Caltech fluid dynamics expert wins annual Feynman Award for excellence in teaching

PASADENA, Calif.-Chris Brennen has many pleasant memories of the "frosh camp" trips he used to make to Catalina Island with famed physicist Richard Feynman. As two California Institute of Technology faculty members who were particularly willing to accompany the new crop of Caltech freshmen on the annual orientation trip, Brennen and Feynman shared various interesting experiences at the rustic Camp Fox.

"I remember him sitting on the low stone wall at Camp Fox surrounded by maybe a hundred frosh," says Brennen, a professor of mechanical engineering, "all enthralled by his stories of particle physics, or lock picking, or Mayan hieroglyphics, or whatever."

Now, two decades later and 16 years after the passing of his friend, Brennen has been named winner of the annual Feynman Prize, which is Caltech's most prestigious teaching honor. The prize is given to a faculty member each year for "exceptional ability, creativity, and innovation in both laboratory and classroom instruction."

Brennen is known to the student body as an especially lucid and helpful teacher of fluid mechanics, which is a crucial field for any future engineer to master if he or she intends to work in pretty much any technical application that concerns fluid flow. The rudiments of fluid mechanics were important to the Wright brothers, and are just as important today to the designers of Mars landers-and someday, perhaps even to the designers of future Europa submarines. Brennen himself has done research on one of the components of the space shuttle's engine, and his interests generally center on the still-imperfectly understood issues of complex multiphase and multicomponent flows.

"These are a ubiquitous part of almost all existing and projected energy systems, yet our understanding of these flows is inadequate for many engineering purposes," Brennen writes on his Web site.

Brennen's research also involves acoustics, and one of the students nominating him for the Feynman Award recalls a student field trip to the Mojave Desert, where the group hiked up several miles to the top of a sand dune, then slid back down to cause the dunes to "boom."

"Professor Brennen's enthusiasm, even in hundred-degree-plus temperatures, was an inspiration," the student said in nominating him. "His scientific intuition in the field taught me a lot."

Another student applauded Brennen's "perpetual enthusiasm that kept me interested through unavoidably dry material." Yet another remarked that he'll never forget Brennen, "dressed up in a suit, riding a bike into the swimming pool at the year-end swimming party-that is, the year-end real-life experimental laboratory in fluid mechanics, where the undergrads compete in underwater bicycle racing."

As for his faculty peers, Caltech mechanical engineering professor Melany Hunt notes that Brennen "has shown us the importance of connecting with students, of encouraging their interests and their abilities, and of enjoying and appreciating student-faculty interactions.

"He has also demonstrated that it is okay to be a little crazy-such as riding a bicycle into a swimming pool-especially if it helps students to appreciate the wonder of fluid mechanics and engineering."

The bicycle stunt is a Brennen original, but is very much in keeping with the spirit and enthusiasm of the Nobel laureate for whom the award is named. Brennen says he is thrilled to be associated with Feynman through the award.

"I regard myself as being truly blessed to have lived out my career at this unique institution, to have interacted with such inspiring colleagues and to have had the privilege of teaching the best students in the world," he says.

Robert Tindol
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New light-emitting device could eliminate the bottleneck that slows down electrical circuits

PASADENA, Calif.--Applied physicists at the California Institute of Technology have invented a light-emitting transistor that could potentially bypass a major bottleneck that slows down electronic circuitry. The new device could pave the way for on-chip optical interconnections that would enable the marriage of two great modern technologies--communications based on the transmission of photons, and computing with silicon-based devices that are driven by electric currents. A successful optical interconnection technology would allow information to move around inside a silicon chip at the speed of light while creating substantially less heat, leading to dramatically faster computers.

Reporting in the current issue of the journal Nature Materials, Caltech graduate student in applied physics Robb Walters and his faculty adviser, Professor Harry Atwater, describe their success in building a nanophotonic device that employs a novel method of turning an electric signal into a light pulse.

"It's been difficult to combine silicon-based integrated circuits and optical devices," says Walters, who invented the device and is the first author of the Nature Materials paper. "Our new device brings us one step closer to a silicon-based light source that may ultimately lead to the light-emitting devices needed for on-chip optical interconnections."

