Showing papers by "Bulgarian Academy of Sciences published in 1969"
TL;DR: In this article, an approximate solution of the Zeldovich-frenkel equation is derived for the transient nucleation rate and for the time-lag, and the analysis shows that the phenomena in the critical region play the decisive role during the establishment of the steady state.
419 citations
01 Jun 1969
TL;DR: In this paper, the potential of the diffuse electric layer was determined by the equilibrium liquid film method, based on calculating theϕ0-potential by means of the DLVO theory of the electrostatic disjoining pressure at known concentration,Cel of the solution forming the microscopic liquid film and at known thickness,hr of the film.
Abstract: The potential,ϕ0, of the diffuse electric layer was determined by the equilibrium liquid film method (1). The method is based on calculating theϕ0-potential by means of the DLVO theory of the electrostatic disjoining pressure at known concentration,Cel of the solution forming the microscopic liquid film and at known thickness,hr of the film. The thickness of the film was measured by the microinterferometric method (7, 8). The calculation of the potential was carrried out by means of the more general eqs. [2] and [3], valid for a wide range ofCel andϕ0. The dependence of the potential of the diffuse electric layer on the concentration of surface activ agent (surfactant) stabilizing the liquid film was found. It was established that ionogenic SAS show a higher potential than the non-ionogenic ones. The potential of SAS-free solutions was determined — ca. 30 mV.
76 citations
TL;DR: In this paper, a non-steady state nucleation beginning in the presence of a previous cluster size distribution is considered and expressions for the transient nucleation rate and for the time-lag are derived.
47 citations
TL;DR: In this paper, the NMR spectra of the erythro and threo forms of compounds of the type PhCHAXCHB(Ph) COOR have been investigated in CDCl3 and DMSO-d6 solutions at normal and in some cases also at higher temperature.
47 citations
TL;DR: The 32P-labelled RNA was isolated from stable cell lines by a SDS -hot phenol procedure and fractionated by electrophoresis on agar gel and it was proved that these fractions originated from mycoplasma contaminants.
46 citations
TL;DR: The coupling constants of the cis and trans isomers of 2-ureidocyclohexane carboxylic (UCHA) and of the erytho and threo isomer of 2,3-diphenyl-3-uridopropionic acid (DPhUPA) with gauche hydrogens are preferred as discussed by the authors.
41 citations
TL;DR: In this paper, the authors investigated the effect of diffusional resistance in the dispersed phase of liquid-liquid dispersions in a turbulent flow field and showed that the so-called correlation factor R depends strongly on the turbulence of the system.
Abstract: Mass transfer in liquid-liquid dispersions in a turbulent flow field has been investigated for the particular case where the overall process rate is governed by the diffusional resistance in the dispersed phase. Experiments with the system water-iodine-carbon tetrachloride have shown that the transfer mechanism in this case is similar to that for single drops at high Reynolds numbers. The results obtained show that the so-called correlation factor R depends strongly on the turbulence of the system. This relationship can be expressed as R ˜ R2, which is valid for the mass transfer rate both in turbulent liquid-liquid dispersions and for some cases of solute diffusion in single oscillating drops.
On a etudie le transfert de masse, a l'interieur de dispersions d'un liquide dans un liquide, dans un champ d'ecoulement turbulent, en considerant le cas particulier ou la vitesse globale du procede est regie par la resistance a la diffusion dans la phase dispersee. Les experiences executees avec le systeme eau-iode-tetrachlorure de carbone ont demontre que le mecanisme de transfert dans ce cas est semblable a celui qu'on rencontre avec de simples gouttes lorsque les nombres de Reynolds sont eleves. Les resultats obtenus indiquent que le soi-disant facteur de correlation R depend fortement de la turbulence du systeme. On peut exprimer la dite relation avec l'expression R ∼ Re2, laquelle est valide pour la vitesse de transfert de masse dans une dispersion turbulente d'un liquide dans un liquide et dans certains cas de diffusion du solute dans des gouttes simples qui oscillent.
40 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: In this article, a unified theory of field and thermionic emission is extended to electron emission into dielectrics, including thin films between two metal electrodes, under the assumption of a parabolic energy-momentum dependence and convenient barrier shape approximations for various thicknesses of the insulating layer.
Abstract: The previously presented unified theory of field and thermionic emission is extended to electron emission into dielectrics, including thin films between two metal electrodes. The current equations are derived under the assumption of a parabolic energy—momentum dependence and convenient barrier shape approximations for various thicknesses of the insulating layer, but the general method is used in the case of any arbitrary barrier shape. Both cases of equal and unequal effective electron masses in the insulator and the metals are considered. The current expressions obtained are applicable to the whole range of fields and temperatures between the limits of thermionic and field emission.
