Search

Abstract: The mineral association of siderite with Cu–Fe sulfides, cronstedtite, and goethite were first recognized when studying the Mikheevskoe Cu(Mo,Au)–porphyry deposit. This association is confined to fault zones, where it fills a network of mineralized fractures developed on porphyry- and argillizite-type ores. Minerals of this association were also identified in some argillizite samples of this deposit. The formation conditions of this mineral association and its relation to the evolution of the Late Paleozoic porphyry system or other endogenic–exogenic processes manifested during the subsequent geological history of the study area were studied. The integrated research included microprobe analysis and the measurement of O and C stable isotopes in minerals of the studied association in the “Geoanalitik” (Yekaterinburg) and “Geonauka” (Syktyvkar) Centers for Collective Use. The study of mineral compositions and their relationships indicates that the studied mineral association deposited at temperature of about 70°C from neutral or low-acid solutions with varying \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{CO}}_{3}^{{2 - }}$$\end{document}, HS–, and aSiO2(aq) contents. The measurements of δ13C (from –5.5 to –18.2‰) and δ18O (from 20.4 to 33.4‰) values in siderite made it possible to calculate the composition of a mineral-forming fluid. It was established that such a fluid has the following parameters: δ18O H2O from –3 to +10‰ and δ13C CO2from 15 to –28‰. It could correspond to magmatogenic water fluids mixed with Corg-bearing surface water. Based on the obtained results, it is suggested that this mineral association is related to argillizites, the development of which occurred at the last stage of endogenic mineral formation at the Mikheevskoe deposit. Nevertheless, it is not excluded that it may be related with other low-Thydrothermal processes at the stage of Meso-Cenozoic tectonomagmatic activation of the Urals. There is no evidence of the relation of the studied mineral association with weathering crusts.

Abstract: The effect of introducing nitrogen into the reaction mixture during magnetron sputtering on the corrosion-electrochemical behavior of Ti–O–N films is studied using electrochemical and gravimetric methods. Polarization studies of electrochemical dissolution of films in an aqueous solution of 3% NaCl in a potentiostatic mode are presented. It is found that, upon dissolution of films, areas of passivation, activation, and trans-passivation of the coating surface associated with the formation of oxide films and titanium chlorides on the sample surface are observed. It is proved that thin films obtained with a high nitrogen content exhibit higher corrosion resistance. The main values of corrosion, namely, mass, depth, and current indicators, are calculated.

Oriented films of TiO2(rutile) were fabricated by oxidation of monocrystal films of pure titanium and those doped with nickel. Oxidation was performed in an atmosphere of pure oxygen or air. Oriented structures were obtained in both cases at the same temperatures. The dependence of optical absorption spectra from the grain (subgrain) size was established. Titanium oxide synthesized in air atmosphere is characterized by a shift in the absorption band edge to the low-energy side, whereas doping with nickel increases the band gap.

We demonstrate the feasibility of low-threshold (10-4 to 10-2 W cm-2) anti-Stokes conversion of photons in the range 1.72 -- 2.00 eV to luminescence at 2.14 -- 2.38eV at temperatures from 77 to 300 K in Zn0.6Cd0.4S crystals with nanoscale complexes of dye molecules and silver subnanoclusters adsorbed on their surface. The spectral characteristics of the centres involved in anti-Stokes frequency conversion indicate that this process in the crystals studied is due to sequential two-photon interband optical transitions. The absorption of a photon by a dye molecule and electron excitation transfer to an adsorbed silver subnanocluster produce a free hole in the valence band. Subsequent photoionisation of the subnanocluster produces a free electron. The last step of the anti-Stokes frequency conversion process is radiative recombination of the electron with a hole localised at an emission centre.

