Electron transfer at lanthanum endohedral fullerenes

The aim of this contribution is to study lanthanum containing fullerenes produced and treated under different conditions. The work was done using solid soot extract giving poorly resolved ESR spectra or separated lanthanofullerenes in solution showing well resolved ESR spectra. ESR experiments in connection with the mass spectrometry give information on the electronic states due to the electron transfer from the endohedral metal to the fullerene cage and the influence of oxygen on endohedral lanthanofullerene. The analysis of ESR spectra indicates the presence of up to nine octets of lanthanum containing fullerenes. These species have different stabilities. Furthermore, a very narrow single ESR line in the lanthanofullerene spectrum was detected having a linewidth ΔB=0.008 mT and ag-factor 2.0025. The electron transfer to the endohedral La@C₈₂ molecule studied by voltammetry and electrochemicalin situ ESR experiments is described. The interaction of the lanthanofullerene with oxygen in solution is also studied. In different solvents the influence of oxygen on line broadening in the ESR spectra of La@C₈₂ was observed.     

Global solvability of the Cauchy-Dirichlet problem for nondiagonal parabolic systems with variational structure in the case of two spatial variables

The Cauchy-Dirichlet problem for quasilinear parabolic systems of second-order equations is considered in the case of two spatial variables. Under the condition that the corresponding elliptic operator has variational structure, the global in time solvability is established. The solution is smooth almost everywhere and the number of singular points is finite. Sufficient conditions that guarantee the absence of singular points are given. Bibliography: 23 titles. Translated fromProblemy Matematicheskogo Analiza No. 16, 1997, pp. 3–40.     

Exciton molecules and exciton liquids in semiconductors

Excitons in many-valley semiconductors form molecules consisting of four and more excitons. The degeneracy factor g of the conduction band in germanium is 8, and in silicon g=12. As in acceptors, the hole ground state in excitons is fourfold degenerate. The same is valid for exciton molecules, because they are quantum objects with spherical symmetry. The exciton binding energy in molecules is close to that in exciton-liquid droplets. Experimental evidence is considered for the existence, besides biexcitons, of stable exciton molecules consisting of three and four, and, possibly, 11 and 12 excitons. Molecules containing from five to ten excitons are apparently unstable. Fiz. Tverd. Tela (St. Petersburg) 40, 929–931 (May 1998)     

Hydrogel composition based on carboxymethylcellulose and agar-agar

The results are given of a study of the rheological properties of concentrated solutions of CNC and agar-agar and the influence of their quantitative ratio on the anomalous flow behavior of their solutions. A hypothesis is put forward of the formation of intermolecular associates from CMC and agar-agar which leads to the formation of a stronger structural network of solutions of the initial polysaccharides.Institute of the Physics and Chemistry of Polymers, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 1 44 26 61. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 357–361, May–June, 1998.     

Modeling of heat transfer in a melt in growing single crystals by the stockbarger method using the accelerated crucible rotation technique (ACRT)

In model experiments, the layer of melt bounded by the crystallization front and the heater for heating the diaphragm in a growing furnace is shown to determine crystal growth by the Stockbarger method under conditions of induced convection and also to control the crystallization process. The free volume of the melt exerts no effect on its hydrodynamic and thermal structures. Optimum values of the exposure time are estimated for constant maximum and minimum velocities of modulated rotation of the growing ampoule. Institute of Mineralogy and Petrography, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 1, pp. 98–104, January–February, 1998.     

Circulatory flow in the inter-jet zone of a system of free turbulent jets

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 97–99, July–August, 1993.     

Simulation of attenuation of millimeter radio waves in dry snowfalls

Attenuation of millimeter waves in dry snowfalls is numerically simulated with allowance for the actual shape of snowflakes. It is shown that for moderate-intensity snowfalls the values of attenuation cross-sections averaged over the snowflake orientations are well approximated by power-law function depending on the equivalent diameter of the snowflakes. This allows us to obtain an analytical expression for the attenuation coefficient of a plane electromagnetic wave by snowfall for size distributions of particles of the gamma-distribution type and its modifications. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 446–455, April, 1998.