Fifty Years of Clearing the Skies

A Milestone in Environmental Science

Ringed by mountains and capped by a temperature inversion that traps bad air, Los Angeles has had bouts of smog since the turn of the 20th century. An outbreak in 1903 rendered the skies so dark that many people mistook it for a solar eclipse. Angelenos might now be living in a state of perpetual midnight—assuming we could live here at all—were it not for the work of Caltech Professor of Bio-organic Chemistry Arie Jan Haagen-Smit. How he did it is told here largely in his own words, excerpted from Caltech's Engineering & Science magazine between 1950 and 1962. (See "Related Links" for the original articles.)

Old timers, which in California means people who have lived here some 25 years, will remember the invigorating atmosphere of Los Angeles, the wonderful view of the mountains, and the towns surrounded by orange groves. Although there were some badly polluted industrial areas, it was possible to ignore them and live in more pleasant locations, especially the valleys . . . Just 20 years ago, the community was disagreeably surprised when the atmosphere was filled with a foreign substance that produced a strong irritation of the eyes. Fortunately, this was a passing interlude which ended with the closing up of a wartime synthetic rubber plant. (November 1962)

Alas, the "interlude" was an illusion. In the years following World War II, visibility often fell to a few blocks. The watery-eyed citizenry established the Los Angeles County Air Pollution Control District (LACAPCD) in 1947, the first such body in the nation. The obvious culprits—smoke-belching power plants, oil refineries, steel mills, and the like—were quickly regulated, yet the problem persisted. Worse, this smog was fundamentally different from air pollution elsewhere—the yellow, sulfur-dioxide-laced smog that killed 20 people in the Pennsylvania steel town of Donora in 1948, for example, or London's infamous pitch-black "pea-soupers," where the burning of low-grade, sulfur-rich coal added soot to the SO2. (The Great Smog of 1952 would carry off some 4,000 souls in four days.) By contrast, L.A.'s smog was brown and had an acrid odor all its own.

Haagen-Smit had honed his detective skills isolating and identifying the trace compounds responsible for the flavors of pineapples and fine wines, and in 1948 he began to turn his attention to smog.

Chemically, the most characteristic aspect of smog is its strong oxidizing action . . . The amount of oxidant can readily be determined through a quantitative measurement of iodine liberated from potassium iodide solution, or of the red color formed in the oxidation of phenolphthalin to the well-known acid-base indicator, phenolphthalein. To demonstrate these effects, it is only necessary to bubble a few liters of smog air through the colorless solutions. (December 1954)

His chief suspect was ozone, a highly reactive form of oxygen widely used as a bleach and a disinfectant. It's easy to make—a spark will suffice—and it's responsible for that crisp "blue" odor produced by an overloaded electric motor. But there was a problem:

During severe smog attacks, ozone concentrations of 0.5 ppm [parts per million], twenty times higher than in [clean] country air, have been measured. From such analyses the quantity of ozone present in the [Los Angeles] basin at that time is calculated to be about 500 tons.

Since ozone is subject to a continuous destruction in competition with its formation, we can estimate that several thousand tons of ozone are formed during a smog day. It is obvious that industrial sources or occasional electrical discharges do not release such tremendous quantities of ozone. (December 1954)

If ozone really was to blame, where was it coming from? An extraordinary challenge lay ahead:

The analysis of air contaminants has some special features, due to the minute amounts present in a large volume of air. The state in which these pollutants are present—as gases, liquids and solid particles of greatly different sizes—presents additional difficulties. The small particles of less than one micron diameter do not settle out, but are in a stable suspension and form so-called aerosols.

The analytical chemist has devoted a great deal of effort to devising methods for the collection of this heterogeneous material. Most of these methods are based on the principle that the particles are given enough speed to collide with each other or with collecting surfaces . . . A sample of Los Angeles' air shows numerous oily droplets of a size smaller than 0.5 micron, as well as crystalline deposits of metals and salts . . . When air is passed through a filter paper, the paper takes on a grey appearance, and extraction with organic solvents gives an oily material. (December 1950)

Haagen-Smit suspected that this oily material, a complex brew of organic acids and other partially oxidized hydrocarbons, was smog's secret ingredient. In 1950, he took a one-year leave of absence from Caltech to prove it, working full-time in a specially equipped lab set up for him by the LACAPCD. By the end of the year, he had done so.

Through investigations initiated at Caltech, we know that the main source of this smog is due to the release of two types of material. One is organic material—mostly hydrocarbons from gasoline—and the other is a mixture of oxides of nitrogen. Each one of these emissions by itself would be hardly noticed. However, in the presence of sunlight, a reaction occurs, resulting in products which give rise to the typical smog symptoms. The photochemical oxidation is initiated by the dissociation of NO2 into NO and atomic oxygen. This reactive oxygen attacks organic material, resulting in the formation of ozone and various oxidation products . . . The oxidation reactions are generally accompanied by haze or aerosol formation, and this combination aggravates the nuisance effects of the individual components of the smog complex. (November 1962)

Professor of Plant Physiology Frits Went was also on the case. Went ran Caltech's Earhart Plant Research Laboratory, which he proudly called the "phytotron," by analogy to the various "trons" operated by particle physicists. (Phyton is the Greek word for plant.) "Caltech's plant physiologists happen to believe that the phytotron is as marvellously complicated as any of the highly-touted 'atom-smashing' machines," Went wrote in E&S in 1949. "[It] is the first laboratory in the world in which plants can be grown under every possible climatic condition. Light, temperature, humidity, gas content of the air, wind, rain, and fog—all these factors can be simultaneously and independently controlled. The laboratory can create Sacramento Valley climate in one room and New England climate in another." Most of Los Angeles was still orchards and fields instead of tract houses, and the smog was hurting the produce. Went, the LACAPCD, and the UC Riverside agricultural station tested five particularly sensitive crops in the phytotron, Haagen-Smit wrote.

