Five Ni-Cr alloys were studied in order to identify the compounds formed on the alloy surface during oxidation under conditions similar to those encountered during dental laboratory procedures prior to application ofporcelain. After the alloys were oxidized, the films covering the surfaces were removed with the aid of a Br-methanol solution. X-ray diffraction was used to analyze the compounds f...

Single-crystal diffuse scattering data have been collected at room temperature on synthetic titanite using both neutrons and high-energy x-rays. A simple ball-and-springs model reproduces the observed diffuse scattering well, confirming its origin to be primarily due to thermal motion of the atoms. Ab initio phonons are calculated using density-functional perturbation theory and are shown to re...

The synthesis of two molecular iron complexes, a dinuclear iron(iii,iii) complex and a nonanuclear iron complex, based on the dinucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)3](3+).

Rate equations and kinetic parameters were obtained for various reactions involved in the bacterial oxidation of pyrite. The rate constants were 3.5 muM Fe per min per FeS(2) percent pulp density for the spontaneous pyrite dissolution, 10 muM Fe per min per mM Fe for the indirect leaching with Fe, 90 muM O(2) per min per mg of wet cells per ml for the Thiobacillus ferrooxidans oxidation of wash...

The East Asian summer monsoon controls the climatic regime of an extended region through temperature and precipitation changes. As the East Asian summer monsoon is primarily driven by the northern hemisphere summer insolation, such meteorological variables are expected to significantly change on the orbital timescale, influencing the composition of terrestrial sediments in terms of both mineral...

Two structurally characterized dinuclear valence tautomers are described. Cobalt ions are bridged by p- and m-phenylene units connected to 2,2'-bipyridines. X-ray crystal structures show that the molecules are in the [(Co(III))(Co(III))] forms at ca. 125 K, while spectroscopic studies show that both molecules can achieve the [(Co(II))(Co(II))] form above 400 K and confirm the [(Co(III))(Co(III)...

The structure and stability of the adduct formed in the reaction between Auoxo3, a dinuclear gold(iii) compound, and the model protein hen egg white lysozyme (HEWL) are investigated by X-ray crystallography, UV-Vis absorption spectroscopy and circular dichroism (CD). It is found that Auoxo3 breaks down completely, undergoes reduction and produces reactive gold(i) species able to bind the protei...

Hydrogenase [hydrogenase: (acceptor) oxidoreductase, EC 1.12. . -1 is present in many bacteria. It is one of the enzymes having potential use in the biophotolysis of water (Weaver et al.. 1980). When we began our research on hydrogenase in 1977, two types of enzymes were known: (i) enzymes containing 12 Fe atoms and an equivalent amount of acid-labile S atoms and (ii) enzymes containing only fo...

OBJECTIVE The aims of the study are to assess the marginal accuracy of base metal and titanium alloy casting and to evaluate the effect of repeated ceramic firing on the marginal accuracy of base metal and titanium alloy castings. MATERIALS AND METHODS Twenty metal copings were fabricated with each casting material. Specimens were divided into 4 groups of 10 each representing base metal alloy...