bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study on magnetically insulated transmission line electrode surface evolution process under MA/cm current density
Authors: Zhang PengFei , Hu Yang , Yang HaiLiang , Sun Jiang , Wang Liangping , Cong Peitian , Qiu Aici
Published: March 2016

The design of high-current density magnetically insulated transmission line (MITL) is a difficult problem of current large-scale Z-pinch device. In particular, a thorough understanding of the MITL electrode surface evolution process under high current density is lacking. On the “QiangGuang-I” accelerator, the load area possesses a low inductance short-circuit structure with a diameter of 2.85 mm at the cathode, and three reflux columns with a diameter of 3 mm and uniformly distributed circumference at the anode. The length of the high density MITL area is 20 mm. A laser interferometer is used to assess and analyze the state of the MITL cathode and anode gap, and their evolution process under high current density. Experimental results indicate that evident current loss is not observed in the current density area at pulse leading edge, and peak when the surface current density reaches MA/cm. Analysis on electrode surface working conditions indicates that when the current leading edge is at 71.5% of the peak, the total evaporation of MITL cathode structure can be realized by energy deposition caused by ohmic heating. The electrode state changes, and diffusion conditions are reflected in the laser interferometer image. The MITL cathode area mainly exists in metal vapor form. The metal vapor density in the cathode central region is higher than the upper limit of laser penetration density (∼4 × 1021/cm3), with an expansion velocity of ∼0.96 km/s. The metal vapor density in the electrode outer area may lead to evident distortion of fringes, and its expansion velocity is faster than that in the center area (1.53 km/s).
A statistical model for relativistic quantum fluids interacting with an intense electromagnetic wave
Authors: Mahajan Swadesh M. , Asenjo Felipe A.
Published: March 2016

A statistical model for relativistic quantum fluids interacting with an arbitrary amplitude circularly polarized electromagnetic wave is developed in two steps. First, the energy spectrum and the wave function for a quantum particle (Klein Gordon and Dirac) embedded in the electromagnetic wave are calculated by solving the appropriate eigenvalue problem. The energy spectrum is anisotropic in the momentum K and reflects the electromagnetic field through the renormalization of the rest mass m to M=m2+q2A2. Based on this energy spectrum of this quantum particle plus field combination (QPF), a statistical mechanics model of the quantum fluid made up of these weakly interacting QPF is developed. Preliminary investigations of the formalism yield highly interesting results—a new scale for temperature, and fundamental modification of the dispersion relation of the electromagnetic wave. It is expected that this formulation could, inter alia, uniquely advance our understanding of laboratory as well as astrophysical systems where one encounters arbitrarily large electromagnetic fields.
Nanopore gating with an anchored polymer in a switching electrolyte bias
Authors: Wells Craig C. , Jou Ining A. , Melnikov Dmitriy V. , Gracheva Maria E.
Published: March 2016

In this work, we theoretically study the interaction between a solid state membrane equipped with a nanopore and a tethered, negatively charged polymer chain subjected to a time-dependent applied electrolyte bias. In order to describe the movement of the chain in the biomolecule-membrane system immersed in an electrolyte solution, Brownian dynamics is used. We show that we can control the polymer’s equilibrium position with various applied electrolyte biases: for a sufficiently positive bias, the chain extends inside the pore, and the removal of the bias causes the polymer to leave the pore. Corresponding to a driven process, we find that the time it takes for a biomolecular chain to enter and extend into a nanopore in a positive bias almost increases linearly with chain length while the amount of time it takes for a polymer chain to escape the nanopore is mainly governed by diffusion.
Aspect ratio effect on shock-accelerated elliptic gas cylinders
Authors: Zou Liyong , Liao Shenfei , Liu Cangli , Wang Yanping , Zhai Zhigang
Published: March 2016

The evolution of an elliptic heavy-gas (SF6) cylinder accelerated by a planar weak shock wave is investigated experimentally using particle image velocimetry (PIV) diagnostics, and the emphasis is on the aspect ratio effect on shock-elliptic cylinder interaction. Experiments are conducted at five different aspect ratios (the ratio of length in streamwise and spanwise directions) varied from 0.25 to 4.0. PIV raw images and quantitative flow field data are obtained at t = 0.6 ms after the shock impact. As the aspect ratio increases, the interface morphology develops faster owing to more vorticity produced along the interface and smaller vortex spacing between the two vortex cores. For each case in this study, the maximal fluctuating velocity locates at the middle point of the two counter-vortices. The histograms of fluctuating velocity reveal that a distinct double-peak structure appears in the largest aspect ratio case in comparison with a single-peak structure in the smallest aspect ratio case. The vortex velocities predicted by the theoretical model [G. Rudinger and L. M. Somers, “Behaviour of small regions of different gases carried in accelerated gas flows,” J. Fluid Mech. 7, 161–176 (1960)] agree well with the experimental ones. With the increase of aspect ratio, the maximal value of vorticity increases as well as the circulation, and more low-magnitude quantities are generated, which indicates the formation of multi-scale flow structure in the late mixing process. It is found that the experimental circulation of the vortex motion is reasonably estimated by the ideal point vortex-pair model.
Communication: Methane dissociation on Ni(111) surface: Importance of azimuth and surface impact site
Authors: Shen Xiangjian , Zhang Zhaojun , Zhang Dong H.
Published: March 2016

