CiteULike: dchen's diffusion http://www.citeulike.org/user/dchen/tag/diffusion CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2767685 <i>Phys. Rev. Lett. 100, 088301 (2008)</i><br /><br />The driving force in diffusion-driven pattern formation is the difference in the diffusional flux of the key species, which in the case of ionic systems builds up a local electric field at the concentration gradients. The arising additional migrational flux not only decreases but also enhances the instability of the base state, depending on the charge distribution among the components. The opposite charges on the slower diffusing autocatalyst and its reacting counterpart favor pattern formation and shift the onset of instability to a smaller difference in the diffusion coefficients. The same charges, in addition to having the opposite effect, may even lead to the complete stabilization of planar reaction fronts unstable in the neutral system. Diffusion-Driven Pattern Formation in Ionic Chemical Solutions Zsanett Virányi Ágota Tóth Dezső Horváth Phys. Rev. Lett. 100, 088301 (2008) 2008-05-07T23:25:52-00:00 Phys. Rev. Lett. 100, 088301 (2008) charge chemical diffusion theory http://www.citeulike.org/user/dchen/article/2763281 <i>Physical Review Letters, Vol. 100, No. 12. (2008)</i><br /><br />Applications of probe diffusion in polymer matrices typically envision that for particles sizes (R) larger than the correlation length of the polymer solution (), the probe (at long times) diffuses as in a continuum polymer solution. We present simulation results for probe diffusion in rod solutions which challenge this conventional wisdom and indicate a new mechanism of a probe diffusion operative for R>. Our simulation results are rationalized by scaling arguments invoking a novel mechanism of the constraint release motion of the rods, and suggest that the dynamical characteristics of the polymer matrix also proves important in developing a complete description of the probe motion. Dynamics of Probe Diffusion in Rod Solutions Victor Pryamitsyn Venkat Ganesan doi:10.1103/PhysRevLett.100.128302 Physical Review Letters, Vol. 100, No. 12. (2008) 2008-05-07T00:55:39-00:00 Physical Review Letters 100 12 APS diffusion dynamics rod tracer http://www.citeulike.org/user/dchen/article/2762175 <i>Physical Review Letters, Vol. 100, No. 15. (2008)</i><br /><br />We present the first time-resolved investigation of motions of proteins in densely grafted layers of spherical polyelectrolyte brushes. Using small-angle x-ray scattering combined with rapid stopped-flow mixing, we followed the uptake of bovine serum albumin by poly(acrylic acid) layer with high spatial and temporal resolution. We find that the total amount of adsorbed protein scales with time as t1/4. This subdiffusive behavior is explained on the basis of directed motion of the protein along the polyelectrolyte chains. Directed Motion of Proteins along Tethered Polyelectrolytes Katja Henzler Sabine Rosenfeldt Alexander Wittemann Ludger Harnau Stephanie Finet Theyencheri Narayanan Matthias Ballauff doi:10.1103/PhysRevLett.100.158301 Physical Review Letters, Vol. 100, No. 15. (2008) 2008-05-06T17:57:50-00:00 Physical Review Letters 100 15 APS 2008 biology diffusion polymer http://www.citeulike.org/user/dchen/article/2759260 <i>(2008)</i><br /><br />The time needed for a particle to exit a confining domain through a small window, called the narrow-escape time (NET), is a limiting factor of various processes, such as some biochemical reactions in cells. Obtaining an estimate of the mean NET for a given geometric environment is therefore a requisite step to quantify the reaction rate constant of such processes, which has raised a growing interest in the past few years. In this Letter, we determine explicitly the scaling dependence of the mean NET on both the volume of the confining domain and the starting point to aperture distance. We show that this analytical approach is applicable to a very wide range of stochastic processes, including anomalous diffusion or diffusion in the presence of an external force field, which cover situations of biological relevance. Narrow-Escape Time Problem: Time Needed for a Particle to Exit a Confining Domain through a Small Windowb O Bénichou R Voituriez (2008) 2008-05-05T21:45:19-00:00 2008 diffusion statistics http://www.citeulike.org/user/dchen/article/2735310 <i>J. Phys. Chem. B, Vol. 101, No. 50. (11 December 1997), pp. 10674-10679.