On the Front Lines of Sustainability

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On the Front Lines of Sustainability
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The chemical processes used to make products ranging from pharmaceuticals to perfumes can have a harmful impact on the environment. However, Caltech chemist and Nobel laureate Robert Grubbs has spent several decades developing catalysts—compounds that speed up a chemical reaction—that can make the synthesis of these products more efficient and ecologically friendly, ultimately reducing their environmental footprint. Similarly, chemist Brian Stoltz is developing new strategies for the synthesis of compounds needed in the chemical, polymer, and pharmaceutical industries. His new processes rely upon oxygen and organometallic catalysts—greener alternatives to the toxic metals that are normally used to drive such reactions.

Switching from paper files to cloud-based data storage might seem like an obvious choice for sustainability, but can we further reduce the environmental impact of storing data? The theoretical work of engineer and computer scientist Adam Wierman suggests that with the right algorithms, we can. Today, data centers—the physical storage facilities Wierman calls the "SUVs of the Internet"—account for more than 1.5 percent of U.S. electricity usage. And as more data goes online, that number is expected to grow. Wierman's work helps engineers design algorithms that will reroute data, with preference to centers that use renewable energy sources like wind and solar.

Energy from the sun—although free and abundant—cannot easily be stored for use on dreary days or transported to cloudy regions. Caltech engineer and materials scientist Sossina Haile hopes to remove that barrier with a specific type of solar reactor she has developed. The reactor is lined with ceramic cerium oxide; when this lining is heated with concentrated sunlight it releases oxygen, priming it to remove oxygen from water molecules or carbon dioxide on cooling, thus creating hydrogen fuel or "syngas"—a precursor to liquid hydrocarbon fuels. This conversion of the sun's light into storable fuel could allow solar-derived power to be available day and night.

Caltech student participants in the Department of Energy's biennial Solar Decathlon competition set out to prove that keeping a house lit up, cooled down, and comfortable for living is possible—even while off the grid. The Techers teamed up with students at the Southern California Institute of Architecture to create CHIP and DALE, their entries in the 2011 and 2013 competitions, respectively. These functional and stylish homes, powered solely by the sun, were engineered with innovative components including a rainwater collection system and moving room modules that optimize heating and cooling efficiency. 

Although many of us take the nearest bathroom for granted, working toilets require resources and infrastructure that may not be available in many parts of the world. Inspired by the "Reinventing the Toilet Challenge" issued by the Bill and Melinda Gates Foundation, environmental scientist and engineer Michael Hoffmann and his team applied his research in hydrogen evolution and water treatment to reengineer the toilet. The Caltech team's design—which won the challenge in 2012—can serve hundreds of people each day, treat its own wastewater, and generate electricity, providing a sustainable and low-cost solution to sanitation and hygiene challenges in the developing world. Prototypes are being tested in India and China for use in urban and remote environments in the developing world.  

Geophysicist Mark Simons studies the mechanics of the Earth—furthering our understanding of what causes our planet to deform over time. His research often involves using satellite data to observe the movement associated with seismic and volcanic activity, but Simons is also interested in changes going on in the icy parts of Earth's surface, especially the dynamics of glaciers. By flying high above Iceland's ice caps, Simons and his colleagues can track the glaciers' melt-and-freeze response in relation to seasonal and long-term variations in temperature—and their potential response to climate change.

The production of industrial nitrogen fertilizer results in 130 million tons of ammonia annually—while also requiring high heat, high pressure, and lots of energy. However, in a process called nitrogen fixation, soil microorganisms that live near the roots of certain plants can produce a similar amount of ammonia each year. The bugs use catalysts called nitrogenases to convert nitrogen from the air into ammonia at room temperature and atmospheric pressure. By mimicking the behavior of these microorganisms, Jonas Peters and his colleagues synthesized an iron-based catalyst that allows for nitrogen fixation under much milder conditions. The catalyst could one day lead to more environmentally friendly methods of ammonia production.

