Photoinduced electron transfer involving radical ions in multicomponent solutions

A phenomenological study of a specific radical ion mechanism of formation of metastable products is presented. Energy level diagrams of fullerene C₆₀, tetramethylbenzidine, perylene, and radical ion pairs in toluene and benzonitrile are constructed. The possibility for obtaining fast optical switching and limiting in solutions of C₆₀ fullerene, tetramethylbenzidine, and perylene in toluene is analyzed.     

Influence of UV pretreatment on the abies wood catalytic delignification in the medium “acetic acid–hydrogen peroxide–TiO2”

Some regularities of abies-wood oxidative delignification by acetic acid–hydrogen peroxide mixture under the action of suspended TiO₂ catalyst and UV pretreatment of wood pulp were studied. The combined action of TiO₂ catalyst and of UV-pretreatment of abies-wood allow to produce at optimal conditions of the delignification process the chemically pure cellulose containing no residual lignin. The major characteristics of cellulose product obtained from abies-wood correspond to the characteristics of microcrystalline cellulose.     

Actual activation energy of electrochemical reactions at stage charge transfer

Relationships between the actual (i.e., determined on the basis of experimental data on the dependence of the overall current on the temperature) and true activation energies of the stages are found and analyzed for the process of stage charge transfer. It is shown that in the case of a significant deviation from equilibrium and in the absence of diffusion rate limitations, the actual real activation energy is the weighted arithmetic mean of the A ₁ and (A ₂ + F _η) values (where A ₁ and A ₂ are the true real activation energies of the corresponding charge transfer stages, η is the polarization). If a pronounced limiting stage is present, the actual activation energy is determined by the value of the true activation energy of the limiting stage.     

DFT study of polymorphism of the DNA double helix at the level of dinucleoside monophosphates

We apply DFT calculations to deoxydinucleoside monophosphates (dDMPs) which represent minimal fragments of the DNA chain to study the molecular basis of stability of the DNA duplex, the origin of its polymorphism and conformational heterogeneity. In this work, we continue our previous studies of dDMPs where we detected internal energy minima corresponding to the “classical” B conformation (BI‐form), which is the dominant form in the crystals of oligonucleotide duplexes. We obtained BI local energy minima for all existing base sequences of dDMPs. In the present study, we extend our analysis to other families of DNA conformations, successfully identifying A, BI, and BII energy minima for all dDMP sequences. These conformations demonstrate distinct differences in sugar ring puckering, but similar sequence‐dependent base arrangements. Internal energies of BI and BII conformers are close to each other for nearly all the base sequences. The dGpdG, dTpdG, and dCpdA dDMPs slightly favor the BII conformation, which agrees with these sequences being more frequently experimentally encountered in the BII form. We have found BII‐like structures of dDMPs for the base sequences both existing in crystals in BII conformation and those not yet encountered in crystals till now. On the other hand, we failed to obtain dDMP energy minima corresponding to the Z family of DNA conformations, thus giving us the ground to conclude that these conformations are stabilized in both crystals and solutions by external factors, presumably by interactions with various components of the media. Overall the accumulated computational data demonstrate that the A, BI, and BII families of DNA conformations originate from the corresponding local energy minimum conformations of dDMPs, thus determining structural stability of a single DNA strand during the processes of unwinding and rewinding of DNA. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2548–2559, 2010     

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.