Events at Physics |
Events During the Week of October 4th through October 11th, 2009
Monday, October 5th, 2009
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Magnetized Pinches: Magnetized Target Fusion to Astrophysics
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: Tom Intrator, Los Alamos National Laboratory
- Abstract: Magnetized plasma pinches can compress magnetic flux and plasma pressure in a variety of contexts. For example Magneto Inertial Fusion (MIF) includes a broad variety of plasma compression schemes for energy applications. Adiabatic compression of a magnetized plasma fuel target inside of some kind of conducting, contracting boundary is a possible path to fusion energy that lies between Magnetic Fusion Energy (MFE) and Inertial Confinement Fusion (ICF). The same MHD dynamics mediated by JxB forces are also important for collisions of flux ropes and magnetic reconnection. Compared with standard inertial compression to a High Energy Density (HED) state, the magnetic field improves confinement, while opening up new parameter space at lower areal mass density. Advantages of MIF include lower implosion speed, or more gain for given implosion speed, longer dwell time, less convergence, and lower cost and higher efficiency drivers. Many choices of compressor technologies include laser, solid linear, plasma liner, and ballistic particle options. There is a LANL-AFRL collaboration to field a solid compressor Magnetized Target Fusion (MTF) experiment that should reach the HED regime. Some related astrophysics and fusion science MHD issues can also be investigated with the Reconnection Scaling Experiment (RSX) whose flux ropes that resemble a Z pinch with flexible plasma wires with mass, inertia, MHD dynamics
Tuesday, October 6th, 2009
- Women of Wisconsin Strengthening Astronomy and Physics Colloquium
- The Two-Body Problem: Dual Career Couples in Science
- Time: 11:00 am
- Place: 3425 Sterling Hall (refreshments at 10:45)
- Speaker: Marc Sher, Department of Physics, The College of William and Mary
- Abstract: A decade ago, Laurie McNeil (now Chair of Physics at UNC) and I conducted a survey concerning dual career couples in physics. The response was overwhelming, and an extensive report was written (which has now been downloaded 40,000 times, and has had a significant impact on policy within federal agencies). The survey results will be discussed in detail, including the extent of the problem, a number of &quot;horror stories&quot;, and various suggested solutions (and, yes, some success stories). Recent developments in academia will also be discussed, as the institutional responses to the &quot;two-body problem&quot; have changed substantially in recent years.<br><br>
- Host: WOWSAP (Women of Wisconsin Strengthening Astronomy and Physics)
- Chaos & Complex Systems Seminar
- Simulation of swarming behavior using anti-Newtonian forces
- Time: 12:05 pm
- Place: 4274 Chamberlin (Refreshments will be served)
- Speaker: Vladimir Zhdankin, UW Department of Physics
- Abstract: The emergent behavior of swarming is investigated by using computer simulation. Each biological agent can be represented as a particle being influenced by forces due to the other agents in the system. A short-range repulsive force and long-range attractive force results in cohesive swarming behavior. However, more complicated dynamics can occur when two distinct species are defined to interact with different force laws. In order to recreate predator and prey swarming behavior that has been observed in nature, an "anti-Newtonian" force will be used between the two species, which violates Newton's Third Law. The resulting dynamics display a lush variety of features, including chaos and emergent behavior. The interesting cases will be demonstrated visually through animations that show the simulations unfold.
- Astronomy Colloquium
- Planetary Nebulae and the Structure and Kinematics of Galactic Disks
- Time: 3:30 pm
- Place: 3425 Sterling Hall
- Speaker: Robin Ciradullo, Penn State
- Abstract: Much of our understanding of dark matter halos comes from the largely-untested assumption that the mass-to-light ratio of spiral disks is constant is radius. To test this hypothesis, we have used planetary nebula kinematics to measure the disk mass surface density of five nearby, low-inclination spiral galaxies. We show that, in general, disks do have a constant M/L out to ~ 3 optical scale lengths, but once outside this radius, the vertical velocity dispersion of old disk stars is independent of distance. We suggest that this is due to the increased importance of a thick disk, and possible disk heating of the thin disk by dark halo substructure. We show that the disks of early type spirals have higher M/L values and are closer to maximal than the disks of later-type spirals, and that the residual unseen dark halos are better fit by pseudo-isothermal laws than by NFW profiles.
