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31.
Gas-phase catalysis by atomic and cluster metal ions: the ultimate single-site catalysts 总被引:5,自引:0,他引:5
Gas-phase experiments with state-of-the-art techniques of mass spectrometry provide detailed insights into numerous elementary processes. The focus of this Review is on elementary reactions of ions that achieve complete catalytic cycles under thermal conditions. The examples chosen cover aspects of catalysis pertinent to areas as diverse as atmospheric chemistry and surface chemistry. We describe how transfer of oxygen atoms, bond activation, and coupling of fragments can be mediated by atomic or cluster metal ions. In some cases truly unexpected analogies of the idealized gas-phase ion catalysis can be drawn with related chemical transformations in solution or the solid state, and so improve our understanding of the intrinsic operation of a practical catalyst at a strictly molecular level. 相似文献
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Diethard Pallaschke 《Applied mathematics and computation》1978,4(3):201-212
In this paper we will show how to construct, in a canonical way, a continuous economy in the sense of R. J. Aumann [1]. This construction is based on W. Hildenbrand's [3] definition of “pure competition” for an exchange economy with countably infinitely many participants. 相似文献
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Neubauer S Rugova A Chu DB Drexler H Ganner A Sauer M Mattanovich D Hann S Koellensperger G 《Analytical and bioanalytical chemistry》2012,404(3):799-808
In this work, accurate MS-based methods for quantitative profiling of nucleotides, nucleosides, and nucleobases in yeast extracts used as additives in animal feedstuff are presented. Reversed-phase chromatography utilizing a stationary phase compatible with 100% aqueous mobile phases resulted in superior analytical figures of merit than HILIC or ion-pair reversed-phase separation. The novel separation method was combined with both molecular and elemental mass spectrometry. By use of RP-LC-MS-MS, excellent limits of detection <1 μmol L(-1) could be obtained for all the compounds investigated. The elemental speciation analysis approach enabled determination of nucleotides by phosphorus detection. Sensitivity of LC-ICP-MS was 1-2 orders of magnitude lower than that of LC-MS-MS. Quantitative analysis of yeast products using complementary MS detection furnished values in good agreement. 相似文献
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J. P. Schreckenbach Klaus Witke Diethard Butte Günter Marx 《Fresenius' Journal of Analytical Chemistry》1999,363(2):211-214
Thin films are potentiodynamically generated on vanadium in Ba2+/acetate electrolyte systems at high voltages. The influence of the anodic potential up to 400 V on the composition and structure
of the about 500 nm thin anodic conversion films are investigated. Raman spectroscopy indicates that different film types
depend on the electrochemical process parameters. The relationship between the Raman laser excitation power and the amorphous
or microcrystalline film structure is also discussed. Beside metastable disordered structures the films contain crystalline
phases of V2O5, V4O9 and barium vanadate, respectively.
Received: 15 July 1997 / Revised: 16 February 1998 / Accepted: 21 February 1998 相似文献