Past Events

  • TODAY'S SEMINAR IS CANCELED Condensed Matter Seminar: "Let it rip: In vivo biomechanics studies of Hydra regeneration from tissue spheres"

    David Rittenhouse Laboratory, A6

    Eva-Marie Shoetz Collins, Swarthmore College


  • Condensed Matter Seminar: "Learning force fields from stochastic trajectories"

    David Rittenhouse Laboratory, A6

    Pierre Ronceray, Princeton University

    From nanometer-scale proteins to micron-scale colloidal particles, particles in biological and soft matter systems undergo Brownian dynamics: their deterministic motion due to the forces competes with the random diffusion due to thermal noise. In the absence of forces, all trajectories look alike: the key information characterizing the system's dynamics thus lies in its force field. However, reconstructing the force field by inspecting microscopy observations of the system's trajectory is a hard problem, for two reasons.

  • Condensed Matter Seminar: "Soft Matter Physics of the Evolution of Multi-Cellularity"

    David Rittenhouse Laboratory, A6

    Peter Yunker, Georgia Institute of Technology

    The evolution of multicellularity set the stage for an incredible increase in the diversity and complexity of life on Earth. The increase in biological complexity associated with multi-cellularity required parallel innovation in the mechanical properties of multi-cellular bodies. Though a cursory review of any multi-cellular organism provides an appreciation of this intertwining of biological and mechanical complexity, little is known about how such mechanical properties may have evolved.

  • Condensed Matter Seminar: "Physics and Applications of Mesoscopic Optics"

    David Rittenhouse Laboratory, A6

    Hui Cao, Yale University

    Random scattering of light, e.g., in paint, clouds, and biological tissue, is a common process of both fundamental interest and practical relevance. The interference of multiply scattered waves also leads to remarkable phenomena in mesoscopic physics such as Anderson localization and universal conductance fluctuations. In applications, optical scattering is the main obstacle to imaging or sending information through turbid media.

  • Condensed Matter Seminar: "The physical chemistry of natural selection: How can we explain the high yields and high rates of biochemical reactions?"

    David Rittenhouse Laboratory, A4

    Jean-Louis Sikorav (Ministère de l'Economie et des Finances)

    The goal of this seminar is to present the main findings of an ongoing inquiry of the foundations of biology (1). The purpose of this investigation is to describe the elements, the logic and the principles of biology, and to construct biological theories using the language and the methods employed in other disciplines. This work brings to the fore the existence of a unity of knowledge, also revealed through the study of the science of research shared by all disciplines (2).

  • Condensed Matter Seminar: "Long Term 3D Imaging by FIBSEM for Neurons and Cell Biology and Correlation to Cryo Fluorescence Microscopy"

    David Rittenhouse Laboratory, A4

    Harald Hess (Howard Hughes Medical Institute, Janelia Research Campus)

    3D Electron microscopy volume data can be acquired by a variety of approaches.  Focused Ion beam – scanning electron microscopy, FIBSEM, offers no limitation on section thickness, so that isotropic voxels with 8 nm or less sampling in x,y,z dimensions can be acquired.  This capability opens a new regime where entire cells can be imaged with 4 nm voxel sampling, thereby surpassing partial cell or section limitations to complete cell data.

  • Condensed Matter Seminar: "Wisdom of hives and mounds: collective problem solving by super-organisms"

    David Rittenhouse Laboratory, A4

    Lakshminarayanan Mahadevan (Harvard University)

    Social insects are capable of solving complex physiological problems using collective strategies. I will discuss our work on some of these problems  that include the physiology and morphogenesis of termite mounds, and  active mechanisms for ventilation, mechanical adaptation and  thermoregulation  in bee aggregates.

  • Condensed Matter Seminar: "Ideas on magma motion within the lithosphere: percolation, channelization, and stress-driven segregation"

    David Rittenhouse Laboratory, A4

    Mousumi Roy (University of New Mexico)

    Although we know that magma is generated by partial melting of rocks at depth, we have less of an understanding of the processes that transport magma from great depths (>100-150 km) into the shallower (20-0 km) crustal plumbing systems of volcanic zones.   I shall discuss how interstitial melt migrates via percolative flow, and ideas on how it eventually becomes focused and reorganized into networks.  Field and geochemical observations suggest that these networks are characterized by thermal and chemical disequilibrium between the magma and surrounding rock.  I

  • Condensed Matter Seminar: "Geometry and mechanics of feet and fins"

    David Rittenhouse Laboratory, A4

    Mahesh M. Bandi (Okinawa Institute of Science and Technology Graduate University)

    The stiffness of propulsive appendages, such as feet and fins, is important in locomotory function. In this talk, I show that curvature-induced stiffness is the common principle underlying the stiffness of both primate feet and rayed fish fins. We use mathematical models, physical models, and biological experiments to arrive at this conclusion. The principle is evident in a drooping dollar bill that significantly stiffens upon slightly curling it in the transverse direction.

  • Condensed Matter Seminar: "Structure and Topology of Band Structures in the 1651 Magnetic Space Groups"

    David Rittenhouse Laboratory, A4

    Ashvin Vishwanath (Harvard University)

    We describe a powerful theoretical approach to studying electronic band structures, which associates them with elements of a vector space. The set of consistent band structures in a space group can then be expanded in terms of a small set of basis vectors. We calculate the dimension of this vector space, and the necessary electron fillings to obtain band insulators in all magnetic space groups.