Center for Fluid Mechanics
And
The Fluids, Thermal And Chemical Processes Group
Of
The Division Of Engineering
Seminar Series
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD | |
in the Laboratory and in the Ocean Using Digital Holography | |
Abstract: The presentation introduces several examples where recent advances in digital holography enable measurements of flow structure and particle dynamics at unprecedented resolution. In the laboratory, digital holographic microscopy is being implemented to study the near-wall flow of a turbulent boundary layer over a smooth wall. The sample volume covers the viscous sublayer, buffer layer and lower portion of logarithmic layer. Resolution is sufficient for studying buffer layer structures and for measuring instantaneous wall shear stress distributions from velocity gradients in the viscous sublayer. Conditional sampling based on local shear stress magnitude identifies characteristic 3-D structures that generate extreme wall stress events as they lift away from the wall and associated length scales.
High-speed holographic cinematography is being used for studying swimming behavior of several marine organisms. The velocity field around a 1 mm copepod has a recirculating pattern in the copepod's frame of reference, which is caused by the combined effects of sinking and a propulsive force generated by the feeding appendages. Using Stokeslets to model this flow, it is possible to estimate the excess weight of the copepod and the propulsive force generated by its feeding appendages. The low Reynolds numbers associated with motion of 0.1 mm naupleus causes it to recoil as it brings its swimming appendages forward to propel itself. Characteristics of the generally helical but complex swimming of 10-30 ?m dinoflagellates vary with introduction of prey into the sample volume. The presentation will conclude with introduction of a submersible, free drifting oceanic holography system. Data from recent deployments display behavior of and interactions among several organisms, such as a dinofalgellate escaping from a naupleus, and clouds of particles around swimming Appendictularians.
Brown Applied Mathematics Pattern Theory and Vision Seminar
Brown University, Providence, RI | |
Abstract: Our research challenges the status quo in protein science, which says that only proteins with a 3-dimensional structure can fulfill a function. Linus Pauling stated in 1946 "Answers to many basic problems of biology-nature of growth, mechanism of duplication of viruses and genes, action of enzymes, mechanism of physiological activity of drugs, hormones, and vitamins, structure and action of nerve and brain tissue-may lie in knowledge of molecular structure and intermolecular reactions". However, in recent years it has been shown that also unstructured or partially structured proteins also fulfill essential functions. Usually these proteins fold upon binding to their targeting protein and, in this way, are critical for mediating numerous regulatory events. My laboratory has identified a large number of these intrinsically unstructured protein or protein domains which are, significantly, particularly important in the brain. Our current efforts are focused on identifying and developing methods that will enable us to determine the 3-dimensional structure of these unstructured proteins. These structures are very different then usual protein structures, since they depend on populations of states, rather den defined distances. This, in turn, will allow us to elucidate the rules that govern their folding upon binding interaction and advance our understanding of this new paradigm of protein: protein interactions.
Brown Univeristy -- Division of Applied Mathematics
Transatlantic Seminar
PDE Seminar
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