Complex Matter and Biophysics Seminar
From WolfWikis
Department of Physics
North Carolina State University
An approximately biweekly seminar and journal club series, jointly hosted by the Ade, Clarke/Bochinski, Daniels, Hallen, Riehn, and Weninger research groups. See CMB Seminar Instructions for organizational details.
To join the announcement list email mj2@lists.ncsu.edu with the subject line "subscribe cmb_seminar myname@ncsu.edu" or go to http://lists.ncsu.edu.
Organizers: Karen Daniels, Robert Riehn
Starting Fall 2008, students may sign up for a 1-credit course to obtain course credit for participating in the seminar series. The fall series will be held Tuesdays at 4pm in 315 Riddick.
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Summer 2008 Schedule
Special seminars irregularly scheduled during the summer months.
June 4
Brian Tighe (Leiden University)
Stress statistics in jammed matter
ABSTRACT: Athermal soft matter systems such as grains, foams, and emulsions display a jamming transition. A jammed system is capable of supporting an applied load, much like an elastic solid; below a critical packing density the system unjams and instead flows under loading. Thus packing density parameterizes the jamming transition much as temperature does an equilibrium phase transition.
How far can we push the analogy to equilibrium statistical mechanics in describing athermal systems? Almost twenty years ago, Edwards proposed that the statistical properties of a jammed system could be described by an ensemble of all jammed states consistent with the imposed boundary conditions. We investigate the consequences of this proposal for the statistics of local stresses -- e.g. contact forces -- in 2d jammed systems. In particular, we show that the probability of large local stresses decays generically as a Gaussian, rather than with the exponential form familiar from the canonical Boltzmann distribution. We verify our predictions within a simple statistical model satisfying all of the assumptions of the Edwards proposal using highly accurate numerics.
Host: Karen Daniels
August 4
4:00 & 4:30 pm, 314 Riddick (double-header) Tea/cookies/coffee beforehand in 415 Riddick
Erika Merschrod (Dept. of Chemistry, Memorial University, Newfoundland)
Hierarchical materials: bridging length scales in structure and properties
ABSTRACT: Biomaterials are often hierarchical in both the formation process and in eventual structure, leading to specialized properties that would not be achievable through compositional control alone. For example, bones achieve their large compressive strength while maintaining light weight by the appropriate blend of protein and mineral components in a complex structure spanning many orders of magnitude in size. I will present several examples of evidence for hierarchical process and structure from my lab, with general guidelines for exploiting the hierarchy inherent in proteins and minerals.
Kristin Poduska (Dept. of Physics and Physical Oceanography, Memorial University, Newfoundland)
A new approach to biocompatible composite materials
ABSTRACT: Coatings that mimic the composition of natural biomaterials have a wide range of potential medical applications. We have developed electrochemical methods to make bone-like mineral films as well as collagen membranes, and our current focus is to study the mineral-protein symbiosis involved in making composite membranes and coatings based on collagen and calcium phosphate. Through a combination of complementary characterization techniques, including Raman scattering spectroscopy and atomic force microscopy, we address details of coating composition, structure and formation.
Host: Karen Daniels