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A phase transition accompanied by the appearance of a spike in the longitudinal resistance of a two-dimensional electron system has been studied using the electron spin resonance near the filling factor ν = 3 in the ZnO/MgZnO heterojunction. This transition occurs when the tilt angle θ of the magnetic field is increased to some critical value θc. An analysis of the spin resonance amplitude has made it possible to demonstrate the spin nature of this phenomenon. For example, the ground state of the system on both sides of the transition has a nonzero spin polarization, which changes by several times when the phase of the system is changed. Strong spin resonance is observed both at θ < θc and at θ > θc. Surprisingly, the spin resonance at the critical angle θc has been detected in only one phase, which lies in the region of magnetic fields below the critical field Bc corresponding to the spike position in the longitudinal resistance. An increase in the magnetic field to this value leads to a decrease in the resonance amplitude and an increase in the resonance width. In the field region above Bc, the spin resonance disappears completely. Such behavior of the spin resonance is most likely due to the formation of domains with different spin polarizations in the electron system. [ABSTRACT FROM AUTHOR]

Abstract—The effect of sulfide sulfur on the crystallization of ultramafic–mafic–intermediate magmatic systems is considered in order to assess its scale and direction during the crystallization of rock-forming phases. The study carried out a theoretical analysis of the effect of sulfur on the activity of the components of the silicate melt according to the Korzhinskii's principle of acid–base interaction. To test the theoretical constructions, published experimental data analyzed to select data allowing a direct comparison of sulfur-saturated and sulfur-free runs. Despite the very limited number of such experiments, they all fit well with theoretically predicted trends. It has been established that the addition of sulfur to the system moderately reduces the liquidus temperature of rock-forming minerals within 20–30°C, and significantly affects their composition. In particular, chrome spinel is enriched in chromium by 10–12 mol % and complementary depleted in aluminum. The composition of plagioclase is enriched in the anorthite component by 3 mol % in dacites and 8 mol % in andesites; this effect was not established in basalts, but its strengthening can be expected. Olivine and orthopyroxene demonstrate an insignificant increase in magnesian content, but the field of their coexistence is significantly reduced in favor of orthopyroxene, which should inevitably lead to a change in their cotectic and peritectic proportions. Natural observations that can be interpreted as the result of the sulfur effect are taken from publications. The results obtained lead to the conclusion that sulfur significantly affects the crystallization of silicate magmas. It follows that the petrological dependences calibrated for sulfur-free experiments should be applied with caution to the interpretation of sulfur-bearing systems. [ABSTRACT FROM AUTHOR]

A mechanism is suggested to explain the transport of sulfide material by means of its dissolution and subsequent redeposition under the effect of an ascending infiltrating flow of intercumulus melt during the compaction of cumulates in layered plutons. Evidences of this process are observable in the Burakovo–Aganozero intrusion. Analysis of data on Cu concentrations in rocks of the pluton (more than 10 000 samples of core material from 160 boreholes) reveals two distribution types of the low-sulfide mineralization. The vertical sections of the first type are characterized by mineralization distributed throughout the whole thickness of the lower unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates and the almost absolute absence of sulfides in all overlying rocks. In the second type, Cu mineralization is constrained to the top part of this unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates, and the overlying rock sequence of the zone of clinopyroxene–orthopyroxene–plagioclase (Cpx–Opx–Pl) cumulates includes intensely mineralized rocks. Physicochemical analysis within the scope of D.S. Korzhinskii's theory of acid–basic interaction and numerical simulations of the effects of major components of the melt on the solubility of the sulfide phase indicate that Ca and Mg play an important role in the liquid immiscibility/dissolution of the sulfides. A model is proposed for the origin of the low-sulfide mineralization of this pluton: clinopyroxene emergence on the liquidus resulted in the onset of liquid immiscibility of sulfide and produced Cu distribution of the first type. The infiltration of the intercumulus melt during the compaction of the cumulus material led to the dissolution and upward transport of the sulfide material for hundreds of meters and thus produced Cu distribution of the second type. [ABSTRACT FROM AUTHOR]

The effect of variations in the fo, fa, en, fs, di, an and ab components in high-Mg basaltic melts on the topology of the spinel liquidus was quantified by conducting simulations with the new SPINMELT-2.0 model for the spinel–melt equilibrium. It has been established that enrichment of the melt in pyroxene components leads to an increase, and conversely, enrichment in plagioclase and olivine components, to a decrease in the solubility of chromite. This effect can be important at the gravitational compaction of cumulates accompanied by the extraction of intercumulus melt and its infiltration upward. In this case, it is reasonable to expect sequential reequilibration of the infiltrating melt with cumulate piles of different composition. This suggests that Cr-spinel can be transferred and concentrated again during the postcumulus solidification stage of layered intrusions. The concentrating process involves Cr-spinel extraction into the melt enriched in pyroxene components and the subsequent redeposition of the mineral during when this melt reacts with the feldspar-rich matrix of proto-anorthosite layers or horizons enriched in olivine. Some of these layers and horizons may be produced by additional injections of more primitive magma. The realism of the proposed mechanism is evident from the well-known spatial relations between the chromite layers with anorthosites and dunite–harzburgites of the Bushveld complex. [ABSTRACT FROM AUTHOR]

