受限、多孔及活性等复杂环境中扩散动力学的理论研究

发布时间：2018-02-03 19:52

本文关键词： 受限空间广义郎之万方程模耦合理论多孔介质活性粒子动力学不均一　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：随着生命和纳米科学技术的不断发展,介观尺度(一般来说,介观尺度的范围大约在10nm～1μm之间)中粒子动力学的研究因其重要性受到了越来越多的关注。通常,介观体系(如细胞,离子通道等)具有非常复杂的内部结构和运动学特征。从结构上看,细胞、离子通道具有空间受限的特征,而其中存在的大量有机物质又使得其表现出多孔介质的特点。从运动学角度上看,细胞等有机体具有将周围环境能量转换成定向驱动力的能力。因此,这些介观系统的内在结构和运动特征可以导致复杂多变的动力学行为,例如粒子定向输运,复杂环境高分子异常扩散和胶粒相分离等。这些问题往往不能用简单的统计力学方程定量描述和理论分析,因此理论结合适当的物理模型进行计算机模拟成了研究这一类介观体系动力学的重要技术方法。本文以介观体系中经常遇到的纳米粒子和高分子作为主要研究对象,采用理论结合模拟的手段研究介观体系中受限、多孔及活性等复杂环境对纳米尺度物质扩散动力学的影响。●受限空间粒子扩散动力学近二三十年来,受限空间粒子扩散的研究因其重要性和在实际介观系统中的应用一直都是物理、化学和生命科学关注的前沿问题。在软凝聚物及生命系统中,存在着大量狭长的通道,物质必须通过这些通道到达指定位置从而实现其功能。本文重点考察了随时间变化的通道中纳米粒子的两个重要动力学行为,熵随机共振和粒子定向输运。研究表明变化的通道对粒子的动力学产生了显著的影响,主要表现为:随机共振强度和粒子输运速度随粒子重力有着非单调的变化趋势。这些现象在静止边界的通道中是无法观测到的。我们利用粗粒化的描述手段,将通道对粒子运动的影响在一定的时间和空间尺度上等效成熵垒的作用,发现粒子在变化通道中受到了来自通道产生的有效熵力的作用。通过对有效熵力的分析,很好的解释了变化通道中观测到的熵随机共振及粒子输运对重力的非平凡的依赖行为。我们还进一步研究了其它与通道特征有关的物理量,例如振荡振幅、频率、相差、对称性等对熵随机共振及粒子输运的影响。●复杂环境高分子扩散动力学细胞等复杂环境中存在着大量的物质,如肌动蛋白纤维、核糖体、t-RNA和m-RNA等,这些物质的存在会对其中高分子的扩散及结构动力学产生重要的影响。例如,其中障碍物粒子的存在会降低酶的催化作用,提高RNA的稳定性甚至是它的熔点,还可以阻碍DNA绑定蛋白的迁移等等。而高分子在这样一种具有大量复杂物质的环境中的扩散问题也是生物物理及化学研究的重要课题之一。在本文中,通过结合模耦合理论和描述高分子运动的广义郎之万方程,我们从理论上研究了多孔介质环境中高分子的扩散及结构动力学行为。研究结果表明,在多孔介质这样拥挤的环境中,高分子出现了异常扩散行为,且末端距涨落的幂率衰减现象也与在一般环境中的高分子存在着时间尺度上的行为差异。进一步的研究表明了多孔介质中基底粒子(无法运动的粒子)的存在是导致异常扩散的主要原因,因为基底粒子的存在导致的系统平移不变性的消失使得高分子所感受到的记忆摩擦核出现了长尾衰减的行为,以此我们也证实了基底粒子对高分子动力学的影响要远远强于可运动的流体粒子。●活性粒子非平衡动力学活性粒子是指那些能将周围环境的能量转换成自身驱动力而具有定向运动能力的人工合成纳米粒子。在最近几年中,由于材料学和纳米科学的蓬勃发展,具有各种功能和形状的活性粒子层出不穷。由于粒子的活性可以推动体系远离平衡态,因此导致了活性粒子体系的大量有趣现象,如粒子集群运动、流体力学作用下的粒子自旋反转、体系相分离等。基于这些有趣的非平衡现象,自组装的研究也因此得到了长足的发展。近来,人们开始从理论及模拟上着手研究粒子活性在玻璃态转变过程中所扮演的角色,其中体系的动力学不均一行为因其重要性受到了特别的关注。在本文中,我们利用描述活性粒子的过阻尼郎之万方程详尽的研究了粒子活性对体系动力学不均一的影响。经研究发现,较高粒子体积分数下体系的动力学不均一程度随着活性的增加表现出了非单调的变化,进一步的研究使得我们还发现在粒子活性较大时,随着粒子体积分数的增加,体系的动力学不均一也表现出非单调变化的行为。上述这些非单调变化都说明了一个结论,即粒子活性在体系非平衡动力学过程中扮演了两种不同的角色,它们分别是活性导致的体系有效高温和活性诱导的粒子之间有效相互作用力。
[Abstract]:With the continuous development of life and nano science and technology, meso scale (generally, the range of meso scale at about 10nm ~ 1 m) in the study of particle dynamics has attracted more and more attention because of its importance. Usually, the mesoscopic system (such as cell ion channels, etc.) with internal structure and kinematic characteristics are very complicated. Look from the structure, characteristics of cells, ion channels have limited space, of which a large number of organic matter exists and makes it show the characteristics of porous media. From the kinematic point of view, such as cell of the organism will convert the energy into the surrounding environment the ability of directional driving force. Therefore, the internal structure and movement characteristics of these mesoscopic systems can lead to complex dynamic behavior, such as particle transport, molecular diffusion and particle complex environment of abnormal phase separation and so on. These problems can not be used to Jane The statistical mechanics equation of quantitative description and theoretical analysis, the theory combined with physical models of the computer simulation technology has become an important method to study this kind of mesoscopic system dynamics. In this paper, mesoscopic systems are often encountered in the nanoparticles and polymer as the main research object, restricted by combining theory with simulation method to study the influence of mesoscopic system. The activity of porous and complex environment such as diffusion kinetics on the nano scale material. The limited space particle diffusion dynamics in recent twenty or thirty years, study on confined space particle diffusion due to its importance and application in practice in mesoscopic systems has always been a frontier problem concerns physics, chemistry and life science. In soft condensed matter and life in the system, there is a narrow channel, so as to realize the function of the material must arrive at the designated location through these channels. This paper focus Two important dynamical behavior of nanoparticles changes with time in the channel of the entropic stochastic resonance and particle transport. The research showed that significantly influenced the dynamics of particle channel, mainly as follows: stochastic resonance intensity and particle transport velocity with particle gravity