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Arxiv.org
by Lorène Champougny; Matthieu Roché; Wiebke Drenckhan; Emmanuelle. Rio
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In this paper, we investigate how the drainage and rupture of surfactant-stabilised bubbles floating at the surface of a liquid pool depend on the concentration of surface-active molecules in water. Drainage measurements at the apex of bubbles indicate that the flow profile is increasingly plug-like as the surfactant concentration is decreased from several times the critical micellar concentration (cmc) to just below the cmc. High-speed observations of bubble bursting reveal that the position...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.03610
Arxiv.org
by Horacio López-Menéndez; José Félix Rodríguez
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The synthetic actin network demands great interest as bio-material due to its soft and wet nature that mimic many biological scaffolding structures. The study of these structures can contribute to a better understanding of this new micro/nano technology and the cytoskeleton like structural building blocks. Inside the cell the actin network is regulated by tens of actin-binding proteins (ABP's), which makes for a highly complex system with several emergent behavior. In particular Calponin is an...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02645
Arxiv.org
by Arghya Majee
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We theoretically study the motion of a rigid dimer of self-propelling Janus particles. In a simple kinetic approach without hydrodynamic interactions, the dimer moves on a helical trajectory and, at the same time, it rotates about its center of mass. Inclusion of the effects of mutual advection using superposition approximation does not alter the qualitative features of the motion but merely changes the parameters of the trajectory and the angular velocity.
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09063
Arxiv.org
by M. Ramazanoglu; R. Salci
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We have studied the quenched random disorder (QRD) effects created by aerosil dispersion in octylcyanobiphenyl (8CB) liquid crystal (LC) using Atomic Force Microscopy (AFM) technique. Gelation process in the 8CB+aerosil gels yields a QRD network which also changes the surface topography. By increasing the aerosil concentration, the original smooth pattern of LC sample surfaces is suppressed by creating a fractal aerosil surface effect, these surfaces become more porous, rougher with more and...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.06346
Arxiv.org
by L. V. Abdurakhimov; M. A. Borich; Yu. M. Bunkov; R. R. Gazizulin; D. Konstantinov; M. I. Kurkin; A. P. Tankeyev
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We present a new theoretical description of the coupled electron-nuclear spin systems which takes into account an indirect relaxation of nuclear spins via the electron subsystem. In our theory the magnitude of the nuclear magnetization is conserved for arbitrary large excitation powers, similar to the Landau-Lifshitz-Gilbert model of relaxation. This is drastically different from the conventional heating scenario based on the phenomenological Bloch equations. The predictions of our theory are...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1703.00614
Arxiv.org
by Nariaki Sakaï; Sébastien Moulinet; Frédéric Lechenault; Mokhtar Adda-Bedia
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We experimentally investigate the phase behaviour of a model two-dimensional granular system undergoing stationary sedimentation. Buoyant cylindrical particles are rotated in liquid-filled drum, thus confined in a harmonic centripetal potential with tunable curvature, which competes with gra- vity to produce various thermal-like states : the system can be driven from liquid-like to solid-like configurations as the rotation rate is increased. We study the statistics of the local hexagonal order...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02209
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by Francesco Alaimo; Christian Köhler; Axel Voigt
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We study the spatiotemporal patterns that emerge when an active nematic film is topologically constraint. These topological constraints allow to control the non-equilibrium dynamics of the active system. We consider ellipsoidal shapes for which the resulting defects are 1/2 disclinations and analyze the relation between their location and dynamics and local geometric properties of the ellipsoid. We highlight two dynamic modes: a tunable periodic state that oscillates between two defect...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03707
Arxiv.org
by Samuel Krüger; Christoph A. Weber; Jens-UweSommer; Frank Jülicher
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Here we investigate how droplet position can be controlled using concentration profiles of a regulator that influences phase separation. We consider a mean field model of a ternary mixture where a concentration gradient of a regulator is imposed by an external potential. We show that novel first order phase transition exists that controls droplet position in a discontinuous manner. Such a droplet switch in concentration gradients could be relevant for the spatial organization of biological...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.07276
Arxiv.org
by M. Trejo; C. Frétigny; A. Chateauminois
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Frictional properties of contacts between a smooth viscoelastic rubber and rigid surfaces are investigated using a torsional contact configuration where a glass lens is continuously rotated on the rubber surface. From the inversion of the displacement field measured at the surface of the rubber, spatially resolved values of the steady state frictional shear stress are determined within the non homogeneous pressure and velocity fields of the contact. For contacts with a smooth lens, a velocity...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08013
Arxiv.org
by M. Scaraggi; L. Dorogin; J. Angerhausen; H. Murrenhoff; B. N. J. Persson
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A huge number of technological and biological systems involves the lubricated contact between rough surfaces of soft solids in relative accelerated motion. Examples include dynamical rubber seals and the human joints. In this study we consider an elastic cylinder with random surface roughness in accelerated sliding motion on a rigid, perfectly flat (no roughness) substrate in a fluid. We calculate the surface deformations, interface separation and the contributions to the friction force and the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02222
Arxiv.org
by Michael-Angelo Y. -H. Lam; Linda J. Cummings; Lou Kondic
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We discuss instabilities of fluid films of nanoscale thickness, with a particular focus on films where the destabilising mechanism allows for linear instability, metastability, and absolute stability. Our study is motivated by nematic liquid crystal films; however we note that similar instability mechanisms, and forms of the effective disjoining pressure, appear in other contexts, such as the well-studied problem of polymeric films on two-layered substrates. The analysis is carried out within...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.03919
Arxiv.org
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The rigid double-torus torsional oscillator (TO) is constructed to reduce any elastic effects in-herent to complicate TO structures, allowing explicit probing for a genuine supersolid signature. We investigated the frequency- and temperature-dependent response of the rigid double-torus TO containing solid 4He with 0.6 ppb 3He and 300 ppb 3He. We did not find evidence to support the frequency-independent contribution proposed to be a property of supersolid helium. The frequency-dependent...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1701.07621
Arxiv.org
by Daniel R. Lester; Richard Buscall; Anthony D. Stickland; Peter J. Scales
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Wall adhesion effects during batch sedimentation of strongly flocculated colloidal gels are commonly assumed to be negligible. In this study in-situ measurements of colloidal gel rheology and solids volume fraction distribution suggest the contrary, where significant wall adhesion effects are observed in a 110mm diameter settling column. We develop and validate a mathematical model for the equilibrium stress state in the presence of wall adhesion under both viscoplastic and viscoelastic...
