bluuebunny/crossref_metadata_2025 huggingface dataset:
The hard sphere diameter of nanocrystals (nanoparticles)
Authors: Zha Xun , Travesset Alex
Published: March 2020

The hard sphere diameter dHS of a nanocrystal (or nanoparticle) is a very important parameter that determines the nearest neighbor separation of their assembled structure, even in those situations where the nanocrystals have large deformations of the ligand shell that prevent them from being described as hard spheres. The parameter dHS is a function of the number of grafted ligands and critically depends on the maximum ligand grafting density σMax, which we calculate by three different methods for the 351 gold nanocrystals with the number of atoms between 38 and 4033. The use of dHS in the interpretation of experimental results is analyzed.
The physics of microemulsions extracted from modeling balanced tensionless surfactant-loaded liquid–liquid interfaces
Authors: Varadharajan Ramanathan , Leermakers Frans A. M.
Published: March 2020

Microemulsions are explored using the self-consistent field approach. We consider a balanced model that features two solvents of similar size and a symmetric surfactant. Interaction parameter χ and surfactant concentration φsb complement the model definition. The phase diagram in χ–φsb coordinates is known to feature two lines of critical points, the Scott and Leibler lines. Only upon imposing a finite distance between the interfaces, we observe that the Scott line meets the Leibler line. We refer to this as a Lifshitz point (LP) for real systems. We add regions that are relevant for microemulsions to this phase diagram by considering the saturation line, which connects (χ, φsb)-points for which the interface becomes tensionless. Crossing this line implies a first-order phase transition as internal interfaces develop, characteristic for one-phase microemulsions. The saturation line ends at the so-called microemulsion point (MP). The MP is shown to connect with the LP by a line of MP-like critical points, found by searching for a “MP” while the distance between interfaces is fixed. A pair of binodal lines that envelop the three-phase (Winsor III) microemulsion region is shown to connect to the MP. The cohesiveness of the middle phase in Winsor III is related to non-monotonic, inverse DLVO-type interaction curves between the surfactant-loaded tensionless interfaces. The mean and Gaussian bending modulus, relevant for the shape fluctuations and the topology of interfaces, respectively, are evaluated along the saturation line. Near the MP, both rigidities are positive and vanish in a power-law fashion with coefficient unity at the MP. Overseeing these results proves that the MP has a pivoting role in the physics of microemulsions.
Poisson stochastic master equation unravelings and the measurement problem: A quantum stochastic calculus perspective
Authors: Keys Dustin , Wehr Jan
Published: March 2020

This paper studies a class of quantum stochastic differential equations, modeling an interaction of a system with its environment in the quantum noise approximation. The space representing quantum noise is the symmetric Fock space over L2R+. Using the isomorphism of this space with the space of square-integrable functionals of the Poisson process, the equations can be represented as classical stochastic differential equations, driven by Poisson processes. This leads to a discontinuous dynamical state reduction which we compare to the Ghirardi-–Rimini–Weber model. A purely quantum object, the norm process, is found, which plays the role of an observer {in the sense of Everett [H. Everett III, Rev. Mod. Phys. 29(3), 454 (1957)]}, encoding all events occurring in the system space. An algorithm introduced by Dalibard et al. [Phys. Rev. Lett. 68(5), 580 (1992)] to numerically solve quantum master equations is interpreted in the context of unraveling, and the trajectories of expected values of system observables are calculated.
Plasma–grain interaction in ultracold complex plasmas
Authors: Sundar Sita , Moldabekov Zhandos A.
Published: March 2020

The present particle-in-cell simulation for grain–plasma interaction at cryogenic temperatures springs from recent experimental realization of ultracold dusty plasmas with atoms and ions at superfluid helium temperatures. In this work, we discuss the results of particle-in-cell simulations (taking into account ion-atom collisions) for dust particle charge, ion drag force, and interaction between grains in ultracold dusty plasmas. The single grain as well as two grain system is investigated, considering both streaming ions and equilibrium ions. The dependence of plasma mediated inter-grain interactions on the streaming velocity of ions and inter-particle separation is delineated in detail. Additionally, ion density distribution around grains is discussed. The interactions at cryogenic temperatures are distinct from those at room temperature by their differences in magnitude and interaction mechanism details. Most remarkable features are (i) the inter-grain attraction in equilibrium plasmas due to plasma absorption on the surface of grains, (ii) the ion drag force directed against ion streaming velocity in the case of a single dust particle, and (iii) non-linear response of the plasma polarization around grains with an increase in the streaming velocity of ions.
Laser-shocked calcium difluoride (CaF2) as a warm dense matter
Authors: Shu Hua , Zhang Youjun , Wang Bihan , Yang Wenge , Dong Hongliang , Tobase Tsubasa , Ye Junjian , Huang Xiuguang , Fu Sizu , Zhou Qiang , Sekine Toshimori
Published: March 2020

