Thu, 21 Aug 2008 09:45:34 BST CiteULike: kdesmond's library [206 articles] http://www.citeulike.org/user/kdesmond/order/to_read CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/kdesmond/article/1201309 <i>Nature, Vol. 410, No. 6825. (March 2001), pp. 259-267.</i> Supercooled liquids and the glass transition Pablo Debenedetti Frank Stillinger doi:10.1038/35065704 Nature, Vol. 410, No. 6825. (March 2001), pp. 259-267. 2007-04-01T02:48:59-00:00 2001 Nature 410 6825 259 267 molecular_glass project_glass review http://www.citeulike.org/user/kdesmond/article/2192344 <i>ArXiv Condensed Matter e-prints (July 2006)</i><br /><br />We review the Random First Order Transition Theory of the glass transition, emphasizing the experimental tests of the theory. Many distinct phenomena are quantitatively predicted or explained by the theory, both above and below the glass transition temperature $T_g$. These include: the viscosity catastrophe and heat capacity jump at $T_g$, and their connection; the non-exponentiality of relaxations and their correlation with the fragility; dynamic heterogeneity in supercooled liquids owing to the mosaic structure; deviations from the Vogel-Fulcher law, connected with strings or fractral cooperative rearrangements; deviations from the Stokes-Einstein relation close to $T_g$; aging, and its correlation with fragility; the excess density of states at cryogenic temperatures due to two level tunneling systems and the Boson Peak. Theory of Structural Glasses and Supercooled Liquids V Lubchenko PG Wolynes ArXiv Condensed Matter e-prints (July 2006) 2008-01-03T21:29:08-00:00 2006 ArXiv Condensed Matter e-prints molecular_glass project_glass review http://www.citeulike.org/user/kdesmond/article/2185718 <i>Physical Review E, Vol. 73, No. 051602. (12 May 2006), pp. 1-7.</i><br /><br />We performed extensive simulations accompanied by a detailed study of a two-segment size random se- quential model on the line. We followed the kinetics towards the jamming state, but we paid particular attention to the characterization of the jamming state structure. In particular, we studied the effect of the size ratio on the mean-gap size, the gap-size dispersion, gap-size skewness, and gap-size kurtosis at the jamming state. We also analyzed the above quantities for the four possible segment-to-segment gap types. We ranged the values of the size ratio from one to twenty. In the limit of a size ratio of one, one recovers the classical car-parking problem. We observed that at low size ratios the jamming state is constituted by short streaks of small and large segments, while at high values of the size ratio the jamming state structure is formed by long streaks of small segments separated by a single large segment. This view of the jamming state structure as a function of the size ratio is supported by the various measured quantities. The present work can help provide insight, for example, on how to minimize the interparticle distance or minimize fluctuations around the mean particle-to-particle distance. Gap-size distribution functions of a random sequential adsorption model of segments on a line NAM Araújo A Cadilhe doi:10.1103/PhysRevE.73.051602 Physical Review E, Vol. 73, No. 051602. (12 May 2006), pp. 1-7. 2008-01-01T17:27:19-00:00 2006 Physical Review E 73 051602 1 7 parking_model http://www.citeulike.org/user/kdesmond/article/1617570 <i>SIAM J. Comput., Vol. 16, No. 1. (February 1987), pp. 78-96.</i> Power diagrams: properties, algorithms and applications F Aurenhammer doi:10.1137/0216006 SIAM J. Comput., Vol. 16, No. 1. (February 1987), pp. 78-96. 2007-09-04T07:06:11-00:00 1987 SIAM J. Comput. 0097-5397 16 1 78 96 Society for Industrial and Applied Mathematics voronoi_construction http://www.citeulike.org/user/kdesmond/article/2184105 <i>Journal of Colloid and Interface Science, Vol. 250, No. 2. (15 June 2002), pp. 457-465.</i><br /><br />In this article, we considered the hydrodynamic interaction between two unequal spheres coated with thin deformable liquids in the asymptotic lubrication regime. This problem is a prototype model for drop coalescence through the so-called "film drainage" mechanism, in which the hydrodynamic contribution comes dominantly from the lubrication region apart from the van der Waals interaction force. First, a general formulation was derived for two unequal coated spheres that experienced a head-to-head collision at a very close proximity. The resulting set of the evolution equations for the deforming film shapes and stress distributions was solved numerically. The film shapes and hydrodynamic interaction forces were determined as functions of the separation distance, film thickness, viscosity ratios, and capillary numbers. The results show that as the two spheres approach each other, the films begin to flatten and eventually to form negative curvature (or a broad dimple) at their forehead areas in which high lubrication pressure is formed. The dimple formation occurs earlier as the capillary number increases. For large capillary numbers, the film liquids are drained out from their forehead areas and the coated liquid films rupture before the two films "touch" each other. Meanwhile, for small capillary numbers, the gap liquid is drained out first and the two liquid films eventually coalesce. Hydrodynamic Interaction between Spheres Coated with Deformable Thin Liquid Films Seung-Man Yang Gary Leal Young-Seok Kim doi:10.1006/jcis.2002.8376 Journal of Colloid and Interface Science, Vol. 250, No. 2. (15 June 2002), pp. 457-465. 