Hans W. Liepmann, 94

Hans Wolfgang Liepmann, a pioneering researcher and passionate educator in fluid mechanics, passed away at the age of 94. Liepmann, the Theodore von Kármán Professor of Aeronautics, Emeritus, at the California Institute of Technology (Caltech), passed away June 24 at his home in La Canada Flintridge. Widely honored for his contributions to aeronautics, Liepmann came to Caltech in 1939 and was the third director of Caltech's Graduate Aeronautical Laboratories (GALCIT), from 1972 to1985.

Liepmann, known for his sharp wit and distinctive accent, was a noted teacher who mentored more than 60 PhD students and hundreds of undergraduates during his career at GALCIT. Through his students and colleagues at GALCIT, Liepmann was highly influential in spreading the fundamental research approach and rigorous curriculum of GALCIT. His students became leaders in the aerospace industry as well as universities around the world.

Liepmann was born in Berlin in 1914 and grew up surrounded by the political turmoil and liberal Berlin society of the 1920s.  His father—a well-known physician and hospital director—had a passion for the humanities and an abhorrence of mathematics.  Insisting that Hans have a classical education despite his interest in physics, his father nearly ended his son's scientific career before it began.  Looking back, Liepmann once observed, "of my 10 years in high school I can remember no more than maybe three teachers who were more than drillmasters." Those experiences likely contributed to Liepmann's passion for teaching at Caltech.

Liepmann's early years in Berlin came to a close shortly after graduating from high school and a stint in the Siemens factory as an apprentice. His father decided to emigrate following the rise of the Nazi government and the infamous Reichstag fire in 1933. Liepmann joined his family in Turkey in 1934 after his father was invited to be head of the gynecology department at the University of Istanbul. He enrolled in the university to study physics, mathematics, astrophysics, and mechanics. The classes were taught in a mix of German, French, and Turkish, under the numerous German expatriates that found Turkey more welcoming than Germany under Hitler. 

After a year in Istanbul and an unproductive term in Prague, Liepmann traveled to Switzerland and found academic success in the physics department at the University of Zürich. His talent as an experimenter was immediately recognized, leading to an invitation to pursue his doctoral studies on low-temperature physics under Richard Bar.  Liepmann's scientific temperament was strongly influenced by the exciting physics scene of 1930s Zürich and the teaching style of Gregor Wentzel, a student of Arnold Sommerfeld, whom many consider the father of modern physics. Throughout his life, Liepmann maintained the perspective of a physicist and emphasized to his students the importance of a scientific approach.

Liepmann came to the U.S. in 1939 after impulsively expressing an interest in "hydrodynamics" during a drinking party at the successful conclusion of his PhD defense. An offer from Theodore von Kármán led to a research position in experimental fluid mechanics at GALCIT, where Kármán was the first director. Liepmann's first experiments, on boundary layer instability and transition to turbulence, were followed by investigations of various turbulent flows that are relevant to engineering application—a recurring theme throughout his career. With the entry of the U.S. into World War II, he began research on problems associated with high-speed flight, including transonic flight phenomena and interaction of shock waves with boundary layers on aerodynamic surfaces. This also marked the beginning of a longtime interaction with the Southern California aircraft industry. With Allen Puckett, he organized short wartime courses on high-speed aerodynamics for working engineers, resulting in their pioneering textbook, "The Aerodynamics of Compressible Flow." It was followed in 1956 by "Elements of Gasdynamics," with Anatol Roshko, which impacted a broader, mainly graduate-student following, and was translated into Russian, Spanish, and Japanese.

In the rapid expansion of scientific and applied research that followed World War II, Liepmann emerged as a respected and influential contributor to the aeronautics scene and to physics of fluid flow. By 1949 he had advanced to professor of aeronautics at Caltech and had developed a vigorous program of research around his group of PhD students and visiting postdoctoral fellows as well as senior scientists, many of them seeking a change from their work in postwar Europe. Believing strongly that experimental research must relate to theoretical foundations and questions, Liepmann sought association for his group with applied mathematicians, visitors as well as Caltech faculty. An outgrowth of this was the establishment, in 1967, of the applied mathematics option at Caltech. As if tying up loose ends, he was also instrumental, along with Caltech's Amnon Yariv, Martin and Eileen Summerfield Professor of Applied Physics and professor of electrical engineering, and Roy W. Gould, Simon Ramo Professor of Engineering, Emeritus, in the establishment of the applied physics option, in 1974.

The work of his group was distinguished by its innovation in experimental apparatus and instrumentation, often designed for the specific needs of particular problems. Pioneering contributions were made to a wide range of topics that frequently anticipated future technology. These include flow instability and transition, turbulent shear flow, transonic flow, shock wave-boundary layer interaction, turbulent skin friction at supersonic speeds, aircraft buffeting, rarefied gas flow, magnetohydrodynamics, plasma physics, fluid mechanics of liquid helium, chemistry of turbulent mixing, and flow control.

