Sat, 26 Jul 2008 08:03:42 BST CiteULike: weeks's brownian-motion http://www.citeulike.org/user/weeks/tag/brownian-motion CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/weeks/article/1875708 <i>Physical Review Letters, Vol. 81, No. 20. (16 November 1998), 4404.</i><br /><br />Using molecular dynamics computer simulations we investigate how the relaxation dynamics of a simple supercooled liquid with Newtonian dynamics differs from the one with a stochastic dynamics. We find that; apart from the early β-relaxation regime; the two dynamics give rise to the same relaxation behavior. The increase of the relaxation times of the system upon cooling; the details of the α relaxation; as well as the wave-vector dependence of the Edwards-Anderson parameters; are independent of the microscopic dynamics. How Does the Relaxation of a Supercooled Liquid Depend on Its Microscopic Dynamics? Tobias Gleim Walter Kob Kurt Binder doi:10.1103/PhysRevLett.81.4404 Physical Review Letters, Vol. 81, No. 20. (16 November 1998), 4404. 2007-11-07T00:33:45-00:00 1998 Physical Review Letters 81 20 4404 American Physical Society brownian-motion glass simulation http://www.citeulike.org/user/weeks/article/2721820 <i>Physics of Fluids, Vol. 20, No. 4. (2008)</i> Shear-induced particle migration in binary colloidal suspensions Denis Semwogerere Eric Weeks Physics of Fluids, Vol. 20, No. 4. (2008) 2008-04-26T14:00:44-00:00 2008 Physics of Fluids 20 4 AIP binary brownian-motion migration http://www.citeulike.org/user/weeks/article/983535 <i>Langmuir, Vol. 22, No. 24. (21 November 2006), pp. 9812-9815.</i><br /><br />Coating a close-packed fluorescent colloid monolayer with a nanometer-thick metal film followed by sonication in liquid produces modulated optical nanoprobes. The metal coating modulates the fluorescence as these structures rotate in suspension, enabling the use of these particles as probes to monitor both rotational and center-of-mass (translational) dynamics in complex environments. Here, we demonstrate methods to simultaneously measure two translational and two rotational degrees of freedom, with excellent agreement to theory. The capability to determine two angles of rotation opens several new avenues of future research. Single-Particle Colloid Tracking in Four Dimensions SM Anthony L Hong M Kim S Granick doi:10.1021/la062094h Langmuir, Vol. 22, No. 24. (21 November 2006), pp. 9812-9815. 2006-12-07T16:14:51-00:00 2006 Langmuir 22 24 9812 9815 brownian-motion methods particle-tracking rotation http://www.citeulike.org/user/weeks/article/1981493 <i>(27 January 2005)</i><br /><br />Early studies by Einstein and Perrin provided some of the first evidence for the existence of molecules. Perrin, a Nobel Laureate, wrote this classic to explain his measurements of displaced particles of a resin suspended in water. It introduced the concept of Avogadro's number, along with other groundbreaking work. 1910 edition. Brownian Movement and Molecular Reality Jean Perrin (27 January 2005) 2007-11-25T16:51:13-00:00 2005 Dover Publications book brownian-motion classic diffusion http://www.citeulike.org/user/weeks/article/1574421 <i>Physics of Fluids, Vol. 17, No. 7. (2005), pp. 073101-073101.</i><br /><br />In microrheology, elastic and viscous moduli are obtained from measurements of the fluctuating thermal motion of embedded colloidal probes. In such experiments, the probe motion is passive and reflects the near-equilibrium (linear response) properties of the surrounding medium. By actively pulling the probe through the material, further information about material properties can be obtained, analogous to large-amplitude measurements in (macro-) rheology. We consider a simple model of such systems: a colloidal probe pulled through a suspension of neutrally buoyant bath colloids. We choose a system with hard-sphere interactions but neglect hydrodynamic interactions, which is simple enough to permit analytic solutions, but nontrivial enough to raise issues important for the interpretation of experiments in active and nonlinear microrheology. We calculate the microstructural deformation