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Features of the crystallization of various compounds on the Nafion polymer substrate from supersaturated aqueous solutions is studied by XRD. The solutions are prepared from natural deionized and deuterium-depleted water. It was earlier established that the swelling of Nafion in natural deionized water clearly demonstrates effects caused by the partial uncoiling of polymer fibers into the liquid volume, but no such effects were observed in deuterium-depleted water. The ab initio calculations performed in the present work show that the uncoiling of lateral Nafion chains with terminal –SO3H groups and the dissociation of these groups with subsequent formation of hydronium ions and structural anionic residues are energetically favorable in the case of the contact with a sufficient amount of water molecules. The influence of these factors on the process of crystal formation on polymer substrates is studied. It is established that the effect of partial uncoiling of polymer chains indeed affects the crystallization, and does it in different ways, depending on the crystal structure. Thus, no differences between XRD patterns of crystals grown on smooth and polymer substrates are observed for the monoclinic lattice of sodium acetate trihydrate. In the case of copper sulfate (with either CuSO4·5H2O pentahydrate crystals (triclinic crystal system) or CuSO4·3H2O trihydrate crystals (monoclinic crystal system)), copper sulfate trihydrate and pentahydrate are formed on the polymer and smooth substrates, respectively. None of the studied crystals exhibited differences between smooth and polymer substrates for the supersaturated solutions based on deuterium-depleted water, and in both cases a triclinic crystal system of the CuSO4·5H2O pentahydrate precipitate is identified for the CuSO4 aqueous solution. For sucrose, the precipitate amorphization upon the deposition onto the Nafion plate is detected. A theoretical model is proposed to explain the effect of partial polymer chain uncoiling on the growth of crystals, depending on their crystal system, unit cell parameters, and the volumetric ratio of hydrophilic and hydrophobic fragments in the molecular structure. [ABSTRACT FROM AUTHOR]

The article presents the results of hydrochemical studies of waterbodies with varying degrees of development of anaerobic conditions (up to the appearance of meromixia with sulfide anoxia) in the Porya Guba Bay (Kandalaksha Bay, White Sea, Kandalaksha State Nature Reserve). It is shown that these waterbodies, which are at different stages of isolation from the sea, have a unique hydrological and hydrochemical structure, formed at a certain stage of their evolution. The vertical stratification of water, with the development of all phenomena accompanying stagnation, is more pronounced in the most distant parts of their water area from the sea, where elevated contents of hydrogen sulfide (up to 16.5 mg/L), phosphates, silicon, nitrite, and ammonium nitrogen are noted in bottom anaerobic water. However, the concentrations of all major ions are comparable to those in seawater and hardly chance at all vertically. Analysis of the distribution of the hydrochemical parameters of the distant reaches of Ozerki Lagoon made it possible to conclude that, due to changes that have occurred with this waterbody over the past 90 years, it can now most likely be classified as meromictic. [ABSTRACT FROM AUTHOR]

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species and Prosthecochlori aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast. [ABSTRACT FROM AUTHOR]

Abstract—Parkinson's disease is a chronic neurodegenerative disease, one of the pathobiochemical manifestations of which is an imbalance of neurotransmitters in the brain. The aim of this work was to study the effect of glycoalkaloids on changes in the level of neurotransmitters and markers of brain neurodegeneration in rats with experimental Parkinson's disease. Parkinson's disease was modeled in animals by intracerebral administration of rotenone. The studied glycoalkaloids were administered orally at a dose of 0.06 mg/kg for 28 days after pathology modeling. The study found that the use of the analyzed glycoalkaloids did not affect the concentration of dopamine and serotonin and also significantly (p < 0.05) reduced the level of ACh by 35.9% and increased the level of GABA by 55.1%, reduced the concentration of S100ß protein by 68.6%, and increased the level of BDNF by 52.4%. [ABSTRACT FROM AUTHOR]

Forbush decreases are sudden drops of cosmic ray intensity recorded by ground based and satellite detectors. This effect is strongly connected with coronal mass ejections from the Sun. Those are the massive eruptions of plasma material from the Sun atmosphere into interplanetary space. Coronal mass ejections affect cosmic ray particles while moving through interplanetary space causing Forbush decrease. In this work, we have studied the behavior of time profiles of cosmic ray intensity during Forbush decreases using data on cosmic proton fluxes recorded by the AMS-02 from 2011 to 2019. [ABSTRACT FROM AUTHOR]

This research focuses on studying of the process of glycolysis of polycarbonate (PC) catalyzed by zinc chloride. The degradation of polyester into monomers (bisphenol A, or BPA, and ethylene carbonate, or EC), which may then interact with one another to generate the matching ethers, was discovered to be the process. As a result, the optimal conditions for the depolymerization of PC to obtain bisphenol A and ethylene carbonate with the highest yield were therefore identified as 190 °C, a molar ratio of 11 between EG and PC, and a mass concentration of 0.4% ZnCl2. A scheme of PC glycolysis has been proposed, and a mathematical model adequately describing the experimental data has been developed. [ABSTRACT FROM AUTHOR]

