Bulletin of the American Physical Society
2007 APS Four Corners Section/SPS Zone 16 Joint Fall Meeting
Volume 52, Number 14
Friday–Saturday, October 19–20, 2007; Flagstaff, Arizona
Session A1: Opening Plenary |
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Chair: Keith Dienes, University of Arizona, Four Corners Section Chair Room: Chemistry (Bldg. 20) Room 106 |
Friday, October 19, 2007 12:48PM - 1:24PM |
A1.00001: Lowell Observatory: Past and Present Invited Speaker: Founded in 1894, Lowell Observatory was one of the earliest research institutions established in the Arizona Territory. Funded and led by Percival Lowell, the Observatory soon established itself as a significant center for astronomical research. While Percival's early ideas about intelligent life on Mars were not correct, other investigations he initiated resulted in fundamentally important discoveries. First among these is the discovery by Vesto Slipher, in the second decade of the twentieth century, of the large redshifts of external galaxies. Perhaps better known to the public, is the 1930 discovery of Pluto. Today, the Lowell Observatory employs a staff of 80, of whom 21 hold Ph.D.s in astronomy, planetary science, or physics. The Observatory operates research facilities at 4 sites, with a new 4.2-meter telescope - the Discovery Channel Telescope -- under construction at a fifth. Lowell astronomers use these facilities, in addition to national facilities around the globe, in the air, and in space, to conduct a diverse program of research. Lowell remains today an institution true to the vision of its founder- independent, private, closely connected to the Lowell family, and welcoming to the public. [Preview Abstract] |
Friday, October 19, 2007 1:24PM - 2:00PM |
A1.00002: Energy Concentrating Phenomena: From Sonoluminescence to Crystal Fusion Invited Speaker: Fluids and solids that are driven off equilibrium do not relax smoothly to equilibrium. Instead they display a wide range of energy focusing phenomena. In sonoluminescence (SL) a pulsating bubble concentrates the ambient acoustic energy density by 12 orders of magnitude to create picosecond flashes of broadband ultraviolet light. At the minimum bubble radius where the contents have been compressed to their van der Waals hard core the acceleration exceeds 10$^{11 }$g and a Mega-Bar level shock wave is emitted into the surrounding fluid. For single bubbles driven at 30 kHz SL is nature's smallest blackbody. At 1 MHz the spectrum resembles Bremsstrahlung from a transparent plasma with a temperature $\sim $1 MK and a nanometer radius. Whether cavitating systems will reach energy densities that initiate thermonuclear fusion is an open question. Ferroelectric crystals, however, can be configured to create nuclear fusion in a palm-sized apparatus. When the temperature of a ferroelectric crystal [e.g. Lithium Tantalate] is slightly varied, electrons are expelled with energies that can exceed 100 keV. By configuring the crystal surface with a field ionization tip, pyroelectricity can be used to generate and accelerate ions to energies where nuclear fusion occurs. Hoped-for applications range from miniature x-ray devices to neutron cameras to ion thrusters. In seeking to improve these devices one faces the question: what physics processes limit the spontaneous polarization [and resulting internal field] that can be produced with a ferroelectric crystal? For $\sim $50 years Lithium Niobate has exhibited the highest ratio of spontaneous polarization to dielectric constant. Why haven't superior materials been discovered? Is there a fundamental limit set by the laws of physics? [Preview Abstract] |
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