bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton transfer through hydrogen bonds in two-dimensional water layers: A theoretical study based on ab initio and quantum-classical simulations
Authors: Bankura Arindam , Chandra Amalendu
Published: January 2015

The dynamics of proton transfer (PT) through hydrogen bonds in a two-dimensional water layer confined between two graphene sheets at room temperature are investigated through ab initio and quantum-classical simulations. The excess proton is found to be mostly solvated as an Eigen cation where the hydronium ion donates three hydrogen bonds to the neighboring water molecules. In the solvation shell of the hydronium ion, the three coordinated water molecules with two donor hydrogen bonds are found to be properly presolvated to accept a proton. Although no hydrogen bond needs to be broken for transfer of a proton to such presolvated water molecules from the hydronium ion, the PT rate is still found to be not as fast as it is for one-dimensional chains. Here, the PT is slowed down as the probability of finding a water with two donor hydrogen bonds in the solvation shell of the hydronium ion is found to be only 25%-30%. The hydroxide ion is found to be solvated mainly as a complex anion where it accepts four H-bonds through its oxygen atom and the hydrogen atom of the hydroxide ion remains free all the time. Here, the presolvation of the hydroxide ion to accept a proton requires that one of its hydrogen bonds is broken and the proton comes from a neighboring water molecule with two acceptor and one donor hydrogen bonds. The coordination number reduction by breaking of a hydrogen bond is a slow process, and also the population of water molecules with two acceptor and one donor hydrogen bonds is only 20%-25% of the total number of water molecules. All these factors together tend to slow down the hydroxide ion migration rate in two-dimensional water layers compared to that in three-dimensional bulk water.
Prediction of the phase equilibria of methane hydrates using the direct phase coexistence methodology
Authors: Michalis Vasileios K. , Costandy Joseph , Tsimpanogiannis Ioannis N. , Stubos Athanassios K. , Economou Ioannis G.
Published: January 2015

The direct phase coexistence method is used for the determination of the three-phase coexistence line of sI methane hydrates. Molecular dynamics (MD) simulations are carried out in the isothermal–isobaric ensemble in order to determine the coexistence temperature (T3) at four different pressures, namely, 40, 100, 400, and 600 bar. Methane bubble formation that results in supersaturation of water with methane is generally avoided. The observed stochasticity of the hydrate growth and dissociation processes, which can be misleading in the determination of T3, is treated with long simulations in the range of 1000–4000 ns and a relatively large number of independent runs. Statistical averaging of 25 runs per pressure results in T3 predictions that are found to deviate systematically by approximately 3.5 K from the experimental values. This is in good agreement with the deviation of 3.15 K between the prediction of TIP4P/Ice water force field used and the experimental melting temperature of ice Ih. The current results offer the most consistent and accurate predictions from MD simulation for the determination of T3 of methane hydrates. Methane solubility values are also calculated at the predicted equilibrium conditions and are found in good agreement with continuum-scale models.
Solvent effects in time-dependent self-consistent field methods. I. Optical response calculations
Authors: Bjorgaard J. A. , Kuzmenko V. , Velizhanin K. A. , Tretiak S.
Published: January 2015

We implement and examine three excited state solvent models in time-dependent self-consistent field methods using a consistent formalism which unambiguously shows their relationship. These are the linear response, state specific, and vertical excitation solvent models. Their effects on energies calculated with the equivalent of COSMO/CIS/AM1 are given for a set of test molecules with varying excited state charge transfer character. The resulting solvent effects are explained qualitatively using a dipole approximation. It is shown that the fundamental differences between these solvent models are reflected by the character of the calculated excitations.
Quantum chi-squared and goodness of fit testing
Authors: Temme Kristan , Verstraete Frank
Published: January 2015

A quantum mechanical hypothesis test is presented for the hypothesis that a certain setup produces a given quantum state. Although the classical and the quantum problems are very much related to each other, the quantum problem is much richer due to the additional optimization over the measurement basis. A goodness of fit test for i.i.d quantum states is developed and a max-min characterization for the optimal measurement is introduced. We find the quantum measurement which leads both to the maximal Pitman and Bahadur efficiencies, and determine the associated divergence rates. We discuss the relationship of the quantum goodness of fit test to the problem of estimating multiple parameters from a density matrix. These problems are found to be closely related and we show that the largest error of an optimal strategy, determined by the smallest eigenvalue of the Fisher information matrix, is given by the divergence rate of the goodness of fit test.
Influence of mesoscale properties on the mechanisms of plastic strain accommodation in plane strain dynamic deformation of concentric Ni-Al laminates
Authors: Olney K. L. , Chiu P.-H. , Ribero Vairo M. S. , Higgins A. , Serge M. , Benson D. J. , Nesterenko V. F.
Published: January 2015