Die fruher vorgelegte einheitliche Theorie der Feld- und Thermoemission wird auf die Elektronenemission in Dielektrika erweitert, einschlieslich dunner Schichten zwischen zwei metallischen Elektroden. Die Stromgleichungen werden unter der Annahme einer parabolischen Energie-Impuls-Abhangigkeit und geeigneter Naherungen fur die Barrierenform fur verschiedene Dicken der isolierenden Schicht abgeleitet, jedoch wird die allgemeine Methode fur den Fall einer beliebigen Barrierenform benutzt. Es werden sowohl der Fall gleicher wie ungleicher effektiver Elektronenmassen im Isolator und Metall berucksichtigt. Die erhaltenen Stromgleichungen sind fur den gesamten Feld- und Temperaturbereich zwischen den Grenzen der thermischen Emission und der Feldemission anwendbar.
26 citations
26 citations
TL;DR: In this article, a kinetic equation for the size distribution function of the clusters is obtained and a relation is indicated between the transition probabilities and the isothermal reversible work required for cluster formation.
TL;DR: In this article, the Wolfsberg-Helmholtz method was used to estimate the activity for hydrogen adsorption of different adorption centers including metal d orbitals on different crystal faces of a face centered cubic nickel crystal.
TL;DR: The absolute configurations of two series of genetically related compounds with a general formula PhCH(X) - CH(Y)Ph are determined by chemical correlation with 2,3-diphenylpropanoic acid (V).
TL;DR: The characteristics of total and rapidly‐labelled RNAs of rat brain were studied by agar gel electrophoresis and the possible significance of these results for the elucidation of ribosomal and messenger RNA metabolism in brain is discussed.
Abstract: — —The characteristics of total and rapidly-labelled RNAs of rat brain were studied by agar gel electrophoresis. The bulk (more than 90 per cent) of total, nuclear and cytoplasmic brain RNA was represented by the 28 S, 18 S and 4 S RNA components. The 28 S/18 S RNA mass ratio in cytoplasmic RNA was 2·55. Lower values for this ratio were obtained with total and nuclear RNAs. Five minor RNA components were detected in total brain RNA with mobilities in agar gel corresponding to 24 S, 22 S, 14 S, 9 S and 6 S. Two broad rapidly labelled RNA components were detected in total and nuclear (but not in cytoplasmic) brain RNA with mobilities corresponding to about 45 S and 31 S. These fractions were of nuclear origin and resembled ribosomal precursor RNAs of other animal tissues. In cytoplasmic RNA the radioactivity and ultraviolet profiles coincided at all labelling times down to 1 hr. The G + C/A + U ratio of brain RNA was 1·50 for total RNA, 1·39 for nuclear RNA and 1·59 for cytoplasmic RNA. The G + C/A + U ratio of 1 hr-labelled total brain RNA (determined by 32P-distribution) was 0·94. This ratio rose to 1·31 at 24 hr labelling. The possible significance of these results for the elucidation of ribosomal and messenger RNA metabolism in brain is discussed.
TL;DR: The influence of RNA concentration, pH, temperature, buffer, and gel concentration on the fractionation and mobility of RNA in agar gel electrophoresis was studied and a linear relationship was found between mobility and square root of gel concentration.
TL;DR: In this paper, the relationship between the increase in intensity of different spectral lines and the intensity of the applied nonhomogeneous magnetic field was investigated using the method of the graphite arc, and the optimal value for the magnetic field intensity, corresponding to the maximal line intensity increase was determined in different regions of the arc.
TL;DR: It is suggested that the instability of rat liver 28s rRNA is due to two factors: the presence of hidden breaks in the polymer chain and a higher susceptibility of some phosphodiester bonds to thermal hydrolysis.
Abstract: Rat liver ribosomal RNA (rRNA) free from nuclease contaminants was isolated by a modification of the phenol technique. The 28s and 18s rRNA species were separated by preparative agar-gel electrophoresis. The two rRNA species were heated at different temperatures under various conditions and the amount of undegraded rRNA was determined by analytical agar-gel electrophoresis. The 18s rRNA remained unaltered after heating for up to 10min. at 90° in water, acetate buffer, pH5·0, or phosphate buffer, pH7·0. Under similar or milder conditions 28s rRNA was partially degraded, giving rise to a well-delimited 6s peak and a heterogeneous material located in the zone between 28s and 6s. The dependence of degradation of 28s rRNA on the temperature and the ionic strength of the medium was studied. The greatest extent of degradation of 28s rRNA was observed on heating at 90° in water. It is suggested that the instability of rat liver 28s rRNA is due to two factors: the presence of hidden breaks in the polymer chain and a higher susceptibility of some phosphodiester bonds to thermal hydrolysis.
TL;DR: In this paper, it was shown that the singlet and triplet transition energies of hydrocarbons can be calculated by means of the generalised Mataga-Nishimoto approximation for the two-center Coulomb integrals.
