668 results match your criteria Jammed Finger


Robust Bijels for Reactive Separation via Silica-Reinforced Nanoparticle Layers.

ACS Nano 2018 Dec 11. Epub 2018 Dec 11.

Department of Chemical and Biomolecular Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.

Pickering emulsions have been successfully used as media for catalysis and separation. However, simultaneous reaction and separation cannot be performed in a continuous mode in these systems, because reagents cannot be readily loaded into or recovered from the dispersed phase. Bicontinuous interfacially jammed emulsion gels (bijels), in which the oil and water phases are continuous throughout the structure, have potential as media for simultaneous reaction and separation in a continuous mode. Read More

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December 2018

Granular hydrogels: emergent properties of jammed hydrogel microparticles and their applications in tissue repair and regeneration.

Curr Opin Biotechnol 2018 Nov 24;60:1-8. Epub 2018 Nov 24.

Department of Biomedical Engineering, Duke University, United States; Department of Dermatology, Duke University, United States; Department of Neurology, Duke University, United States. Electronic address:

Granular hydrogels are emerging as a versatile and effective platform for tissue engineered constructs in regenerative medicine. The hydrogel microparticles (HMPs) that compose these materials exhibit particle jamming above a minimum packing fraction, which results in a bulk, yet dynamic, granular hydrogel scaffold. These injectable, microporous scaffolds possess self-assembling, shear-thinning, and self-healing properties. Read More

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November 2018

Binding of lignin nanoparticles at oil-water interfaces: An ecofriendly alternative to oil spill recovery.

ACS Appl Mater Interfaces 2018 Nov 19. Epub 2018 Nov 19.

Synthetic amphiphiles used for managing large-scale oil spills have toxic impact on the environment and marine life. Developing new oil spill recovery technologies is critical to minimize the environmental and ecological impact of such disasters. Here we show that a mixture of lignin nanoparticles and 1-pentanol form a biocompatible alternative to non-degradable, synthetic amphiphiles used for oil spill recovery. Read More

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November 2018

Universality of jamming of nonspherical particles.

Proc Natl Acad Sci U S A 2018 Nov 31;115(46):11736-11741. Epub 2018 Oct 31.

Laboratoire de Physique Theórique, Département de Physique de l'École Normale Supérieure, École Normale Supérieure, Paris Sciences et Lettres University, Sorbonne Université, CNRS, 75005 Paris, France.

Amorphous packings of nonspherical particles such as ellipsoids and spherocylinders are known to be hypostatic: The number of mechanical contacts between particles is smaller than the number of degrees of freedom, thus violating Maxwell's mechanical stability criterion. In this work, we propose a general theory of hypostatic amorphous packings and the associated jamming transition. First, we show that many systems fall into a same universality class. Read More

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November 2018
1 Read

Strength of Crowd (SOC)-Defeating a Reactive Jammer in IoT with Decoy Messages.

Sensors (Basel) 2018 Oct 16;18(10). Epub 2018 Oct 16.

Division of Information and Computing Technology, College of Science and Engineering, Hamad Bin Khalifa University, Doha 5825, Qatar.

We propose Strength of Crowd (SoC), a distributed Internet of Things (IoT) protocol that guarantees message broadcast from an initiator to all network nodes in the presence of either a reactive or a proactive jammer, that targets a variable portion of the radio spectrum. SoC exploits a simple, yet innovative and effective idea: nodes not (currently) involved in the broadcast process transmit decoy messages that cannot be distinguished (by the jammer) from the real ones. Therefore, the jammer has to implement a best-effort strategy to jam all the concurrent communications up to its frequency/energy budget. Read More

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October 2018

Hard convex lens-shaped particles: metastable, glassy and jammed states.

Soft Matter 2018 Oct;14(40):8205-8218

Department of Chemistry, Department of Physics, Institute for the Science and Technology of Materials, Program for Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA.

We generate and study dense positionally and/or orientationally disordered, including jammed, monodisperse packings of hard convex lens-shaped particles (lenses). Relatively dense isotropic fluid configurations of lenses of various aspect ratios are slowly compressed via a Monte Carlo method based procedure. Under this compression protocol, while 'flat' lenses form a nematic fluid phase (where particles are positionally disordered but orientationally ordered) and 'globular' lenses form a plastic solid phase (where particles are positionally ordered but orientationally disordered), 'intermediate', neither 'flat' nor 'globular', lenses do not form either mesophase. Read More

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October 2018

[Complicated airway foreign body in a child: a case report].