2007-12-31T22:32:23-00:00 2002 Journal of Colloid and Interface Science 250 2 457 465 lubrication qualifier http://www.citeulike.org/user/kdesmond/article/2184098 <i>Physical Review Letters, Vol. 95, No. 26. (2005)</i><br /><br />The flow anisotropy of a concentrated colloidal suspension at the jamming transition is studied. It is shown that the use of rough spherical particles reduces the hydrodynamic lubrication forces between adjacent colloids and makes possible the study of the stress tensor anisotropy. At low shear rates, the suspension exerts an attractive force between two opposite surfaces, whereas at higher shear rates it becomes dilatant. Direct confocal microscopy observation of the particles organization reveal that crystallites form at high shear rate. Dilatant Flow of Concentrated Suspensions of Rough Particles Didier Lootens Henri van Damme Yacine Hémar Pascal Hébraud doi:10.1103/PhysRevLett.95.268302 Physical Review Letters, Vol. 95, No. 26. (2005) 2007-12-31T22:26:03-00:00 2005 Physical Review Letters 95 26 APS lubrication qualifier http://www.citeulike.org/user/kdesmond/article/2184097 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 73, No. 1. (2006)</i><br /><br />We report on molecular-dynamics simulations of the drag force experienced by a smooth sphere as it approaches a smooth planar surface to test the predictions of classical hydrodynamic theory. We use a simple repulsive Lennard-Jones-like model to represent the fluid interactions, and calculate the total force on the sphere as a function of its radius, velocity, and distance from the surface. We find that the presence of static solvation forces complicates the testing of hydrodynamic theory which predicts a divergent repulsive lubrication force as the gap vanishes. The solvation force contribution is most prominent at small gaps and small velocities. For a smooth wall its presence can lead to a total force that is oscillating between positive and negative, quite different from the hydrodynamic prediction. To enable an improved test of the lubrication predictions, we propose a different approach that measures the total force for approaching as well as receding spheres. We suggest a simple general analysis that decouples the dynamic and static force contributions on the sphere. The new decoupling method is applicable to simulations and laboratory experiments alike. We illustrate its power by applying it to the molecular-dynamics data. Molecular simulations of lubrication and solvation forces Sivakumar Challa Frank van Swol doi:10.1103/PhysRevE.73.016306 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 73, No. 1. (2006) 2007-12-31T22:24:24-00:00 2006 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 73 1 APS lubrication qualifier http://www.citeulike.org/user/kdesmond/article/2184093 <i>Journal of Colloid and Interface Science, Vol. 301, No. 2. (15 September 2006), pp. 594-606.</i><br /><br />An analytical description is presented for the head-on collision of two spherical rigid particles that are coated with a thin layer of one liquid and immersed in another. Lubrication theory is used to resolve the spatio-temporal evolution of the coating surfaces, in conjunction with the fluid flow in the gap region between the particles. The analysis is carried out up to the point where the gap region has almost completely been drained; intermolecular forces are neglected. The effects of particle inertia, the ratio of particle radii, surface tension, and the viscosity ratio of the coating and carrier fluids are studied; these are parameterised by St, [beta], Ca and m, respectively. The results of the present work elucidate the effect of the above-mentioned factors on the conditions under which particles rebound (assumed to occur if the distance between the particles becomes very short while the relative velocity does not vanish) or stick. In particular, summarizing flowmaps show that the likelihood of particles rebounding increases with increasing St and decreasing [beta], Ca and m. On the other hand, it is shown that the force on approaching particles depends on all of these parameters in a non-monotonic manner. Collisions of liquid coated solid spherical particles in a viscous fluid OK Matar PDM Spelt F Stepanek doi:10.1016/j.jcis.2006.05.026 Journal of Colloid and Interface Science, Vol. 301, No. 2. (15 September 2006), pp. 594-606. 2007-12-31T22:18:15-00:00 2006 Journal of Colloid and Interface Science 301 2 594 606 lubrication qualifier http://www.citeulike.org/user/kdesmond/article/2184081 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 3. (2006)</i><br /><br />Quasi-two-dimensional bidisperse amorphous systems of steel beads are fluidized by a uniform upflow of air, so that the beads roll on a horizontal plane. The short-time ballistic motion of the beads is stochastic, with non-Gaussian speed distributions and with different average kinetic energies for the two species. The approach to jamming is studied as a function of increasing bead area fraction and also as a function of decreasing air speed. The structure of the system is measured in terms of both the Voronoi tessellation and the pair distribution function. The dynamics of the system is measured in terms of both displacement statistics and the density of vibrational states. These quantities all exhibit tell-tale features as the dynamics become more constrained closer to jamming. In particular the pair distribution function and the Voronoi cell shape distribution function both develop split peaks. And the mean-squared displacement develops a plateau of subdiffusive motion separating ballistic and diffusive regimes. Though the system is driven and athermal, this behavior is remarkably reminiscent of that in dense colloidal suspensions and supercooled liquids. One possible difference is that kurtosis of the displacement distribution peaks at the beginning of the subdiffusive regime. Approach to jamming in an air-fluidized granular bed AR Abate DJ Durian doi:10.1103/PhysRevE.74.031308 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 3. (2006) 2007-12-31T22:03:17-00:00 2006 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 74 3 APS granular_gas jamming_transition qualifier http://www.citeulike.org/user/kdesmond/article/2184079 <i>Nat Phys, Vol. 3, No. 4. (April 2007), pp. 260-264.