The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

X Xie - One of the best experts on this subject based on the ideXlab platform.

Paul A Janmey - One of the best experts on this subject based on the ideXlab platform.

  • Negative normal Stress in semiflexible biopolymer gels
    2016
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh, Technische Universität, Physik-department E Biophysik
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression--even liquids. Solids also resist simple Shear deformations that conserve volume. Under simple Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress 1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, Poynting showed nearly one hundred years ago that elastic rods or wires tend to elongate when subject to torsion 2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the non-linear strain-stiffening behavior of biopolymer gels 3. When viscoelastic materials are deformed by a sinusoidal Shear strain, their stiffness is quantified by the elastic storage and loss Shear moduli calculated from the amplitude and phase shift of the resulting sinusoidal Shear Stress. In some solids like soft hydrogels at moderate to larg

  • fluid Shear Stress threshold regulates angiogenic sprouting
    Proceedings of the National Academy of Sciences of the United States of America, 2014
    Co-Authors: Peter A Galie, Duchuy T Nguyen, Colin K. Choi, Daniel M Cohen, Paul A Janmey, Christopher S Chen
    Abstract:

    The density and architecture of capillary beds that form within a tissue depend on many factors, including local metabolic demand and blood flow. Here, using microfluidic control of local fluid mechanics, we show the existence of a previously unappreciated flow-induced Shear Stress threshold that triggers angiogenic sprouting. Both intraluminal Shear Stress over the endothelium and transmural flow through the endothelium above 10 dyn/cm2 triggered endothelial cells to sprout and invade into the underlying matrix, and this threshold is not impacted by the maturation of cell–cell junctions or pressure gradient across the monolayer. Antagonizing VE-cadherin widened cell–cell junctions and reduced the Applied Shear Stress for a given transmural flow rate, but did not affect the Shear threshold for sprouting. Furthermore, both transmural and luminal flow induced expression of matrix metalloproteinase 1, and this up-regulation was required for the flow-induced sprouting. Once sprouting was initiated, continuous flow was needed to both sustain sprouting and prevent retraction. To explore the potential ramifications of a Shear threshold on the spatial patterning of new sprouts, we used finite-element modeling to predict fluid Shear in a variety of geometric settings and then experimentally demonstrated that transmural flow guided preferential sprouting toward paths of draining interstitial fluid flow as might occur to connect capillary beds to venules or lymphatics. In addition, we show that luminal Shear increases in local narrowings of vessels to trigger sprouting, perhaps ultimately to normalize Shear Stress across the vasculature. Together, these studies highlight the role of Shear Stress in controlling angiogenic sprouting and offer a potential homeostatic mechanism for regulating vascular density.

  • negative normal Stress in semiflexible biopolymer gels
    Nature Materials, 2007
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression—even liquids. Solids also resist simple Shear deformations that conserve volume. Under Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, elastic rods or wires tend to elongate when subject to torsion2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the nonlinear strain-stiffening behaviour of biopolymer gels3.

Antonio Coniglio - One of the best experts on this subject based on the ideXlab platform.

  • flow jam of frictional athermal systems under Shear Stress
    arXiv: Soft Condensed Matter, 2012
    Co-Authors: Raffaele Pastore, Massimo Pica Ciamarra, Antonio Coniglio
    Abstract:

    We report recent results of molecular dynamics simulations of frictional athermal particles at constant volume fraction and constant Applied Shear Stress, focusing on a range of control parameters where the system first flows, but then jams after a time tjam. On decreasing the volume fraction, the mean jamming time diverges, while its sample fluctuations become so large that the jamming time probability distribution P(tjam) becomes a power-law. We obtain an insight on the origin of this phenomenology focusing on the flowing regime, which is characterized by the presence of a clear correlation between the Shear velocity and the mean number of contacts per particles Z, whereby small velocities occur when Z acquires higher values.

