bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Small Variations of Plasma Density on Conditions of Propagation of Electromagnetic Waves of the Whistle Range through the Morning Ionosphere
Authors: Mizonova V. G. , Bespalov P. A.
Published: April 2024

The problem of the effect of plasma-density disturbances caused by infrasonic waves on the propagation and reflection of whistler electromagnetic waves incident on the morning ionosphere from above is considered. The influence of the parameters of an infrasonic wave on the coefficient of reflection of a whistler wave from the ionosphere from above in the general case of oblique propagation is studied. The strongest changes in the reflection coefficient of whistler waves are associated with concentration perturbations at heights of the order of 80–100 km, where the rate of decay of propagating electromagnetic radiation modes increases by more than an order of magnitude within a region that is quite local in height (less than 10–15 km). The features of the parametric effect of plasma density fluctuations in an infrasonic wave on the field of a whistler wave that reached the Earth’s surface are analyzed. At close values of the horizontal wavenumbers of the whistler and infrasonic waves, the field of the whistler wave near the Earth’s surface can increase by several times. The results obtained are important for understanding the relationship between magnetospheric wave processes of different nature. The study of the modulation of the coefficient of reflection of whistler waves from the ionosphere by infrasonic waves from above is relevant for explaining the operating modes of a plasma magnetospheric maser.
The Influence of Oxygen Ions on the Formation of a Thin Current Sheet in the Magnetotail
Authors: Domrin V. I. , Malova H. V. , Popov V. Yu. , Grigorenko E. E. , Zelenyi L. M.
Published: April 2024

A thin current sheet in the Earth’s magnetotail with characteristic thickness of one to several proton gyroradii is often observed during magnetospheric disturbances named substorms, when a relatively thick current configuration in the magnetotail is narrowed to an extremely small thickness and then can spontaneously be destroyed. The current-sheet destruction is usually accompanied by such active processes as plasma acceleration and heating, as well as generation of an induced electric field and magnetohydrodynamic waves. In this paper, we developed and investigated a model of formation of a thin current sheet in which, along with protons, we have taken into account single-charged oxygen ions coming from the ionosphere into the magnetotail current sheet during magnetically active periods. The aim of this simulation is to study the peculiarities of thin current-sheet formation in two-component plasma and investigate its structure. It is shown that equilibrium configuration can have some characteristic properties. In particular, if the system consists only of protons or heavy ions, single-scale current equilibrium supported by quasi-adiabatic particles is formed. When a current sheet is formed in plasma that consists of a mixture of protons and oxygen ions in comparable concentrations, a current sheet can be formed with heavy ions as current carriers and chaotic proton trajectories that make a negative contribution to the current, due to which the current-density profile becomes bifurcated with the minimum at the center and maxima at the periphery of the sheet. The results may be useful for the interpretation of observational data in the Earth’s magnetotail.
A Lunar Printer Experiment on Laser Fusion of the Lunar Regolith in the Luna-Grunt Space Project
Authors: Tomilina T. M. , Kim A. A. , Lisov D. I. , Lysenko A. M.
Published: April 2024

This paper presents the results of laboratory studies on the use of a new technology of selective laser melting to obtain experimental products from the lunar regolith without special additives. The main properties of the natural regolith, which significantly affect the fusion process, are determined. The first samples of a given geometry were obtained from labradorite and gabbro-diabase powders, which are natural analogues of lunar regolith, using this technology. The research results are planned to be used in the preparation of initial data for the development of the Lunar Printer space device as part of the complex of scientific equipment of the promising lunar project Luna-Grunt.
Optimization of Solar-Sail Control When a Vehicle Moves along Cyclic Heliocentric Trajectories
Authors: Rozhkov M. A. , Starinova O. L.
Published: April 2024

This paper considers the problem of constructing time-optimal trajectories for a spacecraft (SC) with a solar sail. The trajectories under consideration consist of repeated cycles of spacecraft movement to the target heliocentric orbit and back to the initial one. A model of a perfectly reflecting sail is used, which allows using the programs for optimal control of the sail angle, obtained on the basis of the Pontryagin maximum principle. The heliocentric motion is modeled in a flat polar coordinate system, and the spacecraft itself makes cyclic flights between two terrestrial planets along a closed trajectory. A boundary-value problem is formulated, in the solution of which the approach of the spacecraft to the target planet with the equalization of velocities is ensured (the encounter problem). Simulations of four cycles of Earth–Mercury–Earth and Earth–Mars–Earth motion with a characteristic acceleration of the solar sail of 0.25 mm/s2 have been carried out, for which the duration of one cycle is on average 2000 and 2341 days, respectively. Optimal sail-orientation control programs are obtained for a wide range of launch dates, and methods of searching for and choosing the initial values of conjugate variables are shown. The obtained results demonstrate the ability of a spacecraft with a solar sail to implement controlled motion along closed trajectories with a minimum duration of individual Earth–destination planet–Earth flights.
Characteristics of Solar Wind and Geomagnetic Conditions of Extreme Geomagnetically Induced Currents at the Vykhodnoy Station (2012–2018)
Authors: Sheveleva D. A. , Apatenkov S. V. , Sakharov Ya. A. , Selivanov V. N. , Gordeev E. I.
Published: April 2024

We investigated 140 events with the largest geomagnetically induced currents (GIC) recorded at the Vykhodnoy station (65 MLat) in 2012–2018. The significant differences between the parameters of the solar wind and geomagnetic indices from typical values are shown. Distinctive increases in solar wind velocity and dynamic pressure, decreases of IMF Bz are found. The Kp, AE, AL, Dst indices, as well as the Dst rate of growth Dst/dt are significantly shifted from the usual values. The relationship with interplanetary shocks in the solar wind is also analyzed.
The Influence of Field-Aligned Currents on Electron Density in the Ionosphere: Combined Observations of SWARM Satellites and ESR Radar
Authors: Lukianova R. Yu.
Published: April 2024

