bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of non covalent interactions in light emitting properties of bis-pyridyl-alkyl-di-imines
Authors: Baig Fayaz , Kant Rajni , Gupta Vivek K. , Sarkar Madhushree
Published: June 2015

Crystallization induced emission is observed for bis-pyridyl-ethyl-di-imine and bis-pyridyl-butyl-di-imine. While in case of bis-pyridyl-di-imines, with no alkyl spacer, the quenching is observed in the solid state.
How to split a G-quadruplex for DNA detection: new insight into the formation of DNA split G-quadruplex
Authors: Zhu Jinbo , Zhang Libing , Dong Shaojun , Wang Erkang
Published: June 2015

A magic “law of 4 : 8” to split the G-quadruplex for DNA detection has been found.
Relationship between particle elasticity, glass fragility, and structural relaxation in dense microgel suspensions
Authors: Seekell, III Raymond P. , Sarangapani Prasad S. , Zhang Zexin , Zhu Yingxi
Published: June 2015

A full spectrum of strong to fragile glass-forming behaviors can be achieved in a single microgel system of increased particle elasticity. The glass fragility and structural relaxation processes of glass-forming dense colloidal liquids show strong dependence on particle elasticity.
Open-top TiO2 nanotube arrays with enhanced photovoltaic and photochemical performances via a micromechanical cleavage approach
Authors: Liao Yulong , Zhang Dainan , Wang Qi , Wen Tianlong , Jia Lijun , Zhong Zhiyong , Bai Feiming , Tang Longhuang , Que Wenxiu , Zhang Huaiwu
Published: June 2015

Easy removal of the disordered nanograss top-layer through a “scotch-tape method” with enhanced photoelectronic performances.
Conjugate gradient algorithm for efficient covariance tracking with Jensen‐Bregman LogDet metric
Authors: Guo Qiang , Wu Chengdong , Feng Yu , Lu Xiaohong
Published: June 2015

Region covariance descriptor that fuses multiple features compactly has proven to be very effective for visual tracking. While working effectively, the exhaustive global search strategy of covariance tracking is still inefficient, and there is much room for improvement. It may cause inconsecutive tracking trajectory and distraction. A suitable region similarity metric for covariance matching between the candidate object region and a given appearance template is of much importance. However, the computational burden of the metric, especially for large matrices under Riemannian space, may hinder its application in gradient‐based algorithms. In this study, the authors propose an algorithm which, by minimising the metric function, exploits an efficient conjugate gradient method to iteratively search the best matched candidate, and determines the search step size by non‐monotonic liner strategy. Then, an inferential reasoning in view of new efficient metric is derived for the gradient‐based algorithm. The authors test the proposed tracking method on test baseline dataset. Both quantitative and qualitative results demonstrate the effectiveness of the proposed algorithm compared with other state‐of‐the‐art methods.
Modelling, synthesis and characterisation of occlusion in videos
Authors: Roy Aditi , Chattopadhyay Pratik , Sural Shamik , Mukherjee Jayanta , Rigoll Gerhard
Published: June 2015

Occlusion is one of the most challenging problems in many video processing applications such as surveillance, gait recognition, activity recognition and so on. Attempts have been made to develop algorithms for handling occlusion and evaluate their performance on various datasets. However, these studies are subjective in nature and the datasets are hardly characterised in terms of the level of occlusion, thereby precluding any form of quantitative comparison of performance. This shows a compelling need to design an explicit, unambiguous and quantitative model, which should be able to objectively represent occlusion in a video. This study proposes an occlusion model based on the position and pose uncertainties of the moving subjects in a video. The proposed occlusion model is able to characterise the level of occlusion present in a video. It is also employed to synthetically generate occlusion for walking sequences, thus providing a direction for controlled dataset generation against which human identification algorithms can be tested. Given an input video with a subject moving without any occlusion, a particle swarm optimisation‐based parameter estimation methodology is presented that generates the desired level of occlusion. The proposed approaches have been tested on the TUM‐IITKGP and PETS2010 datasets. Finally, as an application, the occlusion model has been used to generate an occluded gait datasets and the performances of different gait recognition algorithms have been compared under varying levels of occlusion.
Symmetrical and asymmetrical low‐voltage ride through of doubly‐fed induction generator wind turbines using gate controlled series capacitor
Authors: Mohammadpour Hassan , Ghassem Zadeh Saeed , Tohidi Sajjad
Published: June 2015