Another strongly held principle was that teaching is vital, even in a research-oriented institution like Caltech.  Throughout his career, up to retirement, Liepmann was devoted to teaching both graduate and undergraduate courses. The enthusiasm, clarity, and teaching effectiveness of his lectures are legendary.
 
In recognition of his accomplishments, Liepmann was elected a member of the National Academy of Engineering and the National Academy of Sciences.  He was a recipient of the National Medal of Technology and the Ludwig Prandtl Ring—the highest honor conferred by the German Society for Aeronautics and Astronautics. In 1986, President Ronald Reagan awarded Liepmann the National Medal of Science.

Liepmann leaves behind sons Dorian, Till, Christopher, and Paul, and two grandchildren. His wife, Dietlind, passed away in 1990.

A memorial service for Liepmann will be announced at a later date.

Writer: 
Jon Weiner
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Kent and Joyce Kresa Endow Professorial Chair at Caltech

Professorship creates permanent support for a leading investigator

Kent Kresa, interim chairman of General Motors, and his wife have pledged $2 million to the California Institute of Technology (Caltech) to endow the Joyce and Kent Kresa Professorship in Engineering and Applied Science. Kresa is Chairman of the Caltech Board of Trustees. The Kresa gift is matched with an additional $1 million provided by the Gordon and Betty Moore Matching Program.


"Our very good friends the Kresas have shared their time, vision, and resources with Caltech for many years," said Caltech president Jean-Lou Chameau. "They know our approach: attract leading thinkers, give them the best resources we can, and create an atmosphere in which they can collaborate easily. Kent and Joyce's generous gift will support one great engineer after another and will lead to great discoveries and inventions."


The chair will support and recognize a faculty member in engineering and applied science, with a preference for faculty in aeronautics and aerospace engineering, fields Kresa has helped shape, most notably in 28 years with Northrop Grumman that included 13 as the company's CEO and chairman. Ares Rosakis, the Theodore von Kármán Professor of Aeronautics and Mechanical Engineering and chair of the Division of Engineering and Applied Science, will work with Provost Edward Stolper to select the inaugural Joyce and Kent Kresa Professor.


"Endowed chairs offer our faculty the ultimate freedom to pursue the research thrusts they are most passionate about—and this is truly invaluable to Caltech and our continued vitality," said Rosakis.


Kresa has been a director of GM since 2003, when he retired from Northrop Grumman Corporation. Kresa joined that company in 1975 and was elected president in 1987, CEO in January 1990, and chairman in September 1990. Kent and Joyce Kresa are President's Circle members of the Caltech Associates.


###

 About Caltech:
Caltech is recognized for its highly select student body of 900 undergraduates and 1,200 graduate students, and for its outstanding faculty. Since 1923, Caltech faculty and alumni have garnered 32 Nobel Prizes and five Crafoord Prizes. In addition to its prestigious on-campus research programs, Caltech operates the Jet Propulsion Laboratory (JPL), the W. M. Keck Observatory in Mauna Kea, the Palomar Observatory, and the Laser Interferometer Gravitational-Wave Observatory (LIGO). Caltech is a private university in Pasadena, California. For more information, visit http://www.caltech.edu

Writer: 
Jon Weiner
Images: 
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Scientists Use High-Pressure "Alchemy" to Create Nonexpanding Metals

PASADENA, Calif.—By squeezing a typical metal alloy at pressures hundreds of thousands of times greater than normal atmospheric pressure, scientists at the California Institute of Technology (Caltech) have created a material that does not expand when heated, as does nearly every normal metal, and acts like a metal with an entirely different chemical composition.

The discovery, described in a paper in Physical Review Letters (PRL), offers insight into the exotic behavior of materials existing at high pressures—which represent some 90 percent of the matter in our solar system.

Zero-expanding metal alloys were discovered in 1896 by Swiss physicist Charles Édouard Guillaume, who worked at the International Bureau of Weights and Measures in France. While attempting to develop an inexpensive international standard for the meter, the metric unit of length, Guillaume hit upon an inexpensive iron-nickel alloy that expands very little when heated. He dubbed the material an "Invar" alloy—because the metals are "invariant" when heated, such that the length of a piece of Invar metal does not change as its temperature is increased, as do normal metals. Since Guillaume's discovery—which, in 1920, earned him the Nobel Prize in Physics (besting Albert Einstein, who was awarded the prize in 1921)—other nonexpanding alloys have been identified.

