bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements
Authors: Riva Fabio , Vianello Nicola , Spolaore Monica , Ricci Paolo , Cavazzana Roberto , Marrelli Lionello , Spagnolo Silvia
Published: February 2018

The tokamak scrape-off layer (SOL) plasma dynamics is investigated in a circular limiter configuration with a low edge safety factor. Focusing on the experimental parameters of two ohmic tokamak inner-wall limited plasma discharges in RFX-mod [Sonato et al., Fusion Eng. Des. 74, 97 (2005)], nonlinear SOL plasma simulations are performed with the GBS code [Ricci et al., Plasma Phys. Controlled Fusion 54, 124047 (2012)]. The numerical results are compared with the experimental measurements, assessing the reliability of the GBS model in describing the RFX-mod SOL plasma dynamics. It is found that the simulations are able to quantitatively reproduce the RFX-mod experimental measurements of the electron plasma density, electron temperature, and ion saturation current density (jsat) equilibrium profiles. Moreover, there are indications that the turbulent transport is driven by the same instability in the simulations and in the experiment, with coherent structures having similar statistical properties. On the other hand, it is found that the simulation results are not able to correctly reproduce the floating potential equilibrium profile and the jsat fluctuation level. It is likely that these discrepancies are, at least in part, related to simulating only the tokamak SOL region, without including the plasma dynamics inside the last close flux surface, and to the limits of applicability of the drift approximation. The turbulence drive is then identified from the nonlinear simulations and with the linear theory. It results that the inertial drift wave is the instability driving most of the turbulent transport in the considered discharges.
A simulation study of homogeneous ice nucleation in supercooled salty water
Authors: Soria Guiomar D. , Espinosa Jorge R. , Ramirez Jorge , Valeriani Chantal , Vega Carlos , Sanz Eduardo
Published: February 2018

We use computer simulations to investigate the effect of salt on homogeneous ice nucleation. The melting point of the employed solution model was obtained both by direct coexistence simulations and by thermodynamic integration from previous calculations of the water chemical potential. Using a seeding approach, in which we simulate ice seeds embedded in a supercooled aqueous solution, we compute the nucleation rate as a function of temperature for a 1.85 NaCl mol per water kilogram solution at 1 bar. To improve the accuracy and reliability of our calculations, we combine seeding with the direct computation of the ice-solution interfacial free energy at coexistence using the Mold Integration method. We compare the results with previous simulation work on pure water to understand the effect caused by the solute. The model captures the experimental trend that the nucleation rate at a given supercooling decreases when adding salt. Despite the fact that the thermodynamic driving force for ice nucleation is higher for salty water for a given supercooling, the nucleation rate slows down with salt due to a significant increase of the ice-fluid interfacial free energy. The salty water model predicts an ice nucleation rate that is in good agreement with experimental measurements, bringing confidence in the predictive ability of the model. We expect that the combination of state-of-the-art simulation methods here employed to study ice nucleation from solution will be of much use in forthcoming numerical investigations of crystallization in mixtures.
Dynamics of an excess hole in the 1-methyl-1-butyl-pyrrolidinium dicyanamide ionic-liquid
Authors: Wu Fei , Xu Changhui , Margulis Claudio J.
Published: February 2018

In a set of recent publications [C. J. Margulis et al., J. Am. Chem. Soc. 133, 20186 (2011); C. H. Xu et al., J. Am. Chem. Soc. 135, 17528 (2013); C. H. Xu and C. J. Margulis, J. Phys. Chem. B 119, 532 (2015); and K. B. Dhungana et al., J. Phys. Chem. B 121, 8809 (2017)], we explored for selected ionic liquids the early stages of excess charge localization and reactivity relevant both to electrochemical and radiation chemistry processes. In particular, Xu and Margulis [J. Phys. Chem. B 119, 532 (2015)] explored the dynamics of an excess electron in 1-methyl-1-butyl-pyrrolidinium dicyanamide. When electrons are produced from an ionic liquid, the more elusive hole species are also generated. Depending on the nature of cations and anions and the relative alignment of their electronic states in the condensed phase, the very early hole species can nominally be neutral radicals—if the electron is generated from anions—or doubly charged radical cations if their origin is from cations. However, in reality early excess charge localization is more complex and often involves more than one ion. The dynamics and the transient spectroscopy of the hole are the main objects of this study. We find that in the case of 1-methyl-1-butyl-pyrrolidinium dicyanamide, it is the anions that can most easily lose an electron becoming radical species, and that hole localization is mostly on anionic nitrogen. We also find that the driving force for localization of an excess hole appears to be smaller than that for an excess electron in 1-methyl-1-butyl-pyrrolidinium dicyanamide. The early transient hole species can absorb light in the visible, ultraviolet, and near infrared regions, and we are able to identify the type of states being connected by these transitions.
Franz-Keldysh effect in epitaxial ZnO thin films
Authors: Bridoux G. , Villafuerte M. , Ferreyra J. M. , Guimpel J. , Nieva G. , Figueroa C. A. , Straube B. , Heluani S. P.
Published: February 2018