The device Walters has invented contains at its core a tiny spherical bead called a silicon nanocrystal that absorbs an electron and a positive-charge carrier called a "hole." Inside this nanocrystal, the electron and the hole can be combined to release energy as a photon of near-infrared light that shines out of the transparent side of the bead. In effect, this pulse of light, when launched into a waveguide, takes the place of an electrical signal traveling down a wire in a chip, increasing the speed of data transmission. The bead is literally a nanocrystal, because its diameter is only about three or four nanometers.

So tiny is the bead, in fact, that its very dimensions are responsible for the wavelength of the light emitted, due to quantum effects. The bead size can be used to "tune" the frequency of the photons, a slightly smaller bead emitting slightly higher photon energy and a larger bead, lower energy. The fact that one nanocrystal absorbs one electron and hole, and emits one photon, could also conceivably be useful for future single-photon technologies, says Atwater.

"Eventually, the photons from the nanocrystals will go to a photodetector in a complete, photonic integrated circuit," says Atwater. "The device might also be useful for visible displays. However, this is still basic research and development. We have not yet integrated the device with waveguide detection; but in principle, it will work."

The new device is different from existing silicon light-emitting diodes and other nanocrystal structures in that there is not a constant driving current required for light emission. The new approach, based on field-driven carrier injection, may be far more efficient than any existing technology.

"The current external power efficiency record for a silicon-based LED is about 1 percent," Atwater says. "We hope that our new device will allow that record to be substantially improved."

The title of the paper is "Field Effect Electroluminescence in Si Nanocrystals," and an illustration of the device is on the cover of the February issue. Copies of the paper may be obtained from Ruth Francis at

The research was cofunded by Intel and the Air Force Office of Scientific Research.

Robert Tindol

Caltech Launches New Information Initiative

PASADENA, Calif. — Information is everywhere. Most of us think about it in terms of mere facts--facts gleaned from a teacher or a colleague, from the media, or words from a textbook or the Internet.

But there are other, near-infinite types of information--the instructions encoded in our genome that tell our cells when to divide and when to die, or the daily flow of data into the stock market that somehow motivates people to buy and sell.

Information constantly streams to scientists from around the world, and from other "worlds" as well, thanks to sensors and actuators in the sea or out in space.

What's needed is a way to harness and understand all of this data so that scientists and engineers can continue to unravel the secrets of nature and the human institutions in which we operate. In an unprecedented effort, the California Institute of Technology has launched a university-wide initiative called Information Science and Technology (IST)--drawing back the curtain on the nature of information itself and redefining the way we approach, understand, and use science and engineering. IST will cut across disciplines, eventually involving over 25 percent of all faculty and nearly 35 percent of students on campus, likely altering the Institute's intellectual and organizational landscape.

Caltech has committed to raising $100 million for IST as part of the Institute's five-year, $1.4 billion capital campaign. Nearly $50 million has been raised in the form of separate grants of $25 million from the Annenberg Foundation and $22.2 million from the Gordon and Betty Moore Foundation. The Annenberg Foundation gift will be used to construct the Walter and Leonore Annenberg Center for Information Science and Technology--a new building that will be the physical center of IST. The building will join the existing Watson and Moore laboratories in forming a core of buildings linking together IST researchers.

Funding from the Moore Foundation will provide seed money to establish four new interdisciplinary research centers within IST. These new centers will join two that already exist at Caltech, and together the six groups will anchor and organize Caltech's effort to lead the way in this new field.

IST evolved over the last 50 years from an activity that focused on enabling more efficient calculations to a major intellectual theme that spans disciplines in engineering and the sciences. While other universities created schools of computer science (or computer and information science), these are generally related to computer science and software--a limited view of information science and technology. At Caltech, IST serves as a new intellectual framework on which to build information-based research and instructional programs across the academic spectrum.

"To maintain preeminence in science, the U.S. needs new and unified ways of looking at, approaching, and exploiting information in and across the physical, biological, and social sciences, and engineering," says Jehoshua (Shuki) Bruck, the Gordon and Betty Moore Professor of Computation and Neural Systems and Electrical Engineering and the first director of IST. "Caltech is taking a leadership role by creating an Institute-wide initiative in the science and engineering of information. IST will transform the research and educational environment at Caltech and other universities around the world."

In the same way that the printing press heralded the start of the Renaissance, and the study of physics helped to foster the Industrial Revolution, technological advances in computation and communication in the 20th century have set the stage for the Age of Information. Yet, scientific and technological changes are accelerating so fast they are outpacing existing institutions such as schools, media, industry, and government--structures originally designed for the needs of the Industrial Age. "So we need a new intellectual framework to harness these new advances," says Bruck, "in order to provide for a stable and well-educated society that's prepared to meet the challenges of tomorrow."