It has long been known that Invar behavior is caused by unusual changes in the magnetic properties of the alloys that somehow cancel out the thermal expansion of the material. (Normally, heat increases the vibrations of the atoms that make up a material, and the atoms prefer to move apart a little, causing expansion.)

"Recent computer simulations indicate that electrons in Invar alloys take on a special energy configuration," says Caltech graduate student Michael Winterrose, the first author of the PRL paper. "This energy state is at the borderline between two types of magnetic behavior, and is very sensitive to the precise ratio of elements that make up the alloy. If you move away from the Invar chemical composition by only a couple of percent, the energy configuration will disappear," he says.

Because of their unresponsiveness to temperature change, Invar alloys have been used in devices ranging from watches, toasters, light bulbs, and engine parts to computer and television screens, satellites, lasers, and scientific instruments. "In our day-to-day lives, we are surrounded by items that make essential use of Invar alloys," Winterrose says.

The Caltech scientists did not set out to study Invar behavior—and, in fact, were hoping to avoid it. "We intentionally picked chemical compositions that do not show Invar behavior because I thought it would confuse our interpretations," says Brent Fultz, a professor of materials science and applied physics at Caltech, and a coauthor of the PRL paper.

Instead, Winterrose, Fultz, and their colleagues were examining the effect of pressure on the alloy of palladium (Pd) and iron (Fe) called Pd3Fe, where three of every four atoms are palladium, and one is an iron atom. (In the similarly named but chemically distinct PdFe3—which is a traditional Invar alloy—three of every four atoms are iron, and one is palladium).

 "The Fe and Pd atoms [in the alloy] have very different sizes, and we expected to see some interesting effects from this size difference when we put Pd3Fe under pressure and measured its volume," Winterrose explains. To test this, the scientists squeezed a small sample of the material between two diamond anvils, generating pressures inside the sample that were 326,000 times greater than standard atmospheric pressure.

"Our initial results from these studies showed that the alloy stiffened under pressure, but far more than we expected," he says. To figure out the cause, the scientists simulated the quantum mechanical behavior of the electrons in the alloy under pressure. "The simulations showed that under pressure, the electrons found the special energy levels between strong and weak magnetism that are associated with normal Invar behavior. Up to this point we had been quite unaware of the possibility for Invar behavior in our material," Winterrose says.

Subsequent experiments at the Advanced Photon Source at Argonne National Laboratory in Chicago and the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory in New York confirmed that the intense pressure had indeed suppressed thermal expansion in Pd3Fe, much like tuning the chemical composition.

The scientists had performed a kind of high-pressure "alchemy" on the alloy, where pressure makes the electrons act as if they are around atoms of a different chemical element, Winterrose says.

The research helps unify our understanding of Invar behavior, which is one of the oldest and most-studied unresolved problems in materials research. In addition, using pressure to force electrons into new states can point to directions in materials chemistry where new properties can be found, at least for magnetism.

"Today, materials physics has some excellent computational tools for predicting the structure and properties of materials, although there are suspicions about how well they work for magnetic materials," says Fultz. "It is satisfying that these computational tools worked so well for showing how pressure changed the material into an Invar alloy. Invar behavior is pretty subtle, requiring a very special condition for the electrons in the metal that is usually tuned by precise control of chemical composition. Pressure can make the electrons behave as if they are in a material of different chemical composition, so I really like Mike's use of the word 'alchemy'."

The paper, "Pressure-Induced Invar Behavior in Pd3Fe," was published in the June 12 issue of PRL. In addition to Winterrose and Fultz, the coauthors are Matthew S. Lucas, Alan F. Yue, Itzhak Halevy, Lisa Mauger, and Jorge Munoz (from Caltech); Jingzhu Hu, from the University of Chicago; and Michael Lerche, from the Carnegie Institution for Science.

The work was supported by the Carnegie—Department of Energy (DOE) Alliance Center, funded by the DOE through the Stewardship Sciences Academic Alliance of the National Nuclear Security Administration, and by the DOE's Office of Science, Office of Basic Energy Sciences; by the National Science Foundation and its Consortium for Materials Properties Research in Earth Sciences (COMPRES); and by the W. M. Keck Foundation.

Writer: 
Kathy Svitil
Images: 
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Caltech Announces Initiative for a New $90 Million Sustainability Institute

Initial $30 million in gifts revealed at Institute's commencement ceremony

Pasadena, Calif.—As the U.S. Secretary of Energy and hundreds of graduates and their families looked on, California Institute of Technology (Caltech) president Jean-Lou Chameau began today's commencement ceremony by announcing $30 million in gifts as the first phase of a proposed $90 million initiative for a new institute.

