CiteULike: dchen's library [665 articles] http://www.citeulike.org/user/dchen/order/to_read CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2719755 <i>Phys. Rev. Lett. 96, 138302 (2006)</i><br /><br />The nonlinear rheological response of soft glassy materials is addressed experimentally by focusing on concentrated emulsions where interdroplet attraction is tuned through varying the surfactant content. Velocity profiles are recorded using ultrasonic velocimetry simultaneously to global rheological data in the Couette geometry. Our data show that nonadhesive and adhesive emulsions have radically different flow behaviors in the vicinity of yielding: while the flow remains homogeneous in the nonadhesive emulsion and the Herschel-Bulkley model for a yield stress fluid describes the data very accurately, the adhesive system displays shear localization and does not follow a simple constitutive equation, suggesting that the mechanisms involved in yielding transitions are not universal. Yielding and Flow in Adhesive and Nonadhesive Concentrated Emulsions Lydiane Phys. Rev. Lett. 96, 138302 (2006) 2008-04-25T23:31:45-00:00 Phys. Rev. Lett. 96, 138302 (2006) emulsion shear technique http://www.citeulike.org/user/dchen/article/2710365 <i>Science, Vol. 305, No. 5692. (24 September 2004), pp. 1944-1948.</i><br /><br />The dominant mechanism for creating large irreversible strain in atomic crystals is the motion of dislocations, a class of line defects in the crystalline lattice. Here we show that the motion of dislocations can also be observed in strained colloidal crystals, allowing detailed investigation of their topology and propagation. We describe a laser diffraction microscopy setup used to study the growth and structure of misfit dislocations in colloidal crystalline films. Complementary microscopic information at the single-particle level is obtained with a laser scanning confocal microscope. The combination of these two techniques enables us to study dislocations over a range of length scales, allowing us to determine important parameters of misfit dislocations such as critical film thickness, dislocation density, Burgers vector, and lattice resistance to dislocation motion. We identify the observed dislocations as Shockley partials that bound stacking faults of vanishing energy. Remarkably, we find that even on the scale of a few lattice vectors, the dislocation behavior is well described by the continuum approach commonly used to describe dislocations in atomic crystals. 10.1126/science.1102186 Visualization of Dislocation Dynamics in Colloidal Crystals Peter Schall Itai Cohen David Weitz Frans Spaepen doi:10.1126/science.1102186 Science, Vol. 305, No. 5692. (24 September 2004), pp. 1944-1948. 2008-04-23T22:01:50-00:00 Science 305 5692 1944 1948 cohen schall science shear weitz http://www.citeulike.org/user/dchen/article/553502 <i>Nature, Vol. 440, No. 7082., pp. 319-323.</i> Visualizing dislocation nucleation by indenting colloidal crystals Peter Schall Itai Cohen David Weitz Frans Spaepen doi:10.1038/nature04557 Nature, Vol. 440, No. 7082., pp. 319-323. 2006-03-15T23:36:35-00:00 Nature 0028-0836 440 7082 319 323 Nature Publishing Group defect schall shear weitz http://www.citeulike.org/user/dchen/article/2709675 <i>Physical Review Letters, Vol. 96, No. 19. (2006)</i><br /><br />We have studied the effect of shear on the stability of suspensions made of non-Brownian solid particles. We demonstrate the existence of an irreversible transition where the solid particles aggregate at remarkably low volume fractions (0.1). This shear-induced aggregation is dramatic and exhibits a very sudden change in the viscosity, which increases sharply after a shear-dependent induction time. We show that this induction time is related exponentially to the shear rate, reflecting the importance of the hydrodynamic forces in reducing the repulsive energy barrier that prevents the particles from aggregating. Irreversible Shear-Activated Aggregation in Non-Brownian Suspensions J Guery E Bertrand C Rouzeau P Levitz DA Weitz J Bibette doi:10.1103/PhysRevLett.96.198301 Physical Review Letters, Vol. 96, No. 19. (2006) 2008-04-23T18:01:46-00:00 Physical Review Letters 96 19 APS hydrodynamics shear weitz http://www.citeulike.org/user/dchen/article/1409983 <i>The Journal of Chemical Physics, Vol. 125, No. 7. (2006)</i><br /><br />Coherent anti-Stokes Raman scattering microscopy is performed on glassy systems of poly(methylmethacrylate) colloidal particles in density- and refractive-index-matched solvents. Samples are prepared with varying amounts of linear polystyrene, which induces a depletion driven attraction between the nearly hard-sphere particles. Images collected over several hours confirm the existence of a reentrant glass transition. The images also reveal that the dynamics of repulsive and attractive glasses are qualitatively different. Colloidal particles in repulsive glasses exhibit cage rattling and escape, while those in attractive glasses are nearly static while caged but exhibit large displacements upon (infrequent) cage escape. ©2006 American Institute of Physics Direct imaging of repulsive and attractive colloidal glasses Laura Kaufman David Weitz doi:10.1063/1.2227386 The Journal of Chemical Physics, Vol. 125, No. 7. (2006) 2007-06-25T01:35:08-00:00 The Journal of Chemical Physics 125 7 AIP colloids microscope weitz http://www.citeulike.org/user/dchen/article/733339 <i>J. Phys. Chem. B, Vol. 109, No. 45. (17 November 2005), pp. 21235-21240.</i> Weak Correlations between Local Density and Dynamics near the Glass Transition JC Conrad FW Starr DA Weitz doi:10.1021/jp0514168 J. Phys. Chem. B, Vol. 109, No. 45. (17 November 2005), pp. 21235-21240. 2006-07-03T19:08:55-00:00 J. Phys. Chem. B 109 45 21235 21240 dynamics freevolume structure weitz http://www.citeulike.org/user/dchen/article/765133 <i>Nature, Vol. 416, No. 6883. (25 April 2002), pp. 811-815.