bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel polyoxovanadate-based Co-MOF: highly efficient and selective oxidation of a mustard gas simulant by two-site synergetic catalysis
Authors: Tian Hong-Rui , Zhang Zhong , Liu Shu-Mei , Dang Tian-Yi , Li Xiao-Hui , Lu Ying , Liu Shu-Xia
Published: May 2020

A polyoxovanadate-based cobalt organic framework (V–Co-MOF) was synthesized and it, as a heterogeneous catalyst, can catalyze the rapid selective oxidation of a mustard gas simulant to a non-toxic product by the two-site synergistic effect of VVand CoII.
Size-dependent critical transition in the origin of light emission from core–shell Si–SiO2nanoparticles
Authors: P. Falcão Bruno , Leitão Joaquim P. , Soares Maria R. , Rodrigues Joana , Ricardo Lídia , Águas Hugo , Martins Rodrigo , Pereira Rui N.
Published: May 2020

Here, it is established that the origin of the photoluminescence of Si–SiO2core–shell nanoparticles is strongly size-dependent, with large nanoparticles emitting mostly from the core, whereas small nanoparticles emit predominantly from the shell.
Naringin alleviates methotrexate-induced liver injury in male albino rats and enhances its antitumor efficacy in HepG2 cells
Authors: Elsawy Hany , Algefare Abdulmohsen I. , Alfwuaires Manal , Khalil Mahmoud , Elmenshawy Omar M. , Sedky Azza , Abdel-Moneim Ashraf M.
Published: May 2020

Methotrexate (MTX) is an efficient chemotherapeutic and immunosuppressant drug, but the hepatotoxicity of MTX limits its clinical use. Naringin (Nar) is a flavonoid derived from Citrus paradise, and has been shown to possess several pharmacological activities, including free-radical scavenging and antioxidant properties. In the present study, we first tested the possible protective effects of multiple doses of Nar against MTX-induced acute hepatotoxicity in rats, and then we investigated the growth inhibition and apoptotic effects of MTX and/or Nar against the HepG2 hepatocarcinoma cell line. Our in vivo results showed that Nar significantly reduced MTX-induced increases in serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin levels. Nar also reduced MTX-induced oxidative stress by significantly reducing liver malondialdehyde (MDA) and nitric oxide (NO) content and increasing superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione (GSH). In addition, Nar significantly counteracted MTX-induced increases in hepatic interleukin-6 and tumor necrosis factor-α (TNF-α). Further, Nar greatly protected hepatocyte ultrastructure against MTX-induced injury. In contrast, in vitro MTX and/or Nar treatment of HepG2 cells for 48 h exhibited a cytotoxic effect and induced apoptosis in a dose-dependent manner mediated by a significant increase in the Bax/Bcl-2 protein expression ratio. Noticeably, Nar potentiated the MTX effect on the Bax/Bcl-2 ratio. In conclusion, Nar decreased MTX-induced functional and ultrastructural liver damage in a tumor-free animal model. Also, our data introduce MTX and Nar as promising antiproliferative agents with a distinctive mode of action, inducing apoptosis in HepG2 tumor cells through activation of Bax and down-regulation of Bcl-2 protein expression.
MiR-30e-5p inhibits the migration and invasion of nasopharyngeal carcinoma via regulating the expression of MTA1
Authors: Hu Weiqun , Yao Wenfeng , Li Haolin , Chen Li
Published: May 2020

The study explored the effect of miR-30e-5p on nasopharyngeal carcinoma (NPC). MiR-30e-5p levels in NPC cancer and adjacent normal samples, in metastatic and non-metastatic cancer samples of NPC, and in NP69 cell and five NPC cell lines were determined by quantitative real-time polymerase chain reaction (qRT-PCR). The relationship between miR-30e-5p and MTA1 was confirmed by dual-luciferase reporter assay, Western blot and qRT-PCR. The viability, migration and invasion of 5-8F and 6-10B cells were determined by CCK-8, scratch test and transwell assays, respectively. The levels of migration-related proteins (vimentin and Snail) and invasion-related proteins (MMP2 and MMP3) in NPC cells were detected by Western blot. The results showed that low expression of miR-30e-5p was associated with HNSC cancer, NPC, metastasis of NPC and NPC cell lines. Overexpressed miR-30e-5p in HNSC cancer and NPC was predictive of a better prognosis of patients. In addition, the viability, migration and invasion were reduced by up-regulating miR-30e-5p in 5-8F cells, but promoted by down-regulated miR-30e-5p in 6-10B cells. MiR-30e-5p reversed the migration and invasion of NPC cells regulated by MTA1, and inhibited migration and invasion of NPC cells via regulating MTA1 expression.
Acetate promotes SNAI1 expression by ACSS2-mediated histone acetylation under glucose limitation in renal cell carcinoma cell
Authors: Yao Lv , Jiang Linying , Zhang Fuxing , Li Minghua , Yang Bo , Zhang Fangting , Guo Xiaoqiang
Published: May 2020