Understanding the role of reactant ro-vibrational degrees of freedom (DOFs) in reaction dynamics of polyatomic molecular dissociation on metal surfaces is of great importance to explore the complex chemical reaction mechanism. Here, we present an expensive quantum dynamics study of the dissociative chemisorption of CH4 on a rigid Ni(111) surface by developing an accurate nine-dimensional quantum dynamical model including the DOF of azimuth. Based on a highly accurate fifteen-dimensional potential energy surface built from first principles, our simulations elucidate that the dissociation probability of CH4 has the strong dependence on azimuth and surface impact site. Some improvements are suggested to obtain the accurate dissociation probability from quantum dynamics simulations.
Magnetorheological fluid behavior in high-frequency oscillatory squeeze mode: Experimental tests and modelling
Authors: Chen Peng , Bai Xian-Xu , Qian Li-Jun
Published: March 2016

This paper presents an experimental investigation on the behavior of magnetorheological (MR) fluids in high-frequency oscillatory squeeze mode and proposes a mathematical model to reveal the MR mechanism. A specific MR squeeze structure avoiding the cavitation effect is designed for the experimental tests. The magnetic field- and gap distance-dependent damping force of the MR squeeze structure is presented and compared with the dramatically large damping force under quasi-static excitations, a moderate damping force is observed at high frequencies. Subsequently, in order to interpret the behavior of MR fluids at high frequencies, employing the continuum media theory, a mathematical model is established with consideration of the fluid inertia and hysteresis property. The damping force comparison between the model and experimental tests indicates that in high-frequency oscillatory squeeze mode, the squeeze-strengthen effect does not work and the shear yield stress can be applied well to characterize the flow property of MR fluids. In addition, the hysteresis property has a significant influence on the damping performance.
Effect of excluded volume on the force-extension of wormlike chains in slit confinement
Authors: Li Xiaolan , Dorfman Kevin D.
Published: March 2016

We use pruned-enriched Rosenbluth method simulations to develop a quantitative phase diagram for the stretching of a real wormlike chain confined in a slit. Our simulations confirm the existence of a “confined Pincus” regime in slit confinement, analogous to the Pincus regime in free solution, where excluded volume effects are sensible. The lower bound for the confined Pincus regime in the force-molecular weight plane, as well as the scaling of the extension with force and slit size, agree with an existing scaling theory for this regime. The upper bound of the confined Pincus regime depends on the strength of the confinement. For strong confinement, the confined Pincus regime ends when the contour length in the Pincus blob is too short to have intrablob excluded volume. As a result, the chain statistics become ideal and the confined Pincus regime at low forces is connected directly to ideal chain stretching at large forces. In contrast, for weak confinement, the confined Pincus regime ends when the Pincus blobs no longer fit inside the slit, even though there is sufficient contour length to have excluded volume inside the Pincus blob. As a result, weak confinement leads to a free-solution Pincus regime intervening between the confined Pincus regime for weak forces and ideal chain stretching at strong forces. Our results highlight shortcomings in existing models for the stretching of wormlike chains in slits.
Theoretical study of ionic liquids based on the cholinium cation. Ab initio simulations of their condensed phases
Authors: Campetella Marco , Bodo Enrico , Montagna Maria , De Santis Serena , Gontrani Lorenzo
Published: March 2016

We have explored by means of ab initio molecular dynamics the homologue series of 11 different ionic liquids based on the combination of the cholinium cation with deprotonated amino acid anions. We present a structural analysis of the liquid states of these compounds as revealed by accurate ab initio computations of the forces. We highlight the persistent structural motifs that see the ionic couple as the basic building block of the liquid whereby a strong hydrogen bonding network substantially determines the short range structural behavior of the bulk state. Other minor docking features of the interaction network are also discovered and described. Special cases along the series such as Cysteine and Phenylalanine are discussed in the view of their peculiar properties due to zwitterion formation and additional long-range structural organization.
Ellipsoidal plasma mirror focusing of high power laser pulses to ultra-high intensities
Authors: Wilson R. , King M. , Gray R. J. , Carroll D. C. , Dance R. J. , Armstrong C. , Hawkes S. J. , Clarke R. J. , Robertson D. J. , Neely D. , McKenna P.
Published: March 2016

The design and development of an ellipsoidal F/1 focusing plasma mirror capable of increasing the peak intensity achievable on petawatt level laser systems to >1022 W cm−2 is presented. A factor of 2.5 reduction in the focal spot size is achieved when compared to F/3 focusing with a conventional (solid state) optic. We find a factor of 3.6 enhancement in peak intensity, taking into account changes in plasma mirror reflectivity and focal spot quality. The sensitivity of the focusing plasma optic to misalignment is also investigated. It is demonstrated that an increase in the peak laser intensity from 3×1020 W cm−2 to 1021 W cm−2 results in a factor of 2 increase in the maximum energy of sheath-accelerated protons from a thin foil positioned at the focus of the intense laser light.
Stationary to nonstationary transition in crossed-field devices
Authors: Marini Samuel , Rizzato Felipe B. , Pakter Renato
Published: March 2016

