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European Physical Journal. E, Soft Matter

J Thiery, E Keita, S Rodts, D Courtier Murias, T Kodger, A Pegoraro, P Coussot
The desiccation of porous materials encompasses a wide range of technological and industrial processes and is acutely sensitive to the hierarchical structure of the porous materials resulting in complex dynamics which are challenging to unravel. Macroscopic observations of the surface and geometry of model colloidal gels during desiccation under controlled air flow highlight the role of crack formation in drying. The density of cracks and their rate of appearance depend on the initial solid fraction of the gels and their adherence to the substrate...
December 2016: European Physical Journal. E, Soft Matter
R Tuinier, S Ouhajji, P Linse
The phase behaviour of a colloidal dispersion mediated by weakly adhesive polymers is considered. The polymers are depleted but are weakly adhesive and hence comprise a non-zero polymer concentration at the colloid's surface, in contrast to the classical assumption in depletion theories involving a zero polymer concentration at the surface. The theory is composed of a generalized free-volume theory for colloid-polymer mixtures and a self-consistent mean-field theory for polymers at surfaces. It is found that the weak adhesion of the polymers shifts the phase stability of the colloid-polymer mixtures to higher polymer concentrations as compared to assuming a full depletion effect...
November 2016: European Physical Journal. E, Soft Matter
Matthias Radtke, Roland R Netz
The motion of a single rigid or elastic particle inside a corrugated narrow channel is investigated by means of Brownian dynamics simulations. Periodic oscillations of one of the asymmetric channel surfaces induce directed particle transport. For different surface structures of the resting channel surface, we determine optimal transport properties in terms of the driving frequency, particle size, and corrugation amplitude. The transport direction is changed when switching from perpendicular motion of the oscillating surface to parallel motion with respect to the resting surface, which can be rationalized by a transition from a flashing to a pushing ratchet effect...
November 2016: European Physical Journal. E, Soft Matter
Lila Bouzar, Martin Michael Müller, Pierre Gosselin, Igor M Kulić, Hervé Mohrbach
We theoretically study the conformations of a helical semi-flexible filament confined to a flat surface. This squeezed helix exhibits a variety of unexpected shapes resembling circles, waves or spirals depending on the material parameters. We explore the conformation space in detail and show that the shapes can be understood as the mutual elastic interaction of conformational quasi-particles. Our theoretical results are potentially useful to determine the material parameters of such helical filaments in an experimental setting...
November 2016: European Physical Journal. E, Soft Matter
Giuseppe Gaeta, Epifanio G Virga
Octupolar order in three space dimensions is described by a real-valued, fully symmetric and traceless, third-rank tensor A. The real generalized eigenvalues of A are also the critical values of a real-valued potential [Formula: see text] defined on the unit sphere [Formula: see text] by A. Generalized eigenvalues of A and critical points of [Formula: see text] are equivalent means to describe octupolar order in a molecular assembly according to Buckingham's formula for the probability density distribution...
November 2016: European Physical Journal. E, Soft Matter
S Ancherbak, C Santos, J -C Legros, A Mialdun, V Shevtsova
We present the development of a high-pressure apparatus for measurements of diffusion coefficients in supercritical fluids. The Taylor dispersion method has been adapted to conduct experiments at the pressures up to 25.0 MPa. In order to test the developed set-up, binary diffusion coefficients D at infinite dilution in supercritical carbon dioxide have been measured for a reference system, benzene, at temperatures in the range of 309.50-319.95 K. The effects of flow velocity, number of consecutive injections and absorbance at different wave numbers on the diffusion coefficient have been analysed...
November 2016: European Physical Journal. E, Soft Matter
Dong Wang, Dao Ho-Minh, Danielle S Tan
The Discrete Element Method (DEM) is a discrete, particle-based method commonly used in studies involving granular media, e.g. sediment transport, and geomechanics. It is heavily dependent on particle properties, and one important component is the force model, which relates the relative positions and velocities of the simulated particles to the forces they experience. In this paper we model a collection of lightly compacted granular material, released at a short distance above a flat base in a quiescent fluid --similar to the process whereby sediment tailings are released back into the sea during nodule harvesting...
