bluuebunny/crossref_metadata_2025 huggingface dataset:
FREE SURFACE TWO-DIMENSIONAL PERIODIC DISTURBANCES IN VARIOUS MODELS OF THE FLUID
Authors: Chashechkin Yu. D. , Ochirov A. A.
Published: April 2024

The complete dispersion relations of a flat free surface periodic perturbations with a positive definite frequency and a complex wavenumber taking into account spatial attenuation in a viscous stratified charged liquid were obtained in a linear approximation for the first time by methods of the theory of singular perturbations. Regular components of the complete solution describe plane gravitational-capillary waves. Singular components characterize ligaments – thin flows that are absent in the model of an ideal medium. The obtained dispersion relations in extreme cases uniformly transform into known expressions for inviscid stratified, viscous homogeneous and ideal liquids. The calculated dependencies of the wavelength and thickness of the ligament, the group and phase velocity of the components on the frequency at different values of the media parameters are given.
THE EFFECT OF ACCELERATED ABSORPTION OF LIQUID IN A TUBE DURING LASER CAVITATION ON A LASER HEATING ELEMENT
Authors: Chudnovskii V. M. , Guzev M. A. , Dats E. P. , Kulik A. V.
Published: April 2024

The expansion and collapse of a cavitation bubble during laser heating and subcooled boiling of water in the vicinity of the tip of an optical fiber (laser heating element) installed in a water-filled glass tube with two open ends is studied experimentally and numerically. Cavitation, initiated by continuous laser radiation, is accompanied by the pushing and pulling movement of the heated liquid in the tube and outside it. For the first time, it has been shown that in a tube with an installed laser heating element in a liquid flow moving behind the walls of the bubble, when it collapses at the pole of the bubble surface remote from the end, a liquid jet appears, directed through the bubble to the end of the optical fiber. The jet speeds up the process of sucking liquid into the tube.
CURRENT TRENDS IN THE DEVELOPMENT OF HIGH-ENERGY LASERS
Authors: Garanin S. G. , Derkach V. N. , Makarov K. N. , Ostrovskiy V. A. , Pergament M. I. , Putilin M. V. , Sizmin D. V.
Published: April 2024

Current trends in developing high-energy lasers with pulse energies in the tens and hundreds of joules are considered. Active media are analyzed for their use in such lasers. Yb:YAG active crystalline and ceramic elements (AE) of Russian production are experimentally investigated at temperatures from 100 K to 295 K. The data of the AE cryogenic cooling system are presented. A diode pumping system for AE and a homogenizer of its radiation are described. The physical and technical characteristics of the pumping system are given. Fresnel losses, absorption losses, and losses due to amplified spontaneous emission (ASE), which reduce the energy stored in an inverted population, are experimentally measured. The results of measuring the gain in multipass circuits with different sets of AEs are presented.
DIFFUSION COMBUSTION OF A HYDROGEN MICROJET, OUTFLOWING FROM A CURVLINEAR CHANNEL
Authors: Kozlov V. V. , Dovgal A. V. , Litvinenko M. V. , Litvinenko Yu. A. , Shmakov A. G.
Published: April 2024

The presented work examines the combustion of a hydrogen microjet flowing from a curved channel with a round micronozzle. Jet flows that are generated using rectilinear and curved channels differ in that in the second case, Dean vortices make a noticeable contribution to the formation of the jet and its combustion. The interaction of the latter with Kelvin–Helmholtz vortices, the formation of which is typical for flows with a velocity shift, causes changes in combustion characteristics. They include spatial distortions of the laminar flame zone near the nozzle exit, the area of turbulent combustion downstream, as well as the turbulent flame in the conditions of its separation from the nozzle exit and the cessation of laminar combustion in the initial section of the flow. The results of these studies provide an opportunity to better understand the combustion features of hydrogen microjets under conditions of their hydrodynamic instability.
SYNTHESIS OF 5,5-DISUBSTITUTED N-METHYL-1,3-OXAZINANES CONTAINING MONOTERPENE FRAGMENTS
Authors: Nechepurenko I. V. , Volcho K. P. , Salakhutdinov N. F.
Published: April 2024

A new method for the synthesis of 5,5-disubstituted N-methyl-1,3-oxazinanes as a mixture of diastereomers at position 5 containing monoterpene and branched alkyl substituents at position 5 has been developed. The 1,3-oxazinanes were obtained for the first time by the interaction of 2,2-substituted 3-aminopropane-1-ols with formaldehyde and sodium borohydrides in a single stage.
A COMPLEX APPROACH TO THE UTILIZATION OF ORGANOCHLORINE COMPOUNDS IN TERMS OF VINYL CHLORIDE PRODUCTION WASTES
Authors: Mishakov I. V. , Bauman Y. I. , Diachkova S. G. , Potylitsyna A. R. , Vedyagin A. A.
Published: April 2024

The concept of a complex catalytic processing of organochlorine production wastes using self-organizing nickel-based catalysts is proposed. Using 1,2‑dichloroethane as a model compound, the process of carbon erosion of a bulk Ni‑Cr alloy with the formation of dispersed particles catalyzing the growth of carbon nanofibers has been studied. This approach was found to be versatile and applicable for the processing of multicomponent mixtures of chlorine-substituted hydrocarbons, including the real wastes of polyvinyl chloride production. The prospects of using the carbon nanomaterial obtained from chlorine-containing waste to produce polymer composites are discussed.
SYNTHESIS OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE WITH HIGH MELTING POINT IN OCTAFLUOROBUTANE MEDIUM
Authors: Rasputin N. A. , Vlasov I. A. , Yakovlev S. V. , Artem’ev G. A. , Nikonov I. L. , Kopchuk D. S. , Matern A. I. , Charushin V. N.
Published: April 2024

