Search

We study the problem of estimating the -norms () of solutions to inhomogeneous difference equations. The difference equations are considered as bi-infinite (infinite in both directions) systems of linear equations. We establish estimates in the case of a diagonally dominant Laurent matrix. Using this result and the idea of matrix decomposition into the product of matrices related to the decomposition of the characteristic polynomial, we propose some estimates in the case of an arbitrary nonsingular band Laurent matrix. [ABSTRACT FROM AUTHOR]

A brief overview of chromatographic methods for determining free bisphenol A (BPA) in technical and food products is presented. Bisphenol A is used as a monomer in the production of some plastics and epoxy resins. The concentration of free BPA may exceed the permissible level in food plastic containers and in food products packaged in these containers. The maximum permissible concentration of BPA in water, in water bodies of domestic and drinking water and in cultural and household water use is 0.1 mg/dm3. In European countries, the migration value of BPA for plastics in contact with food products is 0.6 mg/kg. Gas chromatography with preliminary derivatization by the silylation or acylation of the analyte is most often used to determine BPA in plastics, food products, and biological fluids. Direct determination methods have been developed using gas-liquid chromatography on heat-resistant columns. Flame ionization, fluorometric, and mass-selective detectors are used as detection devices. HPLC with optical and mass-selective detectors is used to determine BPA. Thin-layer chromatography has also been used for determining BPA. Solid-phase extraction, liquid−liquid extraction, dispersive liquid−liquid microextraction, and a combined extraction method with separation in acetonitrile (QuEChERS) are used in BPA sample preparation. [ABSTRACT FROM AUTHOR]

The first aqueous silver borate nitrate Ag3B4O6(OH)2(NO3) has a non-centrosymmetric crystal structure (P43212, a = 10.0196(3) Å, c = 9.2594(2) Å). The compound is prepared by soft hydrothermal synthesis inside an evacuated quartz ampoule. The structure of the resulting 1D–5B-borate compound is formed by [B4O6(OH)2]2– chains consisting of two triborate rings with a common (2Δ3□:(‹Δ2□›–‹Δ2□›–)∞ tetrahedron and NO3 triangles with silver atoms between the rings. The relationship between the structures of Ag3B4O6(OH)2(NO3), Tl2B4O6(OH)2·2H2O and the kernite Na2B4O6(OH)2·3H2O (also formed by [B4O6 (OH)2]2– chains) is discussed. [ABSTRACT FROM AUTHOR]

The study presents findings on the application of various beneficiation methods to low-grade hematite ores, originally characterized as a clay rock with an iron content of 17.2%. The study presents the mineralogical composition of the original ore and examines the effectiveness of different beneficiation techniques, including jigging, magnetic separation (after roasting with additives), and flotation. The results reveal that the simplest method, jigging, significantly enhances the iron content in the concentrate, achieving a total iron content of 50%. However, this outcome is heavily influenced by the size of hematite inclusions within the ore. Further refinement through additional beneficiation methods allows the total iron content in the concentrate to reach 60%. [ABSTRACT FROM AUTHOR]

Two azo dyes 2-hydroxy-5-(4-nitrophenylazo)benzaldehyde and 2-hydroxy-5-(4-chlorophenylazo)benzaldehyde dissolved in carbon tetrachloride, hexane, acetone and acetonitrile were irradiated with 365 nm UV light, and processes, occurring in them, were studied by NMR and UV–vis spectroscopy. It was established that reversible trans/cis photoisomerization of the molecules occurs in the non-polar solvents and is not observed in the polar solvents. 2D NOESY NMR spectroscopy was used to identify isomers of the azo compounds. Based on the chemical shifts of the signals, it was established that these compounds are in the trans-form before UV irradiation. Spectra of the azo dyes before and after UV irradiation allowed assignment of the chemical shifts of the cis-isomers. In polar solvents these compounds undergo a hypochromic effect under heating or irradiation with UV light. Both compounds exhibit solvatochromism. The shifts in NMR signals caused by photoisomerization of the molecules were compared with the shifts in the NMR signals of other azo compounds such as Disperse Orange 3, Disperse Red 1 and azobenzene. [ABSTRACT FROM AUTHOR]

