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DTSTART;TZID=America/New_York:20220210T130000
DTEND;TZID=America/New_York:20220210T143000
DTSTAMP:20260415T192001
CREATED:20230824T172419Z
LAST-MODIFIED:20240304T083923Z
UID:10001307-1644498000-1644503400@cmsa.fas.harvard.edu
SUMMARY:Active Matter Controlling Epithelial Dynamics
DESCRIPTION:Abstract: My lab is interested in the active and adaptive materials that underlie control of cell shape.  This has centered around understanding force transmission and sensing within the actin cytoskeleton.  I will first review our current understanding of the types of active matter that can be constructed by actin polymers.  I will then turn to our recent experiments to understand how Cell shape changes in epithelial tissue.  I will describe the two sources of active stresses within these tissues\, one driven by the cell cycle and controlling cell-cell stresses and the other controlled by cell-matrix signaling controlling motility.  I will then briefly describe how we are using optogenetics to locally control active stresses to reveal adaptive and force-sensitive mechanics of the cytoskeletal machinery. Hopefully\, I will convince you that recent experimental and theoretical advances make this a very promising time to study this quite complicated form of active matter.
URL:https://cmsa.fas.harvard.edu/event/active-matter-controlling-epithelial-dynamics/
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-02.10.22-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220127T130000
DTEND;TZID=America/New_York:20220127T143000
DTSTAMP:20260415T192001
CREATED:20230824T171841Z
LAST-MODIFIED:20240304T083455Z
UID:10001306-1643288400-1643293800@cmsa.fas.harvard.edu
SUMMARY:Learning to School in the presence of hydrodynamic interactions
DESCRIPTION:Abstract: Fluids pervade complex systems\, ranging from fish schools\, to bacterial colonies and nanoparticles in drug delivery. Despite its importance\, little is known about the role of fluid mechanics in such applications. Is schooling the result of vortex dynamics synthesized by individual fish wakes or the result of behavioral traits? Is fish schooling energetically favorable?  I will present multifidelity computational studies of collective swimming in 2D and 3D flows. Our studies demonstrate that classical models of collective swimming (like the Reynolds model) fail to maintain coherence in the presence of long-range hydrodynamic interactions. We demonstrate in turn that collective swimming can be achieved through reinforcement learning. We extend these studies to 2D and 3D viscous flows governed by the Navier Stokes equations. We examine various hydrodynamic benefits with a progressive increase of the school size and demonstrate the importance of controlling the vorticity field generated by up to 300 synchronized swimmers.
URL:https://cmsa.fas.harvard.edu/event/learning-to-school-in-the-presence-of-hydrodynamic-interactions/
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Active-Matter-Seminar-01.27.2022-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211202T131500
DTEND;TZID=America/New_York:20211202T143000
DTSTAMP:20260415T192001
CREATED:20240213T113157Z
LAST-MODIFIED:20240304T084850Z
UID:10002504-1638450900-1638455400@cmsa.fas.harvard.edu
SUMMARY:Hydrodynamics and multi-scale order in confluent epithelia
DESCRIPTION:Abstract: In this talk I will review our ongoing theoretical and experimental efforts toward deciphering the hydrodynamic behavior of confluent epithelia. The ability of epithelial cells to collectively flow lies at the heart of a myriad of processes that are instrumental for life\, such as embryonic morphogenesis and wound healing\, but also of life-threatening conditions\, such as metastatic cancer. Understanding the physical origin of these mechanisms requires going beyond the current hydrodynamic theories of complex fluids and introducing a new theoretical framework\, able to account for biomechanical activity as well as for scale-dependent liquid crystalline order.
