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, Luis A. Jauregui, Chris Wilen, , David B Newell, , Yong P Chen
Published: 14 September 2021
Journal of Physics: Condensed Matter; https://doi.org/10.1088/1361-648x/ac268f

Abstract:
Decoherence in quantum bits (qubits) is a major challenge for realizing scalable quantum computing. One of the primary causes of decoherence in qubits and quantum circuits based on superconducting Josephson junctions is the critical current fluctuation. Many efforts have been devoted to suppressing the critical current fluctuation in Josephson junctions. Nonetheless, the efforts have been hindered by the defect-induced trapping states in oxide-based tunnel barriers and the interfaces with superconductors in the traditional Josephson junctions. Motivated by this, along with the recent demonstration of 2D insulator h-BN with exceptional crystallinity and low defect density, we fabricated a vertical NbSe2/h-BN/Nb Josephson junction consisting of a bottom NbSe2 superconductor thin layer and a top Nb superconductor spaced by an atomically thin h-BN layer. We further characterized the superconducting current and voltage (I-V) relationships and Fraunhofer pattern of the NbSe2/h-BN/Nb junction. Notably, we demonstrated the critical current noise (1/f noise power) in the h-BN-based Josephson device is at least a factor of four lower than that of the previously studied aluminum oxide-based Josephson junctions. Our work offers a strong promise of h-BN as a novel tunnel barrier for high-quality Josephson junctions and qubit applications.
Published: 14 September 2021
Quantum Science and Technology; https://doi.org/10.1088/2058-9565/ac26af

Abstract:
We present a novel methodological framework for quantum spatial search, generalising the Childs & Goldstone (CG) algorithm via alternating applications of marked-vertex phase shifts and continuous-time quantum walks. We determine closed form expressions for the optimal walk time and phase shift parameters for periodic graphs. These parameters are chosen to rotate the system about subsets of the graph Laplacian eigenstates, amplifying the probability of measuring the marked vertex. The state evolution is asymptotically optimal for any class of periodic graphs having a fixed number of unique eigenvalues. We demonstrate the effectiveness of the algorithm by applying it to obtain O(√N) search on a variety of graphs. One important class is the n by n3 Rook graph, which has N=n4 vertices. On this class of graphs the CG algorithm performs suboptimally, achieving only O(N-1/8) overlap after time O(N5/8). Using the new alternating phase-walk framework, we show that O(1) overlap is obtained in O(√N) phase-walk iterations.
Arian Aghilinejad, Faisal Amlani, Jing Liu,
Published: 14 September 2021
Physiological Measurement; https://doi.org/10.1088/1361-6579/ac2671

Abstract:
Background: Wave intensity (WI) analysis is a well-established method for quantifying the energy carried in arterial waves, providing valuable clinical information about cardiovascular function. The primary drawback of this method is the need for concurrent measurements of both pressure and flow waveforms. Objective: We have for the first time investigated the accuracy of a novel methodology for estimating wave intensity employing only single pressure waveform measurements; we studied both carotid- and radial-based estimations in a large heterogeneous cohort. Approach: Tonometry was performed alongside Doppler ultrasound to acquire measurements of both carotid and radial pressure waveforms as well as aortic flow waveforms in 2640 healthy and diseased participants (1439 female) in the Framingham Heart Study. Patterns consisting of two forward waves (Wf1, Wf2) and one backward wave (Wb1) along with reflection metrics were compared with those obtained from exact WI analysis. Main Results: Carotid-based estimates correlated well for forward peak amplitudes (Wf1, r=0.85, p<0.05; Wf2, r=0.72, p<0.05) and peak time (e.g., Wf1, r=0.94, p<0.05; Wf2, r=0.98, p<0.05), and radial-based estimates correlated fairly to poorly for amplitudes (Wf1, r=0.62, p<0.05; Wf2, r=0.42, p<0.05) and peak time (Wf1, r=0.04, p=0.10; Wf2, r=0.75, p<0.05). In all cases, estimated Wb1 measures were not correlated. Reflection metrics were well correlated for healthy patients (r=0.67, p<0.05), moderately correlated for valvular disease (r=0.59, p<0.05) and fairly correlated for CVD (r=0.46, p<0.05) and heart failure (r=0.49, p<0.05). Significance: These findings indicate that pressure-only WI produces accurate results only when forward contributions are of primary interest and only for carotid pressure waveforms. The pressure-only WI estimations of this work provide an important opportunity to further the goal of uncovering clinical insights through wave analysis affordably and non-invasively.
, Jacob H. Paiste, Joseph Edoki, Robert R. Arslanbekov, Renato Camata
Plasma Sources Science and Technology; https://doi.org/10.1088/1361-6595/ac2677

Abstract:
We carry out simulations of laser plasmas generated during UV nanosecond pulsed laser ablation of the chalcogens selenium (Se) and tellurium (Te), and compare the results to experiments. We take advantage of a 2D-axisymmetric, adaptive Cartesian Mesh (ACM) framework that enables plume simulations out to centimeter distances over tens of microseconds. Our model and computational technique enable comparison to laser-plasma applications where the long-term behavior of the plume is of primary interest, such as pulsed laser synthesis and modification of materials. An effective plasma absorption term is introduced in the model, allowing the simulation to be constrained by experimental time-of-flight kinetic energy distributions. We show that the effective simulation qualitatively captures the key characteristics of the observed laser plasma, including the effect of laser spot size. Predictions of full-scale experimentally-constrained Se and Te plasmas for 4.0 J/cm2 laser fluence and 1.8 mm2 circular laser spot area show distinct behavior compared to more commonly studied copper (Cu) plumes. The chalcogen plumes have spatial gradients of plasma density that are steeper than those for Cu by up to three orders of magnitude. Their spatial ion distributions have central bulges, in contrast to the edge-only ionization of Cu. For the irradiation conditions explored, the range of plasma temperatures for Se and Te is predicted to be higher than for Cu by more than 0.50 eV.
, Steve A Sabbagh, Y S Park, John Berkery, Jae Heon Ahn, Juan Riquezes, J G Bak, Wonha Ko, , Jongha Lee, et al.
Published: 14 September 2021
Abstract:
High fidelity kinetic plasma equilibrium reconstructions are an essential requirement for accurate stability and disruption prediction analyses to support continuous operation of high beta tokamak plasmas. The present kinetic equilibrium reconstructions of plasmas in the KSTAR device include plasma density and temperature profiles from Thomson scattering and ion temperature from charge exchange spectroscopy diagnostics, and allowance for fast particle pressure. In addition, up to 25 channels of motional Stark effect (MSE) diagnostic data are used to constrain the magnetic field pitch angle profile in the plasma to produce a reliable computation of the safety factor, q, profile. H-mode plasmas exhibit clear pedestal characteristics in the reconstructed pressure profile compared to internal transport barrier or L-mode plasmas. The plasma configuration and vertical position of inner strike points are validated by CCD and infrared camera images. Ideal and resistive MHD stability analyses using the DCON and resistive DCON codes utilize these kinetic equilibrium reconstructions to compare to experimental plasma stability. Equilibria with sufficiently low convergence error can provide reliable computation of ideal and resistive magnetohydrodynamic (MHD) stability analysis.
, Timothy Jamie Healey, Harry E McDonough, Sophie J French, Christopher J McDermott, Pamela J Shaw, Visakan Kadirkamanathan, James J P Alix
Published: 14 September 2021
Physiological Measurement; https://doi.org/10.1088/1361-6579/ac2672

