Caltech Student Recognized as a "New Face" of Engineering

For Javad Lavaei, a PhD candidate in the Division of Engineering and Applied Science at Caltech, seeking a career in engineering came naturally.

"I was very interested in learning advanced mathematics when I was in high school," says Lavaei. "I had a craving to put my knowledge into practice and to design real-world systems."

With strong family support and motivational high-school teachers who encouraged his interest in engineering, Lavaei pursued and completed a bachelor's and master's degree in electrical engineering. Now, he has the chance to influence other young students to pursue engineering careers as part of the New Faces of Engineering program.

Lavaei was highlighted for his "interesting and unique work" by the program, which is organized by the National Engineers Week Foundation and recognizes engineers who have been in the workplace five years or less and have shown outstanding ability in projects that significantly impact public welfare or further professional development and growth.

"I am very happy that my work has been recognized by senior engineers and that they have considered me a successful engineer," says Lavaei, who is working toward a degree in control and dynamical systems. His current research focuses on techniques specialized for power systems that could potentially save energy, reduce costs, and improve reliability, such as the design of a smart grid. A smart grid utilizes digital technology to improve how electricity travels from power plants to consumers. In the past, he has worked in many different areas of electrical and computer engineering, including control, circuits, communications, and networks.

Lavaei encourages students to apply their enthusiasm for engineering to improving communications infrastructures, electrical power grids, and other areas that can benefit society. 

"I think it's very exciting to work on important engineering problems and find solutions for them that can, in principle, affect everyone's lives in the future," he says. "Students can be very successful in engineering if they have a passion for understanding and/or designing real-world systems."

The National Engineers Week Foundation is a coalition of more than 100 engineering societies, major corporations, and government agencies that seeks to increase public understanding and appreciation of engineers' contributions to society. For more information, visit www.eweek.org.

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Katie Neith
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Daraio Awarded Sloan Fellowship

Caltech's Chiara Daraio is among this year's crop of Sloan Research Fellows. Daraio, who this year was promoted from assistant to full professor of aeronautics and applied physics, is one of 118 faculty from across the country to receive the two-year, $50,000 fellowship, given to early-career scientists and scholars in recognition of achievement and the potential to contribute substantially to their fields.

"It's a great honor for me to receive a Sloan Research Fellowship, a very competitive award," says Daraio, whose research focuses on the design and testing of new materials with "unprecedented" mechanical properties. "We design new materials by assembling fundamental building blocks that interact nonlinearly, and we can choose these nonlinear interactions by controlling, for example, the shape and material properties of the building blocks. The materials we design can have several practical applications, from acoustic imaging to shock absorption."

"I am particularly pleased because the fellowship is awarded primarily in the basic sciences—physics, in my case—and this means that our research is being recognized also for its contribution to the basic sciences, beyond its engineering origins," says Daraio. Her group will use the funds to support a new research area related to the study of strongly nonlinear mechanical phenomena at micro- and nanoscales.

Presented annually since 1955 by the Sloan Foundation, the fellowships are awarded in chemistry, computer science, economics, mathematics, evolutionary and computational molecular biology, neuroscience, and physics. Potential fellows must be nominated by their peers and are subsequently selected by an independent panel of senior scholars. Once named, Sloan Research Fellows are free to pursue whatever research most interests them, and they can use their fellowship funds in a wide variety of ways. Thirty-eight Sloan Research Fellows have gone on to win the Nobel Prize in their fields.

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Kathy Svitil
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Caltech-Led Team Pinpoints Aggression Neurons in the Brain

Finding could lead to new treatments for impulsive violence

PASADENA, Calif.—Where does violence live in the brain? And where, precisely, does it lay down its biological roots? With the help of a new genetic tool that uses light to turn nerve cells on and off, a team led by researchers at the California Institute of Technology (Caltech) has tracked down the specific location of the neurons that elicit attack behaviors in mice, and defined the relationship of those cells to the brain circuits that play a key role in mating behaviors.