The paper presents results on the mechanisms of plastic strain accommodation of Ni-Al laminates composed of concentrically aligned thin foils processed at different conditions undergoing a high strain radial collapse in thick walled cylinder experiments. Numerical simulations were conducted to examine the influence of mesoscale parameters (layer size, defects in mesostructure, and ductility) on the mechanisms of large plastic strain accommodation (high amplitude cooperative buckling; high frequency, low amplitude buckling; and kinking) at high strain rates in pure shear (plane strain) conditions. These mechanisms are dramatically different than observed in solid ductile and brittle homogeneous materials where a pattern of shear bands is the major mode of strain accommodation. It was observed that the layer thickness and ductility greatly influenced the dominant mode of plastic strain accommodation. The number of apices was related to the layer thickness. The presence of defects mainly had a localized area of influence. Numerical simulations showed good qualitative agreement with the experiments and provided the ability to simulate additional mesoscale and material dependencies: the role of friction/bonding, relative layer sizes, and sample thickness.
Computing the crystal growth rate by the interface pinning method
Authors: Pedersen Ulf R. , Hummel Felix , Dellago Christoph
Published: January 2015

An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two-phase configurations are stabilized by adding a spring-like bias field coupling to an order-parameter that discriminates between the two phases. Crystal growth is a Smoluchowski process and the crystal growth rate can, therefore, be computed from the terminal exponential relaxation of the order parameter. The approach is investigated in detail for the Lennard-Jones model. We find that the kinetic coefficient scales as the inverse square-root of temperature along the high temperature part of the melting line. The practical usability of the method is demonstrated by computing the kinetic coefficient of the elements Na and Si from first principles. A generalized version of the method may be used for computing the rates of crystal nucleation or other rare events.
Adsorption and ring-opening of lactide on the chiral metal surface Pt(321)S studied by density functional theory
Authors: Franke J.-H. , Kosov D. S.
Published: January 2015

We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321)S. Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.
A note on the onset of recirculation in a 2D Couette flow over a wavy bottom
Authors: Esquivelzeta-Rabell F. M. , Figueroa-Espinoza B. , Legendre D. , Salles P.
Published: January 2015

Laminar Couette flow over a fixed wavy surface was studied with direct numerical simulation in a 2D periodic numerical domain. The mesh was generated by a conformal transformation that sets horizontal flow at the top of the domain, where a constant velocity boundary condition is given. The bottom of the domain is a wavy sinusoidal surface of wave slope 2πa/λ. The combined effect of bottom shape, inertia, and viscosity was explored using different Reynolds numbers (Re) and two dimensionless parameters in terms of channel width h, wavelength λ, and the amplitude of the wavy bottom a. Even if the Reynolds number was large, the simulations were not perturbed so the regime was always laminar. However, a recirculation appeared at the vicinity of the trough. The horizontal location of the eddy center was reported as a function of 2πa/λ and Reλ/h. The conditions for the onset of this recirculation were studied and compared with results from the literature. Two regimes can be clearly identified from the numerical results; a viscous regime with a weak dependence between 2πa/λ and Reλ/h for small Reynolds numbers and an inertial regime with an exponential dependence between 2πa/λ and Reλ/h for large Reynolds numbers, which presents an approximate slope of −1/3. Almost all results collapse in one single curve that characterizes the phenomenon (with the exception of some points where the flow is confined due to a large λ/h ratio).
The Einstein-Hilbert action with cosmological constant as a functional of generic form
Authors: Tolksdorf Jürgen
Published: January 2015

The geometrical underpinnings of a specific class of Dirac operators are discussed. It is demonstrated how this class of Dirac operators allows to relate various geometrical functionals like the Yang-Mills action and the functional of non-linear σ − models (i.e., of (Dirac) harmonic maps). These functionals are shown to be similar to the Einstein-Hilbert action with cosmological constant (EHC). The EHC may thus be regarded as a “generic functional.” As a byproduct, the geometrical setup presented also allows to avoid the issue of “fermion doubling” as usually encountered, for instance, in the geometrical discussion of the Standard Model in terms of Dirac operators. Furthermore, it is demonstrated how the geometrical setup presented allows to derive the cosmological constant term of the EHC from the Einstein-Hilbert functional and the action of a purely gauge coupling Higgs field.
Residual stress in spin-cast polyurethane thin films
Authors: Zhang Hong , Zhang Li
Published: January 2015

