Progress for Paraplegics

Caltech investigators expand project to restore functions to people with spinal-cord injuries

In May 2011, a new therapy created in part by Caltech engineers enabled a paraplegic man to stand and move his legs voluntarily. Now those same researchers are working on a way to automate their system, which provides epidural electrical stimulation to the lower spinal cord. Their goal is for the system to soon be made available to rehab clinics—and thousands of patients—worldwide.

That first patient—former athlete Rob Summers, who had been completely paralyzed below the chest following a 2006 accident—performed remarkably well with the electromechanical system. Although it wasn't initially part of the testing protocol established by the Food and Drug Administration, the FDA allowed Summers to take the entire system with him when he left the Frazier Rehab Institute in Louisville—where his postsurgical physical therapy was done—provided he returns every three months for a checkup.

Joel Burdick, the Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering and Bioengineering at Caltech, and Yu-Chong Tai, a Caltech professor of electrical engineering and mechanical engineering, helped create the therapy, which involves the use of a sheetlike array of electrodes that stimulate Summers' neurons and thus activate the circuits in his lower spinal cord that control standing and stepping. The approach has subsequently been successfully tested on a second paraplegic, and therapists are about to finish testing a third subject, who has shown positive results.

But Tai and Burdick want to keep the technology, as well as the subjects, moving forward. To that end, Tai is developing new versions of the electrode array currently approved for human implantation; these will improve patients' stepping motions, among other advances, and they will be easier to implant. Burdick is also working on a way to let a computer control the pattern of electrical stimulation applied to the spinal cord.

"We need to go further," Burdick says. "And for that, we need new technology."

Because spinal-cord injuries vary from patient to patient, deploying the system has required constant individualized adjustments by clinicians and researchers at the Frazier Institute, a leading center for spinal-cord rehabilitation. "Right now there are 16 electrodes in the array, and for each individual electrode, we send a pulse, which can be varied for amplitude and frequency to cause a response in the patient," Burdick says. Using the current method, he notes, "it takes substantial effort to test all the variables to find the optimum setting for a patient for each of the different functions we want to activate."

The team of investigators, which also includes researchers from UCLA and the University of Louisville, has until now used intelligent guesswork to determine which stimuli might work best. But soon, using a new algorithm developed by Burdick, they will be able to rely on a computer to determine the optimum stimulation levels, based on the patient's response to previous stimuli. This would allow patients to go home after the extensive rehab process with a system that could be continually adjusted by computer—saving Summers and the other patients many of those inconvenient trips back to Louisville. Doctors and technicians could monitor patients' progress remotely.

In addition to providing the subjects with continued benefits from the use of the device, there are other practical reasons for wanting to automate the system. An automated system would be easier to share with other hospitals and clinics around the world, Burdick says, and without a need for intensive training, it could lower the cost.

The FDA has approved testing the system in five spinal-cord injury patients, including the three already enrolled in the trial; Burdick is planning to test the new computerized version in the fourth patient, as well as in Rob Summers during 2013. Once the investigators have completed testing on all five patients, Burdick says, the team will spend time analyzing the data before deciding how to improve the system and expand its use.

The strategy is not a cure for paraplegics, but a tool that can be used to help improve the quality of their health, Burdick says. The technology could also complement stem-cell therapies or other methods that biologists are working on to repair or circumvent the damage to nervous systems that results from spinal-cord injury.

"There's not going to be one silver bullet for treating spinal-cord injuries," Burdick says. "We think that our technique will play a role in the rehabilitation of spinal-cord injury patients, but a more permanent cure will likely come from biological solutions."

Even with the limitations of the current system, Burdick says, the results have exceeded his expectations.

"All three subjects stood up within 48 hours of turning on the array," Burdick says. "This shows that the first patient wasn't a fluke, and that many aspects of the process are repeatable." In some ways, the second and third patients are performing even better than Summers, though it will be some time before the team can fully analyze those results. "We were expecting variations because of the distinct differences in the patients' injuries. Rob gave us a starting point, and now we've learned how to tune the array for each patient and to make adjustments as each patient changes over time.

"I do this work because I love it," Burdick says. "When you work with these people and get to know them and see how they are improving, it's personally inspiring."

