarfs are magnetic, the current precision of measurements is not yet sufficient to reveal it.
Keywords: white dwarfs, stars: magnetic field

A catalogue of Paschen-line profiles in standard stars - Huang, W.; Wallerstein, G.; Stone, M. (Astronomy & Astrophysics, 2012)
We have assembled an atlas of line profiles of the Paschen Delta (Pδ) line at 10 049 Å for the use of stellar modelling. For a few stars we have substituted the Paschen Gamma (Pγ) line at 10 938 Å because the Pδ line blends with other features. Most of the targets are standard stars of spectral types from B to M. A few metal-poor stars have been included. For many of the stars we have also observed the Hydrogen Alpha (Hα) line so as to compare the profiles of lines originating from the meta-stable n = 2 level with lines originating from the n = 3 level. The greatest difference in line profile is found for high luminosity and cool stars where the departures from local thermodynamic equilibrium (LTE) in the population of the n = 2 level is expected to be the greatest. For a few stars, sample line profiles have been calculated in the LTE approximation to demonstrate the usefulness of the tabulated and displayed catalogue.

Unraveling the mechanism of catalytic reduction of O2 by microperoxidase-11 adsorbed within a transparent 3D-nanoporous ITO film - Renault, Christophe; Andrieux, Claude P.; Tucker, Ryan T.; Brett, Michael J.; Balland, Véronique; Limoges, Benoît (Journal of the American Chemical Society, 2012)
Nanoporous films of indium tin oxide (ITO), with thicknesses ranging from 250 nm to 2 μm, were prepared by Glancing Angle Deposition (GLAD) and used as highly sensitive transparent 3D-electrodes for quantitatively interrogating, by time-resolved spectroelectrochemistry, the reactivity of microperoxidase-11 (MP-11) adsorbed within such films. The capacitive current densities of these 3D-electrodes as well as the amount of adsorbed MP-11 were shown to be linearly correlated to the GLAD ITO film thickness, indicating a homogeneous distribution of MP-11 across the film as well as homogeneous film porosity. Under saturating adsorption conditions, MP-11 film concentration as high as 60 mM was reached. This is equivalent to a stack of 110 monolayers of MP-11 per micrometer film thickness. This high MP-11 film loading combined with the excellent ITO film conductivity has allowed the simultaneous characterization of the heterogeneous one-electron transfer dynamics of the MP-11 FeIII/FeII redox couple by cyclic voltammetry and cyclic voltabsorptometry, up to a scan rate of few volts per second with a satisfactory single-scan signal-to-noise ratio. The potency of the method to unravel complex redox coupled chemical reactions was also demonstrated with the catalytic reduction of oxygen by MP-11. In the presence of O2, cross-correlation of electrochemical and spectroscopic data has allowed us to determine the key kinetics and thermodynamics parameters of the redox catalysis that otherwise could not be easily extracted using conventional protein film voltammetry. On the basis of numerical simulations of cyclic voltammograms and voltabsorptograms and within the framework of different plausible catalytic reaction schemes including appropriate approximations, it was shown possible to discriminate between different possible catalytic pathways and to identify the relevant catalytic cycle. In addition, from the best fits of simulations to the experimental voltammograms and voltabsorptograms, the partition coefficient of O2 for the ITO film as well as the values of two kinetic rate constants could be extracted. It was finally concluded that the catalytic reduction of O2 by MP-11 adsorbed within nanoporous ITO films occurs via a 2-electron mechanism with the formation of an intermediate FeIII–OOH adduct characterized by a decay rate of 11 s⁻¹. The spectroelectroanalytical strategy presented here opens new opportunities for characterizing complex redox-coupled chemical reactions not only with redox proteins, but also with redox biomimetic systems and catalysts. It might also be of great interest for the development and optimization of new spectroelectrochemical sensors and biosensors, or eventually new photoelectrocatalytic systems or biofuel cells.