</i><br /><br />Colloids display intriguing transitions between gas, liquid, solid and liquid crystalline phases. Such phase transitions are ubiquitous in nature and have been studied for decades. However, the predictions of phase diagrams are not always realized; systems often become undercooled, supersaturated, or trapped in gel-like states. In many cases the end products strongly depend on the starting position in the phase diagram and discrepancies between predictions and actual observations are due to the intricacies of the dynamics of phase transitions. Colloid science aims to understand the underlying mechanisms of these transitions. Important advances have been made, for example, with new imaging techniques that allow direct observation of individual colloidal particles undergoing phase transitions, revealing some of the secrets of the complex pathways involved. Insights into phase transition kinetics from colloid science Valerie Anderson Henk Lekkerkerker doi:10.1038/416811a Nature, Vol. 416, No. 6883. (25 April 2002), pp. 811-815. 2006-07-19T21:09:52-00:00 Nature 416 6883 811 815 classic colloids depletion nature phase review http://www.citeulike.org/user/dchen/article/2795510 <i>Journal of Non-Crystalline Solids, Vol. 351, No. 8-9. (1 April 2005), pp. 678-690.</i><br /><br />Glass-forming ability characterizes how easily we can avoid crystallization and thus make a glassy state of material from its liquid state upon cooling. Its quantitative measure is given by the critical cooling rate, which is the minimum cooling rate required for the formation of glass, or the avoidance of crystal nucleation. Here we consider what physical factors control the glass-forming ability of a liquid. We argue that short-range bond ordering, which is induced by a symmetry-selective part of the interaction potential, causes frustration against crystallization and helps vitrification if its local symmetry is not consistent with that of the equilibrium crystal. Based on this physical picture, we propose that the degree of short-range bond ordering in a liquid should be a new additional physical factor controlling the glass-forming ability. According to our model, it is also a controlling factor of the fragility, which characterizes how steeply viscosity increases upon cooling. This picture suggests a negative correlation between the glass-forming ability and the fragility. The close relationship between the glass-forming ability and the quasicrystal-forming ability in metallic glass formers is also discussed in the light of our model. Relationship among glass-forming ability, fragility, and short-range bond ordering of liquids Hajime Tanaka doi:10.1016/j.jnoncrysol.2005.01.070 Journal of Non-Crystalline Solids, Vol. 351, No. 8-9. (1 April 2005), pp. 678-690. 2008-05-13T15:47:46-00:00 Journal of Non-Crystalline Solids 351 8-9 678 690 glass order tanaka http://www.citeulike.org/user/dchen/article/2795389 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 71, No. 2. (2005)</i><br /><br />There are two types of isotropic disordered nonergodic states in colloidal suspensions: colloidal glasses and gels. In a recent paper [H. Tanaka, J. Meunier, and D. Bonn, Phys. Rev. E 69, 031404 (2004)], we discussed the static aspect of the differences and the similarities between the two. In this paper, we focus on the dynamic aspect. The kinetics of the liquid-glass transition is called "aging," while that of the sol-gel transition is called "gelation." The former is primarily governed by repulsive interactions between particles, while the latter is dominated by attractive interactions. Slowing down of the dynamics during aging reflects the increasing cooperativity required for the escape of a particle from the cage formed by the surrounding particles, while that during gelation reflects the increase in the size of particle clusters towards the percolation transition. Despite these clear differences in the origin of the slowing down of the kinetics between the two, it is not straightforward experimentally to distinguish them in a clear manner. For an understanding of the universal nature of ergodic-to-nonergodic transitions, it is of fundamental importance to elucidate the differences and the similarities in the kinetics between aging and gelation. We consider this problem, taking Laponite suspension as an explicit example. In particular, we focus on the two types of nonergodic states: (i) an attractive gel formed by van der Waals attractions for high ionic strengths and (ii) a repulsive Wigner glass stabilized by long-range Coulomb repulsions for low ionic strengths. We demonstrate that the aging of colloidal Wigner glass crucially differs not only from gelation, but also from the aging of structural and spin glasses. The aging of the colloidal Wigner glass is characterized by the unique cage-forming regime that does not exist in the aging of spin and structural glasses. Kinetics of ergodic-to-nonergodic transitions in charged colloidal suspensions: Aging and gelation Hajime Tanaka Sara Farouji Jacques Meunier Daniel Bonn doi:10.1103/PhysRevE.71.021402 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 71, No. 2. (2005) 2008-05-13T15:20:47-00:00 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 71 2 APS aging gel simulation tanaka http://www.citeulike.org/user/dchen/article/2791741 <i>Physical Review Letters, Vol. 97, No. 12. (2006)</i><br /><br />We numerically study many-body interactions among colloidal particles suspended in a nematic liquid crystal, using a fluid particle dynamics method, which properly incorporates dynamical coupling among particles, nematic orientation, and flow field. Based on simulation results, we propose a new type of interparticle interaction in addition to well-known quadrupolar interaction for particles accompanying Saturn-ring defects. This interaction is mediated by the defect of the nematic phase: upon nematic ordering, a closed disclination loop binds more than two particles to form a sheetlike dynamically arrested structure. The interaction depends upon the topology of a disclination loop binding particles, which is determined by aggregation history. Colloidal Aggregation in a Nematic Liquid Crystal: Topological Arrest of Particles by a Single-Stroke Disclination Line Takeaki Araki Hajime Tanaka doi:10.1103/PhysRevLett.97.127801 Physical Review Letters, Vol. 97, No. 12. (2006) 2008-05-13T00:24:02-00:00 Physical Review Letters 97 12 APS 2006 colloids defect interaction liquidcrystal simulation tanaka http://www.citeulike.org/user/dchen/article/1117518 <i>Nature, Vol. 445, No. 7130. (21 February 2007), pp. 831-832.