In this work, a new analysis of the isotopic composition of boron nuclei (B) in galactic cosmic rays (GCRs) in the range of rigidities of 1–5 GV (nuclear energies 0.1–1.5 GeV/nucleon) was carried out using data from the PAMELA space experiment 2006–2014 on the rigidity of detected nuclei and their velocity (time-of-flight analysis and ionization losses in the instrument's multilayer calorimeter). The new results of the PAMELA experiment expand the energy range of previous measurements, are consistent with the few existing data, and indicate deviations of the B isotope ratios from the GALPROP simulation data for the GCR, similar to the deviations for the Li and Be isotopes in the PAMELA data, which can be interpreted as evidence of observation against the background of the GCR of the contribution of several local sources from explosions of nearby (hundreds of parsecs) supernovae. [ABSTRACT FROM AUTHOR]

The multi-component Al–Si–Re–O coating with a thickness of 3.5 μm was deposited on the quartz glass surface by the method of pulsed magnetron sputtering. Its structural phase state and optical and mechanical properties have been investigated. According to X-ray diffractometry and transmission electron microscopy, the structure of the coating is amorphous and has the following elemental composition: Al – 9.29 at.%, Si – 23 at.%, Re – 2.35 at.%, and O – 65.7 at.%. The present work studies the problem of crater formation under the bombardment of the quartz glass surface with Al–Si–Re–O coating by iron particles having a speed of 5–8 m/s. The study discovers protective properties of the Al–Si–Re–O coating manifested as an appreciable decrease of the surface density of the craters formed after impacts of iron microparticles as compared to the uncoated quartz glass. This effect is due to changes in the structure, phase composition, and mechanical properties of the glass surface layer coated by the reinforcing coating. The results show that the quartz glass with the Al–Si– Re–O coating remains transparent in the visible (T ≥ 77%) and UV ranges (T ≥ 23.8%). [ABSTRACT FROM AUTHOR]

In 1976 Simmons conjectured that every coloring of a 2-dimensional sphere of radius strictly greater than 1/2 in three colors has a pair of monochromatic points at distance 1 apart. We prove this conjecture. [ABSTRACT FROM AUTHOR]

Using femtosecond laser pulses delivered through an optical contact with a highly refractive zinc sulfide immersion medium, a readable photoluminescent micromark was written in the bulk of diamond. The influence of a highly refractive immersion medium on the position and size of the confocal region when reading a luminescent micromark is shown. It was established that in the materials under study the main mechanism of nonlinear attenuation of laser radiation is moderate two-photon absorption, the coefficients of which have been determined. The applicability of zinc sulfide as an optically consistent, highly refractive immersion medium for laser writing and reading of photoluminescent diamond micromarks has been demonstrated. After pressing the diamond into a zinc sulfide plate by high-temperature plastic deformation in an argon atmosphere, optical spectrophotometry and X-ray phase analysis reveal a noticeable opacity of the immersion material due to surface pyrohydrolysis, which partially impedes the read out of photoluminescent micromarks. [ABSTRACT FROM AUTHOR]

REINVENT 4 is a modern open-source generative AI framework for the design of small molecules. The software utilizes recurrent neural networks and transformer architectures to drive molecule generation. These generators are seamlessly embedded within the general machine learning optimization algorithms, transfer learning, reinforcement learning and curriculum learning. REINVENT 4 enables and facilitates de novo design, R-group replacement, library design, linker design, scaffold hopping and molecule optimization. This contribution gives an overview of the software and describes its design. Algorithms and their applications are discussed in detail. REINVENT 4 is a command line tool which reads a user configuration in either TOML or JSON format. The aim of this release is to provide reference implementations for some of the most common algorithms in AI based molecule generation. An additional goal with the release is to create a framework for education and future innovation in AI based molecular design. The software is available from https://github.com/MolecularAI/REINVENT4 and released under the permissive Apache 2.0 license. Scientific contribution. The software provides an open–source reference implementation for generative molecular design where the software is also being used in production to support in–house drug discovery projects. The publication of the most common machine learning algorithms in one code and full documentation thereof will increase transparency of AI and foster innovation, collaboration and education. [ABSTRACT FROM AUTHOR]

In this paper, a method has been developed for heat treatment of details with a complex surface profile with a rapidly oscillating laser beam with modulated radiation power. This method is an alternative method for the dynamic formation of the distribution of the intensity of the laser spot. A mathematical model for calculating the distribution of the intensity of the oscillating beam and temperature fields induced by laser treatment is created. An algorithm for optimizing the parameters of high-frequency oscillations of the beam based on the solution of the inverse problem of thermal conductivity to obtain uniform heating of the near-surface layer of the material is developed. [ABSTRACT FROM AUTHOR]

The effects of heat treatment with continuous laser radiation on samples of the Fe–18Cr–10Ni alloy of the austenitic-martensitic class that have undergone preliminary megaplastic torsional deformation in the Bridgman chamber are investigated. It is established that the combined application of deformation (deformation in the Bridgman chamber) and thermal (laser heating) effects to the alloy forms the structure of metastable austenite (γ phase), which differs from stable austenite in higher strength characteristics. The nature of this phenomenon is discussed. [ABSTRACT FROM AUTHOR]

