Caltech Mourns the Passing of Wallace L. W. Sargent

 

Wallace "Wal" Sargent passed away on October 29 at the age of 77. He was the Ira S. Bowen Professor of Astronomy, Emeritus, at Caltech. He was an outstanding observational astronomer at the forefront of spectroscopy for over 50 years during an immensely productive and distinguished career. He began his career at the Institute as a research fellow in Astronomy from 1959 to 1962. He returned as an assistant professor in 1966, becoming full professor in 1971 and Bowen Professor in 1981. Sargent served as Caltech's executive officer of astronomy from 1975 to 1981 and again from 1996 to 1997 and as the director of Palomar Observatory from 1997 to 2000.

Sargent was born in 1935 in Elsham, United Kingdom, and he was the first pupil of the Scunthorpe Technical High School to go to a university. He entered the University of Manchester in 1953, where he earned his bachelor's, master's, and PhD degrees, as well as becoming a lifelong supporter of Manchester United. It was shortly after graduation that Sargent came to Caltech as a research fellow. From 1962 to 1964 he was a senior research fellow at the Royal Greenwich Observatory, where he met and married astronomer Anneila Sargent (née Cassells), now the Benjamin M. Rosen Professor of Astronomy at Caltech and the vice president for student affairs.

Perhaps the most remarkable aspect of Sargent's contributions to astrophysics is the range of subjects in which he made fundamental advances. Among his accomplishments were the demonstration that most of the helium in the universe was produced in the Big Bang with which the universe began (with Leonard Searle), the first dynamical evidence for the presence of supermassive black holes at the centers of galaxies (with his student Peter Young), the measurement of the mass of the Milky Way Galaxy using the radial velocities of outer satellites, the discovery that most nearby galaxies harbor low-luminosity nuclear activity, and illuminating studies on the emission from quasars and Seyfert galaxies.

As varied as Sargent's scientific accomplishments have been, there is one area of astrophysics where he both pioneered the field and has remained in the forefront to this day: the astrophysics of the diffuse intergalactic medium and the chemical history of the universe. This field gave us the first glimpses of the high-redshift universe at a time when normal galaxies could only be seen to small cosmological distances.

Sargent is considered the father of quasar absorption line spectroscopy. Using innovative new astronomical detectors developed by his collaborator, Alec Boksenberg, Sargent explored the gas permeating the high-redshift universe. Sargent had the foresight to recognize the advantages for faint-object spectroscopy of a new kind of  electronic detector, the Image Photon Counting System, developed by Boksenberg at University College London. The Sargent-Boksenberg partnership—"Boksenberg's Flying Circus" as Sargent affectionately dubbed it—revolutionized the field by carrying out the first statistically rigorous surveys of  quasar absorption systems. Sargent, with Boksenberg and their collaborators, gave us a key physical insight into the nature of the material between galaxies and brought to the fore the importance of this technique for observational cosmology. They used this information to understand how the material of which we are made has evolved since the first galaxies formed.

Sargent led the second Palomar Observatory Sky Survey, a photographic survey of the entire northern sky that was converted to a digital image format so that it could be analyzed via computers. This process produced a catalog of over 50 million galaxies and half a billion stars, including tens of thousands of quasars, and was a model for the many surveys that have followed using CCDs.

Sargent was a leader in the development of the W. M. Keck Observatory, coleading its science steering committee during the observatory's crucial formative years. With the advent of the Keck telescopes, he capitalized on the new powerful instruments on the world's largest telescopes to extend his research to probe the material between galaxies to the farthest reaches of the universe. Sargent established the existence of metals, the products of stellar nucleosynthesis, in the intergalactic medium only a billion years or so after the Big Bang. This research is helping us to identify and understand the first stars to form in the infant universe, which will be the targets of the next generation of telescopes.

In addition to his research, Sargent had a major influence on astronomy as an educator, particularly through the string of brilliant, accomplished graduate students that he mentored during his career.