Metastasis is the main cause of cancer-associated deaths, yet this complex process is still not well understood. Many studies have shown that acetate is involved in cancer metastasis, but the molecular mechanisms remain to be elucidated. In the present study, we first measured the effect of acetate on zinc finger transcriptional repressor SNAI1 and acetyl-CoA synthetase 2 (ACSS2) under glucose limitation in renal cell carcinoma cell lines, 786-O and ACHN. Then, RNA interference and overexpression of ACSS2 were used to detect the role of acetate on SNAI1 expression and cell migration. Finally, chromatin immunoprecipitation assay (ChIP) was used to investigate the regulatory mechanism of acetate on SNAI1 expression. The results showed that acetate increased the expressions of SNAI1 and ACSS2 under glucose limitation. ACSS2 knockdown significantly decreased acetate-induced SNAI1 expression and cell migration, whereas overexpression of ACSS2 increased SNAI1 level and histone H3K27 acetylation (H3K27ac). ChIP results revealed that acetate increased H3K27ac levels in regulatory region of SNAI1, but did not increase ACSS2-binding ability. Our study identified a novel inducer, acetate, which can promote SNAI1 expression by ACSS2-mediated histone acetylation in partly. This finding has important implication in treatment of metastatic cancers.
Integrative analysis of DNA methylation and gene expression profiles identified potential breast cancer-specific diagnostic markers
Authors: Liu Xinhua , Peng Yonglin , Wang Ju
Published: May 2020

Breast cancer is a common malignant tumor among women whose prognosis is largely determined by the period and accuracy of diagnosis. We here propose to identify a robust DNA methylation-based breast cancer-specific diagnostic signature. Genome-wide DNA methylation and gene expression profiles of breast cancer patients along with their adjacent normal tissues from the Cancer Genome Atlas (TCGA) were obtained as the training set. CpGs that with significantly elevated methylation level in breast cancer than not only their adjacent normal tissues and the other ten common cancers from TCGA but also the healthy breast tissues from the Gene Expression Omnibus (GEO) were finally remained for logistic regression analysis. Another independent breast cancer DNA methylation dataset from GEO was used as the testing set. Lots of CpGs were hyper-methylated in breast cancer samples compared with adjacent normal tissues, which tend to be negatively correlated with gene expressions. Eight CpGs located at RIIAD1, ENPP2, ESPN, and ETS1, were finally retained. The diagnostic model was reliable in separating BRCA from normal samples. Besides, chromatin accessibility status of RIIAD1, ENPP2, ESPN and ETS1 showed great differences between MCF-7 and MDA-MB-231 cell lines. In conclusion, the present study should be helpful for breast cancer early and accurate diagnosis.
Study on the combined characteristics of UHF and optical signals induced by partial discharge at spacer surface in GIS
Authors: Han Xutao , Guo Ruochen , Shen Shuhang , Li Junhao , Sun Wei
Published: May 2020

In this study, to improve the sensitivity and accuracy of the detection of surface partial discharge (PD) in gas insulation switchgears (GISs), a combination of ultra‐high frequency (UHF) and optical methods is proposed based on an integrated sensor. The PD triggered by a fixed metal needle defect attached to the spacer is detected from PD inception to flashover in a real GIS. The characteristics of UHF and optical signals under different applied voltages are compared and analysed in terms of PD waveform, Phase Resolved Partial Discharge (PRPD) pattern, PD count and amplitude. The results show that the surface discharge process can be precisely divided into three stages according to the combined characteristics of the UHF and optical signals. The comparison of the two detection methods shows that the optical method can detect the weak avalanche PD under low voltage while UHF cannot, so it can detect more PDs than UHF method in an AC cycle. In addition, with the deterioration of solid insulation material, the amplitude of the optical signal increases significantly while the amplitude of the UHF signal only increases slightly.
Robust backstepping output voltage controller for standalone voltage‐sourced converters
Authors: Achlerkar Pankaj D. , Panigrahi Bijaya Ketan
Published: May 2020

This work presents a linear state‐feedback controller using a backstepping design approach for output voltage regulation of voltage‐sourced converters feeding to customers' loads in a stand‐alone AC microgrid system. Irrespective of load type and its variations, parameter uncertainties, and other disturbances, the controller is robust enough to achieve a regulated voltage magnitude within the prescribed bounds and exact frequency tracking. The criterion for gain selection using Lyapunov analysis is given. With global exponential convergence feature and better coordination among inner current and outer voltage control loops, improved transient response is achieved. Controller features are examined by eigenvalue analysis and extensive simulation studies. Experimental results demonstrate the feasibility of the proposed controller implementation.
Three‐dimensional obstacle avoidance for UAV based on reinforcement learning and RealSense
Authors: Han Deqiang , Yang Qishan , Wang Rui
Published: May 2020

With the increasingly widespread application of unmanned aerial vehicle (UAV), safety issues such as effectiveness of obstacle avoidance have been paid more attentions. The classical obstacle avoidance algorithms are mostly suitable for mobile robots, but these algorithms are not ideal for UAV using in three‐dimensional space. Most of the three‐dimensional obstacle avoidance algorithms which are more effective using RGB image data as input. Thus, a large amount of image data is involved in complex computing process. This study proposes an effective obstacle avoidance algorithm for UAV with less input data and fewer sensors based on RealSense and reinforcement learning. It combines the feature map of the depth image of RealSense as the input data of reinforcement learning and the current direction of flight of UAV to calculate the direction and angle of avoiding. The proposed algorithm that implements real‐time obstacle avoidance for UAV has been verified by simulation and tested in three‐dimensional space scenario.
TDCOSMO
Authors: Millon M. , Galan A. , Courbin F. , Treu T. , Suyu S. H. , Ding X. , Birrer S. , Chen G. C.-F. , Shajib A. J. , Sluse D. , Wong K. C. , Agnello A. , Auger M. W. , Buckley-Geer E. J. , Chan J. H. H. , Collett T. , Fassnacht C. D. , Hilbert S. , Koopmans L. V. E. , Motta V. , Mukherjee S. , Rusu C. E. , Sonnenfeld A. , Spiniello C. , Van de Vyvere L.
Published: May 2020