The researchers’ hope is that these insights might lead to treatments that can specifically address impulsive violence, a category of behavior that has been historically difficult to grapple with from a medical or psychological perspective.

In a study published in this week's issue of the journal Nature, the researchers were not only able to localize the neuronal circuits mediating attack behavior in mice, but were able to determine that these circuits are "intimately associated, deeply intertwined," with another basic social-behavioral drive—mating—according to David J. Anderson, the Benzer Professor of Biology at Caltech and a Howard Hughes Medical Institute investigator.

Indeed, the neurons for violence and mating live so close together, in a brain region known as the ventrolateral subdivision of the ventromedial hypothalamus (VMH), that "they are like a salt-and-pepper mixture," says Anderson.

And if you think of the brain as the world and the hypothalamus as a country, he adds, then the ventromedial hypothalamus is like a state and the ventrolateral subdivision is like a city within that state. "We've found that these 'mating' and 'fighting' neurons are not only located in the same city, but potentially in the same neighborhood," he says.

To determine whether aggression and mating involve the same—or, rather, distinct but intermingled—neurons, Dayu Lin, a former postdoctoral fellow in Anderson's lab and now an assistant professor at New York University, carried out a series of challenging electrophysiological recording experiments in the VMH. Because the VMH is located deep within the brain, it is exceedingly difficult to target accurately. But by inserting a bundle of 16 wire electrodes into this region, Lin was able to get recordings from multiple neurons during repeated episodes of fighting or mating. "It's the first time in which it's been possible to record electrical activity from deep-brain hypothalamic structures in animals while they are engaging in aggressive and mating behaviors," says Anderson.

Using software developed by Allen E. Puckett Professor of Electrical Engineering Pietro Perona and senior postdoctoral scholar Piotr Dollar—and with the help of several Caltech undergraduates—the researchers annotated behavioral changes on a frame-by-frame basis from video taken at the same time as the electrical recordings were performed. This annotation allowed them to make correlations between neuronal activity and behavior with a temporal resolution of approximately 30 milliseconds.

These experiments indicated that while there is some overlap between "mating" neurons and "fighting" neurons, the majority of these cells are distinct, despite their close proximity. Perhaps most surprising, Anderson notes, is the way that the neurons responsible for aggression and mating communicate—or, rather, how they shut each other up. Sex and violence, it seems, are actually at odds: a neuron that is turned on during aggressive behavior will turn off during mating, and vice versa. "We found that they talk to each other in an inhibitory way," he says.

But a correlation between neuronal activity and fighting behavior doesn't indicate whether the activity causes the behavior or the behavior causes the activity. And so Lin, Anderson, and colleagues carried out experiments to activate or inhibit VMH neurons, to distinguish between those alternatives and to determine the effect of such manipulations on behavior.

In order to activate neurons in the VMH, they used a technique known as optogenetic stimulation. Using a disabled virus as a kind of "disposable molecular syringe," Lin injected VMH neurons with DNA that carries the code for channelrhodopsin-2, a protein from blue-green algae that increases neuronal activity in response to blue light. The sensitized neurons could then be turned on or off with the literal flip of a light switch, allowing the scientists to watch what happens to the behavior of an individual mouse.

Remarkably, says Anderson, for mice in which the injection was targeted to the correct location, blue light induced an attack—even toward an inanimate object such as an inflated latex glove. Conversely, using a technique developed by Caltech’s Bren Professor of Biology Henry A. Lester that allowed the scientists to genetically inhibit neuronal activity, Lin and colleagues were able to show that neuronal activity in the VMH was necessary for normal aggressive behavior, as well.

"This answers an important, long-standing question in the field," says Anderson. "Are regions of the brain that can evoke aggression when artificially stimulated actually necessary for normal aggressive behavior? In this case, the answer is clearly 'yes.'"

The researchers also found that stimulating a male to be aggressive toward a female became more difficult as a mating encounter progressed to its consummatory phase. This result was consistent with the observation that neurons activated during fighting appear to become inhibited in the presence of a female. "The question," says Anderson, "is how that inhibition is achieved."