Crystal size distributions (CSD) of olivine were obtained for 17 samples of plagiodunite and Pl‑bearing dunite from the central part of the Yoko-Dovyren massif, northern Baikal region, Russia. Three types of CSD were identified: loglinear, bimodal, and lognormal. Combining these data with the results of petrological reconstructions, which earlier revealed two main types of the Dovyren magmas (using the method of geochemical thermometry), we proposed a basic scenario of interaction between magmatic suspensions of different temperature to explain the diversity of the CSD. The intratelluric olivine transported by magmas of different temperature, which had not subjected to abrupt cooling or heating in the chamber, retained an original loglinear CSD. For some portions of the hottest magma (∼1290°C), it is assumed that the original olivine evolved into a bimodal CSD due to accelerated crystallization at faster cooling of the high-temperature injections contacting relatively cold crystal mush (∼1190°C). An interpretation of the lognormal CSD suggests that part of the olivine crystals composing the protocumulate systems efficiently interacted with the pore melt infiltrating upward during the compaction of the underlying crystal mush. This led to cycles of partial dissolution and regrowth of the olivine grains resulting in a final lognormal CSD. The infiltrating hot melt, which was undersaturated with immiscible sulfide liquid, could dissolve sulfides preexisting in the low-temperature mush. This produced dunites with lognormal CSD relatively depleted in sulfur and chalcophile elements. The lognormal CSD is considered to be a marker of crystal mush regions through which the focused infiltration of the pore melt proceeded. [ABSTRACT FROM AUTHOR]

The influence of variations in fo-, fa-, en-, fs-, di-, an-, and ab-components in a high-Mg basaltic melt on the topology of the spinellide liquidus was analyzed using the new model of the spinellide–melt equilibrium SPINMELT-2.0. It is shown that enrichment of the melt in the clinopyroxene component results in an increase in chromite solubility, whereas the plagioclase component leads to a decrease in chromite solubility. This effect may be of key importance under the conditions of gravitational shrinkage of cumulates accompanied by removal of the intercumulus melt and its upward infiltration. The successive re-equilibration of the infiltrating melt with cumulative rocks of different compositions may be expected. This allows us to assume the probability of transportation and subsequent accumulation of chrome–spinel at the post-cumulus stage in consolidation of layered intrusions. The nature of accumulation consists in the extraction of chrome–spinel into a melt enriched in the pyroxene component, which is followed by its release during the reaction of this melt with the feldspar matrix of protoanorthosite interlayers. The realism of the mechanism proposed is evident from the spatial relationship of the chromite layers with anorthosite in the Ram Island intrusion and in the Bushveld Complex. [ABSTRACT FROM AUTHOR]

Abstract—: The paper presents newly acquired data on concentrations of chalcophile elements and chalcogens (Se and Te) in sulfide-bearing rocks and Cu-Ni ores from the bottom portion of the Yoko-Dovyren Massif, northern Baikal area, Russia. Positive covariations between Pd, Pt, Au, S, and Te in the samples highlight sulfide control on the behavior of these elements, which was related to the redistribution of essentially Fe-Ni sulfide liquids at a magmatic stage. The character of relationships between Pd, Pt, Te, Cu, and S in the rocks led us to distinguish two groups of genetic trends: the first group combines samples from the chilled zone, plagioperidotites, and olivine gabbronorites that compose underlying sills in the central part of the intrusion, and the second one comprises poor and high-grade ores in the northeastern termination of the intrusion (Ozernyi Prospect). We put forward the hypothesis that the first-group trends reflect different degrees of accumulation of crystallization products of the most primitive sulfide liquids, whereas the trends of the second group pertain to sulfide matter significantly depleted in Cu, Te, and PGE. New data on Fe, Ni, Cu, Co, Se, Te, Zn, Mo, Ag, Cd, Sb, Pb, Rh, PGE, and Au concentrations in sulfides from the chilled gabbronorite and ores of the Baikalskoe deposit are presented. Results of thermodynamic modeling (with the COMAGMAT-5 program package) of sulfide saturation in the intercumulus of a primitive orthocumulate are used to reproduce the composition (Cu, Pd, Pt, Au, and Te) of the parental sulfide liquid. The model concentrations of noble metals in the sulfide are demonstrated to be one to two orders of magnitude higher than the concentrations in the "average sulfide" estimated by LA-ICP-MS. More realistic estimates for the composition of the parental sulfide liquids can be obtained by normalizing the bulk concentrations of these elements to 100% sulfide mass. These estimates are in good agreement with results from thermodynamic simulations. [ABSTRACT FROM AUTHOR]

The paper represents an algorithmic implementation of the SPINMELT-2.0 model designed to simulate Cr-spinel-melt equilibrium, and provides a description of its petrologic options. The properties of the SPINMELT-2.0 model were studied by modeling the topology of the liquidus surface of spinel and its dependence on pressure, redox potential, and concentrations of major components (including CrO and HO) in the melt. Reference simulations were carried out for primitive MORB tholeiite. The spinel composition is demonstrated to depend on variously (and often oppositely) acting factors. Providing an accurate estimate of a parental magma composition, the SPINMELT-2.0 program allows one to evaluate a range of P-T-fO-H O parameters responsible for the composition of an original magmatic spinel. The SPINMELT program makes it possible not only to effectively correlate available independent petrological estimates but also to consciously correct them, which is particularly important when the composition of the model melts should be estimated. This is illustrated by the application of the model to data on the composition of rocks and minerals of two young volcanoes in Kamchatka: Tolbachik and Gorely. [ABSTRACT FROM AUTHOR]

