A novel method for investigation of acoustic and elastic wave phenomena using numerical experiments

The emergence of new types of composite materials,the depletion of existing hydrocarbon deposits,and the increase in the speed of trains require the development of new research methods based on wave scattering.Therefore,it is necessary to determine the laws of wave scattering in inhomogeneous media.We propose a method that combines the advantages of a numerical simulation with an analytical study of the boundary value problem of elastic and acoustic wave equations.In this letter we present the results of the study using the proposed method:the formation of a response from a shear wave in an acoustic medium and the formation of shear waves when a vertically incident longitudinal wave is scattered by a vertical gas-filled fracture.We have obtained a number of analytical expressions characterising the scattering of these wave types.

Evaluation of CDK6 and p16/INK4a-Derived Peptides Interaction

The goal of this work is the development of novel peptides with high efficacy of inhibiting activity of CDK6/CyclinD complex. The peptides were derived from primary sequence of P16 protein and its homologues. The interactions between CDK6 and P16/INK4a-derived peptides are studied with molecular dynamics simulation employing umbrella sampling method. The SASA implicit solvent model was used for simulation, which was accelerated using NVIDIA GPUs.

Cardiac Tissue Engineering with the Aid of Polyhydroxybutyrate Membranes and Nanofibers

The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaffolds for the cardiac tissue engineering, either in a form of thin membranes or electrospun fiber mats. The results show that cardiac cells of various origins can be successfully grown on PHB substrates, in the both forms： membrane and nanofiber matrix. Functioning of obtained tissue patches was tested by visual observation of contractions and with the aid of optical mapping, i.e., registration of excitation waves with fluorescent markers. The latter one allowed ensuring the fact that cultured cells represented electrophysiological syncytium, and the PHB scaffold showed its full compatibility with the excitability of cardiac cells.

The Evolution of the Charge Density Distribution Function for Spherically Symmetric System with Zero Initial Conditions

The evolution of the charge density distribution function is simulated for both the case of a uniformly charged sphere with zero initial conditions and for the case of a non-uniform charged sphere. For the case of a uniformly charged sphere the comparison of a numerical result and an exact analytical demonstrated the agreement between the results. The process of “scattering” of a charged system under the influence of its own electric field has been illustrated on the basis of both the particle-in-cell method and the solution of the Cauchy problem for vector functions of the electric field and vector velocity field of a charged medium.

Reinforced interface endows the lithium anode with stable cycle at high-temperature of 80℃

Embracing ultrahigh theoretical capacity of 3860 mA h g^(-1)and the lowest reduction potential of-3.04 V(versus standard hydrogen electrode),lithium(Li) is considered as the "holy grail" material for pursuing higher energy density,of which application has been challenged due to the unstable interface caused by the non-uniform electrodeposition as well as high chemical activity.Operating at higher temperature can be recommended to uniform electrodeposition of Li metal.Nevertheless,the intrinsic side-reaction between Li metal anode and electrolyte is inevitably aggravated and thus fosters the failure of Li metal anode rapidly with uneven electrodeposition.Here,a kind of temperature-tolerated ionic liquid(1-methyl-3-ethylimidazole bis(fluorosulfo nyl)imide/lithium bis(trifluoromethylsulfo nyl)imide,EF/LT)based electrolyte that matrixed with poly(vinylidene fluoride-hexafluoropropylene) was designed to maintain the interfacial stabilization of Li metal due to the weak interfacial reaction and uniform electrodeposition at high temperature of 80℃.It is the matter that the 660-h cycle with lower polarization is achieved with EF/LT-based electrolyte at temperature of 80 ℃ and the full cell embraces outstanding cyclic performance,without capacity fading within 100 cycles.Delighting,a door for practical application of Li metal anode for higher energy density as the carbon neutrality progresses in the blooming human society has been opened gradually.