Time-delay cosmography of lensed quasars has achieved 2.4% precision on the measurement of the Hubble constant, H0. As part of an ongoing effort to uncover and control systematic uncertainties, we investigate three potential sources: 1- stellar kinematics, 2- line-of-sight effects, and 3- the deflector mass model. To meet this goal in a quantitative way, we reproduced the H0LiCOW/SHARP/STRIDES (hereafter TDCOSMO) procedures on a set of real and simulated data, and we find the following. First, stellar kinematics cannot be a dominant source of error or bias since we find that a systematic change of 10% of measured velocity dispersion leads to only a 0.7% shift on H0 from the seven lenses analyzed by TDCOSMO. Second, we find no bias to arise from incorrect estimation of the line-of-sight effects. Third, we show that elliptical composite (stars + dark matter halo), power-law, and cored power-law mass profiles have the flexibility to yield a broad range in H0 values. However, the TDCOSMO procedures that model the data with both composite and power-law mass profiles are informative. If the models agree, as we observe in real systems owing to the “bulge-halo” conspiracy, H0 is recovered precisely and accurately by both models. If the two models disagree, as in the case of some pathological models illustrated here, the TDCOSMO procedure either discriminates between them through the goodness of fit, or it accounts for the discrepancy in the final error bars provided by the analysis. This conclusion is consistent with a reanalysis of six of the TDCOSMO (real) lenses: the composite model yields H0 = 74.0−1.8+1.7 km s−1 Mpc−1, while the power-law model yields 74.2−1.6+1.6 km s−1 Mpc−1. In conclusion, we find no evidence of bias or errors larger than the current statistical uncertainties reported by TDCOSMO.
Hybrid nanophotonic-nanomagnonic SiC-YiG quantum sensor: II/dark spins quantum sensing with V2 spins and fiber based OP-PELDOR/ODMR
Authors: Tribollet Jérôme
Published: May 2020

First experiments like optically detected (OD) electron paramagnetic resonance (ODMR), photoluminescence detected RABI oscillations, and optical pumping (OP) assisted pulsed EPR measurements of T2 and T1 of V2 spins in bulk SiC, which were previously demonstrated on various home build EPR spectrometers with free space optics, are here all demonstrated for the first time using a commercial X band pulsed EPR spectrometer combined with a single optical fiber and a standard external photoluminescence setup. Quantum sensing of bulk dark spins dipolar coupled to V2 spins in SiC is also demonstrated here for the first time using single fiber based OP assisted pulsed electron electron double resonance spectroscopy (PELDOR). A spin wave resonance study of model permalloy nanostripes is also presented allowing to check the ferromagnetic nanostripes design. These experiments are first key steps towards the fiber-based integration of the recently proposed SiC-YiG quantum sensor device [J. Tribollet, Eur. Phys. J. Appl. Phys.90, 20102 (2020)], to a commercially available and worldwide used pulsed EPR spectrometer, with important applications expected in structural biology, surface chemistry, and quantum computing.
Noether était-elle physicienne ?
Authors: Kosmann-Schwarzbach Yvette
Published: May 2020

Pour célébrer le cent-deuxième anniversaire de la publication de l’article fondamental d’Emmy Noether sur la relation entre symétries et lois de conservation pour les problèmes variationnels, “Invariante Variationsprobleme”, voici une analyse de sa contribution à la résolution d’un problème issu de la théorie de la relativité générale et une esquisse de l’importance de son œuvre dans toutes les théories physiques.
Precise measurement of the temperature of a silicon wafer by an optical-interference contactless thermometer during rapid plasma processing
Authors: Kameda Asaki , Mizukawa Yuri , Hanafusa Hiroaki , Higashi Seiichiro
Published: May 2020

Although silicon substrate temperature is known to be important in many plasma processes, measuring it involves various difficulties due to the complexity of plasmas. In previous work, the authors proposed an optical-interference contactless thermometer (OICT) for interferometric temperature measurements with high temporal resolution and the ability to measure a substrate surface from behind. In the present work, the OICT is improved with accurate values of the thermo-optic coefficient (TOC) of silicon and more realistic simulations. The TOC of silicon is measured precisely from room temperature to 800 K. Transient temperature of a silicon wafer during a thermal plasma jet (TPJ) annealing is measured by the OICT and a thermocouple simultaneously to evaluate the absolute temperature accuracy and response speed of the OICT. The wafer is heated with the TPJ under a wide range of annealing speed from 10 to 105 K/s. The absolute temperature accuracy of the OICT is determined as being around ±1 K in comparison with the thermocouple and the OICT can measure to within around ±2 K even under heating at 105 K/s.
A wide band porous silicon omnidirectional mirror for the near infrared range
Authors: Chavez-Castillo B. A. , Pérez-Huerta J. S. , Madrigal-Melchor J. , Amador-Alvarado S. , Sustaita-Torres I. A. , Agarwal V. , Ariza-Flores D.
Published: May 2020

