Selenium, sources

Practical applications [2] of a GammaMat M model using the new Selenium crawler camera loaded with approx. 1 TBq (30Ci) on a pipeline of diameter 12 and wall thickness of 0.25 showed 6-7 m axial distance to the exposed source as limit of the radiation controlled area (40pSv/h) and 22m perpendicular to the pipeline. Other authors [3] have reported about a comparison for Ir-192 and Selenium source on a 4.5 diameter pipe and 0,125 steel thickness they have found for 0.7 Tbq (18Ci) Selenium a value of 1 Om behind the film (in the unshielded beam) comparing under same conditions to approx. 40m for Iridium. 

Tertiary phosphine sulfides are generally stable compounds and are not easily oxidised by air, although they can be oxidised by hydrogen peroxide or dilute nitric acid. The analogous tertiary phosphine selenides and tellurides are however, more reactive to oxidation. Similar to the sulfides they can be prepared from the direct reaction of elemental chalcogen with a tertiary phosphine (Equation 1). Tertiary phosphine selenides are also accessible from tertiary phosphines using KSeCN as the selenium source instead of the element itself. 

Hopke, et al. (4) and Gaarenstroom, Perone, and Moyers (7) used the common factor analysis approach in their analyses of the Boston and Tucson area aerosol composition, respectively. In the Boston data, for 90 samples at a variety of sites, six common factors were identified that were interpreted as soil, sea salt, oil-fired power plants, motor vehicles, refuse incineration and an unknown manganese-selenium source. The six factors accounted for about 78 of the system variance. There was also a high unique factor for bromine that was interpreted to be fresh automobile exhaust. Large unique factors for antimony and selenium were found. These factors may possibly represent emission of volatile species whose concentrations do not oovary with other elements emitted by the same source. 

Chemical deposition of both M0S2 and MoSei has been reported from ammonium molybdate solution [76,77], For the sulphur and selenium sources, thioacetamide and selenosulphate were used, respectively. Ammonium hydroxide was added to the sulphide solution, while an acetic acid/ammonium acetate buffer was used with the selenide solution (pH values were not given). Reducing agents (either hydrazine [76] or sodium dithionite [77]) were added to the baths. Deposition was started at 90-100°C, followed by lowering to room temperature. 

This lack of reactivity could be circumvented to some extent by the use of an analogous selenolactonization/reduction procedure.76 N-(phenylseleno)phthalimide was used as the electrophilic selenium source in the presence of a catalytic quantity of camphorsulfonic acid. Analysis of the crude product mixture obtained using acids 124 and 126 suggested... 

Clybum, B.S., Richardson, C.R., Montgomery, J.L., Pollard, G.V., Herring, A.D., and Miller, M.F. 2001. Effect of selenium source and vitamin E level on performance and meat quality of feedlot steers. In Science and Technology in the Feed Industry (T.P. Lyons and K.A. Jacques, eds), pp. 377—392. Nottingham University Press, Nottingham, UK. 

The synthesis of metal complexes of type 213 can be performed by reacting metal-carbene complexes with selenium sources such as alkyneselenolates 203.430 Also the stability of unstable selenocarbonyl compounds such as selenoaldehydes can be enhanced by coordination to metal carbonyls and the reactivity of such complexes has been studied. Complex 216 can react with methylthiohexyne and the product is a different complex 217 with the selenium atom still coordinating to the metal carbonyl fragment (Scheme 66).431... 

M. Calomme, J. Hu, K. Van den Branden, D. A. Vanden Berghe, Seleno-lactobacillus -an organic selenium source, Biol. Trace Elem. Res., 47 (1995), 379-383. 

One of the synthetic procedures of metal complexes of type 53 is the reaction of metal-carbene complexes with selenium sources such as alkyneselenolates [109]. The stability of selenobenzaldehyde is enhanced by coordinating to metal carbonyls, and the reactivity of the complexes has been studied [110]. For example, the selenobenzaldehyde complexes reacts with methylthiohexyne even at - 30 °C to afford another type of complex where the selenium atom of the selenocarbonyl group is still coordinated to the metal (Eq. 29) [llOd]. 

Selenium isotope ratios as indicators of selenium sources and oxyanion reduction. Geochim. Cosmochim. Acta 63, 2775-2783. 

Panter KE, James LF, Mayland HF. 1995. Reproductive response of ewes fed alfalfa pellets containing sodium selenate or Astragalus bisulcatus as a selenium source. Vet Hum Toxicol 37(l) 30-32. 

The work of Kuehnelt et provided the first quantitative data on excretion rate and relative quantities of the various selenium metabolites, and showed that selenosugar F13-1 was by far the major metabolite (70%) with smaller quantities of selenosugars F13-2 and F13-3. Differences in excretion rate were also noted depending on the form of selenium ingested, but the metabolic pattern of compounds remained the same. These data support an accepted metabolic pathway for selenium that describes various selenium sources converting to selenide, which is then transformed into selenocysteine and incorporated into selenoproteins. ... 

Selenoureas <90JOC2567> and selenones (derived from a phosphorus yUde and selenium) <92TLI333> can also act as selenium sources for addition across triple bonds (Scheme 11). 

Assuming water is sole selenium source, 2L/daily... 

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