The paper presents results of testing currently used models proposed to describe Cr-spinel-melt equilibrium: models of the MELTS family by M.S. Ghiorso with colleagues, the SPINMELT program by A.A. Ariskin and G.S. Nikolaev, and the 'MELT-CHROMITE spinel calculator' by А.А. Pustovetov and R.L. Roeder. The new calibration of the SPINMELT model presented in this publication enables calculating a sixcomponent (Mg, Fe, Cr, Al, Fe, and Ti) composition of Cr-spinel and the $$T - {f_{{o_2}}}$$ parameters of its stability on the liquidus of basaltic melts under pressures up to 15 kbar. The model is based on results of 392 runs from 43 experimental studies, including systems of normal alkalinity at $${f_{{o_2}}}$$ ≤ QFM + 2. The experimental dataset (which was extended compared to that used for the previous calibration) allowed us not only to estimate the pressure effect, but also apply the model to aluminous and hydrous systems. Tests of the SPINMELT-2.0 model show that the errors of the calculated temperature of the spinel-melt equilibrium increase with pressure from 16°C at 1 atm to 50°C at 15 kbar. Experimental spinel compositions are reproduced by the model accurate to < 3 at % Al and Cr, and no worse 1 at % for the other cations. [ABSTRACT FROM AUTHOR]

The paper provides a review of calculations and experimental approaches to reproducing three types of crystal size distributions (log-linear, bimodal, lognormal CSD) and systematizes publications on CSD data in rocks of ten known layered massifs. For a more detailed discussion, the results for plagiodunite samples from the Yoko-Dovyren massif, northern Baikal region, Russia, harzburgite from the marginal zone of the Monchegorsk pluton, and urtites from the Lovozero intrusion, Murmansk region, Russia, were selected. Possible causes and scenarios for the formation of three types of CSD established for these intrusive objects are presented. [ABSTRACT FROM AUTHOR]

Recently, a scheme based on the method of weak measurements to register the trajectories of photons passing through a nested Mach-Zehnder interferometer was proposed [L. Vaidman, Phys. Rev. A 87, 052104 (2013)] and then realized [A. Danan, D. Farfurnik, S. Bar-Ad, et al., Phys. Rev. Lett. 111, 240402 (2013)]. Interpreting the results of the experiment, the authors concluded that 'the photons do not always follow continuous trajectories.' It is shown in this work that these results can be easily and clearly explained in terms of traditional classical electrodynamics or quantum mechanics implying the continuity of all possible paths of photons. Consequently, a new concept of disconnected trajectories proposed by the authors of work [Phys. Rev. Lett. 111, 240402 (2013)] is unnecessary. [ABSTRACT FROM AUTHOR]

Testing the Ballhaus-Berry-Green Ol-Opx-Sp oxybarometer (BBG) on independent experimental data indicates that it overestimates the oxygen fugacity by 0.6-1.3 log units under mildly reduced conditions (near the C-CO buffer) and by as much as 2-3 log units under reduced conditions (at the IW buffer and below it). A newly developed oxibarometer is suggested to minimize this effect and enhance the capabilities of redoxometry of low-pressure mineral associations, including magmatic melts undersaturated with respect to orthopyroxene ( Opx). The new empirical equation of the oxybarometer is applicable to a wide range of mafic-ultramafic magmas of normal alkalinity, including terrestrial, lunar, and meteoritic systems under pressures of 0.001-25 kbar and oxygen fugacity ranging from IW-3 to NNO + 1. The derived regression fits the ΔQFM values of the calibration dataset (154 experiments) accurate to ~0.5 log units. The new oxybarometer eliminates systematic errors when redox parameters are evaluated for the reduced region (from IW-3 to C-CO) and for crystallization of magmas without Opx on the liquidus. The efficiency of the suggested model is demonstrated by its application to natural rocks: (1) low-Ti lunar basalts, (2) tholeiites from the Shatsky Rise, (3) Siberian flood basalts, (4) rocks of the layered series of the Yoko-Dovyren intrusion, and (5) mantle xenoliths collected in southern Siberia, Mongolia, China, and the southern Russian Far East. The values yielded by such oxybarometers for intrusive rocks, which underwent long-lasting cooling and postcumulus reequilibration, should be regarded with reserve. [ABSTRACT FROM AUTHOR]

An updated version of the COMAGMAT-5.3 program is presented, which enables simulations of the silicate-sulfide immiscibility in parallel to the crystallization of Al–Cr spinel and other rock-forming minerals. The principal changes include a completed recalibration of the previous Fe–Ni sulfide solubility model (Ariskin et al., 2013) and incorporation of equations describing spinel–melt equilibria in a wide range of magmatic systems (Nikolaev et al., 2018a, 2018b). This allowed us to more accurately specify the link between the compositions of immiscible sulfides and magma crystallization temperatures and to correct alumina partitioning between the model spinel and crystallizing melt. The updated COMAGMAT-5.3 can be used for calculations of the crystallization of basaltic to komatiitic magmas, as well as the history of solidification of mafic to ultramafic cumulates, including the relative proportions of Al–Cr spinel and immiscible sulfides. The applications are exemplified by the solidification of sulfide-bearing primitive olivine cumulate from the inner-contact zone of the Yoko-Dovyren intrusion in Northern Transbaikalia, Russia. It is established that maximum crystallization proportions of Al–Cr spinel as high as 3.5 wt% are observed at the Ol–Sp cotectic, which is followed by an abrupt decrease to slightly negative values (because of spinel dissolution) during the crystallization of plagioclase-bearing assemblages. This results in an inflection point on the trend of spinel composition evolution, which changes from a decrease in the Cr/Al ratio in the field of olivine to its increase when plagioclase starts to crystallize. The first estimates are presented for the effect of Cr in pyroxenes on the crystallization proportion and composition of the Al–Cr spinel. A model calculation shows that this factor results in longer lasting spinel dissolution when pyroxenes start to crystallize, and the composition of this spinel is shifted toward Cr-poorer derivatives. [ABSTRACT FROM AUTHOR]

