tag:blogger.com,1999:blog-16516321471684247682016-09-29T00:45:26.171-07:00cond-mat.soft - Soft Condensed MatterSite for <a href="http://communitypeerreview.blogspot.com/">Community Peer Review</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.comBlogger2425125tag:blogger.com,1999:blog-1651632147168424768.post-81431971745755177772013-08-06T00:02:00.019-07:002013-08-06T00:02:32.391-07:001308.0622 (Jian Qin et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0622">Optimizing directed self-assembled morphology</a> [<a href="http://arxiv.org/pdf/1308.0622">PDF</a>]</h2>Jian Qin, Gurdaman S. Khaira, Yongrui Su, Grant P. Garner, Marc Miskin, Heinrich M. Jaeger, Juan J. de Pablo<a name='more'></a><blockquote class="abstract">Directed assembly of block polymers is rapidly becoming a viable strategy for lithographic patterning of nanoscopic features. One of the key attributes of directed assembly is that an underlying chemical or topographic substrate pattern used to direct assembly need not exhibit a direct correspondence with the sought after block polymer morphology, and past work has largely relied on trial-and-error approaches to design appropriate patterns. In this work, a computational evolutionary strategy is proposed to solve this optimization problem. By combining the Cahn-Hilliard equation, which is used to find the equilibrium morphology, and the covariance-matrix evolutionary strategy, which is used to optimize the combined outcome of particular substrate-copolymer combinations, we arrive at an efficient method for design of substrates leading to non-trivial, desirable outcomes.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0622">http://arxiv.org/abs/1308.0622</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-41808676974883539262013-08-06T00:02:00.017-07:002013-08-06T00:02:31.292-07:001308.0636 (Silvia Corezzi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0636">Stress-induced modification of the boson peak scaling behavior</a> [<a href="http://arxiv.org/pdf/1308.0636">PDF</a>]</h2>Silvia Corezzi, Silvia Caponi, Flavio Rossi, Daniele Fioretto<a name='more'></a><blockquote class="abstract">The scaling behavior of the so-called boson peak in glass-formers and its relation to the elastic properties of the system remains a source of controversy. Here, the boson peak in a binary reactive mixture is measured by Raman scattering (i) on cooling the unreacted mixture well below its glass transition temperature and (ii) after quenching to very low temperature the mixture at different times during isothermal polymerization. These different paths to the glassy phase are able to generate glasses with different amounts of residual stresses, as evidenced by the departure of the elastic moduli from a Cauchy-like relationship. We find that the scaling behavior of the boson peak with the properties of the elastic medium --- as measured by the Debye frequency --- holds for states in which the system is able to release internal stress and breaks down in the presence of residual stresses. These findings provide new insight into the boson peak behavior and are able to reconcile the apparently conflicting results presented in literature.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0636">http://arxiv.org/abs/1308.0636</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-77295381636052133862013-08-06T00:02:00.015-07:002013-08-06T00:02:30.323-07:001308.0653 (Chuandong Lin et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0653">Polar coordinate lattice Boltzmann modeling of detonation phenomena</a> [<a href="http://arxiv.org/pdf/1308.0653">PDF</a>]</h2>Chuandong Lin, Aiguo Xu, Guangcai Zhang, Yingjun Li<a name='more'></a><blockquote class="abstract">We present a polar coordinate lattice Boltzmann model for the detonation phenomena. In this model the fluid behavior is describe by a finite-difference lattice Boltzmann(FDLB) model in polar coordinates, and the chemical reaction is described by Cochran's rate function. The released chemical energy is naturally coupled with the flow behavior. We introduce an operator-splitting scheme to both the FDLB equation and Cochran's rate function. The temporal evolutions are calculated analytically and the convection terms are solved via the first-order upwind scheme. The model is validated and verified via comparing simulation results with analytical solution of steady detonation. We simulate the detonation phenomena in two cases: implosion and explosion. Finally, we study some non-equilibrium characteristics in the steady detonation procedure. Numerical results show that, the amplitudes of deviations from thermodynamic equilibrium in front of von-Neumann peak are much higher than those behind the peak. At the von Neumann peak, the system is nearly in its thermodynamic equilibrium. By comparing each component of the high-order moments and its value in equilibrium, we draw qualitative information on the actual distribution functions at the two sides of von-Neumann peak. Such observations are helpful for the physical modeling of detonation phenomena from the macroscopic level.