Abstract:
Objective: Electrical impedance myography (EIM) shows promise as an effective biomarker in amyotrophic lateral sclerosis (ALS). EIM applies multiple input frequencies to characterise muscle properties, often via multiple electrode configurations. Herein, we assess if non-negative tensor factorisation can provide a framework for identifying clinically relevant features within a high dimensional EIM dataset. Approach: EIM data were recorded from the tongue of healthy and ALS diseased individuals. Resistivity and reactivity measurements were made for 14 frequencies, in three electrode configurations. This gives 84 (2 × 14 × 3) distinct data points per participant. Non-negative tensor factorisation (NTF) was applied to the dataset for dimensionality reduction, termed tensor EIM. Significance tests, symptom correlation and classification approaches were explored to compare NTF to using all raw data and feature selection. Main Results: Tensor EIM provides highly significant differentiation between healthy and ALS patients (p < 0.001, AUROC=0.78). Similarly tensor EIM differentiates between mild and severe disease states (p < 0.001, AUROC=0.75) and significantly correlates with symptoms (ρ = 0.7, p < 0.001). A trend of centre frequency shifting to the right was identified in diseased spectra, which is in line with the electrical changes expected following muscle atrophy. Significance: Tensor EIM provides clinically relevant metrics for identifying ALS- related muscle disease. This procedure has the advantage of using the whole spectral dataset, with reduced risk of overfitting. The process identifies spectral shapes specific to disease allowing for a deeper clinical interpretation.
Bo Zhang, Zheyong Fan, ,
Published: 14 September 2021
Journal of Physics: Condensed Matter; https://doi.org/10.1088/1361-648x/ac268d

Abstract:
Lattice thermal conductivity (LTC) is a key parameter for many technological applications. Based on the Peierls-Boltzmann transport equation (PBTE), many unique phonon transport properties of various materials were revealed. Accurate calculation of LTC with PBTE, however, is a time-consuming task, especially for compounds with a complex crystal structure or taking high-order phonon scattering into consideration. Graphical processing units (GPUs) have been extensively used to accelerate scientific simulations, making it possible to use a single desktop workstation for calculations that used to require supercomputers. Due to its fundamental differences from traditional processors, GPUs are especially suited for executing a large group of similar tasks with minimal communication, but require completely different algorithm design. In this paper, we provide a new algorithm optimized for GPUs, where a two-kernel method is used to avoid divergent branching. A new open-source code, GPU_PBTE, is developed based on the proposed algorithm. As demonstrations, we investigate the thermal transport properties of silicon and silicon carbide, and find that accurate and reliable LTC can be obtained by our software. GPU_PBTE performed on NVIDIA Tesla V100 can extensively improve double precision performance, making it two to three orders of magnitude faster than our CPU version performed on Intel Xeon CPU Gold 6248 @ 2.5 GHz. Our work also provides an idea of accelerating calculations with other novel hardware that may come out in the future.
Hainan Lin,
Published: 14 September 2021
Abstract:
We propose that fast radio bursts (FRBs) can be used as the probes to constrain the possible anisotropic distribution of baryon matter in the Universe. Monte Carlo simulations show that, 400 (800) FRBs are enough to detect the anisotropy at 95\% (99\%) confidence level, if the dipole amplitude is at the order of magnitude 0.01. However, much more FRBs are required to tightly constrain the dipole direction. Even 1000 FRBs are far from enough to constrain the dipole direction within angular uncertainty $\Delta\theta<40^{\circ}$ at 95\% confidence level. The uncertainty on the dispersion measure of host galaxy does not significantly affect the results. If the dipole amplitude is in the level of 0.001, however, 1000 FRBs are not enough to correctly detect the anisotropic signal.
Katharine I Hunter, Himashi P Andaraarachchi,
Journal of Physics D: Applied Physics; https://doi.org/10.1088/1361-6463/ac2695

Abstract:
Enhanced optical properties of silicon quantum dots are pertinent for the light emitting applications including luminiscent solar cell concetrators. Surface passivation plays a crucial role in improving photoluminiscent quantum yield and effective carrier lifetimes of silicon nanocrystals and is often achieved by surface grafting of organic ligands. However, organically passivated silicon quantum dots often suffer from a deterioration of the optical properties when exposed to the environment In this work, we explore the effect of an inorganic amorphous silicon nitride shell (SiNx) on silicon quantum dots and their optical properties. Utilizing a dual plasma appraoch with dual injection ports, we synthesized Si/SiNx core-shell nanoparticles using SiH4, NH3, H2, and Ar. The core-shell nanocrystals were characterized using optical and structural methods, which revealed higher nitridation plasma powers could lead to Si precipiation altering the composition of silicon nitride shell. While as-synthesized Si/SiNx core-shell nanocrystals did not exhibit photoluminiscence, oxidized Si/SiNx core-shell nanocrystals show significantly higher quantum yield (35%) and longer carrier lifetime compared to bare oxidized Si analogues even after enviromental exposure for six months.
, Hitoshi Tamura, Nagato Yanagi, Hidetoshi Hashizume
Published: 14 September 2021
Abstract:
Two designs have been proposed for segment-fabrication of the high-temperature superconducting (HTS) helical coils in the FFHR-d1 helical fusion reactor, joint-winding of the HTS coils wound by connecting conductor segments, and the "remountable" HTS magnet (here "remountable" means being able to mount and demount repeatedly) assembled from coil segments with demountable joints. A bridge-type mechanical lap joint and mechanical edge joint are planned to be applied to those two designs, respectively. This paper presents the progress in electrical and mechanical performances of the mechanical joints of HTS conductors and methods to evaluate their quality for segment-fabrication of HTS helical coils. R&D of joint performance has progressed during this decade and it shows acceptable performance for the HTS helical coils. The contact-probing current transfer length (CTL) method and X-ray computer tomography (CT) scanning are promising for quality assessment of the joints and HTS tapes.
Qing Li, Jin-Lou Ma,
Published: 14 September 2021
Abstract:
The eigenstate thermalization hypothesis (ETH) is a mechanism for the thermalization of quantum chaotic systems. Most researches on quantum chaotic systems involve the two-body interaction between spins, fermions, and bosons, but for the JCH model, the emergence of quantum-chaotic properties come from the competition between hopping strength of the photon and photon-atom coupling strength. We use exact diagonalization to prove that the JCH system has the property of quantum chaotic system and verify the validity of ETH ansatz both for diagonal and off-diagonal matrix elements of the photon observables with reasonable experimental parameters.
Snehashish Chatterjee, , Saurav Giri,
Published: 14 September 2021
Journal of Physics: Condensed Matter; https://doi.org/10.1088/1361-648x/ac268c