The answer may lead to new areas of research—and, perhaps, to new treatments for impulsive, violent behaviors. Specifically, notes Anderson, scientists can begin thinking about treatments that target violence-begetting neurons while sparing those involved in normal sexual behavior.

"For the last 500 years, we've really had no viable treatments for pathological violence other than execution or imprisonment," says Anderson. "And part of the reason is that we haven't understood enough about the basic neurobiology of aggression. The new studies are an important step in that direction."

In addition, he says, "mapping out the brain circuitry of aggression will provide a framework for understanding where and how in the brain genetic and environmental influences—nature vs. nurture—exert their influences on aggressive behavior."

The other authors on the Nature paper, "Functional identification of an aggression locus in the mouse hypothalamus," in addition to Anderson, Lin, Dollar, and Perona, are Caltech postdoctoral scholar Hyosang Lee and Maureen Boyle and Ed Lein from the Allen Institute for Brain Science in Seattle.

Their work was funded by the Weston-Havens Foundation, the Jane Coffin Childs Foundation, and the Howard Hughes Medical Institute.

 

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Lori Oliwenstein
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Two Caltech Professors Named to National Academy of Engineering

Two prominent Caltech faculty have been named members of the National Academy of Engineering (NAE). Election to the NAE is among the highest professional distinctions accorded to an engineer, says NAE President Charles M. Vest.

Ares J. Rosakis, the Theodore von Karman Professor of Aeronautics, professor of mechanical engineering, and chair of the Division of Engineering and Applied Science, was elected for his "discovery of intersonic rupture, contributions to understanding dynamic failure, and methods to determine stresses in thin-film structures," according to the NAE.

Michael Hoffmann, the James Irvine Professor of Environmental Science, was elected for his work on "oxidative treatment technologies for the removal of organic and inorganic contaminants from water."

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Lori Oliwenstein
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Plasmonic Metamaterials: From Microscopes to Invisibility Cloaks

A new class of artificial materials called metamaterials—which derive their properties from carefully engineered, nanostructured building blocks rather than from their chemical composition—may one day be used to create ultrapowerful microscopes, advanced sensors, improved solar cells, computers that use light instead of electronic signals to process information, and even an invisibility cloak.

In a Perspectives piece in this week's issue of the journal Science, Caltech's Harry Atwater and Purdue University colleague Alexandra Boltasseva describe advances in a particular subtype of these materials—plasmonic metamaterials. They also describe two of the major limitations in the field: the loss of light or, rather, its absorption by metals such as silver and gold, which are contained in the metamaterial; and difficulties in precisely tuning the materials so they bend incoming light to the required index of refraction.

In their article, Atwater and Boltasseva suggest new approaches to overcoming these obstacles by replacing the silver and gold in the metamaterials with semiconductors made more metallic by the addition of metallic impurities, or by adding non-metallic elements to metals, making them less metallic. Examples of these "intermetallic materials" include aluminum oxides and titanium nitride.

Some of the new metamaterials, the researchers say, are showing promise in uses involving near-infrared light, the range of the spectrum critical for telecommunications and fiber optics. Other materials—such as the negative-index metamaterial developed by Atwater and Caltech graduate student Stanley Burgos and described in an April 2010 Nature Materials article—might even work with light in the visible range of the spectrum.

Future photonics technologies will revolve around new types of optical transistors, switches, and data processors, Atwater and Boltasseva note. Indeed, as they point out in the article's abstract, "these materials can be tailored for almost any application because of their extraordinary response to electromagnetic, acoustic, and thermal waves that transcends the properties of natural materials."

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Lori Oliwenstein
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New Reactor Paves the Way for Efficiently Producing Fuel from Sunlight

PASADENA, Calif.—Using a common metal most famously found in self-cleaning ovens, Sossina Haile hopes to change our energy future. The metal is cerium oxide—or ceria—and it is the centerpiece of a promising new technology developed by Haile and her colleagues that concentrates solar energy and uses it to efficiently convert carbon dioxide and water into fuels.

