Vol 487, No 2 (2019)

In the paper one studies the system of equations of the boundary layer of nonlinearly viscous fluid with the O. A. Ladyzhenskaya law. Previously, these equations were considered, the Mises transform allows to reduce the system of equations to a single quasilinear equation. In this work, we use the Crocco variables, which transform the system of equations of the boundary layer into a quasilinear degenerate parabolic equation. In contrast to the Mises variables, the Crocco transformation allows one to study both stationary and non-stationary equations; moreover, it makes it possible to obtain asymptotic estimates for the solution on the boundary of the domain.

Novel local image descriptor that is tested in the computer vision problem is proposed. The designed descriptor is based on visual primitives and relations between them, namely, coplanarity, cocolority, distance and angle. The designed feature descriptor covers both geometric and appearance information. Proposed descriptor has demonstrated its ability to compute depth maps from image pairs where the performance evaluation via criterion Bad Matching Pixels has shown it superior quality in comparison with other descriptors from state-of-the-art methods.

The work is devoted to the study of caustics of vortex optical beams. An asymptotic method for calculating the caustic surfaces of vortex beams was developed. The formulation of the inverse problem of the formation of axial caustics of the required type is considered. It is shown that the presence of the vortex component leads to the formation of an axisymmetric caustic surface, the characteristic diameter of which increases with increasing topological charge.

Extreme in amplitude and frequency properties of oscillations of a thin elongated flat body of elliptical form in the vicinity of the interface of stably stratified ideal fluids are studied. Numerical and analytical procedures have been developed for solving a self-consistent boundary value problem on an asymptotically large time range. The time-dependences of the amplitude decay and frequency of oscillations are obtained. The comparison with similar characteristics, found early by the authors for floats of other forms, is carried out, and significant quantitative and qualitative differences were established.

Ice formation in unsaturated soil is investigated, in the presence of pressure gradient and capillary forces. It is shown that in linear approximation the problem of determining of the amount of ice formed reduces to solving a non-uniform diffusion equation for water saturation. Similarity solution of the problem in one-dimensional case is obtained. It is found that the pressure drop at the cooling wall causes flow of water towards the crystallization front and leads to an increase in the amount of ice that forms.

Acridine reacts with red phosphorus in KOH/DMSO(H₂O) system upon heating (100 ºC, 3 h) to regioselectively give and 9,10-dihydroacridine in almost quantitative yields. Under similar conditions, the reaction of 9-chloroacridine with the system Pred/KOH/DMSO(H₂O) affords 9,10-dihydroacridine and acridone in 51 and 40% yields respectively.

The results of experimental studies of the nanowhiskers formation under the influence of relativistic electron beams of nanosecond duration on syntactic foam containing tungsten are presented. We demonstrated effects which observed after a single impact of relativistic electron beams with a flux density of 230-240 J/cm² and a total pulse duration of 150 ns. The spheres with diameter of more than 40 µm are destroyed in irradiated syntactic foam. Filamental structure is formed on the surface of such spheres. Its length is up to 10 µm and a diameter of about 100 nm. The complex kinetics substance expansion from the irradiated surface was found out. The speeds of gas-plasma formations expansion reached ~ 13 km/s. It was found that nanowhiskers are not formed near the emission “crater” from syntactic foam, where the duration of the mechanical pressure pulse is minimal and close to the duration of the relativistic electron beam impact.

The results of studying of the methane hydrate formation kinetics were presented. Dispersed frozen polyvinyl alcohol (PVA) solutions were used to form methane hydrate. The experiments were carried out in an unstirred reactor at the temperature near the ice melting point. Based on the obtained results it was found out that the water to hydrate transition time highly reduced (by several times) in the dispersed frozen PVA solutions than that in dispersed ice. It was established that the hydrate formation rate and the water to hydrate transition degree might be higher in the dispersed frozen PVA solutions than in aqueous solutions of surface-active agents and “dry water”.

Although the usual pressures typically only slightly affect the properties of condensed phases and their surface layers, in physical chemistry of surfaces, it was found a quantity, the contact angle on the three-phase contact line, that is very sensitive to pressure. In experiments with an air bubble in water stuck to a solid surface, an increase in hydrostatic pressure of less than doubled gave an increase in the contact angle of more than 10º if the angle itself was sufficient but less than 90º. Сhanging the orientation of the liquid - gas surface. If the angle (no matter sharp or obtuse) is close to 90º, the mobility of the three-phase contact line arises as an alternative way to achieve equilibrium. To explain these phenomena, a thermodynamic theory is formulated. It is shown that with a fixed line of three-phase contact, an increase in pressure in a liquid always causes an increase in the contact angle. At the same time, an increase in the hydrostatic pressure of water by two times is equivalent to an increase in the partial pressure of water vapor inside the bubble by a factor of seven.

