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M Reeks, D C Swailes, A D Bragg
This paper is about the kinetic equation for gas-particle flows, in particular its well-posedness and realizability and its relationship to the generalized Langevin model (GLM) probability density function (PDF) equation. Previous analyses, e.g. [J.-P. Minier and C. Profeta, Phys. Rev. E 92, 053020 (2015)PLEEE81539-375510.1103/PhysRevE.92.053020], have concluded that this kinetic equation is ill posed, that in particular it has the properties of a backward heat equation, and as a consequence, its solution will in the course of time exhibit finite-time singularities...
February 2018: Physical Review. E
José Rafael Bordin, Marcia C Barbosa
We investigate the structural, thermodynamic, and dynamic behavior of a two-dimensional (2D) core-corona system using Langevin dynamics simulations. The particles are modeled by employing a core-softened potential which exhibits waterlike anomalies in three dimensions. In previous studies in a quasi-2D system a new region in the pressure versus temperature phase diagram of structural anomalies was observed. Here we show that for the two-dimensional case two regions in the pressure versus temperature phase diagram with structural, density, and diffusion anomalies are observed...
February 2018: Physical Review. E
K R Prathyusha, Silke Henkes, Rastko Sknepnek
We use Langevin dynamics simulations to study dynamical behavior of a dense planar layer of active semiflexible filaments. Using the strength of active force and the thermal persistence length as parameters, we map a detailed phase diagram and identify several nonequilibrium phases in this system. In addition to a slowly flowing melt phase, we observe that, for sufficiently high activity, collective flow accompanied by signatures of local polar and nematic order appears in the system. This state is also characterized by strong density fluctuations...
February 2018: Physical Review. E
Henning Reinken, Sabine H L Klapp, Markus Bär, Sebastian Heidenreich
In this paper, we systematically derive a fourth-order continuum theory capable of reproducing mesoscale turbulence in a three-dimensional suspension of microswimmers. We start from overdamped Langevin equations for a generic microscopic model (pushers or pullers), which include hydrodynamic interactions on both small length scales (polar alignment of neighboring swimmers) and large length scales, where the solvent flow interacts with the order parameter field. The flow field is determined via the Stokes equation supplemented by an ansatz for the stress tensor...
February 2018: Physical Review. E
Jin Wang, Wei Cao, Ming Ma, Quanshui Zheng
The diffusion of molecules and clusters under nanoscale confinement or absorbed on surfaces is the key controlling factor in dynamical processes such as transport, chemical reaction, or filtration. Enhancing diffusion could benefit these processes by increasing their transport efficiency. Using a nonlinear Langevin equation with an extensive number of simulations, we find a large enhancement in diffusion through surface oscillation. For helium confined in a narrow carbon nanotube, the diffusion enhancement is estimated to be over three orders of magnitude...
February 2018: Physical Review. E
Preeti Vodnala, Nuwan Karunaratne, Laurence Lurio, George M Thurston, Michael Vega, Elizabeth Gaillard, Suresh Narayanan, Alec Sandy, Qingteng Zhang, Eric M Dufresne, Giuseppe Foffi, Pawel Grybos, Piotr Kmon, Piotr Maj, Robert Szczygiel
The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations...
February 2018: Physical Review. E
Mariana Rossi, Venkat Kapil, Michele Ceriotti
Generalized Langevin Equation (GLE) thermostats have been used very effectively as a tool to manipulate and optimize the sampling of thermodynamic ensembles and the associated static properties. Here we show that a similar, exquisite level of control can be achieved for the dynamical properties computed from thermostatted trajectories. We develop quantitative measures of the disturbance induced by the GLE to the Hamiltonian dynamics of a harmonic oscillator, and show that these analytical results accurately predict the behavior of strongly anharmonic systems...
