APS Centennial Meeting Draws Record Crowds to Atlanta
Compiled by Philip F. Schewe and Benjamin Stein of AIP's Public Information Division
To simulate a supernova explosion, energy from the powerful NOVA laser hits a central target. (Photo courtesy of Lawrence Livermore National Laboratory)
It's here at last! The APS will celebrate its 100th anniversary this month at the Centennial Meeting in Atlanta, Georgia. The conclave will constitute the largest physics meeting of all time, with an expected 10,000 physicists in attendance at the Georgia World Congress Center.
The scope is infinite, from atoms to the universe as a whole. All of the APS units will be represented, so one will be able to hear talks about quarks, protons, nuclei, atoms, molecules, DNA, living organisms, crystalline solids, gases, liquids, granular materials, planets, plasmas, stars, galactic clusters, and the microwave background. In temperature, the subject matter extends from billionths to billions of kelvin, in pressure from billionths to billions of pascals. Laser power starts with milliwatts and goes all the way up to petawatts, while computer power goes from single qubits to petabytes. Particles under discussion are sometimes free, or quasi-free, but more often than not are subject to some kind of restraining order while they are subjected to quantum dots, quantum wells, quantum contacts, quantum interference, quantum chaos, quantum gravity, quantum computers, quantum teleportation, quantum logic, and quantum pinball. Indeed, the confinement of electrons, and the implication of this for the movement of information (ultimately a trillion-dollar endeavor), is one of the primary motifs of the meeting.
Selected Technical Highlights:
Photonic Crystal Lasers.
Consisting of slender bars arranged in a regularly repeating pattern, a photonic crystal prevents the escape of light waves having a certain range of colors or wavelengths. Modifying the basic pattern of a photonic crystal can cause it to force light to travel in specific paths. As an "optical waveguide" it redirects light more than three times more efficiently than traditional waveguides. Such waveguides could cause light to bounce back and forth, in essence creating a highly efficient mirror. Physicists have hoped that such mirrors could serve as a basis for a new kind of low-power laser. Now, Attila Mekis of MIT and Lucent Technologies and his colleagues have built a photonic-crystal laser which guides light in two dimensions. They will present experimental measurements of this device. (Paper BC31.07)
Early Cancer Detection with Laser Spectroscopy.
Many physics discoveries and techniques have been successfully applied to medicine. The laser is another example, and physicists are now exploring the ability of laser light to detect subtle visual signatures of disease at an early stage. In the body, the presence of disease alters the chemical composition and shape of the affected tissue. These microscopic alterations can be detected by shining laser light on tissue and studying the spectrum of light reflected from it, enabling diagnosis without the need for an invasive biopsy. Once detected with lasers, such diseased tissue may be treated, effectively ridding the body of the risk of developing potentially deadly diseases, such as cancer. Mary-Ann Mycek of Dartmouth College will illustrate the application of "laser-induced fluorescence spectroscopy" to the detection of epitelial dysplasia: a pre-malignant skin condition leading to cancer. (Paper FC32.01)
New Possibilities for DNA Computers.
In the marriage of computer science and molecular biology known as DNA computing, scientists create fragments of DNA — whose letters represent computer data and instructions — and mix them together in test tubes to solve problems, such as the shortest path through a number of cities. Allen Mills of Bell Labs/Lucent Technologies will show that it is possible to use DNA to construct a massive neural network — computers modeled after the human nervous system — with a connectivity of 1 trillion synapses, or 1% of a human brain. Simon Berkovich of George Washington speculates that the DNA in a biological organism serves a role comparable to a barcode: it provides classification, so that small differences are enough to distinguish between species, and it provides a unique ID number that is responsible for the biological individuality of an organism. (Session BC31)
Silicon, the raw ingredient of computer chips and modern electronics, often has a dark bluish-grey color. However, researchers have discovered that changing its color may lead to more efficient solar panels. By repeatedly shining pulses of femtosecond laser light, Claudia Wu and her Harvard colleagues have made microscopic black spots on silicon. As it turns out, these spots absorb significantly larger amounts of light than comparable areas on traditional silicon. The researchers believe that such "spiked" silicon can lead to highly efficient light absorbers for solar cells and photodetectors. (Paper IC07.10)
Fertilize Locally but Think Globally.
Anthropogenic carbon flow is primarily in the energy sector and has an immense effect on the worldwide economy. The corresponding nitrogen flow is primarily in the agricultural sector and its effects more evident on a local level. For example, fertilizer runoff has created a 1000-square mile hypoxic deadzone for fish where the Mississippi meets the Gulf of Mexico. For these reasons, argues Robert Socolow of Princeton, the sustainability of nitrogen use ought to receive greater attention. (Paper VB15.03)
Petabyte Recreation of the Early Universe.
