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The paper investigates the magnetic and electronic structure of GdX 2 Si 2 (X is Cu, Ag, Au) compounds in terms of the density functional theory with the emphasis on the spin-orbit interaction affecting the electronic structure of the GdX 2 Si 2 (001) surface. It is found that these compounds demonstrate an interlayer antiferromagnetism, which, however, does not affect the electronic structure of the GdX 2 Si 2 (001) surface near the Fermi level. The spin-orbit splitting of two-dimensional states on the GdX 2 Si 2 (001) surface, which combines the intrinsic spin-orbit splitting and Bychkov–Rashba splitting, grows with increasing atomic number of a noble metal in the intermetallic compound. Based on the analysis of the spatial extension of d-shells and their interaction with silicon orbitals, the spin-orbit interaction is explained for compositions containing noble metals. A comparison of rare-earth- and noble metal-based intermetallic compounds and isostructural intermetallic compounds with transition elements, shows that d-shell filling affects the spin-orbit interaction.

The paper presents ab initio calculations of the adsorption and diffusion of atoms of groups 1, 2 and 13 elements on the (0001) surface of antimony telluride (Sb 2 Te 3 ) topological insulator. It is shown that most of the investigated adatoms possess minimum energy when occupying the face-centered cubic (FCC) hollow site. Exceptions are presented only for beryllium, boron, indium and thallium atoms which adsorb at the hexagonal close-packed (HCP) hollow site. The adatom diffusion on Sb 2 Te 3 (0001) surface occurs in two stages, i.e. adatoms hop from an FCC site to an HCP site and vice versa. For beryllium, boron, indium and thallium atoms the order of these hops is modified because the HCP hollow site is more favorable location in terms of the absorption energy. The energy barriers are determined for hops on Sb 2 Te 3 (0001) surface, and the obtained hop frquencies are used to analytically calculate the diffusion lengths. The diffusion activation temperature is determined, when the adatom passes through the interatomic spacing of 2.5 Å in one minute. It is found that the highest (165 K) activation temperature belongs to beryllium, while the lowest (39 K) corresponds to cesium.

Bi–Bi 2 O 3 nanocomposite particles, with average particle size between 22 and 1300 nm, were prepared in a levitation–jet aerosol generator during a condensation of the bismuth vapor in mixed flows of inert gases with air. X–ray diffraction established in the particles the both phases of Bi and Bi 2 O 3 . It was discovered that the nanoparticles exhibit of a ferromagnetic behavior at room temperature. After a long duration of room-temperature aging, an enhancement in the magnetization was established. The maximum value of saturation magnetization observed in the studied nanocomposite particles was about 0.2 emu/g. It is proposed that an existence and interaction of intrinsic defects produced local paramagnetic states on the surface of nanoparticles and in interfacial areas is an origin of such magnetic phenomenon.

Studies of the biological activity of cerium oxide nanoparticles (CONPs) show that this compound exhibits antioxidant, antitumor, antibacterial and antiviral properties. The CONPs were obtained by pulsed electron evaporation in a low-pressure gas with a specific surface area of ∼ 190 m2/g. Strongly-noequilibrium conditions of synthesis led to the formation of high defect structures, which makes it possible to change the Ce3+/Ce4+ions ratio and, consequently, to enhance the level of their biological activity. To analyze the content of cerium with different valences, X-ray photoelectron spectroscopy was performed. To determine the enzyme-like activity of CONPs, a chemical analysis of the interaction with hydrogen peroxide was carried out on a spectrophotometer. The results show a significant presence of Ce3+in CONPs and the inhibition of reactive oxygen species (ROS). The valence of the cerium atoms determines the chemical activity of CONPs; thus, in a more alkaline medium, the CONPs decrease the ROS concentration, while in the acidic medium its activity diminishes. By varying the parameters of the nanopowders obtained and achieving the optimum Ce3+/Ce4+ ratio, one can produce CONPs having properties which enable the creation of pharmaceuticals for protection against ROS or for combating tumors, viruses and bacteria.

The results of a theoretical study of the Fe 3 SiTe 2 compound, belonging to a promising class of the van der Waals systems with high Curie temperature and gigantic magnetoresistance, are presented. It is found out that Fe 3 SiTe 2 represents a ferromagnetic metal characterized by high spin-polarization values at the Fermi level. It is shown that the charge transport occurs due to a contribution from the spin-down electrons and is formed prevailingly in the plane of five-layer blocks.

