bluuebunny/crossref_metadata_2025 huggingface dataset:
High-throughput production of force-fields for solid-state electrolyte materials
Authors: Kobayashi Ryo , Miyaji Yasuhiro , Nakano Koki , Nakayama Masanobu
Published: August 2020

An automatic and high-throughput method to produce interatomic force-fields for solid-state electrolyte materials is proposed. The proposed method employs the cuckoo search algorithm with an automatic update of search space to optimize parameters in empirical potentials to reproduce radial and angular distribution functions and equilibrium volume obtained from the ab initio molecular dynamics simulation. The force-fields for LiZr2(PO4)3 and LaF3 systems parameterized using the present method well reproduce key physical properties required to study ion conductivity of solid-state electrolyte materials. The current approach takes only one or two days to produce a force-field including the ab initio calculation to create reference data, which will greatly enhance the speed of exploration and screening of candidate materials.
Evaluating interface roughness and micro-fluctuation potential of InAs/GaSb superlattices by mid-infrared magnetophotoluminescence
Authors: Chen Xiren , Xu Zhicheng , Zhou Yi , Zhu Liangqing , Chen Jianxin , Shao Jun
Published: August 2020

Interface roughness of the InAs/GaSb type-II superlattice (T2SL) is a key issue for infrared photodetector performance. While numerous studies have been performed on interface roughness from the atomic perspective, the relation with photoelectric performance is not yet straightforward. In this study, we carry out mid-infrared magnetophotoluminescence (MPL) measurements on InAs/GaSb T2SLs with a nominally identical period structure. Micro-fluctuation potential and effective interface roughness are evaluated and compared by the photoluminescence linewidth evolution. The analyses agree qualitatively with the x-ray diffraction linewidth and resolve two types of interface roughness quantitatively: the long lateral-length fluctuation, which is exacerbated by the lattice-mismatch, and the short lateral-length fluctuation, which is related possibly to interfacial atomic exchange. These results suggest that MPL can be an effective tool for evaluating the micro-fluctuation potential of InAs/GaSb T2SLs and understanding the effects of interface roughness on electro-optical performance.
Acoustical ghost imaging
Authors: Li Ming-Qian , Lan Ruo-Ming , Liu Xue-Feng , Yao Xu-Ri , Zhai Guang-Jie
Published: August 2020

Ghost imaging, which is an indirect imaging technique that uses correlations between two beams to retrieve the information of an object, is applicable to any wavelength. It has been performed with a growing range of light sources, including x-rays, the visible, and the infrared, and has also been extended to atoms and electrons recently. In this Letter, we demonstrate acoustical ghost imaging using the correlation between random acoustic patterns, which are generated by the phase and delaying manipulation of a transducer array and the total transmitted intensity signals. Furthermore, the reconstruction quality and resolution can be further improved by compressed sensing. This study shows a demonstration of ghost imaging using mechanical waves. Moreover, this approach requires fewer computational resources and offers great promise for high-speed and high-resolution acoustical imaging.
Impact of nanosecond laser energy density on the C40-TiSi2 formation and C54-TiSi2 transformation temperature
Authors: Esposito L. , Kerdilès S. , Gregoire M. , Benigni P. , Dabertrand K. , Mattei J.-G. , Mangelinck D.
Published: August 2020

The formation of Ti based contacts in new image sensor complementary metal–oxide–semiconductor technologies is limited by the requirement of a low thermal budget. The objectives of these new 3D-technologies are to promote ohmic, low resistance, repeatable, and reliable contacts by keeping the process temperature as low as possible. In this work, ultraviolet-nanosecond laser annealing was performed before classical rapid thermal annealing (RTA) to promote the formation at lower RTA temperatures of the low resistivity C54-TiSi2 phase. The laser energy density was varied from 0.30 to 1.00 J/cm² with three pulses in order to form the C40-TiSi2 phase and finally to obtain the C54-TiSi2 phase by a subsequent RTA at low temperatures. The formed Ti-silicides were characterized by four-point probe measurements, x-ray diffraction, transmission electron microscopy, and atom probe tomography. A threshold in the laser energy density for the formation of the C40-TiSi2 is observed at an energy density of 0.85 J/cm² for the targeted TiN/Ti stack on blanket wafers. The C40-TiSi2 formation by laser annealing prior to RTA enables to reduce the formation temperature of the C54-TiSi2 phase by 150 °C in comparison to a single RTA applied after the Ti/TiN deposition. This specific phase sequence is only observed for a laser energy density close to 0.85 J/cm². At higher energy densities, the presence of C49-TiSi2 or a mixture of C49-TiSi2 and C54-TiSi2 is observed. The underlying mechanisms of the phase sequence and formation are discussed in detail.
Microwave engineering for semiconductor quantum dots in a cQED architecture
Authors: Holman Nathan , Dodson J. P. , Edge L. F. , Coppersmith S. N. , Friesen Mark , McDermott R. , Eriksson M. A.
Published: August 2020