Photoconductance spectroscopy has been studied in epitaxial ZnO thin films with different thicknesses that range between 136 and 21 nm. We report a systematic decrease in photoconductivity and a red shift in band edge photoconductance spectra when the thickness is reduced. For thinner films, it is found that the effective energy gap value diminishes. By time dependent photoconductivity measurements, we found an enhanced contribution of the slow relaxation times for thicker films. These effects are interpreted in terms of a band-bending contribution where the Franz-Keldysh effect and the polarization of ZnO play a major role in thinner films.
Measuring the dynamic polarizability of tungsten atom via electrical wire explosion in vacuum
Authors: Shi Huantong , Zou Xiaobing , Wang Xinxin
Published: February 2018

Electrical explosion of wire provides a practical approach to the experimental measurement of dynamic polarizability of metal atoms with high melting and boiling temperatures. With the help of insulation coating, a section of tungsten wire was transformed to the plasma state while the near electrode region was partially vaporized, which enabled us to locate the “neutral-region” (consisting of gaseous atoms) in the Mach-Zehnder interferogram. In this paper, the polarizability of the tungsten atom at 532 nm was reconstructed based on a technique previously used for the same purpose, and the basic preconditions of the measurement were verified in detail, including the existence of the neutral region, conservation of linear density of tungsten during wire expansion, and neglect of the vaporized insulation coating. The typical imaging time varied from 80 ns to as late as 200 ns and the reconstructed polarizability of the tungsten atom was 16 ± 1 Å3, which showed good statistical consistency and was also in good agreement with the previous results.
Multi-layered zinc oxide-graphene composite thin films for selective nitrogen dioxide sensing
Authors: Ghosh A. , Bhowmick T. , Majumder S. B.
Published: February 2018

In the present work, selective nitrogen dioxide (NO2) sensing characteristics of multi-layered graphene-zinc oxide (G-ZnO) thin films have been demonstrated at 150 °C. The response% of 5 ppm NO2 was measured to be 894% with response and recovery times estimated to be 150 s and 315 s, respectively. In these composite films, the interaction between graphene and zinc oxide is established through X-ray photoelectron spectroscopy in conjunction with the analyses of photoluminescence spectra. Superior NO2 sensing of these films is due to simultaneous chemiadsorption of molecular oxygen and NO2 gases onto graphene and ZnO surfaces, resulting in an appreciable increase in the depletion layer width and thereby the sensor resistance. The sensor responses for other reducing gases (viz., CO, H2, and i-C4H10) are postulated to be due to their catalytic oxidation on the sensor surface, resulting in a decrease in the sensor resistance upon gas exposure. At lower operating temperature, due to the molecular nature of the chemiadsorbed oxygen, poor catalytic oxidation leads to a far lower sensor response for reducing gases as compared to NO2. For mixed NO2 and reducing gas sensing, we have reported that fast Fourier transformation of the resistance transients of all these gases in conjunction with principal component analyses forms a reasonably distinct cluster and, therefore, could easily be differentiated.
Dynamic of microwave breakdown in the localized places of transmitting line driving by Cherenkov-type oscillator
Authors: Xie Jialing , Chen Changhua , Chang Chao , Wu Cheng , Shi Yanchao , Cao Yibing , Song Zhimin , Zhang Yuchuan
Published: February 2018

A breakdown cavity is designed to study the breakdown phenomena of high-power microwaves in transmission waveguides. The maximum electric field within the cavity varies in amplitude from 400 kV/cm to 1.8 MV/cm and may surpass breakdown thresholds. The breakdown cavities were studied in particle-in-cell simulations and experiments, the results of which yielded waveforms that were consistent. The experimental results indicate that the microwave pulse does not shorten, and the amplitude of the electric field does not fall below 800 kV/cm. Moreover, large numbers of electrons are not emitted in microwaves below 670 kV/cm at 9.75 GHz frequency and 25-ns pulse width transmitted in stainless steel waveguides. The radiation waveforms of breakdown cavity with different materials are compared in experiments, with titanium material performing better.
Note: A 102 dB dynamic-range charge-sampling readout for ionizing particle/radiation detectors based on an application-specific integrated circuit (ASIC)
Authors: Pullia A. , Zocca F. , Capra S.
Published: February 2018

An original technique for the measurement of charge signals from ionizing particle/radiation detectors has been implemented in an application-specific integrated circuit form. The device performs linear measurements of the charge both within and beyond its output voltage swing. The device features an unprecedented spectroscopic dynamic range of 102 dB and is suitable for high-resolution ion and X-γ ray spectroscopy. We believe that this approach may change a widespread paradigm according to which no high-resolution spectroscopy is possible when working close to or beyond the limit of the preamplifier’s output voltage swing.
Intense single attosecond pulse generation from near-critical-density plasmas irradiated by a few-cycle laser pulse
Authors: Zhang Y. X. , Qiao B. , Xu X. R. , Chang H. X. , Yu M. Y. , Zhong C. L. , Zhou C. T. , Zhu S. P. , He X. T.
Published: February 2018

Coherent synchrotron emission (CSE) from relativistic near-critical-density (NCD) plasmas irradiated by a few-cycle laser pulse is investigated theoretically and numerically. Due to the unique and larger laser-plasma interaction region in relativistic NCD plasmas, compared to those in solid targets, not only the required stringent conditions for CSE on laser and target are relaxed but also the radiation intensities are enhanced by two orders of magnitude. Moreover, it is found that a single attosecond pulse can also be easily obtained in the transmitted direction through CSE in this regime. Its energy conversion efficiencies from laser to emission can reach 10−3–10−2, which is more than one order of magnitude larger than those of attosecond trains from solids. Two-dimensional particle-in-cell simulations show that an intense single pulse at a peak intensity of ∼1019 W/cm2 and duration of ∼98 as in the transmitted direction is produced by the drive laser at an intensity of I0 = 8.6 × 1020 W/cm2.
Dislocation evolution during plastic deformation: Equations vs. discrete dislocation dynamics study
Authors: Davoudi Kamyar M. , Vlassak Joost J.
Published: February 2018