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0653">http://arxiv.org/abs/1308.0653</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-51557433100425876472013-08-06T00:02:00.013-07:002013-08-06T00:02:29.531-07:001308.0800 (N. Ould-Moussa et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0800">In vitro toxicity of nanoceria: effect of coating and stability in<br /> biofluids</a> [<a href="http://arxiv.org/pdf/1308.0800">PDF</a>]</h2>N. Ould-Moussa, M. Safi, M. A. Guedeau-Boudeville, D. Montero, H. Conjeaud, J. F. Berret<a name='more'></a><blockquote class="abstract">Due to the increasing use of nanometric cerium oxide in applications, concerns about the toxicity of these particles have been raised and have resulted in a large number of investigations. We report here on the interactions between 7 nm anionically charged cerium oxide particles and living mammalian cells. By a modification of the particle coating including low-molecular weight ligands and polymers, two generic behaviors are compared: particles coated with citrate ions that precipitate in biofluids and particles coated with poly(acrylic acid) that are stable and remain nanometric. We find that nanoceria covered with both coating agents are taken up by mouse fibroblasts and localized into membrane-bound compartments. However, flow cytometry and electron microscopy reveal that as a result of their precipitation, citrate-coated particles interact more strongly with cells. At cerium concentration above 1 mM, only citrate-coated nanoceria (and not particles coated with poly(acrylic acid)) display toxicity and moderate genotoxicity. The results demonstrate that the control of the surface chemistry of the particles and its ability to prevent aggregation can affect the toxicity of nanomaterials.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0800">http://arxiv.org/abs/1308.0800</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-68998521890406851032013-08-06T00:02:00.011-07:002013-08-06T00:02:28.474-07:001308.0893 (L. Chevry et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0893">Sub-Piconewton Force Detection using Micron-Size Wire Deflections</a> [<a href="http://arxiv.org/pdf/1308.0893">PDF</a>]</h2>L. Chevry, J. -F. Berret<a name='more'></a><blockquote class="abstract">The mechanical properties of nanostructured wires obtained by co-assembly of iron oxide particles are studied. The intrinsic magnetic properties of the wires are used to induce and quantify the bending of the one-dimensional objects. From the relationship between the deflection and the magnitude of the magnetic field, the elastic rigidity and Young modulus of the wires are determined. Young moduli in the megapascal range are obtained and are consistent with sub-piconewton force detection.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0893">http://arxiv.org/abs/1308.0893</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-26169120271753837802013-08-06T00:02:00.009-07:002013-08-06T00:02:27.421-07:001308.0941 (Franck Celestini et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0941">Room temperature water Leidenfrost droplets</a> [<a href="http://arxiv.org/pdf/1308.0941">PDF</a>]</h2>Franck Celestini, Thomas Frisch, Yves Pomeau<a name='more'></a><blockquote class="abstract">We experimentally investigate the Leidenfrost effect at pressures ranging from 1 to 0.05 atmospheric pressure. As a direct consequence of the Clausius-Clapeyron phase diagram of water, the droplet temperature can be at ambient temperature in a non-sophisticated lab environment. Furthermore, the lifetime of the Leidenfrost droplet is significantly increased in this low pressure environment. The temperature and pressure dependance of the evaporation rate are successfully tested against a recently proposed model. These results may pave a way to reach efficient Leidenfrost micro-fluidic and milli-fluidic applications.