Vol 484, No 4 (2019)

We consider some consimilar problems of searching for disjoint subsets (clusters) in the nite set of points in Euclidean space. In these problems, it is required to maximize the minimum subset size such that the value of each intracluster quadratic variation would not exceed a given fraction (constant) of the total quadratic variation of the points of the input set with respect to its centroid. In the paper, we have proved that all the problems are NP-hard even on a line.

Quasi-classical asymptotic behavior of the spectrum of a non-self-adjoint Sturm–Liouville problem is studied in the case of a one-parameter family of potentials being third-degree polynomials. For this problem, the phase-integral method is used to derive quantization conditions characterizing the asymptotic distribution of the eigenvalues and their concentration near edges of the limit spectral complex. Topologically different types of limit configurations are described, and critical values of the deformation parameter corresponding to type changes are specified.

New generalization of Kravchenko–Kotelnikov theorem by spectra of compactly supported infinitely differentiable functions is discussed. These functions are solutions of linear integral equations of special form. The spectrum of is a multiple infinite product of the spectra of atomic functions. dilated by the argument. Constructed generalized series has fast convergence. This property is confirmed by the presented truncation error bound formula and the results of a numerical experiment.

In this paper, we present experimental results on the effect of nonlinear wave and cavitation processes occurring in flowing working parts of hydrodynamic generators of vortex and flat types with flow bodies of various shapes on the physicomechanical properties of a clay suspension. The model of the vortex-type generator with tangential and radial channels for feeding the working fluid of the generator, which is a flat channel with three bodies of flow around a cylindrical shape, was subjected to research.

The problem of modeling the angular momentum control modes of small spacecraft using electromagnetic systems interacting with the Earth’s magnetic field is considered. The electromagnetic system control law has been constructed for various compositions of measurable parameters. A set of scale factors has been formed to investigate the angular momentum control mode of dynamically similar models. Based on a dynamical test stand, we have carried out experimental studies to model the angular motion dynamics of small spacecraft with a magnetic attitude control system.

The basic conservation laws in the Green–Nagdi model of shallow-water theory are derived from the two-dimensional integral conservation laws of mass and the total momentum describing the plane-parallel flow in an ideal incompressible fluid above a horizontal bottom. This conclusion is based on the concept of a local hydrostatic approximation, which generalizes the concept of the long-wavelength approximation and is used for analyzing the applicability of the Green–Nagdi equations in modeling the wave flows with undular bores.

Amphiphilic diblock-copolymers (DC) of (2,3,4,5,6)-pentafluorostyrene and 2-hydroxyethyl methacrylate were prepared for the first time by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization. The morphology of films of diblock-copolymers that have a composition close to equimolar was studied by transmission electron microscopy. The observed microphase separation and formation of spherical nanodomains is not typical for equimolar diblock-copolymers and seems to result from hydrogen bonding between the hydroxyl and carbonyl groups (OH···OH and C=O···HO) in poly(2-hydroxyethyl methacrylate) blocks. Obviously, it is the ability of diblock-copolymers to self-organization is the cause of formation of fabric coatings with low surface energy (γ = 11.9 mJ/m²) and relatively large water contact angles (θ^Н₂^О = 120±6°) and diiodmetane (θ^CH₂^I₂ = 93±2°).

This paper reports on the creation of a highly porous material with a hierarchical structure using powder metallurgy methods based on nickel nanopowder and ammonium bicarbonate NH₄HCO₃ as a space holder.

A kinetic model was proposed for the response of nerve tissue to an external signal stimulus. The model is based on the views of a multistep and non-linear nature of the dynamic variation of the concentrations of N-acetylaspartic acid and N-acetylaspartate in the human nerve tissue. The substrate inhibition effect in this system is a necessary factor for the self-stabilization of N-acetylaspartate as a key brain metabolite. The existence of three stationary states accounts for the trigger behavior of the system.

Coking of anthracene at 400–600°C in the presence or in the absence of a cobalt catalyst supported on carbon nanotubes (CNTs) was studied for the first time. The coking products were examined by X-ray diffraction and electron microscopy. The CoO-CNTs catalyst considerably (by 50°C) decreased the temperature of the onset of coking and accelerated the coke formation. The presence of CoO-CNTs changed the coke morphology. Whereas coking of pure anthracene affords ~1 micron spherical particles of poorly crystallized carbon, in the presence of the catalyst, a carbon “coating” covering the CNT surface is formed.

