Showing papers by "Sofia University published in 1989"
192 citations
TL;DR: In this paper, a simple cell model is proposed to calculate the disjoining pressure contribution due to the presence of micellar structure inside the thinning liquid films, and the calculated excess energy per unit area of the film exhibits a number of minima corresponding to the metastable states with mousellar layers inside the film.
135 citations
TL;DR: In this paper, the high frequency resistance of a Nafion® perfluorosulfonic membrane is measured by means of the AC impedance technique using a mercury cell, which is able to follow the variation of the resistance as a function of the water content and of the nature of the cation present in the membrane.
87 citations
01 Jul 1989
54 citations
TL;DR: In this article, the collision between a mineral particle and a gas bubble in froth flotations is studied theoretically, and a conclusion is drawn that collisions causing a pronounced deformation of the bubble surface are ineffective for the formation of a three phase contact since the oscillation period is relatively short and there is no sufficient time left for the thinning and rupture of the film between the particle and the bubble and the establishment of strong contact between them.
52 citations
TL;DR: In this article, the automorphismes d a Courbe elliptique are described as recouvrements doubles de T 2 and surfaces abeliennes de polarisation (2,4).
Abstract: Revue sur les varietes abeliennes. Les automorphismes d'une courbe elliptique. Surfaces abeliennes T 2 de polarisation (1,2). Jacobiens hyperelliptiques comme recouvrements doubles de T 2 . Les tores T 2 comme doubles recouvrements des jacobiens hyperelli Courbe de Kowalewski et surfaces abeliennes de polarisation (2,4)
44 citations
TL;DR: In this article, a quantitative spectrophotometric method for the analytical determination of tautomerism was developed to evaluate the influence of various factors affecting the azo-quinonehydrazone equilibrium.
44 citations
TL;DR: In this paper, a novel method of ultrabroadband laser generation is reported, which uses transversal shifting of the frequency components in the gain medium (dye), in order to obtain this shift, a special type of laser resonator with an intracavity grating pair is designed.
39 citations
TL;DR: In this paper, a microcomputer program of practical importance is described that permits the characterization of any mobile phase for normal-phase separations on silica or alumina by means of Snyder's parameters solvent strength, ǫ, localization, m, and polarity, P ′.
31 citations
TL;DR: Systematic errors due to nonlinearity and polarization-dependent sensitivity in the detection system of rotating analyzer ellipsometers are described and post Fourier analysis procedures for detection and correction of these effects are presented.
Abstract: Systematic errors due to nonlinearity and polarization-dependent sensitivity in the detection system of rotating analyzer ellipsometers are described. Post Fourier analysis procedures for detection and correction of these effects are presented.
29 citations
01 Jan 1989
TL;DR: One exogenous surfactant therapy of respiratory distress syndrome (RDS) is to instillate into the lungs enough phospholipid to form a film at the alveolar interface as mentioned in this paper.
Abstract: One exogenous surfactant therapy of respiratory distress syndrome (RDS) is to instillate into the lungs enough phospholipid to form a film at the alveolar interface because it has more similar surface properties that the natural surfactant. Liposomal suspensions are able to transport a large amount of phospholipids in situ; therefore, it is interesting to study the transformation of these vesicles into a surface film.
TL;DR: In this article, a thermal assay probe (enzyme thermistor) was used to study the performance of enzymic analyses by immobilized enzymes in organic solvents and in mixtures of organic and aqueous buffer.
Abstract: A thermal assay probe (enzyme thermistor) was used to study the performance of enzymic analyses by immobilized enzymes in organic solvents and in mixtures of organic solvents and aqueous buffer. It was found that rather small amounts of alcohols (around 5 %, v/v) in the buffer approximately doubled the registered temperature changes for glucose oxidase and catalase, mainly by increasing the total enthalpy change of the reaction. the heat production for peroxidase catalyzed reactions was as much as 45 times higher in toluene compared to buffer. the advantage of increased substrate solubility in organic solvents was demonstrated by operating a lipase column in cyclohexane. All enzymes studied showed good stability in the organic solvents used.