The previous results based on numerical simulations showed that a cold electron beam injected in a crossed field gap does not reach a time independent stationary state in the space charge limited regime [P. J. Christenson and Y. Y. Lau, Phys. Plasmas 1, 3725 (1994)]. In this work, the effect of finite injection temperature in the transition from stationary to nonstationary states is investigated. A fully kinetic model for the electron flow is derived and used to determine the possible stationary states of the system. It is found that although there is always a stationary solution for any set of parameters, depending on the injection temperature the electron flow becomes very sensitive to fluctuations and the stationary state is never reached. By investigating the nonlinear dynamics of a characteristic electron, a theory based on a single free parameter is constructed to predict when the transition between stationary and nonstationary states occurs. In agreement with the previous numerical results, the theory indicates that for vanishing temperatures the system never reaches the time independent stationary state in the space charge limited regime. Nevertheless, as the injection temperature is raised it is found a broad range of system parameters for which the stationary state is indeed attained. By properly adjusting the free parameter in the theory, one can be able to describe, to a very good accuracy, when the transition occurs.
Modified sparse regularization for electrical impedance tomography
Authors: Fan Wenru , Wang Huaxiang , Xue Qian , Cui Ziqiang , Sun Benyuan , Wang Qi
Published: March 2016

Electrical impedance tomography (EIT) aims to estimate the electrical properties at the interior of an object from current-voltage measurements on its boundary. It has been widely investigated due to its advantages of low cost, non-radiation, non-invasiveness, and high speed. Image reconstruction of EIT is a nonlinear and ill-posed inverse problem. Therefore, regularization techniques like Tikhonov regularization are used to solve the inverse problem. A sparse regularization based on L1 norm exhibits superiority in preserving boundary information at sharp changes or discontinuous areas in the image. However, the limitation of sparse regularization lies in the time consumption for solving the problem. In order to further improve the calculation speed of sparse regularization, a modified method based on separable approximation algorithm is proposed by using adaptive step-size and preconditioning technique. Both simulation and experimental results show the effectiveness of the proposed method in improving the image quality and real-time performance in the presence of different noise intensities and conductivity contrasts.
Exquisite growth control and magnetic properties of yttrium iron garnet thin films
Authors: Tang Chi , Aldosary Mohammed , Jiang Zilong , Chang Houchen , Madon Benjamin , Chan Kyle , Wu Mingzhong , Garay Javier E. , Shi Jing
Published: March 2016

A layer-by-layer epitaxial growth up to 227 atomic layers of ferrimagnetic insulator yttrium iron garnet (YIG) thin films is achieved on (110)-oriented gadolinium gallium garnet substrates using pulsed laser deposition. Atomically smooth terraces are observed on YIG films up to 100 nm in thickness. The root-mean-square roughness is as low as 0.067 nm. The easy-axis lies in the film plane, indicating the dominance of shape anisotropy. For (110)-YIG films, there is well-defined two-fold in-plane anisotropy, with the easiest axis directed along [001]. The Gilbert damping constant is determined to be 1.0 × 10−4 for 100 nm thick films.
Lanthanide-based laser-induced phosphorescence for spray diagnostics
Authors: van der Voort D. D. , Maes N. C. J. , Lamberts T. , Sweep A. M. , van de Water W. , Kunnen R. P. J. , Clercx H. J. H. , van Heijst G. J. F. , Dam N. J.
Published: March 2016

Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (∼1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.
Subgap time of flight: A spectroscopic study of deep levels in semi-insulating CdTe:Cl
Authors: Pousset J. , Farella I. , Gambino S. , Cola A.
Published: March 2016

We report on a study of deep levels in semi-insulating CdTe:Cl by means of a time-of-flight spectral approach. By varying the wavelength of a pulsed optical source within the CdTe energy gap, transitions to/from localized levels generate free carriers which are analysed through the induced photocurrent transients. Both acceptor-like centers, related to the A-center, and a midgap level, 0.725 eV from the valence band, have been detected. The midgap level is close to the Fermi level and is possibly a recombination center responsible for the compensation mechanism. When the irradiance is varied, either linear or quadratic dependence of the electron and hole collected charge are observed, depending on the dominant optical transitions. The analysis discloses the potentiality of such a novel approach exploitable in the field of photorefractive materials as well as for deep levels spectroscopy.
Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics
Authors: Li Fangzuo , Liu Zhiguo , Sun Tianxi , Jiang Bowen , Zhu Yu
Published: March 2016

We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis.
Relaxation of hot and massive tracers using numerical solutions of the Boltzmann equation
Authors: Khurana Saheba , Thachuk Mark
Published: March 2016