March 14, 2018: Journal of Chemical Physics
Itay Azizi, Yitzhak Rabin
We use Langevin dynamics simulations to study the growth kinetics and the steady-state properties of condensed clusters in a dilute two-dimensional system of particles that are all different (APD) in the sense that each particle is characterized by a randomly chosen interaction parameter. The growth exponents, the transition temperatures, and the steady-state properties of the clusters and of the surrounding gas phase are obtained and compared with those of one-component systems. We investigate the fractionation phenomenon, i...
March 14, 2018: Journal of Chemical Physics
Junhao Liang, Anwarud Din, Tianshou Zhou
While many physical or chemical systems can be modeled by nonlinear Langevin equations (LEs), dynamical analysis of these systems is challenging in the cases of moderate and strong noise. Here we develop a linear approximation scheme, which can transform an often intractable LE into a linear set of binomial moment equations (BMEs). This scheme provides a feasible way to capture nonlinear behaviors in the sense of probability distribution and is effective even when the noise is moderate or big. Based on BMEs, we further develop a noise reduction technique, which can effectively handle tough cases where traditional small-noise theories are inapplicable...
March 14, 2018: Journal of Chemical Physics
K E Polovnikov, M Gherardi, M Cosentino-Lagomarsino, M V Tamm
Chromosomes are key players of cell physiology, their dynamics provides valuable information about its physical organization. In both prokaryotes and eukaryotes, the short-time motion of chromosomal loci has been described with a Rouse model in a simple or viscoelastic medium. However, little emphasis has been put on the influence of the folded organization of chromosomes on the local dynamics. Clearly, stress propagation, and thus dynamics, must be affected by such organization, but a theory allowing us to extract such information from data, e...
February 23, 2018: Physical Review Letters
Angus McMullen, Hendrick W de Haan, Jay X Tang, Derek Stein
Measurements and Langevin dynamics simulations of filamentous viruses driven through solid-state nanopores reveal a superlinear rise in the translocation velocity with driving force. The mobility also scales with the length of the virus in a nontrivial way that depends on the force. These dynamics are consequences of the buckling of the leading portion of a virus as it emerges from the nanopore and is put under compressive stress by the viscous forces it encounters. The leading tip of a buckled virus stalls and this reduces the total viscous drag force...
February 16, 2018: Physical Review Letters
T V Sachin Krishnan, Kento Yasuda, Ryuichi Okamoto, Shigeyuki Komura
We discuss thermal and active fluctuations of a compressible bilayer vesicle by using the results of hydrodynamic theory for vesicles. Coupled Langevin equations for the membrane deformation and the density fields are employed to calculate the power spectral density matrix of membrane fluctuations. Thermal contribution is obtained by means of the fluctuation dissipation theorem, whereas active contribution is calculated from exponentially decaying time correlation functions of active random forces. We obtain the total power spectral density as a sum of thermal and active contributions...
March 15, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Hanaa Safya, Amine Mellouk, Julie Legrand, Sylvain M Le Gall, Mohcine Benbijja, Colette Kanellopoulos-Langevin, Jean M Kanellopoulos, Pierre Bobé
A previous report has shown that regulatory T cells (Treg) were markedly more sensitive to adenosine-5'-triphosphate (ATP) than conventional T cells (Tconv). Another one has shown that Tregs and CD45RBlow Tconvs, but not CD45RBhigh Tconvs, displayed similar high sensitivity to ATP. We have previously reported that CD45RBlow Tconvs expressing B220/CD45RABC molecules in a pre-apoptotic stage are resistant to ATP stimulation due to the loss of P2X7 receptor (P2X7R) membrane expression. To gain a clearer picture on T-cell sensitivity to ATP, we have quantified four different cellular activities triggered by ATP in mouse T cells at different stages of activation/differentiation, in correlation with levels of P2X7R membrane expression...
2018: Frontiers in Immunology
Johannes Berner, Boris Müller, Juan Ruben Gomez-Solano, Matthias Krüger, Clemens Bechinger
Microscopic colloidal particles suspended in liquids are a prominent example of an overdamped system where viscous forces dominate over inertial effects. Frequently, colloids are used as sensitive probes, e.g., in biophysical applications from which molecular forces are inferred. The interpretation of such experiments rests on the assumption that, even when the particles are driven, the liquid remains in equilibrium. Here we experimentally demonstrate that this is not valid for particles in viscoelastic fluids...