This study proposes a new method to improve low‐voltage ride through of the doubly‐fed induction generator (DFIG) wind turbines (WTs) using gate‐controlled series capacitor (GCSC) in series with the generator rotor. Using GCSC, as soon as a voltage dip occurs at the generator's terminals, the GCSC inserts its capacitor in series with the rotor, increasing the voltage seen by the rotor winding. Consequently, the rotor over‐current is limited and transmission of the inrush energy to the rotor side converter is reduced. Moreover, by this method, the chopper is not required for protecting the DC‐link capacitor. Unlike the Crowbar method, which control of the generator is lost during the fault, the proposed method in this study avoids the loss of control during the grid faults. To validate the effectiveness of the proposed method, extensive time‐domain simulation is performed using MATLAB/SIMULINK on a 1.5 MW DFIG‐based WT.
Performance comparison of two different filter design approaches for torsional vibration damping in a doubly fed induction generator‐based wind turbine
Authors: Liu Libo , Xie Da
Published: June 2015

Conventional band‐pass filter (BPF)‐based damper is commonly employed to damp the vibrations in the drive train caused by turbulent winds. However, for the case of grid disturbances or faults resultant torsional vibrations, the performance of the BPF‐based damper can be compromised because of the potential low‐frequency vibration modes from grid side. To overcome this shortcoming, low‐pass filter (LPF)‐based torsional damper was proposed in this study. The theoretical analysis of the two torsional damper was assessed in frequency domain. Performance comparison of the two dampers was conducted through simulations and the proposed LPF‐based torsional damper outperformed the conventional one in the presence of unexpected low‐frequency vibrations. Results also showed that retuning the BPF by decreasing the quality factor can restore the intended performance of torsional damper.
Rotation of a spheroid in a simple shear at small Reynolds number
Authors: Einarsson J. , Candelier F. , Lundell F. , Angilella J. R. , Mehlig B.
Published: June 2015

We derive an effective equation of motion for the orientational dynamics of a neutrally buoyant spheroid suspended in a simple shear flow, valid for arbitrary particle aspect ratios and to linear order in the shear Reynolds number. We show how inertial effects lift the degeneracy of the Jeffery orbits and determine the stabilities of the log-rolling and tumbling orbits at infinitesimal shear Reynolds numbers. For prolate spheroids, we find stable tumbling in the shear plane and log-rolling is unstable. For oblate spheroids, by contrast, log-rolling is stable and tumbling is unstable provided that the particle is not too disk-like (moderate asphericity). For very flat oblate spheroids, both log-rolling and tumbling are stable, separated by an unstable limit cycle.
Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels
Authors: Vexiau R. , Lepers M. , Aymar M. , Bouloufa-Maafa N. , Dulieu O.
Published: June 2015

We have calculated the isotropic C6 coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X1Σ+. We consider the ten species made up of 7Li, 23Na, 39K, 87Rb, and 133Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.
Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents
Authors: Arrese-Igor S. , Alegría A. , Colmenero J.
Published: June 2015

We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg. On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.
Excitation correlation photoluminescence in the presence of Shockley-Read-Hall recombination
Authors: Borgwardt M. , Sippel P. , Eichberger R. , Semtsiv M. P. , Masselink W. T. , Schwarzburg K.
Published: June 2015

Excitation correlation photoluminescence (ECPL) measurements are often analyzed in the approximation of a cross correlation of charge carrier populations generated by the two delayed pulses. In semiconductors, this approach is valid for a linear non-radiative recombination path, but not for a non-linear recombination rate as in the general Shockley-Read-Hall recombination scenario. Here, the evolution of the ECPL signal was studied for deep trap recombination following Shockley-Read-Hall statistics. Analytic solutions can be obtained for a fast minority trapping regime and steady state recombination. For the steady state case, our results show that the quadratic radiative term plays only a minor role, and that the shape of the measured signal is mostly determined by the non-linearity of the recombination itself. We find that measurements with unbalanced intense pump and probe pulses can directly provide information about the dominant non-radiative recombination mechanism. The signal traces follow the charge carrier concentrations, despite the complex origins of the signal, thus showing that ECPL can be applied to study charge carrier dynamics in semiconductors without requiring elaborate calculations. The model is compared with measurements on a reference sample with alternating layers of InGaAs/InAlAs that were additionally cross-checked with time resolved optical pump terahertz probe measurements and found to be in excellent agreement.
A radio-frequency coil for the microwave characterization of vortex dynamics in thin film superconductors
Authors: Cuadra-Solís Pedro-de-Jesús , Fernández-Martínez Antoni , Hernàndez Joan Manel , García-Santiago Antoni , Vanacken Johan , Moshchalkov Victor V.
Published: June 2015