vary. These non monotonic trend in static boundary channel is not observed. We use a coarse-grained description method, will affect the channel on the motion of particles in a certain time and space scale equivalent to the entropy barrier, found by the effective particle force generated from entropy changes in the channel in the channel. Through the analysis of the effective entropy force, a good explanation of the entropic stochastic resonance and change channel observed in particle transport on the gravity of non trivial dependence behavior. We also further studies and other channels The relevant physical characteristics, such as amplitude, frequency, phase difference, symmetry transport effect on entropy stochastic resonance and particles. There are a lot of material dynamics of cell in complex environment - diffusion complex environment such as polymer, F-actin, ribosome, t-RNA and m-RNA, the presence of these substances will produce the the important effect of diffusion and kinetics of polymer structure. For example, the obstacle particles can reduce the enzyme catalysis, improve the stability of RNA and its melting point, can also hinder the migration of DNA binding protein and so on. One of the important topics of polymer diffusion problems in such a complex with a large number of substances in the environment is the bio physical and chemical research. In this paper, by combining the generalized Lang Zhiwan equation coupled mode theory and describe the motion of the polymer, we theoretically study the The diffusion and the structural dynamics behavior of polymer in porous media in the environment. The results of the study show that, in such a crowded environment in porous medium, the polymer abnormal diffusion behavior, the power fluctuation rate Qiemo end distance attenuation phenomenon and polymer in the general environment there are differences on time scales. Further studies show that the basement the particles in porous media (no moving particle) is the main cause of the abnormal diffusion, because the system shift invariance due to the existence of the substrate particles disappear makes polymer feel memory friction nuclear decay behavior appeared in the long tail, so we also confirmed the effect of substrate particles on the polymer dynamics is much stronger in the fluid movement. The particles can be activated particles non kinetic activity particle equilibrium refers to those of the surrounding environment can be converted into their own energy drive The artificial synthesis of nanoparticles with force capability. The directional movement in recent years, due to the vigorous development of material science and nano science, active particles with various functions and shapes. The particle emerge in an endless stream activity can promote the system away from equilibrium, thus leading to a large number of interesting activity particle systems, such as particle cluster motion spin reversal fluid mechanics under the action of the phase separation of the system. These interesting non-equilibrium phenomena based on self-assembly research has also been considerable development. Recently, people started from theory and simulation to research the particle activity played in the course of glass transition in the role, which the system dynamics is not uniform behavior because of the importance of particular attention. In this paper, we use the Wan Fangcheng Lang description of active particle damping exhaustive research on particle live Influence of heterogeneity on system dynamics. The study found that the kinetics of high particle volume fraction under the system heterogeneity with the increased activity shows a non monotonous variation, makes further study we also found that the activity of particles is larger, with the increase of particle volume fraction, the system dynamics is not uniform performance a non monotonic behavior. These non monotonic changes are explained to a conclusion, namely particle activity in the system of non equilibrium dynamics in the process of playing two different roles, they are between the induction system of high temperature and effective activity caused by the effective particle interactions.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;O631

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