March 8, 2018: Nature Communications
Christian Scholz, Michael Engel, Thorsten Pöschel
Biological organisms and artificial active particles self-organize into swarms and patterns. Open questions concern the design of emergent phenomena by choosing appropriate forms of activity and particle interactions. A particularly simple and versatile system are 3D-printed robots on a vibrating table that can perform self-propelled and self-spinning motion. Here we study a mixture of minimalistic clockwise and counter-clockwise rotating robots, called rotors. Our experiments show that rotors move collectively and exhibit super-diffusive interfacial motion and phase separate via spinodal decomposition...
March 2, 2018: Nature Communications
A Cadilhe, Arthur F Voter
The trajectories of two particles undergoing Langevin dynamics while sharing a common noise sequence can merge into a single (master) trajectory. Here, we present an exact solution for a particle undergoing Langevin dynamics in a harmonic, time-dependent potential, thus extending the idea of synchronization to nonequilibrium systems. We calculate the synchronization level, i.e., the mismatch between two trajectories sharing a common noise sequence, in the underdamped, critically damped, and overdamped regimes...
February 28, 2018: Journal of Chemical Physics
Helene M Langevin, Peter M Wayne
Despite having made substantial progress in academic rigor over the past decades, acupuncture research has been the focus of long-standing and persistent attacks by skeptics. One recurring theme of critics is that the concept of acupuncture points has no scientific validity. Meanwhile, the subject of whether-or-not acupuncture points "exist" has been given too little attention within the acupuncture research community. In this article, we argue that failure to use clear terminology and rigorously investigate the subject of acupuncture points has hindered the growing legitimacy of acupuncture as an evidence-based therapy...
March 1, 2018: Journal of Alternative and Complementary Medicine: Research on Paradigm, Practice, and Policy
Camille Lacour, Louise Seconda, Benjamin Allès, Serge Hercberg, Brigitte Langevin, Philippe Pointereau, Denis Lairon, Julia Baudry, Emmanuelle Kesse-Guyot
Background: Studies investigating diet-related environmental impacts have rarely considered the production method of the foods consumed. The objective of the present study, based on the NutriNet-Santé cohort, was to investigate the relationship between a provegetarian score and diet-related environmental impacts. We also evaluated potential effect modifications on the association between a provegetarian score and the environmental impacts of organic food consumption. Methods: Food intake and organic food consumption ratios were obtained from 34,442 French adults using a food frequency questionnaire, which included information on organic food consumption for each group...
2018: Frontiers in Nutrition
Rachel Langevin, Martine Hébert, Elisa Guidi, Anne-Claude Bernard-Bonnin, Claire Allard-Dansereau
Objectives: The aim of the present study was to explore sleep problems in sexually abused preschoolers over a year. Methods: The sample consisted of 224 abused children and 83 nonabused children aged 3 to 6 years old at enrolment into the study (T1), and 85 abused children and 73 nonabused children at the second evaluation, approximately 1 year later (T2). Sleep problems were assessed using parental reports on the Child Behavior Checklist - Preschool Version . Results: Multivariate analysis of covariance revealed that sexually abused preschoolers presented higher scores of sleep problems than nonabused children on all items related to sleep problems at T1...
August 2017: Paediatrics & Child Health
José M Zamora, Ronald Marquez, Ana M Forgiarini, Dominique Langevin, Jean-Louis Salager
When surfactants adsorb at liquid interfaces, they not only decrease the surface tension, they confer rheological properties to the interfaces. There are two types of rheological parameters associated to interfacial layers: compression and shear. The elastic response is described by a storage modulus and the dissipation by a loss modulus or equivalently a surface viscosity. Various types of instruments are available for the measurements of these coefficients, the most common being oscillating pendent drops instruments and rheometers equipped with bicones...
February 16, 2018: Journal of Colloid and Interface Science
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