Article
Multidisciplinary Sciences
Jidan Yang, Yu Zou, Wentao Tang, Jinxing Li, Mingjun Huang, Satoshi Aya
Summary: The authors report the discovery of chiral polarization meron-like structures in the emergence of quasi-2D ferroelectric nematic domains. The polarization strength plays a crucial role in determining polarization topology.
NATURE COMMUNICATIONS
(2022)
Review
Chemistry, Physical
Sumesh P. Thampi
Summary: This review discusses the different flow states and flow transitions exhibited by channel confined active nematics, revealing the role of hydrodynamics, fluid properties, and geometry in dictating their behavior, and highlighting current research questions in the field.
CURRENT OPINION IN COLLOID & INTERFACE SCIENCE
(2022)
Article
Physics, Multidisciplinary
Federico Caimi, Giovanni Nava, Susanna Fuschetto, Liana Lucchetti, Petra Paie, Roberto Osellame, Xi Chen, Noel A. Clark, Matthew A. Glaser, Tommaso Bellini
Summary: The recently discovered ferroelectric nematic (N-F) liquid-crystal phase possesses both the fluid-like orientation and the large magnitude polarization field. This unique combination results in a distinct electrostatic phenomenon and response to applied fields. In this study, we observe that the polarization field of the N-F phase aligns with the microchannels despite their winding paths when a small electric field is applied. This alignment is due to the fluid superscreening effect, where the electric field components normal to the channel walls are promptly eliminated by polarization reorientation. This finding sheds light on the internal structure and electrical self-organization of channel-confined N-F liquid crystals.
Article
Physics, Multidisciplinary
Davide Revignas, Alberta Ferrarini
Summary: Using Onsager theory, researchers have found that, under arbitrary deformations, hard rod nematics have an intrinsic tendency to twist around their ordering axis, driven by orientational fluctuations of particles. This finding is related to the recent discovery of a double twisted ground state in cylindrically confined lyotropic chromonic liquid crystals.
PHYSICAL REVIEW LETTERS
(2023)
Article
Mathematics
Antonio Lamura
Summary: This study investigates the dynamics and rheology of a vesicle confined in a channel under shear flow at finite temperature. A two-dimensional numerical model is used to analyze the effect of temperature on vesicle motion and system viscosity. It is found that the suspension viscosity is influenced by the viscosity contrast and different temperature-dependent mechanisms.
Article
Multidisciplinary Sciences
Muni Zhou, Vladimir Zhdankin, Matthew W. Kunz, Nuno F. Loureiro, Dmitri A. Uzdensky
Summary: In this study, we investigate the generation of seed magnetic fields through the Weibel instability in an initially unmagnetized plasma driven by a large-scale shear force. We develop an analytical model and confirm its predictions through particle simulations. This work has important implications for magnetogenesis in dilute astrophysical systems.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Chemistry, Physical
E. J. L. de Oliveira, L. V. Mirantsev, M. L. Lyra, I. N. de Oliveira
Summary: In this study, molecular dynamics simulations were used to investigate the behavior of nonchiral and chiral active nematics in a two-dimensional nanoscopic ring-shaped region. It was found that the nonchiral active nematics exhibited a similar orientational order to passive nematics within the same region, while the chiral nematics displayed significantly different orientational order. Additionally, substantial time oscillations in the orientational order were observed when the chirality of active nematic particles was sufficiently strong.
JOURNAL OF MOLECULAR LIQUIDS
(2023)
Article
Chemistry, Physical
Chaitanya Joshi, Zahra Zarei, Michael M. Norton, Seth Fraden, Aparna Baskaran, Michael F. Hagan
Summary: In this study, we computationally investigate the influence of a circular confinement geometry on 2D active nematics. By systematically varying the annulus inner radius and channel width, we discover new steady-state behaviors and reveal the interplay between boundary curvature and confinement. Furthermore, we observe that, below a threshold inner radius, the dynamics are almost insensitive to the presence of the inner hole, and we explain this insensitivity through a simple scaling analysis. Our work sheds further light on design principles for controlling the dynamics of active nematics using confinement.
Article
Physics, Multidisciplinary
Alexander J. H. Houston, Gareth P. Alexander
Summary: This article addresses the challenge of harnessing the non-equilibrium dynamics in active systems. It presents a method for designing colloids with controllable spontaneous propulsion or rotation in active nematics. The study identifies two regimes of behavior for chiral cogs and provides design principles for achieving desired rotational dynamics in active nematic colloids.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Baudouin Saintyves, Romain Pic, L. Mahadevan, Irmgard Bischofberger
Summary: When a hyperelastic hydrogel dries from a lateral boundary, it undergoes elastic deformation and forms air cavities and cellular networks. The size of these cavities is determined by the confinement of the gel and the interfacial tension between air and hydrogel.