A radio-frequency coil for the experimental investigation of the magnetic properties of thin superconducting films under microwave fields at different values of temperature and dc magnetic field has been developed. The system has been used for low-temperature microwave frequency-dependent magnetization measurements in a Pb thin film with an engineered periodical antidot array. The characteristic frequencies and the electric and magnetic fields of the resonant system formed by a multi-turn coil with a sample loaded in its core are estimated using the helical approach. A good agreement of the calculated values with those recorded in swept-frequency spectra is obtained. The relation between the characteristics of the resonant structure and the frequency-driven magnetic response of the sample at different nominal microwave powers documents the capability and sensitivity of the layout.
Direct detection of linearized bursts in turbulence
Authors: Jiménez Javier
Published: June 2015

The relevance of linear transitional mechanisms in fully turbulent shear flows, and in particular of the Orr-like inviscid transient amplification of disturbances, is explored in the context of the prediction of bursting behavior. Although the logarithmic layer of wall-bounded turbulence is used as the primary example, most conclusions should apply to other flows with linearly stable mean profiles that are dominated by large-scale streamwise-velocity streaks and intermittent bursts of the cross-shear velocity. When the linearised problem is solved in the limit of small viscosity, it has previously been shown that statistical properties, such as the bursting time- and length-scales, the energy fluxes between components, and the mean inclination angles, are consistent in linear and nonlinear systems. The question addressed here is whether the individual structures predicted by the linearised solution can be detected in fully nonlinear simulations, and whether the linearized approximation can be used to predict their evolution. It is found that strong bursting of the largest scales is well described linearly, comprising about 65%–70% of the total time, but that weaker fluctuations are not. It is also found that adding an eddy viscosity does not substantially improve predictions.
Non-monotonic resonance in a spatially forced Lengyel-Epstein model
Authors: Haim Lev , Hagberg Aric , Meron Ehud
Published: June 2015

We study resonant spatially periodic solutions of the Lengyel-Epstein model modified to describe the chlorine dioxide-iodine-malonic acid reaction under spatially periodic illumination. Using multiple-scale analysis and numerical simulations, we obtain the stability ranges of 2:1 resonant solutions, i.e., solutions with wavenumbers that are exactly half of the forcing wavenumber. We show that the width of resonant wavenumber response is a non-monotonic function of the forcing strength, and diminishes to zero at sufficiently strong forcing. We further show that strong forcing may result in a π/2 phase shift of the resonant solutions, and argue that the nonequilibrium Ising-Bloch front bifurcation can be reversed. We attribute these behaviors to an inherent property of forcing by periodic illumination, namely, the increase of the mean spatial illumination as the forcing amplitude is increased.
Kinetic-freezing and unfreezing of local-region fluctuations in a glass structure observed by heat capacity hysteresis
Authors: Aji D. P. B. , Johari G. P.
Published: June 2015

Fluctuations confined to local regions in the structure of a glass are observed as the Johari-Goldstein (JG) relaxation. Properties of these regions and their atomic configuration are currently studied by relaxation techniques, by electron microscopy, and by high-energy X-ray scattering and extended x-ray absorption fine structure methods. One expects that these fluctuations (i) would kinetically freeze on cooling a glass, and the temperature coefficient of its enthalpy, dH/dT, would consequently show a gradual decrease with decrease in T, (ii) would kinetically unfreeze on heating the glass toward the glass-liquid transition temperature, Tg, and dH/dT would gradually increase, and (iii) there would be a thermal hysteresis indicating the time and temperature dependence of the enthalpy. Since no such features have been found, thermodynamic consequences of these fluctuations are debated. After searching for these features in glasses of different types, we found it in one of the most stable metal alloy glasses of composition Pd40Ni10Cu30P20. On cooling from its Tg, dH/dT decreased along a broad sigmoid-shape path as local-region fluctuations kinetically froze. On heating thereafter, dH/dT increased along a similar path as these fluctuations unfroze, and there is hysteresis in the cooling and heating paths, similar to that observed in the Tg-endotherm range. After eliminating other interpretations, we conclude that local-region fluctuations seen as the JG relaxation in the non-equilibrium state of a glass contribute to its entropy, and we suggest conditions under which such fluctuations may be observed.
Pulse-shaping assisted multidimensional coherent electronic spectroscopy
Authors: Rodriguez Yuseff , Frei Franziska , Cannizzo Andrea , Feurer Thomas
Published: June 2015

