bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved ultraviolet emission performance from polarization-engineered n-ZnO/p-GaN heterojunction diode
Authors: Jiang Junyan , Zhang Yuantao , Chi Chen , Shi Zhifeng , Yan Long , Li Pengchong , Zhang Baolin , Du Guotong
Published: February 2016

O-polar ZnO films were grown on N-polar p-GaN/sapphire substrates by photo-assisted metal-organic chemical vapor deposition, and further heterojunction light-emitting diodes based O-polar n-ZnO/N-polar p-GaN were proposed and fabricated. It is experimentally demonstrated that the interface polarization of O-polar n-ZnO/N-polar p-GaN heterojunction can shift the location of the depletion region from the interface deep into the ZnO side. When a forward bias is applied to the proposed diode, a strong and high-purity ultraviolet emission located at 385 nm can be observed. Compared with conventional Zn-polar n-ZnO/Ga-polar p-GaN heterostructure diode, the ultraviolet emission intensity of the proposed heterojunction diode is greatly enhanced due to the presence of polarization-induced inversion layer at the ZnO side of the heterojunction interface. This work provides an innovative path for the design and development of ZnO-based ultraviolet diode.
Mapping the process dependent conductivity of carbon nanotube thin-films using a non-invasive contact probing system
Authors: Choi Eunsuk , Lee Seung-Beck
Published: February 2016

We report on a non-invasive contact probing (NICP) system for measuring the distribution of local surface conductivity of macroscopic thin-films of carbon nanotubes. Using the NICP system, we were able to obtain the local sheet resistance of the conducting thin-films continuously at ∼10 μm resolution over few centimeters which would not have been possible using conventional contact probing methods. Measurements performed on carbon nanotube thin-films with various nanotube densities, physical, and chemical treatments revealed that the local variation in electrical characteristics was not reflected in global conductance measurements. This demonstrated the usefulness of the NICP system for evaluating the effect of processing on the electrical uniformity of conducting thin-films made using nanomaterials.
From dimers to collective dipoles: Structure and dynamics of methanol/ethanol partition by narrow carbon nanotubes
Authors: Garate Jose A. , Perez-Acle Tomas
Published: February 2016

Alcohol partitioning by narrow single-walled carbon nanotubes (SWCNTs) holds the promise for the development of novel nanodevices for diverse applications. Consequently, in this work, the partition of small alcohols by narrow tubes was kinetically and structurally quantified via molecular dynamics simulations. Alcohol partitioning is a fast process in the order of 10 ns for diluted solutions but the axial-diffusivity within SWCNT is greatly diminished being two to three orders of magnitude lower with respect to bulk conditions. Structurally, alcohols form a single-file conformation under confinement and more interestingly, they exhibit a pore-width dependent transition from dipole dimers to a single collective dipole, for both methanol and ethanol. Energetic analyses demonstrate that this transition is the result of a detailed balance between dispersion and electrostatics interactions, with the latter being more pronounced for collective dipoles. This transition fully modifies the reorientational dynamics of the loaded particles, generating stable collective dipoles that could find usage in signal-amplification devices. Overall, the results herein have shown distinct physico-chemical features of confined alcohols and are a further step towards the understanding and development of novel nanofluidics within SWCNTs.
Effect of interlayer on interfacial thermal transport and hot electron cooling in metal-dielectric systems: An electron-phonon coupling perspective
Authors: Wang Yan , Lu Zexi , Roy Ajit K. , Ruan Xiulin
Published: February 2016

It was reported that an interlayer with intermediate phonon spectra between two dielectric materials could reduce the phononic interfacial thermal resistance. In this work, we show that an appropriate choice of interlayer materials with relatively strong electron-phonon coupling could significantly enhance interfacial thermal transport across metal-dielectric interfaces. Our Boltzmann transport simulations demonstrate that such enhancement is achieved by the elimination of electron-phonon nonequilibrium near the original metal-dielectric interface. Moreover, we reveal that interlayer can substantially accelerate hot electron cooling in thin films with weak electron-phonon coupling, for example, Cu, Ag, and Au, supported on a dielectric substrate. At the same time, lattice heating in the thin film is largely reduced.
Dynamical properties of water-methanol solutions
Authors: Mallamace Francesco , Corsaro Carmelo , Mallamace Domenico , Vasi Cirino , Vasi Sebastiano , Stanley H. Eugene
Published: February 2016

We study the relaxation times tα in the water-methanol system. We examine new data and data from the literature in the large temperature range 163 < T < 335 K obtained using different experimental techniques and focus on how tα affects the hydrogen bond structure of the system and the hydrophobicity of the alcohol methyl group. We examine the relaxation times at a fixed temperature as a function of the water molar fraction XW and observe two opposite behaviors in their curvature when the system moves from high to low T regimes. This behavior differs from that of an ideal solution in that it has excess values located at different molar fractions (XW = 0.5 for high T and 0.75 in the deep supercooled regime). We analyze the data and find that above a crossover temperature T ∼ 223 K, hydrophobicity plays a significant role and below it the water tetrahedral network dominates. This temperature is coincident with the fragile-to-strong dynamical crossover observed in confined water and supports the liquid-liquid phase transition hypothesis. At the same time, the reported data suggest that this crossover temperature (identified as the Widom line temperature) also depends on the alcohol concentration.
Glass-like dynamics of the strain-induced coil/helix transition on a permanent polymer network
Authors: Ronsin O. , Caroli C. , Baumberger T.
Published: February 2016

