Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session X13: Focus Session: Jamming III |
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Sponsoring Units: GSNP Chair: Ch. Reichardt, Los Alamos National Laboratory Room: B112 |
Thursday, March 18, 2010 2:30PM - 2:42PM |
X13.00001: Hysteresis in the jamming of frictional granular disks Robert Ecke, Mahesh Bandi, Michael Rivera As a system of short, bi-dispersed disks are uniaxially compressed and decompressed, the global pressure exhibits hysteresis and the areal packing fraction at which the pressure begins to increase shifts slowly to higher values. The details of this process depend on the rate at which compression/decompression occurs and on the material making up the disks. We present experimental data on compression-decompression hysteresis for 4 different sets of 1900 disks with static friction coefficients between 0.05 and 0.25. Relationships of this hysteric behavior to similar hysteresis in porous sandstone rock and the implications of these phenomena to the theory of jamming are discussed. [Preview Abstract] |
Thursday, March 18, 2010 2:42PM - 2:54PM |
X13.00002: A toy spin model for jammed solids Shiliyang Xu, Xavier Illa, J.M. Schwarz Experiments and simulations demonstrate a heterogeneous force network in jammed/amorphous solids. We look for correlations in the force network for a system of soft, repulsive spheres near the onset of jamming by, for example, measuring the contact angle distribution as a function of contact force. We find a peak in this distribution at larger angles for larger contact forces. We couple this information with contact number information of the jammed configurations to construct a Potts spin model with both ferromagnetic and antiferromagnetic interactions in which the strongly interacting spins create a backbone in a sea of more weakly interacting spins. We use this backbone to generate an effective one-dimensional Potts spin glass with long-range interactions whose properties we then study in order to draw connections between spin glasses and jammed solids. [Preview Abstract] |
Thursday, March 18, 2010 2:54PM - 3:06PM |
X13.00003: Rotational and Translational Diffusion Near the Colloidal Glass Transition Kazem V. Edmond, Mark T. Elsesser, Gary L. Hunter, David J. Pine, Eric R. Weeks We study concentrated colloidal suspensions, a model system which has a glass transition. Using confocal microscopy we observe the three-dimensional translational and rotational motion of rigid clusters of particles suspended in a dense colloidal suspension of spheres. The clusters are highly ordered packings of fluorescently-labeled, core-shell PMMA particles, fabricated using a variation of a previously developed emulsification technique [1]. We use the dense suspension of spheres as the supercooled glass-forming liquid, while the clusters serve as tracers possessing rotational and translational dynamics. With image analysis and particle tracking software, we track both the translational and rotational motion of the tracer clusters in three dimensions. Far from the glass transition, both types of motion are purely Brownian in character. In contrast, near the glass transition, we observe both types of motion become temporally intermittent. \\[4pt] [1] V. N. Manoharan, M. T. Elsesser, and D. J. Pine, ``Dense Packing and Symmetry in Small Clusters of Microspheres'' Science 301, 483 (2003) [Preview Abstract] |
Thursday, March 18, 2010 3:06PM - 3:18PM |
X13.00004: Self-dynamic response in simple liquids as resolved by Vibration-Transit theory Giulia DeLorenzi-Venneri, Eric Chisolm, Duane Wallace The dynamic response in a simple liquid is described within the approach of Vibration- Transit theory. In this theory the zeroth-order Hamiltonian describes the vibrational motion in a single random valley. This Hamiltonian is tractable, is evaluated \emph{a priori} for monatomic liquids, and the same Hamiltonian is used for equilibrium and nonequilibrium theory. When applied to the self intermediate scattering function $F^{s}(q,t)$ in liquid sodium, it is found that the vibrational contribution is in perfect agreement with Molecular Dynamics through short and intermediate times, at all q. This is direct confirmation that normal mode vibrational correlations are present in the motion of the liquid state. The primary transit effect is diffusive motion of the vibrational equilibrium positions, as the liquid transits rapidly among random valleys. A model of the transit motion as a standard random walk results in a theoretical $F^{s}(q,t)$ in excellent agreement with molecular dynamics results at all q and t. The present approach provides a decisive improvement over traditional non- equilibrium theories. [Preview Abstract] |
Thursday, March 18, 2010 3:18PM - 3:30PM |
X13.00005: Critical Phenomena in Periodically-Sheared Suspensions Emmanouela Filippidi, Laurence Ramos, Paul Chaikin, David Pine Suspensions of non-colloidal particles under slow periodic strain undergo a dynamical phase transition from an absorbing to an active fluctuating state at a critical strain amplitude. We measure the relevant diverging length and time scales in the experiment and in an activated random walker model. Their scaling near criticality suggests that the model belongs to the conserved directed percolation class. [Preview Abstract] |
