Events Archive

Apr
04
2011
"Collapse and stable self-trapping for Bose-Einstein condensates with 1/r^b type attractive interatomic interaction potential" by Pavel Lushnikov
We consider dynamics of Bose-Einstein condensates with long-range attractive interaction proportional to 1/r^b and arbitrary angular dependence. It is shown exactly that collapse of Bose-Einstein condensate without contact interactions is possible only for b greater or equal to 2. Case b=2 is critical and requires number of particles to exceed critical value to allow collapse. Case b>2 is supercritical with expected weak collapse which traps rapidly decreasing number of particles during approach to collapse. For b
Mar
31
2011
"Post-Shuttle Age: The Future of NASA": A Blended Research @ the Library panel discussion
Join us for the first Blended Research @ the Library panel discussion, Post-Shuttle Age: The Future of NASA.  Panelists are David Ballantyne, Assistant Professor in the School of Physics and the Center for Relativistic Astrophysics (CRA); Ashley Korzun, graduate student in the Daniel Guggenheim School of Aerospace Engineering; John Krige, Kranzberg Professor in the School of History, Technology and Society; and David Spencer, Professor in the School of Aerospace Engineering and Director of the Center for Space Systems.  They will be discussing the future of NASA after the end of the space shuttle program, touching on topics...
Mar
30
2011
Ford Lecture: "Looking and Seeing" by Mitchell J. Feigenbaum
  Dr. Feigenbaum received his Ph.D. in theoretical high energy physics from the Massachusetts Institute of Technology in 1970, under Francis E. Low. He was a research associate at Cornell University from 1970 to 1972 and a research associate at Virginia Polytechnic Institute from 1972 to 1974. He then moved to Los Alamos National Laboratory, where he was a staff member from 1974 to 1981 and a fellow from 1981 to 1982. (Dr. Feigenbaum, while creating his work on chaos, shared his office with Murray Gell-Mann in 1976.) From 1982 to 1986 he was a...
Mar
29
2011
"Laser-Cooled Primary Frequency Standards at NIST" by Dr. Steven Jefferts
Mar
17
2011
"Supermassive Black Holes: Rulers of the Universe?" by Gordon Richards
nce the realm of philosophers, black holes have now been shown to exist. Indeed, black holes as massive as 1 million to 1 billion Suns populate the cores of essentially all massive galaxies. Contrary to popular thought, these super-massive black holes are messy eaters, spewing out nearly as much (in the form of mass and energy) as they consume. This "feedback" process has been postulated to be the valve that controls the growth and evolution of their host galaxies, shaping the very evolution of our Universe. I will discuss how statistical analyses of active galactic nuclei and quasars from the Sloan Digital Sky Survey (SDSS) can be used to test the hypothesis that...
Mar
16
2011
"Why Meissner was wrong (or a classical explanation of flux expulsion from superconductors)" by Hanno Essen
The discovery by Meissner and Ochsenfeld in 1933  that the magnetic field inside a conductor is expelled when it is cooled down to become  superconducting was considered very surprising at the time. Meissner wrote that this has no classical explanation. Since then virtually every textbook stresses that this means that a superconductor is in fact not just a zero resistivity perfect conductor but in addition has the mysterious property that it can expel internal magnetic flux. In this colloquium I will present evidence that this is all a misunderstanding based on insufficient knowledge of what classical physics in fact predicts about the...
Mar
15
2011
"Normal metal contacts and small-scale graphene two-terminal junctions"
Graphene has been proposed as a viable replacement for silicon on a number of electronic applications due to its high mobility. At Georgia Tech we have been studying charge transport through graphene junctions contacted to two normal metal contacts, aiming for a quantitatively accurate description. In this talk I will present an overview of the problem, making an emphasis on crucial differences between theory and experiment, that so far preclude quantitative modeling. Then I will present our results, including some very recent developments concerning graphene junctions attached to titanium contacts (titanium has been the metal of choice for contacting graphene in experiments)....
Mar
14
2011
"Random walks, DNA elasticity, and the motion of proteins" by Meredith Betterton
A particle undergoing a random walk is a classic physics problem that underlies our understanding of diffusion, the molecular nature of matter, polymer conformations, and the fluctuation-dissipation theorem. In addition to its conceptual importance in physics, a random walk is a surpisingly good model for some biophysical problems. This talk will present several examples, including DNA conformation and protein motion along a biopolymer, that are well described by a biased or unbiased random walk. I will discuss the physical theory and biophysical applications of several problems from our recent research: finite-length effects in DNA elasticity, the coupling...
Mar
07
2011
"Relating single motor function to ensemble transport in cells" by Jing Xu
Cells are highly ordered and organized. Much of the cell’s order relies on the active transport of material by molecular motors. Disruption in intracellular transport can be detrimental to cells, and is a common early theme in neurodegeneration. While molecular motors have been studied in isolated, cell-free system, how they act in groups in cells, and how their group functions are regulated or disrupted, are not yet understood. To address these questions in a concrete, experimentally tractable system, we studied the effects of a neurodegenerative mutation (“Legs at Odd Angles”, or Loa) on the major molecular motor, dynein. Combining single...
Mar
02
2011
"Microbial Interaction Networks in Soil and in Silico" by Kalin Vetsigian
Soil harbors a huge number of microbial species interacting through secretion of antibiotics and other chemicals. What patterns of species interactions allow for this astonishing biodiversity to be sustained, and how do these interactions evolve? I used a combined experimental-theoretical approach to tackle these questions. Focusing on bacteria from the genus Steptomyces, known for their diverse secondary metabolism and production of antibiotics, I isolated 64 natural strains from several individual grains of soil and systematically measured all pairwise interactions among them. Quantitative measurements on such scale were never possible before. They were...

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