bluuebunny/crossref_metadata_2025 huggingface dataset:
One-step synthesis of seamless graphene-carbon nanotube heterojunctions by chemical vapor deposition
Authors: Cai Le , Xue Xudong , Liu Mengya , Li Hao , Zhou Xiahong , Yu Gui
Published: April 2021

The composite of graphene and carbon nanotubes (CNTs) can increase the electrical conductivity and the electrochemical active sites in favor of the application in energy storage and conversion. However, the fabrication of graphene/CNT hybrid material requires multiple steps to introduce two kinds of catalysts for separate growth of graphene and CNTs. Here, we report a one-step process to in situ grow a seamless graphene/CNT heterojunction using a single catalyst of copper foil. Through precise tuning of the evaporation temperature of ethanol, creation of a method for seamlessly bonding CNTs on the graphene surface without assistance of metal particles has been realized. A study of the growth mechanism shows that the self-limited surface reaction of copper foil leads to many defects in multilayer graphene films, which provides the nucleation sites for the seamless growth of CNTs. The as-grown graphene/CNT heterojunctions have a higher electrical conductivity than the single graphene film, and its optical transmittance is almost equal to that of graphene film.
Translational and reorientational dynamics in deep eutectic solvents
Authors: Reuter D. , Münzner P. , Gainaru C. , Lunkenheimer P. , Loidl A. , Böhmer R.
Published: April 2021

We performed rheological measurements of the typical deep eutectic solvents (DESs) glyceline, ethaline, and reline in a very broad temperature and dynamic range, extending from the low-viscosity to the high-viscosity supercooled-liquid regime. We find that the mechanical compliance spectra can be well described by the random free-energy barrier hopping model, while the dielectric spectra on the same materials involve significant contributions arising from reorientational dynamics. The temperature-dependent viscosity and structural relaxation time, revealing non-Arrhenius behavior typical for glassy freezing, are compared to the ionic dc conductivity and relaxation times determined by broadband dielectric spectroscopy. For glyceline and ethaline, we find essentially identical temperature dependences for all dynamic quantities. These findings point to a close coupling of the ionic and molecular translational and reorientational motions in these systems. However, for reline, the ionic charge transport appears decoupled from the structural and reorientational dynamics, following a fractional Walden rule. In particular, at low temperatures, the ionic conductivity in this DES is enhanced by about one decade compared to expectations based on the temperature dependence of the viscosity. The results for all three DESs can be understood without invoking a revolving-door mechanism previously considered as a possible charge-transport mechanism in DESs.
Smaller molecules crowd better: Crowder size dependence revealed by single-molecule FRET studies and depletion force modeling analysis
Authors: Sung Hsuan-Lei , Sengupta Abhigyan , Nesbitt David
Published: April 2021

The cell is an extremely crowded environment, which is known to have a profound impact on the thermodynamics, functionality, and conformational stability of biomolecules. Speculations from recent theoretical molecular dynamics studies suggest an intriguing size dependence to such purely entropic crowding effects, whereby small molecular weight crowders under constant enthalpy conditions are more effective than larger crowders on a per volume basis. If experimentally confirmed, this would be profoundly significant, as the cellular cytoplasm is also quite concentrated in smaller molecular weight solutes such as inorganic ions, amino acids, and various metabolites. The challenge is to perform such studies isolating entropic effects under isoenthalpic conditions. In this work, we first present results from single-molecule FRET spectroscopy (smFRET) on the molecular size-dependent crowding stabilization of a simple RNA tertiary motif (the GAAA tetraloop–tetraloop receptor), indeed providing evidence in support of the surprising notion in the crowding literature that “smaller is better.” Specifically, systematic smFRET studies as a function of crowder solute size reveal that smaller molecules both significantly increase the RNA tertiary folding rate and, yet, simultaneously decrease the unfolding rate, predicting strongly size-dependent stabilization of RNA tertiary structures under crowded cellular conditions. The size dependence of these effects has been explored via systematic variation of crowder size over a broad range of molecular weights (90–3000 amu). Furthermore, corresponding temperature dependent studies indicate the systematic changes in the folding equilibrium to be predominantly entropic in origin, i.e., consistent with a fundamental picture of entropic molecular crowding without additional enthalpic interactions. Most importantly, all trends in the single-molecule crowding data can be quantitatively recapitulated by a simple analytic depletion force model, whereby excluded volume interactions represent the major thermodynamic driving force toward folding. Our study, thus, not only provides experimental evidence and theoretical support for small molecule crowding but also predicts further enhancement of crowding effects for even smaller molecules on a per volume basis.
Dynamic tuning of near-field radiative transport between an overlapping pair of movable comb-like metamaterials
Authors: Liu Yang , Chen Fangqi , Caratenuto Andrew , Zheng Yi
Published: April 2021

