bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional xenobiotic metabolism and efflux transporters in trout hepatocyte spheroid cultures
Authors: Uchea Chibuzor , Owen Stewart F. , Chipman J. Kevin
Published: January 2015

Prediction of xenobiotic fate in fish is important for the regulatory assessment of chemicals under current legislation.
Amino acids as chiral anionic ligands for ruthenium based asymmetric olefin metathesis
Authors: Ivry Elisa , Ben-Asuly Amos , Goldberg Israel , Lemcoff N. Gabriel
Published: January 2015

Anionic ligand exchange by amino acids readily produce chiral ruthenium benzylidenes that catalyze asymmetric olefin metathesis reactions.
Photoreversible current ON/OFF switching by the photoinduced bending of gold-coated diarylethene crystals
Authors: Kitagawa Daichi , Kobatake Seiya
Published: January 2015

Gold-coated diarylethene crystals exhibited photoreversible bending upon irradiation with UV and visible light without any breaking of the gold layer.
Applications of three-dimensional (3D) printing for microswimmers and bio-hybrid robotics
Authors: Stanton M. M. , Trichet-Paredes C. , Sánchez S.
Published: January 2015

This article will focus on recent reports that have applied 3D printing for designing millimeter to micrometer architecture for robotic motility.
Correction: Nonlinear rheology of entangled polymers at turning point
Authors: Wang Shi-Qing
Published: January 2015

Correction for ‘Nonlinear rheology of entangled polymers at turning point’ by Shi-Qing Wang et al., Soft Matter, 2015, DOI: 10.1039/c4sm02664k.
Nanosized zirconium phosphate/AgCl composite materials: a new synergy for efficient photocatalytic degradation of organic dye pollutants
Authors: Pica Monica , Nocchetti Morena , Ridolfi Berardo , Donnadio Anna , Costantino Ferdinando , Gentili Pier Luigi , Casciola Mario
Published: January 2015

Silver exchanged nanosized zirconium phosphate is used as a source of Ag+ions in the preparation of AgCl. The zirconium phosphate/AgCl composites work better than pure AgCl in the photoassisted degradation of Rhodamine B.
Quadriceps muscle weakness and atrophy are associated with a differential epigenetic profile in advanced COPD
Authors: Puig-Vilanova Ester , Martínez-Llorens Juana , Ausin Pilar , Roca Josep , Gea Joaquim , Barreiro Esther
Published: January 2015

The study reports novel findings on the associations of muscle weakness and atrophy with a differential expression profile of epigenetic events in the quadriceps of patients with advanced COPD, which was not seen in patients without muscle weakness.
Novel MTND1 mutations cause isolated exercise intolerance, complex I deficiency and increased assembly factor expression
Authors: Gorman Grainne S. , Blakely Emma L. , Hornig-Do Hue-Tran , Tuppen Helen A.L. , Greaves Laura C. , He Langping , Baker Angela , Falkous Gavin , Newman Jane , Trenell Michael I. , Lecky Bryan , Petty Richard K. , Turnbull Doug M. , McFarland Robert , Taylor Robert W.
Published: January 2015

We describe the clinical, biochemical and molecular characterization of two adults with progressive exercise intolerance and severe isolated mitochondrial complex I (CI) deficiency due to novel MTND1 mutations. We demonstrate compensatory CI assembly factor up-regulation probably partially rescuing the clinical phenotype.
Levamisole in steroid-sensitive nephrotic syndrome: usefulness in adult patients and laboratory insights into mechanisms of action via direct action on the kidney podocyte
Authors: Jiang Lulu , Dasgupta Ishita , Hurcombe Jenny A. , Colyer Heather F. , Mathieson Peter W. , Welsh Gavin I.
Published: January 2015

Our clinical and laboratory data suggest that levamisole should be added to the list of immunotherapeutic agents that have direct actions on podocytes and point to the usefulness of levamisole in the treatment of adult as well as paediatric patients.
Distributed estimation using online semi‐supervised particle filter for mobile sensor networks
Authors: Yoo Jaehyun , Kim Woojin , Kim Hyoun Jin
Published: January 2015

This study proposes an improved particle filter by incorporating semi‐supervised machine learning for location estimation in mobile sensor networks (MSNs). A time‐varying prior model is learned online as the likelihood of particle filter in order to adapt to dynamic characteristics of state and observation. Thanks to semi‐supervised learning, the proposed particle filter can improve efficiency and accuracy, where the amount of available labelled training data is limited. The authors compare the proposed algorithm with the particle filter based on supervised learning. The algorithms are evaluated for received signal strength indicator (RSSI)‐based distributed location estimation for MSN in which communication bandwidth and accuracy of the range measurement are limited. First, experimental results show that the semi‐supervised algorithm can learn suddenly‐changed RSSI characteristics while the supervised learning cannot. Second, the proposed particle filter is more accurate and robust against variations of the environment such as new obstacle configurations. Furthermore, the suggested particle filter shows low statistical variability during repeated experiments, confirmed by much smaller error deviation than the compared particle filter.
Adaptive‐cross‐approximation‐based acceleration of transient analysis of quasi‐static partial element equivalent circuits
Authors: Antonini Giulio , Romano Daniele
Published: January 2015

