bluuebunny/crossref_metadata_2025 huggingface dataset:
IMPLICIT LEARNING IN SLA AND THE ISSUE OF INTERNAL VALIDITY
Authors: Leow Ronald P. , Hama Mike
Published: May 2013

There is a growing theoretical, empirical, and methodological debate in the SLA field as to whether unawareness plays a role during attention to or processing of new incoming second language (L2) data. Indeed, studies that have methodologically addressed the construct of unawareness in their research designs offer both empirical support (e.g., Leung & Williams, 2011, 2012; Williams, 2004, 2005) and no empirical support (e.g., Faretta-Stutenberg & Morgan-Short, 2011; Hama & Leow, 2010; Leow, 2000) for implicit learning. This article takes a critical look at one recent study (Leung & Williams, 2011) and questions the level of internal validity with respect to the claim that their study provided empirical evidence of implicit learning. It concludes by providing specific criteria that need to be considered in any study purporting to address the construct of awareness or lack thereof in L2 learning.
The communicative contexts of grammatical aspect use in English
Authors: IBBOTSON PAUL , LIEVEN ELENA , TOMASELLO MICHAEL
Published: May 2013

In many of the world's languages grammatical aspect is used to indicate how events unfold over time. In English, activities that are ongoing can be distinguished from those that are completed using the morphological marker -ing. Using naturalistic observations of two children in their third year of life, we quantify the availability and reliability of the imperfective form in the communicative context of the child performing actions. On average, 30% of verbal descriptions refer to child actions that are grounded in the here-and-now. Of these utterances, there are two features of the communicative context that reliably map onto the functions of the imperfective, namely, that events are construed as ongoing and from within. The findings are discussed with reference to how the context in which a child hears aspectual language may limit the degrees of freedom on what these constructions mean.
Participation in Policy Discourse: New Form of Exclusion for Seniors with Disabilities?
Authors: Raymond Émilie , Grenier Amanda
Published: May 2013

Les récents discours sur le vieillissement donnent beaucoup d’importance au thème de la participation sociale des aînés. Cependant, la manière dont la participation est définie dans les politiques et les pratiques sociales ne correspond pas nécessairement aux réalités de tous les aînés. Cet article présente les conclusions d’une analyse critique de discours qui a examiné des politiques sur le vieillissement développées par la province de Québec, au Canada, entre 2005 et 2011. Les résultats montrent que les interprétations émergentes de la participation peuvent être problématiques lorsqu’elles sont associées à des recommandations, des standards et des attentes. Premièrement, les documents analysés montrent que la participation est de plus en plus définie en termes de productivité et que la notion de bien-être des aînés a été remplacée par celle d’utilité. Deuxièmement, le contexte de la participation est passé d’une responsabilité collective à une question de choix personnel et d’ajustement des [aux] communautés locales. Troisièmement, les documents reflètent une polarisation de l’activité et de la perte d’autonomie qui a pour conséquence d’associer participation et bonne santé. Ces résultats suggèrent que bien qu’innovante dans le cadre canadien, l’articulation de la participation telle que proposée dans les politiques québécoises sur le vieillissement est dépourvue des éléments politiques nécessaires à l’inclusion et à la discussion de la différence, de l’altérité et de l’accès aux espaces participatifs. Le cas des personnes vieillissant avec une incapacité physique illustre les défis inhérents à ce nouvel agenda participatif.
Effect of Dy-doping on the microstructure and magnetic properties of Y1−xDyxMnO3
Authors: Zhang A.M. , Zhou G.T. , Sun J. , Xu T. , Guo L.L. , Wu X.S.
Published: May 2013

The effect of Dy3+ doping at A-site in hexagonal YMnO3 on the microstructure and magnetic properties was studied. Polycrystalline Y1−xDyxMnO3 samples with x ranging from 0 to 1 were synthesized by the solid-state reaction method. The microstructures of all the samples were studied by X-ray diffraction, which shows that Y1−xDyxMnO3 with a low concentration (x ≤ 0.5) of Dy3+ retains a hexagonal symmetry. The crystal structure refinements of the hexagonal Y1−xDyxMnO3 using the Rietveld method show that the unit-cell parameters of a, c, and unit-cell volume increase with increasing Dy doping, while the MnO5 trigonal bipyramids remain almost unchanged. The remarkable increasing of magnetic moment at a low temperature with increasing the Dy3+ doping concentration is ascribed to the spin order of Dy3+ and the increasing Dy3+–Mn3+ coupling and Mn3+–O–O–Mn3+ interaction.
The occurrence of melioidosis is related to different climatic conditions in distinct topographical areas of Taiwan
Authors: MU J.-J. , CHENG P.-Y. , CHEN Y.-S. , CHEN P.-S. , CHEN Y.-L.
Published: May 2013

This study assessed the correlations between the incidence of melioidosis and rainfall, wind strength and wind direction in both the flat and hilly regions of Taiwan. Data from the melioidosis and climate databases from 2005 to 2011 were combined and analysed. With the inclusion of a lag time accounting for a possible incubation period for melioidosis, the daily rainfall and wind-speed data were correlated with the number of confirmed melioidosis cases. The incidence of melioidosis in the flat region was related to the wind speed (>19 m/s) and the specific angle (150°, 220°, 280°) of the wind direction. Rainfall is a common environmental factor that contributes to an increase in the incidence of melioidosis in both areas; however, the contribution of wind strength or wind direction to the spread of melioidosis was restricted to areas with specific topographical characteristics, such as hills.
Climate policy and equity principles: fair burden sharing in a dynamic world
Authors: Bretschger Lucas
Published: May 2013