Ultra-high molecular weight polyethylene (UHMWPE) with a high melting point (Tm) up to 144°C was successfully obtained by suspension polymerization in 1,4-H-octafluorobutane medium initiated by Ziegler–Natta catalysts. This method makes it possible successfully to carry out polymerization at a temperature close to ambient one and an ethylene pressure close to atmospheric one. The resulting polyethylenes were characterized by IR spectroscopy, elemental analysis and derivatographic studies. Values of melting points and degrees of crystallinity of the synthesized polymers were obtained using these data.
IONIC LIQUIDS – NEW GAS CHROMATOGRAPHIC PHASES WITH UNIQUE PROPERTIES. A REVIEW
Authors: Shashkov M. V. , Sidelnikov V. N. , Parmon V. N.
Published: April 2024

A necessary and the most difficult element in the study of many chemical processes is a reliable chemical analysis of both the initial reagents and the products of their transformation. One of the most common methods for such analysis is a capillary gas chromatography, which, unfortunately, has a number of limitations. The limitations include, for example, the low thermal stability of high polarity stationary liquid phases (SLF). A way to overcome this limitation is the use of ionic liquids (IL) as SLF. In this review, we focus on the use of liquid phases based on ILs with cations of various chemical classes. The properties of such phases are considered from the point of view of their possible chromatographic selectivity, and examples of the use of columns with ILs for solving specific analytical problems are given. The properties of currently available commercial columns where ILs are used as the phases are discussed.
PREPARATION OF NEW HARD ELASTIC POLYMERIC MATERIAL BASED ON ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE
Authors: Аrzhakova О. V. , Yarusheva А. Yu. , Nazarov A. I. , Dolgova А. А. , Volynskii A. L.
Published: April 2024

A novel approach for the preparation of hard elastic polymeric material based on ultra-high molecular weight polyethylene via the strategy of crazing of polymers has been proposed. This approach includes the process of deformation of the pristine films of ultra-high molecular weight polyethylene via environmental intercrystallite crazing mechanism and subsequent low-temperature spontaneous strain recovery upon stress relaxation. As a result, the material acquires new properties typical for hard elastic materials: restoration of the porous structure upon secondary loading in air up to ~20 vol. % with pore sizes in the nanometer range (up to 10 nm), high reversibility of deformation (50−85%), the effect of opening and closing pores upon cyclic loading. The mechanism of this phenomenon has been proposed and the areas of practical applications of such mechanoresponsive material have been indicated.
HETEROGENEOUS-CATALYTIC PROCESSES OF OXIDATIVE DESULFURIZATION WITH IONIC LIQUIDS PARTICIPATION. A REVIEW
Authors: Tarkhanova I. G. , Bryzhin A. A. , Akopyan A. V. , Anisimov A. V. , Karakhanov E. A.
Published: April 2024

The review analyzes recent publications about the search for new effective desulfurization technologies, in particular, oxidative desulfurization using ionic liquids. This technology is attracting attention due to its relatively mild conditions compared to hydrodesulfurization and its efficiency in removing heavy sulfur derivatives. Particularly effective are solid hybrid compositions consisting of a support (adsorbent) coated with an ionic liquid layer (extractant) containing catalytically active centers. Examples of the use of such systems for the desulfurization of model fuel and real oil feedstock are considered.
Y-SHAPED FLUOROPHORES BASED ON N(2)-ARYL-1,2,3-TRIAZOLES: SYNTHESIS, THEORETICAL CALCULATIONS, OPTICAL PROPERTIES, AND APPLICATION OPPORTUNITIES FOR DETECTION OF NITROAROMATICS
Authors: Lavrinchenko I. A. , Moseev T. D. , Varaksin M. V. , Seleznev Y. A. , Sadieva L. K. , Zyryanov G. V. , Tsmokaluk A. N. , Charushin V. N. , Chupakhin O. N.
Published: April 2024

A five-stage method for the synthesis of Y-shaped push-pull fluorophores based on 2-(4′-methoxyphenyl)-1,2,3-triazole has been described. These molecules proved to possess emission in the range from 350 to 450 nm and high quantum yields QY 90–99% in solvents of various polarity. An opportunity of using the obtained compounds as chemosensors for both aromatic and aliphatic nitroanalytes at concentrations from 300 ppb has been elucidated.
STABILITY OF Pd/C CATALYSTS IN SOLVENTS FOR ORGANIC SYNTHESIS
Authors: Galushko A. S. , Ilyushenkova V. V. , Burykina Yu. V. , Shaidullin R. R. , Pentsak E. O.
Published: April 2024

In this work, we consider the effect of carbon supports and methods of preparing Pd/C catalysts on the ability of palladium-containing particles to leach out into solution during the interaction of a catalyst with a solvent. The leaching of palladium particles from the substrate surface into pure solvents was studied by high resolution mass spectrometry. It is shown that the type of leached palladium particles formed in the solution depend not only on the solvent, but also on the method of catalyst preparation and on the nature of the support. It has been found that the use of phosphorus-doped carbon (PC) as a support also results in palladium being leached into solution. In addition, the catalytic activity of the catalysts supported on graphite and PC equally decreased both in the Suzuki–Miyaura reaction and in the Mizoroki–Heck reaction.
CHIRAL N-(OCTAHYDRO-2H-CHROMEN-4-YL)-2-(DIALKYLAMINO)ACETAMIDES: SYNTHESIS AND ANALGESIC ACTIVITY
Authors: Li-Zhulanov N. S. , Nikolaichuk K. M. , Gatilov Yu. V. , Volcho K. P. , Khvostov M. V. , Tolstikova T. G. , Salakhutdinov N. F.
Published: April 2024