"Some say biology is the science of the 21st century, but information science will provide the unity to all of the sciences," says Caltech president and Nobel Prize-winning biologist David Baltimore. "It will be like the physics of the 20th century in which Einstein went beyond the teachings of Newton--which were enough to put people on the moon--and allowed people's minds to reach into the atom or out into the cosmos. Information science, the understanding of what constitutes information, how it is transmitted, encoded, and retrieved, is in the throes of a revolution whose societal repercussions will be enormous. The new Albert Einstein has yet to emerge, but the time is ripe."

Annenberg Foundation Gift The Annenberg gift is the first portion of a $100 million institutional commitment to IST, and is part of the Institute's capital campaign. Now in the design stage, the Annenberg Center is expected to be completed when the campaign ends in 2007.

"I am delighted that the Annenberg Foundation will be a part of this visionary enterprise," said Leonore Annenberg, foundation president and chairman. "As a publisher, broadcaster, diplomat, and philanthropist, Walter Annenberg was known for breaking new ground. Support for this important new initiative surely would have pleased him as much as it honors the work of the foundation."

Founded in 1989 by Walter H. Annenberg, the Annenberg Foundation exists to advance the public well-being through improved communication. As the principal means of achieving its goal, the foundation encourages the development of more effective ways to share ideas and knowledge.

Gordon and Betty Moore Foundation Gift The Moore Foundation gift is part of a $300 million commitment the foundation made to Caltech in 2001.

The four centers funded by the Moore grant are the following: the Center for Biological Circuit Design, which will address how living things store, process, and share information; the Social and Information Sciences Center, which will investigate how social systems, such as markets, political processes, and organizations, efficiently process immense amounts of information and how this understanding can help to improve society; the Center for the Physics of Information, which will examine the physical qualities of information and will design the computers and materials for the next generation of information technology; and the Center for the Mathematics of Information, which will formulate a common understanding and language of information that unifies researchers from different fields.

The Moore Foundation seeks to develop outcome-based projects that will improve the quality of life for future generations. It organizes the majority of its grant-making around large-scale initiatives that concentrate on: environmental conservation, science, higher education, and the San Francisco Bay Area. 


Fuel Cells: the Next Generation

PASADENA, Calif. — For several years now the Department of Energy (DOE) has been urging the fuel cell community to solve a major problem in the design of solid oxide fuel cells (SOFCs): heat. Such fuel cells could someday provide reliable power for homes and industry, dramatically cutting greenhouse gas emissions as well as other pollutants.

But SOFCs run hot, at temperatures as high as 1000 degrees Celsius (about 1800 degrees Fahrenheit). They're efficient at such temperatures, but only a few costly materials can withstand the heat. Using such materials makes things expensive, and is the reason for the push for lower temperatures by the DOE.

Sossina Haile, an associate professor of materials science and chemical engineering at the California Institute of Technology, is an expert in fuel cells, and she has been whittling away at the heat problem for years. Now she and her colleagues have not only solved the problem, they've smashed it. They've brought the temperature down to about 600 degrees Celsius (1100 degrees Fahrenheit), while achieving more power output than others are achieving at the higher temperatures--about 1 watt per square centimeter of fuel cell area.

They accomplished this by changing the chemical composition of one component of a fuel cell called the cathode. The cathode is where air is fed in to the fuel cell, and it's where the oxygen is electrochemically reduced to oxygen ions. The oxygen ions then migrate across the electrolyte (which conducts electricity), to react with fuel at the anode, another fuel cell component. The electrochemical reduction of oxygen is an essential step in the fuel cell's process of generating power. But the problem with running solid oxide fuel cells at 500 to 700 degrees Celsius is that the cathode becomes inactive when the temperature is less than about 800 degrees Celsius.

Haile and postdoctoral scholar Zongping Shao's insight was to switch out the conventional cathode and replace it with a compound that has a long chemical formula guaranteed to strike fear into the heart of every undergraduate, but is abbreviated as "BSCF" for short.

What BSCF can do that standard cathodes can't is to allow the oxygen to diffuse through it very rapidly. "In conventional cathodes, the oxygen diffuses slowly, so that even if the electrochemical reaction is fast, the oxygen ions are slow in getting to the electrolyte," says Haile. "In BSCF the electrochemical reaction is fast and the oxygen ion transport is fast. You have the best combination of properties." This combination is what gives the very high power outputs from Haile's fuel cells.