We present a theoretical study of nanoscale radiative thermal transport between an overlapping pair of movable comb-like SiO2 gratings by an improved and more accurate near-field radiative heat transfer (NFRHT) method. This method does not rely on the effective medium theory (EMT) that does not take the geometric shape factors of nanostructures into account. Contrary to the EMT treating the grating structure as a homogeneous film, our improved NFRHT method can accurately predict the change of heat flux between the overlapping nanogratings for different scenarios considering surface pattern effects. The longitudinal and lateral movements of the comb-like overlapping nanogratings have been investigated to evaluate the dynamic control of NFRHT, which can be significantly modulated, resulting in heat flux ratios up to 23.5 and 5.5, respectively, for small-scale displacements. Furthermore, the NFRHT between overlapping non-contact metamaterials can exceed the intrinsic heat conduction limit for a contact mode by an order of magnitude while properly adjusting the period and relative position of the overlapping nanogratings. By taking advantage of movable metamaterials, the dynamic tuning of NFRHT and light manipulation can provide great benefit to the fields of energy harvesting and conversion, infrared sensing and detection, and thermal management technology.
Isomorphism between the electro-elastic modeling of the spin transition and Ising-like model with competing interactions: Elastic generation of self-organized spin states
Authors: Ndiaye Mamadou , Singh Yogendra , Fourati Houcem , Sy Mouhamadou , Lo Bassirou , Boukheddaden Kamel
Published: April 2021

Elastic modeling of spin-crossover materials has boomed remarkably these last years. Among these models, the electro-elastic model combining spin and lattice degrees of freedom showed good abilities of fair description of the thermodynamics and spin-crossover solids. In the present work, we explore a new treatment of this model based on a homogeneous description of the lattice spacing with well separate relaxation timescales for the lattice and spin state degrees of freedom. This description is analogous to the Born–Oppenheimer approximation and allows analytic treatment of the elastic part of the model, thus simplifying considerably the model resolution. As a result, we have been able to demonstrate the equivalence between the genuine electro-elastic model and an Ising-like Hamiltonian with competing long-range ferro-like and short-range (nearest neighbors and next-nearest neighbors along diagonals) antiferro-like interactions, whose relationship with the high-spin to low-spin misfit elastic energy has been established. This model generates intrinsic elastic frustration in the lattice, which leads to a rich variety of hysteretic first-order transitions made of one- two-, three-, or four-step behaviors. Complex self-organizations of the spin states are evidenced in the plateau regions in the form of checkerboard-like, stripes-like patterns, constituted of alternate high-spin and low-spin ferro-like stripes or alternate ferro high-spin (or low-spin) and antiferro-like chains, as well labyrinth structures.
Transported and presumed probability density function modeling of the Sandia flames with flamelet generated manifold chemistry
Authors: Jaganath Vasu , Stoellinger Michael
Published: April 2021

The first modeling results for Sandia flames D, E, and F using the flamelet generated manifold reduced chemistry model with a transported probability density function (TPDF) closure model are presented. The micro-mixing is modeled with the simple “interaction by exchange with the mean” model and mean molecular diffusion is accounted for through a mean drift term. By accounting for mean molecular diffusion, stable burning flames D, E, and F could be predicted using the standard value for the mixing rate constant Cϕ=2. The TPDF results are used in an a priori analysis of the main simplifying assumptions typically used in presumed PDF (PPDF) models. A new PPDF model that accounts for the correlation between mixture fraction and progress variable in the joint PDF through a Gaussian copula is presented and included in the analysis. The analysis reaffirmed earlier findings: the marginal PDF of the progress variable is not well approximated by a β-PDF and the mixture fraction and progress variable are not statistically independent. The Gaussian copula PPDF model did show a qualitative improvement over the models that invoke the statistical independence assumption. Quantitative analysis showed that the mean progress variable source term could not be predicted accurately by any of the PPDF models. The PPDF models were then applied in actual simulations of flames D and E. The erroneous predictions of the mean progress variable source term cause relative errors in the PPDF simulation results for the conditional mean temperature exceeding 20%.
Optimization of the in situ cleavage process for III–V/Si(001) investigations by cross-sectional scanning tunneling microscopy
Authors: Farin P. , Gernert U. , Lenz A.
Published: April 2021

Interfaces between epitaxial layers forming electronic devices have long been recognized to have an important impact on their functionality. Cross-sectional measurements have, therefore, attained an important role in the characterization of these layers to acquire a deep understanding of their structural and electronic properties. For cross-sectional measurements relying on in situ cleavage, achieving control over the cleavage process is crucial. Particularly, cross-sectional scanning tunneling microscopy relies on atomically flat cleavage surfaces for the investigation of a multitude of material systems with the greatest possible detail. For the investigation of III–V semiconductors grown on Si(001), samples are normally cleaved by applying a force in the [001¯] direction in order to generate and analyze {110} cleavage surfaces. These surfaces are best suited for cross-sectional investigations as they are perpendicular to the growth surface as well as to each other. In this work, we show that for cleaving Si(001) in such a way, sawing rather than notching samples to create a predetermined breaking point results in significantly improved cleavage surfaces. For this purpose, a statistical investigation of the cleavage of Si(001) wafers is presented. We further demonstrate the proficiency of sawing as the sample-preparation method for cross-sectional scanning tunneling microscopy by investigating the interfacial region of high-quality GaP/Si(001) samples as well as a state-of-the-art GaSb/Si(001) sample.
Non-monotonic boundary resistivity for electron transport in metal nanowires
Authors: Tao Yi , Zhao Yang , Akter Manira , Xu Terry T. , Chen Yunfei , Li Deyu
Published: April 2021