The results are presented of combined measurements by the SWARM spacecraft (SC) and European incoherent scatter radar on Svalbard for two events of simultaneous observations: in the nighttime ionosphere during substorm activation on January 9, 2014, and in the daytime ionosphere under quiet conditions on February 5, 2017. Onboard magnetometers of the SWARM SC provide measurements of field-aligned current density over the ionosphere. The radar, which is under the flyby trajectory at this time, measures the vertical distribution of the electron density (Ne). Experiments have shown that, under disturbed nighttime conditions, at the location of the field-aligned current flowing from the ionosphere, the plasma density increases throughout the entire slab of the ionosphere and the change in Ne is in agreement with theoretical estimates. In the daytime quiet ionosphere, Ne increases only in the F layer, but practically does not change in the E layer. The differences may be due to the fact that, in the first case, the carriers of the upward directed current are represented by the entire energy spectrum of auroral electrons of 1–10 keV, and in the second case only by the low-energy part.
A Catalog of Geoefficient Flare Events of the Current 25th Solar Cycle in a Modern Presentation
Authors: Zabarinskaya L. P. , Ishkov V. N. , Sergeeva N. A.
Published: April 2024

To study the phenomena occurring on the Sun and in interplanetary space and their influence on near-Earth space and on processes in the outer and inner shells of the Earth, the results of continuous long-term observations of solar activity become very valuable. A representative collection of such long-term homogeneous series of systematic observations obtained by the worldwide network of solar and astronomical observatories, as well as by spacecraft, has been collected at the World Data Center for Solar–Terrestrial Physics in Moscow. The article describes a cumulative interactive catalog of the main characteristics of significant solar-flare events of the current 25th cycle of solar activity.
A Method for Calculating the Trajectory of a Single-Impulse Flight to a Halo Orbit around the L2 Libration Point of the Earth–Moon
Authors: Rui Zhou
Published: April 2024

The problem of calculation of low-energy impulse trajectories to halo orbits in the vicinity of the L2 point of the Earth–Moon system is considered. A new method for calculating the trajectories of a single-impulse low-energy flight to a halo orbit is presented. The limited problem of four bodies is analyzed, within which the attraction of the Earth, Moon, and Sun is taken into account, and their position and speed are calculated using high-precision ephemeris support. Particular attention in the development of the method is paid to ensuring its computational stability for calculating trajectories with a long stay of a spacecraft (SC) in the zone of weak stability near the boundary of the Hill sphere of the Earth. The results of the calculation of single-impulse transfer trajectories from low Earth orbit to halo orbit around the L2 point of the Earth–Moon system are given. The analysis of the dependence of the main characteristics of single-impulse trajectories from the date of approach to the halo orbit is carried out.
Designing Low-Energy Low-Thrust Flight to the Moon on a Temporary Capture Trajectory
Authors: Ivanyukhin A. V. , Ivashkin V. V. , Petukhov V. G. , Yoon S. W.
Published: April 2024

The study considers the problem of calculating the low-energy trajectories of a low-thrust spacecraft to the Moon during the ballistic capture. The transfer is carried out using a transit trajectory in the vicinity of one of the collinear libration points L1 or L2 of the Earth-Moon system. Using a transit trajectory allows us to reduce fuel consumptions for the transfer by applying spacecraft dynamic in the Earth-Moon system. After exit from the orbit of ballistic capture, depending on the goal of mission the required lunar orbit can be formed, or the maneuver can be completed for inserting into the required interplanetary trajectory. A method for solving the problem is proposed, which consists in selecting the suitable transit trajectory to ensure sufficiently long duration of staying a spacecraft in the sphere of influence of the Moon, and in calculating the optimal low-thrust trajectories from initial lunar orbit to the transit trajectory to the Moon. To solve the problem of optimal control and calculate the optimal exit point to the transit trajectory, the Pontryagin’s maximum principle is used in combination with the continuation method by parameter. Numerical examples are given for calculating low-energy trajectories to the Moon during the ballistic capture with the optimization of exit point to the transit trajectory.
DIRECTOR DISTRIBUTION IN A CLC HYBRID CELL WITH A SMALL HELICOIDAL PITCH
Authors: Shtykov N. M. , Palto S. P. , Umanskii B. A. , Rybakov D. O. , Simdyankin I. V.
Published: April 2024

Laser light emission in dye-doped chiral liquid crystals (CLCs) has been experimentally demonstrated for the homeotropic–planar (hybrid) orientation. A numerical simulation of this structure showed that the helicoid (helix) pitch period in CLC in the hybrid cell and the director distribution depend significantly on the anchoring energy at the homeotropic sample boundary. The anchoring energy plays the role of a factor facilitating the CLC helix unwinding. The lower anchoring energy, the smaller the pitch is and the closer to the natural CLC pitch it is. In this case, the length of the “screw"-type structure near the homeotropic cell boundary decreases. Thus, as the anchoring energy at the hybrid-cell homeotropic boundary decreases, the director distribution in the cell approaches the distribution in the planar (Grandjean) cell. This is confirmed by the laser light emission in the same spectral range as in the planar cell.
X-RAY REFLECTOMETRY OF THIN FILMS FORMED DURING PHASE SEPARATION OF ORGANIC SOLUTIONS OF ALIPHATIC POLYETHERS IN WATER
Authors: Asadchikov V. E. , Volkov Yu. O. , Roshchin B. S. , Nuzhdin A. D. , Chernavskay E. R. , Tikhonov A. M. , Mironov A. V. , Mariyanac A. O. , Popov V. K.
Published: April 2024