The funds will go towards the creation of the Resnick Sustainability Institute at Caltech. The initial gift of $20 million was made by Stewart and Lynda Resnick, and an additional $10 million came from the Gordon and Betty Moore Matching Program. The plans include a second phase of funding to be initiated next year as part of a challenge grant. Ultimately, the endowment for the new institute will exceed $90 million.

The vision of the Resnick Sustainability Institute is to provide a path to sustainability by focusing on innovative science and engineering developments required for groundbreaking energy technologies.  Such technologies may one day help solve our global energy and climate challenges. With the support of the Resnick Sustainability Institute, some of the brightest minds in the world will apply Caltech's unique approach to interdisciplinary research toward high-risk, high-return energy science and technology. 

"I have enjoyed many conversations with Stewart and Lynda on exciting developments in science and technology and their potential for addressing many of our environmental and economic challenges," says Chameau. "This generous gift from the Resnicks reflects their extraordinary desire and courage to make a difference. With their support, we are poised to launch an initiative at Caltech that will herald a new era in energy research."

"We are passionately committed to finding alternative and sustainable energy solutions," say Stewart and Lynda Resnick.  "We're making this investment because Caltech is truly one of America's greatest research universities, and we are confident that this new institute will develop the breakthrough technologies we need to address the daunting challenges of energy security, rapidly accelerating energy demand, and climate change."

The new institute will leverage prior grants from the Gordon and Betty Moore Foundation and work being done by Caltech researchers such as Harry Atwater, the Howard Hughes Professor and professor of applied physics and materials science, who leads Caltech's Energy Frontier Research Center, recently funded by the Department of Energy; and Harry Gray, the Arnold O. Beckman Professor of Chemistry, and Nate Lewis, the George L. Argyros Professor and professor of chemistry, who lead Caltech's Center for Chemical Innovation, funded by the National Science Foundation.

The Resnicks' existing relationship with Caltech includes Stewart Resnick's role as a member of the Board of Trustees. He is also chairman and, with his wife, Lynda, owner of Roll International Corporation, a private holding company he founded in 1962. The company has diverse interests including Paramount Citrus, Paramount Farming, and Paramount Farms, growers and processors of citrus, almonds, and pistachios; POM Wonderful, the largest grower of pomegranates and makers of POM Wonderful pomegranate juice; Teleflora, the floral-by-wire service; FIJI Water, a leading premium bottled-water brand; and Suterra, one of the largest biorational pest control providers in the world.

The Resnicks have a long history of giving to Los Angeles institutions, including a 2008 pledge of $55 million to the Los Angeles County Museum of Art.

The announcement of the gift was made during Chameau's opening remarks at Caltech's 115th annual commencement ceremony. This year's keynote speaker, Department of Energy Secretary Steven Chu, remarked that the timing of the gift announcement was especially appropriate, as it involved energy science and sustainability, two of his programmatic efforts at the energy department.

# # #

About the Resnicks:

Stewart Resnick is chairman and Lynda Resnick is vice chairman of Roll International Corporation, a privately held Los Angeles-based holding company.  Among their holdings are Paramount Citrus, Paramount Farming, and Paramount Farms, growers and processors of citrus, almonds, and pistachios; POM Wonderful, the largest grower of pomegranates and makers of the all-natural POM Wonderful pomegranate juice; Teleflora, the floral-by-wire service; FIJI Water, a leading premium bottled-water brand; and Suterra, one of the largest biorational pest control providers in the world.

Stewart Resnick is a member of the executive board of the UCLA Medical Sciences; a member of the board of trustees of Bard College, New York; a member of the board of trustees of the J. Paul Getty Trust; a member of the board of Conservation International; and a member of the advisory board of the Anderson School of Management at UCLA.

Lynda Resnick is vice chairman of the Los Angeles County Museum of Art's board of trustees, as well as the chair of the museum's acquisitions committee and executive committees. She is on the executive board of the Aspen Institute; the executive board for the UCLA Medical Sciences; Prostate Cancer Foundation; and the Milken Family Foundation. She is also a trustee of the Philadelphia Museum of Art. Lynda is also the best-selling author of the recently published book Rubies in the Orchards: How to Uncover the Hidden Gems in Your Business.

 

About Gordon and Betty Moore:

Gordon and Betty Moore are the cofounders and directors of the Gordon and Betty Moore Foundation. They have been contributing to science, technology, education, and conservation projects for decades. A California native,  Moore earned a PhD in chemistry from Caltech in 1954. In 1968 he cofounded Intel, and became president and CEO in 1975. He was elected chairman and CEO in 1979. In 1987, he relinquished the CEO title, he was named chairman emeritus in 1997. Moore is also a member of the National Academy of Engineering and an IEEE Fellow. He received the National Medal of Technology in 1990 and was named a Caltech Distinguished Alumni in 1975. Moore served as chairman of the Caltech Board of Trustees from 1995 until the beginning of 2001 and continues as a senior trustee. In 2001, the Moores announced two gifts to Caltech totaling $600 million--the largest donation in history to an institution of higher education.