Wednesday, October 7th, 2009
- Recruiter Infosession
- Shell Exploration & Production Co. Infosession
- Time: 4:30 pm
- Place: 2223 Chamberlin
- Speaker: David Schaper, Shell Exploration & Production Company
- Abstract: Infosession by Shell Exploration & Production Company regarding job and internship opportunities for master's and Ph.D. candidates. Selected interviews will be held on Thursday, Oct. 8. If you are interested in setting up an interview, please submit a resume and transcripts for pre-screening via email to physgrad at physics.wisc.edu
- Host: Jane Schimmel
Thursday, October 8th, 2009
- R. G. Herb Condensed Matter Seminar
- Transport properties of superconductors near critical temperature: conductivity, magneto-tunneling, noise and relaxation
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Alex Levchenko, Argonne National Lab
- Abstract: We study fluctuation effects on transport properties of superconductors (thin films and tunnel junctions) above the transition temperature. The exact frequency dependence of the electron phase relaxation time due to dynamical superconducting fluctuations is important in this regime. It strongly modifies temperature and magnetic field dependence of conductivity, tunneling conductance and noise. A new energy scale appears as the result of these fluctuation effects, which provides a natural reqularization to Maki-Thompson conductivity and leads to peculiar non-monotonous temperature dependence of tunneling conductance. We make a comparative analysis of diffusive and ballistic regimes in the context of tunneling and go beyond the standard paradigm of density of states related effects. Noise measurement may be a powerful tool for probing superconductive fluctuations, since spectral function of current fluctuations exhibits a distinct feature at the Josephson frequency and its magnitude is strong function of temperature.
- Host: Maxim Vavilov
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Parity violation in low energy NN interactions
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Roxanne Springer, Duke University
- Abstract: At low energies, parity violation in NN scattering
(including photons) is described by an effective field theory (EFT)
that includes only contact interactions. I will describe this EFT,
how it improves upon the standard (non-physical) description, how it
echoes the Danilov treatment, and how its predictions compare to
existing (presently under-constraining) measurements. - Host: Michael Ramsey-Musolf
- Introductory Graduate Seminar
- Nuclear Experimental/Theory
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Balantekin, Heeger, Knutson, Ramsey-Musolf, University of Wisconsin Department of Physics
Friday, October 9th, 2009
- Theory/Phenomenology Seminar
- Time: 2:30 pm - 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Subhaditya Bhattacharya, Harish-Chandra Research Institute
- Host: T. Han
- Physics Department Colloquium
- Protein Intrinsic Disorder and Developmental Biology
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee and cookies at 3:30 pm)
- Speaker: Keith Dunker, Department of Biochemistry and Molecular Biology, Indiana University School of Medicine
- Abstract: The standard view is that each protein's amino acid sequence provides the information for it to fold into a specific 3D structure, and this structure is required for its function. Thus, current biology and biochemical textbooks suggest that all proteins act via the sequence-to-structure-to-function paradigm. These views are correct for enzymes, which function as catalysts that accelerate chemical reactions. But a cell is not just a bag of chemical reactions. Biological processes, such as cell division or development of different cell types from a single cell, require regulation and organization of the various chemical reactions. These regulatory functions involve proteins that interact with each other via complex networks. We used computational and bioinformatics methods to show that the regulatory signaling interactions in cells depend not on protein 3D-structure, but rather depend on lack of 3D-structure. For signaling proteins, we propose a new paradigm, given in short as sequence-to-flexible-ensemble-to-function. We will illustrate these ideas using the Wnt signaling pathway, a widespread, well studied and exemplary signaling network that is crucial for developmental biology.
- Host: McCammon