TL;DR: In this article, two and three dipoles approximating the earth's main magnetic field are determined minimizing a sum of squares of differences between the dipole fields and the earth magnetic field.
Abstract: Two and three dipoles approximating the earth's main magnetic field are determined minimizing a sum of squares of differences between the dipole fields and the earth's magnetic field. Numerical results have been obtained by the aid of a digital computer for epochs 1932, 1942, 1950 and 1960.
TL;DR: In this article, the archeomagnetic results for the inclination of ancient magnetic field in Bulgaria are presented, with an amplitude of nearly 14° and a period between 700-900 years for the secular variation of the inclination.
Abstract: The present paper contains the archeomagnetic results for the inclination of ancient magnetic field in Bulgaria. An amplitude of nearly 14° and a period between 700-900 years for the secular variation of the inclination are obtained.The methods and apparatus used are described. Two examples of application of Thellier's method are given.
TL;DR: The change of some kinetic parameters of the enzyme reaction catalyzed by snake venom phosphodiesterase is followed as a function of the length of the substrate molecule, resulting in the increasing reaction rate with progress of the hydrolysis.
TL;DR: Electrophoretic separation in agar gel has been achieved for ribosomes from rat liver and Escherichia coli and their subunits, and provides a means of studying the labelling pattern of the ribosome, contaminants being quantitatively removed by washing of the gel with acid.
Abstract: Electrophoretic separation in agar gel has been achieved for ribosomes from rat liver and Escherichia coli and their subunits. These particles were characterized by their mobility. RNA was extracted from the agar gel zones containing the two subunits of rat liver. It was found that the faster subunit contained only 18 S RNA with a base composition identical with that of 18 S cytoplasmic rat liver RNA. The slow subunit contained 18 S and 28 S RNA, both having the base composition of 28 S cytoplasmic RNA. The technique also provides a means of studying the labelling pattern of the ribosomes, contaminants being quantitatively removed by washing of the gel with acid.
TL;DR: In this paper, the coordinates and the components of the dipole approximating to the highest possible degree the earth's magnetic field are determined minimizing a sum of squares of differences between dipole field and the earth magnetic field.
Abstract: The coordinates and the components of the dipole approximating to the highest possible degree the earth's magnetic field are determined minimizing a sum of squares of differences between the dipole field and the earth's magnetic field. Numerical results by the aid of a digital computer have been obtained for epoch 1932, 1937, 1942, 1945, 1950, 1955 and 1960 on the basis of magnetic data from 61 observatories.
TL;DR: The Tortonian deposits in northwestern Bulgaria show a great variety of structures which are divided into three main classes as discussed by the authors : structures formed during the deposition of gypsum and includes laminae and layers resulting from chemical precipitation and/or mechanical replacement of particles.
TL;DR: Results are consistent with the hypothesis that the induction of cancer cells is related to the irreversible blocking of a special functional operon interconnected with the mitotic operons in a regulatory genetic circuit.
TL;DR: In this article, the existence of dislocations with Burgers vectors of type 1/3 ǫ-1123 is demonstrated, which agrees well with the observed whisker growth in these directions.
Abstract: Crystal imperfections in zinc single crystals were studied by X-ray topography. The zinc single crystals were obtained in a glass ampule from a molten droplet which, after solidification, acted as a nucleus for further growth from the vapour phase. The crystals adhered strongly to the glass support. The X-ray topographs give informations on the modes of plastic deformation, which occurred in the crystals during cooling. The existence of dislocations with Burgers vectors of type 1/3 〈1123〉 is demonstrated. This agrees well with the observed whisker growth in these directions. Some other phenomena connected with the crystal growth are also discussed.
Die Kristallgitterstorungen in Zink-Einkristallen wurden mit rontgentopographischen Verfahren untersucht. Die Zink-Einkristalle wurden in einer Glasampulle aus einem geschmolzenen Tropfen gezuchtet, der nach der Erstarrung als Keim fur weiteres Wachstum aus der Dampfphase wirkte. Die Kristalle haften fest an der Glasunterlage. Die Rontgenaufnahmen geben Aufschlus uber die plastischen Verformungen, die in den Kristallen bei der Abkuhlung ablaufen. Es wird gezeigt, das die wachsenden Kristalle Versetzungen mit Burgersvektoren 1/3 〈1123〉 enthalten, was gut mit dem beobachteten Whiskerwachstum in diesen Richtungen ubereinstimmt. Ferner werden andere, mit dem Kristallwachstum verbundene Erscheinungen diskutiert.
TL;DR: In this paper, an explanation of the multilayer critical coverages observed in vapour deposition on foreign substrates is given based on an idea of Kaischew and Bliznakov.
TL;DR: In this article, the NMR spectra of ammonia adsorbed on silica gel treated at 200 ° and 700 °C and on zeolite (NaX) heated at 77-300 °K have been studied.