The paper argues that negotiation costs can prevent the international community from finding a new international climate agreement. To define a feasible way of facilitating the negotiation process, I analyze basic equity principles and their relationship to climate policy and economic development. Based on the most relevant principles, I propose a general synthetic rule for burden sharing in international climate policy. The rule avoids complexity and comprises both egalitarian and cost-sharing aspects, which appears to be crucial for achieving a climate agreement. Carbon budgets for the different countries are calculated under different parameter assumptions.
Strategic delaying and concessions extraction in accession negotiations to the World Trade Organization: an analysis of Working Party membership
Authors: NEUMAYER ERIC
Published: May 2013

Accession to the World Trade Organization (WTO) is unlike accession to other global organizations. It is extremely demanding on applicant countries, time consuming and essentially power- rather than rule-based. This article argues that existing WTO members select themselves into the Working Party of applicant countries, the body which determines the timing and conditions of accession, in order to have the option to strategically delay membership by the applicant and/or extract concessions from it. Existing members will select themselves into a specific Working Party if their own trade interests are strongly affected, which will be the case if the existing member's bilateral trade with the applicant country forms a large share of its income, unless both countries already have a preferential trade agreement (PTA) between them. Trade interests are also strongly affected if the existing member competes with the applicant in terms of export product and market structure. Conversely, where both member and applicant have more PTAs with third countries of large economic size in common, potential accession will affect the member's trade interests less. An empirical analysis of Working Party membership since 1968 estimates to what extent these three different facets of trade interests are substantively important determinants of Working Party composition.
Longitudinal Effects of Lesions on Functional Networks after Stroke
Authors: Ovadia-Caro Smadar , Villringer Kersten , Fiebach Jochen , Jungehulsing Gerhard Jan , van der Meer Elke , Margulies Daniel S , Villringer Arno
Published: May 2013

While ischemic stroke reflects focal damage determined by the affected vascular territory, clinical symptoms are often more complex and may be better explained by additional indirect effects of the focal lesion. Assumed to be structurally underpinned by anatomical connections, supporting evidence has been found using alterations in the functional connectivity of resting-state functional magnetic resonance imaging (fMRI) data in both sensorimotor and attention networks. To assess the generalizability of this phenomenon in a stroke population with heterogeneous lesions, we investigated the distal effects of lesions on a global level. Longitudinal resting-state fMRI scans were acquired at three consecutive time points, beginning during the acute phase (days 1, 7, and 90 post-stroke) in 12 patients after ischemic stroke. We found a preferential functional change in affected networks (i.e., networks containing lesions changed more during recovery when compared with unaffected networks). This change in connectivity was significantly correlated with clinical changes assessed with the National Institute of Health Stroke Scale. Our results provide evidence that the functional architecture of large-scale networks is critical to understanding the clinical effect and trajectory of post-stroke recovery.
Functional Astrocyte-Neuron Lactate Shuttle in a Human Stem Cell-Derived Neuronal Network
Authors: Tarczyluk Marta A , Nagel David A , O’Neil John D , Parri H Rheinallt , Tse Erin HY , Coleman Michael D , Hill Eric J
Published: May 2013

The NT2.D1 cell line is one of the most well-documented embryocarcinoma cell lines, and can be differentiated into neurons and astrocytes. Great focus has also been placed on defining the electrophysiological properties of the neuronal cells, and more recently we have investigated the functional properties of their associated astrocytes. We now show for the first time that human stem cell-derived astrocytes produce glycogen and that co-cultures of these cells demonstrate a functional astrocyte-neuron lactate shuttle (ANLS). The ANLS hypothesis proposes that during neuronal activity, glutamate released into the synaptic cleft is taken up by astrocytes and triggers glucose uptake, which is converted into lactate and released via monocarboxylate transporters for neuronal use. Using mixed cultures of NT2-derived neurons and astrocytes, we have shown that these cells modulate their glucose uptake in response to glutamate. Additionally, we demonstrate that in response to increased neuronal activity and under hypoglycaemic conditions, co-cultures modulate glycogen turnover and increase lactate production. Similar results were also shown after treatment with glutamate, potassium, isoproterenol, and dbcAMP. Together, these results demonstrate for the first time a functional ANLS in a human stem cell-derived co-culture.
The folding capacity of the mature domain of the dual-targeted plant tRNA nucleotidyltransferase influences organelle selection
Authors: Leibovitch Matthew , Bublak Daniela , Hanic-Joyce Pamela J. , Tillmann Bodo , Flinner Nadine , Amsel Daniel , Scharf Klaus-Dieter , Mirus Oliver , Joyce Paul B. M. , Schleiff Enrico
Published: May 2013