The results of the U—Th—Pb geochronological studies indicate that in the Un’ja-Bom terrane the youngest peaks on the relative probability curves of ages are 207 and 212 Ma for zircons from the metasiltstone of the Kurnal formation and from the metasiltstone of the Amkan formation. Similar age estimates for the youngest peaks were obtained for the detrital zircons from the metasedimentary rocks of the Tukuringra terrain of the eastern part of the Mongol-Okhotsk belt, which indicates that the Lower Mesozoic flyschoid complexes in the structure of this belt are developed much wider than is currently believed. The results obtained in our U—Th—Pb geochronological and Sm—Nd isotope geochemical studies suggest’s that the sedimentary rocks material was carried to the sedimentation basin mainly from the continental massifs of the Amur superterrane.

The experience of LA—ICP determining of the isotopic composition of sulfur pyrite and arsenopyrite of gold deposits of the Baikal-patomsky plateau is considered. The technique is characterized. It is shown that all the studied samples have values δ³⁴S and δ³³S strictly corresponding to the law of mass-dependent fractionation of sulfur isotopes. A regular alleviation of the isotopic composition of sulfur of pyrite as its crystals grow for Sukhoi Log and the isotopic homogeneity of pyrite and pyrrhotite of the Golets Vysokhashiy deposit are established. It is concluded that the possible role of metamorphism of the Mamsko-Oronsky belt in the formation of isotopic homogeneity of ore sulfides.

The article presents the results of U-Pb in zircon and Nd-isotope study of the adakite granites of the Goryachinsky pluton, exposed along the Baikal coast in the section of termination of the package of shear tectonic plates of the Baikal-Muya belt. The Early Cambrian age of granitoids, which is unusual for the Northern Baikal region, is 545 ± 6 Ma. According to the authors, new geological and isotopic data indicate the formation of the studied granitoids at the final stage of the Late Baikal shear tectogenesis, which caused the manifestation of adakite magmatism within the Baikal-Muya belt.

The geometry of supposed coupling zones in the Kamchatka subduction zoneis determined by the earthquake size distribution based on earlier revealed relationship between its shape and rate of inelastic deformations. In the areas of higher aseismic slip, a break of linearity in earthquake size distribution is observed owing to the deficit of large earthquakes. Zones of higher coupling between the oceanic and continental plates are characterized by an excess of large earthquakes and an inverse bend in the earthquake size distribution. The mapping results of the bend value agree with the coupling zones distinguished from satellite geodetic data and inversion of marigrams.

This paper reports the results of the third Russian–Vietnamese expedition (POI FEB RAS and the Institute of Marine Geology and Geophysics, Vietnam Academy of Science and Technology) in the Gulf of Tonkin, South China Sea (April 2016) and field work outcomes from 2016-2017. The studies revealed new specific features of the distribution and origin of gas-geochemical fields in sediments within the rift zone of the Red River along a 150-km profile. Four zones with high amplitude anomalies of hydrocarbon gases, helium, hydrogen, carbon dioxide, and carbon monoxide were revealed. The distribution of the anomalies reflects the tectonic structure of the area and points to the presence of several lithospheric sources of gases including gases of deep origin. The studies were carried out within the scope of the Joint Vietnamese–Russian Laboratory for Marine Geosciences (POI FEB RAS and the Institute of Marine Geology and Geophysics, Vietnam Academy of Science and Technology). The article is dedicated to the year of friendship between Russia and Vietnam.

Avicin A is a bacteriocin from the gram-positive bacterium Enterococcus avium. It exhibits a high microbicidal activity against bacteria of the genus Listeria, a causative agent of the severe human infection listeriosis. We developed a biotechnological method for obtaining avicin A and characterized its structure and biological activity. We also proposed a possible mechanism of the antimicrobial action of avicin A.

In order to select the optimal method for disinfecting the scaffolds prior to decellularization using morphological methods (studying the biomechanical strength of extracellular matrix fibers) and analyzing chemiluminescence in rats, the effect of octenisept and chlorhexidine was studied at different concentrations on the biological matrices of the lungs before and after decellularization. Chlorhexidine at a dilution of 1:10 possessed the least damaging properties for the matrix and most contributed to the decontamination of the cages for further storage and experimental studies.

The molecular and chromosomal localization of the dunce gene was studied. This gene (167.3 kb) consists almost entirely of introns, in which a cluster of seven short tissue-specific genes is located. On the basis of the results of FISH analysis of the gene fragments, we established that the dunce gene is located within nine chromosomal structures (four bands and five interbands), which contradicts the common idea that genes are located in only one structure (band or interband) or at the boundary of these structures. Our results are quite unexpected and original and greatly expand the current understanding of the genetic organization of interphase chromosomes.