A new formulation of the partial element equivalent circuit (PEEC) method is presented, which is well suited to be combined with compression and matrix–vector product acceleration techniques. In particular, taking advantage of the rank‐deficiency of the magnetic and electric field couplings, the adaptive cross approximation (ACA) technique is firstly, adopted to compress PEEC interaction matrices, namely partial inductances and coefficients of potential matrices. Differently from the use of ACA in conjunction with the method of moments, in this study, magnetic and electric field couplings are kept distinct, thus allowing to efficiently compress both magnetic and electric field interaction matrices. Secondly, the compressed matrices are used to accelerate the transient analysis of PEEC circuits. Indeed, Kirchoff voltage and current laws are enforced to PEEC circuits so that matrix–vector products involving the interaction matrices can be significantly accelerated in virtue of their compression, thus leading to very good speed‐ups when using iterative solvers like the generalised method of residuals algorithm. Numerical results demonstrate the validity, accuracy and performance of the proposed approach in terms of both memory usage saving and transient analysis speed‐up.
Magnetic properties and Mössbauer spectroscopy of iron nanowire arrays prepared by electroless deposition in a magnetic field
Authors: Li Fagen , Li Le , Wang Jun
Published: January 2015

One‐dimensional magnetic iron (Fe) nanowire arrays with tunable diameters have been deposited in the pore channels of the anodised aluminium oxide (AAO) template using the electroless chemical method. The AAO template is processed by a facile and simple approach to etch an insulating alumina barrier layer in the base of the template. The morphologies and crystal structures of Fe nanowires are characterised by field emission scanning electron microscopy, atomic force microscopy and X‐ray diffraction. Mössbauer spectroscopy suggests that the nanowires are composed of ferromagnetic particles. The results of magnetic measurements by a superconducting quantum interference device indicate that the nanowire arrays have obvious magnetic anisotropy, and the easy magnetisation direction is oriented along the nanowire axial direction.
Simple and mild biomolecule‐assisted green route to nanosheet‐built zinc indium sulphide microspheres
Authors: Cai Wen , Wang Aiwu , Rao Tingke , Hu Jie , Fu Li , Zhong Jiasong , Xiang Weidong
Published: January 2015

A simple and mild green route has been developed to synthesise zinc indium sulphide nanopowders with L‐cysteine as the sulphur source and complexing agent under hydrothermal conditions at 160 °C for 12 h. The crystal structure, morphologies and chemical composition of the obtained nanopowders are conﬁrmed by X‐ray powder diffraction, field‐emission scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy and selected area electron diffraction. Results reveal that the synthesised nanopowder is comprised of microspheres with nanosheets and the diameter of the microspheres and the thickness of the nanosheets are 100 nm–2 μm and 10–50 nm, respectively. Moreover, a possible formation mechanism for the zinc indium sulphide product is briefly discussed. The present route would provide an alternative strategy to prepare other II–III–VI ternary metal sulphide nanocrystals.
Canonical-ensemble state-averaged complete active space self-consistent field (SA-CASSCF) strategy for problems with more diabatic than adiabatic states: Charge-bond resonance in monomethine cyanines
Authors: Olsen Seth
Published: January 2015