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0941">http://arxiv.org/abs/1308.0941</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-47720687168004453352013-08-06T00:02:00.007-07:002013-08-06T00:02:26.487-07:001308.0972 (Jürg Diemand et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0972">Large Scale Molecular Dynamics Simulations of Homogeneous Nucleation</a> [<a href="http://arxiv.org/pdf/1308.0972">PDF</a>]</h2>Jürg Diemand, Raymond Angélil, Kyoko K. Tanaka, Hidekazu Tanaka<a name='more'></a><blockquote class="abstract">We present results from large-scale molecular dynamics (MD) simulations of homogeneous vapor-to-liquid nucleation. The simulations contain between one and eight billion Lennard-Jones (LJ) atoms, covering up to 1.2 {\mu}s (56 million time-steps). They cover a wide range of supersaturation ratios, S=1.55 to 10^4, and temperatures from kT = 0.3 to 1.0 {\epsilon} (where {\epsilon} is the depth of the LJ potential, and k the Boltzmann constant). We have resolved nucleation rates as low as 10^{17} cm^{-3} s^{-1} (in the argon system), and critical cluster sizes as large as 100 atoms. Recent argon nucleation experiments probe nucleation rates in an overlapping range, making the first direct comparison between laboratory experiments and molecular dynamics simulations possible: We find very good agreement within the uncertainties, which are mainly due to the extrapolations of argon and LJ saturation curves to very low temperatures. The self-consistent, modified classical nucleation model of Girshick and Chiu [J. Chem. Phys. 93, 1273 (1990)] underestimates the nucleation rates by up to 9 orders of magnitudes at low temperatures, and at kT = 1.0 {\epsilon} it overestimates them by up to 10^5. The predictions from a semi-phenomenological model by Laaksonen et al. [Phys. Rev. E 49, 5517 (1994)] are much closer to our MD results, but still differ by factors of up to 104 in some cases. At low temperatures, the classical theory predicts critical clusters sizes, which match the simulation results (using the first nucleation theorem) quite well, while the semi-phenomenological model slightly underestimates them. At kT = 1.0 {\epsilon} the critical sizes from both models are clearly too small. (abridged)</blockquote>View original: <a href="http://arxiv.org/abs/1308.0972">http://arxiv.org/abs/1308.0972</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-41574311489882501202013-08-06T00:02:00.005-07:002013-08-06T00:02:25.437-07:001308.0975 (Farnoush Farahpour et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0975">Peristaltic pumps work in nano scales</a> [<a href="http://arxiv.org/pdf/1308.0975">PDF</a>]</h2>Farnoush Farahpour, Mohammad Reza Ejtehadi<a name='more'></a><blockquote class="abstract">A design for a pump is suggested which is based on well-known peristaltic pumps. In order to simply describe the operation of the proposed pump, an innovative interpretation of low Reynolds number swimmers is presented and thereafter a similar theoretical model would be suggested to quantify the behavior of the pumps. A coarse-grained molecular dynamic simulation is used to examine the theoretical predictions and measure the efficiency of the pump in nano scales. It is shown that this pump with a modest design is capable of being a good option for transport processes in nano scale.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0975">http://arxiv.org/abs/1308.0975</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-73415284842928674532013-08-06T00:02:00.003-07:002013-08-06T00:02:24.512-07:001308.1002 (Nicolas Fernandez et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1002">Microscopic mechanism for the shear-thickening of non-Brownian<br /> suspensions</a> [<a href="http://arxiv.org/pdf/1308.1002">PDF</a>]</h2>Nicolas Fernandez, Roman Mani, David Rinaldi, Dirk Kadau, Martin Mosquet, Helene Lombois-Burger, Juliette Cayer-Barrioz, Hans J. Herrmann, Nicholas D. Spencer, Lucio Isa<a name='more'></a><blockquote class="abstract">We propose a simple model, supported by contact-dynamics simulations as well as rheology and friction measurements, that links the transition from continuous to discontinuous shear-thickening in dense granular pastes to distinct lubrication regimes in the particle contacts. We identify a local Sommerfeld number that determines the transition from Newtonian to shear-thickening flows, and then show that the suspension's volume fraction and the boundary lubrication friction coefficient control the nature of the shear-thickening transition, both in simulations and experiments.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1002">http://arxiv.org/abs/1308.1002</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-1203548950630798992013-08-06T00:02:00.001-07:002013-08-06T00:02:23.377-07:001308.1053 (B. Kociper et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1053">Spatial extension of excitons in triphenylene based polymers given by<br /> range-separated functionals</a> [<a href="http://arxiv.org/pdf/1308.1053">PDF</a>]</h2>B. Kociper, T. A. Niehaus<a name='more'></a><blockquote class="abstract">Motivated by an experiment in which the singlet-triplet gap in triphenylene based copolymers was effectively tuned, we used time dependent density functional theory (TDDFT) to reproduce the main results. By