Traditionally, the photovoltaic cells in solar panels have been expensive and have had limited efficiency—making them a hard sell in the consumer market. Engineer and applied physicist Harry Atwater's work suggests that there is a thinner and more efficient alternative. Atwater, who is also the director of the Resnick Sustainability Institute, uses thin layers of semiconductors to create photovoltaics that absorb sunlight as efficiently as thick solar cells but can be produced with higher efficiency than conventional cells.

The generation of chemical fuels from sunlight could completely change the way we power the planet. Researchers in the laboratory of Caltech chemist Nate Lewis are working to develop different components of a fuel-producing device that could do just that called a photoelectrochemical cell. The cell would consist of an upper layer that could absorb sunlight, carbon dioxide, and water vapor, a middle layer consisting of light absorbers and catalysts that can produce fuels, which are then released through the device's bottom layer. When such a device is created, the Joint Center for Artificial Photosynthesis, of which Lewis is the scientific director, aims to ease the transfer of these technologies to the private sector. 

Clean energy from the wind is a promising alternative to fossil fuels, but giant pinwheel-like wind turbines that are common on many wind farms can create dangerous obstacles for birds as well as being an unpleasant addition to a landscape's aesthetic. To combat this problem, Caltech engineer and fluid-mechanics expert John Dabiri is testing a new design for wind turbines, which looks a bit like a spinning eggbeater emerging from the ground. By placing these columnar vertical wind turbines in a careful arrangement—an arrangement inspired by the vortex of water created behind a swimming fish—his smaller vertical turbines create just as much energy as the "pinwheels" and on a much smaller land footprint.

In the early 1990s, Caltech bioengineer Frances Arnold pioneered "directed evolution"—a new method of engineering custom-built enzymes, or activity-boosting proteins. The technique allows mutations to develop in the enzyme's genetic code; these mutations can give the enzyme properties that don't occur in nature but are beneficial for human applications. The selectively enhanced enzymes help microbes turn plant waste and fast-growing grasses into fuels like isobutanol, which could sustainably replace more than half of U.S. oil imports, Arnold says. She's also exploring ways the technique could help factories to make pharmaceuticals and other products in much cleaner and safer ways.

The combined research efforts of Richard Flagan, John Seinfeld, Mitchio Okumura, and Paul Wennberg aim to improve our understanding of various aspects of climate change. Chemical engineer Flagan is pioneering ways to measure the number and sizes of particles in the air down to that of large molecules. Seinfeld studies where particles in the air come from, how they are produced by airborne chemical reactions, and the effect they have on the world's climate. Chemical physicist Okumura studies the chemical reactions that occur when sunlight encounters air pollution and results in smog. Wennberg, an atmospheric chemist, studies the natural and human processes that affect smog formation, the health of the ozone layer, as well as the lifetime of greenhouse gases. Wennberg and his colleagues join a legacy of Caltech researchers who have improved air quality through key discoveries about pollution.

In the past, researchers have discovered materials that can act as reaction catalysts, driving sunlight to split water into hydrogen fuel and an oxygen byproduct. However, these wonder materials are often expensive and in short supply. The research of chemist Harry Gray, who leads the National Science Foundation-funded Center for Chemical Innovation in Solar Fuels program, tests combinations of Earth-abundant metals to search for an inexpensive catalyst that boosts the water-splitting reaction with the sun. Gray also coleads an outreach project in which students in the classroom can participate in the race for solar fuels by testing thousands of materials and reporting their results to Caltech researchers.

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Although Earth Week has officially come to a close, Caltech's commitment to sustainability continues. In this feature, you will meet some of the researchers at Caltech whose work is contributing to a greener planet and to the long-term improvement of our global environment.

Research for a Greener Future

Today's Earth Week feature highlights three cross-disciplinary research centers where Caltech scientists and engineers collaborate on projects that will have a positive impact on energy, the environment, and Earth's sustainable future.

The Ronald and Maxine Linde Center for Global Environmental Science

The Ronald and Maxine Linde Center for Global Environmental Science brings together researchers from chemistry, engineering, geology, environmental science, and other disciplines, with the goal of understanding the global environment and developing solutions to complex environmental problems. Linde Center scientists investigate how Earth's climate and its atmosphere, oceans, and biosphere have varied in the past and how they may change in the future. They are working on solutions to vexing challenges in climate change prognosis and mitigation, and to improve air and water quality.