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Reconsidering the Global Thermostat

Caltech researcher and colleagues show outcome of geoengineering can be tunable

PASADENA, Calif.—From making clouds whiter and injecting aerosols into the stratosphere, to building enormous sunshades in space, people have floated many ideas about how the planet's climate could be manipulated to counteract the effects of global warming—a concept known as geoengineering. Many of the ideas involve deflecting incoming sunlight before it has a chance to further warm the earth. Because this could affect areas of the planet inequitably, geoengineering has often raised an ethical question: Whose hand would control the global thermostat?

Now a team of researchers from the California Institute of Technology (Caltech), Harvard University, and the Carnegie Institution says there doesn't have to be just a single global control. Using computer modeling, they have shown that varying the amount of sunlight deflected away from the earth by season and by region can significantly improve the parity of the situation. The results appear in an advance online publication of the journal Nature Climate Change.

Previous geoengineering studies have typically assumed uniform deflection of sunlight everywhere on the planet. But the pattern of temperature and precipitation effects that would result from such efforts would never compensate perfectly for the complex pattern of changes that have resulted from global warming. Some areas would end up better off than others, and the climate effects are complex. For example, as the planet warms, the poles are heating up more than the tropics. However, in models where sunlight is deflected uniformly, when enough sunlight is redirected to compensate for this polar warming, the tropics end up colder than they were before man-made activities pumped excess carbon dioxide into the atmosphere.

In the new study, the researchers worked with a climate model of relatively coarse resolution. Rather than selecting one geoengineering strategy, they mimicked the desired effect of many projects by simply "turning down the sun"—decreasing the amount of sunlight reaching the planet. Instead of turning down the sun uniformly, they tailored when and where they reduced incoming sunlight, looking at 15 different combinations. In one, for example, they turned down the sun between January and March while also turning it down more at the poles than at the tropics.

"That essentially gives us 15 knobs that we can tune in order to try to minimize effects at the worst-off regions on the planet," says Doug MacMartin, a senior research associate at Caltech and lead author of the new paper. "In our model, we were able to reduce the residual climate changes (after geoengineering) in the worst-off regions by about 30 percent relative to what could be achieved using a uniform reduction in sunlight."

The group also found that by varying where and when sunlight was reduced, they needed to turn down the sun just 70 percent as much as they would in uniform reflectance to get a similar result. "Based on this work, it's at least plausible that there are ways that you could implement a geoengineering solution that would have less severe consequences, such as a reduced impact on ozone," MacMartin says.

The researchers also used the tuning approach to focus on recovering Arctic sea ice. In their model, it took five times less solar reduction than in the uniform reflectance models to recover the Arctic sea ice to the extent typical of pre-Industrial years.

"These results indicate that varying geoengineering efforts by region and over different periods of time could potentially improve the effectiveness of solar geoengineering and reduce climate impacts in at-risk areas," says Ken Caldeira of the Carnegie Institution. "For example, these approaches may be able to reverse long-term changes in the Arctic sea ice."

The group acknowledges that geoengineering ideas are untested and could come with serious consequences, such as making the skies whiter and depleting the ozone layer, not to mention the unintended consequences that tend to arise when dealing with such a complicated system as the planet. They also say that the best solution would be to reduce greenhouse gas emissions. "I'm approaching it as an engineering problem," MacMartin says. "I'm interested in whether we can come up with a better way of doing the geoengineering that minimizes the negative consequences."  

In addition to MacMartin and Caldeira, David Keith of Harvard University and Ben Kravitz, formerly of the Carnegie Institution but now at the DOE's Pacific Northwest National Lab, are also coauthors on the paper, "Management of trade-offs in geoengineering through optimal choice of non-uniform radiative forcing."

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Engineering with Impact

Watson Lecture Preview

Guruswami (Ravi) Ravichandran is an expert on breakups—of ceramics and metals, not relationships. The John E. Goode, Jr., Professor of Aerospace and professor of mechanical engineering and the director of the Graduate Aerospace Laboratories at Caltech, Ravichandran will talk about his work at the leading edge of impact mechanics on Wednesday, October 24, at 8:00 p.m. in Caltech's Beckman Auditorium. Admission is free.