Equations for dislocation evolution bridge the gap between dislocation properties and continuum descriptions of plastic behavior of crystalline materials. Computer simulations can help us verify these evolution equations and find their fitting parameters. In this paper, we employ discrete dislocation dynamics to establish a continuum-based model for the evolution of the dislocation structure in polycrystalline thin films. Expressions are developed for the density of activated dislocation sources, as well as dislocation nucleation and annihilation rates. We demonstrate how size effect naturally enters the evolution equation. Good agreement between the simulation and the model results is obtained. The current approach is based on a two-dimensional discrete dislocation dynamics model but can be extended to three-dimensional models.
Lock-on physics in semi-insulating GaAs: Combination of trap-to-band impact ionization, moving electric fields and photon recycling
Authors: Chowdhury A. R. , Dickens J. C. , Neuber A. A. , Ness R. , Joshi R. P.
Published: February 2018

The time-dependent photoconductive current response of semi-insulating GaAs is probed based on one-dimensional simulations, with a focus on the lock-on phenomenon. Our results capture most of the experimental observations. It is shown that trap-to-band impact ionization fuels local field enhancements, and photon recycling also plays an important role in pushing the device towards lock-on above a 3.5 kV/cm threshold field. The results compare well with actual data in terms of the magnitudes, the rise times, and the oscillatory behavior seen at higher currents. Moving multiple domains are predicted, and the response shown depended on the location of the photoexcitation spot relative to the electrodes.
Unusual violet photoluminescence in indium-doped ZnO nanowires
Authors: He Haiping , Su Binbin , Duan Hongfeng , Ye Zhizhen
Published: February 2018

Point defects in wide bandgap semiconductors such as ZnO are emerging as promising candidates for single photon sources. However, identification of defect-based luminescence is rather difficult due to the extremely complicated defect physics of ZnO. Here, we report an unusual violet emission centered at 3.1 eV from indium-doped ZnO nanowires. The violet emission can be observed only below 180 K and shows thermal quenching with unexpectedly small activation energy of ∼36 meV. Photoluminescence and X-ray absorption near edge spectroscopy results suggest that the origin of the violet emission is VZn-InZn complex defect. The overall luminescence features can be understood in terms of the configuration coordinate model involving intercross between the potentials of the ground and excited states. Our results may give insights into the defect physics and be essential to the optoelectrical properties of doped ZnO nanostructures.
Large vacuum Rabi splitting between a single quantum dot and an H0 photonic crystal nanocavity
Authors: Ota Yasutomo , Takamiya Daisaku , Ohta Ryuichi , Takagi Hiroyuki , Kumagai Naoto , Iwamoto Satoshi , Arakawa Yasuhiko
Published: February 2018

Strong light matter interactions between semiconductor quantum dots and optical micro/nanocavities are useful resources for developing quantum information processing devices and for exploring diverse quantum optical phenomena. In pursuit of better device performances and novel physics, it is desirable to achieve a larger coupling constant between the quantum dot and the cavity while keeping the high coherence of the coupled system. In this letter, we report the observation of a large vacuum Rabi splitting of ∼328 μeV using a single InAs quantum dot embedded in a GaAs-based H0 photonic crystal nanocavity, which possesses a near-diffraction limited mode volume as well as a high experimental Q factor of ∼52 000. The resulting figure of merit of the strongly coupled systems, defined as a ratio of the coupling constant to the cavity decay rate, reaches 6.4, which is the record high value for semiconductor QD-nanocavity systems reported to date.
Langevin synchronization in a time-dependent, harmonic basin: An exact solution in 1D
Authors: Cadilhe A. , Voter Arthur F.
Published: February 2018

The trajectories of two particles undergoing Langevin dynamics while sharing a common noise sequence can merge into a single (master) trajectory. Here, we present an exact solution for a particle undergoing Langevin dynamics in a harmonic, time-dependent potential, thus extending the idea of synchronization to nonequilibrium systems. We calculate the synchronization level, i.e., the mismatch between two trajectories sharing a common noise sequence, in the underdamped, critically damped, and overdamped regimes. Finally, we provide asymptotic expansions in various limiting cases and compare to the time independent case.
Experimental investigation on the initial expansion stage of vacuum arc on cup-shaped TMF contacts
Authors: Wang Ting , Xiu Shixin , Liu Zixi , Zhang Yanzhe , Feng Dingyu
Published: February 2018

