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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 Matteo Amabili; Alberto Giacomello; Simone Meloni; Carlo Massimo Casciola
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The mechanism of the collapse of the superhydrophobic state is elucidated for submerged nanoscale textures forming a three-dimensional interconnected vapor domain. This key issue for the design of nanotextures poses significant simulation challenges as it is characterized by diverse time and length scales. State-of-the-art atomistic rare events simulations are applied for overcoming the long time scales connected with the large free energy barriers. In such interconnected surface cavities...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.10389
Arxiv.org
by E. DeGiuli; M. Wyart
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The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity-weakening, corresponding to a non-monotonic behavior in the friction law $\mu(I)$, is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.00740
Arxiv.org
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We report on the nature of flow events for the gravity-driven discharge of glass beads through a hole that is small enough that the hopper is susceptible to clogging. In particular, we measure the average and standard deviation of the distribution of discharged masses as a function of both hole and grain sizes. We do so in air, which is usual, but also with the system entirely submerged under water. This damps the grain dynamics and could be expected to dramatically affect the distribution of...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02985
Arxiv.org
by Michael Niemetz; Risto Hänninen; Wilfried Schoepe
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The flow of superfluid $^4$He around a translationally oscillating sphere, levitating without mechanical support, can either be laminar or turbulent, depending on the velocity amplitude. Below a critical velocity $v_c$ that scales as $\omega ^{1/2}$, and is temperature independent below 1 K, the flow is laminar (potential flow). Below 0.5 K the linear drag force is caused by ballistic phonon scattering that vanishes as T$^4$ until background damping, measured in the empty cell, becomes dominant...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1701.05733
Arxiv.org
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The classic Kob-Andersen (KA) binary Lennard-Jones mixtures which are designed to prevent crystallization has been extensively studied in simulation of slow dynamics. Although crystallization can occur if a liquid system is cooled slowly, so far the KA model has not been crystallized. Here we report using molecular simulation the observation of crystal growth in the supercooled KA liquids. The onset of crystallization is observed occurring at temperature $T_c= 0.55$ which is higher than the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.02659
Arxiv.org
by Meera Ramaswamy; Neil Y. C. Lin; Brian D. Leahy; Christopher Ness; Andrew Fiore; James W. Swan; Itai Cohen
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Understanding the correlation between structure and rheology in colloidal suspensions is important as these suspensions are crucial in industrial applications. Moreover, colloids exhibit a wide range of structures under confinement that could considerably alter the viscosity. Here, we use a combination of experiments and simulations to elucidate how confinement induced structures alter the relative contributions of hydrodynamic and repulsive forces to produce up to a ten fold change in the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.02904
Arxiv.org
by I. Ríos de Anda; F. Turci; R. Sear; C. P. Royall
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We perform particle resolved experimental studies on the heterogeneous crystallisation process of two component mixtures of hard spheres. The components have a size ratio of 0.39. We compared these with molecular dynamics simulations of homogenous nucleation. Surprisingly, we found for both experiments and simulations that the final assemblies are not the fixed composition binary and one-component crystals predicted by previous simulation work [Trizac et al., Mol. Phys. 90, 675 (1997)]; we...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.05438
Arxiv.org
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Viscous flows in a quasi-two-dimensional Hele-Shaw geometry can lead to an interfacial instability when one fluid, of viscosity $\eta_{in}$ displaces another of higher viscosity, $\eta_{out}$. Recent studies have shown that there is a delay in the onset of fingering in miscible fluids as the viscosity ratio, $\eta_{in}/\eta_{out}$, increases and approaches unity; the interface can remain stable even though the displacing liquid is less viscous. This paper shows that a delayed onset and stable...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.02674
Arxiv.org
by T. J. S. Munsie; M. N. Wilson; A. Millington; C. M. Thompson; R. Flacau; C. Ding; Z. Gong; S. Guo; A. A. Aczel; H. B. Cao; T. J. Williams; H. A. Dabkowska; F. Ning; J. E. Greedan; G. M. Luke