We study the stress response to a step strain of covalently bonded gelatin gels in the temperature range where triple helix reversible crosslink formation is prohibited. We observe slow stress relaxation towards a T-dependent finite asymptotic level. We show that this is assignable to the strain-induced coil → helix transition, previously evidenced by Courty et al. [Proc. Natl. Acad. Sci. U. S. A. 102, 13457 (2005)], of a fraction of the polymer strands. Relaxation proceeds, in a first stage, according to a stretched exponential dynamics, then crosses over to a terminal simple exponential decay. The respective characteristic times τK and τf exhibit an Arrhenius-like T-dependence with an associated energy E incompatibly larger than the activation barrier height for the isomerisation process which sets the clock for an elementary coil → helix transformation event. We tentatively assign this glass-like slowing down of the dynamics to the long-range couplings due to the mechanical noise generated by the local elementary events in this random elastic medium.
Controlling microstructure, preferred orientation, and mechanical properties of Cr-Al-N by bombardment and alloying with Ta
Authors: Hollerweger R. , Zhou L. , Holec D. , Koller C. M. , Rachbauer R. , Polcik P. , Mayrhofer P. H.
Published: February 2016

Recent ab initio studies showed that the inherent ductility of cubic structured Cr1−xAlxN coatings (as compared with similar hard coatings) significantly increases when alloyed with Ta. As there is only little experimental and theoretical information available, we have performed a combined experimental and ab initio based study on the influence of Ta additions (0, 2, 6, 12, and 26 at. % on the metal sublattice) on structure and mechanical properties of arc evaporated Cr1−x-yAlxTayN coatings with Al/(Cr + Al) ratios >0.61. With increasing Ta-content, the droplet number density decreases and the coating surface smoothens, which is much more pronounced as with increasing the bias potential from −40 to −120 V. Simultaneously, the columnar structure observed for Ta-free Cr0.37Al0.63N significantly changes into a fine-grained structure (crystallite size ∼5 nm) with clearly reduced columnar character. Increasing the Ta content also favors the formation of a preferred 200 growth orientation resulting in a reduction of the indentation moduli E from ∼500 to ∼375 GPa, which is in agreement with ab initio calculations. As the hardness H remains between 34 and 41 GPa, an increased resistance against brittle fracture is indicated with increasing Ta.
Order-disorder phase transition and multiferroic behaviour in a metal organic framework compound (CH3)2NH2Co(HCOO)3
Authors: Yadav Ruchika , Swain Diptikanta , Bhat H. L. , Elizabeth Suja
Published: February 2016

We have investigated the multiferroic and glassy behaviour of metal-organic framework (MOF) material (CH3)2NH2Co(CHOO)3. The compound has perovskite–like architecture in which the metal–formate forms a framework. The organic cation (CH3)2NH2+ occupies the cavities in the formate framework in the framework via N–H···O hydrogen bonds. At room temperature, the organic cation is disordered and occupies three crystallographically equivalent positions. Upon cooling, the organic cation is ordered which leads to a structural phase transition at 155 K. The structural phase transition is associated with a para-ferroelectric phase transition and is revealed by dielectric and pyroelectric measurements. Further, a PE hysteresis loop below 155 K confirms the ferroelectric behaviour of the material. Analysis of dielectric data reveal large frequency dispersion in the values of dielectric constant and tanδ which signifies the presence of glassy dielectric behaviour. The material displays a antiferromagnetic ordering below 15 K which is attributed to the super-exchange interaction between Co2+ ions mediated via formate linkers. Interestingly, another magnetic transition is also found around 11 K. The peak of the transition shifts to lower temperature with increasing frequency, suggesting glassy magnetism in the sample.
Competing descriptions of diffusion profiles with two features: Surface space-charge layer versus fast grain-boundary diffusion
Authors: Schraknepper H. , De Souza R. A.
Published: February 2016

Two different physical processes, (i) fast grain-boundary diffusion (FGBD) of oxygen and (ii) hindered oxygen diffusion in a surface space-charge layer, yield oxygen isotope diffusion profiles in a similar form. Two features are observed, with the short, sharp profile close to the surface being followed by a longer, shallower profile. In this study, we develop a procedure for deciding which of the two descriptions applies to experimentally measured profiles. Specifically, we solve Fick's second law, using finite-element simulations, to obtain oxygen isotope diffusion profiles for the two cases. Each set of profiles is then analysed in terms of the competing description. In this manner, we derive falsifiable conditions that allow physical processes to be assigned unambiguously to the two features of such isotope profiles. Applying these conditions to experimental profiles for SrTiO3 single crystals published in the literature, we find that FGBD is an invalid model for describing the diffusion processes.
Mode transition and hysteresis in inductively coupled radio frequency argon discharge
Authors: Wegner Th. , Küllig C. , Meichsner J.
Published: February 2016