The Case of Nonzero Initial Conditions in the Evolution of the Charge Density Distribution Function for a Spherically Symmetric System

We explored the Cauchy problem for the evolution of the charge density distribution function for a spherically symmetric system with nonzero initial conditions. In our model, the evolution of the charge density distribution function is simulated for the case of a non-uniform charged sphere. The initial speed of the system is nonzero. The solution breaks down into two components: the first one describes the system’s motion as a whole and the second describes the process of the evolution of the charge density function under the influence of its own electric field in the center-of-mass system. In this paper we considered the characteristic features of the implementation of a difference scheme for numerical simulation. We also illustrate the process of “scattering” of a moving charged system under the influence of its own electric field on the basis of the solution of the Cauchy problem for vector functions of the electric field and vector velocity field of a charged medium.

Thermal Energy of Confined Gravitons can Vary Cold Geodesic Curves

Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confinement within the constant energy charge of a moving thermodynamical body. Zero energy-momentum gravitons provide dissipative self-heating and spiral fall of massive stars on gravitating centers. Computed self-heating of the pulsar PSR B1913＋16 quantitatively describes its period decay without an outward emission of metric waves in question. Deviation of warm bodies from geodesic trajectories of cold point matter complies with Einstein＇s directives toward pure field physics of material space plenum without metric singularities.

Model of fractured medium and nondestructive control of composite materials

Non-destructive testing of composites is an important issue in the modern aircraft industry.Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and operation.The continuum model for describing the damaged zone is presented.The slip theory relations used for a continuous distribution of slip planes are applied.At the initial stage,the isotropic background model is used.This model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous addition.In this regime,the govern system of equations becomes rigid.To overcome this difficulty,the explicit-implicit grid-characteristic scheme is proposed.The standard ultrasound diagnostic procedure of damaged composite materials is successfully simulated.Compared with the trivial free-surface fracture model,different reactions on the compression and stretch waves are registered.This approach provided an effective way for the simulation of complex dynamic behavior of damage zones.

Cas9-targeted Nanopore sequencing rapidly elucidates the transposition preferences and DNA methylation profiles of mobile elements in plants

Transposable element insertions(TEIs) are an important source of genomic innovation by contributing to plant adaptation, speciation, and the production of new varieties. The often large,complex plant genomes make identifying TEIs from short reads difficult and expensive. Moreover, rare somatic insertions that refect mobilome dynamics are difficult to track using short reads.To address these challenges, we combined Cas9-targeted Nanopore sequencing(CANS) with the novel pipeline Nano Cas TE to trace both genetically inherited and somatic TEIs in plants. We performed CANS of the EVADé(EVD) retrotransposon in wild-type Arabidopsis thaliana and rapidly obtained up to 40× sequence coverage.Analysis of hemizygous T-DNA insertion sites and genetically inherited insertions of the EVD transposon in the ddm1(decrease in DNA methylation1) genome uncovered the crucial role of DNA methylation in shaping EVD insertion preference.We also investigated somatic transposition events of the ONSEN transposon family, finding that genes that are downregulated during heat stress are preferentially targeted by ONSENs. Finally, we detected hypomethylation of novel somatic insertions for two ONSENs. CANS and Nano Cas TE are effective tools for detecting TEIs and exploring mobilome organization in plants in response to stress and in different genetic backgrounds, as well as screening T-DNA insertion mutants and transgenic plants.

Crystal and electronic structure engineering of tin monoxide by external pressure

Although tin monoxide (SnO) is an interesting compound due to its p-type conductivity,a widespread application of SnO has been limited by its narrow band gap of 0.7 eV.In this work,we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals.Our calculations reveal that a metastable SnO (β-SnO),which possesses space group P2_(1)/c and a wide band gap of 1.9 eV,is more stable than α-SnO at pressures higher than 80 GPa.Moreover,a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa.Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa.Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO →α-SnO.Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure.Finally,our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0-9 GPa)through a semiconductor-to-metal transition,while maintaining transparency in the visible light range.

