College Park, MD (February 3, 2009) -- The March Meeting of the American Physical Society, the largest physics meeting of the year, will take place March 16-20, 2009 in Pittsburgh at the David L. Lawrence Convention Center. Scientists from around the world will present more than 7,000 papers on the latest cutting-edge research in condensed matter physics, new materials, chemical and biological physics, fluids, polymers, and computational physics. A number of sessions will also address the role of physics in industry and various other settings, such as its relevance to education in developing nations, the quantitative study of paintings, and climate change mitigation.
Descriptions of Selected Topics
GRAPHENE STAYS HOT
More than two dozen sessions are devoted to the study of graphene, a two-dimensional form of carbon. The lead-off session of the meeting, session A1, looks at how graphene properties can be tweaked to produce novel effects and possible applications in micro-circuitry. Changing the substrate on which the graphene sits or the triggering of small terraces in a graphene sheet are methods for tuning graphene behavior (Session A1). Other sessions feature new experimental results (Session B1), electronic behavior (Session H1), and electron trajectories in graphene (Session J1).
WHAT THE COMPANY YOU KEEP (ON FACEBOOK) CAN SAY ABOUT YOU
It turns out that you can learn a lot about a person without meeting them, provided you know who his or her online friends are. The insights are readily available via applications such as Facebook and MySpace, which provide tremendous, searchable maps of social interactions. Amanda Traud and Peter Mucha of the University of North Carolina have mapped portions of these social networks at 100 universities across the country. They and their team of collaborators investigated the correlation between individuals' personal traits, like similar college majors or a common high school, and the communities formed online. With such information, it becomes possible to infer limited information about any one student based on the characteristics of the friends in his or her community. (H9.13).
IT’S THE LITTLE THINGS THAT MATTER MOST
Sometimes the smallest things have the biggest impacts. This simple concept about how small variations in a system can cause huge unpredictable changes is a major area of study in physics. It is a concept that applies to numerous fields with large complex systems, including everything from evolutionary changes to market crashes to sudden structural failures. Using phase transitions in condensed matter, Daniel Stein of New York University shows how the presence of even a small amount disordered “noise” in a system can eventually cause the system to completely rearrange itself. These principles have already led to one patent and a second application for methods to make computer hard drives smaller and faster. (D7.1).
CHEAP, BENDY PHOTODETECTORS
Xiong Gong and his colleagues at the University of California, Santa Barbara and CBrite Inc. have developed prototypes of low-cost flexible photodetectors that are sensitive to infrared, visible, and ultraviolet light in the wavelength range of 300 to 1450 nanometers. The photodetectors are made with semiconducting polymers that work much like common commercial silicon-based photodetectors by converting light into electrical signals. They are at least as sensitive as silicon photodetectors, says Gong, and they have the advantage of covering a very broad spectral range as well as being flexible and much cheaper to produce. The potential commercial applications for these new photodetectors are numerous. They include image sensing, communications, chemical, biological, and environmental monitoring, remote control, night-time surveillance, and military applications. Gong predicts that the technology will be commercially available in less than five years. (H20.10).
Physicist Richard Feynman famously pointed out that there’s plenty of room at the bottom, referring of course to the untapped potential of very small devices. But if you want to build tiny things, it’s handy to have some tiny tools to help out. Abha Misra and colleagues at Caltech are shaping carbon nanotubes into minuscule soldering irons. The researchers used electron beams to carve the world’s smallest soldering tips from iron-filled nanotubes, and demonstrated their tiny tool by soldering other carbon nanotubes together. Ultimately, the nano-soldering iron should be ideal for linking together molecular-scale mechanical and electronic devices (J24.2). Before you can solder nanoscopic components together, you have to put them in the right places. But picking up and moving a device that would be dwarfed by a red blood cell has its own challenges. Keith Brown of Harvard will present an innovative proposal to move components with the sharp tip of an Atomic Force Microscope (AFM). In order to prevent nano-objects from sticking to the AFM tips, Brown and his fellow researchers are looking to a method that permits them to hold objects without actually touching them. Applying a radio frequency signal to specially-designed AFM tips allows them to capture small objects while keeping them a small distance away from the AFM tip, like a tiny version of a sci-fi tractor beam (V27.2). Of course, it’s important to image the tiny devices once they’re soldered together, and to get an idea about how well they’re working. Andreas Huber of the Max Planck Institute for Biochemistry will describe an imaging system that provides nanometer resolution and is particularly well suited to analyzing superconductors, semiconductor devices and even individual molecules. The new nanoscope relies on terahertz (THz) light. Imaging devices usually can’t resolve structures smaller than the wavelength of the light they are using, but Huber and colleagues have managed to image objects with resolutions 3000 times smaller than the wavelength of terahertz light, setting a new record for sub-wavelength resolution (P27.13).
