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E. J. Ansaldo J. J. Boyle C. Niedermayer H. Glückler J. L. Tallon A. Mawdsley D. Pooke C. E. Stronach D. R. Noakes R. S. Cary M. R. Davis G. D. Morris 《Hyperfine Interactions》1994,86(1):505-511
A systematic study of the dependence of the critical temperature on the superconducting carrier density, as measured by
+SR, was carried out for a variety of cuprate oxides. We have shown that substitution of Pb for Bi and La for Sr result in well pinned vortex lattices in Bi2Sr2CaCu2Ox, and studied (BiPb)-2212 from the underdoped to the slightly overdoped regime. We also found that Tl-1212 samples, which have optimal maximumT
c=108 K, trace a separate line with parameters comparable to overdoped Tl-2223 at the maximum. These data, together with data on Y-124/247, Tl-2201 and other cuprates result in an larger set of universal correlations between Tc and(0) n
s
/m
* for the high temperature superconductors. 相似文献
34.
Zachmanoglou CE Docrat A Bridgewater BM Parkin G Brandow CG Bercaw JE Jardine CN Lyall M Green JC Keister JB 《Journal of the American Chemical Society》2002,124(32):9525-9546
The electronic influence of unbridged and ansa-bridged ring substituents on a zirconocene center has been studied by means of IR spectroscopic, electrochemical, and computational methods. With respect to IR spectroscopy, the average of the symmetric and asymmetric stretches (nu(CO(av))) of a large series of dicarbonyl complexes (Cp(R))(2)Zr(CO)(2) has been used as a probe of the electronic influence of a cyclopentadienyl ring substituent. For unbridged substituents (Me, Et, Pr(i), Bu(t), SiMe(3)), nu(CO(av)) on a per substituent basis correlates well with Hammett sigma(meta) parameters, thereby indicating that the influence of these substituents is via a simple inductive effect. In contrast, the reduction potentials (E degrees ) of the corresponding dichloride complexes (Cp(R))(2)ZrCl(2) do not correlate well with Hammett sigma(meta) parameters, thereby suggesting that factors other than the substituent inductive effect also influence E degrees. Ansa bridges with single-atom linkers, for example [Me(2)C] and [Me(2)Si], exert a net electron-withdrawing effect, but the effect is diminished upon increasing the length of the bridge. Indeed, with a linker comprising a three-carbon chain, the [CH(2)CH(2)CH(2)] ansa bridge becomes electron-donating. In contrast to the electron-withdrawing effect observed for a single [Me(2)Si] ansa bridge, a pair of vicinal [Me(2)Si] ansa bridges exerts an electron-donating effect relative to that from the single bridge. DFT calculations demonstrate that the electron-withdrawing effect of the [Me(2)C] and [Me(2)Si] ansa-bridges is due to stabilization of the cyclopentadienyl ligand acceptor orbital, which subsequently enhances back-donation from the metal. The calculations also indicate that the electron-donating effect of two vicinal [Me(2)Si] ansa bridges, relative to that of a single bridge, is a result of it enforcing a ligand conformation that reduces back-donation from the metal. 相似文献
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We combine the recent optimal predecessor algorithm with a recent randomized stratified tree algorithm for an ε-approximate nearest neighbor to give an algorithm for an ε-approximate nearest neighbor in a fixed-dimensional space that is optimal with respect to universe size. We also give a deterministic version of the stratified tree algorithm. 相似文献
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Self-consistent-field-Xα-scattered wave calculations on clusters Si2O76? and H6Si2O7 modeling silica have been performed. Incorporation of Si 3d orbitals produces significant changes in the overall valence structure. In addition to σ Si — O bonds, there exists a bonding π character due to the participation of O 2p and Si 3d. Hydrogen terminators do not seem to correct edge effects for these π states. 相似文献
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W. Cary Huffman 《Discrete Mathematics》1979,26(2):129-143
Let C be a binary code of length n and let JC (a, b, c, d) be its biweight enumerator. If n is even and C is self-dual, then JC is an element of the ring R of absolute invariants of a certain group . Under the additional assumption that all codewords of C have weight divisible by 4, a similar result holds with a different group. If n is odd and C is maximal self-orthogonal, then JC is an element of a certain R-module. Again a similar result holds if the codewords of C have weights divisible by 4. The groups involved are related to finite groups generated by reflections. In this paper the structure of these groups is described, and polynomial bases for the rings and modules in question are obtained. This answers a question posed in The Theory of Error- correcting Codes by F.J. MacWilliams and N.J.A. Sloane. 相似文献