Herschel observations of B1-bS and B1-bN: two first hydrostatic core candidates in the Perseus star-forming cloud - Pezzuto, S.; Elia, D.; Schisano, E.; Strafella, F.; Di Francesco, J.; Sadavoy, S.; André, P.; Benedettini, M.; Bernard, J. P.; Di Giorgio, A. M.; Facchini, A.; Hennemann, M.; et al. (Astronomy & Astrophysics, 2012)
We report far-infrared Herschel observations obtained between 70 μm and 500 μm of two star-forming dusty condensations, [HKM99] B1-bS and [HKM99] B1-bN, in the B1 region of the Perseus star-forming cloud. In the western part of the Perseus cloud, B1-bS is the only source detected in all six PACS and SPIRE photometric bands, but it is not visible in the Spitzer map at 24 μm. B1-bN is clearly detected between 100 μm and 250 μm. We have fitted the spectral energy distributions of these sources to derive their physical properties, and find that a simple greybody model fails to reproduce the observed spectral energy distributions. At least a two-component model is required, consisting of a central source surrounded by a dusty envelope. The properties derived from the fit, however, suggest that the central source is not a Class 0 object. We then conclude that while B1-bS and B1-bN appear to be more evolved than a pre-stellar core, the best-fit models suggest that their central objects are younger than a Class 0 source. Hence, they may be good candidates to be examples of the first hydrostatic core phase. The projected distance between B1-bS and B1-bN is a few Jeans lengths. If their physical separation is close to this value, this pair would allow studying the mutual interactions between two forming stars at a very early stage of their evolution.

The spine of the swan: a Herschel study of the DR21 ridge and filaments in Cygnus X - Hennemann, M.; Motte, F.; Schneider, N.; Didelon, P.; Hill, T.; Arzoumanian, D.; Bontemps, S.; Csengeri, T.; André, Ph.; Konyves, V.; Louvet, F.; Marston, A.; et al. (Astronomy & Astrophysics, 2012)
In order to characterise the cloud structures responsible for the formation of high-mass stars, we present Herschel observations of the DR21 environment. Maps of the column density and dust temperature unveil the structure of the DR21 ridge and several connected filaments. The ridge has column densities higher than 10²³ cm-² over a region of 2.3 pc². It shows substructured column density profiles and branches into two major filaments in the north. The masses in the filaments range between 130 and 1400 M⊙, whereas the mass in the ridge is 15 000 M⊙. The accretion of these filaments onto the DR21 ridge, suggested by a previous molecular line study, could provide a continuous mass inflow to the ridge. In contrast to the striations seen in, e.g., the Taurus region, these filaments are gravitationally unstable and form cores and protostars. These coresformed in the filaments potentially fall into the ridge. Both inflow and collisions of cores could be important to drive the observed high-mass star formation. The evolutionary gradient of star formation running from DR21 in the south to the northern branching is traced by decreasing dust temperature. This evolution and the ridge structure can be explained by two main filamentary components of the ridge that merged first in the south.

Globular cluster systems in fossil groups: NGC 6482, NGC 1132, and ESO 306-017 - Alamo-Martínez, K. A.; West, M. J.; Blakeslee, J. P.; González-Lópezlira, R. A.; Jordán, A.; Gregg, M.; Côté, P.; Drinkwater, M. J.; Van den Bergh, S. (Astronomy & Astrophysics, 2012)
We study the globular cluster (GC) systems in three representative fossil group galaxies: the nearest (NGC 6482), the prototype (NGC 1132) and the most massive known to date (ESO 306-017). This is the first systematic study of GC systems in fossil groups. Using data obtained with the Hubble Space Telescope Advanced Camera for Surveys in the F475W and F850LP filters, we determine the GC color and magnitude distributions, surface number density profiles, and specific frequencies. In all three systems, the GC color distribution is bimodal, the GCs are spatially more extended than the starlight, and the red population is more concentrated than the blue. The specific frequencies seem to scale with the optical luminosities of the central galaxy and span a range similar to that of the normal bright elliptical galaxies in rich environments. We also analyze the galaxy surface brightness distributions to look for deviations from the best-fit Sérsic profiles; we find evidence of recent dynamical interaction in all three fossil group galaxies. Using X-ray data from the literature, we find that luminosity and metallicity appear to correlate with the number of GCs and their mean color, respectively. Interestingly, although NGC 6482 has the lowest mass and luminosity in our sample, its GC system has the reddest mean color, and the surrounding X-ray gas has the highest metallicity.