We develop an engineered microwave environment for coupling high Q superconducting resonators to quantum dots using a multilayer fabrication stack for dot control wiring. Analytical and numerical models are presented, which show that high resonator quality factors can be attained by either minimizing the parasitic coupling capacitance to the leads or creating a low effective environmental impedance at the cavity frequency. We implement the later approach by fabricating low characteristic impedance (Zg≈10 Ω) microstrips on-chip for the dot bias wiring and show resonator quality factors of 8140 that can be attained without the addition of explicit filtering. Using this approach, we demonstrate single electron occupation in double and triple dots detected via dipole or quadrupole coupling to a superconducting resonator. Additionally, by using multilayer fabrication, we are able to improve ground plane integrity and keep microwave crosstalk below −20 dB out to 18 GHz while maintaining high wire density, which will be necessary for future circuit quantum electrodynamics quantum dot processors.
Stability analysis of a double similarity transformed coupled cluster theory
Authors: Agarawal Valay , Chakraborty Anish , Maitra Rahul
Published: August 2020

In this paper, we have analyzed the time series associated with the iterative scheme of a double similarity transformed coupled cluster theory. The coupled iterative scheme to solve the ground state Schrödinger equation is cast as a multivariate time-discrete map, and the solutions show the universal Feigenbaum dynamics. Using recurrence analysis, it is shown that the dynamics of the iterative process is dictated by a small subgroup of cluster operators, mostly those involving chemically active orbitals, whereas all other cluster operators with smaller amplitudes are enslaved. Using synergetics, we will indicate how the master-slave dynamics can suitably be exploited to develop a novel coupled-cluster algorithm in a much reduced dimension.
Structural disorder, sublattice melting, and thermo-elastic properties of anti-perovskite Li3OBr under high pressure and temperature
Authors: Zhang Jianzhong , Wang Liping , Zhu Jinlong , Zhao Yusheng
Published: August 2020

In situ synchrotron x-ray diffraction experiments were conducted in the system Li-O-Br at pressures up to 6.5 GPa and temperatures up to the melting points. The thermal equation of state determined from the P–V–T measurements indicates that crystalline anti-perovskite Li3OBr exhibits similar thermo-elastic properties to common salts. At temperatures that are 50–75 °C below the crystal melting, a pre-melting behavior was inferred based on weakened Bragg intensity and a substantial increase in the diffuse scattering. Concurrent with the onset of pre-melting, an anomalous increase in the lattice volume was observed and is interpreted as anion sublattice disorder. These findings support previous ab initio molecular dynamics simulations based on a simple anion interchange mechanism, indicating that structural disorder below crystal melting temperature can be a main driving force for Li-sublattice melting and superionic transition in the Li3OBr anti-perovskite.
Global eigenmodes of thin liquid sheets by means of Volume-of-Fluid simulations
Authors: Della Pia Alessandro , Chiatto Matteo , de Luca Luigi
Published: August 2020

The unsteady dynamics of planar liquid sheet flows, interacting with unconfined gaseous environments located on both sides of the liquid phase, is numerically investigated by means of the Volume-of-Fluid (VOF) technique for supercritical regimes. The global behavior of the non-parallel flow is analyzed by perturbing the initial steady configuration by means of a Gaussian bump in the transverse velocity component of relatively small amplitude, thereby exciting sinuous modes. To gain more physical insights into the fluid system, a theoretical linear one-dimensional model is also developed. A physical interpretation of this model relates the sheet dynamics to transverse vibrations of tensional string forced by terms containing the lateral velocity and subjected to a total damping coefficient, which can assume negative values. The VOF simulation satisfactorily confirms that the velocity impulse perturbation splits into two wave fronts traveling downstream with the theoretical wave velocities. A good agreement is found in comparing the crossing times over the entire domain length of such waves with the almost constant spacing between the frequencies of the eigenvalue spectrum. Surface tension plays a stabilizing role, and for relatively high values of density ratio rρ of gaseous-to-liquid phases, the sheet becomes unstable. It is argued that the distribution of transverse velocity component of the gaseous phase represents the forcing term, which leads the system toward the instability when, for relatively high rρ, the total damping becomes negative. An analogy seems to exist between the global unstable behavior exhibited by the liquid sheet as rρ increases and the shear-induced global instability found by Tammisola et al. [Surface tension-induced global instability of planar jets and wakes,” J. Fluid Mech. 713, 632–658 (2012)] in the presence of surface tension. However, for the gravitational sheet, the surface tension is stabilizing.
Femtosecond photoemission electron microscopy of surface plasmon polariton beam steering via nanohole arrays
Authors: Crampton Kevin T. , Joly Alan G. , El-Khoury Patrick
Published: August 2020

Directional control over surface plasmon polariton (SPP) waves is a prerequisite for the development of miniaturized optical circuitry. Here, the efficacy of single and dual component SPP steering elements is explored through photoemission electron microscopy. Our imaging scheme relies on two-color photoemission and counter-propagating SPP generation, which collectively allow SPPs to be visualized in real space. Wave-vector difference mixing between the two-dimensional nanohole array and photon momenta enables SPP steering with directionality governed by the array lattice constant and input photon direction. In our dual component configuration, separate SPP generation and Bragg diffraction based steering optics are employed. We find that array Bragg planes principally influence the SPP angles through the array band structure, which allows us to visualize both positive and negative refractory waves.
Role of water vapour in the absorption of nanosecond 266-nm laser pulses by atmospheric air
Authors: Kuryak A.N. , Tikhomirov B.A.
Published: August 2020

