RESUMO
Ceramics of binary systems solid solutions (1 - x)NaNbO3 - xCa2Nb2O7 and (1 - x)NaNbO3 - xSr2Nb2O7 with non-isostructural extreme components were prepared by the solid-phase reactions technique with the following sintering using conventional ceramic technology. It was found that ceramics with x ≤ 0.2 have a perovskite structure. Layered type of structure predominates in the concentration range 0.2 < x ≤ 1. Phase diagrams of both systems at room temperature have been determined in the perovskite area. It was shown that this area contains two concentration regions with the different crystal structures and the morphotropic phase boundary between them. Microstructure and dielectric characteristics of selected solid solutions were investigated. The influence of technological regulations, such as mechanical activation and variation of sintering temperatures, on the formation of the microstructure and dielectric characteristics was studied for the individually selected concentrations (x = 0.1 and x = 0.25). Dielectric characteristics of ceramics revealed the presence of the Maxwell-Wagner polarization and its corresponding relaxation in the solid solutions (1 - x)NaNbO3 - xCa2Nb2O7 at x > 0.20.
RESUMO
The tissue oxygen concentration, the serum antioxidant system state and the serum malondialdehyde (MDA) concentration were studied in patients with hepatitis B. The good correlations were studied in patients with hepatitis B. The good correlations between MDA concentration in patients serum and the oxygen concentration in tissues (R-0.79), and the cytoplasmic enzymes activity (R-0.75 for lactate dehydrogenase; R-0.75 for alanine transferase) were found. On the other hand, it was shown an antioxidant activity decrease of ceruloplasmin-transferrin system in patients serum. It is proposed, that the tissue hypoxia and the decrease of the serum antioxidant activity are the general factors leading to the MDA accumulation in the serum of patients with hepatitis B.