USF Physics and Astronomy Colloquium Series

The Physics and Astronomy Colloquia at the University of San Francisco are talks given by invited research scientists, on topics of current interest. The Physics Colloquium Series has been in place since 1994.

All colloquia typically start at 3:30, and will have light refreshments served. Colloquia take place in CS 303, unless otherwise noted.

colloquiumpic

Professor Douglas Osheroff (middle), 1996 Nobel Laureate in Physics, appears here on the occasion of his colloquium at USF, flanked by Professors Camblong (left) and Camperi (right).

PAST COLLOQUIUM SERIES VIDEOS

Fall 2014 Colloquium Series

September 10, 2014 - Dr. Rena Zieve

"Uniaxial Pressure Measurements of Layered Superconductors"

3:30-5:00 in LCSI 303

A major challenge in condensed matter physics is how to determine the electrical and magnetic behavior of a material based on its crystal structure. Applying pressure can be a useful tool, since it produces slight changes in the atomic positions, which can then be compared to effects on the physical properties.  I will describe a pressure apparatus that applies force to a solid sample along a particular direction.  We have used this uniaxial pressure technique to study several materials, particularly superconductors with a layered crystal structure. These samples respond very differently to pressure applied within or perpendicular to the layers. I will explain how our measurements relate to the goal of achieving higher-temperature superconductors.

 

Professor Zieve works in experimental low-temperature physics. Her two main efforts are on the phase diagrams of families of unconventional superconductors, and the motion of quantized vortices in superfluid helium. Her PhD, completed at UC Berkeley in 1992, involved building a rotating microKelvin refrigerator and using it to measure quantized circulation in superfluid 3He. She joined the UC Davis faculty in 1996, after postdoctoral work at the University of Chicago and Yale. She is now the physics department's Vice-Chair for Graduate Affairs and also directs its Research Experience for Undergraduates program.

 

September 17, 2014 - Dr. Christopher McKay

"The Search for Life on Other Planets, with an Update from the Mars Curiosity Rover"

3:30-5:00 in LCSI 303

 The Mars Curiosity Rover has been operating on in Gale Crater for over 500 days. I will present our current status on the search for organics and the prospects for determining the habitability of the site. If we find organics on Mars, the next challenge will be to determine if they are of biological or non-biological origin. There are other worlds in the Solar System that are also of keen interest in the search for life: my favorite is Enceladus, a small moon of Saturn.

 

Chris is a research scientist with the NASA Ames Research Center. His current research focuses on the evolution of the solar system and the origin of life. He is also actively involved in planning for future Mars missions including human exploration.  Chris been involved in research in Mars-like environments on Earth, traveling to the Antarctic dry valleys, Siberia, the Canadian Arctic, and the Atacama, Namib, & Sahara deserts to study life in these Mars-like environments.  He was a co-investigator on the Huygens probe to Saturn’s moon Titan in 2005, the Mars Phoenix lander mission in 2008, and the current Mars Science Laboratory mission (2012).

 

September 24, 2014 - Dr. Pehr Harbury

"Another Look at the Double Helix: Ensembles and Fluctuations"

3:30-5:00 in LCSI 303

Precisely measuring the ensemble of conformers that a macromolecule populates in solution is highly challenging. Thus, it has been difficult to confirm or falsify the predictions of nanometer-scale dynamical modeling. Conformational fluctuations lie at the heart of almost all biological function, yet are largely invisible to modern biophysics. To explore ensembles, we have developed and applied an X-ray interferometry technique. We measure instantaneous distance distribution between pairs of gold-nanocrystal probes conjugated to a macromolecule in solution. The data provide a spatial accuracy matching that of X-ray crystallography. As a benchmarking experiment, we have probed the solution structure and thermally-driven fluctuations of B-form DNA on a length scale comparable to a protein-binding site. It was not previously possible to test the canonical linear elastic-rod model of DNA by observing the nanometer-scale bending and twisting of the helix. The structure and elastic properties we measured are in striking agreement with values derived from DNA–protein crystal structures and measured by force spectroscopy. There were two unexpected observations, however. The data suggest the existence of cooperative stretching in DNA, and also reveal a nonlinearity in its torsional rigidity. 

Dr. Harbury is an Associate Professor of Biochemistry at Stanford University and a member of the Stanford Cancer Institute. He completed his Ph.D. in Biological Chemistry at Harvard Medical School in 1994. His laboratory's innovative work in engineering proteins and elucidating the functional role of their structures, shapes and fluctuations has won support and recognition from the NIH, the MacArthur Foundation, the Lucille Packard Charitable Trust, and many other organizations.