 

Q: What do you do?

A: I study the dynamic behavior of materials. How they deform on impact. How they break up, how they absorb energy and disperse momentum. We subject materials to millions of atmospheres of pressure by shooting projectiles at them, or dropping weights on them, or jabbing them with a bar like a medieval battering ram. You cannot simulate the pressure at the core of the earth, for example, in a normal laboratory. But impact provides a means for creating those conditions, and lets you explore properties of these materials at these extreme conditions.

 

Q: Why is this cool?

A: It is cool because we look at things that you cannot ordinarily look at—not only extremes of temperature and pressure, but time. We have very high-speed optical and thermal infrared cameras that can go up to one hundred million frames per second. That's one frame every 10 nanoseconds, and it lets us visualize phenomena that you normally won't be able to see. We can watch a crack tear through a metal plate in real time, for example, and we can map the shear stresses and temperature fields across the plate as it stretches before giving way.

We are motivated by the big questions. Where did we come from? The extinction of the dinosaurs, how did that occur? And what's our relationship to that period of the earth's history? But we also explore real-life problems, such as how to build protective structures such as armor. If you think of the crash-worthiness of a car, how do you make a better cage to strengthen the passenger compartment?

And we can even create new materials. A few years back, for example, we made some titanium / silicon carbide composites that could not have been made otherwise. They're more ductile than usual, which could be a useful property for aerospace applications.

 

Q: How did you get into this line of work?

A: When I started graduate school at Brown I was already working on impact-related problems. I enjoyed them, so I've kept up with the thing ever since. It just happened to fall into place. But I did always wonder about those Road Runner cartoons—you see a rock or something break apart after an impact, and you think, "Are those crack patterns for real?"

 

Named for the late Caltech professor Earnest C. Watson, who founded the series in 1922, the Watson Lectures present Caltech and JPL researchers describing their work to the public. Many past Watson Lectures are available online at Caltech's iTunes U site.

 

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Developing the Next Generation of Microsensors

Caltech researchers engineer microscale optical accelerometer

PASADENA, Calif.—Imagine navigating through a grocery store with your cell phone. As you turn down the bread aisle, ads and coupons for hot dog buns and English muffins pop up on your screen. The electronics industry would like to make such personal navigators a reality, but, to do so, they need the next generation of microsensors.

Thanks to an ultrasensitive accelerometer—a type of motion detector—developed by researchers at the California Institute of Technology (Caltech) and the University of Rochester, this new class of microsensors is a step closer to reality. Beyond consumer electronics, such sensors could help with oil and gas exploration deep within the earth, could improve the stabilization systems of fighter jets, and could even be used in some biomedical applications where more traditional sensors cannot operate.

Caltech professor of applied physics Oskar Painter and his team describe the new device and its capabilities in an advance online publication of the journal Nature Photonics.

Rather than using an electrical circuit to gauge movements, their accelerometer uses laser light. And despite the device's tiny size, it is an extremely sensitive probe of motion. Thanks to its low mass, it can also operate at a large range of frequencies, meaning that it is sensitive to motions that occur in tens of microseconds, thousands of times faster than the motions that the most sensitive sensors used today can detect.

"The new engineered structures we made show that optical sensors of very high performance are possible, and one can miniaturize them and integrate them so that they could one day be commercialized," says Painter, who is also codirector of Caltech's Kavli Nanoscience Institute.

Although the average person may not notice them, microchip accelerometers are quite common in our daily lives. They are used in vehicle airbag deployment systems, in navigation systems, and in conjunction with other types of sensors in cameras and cell phones. They have successfully moved into commercial use because they can be made very small and at low cost.

Accelerometers work by using a sensitive displacement detector to measure the motion of a flexibly mounted mass, called a proof mass. Most commonly, that detector is an electrical circuit. But because laser light is one of the most sensitive ways to measure position, there has been interest in making such a device with an optical readout. For example, projects such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) rely on optical interferometers, which use laser light reflecting off mirrors separated by kilometers of distance to sensitively measure relative motion of the end mirrors. Lasers can have very little intrinsic noise—meaning that their intensity fluctuates little—and are typically limited by the quantum properties of light itself, so they make it much easier to detect very small movements.