Solar energy has long been touted as the solution to our energy woes, but while it is plentiful and free, it can't be bottled up and transported from sunny locations to the drearier—but more energy-hungry—parts of the world. The process developed by Haile—a professor of materials science and chemical engineering at the California Institute of Technology (Caltech)—and her colleagues could make that possible. 

The researchers designed and built a two-foot-tall prototype reactor that has a quartz window and a cavity that absorbs concentrated sunlight. The concentrator works "like the magnifying glass you used as a kid" to focus the sun's rays, says Haile.

At the heart of the reactor is a cylindrical lining of ceria. Ceria—a metal oxide that is commonly embedded in the walls of self-cleaning ovens, where it catalyzes reactions that decompose food and other stuck-on gunk—propels the solar-driven reactions. The reactor takes advantage of ceria's ability to "exhale" oxygen from its crystalline framework at very high temperatures and then "inhale" oxygen back in at lower temperatures.

"What is special about the material is that it doesn't release all of the oxygen. That helps to leave the framework of the material intact as oxygen leaves," Haile explains. "When we cool it back down, the material's thermodynamically preferred state is to pull oxygen back into the structure."

The ETH-Caltech solar reactor for producing H2 and CO from H2O and CO2 via the two-step thermochemical cycle with ceria redox reactions.

Specifically, the inhaled oxygen is stripped off of carbon dioxide (CO2) and/or water (H2O) gas molecules that are pumped into the reactor, producing carbon monoxide (CO) and/or hydrogen gas (H2). H2 can be used to fuel hydrogen fuel cells; CO, combined with H2, can be used to create synthetic gas, or "syngas," which is the precursor to liquid hydrocarbon fuels. Adding other catalysts to the gas mixture, meanwhile, produces methane. And once the ceria is oxygenated to full capacity, it can be heated back up again, and the cycle can begin anew.

For all of this to work, the temperatures in the reactor have to be very high—nearly 3,000 degrees Fahrenheit. At Caltech, Haile and her students achieved such temperatures using electrical furnaces. But for a real-world test, she says, "we needed to use photons, so we went to Switzerland." At the Paul Scherrer Institute's High-Flux Solar Simulator, the researchers and their collaborators—led by Aldo Steinfeld of the institute's Solar Technology Laboratory—installed the reactor on a large solar simulator capable of delivering the heat of 1,500 suns.

In experiments conducted last spring, Haile and her colleagues achieved the best rates for CO2 dissociation ever achieved, "by orders of magnitude," she says. The efficiency of the reactor was uncommonly high for CO2 splitting, in part, she says, "because we're using the whole solar spectrum, and not just particular wavelengths." And unlike in electrolysis, the rate is not limited by the low solubility of CO2 in water. Furthermore, Haile says, the high operating temperatures of the reactor mean that fast catalysis is possible, without the need for expensive and rare metal catalysts (cerium, in fact, is the most common of the rare earth metals—about as abundant as copper).

In the short term, Haile and her colleagues plan to tinker with the ceria formulation so that the reaction temperature can be lowered, and to re-engineer the reactor, to improve its efficiency. Currently, the system harnesses less than 1% of the solar energy it receives, with most of the energy lost as heat through the reactor's walls or by re-radiation through the quartz window. "When we designed the reactor, we didn't do much to control these losses," says Haile. Thermodynamic modeling by lead author and former Caltech graduate student William Chueh suggests that efficiencies of 15% or higher are possible.

Ultimately, Haile says, the process could be adopted in large-scale energy plants, allowing solar-derived power to be reliably available during the day and night. The CO2 emitted by vehicles could be collected and converted to fuel, "but that is difficult," she says. A more realistic scenario might be to take the CO2 emissions from coal-powered electric plants and convert them to transportation fuels. "You'd effectively be using the carbon twice," Haile explains. Alternatively, she says, the reactor could be used in a "zero CO2 emissions" cycle: H2O and CO2 would be converted to methane, would fuel electricity-producing power plants that generate more CO2 and H2O, to keep the process going.