This work presents a series of successive vegetation experiments in biotesting of samples of sod-podzolic cultivated soil after its treatment with herbicides of the class of sulfonylureas—Magnum, water-dispersable granules (metsulfuron-methyl (600 g/kg) manufactured by August) and Alister Grand, MD (diflufenican 180 g/L + mesosulfuronmethyl 6.0 g/L + iodosulfuron-methyl-sodium 4.5 g/L + antidote mephenpyrdiethyl 27 g/L) manufactured by Bayer. The residual phytotoxicity of these preparations for seedlings of sensitive crops of white lupine (Lupinus albus) and mung bean (Vigna radiata) was studied. The initial soil samples were taken in the field on day 5 after the application of herbicides in winter wheat crops grown using two different tillage technologies: traditional moldboard plowing and zero tillage. The results of biotesting of samples at 20°C and humidity of 60% of field capacity showed that the half-life of herbicides (DT50) comprised 40 ± 3 days after the incubation start, and detoxification to the level of 70–80% occurred 200–240 days after the introduction of herbicides into the sod-podzolic. Regardless of the tillage method and the applied herbicide, the suppression of test crops at the level of >10% relative to the control was detected 2 years after the application of herbicides. White lupine and mung bean are highly sensitive to the effect of microquantities of herbicides of the sulfonylurea group; therefore, it is recommended to use these test crops to determine the residual phytotoxicity of soil. The shown residual effect of sulfonylureas on legumes is important for special crop rotations elaborated for zero tillage. [ABSTRACT FROM AUTHOR]

The paper considers various designs of detectors for the passage of charged microparticles, which can be installed on mass spectrometers in order to record the moment of passage of a microparticle and initiate the measurement process. The largest range of recorded masses and velocities was shown by the detector design, made on the basis of a dielectric base (PLA plastic) using a 3D printer and a nichrome filament. [ABSTRACT FROM AUTHOR]

The influence of antiorthostatic hypokinesia with an inclination angle relative to the horizon of ‒6 degrees for 21 days was used as a ground model of the physiological effects of weightlessness. Ten practically healthy male volunteers (30.7 ± 5.4 years, 78.0 ± 8.5 kg, 179.7 ± 5.3 cm) took part in the experimental study, who successfully passed the medical expert commission of the Institute of Biomedical Problems, Russian Academy of Sciences, familiarized with the study program and signed a voluntary informed consent to participate in the study. The state of the musculoskeletal system was assessed according to the results of force-velocity testing on an isokinetic dynamometer before hypokinesia and on the 3rd day after its completion. Staying in conditions of 21-day antiorthostatic hypokinesia with a body inclination angle of –6° relative to the horizon, as a model of the physiological effects of weightlessness, leads to changes in the functional state of the legs muscle, which manifests itself during force-velocity testing after hypokinesia by a decrease in maximum voluntary force (MVF) of extensors of knee joint from 8 to 14% compared with the base level. The decrease in MVF did not depend on a change in the force gradient, which reflects the ability to exert greater force in the shortest possible time. This indicated that the decrease in the MVF level after hypokinesia was mainly due to a change in the activity of slow motor units. At the same time, we assume that exposure to hypokinesia did not cause a significant change in the activity of fast motor units. This is confirmed by the results of the analysis of the electromyographic activity of the extensor muscles of the knee joint during testing on an isokinetic dynamometer. Also, after hypokinesia, the possibility of using muscle potential significantly decreased, the physiological cost of work increased with a decrease in strength indicators. [ABSTRACT FROM AUTHOR]

The phase diagram of the SrF2–MgF2 system has been studied by differential thermal analysis (DTA) and X-ray powder diffraction (XRD). The stability area of the compound SrMgF4 is very small, and its extent is about 20°С between 870 and 890°С. The formation of compounds by magnesium fluoride and strontium fluoride with other metal fluorides is considered in the M versus X coordinates, where M is the cumulative moment of the cation and X is the cation electronegativity. Two areas of compound formation were identified for each of the fluorides. Magnesium and strontium fluorides are amphoteric compounds in terms of the Lewis acid and base theory. [ABSTRACT FROM AUTHOR]

The composition and structure of the anoxygenic phototrophic bacterial (APB) community in the water column of meromictic Lake Bol'shie Khruslomeny during winter were investigated. The community developed at the depth of 4.25 m, and its activity in the ice-cover period was very low (6.2 µmol C L–1 day–1). The water in the zone of highest development of phototrophic bacteria was of an unusual lemon-yellow color, probably due to the production and accumulation of polysulfides. The near-bottom water was also of lemon-yellow color and was resistant to oxidation by the air oxygen. In the zone of peak APB development the content of BChl d from green-colored green sulfur bacteria was considerably higher than that of BChl e from brown-colored green sulfur bacteria: 77 and 23%, respectively. The cultures of green and purple sulfur bacteria were isolated from lake water, and their physiological and genetic characteristics were determined. Two strains of green sulfur bacteria (brown-colored BrKhr17 and green-colored GrKhr17) contained gas vacuoles in their cells. Phylogenetically they were most closely related to the green-colored strain Chlorobium phaeovibrioides DSM 265 and were identified as new strains of the species Chlorobium phaeovibrioides. [ABSTRACT FROM AUTHOR]

