Experimental Physics I, University of Bayreuth, Universitätsstr. 30, D-95447 Bayreuth, Germany.
Phys Rev E. 2019 Oct;100(4-1):042125. doi: 10.1103/PhysRevE.100.042125.
Single-particle tracking (SPT) is a versatile tool for quantifying diffusional motion in complex soft-matter systems, e.g., in biological specimen. Evaluating SPT data often invokes the fitting of a trajectory's time-averaged mean-square displacement (TA-MSD) with a simple power law, 〈r^{2}(τ)〉{t}∼τ^{α}, where the scaling exponent α can yield important insights into the nature of the transport process. Biological specimen, for example, frequently feature a diffusion anomaly, i.e., an exponent α<1 ("subdiffusion"). However, due to SPT-inherent static and dynamic localization errors, in combination with typically short trajectories, it is often a real challenge to determine the value of α reliably by simply fitting TA-MSDs. Here a straightforward resampling approach is presented and tested that eliminates both localization errors in the TA-MSD of trajectories originating from subdiffusive fractional Brownian motion processes. As a result, the mean anomaly exponent 〈α〉{E} of an ensemble of trajectories is revealed in a robust fashion.
单粒子追踪(SPT)是一种用于量化复杂软物质系统中扩散运动的多功能工具,例如在生物样本中。评估 SPT 数据通常需要将轨迹的时间平均均方根位移(TA-MSD)拟合到简单的幂律关系〈r^{2}(τ)〉{t}∼τ^{α},其中标度指数 α 可以深入了解传输过程的性质。例如,生物样本通常具有扩散异常,即指数 α<1(“亚扩散”)。然而,由于 SPT 固有的静态和动态定位误差,再加上通常较短的轨迹,通过简单地拟合 TA-MSD 来可靠地确定 α 值通常是一个真正的挑战。这里提出并测试了一种简单的重采样方法,该方法消除了源自亚扩散分数布朗运动过程的轨迹的 TA-MSD 中的定位误差。结果,以稳健的方式揭示了轨迹的集合的平均异常指数〈α〉{E}。