Chuck Steidel (PhD '90), the Lee A. DuBridge Professor of Astronomy at Caltech, was a graduate student of Sargent's in the late 1980s and remembers his ability to inject humor into any situation that was in danger of becoming overly serious. "This was quite necessary for calming a young graduate student such as myself," admits Steidel. "Our conversations would almost always end up on a topic other than my thesis—baseball, music, literature, sumo wrestling. Looking back it is hard to recall ever receiving direct advice from Wal, and yet somehow he profoundly influenced the way I view science. As a colleague, Wal has been just as important to me," continues Steidel. "Wal will be missed for much more than his scientific accomplishments."

Alex Filippenko (PhD '84), a professor of astronomy at the University of California, Berkeley, was also mentored by Sargent during his graduate studies at Caltech. At the end of a five-night observing run at Palomar Observatory in 1985 they made a chance discovery of a new type of supernova, and although Sargent had studied supernovae many years earlier, Filippenko recalls that Sargent gave him the lead in the analysis and publication of their results. "This literally changed my career," Filippenko says. "Wal always encouraged his students to capitalize on exciting opportunities that came their way."

Sargent has received many honors—he was named a fellow of the American Academy of Arts and Sciences in 1977, a fellow of the Royal Society in 1981, and a member of the National Academy of Sciences in 2005. He was awarded the Helen B. Warner Prize of the American Astronomical Society in 1969, gave the George Darwin Lecture of the Royal Astronomical Society in 1987, received the Dannie Heineman Prize of the American Astronomical Society and the American Institute of Physics in 1991, received the Catherine Wolfe Bruce Medal of the Astronomical Society of the Pacific in 1994, and was the Henry Norris Russell Lecturer of the American Astronomical Society in 2001. Sargent was a member of more than 30 review and prize committees over the span of his career and a visiting fellow at observatories around the world, from Australia to Europe to Berkeley, California.

Sargent is survived by his wife, Anneila Sargent; two daughters, Lindsay Eleanor Berg and Alison Clare Hubbs; sons-in-law Henry Berg and Dan Hubbs; and four grandsons—Patrick and Charlie Hubbs and Angus and Eric Berg. A public memorial reception will be held at a later date.

Donations can be made in memory of Wallace L. W. Sargent here.

 

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

Two Faculty Members Named Packard Fellows

Two Caltech faculty members have been awarded Packard Fellowships for Science and Engineering. Biologist Alexei Aravin and astronomer John Johnson each were awarded $875,000, to be distributed over five years.

"I'm very excited about this fellowship," says Aravin, an assistant professor of biology. "It will allow my lab to pursue new, ambitious goals that are difficult to fund using traditional sources."

Aravin studies RNA molecules, which encode the information contained in genes to help create proteins. His lab is probing the mechanisms that determine the stability and fate of RNA. He's also trying to figure out how noncoding RNA—which doesn't encode information but nevertheless plays crucial roles in the cell—functions and is produced.

Johnson's research focuses on discovering and characterizing planets around other stars. "My broad goals," he says, "are to gain a better understanding of planet formation, place our solar system in a broader galactic context, and eventually find places in the galaxy where other life forms might reside." He plans to use the money to help support postdocs in his research group and to start a visitor program in which scientists from other institutions are invited to brainstorm and collaborate.

Johnson, an assistant professor of astronomy, was meeting with a student when he got the phone call notifying him of the award. "I don't remember my exact reaction, but it certainly startled the poor student," he says. "I spent the rest of the day grinning like an idiot."

According to the Packard Foundation, the fellowships were established in 1988 to allow promising professors to pursue research early in their careers with few funding and reporting constraints. Each year, presidents from 50 universities each nominate two early-career professors for the fellowship. A panel of scientists and engineers then select 16 fellows. To date, there have been more than 400 professors who have received Packard Fellowships. Aravin and Johnson join 26 members of current and past Caltech faculty who have been named Packard Fellows.