We determined the shock equation of state of CaF2 at pressures of ∼0.4–1.5 TPa using high-power laser shock techniques. The shock velocity-particle velocity was approximated by the universal Hugoniot relationship known to metallic fluids. Our results do not support the incompressible behavior above ∼100 GPa claimed previously. Warm dense CaF2 is a bonded liquid above the melting point and approaches an ideal fluid above ∼1 TPa. The measured reflectivity change of CaF2 at the shock front, similar to the other semiconducting liquids in the warm dense region, suggests a gradual metallization process due to the presence of delocalized electrons at high shock-front temperatures.
Relativistic nonlinear frequency shift of laser pulse on reflection from critical layer in inhomogeneous plasma
Authors: Rajouria Satish Kumar , Kumar Pawan
Published: March 2020

An analytical formalism is developed for the nonlinear frequency shift of intense laser pulse, due to relativistic mass nonlinearity (in the sub-relativistic regime), on reflection from the critical layer in an inhomogeneous plasma. As a higher and higher intensity front of the pulse approaches the critical layer, the reflection layer moves forward to higher densities, due to the relativistic increase in the electron mass, causing a red shift in the reflected wave frequency. The frequency shift increases with shortening laser pulse duration and laser intensity. For the rear portion of the pulse, the critical layer moves backward, causing a blue shift. The effect is more pronounced for shorter pulses and longer density scale lengths, consistent with recent experiments.
The pulsed mode of negative DC corona in nitrogen at atmosphere pressure: Comparison with Trichel pulses in air
Authors: Zhang Xing , Guo Yulin , Sun Anbang , Yao Congwei , Sun Guangyu , Zhang Guanjun
Published: March 2020

The pulsed mode of negative DC corona discharge in nitrogen at atmosphere pressure is investigated in needle–plate electrodes and compared with Trichel pulses in air. Current/voltage waveforms and time-resolved discharge pictures are recorded experimentally. It is found that the pulsed mode only appears in the presence of a large ballast resistor. The slope of pulsed mode time-averaged voltage–current curve is negative, in contrast to that of Trichel pulses. A transition of slope from negative to positive is tracked by increasing the oxygen fraction. The development of pulse discharge in nitrogen can be divided into three stages: (1) current raising stage, (2) current falling stage, and (3) charging stage. At stage 1, the current raises and forms a peak. The leading edge lasts for dozens of nanoseconds, similar to that of Trichel pulses in air. At stage 2, the voltage decreases monotonically, where a second hump can appear in the current waveform. Through intensified charge coupled device (ICCD) pictures and fluid model simulation, the hump is attributed to the further development of temporal glow discharge. The relative value and occurrence time of this hump are shown to be affected by a parallel capacitor, the space between electrodes, and the applied source voltage. At stage 3, the current remains constant, combined with a rise of gap voltage. Meanwhile, the stray capacitor is charged, which is analyzed by an equivalent circuit model. Through this experiment and simulation, we further clarify the mechanisms of pulses in nitrogen and differences between pulses in nitrogen and Trichel pulses in air.
Modeling radiative-shocks created by laser–cluster interactions
Authors: Scott R. H. H. , Booth N. , Hawkes S. J. , Symes D. R. , Hooker C. , Doyle H. W. , Olsson-Robbie S. I. , Lowe H. F. , Price C. J. , Bigourd D. , Patankar S. , Mecseki K. , Gumbrell E. T. , Smith R. A.
Published: March 2020

Radiative-shocks induced by laser–cluster interactions are modeled using radiation-hydrodynamic simulations. A good agreement—in both shock velocity and density profiles—is obtained between experiment and simulations, indicating that non-local thermodynamic equilibrium (NLTE) radiative effects are important in the experimental regime examined, particularly at early times (≤30 ns) due to the elevated temperatures (≥35 eV). The enhanced NLTE radiative emission causes the shock to be reduced in amplitude, increased in width, and reduced in propagation velocity, while the amplitude of the radiative precursor is increased. As the density and temperature conditions are relatively modest, this potentially has important implications for the scalings that are used in laboratory–astrophysics to transform between laboratory and astrophysical scales, which do not hold for non-LTE systems.
Identifying improved microchannel configuration with triangular cavities and different rib structures through evaluation of thermal performance and entropy generation number
Authors: Sikdar Prabir , Datta Aparesh , Biswas Nirmalendu , Sanyal Dipankar
Published: March 2020

Exploration of newer geometrical structures for microsinks stems from the desire to achieve better cooling at a lower pressure drop for more compact electronic devices. In this study, a three-dimensional conjugate heat transfer analysis is performed for a novel microchannel heat sink (MCHS) with disruptive structures in an otherwise rectangular channel. Each of these structural units has a pair of triangular cavities (TCs) on the opposite side walls and one in between the rib positioned symmetrically about the vertical mid-plane. Different units with diamond rib, rectangular rib (RR), backward triangular rib (BTR), and forward triangular rib (FTR) are analyzed. A notable finding of this work is identifying a rib as a disruption leading to thinning of the boundary layer on the side walls in the channel behind the rib. Another important contribution of a rib in both TC-RR and TC-BTR units is shown to promote chaotic advection due to having a longitudinal downstream vortex in each quadrant. The benefit of the lowest wall temperature is evident from the predicted results. Simple thermodynamic models are developed to establish that the minimization of entropy generation number (EGN) leads to the lowest temperature of the channel material for removing a given heat flux by the MCHS, and the maximization of the thermal performance (TP) implies achievement of the lowest pumping power. The corresponding numerical results are exploited for identifying the geometrical parameters over Reynolds number ranging from 197 to 595 that maximize the TP and closely minimize the EGN. The TC-FTR configuration is seen to yield the highest TP of about 1.78 at an intermediate value of Re around 400 along with low EGN of nearly 0.45. Results show that a microchannel with TC-BTR combination yields the highest heat transfer rate with a maximum pressure drop penalty leading to its poor TP. Thus, TC-RR turns out to be the choice in case a low wall temperature happens to be a critical requirement. A small sacrifice in it makes TC-FTR the choice for having the highest TP leading to a compact design.
Theoretical search for possible Li–Ni–B crystal structures using an adaptive genetic algorithm
Authors: Wang Renhai , Sun Yang , Gvozdetskyi Volodymyr , Zhao Xin , Zhang Feng , Xu Lin-Han , Zaikina Julia V. , Lin Zijing , Wang Cai-Zhuang , Ho Kai-Ming
Published: March 2020