Boundary scattering is the most widely encountered size effect in nanoscale transport phenomena, and the scattering rate is usually regarded as a constant that is proportional to the ratio of carrier velocity to the characteristic size. Here, through combined experimental measurements and numerical modeling, we show non-monotonic variations of the boundary scattering rate for free electrons in metal nanowires as temperature escalates. This observation is attributed to the change in the electron-phonon (e-ph) scattering angle as temperature reduces, which alters the surface scattering rate. In particular, at low temperatures, electrons traveling along the wire axis have to be first relaxed by e-ph scattering before they collide with the nanowire surface. Theoretical analysis indicates a transition temperature of 0.29 times Debye temperature. A theoretical model considering the effects of the scattering angle is proposed that can fit the measured experimental data for both copper and silver nanowires over a wide temperature range.
A three-dimensional phase-field lattice Boltzmann method for incompressible two-components flows
Authors: De Rosis Alessandro , Enan Enatri
Published: April 2021

In this paper, a lattice Boltzmann model for the coupled Allen–Cahn–Navier–Stokes equations in three dimensions is presented. Two equations are solved: one for the fluid velocity and one for the order parameter. Both are written within the general multiple-relaxation-time framework, where all the equilibrium and forcing terms are described by using the full set of Hermite polynomials. The resultant practical implementation is compact. The gradient of the order parameter can be computed by the non-local finite differences or the local central moments. The latter suffers from grid-scale oscillations. The very good accuracy properties are demonstrated against nine well-consolidated benchmark tests. Specifically, two groups of tests are tackled. In the former, the velocity field is superimposed. Hence, only the equation for the evolution of the order parameter is solved. These numerical experiments demonstrate the ability of the proposed scheme to capture the correct evolution of the interface. In the latter, two immiscible fluids are considered and the two equations are solved. Simulations of the vertical penetration of a wedge-shaped body, two- and three-dimensional Rayleigh–Taylor instability prove that two-fluids systems can be successfully simulated by our approach.
Zn acceptors in β-Ga2O3 crystals
Authors: Gustafson T. D. , Jesenovec J. , Lenyk C. A. , Giles N. C. , McCloy J. S. , McCluskey M. D. , Halliburton L. E.
Published: April 2021

Electron paramagnetic resonance (EPR) is used to identify and characterize neutral zinc acceptors in Zn-doped β-Ga2O3 crystals. Two EPR spectra are observed at low temperatures, one from Zn ions at tetrahedral Ga(1) sites (the ZnGa10 acceptor) and one from Zn ions at octahedral Ga(2) sites (the ZnGa20 acceptor). These Zn acceptors are small polarons, with the unpaired spin localized in each case on a threefold coordinated oxygen O(I) ion adjacent to the Zn ion. Resolved hyperfine interactions with neighboring 69Ga and 71Ga nuclei allow the EPR spectra from the two acceptors to be easily distinguished: ZnGa10 acceptors interact equally with two Ga(2) ions and ZnGa20 acceptors interact unequally with a Ga(1) ion and a Ga(2) ion. The as-grown crystals are compensated, with the Zn ions initially present as singly ionized acceptors (ZnGa1− and ZnGa2−). Exposing a crystal to 325 nm laser light, while being held at 140 K, primarily produces neutral ZnGa20 acceptors when photoinduced holes are trapped at ZnGa2− acceptors. This suggests that there may be significantly more Zn ions at Ga(2) sites than at Ga(1) sites. Warming the crystal briefly to room temperature, after removing the light, destroys the EPR spectrum from the shallower ZnGa20 acceptors and produces the EPR spectrum from the more stable ZnGa10 acceptors. The ZnGa20 acceptors decay in the 240–260 K region with a thermal activation energy near 0.65 eV, similar to MgGa20 acceptors, whereas the slightly deeper ZnGa10 acceptors decay close to room temperature with an approximate thermal activation energy of 0.78 eV.
Carrier and phonon transport control by domain engineering for high-performance transparent thin film thermoelectric generator
Authors: Ishibe Takafumi , Tomeda Atsuki , Komatsubara Yuki , Kitaura Reona , Uenuma Mutsunori , Uraoka Yukiharu , Yamashita Yuichiro , Nakamura Yoshiaki
Published: April 2021

We develop transparent epitaxial SnO2 films with low thermal conductivity and high carrier mobility by domain engineering using the substrates with low symmetry: intentional control of the domain size and the defect density between crystal domains. The epitaxial SnO2 films on r-Al2O3 (a low symmetry substrate) exhibit a twice higher mobility than the epitaxial SnO2 films on c-Al2O3 (a high symmetry substrate), resulting in twice larger thermoelectric power factor in the SnO2 films on r-Al2O3. This mobility difference is likely attributed to the defect density between crystal domains. Furthermore, both samples exhibit almost the same thermal conductivities (∼5.1 ± 0.4 W m−1 K−1 for SnO2/r-Al2O3 sample and ∼5.5 ± 1.0 W m−1 K−1 for SnO2/c-Al2O3 sample), because their domain sizes are almost the same. The uni-leg type film thermoelectric power generator composed of the domain-engineered SnO2 film generates the maximum power density of ∼54 μW m−2 at the temperature difference of 20 K. This demonstrates that a transparent film thermoelectric power generator based on the domain engineering is promising to run some internet of things sensors in our human society.
The spin selectivity effect in chiral materials
Authors: Waldeck D. H. , Naaman R. , Paltiel Y.
Published: April 2021