The Linde Center was established thanks to support from Caltech alumnus and trustee Ronald Linde and his wife, Maxine. Led by acting director Paul Wennberg, Caltech's R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering, the center is housed in the Linde + Robinson Laboratory, which was constructed in 1932 as an astronomy lab. The building recently underwent extensive renovations, to become one of the nation's most energy-efficient laboratories and the first existing historic building to earn the LEED Platinum rating. In 2012, Linde + Robinson was honored with a 2012 Los Angeles Conservancy Preservation Award for the "exceptionally creative and sensitive approach" of the renovation. The project, the conservancy noted, "not only preserved the building's unique historic features, it found brilliant new uses for them—particularly the solar telescope, built as the centerpiece of the original building but functionally obsolete. Now it tracks the sun and uses the light it captures for both illumination and exploration."

Resnick Sustainability Institute

Caltech's Resnick Sustainability Institute was created to fund and foster innovative Caltech-based sustainability and energy-science research collaborations with the potential to develop renewable-energy technologies that may one day help solve our global energy and climate challenges. The mission of the institute, which was founded with a generous gift from Stewart and Lynda Resnick, spans research, education, and communications. Current projects include research into energy generation, such as advanced photovoltaics, photoelectrochemical solar fuels, cellulosic biofuels, and wind-energy system design; energy conversion work on batteries and fuel cells; and research into technologies for energy efficiency and management, such as fuel-efficient vehicles, green chemical synthesis, and thermoelectric materials, as well as advanced research on electrical grid control and distribution.

This year the Resnick Sustainability Institute debuted two new initiatives: the Resonate Awards, which honor breakthrough achievements in energy science and sustainability, and a prize postdoctoral fellowship program. The Resonate Award winners will be announced at the Fortune Brainstorm GREEN conference in May 2014, and the inaugural class of postdoctoral fellows will be announced this fall.

Led by Harry Atwater, Caltech's Howard Hughes Professor and professor of applied physics and materials science, the institute is collocated with the Joint Center for Artificial Photosynthesis (JCAP) in the recently renovated Jorgensen Laboratory, which has been awarded LEED Platinum certification. In the renovation, Caltech and its partners were able to reuse or recycle over 90 percent of the materials removed from the original facility, a computer science building. Jorgensen has high-efficiency lighting and HVAC systems, a "living roof" composed of evergreen and drought-tolerant grasses, and water-saving plumbing and landscaping, among other green features.

The Joint Center for Artificial Photosynthesis (JCAP)

JCAP, established in 2010 as a U.S. Department of Energy (DOE) Energy Innovation Hub, is the nation's largest research effort focused on artificial photosynthesis. Led by researchers from Caltech (JCAP South, housed at the Jorgensen Laboratory) and partner Lawrence Berkeley National Laboratory (JCAP North), the center aims to create a low-cost artificial generator that uses sunlight, carbon dioxide, and water to make fuel from the sun 10 times more efficiently than current living crops. Once a prototype generator is developed, it will be handed off to private-sector companies to launch a new solar-fuels industry. Such a transformative breakthrough would reduce our country's dependence on oil and enhance energy security.

JCAP researchers include Scientific Director Nathan S. Lewis, Caltech's George L. Argyros Professor and professor of chemistry; Jonas Peters, the Bren Professor of Chemistry; William A. Goddard, Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics; and Harry Atwater.

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Allen E. Puckett

1919–2014

Allen E. Puckett (PhD '49), the engineer who helped father the delta-winged airplane, the guided missile, and the communications satellite, and who turned Hughes Aircraft into the nation's top provider of radar systems and other defense-related electronics, passed away at his home in Pacific Palisades, California, on March 31, 2014, at age 94.