THE LIFE AND TIMES OF PRO ATHLETES
Some professional athletes wash out after only a few short seasons while others hang in for decades -- it’s just hard to predict how any individual player might end up. Fortunately, professional sports are a veritable treasure trove of statistical information with detailed records about careers going back generations. Using this wealth of data, Alexander Petersen of Boston University has for the first time put together a definitive plot of the likely length of a player’s career. He found that the vast majority of professional athletes retire after only a few seasons, while a small but statistically significant number stick around for many years. The trend holds true for different sports in locations around the world. Every sport Petersen analyzed at every location across the globe produced nearly the same statistical plot, strongly indicating that this kind of career distribution is universal in the sporting world. (Q15.11).
NETWORK ANALYSIS REVEALS COMPLEX BIOLOGY
Size matters to organisms like budding yeast, and the organism has hundreds of intricately balanced, interacting genes to help it calculate and maintain its optimal size. Jan Skotheim of Stanford University is presenting the latest understanding of this complicated genetic system, analyzing the system as a network in order to understand its complex biological behavior. The type of yeast Skotheim studies uses a feedback loop to maintain its size. Once it determines that it is sufficiently large, it begins the process of replicating its DNA and budding off a new yeast cell. This process is all-or-nothing, says Skotheim, and once a yeast cell begins replicating, it is fully committed. The decision is triggered by a set of proteins called G1 cyclins that drive the process forward by synchronously activating some 200 other genes involved in replication. The trigger proteins themselves are governed by a strong positive feedback loop, and by studying their expression within living cells, Skotheim has now begun to piece together how this genetic feedback loop governs replication. The work may have downstream medical applications, because humans have proteins and pathways that govern our biology much as those controlling growth in yeast. Some of these networks are implicated in the aberrant cell growth that is a hallmark of cancer, and Skotheim hopes that uncovering generalizations about the networks in yeast will reveal new light on how similar networks work in humans -- and how they go awry in cases of cancer. (A7.1).
In the race to develop the next generation of storage and recording media, a major hurdle has been the difficulty of studying tiny magnetic structures that will serve as their building blocks. Now a team of physicists at the University of California, Davis, has developed a technique to capture the magnetic "fingerprints" of certain nanostructures -- even when they're buried within the boards and junctions of an electronic device. Kai Liu will discuss experiments involving copper nanowires embedded within cobalt nanodisks. The team applied a series of magnetic fields to the wires and measured the responses from the nanodisks. By observing the way various electric fields affect disks, they can determine how the disks switch from one alignment to another and get quantitative information about how many nanomagnets are in one particular phase: for example, whether the magnetic moments are all pointing in the same direction or curling around a disk to form vortices. This in turn tells them how best to encode information with nanomagnets. (J31.8).
A TOUCHING TECHNIQUE FOR IDENTIFYING CANCER CELLS
Distinguishing between healthy cells and cancerous ones is often an inexact science, traditionally relying on visual identification, analysis of cell growth, or genetic tests, among other techniques. Researchers at Clarkson University and the University of Australia have now found that they can tell the difference between normal and cancerous cells through touch. The group used an atomic force microscope (AFM) to study the adhesion of silica beads to malignant and normal cells cultured from the human cervix. They found that analyzing the relative stickiness of cells is a good way to tell cells apart, potentially taking the guesswork out of cell identification and leading to a quicker and more reliable method of cancer diagnosis. Igor Sokolov of Clarkson University will present the study of their novel detection technique. (MV27.4).
HYBRID PROTEIN-NANOPARTICLE MEMORY UNIT
Researchers in Israel have developed a novel memory unit that combines a ring-shaped protein molecule 11 nanometers in diameter with a 5 nanometer particle of silicon. The structure can be electrically charged to store a single bit of information. The achievement is an example of a promising bottom-up approach to building nanoscopic electronics, rather than the top-down technique of carving devices out of silicon, which is getting increasingly challenging as technology moves to ever smaller scales. (A28.11).
TO CRACK, OR NOT TO CRACK
A brittle material fails because cracks form and ruin its structural integrity. This is one of the most basic tenets of material physics, but the propagation of cracks has never been well understood. A new theoretical and experimental analysis offers valuable insights into how a material will fare over time. Materials break around the weakest points, which are usually impurities or defects in the object’s molecular structure. Up to now, it has been very difficult to predict how different stresses would cause these defects to crack and fail. Caltech physicist Laurent Ponson’s new model describes how a material’s natural impurities affect its long term durability. It’s been well known for years that some material impurities can actually increase an object’s life by deflecting cracks, but this new model quantifies the process. This will give engineers a powerful tool for predicting how brittle substances like clay or glass hold up over their lifetimes. (W9.1).