</i> Physical chemistry: Oil on troubled waters David Chandler doi:10.1038/445831a Nature, Vol. 445, No. 7130. (21 February 2007), pp. 831-832. 2007-02-22T10:11:19-00:00 Nature 0028-0836 445 7130 831 832 Nature Publishing Group 2007 interface nature oil water http://www.citeulike.org/user/dchen/article/2006573 <i>Physical Review Letters, Vol. 98, No. 23. (2007)</i><br /><br />Generally, phase transitions are seriously affected by spatial confinement. This effect is important for its own sake, but also for applications to nanotechnology. Here we report the first systematic experimental study on confinement effects on a liquid-liquid transition of a molecular liquid. We found that one liquid can be transformed into another purely by spatial confinement. This indicates that the liquid state cannot be specified by the temperature and pressure alone, but it is also affected by its size in a discontinuous manner: the phase of a liquid in a narrow space can, in principle, be different from that in the bulk. This finding would deepen our basic understanding of the liquid state. Control of the Liquid-Liquid Transition in a Molecular Liquid by Spatial Confinement Rei Kurita Hajime Tanaka doi:10.1103/PhysRevLett.98.235701 Physical Review Letters, Vol. 98, No. 23. (2007) 2007-11-28T18:24:35-00:00 Physical Review Letters 98 23 APS 2007 confinement liquid tanaka transition http://www.citeulike.org/user/dchen/article/2767692 <i>Physical Review Letters, Vol. 100, No. 7. (2008)</i><br /><br />Previous works on single bubble sonoluminescence in sulfuric acid solutions have stressed the fact that the sonoluminescence (SL) emissions are the highest ever found, but at the same time the bubble moves in orbits. We have fixed the SL bubble spatially and at the same time we have reached higher SL emissions using another harmonic acoustic signal to produce the acoustic excitation. Multiple harmonic excitation produces up to a fourfold increase in SL emissions, reaching the peak value of about 40 µW for a moving bubble and 15 µW for a nonmoving bubble. The ability to have a bright stationary bubble also opens new research opportunities. In particular, we develop a new method to measure the absolute radius evolution of the bubble that exploits this stability. Trapping an Intensely Bright, Stable Sonoluminescing Bubble Raúl Urteaga Fabián Bonetto doi:10.1103/PhysRevLett.100.074302 Physical Review Letters, Vol. 100, No. 7. (2008) 2008-05-07T23:29:17-00:00 Physical Review Letters 100 7 APS 2008 bubbles cool http://www.citeulike.org/user/dchen/article/2767689 <i>Physical Review Letters, Vol. 100, No. 8. (2008)</i><br /><br />Modified water models with scaled charges are used to investigate solvent polarity effects on DNA structure. Several intensive molecular dynamics simulations of the DNA EcoRI dodecamer d(CGCGAATTCGCG) in different model solvents are performed. When the polarity of the solvent molecule decreases, from overpolarized to less polarized, DNA experiences the conformational transitions of constrainedB form(A-B)mixA form. We demonstrate that one important cause of these structure changes is the competition between hydration and direct cation coupling to the free oxygen atoms in the phosphate groups on DNA backbones. Solvent-Induced DNA Conformational Transition B Gu FS Zhang ZP Wang HY Zhou doi:10.1103/PhysRevLett.100.088104 Physical Review Letters, Vol. 100, No. 8. (2008) 2008-05-07T23:28:21-00:00 Physical Review Letters 100 8 APS 2008 biology people 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/2767637 <i>Physical Review Letters, Vol. 100, No. 10. (2008)</i><br /><br />We introduce a general methodology based on magnetic colloids to study the recognition kinetics of tethered biomolecules. Access to the full kinetics of the reaction is provided by an explicit measure of the time evolution of the reactant densities. Binding between a single ligand and its complementary receptor is here limited by the colloidal rotational diffusion. It occurs within a binding distance that can be extracted by a reaction-diffusion theory that properly accounts for the rotational Brownian dynamics. Our reaction geometry allows us to probe a large diversity of bioadhesive molecules and tethers, thus providing a quantitative guidance for designing more efficient reactive biomimetic surfaces, as required for diagnostic, therapeutic, and tissue engineering techniques. Measuring the Kinetics of Biomolecular Recognition with Magnetic Colloids Cohen Tannoudji E Bertrand J Baudry C Robic C Goubault M Pellissier A Johner F Thalmann Lee CM Marques J Bibette doi:10.1103/PhysRevLett.100.108301 Physical Review Letters, Vol. 100, No. 10. (2008) 2008-05-07T23:01:32-00:00 Physical Review Letters 100 10 APS 2008 colloids magnetic http://www.citeulike.org/user/dchen/article/2767626 <i>Physical Review Letters, Vol. 100, No. 10. (2008)</i><br /><br />The molecular dynamics of three dipole functionalized hexa-peri-hexabenzocoronenes have been