About Caltech:

Caltech is recognized for its highly select student body of 900 undergraduates and 1,200 graduate students, and for its outstanding faculty. Since 1923, Caltech faculty and alumni have garnered 32 Nobel Prizes and five Crafoord Prizes.

In addition to its prestigious on-campus research programs, Caltech operates the Jet Propulsion Laboratory, the W. M. Keck Observatory in Mauna Kea, the Palomar Observatory, and the Laser Interferometer Gravitational-Wave Observatory (LIGO). Caltech is a private university in Pasadena, California. For more information, visit http://www.caltech.edu

Writer: 
Jon Weiner
Images: 
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Scientists Create Nanoscale Zipper Cavity that Responds to Single Photons of Light

Device could be used for highly sensitive force detection, optical communications, and more

PASADENA, Calif.-Physicists at the California Institute of Technology (Caltech) have developed a nanoscale device that can be used for force detection, optical communication, and more. The device exploits the mechanical properties of light to create an optomechanical cavity in which interactions between light and motion are greatly strengthened and enhanced. These interactions, notes Oskar Painter, associate professor of applied physics at Caltech, and the principal investigator on the research, are the largest demonstrated to date.

The device and the work that led to it are described in a recent issue of the journal Nature.

The fact that photons of light, despite having no mass, nonetheless carry momentum and can interact with mechanical objects is an idea that dates back to Kepler and Newton. The mechanical properties of light are also known to limit the precision with which one can measure an object's position, since simply by using light to do the measurement, you apply a force and disturb the object.

It was important to consider these so-called back-action effects in the design of devices to measure weak, classical forces. Such considerations were part of the development of gravity-wave detectors like the Laser Interferometer Gravitational-Wave Observatory (LIGO). These sorts of interferometer-based detectors have also been used at much smaller scales, in scanning probe instruments used to detect or image atomic surfaces or even single electron spins.

To get an idea of how these systems work, consider a mirror attached to a floppy cantilever, or spring. The cantilever is designed to respond to a particular force-say, a magnetic field. Light shining down on the mirror will be deflected when the force is detected-i.e., when the cantilever moves-resulting in a variation in the light beam's intensity that can then be detected and recorded.

"LIGO is a huge multikilometer-scale interferometer," notes Painter. "What we did was to take that and scale it all the way down to the size of the wavelength of light itself, creating a nanoscale device."

They did this, he explains, because as these interferometer-based detectors are scaled down, the mechanical properties of light become more pronounced, and interesting interactions between light and mechanics can be explored.

"To this end, we made our cantilevers many, many times smaller, and made the optical interaction many, many times larger," explains Painter.

They call this nanoscale device a zipper cavity because of the way its dual cantilevers-or nanobeams, as Painter calls them-move together and apart when the device is in use. "If you look at it, it actually looks like a zipper," Painter notes.

"Zipper structures break new ground on coupling photonics with micromechanics, and can impact the way we measure motion, even into the quantum realm," adds Kerry Vahala, Caltech's Ted and Ginger Jenkins Professor of Information Science and Technology and professor of applied physics, and one of the paper's authors. "The method embodied in the zipper design also suggests new microfabrication design pathways that can speed advances in the subject of cavity optomechanics as a whole."

To create their zipper cavity device, the researchers made two nanobeams from a silicon chip, poking holes through the beams to form an effective optical mirror. Instead of training a light down onto the nanobeams, the researchers used optical fibers to send the light "in plane down the length of the beams," says Painter. The holes in the nanobeams intercept some of the photons, circulating them through the cavity between the beams rather than allowing them to travel straight through the device.

Or, to be more precise, the circulating photons actually create the cavity between the beams. As Painter puts it: "The mechanical rigidity of the structure and the changes in its optical response are predominantly governed by the internal light field itself."

Such an interaction is possible, he adds, because the structure is precisely designed to maximize the transfer of momentum from the input laser's photons to the mechanical nanobeams. Indeed, a single photon of laser light zipping through this structure produces a force equivalent to 10 times that of Earth's gravity. With the addition of several thousand photons to the cavity, the nanobeams are effectively suspended by the laser light.

Changes in the intensity and other properties of the light as it moves along the beams to the far end of the chip can be detected and recorded, just as with any large-scale interferometer.

The potential uses for this sort of optomechanical zipper cavity are myriad. It could be used as a sensor in biology by coating it with a solution that would bind to, say, a specific protein molecule that might be found in a sample. The binding of the protein molecule to the device would add mass to the nanobeams, and thus change the properties of the light traveling through them, signaling that such a molecule had been detected. Similarly, it could be used to detect other ultrasmall physical forces, Painter adds.

