The extreme points of the unit ball of certain spaces of operators

In this note we discuss the set of extreme points of the unit ball of certain spaces of mappings. We prove that a mapping T: E F is an extreme point of the unit ball of the space I (E, F) of integral mappings, if and only if it has the formTx= ₀ >b ₀ , wherea, extS (E) andb ₀extS (F).Translated from Matematicheskie Zametki, Vol. 20, No. 4, pp. 521–527, October, 1976.     

On The Statistical Analysis of the Formation of Secondary Radiation Fields in Remote Control Devices Based on Pulsed Neutron Generators

Physics of Atomic Nuclei - The paper is devoted to the study of the influence of pulsed instability of neutron generation on the efficiency of small transportable HMCs. Experimental diagrams of the...     

Two-dimensional EPR image visualization of a skin effect for a conductive coal cylinder

Two-dimensional spatial distribution of the microwave field in a conductive coal cylinder has been obtained (skin effect visualization) by means of continuous wave electron paramagnetic resonance imaging technique. The algorithm we suggested previously and developed further here has been used. This method is based on the idea that spectra recorded under negative and positive magnetic field gradients are needed to obtain a single complex projection.     

Pyroelectric Properties of Potassium and Rubidium Titanyl—Arsenate Single Crystals in the Temperature Range of 4.2–300 K

The temperature dependences of the pyroelectric coefficients of KTiOAsO₄ and RbTiOAsO₄ single crystals grown by flux crystallization have been investigated in the temperature range of 4.2–300 K. With an increase in temperature, superionic conductivity first arises in KTiOAsO4 (at T > 200 K) and then (at T > 270 K) in RbTiOAsO₄. This conductivity is much higher in the samples polarized at T = 4.2 K. An exponential change in the crystal resistivity along the polar direction is simultaneously observed. The results of measurements in the range of 4.2–200 K indicate larger values of pyroelectric coefficients when compared with potassium and rubidium titanyl-phosphate crystals. A correlation between the pyroelectric coefficients and a change in the lattice constants at isomorphic substitutions of K atoms for Rb and P atoms for As has been revealed within the symmetry approach.     

Magnetic resonance spectrum of localized spins in conductive materials in a linear field gradient

For spins localized in a conductive sample the shape of the magnetic resonance spectrum is calculated in the presence of a linear gradient of the constant magnetic field. It is shown that the shape of the spectrum depends on the sign of the gradient. This result allows one to interpret an experimentally observed inequality of intensities of spectra which arise from skin layers on opposite sides of a sample when a linear gradient is applied across a sample with a given thickness. Results of this work will be helpful when the magnetic resonance imaging methods are used in studying conductive systems.     

Thermal properties of quantum electrodynamics in 2 + 1 dimensions and confinement

Conclusions Thus, we have shown that in QED₃ systematic allowance for screening makes it possible to eliminate infrared divergences and in this respect advance further than in QCD₄, in which the question of the mechanism of their elimination remains open. The comparative simplicity of the model also makes it possible to study systematically the more important question of the general structure of the series of skeleton perturbation theory and the excitation spectrum. We are currently working on this question.All-Union Scientific-Research Center for the Study of Surface and Vacuum Properties. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 69, No. 1, pp. 25–39, October, 1986.     

Two-dimensional spectral-spatial image of highly oriented pyrolytic graphite

Experimentally observed electron paramagnetic resonance (EPR) spectra of highly oriented pyrolytic graphite samples can be considered as a sum of three signals coming from two adjacent faces and crystal edges. Contributions from faces can be analyzed analytically by Dyson’s theory based on an infinite flat conductive plate, while the contribution from edges is not described by this theory. Overlapping of these signals makes it difficult to get useful information about the sample from spectra observed. Implementation of two-dimensional spectral-spatial imaging technique proved to be helpful to solve this problem. It permits the characterization of the EPR spectrum from a selected flat spatial region located far from crystal edges where the model of the infinite flat conductive plate can be applied. By analyzing the EPR signal from spatial slices by Dyson’s equation we have obtained the values of the diffusion coefficient and the surface relaxation rate.