bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic and optical properties of Janus monolayers MoXB2(X=S, Se): first-principles prediction
Authors: Lan Qingwen , Chen Changpeng , Qin Tian
Published: March 2021

By means of comprehensive first-principles calculations, we studied the geometric structure, the stability and electronic properties of the new two-dimensional (2D) Janus MoXB2(X=S, Se) monolayers. Our calculations demonstrated that the predicted Janus MoXB2monolayers are all stable semiconductors with direct band gap. In this paper, we focus on impacts upon the electronic and optical properties of the MoXB2monolayers under the different biaxial strains. With the compressive stress increases, the MoXB2monolayers would become indirect band gap semiconductors, and then behave as semimetal. While under tensile strain, MoXB2still maintain direct band gap. In addition, the optical calculation shows that biaxial strain leads to blue shifts in the optical absorption and reflectivity. The result indicates that MoXB2may be promised nano candidate materials in optoelectronic devices.
Le Health Data Hub (suite)
Authors: Goldberg Marcel , Zins Marie
Published: March 2021

Dans le monde de la recherche et de la santé publique, un consensus existe pour considérer que les données de santé constituent une ressource extrêmement précieuse pour de multiples usages, et qu’il convient d’en faciliter l’accès et le partage. Dans ce domaine, la France dispose de nombreux atouts, notamment de bases de données d’ampleur et de richesse sans doute uniques. Depuis quelques années, les pouvoirs publics ont pris conscience des enjeux autour de ces données et ont mis en place un dispositif technique, légal et réglementaire pour y faire face : le Système national des données de santé (SNDS) accompagné de la Plateforme des données de santé (PDS), plus communément appelée Health Data Hub (HDH). Cette plateforme est une infrastructure officiellement créée par un arrêté ministériel du 30 novembre 2019, destinée à faciliter l’accès et l’utilisation des données de santé afin de favoriser la recherche. On ne peut qu’applaudir une telle initiative qui constitue un progrès majeur et ouvre de nombreuses perspectives pour la recherche et la santé publique. Cependant, tel qu’il est conçu, le HDH pose divers problèmes qui amènent à questionner ses orientations actuelles.
Evolution of inclusions in Mg-RE-Ti treated steels with different Al contents and their influence on acicular ferrite
Authors: Cui Xiaokang , Song Bo , Mao Jinghong
Published: March 2021

The size distribution and composition of inclusions in Mg-RE-Ti treated steels with different Al contents were investigated systematically, while the microstructure and the nucleation potency of inclusions for AF were analyzed. The results show that the inclusions were refined with Mg treatment, and then coarsen following La addition in the samples. The particles in high Al sample were more likely to collide, aggregate and form clusters due to the relatively high amount of inclusions in melt steel. The dominate inclusions were composed of two layer structures with Mg-bearing inclusions cores and La-bearing inclusions shells. With the increase of Al content, the cores evolved from MgO to MgO•Al2O3 and the shells evolved from La2O2S and La2O3 to LaAlO3. The nucleation potency of inclusions for AF decreased due to relatively high lattice misfit between inclusions and α-Fe in high Al sample. The AF fraction decreased with the increase of Al content because of the decrease of the amount of effective inclusions.
An optimal solution for the budgets assignment problem
Authors: Jemmali Mahdi
Published: March 2021

Municipalities are service organizations that have a major role in strategic planning and community development that consider the future changes and society developments, by implementing set of projects with pre-allocated budgets. Projects have standards, budgets and constraints that differ from one community to another and from one city to another. Fair distributing of different projects to municipalities, while ensuring the provision of various capabilities to reach developmental role is NP-Hard problem. Assuming that all municipalities have the same strategic characteristics. The problem is as follows: given a set of projects with different budgets, how to distribute all projects to all municipalities with a minimum budget gap between municipalities. To derive equity distribution between municipalities, this paper developed lower bounds and eleven heuristics to be utilized in the branch-and-bound algorithms. The performance of the developed heuristics, lower bounds and the exact solutions are presented in the experimental study.
Enlightening Diagnosis and Differential Diagnosis of Dental Fluorosis—A Hidden Entity in a Crowd
Authors: Patidar Deepika , Sogi Suma , Patidar Dinesh Chand , Sharma Atul , Jain Mansi , Prasad Priyanka
Published: March 2021

Aim To provide diagnosis as well as differential diagnosis of dental fluorosis.

Background Dental fluorosis is a developmental defect of enamel, due to consecutive exposures of tooth during the formative stage of development to the higher concentration of fluoride, resulting in enamel with lesser mineral content and enhanced porosity. Several epidemiological indices have been utilized for diagnosis and assessment of dental fluorosis on the basis of clinical appearance. Fluorosis of the deciduous teeth occurs less commonly and is milder than that of permanent teeth.

Highlights The diagnostic difficulties are usually associated between fluorotic and nonfluoride opacities. A complete history of the clinical condition, teeth affected with specific areas, pattern of lesion, color and its method of detection are the few important diagnostic criteria for differentiating dental fluorosis from nonfluoride discolorations of the teeth.

