Caltech Names Thomas F. Rosenbaum as New President

To: The Caltech Community

From: Fiona Harrison, Benjamin M. Rosen Professor of Physics and Astronomy, and Chair, Faculty Search Committee; and David Lee, Chair, Board of Trustees, and Chair, Trustee Selection Committee

Today it is our great privilege to announce the appointment of Thomas F. Rosenbaum as the ninth president of the California Institute of Technology.

Dr. Rosenbaum, 58, is currently the John T. Wilson Distinguished Service Professor of Physics at the University of Chicago, where he has served as the university's provost for the past seven years. As a distinguished physicist and expert on condensed matter physics, Dr. Rosenbaum has explored the quantum mechanical nature of materials, making major contributions to the understanding of matter near absolute zero, where such quantum mechanical effects dominate. His experiments in quantum phase transitions in matter are recognized as having played a key role in placing these transitions on a theoretical level equivalent to that which has been developed for classical systems.

But Dr. Rosenbaum's scientific achievements were not solely what captured and held the attention of those involved in the presidential search. We on the search committee were impressed by Dr. Rosenbaum's deep dedication, as Chicago's provost, to both undergraduate and graduate education—both critical parts of Caltech's mission. He has had responsibility for an unusually broad range of institutions and intellectual endeavors. Among his achievements as provost was the establishment of the Institute for Molecular Engineering in 2011, the University of Chicago's very first engineering program, in collaboration with Argonne National Lab.

We also believe that Dr. Rosenbaum's focus on strengthening the intellectual ties between the University of Chicago and Argonne National Lab will serve him well in furthering the Caltech-JPL relationship.

As provost, Dr. Rosenbaum was also instrumental in establishing collaborative educational programs serving communities around Chicago's Hyde Park campus, including the university's founding of a four-campus charter school that was originally designed to further fundamental research in education but which has also achieved extraordinary college placement results for disadvantaged Chicago youths.

This successful conclusion to our eight-month presidential search was result of the hard work of the nine-member Faculty Search Committee, chaired by Fiona Harrison, and the 10-member Trustee Selection Committee, chaired by David Lee. We are grateful both to the trustees and faculty on our two committees who made our job so very easy as well as to those faculty, students, staff, and alumni who provided us with input and wisdom as we scoured the country for just the right person for our Caltech.

"Tom embodies all the qualities the faculty committee hoped to find in our next president," Harrison says. "He is a first-rate scholar and someone who understands at a deep level the commitment to fundamental inquiry that characterizes Caltech. He is also the kind of ambitious leader who will develop the faculty's ideas into the sorts of innovative ventures that will maintain Caltech's position of prominence in the next generation of science and technology."

"The combination of deep management experience and visionary leadership Tom brings will serve Caltech extremely well in the coming years," Lee adds. "The Board is excited about collaborating closely with Tom to propel the Institute to new levels of scientific leadership."

"The Caltech community's palpable and deep commitment to the Institute came through in all my conversations, and it forms the basis for Caltech's and JPL's lasting impact," Dr. Rosenbaum says. "It will be a privilege to work closely with faculty, students, staff, and trustees to explore new opportunities, building on Caltech's storied accomplishments."

Dr. Rosenbaum received his bachelor's degree in physics with honors from Harvard University in 1977, and both an MA and PhD in physics from Princeton University in 1979 and 1982, respectively. He did research at Bell Laboratories and at IBM Watson Research Center before joining the University of Chicago's faculty in 1983. Dr. Rosenbaum directed the university's Materials Research Laboratory from 1991 to 1994 and its interdisciplinary James Franck Institute from 1995 to 2001 before serving as vice president for research and for Argonne National Laboratory from 2002 to 2006. He was named the university's provost in 2007. His honors include an Alfred P. Sloan Research Fellowship, a Presidential Young Investigator Award, and the William McMillan Award for "outstanding contributions to condensed matter physics." Dr. Rosenbaum is an elected fellow of the American Physical Society, the American Association for the Advancement of Science, and the American Academy of Arts and Sciences.