TL;DR: In this paper, it has been shown that explosion occurs as a result of mechanochemical synthesis through a thermal mechanism, and a kinetic equation of explosive synthesis mechanochemical processes has been proposed which accounts for the mechanical activation features and the suggested thermal mechanism of explosion.
TL;DR: In this paper, it was shown that the converse does not hold in general and that if the Betti numbers of M are bounded, then the finiteness of its virtual projective dimension implies that its minimal free resolution eventually becomes periodic of period 2.
TL;DR: In this article, the Fourier deconvolution of the OD stretching spectra of D2O for temperatures from 5 to 90°C and for concentrations (D2O in H2O) from 100 to 10 mol-% were studied.
Abstract: The OD stretching spectra of D2O for temperatures from 5 to 90°C and for concentrations (D2O in H2O) from 100 to 10 mol-% were studied. These spectra were treated by means of the Fourier deconvolution technique for the first time.
Using the positions of the resolved components the coupling constants for intra- and inter-molecular and Fermi resonance interactions and all parameters according to the presented model, for all investigated temperatures, were evaluated. A gradual decrease in all interactions was observed in the concentration study, in accordance with expectations and in agreement with the results for dilute solutions of H2O in D2O.
The temperature behaviour of the coupling constants and other parameters were in accordance with the corresponding data for H2O. The only exception is the temperature behaviour of the intramolecular coupling constant. The greater mass of the D atom is one of the probable reasons that lead to the smaller sensitivity of OD frequency to the hydrogen bond fluctuations.
All the results verify the assignments and assumptions made according to the model presented and support the continuous model for the water structure.
TL;DR: In this article, the polarized Raman spectra from single crystals of Nd2CuO4−y obtained at room temperature and by micro-Raman technique were obtained and three of the four Raman active phonons predicted by factor-group analysis were found at 229 (A1g), 330 (B1g, 488 (Eg) cm−1 and attributed to certain lattice vibrations.
TL;DR: The GC proposed procedures were applied to the analysis of urine samples from humans exposed and not exposed to organophosphates, and the application of different procedures and their limits of detection are discussed.
TL;DR: In this article, the authors explored the thermal activation contribution to the initial thermomagnetic curves with a Hopkinson maximum and incorporated it into the Stoner-Wohlfarth model of magnetization of noninteracting uniaxial single-do-main particles of random orientation.
TL;DR: In this article, a novel saturable absorber for mode-locking of Rhodamine 6G dye laser is presented, which is remarkable for its stability in comparison with the widely used mode-locker DODCI.
01 Jul 1989
TL;DR: In this article, the mechanisms of formation of Black Sea circulation and the distribution of temperature and salinity are considered, and numerical model results provide an explanation of some of the mechanisms controlling the formation of the general circulation in the Black Sea, and its energetic variability.
Abstract: The mechanisms of formation of Black Sea circulation and the distribution of temperature and salinity are considered. Princeton OGCM with horizontal resolution δλ = 1° and δϕ = 0.5° is used to simulate the circulation. Velocity field results are used in a simple model to simulate the distribution of H2S and O2, parameterizing the chemical interaction between H2S and O2 by second order kinetic reaction.
Numerical model results provide an explanation of some of the mechanisms controlling the formation of the general circulation in the Black Sea, and its energetic variability. Simulation of the hydrochemical fields indicates a strong correlation between these fields and both the vertical motions and the horizontal circulation. The chemocline shoals in the central area of the sea as a result of the general upwelling in this region. The depth of the redox layer is approximately 120–150 m, and varies with space.
TL;DR: In this article, three Ni(II)-creatinine complexes are synthesized in organic media and it is proved that the complexes are formed only in nonaqueous media and their dissolution in water is connected with immediate dissociation.
TL;DR: In this article, the polarized Raman spectra of Bi-HTS microcrystals with defined orientation of the c -axis and of different Bi-Ca-Sr-Cu composition (including close to 2122 and 2223) were measured at room temperature by means of the Raman microprobe technique.