Arc behavior and measures to control it directly affect the properties of vacuum circuit breakers. Nowadays, transverse magnetic field (TMF) contacts are widely used for medium voltages. A magnetic field perpendicular to the current direction between the TMF contacts makes the arc move, transmitting its energy to the whole contact and avoiding excessive local ablation. Previous research on TMF arc behavior concentrated mainly on the arc movement and less on the initial stage (from arc ignition to an unstable arc column). A significant amount of experiment results suggest that there is a short period of arc stagnation after ignition. The duration of this arc stagnation and the arc characteristics during this stage affect the subsequent arc motion and even the breaking property of interrupters. The present study is of the arc characteristics in the initial stage. Experiments were carried out in a demountable vacuum chamber with cup-shaped TMF contacts. Using a high-speed camera, both single-point arc ignition mode and multiple-point arc ignition (MPAI) mode were observed. The experimental data show that the probability of MPAI mode occurring is related to the arc current. The influences of arc-ignition mode, arc current, and contact diameter on the initial expansion process were investigated. In addition, simulations were performed to analyze the multiple arc expansion process mechanically. Based on the experimental phenomena and simulation results, the mechanism of the arc expansion motion was analyzed.
High performance of visible-NIR broad spectral photocurrent application of monodisperse PbSe nanocubes decorated on rGO sheets
Authors: Ghorban Shiravizadeh A. , Elahi S. M. , Sebt S. A. , Yousefi Ramin
Published: February 2018

In this work, the photoresponse performance of monodisperse PbSe nanocubes in the range of visible and near-infrared (NIR) (400–1500 nm) regions was enhanced by reduced graphene oxide (rGO). A simple cost-effective method is presented to synthesize monodisperse PbSe nanocubes (NCs) that are decorated on the rGO sheets. By the addition of PbSe/rGO nanocomposites with different rGO concentrations, pristine PbSe NCs were synthesized with the same method. Microscopy images showed that the size of NCs was smaller than the exciton Bohr radius (46 nm) of PbSe bulk. Therefore, the UV-Vis-IR spectroscopy result revealed that the PbSe/rGO samples had absorption peaks in the NIR region around 1650 nm and showed a blue shift compared to the absorption peak of the PbSe bulk. J-V measurements of the samples indicated that monodisperse PbSe/rGO nanocomposites had a higher resistance than the other samples under dark condition. On the other hand, the resistance of the monodisperse PbSe/rGO nanocomposites decreased under different light source illuminations while the resistance of the other samples was increased under illumination. Photodetector measurements indicated that the monodisperse morphology of the PbSe NCs enhanced the photoresponse speed and photocurrent intensity. In addition, responsivity (R) and detectivity (D*) of the samples were higher in the NIR region.
Stability of sputter deposited cuprous oxide (Cu2O) subjected to ageing conditions for photovoltaic applications
Authors: Camacho-Espinosa E. , Rimmaudo I. , Riech I. , Mis-Fernández R. , Peña J. L.
Published: February 2018

Among various metal oxide p-type semiconductors, cuprous oxide (Cu2O) stands out as a nontoxic and abundant material, which also makes it a suitable candidate as a low-cost absorber for photovoltaic applications. However, the chemical stability of the absorber layer is critical for the solar cell lifetime, in particular, for Cu-based materials, concerning to its oxidation state changes. In this paper, we addressed the Cu2O stability depositing films of 170 nm by reactive radio frequency magnetron sputtering and subsequently ageing them in conditions similar to the typical accelerated life test for the solar module, in a period of time from one to five weeks. The stability of the optical, electrical, and structural properties of the Cu2O thin films was investigated using UV-VIS-near infrared transmittance, 4-probes electrical resistance characterization, high precision profilometry, X-ray photoelectron spectroscopy, and grazing incidence X-ray diffraction. Finally, we demonstrated that the aging tests affected only the surface of the films, while the bulk remained unaltered, making Cu2O a promising candidate for production of stable devices, including solar cells.
Large entropy derived from low-frequency vibrations and its implications for hydrogen storage
Authors: Wang Xiaoxia , Chen Hongshan
Published: February 2018

Adsorption and desorption are driven by the energy and entropy competition, but the entropy effect is often ignored in hydrogen storage and the optimal adsorption strength for the ambient storage is controversial in the literature. This letter investigated the adsorption states of the H2 molecule on M-B12C6N6 (M = Li, Na, Mg, Ca, and Sc) and analyzed the correlation among the zero point energy (ZPE), the entropy change, and the adsorption energy and their effects on the delivery capacities. The ZPE has large correction to the adsorption energy due to the light mass of hydrogen. The computations show that the potential energies along the spherical surface centered at the alkali metals are very flat and it leads to large entropy (∼70 J/mol·K) of the adsorbed H2 molecules. The entropy change can compensate the enthalpy change effectively, and the ambient storage can be realized with relatively weak adsorption of ΔH = −12 kJ/mol. The results are encouraging and instructive for the design of hydrogen storage materials.
InGaP solar cell on Ge-on-Si virtual substrate for novel solar power conversion
Authors: Kim T. W. , Albert B. R. , Kimerling L. C. , Michel J.
Published: February 2018