The absorption of the Nd : YAG fourth harmonic in air and binary mixtures of water vapour with nitrogen and oxygen at atmospheric pressure has been measured as a function of pulse energy (peak intensity). The mixtures obtained by adding equal amounts of water vapour to dry nitrogen and oxygen have been found to differ significantly in absorption. Preliminary quantitative data have been obtained for two- and three-photon absorption cross sections of water and oxygen molecules: σ
(2)(H2O) = (4 ± 1) ± 10–49 cm4 s and σ
(3)(O2) = (5.6 ± 1.4) ± 10–78 cm6 s2. The absorption of 266-nm pulses with peak intensities from 0.05 to 2 GW cm–2 in the near-surface atmosphere has been shown to be determined by two-photon absorption in water vapour and three-photon absorption in oxygen. In moist air containing 1 % water vapour, the absorption coefficient for 266-nm laser pulses exceeds that in dry air by four to five times. There is no absorption in nitrogen. We have developed a technique for photoacoustic measurements of multiphoton absorption cross sections in single-component gases and gas mixtures.
Relaxation oscillations in a bipolarised Nd : YAG laser with a Fabry – Perot cavity
Authors: Khandokhin P.A.
Published: August 2020

Based on the model of a bipolarised laser, which takes into account real orientations of absorbing and emitting dipoles of active centres in the unit cell of an Nd : YAG single crystal, we have shown that the appearance of low-frequency relaxation oscillations requires the participation of both competing pump channels through linearly and circularly polarised dipole transitions.
Lasing dynamics of diode-pumped Yb – Er laser with a passive Q switch exposed to high-power external light
Authors: Batura E.O. , Bobretsova Yu.K. , Bogdanovich M.V. , Veselov D.A. , Grigor’ev A.V. , Dudikov V.N. , Kot A.M. , Pikhtin N.A. , Ryabtsev A.G. , Ryabtsev G.I. , Slipchenko S.O. , Shpak P.V.
Published: August 2020

The temporal dynamics of diode-side-pumped Yb – Er laser, with a passive Co2+ : MgAl2O4
Q switch illuminated by a light beam (total fluence of 0.15 – 0.16 J cm−2) from a semiconductor pulsed module, is investigated. It is shown that, using this external illumination, one can change the lasing onset delay and the time jitter ΔT
gi. The dependence of ΔT
gi on the interval between the instant of switching the illumination module on and the lasing peak position t
i has a minimum at |t
i| ≈ 10 μs. The decrease in ΔT
gi with a change in |t
i| from 90 to 10 μs indicates that instant of lasing peak occurrence for the Yb – Er laser is partially controlled by the pulse from the highly stable semiconductor module. If |t
i| < 10 μs, the enhanced luminescence fluence in the cavity of Yb – Er laser exceeds 0.16 J cm−2; the light beam from the module does not affect much the lasing process in the ytterbium – erbium laser; and, as a consequence, the time jitter recovers the initial value.
Localised electromagnetic waves in a rhombic waveguide array with competing nonlinearities
Authors: Maimistov A.I.
Published: August 2020

We consider a model of a discrete photonic system representing a quasi-one-dimensional rhombic array of waveguides, where, in addition to the positive cubic nonlinearity, the negative quintic nonlinearity is taken into account for the material of which the central chain of the waveguides is made. The other two waveguide chains are made of an optically linear material. A continual approximation is used to obtain a solution for a system of coupled waves, which describes a wave localised in the transverse direction. In a certain special case, the competition of nonlinearities leads to the formation of a step-shaped distribution of the field intensities over the waveguides.
Abiotic factors and environmental monitoring.
Authors: Rees Paul A.
Published: August 2020

This chapter contains questions about the physical factors in the environment and their measurement.
The LTB4–BLT1 axis regulates actomyosin and β2-integrin dynamics during neutrophil extravasation
Authors: Subramanian Bhagawat C. , Melis Nicolas , Chen Desu , Wang Weiye , Gallardo Devorah , Weigert Roberto , Parent Carole A.
Published: August 2020

The eicosanoid leukotriene B4 (LTB4) relays chemotactic signals to direct neutrophil migration to inflamed sites through its receptor BLT1. However, the mechanisms by which the LTB4–BLT1 axis relays chemotactic signals during intravascular neutrophil response to inflammation remain unclear. Here, we report that LTB4 produced by neutrophils acts as an autocrine/paracrine signal to direct the vascular recruitment, arrest, and extravasation of neutrophils in a sterile inflammation model in the mouse footpad. Using intravital subcellular microscopy, we reveal that LTB4 elicits sustained cell polarization and adhesion responses during neutrophil arrest in vivo. Specifically, LTB4 signaling coordinates the dynamic redistribution of non-muscle myosin IIA and β2-integrin, which facilitate neutrophil arrest and extravasation. Notably, we also found that neutrophils shed extracellular vesicles in the vascular lumen and that inhibition of extracellular vesicle release blocks LTB4-mediated autocrine/paracrine signaling required for neutrophil arrest and extravasation. Overall, we uncover a novel complementary mechanism by which LTB4 relays extravasation signals in neutrophils during early inflammation response.
Mitotic phosphorylation of Pex14p regulates peroxisomal import machinery
Authors: Yamashita Koichiro , Tamura Shigehiko , Honsho Masanori , Yada Hiroto , Yagita Yuichi , Kosako Hidetaka , Fujiki Yukio
Published: August 2020