  • flow and jam of frictional athermal systems under Shear Stress
    Philosophical Magazine, 2011
    Co-Authors: Raffaele Pastore, Massimo Pica Ciamarra, Antonio Coniglio
    Abstract:

    We report recent results of molecular dynamics simulations of frictional athermal particles at constant volume fraction and constant Applied Shear Stress, focussing on a range of control parameters where the system first flows, but then jams after a time t jam. On decreasing the volume fraction, the mean jamming time diverges, while its sample fluctuations become so large that the jamming time probability distribution becomes a power law. We obtain an insight into the origin of this phenomenology focussing on the flowing regime, which is characterised by the presence of a clear correlation between the Shear velocity and the mean number of contacts per particle Z, whereby small velocities occur when Z acquires higher values.

  • jamming at zero temperature zero friction and finite Applied Shear Stress
    Physical Review Letters, 2009
    Co-Authors: Massimo Pica Ciamarra, Antonio Coniglio
    Abstract:

    Shear Stress, as temperature, induces particle motion, and affects the jamming transition from a fluid to a disordered solid state. Here, we show that at finite Shear Stress, the jamming transition is characterized by the presence of hysteresis, as in a given range of control parameters a flowing or a jammed state can be found, depending on whether the system is prepared coming from the fluid or the jammed phase. At small Shear Stress, where the hysteresis is negligible, the jamming transition has a mixed first-order second-order character close to that found at the glass transition of thermal systems, with discontinuities in the asymptotic values of two time quantities such as the self-intermediate scattering function.

Fred C. Mackintosh - One of the best experts on this subject based on the ideXlab platform.

  • Negative normal Stress in semiflexible biopolymer gels
    2016
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh, Technische Universität, Physik-department E Biophysik
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression--even liquids. Solids also resist simple Shear deformations that conserve volume. Under simple Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress 1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, Poynting showed nearly one hundred years ago that elastic rods or wires tend to elongate when subject to torsion 2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the non-linear strain-stiffening behavior of biopolymer gels 3. When viscoelastic materials are deformed by a sinusoidal Shear strain, their stiffness is quantified by the elastic storage and loss Shear moduli calculated from the amplitude and phase shift of the resulting sinusoidal Shear Stress. In some solids like soft hydrogels at moderate to larg

  • negative normal Stress in semiflexible biopolymer gels
    Nature Materials, 2007
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression—even liquids. Solids also resist simple Shear deformations that conserve volume. Under Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, elastic rods or wires tend to elongate when subject to torsion2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the nonlinear strain-stiffening behaviour of biopolymer gels3.

Sebastian Rammensee - One of the best experts on this subject based on the ideXlab platform.

  • Negative normal Stress in semiflexible biopolymer gels
    2016
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh, Technische Universität, Physik-department E Biophysik
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression--even liquids. Solids also resist simple Shear deformations that conserve volume. Under simple Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress 1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, Poynting showed nearly one hundred years ago that elastic rods or wires tend to elongate when subject to torsion 2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the non-linear strain-stiffening behavior of biopolymer gels 3. When viscoelastic materials are deformed by a sinusoidal Shear strain, their stiffness is quantified by the elastic storage and loss Shear moduli calculated from the amplitude and phase shift of the resulting sinusoidal Shear Stress. In some solids like soft hydrogels at moderate to larg

  • negative normal Stress in semiflexible biopolymer gels
    Nature Materials, 2007
    Co-Authors: Paul A Janmey, Margaret E. Mccormick, Sebastian Rammensee, Jennifer L. Leight, Penelope C. Georges, Fred C. Mackintosh
    Abstract:

    When subject to Stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression—even liquids. Solids also resist simple Shear deformations that conserve volume. Under Shear, however, most materials also have a tendency to expand in the direction perpendicular to the Applied Shear Stress, a response that is known as positive normal Stress1. For example, wet sand tends to dilate when Sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, elastic rods or wires tend to elongate when subject to torsion2. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when Sheared between two plates, they tend to pull the plates together. We show that these negative normal Stresses can be as large as the Shear Stress and that this property is directly related to the nonlinear strain-stiffening behaviour of biopolymer gels3.