InGaP single-junction solar cells are grown on lattice-matched Ge-on-Si virtual substrates using metal-organic chemical vapor deposition. Optoelectronic simulation results indicate that the optimal collection length for InGaP single-junction solar cells with a carrier lifetime range of 2–5 ns is wider than approximately 1 μm. Electron beam-induced current measurements reveal that the threading dislocation density (TDD) of InGaP solar cells fabricated on Ge and Ge-on-Si substrates is in the range of 104–3 × 107 cm−2. We demonstrate that the open circuit voltage (Voc) of InGaP solar cells is not significantly influenced by TDDs less than 2 × 106 cm−2. Fabricated InGaP solar cells grown on a Ge-on-Si virtual substrate and a Ge substrate exhibit Voc in the range of 0.96 to 1.43 V under an equivalent illumination in the range of ∼0.5 Sun. The estimated efficiency of the InGaP solar cell fabricated on the Ge-on-Si virtual substrate (Ge substrate) at room temperature for the limited incident spectrum spanning the photon energy range of 1.9–2.4 eV varies from 16.6% to 34.3%.
The enhanced piezoelectricity in compositionally graded ferroelectric thin films under electric field: A role of flexoelectric effect
Authors: Qiu Ye , Wu Huaping , Wang Jie , Lou Jia , Zhang Zheng , Liu Aiping , Chai Guozhong
Published: February 2018

Compositionally graded ferroelectric thin films are found to produce large strain gradients, which can be used to tune the physical properties of materials through the flexoelectric effect, i.e., the coupling of polarization and the strain gradient. The influences of the flexoelectric effect on the polarization distribution and the piezoelectric properties in compositionally graded Ba1−xSrxTiO3 ferroelectric thin films are investigated by using an extended thermodynamic theory. The calculation results show that the presence of the flexoelectric effect tends to enhance and stabilize polarization components. The polarization rotation induced by the flexoelectric field has been predicted, which is accompanied by more uniform and orderly polarization components. A remarkable enhancement of piezoelectricity is obtained when the flexoelectric field is considered, suggesting that compositionally graded Ba1−xSrxTiO3 ferroelectric thin films with a large strain gradient are promising candidates for piezoelectric devices.
State-of-charge estimation for lithium-ion battery using the Gauss-Hermite particle filter technique
Authors: Li Bin , Peng Kai , Li Guidan
Published: February 2018

The state of charge (SOC) of lithium-ion batteries is the core parameter of the battery management system. Accurate SOC can guide the effective management of the battery system and prevent the battery overcharge and over-discharge, which can extend the battery life. This paper uses an electrochemistry battery model for the SOC estimation of lithium-ion batteries, and then, the forgetting factor least squares method is used for model identification. Then, the Gauss-Hermite particle filter (GHPF) technique is proposed to estimate the SOC. The experiment results show that the GHPF not only improves the estimation accuracy but also reduces the number of sampling particles, which reduces the complexity of the algorithm. The method shows the superiority on accuracy and real-time performance over the standard PF, EPF, and UPF methods.
Initiation of the Worthington jet on the droplet impact
Authors: Yamamoto Ken , Motosuke Masahiro , Ogata Satoshi
Published: February 2018

The deformation of liquid droplets upon impact induces Worthington jets for a certain range of impact velocities. Although the growth of such a jet and its tip velocity are predicted from cases similar to droplet impact, the mechanism behind jet formation is yet to be understood. The present study uses high-speed visualization of droplet impact on a superhydrophobic surface to understand jet initiation in terms of the collapse of an air cavity. Water droplets with diameters of 2.0 and 3.0 mm are generated with the droplet Weber number varying from 2 to 20. The jet velocity is measured from the captured images, from which the maximum velocity is found to be We ∼ 7. The jet velocity at We ∼ 7 is approximately 15 times greater than the impact velocity. Moreover, surface waves are generated upon impact with the solid surface, and they induce an oscillation of the droplet cap as they propagate from the solid–liquid contact line to the top portion of the droplet. Furthermore, we find that the phase of the oscillation is related to the Weber number and greatly influences the jet velocity because it determines the initial conditions for jet generation.
High spatial resolution correlated investigation of Zn segregation to stacking faults in ZnTe/CdSe nanostructures
Authors: Bonef Bastien , Grenier Adeline , Gerard Lionel , Jouneau Pierre-Henri , André Regis , Blavette Didier , Bougerol Catherine
Published: February 2018

The correlative use of atom probe tomography (APT) and energy dispersive x-ray spectroscopy in scanning transmission electron microscopy (STEM) allows us to characterize the structure of ZnTe/CdSe superlattices at the nanometre scale. Both techniques reveal the segregation of zinc along [111] stacking faults in CdSe layers, which is interpreted as a manifestation of the Suzuki effect. Quantitative measurements reveal a zinc enrichment around 9 at. % correlated with a depletion of cadmium in the stacking faults. Raw concentration data were corrected so as to account for the limited spatial resolution of both STEM and APT techniques. A simple calculation reveals that the stacking faults are almost saturated in Zn atoms (∼66 at. % of Zn) at the expense of Cd that is depleted.
0.6ST-0.4NBT thin film with low level Mn doping as a lead-free ferroelectric capacitor with high energy storage performance
Authors: Zhang Yulei , Li Weili , Qiao Yulong , Zhao Yu , Wang Zhenyu , Yu Yang , Xia Hetian , Li Ze , Fei Weidong
Published: February 2018