 

 

October 8, 2014 - Dr. K. Aurelia Ball

"Amyloid-beta & Alzheimer's Disease: Using Physics to Reveal a Toxic Protein's Elusive Structure"

3:30-5:00 in LCSI 303

Alzheimer’s Disease is characterized by large toxic fibrils and plaques in the brain.  Amyloid-beta, a small, naturally occurring protein, is a major component of these fibrils and plaques.  In order to understand the formation of the toxic forms of the protein, we would like to have a picture of Amyloid-beta in the free state, when not part of these fibrils or smaller aggregates.  This is particularly difficult because, unlike most proteins which adopt a single, well-folded structure, Amyloid-beta is very flexible and constantly changes shape.  However, we can use a combination of physics-based computer simulations and biological NMR spectroscopy to understand Amyloid-beta structure and how this structure may influence toxicity and disease.

 

I am originally from outside Seattle, Washington.  I attended Middlebury College in Vermont, where I majored in Physics and studied abroad in Poitiers, France.  I then completed my Ph.D. in Biophysics at UC Berkeley, in the lab of Prof. Teresa Head-Gordon, where I studied the Alzheimer’s protein, Amyloid-beta.  My Ph.D. research is the subject of my talk.  I am currently a post-doctoral scholar at UC San Francisco, where I work with Prof. Matt Jacobson, and am part of a center studying HIV proteins.  My current work focuses on how ubiquitination of proteins can change their structure and dynamics to regulate function.  I am also involved in the field of intrinsically disordered proteins, and this summer chaired a Gordon Research Seminar for students and postdocs that preceded the main Gordon Conference on intrinsically disordered proteins.

October 16, 2014 - Dr. Tesla Jeltema

"Probing Dark Matter with Clusters of Galaxies"

11:30-12:45 in Cowell 106

Astronomical observations have revealed a lot about the nature of dark matter, including that it composes roughly a quarter of the energy density of the universe, that it is not a particle in the Standard Model of particle physics (i.e. all of the particles we have identified so far), and that it is likely a massive, slow moving particle.  However, we still do not know what the dark matter particle is.  I will discuss how observations of the largest structures in the universe, clusters of galaxies, can help to reveal the particle nature of dark matter.

 

Dr. Jeltema is currently an Associate Professor in the Physics Department at University of California, Santa Cruz, and is affiliated with the Santa Cruz Institute for Particle Physics (SCIPP) and the UCO/Lick Observatory.  Her research concentrates on observational cosmology and particle astrophysics, including constraints on the nature of dark matter and dark energy and studies of the evolution of galaxies.  In particular, she studies the formation and evolution of large-scale structure in the universe, using observations covering a broad wavelength range and numerical simulations. Dr. Jeltema received her Bachelor’s at the College of William and Mary and received her PhD from the Massachusetts Institute for Technology.  

 

October 22, 2014 - Dr. John Birmingham

"Incorporating Spike-Rate Adaptation into a Neural Rate Code"

3:30-5:00 in LCSI 303

For a slowly-varying stimulus, the simplest relationship between a sensory neuron's input and output is a rate code, in which the spike rate is a unique function of the stimulus at that instant.  However, most neurons are subject to “spike-rate adaptation”, where the spike rate at any time is also dependent on prior spiking, what we term the “history”.  We have developed a scheme that incorporates “history” into a rate code and have tested it successfully on both a mathematical model of a neuron and on a stretch-sensitive neuron from the crab.  Much to our surprise, our studies of coding in the model system have provided us with insights, not easily obtained via experiment, about biophysical mechanisms in the crustacean system.

 

Professor Birmingham received an A.B. degree in Physics from Princeton University in 1989 and a Ph.D.  in Physics in 1996 from UC Berkeley, where he studied the heat capacity of quantum adsorbates and the far-infrared properties of high-TC superconductors.  After graduate school, he spent four years as a post-doctoral fellow at Brandeis University where he worked in an interdisciplinary neuroscience laboratory.  He has taught at Santa Clara since 2000 and uses physiological and computational approaches in his research lab to study how sensory neurons encode information, and how these codes are modified by neuromodulatory substances.  

 

October 29, 2014 - Dr. Hideo Mabuchi

"TBD"

3:30-5:00 in LCSI 303

Lecture Topic to be announced shortly.

Biography to be announced shortly.

November 12, 2014 - Dr. Hartmut Haffner

"TBD"

3:30-5:00 in LCSI 303

Lecture Topic to be announced shortly.

Biography to be announced shortly.