Theoretical investigation of 1,4-dioxane complexes with water in the <Emphasis Type="Italic">chair</Emphasis> conformation by semiempiric MNDO/PM3 method

The structure and relative stability of 1,4-dioxane-water, (Diox)_n·(H₂O )_m (n = 1, 2, m = 1–6), molecular complexes have been calculated by semiempirical MNDO/PM3 method. A considerable variety of (Diox)_n·(H₂O )_m isomeric structures was stated. The mean energy of O_Diox…H_W-O_W hydrogen bond in (Diox)_n·(H₂O)_m complexes formed by 1,4-dioxane molecules in the chair conformation amounts to ?2.293 ± 0.210 kcal/mol with the average bond length 2.797 0.015 Å.     

Reactions of 2-allylthiobenzimidazole, -oxazole, -thiazole, and the isomeric thiones with dichlorocarbene

The reactions of 2-allylthiobenzimidazole, -oxazole, and-thiazole, and the thiones formed from them on heating, with dichlorocarbene have been investigated under phase transfer catalysis conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 243–248, February, 2000.     

Baric and temperature dependences for the thermal conductivity of sedimentary rocks

The effective thermal conductivity of secondary rocks (sandstone, dolomite, aleurolite) is studied under high pressures of up to 400 MPa and temperatures of 273–523 K. It is established that the temperature and baric functions of thermal conductivity depend substantially on the degree of crystallization and the mosaicity of rock-forming compounds.     

Interrelation between parameters of isotherms of adsorption of fatty acids on the surface of magnetite and volume effects of their dissolution in n-hexane and carbon tetrachloride at 298.15 K

The adsorption of unsaturated C_18:n fatty acids on magnetite and volume effects of their dissolution in n-hexane and carbon tetrachloride are studied. It is established that an increase in the values of limiting adsorption of a series of oleic, linolic, and linolenic acids corresponds to positive volume effects of their dissolution in CCl₄. Opposite picture of the adsorption behavior of studied acids in n-hexane corresponds to negative volume effects of the dissolution of the acids in this solvent.     

Experimental study of heat transfer on the borders of grains in ordered and disordered media

The effect of hydrostatic pressures of up to 400 MPa in the temperature dependence (273–523 K) of the thermal conductivity of polycrystalline (coarse-grained and fine-grained), and single-crystal compounds GaSb is investigated. It is shown that the dependences of the thermal conductivity of ordered and disordered media on pressure are different.     

Analytical estimates of permeability and possible convective heat transfer in compact porous fluid–saturated rocks

The possible occurrence of convection in fine-grained (low-porous <15%) fluid-saturated (argon, water) rocks under hydrostatic pressures of up to 100 MPa is studied. Calculations of the Rayleigh filtration number and the Darcy number are presented. It is shown that the convective motion of fluid does not occur in pore-saturating fluids within the considered range of pressure variation, pore sizes, and temperature differences.     

Limiting partial molar volumes of solutions of oleic, linoleic, and linolenic acids in cyclohexane and benzene

High-precision vibration densimetry was used to measure (with an error of less than 5 × 10^?6 g/cm³) the density of dilute solutions (0≤ x ₂ ≤ 0.01 mole fractions) of oleic, linoleic, and linolenic acids in cyclohexane and benzene at 298.15 K. The limiting $\bar V_2^\infty $ and excess V ₂ ^{E, ∞} partial molar volumes of these C_{18: n} fatty acids in the indicated solvents were calculated. Benzene was demonstrated to selectviely influence the volumetric effects of dissolution (V ₂ ^{E, ∞} ) of the linoleic (n _C=C= 2) and linolenic (n _C=C = 3) polyunsaturated acids.     

Adsorption of fatty acids from solutions in organic solvents on the surface of finely dispersed magnetite: 2. Heats of oleic,linoleic, and linolenic acid adsorption from carbon tetrachloride and hexane

Differential and integral heats of oleic, linoleic, and linolenic acid adsorption on the surface of finely dispersed magnetite from solutions in carbon tetrachloride and hexane are measured by the calorimetric method. The thermodynamic parameters of the adsorption for the systems under examination are calculated from the obtained experimental data. It is discovered that, at low concentrations, the volume filling of micropores in the particle aggregates of the adsorbent occurs with the formation of ordered adsorbate structures in the pores. At high concentrations, the fatty acids are adsorbed in mesopores and on the outer surface of the adsorbent. It is shown that, at high concentrations, the key contributions to the integral heat of adsorption are made by the endothermic processes of desolvation of adsorbates and the adsorbent surface, as well as by the competitive adsorption of solvent and fatty acid molecules on the active sites of the adsorbent surface.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 784–787.Original Russian Text Copyright © 2004 by Korolev, Blinov, Ramazanova.     

New Technology of High-Sensitivity Ferro/Piezoelectric Materials Based on Micro- and Nanostructured Hybrid Polymers

Technical Physics - Fabrication of composites based on micro- and nanostructured hybrid polymers have been studied. A new technology for nanoparticle immobilization in the polymer matrix of the...