Zipper cavities could also be used in optical communications, where circuits route information via optical beams of different colors, i.e., wavelengths. "You could control and manipulate what the optical beams of light are doing," notes Painter. "As the optical signals moved around in a circuit, their direction or color could be manipulated via other control light fields." This would create tunable photonics, "optical circuits that can be tuned with light."

Additionally, the zipper cavity could lead to applications in RF-over-optical communications and microwave photonics as well, where a laser source is modulated at microwave frequencies, allowing the signals to travel for kilometers along optical fibers. In such systems, the high-frequency mechanical vibrations of the zipper cavity could be used to filter and recover the RF or microwave signal riding on the optical wave.

Other authors on the Nature paper, "A picogram- and nanometre-scale photonic-crystal optomechanical cavity," include graduate students Matt Eichenfield (the paper's first author) and Jasper Chan, and postdoctoral scholar Ryan Camacho.

Their research was supported by a Defense Advanced Research Projects Agency seeding effort, and an Emerging Models and Technologies grant from the National Science Foundation.

Writer: 
Lori Oliwenstein
Writer: 

DOE Names Caltech Professor as Director of EFRC Focusing on Light-Material Interactions

Caltech also picked to partner in three additional EFRCs

PASADENA, Calif.--The U.S. Department of Energy (DOE) Office of Science has announced that it will fund the creation of 46 Energy Frontier Research Centers (EFRCs) over the next five years, including one that will be housed at the California Institute of Technology (Caltech). That EFRC will be headed by Harry Atwater, the Howard Hughes Professor and professor of applied physics and materials science.

"It is essential and very appropriate for a place like Caltech to serve as an intellectual center for fundamental scientific research in solar energy," says Atwater. "We have programs that support work on photovoltaic devices, but the Energy Frontier Research Center will address fundamental optical science issues relevant to solar energy. It's the kind of center that is best suited to our strengths."

In addition, Caltech researchers will partner with three additional EFRCs at other institutions.

According to Ares Rosakis, chair of Caltech's Division of Engineering and Applied Science, "Radical new approaches to harnessing solar energy are at the heart of many efforts here at Caltech to help contribute to the world's energy infrastructure with innovative, sustainable, core technologies. This new center brings Caltech one step closer to our goal of providing the resources necessary for some of the best minds in the country to lay the groundwork for a new energy economy."

This $777 million program is a major effort to accelerate the scientific breakthroughs needed to build a new 21st-century economy, the White House said in announcing the initiative. The 46 new EFRCs, which will each be funded at $2-5 million per year for a planned initial five-year period, will be established at universities, national laboratories, nonprofit organizations, and private firms across the nation.

Supported in part by funds made available under President Obama's American Recovery and Reinvestment Act, the EFRCs will bring together groups of leading scientists to address fundamental issues in fields ranging from solar energy and electricity storage to materials sciences, biofuels, advanced nuclear systems, and carbon capture and sequestration.

The EFRCs were selected from a pool of some 260 applications received in response to a solicitation issued in 2008 by the DOE's Office of Science. Over 110 institutions from 36 states plus the District of Columbia will be participating in the EFRC research. In all, the EFRCs will involve nearly 700 senior investigators and employ, on a full- or part-time basis, over 1,100 postdoctoral associates, graduate students, undergraduate students, and technical staff. Roughly a third of these researchers will be supported by Recovery Act funding.

Atwater's EFRC, entitled "Light Material Interactions in Energy Conversion," will include collaborations with scientists at Lawrence Berkeley National Laboratory and the University of Illinois, and some of the work will be done at the Molecular Foundry at Lawrence Berkeley National Laboratory.

"The goal of the center is to understand how to sculpt and mold the flow of light through materials," Atwater explains. "By that I mean we will be working to design structures at the nanoscale that steer and change the speed of light to optimally convert sunlight to electricity and chemical fuels."

The three additional EFRCs that will be partnering with Caltech researchers include

  • Rational Design of Innovative Catalytic Technologies for Biomass Derivative Utilization (headed by the University of Delaware), with Mark Davis, the Warren and Katharine Schlinger Professor of Chemical Engineering at Caltech
  • EFRC for Solid State Lighting Science (headed by Sandia National Laboratories), with Harry Atwater
  • Center for Catalytic Hydrocarbon Functionalization (headed by the University of Virginia), with William Goddard, the Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics at Caltech

# # #

Writer: 
Lori Oliwenstein
Writer: 

Caltech Electrical Engineer Awarded $6 Million to Develop Self-Healing Circuits

PASADENA, Calif.-- Over the past few decades, the transistors in computer chips have become progressively smaller and faster, allowing upwards of a billion individual transistors to be packed into a single circuit, thus shrinking the size of electronic devices. But these circuits have an intractable design flaw: if just a single transistor fails, the entire circuit also fails.

