Showing papers by "Sofia University published in 1969"
TL;DR: In this article, a method for investigation of the surface layers composition and structure is described, using the conversion electrons emitted after recoilles absorption of gamma-rays, which depends on the thickness of the layer the electrons pass across.
107 citations
TL;DR: A homologous series of aliphatic ketones from C 17 to C 35 have been found in the flower wax of Rosa damascena mill as discussed by the authors, which suggest a biogenetic relationship between the ketones and the other hydrocarbon constituents.
36 citations
TL;DR: A catalytic method has been developed for the determination of silver(I), with a sensitivity of 4 x 10(-4)mug ml and +/-7.6% relative error.
25 citations
TL;DR: In this paper, the effect of sulfate ions on the growth of NaClO3 faces was investigated and the heat of adsorption on the active centers of growth for both types of faces was derived from kinetic experimental data.
Abstract: The effect of sulfate ions on the growth of NaClO3 faces (100) and (111) has been investigated. The heat of adsorption on the active centers of growth for both types of faces has been derived from kinetic experimental data. Direct adsorption measurements have been performed which gave the heat of adsorption on the whole surface of each type of faces. A possible explanation of the experimental results is given.
[Russian Text Ignored]
19 citations
TL;DR: In this paper, the change in delocalization energy was traced in building up the metal lattice of lithium, and a space model containing 48 atoms was found to be a satisfactory model for further considerations of the lithium crystal.
15 citations
TL;DR: In this article, the distribution curves of the active centers with respect to their activation energy have been obtained, and it has been established that there are active centers having different activation energy on the surface of both single crystals and polycrystalline samples.
10 citations
TL;DR: In this article, a series of possibilities for increasing the sensitivity of laser microspectral analytical determinations of impurities in minerals, steels, and aluminium alloys are discussed.
Abstract: A series of possibilities are shown of increasing the sensitivity of laser microspectral analytical determinations of impurities in minerals, Steels, and aluminium alloys. When the excitation of the spectrum of the laser beam evaporated substance is transferred to a magnetic field, a considerable increase in the intensity of certain spectral lines of the basic and admixed components and a certain decrease in the intensity of the background, are observed. The intensification factor depends on the regime of the laser and the additional impulse discharge, the intensity of the magnetic field, and the utilized spectral lines.
6 citations
TL;DR: In this paper, the authors examined the relationship between the structure of the stationary phase and activity coefficients in gas-liquid chromatography and made speculations about the possible character of the intermolecular forces between solute and solvent.
6 citations
TL;DR: In this paper, it was shown that the oxidation of iodide with vanadium(V) in sulphuric acid medium and in an atmosphere of nitrogen preceeds according to the kinetic equation: d[I 2 ] d t = (k′[H + ] + k″[ H + ] 2 ) [ V(V)]. [ I − ], where k′ = (1·6 ± 0·1) 10−2 I−2.
4 citations
TL;DR: In this paper, the stability of a space-bounded relativistic beam of electrons accelerated by a nonuniform electric field under conditions where the transverse dimension of the beam is significantly greater than the Debye radius and a collective approach is necessary for describing small oscillations is investigated.
Abstract: The authors investigate the stability of a space-bounded relativistic beam of electrons accelerated by a nonuniform electric field under conditions where the transverse dimension of the beam is significantly greater than the Debye radius and a collective approach is necessary for describing small oscillations. For currents exceeding some critical value, there may develop in such a system an instability analogous to the 'slipping' instability of non-relativistic electron beams with a nonuniform velocity profile. The instability conditions are established and the instability growth rates calculated both in the absence and in the presence of a strong longitudinal magnetic field. The energy spread of the electrons has a stabilizing effect on the beam instability in question. In the Annex it is shown that the slipping instability is characteristic of any non-uniform plasma flow. In particular, it may develop in an isotropic plasma if the flow velocities exceed the thermal velocity of the ions.
3 citations
TL;DR: In this article, the excitation temperature functions of the following spectral lines of carbon have been calculated: C I 5380.34, C I 2478.56, C II 4374.62, C III 5695.33, C IV 2529.98, C V 2270.91 A, assuming a total pressure of 1 atm.
TL;DR: In this article, the authors used the catalogue of the mean light-curves and colours of the Cepheids in the UBV system (Nikolov, 1968), for 240 cepheid, and constructed the curves which represent plots of their U-B versus B-V colour indices.
Abstract: We used the catalogue of the mean light-curves and colours of the Cepheids in the UBV system (Nikolov, 1968), for 240 Cepheids, and constructed the curves which represent plots of their U-B versus B-V colour indices. These curves form three groups: linear curves, open curves, and curves possessing a loop. An opinion that the presence of a loop may be a criterion for Population II objects is not confirmed. It is shown that the slope of such curves (corrected for reddening) with respect to the B-V axis increases with the period. The area delimited by the curves on the U-B/B-V diagram remains almost the same up to a period of about 9 to 10 days, whereafter it increases with the period. The possible causes for this behaviour of the Cepheids on the colour-colour diagram, which is connected with the ultraviolet emission of these stars, are discussed.
TL;DR: In this article, the normalized intensity values as functions of channel-axis temperature have been calculated on an electronic computer for Ar I 3554.31, Ar II 3576.61, Ar III 3503.58, Cu I 5153.585, Cu II 3903.163, Cu III 2643.92, Fe I 5307.365, and Ne II 3334.87 A spectrum lines.
Abstract: The normalized intensity values as functions of channel-axis temperature have been calculated on an electronic computer for Ar I 3554.31, Ar II 3576.61, Ar III 3503.58, Cu I 5153.585, Cu II 3903.163, Cu III 2643.92, Fe I 5307.365, and Ne II 3334.87 A spectrum lines. These data are useful for determining the discharge channel-axis temperature as a function of discharge time if the intensity values of these spectral lines are experimentally measured as functions of time.
TL;DR: In this article, the electron-phonon interaction due to the presence of substitutional impurities is shown to increase the superconductor transition temperature, which increases the transition temperature.