Based on monoterpenoid (–)-isopulegol a number of new derivatives of octahydro-2H-chromene have been synthesized. The structure of the products obtained was determined by 1H and 13C NMR spectroscopy, high resolution mass spectrometry and X-ray diffraction analysis. It was shown that several synthesized compounds exhibit high analgesic activity in in vivo tests. The highest efficiency in both tests (acetic writhing and hot plate) was shown by (4S)-diastereomers of morpholinoacetamide derivatives of octahydro-2H-chromene.
METHYLATION AND AMINATION OF 4H-[1,2,3]TRIAZOLO[4,5-c][1,2,5]OXADIAZOLE SALTS
Authors: Balabanova S. P. , Voronin A. A. , Churakov A. M. , Klenov M. S. , Tartakovsky V. A.
Published: April 2024

The methylation and the amination of 4H-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole salts (K+, Ag+, Et3NH+, DBUH+) were studied for the first time. It is shown that two methylated products are formed in the reaction. In the case of K- and Et3N-salts, 4- and 5-methylated isomers are formed in equal proportions, and in the case of Ag- and DBU-salts, the main product is the 4-isomer. It was found that the main product of amination of both 4H-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole K- and DBU-salts with O-(p-tolylsulfonyl)hydroxylamine is 4-azido-3-amino-1,2,5-oxadiazole. The mechanism of its formation as a result of rearrangement of 5-amino-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole is proposed.
DISJOINING PRESSURE IN THIN SPHERICAL LIQUID FILMS AND VAPOR LAYERS WITH MOLECULAR CORRELATIONS INCLUDED
Authors: Shchekin A. K. , Gosteva L. A.
Published: April 2024

Based on the expression for a grand thermodynamic potential as a molecular density functional, disjoining pressures in thin liquid films around nanosized wettable spherical particles and in thin vapor layers around nonwettable particles are calculated depending the degree of lyophilicity, film thickness and particle size. A characteristic feature of the approach is the full consideration of hard-sphere molecular correlations according to the fundamental measure theory in the density functional method and finding the complete dependence of the grand thermodynamic potential of the system on stable droplet or bubble size. Although the obtained results show a qualitative agreement between the new calculated disjoining pressure dependences and those obtained by us earlier in the framework of a simpler gradient method of the molecular density functional, the new results differ significantly quantitatively. It is confirmed that the disjoining pressure in the liquid film around nanosized lyophilic particle grows with the particle radius and lyophilicity.
CONTROLLED RADICAL POLYMERIZATION OF LAURYL METHACRYLATE IN THE BASE SYNTHETIC POLYALPHAOLEFIN OIL
Authors: Chernikova E. V. , Pavlova M. S. , Plutalova A. V. , Litmanovich E. A. , Maksimov A. L.
Published: April 2024

Controlled radical polymerization of lauryl methacrylate in the base polyalphaolefin oil was performed first in the presence of 2-cyano-2-propyl dodecyl trithiocarbonate. It has been shown that polymerization proceeds to high monomer conversions and leads to the formation of a polymer with a narrow molecular weight distribution. At the same time, the reaction mixtures retain their transparency after polymerization is completed. The synthesized polymers have a thickening ability, which naturally increases with an increase in their number average molecular weight.
QUANTIZATION OF ELECTRICAL CONDUCTANCE IN LAYERED Zr/ZrO2/Au MEMRISTIVE STRUCTURES
Authors: Vokhmintsev A. S. , Petrenyov I. A. , Kamalov R. V. , Karabanalov M. S. , Weinstein I. A. , Rempel A. A.
Published: April 2024

Anodic zirconia nanotubes are a promising functional medium for the formation of non-volatile resistive memory cells. The current-voltage characteristics in the region of low conductivity of the fabricated Zr/ZrO2/Au memristor structures have been studied in this work. For the first time, the reversible mechanisms of formation/destruction of single quantum conductors based on oxygen vacancies, which participate in processes of multiple resistive switching between low- and high-resistance states in a nanotubular dioxide layer, have been analyzed. An equivalent electrical circuit of a parallel resistor connection have been proposed and discussed to describe the observed memristive behavior of the studied layered structures.
ONE-POT SYNTHESIS OF NORBORNENE-CYCLOOCTENE COPOLYMERS
Authors: Gringolts M. L. , Marchenko A. S. , Peregudov A. S. , Denisova Yu. I. , Kudryavtsev Y. V.
Published: April 2024

The one-pot synthesis of random multiblock copolymers of norbornene and cyclooctene has been performed for the first time. It is shown that the first generation Grubbs Ru-carbene complex makes it possible to obtain these copolymers directly from monomers. In the course of one-pot synthesis, the metathesis polymerization of norbornene, which has a markedly higher ring strain, occurs first. Then, cyclooctene polymerizes and simultaneously an interchain cross-metathesis reaction takes place, during which the block structure of the copolymer is formed. Compared to the previously studied interaction of polynorbornene and polycyclooctene, the one-pot method makes it possible to obtain copolymers with a higher molar mass at a lower catalyst consumption.
COMPUTER SIMULATION OF BIPHASIC CATALYTIC PROCESS IN PRESENCE OF POLYMER MICROGELS
Authors: Gumerov R. A. , Anakhov M. V. , Potemkin I. I.
Published: April 2024