Molybdenum-containing composite nanomaterials are synthesized by the thermal decomposition of molybdenum hexacarbonyl in a solution-melt of polyethylene in mineral oil. The concentration of a metal-containing filler in the composite materials varied from 1 to 20 wt %. A technique for preparing film samples for spectroscopic studies is developed, and the samples obtained are studied by UV, IR, and Raman spectroscopy. It is found that additional absorption bands appear in the IR range, whose intensity depends on the concentration of molybdenum-containing nanoparticles in the composite materials. The spectral characteristics of Raman scattering show that all samples are characterized by the stretching of the C–C bond. In the visible light region, the spectrum of nanocomposites has a flat edge of its own absorption located in the region of wave numbers (18–31) × 103 cm–1. [ABSTRACT FROM AUTHOR]

Polymer composites with nanoparticles localized on the surface of polytetrafluoroethylene microgranules are synthesized by the method of thermal decomposition of metal-containing nickel salts. The synthesized nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffraction analysis. The size of the nanoparticles ranged from 3.5 to 8 nm, depending on the precursor. It follows from the data obtained that the particles have a complex composition. The study of magnetic properties shows that the system of magnetic nickel-containing nanoparticles in the samples at room temperature is in a ferromagnetic or superparamagnetic state. The blocking temperature and coercive force are calculated for each sample. [ABSTRACT FROM AUTHOR]

The output voltage, position sensitivity, and spectral sensitivity of a photodetecting element based on high-resistivity photosensitive CdSe layers have been shown for the first time to decrease hyperbolically with increasing layer thickness (in the range 6–60 μm) and increase linearly with increasing input electric current. The high position and spectral sensitivity found in this study (70.8 mV/(mm μA mW) and 375 mV/(μA mW), respectively), which considerably exceeds that of cadmium telluride layers, demonstrate that high-resistivity CdSe layers have considerable potential as a material of position-sensitive photodetectors. [ABSTRACT FROM AUTHOR]

The aspects of monitoring the energy characteristics of radio navigation signals of the global navigation satellite system (GLONASS) have been considered. It has been noted that the power of the incoming radio navigation signal in the lower atmosphere depends on the parameters of the onboard antenna system of the navigation spacecraft, primarily, on the shape of the antenna amplitude pattern. The amplitude pattern of the onboard antenna of the spacecraft has a complex shape, and in order to compensate for changes in the power of the radio navigation signal due to the navigation spacecraft moving away from (or approaching) the signal user, the shape of the amplitude pattern should be axisymmetric, i.e., resembling a figure of revolution. Based on regular monitoring of the energy characteristics of the GLONASS radio navigation signals, the shapes of the amplitude patterns of the onboard antenna feed systems of the spacecraft from the orbital group have been evaluated. As a result, asymmetry in the amplitude patterns of some spacecraft has been detected. It has been shown that the asymmetry of the amplitude pattern leads to a dependence of the power of the incoming radio navigation signal on the spacecraft aspect angle, i.e., the position of the spacecraft emitting antenna system relative to the signal user. The probable cause of such asymmetry has been identified as the gradual aging of the active devices in the antenna feed path. The obtained results indicate the need for regular and prompt monitoring of the energy characteristics of radio navigation signals in the lower atmosphere. The observed effect of asymmetry in the amplitude patterns should be taken into account when developing spacecraft antenna feed systems. [ABSTRACT FROM AUTHOR]

Mechanical characteristics of composite materials based on Fe – 18% Cr – 10% Ni alloy and composed of plastic macroscopic austenite regions distributed in a high-strength martensite matrix are studied. Stress-strain curves are obtained for the specimens with austenite regions differing in size and in shape. The plotted curves are used to determine the shapes of the austenite regions optimal in terms of combining the strength and ductility parameters of the material. [ABSTRACT FROM AUTHOR]

A new technique for the synthesis of luminescent powders of Ca1–x–yYbxEryF2+x+y solid solutions is proposed for the preparation of ceramics using ammonium fluoride and potassium fluoride as fluorinating agents. The phosphors show high upconversion luminescence energy yields (3-5.5%) indicating a low content of luminescence quenching impurities. [ABSTRACT FROM AUTHOR]

The isotopic composition of Li and Be nuclei in the 1–5 GV range of rigidities (nuclear energies of 0.1–1.5 GeV/nucleon) is analyzed using PAMELA flight data from 2006–2014 on the rigidity of detected nuclei and their velocities (time-of-flight analysis and ionization losses in the detector's multilayer calorimeter). The new PAMELA data expand the range of energies in earlier measurements, are consistent with scarce results, and indicate correlated deviations of Li and Be isotope ratios from the GALPROP data for GCRs, which can be interpreted as evidence of contributions from several nearby local sources against the GCR background. Analysis of precision AMS-02 data on the spectra of positrons, antiprotons, and secondary nuclei of Li, Be, and B also indicates correlated increases in intensity at rigidities of ~50–1000 GV, which could also be due to local sources. The contribution from local sources against the GCR background is estimated at levels of tens of percents for rigidities of 1–5 GV and several percent at rigidities of 50–1000 GV. [ABSTRACT FROM AUTHOR]

Intensity of the bands of upconversion luminescence of β-NaYF4:Yb3+/Tm3+ nanopowders in DMSO suspensions vs intensity of exciting radiation were analyzed. Ranges of changes in the intensity of excitation have been established, in which either the processes of energy transfer from the sensitizer ion to the activator ion or the decay of intermediate levels of activator ions dominate. [ABSTRACT FROM AUTHOR]