Residual stress is inevitable during spin-casting. Herein, we report a straightforward method to evaluate the residual stress in as-cast polyurethane thin films using area shrinkage measurement of films in floating state, which shows that the residual stress is independent of radial location on the substrate and decreased with decreasing film thickness below a critical value. We demonstrate that the residual stress is developed due to the solvent evaporation after vitrification during spin-casting and the polymer chains in thin films may undergo vitrification at an increased concentration. The buildup of residual stress in spin-cast polymer films provides an insight into the size effects on the nature of polymer thin films.
Post-deposition control of ferroelastic stripe domains and internal electric field by thermal treatment
Authors: Feigl L. , Janolin P.-E. , Yamada T. , Iwanowska M. , Sandu C. S. , Setter N.
Published: January 2015

The dependence of the formation of ferroelastic stripe domain patterns on the thermal history is investigated by detailed piezoresponse force microscopy and X-ray diffraction experiments after and during annealing of tensile strained tetragonal Pb(Ti,Zr)O3 epitaxial thin films on DyScO3 substrates. In particular, the ferroelastic pattern is reversibly interchanged between a cross-hatched and a stripe domain pattern if the films are cooled at different rates after annealing above the formation temperature of a-domains. Different types of 180° and non-180° patterns can be created, depending on the thermal treatment. The changes in the 180° domain structure and lattice parameters are attributed to a change of oxygen vacancy concentration, which results in a modification of the internal electric field and unit cell size, causing also a shift of TC. Thermal treatment is done on rhombohedral La:BiFeO3 thin films as well. It is observed that also in these films, appropriate heat treatment modifies the domain pattern and films with a stripe domain pattern can be created, confirming the general validity of the developed model.
Effect of source-gate spacing on direct current and radio frequency characteristic of graphene field effect transistor
Authors: Peng Song-ang , Jin Zhi , Peng-Ma  , Zhang Da-yong , Shi Jing-yuan , Wang Xuan-yun , Wang Shao-qing , Mei-Li  , Liu Xin-yu , Yu Guang-hui
Published: January 2015

The effect of source-gate spacing on graphene filed effect transistors has been investigated. Reducing the source gate spacing allows for a significant improvement on both the direct current and radio frequency (RF) performances. Instead of the generally considered output conductance, our results suggest that the access resistances at the un-gated region contribute more to the maximum oscillation frequency (fmax). Further analysis reveals that the ratio of cut off frequency (fT) to fmax is also sensitive to the resistances at source-gate spacing. This work can be used to guide the further optimization of graphene-based RF devices.
Electron vortex magnetic holes: A nonlinear coherent plasma structure
Authors: Haynes Christopher T. , Burgess David , Camporeale Enrico , Sundberg Torbjorn
Published: January 2015

We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.
Diversity of electronic transitions and photoluminescence properties of p-type cuprous oxide films: A temperature-dependent spectral transmittance study
Authors: Yu W. L. , Lin Y. Z. , Zhu X. W. , Hu Z. G. , Han M. J. , Cai S. S. , Chen L. L. , Shao H. H.
Published: January 2015

Cuprous oxide films have been deposited on quartz substrates by a sol-gel method under various annealing temperatures. The X-ray diffraction analysis and Raman scattering show that all the films are of pure Cu2O phase. From comparison of photoluminescence with 488 and 325 nm laser excitations, the electronic transition energies and intensities present the annealing-temperature dependent behavior. The electronic band structures of the Cu2O film annealed at 800 °C, especially for the contribution of exciton series and high energy transitions, have been investigated by temperature dependent transmittance. The extracted refraction index and the high frequency dielectric constant both abruptly decrease until the temperature rises up to 100 K. Six transitions can be clearly identified and the red shift trend of Eo3-Eo5 transition energies with increasing the temperature can be found. Moreover, the anomalous behavior takes place at about 200 K from the Eo6 transition. The singularities indicate that the change in the crystalline and electronic band structure occurs as the temperature near 100 K and 200 K for the film.
Effect of thickness on the stress and magnetoelectric coupling in bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4 films
Authors: Wang Jing , Li Zheng , Wang Jianjun , He Hongcai , Nan Cewen
Published: January 2015

Magnetoelectric bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4(PZT-CFO) films with different PZT thicknesses were grown on (111)Pt/Ti/SiO2/Si substrates using chemical solution spin-coating. Structural characterization by X-ray diffraction and electron microscopy shows pure phases and well-defined interfaces between the PZT and CFO films. The CFO-PZT-substrate structure effectively alleviates the substrate clamping effect for the CFO layer, showing appreciable magnetoelectric responses in the composite films. Both the direct magnetoelectric effect and the magnetic field-induced Raman shifts in the A1(TO1) soft mode of PZT demonstrate the magnetic-mechanical-electric coupling in the films. The results also indicate that with a constant CFO layer thickness, the thickness of the PZT layer plays an important role in the stress relaxation and strong magnetoelectric coupling. The coupling could be further enhanced by increasing the CFO thickness, optimizing the volume (thickness) fraction of the PZT thickness, and releasing the clamping effect from the substrate.
Freestanding single-crystalline magnetic structures fabricated by ion bombardment
Authors: Schoenherr P. , Bischof A. , Boehm B. , Eib P. , Grimm S. , Alvarado S. F. , Gross L. , Allenspach R.
Published: January 2015