Srx(Na0.5Bi0.5)1−xTi0.99Mn0.01O3 (x = 0.2, 0.4, 0.6, and 0.8) relaxor ferroelectric thin films were grown on Pt/Ti/SiO2/Si substrates by the Sol-Gel method. The influence of the Sr content on the microstructures, ferroelectric properties, and energy-storage performances of the thin films were investigated in detail. The Sr0.6(Na0.5Bi0.5)0.4Ti0.99Mn0.01O3 thin film exhibits very slim hysteresis loops with the highest electric breakdown field strength due to reduced oxygen vacancies. Owing to the high breakdown field strength of 3134.3 kV/cm, the Sr0.6(Na0.5Bi0.5)0.4Ti0.99Mn0.01O3 thin film shows a giant recoverable energy-storage density of 33.58 J/cm3. These results indicate that the Sr0.6(Na0.5Bi0.5)0.4Ti0.99Mn0.01O3 thin film is promising for applications of advanced capacitors with high energy-storage density.
Poloidal asymmetries of flows in the Tore Supra tokamak
Authors: Vermare L. , Hennequin P. , Gürcan Ö. D. , Garbet X. , Honoré C. , Clairet F. , Giacalone J. C. , Morel P. , Storelli A. ,   Tore Supra Team
Published: February 2018

Simultaneous measurements of binormal velocity of density fluctuations using two separate Doppler backscattering systems at the low field side and at the top of the plasma show significant poloidal asymmetry. The measurements are performed in the core region between the radii 0.7 < ρ  <  0.95, over a limited number of L-mode discharges covering a wide range of plasma conditions in the Tore Supra tokamak. A possible generation mechanism by the ballooned structure of the underlying turbulence, in the form of convective cells, is proposed for explaining the observation of these poloidally asymmetric mean flows.
Realization of forming-free Ag/ZrO2-based threshold selector with high selectivity by optimizing film thickness and scaling down electrode size
Authors: Wang Chao , Zeng Zhongming
Published: February 2018

The influence of the switching layer thickness and the device size on the threshold switching characteristics has been investigated in Ag/ZrO2/Pt selector device. By optimizing the switching layer thickness, excellent threshold switching characteristics such as forming-free behavior, high selectivity and good endurance was achieved. In addition, we revealed the impact of active metal electrode diffusion on the device performance as the thickness of dielectric material scaled. A two-step set behavior was also observed in the device with 80 nm switching layer under a high compliance current of 1mA. Furthermore, the selectivity was increased highly by decreasing electrode size. In particular, the selectivity was about 2×108 when the electrode size was scaled down to 300 nm.
Camera traps and pitfalls: an evaluation of two methods for surveying reptiles in a semiarid ecosystem
Authors: Richardson Emily , Nimmo Dale G. , Avitabile Sarah , Tworkowski Lauren , Watson Simon J. , Welbourne Dustin , Leonard Steven W. J.
Published: February 2018

Context
Passive infrared cameras have become a widely utilised method for surveying mammals, providing substantial benefits over conventional trapping methods. Cameras have only recently been tested for their ability to survey terrestrial reptiles, and have not yet been tested against other reptile survey methods for their comparative effectiveness.

Aims
To investigate the reliability of passive infrared cameras as a reptile survey method, compared with pitfall trapping. In addition, to test a refinement of a current protocol for using cameras to survey reptiles.

Methods
The study was carried out in the herpetologically diverse, semiarid Mallee region of Victoria, Australia. Paired camera and pitfall lines were set up at 10 sites within Murray Sunset National Park and results from the two methods were compared. A comparison of results from cameras with and without the use of a cork tile substrate was also made.

Key results
Cameras were just as effective as pitfall traps for detecting some common diurnal species – detecting additional species that pitfalls did not – but were significantly less effective overall. Cameras provided lower estimates of species richness and failed to detect nocturnal species. We also discovered that cork tiles, required in other environments for the cameras to be effective in detecting diurnal reptiles, were not needed here.

Conclusions
Cameras can be an effective, efficient non-invasive alternative to conventional trapping methods, such as pitfall trapping, for surveying some terrestrial diurnal reptile species. However, further investigation into using cameras for surveying nocturnal reptile species is still required.

Implications
If the methodological issues identified during this study can be overcome, passive infrared cameras have the potential to be a valuable tool for future herpetological research.
A management experiment reveals the difficulty of altering seedling growth and palatable plant biomass by culling invasive deer
Authors: Ramsey David S. L. , Forsyth David M. , Veltman Clare J. , Richardson Sarah J. , Allen Robert B. , Allen Will J. , Barker Richard J. , Bellingham Peter J. , Jacobson Chris L. , Nicol Simon J. , Robertson Alastair W. , Todd Charles R.
Published: February 2018

Context There is concern that deer are shifting forests towards undesirable trajectories, and culling of deer is often advocated to mitigate these impacts. However, culling deer is expensive and sometimes controversial. To reliably ascertain whether such action is beneficial, management-scale experiments are needed. We conducted a management experiment to evaluate the benefits of culling deer in four New Zealand forests. Aims Our experiment tested the predictions that culling deer should increase (1) canopy tree seedling height relative growth rate (SHRGR), and (2) the foliar biomass of understorey species palatable to deer (FBP). Methods Each forest was divided into two 3600-ha areas, with deer culling randomly assigned to one area. Deer abundances were indexed using faecal pellet counts, and forest variables were measured at the start and end of the 8-year experiment. Deer were already at low abundance in one forest and were not culled there. We used structural equation modelling (SEM) with Bayesian variable selection to update our a priori graphical forest–deer model with data from all four forests. Key results Deer abundances were significantly reduced in one forest but increased or did not change in the other two forests in which deer culling occurred. Culling deer did not increase seedling height relative growth rate (SHRGR) or the foliar biomass of understorey species palatable to deer (FBP) in the three areas subject to deer culling compared with the three areas not subject to deer culling. SEM revealed no significant relationships between local-scale deer abundance and either SHRGR or FBP. Rather, tree basal area and the foliar biomass of unpalatable understorey species were important predictors of FBP and SHRGR, respectively, in some forests. Conclusions Our study revealed that culling deer, as currently practiced by New Zealand land managers, did not generate the desired responses in New Zealand forests, possibly due to deer not being culled to sufficiently low densities and/or because forest dynamics and abiotic drivers determined plant growth more than deer. Implications Managers should consider actions other than ineffective deer culling (e.g. creating canopy gaps) to alter the dynamics of New Zealand forests. Alternatively, managers will need to substantially increase culling effort above what is currently practised for this activity to substantially reduce deer populations and thus potentially alter forest dynamics.
Forecasting the spatial transmission of influenza in the United States
Authors: Pei Sen , Kandula Sasikiran , Yang Wan , Shaman Jeffrey
Published: February 2018