At brazing of dissimilar materials, such as Kovar and Ti (Mo), problems arise due to different physical and mechanical properties of the materials being joined and their chemical composition that affects the wetting of base material by brazing filler metal as well as the formation of the brazed joint structure. The results of investigations of the spreading of ductile silver brazing filler metals (Ag-Cu, Ag-Cu-Sn) over Kovar and titanium, and the influence of barrier nickel coating on the structure of Kovar–titanium brazed joints are shown. X-ray microanalysis revealed that brazed seams with eutectic structure form at the application of brazing filler metal of Ag-Cu system, and at the application of Ag-Cu-Sn brazing filler metal a third copper-based phase, enriched in the tin (up to 16.4 at.%), appears in the brazed seams along the boundaries of the Ag-based solid solution grains. Morphological features were studied of the structure of Kovar–molybdenum brazed joints produced by vacuum brazing, using a brazing filler metal of Cu-Mn-Co system. It is found that the brazed seam structure consists of a copper-based solid solution, separate iron-based grains and a molybdenum-based reaction layer, which crystallizes on the molybdenum–filler interface. Investigation results showed that shortening soaking time at brazing temperature reduces the reaction layer thickness to 1 μm. [ABSTRACT FROM AUTHOR]

The kinetics of butyl lactate production by the interaction of ammonium lactate with n-butanol in the presence of water in the temperature range of 130–170°C in a closed system was studied for the first time as one of the stages of a new integrated technology for the production of lactic acid and polylactide. Also for the first time, a reaction scheme and kinetic model of ammonium lactate esterification with n-butanol were proposed, taking into account the side formation of lactamide and the acid catalysis of esterification by lactic acid. The developed kinetic model can be used for mathematical modeling of a reactor for the synthesis of butyl lactate. [ABSTRACT FROM AUTHOR]

Mysterious Duality has been discovered by Iqbal, Neitzke, and Vafa (Adv Theor Math Phys 5:769–808, 2002) as a convincing, yet mysterious correspondence between certain symmetry patterns in toroidal compactifications of M-theory and del Pezzo surfaces, both governed by the root system series E k . It turns out that the sequence of del Pezzo surfaces is not the only sequence of objects in mathematics that gives rise to the same E k symmetry pattern. We present a sequence of topological spaces, starting with the four-sphere S 4 , and then forming its iterated cyclic loop spaces L c k S 4 , within which we discover the E k symmetry pattern via rational homotopy theory. For this sequence of spaces, the correspondence between its E k symmetry pattern and that of toroidal compactifications of M-theory is no longer a mystery, as each space L c k S 4 is naturally related to the compactification of M-theory on the k-torus via identification of the equations of motion of (11 - k) -dimensional supergravity as the defining equations of the Sullivan minimal model of L c k S 4 . This gives an explicit duality between algebraic topology and physics. Thereby, we extend Iqbal-Neitzke-Vafa's Mysterious Duality between algebraic geometry and physics into a triality, also involving algebraic topology. Via this triality, duality between physics and mathematics is demystified, and the mystery is transferred to the mathematical realm as duality between algebraic geometry and algebraic topology. Now the question is: Is there an explicit relation between the del Pezzo surfaces B k and iterated cyclic loop spaces of S 4 which would explain the common E k symmetry pattern? [ABSTRACT FROM AUTHOR]

Vibration is used to compact the concrete mixture in the manufacture of ferroconcrete parts without molds in long configurations. The transfer of vibrations from a cylindrical punch to filler particles in a viscous concrete mixture is studied. A mathematical description is developed for the motion of a spherical filler particle in a viscous medium set vibrating by a cylindrical punch, and its mean velocity and path in chaotic motion are determined. The range of velocity and path values for punch vibration with industrial frequencies and amplitudes is established. Mathematical modeling is employed. The possibility of varying the mean velocity and path in a viscous medium by adjusting punch vibration is established for particles of different size. [ABSTRACT FROM AUTHOR]

The goals of this study were as follows: (1) select grass mixtures to improve hayfields and pastures in ravine–gully systems exposed to radioactive contamination and (2) evaluate agrotechnical and agrochemical practices used to enhance productivity, restore radioactively contaminated forage lands on slopes, and reduce the accumulation of 137Cs in grass stands. Field works were conducted in 2003–2010 and 2019–2021 in the Plavsk raion, Tula oblast, on medium-loamy leached chernozem soils. The first experiment was conducted to examine yield and 137Cs accumulation dynamics in perennial grasses. The experiment included the following variants: (1) no fertilizers and (2) annual application of N60P60K60. The following plant species were tested: red clover, white clover, burr medic, fodder galega, bird's-foot trefoil, smooth brome, meadow fescue, and timothy. The grass mixture consisting of red clover, burr medic, and smooth brome turned out to be the most productive: 10.5 t/ha in terms of dry matter. The 137Cs content in air-dry herbage of leguminous–gramineous grass mixtures varies from 8.3 to 40.1 Bq/kg. Perennial legumes remove from soil two to three times more 137Cs compared to gramineous species. In the second experiment, mineral and microbiological fertilizers were applied to sown grass stands (smooth brome and smooth brome + fodder galega mixture). In heavy doses, nitrogen fertilizers increase the accumulation of 137Cs in grass stands. Their partial application makes it possible to avoid such an increase. The combined use of nitrogen and microbiological fertilizers doubles the 137Cs content in herbage. In both experiments, the lowest 137Cs accumulation coefficients were recorded in variants involving the application of double superphosphate with potassium chloride and Borofoska fertilizer P30K48 (B). [ABSTRACT FROM AUTHOR]

