活性体系非平衡动力学若干问题的理论研究

发布时间：2018-01-03 18:07

本文关键词：活性体系非平衡动力学若干问题的理论研究　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】：近些年来,活性粒子体系统计动力学行为的研究已经引起了人们广泛的关注,己经成为化学、物理以及生物等多学科交叉领域的前沿问题。活性是一种能将从周围环境获取的能量转化成功并产生定向运动的性质,由于这种独特的特性,活性粒子体系具有一系列热力学平衡体系不具备的动力学性质。所以活性体系的研究有助于帮助我们揭示一些非平衡体系的物理本质以及设计制造生物智能装置和材料。在对活性粒子研究和探索过程中,科研人员花费了大量的时间在解决以下的两个难点:第一个难点在于如何去理解活性体系的复杂群体运动行为产生机理;第二难点在于如何理解活性粒子所组成的活性环境对非活性粒子的动力学行为的影响。本文以活性体系为研究对象,研究了粒子间的相互作用对活性体系相分离的影响以及活性浴对高分子链穿孔动力学的影响。具有各向异性相互作用的活性粒子的"重入"相分离近些年,很多实验和理论工作围绕着活性粒子的相分离行为,而我们主要考虑各向异性相互作用(Janus相互作用)对活性粒子相分离行为的影响。模拟结果表明,由于粒子在janus相互作用下倾向于吸引面互相靠近而排斥面互相远离,所以非活性Janus体系会形成由小团簇(体积分数比较小)或者条带(体积分数比较大)构成的长程有序态。对于活性体系而言,体积分数比较小的时候,单纯的活性作用不能使体系发生相分离,但随着janus相互作用的加入,体系出现了很明显的"重入"行为:过弱和过强的janus相互作用都会破坏体系的相分离,只有强度适中的janus相互作用可以使得体系发生明显的相分离。活性体积分数比较大的时候,活性己经导致体系出现相分离,此时加入janus相互作用可以使得体系的相分离效果更加明显,但过强的janus相互作用还是会破坏相分离使得体系进入无序状态。同时我们通过对局域结构的详细分析尝试给出了定性的解释:活性驱动力会倾向于使体系出现团簇状态,janus相互作用倾向于使得体系出现长程有序状态,两者的相互竞争使得整个活性janus体系随着janus强度的变化而出现"重入"行为。活性浴中的高分子链穿孔问题。高分子链在纳米孔径和生物管道中的穿孔行为引起了人们广泛的关注和深入的研究。一方面,研究高分子链穿孔过程有助于帮助我们理解一些实际生物体系中重要的过程如转录过程,另一方面通过理解实际生物体系中高分子链穿孔的物理本质进而实现一些人为调控是有其长远的技术应用价值。但目前考虑的穿孔环境都是非活性的,所以在本文中我们着重要考虑了活性浴对高分子链穿孔的影响。研究表明,当活性浴中体积分数固定时,高分子链的平均穿孔时间随活性驱动力的增加而出现一个非单调行为:适中的活性驱动力可以使得整个穿孔过程最慢。进一步当活性浴的活性驱动力固定比较大且固定时,高分子链的平均穿孔时间随着活性浴的体积分数增加也会出现一个非单调行为:适中的活性浴体积分数会使得整个穿孔过程最快。通过对等待时间和累计等待时间的分析,我们发现活性浴对高分子链穿孔有两个作用:活性粒子倾向于聚集在孔径附近进而阻碍高分子链穿孔;活性粒子同时也会倾向于聚集在高分子链附近并拉扯高分子链从而促进高分子链穿孔,正是这两种相互作用力的竞争导致了体系出现了非单调行为。最后我们通过进一步的模拟发现穿孔时间与高分子链长之间存在着很好地标度关系,且标度指数依赖于活性浴的活性和体积分数。
[Abstract]:In recent years, research on dynamic behavior of statistical activity of particle system has attracted extensive attention, has become a frontier problem of chemical, physical and biological and other interdisciplinary fields. The activity is a kind of energy conversion can be obtained from the surrounding environment and produce successful directional movement of the nature, because of the unique characteristics, activity particle system has dynamic properties of a series of thermodynamic equilibrium. So the system does not have the activity of the system can help us reveal the physical essence of non equilibrium system as well as the design and manufacture of biological intelligent devices and materials. In the activity of particle research and exploration, researchers spent a lot of time on the two difficult to solve the following: the first problem is how to understand complex behavior activity system mechanism; second is difficult to understand the activity Effect of dynamic behavior of active particles composed of environmental non active particles. In this paper, the activity system as the research object, studied the effects of interactions between particles on the phase separation of active system and activity dynamics of polymer chain bath perforation. In recent years with active particles of the anisotropic interaction "into" the separation, separation of many experimental and theoretical work on active particle behavior, and we mainly consider the anisotropic interaction (Janus interaction) effect on the activity of particle phase separation behavior. The simulation results show that the tendency of particles in the Janus interaction on the suction surface close to each other and reject the face away from each other, so the activity of Janus system will be formed by small clusters (the volume fraction is relatively small) or strip (volume fraction larger) long-range ordered states. For active system, body The integral number is relatively small, the activity of the system can not be the occurrence of phase separation, but with the addition of Janus interaction, the system appears very obvious "into" behavior: phase separation is too weak and too strong Janus interaction will destroy the system, only the strength in Janus interactions the system of obvious phase separation. When the volume fraction of the activity is relatively large, the activity has led to system phase separation, but the addition of Janus interaction can make the system separation effect is more obvious, but the strong Janus interaction will make the system into the disordered state of phase separation. At the same time we break through detailed analysis the local structure to give a qualitative explanation: the active driving force will tend to make the system of cluster state, Janus interactions tend to make system of long-range ordered state, two The competition makes the whole system with the change of activity of Janus Janus and the strength of "heavy" behavior. The polymer chain in the bath. The activity of perforation perforation behavior of polymer chains in nano aperture and biological pipeline has aroused widespread attention and in-depth research. On one hand, the research of polymer chain helps the perforation process to help us understand some of the actual biological systems important processes such as transcription process, on the other hand, by understanding the physical nature of the actual biological system of polymer chain and achieve some of the artificial regulation of perforation has its application value. But the long-term environmental perforation are currently considered the non active, so in this paper we important considering the influence of perforation of the polymer chain activated bath. The results show that when the volume fraction of active bath is fixed, the average time of perforation of polymer chain with active driving force The increase and the emergence of a non monotonic behavior: moderate activity driving force can make the whole process of perforation of the slowest. Further when the active driving force of fixed bath activity is relatively large and fixed, the average time of perforation with polymer chains increases the volume fraction of active bath will also appear in a non monotonic behavior: Bath activity of moderate volume fraction the fastest will make the whole perforation process. Based on the waiting time and total waiting time analysis, we found that the activity of bath has two effects on the polymer chain perforation: active particles tend to congregate in the aperture and thus hinder the polymer chain near the perforation; active particles will also tend to congregate in the polymer chain near the polymer chain to pull promote the polymer chain perforation, it is two kinds of interaction system competition leads to the emergence of non monotonic behavior. Finally, we further found through simulation There is a good scaling relationship between the perforation time and the length of the polymer chain, and the scaling exponent depends on the activity and volume fraction of the active bath.

【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】：O643.1

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