bluuebunny/crossref_metadata_2025 huggingface dataset:
Angular frequency variations at microgrids and its impact on measuring instruments performance
Authors: Tarasiuk Tomasz
Published: June 2016

The aim of this study is to discuss the challenges that will be faced by the designers of measuring instruments in future, in the wake of the proliferation of microgrids. In this context, the fluctuations in the angular frequency of the fundamental component of the voltage and the resulting changes in the duration of the measurement windows are considered. The main objective of this study is to consider this variation in the angular frequency from the point of view of the IEC Standard 61000‐4‐7, using real signals. Numerous results from the experiments conducted in 11 electric power networks, chiefly marine microgrids, are presented, and discussed. A comparative analysis of the behaviour of two measuring instruments is also provided. Both the instruments are based on different signal processing principles. One of them utilises the signal processing method recommended in the IEC 61000‐4‐7 standard, whereas, the other is based on the application of the chirp z‐transform principle.
Non‐local‐based spatially constrained hierarchical fuzzy C‐means method for brain magnetic resonance imaging segmentation
Authors: Chen Yunjie , Li Jian , Zhang Hui , Zheng Yuhui , Jeon Byeungwoo , Wu Qingming Jonathan
Published: June 2016

Owing to the existence of noise and intensity inhomogeneity in brain magnetic resonance (MR) images, the existing segmentation algorithms are hard to find satisfied results. In this study, the authors propose an improved fuzzy C‐mean clustering method (FCM) to obtain more accurate results. First, the authors modify the traditional regularisation smoothing term by using the non‐local information to reduce the effect of the noise. Second, inspired by the mechanism of the Gaussian mixture model, the distance function of FCM is defined by using the form of certain exponential function consisting of not only the distance but also the covariance and the prior probability to improve the robustness. Meanwhile, the bias field is modelled by using orthogonal basis functions to reduce the effect of intensity inhomogeneity. Finally, they use the hierarchical strategy to construct a more flexibility function, which considers the improved distance function itself as a sub‐FCM, to make the method more robust and accurate. Compared with the state‐of‐the‐art methods, experiment results based on synthetic and real MR images demonstrate its accuracy and robustness.
Low‐profile antenna for millimetre‐wave chip‐to‐chip communication
Authors: Chung Jae‐Young
Published: June 2016

Here, the authors report a low‐profile antenna for millimetre‐wave chip‐to‐chip communication. The height of the proposed antenna is limited to 0.18 mm, 1/20 wavelength at 80 GHz. To realise such a low profile, a zeroth‐order resonator antenna with a periodic array of four unit cells was employed, and its geometry was optimised using a full‐wave simulation tool to cover an 8 GHz bandwidth from 76 to 84 GHz. With this, the antenna was capable of radiating in the end‐fire direction parallel to the board length despite the short distance between the ground and the radiator. Simulation and measurement results showed that the optimised design had low reflection coefficients and consistent radiation patterns throughout the target bandwidth.
Dual‐loop antenna with band‐stop matching circuit for WWAN/LTE full metal‐rimmed smartphone application
Authors: Yan Yi , Ban Yong‐Ling , Wu Gang , Sim Chow‐Yen‐Desmond
Published: June 2016

A dual‐loop antenna for hepta‐band wireless wide area network (WWAN)/long term evolution (LTE) narrow‐frame full metal‐rimmed smartphone application is proposed and studied. Compared with recent reported works, the main advantage of this design is the ability to achieve narrow‐frame (smaller ground clearance) with unbroken metal‐rim (or full metal‐rimmed). Due to the modification of top no‐ground portion, a band‐stop matching circuit is used in this case to compensate the impedance mismatch caused by this modification. By combining the six resonant modes induced by the proposed dual‐loop structure with the additional lower resonant mode excited by the matching circuit, the proposed antenna can successfully cover both WWAN bands (GSM850/900/DCS/PCS/UMTS2100) and LTE bands (LTE2300/2500). A prototype of the proposed antenna is fabricated, and the obtained results including reflection coefficients, efficiencies and gains are also presented and discussed.
Review of grid‐tied converter topologies used in photovoltaic systems
Authors: Xiao Weidong , El Moursi Mohamed S. , Khan Omair , Infield David
Published: June 2016

This study provides review of grid‐tied architectures used in photovoltaic (PV) power systems, classified by the granularity level at which maximum power point tracking (MPPT) is applied. Grid‐tied PV power systems can be divided into two main groups, namely centralised MPPT and distributed MPPT (DMPPT). The DMPPT systems are further classified according to the levels at which MPPT can be applied, i.e. string, module, submodule, and cell level. Typical topologies for each category are also introduced, explained and analysed. The classification is intended to help readers understand the latest developments of grid‐tied PV power systems and inform research directions.
Combination of moment‐matching, Cholesky and clustering methods to approximate discrete probability distribution of multiple wind farms
Authors: Li Jinghua , Zhu Dunlin
Published: June 2016