Abstract:
Heusler compounds are a large group of intermetallic compositions with versatile material properties. In the recent times, they are found to be important for their practical applications in the fields of spintronics and shape memory effect. Interestingly, their physical properties can be easily tuned by varying the valence electron concentration through proper doping and substitution. Empirical laws concerning the valence electron concentration, such as Slater-Pauling or Hume-Rothery rules are found to be useful in predicting their electronic, magnetic and structural properties quite accurately. Electrical transport measurements are simple laboratorybased techniques to gather a handful of information on the electronic properties of metals and semiconductors. The present review aimed to provide a comprehensive view of the transport in 3d and 4d transition metal based bulk Heusler compositions. The main emphasis is given on resistivity, magnetoresistance, Hall effect, thermopower as well as spin-dependent transport in spintronics devices. The review primarily focuses on magnetic Heusler compounds and alloys, albeit it also addresses several non-magnetic materials showing superconductivity or large thermopower.
, Mohit Kumar, Pascale Roubin, , , , , David Douai, , , et al.
Published: 14 September 2021
Abstract:
We report on the detection by means of Raman spectroscopy of amorphous beryllium deuteride, BeD2, in magnetron sputtered deposits synthesized in two different laboratories and containing about 20 at.% of deuterium. In contrast, this signature has not been found for the JET limiter samples studied coming from the inner, outer or upper limiters, even when coming from a deposition zone of the limiters. We give a way to disentangle that BeD2 signature from other signatures falling in the same spectroscopic range and mainly related to other phenomena defects. We also analyze the Raman characteristics of the JET sample defects. These results could help in the interpretation of D thermal desorption spectra and in future analyses of JET thick Be deposit divertor tiles.
, Francesco Piva, Carlo de Santi, Matteo Buffolo, Camille Haller, Jean-Francois Carlin, Nicolas Grandjean, , Enrico Zanoni, Matteo Meneghini
Journal of Physics D: Applied Physics; https://doi.org/10.1088/1361-6463/ac2693

Abstract:
We investigate the density of defects and the degradation rate in InGaN light-emitting diodes having identical dislocation density and epitaxial structure, but different indium content in the quantum well (QW, 12 %, 16 %, 20 %). Our results, based on combined steady-state photocapacitance, light-capacitance voltage, and degradation measurements indicate that: (i) the density of defects in the superlattice underlayer is identical for the three wafers, indicating good and reproducible growth conditions; (ii) the density of defects within the active region of the devices shows a monotonic dependence on the indium content in the quantum wells. These results, consistent with previous studies on the topic, prove unequivocally the important role of indium in favouring the incorporation of point defects, further clarifying the possible mechanisms of defect formation, and give a quantitative assessment of the related effect; (iii) in step-stress experiments, the degradation rate was found to be much stronger for devices having high indium content in the QW. This result can be explained by considering a decrease in injection efficiency due to the generation or transport of defects, or an increment in defect-assisted Auger recombination terms due to the propagation of defects.
, Jean Valère Nguepnang, Aurelien Kenfack-Jiotsa, Fobasso F.C. Mbognou, Vanessa Diffo, Mahouton Norbert Hounkonnou
Published: 14 September 2021
Abstract:
We investigate the dynamics and decoherence of the exciton polaron in a 2D transition metal dichalcogenides modulated by a magnetic field barrier. Using the Huybrechts method and an approximate diagonalization of exciton-phonon operators is performed to derive the fundamental energy, the first excited state energy, the effective mass and the mobility of the exciton polaron. It is found that the system presents robust state energies and the dynamic properties like effective mass is reduced. We show that the motion of exciton-polaron is accelerated by increasing the magnetic barrier length. The transition of the exciton polaron from the valence band to the conduction band is also enhanced by the external field. It is found that the decoherence of exciton polaron can be adjusted by the magnetic field barrier. Our results suggest that the magnetic field barrier (i) enhances the confinement of the electron in the system, (ii) increases mobility and the rate of the decoherence of exciton polaron. The results are in agreement with experimental works.
Plasma Sources Science and Technology; https://doi.org/10.1088/1361-6595/ac2676