Abstract A single-phase sample of the LaSrCuO3.58 composition is prepared by solid-state synthesis at 1473 K in air. The conductivity of LaSrCuO3.58 is measured by a four-probe method at direct current in the temperature range from 298 to 1173 K at oxygen partial pressures from 28 to 2.1 × 104 Pa. Heating samples above ~670 K is shown to result in a changeover of the conduction type from semiconducting (p-type) to metallic. Exchange currents at the LSCuO/YSZ interface are measured by impedance spectroscopy. The measurements are carried out in high-density symmetrical cells LSCuO|YSZ|LSCuO, fabricated by hot pressing of powders under a pressure of 3.5 × 109 Pa at 773 K. Experimental exchange currents i0 (varying from 10-3 to 10-4 A/cm2 in the temperature interval from 800 to 1173 K) are comparable with such of materials based of lanthanum-strontium manganite.

Single crystals of the Rb4H2I2O10· 4H2O were synthesized for the first time and studied by X-ray diffraction analysis. The crystals are monoclinic, a= 7.321(6) Å, b= 12.599(8) Å, c= 8.198(8) Å, β = 96.30(7)°, Z= 2, space group P21/c. The H2I2O104–anion is formed by the edge-sharing IO6octahedra. The anions are united by hydrogen bonds into a chain running along the xaxis. The chains are combined by water molecules into a three-dimensional structure through hydrogen bonds. The compound is a proton conductor. The conductivity values measured at 20–60°C vary within 10–6to 10–4ohm–1cm–1.

The crystal and molecular structures of acid salt Rb2H3IO6were determined. The anion part of the structure is united via a hydrogen bonding system to form a layer parallel to the xyplane. The proton conductivity in the temperature range of 40–60°C was found to be 10–7–5 × 10–6Ohm–1cm–1, Ea= 2 eV.

Salts Rb2H3IO6, Rb4H6I2O12, and Rb4H2I2O10and adducts CsHSO4· H6TeO6and Cs2SO4· H6TeO6of the salt · acid type are calculated within density functional theory B3LYP. Calculations for Te, I, Rb, and Cs atoms make use of basis set LanL2DZ complemented by polarization d,p-functions and pseudopotential LanL2; for Li, O, and H atoms, basis set 6-31G** is used. The activation energy for the proton migration is commensurate with that for the water molecule abstraction in the salts and is smaller in rubidium salts than in cesium salts.

The behavior of electrochemical cells Pt(sponge)/Na5TbSi4О12/Na0.65CoО2(cell I) and Pt(sponge)/Na5TbSi4О12/Pt(sponge) (cell II) is studied by, respectively, potentiometric and impedance methods in oxygen and argon atmospheres at 50–300°C. Dependence of potential of cell I on the oxygen concentration is affected by the grain size of platinum sponge and the temperature. At 50–200°C the coarse-grained platinum electrode in contact with solid electrolyte Na5TbSi4О12exhibits an oxygen function characterized by the potential-determining reaction О2(g) + Н2О + 2е = НО–2+ ОН–. An impedance method shows the triple-phase boundary О2, Pt(sponge)/Na5TbSi4О12to be reversible with respect to oxygen. The reversibility is realized by minority charge carriers in the solid electrolyte, i.e. by oxygen ions.

The structure and surface characteristics of SnO2· 1.5H2O and composite materials with heteropolycompounds (HPC) formulated as SnO2· 1.5H2O–HPC (where HPC = (NH4)3PW12O40· nH2O, (NH4)2HPW12O40· nH2O, and H3PW12O40· nH2O) are studied by scanning tunneling microscopy. Hydrated tin oxide is characterized by a globular structure which differs substantially from the morphology of composite materials. The conductivity is studied as a function of both the temperature and humidity of environment and the composition of composite materials. For composite materials containing ((NH4)2HPW12O40· nH2O, the conductivity is shown to vary monotonously with the composition and obey the “mixture rule.” Introduction of (NH4)3PW12O40· nH2O to a composite is found to cause an extremely fast conductivity decay, whereas addition of H3PW12O40· nH2O results in the appearance of a “plateau” on the conductivity vs. composition curve. The explanation given to the phenomena observed is based on the mechanism of protonic transport in heteropolycompounds.