This study focuses on approximating a reduced discrete probability distribution (RDPD) of wind power from the original discrete probability distribution (ODPD), consisting of a large number of observed original scenarios (OSs), to relieve the burden of solving stochastic programs of wind power generation. The proposed method, namely, the MMCC method, aims to achieve high approximation accuracy and computational efficiency by combining an improved moment‐matching (MM) method with the clustering (C) method and the Cholesky decomposition (CD) method. First, the C method is used to reduce the number of OSs by minimising the space distance between the reduced scenarios (RSs) and the OSs. Next, the CD method is used to rectify the correlation of the RSs to satisfy that of the ODPD. Finally, the RS probabilities are optimally determined by the MM method in order to minimise the stochastic features (first four moments and correlation matrix) between the RDPD and the ODPD. Simulations of RDPD approximation for three wind farms with 10, 20, 40, 60, 80, and 100 scenarios were carried out using the Latin hypercube sampling, importance sampling, C, moment‐matching‐clustering (MMC), and MMCC methods. The results showed that the MMCC method exhibits the best performance in terms of capturing the features of the ODPD.
Segmented packed beds for improved thermal energy storage performance
Authors: McTigue Joshua D. , White Alexander J.
Published: June 2016

A scheme for bulk electricity storage known as Pumped Thermal Energy Storage (PTES) is described. PTES uses a heat pump during the charging phase to create a hot and a cold storage space. During discharge, these thermal stores are depleted using a heat engine. This version of PTES uses packed beds (or pebble beds) as the energy store. A relatively new design feature which involves segmenting the packed beds is introduced. Various thermodynamic benefits can be achieved by reservoir segmentation, such as reduced pressure losses and increased energy stored per cycle. This report includes modelling of the storage phases, and it is found that segmentation can reduce the thermal equilibration losses that occur. A simple economic model of the PTES system is introduced so that multi‐objective optimisation of efficiency and capital costs can be carried out. Sensitivity to the economic factors is briefly explored. The results show that cold packed beds in particular benefit from being segmented.
Magnetic equivalent circuit modelling of doubly‐fed induction generator with assessment of rotor inter‐turn short‐circuit fault indices
Authors: Faiz Jawad , Moosavi Seyed M.M. , Abadi Mohsen B. , Cruz Sérgio M.A.
Published: June 2016

In this study, a wound rotor induction machine, as the core of a doubly‐fed induction generator (DFIG) system, is modelled using the magnetic equivalent circuit approach. The entire DFIG system is implemented in Matlab/Simulink environment, including the machine model, power converters, control system and the grid. The model, which includes the ability to simulate rotor inter‐turn short‐circuits (RITSCs), is subsequently used for the investigation and comparison of the impact of this fault in several DFIG quantities, namely in the stator current and in some control variables. This research also deals in detail with the differences found when comparing RITSC and unbalanced rotor resistance (URR) faults. It is observed that on the contrary to the URR, the stator current spectrum is more appropriate than the control signals for the detection of RITSC. Simulation and experimental results obtained with a DFIG system operating at sub‐synchronous and super‐synchronous speeds, for different values of the active and reactive powers injected into the grid, corroborate the findings reported in this study.
Passive radar source localisation based on PSAAA using single small size aircraft
Authors: Hao Benjian , Gu Liming , Li Zan , Xiao Song , Tong Lang
Published: June 2016

This study considers the problem of how to accurately and passively localise the hostile radar's position based on only one small‐size aircraft. Inspired by synthetic aperture sonar, synthetic aperture radar and multi‐static passive radar, a similar concept of passive synthetic aperture antenna array (PSAAA) is introduced in this study. The same single receiver carried by one small aircraft is virtually taken as PSAAA element at different flight track positions at multiple different moments. Taking full advantage of aircraft space movement and radar antenna circular rotation, an effective method is proposed to estimate the virtual time differences of arrival (VTDOAs). The VTDOAs are the passive localisation information defined as the time differences of the radar pulse transmission from the radar position to different virtual receivers. Based on the VTDOAs estimation, the authors propose a construction method for the binary quadratic localisation equation group, and then a closed‐form solution algorithm is given for passive radar position estimation. Simulations corroborate the performance of the proposed methods.
Design optimisation of AlGaN/GaN metal insulator semiconductor high electron mobility transistor with high‐K/low‐K compound gate dielectric layer for millimeter‐wave application
Authors: Du Jiangfeng , Hou Zehong , Pan Peilin , Bai Zhiyuan , Yu Qi
Published: June 2016