The smog indicator plants include spinach, sugar beet, endive, alfalfa and oats. The symptoms on the first three species are mainly silvering or bronzing of the underside of the leaf, whereas alfalfa and oats show bleaching effects. Some fifty compounds possibly present in the air were tested on their ability to cause smog damage—without success. However, when the reaction products of ozone with unsaturated hydrocarbons were tried, typical smog damage resulted. (December 1950)

And yet a third set of experiments was under way. Rubber tires were rotting from the smog at an alarming rate, cracking as they flexed while rolling along the road. Charles E. Bradley, a research associate in biology, turned this distressing development into a cheap and effective analytical tool by cutting rubber bands by the boxful into short segments. The segments—folded double, secured with a twist of wire, and set outside—would start to fall apart almost before one could close the window. "During severe smog initial cracking appears in about four minutes, as compared to an hour or more required on smog-free days, or at night," Haagen-Smit wrote in the December 1954 E&S.

The conclusion that airborne gasoline and nitrogen oxides (another chief constituent of automobile exhaust) were to blame for smog was not well received by the oil refineries, who hired their own expert to prove him wrong. Abe Zarem (MS '40, PhD '44), the manager and chairman of physics research for the Stanford Research Institute, opined that stratospheric ozone seeping down through the inversion layer was to blame. But seeing (or smelling) is believing, so Haagen-Smit fought back by giving public lectures in which he would whip up flasks full of artificial smog before the audience's eyes, which would soon be watering—especially if they were seated in the first few rows. By the end of his talk, the smog would fill the hall, and he became known throughout the Southland as Arie Haagen-Smog.

By 1954, he and Frits Went had carried the day.

[Plant] fumigations with the photochemical oxidation products of gasoline and nitrogen dioxide (NO2) was the basis of one of the most convincing arguments for the control of hydrocarbons by the oil industry. (December 1954)

It probably didn't hurt that an outbreak that October closed schools and shuttered factories for most of the month, and that angry voters were wearing gas masks to protest meetings. By then, there were some two million cars on the road in the metropolitan area, spewing a thousand tons of hydrocarbons daily.

Incomplete combustion of gasoline allows unburned and partially burned fuel to escape from the tailpipe. Seepage of gasoline, even in new cars, past piston rings into the crankcase, is responsible for 'blowby' or crankcase vent losses. Evaporation from carburetor and fuel tank are substantial contributions, especially on hot days. (November 1962)

Haagen-Smit was a founding member of California's Motor Vehicle Pollution Control Board, established in 1960. One of the board's first projects was testing positive crankcase ventilation (PCV) systems, which sucked the blown-by hydrocarbons out of the crankcase and recirculated them through the engine to be burned on the second pass. PCV systems were mandated on all new cars sold in California as of 1963. The blowby problem was thus easily solved—but, as Haagen-Smit noted in that same article, it was only the second-largest source, representing about 30 percent of the escaping hydrocarbons.

The preferred method of control of the tailpipe hydrocarbon emission is a better combustion in the engine itself. (The automobile industry has predicted the appearance of more efficiently burning engines in 1965. It is not known how efficient these will be, nor has it been revealed whether there will be an increase or decrease of oxides of nitrogen.) Other approaches to the control of the tailpipe gases involve completing the combustion in muffler-type afterburners. One type relies on the ignition of gases with a sparkplug or pilot-burner; the second type passes the gases through a catalyst bed which burns the gases at a lower temperature than is possible with the direct-flame burners. (November 1962)

Installing an afterburner in the muffler has some drawbacks, not the least of which is that the notion of tooling around town with an open flame under the floorboards might give some people the willies. Instead, catalytic converters became required equipment on California cars in 1975.

In 1968, the Motor Vehicle Pollution Control Board became the California Air Resources Board, with Haagen-Smit as its chair. He was a member of the 1969 President's Task Force on Air Pollution, and the standards he helped those two bodies develop would eventually be adopted by the Environmental Protection Agency, established in 1970—the year that also saw the first celebration of Earth Day. It was also the year when ozone levels in the Los Angeles basin peaked at 0.58 parts per million, nearly five times in excess of the 0.12 parts per million that the EPA would declare to be safe for human health. This reading even exceeded the 0.5 ppm that Haagen-Smit had measured back in 1954, but it was a triumph nonetheless—the number of cars in L.A. had doubled, yet the smog was little worse than it had always been. That was the year we turned the corner, in fact, and our ozone levels have been dropping ever since—despite the continued influx of cars and people to the region.

Haagen-Smit retired from Caltech in 1971 as the skies began to clear, but continued to lead the fight for clean air until his death in 1977—of lung cancer, ironically, after a lifetime of cigarettes. Today, his intellectual heirs, including professors Richard Flagan, Mitchio Okumura, John Seinfeld, and Paul Wennberg, use analytical instruments descended from ones Haagen-Smit would have recognized and computer models sophisticated beyond his wildest dreams to carry the torch—a clean-burning one, of course—forward.

Douglas Smith
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Oscar Bruno Named SIAM Fellow

The Society for Industrial and Applied Mathematics (SIAM) named Oscar P. Bruno, professor of applied and computational mathematics at Caltech, as a member of its 2013 Class of Fellows.

Bruno is one of 33 fellows selected by SIAM for "exemplary research as well as outstanding service to the community," according to the organization. "Through their contributions, the 2013 Class of Fellows is helping advance the fields of applied mathematics and computational science," the organization stated in a March 29 press release.

"SIAM is an organization that includes many of the leading applied mathematicians from around the world, so I am honored to have been selected for their 2013 Class of Fellows," Bruno says.

Bruno's research group at Caltech focuses on the development of accurate high-performance numerical partial differential equation solvers applicable to realistic scientific and engineering configurations. His research interests include numerical analysis, multiphysics modeling and simulation, and mathematical physics.

Bruno graduated with a Friedrichs Prize for an outstanding dissertation in mathematics from the Courant Institute of Mathematical Sciences at New York University in 1989. He became an associate professor at Caltech in 1995 and a professor of applied and computational mathematics in 1998. He has served as executive officer of Caltech's Applied and Computational Mathematics department, and he is the recipient of a Young Investigator Award from the National Science Foundation and a Sloan Foundation Fellowship.

Bruno is a member of the SIAM Council, and he serves on the editorial boards of the SIAM Journal on Scientific Computing and the SIAM Journal on Applied Mathematics.