The first data on the distribution of cyanobacterial toxins have been obtained and a molecular genetic determination of cyanotoxin producers in the plankton of some lakes in the permafrost zone in Yakutia have been performed for the first time. Most of the lakes are characterized by high concentrations of nitrogen, phosphorus, and chlorophyll a and by an increased content of organic matter, which could be associated with a high anthropogenic load. Water blooms were visually observed in three of the six studied lakes during the summer period. The abundance and biomass of cyanobacteria in the lakes varied within 13.7–676.3 million cells/L and 0.6–4.8 mg/L, respectively. Eight species of potentially toxigenic cyanobacteria were found in phytoplankton using light microscopy. Regions of the mcyE gene involved in the biosynthesis of microcystin were amplified using the polymerase chain reaction method in environmental DNA isolated from planktonic samples. Cyanobacteria capable of producing neurotoxic anatoxin-a, saxitoxins, and hepatotoxic nodularins were absent in the lakes during the study period. The use of genus-specific primers to the mcyE gene enables us to find that the main producers of microcystins were represented by species of the genus Microcystis in most of the lakes and by species of Dolichospermum only in one of the lakes. Up to eight structural variants of microcystins, in general, arginine-containing isoforms MC-LR, MC-RR, MC-YR, MC-LY, MC-HIlR, [Asp3]MC-LR, [Asp3]MC-RR, and [Asp3]MC-YR, were identified in lake plankton using liquid chromatography–mass spectrometry. The maximal concentration of microcystins in plankton (intracellular fraction 803 ng/L) was recorded in a sample from Ytyk-Kyuyol Lake. The calculated content of microcystins per unit biomass of producing cyanobacteria (toxin quota) was low (0.005–0.069 µg/mg). In order to assess the potential hazard of toxigenic species of cyanobacteria to human health, the distribution of cyanotoxins and their producers should be further studied in water bodies of the region. [ABSTRACT FROM AUTHOR]

According to the estimation of experts, the number of breakdowns and accidents, as well as wear of parts of standard equipment, is 3–5 times (in some cases 8–10 times) greater during operation at low temperatures than under temperate climate conditions. Therefore, enhancing the quality of surfaces of various machines and mechanisms operating in the Arctic is relevant. This article suggests a method of combined processing that allows one to increase hardness, reduce roughness, obtain optimal residual stresses, and create regular surface microrelief to keep the lubricant on the surface. However, these properties must be maintained at temperatures down to –50°C. The effect of low temperatures on the surface layer of details after combined processing is studied. This work is useful for experts engaged in the design of machines for operation in the Arctic. [ABSTRACT FROM AUTHOR]

The research results on the influence of adhesive-active elements on the heat resistance of the experimental Ni–Cr–Co–Al–(Ti, Nb, W, Mo, Zr)-based brazing filler and brazed joints of ZhS6U ZhS6U nickel superalloy are presented. Doping with zirconium (>2 wt%) significantly impairs the heat resistance of both the brazing filler metal and the brazed joints. Partial compensation of the zirconium negative influence is possible due to additional dopin g with chromium. It is shown that such additional doping with chromium (up to 15 wt%) can increase the heat resistance of nickel filler metal by almost 30%. It is also proved that additional doping of experimental brazing fillers with titanium and niobium instead of zirconium allows obtaining the heat resistance of both a brazing filler metal and brazed joint. This heat resistance is close to the values of the base metal – heat-resistant nickel superalloy ZhS6U. [ABSTRACT FROM AUTHOR]

Barium lanthanum fluoride powders have been prepared by reacting barium nitrate and lanthanum nitrate in molten sodium nitrate at 350 and 450°C, using a sodium fluoride as a fluorinating agent. A fivefold excess of sodium fluoride has been shown to prevent pyrohydrolysis. We have identified a phase of variable composition with the fluorite structure, Ba1–xLaxF2+x (0.3 < x < 0.5), which has high ionic conductivity (2.3 × 10–4 S/cm at 500 K) and an activation enthalpy for ionic transport of 0.50 ± 0.01 eV. [ABSTRACT FROM AUTHOR]

The grinding of material in a vibrational mill is considered. Grinding is regarded as a random process consisting of a series of uniform events. The process is assumed to be steady, simple, and ordinary. We interpret grinding in a vibrational mill as a random Markov process. The calculation is based on the Kolmogorov equation. The motion of the grinding bodies in the mill is assumed to be accompanied by simultaneous interaction with all the particles of the material to be ground. A kinetic equation is obtained for the grinding process. This equation permits calculation of the particle size at any time on the basis of its initial size. The calculation of the grinding kinetics is illustrated by an example, and the calculation results are analyzed. [ABSTRACT FROM AUTHOR]