The possibilities of X-ray reflectometry for studying the structure of planar liquid-phase membranes are demonstrated by the example of polyester films formed on the surface of deionized water from solutions of polylactoglycolide (PLG) in chloroform and tetraglycol (TG). It is found that the use of solutions with PLG concentrations ranging from 1 to 4 wt % or above 6 wt % leads to a proportional increase in the density of these films with preservation of their structure and thickness up to 25 Å. At a PLG concentration close to 5 wt % the PLG/TG system transits to an unstable state, characterized by intense penetration of PLG aliphatic chains into the water substrate bulk to a depth up to 100 Å.
FEATURES OF VISUALIZATION OF THE THREE-DIMENSIONAL STRUCTURE OF MESOPOROUS PZT FILMS BY FIB-SEM NANOTOMOGRAPHY
Authors: Atanova A. V. , Khmelenin D. N. , Zhigalina O. M.
Published: April 2024

A technique for studying the three-dimensional structure of porous lead zirconate titanate films by FIB-SEM-nanotomography is presented. Such quantitative characteristics as total porosity, specific surface area, and actual pore size (calculated using the local thickness method) have been obtained. According to the FIB-SEM-nanotomography data, the pore size is 77 ± 33 nm for the film with the PVP porogen and only 27 ± 6 nm for the film with the Brij76 porogen; the latter value is close to the limiting resolution for this method. The final 3D model is shown to be strongly influenced by the chosen ion-beam parameters during milling, which can be varied to obtain a structure without distortion or visualize the accumulation of pores at grain boundaries.
PHASE COMPOSITION, STRUCTURE, AND MAGNETIC PROPERTIES OF Cd1–хZnхTe SOLID SOLUTIONS AT LOW Zn CONCENTRATIONS
Authors: Podkur P. L. , Volchkov I. S. , Pavlyuk M. D. , Kvartalov V. B. , Morgunov R. B. , Kanevskii V. M.
Published: April 2024

Polycrystalline Cd1–хZnхTe (x = 0.005, 0.03, 0.05) ingots have been obtained by the modified Obreimov–Shubnikov method. The selected single-crystal blocks are studied applying the X-ray diffraction analysis, measurement of electrical characteristics, and magnetometry. The concentration dependence of changes in the magnetic and electrical properties of crystals is investiga11ted. It is established that at Zn concentrations of x = 0.03 and 0.05 ferromagnetic ordering is observed in clusters (inclusions) containing iron and/or nickel at 2 K, which is not observed for Cd1–хZnхTe (x = 0.005) samples.
GROWTH, STRUCTURE, AND PHASE BEHAVIOR OF DI-TERT-BUTYL-PARA-TERPHENYL CRYSTALS
Authors: Postnikov V. A. , Sorokina N. I. , Kulishov A. A. , Yurasik G. A. , Lyasnikova M. S. , Sorokin T. A. , Skorotetsky M. S. , Borshchev O. V.
Published: April 2024

The results of studying the growth of para-terphenyl derivative (4,4"-di-tert-butyl-para-terphenyl (tBu-3P-tBu)) crystals are presented. The solubility of this compound in toluene at 20°С has been established by spectrophotometry. Using the techniques of growth from solutions and physical vapor transport,tBu-3P-tBu single crystals up to 1 cm long have been obtained for the first time. Their structure at 85 K has been interpreted in the triclinic system, sp. gr. P1 (Z = 8), using single-crystal X-ray diffraction. Flat rectangular crystals with the best morphological characteristics have been grown from vapor. The developed face of these crystals exhibits elementary growth steps 1.4 nm high, corresponding to molecular monolayers oriented in the (001) plane. The presence of a polymorphic transition at 229.2°C and mesomorphic liquid crystal phase above the melting temperature (255.6°С) is found.
New Data on the Isomorphism in Eudialyte-Group Minerals. XII: Refined Structure of the Hydrated Mineral from the Inagli Massif
Authors: Rastsvetaeva R. K.
Published: April 2024

A hydrated eudialyte-group mineral from the Inagli alkaline massif (Kola Peninsula) has been investigated by electron-probe and X-ray diffraction analyses. The parameters of the trigonal unit cell are as follows: a = 14.1558(3) Å, c = 30.998(1) Å, V = 5378.6(3) Å3, sp. gr. R3; the calculated density is 2.661 g/cm3. The crystal structure is refined to the final reliability factor of R = 3.8% within the anisotropic approximation of atomic displacements using 1230 reflections with F 3σ(F). The simplified formula of the mineral (Z = 3) is (H3O)7Na7.5(K,Sr,Ba,Ce)1.5Zr3Ca6[Si24O68(OH)3(O,OH)]Si1.5Cl1(OH)2H2O1.5. The problems of symmetry of calcium-rich hydrated eudialyte-group minerals are discussed.
STRUCTURAL AND PHASE TRANSFORMATIONS ON THE SURFACE OF SUPERPROTONIC CRYSTALS OF ACID SALTS OF POTASSIUM-AMMONIUM SULFATE
Authors: Gainutdinov R. V. , Tolstikhina A. L. , Selezneva E. V. , Makarova I. P. , Vasiliev A. L.
Published: April 2024