Writer: 
Marcus Woo
Frontpage Title: 
New Caltech Fellows
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Noted Physicist Robert F. Christy Dies

Robert F. Christy, one of the last people alive to have worked on the Manhattan Project—which created the atomic bomb during World War II—and whose later research in astrophysics contributed to our understanding of the size of the universe, passed away on October 3 at his home in Pasadena. The former provost and acting president of the California Institute of Technology (Caltech), where he was a longtime professor, was 96 years old.

Christy was credited with designing the explosive core of the first atomic bomb.

"Robert Christy was one of the founders of a very important area of astrophysical research and a major figure at Caltech in the postwar era," says B. Thomas Soifer, professor of physics and chair of the Division of Physics, Mathematics and Astronomy (PMA) at Caltech. "Bob was an outstanding theoretical physicist; his contributions to scientific research, to public policy—and his leadership—helped in shaping what Caltech is today."  

Christy was born in Vancouver, British Columbia, and entered the University of British Columbia (UBC) in 1932 as a 16-year-old sophomore. He graduated in 1935 at the age of 19 with a bachelor's degree in physics, then stayed for two more years at UBC to earn a master's degree in physics and mathematics in 1937, after which he moved to the UC Berkeley, where he studied physics as a graduate student of J. Robert Oppenheimer, also known as the "father of the atomic bomb."

After earning his degree in 1941, Christy was hired to teach at the Illinois Institute of Technology. In the fall of 1941 he was invited to join the Manhattan Project; he started in January of 1942, working with Eugene Wigner at the University of Chicago on the theory of atomic chain reactions. When Enrico Fermi and his team moved to the University of Chicago in March, he asked Christy to work with him on experimental "exponential piles" (chain-reacting systems that were too small to fully chain-react). In the winter of 1942, Christy helped build the first nuclear reactor, Chicago Pile-1, before being invited to Los Alamos by Oppenheimer in early 1943. He also helped design the reactors at Hanford where the plutonium was to be made.

Notably, Christy was involved in the creation of the plutonium core ("pit") of the implosion weapon designed at Los Alamos. The Los Alamos team's idea for the plutonium bomb was to embed a mass of nuclear fuel (specifically, plutonium) within a hollow sphere of high-explosive lenses; when the explosives were detonated, the nuclear fuel would implode into a dense "critical" mass, triggering a chain reaction that would lead to a nuclear explosion. However, the team soon realized, if the shape of the core became unstable and deviated from a perfect sphere, the bomb might fizzle out and fail to explode.

Christy's design of the Pu core consisted of a nearly solid sphere of plutonium metal of slightly less than critical mass, with a small central cavity containing an "initiator" that supplied neutrons to get the fission reaction started as the core imploded. When compressed hard enough, the atoms would be forced close enough together to achieve critical mass, through a process known as fast criticality, triggering the chain reaction and a nuclear blast. This is the design (referred to as the "Christy Gadget" at Los Alamos at the time; the word "bomb" wasn't used by Manhattan Project scientists) that was used in the Trinity bomb test and in the weapon ("Fat Man") dropped on Nagasaki on August 9, 1945.

Following the war, Christy initially returned to the University of Chicago. In 1946, on the recommendation of Oppenheimer, he was hired at Caltech as an associate professor of physics, doing work in theoretical physics and nuclear physics, including the study of cosmic rays. He became a professor of theoretical physics in 1950; Institute Professor of Theoretical Physics in 1983; and Institute Professor, Emeritus, in 1986.