A novel high DC and radio‐frequency (RF) characteristics AlGaN/GaN metal insulator semiconductor high electron mobility transistor (MIS‐HEMT) with a high‐K/low‐K compound gate dielectric layer (CGD) is proposed. Owing to the different dielectric constants, the discontinuity of the electric field at the high‐K/low‐K interface can modulate the distribution of the electric field along the channel under gate. Hence, enhancement of DC and RF characteristics can be achieved. The optimised results of the AlGaN/GaN MIS‐HEMT with CGD structure revealed that the DC transconductance gm and the maximum saturation current Ids increased about 10.5 and 6.9% compared with the traditional AlGaN/GaN MIS‐HEMT with single high‐K gate dielectric layer (SGD), respectively. Also, the cutoff frequency ft and the maximum oscillation frequency fmax of 74.2 GHz and 129.2 GHz are obtained and improved about 18.5 and 14.7% compared with the device with SGD structure.
On modified finite difference method to obtain the electron energy distribution functions in Langmuir probes
Authors: Kang Hyun-Ju , Choi Hyeok , Kim Jae-Hyun , Lee Se-Hun , Yoo Tae-Ho , Chung Chin-Wook
Published: June 2016

A modified central difference method (MCDM) is proposed to obtain the electron energy distribution functions (EEDFs) in single Langmuir probes. Numerical calculation of the EEDF with MCDM is simple and has less noise. This method provides the second derivatives at a given point as the weighted average of second order central difference derivatives calculated at different voltage intervals, weighting each by the square of the interval. In this paper, the EEDFs obtained from MCDM are compared to those calculated via the averaged central difference method. It is found that MCDM effectively suppresses the noises in the EEDF, while the same number of points are used to calculate of the second derivative.
A novel coefficient for detecting and quantifying asymmetry of California electricity market based on asymmetric detrended cross-correlation analysis
Authors: Wang Fang
Published: June 2016

In order to detect and quantify asymmetry of two time series, a novel cross-correlation coefficient is proposed based on recent asymmetric detrended cross-correlation analysis (A-DXA), which we called A-DXA coefficient. The A-DXA coefficient, as an important extension of DXA coefficient ρDXA, contains two directional asymmetric cross-correlated indexes, describing upwards and downwards asymmetric cross-correlations, respectively. By using the information of directional covariance function of two time series and directional variance function of each series itself instead of power-law between the covariance function and time scale, the proposed A-DXA coefficient can well detect asymmetry between the two series no matter whether the cross-correlation is significant or not. By means of the proposed A-DXA coefficient conducted over the asymmetry for California electricity market, we found that the asymmetry between the prices and loads is not significant for daily average data in 1999 yr market (before electricity crisis) but extremely significant for those in 2000 yr market (during the crisis). To further uncover the difference of asymmetry between the years 1999 and 2000, a modified H statistic (MH) and ΔMH statistic are proposed. One of the present contributions is that the high MH values calculated for hourly data exist in majority months in 2000 market. Another important conclusion is that the cross-correlation with downwards dominates over the whole 1999 yr in contrast to the cross-correlation with upwards dominates over the 2000 yr.
Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene
Authors: Tabor Daniel P. , Hewett Daniel M. , Bocklitz Sebastian , Korn Joseph A. , Tomaine Anthony J. , Ghosh Arun K. , Zwier Timothy S. , Sibert Edwin L.
Published: June 2016

Conformation-specific UV-IR double resonance spectra are presented for ethyl, n-propyl, and n-butylbenzene. With the aid of a local mode Hamiltonian that includes the effects of stretch-scissor Fermi resonance, the spectra can be accurately modeled for specific conformers. These molecules allow for further development of a first principles method for calculating alkyl stretch spectra. Across all chain lengths, certain dihedral patterns impart particular spectral motifs at the quadratic level. However, the anharmonic contributions are consistent from molecule to molecule and conformer to conformer. This transferability of anharmonicities allows for the Hamiltonian to be constructed from only a harmonic frequency calculation, reducing the cost of the model. The phenyl ring alters the frequencies of the CH2 stretches by about 15 cm−1 compared to their n-alkane counterparts in trans configurations. Conformational changes in the chain can lead to shifts in frequency of up to 30 cm−1.
Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate
Authors: Leung Chung Ming , Wang Feifei , Wang Ya
Published: June 2016

A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ∼29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ∼2 times larger than the traditional L–T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise.
Hybrid PSO-ASVR-based method for data fitting in the calibration of infrared radiometer
Authors: Yang Sen , Li Chengwei
Published: June 2016