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Neutron diffraction and muon spin relaxation ($\mu$SR) studies are presented for the newly characterized polymorph of NiNb$_2$O$_6$ ($\beta$-NiNb$_2$O$_6$) with space group P4$_2$/n and $\mu$SR data only for the previously known columbite structure polymorph with space group Pbcn. The magnetic structure of the P4$_2$/n form was determined from neutron diffraction using both powder and single crystal data. Powder neutron diffraction determined an ordering wave vector $\vec{k}$ =...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1704.04043
Arxiv.org
by Juha Koivisto; Marko Korhonen; Mikko J. Alava; Carlos P. Ortiz; Douglas J. Durian; Antti Puisto
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We investigate the coupling between interstitial medium and granular particles by studying the hopper flow of dry and submerged system experimentally and numerically. In accordance with earlier studies, we find, that the dry hopper empties at a constant rate. However, in the submerged system we observe the surging of the flow rate. We model both systems using the discrete element method, which we couple with computational fluid dynamics in the case of a submerged hopper. We are able to match...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09584
Arxiv.org
by Andre Förtsch; Matthias Laumann; Diego Kienle; Walter Zimmermann
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Non-neutrally buoyant soft particles in vertical microflows are investigated. We find, soft particles lighter than the liquid migrate to off-center streamlines in a downward Poiseuille flow (buoyancy-force antiparallel to flow). In contrast, heavy soft particles migrate to the center of the downward (and vanishing) Poiseuille flow. A reversal of the flow direction causes in both cases a reversal of the migration direction, i. e. heavier (lighter) particles migrate away from (to) the center of a...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.06590
Arxiv.org
by Shivaraj D. Deshmukh; Yoav Tsori
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We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.04980
Arxiv.org
by Summer Shahzad; Francesco Dal Corso; Davide Bigoni
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Stress field solutions and Stress Intensity Factors (SIFs) are found for $n$-cusped hypocycloidal shaped voids and rigid inclusions in an infinite linear elastic plane subject to nonuniform remote antiplane loading, using complex potential and conformal mapping. It is shown that a void with hypocycloidal shape can lead to a higher SIF than that induced by a corresponding star-shaped crack; this is counter intuitive as the latter usually produces a more severe stress field in the material....
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.06302
Arxiv.org
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Harnessing a model from composite materials science, we show how point-like cusped surface features arise as quasi-particle excitations, termed "ghost fibers", on the surface of a homogeneous soft elastic material. These deformations appear above a critical compressive strain at which ghost fiber dipoles unbind, analogous to vortices in the Kosterlitz-Thouless transition. Finite-length creases can be described in the same framework. Our predictions for crease surface profiles and...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.05530
Arxiv.org
by Élfego Ruiz-Gutiérrez; Ciro Semprebon; Glen McHale; Rodrigo Ledesma-Aguilar
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We present a theoretical study of the statics and dynamics of a partially wetting liquid droplet, of equilibrium contact angle $\theta_{\rm e}$, confined in a solid wedge geometry of opening angle $\beta$. We focus on a mostly non-wetting regime, given by the condition $\theta_{\rm e} - \beta > 90^\circ$, where the droplet forms a liquid barrel -- a closed shape of positive mean curvature. Using a quasi-equilibrium assumption for the shape of the liquid-gas interface, we compute the surface...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.06076
Arxiv.org
by Alex J. Kruchkov; Henrik M. Rønnow
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This paper studies the influence of electric fields on the skyrmion lattice (SkL) in insulating skyrmion compounds with weak magnetoelectric (ME) coupling. The ME coupling mechanism is an interaction between the external electric field $E$ and local magnetization in the sample. Physically, the $E$-field perturbs the spin modulation wave vectors resulting in the distortion of the SkL and the $E$-field induced shift in energy. Due to the relativistic smallness of ME coupling, the important...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1702.08863
Arxiv.org
by Thiago A Sobral; Marcelo A F Gomes; Núbia R Machado; Valdemiro P Brito
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The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.05357
Arxiv.org
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Spin-coating technique is very fast, cheap, reproducible, simple and needs less material to fabricate films of particulate systems/colloids. Their thickness and uniformity may be controlled by means of external fields. We apply magnetic fields during the spin-coating of a moderately concentrated superparamagnetic colloid (made of silica coated magnetite particles). We study the influence of different magnetic field configurations (homogeneous and inhomogeneous) on the resulting spin-coated...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.01956