Authors:
Q L Shi Q Li X F Shen

Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2018 Aug;32(16):1276-1277

A 9 year-old boy suffering from cough for half a month, fever for 4 days was hospitalized. CT three-dimensional reconstruction showed that a metallic needle-like foreign body within the right main bronchial with pneumonia and atelectasis. In the next day, the boy took examination using an open-tube rigid bronchoscope under general anesthesia. Read More

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August 2018
5 Reads

Two Diverging Length Scales in the Structure of Jammed Packings.

Phys Rev Lett 2018 Sep;121(11):115501

The James Franck and Enrico Fermi Institutes and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA.

At densities higher than the jamming transition for athermal, frictionless repulsive spheres we find two distinct length scales, both of which diverge as a power law as the transition is approached. The first, ξ_{Z}, is associated with the two-point correlation function for the number of contacts on two particles as a function of the particle separation. The second, ξ_{f}, is associated with contact-number fluctuations in subsystems of different sizes. Read More

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September 2018

Aging is a log-Poisson process, not a renewal process.

Phys Rev E 2018 Aug;98(2-1):020602

Institut for Fysik Kemi og Farmaci, Syddansk Universitet, DK-5230 Odense M, Denmark.

Aging is a ubiquitous relaxation dynamic in disordered materials. It ensues after a rapid quench from an equilibrium "fluid" state into a nonequilibrium, history-dependent jammed state. We propose a physically motivated description that contrasts sharply with a continuous-time random walk (CTRW) with broadly distributed trapping times commonly used to fit aging data. Read More

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Laning and clustering transitions in driven binary active matter systems.

Phys Rev E 2018 Aug;98(2-1):022603

Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

It is well known that a binary system of nonactive disks that experience driving in opposite directions exhibits jammed, phase separated, disordered, and laning states. In active matter systems, such as a crowd of pedestrians, driving in opposite directions is common and relevant, especially in conditions which are characterized by high pedestrian density and emergency. In such cases, the transition from laning to disordered states may be associated with the onset of a panic state. Read More

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August 2018
2 Reads

Photo/thermoresponsive ABC triblock copolymer-based ion gels: photoinduced structural transitions.

Soft Matter 2018 Nov;14(45):9088-9095

Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.

A photo/thermoresponsive ABC triblock copolymer-based ion gel exhibiting photoinduced structural transitions accompanied by significant rheological changes is newly developed. The ABC triblock copolymer comprises an ionic liquid (IL)-phobic A block, an IL-philic B block, and a photo/thermoresponsive C block containing azobenzene moieties. The IL-phobic A block forms a rigid micellar core in an IL over a wide temperature range and the photo/thermoresponsive C block undergoes upper critical solution temperature (UCST)-type phase transition in ILs. Read More

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November 2018

Evolutions of packing properties of perfect cylinders under densification and crystallization.

J Chem Phys 2018 Sep;149(10):104503

Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.

Cylindrical particles are ubiquitous in nature and industry, and a cylinder is a representative shape of rod-like particles. However, the disordered packing results of cylinders in previous studies are quite inconsistent with each other. In this work, we obtain the MRJ (maximally random jammed) packings and the MDRPs (maximally dense random packings) of perfect cylinders with the aspect ratio (height/diameter) 0. Read More

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September 2018
2 Reads
2.950 Impact Factor

Absence of Hyperuniformity in Amorphous Hard-Sphere Packings of Nonvanishing Complexity.

Phys Rev Lett 2018 Aug;121(7):075503

School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom.

We relate the structure factor S(k→0) in a system of jammed hard spheres of number density ρ to its complexity per particle Σ(ρ) by the formula S(k→0)=-1/[ρ^{2}Σ^{″}(ρ)+2ρΣ^{'}(ρ)]. We have verified this formula for the case of jammed disks in a narrow channel, for which it is possible to find Σ(ρ) and S(k) analytically. Hyperuniformity, which is the vanishing of S(k→0), will therefore not occur if the complexity is nonzero. Read More

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Geometric constraints during epithelial jamming.

Nat Phys 2018 Jun 2;14:613-620. Epub 2018 Apr 2.

Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA.

