Showing papers by "Bulgarian Academy of Sciences published in 1980"
183 citations
TL;DR: In this article, the authors developed a theory for the rupture of Newtonian black films by a mechanism of nucleation of holes in these bimolecular foam films, where two film monolayers are considered as mutually adsorbed on each other and the film thermodynamic equilibrium is described by an adsorption isotherm in mean field approximation.
106 citations
TL;DR: Conclusions concerning pressure-dependence, age-Dependence, and muscular activation-dependency of the wave characteristics are drawn which are in accord with available experimental data.
Abstract: Propagation of small amplitude harmonic waves through a viscous incompressible fluid contained in an initially stressed elastic cylindrical tube is considered as a model of the pulse wave propagation in arteries. The nonlinearity and orthotropy of the vascular material is taken into account. Muscular activity is introduced by means of an "active" tension in circumferential direction of the vessel. The frequency equation is obtained and it is solved numerically for the parameters of a human abdominal aorta. Conclusions concerning pressure-dependence, age-dependence, and muscular activation-dependence of the wave characteristics are drawn which are in accord with available experimental data.
96 citations
TL;DR: In this article, the initial stage of electrodeposition of silver on a glassy carbon electrode was investigated using a double-pulse potentiostatic method, and the concentration dependence of the steady-state nucleation rate I and conclusions were drawn for the probable mechanism of critical nucleus formation.
92 citations
86 citations
TL;DR: It has been found that the defect in recognition and reproduction of rhythms was manifested regardless of the modality of perception, i.e. whether rhythm patterns were perceived by audition, vision, or touch, and that the disturbance of rhythm abilities is supramodal in nature.
79 citations
TL;DR: The 5'-terminal coding sequence for the 37 S precursor to rRNA of Saccharomyces cerevisiae is identified by reverse transcriptase extension and protection mapping with nuclease S1.
Abstract: The 5'-terminal coding sequence for the 37 S precursor to rRNA of Saccharomyces cerevisiae is identified by reverse transcriptase extension and protection mapping with nuclease S1. The sequence of a 419 bp rDNA fragment containing the transcription initiation site and its adjacent region is determined.
72 citations
TL;DR: In this article, it is shown that the kinetics of nucleation in glass-forming systems should be quantitatively described only in terms of the transient, more general Zeldovich-Frenkel formulation of the classical theory of phase formation.
Abstract: Glass-ceramics which have played an ever increasing role in science and technology in the last two decades are the most widely used representative of a new type of partly crystalline or semi-amorphous materials. They can be prepared by induced crystallization of glass-forming melts. This article, which is in two parts, surveys a number of theoretical and experimental investigations providing closer physical insight into the process of formation of glass-ceramic materials. Part 1 outlines the general principles of nucleation in viscous, glass-forming melts. It is shown that the kinetics of nucleation in glass-forming systems should be quantitatively described only in terms of the transient, more general Zeldovich–Frenkel formulation of the classical theory of phase formation. Part 2 (to appear in the next issue) summarizes experimental evidence on the nonsteady-state kinetics of nucleation and on the activity of nucleating catalyst in various glass-forming melts. A theoretical treatment of the act...
67 citations
TL;DR: In this paper, the co-effects of two glass-formers in the TeO2-P2O5 system are studied on the basis of neutron diffraction data, and the curves for the radial distribution function obtained show a high extent of destruction of the short-range order in the tellurite matrix, while the basic co-ordination PO4 polyhedron remains unchanged.
Abstract: The co-effects of two glass-formers in the TeO2-P2O5 system are studied on the basis of neutron diffraction data. The curves for the radial distribution function (RDF) obtained show a high extent of destruction of the short-range order in the tellurite matrix, while the basic co-ordination PO4 polyhedron remains unchanged. The co-ordination number (cn) of the Te atom changes from 4 to 3+1 and marked tendency towards elongation of the Te-O distances over 2.3 A is observed. The considerably higher stability of the PO4 polyhedra and their strong influence on the TeO4 polyhedra is established. The observed “smearing” effect of the Te-Te, Te-second O and O-second O distances in the range of 3.8 to 3.9 A in other tellurite glasses is also characteristic of this system. A structural interpretation of the liquid-liquid immiscibility on the short-range order level in the system is given. A critical composition with 26±5% of the second glass-former is established, above which concentration a stable immiscibility in the tellurite systems is observed. An attempt is made to construct two adequate structural models (microhomogeneous and microheterogeneous) for the short-range order in the glasses studied.
