Far Infrared Reflection Spectra of Ba(Zn,Ta)O3-BaZrO3 Dielectric Resonator Material

The dielectric ceramic materiala Ba(Zn_1/3Ta_2/3)O₃–BaZrO₃ has extremely low dielectric loss at microwave frequencies. To investigate the lattice vibrations of Ba(Zn,Ta)O₃ and Ba(Zr, Zn, Ta)O₃ solid solutions, far infrared reflection spectra were measured from 50 to 4000 cm⁻¹ using a Fourier transform infrared spectrometer. These data were analyzed according to the classical dispersion theory. The spectra of Ba(Zn,Ta)O₃ are well fitted by using the 14 resonant modes, and the spectra of Ba(Zr, Zn, Ta)O₃ solid solution are fitted by assuming the normal distribution on resonant frequencies. The damping constant of these materials is discussed, and the values of tan δ calculated from the dispersion parameters agree with the measured values.     

Structural Analysis of SiO2-Al2O3 Glasses

The structure of SiO₂-Al₂O₃ glasses with up to 60 wt% Al₂O₃ was investigated using the radial distribution function together with the correlation method based on X-ray scattering intensity data. Radial distribution curves are interpreted on the basis of glass-in-glass separation with the constituents of SiO₂-rich and Al₂O₃-rich glasses. The structure of the Al₂O₃-rich glass has a short-range ordering similar to the crystal structure of mullite. The calculated S- i (S) curve of this model gives good agreement with the observed one.     

Pd-SiO2复合膜的氢气选择渗透特性

Palladium membranes were prepared on an a-alumina support by metal-organic compound chemical vapor deposition (MOCVD) method from palladium(Ⅲ) acetate precursor. Permeation properties of hydrogen and helium gas were studied as a function of the number of times of deposition of palladium on the peeling off phenomenon of palladium, which is common in electroless plated membrane, was observed. Silica was introduced into the pores to prevent the palladium grain from peeling off. The palladium-silica conjugated membrane does not show the peeling off phenomenon and can withstand the high temperature up to 800℃ which is the upper limit of our apparatus.The separation factor for hydrogen gas over carbon dioxide gas was improved with the increase of number of times of silica coating by sacrificing the H2 permeation and finally increased to four times. The improvement on the separation of hydrogen gas over carbon dioxide for pulladium-silica conjugated membrane was evaluated and a model of permeation pattern (palladium and silica) was proposed. This model suggests that the separation factor for hydrogen over carbon dioxide could be improved by introducing silica layer because the silica layer fills the pores and reduces the gas permeation without sacrificing the hydrogen permeation through the palladium region. These results indicate that the introduction of silica into the palladium grain is a promising means to improve the hydrogen separation performance of palladium based composite membranes.     

EFFECTS OF LONG-TERM ORAL ADMINISTRATION OF GREEN TEA CULTIVATED IN DIFFERENT DISTRICTS IN JAPAN ON BODY WEIGHT, BLOOD LIPID AND GLUCOSE LEVELS ON db/db MICE

Previous research using short‐term animal experiments has indicated that oral administration of green tea can suppress elevation of blood sugar. However, few data are available on the antihyperglycemia effect of green tea in long‐term experiments. In this study, effects of long‐term (up to 16 weeks) administration of green tea preparations on body weight, blood sugar and lipid content of db/db and db/+m mice were examined. Preparations were prepared by the same procedure from tea leaves cultivated in different districts in Japan. Significant differences (P < 0.05) were observed in the blood parameters and body weight between control and green tea groups of db/db mice. In the case of normal mice, however, no significant difference was observed. In addition, the response to the administration of green tea depended on the source and composition of tea leaves.     

Applications of the Long and Accurate Polymerase Chain Reaction Method in Yeast Molecular Biology: Direct Sequencing of the Amplified DNA and Its Introduction into Yeast

A DNA fragment longer than 10 kb can be amplified by the long and accurate polymerase chain reaction (LA-PCR) method. We demonstrate here applications of this technique in molecular biological studies of Saccharomyces cerevisiae. We have shown that DNA fragments amplified by LA-PCR can be directly used as a template in the chain-termination sequencing protocol, making it possible to quickly identify the DNA insert of yeast genomic library clones. We have also shown that the amplified yeast DNA can easily be introduced into yeast by co-transformation with linearized vector DNA. Overlapping DNA between the amplified yeast fragment and the vector must be more than 20 bp long in order to obtain 90% or more correct recombinant plasmids. These results suggest that simple amplification of yeast clones by LA-PCR can replace the previous procedures of yeast clone recovery, consisting of transformation of Escherichia coli, propagation of plasmids in E. coli and preparation of plasmid DNA. © 1997 John Wiley & Sons, Ltd.