The molecular gas content of the Pipe Nebula - Duarte-Cabral, A.; Chrysostomou, A.; Peretto, N.; Fuller, G. A.; Matthews, B.; Schieven, G.; Davis, G. R. (Astronomy & Astrophysics, 2012)
Context. Star forming regions may share many characteristics, but the specific interplay between gravity, magnetic fields, large-scale dynamics, and protostellar feedback will have an impact on the star formation history of each region. The importance of feedback from outflows is a particular subject to debate, as we are yet to understand the details of their impact on clouds and star formation. Aims. The Pipe Nebula is a nearby molecular cloud hosting the B59 region as its only active star-forming clump. This paper focuses on the global dynamics of B59, its temperature structure, and its outflowing gas, with the goal of revealing the local and global impact of the protostellar outflows. Methods. Using HARP at the James Clerk Maxwell Telescope, we have mapped the B59 region in the J = 3 → 2 transition of 12CO to study the kinematics and energetics of the outflows, and the same transitions of 13CO and C18O to study the overall dynamics of the ambient cloud, the physical properties of the gas, and the hierarchical structure of the region. Results. The B59 region has a total of ~30 M⊙ of cold and quiescent material, mostly gravitationally bound, with narrow line widths throughout. Such low levels of turbulence in the non-star-forming regions within B59 are indicative of the intrinsic initial conditions of the cloud. On the other hand, close to the protostars the impact of the outflows is observed as a localised increase of both C18O line widths from ~0.3 km s-¹ to ~1 km s-¹, and 13CO excitation temperatures by ~2–3 K. The impact of the outflows is also evident in the low column density material which shows signs of being shaped by the outflow bow shocks as they pierce their way out of the cloud. Much of this structure is readily apparent in a dendrogram analysis of the cloud and demonstrates that when decomposing clouds using such techniques a careful interpretation of the results is needed. Conclusions. The low mass of B59 together with its intrinsically quiescent gas and small number of protostars, allows the identification of specific regions where the outflows from the embedded sources interact the dense gas. Our study suggests that outflows are an important mechanism for injecting and sustaining supersonic turbulence at sub-parsec size scales. We find that less than half of the outflow energy is deposited as turbulent energy of the gas, however this turbulent energy is sufficient to slow down the collapse of the region.

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members - Brogaard, K.; Vandenberg, D. A.; Bruntt, H.; Grundahl, F.; Frandsen, S.; Bedin, L. R.; Milone, A. P.; Dotter, A.; Feiden, G. A.; Stetson, P. B.; Sandquist, E.; Miglio, A.; et al. (Astronomy & Astrophysics, 2012)
Context. Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar systems, and in turn, to improve estimates of their age. Aims. In the first paper of this series, we demonstrated how measurements of multiple eclipsing binaries in the old open cluster NGC 6791 sets tighter constraints on the properties of stellar models than has previously been possible, thereby potentially improving both the accuracy and precision of the cluster age. Here we add additional constraints and perform an extensive model comparison to determine the best estimates of the cluster age and helium content, employing as many observational constraints as possible. Methods. We improve our photometry and correct empirically for differential reddening effects. We then perform an extensive comparison of the new colour-magnitude diagrams (CMDs) and eclipsing binary measurements to Victoria and DSEP isochrones in order to estimate cluster parameters. We also reanalyse a spectrum of the star 2–17 to improve [Fe/H] constraints. Results. We find a best estimate of the age of ~8.3 Gyr for NGC 6791 while demonstrating that remaining age uncertainty is dominated by uncertainties in the CNO abundances. The helium mass fraction is well constrained at Y = 0.30±0.01 resulting in ΔY/ΔZ ~  1.4 assuming that such a relation exists. During the analysis we firmly identify blue straggler stars, including the star 2–17, and find indications for the presence of their evolved counterparts. Our analysis supports the RGB mass-loss found from asteroseismology and we determine precisely the absolute mass of stars on the lower RGB, MRGB = 1.15±0.02 M⊙. This will be an important consistency check for the detailed asteroseismology of cluster stars. Conclusions. Using multiple, detached eclipsing binaries for determining stellar cluster ages, it is now possible to constrain parameters of stellar models, notably the helium content, which were previously out of reach. By observing a suitable number of detached eclipsing binaries in several open clusters, it will be possible to calibrate the age-scale and the helium enrichment parameter Δ Y/Δ Z, and provide firm constraints that stellar models must reproduce.