</i><br /><br />Abstract: The prediction of the stability of low-moisture products is complex, particularly close to the glass transition temperature. This study demonstrates that the relations used to evaluate the influence of temperature on the viscosity of carbohydrate media cannot be applied to the diffusivity. The translational diffusion coefficient of a fluorescent molecule (fluorescein) is measured in sucrose-water mixtures as a function of temperature. The main result is that the mobility of the fluorescein is not simply coupled to the viscosity of the diffusion medium at temperatures close to the glass transition temperature. Indeed the WLF equation, which gives a good prediction of the viscosity, does not allow the determination of the diffusivity in a temperature range close to Tg because the translational diffusion follows a weaker temperature dependence. Different possible explanations for this apparent decoupling between translational diffusion and viscosity are suggested: a small change in the hydrodynamic radius of the diffusing molecule due to low water content and/or a connection with the relaxation process. Translational Diffusion in Sucrose Solutions in the Vicinity of Their Glass Transition Temperature D Champion H Hervet G Blond M Le Meste D Simatos doi:10.1021/jp971899i J. Phys. Chem. B, Vol. 101, No. 50. (11 December 1997), pp. 10674-10679. 2008-04-29T19:54:28-00:00 J. Phys. Chem. B 101 50 10674 10679 decoupling diffusion glass http://www.citeulike.org/user/dchen/article/1835891 <i>Physica A: Statistical and Theoretical Physics, Vol. 216, No. 1-2. (1 June 1995), pp. 85-119.</i><br /><br />A systematic theory for the dynamics of hard-sphere suspensions of interacting Brownian particles with both hydrodynamic and direct interactions is presented. A generalized diffusion equation is derived for concentrated suspensions. The volume fraction ([phi]) dependence of the short- and long-time self-diffusion coefficients are thus explored from a unifying point of view. The long-range hydrodynamic interactions due to the Oseen tensor are shown to play a crucial role in both coefficients, while the short-range hydrodynamic interactions just lead to corrections. The importance of the correlation effects between particles due to the long-range hydrodynamic interactions is also stressed. The nonlocal correlation effect is an important factor, leading to the behavior of the long-time self-diffusion coefficient (DSL) as DSL ~ (1 - [phi]/[phi]0)2 near the volume fraction of [phi]0 = 0.5718. The direct interactions are also found to be drastically reduced by the short-range hydrodynamic interactions. On the theory of concentrated hard-sphere suspensions Michio Tokuyama Irwin Oppenheim doi:10.1016/0378-4371(94)00280-7 Physica A: Statistical and Theoretical Physics, Vol. 216, No. 1-2. (1 June 1995), pp. 85-119. 2007-10-29T15:17:13-00:00 Physica A: Statistical and Theoretical Physics 216 1-2 85 119 density diffusion http://www.citeulike.org/user/dchen/article/822249 <i>Physical Review Letters, Vol. 85, No. 8. (2000), 1774.</i><br /><br />We study the dynamics of rigid spheres embedded in viscoelastic media and address two questions of importance to microrheology. First; we calculate the complete response to an external force of a single bead in a homogeneous elastic network viscously coupled to an incompressible fluid. From this response function we find the frequency range where the standard assumptions of microrheology are valid. Second; we study fluctuations when embedded spheres perturb the media around them and show that mutual fluctuations of two separated spheres provide a more accurate determination of the complex shear modulus than do the fluctuations of a single sphere. One- and Two-Particle Microrheology Alex Levine TC Lubensky doi:10.1103/PhysRevLett.85.1774 Physical Review Letters, Vol. 85, No. 8. (2000), 1774. 