List of Events
MRSEC Seminars are normally held at 4:00 p.m. in Abelson 229, unless otherwise noted.
Find Abelson-Bass-Yalem building on the interactive map.
Thursday, November 20, 2014
Speaker: Guillaume Duclos, Institute Curie
Title: Nematic order and defect dynamics in a fibroblast tissue
Abstract: We study the emergence of a nematic order in a two-dimensional tissue of apolar elongated fibroblast cells. Cells are initially very motile and the monolayer is characterized by anomalous density fluctuations, a signature of far-from-equilibrium systems. As the cell density increases because of proliferation, the cells align with each other forming large oriented domains while, at the same time, the cellular movements and the density fluctuations freeze. Topological defects that are characteristic of nematic phases remain trapped at long times thereby preventing the development of infinite domains.
I will present results on the dynamics of these defects in nematic tissues and on the collective cellular motion resulting from their migration. A second part of the talk will deal with the effect of confinement on such nematic tissues. In particular, experiments performed in cross-shaped patterns show that in the situation of two competing populations, both the number of cells and the degree of alignment impact the final orientation.
Host: Z. Dogic
Friday, November 21, 2014
Room: Shapiro Campus Center, Brandeis University
MRSEC On-Campus Retreat
Monday, November 24, 2014
Room: Abelson 229, Brandeis University
Speaker: Jayson Paulose, Dept. of Physics, Leiden University
Title: Topological modes bound to lattice dislocations in mechanical metamaterials
Abstract: The mechanical rigidity of frameworks -- nodes connected by springs or rigid bars -- underlies the structural integrity of bridges, the response of granular materials, and the design of metamaterials with unusual mechanical properties. A fundamental question governing rigidity is the existence of soft modes: motions that do not significantly stretch or compress the constituent elements of the structure. We demonstrate a novel way to introduce soft modes at desired locations in a metamaterial, by exploiting the properties of a recently introduced class of topological metamaterials. These are special periodic frameworks which exhibit localized edge modes, analogous to the electronic edge states of topological insulators. We show that dislocations in such metamaterials are associated with soft modes of topological origin. The existence of the modes is determined by the interplay between two Berry phases -- the Burgers vector of the dislocation and a topological "polarization" characterizing the underlying lattice. Simple prototypes built out of triangular plates joined by hinges provide a visual demonstration of these modes.
Host: Z. Dogic
Wednesday, December 17, 2014
Room: Abelson 307, Brandeis University
Executive Committee Meeting