This paper reviews basic results from a theory of the a priori classical probabilities (weights) in state-averaged complete active space self-consistent field (SA-CASSCF) models. It addresses how the classical probabilities limit the invariance of the self-consistency condition to transformations of the complete active space configuration interaction (CAS-CI) problem. Such transformations are of interest for choosing representations of the SA-CASSCF solution that are diabatic with respect to some interaction. I achieve the known result that a SA-CASSCF can be self-consistently transformed only within degenerate subspaces of the CAS-CI ensemble density matrix. For uniformly distributed (“microcanonical”) SA-CASSCF ensembles, self-consistency is invariant to any unitary CAS-CI transformation that acts locally on the ensemble support. Most SA-CASSCF applications in current literature are microcanonical. A problem with microcanonical SA-CASSCF models for problems with “more diabatic than adiabatic” states is described. The problem is that not all diabatic energies and couplings are self-consistently resolvable. A canonical-ensemble SA-CASSCF strategy is proposed to solve the problem. For canonical-ensemble SA-CASSCF, the equilibrated ensemble is a Boltzmann density matrix parametrized by its own CAS-CI Hamiltonian and a Lagrange multiplier acting as an inverse “temperature,” unrelated to the physical temperature. Like the convergence criterion for microcanonical-ensemble SA-CASSCF, the equilibration condition for canonical-ensemble SA-CASSCF is invariant to transformations that act locally on the ensemble CAS-CI density matrix. The advantage of a canonical-ensemble description is that more adiabatic states can be included in the support of the ensemble without running into convergence problems. The constraint on the dimensionality of the problem is relieved by the introduction of an energy constraint. The method is illustrated with a complete active space valence-bond (CASVB) analysis of the charge/bond resonance electronic structure of a monomethine cyanine: Michler’s hydrol blue. The diabatic CASVB representation is shown to vary weakly for “temperatures” corresponding to visible photon energies. Canonical-ensemble SA-CASSCF enables the resolution of energies and couplings for all covalent and ionic CASVB structures contributing to the SA-CASSCF ensemble. The CASVB solution describes resonance of charge- and bond-localized electronic structures interacting via bridge resonance superexchange. The resonance couplings can be separated into channels associated with either covalent charge delocalization or chemical bonding interactions, with the latter significantly stronger than the former.
Fixed-node diffusion Monte Carlo potential energy curve of the fluorine molecule F2 using selected configuration interaction trial wavefunctions
Authors: Giner Emmanuel , Scemama Anthony , Caffarel Michel
Published: January 2015

The potential energy curve of the F2 molecule is calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC) using Configuration Interaction (CI)-type trial wavefunctions. To keep the number of determinants reasonable and thus make FN-DMC calculations feasible in practice, the CI expansion is restricted to those determinants that contribute the most to the total energy. The selection of the determinants is made using the CIPSI approach (Configuration Interaction using a Perturbative Selection made Iteratively). The trial wavefunction used in FN-DMC is directly issued from the deterministic CI program; no Jastrow factor is used and no preliminary multi-parameter stochastic optimization of the trial wavefunction is performed. The nodes of CIPSI wavefunctions are found to reduce significantly the fixed-node error and to be systematically improved upon increasing the number of selected determinants. To reduce the non-parallelism error of the potential energy curve, a scheme based on the use of a R-dependent number of determinants is introduced. Using Dunning’s cc-pVDZ basis set, the FN-DMC energy curve of F2 is found to be of a quality similar to that obtained with full configuration interaction/cc-pVQZ.
Ultrasonic technique for monitoring of liquid density variations
Authors: Kazys R. , Rekuviene R. , Sliteris R. , Mazeika L. , Zukauskas E.
Published: January 2015

A novel ultrasonic measurement technique for density measurements of different liquids in extreme conditions has been developed. The proposed density measurement method is based on transformation of the acoustic impedance of the measured liquid. The higher accuracy of measurements is achieved by means of the λ/4 acoustic matching layer between the load and the ultrasonic waveguide transducer. Introduction of the matching layer enhances sensitivity of the measurement system. Sometimes, the density measurements must be performed in very complex conditions: high temperature (up to 200 °C), pressure (up to 10 MPa), and high chemical activity of the medium under measurement. In this case, the special geometry metal waveguides are proposed to use in order to protect the piezoelectric transducer surface from influence of a high temperature. The experimental set-up of technique was calibrated using the reference liquids with different densities: ethyl ether, ethyl alcohol, distilled water, and different concentration (20%, 40%, and 60%) sugar-water solutions. The uncertainty of measurements is less than 1%. The proposed measurement method was verified in real conditions by monitoring the density of a melted polypropylene during manufacturing process.
Chemical insight from density functional modeling of molecular adsorption: Tracking the bonding and diffusion of anthracene derivatives on Cu(111) with molecular orbitals
Authors: Wyrick Jonathan , Einstein T. L. , Bartels Ludwig
Published: January 2015

We present a method of analyzing the results of density functional modeling of molecular adsorption in terms of an analogue of molecular orbitals. This approach permits intuitive chemical insight into the adsorption process. Applied to a set of anthracene derivates (anthracene, 9,10-anthraquinone, 9,10-dithioanthracene, and 9,10-diselenonanthracene), we follow the electronic states of the molecules that are involved in the bonding process and correlate them to both the molecular adsorption geometry and the species’ diffusive behavior. We additionally provide computational code to easily repeat this analysis on any system.
Influence of boron diffusion on the perpendicular magnetic anisotropy in Ta|CoFeB|MgO ultrathin films
Authors: Sinha Jaivardhan , Gruber Maria , Kodzuka Masaya , Ohkubo Tadakatsu , Mitani Seiji , Hono Kazuhiro , Hayashi Masamitsu
Published: January 2015

