Speaker Series

The Physics and Biophysics Department hosts a monthly speaker series in which we invite researchers from universities, companies, and laboratories from across the country to talk to our undergraduates about their research. The speakers also discuss their career paths and advise on how to pursue a future career in a related field. The speaker series is held monthly on Tuesdays at 12:15 PM. Come learn about all of the cool things you can do with your physics or biophysics degree! And of course, lunch is also provided!

Fall 2018

Sharon Gerbode, Harvey Mudd College: Sculpting Crystals with Light--Optical Blasting Deforms Crystal Grains

We introduce “optical blasting,” a laser technique that causes local melting in crystals
composed of colloidal particles. Interestingly, we find that optical blasting near the edge of a crystal grain attracts and deforms the grain boundary. We explain this result using a toy model to show that the statistical multiplicity of deformed grain boundaries outweighs their extra energetic cost. This discovery invites new questions about how local disorder can affect the growth of crystal grains and provides a method to investigate fundamental grain boundary properties and ultimately create artificial colloidal crystal grains.

 

colloid crystals rearranged by optical blasting Colloid crystal domains rearranged by optical blasting

Spring 2018

Arlette Baljon, SDSU: Bacteriophages, the “Natural Born Killers” of Bacteria, Hunt for their Prey in Mucosal Surfaces

Physics may be viewed as a collection of concepts.  By combining these concepts we are able to understand a wide range of phenomena.  My area of research, soft matter physics, is only a few decades old.  Hence, unlike in older fields, many phenomena can not be explained in terms of established concepts.  New ones must be developed. The main purpuse of my research is to contribute to the formulation of these new concepts.   To this end, I perform computer simulations of yet unexplained phenomena.  Insights obtained in these studies pave the way for more encompassing theories and constitutive equations with a wide range of applications.

Brian Keating, UCSD: Losing the Nobel Prize

Dr. Brian Keating’s cosmic confidential, Losing the Nobel Prize tells how his research into the Big Bang morphed into a pursuit of the Nobel, an endeavor that led him away from the collaborative spirit that should be the hallmark of scientific inquiry. But along with a reconciliation of his own flaws, he found this is exactly what the Nobel Prize is doing, turning colleagues into competitors, scholars into salesmen, and introverted intellectuals into self-promotors in the winner-takes-all world of modern science. His memoir weaves together three narratives—the intimate tale of a young scientist in love with the night sky, the breathtaking birth story of the cosmos, and the history of a prize that would prove a glittering and unobtainable chimera for him, as it has for countless scientists over the past century. The result is a page-turning tale of ambition and redemption as well as commentary on an award that should represent humanity’s highest ideals—but often comes at a great cost.

Fall 2016

Matt Anderson, SDSU, Keeping it Light: Sculpting the Color and Spatio-temporal Characteristics of Ultrafast Laser Beams Using Spatial Light Modulators

About the photo, from the Anderson Lab website: 
Donut Beams
Photograph by Cory Stinson and Matt Anderson
In this photo, a supercontinuum source (lower right) emits a bright beam which traverses to the left.  It passes through an axicon (lower left), which generates the circular beam pattern.  The beam then reflects off a mirror and expands as it passes to the upper right. This photo was NOT photoshopped.  It was achieved with a 30 second exposure.  The solid beam was traced with a white card, the rings were generated by intercepting the beam with the card at regularly spaced intervals.  During this exposure of the rings, the output of the supercontinuum source was adjusted from red to green.  Finally, the equipment and Dr. Anderson were illuminated with a flashlight for the last few seconds of the exposure. 
dr matt anderson's laser setup
David Mallin colloquium poster

David Mallin, UCI, Low-Temperature Physics: Graduate School and Beyond

Helium was first liquefied in 1908 by Onnes, at a temperature of 4.2 Kelvin.  It was subsequently cooled by evaporation to below 2.1 Kelvin, though at the time no particularly interesting changes were noted.  It was not until 1936 that researchers began to unravel the peculiar properties of what became known as Helium II. The fluid displayed interesting behavior: nearly frictionless flow through narrow channels, incredibly high thermal conductivity, and flow induced by temperature gradients.  The search for a theoretical explanation attracted some of the greatest minds of the time, including Landau, Onsager, and Feynman. Helium was eventually modeled as a quantum fluid, with fluid properties analogous to type II superconductivity. While models have explained some properties of superfluid helium, some still remain.  One of the biggest remaining questions concerns the means of energy dissipation. Just as a supderconductor has a critical current, superfluid helium has a critical velocity. The mechanism for the dissipation involves the production of vortices within the fluid. This has been supported theoretically and experimentally, but the dynamics have yet to be understood.  To this end, The Taborek lab at UCI had constructed an optical cryostat that seeks to directly observe the dynamics of vorticity in superfluid Helium.