The present paper describes a hybrid particle swarm optimization-adaptive support vector regression (PSO-ASVR)-based method for data fitting in the calibration of infrared radiometer. The proposed hybrid PSO-ASVR-based method is based on PSO in combination with Adaptive Processing and Support Vector Regression (SVR). The optimization technique involves setting parameters in the ASVR fitting procedure, which significantly improves the fitting accuracy. However, its use in the calibration of infrared radiometer has not yet been widely explored. Bearing this in mind, the PSO-ASVR-based method, which is based on the statistical learning theory, is successfully used here to get the relationship between the radiation of a standard source and the response of an infrared radiometer. Main advantages of this method are the flexible adjustment mechanism in data processing and the optimization mechanism in a kernel parameter setting of SVR. Numerical examples and applications to the calibration of infrared radiometer are performed to verify the performance of PSO-ASVR-based method compared to conventional data fitting methods.
Isotope tracer investigation and ab-initio simulation of anisotropic hydrogen transport and possible multi-hydrogen centers in tin dioxide
Authors: Watanabe Ken , Sakaguchi Isao , Hashiguchi Minako , Saito Noriko , Ross Emily M. , Haneda Hajime , Ohsawa Takeo , Ohashi Naoki
Published: June 2016

Hydrogen as an impurity in single crystals of tin dioxide was investigated through diffusivity and vibrational-mode analyses performed using isotope tracers and density functional theory calculations. It was found that hydrogen diffusion along the 〈001〉 axis is very fast, even at relatively low temperatures (400 °C), but is considerably slower within the (001) plane. Using transitional state calculations, this diffusion behavior was determined to be the result of anisotropy in the migration barrier for interstitial hydrogen (Hi). In addition, the two distinct vibrational modes observed in the optical spectrum were identified as the O-H stretching modes of Hi and the substitutional hydrogen at the tin sites.
Comparing two tetraalkylammonium ionic liquids. II. Phase transitions
Authors: Lima Thamires A. , Paschoal Vitor H. , Faria Luiz F. O. , Ribeiro Mauro C. C. , Ferreira Fabio F. , Costa Fanny N. , Giles Carlos
Published: June 2016

Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.
Time resolved 3D momentum imaging of ultrafast dynamics by coherent VUV-XUV radiation
Authors: Sturm F. P. , Wright T. W. , Ray D. , Zalyubovskaya I. , Shivaram N. , Slaughter D. S. , Ranitovic P. , Belkacem A. , Weber Th.
Published: June 2016

We present a new experimental setup for measuring ultrafast nuclear and electron dynamics of molecules after photo-excitation and ionization. We combine a high flux femtosecond vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) source with an internally cold molecular beam and a 3D momentum imaging particle spectrometer to measure electrons and ions in coincidence. We describe a variety of tools developed to perform pump-probe studies in the VUV-XUV spectrum and to modify and characterize the photon beam. First benchmark experiments are presented to demonstrate the capabilities of the system.
Self-synchronization in an ensemble of nonlinear oscillators
Authors: Ostrovsky L. A. , Galperin Y. V. , Skirta E. A.
Published: June 2016

The paper describes the results of study of a system of coupled nonlinear, Duffing-type oscillators, from the viewpoint of their self-synchronization, i.e., generation of a coherent field (order parameter) via instability of an incoherent (random-phase) initial state. We consider both the cases of dissipative coupling (e.g., via the joint radiation) and reactive coupling in a Hamiltonian system.
Multiple adsorption of molecular oxygen on small Au/Pd cationic clusters at finite temperature. A van der Waals density functional study
Authors: Fernández Eva María , Balbás Luis Carlos
Published: June 2016

The adsorption of molecular oxygen on cationic bimetallic palladium/gold clusters, AunPdm+ (n + m ≤ 5), is studied by means of self-consistent density functional calculations including long range van der Waals non-local interactions. A single O2 molecule is adsorbed preferably on top of Pd sites for m = 0, 1, but bridge or hollow locations between Pd atoms are preferred for m ≥ 2. In the later cases, both the O2 electronic charge and the O–O distance increase as compared with the values for free O2, leading to negatively charged O2 superoxo species which facilitates the CO oxidation. Multiple sequential adsorption of several O2 is considered for the n + m ≤ 3 clusters, which occurs with decreasing adsorption energy, except when severe distortion of the bimetallic support appears. The Gibbs free energy of AunPd2−n+O2x complexes with n = 1–2 and x = 1–5 is computed at temperatures 0 K, 50 K, 150 K, and 300 K. We obtain that Pd2+ (PdAu+) can adsorb 5 (4) oxygen molecules at ambient temperature; however, Au2+ can adsorb up to three O2 molecules when the temperature is lower than 150 K.
Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory
Authors: Wang Hao , Yang Weitao
Published: June 2016