This contribution presents experimental results about the mode transition of an inductively coupled radio frequency (RF) (13.56 MHz) argon discharge at different total gas pressures. In particular, the positive ion saturation current and the line integrated electron density are measured by Langmuir probe and 160 GHz microwave interferometer, respectively. The mode transition strongly depends on the total gas pressure and can appear stepwise or continuously. The space resolved positive ion saturation current is separately shown for the E- and H-mode at different total gas pressures. Therewith, the pressure dependency of the RF sheath thickness indicates a collisional sheath. The hysteresis phenomenon during the E-H and the inverse H-E transition is discussed within the framework of the matching situation for different total gas pressures. The hysteresis width is analyzed using the absorbed power as well as the coil voltage and current. As a result, the width strongly increases with pressure regarding the power and the coil voltage in the E-mode and remains constant in the H-mode. In addition, the phase shift between the coil voltage and current shows a hysteresis effect, too.
A view on coupled cluster perturbation theory using a bivariational Lagrangian formulation
Authors: Kristensen Kasper , Eriksen Janus J. , Matthews Devin A. , Olsen Jeppe , Jørgensen Poul
Published: February 2016

We consider two distinct coupled cluster (CC) perturbation series that both expand the difference between the energies of the CCSD (CC with single and double excitations) and CCSDT (CC with single, double, and triple excitations) models in orders of the Møller-Plesset fluctuation potential. We initially introduce the E-CCSD(T–n) series, in which the CCSD amplitude equations are satisfied at the expansion point, and compare it to the recently developed CCSD(T–n) series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)], in which not only the CCSD amplitude, but also the CCSD multiplier equations are satisfied at the expansion point. The computational scaling is similar for the two series, and both are term-wise size extensive with a formal convergence towards the CCSDT target energy. However, the two series are different, and the CCSD(T–n) series is found to exhibit a more rapid convergence up through the series, which we trace back to the fact that more information at the expansion point is utilized than for the E-CCSD(T–n) series. The present analysis can be generalized to any perturbation expansion representing the difference between a parent CC model and a higher-level target CC model. In general, we demonstrate that, whenever the parent parameters depend upon the perturbation operator, a perturbation expansion of the CC energy (where only parent amplitudes are used) differs from a perturbation expansion of the CC Lagrangian (where both parent amplitudes and parent multipliers are used). For the latter case, the bivariational Lagrangian formulation becomes more than a convenient mathematical tool, since it facilitates a different and faster convergent perturbation series than the simpler energy-based expansion.
Local immunization program for susceptible-infected-recovered network epidemic model
Authors: Wu Qingchu , Lou Yijun
Published: February 2016

The immunization strategies through contact tracing on the susceptible-infected-recovered framework in social networks are modelled to evaluate the cost-effectiveness of information-based vaccination programs with particular focus on the scenario where individuals belonging to a specific set can get vaccinated due to the vaccine shortages and other economic or humanity constraints. By using the block heterogeneous mean-field approach, a series of discrete-time dynamical models is formulated and the condition for epidemic outbreaks can be established which is shown to be not only dependent on the network structure but also closely related to the immunization control parameters. Results show that increasing the immunization strength can effectively raise the epidemic threshold, which is different from the predictions obtained through the susceptible-infected-susceptible network framework, where epidemic threshold is independent of the vaccination strength. Furthermore, a significant decrease of vaccine use to control the infectious disease is observed for the local vaccination strategy, which shows the promising applications of the local immunization programs to disease control while calls for accurate local information during the process of disease outbreak.
A reactant-coordinate-based wave packet method for full-dimensional state-to-state quantum dynamics of tetra-atomic reactions: Application to both the abstraction and exchange channels in the H + H2O reaction
Authors: Zhao Bin , Sun Zhigang , Guo Hua
Published: February 2016

An efficient and accurate wave packet method is proposed for the calculation of the state-to-state S-matrix elements in bimolecular reactions involving four atoms. This approach propagates an initial state specific wave packet in reactant Jacobi coordinates. The projection in product channels is carried out on projection planes, which have one less degree of freedom, by transforming both the time-dependent wave packet and final product states into a set of intermediate coordinates. This reactant-coordinate-based method is more efficient than product-coordinate-based methods because it typically requires a smaller number of basis functions or grid points and allows the determination of S-matrix elements for multiple product channels from a single propagation. This method is demonstrated in calculating the (Jtot = 0) state-to-state S-matrix elements for both the abstraction and exchange channels of the H + H2O reaction.
Temperature dependent electroluminescence from all-Si-nanocrystal p-i-n diodes grown on dielectric substrates
Authors: Wu L. , Puthen-Veettil B. , Nomoto K. , Hao X. , Jia X. , Lin Z. , Yang T. C. , Zhang T. , Gutsch S. , Conibeer G. , Perez-Wurfl I.
Published: February 2016

