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991.
992.
Philip Yaw Boamah Norbert Haider Gottfried Heinisch 《Journal of heterocyclic chemistry》1989,26(4):933-939
Pyrido[3,4-d]pyridazines 2–5, 21 bearing one, two, or three aryl substituents in the pyridine moiety are shown to be conveniently accessible from 4-aroyl-5-methylpyridazines or 4,5-diaroylpyridazines, respectively, by condensation reactions with appropriate C-N fragments. In addition, the novel pyridazine-annelated pyridones 24, 25 were found to be easily available from ethyl 5-methyl-4-pyridazinecarboxylate. 相似文献
993.
Path integral expressions are given for the wave function and for the density matrix in a theory which describes state vector reduction. The magnitude of the contribution of each classical path to the propagator is not unity, as in ordinary quantum theory, but depends upon the path. 相似文献
994.
995.
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
996.
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
997.
998.
Sulfonation of 3-aroylthiophenes and furans with sulfuric acid in acetic anhydride regioselectively affords the corresponding 2,4-disubstituted heterocycle. Benzylamine derivatives of the parent sulfonamides are obtained either by Mannich reaction of aryl phenols, or via a sequence employing free radical bromination followed by selective ammonolysis. This methodology provides ready access to a wide variety of regioselectively-substituted heterocycles. 相似文献
999.
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
1000.
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