A numerical method using B-splines is used to solve the linear Boltzmann equation describing the energy relaxation of massive tracer particles moving through a dilute bath gas. The smooth and rough hard sphere and Maxwell molecule models are used with a variety of mass ratios and initial energies to test the capability of the numerical method. Massive tracers are initialized with energies typically found in energy loss experiments in mass spectrometry using biomolecules. The method is also used to examine the applicability of known expressions for the kinetic energy decay from the Fokker-Planck equation for the Rayleigh gas, where we find that results are generally good provided that the initial energy is properly bounded. Otherwise, the energy decay is not constant and a more complex behaviour occurs. The validity of analytical expressions for drag coefficients for spherical particles under specular and diffuse scattering is also tested. We find such expressions are generally good for hard spheres but cannot account, as expected, for the softer repulsive walls of the Maxwell (and real) molecules. Overall, the numerical method performed well even when tracers more than 400 times as massive as the bath were initialized with energies very far from equilibrium. This is a range of applicability beyond many of the standard methods for solving the Boltzmann equation.
Clustering and turbophoresis in a shear flow without walls
Authors: De Lillo Filippo , Cencini Massimo , Musacchio Stefano , Boffetta Guido
Published: March 2016

We investigate the spatial distribution of inertial particles suspended in the bulk of a turbulent inhomogeneous flow. By means of direct numerical simulations of particle trajectories transported by the turbulent Kolmogorov flow, we study large and small scale mechanisms inducing inhomogeneities in the distribution of heavy particles. We discuss turbophoresis both for large and weak inertia, providing heuristic arguments for the functional form of the particle density profile. In particular, we argue and numerically confirm that the turbophoretic effect is maximal for particles of intermediate inertia. Our results indicate that small-scale fractal clustering and turbophoresis peak in different ranges in the particles’ Stokes number and the separation of the two peaks increases with the flow’s Reynolds number.
Time-domain model of gyroklystrons with diffraction power input and output
Authors: Ginzburg N. S. , Rozental R. M. , Sergeev A. S. , Zotova I. V.
Published: March 2016

A time-domain theory of gyroklystrons with diffraction input and output has been developed. The theory is based on the description of the wave excitation and propagation by a parabolic equation. The results of the simulations are in good agreement with the experimental studies of two-cavity gyroklystrons operating at the first and second cyclotron harmonics. Along with the basic characteristics of the amplification regimes, such as the gain and efficiency, the developed method makes it possible to define the conditions of spurious self-excitation and frequency-locking by an external signal.
Ultrashort megaelectronvolt positron beam generation based on laser-accelerated electrons
Authors: Xu Tongjun , Shen Baifei , Xu Jiancai , Li Shun , Yu Yong , Li Jinfeng , Lu Xiaoming , Wang Cheng , Wang Xinliang , Liang Xiaoyan , Leng Yuxin , Li Ruxin , Xu Zhizhan
Published: March 2016

Experimental generation of ultrashort MeV positron beams with high intensity and high density using a compact laser-driven setup is reported. A high-density gas jet is employed experimentally to generate MeV electrons with high charge; thus, a charge-neutralized MeV positron beam with high density is obtained during laser-accelerated electrons irradiating high-Z solid targets. It is a novel electron–positron source for the study of laboratory astrophysics. Meanwhile, the MeV positron beam is pulsed with an ultrashort duration of tens of femtoseconds and has a high peak intensity of 7.8 × 1021 s−1, thus allows specific studies of fast kinetics in millimeter-thick materials with a high time resolution and exhibits potential for applications in positron annihilation spectroscopy.
Laser-plasma interactions with a Fourier-Bessel particle-in-cell method
Authors: Andriyash Igor A. , Lehe Remi , Lifschitz Agustin
Published: March 2016

A new spectral particle-in-cell (PIC) method for plasma modeling is presented and discussed. In the proposed scheme, the Fourier-Bessel transform is used to translate the Maxwell equations to the quasi-cylindrical spectral domain. In this domain, the equations are solved analytically in time, and the spatial derivatives are approximated with high accuracy. In contrast to the finite-difference time domain (FDTD) methods, that are used commonly in PIC, the developed method does not produce numerical dispersion and does not involve grid staggering for the electric and magnetic fields. These features are especially valuable in modeling the wakefield acceleration of particles in plasmas. The proposed algorithm is implemented in the code PLARES-PIC, and the test simulations of laser plasma interactions are compared to the ones done with the quasi-cylindrical FDTD PIC code CALDER-CIRC.
Note: Enhancing the sensitivity of roll-angle measurement with a novel interferometric configuration based on waveplates and folding mirror
Authors: Qi J. , Wang Z. , Huang J. H. , Yu B. , Gao J. , Donati S.
Published: March 2016

A novel method for very high resolution measurement of roll angle on a transparent plate is developed theoretically and tested experimentally. The new optical configuration is based on the interferometric readout of phase shift accumulated on the double passage through half wave plate, together with a careful control of polarization state by means of quarter wave plate, and optimizing the tilt of the folding mirror. Sensitivity to roll angle is greatly enhanced and a gain coefficient exceeding 700 is found theoretically, based on Jones’ matrix analysis, with a 6-fold increase respect to previous results. In the experimental setup, at the optimum 36° incidence to retroreflector, we measured a gain coefficient of 340. Correspondingly, with an interferometer phase meter resolving 0.01°, a roll-angle resolution 0.1-arc sec is attained.
Investigation of 0.38 THz backward-wave oscillator based on slotted sine waveguide and pencil electron beam
Authors: Zhang Luqi , Wei Yanyu , Wang Bing , Shen Wenan , Xu Jin , Gong Yubin , Park Gun-Sik
Published: March 2016

