Speaker: Prof. Tamas Vicsek
From: Biological Physics Department, Eotvos University, Budapest, Hungary
Date/Room/Time: Tuesday, November 9, 2004 / 129 DeBartolo Hall/ 4-5 PM

Tea begins at 3:30 PM in Room 257 of Hurley Hall

Title: Two distant examples for motion in life: oscillatory nuclear migration and the propagation of Mexican waves

Abstract:
i) A novel assay based on micro patterning and time-lapse microscopy has been developed for the study of nuclear migration dynamics in cultured mammalian cells. When cultured on 10-20-µm wide adhesive stripes, the motility of C6 glioma and primary mouse fibroblast cells is diminished. Nevertheless, nuclei perform an unexpected auto-reverse motion: when a migrating nucleus approaches the leading edge, it decelerates, changes the direction of motion, and accelerates to move toward the other end of the elongated cell. The observed nuclear movement requires a functioning microtubular system, as revealed by experiments disrupting the main cytoskeletal components with specific drugs. On the basis of our results, we argue that auto-reverse nuclear migration is due to forces determined by the interplay of microtubule dynamics and the changing position of the microtubule organizing center as the nucleus reaches the leading edge.
ii) Can we reliably predict and quantitativly describe how large groups of people behave? Here we discuss an emerging approach to this problem which is based on the quantitative methodsof statistical physics. We demonstrate that in cases when the interactions between the members of a group are relatively well defined (e.g, pedestrian traffic, synchronization, panic, etc) the corresponding models reproduce relevant aspectsof the observed phenomena. The specific case to be discussed in more detail is that of the waves produced by crowds at large sporting events. Our models allow the prediction of crowd behaviour even in cases when experimental methods are obviously not applicable and, thus, are expected to be useful in assessing the level of security in situations involving large groups of excited people.