Arxiv.org
by Kento Yasuda; Ryuichi Okamoto; Shigeyuki Komura
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We discuss a locomotion of a three-sphere microswimmer in a viscoelastic medium and propose a new type of active microrheology. We derive a relation which connects average swimming velocity and frequency-dependent viscosity of the surrounding medium. In this relation, the viscous contribution can exist only when the time-reversal symmetry is broken, whereas the elastic contribution is present only when the structural symmetry of the swimmer is broken. The Purcell's scallop theorem breaks down...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.01224
Arxiv.org
by Santi Prestipino; Gianmarco Munaò; Dino Costa; Carlo Caccamo
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We investigate the structure of a dilute mixture of amphiphilic dimers and spherical particles, a model relevant to the problem of encapsulating globular "guest" molecules in a dispersion. Dimers and spheres are taken to be hard particles, with an additional attraction between spheres and the smaller monomers in a dimer. Using Monte Carlo simulation, we document the low-temperature formation of aggregates of guests (clusters) held together by dimers, whose typical size and shape...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.07318
Arxiv.org
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Randomization of the trap state of defects present at the gate Si-SiO$_2$ interface of MOSFET is responsible for the low-frequency noise phenomena such as Random Telegraph Signal (RTS), burst, and 1/\textit{f} noise. In a previous work, theoretical modelling and analysis of the RTS noise in MOS transistor was presented and it was shown that this 1/\textit{f} noise can be reduced by decreasing the duty cycle ($f_{D}$) of switched biasing signal. In this paper, an extended analysis of this...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1704.00876
Arxiv.org
by Ahmad Rafsanjani; Katia Bertoldi
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We investigate the mechanical response of thin sheets perforated with a square array of mutually orthogonal cuts, which leaves a network of squares connected by small ligaments. Our combined analytical, experimental and numerical results indicate that under uniaxial tension the ligaments buckle out-of-plane, inducing the formation of 3D patterns whose morphology is controlled by the load direction. We also find that by largely stretching the buckled perforated sheets, plastic strains develop in...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.06470
Arxiv.org
by Lorène Champougny; Emmanuelle Rio; Frédéric Restagno; Benoit Scheid
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In this paper, we derive a lubrication model to describe the non-stationary free liquid film that is created when a vertical frame is pulled out of a liquid reservoir at a given velocity. We here focus on the case of a pure liquid, corresponding to a stress-free boundary condition at the liquid/air interfaces of the film, and thus employ an essentially extensional description of the flow. Taking into account van der Waals interactions between the interfaces, we observe that film rupture is...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.02585
Arxiv.org
by Juan L. Aragones; Joshua P. Steimel; Alfredo Alexander-Katz
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Active matter systems are able to exhibit emergent non-equilibrium states due to activity-induced effective interactions between the active particles. Here we study the aggregation and dynamical behavior of active rotating particles, spinners, embedded in 2D passive colloidal monolayers, which constitutes one such non-equilibrium process. Using both experiments and simulations we observe aggregation of active particles or spinners whose behavior resembles classical 2D coarsening. The...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.06930
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by Alessandro Lucantonio; Giovanni Noselli
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Brittle materials fail catastrophically. In consequence of their limited flaw-tolerance, failure occurs by localized fracture and is typically a dynamic process. Recently, experiments on epithelial cell monolayers have revealed that this scenario can be significantly modified when the material susceptible to cracking is adhered to a hydrogel substrate. Thanks to the hydraulic coupling between the brittle layer and the poroelastic substrate, such a composite can develop a toughening mechanism...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.01318
Arxiv.org
by Horacio López-Menéndez; José Félix Rodríguez
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The rheology of F-actin networks has attracted a great attention during the last years. In order to gain a complete understanding of the rheological properties of these novel materials, it is necessary the study in a large deformations regime to alter their internal structure. In this sense, Schmoller et al. 2010 showed that the reconstituted networks of F-actin crosslinked with $\alpha$-actinin unexpectedly harden when they are subjected to a cyclical shear. This observation contradicts the...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.01595