A wide-field near-infrared H₂ 2.122 μm line survey of the Braid Nebula star formation region in Cygnus OB7 - Khanzadyan, T.; Davis, C. J.; Aspin, C.; Froebrich, D.; Smith, M. D.; Magakian, T. Yu.; Movsessian, T.; Moriarty-Schieven, G. H.; Nikogossian, E. H.; Pyo, T.-S.; Beck, T. L. (Astronomy & Astrophysics, 2012)
Context. Outflows and jets are the first signposts of ongoing star formation processes in any molecular cloud, yet their study in optical bands provides limited results due to the large extinction present. Near-infrared unbiased wide-field observations in the H2 1−0 S(1) line at 2.122 μm alleviates the problem, enabling us to detect more outflows and trace them closer to their driving sources. Aims. As part of a large-scale multi-waveband study of ongoing star formation in the Braid Nebula star formation region, we focus on a one square degree region that includes Lynds Dark Nebula 1003 and 1004. Our goal is to find all of the near-infrared outflows, uncover their driving sources and estimate their evolutionary phase. Methods. We use near-infrared wide-field observations obtained with WFCAM on UKIRT, in conjunction with previously-published optical and archival MM data, to search for outflows and identify their driving sources; we subsequently use colour − colour analysis to determine the evolutionary phase of each source. Results. Within a one square degree field we have identified 37 complex MHOs, most of which are new. After combining our findings with other wide-field, multi-waveband observations of the same region we were able to discern 28 outflows and at least 18 protostars. Our analysis suggests that these protostars are younger and/or more energetic than those of the Taurus-Auriga region. The outflow data enable us to suggest connection between outflow ejection and repetitive FU Ori outburst events. We also find that star formation progresses from W to E across the investigated region.

New insights into the mechanism of amine/nitroxide cycling during the hindered amine light stabilizer inhibited oxidative degradation of polymers - Gryn’ova, Ganna; Ingold, K. U.; Coote, Michelle L. (Journal of the American Chemical Society, 2012)
High-level ab initio molecular orbital theory calculations are used to identify the origin of the remarkably high inhibition stoichiometric factors exhibited by dialkylamine-based radical-trapping antioxidants. We have calculated the free energy barriers and reaction energies at 25, 80, and 260 °C in the gas phase and in aqueous solution for a broad range of reactions that might, potentially, be involved in amine/nitroxide cycling, as well as several novel pathways proposed as part of the present work, including that of N-alkyl hindered amine light stabilizer activation. We find that most of the literature nitroxide regeneration cycles should be discarded on either kinetic or thermodynamic grounds; some are even inconsistent with existing experimental observations. We therefore propose a new mechanistic cycle that relies on abstraction of a β-hydrogen atom from an alkoxyamine (R¹R²NOCHR³R⁴). Our results suggest that this cycle is energetically feasible for a range of substrates and provides an explanation for previously misinterpreted or unexplained experimental results. We also explore alternative mechanisms for amine/nitroxide cycling for cases where the alkoxyamines do not possess an abstractable β-hydrogen.

The composite-spectrum binary hypothesis does not explain the λ Bootis stars - Griffin, R. E.; Gray, R. O.; Corbally, C. J. (Astronomy & Astrophysics, 2012)
The existence of the λ Boo type as a class of chemically-peculiar stars in its own right has taxed numerous researchers, and has challenged spectroscopists to produce a model which is plausible, comprehensive and predictive. Stars which are recognized as members of the λ Boo class have late-B to early-F spectral types, and exhibit (often substantially) low abundances of Fe-peak elements although elements such as C, N, O and S may have more nearly solar abundances. Since less than 2% of objects within the relevant spectral-type domain appear to be λ Boo stars their existence has demanded rather special conditions, and has triggered opinion that this group may not in fact exist but that each case can be explained as an unrecognized binary. In this paper we examine those claims by monitoring 10 stars, listed in the literature as possible λ Boo stars but said to be “likely candidates” for composite-spectrum binaries, by employing high-dispersion spectroscopy in an intermittent observing programme designed to reveal the sort of line-profile changes that should be detectable if each object were really a pair of similar stars in an SB2 system. We also monitor two other stars: HR 7903, said to be a binary (but is more like an Ap star), and λ Boo itself. The sample includes 1 possible, 1 marginal and 4 definite λ Boo classifications. In addition, we derive the physical properties of the 12 stars by photometric and spectroscopic synthesis, and measure their radial velocities. Three of the sample show small line-profile variations, but not of the sort that can be attributed to the presence of a companion star; they are the suspected Ap star HR 7903, HR 6878 (which exhibits spectrum peculiarities very similar to those of HR 7903 but has not previously been classified as Bp or Ap), and λ Aql, whose rapid spectrum variations resemble those observed in spotted or CP stars. None of the stars shows any evidence to suggest that it could be a composite-spectrum binary.