means of conventional and long-range corrected exchange correlation functionals, the luminescence energies and the exciton localization were calculated for a triphenylene homopolymer and several different copolymers. The phosphorescence energy of the pure triphenylene chain is predicted accurately by means of the optimally tuned long-range corrected LC-PBE functional and slightly less accurate by the global hybrid B3LYP. However, the experimentally observed fixed phosphorescence energy could not be reproduced because the localization pattern is different to the expectations: Instead of localizing on the triphenylene moiety - which is present in all types of polymers - the triplet state localizes on the different bridging units in the TDDFT calculations. This leads to different triplet emission energies for each type of polymer. Yet, there are clear indications that long-range corrected TDDFT has the potential to predict the triplet emission energies as well as the localization behavior more accurate than conventional local or semi-local functionals.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1053">http://arxiv.org/abs/1308.1053</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-64811664726399752802013-08-05T00:01:00.003-07:002013-08-05T00:01:44.181-07:001308.0525 (Pier Nicola Sergi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0525">In vivo interactions between tungsten microneedles and peripheral nerves</a> [<a href="http://arxiv.org/pdf/1308.0525">PDF</a>]</h2>Pier Nicola Sergi, Winnie Jensen, Silvestro Micera, Ken Yoshida<a name='more'></a><blockquote class="abstract">Tungsten microneedles are currently used to insert neural electrodes into living peripheral nerves. However, the biomechanics underlying these procedures is not yet well characterized. For this reason, the aim of this work was to model the interactions between these microneedles and living peripheral nerves. A simple mathematical framework was especially provided to model both compression of the external layer of the nerve (epineurium) and the interactions resulting from penetration of the main shaft of the microneedle inside the living nerves. The instantaneous Young's modulus, compression force, the work needed to pierce the tissue, puncturing pressure, and the dynamic friction coefficient between the tungsten microneedles and living nerves were quantified starting from acute experiments, aiming to reproduce the physical environment of real implantations. Indeed, a better knowledge of the interactions between microneedles and peripheral nerves may be useful to improve the effectiveness of these insertion techniques, and could represent a key factor for designing robot-assisted procedures tailored for peripheral nerve insertion.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0525">http://arxiv.org/abs/1308.0525</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-11962869854656102422013-08-05T00:01:00.001-07:002013-08-05T00:01:43.078-07:001308.0554 (C. L. Kane et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0554">Topological Boundary Modes in Isostatic Lattices</a> [<a href="http://arxiv.org/pdf/1308.0554">PDF</a>]</h2>C. L. Kane, T. C. Lubensky<a name='more'></a><blockquote class="abstract">Frames, or lattices consisting of mass points connected by rigid bonds or central force springs, are important model constructs that have applications in such diverse fields as structural engineering, architecture, and materials science. The difference between the number of bonds and the number of degrees of freedom of these lattices determines the number of their zero-frequency "floppy modes". When these are balanced, the system is on the verge of mechanical instability and is termed isostatic. It has recently been shown that certain extended isostatic lattices exhibit floppy modes localized at their boundary. These boundary modes are insensitive to local perturbations, and appear to have a topological origin, reminiscent of the protected electronic boundary modes that occur in the quantum Hall effect and in topological insulators. In this paper we establish the connection between the topological mechanical modes and the topological band theory of electronic systems, and we predict the existence of new topological bulk mechanical phases with distinct boundary modes. We introduce model systems in one and two dimensions that exemplify this phenomenon.