Conclusion This review article has enlightened the diagnosis and differential diagnosis of dental fluorosis among various nonfluoride tooth discolorations. A correct diagnosis results in an appropriate and early management of dental fluorosis and plays an important role in oral epidemiology and public health.
Precisely tracking wake center position for wind farm control
Authors: Patrick Chris
Published: March 2021

Approach tracks the lateral and vertical position of the wake center to improve the performance of closed loop control strategies on wind farms.
Modal approach improves insight into scattering of lossy anisotropic materials
Authors: Johnson-Groh Mara
Published: March 2021

Resonance-focused description of scattering in lossy anisotropic materials increases computational speed time and insight into physical behaviors.
A review on thin film fast response heat transfer gauges
Authors: Alam Tanweer , Kumar Rakesh
Published: March 2021

In this paper, an effort has been made to compile various research investigations done so far on fast response gauges for the short duration measurement in the transient state. The review paper is not only about summarization of all-important research work; rather, a detailed review on the development of the fast response gauges, its application, and various methods of heat estimation from the measured transient temperature history is also presented. Before discussing the development of fast response gauges, various heat flux measurement techniques and newer trends in heat transfer gauges are presented. The focus of this Review is mainly on the thin-film gauge, a robust fast response temperature detector best suited for the short duration measurement. The literature on the application of thin-film gauges for various engineering systems such as turbomachinery and aerodynamic heating systems is broadly categorized as single-layered and multi-layered gauges. The applications for the internal combustion engine and low heat flux measurement are also discussed later. The summary tables with studies arranged in chronological order are also provided. Finally, the estimation of the heat transfer rate from the measured transient temperature data is presented.
Doppler backscattering diagnostic with dual homodyne detection on the Globus-M compact spherical tokamak
Authors: Bulanin V. V. , Yashin A. Y. , Petrov A. V. , Gusev V. K. , Minaev V. B. , Patrov M. I. , Petrov Y. V. , Prisiazhniuk D. V. , Varfolomeev V. I.
Published: March 2021

This article considers a four-frequency microwave Doppler backscattering (DBS) system in the compact spherical tokamak Globus-M. The hardware was adequate for the purposes of studying the peripheral plasma in the tokamak. The multichannel DBS system is based on duplication of a dual homodyne detection circuit for four incident Ka-band frequencies. The ray tracing results for a spherical torus are described, and specific requirements for the antenna tilt adjustment are defined. Some new experimental results are given for using DBS diagnostics on the Globus-M tokamak in order to illustrate its efficiency.
Generalized Pauli constraints in large systems: The Pauli principle dominates
Authors: Reuvers Robin
Published: March 2021

Lately, there has been a renewed interest in fermionic one-body reduced density matrices and their restrictions beyond the Pauli principle. These restrictions are usually quantified using the polytope of allowed, ordered eigenvalues of such matrices. Here, we prove that this polytope’s volume rapidly approaches the volume predicted by the Pauli principle as the dimension of the one-body space grows and that additional corrections, caused by generalized Pauli constraints, are of much lower order unless the number of fermions is small. Indeed, we argue that the generalized constraints are most restrictive in (effective) few-fermion settings with low Hilbert space dimension.
A non-local cryogenic thermometer based on Coulomb-coupled systems
Authors: Banerjee Sagnik , Singha Aniket
Published: March 2021

We investigate a quadruple quantum dot setup that can be employed to sense the temperature of an electrically isolated remote target reservoir. Such a setup was conceived earlier by Sánchez et al. [New J. Phys. 19, 113040 (2017)] as non-local thermodynamic engine and relies on the electrostatic interaction between Coulomb-coupled quantum dots. The conjugation of Coulomb-coupling and energy-filtering results in an overall change in conductance with remote reservoir temperature. The performance of the thermometer is then theoretically investigated using density matrix formulation, and it is demonstrated that the quadruple quantum dot design ensures a superior temperature sensitivity and noise robustness compared to a simple thermometer consisting of two Coulomb-coupled quantum dots. In the end, we investigate the regime of operation and comment on the ground state configuration for optimal performance of the thermometer. The setup investigated in this paper can be employed to construct highly efficient non-local cryogenic thermometers.
Wake position tracking using dynamic wake meandering model and rotor loads
Authors: Dong Liang , Lio Wai Hou , Meng Fanzhong
Published: March 2021

The wake position is crucial feedback information for closed loop wind farm control. This paper presents a wake center position tracking approach based on turbine rotor loads, which is feasible to track the wake position while the wake is impinging on the downstream wind turbine. The rotor equivalent wind characteristics are estimated based on the blade root bending moments. Furthermore, a wake-wind model is developed to describe the relationship between rotor averaged wind characteristics and wake position, in which the velocity deficit profile of the wake is defined by the Gaussian model. An adaptive extended Kalman filter is proposed to estimate the lateral and vertical wake position states, in which wake dynamics is described by the dynamic wake meandering model. The wake meandering is driven by a colored noise with a covariance matrix that is gain scheduled according to the rotor averaged wind characteristic. Uncertainties of wake position detection are discussed in various combinations of the ambient atmospheric condition. Simulation results show that the proposed tracking method achieves good estimates in low ambient turbulence intensity, while, for a wind condition with high turbulence intensity, relatively longer time averaging needs to be applied to smooth out short-term fluctuations and highlight longer-term wake trends.
Self-rectifying resistive switching phenomena observed in Ti/ZrN/Pt/p-Si structures for crossbar array memory applications
Authors: Jung Jinsu , Bae Dongjoo , Kim Sungho , Kim Hee-Dong
Published: March 2021