Arxiv.org
by Johannes Bleibel; Alvaro Domínguez; Martin Oettel
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It has been recently shown that a colloidal monolayer, e.g., formed at a fluid interface or by means of a suitable confining potential, exhibits anomalous collective diffusion. This is a consequence of the hydrodynamic interactions mediated by the three-dimensional (3D) ambient fluid when the particles are confined to reside on a two-dimensional (2D) manifold. We study theoretically and with numerical simulations the crossover from normal to anomalous diffusion as the particles are, in real...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.02758
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by Alexander Smith; Alpha Lee; Susan Perkin
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The structure and interactions in electrolytes at high concentration have implications from energy storage to biomolecular interactions. However many experimental observations are yet to be explained in these mixtures, which are far beyond the regime of validity of mean field models. Here, we study the structural forces in a mixture of ionic liquid and solvent that is miscible in all proportions at room temperature. Using the surface force balance to measure the force between macroscopic smooth...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.03242
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by Matthew Dennison; Raymond Kapral; Holger Stark
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Experimental studies of systems containing active proteins that undergo conformational changes driven by catalytic chemical reactions have shown that the diffusion coefficients of passive tracer particles and active molecules are larger than the corresponding values when chemical activity is absent. Various mechanisms have been proposed for such behavior, including, among others, force dipole interactions of molecular motors moving on filaments and collective hydrodynamic effects arising from...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1702.07596
Arxiv.org
by Aboubakry Ly; Arghya Majee; Alois Würger
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We theoretically study the Seebeck effect in the vicinity of a heated metal nanostructure, such as the gold cap of an active Janus colloid in an electrolyte. The thermocharge varies with the surface temperature, thus modulating the diffuse layer of an insulating surface, and inducing polarization charges on an electric conductor. The isopotential boundary condition on a metal surface, results in a reduction of the slip velcoity. Our results agree with recently observed specific-ion effects for...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.03281
Arxiv.org
by T A Sobral; M A F Gomes
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The present work deals with the injection and packing of a flexible polymeric rod of length $L$ into a simply connected rectangular domain of area $XY$. As the injection proceeds, the rod bends over itself and it stores elastic energy in closed loops. In a typical experiment $N$ of these loops can be identified inside the cavity in the jammed state. We have performed an extensive experimental analysis of the total length $L(N, X, Y)$ in the tight packing limit, and have obtained robust power...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.04201
Arxiv.org
by D. Rayneau-Kirkhope; Y. Mao; C. Rauch
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Throughout biology, hierarchy is a recurrent theme in the geometry of structures where strength is achieved with minimal use of material. Acting over vast timescales, evolution has brought about beautiful solutions to problems of optimisation that are only now being understood and incorporated into engineering design. One particular example of this hierarchy is found in the junction between stiff keratinised material and the soft biological matter within the hooves of ungulates. Using this...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.05506
Arxiv.org
by Axelle Amon; Baptiste Blanc; Jean-Christophe Géminard
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We present a one-dimensional numerical model based on elastically coupled sliders on a frictional incline of variable tilt. This very simple approach makes possible to study the precursors to the avalanche and to provide a rationalization of different features that have been observed in experiments. We provide a statistical description of the model leading to master equations describing the state of the system as a function of the angle of inclination. Our central results are the reproduction...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.07080
Arxiv.org
by Jingxi Luo; Bernard Piette
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We present a one-parameter family of mathematical models describing the dynamics of polarons in linear periodic structures such as polypeptides. By tuning the parameter, we are able to recover the Davydov and the Scott models. We describe the physical significance of this parameter. In the continuum limit, we derive analytical solutions which represent stationary polarons. On a discrete lattice, we compute stationary polaron solutions numerically. We investigate polaron propagation induced by...