Dependence of electronic and ionic components of conductance of CsHSO4–SnO2systems on their composition is studied using the method of electrochemical impedance. The total electronic and ionic components of conductance nonmonotonically depend on the composition. To describe completely impedance diagrams of composite materials, an equivalent electrical circuit is proposed, which contains the bulk ionic conductance corresponding to the bulk of CsHSO4grains, and the conductance corresponding to the surface of tin dioxide grains. Each conductance component is separated out. The activation energies for the bulk and surface conduction equal 0.32 ± 0.02 and 0.36 ± 0.02 eV, respectively, and are independent of the system composition. The bulk ionic conductance monotonically decreases with increasing SnO2content and is well described wit percolation theory, whereas dependences of surface ionic and total electronic components have extremums.

Orthoperiodic and orthotelluric acids, their salts MIO6H4(M = Li, Rb, Cs) and CsH5TeO6, and dimers of the salt · acid type are calculated within density functional theory B3LYP and basis set LanL2DZ complemented by the polarizationd,p-functions. According to calculations, the salt · acid dimerization is energetically favorable for compounds MIO6H4· H5IO6(M = Rb, Cs) and CsIO6H4· H6TeO6. The dimerization energy is equal to 138–146 kJ mol–1. With relatively small activation energies equal to 4 kJ mol–1(M = Li) and 11 kJ mol–1(M = Rb, Cs), possible is rotation of octahedron IO6relative to the M atom in monomers of salt molecules. The proton transfer along an octahedron occurs with activation energies of 63–84 kJ mol–1. The activation energy for the proton transfer between neighboring octahedrons of the type salt · acid → acid · salt equals 8–17 kJ mol–1. Quantum-chemical calculations nicely conform to x-ray diffraction and electrochemical data.

Impedance spectroscopy is employed for studying the behavior of the interface of the SmCo0.8Ti0.2O3semiconducting oxide electrode with a sodium-conducting solid electrolyte (Na+–SE) in atmospheres of argon and oxygen. Compounds with the susceptibility to hydration decreasing in the row Na5TbSi4O12→ Na3Zr2Si2PO12→ Na3Sc2(PO4)3are used as the Na+–SE. Only the systems containing the Na5TbSi4O12solid electrolyte, the grain surfaces of which acquire boundary layers formed by hydration products, are sensitive to oxygen. The exchange current of the electrode reaction O2(g) + e ⇆ O2–increases from 1.8 to 19 mA/cm2in the temperature interval 250–300°C. The systems with Na+–SE that are not prone to hydration remain inactive in the oxygen atmosphere probably due to quick blocking of the active centers by nonconducting products of the secondary chemical reaction Na++ O2–→ NaO2.

The acid salt of orthoperiodic acid CsH9I2O12crystallizes in the monoclinic system: base-centered unit cell, space group Cc. Unit cell parameters: a=18.473(5) Å, b= 5.439(2) Å, c= 10.481(3) Å, β = 99.73°. The crystal structure consists of layers parallel to the yzcrystallographic axis. The layers are formed by the Cs+ions, the molecules of orthoperiodic acid IO(OH)5, and by the IO2(OH)–4ions and are joined via hydrogen bonds. The studies of proton conductivity of ceramics reveal their transition into a superionic state at temperatures above 40°C.

