Presowing Treatment of Spring Wheat Seeds by a Pulsed Electron Beam in the Atmosphere

High Energy Chemistry - The purpose of this work is to optimize the conditions of presowing treatment of spring wheat seeds with a low-energy pulsed electron beam. The absorbed dose in wheat has...     

The effect of the medium polarity on the mechanism of the reaction of hydroxybenzenes with hydrazyl radical in aprotic solvents

Mechanisms of the reaction of di- and trihydroxybenzenes with 2,2′-diphenyl-1-picrylhydrazyl (stable radical) in aprotic media of different polarity have been elucidated by experimental and quantum-chemical methods. Kinetic, stoichiometric, and activation parameters of the reaction have been determined. In benzene (nonpolar solvent), the studied reaction occurs via the hydrogen atom transfer mechanism; in the polar solvent with weak ionizing ability (i.e. DMSO), the reaction predominantly occurs via the faster mechanism of coupled electron and proton transfer.     

Study of spectator tagging in the reaction np → ppπwith a deuteron beam

The reaction has been studied in a kinematically complete experiment at a single beam momentum GeV/c (T = 759MeV). All four ejectiles have been detected in the large-acceptance time-of-flight spectrometer COSY-TOF. We analyzed the data along the lines of the spectator model as a means to isolate the quasi-free reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations of the deuteron wave function. Up to a Fermi momentum of roughly 150MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude that the deuteron can indeed be taken as a valid substitute for the neutron.     

Proton Coupled Electron Transfer in the Reaction of Hydroxybenzenes with Hydrazyl Radical in Aqueous Media

Russian Journal of General Chemistry - Possible electron transfer mechanisms have been studied for the reaction of 2,2′-diphenyl-1-picrylhydrazyl with a number of natural hydroxybenzenes in...     

Investigation of the structure of nanocrystalline refractory oxides by X-ray diffraction,electron microscopy,and atomic force microscopy

The structures of nanocrystalline fibrous powders of refractory oxides have been investigated by different methods: determination of coherent-scattering regions, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic-force microscopy (AFM). The sizes of nanograins of different crystalline phases of refractory metal oxides have been determined during the formation of these nanograins and the dynamics of their growth during heat treatment in the temperature range 600–1600°C has been studied. The data on the structure of nanocrystalline refractory oxide powders, obtained by different methods, are in good agreement. According to the data on coherent-scattering regions, the sizes of the ZrO₂ (Y₂O₃) and Al₂O₃ grains formed are in the range 4–6 nm, and the particle sizes determined according to the TEM and AFM data are in the ranges 5–7 and 2–10 nm, respectively. SEM analysis made it possible to investigate the dynamics of nanoparticle growth at temperatures above 1000°C and establish the limiting temperatures of their consolidation in fibers.

     

Transition State Structure and Mechanism of the Reaction of Hydroxybenzenes with N-Centered Radical in Non-Ionizing Media

Experimentaly and theoretically, using the method of density functional theory, the structure of 2,2'-diphenyl-1-picrylhydrazyl radical and the mechanism of its reaction with di- and trihydroxybenzenes in non-ionizing media have been investigated. It was established that in nonpolar solvents the elimination of hydrogen atom from hydroxybenzene by the radical occurs as a conjugate transfer of proton and electron, as confirmed by the existence of a deuterium isotope effect as well as characteristic geometrical and electronic parameters of pre-reaction complexes and transition states of the reaction.     

Classification of singular points in the polarization field of the cosmic microwave background and eigenvectors of the Stokes matrix

An analysis is made of the singularities of the polarization field of the cosmic microwave background, where the polarization is equal to zero. It is found that the classification of the singular points differs from the usual three types known in ordinary differential equations. The new statistical properties of the polarization field are discussed, and new methods to detect the presence of primordial tensor perturbations are indicated. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 6, 395–401 (25 March 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.