A novel backward wave oscillator (BWO) is presented by utilizing a slotted sine waveguide with a pencil electron beam to produce the high power terahertz wave. The high frequency characteristics including dispersion properties, interaction impedances, and transmission characteristics of the slotted sine waveguide are analyzed in detail. The high frequency system including the output coupler, slow wave structure (SWS), and reflector are designed properly. A 3-D particle-in-cell mode is applied to predict the device performance of the BWO based on the novel SWS. The investigation results demonstrate that this device can generate over 8.05 W output power in the frequency range of 363.4–383.8 GHz by using a 30 mA pencil electron beam and adjusting the beam voltage from 20 kV to 32 kV.
GaAs/GaP quantum dots: Ensemble of direct and indirect heterostructures with room temperature optical emission
Authors: Dadgostar S. , Schmidtbauer J. , Boeck T. , Torres A. , Martínez O. , Jiménez J. , Tomm J. W. , Mogilatenko A. , Masselink W. T. , Hatami F.
Published: March 2016

We describe the optical emission and the carrier dynamics of an ensemble of self-assembled GaAs quantum dots embedded in GaP(001). The QD formation is driven by the 3.6% lattice mismatch between GaAs and GaP in the Stranski-Krastanow mode after deposition of more than 1.2 monolayers of GaAs. The quantum dots have an areal density between 6 and 7.6 × 1010 per cm−2 and multimodal size distribution. The luminescence spectra show two peaks in the range of 1.7 and 2.1 eV. The samples with larger quantum dots have red emission and show less thermal quenching compared with the samples with smaller QDs. The large QDs luminescence up to room temperature. We attribute the high energy emission to indirect carrier recombination in the thin quantum wells or small strained quantum dots, whereas the low energy red emission is due to the direct electron-hole recombination in the relaxed quantum dots.
Ultrafast magneto-photocurrents as probe of anisotropy relaxation in GaAs
Authors: Schmidt Christian B. , Priyadarshi Shekhar , Pierz Klaus , Bieler Mark
Published: March 2016

We induce ultrafast photocurrents in a GaAs crystal exposed to a magnetic field by optical femtosecond excitation. The magneto-photocurrents are studied by time-resolved detection of the simultaneously emitted THz radiation. We find that their dynamics differ considerably from the dynamics of other photocurrents which are expected to follow the temporal shape of the optical intensity. We attribute this difference to the influence of carrier-anisotropy relaxation on the magneto-photocurrents. Our measurements show that the anisotropy relaxation for carrier densities ranging between 1016cm−3 and 5×1017cm−3 occurs on two different time scales. While the slow time constant is approximately 100 fs long and most likely governed by electron-phonon scattering, the fast time constant is on the order of 10 fs and presumably linked to the valence band. Our studies not only help to better understand the microscopic origins of optically induced currents but—being even more important—show that magneto-photocurrents can be employed as a probe of anisotropy relaxation in GaAs. This technique is applicable to all non-centrosymmetric bulk semiconductors.
Separating inverse spin Hall voltage and spin rectification voltage by inverting spin injection direction
Authors: Zhang Wenxu , Peng Bin , Han Fangbin , Wang Qiuru , Soh Wee Tee , Ong Chong Kim , Zhang Wanli
Published: March 2016

We develop a method for universally resolving the important issue of separating the inverse spin Hall effect (ISHE) from the spin rectification effect (SRE) signal. This method is based on the consideration that the two effects depend on the spin injection direction: The ISHE is an odd function of the spin injection direction while the SRE is independent on it. Thus, the inversion of the spin injection direction changes the ISHE voltage signal, while the SRE voltage remains. It applies generally to analyzing the different voltage contributions without fitting them to special line shapes. This fast and simple method can be used in a wide frequency range and has the flexibility of sample preparation.
Terahertz GaAs/AlAs quantum-cascade lasers
Authors: Schrottke L. , Lü X. , Rozas G. , Biermann K. , Grahn H. T.
Published: March 2016

We have realized GaAs/AlAs quantum-cascade lasers operating at 4.75 THz exhibiting more than three times higher wall plug efficiencies than GaAs/Al0.25Ga0.75As lasers with an almost identical design. At the same time, the threshold current density at 10 K is reduced from about 350 A/cm2 for the GaAs/Al0.25Ga0.75As laser to about 120 A/cm2 for the GaAs/AlAs laser. Substituting AlAs for Al0.25Ga0.75As barriers leads to a larger energy separation between the subbands reducing the probability for leakage currents through parasitic states and for reabsorption of the laser light. The higher barriers allow for a shift of the quasi-continuum of states to much higher energies. The use of a binary barrier material may also reduce detrimental effects due to the expected composition fluctuations in ternary alloys.
The effects of substituting Ag for In on the magnetoresistance and magnetocaloric properties of Ni-Mn-In Heusler alloys
Authors: Pandey Sudip , Quetz Abdiel , Aryal Anil , Dubenko Igor , Samanta Tapas , Mazumdar Dipanjan , Stadler Shane , Ali Naushad
Published: March 2016