We report the design, fabrication, and characterization of a porous silicon-based omnidirectional mirror for the near infrared range. The structure consists of 300 porous silicon chirped dielectric layers, optimized to have omnidirectional reflectivity response from 1000 to 2000 nm wavelength range. Measurements of reflectivity spectra are presented for non-polarized light at several incident angles (range 8°–65°) with a reflectivity >95% covering a 1μm band-width. Transfer matrix method calculations were carried out to show the complete angular range for both TM and TE polarizations including a simple model to illustrate the interface scattering effects.
The biological effect of 2.45 GHz microwaves on the viability and permeability of bacterial and yeast cells
Authors: Ahortor Evans K. , Malyshev Dmitry , Williams Catrin F. , Choi Heungjae , Lees Jonathan , Porch Adrian , Baillie Les
Published: May 2020

Microwaves are a form of non-ionizing radiation composed of electric (E) and magnetic (H) fields and are absorbed by biological tissues with a high water content. Our study investigated the effect of the E field, H field, and a combination of both (E + H) field’s exposure of structurally diverse micro-organisms, at a frequency of 2.45 GHz. We observed that the exposure to a microwave E field of an amplitude of 9.3 kV/m had no significant effect on cell viability; however, it did increase membrane permeability of Mycobacterium smegmatis to propidium iodide and to a range of different sized dextran particles in Escherichia coli, Staphylococcus aureus, Candida albicans, and M. smegmatis. The permeability of propidium iodide was observed in microwave treated cells (M. smegmatis) but not in heat-treated cells. Permeability of 3 kDa sized fluorescently labeled dextrans was observed across all cell types; however, this was found not to be the case for larger 70 kDa dextran particles. In terms of efflux, DNA was detected following E field exposure of M. smegmatis. In contrast, H field exposure had no effect on cell viability and did not contribute to increase cell’s membrane to dextran particles. In conclusion, this study shows that microwave generated E fields can temporarily disrupt membrane integrity without detrimentally impacting on cell viability. This approach has the potential to be developed as a high efficiency electropermeabilization method and as a means of releasing host DNA to support diagnostic applications.
Exciton–phonon polaritons in organic microcavities: Testing a simple ansatz for treating a large number of chromophores
Authors: Spano Frank C.
Published: May 2020

Polaritons in an ensemble of permutationally symmetric chromophores confined to an optical microcavity are investigated numerically. The analysis is based on the Holstein–Tavis–Cummings Hamiltonian which accounts for the coupling between an electronic excitation on each chromophore and a single cavity mode, as well as the coupling between the electronic and nuclear degrees of freedom on each chromophore. A straightforward ensemble partitioning scheme is introduced, which, along with an intuitive ansatz, allows one to obtain accurate evaluations of the lowest-energy polaritons using a subset of collective states. The polaritons include all three degrees of freedom—electronic, vibronic, and photonic—and can therefore be described as exciton–phonon polaritons. Applications focus on the limiting regimes where the Rabi frequency is small or large compared to the nuclear relaxation energy subsequent to optical excitation, with relaxation occurring mainly along the vinyl stretching coordinate in conjugated organic chromophores. Comparisons are also made to the more conventional vibronic polariton approach, which does not take into account two-particle excitations and vibration–photon states.
The CRYSTAL code, 1976–2020 and beyond, a long story
Authors: Dovesi Roberto , Pascale Fabien , Civalleri Bartolomeo , Doll Klaus , Harrison Nicholas M. , Bush Ian , D’Arco Philippe , Noël Yves , Rérat Michel , Carbonnière Philippe , Causà Mauro , Salustro Simone , Lacivita Valentina , Kirtman Bernard , Ferrari Anna Maria , Gentile Francesco Silvio , Baima Jacopo , Ferrero Mauro , Demichelis Raffaella , De La Pierre Marco
Published: May 2020

CRYSTAL is a periodic ab initio code that uses a Gaussian-type basis set to express crystalline orbitals (i.e., Bloch functions). The use of atom-centered basis functions allows treating 3D (crystals), 2D (slabs), 1D (polymers), and 0D (molecules) systems on the same grounds. In turn, all-electron calculations are inherently permitted along with pseudopotential strategies. A variety of density functionals are implemented, including global and range-separated hybrids of various natures and, as an extreme case, Hartree–Fock (HF). The cost for HF or hybrids is only about 3–5 times higher than when using the local density approximation or the generalized gradient approximation. Symmetry is fully exploited at all steps of the calculation. Many tools are available to modify the structure as given in input and simplify the construction of complicated objects, such as slabs, nanotubes, molecules, and clusters. Many tensorial properties can be evaluated by using a single input keyword: elastic, piezoelectric, photoelastic, dielectric, first and second hyperpolarizabilities, etc. The calculation of infrared and Raman spectra is available, and the intensities are computed analytically. Automated tools are available for the generation of the relevant configurations of solid solutions and/or disordered systems. Three versions of the code exist: serial, parallel, and massive-parallel. In the second one, the most relevant matrices are duplicated on each core, whereas in the third one, the Fock matrix is distributed for diagonalization. All the relevant vectors are dynamically allocated and deallocated after use, making the code very agile. CRYSTAL can be used efficiently on high performance computing machines up to thousands of cores.
First-principles calculations of phonon transport in two-dimensional penta-X2C family
Authors: Liu Xin , Ouyang Tao , Zhang Dingbo , Huang Haifeng , Wang Hui , Wang Hongyan , Ni Yuxiang
Published: May 2020

