Topologically disordered systems at the glass transition

The thermodynamic approach to the viscosity and fragility of amorphous oxides was used to determine the topological characteristics of the disordered network-forming systems. Instead of the disordered system of atoms we considered the congruent disordered system of interconnecting bonds. The Gibbs free energy of network-breaking defects (configurons) was found based on available viscosity data. Amorphous silica and germania were used as reference disordered systems for which we found an excellent agreement of calculated and measured glass transition temperatures. We reveal that the Hausdorff dimension of the system of bonds changes from Euclidian three-dimensional below to fractal 2.55 ± 0.05-dimensional geometry above the glass transition temperature

Opportunistic microbiota of breast milk and antimicrobial activity of milk whey at different periods of lactation

Object of study. The evaluation of the interaction between breast milk opportunistic microorganisms abundance and the milk whey antimicrobial activity at different periods of lactation. Materials and methods. 100 samples of breast milk from healthy breastfeeding mothers were inoculated on solid selective media, and then pure cultures of microorganisms were identified by MALDI-TOF mass spectrometry. The antimicrobial activity of the whey against a model culture of Candida albicans was evaluated by spectrophotometry. Results. 270 isolates represented by 36 species of 13 genera of opportunistic bacteria were obtained. None of the 100 samples contained opportunistic fungi. Staphylococci (7 species) and streptococci (11 species) were predominant. The most common were staphylococci S. epidermidis (70.2%) and S. aureus (20.8%), and streptococci S. mitis (27.7%) and S. oralis (21.8%). The total contamination (median) of opportunistic bacteria in the colostrum was 79 103 CFU/ml, transitional milk 4 103 CFU/ml, mature milk 5 102 CFU/ml. The antimicrobial activity of colostrum whey was 87.489.4%; transitional milk 88.2%; mature milk 63.481.9%. The total contamination had a high inverse correlation with the lactation period (r = 0.806) and a high positive correlation with the antimicrobial activity of whey (r = 0.699). Meanwhile, a significant decrease in contamination was noted after 1 month from the beginning of lactation, while a significant decrease in antimicrobial activity was observed after 8 months. Conclusions. The decrease of the breast milk contamination by opportunistic bacteria during the lactation period was found to be primary compared to the decrease of the whey antimicrobial activity. Thus, changes in the whey antimicrobial protection factors occur in response to changes of the opportunistic microbiota abundance

Correlation effects during liquid infiltration into hydrophobic nanoporous mediums

Correlation effects arising during liquid infiltration into hydrophobic porous medium are considered. On the basis of these effects a mechanism of energy absorption at filling porous medium by nonwetting liquid is suggested. In accordance with this mechanism, the absorption of mechanical energy is a result expenditure of energy for the formation of menisci in the pores on the shell of the infinite cluster and expenditure of energy for the formation of liquid-porous medium interface in the pores belonging to the infinite cluster of filled pores. It was found that in dependences on the porosity and, consequently, in dependences on the number of filled pores neighbors, the thermal effect of filling can be either positive or negative and the cycle of infiltration-defiltration can be closed with full outflow of liquid. It can occur under certain relation between percolation properties of porous medium and the energy characteristics of the liquid-porous medium interface and the liquid-gas interface. It is shown that a consecutive account of these correlation effects and percolation properties of the pores space during infiltration allow to describe all experimental data under discussion