"When I first arrived at Caltech in September 1949," recalls Ward Whaling, Caltech professor of physics, emeritus, and Christy's colleague for more than six decades, "fall classes had not started and the PMA division office could find no one to show me around the Kellogg Radiation Laboratory except a young theoretical physicist named Christy. I had never heard of him—his Los Alamos achievements would remain classified for years—but the prospect of being shown the lab by a theoretical physicist was depressing. Boy, was I wrong! I quickly learned that Bob Christy was quite familiar with that part of the new lab that had already been installed—to replace the wartime weapons-testing facility and an earlier X-ray therapy clinic—and he also knew what was being planned for the future. Later, when I began my own research using the accelerators he had shown me that first day, I learned that he regularly visited the lab, maybe two or the times a week, in the afternoon, with his hands clasped behind his back, just looking, sometimes asking a question, but taking care not to interrupt serious work." As Christy noted in a 1994 oral history interview with the Caltech Archives, "I was an unusual theorist in that my greatest strength was . . . in seeing how theory and experiment related."

In 1960, Christy turned his attention Cepheid variable stars, which had long been used as a so-called standard candle with which to measure distances to other galaxies because their pulsation rate varies with their intrinsic brightness.

At the time "it was unknown why they varied, what made them vary," explained Christy in his oral history. "It was known that they were apparently spherical pulsators. That is, they expanded and contracted—a regular expansion and contraction in spherical symmetry. I thought: Well, this is very much like the spherical hydrodynamics in implosion," he said. "It's basically the same equations we had used—of course, with different substances—but the mathematical approach was very similar to what we had been working on at Los Alamos." The mathematical model that Christy developed helped explain why the stars vibrated and earned him the Royal Astronomical Society's Eddington Medal in 1967. He was elected to the National Academy of Sciences in 1965.

"Christy's analysis of how Cepheid stars pulsate enabled him to say definitively, when a star pulsates at a certain rate, just how bright it would be if we were close to it," says Kip S. Thorne, Richard P. Feynman Professor of Theoretical Physics, Emeritus, at Caltech. "Astronomers could then compare that with how bright the star looks through their telescopes and deduce how far away the star is—the dimmer it appears, the farther it must be. This was crucial in determining the size of our galaxy and thence, combined with much other data, the size of the universe."

Christy held several administrative posts during his tenure at Caltech, including as executive officer for physics from 1968 to 1970, Caltech's faculty chair from 1969 to 1971, vice president and provost from 1970 to 1980, and, when Institute president Harold Brown left to become secretary of defense under Jimmy Carter, as acting president of the Institute from 1977 to 1978.

Because of his wartime experience, Christy was a longtime opponent of the further development of nuclear weapons. In the summer of 1945, he became one of the founding members of the Association of Los Alamos Scientists (ALAS) and helped draft a statement about educating the public on how to manage atomic energy for peaceful uses. He was one of 10 Caltech physicists who had participated in the bomb-building at Los Alamos who signed and paid for a full-page ad that ran in the Los Angeles Times on October 14, 1956, calling for an end to nuclear weapons tests.

In the mid-1980s, Christy became a member of the National Research Council's Committee on Dosimetry, which studied the radiation effects of the Hiroshima and Nagasaki bombs. "He worked on the bomb in good faith, because he wanted to save lives, and he was proud that the work that he'd done helped the war come to an end," says Christy's widow, I.-Juliana Sackmann Christy. "But he later referred to nuclear weapons as 'killing machines.' He was a man of principle."

A skilled dancer who loved to sing, Christy was an avid horseman and learned to ride from Robert Oppenheimer, who gave him his first "half a horse" to lure him to join the Manhattan Project, says Mrs. Christy. "Another scientist owned the other half, and the two often argued about who had the front and who had the back," she says. Christy continued to ride until he was well into his 90s—and after losing his eyesight—on his 240-acre ranch in Ventura County.

Christy is survived by Juliana, his second wife; two daughters, Ilia Juliana Christy and Alexandra Roberta Christy; two sons from his first marriage to Dagmar Elizabeth von Lieven, Thomas Edward "Ted" Christy and Peter Robert Christy; and five grandchildren. Services will be held at 1:30 p.m. on October 20, 2012, at Mountain View Cemetery in Altadena, California.

Writer: 
Kathy Svitil
Frontpage Title: 
Caltech Mourns the Passing of Robert Christy
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

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.