Two-dimensional (2D) materials exhibit enhanced thermoelectric (TE) performance compared to bulk materials, which relies heavily on lattice thermal conductivity. Penta-X2C (X = P, As, and Sb) is a newly predicted 2D material family with promising potential applications in photocatalytic water splitting and photovoltaic and optoelectronic devices. To achieve a combination of photovoltaic and TE technologies and further boost the energy utilization rate, in this paper, we systematically investigate the thermal transport of the penta-X2C family. Density functional theory combined with semiclassical Boltzmann transport approach was used to evaluate the thermal transport. Interestingly, the calculated lattice thermal conductivities (kl) of penta-Sb2C are two orders of magnitude smaller than that of penta-P2C, despite that they share similar atomic structure. The calculated kl of penta-P2C, penta-As2C, and penta-Sb2C are 75.27 W m−1 K−1, 19.11 W m−1 K−1, and 0.72 W m−1 K−1, respectively. Penta-Sb2C also exhibits low average acoustic group velocity, large Grüneisen parameters, strong optical–acoustic phonon coupling, and short phonon mean free path. These results qualify penta-Sb2C as a promising candidate for building outstanding TE devices.
Powerful oversized W-band free-electron maser with advanced Bragg resonator based on coupling of propagating and cutoff waves
Authors: Peskov N. Yu. , Ginzburg N. S. , Golubev I. I. , Golubykh S. M. , Kaminsky A. K. , Kozlov A. P. , Malkin A. M. , Sedykh S. N. , Sergeev A. S. , Sidorov A. I. , Zaslavsky V. Yu.
Published: May 2020

We study, both theoretically and experimentally, a free-electron maser (FEM) with a two-mirror resonator that includes the advanced Bragg structure based on coupling of propagating and cutoff waves as an upstream reflector. Similar to gyrotrons, the presence of a cutoff wave in the feedback loop improves significantly the selectivity of the resonator at large values of the oversize factor and facilitates a stable single-mode oscillation regime in short wavelength bands. Proof-of-principle experiments conducted at the induction linac LIU-3000 (Dubna) demonstrate the operability of the FEM with the proposed modification of the Bragg resonator. At the transverse oversize factor of about 5, stable narrow-band generation was achieved with an output power of up to 7 MW and the oscillation frequency of about 80 GHz corresponding to the frequency of the cutoff mode excited in the advanced Bragg reflector. These investigations encourage the application of the advanced Bragg resonators for the development of high-power long-pulse FELs driven by induction linacs and operating in the subterahertz to terahertz frequency range.
Non-monotonic dependence of polymer chain dynamics on active crowder size
Authors: Liu Xinshuang , Jiang Huijun , Hou Zhonghuai
Published: May 2020

Configuration dynamics of flexible polymer chains is of ubiquitous importance in many biological processes. Here, we investigate a polymer chain immersed in a bath of size-changed active particles in two dimensional space using Langevin dynamics simulations. Particular attention is paid to how the radius of gyration Rg of the polymer chain depends on the size σc of active crowders. We find that Rg shows nontrivial non-monotonic dependence on σc: The chain first swells upon increasing σc, reaching a fully expanded state with maximum Rg, and then, Rg decreases until the chain collapses to a compact coil state if the crowder is large enough. Interestingly, the chain may oscillate between a collapse state and a stretched state at moderate crowder size. Analysis shows that it is the competition between two effects of active particles, one stretching the chain from inside due to persistence motion and the other compressing the chain from outside, that leads to the non-monotonic dependence. Besides, the diffusion of the polymer chain also shows nontrivial non-monotonic dependence on σc. Our results demonstrate the important interplay between particle activity and size associated with polymer configurations in active crowding environments.
Negative magnetoresistance effect of PtSe2 film in variable range hopping regime
Authors: Zhang Yujie , Liu Jing , Wang Gongtang , Wang Wenjie , Xu Jianping , Li Lan
Published: May 2020

The structural disorder-induced localized effect is an essential topic of nanophysics in graphene-like layered materials. Here, we investigate the conductivity behavior and angle-magnetresistance (MR) properties of a 1.4 nm-thick ultrathin PtSe2 film. The observed insulating behavior is dominated by nearest-neighbor hopping and variable-range hopping (VRH) of the localized carriers throughout the measured temperature. At low temperatures, a crossover from the Mott-VRH to Efros-Shklovskii (ES)-VRH conducting process is observed in the conductivity data, suggesting the existence of the Coulomb gap around the Fermi level. In this strong localized regime, the observed negative MR under a perpendicular magnetic field is ascribed to the quantum interference among random hopping paths between hopping sites. When the field aligns with current, the appearance of positive MR can be considered as a consequence of the reduction in hopping probability due to field-induced modification of the charger wavefunction at impurity or defect centers. The charge transport research of ultrathin PtSe2 is of great significance for both fundamental physics and nanoscale electronic applications.
Effect of suction on laminar-flow control in subsonic boundary layers with forward-/backward-facing steps
Authors: Zhao Lei , Dong Ming
Published: May 2020

