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Mechanical Engineering Home > Seminars > Fall 2003 Fall 2003 |
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ME/IE 8773-8774
Main Department Seminar
Host: Joachim V.R. Heberlein On The Detection and Real Time
Processing by Joseph (Pepe) A.C. Humphrey
Some arthropods detect odors by means of antennae attached to their heads. Examples include insects (moths) which are primarily land-based animals living in an aerobic environment, and crustaceans (crayfish and lobsters) which live in an aquatic environment. The odor plumes may consist of pheromones originating from a female moth to attract male moths, or from decomposing organic matter that feeds a lobster. The process of odor detection is multiscale, involving: a macro-scale plume (10 – 1000 m); the meso-scale antennae (10-1 – 10-3 m) on the animal’s body; the micro-scale sensilla (10 – 103 microns) on the antennae, where the chemo-receptor pore sites are located; and the nano-scale pore sites themselves (10 – 102 nm). While much is known about the characteristics of plumes, antennae, sensilla and receptor pores in their respective scale ranges, comparatively less has been said about the overlap between adjacent ranges where the “information transfer” takes place. There are many open questions, such as: How are the space- and time-characteristics of the chemical species in the far-field flow approaching the antennae affected by the animal’s body and the antennae themselves. How does the branched structure of an antenna interact with the near-field flow around it to enhance chemical species transport to a sensillum and, ultimately, chemical species detection at the receptor pore sites? Does the probability of arrival of an odor molecule at a receptor pore depend on three-dimensional Brownian motion in the fluid phase or on two-dimensional Brownian motion along the sensillum surface? What are the chemical kinetics of species adsorption and desorption in the receptor sites, and how do their time scales compare with other characteristic time scales associated with species convection and diffusion and overall neural system response? We present and discuss a physical-chemical model for odor plume detection that addresses some of these and related questions. We discuss possible mechanisms for odor-elicited anemotaxis in moths with emphasis on a cybernetic model system with two feedback loops that explains anemotactic orientation in flight based solely on the displacement of ground patterns as seen by the animal.
Joseph (Pepe) Humphrey joined the Department of Mechanical and Aerospace Engineering of the University of Virginia in the summer of 2000. He is the Wade Professor of Engineering and Applied Science and current Department Chairman. He has earned degrees in chemistry (Ingeniero Quimico Diplomado, Barcelona, Spain, 1970), chemical engineering (M.A.Sc., University of Toronto, Canada, 1973), mechanical engineering (Ph.D., Imperial College, London, U.K., 1977) and received the D.Sc.Eng, degree from London University in 1997. Between 1978 and 1995, Dr. Humphrey rose through the faculty ranks at the University of California at Berkeley. Subsequently he was Head of Aerospace and Mechanical Engineering at the University of Arizona and Dean of Engineering at Bucknell University. Dr. Humphrey's research and teaching interests revolve around the experimental and theoretical investigations of flow, heat and mass transfer phenomena. Prof. Humphrey has over 120 journal papers and is active in various professional societies including the American Society for Mechanical Engineers. He is the founder of the biennial International Symposia on the Mechanics of Plants, Animals and their Environments and a co-founder of the biennial International Symposia on Turbulent and Shear Flow Phenomena.
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