Peroxisomal matrix proteins are imported into peroxisomes via membrane-bound docking/translocation machinery. One central component of this machinery is Pex14p, a peroxisomal membrane protein involved in the docking of Pex5p, the receptor for peroxisome targeting signal type 1 (PTS1). Studies in several yeast species have shown that Pex14p is phosphorylated in vivo, whereas no function has been assigned to Pex14p phosphorylation in yeast and mammalian cells. Here, we investigated peroxisomal protein import and its dynamics in mitotic mammalian cells. In mitotically arrested cells, Pex14p is phosphorylated at Ser-232, resulting in a lower import efficiency of catalase, but not the majority of proteins including canonical PTS1 proteins. Conformational change induced by the mitotic phosphorylation of Pex14p more likely increases homomeric interacting affinity and suppresses topological change of its N-terminal part, thereby giving rise to the retardation of Pex5p export in mitotic cells. Taken together, these data show that mitotic phosphorylation of Pex14p and consequent suppression of catalase import are a mechanism of protecting DNA upon nuclear envelope breakdown at mitosis.
A third Notch in colorectal cancer progression and metastasis
Authors: Koch Ute , Radtke Freddy
Published: August 2020

In this issue of JEM, Varga et al. (https://doi.org/10.1084/jem.20191515) describe a mouse model of invasive and metastatic colorectal cancer (CRC) closely resembling the human consensus molecular subtype (CMS) 4 associated with the poorest overall survival of the four CMSs. Transcriptomic and bioinformatic analysis combined with pharmacological and genetic studies identified Notch3 as a promoter of tumor progression and metastasis. NOTCH3 expression was up-regulated in CMS4 CRC patients and associated with tumor staging, lymph node and distant metastasis. These findings feature NOTCH3 as putative therapeutic target for advanced CMS4 CRC patients.
Cosmological dark matter amplification through dark torsion
Authors: Izaurieta Fernando , Lepe Samuel
Published: August 2020

A cosmological approach based on considering a cosmic background with non-zero torsion is shown in order to give an option of explaining a possible phantom evolution, not ruled out according to the current observational data. We revise some aspects of the formal schemes on torsion and, according them, we develop a formalism which can be an interesting alternative for exploring Cosmology.
Data-driven forward discretizations for Bayesian inversion
Authors: Bigoni D , Chen Y , Trillos N Garcia , Marzouk Y , Sanz-Alonso D
Published: August 2020

This paper suggests a framework for the learning of discretizations of expensive forward models in Bayesian inverse problems. The main idea is to incorporate the parameters governing the discretization as part of the unknown to be estimated within the Bayesian machinery. We numerically show that in a variety of inverse problems arising in mechanical engineering, signal processing and the geosciences, the observations contain useful information to guide the choice of discretization.
Tunable water-based metasurface for anomalous wave reflection
Authors: Jacobsen Rasmus E , Nielsen Jonas Ø , Lavrinenko Andrei V , Arslanagić Samel
Published: August 2020

Metasurfaces (MSs) are artificial structures which enable the full control of electromagnetic waves and they continue to be of great scientific importance. In particular, they can tailor their reflection and transmission properties by using electrically small metallic/dielectric scatterers with imprinted spatial phase variation. In the present work, we design and characterize a water-based MS with a tunable reflection at 1 GHz. The MS comprises a collection of water cylinders and we demonstrate its ability to reflect a normally incident wave at an angle of 51.3° and with a total reflection efficiency of 33%. A prototype was fabricated and is shown to exhibit an excellent agreement with the simulation results. The proposed water-based MS may serve as a cheap and bio-friendly tunable alternative for a variety of microwave communication systems.
Preparation of graphite-like carbon nitride (g-C3N4)/NiCo2S4 nanocomposite toward salient microwave characteristics and evaluation of medium influence on its microwave features
Authors: Peymanfar Reza , Ghorbanian-Gezaforodi Shaghayegh
Published: August 2020

In this paper, NiCo2S4 sulphide spinel nanoparticles are prepared using a modified solvothermal route, after which the obtained siegenite nanoparticles are tailored on graphite-like carbon nitride (g-C3N4) nanosheets. The morphology of tailored nanostructures is accomplished via an ion exchange process. Interestingly, the g-C3N4 stick structures are fabricated based on an innovative approach. Moreover, interfacial polarizations at heterojunction interfaces, and medium effects on microwave characteristics are examined, using polystyrene (PS) and polyvinylidene fluoride (PVDF) as polymeric matrices. The specimens are characterized via Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) analyses. The optical performance of nanostructures is studied by means of diffuse reflection spectroscopy (DRS) analysis, and is suggestive of a narrow band gap for NiCo2S4 and NiCo2S4/g-C3N4 nanostructures. Finally, the material’s microwave absorbing features are clarified using a vector network analyzer (VNA) instrument via a wave guide technique. The resulting significant microwave absorptions reveal that our g-C3N4/NiCo2S4/PVDF 40% nanocomposite exhibited seven notches of reflection loss (RL), more than 30 dB in its curve, at 1.75 mm in thickness, while its maximum RL was 59.39 dB at 13.07 GHz. Interestingly, this composite, in a mass fraction of 60%, illustrates an efficient bandwidth of 5.1 GHz (RL > 10 dB) at only 1 mm thickness. It is worth noting that the maximum RL of g-C3N4 stick structures/PVDF measures 74.53 dB at 14.86 GHz, with a broadband efficient bandwidth of 7.96 GHz (RL > 10 dB). More significantly, both g-C3N4/NiCo2S4/PVDF and NiCo2S4/PVDF demonstrated salient electromagnetic interference shielding effectiveness (SE) > 30 dB across both x- and ku-band frequencies.
Tailoring physical properties of WS2 nanosheets by defects control
Authors: Tao Lei , Song Yongli , Liu Jian , Wang Xianjie , Liu Zhiguo , Huo Mingxue , Wang Yang , Sui Yu
Published: August 2020