People have tried, with limited success, to make miniature versions of these large-scale interferometers. One stumbling block for miniaturization has been that, in general, the larger the proof mass, the larger the resulting motion when the sensor is accelerated. So it is typically easier to detect accelerations with larger sensors. Also, when dealing with light rather than electrons—as in optical accelerometers—it is a challenge to integrate all the components (the lasers, detectors, and interferometer) into a micropackage.

"What our work really shows is that we can take a silicon microchip and scale this concept of a large-scale optical interferometer all the way down to the nanoscale," Painter says. "The key is this little optical cavity we engineered to read out the motion."

The optical cavity is only about 20 microns (millionths of a meter) long, a single micron wide, and a few tenths of a micron thick. It consists of two silicon nanobeams, situated like the two sides of a zipper, with one side attached to the proof mass. When laser light enters the system, the nanobeams act like a "light pipe," guiding the light into an area where it bounces back and forth between holes in the nanobeams. When the tethered proof mass moves, it changes the gap between the two nanobeams, resulting in a change in the intensity of the laser light being reflected out of the system. The reflected laser signal is in fact tremendously sensitive to the motion of the proof mass, with displacements as small as a few femtometers (roughly the diameter of a proton) being probed on the timescale of a second.

It turns out that because the cavity and proof mass are so small, the light bouncing back and forth in the system pushes the proof mass—and in a special way: when the proof mass moves away, the light helps push it further, and when the proof mass moves closer, the light pulls it in. In short, the laser light softens and damps the proof mass's motion.

"Most sensors are completely limited by thermal noise, or mechanical vibrations—they jiggle around at room temperature, and applied accelerations get lost in that noise," Painter says. "In our device, the light applies a force that tends to reduce the thermal motion, cooling the system." This cooling—down to a temperature of three kelvins (about –270°C) in the current devices—increases the range of accelerations that the device can measure, making it capable of measuring both extremely small and extremely large accelerations.

"We made a very sensitive sensor that, at the same time, can also measure very large accelerations, which is valuable in many applications," Painter says.

The team envisions its optical accelerometers becoming integrated with lasers and detectors in silicon microchips. Microelectronics companies have been working for the past 10 or 15 years to try to integrate lasers and optics into their silicon microelectronics. Painter says that a lot of engineering work still needs to be done to make this happen, but adds that "because of the technological advancements that have been made by these companies, it looks like one can actually start making microversions of these very sensitive optical interferometers."

"Professor Painter's research in this area nicely illustrates how the Engineering and Applied Science faculty at Caltech are working at the edges of fundamental science to invent the technologies of the future," says Ares Rosakis, chair of Caltech's Division of Engineering and Applied Science.  "It is very exciting to envision the ways this research might transform the microelectronics industry and our daily lives."

The lead authors on the paper, titled "A high-resolution microchip optomechanical accelerometer," have all worked in Painter's lab. Alexander Krause and Tim Blasius are currently graduate students at Caltech, while Martin Winger is a former postdoctoral scholar who now works for a sensor company called Sensirion in Zurich, Switzerland. This work was performed in collaboration with Qiang Lin, a former postdoctoral scholar of the Painter group, who now leads his own research group at the University of Rochester. The work is supported by the Defense Advanced Research Projects Administration QuASaR program, the National Science Foundation Graduate Research Fellowship Program, and Intellectual Ventures.

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Kimm Fesenmaier
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How I Spent My Summer Vacation

A SURF Video Diary

Last summer, Caltech junior Julie Jester worked on a project that might one day partially counteract blindness caused by a deteriorating retina. Her job: to help Assistant Professor of Electrical Engineering Azita Emami and her graduate students create the communications link between a tiny camera and a novel wireless neural stimulator that can be surgically inserted into the eye.

Now in its 34th year, Caltech's Summer Undergraduate Research Fellowships (SURF) program has paired nearly 7,000 students with real-world, hands-on projects in the labs of Caltech faculty and JPL staff.