The results of comprehensive studies of structural and phase transformations in(K0.43(NH4)0.57)3H(SO4)2 superprotonic crystals under the influence of atmospheric moisture are presented. The real structure, composition, and thickness of the modified surface layers have been analyzed using scanning electron microscopy and X-ray microscopy. The local characteristics of nanostructures, formed on the freshly cleaved (001) crystal surface subjected to the electrostatic effect, have been investigated by conductive atomic force microscopy. A correlation has been established between the time changes in the structure, composition, and magnitude of the electrostatic potential of the crystal surface. The results are considered in the context of evaluation of the chemical stability of the samples and searching for the ways to optimize the compositions and functional properties of superprotonic compounds.
OPTICAL AND X-RAY SPECTROSCOPY OF COLOR CENTERS IN CERIUM-DOPED YTTRIUM‒ALUMINUM GARNET
Authors: Butashin A. V. , Venevtsev I. D. , Fedorov V. A. , Muslimov A. E. , Antonov E. V. , Deryabin A. N. , Kvartalov V. B. , Kanevskii V. M.
Published: April 2024

Yttrium‒aluminum garnet single crystals, including cerium-doped ones, have been grown from melt by Bagdasarov’s method. A comparative spectroscopy study of garnet single crystals and specially prepared ceramics of the same composition has been carried out. The comparative analysis suggests that an increase in the concentration of cerium ions in the garnet crystals improves the spectral-luminescence and scintillation characteristics of the latter and facilitates effective quenching of the substrate luminescence. Ways of optimizing the synthesis conditions to improve the efficiency of scintillators based on {Y1-xCex}3Al5O12 garnet crystal have been proposed.
COVARIANT REPRESENTATION OF MAXWELL’S EQUATIONS IN A MEDIUM WITH SOURCES
Authors: Dyshekov A. A. , Khapachev Yu. P.
Published: April 2024

A geometric approach to describing an electromagnetic field in a medium with sources as a single field object is proposed. The description is based on the coordinate-free covariant approach adopted in the present-day geometrized field theories. Maxwell’s equations in a medium with sources are presented in terms of differential 2-forms for electric and magnetic fields in a four-dimensional space-time continuum. The generalequations include special cases of propagation, scattering, and emission of an electromagnetic field in media with different properties.
THERMOSTIMULATED EVOLUTION OF THE CRYSTAL AND MAGNETIC STRUCTURE OF YTTRIUM FERRITE GARNET NANOPARTICLES
Authors: Kiseleva T. Yu. , Rusakov V. S. , Abbas R. , Lazareva E. V. , Tyapkin P. Yu. , Martinson K. D. , Komlev A. S. , Perov N. S. , Popkov V. I.
Published: April 2024

Iron-containing oxides form one of the most important classes of functional materials, which find a wide variety of applications. A promising approach is their use in biomedical technologies as components of systems for visualization, drug delivery, magnetic hyperthermia, etc. Nanocrystalline particles of Y3Fe5O12 garnet, obtained by glycine-nitrate combustion with subsequent thermal treatment, have been experimentally investigated. The results of studying the evolution of the crystal and magnetic structure of Y3Fe5O12 nanoparticles in dependence of the synthesis temperature are presented. A complex analysis using X-ray diffractometry, scanning electron microscopy, and Mössbauer spectroscopy has been performed. A relationship of the size and structural quality of Y3Fe5O12 nanoparticles with the observed magnetic characteristics is evealed.
Model of Formation of Gold-Bearing Placers in Platform Areas (East of the Siberian Platform)
Authors: Nikiforova Z. S. , Kalinin Y. A. , Naumov V. A. , Lalomov A. V.
Published: April 2024

A model of the formation of gold-bearing placers for platform areas is proposed for the first time. Placers on the platforms are formed mainly due to the Precambrian ore sources spatially confined to the basement outcrops, and, locally, Mesozoic, formed when tectonic-magmatic activation occurs in the zones of paleorifts and deep faults. Placers formed due to the Precambrian sources are characterized by the presence of fine and thin gold with a size of 0.1‒0.25 mm and, as a rule, are not of commercial interest. They bar alluvial and coastal-marine allochtonous placers and are considered as complex, with associated mining of titanium, zirconium and other useful components. Placers formed due to the sources of the Mesozoic stage of ore formation belong to the class of small and medium reserves, the size of gold in them ranges from dust-like to 0.2‒0.25 mm or more and they are usually mined by prospectors' team. Placers on the platforms do not form sheet deposits, since they are formed mainly due to sources of non-placer-generating formations. The presence of such placers indicates the proximity of the ore occurrence, which the type and location can be determined based on the study of the mineralogical and geochemical features of the placer gold itself.
Detection of Microcystin-Producing Cyanobacteria Microcystis, Planktothrix, and Dolichospermum Using Multiprimer Amplification of the mcy Genes
Authors: Sidelev S. I.
Published: April 2024

Abstract—A multiprimer PCR-based technique for the joint molecular detection of microcystin-producing planktonic cyanobacteria of the genera Microcystis, Planktothrix and Dolichospermum was developed. To amplify the mcy genes of microcystin biosynthesis, three pairs of genus-specific primers were selected, while the fourth pair was used to amplify the inter-gene spacer (IGS) cpcBA acting as an inner positive control for the presence of cyanobacterial DNA in the analyzed samples. Four PCR products of predicted size were successfully amplified using a mixture of DNA templates isolated from microсystin-producing strains of M. aeruginosa, P. agardhii, and field colonies of D. lemmermannii colonies retrieved from the environment, as well as аn environmental DNA template from lake plankton. The proposed multiprimer PCR-based approach may be used to design convenient test systems for monitoring aquatic ecosystems to prevent and/or assess the risk of accumulation of harmful cyanobacterial toxins.
Genes of NAD+-Dependent Formate Dehydrogenases in Taxonomy of Aerobic Methylotrophic Bacteria of the Genus Ancylobacter
Authors: Chemodurova A. A. , Reshetnikov A. S. , Agafonova N. V. , Doronina N. V.
Published: April 2024