Topics: Condensed Matter, Other Condensed Matter
Source: http://arxiv.org/abs/1704.02247
Arxiv.org
by Emil Prodan; Kyle Dobiszewski; Alokik Kanwal; John Palmieri; Camelia Prodan
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Mechanical systems can display topological characteristics similar to that of topological insulators. Here we report a large class of topological mechanical systems related to the BDI symmetry class. These are self-assembled chains of rigid bodies with an inversion center and no reflection planes. The particle-hole symmetry characteristic to the BDI symmetry class stems from the distinct behavior of the translational and rotational degrees of freedom under inversion. This and other generic...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.06542
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 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
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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 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
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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
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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
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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 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
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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
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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
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
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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
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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 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
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by Fausto Martelli; Hsin-Yu Ko; Carles Calero Borallo; Giancarlo Franzese
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Biological membranes are essential for the cell life and hydration water provides the driving force for their assembly and stability. Here we study the structural properties of water in a phospholipid membrane. We characterize local structures inspecting the intermediate range order (IRO) adopting a sensitive local order metric, recently proposed by Martelli et al., which measures and grades the degree of overlap of local environments with structures of perfect ice. Close to the membrane, water...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.07835
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All-atom molecular dynamics simulations of an elastohydrodynamic lubrication oil film are performed to study the effect of pressure. Fluid molecules of n-hexane are confined between two solid plates under a constant normal force of 0.1--8.0 GPa. Traction simulations are performed by applying relative sliding motion to the solid plates. A transition in the traction behavior is observed around 0.5--2.0 GPa, which corresponds to the viscoelastic region to the plastic--elastic region, which are...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1703.09790
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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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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
Ferrogels, i.e., hydrogels loaded with magnetic nanoparticles, have the ability to deform in external magnetic fields. The precise shape of deformation and the alignment of the gel in the field, however, depend on the interplay of several factors. In this paper, we introduce a coarse-grained simulation model, which takes into account the configuration of magnetic particles in the gel, the sample shape, and aspects of the polymer network topology. We use this model to show that in gels with an...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.06578
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Magnetic nanoparticles in a colloidal solution self-assemble in various aligned structures, which has a profound influence on the flow behavior. However, the precise role of the microstructure in the development of the rheological response has not been reliably quantified. We investigate the self-assembly of dipolar colloids in simple shear using hybrid molecular dynamics and multi-particle collision dynamics simulations with explicit coarse-grained hydrodynamics; conduct simulated rheometric...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1704.07089
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by René Wittmann; Claudio Maggi; Abhinav Sharma; Alberto Scacchi; Joseph M. Brader; Umberto Marini Bettolo Marconi
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The equations of motion of active systems can be modeled in terms of Ornstein-Uhlenbeck processes (OUPs) with appropriate correlators. For further theoretical studies, these should be approximated to yield a Markovian picture for the dynamics and a simplified steady-state condition. We perform a comparative study of the Unified Colored Noise Approximation (UCNA) and the approximation scheme by Fox recently employed within this context. We review and discuss in detail the approximations...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.09032
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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
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by S. Yashima; V. Romero; E. Wandersman; C. Frétigny; M. K. Chaudhury; A. Chateauminois; A. M. Prevost
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We report on normal contact and friction measurements of model multicontact interfaces formed between smooth surfaces and substrates textured with a statistical distribution of spherical micro-asperities. Contacts are either formed between a rigid textured lens and a smooth rubber, or a flat textured rubber and a smooth rigid lens. Measurements of the real area of contact $A$ versus normal load $P$ are performed by imaging the light transmitted at the microcontacts. For both interfaces, $A(P)$...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.01268
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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 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 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
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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 G Prabhudesai; I Bihi; F Zoueshtiagh; J Jose; M Baudoin
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In this paper, we study the dynamics of cylindrical armoured bubbles excited by mechanical vibrations. A step by step transition from cylindrical to spherical shape is reported as the intensity of the vibration is increased, leading to a reduction of the bubble surface and a dissemination of the excess particles. We demonstrate through energy balance that nonspherical armoured bubbles constitute a metastable state. The vibration instills the activation energy necessary for the bubble to return...
Topics: Condensed Matter, Soft Condensed Matter
Source: http://arxiv.org/abs/1701.05439
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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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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
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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
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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
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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
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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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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
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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
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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
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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
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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
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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
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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
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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
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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 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 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
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 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
Arxiv.org
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
Arxiv.org
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
Arxiv.org
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