A Forbush decrease (FD) is a sudden drop of cosmic-ray intensity arising as an effect of coronal mass ejection (CME) propagation in interplanetary space. The different physical properties of each CME cause variability in the FDs observed by scientific instruments. A comprehensive study of both phenomena is required to properly understand the processes involved in FDs. Most of the current studies in this field use experimental data obtained by ground-based apparatus that measure the flux of cosmic rays via their interaction with Earth's atmosphere. Direct measurements in space of FDs are rather rare. In this work, we present the results obtained by the spacecraft-borne experiment Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA). The experiment took data from 15 June 2006 until January 2016. A series of FDs during the period 2006 – 2013 were studied. Only significant events with amplitude ≥ 10% for the proton flux R = 1.1 – 2.9 GV were taken into account. The dependencies of the recovery times on the particle rigidity were obtained for FD events generated by halo-type CMEs. [ABSTRACT FROM AUTHOR]

A de novo molecular design workflow can be used together with technologies such as reinforcement learning to navigate the chemical space. A bottleneck in the workflow that remains to be solved is how to integrate human feedback in the exploration of the chemical space to optimize molecules. A human drug designer still needs to design the goal, expressed as a scoring function for the molecules that captures the designer's implicit knowledge about the optimization task. Little support for this task exists and, consequently, a chemist usually resorts to iteratively building the objective function of multi-parameter optimization (MPO) in de novo design. We propose a principled approach to use human-in-the-loop machine learning to help the chemist to adapt the MPO scoring function to better match their goal. An advantage is that the method can learn the scoring function directly from the user's feedback while they browse the output of the molecule generator, instead of the current manual tuning of the scoring function with trial and error. The proposed method uses a probabilistic model that captures the user's idea and uncertainty about the scoring function, and it uses active learning to interact with the user. We present two case studies for this: In the first use-case, the parameters of an MPO are learned, and in the second use-case a non-parametric component of the scoring function to capture human domain knowledge is developed. The results show the effectiveness of the methods in two simulated example cases with an oracle, achieving significant improvement in less than 200 feedback queries, for the goals of a high QED score and identifying potent molecules for the DRD2 receptor, respectively. We further demonstrate the performance gains with a medicinal chemist interacting with the system. [ABSTRACT FROM AUTHOR]

Obtaining uniform hardening of the near-surface area to a given depth requires precise selection and control of laser radiation parameters, depending on the geometry of the part and its properties. Since laser irradiation is performed locally with step-by-step processing of the entire surface, the accumulated heat leads to an increase in the hardening depth and surface melting. In order to avoid uneven depths, it is necessary to vary the laser energy supply during processing to maintain stationary heating of the material. Experimental selection of technological parameters usually takes an excessive amount of time and material resources. This article presents a technique for the mathematical modeling of a high-carbon tool steel hardening process by calculating the temperature fields induced by laser radiation. The boundary of the hardening zone was determined as the isotherm of the corresponding austenitizing critical temperature in accordance with the heating rate. Experimental verification of the model was carried out on tool steels with carbon contents of 0.7 and 1.2%. The influence of the main processing technological parameters (radiation power, the laser spot diameter, and scanning speed) on the hardening zone size is shown. The paper also presents the use of the model for selection of the technological parameters of multi-track treatment to harden materials to a constant depth without surface melting. The effect of back tempering in overlapped regions is also considered. [ABSTRACT FROM AUTHOR]

The dynamical properties are studied of a system of a finite number of likely charged particles that interact via a screened Coulomb potential in the field of a parabolic trap. By the normal mode analysis, the spatial distribution of oscillation amplitudes of particles in the system is obtained in the quasiharmonic approximation: high-frequency oscillations are localized in the central region of the system. This leads to the fact that the vibrational spectra of particles are different in different regions of the structure. To generalize this result to a wide temperature range, a numerical analysis of systems of a finite number of particles in a trap is carried out by the classical molecular dynamics method. It is shown that the spectra of thermal vibrations of particles are spatially inhomogeneous: a spectrum is shifted to the low-frequency region as the distance from the subsystem under consideration to the center of the structure increases. Various methods for calculating the amplitude of thermal vibrations of particles, both within the quasiharmonic approximation and by the molecular dynamics method, confirm the inhomogeneity of the radial amplitude profile: the amplitude of thermal vibrations of particles at the periphery of the system is higher than that at the center of the structure. It is shown that, in the local approximation, the dynamical properties of subsystems of structures consisting of a finite number of charged particles in a trap under certain conditions are significantly different from the dynamical properties of systems of charged particles of similar density under periodic boundary conditions (PBCs). The results of this study may be useful in describing the dynamical properties of laboratory dusty plasma and colloidal systems. [ABSTRACT FROM AUTHOR]

The paper studies the magnetron sputter-deposited multilayer, multicomponent Al–Si–N/Ni/Al–Si–N coating possessing higher corrosion resistance. Studied are the phase and elemental composition of the coating and its structural layers. It is found that all coating layers have a columnar structure. The structure of the Al–Si–N coating is nanocrystalline, while the structure of the nickel layer is finely crystalline. The X-ray diffraction (XRD) analysis shows that AlN and Si3N4 phases with the hexagonal closed packed crystal structure are present in the Al–Si–N layer, which is confirmed by the XRD patterns obtained on a transmission electron microscope. According to corrosion tests, the corrosion resistance of specimens coated by the Al–Si–N/Ni/Al–Si–N coating, is higher than that of uncoated specimens. [ABSTRACT FROM AUTHOR]