We developed a new method to calculate the atomic polarizabilities by fitting to the electrostatic potentials (ESPs) obtained from quantum mechanical (QM) calculations within the linear response theory. This parallels the conventional approach of fitting atomic charges based on electrostatic potentials from the electron density. Our ESP fitting is combined with the induced dipole model under the perturbation of uniform external electric fields of all orientations. QM calculations for the linear response to the external electric fields are used as input, fully consistent with the induced dipole model, which itself is a linear response model. The orientation of the uniform external electric fields is integrated in all directions. The integration of orientation and QM linear response calculations together makes the fitting results independent of the orientations and magnitudes of the uniform external electric fields applied. Another advantage of our method is that QM calculation is only needed once, in contrast to the conventional approach, where many QM calculations are needed for many different applied electric fields. The molecular polarizabilities obtained from our method show comparable accuracy with those from fitting directly to the experimental or theoretical molecular polarizabilities. Since ESP is directly fitted, atomic polarizabilities obtained from our method are expected to reproduce the electrostatic interactions better. Our method was used to calculate both transferable atomic polarizabilities for polarizable molecular mechanics’ force fields and nontransferable molecule-specific atomic polarizabilities.
Accelerating rejection-based simulation of biochemical reactions with bounded acceptance probability
Authors: Thanh Vo Hong , Priami Corrado , Zunino Roberto
Published: June 2016

Stochastic simulation of large biochemical reaction networks is often computationally expensive due to the disparate reaction rates and high variability of population of chemical species. An approach to accelerate the simulation is to allow multiple reaction firings before performing update by assuming that reaction propensities are changing of a negligible amount during a time interval. Species with small population in the firings of fast reactions significantly affect both performance and accuracy of this simulation approach. It is even worse when these small population species are involved in a large number of reactions. We present in this paper a new approximate algorithm to cope with this problem. It is based on bounding the acceptance probability of a reaction selected by the exact rejection-based simulation algorithm, which employs propensity bounds of reactions and the rejection-based mechanism to select next reaction firings. The reaction is ensured to be selected to fire with an acceptance rate greater than a predefined probability in which the selection becomes exact if the probability is set to one. Our new algorithm improves the computational cost for selecting the next reaction firing and reduces the updating the propensities of reactions.
Particle-in-cell simulation study of a lower-hybrid shock
Authors: Dieckmann M. E. , Sarri G. , Doria D. , Ynnerman A. , Borghesi M.
Published: June 2016

The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasma's expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma.
Chirp-driven giant phase space vortices
Authors: Trivedi Pallavi , Ganesh Rajaraman
Published: June 2016

In a collisionless, unbounded, one-dimensional plasma, modelled using periodic boundary conditions, formation of steady state phase space coherent structures or phase space vortices (PSV) is investigated. Using a high resolution one-dimensional Vlasov-Poisson solver based on piecewise-parabolic advection scheme, the formation of giant PSV is addressed numerically. For an infinitesimal external drive amplitude and wavenumber k, we demonstrate the existence of a window of chirped external drive frequency that leads to the formation of giant PSV. The linear, small amplitude, external drive, when chirped, is shown to couple effectively to the plasma and increase both streaming of “untrapped” and “trapped” particle fraction. The steady state attained after the external drive is turned off and is shown to lead to a giant PSV with multiple extrema and phase velocities, with excess density fraction, defined as the deviation from the Maxwellian background, Δn/n0≃20%−25%. It is shown that the process depends on the chirp time duration Δt. The excess density fraction Δn/n0, which contains both trapped and untrapped particle contribution, is also seen to scale with Δt, only inhibited by the gradient of the distribution in velocity space. Both single step drive and multistep chirp processes are shown to lead to steady state giant PSV, with multiple extrema due to embedded holes and clumps, long after the external drive is turned off.
Comment on “Static correlations functions and domain walls in glass-forming liquids: The case of a sandwich geometry” [J. Chem. Phys. 138, 12A509 (2013)]
Authors: Krakoviack Vincent
Published: June 2016

In this Comment, we argue that the behavior of the overlap functions reported in the commented paper can be fully understood in terms of the physics of simple liquids in contact with disordered substrates, without appealing to any particular glassy phenomenology. This suggestion is further supported by an analytic study of the one-dimensional Ising model provided as Supplementary Material.
Temperature-dependent resistance switching in SrTiO3
Authors: Li Jian-kun , Ma Chao , Jin Kui-juan , Ge Chen , Gu Lin , He Xu , Zhou Wen-jia , Zhang Qing-hua , Lu Hui-bin , Yang Guo-zhen
Published: June 2016

Resistance switching phenomena were studied by varying temperature in SrTiO3 single crystal. The resistance hysteresis loops appear at a certain temperature ranging from 340 K to 520 K. With the assistance of 375 nm ultraviolet continuous laser, the sample resistance is greatly reduced, leading to a stable effect than that in dark. These resistance switching phenomena only exist in samples with enough oxygen vacancies, which is confirmed by spherical aberration-corrected scanning transmission electron microscopy measurements, demonstrating an important role played by oxygen vacancies. At temperatures above 340 K, positively charged oxygen vacancies become mobile triggered by external electric field, and the resistance switching effect emerges. Our theoretical results based on drift-diffusion model reveal that the built-in field caused by oxygen vacancies can be altered under external electric field. Therefore, two resistance states are produced under the cooperative effect of built-in field and external field. However, the increasing mobility of oxygen vacancies caused by higher temperature promotes internal electric field to reach equilibrium states quickly, and suppresses the hysteresis loops above 420 K.
Broadband dielectric characterization of aqueous saline solutions by an interferometer-based microwave microscope
Authors: Gu Sijia , Lin Tianjun , Lasri Tuami
Published: June 2016