In this Letter, the self-rectifying resistive switching (RS) behavior is demonstrated in Ti/ZrN/Pt/p-Si resistive random access memory (RRAM) devices. Compared to an RS characteristic of the conventional Ti/ZrN/Pt structures, the memory cell with a p-Si bottom layer shows a larger current ratio. However, a current-limited region is also more clearly obtained in a low voltage region, which can result in one diode-type RRAM with self-selecting properties. Consequently, these results infer that the proposed ZrN-based RRAM cells with a Pt/p-Si selector warrant the realization of the self-selecting RRAM cell without any additional peripheral elements to suppress a disturbance in the reading operation.
Applying deep reinforcement learning to active flow control in weakly turbulent conditions
Authors: Ren Feng , Rabault Jean , Tang Hui
Published: March 2021

Machine learning has recently become a promising technique in fluid mechanics, especially for active flow control (AFC) applications. A recent work [Rabault et al., J. Fluid Mech. 865, 281–302 (2019)] has demonstrated the feasibility and effectiveness of deep reinforcement learning (DRL) in performing AFC over a circular cylinder at Re = 100, i.e., in the laminar flow regime. As a follow-up study, we investigate the same AFC problem at an intermediate Reynolds number, i.e., Re = 1000, where the weak turbulence in the flow poses great challenges to the control. The results show that the DRL agent can still find effective control strategies, but requires much more episodes in the learning. A remarkable drag reduction of around 30% is achieved, which is accompanied by elongation of the recirculation bubble and reduction of turbulent fluctuations in the cylinder wake. Furthermore, we also perform a sensitivity analysis on the learnt control strategies to explore the optimal layout of sensor network. To our best knowledge, this study is the first successful application of DRL to AFC in weakly turbulent conditions. It therefore sets a new milestone in progressing toward AFC in strong turbulent flows.
Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation
Authors: Feng Y. , Miranda-Fuentes J. , Jacob J. , Sagaut P.
Published: March 2021

Lattice Boltzmann (LB) method for atmospheric dynamics is developed by considering the characteristics of the anelastic approximation. After introducing reference base state values in atmospheric flows, an LB model, with an external force term, has been constructed in anelastic framework. In the proposed anelastic LB model, mass and momentum conservation equations are solved by the LB method with a regularization procedure, and temperature field or scalar transport is simulated by finite volume method. The derived macroscopic governing equations from the anelastic model are analyzed and discussed in Chapman–Enskog asymptotic expansion. The anelastic LB model is assessed considering three benchmarks including a non-hydrostatic atmospheric inviscid convection, two-dimensional density currents, and inertia-gravity waves in stably stratified atmospheric layer. The validations demonstrate that the anelastic extension of the LB method can simulate atmospheric flows effectively and accurately. Besides, the proposed model offers a unified framework for both Boussinesq approximation and anelastic approximation, which is largely free of characteristic depth of atmospheric flows.
Dynamics of flame extinction in narrow channels with cold walls: Heat loss vs acceleration
Authors: Dion Claude M. , Valiev Damir M. , Akkerman V'yacheslav , Demirgok Berk , Ugarte Orlando J. , Eriksson Lars-Erik , Bychkov Vitaly
Published: March 2021

Propagation of a premixed flame from a closed to an open end in micro-channels with smooth non-slip isothermal walls is considered in the context of flame extinction dynamics. Powerful exponential flame acceleration in micro-channels with adiabatic walls has been demonstrated at the initial quasi-isobaric stage of the process [Bychkov et al., Phys. Rev. E 72, 046307 (2005)]. In contrast to the previous studies, here we investigate flame propagation in channels with isothermal walls. The problem is solved by means of high-fidelity laminar numerical simulations of the complete set of the Navier–Stokes combustion equations. For most of the problem parameter sets chosen, we obtain initial flame acceleration after ignition at the closed channel end. This acceleration resembles qualitatively the adiabatic case, but it develops noticeably slower, in an approximately linear regime instead of the exponential one and persists only for a limited time interval. Subsequently, heat loss to the walls reduces the temperature and hence the volume of the burnt gas behind the flame front, which produces a reverse flow in the direction of the closed channel end. When the amount of the burnt gas becomes sufficiently large, the reverse flow stops the acceleration process and drives the flame backwards with modifications of the flame front shape from convex to concave. Eventually, the flame extinguishes. Qualitatively, the process obtained reproduces a possible combustion failure during deflagration-to-detonation transition observed in previous experiments. We investigate the key characteristics of initial flame acceleration such as the acceleration rate and the maximum speed of the flame tip.
Large-eddy simulation of flow past a circular cylinder for Reynolds numbers 400 to 3900
Authors: Jiang Hongyi , Cheng Liang
Published: March 2021