In this work, we demonstrate for the first time the electroluminescence (EL) from a mesa isolated p-i-n diode based on silicon nanocrystals (Si NCs) embedded in a SiO2 matrix fabricated on a dielectric substrate. The structure fabricated on a dielectric substrate ensures that the EL signal originates entirely from the Si NC material. A small offset between the EL (1.28 eV) and photoluminescence (PL) (1.33 eV) peak energies has been observed at room temperature. We attribute this discrepancy to the different subset of light-emitting Si NCs in EL and PL. A model classifying Si NCs into connected NCs and isolated NCs is proposed. Atom probe tomography is employed to visualize the existence of isolated NCs and connected NCs. This model has been further studied using temperature dependent EL and PL, where a blue-shift of peak energy is observed as the temperature is increased. The blue-shift is attributed to the temperature dependent transport between the two subsets of NCs and the quenching of the PL emission from the connected NCs at higher temperatures.
Artificial perfect electric conductor-perfect magnetic conductor anisotropic metasurface for generating orbital angular momentum of microwave with nearly perfect conversion efficiency
Authors: Chen Menglin L. N. , Jiang Li Jun , Sha Wei E. I.
Published: February 2016

Orbital angular momentum (OAM) is a promising degree of freedom for fundamental studies in electromagnetics and quantum mechanics. The unlimited state space of OAM shows a great potential to enhance channel capacities of classical and quantum communications. By exploring the Pancharatnam-Berry phase concept and engineering anisotropic scatterers in a metasurface with spatially varying orientations, a plane wave with zero OAM can be converted to a vortex beam carrying nonzero OAM. In this paper, we proposed two types of novel perfect electric conductor-perfect magnetic conductor anisotropic metasurfaces. One is composed of azimuthally continuous loops and the other is constructed by azimuthally discontinuous dipole scatterers. Both types of metasurfaces are mounted on a mushroom-type high impedance surface. Compared to previous metasurface designs for generating OAM, the proposed ones achieve nearly perfect conversion efficiency. In view of the eliminated vertical component of electric field, the continuous metasurface shows very smooth phase pattern at the near-field region, which cannot be achieved by convectional metasurfaces composed of discrete scatterers. On the other hand, the metasurface with discrete dipole scatterers shows a great flexibility to generate OAM with arbitrary topological charges. Our work is fundamentally and practically important to high-performance OAM generation.
Dynamics of ion temperature gradient turbulence and transport with a static magnetic island
Authors: Izacard Olivier , Holland Christopher , James Spencer D. , Brennan Dylan P.
Published: February 2016

Understanding the interaction mechanisms between large-scale magnetohydrodynamic instabilities and small-scale drift-wave microturbulence is essential for predicting and optimizing the performance of magnetic confinement based fusion energy experiments. We report progress on understanding these interactions using both analytic theory and numerical simulations performed with the BOUT++ [Dudson et al., Comput. Phys. Commun. 180, 1467 (2009)] framework. This work focuses upon the dynamics of the ion temperature gradient instability in the presence of a background static magnetic island, using a weakly electromagnetic two-dimensional five-field fluid model. It is found that the island width must exceed a threshold size (comparable with the turbulent correlation length in the no-island limit) to significantly impact the turbulence dynamics, with the primary impact being an increase in turbulent fluctuation and heat flux amplitudes. The turbulent radial ion energy flux is shown to localize near the X-point, but does so asymmetrically in the poloidal dimension. An effective turbulent resistivity which acts upon the island outer layer is also calculated and shown to always be significantly (10×–100×) greater than the collisional resistivity used in the simulations.
Laser plasma interaction on rugby hohlraum on the Omega Laser Facility: Comparisons between cylinder, rugby, and elliptical hohlraums
Authors: Masson-Laborde P. E. , Monteil M. C. , Tassin V. , Philippe F. , Gauthier P. , Casner A. , Depierreux S. , Neuville C. , Villette B. , Laffite S. , Seytor P. , Fremerye P. , Seka W. , Teychenné D. , Debayle A. , Marion D. , Loiseau P. , Casanova M.
Published: February 2016

Gas-filled rugby-shaped hohlraums have demonstrated high performances compared to a classical similar diameter cylinder hohlraum with a nearly 40% increase of x-ray drive, 10% higher measured peak drive temperature, and an increase in neutron production. Experimental comparisons have been done between rugby, cylinder, and elliptical hohlraums. The impact of these geometry differences on the laser plasma instabilities is examined. Using comparisons with hydrodynamic simulations carried out with the code FCI2 and postprocessed by Piranah, we have been able to reproduce the stimulated Raman and Brillouin scattering spectrum of the different beams. Using a methodology based on a statistical analysis for the gain calculations, we show that the behavior of the laser plasma instabilities in rugby hohlraums can be reproduced. The efficiency of laser smoothing techniques to mitigate these instabilities are discussed, and we show that while rugby hohlraums exhibit more laser plasma instabilities than cylinder hohlraum, the latter can be mitigated in the case of an elliptical hohlraum.
An automated microfluidic system for screening Caenorhabditis elegans behaviors using electrotaxis
Authors: Liu Dingsheng , Gupta Bhagwati , Selvaganapathy Ponnambalam Ravi
Published: February 2016