As an injury heals, an embryo develops, or a carcinoma spreads, epithelial cells systematically change their shape. In each of these processes cell shape is studied extensively whereas variability of shape from cell-to-cell is regarded most often as biological noise. But where do cell shape and its variability come from? Here we report that cell shape and shape variability are mutually constrained through a relationship that is purely geometrical. Read More

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June 2018
6 Reads

The physics of jamming for granular materials: a review.

Rep Prog Phys 2018 Aug 22;82(1):012601. Epub 2018 Aug 22.

Department of Physics & Center for Non-linear and Complex Systems, Duke University, Durham, NC, United States of America. Dr Robert Behringer passed away in July 2018.

Granular materials consist of macroscopic grains, interacting via contact forces, and unaffected by thermal fluctuations. They are one of a class systems that undergo jamming, i.e. Read More

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Influence of surface commensurability on the structure and relaxation dynamics of a confined monatomic fluid.

J Chem Phys 2018 Aug;149(6):064503

Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India.

Molecular dynamics simulations are carried out for a single component, monatomic Lennard-Jones fluid confined between two mica surfaces to investigate the structure and relaxation dynamics of the confined fluid as a function of surface separation. Due to the underlying symmetry of the potassium ions on the mica surface, the contact layers prefer to adopt an incommensurate square or rhombic symmetry. The inner layers adopt a symmetry varying between rhombic, triangular, and square, depending on the density and surface separation. Read More

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Driving Forces for Accumulation of Cellulose Nanofibrils at the Oil/Water Interface.

Langmuir 2018 09 28;34(36):10757-10763. Epub 2018 Aug 28.

Understanding the adsorption and organization of nanocelluloses at oil/water interfaces is crucial to develop a promising route to fabricate functional materials from the bottom-up. Here, we prepare acetylated cellulose nanofibrils (CNFs) with 2 degrees of substitution and investigate their assembly behavior at the oil/water interface. We study the adsorption process by tracking the dynamic interfacial tension using pendant drop tensiometry and further characterize the viscoelasticity of the CNF interfacial films as a function of ionic strength. Read More

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September 2018

Sinking in a bed of grains activated by shearing.

Phys Rev E 2018 Jul;98(1-1):010901

Department of Physics & Center for Nonlinear and Complex Systems, Duke University, Durham, North Carolina 27708, USA.

We show how a weak force f enables intruder motion through dense granular materials subject to external mechanical excitations, in the present case, stepwise shearing. A force acts on a Teflon disk in a two-dimensional system of photoelastic disks. This force is much smaller than the smallest force needed to move the disk without any external excitation. Read More

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July 2018
4 Reads

Random sequential adsorption on mobile patches.

Phys Rev E 2018 Jul;98(1-1):012125

Departamento de Física, Faculdade de Ciências, and Centro de Física Teórica e Computacional, Universidade de Lisboa, Campo Grande, P-1749-016 Lisboa, Portugal.

An extension of the random sequential adsorption model has been proposed recently, motivated by the coverage of oil droplets by DNA-functionalized colloidal particles. Particles arrive to a flat substrate with a uniform flux F but they can only adsorb on patches. Patches diffuse on the substrate with a diffusion coefficient D if they are free and they remain immobile when attached to an adsorbed particle. Read More

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July 2018
6 Reads

Guiding kinetic trajectories between jammed and unjammed states in 2D colloidal nanocrystal-polymer assemblies with zwitterionic ligands.

Sci Adv 2018 Aug 3;4(8):eaap8045. Epub 2018 Aug 3.

The Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA.

Mesostructured matter composed of colloidal nanocrystals in solidified architectures abounds with broadly tunable catalytic, magnetic, optoelectronic, and energy storing properties. Less common are liquid-like assemblies of colloidal nanocrystals in a condensed phase, which may have different energy transduction behaviors owing to their dynamic character. Limiting investigations into dynamic colloidal nanocrystal architectures is the lack of schemes to control or redirect the tendency of the system to solidify. Read More

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August 2018
3 Reads

Self-Healing Micellar Ion Gels Based on Multiple Hydrogen Bonding.

Adv Mater 2018 Jul 31:e1802792. Epub 2018 Jul 31.

Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan.