The benchmarking case of flow past a circular cylinder at the Reynolds number (Re) of 3900 is computed with two open-source codes, OpenFOAM and Nektar++, which are based on the conventional finite volume method (FVM) and the high-order spectral/hp element method, respectively. By using the Nektar++ model, mesh convergence for the case Re = 3900 is demonstrated (perhaps for the first time) through a systematic mesh dependence study, which includes separate examinations of the spanwise domain length (Lz/D), spanwise resolution, and the resolution in the plane perpendicular to the spanwise direction. The computational efficiencies for the Nektar++ and OpenFOAM approaches are then compared. This benchmarking study adds value to the broad Nektar++ and OpenFOAM communities and to the numerical modeling of bluff-body flows in general. Based on the Nektar++ approach, the computations are then generalized to a range of Re = 400–3900. It is found that Lz/D = 3 is adequate for Re = 2500–3900, while an increased Lz/D = 6 is recommended for Re = 400–2000. Based on the present high-fidelity numerical data, the physical mechanisms for the variations in the wake recirculation length and the hydrodynamic forces and pressure on the cylinder with Re are explored. In particular, the physics behind the inverse correlation between the root mean square lift coefficient (CL′) and the wake recirculation length, which includes a significant decrease in CL′ over Re = 270–1500, is highlighted.
On the time irreversibility of compressible turbulence reflected by particles of various inertias
Authors: Zhang Qingqing , Xiao Zuoli
Published: March 2021

Time irreversibility of compressible homogeneous isotropic turbulence (HIT) is investigated from a Lagrangian point of view and single-particle statistics. For this purpose, direct numerical simulation (DNS) is implemented for compressible HIT at Taylor-mircoscale Reynolds number Reλ∼100 and turbulent Mach number Mt up to 1.01, in which tracers and inertial particles in a wide Stokes number (St) range are instantaneously tracked with time. The statistics of instantaneous power of particles corroborates that the violation of detailed balance of turbulence in compressible HIT is much stronger than in incompressible HIT. It turns out that the third moment of dimensionless instantaneous power (Ir) of tracers scales as Mt4. A possible explanation based on Kolmogorov-like argument proves to be plausible due to the lacks of direct verification and generality for other moments of the power. A further analysis from an Eulerian point of view suggests that the underlying mechanism for time irreversibility of highly compressible turbulence is quite different from that for weakly compressible or incompressible turbulence. For inertial particles, the moments of instantaneous power are suggested to scale as St−2n/3 at relatively large St numbers, and be dependent only on Mach number or Reynolds number at the small-St number end, which are manifested by the present numerical data. It is further shown that the empirical Mt4 scaling of Ir also approximately applies to various inertial particles, but only at high Mt numbers due to the diminishing effect of compressibility to the low-Mach number end. The time irreversibility announced by the Lagrangian statistical properties of particles of different inertias is shown to be highly associated with their responses to the vortex and shocklet structures in compressible turbulence.
Equation-of-motion coupled-cluster method with double electron-attaching operators: Theory, implementation, and benchmarks
Authors: Gulania Sahil , Kjønstad Eirik F. , Stanton John F. , Koch Henrik , Krylov Anna I.
Published: March 2021

We report a production-level implementation of the equation-of-motion (EOM) coupled-cluster (CC) method with double electron-attaching (DEA) EOM operators of 2p and 3p1h types, EOM-DEA-CCSD. This ansatz, suitable for treating electronic structure patterns that can be described as two-electrons-in-many orbitals, represents a useful addition to the EOM-CC family of methods. We analyze the performance of EOM-DEA-CCSD for energy differences and molecular properties. By considering reduced quantities, such as state and transition one-particle density matrices, we compare EOM-DEA-CCSD wave functions with wave functions computed by other EOM-CCSD methods. The benchmarks illustrate that EOM-DEA-CCSD is capable of treating diradicals, bond-breaking, and some types of conical intersections.
Direct numerical simulation of electroconvection with thin Debye layer matching canonical experiments
Authors: Shi Pengpeng
Published: March 2021

Electroconvection has the potential to be applied in electrochemical technologies such as electrodialysis and energy storage, and has thus aroused considerable research interest. This paper describes the direct numerical simulation (DNS) of the dimensionless Poisson–Nernst–Planck and Stokes equations for electroconvection to determine why the dimensionless thin Debye layer in existing simulations does not match the results of canonical experiments. Our DNS results show that the discrepancy between the simulation results and the experimental data is mainly caused by differences in the structural characteristics of the extended space charge layer. A dimensionless thin Debye layer matching those in canonical experiments enhances the driving force of the extended space charge layer, resulting in massive vortices near the permselective membranes that cause the electroconvective flow to transition from the steady state to time-dependent spatiotemporal dynamics. Our DNS results show that choosing the thickness of the dimensionless thin Debye layer to be consistent with canonical experiments is a key factor in the high-precision quantitative analysis of electroconvection characteristics such as the vortex height, dynamic evolution, and pattern formation. These results provide important guidance for the design and instability control of microfluidic chips.
Paradoxical androgen receptor regulation by small molecule enantiomers
Authors: Patsch Katherin , Liu Chao , Zapotoczny Grzegorz , Sun Yuanye , Sura Harish , Ung Nolan , Sun Ren X. , Haliday Bethany , Yu Chen , Aljehani Mayada , Lee Jerry S. H. , Kashemirov Boris A. , Agus David B. , McKenna Charles E. , Ruderman Daniel
Published: March 2021