NETWORKS NIX VIRAL EXPANSION
All network nodes are not created equal. A new simulation by Jian Kui He and colleagues of Rice University shows that when tracking the spread of a computer virus it’s important to remember that not everyone is equally interconnected. A virus infects an email network by attacking a single computer then spreading to many others. The researchers introduced a hierarchical organization to the links between the network nodes to better mimic real world email users. Nodes were arranged into clusters; clusters were arranged into larger groups, and so on. It turns out that viruses spread more slowly through hierarchical networks than networks where everyone is equally interconnected. (H9.10).
MATHEMATICS OF IMMUNITY SUGGESTS NEW VACCINE STRATEGY
Influenza viruses mutate quickly as they circulate around the globe -- so rapidly, in fact, that they render one year's flu shot ineffective against the next year's strain. This is why the federal government recommends a slightly different flu vaccine every year (and one of the reasons why flu shots don't always afford perfect protection). Now Michael Deem and his colleagues at Rice University have created a mathematical model that can predict how effective a vaccine against one strain of influenza will be against another strain. The model tracks mutations in the virus's coat of proteins and represents the difference between two strains as a numeric score. When tested against several decades of epidemiological data on the effectiveness of flu vaccine, this score closely predicts the clinical data. The goal is to understand how vaccines put pressure on viruses to evolve. Deem will also present work on Dengue fever virus, a tropical mosquito-borne pathogen that infects some 50 million people a year worldwide. Work in Deem's laboratory has suggested a novel approach to Dengue vaccination, which has been confounded to date by the fact that there are four distinct types of the virus and no one shot is an effective vaccine against all four. Deem's hypothesis -- as yet untested clinically -- is that giving four different shots for each separate viral type in four different veins may be an effective solution. (W39.15).
These new materials--the first superconductors above a temperature of 50 Kelvin not made from copper-oxide planes--have made a big splash over the past year. Last year’s meeting featured no session on this topic. This year: a dozen sessions. Topics include the possible ways in which electrons pair up on the Fe-based materials, summaries of how the materials are made, electronic properties, theoretical explanations, and the manifestation of the Josephson effect and other superconducting phenomena.
SPECIAL MICROENVIRONMENT FOR BIOFUEL OPTIMIZATION
Princeton University’s Troy Mestler, Andre Estevez-Torres, and t Robert Austin have created a specialized silicon surface that allows them to grow algae while carefully controlling nutrients and monitoring the growth via Raman spectroscopy. The goal is to direct the evolution of the organism by selecting for strains with desirable properties -- in particular, the ability to produce large amounts of oil that could then be converted into diesel fuel. (H40.7).
In 2004 Penn State physicist Moses Chan presented preliminary evidence of superfluid behavior in a sample of solid helium. This evidence consisted of the sample, or least part of the sample, remaining stationary even when its container was given a quick twist. Since then the experimental observations of Chan have been confirmed in at least six other laboratories. However, the exact physical mechanisms responsible for the observation are still unclear. What is clear is that superfluidity in solid helium is quite different from that in liquid helium. (Session W1). (V16).
A POLYMER THAT BEATS LIKE A HEART
The overall function of certain biological tissues like the heart emerges from the fact that its cells can join together in coordinated movements like a heartbeat in response to a triggering signal. Now this ability has inspired researchers to design polymer materials that can do the same sort of thing. Anna Balazs of the University of Pittsburgh will describe her research on one such material: a polymer gel that’s sensitive to pressure and beats like a heart when touched. The gel contains a metal catalyst, and touching it in one spot induces a cyclic chemical reaction that spreads over the entire material and causes the whole gel to vibrate. Balazs has developed the first computational model describing the microscopic shape changes that occur in these touch-sensitive gels. Balazs and her group have also designed polymeric materials that vibrate in response to light and will actually wiggle away from a light source when exposed to it. The overall goal of the research, she says, is to impart lifelike functions, such as the sensitivity to touch, on inanimate objects. Touch-sensitive robots and damage sensors on airplanes and other vehicles are some of the more obvious applications. (X4.1).
BUILDING NEW MATERIALS WITH DNA AND NANOPARTICLES
One of nature's most utilitarian polymers is DNA. Now Francis W. Starr of Wesleyan University and his collaborators are developing manmade DNA-based materials. Single strands of DNA can easily be attached to nanoparticles with interesting chemical properties, and the base-pairing ability of DNA allows it to form networks of such nanoparticles, self-assembling into new materials with novel properties such as multiple melting points. Attempting to understand the basic physics of such materials, Starr will present simulations in Pittsburgh that show how his DNA-nanoparticles assemble and pack. Coatings containing low-density DNA-nanoparticle arrays would be valuable for numerous optical applications because they can change the properties of light. The large cavities in these materials may also make them useful for applications such as drug delivery. (J5.5).