Abstract:
Plasmas interacting with liquid microdroplets are gaining momentum due to their ability to significantly enhance the reactivity transfer from the gas phase plasma to the liquid. This is, for example, critically important for efficiently decomposing organic pollutants in water. In this contribution, the role of ·OH as well as non-·OH–driven chemistry initiated by the activation of small water microdroplets in a controlled environment by diffuse RF glow discharge in He with different gas admixtures (Ar, O2 and humidified He) at atmospheric pressure is quantified. The effect of short-lived radicals such as O· and H· atoms, singlet delta oxygen (O2(a1∆g)), O3 and metastable atoms of He and Ar, besides ·OH radicals, on the decomposition of formate dissolved in droplets was analyzed using detailed plasma diagnostics, droplet characterization and ex situ chemical analysis of the treated droplets. The formate decomposition increased with increasing droplet residence time in the plasma, with ∼70% decomposition occurring within ∼15 ms of the plasma treatment time. The formate oxidation in the droplets is shown to be limited by the gas phase ·OH flux at lower H2O concentrations with a significant enhancement in the formate decomposition at the lowest water concentration, attributed to e−/ion−induced reactions. However, the oxidation is diffusion limited in the liquid phase at higher gaseous ·OH concentrations. The formate decomposition in He/O2 plasma was similar, although with an order of magnitude higher O· radical density than the ·OH density in the corresponding He/H2O plasma. Using a one-dimensional reaction-diffusion model, we showed that O2(a1∆g) and O3 did not play a significant role and the decomposition was due to O·, and possibly ·OH generated in the vapor containing droplet-plasma boundary layer.
Tim Kidd, , Lukas Stuelke, Colin Gorgen, S. J Roberts, Genda Gu,
Published: 14 September 2021
Abstract:
The stability and diffusion of ultra-thin thermally deposited Au films on Bi2Se3 was studied using scanning tunneling microscopy and density functional theory calculations. The Au/Bi2Se3 interface is of interest as gold is predicted to provide excellent electrical contact while maintaining the spin-polarized characteristics of the electronic states in Bi2Se3 that make the material attractive for spintronic applications. When deposited at room temperature, Au covers the surface with tightly packed islands of nanometer scale dimension. The surface morphology is stable up to 400K. At this annealing temperature, Au atoms have sufficient energy to diffuse across the surface and aggregate into larger nanostructures. At 550K, the Bi2Se3 surface is only sparsely covered, and the Au has formed clusters with length scales 5-10 times larger than the original islands formed at room temperature. Comparison of the experiment and first principle calculation lead to the conclusion that the diffusion energy barrier for Au on Bi2Se3 is as high as 0.47 eV, which is much larger than diffusion barriers on other van der Waals materials.
, Hiroyasu Tanigawa, Takaki Kojima, Takamoto Itoh, Noritake Hiyoshi, Mitsuru Ohata, Taichiro Kato, Masami Ando, Motoki Nakajima, Takanori Hirose, et al.
Published: 14 September 2021
Abstract:
The paper summarizes the current status of the materials property handbook for a structural design using Japanese reduced activation ferritic/martensitic steel F82H. Specifically, the key structural parameters, e.g., time-independent/dependent design stresses and fatigue design curves, were determined following the French structural design code RCC-MRx. Besides, under the Japan-U.S. collaboration, tensile data were newly added to the benchmark heavy irradiation data up to 80 dpa, as critical input information in the intermediate check and review in Japan. Furthermore, the status of structural material data and the near-term and long-term issues were clarified by the evaluation using the attribute guides. In parallel, the structural design approaches which were newly introduced and extended to cope with the structural design issues under the complex environmental conditions peculiar to the DEMO reactor were noted with the initial R&D results. Of many design issues, the multi-axial loading condition due to the complexity of the DEMO reactor as well as the coolant compatibility and the irradiation effect is mentioned. For example in the paper, the multi-axial fatigue-creep testing and evaluation using the modified universal slope method and the brittle/ductile fracture testing and evaluation by the local approach are explained toward DEMO.
, , Chenrui Diao, Yanjie Li, Lei Lin,
Published: 14 September 2021
Environmental Research Letters; https://doi.org/10.1088/1748-9326/ac269d

Abstract:
Frequent and severe PM2.5 pollution over China seriously harms natural environment and human health. Changes in meteorological conditions in the recent decades has been recognized to contribute to the long-term increase in PM2.5 pollution in North China (NC). However, the dominant climatic factors driving the interdecadal changes of the weather conditions conducive to PM2.5 pollution remain unclear. Here we identify a potential global teleconnection mechanism: the decadal reduction in European aerosol emissions since the 1980s may have partially contributed to the interdecadal increase in weather conditions conducive to PM2.5 pollution in NC, measured by an Emission-weighted Air Stagnation Index (ASIE) that increases at a rate of 6.2% decade-1 (relative to the 1981–1985 level). By regression analysis, we show that the decreased European aerosol loadings can warm the lower atmosphere and induce anomalous ascending motion in Europe, which potentially stimulate two anomalous Rossby wave trains in the upper troposphere travelling eastward across Eurasia. The teleconnection patterns project on NC by weakening the near-surface horizontal dispersion, which may be favorable to the increase in local ASIE and air pollution build-up. The suggested mechanism is further supported by the results from a set of large-ensemble simulations, showing that the European aerosol emission decline since the 1980s excite similar local heating and ascending motion and lead to increasing trends of 0.1 to 0.5 μg m-3 (38year)-1 in surface sulfate concentrations over most of NC. This proposed "West-to-East Aerosol-to-Aerosol" teleconnection mechanism helps resolve opposite views on the impact of global versus local aerosol forcing on PM2.5 pollution weather in NC. The policy implication is that the sustained decline in European aerosol emissions in coming decades, in conjunction with unabated global and regional warming, could further exacerbate air pollution in NC, thus imposing stronger pressure to reduce local emission sources quicker and deeper.
Yue Bai, Limin Gu, Xiaole Wang, Zhenyu Huang
Journal of Physics D: Applied Physics; https://doi.org/10.1088/1361-6463/ac2692

Abstract:
Effective control of the sound source directly is the fundamental solution to the noise problem. Herein, we propose a passive, non-closed, and remote scheme for omnidirectional reduction of the sound power radiated from vibrating sources. The physical mechanism of this scheme is to design an acoustic superscatterer based upon the idea of transformation media so that the virtual boundary of the acoustic superscatterer can overlap with the radiation boundary of the sound source to construct drastic multiple scattering effects. Through theoretical analyses and numerical simulations, we confirm the effectiveness of adopting the acoustic superscatterer to significantly suppress the sound radiation power generated by some typical dipolar sources in the air. Our study shows that by arranging no more than two acoustic superscatterers at the designed positions away from a dipolar thin rod, about 90% of the sound radiation power, i.e., 10 dB, can be suppressed in all directions of the dipole axis. This preliminary work would enlighten the research of using passive methods to achieve non-contact omnidirectional noise control of vibrating sources.
Published: 13 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac2655

Abstract:
Dry sliding friction is a complex but ubiquitous phenomenon. Experimental studies of friction produce large amounts of data, while most models are phenomenological rather than deduced from fundamental principles. Proper identification of relevant degrees of freedom is crucial for the development of adequate frictional models, such as the state-and-rate models. Topological data analysis is a mathematical method for the dimensionality reduction for datasets characterizing surface roughness, contact of rough surfaces and frictional sliding. We study tribological systems including the surface roughness and multiasperity contacts using 3×3, 4×4, and 5×5 pixel patches. Depending on whether the surface is isotropic or anisotropic with particular lay directions, the data tends to concentrate at certain "primary" and "secondary" circles yielding different values of the Betti numbers. Scale dependency of corresponding structures is analyzed with persistence diagrams. Moreover, statistics of stick-slip zones can provide insights on relevant internal degrees of friction.
Published: 13 September 2021
Journal of Neural Engineering; https://doi.org/10.1088/1741-2552/ac2629