Caenorhabditis elegans (C. elegans) is a widely used animal model to study mechanisms of biological processes and human diseases. To facilitate manipulations of C. elegans in the laboratory, researchers have developed various tools that permit careful monitoring of behavior and changes in cellular processes. Earlier, we had reported a novel microfluidic assay device to study the neuronal basis of movement and to investigate the effects of cellular and environmental factors that can induce degeneration in certain neurons leading to movement disorder. The system involved the use of an electric field to perform electrotaxis assays, which allows detailed examination of movement responses of animals. One of the potential uses of this system is to perform genetic and chemical screenings for neuroprotective factors; however, it could not be done due to manual operations and low throughput. In this paper, we present an integrated microfluidic system that automates screening of C. elegans behavioral response using electrotaxis. The core component of system is a multilayer poly dimethyl siloxane (PDMS) device, which enables C. elegans loading, capture, flush, release, electrotaxis, and clean sequentially with the help of other components. The system is capable of screening C. elegans, at a throughput of more than 20 worms per hour, automatically and continually without human intervention. To demonstrate the effectiveness of the system, C. elegans neuronal mutants were screened, and the phenotype data were extracted and analyzed. We envision that the automatic screening potential of the system will accelerate the study of neuroscience, drug discovery, and genetic screens in C. elegans.
Role of charge separation on two-step two photon absorption in InAs/GaAs quantum dot intermediate band solar cells
Authors: Creti A. , Tasco V. , Cola A. , Montagna G. , Tarantini I. , Salhi A. , Al-Muhanna A. , Passaseo A. , Lomascolo M.
Published: February 2016

In this work, we report on the competition between two-step two photon absorption, carrier recombination, and escape in the photocurrent generation mechanisms of high quality InAs/GaAs quantum dot intermediate band solar cells. In particular, the different role of holes and electrons is highlighted. Experiments of external quantum efficiency dependent on temperature and electrical or optical bias (two-step two photon absorption) highlight a relative increase as high as 38% at 10 K under infrared excitation. We interpret these results on the base of charge separation by phonon assisted tunneling of holes from quantum dots. We propose the charge separation as an effective mechanism which, reducing the recombination rate and competing with the other escape processes, enhances the infrared absorption contribution. Meanwhile, this model explains why thermal escape is found to predominate over two-step two photon absorption starting from 200 K, whereas it was expected to prevail at lower temperatures (≥70 K), solely on the basis of the relatively low electron barrier height in such a system.
Thermal equation of state of silicon carbide
Authors: Wang Yuejian , Liu Zhi T. Y. , Khare Sanjay V. , Collins Sean Andrew , Zhang Jianzhong , Wang Liping , Zhao Yusheng
Published: February 2016

A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature (P-T) up to 8.1 GPa and 1100 K. The obtained pressure–volume–temperature data were fitted to a modified high-T Birch-Murnaghan equation of state, yielding values of a series of thermo-elastic parameters, such as the ambient bulk modulus KTo = 237(2) GPa, temperature derivative of the bulk modulus at a constant pressure (∂K/∂T)P = −0.037(4) GPa K−1, volumetric thermal expansivity α(0, T) = a + bT with a = 5.77(1) × 10−6 K−1 and b = 1.36(2) × 10−8 K−2, and pressure derivative of the thermal expansion at a constant temperature (∂α/∂P)T = 6.53 ± 0.64 × 10−7 K−1 GPa−1. Furthermore, we found the temperature derivative of the bulk modulus at a constant volume, (∂KT/∂T)V, equal to −0.028(4) GPa K−1 by using a thermal pressure approach. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy. The computed results generally agree well with the experimentally determined values.
Development of hydrocarbon biofuel from sunflower seed and sunflower meat oils over ZSM-5
Authors: Zhao Xianhui , Wei Lin , Cheng Shouyun , Julson James , Anderson Gary , Muthukumarappan Kasiviswanathan , Qiu Changling
Published: February 2016

Individually, sunflower oil produced from inedible sunflower seeds with hulls and sunflower meats without hulls were catalytically cracked over the ZSM-5 catalyst in a fixed-bed reactor at three reaction temperatures (450 °C, 500 °C, and 550 °C). Characterizations of hydrocarbon biofuel, distillation residual, and non-condensable gas were carried out. The reaction temperature on the hydrocarbon biofuel yield and quality from sunflower seed oil and sunflower meat oil were discussed and compared. In addition, a preliminary cost analysis of the sunflower seed dehulling was carried out. The results showed that the highest hydrocarbon biofuel yield was obtained from upgrading sunflower meat oil at 500 °C. The highest meat hydrocarbon biofuel yield was 8.5% higher than the highest seed hydrocarbon biofuel yield. The reaction temperature had a significant effect on the distribution of non-condensable gas components. Furthermore, the reaction temperature affected the yield and properties of hydrocarbon biofuel. The unit cost of producing sunflower meat oil was lower than that of producing sunflower seed oil. Comprehensively, sunflower meat could be a more economical feedstock than sunflower seed to produce hydrocarbon biofuel.
Tuning negative refractive collimation beam by square lattice sonic crystal with concave incident surface
Authors: Shen F.
Published: February 2016

Negative refractive collimation beam at the low frequency region is achieved in a square lattice sonic crystal with the small magnitude of effective refractive index. A simple tuning approach for such acoustic beam is also proposed by attaching an additional concave surface of incidence to the crystal slab. This can increase the propagation distance of collimation beam, enhance or suppress the beam intensity. The proposed approach is rather general and applicable to other acoustic materials as long as their effective index can be retrieved. Moreover, the results can be applied to wavefront manipulation and transmission enhancement.
Raman spectra and cross sections of ammonia, chlorine, hydrogen sulfide, phosgene, and sulfur dioxide toxic gases in the fingerprint region 400-1400 cm−1
Authors: Aggarwal R. L. , Farrar L. W. , Di Cecca S. , Jeys T. H.
Published: February 2016