The structural diversity of rare-earth and transition metal borides indicates that alkali-transition metal borides (A-T-B) show tremendous promise in exhibiting a variety of crystal structures with different dimensionalities of T-B frameworks. On the other hand, the A-T-B ternary systems are severely underexplored because of the synthetic challenges associated with their preparation. Accurate and efficient computational predictions of low-energy stable and metastable phases can identify the optimal compositions of the hypothetical compounds in the A-T-B systems to guide the synthesis. In this work, we have computationally discovered several new phases in the Li–Ni–B ternary system. The newly discovered LiNiB, Li2Ni3B, and Li2NiB phases expand the existing theoretical database, and the convex-hull surface of Li–Ni–B has been re-constructed. The lowest energy structure of the LiNiB compound has been found by an adaptive genetic algorithm with layered motif, which matches with the experimentally determined structure. According to our electrochemical calculations, LiNiB and another predicted layered Li2NiB compounds have great potential as anode materials for lithium batteries. The Li2Ni3B compound with the space group P4332 was predicted to crystallize in a cubic structure composed of distorted octahedral units of BNi6, which is isostructural to two noncentrosymmetric superconductors Li2Pd3B and Li2Pt3B. While we were unable to experimentally confirm the Li2Ni3B compound utilizing the hydride synthetic route, attempts to synthesize this compound by alternate methods remain highly desirable, considering its potential superconducting properties.
Effects of chemical potentials on isothermal ion-acoustic solitary waves and their three-dimensional instability in a magnetized ultra-relativistic degenerate multicomponent plasma
Authors: El-Shamy E. F. , Selim M. M. , El-Depsy A. , Abdellahi M. O. , Al-Hagan O. , Al-Mogeeth A. , Alelyani L.
Published: March 2020

The three-dimensional instability of isothermal ion-acoustic (IIA) solitary waves is examined in a magnetized ultra-relativistic degenerate multicomponent plasma, comprising nondegenerate inertial warm ions and ultra-relativistic degenerate inertialess electrons as well as positrons, by applying a small-k (long wavelength) expansion method. The nonlinear dynamics of IIA solitary waves in such a plasma model are governed by the nonlinear Zakharov–Kuznetsov equation. To perform the analysis, the instability criterion and the growth rate of the instability of IIA solitary waves have been obtained. A careful investigation shows that the amplitude, the width, the growth rate, and the instability of IIA solitary waves increase with the increasing chemical potential of electrons. The stable region of IIA solitary waves increases with the increasing fermion population and the angle between the directions of propagation and the uniform magnetic field. The present study may be helpful for elucidating the physical nature of nonlinear waves in compact objects such as white dwarfs and neutron stars where the concentration of degenerate ultra-relativistic electrons and positrons and their chemical potentials play a crucial role.
Deformation mode analysis by eigenvectors of atomic elastic stiffness in static uniaxial tension of various fcc, bcc, and hcp metals
Authors: Yashiro K.
Published: March 2020

In order to clarify the physical meaning of the eigenvector of the atomic elastic stiffness matrix, Bija=Δσia/Δεj, static calculations of uniaxial tension are performed on various fcc, bcc, and hcp metals with four different embedded atom method (EAM) potentials. Many fcc metals show instability for the constant volume mode, or the eigenvector of (Δεxx, Δεyy, Δεzz) = (±1, ∓1, 0), under the [001] tension. Bcc also loses resistance against other constant volume mode, (Δεxx, Δεyy, Δεzz) = (±1, ±1, ∓2), in the [001] tension. Hcp shows shear modes Δγyz and Δγzx under the [0001] tension, which correspond to atom migration by dislocation on the slip plane. Similar shear modes appear in the [111] tension of fcc and [110] tension of bcc. Hcp also changes the mode to constant volume and shear in the [1¯010] tension, which imply the deformation in the pyramidal and prismatic planes.
Predicting metal–metal interactions. II. Accelerating generalized schemes through physical insights
Authors: Choksi Tej S. , Streibel Verena , Abild-Pedersen Frank
Published: March 2020