The controllable growth of high-quality transition metal dichalcogenides (TMDs) is crucial for their device applications, which rely on the atomic and quantitative understanding of the growth mechanism of TMDs. In this work, we propose a comprehensive picture of the growth of WS2 nanosheets via Monte Carlo simulation, and an extension of diffusion-limited growth under transition state theory is developed to describe heteroepitaxy growth of WS2. Theoretical results are in good agreement with the results of chemical vapor deposition that growth temperature dominates growth processes leading to samples with various densities of vacancy defects. The vacancy defects modify the photoluminescence and ferromagnetic behavior. Our work provides a pathway toward realizing controllable physical properties in 2D materials.
Molecular dynamics simulation of amine groups formation during plasma processing of polystyrene surfaces
Authors: Michlíček Miroslav , Hamaguchi Satoshi , Zajíčková Lenka
Published: August 2020

Plasma treatment and plasma polymerization processes aiming to form amine groups on polystyrene surfaces were studied in-silico with molecular dynamics simulations. The simulations were compared with two experiments, (i) plasma treatment in N2/H2 bipolar pulsed discharge and (ii) plasma polymerization in cyclopropylamine/Ar radio frequency (RF) capacitively coupled discharge. To model favorable conditions for the incorporation of primary amine groups, we assumed the plasma treatment as the flux of NH2 radicals and energetic NH3 ions, and the plasma polymerization as the flux of cyclopropylamine molecules and energetic argon ions. It is shown in both the simulation and the experiment that the polystyrene treatment by the bipolar pulsed N2/H2 plasmas with an applied voltage of about ±1 kV formed a nitrogen-rich layer of a thickness of only a few nm. The simulations also showed that, as the NH3 incident energy increases, the ratio of primary amines to the total number of N atoms on the surface decreases. It is because the energetic ion bombardment brakes up N–H bonds of primary amines, which are mostly brought to the surface by NH2 radical adsorption. Our previous experimental work on the CPA plasma polymerization showed that increased RF power invested in the plasma leads to the deposition of films with lower nitrogen content. The MD simulations showed an increase of the nitrogen content with the Ar energy and a limited impact of the energetic bombardment on the retention of primary amines. Thus, the results highlighted the importance of the gas-phase processes on the nitrogen incorporation and primary amines retention in the plasma polymers. However, the higher energy flux towards the growing film clearly decreases amount of hydrogen and increases the polymer cross-linking.
Influence of near-anode cusped magnetic field on the performance of a miniaturized cylindrical Hall thruster
Authors: Gao Yuanyuan , Fan Weina , Hu Peng , Liu Hui , Yu Daren
Published: August 2020

A near-anode cusped magnetic field topology is proposed for a 3 cm cylindrical Hall thruster (CHT), and its performance characteristics are investigated. The experimental results indicate that on imposing an anode voltage of 400 V, the thruster achieves a 2071 s specific impulse with a highly collimated plume. Compared with a conventional direct magnetic field, its thrust and anode efficiency are improved by 10.8% and 27.9%, respectively, which is due to the dramatic increase in the plume divergence efficiency (28.9%) and voltage utilization efficiency (6.7%). According to the analyses on the distribution characteristics of ion current density and ion energy, these performance improvements should be attributed to the downstream shift of both the ionization and acceleration regions. This work provides some design ideas on the magnetic field optimization of CHTs.
Differences in power law growth over time and indicators of COVID-19 pandemic progression worldwide
Authors: Merrin Jack
Published: August 2020

Error analysis and data visualization of positive COVID-19 cases in 27 countries have been performed up to August 8, 2020. This survey generally observes a progression from early exponential growth transitioning to an intermediate power-law growth phase, as recently suggested by Ziff and Ziff. The occurrence of logistic growth after the power-law phase with lockdowns or social distancing may be described as an effect of avoidance. A visualization of the power-law growth exponent over short time windows is qualitatively similar to the Bhatia visualization for pandemic progression. Visualizations like these can indicate the onset of second waves and may influence social policy.
Shape of population interfaces as an indicator of mutational instability in coexisting cell populations
Authors: Castillo Clarisa E , Lavrentovich Maxim O
Published: August 2020

Cellular populations such as avascular tumors and microbial biofilms may ‘invade’ or grow into surrounding populations. The invading population is often comprised of a heterogeneous mixture of cells with varying growth rates. The population may also exhibit mutational instabilities, such as a heavy deleterious mutation load in a cancerous growth. We study the dynamics of a heterogeneous, mutating population competing with a surrounding homogeneous population, as one might find in a cancerous invasion of healthy tissue. We find that the shape of the population interface serves as an indicator for the evolutionary dynamics within the heterogeneous population. In particular, invasion front undulations become enhanced when the invading population is near a mutational meltdown transition or when the surrounding ‘bystander’ population is barely able to reinvade the mutating population. We characterize these interface undulations and the effective fitness of the heterogeneous population in one- and two-dimensional systems.
Formation of α’ titanium welds by friction stir welding
Authors: Amirov A I , Eliseev A A , Beloborodov V A , Chumaevskii A V , Gurianov D A
Published: August 2020