tRNA-NTs (tRNA nucleotidyltransferases) are required for the maturation or repair of tRNAs by ensuring that they have an intact cytidine-cytidine-adenosine sequence at their 3′-termini. Therefore this enzymatic activity is found in all cellular compartments, namely the nucleus, cytoplasm, plastids and mitochondria, in which tRNA synthesis or translation occurs. A single gene codes for tRNA-NT in plants, suggesting a complex targeting mechanism. Consistent with this, distinct signals have been proposed for plastidic, mitochondrial and nuclear targeting. Our previous research has shown that in addition to N-terminal targeting information, the mature domain of the protein itself modifies targeting to mitochondria and plastids. This suggests the existence of an as yet unknown determinate for the distribution of dual-targeted proteins between these two organelles. In the present study, we explore the enzymatic and physicochemical properties of tRNA-NT variants to correlate the properties of the enzyme with the intracellular distribution of the protein. We show that alteration of tRNA-NT stability influences its intracellular distribution due to variations in organelle import capacities. Hence the fate of the protein is determined not only by the transit peptide sequence, but also by the physicochemical properties of the mature protein.
Novel high-temperature and pressure-compatible ultrasonic levitator apparatus coupled to Raman and Fourier transform infrared spectrometers
Authors: Brotton Stephen J. , Kaiser Ralf I.
Published: May 2013

We describe an original apparatus comprising of an acoustic levitator enclosed within a pressure-compatible process chamber. To characterize any chemical and physical modifications of the levitated particle, the chamber is interfaced to complimentary, high-sensitivity Raman (4390–170 cm−1), and Fourier transform infrared (FTIR) (10 000–500 cm−1) spectroscopic probes. The temperature of the levitated particle can be accurately controlled by heating using a carbon dioxide laser emitting at 10.6 μm. The advantages of levitating a small particle combined with the two spectroscopic probes, process chamber, and infrared laser heating makes novel experiments possible relevant to the fields of, for example, planetary science, astrobiology, and combustion chemistry. We demonstrate that this apparatus is well suited to study the dehydration of a variety of particles including minerals and biological samples; and offers the possibility of investigating combustion processes involving micrometer-sized particles such as graphite. Furthermore, we show that the FTIR spectrometer enables the study of chemical reactions on the surfaces of porous samples and scientifically and technologically relevant, micrometer-thick levitated sheets. The FTIR spectrometer can also be used to investigate non-resonant and resonant scattering from small, irregularly-shaped particles across the mid-infrared range from 2.5 μm to 25 μm, which is relevant to scattering from interplanetary dust and biological, micrometer-sized samples but cannot be accurately modelled using Mie theory.
SCC-DFTB calculation of the static first hyperpolarizability: From gas phase molecules to functionalized surfaces
Authors: Nénon Sébastien , Champagne Benoît
Published: May 2013

The performance of the self-consistent charge density functional tight binding (SCC-DFTB) method for calculating the first hyperpolarizability of π-conjugated compounds has been assessed with respect to results obtained with high-level ab initio methods and density functional theory (DFT). The SCC-DFTB method performs similarly or better than DFT with the PBE XC functional. Thus, if for small π-conjugated linkers SCC-DFTB can reproduce trends, for longer chains the first hyperpolarizabilities are overestimated. In the case of push-pull thiophenes, the β values are strongly overestimated, as it is also the case with the B3LYP and PBE XC functionals. On the other hand, the SCC-DFTB method closely reproduces the evolution of β in p-disubstituted benzenes as a function of the donor and acceptor groups, as estimated at the MP2 level. The reliability of SCC-DFTB to determine the bond length alternation and the dihedral angles between the aromatic rings has also been tackled, demonstrating that both are underestimated. Overall, the SCC-DFTB calculations are of the same quality as those performed with the conventional PBE XC functional on which the method was parameterized but the SCC-DFTB calculations are computationally very little demanding, and it can therefore be adopted for very large systems for screening nonlinear optical materials as well as for assessing structure-property relationships. This is illustrated with an application on the first hyperpolarizability of an indolino-oxazolidine molecular switch grafted on a SiO2 surface. This has enabled to pinpoint (i) the effect of the surface on the donor/acceptor character of the linking substituent, (ii) the impact of molecular orientation, (iii) the role of a spacer between the π-conjugated switch and the surface, (iv) the global effect of the surface on the β contrast, and also (v) the fact that the molecular switches can maintain this contrast when adsorbed.
Novel carbon materials: New tunneling systems (Review Article)
Authors: Strzhemechny M. A. , Dolbin A. V.
Published: May 2013

This review covers recent achievements in the studies of quantum properties of the novel carbon materials (fullerite C60 and bundles of single-walled nanotubes (SWNT)) saturated with such light-mass species as helium isotopes, the homonuclear molecular hydrogens, and neon. It is shown that even some heavy dopants demonstrate kinetic phenomena, in which coherent effects play an essential role. Two theoretical concepts are surveyed which have been suggested for the explanation of the anomalous phenomena in saturation kinetics and linear thermal expansion of doped C60. Most unusual effects have been also observed in the low-temperature radial expansion of bundles of single-walled carbon nanotubes saturated with the helium isotopes. First, it was shown that low-temperature radial expansion of pure SWNT is negative, i.e., a nanotube shrinks with warming. Second, saturation of SWNT bundles with the helium isotopes entails a huge increase of the negative expansion effect, when the dopant is He. So far, no detailed physical picture has been put forward. It is worth mentioning that the dynamics of a single helium atom on an isolated nanotube corresponds to that of a tight-bound quasiparticle with a band width of about 10 K.
Structural evolution of ferromagnetic 3He multilayers adsorbed on exfoliated graphite
Authors: Antsygina T. N. , Chishko K. A.
Published: May 2013