Plasma and magnetoplasma excitations in high-quality undoped two-dimensional electron systems based on SiGe/Si quantum wells are studied in detail. A two-dimensional electron system is formed by applying a vo-ltage to the top gate, which is partially transparent to subterahertz radiation in the frequency range of 20‒160 GHz. The results for SiGe/Si quantum wells with a Sb δ-doping layer are also presented for comparison. The transport and quantum scattering times for both structures are directly determined. It has been found that the effective electron mass is almost independent of the two-dimensional electron density in a wide density range. [ABSTRACT FROM AUTHOR]

Vinylation of silanes and disiloxanes has been studied. It has been shown that in the reactions of silanes with vinyl chloride and magnesium or sodium the sole product formed is tetravinylsilane. In the reactions of hexaethoxydisiloxane with vinyl chloride and magnesium, tetravinylsilane is the sole product formed. Hexavinyldisiloxane with yield up to 85% is formed in the reaction of hexaethoxydisiloxane with vinyl chloride and magnesium in the presence of copper(II) salts as alkylation catalyst. [ABSTRACT FROM AUTHOR]

Relaxation of an excited state of an atom in the vicinity of a nanoparticle has been described taking into account the rotational degrees of freedom of the atom. The description has been compared with the widely used generalized (vector) two-level model of an atom and the classical oscillator model. Relaxation dynamics of real atoms (excluding the atoms with the angular momenta J = 1 and J = 0 of the upper and lower levels, respectively) has been found to differ significantly from the predictions of those models. [ABSTRACT FROM AUTHOR]

1,3,5-Trimethyl-1,3,5-tris(hexafluoroalkyl)cyclotrisiloxanes were synthesized by hydrolytic polycondensation of methyl(hexafluoroalkyl)dichlorosilanes, and 1,1,3,3,5-pentamethyl-5-(trifluoromethyltrifluorobicyclo[2.2.1]heptyl)cyclotrisiloxane was synthesized by heterofunctional condensation. The effect of hexafluoroalkyl substituents at the silicon atom on the reactivity of the siloxane bonds has been studied. [ABSTRACT FROM AUTHOR]

The institute VNIIMETMASh has designed a new sleeve named VM-sinus for the continuous casting of round semifinished products. The working cavity of the sleeve is designed so as to ensure that it comes into intimate contact with the skin of the solidifying ingot both along the sleeve and about the perimeter of its cross section. Use of the sleeve has made it possible to produce commercial-sized batches of round semifinished products having the required geometric parameters. [ABSTRACT FROM AUTHOR]

Reaction of hexafluoropropene with butadiene and cyclopentadiene in a stationary system was studied. The reaction of hexafluoropropene with burtadiene was shown to proceed along the scheme of [2+2]-cycloaddition, and with cyclopentadiene, as [2+4]-cycloaddition. [ABSTRACT FROM AUTHOR]

Present situation in the field of friction materials science is discussed and new antifriction materials are described. Special attention is paid to polymer carbon plastics UGET and FUT and their modification for the friction units with water lubricant. The advantages of the developed carbon plastics and their modified types consist in high mechanical strength, impact resistance, reliable work under dynamic stresses and high hydrostatic pressures with almost all types of lubrication (water, acids, alkali, oils, hydraulic liquids, and others) and counter-bodies made of different materials (steel, bronze, titanium alloys, ceramics, etc.). [ABSTRACT FROM AUTHOR]

We establish a relation between bijective functions and renormalization group transformations and find their renormalization group invariants. For these functions, taking into account that they are globally one-to-one, we propose several improved approximations (compared with the power series expansion) based on this relation. We propose using the obtained approximations to improve the subsequent approximations of physical quantities obtained, in particular, by one of the main calculation techniques in theoretical physics, i.e., by perturbation theory. We illustrate the effectiveness of the renormalization group approximation with several examples: renormalization group approximations of several analytic functions and calculation of the nonharmonic oscillator ground-state energy. We also generalize our approach to the case of set maps, both continuous and discrete. [ABSTRACT FROM AUTHOR]

Experimentally determined resonant frequencies and damping of flexural and torsional vibrations of rod-type rectangular test specimens made of an orthotropic GFRP fabric with different ratios of cross-sectional sizes are used for calculating six principal complex elastic and shear moduli. The application of the classical theories of flexural and torsional vibrations, the theory of flexural vibrations of a Timoshenko beam, and a refined theory of torsional vibrations of free-free orthotropic rods is analyzed. [ABSTRACT FROM AUTHOR]