URL:https://cmsa.fas.harvard.edu/event/hydrodynamics-and-multi-scale-order-in-confluent-epithelia/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211111T130000
DTEND;TZID=America/New_York:20211111T143000
DTSTAMP:20260415T192001
CREATED:20240213T112818Z
LAST-MODIFIED:20240304T084803Z
UID:10002501-1636635600-1636641000@cmsa.fas.harvard.edu
SUMMARY:Nonreciprocal matter: living chiral crystals
DESCRIPTION:Abstract: Active crystals are highly ordered structures that emerge from the nonequilibrium self-organization of motile objects\, and have been widely studied in synthetic and bacterial active matter. In this talk\, I will describe how swimming sea star embryos spontaneously assemble into chiral crystals that span thousands of spinning organisms and persist for tens of hours. Combining experiment\, hydrodynamic theory\, and simulations\, we demonstrate that the formation\, dynamics\, and dissolution of these living crystals are controlled by the natural development of the embryos. Remarkably\, due to nonreciprocal force and torque exchange between the embryos\, the living chiral crystals exhibit self-sustained oscillations with dynamic signatures recently predicted to emerge in materials with odd elasticity.
URL:https://cmsa.fas.harvard.edu/event/nonreciprocal-matter-living-chiral-crystals/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211028T130000
DTEND;TZID=America/New_York:20211028T143000
DTSTAMP:20260415T192001
CREATED:20240213T112644Z
LAST-MODIFIED:20240304T084647Z
UID:10002498-1635426000-1635431400@cmsa.fas.harvard.edu
SUMMARY:Drivers of Morphological Complexity
DESCRIPTION:Abstract: During development\, organisms interact with their natural habitats while undergoing morphological changes\, yet we know little about how the interplay between developing systems and their environments impacts animal morphogenesis. Cnidaria\, a basal animal lineage that includes sea anemones\, corals\, hydras\, and jellyfish\, offers unique insight into the development and evolution of morphological complexity.  In my talk\, I will introduce our research on “ethology of morphogenesis\,” a novel concept that links the behavior of organisms to the development of their size and shape at both cellular and biophysical levels\, opening new perspectives about the design principle of soft-bodied animals. In addition\, I will discuss a fascinating feature of cnidarian biology. For humans\, our genetic code determines that we will grow two arms and two legs. The same fate is true for all mammals. Similarly\, the number of fins of a fish or legs and wings of an insect is embedded in their genetic code. I will describe how sea anemones defy this rule. \nReferences\nAnniek Stokkermans\, Aditi Chakrabarti\, Ling Wang\, Prachiti Moghe\, Kaushikaram Subramanian\, Petrus Steenbergen\, Gregor Mönke\, Takashi Hiiragi\, Robert Prevedel\, L. Mahadevan\, and Aissam Ikmi. Ethology of morphogenesis reveals the design principles of cnidarian size and shape development. bioRxiv 2021.08.19.456976 \nIkmi A\, Steenbergen P\, Anzo M\, McMullen M\, Stokkermans M\, Ellington L\, and Gibson M (2020). Feeding-dependent tentacle development in the sea anemone Nematostella vectensis. Nature communications\, Sept 02; 11:4399 \nHe S\, Del Viso F\, Chen C\, Ikmi A\, Kroesen A\, Gibson MC (2018). An axial Hox code controls tissue segmentation and body patterning in Nematostella vectensis. Science\, Vol. 361\, Issue 6409\, pp. 1377-1380.\nIkmi A\, McKinney SA\, Delventhal KM\, Gibson MC (2014). TALEN and CRISPR/Cas9 mediated genome editing in the early-branching metazoan Nematostella vectensis. Nature communications. Nov 24; 5:5486.
URL:https://cmsa.fas.harvard.edu/event/drivers-of-morphological-complexity/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211014T130000
DTEND;TZID=America/New_York:20211014T143000
DTSTAMP:20260415T192001
CREATED:20240213T113426Z
LAST-MODIFIED:20240304T084942Z
UID:10002506-1634216400-1634221800@cmsa.fas.harvard.edu
SUMMARY:Stochastic PDE as scaling limits of interacting particle systems
DESCRIPTION:Abstract: Interacting particle models are often employed to gain understanding of the emergence of macroscopic phenomena from microscopic laws of nature. These individual-based models capture fine details\, including randomness and discreteness of individuals\, that are not considered in continuum models such as partial differential equations (PDE) and integral-differential equations. The challenge is how to simultaneously retain key information in microscopic models as well as efficiency and robustness of macroscopic models. In this talk\, I will illustrate how this challenge can be overcome by elucidating the probabilistic connections between models of different levels of detail. These connections explain how stochastic partial differential equations (SPDE) arise naturally from particle models. \nI will also present some novel scaling limits including SPDE on graphs and coupled SPDE. These SPDE not only interpolate between particle models and PDE\, but also quantify the source and the order of magnitude of stochasticity. Scaling limit theorems and duality formulas are obtained for these SPDE\, which connect phenomena across scales and offer insights about the genealogies and the time-asymptotic properties of the underlying population dynamics.