Brian Bell
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Caltech Senior Wins Gates Cambridge Scholarship

Catherine Bingchan Xie, a senior bioengineering major and English minor at Caltech, has been selected to receive a Gates Cambridge Scholarship, which will fund her graduate studies at the University of Cambridge for the next academic year. Xie, a Canadian citizen, is one of 51 new international recipients selected from a pool of more than 4,000 applicants based not only on intellectual ability, but also on leadership capacity and a commitment to improving the lives of others.

As a Gates Cambridge Scholar, Xie, 20, will pursue a Master of Philosophy in translational medicine and therapeutics. "The research program and the knowledge that I'm going to gain will provide me with an essential foundation for becoming a physician-scientist, translating research findings in the lab into revolutionary therapies," she says. "I'm really excited to join the Gates Cambridge community and be surrounded by people like me who want to make an impact on other people by taking on important roles and issues in society. I think the energy and enthusiasm of rising toward this common goal will be really invigorating."

Having lived in China, Australia, Canada, and the United States, Xie has been exposed to a variety of cultures—something that she says motivated her to want to become a highly involved leader in a diverse and multicultural society.

As an undergraduate student, Xie has taken full advantage of opportunities to pursue research projects in the laboratory with outstanding scientists. During her freshman year, she began working in the lab of Frances Arnold, the Dick and Barbara Dickinson Professor of Chemical Engineering, Bioengineering and Biochemistry, engineering ways to improve the thermostability of enzymes used to make biofuels. The summer following her sophomore year, Xie joined the lab of C. Garrison Fathman, professor of medicine and chief of the Division of Immunology and Rheumatology at the Stanford School of Medicine, to study a novel transcription factor regulator involved in the pathogenesis of Type I diabetes. When she returned to Caltech, she immediately joined the lab of David Baltimore, the Robert Andrews Millikan Professor of Biology, where she is currently working. There, her research focuses on microRNAs—tiny snippets of RNA that are only about 20 nucleotides long—and the regulatory role they play in the development of leukemia. 

"Catherine is a student with broad interests, an engaging personal style, and great effectiveness," Baltimore says. "She has been a pleasure to have in the laboratory, and I am not surprised that she has won this prestigious scholarship and chosen to broaden her knowledge by focusing on public health issues while she is at Cambridge."

Xie says her ultimate goal in life "is to be able to not only improve our understanding of disease mechanisms, but also to be able to use that understanding to create novel, innovative therapies in order to help people battle their diseases."

Xie's desire to help others was clear during her time at Caltech—she led Caltech Y service trips, during which she and other students helped to rebuild houses for low-income families, assisted in beach and riverbed cleanups, and worked at a homeless shelter. As a freshman, she started the annual Caltech Student Health Fair to make students more aware of the physical, mental, and emotional health resources on campus and throughout the community. She has also served on campus as the vice chair of the Academics and Research Committee and as a member of the Caltech Y Student Executive Committee.

"I'm so excited that Catherine has been chosen to receive this fellowship," says Athena Castro, executive director of the Caltech Y. "I just love her. She's enthusiastic, dedicated, positive, thoughtful, and committed."

In the summer of 2012, Xie broadened her horizons even more when she traveled to Switzerland as a recipient of Caltech's SanPietro Travel Prize. "Catherine demonstrated her ability to adapt quickly and truly engage in another culture on that trip," says Lauren Stolper, director of fellowships advising and study abroad. "She will represent Caltech well as a Gates Cambridge Scholar."

Xie says she is thankful to everyone who has contributed to her experience at Caltech. "My achievements wouldn't have been possible without people giving me opportunities, encouraging me, and providing me with feedback, allowing me to grow as a scientist and as an individual," she says. "Caltech has shown me that intellectual curiosity and passion are vital driving forces behind finding innovative solutions that will have a profound and meaningful impact on solving issues that confront society."

The 51 newly announced international scholars will join 39 new American Gates Cambridge Scholars. The Gates Cambridge Scholarship program was established in 2000 through a donation from the Bill and Melinda Gates Foundation to the University of Cambridge. Xie is the sixth Caltech undergraduate student to receive the fellowship. 

Kimm Fesenmaier
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The Caltech Space Challenge: Mission to a Martian Moon

The mission: travel to one of Mars's two moons, explore its surface, collect some rocks, and return to Earth in one piece. Now plan it—in five days.

Dozens of students from Caltech and around the world converged on campus during the last week of March to do just that, compete in the Caltech Space Challenge, which pits two teams against each other to design the best manned space mission.

"It was an intense, challenging, and exciting experience," says Melissa Tanner, a fourth-year graduate student in mechanical engineering at Caltech and member of Team Voyager, which faced off against Team Explorer.

The Space Challenge, which was led by aeronautics graduate students Nick Parziale and Jason Rabinovitch, featured lectures and workshops given by expert rocket scientists from Caltech, the Jet Propulsion Laboratory, and the aerospace industry. The two 16-member teams were even treated to an appearance by astronaut Buzz Aldrin, the second human to have walked on the moon. "I think one of the coolest parts of the experience was having world-class mentors," Tanner says.

Most of the week, however, was filled with hard work and little sleep. The students—a mix of undergraduates and graduates—had to plan and consider every aspect of long-term space travel, from choosing a propulsion system to keeping the astronauts healthy and fit. (Both teams emphasized the importance of exercise; Team Voyager proposed mandatory Jazzercise classes.)

Landing on a martian moon is considered a stepping-stone toward the ultimate goal of landing a human on Mars and was one of the recommendations that the U.S. Human Space Flight Plans Committee, an independent review commissioned by the White House, made in 2009. A round-trip to one of Mars's moons is much easier than one to Mars, primarily because Mars's gravity is so much stronger than that of its moons. Landing on any planetary body is a difficult and harrowing task—the Curiosity rover famously went through a landing sequence akin to a Rube Goldberg machine and was dubbed the "seven minutes of terror." And, no previous Mars mission—let alone a manned one—has ever landed on the surface and returned to Earth.

The Martian moons—Phobos and Deimos—are like asteroids, with gravity so weak that a spacecraft can approach one of the moons and grab onto its surface. The gravity on Phobos—the larger of the two, yet with a radius of just 11 kilometers (roughly 7 miles)—is so slight that an object dropped from 1 meter above its surface would take more than 18 seconds to "fall."

