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91.
图雅  白金亮  周群  孙素琴 《分析化学》2011,39(4):481-485
采用傅立叶变换红外光谱法并借助于二阶导数谱以及二维相关红外光谱(2D-FTIR)研究了蒙药草乌花原药材及不同溶剂提取物(依次采用乙醚,乙醇和水提取)所含化学成分的红外谱图整体变化规律.结果显示:在草乌花原药材中具有明显的多糖类化合物的红外特征吸收峰,证明该药材中含有大量多糖类成分.草乌花药材乙醚和醇提物的红外光谱较相似...  相似文献   
92.
Helium broadening coefficients for the R(10) and the P(2) lines in the ν3 band of 13CO2 have been measured over a large range of temperature (70 K-300 K). Helium pressure shifts for the R(10) line at several temperatures between 100 K and 300 K have also been determined. These measurements were obtained with a cold Herriott cell, using the collisional cooling technique to reach the lowest temperatures. They provide an extended dataset for the temperature dependence of widths and shifts. This dataset was compared to theoretical He-broadening coefficients combining quantum scattering calculations and the latest potential energy surface for the system He-CO2 from Korona et al. [T. Korona, R. Moszynski, F. Thibault, J.-M. Maunay, B. Bussery-Honvault, J. Boissoles, P.E.S. Wormer, J. Chem. Phys. 115 (2001) 3074-3084].  相似文献   
93.
A method of experimental determination of the Lorentz-factor tensor in uniaxial liquid crystals is suggested. The specific features of the local field tensor of the light wave in a nematic liquid crystal with low optical anisotropy have been investigated experimentally. Anisotropy of the local field and Lorentz-factor tensors has been found to decrease with the decreasing optical and molecular-optical anisotropies. These results appear to contradict the existing polarization theories of liquid crystals. The local field problem in cholesteric liquid crystals has been considered. A new approach to the local field problem in uniaxial liquid crystals with arbitrary optical anisotropy is developed and the experimental results are explained.  相似文献   
94.
Isosteviol (ent-16-ketobeyeran-19-oic acid, I) is a tetracyclic diterpenoid with a beyerane skeleton obtained by acid hydrolysis of stevioside.1 Several tetracyclic diterpenoids, specially the kaurenes, have important biological activities. Recent studies on the microbial transformation of isosteviol have revealed that it is metabolized by Cunninghamella bainieri, Actinoplanes sp., Mucor recurvatus, and Cunninghamella blackesleeana to yield five new metabolites.2 The hydroxylation pattern of these bioactive compounds may influence their binding on to the receptors, as was proposed for the Rabdosia diterpenoids. Therefore, the introduction of hydroxyl groups or unsaturated bonds in saturated and non-hydroxylated diterpenoids, like isosteviol, may enhance existing properties or lead to new biological activities. Although some beyeranes have been subjected to biotransformations by fungi,4 there are few report in the literature related the chemical transformation of Isosteviol. In the present study, we try to develop the chemical transformation of isosteviol and other beyeranes in order to obtaining some bioactive compounds with beyerane skeleton. Seven isosteviol derivatives, Ⅱ-Ⅷ, were therefore synthesized and characterized. The X-ray crystal strcture of H(R = H) was also determined.  相似文献   
95.
采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO2和SiO2薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明:3种基底中, 单晶硅基底上TiO2和SiO2薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO2薄膜折射率和透光率差异较大;SiO2薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。  相似文献   
96.
The derivative nonlinear Schrodinger equation for the low frequency circular polarized wave, propagating parallel to the bias magnetic field in a ferromagnetic system, is derived by the reductive perturbation expansion method.  相似文献   
97.
In this paper we generalize the definition of Levy flight (LF). With the help of a useful definition for the critical exponents of LF by introducing the concept of cutoff steplength, we calculate analytically the exponents of FDLFs in arbitrary d dimensions, utilizing the generating function method.  相似文献   
98.
The infrared spectrum of C3O2 was recorded with the vacuum Fourier transform interferometer of Laboratoire Aimé Cotton at a resolution of 0.005 cm?1. The ground state molecular constants were calculated from lower state combination relations in a simultaneous analysis of six ground state transitions situated in the region 3000 to 5000 cm?1. Through the analysis of a difference band we established that 70 is 60.7022 ± 0.0005 cm?1 above the ground vibrational state. Accurate molecular constants were also determined for this vibrational level.  相似文献   
99.
The absorption line parameters including self- and nitrogen-broadening coefficients of 17 H2O lines in the 10- to 15-μm spectral region have been measured using tunable diode laser techniques. Many of the H2O lines are pure rotational lines, and their line-widths exhibit the expected general narrowing trend as the rotational quantum number increases.  相似文献   
100.
程亚  陈建文 《物理学报》1995,44(10):1691-1696
将固体理论中的LLP变换用于研究自由电子激光场的量了态,并求得了小信号增益,这种新方法简捷且有助于深入地探讨自由电子激光场的量子特性. 关键词:  相似文献   
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