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 new method has been developed to synthesise bis η(5)-cyclopentadienyl dithiolene complexes of molybdenum and tungsten. This procedure involves the in situ thermolysis of the azo compounds, 2,2'-azobisisobutyronitrile (AIBN) or 1,1'-azobiscyclohexanecarbonitrile (ACCN) (R'(2)N(2), R' = CMe(2)CN or C(6)H(10)CN, respectively), which initiates a reaction between [Cp(2)M(S(4))] (M = Mo or W) and a...

A tungsten-carbon multilayer system deposited by magnetron sputtering was used as a model system to study deuterium diffusion in tungsten, carbon and related carbides. After deposition the as-deposited multilayer films were annealed at different temperatures to achieve different structures. The structural changes due to annealing were investigated by Rutherford backscattering spectrometry and X...

In mechanical tests of tantalum-tungsten alloys with nominal tungsten contents between 0 and 10 wt% for strain rates between 0.000016 and 6800 sr and temperatures between 77 and 400 K, the addition of tungsten noticeably reduces the strain-rate dependence of the flow stress of tantalum near yield. It also subtly alters the strain-rate behavior of the work hardening, making it more like that of ...

Single-crystal tungsten nanobelts with thicknesses from tens to hundreds of nanometers, widths of several micrometers and lengths of tens of micrometers were synthesized using chemical vapor deposition. Surface energy minimization was believed to have played a crucial role in the growth of the synthesized nanobelts enclosed by the low-energy {110} crystal planes of body-centered-cubic structure...

Tungsten-based defect-pyrochlores CsM x W2?x O6 are used as model oxides to investigate the high number of possible M cations that can be form defect-pyrochlore crystal structure. A large variety compounds presented, several which have been unknown so far. These in photocatalytic hydrogen evolution correlations between activity and varying elemental compositions.

For the Accelerator Production of Tritium (APT) and the Accelerator Driven Transmutation Facility (ADTF), tungsten is being proposed as a target material to produce neutrons. Previous work showed that the mechanical properties of tungsten are degraded from irradiation in a neutron flux but little work had been performed on the irradiation of tungsten in a high energy proton beam. In this study,...

objective: increased enamel surface roughness following orthodontic bracket debonding leads to increased plaque accumulation and enamel decalcification. therefore, different methods are employed to achieve smoother enamel surfaces after bracket debonding. this study compared enamel surface roughness following orthodontic bracket debonding and composite resin removal using white stone and tungst...

Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over ge...