Raman spectra of ammonia (NH3), chlorine (Cl2), hydrogen sulfide (H2S), phosgene (COCl2), and sulfur dioxide (SO2) toxic gases have been measured in the fingerprint region 400-1400 cm−1. A relatively compact (<2′x2′x2′), sensitive, 532 nm 10 W CW Raman system with double-pass laser and double-sided collection was used for these measurements. Two Raman modes are observed at 934 and 967 cm−1 in NH3. Three Raman modes are observed in Cl2 at 554, 547, and 539 cm−1, which are due to the 35/35 35/37, and 37/37 Cl isotopes, respectively. Raman modes are observed at 870, 570, and 1151 cm−1 in H2S, COCl2, and SO2, respectively. Values of 3.68 ± 0.26x10−32 cm2/sr (3.68 ± 0.26x10−36 m2/sr), 1.37 ± 0.10x10−30 cm2/sr (1.37 ± 0.10x10−34 m2/sr), 3.25 ± 0.23x10−31 cm2/sr (3.25 ± 0.23x10−35 m2/sr), 1.63 ± 0.14x10−30 cm2/sr (1.63 ± 0.14x10−34 m2/sr), and 3.08 ± 0.22x10−30 cm2/sr (and 3.08 ± 0.22x10−34 m2/sr) were determined for the differential Raman cross section of the 967 cm−1 mode of NH3, sum of the 554, 547, and 539 cm−1 modes of Cl2, 870 cm−1 mode of H2S, 570 cm−1 mode of COCl2, and 1151 cm-1 mode of SO2, respectively, using the differential Raman cross section of 3.56 ± 0.14x10−31 cm2/sr (3.56 ± 0.14x10−35 m2/sr) for the 1285 cm−1 mode of CO2 as the reference.
Enhancement of a cyclic endurance of phase change memory by application of a high-density C15(Ge21Sb36Te43) film
Authors: Park J. H. , Kim S. W. , Kim J. H. , Ko D. H. , Wu Z. , Ahn D. , Ahn D. H. , Lee J. M. , Kang S. B. , Choi S. Y.
Published: February 2016

The lower cyclic endurance of Phase Change Memory (PCM) devices limits the spread of its applications for reliable memory. The findings reported here show that micro-voids and excess vacancies that are produced during the deposition process and the subsequent growth in sputtered carbon-doped GeSbTe films is one of the major causes of device failure in PCM with cycling. We found that the size of voids in C15(Ge21Sb36Te43) films increased with increasing annealing temperature and the activation energy for the growth rate of voids was determined to be 2.22 eV. The film density, which is closely related to voids, varies with the deposition temperature and sputtering power used. The lower heat of vaporization of elemental Sb and Te compared to that for elemental Ge and C is a major cause of the low density of the film. It was possible to suppress void formation to a considerable extent by optimizing the deposition conditions, which leads to a dramatic enhancement in cyclic endurance by 2 orders of magnitude in PCM devices prepared at 300oC-300W compared to one prepared at 240oC-500W without change of compositions.
Two-dimensional nanoplates of Bi2Te3 and Bi2Se3 with reduced thermal stability
Authors: Kang Sung Min , Ha Sung-Soo , Jung Wan-Gil , Park Mansoo , Song Hyon-Seok , Kim Bong-Joong , Hong Jung-Il
Published: February 2016

Free-standing thin nanoplates of Bi2Te3 and Bi2Se3 were synthesized by solvothermal method. It was demonstrated that the thickness of the nanoplates can be controlled by introducing a controlled amount of polyvinylpyrrolidone (PVP) in the synthesis reaction. PVP bonds to the polar basal planes of hexagonal crystal structure of Bi2Te3 and Bi2Se3, and they suppress the growth (speed) of the hexagonal crystals in the c-axis direction. Highly anisotropic growth yielded the formation of 2-dimensional nanostructures of nanoplates. The plates were examined directly with transmission electron microscopy (TEM) with in-situ heating. These crystalline nanoplates with extremely high width to thickness ratios were found to exhibit much lower thermal stability compared to the bulk counterpart or the conventional nanoparticles as represented by the reduced melting temperature. The melting temperature of a nanoplate decreased by more than 100°C compared to the melting temperature of the bulk material. While it is widely known that the meting temperature decreases for nanoparticles with reduced sizees in all three spatial dimensions, we demonstrate that the reduction in one dimension, i.e. thickness of the platelets in the present study, is effective enough to induce much greater decrease of the melting point than the decrease as observed for the case of nanoparticles.
Using vital statistics and core-habitat maps to manage critically endangered orchids in the Western Australian wheatbelt
Authors: Brundrett Mark C.
Published: February 2016