Ion gels, composed of macromolecular networks filled by ionic liquids (ILs), are promising candidate soft solid electrolytes for use in wearable/flexible electronic devices. In this context, the introduction of a self-healing function would significantly improve the long-term durability of ion gels subject to mechanical loading. Nevertheless, compared to hydrogels and organogels, the self-healing of ion gels has barely investigated been because of there being insufficient understanding of the interactions between polymers and ILs. Read More

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July 2018
7 Reads

Mean-field model for the density of states of jammed soft spheres.

Phys Rev E 2018 Jun;97(6-1):062157

Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185 Rome, Italy.

We propose a class of mean-field models for the isostatic transition of systems of soft spheres, in which the contact network is modeled as a random graph and each contact is associated to d degrees of freedom. We study such models in the hypostatic, isostatic, and hyperstatic regimes. The density of states is evaluated by both the cavity method and exact diagonalization of the dynamical matrix. Read More

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Perspective: Basic understanding of condensed phases of matter via packing models.

Authors:
S Torquato

J Chem Phys 2018 Jul;149(2):020901

Department of Chemistry, Department of Physics, Princeton Center for Theoretical Science, Princeton Institute for the Science and Technology of Materials, and Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA.

Packing problems have been a source of fascination for millennia and their study has produced a rich literature that spans numerous disciplines. Investigations of hard-particle packing models have provided basic insights into the structure and bulk properties of condensed phases of matter, including low-temperature states (e.g. Read More

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Irreducible Dislocations of the Proximal Interphalangeal Joint: Algorithm for Open Reduction and Soft-tissue Repair.

Plast Reconstr Surg Glob Open 2018 May 18;6(5):e1729. Epub 2018 May 18.

Hand Surgery, Kantonsspital Baselland, Liestal, Switzerland.

The "jammed finger" is among the most common hand injuries and may include simple sprains, dislocations, fractures, and fracture-dislocations. In contrast, irreducible dislocations of the proximal interphalangeal joint are rare injuries. However, they must not be overlooked in the primary assessment, because persistent subluxation may lead to joint contracture, severely compromising hand function. Read More

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May 2018
2 Reads

Stress relaxation in quasi-two-dimensional self-assembled nanoparticle monolayers.

Phys Rev E 2018 May;97(5-1):052803

Department of Physics, University of California San Diego, La Jolla, California 92093, USA.

We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. Read More

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Clogging and depinning of ballistic active matter systems in disordered media.

Phys Rev E 2018 May;97(5-1):052613

Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

We numerically examine ballistic active disks driven through a random obstacle array. Formation of a pinned or clogged state occurs at much lower obstacle densities for the active disks than for passive disks. As a function of obstacle density, we identify several distinct phases including a depinned fluctuating cluster state, a pinned single-cluster or jammed state, a pinned multicluster state, a pinned gel state, and a pinned disordered state. Read More

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Constitutive relation for the system-spanning dynamically jammed region in response to impact of cornstarch and water suspensions.

Phys Rev E 2018 May;97(5-1):052602

Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA.

We experimentally characterize the impact response of concentrated suspensions consisting of cornstarch and water. We observe that the suspensions support a large normal stress-on the order of MPa-with a delay after the impactor hits the suspension surface. We show that neither the delay nor the magnitude of the stress can yet be explained by either standard rheological models of shear thickening in terms of steady-state viscosities, or impact models based on added mass or other inertial effects. Read More

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System-spanning dynamically jammed region in response to impact of cornstarch and water suspensions.

Phys Rev E 2018 May;97(5-1):052603

Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA.

We experimentally characterize the structure of concentrated suspensions of cornstarch and water in response to impact. Using surface imaging and particle tracking at the boundary opposite the impactor, we observed that a visible structure and particle flow at the boundary occur with a delay after impact. We show the delay time is about the same time as the strong stress response, confirming that the strong stress response results from deformation of the dynamically jammed structure once it spans between the impactor and a solid boundary. Read More

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May 2018
2 Reads

Testing constitutive relations by running and walking on cornstarch and water suspensions.

Phys Rev E 2018 May;97(5-1):052604

Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA.

The ability of a person to run on the surface of a suspension of cornstarch and water has fascinated scientists and the public alike. However, the constitutive relation obtained from traditional steady-state rheology of cornstarch and water suspensions has failed to explain this behavior. In another paper we presented an averaged constitutive relation for impact rheology consisting of an effective compressive modulus of a system-spanning dynamically jammed structure [R. Read More

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Frustration-induced internal stresses are responsible for quasilocalized modes in structural glasses.

