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1.
W. Jaegermann T. Sakata E. Janata H. Tributsch 《Journal of Electroanalytical Chemistry》1985,189(1):65-84
Laser-pulse transient measurements have been performed at single crystalline n-PtS2 electrodes with the aim of understanding light-induced hydroxide, oxide and oxygen formation. Different detected time constants permit the identification of distinct reaction products. They form surface states which function both as centers for recombination and charge accumulation in the interface. The rate constants determined are influenced by the RC-constant of the measuring circuit and can be interpreted only qualitatively. In the presence of recombination processes time constants faster than RLCSC are found. Evidence is given that the reaction step leading to oxygen evolution is dependent on the building-up of an electric field in the Helmholtz layer. This result may be of importance for the development of materials for the photoelectrolysis of water. 相似文献
2.
Hiizu Iwamura Hiroshi Kihara Soichi Misumi Yoshiteru Sakata Teruo Umemoto 《Tetrahedron》1978,34(23):3427-3434
Various modes of the out-of-plane deformation of a benzene ring have been examined theoretically the MINDO/2 methods. Deformation to the boat conformation is predicted to be more facile than that to the half-boat or the chair conformation as observed in triple-layered[2.2]-metacyclophanes. The energy partitioning analysis reveals that a minimal loss of resonance energy at the gunwale of benzene boats appears to be responsible for the ease of boat deformations. The out-of-plane bending of the H atom at the bow of die benzene boats is coupled to the displacement of the H at the gunwale in such a way that the torsion of the bond between the bow and gunwale C atoms may be kept as small as possible. 相似文献
3.
Junjie Chai Na Lei Ying LiPeng Xia 《Journal of Computational and Applied Mathematics》2011,235(10):3207-3214
Multivariate Birkhoff interpolation problem has many important applications, such as in finite element method. In this paper two algorithms are given to compute the basis of the minimal interpolation space and the lower interpolation space respectively for an arbitrary given node set and the corresponding interpolation conditions on each node. We can get the monomial basis, Newton-type basis as well as Lagrange-type basis. The interpolation polynomial can be derived from the basis directly. 相似文献
4.
Alexandre M. de Bettencourt Maria Filomena Duarte Maria Helena Florêncio Fernando F. Henriques Paulo A. Madeira Maria Inês Portela Luis Filipe Vilas-Boas 《Microchemical Journal》2011,99(2):218-234
Arsenic is a type 1 carcinogen and its toxicity is critically dependent on chemical speciation. However, after decades of research, the biogenesis of at least fifty naturally occurring arsenic species is still not well understood.Here, based on experimental work, it is proposed a set of pathways for the formation of multiple arsenic species that might help to clarify the present situation.These are focused on the thiol protein arsenic bond and on its interaction with reactive metabolites. In fact, arsenic bound to glutathione interacting with sulfur adenosyl methionine (SAM), MethylCB12 and AdoCB12, forms a number of complexes that might be key intermediates in arsenic biochemistry. These include dimethylarsino glutathione (DMAG) m/z 412 [M + H]+, synthesized non-enzymatically from glutathione and cacodylate. Trimethylarsonio glutathione (TMAG) m/z 426 [M]+ synthesized from DMA, GSH and SAM, apparently by a classical Challenger methylcarbonium attack. Tetramethyl arsonium ion m/z 135 [M]+ is formed in a third step, apparently by carbanion methylation. The presence of trimethylarsine oxide (TMAO) m/z 137 [M + H]+ is attributed to the hydrolysis of TMAG or TMA, or to carbanion methylation of dimethylarsinoyl glutathione (m/z 428 [M]+) formed from cacodylate and GSH. Cantoni type attacks of DMAG on SAM were unsuccessful, eventually due to competition of the trivalent S+ atom of SAM for the AsIII atom attack. The presence of dimethylarsonio diglutathione (DMADG m/z 717 [M]+), is suggested to result from a GS- attack on dimethylarsenoyl glutathione (m/z 428 [M + H]+). The presence