On the Semianalytical Two-Body Regularization in N-Body Simulations

A two-body regularization for N-body problem based on perturbation theory for Keplerian problem is discussed. We provide analytical estimations of accuracy and conduct N-body experiments in order to compare it with state-of-the-art Hermite integrator. It is shown that this regularization keeps some features that allow overcoming KS-regularization in some particular cases.

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

In this paper,we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode.We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration.Measurements of terahertz pulses energy as a function of emitted charge density,incidence angle of optical radiation and applied electric field have been provided.Spectral and polarization characteristics of generated terahertz pulses have also been studied.The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.

Organic-inorganic hybrid Sn-based perovskite photodetectors with high external quantum efficiencies and wide spectral responses from 300 to 1000 nm

Organic-inorganic hybrid perovskites are ideal materials for photodetection owing to their high charge carrier mobility, long charge carrier diffusion length, low dark current density and sharp absorption edge. However, a relatively small band gap(1.6 e V) limits their photonharvesting efficiency in the near-infrared region. In the present work, we demonstrate a hybrid methylamine iodide and Pb-Sn binary perovskite as the light absorption layer in photodetectors. Experimentally, the wavelength of photoresponse onset for the photodetectors can be extended to as great as 1,000 nm when the Sn content of the hybrid perovskite is increased to 30 mol%. In addition, the photodetectors exhibit a photoresponsivity of 0.39 A W^-1, a specific detectivity of 7×10^12 Jones, a fast photoresponse with rise and decay time constants and an external quantum efficiency greater than 50% in the wavelength range of350–900 nm, with a maximum value of about 80% at 550 nm.

Multispectral sensing of biological liquids with hollow-core microstructured optical fibres

The state of the art in optical biosensing is focused on reaching high sensitivity at a single wavelength by using any type of optical resonance.This common strategy,however,disregards the promising possibility of simultaneous measurements of a bioanalyte’s refractive index over a broadband spectral domain.Here,we address this issue by introducing the approach of in-fibre multispectral optical sensing(IMOS).The operating principle relies on detecting changes in the transmission of a hollow-core microstructured optical fibre when a bioanalyte is streamed through it via liquid cells.IMOS offers a unique opportunity to measure the refractive index at 42 wavelengths,with a sensitivity up to ~3000 nm per refractive index unit(RIU)and a figure of merit reaching 99 RIU^(−1) in the visible and near-infra-red spectral ranges.We apply this technique to determine the concentration and refractive index dispersion for bovine serum albumin and show that the accuracy meets clinical needs.

Hole-doping of mechanically exfoliated graphene by confined hydration layers

By the use of non-contact atomic force microscopy （NC-AFM） and Kelvin probe force microscopy （KPFM）, we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CAF2（111）. Hydration layers confined between the graphene and the CaF2 substrate, resulting from the graphene＇s preparation under ambient conditions on the hydrophilic substrate surface, are found to electronically modify the graphene as the material＇s electron density transfers from graphene to the hydration layer. Density functional theory （DFT） calculations predict that the first 2 to 3 water layers adjacent to the graphene hole-dope the graphene by several percent of a unit charge per unit cell.

Quenching of second-harmonic generation by epsilon-near-zero media

Epsilon-near-zero(ENZ)media were demonstrated to exhibit unprecedented strong nonlinear optical properties including giant second-harmonic generation(SHG)due to their field-enhancement effect.Here,on the contrary,we report the quenching of SHG by the ENZ media.We find that when a tiny nonlinear particle is placed very close to a subwavelength ENZ particle,the SHG from the nonlinear particle can be greatly suppressed.The SHG quenching effect originates from the extraordinary prohibition of electric fields occurring near the ENZ particle due to evanescent scattering waves,which is found to be universal in both isotropic and anisotropic ENZ particles,irrespective of their shapes.Based on this principle,we propose a kind of dynamically controllable optical metasurface exhibiting switchable SHG quenching effect.Our work enriches the understanding of optical nonlinearity with ENZ media and could find applications in optical switches and modulators.

