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101.
A. I. Smirnova N. V. Zharnikova B. Donnio D. V. Brus 《Russian Journal of General Chemistry》2010,80(7):1331-1340
Several series of new tetracatenar mesogens consisting of a five-ring aromatic core and bearing one or more apolar lateral
substituents in the central benzene ring of the molecule have been synthesized and their mesomorphism is characterized by
polarization microscopy, differential scanning calorimetry, and X-ray diffraction methods. Introduction of one, two, or four
methyl groups into these tetracatenar mesogens destabilized columnar organization typical of the long-chain homologs, but
did not suppress smectic C and nematic phases. Introduction of larger substituents did, however, suppress lamellar organization
(C15H31) or mesomorphism (tert-butyl) totally. 相似文献
102.
反相高效液相色谱法对秦岭21种蕨类植物中槲皮素与山柰酚含量的测定 总被引:2,自引:0,他引:2
运用反相高效液相色谱(RP/HPLC)法对21种蕨类植物中槲皮素、山柰酚的含量进行测定。使用Shimadzu C18(250 mm×4.6 mm,5μm)色谱柱,以甲醇-水溶液为流动相进行等度洗脱,流速1.0 mL/min,检测波长360 nm,进样量20μL,柱温28℃。各对照品的质量浓度与色谱峰面积线性关系良好,具有较好的精确度和重复性,槲皮素、山柰酚的加标回收率分别为93%和95%。采用该方法分别对采自秦岭的21种蕨类植物的地上和地下部分进行测定,地上部分有19种含槲皮素、15种含山柰酚,其中毡毛石韦中槲皮素含量最高(2.11 mg/g),蜈蚣草中山柰酚含量最高(19.80 mg/g);而地下部分除有边瓦韦、大瓦韦含槲皮素(含量分别为0.11、0.12 mg/g)外,其余根状茎中几乎没有这两种黄酮类化合物;表明槲皮素与山柰酚在蕨类植物的地上部分广泛存在。 相似文献
103.
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106.
大尺度光学列阵的成像特性 总被引:2,自引:1,他引:1
本文由光线光学理论出发,分析了无单元像差的光学元件大尺度列阵的成像特性,得到了较傍轴近似更普适的成像特性变换矩阵,其结果包含了列阵的傍轴近似成像理论.并进一步证明了大尺度平面列阵的成像特性只具有近似的准相位共轭特性,且只有在傍轴近似下才是较完善的准相位共轭成像.该结论与以往理论相比更接近实际,且能更好地解释迄今为止所观察到的实验结果及本文的实验结果. 相似文献
107.
The temporal evolution of fluorescence from isolated single-wall carbon nanotubes (SWNTs) has been investigated using optical Kerr gating. The fluorescence emission is found to decay on a time scale of 10 ps. This fast relaxation arises from nonradiative processes, the existence of which explains the relatively low observed fluorescence efficiency in isolated SWNTs. From the measured decay rate and a determination of fluorescence quantum efficiency, we deduce a radiative lifetime of 110 ns. 相似文献
108.
设a,b是不同的正整数,本文证明了当max(a,b)>10126时,Pell方程组x2-ay2=1和z2-by2=1至多有2组正整数解(x,y,z). 相似文献
109.
Theoretical calculation and analysis of (13)C-{(1)H} dipolar spectra of small-size spin clusters is presented. Dipolar spectra simulated using the time-independent average Hamiltonian are compared with the dipolar profiles obtained by 2D and 3D (1)H-(13)C correlation experiments employing Lee-Goldburg off-resonance cross-polarization (LG-CP). It is demonstrated that the structural parameters such as interatomic distances as well as mutual orientation of internuclear vectors can be derived from the dipolar profiles of simple spin clusters. Simplified analysis of the dipolar spectra based on isolated-like spin-pair approach can be used only if interacting spin cluster is reduced to the three-spin system in which the angle between both internuclear vectors ranges from 45 degrees to 135 degrees . For other local arrangements of spin systems the produced dipolar spectra must be analyzed with high caution. Contributions of all interacting spins to dipolar evolution of (13)C magnetization are mutually mixed and cannot be easily separated. However, simplification of the dipolar spectra is achieved by selective excitation. Enhanced selectivity of LG-CP transfer due to the initial (1)H chemical-shift-evolution period makes it possible to construct the dipolar spectra from (1)H-(13)C cross-peak intensities for every detected (1)H-(13)C spin-pair. Consequently, isolated-like spin pair evolution of the detected (1)H-(13)C coherence dominates to the resulting dipolar profile, while the influence of other interacting spins is suppressed. However, this suppression is not quite complete and analysis of the selective dipolar spectra based on isolated-like spin-pair approach cannot be used generally. Especially evolution of long-range (1)H-(13)C coherence is still significantly affected by spin states of other coupled hydrogen atoms. 相似文献
110.
WANG Yue BI Xiao-Jun CUI Shu-Wang DING Lin-Kai DAN Zeng-Luo-Bu DING Xiao-Hong FAN Chao FENG Cun-Feng FENG Zhao-Yang FENG Zhen-Yong GAO Xiao-Yu GENG Qing-Xi GUO Hong-Wei HE Hui-Hai HE Mao HU Hai-Bing HU Hong-Bo HUANG Qing JIA Huan-Yu LA Ba-Ci-Ren LE Gui-Ming LI Ai-Feng LI Jin-Yu LOU Yu-Qing LU Hong LU Sui-Ling MENG Xian-Ru MU Jun REN Jing-Ru TAN You-Heng WANG Bo WANG Hui WANG Yong-Gang WU Han-Rong XUE Liang YANG Xian-Chu YE Zong-Hai YU Guang-Ce YUAN Ai-Fang ZHANG Hui-Min ZHANG Ji-Long ZHANG Nai-Jian ZHANG Xue-Yao ZHANG Yong ZHANG Yi ZHA Xi-Sang-Zhu ZHOU Xun-Xiu YUAN Qiang 《中国物理C(英文版)》2008,32(11)
Using the data taken from Tibet Ⅱ High Density (HD) Array (1997 February--1999 September) and Tibet-Ⅲ array (1999 November--2005 November), our previous northern sky survey for TeV γ-ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0° to 60.0° in declination (Dec) range, no new TeV γ-ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV T-ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits. 相似文献