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Daniele Cauzzi Roberto Giordano Enrico Sappa Antonio Tiripicchio Marisa Tiripicchio Camellini 《Journal of Cluster Science》1993,4(3):279-296
The title complex (complex1) was the first alkyne-substituted triruthenium dihydrido cluster to be reported and was characterized by spectroscopy as a triangular cluster with the alkyne parallel to a Ru-Ru edge. Recently, we have found that1 is a key intermediate in the homogeneous hydrogenation of diphenylacetylene catalyzed by tetrahedral Ru4 and FeRu3 clusters. Since the discovery of1, a great number of complexes with alkynes parallel to a cluster edge have been reported; at present this is the more common bonding mode for alkynes on trinuclear clusters. The structural features of1 allow a comparison with those of other ruthenium-containing derivatives and help to draw suggestions of the role of1 in hydrogenation catalysis. 相似文献
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P. C. Morais A. C. Oliveira V. K. Garg M. L. Silva E. F. C. Alcântara F. Q. Soares D. Rabelo 《Hyperfine Interactions》2007,177(1-3):51-56
We have used time-differential perturbed angular correlation (PAC) spectroscopy with 181Ta-probes to study the electric field gradient at Zr-sites in synthetic zircon and hafnon between room temperature and 1,200°C. PAC spectra are similar to those obtained from naturally occurring zircons. In particular, a change in slope of the quadrupole coupling vs. temperature is observed in the synthetic zircon at the same temperature as seen in natural zircons from the Mud Tank carbonatite (Australia). The synthetic hafnon data also shows this feature but at somewhat higher temperature. Low-temperature PAC spectra of both synthetic zircon and hafnon have a clearly reduced anisotropy. We believe that the cause for this is a electronic defect, possibly created during the β-decay of the probe parent nucleus. 相似文献
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Using Lagrange's multiplier rule, we find upper and lower bounds of the energy of a bipartite graph G, in terms of the number of vertices, edges and the spectral moment of fourth order. Moreover, the upper bound is attained in a graph G if and only if G is the graph of a symmetric balanced incomplete block design (BIBD). Also, we determine the graphs for which the lower bound is sharp. 相似文献
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Telecommunications systems have recently undergone significant innovations. These call for suitable statistical models that can properly describe the behaviour of the input traffic in a network. Here we use fractional Brownian motion (FBM) to model cumulative traffic network, thus taking into account the possible presence of long‐range dependence in the data. A Bayesian approach is devised in such a way that we are able to: (a) estimate the Hurst parameter H of the FBM; (b) estimate the overflow probability which is a parameter measuring the quality of service of a network: (c) develop a test for comparing the null hypothesis of long‐range dependence in the data versus the alternative of short‐range dependence. In order to achieve these inferential results, we elaborate an MCMC sampling scheme whose output enables us to obtain an approximation of the quantities of interest. An application to three real datasets, corresponding to three different levels of traffic, is finally considered. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Siegfried Grossmann Denis Jérome Antonio Paoletti 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):447
We mourn the death of Professor Dr. Gilbert Grynberg, April 17, 1948 - January 27, 2003. We have lost an excellent and highly esteemed scientist, an outstanding character and a good friend. He has been a very active colleague in the merger of Zeitschrift für Physik and Journal de Physique in the early days. As one of the Co-Editors-in-Chief of The European Physical Journal D, from its start, he has formed the scienti.c standards of EPJ. Untiringly he has served our Journal with greatest dedication. We are grateful that he has been with us. The editorial board and o.ce of EPJ B Siegfried Grossmann, Denis Jérome, Antonio Paoletti 相似文献
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Antonio Zecca 《International Journal of Theoretical Physics》2003,42(7):1621-1628
The superposition relation extended to the statistical operators is shown to be invariant under tensor product and partial trace operations. Particular mathematical examples of superposition are characterized as well as the nature of the Schmidt decomposition of pure states superposition of other pure states. 相似文献