Observation of Brownian motion on the time scale of hydrodynamic interactions

1993 ◽  
Vol 70 (2) ◽  
pp. 242-245 ◽  
Author(s):  
M. H. Kao ◽  
A. G. Yodh ◽  
D. J. Pine
Keyword(s):  
Brownian Motion ◽  
Time Scale ◽  
Hydrodynamic Interactions

Smooth first-passage densities for one-dimensional diffusions

1987 ◽  
Vol 24 (02) ◽  
pp. 370-377 ◽  
Author(s):  
E. J. Pauwels
Keyword(s):  
Differential Equation ◽  
Brownian Motion ◽  
Stochastic Differential Equation ◽  
Time Scale ◽  
First Passage ◽  
One Dimensional ◽  
Drift Coefficient

The purpose of this paper is to show that smoothness conditions on the diffusion and drift coefficient of a one-dimensional stochastic differential equation imply the existence and smoothness of a first-passage density. In order to be able to prove this, we shall show that Brownian motion conditioned to first hit a point at a specified time has the same distribution as a Bessel (3)-process with changed time scale.

scholarly journals Simulations of dynamically cross-linked actin networks: Morphology, rheology, and hydrodynamic interactions

2021 ◽  
Vol 17 (12) ◽  
pp. e1009240
Author(s):  
Ondrej Maxian ◽  
Raúl P. Peláez ◽  
Alex Mogilner ◽  
Aleksandar Donev
Keyword(s):  
Time Scale ◽  
Stochastic Simulations ◽  
Hydrodynamic Interactions ◽  
Short Time Scale ◽  
Slender Body Theory ◽  
Small Amplitude Oscillatory Shear ◽  
Actin Networks ◽  
Cross Links ◽  
The Cross

Cross-linked actin networks are the primary component of the cell cytoskeleton and have been the subject of numerous experimental and modeling studies. While these studies have demonstrated that the networks are viscoelastic materials, evolving from elastic solids on short timescales to viscous fluids on long ones, questions remain about the duration of each asymptotic regime, the role of the surrounding fluid, and the behavior of the networks on intermediate timescales. Here we perform detailed simulations of passively cross-linked non-Brownian actin networks to quantify the principal timescales involved in the elastoviscous behavior, study the role of nonlocal hydrodynamic interactions, and parameterize continuum models from discrete stochastic simulations. To do this, we extend our recent computational framework for semiflexible filament suspensions, which is based on nonlocal slender body theory, to actin networks with dynamic cross linkers and finite filament lifetime. We introduce a model where the cross linkers are elastic springs with sticky ends stochastically binding to and unbinding from the elastic filaments, which randomly turn over at a characteristic rate. We show that, depending on the parameters, the network evolves to a steady state morphology that is either an isotropic actin mesh or a mesh with embedded actin bundles. For different degrees of bundling, we numerically apply small-amplitude oscillatory shear deformation to extract three timescales from networks of hundreds of filaments and cross linkers. We analyze the dependence of these timescales, which range from the order of hundredths of a second to the actin turnover time of several seconds, on the dynamic nature of the links, solvent viscosity, and filament bending stiffness. We show that the network is mostly elastic on the short time scale, with the elasticity coming mainly from the cross links, and viscous on the long time scale, with the effective viscosity originating primarily from stretching and breaking of the cross links. We show that the influence of nonlocal hydrodynamic interactions depends on the network morphology: for homogeneous meshworks, nonlocal hydrodynamics gives only a small correction to the viscous behavior, but for bundled networks it both hinders the formation of bundles and significantly lowers the resistance to shear once bundles are formed. We use our results to construct three-timescale generalized Maxwell models of the networks.

scholarly journals Nanoparticle Brownian motion and hydrodynamic interactions in the presence of flow fields

2011 ◽  
Vol 23 (7) ◽  
pp. 073602 ◽  
Author(s):  
B. Uma ◽  
T. N. Swaminathan ◽  
R. Radhakrishnan ◽  
D. M. Eckmann ◽  
P. S. Ayyaswamy
Keyword(s):  
Brownian Motion ◽  
Flow Fields ◽  
Hydrodynamic Interactions

Brownian Motion Indexed by a Time Scale

2011 ◽  
Vol 29 (3) ◽  
pp. 457-472 ◽  
Author(s):  
David Grow ◽  
Suman Sanyal
Keyword(s):  
Brownian Motion ◽  
Time Scale
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