Joining the Caltech faculty will be Dr. Rosenbaum's spouse, Katherine T. Faber, the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University. Dr. Faber's research focuses on understanding stress fractures in ceramics, as well as on the fabrication of ceramic materials with controlled porosity, which are important as thermal and environmental barrier coatings for engine components. Dr. Faber is also the codirector of the Northwestern University-Art Institute of Chicago Center for Scientific Studies in the Arts (NU-ACCESS), which employs advanced materials science techniques for art history and restoration. Dr. Rosenbaum and Dr. Faber have two sons, Daniel, who graduated from the University of Chicago in 2012, and Michael, who is currently a junior there.

Dr. Rosenbaum will succeed Jean-Lou Chameau, who served the Institute from 2006 to 2013, and will take over the helm from interim president and provost Ed Stolper on July 1, 2014. The board, the search committee, and, indeed, the entire Institute owes Dr. Stolper a debt of gratitude for his unwavering commitment to Caltech, and for seamlessly continuing the Institute's forward momentum through his interim presidency.

As you meet Dr. Rosenbaum today and over the coming months, and learn more about his vision for Caltech's future, we believe that you will quickly come to see why he is so well suited to guide Caltech as we continue to pursue bold investigations in science and engineering, to ready the next generation of scientific and thought leaders, and to benefit humankind through research that is integrated with education.

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Caltech Students Arrive at Solar Decathlon 2013

DALE is nearly ready to face the judges. The Dynamic Augmented Living Environment, Caltech's collaboration with the Southern California Institute of Architecture (SCI-Arc) is now on-site at the Department of Energy's 2013 Solar Decathlon competition site in Irvine, California.

The SCI-Arc/Caltech team has been planning DALE, its unique and completely solar-powered home, since its competition proposal was accepted in January 2012, along with proposals from 19 other American and international teams. Nearly 40 Caltech students participated in the design process, most of which took place in an engineering project course called Introduction to Multidisciplinary Systems Engineering, and offered during the 2012-2013 academic year. Of the students in this course, taught by Melany Hunt, Dotty and Dick Hayman Professor of Mechanical Engineering and a vice provost, seven stayed on, spending their summer actually building the sustainable house.

Once the majority of construction was complete in late September, the SCI-Arc/Caltech team had to pack up DALE and physically move the entire house from its construction site on the SCI-Arc campus in downtown Los Angeles more than 40 miles south to Orange County Great Park in Irvine, where this year's competition will be held starting on October 3.

While some of DALE's competitors had to employ the use of large cranes to transport their entries or coordinate weeks-long international transportation to the competition site, project manager Andrew Gong (BS '12) says that DALE only spent about three-and-a-half hours in transit. "We picked up DALE with a heavy-duty forklift and placed it on long trucks," Gong says. "And there wasn't any damage other than expected small scrapes to the bottom from the forks."

DALE's design consists of two configurable, box-like modules—one kitchen and bathroom module, and one living and sleeping space module—that can move together or apart. When in the open configuration, DALE's design exploits the ambient outdoor temperature to heat or cool the house, helping to maintain a comfortable temperature within the house without using extra energy for heating and air-conditioning. This moving house was designed with sustainability in mind, but the modules also made it easier for team DALE to truck its house down the interstate to Irvine. "Since the house is composed of modules, it was actually fairly simple to pack up and ship. The main issue was just making sure everything got packed on time," Gong says.

The SCI-Arc/Caltech collaboration is one of 20 teams in the Department of Energy competition, each challenged to design and build affordable, attractive, energy-efficient houses that have the comforts of modern living but are powered only by the sun. As the name "Solar Decathlon" implies, teams will compete for the best total number of points in 10 contests. A panel of experts will use the contests to judge and score the entries based on features ranging from architecture and market appeal to affordability and each house's ability to host a movie night—called the Home Entertainment Contest.

