Recovered-voltage phenomenon and prospects for its use for assessment of the condition of polymers

A general theory of the phenomenon of recovered voltage in polymers was considered on the basis of representation of an actual poling process by a discrete set of Debye relaxators. Examples of numerical solution of the direct and inverse problems are given. A correlation expression between intentionally aged polymer specimens and recovered-voltage curves was proposed for use in the assessment of the material state of a polymer under actual service conditions. It was shown that it is sufficient to restrict consideration to three relaxation processes in analysis of the phenomenon.     

Gain saturation in quantum-well heterostructures

The effect of radiation gain saturation in quantum-well heretostructures was investigated in the system GaAs—AlGaAs with regard to the spectral line broadening and the type of radiation polarization. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 797–800, November–December, 1997.     

Dispersion properties of a periodic semiconductor structure in a magnetic field directed along the periodicity axis

The band spectrum of natural waves in a periodic structure formed by alternating dielectric and semiconductor layers is investigated for the propagation of waves at some angle with respect to a magnetic field applied along the periodicity axis. A method is presented for deriving a dispersion equation, and its properties are analyzed numerically. It is shown that, in the absence of dissipation, there are two independent spectra of natural waves in the structure being considered, and the regions of existence of various types of such waves are classified. It is established that the transmission bands of the two spectra may supplement one another or overlap. It is found that, for the chosen magnetic-field direction, there exist numerous bands of transmission of cyclotron waves.     

Immunoenzyme method for the determination of citrinin

A rapid method for the determination of citrinin in feed using an indirect competitive enzymelinked immunosorbent assay after analyte extraction from test samples with aqueous acetonitrile was developed. Within the analytical concentration range 20–500 μg/kg for citrinin, the relative characteristics of the repeatability (precision) and intralaboratory intermediate precision (reproducibility) of analytical results were 0.11 and 0.16, respectively.     

Effect of replacing the primary quinone by different species on the ultrafast photosynthetic electron transfer in bacterial reaction centres

Using picosecond absorption spectroscopy it has been shown that in Rhodobacter sphaeroides reaction centres the substitution of the primary quinone acceptor (QA), ubiquinone-10, by other quinone species (with redox potentials higher or lower than that of ubiquinone-10) has essentially no modifying effect on the reaction centre protein. The molecular relaxation processes that accompany the localization and stabilization of a photo-excited electron on the intermediate acceptor, bacteriopheophytin (I), are not affected, although the subsequent transfer of the electron from I to QA is slowed down. Consequently, this leads to a lower quantum efficiency of high rate of direct I-----QA reaction is normally due to the specificity of the primary quinone species and its binding site in the reaction centre protein which provide optimum steric and chemical conditions for an effective interaction between I and QA.     

Electrokinetic Phenomena in Sulfonated Cation-Exchange Membranes with Tetraalkylammonium Ions

The electric transport of solvent ions and molecules through membrane systems containing cations of tetraalkylammonium bases is studied. The interrelation between electrokinetic characteristics of sulfonated cation-exchange membranes at different degrees of their saturation with tetrabutylammonium ions and the content of water in membranes at equilibrium is established. A new type of conductor-insulator percolation transitions is revealed for homogeneous MF-4SK perfluorinated membranes saturated with organic counterions. This transition is interpreted with allowance for the concept of the governing role of narrow channels in the membrane microstructure. The electroosmotic permeability of MF-4SK membranes in solutions of sodium and tetraethylammonium chloride, as well as in their mixtures, is studied. An experimentally observed abnormally high amount of water transferred by tetraethylammonium ions is discussed with allowance for the dynamic hydration characteristics of ions.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 485–493.Original Russian Text Copyright © 2005 by Kononenko, Berezina, Shkirskaya.