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11.
Three New Diarylpropanes from Dioscorea composita 总被引:1,自引:0,他引:1
ShunLiYANG XiKuiLIU 《中国化学快报》2005,16(1):57-60
Three new diarylpropanes were isolated from the dried rhizomes of Dioscorea composita Hemsl., and their structures were determined as 1, 3-bis-(2-hydroxy-4-methoxyphenyl) propane (1), 1, 3-bis-(2, 4-dihydroxyphenyl)propane (2), 1-(2′-hydroxy-4′-O-β-D- glucopymnosy-phenyl)-3-(2“, 4“-dihydroxyphenyl)propane (3), by spectroscopic analysis, respectively. 相似文献
12.
Hee Seok Choi Young Han Kim Shun Myung Shin 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2428-2439
An in‐line monitoring device using a quartz crystal resonator for thin film polymerization was proposed, and its performance has been evaluated by implementing in the UV polymerization of 2‐hydroxyethyl methacrylate with a photoinitiator of 1‐chloroanthraquinone. Because the variation of resonant resistance of the resonator is proportional to the square root of viscosity change that is closely related to the polymerization degree, the resistance can be used as a measure of the polymerization degree. The resistance measurements were compared with the outcome of instrumental analyses of polymerization degree using an FTIR spectrometer and a gel permeation chromatograph. The experimental results showed that the resistance measurements were consistent with the experimental outcome of the instrumental analyses, and this indicates the effectiveness of the proposed device. Owing to the simplicity and availability of the resonator system, its wide utilization in the monitoring of a variety of film polymerization processes, including photoresistor application, is expected. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2428–2439, 2006 相似文献
13.
初级产品生产行业有两大特点:一是其初级投资有较大的不可逆转性,二是其产品价格具有较大的随机性(不确定性)。这两点的同时存在,给进入和退出初级产品行业造成壁垒。 相似文献
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Machio Iwasaki Kazumi Toriyama Hachizo Muto Keichi Nunome 《Chemical physics letters》1976,39(1):90-94
The ESR spectra of X-irradiated (at 1.5 and 4.2 K) single crystals of n-decane-d22, n-decane-h22 and their mixtures have been measured at 1.5 and 4.2 K. It is concluded that almost all alkyl radicals are inherently formed in pairs in a fairly random fashion and that the spacial distribution of the radicals depends on the irradiation temperatures. In the crystal of n-decane-d22, a 1,3-carbon intrachain radical pair is identified together with a number of very close interchain pairs which are formed between almost all kinds of the first neighboring chains. The crystal of n-decane-h22 gives considerably larger spacial distribution of radicals, indicating a remarkable mass effect on the radical pair formation. 相似文献
17.
Shyh‐Jong Chen Cheng Chen Yaw‐Shun Hong 《International journal of quantum chemistry》2005,103(2):198-214
This investigation conducted reaction channels of weakly bound complexes CO2…HF, CO2…HF…NH3, CO2…HF…NH2CH3, CO2…HF…NH(CH3)2, and CO2…HF…N(CH3)3 systems, using the Gaussian 98 package at the B3LYP/6‐311++G(3df,2pd) level. The syn‐fluoroformic acid or syn‐fluoroformic acid plus NH3 or amine conformers are more stable than the related anti‐fluoroformic acid or anti‐fluoroformic acid plus NH3 or amine conformers. However, the above‐mentioned weakly bound complexes are more stable than both the related syn‐ and anti‐type fluoroformic acid or acid plus NH3 or amine conformers and their related decomposed into CO2 + HF or CO2 + NHR3F (R?H, CH3) combined molecular systems. Five reaction channels of the weakly bound complexes exist. Each channel includes weakly bound complexes and their related above‐mentioned systems. Moreover, each reaction channel contains two transition states. The transition state between the weakly bound complex and anti‐fluoroformic acid type structure (T13) is significantly higher than that of internal rotation (T23) between syn‐ and anti‐FCO2H (or FCO2H…NR3) structures. However, the above‐mentioned T13 can significantly decrease its energy by adding the third molecule NH3 or NR3 (R?H or CH3). The more CH3 that is substituted in NR3 of the reaction channel, the lower the activation energy of the transition state in the system is affected. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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用量子化学从头算方法(HF/6-31G)和密度泛函理论(DFT)的B3LYP方法,以6-31G标准基组加一个极化函数,对(ClAlNH)n(n=1-10)簇合物的几何构型,电子结构和红外光谱进行了优化,并讨论了聚合反应(ClAlNH)m→(ClAlNH)n的热力学效应,结果表明,(ClAlNH)n系列簇合物的基态稳定结构为Cs(n=1),D2h(n=2),D3h(n=3),Td(n=4),Cs(n=5),D3d(n=6),Cs(n=7),S4(n=8),D3h(n=9),C2h(n=10,n=2,4,6,8,10等偶数对应的(ClAlNH)n簇化合物的结构比n等于奇数量更稳定。 相似文献
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The evaluation of matrix elements of two electron atoms is fundamental for the study of the electronic properties of those systems. We add to this knowledge by presenting an explicit expression for the matrix elements of the inverse of the interelectronic distance of two-electron atoms in any spatial dimension D. The basis functions used are the D-dependent hydrogenic wavefunctions {1s
2,2p
2,3d
2,4f
2,5g
2,...,21y
2,...}, extending and including, in this way, the results of the previous basis set {1s
2,2p
2,3d
2,4f
2}. The methodology used does not employ Fourier integral transforms as in previous works but hypergeometric transformation formulas. 相似文献