We consider the planar circular restricted four-body problem. A small body of negligible mass moves in the Newtonian gravitational field of three attracting massive bodies (primaries). The primaries are located at the triangular libration points of a plane circular restricted three-body problem, i.e. they move in circular orbits and form an equilateral triangle. All four bodies move in a plane. It is assumed the stability of these triangular libration points are stable, that is the Routh's necessary stability condition is fulfilled. The equations of motion of the planar restricted circular four-body problem admit particular solutions describing the so-called central configurations, in which all four bodies form a quadrilateral of constant form and size. If the Routh's necessary stability condition is satisfied, then eight central configurations are possible, of which three can be stable in the linear approximation. By using the method of normal form and KAM theory, we performed nonlinear analysis of the stability of these central configurations. A numerical analysis of the coefficients of the Hamiltonian normal form of the equations of perturbed motion was performed and rigorous conclusions about stability were obtained. In the limiting case, when one of the three attracting bodies is small, analytical expressions for the coefficients of the Hamiltonian normal form were obtained by using method of the small parameter. It is shown that the results of analytical and numerical stability studies are in good agreement. [ABSTRACT FROM AUTHOR]

This paper considers geological, mineralogical, and geochemical features of the epithermal Au‒Ag mineralization at the Televeem volcanic dome uplift (VDU) which complicates the Verkhne-Pykarvaam volcano-tectonic depression (VTD) in the Central Chukchi sector of the Okhotsk–Chukchi volcanogenic belt (OCVB). The structure of this ore occurrence is due to its localization within the eponymous VDU. The main vein zone (MVZ) of the Televeem ore occurrence, as wide as 500 m, extends for 2.5 km in the north–south direction. Along the MVZ direction, en-echelon proximal quartz–adularia veins are successively replaced with zones of thin streaks and brecciation in secondary quartzites and argillisites. The gold concentrations in these rocks vary between 1.4 and 17.3 g/t, that of gold is between 7.6 and 144.6 g/t. The ores contain abundant brecciated, framboidal lamellar, geode, and fine streaky structures. The more frequent ore minerals are pyrite, arsenopyrite, acanthite, grey ores of the freibergite–tetrahedrite series, stephanite, polybasite, low-fineness native gold (fineness varies in the range 249–532‰), and titanite. The amount of ore minerals in veins does not commonly exceed 0.5%, reaching 3% in some rare cases. Based on mineralogical evidence, this ore occurrence can be classified as belonging to low- or medium-eroded ones. The low erosion suggests a high probability of detecting buried ore bodies. [ABSTRACT FROM AUTHOR]

The first aqueous silver borate nitrate Ag3B4O6(OH)2(NO3) has a non-centrosymmetric crystal structure (P43212, a = 10.0196(3) Å, c = 9.2594(2) Å). The compound is prepared by soft hydrothermal synthesis inside an evacuated quartz ampoule. The structure of the resulting 1D–5B-borate compound is formed by [B4O6(OH)2]2– chains consisting of two triborate rings with a common (2Δ3□:(‹Δ2□›–‹Δ2□›–)∞ tetrahedron and NO3 triangles with silver atoms between the rings. The relationship between the structures of Ag3B4O6(OH)2(NO3), Tl2B4O6(OH)2·2H2O and the kernite Na2B4O6(OH)2·3H2O (also formed by [B4O6 (OH)2]2– chains) is discussed. [ABSTRACT FROM AUTHOR]

The study is devoted to enhanced CeO2 evaporation in the temperature range between 2130 and 2650 K from refractory crucibles made of different materials: molybdenum, tantalum, and tungsten. The composition datum of vapor and films deposited on collectors receiving evaporation products were obtained by quadrupole mass spectroscopy and by energy-dispersive X-ray spectroscopy. One of approximation coefficients of the temperature dependence of CeO2 vapor in the range between 2150 and 2220 K was measured. The study is of interest for a variety of technologies utilizing refractory oxide evaporation with high productivity, including the plasma mass separation methods. [ABSTRACT FROM AUTHOR]

On the White Sea islands and coast of North Karelia, in the Chupa sector of the Belomorian mobile belt (BMB), carbonate–silicate and quartz veins are localized in bodies of Early Proterozoic metabasites and their contacts with host gneisses. The isotopic characteristics of coarse crystal vein carbonates (δ18O and δ13C), as well as associated quartz (δ18O) and biotite (δ18O and δD), were studied. The isotopic composition of oxygen suggests biotite–quartz–carbonate equilibria during the formation of veins at temperatures of 520–450°C. The O and H isotopic characteristics of biotite correspond to the equilibrium of the fluid with metamorphic rocks. At the same time, the isotopic compositions of O and C carbonates indicate different CO2 sources in fluids. There are three groups of carbonates according to δ18О and δ13С. The first group shows "magmatic" isotopic characteristics of the CO2 source (δ18ОVSMOW = 7.1...12.1‰; δ13СVPDB = –6.3...–4.5‰). Carbonates of the second group have high δ18О and δ13С, characteristic of Precambrian sedimentary carbonates (δ18ОVSMOW = 21.9...24.7‰; δ13СVPDB = –2.2...–2‰), similar to those described earlier in the neighboring Engozero sector of the BMB. In the third group, the δ13С values are similar to the carbonates of the first group, and δ18О, to the second group (δ13СVPDB = –1.7...0.9‰, δ18ОVSMOW = 6...12‰). The O and C isotopic compositions of carbonates of the third group can be obtained from the action of a putative magmatic fluid on both the primary sedimentary source of metamorphic fluids and redeposited vein carbonates. [ABSTRACT FROM AUTHOR]