Understanding nuclear and electronic dynamics of molecular systems has advanced considerably by probing their nonlinear responses with a suitable sequence of pulses. Moreover, the ability to control crucial parameters of the excitation pulses, such as duration, sequence, frequency, polarization, slowly varying envelope, or carrier phase, has led to a variety of advanced time-resolved spectroscopic methodologies. Recently, two-dimensional electronic spectroscopy with ultrashort pulses has become a more and more popular tool since it allows to obtain information on energy and coherence transfer phenomena, line broadening mechanisms, or the presence of quantum coherences in molecular complexes. Here, we present a high fidelity two-dimensional electronic spectroscopy setup designed for molecular systems in solution. It incorporates the versatility of pulse-shaping methods to achieve full control on the amplitude and phase of the individual exciting and probing pulses. Selective and precise amplitude- and phase-modulation is shown and applied to investigate electronic dynamics in several reference molecular systems.
Second-sound studies of coflow and counterflow of superfluid 4He in channels
Authors: Varga Emil , Babuin Simone , Skrbek L.
Published: June 2015

We report a comprehensive study of turbulent superfluid 4He flow through a channel of square cross section. We study for the first time two distinct flow configurations with the same apparatus: coflow (normal and superfluid components move in the same direction), and counterflow (normal and superfluid components move in opposite directions). We realise also a variation of counterflow with the same relative velocity, but where the superfluid component moves while there is no net flow of the normal component through the channel, i.e., pure superflow. We use the second-sound attenuation technique to measure the density of quantised vortex lines in the temperature range 1.2 K ≲ T ≲ Tλ ≈ 2.18 K and for flow velocities from about 1 mm/s up to almost 1 m/s in fully developed turbulence. We find that both the steady-state and temporal decay of the turbulence significantly differ in the three flow configurations, yielding an interesting insight into two-fluid hydrodynamics. In both pure superflow and counterflow, the same scaling of vortex line density with counterflow velocity is observed, L∝Vcf2, with a pronounced temperature dependence; in coflow instead, the vortex line density scales with velocity as L ∝ V3/2 and is temperature independent; we provide theoretical explanations for these observations. Further, we develop a new promising technique to use different second-sound resonant modes to probe the spatial distribution of quantised vortices in the direction perpendicular to the flow. Preliminary measurements indicate that coflow is less homogeneous than counterflow/superflow, with a denser concentration of vortices between the centre of the channel and its walls.
Rotational spectroscopy and three-wave mixing of 4-carvomenthenol: A technical guide to measuring chirality in the microwave regime
Authors: Shubert V. Alvin , Schmitz David , Medcraft Chris , Krin Anna , Patterson David , Doyle John M. , Schnell Melanie
Published: June 2015

We apply chirality sensitive microwave three-wave mixing to 4-carvomenthenol, a molecule previously uncharacterized with rotational spectroscopy. We measure its rotational spectrum in the 2-8.5 GHz range and observe three molecular conformers. We describe our method in detail, from the initial step of spectral acquisition and assignment to the final step of determining absolute configuration and enantiomeric excess. Combining fitted rotational constants with dipole moment components derived from quantum chemical calculations, we identify candidate three-wave mixing cycles which were further tested using a double resonance method. Initial optimization of the three-wave mixing signal is done by varying the duration of the second excitation pulse. With known transition dipole matrix elements, absolute configuration can be directly determined from a single measurement.
Controlling guided modes in plasmonic metal/dielectric multilayer waveguides
Authors: Wickremasinghe N. , Thompson J. , Wang X. , Schmitzer H. , Wagner H. P.
Published: June 2015

We investigate the mode properties of planar dielectric aluminum-quinoline (Alq3) multilayer waveguides comprising one single or three equally spaced embedded nanometer-thin (∼10 nm thick) Alq3-Mg0.9:Ag0.1 composite metal-island layers. The plasmonic waveguides were fabricated by organic molecular beam deposition. Transverse magnetic (TM) and transverse electric (TE) modes were selectively excited using the m-line method. The symmetric plasmonic TM0 mode was launched in all waveguides and—in addition—two higher order plasmonic TM1 and TM2 modes were generated in waveguides comprising three metal layers. Other TM modes have hybrid dielectric-plasmonic characters, showing an increased effective refractive index when one electric field antinode is close to a metallic layer. TM modes which have all their antinode(s) in the dielectric layers propagate essentially like dielectric modes. TE modes with antinode(s) at the position of the metal layer(s) are strongly damped while the losses are low for TE modes comprising a node at the position of the composite metal film(s). The possibility to control the effective refractive index and the losses for individual hybrid plasmonic-dielectric TM and dielectric TE modes opens new design opportunities for mode selective waveguides and TM-TE mode couplers.
Measuring flexural rigidity of mullite microfibers using magnetic droplets
Authors: Chen Zhaoxi , Gu Yu , Zhang Zhao , Kornev Konstantin G. , Luzinov Igor , Peng Fei
Published: June 2015