November 2016: European Physical Journal. E, Soft Matter
Yu A Budkov, A L Kolesnikov
We present a new simple self-consistent field theory of a polarizable flexible polymer chain under an external constant electric field with account for the many-body electrostatic dipole correlations. We show the effects of electrostatic dipole correlations on the electric-field-induced globule-coil transition. We demonstrate that only when the polymer chain is in the coil conformation, the electrostatic dipole correlations of monomers can be considered as pairwise. However, when the polymer chain is in a collapsed state, the dipole correlations have to be considered at the many-body level...
November 2016: European Physical Journal. E, Soft Matter
Qiaoyue Chen, Lili Zhang, Mingming Ding, Xiaozheng Duan, Yineng Huang, Tongfei Shi
We study the effects of the nanopore size on the flow-induced capture of the star polymer by a nanopore and the afterward translocation, using a hybrid simulation method that couples point particles into a fluctuating lattice-Boltzmann fluid. Our simulation demonstrates that the optimal forward arm number decreases slowly with the increase of the length of the nanopore. Compared to the minor effect of the length of the nanopore, the optimal forward arm number obviously increases with the increase of the width of the nanopore, which can clarify the current controversial issue for the optimal forward arm number between the theory and experiments...
November 2016: European Physical Journal. E, Soft Matter
M Rückl, S Rüdiger
Calcium signals in cells occur at multiple spatial scales and variable temporal duration. However, a physical explanation for transitions between long-lasting global oscillations and localized short-term elevations (puffs) of cytoplasmic Ca(2+) is still lacking. Here we introduce a phenomenological, coarse-grained model for the calcium variable, which is represented by ordinary differential equations. Due to its small number of parameters, and its simplicity, this model allows us to numerically study the interplay of multi-scale calcium concentrations with stochastic ion channel gating dynamics even in larger systems...
November 2016: European Physical Journal. E, Soft Matter
Huanshu Tan, Shuhua Peng, Chao Sun, Xuehua Zhang, Detlef Lohse
In the study of nanobubbles, nanodroplets or nanolenses immobilised on a substrate, a cross-section of a spherical cap is widely applied to extract geometrical information from atomic force microscopy (AFM) topographic images. In this paper, we have developed a comprehensive 3D spherical-cap fitting procedure (3D-SCFP) to extract morphologic characteristics of complete or truncated spherical caps from AFM images. Our procedure integrates several advanced digital image analysis techniques to construct a 3D spherical-cap model, from which the geometrical parameters of the nanostructures are extracted automatically by a simple algorithm...
November 2016: European Physical Journal. E, Soft Matter
Erol Akpinar, Meric Turkmen, Cihan Canioz, Antônio Martins Figueiredo Neto
Three lyotropic quaternary systems of ionic surfactants were prepared to investigate the role of kosmotrope-chaotrope interactions at the micelle surfaces on stabilizing the different nematic phases. The ionic surfactants were potassium laurate (KL), sodium dodecylsulfate (SDS) and tetradecyltrimethylammonium bromide (TDTMABr), where KL is a kosmotrope surfactant, and others are chaotrope. The first system consisted of KL/decanol (DeOH)/water/alkali sulfate and the second of SDS/DeOH/water/alkali sulfate. The third system was prepared by adding sodium salts of chaotropic or kosmotropic anions to the primary mixture of TDTMABr/DeOH/water, separately...
November 2016: European Physical Journal. E, Soft Matter
Helmut R Brand, Harald Pleiner, Daniel Svenšek
We present the derivation of the macroscopic equations for uniaxial polar nematic gels and elastomers. We include the strain field as well as relative rotations as independent dynamic macroscopic degrees of freedom. As a consequence, special emphasis is laid on possible static and dynamic cross-couplings between these macroscopic degrees of freedom associated with the network, and the other macroscopic degrees of freedom including reorientations of the macroscopic polarization. In particular, we find static and dissipative dynamic cross-couplings between strain fields and relative rotations on one hand and the macroscopic polarization on the other that allow for new possibilities to manipulate polar nematics...