Small molecules that target the androgen receptor (AR) are the mainstay of therapy for lethal castration-resistant prostate cancer (CRPC), yet existing drugs lose their efficacy during continued treatment. This evolution of resistance is due to heterogenous mechanisms which include AR mutations causing the identical drug to activate instead of inhibit the receptor. Understanding in molecular detail the paradoxical phenomenon wherein an AR antagonist is transformed into an agonist by structural mutations in the target receptor is thus of paramount importance. Herein, we describe a reciprocal paradox: opposing antagonist and agonist AR regulation determined uniquely by enantiomeric forms of the same drug structure. The antiandrogen BMS-641988, which has (
R
)-chirality at C-5 encompasses a previously uncharacterized (
S
)-stereoisomer that is, surprisingly, a potent agonist of AR, as demonstrated by transcriptional assays supported by cell imaging studies. This duality was reproduced in a series of novel compounds derived from the BMS-641988 scaffold. Coupled with in silico modeling studies, the results inform an AR model that explains the switch from potent antagonist to high-affinity agonist in terms of C-5 substituent steric interactions with helix 12 of the ligand binding site. They imply strategies to overcome AR drug resistance and demonstrate that insufficient enantiopurity in this class of AR antagonist can confound efforts to correlate structure with function.
Tubulin acetylation increases cytoskeletal stiffness to regulate mechanotransduction in striated muscle
Authors: Coleman Andrew K. , Joca Humberto C. , Shi Guoli , Lederer W. Jonathan , Ward Christopher W.
Published: March 2021

Microtubules tune cytoskeletal stiffness, which affects cytoskeletal mechanics and mechanotransduction of striated muscle. While recent evidence suggests that microtubules enriched in detyrosinated α-tubulin regulate these processes in healthy muscle and increase them in disease, the possible contribution from several other α-tubulin modifications has not been investigated. Here, we used genetic and pharmacologic strategies in isolated cardiomyocytes and skeletal myofibers to increase the level of acetylated α-tubulin without altering the level of detyrosinated α-tubulin. We show that microtubules enriched in acetylated α-tubulin increase cytoskeletal stiffness and viscoelastic resistance. These changes slow rates of contraction and relaxation during unloaded contraction and increased activation of NADPH oxidase 2 (Nox2) by mechanotransduction. Together, these findings add to growing evidence that microtubules contribute to the mechanobiology of striated muscle in health and disease.
Cryogenic suspension design for a kilometer-scale gravitational-wave detector
Authors: Ushiba Takafumi , Akutsu Tomotada , Araki Sakae , Bajpai Rishabh , Chen Dan , Craig Kieran , Enomoto Yutaro , Hagiwara Ayako , Haino Sadakazu , Inoue Yuki , Izumi Kiwamu , Kimura Nobuhiro , Kumar Rahul , Michimura Yuta , Miyoki Shinji , Murakami Iwao , Namai Yoshikazu , Nakano Masayuki , Ohashi Masatake , Okutomi Koki , Shishido Takaharu , Shoda Ayaka , Somiya Kentaro , Suzuki Toshikazu , Takada Suguru , Takahashi Masahiro , Takahashi Ryutaro , Terashima Shinichi , Tomaru Takayuki , Travasso Flavio , Ueda Ayako , Vocca Helios , Yamada Tomohiro , Yamamoto Kazuhiro , Zeidler Simon
Published: March 2021

We report the mirror suspension design for large-scale cryogenic gravitational wave telescope, KAGRA, during bKAGRA phase 1. Mirror thermal noise is one of the fundamental noises for room-temperature gravitational-wave detectors such as Advanced LIGO and Advanced Virgo. Thus, reduction of thermal noise is required for further improvement of their sensitivity. One effective approach for reducing thermal noise is to cool the mirrors. There are many technical challenges that must be overcome to cool the mirrors, such as cryocooler induced vibrations, thermal drift in suspensions, and reduction in duty cycling due to the increased number of potential failure mechanisms. Our mirror suspension has a black coating that makes radiative cooling more efficient. For conduction cooling, we developed ultra high purity aluminum heat links, which yield high thermal conductivity while keeping the spring constant sufficiently small. A unique inclination adjustment system, called moving mass, is used for aligning the mirror orientation in pitch. Photo-reflective displacement sensors, which have a large range, are installed for damping control on marionette recoil mass and intermediate recoil mass. Samarium cobalt magnets are used for coil-magnet actuators to prevent significant change of magnetism between room temperature and cryogenic temperature. In this paper, the design of our first cryogenic payload and its performance during bKAGRA phase 1 are discussed.
Lattice elasticity, waves and temperature from an interaction potential
Authors: Ocaya R O
Published: March 2021

Kinetic theory is taught to first-year students of physics as a plausible account of thermal equilibrium on the microscopic scale. However, it does not adequately clarify important properties like elasticity, lattice waves, phonons, optical oscillations, bandgap and so on, that are postulated through atomic vibrations. In this article, we apply simple computational tools in four computational experiments to study the effects of the vibrations of 373 atoms of a face-centered cubic crystal such as copper. We also discuss the perturbation modelling approach, the Sutton–Chen potential, and discrete integration. The experiments have different aims e.g. determining the steady-state atom arrangement starting from an arbitrarily specified cluster, the elasticity, the ensuing wave motion, lattice resonance, acoustic properties, and temperature rise. The calculated results agree well with their literature values.
Extrapolating from neural network models: a cautionary tale
Authors: Pastore A , Carnini M
Published: March 2021