The SCI-Arc/Caltech team wants DALE to score well in the overall competition, but the Caltech team members hope they score especially well in one particular aspect: the Engineering Contest. In this contest, a jury made up of professional engineers will judge each house based on the home's functionality, efficiency, innovation, reliability, and project documentation. "In 2011, with CHIP—our first Solar Decathlon entry—we came in second place. With DALE, we took that second place as a challenge," says Gong, "because now we have to get first, obviously!"

To optimize DALE's energy efficiency, the Caltech members of the team spent months calculating and modeling the home's likely energy usage during the competition. Thirty years of Orange County weather data were used to predict heating and air-conditioning needs for the October competition. "The contests are held on different days of the competition, and we based the energy budget on the contests we will have on a given day: the cooking contest, movie night, heating and air-conditioning test, etc.," Gong says. "With our competition energy budget, we then modeled out the performance required from the solar panels to meet that energy demand," Gong says.

According to their calculations, DALE's oversized solar panels will allow the house to be net-zero during the decathlon—meaning it will produce as much energy as it consumes. And in the future, if the house was used in the longer daylight hours of summer, DALE could produce far more energy than it uses, Gong adds.

The SCI-Arc/Caltech team also designed an energy-saving mobile app for DALE that would allow its owner to monitor the home's real-time energy supply and consumption and take steps to use less energy. "As a team, we are aiming to create a house that is not only energy efficient by itself, but also encourages the inhabitants to live a greener lifestyle," Caltech electrical engineering student Do Hee Kim says on the DALE website. "We have made it simple for homeowners to execute these actions by having the ability to remotely turn on and off home appliances," Kim says.

Visitors will be able to interact with DALE and explore its innovative features during public viewings scheduled for October 3–6 and 10–13 from 11 a.m. to 7 p.m. In addition, visitors arriving at 2:30 will get to see the home reconfigured in real time, a feature that sets DALE apart from the other Solar Decathlon entries. The winners will be announced on October 12, and just a few days later, the team will pack up for the move back to Los Angeles. After the competition, DALE will be displayed at the SCI-Arc campus.

And for any house hunters visiting the competition, the SCI-Arc/Caltech team has good news: DALE is for sale and can be delivered to a new owner. Although the Department of Energy provides a limited amount of seed money for Solar Decathlon teams, fundraising is necessary to cover the actual costs of production; funds from the sale of the home will go to recoup some this year's competition costs and could also help support an entry bid for the 2015 Solar Decathlon.

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Caltech Named World's Top University in Times Higher Education Global Ranking

For the third year in a row, the California Institute of Technology has been rated the world's number one university in the Times Higher Education global ranking of the top 200 universities.

Harvard University, Oxford University, Stanford University, and the Massachusetts Institute of Technology round out the top five schools in the 2013–2014 rankings.

Times Higher Education compiled the listing using the same methodology as in the 2011–2012 and 2012–2013 surveys. 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. The data were collected, analyzed, and verified by Thomson Reuters.

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

Kathy Svitil
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Spirals of Light May Lead to Better Electronics

A group of researchers at the California Institute of Technology (Caltech) has created the optical equivalent of a tuning fork—a device that can help steady the electrical currents needed to power high-end electronics and stabilize the signals of high-quality lasers. The work marks the first time that such a device has been miniaturized to fit on a chip and may pave the way to improvements in high-speed communications, navigation, and remote sensing.

"When you're tuning a piano, a tuning fork gives a standardized pitch, or reference sound frequency; in optical resonators the 'pitch' corresponds to the color, or wavelength, of the light. Our device provides a consistent light frequency that improves both optical and electronic devices when it is used as a reference," says Kerry Vahala, Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics. Vahala is also executive officer for applied physics and materials science and an author on the study describing this new work, published in the journal Nature Communications.

A good tuning fork controls the release of its acoustical energy, ringing just one pitch at a particular sound frequency for a long time; this sustaining property is called the quality factor. Vahala and his colleagues transferred this concept to their optical resonator, focusing on the optical quality factor and other elements that affect frequency stability.