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0554">http://arxiv.org/abs/1308.0554</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-16657208846057133502013-08-01T00:32:00.005-07:002013-08-01T00:32:01.835-07:001307.8133 (Zafir Zaman et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8133">Slow axial drift in three-dimensional granular tumbler flow</a> [<a href="http://arxiv.org/pdf/1307.8133">PDF</a>]</h2>Zafir Zaman, Umberto D'Ortona, Paul B. Umbanhowar, Julio M. Ottino, Richard M. Lueptow<a name='more'></a><blockquote class="abstract">Models of monodisperse particle flow in partially filled three-dimensional tumblers often assume that flow along the axis of rotation is negligible. We test this assumption, for spherical and double cone tumblers, using experiments and discrete element method simulations. Cross sections through the particle bed of a spherical tumbler show that, after a few rotations, a colored band of particles initially perpendicular to the axis of rotation deforms: particles near the surface drift toward the pole, while particles deeper in the flowing layer drift toward the equator. Tracking of mm-sized surface particles in tumblers with diameters of 8-14 cm shows particle axial displacements of one to two particle diameters, corresponding to axial drift that is 1-3% of the tumbler diameter, per pass through the flowing layer. The surface axial drift in both double cone and spherical tumblers is zero at the equator, increases moving away from the equator, and then decreases near the poles. Comparing results for the two tumbler geometries shows that wall slope causes axial drift, while drift speed increases with equatorial diameter. The dependence of axial drift on axial position for each tumbler geometry is similar when both are normalized by their respective maximum values.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8133">http://arxiv.org/abs/1307.8133</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-22468520874639203452013-08-01T00:32:00.003-07:002013-08-01T00:32:00.899-07:001307.8175 (Jie Xiang et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8175">Blue-phase-polymer-templated nematic with sub-millisecond<br /> broad-temperature range electro-optic switching</a> [<a href="http://arxiv.org/pdf/1307.8175">PDF</a>]</h2>Jie Xiang, Oleg D. Lavrentovich<a name='more'></a><blockquote class="abstract">We report on fast electro-optic switching (response time 0.1 ms) of a blue-phase-polymer templated nematic with a broad-temperature range of thermodynamic stability and hysteresis-free performance. The nematic fills a polymer template that imposes a periodic structure with cubic symmetry and submicron period. In the field-free state, the nematic in polymer template is optically isotropic. An applied electric field causes non-zero optical retardance. The approach thus combines beneficial structural and optical features of the blue phase (cubic structure with submicron periodicity) and superior thermodynamic stability and electro-optic switching ability of the nematic filler.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8175">http://arxiv.org/abs/1307.8175</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-3790928675948996512013-08-01T00:32:00.001-07:002013-08-01T00:32:00.250-07:001307.8193 (Volodymyr Borshch et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8193">Nanosecond electro-optic switching of a liquid crystal</a> [<a href="http://arxiv.org/pdf/1307.8193">PDF</a>]</h2>Volodymyr Borshch, Sergij V. Shiyanovskii, Oleg D. Lavrentovich<a name='more'></a><blockquote class="abstract">Electrically induced reorientation of nematic liquid crystal (NLC) molecules caused by dielectric anisotropy of the material is a fundamental phenomenon widely used in modern technologies. Its Achilles heel is a slow (millisecond) relaxation from the field-on to the field-off state. We present an electro-optic effect in an NLC with a response time of about 30 ns to both the field-on and field-off switching. This effect is caused by the electric field induced modification of the order parameters (EMOP) and does not require reorientation of the optic axis (director).</blockquote>View original: <a href="http://arxiv.org/abs/1307.8193">http://arxiv.org/abs/1307.8193</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-77927835749586178582013-08-01T00:31:00.001-07:002013-08-01T00:31:56.566-07:001307.8296 (Adrian R. Rennie et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8296">Learning about SANS Instruments and Data Reduction from Round Robin<br /> Measurements on Samples of Polystyrene Latex</a> [<a href="http://arxiv.org/pdf/1307.8296">PDF</a>]</h2>Adrian R. Rennie, Maja S. Hellsing, Kathleen Wood, Elliot P. Gilbert, Lionel Porcar, Ralf Schweins, Charles D. Dewhurst, Peter Lindner, Richard K. Heenan, Sarah E. Rogers, Paul D. Butler, Jeffery R. Krzywon, Ron E. Ghosh, Andrew J. Jackson, Marc Malfois<a name='more'></a><blockquote class="abstract">Measurements of a well-characterised standard sample can verify the performance of an instrument. Typically, small-angle neutron scattering instruments are used to investigate a wide range of