On the basis of our theoretical results describing two-dimensional spin-1/2 Heisenberg model in an external magnetic field we analyze and interpret known from literature experimental data on magnetization of pure 3He monolayers on graphite at ferromagnetic coverages. We clarify the experimentally observed temperature dependences for 2D 3He magnetization under magnetic fields of different magnitude. The cluster size effect in the temperature dependence of the magnetization is studied. We interpret the spin exchange variation in 2D multilayered 3He system during successive promotion of the second, third and fourth layers over first paramagnetic layer strongly coupled with graphite substrate.
Compressible laminar streaks with wall suction
Authors: Ricco Pierre , Shah Daniel , Hicks Peter D.
Published: May 2013

The response of a compressible laminar boundary layer subject to free-stream vortical disturbances and steady mean-flow wall suction is studied. The theoretical frameworks of Leib et al. [J. Fluid Mech. 380, 169–203 (1999)10.1017/S0022112098003504] and Ricco and Wu [J. Fluid Mech. 587, 97–138 (2007)10.1017/S0022112007007070], based on the linearized unsteady boundary-region equations, are adopted to study the influence of suction on the kinematic and thermal streaks arising through the interaction between the free-stream vortical perturbations and the boundary layer. In the asymptotic limit of small spanwise wavelength compared with the boundary layer thickness, i.e., when the disturbance flow is conveniently described by the steady compressible boundary region equations, the effect of suction is mild on the velocity fluctuations and negligible on the temperature fluctuations. When the spanwise wavelength is comparable with the boundary layer thickness, small suction values intensify the supersonic streaks, while higher transpiration levels always stabilize the disturbances at all Mach numbers. At larger spanwise wavelengths, very small amplitudes of wall transpiration have a dramatic stabilizing effect on all boundary layer fluctuations, which can take the form of transiently growing thermal streaks, large amplitude streamwise oscillations, or oblique exponentially growing Tollmien-Schlichting waves, depending on the Mach number and the wavelengths. The range of wavenumbers for which the exponential growth occurs becomes narrower and the location of instability is significantly shifted downstream by mild suction, indicating that wall transpiration can be a suitable vehicle for delaying transition when the laminar breakdown is promoted by these unstable disturbances. The typical streamwise wavelength of these disturbances is instead not influenced by suction, and asymptotic triple deck theory predicts the strong changes in growth rate and the very mild modifications in streamwise wavenumber in the limit of larger downstream distance and small spanwise wavenumber.
Form factors and complete spectrum of XXX antiperiodic higher spin chains by quantum separation of variables
Authors: Niccoli G.
Published: May 2013

The antiperiodic transfer matrices associated to higher spin representations of the rational 6-vertex Yang-Baxter algebra are analyzed by generalizing the approach introduced recently in the framework of Sklyanin's quantum separation of variables (SOV) for cyclic representations, spin-1/2 highest weight representations, and also for spin-1/2 representations of the 6-vertex reflection algebra. Such SOV approach allow us to derive exactly results which represent complicate tasks for more traditional methods based on Bethe ansatz and Baxter Q-operator. In particular, we both prove the completeness of the SOV characterization of the transfer matrix spectrum and its simplicity. Then, the derived characterization of local operators by Sklyanin's quantum separate variables and the expression of the scalar products of separate states by determinant formulae allow us to compute the form factors of the local spin operators by one determinant formulae similar to those of the scalar products.
Self-assembled two-dimensional graphene grating on a dielectric substrate
Authors: Kaplas Tommi , Silvennoinen Martti , Paivasaari Kimmo , Svirko Yuri
Published: May 2013

We present a technique for spatially controlled chemical vapor deposition of graphene on a dielectric substrate. The technique is based on the surface melting of a thin Cu catalyst film pre-deposited on a dielectric substrate with spatially modified surface. The self-assembling of the liquefied copper in predefined fashion on the substrate enables spatially controlled deposition of graphene on the copper-silica interface. The developed technique that involves neither pre- nor post-deposition patterning of the graphene allowed us to fabricate the two dimensional graphene grating with period of 10 μm.
Cascade units for neon isotope production by rectification
Authors: Bondarenko V. L. , Simonenko Yu. M. , Diachenko O. V. , Matveyev E. V.
Published: May 2013

The basics of neon isotope separation by the distillation method at T = 28 K are discussed. The required numbers of transfer units at the top and bottom column sections are calculated for different loads. The experimental characteristics of packed rectification columns are presented and examples of the cascade are discussed. A configuration for a cryogenic circuit based on a high-pressure throttle neon cycle with intermediate nitrogen cooling is presented. The necessity for and the technical feasibility of creating a driver pressure difference between the columns for different stages are demonstrated.
Comparative study of thermo-stimulated luminescence and electron emission of nitrogen nanoclusters and films
Authors: Boltnev R. E. , Bykhalo I. B. , Krushinskaya I. N. , Pelmenev A. A. , Khmelenko V. V. , Lee D. M. , Khyzhniy I. V. , Uyutnov S. A. , Savchenko E. V. , Ponomaryov A. N. , Gumenchuk G. B. , Bondybey V. E.
Published: May 2013