The functional status of the central nervous system (CNS), the character of the regulation of the heart rhythm, and general operative efficiency were studied in 96 five-, six-, and seven-year-old children working with a personal computer (PC). The study revealed certain age-specific features in the childrens' physiological reactions to this work: five-year-old children differed significantly from their six–seven-year-old counterparts both in their basal physiological status and in their reactions to working with a PC. Five-year-olds also displayed the least favorable time of the CNS functional parameters and operative efficiency (60% of these children displayed various signs of fatigue). Similar age-specific features were also found in the regulation of the heart rhythm while working with a PC. In spite of the fact that 58% of all the children examined showed an optimal strength of their autonomic regulatory mechanisms, a highly stressed state of the regulation of the heart rhythm was observed in 21 and 28% of five-year-old children before and after working with a PC, contrasted with 10–16 and 17–25% in six- to seven-year-old children, respectively. It was concluded that the physiological and hygienic norm setting for children working with a PC should consider the five-year-olds as a separate group.

The protonic and electronic conductivity of the specimens SnO2·nH2O, SnO2·Sb2O4·nH2O and SnO2at the temperature range from −20 to +60°C and the processes of ion transport through the interface SnO2·nH2O|Pt in hydrogen containing environments are investigated. A similarity of mechanisms of protonic transport in hydrated and non-hydrated specimens is shown.

Not Available

Auxins (IAA, NAA, p-CPA) caused 20–30% promotion of respiration of auxin-dependent cell cultures ofNicotiana tabacum, Glycine max, Taraxacum mongolica, andAtriplexsp. and had small if any effect on respiration of auxin-independent cell cultures ofRubussp. andScorzonera hispanica. Antiauxin (p-CPIBA) did not affect the respiration. The auxin effect on the respiration of tobacco cells was revealed 10 min after its addition to the suspension and reached a maximum value in 60 min. This stimulation preceded the induction of cell division by auxin. Mitochondria isolated from auxin-treated tobacco cells had greater oxidative and phosphorylative activity than mitochondria from untreated cells. However, isolated mitochondria did not respond to auxin. The inhibitors of respiration (cyanide, monoiodoacetate, malonate, and 2,4-dinitrophenol) eliminated auxin effect on the respiration and cell division. It is concluded that the promotion of respiration is a common event for the auxin effects both on cell extension and on cell division. This promotion is necessary for the induction of cell division and is exerted via direct activation of mitochondriain situ.

Not Available

Not Available

Without Abstract:

Nitrogen-doped titanium dioxide (N-TiO2) nanofilms were deposited by reactive magnetron sputtering under different bias voltage. The mode of sputtering influences to formation and properties of titanium films. X-ray diffraction (XRD) was used to study the phase transition and crystallinity of the nanofilms. A technique of layer-by-layer measurement of Raman scattering from nanostructured titanium dioxide films based on a preliminary sputtering of the films by argon beam under an angle of 45deg and less has been developed. Experimentally confirmed low dissolution rate of the coating in NaCl saline (0.9%).

To improve hemocompatibility of cardiovascular stents the coatings based on titanium oxides and oxynitrides were used. In the present work the morphology, surface properties (wettability and surface energy), and in vitro solubility of the ternary system Ti-N-O coating were investigated. Experimentally, low dissolution rate of the coating in saline NaCl (0,9%) was confirmed. Instrumental methods of quantitative analysis (XRF, AES) revealed that the Ti-N-O coating is chemical-resistant and does not change the qualitative and quantitative composition of body fluids.

We demonstrate the feasibility of low-threshold (10-4to 10-2W cm-2) anti-Stokes conversion of photons in the range 1.72 — 2.00 eV to luminescence at 2.14 — 2.38eV at temperatures from 77 to 300 K in Zn0.6Cd0.4S crystals with nanoscale complexes of dye molecules and silver subnanoclusters adsorbed on their surface. The spectral characteristics of the centres involved in anti-Stokes frequency conversion indicate that this process in the crystals studied is due to sequential two-photon interband optical transitions. The absorption of a photon by a dye molecule and electron excitation transfer to an adsorbed silver subnanocluster produce a free hole in the valence band. Subsequent photoionisation of the subnanocluster produces a free electron. The last step of the anti-Stokes frequency conversion process is radiative recombination of the electron with a hole localised at an emission centre.