Sun, 27 Jul 2008 11:15:33 BST CiteULike: dchen Tee http://www.citeulike.org/user/dchen/author/Tee CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/822252 <i>Physical Review E, Vol. 65, No. 5. (20 May 2002), 051505.</i><br /><br />Experiments investigating the local viscoelastic properties of a simple uncross-linked flexible polymer are performed on polyethylene oxide solutions in the semidilute regime using polystyrene beads of varying sizes and surface chemistry as probes. We measure the thermal motions of the beads to obtain the elastic and viscous moduli of our sample. Two different dynamic light scattering techniques; diffusing wave spectroscopy and quasielastic light scattering (QELS); are used to determine the dynamics of the probe particles. Diffusing wave spectroscopy probes the short time dynamics of the scatterers while QELS or single scattering measures the dynamics at larger times. This results in a larger frequency overlap of the data obtained from the microrheological techniques with the data obtained from the conventional bulk measurements. The moduli are estimated using a modified algebraic form of the generalized Stokes-Einstein equation. Comparison of microrheology with bulk measurements shows excellent similarity confirming the applicability of this method for simple; uncross-linked polymeric systems. Microrheology of polyethylene oxide using diffusing wave spectroscopy and single scattering Bivash Dasgupta Shang-You Tee John Crocker BJ Frisken DA Weitz doi:10.1103/PhysRevE.65.051505 Physical Review E, Vol. 65, No. 5. (20 May 2002), 051505. 2006-08-30T16:29:17-00:00 2002 Physical Review E 65 5 051505 American Physical Society dws microrheology weitz http://www.citeulike.org/user/dchen/article/2713643 <i>Journal of Fluid Mechanics, Vol. 501, No. -1. (2004), pp. 71-104.</i> A model for velocity fluctuations in sedimentation Peter Mucha Shang-You Tee David Weitz Boris Shraiman Michael Brenner Journal of Fluid Mechanics, Vol. 501, No. -1. (2004), pp. 71-104. 2008-04-24T18:08:14-00:00 2004 Journal of Fluid Mechanics 501 -1 71 104 flow gravity weitz http://www.citeulike.org/user/dchen/article/2683168 <i>Journal of Fluid Mechanics, Vol. 596, No. -1. (2008), pp. 467-475.</i><br /><br />The velocity fluctuations of particles in a low-Reynolds-number fluidized bed have important similarities and differences with the velocity fluctuations in a low-Reynolds-number sedimenting suspension. We show that, like sedimentation, the velocity fluctuations in a fluidized bed are described well by the balance between density fluctuations due to Poisson statistics and Stokes drag. However, unlike sedimentation, the correlation length of the fluctuations in a fluidized bed increases with volume fraction. We argue that this difference arises because the relaxation time of density fluctuations is completely different in the two systems. Velocity fluctuations in a low-Reynolds-number fluidized bed Shang-You Tee PJ Mucha MP Brenner DA Weitz Journal of Fluid Mechanics, Vol. 596, No. -1. (2008), pp. 467-475. 2008-04-17T18:54:33-00:00 2008 Journal of Fluid Mechanics 596 -1 467 475 flow grain