A paper about the work, "High-Flux Solar-Driven Thermochemical Dissociation of CO2 and H2O Using Nonstoichiometric Ceria," was published in the December 23 issue of Science. The work was funded by the National Science Foundation, the State of Minnesota Initiative for Renewable Energy and the Environment, and the Swiss National Science Foundation.

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Kathy Svitil
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Caltech-Led Team Creates Damage-Tolerant Metallic Glass

Amorphous palladium-based alloy demonstrates unprecedented level of combined toughness and strength; could be of use in biomedical implants

PASADENA, Calif.—Glass is inherently strong, but when it cracks or otherwise fails, it proves brittle, shattering almost immediately. Steel and other metal alloys tend to be tough—they resist shattering—but are also relatively weak; they permanently deform and fail easily.

The ideal material, says Marios Demetriou, a senior research fellow at the California Institute of Technology (Caltech), has the advantage of being both strong and tough—a combination called damage tolerance, which is more difficult to come by than the layperson might think. "Strength and toughness are actually very different, almost mutually exclusive," he explains. "Generally, materials that are tough are also weak; those that are strong, are brittle."

And yet, Demetriou—along with William Johnson, Caltech's Ruben F. and Donna Mettler Professor of Engineering and Applied Science, and their colleagues—report in a recent issue of the journal Nature Materials that they have developed just such a material. Their new alloy—a combination of the noble metal palladium, a small fraction of silver, and a mixture of other metalloids—has shown itself in tests to have a combination of strength and toughness at a level that has not previously been seen in any other material.

"Our study demonstrates for the first time that this class of materials, the metallic glasses, has the capacity to become the toughest and strongest ever known," Demetriou says. Indeed, the researchers write in their paper, these materials allow for "pushing the envelope of damage tolerance accessible to a structural metal."

What gives metallic glasses their unusual qualities is the fact that they are made of metals—with the inherent toughness that comes with that class of material—but have the internal structure of glass, and thus its strength and hardness. (Despite its name, it is this internal structure that is the only glasslike thing about metallic glass: the material is not transparent, Demetriou notes, and is both optically and electronically like metal.)

The problem with trying to increase strength in ordinary metals is that their atoms are organized in a crystal lattice, Demetriou explains. "And whenever you try to make something as perfect as a crystal, inevitably you will create defects," he says. Those defects, under stress, become mobile, and other atoms move easily around them, producing permanent deformations. While this rearrangement around defects results in an ability to block or cap off an advancing crack, producing toughness, it also limits the strength of the material.

A notched, glassy palladium sample does not shatter after severe bending, despite the generation of multiple cracks.
Credit: LBNL/Maximilien E. Launey

On the other hand, glass has an amorphous structure, its atoms scattered about without a specific discernible pattern. In metallic glasses—also called amorphous metals because of their structure—this results in an absence of the extended defects found in crystalline metals. The actual defects in glasses are generally much smaller in size and only become active when exposed to much higher stresses, resulting in higher strengths. However, this also means that the strategy used in ordinary metals to stop a crack from growing ever longer—the easy and rapid rearrangement of the atoms around defects into a sort of cap at the leading edge of a crack—is not available.

"When defects in the amorphous structure become active under stress, they coalesce into slim bands, called shear bands, that rapidly extend and propagate through the material," says Demetriou. "And when these shear bands evolve into cracks, the material shatters."

It was this tendency to shatter that was thought to be one of the limiting factors of metallic glasses, which were first developed in the 1960s at Caltech. The assumption was that, despite their many benefits, they could never match or exceed the toughness of the toughest steels.

But what the Caltech scientists found, much to their surprise, was that creating more of a problem could actually solve the problem.