In a subsonic boundary layer, a forward-facing step (FFS) or a backward-facing step (BFS) usually destabilizes the oncoming Tollmien–Schlichting (T-S) waves, leading to a promotion of laminar–turbulent transition. This paper studies a laminar-flow control strategy by introducing wall suction immediately ahead of the FFS or behind the BFS. The impact of the step–suction combination on an oncoming T-S wave is quantified by a transmission coefficient, defined as the ratio of the asymptotic amplitude downstream of the step and suction to that upstream. In order to solve this problem, a local scattering theory based on the large-Reynolds number (large-R) asymptotic framework and a Harmonic linearized Navier–Stokes approach, that calculates the perturbation field at finite Reynolds numbers, are employed. The latter approach is confirmed to be accurate by comparing its results with direct numerical simulations, and the results given by the two approaches agree when the Reynolds number is asymptotically large. According to the large-R triple-deck formulism, a few control parameters, such as the Mach number, Reynolds number, and wall temperature, disappear, which makes a systematical parametric study possible. The destabilizing effect of a step increases with its height, while the stabilizing effect of suction increases with its flux. For a step with a moderate height, suction with a small flux is sufficient to compensate the destabilizing effect of the step.
A general non-adiabatic quantum instanton approximation
Authors: Lawrence Joseph E. , Manolopoulos David E.
Published: May 2020

We present a general quantum instanton approach to calculating reaction rates for systems with two electronic states and arbitrary values of the electronic coupling. This new approach, which we call the non-adiabatic quantum instanton (NAQI) approximation, reduces to Wolynes theory in the golden rule limit and to a recently proposed projected quantum instanton method in the adiabatic limit. As in both of these earlier theories, the NAQI approach is based on making a saddle point approximation to the time integral of a reactive flux autocorrelation function, although with a generalized definition of the projection operator onto the product states. We illustrate the accuracy of the approach by comparison with exact rates for one dimensional scattering problems and discuss its applicability to more complex reactions.
Theoretical investigation of antiferromagnetic skyrmions in a triangular monolayer
Authors: Liu Zhaosen , Santos Dias Manuel dos , Lounis Samir
Published: May 2020

The chiral spin textures of a two-dimensional (2D) triangular system, where both antiferromagnetic (AF) Heisenberg exchange and chiral Dzyaloshinsky–Moriya interactions co-exist, are investigated numerically with an optimized quantum Monte Carlo method based on mean-field theory. We find that: helical, skyrmionic and vortical AF crystals can be formed when an external magnetic field is applied perpendicular to the 2D monolayer; the sizes of these skyrmions and vortices change abruptly at several critical points of the external magnetic field; each of these AF crystals can be decomposed into three periodical ferromagnetic sublattices. The quantum ingredient implemented into the theoretical framework helps to track the existence of AF skyrmion lattices down to low temperatures.
Boundedness for reaction–diffusion systems with Lyapunov functions and intermediate sum conditions
Authors: Morgan Jeff , Tang Bao Quoc
Published: May 2020

We study the uniform boundedness of solutions to reaction–diffusion systems possessing a Lyapunov-like function and satisfying an intermediate sum condition. This significantly generalizes the mass dissipation condition in the literature and thus allows the nonlinearities to have arbitrary polynomial growth. We show that two dimensional reaction–diffusion systems, with quadratic intermediate sum conditions, have global solutions which are bounded uniformly in time. In higher dimensions, bounded solutions are obtained under the condition that the diffusion coefficients are quasi-uniform, i.e. they are close to each other. Applications include boundedness of solutions to chemical reaction networks with diffusion.
Bayesian inference of particle source and sink in a closed-divertor using Balmer line spectroscopy
Authors: Nishizawa T , Cavedon M , Reimold F , Dux R , Brida D , Wu H
Published: May 2020

A new analysis technique for Balmer line spectroscopy that enables recombination rate (particle sink) and ionization rate (particle source) inference in a closed divertor configuration is reported. Bayesian inference is employed to systematically utilize all available information from multiple Balmer lines and constrain parameter ranges by using prior knowledge about plasmas. While a closed-divertor facilitates detachment, neutral plugging typically leads to large spatial variations in plasma parameters. A forward model is developed to take into account non-uniformity in the plasma parameters and applied to test data generated by divertor plasma simulations. It is shown that the forward model robustly provides particle source and sink inference over a wide parameter range. In addition, the precision improves as more Balmer lines are resolved simultaneously. The new analysis technique is also applied to an L-mode ASDEX Upgrade plasma in the high-recycling regime. The inferred quantities and their profiles are consistent with the expectations of a high-recycling divertor plasma. The further insight into the detachment physics will be provided by using this new analysis technique.
The standard model, the Pati–Salam model, and ‘Jordan geometry’
Authors: Boyle Latham , Farnsworth Shane
Published: May 2020

We argue that the ordinary commutative and associative algebra of spacetime coordinates (familiar from general relativity) should perhaps be replaced, not by a noncommutative algebra (as in noncommutative geometry), but rather by a Jordan algebra (leading to a framework which we term ‘Jordan geometry’). We present the Jordan algebra (and representation) that most nearly describes the standard model of particle physics, and we explain that it actually describes a certain (phenomenologically viable) extension of the standard model: by three right-handed (sterile) neutrinos, a complex scalar field φ, and a U(1)
B−L
gauge boson which is Higgsed by φ. We then note a natural extension of this construction, which describes the SU(4) × SU(2)L × SU(2)R Pati–Salam model. Finally, we discuss a simple and natural Jordan generalization of the exterior algebra of differential forms.
A novel (2+1)-dimensional integrable KdV equation with peculiar solution structures*
Authors: Lou Sen-Yue
Published: May 2020