Abstract—Comparative phylogenetic analysis of NAD+-dependent formate dehydrogenases (NAD+–FDH) genes, which have been detected in all available genomes of methylotrophs of the genera Ancylobacter, Starkeya and Angulomicrobium, as well as in other members of the family Xanthobacteraceae (Xanthobacter, Aquabacter, Azorhizobium), was carried out. The position of Xanthobacteraceae on the tree constructed based on comparison of NAD+–FDH amino acid sequences was found to correlate with the 16S rRNA gene-based phylogeny. The sequences of the NAD+–FDH proteins of the genera Ancylobacter, Starkeya, and Angulomicrobium exhibited 87.8–98.3% identity, indicating that this protein is very conservative within this group of methylotrophs. For the first time, analysis of the NAD+–FDH functional genes is recommended as a supplementary criterion for interspecies differentiation between methylotrophic bacteria of the genus Ancylobacter.
Sulfurospirillum tamanensis sp. nov., a Facultative Anaerobic Alkaliphilic Bacterium from a Terrestrial Mud Volcano
Authors: Frolova A. A. , Merkel A. Yu. , Kevbrin V. V. , Kopitsyn D. S. , Slobodkin A. I.
Published: April 2024

Abstract—An alkaliphilic, facultatively anaerobic bacterium (strain T05bT) was isolated from a terrestrial mud volcano on the Taman Peninsula, Russia. The cells of the isolate were motile spirilla 0.5 µm thick and 1.5–2.5 µm long. Strain T05bT grew at 6–42°C (optimum at 30°C), pH 8.0–11.0 (optimum at 9.0), and 0–14% NaCl (wt/vol). Lactate, formate, malate, pyruvate, H2, elemental sulfur, sulfite, thiosulfate, and sulfide were used as electron donors; nitrate, fumarate, elemental sulfur, sulfite, thiosulfate, dimethyl sulfoxide, arsenate, and oxygen could be used as electron acceptors. Nitrate was reduced to ammonium. Malate, pyruvate, and fumarate were fermented. Microaerobic growth was possible at up to 3% О2 (vol/vol). Strain T05bT did not use sulfate and Fe(III) as electron acceptors, was unable of elemental sulfur, sulfite, or thiosulfate disproportionation, and did not ferment glucose, fructose, sucrose, lactate, formate, maleate, yeast extract, or peptone. The predominant fatty acids were C16:1 ω7 (45.9%), C16:0 (25.8%), and C18:1 ω7 (20.9%). The genome of strain T05bT was 2.46 Mb in size and had the G + C DNA content of 45.5%. It contained the genes encoding the following enzymes of energy metabolism: Nap nitrate reductase periplasmic complex, Phs/Psr thiosulfate/polysulfide reductase, Sqr sulfide:quinone oxidoreductase, and Arr respiratory arsenate reductase. Ac-cording to analysis of the 16S rRNA gene nucleotide sequence, strain T05bT exhibited 98.61% similarity to the type strain of Sulfurospirillum alkalitolerans (phylum “Campylobacterota”). Based on its phenotypic characteristics and the results of phylogenetic analysis, assignment of the isolate to a new Sulfurospirillum species, Sulfurospirillum tamanensis sp. nov., is proposed, with the type strain T05bT (=DSM 112596T = VKM B-3538T).
Transformation of Methoxylated Aromatic Compounds by Anaerobic Microorganisms
Authors: Khomyakova M. A. , Slobodkin A. I.
Published: April 2024

Abstract—Methoxylated aromatic compounds (MAC) are widely distributed in various habitats and are components of lignin, the second most abundant biopolymer on Earth. This review summarizes the results on microbiology, ecology, and biochemistry of anaerobic MAC catabolism in bacteria and archaea. We analyzed the genomes of 46 prokaryotes anaerobically degrading MAC for the presence of O-demethylase, CO-dehydrogenase/acetyl-CoA synthase, and benzoyl-CoA reductase genes, which determine the possibility of methoxydotrophic growth. It was found that facultative anaerobes of the phylum Pseudomonadota do not have any known genetic determinants of anaerobic O-demethylase reaction as well as of aromatic ring reduction. Thus, the MAC transformation by anaerobic microorganisms can be carried out by diverse biochemical mechanisms and probably plays a more significant role in the global carbon cycle than previously supposed.
Inhibitory Action of Low-Molecular Chitosan on Growth of Bacteria with Different Tinctorial Properties
Authors: Korobov V. P. , Shagdarova B. Ts. , Varlamov V. P. , Esaev A. L. , Polyudova T. V.
Published: April 2024

Abstract—Inhibitory effect of chitosan (molecular mass 28 kDa, deacetylation 94%) and of its quaternized derivative with 60% substitution on bacteria of various taxonomic groups was investigated. Bacteria differing in the cell wall surface characteristics and affinity to dyes were found to differ in theri sensitivity to chitosan. Correlation dependencies between antibacterial activity of quaternized chitosan and the surface characteristics of bacterial cell walls were revealed.
Search for Novel Halophilic and Halotolerant Producers of Antimicrobial Compounds in Various Extreme Ecosystems
Authors: Gavrilov S. N. , Barashkova A. S. , Cherdyntseva T. A. , Prokofeva M. I. , Tresvyatskii O. V. , Lukianov D. A. , Nikandrova A. A. , Haertle T. , Merkel A. Yu. , Bonch-Osmolovskaya E. A. , Rogozhin E. A.
Published: April 2024

