Events at Physics |
Events on Tuesday, March 31st, 2009
- R. G. Herb Condensed Matter Seminar
- Room Temperature demonstration of Quantum Cellular Automata formed by Single Si Atom Quantum Dots
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Baseer Haider, University of Alberta
- Abstract: A device architecture for computing with quantum dots, Quantum Cellular Automata, points to a new paradigm for computation that goes beyond the conventional semiconductor technology roadmap to achieve ultra low power consumption. The Quantum Cellular Automata scheme is based upon "cells" of tunnel coupled quantum dots and electrostatic interaction between adjacent cells to transmit binary information and perform computations. Efforts to fabricate Quantum Cellular Automata devices have so far been limited by the need for extreme cryogenic conditions and by the debilitating effects of stray charges. It is conceivable that fabrication on a smaller scale can circumvent these limitations. Here we demonstrate that single atoms in a solid state environment can serve as quantum dots and that such quantum dots can be controllably tunnel coupled to embody the building block of a Quantum Cellular Automata Cells. Such cells exhibit "selfbiasing" effect, that is, the electron occupation is set by cell geometry. The binary state of the cell may be controlled electrostatically. This cell operates at room temperature and is largely immune to stray charges that are more than 30 Angstroms away from the cell.
- Host: Mark Friesen
- Chaos & Complex Systems Seminar
- The origins of emergent behavior in bacterial communities
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Douglas B. Weibel, UW Department of Biochemistry
- Abstract: Bacteria sense surfaces and undergo physiological changes, which programs their growth and motility and coordinates their behavior. The resulting bacterial communities display 'emergent' properties in which the coordination of the behavior of cells is not predictable from the sum of the individual components (e.g. cells). The resulting structures behave as multicellular organisms and collectively colonize niches in search of nutrients and other growth factors. The transition of a group of 'individual' bacterial cells to collective, multicellular behavior is accompanied by the upregulation of pathogenic factors, suggesting that in this state the organisms are preparing to invade a host. An understanding of the mechanisms that control and regulate the switch from individual behavior to multicellular behavior will identify mechanisms and targets that may play a role in preventing and treating microbial pathogenesis. We are particularly fascinated by the mechanisms that cells use to coordinate their movement on surfaces. In contrast to our understanding of the biophysics involved in the motility of bacterial cells (e.g. Escherichia coli) in bulk fluids, almost nothing is known about the mechanisms that play a role in cell motility on surfaces. We are exploring two physical mechanisms that may play a role in the coordination of cellular movement on surfaces based on: i) physical interactions between cells mediated by bundling between flagella on adjacent cells; and ii) physical interactions between cells in close proximity to each other that are produced by the disturbance in the local fluid field by the rotation of the cells during motility. In this talk I present recent work from our group on both mechanisms and demonstrate that bacterial 'swarming' may be one of the most tractable experimental systems for identifying the mechanisms that drive systems toward emergent behavior. These experiments may shed light on systems that extend far beyond microbial systems, and include financial markets, weather, and population dynamics.
- High Energy Seminar
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- DUSEL - Progress on the Deep Underground Science and Engineering Laboratory
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin(Coffee and Cookies at 3:45 pm)
- Speaker: Kevin Lesko, Lawrence Berkeley National Laboratory
- Host: Karsten Heeger
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- DUSEL - Progress on the Deep Underground Science and Engineering Laboratory
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Kevin Lesko, Lawrence Berkeley National Laboratory
- Abstract: Joint HEP Seminar/NPAC Forum
- Host: Karsten Heeger