In the paper are given the results of the first performed U-Pb dating of zircons from dacites and volcanic paleostructure of the Eastern zone andesite-dacite complex of the Urals orogen middle-uralian part, consisting of retro-overthrusted and cover-folded structural subzones. Volcanogenic complex, including vent and nearvent facies, occurs among flyschoid and carbonate deposits with the Middle Devonian fauna in cover-folded structural subzone forming an extreme eastern orogen limitation. Zircon grain age made up 389±5,6 Ma that also correlates with Middle Devonian. Consequently the formation of sedimentary and volcanogenic complexes occurred in a close age interval, but judging by their composition and structure, in different environmental conditions. Sedimentary formations accumulated in shallow basins, and the volcanic ones have been formed, apparently, under sub-areal conditions surrounded by the shallow sea basin. It is assumed that the manifestation of andesite-dacite volcanism, most probably, testifies to the spatial and age displacement of geodynamical and facies conditions to the eastern periphery of the orogen.

During the field works in the summer of 2018, in the Lena River delta on the Sardakh-Sisse Island, prints of leaf flora belonging to species of broad and small-leaved deciduous trees were found. The prints found by us are confined to the layer of ferruginous sandstones at the base of the section. The following taxa established: Platanus sp., Alnus sp., Fagus sp., Salix sp. In addition, a fossilized fruit belonging to Magnolia sp. The findings allow to conclude that there are mixed forests in the early-middle Miocene in this region, consisting of coniferous, small- and broad-leaved deciduous species of trees and shrubs.

Based on the data of atomistic modeling, various schemes of the isomorphic occurrence of K⁺ and Na⁺ ions in the crystal structures of CaSiO₃ and MgSiO₃ in the pressure range 18-25 GPa and temperatures of 1873-2223 K were analyzed. Under these PT parameters, the content of K⁺ and Na⁺ in structures under investigation was estimated. The semiempirical simulation data are in good agreement with the results of experiments with perovskite structure phases.

For the first time in natural conditions in the samples of lunar regolith from the Mare Crisium (“Luna-24” station) a high-temperature condensate was found in the form of binary glass balls of dimensions in the order of 200-400 nm, consisting of an oxide Al-Ca core covered with an uniform film of high-silicon glass, containing iron nano-inclusions. Previously, high-temperature condensate was only theoretically predicted on the basis of laser evaporation experiments.

The main objective of this work is to study the oxygen isotope composition of late Pleistocene syngenetic ice wedges and to obtain a high-resolution isotope diagram from a carefully sampled outcrop of Seyaha yedoma within of the third lagoon-marine terrace near the Seyaha (Zelyonaya - Green) river mouth, on the bank of the Ob Bay. According to 3 new radiocarbon ages: from 25.2 to 23.3 kyr BP from +2 to +5 m a.s.l., as well as dates: 17.3 kyr from +18.8 m a.s.l. and 11.6 kyr BP from +21.2 m a.s.l., the age of the ice wedge is from 23 to 15 to 18 kyr BP approximately. Values of δ¹⁸O in the upper fragment of the ice wedge vary from -25.75 to -3.15‰. Horizontal variations of δ¹⁸O values at a height of +15.2 m amounted to 1.49‰, from -23.41 to -24.9‰. The ice of the lower fragment of the ice wedge, at +6 m a.s.l., is characterized by a wider range of δ¹⁸O values than in the upper fragment. The horizontal values of δ¹⁸O range from -23.41 to -26.63‰.  The obtained oxygen isotope diagram in the upper fragment of the ice wedge has resolution of 80-100 years. According to palaeoreconstruction the average January temperature 23-15 (18) kyr BP ranged from -35 to -39 °C.

An isotopic-geochemical study was carried out for the waters of Tsivolki and Sedov bays (southeastern coast of the Novaya Zemlya archipelago). Waters of these bays can be freshened by several potential sources, which are river runoff from the continent, atmospheric precipitation of the region, waters coming from the archipelago. The possibility to use deuterium excess for identification of freshwater components in the waters, which enter the studied bays, is shown. Calculations made on the material sampled in 2015 showed the presence of the Ob River estuary waters in the surface waters of the Sedov Bay. At the same period, the waters of the halocline of Tsivolki Bay show freshening by local sources - runoff from the Novaya Zemlya archipelago.

The effect of aqueous unmodified fullerene C₆₀ dispersions (AFD) at a concentration of 5 mg/l on the total number and metabolic activity of heterotrophic river bacteroplankton has been investigated. The stimulating effect of AFD on the number of bacterioplankton and on the activity of electron transport chains in its cells is shown. It is established that in the presence of AFD decreases the bactericidal activity of antibiotics. The stimulating effect of fullerene on the natural heterotrophic bacterioplankton, which we found out, casts doubt on the expediency of using AFD as a bacteriostatic agent.