The researchers were able to stabilize the light's frequency by developing a silica glass chip resonator with a specially designed path for the photons in the shape of what is called an Archimedean spiral. "Using this shape allows the longest path in the smallest area on a chip. We knew that if we made the photons travel a longer path, the whole device would become more stable," says Hansuek Lee, a senior researcher in Vahala's lab and lead author on the paper.

Frequency instability stems from energy surges within the optical resonator—which are unavoidable due to the laws of thermodynamics. Because the new resonator has a longer path, the energy changes are diluted, so the power surges are dampened—greatly improving the consistency and quality of the resonator's reference signal, which, in turn, improves the quality of the electronic or optical device.

In the new design, photons are applied to an outer ring of the spiraled resonator with a tiny light-dispensing optic fiber; the photons subsequently travel around four interwoven Archimedean spirals, ultimately closing the path after traveling more than a meter in an area about the size of a quarter—a journey 100 times longer than achieved in previous designs. In combination with the resonator, a special guide for the light was used, losing 100 times less energy than the average chip-based device.

In addition to its use as a frequency reference for lasers, a reference cavity could one day play a role equivalent to that of the ubiquitous quartz crystal in electronics. Most electronics systems use a device called an oscillator to provide power at very precise frequencies. In the past several years, optical-based oscillators—which require optical reference cavities—have become better than electronic oscillators at delivering stable microwave and radio frequencies. While these optical oscillators are currently too large for use in small electronics, there is an effort under way to miniaturize their key subcomponents—like Vahala's chip-based reference cavity.

"A miniaturized optical oscillator will represent a shift in the traditional roles of photonics and electronics. Currently, electronics perform signal processing while photonics rule in transporting information from one place to another over fiber-optic cable. Eventually, oscillators in high-performance electronics systems, while outwardly appearing to be electronic devices, will internally be purely optical," Vahala says.

"The technology that Kerry and his group have introduced opens a new avenue to move precision optical frequency sources out of the lab and onto a compact, robust and integrable silicon-based platform," says Scott Diddams, physicist and project leader at the National Institute of Standards and Technology, recent Moore Distinguished Scholar at Caltech and a coauthor on the study. "It opens up many new and unexplored options for building systems that could have greater impact to 'real-world' applications," Diddams says.

The paper, titled "Spiral resonators for on-chip laser frequency stabilization," was published online in Nature Communications on September 17. Other Caltech coauthors on the study include graduate students Myoung Gyun Suh and Tong Chen (PhD '13), and postdoctoral scholar Jiang Li (PhD '13). The project was in collaboration with Caltech startup company hQphotonics. This work was funded by the Defense Advanced Research Projects Agency; the Caltech's Kavli Nanoscience Institute; and the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation.

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New Gut Bacterium Discovered in Termite's Digestion of Wood

Caltech researchers find new species of microbe responsible for acetogenesis, an important process in termite nutrition.

When termites munch on wood, the small bits are delivered to feed a community of unique microbes living in their guts, and in a complex process involving multiple steps, these microbes turn the hard, fibrous material into a nutritious meal for the termite host. One key step uses hydrogen to convert carbon dioxide into organic carbon—a process called acetogenesis—but little is known about which gut bacteria play specific roles in the process. Utilizing a variety of experimental techniques, researchers from the California Institute of Technology (Caltech) have now discovered a previously unidentified bacterium—living on the surface of a larger microorganism in the termite gut—that may be responsible for most gut acetogenesis.

"In the termite gut, you have several hundred different species of microbes that live within a millimeter of one another. We know certain microbes are present in the gut, and we know microbes are responsible for certain functions, but until now, we didn't have a good way of knowing which microbes are doing what," says Jared Leadbetter, professor of environmental microbiology at Caltech, in whose laboratory much of the research was performed. He is also an author of a paper about the work published the week of September 16 in the online issue of the Proceedings of the National Academy of Sciences (PNAS).