Vital-statistics data concerning population viability were gathered for four of the rarest orchids in Western Australia using surveys to define population sizes and habitat areas and annual measurements of plant demographics. These orchids were Caladenia melanema, C. graniticola, C. williamsiae and Drakaea isolata from the wheatbelt of Western Australia. This agricultural area has a Mediterranean climate with unreliable rainfall, and is >80% cleared of native vegetation. Surveys with 10–30 volunteers increased population-size estimates by up to 10 times and provided spatial data to define core habitat areas. These areas included most of the individuals of a species, but were only 2–10 ha in size. Within these areas, orchids were often highly aggregated in patches a few metres wide, potentially resulting in a high degree of intraspecific competition. Vital statistics were obtained using 4-m wide and 30–50-m-long transects to measure rates of emergence, flowering, grazing and seed-set for each orchid. Plants emerging at the same position in different years were considered to be the same individual, but most emerged in new positions. Many plants emerged just once in 4 years, and 2–3 years of dormancy was common. Emergence frequencies were used to provide estimates of population sizes that were two or three times larger than suggested by data from a single year. Seed production was typically very low. Grazing by kangaroos and rabbits was most severe for C. melanema, but was greatly reduced by fencing. Severe drought prevented flowering of C. graniticola in the driest year, whereas other species were more resilient. These orchids are likely to persist as long as there are some years where rainfall is sufficient for flowering and seed set followed by a year with adequate rain for seed germination. Populations of all these orchids were stable or increasing, but they are still at high risk of extinction because of the impacts of increasing soil salinity or fire on their habitats. These species are unlikely to spread elsewhere in the highly cleared and fragmented wheatbelt. Intervention by hand-pollination, grazing protection and translocation to new locations is required to mitigate these risks. Results were summarised in vital statistics report cards with thresholds set to inform conservation management for these species. Core habitat maps and vital-statistics report cards should also be valuable new tools for terrestrial-orchid conservation in other biomes.
Factors affecting frog density in the Solomon Islands
Authors: Pikacha Patrick , Filardi Chris , Morrison Clare , Leung Luke
Published: February 2016

This paper identifies some important factors affecting the density of frogs in the Solomon Islands. Distance sampling was used to estimate frog density in all major frog habitats across 13 islands. A total of 109 transects, covering five forest types (coastal, freshwater marshes, lowland forest, hill or ridge, and montane forest) were used, with 16 species being sampled. Estimated densities ranged from 2 ha–1 to 675 ha–1. Akaike’s Information Criterion (AIC) was used to select the most parsimonious model of frog density. Factors identified in the selected model to predict density of Batrachylodes elegans, Batrachylodes vertebralis, Ceratobatrachus guentheri, Discodeles bufoniformis, Discodeles guppyi, Discodeles malukuna, Litoria thesaurensis, Palmatorappia solomonis, Platymantis guppyi, Platymantis neckeri, Platymantis solomonis, Platymantis sp., Platymantis weberi, and Rana kreffti were island, landform, and forest type. Additional factors such as disturbance, leaf litter, shrub, and understorey were also described by the regression model as predictors of density for B. vertebralis, C. guentheri, D. guppyi, D. malukuna, Pal. solomonis, P. guppyi, and R. kreffti. These findings have important management implications for the conservation of frogs in the Solomon Islands. High densities of most species were strongly related with forest type and low disturbance. Preservation of rainforest, in especially high conservation value old-growth forests, is imperative to protecting these species.
Auditory word recognition across the lifespan
Authors: Blumenfeld Henrike K. , Schroeder Scott R. , Bobb Susan C. , Freeman Max R. , Marian Viorica
Published: February 2016

Recent research suggests that bilingual experience reconfigures linguistic and nonlinguistic cognitive processes. We examined the relationship between linguistic competition resolution and nonlinguistic cognitive control in younger and older adults who were either bilingual or monolingual. Participants heard words in English and identified the referent among four pictures while eye-movements were recorded. Target pictures (e.g., cab) appeared with a phonological competitor picture (e.g., cat) and two filler pictures. After each eye-tracking trial, priming probes assessed residual activation and inhibition of target and competitor words. When accounting for processing speed, results revealed that age-related changes in activation and inhibition are smaller in bilinguals than in monolinguals. Moreover, younger and older bilinguals, but not monolinguals, recruited similar inhibition mechanisms during word identification and during a nonlinguistic Stroop task. Results suggest that, during lexical access, bilinguals show more consistent competition resolution and recruitment of cognitive control across the lifespan than monolinguals.
The effect of language skills on dementia in a Swedish longitudinal cohort
Authors: Ljungberg Jessica K. , Hansson Patrik , Adolfsson Rolf , Nilsson Lars-Göran
Published: February 2016

Recent findings indicate that bilingualism delay the onset of dementia. Using data from the Betula longitudinal cohort study on memory, health and aging (www.betula.su.se) the issue of a possible protective effect of bilingualism was addressed.

Monolingual (n = 736) and bilingual (n = 82) participants (≥ 60 years) without dementia at inclusion were followed for incident dementia over a time-period up to 10 years. In total, 112 participants developed dementia. Analyses were performed with Cox proportional hazards regression adjusted for age, sex, and presence/absence of the Apolipoprotein E (APOE) ɛ4 allele, with dementia outcome as the dependent variable.

