Non-uniqueness of the heat current operator and the hopping thermoelectric and Nernst-Ettingshausen effects in amorphous semiconductors

The Hardy correction in the heat current operator is generalized to the case of non-zero electron-phonon coupling constantg. It is then shown that not only the lowest (minus first) order but also the fist order contribution ing to the thermoelectric power of amorphous semiconductors in the hopping regime disappears. Consequently, since the lowest (zero) order contribution to the thermoelectric effects in the magnetic field yields no Nernst-Ettingshausen effect in these materials, the last effect is of the second order ing, at least.     

The effect of carbon content on the beginning of slip in single crystals of Fe-3·2 wt%Si alloy

Specimens with 18 ppm and 100 ppm carbon of different orientations were deformed by compression (?～1·1×10^?4 s^?1) at the temperatures 150 °K, 195 °K, 293 °K, 393 °K and 483 °K. The measuredΨ(χ) andτ(χ) curves are presented. The changes of the curves caused by increased carbon content are discussed from the point of view of the low temperature induced cross-slip. Deviations from the Schmid law of critical resolved shear stress are found for both carbon contents. The dependence of the CRSS on temperature for specimens of standard purity has a slightly different course for orientationχ=?30° than for orientationsχ=0° andχ=+30°. These deviations are discussed in terms of the influence of normal stress on the slip. The course ofΔτ (difference between the CRSS in the MRSS plane for specimens with 100 ppm and 18 ppm of carbon) onχ is discussed using different models of lattice hardening due to interstitial impurities. These models can also be applied to the explanation of deviations ofτ(χ) curves from the Schmid law.     

Representations of an algebra of the Gell-Mann-Dashen type

LetG denote the infinitedimensional Lie algebra given by communtation relations [a _m ,a _n ] =c a _m+n (m, n=0, 1, ...), wherec are structure constants of the arbitrary centerless Lie algebra. The paper is devoted to the construction of a certain class of skewsymmetric irreducible representations (so called F-representations) of the algebraG .     

Optical information processing by the Fabry-Perot resonator

Properties of the Fabry-Perot resonator as a part of an optical imaging system are discussed from the point of view of optical information theory. Information capacity of the system is derived and expressed in terms of the number of degrees of freedom of the optical wave field at the output. It is pointed out that the Fabry-Perot resonator is well suited for processing of image signals having a periodic structure.     

Manifestation of microgel-like particles of styrene-ethylene dimethacrylate copolymers in solution in 1H and 13C NMR spectra

From the integrated intensities of ¹H NMR bands it has been found that in solutions of styrene (St)-ethylene dimethacrylate (EDMA) copolymers, a considerable part of the monomer units do not show directly in high-resolution ¹H NMR spectra and it is suggested that these monomer units form compact structures, probably acting as cores of microgel-like particles. In ¹³C NMR spectra all monomer units are shown, including those which are part of the compact microgel structures. From a comparison of ¹H NMR spectra with other analytical methods (elemental analysis, infrared spectra) it follows that the composition of the copolymer in the core of the microgel is the same as the overall composition of the copolymer. The content of the compact structures in the microgel increases with the content of the EDMA component. The results are discussed from the point of view of structural features and of the motional restrictions of the St/EDMA copolymers in CCl₄ solution. The consequences for ¹H NMR analysis of copolymer composition are also discussed.     

Polarometrische Bestimmung von Methylenblau mit Phosphorwolframsäure

Zusammenfassung Ein Mol Phosphorwolframsäure reagiert in 2,5M Salzsäure mit 5 Mol Methylenblau unter Bildung eines Niederschlages, der in Wasser und verdünnten Mineralsäuren unlöslich ist. Diese Reaktion wurde zur polarometrischen Bestimmung von Methylenblau benützt. Bei Einhaltung aller Versuchsbedingungen, besonders der Acidität der Lösung, sind die Resultate gut. Der Äquivalenzpunkt der Titration wurde unter Verwendung einer modifizierten Rechenmethode bestimmt.

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Polarometric determination of methylene blue with phosphotungstic acid

Summary One mol phosphotungstic acid reacts in 2.5M hydrochloric acid with 5 mol Methylene Blue creating a precipitate insoluble in water and in diluted mineral acids. The given reaction was applied for the polarometric determination of Methylene Blue. Under keeping of all experimental conditions, especially of the solution acidity, the results are good. The equivalence point of the titration was determined using a modified method of calculation.