Dissipative particle dynamics were used for the first time to simulate the reaction of biphasic catalysis with microgels adsorbed at the phase boundary with catalytic groups. It is shown that the rate of the catalytic process increases with the degree of deformation of the polymer network, which depends on the amount of the crosslinker and the solubility of the polymer in both phases. In this case, the highest rate of catalysis was observed for the microgel soluble in both phases due to an increase in its porosity (compared to amphiphilic microgels) and the “water–microgel–oil” contact area with a simultaneous decrease in the time for reagents to reach the catalytic groups due to the flattening of the microgel. The results obtained can be useful for increasing the efficiency of a wide range of catalytic reactions of the considered type through the use of network macromolecules.
STEARIN AS A STARTING MATERIAL FOR THE SYNTHESIS OF BIOLOGICALLY ACTIVE IONIC LIQUIDS
Authors: Seitkalieva M. M. , Vavina A. V. , Strukova E. N.
Published: April 2024

For the first time, the possibility of using widely available stearin for the production of fatty acid-derived ionic liquids (ILs) has been shown. New amphiphilic ILs based on imidazolium, pyridinium, and quaternary ammonium cations containing long-chain alkyl substituents were obtained. The synthesized compounds are shown to have biological activity comparable to known antimicrobial compounds. ILs with one alkyl substituent have higher cytotoxicity and antimicrobial activity compared to disubstituted derivatives.
SYNTHESIS OF NEW POLYFUNCTIONAL CYCLIC KETALS BASED ON SUBSTITUTED 4-METHYLENE-1,3-DIOXOLANES
Authors: Borisova Yu. G. , Raskildina G. Z. , Belyaeva E. R. , Musin A. I. , Sultanova R. M. , Zlotskii S. S.
Published: April 2024

Methods for the preparation of new polyfunctional heterocyclic compounds based on the addition dichlorocarbene and ethanol to the terminal double bond of 2,2-disubstituted 4-methylene-1,3-dioxolanes, as well as on hydrogenation and ozonolysis of this bond, are proposed.
SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF HIGH-ENTROPY CARBIDES IN THE REGIME OF A GASLESS THERMAL EXPLOSION
Authors: Vergunova Yu. S. , Vadchenko S. G. , Kovalev I. D. , Kovalev D. Yu. , Rogachev A. S. , Alymov M. I.
Published: April 2024

High-entropy carbides are a new class of inorganic compounds promising for a wide range of applications. The paper presents a new concept for the synthesis of powders of high-entropy carbides by the method of self-propagating high-temperature synthesis (SHS) in the gasless thermal explosion mode from previously mechanically synthesized and structured reaction mixtures. For the first time, high-entropy carbides TaTiNbVWC5 and TaNbVMoWC5 were obtained by this method, their crystal structure was determined, which was compared with similar compositions obtained by sintering.
INFORMATION ENTROPY OF CATALYTIC REACTION
Authors: Zimina A. D. , Tukhbatullina A. A. , Sabirov D. Sh.
Published: April 2024

The indices based of information entropy are widely used as structural descriptors in chemistry. The change in information entropy in a chemical reaction is calculated as the deference between the values that correspond to the ensemble of products and ensemble of reactants. For the generalized scheme of a catalytic reaction, we derived the analytical expressions that connect its information entropy with the parameters of separate stages and corresponding summative equation. As found, the sum of the parameters of separate stages is proportional to the information entropy change in the formal non-catalytic reaction, and the fraction of the atoms of reacting (forming) molecules in the ensemble of initial substances (or products).
SYNTHESIS AND ANTIVIRAL ACTIVITY OF COPOLYMERS OF OXYCINNAMIC ACID WITH N-VINYLAMIDES
Authors: Nesterova N. А. , Shtro А. А. , Panarin Е. F.
Published: April 2024

Radical copolymerization of coumarin with N-vinylamides (N‑vinylpyrrolidone, N-methyl-N-vinylacetamide, N-vinylformamide) was used to prepare copolymers of various natures and varied molecular masses. After the subsequent reactions in polymer chains, water-soluble copolymers of salts of oxycinnamic acid and its hydrazides were obtained. The synthesized copolymers of salts and hydrazides of oxycinnamic acid with N-vinylamides have low cytotoxicity and demonstrate the pronounced antiviral activity against human respiratory syncytial virus (strain A2).
MONOCATIONIC CHLORIN PHOTOSENSITIZER FOR EFFICIENT PHOTOINACTIVATION OF ANTIBIOTIC RESISTANT GRAM-NEGATIVE MICROORGANISMS
Authors: Kustov A. V. , Kukushkina N. V. , Lyalyakina E. V. , Solomonova N. N. , Gagua A. K. , Koifman O. I. , Berezin D. B.
Published: April 2024

We propose a monocationic chlorin photosensitizer for antimicrobial photodynamic therapy of superficial localized infections. The antimicrobial activity of this specie towards planktonic forms of nosocomial anti-biotic resistant pathogens, viz. Pseudomonas aeruginosa, Enterobacter cloacae и Acinetobacter baumannii was studied and compared with the activity of the well-established photosensitizer “Fotoran e6”. Our results do indicate that monocationic chlorin provides efficient photoinactivation of all the three microorganisms and can be considered as a new agent for antimicrobial photodynamic therapy.
CITRUS PECTIN COMPLEXES WITH NIFEDIPINE: PREPARATION AND PHYSICOCHEMICAL PROPERTIES
Authors: Minzanova S. T. , Chekunkov E. V. , Khabibullina A. V. , Arkhipova D. M. , Mironova L. G. , Hamatgalimov A. R. , Milyukov V. A. , Mironov V. F.
Published: April 2024

The formation of stable complexes of pectin polysaccharides with the hypotensive drug “Nifedipine” was confirmed by IR and UV spectroscopy, their stoichiometry was determined and the conditions of their production were optimized. Peculiarities of thermal decomposition of pectin and synthesized complexes with nifedipine were studied by TGA/DSC method. The results obtained are a scientific basis for the creation of a new water-soluble non-toxic dosage form of nifedipine, which will significantly expand the use of the drug in medicine.
NEW CONCEPTS OF COLLOID SCIENCE: NANO-ADSORBENT AND PROTOMICELLE
Authors: Rusanov A. I. , Movchan T. G. , Plotnikova E. V.
Published: April 2024