66 citations
TL;DR: In this article, the dependence of the number of nuclei on time was investigated in a wide overvoltage interval using different glassy carbon electrodes and the data for the steady-state nucleation rate were interpreted on the basis of both classical and atomistic theoretical concepts.
56 citations
01 Jan 1980
TL;DR: In this paper, the collision dynamics of adiabatic processes are considered in detail and the nonadiabatic transitions in molecular collisions are treated in a more concise form; see Section 2.1.
Abstract: We will first consider in detail the collision dynamics of adiabatic processes. The nonadiabatic transitions in molecular collisions will be treated later in a more concise form.
TL;DR: In this paper, the authors deal with the extension of the method of fractional steps to hydrodynamic and thermal problems for fully developed steady flow of viscous incompressible fluid in a curved circular tube.
TL;DR: In this article, the effect of the rotational depolarization of the values of the order parameters of a nematic liquid crystal, determined by polarization flourescence measurements, was considered using the theory recently developed by Zannoni.
TL;DR: In this article, a generalized eddy-viscosity function ν T is introduced in order to express the Reynolds stress in an incompressible dusty gas as a linear combination of the Kronecker and rate-of-strain tensors.
Abstract: A generalized eddy-viscosity function ν T , is introduced in order to express the Reynolds stress in an incompressible dusty gas as a linear combination of the Kronecker and rate-of-strain tensors. On the basis of Saffman's dusty-gas model a transport equation for the eddy viscosity is derived from the general turbulence energy equations, thereby introducing two additional functions, the specific turbulence kinetic energy E 1 , and a scale variable s . In order to determine the three variables modified Prandtl–Wieghardt relation among them is accepted and a transport equation for s is postulated in the same manner as in the clean-gas turbulence transport model (firstly proposed by Harlow & Nakayama 1967) but with the inclusion of an additional term accounting for the dust particles stabilizing action. We are considering values of loading (mass ratio of particles) of order of unity, with particle/gas density ratios of order of 10 3 and volume concentrations of the order of 10 −3 , so that particle–particle interactions are neglected. Supposing that the particles nearly follow the gas motion, following well at large scales and poorly at small, an application of the theory to problem of numerical calculations of the dusty-gas parameters such as mean velocity profile of turbulent pipe flow is given.
TL;DR: The histone patterns of rat liver, spleen, kidney and brain were compared by means of a two-dimensional electrophoresis and it was found that the high salt induced H2a specific proteolytic activity was very high inSpleen, very low in liver and kidney and absent in brain.
TL;DR: The catalytic activity of tungsten carbide for the evolution of hydrogen in acid medium has been investigated by taking current density values at a given potential in the straight line portion of Tafel curves as discussed by the authors.
TL;DR: Soliton solutions for a class of non-linear Schrodinger-like equations are obtained in this paper, where the parameters of the soliton solutions are explicitly written out. But they do not consider the non-convex case.
TL;DR: In this paper, the decomposition of cobaltous compounds (nitrate, hydroxide, carbonate, oxalate and oxyhydroxide) in vacuo has been investigated by magnetic methods and thermogravimetry.
TL;DR: In this paper, the radiation damage in a Si-SiO2 system exposed to O2 plasma in a planar reactor is investigated in dependence on the exposure time, the substrate temperature, and the pressure of O2.
Abstract: The radiation damage in a Si-SiO2 system exposed to O2 plasma in a planar reactor is investigated in dependence on the exposure time, the substrate temperature, and the pressure of O2. Capacitance-voltage (C-U) techniques and a static method are used to monitor charge trapping in the metal-oxide-semiconductor (MOS) capacitors. In all experiments a negative and a positive charging effect is observed as a result of plasma influence. Low and high temperature annealing is performed in order to eliminate radiation damage induced by the plasma. It is concluded that high temperature annealing is necessary prior to metallization to remove completely the radiation damage produced at substrate temperatures sufficiently above 20 °C. Metallized Si-SiO2 systems are also investigated and it is found that the metal layer gives a complete protection against the influence of the plasma.
Strahlungsdefekte in Si-SiO2-Strukturen, die wahrend der Behandlung einer Struktur im Sauerstoffplasma eines Planarplasmareaktors entstehen, werden in Abhangigkeit von Bearbeitungszeit, Substrattemperatur und O2-Gasdruck untersucht. Auf dem plasmabehandelten Si-SiO2-System werden Metallpunkte aufgebracht und an den MOS-Kondensatoren C-U- und statische Q-U. Messungen durchgefuhrt. Positive und negative Ladungen im Dielektrikum werden als Folge der Plasmawirkung beobachtet. Zur Beseitigung der Strahlungsdefekte wird eine Temperung bei Hoch- und Niedertemperaturen durchgefuhrt. Ist die Substrattemperatur wahrend der Plasmabehandlung wesentlich hoher als 20 °C, dann ist zur vollkommenen Ausheilung der Defekte eine Hochtemperaturbehandlung vor der Metallisierung notwendig. Die Plasmabehandlung der mit Metallpunkten versehenen Strukturen zeigt, das das Metall als vollstandiger Schutz gegen einen Plasmaeinflus dienen kann.