We overview experiments performed on the chiral induced spin selectivity (CISS) effect using various materials and experimental configurations. Through this survey of different material systems that manifest the CISS effect, we identify several attributes that are common to all the systems. Among these are the ability to observe spin selectivity for two point contact configurations, when one of the electrodes is magnetic, and the correlation between the optical activity of the chiral systems and a material’s spin filtering properties. In addition, recent experiments show that spin selectivity does not require pure coherent charge transport and the electron spin polarization persists over hundreds of nanometers in an ordered medium. Finally, we point to several issues that still have to be explored regarding the CISS mechanism. Among them is the role of phonons and electron–electron interactions.
Regulation of longevity by depolarization-induced activation of PLC-β–IP
3
R signaling in neurons
Authors: Wong Ching-On , Karagas Nicholas E. , Jung Jewon , Wang Qiaochu , Rousseau Morgan A. , Chao Yufang , Insolera Ryan , Soppina Pushpanjali , Collins Catherine A. , Zhou Yong , Hancock John F. , Zhu Michael X. , Venkatachalam Kartik
Published: April 2021

Significance

We demonstrate that depolarization of
Drosophila
glutamatergic neurons augmented inositol trisphosphate receptor (IP
3
R)-dependent release of endoplasmic reticulum (ER) Ca
2+
, which in turn potentiated mitochondrial Ca
2+
uptake and ATP production. Perturbations that induced chronic depolarization, including the expression of neurodegeneration-related transgenes, led to the diversion of released ER Ca
2+
into lysosomes and an attendant shortening of animal lifespan. Thus, genetic disruption of PLC-β–IP
3
R signaling or lysosomal Ca
2+
uptake restored longevity in animals with chronically depolarized glutamatergic neurons. Our findings point to aberrant Ca
2+
signaling between the ER and lysosomes as a mechanism by which hyperexcitable glutamatergic neurons shorten animal lifespan.
Coccus celatus (coffee green scale).
Authors: Bigger Mike
Published: April 2021

The female lays eggs which hatch within a matter of hours. There are three nymphal stages which are mobile. The adult female is sedentary and covered by an ovoid, green scale, about 3.5 mm long and only slightly convex. All stages feed principally on the underside of the leaf generally close to a vein but may also be found on green shoots, fruits and other parts of the plant. In Uganda it was reported (as C. consimilis) to be found on the collar of the plant at or just below ground level (De Lotto, 1960). Associations: Ants such as Tetramorium aculeatum (Uganda; De Lotto, 1960) and Solenopsis geminata (Papua New Guinea; Buckley and Gullan, 1991) which feed on the honeydew, build earth covers over the colonies. Oecophylla longinoda (Ivory Coast; Couturier et al., 1985), Crematogaster sp. (Papua New Guinea; Murphy, 1985), Paratrechina sp. (Papua New Guinea; Murphy, 1985), Pheidole sp. (Papua New Guinea; Murphy, 1985) and Technomyrmex albipes (Papua New Guinea; Murphy, 1985) also tend colonies. The presence of ants undoubtedly hinders attacks by natural enemies both by shielding the colonies and by removing honeydew. Murphy et al. (2011) attest that in Papua New Guinea 14 species of ant attend C. celatus/C. viridis populations of which only two are native (Rhoptromyrmex sp1 and Rhoptromyrmex melleus). By contrast six exotics and six species (origin unknown) attend the scales. The three spatially most common and abundant exotic species were Anoplolepis gracilipes (yellow crazy ant), Pheidole megacephala (African big-headed ant) and T. albipes (white footed ant).
Article Commentary: A Health Crisis within a Health Crisis: Opioid Access in the COVID-19 Pandemic
Authors: Narayan Aditya , Balkrishnan Rajesh
Published: April 2021

The novel coronavirus has thrown large sections of our healthcare system into disarray, with providers overburdened by record breaking number of hospitalizations and deaths. The U.S., in particular, has remained the nation with one of the fastest growing case counts in the world. As a consequence, many other critical healthcare needs have not received the necessary resources or consideration. This commentary draws attention to substance use and opioid access during the ongoing crisis, given the potential for breakdowns in treatment access for addiction, the growing concern of mental health comorbidities, and the lack of access for those who require opioids for adequate pain management. Further, the commentary will offer policy and practice recommendations that may be implemented to provide more equitable distribution of care.
Impact of compressive and tensile epitaxial strain on transport and nonlinear optical properties of magnetoelectric BaTiO3-(LaCa)MnO3 tunnel junction
Authors: Ivanov M S , Buryakov A M , Vilarinho P M , Mishina E D
Published: April 2021