The effect of substituting Ag for In on the structural, magnetocaloric, and thermomagnetic properties of Ni50Mn35In15−xAgx (x = 0.1, 0.2, 0.5, and 1) Heusler alloys was studied. The magnitude of the magnetization change at the martensitic transition temperature (TM) decreased with increasing Ag concentration. Smaller magnetic entropy changes (ΔSM) were observed for the alloys with larger Ag concentrations and the martensitic transition shifted to higher temperature. A shift of TM by about 25 K to higher temperature was observed for an applied hydrostatic pressure of P = 6.6 kbar with respect to ambient pressure. A large drop in resistivity was observed for large Ag concentration. The magnetoresistance was dramatically suppressed due to an increase in the disorder of the system with increasing Ag concentration. Possible mechanisms responsible for the observed behavior are discussed.
Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes
Authors: Ma Ying , Wang Xiaoqian , Srivastava A. K. , Chigrinov V. G. , Kwok H.-S.
Published: March 2016

In this article, we reveal a theoretical and experimental illustration of the Ferroelectric liquid crystal (FLC) grating fabricated by mean of patterned alignment based on photo-alignment. The complexity related to the mismatching of the predefined alignment domains on the top and bottom substrate has been avoided by incorporating only one side photo aligned substrate while the other substrate does not have any alignment layer. Depending on the easy axis in the said alignment domains and the azimuth plane of the impinging polarized light, the diffracting element can be tuned in two modes i.e. DIFF/OFF switchable and DIFF/TRANS switchable modes, which can be applied to different applications. The diffraction profile has been illustrated theoretically that fits well with the experimental finding and thus the proposed diffraction elements with fast response time and high diffraction efficiency could find application in many modern devices.
Exploring Aboriginal patients’ experiences of cardiac care at a major metropolitan hospital in Melbourne
Authors: Worrall-Carter Linda , Daws Karen , Rahman Muhammad Aziz , MacLean Sarah , Rowley Kevin , Andrews Shawana , MacIsaac Andrew , Lau Phyllis M. , McEvedy Samantha , Willis John , Arabena Kerry
Published: March 2016

Objectives The aim of the present study was to explore Aboriginal patients’ lived experiences of cardiac care at a major metropolitan hospital in Melbourne. Methods The study was a qualitative study involving in-depth interviews with a purposive sample of 10 Aboriginal patients who had been treated in the cardiology unit at the study hospital during 2012–13. A phenomenological approach was used to analyse the data. Results Eight themes emerged from the data, each concerning various aspects of participants’ experiences: ‘dislike of hospitals’, ‘system failures’, ‘engagement with hospital staff’, ‘experiences of racism’, ‘health literacy and information needs’, ‘self-identifying as Aboriginal’, ‘family involvement in care’ and ‘going home and difficulties adapting’. Most participants had positive experiences of the cardiac care, but hospitalisation was often challenging because of a sense of dislocation and disorientation. The stress of hospitalisation was greatly mediated by positive engagements with staff, but at times exacerbated by system failures or negative experiences. Conclusion Cardiac crises are stressful and hospital stays were particularly disorienting for Aboriginal people dislocated from their home land and community. What is known about the topic? Aboriginal people have higher mortality rates due to cardiovascular diseases compared with other Australians. Along with different factors contributing to the life expectancy gap, Aboriginal people also face significant barriers in the use of the healthcare system. What does this paper add? Aboriginal patients’ lived experience of cardiac care at a major metropolitan hospital in Melbourne is explored in this paper. Different issues were revealed during their interaction with the hospital staff and the hospital system in conjunction with their cultural aspect of patient care. What are the implications for practitioners? Positive interactions with staff, ongoing support from family and community, culturally appropriate cardiac rehabilitation programs can improve the cardiac care experiences of Aboriginal patients.
Paediatric emergency department referrals from primary care
Authors: Turbitt Erin , Freed Gary Lee
Published: March 2016