Puckett was born on July 25, 1919, in Springfield, Ohio. He earned his bachelor's and master's degrees in engineering at Harvard (in 1939 and 1941, respectively) before coming to Caltech to pursue his doctorate in aeronautics under Theodore von Kármán, the leading aerodynamicist of the era. Puckett's PhD thesis, "Supersonic Wave Drag on Thin Airfoils," laid the foundation for designing the triangular-shaped delta wings found on such diverse aircraft as supersonic fighter jets, the SR-71 Blackbird spy plane, and the Space Shuttle orbiter.

Puckett launched his Caltech career in 1942 by helping build the first supersonic wind tunnel in the United States that could operate continuously at Mach 4, or four times the speed of sound. He used this expertise the following year to design a similar but much larger tunnel for testing supersonic artillery shells at the Army Ordnance Corps' Aberdeen Proving Grounds in Maryland. This wind tunnel, built at the height of World War II, remained in use well into the Cold War. While a graduate student, Puckett also served as the wind tunnel section chief at Caltech's Jet Propulsion Laboratory, then an Army research facility, and as the chair of the Subcommittee on High-Speed Aerodynamics for the National Advisory Committee for Aeronautics (NACA, the forerunner of NASA).

Upon graduating in 1949, Puckett joined Hughes Aircraft as the head of the aerodynamics department of the Guided Missile Laboratory, and cowrote the seminal Introduction to Aerodynamics of a Compressible Fluid with Caltech aeronautics professor Hans W. Liepmann. (A decade later, Puckett and Simon Ramo [PhD '36] would coedit the equally seminal Guided Missile Engineering.) Puckett remained at Hughes for his entire professional career, becoming chairman and CEO in 1978 and retiring in 1987.

Puckett served on the boards of directors of corporations including General Dynamics, the Fluor Corporation, and the Delco Electronics Corporation as well as numerous government, private, and charitable organizations. He was a fellow and past president of the American Institute of Aeronautics and Astronautics, and a member of the American Association for the Advancement of Science, the International Academy of Aeronautics, the National Academy of Engineering, and the National Academy of Sciences.

Among other honors, Puckett won the Lawrence Sperry Award of the Institute of Aeronautical Sciences (now the American Institute of Aeronautics and Astronautics) in 1948. He was named a Caltech Distinguished Alumnus in 1970, the California Manufacturer of the Year in 1980, a Chevalier of the French Legion of Honor in 1984, and was awarded the National Medal of Technology by President Reagan in 1985.

"Dr. Puckett's research and innovations contributed greatly to the security of our nation," says Guruswami Ravichandran, the John E. Goode, Jr., Professor of Aerospace and Professor of Mechanical Engineering and the director of the Graduate Aerospace Laboratories at Caltech. "He was a visionary in the field of space engineering, and the impact of his work will be felt long into the future."

At Caltech, Puckett endowed a chair in the Division of Engineering and Applied Science. Robert McEliece, who developed new systems for storing and transmitting large volumes of information (such as images from far-flung spacecraft), is the Allen E. Puckett Professor and Professor of Electrical Engineering, Emeritus; Pietro Perona, who works on building machines that can see the way humans can, is the Allen E. Puckett Professor of Electrical Engineering. Even in his 90s, Puckett retained "his vivacious intellect and curiosity," says Perona.

Caltech's Guggenheim Aeronautical Laboratory, the building where Puckett spent his time on campus as a grad student, was extensively renovated in 2008. The west end of the third floor now houses the Allen Puckett Laboratory of Computational Fluid Mechanics, which includes a seminar room, a computer lab, and open-plan workspaces for graduate students.

Puckett is survived by Marilyn Puckett, his wife of 50 years, five children, six grandchildren, and 14 great-grandchildren.

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Douglas Smith
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Monday, May 5, 2014
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Experiences from two years of MOOCs at Caltech: A WEST Public Seminar

Friday, April 11, 2014
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Quantum Photon Properties Revealed in Another Particle—the Plasmon

For years, researchers have been interested in developing quantum computers—the theoretical next generation of technology that will outperform conventional computers. Instead of holding data in bits, the digital units used by computers today, quantum computers store information in units called "qubits." One approach for computing with qubits relies on the creation of two single photons that interfere with one another in a device called a waveguide. Results from a recent applied science study at Caltech support the idea that waveguides coupled with another quantum particle—the surface plasmon—could also become an important piece of the quantum computing puzzle.