This work is devoted to disclosing the effect of epitaxial strain on crystallographic, transport, and nonlinear optical properties of a bilayer structure consisting of one ferroelectric (FE) (BaTiO3 with a thickness of 4 nm) and one ferromagnetic (La0.7Ca0.3MnO3 with the thickness of 12 nm) layers. Both tensile (of about ∼6% caused by the MgO substrate) and compressive (of about ∼1% caused by the SrTiO3 substrate) strains reduce the bulk metal-to-insulator phase transition temperature of the La0.7Ca0.3MnO3 layer from 240 K towards 195 K and 160 K, respectively. The appearance of the effect of colossal electroresistance, linear and nonlinear current–voltage behaviours and contribution of FE polarization switching in the BaTiO3 layer to the conductivity are associated with the influence of epitaxial strain. The predominance of the compressive over the tensile strain leads to the hysteresis behaviour of electroresistance, maximum conductivity caused by the resonant-tunnelling mechanism, and strong nonlinear optical dependence on the applied electric field.
An effective determination of the minimum circumscribed circle and maximum inscribed circle using the subzone division approach
Authors: Huang Jingzhi , Yang Runze , Ge Haiqiao , Tan Jiubin
Published: April 2021

Aiming to develop a more effective circularity evaluation method that satisfies the definition of a particular reference circle criterion, this paper proposes a strategy to determine the minimum circumscribed circle (MCC) and maximum inscribed circle (MIC) using the subzone division approach. The whole circumference zone space that encloses all the sampling data points is divided into different subzones to determine the target candidate feature points, which are used for constructing the MCC or MIC. The first feature point of the MCC/MIC is evaluated according to the farthest/nearest distance from the center of the least squares circle (LSC) within the whole circumference subzone. Subzone with a 120° central angle is designated in the direction of the first feature point that is mapped about the center of the LSC. The second candidate feature point is constrained and determined within this subzone. The third subzone, which contains the third feature point, is formed in the direction of the first and second feature points that are mapped about the center of the LSC. The mathematical model of the MCC or MIC is then constructed using these three feature points. Experimental examples (using five different datasets) and a comparison with previous studies demonstrate that the proposed method yields the exact solution for the MIC and MCC in only 1–2 iterations.
Structural and physical-chemical characterization of redox active CeO2 nanoparticles synthesized by precipitation in water-alcohol solutions
Authors: Shlapa Yuliia , Timashkov Illia , Veltruska Katerina , Siposova Katarina , Garcarova Ivana , Musatov Andrey , Solopan Sergii , Kubovcikova Martina , Belous Anatolii
Published: April 2021

A set of cerium dioxide nanoparticles (CeO2 NPs) was synthesized by precipitation in water-alcohol solutions under conditions when the physical-chemical parameters of synthesized NPs were controlled by changing the ratio of the reaction components. The size of CeO2 NPs is controlled largely by the dielectric constant of the reaction solution. An increase of the percentage of Ce3+ ions at the surface was observed with a concomitant reduction of the NP sizes. All synthesized CeO2 NPs possess relatively high positive values of zeta-potential (ζ > 40 mV) suggesting good stability in aqueous suspensions. Analysis of the valence- and size-dependent rate of hydrogen peroxide decomposition revealed that catalase/peroxidase-like activity of CeO2 NPs is higher at a low percentage of Ce3+ at the NP surface. In contrast, smaller CeO2 NPs with a higher percentage of Ce3+ at the NP surface display a higher oxidase-like activity.
Microdosimetry in low energy proton beam at therapeutic-equivalent fluence rate with silicon 3D-cylindrical microdetectors
Authors: Guardiola C , Bachiller-Perea D , Prieto-Pena J , Jiménez-Ramos M C , García López J , Esnault C , Fleta C , Quirion D , Gómez F
Published: April 2021

In this work we show the first microdosimetry measurements on a low energy proton beam with therapeutic-equivalent fluence rates by using the second generation of 3D-cylindrical microdetectors. The sensors belong to an improved version of a novel silicon-based 3D-microdetector design with electrodes etched inside silicon, which were manufactured at the National Microelectronics Centre (IMB-CNM, CSIC) in Spain. A new microtechnology has been employed using quasi-toroid electrodes of 25 μm diameter and a depth of 20 μm within the silicon bulk, resulting in a well-defined cylindrical radiation sensitive volume. These detectors were tested at the 18 MeV proton beamline of the cyclotron at the National Accelerator Centre (CNA, Spain). They were assembled into an in-house low-noise readout electronics to assess their performance at a therapeutic-equivalent fluence rate. Microdosimetry spectra of lineal energy were recorded at several proton energies starting from 18 MeV by adding 50 μm thick tungsten foils gradually at the exit-window of the cyclotron external beamline, which corresponds to different depths along the Bragg curve. The experimental

y

F

¯

values in silicon cover from (5.7 ± 0.9) to (8.5 ± 0.4) keV μm−1 in the entrance to (27.4 ± 2.3) keV μm−1 in the distal edge. Pulse height energy spectra were crosschecked with Monte Carlo simulations and an excellent agreement was obtained. This work demonstrates the capability of the second generation 3D-microdetectors to assess accurate microdosimetric distributions at fluence rates as high as those used in clinical centers in proton therapy.
Magnetic field amplification by high power lasers in underdense plasma
Authors: Wilson T C , Sheng Z-M , Eliasson B , McKenna P
Published: April 2021