The celebrated (1+1)-dimensional Korteweg de–Vries (KdV) equation and its (2+1)-dimensional extension, the Kadomtsev–Petviashvili (KP) equation, are two of the most important models in physical science. The KP hierarchy is explicitly written out by means of the linearized operator of the KP equation. A novel (2+1)-dimensional KdV extension, the cKP3–4 equation, is obtained by combining the third member (KP3, the usual KP equation) and the fourth member (KP4) of the KP hierarchy. The integrability of the cKP3–4 equation is guaranteed by the existence of the Lax pair and dual Lax pair. The cKP3–4 system can be bilinearized by using Hirota’s bilinear operators after introducing an additional auxiliary variable. Exact solutions of the cKP3–4 equation possess some peculiar and interesting properties which are not valid for the KP3 and KP4 equations. For instance, the soliton molecules and the missing D–Alembert type solutions (the arbitrary travelling waves moving in one direction with a fixed model dependent velocity) including periodic kink molecules, periodic kink-antikink molecules, few-cycle solitons, and envelope solitons exist for the cKP3–4 equation but not for the separated KP3 equation and the KP4 equation.
Structural, electronic, and magnetic properties of quaternary Heusler CrZrCoZ compounds: A first-principles study*
Authors: Wei Xiao-Ping , Cao Tie-Yi , Sun Xiao-Wei , Gao Qiang , Gao Peifeng , Gao Zhi-Lei , Tao Xiao-Ma
Published: May 2020

Using the first-principles calculations, we study the structural, electronic, and magnetic properties along with exchange interactions and Curie temperatures for CrZrCoZ (Z = Al, Ga, In, Tl, Si, Pb) quaternary Heusler alloys. The results show that the CrZrCoZ alloys are half-metallic ferrimagnets, and their total spin magnetic moments, which are mainly carried by the Cr atom, obey the Slater–Pauling rule. Analysis of local density of states confirms that the exchange splitting between eg and t2g states leads to the formation of half-metallic gap. According to the calculated Heisenberg exchange coupling parameters, it is found that the Cr(A)–Cr(A) and Cr(A)–Zr(B) exchanges dominate the appearance of ferrimagnetic states in CrZrCoZ (Z = Al, Ga, In, Tl, Pb) alloys, and it is the Cr(A)–Zr(B) and Zr(B)–Zr(B) exchanges for CrZrCoSi alloy. Finally, we estimate the Curie temperatures of CrZrCoZ by using mean-field approximation, it is found that the CrZrCoZ (Z = Al, Ga, In, Tl, Pb) alloys have noticeably higher Curie temperatures than room temperature. So, we expect that the CrZrCoZ alloys are promising candidates in spintronic applications in future.
Thermal effects and evolution of the defect concentration based on shear modulus relaxation data in a Zr-based metallic glass*
Authors: Hao Qi , Qiao Ji-Chao , Goncharova E V , Afonin G V , Liu Min-Na , Cheng Yi-Ting , Khonik V A
Published: May 2020

A relationship between thermal effects and relaxation of the high-frequency shear modulus upon heat treatment of bulk Zr48(Cu5/6Ag1/6)44Al8 metallic glass is found. This relationship is attributed to the relaxation of a interstitial-type defect system frozen-in from the melt upon glass production. Calorimetric data show that thermal effects occurring on heating include heat release below the glass transition temperature, heat absorption above it and heat release caused by crystallization. The equation derived within the Interstitialcy theory can be used to calculate the shear modulus relaxation using the calorimetric data. The obtained results are used to trace the defect concentration as functions of temperature and thermal prehistory.
Influential nodes identification in complex networks based on global and local information
Authors: Yang Yuan-Zhi , Hu Min , Huang Tai-Yu
Published: May 2020

Identifying influential nodes in complex networks is essential for network robust and stability, such as viral marketing and information control. Various methods have been proposed to define the influence of nodes. In this paper, we comprehensively consider the global position and local structure to identify influential nodes. The number of iterations in the process of k-shell decomposition is taken into consideration, and the improved k-shell decomposition is then put forward. The improved k-shell decomposition and degree of target node are taken as the benchmark centrality, in addition, as is well known, the effect between node pairs is inversely proportional to the shortest path length between two nodes, and then we also consider the effect of neighbors on target node. To evaluate the performance of the proposed method, susceptible-infected (SI) model is adopted to simulate the spreading process in four real networks, and the experimental results show that the proposed method has obvious advantages over classical centrality measures in identifying influential nodes.
Mesoscale eddies and their dispersive environmental impacts in the Persian Gulf
Authors: Raeisi Amin , Bidokhti Abbasali , Jafar Nazemosadat Seyed Mohammad , Lari Kamran
Published: May 2020

