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41.
Ramon M. Barnes 《Analytical and bioanalytical chemistry》1998,361(3):246-251
This report focuses on the status, requirements, and potentials of CE-ICP-MS. The ultimate goal of a viable CE-ICP-MS system is to obtain quantitative elemental speciation information and isotopic ratio data for practical biological and environmental metal containing compounds. To make use of the CE separation features, the CE analyte must be introduced efficiently into the ICP. For practical samples, pre- and post-separation enrichment techniques probably are required. The features of electrospray ion sources that can be incorporated in CE-ICP-MS and the potential for microfabricated CE are discussed. 相似文献
42.
Comparison of microwave-assisted acid leaching techniques for the determination of heavy metals in sediments, soils, and sludges 总被引:2,自引:0,他引:2
Microwave-assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges
was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was
investigated. The extraction efficiencies for four certified reference materials applying EPA method 3051, an optimized nitric
acid procedure, and an aqua regia (HCl/HNO3 3:1) procedure were compared. Digestions were carried out in a high-pressure microwave system offering simultaneous temperature
and pressure control for all digestion vessels employed. Eight elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were determined
by ICP-AES and ICP-MS. Extraction efficiency strongly depended on the applied leaching parameters and varied for certain elements
among different materials when a nitric acid procedure was applied. In general, element recoveries obtained from the aqua regia procedure were superior to those obtained from nitric acid procedures and showed good agreement with the 95% confidence interval
of the certified value for most of the elements investigated.
Received: 27 March 1998 / Revised: 29 June 1998 / Accepted: 3 July 1998 相似文献
43.
44.
N. Barnes P. Healey P. McKee A. W. O'Neill M. A. Z. Rejman-Greene E. G. Scott R. P. Webb B. R. White D. Wood 《Optical and Quantum Electronics》1992,24(4):S505-S516
An experimental 16-channel parallel interconnection system able to support 100 Mbits–1 per channel and an opto-electronic neural network operating at up to 50 Mbits–1 have been constructed to demonstrate the potential of optics in processing systems. Both experiments operate at a wavelength of 1.5m. Components developed for these systems include arrays of InGaAs/InP MQW surface modulators for low-power electrical-to-optical conversion; InGaAs/InP for detector arrays, which are hybrid integrated with GaAs amplifier arrays; and computer-generated holograms for efficient beam splitting and to encode weights in the optical beam intensities. Each of these demonstrations has considerable scope for increasing the degree of parallelism and the operating speed. Recent modifications to the neural network enable the weights to be varied and training has been demonstrated with a novel algorithm that uses the high operating speed to advantage. 相似文献
45.
Alam MS Kim IJ Nemati B O'Neill JJ Romero V Severini H Sun CR Wang P Zoeller MM Crawford G Fulton R Gan KK Kagan H Kass R Lee J Malchow R Morrow F Sung M White C Whitmore J Wilson P Butler F Fu X Kalbfleisch G Lambrecht M Skubic P Snow J Bortoletto D Brown DN Dominick J McIlwain RL Miao T Miller DH Modesitt M Schaffner SF Shibata EI Shipsey IP Battle M Ernst J Kroha H Roberts S Sparks K Thorndike EH Wang C Artuso M Goldberg M Haupt T Horwitz N Kennett R Moneti GC Playfer S Rozen Y Rubin P 《Physical review D: Particles and fields》1992,46(11):4822-4827
46.
47.
48.
Kubota Y Nelson JK Perticone D Poling R Schrenk S Crawford G Fulton R Jensen T Johnson DR Kagan H Kass R Malchow R Morrow F Whitmore J Wilson P Bortoletto D Brown D Dominick J McIlwain RL Miller DH Modesitt M Ng CR Schaffner SF Shibata EI Shipsey IP Battle M Kroha H Sparks K Thorndike EH Wang C Alam MS Kim IJ Li WC Nemati B Romero V Sun CR Wang P Zoeller MM Goldberg M Haupt T Horwitz N Jain V Mestayer MD Moneti GC Rozen Y Rubin P Skwarnicki T Stone S Thusalidas M Yao W Zhu G Barnes AV Bartelt J 《Physical review D: Particles and fields》1991,44(3):593-600
49.
LetA
1,,A
n
be distinctk-dimensional vectors. We consider the problem of partitioning these vectors intom sets so as to maximize an objective which is a quasi-convex function of the sum of vectors in each set. We show that there exists an optimal partition whose sets have (pairwise) disjoint conic hulls. We also show that if the number of vectors in each of the sets is constrained, then a weaker conclusion holds, namely, there exists an optimal partition whose sets have (pairwise) disjoint convex hulls. The results rely on deriving necessary and sufficient conditions for a point to be an extreme point of a corresponding polytope.Research of this author was partially supported by NSF Grant ECS-83-10213 and by a Grant for the Promotion of Research at the Technion. 相似文献
50.
[reaction: see text] The tricyclic benzothiazine 15 was prepared in a straightforward fashion via a completely stereoselective intramolecular Friedel-Crafts alkylation. This compound represents a potential precursor to the antitubercular agent, pseudopteroxazole. Its synthesis proceeded via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an alpha,beta-unsaturated ester, followed by functional group manipulations. 相似文献