bluuebunny/crossref_metadata_2025 huggingface dataset:
ON HYPERSTABILITY OF ADDITIVE MAPPINGS ONTO BANACH SPACES
Authors: DONG YUNBAI , ZHENG BENTUO
Published: December 2014

Let$(X,+)$be an Abelian group and$E$be a Banach space. Suppose that$f:X\rightarrow E$is a surjective map satisfying the inequality$$\begin{eqnarray}|\,\Vert f(x)-f(y)\Vert -\Vert f(x-y)\Vert \,|\leq {\it\varepsilon}\min \{\Vert f(x)-f(y)\Vert ^{p},\Vert f(x-y)\Vert ^{p}\}\end{eqnarray}$$for some${\it\varepsilon}>0$,$p>1$and for all$x,y\in X$. We prove that$f$is an additive map. However, this result does not hold for$0
0$and$p>1$$$\begin{eqnarray}|\,\Vert f(x)-f(y)\Vert -\Vert f(u)-f(v)\Vert \,|\leq {\it\epsilon}\min \{\Vert f(x)-f(y)\Vert ^{p},\Vert f(u)-f(v)\Vert ^{p}\}\end{eqnarray}$$whenever$\Vert x-y\Vert =\Vert u-v\Vert$, then$f$preserves equality of distance. Moreover, if$\dim E\geq 2$, there exists a constant$K\neq 0$such that$Kf$is an affine isometry. This improves a result of Vogt [‘Maps which preserve equality of distance’,Studia Math.45(1973) 43–48].
Adaptive bilateral control for nonlinear uncertain teleoperation with guaranteed transient performance
Authors: Chen Zhang , Liang Bin , Zhang Tao , Wang Xueqian , Zhang Bo
Published: December 2014

Due to the special working environment of teleoperation, there are usually uncertainties existing in the dynamics of teleoperating robots. In this paper, an adaptive bilateral control scheme is proposed for the nonlinear teleoperation with parameterized dynamic uncertainties and time delays. Compared to the existing time-delay adaptive bilateral controllers, the proposed scheme has the advantage of faster and more accurate parameter adaptation. In this way, the transient performance of teleoperators can be improved without increasing the control gains, which is helpful for stability of teleoperation. The adaptive bilateral controller is designed to be applicable both in free motion and in constrained motion. The synchronization errors in the unconstrained subspace are asymptotically convergent under time delays. In the constrained subspace, the contact force remains bounded with the proposed controller. The stability of teleoperation is proved using Lyapunov methods and the passivity theory. Simulation results demonstrate the effectiveness of the proposed method.
Coexistence of morphologically similar bats (Vespertilionidae) on Madagascar: stable isotopes reveal fine-grained niche differentiation among cryptic species
Authors: Dammhahn Melanie , Rakotondramanana Claude Fabienne , Goodman Steven M.
Published: December 2014

Based on niche theory, closely related and morphologically similar species are not predicted to coexist due to overlap in resource and habitat use. Local assemblages of bats often contain cryptic taxa, which co-occur despite notable similarities in morphology and ecology. We measured in two different habitat types on Madagascar levels of stable carbon and nitrogen isotopes in hair (n = 103) and faeces (n = 57) of cryptic Vespertilionidae taxa to indirectly examine whether fine-grained trophic niche differentiation explains their coexistence. In the dry deciduous forest (Kirindy), six sympatric species ranged over 6.0‰ in δ15N, i.e. two trophic levels, and 4.2‰ in δ13C with a community mean of 11.3‰ in δ15N and −21.0‰ in δ13C. In the mesic forest (Antsahabe), three sympatric species ranged over one trophic level (δ15N: 2.4‰, δ13C: 1.0‰) with a community mean of 8.0‰ δ15N and −21.7‰ in δ13C. Multivariate analyses and residual permutation of Euclidian distances in δ13C–δ15N bi-plots revealed in both communities distinct stable isotope signatures and species separation for the hair samples among coexisting Vespertilionidae. Intraspecific variation in faecal and hair stable isotopes did not indicate that seasonal migration might relax competition and thereby facilitate the local co-occurrence of sympatric taxa.
Exploring the Ecology of Canada’s Publicly Funded Residential Long-Term Care Bed Supply
Authors: Sivananthan Saskia N. , Doupe Malcolm , McGregor Margaret J.
Published: December 2014

Malgré l'augmentation de la population des personnes âgées au Canada, et la variation de stratégies de soins de longue durée (SLD) que les provinces ont mis en place, peu de recherches ont porté sur la compréhension de la mesure dans laquelle l'approvisionnement de lits des SLD résidentiels financés par l'État varient parmi les provinces, ou les facteurs influençant cette variation. Notre étude a porté sur une analyse dans laquelle nous avons examiné l'association de trois caractéristiques juridictionnelles sélectionnés avec la fourniture des lits LTC: la démographie de l'âge de la population, les ressources économiques des provinces, et les investissements provinciaux dans les soins à domicile. On n'a pas trouvé de l'écologie interjuridictionelle importante ni d'interrelation entre la variation de l'approvisionne-ment de lits des SLD avec aucune des variables étudiées. La variation entre les provinces pour le disponibilité de lits n'a également pas influencé statistiquement du jour à l'autre le niveau de soins spécifiques pour l'attente des SLD, ce qui suggère que ces jours ne sont pas influencés simplement par des différences dans l'approvisionnement de lits des SLD, et que d'autres facteurs au niveau provincial étaient en jeu.
Using synergy of experimental and computational techniques to solve monomer–trimer dilemma
Authors: Jung Dubravka Šišak , Hrenar Tomica , Jović Ozren , Kalinovičić Petra , Primožič Ines
Published: December 2014