We present three different methods to estimate error bars on the predictions made using a neural network (NN). All of them represent lower bounds for the extrapolation errors. At first, we illustrate the methods through a simple toy model, then, we apply them to some realistic case related to nuclear masses. By using theoretical data simulated either with a liquid-drop model or a Skyrme energy density functional, we benchmark the extrapolation performance of the NN in regions of the Segrè chart far away from the ones used for the training and validation. Finally, we discuss how error bars can help identifying when the extrapolation becomes too uncertain and thus not reliable.
First-principles study of the liquid and amorphous phases of Sb2Te phase change memory material
Authors: Kang Lei , Chen Leng
Published: March 2021

We have investigated the local structure of liquid and amorphous phases of Sb2Te phase change memory material by the means of density functional theory-molecular dynamics simulations. The models of liquid and amorphous states were generated by quenching from the melt. The results show that the local environment of liquid Sb2Te is a mixed bonding geometry, where the average coordination numbers (CNs) of Sb and Te atoms are 4.93 and 4.23, respectively. Compared with crystalline state, there are more Sb–Sb bonds (∼53%) and less Sb–Te bonds (∼42%) with the presence of Te–Te bonds (∼5%) in liquid Sb2Te. Therefore, the formation of homopolar bonds and the breaking of heteropolar bonds are important structural transformations in melt process. For amorphous Sb2Te, the average CNs of Sb and Te atoms are 4.54 and 3.57, respectively. They are mostly in an octahedral environment, similar to the case in crystalline phase. The fractions of Sb–Sb, Te–Te, and Sb–Te bonds are ∼52%, ∼2%, and ∼46%, respectively. Thus, the increase in the fraction of octahedron accompanied with the decrease in average CN is the major structural changes in quenching process. Furthermore, the octahedral geometry in both the crystalline and amorphous Sb2Te increases the local structural similarity, facilitating the rapid low-energy crystallization.
Improved synaptic functionalities of Li-based nano-ionic synaptic transistor with ultralow conductance enabled by Al2O3 barrier layer
Authors: Lee Kyumin , Kwak Myounghoon , Choi Wooseok , Lee Chuljun , Lee Jongwon , Noh Sujung , Lee Jisung , Lee Hansaem , Hwang Hyunsang
Published: March 2021

In this study, we investigated the effect of an Al2O3 barrier layer in an all-solid-state inorganic Li-based nano-ionic synaptic transistor (LST) with Li3PO4 electrolyte/WO
x
channel structure. Near-ideal synaptic behavior in the ultralow conductance range (∼50 nS) was obtained by controlling the abrupt ion migration through the introduction of a sputter-deposited thin (∼3 nm) Al2O3 interfacial layer. A trade-off relationship between the weight update linearity and on/off ratio with varying Al2O3 layer thickness was also observed. To determine the origin of the Al2O3 barrier layer effects, cyclic voltammetry analysis was conducted, and the optimal ionic diffusivity and mobility were found to be key parameters in achieving ideal synaptic behavior. Owing to the controlled ion migration, the retention characteristics were considerably improved by the Al2O3 barrier. Finally, a highly improved pattern recognition accuracy (83.13%) was achieved using the LST with an Al2O3 barrier of optimal thickness.
Pupillometric recordings to detect glaucoma
Authors: Bhowmik Susmit , Arjunan Sridhar P , Sarossy Marc , Radcliffe PeterJones , Kumar Dinesh K
Published: March 2021

Objective. Glaucoma is the second cause of vision loss with early diagnosis having significantly better prognosis. We propose the use of hippus, the steady-state pupil oscillations, obtained from an eye-tracker for computerised detection of glaucoma. Approach. Pupillary data were recorded using a commercial eye-tracker device directly to the laptop. A total of 40 glaucoma patients and 30 age-matched controls were recruited for the study. The signals were de-noised, and the entropy of the steady-state oscillations was obtained for two light intensities, 34 and 100 cd m−2. Main results. The results show that at 100 cd m−2, there was significant difference (p < 0.05) between the sample entropy of the healthy eyes (0.55 ± 0.017) and glaucoma eyes (0.7 ± 0.034). The results at 34 cd m−2 were also significantly different, though to a lesser extent. Significance. Entropy of the pupillary oscillations, or hippus, obtained using an eye-tracking device showed a significant difference between glaucoma and healthy eyes. The method used commercially available inexpensive hardware and thus has the potential for wide-scale deployment for computerized detection of glaucoma.
Impact of three-dimensional magnetic perturbations on turbulence in tokamak edge plasmas
Authors: Luce B , Tamain P , Ciraolo G , Ghendrih Ph , Giorgiani G , Serre E
Published: March 2021

The impact of resonant magnetic perturbations (RMPs) on the plasma edge equilibrium and on the turbulence is investigated in a circular limited configuration. The study is based on a Braginski-based isothermal fluid model. The flow response of an unperturbed case to a small amplitude three-dimensional single mode RMP is studied and a scan in amplitude and poloidal and toroidal mode number is performed. Special attention is given when magnetic islands appear in the simulation domain on flux surfaces of rational safety factor. Results show an impact of magnetic perturbations (MPs) on both the plasma equilibrium and on the turbulence properties, with a deviation to the reference solution which depends on the MPs amplitude and on their wavenumbers. The impact of MPs on turbulence is however globally weaker than on the plasma equilibrium, suggesting a stabilizing effect of the MP on turbulent transport. Experimental trends are recovered such as the density pump-out and the increase of the radial electric field as well as the reorganization of the parallel velocity. The ballooning of the transport is modified under the effect of the perturbations, with a shift of the peaked poloidal region from the upper to the lower outer midplane. In the present model, the SOL width is observed decreasing in the presence of MPs. Turbulence properties are also impacted with the density fluctuations level decreasing in perturbed solutions and the intermittency is globally weakened.
Controlling: the composition of plasma-activated water by Cu ions
Authors: Kutasi Kinga , Krstulović Nikša , Jurov Andrea , Salamon Krešimir , Popović Dean , Milošević Slobodan
Published: March 2021