Starting from an ultrathin Fe film grown epitaxially on top of a GaAs(001) substrate, we show that freestanding structures can be created by ion-beam treatment. These structures are single-crystalline blisters and only a few nanometers thick. Anisotropic stress in the rim of a blister induces magnetic domain states magnetized in the direction normal to the blister edge. Experimental evidence is provided that the lateral size can be confined by starting from a nanostructured template.
Tuning the polarization-induced free hole density in nanowires graded from GaN to AlN
Authors: Golam Sarwar A. T. M. , Carnevale Santino D. , Kent Thomas F. , Yang Fan , McComb David W. , Myers Roberto C.
Published: January 2015

We report a systematic study of p-type polarization-induced doping in graded AlGaN nanowire light emitting diodes grown on silicon wafers by plasma-assisted molecular beam epitaxy. The composition gradient in the p-type base is varied in a set of samples from 0.7%Al/nm to 4.95%Al/nm corresponding to negative bound polarization charge densities of 2.2 × 1018 cm−3 to 1.6 × 1019 cm−3. Capacitance measurements and energy band modeling reveal that for gradients greater than or equal to 1.30%Al/nm, the deep donor concentration is negligible and free hole concentrations roughly equal to the bound polarization charge density are achieved up to 1.6 × 1019 cm−3 at a gradient of 4.95%Al/nm. Accurate grading lengths in the p- and n-side of the pn-junction are extracted from scanning transmission electron microscopy images and are used to support energy band calculation and capacitance modeling. These results demonstrate the robust nature of p-type polarization doping in nanowires and put an upper bound on the magnitude of deep donor compensation.
1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range
Authors: Sadeev T. , Arsenijević D. , Franke D. , Kreissl J. , Künzel H. , Bimberg D.
Published: January 2015

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.
Optically monitored spray coating system for the controlled deposition of the photoactive layer in organic solar cells
Authors: Vak Doojin , van Embden Joel , Wong Wallace W. H. , Watkins Scott
Published: January 2015

A spray deposition process equipped with an in situ optical thickness monitoring system has been developed to fabricate the photoactive layer of solar cells. Film thickness is monitored by a photodiode–LED couple after each deposition cycle. Using optimized conditions, the thickness of the spray deposited photoactive films can be tuned to increase linearly with the number of deposition cycles over a wide range of deposition conditions. After instrument calibration, optimization of the active layer thickness can be accomplished by simply setting the desired absorbance of the film. The simple process outlined here may be used for the rapid optimization of thin film photovoltaic devices. As proof of this, we fabricate a poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester as well as a P3HT and indene-C60 bis-adduct organic solar cells, which achieve a champion power conversion efficiency of 4.2%.
Dependence of inverse-spin Hall effect and spin-rectified voltage on tantalum thickness in Ta/CoFeB bilayer structure
Authors: Kim Sang-Il , Kim Dong-Jun , Seo Min-Su , Park Byong-Guk , Park Seung-Young
Published: January 2015

Ta-layer thickness (tTa) dependence of the measured DC voltage V from the inverse-spin Hall effect (ISHE) in Ta/CoFeB bilayer structure is experimentally investigated using the ferromagnetic resonance in the TE011 resonant cavity. The ISHE signals excluding the spin-rectified effect (SRE) were separated from the fitted curve of V against tTa. For tTa ≈ λTa (Ta-spin diffusion length = 2.7 nm), the deviation in ISHE voltage VISH between the experimental and theoretical values is significantly increased because of the large SRE contribution, which also results in a large deviation in the spin Hall angle θSH (from 10% to 40%). However, when tTa ≫ λTa, the VISH values are consistent with theoretical values because the SRE terms become negligible, which subsequently improves the accuracy of the obtained θSH within 4% deviation. The results will provide an outline for an accurate estimation of the θSH for materials with small λ value, which would be useful for utilizing the spin Hall effect in a 3-terminal spintronic devices in which magnetization can be controlled by in-plane current.
Heavy and light hole transport in nominally undoped GaSb substrates
Authors: Kala Hemendra , Umana-Membreno Gilberto A. , Jolley Gregory , Akhavan Nima Dehdashti , Patrashin Mikhail A. , Akahane Kouichi , Antoszewski Jaroslaw , Faraone Lorenzo
Published: January 2015