An example of commercially available product, 2-(methylideneamino)acetonitrile (MAAN). This paper will address problems in discerning monomer–polymer ambiguity in organic compounds. Reliable three-step analysis of organic polymers will be proposed using the synergy of computational [density functional theory (DFT)] and experimental [infrared spectroscopy (IR); X-ray powder diffraction (XRPD)] techniques. First, possible conformations of monomeric and trimeric MAAN were calculated using stochastic search and DFT. Second, identification of the commercial sample was performed by comparing the measured IR spectrum with those calculated for monomer and trimer. Third, the examination of sample purity and structural analysis were carried out using XRPD data.
Using key part-of-speech analysis to examine spoken discourse by Taiwanese EFL learners
Authors: Lin Yen-Liang
Published: December 2014

This study reports on a corpus analysis of samples of spoken discourse between a group of British and Taiwanese adolescents, with the aim of exploring the statistically significant differences in the use of grammatical categories between the two groups of participants. The key word method extended to a part-of-speech level using the web-based corpus analytical tool,Wmatrix, highlights those linguistic domains which deserve particular attention. Specifically, it reveals the lexical and grammatical categories that occur unusually frequently or unusually infrequently in the English learners’ discourse when compared with the language used by the native speakers of English in the sample. The research findings delineate the pedagogical merit of key domain analysis and thus help to inform English as a foreign language teachers and materials developers in the design of courses emphasising spoken interaction.
‘Moving’ through the past: Thirty years of avoir été in Ontario French
Authors: SAMMONS OLIVIA N. , NADASDI TERRY , MOUGEON RAYMOND
Published: December 2014

This article examines a case of real-time language change in the spoken French of adolescents residing in four localities in Ontario, Canada. The focus of the study is the alternation between verb forms meaning ‘went/have gone’ over a three-decade timespan (1978–2005), and involves three main variants:avoir été, être alléandavoir allé. This study investigates the influence of both social and linguistic factors on variant choice, showing evidence for both devernacularization and regularization as a result of social change.
Public or private interests? The investment behaviour of public officials in Antwerp during the early modern period
Authors: De Vijlder Nicolas , Limberger Michael
Published: December 2014

Indebted cities were a widespread phenomenon during theAncien Régime. However, some found ways to innovate the management of their municipal debt, whilst others fell prey to over-indebtedness or default. In this article we have left the success stories aside and focused on the latter. Using early modern Antwerp as a case study, we have disentangled the underlying mechanisms that ultimately lead to over-indebtedness and (in some cases) default. Whilst the economic climate and the relationship between city and state have been rightly identified as major factors in the previous literature, our contribution brings another element to the table, namely, the inflexibility of long-established rent arrangements and the entanglement between the ruling elite and therentiers. We show that there was a strong overlap between both groups, which had a huge impact on the financial policy of cities during the early modern period.
Abdominal aorta interruption and CHD
Authors: Oliveira Lia , Torres Erica , Anjos Rui
Published: December 2014

We report a rare case of CHD and abdominal aorta interruption. Renal hypertension was the first sign of the abdominal aortic malformation. The aetiology of abdominal aortic interruption remains unclear, it could be congenital or acquired.
A functional approach to cross-linguistic influence in ab initio L3 acquisition
Authors: SANZ CRISTINA , PARK HAE IN , LADO BEATRIZ
Published: December 2014

The present study follows the role of the first (L1, English) and second (L2, Japanese or Spanish) languages in ab initio third language (L3, Latin) acquisition. Participants (N = 25) were L2 classroom learners without immersion experience. In order to complement previous generativist studies and to offer a fuller developmental account of how transfer operates at the morphosyntactic level, the Competition Model (CM) was adopted as theoretical framework. Positive changes in overall accuracy and sentence processing patterns in role assignment in L3 Latin show L3 development as largely modulated by the L1, suggesting that higher levels of L2 resonance are necessary for integrated patterns of L1 and L2 cues to emerge.
Modeling Intelligibility of Written Germanic Languages: Do We Need to Distinguish Between Orthographic Stem and Affix Variation?
Authors: Heeringa Wilbert , Swarte Femke , Schüppert Anja , Gooskens Charlotte
Published: December 2014

We measured orthographic differences between five Germanic languages. First, we tested the hypothesis that orthographic stem variation among languages does not correlate with orthographic variation in inflectional affixes. We found this hypothesis true when considering the aggregated stem and affix distances between the languages. We also correlated the stem and affix distances within the cognate pairs in each language pair. We found low correlations, the lowest of them being not significant. Second, we tested the hypothesis that orthographic stem variation among languages is larger than orthographic variation in inflectional affixes. This hypothesis was also found to be true. Orthographic distance is likely to be a potential predictor of written intelligibility, but our results suggest that when modeling written intelligibility, a distinction needs to be made between stem and affix distances.*
Synthesis and characterization of N-2-aryl-1,2,3-triazole based iridium complexes as photocatalysts with tunable photoredox potential
Authors: Cai Rong , Yan Wuming , Bologna Matthew G. , de Silva Kaushalya , Ma Zhao , Finklea Harry O. , Petersen Jeffrey L. , Li Minyong , Shi Xiaodong
Published: December 2014

