WPI: Graduate Studies & Enrollment

WPI: Graduate Studies & Enrollment http://www.socialweb.net/Clients/WPI/gradfull.lasso Calendar of Events en-us Copyright 2010, Social Web http://blogs.law.harvard.edu/tech/rss 60 Social Web webmaster@socialweb.net (Troy B. Thompson) Tue, 09 Feb 2010 09:57:38 GMT Mon, 01 Feb 2010 14:31:38 GMT Phyiscs Faculty Candidate, "Forces in Collective Cell Motion," by Dr. Thomas Angelini, Harvard University (Fri, Feb 12) http://www.socialweb.net/Clients/WPI/gradfull.lasso?id=105257 http://www.socialweb.net/Clients/WPI/gradfull.lasso?id=105257#2010-02-12-16:00:00 etuzel@wpi.edu 4:00 PM-5:00 PM, WPI: Olin Hall, 10, 100 Institute Road, Worcester, MA Individual living cells generate forces and direct their motion in well known ways. For example, planktonic bacteria swim through fluids by rapidly turning their flagella, and individual tissue cells migrate across surfaces in a cyclic process of expansion, adhesion, and retraction. These canonical types of motion, however, are not characteristic of cells within large, dense aggregates, such as bacterial colonies or the tissues of complex organisms. In this talk I will discuss tools and concepts of condensed matter physics that I have adapted to study the collectively generated forces that control multi-cellular motion within enormous cell aggregates. I will present research on bacterial biofilms, showing how they can spread by generating molecular gradients throughout the colony. I will also discuss collective motion within two-dimensional confluent sheets of mammalian tissue cells, showing how sub-cellular motions as well as multi-cellular forces, transmitted across long distances, each influence collective migration in different ways. Refreshments will be served in Olin Hall 118 at 3:30 p.m. Sponsored by: WPI Physics Department, Dr. Erkan Tuzel. Cost: FREE Mon, 01 Feb 2010 14:31:38 GMT Physics Faculty Candidate, "Collective motion and density fluctuations in bacterial colonies" by Dr. Hepeng Zhang, University of Texas at Austin (Mon, Feb 15) http://www.socialweb.net/Clients/WPI/gradfull.lasso?id=105209 http://www.socialweb.net/Clients/WPI/gradfull.lasso?id=105209#2010-02-15-16:00:00 etuzel@wpi.edu 4:00 PM-12:00 AM, WPI: Olin Hall, 107, 100 Institute Road, Worcester, MA The emergence of collective motion such as in bird flocks, fish schools, and insect swarms is a ubiquitous self-organization phenomenon. Such collective behavior plays an important role in a range of problems, such as spreading of diseases in animal or fish groups. Current models have provided a qualitative understanding of collective motion, but progress in quantitative modeling is hindered by the lack of experimental data. Here we examine a model microscopic system, where we are able to measure simultaneously the positions, velocities, and orientations of up to a thousand bacteria (wild-type Bacillus subtilis) in a colony. The motile bacteria form closely-packed dynamic clusters within which they move cooperatively. Physical dimensions of clusters scale with the square-root of their sizes, defined as the number of the constituent bacteria. Cluster size exhibits a power-law distribution truncated by an exponential tail, and the probability of finding large clusters grows markedly as bacterial density increases. Mobile clusters cause anomalous fluctuations in bacterial density, as found in mathematical theories and numerical models. Our results demonstrate that bacteria are an excellent system to study general phenomena of collective motion. Refreshments will be served in Olin Hall 118 at 3:30 P.M. Sponsored by: WPI Physics Department, Dr. Erkan Tuzel. Cost: FREE Fri, 29 Jan 2010 20:16:59 GMT