Nos travaux s’insèrent dans un projet du réseau ARTCADHi visant à offrir aux chercheurs en Sciences Humaines des assistants à la construction du sens dans des bibliothèques numériques spécialisées. Dans ce cadre, limiter la description des documents à une indexation unique, fixe et effectuée par un tiers, revient à nier leur expertise. Porphyry propose l’instrumentation du travail des chercheur...

A procedure was developed that allows precise determination of molybdenum isotope abundances in natural samples. Purification of molybdenum was first achieved by solvent extraction using di(2-ethylhexyl) phosphate. Further separation of molybdenum from isobar nuclides was obtained by ion chromatography using AG1-X8 strongly basic anion exchanger. Finally, molybdenum isotopic composition was mea...

In Methanobacterium wolfei two formylmethanofuran dehydrogenases are present, one of which is a molybdenum- and the other a tungsten enzyme. We report here that also the 'molybdenum' enzyme contained tungsten when the archaeon was grown on molybdenum-deprived medium supplemented with tungstate (1 microM). Unexpectedly the tungsten-substituted molybdenum enzyme was catalytically active and displ...

A series of molybdenum(VI) complexes containing bidentate ligands: toluene-3,4-dithiol (1), 2-mercaptophenol (2), 2-aminothiophenol (3), ethane-1,2-dithiol (4), dithiooxamide (5) and 2-thiopheno-carboxamide (6) are reported. The hexacoordinated molybdenum tris-chelates compounds: tris-(toluene-3, 4-dithiolate)molybdenum(VI) (7), tris-(2-mercaptophenolate)molybdenum(VI) (8), tris-(2-aminothiophe...

To reconstruct the magmatic–hydrothermal processes leading to porphyry Mo ore formation at the Climax Mo mine, Colorado, four magma units that were emplaced before, during and shortly after the mineralization events were investigated: (1) a pre-mineralization white dike of the Alma district; (2) the syn-mineralization Chalk Mountain Rhyolite; (3) a lateto post-mineralization rhyolite porphyry d...

Klebsiella pneumoniae accumulates molybdenum during nitrogenase derepression. The molybdenum is primarily in nitrogenase component I in the form of iron-molybdenum cofactor (FeMo-co). Mutations in any of three genes (nifB, nifN, and nifE) involved in the biosynthesis of FeMo-co resulted in very low molybdenum accumulation and in a molybdenum-free nitrogenase component I. A mutant lacking both s...

A combination of SEM, AES and angle-resolved XPS (ARXPS) has been applied to analyse the distribution of chemical compounds in the surface region of electrochemically etched molybdenum tips and to determine the contamination layer thickness. Carbon monoxide, graphite, molybdenum carbide and molybdenum oxide were found to be the main surface contaminants on molybdenum tips. Auger line profiling ...

I . The oral administration of sodium molybdate caused a rapid rise of molybdenum in the milk of cows and goats fed on a low-molybdenum diet, but did not affect the xanthine oxidase activities of the milk of either species. 2. In the milks of cows not dosed with sodium molybdate, the regression of the xanthine oxidase activity ( y ) on the molybdenum content (x) was found to be (r = +0.9386; P ...

The reduction mechanism of molybdenum-methyl thymol blue (MTB)-chlorate system has been investigated in water on a mercury electrode. As this system is very sensitive for ultratrace determination of molybdenum, the actual mechanism involved was studied. Electrochemical techniques, including dc tast polarography and cyclic voltammetry were employed. It is shown that, the cathodic wave of mol...