N-2-Aryl chelated 1,2,3-triazole-Ir(iii) complexes with various substituents were prepared for the first time.
Binary reducing agents containing dichloroindium hydride for the selective, partial, or tandem reductions of bifunctional compounds consisting of halo-nitriles, halo-esters and halo-carboxylic acids
Authors: Snelling Rachel , Saavedra Jaime Z. , Bayrasy Panathda , Abdollahian Yashar , Singaram Bakthan
Published: December 2014

Selective, partial, or tandem reductions of bifunctional organic halides is reported.
Hg(OAc)2 mediated highly regio- and/or diastereoselective allylic tert-acetylation of olefins
Authors: Dethe Dattatraya H. , Dherange Balu D. , Boda Raghavender
Published: December 2014

We have developed a novel, highly regio- and/or diastereoselective tertiary allylic acetylation of geminally disubstituted olefins using Hg(OAc)2.
Liquid crystalline and charge transport properties of novel non-peripherally octasubstituted perfluoroalkylated phthalocyanines
Authors: Sosa-Vargas Lydia , Nekelson Fabien , Okuda Daiju , Takahashi Minokazu , Matsuda Yukimasa , Dao Quang-Duy , Hiroyuki Yoshida , Fujii Akihiko , Ozaki Masanori , Shimizu Yo
Published: December 2014

Enhancement of the Col mesophase thermal stability, high carrier mobility in ambipolar nature and strong tendency towards homeotropic alignment.
Accurate nonrelativistic ground-state energies of 3d transition metal atoms
Authors: Scemama A. , Applencourt T. , Giner E. , Caffarel M.
Published: December 2014

We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |Ec|.
Two-phase flow in a chemically active porous medium
Authors: Darmon Alexandre , Benzaquen Michael , Salez Thomas , Dauchot Olivier
Published: December 2014

We study the problem of the transformation of a given reactant species into an immiscible product species, as they flow through a chemically active porous medium. We derive the equation governing the evolution of the volume fraction of the species, in a one-dimensional macroscopic description, identify the relevant dimensionless numbers, and provide simple models for capillary pressure and relative permeabilities, which are quantities of crucial importance when tackling multiphase flows in porous media. We set the domain of validity of our models and discuss the importance of viscous coupling terms in the extended Darcy’s law. We investigate numerically the steady regime and demonstrate that the spatial transformation rate of the species along the reactor is non-monotonous, as testified by the existence of an inflection point in the volume fraction profiles. We obtain the scaling of the location of this inflection point with the dimensionless lengths of the problem. Eventually, we provide key elements for optimization of the reactor.
Stochastic algorithm for size-extensive vibrational self-consistent field methods on fully anharmonic potential energy surfaces
Authors: Hermes Matthew R. , Hirata So
Published: December 2014

A stochastic algorithm based on Metropolis Monte Carlo (MC) is presented for the size-extensive vibrational self-consistent field methods (XVSCF(n) and XVSCF[n]) for anharmonic molecular vibrations. The new MC-XVSCF methods substitute stochastic evaluations of a small number of high-dimensional integrals of functions of the potential energy surface (PES), which is sampled on demand, for diagrammatic equations involving high-order anharmonic force constants. This algorithm obviates the need to evaluate and store any high-dimensional partial derivatives of the potential and can be applied to the fully anharmonic PES without any Taylor-series approximation in an intrinsically parallelizable algorithm. The MC-XVSCF methods reproduce deterministic XVSCF calculations on the same Taylor-series PES in all energies, frequencies, and geometries. Calculations using the fully anharmonic PES evaluated on the fly with electronic structure methods report anharmonic effects on frequencies and geometries of much greater magnitude than deterministic XVSCF calculations, reflecting an underestimation of anharmonic effects in a Taylor-series approximation to the PES.
Direct path integral estimators for isotope fractionation ratios
Authors: Cheng Bingqing , Ceriotti Michele
Published: December 2014

Fractionation of isotopes among distinct molecules or phases is a quantum effect which is often exploited to obtain insights on reaction mechanisms, biochemical, geochemical, and atmospheric phenomena. Accurate evaluation of isotope ratios in atomistic simulations is challenging, because one needs to perform a thermodynamic integration with respect to the isotope mass, along with time-consuming path integral calculations. By re-formulating the problem as a particle exchange in the ring polymer partition function, we derive new estimators giving direct access to the differential partitioning of isotopes, which can simplify the calculations by avoiding thermodynamic integration. We demonstrate the efficiency of these estimators by applying them to investigate the isotope fractionation ratios in the gas-phase Zundel cation, and in a few simple hydrocarbons.
Spatial-decomposition analysis of electrical conductivity in ionic liquid
Authors: Tu Kai-Min , Ishizuka Ryosuke , Matubayasi Nobuyuki
Published: December 2014