We have studied thermo-stimulated luminenscence and electron emission of nitrogen films and nanoclusters containing free radicals of atomic nitrogen. Thermo-stimulated electron emission from N2 nanoclusters was observed for the first time. Thermo-stimulated luminescence spectra obtained during the destruction of a N2–He sample are similar to those detected from N2 films pre-irradiated by an electron beam. This similarity reveals common mechanisms of energy transfer and relaxation. The correlation of luminescence intensity and electron current in both systems points to the important role of ionic species in relaxation cascades. Sublimation of solid helium shells isolating nitrogen nanoclusters is a trigger for the initiation of thermo-stimulated luminescence and electron emission in these nitrogen–helium condensates.
Dual beam differential photopyroelectric setup for broadband thermal effusivity investigation of glass transitions in polymers
Authors: Paoloni S. , Zammit U. , Marinelli M. , Mercuri F. , Pizzoferrato R.
Published: May 2013

The behaviour of the thermal effusivity squared over the glass transition in polystyrene is measured over a considerable frequency range using a novel dual beam front detection photopyroelectric configuration, which ensures a very effective processing of the obtained signal. This has enabled the detection of the very small changes taking place in such a parameter, despite the non-favourable sensitivity conditions due to the large mismatch between the thermal effusivities of the pyroelectric transducer and of the sample. The effect of the thermal contact resistance between the sample and the pyroelectric detector is also considered and discussed.
Temperature and entropy in supersonic free jets
Authors: Montero S.
Published: May 2013

Translational temperature (Tt), flow velocity (v), and entropy increment (ΔS) along the paraxial zone of silence of supersonic free jets are studied in the frame of the Navier-Stokes (NS) equations. Expressions for the experimentally non-accessible quantities Tt, v, and ΔS are formulated in terms of the experimentally accessible number density (n) and rotational temperature (Tr). The scope of the inviscid-adiabatic and isentropic flow approximations is discussed with emphasis in the dissipative effects onto the flow variables. The influence of dissipative contributions due to viscosity and heat conductivity onto the translational temperature and entropy of pure helium supersonic jets is illustrated. Two sources of entropy increment in the jets have been identified and formulated quantitatively, namely, the dissipative effects, and the Tr ≠ Tt non-equilibrium in gases including molecular species. As far as the rarefaction of the jet allows for the use of the NS-equations, a number of “exact” expressions relating the flow variables n, Tt, Tr, v, and ΔS along mixed supersonic jets of atoms and molecules are reported. These expressions are aimed at an optimal experimental diagnostics of the jets.
Instabilities in evaporating liquid layer with insoluble surfactant
Authors: Mikishev Alexander B. , Nepomnyashchy Alexander A.
Published: May 2013

The stability of an evaporating liquid layer with insoluble surfactant distributed over the free deformable surface is studied theoretically. The insoluble surfactant hinders the evaporation, and mass flux through the interface is a decreasing function of surfactant concentration. Density, viscosity, and thermal conductivity of the gaseous phase are assumed to be small compared with those of the liquid phase, and a one-sided model is applied. A system of nonlinear equations is obtained using the long-wave approximation and the assumption of a slow time evolution. These equations incorporate basic physical effects which take place in the system. Linear stability analysis of the base state is performed for long-wave disturbances in the framework of the frozen interface approximation. The cases of quasi-equilibrium evaporation (when the interfacial temperature equals the equilibrium one) and nonequilibrium evaporation are considered. In addition to a monotonic instability mode, an oscillatory mode has been found.
A strong anisotropy of spin dephasing time of quasi-one dimensional electron gas in modulation-doped GaAs/AlGaAs wires
Authors: Ishihara J. , Ono M. , Ohno Y. , Ohno H.
Published: May 2013

We investigated the wire orientation dependence of ensemble electron spin dynamics by using a time-resolved Kerr rotation technique in wires made from a modulation-doped GaAs/AlGaAs quantum well. We observed a strong anisotropy of the electron spin dephasing time of as large as 40 depending on the wire orientation at 5 K by tuning the spin-orbit interaction. The wire width dependence of the spin dynamics is reproduced in a Monte Carlo simulation. In addition, two characteristic spin decay rates were observed in wires whose widths were close to the spin precession length. The dependence of the magnetic field direction on the spin dynamics of the wires was also studied to determine the difference from that of two dimensional electron gas.
On discrete field theory properties of the dimer and Ising models and their conformal field theory limits
Authors: Kriz Igor , Loebl Martin , Somberg Petr
Published: May 2013

We study various mathematical aspects of discrete models on graphs, specifically the Dimer and the Ising models. We focus on proving gluing formulas for individual summands of the partition function. We also obtain partial results regarding conjectured limits realized by fermions in rational conformal field theories.
High frame-rate fluorescence confocal angle-resolved linear dichroism microscopy
Authors: Wang Xiao , Kress Alla , Brasselet Sophie , Ferrand Patrick
Published: May 2013