Abstract:
Objective. Unobtrusive EEG monitoring in everyday life requires the availability of highly miniaturized EEG devices (mini-EEGs), which ideally consist of a wireless node with a small scalp area footprint, in which the electrodes, amplifier and wireless radio are embedded. By attaching a multitude of mini-EEGs at relevant positions on the scalp, a wireless 'EEG sensor network' (WESN) can be formed. However, each mini-EEG in the network only has access to its own local electrodes, thereby recording local scalp potentials with short inter-electrode distances. This is unlike using traditional cap-EEG, which by the virtue of re-referencing can measure EEG across arbitrarily large distances on the scalp. We evaluate the implications and limitations of such far-driven miniaturization on neural decoding performance. Approach. We collected 255-channel EEG data in an auditory attention decoding (AAD) task. As opposed to previous studies with a lower channel density, this new high-density dataset allows emulation of mini-EEGs with inter-electrode distances down to 1 cm in order to identify and quantify the lower bound on miniaturization for EEG-based stimulus decoding. Main Results. We demonstrate that the performance remains reasonably stable for inter-electrode distances down to 3 cm, but decreases quickly for shorter distances, if the mini-EEG nodes can be placed at optimal scalp locations and orientations selected by a data-driven algorithm. Significance. The results indicate the potential for the use of mini-EEGs in a WESN context for AAD applications and provide guidance on inter-electrode distances while designing such devices for neuro-steered hearing devices.
, Marc Missirlian, Mehdi Firdaouss, Bernd Böswirth, Mathilde Diez, Henri Greuner, Jean-Claude Hatchressian, Nadia Pérot, M. Ramaniraka, Helene Roche
Published: 13 September 2021
Abstract:
The activelly cooled plasma facing units (PFUs) constituting the WEST lower divertor must meet strict technical specifications before their installation into the WEST tokamak. The tests performed at CEA lead mainly: to provide information on the feasibility to attach mechanically PFUs on sectors, to ensure geometrical tolerances for the welding of PFUs to water manifolds, to check the PFU vacuum tightness and to confirm the PFUs heat exhaust capability. Using high heat flux (HHF) test facilities, such as HADES at CEA-Cadarache and GLADIS at IPP-Garching, ~5% of the PFU production was tested. Infrared thermography (IR) tests were also performed (~24% of the PFU production tested). We show that PFUs are with a quality in agreement to the requirements and that the assessement of the heat exhaust capability during the series production is needed. Based on statistical approaches, this work also provides information on the methods to assess the quality of tested components using statistic process control.
, , , Pramod Aggarwal, Miranda P.M. Meuwissen
Published: 13 September 2021
Environmental Research Letters; https://doi.org/10.1088/1748-9326/ac263d

Abstract:
With a global market of 30 billion USD, agricultural insurance plays a key role in risk finance and contributes to climate change adaptation by achieving Sustainable Development Goals (SDGs) including no poverty, zero hunger, and climate action. The existing evidence in agricultural insurance is scattered across regions, topics and risks, and a structured synthesis is unavailable. To address this gap, we conducted a systematic review of 796 peer-reviewed papers on agricultural insurance published between 2000 and 2019. The goal of this review was twofold: 1) categorizing agricultural insurance literature by agricultural product insured, research theme, geographical study area, insurance type and hazards covered, and 2) mapping country-wise research intensity of these indicators vis-à-vis historical and projected risk and crisis events—extreme weather disasters, projected temperature increase under SSP5 (Shared Socioeconomic Pathways) scenario and livestock epidemics. We find that insurance research is focused on high-income countries while crops are the dominating agricultural product insured (33% of the papers). Large producers in production systems like fruits and vegetables (South America), millets (Africa) and fisheries and aquaculture (South-east Asia) are not focused upon in the literature. Research on crop insurance is taking place where historical extreme weather disasters are frequent (correlation coefficient of 0.75), while we find a surprisingly low correlation between climate change induced temperature increases in the future and current research on crop insurance, even when sub-setting for papers on the research theme of climate change and insurance (-.04). There is also limited evidence on the role of insurance to scale adaptation and mitigation measures to de-risk farming. Further, we find that the study area of livestock insurance papers is weakly correlated to the occurrence of livestock epidemics in the past (-.06) and highly correlated to the historical drought frequency (.51). For insurance to play its relevant role in climate change adaptation as described in the Sustainable Development Goals (SDGs), we recommend governments, insurance companies and researchers to better tune their interest to risk-prone areas and include novel developments in agriculture which will require major investments, and, hence, insurability, in the coming years.
, , Wei Xu, Yuling He, Shuangshuang Lu
Published: 13 September 2021
Abstract:
Systematic toroidal modeling of the plasma response to the n = 1-4 (n is the toroidal mode number) resonant magnetic perturbation (RMP) field is carried out, in order to understand the plasma shaping effect on controlling the type-I edge localized modes (ELMs) in tokamak experiments. Considered are large variations of the plasma elongation and triangularity at fixed edge safety factor qa, for limiter plasmas with both single-null (SN) and double-null (DN) divertor-like boundary shapes. Numerical results assuming conformal 3-D RMP coils show that (i) the optimum coil phasing between the upper and lower rows for ELM control becomes increasingly sensitive to the plasma elongation with higher-n toroidal spectra, (ii) the optimum coil phasing is however essentially independent of plasma triangularity for all n=1-4 RMP fields, (iii) with the same coil current and the optimum coil phasing, high elongation generally favors ELM control but it may be more challenging for plasmas with intermediate elongation and with lower-n (n=1-2) RMPs, (iv) higher triangularity is generally always better for ELM control with all n=1-4 fields, for both DN and SN divertor-like plasma boundary shapes.
, DaeGeun Jo, Hyun-Woo Lee, Mathias Klaeui, Yuriy Mokrousov
Published: 13 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac2653

Abstract:
In solids, electronic Bloch states are formed by atomic orbitals. While it is natural to expect that orbital composition and information about Bloch states can be manipulated and transported, in analogy to the spin degree of freedom extensively studied in past decades, it has been assumed that orbital quenching by the crystal field prevents significant dynamics of orbital degrees of freedom. However, recent studies reveal that an orbital current, given by the flow of electrons with a finite orbital angular momentum, can be electrically generated and transported in wide classes of materials despite the effect of orbital quenching in the ground state. Orbital currents also play a fundamental role in the mechanisms of other transport phenomena such as spin Hall effect and valley Hall effect. Most importantly, it has been proposed that orbital currents can be used to induce magnetization dynamics, which is one of the most pivotal and explored aspects of magnetism. Here, we give an overview of recent progress and the current status of research on orbital currents. We review proposed physical mechanisms for generating orbital currents and discuss candidate materials where orbital currents are manifest. We review recent experiments on orbital current generation and transport and discuss various experimental methods to quantify this elusive object at the heart of orbitronics - an area which exploits the orbital degree of freedom as an information carrier in solid-state devices.
, Dennis Wong, Chrisitan Schulz, F. Rodrı́guez,
Published: 13 September 2021
Journal of Physics: Condensed Matter; https://doi.org/10.1088/1361-648x/ac2648