Topics: Soft Condensed Matter, Condensed Matter
Source: http://arxiv.org/abs/1401.0051
Arxiv.org
by Cemil Yigit; Matej Kanduc; Matthias Ballauff; Joachim Dzubiella
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We study the adsorption of charged patchy particle models (CPPMs) on a thin film of a like-charged and dense polyelectrolyte (PE) brush (of 50 monomers per chain) by means of implicit-solvent, explicit-salt Langevin dynamics computer simulations. Our previously introduced set of CPPMs embraces well-defined one-, and two-patched spherical globules, each of the same net charge and (nanometer) size, with mono- and multipole moments comparable to those of small globular proteins. We focus on...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02457
Arxiv.org
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Despite about forty years of investigations, the nature of the melting transition in two dimensions is not completely clear. In the framework of the most popular Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young (BKTHNY) theory, 2D systems melt through two continuous Berezinskii-Kosterlitz-Thouless (BKT) transitions with intermediate hexatic phase. The conventional first-order transition is also possible. On the other hand, recently on the basis of computer simulations the new melting...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.03643
Arxiv.org
by Yimin Jiang; Mario Liu
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Accounting for elasto-plastic motion in granular media, hypoplasticity is a state-of-the-art constitutive model derived from data accumulated over many decades. In contrast, GSH, a hydrodynamic theory, is derived from general principles of physics, with comparatively few inputs from experiments, yet sporting an applicability ranging from static stress distribution via elasto-plastic motion to fast dense flow, including non-uniform ones such as a shear band. Comparing both theories, we find...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.06813
Arxiv.org
by Jiajia Zhou; Ying Jiang; Masao Doi
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When a liquid film of colloidal solution consisting of particles of different sizes is dried on a substrate, the colloids often stratify, where smaller colloids are laid upon larger colloids. This phenomenon is counter intuitive because larger colloids which have smaller diffusion constant are expected to remain near the surface during the drying process, leaving the layer of larger colloids on top of smaller colloids. Here we show that the phenomenon is caused by the interaction between the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.03182
Arxiv.org
by Antina Ghosh; Zoe Budrikis; Vijayakumar Chikkadi; Alessandro Sellerio; Stefano Zapperi; Peter Schall
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When strained beyond the linear regime, soft colloidal glasses yield to steady-state plastic flow in a way that is similar to the deformation of conventional amorphous solids. Due to the much larger size of the colloidal particles with respect to the atoms comprising an amorphous solid, colloidal glasses allow to obtain microscopic insight into the nature of the yielding transition, as we illustrate here combining experiments, atomistic simulations, and mesoscopic modeling. Our results...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.03225
Arxiv.org
by Yunhuan Nie; Hua Tong; Jun Liu; Mengjie Zu; Ning Xu
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By introducing four fundamental types of disorders into a two-dimensional triangular lattice separately, we determine the role of each type of disorder in the vibration of the resulting mass-spring networks. We are concerned mainly with the origin of the boson peak and the connection between the boson peak and the transverse Ioffe-Regel limit. For all types of disorders, we observe the emergence of the boson peak and Ioffe-Regel limits. With increasing disorder, the boson peak frequency...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.00114
Arxiv.org
by T A Sobral; M A F Gomes
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The continuous packing of a flexible rod in two-dimensional cavities yields a countable set of interacting domains that resembles non-equilibrium cellular systems and belongs to a new class of light-weight material. However, the link between the length of the rod and the number of domains requires investigation especially in the case of non-simply connected cavities, where the number of avoided regions emulates an effective topological temperature. In the present article we report the results...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03761
Arxiv.org
by Andreas Reindl; Markus Bier; S. Dietrich
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Density functional theory is used to describe electrolyte solutions in contact with electrodes of planar or spherical shape. For the electrolyte solutions we consider the so-called civilized model, in which all species present are treated on equal footing. This allows us to discuss the features of the electric double layer in terms of the differential capacitance. The model provides insight into the microscopic structure of the electric double layer, which goes beyond the mesoscopic approach...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09661
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by Sayantan Acharya; Ujjwal Kumar Nandi; Sarika Maitra Bhattacharyya
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We present a study of the dynamics of small solute particles in a solvent medium where the solute is much smaller in size, mimicking the diffusion of small particles in crowded environment. The solute exhibits Fickian diffusion arising from non-Gaussian Van Hove correlation function. Our study shows that there are at least two possible origins of this non-Gaussian behaviour: the decoupling of the solute-solvent dynamics and the intermittency in the solute motion, the latter playing a dominant...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.03260
Arxiv.org
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The peptides in biosystems are homochiral polymers of L-amino acids, but razemisate slowly by an active isomerization kinetics. The chemical reactions in biosystems are, however, reversible and what racemisates the peptides at the water activity in the biosystems can ensure homochirality at a smaller activity. Here we show by a thermodynamics analysis and by comprehensive Molecular Dynamics simulations of models of peptides, that the isomerization kinetics racemisates the peptides at a high...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.01623
Arxiv.org
by Alessio Caciagli; Darshana Joshi; Jurij Kotar; Erika Eiser
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We demonstrate the realization of (laterally) optically bounded colloidal structures on a liquid-liquid interface of an emulsion droplet. We use DNA tethers to graft the particles to the droplet surface, effectively confining them to a quasi-2D plane with minimum constraints on the lateral movement even when optically trapped in a common single-beam configuration. We show that relatively weak interactions such as depletion can be measured in the optically bounded crystals by video-microscopy...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08210
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Water radiolysis by low-energy carbon projectiles is studied by first-principles molecular dynamics. Carbon projectiles of kinetic energies between 175 eV and 2.8 keV are shot across liquid water. Apart from translational, rotational and vibrational excitation, they produce water dissociation. The most abundant products are H and OH fragments. We find that the maximum spatial production of radiolysis products, not only occurs at low velocities, but also well below the maximum of energy...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.06161
Arxiv.org
by Pepijn G. Moerman; Henrique W. Moyses; Ernest B. van der Wee; David G. Grier; Alfons van Blaaderen; Willem K. Kegel; Jan Groenewold; Jasna Brujic
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Concentration gradients play a critical role in embryogenesis, bacterial locomotion, as well as the motility of active particles. Particles develop concentration profiles around them by dissolution, adsorption, or the reactivity of surface species. These gradients change the surface energy of the particles, driving both their self-propulsion and governing their interactions. Here we uncover a regime in which solute-gradients mediate interactions between slowly dissolving droplets without...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.06765
Arxiv.org
by Tonatiuh Sosme-Sánchez; Néstor Gutiérrez-Méndez; José Manuel Nápoles-Duarte; Luz María Rodríguez-Valdez; Marco Antonio Chávez-Rojo
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In this work, we present a computer simulation study of the acid coagulation of casein micelles. For different conditions, we predict the acidity (pH value) at which aggregation transition occurs. The interaction potential implemented consists of three contributions, the electrostatic repulsion, the steric repulsion between the polyelectrolyte brush formed by the $\kappa$-casein exposed segments, and finally, the van der Waals attraction which is responsible for aggregation when the repulsive...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08555
Arxiv.org
by Michele Curatolo; Paola Nardinocchi; Eric Puntel; Luciano Teresi
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We investigate the swelling dynamics driven by solvent absorption in a hydrogel sphere immersed in a solvent bath, through an accurate computational model and numerical study. We extensively describe the transient process from dry to wet and discuss the onset of surface instabilities through a measure of the lack of smoothness of the outer surface and a morphological pattern of that surface with respect to the two material parameters driving the swelling dynamics.