Large molecules of dyes or other substances can play the role of a nano-adsorbent in aqueous surfactant solutions and, coated with surfactant molecules, resemble surfactant micelles with a solubilizate. Such micelle-like particles were called protomicelles. Their formation does not require a critical micelle concentration (CMC) and begins immediately when the surfactant is introduced into the solution. In this spectrophotometric study of Nile red (NR) in aqueous solutions of nonanoic acid (NOA), the case where protomicelles are more important than micelles is demonstrated for the first time. It has been shown that the solubilization of NR in both premicellar and micellar solutions proceeds through protomicelles rather than NOA micelles. The article also contains a theoretical part. In it, on the basis of the chemical potential of the nano-adsorbent, it is proved that the addition of a surfactant to a solution always increases the solubility of the nano-adsorbent. The dependence of adsorption on the curvature of the nano-adsorbent surface is considered and it is shown that the adsorption equations for flat surfaces can be used for curved surfaces with high accuracy.
STRUCTURAL DESIGN OF Eu2+-CONTAINING GLASS AND GLASS-CERAMICS BASED ON THE SYSTEM BaO–ZrO2–SiO2–MgF2 FOR LED APPLICATION
Authors: Evstropiev S. K. , Stolyarova V. L. , Kyazyan N. B. , Manukyan G. G. , Shashkin A. V.
Published: April 2024

For the first time, an approach to designing the structure of Eu2+ containing silicate glass-ceramics materials has been experimentally implemented, which consists in the fact that rare earth activator is introduced into various crystals formed during glass crystallization. Transparent Eu-containing glass and glass ceramics based on the system BaO–ZrO2–SiO2–MgF2 were prepared by the traditional glass melting method at 1450°C. The crystal structure and properties of materials were characterized by XRD analysis and photoluminescence spectroscopy during different stages of glass crystallization. It is shown that the simultaneous incorporation of Eu into different silicate crystals (Ba2SiO4, BaMgSiO4, and BaSiO3) formed during the glass crystallization leads to the formation of a material with a wide luminescence band in the visible part of the spectrum. The study of photoluminescence and luminescence excitation spectra of the glass suggests the possibility of energy transfer from Eu2+ to Eu3+ ions. The structures of Eu2+ luminescent centers are similar in the glass and glass-ceramics that is related to some phase separation in the glass before crystallization. The study of luminescence properties of prepared materials showed that these materials can be promising for the application in LEDs techniques.
A NEW STRATEGY FOR THE SYNTHESIS OF HIGHLY ACTIVE CATALYSTS BASED ON g-C3N4 FOR THE PHOTOCATALYTIC PRODUCTION OF HYDROGEN UNDER VISIBLE LIGHT
Authors: Potapenko K. O. , Cherepanova S. V. , Kozlova E. A.
Published: April 2024

In this work, materials based on graphite-like carbon nitride were synthesized by thermal treatment of a mixture of melamine and urea and the effect of synthesis conditions on the photocatalytic activity of the samples was studied. As a cocatalyst, platinum (1 wt. %) was deposited on the surface of the synthesized g‑C3N4 samples. The photocatalysts were characterized by X-ray phase analysis, diffuse reflectance UV-vis spectro-scopy in the UV and visible range, and low-temperature nitrogen adsorption. Photocatalytic activity was determined in the reaction of hydrogen evolution from an aqueous solution of triethanolamine (10 vol. %) under visible light irradiation (λ = 425 nm). The optimal conditions for the synthesis of the photocatalyst 1% Pt/g-C3N4, obtained by calcination of a mixture of melamine and urea (1 : 3), were found, using which the rate of H2 evolution was 5.0 mmol g–1 h–1 with an apparent quantum efficiency of 2.5%. The developed synthetic approach makes it possible to obtain highly active catalysts due to the formation of an intermediate supramolecular melamine-cyanuric acid complex during the synthesis, which, upon further heating, turns into g-C3N4, which is characterized by a high specific surface area exceeding 100 m2 g–1.
CONCENTRATION TETRAHEDRON OF THE Li–Mn–Eu–O SYSTEM
Authors: Buzanov G. A. , Nipan G. D.
Published: April 2024

Based on fragmentary experimental data, an isothermal concentration tetrahedron of the Li–Mn–Eu–O system was constructed for the first time by the method of topological modeling, which describes possible solid-state transformations in the system occurring at a constant temperature with a change in pressure. Thirty-two equilibria involving four crystalline phases have been identified.
ON HIGHER INTEGRABILITY OF THE GRADIENT OF SOLUTIONS TO THE ZAREMBA PROBLEM FOR p-LAPLACE EQUATION
Authors: Alkhutov Yu. A. , D’Apice C. , Kisatov M. A. , Chechkina A. G.
Published: April 2024

A higher integrability of the gradient of a solution to the Zaremba problem in a bounded Lipschitz plane domain is proved for the inhomogeneous p-Laplace equation.
ON INTERPRETATIONS OF PRESBURGER ARITHMETIC IN BÜCHI ARITHMETICS
Authors: Zapryagaev A. A.
Published: April 2024

