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Coherent states via decoherence 总被引:1,自引:0,他引:1
25.
The molecular structure and properties of 7-azaindole in its first four singlet states were studied with a view to improving current understanding of the photophysical behavior of its C(2h) dimer. This dimer, which exhibits a double proton transfer via its two hydrogen bonds upon electronic excitation, has for 35 years been used as a model for the photophysical behavior of DNA base pairs. Electronic excitation of 7-azaindole simultaneously increases its acidity and basicity; these changes facilitate a concerted mechanism for the double proton transfer in the dimer. In this work, we found the acidity and basicity changes to occur only in its first pi,pi(*) excited singlet state. 相似文献
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27.
Ricardo H. M. Godoi Ana F. L. Godoi Anna Worobiec Sandro J. Andrade Johan de Hoog Mary R. Santiago-Silva Rene Van Grieken 《Mikrochimica acta》2004,145(1-4):53-56
Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, São Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world. 相似文献
28.
Eulogio Jimenez Luis Romani Maria Inmaculada Paz Andrade Geneviève Roux-Desgranges Jean-Pierre E. Grolier 《Journal of solution chemistry》1986,15(11):879-890
Molar excess volumes V
E
at 25°C have been determined by vibrating-tube densimetry, as a function of mole fraction x for different series of an alkanoate (H
2m+1
C
m
COOC
n
H
2n+1
)+cyclohexane. Three types of alkanoates were investigated, i.e., methanoates (m=0, with n=3 and 4), ethanoates (m=1, with n=2, 3, and 4) and propanoates (m=2, with n=1, 2, and 3). In addition, a Picker flow calorimeter was used to obtain molar excess heat capacities C
p
E
at constant pressure at the same temperature. V
E
is positive for all systems and rather symmetric, with V
E
(x=0.5) amounting to almost identical values in a series of mixtures containing an alkanoate isomer of same formula (say C4H8O2, C5H10O2, or C6H12O2). The composition dependence of C
p
E
is rather unusual in that two more or less marked minima are observed for most of the mixtures, especially when the alkanoate is a methanoate or an ethanoate. These results are discussed in terms of possible changes in conformation of both the ester and cyclohexane. 相似文献
29.
I. R. Bonilla P. da R. Andrade A. Bristoti 《Journal of Thermal Analysis and Calorimetry》1975,8(3):387-392
Dielectric constant measurements as a function of temperature and thermal analysis were performed in copper sulphate pentahydrate and sodium nitrite to study the nature of the decomposition reactions. The application of these combined techniques to the study of several possible mechanisms of thermal decomposition is advanced. 相似文献
30.
The conditional solubility of scheelite CaWO4 in molten NaCl?KCl (1:1) has been studied either in oxobasic or oxoacidic media. In the former case it is increased by formation of sparingly soluble CaO according to:Ca2+ + O2CaO(s), pKsCaO = 10800/T ? 5.8 (molality scale) In the later case, WO42- behaves as an oxobase according to the following equilibria:WO42?WO3 (s) + O2? pK0 = 10.0 at 1000 K3 WO42?W3O102? pK3 = 12.7 at 1000KThe latter equilibrium favours an increase in the WVI solubility when pO2- is increased, for instance by injection of HCl. The whole set of results has been summarized by a conditional solubility diagram of scheelite versus pO2-. 相似文献