Jordan Hanson, OSU: The Future of Ultra-High Energy Multimessenger Astroparticle Physics

Dr. Hanson discusses his work in the Barwick group at UC Irvine on the AMANDA-II detector in Antarctica.

The dream, now more than 40 years old, of constructing a radically different telescope has been realized by the innovative AMANDA project. Instead of sensing light, like all telescopes since the time of Galileo, AMANDA responds to a fundamental particle called a neutrino. Neutrino messengers provide a startlingly new view of the Universe. Members of UCI team designed the first practical implementation of the generic ideas formulated many years ago, an re--introduced in late 80's with the twist of using Antarctic ice instead of water. Due to the remoteness of the site in Antarctica, we decided to minimize complexity of the design while recognizing that the simplest devices and system architectures were sufficient to answer the key questions. This concept proved highly effective. AMANDA is now an international collaboration involving institutions from the US, Germany, Sweden, Belgium, and Venezuela.

Animation of a neutrino detection event in the AMANDA-II detector.

Spring 2016

Michael Rust, U of Chicago: How Cyanobacteria Use Three Proteins to Predict the Future

The rotation of the Earth on its axis causes organisms to face regularly fluctuating environments. Organisms across all kingdoms of life have evolved biochemical oscillators, called circadian clocks, that allow them to anticipate and prepare for environmental changes.  We are studying the simplest known circadian clock from photosynthetic bacteria. This bacterial oscillator can be reconstituted using a mixture of three purified proteins (KaiA, KaiB, and KaiC), allowing us study the biophysical mechanisms underlying daily timekeeping. Recently, we have developed a microscopy approach that allows to make movies of growth and division of bacterial cells while monitoring their clock state using fluorescence imaging. By tracing the life histories of single cells, we find that the clock serves to control growth and division of the cell, and that slowed growth as dusk approaches allows the cell to tolerate the starvation associated with nightfall. We have developed a simple mathematical model of how oscillating physiology functions in a cycling environment. This model suggests that circadian clocks are finely tuned strategies that exploit deterministic regularities in the environment. Importantly, these strategies can fail catastrophically in irregular environments, with implications for work schedules in modern society.
diagrammatic illustration of Rust Lab circadian clock experimental setup
Cartoon of the microtubules the Ross Lab studies.

Jennifer Ross, UMass Amherst: Building a Cell with Undergraduate Research

Biology utilizes energy to organize itself from the nanoscale to the macroscopic scale. We seek to determine the universal principles of organization from the molecular scale that give rise to architecture on the cellular scale. We are specifically interested in the organization of the microtubule cytoskeleton, a rigid, yet versatile network in most cell types. Microtubules in the cell are organized by motor proteins and protein crosslinkers. This work, initiated solely through undergraduate researchers, applies the ideas of statistical mechanics and condensed matter physics to the non-equilibrium pattern formation behind intracellular organization using the microtubule cytoskeleton as the building blocks. We examine these processes in a bottom-up manner by adding increasingly complex protein actors into the system. Our systematic experiments expose nature’s laws for nanoscale to micron scale organization and have large impacts on biology as well as illuminating new frontiers of non-equilibrium physics.

Fall 2015

Matt Block, CSU Sacramento: Computational Studies of Many-Body Magnetic Models

One of the striking results of the study of materials is that, in the absence of a flowing current, all magnetism has a quantum mechanical origin in the so-called "spin" of subatomic particles. Each spin constitutes a dipole moment and therefore generates a tiny magnetic field. A collection on the order of Avogadro's number of such spins accounts for all the macroscopic magnetic effects observed in nature, aside from those induced by electric currents.  Theoretical condensed matter physicists attempt to write down models of spins living on solid lattices so as to better understand the ground states, or lowest energy states, and the low-energy excited states of real-world materials. In general, this can be a very difficult problem to solve depending on the particular model in question.  In this talk, I will present a highly simplified model of spins on a one-dimensional chain called the classical Ising model as a means of illustrating the language of spin physics. Throughout, I will explain in a relatively non-technical manner some of the basic concepts essential to any discussion of theoretical condensed matter physics including energy, temperature, long-range order, and both thermal and quantum fluctuations. Finally, I will also discuss how and why computational methods have taken center stage in the study of exotic quantum phases and quantum phase transitions in theoretical spin models.

A 2D frustrated magnetic lattice model, from Steven R. White, University of California, Irvine

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