Significance

In the last two decades, multiple outbreaks of emerging pathogens have unexpectedly swept the planet. In these public health emergencies, pathogens invade new regions in the span of just a few weeks to months, leaving a critical window of opportunity during which real-time warning could be sounded. As such, accurate prediction of the spatial spread of pathogens could provide invaluable benefits to global public health. Here we develop and validate an operational forecast system that is capable of predicting the spatial transmission of influenza in the United States. In particular, the onset week of local outbreaks can be accurately predicted up to 6 wk in advance at state level.
Decline and poleward shift in Indian summer monsoon synoptic activity in a warming climate
Authors: Sandeep S. , Ajayamohan R. S. , Boos William R. , Sabin T. P. , Praveen V.
Published: February 2018

Significance

Propagating atmospheric vortices contribute more than half of the total rainfall received by the fertile and highly populated Gangetic plains of India. How the activity of these storms will change in a warming climate is not yet understood, due to both the inadequate representation of these disturbances in global climate models and a lack of theory for their fundamental dynamics. Here we show that both a high-resolution atmospheric model and a statistical model predict that the activity of these storms weakens and shifts poleward from ocean to land in a warmer environment. The associated changes in seasonal mean rainfall and precipitation extremes are expected to have serious implications for the hydrological cycle of South Asia.
Grip and slip of L1-CAM on adhesive substrates direct growth cone haptotaxis
Authors: Abe Kouki , Katsuno Hiroko , Toriyama Michinori , Baba Kentarou , Mori Tomoyuki , Hakoshima Toshio , Kanemura Yonehiro , Watanabe Rikiya , Inagaki Naoyuki
Published: February 2018

Significance

Cell migration directed by substrate-bound chemical cues is called haptotaxis. This study shows that grip and slip between the cell adhesion molecule (CAM) L1-CAM and the adhesive substrates, which occur asymmetrically under the growth cone, direct growth cone migration mediated by laminin. This mechanism is disrupted in a human patient of L1-CAM syndrome, suffering corpus callosum agenesis and corticospinal tract hypoplasia. These findings provide a conceptual framework for understanding the regulation and dysregulation of cell migration on the bases of force generation.
Early anthropogenic impact on Western Central African rainforests 2,600 y ago
Authors: Garcin Yannick , Deschamps Pierre , Ménot Guillemette , de Saulieu Geoffroy , Schefuß Enno , Sebag David , Dupont Lydie M. , Oslisly Richard , Brademann Brian , Mbusnum Kevin G. , Onana Jean-Michel , Ako Andrew A. , Epp Laura S. , Tjallingii Rik , Strecker Manfred R. , Brauer Achim , Sachse Dirk
Published: February 2018

Significance

Modern human societies live in strongly altered ecosystems. However, anthropogenic environmental disturbances occurred long before the industrial revolution. About 2,600 y ago, a forest–savannah mosaic replaced dense rainforests in Western Central Africa. This rainforest crisis was previously attributed either to the impact of climate change or, to a lesser extent, to the expansion of Bantu peoples through Central Africa. A 10,500-y sedimentary record from Lake Barombi, Southwest Cameroon, demonstrates that the rainforest crisis was not associated with any significant hydrological change. Based on a detailed investigation of a regional archaeological database, we present evidence that humans altered the rainforest ecosystem and left detectable traces in the sediments deposited in Lake Barombi.
Convergence of marine megafauna movement patterns in coastal and open oceans
Authors: Sequeira A. M. M. , Rodríguez J. P. , Eguíluz V. M. , Harcourt R. , Hindell M. , Sims D. W. , Duarte C. M. , Costa D. P. , Fernández-Gracia J. , Ferreira L. C. , Hays G. C. , Heupel M. R. , Meekan M. G. , Aven A. , Bailleul F. , Baylis A. M. M. , Berumen M. L. , Braun C. D. , Burns J. , Caley M. J. , Campbell R. , Carmichael R. H. , Clua E. , Einoder L. D. , Friedlaender Ari , Goebel M. E. , Goldsworthy S. D. , Guinet C. , Gunn J. , Hamer D. , Hammerschlag N. , Hammill M. , Hückstädt L. A. , Humphries N. E. , Lea M.-A. , Lowther A. , Mackay A. , McHuron E. , McKenzie J. , McLeay L. , McMahon C. R. , Mengersen K. , Muelbert M. M. C. , Pagano A. M. , Page B. , Queiroz N. , Robinson P. W. , Shaffer S. A. , Shivji M. , Skomal G. B. , Thorrold S. R. , Villegas-Amtmann S. , Weise M. , Wells R. , Wetherbee B. , Wiebkin A. , Wienecke B. , Thums M.
Published: February 2018