Writer: 
Kathy Svitil
Frontpage Title: 
Caltech Again Named World's Top University by <i>Times Higher Ed</i>
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

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. 

Writer: 
Kimm Fesenmaier
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Dennis Kochmann Wins International Solid Mechanics Award

Caltech assistant professor of aerospace Dennis Kochmann received the 2012 IUTAM Bureau Prize in solid mechanics from the International Union of Theoretical and Applied Mechanics (IUTAM). Kochmann accepted the award at the organization's quadrennial congress in Beijing on August 24.

IUTAM Bureau Prizes are awarded once every four years to three individuals under 35 years of age. Kochmann won the prize for his paper and presentation in solid mechanics. IUTAM also awarded France's Mickaël Bosco for his lecture on fluid mechanics, and the organization's poster presentation prize went to Huachuan Wang of the United States.

"This prize is a great honor for me because it is awarded by the international solid mechanics community," says Kochmann. "It shows that the research we do in my still very young research group here at Caltech is well received."

Kochmann's presentation, "Making positive use of instability—ultra-high stiffness and damping composites and structures due to constrained instabilities," highlighted recent results of his research, describing how engineers can make positive use of mechanical instabilities.

"While engineering design commonly aims to prevent instabilities of any kind, leading to failure or collapse," Kochmann says, "controlled and careful use of mechanical instabilities can result in new material and structural systems that possess superior properties such as very high stiffness and damping."

More information on the activities of Kochmann's research group at Caltech can be found at www.kochmann.caltech.edu.

Writer: 
Brian Bell
Writer: 
Exclude from News Hub: 
Yes

Weighing Molecules One at a Time

Caltech-led physicists create first-ever mechanical device that measures the mass of a single molecule

PASADENA, Calif.—A team led by scientists at the California Institute of Technology (Caltech) has made the first-ever mechanical device that can measure the mass of individual molecules one at a time.

This new technology, the researchers say, will eventually help doctors diagnose diseases, enable biologists to study viruses and probe the molecular machinery of cells, and even allow scientists to better measure nanoparticles and air pollution.

The team includes researchers from the Kavli Nanoscience Institute at Caltech and Commissariat à l'Energie Atomique et aux Energies Alternatives, Laboratoire d'électronique des technologies de l'information (CEA-LETI) in Grenoble, France. A description of this technology, which includes nanodevices prototyped in CEA-LETI's facilities, appears in the online version of the journal Nature Nanotechnology on August 26.

The device—which is only a couple millionths of a meter in size—consists of a tiny, vibrating bridge-like structure. When a particle or molecule lands on the bridge, its mass changes the oscillating frequency in a way that reveals how much the particle weighs.

"As each particle comes in, we can measure its mass," says Michael Roukes, the Robert M. Abbey Professor of Physics, Applied Physics, and Bioengineering at Caltech. "Nobody's ever done this before."

The new instrument is based on a technique Roukes and his colleagues developed over the last 12 years. In work published in 2009, they showed that a bridge-like device—called a nanoelectromechanical system (NEMS) resonator—could indeed measure the masses of individual particles, which were sprayed onto the apparatus. The difficulty, however, was that the measured shifts in frequencies depended not only on the particle's actual mass, but also on where the particle landed. Without knowing the particle's landing site, the researchers had to analyze measurements of about 500 identical particles in order to pinpoint its mass.

But with the new and improved technique, the scientists need only one particle to make a measurement. "The critical advance that we've made in this current work is that it now allows us to weigh molecules—one by one—as they come in," Roukes says.

To do so, the researchers analyzed how a particle shifts the bridge's vibrating frequency. All oscillatory motion is composed of so-called vibrational modes. If the bridge just shook in the first mode, it would sway side to side, with the center of the structure moving the most. The second vibrational mode is at a higher frequency, in which half of the bridge moves sideways in one direction as the other half goes in the opposite direction, forming an oscillating S-shaped wave that spans the length of the bridge. There is a third mode, a fourth mode, and so on. Whenever the bridge oscillates, its motion can be described as a mixture of these vibrational modes.

