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21.
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Given an expansive action α of ?2 by automorphisms of a compact connected metrizable abelian groupX, we show how the entropy of the action may be decomposed into local contributions, 1 $$h(\alpha ) = \sum\limits_{p \leqslant \infty } {h_p^{(a,b)} } (\alpha )$$ in which the summandh p (a,b) (α) represents thep-adic entropy due to arithmetic or geometric hyperbolicity in the direction (a, b). We recognize thep-adic contribution as an integral over thep-adic unit circle, in analogy with the global counterpart. As (a, b) changes, the decomposition (1) changes only when the line through (a, b) passes through one of a finite collection of critical directions, which are explicitly identified. 相似文献
23.
Cellular algebras 总被引:4,自引:0,他引:4
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Graham R. Underwood Brajeswar Paul M. Alice Becker 《Journal of heterocyclic chemistry》1976,13(6):1229-1232
Pyridoxol, protected by acetylation of the hydroxyl groups, has been converted to its N-oxide which upon reaction with perfluoroacetie anhydride yields a 2-nor-2-hydroxymethylpyridoxol derivative as an intermediate. This compound undergoes acyl migration from the 3-position. Protection of the pyridoxol hydroxyls by benzylalion followed by the same treatment yields the unrearranged α2-hydroxy derivative. This compound has been converted to a series of α2-substituted pyridoxols (X = -Cl, -Br, -OCOCH3, -OCH3, -OC2H5). 相似文献
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27.
Roothaan's SCF method [2] is reformulated so that two non-SCP methods are developed to solve the eigenequation. The results from these methods can be used as starting eigenfunctions for Roothaan's SCF method.
The title Theoretical Chemistry has been transferred to the Division of Physical Chemistry. 相似文献
Zusammenfassung Die self-consistent field Methode von Roothaan [2] wird neu formuliert: dabei werden zwei Nicht-SCF Methoden zur Lösung der Eigenwertgleichung entwickelt. Deren Resultate können als Anfangsfunktionen bei Rechnungen mit der SCF-Methode von Roothaan benutzt werden.
Résumé La méthode SCF de Roothaan [2] est reformulée en développant deux méthodes non-SCF pour la solution de l'équation aux valeurs propres. Les résultats de ces deux méthodes peuvent être utilisées comme fonctions de départ pour la méthode SCF de Roothaan.
The title Theoretical Chemistry has been transferred to the Division of Physical Chemistry. 相似文献
28.
Reaction of Ph3GeLi with [Et4N][HFe3(CO)11] affords the new carbonylferrate salt [Et4N][Ph3GeFe(CO)4] and the same reaction provides an alternative route to the known silicon and tin analogs. Protonation of [Et4N][Ph3GeFe(CO)4] with HCl in ether-THF forms the air-sensitive, thermally rather unstable cis-Ph3GeFeH(CO)4. The latter protonates chloride ions in dichloromethane. 相似文献
29.
The transferability of atomic and functional group properties is an implicit concept in chemistry. The work presented here describes the use of Transferable Atom Equivalents (TAE) to represent molecular electrostatic potential fields through the use of integrated atomic multipole moments that are associated with each TAE atom type used in the reconstruction. TAE molecular surface distributions of electrostatic potentials are compared with analytical ab initio and empirical (Gasteiger) partial charge reference models for several conformations of test peptides. Surface electrostatic potential distributions computed using TAE multipole representations were found to converge at the octopole level, with incremental improvement observed when hexadecapoles were included. Molecular electrostatic potential fields that were produced using the TAE method were observed to be responsive to conformational changes and to compare well with ab initio reference distributions. Generation of TAE atom types and their associated multipoles does not involve fitting to sample electrostatic potential fields, but rather utilizes integrated AIM atomic electron density distributions within representative chemical environments. The RECON program was used for TAE reconstruction. RECON is capable of processing 5,000 drug-sized molecules or 25 proteins per minute per 1.7 GHz P4 Linux processor. 相似文献
30.
The synthesis of the novel boron-containing nucleobase 2-benzyl-1,4-dihydro-1-hydroxythieno[3,2-c]-[1,5,2]diazaborin-3(2H)-one ( 8 ), a thieno-fused 4-borauracil, is described. Compound 8 was prepared in three steps starting from 2-thiophenecarbonyl chloride ( 4 ). A multinuclear and multisolvent nmr study of 8 indicates that the boron atom maintains a trigonal geometry in the solvents used. 相似文献