A model is proposed for the formation of the workpiece–tool contact zone in belt grinding of blades for gas turbine engines on CNC machine tools. The model takes account of fluctuation of the forces applied to the contact element; and the complex shape of the contact element and the workpiece. The Femlab modeling software employed permits assessment of the contact area and conclusions regarding the distribution of the belt pressure over the workpiece surface. [ABSTRACT FROM AUTHOR]

The shaping of the working surface is investigated theoretically and experimentally for a cutting tool in the form of a grinding belt. The variation of the surface as a result of erosion is studied. By means of models, the structure of the working layer may be determined (including the case of structured abrasive belts), and the density of the abrasive grains and their distribution in terms of the height above the base may be calculated. [ABSTRACT FROM AUTHOR]

The use of artificial intelligence technologies in image analysis tasks is rapidly developing every year, thanks to which the possibilities of using artificial neural networks in the diagnosis of various diseases have reached a completely new level. The results of thousands of studies using neural networks in ophthalmology show diagnostic accuracy results comparable and sometimes even superior to those achieved by a human performer. However, the transparency of the results obtained and the adaptability of the operation of such systems remain low. In the future, the use of convolutional neuro-fuzzy networks in image analysis tasks will probably improve the results. The work examines the existing experience in using neuro-fuzzy networks for problems of classification of medical images and demonstrates the possibilities of practical implementation of a neuro-fuzzy network for problems of classification of glaucoma ophthalmic images. [ABSTRACT FROM AUTHOR]

A method is proposed for calculating low interfacial tension (IFT) based on molecular dynamics simulation of systems with superdense packing of surfactant molecules at the water–liquid hydrocarbon interface. The interfacial tension was calculated by the molecular dynamics method using the all-atom and coarse-grained models in water–alkane (decane, dodecane) two-phase systems in the presence of various individual surfactants. The following ionic and nonionic surfactants were considered: sodium dodecyl sulfate (SDS), cetyltrimethylammonium chloride (CTAC), sodium dodecylbenzenesulfonate (SDBS), sodium decet-6 sulfate C10E6SO4Na, hexaethylene glycol monodecyl ether (C10E6), triethylene glycol monononadecyl ether (C19E3), and octapropoxypentaethylene glycol monododecyl ether (C12P8E5). It was shown that the interfacial tension decreases to zero when surfactant adsorption increases to the limiting values. [ABSTRACT FROM AUTHOR]

Using fluorescence microscopy, we studied the involvement of Ca2+-binding proteins in the exo-endocytotic vesicular cycle of quantal neurotransmitter release at the somatic neuromuscular junction of the earthworm Lumbricus terrestris. Inhibition of calcineurin, calmodulin, and Ca2+/calmodulin-dependent protein kinases led to an enhancement of synaptic vesicle endocytosis. Blocking the phosphorylation of synaptic calcium-binding proteins boosted vesicular endocytosis, increased the size of the total vesicular pool, and accelerates synaptic vesicle turnover. It can be concluded that calcium modulation of synaptic vesicle exo- and endocytosis in the motor nerve endings of evolutionarily primitive somatic muscles of annelids occurs with the involvement of calcineurin, calmodulin and Ca2+/calmodulin-dependent protein kinases. [ABSTRACT FROM AUTHOR]

Research was carried out on changes in the moisture supply of the territory in the dry steppe subzone of the southern part of Western Siberia (geographic coordinates 50.5°–54.5° N, 77.5°–83.0° E) for the period 1980–2050. The hydrothermal humidification coefficient of G.T. Selyaninov is used as the main indicator of the level of moisture supply in the region. The information basis for this study is the results of six climate models of the CMIP6 family, obtained for the modern period 1980–2015, as well as within the framework of scenarios SSP2-4.5 and SSP5-8.5 of the possible evolution of the global climate system for 2015–2050. The long-term dynamics, boundaries of variations, and trends of the hydrothermal coefficient for the southern part of Western Siberia have been established. An analysis of the influence of the total amount of precipitation and the surface air temperature on the nature and rate of change in the level of moisture supply in the region was carried out. The spatial distribution of moisture supply in the region and the rate of its change for the period under study have been established. [ABSTRACT FROM AUTHOR]