We have studied structural and magnetic properties of Ta|CoFeB|MgO heterostructures using cross-section transmission electron microscopy (TEM), electron energy loss spectrum (EELS) imaging, and vibrating sample magnetometry. From the TEM studies, the CoFeB layer is found to be predominantly amorphous for as deposited films, whereas small crystallites, diameter of ∼5 nm, are observed in films annealed at 300 °C. We find that the presence of such nanocrystallites is not sufficient for the occurrence of perpendicular magnetic anisotropy. Using EELS, we find that boron diffuses into the Ta underlayer upon annealing. The Ta underlayer thickness dependence of the magnetic anisotropy indicates that ∼0.2 nm of Ta underlayer is enough to absorb the boron from the CoFeB layer and induce perpendicular magnetic anisotropy. Boron diffusion upon annealing becomes limited when the CoFeB layer thickness is larger than ∼2 nm, which coincides with the thickness at which the saturation magnetization MS and the interface magnetic anisotropy KI drop by ∼20%. These results show the direct role which boron plays in determining the perpendicular magnetic anisotropy in CoFeB|MgO heterostructures.
Structure of classical affine and classical affine fractional W-algebras
Authors: Suh Uhi Rinn
Published: January 2015

We introduce a classical BRST complex (See Definition 3.2.) and show that one can construct a classical affine W-algebra via the complex. This definition clarifies that classical affine W-algebras can be considered as quasi-classical limits of quantum affine W-algebras. We also give a definition of a classical affine fractional W-algebra as a Poisson vertex algebra. As in the classical affine case, a classical affine fractional W-algebra has two compatible λ-brackets and is isomorphic to an algebra of differential polynomials as a differential algebra. When a classical affine fractional W-algebra is associated to a minimal nilpotent, we describe explicit forms of free generators and compute λ-brackets between them. Provided some assumptions on a classical affine fractional W-algebra, we find an infinite sequence of integrable systems related to the algebra, using the generalized Drinfel’d and Sokolov reduction.
The thermal decomposition of the benzyl radical in a heated micro-reactor. I. Experimental findings
Authors: Buckingham Grant T. , Ormond Thomas K. , Porterfield Jessica P. , Hemberger Patrick , Kostko Oleg , Ahmed Musahid , Robichaud David J. , Nimlos Mark R. , Daily John W. , Ellison G. Barney
Published: January 2015

The pyrolysis of the benzyl radical has been studied in a set of heated micro-reactors. A combination of photoionization mass spectrometry (PIMS) and matrix isolation infrared (IR) spectroscopy has been used to identify the decomposition products. Both benzyl bromide and ethyl benzene have been used as precursors of the parent species, C6H5CH2, as well as a set of isotopically labeled radicals: C6H5CD2, C6D5CH2, and C6H513CH2. The combination of PIMS and IR spectroscopy has been used to identify the earliest pyrolysis products from benzyl radical as: C5H4=C=CH2, H atom, C5H4—C ≡ CH, C5H5, HCCCH2, and HC ≡ CH. Pyrolysis of the C6H5CD2, C6D5CH2, and C6H513CH2 benzyl radicals produces a set of methyl radicals, cyclopentadienyl radicals, and benzynes that are not predicted by a fulvenallene pathway. Explicit PIMS searches for the cycloheptatrienyl radical were unsuccessful, there is no evidence for the isomerization of benzyl and cycloheptatrienyl radicals: C6H5CH2⇋C7H7. These labeling studies suggest that there must be other thermal decomposition routes for the C6H5CH2 radical that differ from the fulvenallene pathway.
Theoretical analysis of selectivity mechanisms in molecular transport through channels and nanopores
Authors: Agah Shaghayegh , Pasquali Matteo , Kolomeisky Anatoly B.
Published: January 2015

Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed.
Hypervelocity nanoparticle impacts on free-standing graphene: A sui generis mode of sputtering
Authors: Eller Michael J. , Liang Chao-Kai , Della-Negra Serge , Clubb Aaron B. , Kim Hansoo , Young Amanda E. , Schweikert Emile A.
Published: January 2015

