Is this you? As a journalist, you can create a free Muck Rack account to customize your profile, list your contact preferences, and upload a portfolio of your best work.
Claim your profile
Articles by Ricard Alert
Physics > Biological Physics
arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs.
Tissue flow acts as a guidance cue for immune cell polarization and directional migration
Abstract Embryonic myeloid (EM) cells are the first immune-cell population to emerge during development and must disperse throughout the embryo to act as the first line of defence against infection. Although EM cells migrate directionally toward wounds, how they navigate through unwounded tissues during early colonization remains unclear.
Elevated contractility drives implantation failure in mouse embryos from aged females
Abstract Women in their mid-30s experience a marked decline in fertility. The origin of these fertility defects resides in the implantation capacity of the embryo itself, but the mechanistic basis of this impairment is not well understood. Here we identify a core mechanical defect in embryos from aged females that impairs their implantation competence.
Hamiltonian description of non-reciprocal interactions
Abstract In many systems, including sedimenting particles and bird flocks, interactions do not derive from a potential and are generally non-reciprocal, meaning that they do not obey the action–reaction principle. As a result, one cannot define a conventional energy function or use analytical and numerical tools that rely on it. Here we address this limitation by constructing a Hamiltonian with auxiliary degrees of freedom that, under a constraint, generates the original non-reciprocal dynamics.
Forschungsportal der TU Dresden
Active fluids display spontaneous turbulentlike flows known as active turbulence. Recent work revealed that these flows have universal features, independent of the material properties and of the presence of topological defects. However, the differences between defect-laden and defect-free active turbulence remain largely unexplored. Here, by means of large-scale numerical simulations, we show that defect-free active nematic turbulence can undergo dynamical arrest.
Discontinuous transition to active nematic turbulence - Nature Communications
Abstract Active fluids exhibit chaotic flows at low Reynolds number known as active turbulence. Whereas the statistical properties of the chaotic flows are increasingly well understood, the nature of the transition from laminar to turbulent flows as activity increases remains unclear. Here, through simulations of a minimal model of unbounded and defect-free active nematics, we find that the transition to active turbulence is discontinuous.
Capillary interactions drive the self-organization of bacterial colonies
Many bacteria inhabit thin water layers on solid surfaces. These thin films occur both naturally—in soils, on hosts and on textiles—and in the laboratory on agar hydrogels. In these environments, cells experience capillary forces, but it is unclear how these forces shape bacterial collective behaviour. Here we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another.
Capillary interactions drive the self-organization of bacterial colonies - Nature Physics
Abstract Many bacteria inhabit thin water layers on solid surfaces. These thin films occur both naturally—in soils, on hosts and on textiles—and in the laboratory on agar hydrogels. In these environments, cells experience capillary forces, but it is unclear how these forces shape bacterial collective behaviour. Here we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another.
Nonlinear Spontaneous Flow Instability in Active Nematics
Active nematics exhibit spontaneous flows through a well-known linear instability of the uniformly aligned quiescent state. Here, we show that even a linearly stable uniform state can experience a nonlinear instability, resulting in a discontinuous transition to spontaneous flows. In this case, quiescent and flowing states may coexist.
Frictiotaxis underlies focal adhesion-independent durotaxis - Nature Communications
Abstract Cells move directionally along gradients of substrate stiffness — a process called durotaxis. In the situations studied so far, durotaxis relies on cell-substrate focal adhesions to sense stiffness and transmit forces that drive directed motion. However, whether and how durotaxis can take place in the absence of focal adhesions remains unclear. Here, we show that confined cells can perform durotaxis despite lacking focal adhesions.
Local polar order controls mechanical stress and triggers layer formation in Myxococcus xanthus colonies - Nature Communications
Abstract Colonies of the social bacterium Myxococcus xanthus go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to survive starvation. The biological pathways that control the decision to form a fruiting body have been studied extensively. However, the mechanical events that trigger the creation of multiple cell layers and give rise to droplet formation remain poorly understood.
Local polar order controls mechanical stress and triggers layer formation in Myxococcus xanthus colonies
Colonies of the social bacterium Myxococcus xanthus go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to survive starvation. The biological pathways that control the decision to form a fruiting body have been studied extensively. However, the mechanical events that trigger the creation of multiple cell layers and give rise to droplet formation remain poorly understood.
Buckling by disordered growth
Abstract Buckling instabilities driven by tissue growth underpin key developmental events such as the folding of the brain. Tissue growth is disordered due to cell-to-cell variability, but the effects of this variability on buckling are unknown. Here, we analyze what is perhaps the simplest setup of this problem: the buckling of an elastic rod with fixed ends driven by spatially varying, yet highly symmetric growth.