This article describes an innovative technical solution developed by the authors that can be used to improve the quality, reliability, safety, and service life of hydraulic units. The problems of vibration control are discussed. Phase-chronometric diagnostics are proposed. The possibilities of significantly increasing the accuracy of hydraulic unit operation control are presented. [ABSTRACT FROM AUTHOR]

As examples of applying the formulas from part I we examine scattering in a one-dimensional medium for which all the characteristics of the radiative field are expressed in terms of elementary functions and (three-dimensional) isotropic monochromatic scattering. Some properties of the Ambartsumyan function are studied and the asymptotes of the average numbers of photon scattering events in an optically thick plane layer are derived. [ABSTRACT FROM AUTHOR]

The article examines the possible impact of the planned write-off of two-thirds of the region's debts on budget loans on the sustainability of regional debt. Based on the analysis of statistical data on the debts of individual regions, it was concluded that writing off debts will significantly reduce the debt burden on the budgets of the most vulnerable constituent entities of the Russian Federation. At the same time, one of the tasks in this context is maintaining budget discipline in the regions. This will require further development of the sphere of regulation and control of regional finances, including through the mechanisms of fiscal rules at the regional level. [ABSTRACT FROM AUTHOR]

The crystallization process of an Al87Ni6Nd7 amorphous alloy has been studied. It has been established that the crystallization of an amorphous alloy occurs in three stages, and the temperatures and activation energies of each crystallization stage have been determined. At the first crystallization stage, Al nanocrystals are formed; at the second stage, in addition to Al nanocrystals, the crystals of an Al11Nd3 phase are precipitated from the remaining amorphous phase. At the third crystallization stage, a previously unknown crystalline phase is formed. The structure of the new phase has been determined. [ABSTRACT FROM AUTHOR]

The article considers the problem of estimating solutions and inverse matrices of systems of linear equations with a circulant matrix in the -norm, . An estimate for a diagonally dominant circulant matrix is obtained. Based on this result and the idea of decomposing a matrix into a product of matrices associated with the decomposition of a characteristic polynomial, an estimate for the general circulant matrix is proposed. [ABSTRACT FROM AUTHOR]

The deuteron beam vector polarization was obtained at the Nuclotron Internal Target Station using the proton–proton quasielastic scattering on the polyethylene target at the beam energies of 200, 500, 550, and 650 MeV/nucleon. The selection of useful events was performed using the time and amplitude information from the scintillation counters. The asymmetry on hydrogen was obtained by the subtraction of the carbon background. The obtained values are compared with the data obtained using the deuteron–proton elastic scattering at the beam energy of 135 MeV/nucleon. [ABSTRACT FROM AUTHOR]

The Spin Physics Detector is an experiment at NICA designed to study the spin structure of the proton and deuteron and other spin-related phenomena using polarized beams. Two Beam-Beam Counters (BBCs) will be installed symmetrically aside from the interaction point in the end-cups of SPD setup and will serve as a tool for beam diagnostics including local polarimetry. The outer part of the BBC wheel is based on fast scintillator tiles and cover the polar angels between 60 and 500 mrad. Different material configurations for the BBC prototype based on scintillator tiles were tested. The light collection depends on material combinations—fiber (Saint Gobain BCF91AS, BCF92S, and Kuraray Y-11), tile surface cover (Matted and double covered with Tyvek sheets tiles), and optical cement (CKTN mark E, OK-72). SensL 1 1 mm2 and 3 3 mm2 SiPMs were used as photosensors in the prototype tiles. The studies were performed with a cosmic rays test setup equipped with CAEN FERS-5200 readout system. [ABSTRACT FROM AUTHOR]

The Spin Physics Detector is a collider experiment at NICA designed to study the spin structure of the proton and deuteron and other spin-related phenomena using polarized beams. The collision energy is up to 27 GeV and the luminosity is up to 1032 cm–2 s–1 in pp mode. Two scintillator-based detectors, Beam-Beam Counters (BBC), will be installed upstream and downstream the interaction point and will serve as a tool for beam diagnostics including local polarimetry. The BBCs will be designed as high granularity scintillation detectors. In this paper we present the tests of a BBC prototype based on the tiles with the green wavelength shifter and silicon photomultiplier (SiPM) readout. The prototype was tested with 1 × 1 mm2 and 3 × 3 mm2 SensL SiPM using CAEN FERS-5200 front-end readout system. Amplitude and time response to cosmic rays was compared for different tile configurations. [ABSTRACT FROM AUTHOR]

The deuteron beam vector polarization was obtained at the Nuclotron Internal Target Station using proton-proton quasielastic scattering on the polyethylene target at the beam energies of 200, 500, 550, and 650 MeV/nucleon. The proton beam polarization was obtained at the beam energy of 500 MeV. The selection of useful events was performed using the time and amplitude information from the scintillation counters and the subtraction of the carbon background, both for the deuteron and proton beams. [ABSTRACT FROM AUTHOR]

