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高碘酸钠氧化法测定肌醇含量 总被引:5,自引:0,他引:5
高碘酸钠氧化法测定肌醇含量张楚富,林清华,梁会(武汉大学生命科学学院武汉430072)王泽胜(湖南兰龙科技实业公司长沙410006)关键词植酸钙,肌醇,高碘酸钠氧化法分类号Q508肌醇是一种环己六醇,它以植酸盐的形式主要存在于米糠和其他油料作物种子中... 相似文献
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Shi Xunqing Wang Zhiping John HL Pang Zhang Xueren Nie Jingxu 《Acta Mechanica Sinica》2002,18(3):274-287
In this study, a new unified creep constitutive relation and a modified energy-based fatigue model have been established respectively
to describe the creep flow and predict the fatigue life of Sn−Pb solders. It is found that the relation successfully elucidates
the creep mechanism related to current constitutive relations. The model can be used to describe the temperature and frequency
dependent low cycle fatigue behavior of the solder. The relation and the model are further employed in part II to develop
the numerical simulation approach for the long-term reliability assessment of the plastic ball grid array (BGA) assembly.
The project supported by the National Natural Science Foundation of China (59705008) 相似文献
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介绍一种应用电光晶体补偿位相测量微小位移的方法,着重分析其测量精度,并应用这种方法校正压电陶瓷的线性,精度优于1%波长。 相似文献
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The absorption spectra of the charge-transfer complexes of sym-tetracyanobenzene (TCNB) with phenanthrene, 9-bromophenanthrene, and 9,10-dibromophenanthrene are measured in chloroform solutions at room temperature. The total emission and phosphorescence spectra of the donors and the complexes are measured at 77 K in rigid glasses. The phosphorescence decay lifetimes are determined for phenanthrene, TCNB, and for the phenanthrene-TCNB complex, and a decrease in the phenanthrene-TCNB complex lifetime relative to the lifetimes of the two components is observed. The luminescence spectra of the complexes exhibit both a red shift and a lack of structure as compared with the donor spectra. The results are interpreted, in agreement with the results of Iwata et al. for the phenanthrene-TCNB complex (1), as an indication that there is a considerable degree of charge-transfer character in the lowest triplet state (T1). Bromine substitution leads to a decrease in the energy of the phenanthrene triplet state. As a result, the energy gap between the donor molecule triplet state and the complex charge-transfer triplet state decreases from phenanthrene, to 9-bromophenanthrene, to 9,10-dibromophenanthrene. The results suggest that the proximity of these two triplet states in 9,10-dibromophenanthrene and its charge-transfer complex leads to some local donor triplet state character in the emitting complex triplet state. 相似文献
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Roderick E. Wasylishen Kalvin Chum John Bukata 《Magnetic resonance in chemistry : MRC》1977,9(8):473-476
Carbon-13, proton coupling constants have been measured in eighteen different 2-substituted propanes. 1J(C-2,H) shows variations similar to those observed previously for monosubstituted methanes. 2J(C-2,H) is essentially independent of the substituent at C-2, while 2J(C-1,H) varies over a range of at least 5 Hz. The latter coupling constant becomes more positive as the electronegativity of the substituent increases while 3J(CH) decreases as the electronegativity of the substituent increases. The observed trends in nJ(CH) are compared with those calculated using semi-empirical molecular orbital theory at the INDO level of approximation. 相似文献
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The precise quantitative analysis of biomass sugars is a very important step in the conversion of biomass feedstocks to fuels
and chemicals. However, the most accurate method of biomass sugar analysis is based on the gas chromatography analysis of
derivatized sugars either as alditol acetates or trimethylsilanes. The derivatization method is time consuming but the alternative
high-performance liquid chromatography (HPLC) method cannot resolve most sugars found in biomass hydrolysates. We have demonstrated
for the first time that by careful manipulation of the HPLC mobile phase, biomass monomeric sugars (arabinose, xylose, fructose,
glucose, mannose, and galactose) can be analyzed quantitatively and there is excellent baseline resolution of all the sugars.
This method was demonstrated for standard sugars, pretreated corn stover liquid and solid fractions. Our method can also be
used to analyze dimeric sugars (cellobiose and sucrose). 相似文献
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Zuo Z Gang C Zou H Mok PC Zhu W Chen K Jiang H 《Computational Biology and Chemistry》2007,31(3):186-195
Beta-secretase is a potential target for inhibitory drugs against Alzheimer's disease as it cleaves amyloid precursor protein (APP) to form insoluble amyloid plaques and vascular deposits in the brain. Beta-secretase is matured from its precursor protein, called beta-secretase zymogen, which, different from most of other zymogens, is also partially active in cleaving APP. Hence, it is important to study on the mechanism of the zymogen's activation process. This study was to model the 3-D structure of the zymogen, followed by intensive molecular dynamics (MD) simulations to identify the most probable 3-D model and to study the dynamic structural behavior of the zymogen for understanding the effects of pro-segment on the function of the enzyme. The results revealed that the dropping in catalytic activity of the beta-secretase zymogen could be attributed to the occupation of the entrance of the catalytic site of the zymogen by its pro-segment. On the other hand, the partial catalytic activity of the zymogen could be explained by high fluctuation of the pro-segment in comparison with that of other zymogens, resulting in the occasionally exposure of the catalytic site for access its substrate APP. Indeed, steered MD (SMD) simulation revealed a weak pulling force at quasi-equilibrium state for the pro-segment of the zymogen leaving from the entrance, indicating that this swinging process could take place spontaneously. Furthermore, MM-PBSA calculation revealed a small change of free energy of 10.56 kal/mol between the initial and final states of the process of pro-segment swung outside the binding pocket of beta-secretase zymogen. These results not only account for the partial catalytic activity of beta-secretase zymogen, but also provide useful clues for discovering new potent ligands, as new type of drug leads for curing Alzheimer's disease, to prevent the pro-segment of the zymogen from leaving its catalytic site. 相似文献