The complex dielectric permittivity of aqueous saline solutions has been determined in the frequency range [2–18 GHz] with a home-made near-field microwave microscope. The instrument is built on a vector network analyzer, a matching network, and an evanescent microwave probe. The interferometer-based matching network enables highly reproducible, sensitive, and accurate measurements on the entire frequency band of operation. NaCl solutions concentrations ranging from 0 to 160 mg/ml are investigated at 25 °C. A maximum measurement sensitivity for NaCl concentrations is found to be equal to 2.3 dB/(mg/ml) and 7.7°/(mg/ml) for magnitude and phase-shift, respectively. To translate the measurement data (S parameters) to the corresponding complex permittivities, an inversion procedure based on a simple calibration model is applied. The resulting complex permittivities are found to be in a very good agreement with those calculated by Cole-Cole model.
Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions
Authors: Tao L. L. , Wang J.
Published: June 2016

We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO3 (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that the asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.
Elastocaloric effect in poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymer
Authors: Yoshida Yukihiro , Yuse Kaori , Guyomar Daniel , Capsal Jean-Fabien , Sebald Gael
Published: June 2016

The elastocaloric properties of poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] terpolymer were directly characterized using an infrared imaging camera. At a strain of 12%, a reversible adiabatic temperature variation of 2.15 °C was measured, corresponding to an isothermal entropy variation of 21.5 kJ m−3 K−1 or 11 J kg−1 K−1. In comparison with other elastocaloric materials, P(VDF-TrFE-CTFE) appears to represent a trade-off between the large required stresses in shape memory alloys and the large required strains in natural rubber. The internal energy of the P(VDF-TrFE-CTFE) polymer was found to be independent of the strain, resulting in complete conversion of the mechanical work into heat, as for pure elastomeric materials. The elastocaloric effect therefore originates from a pure entropic elasticity, which is likely to be related to the amorphous phase of the polymer only.
Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals
Authors: Lv Yang-Yang , Zhang Bin-Bin , Li Xiao , Yao Shu-Hua , Chen Y. B. , Zhou Jian , Zhang Shan-Tao , Lu Ming-Hui , Chen Yan-Feng
Published: June 2016

Recently, the extremely large magnetoresistance (MR) observed in transition metal telluride, like WTe2, attracted much attention because of the potential applications in magnetic sensor. Here, we report the observation of extremely large magnetoresistance as 3.0 × 104% measured at 2 K and 9 T magnetic field aligned along [001]-ZrSiS. The significant magnetoresistance change (∼1.4 × 104%) can be obtained when the magnetic field is titled from [001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can be understood by electron-hole compensation and the open orbital of Fermi surface. Because of these superior MR properties, ZrSiS may be used in the magnetic sensors.
Phonon-mediated superconductivity in borophenes
Authors: Zhao Yinchang , Zeng Shuming , Ni Jun
Published: June 2016

We use first-principles calculations to systematically investigate electronic, vibrational, and superconducting properties in borophenes (boron monolayer sheets). Remarkably, superconducting transition temperature Tc is a V-like function of hexagon hole density and has a similar tendency to the variations of the total energy and density of states at the Fermi level, which shows that the larger density of states at the Fermi level corresponds to the higher Tc. In consideration of substrate, the Ag(111) surfaces weaken the superconductivity in borophenes, which results in Tcμ*=0.1 of about 5.2 K in the buckled triangular sheet. As synthesis of borophenes was reported, superconducting boron sheets are feasible.
Characterization of point defects in CdTe by positron annihilation spectroscopy
Authors: Elsharkawy M. R. M. , Kanda G. S. , Abdel-Hady E. E. , Keeble D. J.
Published: June 2016

Positron lifetime measurements on CdTe 0.15% Zn-doped by weight are presented, trapping to monovacancy defects is observed. At low temperatures, localization at shallow binding energy positron traps dominates. To aid defect identification density functional theory, calculated positron lifetimes and momentum distributions are obtained using relaxed geometry configurations of the monovacancy defects and the Te antisite. These calculations provide evidence that combined positron lifetime and coincidence Doppler spectroscopy measurements have the capability to identify neutral or negative charge states of the monovacancies, the Te antisite, A-centers, and divacancy defects in CdTe.
Magnetic moment orientation of nano-islands by electrostriction along two directions
Authors: Wang Y. , Chen Y. W. , Cao J. W. , Wang T. , Bai J. M. , Wei F. L.
Published: June 2016