URL:https://cmsa.fas.harvard.edu/event/stochastic-pde-as-scaling-limits-of-interacting-particle-systems/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210930T130000
DTEND;TZID=America/New_York:20210930T143000
DTSTAMP:20260415T192001
CREATED:20230824T171544Z
LAST-MODIFIED:20240304T084438Z
UID:10001305-1633006800-1633012200@cmsa.fas.harvard.edu
SUMMARY:Cytoskeletal Energetics and Energy Metabolism
DESCRIPTION:Abstract: Life is a nonequilibrium phenomenon. Metabolism provides a continuous flux of energy that dictates the form and function of many subcellular structures. These subcellular structures are active materials\, composed of molecules which use chemical energy to perform mechanical work and locally violate detailed balance. One of the most dramatic examples of such a self-organizing structure is the spindle\, the cytoskeletal based assembly which segregates chromosomes during cell division. Despite its central role\, very little is known about the nonequilibrium thermodynamics of active subcellular matter\, such as the spindle. In this talk\, I will describe ongoing work from my lab aimed at understanding the flows of energy which drive the nonequilibrium behaviors of the cytoskeleton in vitro and in vivo.
URL:https://cmsa.fas.harvard.edu/event/cytoskeletal-energetics-and-energy-metabolism/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210923T130000
DTEND;TZID=America/New_York:20210923T143000
DTSTAMP:20260415T192001
CREATED:20240213T112248Z
LAST-MODIFIED:20240304T084241Z
UID:10002493-1632402000-1632407400@cmsa.fas.harvard.edu
SUMMARY:The many phases of a cell
DESCRIPTION:Abstract: I will begin by introducing an emerging paradigm of cellular organization – the dynamic compartmentalization of biochemical pathways and molecules by phase separation into distinct and multi-phase condensates. Motivated by this\, I will discuss two largely orthogonal problems\, united by the theme of phase separation in multi-component and chemically active fluid mixtures. \n1. I will propose a theoretical model based on Random-Matrix Theory\, validated by phase-field simulations\, to characterizes the rich emergent dynamics\, compositions\, and steady-state properties that underlie multi-phase coexistence in fluid mixtures with many randomly interacting components. \n2. Motivated by puzzles in gene-regulation and nuclear organization\, I will propose a role for how liquid-like nuclear condensates can be organized and regulated by the active process of RNA synthesis (transcription) and RNA-protein coacervation. Here\, I will describe theory and simulations based on a Landau formalism and recent experimental results from collaborators.
URL:https://cmsa.fas.harvard.edu/event/the-many-phases-of-a-cell/
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210902T130000
DTEND;TZID=America/New_York:20210902T143000
DTSTAMP:20260415T192001
CREATED:20240213T112100Z
LAST-MODIFIED:20240304T084111Z
UID:10002491-1630587600-1630593000@cmsa.fas.harvard.edu
SUMMARY:Eppur si muovono: rotations in active matter
DESCRIPTION:Abstract: Living matter relies on the self organization of its components into higher order structures\, on the molecular as well as on the cellular\, organ or even organism scale. Collective motion due to active transport processes has been shown to be a promising route for attributing fascinating order formation processes on these different length scales. Here I will present recent results on structure formation on actively transported actin filaments on lipid membranes and vesicles\, as well as the cell migration induced structure formation in the developmental phase of mammary gland organoids. For both systems spherical structures with persistent collective rotations are observed.
URL:https://cmsa.fas.harvard.edu/event/eppur-si-muovono-rotations-in-active-matter/
CATEGORIES:Active Matter Seminar
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