The process by which an existing magnetic field of ∼102–103 T may be amplified by an order of magnitude along the axis of laser propagation in underdense plasma by an intense laser pulse is investigated. The mechanism underlying the effect is understood to be ponderomotive in nature, initiated by the

E

×

B

drift motion of electrons displaced by the laser pulse as they relax towards the axis, and sustained by a combination of quasistatic magnetic field structures and electron Hall and diamagnetic currents. We employ two- and three-dimensional particle-in-cell simulations to numerically investigate the process and find qualitative agreement with the scaling relations found in our theory model. The lifetime of the process is considered, and we find the major factor limiting its growth and lifetime is ion motion, which disrupts the electron currents necessary to sustain the induced magnetic field. This field is found to be of sufficient strength, and is long-lived enough to be relevant for study in relation to applications in radiation production and laboratory astrophysics.
Hosting of exceptional points in an atom-field interaction Hamiltonian and manipulation of light states
Authors: Paul Anubhav , Laha Arnab , Ghosh Somnath
Published: April 2021

We report an analytical model to investigate an atom-cavity interaction phenomenon with the consideration of a two-level atom and a quantized mode of the cavity field in the form of harmonic oscillation. Accordingly, we consider the matrix form of a special type of two-level Hamiltonian consisting of three units, explaining a two-level atom, a quantum harmonic oscillator to be equivalent to a quantized cavity-mode field, and an interaction matrix between them, which are connected by some iteration parameters. The iteration parameters of the proposed Hamiltonian have judiciously been modulated to encounter an exceptional point (EP). A specific closed parameter space encircling the embedded EP has been considered to study the dynamics of the coupled states in the context of a flip-of-state phenomenon. We also incorporate a deliberate phase difference between the two unperturbed levels associated with the atomic system and study the phase induced interaction between them in the context of state-flipping around the identified EP. The proposed analytical model indeed opens up a fertile platform to explore a range of interesting applications associated with the atom-cavity interaction.
Generation of nonclassical states by superposition of number-conserving operations on squeezed thermal state
Authors: Ye Wei , Guo Ying , Zhang Huan , Xia Ying , Mao Yun
Published: April 2021

The nonclassicality is the prerequisite for quantum states to be applied into quantum information, especially for quantum metrology. Here we theoretically investigate the non-classical properties of the non-Gaussian state generated by repeatedly operating a number-conserving generalized superposition of products (GSP), i.e., (s
1
aa
† + t
1
a
†
a)m with

s

1

2

+

t

1

2

=
1
,

on the squeezed thermal state (STS), in terms of second-order correlation function, Mandel’s Q parameter, quadrature squeezing and Wigner function (WF). It is shown that, compared to the cases of the STS, the GSP-STS with the high-order GSP operations (m > 1) at the small-squeezing levels can be beneficial to the existence of the photon-antibunching effect, the sub-Poissonian distribution and the partial negativity of the WF, apart from the quadrature squeezing. In addition, for the case of m = 1, we also compare with the non-classical properties of several different non-Gaussian resources, involving the photon-subtracted-then-added (PSTA) STS, the GSP-STS and the photon-added-then-subtracted (PATS) STS. It is found that the PSTA-STS with respect to the sub-Poissonian distribution and the partial negativity of the WF has a better performance than others. Significantly, the generated GSP-STS has an obvious advantage of showing the photon-antibunching effects, compared to the PSTA-STS and the PATS-STS, which means that our scheme may have an excellent guidance for the practical implementations in quantum information.
Released energy formula for proton radioactivity based on the liquid-drop model*
Authors: Pan Xiao , Zou You-Tian , Liu Hong-Ming , He Biao , Li Xiao-Hua , Xiang Dong
Published: April 2021

In this work, based on the liquid-drop model and considering the shell correction, we propose a simple formula to calculate the released energy of proton radioactivity (Q

p
). The parameters of this formula are obtained by fitting the experimental data of 29 nuclei with proton radioactivity from ground state. The standard deviation between the theoretical values and experimental ones is only 0.157 MeV. In addition, we extend this formula to calculate 51 proton radioactivity candidates in region 51 ≤ Z ≤ 83 taken from the latest evaluated atomic mass table AME2016 and compared with the Q

p
calculated by WS4 and HFB-29. The calculated results indicate that the evaluation ability of this formula for Q

p
is inferior to WS4 while better than HFB-29.
A new method of power quality disturbance classification based on deep belief network
Authors: Wang Kang , Xi Yanhui
Published: April 2021