The work was reported in a recent issue of the journal Nature. Because they are using relatively conventional anodes and electrolytes with this new cathode, says Haile, it would be easy to switch out cathodes in existing fuel cells. That will probably be their next step, says Haile: to partner with a company to produce the next generation of solid-oxide fuel cells.

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National Institutes of Health Name Phillips, Quake as Director's Pioneer Award Winners

PASADENA, Calif.—The National Institutes of Health (NIH) has announced that California Institute of Technology mechanical engineering and applied physics professor Rob Phillips is one of nine recipients of the first annual Director's Pioneer Award. Stephen Quake, the Thomas E. and Doris Everhart Professor of Applied Physics and Physics at Caltech, currently at Stanford University, is also among this year's recipients.

The Director's Pioneer Award will provide Phillips with $2.5 million in funding for the next five years as part of the NIH's new "Roadmap for Medical Research" program. Phillips, an authority on the nanoscale mechanics of biological systems, says he will use the funding to enter into novel research areas.

"The NIH Director's Pioneer Award is both a huge honor and a privilege for which I am tremendously grateful," Phillips says. "Quite frankly, this award is going to completely transform my scientific life and will permit me to pursue some questions about the dynamics of complex systems such as cells that have been gnawing at me since I was a teenager.

"My background is of someone who builds mathematical models of these kinds of systems," he adds. "As a result of this award, we can now design and build experiments aimed at concretely exploring the extent to which our models are correct.

"In the short run, this overall vision will be played out in the context of a few key case studies, including how viruses manage the physical requirements of packing and releasing their genomes, how macromolecules conspire to decide when genes are turned on and off, and how cells respond to mechanical forces." A graduate of Washington University, Phillips has worked recently on DNA injection and packing that occur during the life cycles of bacterial viruses, as well as on how certain classes of ion channels are gated by mechanical forces. He is the author of a book titled Crystals, Defects and Microstructures that is based on his extensive work in modeling materials and which served as his jumping-off point for modeling living materials.

According to a statement from the NIH, the Director's Pioneer Award is intended to provide substantial support for researchers "willing and able to explore ideas that were considered risky at their inception.

"Such individuals are more likely to take such risks when they are assured of adequate funds for a sufficient period of time, and with the freedom to set their own research agenda," the statement continued. "Many of the new opportunities for [biomedical] research involve crossing traditional disciplinary lines and bringing forward different conceptual frameworks as well as methodologies. These developments appear to justify support for more aggressive risk-taking and innovation."

The nine recipients were formally announced at 9 a.m. PDT Wednesday by NIH director Elias A. Zerhouni, M.D. During a telebriefing, Zerhouni and the Pioneer Award program cochairs, Stephen E. Straus, M.D., and Ellie Ehrenfeld, Ph.D., will discuss the selection process and the areas of research the awardees will explore.


Science by the Seat of the Pants

PASADENA, Calif. — Sliding down a sand dune on your derriere might at first take seem a bit undignified for a professor from the California Institute of Technology. But for mechanical engineering professor Melany Hunt, it's all in the name of science.

Hunt wants to know why many desert sand dunes give off sound--and a loud, droning sound to boot--whenever the dune avalanches, or a strong wind blows, or a scientist slides down its side. While the phenomenon has been known about for centuries (Hunt has a book, Tales of Travel, circa 1923, that mentions Marco Polo knew about it), what causes the sound remains a mystery. Most believe the answer is friction--tiny grains of sand rubbing together. But that's only part of the story, Hunt believes, noting that the sound continues even after the movement has stopped. And further, the sound a sand dune makes in winter differs from the sound it makes in summer.

Intriguing questions, says Hunt, and it ties into her research concerning the flow of particulates and granular materials, including the natural environment of both sand and debris flows. Which is why she has spent the last few summers investigating the phenomenon of sand dune sound as a mentor with Caltech's Summer Undergraduate Research Fellowships (SURF) program. (Every summer, the SURF program brings undergraduate students from various schools to Caltech to conduct independent research with faculty members.)

So several times each summer, Hunt, her research colleague, mechanical engineering professor Chris Brennen, and her students make the long drive to the Eureka Dunes in Death Valley, California, or the Dumont Dunes nearby, or to the Kelso Dunes in the Mojave National Preserve, CA. Once there, they slog up to the dune's crest line, carting a radar unit, geophones (a type of microphone), and lots of water to combat the common 100-plus degree temperatures.