Flexural rigidity of many microfibers is known to deviate from the Bernoulli-Euler predictions that neglect shear deformations. We examine mullite microfibers formed by electrospinning of sol-gel precursors. The formed fibers have diameters smaller than 10 μm. A magnetic drop was placed on the free end of a dangling fiber, and the fiber was flexed by applying a non-uniform magnetic field. By applying different magnetic fields, we generated a series of different fiber profiles and filmed the process of fiber bending. Mullite microfibers were found to follow the Bernoulli-Euler predictions, and the shear deformations in the material were insignificant. This was confirmed by employing the Euler elastica model to describe the fiber profiles. The bending test provided a Young modulus of E = 100 GPa, which appeared to be very close to that found from the tensile test.
Thermally enhanced perpendicular magnetic anisotropy behaviors of ultrathin [Co/Pd]n multilayers via NiOx capping layer
Authors: Chung Woo Seong , Lee Ja Bin , An Gwang Guk , Yang Seung Mo , Kim Jae Hong , Hong Jin Pyo
Published: June 2015

We report the enhanced perpendicular magnetic anisotropy (PMA) features of ultrathin [Co/Pd]3 multilayers (MLs) employing a NiOx insertion layer at high annealing temperatures. Thermally enhanced PMA in [Co/Pd]3/NiOx (capping layer) MLs were achieved at a specific capping layer thickness, while no PMA responses were observed for a NiOx (buffer layer)/[Co/Pd]3 ML, regardless of NiOx thickness. X-ray diffraction observations, including rocking curves, identified the relatively different crystalline characteristics of the NiOx capping and buffer layers. Origin of the enhanced PMAs of [Co/Pd]3 MLs containing a NiOx capping layer is described based on the NiOx capping effect possibly providing additional Co/Oxide i-PMA under high-temperature annealing.
Landau damping of geodesic acoustic mode in toroidally rotating tokamaks
Authors: Ren Haijun , Cao Jintao
Published: June 2015

Geodesic acoustic mode (GAM) is analyzed by using modified gyro-kinetic (MGK) equation applicable to low-frequency microinstabilities in a rotating axisymmetric plasma. Dispersion relation of GAM in the presence of arbitrary toroidal Mach number is analytically derived. The effects of toroidal rotation on the GAM frequency and damping rate do not depend on the orientation of equilibrium flow. It is shown that the toroidal Mach number M increases the GAM frequency and dramatically decreases the Landau damping rate.
Generalized correlation integral vectors: A distance concept for chaotic dynamical systems
Authors: Haario Heikki , Kalachev Leonid , Hakkarainen Janne
Published: June 2015

Several concepts of fractal dimension have been developed to characterise properties of attractors of chaotic dynamical systems. Numerical approximations of them must be calculated by finite samples of simulated trajectories. In principle, the quantities should not depend on the choice of the trajectory, as long as it provides properly distributed samples of the underlying attractor. In practice, however, the trajectories are sensitive with respect to varying initial values, small changes of the model parameters, to the choice of a solver, numeric tolerances, etc. The purpose of this paper is to present a statistically sound approach to quantify this variability. We modify the concept of correlation integral to produce a vector that summarises the variability at all selected scales. The distribution of this stochastic vector can be estimated, and it provides a statistical distance concept between trajectories. Here, we demonstrate the use of the distance for the purpose of estimating model parameters of a chaotic dynamic model. The methodology is illustrated using computational examples for the Lorenz 63 and Lorenz 95 systems, together with a framework for Markov chain Monte Carlo sampling to produce posterior distributions of model parameters.
Computationally efficient dielectric calculations of molecular crystals
Authors: Schwarz Kathleen A. , Sundararaman Ravishankar , Arias T. A.
Published: June 2015

The microscopic dielectric response is a key quantity for electronic materials such as organic semiconductors. Calculations of this response for molecular crystals are currently either expensive or rely on extreme simplifications such as multipole expansions which lack microscopic detail. We present an alternate approach using a microscopic analogue of the Clausius-Mossotti equation, which constructs the dielectric response of a crystal from an eigenvalue decomposition of the dielectric response of individual molecules. This method can potentially be used to examine the effects of defects, disorder, and surfaces on the dielectric properties of molecular solids.
Wave-particle duality of gated p-i-n fin field-effect transistors based on tunneling and diffusion transportation
Authors: Lin Yu-Hsien , Tsai Wan-Ting
Published: June 2015