This article introduces a new method to realize the 180° magnetic moment reversal of a ferromagnetic and ferroelectric heterostructure through electrostriction-induced magnetic anisotropy. A rectangular magnetic FeAl alloy island with a large magnetostrictive coefficient on a PZN (011) substrate was adopted in our investigation through micromagnetic simulation. Using electrostriction along the [11-1] and [1-11] directions, the magnetic moment was rotated from the long axis of the rectangular island to the direction of the strain and finally reversed to the opposite direction despite the strain sequence. The magnetic moment can be oriented to a certain direction through a certain sequence of strain if a several hundred Oe magnetic field is applied along the short axis of the island. The suitable stress-induced magnetic anisotropy energy and external magnetic field were also investigated. In consideration that a high magnetic field along the short axis leads to small thermal stability of the magnetic moment, the suitable value of stress-induced anisotropy energy is around the critical value where the stress can reverse the magnetic moment without a magnetic field. We compared the stress-induced magnetic reversal processes for same-sized semicircular, elliptical, and rectangular islands and found that the semicircular island can be more easily reversed.
A novel stochastic modeling method of wind power time series considering the fluctuation process characteristics
Authors: Liu Chun , Li Chi , Huang Yuehui , Wang Yuefeng
Published: June 2016

With rapid increasing of wind power generating capacity, the influence of wind power on power system planning and operation becomes more and more severe. Wind power time series modeling is the basis of evaluating the influence accurately of wind power on power system, which is very important to annual wind power dispatch planning and installed capacity optimization. In this paper, a novel modeling method of wind power time series based on the definition and identification of the fluctuation process is proposed. The Gaussian function is proved to be a good choice to sketch the fluctuation process and the visualization self-organizing map clustering algorithm is used to classify the fluctuation process. The expected wind power time series is achieved by studying the statistical feature of the sample data and by analyzing the transfer characteristic of the fluctuation processes. The comparative analysis on the statistical feature of the generated time series and the sample data is presented. In terms of the 15 min and 1 h variation, autocorrelation function, monthly mean and hourly mean of the generated wind power, the proposed method in this paper are better than the commonly used Markov Chain Monte Carlo method. The proposed method can keep the variation and process characteristic of the wind power, which is very important for the study of stochastic planning and operation of the wind power in power system.
Changes in endogenous hormones and seed-coat phenolics during seed storage of two Suaeda salsa populations
Authors: Xu Yan-ge , Liu Ranran , Sui Na , Shi Weiwei , Wang Lei , Tian Changyan , Song Jie
Published: June 2016

Changes in endogenous hormones and seed-coat phenolics during the storage of the dimorphic seeds of two Suaeda salsa populations were investigated. The results showed that, regardless of salinity, storage did not reduce the germination of brown or black seeds from an inland population, but it significantly decreased the germination of dimorphic seeds from an intertidal population. Abscisic acid (ABA) concentration was significantly higher in old seeds than in fresh seeds (freshly harvested dry seeds), whereas the opposite trend was evident for gibberellic acid (GA, including GA1 and GA3) concentration and GA : ABA ratio in both populations, and especially in the intertidal population. Concentration of seed-coat phenolics extracted from brown seeds was much higher than in black seeds in both populations, regardless of extracting time and storage. Storage increased the concentration of phenolics extracted from brown seeds in the inland population, whereas the opposite trend was evident in the intertidal population. Storage did not significantly change seed-coat phenolics extracted from black seeds relative to brown seeds in either population. The results indicated that changes in seed vigour during storage in dimorphic seeds of the two S. salsa populations are related to changes in endogenous hormones and seed-coat phenolics.
Hydrophilic Magnetite Nanoparticles Enhance Anticancer Activity of Anthracyclines In Vitro
Authors: Yang Bin , Luo Lin , Ma Ying , Chen Chunyan , Chen Xiaoming , Cai Changqun
Published: June 2016

A novel method for enhancing the anticancer activity of anthracyclines in vitro was proposed by using hydrophilic magnetic nanoparticles. Citric acid-coated magnetite nanoparticles Fe3O4 (nano-Fe3O4-CA) interacted with anthracyclines by electrostatic and hydrophobic forces, resulting in the formation of aggregates (nano-Fe3O4-CA-drug). The aggregate was studied by resonance light scattering and fluorescence spectroscopy. The results indicated that in comparison with anthracyclines, the nano-Fe3O4-CA-drug showed high activity towards incorporation in the DNA chain. Furthermore, the cytotoxicity of nano-Fe3O4-CA-drug was investigated by cytotoxicity experiment and cell morphology study. The results confirmed that the nano-Fe3O4-CA-drug could inhibit the growth of cells more effectively than the drug alone. In conclusion, usage of nano-Fe3O4-CA affords reduction of the dosage of anthracyclines in vitro.
In vivo and in vitro approaches demonstrate proline is not directly involved in the protection against superoxide, nitric oxide, nitrogen dioxide and peroxynitrite
Authors: Signorelli Santiago , Imparatta Camila , Rodríguez-Ruiz Marta , Borsani Omar , Corpas Francisco J. , Monza Jorge
Published: June 2016