POISSON’S SPOT WITH MOLECULAR WAVES
In the early 19th century, the theory that described light as being made of particles was challenged by a series of experiments showing the wavelike nature of light. One of these was the phenomenon known as the Poisson spot, in which a beam of light that streams past a tiny disk will diffract around the edge in such a way as to create a pattern with a single bright spot at the very place where the beam should be darkest-behind the center of the obstruction. Now a Bergen/Graz/MIT team of scientists has reproduced this experiment using molecules consisting of two deuterium atoms, in keeping with the central principle of quantum mechanics which says that particles (even those as large as deuterium molecules) can behave as waves. At the meeting Thomas Reisinger and his colleagues will present their observations of a tiny bright spot of atom waves behind the center of a 60-micron-wide disk interrupting a deuterium beam with an effective wavelength of about one angstrom. (H16.2).
TITANIUM DIOXIDE KILLS SKIN CELLS
Titanium dioxide is a common pigment used in everything from paint to sunscreen -- even breath mints -- but despite its ubiquity in commercial products, its safety may be a cause for concern, according to Miriam Rafailovich and her colleagues at Stony Brook University. The problem, she says, is that titanium dioxide produces peroxide and other chemicals that can damage cells when it is exposed to UV light. Using cultures of a common type of skin cell known as "dermal fibroblasts," Rafailovich and her colleagues showed how titanium dioxide can damage the cells' DNA and lead to cell death. They also showed that coating the particles with electrically active polymers can protect the cells from damage. (J40.7).
PHYSICS AND CULTURE
Speakers in two sessions will examine the ways physics relates to a variety of artistic ventures, from the paintings of Van Gogh, Monet, and Pollock, to the architecture of medieval Islam and contemporary China (such as the Olympic Water Cube in Beijing), to the overlap of science, scientists, and the making of movies in Hollywood. (Session Q3). (Session W5).
10,000 PHYSICS MAJORS
Science is the engine of technological innovation, and many leaders are calling for more funding and encouragement for science/technology/engineering/mathematics (STEM) education majors. Right now, only about 1.4 percent of STEM graduates are in physics. Both the American Physical Society (APS) and the American Association of Physics Teacher (AAPT) have issued statements calling for doubling the number of undergraduate physics majors in this country. Roughly 5,700 physics baccalaureate degrees are presented annually. Theodore Hodapp, APS director of education and diversity, will present the rationale for having 10,000 physics majors. A main reason is that an education in physics prepares a student for tackling many of the large technical issues facing society. (B3.1).
PERIODIC TABLE FOR QUANTUM DOTS
A quantum dot is a tiny speck of semiconducting material in which electrons are confined to an essentially zero-dimensional point. Quantum science then says that the allowed energies of those electrons-just like the electrons confined to the interior of an atom-are restricted. Indeed, a quantum dot is sometimes referred to as an artificial atom; a lone electron, freed from an atom in the dot by laser light, along with the migrating vacancy left behind, form a composite object called an exciton. That exciton within the confines of the dot constitutes an artificial hydrogen atom, with a unique energy spectrum of its own. Maneuver to have two such excitons in the dot and you have an artificial helium atom. McGill University physicist Patanjali Kambhampati will report on the first detailed studies of a “helium” quantum dot. Artificial “lithium” and indeed many other atoms seem to be in the offing. (H10.28).
Pressures of 100 GPa (billion Pascals), equivalent to a million times atmospheric pressure, are comparable to the chemical strengths of solids made of molecules, such as H2, CO2, and N2. Much higher pressures than that can be brought to bear on materials, either through static methods, such as with diamond anvil cells, where pressures can reach 360 GPa, or dynamic methods, such as with laser pulses or explosions that can reach pressures over a trillion Pascal (TPa). Choong-Shik Yoo, a scientist at Washington State University, will discuss TPa chemistry and will report on specific molecular-to-nonmolecular transitions observations in his lab under high pressure. Examples include quartz-like and silica-like forms of carbon dioxide. (P13.4).
PHOTON MACHINE GUN
Photons are parcels of light and often come trillions at a time, in the form of light rays. They’re also interesting and useful one at a time. A source of single photons on demand, under the name of a “photon machine gun,” is available at: A17.3.
Headquartered in College Park, MD, the American Institute of Physics is a not-for-profit membership corporation chartered in New York State in 1931 for the purpose of promoting the advancement and diffusion of the knowledge of physics and its application to human welfare. Web site: http://www.aip.org.