More than 7000 physicists will converge on Denver, Colorado this month for the APS March Meeting, usually the largest physics meeting of the year. The meeting will take place at the Convention Center in Denver, at the threshold of the beautiful Rocky Mountains, March 5-9, 2007. The principal topic areas will be condensed matter physics, industrial applications, new materials, chemical and biological physics, fluids, polymers, and computation. A number of sessions will address social issues. Happy Anniversaries
. Two momentous occasions in the 20th century history of physics will be celebrated at the Denver meeting. The first is the 20th anniversary of the so-called “Woodstock of Physics”: a mammoth session at the 1987 APS March Meeting devoted to the new class of ceramic superconductor discovered not so many months before. After decades of poring over materials which became superconducting only at liquid helium temperatures, the prospect of critical temperatures above 100 Kelvin electrified scientists and the public alike. Speakers reporting fresh results on so-called high temperature superconductors (HTSC) went on until 3:15 am. Now, 20 years later, another set of talks (a few by the same practitioners from 1987) will review what has been learned and what we can look forward to when it comes to superconductivity (B1).
While the HTSC anniversary might command more attention, the anniversary of the highly successful theory of low-temperature superconductivity is also important. Named for its three originators–John Bardeen, Leon Cooper, and Robert Schrieffer, who shared a Nobel prize for their efforts –the BCS theory explains superconductivity as arising from the pairing of electrons through the mediation of subtle vibrations rippling through the material. Physicist Paul Grant calls the BCS work “the most monumental theoretical achievement of condensed matter physics in the 20th century.” A special evening session at the March Meeting will look at the impact of this theory on the study of not only atoms and solids but also nuclei, quarks, and the cosmos itself. (G1) Latest Quantum Computer Hardware
. Physicists are pursuing several hardware options for making truly powerful quantum computers that would fulfill their potential of performing ultra-fast database searches, rapidly cracking secret encrypted codes, and greatly improving molecular-level simulations for designing drugs and other new materials. At the Denver meeting, researchers will describe quantum-computer designs based on a newer approach, the use of superconducting electronic components, which could be made with existing manufacturing methods and are inherently less noisy than classical semiconductor circuits. Developments include the construction of a component called a controlled-not quantum logic gate, the first proposed superconductor-based quantum computing architecture that enables error correction, and a “dial” that can vary how strongly the superconducting quantum bits (qubits) interact. (N2)
Several other researchers will discuss quantum computing designs based on trapped ions, presently the most technically advanced approach. NIST-Boulder’s David Wineland (D2.2) will discuss a promising new multiple-electrode, single-plane ion-trap design that potentially prevents ions from overheating, currently the bane of all ion-trap groups. Lucent’s Dick Slusher (D2.4) will talk about silicon-based VLSI (very-large-scale integration) processes for scaling up the number of traps so that they would contain enough ions to perform useful quantum simulations of real-world materials. Additional meeting talks feature semiconductor-based (B43.4), exotic-particle-based (D7.4), and optics-based (S33.3) quantum-computing designs. Natural Glue
. Studying adhesives in natural composite materials such as bone and mollusk shells at the nanometer scale, microscopy pioneer Paul Hansma and his colleagues have learned a few lessons which they have concluded can lead to a new class of tough, lightweight, and damage-resistant artificial materials. Natural composites are held together by organic glues that make up just a few percent of the composite by weight. These glues hold together the stronger elements in the composite. They yield just before the strong elements otherwise break. They heal themselves by re-forming chemical bonds. According to calculations by Hansma and colleagues, combining stiff and strong nanostructures such as carbon nanotubes or graphene with just a few percent by weight of biologically-inspired adhesives could lead to a new generation of high-performance materials (A4.3).
The Cost of Light
Photo: Los Alamos National Laboratory
Multi-color light emitting diodes
. Lighting in the US is a $50 billion business and accounts for 22 percent of electricity use. Solid-state lighting, as manifested in light emitting diodes, seeks to get the most light out of available electricity. LED light flourishes in niche markets, such as brake and traffic lights, and future conquests are in sight. Performance of 138 lm/W(lumen per watt) have been achieved in the lab for low power devices and over 90 lm/W for high power devices. According to George Craford (Philips Lumileds Lighting Company), “high power commercial products with performance in excess of 100 lm/W will become available soon, which is substantially more efficient than incandescents (15 lm/W) and compact fluorescents (60 lm/W) and equivalent to high performance fluorescent lighting.” Representatives from a variety of labs pursuing solid-state light will provide reports on their progress. (J3) Knowing Left From Right
. Like many other biomolecules, RNA and DNA exist in nature in right-handed but not in left-handed form. This asymmetry, known as chirality, is one of the most mysterious open questions about the origin of life. A previously unknown difference between the two versions of the RNA molecule has now emerged. Raman spectroscopy seems to suggest that the energy levels of certain electrons are slightly different in the two versions. This slight asymmetry could be an effect of the weak nuclear force. Future studies will use a new free-electron laser to probe other electron energy levels in RNA. (V35.7) Security Scanners Look to the Stars
. A new imaging system could surreptitiously identify people carrying concealed weapons with the use of detectors derived from instrumentation that has long been a mainstay in astronomical observations. The system that Panu Helisto (VTT Technical Research Centre of Finland) will describe detects the terahertz radiation that people and warm objects naturally emit all the time. Terahertz imaging provides higher resolution than infrared monitors and works at ranges of 10 to 30 meters. Because they detect temperature variations, they don’t reveal anatomical details that show up on some other clothes-piercing scanners. Such a technology would be an ideal security scanner for airports and other public spaces. (Y39.1) Energy Boosts from Land and Sea
. Douglas Schmitt (University of Alberta) will report on new seismic imaging methods to track the flow of heavy oils, such as those in Colorado’s shale and Canada’s abundant oil sands, when they are extracted via the injection of solvents or steam into the ground. Accurate imaging of reservoirs will be vital if sand or shale oils are ever to become significant energy sources. Later in the same session, Timothy Collett (U.S. Geological Survey) will provide an assessment of the promise of another unconventional energy source–icy combinations of natural gas and water known as hydrates. Collett will summarize the latest estimates of hydrate reserves and survey the various methods for extracting natural gas from them. (A2) To Mars!