</i> Measurement of growing dynamical length scales and prediction of the jamming transition in a granular material Aaron Keys Adam Abate Sharon Glotzer Douglas Durian doi:10.1038/nphys572 Nat Phys, Vol. 3, No. 4. (April 2007), pp. 260-264. 2007-12-31T22:01:32-00:00 2007 Nat Phys 3 4 260 264 granular jamming jamming_transition qualifier http://www.citeulike.org/user/kdesmond/article/2184078 <i>Physical Review Letters, Vol. 98, No. 5. (2007)</i><br /><br />Recent simulations have predicted that near jamming for collections of spherical particles, there will be a discontinuous increase in the mean contact number Z at a critical volume fraction c. Above c, Z and the pressure P are predicted to increase as power laws in -c. In experiments using photoelastic disks we corroborate a rapid increase in Z at c and power-law behavior above c for Z and P. Specifically we find a power-law increase as a function of -c for Z-Zc with an exponent around 0.5, and for P with an exponent around 1.1. These exponents are in good agreement with simulations. We also find reasonable agreement with a recent mean-field theory for frictionless particles. Jamming Transition in Granular Systems TS Majmudar M Sperl S Luding RP Behringer doi:10.1103/PhysRevLett.98.058001 Physical Review Letters, Vol. 98, No. 5. (2007) 2007-12-31T21:59:04-00:00 2007 Physical Review Letters 98 5 APS granular jamming jamming_transition qualifier http://www.citeulike.org/user/kdesmond/article/2184072 <i>Physics of Fluids, Vol. 9, No. 3. (1997), pp. 540-550.</i><br /><br />  Cavity dynamics in high-speed water entry M Lee RG Longoria DE Wilson Physics of Fluids, Vol. 9, No. 3. (1997), pp. 540-550. 2007-12-31T21:53:14-00:00 1997 Physics of Fluids 9 3 540 550 AIP liquid_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184068 <i>Physics of Fluids, Vol. 10, No. 10. (1998), pp. 2489-2499.</i><br /><br />  Numerical simulation of circular disks entering the free surface of a fluid S Gaudet Physics of Fluids, Vol. 10, No. 10. (1998), pp. 2489-2499. 2007-12-31T21:50:26-00:00 1998 Physics of Fluids 10 10 2489 2499 AIP liquid_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184063 <i>Physical Review Letters, Vol. 96, No. 15. (2006)</i><br /><br />When a solid sphere impacts a shallow layer of sand deposited on a solid surface, a crater can be obtained. The dynamics of the opening of the crater can be followed accurately. During this opening, the radius of the crater can be conveniently modeled by an exponential saturation with a well-defined time constant. The crater then closes up partially once the opening phase is over as the sand avalanches down the slope of the crater. We here present a detailed study of the full dynamics of the crater formation as well as the dynamics of the corrola formed during this process. A simple model accounts for most of our observations. Dynamics of Impact Cratering in Shallow Sand Layers JF Boudet Y Amarouchene H Kellay doi:10.1103/PhysRevLett.96.158001 Physical Review Letters, Vol. 96, No. 15. (2006) 2007-12-31T21:43:41-00:00 2006 Physical Review Letters 96 15 APS granular granular_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184059 <i>Nat Phys, Vol. 3, No. 6. (June 2007), pp. 420-423.</i> Unified force law for granular impact cratering Hiroaki Katsuragi Douglas Durian doi:10.1038/nphys583 Nat Phys, Vol. 3, No. 6. (June 2007), pp. 420-423. 2007-12-31T21:38:11-00:00 2007 Nat Phys 3 6 420 423 granular granular_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184055 <i>Journal of Non-Newtonian Fluid Mechanics, Vol. 135, No. 2-3. (30 May 2006), pp. 97-108.</i><br /><br />We present an experimental study of the impact of a solid sphere on the free surface of a viscoelastic wormlike micellar fluid. Spheres of various densities and diameters are dropped from different heights above the fluid surface, reaching it with a nonzero velocity which determines the subsequent dynamics. Measurements of the initial sphere penetration are found to scale with the ratio of the kinetic energy of the sphere at impact to the elastic modulus of the fluid. The cavity formed in the wake of the sphere, observed with high-speed video imaging, also undergoes transitions from a smooth to fractured surface texture, dependent on both the Deborah number and the ratio of the gravitational force to elasticity. Impact dynamics of a solid sphere falling into a viscoelastic micellar fluid Benjamin Akers Andrew Belmonte doi:10.1016/j.jnnfm.2006.01.004 Journal of Non-Newtonian Fluid Mechanics, Vol. 135, No. 2-3. (30 May 2006), pp. 97-108. 2007-12-31T21:34:59-00:00 2006 Journal of Non-Newtonian Fluid Mechanics 135 2-3 97 108 liquid_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184053 <i>Canadian Journal of Physics, Vol. 82, No. 6. (3 June 2004), pp. 439-446.</i> Penetration of spheres into loose granular media John de Bruyn Amanda Walsh Canadian Journal of Physics, Vol. 82, No. 6. (3 June 2004), pp. 439-446. 2007-12-31T21:32:24-00:00 2004 Canadian Journal of Physics 82 6 439 446 granular granular_impact qual qualifier http://www.citeulike.org/user/kdesmond/article/2184047 <i>Physical Review Letters, Vol. 91, No. 10. (2003), 104301.