Quantitative investigation of Cu-Ni and Ag-Pd alloys with a laser microprobe mass analyzer

Summary Quantitative Investigation of Cu-Ni and Ag-Pd Alloys with a Laser Microprobe Mass Analyzer The analytical capability of the LAMMA-1000 instrument is discussed with respect to the evaporation and ionization probability for known concentrations of binary alloys with gradually changing composition. The relative sensitivity coefficients of Ni to Cu and Pd to Ag were found to be constant at 0.95±0.20 and 0.54±0.09, respectively, for a variety of binary alloy. No correlation with the alloy density was found for a variety of binary alloys. The ionization probability remains constant when the alloy composition changes. It is assumed that the selective evaporation does not occur within and near the laser focus. The phase transition and evaporation kinetics with respect to time and space seem to be a less dominant factor for ion formation in the LAMMA instrument. The absolute quantitative analysis is possible by the use of a calibration curve, if the total ions or the sampling volume can be determined. The use of the relative sensitivity coefficients is an effective method for a quantitative analysis with an error of 10–30%.     

Ionicity scale and piezoelectricity of crystals with zincblende- and wurtzite-type structure

We have tried to determine the ionicity of crystals with a dynamical effective ionic charge defined by the observed TO-LO splitting. We find excellent agreement between our results and the ionicity scale derived by Phillips from band gap theory. We confirm that the observed piezoelectric constants can be well accounted for on the basis of the Born lattice-dynamical treatment by adding the concept of charge transfer, and we have made an estimate of the latter.     

Characterization of metal/GaN Schottky interfaces based on I–V–T characteristics

Interface properties of metal/n- and p-GaN Schottky diodes are studied by I–V–T and C–V–T measurements, and simulation of their characteristics. On the basis of the previously proposed “surface patch” model, the gross behavior of I–V–T characteristics, which includes Richardson plots together with temperature dependence of the effective Schottky barrier heights (SBHs) and n-values, can be well reproduced. Furthermore, the dependence of the true SBH on the metal work function was also deduced from high-temperature I–V curves, giving S-values of 0.28 and 0.20 for n- and p-GaN samples, respectively, and the interface Fermi level tends to be pinned at a characteristic energy of about two-third of the bandgap.     

On a certain covariant representation functor and irreducible modules of Chevalley groups

This research was supported by the Alexander von Humboldt Foundation and the German Research Association (DFG).     

A simple preparation of 1,3,5-triazine derivatives from 4-pyridones

The reaction of 4-pyridone or 4-quinolone with methyl or benzyl isocyanate in the presence of triethylamine or 1,1,3,3-tetramethylguanidine base gave the corresponding 1,3,5-triazine derivative (e. g., II) in a good yield via stepwise additions.     

Purification and properties of multiple forms of dihydrodiol dehydrogenase from monkey liver

Two major and two minor forms of dihydrodiol dehydrogenase with similar molecular weights of around 36000 were purified from monkey liver cytosol. All the forms oxidized trans-dihydrodiols of benzene and naphthalene and reduced aromatic aldehydes, but showed differences in charge, specificity for other substrates and inhibitor sensitivity. One major (pI 8.7) and one minor (pI 7.9) form of the enzyme exhibited high activity for alicyclic alcohols and sensitivity to o-phenanthroline. The other major form (pI 6.2) oxidized 3 alpha-hydroxysteroids and was inhibited by dexamethasone and indomethacin, whereas the other minor form (pI 5.8) showed high reductase activity for aldehydes including D-glucuronate and sensitivity to barbital and sorbinil, and cross-reacted with human aldehyde reductase. The results indicate that the multiple forms of monkey liver dihydrodiol dehydrogenase are indanol dehydrogenases, 3 alpha-hydroxysteroid dehydrogenase and aldehyde reductase.