A cascade transfer of light energy to a resonance atom situated near a spherical nanoparticle and then, by a nonradiative mechanism, to the nanoparticle itself is considered. It is established that the efficiency of the cascade transfer essentially depends on the frequency and polarization of light, on the distance between the atom and the particle, on the optical properties of the particle, and on the time conditions of radiation. The rate of light absorption by a metal nanoparticle via cascade energy transfer may be 104–105 times higher than the direct absorption of light by a nanoparticle. For a fixed frequency of light, the cascade transfer of energy is a sharply selective function of the distance between the atom and the particle (the resonance width is about 10−2 of the particle radius). Atomic fluorescence exhibits similar behavior. This feature can form the basis for a new method of optical scanning microscopy and location and localization of atoms near the surface of a particle. [ABSTRACT FROM AUTHOR]

In a collaboration with the Moldavian Metallurgical Plant, VNIIMETMASh has used the results of studies of the design elements of continuous-caster molds to develop and succesfully produce a new liner for such molds - the VM-sinus. The main feature of this liner is the presence of convexity on the central sections of its walls. The convexity makes it possible to center the solidifying skin of the casting inside the liner when the skin is just beginning to form. Gradual straightening of the sinusoidal sections of the skin miminizes the size of the gas-filled gap between the skin and the walls of the liner. Gap size is minimized not only along the surfaces of the liner, but also at the corners. The new liners are being made at the pilot plant operated by VNIIMETMASh. [ABSTRACT FROM AUTHOR]

In investigations of predicted new types of photon echoes — an echo from a homogeneous ensemble of atoms and an echo of a single light pulse — have established that the magnitude and form of these new types of photon echoes are completely determined by the type of optical transition and by the “area” and polarization of the exciting light pulses (and the form can be controlled by varying the magnetic field). It is also established that the echo amplitude decreases for both small (compared to 1) and large light-pulse areas, and the optimal areas for which the maximum echo is obtained have been found. Investigations show that such photon echoes can also appear under conditions when an ordinary photon echo is absent (in atomic or molecular gases at high pressure, in the far-IR region of the spectrum, from cooled trapped atoms or ions, and so on). © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Over the next five years the development of the training of engineers in machinery and instrument construction in the USSR should be brought up to the requirements of the continuously accelerating pace of scientific and technological progress and the further raising of the political ideological level of Soviet specialists. [ABSTRACT FROM AUTHOR]

Polymethyl(hexafluoroalkyl)siloxane rubbers were synthesized by anionic and cationic polymerization of 1,3,5-trimethyl-1,3,5-tris(hexafluoroalkyl)cyclotrisiloxanes and 1,1,3,3,5-pentamethyl-5-(trifluoromethyltri-fluorobicyclo[2.2.1]heptyl)cyclotrisiloxane. The thermal properties of the new fluorosiloxane polymers were studied by thermal gravimetric analysis and differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

Methyldichlorosilanes with fluorinated cyclic substituents at silicon are prepared by the reaction of hydrosilylation of the corresponding hexafluoroolefins with methyldichlorosilane. [ABSTRACT FROM AUTHOR]

The paper presents results of petrological and geochemical studies of sulfide-bearing rocks from a bottom apophysis in the central part of the Yoko-Dovyren massif, northern Transbaikalia, Russia. It is composed of plagioperidotite and was sampled in a bulge up to 300 m thick throughout the whole vertical section, from its upper to lower contact. The observed diversity of sulfide-bearing rocks is subdivided into four types: (1) picrodolerite with droplet-shaped sulfides, (2) olivine gabbronorite with sulfides varying from droplet-shaped to irregular globules, (3) olivine gabbronorite with larger globules and patchy net-textured domains, and (4) net-textured ores. These varieties occur in the basal zone of the apophysis, in the interval up to 30 m inward from the lower contact. Petrographic features of these rocks correspond to olivine ortho- and mesocumulates, with the only exception of the quenched picrodolerite with an ophitic groundmass. The association of sulfides (pyrrhotite, chalcopyrite, pentlandite, and cubanite) has a pretty little varying composition, except only a relative decrease in the proportion of chalcopyrite in samples with more than 5% sulfides. The results of X-ray computed tomography show an increase in the sulfide connectivity in the rocks (from 25 to 95%) with increasing sulfide abundance. These characteristics, supported by visualized 3D models, allowed us to identify a morpho-structural trend tended from the rocks with sulfide droplets to the net-textured ores. The first ever data were obtained on the chemostratigraphy (PGE and tellurium) of rocks composing this apophysis. Covariations of Au, Pt and Pd with S and Te indicate that the precious metals have a single sulfide precursor. The 100%-sulfide compositions calculated for these rocks indicate that the most primitive and PGE rich sulfides correspond to droplets it the lowerest part of the apophysis, whereas the net-textured ores are depleted in these elements. The geochemical estimates are supported with COMAGMAT-5 modeling which made it possible to calculate the average Au, PGE, and Te contents in the protosulfide melt (in ppm): 2.9 Au, 14.4 Pt, 25.1 Pd, and 44.3 Te. Results of the geochemical studies of different fragments of the net-textured ores reveal a heterogeneity in the form of domains relatively enriched in copper, PGE, and tellurium, whose characteristic size is a few dozen centimeters. This can be considered as a signature of the porous migration and accumulation of the crystallization products of the original sulfide liquid at the subsolidus stage of cooling down the ore-bearing cumulates. [ABSTRACT FROM AUTHOR]