The work was published in the print version of the journal Nature Photonics the week of March 31.

As their name suggests, surface plasmons exist on a surface—in this case the surface of a metal, at the point where the metal meets the air. Metals are conductive materials, which means that electrons within the metal are free to move around. On the surface of the metal, these free electrons move together, in a collective motion, creating waves of electrons. Plasmons—the quantum particles of these coordinated waves—are akin to photons, the quantum particles of light (and all other forms of electromagnetic radiation).

"If you imagine the surface of a metal is like a sea of electrons, then surface plasmons are the ripples or waves on this sea," says graduate student Jim Fakonas, first author on the study.

These waves are especially interesting because they oscillate at optical frequencies. Therefore, if you shine a light at the metal surface, you can launch one of these plasmon waves, pushing the ripples of electrons across the surface of the metal. Because these plasmons directly couple with light, researchers have used them in photovoltaic cells and other applications for solar energy. In the future, they may also hold promise for applications in quantum computing.

However, the plasmon's odd behavior, which falls somewhere between that of an electron and that of a photon, makes it difficult to characterize. "According to quantum theory, it should be possible to analyze these plasmonic waves using quantum mechanics"—the physics that governs the behavior of matter and light at the atomic and subatomic scale—"in the same way that we can use it to study electromagnetic waves, like light," Fakonas says. However, in the past, researchers were lacking the experimental evidence to support this theory.

To find that evidence, Fakonas and his colleagues in the laboratory of Harry Atwater, Howard Hughes Professor of Applied Physics and Materials Science, looked at one particular phenomenon observed of photons—quantum interference—to see if plasmons also exhibit this effect.

The applied scientists borrowed their experimental technique from a classic test of quantum interference in which two single, identical photons are launched at one another through opposite sides of a 50/50 beam splitter, a device that acts as an imperfect mirror, reflecting half of the light that reaches its surface while allowing the the other half of the light to pass through. If quantum interference is observed, both identical photons must emerge together on the same side of the beam splitter, with their presence confirmed by photon detectors on both sides of the mirror.

Since plasmons are not exactly like photons, they cannot be used in mirrored optical beam splitters. Therefore, to test for quantum interference in plasmons, Fakonas and his colleagues made two waveguide paths for the plasmons on the surface of a tiny silicon chip. Because plasmons are very lossy—that is, easily absorbed into materials that surround them—the path is kept short, contained within a 10-micron-square chip, which reduces absorption along the way.

The waveguides, which together form a device called a directional coupler, act as a functional equivalent to a 50/50 beam splitter, directing the paths of the two plasmons to interfere with one another. The plasmons can exit the waveguides at one of two output paths that are each observed by a detector; if both plasmons exit the directional coupler together—meaning that quantum interference is observed—the pair of plasmons will only set off one of the two detectors.

Indeed, the experiment confirmed that two indistinguishable photons can be converted into two indistinguishable surface plasmons that, like photons, display quantum interference.

This finding could be important for the development of quantum computing, says Atwater. "Remarkably, plasmons are coherent enough to exhibit quantum interference in waveguides," he says. "These plasmon waveguides can be integrated in compact chip-based devices and circuits, which may one day enable computation and measurement schemes based on quantum interference."

Before this experiment, some researchers wondered if the photon–metal interaction necessary to create a surface plasmon would prevent the plasmons from exhibiting quantum interference. "Our experiment shows this is not a concern," Fakonas says.

"We learned something new about the quantum mechanics of surface plasmons. The main thing is that we were able to validate the theoretical prediction; we showed that this type of interference is possible with plasmons, and we did a pretty clean measurement," he says. "The quantum interference displayed by plasmons appeared to be almost identical to that of photons, so I think it would be very difficult for someone to design a different structure that would improve upon this result."