In the present study, investigation of the macrostructure of α’ titanium alloy weld produced by the friction stir welding has been carried out. The welding process modes were also selected. It is shown that in case of insufficient load on the tool, an open weld defect is formed. Increasing the load (with decreasing RPM) eliminates the open tunnel and minimizes defects. Despite the presence of defects, the strength of welds has reached the strength of the initial material. As a result of FSW, grain size has been reduced by 7.3 times, but the load increase has not affected the grain structure. The results of the research show that the part of welding tool had been stirred in the structure of weld. However, nickel base alloy tool had passed about 500 mm of weld, before starting to wear out.
Deformation behavior of stainless steel under uniaxial tension
Authors: Nikonova A M , Li Y V , Barannikova S A
Published: August 2020

The present work is devoted to the study of the laws of macroscopic localization of plastic deformation of austenitic stainless steel AISI 321 at low and high temperatures. The studies of AISI 321 steel found that at the stages of linear strain hardening, the propagation velocity of the localized plastic deformation centers and the spatial period of local elongation change when test temperature increases by the exponential law. Patterns of plastic strain localization as single bands are due to the Portevin – Le Chatelier effect on jerky flow.
The structure of multi-walled carbon nanotubes as a factor affecting the life of E. Coli
Authors: Popov A P , Dimitrieva A I , Kovalenko A V , Yumanov D S , Stepanov A V , Shemukhin A A , Vorobyeva E A , Elsehly Emad M
Published: August 2020

In this work, we investigated the relationship between the structural properties of materials based on multi-walled carbon nanotubes and the vital activity of bacteria E. Coli strain M-17. In the course of research using scanning electron microscopy and Raman spectroscopy, the structure of nanotubes was analyzed. Nanotube samples were tested for wettability. The effect of carbon nanotube samples on the growth of the bacterial culture of E. Coli strain M-17 using spectrophotometry was investigated. As a result, it was shown that samples containing more disordered defective nanotubes on the surface are more hydrophilic and also show worse biocompatibility properties for E. Coli bacteria.
The synthesis of Fe-Ag and Fe-Cu bimetallic nanoparticles by electrical explosion of wires
Authors: Chjou V R , Varnakova E A , Bakina O V , Naumova L B
Published: August 2020

In the present study, we obtained antibacterial Fe-Cu and Fe-Ag bimetallic nanoparticles by electrical explosion of two twisted wires. This method allows obtaining nanoparticles of a given composition and morphology. As-synthesized nanoparticles were characterized by electron microscopy, X-ray diffraction, micro electrophoresis techniques and magnet technique. In result we observed the formation of nanoparticles with Janus-like structure with distinct separation of components inside the particle. These nanoparticles have a strong antibacterial activity against two bacteria strains. The high antimicrobial activity of the nanoparticles is due to the prolonged ion release in media. Taking into account the possibility of easy magnetic separation of the novel bimetallic demonstrate the potential for their use as promising new generation antibacterial agents for advanced antimicrobial water treatment technologies.
The influence of the energy density of the electron beam on the morphology of surface and mechanical properties of the surface layer of NiTi alloy
Authors: D’yachenko F A , Atovullaeva A A , Meisner L L
Published: August 2020

This work comprises a study of the influence of the energy density E

s
of the low-energy high-current electron beam (LEHCEB) exposure on the morphology of surface and mechanical properties of the surface layer of nickel titanium alloy (NiTi alloy). It was found that the formation of crater-like relief on the surface of NiTi alloy after electron beam treatment is determined by the structure and distribution of the particles of second and impurity phases. The mechanical properties in a modified surface layer of no more than ∼ 500 nm thickness change at different values of the energy density E

s
of electron beam.
Beam-produced plasma generated by the pulsed large-radius electron beam in the forevacuum pressure range
Authors: Kazakov A V , Medovnik A V , Oks E M , Panchenko N A
Published: August 2020

The research of plasma produced by a pulsed low-energy large-radius electron beam generated by the plasma-cathode electron source in the forevacuum pressure range 4-13 Pa is presented. The beam-produced plasma has been generated in nitrogen by the electron beam with energy of 8 keV and pulse duration of 1.5 ms. The emission spectrum analysis and probe measurements have been used to investigate plasma parameters. Density of beam-produced plasma increases linearly with increasing electron beam current. The probe measurements have demonstrated almost linear dependence of plasma density on gas pressure in the pressure range 4-13 Pa, while intensities of spectral lines came from exited plasma ions are linear dependent on beam current only in pressure range 6-13 Pa. These spectral lines have low intensities at gas pressure below 6 Pa.
Maximal current of a pulsed constricted arc discharge operating in the forevacuum plasma electron source
Authors: Kazakov A V , Medovnik A V , Oks E M , Panchenko N A
Published: August 2020