The paper presents data on sulfide globules in picrodolerites from a bottom apophysis of the Yoko-Dovyren massif, northern Transbaikalia. Textural features of the rocks indicate that they crystallized at rapid magma cooling. Their composition is similar to that of chilled olivine gabbronorites from the lower contact of the massif. Many droplet-shaped sulfides, which range from 2 to 15 mm, were identified in one of the samples using X-ray computed tomography. The largest of these globules was drilled out and studied in detail to clarify its inner structure, which consists of the main spheroid and a surrounding halo of disseminated sulfides. The main globule and surrounding halo significantly differ in composition (the halo is richer in Cu), as was calculated using the average compositions of the dominant sulfide phases and their relative proportions. The weighted mean (with regard for halo) composition can be assumed as an approximation of the composition of the initial sulfide liquid that was formed near the chill zone of the gabbronorite apophysis from the main intrusive chamber. The Cu content in the initial sulfide corresponds to the results of thermodynamic modeling (with the COMAGMAT-5 program package) of the geochemistry of primitive sulfides in ultramafite rocks from the basal zone of the massif. The differences in the composition of the halo and the main globule indicate the possibility of local migration (within a few millimeters) of the residual sulfide liquids enriched in Cu when the protosulfide melt differentiated. As a physical mechanism that produced the halo, we assumed that the latest sulfide fraction was pressed off into the pore space of rapidly crystallizing olivine orthocumulates. [ABSTRACT FROM AUTHOR]

Using electrophysiology, the effect of nicotinic acetylcholine receptor (nAChR) ligands on acetylcholine-induced depolarization in the neurons of Helix lucorum snail was studied. It was found that the α-conotoxin PnIA [R9, L10], a selective antagonist of α7 nAChR, and α-cobratoxin (antagonist of α7 and muscle-type nAChR) suppressed neuronal depolarization. Fluorescence microscopy showed staining of the neurons with fluorescently labeled α-bungarotoxin; this staining was reduced by pretreatment with α-cobratoxin. Induced depolarization was also suppressed by α-conotoxin RgIA, a selective inhibitor of α9 nAChR. In contrast to Lymnaea stagnalis nAChR, which are weakly sensitive to neurotoxin II and α-conotoxin GI, antagonists of muscle-type nAChR, H. lucorum receptors were most effectively inhibited by these antagonists. The results obtained, as well as the previously found sensitivity of the receptors studied in this work to muscarinic receptor ligands, indicate an unusual atypical pharmacological profile of H. lucorum nAChR. [ABSTRACT FROM AUTHOR]

The article focuses on the properties of vulcanisates based on polydimethyl methyl siloxane rubber. It shows that the vulcanisates were tested for swelling in T-6 fuel and toluene with vulcanisates of standard-produced rubbers. It also presents the physicomechanical properties of unfilled vulcanisates, swelling of vulcanisates of fluorosiloxane rubbers and the properties of filled vulcanisates.

The article presents a study which investigates the use of organosilicon hydroperoxides as vulcanising agents for rubber mixes based on siloxane rubbers. The study used infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy in investigating the physicomechanical properties of all rubber mixes based on polydimethylsiloxane SKTV. Results reveal a significant increase in the elongation at break and strength characteristics in the use of organosilicon hydroperoxides as vulcanising agents.

An Erratum to this paper has been published: https://doi.org/10.1134/S0021364023380010 [ABSTRACT FROM AUTHOR]

This paper presents principles of the method of modeling metal concentrations in sulfide at the occurrence of silicate-sulfide liquid immiscibility during middle and late stages of the crystallization of mafic-ultramafic magmas. The proposed approach combines the preliminary modeling of the crystallization of heterogeneous (melt + crystals) and initially sulfide-undersaturated systems with the calculation of the trace-element composition of sulfide liquid after its appearance in the system. The first part of the problem is solved using the sulfide version of the COMAGMAT-5 program, and the second part employs the modified Campbell-Naldrett equation. It was shown that a delay in silicate-sulfide liquid immiscibility and the low proportion of separated sulfide to major minerals are important factors of the geochemical evolution of sulfide liquid. By the example of the behavior of Cu, Pd, and Re, we discussed the reasons for differences between calculations for crystallizing multiphase cumulates and simplified (sulfide-silicate melt) systems. [ABSTRACT FROM AUTHOR]

The anticonvulsant effect of ethosuximide (T-type calcium channel blocker) was evaluated in Krushinsky–Molodkina rats predisposed to audiogenic epilepsy. Ethosuximide given with drinking water (300 mg/kg/day) over 45 days slightly reduced proneness to audiogenic epilepsy and increased locomotor activity of the animals at the periphery of the open field. Neonatal administration of ethosuximide (3-4 mg per animal, from 2 to 10 days of life) insignificantly modulated the parameters of audiogenic epilepsy in these animals at the age of 1.5 months and reduced manifestation of audiogenic myoclonic convulsion that developed after long daily sound presentation started at the age of 3 months. The findings attested to a weak anticonvulsant effect of ethosuximide on tonic convulsions with its predominant effect on convulsions with forebrain focus location. [ABSTRACT FROM AUTHOR]