The results of a theoretical study of the Fe.sub.3SiTe.sub.2 compound, belonging to a promising class of the van der Waals systems with high Curie temperature and gigantic magnetoresistance, are presented. It is found out that Fe.sub.3SiTe.sub.2 represents a ferromagnetic metal characterized by high spin-polarization values at the Fermi level. It is shown that the charge transport occurs due to a contribution from the spin-down electrons and is formed prevailingly in the plane of five-layer blocks.

Inhomogeneous pseudo-random sequences of non-maximal length formed by shift registers with linear feedbacks based on a characteristic polynomial of degree n of the form ϕ( x )=ϕ 1 ( x )ϕ 2 ( x ), where ϕ 1 ( x ) = x m 1 ⊕ 1, and ϕ 2 ( x ) of degree m 2 is primitive ( m 1 = 2 k , k is a positive integer, n = m 1 + m 2 ) are considered. Three schemes that are equivalent in terms of periodic sequence structures were considered. Of the greatest interest are the shift registers connected in an arbitrary way using a modulo-two adder, the feedbacks in which correspond to the multipliers ϕ 1 ( x ) and ϕ 2 ( x ) the polynomials ϕ( x ). In this case, there is a complex process of forming output sequences, which involves both direct and inverse M-sequences. The statement about the singularity of the generated sequences at m 1 = 4 is proved, which is confirmed by their decimation with an index equal to the period of the primitive polynomial.

We consider homogeneous and nonhomogeneous pseudo-random sequences of non-maximal length formed by Galois generator based on characteristic polynomial in degree. We discovered periodic polynomial structures in degree in general form and on characteristic examples. We presented and applied the decimation method of periodic sequences, giving their decomposition on elementary M-sequences and constant components. We solved the tasks of analyzing of the diversity of generated sequences, which are organized and ordered from elements of direct and inverse M-sequences, and zero and one constants. We have obtained a general analytical relationship between decimation results and probabilistic properties. We discovered conditions for forming equal probability properties of the resulting sequences and determined the boundary relations of the generator parameters with the initial task of the minimum order of elementary M-sequences.

The epithermal Au–Ag mineralization at the Pechalnoe deposit is of considerable interest, since it was formed in carbonaceous terrigenous rock sequences making the basement of a volcanic dome structure at a distance of about 200 km from the boundary of the Okhotsk–Chukchi marginal continental volcanic belt. The geological structure of the Pechalnoe deposit consists of two levels, quartz–adularia and quartz Au–Ag veins are localized in keratinized terrigenous rocks of the lower level, while the quartz rhyolites and comendites of the Pechalninskaya rock sequence in the upper level harbor potential industrially valuable REE mineralization. The productive veins make three zones striking nearly east–west; the veins in these zones are 200–300 m long, occasionally reaching 640, 840 m; the mean thickness is 0.1–3 m, rarely reaching 6.2 m; the mean concentrations are Ag 266 g/t, Au 4.4 g/t. The following mineralogical features of the ores have been identified: low sulfides (1‒2%); the productive minerals are native Ag, low fineness Au, polybasite, and high-selenium acanthite. In addition, the ores have abundant enough arseniferous pyrite, arsenopyrite, pyrrhotine, ferruginous sphalerite, chalcopyrite, and marcasite. The geochemical features of the ores are in good agreement with their mineral composition. The ores are enriched in a wide range of trace elements (arranged in decreasing concentration): Ag, Au, As, Sb, Sе, W, Tl, Li, Be, Bi, Cs, and Mo; light lanthanoids prevail over heavy ones; very low Eu/Sm ratios ( ), little inclined near-chondrite distributions (without distinct europium maxima or minima); the relationship between Ce/Ce* and Eu/Eu* indicates oxidizing conditions during the mineralization; the REE spectra are dominated by light “hydrophile” lanthanoids of the “cerium” group; ΣREE varies in a wide range. The mineralogical and geochemical data obtained enable us to classify the Pechalninskaya mineralization as belonging to the selenium subtype of the low sulfide class of epithermal deposits. According to geological and mineralogic-geochemical evidence, the deposit can be classified as poorly eroded, which suggests future identification of new ore bodies not at the ground surface.

We consider nonhomogeneous pseudorandom sequences of nonmaximal length formed by a shift register with linear feedback (Fibonacci generators), and with internal half-adders (Galois generators). As a basis, we consider characteristic polynomial raised to the power of n of a form φ(x)=φ0m(x)φ1(x), where φ0 (x) and φ1 (x) are primitive polynomials respectively raised to the power of m1 and m1, m0 · m + m1 = n. We discovered periodic polynomial structures. Examples demonstrate a diversity of generated practical sequences, which are organized and ordered from elements of direct and inverse M-sequences. We investigated probabilistic properties of the formed sequences.