In this work, we report results of a study of electronic transport in nominally undoped p-type GaSb wafers typically employed as substrate material for the epitaxial growth of InAs/GaInSb type-II superlattices. Magnetic field dependent Hall-effect measurements and high-resolution mobility spectrum analysis clearly indicate p-type conductivity due to carriers in both the heavy and light hole bands. The extracted hole concentrations indicate a thermal activation energy of 17.8 meV for the dominant native acceptor-like defects. A temperature-independent effective mass ratio of 9.0 ± 0.8 was determined from the ratio of measured heavy and light hole concentrations. Over the 56 K–300 K temperature range, the light hole mobility was found to be 4.7 ± 0.7 times higher than the heavy hole mobility. The measured room temperature mobilities for the light and heavy holes were 2550 cm2/Vs and 520 cm2/Vs, respectively.
Break Snoek limit via superparamagnetic coupling in Fe3O4/silica multiple-core/shell nanoparticles
Authors: Zhang Xuefeng , Liu Yuanyuan , Qin Gaowu
Published: January 2015

Natural materials that maintain significant permeability at microwave frequencies are a challenge due to the Snoek limit, but manipulation of matter-microwave interaction in artificial composites provides a possibility to achieve breakthroughs. Herein, we synthesized Fe3O4/silica core/shell nanoparticles comprised of multiple Fe3O4 cores in each particle (denoted as multiple-Fe3O4/silica). In comparison to conventional magnetic natural resonance at megahertz frequencies, the resonance of multiple-Fe3O4/silica composite appears at 9.3 GHz relying on superparamagnetic coupling, which is the highest value reported currently. Our study opens up a fantastic avenue for optimizing micromagnetism by nanoscale architectures.
Correlative analysis of conducting filament distribution at interfaces and bias-dependent noise sources in TiN/TiOx/Pt and Pt/TiOx/TiOy/Pt bipolar resistive switching frames
Authors: Kim Joo Hyung , Bae Yoon Cheol , Lee Ah Rahm , Baek Kwang Ho , Hong Jin Pyo
Published: January 2015

We evaluated conducting filament distributions occurring at interfaces of TiN/TiOx/Pt and Pt/TiOx/TiOy/Pt bipolar resistive switching elements after electroforming by identifying bias-dependent low-frequency noise sources. The TiN/TiOx/Pt switching element showed higher noise features at low and high resistance states (LRS and HRS) than the Pt/TiOx/TiOy/Pt one. These behaviors are predominantly associated with the presence of different resistance distributions at LRS and HRS observed in both switching I-V curves. We propose a possible mechanism to explain the unique observed features by employing the role of the oxygen reservoir and conducting filament stability at interfaces of the two switching elements.
Optically detected magnetic resonance imaging
Authors: Blank Aharon , Shapiro Guy , Fischer Ran , London Paz , Gershoni David
Published: January 2015

Optically detected magnetic resonance provides ultrasensitive means to detect and image a small number of electron and nuclear spins, down to the single spin level with nanoscale resolution. Despite the significant recent progress in this field, it has never been combined with the power of pulsed magnetic resonance imaging techniques. Here, we demonstrate how these two methodologies can be integrated using short pulsed magnetic field gradients to spatially encode the sample. This result in what we denote as an "optically detected magnetic resonance imaging" technique. It offers the advantage that the image is acquired in parallel from all parts of the sample, with well-defined three-dimensional point-spread function, and without any loss of spectroscopic information. In addition, this approach may be used in the future for parallel but yet spatially selective efficient addressing and manipulation of the spins in the sample. Such capabilities are of fundamental importance in the field of quantum spin-based devices and sensors.
Edge-enhanced Raman scattering in narrow sGe fin field-effect transistor channels
Authors: Nuytten T. , Hantschel T. , Kosemura D. , Schulze A. , De Wolf I. , Vandervorst W.
Published: January 2015

We report micro-Raman spectroscopy results on strained Ge narrow (20 nm) channels for finFET nanoelectronics technology. It is found that the Raman activity of the structures is strongly dependent on the relative orientation of the excitation laser polarization and the structure geometry. While the observation of the typical Ge Raman signatures is challenging for the antiparallel orientation, a dramatic enhancement of the signal is found for a parallel orientation. Simulations confirm that a significant concentration of the light's electromagnetic field in the vicinity of the edges of the structures is at the origin of the strong Raman enhancement. The edge enhancement of the Raman scattering is a promising tool for the non-destructive characterization of nanometer-scale semiconductor structures and devices.
Effect of ambient combinations of argon, oxygen, and hydrogen on the properties of DC magnetron sputtered indium tin oxide films
Authors: Marikkannan M. , Subramanian M. , Mayandi J. , Tanemura M. , Vishnukanthan V. , Pearce J. M.
Published: January 2015