It is demonstrated that Cu ions can be used to control the ageing of plasma-activated liquids through the Fenton-type reaction, which acts as a competitor to the

N
O

2

−

+ H2O2 + H+ → products reaction, and thus moderates the recombination of

N
O

2

−

ions. It is shown that the ageing dynamics is influenced by the type of Cu-ions source used, due to the different ion dissolution dynamics. Using CuNP-colloidal and copper acetate salt solutions, respectively, similar ageing dynamics can be achieved: the lifetime of

N
O

2

−

can be increased to 104 min comparing to 102 min obtained in plasma-activated water, while the H2O2 concentration decreases to about half of its initial value. While the treated salt solutions contain the degradation products of the salt compounds, the CuNPs can be filtered out from the plasma-activated colloid (PAC). It is shown that filtration does not influence the concentration of active species, while the ageing of the filtrated PAC depends on the moment of filtration, which determines the concentration of dissolved Cu ions. Using copper foil, the dissolved Cu-ion concentration can be controlled by removing the foil during ageing, and in this way the lifetime of species and the H2O2 concentration can be adjusted. The effect has been validated in the case of two different plasma sources: a surface-wave microwave discharge and a kHz plasma jet, which produce PALs with different

[

N
O

2

−

]

/

[

H

2

O

2

]

concentration ratio, which is the main governor of the ageing process.
Diffusion of confined fluids in microporous zeolites and clay materials
Authors: Mitra S , Sharma V K , Mukhopadhyay R
Published: March 2021

Fluids exhibit remarkable variation in their structural and dynamic properties when they are confined at the nanoscopic scale. Various factors, including geometric restriction, the size and shape of the guest molecules, the topology of the host, and guest–host interactions, are responsible for the alterations in these properties. Due to their porous structures, aluminosilicates provide a suitable host system for studying the diffusion of sorbates in confinement. Zeolites and clays are two classes of the aluminosilicate family, comprising very ordered porous or layered structures. Zeolitic materials are important due to their high catalytic activity and molecular sieving properties. Guest molecules adsorbed by zeolites display many interesting features including unidimensional diffusion, non-isotropic rotation, preferred orientation and levitation effects, depending on the guest and host characteristics. These are useful for the separation of hydrocarbons which commonly exist as mixtures in nature. Similarly, clay materials have found application in catalysis, desalination, enhanced oil recovery, and isolation barriers used in radioactive waste disposal. It has been shown that the bonding interactions, level of hydration, interlayer spacing, and number of charge-balancing cations are the important factors that determine the nature of diffusion of water molecules in clays. Here, we present a review of the current status of the diffusion mechanisms of various adsorbed species in different microporous zeolites and clays, as investigated using quasielastic neutron scattering and classical molecular dynamics simulation techniques. It is impossible to write an exhaustive review of the subject matter, as it has been explored over several decades and involves many research topics. However, an effort is made to cover the relevant issues specific to the dynamics of different molecules in microporous zeolites and clay materials and to highlight a variety of interesting features that are important for both practical applications and fundamental aspects.
Generation of high-quality GeV-class electron beams utilizing attosecond ionization injection
Authors: Lécz Zsolt , Andreev Alexander , Kamperidis Christos , Hafz Nasr
Published: March 2021

Acceleration of electrons in laser-driven plasma wakefields has been extended up to the 10 GeV energy within a distance of 10s of centimeters. However, in applications, requiring small energy spread within the electron bunch, only a small portion of the bunch can be used and often the low-energy electrons represent undesired background in the spectrum. We present a compact and tunable scheme providing clean and mono-energetic electron bunches with less than one percent energy spread and with central energy on the GeV level. It is a two-step process consisting of ionization injection with attosecond pulses and acceleration in a capillary plasma wave-guide. Semi-analytical theory and particle-in-cell simulations are used to accurately model the injection and acceleration steps.
n-dimensional PDM-damped harmonic oscillators: linearizability, and exact solvability
Authors: Mustafa Omar
Published: March 2021

We consider position-dependent mass (PDM) Lagrangians/Hamiltonians in their standard textbook form, where the long-standing gain-loss balance between the kinetic and potential energies is kept intact to allow conservation of total energy (i.e.,

L
=
T
−
V

,

H
=
T
+
V

, and

dH

/

dt
=
dE

/

dt
=
0

). Under such standard settings, we discuss and report on n-dimensional PDM damped harmonic oscillators (DHO). We use some n-dimensional point canonical transformation to facilitate the linearizability of their n-PDM dynamical equations into some n-linear DHOs’ dynamical equations for constant mass setting. Consequently, the well know exact solutions for the linear DHOs are mapped, with ease, onto the exact solutions for PDM DHOs. A set of one-dimensional and a set of n-dimensional PDM-DHO illustrative examples are reported along with their phase-space trajectories.
On preheating in Higgs inflation
Authors: Hamada Yuta , Kawana Kiyoharu , Scherlis Adam
Published: March 2021

Recently, the problem of unitarity violation during the preheating stage of Higgs inflation with a large non-minimal coupling has been much discussed in the literature.