In the new palladium alloy, so many shear bands form when the material is put under stress that it "actually leads to higher toughness, because the bands interact and form networks that block crack propagation," Demetriou explains. In other words, the number of shear bands that form, intersect, and multiply at the tip of an evolved crack is so high that the crack is blocked and cannot travel very far. In essence, then, the shear bands act as a shield, preventing shattering. Thus, the palladium glass acts very much like the toughest of steels, using an analogous blocking mechanism of arresting cracks.

"And," Demetriou adds, "this high toughness does not come at the expense of strength. This material has both strength and toughness, which is why it falls so far outside what's previously been possible. That's why this material is so special."

The palladium alloy described in the paper could soon be of use in biomedical implants, says Demetriou. "One example is dental implants," Demetriou says. "Many noble-metal alloys, including palladium, are currently used in dentistry due to their chemical inertness and resistance to oxidation, tarnish, and corrosion. Owing to its superior damage tolerance, the present palladium glass can be thought of as a superior alternative to conventional palladium dental alloys. Plus, the absence of any elements considered toxic or allergenic—nickel, copper, aluminum—from the composition of this alloy will likely promote good biological compatibility."

The class of such tough metallic glasses potentially could be used in other structural applications like automotive and aerospace components, the team says. But this particular alloy is unlikely to be part of any large-scale manufacturing process. "It's prohibitively expensive," says Demetriou. "The cost is much too high for any large-scale, widespread use."

Still, he notes, the fact that it was created at all, with these particular properties, tells scientists that this level of toughness and strength is well within reach. Now it's just a matter of figuring out specifically what gives this alloy its unique damage tolerance, and how that can be replicated with an alloy containing less-expensive, less-precious metals. 

In addition to Demetriou and Johnson, the other authors on the Nature Materials paper, "A Damage-Tolerant Glass," are Caltech graduate student Glenn Garrett, visitor in applied physics and materials science Joseph Schramm, and lecturer in applied physics and materials science Douglas Hofmann; Robert Ritchie from the Lawrence Berkeley National Laboratory (LBNL) and UC Berkeley; and Maximilien Launey, formerly of LBNL and now at the Cordis Corporation. Their work was supported by the National Science Foundation and the U.S. Department of Energy.

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Lori Oliwenstein
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John Dabiri Named to EBONY "Power List"

Congratulations to Caltech's John Dabiri, who has been named to EBONY magazine's annual Power 100 List. Among his companions there: President Barack Obama, Wyclef Jean, Michael Jordan, and Will Smith.

"I'm honored to be included in a list with so many distinguished leaders from all walks of life," Dabiri says. "I hope that my inclusion in the list encourages the next generation of young people that they too can use science and engineering to positively impact their communities. And I especially hope that we will start to see them in greater numbers here at Caltech."

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Kathy Svitil
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Engineering for the Other Half

"Nothing happens in industry from the sole effort of a single mind working in isolation." That, says Visiting Professor of Mechanical Engineering Ken Pickar, is a lesson every young engineer needs to learn. And it's a recurring theme of his course E/ME 105, "Product Design for the Developing World." The course, created with input from the Caltech chapter of Engineers for a Sustainable World (ESW), emphasizes that products don't bring themselves to market unaided—that engineers can be the agents of lasting global change—and that there's more to innovation than just cleverness.

This year's class consisted of sixteen Techers, along with another sixteen attending SaintGITS, a technical university in southwestern India. Their task: define and attempt to solve a number of problems affecting India's poorest residents.

Under the guidance of Professor Jason Issac, the SaintGITS students did much of the initial research, interviewing local business owners, farmers, and professionals. They uncovered several recurring themes, including reduced costs and the empowerment of women, who are largely underrepresented in the workforce. Ultimately, the group proposed seven projects: three involving India's rice and rubber industries, two dealing with health care, and two addressing the insufficiencies of the country's power grid. Teams then began brainstorming via instant messaging and videoconferences (evening in Pasadena corresponds to morning in India), and on December 7 they presented their results.