One novel way around the problem is a so-called "self-healing" circuit--one that can detect, isolate, and fix its own flaws, both by working around the defective transistors by modifying the properties of the rest of the system and introducing additional transistors into the system in a seamless fashion.

Such circuits are "inspired by biological systems that constantly heal themselves in the presence of random and intentional failures," says Ali Hajimiri, a professor of electrical engineering at the California Institute of Technology (Caltech).

Toward this end, Hajimiri has been awarded a four-year, $6 million grant by the Defense Advanced Research Projects Agency (DARPA) to develop self-healing circuits for millimeter and microwave frequencies, with applications in imaging, sensing, communications, and radar.

DARPA's Self-HEALing mixed-signal Integrated Circuits, or HEALICs, program is designed to enable the continuation of the Moore's scaling law, which predicts an exponential increase in the number of transistors that can be placed on an integrated circuit (one that performs multiple functions), in the face of inevitable imperfections in those transistors.

"As transistors approach atomic dimensions and run at very high frequencies, even very fine-scale variations within seemingly identical transistors can make a large difference in performance," generating unpredictable behavior, Hajimiri says. "Some circuits may run faster, some slower. Some may actually fail," he says.

Hajimiri's solution is to employ sensors that can detect the conditions within a circuit--and determine, for example, that a particular transistor is not working up to par, or at all--along with actuators that can then modify the system. For example, the actuators could swap functional transistors for failing ones, or add "helper" transistors that would boost the functional capability of a transistor running at sub-optimal speeds. All of these modifications ideally would be made within thousandths to millionths of a second, effectively fixing failing circuits on the fly.

Self-healing circuits are applicable to many integrated circuits, such as the world's first "radar on a chip," a novel radar antenna array system miniaturized onto a single silicon chip, which Hajimiri developed in 2004.

"The way we see it, in a few years seal-healing circuits will allow faster, cheaper, and more robust circuits, making it possible to continue Moore's scaling law by making integrated circuits resemble living organisms in their ability to self-heal and adjust to changes in the environment," Hajimiri says.

Writer: 
Kathy Svitil
Writer: 

Thomas McGill, 66

Thomas McGill, professor of applied physics, emeritus, at the California Institute of Technology (Caltech) passed away on March 19. He was 66.

Born on March 20, 1942, in Port Arthur, Texas, McGill was the oldest of five children.

His research had been aimed at the development of new devices based on the fundamentals of solid-state physics, including Schottky barriers and amorphous materials, as well as the applications of heterojunctions and superlattices to a wide class of devices. McGill directed the theses of over 50 PhD students in electrical engineering, physics, and applied physics. He served for nearly 30 years as a consultant to the Defense Science Research Council of the Defense Advanced Research Project Agency, was a member of the congressionally mandated Semiconductor Technology Council, and served as chief of the Naval Operations Executive Panel.

McGill joined Caltech in 1971 as a member of the Division of Engineering and Applied Science. He was the first faculty member hired in the new discipline of applied physics. He received his BS from Lamar State College of Technology in 1964, and his MS and PhD from Caltech in 1965 and 1969, respectively, under Carver Mead. He was Fletcher Jones Professor of applied physics from 1985 to 1999, and became emeritus in 2008.

McGill authored or coauthored hundreds of publications and was personally known as an engaging lecturer and teacher, a caring mentor, a passionate scientific leader and contributor in many areas, as well as an important contributor and leader in many advisory and working groups for the government.

Married in 1966, he is survived by his wife, Toby Cone McGill, and two daughters, Angela McGill Avogaro and Sarah McGill.

In lieu of flowers, the family suggests a contribution to the Pasadena Humane Society.

# # #

Writer: 
Jon Weiner
Images: 
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Scientists Create Titanium-Based Structural Metallic-Glass Composites

The new alloys are lighter and less expensive, but are still tough and ductile enough for use in aerospace applications

PASADENA, Calif.--Scientists from the California Institute of Technology (Caltech) have created a range of structural metallic-glass composites, based in titanium, that are lighter and less expensive than any the group had previously created, while still maintaining their toughness and ductility--the ability to be deformed without breaking.

A paper describing these breakthrough metallic-glass alloys is now online in the Proceedings of the National Academy of Sciences (PNAS) Early Edition in advance of an upcoming print publication.

Earlier this year, the same Caltech group had published a paper in the journal Nature, describing new strategies for creating the liquid-metal composites. This research resulted in "alloys with unrivaled strength and toughness," notes Douglas Hofmann, visiting scientist and lead author on the PNAS paper that, along with the Nature paper, describes work he did while a graduate student at Caltech. "They are among the toughest engineering materials that currently exist."

