Videomicroscopy, diffusion studies

Use of Videomicroscopy in Diffusion Studies of Oil-Water-Surfactant Systems... 

Amblard, et al., used videomicroscopy and magnetic tweezers to study probe motion in viscoelastic F-actin systems(95). Videomicroscopy determines particle positions the tweezers apply known forces to a particle. The F-actin filaments had an estimated length of 20 p.m, persistence length c. 14 p.m, and at 0.1 g/1 a mesh size 1 p.m. With small beads (diameter d < ), diffusion followed x t)) t. ... 

Tests of the validity of the Kirkwood-Riseman picture, inquiring directly if diffusing objects actually have cross-diffusion tensors that match their supposed hydrodynamic interactions, have recently been accomplished Crocker used videomicroscopy and optical tweezers to study the correlated Brownian motions of a pair of 0.9 xm polystyrene spheres, thereby determining their cross-diffusion ten-sors(3). Crocker found that the diffusion tensors are accurately described by the hydrodynamic interaction tensors, exactly as Kirkwood and Riseman had assumed. An optical trap experiment by Meiners and Quake observed the motions of two Brownian particles, further confirming the validity of the Oseen approximation for hydrodynamic interactions(4). 

---