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991.
In this text, we use inexpensive and natural amino acid, successfully obtained the asymmetric crystallization of three PTCs, [Tis(O~iPr)_(14)(μ_2-O)(μ_3-O)_2(D/L-pGlu)_2](D-PTC-53; L-PTC-53; H2 pGlu=pyroglutamic acid) and [Ti_6(O~iPr)_(14)(μ_2-O)(μ_3-O)_2(D-pGlu)_2][Ti_6(O~iPr)_(14)((μ_2-O)(μ_3-O)_2(L-pGlu)_2](D,L-PTC-53). Interestingly, in situ lactamide reaction starting from glutamic acid to pyroglutamic acid was observed. In addition,the chirality features of these PTCs have been thoroughly discussed.The two enantiomers crys tallize in chiral P21 space group.The optically pure pGlu ligands transform its chirality to the inorganic titanium oxo clusters. As a result, the stack of these inorganic clusters generates homochiral helical chains along the characteristic axial direction.Apart from the microscopic structural analysis, the macroscopic solid-state samples exhibit unusual strong circular dichroism(CD) signals,further verified the homochiral feature of the enantiomers. 相似文献
992.
Rotaxane is a kind of classic supramolecule, which is usually constructed from a number of macrocycles and one axis molecule. Herein, we have expanded the supramolecular structure of [n]rotaxane to offer a precise definition of (pseudo)[n,m]rotaxane for accurately describing the two kinds of (pseudo)rotaxanes structures, which are self‐assembled from cucurbit[7/8]uril (CB[7/8]) and viologen‐naphthalene derivative, respectively. Furthermore, these CB‐based pseudorotaxanes exhibit varied photophysical properties, stimuli‐responsive behavior triggered by competitive guest, and self‐sorting behavior. 相似文献
993.
994.
反应性复合乳液的合成、表征及其交联反应 总被引:1,自引:0,他引:1
利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa. 相似文献
995.
IntroductionMicellarelectrokineticchromatography (MEKC)wasinventedtoextendtheutilityofcapillaryelectrophoresis(CE)andpermittedtheseparationandanalysisofneutralcompounds .ButjustlikeothermodesofCE ,MEKCarehamperedbythelowconcentrationsensitivityoftheultra … 相似文献
996.
Xin Yang Chuan Dong Jun Zhang Yan-sheng Wei Wei-Jun Jin Chang-song Liu 《Microchemical Journal》1997,57(3):294-304
Six polycyclic aromatic hydrocarbons (PAHs) are studied by chemical deoxygenation microemulsion-stabilized room temperature phosphorimetry with sodium sulfite as an oxygen scavenger and thallous nitrate as a heavy atom perturber in sodium dodecyl sulfate medium. Several factors influencing room temperature phosphorescence such as the concentration of sodium dodecyl sulfate, the heavy atom concentration, the pH, and the concentration of sodium sulfite are discussed and the quenching effect of NO2−on room temperature phosphorimetry of PAHs was compared in the microemulsion and micelle media. 相似文献
997.
Journal of Global Optimization - Improperly efficient solutions in the sense of Geoffrion in linear fractional vector optimization problems with unbounded constraint sets are studied systematically... 相似文献
998.
999.
Anti-Controlling Codimension-2 Bifurcation of Discrete Dynamical Systems in 1 : 2 Resonance北大核心CSCD 下载免费PDF全文
从分岔反控制的角度设计了一套非线性反馈控制策略,来实现离散动力系统1∶2共振情形下余维二分岔的各种分岔解。首先,针对传统分岔准则在确定高余维分岔点时存在的局限性,建立了一个1∶2共振情形下的余维二分岔的新显式准则,基于这个显式准则通过设计线性控制增益来确保此类余维二分岔的存在性。然后,推导了1∶2共振的中心流形,并基于范式方法通过设计非线性控制增益,分析了1∶2共振情形下余维二分岔解的类型和稳定性。最后,以一个Arneodo-Coullet-Tresser映射为例,在指定的参数点处通过控制实现了具有1∶2共振分岔特性的各种分岔解,进一步验证了理论分析。 相似文献
1000.
A second order accurate method in the infinity norm is proposed for general three dimensional anisotropic elliptic interface problems in which the solution and its derivatives, the coefficients, and source terms all can have finite jumps across one or several arbitrary smooth interfaces. The method is based on the 2D finite element-finite difference (FE-FD) method but with substantial differences in method derivation, implementation, and convergence analysis. One of challenges is to derive 3D interface relations since there is no invariance anymore under coordinate system transforms for the partial differential equations and the jump conditions. A finite element discretization whose coefficient matrix is a symmetric semi-positive definite is used away from the interface; and the maximum preserving finite difference discretization whose coefficient matrix part is an M-matrix is constructed at irregular elements where the interface cuts through. We aim to get a sharp interface method that can have second order accuracy in the point-wise norm. We show the convergence analysis by splitting errors into several parts. Nontrivial numerical examples are presented to confirm the convergence analysis. 相似文献