Magnetic properties of an amorphous microconductor in the microwave range

The frequency dispersion of the magnetic permeability is taken into account in a calculation of the impedance of an amorphous microconductor. Possible methods of measuring the magnetic parameters are analyzed, and the main characteristics of an amorphous microconductor in the microwave range are described. Zh. Tekh. Fiz. 68, 136–137 (January 1998)     

The effect of fluctuations of a classical exterior medium on tunneling nonradiative processes in molecules

We examine nonradiative transitions in molecules with allowance for the effect of a classical polar exterior medium on tunneling charge transport. The approach allows for the vibrational frequencies of a molecule in the electron transition. In the case of slow fluctuations, the theory predicts a low-temperature (non-Arrhenius) increase in the tunneling nonradiative transition rate, and the results agree qualitatively with the experimental data. When the fluctuations of the exterior medium are rapid, at certain values of the molecular parameters the tunneling decay rate is found to decrease with increasing temperature because the conditions needed for resonant tunneling are violated. Zh. éksp. Teor. Fiz. 114, 1944–1953 (December 1998)     

Influence of humic substances on sorption and methylation processes of inorganic- and organo-tin species

The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents.     

Lattices of processes for graphs

The structure of the lattice of processes of a finite digraph with entries is investigated. Necessary and sufficient conditions for the isomorphism of a given lattice to the lattice of processes of a certain digraph are obtained. Bibliography: 5 titles. Translated by K. V. Shakhbazyan. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 202, 1992, pp. 135–153.