Spectral Properties of Thioflavin T and Its Complexes with Amyloid Fibrils

Comparative analysis of the absorption and fluorescence spectra and fluorescence excitation spectra of thioflavin T (ThT) in various solvents and in the composition of amyloid fibrils has shown that ThT, when excited in the region of the long-wavelength absorption band, fluoresces in the spectral region with a maximum at 478–484 nm. The appearance in aqueous and alcohol solutions of a fluorescence band with a maximum near 440 nm has been attributed to the presence in the composition of the ThT preparations of an impurity with an absorption band in the 340–350-nm range. The literature data showing that in glycerol ThT has a wide fluorescence spectrum with two maxima are due to the artifact connected with the use of a high concentration of the dye. It has been suggested that the cause of the low quantum yield of ThT aqueous and alcohol solutions is the breakage of the system of conjugated bonds due to the reorientation of the benzothiozole and benzaminic rings of ThT in the excited state with respect to one another. The main factor determining the high quantum yield of fluorescence of ThT incorporated in fibrils is the steric restriction of the rotation of the rings about one another under these conditions. The suggestions made have been verified by the quantum-chemical calculation of the ThT molecule geometry in the ground and excited states.     

Algorithmic Complexity of a Problem of Idempotent Convex Geometry

Properties of the idempotently convex hull of a two-point set in a free semimodule over the idempotent semiring R _{max min} and in a free semimodule over a linearly ordered idempotent semifield are studied. Construction algorithms for this hull are proposed.     

Critical stretch for formation of a cylindrical void in a compressible hyperelastic material

Formation of a cylindrical void in an infinitely long compressible hyperelastic cylinder under axial and radial stretches is examined. The cavitation phenomenon is viewed here as a bifurcation of a solution with a cavity from the homogeneously deformed configuration, taking place when the applied radial stretch reaches a certain critical value. This amounts to modeling the underlying phenomenon as a kind of elastic instability. A formulation of shooting-method type is presented to derive an equation which gives the critical radial stretch for a prescribed axial stretch. For a special class of hyperelastic solids, called modified Blatz-Ko material, the obtained equation leads to an explicit expression for the critical stretches and stresses. Some analytical as well as numerical calculations are carried out to explicitly obtain the critical values for cavitation. The results are summarized in the form of cavitation curves in the two-dimensional space of axial and radial stretches or stresses. Influence of the axial stretch on the critical radial stretch is discussed. Throughout the paper, the corresponding results for a spherically symmetric void formation are referred to when appropriate and compared with the cylindrical case of the present interest. It is then indicated that in the state of equitriaxial stretch, cavitation into a cylindrical shape is likely to occur at lower stretch than into a spherical one.     

The probability of generating a soluble subgroup of a finite group

It is proved that for finite groups G, the probability thattwo randomly chosen elements of G generate a soluble subgrouptends to zero as the index of the largest soluble normal subgroupof G tends to infinity.     

Polarization dynamics of longitudinally monomode bipolarized microchip solid-state lasers

This paper is devoted to the polarization dynamics of a longitudinally monomode bipolarized Nd:YAG laser: the low-frequency polarization dynamics of a microchip laser is studied experimentally and theoretically. The intensities and the relaxation oscillation spectrum of orthogonally polarized modes versus the direction of pump polarization is observed. A phase-sensitive model of a longitudinally monomode bipolarized solid-state laser with linear polarized diode laser pump is developed to account for the experimental observations.     

Production of high purity proteins by elution of individual fractions from two-dimensional gels.

Results are presented on the production of purified myocardial proteins from two-dimensional (2-D) gels. Proteins were fixed in a native condition using potassium acetate and then eluted into an aqueous solution. Homogeneous tropomyosin and myosin light chain fractions and a number of nonidentified myocardial proteins present on 2-D gels were obtained.     

Homogenization of a problem with many scales in magnetic hydrodynamics

The problem of magnetic hydrodynamics is considered in the case of rapidly oscillating magnetic field. The dependence on a small parameter is assumed to be many-scaled. The limit problems are constructed and the homogenization theorem is proved. Bibliography: 2 titles. __________ Translated from Problemy Matematicheskogo Analiza, No. 35, 2007, pp. 133–138     

Phase transitions in small particles formed at the initial stages of electrocrystallization of metals

The diagram of possible phase transitions occurring in small particles with variations in the electrodeposition parameters is constructed and justified using the data obtained from experimental investigations into the formation and evolution of pentagonal crystals on an indifferent substrate during electrocrystallization of copper.