Systematic study of compositional and synthetic control of vacancy and magnetic ordering in oxygen-deficient perovskites Ca2Fe2–xMnxO5+y and CaSrFe2–xMnxO5+y(x= 1/2, 2/3, and 1;y= 0–1/2) - Ramezanipour, Farshid; Greedan, John E.; Cranswick, Lachlan M. D.; Garlea, V. Ovidiu; Donaberger, Ronald L.; Siewenie, Joan (Journal of the American Chemical Society, 2012)
Ten compounds belonging to the series of oxygen-deficient perovskite oxides Ca2Fe2–xMnxO5 and CaSrFe2–xMnxO5+y, where x = 1/2, 2/3, and 1 and y ≈ 0–0.5, were synthesized and investigated with respect to the ordering of oxygen vacancies on both local and long-range length scales and the effect on crystal structure and magnetic properties. For the set with y ≈ 0 the oxygen vacancies always order in the long-range sense to form the brownmillerite structure containing alternating layers of octahedrally and tetrahedrally coordinated cations. However, there is a change in symmetry from Pnma to Icmm upon substitution of Sr for one Ca for all x, indicating local Td chain (vacancy) disorder. In the special case of CaSrFeMnO5 the neutron diffraction peaks broaden, indicating only short-range structural order on a length scale of 160 Å. This reveals a systematic progression from Ca2FeMnO5 (Pnma, well-ordered tetrahedral chains) to CaSrFeMnO5 (Icmm, disordered tetrahedral chains, overall short-range order) to Sr2FeMnO5 (Pm3m, destruction of tetrahedral chains in a long-range sense). Systematic changes occur in the magnetic properties as well. While long-range antiferromagnetic order is preserved, the magnetic transition temperature, Tc, decreases for the same x when Sr substitutes for one Ca. A review of the changes in Tc for the series Ca2Fe2–xMxO5, taking into account the tetrahedral/octahedral site preferences for the various M3+ ions, leads to a partial understanding of the origin of magnetic order in these materials in terms of a layered antiferromagnetic model. While in all cases the preferred magnetic moment direction is (010) at low temperatures, there is a cross over for x = 0.5 to (100) with increasing temperature for both the Ca2Fe2–xMnxO5 and the CaSrFe2–xMnxO5 series. For the y > 0 phases, while a brownmillerite ordering of oxygen vacancies is preserved for the Ca2 phases, a disordered Pm3m cubic perovskite structure is always found when Sr is substituted for one Ca. Long-range magnetic order is also lost, giving way to spin glass or cluster-glass-like behavior below 50 K. For the x = 0.5 phase, neutron pair distribution function (NPDF) studies show a local structure related to brownmillerite ordering of oxygen vacancies. Neutron diffraction data at 3.8 K show a broad magnetic feature, incommensurate with any multiple of the chemical lattice, and with a correlation length (magnetic domain) of 6.7(4) Å.