studied using site-specific NMR techniques and dielectric spectroscopy as a function of temperature and pressure. These probes (i) suggest that the thermodynamic state completely controls the dynamic response, (ii) clarify the origin of two dynamic processes associated with the presence of two glass temperatures, and (iii) provide the first phase diagram for substances of this kind. Origin of the Complex Molecular Dynamics in Functionalized Discotic Liquid Crystals MM Elmahdy G Floudas M Mondeshki HW Spiess X Dou K Müllen doi:10.1103/PhysRevLett.100.107801 Physical Review Letters, Vol. 100, No. 10. (2008) 2008-05-07T22:55:49-00:00 Physical Review Letters 100 10 APS 2008 glass liquidcrystal phase http://www.citeulike.org/user/dchen/article/2581281 <i>Physical Review Letters, Vol. 100, No. 11. (2008)</i><br /><br />Fringing-field-induced phase separation dynamics in liquid-crystal–(LC-)monomer mixtures is investigated via a microscope. At a low LC concentration, the fringing field converts the randomly dispersed LC droplets to an ordered droplet array, while at a high LC concentration the fringing field converts the amorphous LC-monomer system to a composite film. Because the LC and monomer are immiscible, the converted morphologies are stable even after the voltage is removed. Using the fringing field-induced phase separation, it is possible to prepare different polymer-dispersed LC morphologies. In Situ Observation of Fringing-Field-Induced Phase Separation in a Liquid-Crystal--Monomer Mixture Hongwen Ren Shin Wu Yi Lin doi:10.1103/PhysRevLett.100.117801 Physical Review Letters, Vol. 100, No. 11. (2008) 2008-03-24T17:17:09-00:00 Physical Review Letters 100 11 APS 2008 cool liquidcrystal phase polymer http://www.citeulike.org/user/dchen/article/2767406 <i>Physical Review Letters, Vol. 100, No. 11. (2008)</i><br /><br />Biological activity gives rise to nonequilibrium fluctuations in the cytoplasm of cells; however, there are few methods to directly measure these fluctuations. Using a reconstituted actin cytoskeleton, we show that the bending dynamics of embedded microtubules can be used to probe local stress fluctuations. We add myosin motors that drive the network out of equilibrium, resulting in an increased amplitude and modified time dependence of microtubule bending fluctuations. We show that this behavior results from steplike forces on the order of 10 pN driven by collective motor dynamics. Nonequilibrium Microtubule Fluctuations in a Model Cytoskeleton Clifford Brangwynne Gijsje Koenderink Frederick Mackintosh David Weitz doi:10.1103/PhysRevLett.100.118104 Physical Review Letters, Vol. 100, No. 11. (2008) 2008-05-07T21:19:39-00:00 Physical Review Letters 100 11 APS 2008 biology weitz http://www.citeulike.org/user/dchen/article/2767397 <i>Physical Review Letters, Vol. 100, No. 11. (2008)</i><br /><br />Optical tweezers are employed to measure the forces of interaction within a single pair of DNA-grafted colloids, dependent on the molecular weight of the DNA chains, and the concentration and valence of the surrounding ionic medium. The resulting forces are short range and set in as the surface-to-surface distance between the colloidal cores reaches the value of the brush height. The measured force-distance relation is analyzed by means of a theoretical treatment that quantitatively describes the effects of compression of the chains on the surface of the opposite-lying colloid. Quantitative agreement with the experiment is obtained for all parameter combinations. Polyelectrolyte-Compression Forces between Spherical DNA Brushes Kati Kegler Martin Konieczny Gustavo Espinosa Christof Gutsche Matthias Salomo Friedrich Kremer Christos Likos doi:10.1103/PhysRevLett.100.118302 Physical Review Letters, Vol. 100, No. 11. (2008) 2008-05-07T21:14:58-00:00 Physical Review Letters 100 11 APS biology colloids interaction opticaltweezer http://www.citeulike.org/user/dchen/article/2766831 <i>Physical Review Letters, Vol. 100, No. 14. (2008)</i><br /><br />We investigate the collective organization of paramagnetic colloidal particles externally driven above the periodic stripes of a uniaxial ferrimagnetic garnet film. An external field modulation induces vibration of the stripe walls and produces random motion of the particles. Defects in the stripe pattern break the symmetry of the potential and favor particle nucleation into large clusters above a critical density. Mismatch between particle size and pattern wavelength generates assemblies with different morphological order. At even higher field strengths, repulsive dipolar interactions between the particles induce cluster melting. We propose a novel approach to generate and externally control a variety of colloidal assemblies. Colloidal Assembly on Magnetically Vibrated Stripes Pietro Tierno Thomas Fischer Tom Johansen Francesc Sagués doi:10.1103/PhysRevLett.100.148304 Physical Review Letters, Vol. 100, No. 14. (2008) 2008-05-07T15:36:01-00:00 Physical Review Letters 100 14 APS clusters colloids magnetic http://www.citeulike.org/user/dchen/article/2762925 <i>Physical Review Letters, Vol. 100, No. 14. (2008)</i><br /><br />A novel thermal convection cell consisting of half a soap bubble heated at the equator is introduced to study thermal convection and the movement of isolated vortices. The soap bubble, subject to stratification, develops thermal convection at its equator. A particular feature of this cell is the emergence of isolated vortices. These vortices resemble hurricanes or cyclones and similarities between our observed structures and these natural objects are found. This is brought forth through a study of the mean square displacement of these objects showing signs of superdiffusion. Thermal Convection and Emergence of Isolated Vortices in Soap Bubbles F Seychelles Y Amarouchene M Bessafi H Kellay