The electrical conductivity of room temperature ionic liquid (IL) is investigated with molecular dynamics simulation. A trajectory of 1 μs in total is analyzed for the ionic liquid [C4mim][NTf2] (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the anion is also called TFSI or TFSA), and the ion motions are examined in direct connection to the conductivity within the framework formulated previously [K.-M. Tu, R. Ishizuka, and N. Matubayasi, J. Chem. Phys. 141, 044126 (2014)]. As a transport coefficient, the computed electrical conductivity is in fair agreement with the experiment. The conductivity is then decomposed into the autocorrelation term of Nernst-Einstein form and the cross-correlation term describing the two-body motions of ions, and the cross-correlation term is further decomposed spatially to incorporate the structural insights on ion configurations into the dynamic picture. It is observed that the ion-pair contribution to the conductivity is not spatially localized and extends beyond the first coordination shell. The extent of localization of the cross-correlation effect in the conductivity is in correspondence to that of the spatial correlation represented by radial distribution function, which persists over nanometer scale.
Concentration dependence of the Flory-Huggins interaction parameter in aqueous solutions of capped PEO chains
Authors: Chaudhari M. I. , Pratt L. R. , Paulaitis M. E.
Published: December 2014

The dependence on volume fraction φ of the Flory-Huggins interaction parameter χwpφ describing the free energy of mixing of polymers in water is obtained by exploiting the connection of χwpφ to the chemical potential of the water, for which quasi-chemical theory is satisfactory. We test this theoretical approach with simulation data for aqueous solutions of capped PEO (polyethylene oxide) oligomers. For CH3(CH2–O–CH2)mCH3 (m = 11), χwpφ depends strongly on φ, consistent with experiment. These results identify coexisting water-rich and water-poor solutions at T = 300 K and p = 1 atm. Direct observation of the coexistence of these two solutions on simulation time scales supports that prediction for the system studied. This approach directly provides the osmotic pressures. The osmotic second virial coefficient for these chains is positive, reflecting repulsive interactions between the chains in the water, a good solvent for these chains.
Effects of reactant rotational excitations on H2 + NH2 → H + NH3 reactivity
Authors: Song Hongwei , Guo Hua
Published: December 2014

Rotational mode specificity of the title reaction is examined using an initial state selected time-dependent wave packet method on an accurate ab initio based global potential energy surface. This penta-atomic reaction presents an ideal system to test several dynamical approximations, which might be useful for future quantum dynamics studies of polyatomic reactions, particularly with rotationally excited reactants. The first approximation involves a seven-dimensional (7D) model in which the two non-reactive N–H bonds are fixed at their equilibrium geometry. The second is the centrifugal sudden (CS) approximation within the 7D model. Finally, the J-shifting (JS) model is tested, again with the fixed N–H bonds. The spectator-bond approximation works very well in the energy range studied, while the centrifugal sudden and J-shifting integral cross sections (ICSs) agree satisfactorily with the coupled-channel counterparts in the low collision energy range, but deviate at the high energies. The calculated integral cross sections indicate that the rotational excitation of H2 somewhat inhibits the reaction while the rotational excitations of NH2 have little effect. These findings are compared with the predictions of the sudden vector projection model. Finally, a simple model is proposed to predict rotational mode specificity using K-averaged reaction probabilities.
A new configurational bias scheme for sampling supramolecular structures
Authors: De Gernier Robin , Curk Tine , Dubacheva Galina V. , Richter Ralf P. , Mognetti Bortolo M.
Published: December 2014

We present a new simulation scheme which allows an efficient sampling of reconfigurable supramolecular structures made of polymeric constructs functionalized by reactive binding sites. The algorithm is based on the configurational bias scheme of Siepmann and Frenkel and is powered by the possibility of changing the topology of the supramolecular network by a non-local Monte Carlo algorithm. Such a plan is accomplished by a multi-scale modelling that merges coarse-grained simulations, describing the typical polymer conformations, with experimental results accounting for free energy terms involved in the reactions of the active sites. We test the new algorithm for a system of DNA coated colloids for which we compute the hybridisation free energy cost associated to the binding of tethered single stranded DNAs terminated by short sequences of complementary nucleotides. In order to demonstrate the versatility of our method, we also consider polymers functionalized by receptors that bind a surface decorated by ligands. In particular, we compute the density of states of adsorbed polymers as a function of the number of ligand–receptor complexes formed. Such a quantity can be used to study the conformational properties of adsorbed polymers useful when engineering adsorption with tailored properties. We successfully compare the results with the predictions of a mean field theory. We believe that the proposed method will be a useful tool to investigate supramolecular structures resulting from direct interactions between functionalized polymers for which efficient numerical methodologies of investigation are still lacking.
Analytical model for steady flow through a finite channel with one porous wall with arbitrary variable suction or injection
Authors: Hartwig Jason , Darr Samuel
Published: December 2014