PHYSICAL REVIEW LETTERS
(2023)
Article
Polymer Science
Eni Kume, Patrick Baroni, Laurence Noirez
Summary: This study presents an innovative thermal approach to investigate solid-like properties of liquids, identifying a dynamic thermo-elastic mesoscopic behavior. The research shows that a portion of shear strain energy is converted into thermal energy in cold and hot shear bands that synchronize with the applied shear field, indicating a coupling to shear elastic modes in agreement with low frequency shear elasticity.
Article
Engineering, Geological
Zhaowei Ding, Wei Hu, Yan Li
Summary: This paper presents a study on the nonlinear behavior of confined shear flow using the discrete element method (DEM). The DEM simulation allows for a detailed analysis of the microscopic mechanisms of granular matter and provides insights into the behavior of confined shear flow. The study explores the role of side friction and the effect of different boundary conditions on the velocity profile of the particle assemblage.
Article
Cell Biology
Shubhadeep Sadhukhan, Samo Penic, Ales Iglic, Nir S. Gov
Summary: Cell spreading and motility on an adhesive substrate are driven by active physical forces generated by the actin cytoskeleton. Coupling curved membrane complexes to protrusive forces provided by actin polymerization can lead to spontaneous membrane shapes and patterns. In the presence of an adhesive substrate, this model produces an emergent motile phenotype. The impact of external shear flow on cell shape and migration on a uniform adhesive flat substrate is explored using a minimal-cell model.
FRONTIERS IN CELL AND DEVELOPMENTAL BIOLOGY
(2023)
Article
Multidisciplinary Sciences
Rebecca A. Moriarty, Stavroula Mili, Kimberly M. Stroka
Summary: Cancer cells can alter their migratory mechanisms under mechanical confining forces. mRNA localization in cell protrusions contributes to cell migration, regulated by the APC protein. The mechanical activity of cells determines the peripheral localization of RNAs and their role in confined cell migration.
Article
Computer Science, Interdisciplinary Applications
A. Grabowski, M. Nitka, J. Tejchman
Summary: The paper investigates the quasi-static confined flow of cohesionless sand in a plane strain model silo through numerical modelling using the discrete element method. By comparing DEM simulation outcomes with experimental and theoretical solutions, the study focuses on the formation and evolution of wall and internal shear zones during sand flow, as well as the impact of particle displacements, rotations, contact forces, void ratios, and wall stresses.
COMPUTERS AND GEOTECHNICS
(2021)
Article
Physics, Multidisciplinary
Carles Blanch-Mercader, Pau Guillamat, Aurelien Roux, Karsten Kruse
Summary: Research shows that cell monolayers exert compressive stresses at defect centers, leading to localized cell differentiation and formation of three-dimensional shapes in these regions.
PHYSICAL REVIEW LETTERS
(2021)
Article
Biochemistry & Molecular Biology
John Robert Davis, Anna P. Ainslie, John J. Williamson, Ana Ferreira, Alejandro Torres-Sanchez, Andreas Hoppe, Federica Mangione, Matthew B. Smith, Enrique Martin-Blanco, Guillaume Salbreux, Nicolas Tapon
Summary: This research on Drosophila reveals that the development of adult abdominal epidermis is driven by cell divisions initiated by enzymes secreted by neighboring larval epidermal cells. The study also shows that the development involves changes in the tissue microenvironment and a rapid exit from the cell cycle.
Article
Physics, Multidisciplinary
Christian Bacher, Diana Khoromskaia, Guillaume Salbreux, Stephan Gekle
Summary: A three-dimensional computational model of the cell cortex was developed to study dynamic processes such as cell motility, furrow formation, and cytokinesis. The study validated a reorientation mechanism where cells autonomously realign their axis perpendicular to the furrow plane under the influence of non-axisymmetric disturbances, contributing to the robustness of cell division in realistic environmental conditions.
FRONTIERS IN PHYSICS
(2021)
Article
Biochemistry & Molecular Biology
Sophie Hecht, Gantas Perez-Mockus, Dominik Schienstock, Carles Recasens-Alvarez, Sara Merino-Aceituno, Matt Smith, Guillaume Salbreux, Pierre Degond, Jean-Paul Vincent
Summary: This study explores the mechanisms behind cell growth termination and suggests that mechanical feedback may play a role via adherens junctions. It also proposes that nuclei may play a role in sensing mechanical stress and gravity. By developing a model, the research provides important insights into nuclear migration and mechanical effects during growth.
