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991.
Two series of novel tolane-type liquid crystals(LCs) comprising of hydrogen-bonded organic acids were synthesized.The formation of dimerized H-bond LCs was confirmed by IR spectroscopy,and mesomorphic properties of the LCs were investigated by differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).It was found that the end groups of the liquid crystals as well as the unsaturated rigid core had effect on the mesomorphic properties. 相似文献
992.
Yao Yun Hu Jing Mei Yin Da Bin Gao Ying Ping Jia Guang Yun Zhou Ying Na Cui Shen Min Li 《中国化学快报》2008,19(5):529-532
Photopromoted carbonylation of 1-bromo-6-chlorohexane with CO catalyzed by CuBr2 and CdI2 has been carried out under ambient conditions. The results indicate that the carbonylation proceeds with the major product of chloroester ClCH2(CH2)5COOCH3 under catalysis of CuBr2. Furthermore, the activity of the carbonylation can be improved by addition of basic additives (NaOAc, Na3PO4 or (n-C4H9)3N). Among these additives, (n-C4H9)3N is the most efficient in terms of the yield of ClCH2(CH2)5COOCH3. However, the methoxycarbonyl substituting chlorine product of BrCH2(CH2)5COOCH3 is not obtained in the presence of CdI2. This is quite different from the carbonylation of monochloroalkane. 相似文献
993.
994.
Retention Behaviors of Uronic Acid-containing Polysaccharides and Neutral Polysaccharides in HPGPC 总被引:2,自引:0,他引:2
Cui Ping LIU Xing Feng BAO Ji Nian FANG* Shanghai Institute of Materia Medica Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 《中国化学快报》2001,(10)
The determination of molecular weights (Mw) of polysaccharides has served as an important process since the physical properties of the polysaccharides are closely related to their Mw and/or molecular weights distribution (MWD). For Mw and MWD determinations, high performance gel permeation chromatography (HPGPC) has gained wide acceptance as a preferred method due to its high sensitivity, speed and reproducibility. In chromatography, it is well known that the molecular weights are determ… 相似文献
995.
996.
Lian Peng Tong ;Jing Nan Cui ;Wei Min Ren ;Xing Yong Wang ;Xu Hong Qian 《中国化学快报》2008,19(10):1179-1182
Regio- and enantioselective reduction of substituted acenaphthenequinones were conducted under mild reaction conditions using plant enzymatic systems. A screening of 15 plants allowed the selection of two suitable plants fulfilling enantiocomple- mentarity. The (+)- and (-)-mono hydroxyacenaphthenones were achieved with high conversion and good enantiomeric purity using peach (Prunus persica (L.) Batsch., conversion 98%, 71% ee) and carrot (Daucus carota L., conversion 95%, 81% ee), respectively. 相似文献
997.
In this study, one kind of lithium aluminosilicate-β-quartz glass-ceramic containing Na2O has been chosen, which can be used for low-temperature bonding with a higher bonding rate for the manufacture of microelectronic mechanical systems. The microstructure of the glass-ceramic is analyzed by transmission electron microscopy, high resolution transmission electron microscopy, selected-area diffraction, energy dispersive spectrometry and X-ray diffraction. The influence of the heat treatment process of the glass on the properties and the microstructure of the glass-ceramics is discussed. The microstructure of the glass-ceramic has the continuous glassy region with higher alkali metal ion content, which benefits the low-temperature anodic bonding. 相似文献
998.
Let U be a multiply-connected fixed attracting Fatou domain of a rational map f.We prove that there exist a rational map g and a completely invariant Fatou domain V of g such that(f,U) and(g,V) are holomorphically conjugate,and each non-trivial Julia component of g is a quasi-circle which bounds an eventually superattracting Fatou domain of g containing at most one postcritical point of g.Moreover,g is unique up to a holomorphic conjugation. 相似文献
999.
For neural networks with all the parameters unknown, we focus on the global robust synchronization between two coupled neural networks with time-varying delay that are linearly and unidirectionally coupled. First, we use Lyapunov functionals to establish general theoretical conditions for designing the coupling matrix. Neither symmetry nor negative (positive) definiteness of the coupling matrix are required; under less restrictive conditions, the two coupled chaotic neural networks can achieve global robust synchronization regardless of their initial states. Second, by employing the invariance principle of functional differential equations, a simple, analytical, and rigorous adaptive feedback scheme is proposed for the robust synchronization of almost all kinds of coupled neural networks with time-varying delay based on the parameter identification of uncertain delayed neural networks. Finally, numerical simulations validate the effectiveness and feasibility of the proposed technique. 相似文献
1000.
Let A be a standard operator algebra on a complex Hilbert space H of dimension greater than 2. By invariants of certain functional values of operator products, we characterize some surjective maps on A. Furthermore, several kinds of general preserver problems on standard operator algebras are solved when we take respectively the functional as, for example, k-numerical radius (k?1), operator norm, Ky Fan k-norm, Schatten p-norm (1?p<∞), and so on. 相似文献