Significance

Understanding the key drivers of animal movement is crucial to assist in mitigating adverse impacts of anthropogenic activities on marine megafauna. We found that movement patterns of marine megafauna are mostly independent of their evolutionary histories, differing significantly from patterns for terrestrial animals. We detected a remarkable convergence in the distribution of speed and turning angles across organisms ranging from whales to turtles (epitome for the slowest animals on land but not at sea). Marine megafauna show a prevalence of movement patterns dominated by search behavior in coastal habitats compared with more directed, ballistic movement patterns when the animals move across the open ocean. The habitats through which they move will therefore need to be considered for effective conservation.
Strain-induced accelerated asymmetric spatial degradation of polymeric vascular scaffolds
Authors: Wang Pei-Jiang , Ferralis Nicola , Conway Claire , Grossman Jeffrey C. , Edelman Elazer R.
Published: February 2018

Significance

Bioresorbable scaffolds (BRS) were thought to represent the next cardiovascular interventional revolution yet they failed compared with metal stents. When BRS were tested using methods for MS, no signal of concern emerged––perhaps because BRS are not metal stents. BRS not only degrade, they also possess significant localized structural irregularities that cause asymmetric degradation. We posit these microstructural irregularities are responsible for variability in device performance in first-generation BRS. We correlated nonuniform degradation with variation in polymer microstructure and tolerance to integrated strain generated during fabrication and implantation. Differentiating failure modes in metallic and polymeric devices explains clinical results and suggests optimization strategies for the design and fabrication of next-generation BRS, indeed all devices using degradable materials.
Rapid regulatory evolution of a nonrecombining autosome linked to divergent behavioral phenotypes
Authors: Sun Dan , Huh Iksoo , Zinzow-Kramer Wendy M. , Maney Donna L. , Yi Soojin V.
Published: February 2018

Significance

The evolution of nonrecombining chromosomes such as sex chromosomes involves degeneration leading to loss of genetic information. We do not know, however, what happens during the incipient stages of such chromosomes, before appreciable degeneration. We studied this process in white-throated sparrows, a species that occurs in two alternative behavioral phenotypes determined by a nonrecombining autosomal rearrangement. We report that this rearrangement shows few signs of large-scale genetic degeneration. Instead, substantial changes have evolved at the level of gene expression, some of them consistent with adaptive evolution. Our work with this chromosome reveals that rapid changes in gene expression and dosage compensation, not necessarily large-scale genetic degeneration, characterize the early evolution of heteromorphic chromosomes and the associated divergent phenotypes.
Citywide cluster randomized trial to restore blighted vacant land and its effects on violence, crime, and fear
Authors: Branas Charles C. , South Eugenia , Kondo Michelle C. , Hohl Bernadette C. , Bourgois Philippe , Wiebe Douglas J. , MacDonald John M.
Published: February 2018

Significance

Blighted and vacant urban land is a widespread and potentially risky environmental condition encountered by millions of people every day. About 15% of the land in US cities is deemed vacant or abandoned, translating into an area roughly the size of Switzerland: over 3 million hectares of otherwise beneficial spaces remain neglected. Urban residents, especially in low-income neighborhoods, point to these spaces as primary threats to their health and safety. Cities continue to seek meaningful, evidence-based interventions for remediating vacant land. Standardized processes for the restoration of vacant urban land were experimentally tested on a citywide scale and found to significantly reduce gun violence, crime, and fear.
Multifrequency AFM reveals lipid membrane mechanical properties and the effect of cholesterol in modulating viscoelasticity
Authors: Al-Rekabi Zeinab , Contera Sonia
Published: February 2018

Significance

The lipid bilayer mediates a number of cellular processes including cell recognition, signaling, transfer of ions, adhesion, and fusion. In orchestrating these functions, the cell membrane behaves as both an elastic and a viscous material. Although the physical properties of the lipid bilayer have been extensively studied, a thorough description of the viscoelasticity of the membrane is significantly less well characterized. In our study, we utilize multifrequency atomic force microscopy (AFM) as a tool to extract quantitative viscoelastic information of a model lipid system with molar fraction inserts of cholesterol (Chol). Using this approach, we provide evidence that the lipid bilayer appears to exhibit both elastic and viscous properties, an important aspect in its role in mechanotransduction.
Infants expect ingroup support to override fairness when resources are limited
Authors: Bian Lin , Sloane Stephanie , Baillargeon Renée
Published: February 2018

Significance

Recent research suggests that infants possess principles of fairness and ingroup support. We examined whether 1.5- and 2.5-y-olds would prioritize fairness or ingroup support when the two were pitted against each other. Children watched mixed-recipients resource-allocation events in which a puppet distributor faced two potential recipients, an ingroup and an outgroup puppet. Expectations about the distributor’s actions depended on how many allocation items were available. When there were as many items as puppets, children expected fairness to prevail; when there were fewer items than puppets, however, children expected ingroup support to prevail. Thus, beginning early in life, children expect fairness in mixed-recipients scenarios unless there is a shortage of resources, in which case they expect ingroup support to override fairness.