Phys Rev E 2018 Mar;97(3-1):032140

Chemical and Biological Physics Department, Weizmann Institute of Science, Rehovot 7610001, Israel.

It has been recently shown [E. Lerner, G. Düring, and E. Read More

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Motion of Knots in DNA Stretched by Elongational Fields.

Phys Rev Lett 2018 May;120(18):188003

Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02142, USA.

Knots in DNA occur in biological systems, serve as a model system for polymer entanglement, and affect the efficacy of modern genomics technologies. We study the motion of complex knots in DNA by stretching molecules with a divergent electric field that provides an elongational force. We demonstrate that the motion of knots is nonisotropic and driven towards the closest end of the molecule. Read More

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May 2018
2 Reads

Standard and inverse bond percolation of straight rigid rods on square lattices.

Phys Rev E 2018 Apr;97(4-1):042113

Departamento de Física, Instituto de Física Aplicada, Universidad Nacional de San Luis-CONICET, Ejército de los Andes 950, D5700HHW, San Luis, Argentina.

Numerical simulations and finite-size scaling analysis have been carried out to study standard and inverse bond percolation of straight rigid rods on square lattices. In the case of standard percolation, the lattice is initially empty. Then, linear bond k-mers (sets of k linear nearest-neighbor bonds) are randomly and sequentially deposited on the lattice. Read More

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From jamming to collective cell migration through a boundary induced transition.

Soft Matter 2018 May;14(19):3774-3782

Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, Technikerstrasse 21a, A-6020 Innsbruck, Austria.

Cell monolayers provide an interesting example of active matter, exhibiting a phase transition from flowing to jammed states as they age. Here we report experiments and numerical simulations illustrating how a jammed cellular layer rapidly reverts to a flowing state after a wound. Quantitative comparison between experiments and simulations shows that cells change their self-propulsion and alignment strength so that the system crosses a phase transition line, which we characterize by finite-size scaling in an active particle model. Read More

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May 2018
1 Read

Quantifying flow and stress in ice mélange, the world's largest granular material.

Proc Natl Acad Sci U S A 2018 05 30;115(20):5105-5110. Epub 2018 Apr 30.

Department of Physics and Astronomy, University of California, Irvine, CA 92697.

Tidewater glacier fjords are often filled with a collection of calved icebergs, brash ice, and sea ice. For glaciers with high calving rates, this "mélange" of ice can be jam-packed, so that the flow of ice fragments is mostly determined by granular interactions. In the jammed state, ice mélange has been hypothesized to influence iceberg calving and capsize, dispersion and attenuation of ocean waves, injection of freshwater into fjords, and fjord circulation. Read More

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Controlled Viscosity in Dense Granular Materials.

Phys Rev Lett 2018 Mar;120(13):138001

Institute for Complex Systems-CNR, Piazzale Aldo Moro 2, 00185 Rome, Italy.

We experimentally investigate the fluidization of a granular material subject to mechanical vibrations by monitoring the angular velocity of a vane suspended in the medium and driven by an external motor. On increasing the frequency, we observe a reentrant transition, as a jammed system first enters a fluidized state, where the vane rotates with high constant velocity, and then returns to a frictional state, where the vane velocity is much lower. While the fluidization frequency is material independent, the viscosity recovery frequency shows a clear dependence on the material that we rationalize by relating this frequency to the balance between dissipative and inertial forces in the system. Read More

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Shaken and stirred: Random organization reduces viscosity and dissipation in granular suspensions.

Sci Adv 2018 Mar 30;4(3):eaar3296. Epub 2018 Mar 30.

Department of Applied Mathematics and Theoretical Physics (DAMTP), Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, UK.

The viscosity of suspensions of large (≥10 μm) particles diverges at high solid fractions due to proliferation of frictional particle contacts. Reducing friction, to allow or improve flowability, is usually achieved by tuning the composition, either by changing particle sizes and shapes or by adding lubricating molecules. We present numerical simulations that demonstrate a complementary approach whereby the viscosity divergence is shifted by driven flow tuning, using superimposed shear oscillations in various configurations to facilitate a primary flow. Read More

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March 2018
2 Reads

High internal phase emulsion (HIPE)-templated biopolymeric oleofilms containing an ultra-high concentration of edible liquid oil.

Food Funct 2018 Apr;9(4):1993-1997

Laboratory of Food Technology and Engineering, Department of Food Safety and Quality, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium.