Operando-computational frameworks that integrate descriptors for catalyst stability within catalyst screening paradigms enable predictions of rates and selectivity on chemically faithful representations of nanoparticles under reaction conditions. These catalyst stability descriptors can be efficiently predicted by density functional theory (DFT)-based models. The alloy stability model, for example, predicts the stability of metal atoms in nanoparticles with site-by-site resolution. Herein, we use physical insights to present accelerated approaches of parameterizing this recently introduced alloy-stability model. These accelerated approaches meld quadratic functions for the energy of metal atoms in terms of the coordination number with linear correlations between model parameters and the cohesive energies of bulk metals. By interpolating across both the coordination number and chemical space, these accelerated approaches shrink the training set size for 12 fcc p- and d-block metals from 204 to as few as 24 DFT calculated total energies without sacrificing the accuracy of our model. We validate the accelerated approaches by predicting adsorption energies of metal atoms on extended surfaces and 147 atom cuboctahedral nanoparticles with mean absolute errors of 0.10 eV and 0.24 eV, respectively. This efficiency boost will enable a rapid and exhaustive exploration of the vast material space of transition metal alloys for catalytic applications.
Fat tails and black swans: Exact results for multiplicative processes with resets
Authors: Zanette D. H. , Manrubia S.
Published: March 2020

We consider a class of multiplicative processes which, added with stochastic reset events, give origin to stationary distributions with power-law tails—ubiquitous in the statistics of social, economic, and ecological systems. Our main goal is to provide a series of exact results on the dynamics and asymptotic behavior of increasingly complex versions of a basic multiplicative process with resets, including discrete and continuous-time variants and several degrees of randomness in the parameters that control the process. In particular, we show how the power-law distributions are built up as time elapses, how their moments behave with time, and how their stationary profiles become quantitatively determined by those parameters. Our discussion emphasizes the connection with financial systems, but these stochastic processes are also expected to be fruitful in modeling a wide variety of social and biological phenomena.
Blue phase stabilization by CoPt-decorated reduced-graphene oxide nanosheets dispersed in a chiral liquid crystal
Authors: Lavrič Marta , Cordoyiannis George , Tzitzios Vasileios , Lelidis Ioannis , Kralj Samo , Nounesis George , Žumer Slobodan , Daniel Matej , Kutnjak Zdravko
Published: March 2020

We report on the effect of reduced-graphene oxide nanosheets decorated by CoPt nanoparticles on the blue phase range of a chiral liquid crystal. By means of high-resolution ac calorimetry and polarizing optical microscopy, it is demonstrated that a small concentration of these nanosheets induces the stabilization of a single blue phase structure in comparison to three blue phases existing in the pure compound. The results are compared with other liquid crystal-dispersed graphene studies, and, moreover, a short theoretical discussion of the stabilization effect is included.
Effects of magnetic field on resistive switching in multiferroic based Ag/BiFeO3/FTO RRAM device
Authors: Jena A. K. , Sahoo Ajit Kumar , Mohanty J.
Published: March 2020

We report the effects of the magnetic field on resistive switching behavior in the Ag/BiFeO3/FTO RRAM device through conventional I–V characteristics. The switching of the device from a high resistance state (HRS) to a low resistance state (LRS) at a certain threshold voltage (Vt) evidences a shift under the magnetic influence. The shifting of Vt toward higher voltage is due to the appearance of the Lorentz force and magnetoelectric effect when the magnetic field is applied perpendicular to the flow of current. The resistance of the HRS and LRS increases simultaneously under the application of the magnetic field due to the induced Hall resistance effect. The OFF/ON ratio∼12, which is repeatable for 100 multiple cycles. The discrete RESET state of the device is achieved by pulse-width and pulse-height modulation. Substantially, the resistance of these states increases systematically under the action of the magnetic field. The control of resistance states with the pulse-height and magnetic field in Ag/BiFeO3/FTO shows promise for future multilevel non-volatile memory technology.
Theoretical and numerical analysis of density perturbation development induced by high velocity impact
Authors: Gorodnichev Kirill , Zakharov Pavel , Kuratov Sergei , Menshov Igor , Gorodnichev Evgenii
Published: March 2020

The problem of high velocity impact between two solid plates where one of them has a non-uniformly disturbed density field is studied. The nature of an initial perturbation here differs from one considered in the classical Richtmyer–Meshkov instability (RMI). We consider the instability that develops from the initial perturbations of the density field with a flat interface between plates, while RMI is triggered by a shock passing through the corrugated interface. The structure of perturbation fields generated in the plates due to impact and the interface evolution are studied via the analytic linear and nonlinear models for normal modes using the Euler equations for compressible fluids and appropriate boundary conditions. Such analysis reveals three different regimes in which the generated disturbances can develop depending on the direction of the perturbation wave vector. The obtained theoretical findings are in good quantitative agreement with our detailed numerical simulations.
Crystal defects in monocrystalline silicon induced by spot laser melting
Authors: Menold T. , Hadjixenophontos E. , Lawitzki R. , Schmitz G. , Ametowobla M.
Published: March 2020

