Bismuth in quaternary and quinary solid solutions based on A<Subscript>3</Subscript>B<Subscript>5</Subscript> compounds

The heterophase equilibria in the InBiAsSb and GaInBiAsSb systems are analyzed in the context of simple solutions. Linear interpolation is to determine the thermodynamic and crystal-chemical parameters for virtual GaBi compound. The boundaries of existence for InBiAsSb and GaInBiAsSb solid solutions are calculated and the thermodynamic limits that characterize their synthesis are determined for the temperature range of 650–780 K. Heteroepitaxial InBiAsSb/InSb structures are formed on the basis of our analysis by zone recrystallization according to temperature gradient (ZRTG).     

New possibilities of X-ray nanocrystallography of biological macromolecules based on X-ray free-electron lasers

X-ray serial nanocrystallography is a new technique for determining the three-dimensional structure of biological macromolecules from data on the diffraction of ultrashort pulses generated by X-ray free-electron lasers. The maximum achievable resolution for a set of experimental data as a function of the sample sizes and parameters of the equipment is estimated based on simulations of the diffraction process with allowance for changes in the electronic structure of the atoms of the sample under the influence of X-rays. Estimates show that nanocrystallography greatly enhances the possibilities of X-ray analysis, reducing the requirements for the minimum permitted size of the crystals and enabling to explore poorly crystallizable molecular objects, such as many membrane proteins and complexes of macromolecules.     

Hydrocarbon specificity in the selective catalytic reduction of NOx over Cu-ZSM-5 and Co-ZSM-5 catalysts

Transformation of surface nitrates under CH₄ (CH₄+O₂) was found to ensure steady-state activity of Co-ZSM-5 in the selective catalytic reduction of nitrogen oxides by methane (CH₄-SCR). For Cu-ZSM-5, such species are mainly converted into NO. Relaxation of the coordination sphere due to oxygen and NO adsorption, stability of C,N-containing intermediates and activation routes of hydrocarbons (methane, propane) were analyzed as factors determining catalytic properties of Cu and Co cations.     

Influence of growth conditions on the surface quality and structural perfection of multicomponent heterostructures based on group A3B5 compounds

The surface quality of epitaxial multicomponent layers based on group A³B⁵ compounds, which are grown under different conditions via floating-zone refining with a temperature gradient, is comprehensively analyzed. The main parameters (temperature gradient, solution-melt composition, supercooling level, matching between lattice parameters and the thermal expansion coefficients of the layer and substrate, and substrate orientation) affecting the surface quality and structural perfection of the heterostructures are determined.     

ENDOR study of anthraquinone paramagnetic complexes with Lewis acid centers of aluminium oxide

Paramagnetic complexes with charge transfer formed upon adsorption of anthraquinone on the surface of aluminium oxide were studied with EPR and ENDOR methods. A hyper-fine structure due to the interaction of unpaired electron with one and two²⁷Al nuclei of surface Lewis acid centers was observed. The process of complex decomposition in the presence of water on the surface was studied.     

Convergence and divergence sets of sequences of real continuous functions on a metric space

A general theorem is proved describing convergence and divergence sets of real continuous functions defined on a metric space E. A result is obtained that is new even for E=[0,1] with distance (x, y)=¦x–y¦.Translated from Matematicheskie Zametki, Vol. 17, No. 2, pp. 205–217, February, 1975.In conclusion the author wishes to thank P. L. Ul'yanov for suggesting this problem and for directing the work.     

Electrochemical Sensors for the Stripping Voltammetric Determination of Antimony(III)

The conditions of the modification of a glassy-carbon electrode with various polyphenols were studied by multicyclic voltammetry over a wide range of pH. The state of the electrode surface was additionally monitored by measuring cyclic voltammograms of ferrocyanide ions in the presence of a phosphate buffer solution (pH 7.0). It was found that the electrooxidation of all the studied polyphenols at the electrode surface resulted in the formation of a water-insoluble film which is capable of accumulating antimony(III) from aqueous solutions. The surface concentration of chemically active cites was of the order n × 10^–9 M/cm². The electrochemical sensors thus prepared were found to be suitable for the selective determination of antimony(III) by adsorption stripping voltammetry. The maximum signals of antimony(III) were obtained at electrodes modified with pyrocatechol and pyrogallol upon metal deposition from acetate buffer solutions (pH 4.5). The detected peak areas S (A · s) were directly proportional to the deposition time t _d (min) and the concentration of antimony(III). The analytical range was 10–250 g/L at t _d = 5.0 min, and the detection limit was 6 g/L. It was found that a sensor based on a pyrogallol film can selectively determine antimony(III) in the presence of Sb(V), Cu(II), and Pb(II), and can be used for the analysis of natural water.     

Thin-layer GaInSbAsPBi/GaSb heterostructures obtained from liquid phase in a temperature-gradient field

The results of growing thin epitaxial GaInSbAsPBi layers on a GaSb substrate from a liquid bismuth-containing zone in a temperature-gradient field are discussed. The composition and properties of GaInSbAsPBi/GaSb heterostructures are investigated.     

Silylation effect on the catalytic properties of FeZSM-11 in benzene oxidation to phenol

The outer surface of FeZSM-11 zeolite was selectively silylated without affecting the inner system of its channels. SiO₂ deposition suppressed both the acidity and catalytic activity of the outer surface in mesitylene isomerization. Neither zeolite activity, nor its stability in N₂O benzene oxidation to phenol have changed upon silylation. This fact gives evidence that the latter reaction proceeds primarily within the zeolite channels.