Search

A study is performed of the effect TiO2 nanoparticles have on the temperature dependence of the direct current conductivity of epoxy polymers. The value of direct current conductivity is determined by analyzing the frequency dependence of the complex permittivity in the 102–105 Hz range of frequencies. Two characteristic regions are found on the temperature dependence of direct current conductivity: the Vogel–Fulcher–Tammann dependence above the glass transition temperature (Tg), and the Arrhenius dependence below Tg, due apparently to a change in the mechanism of conduction after the freezing of ionic mobility at temperatures g. It is found the calculated energy of activation of the Arrhenius process changes upon raising the concentration of TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

The joint crystallization of the stable phase (a number of solid solutions of chromium-containing beryllian indialite) and metastable phases (crystalline modifications) of the compound with β-quartz structure (Si0.64Al0.28Mg0.21Be0.09)IVO2 ~ Mg1.89Be0.81Al2.52Si5.76O18 admixed with Cr2O3 phases of khmaralite Mg1.21Cr0.01Be0.46Al1.78Si3.38O20 and spinel {(Mg0.95Be0.045Si0.005)IV(Al1.31Cr0.67Mg0.02)VI}O4 is performed using melted chromium-beryllian indialite preliminarily obtained by solid-phase synthesis as a precursor. Simultaneously, the residual X-ray amorphous melt of composition Mg1.83Cr0.01Be1.04Al2.64Si5.57O18 is hardened. Thus, a reconstructive transition from the beryllian indialite melt to a phase with the β-quartz structure is implemented, and the chemical similarity of these compounds is demonstrated. The rate of change in the crystallization isotherm of 2°С/h and increased heat outflow through the highly heat-conducting walls of the Pt-Rh crucible (taper) contribute to this process. [ABSTRACT FROM AUTHOR]

The regularities of formation of the structure of amphiphilic network copolymers on radical copolymerization of N-isopropylacrylamide and polyester dimethacrylate are investigated. The kinetic laws of the consumption of functional groups and the increase in the gel content during formation of a crosslinked product are studied. It is shown that the synthesis of crosslinked amphiphilic copolymers proceeds via competing reactions of N-isopropylacrylamide homopolymerization and its copolymerization with polyester dimethacrylate. With the excess of the monofunctional monomer, a homogeneous rubber-like network copolymer is formed, whereas the excess of the bifunctional reagent results in the morphological inhomogeneity of the reaction product. [ABSTRACT FROM AUTHOR]

The general toxic and hepatocarcinogenic effects of diethylnitrosamine after stimulation of its metabolism with 1,4-bis[2-(3,5-dichloropyridyloxy)]-benzene (TCPOBOP) were studied. The hydroxylating activity of liver microsomes of C57Bl/6Mv mice towards p-nitrophenol increased more than 4-fold 3 days after injection of TCPOBOP. Injection of diethylnitrosamine 3 days after TCPOBOP caused a lesser body weight loss and decrease of food consumption in C57Bl/6Mv mice than in response to diethylnitrosamine without preinduction. Injection of diethylnitrosamine to suckling ICR mice after TCPOBOP induction of cytochrome P450 2e1 activity led to development of 2-fold lesser number of tumors and pretumorous nodes in the liver in comparison with animals injected with diethylnitrosamine without induction. These data indicated that metabolism stimulation reduced the general toxic and hepatocarcinogenic effects of diethylnitrosamine. [ABSTRACT FROM AUTHOR]

Antimetastatic activity of Platin in lyophilized liposomes stored for 7 years after fabrication was evaluated. The main flaw of liposomes as vehicles for drug delivery to the tumors is their high affinity for the liver, which accumulates a great amount thereof. This property of liposomes can be used for adjuvant therapy of operable primary tumors metastasizing to the liver. It is shown on the model of mouse GA-1 tumor metastases in the liver that platinum(II) complex compound Platin in phosphatidylcholine-cholesterol liposomes, stored for 7 years after lyophilization, causes complete cure of 40% animals, while free Platin prolongs the lifespan of mice with tumors by only 31.7% vs. control (no treatment). [ABSTRACT FROM AUTHOR]