This study demonstrated a gated p-i-n (PIN) fin-shaped field-effect transistor, which exhibits wave behavior in a tunneling-field-effect transistor (TFET) and particle behavior in a diffusion-field-effect transistor (DFET). The conducting mechanisms correspond to the transfer and output behaviors, which differ markedly for Fin-TFET band-to-band-tunneling and Fin-DFET diffusion. The characteristics of the temperature effect are discussed to illustrate the difference between the two conducting mechanisms. The simulations of energy band diagrams are used to explain the carrier transportation of the Fin-TFET and the Fin-DFET. The results show that the Fin-TFET has a low Ioff (∼10−15 A), a high Ion/Ioff (6.93 × 105), and a relatively steep subthreshold swing (94 mV/dec). By contrast, the Fin-DFET has a high Ion (10−5 A) and a high Ion/Ioff (7.59 × 107), and its performance is satisfactory. A single gated PIN transistor can perform the tunneling current (wave property) of the Fin-TFET and diffusion current (particle property) of the Fin-DFET. This paper presents a novel concept and flexibility for designers of low-power and high-performance circuits.
Chiral mirrors
Authors: Plum Eric , Zheludev Nikolay I.
Published: June 2015

Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.
Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition
Authors: Lo Fang-Yuh , Ting Yi-Chieh , Chou Kai-Chieh , Hsieh Tsung-Chun , Ye Cin-Wei , Hsu Yung-Yuan , Chern Ming-Yau , Liu Hsiang-Lin
Published: June 2015

Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescence spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.
Analytical results of zero-gap states in periodic potentials
Authors: Xie Qiongtao , Rong Shiguang
Published: June 2015

We develop a method to construct various classes of one-dimensional periodic potentials with two intersecting energy bands. Analytical exact results for the zero-gap states are presented in an explicit form under certain parameter conditions. The position of the energies of these zero-gap states in the energy bands is identified numerically.
On-chip electrically controlled routing of photons from a single quantum dot
Authors: Bentham C. , Itskevich I. E. , Coles R. J. , Royall B. , Clarke E. , O'Hara J. , Prtljaga N. , Fox A. M. , Skolnick M. S. , Wilson L. R.
Published: June 2015

Electrical control of on-chip routing of photons emitted by a single InAs/GaAs self-assembled quantum dot (SAQD) is demonstrated in a photonic crystal cavity-waveguide system. The SAQD is located inside an H1 cavity, which is coupled to two photonic crystal waveguides. The SAQD emission wavelength is electrically tunable by the quantum-confined Stark effect. When the SAQD emission is brought into resonance with one of two H1 cavity modes, it is preferentially routed to the waveguide to which that mode is selectively coupled. This proof of concept provides the basis for scalable, low-power, high-speed operation of single-photon routers for use in integrated quantum photonic circuits.
The efficiency limit of CH3NH3PbI3 perovskite solar cells
Authors: Sha Wei E. I. , Ren Xingang , Chen Luzhou , Choy Wallace C. H.
Published: June 2015

With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics.
Steering in-plane shear waves with inertial resonators in platonic crystals
Authors: Achaoui Younes , Diatta André , Guenneau Sébastien
Published: June 2015

Numerical simulations shed light on control of shear elastic wave propagation in plates structured with inertial resonators. The structural element is composed of a heavy core connected to the main freestanding plate through tiny ligaments. It is shown that such a configuration exhibits a complete band gap in the low frequency regime. As a byproduct, we further describe the asymmetric twisting vibration of a single scatterer via modal analysis, dispersion, and transmission loss. This might pave the way to functionalities such as focusing and self-collimation in elastic plates.
Beam tracking approach for single–shot retrieval of absorption, refraction, and dark–field signals with laboratory x–ray sources
Authors: Vittoria Fabio A. , Kallon Gibril K. N. , Basta Dario , Diemoz Paul C. , Robinson Ian K. , Olivo Alessandro , Endrizzi Marco
Published: June 2015

We present the translation of the beam tracking approach for x–ray phase–contrast and dark–field imaging, recently demonstrated using synchrotron radiation, to a laboratory setup. A single absorbing mask is used before the sample, and a local Gaussian interpolation of the beam at the detector is used to extract absorption, refraction, and dark–field signals from a single exposure of the sample. Multiple exposures can be acquired when high resolution is needed, as shown here. A theoretical analysis of the effect of polychromaticity on the retrieved signals, and of the artifacts this might cause when existing retrieval methods are used, is also discussed.
Effect of thermal treatment on Zn nanodisks
Authors: Acuña-Avila Pedro E. , López Roberto , Vigueras-Santiago Enrique , Hernández-López Susana , Camacho-López Marco , Ornelas-Gutierrez Carlos , Antunez Wilber
Published: June 2015