The paper presents results of investigation of maximal current of the pulsed constricted arc discharge generating emission plasma in the forevacuum plasma electron source. Distinctive feature of the forevacuum plasma electron source is the absence of pressure differential between region of formation of emission plasma and the region of acceleration and propagation of electron beam. Therefore, the operating conditions of the constricted arc in the forevacuum plasma source are significantly different from the conditions in the plasma electron sources generating electron beams at pressure 10–3–10–1 Pa. The constriction of the positive column of the arc discharge provides, as it known, to reduce influence of instability and chaotic behavior of the cathode spot of the arc on the formation of emission plasma. In the investigated pressure range 3–20.5 Pa, the maximal current of the constricted arc discharge has been limited either by extinction of the arc or by initiation of the cathode spots on the constricting electrode and transition of the arc operation to the cascade mode. Increase of gas pressure and the use of working gas with larger ionization cross section (e.g. argon) have provided increase of the maximal arc current. The increase in the constricting channel diameter has provided the increase of maximal current and provided lower minimal gas pressure, at which stable operation of the constricted arc ensured. The decrease of length of the constricting channel has provided noticeable increase in the maximal arc current only at gas pressure more than 12 Pa.
Separation of ammonium fluorometallates during hydrometallurgical processing of titanomagnetite ore
Authors: Sachkov V I , Nefedov R A , Amelichkin I V , Orlov V V , Medvedev R O
Published: August 2020

In this work, we used the hydrometallurgical method for processing titanomagnetite ore with an aqueous solution containing ammonium fluoride and hydrofluoric acid, with the aim of obtaining and subsequent separation of the resulting reaction products. Separation of compounds was carried out by precipitation of ammonium fluorometallates with an ammonia solution. The results of product separation by changing pH are presented. At pH 8, silicon ((NH4)2SiF6 – 55 % wt) and iron ((NH4)0.75Fe3F9 – 11 % wt and (NH4)2FeF5 – 6 % wt) compounds are mostly precipitated. At pH 9, the precipitate consists of titanium compounds: (NH4)2TiF4O – 67 % wt and NH4TiOF3 – 33 % wt.
A voltammetric sensor for simultaneous determination of tryptophan and 5-hydroxytryptophan
Authors: Altyev A M , Shelkovnikov V V , Fryanova M S
Published: August 2020

The present work proposes a method for simultaneous determination of tryptophan and 5-hydroxytryptophan on the carbon-bearing electrode modified with multiwall carbon nanotubes and polyfolic acid. Analytical signals are conditioned by oxidation of tryptophan and 5–hydroxytryptophan from the complex containing polyfolic acid. Preparation of the electrode consists in the formation of the B9 vitamin film on the surface of the carbon-bearing electrode, modified with multiwall carbon nanotubes by the method of cyclic voltammetry. The detection limit of tryptophan and 5-hydroxytryptophan is 1 × 10–7 M.
Physical Modeling of Oil Displacement in the Multifunctional Surfactant-based Chemical Composition
Authors: Kozlov V V , Altunina L K , Chernova U V , Sholidodov M R
Published: August 2020

The paper presents the test results of a new multifunctional chemical composition based on surfactants in the process of displacement of heavy high-viscosity oil. Physical modeling of the oil displacement process was carried out in a laboratory setup which allows modeling heterogeneity of the oil-saturated formation. As a result of experiments it was found that the use of a multifunctional chemical oil-displacing composition based on a surfactant leads not only to a change in the filtration flows within the heterogeneous reservoir model but also to an increase in the oil displacement coefficient.
Influence of size of metal-ceramic composites on their electron-beam sintering in the forevacuum pressure range
Authors: Klimov A S , Yu Bakeev I , Tran V T , Zenin A A
Published: August 2020

Ceramic-metal composite materials combine high strength of ceramic and plasticity of metal. The combination of these properties allows the use of cermet in many industries and medicine. Cermet materials are made using powder technology by sintering a compact consisting of a mixture of pressed powders. The properties of the resulting product are determined by both the initial component composition and the sintering method. In the present work, electron beam sintering in the fore-vacuum pressure range was used to obtain cermet. The feature of this method is the possibility of flexible control of the sintering process by changing the parameters of the electron beam. To heat compacts consisting of pressed powders of alumina ceramics and titanium, the surface of compacts was scanned with an electron beam with the diameter of less than 1 mm and the power of 500 W. The surface temperature of the compact during sintering was 1600 °C, and the time of isothermal exposure was 10 minutes. It has been shown that compact thickness has a significant effect on obtaining homogeneous sintered material. Samples with a microhardness of 27 GPa were obtained. The ways of further improving the technology of electron beam sintering of cermet are determined.
Synthesis and application of cobalt and polyoxomolybdate-containing alumina systems
Authors: Akimov A S , Sviridenko N N , Akimov Al S
Published: August 2020

The work is devoted to the synthesis and study of the activity of cobalt and polyoxomolybdate-containing alumina catalyst. The synthesized catalytic system was characterized using the following analysis methods: scanning electron microscopy, x-ray phase analysis, x-ray diffraction analysis, IR spectroscopy. It was found that the CoMo/Al2O3 system is active in the hydrodesulfurization reaction of model raw materials.
Mathematical modeling of helium atom motion inside the fullerene C60 molecule
Authors: Tarasov E A
Published: August 2020

In this research, author modeled numerically the process of motion of a helium atom with different velocities inside the C60 fullerene sphere. The approaches of classical mechanics and the formalism of the intermolecular interaction potential (Lennard-Jones potential) were used to create physical and mathematical models. The transverse dimensions of the area inside the fullerene molecule in which the selected particle (helium atom) moves was obtained.
Evaluating the influence of the magnetic permeability of the microstrip modal filter substrate on its frequency characteristics
Authors: Chernikova E B , Kvasnikov A A , Zabolotsky A M , Kuksenko S P
Published: August 2020