TL;DR: A mean frequency of 20.6 sister chromatid exchanges (SCEs) per cell has been observed in a reconstructed karyotype of Hordeum vulgare by application of the FPG technique after unifilar incorporation of BrdU into chromosomes.
Abstract: A mean frequency of 20.6 sister chromatid exchanges (SCEs) per cell has been observed in a reconstructed karyotype of Hordeum vulgare by application of the FPG technique after unifilar incorporation of BrdU into chromosomes. The involvement in SCEs of the 48 segments into which the chromosome set had been subdivided was, with a single deviation, length proportional and independent of the segment's heterochromatin content. Asymmetric bands, indicative of an uneven distribution of adenine and thymidine between the DNA strands in adenine (A)-thymidine (T) rich chromosome regions, could not be detected after incubation of the cells in BrdU for one cycle of DNA replication.
TL;DR: The venom exonuclease from Crotalus adamanteus venom has only threonine as N-terminimal amono acid residue and the analysis of the carbohydrate residues in the enzyme proves that it is a glycoprotein.
TL;DR: In this paper, the authors examined the scope and limitations of different approaches which enable π electronic systems of topologically equivalent structures to be compared and paid particular attention to analyses in terms of molecular subsystems.
Abstract: Scope and limitations of different approaches which enable π electronic systems of topologically equivalent structures to be compared have been examined. Particular attention has been paid to analyses in terms of molecular subsystems.
TL;DR: Evidence is presented here in favour of the third possibility by showing that the histones synthesized in the absence of DNA synthesis enter chromatin and become organized in nucleosomes.
Abstract: It is well established that DNA and histone synthesis are tightly coupled1,2. Nevertheless, these two processes can be partially uncoupled by drugs specifically inhibiting protein3,4 or DNA5,6 synthesis, and also during n-butyrate-induced differentiation of Friend cells7. The fate of the histones synthesized in the absence of DNA synthesis is unknown; they could be: (1) degraded without joining chromatin; (2) deposited on chromatin as extra histones; or (3) replace original chromatin histones. The only data concerning this problem are a recent report5 supporting the second possibility. We present evidence here in favour of the third possibility by showing that the histones synthesized in the absence of DNA synthesis enter chromatin and become organized in nucleosomes.
TL;DR: The ribosome is not only the principal organelle in gene expression, but it is also one of the best-understood models of the structure, function, and coordination of a large number of genes operating in the eukaryotic cell.
Abstract: The biogenesis of ribosomes in eukaryotes involves the generation in the cell of the constituent core rRNA molecules and their interaction with about 80 distinct proteins to form the two mature ribosomal particles. Therefore, the ribosome is not only the principal organelle in gene expression, but it is also one of the best-understood models of the structure, function, and coordination of a large number of genes operating in the eukaryotic cell. Furthermore, ribosomes are made in the nucleolus, but they operate in the cytoplasm. In this respect, studies on the biogenesis of ribosomes contribute to our understanding of the molecular architecture of the cell.
TL;DR: In this article, a survey of experimental results concerning the kinetics of nucleation and the mechanism of crystal growth in glass forming systems is given, with the main aim of the review being to correlate the kinetic of overall crystallization processes in glass-forming melts with structural changes taking place in the initial melt during crystallization.
TL;DR: The differential effect of cycloheximide inhibition of protein synthesis on in vivo and in vitro rRNA synthesis suggests the existence of elongation control protein(s) characterized by a rapid turnover and a loose association with the nucleus.
TL;DR: The surface textures of quartz grains deposited in the Persian Gulf during the last 30,000 years have been studied via scanning electron microscopy as mentioned in this paper, revealing a mixture of all different surface textures observed in Persian Gulf samples, reflecting the importance of turbidites for the sedimentation in the Gulf of Oman.
TL;DR: In this article, the activation energies for surface diffusion of entities composed of chains of atoms connected by springs are calculated as a function of the misfit, chain length (island size) and the energy parameters assuming that plastic deformations in solids can be explained by the dislocation slip mechanism suggested by Frenkel and Kontorova.