diffusion

An information model of the city educational environment have been described, the processes of educational qualification growth of the individual from the birth up to full profession readiness and further increment of the knowledge potential have been analyzed. There have been suggested processes of the knowledge potential propagation within socio-communicative environment in the form of the diffusion-like model.

A series of catalysts with the deactivated external surface on the basis of HZSM-5 have been prepared by extracting aluminium atoms from zeolite crystals or by covering this zeolite surface by the products of tetraethoxysilane thermal destruction. The external surface deactivation has been found to be not the main factor of increasing the para-selectivity in the reaction of toluene to benzene and p-xylene disproportionation: decreasing the diffusion of o- and p-xylene from the catalyst pores on the external surface of zeolite crystals seems to be as the determinant.

Dependence of acrylate macroradicals concentration in polymeric matrix of 1,6-hexanediol diacrylate on time within temperature range of 45-80С has been investigated by means of ESR-spectroscopy. It has been established that experimental data do not linearize in coordinates of equation of the second order reaction, what coordinates with bimolecular mechanism of macroradicals decay. It has been suggested, that the effect of decreasing of the rate constant of bimolecular macroradicals decay in time is related with their propagation in chain propagation reaction.

In this study the mathematical model of the extraction process from plant material is developed, taking into account the anatomical structure of plant material, namely the presence of cellular and intercellular spaces. The solution of the model enables to determine its kinetic coefficients Dc, Dt, process conditions, and predict the kinetics of the extraction process implementation in practice.

Adequacy of mathematical model of the extraction process of cellular structure solid bodies (plant material) has been proved taking into account its anatomical structure, namely the presence of cellular and intercellular environment. Diffusion coefficients through the cellular membrane Dc and in intercellular environment Dт have been determined. Experimental verification of the accumulation of intracellular substances in intercellular environment during the extraction process flow has been made.

Adequacy of mathematical model of the extraction process of solid bodies of cellular structure (plant material) was proved with taking into account its anatomical structure, namely the presence of cellular and intercellular environment. Experimental verification of the mechanism of extracting of intracellular substance during extraction process flow was made. An order of diffusion coefficients through cellular membrane – Dc and in intercellular environment Dт was confirmed.

A mathematical model of mass transfer from lamina (plant leaf) into the extractant is constructed considering its anatomical organization in particular the existence of cellular and intercellular space. Its solution allows to predict kinetics of the extraction process of the whole leaves at its implementation in practice.

We present results of development of mathematical models of external mass exchange in extraction of desired products from vegetable raw materials and mathematical models for the determination of the minimum time of achievement of the equilibrium state of the system and the current concentration of a soluble substance for their using in the optimization of operation of solid-phase extraction equipment.

The kinetics of controlled release of medicinal substances from chitosan films has been investigated. Correlation between values of diffusion coefficients and the sedate indicator characterizing diffusion of medicinal substance from a film and shares of medicinal substance connected with a polymeric chain has been established. With the increase in amount of the entered medicinal substance the rate of release of medicines decreases.

The structure of extruded films based on blends of polyvinyl alcohol and poly(3-hydroxybutyrate) (PHB) was studied for various compositions. The methods of DSC and X-ray analysis were used. As the phase-sensitive characteristics of the composite films, diffusion and water vapor permeability were also investigated. In addition, the tensile modulus and relative elongation-at-break were measured. Changes in the glass transition temperature of the blends and constant melting points of the components show their partial compatibility in intercrystallite regions.