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January 28, 2014

January 30 Colloquium

Kun Zhao, University of California, Los Angeles

From Colloids to Bacteria:Anisotropy in Self-Organizing Systems at the Mesoscopic Scale

Abstract:  Many complex mesoscopic systems, ranging from inorganic colloids to active biological cells, exhibit a rich variety of pattern-forming behavior. In this talk, I will show you how anisotropy in two model systems, anisotropic shaped colloids and bacterial communities, affect complex pattern formation. During the directed self-assembly of colloidal systems, shape anisotropy can greatly influence resulting structures. We have developed a technique called roughness controlled depletion attraction which allows us to probe the phase space of 2D Brownian systems for a variety of anisotropic shapes such as triangles, squares, and other polygons. We have discovered several unanticipated effects, such as local symmetry breaking in a triatic liquid crystal phase of uniform triangles. Anisotropy also plays a large role in the formation of bacterial communities called biofilms. Biofilms are a major human health hazard as well as being an impediment in many industrial and medical settings. By using condensed matter techniques, we present for the first time the dynamics of colony formation at early stages of biofilm development for Pseudomonas aeruginosa. We found that Pseudomonas aeruginosa does not follow an isotropic random walk as commonly assumed, but instead obeys a new form of polysaccharide-guided dynamics such that the distribution of surface.

Host: Raghuveer Parthasarathy

January 23, 2014

January 23 Colloquium

Liam Fitzpatrick, Stanford University

Effective Field Theory and the Emergence of New Dynamics

I describe applications of Effective Field Theory (EFT) to a broad range of scenarios where novel physics has been observed but the details remain poorly constrained. I discuss how EFT allows one to simplify and organize existing models, as well as providing an efficient framework for envisioning and parameterizing general possibilities in a more model-independent manner. Applications covered will be inflation in the early universe, experiments looking for direct detection of dark matter, and novel phases in superconducting metals.

January 16, 2014

January 16 Colloquium

Jay Wacker, SLAC National Laboratory

The Search For New Physics in the LHC Age

The first run of the LHC has just completed and the first set of analyses have just come out. I will review the state of searches for new physics at the LHC and give interpretations of the results. I will focus on the interplay between the discovery of the Higgs boson and the implications for supersymmetric extensions of the Standard Model.

January 9, 2014

January 9 Colloquium

Megan McClean, Princeton University

Elucidating Principles of Biological Signal Processing Using Microfluidic and Optogenetic Tools

Biological networks, like electrical circuits, take specific inputs (nutrient availability, stress, hormones) and convert them into appropriate outputs (transcriptional responses, metabolic remodeling). Electrical engineers uncover the inner workings of such circuits by measuring the transfer function between input voltage and output voltage. However, unlike electrical engineers, biologists are more limited in the input signals they can generate to interrogate such networks. We are developing microfluidic and optogenetic tools to generate dynamic inputs to interrogate and control natural and synthetic biological networks. In this talk I will discuss our use of microfluidics to dissect the mechanisms and kinetics of signaling in stress response networks in the budding yeast Saccharomyces cerevisiae. In addition, I will discuss our recent efforts to develop real-time optogenetic control of protein concentration as a tool for manipulating biological networks.

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