samples and may often be used in a number of configurations. Appropriate standard samples are useful to test different aspects of the performance of hardware as well as that of the data reduction and analysis software. Measurements on a number of instruments with different intrinsic characteristics and designs in a round robin can not only better characterise the performance for a wider range of conditions but also, perhaps more importantly, reveal the limits of the current state of the art of small-angle scattering. The exercise, followed by detailed analysis, tests the limits of current understanding as well as uncovers often forgotten assumptions, simplifications and approximations that underpin the current practice of the technique. This paper describes measurements of polystyrene latex, radius 72 nm with a number of instruments. Scattering from monodisperse, uniform spherical particles is simple to calculate and displays sharp minima. Such data test the calibrations of intensity, wavelength and resolution as well as the detector response. Smoothing due to resolution, multiple scattering and polydispersity has been determined. Sources of uncertainty are often related to systematic deviations and calibrations rather than random counting errors. The study has prompted development of software to treat modest multiple scattering and to better model the instrument resolution. These measurements also allow checks of data reduction algorithms and have identified how they can be improved. The reproducibility and the reliability of instruments and the accuracy of parameters derived from the data are described.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8296">http://arxiv.org/abs/1307.8296</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-70289727172694631632013-07-31T00:17:00.007-07:002013-07-31T00:17:28.661-07:001307.7734 (Levon Mkrtchyan et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7734">Electrocapillary instability of magnetic fluid peak</a> [<a href="http://arxiv.org/pdf/1307.7734">PDF</a>]</h2>Levon Mkrtchyan, Arthur Zakinyan, Yuri Dikansky<a name='more'></a><blockquote class="abstract">The paper presents an experimental study of the capillary electrostatic instability occurring under effect of a constant electric field on a magnetic fluid individual peak. The peaks under study occur at disintegration of a magnetic fluid layer applied on a flat electrode surface under effect of a perpendicular magnetic field. The electrocapillary instability shows itself as an emission of charged drops jets from the peak point in direction of the opposing electrode. The charged drops emission repeats periodically and results in the peak shape pulsations. It is shown that a magnetic field affects the electrocapillary instability occurrence regularities and can stimulate its development. The critical electric and magnetic field strengths at which the instability occurs have been measured; their dependence on the peak size is shown. The hysteresis in the system has been studied; it consists in that the charged drops emission stops at a lesser electric (or magnetic) field strength than that of the initial occurrence. The peak pulsations frequency depending on the magnetic and electric field strengths and on the peak size has been measured.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7734">http://arxiv.org/abs/1307.7734</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-10032659536508783772013-07-31T00:17:00.005-07:002013-07-31T00:17:28.008-07:001307.7742 (E. Katzav et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7742">Stability and roughness of tensile cracks in disordered materials</a> [<a href="http://arxiv.org/pdf/1307.7742">PDF</a>]</h2>E. Katzav, M. Adda-Bedia<a name='more'></a><blockquote class="abstract">We study the stability and roughness of propagating cracks in heterogeneous brittle two-dimensional elastic materials. We begin by deriving an equation of motion describing the dynamics of such a crack in the framework of Linear Elastic Fracture Mechanics, based on the Griffith criterion and the Principle of Local Symmetry. This result allows us to extend the stability analysis of Cotterell and Rice to disordered materials. In the stable regime we find stochastic crack paths. Using tools of statistical physics we obtain the power spectrum of these paths and their probability distribution function, and conclude they do not exhibit self-affinity. We show that a real-space fractal analysis of these paths can lead to the wrong conclusion that the paths are self-affine. To complete the picture, we unravel the systematic bias in such real-space methods, and thus contribute to the general discussion of reliability of self-affine measurements.