Thursday, March 18, 2010 3:30PM - 3:42PM |
X13.00006: Force Network of a 2D Frictionless Emulsion System Kenneth Desmond, Eric R. Weeks We use a quasi-two-dimensional emulsion as a new experimental system to measure various jamming transition properties. Our system consist of confining oil-in-water emulsion droplets between two parallel plates, so that the droplets are squeezed into quasi-two dimensional disks, analogous to granular photoelastic disks. By varying the droplet area fraction, we investigate the force network of this system as we cross through the jamming transition. At a critical area fraction, the composition of the system is no longer characterized primarily by circular disks, but by disks deformed to varying degrees. Quantifying the deformation provides information about the forces acting upon each droplet, and ultimately the force network. The probability distribution of forces is similar to that found for photoelastic disks, with the width of the force distribution narrowing with increasing packing fraction. [Preview Abstract] |
Thursday, March 18, 2010 3:42PM - 3:54PM |
X13.00007: Critical correlations and dynamics of force networks in a model of jammed granular solids Konstantin Turitsyn, Ilya Gruzberg, Julie Stern, Bernard Nienhuis Distribution and correlations of contact forces in two-dimensional static granular packings is studied within a framework of (Edwards) Force Network Ensemble. A two-dimensional ``snooker'' model without friction is shown to be critical. An explicit expression for the force correlation function is derived using Bethe Ansatz. The force correlation function decays algebraically with universal exponent -2. This result implies that the system satisfies (extended) Harris criterion, and that the scale invariant force networks (studied by Ostojic et. al. Nature, 439, 2006) belong to the universality class of the usual percolation transition. These analytical results are confirmed by direct numerical sampling from the ensemble. It is also shown that the microscopic dynamics of forces experiences critical slowdown: the force network relaxation time grows like the sixth power of the system size. This result explains the slow convergence of standard Monte Carlo algorithms, and suggests novel approaches for studying the model. [Preview Abstract] |
Thursday, March 18, 2010 3:54PM - 4:06PM |
X13.00008: Density of States in 2D Colloidal Systems Ke Chen, Wouter Ellenbroek, Zexin Zhang, Ning Xu, Peter Yunker, Andrea Liu, Arjun Yodh The vibrational density of states (VDOS) of particles in a two-dimensional binary colloidal system was investigated using video microscopy. NIPA particles, whose diameters can be tuned by small temperature variations, were loaded into parallel-plate microscope cells, and their motions tracked with video microscopy. This approach permits in-situ observation over a wide range of particle packing fractions, from colloidal fluids to highly-compressed colloidal glasses well above random close-packing density. Using displacement correlation matrix, we extracted the vibraitonal modes from the `shadow system' of \textbf{undamped} particles with the same interactions in the same configurations. At densities above the jamming transition, we find vibrational modes in excess of the Debye prediction, which shift upwards in frequency with compression. At low frequencies, these modes are quasi-localized, in agreement with recent predictions. [Preview Abstract] |
Thursday, March 18, 2010 4:06PM - 4:18PM |
X13.00009: Microfluidic Rheology of Soft Colloids near Jamming Kerstin Nordstrom, E. Verneuil, P.E. Arratia, J.P. Gollub, D.J. Durian The rheology near jamming of a suspension of soft colloidal spheres is studied using pressure-driven flow in a deep 25 $\mu $m wide microchannel. The system is composed of N-isopropylacrylamide (NIPA) microgel particles which exhibit thermoresponsive behavior; the suspension packing fraction is modified with a slight change in temperature. We use a force balance argument to infer the shear stress in the channel and use particle image velocimetry (PIV) to measure the strain rate. Stress vs. strain rate curves show clear non-Newtonian behavior below the jamming point and yield stress behavior above the jamming point. The data may be collapsed onto two branches but with different critical exponents than those obtained by Olsson and Teitel [1]. These results give credence to the idea that jamming is similar to a phase transition, but with interaction-dependent critical exponents. [1] Olsson and Teitel, PRL 2007 [Preview Abstract] |
Thursday, March 18, 2010 4:18PM - 4:30PM |
X13.00010: The ``jammed state'' of a simulated transient polymeric network Arlette Baljon, Joris Stegen, Joris Billen, Mark Wilson, Avinoam Rabinovitch Novel hybrid Molecular Dynamics/Monte Carlo simulations are employed to study transient polymeric networks -- e.g. hydrophilic polymers with hydrophobic endgroups -- computationally. Endgroups of short polymeric chains form junctions that continuously form and break over time. When the temperature is lowered, the probability that a junction breaks decreases. Below a critical temperature the system jams: it stops flowing and exhibits a yield stress under an applied shear. We will report on the underlying topological changes that occur in the polymeric network at this transition point. We will also discuss the behavior of the system under the influence of external stress. Results will be compared with observations in other jammed systems. [Preview Abstract] |