 

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Doug Smith
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A "Gifted" Professor

A Group of Caltech Alumni Come Together to Create a Professorial Chair to Honor Their Mentor, Frank Marble

Gifted teacher. Inspired researcher. Knowledgeable adviser. Personal friend. These are a few of the ways in which professor emeritus Frank Marble's former students describe him.

Not too surprisingly, these sentiments also capture some of the many reasons why 20 of Marble's former PhD and graduate student advisees have joined together to honor and thank their mentor by creating an endowed professorship in his and his wife's names. They have also seeded the initial funds for a graduate fellowship in the Marbles' honor.

The Frank and Ora Lee Marble Endowed Professorship will benefit a faculty member in the Division of Engineering and Applied Science. The $3 million professorship was made possible with a lead gift from alumnus Laurence B. Zung (MS '63, PhD '67) and his wife, Coralie, as well as accompanying gifts from other Marble advisees, and a $1 million match from the Gordon and Betty Moore Matching Program. Another $177,000 has also been collectively pledged to begin the establishment of what will be the Frank and Ora Lee Marble Graduate Fellowship.

"I wanted to do something so that the Marbles could both witness our appreciation and participate in it," says Zung. "The things I learned from him have benefited me throughout my life and my career. He trained me to learn how to learn and to learn how to think."

Marble, the Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering and Professor of Jet Propulsion, Emeritus, advised more than three dozen PhD students during his tenure of more than 40 years at Caltech (from 1948 to 1989), all the while making major fundamental, theoretical, and experimental contributions to the fields of internal aerodynamics, combustion, and propulsion—especially with respect to gas turbines and rockets. Marble is a member of both the National Academy of Engineering and the National Academy of Science, and a recipient of the Daniel Guggenheim Medal.

Ann Karagozian and Frank MarbleCALTECH ALUMNA ANN KARAGOZIAN RECONNECTS WITH HER FORMER MENTOR, FRANK MARBLE, AT A RECENT CALTECH EVENT CELEBRATING A GIFT MADE IN HIS HONOR.
Credit: Bob Paz

"It was a privilege to learn from Dr. Marble," says Ann Karagozian (MS '79, PhD '82), who helped initiate the campaign for a graduate fellowship in Marble's honor. "He always gave me excellent advice, whether it was on research or career choices or embarking in new directions."

With his wife, Ora Lee, Marble also helped create a "home away from home" for many of his students. The couple regularly invited Caltech students into their house for dinners and special gatherings at which they could mingle with one another as well as with professors.

"By their example, the Marbles gave us a lasting lesson on how to live a fulfilling life," says Gerald "Jerry" Marxman (PhD '62). "I hope this gift will serve as a permanent symbol of the Marbles' wonderful impact on so many others' lives, and as a reminder of the gratitude felt by all those graduate students who have benefited so much from knowing them."

Marble initially came to Caltech as a student himself—earning an engineer's degree in 1947 and a PhD in 1948 under the advisement of Theodore von Kármán. He credits much of his teaching and mentoring style—in which he encouraged students to pursue their passions, wherever they led them—to the lessons he learned from his own mentor.

"I will never forget what my students and friends have done," says Marble, who considers all his doctoral students to be his "academic children." "This is about as impressive an act as I can think of. It allows the administration a significant hand in choosing faculty members who represent new fields of research and new fields of teaching."

Ares Rosakis, chair of the Division of Engineering and Applied Science (EAS) at Caltech says, "Inspirational teachers and researchers like Frank Marble and his adviser Theodore von Kármán create new schools of thought which nurture generation after generation of academics.  It is this long term commitment to education and research that helps the Engineering and Applied Science Division and Caltech maintain their number one position in the recently announced world university rankings."

Several of Marble's former colleagues, students, and their families gathered at Caltech in September to celebrate the Marbles' enduring contributions and the establishment of the professorial chair. Both the chair and the eventual fellowship will be awarded to individuals with interests in aerospace and mechanical engineering, the fields in which Marble made his greatest scientific and engineering contributions.

"For the family, this is a humbling experience, without a doubt," says Marble's son, Steve Marble. "It's a very sweet validation of what my father spent so much of his life doing. The idea that his former colleagues and friends would do something of this sort to honor him, especially in his lifetime, is profoundly meaningful for him . . . and it underscores the importance of a teacher who gets such pleasure from stirring the passions of his students."