This paper considers the possibility of improving the characteristics of modal filters by using composite materials with a relative magnetic permeability of μ
r
>1. The influence of the magnetic permeability of the microstrip modal filter substrate on its frequency characteristics is investigated. The paper presents the frequency dependences |S
21| of the filter with lengths l=1, 0.5, and 0.2 m and with μ
r
= 1, 4, 7, and 10. It is shown that the increase of the the μ
r
value leads to a decrease in the filter bandwidth.
Enhanced Oil Recovery for Deposits of High Viscosity Oils Using Multifunctional Systems Based on Surfactants
Authors: Altunina L K , Kuvshinov V A , Stasieva L A , Kuvshinov I V
Published: August 2020

To enhance the oil recovery of high-viscosity oil deposits in the temperature range of 20-210 °C, the multifunctional composition based on surfactants, aluminum and ammonium salts, an adduct of inorganic acid, carbamide and polyol with an adjustable viscosity and high oil-displacing ability was created. The composition has a low interfacial tension, a high buffer capacity in a wide pH range, 2.5-10 units pH, a delayed reaction with carbonate rocks, prevents the precipitation of insoluble reaction products, increases the permeability of reservoirs. The composition is both oil-displacing and flow-diverting, provides an enhance in the oil recovery factor (ORF) due to the increase in the oil displacement and formation sweep by water or steam flooding. Practical recommendations are given on the application of the composition at the Permian-Carboniferous deposits of the Usinsk oilfield.
W-rich mixed oxide solid solutions under pressure
Authors: Petrushina M Yu , Dedova E.S. , Yusenko K V , Portnyagin A S , Papynov E K , Filatov E Yu , Korenev S V , Gubanov A I
Published: August 2020

We report high-pressure synchrotron X-ray powder diffraction data for the W-rich cubic ZrW2-xMoxO8 (x=0.4) up to 10 GPa with open decompression. This study shows that cubic- ZrW1.6Mo0.4O8 transforms to orthorhombic phase at the 5.04 GPa. Pressure-induced reversable amorphization of material was observed at 8.13 GPa. The obtained data suggest that W-rich cubic ZrW2-xMoxO8 (x=0.4) solid solutions are more attractive for creating products working under extreme conditions and mechanic stress.
Kinetics of thermal destruction of highly porous anion-exchange resin TOKEM-320Y
Authors: Kuznetsova S A , Khalipova O S , Lisitsa K V , Ditts A A , Malchik A G , Kozik V V
Published: August 2020

Temperature characteristics, stages and thermal effects of the processes occurring during the thermolysis of TOKEM-320Y anion-exchange resin in an atmosphere of air were determined by differential thermal analysis. The activation energies and the orders of reactions of thermal decomposition of the resin were calculated by the Kissinger and Metzger-Horowitz methods using the TG curves obtained at different heating rates of the resin. Models are proposed that most accurately describe the decomposition of TOKEM-320Y in air in the temperature range 25–800 °C.
On fine particles synthesis using three-zone reactor
Authors: Markov A A
Published: August 2020

This paper reports a numerical study on thermal and mass dispersion in carbon combustion synthesis of oxides (CCSO) in porous media. A volume averaging of the microscopic conservation equations over an elementary volume is applied to derive the macroscopic conservation equations for convective and conductive heat and mass transfer in a porous media consisting of gas components mixture and solid particles of reactant species. The governing system of macroequations is the conservation of momentum, mass and energy for multicomponent gas-solid media using the heat and mass exchange between gas and solid phases. The model developed in dimensionless variables and similarity parameters is applied to numerical simulation of barium titanate micron particles synthesis in three-zone reactor using the thermal and mass dispersion. The results are in satisfactory agreement with experimental measurements. The dispersion strongly influences on the thermal front propagation as well as on the barium titanate synthesis rate. The three-zone reactor is more efficient compared to the flow-reactor.
Sorption activity of polyhexamethylene guanidine hydrochloride hydrogels towards extracts of medicinal plants
Authors: Ochirov O S , Olennikov D N , Turtueva T A , Grigor’eva M N , Stelmakh S A , Mognonov D M
Published: August 2020

The study aims to obtain polyhexamethylene guanidine hydrochloride hydrogel compositions with extracts of medicinal plants growing in the Baikal region (Bergenia crassifolia, Calendula officinalis, Tussilago farfara) to evaluate sorption activity and consider the subsequent use of the compositions as an external wound healing agent. It has been shown that hydrogel sorbs mainly caffeinequinic acids in various compositions. It has been made an assumption about a link of sorption process with formation of secondary amino groups’ complex in the hexahydrotriazine cycle, which is formed as a result of gelation of PHMGhch, and carboxyl groups of extract substances. It is planned to study the wound healing activity of compositions by modeling skin damage of laboratory animals in future researches.
Composite fluoropolymer piezoelectric membranes for reconstructive surgery
Authors: Tverdokhlebova T T , Bolbasov E N , Khanova M Yu , Antonova L V , Buznik V M
Published: August 2020

The work represents the results of researchers on the formation of composite fluoropolymer piezoelectric membranes based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and polyethylpyrrolidone (PVP) by the electrospinning method. The effect of the PVP content on the structure of the formed membranes was measured using scanning electron microscopy. The biocompatibility of the obtained membranes was studied by fluorescence microscopy on a model of human skin fibroblasts. The studied samples with a 0, 5 and 15% PVP content have good adhesive characteristics, preserve the viability and potential of cells to divide and therefore are most suitable for further use in regenerative medicine.