Thursday, March 18, 2010 4:30PM - 4:42PM |
X13.00011: Phase behavior of PNiPAM-PEG microgel suspensions Joaquim Clara-Rahola, Benjamin Sierra-Martin, Andrew Lyon, Alberto Fernandez-Nieves Cross-linked Poly($N$-isopropylacrylamide) (PNiPAM) microgels have been a focus of research in the last decade, with particular interest in the swelling and de-swelling response of particles with temperature, ionic strength and pH. In this work we investigate the phase behavior of PNiPAM microgels cross-linked with Poly(ethylene glycol) (PEG) in aqueous suspensions. We characterize this class of microgels at low concentrations employing light scattering techniques and find that in contrast with other cross-linkers, the properties of PEG at different temperatures result in an unusual intra-particle configuration that guarantees a repulsive interaction between particles throughout the spanned temperature range. We study the dynamic and mechanical properties of PNiPAM-PEG microgel suspensions as a function of temperature at a generalized volume fraction of \textit{$\zeta $} = n$_{p}$ V$_{0}$ = 1.5, with n$_{p}$ the particle number density and V$_{0}$ the volume of a particle at low concentrations. Interestingly, despite we keep \textit{$\zeta $ }constant, we find dramatic changes in behavior with temperature. As a result, the phase behavior of these systems also changes; it exhibits analogies and mark differences with hard sphere behavior. [Preview Abstract] |
Thursday, March 18, 2010 4:42PM - 4:54PM |
X13.00012: Soft Glassy Rheology of Nanosacle Ionic Materials (NIMs) Praveen Agarwal, Haibo Qi, Lynden Archer Nanoscale ionic materials (NIMs) are a recently discovered class of organic-inorganic hybrid materials which are able to relax to equilibrium in absence of any solvent. Linear rheology of these materials manifests classical traits of soft glasses, including a yield stress, slow dynamics and divergence of the viscosity. The frequency response of NIMs in the nonlinear shear regime reveals several heretofore unexplored features of soft glasses. In particular, we report that the dynamic response of NIMs at multiple, discrete strains can be superimposed to produce universal master curves spanning fifteen or more decades in time. This universal behavior, termed `time strain superposition' (TSS), is analogous to time temperature superposition in many regards, including the fact that the shift factors obey a WLF-like relation. This feature was found to be valid in both steady and oscillatory shear rheology. We discuss these findings using Soft Glassy Rheology (SGR) model and propose that `time strain superposition' (TSS) is a generic feature of soft glasses. Along with soft glassy rheological behavior we have also studied the thermal glass transition of in NIMs based on different corona chemistry. [Preview Abstract] |
Thursday, March 18, 2010 4:54PM - 5:06PM |
X13.00013: Structural and Dynamical Study of a Monodisperse Hard-Sphere Glass Former Patrick Charbonneau, Atsushi Ikeda, Jacobus A. van Meel, Kunimasa Miyazaki There exists a variety of theories of jamming and of the glass transition, and many more numerical models. But because the models need built-in complexity to prevent crystallization, comparisons with the theories are sometimes difficult. We address this problem by studying the structure and dynamics of deeply supersaturated monodisperse hard-sphere fluids in four dimension (4D), which have a very low nucleation rate. We examine the predictions of two mean-field treatments of jamming in light of the structural results of the model. We also compare the mode-coupling theory (MCT) of glass formation to the dynamical results. We find MCT to describe this system better than any other structural glass formers in lower dimensions. The reduction in dynamical heterogeneity in 4D suggested by a milder violation of the Stokes-Einstein relation could explain the agreement. These observations are consistent with a dynamical mean-field scenario of the glass transition. [Preview Abstract] |
Thursday, March 18, 2010 5:06PM - 5:18PM |
X13.00014: Jamming, Clogging, and Dynamical Heterogeneities for Vortex Matter in Nanostructured Superconductors Cynthia J. Olson Reichhardt, Charles Reichhardt We show that vortex matter in an asymmetric funnel geometry exhibits a rich variety of dynamical phases, commensurability effects, jamming and clogging behaviors. For vortex flow in the easy direction of the funnel, a series of commensuration peaks appear in the vortex velocity at the matching fields and the overall depinning force increases with increasing vortex density due to jamming of the vortices at the tip of the funnel. For driving in the hard direction, a clogging phase appears in which the flowing vortices organize into a heterogeneous state with a large fraction of the vortices trapped in a small number of funnels, shutting off the flow. Our results should also be relevant for colloids, emulsions, and granular media flowing through funnel geometries. [Preview Abstract] |
Thursday, March 18, 2010 5:18PM - 5:30PM |
X13.00015: ABSTRACT WITHDRAWN |
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