The Spin Physics Detector is an experiment at NICA designed to study the spin structure of the proton and deuteron and the other spin-related phenomena using polarized beams. The collision energy is up to 27 GeV and the luminosity is up to 10 cm s in pp mode. Two scintillator-based detectors, Beam–Beam Counters (BBC), will be installed upstream and downstream the interaction point and will serve as a tool for beam diagnostics including local polarimetry. In this paper, we present the design of the BBC prototype based on the tiles with green WLS and SensL SiPM readout. FERS-5200 is used as the front-end readout system. The amplitude and timing resolutions for different tiles using radioactive source and cosmic rays are obtained. [ABSTRACT FROM AUTHOR]

The development of advanced methods for the synthesis of nano- and microparticles for biomedical applications is of considerable interest. A method for synthesizing submicron silver-shelled calcium carbonate particles using a microfluidic chip designed to control the particle formation is proposed. Precise control of reaction parameters enables controlled formation of silver shell and calcium carbonate particles. The distribution of pores in the hybrid particles was analyzed using small-angle X-ray scattering, which gained insight into the complex structure of the pores. The results provide information on the particle morphology and may facilitate the development of new calcium carbonate-based materials for various applications. [ABSTRACT FROM AUTHOR]

Crystals of a new high-symmetry structural modification of Cs2HIn(IO3)6 which crystallizes in sp. gr. R with the unit cell parameters a = 11.8999(4) Å, c = 11.6513(5) Å, was obtained under hydrothermal conditions. The crystal-chemical comparison with the previously characterized triclinic modification of this compound was carried out. Both structures are composed of isolated [In(IO3)6]3– blocks. The new modification belongs to the family of trigonal iodates isostructural with the compound K2Ge(IO3)6. The local symmetry of individual [M(IO3)6] blocks (M = Ge, Ti, Sn, Ga, In, and some other metals) was analyzed. The structural systematics of iodate families was proposed based on the comparative crystal-chemical analysis. The influence of the cation composition and the synthesis conditions on the symmetry and topology of the crystal structures and the effect of the local symmetry of individual blocks on the physical properties of the compounds are discussed. [ABSTRACT FROM AUTHOR]

We investigate strongly correlated solid solutions of Fe1 – xCoxSi with a disrupted B20 cubic structure. Within the framework of spin-fluctuation theory and a model of the density of electronic states derived from first-principles calculations using the generalized gradient approximation with the inclusion of strong Coulomb correlations (GGA + U), temperature transitions in Fe1 – xCoxSi alloys (illustrated with the examples of x = 0.2 and 0.3) with Dzyaloshinskii–Moriya interaction are examined. In the considered compounds, a "blurred" temperature-dependent first-order magnetic phase transition occurs, which is accompanied by a change in the sign of the intermode-coupling parameter in the Ginzburg–Landau functional. During such a transition, skyrmion A phases emerge within limited temperature ranges and external magnetic fields, beyond which experimentally observable fluctuations of the magnetic moments of spin spirals occur. The (h–T) diagrams are plotted, indicating regions of long-range order, and fluctuational and skyrmion phases. Fe1 – xCoxSi phases with x = 0.2 and 0.3 align well with experimental observations. [ABSTRACT FROM AUTHOR]

The paper shows the effect of introducing Lactiplantibacillus plantarum AG10 biomass into quail feed. Quails that received a probiotic feed additive for seven weeks demonstrated a significant improvement in such economic indicators as the dynamics of live weight, the mass of gutted carcasses and feed consumption per kg of gain. Using the analysis of 16S rRNA gene sequence libraries sequenced on the Illumina MiSeq platform, shifts in the microbiota of the cecum have been detected, which may contribute to improving the morphological and physiological parameters of quails. [ABSTRACT FROM AUTHOR]

The problem of constructing n-linear (n ≥ 2) plane vector fields with an isolated critical point and given separatrices of prescribed types is considered. Such constructions are based on the use of vector algebra, the qualitative theory of second-order dynamic systems and classical methods for investigating their critical points. This problem is essentially an inverse problem of the qualitative theory of ordinary differential equations, and its solution can be used to synthesize mathematical models of controlled dynamical systems of various physical nature. [ABSTRACT FROM AUTHOR]

We report a developed methodology for studying the main parameters and identifying the features of chirped volume Bragg gratings (CVBGs). The results of diagnostics of the first fused silica CVBG samples inscribed by femtosecond laser pulses using a phase mask are presented: the linear absorption coefficient, phase and polarization distortions arising during grating inscription, and spectral and dispersion characteristics are studied. The results of the studies indicate the prospects for using gratings of this type in high-average-power laser systems. [ABSTRACT FROM AUTHOR]