Laser processing of monocrystalline silicon has become an important tool for a wide range of applications. Here, we use microsecond spot laser melting as a model experiment to investigate the generation of crystal defects and residual stress. Using Micro-Raman spectroscopy, defect etching, and transmission electron microscopy, we find no dislocations in the recrystallized volume for cooling rates exceeding |dT/dt|=2×107 K/s, and the samples remain free of residual stress. For cooling rates less than |dT/dt|=2×107 K/s, however, the experiments show a sharp transition to a defective microstructure that is rich in dislocations and residual stress. Moreover, transmission electron microscopy indicates dislocation loops, stacking-fault tetrahedra, and voids within the recrystallized volume, thereby indicating supersaturation of intrinsic point defects during recrystallization. Complementing photoluminescence spectroscopy indicates even three regimes with decreasing cooling rate. Spectra of regime 1 do not contain any defect related spectral lines. In regime 2, spectral lines appear related to point defect clusters. In regime 3, the spectral lines related to point defect clusters vanish, but dislocation-related ones appear. We propose a quantitative model explaining the transition from dislocation-free to dislocation-rich recrystallization by means of the interaction between intrinsic point defects and dislocations.
3D printing of polymer-bonded anisotropic magnets in an external magnetic field and by a modified production process
Authors: Sonnleitner Klaus , Huber Christian , Teliban Iulian , Kobe Spomenka , Saje Boris , Kagerbauer Daniel , Reissner Michael , Lengauer Christian , Groenefeld Martin , Suess Dieter
Published: March 2020

The possibility of producing polymer-bonded magnets with the aid of additive processes, such as 3D printing, opens up a multitude of new areas of application. Almost any structures and prototypes can be produced cost-effectively in small quantities. Extending the 3D printing process allows the manufacturing of anisotropic magnetic structures by aligning the magnetic easy axis of ferromagnetic particles inside a paste-like compound material along an external magnetic field. This is achieved by two different approaches. First, the magnetic field for aligning the particles is provided by a permanent magnet. Second, the 3D printing process itself generates an anisotropic behavior of the structures. An inexpensive and customizable end-user fused filament fabrication 3D printer is used to print magnetic samples. The magnetic properties of different magnetic anisotropic Sr ferrite and SmFeN materials are investigated and discussed.
Tunable Curie temperature in layered ferromagnetic Cr5+xTe8 single crystals
Authors: Zhang Luo-Zhao , He Xiu-De , Zhang An-Lei , Xiao Qi-Ling , Lu Wen-Lai , Chen Fei , Feng Zhenjie , Cao Shixun , Zhang Jincang , Ge Jun-Yi
Published: March 2020

The relatively low Curie temperature (Tc) in recently discovered two-dimensional ferromagnetic (FM) materials has limited their potential applications in designing next generation electronics. Searching for new low-dimensional layered materials with room-temperature Tc is highly needed. Here, we report the study of layered FM materials Cr5+xTe8 (x = −0.10, 0.11, 0.56, 1) in which Tc can be well manipulated by the Cr content. Single crystalline Cr5+xTe8 samples have been synthesized and characterized by energy dispersive x-ray spectroscopy, x-ray diffraction, and magnetization measurements. We have found that Tc increases monotonically with Cr content and reaches 313 K at x = 1. While the FM coupling is enhanced with an increase in the Cr content, the antiferromagnetic (AFM) phase at low temperatures is suppressed. Due to the competition of FM and AFM phases, a wasp-waist loop is observed on isothermal magnetization curves. A magnetic flip occurs by changing the temperature and magnetic field to overcome the flipping energy barrier. Our results indicate that the Cr5+xTe8 system serves as a promising platform to tune the 2D ferromagnetism in layered materials.
Instantaneous pressure determination from unsteady velocity fields using adjoint-based sequential data assimilation
Authors: He Chuangxin , Liu Yingzheng , Gan Lian
Published: March 2020

A sequential data assimilation (DA) method is developed for pressure determination of turbulent velocity fields measured by particle image velocimetry (PIV), based on the unsteady adjoint formulation. A forcing term F, which is optimized using the adjoint system, is added to the primary Navier–Stokes (N–S) equations to drive the assimilated flow toward the observations at each time step. Compared with the conventional unsteady adjoint method, which requires the forward integration of the primary system and the backward integration of the adjoint system, the present approach integrates the primary-adjoint system all the way forward, discarding the requirement of data storage at every time step, being less computationally resource-consuming, and saving space. The pressure determination method of integration from eight paths [J. O. Dabiri et al., “An algorithm to estimate unsteady and quasi-steady pressure fields from velocity field measurements,” J. Exp. Biol. 217, 331 (2014)] is also evaluated for comparison. Using synthetic PIV data of a turbulent jet as the observational data, the present DA method is able to determine the instantaneous pressure field precisely using the three-dimensional velocity fields, regardless of the observational noise. For the two-dimensional three-component (3C) or two-component (2C) velocity fields, which are not sufficient for pressure determination by the integration method due to the lack of off-plane derivatives, the present DA method is able to reproduce pressure fields whose statistics agree reasonably well with those of the referential results. The 3C and 2C velocity fields yield quite similar results, indicating the possibility of pressure determination from only planar-PIV measurements in turbulent flows. The tomography PIV measurements are also used as observational data, and a clear pressure pattern is obtained with the present DA method.
Modifications of magnetic anisotropy of Fe3GeTe2 by the electric field effect
Authors: Wang Yun-Peng , Chen Xiao-Yan , Long Meng-Qiu
Published: March 2020