Acetogenesis is the production of acetate (a source of nutrition for termites) from the carbon dioxide and hydrogen generated by gut protozoa as they break down decaying wood. In their study of "who is doing what and where," Leadbetter and his colleagues searched the entire pool of termite gut microbes to identify specific genes from organisms responsible for acetogenesis.

The researchers began by sifting through the microbes' RNA—genetic information that can provide a snapshot of the genes active at a certain point in time. Using RNA from the total pool of termite gut microbes, they searched for actively transcribed formate dehydrogenase (FDH) genes, known to encode a protein necessary for acetogenesis. Next, using a method called multiplex microfluidic digital polymerase chain reaction (digital PCR), the researchers sequestered the previously unstudied individual microbes into tiny compartments to identify the actual microbial species carrying each of the FDH genes. Some of the FDH genes were found in types of bacteria known as spirochetes—a previously predicted source of acetogenesis. Yet it appeared that these spirochetes alone could not account for all of the acetate produced in the termite gut.

Initially, the Caltech researchers were unable to identify the microorganism expressing the single most active FDH gene in the gut. However, the first authors on the study, Adam Rosenthal, a postdoctoral scholar in biology at Caltech, and Xinning Zhang (PhD '10, Environmental Science and Engineering), noticed that this gene was more abundant in the portion of the gut extract containing wood chunks and larger microbes, like protozoans. After analyzing the chunkier gut extract, they discovered that the single most active FDH gene was encoded by a previously unstudied species from a group of microbes known as the deltaproteobacteria. This was the first evidence that a substantial amount of acetate in the gut may be produced by a non-spirochete.

Because the genes from this deltaproteobacterium were found in the chunky particulate matter of the termite gut, the researchers thought that perhaps the newly identified microbe attaches to the surface of one of the chunks. To test this hypothesis, the researchers used a color-coded visualization method called hybridization chain reaction-fluorescent in situ hybridization, or HCR-FISH.

The technique—developed in the laboratory of Niles Pierce, professor of applied and computational mathematics and bioengineering at Caltech, and a coauthor on the PNAS study—allowed the researchers to simultaneously "paint" cells expressing both the active FDH gene and a gene identifying the deltoproteobacterium with different fluorescent colors simultaneously. "The microfluidics experiment suggested that the two colors should be expressed in the same location and in the same tiny cell," Leadbetter says. And, indeed, they were. "Through this approach, we were able to actually see where the new deltaproteobacterium resided. As it turns out, the cells live on the surface of a very particular hydrogen-producing protozoan."

This association between the two organisms makes sense based on what is known about the complex food web of the termite gut, Leadbetter says. "Here you have a large eukaryotic single cell—a protozoan—which is making hydrogen as it degrades wood, and you have these much smaller hydrogen-consuming deltaproteobacteria attached to its surface," he says. "So, this new acetogenic bacterium is snuggled up to its source of hydrogen just as close as it can get."

This intimate relationship, Leadbetter says, might never have been discovered relying on phylogenetic inference—the standard method for matching a function to a specific organism. "Using phylogenetic inference, we say, 'We know a lot about this hypothetical organism's relatives, so without ever seeing the organism, we're going to make guesses about who it is related to," he says. "But with the techniques in this study, we found that our initial prediction was wrong. Importantly, we have been able to determine the specific organism responsible and a location of the mystery organism, both of which appear to be extremely important in the consumption of hydrogen and turning it into a product the insect can use." These results not only identify a new source for acetogenesis in the termite gut—they also reveal the limitations of making predictions based exclusively on phylogenetic relationships.