Results showed no delayed onset of dementia in bilinguals compared to monolinguals. However, because of the findings from a study using participants from the same population showing beneficial longitudinal effects of bilingualism on episodic memory; we argue that our results may depend on the frequency of use of the second language after retirement.
Language reclamation strategies
Authors: Bradley David
Published: February 2016

Language endangerment confronts many Tibeto-Burman (TB) languages. This paper provides a general typology of methods for reclaiming such languages, using TB examples where possible, and discusses the problems which may arise. This is followed by a case study of one such endangered language, Gong in Thailand, and attempts for its reclamation.
Feminist revision of oral history methodology for the study of armed conflicts
Authors: Rodríguez Lara Zuriñe , Villanueva Baselga Sergio
Published: February 2016

This article sets out presenting the methodological toolbox created for the study of very specific reality: the gathering of oral information in the study of armed conflicts. Taking as a valid reference the oral history technique, we explored new methodological processes that allowed us to reach the lives and stories of the people interviewed more deeply, with a closer approach to their lives, but at the same time respecting and ensuring maximum access and confidentiality. To do this, the oral history methodology was reviewed with the main contributions of feminist epistemology. Thereby, we created ex profeso new methodological processes adapted to study the role of women as violence perpetrators in armed conflicts. Our proposal expands up to 5 different phases with either technical or emotional functions. The validity of this new methodological toolbox has been tested through an extensive research in the armed conflict of the Basque Country (Spain) performing oral histories to 25 women and 10 men.
“I won’t change who I am for anyone”
Authors: Scranton Audrey
Published: February 2016

In the United States today, Muslim women are portrayed as weak, submissive, one-dimensional, and occupying a place of contradiction. These master narratives of Muslim women as uncivilized or anti-American lead them to be misunderstood at best and victims of hate crimes at worst. In this environment, a space emerges to explore counterstories, or narratives that depict a group as desirable in the face of a detrimental dominant narrative. In order to study how Muslim women construct their identities in this environment, a thematic analysis of stories told by Muslim women in an online setting was conducted. Findings reveal four prominent constructions or responses to this narrative: (1)I am multidimensional, (2)I am strong, (3)I change the world, and (4)I am special. Implications for the study of counterstories and future directions for research are discussed.
Language learning ‘in the wild’ in transnational encounters
Authors: Moore Emilee
Published: February 2016

This article draws on a corpus of transnational encounters that are nota prioriabout learning, recorded at a university in Catalonia immersed in processes of internationalization. However, by taking a CA-for-SLA approach to the data, it is shown how opportunities for language teaching and learning emerge across the settings, from the most institutional (i.e. formal ceremonies) to the most informal interactions (i.e. friendly conversation), and are mediated by available plurilingual and multimodal resources. In this regard, the analysis yields results that differ from previous research conducted in similar higher education contexts in which categorizations of participants as language ‘experts’/‘non-experts’ or ‘teachers’/‘learners’ were avoided (e.g. Kurhila, 2004). Such data prompts the author to argue that beyond simply recognizing the potential for second language learning ‘in the wild’ at universities going about internationalization, active steps could be taken to implement strategies that would enhance opportunities for language learning to happen.
The discourses of sustainability in news magazines
Authors: Orna-Montesinos Concepción
Published: February 2016

Sustainability has become a key concept in the debate over global environmental challenges. With the view that at the heart of the environmental debate is undoubtedly the text, this paper examines the rhetorical construction of text and provides linguistic insights into how the concept of sustainability is textualized. Corpus findings show that the discourse of sustainability is constructed by interwoven discourses which depict sustainability as a goal, as a problem, or as an object of analysis or study and implemented by companies and institutions. The rhetorical construction of the argumentation of the discourses of sustainability further suggests that the news magazines convey a multiplicity of obvious or hidden communicative purposes. This paper critically examines how resources such as evaluation, hedging or intertextuality are used in journalistic discourse to convey the author’s stance towards sustainability, trying to position the audience and thus to shape the public awareness and acceptance of sustainability.
Análisis discursivo del ciberconsejo en el género foro virtual de discusión/consulta médica no especializada
Authors: Rodríguez Muñoz Francisco J.
Published: February 2016

The present research, firstly, aims to determine the global structure of the virtual discussion forum/unspecialized medical appointment genre from the analysis of its superstructure. The pattern of the genre presents a tripartite division in which three types of postings succeed each other: problem messages, advice messages and thanks messages. Secondly, the study of the sections and movements that establish the formal structure of these types of messages is completed with the description of the macrostructural level, in which the content or semantic structure of textual productions is covered, without sacrificing the functional exponents and the microstructural supports that contribute to its elucidation.
What factors shape the collaborative pattern of group interaction during peer feedback in the L2 writing classroom?
Authors: Yu Shulin
Published: February 2016

While research on peer interaction in language learning has proliferated over the past two decades, little is known regarding why students interact differently with their peers and how collaborative patterns can be developed to promote the effectiveness of small group work in L2 learning. To fill such a void in the research literature, the present case study investigates the factors that shape the collaborative pattern of a small group of Chinese EFL learners in peer feedback activities. Multiple sources of data were collected, including video recordings of peer feedback sessions, semi-structured interviews, stimulated recalls, and student drafts of writing. The findings show that students’ beliefs and values, students’ motives and goals, the use of mediating artifacts, and the power relationship among the students shape the patterns of group interaction considerably. This study deepens our understanding of the nature of peer interaction in peer feedback for L2 writing and contributes new knowledge to the research on pair and small group work in L2 learning.