As the mesoscale eddies in oceans and semi-enclosed seas are significant in horizontal dispersion of pollutants, we investigate the seasonal variations of these eddies in the Persian Gulf (PG) that are usually generated due to seasonal winds and baroclinic instability. The sea surface height (SSH) data from 2010 to 2014 of AVISO are used to identify and track eddies, using the SSH-based method. Then seasonal horizontal dispersion coefficients are estimated for the PG, using the properties of eddies. The results show an annual mean of 78 eddies with a minimum lifetime of one week. Most of the eddies are predominantly cyclonic (59.1%) and have longer lifetimes and higher diffusion coefficients than the anti-cyclonic eddies. The eddy activity is higher in warm seasons, compared to that of cold seasons. As locations with high eddy diffusion coefficients are high-risk areas by using maps of horizontal eddy diffusion coefficients, perilous times and locations of the release of pollutants are specified to be within the longitude from 51.38°E to 55.28°E. The mentioned areas are located from the Strait of Hormuz towards the northeast of the PG, closer to Iranian coast. Moreover, July can be considered as the most dangerous time of pollution release.
The search algorithm for the optimal control of multilevel hierarchical system based on the use of fuzzy logic and the principle of optimality of Bellman
Authors: Chertov V A , Orlova D E
Published: May 2020

Developed search algorithm for the optimal control of multilevel hierarchical systems. The basis of the algorithm are the theory of fuzzy sets together with the Bellman optimality principle. The computational experiment confirms the convergence of the algorithm.
A nonlinear model of the non-isothermal slip flow between two parallel plates
Authors: Domnich A A , Baranovskii E S , Artemov M A
Published: May 2020

We study a mathematical model describing the steady-state non-isothermal flow of a viscous fluid between two parallel plates under the Navier slip boundary condition. The flow is driven by an applied pressure gradient. The dependence of the viscosity, thermal conductivity and slip coefficients on the temperature is taking into account. The model under consideration is a boundary value problem for a system of nonlinear coupled ordinary differential equations. We give the weak formulation of this problem and establish sufficient conditions for the existence and uniqueness of a weak solution. To construct weak solutions, we propose an algorithm based on the Galerkin procedure, methods of the topological degree theory, and compactness arguments. Moreover, explicit expressions for the velocity and the temperature on the plates are obtained.
On some pseudo-differential equations and transmutation operators
Authors: Vasilyev Vladimir
Published: May 2020

We describe some operators for solving model elliptic pseudo-differential equations in special canonical domains. It helps us to write a general solution of corresponding pseudo-differential equation in an explicit form. Moreover, knowing a general solution we can choose additional (possibly boundary) conditions to determine uniquely the solution. All considerations we give in Sobolev–Slobodetskii spaces.
Fuzzy request handler for Mongo QL derived from SQL
Authors: Astachova I F , Samoilov N K , Kiseleva E I
Published: May 2020

Relational DBMS are often used to store fuzzy values, but problems arise with putting such data in a tabular form. Moreover, there appears a problem of storing both the crisp and fuzzy data related to one subject domain in one column of a relational table. This article considers the mechanism of storing crisp and fuzzy values and linguistic variables in the document-oriented Mongo DBMS. The data are stored in the collection as GeoJSON geometry; different geometries are used for different data options. The possibility of storing crisp scalar values, crisp value sets, crisp value intervals and fuzzy values in the collection documents is described. For data processing by means of SQL queries, the context-free grammar of the SQL subset is described, according to which lexer and parser are generated. In order to form the structure of an abstract syntactic tree, a corresponding object model has been implemented. A translator application has been developed, which allows converting SQL queries related to the crisp and fuzzy data into Mongo QL queries. The algorithm of fuzzy queries translation process is suggested; the geometrical interpretation of data comparison operations is described. The examples show the options of fuzzy comparison operations for different value options.
On development of models and algorithms for automated metallographic measurement of visible metal slice grain sizes
Authors: Kovun V A , Kashirina I L
Published: May 2020

The article proposes an approach to metallographic research based on solving the problem of semantic segmentation using a trained neural network classifier. To solve the problem of isolating grains in micrographs of longitudinal and transverse slices of metal, the neural network model U-Net was adapted. In order to obtain closed image contours, a post-processing algorithm was developed using the OpenCV open source computer vision library. The article describes the training of a neural network and the conversion of its results, as well as the comparative analysis of the histograms between the reference grain area distribution and the distribution obtained using the proposed algorithm.
Signal approximations by shifted Gaussians: a direct approach by finite linear systems
Authors: Sitnik Sergei M , Timashov Alexandr S , Ushakov Sergei N
Published: May 2020

In this paper we consider interpolation problem connected with series by integer shifts of Gaussians. Known approaches for these problems met numerical difficulties. Due to it another method is considered based on finite–rank approximations by linear systems. The main result for this approach is to establish correctness of the finite–rank linear system under consideration. And the main result of the paper is to prove correctness of the finite–rank linear system approximation. For that an explicit formula for the main determinant of the linear system is derived to demonstrate that it is non–zero.
Optimizing the selection of combination of alternative functions of ergatic system multifunctional elements
Authors: Zverev G I , Menshikh V V
Published: May 2020

Ergatic systems have found their application in those areas where operator’s participation is an integral part of the effective functioning of these systems, that is, it has the ability to quickly solve problems and contingencies that arise during work process. Critical application systems are one of the varieties of ergatic systems. For their successful functioning, it is necessary to choose the optimal set of alternative functions of multifunctional elements. The relevance of this problem lies in the wide distribution of this type systems, as well as in their special importance. So this article provides a description of the structural and parametric models and functional capabilities of ergatic systems. As a model, it is proposed to use weighted hypergraphs. The statement of the problem of optimizing the choice of a combination of alternative functions of multifunctional elements of such systems is given. The description of the developed numerical method based on the use of the scheme of branches and boundaries is also given. The final part of the article presents a numerical example, divided into initial, intermediate and final stages of optimization, for demonstration of the described numerical method operation.