Generic Phenomenological Theory of Vitrification

In the framework of the thermodynamics of irreversible processes and using a graphical approach based on the simple theorems of differential geometry, a generic phenomenological treatment of the glass transition is developed. A thermodynamic derivation of the basic kinetic condition for vitrification—the Frenkel–Kobeko–Reiner equation—is given in a new generalized form. The temperature course of the thermodynamic functions and the kinetic characteristics of vitrifying systems are constructed using one of the general principles of irreversible thermodynamics. The results thus obtained underline the substantial differences and formal similarities between vitrification, considered as a diffuse kinetic transition and thermodynamic phase transformations. A general reconsideration of the axiomatics of the thermodynamics and kinetics and kinetics of glass transition and relaxation is attempted.     

Coexistence of ultraviolet photo-response and room-temperature ferromagnetism in polycrystalline ZnO thin films

The coexistence of ultraviolet (UV) photoconductivity (PC) and room-temperature ferromagnetism (RTFM) is observed in polycrystalline ZnO thin films deposited by unbalanced magnetron sputtering under high oxygen pressure. A significant increase in PC (∼ 870% to 40 000%) is observed with increasing film thickness and the consequent structural disorder and film porosity. In contrast, the saturation magnetization (M_S) at room temperature is found to decrease from 1.02 emu/g to 0.53 emu/g with increasing film thickness from 50 to 150 nm.     

Calculation results from radiation embrittlement of VVER pressure vessel at Kozloduy NPP

A calculational procedure for the evaluation of the transition temperature shift on the basis of neutron fluence has been applied for assessing the reactor pressure vessel (RPV) embrittlement and life time for a VVER-440/230. The calculated results are lower than the passport values, because the real fuel regimes, the low-leakage schemes and loadings with dummy cassettes have been taken into consideration in neutron fluence calculation. The temperature of the outer wall of the RPV has been measured. No significant deviation between the measurement and the data given in the reactor passport has been observed. This shows the correct application of the calculational procedure.     

Plasma renin activity in tachistin-stimulated hypercalcemia and under the effect of chlorazine

The aim of the present study was to elucidate the correlation between the Renin secretion and increased Plasma Calcium concentration and the role of Calmodulin in this process. Plasma Renin activity was determined radioimmunologically in 31 white rats, that were grouped as follows: group I - 7 controls loaded for 6 days perorally with 0.5 ml/200 g b.w. glycerin and injected i.m. for 6 days with 0.1 ml/200 g b.w. with 0.9% NaCl; group II - 8 rats, treated for 6 days with Tachistin 0.0025 mg/200 g b.w., dissolved in glycerin 0.5 ml/200 g b.w.; group III - 5 rats, treated with Tachistin 0.005 mg/200 g b.w. in the same manner; group IV - 5 rats injected i.m. with Chlorazin 0.5 mg/200 g b.w. for 6 days; group V - 6 rats, loaded with double dose Tachistin and with Chlorazin 0.5 mg/200 g b.w. for 6 days. Blood samples were taken intracardially on the seventh day from the beginning of the experiment and were analyzed with kits of Sorin-Biomedica-Italy. Our results suggest that the hypercalcemia induced by Tachistin caused a dose-dependent increase of PRA and Ca-Calmodulin complex is the dominant second messenger of Renin secretion.     

Engineering geological characteristics of the pliocene clays of Bulgaria

The wide distribution of the Pliocene clays over the territory of Bulgaria and the landslides which appear in them draw the attention of a great number of specialists. Three types of clays may be distinguished: sandy and silty clays, heavy clays with silty seams, and fat clays overlying coal layers. They are water-saturated and show a plastic consistence. With increasing depth, the density decreases and the moisture increases. Sandy and silty clays show the upper-most degree of lithification. Fat clays are at the first stage of physical ageing. The processes of lithification are the cause or a dense system of fissures, some showing a constant dip, about 45°, which reduces the strength of the clays. The internal friction angle and the cohesion are independently determined in laboratory conditions. The possibility of determining, with the help of different-size samples, how the fissuration affects the shear strength is examined. The authors propose to use the residual resistivity of fissured clays for calculating the long-term stability of slopes.

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Résumé L’étendue considérable des argiles pliocènes sur le territoire de la Bulgarie et les glissements de terrains qui s’y développent attirent l’attention d’un grand nombre de spécialistes. On distingue des argiles sableuses et silteuses, des argiles lourdes à passées silteuses et des argiles grasses reposant sur des couches de charbon. Elles sont saturées en eau et ont une consistance plastique. En profondeur, la densité diminue et l’humidité augmente. Les argiles sableuses et silteuses ont le plus haut degré de lithircation. Les argiles grasses sont au premier stade d’un vieillissement physique. Les processus de lithification sont cause de la formation d’un système dense de fissures dont certaines ont un pendage constant, environ 45°, ce qui diminue la résistance des argiles. On propose de déterminer indépendamment, dans les conditions de laboratoire, l’angle du frottement interne et la cohésion. On étudie la possibilité de déterminer, à l’aide d’échantillons de dimensions différentes, le degré d’influence de la fissuration sur la résistance au cisaillement. Les auteurs proposent d’utiliser la résistivité résiduelle des argiles fissurées pour calculer la stabilité des pentes à long terme.

     

Artisanal cheeses relying on spontaneous fermentation as sources of unusual microbiota – The example of the Bulgarian ‘mehovo sirene’ skin bag cheese

The Bulgarian ‘mehovo sirene’ cheese is a type of regional artisanal cheese prepared from raw ewe milk in a skin bag relying on spontaneous fermentation. A metagenomics study revealed an unusual microbiome comprising beneficial bacteria such as Staphylococcus equorum, Lactococcus lactis, Streptococcus thermophilus, Lactobacillus delbrueckii, Lactobacillus kefiranofaciens, Lactococcus raffinolactis, Lactiplantibacillus plantarum, Limosilactobacillus fermentum and Loigolactobacillus coryniformis. Our findings suggest that ‘mehovo sirene’ could have some functional food properties and is a source of beneficial microorganisms.