Sputtering has been well-developed industrially with singular ambient gases including neutral argon (Ar), oxygen (O2), hydrogen (H2) and nitrogen (N2) to enhance the electrical and optical performances of indium tin oxide (ITO) films. Recent preliminary investigation into the use of combined ambient gases such as an Ar+O2+H2 ambient mixture, which was suitable for producing high-quality (low sheet resistance and high optical transmittance) of ITO films. To build on this promising preliminary work and develop deeper insight into the effect of ambient atmospheres on ITO film growth, this study provides a more detailed investigation of the effects of ambient combinations of Ar, O2, H2 on sputtered ITO films. Thin films of ITO were deposited on glass substrates by DC magnetron sputtering using three different ambient combinations: Ar, Ar+O2 and Ar+O2+H2. The structural, electrical and optical properties of the three ambient sputtered ITO films were systematically characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, four probe electrical conductivity and optical spectroscopy. The XRD and Raman studies confirmed the cubic indium oxide structure, which is polycrystalline at room temperature for all the samples. AFM shows the minimum surface roughness of 2.7 nm for Ar+O2+H2 sputtered thin film material. The thickness of the films was determined by the cross sectional SEM analysis and its thickness was varied from 920 to 817 nm. The columnar growth of ITO films was also discussed here. The electrical and optical measurements of Ar+O2+H2 ambient combinations shows a decreased sheet resistance (5.06 ohm/□) and increased optical transmittance (69%) than other samples. The refractive index and packing density of the films were projected using optical transmission spectrum. From the observed results the Ar+O2+H2 ambient is a good choice to enhance the total optoelectronic properties of the ITO films. The improved electrical and optical properties of ITO films with respect to the Ar+O2+H2 ambient sample were discussed in detail. In addition, the physical properties were also discussed with the influence of this ambient combination with respect to Ar, Ar+O2 and Ar+O2+H2.
Dynamical spin injection at a quasi-one-dimensional ferromagnet-graphene interface
Authors: Singh S. , Ahmadi A. , Cherian C. T. , Mucciolo E. R. , del Barco E. , Özyilmaz B.
Published: January 2015

We present a study of dynamical spin injection from a three-dimensional ferromagnet into two-dimensional single-layer graphene. Comparative ferromagnetic resonance (FMR) studies of ferromagnet/graphene strips buried underneath the central line of a coplanar waveguide show that the FMR linewidth broadening is the largest when the graphene layer protrudes laterally away from the ferromagnetic strip, indicating that the spin current is injected into the graphene areas away from the area directly underneath the ferromagnet being excited. Our results confirm that the observed damping is indeed a signature of dynamical spin injection, wherein a pure spin current is pumped into the single-layer graphene from the precessing magnetization of the ferromagnet. The observed spin pumping efficiency is difficult to reconcile with the expected backflow of spins according to the standard spin pumping theory and the characteristics of graphene, and constitutes an enigma for spin pumping in two-dimensional structures.
O3-sourced atomic layer deposition of high quality Al2O3 gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors
Authors: Huang Sen , Liu Xinyu , Wei Ke , Liu Guoguo , Wang Xinhua , Sun Bing , Yang Xuelin , Shen Bo , Liu Cheng , Liu Shenghou , Hua Mengyuan , Yang Shu , Chen Kevin J.
Published: January 2015

High quality Al2O3 film grown by atomic layer deposition (ALD), with ozone (O3) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al–O–H and Al–Al bonds in ALD-Al2O3 has been realized by substituting conventional H2O source with O3. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O3-Al2O3 and 2-nm H2O-Al2O3 interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 1012 cm−2, contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance RON,sp of 0.49 mΩ cm2.
Detailed balance analysis of area de-coupled double tandem photovoltaic modules
Authors: Strandberg Rune
Published: January 2015

This paper describes how layers of area de-coupled top and bottom cells in photovoltaic tandem modules can increase the efficiency of two-terminal tandem devices. The point of the area de-coupling is to allow the number of top cells to differ from the number of bottom cells. Within each of the layers, the cells can be horizontally series-connected and the layers can then be current- or voltage-matched with each other in a tandem module. Using detailed balance modeling, it is shown that two-terminal tandem modules of this type can achieve the same theoretical efficiency as stacks of independently operated cells, often referred to as four-terminal cells. Optimal ratios of the number of bottom cells to the number of top cells are calculated. Finally, it is shown that modules with a bottom layer consisting of 60 cells with a band gap of 1.11 eV, resembling standard silicon modules, offer sufficient resolution to optimize the number of top cells and achieve high efficiency over a large range of top cell band gaps. This result extends the list of materials that can be used as top cells in two-terminal tandem modules with silicon bottom cells.
V
H
replacement in primary immunoglobulin repertoire diversification
Authors: Sun Amy , Novobrantseva Tatiana I. , Coffre Maryaline , Hewitt Susannah L. , Jensen Kari , Skok Jane A. , Rajewsky Klaus , Koralov Sergei B.
Published: January 2015

