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1.
对传统的超重、失重演示实验进行了改进,使弹簧秤的指针能静止在超重(或失重)的位置上,从而能准确地读出读数,提高演示效果. 相似文献
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区域经济的发展受许多不同因素的影响,本结合西藏社会经济发展的特点,选取了总产值指标、第一产业指标、第二产业指标和第三产业指标等四大类指标体系,采用灰色关联分析法对西藏的区域经济系统进行了简要的分析评价,以研究西藏区域经济的发展状况,从社会经济的角度探讨西藏经济发展落后的原因,以期能为西藏经济发展政策提供参考依据。 相似文献
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The ab initio molecular fragment approach is applied to a characterization study of the ground state of the zwitterion of glycine. Included among the properties studied are the — conformational energy surface, the electronic structure, and the magnitude and direction of the dipole moment. The results of the present study are compared to the results of other theoretical and experimental studies.This work was supported in part by the National Science Foundation, the University of Kansas, and the Upjohn Company, Kalamazoo, Michigan 49001.NSF Trainee (1969-1972).Alfred P. Sloan Research Fellow (1971–1973). 相似文献
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J. D. Petke Gerald M. Maggiora‡ Lester Shipman‡ Ralph E. CHRISTOFFERSEN‡ 《Photochemistry and photobiology》1979,30(2):203-223
Abstract— Ab initio configuration interaction wavefunctions and energies are reported for the ground state and many low-lying excited singlet and triplet states of ethyl pheophorbide a (Et-Pheo a) and ethyl chlorophyllide a (Et-Chl a), and are employed in an analysis of the electronic absorption spectra of these systems. In both molecules the visible spectrum is found to consist of transitions to the two lowest-lying 1(π, π*) states, S1 and S2. The configurational compositions of S1 and S2 in both molecules are similar, and are described qualitatively in terms of a four-orbital model. The S1← S0 transition in each case is predicted to be intense, and is largely in-plane y-polarized, while the S2← S0 transition is predicted to be extremely weak and in-plane polarized. The orientation of the S2← S0 transition dipole is not conclusively established in the present calculations. The Soret band in both molecules is composed of transitions to no less than ten states (S3-S12 in Et-Chl a and S3-S7S9-S12. and S14 in Et-Pheo a), which exhibit primarily (π, π*) character. The configurational compositions of these states are generally a complex mixture of excitations from both occupied macrocyclic π molecular orbitals and occupied orbitals with electron density in the cyclopen-tanone ring and the carbomethoxy chain. No clear correspondences are evident between respective Soret states of the two systems. Transitions to these states are generally intense and display a variety of in-plane polarizations. Two additional Soret states of Et-Pheo a, S8 and S13, exhibit primarily (n. π*) character. S8 is characterized by excitations from u and non-bonding regions of the carbomethoxy chain, while S13 is described by n →π* excitations involving the nitrogen atom of ring II. No corresponding (n, π*) states were found for Et-Chl a. In both molecules the lowest two triplet states, T1 and T2, are found to lie lower in energy than S1. while T, and S1 are approximately degenerate. The configurational compositions of T1-T4 of both molecules are nearly identical, and may be described by a four-orbital model. However, the compositions of T1-T4 differ sharply from those of S1 and S2. A number of higher-lying 3(π, π*) states of both molecules (T5-T13 in Et-Chi a and T8-T9, T11-T13 in Et-Pheo a) are found to have energies similar to the singlet Soret states, relative to S0. They are characterized by a complex mixture of configurations which do not include significant contributions involving the four-orbital model. In addition, two 3(n, π*) states of Et-Pheo a, T10 and T14, are found, which are somewhat analogous to S8 and S13. Additional data presented include the charge distributions and molecular dipole moments of the S0. S1, and T1 states of both molecules, as well as energies and oscillator strengths of computed Sn←S1 and Tn←1 transitions. 相似文献
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PHOTOINACTIVATION OF CATALASE 总被引:6,自引:0,他引:6
Abstract— Inactivation of catalase with visible light (>400nm) has been studied in purified bovine liver catalase and in peroxisomal catalase in the mitochondrial fraction of rat liver. Light corresponding to that of maximal absorbance of the heme site (405 nm) was most effective in inactivation. Although photoinactivation is O2 dependent, scavengers of OH radical, 1 O2 and O− 2 did not protect against loss of activity in either system. Superoxide dismutase partially protected purified catalase added into the mitochondrial fraction system. However, complete protection of catalase was afforded by low concentrations of substrates such as formic acid or methanol which rapidly convert Compound I to Ferricatalase. 相似文献
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用自制的带甲基侧基的环氧树脂(TMBP)作为界面增容剂, 从拉伸性能、键合胶含量、动态性能、扫描电镜和流变性能等方面, 研究了TMBP对炭黑在丁苯橡胶中分散度的影响, 并与市售通用双酚A型环氧树脂(E-51)和橡胶工业常用软化剂邻苯二甲酸二辛酯(DOP)进行了比较. 结果表明, 带甲基侧基的环氧树脂TMBP在提高炭黑分散性方面的效果远比E-51好, 其作用模式具有典型的增容特性. 相似文献
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Very recently, we[1] found that L-proline amides and dipeptides acted as efficient catalysts for the asymmetric direct aldol reaction. We report here that L-proline-based peptides 1~5 can catalyze the aldol reactions of hydroxyacetone with aldehydes 6 in aqueous media, to give 1,4-diols (7), the disfavored products with either aldolase or L-proline. Both peptides 3 and 4 give good results. 相似文献