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71.
Poul Hjorth Petr Lisonek Steen Markvorsen Carsten Thomassen 《Linear algebra and its applications》1998,270(1-3):255-273
We prove that, if a finite metric space is of strictly negative type, then its transfinite diameter is uniquely realized by the infinite extender (load vector). Finite metric spaces that have this property include all spaces on two, three, or four points, all trees, and all finite subspaces of Euclidean spaces. We prove that, if the distance matrix is both hypermetric and regular, then it is of strictly negative type. We show that the strictly negative type finite subspaces of spheres are precisely those which do not contain two pairs of antipodal points. In connection with an open problem raised by Kelly, we conjecture that all finite subspaces of hyperbolic spaces are hypermetric and regular, and hence of strictly negative type. 相似文献
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73.
The mass spectral decompositions of cyclic and acyclic borates have been examined. Straight chain trialkyl borates fragment by C? O cleavage reactions accompanied by transfer of one or two hydrogen atoms, whereas tri-(sec-alkyl) borates primarily undergo α-cleavage reactions. Both types of cleavage are observed in the fragmentation of cyclic borates. B? O bonds are not broken in the formation of most major fragment ions. The fragmentations of borates are compared with those of phenylboronates with special emphasis on the rearrangements leading to hydrocarbon ions in the spectra of the latter. 相似文献
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Boltalina OV Streletskii AV Ioffe IN Hvelplund P Liu B Nielsen SB Tomita S 《The Journal of chemical physics》2005,122(2):021102
The first experimental observation of long-lived triply charged fluorofullerene anions in the gas phase obtained from C60F48 is reported. The existence of a Coloumb barrier trapping the third electron in the trianion is supposed to be responsible for detection of the species which is estimated to have negative third electron affinity. 相似文献
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Steen Hildebrandt 《European Journal of Operational Research》1981,8(2):123-129
The article deals with information in the OR process. The value of an ‘optimal’ model solution which is not implemented is not very high. Many errors are due to a too narrow formulation of the problem, often a formulation which has focused on purely technical and economic aspects, or a formulation which has been adapted for a standard model. The concepts and models treated in the article take their point of departure in the actual problem. The models can be used as a frame of reference by various individuals and groups which are involved in OR work. 相似文献