</i><br /><br />We present the results of experiments on impact craters formed by dropping a steel ball vertically into a container of small glass beads. As the energy of impact increases; we observe a progression of crater morphologies analogous to that seen in craters on the moon. We find that both the diameter and the depth of the craters are proportional to the 1/4 power of the energy. The ratio of crater diameter to rim-to-floor depth is constant for low-energy impacts; but increases at higher energy; similar to what is observed for lunar craters. Morphology and Scaling of Impact Craters in Granular Media Amanda Walsh Kristi Holloway Piotr Habdas John de Bruyn doi:10.1103/PhysRevLett.91.104301 Physical Review Letters, Vol. 91, No. 10. (2003), 104301. 2007-12-31T21:24:11-00:00 2003 Physical Review Letters 91 10 104301 American Physical Society granular granular_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184043 <i>Powder Technology, Vol. 88, No. 1. (July 1996), pp. 95-99.</i><br /><br />The penetration behaviour of impacting particles into glycerol solutions has been studied. A high-speed video technique has been used to observe the particle motion during penetration and to measure the transient displacement of the particle. The experimental range is 10<=Re0<=61 000, 410<=Fr070 000 and 0.287 <=[varrho] 0.953, where Re0 Fr0 and [varrho]' are the particle Reynolds number (v0dp[varrho]/[mu]), the particle Froude number (v02/dpg) and the solid to liquid density ration ([varrho]p/[varrho]) respectively. Comparing a of an equation of motion for a particle penetrating a liquid interfece with the corresponding experimental results revealed that the standard drag coefficients are inappropriate to represent particle impacts owing to the dynamic nature of the flow. This effect was more pronounced with increasing [varrho]'. The critical condition for particle penetration is Re0 [approximate] 250. Characterization of phenomena associated with impacting of spheres into glycerol solutions AN Mouchacca DE Langberg M Nilmani doi:10.1016/0032-5910(96)86778-7 Powder Technology, Vol. 88, No. 1. (July 1996), pp. 95-99. 2007-12-31T21:18:35-00:00 1996 Powder Technology 88 1 95 99 liquid_impact qualifier http://www.citeulike.org/user/kdesmond/article/2184014 <i>Nature, Vol. 413, No. 6854. (2001), pp. 407-409.</i> The jamming route to the glass state in weakly perturbed granular media G D'Anna G Gremaud doi:10.1038/35096540 Nature, Vol. 413, No. 6854. (2001), pp. 407-409. 2007-12-31T21:09:45-00:00 2001 Nature 413 6854 407 409 granular jamming qualifier http://www.citeulike.org/user/kdesmond/article/1929802 <i>Physical Review E, Vol. 66, No. 5. (26 November 2002), 051504.</i><br /><br />We analyze the rotational and translational motion of two close spheres in a fluid at low Reynolds number to investigate if their surfaces come into mechanical contact. The rotational motion of a sphere settling close to another fixed ball is calculated from a model in which contact interactions between the spheres are added to the gravitational and hydrodynamic forces. The model predicts a transition from pure rolling to rolling with slip; determined by the Coulomb’s law; when the ratio of the mechanical friction to the load increases up to the static friction coefficient. The dependence of the angular and translational velocities on the kinetic friction coefficient and on the separation between the particle surfaces is analyzed. The angular and translational velocities of a millimeter size bead in a viscous oil; close to a fixed bead of a similar size; are measured from video images. Interferometric data on translational motion are also collected according to the method introduced in our earlier studies. A systematic fitting procedure of the model to the experiment is developed and applied to the rotational and translational measurements. The model parameters are determined. Rotation due to hydrodynamic interactions between two spheres in contact ML Ekiel-Jeżewska N Lecoq R Anthore F Bostel F Feuillebois doi:10.1103/PhysRevE.66.051504 Physical Review E, Vol. 66, No. 5. (26 November 2002), 051504. 2007-11-17T07:34:24-00:00 2002 Physical Review E 66 5 051504 American Physical Society hydrodynamic-interactions http://www.citeulike.org/user/kdesmond/article/2806310 <i>Physical Review E, Vol. 59, No. 3. (1 March 1999), 3182.</i> Hydrodynamic interactions between two spheres at contact ML Ekiel-Jeżewska F Feuillebois N Lecoq K Masmoudi R Anthore F Bostel E Wajnryb doi:10.1103/PhysRevE.59.3182 Physical Review E, Vol. 59, No. 3. (1 March 1999), 3182. 2008-05-17T03:38:11-00:00 1999 Physical Review E 59 3 3182 American Physical Society hydrodynamic-interactions http://www.citeulike.org/user/kdesmond/article/2800778 <i>Physical Review Letters, Vol. 82, No. 1. (4 January 1999), 205.</i> Slow Drag in a Granular Medium R Albert MA Pfeifer AL Barabási P Schiffer doi:10.1103/PhysRevLett.82.205 Physical Review Letters, Vol. 82, No. 1. (4 January 1999), 205. 2008-05-15T05:55:40-00:00 1999 Physical Review Letters 82 1 205 American Physical Society granular_drag qual qualifier http://www.citeulike.org/user/kdesmond/article/2477183 <i>Annual Review of Fluid Mechanics, Vol. 35, No. 1. (2003), pp. 267-293.</i><br /><br />Abstract The recent avalanche of research activity in the field of granular matter has yielded much progress. The use of state-of-the-art (and other) computational and experimental methods has led to the discovery of new states and patterns and enabled detailed tests of theories and models. The application of statistical mechanical methods and phenomenology has contributed to the understanding of the microscopic a nd macroscopic properties of granular systems. Some previously open problems seem to be solved. Fluidized granular systems (rapid granular flows), recently referred to as granular gases, are often modeled by hydrodynamic equations of motion, some of which are based on systematic expansions applied to the pertinent Boltzmann equation. The undeniable success of granular hydrodynamics is somewhat surprising in view of the lack of scale separation in these systems and the neglect of certain correlations in most derivations of the hydrodynamic equations. Microstructures have been recognized as key features of granular gases; explanations for their existence have been proposed, and many of their properties elucidated. Granular-gas multistability can often be traced back to microstructure dynamics. In spite of these and other impressive advances, this field still poses serious challenges. RAPID GRANULAR FLOWS Isaac Goldhirsch doi:10.1146/annurev.fluid.35.101101.161114 Annual Review of Fluid Mechanics, Vol. 35, No. 1. (2003), pp. 267-293. 