Widths and optimal quadrature formulas for convolution classes

We compute Kolmogorov widths in the space L₁ for classes of periodic functions representable in the form of a kernel convolution that does not increase the number of sign changes with values in a given transposition invariant set of functions, and solve the optimization problem for quadrature formulas in these classes.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 9, pp. 1135–1148, September, 1991.     

Two- and three-dimensional analysis of bose-einstein correlations inπ +/K+p interactions at 250 GeV/c

The NA22 data onπ ^? π ^? correlations are analyzed in terms of a number of two- and three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e⁺e^? andµp collisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball-like models, both when including and excluding hydrodynamical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolution than in nuclear collisions.     

Relationship between the chemical structure and pharmacological action of cardiac glycosides of the strophanthidin series

The possibility has been shown of finding and creating highly effective cardiotonic drugs for pediatric practice on the basis of cardenolides obtained by the chemical transformation of natural cardiac glycosides.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 581–585, July–August, 1995. Original article submitted November 21, 1994.     

An estimate for the convergence rate of difference schemes for second-order elliptic equations in domains of arbitrary shape

Using the dummy-domains method, a difference scheme is constructed for solving the first boundary-value problem for elliptic equations of the second order in domains of arbitrary shape. An estimate for the convergence rate of order O(h^1/2) in the norm of W ₂ ¹ is found. Bibliography:5 titles. Translated fromObchyslyuval’na ta Prykladna Matematyka, No. 77, 1993, pp. 12–18     

The phase diagram of the lyotropic nematic mesophase in the TTAB/NaBr/water system

The phase diagram of the nematic mesophase present in the tetradecyltrimethylammonium bromide/sodium bromide/water ternary system was determined. A calamitic nematic mesophase (N_C) was observed which extends to very high concentrations of electrolyte. The order parameters of the surfactant head group in the mesophases were studied by the NMR quadrupolar splitting of the deuterated surfactant. On increasing the temperature of nematic mesophases with low electrolyte concentrations, a phase separation occurs with the formation of a more highly ordered hexagonal phase and an isotropic phase. Diffusion measurements of the isotropic micellar solution by the NMR PFG method were used to estimate hydrodynamic radii at low surfactant concentrations and to study micelle diffusion as the concentration of the surfactant was increased to the liquid crystalline region. At higher surfactant concentrations, the diffusion coefficient reached a limiting value. The calamitic nematic mesophase in this surfactant/electrolyte/water system appears to be formed by long wormlike micelles.     

Applicability of the critical chromatography concept to proteomics problems: Dependence of retention time on the sequence of amino acids

A peptide separation model based on the technique of liquid chromatography of macromolecules at the critical condition was proposed. In terms of this model, the array of experimental data on the separation of peptides is considered. The main phenomenological parameters of the model—effective adsorption energies of amino acid residues—were determined, thus allowing the influence of character of their alternation in the chain on retention times to be predicted. The model is applicable to investigation into the feasibility of separation in different chromatographic modes of not only peptides with the same amino acid composition and different sequences of units in the chain but also peptides containing amino acid isomers and mirror sequences with different terminal groups.