The Space Challenge's 32 participants came from 21 universities and 11 countries, and were chosen from 175 applicants. They were selected because they brought a particular skill or expertise to their team. For example, Tanner's research at Caltech is in robotics; in particular, she works on the Axel rover, which is a tethered, two-wheeled robot designed to explore cliffs and other extreme terrain on other planets. Because of that expertise, she helped her team determine how its astronauts would explore the surface of a martian moon.

"I think the most rewarding part was meeting all these other people who know so much," says Jay Qi, a first-year mechanical engineering graduate student at Caltech and a member of Team Explorer. "It was really crazy how much I learned just from talking to people."

Although members from the two teams interacted freely—some of the visiting students even roomed with opposing team members—they were careful not to influence each other's designs so as to maintain the spirit of competition, Qi says.

Still, because both teams were faced with the same problems, they often came up with the same solutions. Both teams ended up with similar mission designs, choosing to go to Phobos, for example, because its bigger size offered potentially more interesting scientific discoveries. And both decided to use a multistage spacecraft assembled in low-Earth orbit that would depart for a six-month trip to Phobos in April 2033. Furthermore, in each plan, the spacecraft would separate into two parts: one that remained in orbit around Phobos and a second—equipped with robotic claws to cling onto the moon's surface—that would transport two astronauts to the moon. After exploring Phobos for about a month, the astronauts would return home.

But there were many differences between the two mission plans. For example, while Team Voyager opted to send three astronauts, the Explorer mission wanted to send four. Team Voyager also included a more detailed robotic precursor mission that would visit both Phobos and Deimos, whereas Team Explorer's manned mission itself included exploring robots.

A group of jurors consisting of experts from Caltech, JPL, and the aerospace industry evaluated the two teams based on their final presentations and reports. The competition was close, said lead juror Joe Parrish, deputy manager of the Mars Program Formulation Office at JPL. "It was never immediately obvious which team was going to prevail," he said at the closing banquet held at the Athenaeum. "Both teams did an unbelievable job." The jury went back and forth but finally decided that Team Voyager presented the better proposal, awarding it a bonus to the stipend that each member received to support his or her trip to Pasadena.

Caltech graduate students Prakhar Mehrotra and Jonathan Mihaly came up with the Caltech Space Challenge; the first challenge, held in 2011, was to plan a manned mission to a near-Earth asteroid. The two faculty advisors for the program are Guillaume Blanquart, assistant professor of mechanical engineering, and Joseph Shepherd, the C. L. Kelly Johnson Professor of Aeronautics and Professor of Mechanical Engineering. The program is organized by the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT) and supported by Caltech, JPL, the Keck Institute for Space Studies, and corporate and individual sponsors.

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Counting White Blood Cells at Home

Caltech engineers lead development of a new portable counter

PASADENA, Calif.—White blood cells, or leukocytes, are the immune system's warriors. So when an infection or disease attacks the body, the system typically responds by sending more white blood cells into the fray. This means that checking the number of these cells is a relatively easy way to detect and monitor such conditions.

Currently, most white blood cell counts are performed with large-scale equipment in central clinical laboratories. If a physician collects blood samples from a patient in the office—usually requiring a full vial of blood for each test—it can take days to get the results. But now engineers at the California Institute of Technology (Caltech), working with a collaborator from the Jerusalem-based company LeukoDx, have developed a portable device to count white blood cells that needs less than a pinprick's worth of blood and takes just minutes to run.

"The white blood cell counts from our new system closely match the results from tests conducted in hospitals and other central clinical settings," says Yu-Chong Tai, professor of electrical engineering and mechanical engineering at Caltech and the project's principal investigator. "This could make point-of-care testing possible for the first time."

Portable white blood cell counters could improve outpatient monitoring of patients with chronic conditions such as leukemia or other cancers. The counters could be used in combination with telemedicine to bring medical care to remote areas. The devices could even enable astronauts to evaluate their long-term exposure to radiation while they are still in space. The researchers describe the work in the April 7 issue of the journal Lab on a Chip.

There are five subtypes of white blood cells, and each serves a different function, which means it's useful to know the count for all of them. In general, lymphocytes use antibodies to attack certain viruses and bacteria; neutrophils are especially good at combating bacteria; eosinophils target parasites and certain infections; monocytes respond to inflammation and replenish white blood cells within bodily tissue; and basophils, the rarest of the subtypes, attack certain parasites.

"If we can give you a quick white blood cell count right in the doctor's office," says Wendian Shi, a graduate student in Tai's lab and lead author of the new paper, "you can know right away if you're dealing with a viral infection or a bacterial infection, and the doctor can prescribe the right medication."

The prototype device is able to count all five subtypes of white blood cells within a sample. It provides an accurate differential of the four major subtypes—lymphocytes, monocytes, eosinophils, and neutrophils. In addition, it could be used to flag an abnormally high level of the fifth subtype, basophils, which are normally too rare (representing less than one percent of all white blood cells) for accurate detection in clinical tests.

The entire new system fits in a small suitcase (12" x 9" x 5") and could easily be made into a handheld device, the engineers say.

A major development reported in the new paper is the creation of a detection assay that uses three dyes to stain white blood cells so that they emit light, or fluoresce, brightly in response to laser light. Blood samples are treated with this dye assay before measurement in the new device. The first dye binds strongly to the DNA found in the nucleus of white blood cells, making it simple to distinguish between white blood cells and the red blood cells that surround and outnumber them. The other two dyes help differentiate between the subtypes.

The heart of the new device is a 50-micrometer-long transparent channel made out of a silicone material with a cross section of only 32 micrometers by 28 micrometers—small enough to ensure that only one white blood cell at a time can flow through the detection region. The stained blood sample flows through this microfluidic channel to the detection region, where it is illuminated with a laser, causing it to fluoresce. The resulting emission of the sample is then split by a mirror into two beams, representing the green and red fluorescence.

Thanks to the dye assay, the white blood cell subtypes emit characteristic amounts of red and green light. Therefore, by determining the intensity of the emissions for each detected cell, the device can generate highly accurate differential white blood cell counts.