Büchi arithmetics BAn, \(n \geqslant 2\), are extensions of Presburger arithmetic with an unary functional symbol \({{V}_{n}}(x)\) denoting the largest power of n that divides x. Definability of a set in BAn is equivalent to its recognizability by a finite automaton receiving numbers in their n-ary expansion. We consider the interpretations of Presburger Arithmetic in the standard model of BAn and show that each such interpretation has an internal model isomorphic to the standard one. This answers a question by A. Visser on the interpretations of certain weak arithmetical theories in themselves.
ON OBTAINING INITIAL APPROXIMATION FOR FULL WAVE INVERSION PROBLEM USING CONVOLUTIONAL NEURAL NETWORK
Authors: Petrov I. B. , Stankevich A. S. , Vasyukov A. V.
Published: April 2024

The paper considers the problem of choosing the initial approximation when using gradient optimization methods for solving the inverse problem of restoring the distribution of velocities in a heterogeneous continuous medium. A system of acoustic equations is used to describe the behavior of the medium, and a finite-difference scheme is used to solve the direct problem. L-BFGS-B is used as a gradient optimization method. Adjoint state method is used to calculate the gradient of the error functional with respect to the medium parameters. The initial approximation for the gradient method is obtained using a convolutional neural network. The network is trained to predict the distribution of velocities in the medium from the wave response from it. The paper shows that a neural network trained on responses from simple layered structures can be successfully used to solve the inverse problem for a complex Marmousi model.
AN ANALOGUE OF MAHLER’S TRANSFERENCE THEOREM FOR MULTIPLICATIVE DIOPHANTINE APPROXIMATION
Authors: German O. N.
Published: April 2024

Khintchine’s and Dyson’s transference theorems can be very easily deduced from Mahler’s transference theorem. In the multiplicative setting an obstacle appears, which does not allow deducing the multiplicative transference theorem immediately from Mahler’s theorem. Some extra considerations are required, for instance, induction by the dimension. In this paper we propose an analogue of Mahler’s theorem which implies the multiplicative transference theorem immediately.
GRADIENT FLOWS IN THE SHAPE OPTIMIZATION THEORY
Authors: Plotnikov P. I. , Sokolowski J.
Published: April 2024

The identification problem of an inclusion is considered in the paper. The inclusion is unknown subdomain of a given physical region. The available information on the inclusion is governed by measurements on the boundary of this region. In particular, the single measurement problem of impedance electrotomography and other inverse problems are included in our approach. The shape identification problem can be solved by the minimization of an objective function taking into account the measurement data. The best choice of such objective function is the Kohn-Vogelius energy functional. The standard regularization of the Kohn-Vogelius functional include the perimeter and Willmore curvature functional evaluated for an admissible inclusion boundary. In the two-dimensional case, a nonlocal existence theorem of strong solutions is proved for the gradient flow dynamical system generated for such a regularization of the Kohn-Vogelius functional.
HIDDEN BOUNDARY OF GLOBAL STABILITY IN THE KAPRANOV CONJECTURE ON THE PULL-IN RANGE
Authors: Kuznetsov N. V. , Lobachev M. Y. , Mokaev T. N.
Published: April 2024

Within the framework of the development of the theory of hidden oscillations, the problem of determining the boundary of global stability and revealing its hidden parts corresponding to the non-local birth of hidden oscillations is considered. For a phase-locked loop with a proportional-integrating filter and a piecewise-linear phase detector characteristic, effective methods for determination of bifurcations of the global stability loss, for obtaining analytical formulas of the bifurcation values, and for constructing trivial and hidden parts of the global stability boundary are suggested.
MULTIDIMENSIONAL CUBATURES WITH SUPER-POWER CONVERGENCE
Authors: Belov A. A. , Tintul M. A.
Published: April 2024

In many applications, multidimensional integrals over the unit hypercube arise, which are calculated using Monte Carlo methods. The convergence of the best of them turns out to be quite slow. In this paper, fundamentally new cubatures with super-power convergence based on the improved Korobov grids and special variable substitution are proposed. A posteriori error estimates are constructed, which are practically indistinguishable from the actual accuracy. Examples of calculations illustrating the advantages of the proposed methods are given.
DYNAMICS OF SYSTEMS WITH ONE-SIDED DIFFERENTIAL CONSTRAINTS
Authors: Salnikova T. V. , Kugushev E. I. , Demidov A. A.
Published: April 2024

A dynamical system with constraints in the form of linear differential inequalities is considered. It is proved that in the general case, in the presence of such connections, the motion is shockless. The possibility of realizing such bonds by viscous friction forces is shown. An example of a nonholonomic system is given, for which, using numerical simulation, it is shown how, with an increase in the degree of anisotropy, the transition from a system with anisotropic viscous friction to a system with one-sided differential constraints occurs.
ON ATTRACTORS OF GINZBURG–LANDAU EQUATIONS IN DOMAIN WITH LOCALLY PERIODIC MICROSTRUCTURE. SUBCRITICAL, CRITICAL AND SUPERCRITICAL CASES
Authors: Bekmaganbetov К.А. , Tolemys A. A. , Chepyzhov V. V. , Chechkin G.А.
Published: April 2024

In the paper we consider a problem for complex Ginzburg–Landau equations in a medium with locally periodic small obstacles. It is assumed that on the obstacle surface one can have different conductivity coefficients. We prove that the trajectory attractors of this system converge in a certain weak topology to the trajectory attractors of the homogenized Ginzburg–Landau equations with an additional potential (in the critical case), without the additional potential (in the subcritical case) in a medium without obstacles, or simply disappear (in the supercritical case).
ESTIMATE FOR DOMAIN OF UNIVALENCE ON THE CLASS OF HOLOMORPHIC SELF-MAPS OF A DISC WITH TWO BOUNDARY FIXED POINTS
Authors: Goryainov V. V. , Kudryavtseva O. S. , Solodov A. P.
Published: April 2024