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.08201
Arxiv.org
by Colm P. Kelleher; Rodrigo E. Guerra; Andrew D. Hollingsworth; Paul M. Chaikin
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We study the phase behavior of a system of charged colloidal particles that are electrostatically bound to an almost flat interface between two fluids. We show that, despite the fact that our experimental system consists of only $10^{3}$ - $10^{4}$ particles, the phase behavior is consistent with the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY). Using spatial and temporal correlations of the bond-orientational order parameter, we classify our samples into...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08727
Arxiv.org
by C. S. Dias; N. A. M. Araújo; M. M. Telo da Gama
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Network fluids are structured fluids consisting of chains and branches. They are characterized by unusual physical properties, such as, exotic bulk phase diagrams, interfacial roughening and wetting transitions, and equilibrium and nonequilibrium gels. Here, we provide an overview of a selection of their equilibrium and dynamical properties. Recent research efforts towards bridging equilibrium and non-equilibrium studies are discussed, as well as several open questions.
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02339
Arxiv.org
by Georgios G. Vogiatzis; Grigorios Megariotis; Doros N. Theodorou
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A mesoscopic, mixed particle- and field-based Brownian dynamics methodology for the simulation of entangled polymer melts has been developed. Polymeric beads consist of several Kuhn segments, and their motion is dictated by the Helmholtz energy of the sample, which is a sum of the entropic elasticity of chain strands between beads, slip springs, and nonbonded interactions. The entanglement effect is introduced by the slip springs, which are springs connecting either nonsuccessive beads on the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08983
Arxiv.org
by Andreas Reindl; Markus Bier; S. Dietrich
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Within the Poisson-Boltzmann (PB) approach electrolytes in contact with planar, spherical, and cylindrical electrodes are analyzed systematically. The dependences of their capacitance $C$ on the surface charge density $\sigma$ and the ionic strength $I$ are examined as function of the wall curvature. The surface charge density has a strong effect on the capacitance for small curvatures whereas for large curvatures the behavior becomes independent of $\sigma$. An expansion for small curvatures...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09591
Arxiv.org
by Sonia Garcia-Jimeno; Joan Estelrich; Jose Callejas-Fernandez; Sandalo Roldan-Vargas
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Understanding stabilization and aggregation in magnetic nanoparticle systems is crucial to optimizing the functionality of these systems in real physiological applications. Here we address this problem for a specific, yet representative, system. We present an experimental and analytical study on the aggregation of superparamagnetic liposomes in suspension in the presence of a controllable external magnetic field. We study the aggregation kinetics and report an intermediate time power law...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09586
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We use molecular dynamics simulations to study the behavior of a compressible Lennard-Jones fluid in simple shear flow in a two-dimensional nanochannel. The system is equilibrated in the fluid phase close to the triple point at which gas, liquid and solid phases coexist and is subjected to steady shear in Couette geometry. It is observed that at higher shear rates, the system develops a density gradient perpendicular to the direction of flow and exhibits solid-like layering near the boundaries....