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Caltech Again Named World's Top University in <i>Times Higher Education</i> Global Ranking

PASADENA, Calif.—The California Institute of Technology (Caltech) has been rated the world's number one university in the 2012–2013 Times Higher Education global ranking of the top 200 universities.

Oxford University, Stanford University, Harvard University, and MIT round out the top five.

"We are pleased to be among the best, and we celebrate the achievements of all our peer institutions," says Caltech president Jean-Lou Chameau. "Excellence is achieved over many years and is the result of our focus on extraordinary people. I am proud of our talented faculty, who educate outstanding young people while exploring transformative ideas in an environment that encourages collaboration rather than competition."

Times Higher Education compiled the listing using the same methodology as in last year's survey. Thirteen performance indicators representing research (worth 30 percent of a school's overall ranking score), teaching (30 percent), citations (30 percent), international outlook (which includes the total numbers of international students and faculty and the ratio of scholarly papers with international collaborators, 7.5 percent), and industry income (a measure of innovation, 2.5 percent) make up the data. Included among the measures are a reputation survey of 17,500 academics; institutional, industry, and faculty research income; and an analysis of 50 million scholarly papers to determine the average number of citations per scholarly paper, a measure of research impact.

In addition to placing first overall in this year's survey, Caltech came out on top in the teaching indicator as well as in subject-specific rankings for engineering and technology and for the physical sciences.

"Caltech held on to the world's number one spot with a strong performance across all of our key performance indicators," says Phil Baty, editor of the Times Higher Education World University Rankings. "In a very competitive year, when Caltech's key rivals for the top position reported increased research income, Caltech actually managed to widen the gap with the two universities in second place this year—Stanford University and the University of Oxford. This is an extraordinary performance."

Data for the Times Higher Education's World University Rankings were provided by Thomson Reuters from its Global Institutional Profiles Project, an ongoing, multistage process to collect and validate factual data about academic institutional performance across a variety of aspects and multiple disciplines.

The Times Higher Education site has the full list of the world's top 400 schools and all of the performance indicators.

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Caltech Again Named World's Top University by <i>Times Higher Ed</i>
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Caltech Faculty Members Honored by Popular Mechanics

Caltech engineers and scientists often work at the frontiers of science—pushing the limits of what is known and what is possible. Now, with its eighth annual Breakthrough Awards, Popular Mechanics magazine is recognizing two projects that fall into this category and in which Caltech faculty members have played major roles—the development of ultralight micro-lattices by materials scientist Julia Greer and colleagues, and the Voyager 1 and 2 missions, whose project scientist, physicist Ed Stone, has been at Caltech for the missions' entire 35-year ride.

The Breakthrough Awards recognize "innovators and products that have dramatically advanced the fields of technology, medicine, space exploration, automotive design, environmental engineering and more."  This year's recipients will receive their awards during a ceremony on October 4 in New York City.

"I am delighted that Professor Greer is being honored with this award," says Ares Rosakis, chair of the Division of Engineering and Applied Science (EAS) at Caltech. "She is a great example of how we in EAS are working at the edges of fundamental science to invent the technologies of the future."

Greer, an assistant professor of materials science and mechanics at Caltech, is being honored as part of the team that engineered a metallic lattice celebrated late last year as the world's lightest solid material. Including engineers and researchers from HRL Laboratories and UC Irvine, the team was able to make three-dimensional lattices composed of tiny, metallic hollow tubes. The end product has a density of just 0.9 milligrams per cubic centimeter, making it approximately 100 times lighter than Styrofoam. 

"Having developed the micro-truss is a nice beginning," says Greer, "but it's not the end of the story in any way. Now we can start dreaming big, developing completely new materials for a variety of applications, without being limited by their classical processing routes."

In fact, since the group described the micro-trusses in the journal Science in November 2011, Greer has received several grants to work on potential applications ranging from lightweight, damage-tolerant, and radiation-resistant materials for use in space to planar structures that could hold thousands of modular solar cells at different angles in order to capture more of the solar spectrum. 