Background Over the last decade, paediatric referrals from general practitioners (GPs) to the emergency department (ED) have increased by 60% in Australia. Objective To investigate the characteristics of Victorian children referred by GPs to the ED with lower-urgency conditions. Method Data were collected from four hospital EDs in Victoria, May–November 2014. Parents attending the ED with their child triaged as lower urgency were surveyed. Descriptive, frequency, and bivariate analyses were performed. Results Of the 1150 responses, 28% (320) visited their GP before attending ED. Of these 66% (212), were referred by their GP. A greater proportion with injury than illness (84% vs 59%; P < 0.0001) was referred to the ED if they had first visited their GP. Conclusion Motivations of GPs to send lower-urgency injured and ill children to ED are not well understood. The high number of referrals from GPs to the ED for lower urgency conditions suggests attention by policy makers and health professionals must be paid to the current patterns of care of children in general practice. What is known about the topic? Paediatric referrals in Australia from GPs to EDs have increased in the last decade, along with the absolute number of children in Victoria presenting to the ED. What does this paper add? A significant number of children (66%) who attend the GP before visiting the ED are referred to the ED for their lower urgency condition. What are the implications for practitioners? It may be appropriate for GPs to be further supported to manage lower urgency conditions, through better resources or education.
Meat quality traits of Nellore bulls according to different degrees of backfat thickness: a multivariate approach
Authors: Baldassini W. A. , Chardulo L. A. L. , Silva J. A. V. , Malheiros J. M. , Dias V. A. D. , Espigolan R. , Baldi F. S. , Albuquerque L. G. , Fernandes T. T. , Padilha P. M.
Published: March 2016

Subcutaneous fat deposition measured as backfat thickness (BFT) increases protection for the bovine carcass during cooling, conferring to BFT an important characteristic for the meat industry. To study the influence of BFT on meat quality traits of Nellore bulls (Bos indicus), data from 1652 animals aged 20–24 months in feedlot finishing were used. The principal component analysis (PCA) was performed to characterise meat quality variables in longissimus thoracis muscle. Measurements comprised the rib eye area, BFT, marbling, shear force, myofibril fragmentation index, cooking losses, intramuscular lipid content and colour (lightness, yellowness, redness, chromaticity and hue). Considering BFT as a separation criterion, the K-means cluster analysis was applied to classify beef samples. The first four PC explained roughly 66% of total variability and meat colour (yellowness and chromaticity) was more effective to define the first PC. Tenderness or toughness (shear force and cooking losses) and fatness (BFT and intramuscular lipid content) were more effective to define the second and third PC, respectively. Three BFT groups were formed and projected in the gradient defined by PC 2 and PC 3. BFT means in the clusters were 10.82 ± 3.19 (I), 5.03 ± 1.01 (II) and 2.54 ± 0.63 (III) mm with 185, 947 and 520 animals in each group, respectively. The projection of I, II and III in the gradient allowed to distinguish fatness between beef samples and tenderness between I and III. Additionally, 57.32% of animals (Group II) were placed between the two previous groups. Beef samples with higher values of shear force and cooking losses (tough meat) showed lower BFT and myofibril fragmentation index values, possibly due to fibre shortening. PCA and K-means cluster analysis presented as interesting multivariate techniques to identify Nellore bulls regarding meat quality as some of the traits used in the study are difficult to measure. The three-cluster solution represented the main biological type of Nellore bulls finished on feedlot in Brazil showing that only 11.2% of beef samples (Cluster I) can be considered tender. This information can be useful for breeding programs of Nellore bulls. In this study, Cluster I shows optimal beef quality (SF = 4.52 ± 1.17 kg) with better marbling level and less cooking losses. Nellore cattle producers should target BFT at least 5.00 mm to prevent fibre shortening. However, the only condition which provides optimal beef tenderness (i.e. shear force values lower than 4.9 kg) was found in Cluster I. The BFT does not seem to be a suitable characteristic for the selection of animals to improve tenderness due the weak relationship between BFT and shear force.
Effect of iron source on iron absorption by in situ ligated intestinal loops of broilers
Authors: Li Xiaofei , Zhang Lingyan , Zhang Liyang , Lu Lin , Luo Xugang
Published: March 2016

Two experiments were conducted to investigate the effect of iron (Fe) source on Fe absorption by in situ ligated intestinal loops of broilers. In Experiment 1, in situ ligated intestinal loops from Fe-deficient chicks (29 days old) were perfused with solutions containing 0.45 mmol Fe/L from FeSO4 (FeSO4·7H2O), Fe-Gly chelate, Fe-Met chelate, one of three Fe-amino acid or protein complexes with weak, moderate or extremely strong complex strength (Fe-Met W, Fe-Pro M, or Fe-Pro ES), or the mixtures of FeSO4 with either Gly or Met (Fe + Gly or Fe + Met), respectively, up to 30 min. In Experiment 2, in situ ligated duodenal loops from Fe-deficient chicks (29 days old) were perfused with solutions containing 0–3.58 mmol Fe/L from FeSO4, Fe-Met W, Fe-Pro M, or Fe-Pro ES up to 30 min. The absorptions of Fe from both inorganic and organic Fe sources in the ligated duodenum were ~1.35–2.8 times higher (P < 0.05) than that in the ligated jejunum or ileum. The absorption of Fe as Fe-Pro M or Fe-Pro ES was higher (P < 0.05) than that of Fe as inorganic Fe or Fe-Met W at Fe concentration of 3.58 mmol/L. The absorption kinetics of Fe from organic and inorganic Fe sources in the ligated duodenal loops followed a saturable process as determined by regression analysis of concentration-dependent absorption rates. The maximum absorption rate and Michaelis–Menten constant values in the ligated duodenal loops were higher (P < 0.05) for Fe-Pro M and Fe-Pro ES than for FeSO4 and Fe-Met W. The results from this study indicate that the duodenum was the main site of Fe absorption in the intestines of broilers; organic Fe sources with stronger complex strength values showed higher Fe absorptions at a higher concentration of added Fe; and the simple mixture of FeSO4 with amino acids did not increase Fe absorption.
Incidental impacts from major road construction on one of Asia’s most important wetlands: the Inner Gulf of Thailand
Authors: Tantipisanuh Naruemon , Gale George A. , Round Philip D.
Published: March 2016