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.10461
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by Denny Vitasari; Simon Cox
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We describe the extension of a "viscous froth" model to the dynamics of a wet foam in a Hele-Shaw cell. The two-dimensional model includes the friction experienced by the soap films as they are dragged along the cell walls, while retaining accurate geometrical information. To explore the consequences of changing the liquid content in this situation, we consider a simple foam geometry known as a bubble lens: a bubble partially filling a narrow, straight channel with a single film...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.00602
Arxiv.org
by F. Puosi; O. Chulkin; S. Bernini; S. Capaccioli; D. Leporini
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We investigate by thorough Molecular Dynamics simulations the thermodynamic scaling (TS) of a polymer melt. Two distinct models, with strong and weak virial-energy correlations, are considered. Both evidence the joint TS with the same characteristic exponent $\gamma_{ts}$ of the fast mobility - the mean square amplitude of the picosecond rattling motion inside the cage -, and the much slower structural relaxation and chain reorientation. If the cage effect is appreciable, the TS master curves...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02211
Arxiv.org
by E. P. Montellà; M. Toraldo; B. Chareyre; L. Sibille
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We present analytical and numerical results on localized fluidization within a granular layer subjected to a local injection of fluid. As the injection rate increases the three different regimes previously reported in the literature are recovered: homogeneous expansion of the bed, fluidized cavity in which fluidization starts developing above the injection area, and finally the chimney of fluidized grains when the fluidization zone reaches the free surface. The analytical approach is at the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.02319
Arxiv.org
by Paula A. Gago; Diego Maza; Luis A. Pugnaloni
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Static granular packs have been studied in the last three decades in the frame of a modified equilibrium statistical mechanics that assumes ergodicity as a basic postulate. The canonical example on which this framework is tested consists in the series of static configurations visited by a granular column subjected to taps. By analyzing the response of a realistic model of grains, we demonstrate that volume and stress variables visit different regions of the phase space at low tap intensities in...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03384
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by Norbert Stoop; Jörn Dunkel
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Topological defects shape the material and transport properties of physical systems. Examples range from vortex lines in quantum superfluids, defect-mediated buckling of graphene, and grain boundaries in ferromagnets and colloidal crystals, to domain structures formed in the early universe. The Kibble-Zurek (KZ) mechanism describes the topological defect formation in continuous non-equilibrium phase transitions with a constant finite quench rate. Universal KZ scaling laws have been verified...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03540
Arxiv.org
by Daniel Rayneau-Kirkhope; Chengzhao Zhang; Louis Theran; Marcelo A. Dias
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Recent progress in advanced additive manufacturing techniques has stimulated the growth of the field of mechanical metamaterials. One area particular interest in this subject is the creation of auxetic material properties through elastic instability. This paper focuses on a novel methodology in the analysis of auxetic metamaterials through analogy with rigid link lattice systems. Our analytic methodology gives extremely good agreement with finite element simulations for both the onset of...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.05150
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by M. C. F. Pereira; C. A. Brackley; J. S. Lintuvuori; D. Marenduzzo; E. Orlandini
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We study the compression and extension dynamics of a DNA-like polymer interacting with non-DNA binding and DNA-binding proteins, by means of computer simulations. The geometry we consider is inspired by recent experiments probing the compressional elasticity of the bacterial nucleoid (DNA plus associated proteins), where DNA is confined into a cylindrical container and subjected to the action of a "piston" - a spherical bead to which an external force is applied. We quantify the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.06067
Arxiv.org
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We consider possibility of embedding large sheets of polymer piezoelectrics in clothing for sensing and energy harvesting for wearable electronic applications. Power is generated by the crumpling of clothes due to human body movements. From the mechanics of a gently crumpled foil we develop theoretical models and scaling laws for the open circuit voltage and short circuit current and verify via experiments. It is concluded that stretching is the dominant charge generation mechanism with the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.05586
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by Alexander Geiseler; Peter Hänggi; Fabio Marchesoni
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Contrary to microbial taxis, where a tactic response to external stimuli is controlled by complex chemical pathways acting like sensor-actuator loops, taxis of artificial microswimmers is a purely stochastic effect associated with a non-uniform activation of the particles' self-propulsion. We study the tactic response of such swimmers in a spatio-temporally modulated activating medium by means of both numerical and analytical techniques. In the opposite limits of very fast and very slow...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.08763
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In deep supercooled liquids, particles get trapped in transient cages made up of neighbouring particles. Here we define a cage from a geometrical quantity, free volume, such that the free volume of a particle is the cage volume. First we show that the relationship between the average cage volume and the structural relaxation time questions the existence of glass transition in hard sphere systems. Our observation suggests that the cage volume is zero at the transition. Further we show that cage...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.06962
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by Ning Xu; Andrea J. Liu; Sidney R. Nagel
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We consider the contribution to the density of vibrational states and the distribution of energy barrier heights of incipient instabilities in a glass modeled by a jammed packing of spheres. On approaching an instability, the frequency of a normal mode and the height of the energy barrier to cross into a new ground state both vanish. These instabilities produce a contribution to the density of vibrational states that scales as $\omega^3$ at low frequencies $\omega$, but which vanishes in the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.00900
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by René Wittmann; Joseph M. Brader
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A simple theoretical approach is used to investigate active colloids at the free interface and near repulsive substrates. We employ dynamical density functional theory to determine the steady-state density profiles in an effective equilibrium system [Farage et al., Phys. Rev. E, 91 (2015) 042310]. In addition to the known accumulation at surfaces, we predict wetting and drying transitions at a flat repulsive wall and capillary condensation and evaporation in a slit pore. These new phenomena are...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.00656
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Using a recently introduced formulation of the ground-state inverse design problem for a targeted lattice [Pi\~neros et al., J. Chem. Phys. 144} 084502 (2016)], we discover purely repulsive and isotropic pair interactions that stabilize low-density truncated square and truncated hexagonal crystals, as well as promote their assembly in Monte Carlo simulations upon isochoric cooling from a high-temperature fluid phase. The results illustrate that the primary challenge to stabilizing very open...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08615
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We perform an extensive computational study of binary mixtures of water and short-chain alcohols resorting to two-scale potential models to account for the singularities of hydrogen bonded liquids. Water molecules are represented by a well studied core softened potential which is known to qualitatively account for a large number of water's characteristic anomalies. Along the same lines, alcohol molecules are idealized by dimers in which the hydroxyl groups interact with each other and with...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08670
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Active particles driven by colored noise can be approximately mapped onto a system that obeys detailed balance. The effective interactions which can be derived for such a system allow to describe the structure and phase behavior of the active fluid by means of an effective free energy. In this paper we explain why the related thermodynamic results for pressure and interfacial tension do not represent the results one would measure mechanically. We derive a dynamical density functional theory,...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.00337
Arxiv.org
by Benaoumeur Bakhti
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We present new method for studying the equilibrium properties of interacting fluids in an arbitrary external filed. The method is valid in any dimension and it yields an exact results in one dimension. Using this approach, we derive a recurrence relation for the pair distribution function of a three dimensional in-homogeneous fluids, constitute of spherical molecules with arbitrary nearest neighbour interaction that extends to two molecules diameter. By integrating this recurrence relation, we...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.04905
Arxiv.org
by Mathias Boström; Oleksandr I. Malyi; Prachi Parashar; K. V. Shajesh; Priyadarshini Thiyam; Kimball A. Milton; Clas Persson; Drew F. Parsons; Iver Brevik
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At air-water interfaces, the Lifshitz interaction by itself does not promote ice growth. On the contrary, we find that the Lifshitz force promotes the growth of an ice film, up to 1-8 nm thickness, near silica-water interfaces at the triple point of water. This is achieved in a system where the combined effect of the retardation and the zero frequency mode influences the short-range interactions at low temperatures, contrary to common understanding. Cancellation between the positive and...