We report, for the first time, the fabrication of oleofilms (containing more than 97 wt% edible liquid oil) using high internal phase emulsions (with oil volume fraction φoil = 0.82) as templates. Advanced microscopy studies revealed an interesting microstructure of these films where jammed oil droplets were embedded in a dried matrix of biopolymeric complexes. Read More

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April 2018
4 Reads

Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium.

Phys Rev E 2018 Feb;97(2-1):022901

Laboratoire PMMH, UMR 7636 CNRS/ESPCI Paris/PSL Research University/Sorbonne Universités, UPMC Univ Paris 06,/Univ Paris Diderot, 10 rue Vauquelin, 75231 Paris cedex 05, France.

We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L/L_{c}, which is the ratio of the length of the flexible beam L to L_{c}, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. Read More

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February 2018

Hypostatic jammed packings of frictionless nonspherical particles.

Phys Rev E 2018 Jan;97(1-1):012909

Department of Physics, Yale University, New Haven, Connecticut 06520, USA.

We perform computational studies of static packings of a variety of nonspherical particles including circulo-lines, circulo-polygons, ellipses, asymmetric dimers, dumbbells, and others to determine which shapes form packings with fewer contacts than degrees of freedom (hypostatic packings) and which have equal numbers of contacts and degrees of freedom (isostatic packings), and to understand why hypostatic packings of nonspherical particles can be mechanically stable despite having fewer contacts than that predicted from naive constraint counting. To generate highly accurate force- and torque-balanced packings of circulo-lines and cir-polygons, we developed an interparticle potential that gives continuous forces and torques as a function of the particle coordinates. We show that the packing fraction and coordination number at jamming onset obey a masterlike form for all of the nonspherical particle packings we studied when plotted versus the particle asphericity A, which is proportional to the ratio of the squared perimeter to the area of the particle. Read More

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January 2018
1 Read

Compression-driven jamming of athermal frictionless spherocylinders in two dimensions.

Phys Rev E 2018 Jan;97(1-1):012905

Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.

We simulate numerically the compression-driven jamming of athermal, frictionless, soft-core spherocylinders in two dimensions, for a range of particle aspect ratios α. We find the critical packing fraction ϕ_{J}(α) for the jamming transition and the average number of contacts per particle z_{J}(α) at jamming. We find that both are nonmonotonic, with a peak at α≈1. Read More

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January 2018

Characterization of maximally random jammed sphere packings. III. Transport and electromagnetic properties via correlation functions.

Phys Rev E 2018 Jan;97(1-1):012118

Department of Chemistry, Department of Physics, Princeton Institute for the Science and Technology of Materials, and Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA.

In the first two papers of this series, we characterized the structure of maximally random jammed (MRJ) sphere packings across length scales by computing a variety of different correlation functions, spectral functions, hole probabilities, and local density fluctuations. From the remarkable structural features of the MRJ packings, especially its disordered hyperuniformity, exceptional physical properties can be expected. Here we employ these structural descriptors to estimate effective transport and electromagnetic properties via rigorous bounds, exact expansions, and accurate analytical approximation formulas. Read More

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January 2018

Yielding and Flow of Soft-Jammed Systems in Elongation.

Phys Rev Lett 2018 Jan;120(4):048001

Université Paris-Est, Laboratoire Navier (ENPC-IFSTTAR-CNRS), 2 Allée Kepler, 77420 Champs sur Marne, France.

So far, yielding and flow properties of soft-jammed systems have only been studied from simple shear and then extrapolated to other flow situations. In particular, simple flows such as elongations have barely been investigated experimentally or only in a nonconstant, partial volume of material. We show that using smooth tool surfaces makes it possible to obtain a prolonged elongational flow over a large range of aspect ratios in the whole volume of material. Read More

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January 2018

Rate Dependence of Elementary Rearrangements and Spatiotemporal Correlations in the 3D Flow of Soft Solids.

Phys Rev Lett 2018 Jan;120(1):018001

Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington, DC 20057, USA.

We use a combination of confocal microscopy, rheology, and molecular dynamics simulations to investigate jammed emulsions under shear, by analyzing the 3D droplets rearrangements in the shear frame. Our quantitative analysis of local dynamics reveals elementary nonaffine rearrangements that underlie the onset of the flow at small strains. We find that the mechanism of unjamming and the upturn in the material flow curve are associated to a qualitative change in spatiotemporal correlations of such rearrangements with the applied shear rate. Read More

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January 2018
1 Read

Subjamming transition in binary sphere mixtures.

