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Full-Text Articles in Physics
Generic Phases Of Cross-Linked Active Gels: Relaxation, Oscillation And Contractility, Shiladitya Banerjee, Tanniemola B. Liverpool, M. C. Marchetti
Generic Phases Of Cross-Linked Active Gels: Relaxation, Oscillation And Contractility, Shiladitya Banerjee, Tanniemola B. Liverpool, M. C. Marchetti
Physics - All Scholarship
We study analytically and numerically a generic continuum model of an isotropic active solid with internal stresses generated by non-equilibrium `active' mechano-chemical reactions. Our analysis shows that the gel can be tuned through three classes of dynamical states by increasing motor activity: a constant unstrained state of homogeneous density, a state where the local density exhibits sustained oscillations, and a steady-state which is spontaneously contracted, with a uniform mean density.
Substrate Rigidity Deforms And Polarizes Active Gels, Shiladitya Banerjee, M. C. Marchetti
Substrate Rigidity Deforms And Polarizes Active Gels, Shiladitya Banerjee, M. C. Marchetti
Physics - All Scholarship
We present a continuum model of the coupling between cells and substrate that accounts for some of the observed substrate-stiffness dependence of cell properties. The cell is modeled as an elastic active gel, adapting recently developed continuum theories of active viscoelastic fluids. The coupling to the substrate enters as a boundary condition that relates the cell's deformation field to local stress gradients. In the presence of activity, the coupling to the substrate yields spatially inhomogeneous contractile stresses and deformations in the cell and can enhance polarization, breaking the cell's front-rear symmetry.
Active Jamming: Self-Propelled Soft Particles At High Density, Silke Henkes, Yaouen Fily, M. Christina Marchetti
Active Jamming: Self-Propelled Soft Particles At High Density, Silke Henkes, Yaouen Fily, M. Christina Marchetti
Physics - All Scholarship
We study numerically the phases and dynamics of a dense collection of self-propelled particles with soft repulsive interactions in two dimensions. The model is motivated by recent in vitro experiments on confluent monolayers of migratory epithelial and endothelial cells. The phase diagram exhibits a liquid phase with giant number fluctuations at low packing fraction and high self-propulsion speed and a jammed phase at high packing fraction and low self-propulsion speed. The dynamics of the jammed phase is controlled by the low frequency modes of the jammed packing.
Nonlinear Hydrodynamics Of Disentangled Flux-Line Liquids, Panayotis Benetatos, M. Cristina Marchetti
Nonlinear Hydrodynamics Of Disentangled Flux-Line Liquids, Panayotis Benetatos, M. Cristina Marchetti
Physics - All Scholarship
In this paper we use non-Gaussian hydrodynamics to study the magnetic response of a flux-line liquid in the mixed state of a type-II superconductor. Both the derivation of our model, which goes beyond conventional Gaussian flux liquid hydrodynamics, and its relationship to other approaches used in the literature are discussed. We focus on the response to a transverse tilting field which is controlled by the tilt modulus, c44, of the flux array. We show that interaction effects can enhance c44 even in infinitely thick clean materials. This enhancement can be interpreted as the appearance of a disentangled flux-liquid fraction. In …
Theory Of Double-Sided Flux Decorations, M. Cristina Marchetti, David R. Nelson
Theory Of Double-Sided Flux Decorations, M. Cristina Marchetti, David R. Nelson
Physics - All Scholarship
A novel two-sided Bitter decoration technique was recently employed by Yao et al. to study the structure of the magnetic vortex array in high-temperature superconductors. Here we discuss the analysis of such experiments. We show that two-sided decorations can be used to infer {\it quantitative} information about the bulk properties of flux arrays, and discuss how a least squares analysis of the local density differences can be used to bring the two sides into registry. Information about the tilt, compressional and shear moduli of bulk vortex configurations can be extracted from these measurements.
Cooperative Self-Propulsion Of Active And Passive Rotors, Yaouen Fily, Aparna Baskaran, M. Cristina Marchetti
Cooperative Self-Propulsion Of Active And Passive Rotors, Yaouen Fily, Aparna Baskaran, M. Cristina Marchetti
Physics - All Scholarship
Using minimal models for low Reynolds number passive and active rotors in a fluid, we characterize the hydrodynamic interactions among rotors and the resulting dynamics of a pair of interacting rotors. This allows us to treat in a common framework passive or externally driven rotors, such as magnetic colloids driven by a rotating magnetic field, and active or internally driven rotors, such as sperm cells confined at boundaries. The hydrodynamic interaction of passive rotors contains an azimuthal component 1/r2 to dipolar order that can yield the recently discovered “cooperative self-propulsion” of a pair of rotors of opposite vorticity. While this …
Motor-Driven Dynamics Of Cytoskeletal Filaments In Motility Assays, Shiladitya Banerjee, M. Cristina Marchetti, Kristian Muller-Nedebock
Motor-Driven Dynamics Of Cytoskeletal Filaments In Motility Assays, Shiladitya Banerjee, M. Cristina Marchetti, Kristian Muller-Nedebock
Physics - All Scholarship
We model analytically the dynamics of a cytoskeletal filament in a motility assay. The filament is described as rigid rod free to slide in two dimensions. The motor proteins consist of polymeric tails tethered to the plane and modeled as linear springs and motor heads that bind to the filament. As in related models of rigid and soft two-state motors, the binding/unbinding dynamics of the motor heads and the dependence of the transition rates on the load exerted by the motor tails play a crucial role in controlling the filament's dynamics. Our work shows that the filament effectively behaves as …
Polar Patterns In Active Fluids, Luca Giomi, M. Cristina Marchetti
Polar Patterns In Active Fluids, Luca Giomi, M. Cristina Marchetti
Physics - All Scholarship
We study the spatio-temporal dynamics of a model of polar active fluid in two dimensions. The system exhibits a transition from an isotropic to a polarized state as a function of density. The uniform polarized state is, however, unstable above a critical value of activity. Upon increasing activity, the active fluids displays increasingly complex patterns, including traveling bands, traveling vortices and chaotic behavior. The advection arising from the particles self-propulsion and unique to polar fluids yields qualitatively new behavior as compared to that obtain in active nematic, yielding traveling-wave structures. We show that the nonlinear hydrodynamic equations can be mapped …