Nonlinear waves in a waveguide partially filled with a plasma

Nonlinear waves have been studied in a circular waveguide partially filled with a cold magnetized collisionless plasma. The solution obtained is periodical with the frequency increasing as a square root of the amplitude of the solution in the first approximation.The author is indebted to K.Jungwirth, R.Klíma and J.Preinhaelter for valuable discussions.     

Local transient phenomena induced in an inert gas plasma by a short pulse

A microsecond periodic pulse was applied on thin probes in a positive column of a neon or helium glow discharge. The local transient phenomena provoked by this pulse were detected by a photomultiplier and presented in a time-distance display. They are qualitatively described and explained. The results are in good agreement with previous theories.     

Determination of diffusion coefficient in melts by the method of stationary diffusion source

This method eliminates some shortcomings encountered with other methods currently used for determination of the diffusion coefficients in melts. There are, with reasonable accuracy, fulfilled the starting and boundary conditions of a diffusion equation, and the diffusion process is not disturbed by melt flowing. This method considers a diffusion source at the boundary of a diffusion range and, when fulfilling certain conditions, both the solution of the diffustion equation and the evaluation of the diffusion coefficients is very simple. The required diffusion source, having a constant power, can be simulated by contacting the saturated gases of a substance, the diffusion of which is being investigated, with melt surface in which the diffusion takes place. The method takes into account application of radionuclides and this article brings about some criteria for application of that method. Simplicity is the main feature of the experimental arrangement.This work has been carried out in the scope of the State Research Task III-5-8 Equilibrium States of Metallurgical Systems.     

Optical constants of thin oxide films on titanium

Thin oxide films on titanium formed by heating were studied by the ellipsometric method. To obtain the complex refractive index and film thicknesses, the ellipsometric measurements were performed by means of the immersing method: each sample was measured first in air and then in a liquid of known refractive index (in our case CCl₄). The optical constants and the oxide film thickness were computed by means of a computer from two pairs of ellipsometric values. To state the optical constants of clean titanium surface the graphic-computational method was proposed and applied. The measurements were carried out at two wavelengths on oxide films grown in air and dry oxygen by thermal oxidation at temperatures from 150 to 700 °C. It has been shown that when increasing the film thickness the refractive index of the film decreases, whereas the absorption coefficient is independent on the film thickness. Optical constants of oxide films growing in dry oxygen are smaller than those growing in air.     

Dependence of V-A characteristics of amorphous semiconductor Ge15Te81S2As2 on hydrostatic pressure

The paper presents the functional expression of V-A characteristics dependent on hydrostatic pressure up to 5 kbar for chalcogenide glass Ge₁₅Te₈₁S₂As₂. The measured V-A characteristics and those derived on the assumption of a linear decrease of the energy gap due to pressure have been compared. Temperature changes caused by current passing through the sample in thermal contact with the environment have been taken into consideration similarly as in the case of paper (2).In conclusion we wish to express our thanks to Doc. J.Krempaský CSc., Ing. P.Dieka, Ing. J.Bielek for their kind help in discussing various points of the problem.     

2-(4'-Isocyanatophenyl)-6-methylbenzthiazol als neues,hochempfindliches Fluoreszenzreagens zur Identifizierung und Bestimmung organischer Verbindungen

Zusammenfassung Ein neues Fluoreszenzreagens mit hochreaktiver Isocyanatgruppe wurde hergestellt, dessen Eignung zum Nachweis und zur Bestimmung aliphatischer und aromatischer Amine, Aminosäuren, Alkohole und Phenole geprüft wurde. Die Identität der mit diesen Substanzen hergestellten Derivate wurde elementaranalytisch bestätigt. Sie eignen sich für die chromatographische Identifizierung. Das Maximum der Fluoreszenz dieser Derivate liegt bei 383 nm. Die große Reaktivität und die intensive, mit dem Reagens erzielbare Fluoreszenz bieten die Möglichkeit zur Anwendung in der Spurenanalyse, z. B. für Umweltuntersuchungen.

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2-(4'-Isocyanatophenyl)-6-methylbenzthiazole as a new highly sensitive fluorescent reagent for identification and determination of organic compounds

Summary A new fluorescent reagent with a highly reactive isocyanate group was produced and its suitability for demonstration and determination of aliphatic aromatic amines, amino acids, alcohols and phenols was tested. The identity of the derivatives produced with these substances was confirmed by elemental analysis. They are suitable for Chromatographic identification. The fluorescence maximum of these derivatives is at 383 nm. The great reactivity and the intensive fluorescence which can be achieved with the reagent enabled it to be used in trace analysis, e. g. for environmental studies.