The study of the interaction of hypervelocity nano-particles with a 2D material and ultra-thin targets (single layer graphene, multi-layer graphene, and amorphous carbon foils) has been performed using mass selected gold nano-particles produced from a liquid metal ion source. During these impacts, a large number of atoms are ejected from the graphene, corresponding to a hole of ∼60 nm2. Additionally, for the first time, secondary ions have been observed simultaneously in both the transmission and reflection direction (with respect to the path of the projectile) from a 2D target. The ejected area is much larger than that predicted by molecular dynamic simulations and a large ionization rate is observed. The mass distribution and characteristics of the emitted secondary ions are presented and offer an insight into the process to produce the large hole observed in the graphene.
Si membrane based tactile sensor with active matrix circuitry for artificial skin applications
Authors: Park Minhoon , Kim Min-Seok , Park Yon-Kyu , Ahn Jong-Hyun
Published: January 2015

The fabrication and the characteristics of an inorganic silicon-based flexible tactile sensor equipped with active-matrix circuitry compatible with a batch microfabrication process are reported. An 8 × 8 array of 260 nm-thick silicon strain gauges along with individual thin film transistor switches was built on a plastic substrate with 1 mm spacing, corresponding to a human spatial resolution at the fingertip. We demonstrated that the sensor shows excellent performances in terms of repeatability of 1.1%, hysteresis of 1.0%, scanning speed of as much as 100 kHz and resolution of 12.4 kPa while maintaining low power consumption and signal crosstalk through a series of experiments.
On how differently the quasi-harmonic approximation works for two isostructural crystals: Thermal properties of periclase and lime
Authors: Erba A. , Shahrokhi M. , Moradian R. , Dovesi R.
Published: January 2015

Harmonic and quasi-harmonic thermal properties of two isostructural simple oxides (periclase, MgO, and lime, CaO) are computed with ab initio periodic simulations based on the density-functional-theory (DFT). The more polarizable character of calcium with respect to magnesium cations is found to dramatically affect the validity domain of the quasi-harmonic approximation that, for thermal structural properties (such as temperature dependence of volume, V(T), bulk modulus, K(T), and thermal expansion coefficient, α(T)), reduces from [0 K-1000 K] for MgO to just [0 K-100 K] for CaO. On the contrary, thermodynamic properties (such as entropy, S(T), and constant-volume specific heat, CV(T)) are described reliably at least up to 2000 K and quasi-harmonic constant-pressure specific heat, CP(T), up to about 1000 K in both cases. The effect of the adopted approximation to the exchange-correlation functional of the DFT is here explicitly investigated by considering five different expressions of three different classes (local-density approximation, generalized-gradient approximation, and hybrids). Computed harmonic thermodynamic properties are found to be almost independent of the adopted functional, whereas quasi-harmonic structural properties are more affected by the choice of the functional, with differences that increase as the system becomes softer.
Exploiting a nonlinear restoring force to improve the performance of flow energy harvesters
Authors: Bibo Amin , Alhadidi Ali H. , Daqaq Mohammed F.
Published: January 2015

This paper investigates employing a nonlinear restoring force to improve the performance of flow energy harvesters (FEHs). To that end, a galloping FEH possessing a quartic potential energy function of the form V=12μy2+14γy4 is considered. This potential function is used to model either a softening (μ > 0, γ < 0), hardening (μ > 0, γ > 0), or bi-stable (μ < 0, γ > 0) restoring force. A physics-based model of the harvester is obtained assuming piezoelectric transduction and a quasi-steady flow field. The model is validated against experimental data and used to obtain a closed-form solution of the response by employing a multiple scaling perturbation analysis using the Jacobi elliptic functions. The attained solution is subsequently used to investigate the influence of the nonlinearity on the performance of the harvester and to illustrate how to optimize the restoring force in order to maximize the output power for given design conditions and airflow parameters. Specifically, it is shown that for similar design parameters and equal magnitudes of μ, and γ, a bi-stable energy harvester outperforms all other configurations as long as the inter-well motions are activated. On the other hand, if the motion of the bi-stable harvester is limited to a single well, then a harvester incorporating a softening nonlinear restoring force outperforms all other configurations. Furthermore, when comparing two FEHs incorporating the same type of restoring force at the optimal load and similar values of μ, then the FEH with the smaller γ is shown to provide higher output power levels.
Growth dynamics of copper oxide nanowires in plasma at low pressures
Authors: Filipič Gregor , Baranov Oleg , Mozetič Miran , Cvelbar Uroš
Published: January 2015

The growth time dynamics of the copper oxide nanowires (NWs) in radiofrequency plasma discharge were investigated. Grounded copper samples were treated in argon-oxygen plasma with the discharge power of 150 W for sequenced times up to 20 min. After the treatment, the samples were analysed with scanning electron microscopy and image processing to obtain the length and aspect ratio of the NWs. A growth mode with the saturation was observed in dependence to NW length, where the maximal length of 5 μm was achieved in 20 min. However, the best NW aspect ratio had maximum of about 40 after 10 min of plasma treatment. To describe and understand nanowire growth mechanism, a theoretical model was developed and it is in agreement with the experiment. The model results indicate that different densities of the ion current to the side and top area of NW modify the NW growth in height and width. The NW growth is enhanced by presence of ions, and thus this implies that it can be controlled by discharge power. This explains much faster growth of copper oxide nanowires in plasma environment compared to prolonged thermal treatments.
Momentum resolution in inverse photoemission
Authors: Zumbülte A. , Schmidt A. B. , Donath M.
Published: January 2015