Topics: Condensed Matter, Other Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.01332
Arxiv.org
by Tina Hecksher; Darius H. Torchinsky; Christoph Klieber; Jeremy A. Johnson; Jeppe C. Dyre; Keith A. Nelson
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Diverse material classes exhibit practically identical behavior when made viscous upon cooling toward the glass transition, suggesting a common theoretical basis. The first-principles scaling laws that have been proposed to describe the evolution with temperature have yet to be appropriately tested due to the extraordinary range of time scales involved. We used seven different measurement methods to determine the structural relaxation kinetics of a prototype molecular glass former over a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.01310
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by Benjamin W. Zingsem; Michael Winklhofer; Ralf Meckenstock; Michael Farle
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In this work, we define a set of analytic tools to describe the dynamic response of the magnetization to small perturbations, which can be used on its own or in combination with micromagnetic simulations and does not require saturation. We present a general analytic description of the ferromagnetic high frequency susceptibility tensor to describe angular as well as frequency dependent ferromagnetic resonance spectra and account for asymmetries in the line shape. Furthermore, we expand this...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1701.09078
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by Vikram Rathee; Daniel L. Blair; Jeffery S. Urbach
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The mechanical response of solid particles dispersed in a Newtonian fluid exhibits a wide range of nonlinear phenomena including a dramatic increase in the viscosity \cite{1-3} with increasing stress. If the volume fraction of the solid phase is moderately high, the suspension will undergo continuous shear thickening (CST), where the suspension viscosity increases smoothly with applied shear stress; at still higher volume fractions the suspension can display discontinuous shear thickening...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02068
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by G Ferre; M. C. Gordillo; J. Boronat
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We have studied the ground-state properties of para-hydrogen in one dimension and in quasi-one-dimensional configurations using the path integral ground state Monte Carlo method. This method produces zero-temperature exact results for a given interaction and geometry. The quasi-one-dimensional setup has been implemented in two forms: the inner channel inside a carbon nanotube coated with H$_2$ and a harmonic confinement of variable strength. Our main result is the dependence of the Luttinger...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1702.02335
Arxiv.org
by Shankar Ghosh; A. P. Merin; Nitin Nitsure
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In this note we introduce a hierarchy of phase spaces for static friction, which give a graphical way to systematically quantify the directional dependence in static friction via subregions of the phase spaces. We experimentally plot these subregions to obtain phenomenological descriptions for static friction in various examples where the macroscopic shape of the object affects the frictional response. The phase spaces have the universal property that for any experiment in which a given object...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.04545
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by Rakhi Dhuria; Varun Dalia; P Sunthar
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Observations of an enhanced mass transfer in nanofluids have led to several propositions for the underlying cause, but none of them have been clearly established. Here, we reproduce the enhancement phenomenon within a glass capillary containing fluorescein di-sodium dye solution on one side and alumina nanoparticle suspension on the other, avoiding convective interferences present earlier. The enhancement is explained by the counter-convective motion of the dye solution in response to the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.01644
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by S. Sharma; E. K. U. Gross; A. Sanna; J. K. Dewhurst
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Spin-dependent exchange-correlation energy functionals in use today depend on the charge density and the magnetization density: $E_{\rm xc}[\rho,{\bf m}]$. However, it is also correct to define the functional in terms of the curl of ${\bf m}$ for physical external fields: $E_{\rm xc}[\rho,\nabla\times{\bf m}]$. The exchange-correlation magnetic field, ${\bf B}_{\rm xc}$, then becomes source-free. We study this variation of the theory by uniquely removing the source term from local and...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1704.04604
Arxiv.org
by Amandeep Sekhon; Ajith VJ; Shivprasad Patil
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The flow of water confined to nanometer-sized pores is central to a wide range of subjects from biology to nanofluidic devices. Despite its importance, a clear picture about nanoscale fluid dynamics is yet to emerge. Here we measured dissipation in less than 20 nm thick water films and it was found to decrease for both wetting and non-wetting confining surfaces. The fitting of Carreau-Yasuda model of shear thinning to our measurements implies that flow is non-Newtonian and for wetting surfaces...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.05208
Arxiv.org
by Alan Murray; Fernando Alonso-Marroquin
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We describe a simple experiment involving spheres rolling down an inclined plane towards a bottleneck and through a gap. Results of the experiment indicate that flow rate can be increased by placing an obstruction at optimal positions near the bottleneck. We use the experiment to develop a computer simulation using the PhysX physics engine. Simulations confirm the experimental results and we state several considerations necessary to obtain a model that agrees well with experiment. We...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.07395
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by Matthias Krüger; David S. Dean
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Assuming an effective quadratic Hamiltonian, we derive an approximate, linear stochastic equation of motion for the density-fluctuations in liquids, composed of overdamped Brownian particles. From this approach, time dependent two point correlation functions (such as the intermediate scattering function) are derived. We show that this correlation function is exact at short times, for any interaction and, in particular, for arbitrary external potentials so that it applies to confined systems....
