Solvent effect on ageing of silica gels

The structure of silica gels derived from tetraethoxysilane (TEOS) with molar compositions of TEOSH₂OHNO₃=1100.4 and then aged in various solvents, was studied. The effect of various solvents having different physical properties on the gel structure, as well as the relationship between the solvent properties and the dried gel structure, were investigated. The density, surface area and pore-size distribution were measured. The results of the pore structure and SEM showed the aged gels to have a slit-shaped micropore, narrow pore-size distribution, and homogeneous microstructure. The density, surface area, pore size and pore volume of dried gels changed as the gels were subjected to ageing in various solvents. The surface area could be related to the polarity parameter of the ageing solvent.     

Filter elements of the wound type

NTF Inprokom (St. Petersburg). Translated from Khimicheskie Volokna, No. 5, pp. 46–48, September–October, 1993.     

Standing waves of gaseous chemical reactions in inert porous media

Standing waves of gaseous, exothermic, chemical reactions in inert porous media are investigated in the two-temperature and one-temperature approximations. A semiinfinite reaction zone method is developed to solve the problem analytically. It is shown that the wave solutions obtained by this method form a large set. Traditional solutions with strong heat transfer at the end of the wave make up but a small fraction of this set.LENIIKhIMMASh, St. Petersburg 193167. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 11–20, July–August, 1994.     

Antitumor Organometallics. IV. The Mutagenic Potential of Some Diphenylantimony(III) Dithiophosphorus Derivatives

Two diphenylantimony(III) derivatives of dithiophosphorus ligands, i.e. Ph(2)SbS(2)PPh(2) and Ph(2)SbS(2)P(OPr-i)(2), which were previously found to exhibit antitumor properties, have been now investigated for potential mutagenic effects in healthy and Ehrlich ascites tumor-bearing mice. Two short-term tests, i.e. the micronucleus test and the cytogenetic analysis, were used as end-points for mutagenicity. The results are consistent with a mutagenic potential for both organoantimony(III) compounds tested, the effect being higher for the phosphorodithioato derivative.     

Liquid crystal oligo(cyclosiloxanes)

The synthesis and properties of individual liquid crystal oligo(cyclosiloxanes),, wherex=4–8 andR is a 4-methoxyphenyl-4-alkyloxybenzoate type of mesogenic group, is described. Preliminary results concerning the effect of ring size on the mesophase formation are included. X-ray diffraction studies have shown that the cyclosiloxanes form a smectic A₁ phase.     

Economic and legal aspects of the organization of planning and construction of structures on the continental shelf of Arctic Seas of Russia

Power Technology and Engineering -     

Quasi three-dimensional, n-bit optical memory based on the ellipsometric principle: model calculations

Model calculations on the ellipsometric memory are presented. The ellipsometric memory is an n-bit optical memory whose information is extracted by use of the ellipsometric principle. The memory cells of the device consist of thin-film multilayer structures, and the information of each memory cell is contained in the optical properties of the thin films. Several thin-film multilayer structures were examined in order to find out how different choices of layer materials and other system parameters such as layer thicknesses and wavelength affect resolutions and limitations of the ellipsometric memory. Such calculations are also useful for optimizing the readout resolution. It was found that it is possible to use memory cells having up to at least eight layers, which would permit 8-bit words to be stored at each location. It was also found that, in principle, several types of materials can be used as layer materials, and various aspects of different choices of materials are discussed.     

FeCl3-doped polyvinylidene fluoride

Infrared (350–4000 cm^–1) and optical (1.15×10⁴–2.95×10⁴cm^–1) spectra, differential thermal analysis (DTA) and d.c. electrical resistivity of FeCl₃- doped polyvinylidene fluoride (PVDF) films, over the doping mass fraction range 0 w 0.40, have been measured. The i.r. spectra provided evidence of: (a) the presence of both and phases in the undoped, and a phase in the doped PVDF films; (b) a head-to-head content of 20%; and (c) a different doping mode beyond a 0.25 doping level. The optical spectra resulted in two induced energy bands, and a probable interband electronic transition, due to doping. Dipole relaxation and premelting endothermic peaks were identified by DTA. Electrical conduction is thought to proceed by interpolaron hopping among the polaron and bipolaron states induced by doping. The hopping distance, R _o, is calculated according to the Kuivalainen model. A numerical equation is adopted to formulate the dependence of R _oon doping level and temperature. It is found that R _o< CC separation length. This implies that, in doped PVDF, charge carrier hopping is not an intrachain process.