Holomorphic self-maps of the unit disc with two boundary fixed points, one of which is a Denjoy–Wolff point are investigated. An upper estimate for domain of univalence is obtained for functions in such class, which depends on the value of the angular derivative at the repulsive boundary fixed point.
INVARIANT FORMS OF GEODESIC, POTENTIAL, AND DISSIPATIVE SYSTEMS ON TANGENT BUNDLE OF FINITE-DIMENSIONAL MANIFOLD
Authors: Shamolin M. V.
Published: April 2024

As is well-known [1–3], finding a sufficient number of tensor invariants (not only the first integrals) allows you to accurately integrate a system of differential equations. For example, the presence of an invariant differential form of the phase volume makes it possible to reduce the number of required first integrals. For conservative systems, this fact is natural, but for systems with attractive or repulsive limit sets, not only some first integrals, but also the coefficients of the available invariant differential forms should, generally speaking, include functions with essentially special points (see also [4–6]). In this paper, complete sets of invariant differential forms for homogeneous systems on tangent bundles to smooth finite-dimensional manifolds are presented for the class of dynamical systems under consideration.
THE METHOD OF FICTITIOUS EXTREMA LOCALIZATION IN THE PROBLEM OF GLOBAL OPTIMIZATION
Authors: Evtushenko Yu. G. , Tret’yakov A. A.
Published: April 2024

The problem of finding the global extremum of a non-negative function on a positive parallelepiped in n-dimensional Euclidean space is considered. A method of fictitious extrema localization in a bounded area near the origin is proposed, which allows to separate the global extremum point from fictitious extrema by discarding it at a significant distance from the localization set of fictitious minima. At the same time, due to the choice of the starting point in the gradient descent method, it is possible to justify the convergence of the iterative sequence to the global extremum of the minimized function.
ON THE INTEGRAL CONVERGENCE OF NUMERICAL SCHEMES CALCULATING GAS-DYNAMIC SHOCK WAVES
Authors: Ostapenko V. V. , Polunina E. I. , Khandeeva N. A.
Published: April 2024

A comparative experimental accuracy study of shock-capturing schemes such as RBM(Rusanov-Burstein-Mirin), CWA(Compact high order Weak Approximation) and A-WENO(Alternative Weighted Essentially Non-Oscillatory) schemes is carried out by numerically solving a Cauchy problem with smooth periodic initial data for the Euler equations of gas dynamics. It is shown that in the presence of shock waves, RBM and CWA schemes(in the construction of which nonlinear flux correction is not used) have a higher order of integral convergence, which provides significantly higher accuracy to these schemes (compared to A-WENO scheme) in the areas of shock waves influence, despite noticeable non-physical oscillations at their fronts. This makes it possible to use RBM and CWA schemes as basic ones when constructing combined schemes that monotonically localize shock wave fronts and at the same time maintain higher order accuracy in their influence areas.
A STABILITY ESTIMATE IN THE SOURCE PROBLEM FOR THE RADIATIVE TRANSFER EQUATION
Authors: Romanov V. G.
Published: April 2024

It is given a stability estimate of a solution of a source problem for the stationary radiative transfer equation. It is suppose that the source is an isotropic distribution. Earlier stability estimates for this problem were known in a partial case of the emission tomography problem only, when the scattering operator vanishes, and for the complete transfer equation under additional and difficult in checking conditions for the absorption coefficient and the scattering kernel. In the present work, we suggest a new and enough simple approach for obtaining a stability estimate for the problem under the consideration. The transfer equation is considered in a circle of the two-dimension space. In the forward problem, it is assumed that incoming radiation is absent. In the inverse problem for recovering the unknown source some data for solutions of the forward problem related to outgoing radiation are given. The obtained result can be used for an estimation of the summary density of distributed sources of the radiation.
THREE-LAYER SCHEME FOR SOLVING THE RADIATION DIFFUSION EQUATION
Authors: Chetverushkin B. N. , Olkhovskaya O. G. , Gasilov V. A.
Published: April 2024

A method has been developed for the numerical solution of a nonlinear equation describing the diffusion transfer of radiation energy. The method is based on the introduction of the second time derivative with a small parameter into the parabolic equation and an explicit difference scheme. Explicit approximation of the initial equation makes it possible to implement on its basis an algorithm that is effectively adapted to the architecture of high-performance computing systems. The new scheme provides, in comparison with the original scheme, a larger time integration step and a sufficiently high resolution quality of the solution structure, providing the second order of accuracy. A heuristic algorithm for choosing the parameters of a three-layer difference scheme is proposed. A promising field of application of the method can be problems of plasma physics and astrophysics.
EXISTENCE OF MAXIMUM OF TIME AVERAGED HARVESTING IN THE KPP-MODEL ON SPHERE WITH PERMANENT AND IMPULSE COLLECTION
Authors: Vinnikov E. V. , Davydov A. A. , Tunitsky D. V.
Published: April 2024

On a two-dimensional sphere, a distributed renewable resource is considered, the dynamics of which is described by a model of the Kolmogorov–Petrovsky–Piskunov–Fisher type, and the exploitation of this resource, carried out by constant or periodic impulse harvesting. It is shown that after choosing an admissible exploitation strategy, the dynamics of the resource tend to the limiting dynamics corresponding to this strategy, and that there is an admissible harvesting strategy that maximizes the time averaged harvesting of the resource.
OPERATOR GROUP GENERATED BY A ONE-DIMENSIONAL DIRAC SYSTEM
Authors: Savchuk A. M. , Sadovnichaya I. V.
Published: April 2024

