Sun, 27 Jul 2008 07:54:26 BST CiteULike: dchen's Love http://www.citeulike.org/user/dchen/author/Love CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2358310 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 76, No. 6. (2007)</i><br /><br />We use a continuous acquisition, high-speed camera with integrated centroid tracking to simultaneously measure the positions of a ring of micron-sized particles held in holographic optical tweezers. Hydrodynamic coupling between the particles gives a set of eigenmodes, each one independently relaxing with a characteristic decay rate (eigenvalue) that can be measured using our positional data. Despite the finite particle size, we find an excellent agreement between the measured eigenvalues and those numerically predicted by Oseen theory applied to the two-dimensional (2D) ring geometry. Particle motions are also analyzed in terms of the alternative eigenmode set obtained by wrapping onto the ring the eigenmodes of a 1D periodic chain. We identify the modes for which the periodic chain is a good approximation to the ring and those for which it is not. Eigenmodes of a hydrodynamically coupled micron-size multiple-particle ring R Di Leonardo S Keen J Leach CD Saunter GD Love G Ruocco MJ Padgett doi:10.1103/PhysRevE.76.061402 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 76, No. 6. (2007) 2008-02-09T18:56:22-00:00 2007 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 76 6 APS 2008 hydrodynamics opticaltweezer pre structure technique http://www.citeulike.org/user/dchen/article/1243619 <i>Physical Review Letters, Vol. 98, No. 15. (2007)</i><br /><br />We describe a new nematic liquid-crystal colloid system which is characterized by both charge stabilization of the particles and an interaction force. We estimate the effective charge of the particles by electrophoretic measurements and find that in such systems the director anchoring energy W is very low and the particles have little director distortion around them. The interaction force is created by producing a radial distribution of the nematic order parameter around a locally isotropic region created by ir laser heating. We theoretically describe this as being due to the induced flexoelectric polarization, the quadrupolar symmetry of which provides the required long-range force acting on charged particles. Colloidal Interactions and Transport in Nematic Liquid Crystals SA Tatarkova DR Burnham AK Kirby GD Love EM Terentjev doi:10.1103/PhysRevLett.98.157801 Physical Review Letters, Vol. 98, No. 15. (2007) 2007-04-22T14:04:11-00:00 2007 Physical Review Letters 98 15 APS 2007 charge colloids liquidcrystal