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.07649
Arxiv.org
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This paper investigates the relation between the density-scaling exponent $\gamma$ and the virial potential-energy correlation coefficient $R$ at several thermodynamic state points in three dimensions for the generalized $(2n,n)$ Lennard-Jones (LJ) system for $n=4, 9, 12, 18$, as well as for the standard $n=6$ LJ system in two, three, and four dimensions. The state points studied include many low-density states at which the virial potential-energy correlations are not strong. For these state...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.05470
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by Saientan Bag; Prabal K. Maiti
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Achieving high charge carrier mobility is the holy grail of organic electronics. In this letter we report a record charge carrier mobility of 14.93 cm$^2$ V$^{-1}$s$^{-1}$ through a coronene stack encapsulated in a single walled carbon nanotube (CNT) by using a multiscale modeling technique which combines MD simulations, first principle calculations and Kinetic Monte Carlo simulations. For the CNT having a diameter of 1.56 nm we find a highly ordered defect free organization of coronene...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.10991
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by M. Scaraggi; J. Angerhausen; L. Dorogin; H. Murrenhoff; B. N. J. Persson
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Machine elements and mechanical components have often surfaces with anisotropic roughness, which may result from the machining processes, e.g. grinding, or from wear. Hence, it is important to understand how surface roughness anisotropy affects contact mechanics properties, such as friction and the interface separation, which is important for lubricated contacts. Here we extend and apply a multiscale mean-field model to the lubricated contact between a soft (e.g. rubber) elastic solid and a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.01797
Arxiv.org
by Anupam Pandey; Stefan Karpitschka; Luuk A. Lubbers; Joost H. Weijs; Lorenzo Botto; Siddhartha Das; Bruno Andreotti; Jacco H. Snoeijer
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Recent experiments have shown that liquid drops on highly deformable substrates exhibit mutual interactions. This is similar to the Cheerios effect, the capillary interaction of solid particles at a liquid interface, but now the roles of solid and liquid are reversed. Here we present a dynamical theory for this inverted Cheerios effect, taking into account elasticity, capillarity and the viscoelastic rheology of the substrate. We compute the velocity at which droplets attract, or repel, as a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.01820
Arxiv.org
by Marceau Hénot; Eric Drockenmuller; Liliane Léger; Frédéric Restagno
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The slip behavior of polydimethylsiloxane (PDMS) polymer melts flowing on non-adsorbing surfaces made of short non-entangled PDMS chains densely end-grafted to silica has been characterized. For high enough shear rates, constant slip lengths proportional to the bulk fluid viscosity have been observed, in agreement with Navier's interfacial equation, and demonstrating that the interfacial Navier's friction coefficient is a local quantity, independent of the polymer molecular weight. Comparing...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.02742
Arxiv.org
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Topological solitons are knots in continuous physical fields classified by non-zero Hopf index values. Despite arising in theories that span many branches of physics, from elementary particles to condensed matter and cosmology, they remain experimentally elusive and poorly understood. We introduce a method of experimental and numerical analysis of such localized structures in liquid crystals that, similar to the mathematical Hopf maps, relates all points of the medium's order parameter space to...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.08196
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by Loreto Oyarte Galvez; Sissi de Beer; Devaraj van der Meer; Adeline Pons
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Suspensions of cornstarch in water exhibit strong dynamic shear-thickening. We show that partly replacing water by ethanol strongly alters the suspension rheology. We perform steady and non-steady rheology measurements combined with atomic force microscopy to investigate the role of fluid chemistry on the macroscopic rheology of the suspensions and its link with the interactions between cornstarch grains. Upon increasing the ethanol content, the suspension goes through a yield-stress fluid...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.05601
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by Yu Abe; Bo Zhang; Leonardo Gordillo; Alireza Mohammad Karim; Lorraine F. Francis; Xiang Cheng
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Colloidal particles can self-assemble into various ordered structures in fluid flows that have potential applications in biomedicine, materials synthesis and encryption. These dynamic processes are also of fundamental interest for probing the general principles of self-assembly in non-equilibrium conditions. Here, we report a simple microfluidic experiment, where charged colloidal particles self-assemble into flow-aligned 1D strings with regular particle spacing near a solid boundary. Using...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08408
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by Nababrata Ghoshal; Soumyajit Pramanick; Sudeshna DasGupta; Soumen Kumar Roy
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We present a high accuracy Monte Carlo simulation study of the Isotropic - Nematic phase transition of a lattice dispersion model of biaxial liquid crystals. The NI coexistence curve terminating at the Landau critical point have been determined using multiple histogram reweighting technique. A close investigation reveals a sharp departure in the nature of the $N$-$I$ coexistence curve in temperature- biaxiality parameter phase diagram in comparison to the earlier theoretical (either mean-field...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.04351
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by Annemarie Nack; Julian Seifert; Christopher Passow; Joachim Wagner
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The viscoelastic behavior of composites consisting of spindle-shaped hematite particles in poly-N-isopropylacrylamide hydrogels is investigated both, by means of rheological oscillatory shear experiments, and the field-induced alignment of these mesoscale, anisotropic particles in external magnetic fields. Due to their magnetic moment and magnetic anisotropy hematite spindles align with their long axis perpendicular to the direction of an external magnetic field. The field induced torque acting...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.05659
The energy functional, the governing partial differential equation(s) (PDE), and the boundary conditions need to be consistent with each other in a modeling system. In electrolyte solution study, people usually use a free energy form of an infinite domain system (with vanishing potential boundary condition) and the derived PDE(s) for analysis and computing. However, in many real systems and/or numerical computing, the objective domain is finite, and people still use the similar energy form,...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.01115
In this note, we report about two, as it seems to us, rather unusual observations made in molecular dynamics simulations of the single component systems of particles interacting through the harmonic-repulsive pair potential in 3D. In particular, at some densities, we observed deeply supercooled liquid states which did not exhibit crystallization in rather long MD runs. This observation is unusual because usually liquids formed by particles of only one type rather readily crystallize on...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.05648
Although 3D printing has the potential to transform manufacturing processes, the strength of printed parts often does not rival that of traditionally-manufactured parts. The fused-filament fabrication method involves melting a thermoplastic, followed by layer-by-layer extrusion of the molten viscoelastic material to fabricate a three-dimensional object. The strength of the welds between layers is controlled by interdiffusion and entanglement of the melt across the interface. However, diffusion...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09295
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by Mihir Durve; Arnab Saha; Ahmed Sayeed