for arbitrary probe size and pulling rate (expressed as a dimensionless Péclet number Pe). From this, we determine the average retarding effect on the probe due to the microstructure, as well as fluctuations about this average. The high-Pe limit is singular, giving a finite Brownian contribution even in the limit of negligible diffusion. Significantly, different results are obtained for probes driven at constant velocity and constant force. Furthermore, we demonstrate that a probe pulled with an optical tweezer (roughly a harmonic well) can behave as fixed-force, fixed-velocity, or as a mixture of those modes, depending on the strength of the trap and on the pulling speed. More generally, we discuss how these results relate to previous work on the rheology of colloidal suspensions. Not surprisingly, the present theory (which ignores hydrodynamic interactions) gives shear thinning but no shear thickening; we expect that the incorporation of hydrodynamics would result in shear thickening as well. The effective micro- and macro-viscosities, when appropriately scaled, are in semi-quantitative agreement. This seems remarkable, given the rather significant difference in the two methods of measurement. However, for more complicated or unknown materials, where such scaling relations may not be known in advance, the comparison between micro- and macro may not be so favorable, which raises important questions about the relation between micro- and macrorheology. Finally, by analogy with previous work on macrorheology, we propose methods to scale up the present (dilute) theory to account for more concentrated suspensions, and suggest new active microrheological experiments to probe different aspects of suspension behavior. ©2005 American Institute of Physics A simple paradigm for active and nonlinear microrheology Todd Squires John Brady doi:10.1063/1.1960607 Physics of Fluids, Vol. 17, No. 7. (2005), pp. 073101-073101. 2007-08-18T21:56:30-00:00 2005 Physics of Fluids 17 7 073101 073101 AIP brownian-motion microrheology poking theory http://www.citeulike.org/user/weeks/article/1899401 <i>Philosophical Magazine, Vol. 9 (1905), 781.</i> A dynamical theory of diffusion for non-electrolytes and the molecular mass of albumin W Sutherland Philosophical Magazine, Vol. 9 (1905), 781. 2007-11-11T18:29:48-00:00 1905 Philosophical Magazine 9 781 brownian-motion classic http://www.citeulike.org/user/weeks/article/1899390 <i>Annalen der Physik (Leipzig), Vol. 17 (1905), pp. 549-560.</i><br /><br />In this paper it will be shown that according to the molecular-kinetic theory of heat, bodies of microscopically-visible size suspended in a liquid will perform movements of such magnitude that they can be easily observed in a microscope, on account of the molecular motions of heat. It is possible that the movements to be discussed here are identical with the so-called "Brownian molecular motion"; however, the information available to me regarding the latter is so lcking in precision, that I can form no judgement in the matter. On the movement of small particles suspended in a stationary liquid demanded by the molecular-kinetic theory of heat A Einstein Annalen der Physik (Leipzig), Vol. 17 (1905), pp. 549-560. 2007-11-11T18:26:05-00:00 1905 Annalen der Physik (Leipzig) 17 549 560 brownian-motion classic http://www.citeulike.org/user/weeks/article/1378517 <i>Physical Review Letters, Vol. 95, No. 16. (2005)</i><br /><br />The thermal position fluctuations of a single micron-sized sphere immersed in a fluid were recorded by optical trapping interferometry with nanometer spatial and microsecond temporal resolution. We find, in accord with the theory of Brownian motion including hydrodynamic memory effects, that the transition from ballistic to diffusive motion is delayed to significantly longer times than predicted by the standard Langevin equation. This delay is a consequence of the inertia of the fluid. On the shortest time scales investigated, the sphere's inertia has a small, but measurable, effect. Direct Observation of Nondiffusive Motion of a Brownian Particle B Lukic S Jeney C Tischer AJ Kulik L Forro EL Florin doi:10.1103/PhysRevLett.95.160601 Physical Review Letters, Vol. 95, No. 16. (2005) 2007-06-11T11:57:16-00:00 2005 Physical Review Letters 95 16 APS brownian-motion journal-club http://www.citeulike.org/user/weeks/article/1683144 <i>Journal of Colloid and Interface Science, Vol. 314, No. 1. (1 October 2007), pp. 98-106.