We present a method to determine the electron beam divergence, and thus the momentum resolution, of an inverse-photoemission setup directly from a series of spectra measured on Cu(111). Simulating these spectra with different beam divergences shows a distinct influence of the divergence on the appearance of the Shockley surface state. Upon crossing the Fermi level, its rise in intensity can be directly linked with the beam divergence. A comparison of measurement and simulation enables us to quantify the momentum resolution independent of surface quality, energy resolution, and experimental geometry. With spin resolution, a single spectrum taken around the Fermi momentum of a spin-split surface state, e.g., on Au(111), is sufficient to derive the momentum resolution of an inverse-photoemission setup.
Development of modulated optical transmission system to determinate the cloud and freezing points in biofuels
Authors: Jaramillo-Ochoa Liliana , Ramirez-Gutierrez Cristian F. , Sánchez-Moguel Alonso , Acosta-Osorio Andrés , Rodriguez-Garcia Mario E.
Published: January 2015

This work is focused in the development of a modulated optical transmission system with temperature control to determine the thermal properties of biodiesels such as the cloud and freezing points. This system is able to determine these properties in real time without relying on the operator skills as indicated in the American Society for Testing Materials (ASTM) norms. Thanks to the modulation of the incident laser, the noise of the signal is reduced and two information channels are generated: amplitude and phase. Lasers with different wavelengths can be used in this system but the sample under study must have optical absorption at the wavelength of the laser.
Modal and transient analysis of membrane acoustic metasurfaces
Authors: Lani Shane , Sabra Karim G. , Degertekin F. Levent
Published: January 2015

Dispersive surface waves on an acoustic 2D metamaterial, a metasurface consisting of membranes on a rigid surface, have certain propagation characteristics with potential applications for resonance based sensing and subwavelength imaging. The trapped modes of the system that is responsible for the dispersive properties of these acoustic waves are analyzed through modal analysis for a small linear membrane array to obtain the mode shapes, resonant frequencies, quality factors, and wavenumbers. Transient analysis is used for larger arrays to obtain the dispersive properties of the traveling waves and is compared to the modal analysis. Equifrequency contours of the 2D metasurface illustrate interesting features of the metasurface at different frequency regimes around the membrane resonance. These features include anisotropic wave propagation, directional band gap, negative refraction, and complete band gap. Effects of membrane pitch, randomness of resonance, and aperiodic membrane spacing on dispersion, band gaps, and quality factor of the trapped modes on the metasurface are investigated as they relate to realistic implementations for different applications.
Sound velocity, equation of state, temperature and melting of LiF single crystals under shock compression
Authors: Liu Qiancheng , Zhou Xianming , Zeng Xiaolong , Luo S. N.
Published: January 2015

Internal particle velocity history measurements are performed on [100] LiF single crystals under plate impact to 2–152 GPa, to investigate the Gruneisen equation of state and shock-induced melting. Hugoniot and sound velocities of LiF are obtained via the Lagrangian analysis. The drop in the longitudinal sound velocity to bulk sound velocity between 134 and 152 GPa, suggests that shock-induced melting initiates at 134–152 GPa. The Gruneisen parameter as a function of shock-state density is determined. Given high-pressure Gruneisen parameters, shock temperature and melting curve of B1 phase LiF are calculated, and consistent with previous molecular dynamics and ab initio calculations, as well as diamond-anvil cell and shock wave measurements. Our calculation suggests that shock-induced melting initiates at 142 GPa, in agreement with our sound velocity measurements.
The Rayleigh–Plateau instability and jet formation during the extrusion of liquid metal from craters in a vacuum arc cathode spot
Authors: Mesyats G. A. , Zubarev N. M.
Published: January 2015

We consider the displacement of molten metal from a crater being formed on the cathode during the operation of a vacuum arc under the pressure of the cathode plasma and formulate a criterion for the formation of a thin ridge of expelled liquid metal (a sheet-like jet) at the crater edge. When the ridge height is substantially greater than its thickness, conditions arise for the development of the Rayleigh–Plateau capillary instability, which breaks the axial symmetry of the problem. Estimates are presented, which suggest that this instability is responsible for the breakup of the liquid ridge into jets, which play an important role in the self-sustained operation of a discharge.
A charge carrier transport model for donor-acceptor blend layers
Authors: Fischer Janine , Widmer Johannes , Kleemann Hans , Tress Wolfgang , Koerner Christian , Riede Moritz , Vandewal Koen , Leo Karl
Published: January 2015

Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C60 in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (Et = 0.14 eV, Nt = 1.2 × 1018 cm−3) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for this blend layer.
Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers
Authors: Wei Yajun , Akansel Serkan , Thersleff Thomas , Harward Ian , Brucas Rimantas , Ranjbar Mojtaba , Jana Somnath , Lansaker Pia , Pogoryelov Yevgen , Dumas Randy K. , Leifer Klaus , Karis Olof , Åkerman Johan , Celinski Zbigniew , Svedlindh Peter
Published: January 2015

Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO2 substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 Å, the thickness of the Cu spacer was varied from 5 to 50 Å. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm2 for the sample with a 5 Å Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.
Experimental investigation of a 1 kA/cm2 sheet beam plasma cathode electron gun
Authors: Kumar Niraj , Narayan Pal Udit , Kumar Pal Dharmendra , Prajesh Rahul , Prakash Ram
Published: January 2015

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm2 from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.
High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors
Authors: Lee Ching-Ting , Lin Yung-Hao , Lin Jhong-Ham
Published: January 2015

Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance gm change, threshold voltage VT change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.
A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics
Authors: Boschini F. , Hedayat H. , Piovera C. , Dallera C. , Gupta A. , Carpene E.
Published: January 2015

A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO2 single crystals as a benchmark.
Influence of microstructural changes on magnetic refrigeration performance for La(Fe0.94Co0.06)11.8Si1.2 alloys during magnetic field cycling
Authors: Yuan Z. M. , He J. , Yang L. , Xia Z. J. , Zhao D. L. , You C. Y. , Ren W. J.
Published: January 2015

NaZn13-type La(Fe0.94Co0.06)11.8Si1.2 alloys were manufactured to investigate the influence of their microstructural change on magnetic refrigeration performance during magnetic field cycling. The magnetic refrigeration performance measurements indicate that both the large magnetic entropy change value (ΔS = 14.1 J kg−1 K−1) and maximum adiabatic temperature change (ΔT = 2.2 K) are favorable for the alloys to be superior candidate of magnetic refrigerants. However, the alloys exhibit nearly 10% decrease of ΔS and ΔT when they performed cycling ten-thousand times. More than thousand times of cycles induce local stress and grain cleavages presented by the accumulation of irreversible microstructure changes such as micro-cracks and sub-boundaries. According to the domain observation for the alloys with different field cycles, these microstructure characteristics accompany with the reconfiguration of the local magnetic domains and increase of domain wall energy, which are considered to be the reason of the decrease of ΔS.
Resistance transition assisted geometry enhanced magnetoresistance in semiconductors
Authors: Luo Zhaochu , Zhang Xiaozhong
Published: January 2015

Magnetoresistance (MR) reported in some non-magnetic semiconductors (particularly silicon) has triggered considerable interest owing to the large magnitude of the effect. Here, we showed that MR in lightly doped n-Si can be significantly enhanced by introducing two diodes and proper design of the carrier path [Wan, Nature 477, 304 (2011)]. We designed a geometrical enhanced magnetoresistance (GEMR) device whose room-temperature MR ratio reaching 30% at 0.065 T and 20 000% at 1.2 T, respectively, approaching the performance of commercial MR devices. The mechanism of this GEMR is: the diodes help to define a high resistive state (HRS) and a low resistive state (LRS) in device by their openness and closeness, respectively. The ratio of apparent resistance between HRS and LRS is determined by geometry of silicon wafer and electrodes. Magnetic field could induce a transition from LRS to HRS by reshaping potential and current distribution among silicon wafer, resulting in a giant enhancement of intrinsic MR. We expect that this GEMR could be also realized in other semiconductors. The combination of high sensitivity to low magnetic fields and large high-field response should make this device concept attractive to the magnetic field sensing industry. Moreover, because this MR device is based on a conventional silicon/semiconductor platform, it should be possible to integrate this MR device with existing silicon/semiconductor devices and so aid the development of silicon/semiconductor-based magnetoelectronics. Also combining MR devices and semiconducting devices in a single Si/semiconductor chip may lead to some novel devices with hybrid function, such as electric-magnetic-photonic properties. Our work demonstrates that the charge property of semiconductor can be used in the magnetic sensing industry, where the spin properties of magnetic materials play a role traditionally.
Influence of the local heating position on the terahertz emission power from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesas
Authors: Watanabe C. , Minami H. , Kitamura T. , Asanuma K. , Nakade K. , Yasui T. , Saiwai Y. , Shibano Y. , Yamamoto T. , Kashiwagi T. , Klemm Richard A. , Kadowaki K.
Published: January 2015