The paper proposes a method for detecting small oscillations in the length of interference fiber-optic sensors, which makes it possible to compensate for the problem of slow drift of the working point with a remote sensor. The result is achieved by combining homodyne demodulation methods with a tandem low-coherence interferometer. Theoretically and experimentally, the possibility of detecting acoustic effects in the operating frequency band of 4 kHz with a sensitivity of up to 0.3 nm has been shown. [ABSTRACT FROM AUTHOR]

A numerical simulation of the gasdynamic processes accompanying the formation and propagation of vortex rings obtained with the use of a piston-type generator has been performed. The formation of a vortex ring, the capture of particles of a disperse admixture by it, and their carry by the ring are considered. The numerical calculations were conducted with the use of nonstationary Navier–Stokes equations, and the movement of particles was defined using the discrete-trajectory method. The distribution of the admixture particles in a vortex ring was determined depending on the conditions of its formation. The influence of the characteristics of a vortex ring on the carry of a passive admixture by it was investigated. The reasons for the qualitative and quantitative differences between the losses of particles in a vortex ring in the path of its movement in different regimes are discussed. [ABSTRACT FROM AUTHOR]

We obtain a contrast-structure type solution of a system of equations for the baretting effect that include a nonlinear singularly perturbed parabolic equation and an additional nonlocal integral relation. We prove the existence of the solution with an internal transition layer and construct the asymptotic approximation of this solution. We obtain estimates of the main physical model parameters, which coincide with experimental data and the estimates obtained previously by other methods. [ABSTRACT FROM AUTHOR]

Immunofluorescent labeling revealed calmodulin, Ca2+/calmodulin-dependent protein kinases I and II, synaptotagmin II and VII, and calcineurin A in somatic motor muscles of the earthworm Lumbricus terrestris. These Ca2+ sensor proteins are detected in both synaptic and extrasynaptic regions. However, synaptotagmin II and VII, as well as calcineurin A, are mainly localized in the area of neuromuscular junctions, with the synaptic localization for synaptotagmin VII and calcineurin A being pronounced most distinctly. [ABSTRACT FROM AUTHOR]

We consider a periodic problem for a singularly perturbed parabolic reaction–diffusion–advection equation of the Burgers type with the modulus advection; it has a solution in the form of a moving front. We formulate conditions for the existence of such a solution and construct its asymptotic approximation. We pose a control problem where the required front propagation law is implemented by a specially chosen boundary condition. We construct an asymptotic solution of the boundary control problem. Using the asymptotic method of differential inequalities, we estimate the accuracy of the solution of the control problem. We propose an original numerical algorithm for solving singularly perturbed problems involving the modulus advection. [ABSTRACT FROM AUTHOR]

Frequency response analysis has become widely used in the world in recent years to assess the mechanical and electrical condition of the active part of power transformers. To date, the measurement technique has been developed and standardized in IEC, IEEE, and GOST standards. However, the issues of interpretation at the world level have not been fully resolved, and the interpretation of results is often a subjective expert opinion. A practical example of assessing the technical condition of a special single-phase high-power test transformer with an internal damage occurred during operation is presented. The results of measurements and analysis of the winding frequency responses, including those obtained by non-standard measurements, are discussed. It is shown that the application of the DL/T 911 methodology based on the pair correlation coefficients can lead to an erroneous assessment of the condition of the transformer. Calculated frequency dependences of the fault conductance, impedance, and inductance of the winding, as well as inter-winding capacitance are presented. The diagnostic parameters calculated from the frequency responses of the windings and from traditional diagnostic measurements are compared. The inspection of the active part of the transformers after opening the transformer tank confirmed the main conclusions on the condition of the transformer drawn after the comprehensive diagnostic examination. [ABSTRACT FROM AUTHOR]