In this paper, we construct a strongly continuous operator group generated by a one-dimensional Dirac operator acting in the space \(\mathbb{H} = {{\left( {{{L}_{2}}[0,\pi ]} \right)}^{2}}\). The potential is assumed to be summable. It is proved that this group is well-defined in the space \(\mathbb{H}\) and in the Sobolev spaces \(\mathbb{H}_{U}^{\theta }\), \(\theta 0\), with fractional index of smoothness \(\theta \) and under boundary conditions \(U\). Similar results are proved in the spaces \({{\left( {{{L}_{\mu }}[0,\pi ]} \right)}^{2}}\), \(\mu \in (1,\infty )\). In addition we obtain estimates for the growth of the group as \(t \to \infty \).
INVARIANTS OF FIVE-ORDER HOMOGENEOUS DYNAMICAL SYSTEMS WITH DISSIPATION
Authors: Shamolin M. V.
Published: April 2024

New cases of integrable dynamical systems of the fifth order homogeneous in terms of variables are obtained, in which a system on a tangent bundle to a two-dimensional manifold can be distinguished. In this case, the force field is divided into an internal (conservative) and an external one, which has a dissipation of a different sign. The external field is introduced using some unimodular transformation and generalizes the previously considered fields. Complete sets of both first integrals and invariant differential forms are given.
REFINED MATHEMATICAL MODEL OF ECONOMIC DYNAMICS UNDER HIGH INFLATION AND UNSTABLE DEVELOPMENT
Authors: Sadovnichiy V. A. , Akaev A. A. , Zvyagintsev A. I. , Sarygulov A. I.
Published: April 2024

Previously, the authors proposed two mathematical models that describe the dynamics of economic development rates and forecasting inflation rates. The events that took place after February 2022 introduced an element of significant turbulence into the processes of macroeconomic dynamics in Russia, which required some correction of the previous models. This is reflected in this article. The processes simulated on the basis of new models show that in order to restore economic growth and reduce inflation in the medium term, a significant reduction in the interest rate and a steady increase in the money supply are required. It is shown that in the current era of geopolitical changes and the collapse of many liberal market dogmas, the role of the state and planning in managing economic processes is increasing.
FOUNDATIONS OF MATHEMATICAL EDUCATION IN THE DIGITAL AGE
Authors: Semenov A. L. , Abylkassymova A. E. , Polikarpov S. A.
Published: April 2024

The article formulates the foundations of modern mathematical education that meet the new goals and objectives of mathematical education dictated by: changes in mathematics itself over the last century, changes in its role in the modern digital world, changes in the world itself. The basic system of concepts is described, starting from which all modern mathematics of finite as well as primary mathematical education is built. For all levels of mathematical education and for all learners, independent, with the help and support of a motivating teacher, solving problems that are not known (to the student) how to solve, are fundamental. A significant role is played by a computer mathematical experiment and the transfer of tasks to the computer, the solution of which is found by the student. The article also describes the real state of affairs in the Russian mass school and proposes the necessary actions to implement the formulated principles of modern mathematical education in Russia. The results achieved in this direction are described. Most of the articles in this issue demonstrate and detail the implementation of formulated principles.
ERROR-FREE 2D PICTOGRAMMIC SYNTAX IN A PROGRAMMING LEARNING ENVIRONMENT FOR PRESCHOOL CHILDREN
Authors: Kushnirenko A. G. , Leonov A. G. , Polikarpov S. A.
Published: April 2024

When mastering the basics of programming by preschoolers, serious difficulties are created by the need to diagnose and correct syntactic errors. With the traditional method of “on-screen” program editing, these difficulties can be avoided by blocking the child’s actions that lead to syntactic violations. Today, the technique of compiling programs from material objects (tangible objects) with command icons printed on them is gaining popularity. When using this technique, no blocking of user actions is possible. In this situation, the authors propose to protect the child from syntactical errors by postulating the two-dimensionality of the program and defining the syntax and semantics of the pictogram programming language for beginners using indentation so that any placement of pictograms in the cells of a two-dimensional table gives a syntactically correct and executable program. This approach has been implemented and tested in the domestic educational environment “PictoMir” of pictogram programming for preschoolers.
MATHEMATICAL ELEMENTS OF ELEMENTARY EDUCATION
Authors: Posicelskaya M. A. , Rudchenko T. A. , Semenov A. L.
Published: April 2024

In recent decades, several Russian schools have been implementing a unique for the world education program of mathematics for elementary schools. In it, the landscape of school arithmetic is radically expanded due to the basic objects of modern mathematics and computer science. These objects and their operations are visual, making them much more accessible than traditional arithmetic. The range of activities is also expanding due to, for example, the introduction of strategies for enumeration, winning the game, algorithms (also operating in a visual environment). At the same time, the student’s position is changing – they independently discover and builds mathematics, constantly solves personally new, but feasible tasks, which are “not-known-how-to-solve”. The student’s resources are saved by using a computer to perform routine arithmetic operations that they have already discovered and understood. The paper presents in detail the implementation of this approach, illustrated by real examples of tasks representative of the program under consideration and for our vision.
CONSTRUCTIVE COMBINATORICS IN PRIMARY SCHOOL MATHEMATICS
Authors: Posicelskaya M. A.
Published: April 2024

The paper is describing the class of educational problems from the course of mathematics and computer science for elementary school. This course has been implemented over the past decades by a team led by A.L. Semenov. In the problems it is required to find, build, list all objects that satisfy a certain system of conditions. The student conducts these activities in the visual world of the basic objects of discrete mathematics and computer science: strings (finite sequences of symbols), bags (multisets), tables, trees, and statements containing quantifiers. The connections of these problems with problems of computational combinatorics (“counting the number of options”), search problems of the theory of computational complexity, with “big ideas”, general cognitive strategies in their formation are considered. The content of education in our approach is more adequate to the context of the modern world.