Phys Rev E 2017 Nov 20;96(5-1):052905. Epub 2017 Nov 20.

Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.

We study the influence of particle-size asymmetry on structural evolution of randomly jammed binary sphere mixtures with varying large-sphere and small-sphere composition. Simulations of jammed packings are used to assess the transition from large-sphere dominant to small-sphere dominant mixtures. For weakly asymmetric particle sizes, packing properties evolve smoothly, but not monotonically, with increasing small-sphere composition, f. Read More

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November 2017

Force percolation transition of jammed granular systems.

Phys Rev E 2017 Oct 3;96(4-1):042901. Epub 2017 Oct 3.

Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.

The mechanical and transport properties of jammed materials originate from an underlying percolating network of contact forces between the grains. Using extensive simulations we investigate the force-percolation transition of this network, where two particles are considered as linked if their interparticle force overcomes a threshold. We show that this transition belongs to the random percolation universality class, thus ruling out the existence of long-range correlations between the forces. Read More

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October 2017
1 Read

Response of jammed packings to thermal fluctuations.

Phys Rev E 2017 Dec 1;96(6-1):062902. Epub 2017 Dec 1.

Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA.

We focus on the response of mechanically stable (MS) packings of frictionless, bidisperse disks to thermal fluctuations, with the aim of quantifying how nonlinearities affect system properties at finite temperature. In contrast, numerous prior studies characterized the structural and mechanical properties of MS packings of frictionless spherical particles at zero temperature. Packings of disks with purely repulsive contact interactions possess two main types of nonlinearities, one from the form of the interaction potential (e. Read More

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December 2017
2 Reads

Experimental investigation of mesoscopic heterogeneous motion of laser-activated self-propelling Janus particles in suspension.

Phys Rev E 2017 Dec 1;96(6-1):062601. Epub 2017 Dec 1.

Many-body System Laboratory, Department of Physics, National Chung-Cheng University, Chiayi 62102, Taiwan (R.O.C.).

The mesoscopic collective motion of self-propelling active particle suspension is experimentally investigated. The active particles are silica micro spheres with Au hemisphere coating, and their propelling strength is activated by laser irradiation. The suspension is driven from equilibrium to near equilibrium and far from equilibrium by tuning the excitation laser intensity. Read More

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December 2017

Criticality of the zero-temperature jamming transition probed by self-propelled particles.

Authors:
Qinyi Liao Ning Xu

Soft Matter 2018 Jan;14(5):853-860

CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale & Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China.

We perform simulations of athermal systems of self-propelled particles (SPPs) interacting via harmonic repulsion in the vicinity of the zero-temperature jamming transition at point J. Every particle is propelled by a constant force f pointing to a randomly assigned and fixed direction. When f is smaller than the yield force f, the system is statically jammed. Read More

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January 2018
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Jammed Spin Liquid in the Bond-Disordered Kagome Antiferromagnet.

Phys Rev Lett 2017 Dec 11;119(24):247201. Epub 2017 Dec 11.

Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany.

We study a class of continuous spin models with bond disorder including the kagome Heisenberg antiferromagnet. For weak disorder strength, we find discrete ground states whose number grows exponentially with system size. These states do not exhibit zero-energy excitations characteristic of highly frustrated magnets but instead are local minima of the energy landscape. Read More

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December 2017

Adhesion forces and cortical tension couple cell proliferation and differentiation to drive epidermal stratification.

Nat Cell Biol 2018 Jan 11;20(1):69-80. Epub 2017 Dec 11.

Paul Gerson Unna Group 'Skin Homeostasis and Ageing', Max Planck Institute for Biology of Ageing, Cologne, Germany.

To establish and maintain organ structure and function, tissues need to balance stem cell proliferation and differentiation rates and coordinate cell fate with position. By quantifying and modelling tissue stress and deformation in the mammalian epidermis, we find that this balance is coordinated through local mechanical forces generated by cell division and delamination. Proliferation within the basal stem/progenitor layer, which displays features of a jammed, solid-like state, leads to crowding, thereby locally distorting cell shape and stress distribution. Read More

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January 2018
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19.680 Impact Factor