</i><br /><br />We report an experimental method to characterize the dynamics of colloidal rods by measuring their rotation and translation in three dimensions with confocal microscopy. The method relies on solvent viscosification to retard dynamics to time scales that are compatible with 3D confocal optical microscopy. Because the method yields a full three-dimensional characterization of rod displacement and orientation, it is applicable to situations in which complex, anisotropic dynamics emerge. Examples include behavior in liquid crystal phases with both orientational and positional order, suspensions subjected to applied fields such as shear flow or sedimentation, and the emerging area of anisotropic particle dynamics. We demonstrate the performance of the method by quantifying the Brownian motion of fluorescent poly(methyl methacrylate) rods (aspect ratio, L/D=3.1 and 7.0) grafted with poly(dimethylsiloxane) stabilizer. The rods are dispersed at dilute concentration in a solvent mixture of viscosity 2.0 Pa[thin space]s. Rod translational and rotational diffusivities are extracted from the measured translational mean square displacement of the centroid positions and of the rod unit vector u(t), respectively. Rod orientational dynamics are characterized relative to both their azimuthal and polar angles. Probability distributions for the translation and rotation in the frame of rod are computed from the measurements. Experimental values obtained agree well with theory available for the dynamics of isolated rods. Translational and rotational dynamics of colloidal rods by direct visualization with confocal microscopy Deshpremy Mukhija Michael Solomon doi:10.1016/j.jcis.2007.05.055 Journal of Colloid and Interface Science, Vol. 314, No. 1. (1 October 2007), pp. 98-106. 2007-09-21T19:04:19-00:00 2007 Journal of Colloid and Interface Science 314 1 98 106 brownian-motion confocal diffusion rods rotation http://www.citeulike.org/user/weeks/article/1678095 <i>The Physics Teacher, Vol. 44, No. 5. (2006), pp. 276-279.</i><br /><br />Most people do not realize that many substances they use in the kitchen and the bathroom are not simple liquids or solids. Everyone is familiar with three states of matter: solids, liquids, and gases. However, creams, shampoo, toothpaste, and ketchup all have properties of both liquids and solids. This paper describes demonstrations and laboratory exercises1 that show intriguing properties of squishy substances, defined as materials that are not unambiguously solid, liquid, or gas. Unlike some areas of physics, the concepts behind squishy materials are understandable even by beginning students. Squishy physics can be used to show physics questions arising from everyday life and to convey the excitement of current research. Squishy Materials Piotr Habdas Eric Weeks David Lynn doi:10.1119/1.2195396 The Physics Teacher, Vol. 44, No. 5. (2006), pp. 276-279. 2007-09-20T04:08:32-00:00 2006 The Physics Teacher 44 5 276 279 AAPT brownian-motion complex-fluids teaching http://www.citeulike.org/user/weeks/article/1676507 <i>J. Fluid Mech., Vol. 581 (2007), pp. 437-451.</i> Development of particle migration in pressure-driven flow of a Brownian suspension D Semwogerere JF Morris ER Weeks J. Fluid Mech., Vol. 581 (2007), pp. 437-451. 2007-09-19T16:15:32-00:00 2007 J. Fluid Mech. 581 437 451 brownian-motion colloids confocal migration http://www.citeulike.org/user/weeks/article/1676505 <i>J. Fluid Mech, Vol. 493 (2003), pp. 363-378.</i> Particle migration in pressure-driven flow of a Brownian suspension M Frank D Anderson ER Weeks JF Morris J. Fluid Mech, Vol. 493 (2003), pp. 363-378. 2007-09-19T16:15:32-00:00 2003 J. Fluid Mech 493 363 378 brownian-motion colloids confocal migration pmma