The galvanomagnetic characteristics of SmB6 single crystals are studied within the temperature range of 1.9‒3.6 K at different orientations of the crystal faces. As a result, the electrical resistivities of the surfaces corresponding to the (100), (110), (111), and (211) crystallographic planes are determined. It is shown that the effective parameters of charge carriers, which determine the surface conductivity in SmB6, depend both on the orientation of the surface and on the method of its processing. It is found that the etching of polished polar surfaces formed by (100) planes leads at 1.9 K to a decrease in the density and to an increase in the mobility of surface n-type charge carriers from 113/a2 and 1.12 cm2/(V s) to 0.76/a2 and 18 cm2/(V s), respectively (lattice parameter a ≈ 4.134 Å). For etched nonpolar surfaces corresponding to the (110) and (111) planes, the maximum density of surface charge carriers (per unit area of the surface Brillouin zone) is found to increase by factors of 2.3 and 3.9, respectively. It is proposed to use this parameter as a simple criterion to identify the features of electron transport due to the nontrivial topology of the band structure of SmB6. [ABSTRACT FROM AUTHOR]

A technique for synthesizing Tb nanoparticles using laser ablation in various liquid media (MQ water, ethanol, isopropyl alcohol, and isobutanol) is considered with the aim of preparing colloidal solutions of Tb nanoparticles, containing different amounts of oxidized particles. The synthesis of nanoparticles in isobutyl alcohol exhibits the lowest percentage of oxidized particles relative to the total number of particles in the resulting colloid, with a final ratio of oxidized Tb2O3 particles to all particles close to 5%. The influence of oxidized particles on the intensity of physicochemical processes (formation of plasma, shock waves, acoustic signals, and chemical products as a result of dissociation of water molecules) occurring during optical breakdown of colloidal solutions, has been investigated. The general tendency of the influence of oxidized particles consists in an increase in the intensity of the aforementioned characteristics upon laser breakdown with an increase in the Tb2O3 fraction with respect to the total number of particles in the colloid. The observed effect is presumably related to the high aggregability of Tb2O3 particles, while the absorption coefficient of particles is of minor importance. [ABSTRACT FROM AUTHOR]

The influence of the rotation speed of the forming cylinder and the conveyor belt velocity on the web height has been studied. The mathematical dependence of the corresponding tests has been determined. [ABSTRACT FROM AUTHOR]

An important characteristic of a natural water body is the distribution of pigment composition of different groups of photosynthesizing organisms over depth and its variations in different seasons. Optical methods are widely used to monitor the concentrations of chlorophylls in algae or cyanobacteria in aqueous ecosystems, but they have very limited application in monitoring the bacteriochlorophyll (BChl) concentration in phototrophic bacteria. The paper describes comprehensively three new methods of quantitative analysis of the photosynthetic pigment of BChl d of green sulfur bacteria using spectral measurements in both initial samples of natural water (absorption spectra), and in pigment extracts in organic solvents (absorption and fluorescence spectra). A comparative analysis of the results from different methods is carried out using, as an example, natural water from the chemocline region in Lake Trekhtzvetnoe, one of the meromictic water bodies in the Kandalaksha Bay in the White Sea. Conclusions are drawn about the applicability conditions of different methods, their advantages and limitations. All three methods suggested have been proven to be efficient using, as an example, samples of natural water with BChl concentrations differing by orders of magnitude, from 5 to 5000 mg/m3. [ABSTRACT FROM AUTHOR]

Phytoplankton of the stratified Kislo-Sladkoe Lake (White Sea coast) was studied using chlorophyll fluorescence methods in 2018. A layer of red water was observed with a chlorophyll a concentration of 1.7 µg/L at a depth of 3.3 m in the chemocline (at the aerobic and anaerobic zone interface). Cryptomonad algae (Rhodomonas sp.) were dominant in the layer; high functional activity of the photosynthetic apparatus was recorded in the algae based on the PIABS fluorescence parameter (high values of the quantum yield of the primary photochemical reaction in photosystem 2 (PS2) (FV/FM)); the proportion of active reaction centers (RCs) (RC/ABS); and the quantum yield of electron transport in PS2 (). The high functional activity of the photosynthetic apparatus of cryptomonad algae in the chemocline points toward their stability in the presence of hydrogen sulfide. By comparison, the phytoplankton in the surface water layer showed lower photosynthetic activity. Experiments with photoinhibition showed that the chemocline phytoplankton community is characterized by a greater reparative capacity after photooxidative stress despite the increased photosensitivity. It is proposed to employ chlorophyll fluorescence methods to study a state of phytoplankton in stratified meromictic water bodies. [ABSTRACT FROM AUTHOR]

We have synthesized and investigated sodium sulfate-based materials with Na+ ion conductivity: Na2SO4, Na2SO4:3.5% Yb, and Na3Ga(SO4)3. The addition of Yb3+ heterovalent cations leads to a considerable increase in the electrical conductivity of Na2SO4 (by ~240 times at 573 K) as a result of sodium vacancy formation and stabilization of the high-temperature (hexagonal) phase (sp. gr. P63/mmc). The sodium vacancy concentration and mobility in the (Na0.895Yb0.035)2SO4 solid solution are nvac = 7.93 × 1020 cm−3 and μvac = 2.7 × 10−5 cm2/(V s) (573 K), respectively. [ABSTRACT FROM AUTHOR]