Rheological properties and the mechanism of a viscous flow of aqueous pectin solutions

The rheological properties and mechanisms of a viscous flow of diluted apple pectin solutions are investigated. It is found that the rise in solution viscosity upon an increase in concentration and a drop in temperature is, along with the corresponding degree to which the interaction between pectin molecules and solvent is reduced, associated with the processes of structuring. The entropy of a viscous flow of pectin solutions is found to be positive: it grows with a rise in concentration is virtually temperature independent. It is established that the entropy factor makes the main contribution to the free energy value of a viscous flow.     

On the invariance of a boundary-value problem for a nonlinear evolution equation

We obtain an invariance group for one boundary-value problem in the physics of the sea. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 9, pp. 1281–1283, September, 1998.     

Position of the edge of fundamental absorption band of solutions of ferroelectric crystals

Journal of Applied Spectroscopy -     

On One Nonlocal Problem with Free Boundary

We investigate group-theoretic properties of a nonlocal problem with free boundary for a degenerating quasilinear parabolic equation. We establish conditions for the invariant solvability of this problem, perform its reduction, and obtain an exact self-similar solution.     

The self-diffusion of water and saturated aliphatic alcohols in cation-exchange membranes

The self-diffusion of water, methanol, ethanol, isopropanol, and butanol in membranes based on polyethylene and sulfonated copolymer of styrene and divinylbenzene (MK-100) and membranes based on sulfo-containing aromatic polyamides (PA) and a copolymer of 1,2,4,5-benzenetetracarboxylic acid with 4,4′-diaminodiphenyl oxide (PAK) was investigated by the pulsed magnetic field gradient NMR technique. In MK-100 sulfo cation-exchange membranes and PAK carboxylic membranes, two types of sorbate molecules with translational mobilities differing by an order of magnitude were observed. It was established that, in these membranes, the major diffusant portion was transferred trough transport channels formed by functional groups of membranes, counterions, and diffusant molecules (ionogenic channels). The conclusion was drawn that, in PA membranes, water and alcohol molecules were distributed uniformly and carbonyl croups of the polymeric matrix participated in the formation of transport channels. Relations between the structure of membranes, the character of diffusant-polymeric matrix interaction, and the translational mobility of sorbate molecules were found.     

Group analysis of boundary-value problems of mathematical physics

We obtain conditions for invariance and invariant solvability of boundary-value problems of mathematical physics. Institute of Mathematics, Ukrainian Academy of Sciences, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 51, No. 1, pp. 140–144, January, 1999.     

MIS structure with polyamide insulator under the conditions of water vapor sorption

A silicon MIS structure with sulfonate-containing aromatic polyamide as a gate insulator is prepared with the aim of using it as a capacitive-type humidity detector. A detector made of this material offers a high sensitivity at an elevated relative humidity and a high speed of response. Measurements of the capacitance of the structure at different frequencies basically make it possible to determine the water distribution in the polymer matrix. The high-frequency (1 MHz) capacitance versus relative humidity dependence (i.e., the calibration curve of the detector) is typical of the isotherms of water vapor sorption by similar polymers.     

Electrodialysis of pectin-containing solutions of hydrochloric acid with ion-exchange membranes

The process of electrodialysis of 0.05 M hydrochloric acid solutions containing 0.2% pectins with different molecular mass was studied using ion-exchange membranes. It is found that occurrence of the process at the current density of 5 mA/cm² allows achieving the solution demineralization degree of 87–90% and acid regeneration degree of 86–92% at current efficiency of 63–77%. Higher process indicators are observed in the case of electrodialysis of solutions containing pectin of a lower molecular mass.