The Fe3GeTe2 material is the only metallic ferromagnet with a van der Waals layered structure, which has been used as a ferromagnetic electrode in spintronic devices. The tunability of magnetic properties of few-layer Fe3GeTe2 by electrostatic gating is demonstrated in experiments. In this work, we present a theoretical investigation of the electric field effect on the magnetic anisotropy of the Fe3GeTe2 monolayer using the first-principles approach. The calculated magnetic anisotropy energy exhibits strongly oscillating behavior at the electron-doping side, in strong contrast to the hole-doping side. The significant variation of the magnetic anisotropy energy vs electron doping concentration agrees well with experimental results. While the rigid-band approximation works well at the hole-doping side, electron doping induces significant changes in the electronic structure near the Fermi energy. The analysis of the electronic structure shows that the occupation and splitting of the Te(pz)-Fe(dz2) bond states play a critical role in modifying the magnetic anisotropy.
The effect of oxygen vacancy plate on the domain structure in BiFeO3 thin films by phase field simulations
Authors: Tian X. H. , Wang Y. J. , Tang Y. L. , Zhu Y. L. , Ma X. L.
Published: March 2020

Domain walls in ferroelectric materials attract great interest since they can possess fascinating functionalities. Therefore, it is very important to modulate domain structures. Our recent experiments showed that oxygen vacancy plates could induce charged domain walls with different types. However, the detailed transition behavior between different charged domain walls was not explored. In this work, systematical phase field simulations were performed to reveal the evolution of domain structures with the size and charge density of the oxygen vacancy plate. These results could provide a route to build complex patterns of charged domain walls.
A comparative study on the large-scale-resolving capability of wall-modeled large-eddy simulation
Authors: Wang Limin , Hu Ruifeng , Zheng Xiaojing
Published: March 2020

Wall-modeled large-eddy simulation (WMLES) could be a useful predictive tool in high-Reynolds-number wall-bounded turbulent flows that are ubiquitous in nature and engineering, but its capability to resolve large-scale energy-containing outer motions has yet to be assessed comprehensively. In this study, moderately high-Reynolds-number turbulent channel flows up to Reτ ≈ 5200 are simulated by WMLES with various subgrid-scale (SGS) models and wall models in comparison with direct-numerical simulation data. The main objective is to assess the predictive capability of WMLES in the context of the turbulence kinetic energy spectrum in the outer region. Four classical eddy-viscosity-type SGS models are compared, i.e., the Smagorinsky model, the Lagrangian dynamic model, the Lagrangian scale-dependent (LASD) model, and the Vreman model. It is shown that the performance of the LASD model is superior to others in predicting one-point statistics as well as kinetic energy spectra. Three types of wall models are involved, i.e., the equilibrium wall model, the slip-wall model, and the integral wall model. We find that the wall model does not significantly affect prediction of turbulence fluctuations in the outer region. Although near-wall turbulent motions are not fully resolved in WMLES, we clearly show that the spectral characteristics of large-scale energy-containing turbulent motions in the outer region can reasonably be predicted with appropriate models. We also provide a preliminary discussion on the effects of domain setup and grid resolution. The difference in the spectral energy distribution between full- and half-channel flows is also reported.
Optical properties of periodically driven open nonequilibrium quantum systems
Authors: Cabra Gabriel , Franco Ignacio , Galperin Michael
Published: March 2020

Characterization and control of matter by optical means is at the forefront of research both due to fundamental insights and technological promise. Theoretical modeling of periodically driven systems is a prerequisite to understanding and engineering nanoscale quantum devices for quantum technologies. Here, we develop a theory for transport and optical response of molecular junctions, open nonequilibrium quantum systems, under external periodic driving. Periodic driving is described using the Floquet theory combined with nonequilibrium Green’s function description of the system. Light–matter interaction is modeled by employing the self-consistent Born approximation. A generic three-level model is utilized to illustrate the effect of the driving on optical and transport properties of junctions.
Initial-switched boosting bifurcations in 2D hyperchaotic map
Authors: Bao B. C. , Li H. Z. , Zhu L. , Zhang X. , Chen M.
Published: March 2020

Recently, the coexistence of initial-boosting attractors in continuous-time systems has been attracting more attention. How do you implement the coexistence of initial-boosting attractors in a discrete-time map? To address this issue, this paper proposes a novel two-dimensional (2D) hyperchaotic map with a simple algebraic structure. The 2D hyperchaotic map has two special cases of line and no fixed points. The parameter-dependent and initial-boosting bifurcations for these two cases of line and no fixed points are investigated by employing several numerical methods. The simulated results indicate that complex dynamical behaviors including hyperchaos, chaos, and period are closely related to the control parameter and initial conditions. Particularly, the boosting bifurcations of the 2D hyperchaotic map are switched by one of its initial conditions. The distinct property allows the dynamic amplitudes of hyperchaotic/chaotic sequences to be controlled by switching the initial condition, which is especially suitable for chaos-based engineering applications. Besides, a microcontroller-based hardware platform is developed to confirm the generation of initial-switched boosting hyperchaos/chaos.
Sweet potato (Ipomoea batatas) vine silage: a cost-effective supplement for milk production in smallholder dairy-farming systems of East Africa?
Authors: Gakige J. K. , Gachuri C. , Butterbach-bahl K. , Goopy J. P.
Published: March 2020

Context
Dairy production in East Africa is dominated by smallholder production systems, but is dogged by suboptimal milk production mediated by poor nutrition. Grain-based concentrates can be used to make the energy and protein deficits in rain-fed systems, but this strategy faces several hurdles. For livestock production systems to be sustainable, it is important that less human-edible food is fed to animals and sweet potato can serve both as a source of human food (tuber) and animal feed (vines). Smallholder scale-appropriate technology has been used to allow feed preservation of the perishable sweet potato vines for use throughout the year.