The anticonvulsant effect of ethosuximide (T-type calcium channel blocker) was evaluated in Krushinsky–Molodkina rats predisposed to audiogenic epilepsy. Ethosuximide given with drinking water (300 mg/kg/day) over 45 days slightly reduced proneness to audiogenic epilepsy and increased locomotor activity of the animals at the periphery of the open field. Neonatal administration of ethosuximide (3-4 mg per animal, from 2 to 10 days of life) insignificantly modulated the parameters of audiogenic epilepsy in these animals at the age of 1.5 months and reduced manifestation of audiogenic myoclonic convulsion that developed after long daily sound presentation started at the age of 3 months. The findings attested to a weak anticonvulsant effect of ethosuximide on tonic convulsions with its predominant effect on convulsions with forebrain focus location. [ABSTRACT FROM AUTHOR]

The effect of the 2′-(3-trifluoromethyl-2,2,3-trifluorocyclobutyl)ethyl radical in fluorosiloxane on the thermodynamics of dissolution of various low-molecular-mass compounds in this polymer is studied via inverse gas chromatography. The activity coefficients at infinite dilution, Ω, in the temperature range 20-100°C are determined for C-C n-alkanes, cyclohexane, benzene, toluene, tetrachloromethane, trichloromethane, 2-butanone, and ethyl acetate. Flory-Huggins interaction parameters χ are calculated. It is shown that hydrocarbons are poor solvents (Ω > 6, χ > 0.5) and that the studied fluorosiloxane is not inferior to commercial polymethyl(3,3,3-trifluoropropyl)siloxane with respect to stability in nonpolar liquid media in the range 20-70°C. Trichloromethane (above 50°C) and compounds containing a carbonyl group are found to be good solvents. The dispersion component of the solubility of the polymer, δ, is determined to be 14.0 (J/cm) at 20°C and slightly lower, 13.5 (J/cm), at 100°C. Possible causes of these low values of δ are discussed. [ABSTRACT FROM AUTHOR]

The product of condensation of tetraethoxysilane with diphenylsilanediol was studied by gel permeation chromatography, Si NMR, and IR spectroscopy, and its structure was suggested. [ABSTRACT FROM AUTHOR]

The article offers information on the polyphenylsilsesquioxane (PPSSO)-polydimethylsiloxane block copolymer produced at the Scientific Research Institute for Synthetic Rubber (NIISK), the fractional analysis of rubber, and the polymer that was considered as nanocomposite material. Also mentioned are the glass transition temperature and the temperature range by block copolymer.

The article discusses modification process of acrylonitrile butadiene rubber (NBR) with small siloxane. Topics discussed include the use of dielectric relaxation to investigate blends of NBR, change in dielectric permittivity in glass transition of dielectric segment of rubber, and modification of rubber structure with small additions of siloxanes which changes the interaction with carbon black.

Influence of various Pt-containing catalytic systems and additives to them on regioselectivity of styrene hydrosilylation by methyldichlorosilane was studied. The regiospesific approach to methyl(2-phenylethyl)dichlorosilane in the presence of tetrakis(triphenylphosphine)platinum Pt(0) is developed. [ABSTRACT FROM AUTHOR]

Oxygen isotope composition was studied in 33 monomineralic fractions of olivine from plagioclase lherzolite, dunite, troctolite, and olivine gabbronorite of the Yoko-Dovyren layered massif. The δ18O values of the least altered rocks not contaminated with crustal materials range within 5.8 ± 0.2‰ (n = 27). These values for the dunite contaminated with carbonate material are notably higher and average at 6.2 ± 0.3‰. This is similar to characteristics of the Bushveld and Jinchuan mineralized complexes. Using the COMAGMAT-5 model, the temperatures of equilibrium of 98% crystals with late portions of the residual melts were evaluated at 1131–1266°C (1176 ± 34°C on average). These estimates are viewed as the closing temperatures of the cumulate systems with respect to the efficient exchange of 18O and 16O isotopes between olivine and mobile melt/fluid. For the uncontaminated systems, the δ18O values of the parental melt calculated using the modeled temperatures are 6.6 ± 0.2‰, and are 7.1 ± 0.3 ‰ for melts with signatures of crustal contamination. Such relations are consistent with insignificant (no more than a few percent) contamination of the parental magmas with carbonate materials from the host rocks. [ABSTRACT FROM AUTHOR]

2D carbon structures were prepared by carbonization of biopolymers (starch) via self-propagating high-temperature synthesis process. Electron microscopic, Raman spectroscopic, and X-ray diffraction examinations showed that the structure of the resultant particles corresponded to graphene nanoplatelets. Based on the Raman spectroscopy data, the average number of graphene layers in a graphene nanoplatelets particle was estimated at 2–5. The graphene nanoplatelets synthesized were applied as a support of a platinum-based catalyst (Speier's catalyst). The resultant supported catalyst was successfully used in the hydrosilylation of 1-hexene with methyldichlorosilane and then separated from the reaction products and reused. The catalytic activity of the supported catalyst was maintained for 4 months. [ABSTRACT FROM AUTHOR]

The dependence of the threshold pump energy of dye lasers on the quantum yield of fluorescence of active solutions in the case of laser excitation was studied. The rate of increase in the threshold pump energy was found to be considerably lower than the rate of decrease in quantum yield. The results were interpreted in terms of the development of the cooperative interaction between active centers in the high-intensity coherent pump field. [ABSTRACT FROM AUTHOR]