When particles smash into each other at high energy accelerators a miniature fireball is ignited; in a volume less than the size of an atom, hothouse conditions resembling those of the very early universe are created. The fiery collisions are often followed by a prompt blizzard of secondary particles spawned courtesy of E=mc2. Tracking, sorting, and assessing this jumble requires the world's fastest electronics, consisting of such items as silicon microstrip detectors, lead glass scintillators, vertex trackers, and drift chambers. At the highest energy colliders, such as the Tevatron at Fermilab, the Relativistic Heavy Ion Collider (opening later this year at Brookhaven), and the Large Hadron Collider (at CERN by 2005), computers will have to keep up with, and control, the furious pace of data collection, probably at the petabyte scale. (Session OB09)
History of Physics in National Defense.
Hans Bethe, who wrote out the nuclear reactions that govern the production of energy in the Sun, was in charge of the theory division on the Manhattan Project, which lead to the construction of the first atomic bombs. He will discuss his personal recollections of the World War II project, including the Trinity test in New Mexico where the first atomic bomb was exploded. C. Paul Robinson, the president of Sandia National Labs, will argue that the success or failure of the international Chemical Weapons Convention and the proposed Biological Weapons Convention will depend upon new technology to enable the monitoring of these challenging and unique threats. A.D. Wheelon of the National Oceanic and Atmospheric Administration will discuss details about physicists' role in developing strategic reconnaissance programs during the Cold War. (Session SA03)
The Rental Car Problem.
Kristen Joan Russell of the Northwestern State University of Louisiana will discuss an intriguing mathematical connection between Fermat's principle — in which light chooses a path that minimizes the time of travel as it passes through different substances — and the often vexing "rental car problem," in which one tries to minimize the cost of fuel in a round trip between cities with varying prices of fuel along the way... all while returning with a full tank. (Paper OC38.17) Incidentally, Russell is an undergraduate. This talk and many other examples of creative undergraduate physics research will be showcased at four Society of Physics Students sessions. (Sessions BC11, IC11, LC11, OC38)
Nuclear Physics with Lasers.
Irradiating solid targets at very high intensities with a very short pulse of laser light from a short-pulse laser like Livermore's Petawatt laser (the most powerful in the world) can create not only very high-energy electrons, but also provides very bright beams of gamma rays that can induce nuclear reactions in the target materials. Following up on late-breaking results presented in November, Tom Cowan of Livermore will provide a review and update on these experiments, which includes the creation of 100 MeV electrons (a new record for electrons coming from a solid), positrons moving at relativistic speeds, and various photo-nuclear reactions. (Paper RP01.88)
Supernovae in the Universe and on Lasers.
Core-collapse supernovas (SNs) represent one of nature's most dramatic events, the catastrophic explosion of a massive star. Owing to their intrinsic brightness, they are used to gauge the distances to the outermost reaches of the space, allowing the rate of expansion of the universe to be assessed, and providing the shocking recent evidence that the universal expansion is accelerating. However, the basic mechanisms and fundamental physics behind the triggering of a SN still have many open questions. In a burgeoning new subfield of plasma physics, intense lasers are being used to recreate small-scale laboratory versions of certain exploding SN plasmas for more careful scrutiny. Bruce Remington of Livermore will describe these experiments and mention numerous other examples of "laboratory astrophysics." (Paper XB21.02)
Eberhard Bodenschatz of Cornell will report on the use of wax sheets as a model for the movement of tectonic plates. Simulating in an afternoon what geologic forces took millions of years to do, Bodenschatz gets good agreement between his lab specimens and the actual patterns observed in oceanic rifts. (Session QC28.)
Physics in the Petroleum Industry.
R.L. Kleinberg of Schlumberger-Doll Research in Ridgefield, CT will describe how nuclear magnetic resonance (NMR) — the basic technology used in magnetic resonance imaging (MRI) — is now being used by oil companies to characterize hydrocarbon reservoirs on-site. Daniel Rothman of MIT will discuss the complex, beautiful structures and patterns of eroding landscapes; he will also discuss efforts to model the erosion process so that physicists can, in essence, go backward in time to infer the structure of sedimentary basins before the onset of erosion. Jim Black of Landmark Graphics Corporation in Colorado will discuss the latest advances in using seismic waves to construct 3-D images of hydrocarbon reservoirs. Nicholas Cernansky will describe ideas for scientists to improve the internal combustion engine in cars. (Session JC08)
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