2008-03-06T05:32:38-00:00 2003 Annual Review of Fluid Mechanics 35 1 267 293 granular_flow qual qualifier review http://www.citeulike.org/user/kdesmond/article/2796706 <i>(1985)</i> Fluid Mechanics Robert Granger (1985) 2008-05-14T06:11:56-00:00 1985 Dover fluid_mechanics qual http://www.citeulike.org/user/kdesmond/article/1364758 <i>(2000)</i> Sands, Powders, and Grains: An Introduction to the Physics of Granular Materials Jacques Duran (2000) 2007-06-04T21:53:35-00:00 2000 Springer granular qual http://www.citeulike.org/user/kdesmond/article/2783192 <i>Physical Review E, Vol. 62, No. 3. (2000), 4442.</i> Hysteresis and packing in gas-fluidized beds R Ojha N Menon DJ Durian doi:10.1103/PhysRevE.62.4442 Physical Review E, Vol. 62, No. 3. (2000), 4442. 2008-05-10T19:33:45-00:00 2000 Physical Review E 62 3 4442 American Physical Society granular_compaction qual qualifier http://www.citeulike.org/user/kdesmond/article/2783161 <i>EPL (Europhysics Letters), Vol. 60, No. 5. (2002), pp. 677-683.</i><br /><br />We report new experimental results on granular compaction under consecutive vertical taps. The evolution of the mean volume fraction and of the mean potential energy of a granular packing presents a slow densification until a final steady state, and is reminiscent of usual relaxation in glasses via a stretched exponential law. The intensity of the taps seems to rule the characteristic time of the relaxation according to an Arrhenius's type relation. Finally, the analysis of the vertical volume fraction profile reveals an almost homogeneous densification in the packing. Compaction dynamics of a granular medium under vertical tapping P Philippe D Bideau doi:10.1209/epl/i2002-00362-7 EPL (Europhysics Letters), Vol. 60, No. 5. (2002), pp. 677-683. 2008-05-10T19:04:42-00:00 2002 EPL (Europhysics Letters) 60 5 677 683 granular_compaction qual qualifier http://www.citeulike.org/user/kdesmond/article/1360909 <i>Physical Review E, Vol. 57, No. 2. (February 1998), 1971.</i><br /><br />We report systematic measurements of the density of a vibrated granular material as a function of time. Monodisperse spherical beads were confined to a cylindrical container and shaken vertically. Under vibrations; the density of the pile slowly reaches a final steady-state value about which the density fluctuates. We have investigated the frequency dependence and amplitude of these fluctuations as a function of vibration intensity Γ. The spectrum of density fluctuations around the steady state value provides a probe of the internal relaxation dynamics of the system and a link to recent thermodynamic theories for the settling of granular material. In particular; we propose a method to evaluate the compactivity of a powder; first put forth by Edwards and co-workers; that is the analog to temperature for a quasistatic powder. We also propose a stochastic model based on free volume considerations that captures the essential mechanism underlying the slow relaxation. We compare our experimental results with simulations of a one-dimensional model for random adsorption and desorption. Density fluctuations in vibrated granular materials Edmund Nowak James Knight Eli Ben-Naim Heinrich Jaeger Sidney Nagel doi:10.1103/PhysRevE.57.1971 Physical Review E, Vol. 57, No. 2. (February 1998), 1971. 2007-06-03T19:15:17-00:00 1998 Physical Review E 57 2 1971 American Physical Society granular_compaction qualifier http://www.citeulike.org/user/kdesmond/article/2754535 <i>Biophys. J., Vol. 76, No. 1. (1 January 1999), pp. 580-587.</i><br /><br />The technique of electrorotation was used to apply torque to cells of the bacterium Escherichia coli tethered to glass coverslips by single flagella. Cells were made to rotate backward, that is, in the direction opposite to the rotation driven by the flagellar motor itself. The torque generated by the motor under these conditions was estimated using an analysis that explicitly considers the angular dependence of both the viscous drag coefficient of the cell and the torque produced by electrorotation. Motor torque varied approximately linearly with speed up to over 100 Hz in either direction, placing constraints on mechanisms for torque generation in which rates of proton transfer for backward rotation are limiting. These results, interpreted in the context of a simple three-state kinetic model, suggest that the rate-limiting step in the torque-generating cycle is a powerstroke in which motor rotation and dissipation of the energy available from proton transit occur synchronously. Torque Generated by the Flagellar Motor of Escherichia coli while Driven Backward Richard Berry Howard Berg Biophys. J., Vol. 76, No. 1. (1 January 1999), pp. 580-587. 2008-05-04T21:32:13-00:00 1999 Biophys. J. 76 1 580 587 bacteria_flagella_project http://www.citeulike.org/user/kdesmond/article/2747288 <i>Nature, Vol. 427, No. 6974. (5 February 2004), pp. 503-504.</i> Stress propagation: Getting to the bottom of a granular medium Matthew Stone David Bernstein Rachel Barry Matthew Pelc Yee-Kin Tsui Peter Schiffer doi:10.1038/427503a Nature, Vol. 427, No. 6974. (5 February 2004), pp. 503-504. 