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971.
J.N. Miller D.T. Ling M.L. Shek D.L. Weissman P.M. Stefan I. Lindau W.E. Spicer 《Surface science》1980,94(1):16-28
Employing the enhanced sensitivity obtained by using synchrotron radiation near the Cooper minimum for the 5d valence electrons, we have located the oxygen 2p and 2s levels for oxygen chemisorbed on a Pt 6(111) × (100) crystal. We find the oxygen 2p level located ?6 eV with a FWHM of 3 eV and the 2s at ?21.6 eV. A factor of four difference in saturation coverage is measured between temperatures of 300 and 120 K, but the position and width of the 2p level is independent of temperature. We observe also the 1b1 orbital of weakly adsorbed H2O molecules, which has pure O 2p parentage; from the intensity of this orbital, we are able to suggest why it is difficult to observe the oxygen 2p signal at low photon energies. In addition, we note a strong preferential attenuation in the Pt states near Ef for the adsorbed H2O in spite of the weak nature of the bond. 相似文献
972.
Stefan Förste 《Zeitschrift fur Physik C Particles and Fields》1993,57(4):663-670
We consider correlation functions in Neveu-Schwarz string theory coupled to two dimensional gravity. The actionfor the 2D gravity consists of the string induced Liouville action and the Jackiw-Teitelboim action describing pure 2D gravity. Then gravitational dressed dimensions of vertex operators are equal to their bare conformal dimensions. There are two possible interpretations of the model. Considering the 2D dilaton and the Liouville field as additional target space coordinates one gets ad+2-dimensional critical string. In thed-dimensional non critical string picture gravitational fields retain their original meaning and ford=4 one can get a mass spectrum via consistency requirements. In both cases a GSO projection is possible. 相似文献
973.
The transportation problem with fuzzy supply values of the deliverers and with fuzzy demand values of the receivers is analysed. For the solution of the problem the technique of parametric programming is used. This makes it possible to obtain not only the maximizing solution (according to the Bellman-Zadeh criterion) but also other alternatives close to the optimal solution. 相似文献
974.
Stefan Waner 《Topology and its Applications》1984,17(1):1-26
Let G be a finite group. The RO(G)-graded bordism theories of Pulikowski [7] and Kosniowski [3] are studied. Representing equivariant Thom spectra are constructed, and the relevant transversality results proved. New methods for splitting away from the order of G are described, and behavior in the presence of a gap hypothesis is examined. 相似文献
975.
976.
J. Henrique Teles Johann-Peter Melder Klaus Ebel Regina Schneider Eugen Gehrer Wolfgang Harder Stefan Brode Dieter Enders Klaus Breuer Gerhard Raabe 《Helvetica chimica acta》1996,79(1):61-83
Stable carbenes derived from thiazole, 1H-imidazole, and 4H-1,2,4-triazole are efficient catalysts for benzointype condensations of formaldehyde. Catalysts derived from N-substituted thiazolium salts trimerize formaldehyde to dihydroxyacetone ( II ). Catalysts based on 1,4-disubstituted 4H-1,2,4-triazol-1-ium salts give glycolaldehyde ( I ) as the main product and no II , whereas N,N′-disubstituted 1H-imidazol-3-ium salts yield mixtures of both products. The isolation of several intermediates in the catalytic cycle provide a better insight into the reaction mechanism. 相似文献
977.
Ulrich Pinkernella Stefan Effkemann Frank Nitzsche Uwe Karst 《Journal of chromatography. A》1996,730(1-2):203-208
The selective oxidation of methyl p-tolyl sulfide (MTS) to the corresponding sulfoxide (MTSO) by peroxyacetic acid and the subsequent rapid separation of the sulfide and sulfoxide are the basis for a fast and reliable HPLC method for the determination of this oxidizing agent in the presence of hydrogen peroxide. The time required for chromatographic separation was reduced to less than 1 min. To improve the long-term stability of the sulfoxide solution, hydrogen peroxide was decomposed catalytically by manganese dioxide. Even in the presence of a tenfold molar excess of hydrogen peroxide, a storability of at least 20 h without a significant increase in MTSO concentration was achieved. External calibration can be performed using the stable and commercially available MTSO. Real samples from a brewery cleaning-in-place disinfection process were analysed and the results were compared with those of the classical two-step titration. 相似文献
978.
979.
Stefan E. Schmidt 《Results in Mathematics》1993,23(3-4):384-386
This note presents a proof of Wedderburn’s theorem concerning the classification of semisimple rings within the conceptual frame of projective lattice geometry. 相似文献
980.
The vinylation of 9H-carbazole ( 1 ), 1H-indole ( 3a ), and 1H-pyrrolo[2,3-b]pyridine ( 3b ) with propiolic acid ethyl ester resulting in N-acrylic esters is reported here. 相似文献