Non-cubic layered structure of Ba(1-x)K(x)BiO3 superconductor

Bismuthate superconductor Ba(1-x)K(x)BiO3 (x=0.27-0.49, Tc=25-32K) grown by an electrolysis technique was studied by electron diffraction and high-resolution electron microscopy. The crystalline structure thereof has been found to be non-cubic, of the layered nature, and non-centrosymmetric, with the lattice parameters a ~ ap, c ~ 2ap (ap is a simple cubic perovskite cell parameter) containing an ordered arrangement of barium and potassium. The evidence for the layered nature of the bismuthate superconductor removes the principal crystallographic contradiction between bismuthate and cuprate high-Tc superconductors.Comment: 4 pages, 3 figures, to be published in Physical Review B as a Rapid Communicatio

Hump Structure below Tc in the thermal conductivity of MgB2 superconductor

A reasonable cause of absence of hump structure in thermal conductivity of MgB2 below the superconducting transition temperature (Tc) lies in the appearance of multigap structure. The gaps of lower magnitude can be suppressed by defects so that this system becomes effectively a single gap superconductor. When such a situation is created, it is hoped that thermal conductivity will show hump below Tc. Proceeding along these lines, a sample of MgB2 with a relatively higher residual resistivity (33.3 mili-Ohm-cm)has been found to show a hump structure below Tc. The actual electronic thermal conductivity kel of this sample is less than that expected from the Wiedeman- Franz law by more than a factor of 2.6 in the considered temperature range. Modifying the Wiedeman- Franz law for the electronic contribution by replacing the Lorenz number by an effective Lorenz number Leff (L0) we have obtained two sets of kel, namely those with Leff = 0.1L0 and 0.2L0. Corresponding to these two sets of kel, two sets of the phonon thermal conductivity kph are obtained. kph has been analyzed in terms of an extended Bardeen- Rickayzen- Tewordt theory. The main result of this analysis is that the hump structure corresponds to a gap ratio of 3.5, and that large electron-point defect scattering is the main source of drastic reduction of the electronic thermal conductivity from that given by the usual Wiedeman- Franz law.Comment: 18 pages of Text + Figs: comments welcome ([email protected]

The influence of the antibiotic lincomycin on the proteolysis in the gum of rats

Введение крысам с питьевой водой линкомицина в дозах 30, 50 или 70 мг/кг в течение 5, 10 или 15 дней вызывает дозозависимую и увеличивающуюся со временем активацию протеолиза. Параллельно в десне снижается содержание растворимых белков, особенно лизоцима (снижение в 3,5 раза). Делается вывод о том, что антибиотикотерапия может способствовать развитию пародонтита, снижать уровень тканевого иммунитета и вызывать процесс рецессии тканей пародонта.Уведення щурам з питною водою лінкоміцина в дозах 30, 50 або 70 мг/кг протягом 5, 10 або 15 днів викликає дозозалежну активацію протеоліза, яка збільшується з часом. Паралельно в яснах знижується вміст розчинних білків, особливо лізоцима (зниження у 3,5 раза). Робиться висновок про те, що антибіотикотерапія може сприяти розвитку пародонтиту, знижувати рівень тканинного імунітету і викликати процес рецесії тканин пародонта.Introduction to rats with the drinking water of lincomycin at the doses 30, 50 or 70 mg/kg during 5, 10 or 15 days causes the dose-dependent and being increased in the course of time activation of proteolysis. In parallel in the gum is reduced the content of the dissoluble proteins, especially lysozyme (decrease in 3,5). Is done the conclusion that the antibiotic therapy can contribute to the development of periodontitis, reduce the level of tissue immunity and cause the process of the recession of the tissues of periodontium