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We consider flocking of self-propelling agents in two dimensions, each of which communicates with its neighbors within a limited vision cone. Also, the communication occurs with some delay. The communication among the agents are modeled by Vicsek rules. In this study we explore the effect of non-reciprocal interaction among the agents, induced by their vision cone, together with the delayed interactions on the dynamical pattern formation within the flock. We find that under these two influences...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09596
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by Timothy R. Prisk; Matthew S. Bryan; Paul. E. Sokol; Garrett E. Granroth; Saverio Moroni; Massimo Boninsegni
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We report high-resolution neutron Compton scattering measurements of liquid $^4$He under saturated vapor pressure. There is excellent agreement between the observed scattering and ab initio predictions of its lineshape. Quantum Monte Carlo calculations predict that the Bose condensate fraction is zero in the normal fluid, builds up rapidly just below the superfluid transition temperature, and reaches a value of approximately $7.5\%$ below 1 K. We also used model fit functions to obtain from the...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1703.03018
Arxiv.org
by Marcos A. Madrid; J. R. Darias; Luis. A. Pugnaloni
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The Beverloo's scaling for the gravity flow of granular materials through orifices has two distinct universal features. On the one hand, much highlighted in the literature, the flow rate is independent of the height of the granular column. On the other hand, less celebrated yet more striking, the flow rate is fairly insensitive to the material properties of the grains (density, Young's modulus, friction coefficient, etc.). We show that both universal features are lost if work is done on the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03519
Arxiv.org
by Yekaterina Rokhlenko; Paweł W. Majewski; Steven R. Larson; Padma Gopalan; Kevin G. Yager; Chinedum O. Osuji
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Recent experiments have highlighted the intrinsic magnetic anisotropy in coil-coil diblock copolymers, specifically in poly(styrene-b-4-vinylpyridine) (PS-b-P4VP), that enables magnetic field alignment at field strengths of a few tesla. We consider here the alignment response of two low molecular weight (MW) lamallae-forming PS-b-P4VP systems. Cooling across the disorder-order transition temperature ($\mathrm{T_{odt}}$) results in strong alignment for the higher MW sample (5.5K), whereas little...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.07508
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by N. Lebovka; L. Bulavin; V. Kovalchuk; I. Melnyk; K. Repnin
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The two-step percolation behavior in aggregating systems was studied both experimentally and by means of Monte Carlo (MC) simulations. In experimental studies, the electrical conductivity, $\sigma$, of colloidal suspension of multiwalled carbon nanotubes (CNTs) in decane was measured. The suspension was submitted to mechanical de-liquoring in a planar filtration-compression conductometric cell. During de-liquoring, the distance between the measuring electrodes continuously decreased and the CNT...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.10373
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by Hervé Elettro; Paul Grandgeorge; Sébastien Neukirch
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Capillary forces acting at the surface of a liquid drop can be strong enough to deform small objects and recent studies have provided several examples of elastic instabilities induced by surface tension. We present such an example where a liquid drop sits on a straight fiber, and we show that the liquid attracts the fiber which thereby coils inside the drop. We derive the equilibrium equations for the system, compute bifurcation curves, and show the packed fiber may adopt several possible...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.04093
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We provide experimental results to show that self-propulsion of Janus particles made by coating platinum on the hemisphere of dielectric particles in hydrogen peroxide solution is similar to selfelectrophoresis. By different surface treatments and measuring the motion of particles and their {\zeta}-potentials, we find that the speed and direction of motion are determined by the {\zeta}-potential in a given concentration of hydrogen peroxide solution. When sign of {\zeta}-potential is changed...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.03743
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by D. T. Nguyen; E. Wandersman; A. Prevost; Y. Le Chenadec; C. Fretigny; A. Chateauminois
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We report on measurements of the local friction law at a multi-contact interface formed between a smooth rubber and statistically rough glass lenses, under steady state friction. Using contact imaging, surface displacements are measured, and inverted to extract both distributions of frictional shear stress and contact pressure with a spatial resolution of about 10~$\mu$m. For a glass surface whose topography is self-affine with a Gaussian height asperity distribution, the local frictional shear...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08001
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We study the effect of the molecular architecture of amphiphilic star polymers on the shape of aggregates they form in water. Both solute and solvent are considered at a coarse-grained level by means of dissipative particle dynamics simulations. Four different molecular architectures are considered: the miktoarm star, two different diblock stars and a group of linear diblock copolymers, all of the same composition and molecular weight. Aggregation is started from a closely packed bunch of...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.10401
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by Felix X. -F. Ye; Panos Stinis; Hong Qian
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We revisit the celebrated Wilemski-Fixman (WF) treatment for the looping time of a free-draining polymer. The WF theory introduces a sink term into the Fokker-Planck equation for the $3(N+1)$-dimensional Ornstein-Uhlenbeck process of the polymer dynamics, which accounts for the appropriate boundary condition due to the formation of a loop. The assumption for WF theory is considerably relaxed. A perturbation method approach is developed that justifies and generalizes the previous results using...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.04361
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by Martin Wagner; Marisol Ripoll
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Self-propelled phoretic colloids have recently emerged as a promising avenue for the design of artificial swimmers. These swimmers combine purely phoretic interactions with intricate hydrodynamics which critically depend on the swimmer shape. Thermophobic dimer shaped colloids are here investigated by means of hydrodynamic simulations, from the single particle motion to their collective behavior. The combination of phoretic repulsion with hydrodynamic lateral attraction favors the formation of...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.07071
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by Hauke Carstensen; Vassilios Kapaklis; Max Wolff
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Colloidal systems offer unique opportunities for the study of phase formation and structure since their characteristic length scales are accessible to visible light. As a model system the two dimensional assembly of colloidal magnetic and non-magnetic particles dispersed in a ferrofluid (FF) matrix is studied by transmission optical microscopy. We present a method to statistically evaluate images with thousands of particles and map phases by extraction of local variables. Different lattice...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08350
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by Colm P. Kelleher; Anna Wang; Guillermo Iván Guerrero-García; Andrew D. Hollingsworth; Rodrigo E. Guerra; Bhaskar Jyoti Krishnatreya; David G. Grier; Vinothan N. Manoharan; Paul M. Chaikin
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Hydrophobic PMMA colloidal particles, when dispersed in oil with a relatively high dielectric constant, can become highly charged. In the presence of an interface with a conducting aqueous phase, image charge effects lead to strong binding of colloidal particles to the interface, even though the particles are wetted very little by the aqueous phase. In this paper, we study both the behavior of individual colloidal particles as they approach the interface, and the interactions between particles...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.08801