Manned missions to Mars and a semi-permanent lunar base are currently high on NASA’s priorities. Unfortunately, once we leave the protection of Earth’s magnetic field and atmosphere, we are mercilessly exposed to numerous sources of radiation. In order to survive trips to Mars and even extended stays on the moon, we are going to have to come up with light, effective shielding. Ram Tripathi (NASA) will discuss some of the shielding options, including carbon nanofibers, that could offer long term protection to space travelers. (W28.13) Brainy Amoebae
. For the first time, the hunting strategy of an amoeba has been shown to be somewhat better than random. The amoeba called Dictyostelium seems to remember its previous steps–which it performs by pumping itself into protuberances known as pseudopods–and to explore new grounds, increasing its chances of finding food. One hypothesis is that the formation of pseudopods leaves temporary “scars” in the cell’s cytoskeleton, making it more likely that the next pseudopod will point in a new direction. A similar mechanism might exist in a variety of other single-cell organisms and even in human cells such as neurons. (U35.4) Mapping Protein Folding
. Understanding how proteins fold is one of the questions at the heart of biophysics. Atomic force microscopes allow one to unfold proteins essentially by hand, and to compare the energy of the folded and unfolded configurations. A new technique uses a microscopic cantilever, attached to the AFM tip, to pull and stretch a protein while measuring the protein’s reaction force by how much it bends the cantilever. This way, the protein’s energy landscape can be mapped along the entire unfolding process, something that was previously only estimated by theoretical methods or simulations. The new technique can be applied to any protein, as well as to DNA and RNA. (V15.10). Liar, Liar
. A new network theory model could be the closest analogue yet to the classic Washington game of who-knows-whom and how best to leak information (and disinformation) to the press. When individuals try to get in contact with people who can lead them to the information they want, the result is a dynamically evolving web of social connections. The new model shows that if too many of the individuals spread false information, the result is a global breakdown of the network, with true information sent on ever longer paths and essentially lost. (P22.2) Down to the (Nano)Bone
. Bone contains important nanometer-scale structures that endow it with much of its strength. Christine Ortiz (MIT) will describe experiments involving “nanogranular friction,” the resistance to motion caused by nanometer-scale mineral particles in bone, which help to increase the strength of bone when compressed. Ortiz and her colleagues are studying the variations in its composition and porosity in different points of its structure, and are proposing that these structural variations lead to a new mechanism of energy dissipation that might enhance certain bone properties such as ductility, the ability of bone to change shape. (Y4.5) Climate Change
. Susan Solomon (National Oceanic & Atmospheric Administration) is a co-chair of the current study by the Intergovernmental Panel on Climate Change (IPCC), the organization jointly established by the World Meteorological Organization and the United Nations Environment Programme (UNEP) in 1988. An expert on the ozone hole, Solomon will discuss the upcoming report of the IPCC Working Group 1. Doug Nychka (National Center for Atmospheric Research) was a member of a recent NAS panel exploring the “hockey stick” shaped curve of temperature versus time. The NAS came up with a reasonable judgement that the statistics used in making the curve were not perfect but that this inaccuracy wouldn’t change the net conclusion much, namely that anthropogenic warming was taking place. David Randall (Colorado State) will talk about counting clouds and, more generally, how to address the problem of accommodating such widely different size scales in climate modeling. (V7) Entrepreneurial Physics
. Spinning a promising new technology into a viable commercial business has its pitfalls. Philip Wyatt of Wyatt Technology Corporation will share his experiences starting his own company. His first attempt failed, but he took the lessons learned and successfully started a second venture, commercializing new instrumentation for studying the laser-scattering properties of cola beverages. Other speakers offering their entrepreneurial insights at the session include James Wyant (University of Arizona), founder of the WYKO Corporation; Virgil Elings, co-founder of Digital Instruments; and John Woollam, founder of J.A. Woollam Co. (H6) Pauli as Mephistopheles
. Quantum physicists attending a 1932 meeting at Niels Bohr’s Copenhagen Institute amused themselves by staging an updated version of Goethe’s Faust. The plot featured Pauli tempting Paul Ehrenfest to accept the idea of a chargeless, massless particle, then called the neutron. George Gamow’s second wife, Barbara, translated the anonymous Faust: Eine Histoire, which was published in Gamow’s Thirty Years That Shook Physics. Karen Keck of the Net Advance of Physics will talk about the parallels between Goethe’s original and the parody, and how Barbara Gamow’s translation compares to both. (U20.2)