Metallic Zn nanodisks with hexagonal morphology were obtained onto glass substrate under vacuum thermal evaporation. A thermal characterization of Zn nanodiks showed a lower oxidation temperature than source powder Zn. Different thermal treatment on Zn nanodisks played an important role on the morphology, crystal size and surface vibrational modes of ZnO. The growth of ZnO nanoneedles started at the edge of metallic zinc hexagonal structures according with SEM images, the higher temperature the longer needles were grown. XRD diffractogram confirmed the wurtzite structure of ZnO with metallic nuclei. A wide band between 530 and 580 cm−1 of Raman scattering corresponded at surface vibrational modes not observed at higher temperature.
Piezoelectric actuator-based cell microstretch device with real-time imaging capability
Authors: Deguchi Shinji , Kudo Shoko , Matsui Tsubasa S. , Huang Wenjing , Sato Masaaki
Published: June 2015

Cellular response to physical stretch has been extensively studied as a regulator of various physiological functions. For live cell microscopy combined with stretch experiments, cells are typically seeded on an extensible elastomer sheet. In this case, the position of the cells of interest tends to shift out of the field of view upon stretch, making real-time imaging of identical cells difficult. To circumvent this situation, here we describe a robust methodology in which these cell shifts are minimized. Cells are plated in a custom-designed stretch chamber with an elastomer sheet of a small cell culture area. The cell-supporting chamber is stretched on an inverted microscope by using a piezoelectric actuator that provides small, but precisely controlled displacements. Even under this small displacement within the filed of view, our device allows the cells to undergo physiologically relevant levels of stretch. Identical cells can thus be continuously observed during stretching, thereby potentially enabling imaging of stretch-triggered fast dynamics.
Integrated nutrient removal and biogas production by Chlorella vulgaris cultures
Authors: Calicioglu Ozgul , Demirer Goksel N.
Published: June 2015

Changes in global nutrient cycles as a result of industrialization affect both ecosystems and human well-being. A clear example of human manipulation on ecosystems is eutrophication; a phenomenon caused in receiving water bodies by discharge of urban sewage rich in nutrients such as nitrogen (N) and phosphorus (P). Microalgal nutrient removal is a viable alternative for biological wastewater treatment, considering high nutrient uptake capabilities of microalgae. These systems are also advantageous in terms of nutrient recycling and conversion into microalgal biomass, which, in turn, is a beneficial resource for biofuel production. In addition, microalgae can also aid reduction in atmospheric carbon dioxide levels, as a result of photosynthetic anabolism. In this study, a semi-continuous photobioreactor was operated for investigation of nutrient removal efficiency of unialgal culture, Chlorella vulgaris. Maximum N and P removal efficiencies of 99.6% and 91.2% were achieved in the photobioreactor. Biogas production from biomass obtained from semi-continuous photobioreactor was investigated via Biochemical Methane Potential assays. The results illustrated that maximum biogas yield of 442 ml/g Volatile Solids (VS) added could be achieved in anaerobic batch reactors fed with microalgal slurry.
Financial competitiveness of organic agriculture on a global scale
Authors: Crowder David W. , Reganold John P.
Published: June 2015

Significance

Some recognize organic agriculture as being important for future global food security, whereas others project it to become irrelevant. Although organic agriculture is rapidly growing, it currently occupies only 1% of global cropland. Whether organic agriculture can continue to expand will likely be determined by whether it is economically competitive with conventional agriculture. Accordingly, we analyzed the financial performance of organic and conventional agriculture from 40 y of studies covering 55 crops grown on five continents. We found that, in spite of lower yields, organic agriculture was significantly more profitable than conventional agriculture and has room to expand globally. Moreover, with its environmental benefits, organic agriculture can contribute a larger share in sustainably feeding the world.
Tau stabilizes microtubules by binding at the interface between tubulin heterodimers
Authors: Kadavath Harindranath , Hofele Romina V. , Biernat Jacek , Kumar Satish , Tepper Katharina , Urlaub Henning , Mandelkow Eckhard , Zweckstetter Markus
Published: June 2015