Significance

The recombinatorial process of V(D)J rearrangement generates a vast antibody repertoire from a limited number of genes. The joints generated in the course of V(D)J recombination are imprecise thus yielding greater diversity but also resulting in frequent generation of nonproductive VDJ rearrangements. We have previously shown that B cells with two nonproductive IgH rearrangements can be efficiently rescued by a form of secondary V(D)J recombination called V
H
replacement. We now demonstrate that V
H
replacement also contributes to the diversity of the immune repertoire by modifying productive IgH rearrangements. Results presented herein suggest that V
H
replacement occurs exclusively during early stages of B-cell development and therefore does not contribute to the editing of self-reactive antibodies.
Socio‐economic status and motor performance of children and adolescents
Authors: Klein Markus , Fröhlich Michael , Pieter Andrea , Emrich Eike
Published: January 2015

The study examines the question to what extent children and adolescents differ in terms of motor performance in dependence of their socio‐economic status (SES). A sample of 1389 students in Saarland (Germany) in various grades (1st grade: age 7.26 ± 0.38 years, 4th grade: 10.3 ± 0.4 years, 7th grade: 13.44 ± 0.49 years, 10th grade: 16.36 ± 0.69 years) has been examined. Their motor performance has been measured by means of 20‐m sprint, standing long jump and a 6‐minute run, and the SES by means of a parent survey. Based on the indicators school education, professional education, job position and household income, the SES was categorised in a three‐step approach (low, middle, high). The influence on dependent variables was analysed by using multivariate analysis of variance. Students with a higher SES exhibit a higher motor performance compared with that of lower SES (results of the multivariate: Pillai's Trace =. 05, F[6; 2526] = 12.56, p =. 001; = 0.03). In addition, the data for students of higher SES differ significantly from the data of a German reference sample (higher motor performance compared with standard values). In contrast, persons of lower SES do not differ from the reference sample, and those of middle SES differ only slightly from the reference sample. The results are relevant when considering specific prevention efforts concerning motor performance of certain groups. Especially those institutions and schools should be focused upon whose catchment area includes a high share of socially disadvantaged population groups.
The Problem of Noncounterfactual Conditionals
Authors: Etlin David
Published: January 2015

I defend a formulation of the Ramsey Test with a condition for accepting negations of conditionals. It is implicit in the assumptions of the triviality theorems of Gärdenfors, Harper, and Lewis; and it allows for a unified proof of those theorems, from weaker assumptions about belief revision. This leads to a proof of McGee's thesis that iterated conditionals do not obey modus ponens.
Prospects for Naturalizing Color
Authors: Isaac Alistair
Published: January 2015

Paul Churchland has recently offered a novel argument for the “objective reality” of color. The strategy he employs to make this argument is an instance of a more general research program for interpreting perceptual content, “domain-portrayal semantics.” In the first half of the article, I point out some features of color vision that complicate Churchland's conclusion, in particular, the context-sensitive and inferential nature of color perception. In the second half, I examine and defend the general research program, concluding it is naturalistic in a minimal sense and should be of interest to naturalists and nonnaturalists alike.
How Values in Scientific Discovery and Pursuit Alter Theory Appraisal
Authors: Elliott Kevin C. , McKaughan Daniel J.
Published: January 2015

Philosophers of science readily acknowledge that nonepistemic values influence the discovery and pursuit of scientific theories, but many tend to regard these influences as epistemically uninteresting. The present paper challenges this position by identifying three avenues through which nonepistemic values associated with discovery and pursuit in contemporary pollution research influence theory appraisal: (1) by guiding the choice of questions and research projects, (2) by altering experimental design, and (3) by affecting the creation and further investigation of theories or hypotheses. This analysis indicates that the effects of these values are sufficiently complex and epistemically significant to merit further attention.
A New Look at Relational Holism in Quantum Mechanics
Authors: Morganti Matteo
Published: January 2015

Teller argued that violations of Bell's inequalities are to be explained by interpreting quantum entangled systems according to ‘relational holism’, that is, by postulating that they exhibit irreducible (‘inherent’) relations. Teller also suggested a possible application of this idea to quantum statistics. However, the basic proposal was not explained in detail nor has the additional idea about statistics been articulated in further work. In this article, I reconsider relational holism, amending it and spelling it out as appears necessary for a proper assessment, and application, of the position.
Ecological Explanation between Manipulation and Mechanism Description
Authors: Pâslaru Viorel
Published: January 2015