In view of the low accuracy of single disturbances under the problem of noise interference, a new method of power quality disturbance classification based on deep belief network was proposed. A smooth wavelet multiscale transform is performed on the power quality disturbance signal, and then the soft threshold function is used to process the estimated wavelet coefficients for reconstructing the original signal. Further, it is proposed to use deep confidence network to classify and recognize the reconstructed single disturbance signal. The simulation results demonstrate that the recognition rate of this method for seven typical single disturbances is high. Even under 20dB noise interference, the classification accuracy rate is as high as 93% or more, which proves that the method has a strong ability to resist noise interference.
Salient object detection based on Two-stream edge attention guidance
Authors: Wei Li , chunlei Li , yue Miao
Published: April 2021

The existing U-Net structure convolutional neural network is widely used in salient object detection, but the problem of target boundary blur is caused by the convolution pooling operation. In order to keep the edge structure of salient objects clear, a two-stream edge attention guided convolutional neural network (SEANet) method is proposed to strengthen the guided learning of edge features, mainly by guiding the edge features to compare the original image features and the depth features are enhanced to improve the accuracy of salient object detection. The loss is minimized by using consistent cross entropy loss and IOU loss to maximize the coincidence rate of the true value map and the predicted map, as well as the actual boundary and the predicted boundary. At the same time, the obtained prediction map is compared with the current mainstream nine models, and good results have been achieved. Four sets of experiments are carried out in the ablation experiment, and the experimental results also confirmed that the model has a great improvement effect on the performance of salient object detection.
Research of Three Phase PWM Rectifier based on Direct Vector Control Method
Authors: Yan Pang
Published: April 2021

In oilfield worldwide, beam pumping units are wildly used to produce oil. the working mechanism of beam pumping unit determines that its driving motor frequently enters into the state of power generation, so PWM reversible rectifier is an ideal choice for recycle the generated energy, therefore it is necessary to research the control theory of PWM reversible rectifier. The paper presents a digital algorithm for the PWM rectifier, on the basis of coordinate analyzing theory and SVPWM method. The method that directly calculates the basic vector operation time and position is adopted, so the arc-tangent calculation is avoided, calculation process is simplified. Based on the vector coordinate transformation of three-phase reversible PWM rectifier, the control equation of direct current control method is derived in this paper. The rectifier control algorithm is realized with high performance DSP TMS320F28335. The experimental results prove that the method proposed in the paper is practical and correct.
Non-uniqueness of the solution of one mathematical model of an autocatalytic reaction with diffusion and the Showalter – Sidorov condition
Authors: Gavrilova O V , Manakova N A
Published: April 2021

The article is devoted to the numerical study of the phase space of one mathematical model of an autocatalytic reaction with diffusion, based on a degenerate system of equations for a distributed brusselator. We will obtain conditions for the existence, uniqueness or multiplicity of solutions to the Showalter – Sidorov problem and reveal the dependence of these conditions on the parameters of the system. The approach used in the numerical research of this problem is based on the reduction of the semilinear Sobolev-type equation to a system of algebraic-differential equations with the subsequent solution of this system using the Runge – Kutta method of order 4-5. The article also provides the result of a computational experiment which illustrates the operation of a program complex based on an algorithm for the numerical solution of the problem. The results of numerical simulation in the case of existence of two solutions of the investigated model are presented.
Determination of functional parameters in boundary conditions of linear hyperbolic systems by optimal control methods
Authors: Arguchintsev A V , Kedrina M S
Published: April 2021

An inverse problem of a functional parameter determination is considered for a hybrid system of population dynamics. Dynamics of several interacting populations is described by a system of first-order linear hyperbolic equations. The boundary conditions for this system are determined from the initial problem for ordinary differential equations. The problem is interpreted as an optimal control problem. A non-classic optimality condition of variational maximum principle type is proved. The original problem in distributed parameter systems is reduced to the optimal control problem for ordinary differential equations.
Application of hierarchical structures based on binary matrices with the generalized arithmetic of Pascal’s triangle in route building problems
Authors: Kuzmin O V , Starkov B A
Published: April 2021

The paper describes a method for constructing binary matrices based on Pascal’s triangle. It provides the definitions of vertical and horizontal generatrices, consisting of binary elements, and the recurrent rule of Pascal’s triangle, with the help of which a binary matrix is formed. The possibility of parametrization of generatrices is shown by identifying a combinatorial root word, called a generatrix pattern, in terms of word combinatorics. A comparative analysis is provided with the method of generalizing Pascal’s triangle using reduction modulo a prime. Combinatorial differences are shown. Discrete mathematical objects (an integer lattice and combinatorial lattice paths) are described. The paper provides the definitions of lattice paths and describes specific types of paths - the Motzkin paths and the McMahon paths. It gives some combinatorial properties of the Motzkin paths. A method for mapping a binary matrix of the Pascal triangle type to the set of points of an integer combinatorial lattice is described. A method for constructing and predicting the qualitative characteristics of navigation routes by combining binary matrices and integer lattices is developed. Possibilities of parametrization of a binary matrix and an integer lattice, taking into account practical problems, are presented.
Representations of simple Lie algebras with vectors having a zero stationary subalgebra
Authors: Yu Kuzmina E
Published: April 2021