Abstract:
We investigate the electronic structure of Cs$_2$CuCl$_4$, a material discussed in the framework of a frustrated quantum antiferromagnet, by means of resonant inelastic x-ray scattering (RIXS) and Density Functional Theory (DFT). From the non-dispersive highly localized \textit{dd} excitations, we resolve the crystal field splitting of the Cu$^{2+}$ ions in a strongly distorted tetrahedral coordination. This allows us to model the RIXS spectrum within the Crystal Field Theory (CFT), assign the \textit{dd} orbital excitations and retrieve experimentally the values of the crystal field splitting parameters \textit{D}$_q$, \textit{D}$_s$ and \textit{D}$_{\tau}$. The electronic structure obtained \textit{ab-initio} agrees with the RIXS spectrum and modelled by CFT, highlighting the potential of combined spectroscopic, cluster and DFT calculations to determine the electronic ground state of complex materials.
, Rei Hashimoto, Kei Kaneko, Tsutomu Kakuno, Yuanzhao Yao, Naoki Ikeda, Yoshimasa Sugimoto, , , Hirotaka Tanimura, et al.
Published: 13 September 2021
Applied Physics Express, Volume 14; https://doi.org/10.35848/1882-0786/ac2240

Abstract:
Photonic crystal resonators with the C4v symmetry were designed and fabricated on quantum cascade lasers with a strain-compensated multiple quantum well to achieve single-mode and vertical surface emission at 4.32 μm. Their fabrication accuracy was confirmed by high-resolution reflection spectroscopy. The maximum output power was 10 mW at 77 K. A far-field pattern with a small divergence angle below 1 degree was observed. Its main peak had a donut shape, which was attributed to the spatial symmetry of the resonance mode of the photonic crystal.
, , Kathryn Humphrey, , R A Cairns, Frederico Fiuza, ,
Published: 13 September 2021
Plasma Physics and Controlled Fusion; https://doi.org/10.1088/1361-6587/ac2613

Abstract:
Brillouin amplification in plasma is more resilient to fluctuations in the laser and plasma parameters than Raman amplification, making it an attractive alternative to Raman amplification. In this work, we focus on high plasma densities, n_0 > n_cr/4, where stimulated Raman scattering is not possible and laser beam filamentation is the dominant competing process. Through analytic theory and multi-dimensional particle-in-cell simulations, we identify a parameter regime for which Brillouin amplification can be efficient while maintaining filamentation of the probe at a controlled level. We demonstrate pump-to-probe compression ratios of up to 72 and peak amplified probe fluences over 1 kJ/cm2 with ~ 50% efficiency. High pulse quality is maintained through control of parasitic filamentation, enabling operation at large beam diameters. Provided the pump and probe pulse diameters can be increased to 1 mm, our results suggest that Brillouin amplification can be used to produce sub-picosecond pulses of petawatt power.
Published: 13 September 2021
Fluid Dynamics Research; https://doi.org/10.1088/1873-7005/ac2620

Abstract:
The nonlinear motion of two interfaces in a three-layer fluid with density stratification is investigated theoretically and numerically. We consider the situation such that a uniform current is present in one of the three layers. The linear dispersion relation is calculated by the Newton's method, from which the initial conditions for numerical computations are determined. When the uniform current is present in the upper (lower) layer, strong vorticity is induced on the upper (lower) interface, and it rolls up involving the other interface at the late stage of computations. When the current is present in the middle layer, a varicose wave appears at the initial stage, and it evolves into an asymmetric heart-shaped vortex sheet at the last computed stage. These phenomena are presented using the vortex sheet model (VSM) with and without regularizations.
Published: 13 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac2654

Abstract:
We relate the anomaly in the noise color of spin ice to the emergent nature of its magnetic monopoles and their random walk. Monopoles are quasi-particles, and the spin vacuum in which they wander is not structureless. Rather, the underlying spin ensemble filters the thermal white noise, leading to non-trivial coevolution. Thus, monopoles can be considered as "dressed" random walkers, activated by a non-trivial stochastic noise that subsumes mutual interactions and the coevolution of their spin vacuum. From this, we suggest that recent experimental results are interpretable in terms of monopole subdiffusion. We then conjecture relations between the color of the noise and other observables, such as relaxation time, monopole density, the dynamic exponent, and the order of the annihilation reaction, which suggests to us the introduction of spin-ice-specific critical exponents in a neighborhood of the ice manifold criticality.
, Arnaud Badel, Blandine Rozier, Pascal Tixador
Superconductor Science and Technology; https://doi.org/10.1088/1361-6668/ac2623

Abstract:
Different means are investigated today to protect a REBCO coil against local thermal runaway, what is commonly called a "Quench". Metal Insulated Coil or No-Insulated coil have been successfully introduced. However, these protections method may show other issues and are limited in terms of dynamics, making them impractical for fast applications. We successfully tested early detection of dissipative voltage followed by current dumping as a method to protect REBCO insulated test coils, even with engineering current density in the kA/mm² range. Pick up coils can be used to compensate inductive coil voltage. In previous works we highlighted the presence of transient voltage due to the hysteretic current distribution in REBCO tape width, which can complicate the detection. We then developed a numerical electromagnetic model that reproduce the transient behaviour of REBCO coils. Here we study a small REBCO coil instrumented with three different pick-up coils, including a co-wound pick-up whose coupling is close to perfect. The post processing and analysis of the simulation results makes it possible to identify in the transient coil voltage the contribution due to transient losses and coil inductance variation. The resulting evaluation of the REBCO coil inductance and its variations is validated by analysis of the pick-up coil signals. From a practical point of view, this work shows the possibility to have very sensitive early detection of thermal runaway if the threshold is adjusted based on the expected coil compensated voltage drift. The interest of using isolated high-strength co-wound reinforcement tape as pick-up coil is also highlighted.
Jia Bao, Yanhong Liu,
Published: 13 September 2021
Journal of Physics: Condensed Matter; https://doi.org/10.1088/1361-648x/ac2647

Abstract:
We study the global quantum discord (GQD) in the Lipkin-Meshkov-Glick (LMG) model at zero and finite temperatures, in which all spins are mutually interacted and introduced in an external magnetic field (denoted by $h$). We confirm that the high coordinate number is one of the most distinguishing features of the LMG model, which directly results in the nontrivial behaviors of quantum correlations. We compare the GQD with other quantum correlations measures (such as concurrence, quantum discord, and global entanglement) and find the remarkable difference between them. For instance, we find that GQD spreads in the entire system and captures more information on quantum correlations when comparing with concurrence and quantum (pairwise) discord. We discover that GQD can characterize multipartite correlations in the both broken phase ($h0$ in the anisotropic cases for any fixed magnetic field. We further show that GQD behaves as $\mathcal{G}|_{s_n} \sim k \cdot \frac{1}{N}+c$ with $k<0$ in the isotropic cases for any Dicke state $|s_n\rangle$. Herein $k$ and $c$ are the fitting parameters. We also find that the thermal stability of the GQD at low temperatures depends on the energy gap. We further reveal that the extraordinary behaviors of the thermal-state GQD in the isotropic LMG model are explained by the contribution theory of the energy levels.
Published: 13 September 2021
Journal of Physics Communications; https://doi.org/10.1088/2399-6528/ac261c