Significance

Tau is an important microtubule-associated protein. Although the structure–function relationship of Tau has been intensively studied for many years primarily by molecular biology and biochemical approaches, little is still known about the molecular mechanisms by which Tau interacts with microtubules and promotes microtubule assembly. Here, we provide detailed insight into the Tau–microtubule association by using NMR spectroscopy and mass spectrometry. We show that Tau binds to microtubules by using small groups of residues, which are important for pathological aggregation of Tau. We further show that Tau stabilizes a straight protofilament conformation by binding to a hydrophobic pocket in between tubulin heterodimers. Our work is thus relevant to normal Tau action development and in Tau-related neurodegenerative diseases.
Evolutionary comparison reveals that diverging CTCF sites are signatures of ancestral topological associating domains borders
Authors: Gómez-Marín Carlos , Tena Juan J. , Acemel Rafael D. , López-Mayorga Macarena , Naranjo Silvia , de la Calle-Mustienes Elisa , Maeso Ignacio , Beccari Leonardo , Aneas Ivy , Vielmas Erika , Bovolenta Paola , Nobrega Marcelo A. , Carvajal Jaime , Gómez-Skarmeta José Luis
Published: June 2015

Significance

Mammalian chromatin is compartmentalized in topologically associating domains (TADs), genomic regions within which sequences preferentially contact each other. This organization has been proposed to be essential to organize the regulatory information contained in mammalian genomes. We show that
Six
homeobox genes, essential developmental regulators organized in gene clusters across different animal phyla, share a deeply conserved chromatin organization formed by two abutting TADs that predates the Cambrian explosion. This organization is required to generate separate regulatory landscapes for neighboring genes within the cluster, resulting in very different gene expression patterns. Finally, we show that this extremely conserved 3D architecture is associated with a characteristic arrangement of CCCTC-binding factor (CTCF) binding sites in diverging orientations, revealing a genome-wide conserved signature for TAD borders.
Predictive Validity of the Short-Term Assessment of Risk and Treatability (START) for Aggression and Self-Harm in a Secure Mental Health Service: Gender Differences
Authors: O'Shea Laura E. , Dickens Geoffrey L.
Published: June 2015

The START predicts aggressive outcomes and to some extent self-harm. However, it is not known whether gender moderates its performance. This study used routinely collected data to investigate the predictive ability of the START for aggression and self-harm in secure psychiatric patients. Utility of the START was examined separately for men and women. The START was a stronger predictor of aggression and self-harm in women than men. The specific risk estimates produced large effect sizes for the prediction of aggression and self-harm in women; none of the AUC values reached the threshold for a large effect size in the male sample.
Do future thoughts reflect personal goals? Current concerns and mental time travel into the past and future
Authors: Cole Scott N. , Berntsen Dorthe
Published: June 2015

Our overriding hypothesis was that future thinking would be linked with goals to a greater extent than memories; conceptualizing goals as current concerns (i.e., uncompleted personal goals). We also hypothesized that current-concern-related events would differ from non-current-concern-related events on a set of phenomenological characteristics. We report novel data from a study examining involuntary and voluntary mental time travel using an adapted laboratory paradigm. Specifically, after autobiographical memories or future thoughts were elicited (between participants) in an involuntary and voluntary retrieval mode (within participants), participants self-generated five current concerns and decided whether each event was relevant or not to their current concerns. Consistent with our hypothesis, compared with memories, a larger percentage of involuntary and voluntary future thoughts reflected current concerns. Furthermore, events related to current concerns differed from non-concern-related events on a range of cognitive, representational, and affective phenomenological measures. These effects were consistent across temporal direction. In general, our results agree with the proposition that involuntary and voluntary future thinking is important for goal-directed cognition and behaviour.
The influence of linguistic and cognitive factors on the time course of verb-based implicit causality
Authors: Koornneef Arnout , Dotlačil Jakub , van den Broek Paul , Sanders Ted
Published: June 2015

In three eye-tracking experiments the influence of the Dutch causal connective “want” ( because) and the working memory capacity of readers on the usage of verb-based implicit causality was examined. Experiments 1 and 2 showed that although a causal connective is not required to activate implicit causality information during reading, effects of implicit causality surfaced more rapidly and were more pronounced when a connective was present in the discourse than when it was absent. In addition, Experiment 3 revealed that—in contrast to previous claims—the activation of implicit causality is not a resource-consuming mental operation. Moreover, readers with higher and lower working memory capacities behaved differently in a dual-task situation. Higher span readers were more likely to use implicit causality when they had all their working memory resources at their disposal. Lower span readers showed the opposite pattern as they were more likely to use the implicit causality cue in the case of an additional working memory load. The results emphasize that both linguistic and cognitive factors mediate the impact of implicit causality on text comprehension. The implications of these results are discussed in terms of the ongoing controversies in the literature—that is, the focusing-integration debate and the debates on the source of implicit causality.