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981.
Gies P Roy C McLennan A Pailthorpe M Hilfiker R Osterwalder U Monard B Moseley H Sliney D Wengraitis S Wong J Human S Bilimis Z Holmes G 《Photochemistry and photobiology》2003,77(1):58-67
In recent years the need to standardize measurement protocols for quantifying the degree of ultraviolet radiation (UVR) protection provided by clothing has led to the introduction of a number of standards around the world. To date, these standards have specified spectral measurements of UVR transmission by clothing and fabrics. Development of a standard test method has become an important part of the testing process, and this article presents results from an intercomparison involving 10 independent testing laboratories and 11 different UVR transmission measurement instruments. In addition to comparing the measured ultraviolet protection factors (UPF), this intercomparison also incorporates detailed scan results from all 10 laboratories and highlights differences in performance of the various instruments in different wavelength regions. Careful examination of these differences can indicate where changes to the systems could be made to allow improvements both in equipment performance and in agreement of the final results. The variability in the measurements of UPF in this study suggest that the protection categories in standards may need to be broadened. 相似文献
982.
Herbert C. Brown Uday S. Racherla Shankar M. Singh Richard B. Wetherill 《Tetrahedron letters》1984,25(23):2411-2414
A wide variety of α,β-acetylenic ketones were synthesized in very high yields via an exceptionally facile intermolecular reaction of lithium alkynyltrifluoroborates and carboxylic acid anhydrides. 相似文献
983.
Michael Charwath Prof. Dr. Kurt Utvary Joseph M. Kanamueller 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1093-1097
Prolonged heating of (CH3NPF3)2 in a sealed tube at 120°C yields (CH3N)4P3F7 and PF5. Under the experimental conditions these compounds react to (CH3N)4P3F6
+PF6
–. Reaction of (CH3NPF3)2 in the presence of PF5 leads to a marked decrease in the formation of the ionic compound. The influence of the fluoride donating saltsMF (M=Li, Na, K, Cs) is investigated.
Mit 1 Abbildung
Früher: Alkyliminophosphorsäuretrihalogenide, 1. und 2. Mitt. 相似文献
Mit 1 Abbildung
Früher: Alkyliminophosphorsäuretrihalogenide, 1. und 2. Mitt. 相似文献
984.
High-performance liquid chromatography was used to assay serum acid and alkaline phosphatase. Samples were incubated with adenosine-5'-monophosphoric acid (AMP) in a buffer of required pH, 5'-nucleotidase was inhibited with Ni2+ ions, and the phosphatase activity was determined by measuring the concentration of the reaction product, adenosine. The analysis time, after the incubation is terminated, is short (7 min), and the assay is quantitative and reproducible. Complete separation of the reaction product from the substrate and the naturally occurring serum constituents and the high sensitivity of the ultraviolet detection system eliminate some of the problems commonly encountered in spectrophotometric assays. 相似文献
985.
The potential of a charge distribution due to a lattice of point charges may be evaluated by the classical multipole expansion method. The leading terms in the resultant expressions are just those used in some of our previous calculations [1–3]. In addition, for cases where the leading terms vanish because of the effect of orthogonality of the basis functions upon the Mulliken expansion (this being especially serious in the case of a one-centre charge distribution), we have derived the first nonvanishing term, involving |r|. In other cases it may be necessary to proceed to still higher multipole terms before a non-zero contribution is obtained. The entire procedure is formulated in such a way that it can be easily applied to LCAO-MO calculations for polyatomic ions in ionic lattices. 相似文献
986.
Michael Werner 《Journal of Geometry》1984,22(2):189-192
Lie theory renders a concept of curvature for the geometries (,) introduced by W. Benz [1]. Among regular curves in
the chains of (,
) are characterized by =0. 相似文献
987.
988.
On the Preparation of Arsenic Dichloride Trifluoride, AsCl2F3 AsCl2F3 is prepared by pyrolysis of [AsCl4]+ [AsF6]?. The vibrational spectra of the new low temperature compound are reported and the valence force constants are calculated. The formation of AsCl2F3 by ligand exchange reactions is discussed. 相似文献
989.
Kenneth S. Brown 《Journal of Pure and Applied Algebra》1984,32(1):1-10
New expansions for global semigroup theory are developed. Many expansions have a left and a right version, each with specific (dual) properties; e.g., the Rhodes expansions ?, resp. ?, have unambiguous -resp. -order. In applications one sometimes needs expansions having both properties simultaneously; these can be constructed by alternately applying the left and the right expansion (possibly infinitely often) while keeping the same set of generators. Thus one obtains an expansion which is invariant under application of the old two expansions and thus has the properties of both (e.g., one obtains -+ with , and so -+ has unambiguous -and -order). It is proved that, in the case of the Rhodes expansion, the new expansion is ‘close’ to the original semigroup; in particular (and this is the main result of the paper), ?+A is finite (resp. finite -above) if S is finite (resp. finite-above). 相似文献
990.
Michael T. Cleary James L. Owens Glenn Dryhurst 《Journal of Electroanalytical Chemistry》1981,123(2):265-290
The electrochemical oxidation of 9-methylxanthine proceeds via four voltammetric oxidation peaks at the pyrolytic graphite electrode. The first voltammetric oxidation peak (peak Ia) is a 1e reaction giving a radical which dimerizes to 8,8′-bi-9-methyl-9H-purine-2,6-(1H, 3H)-dione. Peak IIa is a further 2e electrooxidation of the peak Ia dimer to another yellow dimer 8,8′-bi-9-methyl-9H-purine-2,6-(1H)-dione-3,5-(3H)-diiminylidene. This dimer is not very stable and it hydrolyzes to 1-methyl allantoin. Peak IIIa is an adsorption pre-peak to peak IVa which corresponds, overall, to a direct 4e?4H+ electrooxidation of 9-methylxanthine to an unstable diimine of 9-methyluric acid. Hydrolysis of this diimine leads to a variety of ultimate products. 相似文献