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7742">http://arxiv.org/abs/1307.7742</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-16011146380027153722013-07-31T00:17:00.003-07:002013-07-31T00:17:26.544-07:001307.7914 (Sebastian Weitz et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7914">Attractive asymmetric inclusions in elastic membranes under tension:<br /> cluster phases and membrane invaginations</a> [<a href="http://arxiv.org/pdf/1307.7914">PDF</a>]</h2>Sebastian Weitz, Nicolas Destainville<a name='more'></a><blockquote class="abstract">Up-down asymmetric inclusions impose a local, spontaneous curvature to an elastic membrane. When several of them are inserted in a same membrane, they feel effective forces mediated by the membrane, both of elastic and entropic nature. Following an approach initiated by Dommersnes and Fournier in the vanishing tension case [Eur. Phys. J. B 12, 9 (1999)], and also using a pseudo-analytical micellization theory, we derive the statistical mechanics of asymmetric inclusion assemblies when they are also subject to an additional short-range, attractive interaction. Our main conclusion is that generically, when the membrane is under tension, these inclusions live in small clusters at equilibrium, leading to local membrane invaginations. We also propose a novel curvature-induced demixing mechanism: when inclusions imposing local curvatures of opposite sign coexist, they tend to demix in distinct clusters under realistic conditions. This work has potential implications in the context of the thermodynamics of proteins embedded in biological lipid bilayers.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7914">http://arxiv.org/abs/1307.7914</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-85738413667130402142013-07-31T00:17:00.001-07:002013-07-31T00:17:25.359-07:001307.8078 (Igor Lesanovsky et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8078">Kinetic constraints, hierarchical relaxation and onset of glassiness in<br /> strongly interacting and dissipative Rydberg gases</a> [<a href="http://arxiv.org/pdf/1307.8078">PDF</a>]</h2>Igor Lesanovsky, Juan P. Garrahan<a name='more'></a><blockquote class="abstract">We show that the dynamics of a laser driven Rydberg gas in the limit of strong dephasing is described by a master equation with manifest kinetic constraints. The equilibrium state of the system is uncorrelated but the constraints in the dynamics lead to spatially correlated collective relaxation reminiscent of glasses. We study and quantify the evolution towards equilibrium in one and two dimensions, and analyze how the degree of glassiness and the relaxation time are controlled by the interaction strength between Rydberg atoms. We also find that spontaneous decay of Rydberg excitations leads to an interruption of glassy relaxation that takes the system to a highly correlated non-equilibrium stationary state. The results presented here, which are in principle also applicable other systems such as polar molecules and atoms with large magnetic dipole moments, show that the collective behavior of cold atomic and molecular ensembles can be similar to that found in soft condensed-matter systems.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8078">http://arxiv.org/abs/1307.8078</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-71551104663770445552013-07-30T00:05:00.019-07:002013-07-30T00:05:48.916-07:001307.7312 (Eligiusz Wajnryb et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7312">Generalization of the Rotne-Prager-Yamakawa mobility and shear<br /> disturbance tensors</a> [<a href="http://arxiv.org/pdf/1307.7312">PDF</a>]</h2>Eligiusz Wajnryb, Krzysztof A. Mizerski, Pawel J. Zuk, Piotr Szymczak<a name='more'></a><blockquote class="abstract">Rotne-Prager-Yamakawa approximation is one of the most commonly used methods of including hydrodynamic interactions in modelling of colloidal suspensions and polymer solutions. The two main merits of this approximation is that it includes all long-range terms (i.e. decaying as R^-3 or slower in interparticle distances) and that the diffusion matrix is positive definite, which is essential for Brownian dynamics modelling. Here, we extend the Rotne-Prager-Yamakawa approach to include both translational and rotational degrees of freedom, and derive the regularizing corrections to account for overlapping particles. Additionally, we show how the Rotne-Prager-Yamakawa approximation can be generalized for other geometries and boundary conditions.