James Woodward offers a conception of explanation and mechanism in terms of interventionist counterfactuals. Based on a case from ecology, I show that ecologists’ approach to that case satisfies Woodward's conditions for explanation and mechanism, but his conception does not fully capture what ecologists view as explanatory. The new mechanistic philosophy likewise aims to describe central aspects of mechanisms, but I show that it is not sufficient to account for ecological mechanisms. I argue that in ecology explanation involves identification of invariant and insensitive causal relationships and descriptions of the mechanistic characteristics that make these relations possible.
A Consumer-Based Teleosemantics for Animal Signals
Authors: Stegmann Ulrich E.
Published: January 2015

Ethological theory standardly attributes representational content to animal signals. In this article I first assess whether Ruth Millikan's teleosemantic theory accounts for the content of animal signals. I conclude that it does not, because many signals do not exhibit the required sort of cooperation between signal-producing and signal-consuming devices. It is then argued that Kim Sterelny's proposal, while not requiring cooperation, sometimes yields the wrong content. Finally, I outline an alternative view, according to which consumers alone are responsible for conferring representational status and determining content. I suggest that consumer-based teleosemantics reconstruct the content of both cooperative and noncooperative signals and explain how a given trait can mean different things to different consumers.
Prediction in Selectionist Evolutionary Theory
Authors: Winther Rasmus Gr⊘nfeldt
Published: January 2015

Selectionist evolutionary theory has often been faulted for not making novel predictions that are surprising, risky, and correct. I argue that it in fact exhibits the theoretical virtue of predictive capacity in addition to two other virtues: explanatory unification and model fitting. Two case studies show the predictive capacity of selectionist evolutionary theory: parallel evolutionary change inE. coliand the origin of eukaryotic cells through endosymbiosis.
Cosmic Confusions: Not Supporting versus Supporting Not
Authors: Norton John D.
Published: January 2015

Bayesian probabilistic explication of inductive inference conflates neutrality of supporting evidence for some hypothesis H (“not supporting H”) with disfavoring evidence (“supporting not-H”). This expressive inadequacy leads to spurious results that are artifacts of a poor choice of inductive logic. I illustrate how such artifacts have arisen in simple inductive inferences in cosmology. In the inductive disjunctive fallacy, neutral support for many possibilities is spuriously converted into strong support for their disjunction. The Bayesian “doomsday argument” is shown to rely entirely on a similar artifact.
Rubens’sLife of Maria de’ Medici:Dissimulation and the Politics of Art in Early Seventeenth-Century France*
Authors: Galletti Sara
Published: January 2015

TheLife of Maria de’ Medici,the biographical series of twenty-four large-size paintings executed for the Queen Mother of France by Peter Paul Rubens in 1622–25, is traditionally regarded by historians as both a masterpiece of Baroque art and a monument of political naïveté. According to this view, the series was a disrespectful visual bravado that exposed both patron and painter to scandal by publicly advertising the queen’s political ideas and ambitions, which were not only audacious, but often in opposition to those of her son King Louis XIII. This article challenges this assessment by reading theLifewithin the context of seventeenth-century uses of dissimulation and spatial control as strategies to limit both intellectual and physical access to information. It argues that the series was imbued with multiple layers of meaning, intended for different audiences, and that access to these was strictly controlled by the queen and her circle.
Bidirectional inward migration of particles lagging behind a Poiseuille flow in a rectangular microchannel for 3D particle focusing
Authors: Kim Young Won , Yoo Jung Yul
Published: January 2015

Electrophoretic mobility of particles dispersed in an electrolyte solution induces the particles to lag behind a Poiseuille flow in a rectangular microchannel, which causes bidirectional inward migration of particles to the central axis of the channel. As a result, in the present theoretical and experimental study, three-dimensional (3D) particle focusing is clearly realized in such a manner that the particles are aligned in a single file along the axis of the channel as they are transported downstream. Theoretical prediction on the particle migration time provides an excellent assessment of the experimental results. The method proposed in the present study has potential for development of low-cost rapid manufacturing process of sheathless monolayer microchips for 3D particle focusing.
Energy efficiency standards and innovation
Authors: Morrison Geoff
Published: January 2015

Van Buskirk et al (2014 Environ. Res. Lett.

9
114010) demonstrate that the purchase price, lifecycle cost and
price of improving efficiency (i.e. the incremental price of efficiency gain)
decline at an accelerated rate following the adoption of the first energy
efficiency standards for five consumer products. The authors show these trends
using an experience curve framework (i.e. price/cost versus cumulative
production). While the paper does not draw a causal link between standards and
declining prices, they provide suggestive evidence using markets in the US and
Europe. Below, I discuss the potential implications of the work.