The team found that by looking at how the first two modes change frequencies when a particle lands, they could determine the particle's mass and position, explains Mehmet Selim Hanay, a postdoctoral researcher in Roukes's lab and first author of the paper. "With each measurement we can determine the mass of the particle, which wasn't possible in mechanical structures before."

Traditionally, molecules are weighed using a method called mass spectroscopy, in which tens of millions of molecules are ionized—so that they attain an electrical charge—and then interact with an electromagnetic field. By analyzing this interaction, scientists can deduce the mass of the molecules.

The problem with this method is that it does not work well for more massive particles—like proteins or viruses—which have a harder time gaining an electrical charge. As a result, their interactions with electromagnetic fields are too weak for the instrument to make sufficiently accurate measurements.

The new device, on the other hand, does work well for large particles. In fact, the researchers say, it can be integrated with existing commercial instruments to expand their capabilities, allowing them to measure a wider range of masses.

The researchers demonstrated how their new tool works by weighing a molecule called immunoglobulin M (IgM), an antibody produced by immune cells in the blood. By weighing each molecule—which can take on different structures with different masses in the body—the researchers were able to count and identify the various types of IgM. Not only was this the first time a biological molecule was weighed using a nanomechanical device, but the demonstration also served as a direct step toward biomedical applications. Future instruments could be used to monitor a patient's immune system or even diagnose immunological diseases. For example, a certain ratio of IgM molecules is a signature of a type of cancer called Waldenström macroglobulinemia. 

In the more distant future, the new instrument could give biologists a view into the molecular machinery of a cell. Proteins drive nearly all of a cell's functions, and their specific tasks depend on what sort of molecular structures attach to them—thereby adding more heft to the protein—during a process called posttranslational modification. By weighing each protein in a cell at various times, biologists would now be able to get a detailed snapshot of what each protein is doing at that particular moment in time.

Another advantage of the new device is that it is made using standard, semiconductor fabrication techniques, making it easy to mass-produce. That's crucial, since instruments that are efficient enough for doctors or biologists to use will need arrays of hundreds to tens of thousands of these bridges working in parallel. "With the incorporation of the devices that are made by techniques for large-scale integration, we're well on our way to creating such instruments," Roukes says. This new technology, the researchers say, will enable the development of a new generation of mass-spectrometry instruments.

"This result demonstrates how the Alliance for Nanosystems VLSI, initiated in 2006, creates a favorable environment to carry out innovative experiments with state-of-the-art, mass-produced devices," says Laurent Malier, the director of CEA-LETI. The Alliance for Nanosystems VLSI is the name of the partnership between Caltech's Kavli Nanoscience Institute and CEA-LETI. "These devices," he says,"will enable commercial applications, thanks to cost advantage and process repeatability."

In addition to Roukes and Hanay, the other researchers on the Nature Nanotechnology paper, "Single-protein nanomechanical mass spectrometry in real time," are Caltech graduate students Scott Kelber and Caryn Bullard; former Caltech research physicist Akshay Naik (now at the Centre for Nano Science and Engineering in India); Caltech research engineer Derrick Chi; and Sébastien Hentz, Eric Colinet, and Laurent Duraffourg of CEA-LETI's Micro and Nanotechnologies innovation campus (MINATEC). Support for this work was provided by the Kavli Nanoscience Institute at Caltech, the National Institutes of Health, the National Science Foundation, the Fondation pour la Recherche et l'Enseignement Superieur from the Institut Merieux, the Partnership University Fund of the French Embassy to the U.S.A., an NIH Director's Pioneer Award, the Agence Nationale pour la Recherche through the Carnot funding scheme, a Chaire d'Excellence from Fondation Nanosciences, and European Union CEA Eurotalent Fellowships.  

