二维基于微管的活性向列相中密度变化的建模

中文摘要 AI 辅助

由分子马达驱动的密集二维对齐微管（MTs）层是活性材料的典型实验室模型，也是细菌湍流、有丝分裂纺锤体和形态发生等生物系统的合成类似物。该材料表现出向列有序及相关的拓扑缺陷，这些缺陷展现出复杂的涌现动力学，包括缺陷的产生与湮灭，以及缺陷在复杂的混沌舞蹈中相互缠绕。尽管在研究中有突出地位，基于MT的活性向列材料缺乏一个完善的理论模型来准确捕捉实验中显著出现的丰富密度变化——这些密度变化实际上是向列结构本身的实验特征。MT系统通常使用两个场进行建模：Q张量（编码向列相的有序度和取向）和流体速度；关键的是，微管密度被假定为常数。这一传统模型借鉴了经典的Landau-de Gennes液晶理论。在此，我们提出了一种根本不同的建模基于MT的活性向列相的方法，该方法明确地纳入了密度变化，产生的模拟与实验视频高度相似，包括特征性的条纹图案。它还重现了系统被限制在圆形井中的重要行为——这种行为在实验中被观察到，但当前理论未能捕捉。在构建我们的模型时，我们为拓扑缺陷的产生与湮灭提供了一种不依赖于经典各向同性-向列相变的Landau-de Gennes理论的替代方案。

英文摘要

A dense two-dimensional layer of aligned microtubules (MTs), powered by molecular motors, is a canonical laboratory model of active materials and a synthetic analog of biological systems such as bacterial turbulence, mitotic spindles, and morphogenesis. This material exhibits nematic ordering and associated topological defects, which display complex emergent dynamics, including the creation and annihilation of defects and the braiding of defects around one another in a complicated chaotic dance. Despite its prominent role in research, the MT-based active nematic material lacks a well established theoretical model that accurately captures the rich density variations prominently seen in experiments---density variations that are, in fact, the experimental signature of the nematic structure itself. The MT-system is typically modeled using two fields: the Q-tensor (encoding the order and orientation of the nematic phase) and the fluid velocity; critically, the microtubule density is assumed to be constant. This traditional model is adopted from classical Landau-de Gennes liquid crystal theory. Here, we present a fundamentally different approach to modeling MT-based active nematics that explicitly incorporates density variations, producing simulations that strongly resemble experimental videos, including the characteristic striation patterns. It also reproduces important behavior of the system confined to a circular well---behavior seen experimentally, but not captured by current theory. In crafting our model, we present an alternative to Landau-de Gennes theory for the creation and annihilation of topological defects that does not rely on the classic isotropic-nematic phase transition.

发表机构

• University of California, Merced（加州大学默塞德分校）
• Johns Hopkins University（约翰斯·霍普金斯大学）

机构由 AI 辅助整理，请以论文原文为准。