Angle-resolved linear dichroism is a recent technique that exploits images recorded using an illumination field whose polarization angle is sequentially rotated during acquisition. It allows to retrieve orientation information of the fluorescent molecules, namely the average orientation angle and the amplitude of the fluctuations around this average. In order to boost up the acquisition speed without sacrificing the axial sectioning, we propose to combine a spinning disk confocal excitation scheme together with an electrooptical polarization switching and a camera acquisition. The polarization distortions induced when passing through the spinning disk system have been quantified and effectively compensated. The signal to noise features of the camera have been analyzed in detail so that the precision of the method can be quantified. The technique has been successfully tested on giant unilamellar vesicles and on living cells labeled with different fluorescent lipid probes, DiIC18 and di-8-ANEPPQ. It was able to acquire precise orientation images at full frame rates in the range of a second, ultimately limited by the fluorophore brightness and the camera sensitivity.
Cluster approach to formation of nitrogen–rare gas cryoalloys
Authors: Solodovnik A. A. , Danchuk V. V. , Mysko N. S.
Published: May 2013

The structure of solid binary N2–Kr and N2–Ar solutions was studied by transmission electron diffraction (THEED). The samples were prepared in situ by deposition of a gaseous mixture onto an Al substrate cooled to 20 K. The lattice parameters for low concentrations of one of the components were measured. The relative change of the lattice parameter per unit concentration is determined for N2 impurity in Kr and Ar, as well as for Kr and Ar in N2. Analysis of the concentration dependence of the lattice parameters for low fractions of both components was performed within a cluster model in the three-particle approximation.
The direct scattering problem for a crack buried in a piecewise homogenous medium
Authors: Guo Jun , Yan Guozheng , Ye Jianguo
Published: May 2013

We consider a kind of scattering problem which models the scattering of an electromagnetic time-harmonic plane wave by an infinite cylinder having an open arc and a penetrable obstacle in R2 as cross section, and the open arc is buried in a piecewise homogeneous medium. To this end, we solve a scattering problem for the Helmholtz equation in R2 where the scattering object is a crack Γ which is buried inside the bounded domain D, and we have Dirichlet-Impedance type boundary condition on Γ and transmission boundary condition on the boundary of D. Applying potential theory, the problem can be reformulated as a boundary integral system. We establish the existence and uniqueness of a weak solution to the system by using the modified Fredholm theory.
Bäcklund transformation and smooth multisoliton solutions for a modified Camassa-Holm equation with cubic nonlinearity
Authors: Matsuno Yoshimasa
Published: May 2013

We present a compact parametric representation of the smooth bright multisoliton solutions for the modified Camassa-Holm (mCH) equation with cubic nonlinearity. We first transform the mCH equation to an associated mCH equation through a reciprocal transformation and then find a novel Bäcklund transformation between solutions of the associated mCH equation and a model equation for shallow-water waves (SWW) introduced by Ablowitz et al. We combine this result with the expressions of the multisoliton solutions for the SWW and modified Korteweg-de Vries equations to obtain the multisoliton solutions of the mCH equation. Subsequently, we investigate the properties of the one- and two-soliton solutions as well as the general multisoliton solutions. We show that the smoothness of the solutions is assured only if the amplitude parameters of solitons satisfy certain conditions. We also find that at a critical value of the parameter beyond which the solution becomes singular, the soliton solution exhibits a different feature from that of the peakon solution of the CH equation. Then, by performing an asymptotic analysis for large time, we obtain the formula for the phase shift and confirm the solitonic nature of the multisoliton solutions. Finally, we use the Bäcklund transformation to derive an infinite number of conservation laws of the mCH equation.
Bound states of the spin-orbit coupled ultracold atom in a one-dimensional short-range potential
Authors: Juršėnas Rytis , Ruseckas Julius
Published: May 2013

We solve the bound state problem for the Hamiltonian with the spin-orbit and the Raman coupling included. The Hamiltonian is perturbed by a one-dimensional short-range potential V which describes the impurity scattering. In addition to the bound states obtained by considering weak solutions through the Fourier transform or by solving the eigenvalue equation on a suitable domain directly, it is shown that ordinary point-interaction representations of V lead to spin-orbit induced extra states.
Some observations on cosmological time functions
Authors: Ebrahimi N.
Published: May 2013

A new characterization for global hyperbolicity is given. The concept of cosmological time function and its regularity was considered by Anderson et al. [“The cosmological time function,” Class. Quantum Grav. 15, 309 (1998)]10.1088/0264-9381/15/2/006 and it was proved that if the cosmological time function of (M, g) is regular then it is globally hyperbolic. In this paper it is proved that if (M, g) is globally hyperbolic then there is a smooth function Ω > 0 such that the cosmological time function of (M, Ωg) is regular. It is also proved that the cosmological time function of Friedman-Robertson-Walker spacetime ((a, b) × f H, −dt2 + f h), a, b < ∞, is regular and in addition the regularity of cosmological time function for this kind of spacetimes is stable in \documentclass[12pt]{minimal}\begin{document}$\rm {Lor}(\it M)$\end{document} Lor (M).
Quantized conductance and evidence for zitterbewegung in InAs spin filters
Authors: Benter Till , Lehmann Hauke , Matsuyama Toru , Hansen Wolfgang , Heyn Christian , Merkt Ulrich , Jacob Jan
Published: May 2013