Plants accumulate proline under diverse types of stresses, and it has been suggested that this α-amino acid has the capacity to protect against oxidative stress. However, it is still controversial whether its protection is due to the direct scavenging of reactive oxygen species (ROS). To solve this issue and considering that nitrosative stress is directly related with an oxidative stress condition, we evaluated whether proline can protect against nitrosative damage. Using proteins of Lotus japonicus (Regel) K.Larsen leaves exposed to a peroxynitrite (ONOO–/ONOOH) generator in presence and absence of 100mM proline, the potential of proline to protect was analysed by the protein nitration profile and NADP-dependent isocitrate dehydrogenase activity, which is inhibited by nitration. In both cases, the presence of proline did not diminish the peroxynitrite effects. Additionally, proline biosynthesis Arabidopsis knockout (KO) mutant plants of Δ(1)-pyrroline-5-carboxylate synthetase1 (P5CS1) gene, designated as Atp5cs1-1 and Atp5cs1-4, showed similar protein nitration levels as wild-type plants under salinity-induced oxidative stress, despite mutants having higher levels of lipid oxidation, H2O2 and superoxide (O2·–). Finally, by a fluorometric assay using specific fluorescent probes, it was determined that the presence of 100mM proline did not affect the time-course content of peroxynitrite or nitric oxide generation in vitro. Our results reveal the relevance of proline accumulation in vivo under stress, but unequivocally demonstrate that proline is not a direct scavenger of peroxynitrite, superoxide, ·NO and nitrogen dioxide (·NO2).
Autonomic activity during sleep predicts memory consolidation in humans
Authors: Whitehurst Lauren N. , Cellini Nicola , McDevitt Elizabeth A. , Duggan Katherine A. , Mednick Sara C.
Published: June 2016

Significance

We present the first evidence, to our knowledge, that the autonomic nervous system (ANS) plays a role in associative memory consolidation during sleep. Compared with a Quiet Wake control condition, performance improvement was associated with vagally mediated ANS activity [as measured by high-frequency (HF) heart rate variability (HRV)] during rapid eye movement (REM) sleep. In particular, up to 73% of the proportion of improvement in associative memory performance could be accounted for by considering both traditionally reported sleep features (i.e., minutes spent in sleep stages and sleep spindles) and HF HRV. We hypothesize that central nervous system processes that favor peripheral vagal activity during REM sleep may lead to increases in plasticity that promote associative processing.
Temperature-responsive in vitro RNA structurome of
Yersinia pseudotuberculosis
Authors: Righetti Francesco , Nuss Aaron M. , Twittenhoff Christian , Beele Sascha , Urban Kristina , Will Sebastian , Bernhart Stephan H. , Stadler Peter F. , Dersch Petra , Narberhaus Franz
Published: June 2016

Significance

The RNA structure is critical for RNA function in all domains of life. We determined the transcriptome-wide RNA structurome of
Yersinia pseudotuberculosis
, a food-borne pathogen, at three physiologically relevant temperatures. Our analysis shows that mRNAs tend to have a poorly structured ribosome binding site. Transcripts that deviate from this general principle are very good candidates as translational repressor elements, and we identified 16 RNA thermometers able to control gene expression in a temperature-dependent manner. Our analysis demonstrates the power of high-throughput RNA structure probing approaches to identify new sensory and regulatory RNA structures.
Profiling DNA damage-induced phosphorylation in budding yeast reveals diverse signaling networks
Authors: Zhou Chunshui , Elia Andrew E. H. , Naylor Maria L. , Dephoure Noah , Ballif Bryan A. , Goel Gautam , Xu Qikai , Ng Aylwin , Chou Danny M. , Xavier Ramnik J. , Gygi Steven P. , Elledge Stephen J.
Published: June 2016

Significance

The DNA damage response (DDR) promotes survival and genome maintenance. It involves a network of kinases that phosphorylate a multitude of effector proteins. Although the protein kinases involved have been studied extensively, many targets remain to be discovered. We have used an unbiased approach to profile DDR phosphorylation in budding yeast. We reveal a link between DDR signaling and the metabolic pathways of inositol phosphate and phosphatidyl inositol synthesis, which are required for resistance to DNA damage. Taken together, these data shed new light on the organization of DDR signaling in budding yeast.