Other Caltech coauthors on the paper titled "Localizing transcripts to single cells suggests an important role of uncultured deltaproteobacteria in the termite gut hydrogen economy," are graduate student Kaitlyn S. Lucey (environmental science and engineering), Elizabeth A. Ottesen (PhD '08, biology), graduate student Vikas Trivedi (bioengineering), and research scientist Harry M. T. Choi (PhD '10, bioengineering). This work was funded by the U.S. Department of Energy, the National Science Foundation, the National Institutes of Health, the Programmable Molecular Technology Center within the Beckman Institute at Caltech, a Donna and Benjamin M. Rosen Center Bioengineering scholarship, and the Center for Environmental Microbial Interactions at Caltech.

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Team Led by Caltech Wins Second $10 Million Award for Research in Molecular Programming

During the past century, programmable technologies evolved from spinning gears and vacuum tubes to transistors and microchips. Now, a group of Caltech researchers and their colleagues at the University of Washington, Harvard University, and UC San Francisco are exploring how biologically important molecules—like DNA, RNA, and proteins—could be the next generation of programmable devices.

Erik Winfree, professor of computer science, computation, and neural systems, and bioengineering, along with collaborators at Caltech and the University of Washington, began the Molecular Programming Project (MPP) in 2008, as part of an NSF Expeditions in Computing award to develop practices for programming biomolecules—much like a computer code—to perform designated functions. Over the past five years, the researchers have programmed DNA to carry out a number of tasks, from solving basic math and pattern-recognition problems to more mechanical tasks like programming RNA and DNA to selectively amplify fluorescent signals for biological microscopy. Through these initial experiments, the researchers have shown that it is possible to systematically encode specialized tasks within DNA molecules.

"Computer science gave us this idea that many tasks can actually be done with different types of devices," Winfree says. For example, a 19th-century cash register and a 21st-century computer can both be used to calculate sums, though they perform the same task very differently. At first glance, writing a computer program and programming a DNA molecule may seem like very different endeavors, but "each one provides a systematic way of implementing automated behaviors, and they are both based on similar principles of information technology," Winfree says.

Expanding the team to include five additional faculty who bring expertise in structural and dynamic DNA nanotechnology, synthetic biology, computer-aided design, programming languages, and compilers, Winfree and his colleagues recently received a second Expeditions in Computing award to take their work in molecular programming to the next level: from proof-of-principle demonstrations to putting the technology in the hands of users in biology, chemistry, physics, and materials science.

The researchers aim to use molecular programming to establish general-purpose, reliable, and easy-to-use methods for engineering complex nanoscale systems from biomolecules. In the hands of users, these methods could be used to create novel self-assembling electronic and optical devices, powerful nanoscale tools for the study of biology, and programmable molecular circuits for the diagnosis and treatment of disease. In one application, the researchers hope to program DNA molecules to carry out recognition and logical circuitry for exquisitely targeted drug delivery, thus reducing drug side effects and increasing efficacy.

Today, the largest synthetic molecular programs—human-designed sequences of the A, T, C, and G bases that make up DNA—contain on the order of 60,000 bases. "That's comparable to the amount of RAM memory in my first computer, a 1983 Apple II+," says Winfree. Designed systems in the future will only become more complex, a challenge that MPP researchers aim to tackle by approaching biological systems with something computer scientists call the abstraction hierarchy.

"In some sense computer science is the art of managing complexity, because you design things that have billions of components, but a single person simply cannot understand all the details and interactions," he says. "Abstraction is a way of hiding a component's details while making it easy to incorporate into higher-order components—which, themselves, can also be abstracted. For example, you don't need to know the details of a multiplication circuit in order to use it to make a circuit for factoring." In the molecular world, the task might be different—like transporting a molecular cargo to a designated location—but abstraction is still essential for combining simpler systems into larger ones to perform tasks of greater complexity.

"Over the next several decades, the MPP seeks to develop the principles and practice for a new engineering discipline that will enable the function of molecules to be programmed with the ease and rigor that computers are today, while achieving the sophistication, complexity, and robustness evident in the programmable DNA, RNA, and protein machinery of biology," says Niles Pierce, professor of applied and computational mathematics and bioengineering at Caltech and member of the MPP.