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7312">http://arxiv.org/abs/1307.7312</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-62810874042292406672013-07-30T00:05:00.017-07:002013-07-30T00:05:47.896-07:001307.7337 (Panayotis Benetatos et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7337">Bundling in brushes of directed and semiflexible polymers</a> [<a href="http://arxiv.org/pdf/1307.7337">PDF</a>]</h2>Panayotis Benetatos, Eugene M. Terentjev, Annette Zippelius<a name='more'></a><blockquote class="abstract">We explore the effect of an attractive interaction between parallel aligned polymers, which are perpendicularly grafted on a substrate. Such an attractive interaction could, e.g., be due to reversible cross-links. The competition between permanent grafting favoring a homogeneous state of the polymer brush and the attraction, which tends to induce in-plane collapse of the aligned polymers, gives rise to an instability of the homogeneous phase to a bundled state. In this latter state the in-plane translational symmetry is spontaneously broken and the density is modulated with a finite wavelength, which is set by the length scale of transverse fluctuations of the grafted polymers. We analyse the instability for two models of aligned polymers: directed polymers with a line tension and weakly bending chains with a bending stiffness.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7337">http://arxiv.org/abs/1307.7337</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-23251039258386410362013-07-30T00:05:00.015-07:002013-07-30T00:05:45.509-07:001307.7356 (Jens Boberski et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7356">Evolution of the force distributions in jammed packings of soft<br /> particles</a> [<a href="http://arxiv.org/pdf/1307.7356">PDF</a>]</h2>Jens Boberski, M. Reza Shaebani, Dietrich E. Wolf<a name='more'></a><blockquote class="abstract">The evolution of the force distributions during the isotropic compression of two dimensional packings of soft frictional particles is investigated numerically. Regardless of the applied deformation, the normal contact force distribution $P(f_n)$ can be fitted by the product of a power-law, and a stretched exponential, while the tangential force distribution $P(f_t)$ is well fitted by a Gaussian. With increasing strain, both $P(f_n)$ and $P(f_t)$ exhibit a broadening, while, when scaled with the average forces, their widths decrease. Thus, a more homogeneous force network is observed for packings under large deformation. Furthermore, the distribution of friction mobilization $P(\eta)$ is a decreasing function of $\eta=|f_t|/(\mu f_n)$, except for an increased probability of fully mobilized contacts ($\eta=1$). The excess coordination number of the packings increases with the applied strain, indicating that the more a packing is compressed the more stable it becomes.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7356">http://arxiv.org/abs/1307.7356</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-80135031623696331522013-07-30T00:05:00.013-07:002013-07-30T00:05:44.782-07:001307.7366 (T. E. Raptis et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.7366">Understanding coil-to-globule transition of polymers with the aid of a<br /> novel cluster analysis technique</a> [<a href="http://arxiv.org/pdf/1307.7366">PDF</a>]</h2>T. E. Raptis, Vasilios E. Raptis<a name='more'></a><blockquote class="abstract">In this note, a novel cluster analysis algorithm recently applied in simple Molecular Dynamics simulations of systems that tend to phase separate, was employed in the study of polymer coil to globule transition via single chain Monte Carlo simulations. The method has been described in detail in http://arxiv.org/abs/1306.3460. Findings tend to favour a two-stage model of collapse kinetics, although the existence of an intermediate fuzzy phase is also observed, when looking at the details of cluster formation along the backbone chain.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7366">http://arxiv.org/abs/1307.7366</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-1651632147168424768.post-44924371667164841502013-07-30T00:05:00.011-07:002013-07-30T00:05:41.716-07:001307.7386 (José Jorge Nader)<h2 class="title"><a href="http://arxiv.org/abs/1307.7386">Pore pressure development in small-strain undrained loading of soils<br /> according to a simple model</a> [<a href="http://arxiv.org/pdf/1307.7386">PDF</a>]</h2>José Jorge Nader<a name='more'></a><blockquote class="abstract">This note discusses a simple equation that may be useful in the study of pore pressures generated in the undrained loading of soils. The equation is employed to describe the pore pressure development accompanying a small stress increment in the undrained triaxial compression test and in the undrained simple shear test. The cases of incompressible and compressible pore fluids are examined.</blockquote>View original: <a href="http://arxiv.org/abs/1307.7386">http://arxiv.org/abs/1307.7386</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0