Abstract—The recent increase of antibiotic resistance in pathogenic microorganisms stimulated interest in the search for new antimicrobial compounds and their producers. Among the latter, halophilic microorganisms are considered to be the most promising group, since actinomycetes, producers of the majority of the known clinically important classes of antibiotics, are widely represented in this group. The present work reports the results of the search with three different approaches for new antimicrobial compounds in halophilic and halotolerant microorganisms inhabiting three different types of extreme ecosystems. Metagenomic analysis of microbial communities of subsurface thermal mineral waters revealed biosynthetic clusters of putative antimicrobial compounds, which belong to bacteria and archaea of uncultured lineages. Enrichment cultures with antimicrobial activity were obtained from the cold, deep oceanic sediments; analysis of their phylogenetic diversity resulted in identification of the potential producers of antimicrobial compounds as the members of class Desulfuromonadia. Finally, antimicrobial activity of a new species of soil natronophilic streptomycetes, Streptomyces sp. ACA25, was characterized; it was active only against gram-positive bacteria. The genome of this organism was sequenced, and the pathways for biosynthesis of polypeptide, polyketide, and beta-lactam antibiotics were identified. Active fractions of the ACA25 culture, containing antimicrobial compounds of polyketide and beta-lactam nature, were obtained. The active polyketide was identified as rosamycin, an antibiotic of the macrolide structural group. However, the fact that it did not inhibit bacterial translation highlighted structural differences between the new polyketide and rosamycin.
Seven New Actinobacterial Species of the Genus Kribbella with Unique Cell Wall Glycopolymers, and Emended Description of the Genus Kribbella
Authors: Avtukh A. N. , Ariskina E. V. , Baryshnikova L. M. , Tul’skaya E. M. , Potekhina N. V. , Shashkov A. S. , Suzina N. E. , Prisyazhnaya N. V. , Starodumova I. P. , Vasilenko O. V. , Dorofeeva L. V. , Evtushenko L. I.
Published: April 2024

Abstract—Seven actinomycete strains assigned to seven new species of the genus Kribbella were isolated from soils of different regions in Russia. The strains exhibited 98.2–99.3% similarity of the 16S rRNA gene sequences to each other and 96.2–99.7% similarity to the type strains of the known Kribbella species. The evolutionary distances calculated on the basis of concatenated gene sequences (gyrB–rpoB–recA–relA–atpD, 4108 nt) for the studied organisms and type strains of the known species were within the range reported for Kribbella species (0.014–0.101). The dDDH and ANIb values for the strains studied and the type strains of validly described species with available genomes were below the threshold (49.8 and 92.6%, respectively) for prokaryote specie delineation. Members of the putative new species possessed individual phenotypic profiles; some species were found (for the first time in Kribbella) to produce sporangium-like structures, up to 4 μm in diameter. The cell walls of the studied strains contained the teichuronic and/or teichulosonic acids specific for the species or species groups and not described previously for other prokaryotes. The unique branched α-mannan occurred in all studied strains of the genus. Based on the data obtained and the previously published data, the following new species are proposed: Kribbella orskensis sp. nov. (type strain ВКМ Ас-2538T), Kribbella rubisoli sp. nov. (type strain VKM Aс-2540T), Kribbella antiqua sp. nov. (type strain VKM Ас-2541T), Kribbella kalugense sp. nov. (type strain VKM Ас-2570T), Kribbella steрpae sp. nov. (type strain ВКМ Ас-2572T), Kribbella pratae sp. nov. (type strain ВКМ Ас-2574T), and Kribbella voronezhensis sp. nov. (type strain VKM Ас-2575T) with emended description of the genus Kribbella.
Transcriptome Analysis of Escherichia coli Dormant Cystlike Cells
Authors: Nikolaev Yu. A. , Loiko N. G. , Galuza O. A. , Mardanov A. V. , Beletskii A. V. , Deryabin D. G. , Demkina E. V. , El’-Registan G. I.
Published: April 2024

Abstract—The transcriptome of Esherichia coli cystlike dormant cells was investigated. RNA content in a single dormant cell was 0.26 fg, i.e., 13.5 times less than in a cell of a growing culture. The presence of mRNA in E. coli dormant cells has not been reported previously. The pools of gene reads for the dormant and growing cells were characterized, as well as the differential expression of all genes, calculated according to the special algorithm considering the average mRNA amount in a single cell. The notion of the genes active in every cell of the population was introduced. In each cell of the dormant and growing E. coli population, such genes were represented by the transcripts of 21 and 16% of the genes, respectively. The revealed cell heterogeneity in the set of active genes is one of the reasons (and forms) of heterogeneity of bacterial populations. Sixty genes were revealed, for which activity increased twice or more during formation of E. coli dormant cells. These were the genes responsible for genome activity, structure and properties of the cell envelope, cell proliferation, stress adaptation, biofilm formation and functioning, and collective behavior, as well as the genes providing for survival of the cell population during germination of the dormant cells.
Collective and Quasi-Local Modes in the Optical Spectra of YB6 and YbB6 Hexaborides with Jahn–Teller Structural Instability
Authors: Sluchanko N. E , Zhukova E. S , Alyab'eva L. N , Gorshunov B. P , Muratov A. V , Aleshchenko Yu. A , Azarevich A. N , Anisimov M. A , Shitsevalova N. Yu
Published: April 2024