2006-08-30T16:26:55-00:00 Physical Review Letters 85 8 1774 American Physical Society cooperative diffusion microrheology http://www.citeulike.org/user/dchen/article/1305143 <i>Physical Review Letters, Vol. 94, No. 10. (2005)</i><br /><br />The microrheology of viscoelastic fluids is obtained from rotational diffusion of optically anisotropic spherical colloidal probes, measured by depolarized dynamic light scattering. The storage and loss moduli obtained from the rotational mean squared displacement is in excellent agreement with those obtained from translational diffusion and by mechanical measurements. We also show that this method is applicable to samples with strong light scattering components. This extends the capabilities of the microrheological methods based on the diffusional motion of colloidal probes. Microrheology from Rotational Diffusion of Colloidal Particles Efren Reyes Pedro Leyva Jose doi:10.1103/PhysRevLett.94.106001 Physical Review Letters, Vol. 94, No. 10. (2005) 2007-05-18T11:12:10-00:00 Physical Review Letters 94 10 APS colloids diffusion microrheology rotation http://www.citeulike.org/user/dchen/article/2719832 <i>The Journal of Chemical Physics, Vol. 116, No. 23. (2002), pp. 10529-10535.</i><br /><br />View This Record in Scopus Measurement of the full shear-induced self-diffusion tensor of noncolloidal suspensions V Breedveld D van den Ende M Bosscher RJJ Jongschaap J Mellema The Journal of Chemical Physics, Vol. 116, No. 23. (2002), pp. 10529-10535. 2008-04-26T00:14:23-00:00 The Journal of Chemical Physics 116 23 10529 10535 AIP diffusion shear theory http://www.citeulike.org/user/dchen/article/2719828 <i>Physical Review Letters, Vol. 61, No. 22. (28 November 1988), 2554.</i> Self-Diffusion of Interacting Colloids Far from Equilibrium Xia Qiu Daniel Ou-Yang DJ Pine PM Chaikin doi:10.1103/PhysRevLett.61.2554 Physical Review Letters, Vol. 61, No. 22. (28 November 1988), 2554. 2008-04-26T00:12:25-00:00 Physical Review Letters 61 22 2554 American Physical Society colloids diffusion shear http://www.citeulike.org/user/dchen/article/2719826 <i>Journal of Fluid Mechanics, Vol. 401, No. -1. (2000), pp. 243-274.</i> Self-diffusion in sheared suspensions by dynamic simulation David Foss John Brady Journal of Fluid Mechanics, Vol. 401, No. -1. (2000), pp. 243-274. 2008-04-26T00:10:55-00:00 Journal of Fluid Mechanics 401 -1 243 274 diffusion shear simulation http://www.citeulike.org/user/dchen/article/2563095 <i>Physical Review Letters, Vol. 98, No. 4. (2007)</i><br /><br />X-ray photon-correlation spectroscopy is used to measure the dynamic structure factor f(q,) of gold particles moving on the surface of thin polymer films. Above the glass transition of the polymer the peculiar form f(q,)~exp[-()] is found with 0.7<<1.5, depending on sample age and temperature. The relaxation rates scale linearly with q, excluding a simple Brownian diffusive motion. This type of behavior, already observed in aging bulk soft matter systems, is explained by a power law distribution of particle velocities due to ballistic motion. Two-Dimensional Dynamics of Metal Nanoparticles on the Surface of Thin Polymer Films Studied with Coherent X Rays S Streit C Gutt V Chamard A Robert M Sprung H Sternemann M Tolan doi:10.1103/PhysRevLett.98.047801 Physical Review Letters, Vol. 98, No. 4. (2007) 2008-03-19T17:03:19-00:00 Physical Review Letters 98 4 APS 2007 diffusion experiment film nano polymer http://www.citeulike.org/user/dchen/article/1826085 <i>Physical Review Letters, Vol. 99, No. 4. (July 2007), 048102.</i><br /><br />The motion of an artificial microscale swimmer that uses a chemical reaction catalyzed on its own surface to achieve autonomous propulsion is fully characterized experimentally. It is shown that at short times it has a substantial component of directed motion, with a velocity that depends on the concentration of fuel molecules. At longer times, the motion reverts to a random walk with a substantially enhanced diffusion coefficient. Our results suggest strategies for designing artificial chemotactic systems. Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk JR Howse RAL Jones AJ Ryan T Gough R Vafabakhsh R Golestanian doi:10.1103/PhysRevLett.99.048102 Physical Review Letters, Vol. 99, No. 4. (July 2007), 048102. 2007-10-26T18:01:29-00:00 Physical Review Letters 99 4 048102 2007 diffusion system http://www.citeulike.org/user/dchen/article/2552968 <i>Physical Review Letters, Vol. 99, No. 6. (2007)</i><br /><br />Comprehensive three-dimensional dissipative particle dynamics simulations are carried out to elucidate the diffusion mechanism of a strongly adsorbed polymer chain on a solid surface in dilute solutions. We find Rouse and reptation dynamics for polymer chain diffusing on smooth and rough surfaces (with obstacles or sticking points), respectively. Combining with scaling analysis, we find that the interactions between the surface and the fluid screen the hydrodynamic interaction. The different scaling as found for a polymer chain diffusing on a fluid membrane [Phys. Rev. Lett. 82, 1911 (1999)] and on a solid surface [Nature (London) 406, 146 (2000)] may be explained by the solid surface inhomogeneity that induces reptation. Surface Diffusion Dynamics of a Single Polymer Chain in Dilute Solution Hu Qian Li Chen Zhong Lu Ze Li doi:10.1103/PhysRevLett.99.068301 Physical Review Letters, Vol. 99, No. 6. (2007) 2008-03-18T21:08:38-00:00 Physical Review Letters 99 6 APS 2007 diffusion people polymer surface http://www.citeulike.org/user/dchen/article/2552923 <i>Physical Review Letters, Vol. 99, No. 10. (2007)</i><br /><br />For a large class of fluids exhibiting ultrasoft bounded pair potentials, particles form crystals consisting of clusters located in the lattice sites, with a density-independent lattice constant. Here we present an investigation on the dynamic features of a representative example of this class. It is found that particles can diffuse between lattice sites, maintaining the lattice structure, through an activated hopping mechanism. This feature yields finite values for the diffusivity and full relaxation of density correlation functions. Simulations suggest the existence of a localization transition which is avoided by hopping and a dynamic decoupling between self- and collective correlations. Diffusion and Relaxation Dynamics in Cluster Crystals Angel Moreno Christos Likos doi:10.1103/PhysRevLett.99.107801 Physical Review Letters, Vol. 99, No. 10. (2007) 2008-03-18T20:36:27-00:00 Physical Review Letters 99 10 APS 2007 diffusion foam http://www.citeulike.org/user/dchen/article/2552883 <i>Physical Review Letters, Vol. 99, No. 13. (2007)</i><br /><br />The three-dimensional motion of single colloidal particles close to a plane wall is measured by optical microscopy. In accordance with classical theoretical predictions, we find an asymmetric motion of the particles in the directions parallel and perpendicular to the wall. We also find that, close to the wall, the distribution functions of perpendicular steps are asymmetric, being shorter toward the wall and longer away from it. Asymmetry in Colloidal Diffusion near a Rigid Wall Mauricio Ricardo Fernandez José doi:10.1103/PhysRevLett.99.138303 Physical Review Letters, Vol. 99, No. 13. (2007) 2008-03-18T20:20:26-00:00 Physical Review Letters 99 13 APS 2007 colloids diffusion http://www.citeulike.org/user/dchen/article/2547842 <i>Physical Review Letters, Vol. 100, No. 10. (2008)</i><br /><br />Thermophoresis is particle drift induced by a temperature gradient. By measuring the full temperature dependence of this effect for polystyrene latex suspensions, we show that the thermophoretic mobility (or “thermal diffusion coefficient”) DT is basically independent on particle size, in particular, when the interfacial properties of the colloidal particles are carefully standardized by adsorbing a surfactant layer on the particle surface. Even more, all investigated systems show values of DT which are very close to those measured for simple micellar solutions of the adsorbed surfactant. Our findings could be of relevance for downsizing microfluidics to the nanometric range. Does Thermophoretic Mobility Depend on Particle Size? Marco Braibanti Daniele Vigolo Roberto Piazza doi:10.1103/PhysRevLett.100.108303 Physical Review Letters, Vol. 100, No. 10. (2008) 2008-03-17T22:30:55-00:00 Physical Review Letters 100 10 APS 2008 diffusion dynamics http://www.citeulike.org/user/dchen/article/2453930 <i>J. Phys. Chem. B, Vol. 110, No. 1. (12 January 2006), pp. 507-511.