The work was published in a paper titled "Two-plasmon quantum interference." In addition to Fakonas and Atwater, the other coauthors are Caltech undergraduate Hyunseok Lee and former undergraduate Yousif A. Kelaita (BS '12). The work was supported by funding from the Air Force Office of Scientific Research, and the waveguide was fabricated at the Kavli Nanoscience Institute at Caltech.

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Wednesday, April 16, 2014
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Teaching & Learning in the American System: Student-Teacher Interactions

Raiders of the Lost Can

There is more than one way to get an empty soup can to the top of a five-foot pyramid. One option might be to pick up the soup can with your hand, walk to the pyramid, and place it on top. But that would be the easy way out, and that's not how Caltech's mechanical engineering majors roll.

In fact, the students in this year's Mechanical Engineering 72 (ME72) class, a two-term engineering design lab for mechanical engineering majors, not only rolled, they crawled and flew their robotic inventions to deliver their team's soup can to the top of a wooden pyramid outfitted with steel ramps, while simultaneously deploying other robotic vehicles to conduct defensive maneuvers, preventing the opposing team from beating them to the top with their own color-coded soup can.

This was the 29th year of the ME72 competition, which doubles as the final exam for students enrolled in the class. Gathering in the Brown Gymnasium on March 11th were six teams, each composed of 3–5 students, along with 250 visiting middle school students from the Pasadena Unified School District and an enthusiastic crowd of alumni, onlookers, and photographers.

"This is the only time I have ever watched any sort of competition in a gym while I've been at Caltech," says Erika DeBenedictis, a senior from Blacker House. The spirit of competition was palpable as teams with names such as the Avengers, 40 Pc Chicken McNuggets, and Fellowship of the Can rallied to send their robots to the summit. There were midair collisions and numerous ground-based encounters that sometimes sent the much-sought soup can careening toward the bleachers while team members paced around the perimeter, driving their vehicles with handheld controllers.

The rules of this year's competition and the precise dimensions of the central pyramid were developed over the summer by ME72's instructor, Carl Ruoff, division technologist at the Jet Propulsion Laboratory. Last October when the class began, each team was given $400 worth of controllers and batteries and an $800 budget to construct whatever vehicles they dreamed up to meet the soup can challenge. Working with Ruoff, lecturer John Van Deusen, four teaching assistants, and a machine shop assistant, students periodically demonstrated their vehicles in front of their competitors, although, says Sandra Fang, one of course's teaching assistants and a senior in mechanical engineering at Caltech, "they often conceal some of the capabilities of their vehicles from other teams."

Fang declined to declare a favorite at the outset of the competition. As a student in last year's ME72 class, she knows how rugged the process can be, though she admits, "most of the TAs do have a favorite. After watching them work so hard all year, you really want to see your favorite team win."

The Avengers team opted for two tractor-like vehicles named "The Hulk" and "Iron Man." "During the first term," says junior Derek Kearney, an Avenger team member, "we figured out how to drive them and turn them right and left. In the second term we worked on getting them to pick up the can and climb up the ramp." Caltech junior Richie Hernandez, another Avenger team member, pointed out the intricate network of bicycle chain, sprockets, rubber bands, and magnets that made "The Hulk" a formidable warrior in the competition.

For the visiting middle schoolers, Raiders of the Lost Can was the culmination of a day spent on the Caltech campus "taking a lab tour, hearing a lecture on neuroscience, and talking about the relationship between neuroscience and programming robotics," according to Mitch Aiken, Caltech's associate director for educational outreach.

The competition got off to a rocky start. In the first three heats (teams competed two at a time, in four-minute heats), no one had successfully moved their soup can to the top of the pyramid, though they came close several times, either pitching it over the top or pushing it partway up a ramp. But finally success was achieved, and at the end of the double-elimination competition, 40 Pc Chicken McNuggets emerged victorious. One suspects they retired to the golden arches to enjoy the product that fueled their success.