Stone, the David Morrisroe Professor of Physics at Caltech, will accept a special Mechanical Lifetime Achievement Award on behalf of the entire Voyager team, along with Suzanne Dodd (BS '84), the project manager, and Jefferson Hall, the mission flight director. The Voyager spacecraft were built by the Jet Propulsion Laboratory (JPL), which continues to operate both. Caltech manages JPL for NASA.

Voyager 1 recently celebrated the 35th anniversary of its launch in 1977. It lifted off just 16 days after its twin, Voyager 2 (which reached Jupiter second despite being the first to launch). The long-lasting probes have revealed much about our solar system—"things we hadn't really thought about or imagined," Stone says. Today, both spacecraft continue to relay data, and Voyager 1 is expected to enter interstellar space soon.

"We are once again excited to recognize this year's list of incredible honorees for their role in shaping the future," said James B. Meigs, editor-in-chief of Popular Mechanics, in a press release. "From a featherweight metal to the world's fastest and most electrically efficient supercomputer, this year's winners embody the creative spirit that the Breakthrough Awards were founded upon."

The winners were chosen by the editors of the magazine after recommendations were solicited from a wide range of experts and past Breakthrough Award winners, in fields ranging from aerospace and robotics to medicine and energy. 

To read more about all of the awards, visit the Popular Mechanics website. Full descriptions are also available in the magazine's November issue, available on newsstands October 16. 

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Kimm Fesenmaier
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Ready for Your Close-Up?

Caltech study shows that the distance at which facial photos are taken influences perception

PASADENA, Calif.—As the saying goes, "A picture is worth a thousand words." For people in certain professions—acting, modeling, and even politics—this phrase rings particularly true. Previous studies have examined how our social judgments of pictures of people are influenced by factors such as whether the person is smiling or frowning, but until now one factor has never been investigated: the distance between the photographer and the subject. According to a new study by researchers at the California Institute of Technology (Caltech), this turns out to make a difference—close-up photo subjects, the study found, are judged to look less trustworthy, less competent, and less attractive.

The new finding is described in this week's issue of the open-access journal PLoS One.

Pietro Perona, the Allen E. Puckett Professor of Electrical Engineering at Caltech, came up with the initial idea for the study. Perona, an art history enthusiast, suspected that Renaissance portrait paintings often featured subtle geometric warping of faces to make the viewer feel closer or more distant to a subject. Perona wondered if the same sort of warping might affect photographic portraits—with a similar effect on their viewers—so he collaborated with Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology, and CNS graduate student Ronnie Bryan (PhD '12) to gather opinions on 36 photographs representing two different images of 18 individuals. One of each pair of images was taken at close range and the second at a distance of about seven feet.

"It turns out that faces photographed quite close-up are geometrically warped, compared to photos taken at a larger distance," explains Bryan. "Of course, the close picture would also normally be larger, higher resolution and have different lighting—but we controlled for all of that in our study. What you're left with is a warping effect that is so subtle that nobody in our study actually noticed it. Nonetheless, it's a perceptual clue that influenced their judgments."

That subtle distance warping, however, had a big effect: close-up photos made people look less trustworthy, according to study participants. The close-up photo subjects were also judged to look less attractive and competent.

"This was a surprising, and surprisingly reliable, effect," says Adolphs. "We went through a bunch of experiments, some testing people in the lab, and some even over the Internet; we asked participants to rate trustworthiness of faces, and in some experiments we asked them to invest real money in unfamiliar people whose faces they saw as a direct measure of how much they trusted them."

Across all of the studies, the researchers saw the same effect, Adolphs says: in photos taken from a distance of around two feet, a person looked untrustworthy, compared to photos taken seven feet away. These two distances were chosen by the researchers because one is within, and the other outside of, personal space—which on average is about three to four feet from the body.

In some of the studies, the researchers digitally warped images of faces taken at a distance to artificially manipulate how trustworthy they would appear. "Once you know the relation between the distance warp and the trustworthiness judgment, you could manipulate photos of faces and change the perceived trustworthiness,'' notes Perona.