doi:10.1103/PhysRevLett.100.144501 Physical Review Letters, Vol. 100, No. 14. (2008) 2008-05-06T21:07:23-00:00 Physical Review Letters 100 14 APS 2008 bubble cool http://www.citeulike.org/user/dchen/article/2763287 <i>Physical Review Letters, Vol. 100, No. 12. (2008)</i><br /><br />Recent studies of the minute morphology of the skin by optical coherence tomography showed that the sweat ducts in human skin are helically shaped tubes, filled with a conductive aqueous solution. A computer simulation study of these structures in millimeter and submillimeter wave bands show that the human skin functions as an array of low-Q helical antennas. Experimental evidence is presented that the spectral response in the sub-Terahertz region is governed by the level of activity of the perspiration system. It is also correlated to physiological stress as manifested by the pulse rate and the systolic blood pressure. Human Skin as Arrays of Helical Antennas in the Millimeter and Submillimeter Wave Range Yuri Feldman Alexander Puzenko Paul Ishai Andreas Caduff Aharon Agranat doi:10.1103/PhysRevLett.100.128102 Physical Review Letters, Vol. 100, No. 12. (2008) 2008-05-07T01:00:17-00:00 Physical Review Letters 100 12 APS 2008 biology cool 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/2761599 <i>Physical Review Letters, Vol. 100, No. 15. (2008)</i><br /><br />Two species of particles in a binary granular system typically do not have the same mean kinetic energy, in contrast to the equipartition of energy required in equilibrium. We investigate the role of the heating mechanism in determining the extent of nonequipartition of kinetic energy. In most experiments, different species are unequally heated at the boundaries. We show by event-driven simulations that differential boundary heating affects nonequipartition even in the bulk of the system. This conclusion is fortified by studying numerical and solvable stochastic models without spatial degrees of freedom. In both cases, even in the limit where heating events are rare compared to collisions, the effect of the heating mechanism persists. Heating Mechanism Affects Equipartition in a Binary Granular System Hong Wang Narayanan Menon doi:10.1103/PhysRevLett.100.158001 Physical Review Letters, Vol. 100, No. 15. (2008) 2008-05-06T14:42:31-00:00 Physical Review Letters 100 15 APS 2008 grains people temperature http://www.citeulike.org/user/dchen/article/2759277 <i>Science, Vol. 309, No. 5732. (8 July 2005), pp. 257-262.</i><br /><br />A wide variety of experimental results and theoretical investigations in recent years have convincingly demonstrated that several transition metal oxides and other materials have dominant states that are not spatially homogeneous. This occurs in cases in which several physical interactions--spin, charge, lattice, and/or orbital--are simultaneously active. This phenomenon causes interesting effects, such as colossal magnetoresistance, and it also appears crucial to understand the high-temperature superconductors. The spontaneous emergence of electronic nanometer-scale structures in transition metal oxides, and the existence of many competing states, are properties often associated with complex matter where nonlinearities dominate, such as soft materials and biological systems. This electronic complexity could have potential consequences for applications of correlated electronic materials, because not only charge (semiconducting electronic), or charge and spin (spintronics) are of relevance, but in addition the lattice and orbital degrees of freedom are active, leading to giant responses to small perturbations. Moreover, several metallic and insulating phases compete, increasing the potential for novel behavior. 10.1126/science.1107559 Complexity in Strongly Correlated Electronic Systems Elbio Dagotto doi:10.1126/science.1107559 Science, Vol. 309, No. 5732. (8 July 2005), pp. 257-262. 2008-05-05T22:04:34-00:00 Science 309 5732 257 262 phase review science system http://www.citeulike.org/user/dchen/article/2759268 <i>Physical Review Letters, Vol. 100, No. 16. (2008)</i><br /><br />We report a study of colloidal suspensions of highly monodisperse semiflexible chiral rodlike viruses, denoted fd, in the range of high concentrations. Small angle x-ray scattering experiments reveal the existence of two hexagonal phases: the first one is crystalline and the second one is hexatic columnar, as shown by its short-range positional order. The suspension of rodlike viruses is the first experimental system showing the whole phase sequence with increasing particle concentration theoretically predicted for systems of hard rods, ranging from the chiral nematic via the smectic to columnar and crystalline phases. Hexagonal Order in Crystalline and Columnar Phases of Hard Rods Eric Grelet doi:10.1103/PhysRevLett.100.168301 Physical Review Letters, Vol. 100, No. 16. (2008) 2008-05-05T21:53:20-00:00 Physical Review Letters 100 16 APS 2008 crystal phase rod 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/2759228 <i>Physical Review Letters, Vol. 100, No. 16. (2008)</i><br /><br />With a model that incorporates hydrodynamics directly, we show that flow experiments can be used for detecting some characteristics of the DNA elasticity which manifest themselves clearly at large length scales but cannot be observed by mechanical forcing experiments even at very small length scales. By systematic analysis, the conclusiveness of different experimental methods is evaluated. For the wormlike chain, confirmed as the correct model for DNA, we find an underlying scaling relation between its extension and flow velocity of the form Lp~v0.155, which emphasizes the significance of hydrodynamics. Analysis of DNA Elasticity RP Linna K Kaski doi:10.1103/PhysRevLett.100.168104 Physical Review Letters, Vol. 100, No. 16. (2008) 2008-05-05T21:17:56-00:00 