November 2016: European Physical Journal. E, Soft Matter
Leonid V Mirantsev
The dynamics of a magnetic (electric) field induced perturbation in a homeotropic smectic A (SmA) structure in liquid crystal cells with substrates having periodic microrelief has been investigated. It has been shown that relaxation times of such perturbation in both switching-on and switching-off regimes are of the order of 10(-5)-10(-4)s. The results obtained show that previously proposed novel electro (magneto) optic effect in such SmA cell can be utilized in manufacturing of liquid crystal displays with operating times much shorter than those of ordinary modern displays based on the Freedericksz transitions in nematic liquid crystals...
November 2016: European Physical Journal. E, Soft Matter
Anand U Oza, Sebastian Heidenreich, Jörn Dunkel
In describing the physics of living organisms, a mathematical theory that captures the generic ordering principles of intracellular and multicellular dynamics is essential for distinguishing between universal and system-specific features. Here, we compare two recently proposed nonlinear high-order continuum models for active polar and nematic suspensions, which aim to describe collective migration in dense cell assemblies and the ordering processes in ATP-driven microtubule-kinesin networks, respectively. We discuss the phase diagrams of the two models and relate their predictions to recent experiments...
October 2016: European Physical Journal. E, Soft Matter
M Orlishausen, W Köhler
Aqueous solutions of highly entangled ultra-high molar mass ( 2.4×10(6) g/mol) poly(N-isopropylacrylamide) (PNIPAM) have been subjected to an inhomogeneous temperature field by selective heating of a single embedded gold nanoparticle (GNP) by means of a focused laser beam. Randomly distributed tracer GNPs are trapped in the meshes of the transient entanglement network and serve as tracers for the monitoring of the network deformation field. Because of the positive Soret coefficient of PNIPAM in water, the viscoelastic polymer network is expanded by thermophoretic forces pointing away from the hot center...
October 2016: European Physical Journal. E, Soft Matter
Fabio Giavazzi, Alessandro Fornasieri, Alberto Vailati, Roberto Cerbino
When a macroscopic concentration gradient is present across a binary mixture, long-ranged non-equilibrium concentration fluctuations (NCF) appear as a consequence of the coupling between the gradient and spontaneous equilibrium velocity fluctuations. Long-ranged equilibrium concentration fluctuations (ECF) may be also observed when the mixture is close to a critical point. Here we study the interplay between NCF and critical ECF in a near-critical mixture aniline/cyclohexane in the presence of a vertical concentration gradient...
October 2016: European Physical Journal. E, Soft Matter
Wang Heping, Geng Xingguo, Li Xiaoguang, Zang Duyang
This paper presents an exploration of the separation behavior and pattern formation in a shear binary fluid with dynamic temperature after slow cooling via coupled lattice Boltzmann method. The phase separation procedure can be divided into three different stages: spinodal decomposition, domain growth, and domain stretch. The effect of thermal diffusion was observed to be more significant than that of shear convection in the spinodal decomposition stage, while the opposite was observed in the domain growth stage...
October 2016: European Physical Journal. E, Soft Matter
Sarthok Sircar, Giang Nguyen, Andrei Kotousov, Anthony J Roberts
A self-consistent model is developed to investigate attachment/detachment kinetics of two static, deformable microspheres with irregular surface and coated with flexible binding ligands. The model highlights how the microscale binding kinetics of these ligands as well as the attractive/repulsive potential of the charged surface affects the macroscale static deformed configuration of the spheres. It is shown that in the limit of smooth, neutrally charged surface (i.e., the dimensionless inverse Debye length, [Formula: see text]), interacting via elastic binders (i...
October 2016: European Physical Journal. E, Soft Matter
D R Daniels
Using rigorous low-Reynolds-number hydrodynamic theory on curved surfaces, we provide, via a Stokeslet-type approach, a general and concise expression for the leading-order curvature correction to the canonical, planar, Saffman-Delbrück value of the diffusion constant for a small inclusion embedded in an arbitrarily (albeit weakly) curved fluid membrane. In order to demonstrate the efficacy and utility of this general result, we apply our theory to the specific case of calculating the diffusion coefficient of a locally curvature inducing membrane inclusion...
October 2016: European Physical Journal. E, Soft Matter
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