Bulletin of the American Physical Society
76th Annual Meeting of the Southeastern Section of APS
Volume 54, Number 16
Wednesday–Saturday, November 11–14, 2009; Atlanta, Georgia
Session HA: Nonequilibrium Materials Science: Theory, Simulation, and Experiment |
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Chair: Alan Dorsey, University of Florida Room: Brussels |
Friday, November 13, 2009 10:45AM - 11:15AM |
HA.00001: A Statistical Physicist Looks at Evolution and Ecology Invited Speaker: Biological evolution and ecology pose many questions that can be seen as involving large many-particle systems with complicated, nonlinear (and often poorly understood) interactions. Over the last two decades, this has inspired many statistical physicists to construct and study models in this interdisciplinary area. In this Colloquium I will discuss and compare the dynamics and community structures generated by two individual-based models of biological coevolution of interacting species that I have recently developed and studied with my students and collaborators. I will focus on fluctuations in the number of species (aka. diversity) and population size, probability distributions for species lifetimes and the duration of evolutionarily quiet periods, and comparisons of degree distributions for simulated food webs with data from real food webs. Finally, I will discuss our most recent results on a spatially extended generalization of one of these models. [Preview Abstract] |
Friday, November 13, 2009 11:15AM - 11:45AM |
HA.00002: Toward an understanding of non-equilibrium steady states Invited Speaker: Though non-equilibrium phenomena abound in nature, they are still only very poorly understood at a fundamental level. Even the study of nonequilibrium steady states, being the simplest generalizations of thermal equilibrium, is still in its early stages. However, investigations of simple model systems have revealed a wealth of unexpected behaviors which differ remarkably from our equilibrium-trained expectations. In my talk, I will discuss some distinguishing features of equilibrium and far-from-equilibrium statistical mechanics and provide a short overview of some recent approaches [1] towards a general classification of non-equilibrium steady states.\\[4pt] [1] R.K.P. Zia and B. Schmittmann, Journal of Statistical Mechanics P07012 (2007); online at stacks.iop.org/JSTAT/2007/P07012; cond-mat/0701763. [Preview Abstract] |
Friday, November 13, 2009 11:45AM - 12:15PM |
HA.00003: State variables in dense granular materials Invited Speaker: Granular materials are integral to many parts of our daily lives, from the coffee beans that fuel our mornings to the coal that fuels our power plants. Two related aspects of their dynamics are particularly striking: their ability to exhibit both solid-like and liquid-like behavior, and the presence of highly heterogeneous force chains in which the magnitude of the local stress varies widely over short distances. These distinctive behaviors are connected to the fact that granular materials are always out of equilibrium: first, because they are typically both driven and dissipative, but also because they remain in metastable states even when they aren't being driven. I will present recent results from several experiments ranging from the theoretically-motivated (the equilibration of state variables within a non-equilibrium system) to the practical (particle-segregation by size). The results of these experiments elucidate the complex behaviors which underlay granular dynamics, and provide a reason to hope that statistical physics might hold the keys to explaining the observed phenomena. [Preview Abstract] |
Friday, November 13, 2009 12:15PM - 12:45PM |
HA.00004: Physics of Age Related Macular Degeneration Invited Speaker: Age-related macular degeneration (AMD) is the leading cause of blindness beyond the age of 50 years. The most common pathogenic mechanism that leads to AMD is choroidal neovascularization (CNV). CNV is produced by accumulation of residual material caused by aging of retinal pigment epithelium cells (RPE). The RPE is a phagocytic system that is essential for renewal of photoreceptors (rods and cones). With time, incompletely degraded membrane material builds up in the form of lipofuscin. Lipofuscin is made of free-radical-damaged protein and fat, which forms not only in AMD, but also Alzheimer's disease, and Parkinson's disease. The study of lipofuscin formation and growth is important, because of their association with cellular aging. In this talk I will discuss a model of non-equilibrium cluster growth that we have developed for studying the formation and growth of lipofuscin in AMD [K.I. Mazzitello, C.M. Arizmendi, Fereydoon Family, H. E. Grossniklaus, Physical Review E (2009)]. I will also present an overview of our theoretical and computational efforts in modeling some other aspects of the physics of AMD, including CNV and the breakdown of Bruch's membrane [Ongoing collaboration with Abbas Shirinifard and James A. Glazier, Biocomplexity Institute and Department of Physics, Indiana University, Y. Jiang, Los Alamos, and Hans E. Grossniklaus, Department of Ophthalmology, Emory University]. [Preview Abstract] |
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