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221.
Molecular structures of the isolated tetrahedral oxovanadium(IV) and bridged μ-oxo-divanadium(IV) complexes hosted by the
clusters mimicking surfaces of amorphous silica-based materials were investigated using density functional theory (DFT) calculations.
Principal values of the g and A tensors for the monomer vanadyl species were obtained using the coupled-perturbed DFT level of theory and the spin–orbit
mean-field approximation (SOMF). Magnetic exchange interaction for the μ-oxo bridged vanadium(IV) dimer was investigated within
the broken symmetry approach. An antiferromagnetic coupling of the individual magnetic moments of the vanadium(IV) centers
in the [VO–O–VO]2+ bridges was revealed and discussed in detail. The coupling explains pronounced decrease of the electron paramagnetic resonance
signal (EPR) intensity, observed for the reduced VO
x
/SiO2 samples with the increasing coverage of vanadia, in terms of transformation of the paramagnetic monomer species into the
dimers with S = 0 ground state. 相似文献
222.
Zbigniew Florjaczyk Wodzimierz Krawiec Wadysaw Wieczorek Maciej Siekierski 《Journal of Polymer Science.Polymer Physics》1995,33(4):629-635
The conducting properties of solid electrolytes comprising random poly(ethylene oxide-co-propylene oxide) (of 84 : 16 monomer units mole ratio) and lithium, sodium, potassium, cesium, and rubidium salts have been studied. The systems containing some lithium or sodium salts achieved conductivity levels as high as 10?5–10?4 S/cm at ambient temperature and greater than 10?3 S/cm at 100°C. However, the systems with rubidium and cesium salts exhibit conductivities a few orders of magnitude smaller. DSC studies show that the electrolytes studied are characterized by a high content of an amorphous phase (95–100%). It is suggested that the copolymer exhibits lower complexing abilities than that of poly(ethylene oxide), which results in a higher flexibility of electrolytes containing small cations and poor dissociation of the salts having large cations. © 1995 John Wiley & Sons, Inc. 相似文献
223.
Zbigniew Binderman 《Mathematische Nachrichten》1993,161(1):239-252
In this paper, shifts for a right invertible operator D induced by an analytic function acting in a linear complete metric space are considered. The case when these shifts coincide with the operator - valued function on a set which contains the set of all D-polynomials and the set of all exponentials is studied. It is shown that in this case these shifts are R-shifts and D-shifts (cf. [1], [10]). 相似文献
224.
225.
Infrared spectra of perchlorate, halide and nitrate solutions in acetone are studied. The CO and CCC band frequency changes are discussed in terms of the electronic structure of acetone molecules complexed with cation and anion. The correlation between the shift of the CO and CCC bands and the reactivity of acetone molecules in aldolic condensation reaction is given. An explanation of the anion effect in aldolic condensation is proposed. 相似文献
226.
The tensor of the hole drift mobility is determined in monoclinic tetracyanoethylene by the transient photoconductivity technique. The principal tensor components amount to μ1 = 0.21, μ2 = 0.10 and μ3 = 0.15 cm2/V s at room temperature. Above 250 K the mobility is a decreasing function of temperature and follows an exp(E/kT) dependence (E = 0.08 eV) which is inconsistent with both band and hopping models. Below 250 K the mobility is controlled by a hole trapping level of 0.28 eV deep. The photogeneration efficiency is found to be independent of temperature and proportional to the light intensity. 相似文献
227.
Janusz Jurczak Andrzej Konowal Zbigniew Krawczyk Andrzej Ejchart 《Magnetic resonance in chemistry : MRC》1981,15(2):193-196
The diastereomeric differences (Δδ) were measured by 13C NMR spectroscopy for a series of 11 (?)-ω-camphanic esters of secondary alcohols of known absolute configuration. This method cannot be used for the determination of the absolute configuration, but it can be applied to the estimation of the enantiomeric purity of chiral alcohols. 相似文献
228.
Zbigniew Lonc 《Journal of Graph Theory》1988,12(2):295-303
A partition of the edge set of a graph H into subsets inducing graphs H1,…,Hs isomorphic to a graph G is said to be a G-decomposition of H. A G-decomposition of H is resolvable if the set {H1,…,Hs} can be partitioned into subsets, called resolution classes, such that each vertex of H occurs precisely once in each resolution class. We prove that for every graceful tree T of odd order the obvious necessary conditions for the existence of a resolvable T-decomposition of a complete graph are asymptotically sufficient. This generalizes the results of Horton and Huang concerning paths and stars. 相似文献
229.
230.
A mechanism is proposed for the reaction of gamma-butyrolactone with the potassium anion as a two-electron-transfer reagent. Potassium hydride and potassium 4-potassiobutyrate are formed in this process as intermediates. These compounds deprotonate gamma-butyrolactone. Potassium lactone enolate, potassium butyrate, and hydrogen are the final reaction products. 相似文献