Upper and lower bounds on the control field and the quality of achieved optimally controlled quantum molecular motion

A large class of problems in optimally controlled quantum or classical molecular dynamics has multiple solutions for the control field amplitude. A denumerably infinite number of solutions may exist depending on the structure of the design cost functional. This fact has been recently proved with the aid of perturbation theory by considering the electric field as the perturbating agent. In carrying out this analysis, an eigenvalue (i.e., a spectral parameter) appears which gives the degree of deviation of the control objective from its desired value. In this work, we develop a scheme to construct upper and lower bounds for the field amplitude and spectral parameter for each member of the denumerably infinite set of control solutions. The bounds can be tightened if desired. The analysis here is primarily restricted to the weak field regime, although the bounds for the strong field nonlinear case are also presented.     

Optimal control of molecular motion: Nonlinear field effects

This paper is concerned with some of the consequences of strong optical fields and corresponding nonlinear field effects upon the optimal control of molecular motion. It is shown that the presence of nonlinear interactions can give rise to the existence of multiple field solutions to the problem of optimally controlling molecular motion where each of the fields produces exactly the same physical effects on the molecule. Secondly, it is argued that nonlinear field interactions may either act as a constraint on the control of molecular motion or an enhancement of that process depending on the circumstances. These variation phenomena are illustrated through consideration of control over the motion of harmonic molecules.     

High-tech applications of self-assembling supramolecular nanostructured gel-phase materials: from regenerative medicine to electronic devices

It is likely that nanofabrication will underpin many technologies in the 21st century. Synthetic chemistry is a powerful approach to generate molecular structures that are capable of assembling into functional nanoscale architectures. There has been intense interest in self-assembling low-molecular-weight gelators, which has led to a general understanding of gelation based on the self-assembly of molecular-scale building blocks in terms of non-covalent interactions and packing parameters. The gelator molecules generate hierarchical, supramolecular structures that are macroscopically expressed in gel formation. Molecular modification can therefore control nanoscale assembly, a process that ultimately endows specific material function. The combination of supramolecular chemistry, materials science, and biomedicine allows application-based materials to be developed. Regenerative medicine and tissue engineering using molecular gels as nanostructured scaffolds for the regrowth of nerve cells has been demonstrated in vivo, and the prospect of using self-assembled fibers as one-dimensional conductors in gel materials has captured much interest in the field of nanoelectronics.     

沸石类分子筛合成研究新进展

对当前国际上沸石和沸石类分子筛材料的合成研究进行了综述, 分析了合成研究动向, 指出了合成研究中值得注意的几点问题, 并提出了研究展望。     

Molecular conduction: do time-dependent simulations tell you more than the Landauer approach?

A dynamical method for simulating steady-state conduction in atomic and molecular wires is presented which is both computationally and conceptually simple. The method is tested by calculating the current-voltage spectrum of a simple diatomic molecular junction, for which the static Landauer approach produces multiple steady-state solutions. The dynamical method quantitatively reproduces the static results and provides information on the stability of the different solutions.     

分子生物色谱用于中药活性成分筛选及质量控制方法的研究

报道了近期工作进展,首先阐述了分子生物色谱的基本原理及特点,然后介绍了分子生物色谱对多种中药、不同产地的同种中药活性成分谱图模式的比较,结合已有的工作对活性成分筛选方法、相互作用研究、质量控制方法发展做了细致的说明,并讨论了其发展方向及前景。     

Effect of magnetic field on phase transitions in solutions of cellulose derivatives

LC transitions occurring in mixtures of cyanoethyl cellulose with DMAA or DMF and hydroxypropyl cellulose with ethanol, DMAA, or water in the presence and absence of magnetic field have been studied. With an increase in the polarity of solvent molecules and a decrease in the molecular mass of the polymer, the LC phase develops at higher concentrations and lower temperatures. Under application of magnetic field, the domain structure is formed in solutions and the temperature-concentration region of the LC phase widens. Cyanoethyl cellulose and hydroxypropyl cellulose solutions are found to possess memory: after the magnetic field is switched off, the orientation of macromolecules and the increased temperature of phase transitions are preserved for many hours. As the molecular mass of the polymer is increased, the ability of macromolecules to orient themselves in the magnetic field declines. The threshold mechanism governing the effect of magnetic field on LC transitions in polymer solutions has been discovered. The critical value of magnetic intensity that brings about a shift in boundary curves is consistent with the value of H _cr necessary for the cholesteric liquid crystal-nematic liquid crystal phase transition.     

