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151.
William R. Roush Michael A. Marletta Sandra Russo-Rodriguez Joanne Recchia 《Tetrahedron letters》1985,26(43):5231-5234
The preparation and structure determination of the title compound is described. 相似文献
152.
A study of the adsorptive stripping voltammetry of cadmium and zinc is reported in which ligands containing sulphur donor atoms were examined. This type of ligand showed good adsorptive behaviour and strong metal complexation. It was found that the ligand 2,5-dimer-capto-1,3,4-thiadiazole (DMTD) was very suitable for the determination of cadmium and zinc using this technique.The method was applied to the direct determination of these metals in biological samples using benzyl trimethylammonium methoxide as digesting solvent for the samples. 相似文献
153.
Uptake of radionuclides on antimony silicate 总被引:1,自引:0,他引:1
L. Al-Attar Alan Dyer R. Harjula 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(1):199-203
The uptake of fission products 137Cs, 85Sr, 57Co, onto an antimony silicate, and its Na, K, Ca ion-exchanged forms have been studied. Distribution coefficients have been
determined as a function of the concentrations of sodium, potassium and calcium nitrate solutions (0.01, 0.1 and 1M). Plots
of log distribution coefficients against concentrations enabled the elucidation of exchange mechanisms in some cases. Potassium
had the least, and calcium the most effect on isotope uptake when present as macro ions. The presence of sodium promoted hydrolysis
that also affected the exchange selectivity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
154.
Consider the hypercube [0, 1]n in Rn. This has 2n vertices and volume 1. Pick N = N(n) vertices independently at random, form their convex hull, and let Vn be its expected volume. How large should N(n) be to pick up significant volume? Let k=2/√≈1.213, and let ? > 0. We shall show that, as n→∞, Vn→0 if N(n)?(k??)n →1 if N(n) ? (k + ?)n. A similar result holds for sampling uniformly from within the hypercube, with constant . 相似文献
155.
156.
Singh SB Zink DL Doss GA Polishook JD Ruby C Register E Kelly TM Bonfiglio C Williamson JM Kelly R 《Organic letters》2004,6(3):337-340
[structure: see text] Screening of natural products extracts led to the discovery of citrafungins A and B, two new fungal metabolites of the alkylcitrate family that are inhibitors of GGTase I of various pathogenic fungal species with IC(50) values of 2.5-15 microM. These compounds exhibited antifungal activities with MIC values of 0.40-55 microM. The isolation, structure elucidation, relative and absolute stereochemistry, and biological activities of citrafungins are described. 相似文献
157.
Carroll AR Arumugan G Quinn RJ Redburn J Guymer G Grimshaw P 《The Journal of organic chemistry》2005,70(5):1889-1892
Two novel indolizidine alkaloids, grandisine A (1) and B (2), and the known alkaloid (-) isoelaeocarpiline (3) were isolated from the leaves of Elaeocarpus grandis and their structures determined by 1D and 2D NMR spectroscopy. The compounds showed affinity for the human delta-opioid receptor. Grandisine A contains a unique tetracyclic skeleton, while grandisine B possesses the unique combination of isoquinuclidinone and indolizidine groups in one molecule. 相似文献
158.
A erenkov counting technique is presented for the radioassay of106Ru in aqueous solutions containing nitrate, nitric acid, chloride as well as inactive ruthenium nitrosyl complex carrier. The counting efficiency was found to be a function of colour quenching by these substances in the UV and visible range. Measurements made on a three-channel automatic liquid scintillation spectrometer indicated that the counting efficiency can be calculated by use of the experimentally determined channel ratio of a quenched sample, without prior knowledge of the quencher concentration. The technique can be useful during studies on the removal of106Ru from nuclear waste solutions. Special settings of discriminator windows enable radioassays in presence of weak -emitters such as137Cs. The possibility of determining106Ru in presence of90(Sr/Y) was also investigated. 相似文献
159.
Joanne Davies 《Analytica chimica acta》2003,479(2):215-223
In thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) a nickel atomization tube is placed in the acetylene/air flame on a holder built onto a standard AAS burner head. The liquid to be analyzed is transported by a low or high-pressure pump through a very hot, simple, inexpensive ceramic capillary tip acting as a flame-heated thermospray into the flame furnace. This results in complete sample introduction and increases the residence time of the sample in the absorption volume. This leads for 17 elements to a 3-110-fold improvement in the power of detection compared to conventional flame AAS. The absolute detection limits (3s values, N=25) lie between 0.2 μg l−1 (Zn) and 310 μg l−1 (Se) according to the element. The R.S.D. (N=15) is 1.4-5.5% according to the element and applied concentration. TS-FF-AAS can easily be incorporated on any standard flame AAS instrument and can be automated with a standard autosampler. 相似文献
160.
1,3-Dimethyl-1,2-dihydro-2-imino-4(3H)pyrimidinone (1,3-dimethylisocytosine) was prepared by methylation of 2-amino-3-methyl-4(3H)pyrimidinone and was degraded in alkaline solution to a mixture of 3-methyl-2-methylamino-4(3H)pyrimidinone, 1,3-dimethyl-2,4-(1H,3H)pyrimid-indione, 2-methylamino-l-methyl-4(1H)pyrimidinone, 1-methyl-2,4-(1H,3H)pyrimidindione and 3-methyl-2,4-(1H,3H)pyrimidindione. Thiation of the title compound gave both 1,2-dihydro-1,3-dimethyl-2-thio-4(3H)pyrimidinone and 1,3-dimethyl-2,4-(1H,3H)pyrimidinedithione. The title compound is a tautomerically fixed pyrimidine and its uv spectra were compared with related compounds, notably 3-methyl-2-dimethylarnino-4(3H)pyrimidinone which is also tautomerically fixed. 相似文献