Shi says his ultimate goal is to develop a portable device that can help patients living with chronic diseases at home. "For these patients, who struggle to find a balance between their treatment and their normal quality of life, we would like to offer a device that will help them monitor their conditions at home," he says. "It would be nice to limit the number of trips they need to make to the hospital for testing."

The Lab on a Chip paper is titled "Four-part leukocyte differential count based on sheathless microflow cytometer and fluorescent dye assay." In addition to Tai and Shi, the coauthors on the paper are Luke Guo, a graduate student at MIT who worked on the project as an undergraduate student at Caltech, and Harvey Kasdan of LeukoDx Inc. in Jerusalem, Israel. The work was supported by the National Space Biomedical Research Institute under a NASA contract.

Kimm Fesenmaier
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Francis Clauser

1913 – 2013

Francis H. Clauser (BS '34, MS '35, PhD '37), the Clark Blanchard Millikan Professor of Engineering, Emeritus, passed away on March 3, 2013, at age 99. Born in the decade following the Wright Brothers' first powered flight, he was a founder of modern aeronautics and helped usher in the Space Age.

Francis was the younger of identical twins born to Celeste and Claude Clauser in Kansas City, Missouri, on May 25, 1913. When Francis and his brother, Milton, were 17, their father died, leaving the boys to support their mother and younger sister, Betty. Fortunately, Celeste "was talented and resourceful," says Clauser's daughter, Caroline Ryan. "She made puppets with papier-mâché heads and elaborate costumes, and she and the boys supported the family by staging marionette shows to the accompaniment of a hand-cranked Victrola." The twins enrolled in Kansas City Junior College, but upon learning of Caltech's constellation of luminaries, they decided to apply as transfer students. When they were accepted, the entire family packed up and moved to Pasadena.

As Caltech undergrads, the twins joined a local magician's society, the Mystic Thirteen. Their act consisted of one brother doing a trick before disappearing behind a screen. The other brother would then emerge in a totally different outfit and perform another trick. They did this faster and faster until the costume changes got impossibly short, at which point the screen would "accidentally" fall to reveal one brother in bright red undershorts.

Upon earning bachelor's degrees in physics, the Clausers entered the aeronautics program run by Theodore von Kármán. Unable to tell the twins apart but well aware of their hijinks, von Kármán made it clear that he expected two separate and distinct dissertations, saying, "Each of you can do one, one of you can do both, or both of you can do both." Thus Milton and Francis produced an experiment-based thesis on "The Effect of Curvature on the Transition from Laminar to the Turbulent Boundary Layer," while Francis and Milton wrote a mathematical treatise on "New Methods of Solving the Equations for the Flow of a Compressible Fluid."

On July 30, 1937, a month after receiving their doctorates, Francis married Catharine McMillan, Caltech's humanities librarian and sister of future chemistry Nobel laureate Edwin McMillan (BS '28, MS '29), in a double ceremony with Milton and his bride, Virginia Randall.

The brothers joined the Douglas Aircraft Company in Santa Monica, where Francis soon became the director of aerodynamic design research. There he assembled a team that included several future Caltech faculty members and profoundly influenced aviation design by developing mathematical methods for shaping tails, wings, engine nacelles, and air scoops.  

When Germany fell to the Allies in 1945, Clauser "was temporarily inducted into the U.S. military as an instant full colonel" as part of Operation Paperclip, says his son, John Clauser. Such high ranks were routinely given to civilian experts sent into the war zone in order to expedite the American effort to collect as many of Germany's best scientists and as much of its key hardware as possible before the Russians did.

Soon after Clauser's return, Henry "Hap" Arnold, the commander of the Army Air Forces, commissioned Clauser's design team to study the feasibility of spaceflight. The 340-page "Preliminary Design of an Experimental World-Circling Spaceship," dated May 2, 1946, concluded that a rocket based on the German V-2 could put a 500-pound payload into orbit for at least 10 days and outlined the military, scientific, and telecommunications uses to which such a satellite might be put. Unfortunately the estimated cost—$150 million over five years—was deemed too high, and the US ceded first rights to the final frontier to Sputnik, launched by the USSR a decade later. The report also noted that "there is good reason to hope that future satellite vehicles will be built to carry human beings," recommending a winged, reusable spacecraft as the best way to return them safely to Earth. This report was the first to be produced by what Arnold dubbed the RAND (for Research and Development) Project; several of the people who wrote it went on to become founding members of the RAND Corporation when it was spun off from Douglas Aircraft in 1948.

Clauser, however, left the company in 1946 to found the aeronautics department at Johns Hopkins University. He chaired the department until 1960, recruiting leaders in the field from many countries to create a world-class research center. The department's facilities included three large wind tunnels, one of which was supersonic and "all of which Clauser personally designed," John says, "so that they exhibited very low residual turbulence in their test sections."

Turbulence and the so-called boundary layer, the thin layer of fluid immediately adjacent to a solid surface, had been particular interests of Clauser's since graduate school. In fact, his first assignment at Douglas had been to figure out why the DC-3, which had just debuted as a transcontinental passenger plane and would remain in military production through World War II, tended to roll onto its back upon stalling. An aerodynamic "stall" occurs when the tilt of a wing's leading edge—the so-called angle of attack—increases to the point where lift is no longer generated. Clauser realized that as one wing fell, the angle of attack at its tip would increase, making it stall more. To break this runaway feedback, he invented the now-standard "washout" wing twist, in which the wing tips are more or less horizontal and the angle of attack increases closer to the fuselage. Any stall thus begins near the fuselage, where the wing's lever action is minimal, while the ailerons out near the wing tips do not stall and the pilot remains in control of the aircraft.

Clauser wrote two seminal papers on the turbulent boundary layer in 1954 and 1956. As emeritus professor of aeronautics Donald Coles (MS '48, PhD '53) explains, "Normally, as you follow the boundary layer across the wing, the velocity profile will be controlled by the pressure variation. Clauser invented what he called 'equilibrium flows' in which he controlled the pressure gradient so that the velocity field didn't change as you went along the flow. The pressure was still rising, but he had a trick for adjusting the rate at which it rose, so that the velocity obeyed a 'similarity law.' It didn't matter where you measured the velocity profile, because it always followed the same curve. And anybody could duplicate his family of flows in their own wind tunnels just by properly shaping the channel."

