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Join the Department of Mechanical Engineering for the 22nd annual James F. Bell Memorial Lecture in Continuum Mechanics. Frans Spaepen, the John C. and Helen F. Franklin Professor of Applied Physics at Harvard University, will present “Mechanical Properties of Colloidal Crystals.” The lecture begins at 3 p.m. in 210 Hodson Hall on Thursday, October 27. A reception will follow in the second floor lobby area of Hodson Hall.
Colloidal particles in suspension can form liquid, crystalline and glassy phases similar to those formed by atoms. Since the particles are “fat” (~1µm) and “slow” (~0.1s), they can be individually tracked in space and time by confocal microscopy. Dense colloidal systems therefore serve as “analog computers” to study the mechanics of crystals and glasses. Colloidal crystals and glasses have small (~ mPa) but non-zero elastic constants of largely entropic origin, which can be measured in a number of ways, for example from thermal fluctuations or variations in lattice constant. The non-zero stiffness of these phases creates elastic stress fields that can interact. This will be illustrated by observations of the nucleation and propagation of misfit dislocations during the epitaxial growth of colloidal single crystals. Nucleation and propagation of dislocations upon plastic deformation, such indentation, as well as their interaction with grain boundaries can be observed directly. By measuring the local strain fields in glasses, the Eshelby-like shear transformations that govern plastic deformation in these structures can be identified, and their dynamics can be observed directly.
Frans Spaepen is the John C. and Helen F. Franklin Professor of Applied Physics at Harvard University. He received his undergraduate degree in Metallurgical Engineering at the K.U. Leuven in 1971, and a PhD in Applied Physics from Harvard University in 1975. He joined the faculty of the Division of Applied Sciences at Harvard in 1977 as Assistant Professor, was appointed Associate Professor in 1981, and Full Professor in 1983. From 1990 till 1998 he was Director of the Harvard Materials Research Laboratory/Materials Research Science and Engineering Center. From 2002 to 2013 he was the Director of the Rowland Institute at Harvard. In 2008-9 he was Interim Dean of the School of Engineering and Applied Sciences and in 2009-10 Interim Director of Center for Nanoscale Systems. His research interests span a wide range of experimental and theoretical topics in materials science, such as amorphous metals and semiconductors (viscosity, diffusion, mechanical properties), the structure and thermodynamics of interfaces (crystal/melt, amorphous/crystalline semiconductors, grain boundaries), mechanical properties of thin films, the perfection of silicon crystals for metrological applications, and colloidal systems as models for the study of dynamics and defects in crystals and glasses.
Robert M. Nerem (Georgia Institute of Technology) presents “Regenerative Medicine: The Hype, the Hope, and the Future” as part of a special seminar hosted by the Department of Biomedical Engineering, the Institute for NanoBioTechnology, and the Translational Tissue Engineering Center.
Abstract: Although the underlying concepts of tissue engineering and regenerative medicine go back more than 75 years, the term tissue engineering actually was only “coined” in the 1980s. This was followed by the 1990s being the “go-go” years with stem cells emerging as a technology, an industry developing, and the term regenerative medicine beginning to be used. There also was a lot of hype, and following the turn of the century the field entered what might be called the “sobering” years, with private sector activity falling significantly even though the science continued to advance. The last decade, however, has all the marks of being “back to the future.” Advances in cell-based therapies have been fueled by advances in stem cell science and technology and the discovery of what is required to reprogram somatic cells into stem cells, known as induced pluripotent stem (iPS) cells. For cellular therapies, a key question is what is the mechanism of action? For a specific therapy, is the mechanism one of cell replacement or is it a paracrine effect? If the latter, is it possible that one could introduce the appropriate biological signals without the use of cells? In this case the discussion shifts from “my cell is better than your cell” to “my biological signals are better than yours.” Whatever the case, one of the “holy grails” is the neurodegenerative diseases/disorders and the repair/regeneration of the central nervous system. Instead of the mixture of hype and hope in the past, and with an aging population providing the threat of a “tsunami” of neural disorders, regenerative medicine offers the real possibility of cures to these diseases/disorders in the future.
The Johns Hopkins Department of Mechanical Engineering hosts the 23rd Annual James F. Bell Memorial Lecture in Continuum Mechanics. Subra Suresh, president-designate and Distinguished University Professor ad the Nanyang Technological University, will present “Study of Human Diseases at the Intersections of Engineering, Sciences, and Medicine.”