Aims
We assessed the efficacy of sweet potato vine silage plus wheat bran (SPVSWB) as a supplement to maintain milk production at a lower cost than that of grain-based commercial dairy concentrate (CDC).

Methods
Multiparous Holstein–Friesian cattle (n = 12) were given a basal diet of Napier grass (Pennisetum purpureum cv. South Africa), ad libitum, plus a fixed amount of either SPVSWB or CDC, (designed to be both iso-nitrogenous and iso-caloric) during late (LL) and early (EL) lactations.

Key results
Daily milk yield was lower for SPVSWB than for CDC groups, although comparable (not significant), in both LL (6.2 vs 7.5 L/day) and EL (14.2 vs 16.0 L/day); however, the lower cost of production for SPVSWB (23.2 vs 48.7 KES/kg DM) ensured that margins on milk income over feed (per cow per day) were greater for SPVSWB in both periods. (LL: 71 vs 14.5; and EL: 426 vs 400 KES/day). The lower intake for SPVSWB than for CDC is most probably due to high neutral detergent fibre content in the supplement and the lower milk production, owing to either, or both, of lower energy and protein intake.

Conclusions
It is suggested that some reformulation of SPVS, replacing in part or in whole the Napier grass with rejected sweet potato tubers, will decrease the neutral detergent fibre content, increase the metabolisable energy content, reducing the need for additional wheat bran and may, thereby, enhance the production response to equate with that of CDC.

Implications
It is clear that, despite SPVSWB eliciting lower milk production (LL 6.2 and EL14.2 L/day) than does CDC (LL 7.5 and EL 16.0 L/day), SPVSWB is a cost-effective, accessible alternative to grain-based supplementation in small-holder dairy-farming systems of Kenya.
Variation in Matukar Panau kinship terminology
Authors: Barth Danielle
Published: March 2020

Referential kinship terms in Matukar Panau (Oceanic, Papua New Guinea) are obligatorily possessed. Traditionally, kinship terms are directly possessed in Oceanic languages (with an obligatory suffix on the root that agrees with the person and number of the possessor). In Matukar Panau, some kinship terms are also indirectly possessed (with a classifier that agrees with the person and number of the possessor). A third pattern shows double-marking of possessors with directly possessed terms co-occurring with a classifier. I present a multivariate analysis of the predictors that influence the choice of the direct, indirect or double-marked patterns. Older women and younger men are most likely to use the indirect pattern, particularly when discussing their own kin from their households, especially in conversational situations. The indirect possession pattern, then, is used for more integral relationships, what has previously been the semantic domain of direct possession in Oceanic.
Variable number marking in Vera’a
Authors: Schnell Stefan
Published: March 2020

The number interpretation of Noun Phrase structures (NPs) with different animacy values and variable overt marking
of number is investigated in a corpus from the Oceanic language Vera’a. It is found that number marking is optional for all nouns
and that number marking is essentially semantic, expressing collectivity and distributivity. While statistical patterns of greater
likelihood of number marking comply with the animacy hierarchy, the central motivating factor for number marking is found to be
likelihood of individuatedness. This study thus contributes to a functionalist account of cross-linguistically observed patterns
of hierarchical number marking.
The spatialization and temporalization of environmental suffering
Authors: Sullivan Daniel , Palitsky Roman , Schmitt Harrison
Published: March 2020

Many people live in circumstances of environmental suffering: exposure to contaminated natural resources and toxic chemicals due to a history of accident or misuse. Environmental suffering is disproportionately experienced by politically, ethnically, and economically disadvantaged group members. An analysis rooted in the concept offalse consciousness(Gabel, 1975) suggests that environmental suffering narratives tend toward perspectival distortions. Although narratives from disadvantaged group members may contain defensive distortions, these are warranted by experiences of environmental suffering, and expert narratives also regularly contain distortions. Disadvantaged narratives of environmental suffering tend towardspatializingdistortions: emphasizing spatial aspects, objectifying people and agents, and fixating on a tragic past. Advantaged narratives of environmental suffering tend towardtemporalizingdistortions: emphasizing temporal aspects, refusing to clearly assign blame, and fixating on a “miraculous” future. We present a preliminary supporting study, using quantitative text analysis, of parallel environmental suffering narratives from community members, EPA officials, and other experts.
“And in Israel we became Russians straight away”
Authors: Maydell Elena
Published: March 2020