Effect of suction process on the growth of a convective gas bubble in diver's tissues

The motivation of this research is to study the effect of suction process on a growing gas bubble and concentration distribution around this bubble in tissues of divers who surface too quickly.The effect of bubble motion is also considered.The method of combined variables is used to solve the problem by combining the radial and time variables into one variable by using a suitable similarity transformation that enables to divide the diffusion equation into two ODEs,the first concerns to concentration distribution and the other concerns to the bubble radius evolution.The resultant formulae are valid for both growth stages whenever the ambient pressure is variable at ascending of the diver,or constant as the diving stops or at sea-level.The effects of physical parameters are discussed when applying suction process and show that the dominant parameter is the initial void fraction.The research findings reveal the role of suction process to activate the systemic blood circulation and delay the growth of gas bubbles in the tissues and reduce the incidence of decompression illness(DCI).This research also provides evidenceand agrees with the previous experimental studies to support the use of suction therapy to reduce the DCI harmful effects.

Stability of the Fe12O12 cluster

Superexchange effects play an important role in the determination of crystal structures; however, there has been much less reported on how they determine the stability of dusters. Using evolutionary search strategies and DFT＋U （density functional theory with the Hubbard U correction） calculations, we investigate the global minimum-energy structures of Fe12O12 clusters. Among predicted Fe12O12 dusters, a cage-shaped Fe12O12 cluster with unexpected stability was observed. In addition, the bare Fe12O12 cluster is shown to possess an extremely large energy gap （2.00 eV）, which is greater than that of C60, Au20 and Al13- clusters. Using a Heisenberg model, we traced the origin of the unexpected stability of the bare Fe12O12 cluster to magnetic competition between the nearestneighbor exchange constant h and the next-nearest neighbor exchange constant J2 that was induced by the superexchange interactions. The bare Fe12O12 cluster is thus a unique molecule that is stable and chemically inert.

High yield production of ultrathin fibroid semiconducting nanowire of Ta2Pd3Se8

Immediately after the demonstration of the high-quality electronic properties in various two dimensional(2D)van der Waals(vdW)crystals fabricated with mechanical exfoliation,many methods have been reported to explore and control large scale fabrications.Comparing with recent advancements in fabricating 2D atomic layered crystals,large scale production of one dimensional(1D)nanowires with thickness approaching molecular or atomic level still remains stagnant.Here,we demonstrate the high yield production of a 1D vdW material,semiconducting Ta2Pd3Se8 nanowires,by means of liquid-phase exfoliation.The thinnest nanowire we have readily achieved is around 1 nm,corresponding to a bundle of one or two molecular ribbons.Transmission electron microscopy(TEM)and transport measurements reveal the as-fabricated Ta2Pd3Se8 nanowires exhibit unexpected high crystallinity and chemical stability.Our low-frequency Raman spectroscopy reveals clear evidence of the existing of weak inter-ribbon bindings.The fabricated nanowire transistors exhibit high switching performance and promising applications for photodetectors.

Recent advances in laser self-injection locking to high-Q microresonators

The stabilization and manipulation of laser frequency by means of an external cavity are nearly ubiquitously used in fundamental research and laser applications. While most of the laser light transmits through the cavity, in the presence of some back-scattered light from the cavity to the laser, the self-injection locking effect can take place, which locks the laser emission frequency to the cavity mode of similar frequency. The self-injection locking leads to dramatic reduction of laser linewidth and noise. Using this approach, a common semiconductor laser locked to an ultrahigh-Q microresonator can obtain sub-Hertz linewidth, on par with state-of-the-art fiber lasers. Therefore it paves the way to manufacture high-performance semiconductor lasers with reduced footprint and cost. Moreover, with high laser power, the optical nonlinearity of the microresonator drastically changes the laser dynamics, offering routes for simultaneous pulse and frequency comb generation in the same microresonator. Particularly, integrated photonics technology, enabling components fabricated via semiconductor CMOS process, has brought increasing and extending interest to laser manufacturing using this method. In this article, we present a comprehensive tutorial on analytical and numerical methods of laser self-injection locking, as well a review of most recent theoretical and experimental achievements.