The equipment is being used to confirm Hunt's theory about the loud sound that's generated--she believes it's a resonance effect, much like a string being plucked on a musical instrument. Over a long period of time, whatever rain that falls in this desert environment percolates into the sand dune, eventually forming a band of moisture some two meters (6.6 feet) down. In time this sand hardens, says Hunt, forming a hard, cement-like crust. When the sand on the surface is disturbed, friction between sand grains creates a noise that reverberates, back and forth, between the dry sand on the surface and the wet sand below.

"That may be why smaller dunes don't make sound," says Hunt, "because they haven't been around long enough to form that hard layer of sand." The minimum needed is about two meters of thickness, she says. The loudest dunes are the tallest and the steepest, those with a maximum 30-degree angle of repose; that is, the steepest the dune's face can be without collapsing. It's also the reason she believes the sound varies by the season, which affects how much moisture is in the sand.

Hunt and her students dragged the radar to the top of the dune and used it to confirm the existence of the band of wet, hard sand down below. The geophone was used to record the noise as the students slid down the dune.

Hunt plans at least one more trip to a sand dune sometime in September; intrepid reporters are invited to attend. Meanwhile, for a QuickTime movie, complete with sound, of students sliding down a dune, please see the website of Kathy Brantley, one of Hunt's former students, at

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Jennings Named Caltech Provost

PASADENA, Calif.— Paul Jennings, professor emeritus in civil engineering and applied mechanics at the California Institute of Technology, has been named provost of the Institute. He takes the post on August 1.

Jennings, who has been on the Caltech campus as a student, professor, and administrator for 44 years, returns to the provost position after a nine-year hiatus. He served as vice president and provost from 1989 to 1995. Thus, he was the Institute's sixth, and is now its eighth, provost since the post was created in 1962.

"Paul is an exciting choice," said Caltech President David Baltimore. "At a time when so many things are happening on campus--the $1.4 billion capital campaign is in mid-stream, there are a number of building and renovation projects projected, there are budgetary challenges to be met--he brings a wealth of knowledge and experience to the office. He is an effective administrator, a great leader and an eloquent spokesman. I personally enjoyed very much working with Paul when he filled in as acting vice president for business and finance a few years ago, and I look forward to having the opportunity to work closely with him again."

Jennings is an expert in the design of earthquake-resistant structures and in how the earth moves during a temblor. He played an active role in investigating the effects of damaging earthquakes.

He was chair of Caltech's Division of Engineering and Applied Science from 1985 to 1989, served as the acting vice president for business and finance in 1995 and again in 1998-99, and as executive officer for civil engineering and applied mechanics from 1975 to 1980.

Jennings, who is highly regarded within the Caltech community for his energy, enthusiasm, and organizational skills, is also internationally renowned in the seismology and engineering fields. He has been the president of the Seismological Society of America and of the Earthquake Engineering Research Institute. He was a member of the National Science Foundation's advisory committee on earthquake engineering and a chairman of the National Research Council's committee on seismology.

Jennings earned a B.S. from Colorado State University in 1958, an M.S. from Caltech in 1960, and a Ph.D. from Caltech in 1963. He was a research fellow at Caltech in civil engineering in 1965 and swiftly moved up the academic ladder to become a full professor in 1972. He has been an emeritus professor since 2002. He also served on the teaching staff of the U.S. Air Force Academy from 1963 to 1965.

Jennings replaces Steve Koonin who served as provost from 1995 until early this year when he stepped down from the administrative role to become chief scientist of BP in London. Koonin is on a leave of absence from his faculty appointment as professor of theoretical physics.

Jennings is a hiker and avid fly fisherman. His wife is Missy and he has two grown daughters, Kathryn and Margaret.


Media Contact: Jill Perry, Media Relations Director (626) 395-3226

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Inaugural Wouk Lecture on Advanced Technology for Space Exploration

PASADENA, Calif.- Erik Antonsson, the chief technologist at the Jet Propulsion Laboratory and a professor of mechanical engineering at the California Institute of Technology, will give the inaugural Victor Wouk Lecture at 4 p.m. May 19 in Lees-Kubota Lecture Hall, 101 Guggenheim Laboratory of Aeronautics and Applied Science on the Caltech campus. Antonsson will discuss "Advanced Technology for Space Exploration" and will provide an overview of the JPL Strategic Technology Plan, along with highlights of recent successes and future missions. A wine and cheese reception will follow. The program is free and open to the public.