2008-05-03T00:07:18-00:00 2004 Nature 427 6974 503 504 granular_impact qualifier http://www.citeulike.org/user/kdesmond/article/2747286 <i>Chaos: An Interdisciplinary Journal of Nonlinear Science, Vol. 14, No. 4. (2004), pp. S4-S4.</i><br /><br />View this record in Web of Science Dynamics of meteor impacts Karen Daniels Joyce Coppock Robert Behringer Chaos: An Interdisciplinary Journal of Nonlinear Science, Vol. 14, No. 4. (2004), pp. S4-S4. 2008-05-03T00:06:18-00:00 2004 Chaos: An Interdisciplinary Journal of Nonlinear Science 14 4 S4 S4 AIP granular_impact qualifier http://www.citeulike.org/user/kdesmond/article/2747284 <i>Physical Review E, Vol. 54, No. 2. (1996), 2005.</i> Anomalous density dependence of static friction in sand Viktor Horváth Imre Jánosi Péter Vella doi:10.1103/PhysRevE.54.2005 Physical Review E, Vol. 54, No. 2. (1996), 2005. 2008-05-03T00:04:28-00:00 1996 Physical Review E 54 2 2005 American Physical Society granular qualifier http://www.citeulike.org/user/kdesmond/article/2747282 <i>The European Physical Journal B - Condensed Matter and Complex Systems, Vol. 11, No. 3. (19 October 1999), pp. 525-533.</i><br /><br />Abstract:   We report sets of precise and reproducible measurements on the static pressure at the bottom of a granular column. We make a quantitative analysis of the pressure saturation when the column height is increased. We evidence a great sensitivity of the measurements with the global packing fraction and the eventual presence of shear bands at the boundaries. We also show the limit of the classical Janssen model and discuss these experimental results under the scope of recently proposed theoretical frameworks. Pressure screening and fluctuations at the bottom of a granular column L Vanel E Clément doi:10.1007/s100510050965 The European Physical Journal B - Condensed Matter and Complex Systems, Vol. 11, No. 3. (19 October 1999), pp. 525-533. 2008-05-03T00:03:46-00:00 1999 The European Physical Journal B - Condensed Matter and Complex Systems 11 3 525 533 granular_pressure qualifier http://www.citeulike.org/user/kdesmond/article/2747280 <i>Physical Review E, Vol. 68, No. 5. (7 November 2003), 051301.</i> Compaction force in a confined granular column D Arroyo-Cetto G Pulos R Zenit MA Jiménez-Zapata CR Wassgren doi:10.1103/PhysRevE.68.051301 Physical Review E, Vol. 68, No. 5. (7 November 2003), 051301. 2008-05-03T00:02:33-00:00 2003 Physical Review E 68 5 051301 American Physical Society granular_flow qualifier http://www.citeulike.org/user/kdesmond/article/2280858 <i>Science, Vol. 269, No. 5223. (28 July 1995), pp. 513-515.</i><br /><br />Experimental observations and numerical simulations of the large force inhomogeneities present in stationary bead packs are presented. Forces much larger than the mean occurred but were exponentially rare. An exactly soluble model reproduced many aspects of the experiments and simulations. In this model, the fluctuations in the force distribution arise because of variations in the contact angles and the constraints imposed by the force balance on each bead in the pile. 10.1126/science.269.5223.513 Force Fluctuations in Bead Packs Liu SR Nagel DA Schecter SN Coppersmith S Majumdar O Narayan TA Witten doi:10.1126/science.269.5223.513 Science, Vol. 269, No. 5223. (28 July 1995), pp. 513-515. 2008-01-23T15:01:10-00:00 1995 Science 269 5223 513 515 force_chains qualifier http://www.citeulike.org/user/kdesmond/article/2477160 <i>Annual Review of Fluid Mechanics, Vol. 40, No. 1. (2008), pp. 1-24.</i><br /><br />We review flows of dense cohesionless granular materials, with a special focus on the question of constitutive equations. We first discuss the existence of a dense flow regime characterized by enduring contacts. We then emphasize that dimensional analysis strongly constrains the relation between stresses and shear rates, and show that results from experiments and simulations in different configurations support a description in terms of a frictional visco-plastic constitutive law. We then discuss the successes and limitations of this empirical rheology in light of recent alternative theoretical approaches. Finally, we briefly present depth-averaged methods developed for free surface granular flows. Flows of Dense Granular Media Yoel Forterre Olivier Pouliquen doi:10.1146/annurev.fluid.40.111406.102142 Annual Review of Fluid Mechanics, Vol. 40, No. 1. (2008), pp. 1-24. 2008-03-06T05:28:36-00:00 2008 Annual Review of Fluid Mechanics 40 1 1 24 granular_flow qual qualifier http://www.citeulike.org/user/kdesmond/article/2747273 <i>EPL (Europhysics Letters), Vol. 72, No. 1. (2005), pp. 137-143.</i><br /><br />The average drag forces on intruders slowly plunging into and withdrawing from shallow beds of monodisperse smooth glass beads and of sifted rough sand scale with the immersion depth and lateral dimensions of the intruder. The withdrawal forces are comparable for both types of media; however, the plunging forces for sand are substantially greater than for smooth glass beads. Furthermore, for glass beads, the rescaled plunging and withdrawal forces have two different power law dependences on the immersion depth, with exponents greater than unity. Scaling vertical drag forces in granular media G Hill S Yeung SA Koehler doi:10.1209/epl/i2005-10203-3 EPL (Europhysics Letters), Vol. 72, No. 1. (2005), pp. 137-143. 