One proposed device, roughly the size of a deck of cards, is intended to be strapped outside the window of a commuter bus. Over the course of a one-hour ride, its tiny wind-driven turbine would provide enough electricity to charge a cell phone battery. Another project, a personal sleeping fan, proposes to combat India's fierce equatorial heat without air conditioning. It resembles a similar device currently marketed by a UK company, but by lowering the engineering tolerances ("do all the vents need to be exactly the same diameter?"), the team was able to drop costs dramatically.

Given the specific problems being addressed, not every one of the group's projects would likely find a market in the West. However, Pickar encouraged his students to consider the possibility of filing for intellectual property protection where appropriate. For instance, one concept, arising from discussions with medical professionals, was a device to simplify the process of transferring hospital patients between bed and wheelchair. Its design elegantly integrates quick-release hinges and rollers into a large collapsible board. Another was a set of crutches adaptable for use on staircases. By providing extra contact surfaces, they would replace the traditional plant-swing-and-hop procedure with a much gentler lift-and-lower motion, reducing the likelihood of tumbles. In fact, the team's first two prototypes (fashioned from PVC pipe and metal tubing) proved so stable, a tester reported having successfully suspended himself in midair for a full minute.

Throughout the course, at least as much attention is devoted to surprises, failures, and lessons learned as to successes. It's all part of the process, Pickar says: Engineering is mostly trial and error, and students must learn to welcome both of those phases, not to fear them.

"They need to make mistakes in a safe environment," he grins, "before they do it for real."

For more on the course, read "Product Design for the Developing World."

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Dave Zobel
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Caltech Applied Physicist Amnon Yariv Awarded National Medal of Science

PASADENA, Calif., October 15, 2010—Amnon Yariv, the Martin and Eileen Summerfield Professor of Applied Physics and professor of electrical engineering—a pioneer in the field of optoelectronics—has been named one of 10 recipients of the National Medal of Science, the highest honor bestowed by the United States government on scientists.

Yariv was honored for "scientific and engineering contributions to photonics and quantum electronics that have profoundly impacted lightwave communications and the field of optics as a whole,"

according to a National Science Foundation (NSF) press release. (The NSF administers the National Medal of Science and its companion, the National Medal of Technology and Innovation, on behalf of the White House.)

"The extraordinary accomplishments of these scientists, engineers, and inventors are a testament to American industry and ingenuity," said President Barack Obama when announcing the awards. "Their achievements have redrawn the frontiers of human knowledge while enhancing American prosperity, and it is my tremendous pleasure to honor them for their important contributions."

Yariv's award brings the number of Caltech faculty and alumni recipients of the National Medal of Science to 55.

Yariv describes the thread of his research over the years as "fascination with light waves: learning how to generate them, manipulate them, and make them play new 'games.'" In the process, he developed mathematical theories widely used today to describe energy exchange among light waves, as well as experimental and fabrication techniques to demonstrate some of the resulting applications.

"A high point of my group's research," he says, "was the invention of the semiconductor Distributed Feedback Laser, which today powers the Internet's fiber-optic network." He also points to work he did with two colleagues to formulate the quantum theory of nonlinear optics. "Years after its development," he says, "it has become the starting point for the new and futuristic field of quantum communication." Current research in his group is aimed at getting a large number of lasers to collaborate and exchange information, thus realizing new functionalities.

"In addition to being the academic father of applied physics at Caltech, Amnon has personally mentored many of our most successful faculty members and continues to be one of the most constructive and imaginative forces within our division," says Ares Rosakis, the Theodore von Kármán Professor of Aeronautics, professor of mechanical engineering, and chair of the Division of Engineering and Applied Science. "We are indeed lucky to have him at Caltech."

Yariv earned his BS, MS, and PhD degrees from the University of California, Berkeley, in 1954, 1956, and 1958. He joined the Caltech faculty as an associate professor in 1964 and became a full professor in 1966. He was named the Summerfield Professor in 1996.

Yariv and his fellow medal recipients will receive their awards at a White House ceremony later this year.

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Lori Oliwenstein
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