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981.
Karol Jackowski Micha? Jaszuński W?odzimierz Makulski 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,127(2):139-143
New experimental and theoretical results are presented for the NMR shielding of oxygen in the carbonyl group. The experimental values clearly demonstrate that the solvent effects are very significant. The new results for the chemical shifts are in better agreement than the previous literature data with the corresponding ab initio values calculated for isolated molecules. 相似文献
982.
983.
We prove that the class of finite dimensional selfinjective algebras over a field which admit Galois coverings by the repetitive
algebras of the quasitilted algebras, with Galois groups generated by compositions of the Nakayama automorphisms with strictly
positive automorphisms, is invariant under stable and derived equivalences.
Dedicated to Claus Michael Ringel on the occasion of his sixtieth birthday 相似文献
984.
Krzysztof Lewiski Julita Eilmes 《Journal of inclusion phenomena and macrocyclic chemistry》2005,52(3-4):261-266
Recrystallization of the title Cu(II) complex from pyridine afforded solid (1:1) pyridine inclusion compound. The crystal structure revealed a pleated-sheet-like arrangement of saddle-shaped molecules of the host, with molecules of pyridine enclathrated within intermolecular cavities. Careful analysis of intermolecular contacts showed that weak aromatic edge-to-face (C–H···Fπ) interactions occur between pyridine and host molecules. The crystal packing appeared to be also stabilized by the host–host C–H···O hydrogen bonds.in final form: 22 December 2004This revised version was published online in July 2005 with a corrected issue number. 相似文献
985.
Wojciech Kroszczyski Ewa Olszewska Piotr Saaski Janusz Jurczak 《Helvetica chimica acta》2004,87(6):1488-1492
A simple and effective method to deprotect of sterically hindered steroid esters is described. Deprotection was carried out in MeOH in the presence of a catalytic amount of Et3N under high‐pressure conditions. Enzymatic, anionite, and high‐pressure methods are compared. 相似文献
986.
987.
Z. M. Stepień 《Czechoslovak Journal of Physics》1993,43(9-10):1029-1033
The initial stages of oxide formation on Mo field emitter tips have been examined with the field emission microscopy and field electron spectroscopy. The oxide formed in situ on Mo tips by thermal treatment in pure oxygen atmosphere was found to be non-uniform with little evidence for coherent structure. The electron spectroscopy results are discussed in terms of the hypothesis that the emission process is a hot-electron emission. 相似文献
988.
The hexatic smectic B (Hex B) phase is commonly encountered among hydrogen-bonded liquid crystal materials. Among enaminoketone and Schiff's base compounds, twenty homologous series (c. 102 compounds) exhibiting orthogonal mono-or bi-layer hexatic phases were identified by combined microscopy and DSC. Phase transitions from crystal B (CrB) of Sf to Hex B as well as from Hex B to Sf, Sa or Sc phases were observed within the range 50 to 190°C. Temperature ranges of the Hex B phase detectable by DSC varied from 0.2 to 20°C. Within two groups of three-ring enaminoketones, the formation of the Hex B phase was found to be controlled by both inductive and mesomeric components of the Hammett constants of the terminal substituents of the molecules. 相似文献
989.
Georg Ch. Pflug Andrzej Ruszczyński Rüdiger Schultz 《Mathematical Methods of Operations Research》1998,47(1):39-49
Expected recourse functions in linear two-stage stochastic programs with mixed-integer second stage are approximated by estimating the underlying probability distribution via empirical measures. Under mild conditions, almost sure uniform convergence of the empirical means to the original expected recourse function is established. 相似文献
990.
The paper presents quasi-static FE-simulations of the crack formation in a reinforced concrete bar without stirrups subject to tension. The material was modeled with a continuum smeared crack model using an elasto-plastic constitutive law. A linear Rankine criterion with isotropic softening and associated flow rule was adopted in a tensile regime. To ensure the mesh-independency, the softening parameter was enhanced by a characteristic length of micro-structure by means of a non-local theory. Attention was laid to the effect of a different characteristic length of micro-structure and initial bond-slip stiffness on the spacing of localized zones. 相似文献