Article
Multidisciplinary Sciences
Manasi Kelkar, Pierre Bohec, Matthew B. Smith, Varun Sreenivasan, Ana Lisica, Leo Valon, Emma Ferber, Buzz Baum, Guillaume Salbreux, Guillaume Charras
Summary: Proper orientation of the mitotic spindle is essential for embryo development, tissue development, and maintenance of tissue integrity and homeostasis in adults. This study used optogenetics and computational modeling to investigate how mitotic spindles respond to inhomogeneous tension within the actomyosin cortex. The results showed that the activation of RhoA at both poles of the cell influences spindle orientation by reducing pulling forces exerted by cortical regulators on astral microtubules. This perturbation of torque balance leads to spindle rotation in response to mechanical stress.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Physics, Multidisciplinary
V. Yashunsky, D. J. G. Pearce, C. Blanch-Mercader, F. Ascione, P. Silberzan, L. Giomi
Summary: Collectively migrating cells in living organisms are often guided by their local environment, including physical barriers and internal interfaces. In this study, the impact of physical boundaries on highly active, chaotic, multicellular systems is investigated. The researchers demonstrate the presence of self-organized defects at the boundary which act as local sources of chiral active stress generating directed edge flows. This work highlights the importance of topology and chirality in the emergence of collective cellular flows at boundaries.
Article
Biochemical Research Methods
Alejandro Torres-Sanchez, Max Kerr Winter, Guillaume Salbreux
Summary: We propose a modelling and simulation framework for cell aggregates in three dimensions based on interacting active surfaces. The framework captures cell mechanics, inter-cell forces, and the effect of adhesion molecules. We discretize the model equations using a finite element method and implement it in C++. This framework allows for the systematic exploration of the mechanics of cell aggregates at the cell to tissue-scale, which is important in the morphogenesis of embryos and organoids.
PLOS COMPUTATIONAL BIOLOGY
(2022)
Article
Biology
Diana Khoromskaia, Guillaume Salbreux, Michael M. Kozlov
Summary: This study investigates the shape transformations of epithelial tissues in three dimensions and identifies the active forces generated by the cytoskeleton as crucial. The interplay between local differential tensions, tissue geometry, and external forces is explored, revealing the mechanical equilibrium shapes and dynamic deformations of epithelial sheets.
Article
Biology
Xiuyu Wang, David Gonzalez-Rodriguez, Thomas Vourc'h, Pascal Silberzan, Abdul I. Barakat
Summary: Smooth muscle cells (SMCs) are essential for tissue contraction. Abnormalities in SMC organization are associated with various diseases. Studies have found that SMCs cultured on flat surfaces can form three-dimensional clusters resembling pathological tissues, but the mechanism behind it is unknown.
COMMUNICATIONS BIOLOGY
(2023)
Article
Multidisciplinary Sciences
Trinish Sarkar, Victor Yashunsky, Louis Brezin, Carles Blanch Mercader, Thibault Aryaksama, Mathilde Lacroix, Thomas Risler, Jean-Francois Joanny, Pascal Silberzan
Summary: This study identifies an alternative mechanism for the crisscross bilayering of myoblasts in vitro, which is caused by the prior local organization of cells in the initial monolayer. The secretion of extracellular matrix plays a crucial role in this coordinated process.
Article
Physics, Multidisciplinary
Guillaume Salbreux, Frank Juelicher, Jacques Prost, Andrew Callan-Jones
Summary: We present a fully covariant theory of the hydrodynamics of nematic and polar active surfaces, analyzing their symmetries and providing examples of physical realizations. We derive expressions for equilibrium tensions, moments, and external forces and torques on passive polar or nematic surfaces, calculate entropy production rates, and obtain constitutive equations for active surfaces with different symmetries. We also investigate the instabilities of confined planar-chiral polar active layers and deformable polar active surfaces with broken up-down symmetry.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Physics, Fluids & Plasmas
Luca Cocconi, Guillaume Salbreux, Gunnar Pruessner
Summary: Entropy production plays a fundamental role in studying nonequilibrium systems by quantitatively measuring the degree of time-reversal symmetry breaking. The relationship between entropy production at different resolutions is crucial for coarse-grained and continuum descriptions of phenomena. This work derives the scaling of entropy production under iterative coarse graining based on microscopic transition rates, providing a criterion to distinguish between equilibrium-like and genuinely nonequilibrium macroscopic phenomena.
Article
Physics, Multidisciplinary
Benjamin Walter, Gunnar Pruessner, Guillaume Salbreux
Summary: The study introduces a perturbative method for calculating all moments of the first passage time distribution in stochastic one-dimensional processes under the influence of both white and colored noise. The focus is on thermal active matter, such as self-propelled particles subject to diffusion, where the perturbation theory considers the effect of self-propulsion to be minor compared to thermal fluctuations. The method is applied to active thermal particles in a harmonic trap and on a ring, with first-order corrections calculated for the moment-generating function of first passage times. Comparisons are made between analytical results and numerical simulations.
PHYSICAL REVIEW RESEARCH
(2021)