This new lectureship is named in honor of Caltech alumnus Victor Wouk, who received his master's and doctorate degrees in electrical engineering from Caltech in 1940 and 1942, respectively. He devoted himself largely to developing hybrid motor vehicles and using semiconductors in electric vehicles. He designed and built a high-performance electric vehicle and a high-performance, low-emission, improved-fuel-use hybrid. He continues to promote the continuing development of hybrid automobiles powered by both electricity and gasoline, such as the Toyota Prius, Honda Insight, and Ford Escape Hybrid.

The range of Wouk's activities is wide, and he has consulted for several institutions and the government on the problems of energy. A space-travel buff since childhood, he also worked with the team that developed fuel gauges for the "dune buggies" that roamed the surface of the moon during the Apollo program.

The Victor Wouk Lectureship was established by the Wouk family in December 2004 to bring to campus experts on the latest advances in science and technology.

Due to health limitations, Wouk himself will not be able to attend the lecture, but his brother Herman, the author, and Victor's son, Jonathan, will attend.

Antonsson is currently on leave from Caltech as he serves in his position at JPL, in which he has responsibility for planning, implementing, and leading JPL's technology strategy. He also serves as a member of JPL's executive council and as the senior representative for JPL basic technology research to NASA headquarters and other NASA centers and government agencies



White House Names Three from Caltech Faculty as Presidential Early Career Award Winners

PASADENA, Calif.—Three members of the faculty at the California Institute of Technology have been named among the most recent winners of the prestigious Presidential Early Career Award for Scientists and Engineers (PECASE). The honor was announced today by the White House.

The three are Babak Hassibi, an electrical engineer who studies data transmission and wireless communications system; Mark Simons, a geophysicist who specializes in understanding the mechanical behavior of Earth using radar and other satellite observations of the motions of Earth's surface; and Brian Stoltz, an organic chemist who specializes in the synthesis of structurally complex, biologically active molecules.

Hassibi was cited by the White House for his "fundamental contributions to the theory and design of data transmission and reception schemes that will have a major impact on new generations of high-performance wireless communications systems. He has nurtured creativity in his undergraduate and graduate students by involving them in research and inspiring them to apply new approaches to communications problems."

An associate professor of electrical engineering at Caltech and a faculty member since 2001, Hassibi earned his bachelor's degree from the University of Tehran in 1989, and his master's and doctorate degrees from Stanford in 1993 and 1996, respctively. He is the holder or coholder of four patents for communications technology, and is the winner of several awards, including the 2002 National Science Foundation Career Award, the 1999 American Automatic Control Council O. Hugo Schuck Best Paper Award, the 2003 David and Lucille Packard Fellowship for Science and Engineering, and the 2002 Okawa Foundation Grant for Telecommunications and Information Sciences.

Simons, an associate professor of geophysics, combines satellite data with continuum mechanical models of Earth to study ongoing regional crustal dynamics, including volcanic and tectonic deformation in Iceland, crustal deformation and the seismic cycle in California, Chile, and Japan, and volcanic and tectonic deformation in and around Long Valley, California. He also uses the gravity fields of the terrestrial planets to study the large-scale geodynamics of mantle convection and its relationship to tectonics.

Simons earned his bachelor's degree at UCLA in 1989, and his doctorate from MIT in 1995. He was a postdoctoral scholar at Caltech for two years before joining the faculty in 1997.

Stoltz has been an assistant professor of chemistry at Caltech since 2000. He earned his bachelor's degree at Indiana University of Pennsylvania in 1993, his master's and doctorate degrees at Yale University in 1996 and 1997, respectively. Before joining the Caltech faculty he spent two years at Harvard University as a National Institutes of Health (NIH) Postdoctoral Fellow. His work is aimed at developing new strategies for creating complex molecules with interesting structural, biological, and physical properties. The goal is to use these complex molecules to guide the development of new reaction methodology to extend fundamental knowledge and to potentially lead to useful biological and medical applications.