Simultaneous measurements of spectroscopic terahertz emissions from and SiC photoluminescent local temperature T(r) distributions of high transition temperature Tc superconducting Bi2Sr2CaCu2O8+δ rectangular mesa devices were made. A local region with T(r) > Tc known as a hot spot can emerge with current bias changes. When the hot spot position was moved to a mesa end by locally heating the mesa surface with a laser beam, the intensity of the emission increased, but no changes to its frequency or line width were observed. These results suggest that higher power radiation is attainable by adjusting the hot spot position.
Measurement and discrete element simulation of a fixed-obstacle disturbed rapid granular chute flow
Authors: Kuo Chih-Yu , Sheng Li-Tsung , Chiu Shang-Yu , Yang Yan-Zhi , Tai Yih-Chin , Hsiau Shu-San
Published: January 2015

We describe the experimental measurements and discrete element simulations of steady rapid granular chute flows disturbed by a small fixed semi-cylindrical obstacle. The flow chute has a width of 5 cm, a length of 150 cm, an inclination of 30°, with an obstacle installed at approximately the center of the chute. The steady disturbed flow has a region that exhibits substantial but smooth changes in flow characteristics, like a very diffused weak shock. Our measurements include the streamwise flow depth, velocity, and flux-averaged solid fraction. We compare the velocity profile from far upstream of the disturbed flow region with the prediction of an analytical solution based on the kinetic theory. We construct a control volume method to calculate the force exerted by the obstacle on the flow based on the influenced distance of the obstacle. Comparison showed satisfactory agreement between the measured obstacle forces with the discrete element simulations.
Interacting nonlinear wave envelopes and rogue wave formation in deep water
Authors: Ablowitz Mark J. , Horikis Theodoros P.
Published: January 2015

A rogue wave formation mechanism is proposed within the framework of a coupled nonlinear Schrödinger (CNLS) system corresponding to the interaction of two waves propagating in oblique directions in deep water. A rogue condition is introduced that links the angle of interaction with the group velocities of these waves: different angles of interaction can result in a major enhancement of rogue events in both numbers and amplitude. For a range of interacting directions, it is found that the CNLS system exhibits significantly more extreme wave amplitude events than its scalar counterpart. Furthermore, the rogue events of the coupled system are found to be well approximated by hyperbolic secant functions; they are vectorial soliton-type solutions of the CNLS system, typically not considered to be integrable. Overall, our results indicate that crossing states provide an important mechanism for the generation of rogue water wave events.
Effects of nonthermal electrons on plasma expansion into vacuum
Authors: Bennaceur-Doumaz D. , Bara D. , Benkhelifa E. , Djebli M.
Published: January 2015

The expansion of semi-infinite plasma into vacuum is analyzed with a hydrodynamic model for cold ions assuming electrons modelled by a kappa-type distribution. Similarly to Mora study of a plasma expansion into vacuum [P. Mora, Phys. Rev. Lett. 90, 185002 (2003)], we formulated empirical expressions for the electric field strength, velocity, and position of the ion front in one-dimensional nonrelativistic, collisionless isothermally expanding plasma. Analytic expressions for the maximum ion energy and the spectrum of the accelerated ions in the plasma were derived and discussed to highlight the electron nonthermal effects on enhancing the ion acceleration in plasma expansion into vacuum.
Proximity induced ferromagnetism, superconductivity, and finite-size effects on the surface states of topological insulator nanostructures
Authors: Sengupta Parijat , Kubis Tillmann , Tan Yaohua , Klimeck Gerhard
Published: January 2015

Bi2Te3 and Bi2Se3 are well known 3D-topological insulators (TI). Films made of these materials exhibit metal-like surface states with a Dirac dispersion and possess high mobility. The high mobility metal-like surface states can serve as building blocks for a variety of applications that involve tuning their dispersion relationship and opening a band gap. A band gap can be opened either by breaking time reversal symmetry, the proximity effect of a superconductor or ferromagnet or adjusting the dimensionality of the TI material. In this work, methods that can be employed to easily open a band gap for the TI surface states are assessed. Two approaches are described: (1) Coating the surface states with a ferromagnet which has a controllable magnetization axis. The magnetization strength of the ferromagnet is incorporated as an exchange interaction term in the Hamiltonian. (2) An s-wave superconductor, because of the proximity effect, when coupled to a 3D-TI opens a band gap on the surface. Finally, the hybridization of the surface Dirac cones can be controlled by reducing the thickness of the topological insulator film. It is shown that this alters the band gap significantly.