</i><br /><br />Abstract: Self-diffusion coefficients for the low molecular weight glass former o-terphenyl have been measured near Tg by isothermally desorbing thin film bilayers of deuterio and protio o-terphenyl in a vacuum chamber. We observe translational diffusion that is about 100 times faster at Tg + 3 K than the Stokes-Einstein prediction. Predictions from random first order transition theory and a dynamic facilitation approach are in reasonable agreement with our results; in these approaches, enhanced translational diffusion is associated with spatially heterogeneous dynamics. Self-diffusion controls crystallization in o-terphenyl for most of the supercooled liquid regime, but at temperatures below Tg + 10 K, the reported crystallization rate increases suddenly while the self-diffusion coefficient does not. This work and previous work on trisnaphthylbenzene both find a self-diffusion-controlled crystal growth regime and an enhancement in self-diffusion near Tg, suggesting that these phenomena are general characteristics of fragile low molecular weight glass formers. We discuss the width of the relaxation time distributions of o-terphenyl and trisnaphthylbenzene as they relate to the observation of enhanced translational diffusion. Self-Diffusion of Supercooled <i>o</i>-Terphenyl near the Glass Transition Temperature MK Mapes SF Swallen MD Ediger doi:10.1021/jp0555955 J. Phys. Chem. B, Vol. 110, No. 1. (12 January 2006), pp. 507-511. 2008-03-01T22:46:20-00:00 J. Phys. Chem. B 110 1 507 511 diffusion ediger supercooled http://www.citeulike.org/user/dchen/article/2453757 <i>Physical Review E, Vol. 67, No. 5. (23 May 2003), 051504.</i><br /><br />We have carried out extensive molecular dynamics simulations of a supercooled polydisperse Lennard-Jones liquid with large variations in temperature at a fixed pressure. The particles in the system are considered to be polydisperse in both size and mass. The temperature dependence of dynamical properties such as the viscosity (η) and the self-diffusion coefficients ( D i ) of different size particles is studied. Both viscosity and diffusion coefficients show super-Arrhenius temperature dependence and fit well to the well-known Vogel-Fulcher-Tammann equation. Within the temperature range investigated; the value of Angell’s fragility parameter ( D ≈1.4) classifies the present system as a very fragile liquid. The critical temperature for diffusion ( T o D i ) increases with the size of the particles. The critical temperature for viscosity ( T o η ) is larger than that for diffusion; and sizable deviations appear for the smaller size particles; implying a decoupling of translational diffusion from viscosity in deeply supercooled liquids. Indeed; the diffusion shows markedly non-Stokesian behavior at low temperatures where a highly nonlinear dependence on size is observed. An inspection of the trajectories of the particles shows that at low temperatures the motions of both the smallest and largest size particles are discontinuous (jump type). However; the crossover from continuous Brownian to large length hopping motion takes place at shorter time scales for the smaller size particles. Diffusion and viscosity in a supercooled polydisperse system Rajesh Murarka Biman Bagchi doi:10.1103/PhysRevE.67.051504 Physical Review E, Vol. 67, No. 5. (23 May 2003), 051504. 2008-03-01T21:03:11-00:00 Physical Review E 67 5 051504 American Physical Society diffusion polydisperse viscosity