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by Carl A. Whitfield; Tapan Chandra Adhyapak; Adriano Tiribocchi; Gareth P. Alexander; Davide Marenduzzo; Sriram Ramaswamy
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We describe the basic properties and consequences of introducing active stresses, with principal direction along the local director, in cholesteric liquid crystals. The helical ground state is found to be linearly unstable to extensile stresses, without threshold in the limit of infinite system size, whereas contractile stresses are hydrodynamically screened by the cholesteric elasticity to give a finite threshold. This is confirmed numerically and the non-linear consequences of instability, in...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.05022
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by Sebastien Kosgodagan Acharige; Justine Laurent; Audrey Steinberger
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We investigate the capillary force that applies on a tilted cylinder as a function of its dipping angle i, using a home-built tilting Atomic Force Microscope (AFM) with custom made probes. A micrometric-size rod is glued at the end of an AFM cantilever of known stiffness, whose deflection is measured when the cylindrical probe is dipped in and retracted from reference liquids. We show that a torque correction is necessary to understand the measured deflection. The results are compatible with a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.06881
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by I. A. Zaluzhnyy; R. P. Kurta; E. A. Sulyanova; O. Yu. Gorobtsov; A. G. Shabalin; A. V. Zozulya; A. P. Menushenkov; M. Sprung; A. Krowczynski; E. Gorecka; B. I. Ostrovskii; I. A. Vartanyants
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We report on X-ray studies of freely suspended hexatic films of three different liquid crystal compounds. By applying angular X-ray cross-correlation analysis (XCCA) to the measured diffraction patterns the parameters of the bond-orientational (BO) order in the hexatic phase were directly determined. The temperature evolution of the BO order parameters was analyzed on the basis of the multicritical scaling theory (MCST). Our results confirmed the validity of the MCST in the whole temperature...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.01198
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In previous approaches to form quasicrystals, multiple competing length scales involved in particle size, shape or interaction potential are believed to be necessary. It is unexpected that quasicrystals can be self-assembled by monodisperse, isotropic particles interacting via a simple potential without multiple length scales. Here we report the surprising finding of the self-assembly of such quasicrystals in two dimensional systems of soft-core disks interacting via repulsions. We find not...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.08783
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by Vinay Kumar Gupta; Priyanka Shukla; Manuel Torrilhon
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Grad's method of moments is employed to develop higher-order Grad's moment equations---up to first 26-moments---for granular gases within the framework of the (inelastic) Boltzmann equation. The homogeneous cooling state of a freely cooling granular gas is investigated with the Grad's 26-moment equations in a semi-linearized setting and it is shown that the granular temperature in the homogeneous cooling state still decays according to Haff's law while the other higher-order moments decay on a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.09052
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by Matthew L. Blow; Marco Aqil; Benno Liebchen; Davide Marenduzzo
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We provide a minimal model for an active nematic film in contact with both a solid substrate and a passive isotropic fluid, and explore its dynamics in one and two dimensions using a combination of hybrid Lattice Boltzmann simulations and analytical calculations. By imposing nematic anchoring at the substrate while active flows induce a preferred alignment at the interface ("active anchoring"), we demonstrate that directed fluid flow spontaneously emerges in cases where the two...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.04695
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by M. Klopotek; H. Hansen-Goos; M. Dixit; T. Schilling; F. Schreiber; M. Oettel
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Growth of hard--rod monolayers via deposition is studied in a lattice model using rods with discrete orientations and in a continuum model with hard spherocylinders. The lattice model is treated with kinetic Monte Carlo simulations and dynamic density functional theory while the continuum model is studied by dynamic Monte Carlo simulations equivalent to diffusive dynamics. The evolution of nematic order (excess of upright particles, "standing--up" transition) is an entropic effect and...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.05830
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We study theoretically shear banding in soft glassy materials subject to large amplitude time-periodic shear flows, considering separately the protocols of large amplitude oscillatory shear strain, large amplitude square/triangular/sawtooth strain rate, and large amplitude oscillatory shear stress. In each case, we find shear banding to be an important part of the material's flow response for a broad range of values of the frequency $\omega$ and amplitude of the imposed oscillation. Crucially,...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.08332
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by Yael Katsir; Yoav Tsori
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When immiscible liquids are subject to electric fields interfacial forces arise due to a difference in the permittivity or the conductance of the liquids, and these forces lead to shape change in droplets or to interfacial instabilities. In this Topical Review we discuss recent advances in the theory and experiments of liquids in electric fields with an emphasis on liquids which are initially miscible and demix under the influence of an external field. In purely dielectric liquids demixing...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02482
Arxiv.org
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We studied in-plane bistable alignments of nematic liquid crystals confined by two frustrated surfaces by means of Monte Carlo simulations of the Lebwohl-Lasher spin model. The surfaces are prepared with orientational checkerboard patterns, on which the director field is locally anchored to be planar yet orthogonal between the neighboring blocks. We found the director field in the bulk tends to be aligned along the diagonal axes of the checkerboard pattern, as reported experimentally [J.-H. Kim...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.07585
Arxiv.org
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We present large-scale molecular dynamics simulations for a coarse-grained model of polymer melts in equilibrium. From detailed Rouse mode analysis we show that the time-dependent relaxation of the autocorrelation function (ACF) of modes $p$ can be well described by the effective stretched exponential function due to the crossover from Rouse to reptation regime. The ACF is independent of chain sizes $N$ for $N/p
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02702
Arxiv.org
by Debarghya Banerjee; Anton Souslov; Alexander G. Abanov; Vincenzo Vitelli
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Chiral active fluids are materials composed of self-spinning rotors that continuously inject energy and angular momentum at the microscale. Out-of-equilibrium fluids with active-rotor constituents have been experimentally realized using nanoscale biomolecular motors, microscale active colloids, or macroscale driven chiral grains. Here, we show how such chiral active fluids break both parity and time-reversal symmetries in their steady states, giving rise to a dissipationless linear-response...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02393
Arxiv.org
by Tong Gao; Meredith D. Betterton; An-Sheng Jhang; Michael J. Shelley
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We analyze one of the simplest active suspensions with complex dynamics: a suspension of immotile "Extensor" particles that exert active extensile dipolar stresses on the fluid in which they are immersed. This is relevant to several experimental systems, such as recently studied tripartite rods that create extensile flows by consuming a chemical fuel. We first describe the system through a Doi-Onsager kinetic theory based on microscopic modeling. This theory captures the active...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.00969