Plasma molybdenum

Ward and Nagy 1976). Domestic sheep appear to be more resistant than cattle, and tolerate plasma molybdenum levels of 100-200 tgL , or approximately 20- to 40-fold normal plasma molybdenum levels (Suttle 1975), while he-goats tolerated a plasma molybdenum level >1100 tgL ... 

Plasma molybdenum reflects dietary molybdenum intake. J. Nutr. Biochem., 15, 90-95. 

The Tribaloy aUoy T-800, is from an aUoy family developed by DuPont in the eady 1970s, in the search for resistance to abrasion and corrosion. Excessive amounts of molybdenum and sUicon were aUoyed to induce the formation during solidifica tion of hard and corrosion-resistant intermetaUic compounds, known as Laves phase. The Laves precipitates confer outstanding resistance to abrasion, but limit ductUity. As a result of this limited ductUity the aUoy is not generaUy used in the form of plasma-sprayed coatings. 

Samples Analyzed by Inductively Coupled Plasma (ICP) Metals — Where two or more of the following analytes are requested on the same filter, an ICP analysis may be conducted. However, the Industrial Hygienist should specify the metals of interest in the event samples cannot be analyzed by the ICP method. A computer print-out of the following 13 analytes may be typically reported Antimony, Beryllium, Cadmium, Chromium, Cobalt, Copper, Iron, Lead, Manganese, Molybdenum, Nickel, Vanadium, Zinc. Arsenic — Lead, cadmium, copper, and iron can be analyzed on the same filter with arsenic. 

Flame sprayed molybdenum articles have poor corrosion resistance, no doubt owing to the porosity of the coating. However, modern plasma spraying techniques produce a dense coating and this should lead to more widespread use of clad materials such as molybdenum clad steel where the clad product should have the same corrosion resistance as the solid material. 

Plasma spraying Metals, or refractory materials or composites are applied by melting in an ionised inert gas M, tantalum, molybdenum, alumina, zirconia M2 a variety of metallic substrates... 

Properties of the deposits Almost any material which can be melted is suitable for plasma spraying, giving a vast range of possible coatings of single or mixed metallic or non-metallic substances. It is often possible to produce types of coatings which are not obtainable in any other way. Typical of the materials which are plasma sprayed are copper, nickel, tantalum, molybdenum. Stellites, alumina, zirconia, tungsten and boron carbides, and stainless steels. 

In addition to the thermal CVD systems mentioned above, molybdenum is deposited by plasma CVD using Reaction (3) in hydrogen.Annealing is required to remove incorporated carbon and oxygen. 

Figure 5.2. Two of the more common types of low pressure CVD reactor, (a) Hot Filament Reactor - these utilise a continually pumped vacuum chamber, while process gases are metered in at carefully controlled rates (typically a total flow rate of a few hundred cubic centimetres per minute). Throttle valves maintain the pressure in the chamber at typically 20-30 torr, while a heater is used to bring the substrate up to a temperature of 700-900°C. The substrate to be coated - e.g. a piece of silicon or molybdenum - sits on the heater, a few millimetres beneath a tungsten filament, which is electrically heated to temperatures in excess of 2200 °C. (b) Microwave Plasma Reactor - in these systems, microwave power is coupled into the process gases via an antenna pointing into the chamber. The size of the chamber is altered by a sliding barrier to achieve maximum microwave power transfer, which results in a ball of hot, ionised gas (a plasma ball) sitting on top of the heated substrate, onto which the diamond film is deposited.

Specht and Beauchemin [506] have described an automated system to provide online addition of isotopic spikes to seawater samples in the determination of molybdenum by inductively coupled plasma mass spectrometry. 

Molybdenum Co-precipitation with Zr(OH)4 Inductively coupled plasma AES - [896]... 

Proposed criteria for human health protection include drinking water concentrations less than 50 pg Mo/L, and daily dietary intakes less than 7 pg Mo/kg food — based on a 70-kg adult (Table 30.5). Molybdenum concentrations in blood of healthy people averaged 14.7 pg Mo/L, distributed between the plasma and erythrocytes. Anemic people had significantly lower blood molybdenum levels. In leukemia patients, molybdenum levels increased significantly in whole blood and erythrocytes but not in plasma (Shamberger 1979). Additional work is recommended on the use of blood in fish and wildlife as an indicator of molybdenum stress and metabolism (Eisler 1989). 

Osman, N.H.I. and A.R. Sykes. 1989. Comparative effects of dietary molybdenum concentration on distribution of copper in plasma in sheep and red deer (Cervus elaphus). Proc. N.Z. Soc. Anim. Product. 49 15-19. 

Bednar AJ, Mirecki JE, Inouye LS, Winfield LE, Larson SL, Ringelberg DB. The determination of tungsten, molybdenum, and phosphorus oxyanions by high performance liquid chromatography inductively coupled plasma mass spectrometry. Talanta 2007 72 1828-1832. 

Russel WA, Papanastassiou DA, Tomhrello TA (1978) Ca isotope fractionation on the Earth and other solar system materials. Geochim Cosmochim Acta 42 1075-1090 Sakata KI, Kawahata K (1994) Reduction of fundamental polyatomic ions in inductively coupled plasma mass spectrometry. Spectrochim Acta Atom Spectrosc PartB 49 1027-1038 Siehert, C, Nagler, TF, Kramers JD (2001) Determination of molybdenum isotope fractionation by doublespike multicollector inductively coupled plasma mass spectrometry. Geochem Geophys Geosyst 2 2000GC000124... 

A second example of a membrane-bound arsenate reductase was isolated from Sulfurospirillum barnesii and was determined to be a aiPiyi-heterotrimic enzyme complex (Newman et al. 1998). The enzyme has a composite molecular mass of 100kDa, and a-, P-, and y-subunits have masses of 65, 31, and 22, respectively. This enzyme couples the reduction of As(V) to As(III) by oxidation of methyl viologen, with an apparent Kra of 0.2 mM. Preliminary compositional analysis suggests that iron-sulfur and molybdenum prosthetic groups are present. Associated with the membrane of S. barnesii is a h-type cytochrome, and the arsenate reductase is proposed to be linked to the electron-transport system of the plasma membrane. 

For the routine determination of analytes in the quality control of the production of speciality chemicals, a combination of direct current plasma emission spectroscopy (DCP-OES) with flow injection analysis (FIA) has been used. Results obtained for the determination of boron, copper, molybdenum, tungsten and zinc in non-aqueous solutions have been published by Brennan and Svehla [3], The principle has been extended to other analytes, carrier liquids, and solvents, and the details of a fully automatic system have been described by Brennan et al. [4]. 

Workers at a molybdenum-roasting plant with time-weighted average (TWA) exposures of approximately 9.5mgMo/m to soluble dusts had increased plasma and urine levels of molybdenum the only adverse biochemical findings were large elevations in serum ceruloplasmin levels and some increase in serum uric acid levels. ... 

Molybdenum isotope ratio measurements by MC-ICP-MS (Plasma 54) have been carried out using Zr or Ru elemental spikes to study the mass discrimination during the whole analytical procedure including sample preparation.146 A laboratory fractionation of Mo isotopes of about 0.15 % is observed during ion exchange by offline Mo separation. Using this analytical technique, possible natural isotope variation of Mo can be determined with a precision of 0.02 %. 

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