Oxidation of Sn(II) in methanesulfonate electrolytes in presence of antioxidants

The influence of copper(II) ions and some aromatic organic compounds on the oxidation of Sn²⁺ ions in the methanesulfonate electrolyte was studied.     

Anisotropic magnetoresistance of partially relaxed SrRuO3 films

The SrRuO₃ films (50 nm thick) grown by laser evaporation on (001)(LaAlO₃)_0.3 + (Sr₂AlTaO₆)_0.7 substrates were under partially relaxed biaxial compressive mechanical stresses. The films consisted of crystallites with lateral dimensions of 40–100 nm and a relative azimuthal misorientation of about 0.9°. Ferromagnetic ordering of spins in the SrRuO₃ films was manifested by a change in the slope of the temperature dependence of their electrical resistivity ρ at T ≈ 155 K. For a magnetic field H parallel to the measuring current, the maximum values (∼7.5%) of the magnetoresistance MR = [ρ(μ₀ H = 5 T) − ρ(μ₀ H = 0)]/ρ(μ₀ H = 0) were observed at temperatures of about 100 K. At T = 95 K (μ₀ H = 5 T), the anisotropic magnetoresistance of the films was 8% and increased by a factor of approximately 1.5 with decreasing temperature to 4.2 K.     

X-ray determination of the volume fraction of the B19′ martensite in nickel-titanium alloys

An X-ray method has been considered for determining the volume fraction of the B19′ martensite in semi-product NiTi alloys, which is based on comparing the total integrated intensity of its strongest reflections with the total integrated intensity of reflections from the matrix B2 phase. It has been shown that the method enables one to determine the volume fraction of martensite with an error of about 1% both in textured and textureless samples.     

Study of the diffraction scattering 12C + 12C with the excitation of the 12C exotic state 0 2 + (the Hoyle state)

New results from a series of experiments dedicated to the study of the ¹²C exotic state (the so-called Hoyle state) are presented. In spite of the many investigations that have been carried out, the structure of this state (which lies above the threshold for breaking up into three alpha particles) is still unknown. The different models assume that the nucleus has an abnormally large size in this excited state. However, until recently, methods for measuring the radii of unbound states have not been suggested. The best way to solve this problem seems to be by measuring the angular distributions of elastic and inelastic scattering of ¹²C on different target nuclei, and the determination of the radii is based on the fact that, at small scattering angles, the cross sections for direct reactions at high enough energies behave like Frauenhofer diffraction on a black ball. Accordingly, an experiment was performed aimed at measuring the elastic and inelastic angular distributions of ¹²C with an energy of (121.5 ± 0.5) MeV on a ¹²C target. The elastic scattering was measured in the angular range from 18° to 50° in the c.m. system with uncertainty in the angle of measurement equal to Δθ = ± 0.6°. The inelastic cross section was measured for the ¹²C excited state 2⁺ (4.44 MeV) and 0⁺ (7.65 MeV). Estimates were made for the diffraction radii for the ground and excited states. An increase was observed in the radius of the state at 7.65 MeV compared to those of the ground and first excited states.     

An undecaprenyl phosphate analog containing the phenoxy group at the ω-end of the oligoisoprene chain

A simple method for the preparation of a biologically active analog of bacterial undecaprenyl phosphate bearing the phenoxy group at the ω-end of the chain was developed on the basis of accessible polyprenols from mulberry (Morus nigra) leaves. It includes the selective van Tamelen epoxidation of the ω-terminal isoprene unit of polyprenyl acetates, conversion of the epoxides into ω-terminal aldehydes, their hydride reduction into hydroxy acetates followed by the Mitsunobu condensation with phenol, and phosphorylation of the resulting phenoxy alcohols. The biological activity of the obtained phosphates was tested by the radiometry method in the initiation of O-antigenic polysaccharide assembly reaction using the cell membrane preparations from the Gram-negative bacteria Salmonella arizona O:59 and Aeromonas hydrophila AH-1.     

Oxygen evolution on lead dioxide modified with fluorine and iron

In the oxygen evolution reaction in a sulfuric acid solution, the electrocatalytic activity of lead dioxide doped with fluorine or iron changes. At low and elevated dopant concentrations, the reaction rate is limited by the transfer of the second and first electrons, respectively. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.     

Mechanism of nitrate electroreduction on Pt(100)

Kinetics and mechanism of nitrate anion reduction on the Pt(100) electrode in perchloric and sulfuric acid solutions are studied. Analysis of the results of electrochemical measurements (combination of potentiostatic treatment and cyclic voltammetry) and the data of in situ IR spectroscopy allow suggesting the following scheme of the nitrate reduction process on Pt(100) differing from that in the literature. If the potential of 0.85 V is chosen as the starting potential for a clean flame-annealed electrode surface and negativegoing (cathodic) potential sweep is applied, then an NO adlayer with the coverage of about 0.5 monolayer is formed on Pt(100) in the nitrate solution already at 0.6 V. The further decrease in the potential results in NO reduction to hydroxylamine or/and ammonia, desorbing products vacate the adsorption sites for nitrate and hydrogen adatoms. At E < 0.1 V, adsorbed hydrogen is mostly present on the surface. During positive-going (anodic) potential sweep, the process of nitrate reduction starts after partial hydrogen desorption, the cathodic peak of nitrate reduction to hydroxylamine or ammonia is observed at 0.32 V on cyclic voltammograms. The process of nitrate anion reduction continues up to 0.7 V; at higher potentials, the surface redox process with participation of hydroxylamine or ammonia (the anodic peak at 0.78 V) and nitrate (the cathodic peak at 0.74 V is due to nitrate reduction to NO on the vacant adsorption sites) occurs.     

The Spectrum of the Two-Dimensional Periodic Schrödinger Operator

The absence of eigenvalues (of infinite multiplicity) for the two-dimensional periodic Schrödinger operator with a variable metric is proved. The method of proof does not use the change of variables reducing the metric to a scalar form.     

Modeling the wave parameters of a narrow slotted transmission line based on a superconducting film

An analytical expression for calculating the wave parameters of a narrow-slot transmission line is found in the quasistatic approximation. A two-fluid model is used for analyzing processes in a superconducting film of thickness comparable to the London penetration depth. The wave parameters of the slotted line are calculated under assumptions about the current distribution near the edges of the slot which are analogous to those used previously for analyzing microstrip and coplanar lines. Zh. Tekh. Fiz. 67, 94–97 (September 1997)