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961.
Philip J. Kuntz 《Chemical physics》1985,94(3):371-384
Potential energy surfaces for Na(2S, 2P) interacting with a partially covered tungsten surface are computed within the framework of the method of diatomics-in-molecules (DIM). Only two sodium atoms are considered explicitly but the effect of all of the adsorbed sodium is taken into account through its influence on the fragment matrix elements in the DIM formulation. Na2+ wavefunctions are approximated by valence-bond calculations for the 2Σg+ and 2Σu+ manifolds. The three lowest potential energy surfaces of the polyatomic system suggest plausible pathways for the production of Na+ and Na2+ ions from the interaction of Na(2P) atoms with the metal surface as observed by Auschwitz and Lacmann. 相似文献
962.
Philip W. Steitz 《Israel Journal of Mathematics》1992,77(3):335-343
We establish a sharp upper bound for growth in the sequences
k
(T):=the number ofk-types consistent withT, forT ω-categorical andω-stable.
This paper forms part of the author’s doctoral dissertation written at the University of Maryland under the direction of David
W. Kueker. 相似文献
963.
Philip L. Bowers 《Geometriae Dedicata》1989,29(2):125-132
It is proved that every convex, complete, two-point homogeneous metric for which small spheres are connected has maximal symmetry. This in turn implies that the standard metrics on the classical spaces of geometry are maximally symmetric. 相似文献
964.
The [Co(tmen)3]3+ complex ion (tmen = 2,3-dimethylbutane-2,3-diamine) has been synthesized and its redox characteristics compared to those of its parent ion [Co(en)3]3+. The 12 peripheral Me groups significantly affect the properties of the [Co(tmen)3]3+ ion. The ligand-field bands are shifted to lower energies by about 1700 cm?1 compared to [Co(en)3]3+. The reduction potential for [Co(tmen)3]3+ is +0.28 V (vs. NHE) compared to ?0.18 V for [Co(en)3]3+. The rate of the self-exchange reaction for the [Co(tmen)3]3+/2+ couple, k = 8.5 × 10?8 M?1·S?1 was determined by applying the Marcus cross-relation with the reductants Cr2+, V2+, Eu2+, Ru2+, and [Co(sepulchrate)]2+. 相似文献
965.
This paper reports the results of the study of anisotropy in elastic wave propagation in single crystal superconducting BSCCO.
The inverse and group velocities of elastic waves propagating in different directions have been computed and the corresponding
slowness and ray velocity surfaces plotted, taking elastic constant data from literature. In addition, the phenomenon of phonon
focussing has been investigated in this material by computing the phonon enhancement factor along different directions in
spherical polar coordinates. The abnormally high values in phonon enhancement factor exhibited in certain directions for the
phonon modes are interpreted as due to caustics occurring in the geometrical acoustics approximation adopted in the computational
analysis. The results in LSCO and YBCO are found to be similar to those in BSCCO. 相似文献
966.
A model for BaBiO3 was introduced by Rice and Sneddon, which treats this material as a simple three-dimensional version of a Peierls insulator, where the insulating gap is a consequence of the ordered distortion of the oxygen atoms. Charge accumulates on half the atoms and depletes from the other half. Experimentally, when holes are added to BaBiO3 by doping, it remains insulating until a very large hole concentration is reached, at which point it becomes superconducting. In the Rice-Sneddon model, at large enough electron-phonon coupling, a mechanism for insulating behavior of doped samples is formation of small polarons or bipolarons which trap carriers in bound states in the Peierls gap. A variational calculation of the polaron binding in this model is given, and compared with “exact” numerical results on large clusters with periodic boundary conditions. 相似文献
967.
Attila Vértes Ilona Czakó-Nagy Philip Deck Henry Leidheiser Jr. 《Hyperfine Interactions》1988,41(1):729-732
The emission Mössbauer technique is used to study the chemical structure of the interphase formed between a cobalt substrate and a polyimide coating. The results are interpreted to indicate that the coating is bonded to the cobalt substrate by means of carboxylate bonds with Co2+ ions in the oxide film at the interface. 相似文献
968.
Treatment of the readily prepared enzymes 12, 21 and 45 with Co2(CO) at ca 110° results in high yields (80%) of substituted bicyclo[3.3.0]octenones, that are suitable for straightforward elaboration into coriolin and hirsutic acid precursors. A mechanistic hypothesis to explain the observed stereospecificity is presented. 相似文献
969.
Philip Rabinowitz 《Numerical Algorithms》1992,3(1):17-28
Extrapolation methods have been used for many years for numerical integration. The most well-known of these methods is Romberg integration. A survey by Joyce on the use of extrapolation in numerical analysis appeared in 1971 in which a substantial portion is devoted to numerical integration. In this paper, we shall survey progress made in this field since 1971. The topics surveyed include partition-extrapolation methods for dealing with singular integrands, the work of Lyness and others in generating asymptotic expansions for the error functional in one and several dimensions, the work of de Doncker and others on adaptive extrapolation and the work of Sidi and others on the evaluation of highly oscillatory infinite integrals by extrapolation. Other extrapolation techniques will be mentioned briefly. 相似文献
970.