This gradient generates the wing's lift and begins as a zone of low pressure near the wing's leading edge, extending outward and backward until ambient atmospheric pressure is restored. If not handled properly, it can force the airflow to leave the wing prematurely—as it did in the stall that had plagued the DC-3. The gradient's behavior depends on the interplay between the wing's shape and the boundary layer itself, which in turn is governed by a set of deceptively simple differential equations whose exact solutions often still tax modern supercomputers. Clauser's work was so important because in the days when designs were primarily worked out with slide rules and pad after pad of graph paper, the fewer variables one had to manipulate experimentally, the better.

"Clauser was one of the four founders of the science of boundary layers as it stands today," Coles says. "In a 10-year period, these people put together a consistent, coherent description that is still the place where you start teaching the subject."

Clauser was a member of the 1968 Task Force on Space, chaired by Nobel laureate Charles Townes (PhD '39). Clauser again championed the notion of a winged, reusable space vehicle. This time, the idea got traction and the Space Shuttle was born.

During the Hopkins years, Clauser acquired a reputation for educational innovation, establishing cross-disciplinary courses designed to illuminate basic principles that could later be applied to whatever field a student might choose. He was invited to the newly created University of California campus in Santa Cruz in 1965 to set up the engineering school, and he served variously as the academic vice chancellor, vice chancellor for science and engineering, and professor of applied science.

In 1969, Clauser returned to Caltech to chair the Division of Engineering and Applied Science. He stepped down in 1974 but remained the Clark Millikan Professor of Engineering until his retirement in 1980.

Clauser, having arrived at the dawn of the environmental movement, launched Caltech's interdisciplinary graduate program in environmental engineering science in 1971. The following year he established the Environmental Quality Laboratory, or EQL, as an "action-oriented unit," in his words, along the lines of JPL—"associated with Caltech, carrying on Caltech's high standards but not engaged in teaching." Organized in partnership with JPL, the RAND Corporation, and the Aerospace Corporation, the EQL studied the scientific, engineering, economic, and political aspects of issues such as pollution control, water and energy policy, and sewage disposal. 

The interdisciplinary applied physics option was initiated during Clauser's term as well, providing an academic home for the solid-state physicists and electronics engineers who were powering the computer revolution. Clauser also oversaw the construction of the Earle M. Jorgensen Laboratory of Information Science. This building housed not only computer scientists but the Campus Computing Center, which ran the mainframe computers that were becoming important research tools in many disciplines.

In 1973, Clauser established the Sherman Fairchild Distinguished Scholars Program, which he intended to be "as desirable and prestigious as a Guggenheim Fellowship" and which brought up to 30 eminent scientists per year to Caltech. The inaugural group included Apollo 17 astronaut Harrison Schmitt (BS '57), the only geologist to walk on the moon, and a then-obscure cosmologist named Stephen Hawking.

Upon his brother Milton's death in 1980, Clauser, his wife, and his sister-in-law established the annual Milton and Francis Clauser Doctoral Prize, awarded for the thesis judged to have the greatest potential for opening up entirely new lines of research.

A noted raconteur with a prodigious memory, Clauser was a regular at the legendary Round Table at the Caltech faculty club, the Athenaeum. Says Marshall Cohen, professor of astronomy, emeritus, "He was known as 'The Dean of the Round Table' for a couple of reasons: He was the oldest, and he would dominate the discussion. He'd say, 'Let's change the subject—I want to talk about the new style of sailboat.'" Politics, biblical archaeology, and ancient Egypt were other favorite topics, Cohen recalls. "He knew dates. And names. He knew dynasties. A decade ago I mentioned that I was interested in hieroglyphs. He said, 'I can recommend a book for you.' It turns out he and Catharine had taken a course in hieroglyphics back in the 1960s, and he still remembered the name of the textbook."

Clauser's favorite subject was travel. He and Catharine had driven through 117 countries and across every major desert on Earth—usually in a rented Volkswagen Beetle. One such trip went from Alaska to Tierra del Fuego, where he eased into the Straits of Magellan until the Bug's front bumper was submerged. Another trip followed the Silk Road through Central Asia.

The Clausers' most-storied trip took them from Tunis to Timbuktu. As recounted in Caltech's Engineering & Science magazine in 1972, the preferred method for crossing the Sahara was in Land Rovers traveling in pairs. The Clausers drove alone in a Renault R4, a vehicle light enough for them to push when it got stuck in the sand. Things went well for the first 1,600 miles or so, until the clutch gave out in central Niger. They hitched a ride to Tahoua, the nearest town, where, as Francis told E&S, they found "a 52nd-hand car dealer who let us have an ancient clutch for $24. Then we rented a set of tools for $10 from a German mechanic and went out and sat by the road for two hours before we caught a 70-mile ride back to our car." The next day, they dismantled the engine in front of an audience of Fulani herdsmen and Tuaregs on camels, only to discover that the new old clutch didn't fit. An examination of the old old clutch revealed that it had packed itself full of sand as they tobogganed through the dunes. They extracted the sand with a paring knife and a safety pin, and drove back to Tahoua, where they resold the new old clutch back to the 52nd-hand dealer for $20.

Catharine died in 1999, but Francis remained in the family home in La Cañada until he lost his right leg to the flesh-eating bacterium Clostridium septicum in 2008. He moved into Villa Gardens to recuperate—on the condition that he not miss lunch at the Round Table. A shuttle would drop him off daily, says Cohen, "but occasionally he'd drive himself home in his electric wheelchair by way of his dentist."

Clauser's publications included papers on nonlinear mechanics, guided missile technology, magnetohydrodynamics, and partial differential equations as well as a book, Plasma Dynamics, compiled in 1960 following a symposium he chaired on what was then a very young field. He was a Fellow of the American Institute of Aeronautics and Astronautics, the American Physical Society, and the American Association for the Advancement of Science. He was also a member of the National Academy of Engineering, the scientific research society Sigma Xi, the engineering honor society Tau Beta Pi, and Caltech's Gnome Club.  He was named a Distinguished Alumnus in 1966, one of the initial class of 23 to be so honored.