Two mineral species of the labuntsovite group from Khibiny (sample 1) and Lovozero (sample 2) alkaline massifs are analyzed by single crystal X-ray diffraction and Raman spectroscopy. They are intermediate members of the tsepinite-Na–"tsepinite-Ba"–tsepinite-K solid solution, which are characterized by a high degree of hydration and a low concentration of extra-frame cations. Parameters of monoclinic cells are: a = 14.5086(6) Å, b = 14.2174(6) Å, c = 7.8712(3) Å, β = 117.119(4)°, V = 1444.09(11) Å3 (sample 1) and a = 14.2582(4) Å, b = 13.7541(6) Å, c = 7.7770(2) Å, β = 116.893(4)°, V = 1360.20(9) Å3 (sample 2). Crystal chemical formulas (Z = 2) are: |A[Na0.84K0.6[(H2O)4]5.2]BK0.2CBa0.25D[Ca0.35Na0.15Fe0.025(H2O)]| {M1(Ti1.2Nb0.8)M2(Ti1.1Nb0.9)(O,OH)4(Si4O12)2} for sample 1 and |A[Na1.6(H2O,H3O)0.4]BK2C(Ba0.51Sr0.21)D [Mn0.3Ca0.2(H2O)](H2O)4|{M1(Ti1.94Nb0.06)M2(Ti1.88Nb0.12)(O,OH)4(Si4O12)2} for sample 2. The high degree of hydration of sample 1 is expressed in the presence of proton hydrate complexes and tetrahedral [H2O]4-associates. Labuntsovite group minerals (LGMs) are characterized by so-called block isomorphism due to different distributions of D cations. Our analysis of heteropolyhedral MT-frameworks in LGMs allows us to determine the topological features of cation networks. [ABSTRACT FROM AUTHOR]

The work is devoted to modeling the heating of moving active elements from CdSe and estimates emerging optical inhomogeneities. Active elements in the form of a parallelepiped are considered, which rotated in a circle perpendicular to the generation axis. As a result of calculations, it was found that the temperature distribution in the active element that occurs during the operation of the laser can be represented as the sum of two components. The first component is formed due to the balance between heat emission in the active element due to pumping and heat removal from it, which leads to the appearance of an aberration, which is the sum of "tilt" and "defocusing". The second component is formed directly during the passage of the pump spot through the active element, is determined only by the heat release density and is not related to the cooling method of the active element. It leads to the appearance of "Gaussian" aberration, the amplitude of this aberration is directly proportional to the power of heat emission and inversely proportional to the frequency of rotation of the active element. [ABSTRACT FROM AUTHOR]

The structure dynamics in the temperature range of the melting phase transition of a dimyristoyl-phosphatidylserine multilayer on the surface of a colloidal silica solution with a particle diameter of 5 nm has been investigated by X-ray reflectometry and grazing diffraction of 71-keV photons. The joint model and model-free analysis of the reflectometry data revealed a structure consisting of a surface lipid monolayer and a set of lamellar bilayers sandwiched between water layers, with a period of ~150 Å. With an increase in temperature above the critical value one can observe a surface monolayer transition from a crystalline phase with a minimum area per lipid molecule of 40 ± 1 Å2 to a disordered (liquid) phase with a calculated area per molecule of 52 ± 2 Å2. At low temperatures, the data indicate that from five to eight H2O molecules are tightly bound to the PS fragment of the lipid in both the monolayer and the bilayer structures. However, above the transition temperature, approximately 14 water molecules are attached to the headgroups of the bilayer: this is almost twice as many molecules as the eight H2O molecules-per-headgroup in the surface monolayer. [ABSTRACT FROM AUTHOR]

In this study, existing and promising methods of processing fine fractions and dust of aspiration systems for the production of ferroalloys were analyzed. The technological properties of high-carbon ferrochrome screenings and dust of the ferrochrome crushing aspiration system of the Aktobe Ferroalloy Plant as raw materials for the production of low-carbon ferrochrome briquettes using the vacuum-thermal method were studied. The contents of basic and impurity elements, including gas-forming ones, were determined. The oxygen content in the dust reached 4.2 and 0.12% in the screening. The average size of aspiration dust particles was 9.6 μm, whereas that of the ferrochrome screenings was 1.44 mm. In the dust and screening samples, the main phase was Cr7C3, and graphite was present in the dust sample. During thermal analysis, the dust sample completely melted at 1453 °C, and a liquid phase was not observed when ferrochrome was heated. At 1340 °C, the formation of iron silicide was noted. With increasing temperature, the concentrations of carbon and chromium carbide decreased. From thermodynamic calculations, recommendations were given on the parameters of vacuum-thermal decarburization of high-carbon ferrochrome. The results of preliminary experiments confirmed the possibility of removing carbon from screenings and aspiration dust. From samples containing 9.04–9.11% carbon, ferrochrome with a content of 0.10% carbon could be obtained. At the next stage of our work, we plan to work out in detail the parameters affecting the vacuum-heat treatment of ferrochrome. We assume that ferrochrome with a carbon content of 0.00x% can be obtained. [ABSTRACT FROM AUTHOR]