Large-scale infrastructure development projects can have devastating impacts upon biodiversity. We investigated the impacts of roads on land-use change in a coastal area of South-east Asia, an area of high biodiversity subject to intense human pressure. The objectives of this study were (1) to examine impacts of major roads on rates of land-use change and habitat conversion in and around the Inner Gulf of Thailand, a large wetland of international importance; and (2) to evaluate the conversion rate of salt-pans (a critical habitat for several species of threatened shorebirds) between 1990 and 2011. Nine land-use types were categorised into two groups: seminatural and human-dominated. Proportions of each land-use type at different distances from major roads were determined using GIS data. More than 40% of the area was used for aquaculture during the entire study period. The amount of seminatural habitats was positively correlated with distance from major roads. Agriculture and urban areas showed the greatest changes in area (decreasing and increasing, respectively). Habitats that changed from seminatural to human-dominated were negatively correlated with distance from major roads. Most of the converted salt-pans were lost to aquaculture. To protect important wetlands from further biodiversity loss: (1) new major road construction should be avoided or minimised; and (2) land-use strategies that both satisfy short-term human needs and maintain ecosystem capacity to provide services in the long term should be adopted.
Local effect of lysophosphatidic acid on prostaglandin production in the bovine oviduct
Authors: Yoshimoto Yuka , Kobayashi Yoshihiko , Woclawek-Potocka Izabela , Sinderewicz Emilia , Yamamoto Yuki , Kimura Koji , Okuda Kiyoshi
Published: March 2016

The mammalian oviduct plays an important role in the fertilisation and transport of gametes and embryo. Prostaglandins (PGs) are local mediators of oviductal functions and are involved in fertilisation and the transport of gametes and embryo. Lysophosphatidic acid (LPA), a kind of phospholipid, is involved in various physiological actions. We hypothesised that LPA regulates PG production in the bovine oviduct. To test this hypothesis, we examined the mRNA expression of LPA receptors (LPAR1–6) and LPA-producing enzymes (ATX, PLA1α, PLA1β) in ampullary and isthmic tissues and in cultured epithelial and stromal cells isolated from the bovine oviduct. We also investigated the effects of LPA on PG synthase expression and PG production in cultured cells. The mRNA of LPAR1–4, 6, ATX and PLA1α were expressed in cultured epithelial and stromal cells. The expressions of LPAR1–3 were significantly lower and the expression of LPAR4 was significantly higher in the isthmic than in the ampullary tissues. Lysophosphatidic acid significantly stimulated PG production in the cultured isthmic stromal cells. The overall findings suggest that LPA stimulates PG production via LPAR4 in the bovine oviduct. Since PGs are important for fertilisation and the transport of gametes and embryo, these findings show that locally produced LPA regulates oviductal functions.
Population-based 3D genome structure analysis reveals driving forces in spatial genome organization
Authors: Tjong Harianto , Li Wenyuan , Kalhor Reza , Dai Chao , Hao Shengli , Gong Ke , Zhou Yonggang , Li Haochen , Zhou Xianghong Jasmine , Le Gros Mark A. , Larabell Carolyn A. , Chen Lin , Alber Frank
Published: March 2016

Significance

We provide a method for population-based structure modeling of whole diploid genomes using Hi-C data. The method considers the stochastic nature of chromosome structures, which allows a detailed analysis of the dynamic landscape of genome organizations. We predict and experimentally validate the presence of chromosome-specific higher-order centromere clusters, which can play a key role in the spatial organization of the human genome, specifically influencing the overall chromosome positioning, as well as the preference of specific chromosome conformations. Our approach generate predictive structural models of diploid genomes from Hi-C data, which can provide insights into the guiding principles of 3D genome organizations.
Global characterization of in vivo enzyme catalytic rates and their correspondence to in vitro
k
cat
measurements
Authors: Davidi Dan , Noor Elad , Liebermeister Wolfram , Bar-Even Arren , Flamholz Avi , Tummler Katja , Barenholz Uri , Goldenfeld Miki , Shlomi Tomer , Milo Ron
Published: March 2016

Significance

The
k
cat
values of enzymes are important for the study of metabolic systems. However, the current use of
k
cat
presents major difficulties, as values for most enzymes have not been experimentally measured, and experimentally available values are often measured under nonphysiological conditions, thereby casting doubt on the relevance of
k
cat
under in vivo conditions. We present an approach that utilizes omics data to quantitatively analyze the relationship between in vitro
k
cat
values and the maximal catalytic rate of enzymes in vivo. Our approach offers a high-throughput method to obtain enzyme kinetic constants, which reflect in vivo conditions, and are useful for more accurate and complete cellular metabolic models.