Assembling photoluminescent silicon nanocrystals into periodic mesoporous organosilica - Guan, Min; Wang, Wendong; Henderson, Eric J.; Dag, Ömer; Kübel, Christian; Chakravadhanula, Venkata sai kiran; Rinck, Julia; Moudrakovski, Igor L.; Thomson, Jordan; Mcdowell, Jeffrey; Powell, Annie K.; Zhang, Haixia; et al. (Journal of the American Chemical Society, 2012)
A contemporary question in the intensely active field of periodic mesoporous organosilica (PMO) materials is how large a silsesquioxane precursor can be self-assembled under template direction into the pore walls of an ordered mesostructure. An answer to this question is beginning to emerge with the ability to synthesize dendrimer, buckyball, and polyhedral oligomeric silsesquioxane PMOs. In this paper, we further expand the library of large-scale silsesquioxane precursors by demonstrating that photoluminescent nanocrystalline silicon that has been surface-capped with oligo(triethoxysilylethylene), denoted as ncSi:(CH2CH2Si(OEt)3)nH, can be self-assembled into a photoluminescent nanocrystalline silicon periodic mesoporous organosilica (ncSi-PMO). A comprehensive multianalytical characterization of the structural and optical properties of ncSi-PMO demonstrates that the material gainfully combines the photoluminescent properties of nanocrystalline silicon with the porous structure of the PMO. This integration of two functional components makes ncSi-PMO a promising multifunctional material for optoelectronic and biomedical applications.

Toward a mechanistic understanding of exciton-mediated hydrosilylation on nanocrystalline silicon - Huck, Lawrence A.; Buriak, Jillian M. (Journal of the American Chemical Society, 2012)
White-light initiated hydrosilylation of nanocrystalline porous silicon was found to be far more efficient (in terms of both kinetics and yield) in the presence of electron-accepting molecules with suitably high reduction potentials, particularly halocarbons. It is known that absorption of visible light by nanocrystalline silicon results in the formation of excitons (electron/hole pairs) and that this exciton can be harnessed to drive a hydrosilylation reaction with an alkene; the Si–C bond forms as a result of attack of the π-electrons of the alkene on the positively charged holes. In order to better understand the white-light initiated mechanism through which this reaction takes place, and to compare with UV-mediated photoemission on Si(111)–H, a series of electron acceptors were screened for their effect on surface alkene hydrosilylation. A very strong correlation between reduction potentials (Ered) of the oxidant and reaction efficiency was observed, with a minimum “turn-on” Ered required for an increase to take place. The oxidant appears to accept, or remove, the electron from the nanocrystallite-bound exciton, favoring attack by the alkene on the positively charged Si nanocrystallite, leading to Si–C bond formation. Radical reactions were discounted for a number of reasons, including lack of effect of radical traps, no apparent Si–Cl bond formation, lack of oxidation of the surfaces, and others. Unlike with other oxidants such as nitro-aromatics, halocarbons do not cause additional surface reactions and promote very clean, fast, and selective hydrosilylation chemistry.

The M 16 molecular complex under the influence of NGC 6611 - Hill, T.; Motte, F.; Didelon, P.; White, G. J.; Marston, A. P.; Nguyên Luong, Q.; Bontemps, S.; André, Ph.; Schneider, N.; Hennemann, M.; Sauvage, M.; Di Francesco, J.; et al. (Astronomy & Astrophysics, 2012)
We present Herschel images from the HOBYS key program of the Eagle Nebula (M 16) in the far-infrared and sub-millimetre, using the PACS and SPIRE cameras at 70 μm, 160 μm, 250 μm, 350 μm, 500 μm. M 16, home to the Pillars of Creation, is largely under the influence of the nearby NGC 6611 high-mass star cluster. The Herschel images reveal a clear dust temperature gradient running away from the centre of the cavity carved by the OB cluster. We investigate the heating effect of NGC 6611 on the entire M 16 star-forming complex seen by Herschel including the diffuse cloud environment and the dense filamentary structures identified in this region. In addition, we interpret the three-dimensional geometry of M 16 with respect to the nebula, its surrounding environment, and the NGC 6611 cavity. The dust temperature and column density maps reveal a prominent eastern filament running north-south and away from the high-mass star-forming central region and the NGC 6611 cluster, as well as a northern filament which extends around and away from the cluster. The dust temperature in each of these filaments decreases with increasing distance from the NGC 6611 cluster, indicating a heating penetration depth of ~10 pc in each direction in 3–6  ×  1022 cm-2 column density filaments. We show that in high-mass star-forming regions OB clusters impact the temperature of future star-forming sites, modifying the initialconditions for collapse and effecting the evolutionary criteria of protostars developed from spectral energy distributions. Possible scenarios for the origin of the morphology seen in this region are discussed, including a western equivalent to the eastern filament, which was destroyed by the creation of the OB cluster and its subsequent winds and radiation.