Molecular dynamics simulations applied to electric field induced second harmonic generation in dipolar chromophore solutions

Electric field induced second harmonic generation (EFISH) is an important experimental technique in extracting the first hyperpolarizability of an organic chromophore molecule. Such experiments are carried out in solutions with chromophore molecules dissolved in some common solvents. A known fact is that the first hyperpolarizabilities extracted from EFISH experiments are subject to the use of local field factors. In this work, we apply simulations to study the EFISH properties of chromophore solutions. By combining quantum chemistry calculations with the results derived from molecular dynamics simulations, we show how macroscopic EFISH properties can be modeled, using 4-(dimethylamino)-4'-nitroazobenzene dissolved in chloroform as a demonstration case. The focus of the study is on deriving accurate local field factors. We find that the local field approach applies very well to dipolar solutions, such as the one studied here, but that the local field factors derived are much smaller than the commonly used Onsager or Lorentz local field factors. Our study indicates that many of the reported first hyperpolarizabilities for dipolar molecules from EFISH experiments are most probably underestimated because the Onsager/Lorentz approach, commonly used in extracting the molecular first hyperpolarizability, neglects the effects of the shapes of dipolar chromophore molecules on the local field factors.     

有机铁磁体的探索

有机铁磁体是新型交叉的学科领域.它的出现打破了有机物与铁磁无缘的传统概念,是对磁矩起源和磁相互作用等基本概念的挑战,具有非常重要的科学意义.不仅如此,它在电磁屏蔽和作为软磁盘和光磁盘记录介质等技术上呈现应用效果.本文介绍有机铁磁体的理论、分子设计、实验探索、应用前景以及研究方向.     

分子信标的构建及其应用研究进展

分子信标（molecular beacon,MB）是一种寡聚核苷酸荧光探针,其具有灵敏度高、特异性强、操作简单以及不必与未反应的探针分离即可实时检测等优点,在分子生物学和基因组学及分子医学等领域具有十分重要的应用价值。 本文介绍了近年来出现的各种新型分子信标的结构及工作原理,概述了分子信标技术在生命科学领域中的应用,展望了分子信标技术的发展趋势。     

光控二芳烯化学传感器及其研究进展

有机光致变色材料由于在光学记忆及分子开关器件等领域具有潜在的应用价值而备受关注。在众多有机光致变色系统中,二芳烯类光致变色化合物具有热稳定性好、耐疲劳、响应速度快和灵敏度高等优点,在光电材料和生物医学领域具有广阔的应用前景。近年来,围绕二芳烯构建可调控光化学传感器已成为功能材料领域的一大研究热点。本文主要介绍以二芳烯作为光调控单元合成具有多重调控功能的化学传感器的研究进展,并展望了该领域的应用前景和研究方向。     

Phase transitions in liquid crystalline solutions of hydroxypropyl cellulose under deformation

Phase transitions and the physical state of the hydroxypropyl cellulose-dimethylacetamide system under static conditions and in a shear field were studied by the cloud-point and polarized optical microscopy techniques with a polarization-photoelectric setup and a modified plasticorder. The deformation of solutions leads to a change in their structure and elevation of liquid-crystalline phase formation temperatures, a result that is due to the additional orientation of macromolecules in the flow direction. The ability of macromolecules to be oriented in a shear field decreases with an increase in the molecular mass of the polymer. The influence of deformation on phase transitions in hydroxypropyl cellulose solutions is nonmonotonic in character.     

表面活性剂界面自组装的分子动力学模拟

主要介绍了表面活性剂在液／液、气／液和固／液界面的自组装,详细讨论了分子动力学模拟在表面活性剂界面自组装体系的应用,指出了近年来该领域的发展现状及应用前景。     

结构可控的功能化聚烯烃设计与合成

聚烯烃的功能化是聚烯烃研究领域的热点,设计和合成结构可控的功能化聚烯烃 是目前聚烯烃功能化的主要研究方向.本文首先对功能化聚烯烃进行结构上的归纳分类,然后针对不同结构的功能化聚烯烃,分别综述了其设计与合成方面近年来的研究进展,并展望了聚烯烃功能化研究的前景.     

