Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session L29: FIAP Plenary: Physics that Changed the WorldIndustry Invited Undergraduate
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Sponsoring Units: FIAP Chair: Eli Yablonovitch, University of California, Berkeley Room: 292 |
Wednesday, March 15, 2017 11:15AM - 11:51AM |
L29.00001: Energy Efficient GaN Lighting Invited Speaker: Steven Denbaars |
Wednesday, March 15, 2017 11:51AM - 12:27PM |
L29.00002: Laser Refractive Surgery Invited Speaker: James Wynne Refractive surgery has its roots in corneal transplant surgery, first performed in 1905, where the damaged or diseased cornea of a living individual is replaced by donated corneal tissue taken from a recently deceased individual. Since the cornea has no blood supply, there is no danger of organ rejection. Recognizing the exceptional healing power of corneal tissue, ophthalmologists began to explore methods of reshaping the cornea to improve the visual acuity of patients suffering from myopia, hyperopia, and astigmatism. In 1964, a procedure known as keratomileusis was introduced. In 1974, radial keratotomy (RK) was introduced. In 1981, excimer laser surgery was discovered by the speaker and his IBM Research colleagues. In 1983, the excimer laser was used to create clean, precise incisions in the cornea of enucleated calf eyes, derived from slaughter, launching the era of laser refractive surgery, with more precise and safer techniques to correct myopia, hyperopia, and stigmatism. This talk will describe the widely practiced surgical procedures known as photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK), which have improved the visual acuity of more than 35 million people. Most patients undergoing PRK or LASIK end up with uncorrected vision better than 20/20. In 2007, development commenced on a new procedure known as small incision lenticule extraction (SMILE), employing a femtosecond laser and no excimer laser. SMILE is promoted as minimally invasive and combining the advantages of PRK and LASIK. However, long term stability of visual acuity following SMILE surgery is yet to be determined. [Preview Abstract] |
Wednesday, March 15, 2017 12:27PM - 1:03PM |
L29.00003: Magnetic Resonance Medical Imaging (MRI)--from the inside Invited Speaker: Paul Bottomley There are about 36,000 magnetic resonance imaging (MRI) scanners in the world, with annual sales of \textasciitilde 2500. In the USA about 34 million MRI studies are done annually, and 60-70{\%} of all scanners operate at 1.5 Tesla (T). In 1982 there were none. How MRI got to be--and how it got to1.5T is the subject of this talk. Its an insider's view--mine--as a physics PhD student at Nottingham University when MRI (almost) began, through to the invention of the 1.5T clinical MRI scanner at GE's research center in Schenectady NY.Before 1977 all MRI was done on laboratory nuclear magnetic resonance instruments used for analyzing small specimens via chemical shift spectroscopy (MRS). It began with Lauterbur's 1973 observation that turning up the spectrometer's linear gradient magnetic field, generated a spectrum that was a 1D projection of the sample in the direction of the gradient. What followed in the 70's was the development of 3 key methods of 3D spatial localization that remain fundamental to MRI today.As the 1980's began, the once unimaginable prospect of upscaling from 2cm test-tubes to human body-sized magnets, gradient and RF transmit/receive systems, was well underway, evolving from arm-sized, to whole-body electromagnet-based systems operating at \textless 0.2T. I moved to Johns Hopkins University to apply MRI methods to localized MRS and study cardiac metabolism, and then to GE to build a whole-body MRS machine. The largest uniform magnet possible--then, a 1.5T superconducting system--was required. Body MRI was first thought impossible above 0.35T due to RF penetration, detector coil and signal-to-noise ratio (SNR) issues. When GE finally did take on MRI, their plan was to drop the field to \textasciitilde 0.3T. We opted to make MRI work at 1.5T instead. The result was a scanner that could study both anatomy and metabolism with a SNR way beyond its lower field rivals. MRI's success truly reflects the team efforts of many: from the NMR physics to the engineering of magnets, gradient and RF systems. [Preview Abstract] |
Wednesday, March 15, 2017 1:03PM - 1:39PM |
L29.00004: Batteries that Changed the World Invited Speaker: Peter Littlewood |
Wednesday, March 15, 2017 1:39PM - 2:15PM |
L29.00005: How Does My Cellphone GPS Work?--The Physics of Precision Time-Keeping Invited Speaker: Steven Chu The most precise measurements in all of science are frequency and frequency difference measurements, or alternatively, phase and phase change of electromagnetic waves. Improvements in time-keeping have opened up many horizons in fundamental and applied physics that range from the detection of gravity waves to the melting of glaciers and the depletion of underground aquifers. Precision time keeping has also had important practical applications such as in the navigation, beginning with the determination of the longitude position of sailing ships. We now use our cell phones to help us navigate city streets and hail taxis from Uber and Lyft based on our geographical position within a few meters. How did this come about? What will the new time-keeping technologies enable in the future? [Preview Abstract] |
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