30 May 2012, h.15:00 - Sala 201 DEI/A

Abstract:

The binding of individual components to form aggregate structures is a ubiquitous phenomenon in physics, chemistry and material science. Nucleation events may be heterogeneous, where particles are attracted to an initial exogenous site or homogeneous where identical particles spontaneously cluster upon contact. Particle nucleation and cluster growth have been extensively studied in the past decades, often assuming infinitely large numbers of building blocks and unbounded cluster sizes. These assumptions led to the use of mass-action, mean field descriptions such as the well known Becker Doering equations.
In cellular biology, however, nucleation events often take place in confined spaces, with a finite number of components, so that discrete and stochastic effects must be taken into account.  In this talk we examine finite sized homogeneous nucleation by considering a fully stochastic master equation, solved via Monte-Carlo simulations and via analytical insight. We find striking differences between the mean cluster sizes obtained from our discrete, stochastic treatment and those predicted by mean field treatments.  We also consider heterogeneous nucleation stochastic treatments, first passage time results and possible applications to prion unfolding and clustering dynamics.

Biography:

Maria Rita D'Orsogna is an Associate Professor of the Mathematics Department at California State University, Northridge (CSUN). She received the Laurea degree in Physics from the University of Padova in 1996, the Master degree in Physics at the University of Maryland, College Park in 1998, and the Ph.D. in Physics at the University of California, Los Angeles, in 2003. In 1998-1999 she worked as analyst at IBM in Milan. Then, she was Research associate at the Chemistry Department of Caltech, Pasadena in 2003-2004, and then Research associate at the Mathematics Department of UCLA, during years 2004-2007. Her research interests are in the fields of statistical mechanics, mathematical modeling, computer simulations of biological and complex dynamical systems.
More details can be found at her personal webpage: http://www.csun.edu/~dorsogna/index.htm