of dimethylarsenoyladenosine (m/z 372 [M + H]+), trimethylarsenosugar adenine (m/z 370 [M]+), and dimethylthioarsenosugar adenine (m/z 388 [M + H]+), is explained by the synthesis of the pecursor dimethylarsonio-adenosine glutathione DMAAG (m/z 661 [M]+), a likely source of oxo-and trimethylated arsenosugars, as well as of thio-arsenosugars by the cleavage of its S-C bond. The results gathered suggest that cell vacuoles might play a major role in arsenic metabolism, and that the dominance of oxo-As sugars, in algae extracts, may be supported by a mechanism of synthesis independent of DMAAG (m/z 661).They also offer an explanation for the reason why arsenobetaine, and tetramethylarsonium are loosely bound to biotic tissues. Four arsenic species new to science, to the best of our knowledge, and a number of known arsenic compounds were synthesized in this work, identified by HPLC–ESI-MSn and FTICR–ESI-MS, and suggestions regarding their mechanisms of synthesis were advanced. These results provide a framework for arsenic biochemistry which may explain the origin of a significant part of arsenic known metabolites. 相似文献
5.
Y. Achiba T. Yamazaki K. Kimura 《Journal of Electron Spectroscopy and Related Phenomena》1981,22(2):187-190
Angle-resolved photoelectron spectroscopy (ARPES) is now a sophisticated and particularly powerful technique for studying the electronic structure of matter; in addition, the photoelectric effect has been of great significance in the history of 20th-century physics. This article seeks to uncover the origins and chart the development of the ARPES field, and focuses on the first half of this century; that is, up to the beginnings of the modern phase in the late 1960's. It is suggested that present workers will find interest in, and indeed profit from a knowledge of, the enormous experimental effort that was made to acquire quality data, the frustrating attempts that were initially made to understand them theoretically, and the contribution of early wave-mechanics, which brought order to a troubled field and thereby provided the necessary foundation for current studies. In addition, it is noted that the physicists involved often obtained inspiration and important insights which led them into studies of other significant problems of 20th-century physics. 相似文献
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7.
In this paper, under the condition of two pairs of strict lower and upper solutions and using the concept of (e1,B)-limit increasing operator, some multiplicity results for an operator equation are obtained by the method of the fixed point index. 相似文献
8.
A. P. Kombarov 《Journal of Mathematical Sciences》2005,131(4):5738-5764
Topological properties similar to normality are considered in subspaces of products and powers of topological spaces, of spaces
of closed subsets, and of spaces having the form
(X), where
is a normal functor.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 9, No. 2, pp. 57–98, 2003. 相似文献
9.
Celso Pesco Elvio Antonio de Campos Creusa Maieru Macedo Costa 《Mikrochimica acta》1997,127(3-4):229-232
Silica gel was chemically modified with anN-acyl-N-benzoylthiourea group. This material behaved as a selective means of preconcentrating Cu(II), Zn(II) and Cd(II) from ethanol by the column technique. Ethanolic solutions having 6 mol of the metal ions were percolated through the column and retentions of 100% were achieved for all metals. Zinc and copper were eluted quantitatively from the column bed with 5mL of ethanolic O.1molL–1 (for Zn) and 0.9 mol L–1 (for Cu) citric acid. Cadmium was recovered totally with 60 mL of ethanolic 2.0 mol L–1 citric acid. The modified silica was shown to be chemically stable after various adsorption-elution cycles (at least twenty). 相似文献
10.
Iwao Ohmine 《Chemical physics letters》1980,72(1):53-58
A simplified method to calculate the excitation spectra of π-electron systems is proposed. The method is based on the assumption that a “cluster” approximation can be applied to excited states. It is demonstrated that, for the low-lying triplet and optically allowed states of butadiene, hexatriene and benzene, the method yields good agreement with complete CI calculations in the Pariser–Pan–Pople approximation. 相似文献