The last subconstituent of the Hemmeter graph

We prove that when q is any odd prime power, the distance-2 graph on the set of vertices at maximal distance D from any fixed vertex of the Hemmeter graph Hem_D(q) is isomorphic to the graph Quad_D-1(q) of quadratic forms on .     

Problems on Nonstationary Interaction of Structural Elements with Shock Waves

Experimental investigations into the interaction of rigid and elastic structure elements with a shock wave in water and in air are reviewed. Investigation techniques are described and the nonstationary behavior of elements is analyzed     

The elasticity of a magnetic-fluid membrane

For a magnetic-fluid membrane, the critical pressure drop is determined experimentally using thermodynamic and hydrostatic methods. It is found that the value of the critical pressure drop calculated from the data of the thermodynamic method exceeds by ～30% the value of this parameter measured by the hydrostatic method. The overstated value of the critical pressure drop obtained using the indirect thermodynamic method is explained by the approximate nature of the analytical model lying at its basis, which does not take into account the relaxation character of pondermotive elasticity. The static and thermodynamic coefficients of pondermotive elasticity of a magnetic-fluid membrane sample are calculated, and the results are used to estimate the membrane displacement by the moment of its breakage.     

Electrochemical synthesis of perfluoropolyethers by the Kolbe method

Electrochemical dimerization of hexafluoropropylene oxide dimer and trimer acids on SU-2000 glassy carbon, bulk platinum, and SU-2000 electrodes modified with platinum-group metals in acetonitrile in the presence of water was studied at various concentrations of the starting substance and different degrees of neutralization of the starting acid. Also, the possibility was examined of obtaining some perfluoropolyethers in a single process by cross-condensation of several starting perfluorocarboxylic acids, followed by separation of the products by physicochemical methods.     

On hyperbolic systems of equations with zero generalized Laplace invariants

A criterion for the interruption of the sequence of generalized Laplace invariants is found. A general solution of a system of linear hyperbolic equations with zero invariants is constructed.     

The influence of high-frequency electromagnetic fields on the critical micelle concentration in aqueous solutions of sodium dodecyl sulfate

It was established that the critical micelle concentration in solutions of sodium dodecyl sulfate changed under the action of high-frequency electromagnetic fields (60, 120, and 160 MHz). The thermodynamic functions of micelle formation were calculated. Original Russian Text ? I.E. Stas’, O.P. Mikhailova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 2, pp. 397–399.     

Destruction of polymeric cobalt(ii) trimethylacetate. Synthesis and structures of new complexes Co9(μ3-OH)6(μ-OOCCMe3)12(OCMe2)4 and Co6(μ4-O)2(μ-OOCCMe3)10(η-HOOCCMe3)4

Russian Chemical Bulletin -     

Adsorption of Cationic Surfactants on Highly Dispersed Silica

Comparative study was made of adsorption of cationic surfactants, decamethoxine, ethonium, and cetyltrimethylammonium bromide, on a highly dispersed amorphous silica at different pH values. Contrary to the adsorption of monoquaternary ammonium compound, cetyltrimethylammonium bromide, the adsorption of bis(quaternary ammonium) compounds, ethonium and decamethoxine, was found to be caused mainly by electrostatic interaction. The adsorption of antiseptic decamethoxine is reversible at pH 6; this may be used to design carriers capable of controlled drug release into the surrounding medium.     

Molecular properties of conjugates formed by synthetic hydrophilic polymers and sterically hindered phenols

Water-soluble conjugates are prepared via the chemical modification of poly(vinyl alcohol) and poly(ethylene glycol) by antioxidants taken from the family of sterically hindered phenols. The effects of the degree of substitution of conjugates on the dimensions of molecules and their aggregates are studied by viscometry and light scattering in dilute solutions. It is shown that an increase in the amount of antioxidant groups incorporated into the poly(vinyl alcohol) chain leads to a decrease in the dimensions of single conjugate molecules owing to attraction of hydrophobic groups. Poly(ethylene glycol) molecules carrying end groups of sterically hindered phenols form micellar aggregates that are absent in the solution of the initial polymer. The mean number of molecules involved in such an aggregate is 83. It is found that the presence of hydrophobic end groups in poly(ethylene glycol) molecules causes a sharp reduction in the lower critical solution temperature of a solution relative to that of the initial polymer.