For the first time by the method of scanning electron microscopy, REE mineralization studies are conducted in alkaline rhyolites of the Pechalninskii ore field (Northeast Russia), a potentially large-volume source of HREEs. It is shown using the methods of electron microprobe analysis and cathodoluminescence that microcrystalline aggregates of pyroxenes and/or amphiboles in alkaline rhyolites contain the finest inclusions of REE segregations (5–7 µm). Using SEM, it is determined that the largest segregation is cerium phosphate. Concentrically zonal and radial-fibrous REE segregations are revealed in the relics of titanomagnetite crystals by EDS. The first ones are represented by silicates enriched with Y and REEs and the content of each REE varies regularly from the center to the edge. The radial-fibrous aggregates are represented by oxides and/or carbonates containing REEs (La, Ce, and Nd predominate). The results obtained can be used in the development of enrichment technology. [ABSTRACT FROM AUTHOR]

Catalyst-free addition of diphenylphosphine oxide to 1,4-diorganyl-4-(organylamino)-alk-2-yn-1-ones proceeded chemo-, regio-, and stereoselectively to afford new Z-3-diphenylphosphoryl-1,4-diorganyl-4-(organylamino)alk-2-en-1-ones in up to 75% yield. The synthesized compounds are promising candidates for organic synthesis and pharmaceutical research. [ABSTRACT FROM AUTHOR]

Mn5Ge3 is a ferromagnetic hexagonal crystal promising for spintronics and magnetocalorics. A systematic study and analysis of the magnetic properties of the Mn5Ge3 thin film grown on Si(111) were performed. The magnetic anisotropy of the film is determined by the shape anisotropy and the easy magnetization axis aligned along the c axis of the crystal. The uniaxial anisotropy constant Ku fully corresponds to that for a bulk single crystal, which indicates that c axis coincides with film normal. Mn5Ge3 film demonstrates high saturation magnetization MS = 900 emu/cm3 (900 kA/m) at T = 100 K and magnetocaloric effect ΔS = 3.16 ± 0.22 J kg−1 K−1 at 300 K and B = 1.5 T. ΔS is comparable to that for multicomponent or Gd rare earth films. Furthermore, a different anisotropy of the magnetocaloric effect compared to bulk Mn5Ge3 was found, which may be related to the anisotropy of the film shape and, possibly, to the domain structure. The results obtained are promising for the design and development of magnetocaloric, spintronic, and spin-caloritronic devices on a silicon platform. [ABSTRACT FROM AUTHOR]

The paper analyses the ignition of propane-air fuel mixtures with different excess air ratios near the discharge initiator antenna by a pulsed subcritical microwave discharge. An approximate model that describes the gas dynamics of combustion with a detailed scheme of chemical reactions, external energy supply, and an additional set of reactions, which take into account plasma-chemical effects, is used for calculations. The distributions of temperature, composition of the medium in the vicinity of the antenna and the component-wise mass flow of combustion products after exposure are presented. [ABSTRACT FROM AUTHOR]

The lepton decays are described in the NJL quark model. The contact channel and intermediate channels with axial-vector, vector and pseudoscalar mesons are taken into account. It is shown that the strange scalar meson plays an important role in these processes in addition to the intermediate vector meson . The obtained results are in satisfactory agreement with the recent experimental data within the experimental and theoretical uncertainties. [ABSTRACT FROM AUTHOR]

The first stage of the linear accelerator of the Siberian Circular Photon Source (SKIF) accelerator facility has been successfully commissioned at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences (BINP). This test accelerator facility includes the radiofrequency (RF) gun, magnet system, RF accelerating structures, and diagnostic and control system elements. The aim of the work at the facility is to verify the correctness of solutions chosen for the accelerator design, as well as to get operation experience and to measure the beam parameters that will determine the successful work of the overall SKIF complex. This article describes the main subsystems of the test accelerator facility and briefly presents the first operation results concerning the beam parameters. [ABSTRACT FROM AUTHOR]

In November 2020, the IceCube Neutrino Observatory registered a neutrino event with an energy of 150 TeV directed at the Cygnus Cocoon gamma-ray source. In the Carpet-2 experiment, as part of the Baksan Neutrino Observatory (BNO), a sharp increase in the flow of events with an energy above 300 TeV was recorded from the same direction within the angular accuracy of the events. This flux is 4 orders of magnitude higher than the expected intensity of gamma quanta of this energy region according to data in the region of less than 100 TeV. It was expected that such a powerful flare could be registered by the TAIGA-HiSCORE installation of the TAIGA astrophysical complex. We analyzed the events of the EAS recorded by the installation of TAIGA-HiSCORE for 18 h in October–November 2020 from the Cygnus Cocoon source. This article provides the upper limit of the expected excess flow. [ABSTRACT FROM AUTHOR]

A new algorithm for selecting signals caused by the detection of neutrons is described. The estimates of its effectiveness for the PRISMA-32 and URAN arrays are presented. Using this algorithm, for various air-shower sizes the number of neutrons was reconstructed, the time distributions of neutrons and their lateral distribution functions were obtained. [ABSTRACT FROM AUTHOR]