This paper presents an exact solution of two-dimensional laminar flow through a finite length channel with one porous wall. It improves upon previous solutions by (1) satisfying the no-slip boundary condition at the channel dead end, (2) adding a turbulent term to the porous wall boundary condition, (3) allowing for arbitrary variable suction or injection across the porous wall, and (4) model validation against new cryogenic liquid hydrogen and oxygen experimental data. Of particular interest in the current work is the modeling of cryogenic propellant flow through a porous liquid acquisition device (LAD) screen and channel inside a propellant tank. First, a detailed review of the literature is presented for previously attempted solutions to channel flow with one porous wall. Next, the governing equations, boundary conditions, and model assumptions are used to derive the analytical flow solution and present general model results for pressure and velocity fields within the channel. Then, the model solution is compared with horizontal LAD channel flow data in liquid oxygen as well as vertical LAD channel flow data in an inverted outflow configuration in liquid hydrogen. Model results are used to update the static cryogenic bubble point pressure model with a dynamic bubble point term which factors in enhanced convection and cooling at the screen during propellant outflow. Convective heat transfer at the LAD screen during outflow is also quantified by comparing model and data. The new analytical flow solution with the dynamic bubble point model is shown to compare well with available cryogenic experimental data.
Laser flash-Raman spectroscopy method for the measurement of the thermal properties of micro/nano wires
Authors: Liu Jinhui , Wang Haidong , Hu Yudong , Ma Weigang , Zhang Xing
Published: December 2014

This paper introduces a new method for measuring the thermal diffusivity and thermal conductivity of individual micro/nano wires using Raman spectroscopy. This method uses a focused short pulsed laser and a continuous-wave laser in a Raman spectroscopy system as the local heater, Raman signal excitation source, and temperature sensor. Unsteady and steady thermal conduction models are used to get two independent equations for the thermal diffusivity (α) and laser absorptivity (η). This new method is verified by comparing experimental results for graphite carbon fiber with measurement using the 3ω method. The method was then used to measure the temperature dependent thermal diffusivity and thermal conductivity of individual carbon nanotubes.
Experimental study of the effect of noncondensables on buoyancy-thermocapillary convection in a volatile low-viscosity silicone oil
Authors: Li Y. , Grigoriev R. , Yoda M.
Published: December 2014

The convective flow in a layer of volatile silicone oil with a kinematic viscosity of 0.65 cSt confined to a sealed cavity with a transverse aspect ratio of 3.2 was visualized using particle pathlines and quantified by particle-image velocimetry at dynamic Bond numbers estimated to be of order unity and laboratory Marangoni numbers as great as 3600. The effect of noncondensables (i.e., air) was studied by comparing convection in the liquid layer below a vapor space at pressures ranging from 4.8 kPa to 101 kPa, corresponding to air molar fractions ranging from 14% to 96%, respectively, and silicone-oil vapor, under otherwise identical conditions. The results for convection at 101 kPa are in qualitative agreement with previous studies, and clarify the time-dependent flow observed at high Marangoni numbers. The results show that decreasing the relative air concentration increases the critical Marangoni numbers for transition between different flow states, even though the air concentration does not appear to affect the speeds near the interface. Linear stability analysis shows that transitions are suppressed due to the latent heat generated or absorbed at the interface due to the enhancement of phase change. Furthermore, the experimental results suggest that air, even at relative concentrations as small as 14%, or partial pressures of O(102 Pa), has a significant effect on the vapor flow, and that the fluid in the vapor space should be modeled as a binary mixture in many cases of practical interest.
Elementary stratified flows with stability at low Richardson number
Authors: Barros Ricardo , Choi Wooyoung
Published: December 2014

We revisit the stability analysis for three classical configurations of multiple fluid layers proposed by Goldstein [“On the stability of superposed streams of fluids of different densities,” Proc. R. Soc. A. 132, 524 (1931)], Taylor [“Effect of variation in density on the stability of superposed streams of fluid,” Proc. R. Soc. A 132, 499 (1931)], and Holmboe [“On the behaviour of symmetric waves in stratified shear layers,” Geophys. Publ. 24, 67 (1962)] as simple prototypes to understand stability characteristics of stratified shear flows with sharp density transitions. When such flows are confined in a finite domain, it is shown that a large shear across the layers that is often considered a source of instability plays a stabilizing role. Presented are simple analytical criteria for stability of these low Richardson number flows.
Coil-to-globule transitions of homopolymers and multiblock copolymers
Authors: Wang Wei , Zhao Peng , Yang Xi , Lu Zhong-Yuan
Published: December 2014

We study the coil-to-globule transitions of both homopolymers and multiblock copolymers using integrated tempering sampling method, which is a newly proposed enhanced sampling method that can efficiently sample the energy space with low computational costs. For homopolymers, the coil-to-globule structure transition temperatures (Ttr) are identified by the radius of gyration of the chain. The transition temperature shows a primary scaling dependence on the chain length (N) with Ttr ∼ N−1/2. For multiblock copolymers, the coil-to-globule transition can be identified as first order, depending on the block size and the difference in attractive interactions of blocks. The influence of mutating a small portion of strongly attractive blocks to weakly attractive blocks on the coil-to-globule transition is found to be related to the position of the mutation.
A systematic way for the cost reduction of density fitting methods
Authors: Kállay Mihály
Published: December 2014