2008-05-02T23:58:00-00:00 2005 EPL (Europhysics Letters) 72 1 137 143 granular_flow qual qualifier http://www.citeulike.org/user/kdesmond/article/2747272 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 72, No. 2. (2005)</i><br /><br />We study the plane shear flow of a dense assembly of dissipative disks using discrete simulation and prescribing the pressure and the shear rate. Those shear states are steady and uniform, and become intermittent in the quasistatic regime. In the limit of rigid grains, the shear state is determined by a single dimensionless number, called the inertial number I, which describes the ratio of inertial to pressure forces. Small values of I correspond to the quasistatic critical state of soil mechanics, while large values of I correspond to the fully collisional regime of kinetic theory. When I increases in the intermediate dense flow regime, we measure an approximately linear decrease of the solid fraction from the maximum packing value, and an approximately linear increase of the effective friction coefficient from the static internal friction value. From those dilatancy and friction laws, we deduce the constitutive law for dense granular flows, with a plastic Coulomb term and a viscous Bagnold term. The mechanical characteristics of the grains (restitution, friction, and elasticity) have a small influence in the dense flow regime. Finally, we show that the evolution of the relative velocity fluctuations and of the contact force anisotropy as a function of I provides a simple explanation of the friction law. Rheophysics of dense granular materials: Discrete simulation of plane shear flows Frédéric da Cruz Sacha Emam Michaël Prochnow Jean Roux Fran\ccois Chevoir doi:10.1103/PhysRevE.72.021309 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 72, No. 2. (2005) 2008-05-02T23:57:00-00:00 2005 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 72 2 APS granular_flow qual qualifier http://www.citeulike.org/user/kdesmond/article/2747227 <i>Granular Matter, Vol. 7, No. 4. (11 November 2005), pp. 185-190.</i><br /><br />We describe a dynamic light scattering experiment designed in order to study creep motion in granular materials. This method is based on the recording of the speckle pattern with a charge coupled device (CCD) camera. The autocorrelation function of the scattered electric field is calculated and related to the displacement field of the beads. As an application, the measurement of the thermal expansion of a granular material subjected to temperature variations is presented. Probing creep motion in granular materials with light scattering Linda Djaoui Jérôme Crassous doi:10.1007/s10035-005-0210-5 Granular Matter, Vol. 7, No. 4. (11 November 2005), pp. 185-190. 2008-05-02T23:12:19-00:00 2005 Granular Matter 7 4 185 190 granular_flow qualifier http://www.citeulike.org/user/kdesmond/article/781292 <i>J. Stat. Mech., Vol. 2006, No. 07. (July 2006), P07020.</i> Flow of dense granular material: towards simple constitutive laws O Pouliquen C Cassar P Jop Y Forterre M Nicolas doi:10.1088/1742-5468/2006/07/P07020 J. Stat. Mech., Vol. 2006, No. 07. (July 2006), P07020. 2006-08-01T00:34:07-00:00 2006 J. Stat. Mech. 1742-5468 2006 07 P07020 Institute of Physics Publishing granular_flow qualifier http://www.citeulike.org/user/kdesmond/article/2747217 <i>Comptes Rendus Physique, Vol. 3, No. 2. (2002), pp. 163-175.</i><br /><br />The behavior of dense assemblies of dry grains submitted to continuous shear deformation is still not well understood. Recently it has been the subject of several experiments and discrete particle simulations. For both confined and free surface geometries, we present the general features of such flows as well as grain-level information. We then describe the main rheological models and their predictions. To cite this article: O. Pouliquen, F. Chevoir, C. R. Physique 3 (2002) 163-175. Dense flows of dry granular material Olivier Pouliquen François Chevoir doi:10.1016/S1631-0705(02)01309-9 Comptes Rendus Physique, Vol. 3, No. 2. (2002), pp. 163-175. 2008-05-02T23:02:34-00:00 2002 Comptes Rendus Physique 3 2 163 175 granular_flow qualifier http://www.citeulike.org/user/kdesmond/article/2747139 <i>The European Physical Journal E - Soft Matter, Vol. 14, No. 4. (2004), pp. 341-365.</i><br /><br />The behaviour of dense assemblies of dry grains submitted to continuous shear deformation has been the subject of many experiments and discrete particle simulations. This paper is a collective work carried out among the French research group Groupement de Recherche Milieux Divisés (GDR MiDi). It proceeds from the collection of results on steady uniform granular flows obtained by different groups in six different geometries both in experiments and numerical works. The goal is to achieve a coherent presentation of the relevant quantities to be measured i.e. flowing thresholds, kinematic profiles, effective friction, etc. First, a quantitative comparison between data coming from different experiments in the same geometry identifies the robust features in each case. Second, a transverse analysis of the data across the different configurations, allows us to identify the relevant dimensionless parameters, the different flow regimes and to propose simple interpretations. The present work, more than a simple juxtaposition of results, demonstrates the richness of granular flows and underlines the open problem of defining a single rheology. On dense granular flows GDR Midi doi:10.1140/epje/i2003-10153-0 The European Physical Journal E - Soft Matter, Vol. 14, No. 4. (2004), pp. 341-365. 2008-05-02T21:47:15-00:00 2004 The European Physical Journal E - Soft Matter 14 4 341 365 granular_flow qual qualifier http://www.citeulike.org/user/kdesmond/article/1234059 <i>J Mol Biol, Vol. 138, No. 3. (15 April 1980), pp. 563-597.</i> The steady-state counterclockwise/clockwise ratio of bacterial flagellar motors is regulated by protonmotive force. S Khan RM Macnab J Mol Biol, Vol. 138, No. 3. (15 April 1980), pp. 563-597. 2007-04-18T13:34:20-00:00 1980 J Mol Biol 0022-2836 138 3 563 597 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746774 <i>Journal of molecular biology, Vol. 138, No. 3. (15 April 1980), pp. 599-614.