Writer: 
Marcus Woo
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

It's Always Sunny in Caltech Lab

Researchers reproduce plasma loops to help understand solar physics

PASADENA, Calif.—In orbit around Earth is a wide range of satellites that we rely on for everything from television and radio feeds to GPS navigation. Although these spacecraft soar high above storms on Earth, they are still vulnerable to weather—only it's weather from the sun. Large solar flares—or plasma that erupts from the sun's surface—can cause widespread damage, both in space and on Earth, which is why researchers at the California Institute of Technology (Caltech) are working to learn more about the possible precursors to solar flares called plasma loops. Now, they have recreated these loops in the lab.

"We're studying how these solar loops work, which contributes to the knowledge of space weather," says Paul Bellan, professor of applied physics at Caltech, who compares the research to studying hurricanes. For example, you can't predict a hurricane unless you know more about the events that precede it, like high-pressure and low-pressure fronts. The same is true for solar flares. "It takes some time for the plasma to get to Earth from the sun, so it's possible that with more research, we could have up to a two-day warning period for massive solar flares."

The laboratory plasma loop studies were conducted by graduate student Eve Stenson together with Bellan and are reported in the August 13 issue of the journal Physical Review Letters.

They found that two magnetic forces control the behavior of arching loops of plasma, which is hot, ionized gas. "One force expands the arch radius and so lengthens the loop while the other continuously injects plasma from both ends into the loop," Bellan explains. "This latter force injects just the right amount of plasma to keep the density in the loop constant as it lengthens." 

The duo says that in simpler terms, this process is like squeezing toothpaste into a tube from both ends, except that the toothpaste has little magnets in it, so there are magnetic forces acting internally. Stenson and Bellan studied plasma loops that they generated with a pulse-powered, magnetized plasma gun. Inside a vacuum chamber, electromagnets create an arched magnetic field. Then, hydrogen and nitrogen gas is released at the two footpoints of the arch. Finally, a high-voltage electrical current is applied at the footpoints to ionize the gas and turn it into plasma, which travels at a minimum speed of about six miles per second.

"All three steps—the magnetic field, and the gas, and the high voltage—happen in just a flash of light inside the chamber," says Stenson. "We use high-speed cameras with optical filters to capture the behavior of the plasmas."

By color-coding the inflowing plasma, the optical filters vividly demonstrated the flow from the two ends of the loop. According to Bellan, no one has ever used this technique before. On camera, red plasma flows into the loop from one footpoint while blue plasma simultaneously flows into the loop from the other end.

"For each experiment, you'll only see the light from the hydrogen side or the nitrogen side in the images," explains Stenson. "But these experiments are very reproducible, so we can put separate images on top of each other to see both plasmas in one picture."

Next, Bellan's lab will test how two loops interact with each other. "We want to see if they can merge and form one big loop," says Bellan. "Some people believe that this is how larger plasma loops on the sun are formed."

Funding for the research outlined in the Physical Review Letters paper, "Magnetically Driven Flows in Arched Plasma Structures," came from the National Science Foundation, the U.S. Department of Energy, and the Air Force Office of Scientific Research. 

Writer: 
Katie Neith
Tags: 
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Caltech Professor Barry Simon Wins Henri Poincare Prize

Barry Simon, IBM Professor of Mathematics and Theoretical Physics at Caltech, is a 2012 recipient of the Henri Poincaré Prize, awarded by the International Association of Mathematical Physics and funded by the Daniel Iagolnitzer Foundation.

Originating in 1997, the prize is awarded every three years in recognition of outstanding contributions in mathematical physics and accomplishments leading to novel developments in the field.