We present a simple approach for the reduction of the size of auxiliary basis sets used in methods exploiting the density fitting (resolution of identity) approximation for electron repulsion integrals. Starting out of the singular value decomposition of three-center two-electron integrals, new auxiliary functions are constructed as linear combinations of the original fitting functions. The new functions, which we term natural auxiliary functions (NAFs), are analogous to the natural orbitals widely used for the cost reduction of correlation methods. The use of the NAF basis enables the systematic truncation of the fitting basis, and thereby potentially the reduction of the computational expenses of the methods, though the scaling with the system size is not altered. The performance of the new approach has been tested for several quantum chemical methods. It is demonstrated that the most pronounced gain in computational efficiency can be expected for iterative models which scale quadratically with the size of the fitting basis set, such as the direct random phase approximation. The approach also has the promise of accelerating local correlation methods, for which the processing of three-center Coulomb integrals is a bottleneck.
A development scenario connecting the ternary symmetric horseshoe with the binary horseshoe
Authors: Gonzalez F. , Jung C.
Published: December 2014

It is explained in which way the ternary symmetric horseshoe can be obtained along a development scenario starting with a binary horseshoe. We explain the case of a complete ternary horseshoe in all detail and then give briefly some further incomplete cases. The key idea is to start with a three degrees of freedom system with a rotational symmetry, reduce the system with the help of the conserved angular momentum to one with two degrees of freedom where the value of the conserved angular momentum acts as a parameter and then let its value go to zero.
Study of stacked-emitter layer for high efficiency amorphous/crystalline silicon heterojunction solar cells
Authors: Lee Youngseok , Kim Heewon , Iftiquar S. M. , Kim Sunbo , Kim Sangho , Ahn Shihyun , Lee Youn-Jung , Dao Vinh Ai , Yi Junsin
Published: December 2014

A modified emitter, of stacked two layer structure, was investigated for high-efficiency amorphous/crystalline silicon heterojunction (HJ) solar cells. Surface area of the cells was 181.5 cm2. The emitter was designed to achieve a high open circuit voltage (Voc) and fill factor (FF). When doping of the emitter layer was increased, it was observed that the silicon dihydride related structural defects within the films increased, and the Voc of the HJ cell decreased. On the other hand, while the doping concentration of the emitter was reduced the FF of the cell reduced. Therefore, a combination of a high conductivity and low defects of a single emitter layer appears difficult to obtain, yet becomes necessary to improve the cell performance. So, we investigated a stacked-emitter with low-doped/high-doped double layer structure. A low-doped emitter with reduced defect density was deposited over the intrinsic hydrogenated amorphous silicon passivation layer, while the high-doped emitter with high conductivity was deposited over the low-doped emitter. The effects of doping and defect density of the emitter, on the device performance, were elucidated by using computer simulation and an optimized device structure was formulated. The simulation was performed with the help of Automat for the Simulation of Heterostructures simulation software. Finally, based on the simulation results, amorphous/crystalline heterojunction silicon solar cells were optimized by reducing density of defect states in the stacked-emitter structure and we obtained 725 mV, 77.41%, and 19.0% as the open-circuit voltage, fill factor, and photo-voltaic conversion efficiency of the device, respectively.
Verification of gyrokinetic particle simulation of current-driven instability in fusion plasmas. II. Resistive tearing mode
Authors: Liu Dongjian , Zhang Wenlu , McClenaghan Joseph , Wang Jiaqi , Lin Zhihong
Published: December 2014

Global gyrokinetic particle simulation of resistive tearing modes has been developed and verified in the gyrokinetic toroidal code (GTC). GTC linear simulations in the fluid limit of the kink-tearing and resistive tearing modes in the cylindrical geometry agree well with the resistive magnetohydrodynamic eigenvalue and initial value codes. Ion kinetic effects are found to reduce the radial width of the tearing modes. GTC simulations of the resistive tearing modes in the toroidal geometry find that the toroidicity reduces the growth rates.
Ultrafast pulse amplification in mode-locked vertical external-cavity surface-emitting lasers
Authors: Böttge C. N. , Hader J. , Kilen I. , Moloney J. V. , Koch S. W.
Published: December 2014

A fully microscopic many-body Maxwell–semiconductor Bloch model is used to investigate the influence of the non-equilibrium carrier dynamics on the short-pulse amplification in mode-locked semiconductor microlaser systems. The numerical solution of the coupled equations allows for a self-consistent investigation of the light–matter coupling dynamics, the carrier kinetics in the saturable absorber and the multiple-quantum-well gain medium, as well as the modification of the light field through the pulse-induced optical polarization. The influence of the pulse-induced non-equilibrium modifications of the carrier distributions in the gain medium and the saturable absorber on the single-pulse amplification in the laser cavity is identified. It is shown that for the same structure, quantum wells, and gain bandwidth the non-equilibrium carrier dynamics lead to two preferred operation regimes: one with pulses in the (sub-)100 fs-regime and one with multi-picosecond pulses. The recovery time of the saturable absorber determines in which regime the device operates.
Characterization of reactively sputtered c-axis aligned nanocrystalline InGaZnO4
Authors: Lynch David M. , Zhu Bin , Levin Barnaby D. A. , Muller David A. , Ast Dieter G. , Greene Raymond G. , Thompson Michael O.
Published: December 2014