The paper solves the problem of describing the representations V of compact Lie groups G and vectors v ∈ V with single stationary subgroups. It builds the classification of the representation of simple Lie algebras with vectors having a zero stationary subalgebra. If the codimension of the submanifold M
0 of dimension m in an N-dimensional Euclidean space RN
is less than the dimension and the group G is simple, then all these cases are described in the corresponding tables in sections 3 and 4.
Optimization of isolated power systems with renewables and storage batteries based on nonlinear Volterra models for the specially protected natural area of lake Baikal
Authors: Karamov D N , Sidorov D N , Muftahov I R , Zhukov A V , Liu F
Published: April 2021

Lake Baikal conservation as UNESCO World Heritage property, national and international environmental laws dictate specific requirements and rules for the operation of energy facilities in the specially protected areas of Lake Baikal. Such restrictions have given particular strength to penetration of the renewables and storage systems. This article presents the universal method for optimizing the structure and installed capacity of isolated power systems using the example of a real tourist base. On the basis of the pool of mathematical models and control algorithms for power equipment the unified model of isolated power system was formed. The choice of mathematical models is made in accordance to the problem specifics and the climatic indicators. For optimal control of the processes of charging and discharging and determining the operating modes of the storage batteries the model based on nonlinear integral Volterra equations was used, which takes into account the nonlinear dependence of efficiency on the state of charge. In order to solve the problem of optimizing the installed capacity of the equipment the brute-force method was used. The results showed that the optimal use is polycrystalline solar panels with a total capacity of 60 kW and storage batteries with a capacity of 336 kWh.
Mathematical modelling and design of isolation diaphragms for pressure gauges
Authors: Karyakin M I , Ustinov Yu A
Published: April 2021

The paper discusses some questions of equilibrium, stability and shape optimization of circular membranes with arbitrary profile along the meridian. Such membranes can be used as a flexible barrier to isolate the media on one side of a diaphragm from media on the other side, whilst allowing the transmission of pressure with minimal loss. The main goal of the analysis is to propose techniques for designing such shape of corrugated membranes that satisfy the requirements of so call “slow growing linear or almost linear” behavior of the pressure-volume diagram. The applied Kirchhoff-Love theory for non-shallow shells was used as a base for deriving nonlinear as well as linearized boundary value problems of equilibrium. A genetic algorithm was used to evaluate and optimize the characteristics of corrugated membranes. The presented analysis of the membrane with the maximum linear stroke showed its efficiency and reliability. At the same time, special attention should be paid to the basic parametrization used in modelling, since the mathematically optimal solution is not always suitable from the point of view of membrane production technology.
Finite element simulation of fibrous composites strain with stress concentrators
Authors: Polatov A M , Khaldjigitov A A , Ikramov A M , Pulatov S I
Published: April 2021

In the paper the problems of numerical modeling of nonlinear physical processes of elements stress-strain state of the construction materials are considered. The effect and mutual influence of stress concentrators in the form of a circular cavity, vertically located two cavities and a horizontally located system of two cavities on the strain of construction is studied.
Choosing a solvation model for simulating reactions in KOH(KOBut)/DMSO superbasic media
Authors: Kobychev V B
Published: April 2021

The ability of protocols based on the B2PLYPD/6-311+G**//B3LYP/6-31+G* method with various schemes for accounting for nonspecific solvation to reproduce C-H, N-H, O-H and S-H acidity in a dimethyl sulfoxide medium is considered. For a selected set of 20 compounds, typical reagents for reactions in superbasic media, the IEFPCM scheme with UFF cavity and α = 1.35 multiplier yields better results than the popular SMD model.
Discrimination of the mechanistic hypotheses for two- and three-component cross-coupling reactions by using mathematical modeling of the differential selectivity patterns
Authors: Kurokhtina A A , Larina E V , Vidyaeva E V , Lagoda N A , Schmidt A F
Published: April 2021

Distinguishing between several probable mechanistic hypotheses for complex catalytic reactions is a very complicated task. The main cause of such complication is the simultaneous realization of several consecutive-parallel processes under the reactions proceeding including side reactions with the participation of a catalyst. Under these circumstances, using kinetic studies of the reactions can provide unique possibilities to discriminate alternative mechanistic proposals. To achieve the goal, we offer to use the studies of the differential selectivity of such complex reactions by analysing possible correspondence of its patterns to different mathematical models describing alternative mechanistic hypotheses. Using this approach the fine mechanistic details of the catalytic cycles of two-component cross-coupling Suzuki-Miyaura and Mizoroki-Heck reactions as well as of three-component Sonogashira-type reaction coupling have been established.
The effect of the reagents nature on nucleophilic addition of acetylenes to the C=N bond of aldimines: a quantum-chemical investigation
Authors: Zubarev A A , Orel V B
Published: April 2021

A quantum-chemical simulation of the mechanism of ethynylation of aldimines with substituted acetylenes was carried out. Kinetic and thermodynamic characteristics of this reaction for various reacting pairs were estimated by the B2PLYPD/6-311+G**//B3LYP/6-31+G * method. It was shown that in the reaction with N-alkylaldimines, the ethynylation barrier was significantly higher than in the reaction with N-arylaldimines. The change in the substituents at acetylene has no effect on the ethynylation barriers.