Colloquium Schedule

Spring 2015

Detection and Analysis of Individual Biological Structures at the Nanoscale

James Baker, Cornell University
Tue., Jan. 26, 2016, 4:30 PM in Science Center 128

In his 1959 lecture ‘There’s Plenty of Room at the Bottom,’ Richard Feynman posed an “invitation to enter a new field of physics,” and challenged the scientific community to expand their capabilities to observe, measure, and manipulate materials at the nanoscale. While recognition and manipulation have occurred at the nanoscale in biological systems since the origin of life, our ability to observe and characterize these interactions is still emerging. Today’s physicists continue to play a role in this progress, as the application of fundamental physical principals remains vital in the continued development of new measurement approaches for studying nanoscale systems. In this talk, I will discuss two experimental approaches to the detection and analysis of individual biological structures at the nanoscale: nanophotonic resonators and magnetic tweezers. The applications of such developments range from the study of fundamental biophysical interactions to the development of point-of-care medical diagnostics and beyond.

 

Identification of Plasma Fluctuations Using Fast Imaging

Adam Light, Earlham College
Thu., Jan. 28, 2016, 4:30 PM in Science Center 128

Fluctuations in magnetized plasmas are ubiquitous and complex. Although they often produce detrimental effects, like increasing heat and particle transport in fusion energy devices, fluctuations also provide a diagnostic opportunity. Identification of a fluctuation with a wave or instability gives detailed information about the properties of the underlying plasma. In addition to introducing plasma as a complex system, I will describe imaging measurements of coherent waves in a cylindrical plasma column. Visible light from Ar II line emission is collected at high frame rates (>50,000 frames/second!) using a fast digital camera. Experimental wave-dispersion-relations are constructed using imaging data alone, and can be compared directly with theoretical models. I will discuss the identification of both electron-drift waves and Kelvin-Helmholtz fluctuations, as well as imaging measurements of nonlinear mode coupling.

 

Using Stars to Study Galaxy Formation and Evolution

Aaron Grocholski, Louisiana State University
Tue., Mar. 23, 2016, 4:30 PM in Science Center 128

Studies of galaxy formation and evolution generally take one of two main approaches: survey the distant Universe or focus on nearby galaxies. The distant Universe provides myriad galaxies covering a vast range in physical properties, such as mass, luminosity, and structure. The drawback of these studies is that, with current technology, distant galaxies often span only a few tens of pixels on an image, thus leaving the subtle details of these galaxies unresolved. In contrast, the galaxies of the Local Group and other nearby galaxy groups give us a much smaller sample to study. Their proximity, however, allows us to resolve individual stars and thereby study the stellar populations of nearby galaxies at a level of detail that is not possible at large distances. In this talk I will discuss what information stars provide about their host galaxy and present some of the results from my research on galaxies in the nearby Universe.

 

Uncovering the Unbound Stellar Population in and Around the Milky Way

Lauren Campbell, Vanderbilt University
Mon., Mar. 28, 2016, 4:30 PM in Science Center 128

A significant fraction of a galaxy's light may come from a population of unbound stars, and this population can inform us about the dynamical state and stellar content of the galaxy. In galaxy clusters this unbound fraction is known as intracluster light (ICL), identified as a diffuse excess of light in the outskirts of the galaxy. ICL has been observed around distant galaxies and a similar intracluster stellar glow ought to exist around the Milky Way. We developed a technique to identify distant M-giants within the Sloan Digital Sky Survey (SDSS) based solely on color. Using this technique, we identified 700 candidate M-giant stars at intragroup distances, beyond 300 kpc, that we call intragroup stars (IGS). These IGS may constitute rare tracers of an underlying ICL population surrounding the Milky Way. One possible explanation for the origin of these IGS is that they were ejected from the center of the Galaxy through interactions with our supermassive black hole as hypervelocity stars (HVSs). There are only 18 confirmed HVSs and all are young, massive, B-type stars. We identify candidate HVSs from a sample of SDSS G- and K-dwarfs. Using the observed positions and velocities, we calculate the orbits of these candidates in order to determine their place of origin within the Galaxy. We find that nearly half of the candidates exceed their escape velocities with at least 98% probability and no candidate's orbit is consistent with a Galactic Center origin.

 

Making Model Cells to Study How Proteins Reshape Cell Membranes

Catherine Crouch, Swarthmore College
Fri., Apr. 22, 2016, 12:30 PM

Understanding how cells reshape themselves, and the roles that proteins play in that process, is an active area of current research by scientists across many disciplines. To understand the underlying physics and chemistry of such a complex cellular process requires developing simple model systems. This talk will describe progress toward optimizing a model system in which we can study the role of the M2 protein of influenza A in the reshaping processes required for virus budding. Specifically, the talk will present our optimization of the process of incorporating the protein into synthetic lipid vesicles, including the development of optical techniques for monitoring the incorporation process.

 

Accelerator Technology for Dark Matter Searches and Quantum Computing

Daniel Bowring, Fermi National Accelerator Laboratory
Mon., Apr. 25, 2016, 12:30 PM in Science Center 183

The accelerator complex at Fermi National Accelerator Laboratory creates, focuses, steers, and collides high-energy/intensity proton beams. The technology developed to accelerate and control energetic beams can sometimes find its way into other areas of research. For example, MRI magnets are now relatively cheap and stable because, in the 1970s, Fermilab had to develop the physics and engineering techniques required to build powerful magnets for steering energetic particle beams. In this talk, we'll discuss the ways in which accelerator technology carries over into other fields. Specifically, we'll discuss how resonant accelerating structures can be used to search for dark matter. This technology can also be applied to quantum computing, in order to improve the coherence of qubits.