We point out that this problem can be translated into a strong coupling problem for the dimensionless effective coupling, and that the existence of these problems is highly dependent on the choice of higher-dimensional operators because they can significantly change the background dynamics and the canonical normalization of the fluctuations around it.

Correspondingly, the typical energy of particles produced during the first stage of preheating can remain comparable to or below the cutoff scale of the theory.
As an example, we numerically calculate the particle production in the presence of a specific four-derivative operator of the Higgs field, and confirm the statement above.

Our argument also applies to multi-field inflation with non-minimal couplings.
The cosmic neutrino background as a collection of fluids in large-scale structure simulations
Authors: Chen Joe Zhiyu , Upadhye Amol , Wong Yvonne Y.Y.
Published: March 2021

A significant challenge for modelling the massive neutrino as a hot dark matter is its large velocity dispersion. In this work, we investigate and implement a multi-fluid perturbation theory that treats the cosmic neutrino population as a collection of fluids with a broad range of bulk velocities. These fluids respond linearly to the clustering of cold matter, which may be linear and described by standard linear perturbation theory, or non-linear, described using either higher-order perturbation theory or N-body simulations. We verify that such an alternative treatment of neutrino perturbations agrees closely with state-of-the-art neutrino linear response calculations in terms of power spectrum and bispectrum predictions. Combining multi-fluid neutrino linear response with a non-linear calculation for the cold matter clustering, we find for a reference νΛCDM cosmology with neutrino mass sum ∑ m
ν = 0.93 eV an enhancement of the small-scale neutrino power by an order of magnitude relative to a purely linear calculation.
The corresponding clustering enhancement in the cold matter, however, is a modest ∼ 0.05%. Importantly, our multi-fluid approach uniquely enables us to identify that the slowest-moving 25% of the neutrino population clusters strongly enough to warrant a non-linear treatment. Such a precise calculation of neutrino clustering on small scales accompanied by fine-grained velocity information would be invaluable for experiments such as PTOLEMY that probe the local neutrino density and velocity in the solar neighbourhood.
The first photometric investigations of the G-type shallow contact binary IO Cnc
Authors: Liao Wen-Ping , Li Lin-Jia , Zhou Xiao , Wang Qi-Shan
Published: March 2021

IO Cnc was classified to be a new G-type (G0) W UMa-type eclipsing binary system. Our first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor off= 16.1% and a low mass ratio ofq= 3.12 (or 1/q= 0.32). During orbital period investigations, a cyclic variation and a downward parabolic variation with a rate of (−1.28 ± 0.43) × 10−7d yr−1was discovered in the observed–calculated (O−C) curve. The cyclic variation was analyzed by the light travel time effect (LTTE) via a potential red dwarf companion star, an orbital semi-major axis shorter than 4.88 ± 0.82 AU was obtained. Finally, we collect physical parameters of a sample of 50 G-type shallow contact binaries (f≤ 20%), it is suggested that most of the G-type shallow contact binaries are undergoing a long-term and periodic orbital period changes, especially more systems show long-term decreases. The long-term orbital period decrease indicates that IO Cnc is in a mass transferring from the more massive component to the less massive one. With the long-term decrease of the orbital period, this shallow contact binary will evolve into a deeper contact one.
Interacting system NGC 7805/6 (Arp 112) and its tidal dwarf galaxy candidate
Authors: Fu Zhen-Xing , Sengupta Chandreyee , Sethuram Ramya , Pradhan Bikram , Singh Mridweeka , Misra Kuntal , Scott Tom. C. , Ma Yin-Zhe
Published: March 2021

We present results from our Giant Metrewave Radio Telescope (GMRT) Hi, Himalayan Chandra Telescope (HCT) Hα, 1 m Sampurnanand Telescope (ST) and 1.3 m Devasthal Fast Optical Telescope (DFOT) deep optical observations of the NGC 7805/6 (Arp 112) system to test KUG 2359+311’s tidal dwarf galaxy (TDG) candidacy and explore the properties of the interacting system. Our GMRT H I map shows no H I detection associated with KUG 2359+311, nor any H I tail or bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system. Our HCT Hα image, on the other hand, displays strong detections in KUG 2359+311, with net SFR ∼ 0.035 ± 0.009 M
⊙ yr−1. The Hα data constrain the redshift of KUG 2359+311 to 0.00 ≤ z ≤ 0.043, compared to the redshift of NGC 7806 of ∼ 0.015. TDGs detected to date have all been H i rich, and displayed H i, ionised gas and stellar tidal debris trails (bridges or tails) linking them to their parent systems. However, neither our H i data nor our optical imaging, while three magnitudes deeper than SDSS, reveals a tidal trail connecting KUG 2359+311 to NGC 7805/6. Lack of H i, presence of an old stellar population, ongoing star formation and reasonably high SFR compared to normal dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG. It is most likely a case of a regular gas-rich dwarf galaxy undergoing a morphological transformation after having lost its entire gas content to an interaction with the Arp 112 system. Redshift and metallicity from future spectroscopic observations of KUG 2359+311 would help clarify the nature of this enigmatic structure.