The broad-band reflection spectra of YB6 and YbB6 hexaborides with Jahn–Teller instability of the boron cage have been measured at room temperature. An optical conductivity analysis has revealed, along with the Drude electronic components, heavily overdamped collective modes, which are notable in YB6 for high dielectric contributions, Δε = 2000–5700. The fraction of nonequilibrium charge carriers in YB6, which is at the boundary of structural instability in the hexaboride family, reaches 85–90%, whereas this fraction in doped YbB6 semiconductor is not higher than 25%. It has been shown that unlike the predictions of the topological Kondo insulator model, the surface “metallization” in Yb2+B6 crystals can be explained by additional doping of a surface layer with Yb3+ ions.
On the Stability of Axisymmetric States in the Ginzburg–Landau Theory
Authors: Podolyak E. R
Published: April 2024

The stability of superconducting states with a trapped magnetic flux in a spherical sample is investigated. Superconductors with a finite value of the Ginzburg–Landau parameter are considered (in particular, type I superconductors for which the magnetic field distortion near the sample plays an important role). It is assumed that the sample size is not too large as compared to correlation length ξ(T), and the superconducting state is axially symmetric. The possibility of the existence of states with a trapped flux in zero external field is considered. The results are compared to those for a cylindrical sample.
Interaction of Two Charged Dielectric Spheres with a Point Charge
Authors: Rodin M. M , Filippov A. V
Published: April 2024

We consider the problem of interaction of three charged particles, the size of one of which can be disregarded. The equations for the expansion coefficients of the electric field potential are derived using the method of expansion in spherical harmonics. Expressions are obtained for the Cartesian components of the interaction force and the torque due to this force. It is shown that in spite of the axial symmetry breaking after the addition of the third particle, if the free charge is distributed uniformly over the surface of a spherical particle, all vector components of the torque acting on this particle are equal to zero. By separating the contributions from image charges in explicit form, we have derived the expressions for the surface charge density and the force of interaction of the particles. The conditions for the emergence of attraction between similarly charged spherical particles depending on the position of the point particle are investigated.
Dynamic Transformation of Domain Walls in Chiral Ferrimagnets
Authors: Kulagin N. E
Published: April 2024

The dynamics of domain walls in ferrimagnets in which spatial dynamics invariance is violated because of the presence of the chiral Dzyaloshinskii–Moriya interaction with energy linear in sublattice spin density gradients is investigated theoretically. Analysis is performed based on numerical integration of equations in the sigma model generalized to the case of a ferrimagnet near the sublattice spin compensation point. It is shown that in contrast to conventional or chiral ferromagnets, chiral ferrimagnets can exhibit effects of dynamic transformation of the domain wall structure with the formation of more complex walls with a nonmonotonic behavior of the spin density in a wall upon an increase in the wall velocity. These effects are possible in a quite narrow neighborhood of the compensation point, and the width of this region increases upon an increase in the Dzyaloshinskii–Moriya interaction constant.
On Galvanomagnetic Properties of the 2D Rayleigh Model
Authors: Balagurov B. Ya
Published: April 2024

periodic arrangement of circular inclusions) with the metal–insulator phase transition are considered. The expression obtained for the corresponding effective conductivity tensor σ^e is valid in the entire subthreshold critical region (up to the contacts of circles) in the vicinity of the transition point. The behavior of components of tensor σ^e in weak and strong magnetic fields is determined.
Entropy of Coherent States of Optical Fields
Authors: Eskanderi M. M , Kilin S. Ya , Khoroshko D. B
Published: April 2024

We consider statistical mixtures of two and three arbitrary coherent states that are the states of a data carrier in an optical communication channel. The eigenvalues and eigenvectors of the corresponding density operators are obtained in analytic form. For this purpose, an original parameterization of triangles on the complex phase plane is introduced. Analytic expressions are obtained for the von Neumann entropy of mixtures of two and three arbitrary coherent states, and its maximal value for a given average number of photons is calculated. It is found that the use of three coherent states for a given average number of photons ensures a larger capacity of an optical communication channel as compared to two states.
Solar Cosmic Ray Acceleration by a Shock Wave in the Lower Solar Corona on May 7, 1978
Authors: Taneev S. N
Published: April 2024

Based on the theory of diffusive shock acceleration of charged particles, we have theoretically studied the spectra of protons produced by a shock wave driven by a coronal mass ejection (CME) in the lower solar corona with known solar plasma parameters for the solar cosmic ray (SCR) event recorded near the Earth’s orbit on May 7, 1978 (ground level enhancement no. 31, GLE31) using numerical methods. The proton flux data from the CPME instrument installed on the IMP-8 spacecraft and the worldwide network of ground-based neutron monitors combined with the particle measurements by the telescopes on the IMP-7 and IMP-8 satellites have been used to analyze the event. In our calculations, to satisfactorily reproduce the proton spectrum measured at the Earth’s orbit, the CME velocity was assumed to be constant and equal to 600 km s–1. The shock acceleration of SCRs proceeded up to 1.4 R⊙ solar radii for 256 s.
Pure Spin Current Injection into a Helimagnet
Authors: Yasyulevich I. A , Bebenin N. G , Ustinov V. V
Published: April 2024