According to his citation, Simon was recognized for "his impact on many areas of mathematical physics including, in particular, the spectral theory of Schroedinger operators, for his mentoring of generations of young scientists, and for his lucid and inspirational books.
The prize was awarded on August 6 at the International Congress of Mathematical Physics in Allborg, Denmark. Other 2012 Henri Poincaré Prize winners are Nalini Anantharaman of Université de Paris-Sud; Freeman Dyson of the Institute of Advanced Study, Princeton University; and Sylvia Serfaty, Université Pierre et Marie Curie, Paris, and the Courant Institute, New York University.
Writer: 
Brian Bell
Writer: 
Exclude from News Hub: 
Yes

Caltech Physicist Wins $3 Million Fundamental Physics Prize

New award is largest academic prize in the world

PASADENA, Calif.—Alexei Kitaev, professor of theoretical physics, computer science, and mathematics at the California Institute of Technology (Caltech), has been named an inaugural winner of the Fundamental Physics Prize—a $3 million award that represents the largest academic prize given to an individual in the history of science.

The prize, funded by Yuri Milner, a Russian entrepreneur and venture capitalist, was given with "the aim of providing the recipients with more freedom and opportunity to pursue even greater future accomplishments," according to the Fundamental Physics Prize Foundation website. In addition to Kitaev, eight other physicists received the award, for a grand total of $27 million in prize money. The individual awards are more than twice what Nobel laureates receive, and that amount—about $1.2 million—is often split among a few winners.

"It was a great surprise and honor to learn that I was a recipient of the prize along with some very famous and renowned physicists," says Kitaev. "At first, I was confused because I didn't think that the money could be just for me—I assumed such a big prize would be shared among all the recipients. I feel very happy and extremely lucky."

Kitaev, a member of the new Institute for Quantum Information and Matter (IQIM) at Caltech, is known for developing algorithms and theories to enable quantum computing, which has the potential to perform in seconds certain tasks that would take an ordinary computer thousands of years to complete. The award citation recognized his "theoretical idea of implementing robust quantum memories and fault-tolerant quantum computation using topological quantum phases with anyons and unpaired Majorana modes."

"I'm delighted that Alexei is getting the recognition he so richly deserves for making the fundamental and profound contributions to one of the most exciting areas of fundamental physics," says Tom Soifer, professor of physics and chair of the Division of Physics, Mathematics and Astronomy at Caltech. "His work is blazing the path toward what we hope will be the next major technical revolution in computing, the realization of quantum computers."

With a joint appointment at Caltech in the Division of Physics, Mathematics and Astronomy and the Division of Engineering and Applied Science, Kitaev explores the mysterious behavior of quantum systems and their implications for developing practical applications, such as quantum computers.

"Every physicist is excited to get new opportunities to test theories, and quantum computing would eliminate a lot of stumbling blocks that we face in making connections between theory and experiments," says Kitaev, who was named a MacArthur Fellow in 2008. He is unsure how he will use the prize money. Beyond his family needs and personal spending, he would like to help support educational efforts.

Kitaev received an MS from the Moscow Institute of Physics and Technology in 1986 and his PhD from Russia's Landau Institute for Theoretical Physics in 1989, where he continued to work until 1998. He was a researcher at Microsoft Research from 1999 until 2001 and spent a year at Microsoft Station Q in 2005–2006. He first came to Caltech as a visiting associate and lecturer in 1998, and he was named professor of theoretical physics and computer science in 2002.

Milner chose the inaugural recipients of the prize, but these recipients will work together to choose next year's winner, or winners. The recipients are also invited to give annual public lectures as part of an effort to raise the profile of fundamental physics and communicate advances to a wider audience.

The other winners are Nima Arkani-Hamed, Juan Maldacena, Nathan Seiberg, and Edward Witten from the Institute for Advanced Study at Princeton University; Alan Guth from MIT; Maxim Kontsevich from the Institute of Advanced Scientific Studies in France; Andrei Linde from Stanford; and Ashoke Sen from the Harish-Chandra Research Institute in India.

Caltech's IQIM is a Physics Frontier Center supported by the National Science Foundation and the Gordon and Betty Moore Foundation.

Writer: 
Katie Neith
Frontpage Title: 
Physicist Wins $3 Million Physics Prize
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Pages

Subscribe to RSS - PMA