Crystallinity and texturing of RF sputtered c-axis aligned crystal InGaZnO4 (CAAC IGZO) thin films were quantified using X-ray diffraction techniques. Above 190 °C, nanocrystalline films with an X-ray peak at 2θ = 30° (009 planes) developed with increasing c-axis normal texturing up to 310 °C. Under optimal conditions (310 °C, 10% O2), films exhibited a c-axis texture full-width half-maximum of 20°. Cross-sectional high-resolution transmission electron microscopy confirmed these results, showing alignment variation of ±9° over a 15 × 15 nm field of view and indicating formation of much larger aligned domains than previously reported. At higher deposition temperatures, c-axis alignment was gradually lost as polycrystalline films developed.
Increasing the achievable state of order in Ni-based Heusler alloys via quenched-in vacancies
Authors: Neibecker Pascal , Leitner Michael , Benka Georg , Petry Winfried
Published: December 2014

The ability to tune the degree of L21 order is of utmost importance for the magneto-mechanical properties of Ni-Mn-based Heusler alloys, e.g., the appearance of a martensitic phase in the Ni2MnAl system. Here, differential scanning calorimetry is established as a convenient tool for determining the state of order by way of its effect on the magnetic transition temperature, and it is used for studying the low-temperature ordering kinetics in Ni2MnAl. A significant acceleration of ordering kinetics due to excess vacancies retained after high-temperature quenching is demonstrated. Using this effect, equilibrium of order could be attained at temperatures as low as 623 K, where ordering under equilibrium vacancy concentration would take unpractically long.
A molecular dynamics study of tilt grain boundary resistance to slip and heat transfer in nanocrystalline silicon
Authors: Chen Xiang , Xiong Liming , Chernatynskiy Aleksandr , Chen Youping
Published: December 2014

We present a molecular dynamics study of grain boundary (GB) resistance to dislocation-mediated slip transfer and phonon-mediated heat transfer in nanocrystalline silicon bicrystal. Three most stable ⟨110⟩ tilt GBs in silicon are investigated. Under mechanical loading, the nucleation and growth of hexagonal-shaped shuffle dislocation loops are reproduced. The resistances of different GBs to slip transfer are quantified through their constitutive responses. Results show that the Σ3 coherent twin boundary (CTB) in silicon exhibits significantly higher resistance to dislocation motion than the Σ9 GB in glide symmetry and the Σ19 GB in mirror symmetry. The distinct GB strengths are explained by the atomistic details of the dislocation-GB interaction. Under thermal loading, based on a thermostat-induced heat pulse model, the resistances of the GBs to transient heat conduction in ballistic-diffusive regime are characterized. In contrast to the trend found in the dislocation-GB interaction in bicrystal models with different GBs, the resistances of the same three GBs to heat transfer are strikingly different. The strongest dislocation barrier Σ3 CTB is almost transparent to heat conduction, while the dislocation-permeable Σ9 and Σ19 GBs exhibit larger resistance to heat transfer. In addition, simulation results suggest that the GB thermal resistance not only depends on the GB energy but also on the detailed atomic structure along the GBs.
Si doping effects on (In,Ga)N nanowires
Authors: Kamimura J. , Ramsteiner M. , Geelhaar L. , Riechert H.
Published: December 2014

Si doped (In,Ga)N nanowires (In content up to 0.4) are grown on Si(111) substrates by plasma-assisted molecular beam epitaxy. By increasing the Si doping level, coalescence between nanowires is reduced and a more uniform morphology is obtained. The Raman spectra from highly doped samples show a characteristic broad band in the optical phonon frequency range, which became more prominent at higher doping levels. This Raman band can be explained by plasmon-phonon scattering from a free electron gas with strong wave-vector nonconservation, providing evidence for successful n-type doping. The measured plasmon-phonon modes are explained by lineshape simulations taking into account the simultaneous contribution of both the charge-density fluctuation and the impurity induced Fröhlich scattering mechanisms. The according lineshape analysis allows for an estimate of the carrier concentration.
Thermal conductivity tensors of the cladding and active layers of interband cascade lasers
Authors: Zhou Chuanle , Cui Boya , Vurgaftman I. , Canedy C. L. , Kim C. S. , Kim M. , Bewley W. W. , Merritt C. D. , Abell J. , Meyer J. R. , Grayson M.
Published: December 2014

The cross-plane and in-plane thermal conductivities of the W-active stages and InAs/AlSb superlattice optical cladding layer of an interband cascade laser (ICL) were characterized for temperatures ranging from 15 K to 324 K. The in-plane thermal conductivity of the active layer is somewhat larger than the cross-plane value at temperatures above about 30 K, while the thermal conductivity tensor becomes nearly isotropic at the lowest temperatures studied. These results will improve ICL performance simulations and guide the optimization of thermal management.
Human mutations in methylenetetrahydrofolate dehydrogenase 1 impair nuclear de novo thymidylate biosynthesis
Authors: Field Martha S. , Kamynina Elena , Watkins David , Rosenblatt David S. , Stover Patrick J.
Published: December 2014