We present measurements of the electron transport in top-gated InAs spin-filter cascades. The cascades consist of a first filter stage that acts as a polarizer, a center wire, and a second filter stage that acts as an analyzer. Conductance quantization indicates quasi-ballistic transport in these rather large devices. Oscillations of the conductances of the second filter's outputs with the strength of an in-plane magnetic field perpendicular to the center wire provide evidence of the so-called zitterbewegung and substantiate the interpretation of the conductance imbalance at the second filter as the consequence of a spin polarization.
A study of quantum well solar cell structures with bound-to-continuum transitions for reduced carrier recombination
Authors: Jolley G. , Faraone L. , Fu L. , Lu H. F. , Tan H. H. , Jagadish C.
Published: May 2013

A bound-to-continuum quantum well solar cell structure is proposed, and the band structure and absorption spectra are analyzed by the use of an eight band k·p model. The structure is based on quantum wells that only support bound states for the valence band. The absence of bound conduction band states has a number of potential advantages, including a reduction of electron trapping and, therefore, a reduction of quantum well induced photocarrier recombination due to reduced spatial overlap of the electron and hole wavefunctions.
Enhanced thermoelectric performance in spark plasma textured bulk n-type BiTe2.7Se0.3 and p-type Bi0.5Sb1.5Te3
Authors: Bhame Shekhar D. , Pravarthana Dhanapal , Prellier Wilfrid , Noudem Jacques G.
Published: May 2013

Bulk p and n-type bismuth tellurides were prepared using spark plasma texturization method. The texture development along the uniaxial load in the 001 direction is confirmed from both x-ray diffraction analysis and electron backscattering diffraction measurements. Interestingly, those textured samples outperform the samples prepared by conventional spark plasma sintering (SPS) leading to a reduced thermal conductivity in the ab-plane. The textured samples of n-type BiTe2.7Se0.3 and p-type Bi0.5Sb1.5Te3 showed a 42% and 33% enhancement in figure of merit at room temperature, respectively, as compared to their SPS counterparts, opening the route for applications.
Field effect modulated nanofluidic diode membrane based on Al2O3/W heterogeneous nanopore arrays
Authors: Wu Songmei , Wildhaber Fabien , Bertsch Arnaud , Brugger Juergen , Renaud Philippe
Published: May 2013

We developed Al2O3/W heterogeneous nanopore arrays for field effect modulated nanofluidic diodes. They are fabricated by transferring self-organized nanopores of anodic aluminium oxide into a W thin film. The nanopores are ∼20 nm in diameter and 400 nm in length. After mild oxidation, approximately 10 nm WO3 grows on the surface of W, forming a conformal and dense dielectric layer. It allows the application of an electrical field through the surrounding W electrode to modulate the ionic transport across the entire membrane. Our experimental findings have potential applications in high throughput controlled delivery and electrostatic sorting of biomolecules.
High-resolution inkjet printing of electrically conducting lines of silver nanoparticles by edge-enhanced twin-line deposition
Authors: Bromberg Vadim , Ma Siyuan , Singler Timothy J.
Published: May 2013

We report a process for inkjet printing electrically continuous micron-wide lines of silver nanoparticles by exploiting edge-enhanced evaporation commonly associated with the coffee-stain effect. In situ and real-time flow observation confirmed preferential nanoparticle deposition at the contact line of printed rivulets. The resulting twin-pair of parallel continuous lines showed characteristic width (2–8 μm), height (100–300 nm), and pair spacing (100–600 μm) that depended on substrate and printing conditions in a theoretically predictable way. Thermally sintered lines were used to form rectilinear grids showing ∼5 Ω/◻ effective sheet resistance. The robustness of the deposition process was investigated, and line pathologies were found to depend on substrate surface wettability.
Self-organized micro-holes on titania based sol-gel films under continuous direct writing with a continuous wave ultraviolet laser
Authors: Bakhti S. , Destouches N. , Balan L. , Gamet E. , Reynaud S.
Published: May 2013

The microstructuring of titania based sol-gel films is investigated by direct writing with a continuous wave ultraviolet laser beam emitting at 244 nm. Depending on the exposure conditions, the films exhibit a volume expansion, a volume shrinkage, a self-shaped delamination, or are damaged. This paper is mainly focused on the regime where spontaneous local delamination occurs, which corresponds to a narrow range of laser irradiances and writing speeds. In this regime, self-organized round-shape micro-holes opened on the substrate are generated.
Primary and secondary droplet and charge transmission characteristics of desorption electro-flow focusing ionization
Authors: Forbes Thomas P. , Brewer Tim M. , Gillen Greg
Published: May 2013

We present the investigation of droplet charging and charge transmission characteristics of an electro-flow focusing nozzle for desorption-based ambient ionization mass spectrometry. The electro-flow focusing geometry utilizes a concentrically flowing gas to focus a charged solvent stream through a small orifice, generating a steady liquid jet and charged droplet stream that impinges and ionizes the analyte and surface. Transmitted current measurements and a scaling analysis were incorporated to decouple analyte desorption and ionization from secondary droplet charging and to identify the regimes of operation, secondary droplet charge transport characteristics, and parameters limiting transmitted charge relevant for ambient ionization mass spectrometry.
A study of subgrain formation in Al 3003 H-18 foils undergoing ultrasonic additive manufacturing using a dislocation density based crystal plasticity finite element framework
Authors: Pal D. , Stucker B.
Published: May 2013

