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151.
Julia Pérez-Iglesias Hervilia M. Seco-Lago Jesús M. Castro-Romero José M. Fernández-Solis Victoria González-Rodríguez 《The Chemical Educator》2000,5(1):27-30
Spectrophotometry is an analytical technique that is studied at the university level because of its ease of operation and low expense. Three different experimental methods of gradual difficulty are proposed for the application of this technique to the simultaneous determination of two metals. The techniques are applicable to the practice of all subdisciplines of experimental chemistry. These techniques are (1) absorption spectrophotometry, the determination of cobalt (II) and copper (II); (2) first-derivative spectrophotometry, the determination of chromium (III) and copper (II); and (3) first-derivative spectrophotometry using the zero-crossing method, the determination of copper (II) and mercury (II). 相似文献
152.
This article focuses on two issues related to educational opportunity: (1) the relationship between risk-taking behavior and mathematics performance, and (2) whether there are gender differences in risk-taking behavior. From a review of literature it was concluded that students who are greater risk-takers perform better on mathematics tests and that males are greater risk-takers than females. It follows, therefore, that males perform better on mathematics tests in which risk-taking plays a role. It was further concluded that these differences effect the opportunities that girls are afforded in their desires to attend college, the availablitity of scholarships, and their self-confidence in mathematics. 相似文献
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154.
Theresa Julia Zielinski 《International journal of quantum chemistry》1982,22(3):639-647
Ab initio molecular orbital calculations with an STO -3G basis have been performed to investigate the energetics and electronic properties of some 5-substituted uracils and their 4-OH tautomer forms with R including F, CH3, and OMe. In all cases, the diketo form is more stable. An excellent linear correlation between the calculated and experimental ionization potentials was found. 相似文献
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156.
Julia Mueller 《Journal of Number Theory》1982,14(3):327-331
Let 0 < γ1 ≤ γ2 ≤ … be the imaginary part of the zeros, and . Assuming the Riemann hypothesis, it is known that μ ≤ 0.68 and λ > 1. One suspects that μ = 0 and λ = +∞. The object of this note is to show that λ ≥ 1.9. 相似文献
157.
An iterative analysis of the PMR spectrum of the title compound was performed and the calculated values of spectral parameters, relative chemical shifts, proton-proton and direct carbon-proton couplings are compared with those of pyridine. 相似文献
158.
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160.
The molecular structures and the electronic spectra of the geometric isomers of a model carotenoid polyene, 6,11-dimethylhexadecaheptaene, were calculated. It was concluded that solvent effects and conformational isomerization must be taken into account in order to satisfactorily explain the observed spectra. Molecular structures were calculated using molecular mechanics (MM2), and electronic spectra using the VESCF-MO-CI method including all singly-excited configurations. A method based on the calculated and observed spectra of simple linear polyenes was devised to estimate the solvent effects. 相似文献