Still, there were shortcomings to the alloys presented in Nature. Because they were created for use in the aerospace industry--among other structural applications--they needed to have very low densities. Ideally, the alloys would have had densities in or around those of crystalline titanium alloys, which fall between 4.5 and 5 grams per cubic centimeter (g/cc). The original alloys, made predominantly of zirconium, fell between 5.6 and 6.4 g/cc, putting them "in a no-man's-land of densities for aerospace structures," says Hofmann.

And so Hofmann and his colleagues--including William Johnson, Caltech's Ruben F. and Donna Mettler Professor of Engineering and Applied Science, and a pioneer in the creation of metallic glass--began tweaking the components in their composites, eventually coming up with a group of alloys with a high percentage of titanium, but which maintained the properties of the previously created zirconium alloys.

"Despite being based in titanium," Hofmann notes, "these alloys exhibit the same impressive properties as the zirconium alloys. They are still tough--in other words, they resist cracking--and they are still ductile. In fact, they are even more ductile than the alloys we'd created in the past."

This decrease in density also resulted in a reduction in cost, adds Hofmann, since zirconium is a more expensive metal than is titanium.

The work detailed in the paper, "Development of tough, low-density titanium-based bulk metallic glass matrix composites with tensile ductility," was supported by the U.S. Office of Naval Research. Hofmann was supported by the U.S. Department of Defense through the National Defense Science and Engineering Graduate Fellowship program.

The paper's coauthors included Johnson; Caltech graduate students Jin-Yoo Suh and Aaron Wiest; Mary-Laura Lind, a visitor in materials science; and Marios Demetriou, a senior research fellow in materials science.

Writer: 
Lori Oliwenstein
Writer: 

George W. Housner, 97

George W. Housner, often considered the father of earthquake engineering, passed away on November 10 at the age of 97. Housner died of natural causes in Pasadena, California.

Housner was Braun Professor of Engineering, Emeritus, at the California Institute of Technology (Caltech).

Born in Michigan in 1910, Housner received his bachelor's degree from the University of Michigan and his master's and PhD degrees from Caltech.

Housner's interest in earthquake engineering began after the Long Beach quake of 1933. After receiving his PhD, he worked for the Army Corps of Engineers before advising the Air Force during World War II.

Housner spent much of his time during the war in North Africa, where he devised an equation that helped increase the success of pilots navigating barrage balloons--designed to prevent attacks on oil fields--and a new tactic for Air Force bombers to attack bridges, improving their effectiveness.

In 1945 he was honored with the Distinguished Civilian Service Award given by the U.S. War Department.

After the war, Housner joined Caltech as an assistant professor of applied mechanics. He later became the Braun Professor before retiring in 1981. He was named a Caltech Distinguished Alumni in 2006, the Institute's highest honor bestowed on graduates.

Housner's interests included civil projects, such as California's statewide water system. His earthquake-engineering techniques were used to strengthen the dozens of dams and aqueducts running through California--one of the first times modern earthquake engineering was used for this purpose.

"George really has to be considered one of the most original and clearest thinkers ever within the entire engineering profession," said John Hall, professor of civil engineering and dean of students at Caltech.

His expertise in earthquakes led to his chairing a National Academy of Sciences engineering committee evaluating the damage left by the 1964 Alaska earthquake. Soon after, he became a member of the National Academy of Engineering. He was elected to the National Academy of Sciences in 1972 and to the American Academy of Arts and Sciences.

Housner was the founding member of the Earthquake Engineering Research Institute, and a medal is given by the organization each year in his name. He was also instrumental in the formation of the International Association for Earthquake Engineering and Caltech's Earthquake Research Affiliates.

"George was a man of great intellect, which he used diligently to reduce the impact of earthquakes on our society," said Tom Heaton, professor of engineering seismology at Caltech. "He was one of those special people who changed our world."

In 1981, Housner was given the Harry Fielding Reid Medal from the Seismological Society of America, awarded annually for outstanding contributions in seismology and earthquake engineering.

In a 1988 White House ceremony, President Ronald Reagan awarded the National Medal of Science to Housner. The award citation honored Housner "for his profound and decisive influence on the development of earthquake engineering worldwide. His research contributions have guided the development of earthquake engineering and have had an important impact on other major disciplines."

After the 1989 Loma Prieta earthquake in Northern California, Governor George Deukmejian named Housner chair of the board investigating the collapse of freeways and bridges. He also served as chair of the Caltrans Seismic Advisory Board.

Housner never married and will be cremated and interred at Mountain View Cemetery in Altadena, California.

Writer: 
Jon Weiner
Images: 
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Pages

Subscribe to RSS - EAS