Abstract:
The principle of complementarity is one of the cornerstones of quantum theory. The aim of this study was to advance our understanding of complementarity by analyzing the role of delayed choice and quantum erasers in two-slit experiments, and by proposing experiments for verifying the analysis. The analysis is based on models consisting of measurable spaces and probability measures involved in the experiments. The main findings are as follows: (a) The complementarity principle manifests itself in such a way that wave and particle behaviors cannot be simultaneously observed almost surely with respect to any single, fixed measure. (b) Described by different measures, complementary properties can coexist in the same experimental setup. (c) Which-way information will not preclude or erase interference fringes. (d) Delayed choice and quantum erasers are irrelevant to testing complementarity. (e) It is possible for us to know through which slit each quantum object passed almost surely with respect to the measure corresponding to the slit while the interference pattern is intact. Based on the experiments analyzed, realizable experiments are proposed for verifying the above results.
Marco Laurence Budlayan, Jonathan N. Patricio, Jeanne Phyre L. Oracion, Lyka B. De La Rosa, Susan D. Arco, Arnold C. Alguno, Eleanor S. Austria, Jonathan P. Manigo,
Published: 12 September 2021
Functional Composites and Structures; https://doi.org/10.1088/2631-6331/ac25e9

Abstract:
Copper contamination to water bodies is an environmental concern of significant risk due to its harmful effect on aquatic life forms and human beings. Herein, a paper-based colorimetric sensor was fabricated by immobilizing polyethyleneimine-capped silver nanoparticles (PEI-AgNPs) on commercial filter paper. The sensitivity and selectivity of the paper-based sensor's colorimetric response to copper ions in water were investigated. PEI-AgNPs with an average diameter of 12.66 ± 4.07 nm were successfully immobilized on the filter paper by the simple dipping technique, as evidenced by the SEM-EDX result. A color change from pale yellow to dark yellow green was noted after exposing the paper sensor in a water sample with copper ions. This colorimetric response was exclusively observed for copper ions only, suggesting the selectivity of the paper sensor towards copper ions. Moreover, UV-Vis spectroscopy results revealed that the detection limit of the paper sensor was observed to about 1.0 ppm. Meanwhile, color analysis on the sensor's digital images revealed the linear response of the sensor with decreasing copper ion concentration down to 1.0 ppm. The selectivity of the sensor was also observed by the color intensity profile of the sensor. This work presents promising results that can be utilized as a reference for developing affordable, fast, portable, and reliable sensing devices for on-site water quality monitoring and other applications.
, Nalin Mishra, Aditya Sankar Medury
Published: 10 September 2021
Semiconductor Science and Technology; https://doi.org/10.1088/1361-6641/ac256e

Abstract:
The accurate calculation of channel electrostatics parameters in ultra-thin body devices requires self-consistent solution of the Poisson's equation and the full-band structure of the thin channel. For silicon channel, the full-band structure is obtained using the semi-empirical sp3d5s* tight-binding model. To make this approach computationally tractable for a wide range of channel thicknesses, in terms of time and resource, only significant k-points in the irreducible Brillouin zone need to be considered. In this work, we present a scheme for precisely identifying the significant k-points based on Fermi-Dirac probability and show that the band-structure approach using those significant k-points can be applied over a wide range of channel thicknesses, oxide thicknesses, device temperatures and different channel orientations. The benchmarking of the obtained channel electrostatics parameters is performed with the results from accurate full-band structure simulations showing excellent agreement (maximum error within 0.5%) along with significant reduction in computational time.
, Masahiro Fukuda, JiHee Jeon, Mitsuo Sakashita, Shigehisa Shibayama,
Published: 10 September 2021
Japanese Journal of Applied Physics; https://doi.org/10.35848/1347-4065/ac25da

Abstract:
We investigated the photoluminescence (PL) properties of heavily Sb doped Ge1−xSnx layer and demonstrated the formation of double heterostructure (DHS) for Ge1−xSnx active layer. First, we found that a single PL peak is observed for Ge1−xSnx layers thicker than 80 nm with increasing Sb doping concentration up to 1020 cm−3, which is attributed by superior crystallinity and pseudo direct transition mechanism, while the 15-nm-thick Ge1−xSnx layer did not show PL signal. Next, a favorable heterostructure for Ge1−xSnx was proposed from the viewpoint of increasing valence band offset (ΔEv) using n-SiyGe1−y as clad layer. We demonstrated the formation of n-SiyGe1−y(15 nm)/n+-Ge1−xSnx(15 nm)/n-SiyGe1−y(15 nm) DHS with superior crystallinity and a strong PL peak intensity comparable to the thick Ge1−xSnx. Finally, we discussed reasons for the PL performance improvement by forming the DHS, which would be due to the sufficient carrier confinement and the suppression of surface recombination.
, A. K. Rao
Published: 10 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac25a8

Abstract:
We demonstrate that the standard St{$\ddot u$}ckelberg-modified Proca theory (i.e. a massive Abelian 1-form theory) respects the classical gauge and corresponding quantum (anti-)BRST symmetry transformations in any arbitrary dimension of spacetime within the framework of Becchi-Rouet-Stora-Tyutin (BRST) formalism. We further show that the St{$\ddot u$}ckelberg formalism gets modified in the two (1+1)-dimensions of spacetime due to a couple of discrete duality symmetry transformations in the theory which turn out to be responsible for the existence of the nilpotent (anti-)co-BRST symmetry transformations corresponding to the nilpotent (anti-)BRST symmetry transformations of our theory. These nilpotent symmetries exist together in the modified version of the two (1+1)-dimensional (2D) Proca theory. We provide the mathematical basis for the modification of the St{$\ddot u$}ckelberg-technique, the existence of the discrete duality as well as the continuous (anti-)co-BRST symmetry transformations in the 2D modified version of Proca theory.
, Jiu-Lin Du
Communications in Theoretical Physics; https://doi.org/10.1088/1572-9494/ac256c

Abstract:
Self-consistency in nonextensive statistical mechanics is studied as a recourse to parameter transformation, where different nonextensive parameters are presented for various theoretical branches. The unification between the first and third choices of the average definition and that between the normal and escort distributions are both examined. The problem of parameter inversion in the generalized H theorem is also investigated. The inconsistency between the statistical ensemble pressure and molecular dynamics pressure can be eliminated. This work also verifies the equivalence of physical temperature and gravitational temperature in nonextensive statistical mechanics. In these parameter transformations, the Tsallis entropy form is observed to remain invariant.
, Shaolong Wan
Communications in Theoretical Physics; https://doi.org/10.1088/1572-9494/ac256d