Significance

These studies have identified that human genetic mutations, which impair the function of the folate-dependent enzyme methylene tetrahydrofolate dehydrogenase I (MTHFD1), depress rates of de novo thymidylate synthesis, elevate uracil levels in human DNA, and increase genome instability. These findings provide insights into the role of MTHFD1 and thymidylate biosynthesis in the etiology of SCID and megaloblastic anemia.
Detecting nanoscale vibrations as signature of life
Authors: Kasas Sandor , Ruggeri Francesco Simone , Benadiba Carine , Maillard Caroline , Stupar Petar , Tournu Hélène , Dietler Giovanni , Longo Giovanni
Published: December 2014

Significance

The quest to find life in extreme and extraterrestrial environments is exciting and touches many research fields. One of the common signatures of life is movement: Even small microorganisms vibrate in response to their metabolic activity. Thus, we have devised a nanomotion detector to study these fluctuations and to associate them to the metabolic activity of the specimens. This technique does not measure the chemical response of life, which would require prior knowledge of the metabolic pathways involved. Instead, it monitors the physical manifestation of any kind of metabolic activity the microorganisms might have. Here, we show how this nanomotion detector can study any living system, paving the way to a complementary approach to the study of life in extreme environments.
Structure of CrgA, a cell division structural and regulatory protein fromMycobacterium tuberculosis, in lipid bilayers
Authors: Das Nabanita , Dai Jian , Hung Ivan , Rajagopalan Malini , Zhou Huan-Xiang , Cross Timothy A.
Published: December 2014

Significance

Understanding the structure and function of the cell division apparatus ofMycobacterium tuberculosisis crucial for advancing drug development against tuberculosis. Here, we report the solid-state NMR structure of a transmembrane protein, CrgA, that is a central component of theM. tuberculosisdivisome. Small helical membrane protein structures are particularly sensitive to their environment, and consequently, we characterized CrgA in an environment that models well the biophysical properties of the native membrane. To determine the structure, both oriented sample and magic-angle spinning NMR data from liquid–crystalline lipid bilayer preparations were used along with refinement by restrained molecular dynamics simulations in the same lipid environment. The structure suggests how CrgA serves as a platform for binding and recruiting other proteins of the divisome.
β-Catenin–related protein WRM-1 is a multifunctional regulatory subunit of the LIT-1 MAPK complex
Authors: Yang Xiao-Dong , Karhadkar Tejas R. , Medina Jessica , Robertson Scott M. , Lin Rueyling
Published: December 2014

Significance

Vertebrate β-catenin has two functions: as a structural component in cell adhesion and as the T-cell factor coactivator in canonical Wnt (wingless-related integration site) signaling. These two functions are split between three β-catenin–related proteins in
Caenorhabditis elegans
. A fourth worm β-catenin–related protein, worm arm motif 1 (WRM-1), exhibits neither of these functions but is essential, together with loss of intestine 1 (LIT-1) MAPK, for transcriptional activation of Wnt target genes. Here we characterize previously unidentified mechanisms by which the LIT-1 kinase is activated and the different regulatory roles that WRM-1 plays in LIT-1 activation and LIT-1 subcellular localization. This study suggests the potential for novel and as yet undiscovered functions for vertebrate β-catenin.
Adaptive simplification and the evolution of gecko locomotion: Morphological and biomechanical consequences of losing adhesion
Authors: Higham Timothy E. , Birn-Jeffery Aleksandra V. , Collins Clint E. , Hulsey C. Darrin , Russell Anthony P.
Published: December 2014

Significance

The gecko adhesive system has garnered considerable interest from scientists over the past several decades. Most research has focused on the function and microanatomy of the adhesive system. However, it is currently unclear what impact the secondary loss or simplification of the adhesive system might have on the evolutionary biomechanics of gecko locomotion, which is critical for pinpointing the constraints that accompany such an innovation, and ultimately the release from these constraints. We found that geckos exhibit elevated rates of morphological and kinematic evolution when their adhesive system is lost/simplified, providing evidence that the loss of an innovation can have profound evolutionary impacts on organismal structural and functional divergence
Crystal structures of alkylperoxo and anhydride intermediates in an intradiol ring-cleaving dioxygenase
Authors: Knoot Cory J. , Purpero Vincent M. , Lipscomb John D.
Published: December 2014

Significance

Vast quantities of aromatic compounds enter the environment due to the natural breakdown of lignin as well as industrial and agricultural pollution. Intradiol aromatic ring-cleaving dioxygenases play a pivotal role in the biodegradation of these aromatics. Despite exhaustive study, the mechanism of intradiol dioxygenases has remained elusive because the reaction cycle intermediates in which O
2
is activated and inserted into the aromatic are too fleeting to be trapped and characterized. Here the intradiol dioxygenase reaction is carried out in a crystal, allowing the two reaction cycle intermediates that most clearly define the mechanism to be trapped and their structures solved.
Direct coupling of haptic signals between hands
Authors: Dupin Lucile , Hayward Vincent , Wexler Mark
Published: December 2014

Significance

When we actively explore objects by touch, the brain receives two types of signals, tactile sensory inputs and signals about the exploratory movement, which must be combined to perceive the shape and location of objects in space. Whereas these signals usually come from the same body part, we have developed a technique to separate them, directing the tactile signals to one hand and the movement signals to the other. We find that separated and synchronized signals are combined as if they arose from the same hand. Our results suggest that to solve the difficult problem of multidimensional signal combination in touch perception, the brain uses a simplified, source-independent representation of movement.