The bottom part of the Yoko-Dovyren layered mafic–ultramafic intrusion hosts the Baikalskoe deposit of Cu–Ni sulfide ores with Pt–Pd mineralization, and the stratigraphically higher portion of the intrusion includes units and pockets with low-sulfide ore with Pt–Pd mineralization. The maximum Pd, Pt, Au, Ag, Hg, and Cd concentrations and the greatest number of noble-metal minerals, including those containing Ge, are typical of vein-shaped sulfide-bearing anorthosite bodies and pegmatoid anorthosites in the upper part of the Critical Unit, at the boundary between the troctolite unit and overlying gabbronorite. The noble-metal minerals were produced mostly by postmagmatic pneumatolytic (fluid–metasomatic) processes. These minerals are kotulskite, moncheite, zvyagintsevite, telargpalite, paolovite, and other Pd and Pt chalcogenides and intermetallic compounds, including palladogermanide that contains 19.8 wt % Ge (the first find in Russia), paolovite with 8.1 wt % Ge (first find), and Au-rich zvyagintsevite that bears 0.55 wt % Ge. The palladogermanide has the composition Pd2.03(Ge0.80As0.15Bi0.02)0.97, and much of its Ge is substituted for As, as is typical of endogenic Ge minerals. The composition of the Ge-paolovite is Pd2.02(Sn0.54Ge0.35Sb0.05As0.04)0.98. The possible source of the germanium is contact-metasomatic pyrite-bearing paralic carbonaceous shales hosting the intrusion. [ABSTRACT FROM AUTHOR]

Hg and Cd are rare chemical elements found in magmatic PGE and Au mineralization and typical of this mineralization in the Late Riphean Yoko-Dovyren plagioperidotite–troctolite–gabbronorite intrusion hosted in the Baikalides of the Baikal area. The paper discusses variations in the composition, associations, and distribution traits of the Hg- and Cd-bearing Pt, Pd, Au, and Ag minerals. Many of the precious-metal minerals are Pt, Pd, and Au chalcogenides and intermetallic compounds of postmagmatic genesis and occur as single crystals and stringers in sulfides and silicate matrix and at their contacts. The minerals were formed with the participation of fluids from the crystallizing Fe–Cu–Ni sulfide melts. They are constrained to the central part of the intrusion and found in sulfide-bearing plagiolherzolite (PL) in the lower part of the intrusion, in sulfide-bearing pegmatoid troctolite (T) in the bottom portion of the troctolite unit, and in sulfide-bearing pegmatoid anorthosite (A) in the top part of the troctolite unit. From PL to T and further to A, the content and diversity of the Hg-bearing minerals remarkably increase, with Hg distributed in these minerals very unevenly, and with Cd-bearing minerals identified only in A. The leading Hg concentrators in T and A are pneumatolytic (fluid–metasomatic) moncheite and, particularly, later telargpalite (Pd,Ag)3(Te,Pd,Hg), which contains up to 11 wt % Hg. The latter mineral is sometimes found in association with Hg-electrum, kustelite, and potarite. Potarite in T is Pb-rich, and this mineral in A is Pb-free. Appreciable Hg concentrations in precious-metal minerals in the Yoko-Dovyren intrusion suggest that these minerals crystallized in a closed system at high temperatures. Potarite content in A is much higher, and Hg concentration in telargpalite in A is notably lower (2.9 wt % Hg on average) than in this mineral in T (5.9 wt % Hg on average). The potarite might have been produced by epigenetic serpentinization processes (low-grade metamorphism) at the expense of the material of pneumatolytic Hg-bearing telatgpalite, kotulskite, and zvyagentsivite. This corresponds to specifics in Hg distribution in the telatgpalite, kotulskite, and zvyagentsivite in T and A and much higher intensity of metamorphism. [ABSTRACT FROM AUTHOR]

We present the results of electrochemical measurements of the intrinsic oxygen fugacity of olivine separates representing seven rock types from the central part and southwestern termination of the Yoko-Dovyren mafic-ultramafic massif. The $${f_{{O_2}}}$$ values were determined using a high-temperature solid-electrolyte double-cell assembly developed at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. A total of 59 experiments were performed (from 7 to 16 for each sample) at the atmospheric pressure and within the temperature range of 800-1050°C at the 30-50°C increment. The results were interpreted using the calculated log $${f_{{O_2}}}$$ - 1/ T(K) and log $${f_{{O_2}}}$$ - T(°C) dependences. It was shown that the subsolidus temperature range of the rocks (below ~1050°C) is characterized by lowest intrinsic oxygen fugacity of olivine, which is 1-4 log units below the QFM buffer. For the solidus temperatures of ~1100°C, the more oxidized conditions ranging approximately from QFM to ~QFM-3 were measured. Extrapolating the log $${f_{{O_2}}}$$ - T°C dependences to the temperatures of the original magmas (~1200-1300°C) produces the maximum scatter in oxygen fugacities from ~QFM+2.5 to QFM-1. The estimated range of redox conditions for the Dovyren magma crystallization lies between the QFM and ~QFM-2.5 buffer equilibria. This is consistent with the complete absence of primary magmatic titanomagnetite and the presence of ilmenite in the Dovyren rocks. [ABSTRACT FROM AUTHOR]

The kinetically and sedimentation stable sols were synthesized on the basis of methyltriethoxysilane and additives of polyphenylsilsesquioxane-polymethyl-(3,3,3- trifluoropropyl)siloxane block copolymers and hydrogenated aerosil. The method of obtaining hydrophobic and superhydrophobic coatings based on the sol-gel compositions was developed. The resulting coatings are transparent; they have got an improved adhesion to glass. [ABSTRACT FROM AUTHOR]