[en] The problems are discussed of the thermal pollution of rivers and water reservoirs by discharges of heated water from thermal and nuclear power plants. The problems concerned are quantitative and qualitative changes in biocenoses, the disturbance or extinction of flora and fauna, physiological changes in organisms and changes in the hydrochemical regime. (Z.M.)

[en] Melts of mixtures of alkali metal flourides were investigated by pulse radiolysis with optical recording. The parameters of the optical spectra and radiation chemical yields of solvated electrons in these systems are close to the corresponding values in melts of other halides. The optical absorption of the oxidative component of radiolysis was detected; its parameters were substantially different from those in molten chlorides, bromides, and iodides, which may be associated with a rapid reaction of F₃^- formation. 9 refs., 4 figs., 1 tab

[en] The influence of interlayer hoppings on the superconducting transition temperature (T_c) in bilayer cuprates has been studied. The parameter of hopping between layers is expressed as t_⊥(k) = t_⊥(cos(k_x) − cos(k_y))² and treated as a small perturbation for the states of two CuO₂ planes described by the t-t′-t″-J* model. In the generalized mean field approximation for d_x² - y² symmetry of the superconducting gap, neither the interlayer hopping or exchange interaction, nor the pair hopping between CuO₂ layers provides an additional mechanism of Cooper pair formation or an increase in T_c. In the concentration dependence of T_c, the bilayer splitting of the upper Hubbard band of quasi-holes is manifested as two peaks with temperatures slightly lower than the maximum T_c for a single-layer cuprate. Interlayer antiferromagnetic spin correlations suppress bilayer splitting.

[en] The band structure of La_2CuO_4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La_2CuO_4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La_2CuO_4 with increasing temperature

[en] We present a theoretical study of the electronic structure of bilayer HTSC cuprates and its evolution under doping and in a high magnetic field. Analysis is based on the t-t′-t″-J* model in the generalized Hartree-Fock approximation. Possibility of tunneling between CuO2 layers is taken into account in the form of a nonzero integral of hopping between the orbitals of adjacent planes and is included in the scheme of the cluster form of perturbation theory. The main effect of the coupling between two CuO₂ layers in a unit cell is the bilayer splitting manifested in the presence of antibonding and bonding bands formed by a combination of identical bands of the layers themselves. A change in the doping level induces reconstruction of the band structure and the Fermi surface, which gives rise to a number of quantum phase transitions. A high external magnetic field leads to a fundamentally different form of electronic structure. Quantum phase transitions in the field are observed not only under doping, but also upon a variation of the field magnitude. Because of tunneling between the layers, quantum transitions are also split; as a result, a more complex sequence of the Lifshitz transitions than in single-layer structures is observed.

[en] The arrival directions of ultrahigh energy extensive air showers (EAS) by Yakutsk, AGASA, P. Auger array data are analyzed. For the first time, the maps of equal exposition of celestial sphere for the distribution of particles by AGASA and P. Auger arrays data have been constructed. The large-scale anisotropy of cosmic particles at E >4.10¹⁹ eV by Yakutsk, AGASA and P. Auger array data has been detected. The problem of cosmic particle origin is discussed. (authors)

[en] Structural and morphological evolution of polyacrylonitrile (PAN) samples from starting powder of a ternary copolymer to fibers produced from concentrated solutions of PAN in N-methylmorpholine-N-oxide (NMMO) was studied using x-ray diffraction for the first time. X-ray exposures in transmission and reflection geometries allowed the structures of outer and inner parts of the PAN fibers to be differentiated. It was shown that a shell—core structure formed in the precipitation bath during fiber spinning. A comparison of x-ray diffraction patterns of fibers spun using the NMMO process and industrial samples spun from DMSO and aqueous sodium thiocyanate solutions did not reveal fundamental structural differences.

[en] The magnicon belongs to the class of high power RF sources, where a modulation is provided by the beam circular deflection and it is an advanced version of a gyrocon. The first magnicon has been built and tested in Novosibirsk in the middle of the 80's. The power of 2.6 MW has been obtained for the frequency 91.5 MHz and pulse duration 30 mcsec. The electron efficiency has been 85%. Good results obtained during investigations show that the magnicon can be an adequate RF source for the next generation of accelerators, especially for future linear colliders and accelerators for transmutation of nuclear waste. The magnicon conception described in the present paper allows to increase significantly the beam perveance, compared with the first magnicon, and to achieve the pulse power of tens and hundreds megawatts at the beam voltage not greater than 400-600 kV. The device is an amplifer working in frequency doubling mode and is a prototype of a RF source for linear colliders with high acceleration gradient. The magnicon is designed for an output power of 50 MW, an operating frequency of 7 GHz and a pulse duration of 2 mcsec

[en] For the first time the composite fibers based on cellulose with additives of vinyltriethoxysilane (VTEOS) have been obtained. The choice of the additive was justified by the chemical structure of the VTEOS, namely the Si-C links content and the low C/O ratio. Composite fibers were prepared from solid phase pre-solutions of cellulose with VTEOS in N-methylmorpholine-N-oxide (NMMO). An investigation of the rheological behavior of the filled cellulose solutions with VTEOS showed a slight effect of the additive on the viscosity properties of the system. Introduction of 5% of VTEOS to cellulose does not lead to significant structural changes and, as a result, mechanical properties of the fibers. The thermal behavior of composite fibers differs from cellulose fibers. (paper)

No abstract available