This Week at Physics

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This Week at Physics

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Events During the Week of November 27th through December 3rd, 2011

Monday, November 28th, 2011

Plasma Physics (Physics/ECE/NE 922) Seminar
Time: 12:05 pm
Place: 2317 Engineering Hall
Speaker: TBD
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Tuesday, November 29th, 2011

Chaos & Complex Systems Seminar
Feeding behavior elicited from the prefrontal cortex: a case of lower-level brain centers for homeostatic energy-balance control “taking orders from above?”
Time: 12:05 pm
Place: 4274 Chamberlin
Speaker: Brian A. Baldo, UW Department of Psychiatry
Abstract: Feeding is a simple behavior that is required for the survival of the individual. Fundamentally, feeding replenishes chemical energy and maintains an energy reserve for adaptive behavior and physiological housekeeping functions. Nevertheless, the neural controls over this simple behavior are exceedingly complex. There appear to be specialized brain circuits for distinguishable aspects of feeding, for example, feeding elicited by negative energy balance (hunger/starvation), by the anticipated experience of pleasurable taste (the "dessert stomach"), or by stress ("emotional eating"). My lab explores how these diverse circuits interact, by chemically stimulating discrete brain sites in rats and observing the effects upon the organization of feeding behavior. Recently, we found that stimulating a specific neurochemical system within the prefrontal cortex, usually viewed as a seat of higher cognition, decision-making, and impulse control, produces a remarkable set of behaviors characterized by intense hyperactivity and abrupt, disorganized feeding responses. The neurochemical system under study was the mu-opioid peptide system (the "brain's own heroin"), known to mediate drug reward and to play a role in drug craving and relapse. Our studies were the first to show that feeding behavior can be driven by stimulating specific opioid-sensitive "hot spots" within the prefrontal cortex. Moreover, we showed that stimulating opioid systems in these cortical hot spots activates simpler downstream brain systems that regulate the homeostatic control of energy balance and body weight. Finally, we have obtained preliminary evidence that opioid stimulation of these same hot spots degrades cognitive function, as measured in a task of working memory. Taken together, our results indicate that mu-opioid-mediated activation of the prefrontal cortex simultaneously degrades higher cognitive function and elicits dysregulated feeding responses by "usurping" control of lower brain systems that regulate energy balance. Our findings may have implications for understanding eating disorders and addiction, which are characterized by the loss of control over food- or drug-seeking behaviors.
Host: Sprott
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Theory Seminar (High Energy/Cosmology)
Nonstandard Dark Matter Signatures at the LHC
Time: 4:00 pm
Place: 5280 Chamberlin Hall
Speaker: Yang Bai, SLAC
Abstract: Null results from dark matter direct detection experiments may indicate a nontrivial story in the dark matter sector. One example is the inelastic dark matter model with a mass splitting above 1 MeV, where the dark matter kinetic energy is not large enough to induce the inelastic scattering. Another example is the strongly interacting dark matter model with dark matter stopped inside the Earth before reaching detectors. Fortunately, the LHC can explore both scenarios and test them in spectacular signatures including mono-jet plus displaced pions and trackless jets.
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Wednesday, November 30th, 2011

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, December 1st, 2011

Graduate Introductory Seminar
Medical Physics Seminar
Time: 5:30 pm
Place: 2223 Chamberlin Hall
Speaker: Birn, Christian, Nickles
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Friday, December 2nd, 2011

Physics Department Colloquium
Strong-Arming Electron Spin Dynamics
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Jason Petta, Princeton University
Abstract: Over ten years ago, Daniel Loss and David DiVincenzo proposed using the spin of a single electron as a quantum bit. At the time of the proposal, it was not possible to trap a single electron in a device and measure its spin, let alone demonstrate control of quantum coherence. In this talk I will describe recent progress in the field, focusing on two new methods for single spin control that have been developed by my group at Princeton. The first method is based on quantum interference and implements spin-interferometry on a chip. The second method utilizes the strong spin-orbit coupling of InAs. By shifting the orbital position of the electronic wavefunction at gigahertz frequencies, we can control the orientation of a single electron spin and measure the full g-tensor, which exhibits a large anisotropy due to spin-orbit interactions. Both methods for single spin control are orders of magnitude faster than conventional electron spin resonance and allow investigations of single spin coherence in the presence of fluctuating nuclear and spin-orbit fields.
Host: Eriksson
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