He says that the group is now planning to build on these findings, using machine-vision techniques—technologies that can automatically analyze data in images. For example, one application would be for a computer program to have the ability to evaluate any face image in a magazine or on the Internet and to estimate the distance at which the photo was taken.

"The work might also allow us to estimate the perceived trustworthiness of a particular face image," says Perona. "You could imagine that many people would be interested in such applications—particularly in the political arena."

The study, "Perspective Distortion from Interpersonal Distance Is an Implicit Visual Cue for Social Judgments of Faces," was funded by grants from the National Institute of Mental Health and from the Gordon and Betty Moore Foundation.

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Katie Neith
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When Judging Portraits, Distance Matters
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Working Optimally

Venkat Chandrasekaran, an assistant professor of computing and mathematical sciences, arrived at Caltech in early September. Chandrasekaran, who was born in Mumbai, India, and grew up in a number of different Indian and Middle Eastern cities, studied mathematics and electrical engineering as an undergraduate student at Rice University and earned his master's and PhD at MIT. Before joining Caltech's faculty, he completed a postdoctoral fellowship at UC Berkeley. We recently asked him some questions about his work and what drew him to Caltech.

What kind of research do you work on?

My area of research is mathematical optimization. Almost anything we wish to do in engineering design is about maximizing objectives subject to certain constraints—trading off different aspects of a system to optimize a few others. For instance, if you work in jet-engine design, you have certain constraints in the amount of material you can use, the weight of these materials, aerodynamic issues, etc. But then you want to be able to design your wings and so on in such a way that you maximize, for example, how fast you are able to go. If you work in finance, you might want to maximize your returns given that you have a certain amount to invest and have other constraints based on market volatility.

So optimization is fairly broad. My specific focus deals with trying to look at optimization problems that (a) are tractable to solve—not all optimization problems are ones that can be efficiently solved on a computer—and (b) arise in the information sciences.

Can you give some examples of the types of problems you work on?

For my PhD, I worked on a problem in statistical modeling. The idea is you get measurements of a bunch of variables—these could be the prices of different stocks in the stock market, it could be a bunch of physiological attributes of a patient, it could be any collection of variables—and would like to understand the relationships between these variables. In the first case, with stock prices, you want to be able to figure out how A affects B affects C in very complicated ways to be able to make better investments. In the second case, you'd like to be able to figure out the correlations between weight, age, and something else, versus blood pressure, for instance. Frequently, in trying to understand the relationships, interactions, or correlations between these variables, there are some relevant variables that you don't observe, which is a big challenge. So, for instance, in the stock market example, there may be some geopolitical factor that is not directly observable but that influences the way stock prices move. The question is: by looking at the original set of variables that you do get to observe, can you potentially infer the existence of hidden effects that you can't observe directly? If I can account for these, then I can discover a really simple, nice set of relationships, interactions, or rules governing the original set of variables. We have developed efficient tools based on optimization to solve this problem.

Another problem that I have been working on for the past year or so deals with statistics and what people have described as "big data." It is often the case that as datasets scale up, the algorithms that ran efficiently on smaller sets now fail to run. But more data should never be a constraint—it should be helping, not hurting me. So the idea is: as I get more data, can I run a different algorithm that actually runs in less time on larger and larger data sets? I'm currently working on algorithms that would do less optimal processing on each individual data point, thereby reducing the overall run time on a larger dataset, while still providing the same level of performance.

What brought you to Caltech?

One of the things I really liked was the close interaction between folks in applied math and folks in electrical engineering/computer science. I think one of the great things at Caltech—since it's a relatively smaller place—is that even on my floor, there are people who do very, very different things than what I do. I think that fosters interaction among people who are much farther away from each other, in terms of scientific discipline, than at many other places. That's only useful if you share a common language, and this is something else that Caltech does very well—there is a commitment to mathematical rigor. Everybody knows their math. And so while we may be working in very different disciplines, there is this common language, this common technical background, that we all share, making us able to talk to each other. I think the opportunity to learn from someone else is absolutely maximized if you share broadly the same language but have maybe a different perspective. You get exposed to very different ways of thinking.

Writer: 
Kimm Fesenmaier
Frontpage Title: 
Venkat Chandrasekaran: Working Optimally
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