A novel dislocation density based crystal plasticity finite element model (DDCP-FEM) framework has been extended to predict subgrain formation during ultrasonic additive manufacturing of Al 3003 H-18 tempered foils. The present study identifies various microstructural transitions such as recrystallization and dislocation density evolutions that occur during the processing of these foils as a function of input processing parameters such as normal force, ultrasonic oscillation amplitude, and initial microstructure. Furthermore, changes in average grain sizes in the Al 3003 H-18 foils have been calculated before and after processing from both microstructures and the simulation study. The simulation predictions were in good agreement with experimental results. This provides evidence that DDCP-FEM can be used as a tool for optimizing input processing parameters so that minimal grain fragmentation occurs during processing leading to better mechanical properties for 3 dimensional components made using ultrasonic additive manufacturing.
Note: Simple and compact piezoelectric mirror actuator with 100 kHz bandwidth, using standard components
Authors: Chadi A. , Méjean G. , Grilli R. , Romanini D.
Published: May 2013

We propose a mounting scheme to control the displacement of a mirror (or other small object) by a cylindrical piezoelectric actuator, giving uniform response and no phase lag up to high frequencies. This requires a simple ring holder, and unmodified off-the-shelf components. In our implementation, the piezo-mirror assembly has its first mechanical resonance around 120 kHz, close to the resonance for the bare piezo. The idea is to decouple the fundamental elongation mode of the piezo-mirror assembly from the holder by side-clamping the assembly at its zero-displacement plane for this mode. The main drawback is a reduced mirror displacement, by a factor 2 in our case (mirror displacement is ∼2.5 μm). Also, the mirror needs to be light with respect to the piezo: still, we use a standard half-inch mirror. The resulting system is very compact as it fits inside a 1-in. commercial steering mirror post.
Nanostructured silver nanowires-graphene hybrids for enhanced electrochemical detection of hydrogen peroxide
Authors: Zhang Mei , Wang Zuankai
Published: May 2013

We report a facile one-step strategy to synthesize interconnected Ag nanowires (NWs)-graphene hybrids with excellent interfacial electron transfer ability for the electrochemical detection of hydrogen peroxide. The simple approach combines the advantages with individual components and also avoids the interface problem typically encountered in the multiple-step process. Moreover, we show that in the one-step process, the presence of graphene promotes the preferential growth of long NWs whereas the growth of Ag NWs prevents the aggregation of individual graphene sheets. Owing to the synergistic cooperation effects, the nanostructured Ag NWs-graphene hybrids exhibit enhanced detection performances compared with their single component counterpart.
Analysis of strained surface layers of ZnO single crystals after irradiation with intense femtosecond laser pulses
Authors: Schneider Andreas , Wolverson Daniel , Sebald Kathrin , Hodges Chris , Kuball Martin , Voss Tobias
Published: May 2013

Structural modifications of ZnO single crystals that were created by the irradiation with femtosecond laser pulses at fluences far above the ablation threshold were investigated with micro-Raman spectroscopy. After light-matter interaction on the femtosecond time scale, rapid cooling and the pronounced thermal expansion anisotropy of ZnO are likely to cause residual strains of up to 1.8% and also result in the formation of surface cracks. This process relaxes the strain only partially and a strained surface layer remains. Our findings demonstrate the significant role of thermoelastic effects for the irradiation of solids with intense femtosecond laser pulses.
Size-dependent magnetization switching characteristics and spin wave modes of FePt nanostructures
Authors: Brandt R. , Rückriem R. , Gilbert D. A. , Ganss F. , Senn T. , Liu Kai , Albrecht M. , Schmidt H.
Published: May 2013

We present a comprehensive investigation of the size-dependent switching characteristics and spin wave modes of FePt nanoelements. Curved nanomagnets (“caps”) are compared to flat disks of identical diameter and volume over a size range of 100 to 300 nm. Quasi-static magnetization reversal analysis using first-order reversal curves shows that spherical caps have lower vortex nucleation and annihilation fields than the flat disks. As the element diameter decreases, the reversal mechanism in the caps crosses over sooner to coherent rotation than in the disks. The magnetization dynamics are studied using optically induced small angle precession and reveal a strong size dependence that differs for the two shapes. Flat disks exhibit well-known center and edge modes at all sizes, but as the diameter of the caps increases from 100 to 300 nm, additional oscillation modes appear in agreement with dynamic micromagnetic simulations. In addition, we show that the three-dimensional curvature of the cap causes a much greater sensitivity to the applied field angle, which provides an additional way for controlling the ultrafast response of nanomagnetic elements.
Narrow-bandgap photovoltaic devices operating at room temperature and above with high open-circuit voltage
Authors: Lotfi Hossein , Hinkey Robert T. , Li Lu , Yang Rui Q. , Klem John F. , Johnson Matthew B.
Published: May 2013

Narrow-bandgap (<0.25 eV) photovoltaic (PV) devices are demonstrated at room temperature and above. These PV devices are based on interband cascade (IC) structures and can achieve a high open-circuit voltage (∼0.65 V at 300 K) that significantly exceeds the single bandgap limited value. This work demonstrates the capabilities and advantages of ICPV devices designed to effectively convert long wavelength (>5 μm) infrared photons from relatively low-temperature radiation sources (<1000 K) into electricity. Detailed characteristics of these PV devices are presented and discussed.