Physical Review Letters 100 16 APS 2008 biology elasticity flow protein http://www.citeulike.org/user/dchen/article/2759188 <i>Physical Review Letters, Vol. 100, No. 16. (2008)</i><br /><br />Fluorescence spectroscopy of single proteins at liquid-helium temperatures reveals a relation between structural dynamics and biological functions of the proteins. The technical difficulties in detecting visible fluorescence are chromatic aberration and optical background. They were overcome by a new optical design using reflective optics and employing two-photon excitation. The fluorescence spectrum of single green-fluorescent proteins taken at a temperature of 1.5 K makes a distinction between different metastable conformations that last for tens of seconds. Visible Fluorescence Spectroscopy of Single Proteins at Liquid-Helium Temperature Satoru Fujiyoshi Masanori Fujiwara Michio Matsushita doi:10.1103/PhysRevLett.100.168101 Physical Review Letters, Vol. 100, No. 16. (2008) 2008-05-05T20:53:11-00:00 Physical Review Letters 100 16 APS 2008 biology microscope protein structure technique http://www.citeulike.org/user/dchen/article/2759168 <i>Physical Review Letters, Vol. 100, No. 16. (2008)</i><br /><br />Polydispersity is found to have a significant effect on the potential energy landscape; the average inherent structure energy decreases with polydispersity. Increasing polydispersity at a fixed volume fraction decreases the glass transition temperature and the fragility of glass formation analogous to the antiplasticization seen in some polymeric melts. An interesting temperature dependent crossover of heterogeneity with polydispersity is observed at low temperature due to the faster buildup of dynamic heterogeneity at lower polydispersity. Energy Landscape, Antiplasticization, and Polydispersity Induced Crossover of Heterogeneity in Supercooled Polydisperse Liquids Sneha Abraham Sarika Bhattacharrya Biman Bagchi doi:10.1103/PhysRevLett.100.167801 Physical Review Letters, Vol. 100, No. 16. (2008) 2008-05-05T20:40:53-00:00 Physical Review Letters 100 16 APS 2008 polydisperse simulation supercooled http://www.citeulike.org/user/dchen/article/2759114 <i>Physical Review Letters, Vol. 100, No. 17. (2008)</i><br /><br />The full 2D analysis of roughness profiles of fracture surfaces resulting from quasistatic crack propagation in gelatin gels reveals an original behavior characterized by (i) strong anisotropy with maximum roughness at V-independent symmetry-preserving angles and (ii) a subcritical instability leading, below a critical velocity, to a cross-hatched regime due to straight macrosteps drifting at the same magic angles and nucleated on crack-pinning network inhomogeneities. Step height values are determined by the width of the strain-hardened zone, governed by the elastic crack blunting characteristic of soft solids with breaking stresses much larger than low strain moduli. Magic Angles and Cross-Hatching Instability in Hydrogel Fracture T Baumberger C Caroli D Martina O Ronsin doi:10.1103/PhysRevLett.100.178303 Physical Review Letters, Vol. 100, No. 17. (2008) 2008-05-05T20:13:26-00:00 Physical Review Letters 100 17 APS defect gel interface structure http://www.citeulike.org/user/dchen/article/2759111 <i>Physical Review Letters, Vol. 100, No. 17. (2008)</i><br /><br />We determine the structure of charge-stabilized colloidal suspensions at low ionic strength over an extended range of particle volume fractions using a combination of light and small angle neutron scattering experiments. The variation of the structure factor with concentration is analyzed within a one-component model of a colloidal suspension. We show that the observed structural behavior corresponds to a nonmonotonic density dependence of the colloid effective charge and the mean interparticle interaction energy. Our findings are corroborated by similar observations from primitive model computer simulations of salt-free colloidal suspensions. Density Dependent Interactions and Structure of Charged Colloidal Dispersions in the Weak Screening Regime Rojas Ochoa Casta\ V Lobaskin A Stradner F Scheffold P Schurtenberger doi:10.1103/PhysRevLett.100.178304 Physical Review Letters, Vol. 100, No. 17. (2008) 2008-05-05T20:12:24-00:00 Physical Review Letters 100 17 APS 2008 charge colloids structure http://www.citeulike.org/user/dchen/article/2758383 <i>Physical Review Letters, Vol. 96, No. 12. (2006)</i><br /><br />Phonon dispersion curves were obtained from inelastic x-ray and neutron scattering measurements on -uranium single crystals at temperatures from 298 to 573 K. Both measurements showed a softening and an abrupt loss of intensity in the longitudinal optic branch along [00] above 450 K. Above the same temperature a new dynamical mode of comparable intensity emerges along the [01] zone boundary with energy near the top of the phonon spectrum. The new mode forms without a structural transition but coincides with an anomaly in the mechanical deformation behavior. We argue that the mode is an intrinsically localized vibration and formed as a result of a strong electron-phonon interaction. Formation of a New Dynamical Mode in alpha-Uranium Observed by Inelastic X-Ray and Neutron Scattering ME Manley M Yethiraj H Sinn HM Volz A Alatas JC Lashley WL Hults GH Lander JL Smith doi:10.1103/PhysRevLett.96.125501 Physical Review Letters, Vol. 96, No. 12. (2006) 2008-05-05T16:32:03-00:00 Physical Review Letters 96 12 APS 2006 cool crystal elasticity focus http://www.citeulike.org/user/dchen/article/2758380 <i>Physical Review Letters, Vol. 96, No. 6. (2006)</i><br /><br />Reducing skin friction is important in nature and in many technological applications. This reduction may be achieved by reducing stresses in turbulent boundary layers, for instance tailoring biomimetic rough skins. Here we take a second