</i> Proton chemical potential, proton electrical potential and bacterial motility. S Khan RM Macnab Journal of molecular biology, Vol. 138, No. 3. (15 April 1980), pp. 599-614. 2008-05-02T18:28:34-00:00 1980 Journal of molecular biology 0022-2836 138 3 599 614 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746768 <i>Cell, Vol. 49, No. 5. (5 June 1987), pp. 643-650.</i><br /><br />Bacterial flagella are driven by a rotary motor that utilizes the free energy stored in the electrochemical proton gradient across the cytoplasmic membrane to do mechanical work. The flux of protons coupled to motor rotation was measured in Streptococcus and found to be directly proportional to motor speed. This supports the hypothesis that the movement of protons through the motor is tightly coupled to the rotation of its flagellar filament. Under this assumption the efficiency of energy conversion is close to unity at the low speeds encountered in tethered cells but only a few percent at the high speeds encountered in swimming cells. This difference appears to be due to dissipation by processes internal to the motor. The efficiency at high speeds exhibits a steep temperature dependence and a sizable deuterium solvent isotope effect. The proton flux through the bacterial flagellar motor. M Meister G Lowe HC Berg Cell, Vol. 49, No. 5. (5 June 1987), pp. 643-650. 2008-05-02T18:25:04-00:00 1987 Cell 0092-8674 49 5 643 650 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746760 <i>Biophys. J., Vol. 78, No. 5. (1 May 2000), pp. 2280-2284.</i><br /><br />We studied changes in speed of the flagellar rotary motor of Escherichia coli when tethered cells or cells carrying small latex spheres on flagellar stubs were shifted from H2O to D2O or subjected to changes in external pH. In the high-torque, low-speed regime, solvent isotope effects were found to be small; in the low-torque, high-speed regime, they were large. The boundaries between these regimes were close to those found earlier in measurements of the torque-speed relationship of the flagellar rotary motor (Berg and Turner, 1993, Biophys. J. 65:2201-2216; Chen and Berg, 2000, Biophys. J., 78:1036-1041). This observation provides direct evidence that the decline in torque at high speed is due primarily to limits in rates of proton transfer. However, variations of speed (and torque) with shifts of external pH (from 4.7 to 8.8) were small for both regimes. Therefore, rates of proton transfer are not very dependent on external pH. Solvent-Isotope and pH Effects on Flagellar Rotation in Escherichia coli Xiaobing Chen Howard Berg Biophys. J., Vol. 78, No. 5. (1 May 2000), pp. 2280-2284. 2008-05-02T18:23:23-00:00 2000 Biophys. J. 78 5 2280 2284 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746757 <i>Nature, Vol. 309, No. 5967. (31 May 1984), pp. 470-472.</i> Successive incorporation of force-generating units in the bacterial rotary motor Steven Block Howard Berg doi:10.1038/309470a0 Nature, Vol. 309, No. 5967. (31 May 1984), pp. 470-472. 2008-05-02T18:22:41-00:00 1984 Nature 309 5967 470 472 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746755 <i>Science, Vol. 242, No. 4886. (23 December 1988), pp. 1678-1681.</i><br /><br />Paralyzed motors of motA and motB point and deletion mutants of Escherichia coli were repaired by synthesis of wild-type protein. As found earlier with a point mutant of motB, torque was restored in a series of equally spaced steps. The size of the steps was the same for both MotA and MotB. Motors with one torque generator spent more time spinning counterclockwise than did motors with two or more generators. In deletion mutants, stepwise decreases in torque, rare in point mutants, were common. Several cells stopped accelerating after eight steps, suggesting that the maximum complement of torque generators is eight. Each generator appears to contain both MotA and MotB. 10.1126/science.2849208 Restoration of torque in defective flagellar motors DF Blair HC Berg doi:10.1126/science.2849208 Science, Vol. 242, No. 4886. (23 December 1988), pp. 1678-1681. 2008-05-02T18:21:55-00:00 1988 Science 242 4886 1678 1681 bacteria_flagella_project biophysics http://www.citeulike.org/user/kdesmond/article/2746753 <i>Proceedings of the National Academy of Sciences, Vol. 74, No. 7. (15 July 1977), pp. 3060-3064.</i><br /><br />Streptococcus strain V4051 is motile in the presence of glucose. The cells move steadily along smooth paths (run), jump about briefly with little net displacement (twiddle), and then run in new directions. They stop swimming when deprived of glucose. These cells become motile when an electrical potential or a pH gradient is imposed across the membrane. Starved cells suspended in a potassium-free medium respond to the addition of valinomycin by a brief period of vigorous twiddling. They also twiddle, although less vigorously, when the external pH is lowered. Valinomycin-induced twiddling occurs in the absence of external alkali or alkaline earth cations and without significant net synthesis of ATP. When a chemoattractant is added to cells swimming in the presence of glucose, twiddles are transiently suppressed, and the cells run for a time. Similarly, when starved cells are suspended in a potassium-free medium containing both valinomycin and an attractant, many cells initially run rather than twiddle. We conclude that the flagella are driven by a protonmotive force. 10.1073/pnas.74.7.3060 A Protonmotive Force Drives Bacterial Flagella Michael Manson Pat Tedesco Howard Berg Franklin Harold Chris Drift doi:10.1073/pnas.74.7.3060 Proceedings of the National Academy of Sciences, Vol. 74, No. 7. (15 July 1977), pp. 3060-3064. 2008-05-02T18:21:07-00:00 1977 Proceedings of the National Academy of Sciences 74 7 3060 3064 bacteria_flagella_project biophysics