Table of contents

Theoretical ideas for deriving singularities of thermodynamical functions at the second-order phase transitions in spin systems with weak quenched disorder are considered. In particular, p-component vector magnets and the two-dimensional Ising model with disorder in spin-spin interactions are studied. Generalisation of the traditional renormalisation-group scheme, which takes into account non-perturbative spin-glass degrees of freedom, is proposed. Low-temperature properties and the phase transition in the Ising systems with quenched random fields are also considered.

A review is given of theoretical and experimental data on spontaneous phase separation in nonsuperconducting degenerate magnetic semiconductors and related cuprate high-temperature superconductors. The following phenomena are considered: (1) The electronic phase separation occuring at frozen impurity positions as a result of charge carrier concentration in regions with a changed magnetic state; (2) impurity (chemical) phase separation when a nonuniform impurity distribution over a crystal is driven simultaneously by interaction between impurity atoms and by their tendency to concentrate inside regions with a changed magnetic ordering.

Structure formation and autowave processes in active media far from equilibrium are the subject of special division of the theory of nonlinear dynamic systems. In the present review the protoplasm of amoeboid cells is considered as an active medium, in which gel-like structures continuously assemble and disassemble. Local parts of these structures also spontaneously contract and relax, causing rather complex circular or shuttle-type flows of sol-like protoplasm. We consider several mathematical models of the resulting movements, wherein dissipative structures and the autowave processes multually generate each other. The main quantitative features of the protoplasm dynamics in Physarum plasmodium are consistent with a model that postulates the existence of positive feedback between a local deformation and the free calcium level controlling the network contraction. The potentialities of different physical methods used to determine the values of parameters in the mathematical models are discussed.

Three problems have been claimed for solar neutrinos. First, it has been said for over 20 years that the flux of high energy neutrinos was substantially less than that predicted from solar evolutionary models. Second, it was claimed that there were violent fluctuations in the high energy neutrino flux and that their periodicity was close to that of the sunspot cycle. Third, recently evidence was presented that low energy neutrinos may also have a flux deficit. The second problem is shown to be unreasonable and in disagreement with the more recent Kamiokande experiment. The other two problems of flux are shown to be vanishing with time. This is not from a single cause but from a series of improvements of the input data to the models, to a better appreciation of the errors which had sometimes been significantly underestimated, and also some of the experimental values have increased with time indicating a learning curve for some of these very difficult experiments with very low statistics. Finally it is concluded that the evidence for any solar neutrino problem is not compelling.

Some of the most important achivements in modern electronics and energetics, based on the physics of semiconductors, are discussed very briefly.