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Cynthia Eller
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Students Face Off in Mechanical Engineering Competition
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Caltech Appoints Diana Jergovic to Newly Created Position of Vice President for Strategy Implementation

Caltech has named Diana Jergovic as its vice president for strategy implementation. In the newly created position, Jergovic will collaborate closely with the president and provost, and with the division chairs, faculty, and senior leadership on campus and at the Jet Propulsion Laboratory, to execute and integrate Caltech's strategic initiatives and projects and ensure that they complement and support the overall education and research missions of the campus and JPL. This appointment returns the number of vice presidents at the Institute to six.

"Supporting the faculty is Caltech's highest priority," says Edward Stolper, provost and interim president, "and as we pursue complex interdisciplinary and institutional initiatives, we do so with the expectation that they will evolve over a long time horizon. The VP for strategy implementation will help the Institute ensure long-term success for our most important new activities."

In her present role as associate provost for academic and budgetary initiatives at the University of Chicago, Jergovic serves as a liaison between the Office of the Provost and the other academic and administrative offices on campus, and advances campus-wide strategic initiatives. She engages in efforts spanning every university function, including development, major construction, and budgeting, as well as with faculty governance and stewardship matters. Jergovic also serves as chief of staff to University of Chicago provost Thomas F. Rosenbaum, Caltech's president-elect.

"In order to continue Caltech's leadership role and to define new areas of eminence, we will inevitably have to forge new partnerships and collaborations—some internal, some external, some both," Rosenbaum says. "The VP for strategy implementation is intended to provide support for the faculty and faculty leaders in realizing their goals for the most ambitious projects and collaborations, implementing ideas and helping create the structures that make them possible. I was looking for a person who had experience in delivering large-scale projects, understood deeply the culture of a top-tier research university, and could think creatively about a national treasure like JPL."

"My career has evolved in an environment where faculty governance is paramount," Jergovic says. "Over the years, I have cultivated a collaborative approach working alongside a very dedicated faculty leadership. My hope is to bring this experience to Caltech and to integrate it into the existing leadership team in a manner that simultaneously leverages my strengths and allows us together to ensure that the Institute continues to flourish, to retain its position as the world's leading research university, and to retain its recognition as such."

Prior to her position as associate provost, Jergovic was the University of Chicago's assistant vice president for research and education, responsible for the financial management and oversight of all administrative aspects of the Office of the Vice President for Research and Argonne National Laboratory. She engaged in research-related programmatic planning with a special emphasis on the interface between the university and Argonne National Laboratory. This ranged from the development of the university's Science and Technology Outreach and Mentoring Program (STOMP), a weekly outreach program administered by university faculty, staff, and students in low-income neighborhood schools on the South Side of Chicago, to extensive responsibilities with the university's successful bid to retain management of Argonne National Laboratory.

From 1994 to 2001, Jergovic was a research scientist with the university-affiliated National Opinion Research Center (NORC) and, in 2001, served as project director for NORC's Florida Ballot Project, an initiative that examined, classified, and created an archive of the markings on Florida's 175,000 uncertified ballots from its contested 2000 presidential election.

Jergovic earned a BS in psychology and an MA and PhD in developmental psychology, all from Loyola University Chicago, and an MBA from the Booth School of Business at the University of Chicago.

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An Equation to Describe the Competition Between Genes

Caltech researchers develop and verify predictive mathematical model

In biology, scientists typically conduct experiments first, and then develop mathematical or computer models afterward to show how the collected data fit with theory. In his work, Rob Phillips flips that practice on its head. The Caltech biophysicist tackles questions in cellular biology as a physicist would—by first formulating a model that can make predictions and then testing those predictions. Using this strategy, Phillips and his group have recently developed a mathematical model that accounts for the way genes compete with each other for the proteins that regulate their expression.

A paper describing the work appears in the current issue of the journal Cell. The lead authors on the paper are Robert Brewster and Franz Weinert, postdoctoral scholars in Phillips's lab.

"The thing that makes this study really interesting is that we did our calculations before we ever did any experiments," says Phillips, the Fred and Nancy Morris Professor of Biophysics and Biology at Caltech and principal investigator on the study. "Just as it is amazing that we have equations for the orbits of planets around stars, I think it's amazing that we are beginning to be able to write equations that predict the complex behaviors of a living cell."

