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排序方式: 共有205条查询结果,搜索用时 174 毫秒
21.
Sabrina Brait Stefano Deabate Selby A. R. Knox Enrico Sappa 《Journal of Cluster Science》2001,12(1):139-173
A survey of the synthetic pathways and of the reactivity and catalytic activity of transition metal carbonyl clusters substituted with benzyne (and, for comparison, benzene and diene) ligands is given. Cluster-surface analogies are helpful in gaining an understanding of the homogeneous and heterogeneous catalytic behaviour of the clusters. 相似文献
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L. W. Andrews H. Morawitz E. Rupp H. Bauer W. F. Schirmer Karin Thaulow H. Lescoeur E. Biilman F. Lehmann J. Knox P. W. Robertson H. Wastenson G. S. Jamieson F. Utz L. Garnier F. Reinthaler J. A. Muller A. Kolb A. Feldhofen G. Adanti B. Oddo L. Vignon H. R. Procter und R. A. Seymour-Jones 《Fresenius' Journal of Analytical Chemistry》1923,62(10):401-407
Ohne Zusammenfassung 相似文献
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A. S. Knox D. I. Kaplan T. G. Hinton 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(1):169-173
We assessed the ability of netted chain fern (Woodwardia areolata) to uptake U and Th from wetland soils on the U.S. Department of Energy’s Savannah River Site in South Carolina. Netted chain
fern had the highest Th and U concentrations of all plants collected from the wetland. Ferns grown in contaminated soil (329
mg·kg−1 Th, 44 mg·kg−1 U) in a greenhouse contained 6.4 mg·kg−1 Th and 5.3 mg·kg−1 U compared with 0.13 mg·kg−1 Th and 0.035 mg·kg−1 U in Bermuda grass (Cynodon dactylon). Netted chain fern has potential for the phytoremediation of soils contaminated with Th and U. 相似文献
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Unsigned book reviews are by the Book Review Editor. 相似文献
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W. H. Knox 《Applied physics. B, Lasers and optics》1994,58(3):225-235
Dispersive phenomena provide limits in the generation, measurement and applications of femtosecond optical pulses. Optical elements such as prisms, gratings, air, mirrors, filters, and laser crystals all contribute to the total dispersion in optical systems. Interferometric techniques enable measurements of dispersion of individual elements, and new techniques allow dispersion measurement inside the cavity of operating modelocked femtosecond tunable lasers. These techniques provide access to detailed information about dispersion errors which can distort pulses and produce undesirable effects in modelocked lasers. In this article, we review techniques for the measurement of dispersion in optical components and systems. In several cases, we compare measurements made with intracavity dispersion techniques with extracavity measurements and point out common features. 相似文献
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Using a DC-biased room-temperature photoconductive switching element, a picosecond resolution optical streak camera is operated at sweep rates up to 7 ps/mm. Single-shot jitter is 2 ps with complete absence of short and long-term drift characteristic of all other sweep drivers. This high accuracy allows the streak camera to be used in a single-shot averaging mode which leads to a sub-picosecond absolute timing accuracy. When operated in this manner, the streak camera becomes a highly reliable and accurate device for measuring transient events on a time scale of single picoseconds. The simplicity of this method makes it highly attractive for many applications in laser fusion and picosecond chemistry and photophysics studies where reliable no-drift operation is highly desirable. 相似文献
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Cheryl A. Hanzlik Robert S. Knox † Scott L. Gibson Russell Hilf 《Photochemistry and photobiology》1989,50(1):45-53
Hematoporphyrin derivative (HPD) and other porphyrin samples were excited by 20-ps 532-nm laser pulses. Fluorescence was detected using a low-jitter streak camera. Data were fitted to a sum of exponential decay times on the order of picoseconds. Fluorescence of porphyrins in aqueous solution show various behaviors depending on the hydrophobicity of the porphyrins. The most hydrophilic porphyrins show long decays only (greater than 500 ps). Porphyrins intermediate in hydrophobicity have intensity-dependent fast decays. The most hydrophobic have fast decays (less than 20 ps). Picosecond fluorescences of mitochondria prepared from rat tumors treated in vivo with HPD or Photofrin II show an increase in the ratio of fast to slow decays when compared to the injected porphyrins. These results are consistent with the concentration of the more hydrophobic porphyrins in mitochondria in photosensitization treatment. Thus picosecond fluorescence studies of porphyrins may provide a means to obtain photoproperties which differentiate between effective and ineffective in vivo photosensitizers. 相似文献