approach consisting of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence. Delaying Transition to Turbulence by a Passive Mechanism Jens Fransson Alessandro Talamelli Luca Brandt Carlo Cossu doi:10.1103/PhysRevLett.96.064501 Physical Review Letters, Vol. 96, No. 6. (2006) 2008-05-05T16:29:56-00:00 Physical Review Letters 96 6 APS 2006 cool flow focus friction http://www.citeulike.org/user/dchen/article/2758375 <i>Physical Review Letters, Vol. 96, No. 12. (2006)</i><br /><br />We present a detailed study of the effects of interface spin-orbit coupling on the critical field behavior of ultrathin superconducting Be/Au bilayers. Parallel field measurements were made in bilayers with Be thicknesses in the range of d=2–30 nm and Au coverages of 0.5 nm. Though the Au had little effect on the superconducting gap, it produced profound changes in the spin states of the system. In particular, the parallel critical field exceeded the Clogston limit by an order of magnitude in the thinnest films studied. In addition, the parallel critical field unexpectedly scaled as Hc||/01/d, suggesting that the spin-orbit coupling energy was proportional to 0/d2. Tilted field measurements showed that, contrary to recent theory, the interface spin-orbit coupling induces a large in-plane superconducting susceptibility but only a very small transverse susceptibility. Spin Proximity Effect in Ultrathin Superconducting Be-Au Bilayers XS Wu PW Adams Y Yang RL Mccarley doi:10.1103/PhysRevLett.96.127002 Physical Review Letters, Vol. 96, No. 12. (2006) 2008-05-05T16:25:55-00:00 Physical Review Letters 96 12 APS 2006 focus magnetic material http://www.citeulike.org/user/dchen/article/2758347 <i>Physical Review Letters, Vol. 96, No. 8. (2006)</i><br /><br />We measure the relation between convective heat flux and temperature gradient in a vertical channel filled with water, the average vertical mass flux being zero. Compared to the classical Rayleigh-Bénard case, this situation has the advantage of avoiding plates and, thus, their neighborhood, in which is usually concentrated most of the temperature gradient. Consequently, inertial processes should control the convection, with poor influence of the viscosity. This idea gives a good account of our observations, if we consider that a natural vertical length, different from the channel width, appears. Our results also suggest that heat fluxes can be deduced from velocity measurements in free convective flows. This confers to our results a wide range of applications. High-Rayleigh-Number Convection in a Vertical Channel M Gibert H Pabiou F Chillà B Castaing doi:10.1103/PhysRevLett.96.084501 Physical Review Letters, Vol. 96, No. 8. (2006) 2008-05-05T16:13:23-00:00 Physical Review Letters 96 8 APS 2006 boundary flow focus http://www.citeulike.org/user/dchen/article/2758339 <i>Physical Review Letters, Vol. 96, No. 14. (2006)</i><br /><br />By means of spin-polarized low-energy electron microscopy, we show that the magnetic easy axis of one to three atomic-layer thick cobalt films on Ru(0001) changes its orientation twice during deposition: One-monolayer and three-monolayer thick films are magnetized in plane, while two-monolayer films are magnetized out of plane. The Curie temperatures of films thicker than one monolayer are well above room temperature. Fully relativistic calculations based on the screened Korringa-Kohn-Rostoker method demonstrate that only for two-monolayer cobalt films does the interplay between strain, surface, and interface effects lead to perpendicular magnetization. Imaging Spin-Reorientation Transitions in Consecutive Atomic Co Layers on Ru(0001) Farid Gabaly Silvia Gallego Carmen Noz Laszlo Szunyogh Peter Weinberger Christof Klein Andreas Schmid Kevin Mccarty Juan doi:10.1103/PhysRevLett.96.147202 Physical Review Letters, Vol. 96, No. 14. (2006) 2008-05-05T16:10:21-00:00 Physical Review Letters 96 14 APS 2006 atom film focus magnetic material http://www.citeulike.org/user/dchen/article/2758321 <i>Physical Review Letters, Vol. 96, No. 16. (2006)</i><br /><br />We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wave-front helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization. Optical Spin-to-Orbital Angular Momentum Conversion in Inhomogeneous Anisotropic Media L Marrucci C Manzo D Paparo doi:10.1103/PhysRevLett.96.163905 Physical Review Letters, Vol. 96, No. 16. (2006) 2008-05-05T16:01:46-00:00 Physical Review Letters 96 16 APS 2006 cool focus optical technique http://www.citeulike.org/user/dchen/article/2758296 <i>Physical Review Letters, Vol. 96, No. 24. (2006)</i><br /><br />Computer simulations show that end-grafted immiscible homopolymers can confer multivalence to nanoparticles, resulting in soft nanopolyhedra with structures identical to those found in small clusters of colloidal microspheres. Unprecedented structure tunability is demonstrated by several structure transition sequences, including a reentrant transition, induced by varying composition, polymer lengths, or grafting patterns. These results suggest a new method for fabricating nanoparticles with precisely controlled numbers and locations of functional sites (i.e., multivalent nanoparticles). Soft Nanopolyhedra as a Route to Multivalent Nanoparticles Jiunn Roan doi:10.1103/PhysRevLett.96.248301 Physical Review Letters, Vol. 96, No. 24. (2006) 2008-05-05T15:43:40-00:00 Physical Review Letters 96 24 APS 2006 cool focus material nano polymer simulation http://www.citeulike.org/user/dchen/article/2754715 <i>Physical Review Letters, Vol. 96, No. 8. (2006)</i><br /><br />We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modeling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc.) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration. Microevaporators for Kinetic Exploration of Phase Diagrams Jacques Leng Barbara Lonetti Patrick Tabeling Mathieu Joanicot Armand Ajdari doi:10.1103/PhysRevLett.96.084503 Physical Review Letters, Vol. 96, No. 8. (2006) 2008-05-05T00:02:09-00:00 Physical Review Letters 96 8 APS 2006 cool crystal drying focus microrheology phase http://www.citeulike.org/user/dchen/article/2754674 <i>Physical Review, Vol. 43, No. 6. (15 March 1933), 491.</i> The Positive Electron Carl Anderson doi:10.1103/PhysRev.43.491 Physical Review, Vol. 43, No. 6. (15 March 1933), 491. 2008-05-04T23:52:49-00:00 Physical Review 43 6 491 American Physical Society 2006 classic focus nobel http://www.citeulike.org/user/dchen/article/963666 <i>Physical Review Letters, Vol. 97, No. 21. (2006)</i><br /><br />We report the statistical analysis of the movement of a submicron particle confined in a harmonic potential in the presence of a torque. The absolute value of the torque can be found from the auto- and cross-correlation functions of the particle's coordinates. We experimentally prove this analysis by detecting the torque produced onto an optically trapped particle by an optical beam with orbital angular momentum. Torque Detection using Brownian Fluctuations Giovanni Volpe Dmitri Petrov doi:10.1103/PhysRevLett.97.210603 Physical Review Letters, Vol. 97, No. 21. (2006) 2006-11-27T18:32:15-00:00 Physical Review Letters 97 21 APS 2006 focus opticaltweezer rotation http://www.citeulike.org/user/dchen/article/2754623 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 3. (2006)</i><br /><br />By considering the structure of holococcoliths (calcite plates that cover holococcolithophores, a haploid phase of the coccolithophore life cycle) as a photonic structure, we apply a discrete dipolar approximation to study the light backscattering properties of these algae. We show that some holococcolith structures have the ability to scatter the ultraviolet radiation. This property may represent an advantage for holococcolithophores possessing it, by allowing them to live higher in the water column than other coccolithophores. Strong far-field coherent scattering of ultraviolet radiation by holococcolithophores Quintero Torres JL Aragón M Torres M Estrada L Cros doi:10.1103/PhysRevE.74.032901 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 3. (2006) 2008-05-04T23:04:15-00:00 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 74 3 APS 2006 biology cool focus http://www.citeulike.org/user/dchen/article/2754606 <i>Physical Review, Vol. 30, No. 6. (1 December 1927), 705.</i> Diffraction of Electrons by a Crystal of Nickel C Davisson LH Germer doi:10.1103/PhysRev.30.705 Physical Review, Vol. 30, No. 6. (1 December 1927), 705. 2008-05-04T22:40:03-00:00 Physical Review 30 6 705 American Physical Society 2006 classic focus nobel http://www.citeulike.org/user/dchen/article/2754601 <i>Physical Review Letters, Vol. 96, No. 20. (2006)</i><br /><br />We report on the observation of an anomalously high damping measured by a vibrating-wire resonator (VWR) immersed into superfluid 3He-B at ultralow temperatures. The observed dissipation is orders of magnitude above that corresponding to friction with the dilute normal fraction and superfluid vortices. A clear pinning behavior is also observed, as well as a strong magnetic field dependence. Our analysis points to the interaction of the VWR with a planar topological defect, analogue to cosmological vacua defects, as proposed by Salomaa and Volovik. Probing “Cosmological” Defects in Superfluid [sup 3]He-B with a Vibrating-Wire Resonator CB Winkelmann J Elbs Yu H Godfrin doi:10.1103/PhysRevLett.96.205301 Physical Review Letters, Vol. 96, No. 20. (2006) 2008-05-04T22:37:24-00:00 Physical Review Letters 96 20 APS 2006 defect focus quench http://www.citeulike.org/user/dchen/article/2754427 <i>Physical Review Letters, Vol. 95, No. 25. (2005)</i><br /><br />We observe that the group velocity of light is reduced to an extremely low value of 0.091 mm/s in a biological thin film of bacteriorhodopsin at room temperature. By exploiting unique features of a flexible photoisomerization process for coherent population oscillation, the velocity is all-optically controlled over an enormous span, from snail-paced to normal light speed, with no need of modifying the characteristics of the incident pulse. Because of the large quantum yield for the photoreaction in this biochemical system, the ultraslow light is observed even at low light levels of microwatts, indicating high energy efficiency. Controllable Snail-Paced Light in Biological Bacteriorhodopsin Thin Film Pengfei Wu Rao doi:10.1103/PhysRevLett.95.253601 Physical Review Letters, Vol. 95, No. 25. (2005) 2008-05-04T19:36:43-00:00 Physical Review Letters 95 25 APS 2006 biology cool film focus material optical http://www.citeulike.org/user/dchen/article/2087003 <i>Physical Review Letters, Vol. 96, No. 25. (2006)</i><br /><br />We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle level are the same as those found in simulations of equilibrium hard disks. This direct mapping suggests that the study of equilibrium systems can be effectively applied to study nonequilibrium steady states such as those found in our driven and dissipative granular system. Crystallization of a Quasi-Two-Dimensional Granular Fluid PM Reis RA Ingale MD Shattuck doi:10.1103/PhysRevLett.96.258001 Physical Review Letters, Vol. 96, No. 25. (2006) 2007-12-10T22:23:17-00:00 Physical Review Letters 96 25 APS 2006 2d crystallization flow focus grains journalclub http://www.citeulike.org/user/dchen/article/1269832 <i>Physical Review, Vol. 69, No. 1-2. (1 January 1946), 37.</i> Resonance Absorption by Nuclear Magnetic Moments in a Solid EM Purcell HC Torrey RV Pound doi:10.1103/PhysRev.69.37 Physical Review, Vol. 69, No. 1-2. (1 January 1946), 37. 2007-05-01T07:36:30-00:00 Physical Review 69 1-2 37 American Physical Society 2006 classic focus nmr technique