The injection of a pure spin current into a conducting helimagnet is investigated. The characteristic decay lengths for the spin current injected into the helimagnet are determined, and their physical meaning is described. It is shown that instead of the spin diffusion length, helimagnets are characterized by the decay length that is always smaller than the spin diffusion length, the difference in these lengths being determined by the ratio of the helimagnet spiral period to the spin diffusion length. We predict the existence of the “effect of the chiral polarization of a pure spin current,” i.e., the emergence of the spin current with longitudinal (transverse) polarization, which depends on the spiral chirality, upon the injection of a pure spin current with the transverse (longitudinal) polarization relative to the spiral axis.
Calibration of Troitsk Nu-Mass Detector Readout Electronics by Signal Digital Filters
Authors: Abdiganieva S. B , Berlev A. I , Bochkov M. A , Likhovid N. A , Pantuev V. S , Zadorozhnyy S. V
Published: April 2024

We present the results of tuning and calibration of the detector electronics in the signal digitization mode. The goal of the experiment is to search for a possible sterile neutrino signature in tritium beta-decay. The read-out electronics work in direct oscilloscope mode, which requires to optimize time frame the with the goal to minimize noise and energy resolution. We use a 7-pixel silicon drift detector (SDD) and a CMOS charge sensitive preamplifier with very low integration capacitor. Amplifier forms a slowly rising output shape and operates in pulse-reset mode. The 125 MHz ADC digitizes the signals. Using calibration data from Fe55 and Am241 gamma sources we check triangular and trapezoid digital filters to obtain the best noise and energy resolution performance. We are also examining the option to differentiate the output signal.
Influence of Structural Parameters on the Electronic Structure of Topological Surface States in MnBi2Te4
Authors: Makarova T. P , Shikin A. M , Eryzhenkov A. V , Tarasov A. V
Published: April 2024

Experimental investigations of antiferromagnetic topological insulator MnBi2Te4 have shown that the energy gap in samples may vary in a wide range. Since the energy gap is a key parameter of this system when used in developing new functional electronic devices, the reason for variation of the MnBi2Te4 energy gap at the Dirac point and its possible interrelation with magnetic interactions are matters of great importance and call for thorough analysis. To elucidate factors influencing the energy gap, we analyzed the variation of the electronic structure of the given topological insulator with surface van der Waals gap. Calculation data have shown that the energy gap at such structure modifications may vary in a wide range from 80–88 meV to 4–5 meV because of an intense spatial redistribution of topological surface states between septuple-layer MnBi2Te4 blocks with oppositely directed Mn magnetic moments. Our results suggest that the spatial localization of topological surface states is a primary factor governing the value of the energy gap, this localization being strongly dependent on structure modifications on the crystal surface.
Ionization transition rates in the intermediate regime of the Keldysh parameter for a (0,1)*LG spiral amplitude modulated laser field
Authors: Miladinović T. B , Simić S. , Danilović N.
Published: April 2024

The mechanisms of the tunnel and multiphoton ionization transitions of hydrogen-like atoms and noble gas atoms are discussed. Atoms potassium and argon, with ionization energy of 4.34 and 15.76 eV, were chosen as the target. The atoms are exposed to Ti:Sapphire, (0,1)*LG, spiral amplitude modulated, laser beam at λ = 800 nm wavelength in a broad intensity range 1012 to 1015 W/cm2. The computational approach to describe tunnel and multiphoton processes was based on using the ADK theory. Stark and ponderomotive effects are also included to study their influence on the transition rate. Obtained results show that, for the lower γ values, the contribution of multiphoton ionization was less significant than the tunnel ionization contribution. In comparison, for higher γ values, multiphoton ionization dominated over tunnel ionization in a total transition rate. It is found that, in this particular case of spiral amplitude modulated mode, the intermediate regime, where both processes equally contribute, strongly depends on the atom selection and laser field intensity. Ionization in the intermediate regime occurs for γ ≈ 10 and 12 for low laser intensities, as γ ≈ 2 and 2.5 for the higher values, in the case of potassium and argon respectively. Our analysis indicated that the Stark and ponderomotive effects have a significant influence on the total transition rate. It is shown that these effects decrease the transition rate value and move the intermediate regime’s position toward lower values of the γ parameter, mainly in the case of higher laser field intensity.
Influence of Impurities on the Oxygen Adsorption on the Ti5Si3(0001) Surface
Authors: Bakulin A. V , Chumakova L. S , Kul'kova S. E
Published: April 2024

The influence of simple and transition metal impurities, as well as interstitial impurities (B, C, and N), on the oxygen adsorption on the Ti5Si3 titanium silicide surface has been studied using the of projector augmented wave method within the electron density functional theory. It has been shown that titanium-substituting impurities belonging to the latter halves of the 3d–5d periods cause most significant changes in the adsorption energy. In addition, simple metals and interstitial impurities reduce the oxygen–surface interaction. By analyzing local electron densities of states, charge density difference distribution, charge transfer, and the overlap population of oxygen bonds to nearest-neighbor atoms, we have revealed special aspects of impurity influence on chemical bonding between the titanium silicide surface and oxygen. Factors responsible for an increase/decrease in the adsorption energy of oxygen on the doped surface are discussed. A correlation between the change in adsorption energy and the electronegativity of impurities has been found.
Acoustic Solitons in Helicoids and Spiral Graphene Nanoribbons
Authors: Savin A. V , Savina O. I
Published: April 2024

The dynamics of local regions of longitudinal compression in graphene helicoids and spiral carbon nanoribbons has been numerically simulated. It has been shown that a supersonic acoustic soliton can constantly move without radiation of phonons only in helicoids with transverse radius R 0.62 nm. Dimensionless velocity s of the soliton in this case falls into the interval 1.0–1.4. In larger radius helicoids and all spiral carbon nanoribbons, the motion of a soliton-like excitation is always accompanied by the intense radiation of phonons (the more the size of the spiral structure, the more intense the radiation).