Abstract: The polarized Raman spectra of Bi-HTS microcrystals with defined orientation of the c -axis and of different Bi-Ca-Sr-Cu composition (including close to 2122 and 2223) were measured at room temperature by means of the Raman microprobe technique. The phonon lines at 635 cm -1 (A 1g ), 460 cm -1 (B 1g , near 300 cm -1 (A 1g ) and at 115 cm -1 (A 1g ) appear for alll microcrystals, whereas the position of the relatively strong (A 1g ) line in the low frequency region depends on the crystal. The Raman lines are assigned to certain lattice vibrations on the basis of comparison of the Raman spectra of Y-123 and Bi-HTS and of the structural data for Y-123 and Bi-2122. Earlier assignments of the Raman lines in the orthorhombic and tetragonal Y-123 are revised.
TL;DR: In this paper, Fourier deconvolution is applied to resolve the overlapped components in the corresponding isotropic and anisotropic spectra of the Raman CH stretching spectra.
TL;DR: The results reveal k-k system activation in ARDS patients, with a significant fall in factor XII, prekallikrein, alpha-2-macroglobulin, and high molecular —weight kininogens in comparison with patients with CPO.
Abstract: In order to assess the role of the kallikreinkinin (k-k) system in the pathogenesis of pulmonary oedema, we studied the contact phase factors of blood coagulation, as well as the haemodynamics and blood gas changes in 34 patients with pulmonary oedema, 23 of them with Adult Respiratory Distress Syndrome (ARDS) and 11 with cardiogenic pulmonary oedema (CPO). We have verified significant differences in the haemodynamic pattern and blood gases between the two groups of patients, which corroborate the previously established differences between both types of pulmonary oedema. Our results reveal k-k system activation in ARDS patients, with a significant fall in factor XII (p<0.05), prekallikrein (p<0.01), alpha-2-macroglobulin (p<0.01) and high molecular —weight kininogens (p<0.005), with a rise in C1-esterase inhibitor (p<0.001) in comparison with patients with CPO. All of the CPO patients had normal prekallikrein levels, whereas 15 out 23 ARDS cases (65%) had decreaed prekallikrein values. Our results suggest that the k-k system activation could play a role in the pathogenesis of ARDS. Estimation of prekallikrein levels may be helpful in the differential diagnosis of ARDS.
TL;DR: In this paper, the adsorption of dipalmitoylphosphatidylcholine (DPPC) and palmitic acid from multilamellar lipid dispersions in excess water onto hydrophilic and hydrophobic glass surfaces was studied.
TL;DR: In this paper, the basic equilibrium and kinetic exchange parameters are determined for cesium and strontium radionuclides in different locations in Bulgaria and the influence of the mineralogical and chemical composition of the zeolite rocks on the ion exchange properties is shown.
Abstract: Zeolite rocks from different locations in Bulgaria are characterized in geological-mineralogical respect and as ion exchangers for cesium and strontium radionuclides. The basic equilibrium and kinetic exchange parameters are determined. The influence of the mineralogical and chemical composition of the zeolite rocks on the ion exchange properties is shown.
TL;DR: In this article, a diagramme R3/R6 (rapport des raies [S11]/[O11]) is used for the estimation du rougissement dans 25 galaxies prises dans la litterature.
Abstract: L'utilisation de raies interdites de densite approximativement egale est suggeree comme indicateur du rougissement pour les regions a raies etroites des noyaux actifs de galaxies. Un diagramme R3/R6 (rapport des raies [S11]/[O11]) est utilise pour les estimations du rougissement dans 25 galaxies prises dans la litterature
TL;DR: Srinorg geochemistry in coal has been studied on the basis of its distribution in 457 samples of coal, coaly shales and mineral interlayers from several Bulgarian coal deposits as mentioned in this paper.
TL;DR: In this article, the application of high-performance liquid chromatography with spectrophotometric or electrochemical detection was demonstrated for the determination of some alkylenebis(dithiocarbamates) and some of their degradation products and metabolites, especially alkylenethiourea, for toxicological investigation.
TL;DR: Four known three-valued logics are formulated axiomatically and several completeness theorems with respect to nonstandard intuitive semantics, connected with the notions of information, contrariety and subcontrariety are given.
Abstract: Four known three-valued logics are formulated axiomatically and several completeness theorems with respect to nonstandard intuitive semantics, connected with the notions of information, contrariety and subcontrariety is given.