Clauser is survived by his sister, Betty Celeste Valois of Denver; his son, Wolf laureate in physics John Francis Clauser (BS '64) of Walnut Creek, California; and his daughter, Caroline Helen Ryan, of New York City. A memorial service will be held at 11:00 a.m. at the Caltech Athenaeum on May 25, the day that would have been his hundredth birthday.

Douglas Smith
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Creating Indestructible Self-Healing Circuits

Caltech engineers build electronic chips that repair themselves

PASADENA, Calif.—Imagine that the chips in your smart phone or computer could repair and defend themselves on the fly, recovering in microseconds from problems ranging from less-than-ideal battery power to total transistor failure. It might sound like the stuff of science fiction, but a team of engineers at the California Institute of Technology (Caltech), for the first time ever, has developed just such self-healing integrated chips.

The team, made up of members of the High-Speed Integrated Circuits laboratory in Caltech's Division of Engineering and Applied Science, has demonstrated this self-healing capability in tiny power amplifiers. The amplifiers are so small, in fact, that 76 of the chips—including everything they need to self-heal—could fit on a single penny. In perhaps the most dramatic of their experiments, the team destroyed various parts of their chips by zapping them multiple times with a high-power laser, and then observed as the chips automatically developed a work-around in less than a second.

"It was incredible the first time the system kicked in and healed itself. It felt like we were witnessing the next step in the evolution of integrated circuits," says Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering at Caltech. "We had literally just blasted half the amplifier and vaporized many of its components, such as transistors, and it was able to recover to nearly its ideal performance."

The team's results appear in the March issue of IEEE Transactions on Microwave Theory and Techniques.

Until now, even a single fault has often rendered an integrated-circuit chip completely useless. The Caltech engineers wanted to give integrated-circuit chips a healing ability akin to that of our own immune system—something capable of detecting and quickly responding to any number of possible assaults in order to keep the larger system working optimally. The power amplifier they devised employs a multitude of robust, on-chip sensors that monitor temperature, current, voltage, and power. The information from those sensors feeds into a custom-made application-specific integrated-circuit (ASIC) unit on the same chip, a central processor that acts as the "brain" of the system. The brain analyzes the amplifier's overall performance and determines if it needs to adjust any of the system's actuators—the changeable parts of the chip.

Interestingly, the chip's brain does not operate based on algorithms that know how to respond to every possible scenario. Instead, it draws conclusions based on the aggregate response of the sensors. "You tell the chip the results you want and let it figure out how to produce those results," says Steven Bowers, a graduate student in Hajimiri's lab and lead author of the new paper. "The challenge is that there are more than 100,000 transistors on each chip. We don't know all of the different things that might go wrong, and we don't need to. We have designed the system in a general enough way that it finds the optimum state for all of the actuators in any situation without external intervention."

Looking at 20 different chips, the team found that the amplifiers with the self-healing capability consumed about half as much power as those without, and their overall performance was much more predictable and reproducible. "We have shown that self-healing addresses four very different classes of problems," says Kaushik Dasgupta, another graduate student also working on the project. The classes of problems include static variation that is a product of variation across components; long-term aging problems that arise gradually as repeated use changes the internal properties of the system; and short-term variations that are induced by environmental conditions such as changes in load, temperature, and differences in the supply voltage; and, finally, accidental or deliberate catastrophic destruction of parts of the circuits.

The Caltech team chose to demonstrate this self-healing capability first in a power amplifier for millimeter-wave frequencies. Such high-frequency integrated chips are at the cutting edge of research and are useful for next-generation communications, imaging, sensing, and radar applications. By showing that the self-healing capability works well in such an advanced system, the researchers hope to show that the self-healing approach can be extended to virtually any other electronic system.

"Bringing this type of electronic immune system to integrated-circuit chips opens up a world of possibilities," says Hajimiri. "It is truly a shift in the way we view circuits and their ability to operate independently. They can now both diagnose and fix their own problems without any human intervention, moving one step closer to indestructible circuits."

Along with Hajimiri, Bowers, and Dasgupta, former Caltech postdoctoral scholar Kaushik Sengupta (PhD '12), who is now an assistant professor at Princeton University, is also a coauthor on the paper, "Integrated Self-Healing for mm-Wave Power Amplifiers." A preliminary report of this work won the best paper award at the 2012 IEEE Radio Frequency Integrated Circuits Symposium. The work was funded by the Defense Advanced Research Projects Agency and the Air Force Research Laboratory.

Kimm Fesenmaier
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Under the Hood of the Earthquake Machine

Watson Lecture Preview


What makes an earthquake go off? Why are earthquakes so difficult to forecast? Professor of Mechanical Engineering and Geophysics Nadia Lapusta gives us a close-up look at the moving parts, as it were, at 8:00 p.m. on Wednesday, February 13, 2013, in Caltech's Beckman Auditorium. Admission is free.


Q: What do you do?

A: I study friction as it relates to earthquakes. At a depth of five miles, which is the average depth at which large earthquakes in Southern California occur, the compression on the two sides of the fault is roughly equivalent to a pressure of 1,500 atmospheres. So you can imagine that friction plays an important role. I make computational models that combine our theories about friction with laboratory studies of how materials behave. We try to reproduce what seismologists, geodesists, and geologists see actual earthquakes doing, in order to infer the physical laws that govern them.

Our planet's surface is made up of a bunch of plates that are always moving, and an earthquake happens when the locked boundaries of the plates rapidly catch up with the slow motion of the plates themselves. You get a sudden shearing—a sideways motion that generates the destructive waves that we perceive as shaking.

A number of factors affect this process. If you rub your palms together, you generate heat. An earthquake is a very intensive rubbing of palms, if you will, and so a lot of heat is produced—enough to weaken the rocks and perhaps even melt them.

However, there are pore fluids permeating the rocks—we often get our drinking water from underground aquifers, for example. As these fluids heat up, they expand, which modifies the shearing process. They produce expanding cushions of steam, essentially, which reduce the friction.

The waves generated by the shearing motion put an additional load on the fault ahead of the shear zone, so they actually affect how the shearing progresses. The shear tip sprouts at about three kilometers per second, or 6,700 miles per hour. So an earthquake is a highly dynamic, nonlinear system.