Abstract:
Out-of-time-ordered correlation (OTOC) functions have been used as an indicator of quantum chaos in a lot of physical systems. In this work, we numerically demonstrate that zero temperature OTOC can detect quantum phase transition in anisotropic Dicke model. The phase diagram is given with OTOC. The finite-size effect is studied. Finally, the temperature effect is discussed.
Hongxia Huang, Xin Jin, Yue Tan, Jialun Ping
Published: 10 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac25aa

Abstract:
In recent two decades, a large number of exotic hadron states have been observed in experiments, which arouses great attentions in hadron physics community. In this short review, we briefly summarize progresses of our group on several exotic hadron states. Two approaches, quenched and unquenched quark models, are adopted in the calculation. The channel coupling effects, the multiquark states couple to open-channels and the quark-antiquark states couple to meson-meson states, are emphasized. X(3872) is showed to be a mixture state of ccbar and DDbar* in the unquenched quark model. X(2900) can be explained as a resonance state Dbar*K* with the quantum numbers IJP=00+ in both the quark delocalization color screening model and the chiral quark model. The reported state X(6900) can be explained as a compact resonance state with IJP=00+ in both two quark models, and several fully heavy tetraquark states are predicated. The possible hidden-charm pentaquarks are systematically investigated in QDCSM, and seven resonance states are obtained in the corresponding baryon-meson scattering process, among which the ΣcD with JP=1/2-, ΣcD* with JP=3/2- and JP=1/2- are consistent with the experimental report of Pc(4312), Pc(4440), and Pc(4457), respectively. Experimental search for more exotic hadron states will provide more information for understanding the exotic hadron states in quark models.
, Azadeh Mohammadi
Published: 10 September 2021
Classical and Quantum Gravity; https://doi.org/10.1088/1361-6382/ac25e0

Abstract:
We propose a modification of the partial wave approach to deal with the relativistic quantum scattering of bosonic and fermionic particles in a class of models concerning gravitating cosmic string spacetimes. These spacetimes are characterized by the Minkowski line element at the center of the vortex, non-vanishing curvature at a finite distance from the center but with a conical structure far from the core. We find the correction in the partial wave expansion and the phase shift. Consequently, we show the explicit form of the scattering amplitude and the correction to the differential cross-section for a massive scalar field. We also implement our formalism in a toy model mimicking this class of gravitating cosmic string spacetime. Moreover, we discuss the procedure to apply this formalism to a massive Dirac field.
Published: 10 September 2021
Abstract:
Nano-structure ferromagnetic-ferroelectric composite materials produced by the sol gel method have great attention in different applications due to their desired properties and applications. Potassium Barium titanate doped with different concentrations of Ni2+ nanoparticles (K0.1Ba0.9Ti(1-x)NixO3; x = 0.0-0.3) were prepared by sol-gel process. The final nanoparticles were obtained through drying and calcination at 200 oC and 600 oC, respectively. The crystalline, nanoparticles' nature and the optical characteristics of the Ni-KBTO nanoparticles are investigated using XRD, SEM, TEM, and optical properties. The XRD and TEM results demonstrate that the Ni2+ NPs were superlatively incorporated within the semi-crystalline KBTO structure. TGA thermogram of all samples shows two weight loss events. The first event is assigned for impurities and/or adsorbed water releasing. The second event was at a higher temperature and assigned as degradation of the nanoparticles. The thermal stability was enhanced by Ni2+ incorporation. The KBTO nanoparticles exhibit enhancement optical bandgap, which decreases from 3 eV to 2.3 eV with increasing Ni2+ in KBTO NPs. This can be ascribed to the change in nanoparticles arrangement and resembles band structures between Ti4+ and Ni2+, resulting in the efficient transfer of charge carriers. The dielectric constant was in the range 106 to 107 at low frequency and about 101 to 102 at high frequency. The Curie temperature of pure Potassium barium titanate is 373 K and 328 K for Potassium barium titanate doped with 20% of Ni2+.
Published: 10 September 2021
Classical and Quantum Gravity; https://doi.org/10.1088/1361-6382/ac25e4

Abstract:
A type of exponential correction to General Relativity gives viable modified gravity model of dark energy. The model behaves as $R-2\Lambda$ at large curvature where an effective cosmological constant appears, but it becomes zero in flat space time. The cosmic evolution of the main density parameters is consistent with current observations. The thin shell conditions for the Solar system were analyzed. Apart from satisfying cosmological and local gravity restrictions, the model may also show measurable differences with $\Lambda$CDM at recent times. The current value of the deviation parameter $m$ for scales relevant to the matter power spectrum can be larger than $10^{-6}$. The growth index of matter density perturbations is clearly different from that of the $\Lambda$CDM. The theoretical predictions of the model for the weighted growth rate were analyzed in the light of the $f\sigma_8$-tension.
, Pierre Le Doussal
Published: 10 September 2021
EPL (Europhysics Letters); https://doi.org/10.1209/0295-5075/ac25a9

Abstract:
We obtain a simple formula for the stationary measure of the height field evolving according to the Kardar-Parisi-Zhang equation on the interval [0, L] with general Neumann type boundary conditions and any interval size. This is achieved using the recent results of Corwin and Knizel (arXiv:2103.12253) together with Liouville quantum mechanics. Our formula allows to easily determine the stationary measure in various limits: KPZ fixed point on an interval, half-line KPZ equation, KPZ fixed point on a half-line, as well as the Edwards-Wilkinson equation on an interval.
, , Jennifer Schwarz
Published: 9 September 2021
Abstract:
The ability of cells to move through small spaces depends on the mechanical properties of the cellular cytoskeleton and on nuclear deformability. In mammalian cells, the cytoskeleton is composed of three interacting, semi-flexible polymer networks: actin, microtubules, and intermediate filaments (IF). Recent experiments of mouse embryonic fibroblasts with and without vimentin have shown that the IF vimentin plays a role in confined cell motility. Here, we develop a minimal model of a cell moving through a microchannel that incorporates explicit effects of actin and vimentin and implicit effects of microtubules. Specifically, the model consists of a cell with an actomyosin cortex and a deformable cell nucleus and mechanical linkages between the two. By decreasing the amount of vimentin, we find that the cell speed increases for vimentin-null cells compared to cells with vimentin. The loss of vimentin increases nuclear deformation and alters nuclear positioning in the cell. Assuming nuclear positioning is a read-out for cell polarity, we propose a new polarity mechanism which couples cell directional motion with cytoskeletal strength and nuclear positioning and captures the abnormally persistent motion of vimentin-null cells, as observed in experiments. The enhanced persistence indicates that the vimentin-null cells are more controlled by the confinement and so less autonomous, relying more heavily on external cues than their wild-type counterparts. Our modeling results present a quantitative interpretation for recent experiments and have implications for understanding the role of vimentin in the epithelial-mesenchymal transition.
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