定量结构―活性相关性在药物空间结构研究中的应用

定量构效关系研究是目前国际上一个比较活跃的领域。定量结构―活性相关性(QSAR)在新药研制中的研究方法包括取代基多参数法(Hansch法)、比较分子力场分析法(CoMFA)等。QSAR在癌症、AIDS等药物研制方面取得良好的成果,为药物研究开拓了新的领域。构建癌症药物理想的QSAR模型,为设计活性更高的抗癌化合物提供了理论指导,QSAR在新药结构设计方面具有良好的研究前景。     

Multivalent nanofibers of a controlled length: regulation of bacterial cell agglutination

Control of the size and shape of molecular assemblies on the nanometer scale in aqueous solutions is very important for the regulation of biological functions. Among the well-defined supramolecular structures of organic amphiphiles, one-dimensional nanofibers have attracted much attention because of their potential applications in biocompatible materials. Although much progress has been made in the field of self-assembled nanofibers, the ability to control the fiber length remains limited. The approach for control of the fiber length presented herein overcomes this limitation through the coassembly of amphiphilic rod-coil molecules in which the crystallinity of the aromatic segment can be regulated by π-π stacking interactions. The introduction of carbohydrate segments into the fiber exterior endows the nanofibers with the ability to adhere to bacterial cells. Notably, the fiber length systematically regulates the agglutination and proliferation of bacterial cells exposed to these fibers.     

16-fold degeneracy of peptide plane orientations from residual dipolar couplings: analytical treatment and implications for protein structure determination

Residual dipolar couplings (RDCs) measured for internally rigid molecular fragments provide important information about the relative orientations of these fragments. Dependent on the symmetry of the alignment tensor and the symmetry of the molecular fragment, however, there generally exist more than one solution for the fragment orientation consistent with the measured RDCs. Analytical solutions are presented that describe the complete set of orientations of internally rigid fragments that are consistent with multiple dipolar couplings measured in a single alignment medium that is rhombic. For the first time, it is shown that, for a planar fragment such as the peptide plane, there generally exist 16 different solutions with their analytical expressions presented explicitly. The presence of these solutions is shown to be highly relevant for standard structure determination protocols using RDCs to refine molecular structures. In particular, when using standard protein structure refinement with RDCs that were measured in a single alignment medium as constraints, it is found that often more than one of the peptide plane solutions is physically viable; i.e., despite being consistent with measured RDCs, the local backbone structure can be incorrect. On the basis of experimental and simulated examples, it is rationalized why protein structures that are refined against RDCs measured in a single medium can have lower resolution (precision) than one would expect on the basis of the experimental accuracy of the RDCs. Conditions are discussed under which the correct solution can be identified.     

分子印迹聚合物模拟酶催化剂的设计合成

分子印迹法是制备对特定分子具有选择性识别能力的聚合物的新兴技术,它的应用研究领域之一是作为模拟酶催化剂。本文综述了自1989年首次报道成功制备MIPs(Molecular Impfinting Polymers)催化剂以来,制备MIPs催化剂的几种主要方法：印迹过渡态类似物(Translate State Analogue,TSA),印迹底物或其类似物,运用预组织法制备MIPs催化剂。最后,指出了目前存在的问题以及未来的发展方向。     

高耐压等级聚乙烯管材树脂的研究进展

高耐压等级聚乙烯管材树脂主要用于生产给水管、燃气管及各种工业用管,是一类技术含量较高、市场前景较好的聚乙烯专用树脂。高耐压等级聚乙烯管材树脂多为双峰或多峰结构,采用茂金属催化剂或具有高共聚性能的齐格勒纳塔(Z-N)催化剂双釜或多釜串联聚合生产。本文介绍了高耐压等级聚乙烯管材树脂的分子结构和性能特点,以及制备该类树脂的催化剂和工艺技术,并对国内的相关催化剂及制备技术作了评述。