A number of research teams are interested in modeling gene expression—accurately describing all the processes involved in going from a gene to the protein or other product encoded by that DNA. For simplicity's sake, though, most such models do not take competition into consideration. Instead, they assume that each gene has plenty of whatever it needs in order to be expressed—including the regulatory proteins called transcription factors. However, Phillips points out, there often is not enough transcription factor around to regulate all of the genes in a cell.  For one thing, multiple copies of a gene can exist within the same cell. For example, in the case of genes expressed on circular pieces of DNA known as plasmids, it is common to find hundreds of copies in a single cell. In addition, many transcription factors are capable of binding to a variety of different genes. So, as in a game of musical chairs, the genes must compete for a scarce resource—the transcription factors.

Phillips and his colleagues wanted to create a more realistic model by adding in this competition. To do so, they looked at how the level of gene expression varies depending on the amount of transcription factor present in the cell. To limit complexity, they worked with a relatively simple case—a gene in the bacterium E. coli that has just one binding site where a transcription factor can attach. In this case, when the transcription factor binds to the gene, it actually prevents the gene from making its product—it represses expression.

To build their mathematical model, the researchers first considered all the various ways in which the available transcription factor can interact with the copies of this particular gene that are present in the cell, and then developed a statistical theory to represent the situation.

"Imagine that you go into an auditorium, and you know there are a certain number of seats and a certain number of people. There are many different seating arrangements that could accommodate all of those people," Phillips says. "If you wanted to, you could systematically enumerate all of those arrangements and figure out things about the statistics—how often two people will be sitting next to each other if it's purely random, and so on. That's basically what we did with these genes and transcription factors."

Using the resulting model, the researchers were able to make predictions about what would happen if the level of transcription factor and the number of gene copies were independently varied so that the proteins were either in high demand or there were plenty to go around, for example.

With predictions in hand, the researchers next conducted experiments while looking at E. coli cells under a microscope. To begin, they introduced the genes on plasmids into the cells. They needed to track exactly how much transcription factor was present and the rate of gene expression in the presence of that level of transcription factor. Using fluorescent proteins, they were able to follow these changes in the cell over time: the transcription factor lit up red, while the protein expressed by the gene without the transcription factor attached glowed green. Using video fluorescence microscopy and a method, developed in the lab of Caltech biologist Michael Elowitz, for determining the brightness of a single molecule, the researchers were able to count the level of transcription factor present and the rate at which the green protein was produced as the cells grew and divided.

The team found that the experimental data matched the predictions they had made extremely well. "As expected, we find that there are two interesting regimes," says Brewster. "One is that there's just not enough protein to fill the demand. Therefore, all copies of the gene cannot be repressed simultaneously, and some portion will glow green all the time. In that case, there are correlations between the various copies of the genes. They know, in some sense, that the others exist. The second case is that there is a ton of this transcription factor around; in that case, the genes act almost exactly as if the other genes aren't there—there is enough protein to shut off all of the genes simultaneously."

The data fit so well with their model, in fact, that Phillips and his colleagues were able to use plots of the data to predict how many copies of the plasmid would be found in a cell as it grew and multiplied at various points throughout the cell cycle.

"Many times in science you start out trying to understand something, and then you get so good at understanding it that you are able to use it as a tool to measure something else," says Phillips. "Our model has become a tool for measuring the dynamics of how plasmids multiply. And the dynamics of how they multiply isn't what we would have naively expected. That's a little hint that we're pursuing right now."

Overall, he says, "this shows that the assertion that biology is too complicated to be predictive might be overly pessimistic, at least in the context of bacteria."

The work described in the paper, "The Transcription Factor Titration Effect Dictates Level of Gene Expression," was supported by the National Institutes of Health and by the Fondation Pierre-Gilles de Gennes. Additional coauthors are Mattias Rydenfelt, a graduate student in physics at Caltech; Hernan Garcia, a former member of Phillips's lab who is now at Princeton University; and Dan Song, a graduate student at Harvard Medical School.

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