Optogenetic generation of leader cells reveals a force–velocity relation for collective cell migration - Nature Physics
Abstract During development, wound healing and cancer invasion, migrating cell clusters feature highly protrusive leader cells at their front. Leader cells are thought to pull and direct their cohort of followers, but whether their local action is enough to guide the entire cluster, or if a global mechanical organization is needed, remains controversial.
Capillary interactions drive the self-organization of bacterial colonies
Abstract Many bacteria inhabit thin layers of water on solid surfaces both naturally in soils or on hosts or textiles and in the lab on agar hydrogels. In these environments, cells experience capillary forces, yet an understanding of how these forces shape bacterial collective behaviors remains elusive. Here, we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another.
How to bridge the gap between theory and experiments in biological physics - Nature Physics
Creating a common culture and language for successful collaboration across disciplines benefits both researchers and scientific discovery. Then another PhD student in the room — a theorist — intervened. The theorist had noticed that the dynamics of tissue adhesion and de-adhesion presented by the experimentalist were reminiscent of the processes of wetting and de-wetting familiar from fluid dynamics.
Curvature induces active velocity waves in rotating spherical tissues - Nature Communications
Mammary cell spheroid culture and immunofluorescence staining MCF10A cells were purchased from ATCC and cultured in a DMEM/F12 medium (Invitrogen, 11965-118) supplemented with 20 ng/ml epidermal growth factor (Peprotech, AF-100-15), 5% horse serum (Invitrogen, 16050-122), 100 ng/ml cholera toxin (Sigma, C-8052), 0.5 μg/ml hydrocortisone (Sigma, H-0888), 10 μg/ml insulin (Sigma, I-1882) and 1% penicillin and streptomycin (Thermo Fisher, 15140122).
Stiffness-dependent active wetting enables optimal collective cell durotaxis - Nature Physics
Abstract The directed migration of cellular clusters enables morphogenesis, wound healing and collective cancer invasion. Gradients of substrate stiffness direct the migration of cellular clusters in a process called collective durotaxis, but the underlying mechanisms remain unclear. Here we unveil a connection between collective durotaxis and the wetting properties of cellular clusters. We show that clusters of cancer cells dewet soft substrates and wet stiff ones.
Journal of Physics A: Mathematical and Theoretical
Active matter is driven internally by its own constituents, be they molecular motors, cells, animals, or artificial self-propelled particles. As a result, active fluids exhibit striking phenomena such as spontaneous flows without external driving [1, 2], turbulence at low Reynolds numbers [3], and phase separation of repulsive particles [4]. These distinctive phenomena arise from activity-induced bulk instabilities. Very often, however, active fluids form finite droplets.
Active Turbulence
Annual Review of Condensed Matter Physics Vol.
Active phase separation by turning towards regions of higher density
Abstract Studies of active matter, from molecular assemblies to animal groups, have revealed two broad classes of behaviour: a tendency to align yields orientational order and collective motion, whereas particle repulsion leads to self-trapping and motility-induced phase separation. Here we report a third class of behaviour: orientational interactions that produce active phase separation.
Topological defects promote layer formation in Myxococcus xanthus colonies
Abstract The soil bacterium Myxococcus xanthus lives in densely packed groups that form dynamic three-dimensional patterns in response to environmental changes, such as droplet-like fruiting bodies during starvation1. The development of these multicellular structures begins with the sequential formation of cell layers in a process that is poorly understood2. Here, using confocal three-dimensional imaging, we find that motile, rod-shaped M.
Universal scaling of active nematic turbulence
Abstract A landmark of turbulence is the emergence of universal scaling laws, such as Kolmogorov’s E(q) ~ q−5∕3 scaling of the kinetic energy spectrum of inertial turbulence with the wavevector q. In recent years, active fluids have been shown to exhibit turbulent-like flows at low Reynolds number. However, the existence of universal scaling properties in these flows has remained unclear.
Nonuniform growth and surface friction determine bacterial biofilm morphology on soft substrates
Technical advances have given rise to a different way of looking at the evolution of cells: perhaps cell types are evolutionary units in their own right, with their own phylogeny.
Active wetting of epithelial tissues
Abstract Development, regeneration and cancer involve drastic transitions in tissue morphology. In analogy with the behaviour of inert fluids, some of these transitions have been interpreted as wetting transitions. The validity and scope of this analogy are unclear, however, because the active cellular forces that drive tissue wetting have been neither measured nor theoretically accounted for.
Show More
loading
Actions
Is this you?
As a journalist, you can create a free Muck Rack account to customize your profile, list your contact preferences, and upload a portfolio of your best work.Get in touch with Ricard
Contact Ricard, search articles and posts on X, monitor coverage, and track replies from one place.
Learn more about Muck Rack