Social constructionism suggests that identities are created through interactions with others, as well as the wider socio-cultural environment. This research employs constructionist narrative analysis for a case study of a Russian-Jewish woman who emigrated from Russia to Israel and then to New Zealand. Lara’s first two societies of settlement, Russia and Israel, seem pre-occupied with the ethnic demarcation of their members, which contradicts to how she feels “deep inside”. Ascribed an inferior identity in both, Lara provides rich explanations for her husband’s remark that in Russia they were “bloody Jews” and in Israel they became “bloody Russians”. While making sense of her life experiences, she articulates the complex process of changes and assigns positive meanings to her identity using available cultural resources. Her fascinating narrative provides a unique in-depth account, allowing for a better understanding of the interplay between such notions as identity, agency, and community across different cultural environments.
The Family Business in Iran since the
Islamic Revolution as a Mode of
Coordination
Authors: Coville Thierry
Published: March 2020

There has been very little research on
family businesses (FBs) in Iran. Taking an
institutional point of view, this article, based
on a survey conducted in Iran, demonstrates that
since the 1979 revolution FBs in Iran have been
key intermediaries between political pressure from
the top and societal trends from below. FBs in
Iran since the revolution can be considered as a
perfect mode of coordination reflecting
“capitalism from below.” Based on unconditional
support among the family members, they are
perfectly adapted to the low-trust environment in
Iran since the revolution. As a mode of
coordination, the family business was also
essential in protecting the modernization of
Iranian society in promoting the role of women and
the value of competency. It was also a mode of
coordination which enabled FBs to protect their
property rights which were threatened by a
predatory state.
Women’s Writing in Action: On Female-authored Hajj Narratives in Qajar Iran
Authors: Bachtin Piotr
Published: March 2020

This paper examines the textual and performative functions of early women’s writings on the example of three accounts of the pilgrimage to Mecca written during the Qajar era by Mehrmāh Khānom ʿEsmat al-Saltaneh (1880–81), the anonymous Hājiyeh Khānom ʿAlaviyeh Kermāni (1892–94), and Sakineh Soltān Vaqār al-Dowleh Esfahāni Kuchak (1899–1901). It ponders on the relationships between the female writers and textuality, their readers and, finally, the diary personas they created. It claims that their writings emerged in the process of negotiating the then existing, masculine models of textuality and authorial authority. By rejecting the monologic authoritativeness of literature and textuality, the women diarists transformed their texts into a space for dialogue—including dialogue with themselves.
Investigation of optical fiber-tip probes for common and ultrafast SERS
Authors: Morozov Yevhenii M , Lapchuk Anatoliy S , Prygun Alexander V , Kryuchyn Andriy A , Dostalek Jakub
Published: March 2020

In this study, we performed a three-dimensional computational experiment on ultrashort pulse propagation in an optical fiber-tip probe that is decorated with gold nanoparticles (NPs) using a constant structure for the probe’s dielectric taper and different spatial configurations of the gold nanoparticles. Interestingly, a hot spot with the highest amplitude of the electric field was found not along the same chain of the NPs but between terminal NPs of neighboring chains of NPs at the probe’s tip (the amplitude of the electric field in the hot spots between the NPs along the same chain was of the order of 101, while that between terminal NPs of neighboring chains was of the order of 103). We eventually identified a configuration with only six terminal nanoparticles (Config4) which is characterized by the highest electric field amplitude enhancement and can provide the highest spatial resolution in the SERS interrogation of an object of interest. The ultrashort temporal responses of the hot spots for all configurations exhibited relatively high pulse elongation (relative elongation was greater than 4.3%). At the same time, due to the reflection of the incident pulse and consequent interference, the temporal responses of most hot spots contained several peaks for all configurations except for the optimum Config4. Nonetheless, the ultrashort temporal responses of all hot spots for Config4 were characterized by a single peak but with a relatively large pulse elongation (relative elongation was 234.1%). The results indicate that further examination of this new structure of a nanoparticles-coated optical fiber-tip probe with only six terminal NPs may provide attractive characteristics for its practical applications.
Activation robustness with directional leads and multi-lead configurations in deep brain stimulation
Authors: Janson Andrew P , Anderson Daria Nesterovich , Butson Christopher R
Published: March 2020

Objective. Clinical outcomes from deep brain stimulation (DBS) can be highly variable, and two critical factors underlying this variability are the location and type of stimulation. In this study we quantified how robustly DBS activates a target region when taking into account a range of different lead designs and realistic variations in placement. The objective of the study is to assess the likelihood of achieving target activation. Approach. We performed finite element computational modeling and established a metric of performance robustness to evaluate the ability of directional and multi-lead configurations to activate target fiber pathways while taking into account location variability. A more robust lead configuration produces less variability in activation across all stimulation locations around the target. Main results. Directional leads demonstrated higher overall performance robustness compared to axisymmetric leads, primarily 1–2 mm outside of the target. Multi-lead configurations demonstrated higher levels of robustness compared to any single lead due to distribution of electrodes in a broader region around the target. Significance. Robustness measures can be used to evaluate the performance of existing DBS lead designs and aid in the development of novel lead designs to better accommodate known variability in lead location and orientation. This type of analysis may also be useful to understand how DBS clinical outcome variability is influenced by lead location among groups of patients.