To make things even more interesting, a fault doesn't just sit still for hundreds of years, waiting for the next big earthquake. It's more like a living thing—there are slow slippages between earthquakes that constantly redistribute the forces in the system, and the exact point where an earthquake initiates depends a lot on these slow motions. So we simulate thousands of years of fault history that includes a few occasional, very fast events that last for a few seconds. These calculations are very time-consuming and memory-intense. The Geological and Planetary Sciences Division's supercomputer has several thousand processors, and we routinely use 200 to 400 of them, sometimes for weeks at a time. We would happily use the entire machine, but of course people would yell at us.


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

A: I've loved both mathematics and physics since I was a child. I was born in Ukraine, where my mom was a professor of applied mathematics and my dad was a civil engineer. They used to give me math and physics problems from a very early age. I did my undergraduate studies in applied mathematics in Kiev, and I was thinking of going into materials science. I came to the U.S. for graduate school, and my advisor at Harvard was working on materials failure and on earthquakes, which I found very interesting because it combined math and physics with a problem relevant to society.

My PhD was on frictional sliding and some initial models of earthquakes. Caltech is actually the perfect place to continue that, because it has world-class expertise in all relevant disciplines. I have wonderful colleagues, and the really fun part is working with them. I enjoy interacting with the experimentalists and talking to the people who make field observations or do radar measurements from satellites. They have different perspectives, different terminologies, and different views of the problem, so it's fun to try to explain to them what you mean, and to try to understand what they mean. And the most fun, of course, is when you come to an understanding that leads to new science in the end.


Q: Speaking of societal relevance, what does your work mean for us here in L.A.?

A: Large earthquakes, fortunately, are relatively rare, so we don't have detailed observations of very many of them. Our models, however, allow us to explore scenarios for potentially very damaging earthquakes that we haven't experienced. For example, faults have locked segments and creeping segments. The San Andreas fault has a creeping segment between Los Angeles and San Francisco, and the assumption has been that this segment will confine a large earthquake to either the southern or the northern part of the fault. Only one large urban area would be affected. However, our models show that a through-going rupture may be possible. If that happens, both Los Angeles and San Francisco are affected, and you have a much bigger problem on your hands.


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.

Douglas Smith
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Watson Lecture: "Under the Hood of the Earthquake Machine"
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Murray and Ortiz Elected to the National Academy of Engineering

Election brings Caltech faculty's membership in the academy to 35

PASADENA, Calif.—Richard M. Murray and Michael Ortiz of the California Institute of Technology (Caltech) have been elected to the National Academy of Engineering (NAE), an honor considered among the highest professional distinctions an engineer can receive. In total, the academy welcomed 69 new American members and 11 foreign associates this year.

"I am absolutely delighted that the Academy has elected Richard and Michael," says Ares Rosakis, the Theodore von Kármán Professor of Aeronautics, professor of mechanical engineering, and chair of the Division of Engineering and Applied Science at Caltech. "This is not only a recognition of their great contributions and unwavering commitment to engineering research and education, but also a confirmation of the great impact Caltech engineers and applied scientists are having on the field."

Richard Murray, the Thomas E. and Doris Everhart Professor of Control and Dynamical Systems and Bioengineering, was cited by the National Academy of Engineering for his "contributions in control theory and networked control systems with applications to aerospace engineering, robotics, and autonomy." His current work focuses on the application of feedback and control to networked systems, especially in the biological realm where he is interested in engineered biological circuits.

"It's a great honor to be elected as a member of the NAE," Murray says. "Caltech's strong support for junior faculty, our ability to recruit outstanding students and postdocs, and the highly collaborative nature of the academic environment have allowed my group to help identify important problem areas and make rapid progress in our research. I am particularly appreciative of all of the encouragement, mentoring, and support that I received as a junior faculty member from the Division of Engineering and Applied Science and my colleagues in mechanical engineering and control and dynamical systems."

Murray earned his BS in electrical engineering from Caltech in 1985, and his MS and PhD, both from the University of California, Berkeley in 1988 and 1990. He returned to his alma mater as an assistant professor of mechanical engineering in 1991 and was made an associate professor in 1997, a professor in 2000, the Everhart Professor of Control and Dynamical Systems in 2006, and the Everhart Professor of Control and Dynamical Systems and Bioengineering in 2009. He served as the chair of the Division of Engineering and Applied Science from 2000 until 2005 and as the director of Information Science and Technology from 2006 until 2009. Murray holds many distinctions. Among them, he is a fellow of the Institute for Electrical and Electronic Engineers, holds an honorary doctorate from Lund University, and won the 2006 Richard P. Feynman Prize for Excellence in Teaching.

Michael Ortiz, the Dotty and Dick Hayman Professor of Aeronautics and Mechanical Engineering, was cited for his "contributions to computational mechanics to advance the underpinnings of solid mechanics." He is currently the director of Caltech's Department of Energy/Predictive Science Academic Alliance Program's Center on High-Energy Density Dynamics of Materials. His research focuses on the multiscale modeling of materials in order to design and optimize novel materials.

"This is a wonderful and most pleasant surprise for me, especially given the support from colleagues and peers that it implies," Ortiz says of his election to the academy. "I regard this honor really as a recognition not only of the work done by myself, but also of the work of all my students and collaborators over the years. I am forever indebted to them."

Ortiz earned his BS in civil engineering from the Polytechnic University of Madrid, Spain, in 1977, and his MS and PhD in the same field from the University of California, Berkeley in 1978 and 1981. He served on the faculty at Brown University from 1984 until 1995, when he accepted a professorship at Caltech. Ortiz became the Dotty and Dick Hayman Professor of Aeronautics and Mechanical Engineering in 2004. He is a fellow of the American Academy of Arts and Sciences, the U.S. Association for Computational Mechanics and the International Association for Computational Mechanics, and has won many prizes, including the Humboldt Research Award for Senior U.S. Scientists and the Rodney Hill Prize in Solid Mechanics.

The election of Murray and Ortiz brings Caltech's total representation in the NAE to 35 faculty members and 11 trustees. The full class of new members brings the total NAE membership to 2,250 members and 211 foreign associates. 

Kimm Fesenmaier
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