Stoltz, an Alfred P. Sloan Fellow, is the recipient of a Research Corporation Cottrell Scholars Award, the Camille and Henry Dreyfus New Faculty Award, and the Pfizer Research Laboratories Creativity in Synthesis Award. Additionally, he was named as an Eli Lilly Grantee in 2003 and has won a number of young faculty awards from pharmaceutical companies such as Merck Research Laboratories, Abbott Laboratories, GlaxoSmithKline, Johnson & Johnson, Amgen, Boehringer Ingelheim, and Roche. At Caltech he won the 2001 Graduate Student Council Teaching Award and Graduate Student Council Mentoring Award.

The PECASE awards were created in 1996 by the Clinton Administration "to recognize some of the nation's most promising junior scientists and engineers and to maintain U.S. leadership across the frontiers of scientific research." The awards are made to those whose innovative work is expected to lead to future breakthroughs.



Robert Tindol
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Researchers demonstrate existenceof earthquake supershear phenomenon

PASADENA, Calif.--As if folks living in earthquake country didn't already have enough to worry about, scientists have now identified another rupture phenomenon that can occur during certain types of large earthquakes. The only question now is whether the phenomenon is good, bad, or neutral in terms of human impact.

Reporting in the March 19 issue of the journal Science, California Institute of Technology geophysics graduate student Kaiwen Xia, aeronautics and mechanical engineering professor Ares Rosakis, and geophysics professor Hiroo Kanamori have demonstrated for the first time that a very fast, spontaneously generated rupture known as "supershear" can take place on large strike-slip faults like the San Andreas. They base their claims on a laboratory experiment designed to simulate a fault rupture.

While calculations dating back to the 1970s have predicted that such supershear rupture phenomena may occur in earthquakes, seismologists only recently began assuming that supershear was real. The Caltech experiment is the first time that spontaneous supershear rupture has been conclusively identified in a controlled laboratory environment, demonstrating that super-shear fault rupture is a very real possibility rather than a mere theoretical construct.

In the lab, the researchers forced two plates of a special polymer material together under pressure and then initiated an "earthquake" by inserting a tiny wire into the interface, which is turned into an expanding plasma by the sudden discharge of an electrical pulse. By means of high-speed photography and laser light, the researchers photographed the rupture and the stress waves as they propagated through the material.

The data shows that, under the right conditions, the rupture propagates much faster than the shear speed in the plates, producing a shock-wave pattern, something like the Mach cone of a jet fighter breaking the sound barrier.

The split-second photography also shows that such ruptures may travel at about twice the rate that a rupture normally propagates along an earthquake fault. However, the ruptures do not reach supershear speeds until they have propagated a certain distance from the point where they originated. Based on the experiments, a theoretical model was developed by the researchers to predict the length of travel before the transition to supershear.

In the case of a strike-slip fault like the San Andreas, the lab results indicate that the rupture needs to rip along for about 100 kilometers and the magnitude must be about 7.5 or so before the rupture becomes supershear. Large earthquakes along the San Andreas tend to be at least this large if not larger, typically involving rupture lengths of about 300 to 400 kilometers.

"Judging from the experimental result, it would not be surprising if supershear rupture propagation occurs for large earthquakes on the San Andreas fault," said Kanamori.

Similar high-speed ruptures propagating along bimaterial interfaces in engineering composite materials have been experimentally observed in the past (by Rosakis and his group, reporting in an August 1999 issue of Science). These ruptures took place under impact loading; only in the current experiment have they been initiated in an earthquake-like set-up.

According to Rosakis, an expert in crack propagation, the new results show promise in using engineering techniques to better understand the physics of earthquakes and its human impact.

According to Kanamori, the human impact of the finding is still debatable. The most damaging effect of a strike-slip earthquake is believed to be caused by a pulse-like motion normal to the fault caused by the combined effect of the rupture and shear wave. The supershear rupture suppresses this pulse, which is good, but the persistent shock-wave (Mach wave) emitted by the supershear rupture enhances the fault-parallel component of motion (the ground motion that runs in the same direction that the plates slip) and could amplify the destructive power of ground motion, which is bad.

The outstanding question about supershear at this point is which of these two effects dominates. "This is still being debated," says Kanamori. "We're not committed to one view or the other." Only further laboratory-level experimentation can answer this question conclusively.

Several seismologists believe that supershear was exhibited in some large earthquakes, including those that occurred in Tibet in 2001 and in Alaska in 2002. Both earthquakes were located in a remote region and had little, if any, human impact, but analysis of the evidence shows that the fault rupture propagated much faster than would normally be expected, thus implying supershear.

Robert Tindol


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