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2010 Summer Meeting

2011 AAPT Summer Meeting
July 30-August 3, 2011
Omaha, Nebraska

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From Brownian Motion to Random Walks: Diffusion in the IPLS Class
  Location: SS 104
  Date: Tuesday, Aug.2
  Time: 2:15 PM -3:15 PM
  Author: Mark Reeves, George Washington University
  Co-Author(s): Carl Pearson , Rahul Simha , Robert Donaldson
  Abstract: Diffusion and entropy are very important for understanding biophysical processes at the cellular level, but students have and maintain very strong misconceptions about these two topics. We have developed a first-semester IPLS course, in which roughly 1/3 of the class time is dedicated to teaching statistical physics. Students are introduced to statistics by considering simple coins flips. We move on from these to large numbers of coins and flips per coin and thereby to a meaningful physical model by connecting to Java-based simulations of the random walk problem. The class discussions and simulations are complemented by laboratories in which diffusion, Brownian motion, and laser trapping are directly observed and quantitatively measured. From the measurements and in-class discussions, the connection is made between the microscopic model/observation and its macroscopic realization. That is we connect by modeling and experiment Brownian motion to diffusion. The same line of argument is used to establish the equipartition theorem in terms of observations of laser trapping and this is then extended to discussions of protein folding and membrane formation. In this way the entire suite of hydrophobic forces are shown to have their origin in statistical models for entropy in thermodynamics.
  Footnotes: This research is supported by the NSF/CCLI program. More information can be found at
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