To integrate these fields, the MPP has brought together an interdisciplinary team of computer scientists, chemists, electrical engineers, physicists, roboticists, mathematicians, and bioengineers—all of whom have a strong research interest in the intersection of information, biology, and the molecular world. The team will explore the potential of molecular programming from many perspectives.

"Because of the diverse expertise that is required to work on these challenges, the participating students and faculty come from an unusual array of fields," Pierce says. "It's a lot of fun to be in a room with this group of people to see where the discussions lead."

The 2013 Expeditions award was granted for the proposal "Molecular Programming Architectures, Abstractions, Algorithms, and Applications." Winfree and Pierce are joined on the project by four other collaborators at Caltech: Jehoshua (Shuki) Bruck, Gordon and Betty Moore Professor of Computation and Neural Systems and Electrical Engineering; Richard Murray, Thomas E. and Doris Everhart Professor of Control and Dynamical Systems and Bioengineering; Lulu Qian, assistant professor of bioengineering; and Paul Rothemund, senior research associate in bioengineering, computing and mathematical sciences, and computation and neural systems. Other collaborators include Eric Klavins and Georg Seelig from the University of Washington, Peng Yin and William Shih from Harvard, and Shawn Douglas from UC San Francisco.

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Caltech to Offer Online Courses through edX

To expand its involvement in online learning, the California Institute of Technology will offer courses through the online education platform edX beginning this October.

The edX course platform is an online learning initiative launched in 2012 by founding partners Harvard University and the Massachusetts Institute of Technology (MIT). Caltech's rigorous online course offerings will join those of 28 other prestigious colleges and universities in the edX platform's "xConsortium."

This new partnership with edX comes one year after Caltech offered three courses through the online learning platform Coursera in fall 2012. The Institute will now offer courses through both platforms.

"Coursera and edX have some foundational differences which are of interest to the faculty," says Cassandra Horii, director of teaching and learning programs at Caltech. Both organizations offer their courses at no cost to participating students; edX, however, operates as a nonprofit and plans to partner with only a small number of institutions, whereas Coursera—a for-profit, self-described "social entrepreneurship company"—partners with many institutions and state university systems.

The two platforms also emphasize different learning strategies, says Horii. "Coursera has a strong organizational principle built around lectures, so a lot of the interactivity is tied right into the video," she says. Though edX still enables the use of video lectures, a student can customize when he or she would like to take quizzes and use learning resources. In addition, edX allows faculty to embed a variety of learning materials—like textbook chapters, discussions, diagrams, and tables—directly into the platform's layout.

In the future, data collected from both platforms could provide valuable information about how students best learn certain material, especially in the sciences. "Caltech occupies this advanced, really rigorous scientific education space, and in general our interest in these online courses is to maintain that rigor and quality," Horii says. "So, with these learning data, we have some potential contributions to make to the general understanding of learning in this niche that we occupy."

Even before joining edX and Coursera, Caltech had already become an example in the growing trend of Massive Open Online Courses (MOOCs). Yaser Abu-Mostafa, professor of electrical engineering and computer science, developed his own MOOC on machine learning, called "Learning from Data," and offered it on YouTube and iTunes U beginning in April 2012.

Since its debut, Abu-Mostafa's MOOC has reached more than 200,000 participants, and it received mention in the NMC Horizon Report: 2013 Higher Education Edition—the latest edition of an annual report highlighting important trends in higher education. The course will be offered again in fall 2013 on iTunes U, and is now also open for enrollment in edX.

Although Caltech is now actively exploring several outlets for online learning, the Institute's commitment to educational outreach is not a recent phenomenon. In the early 1960s, Caltech physicist Richard Feynman reorganized the Institute's introductory physics course, incorporating contemporary research topics and making the course more engaging for students. His lectures were recorded and eventually incorporated into a widely popular physics book, The Feynman Lectures on Physics, which has sold millions of copies in a dozen languages.

Continuing in the tradition set by Feynman, the MOOCs at Caltech seek to provide a high-quality learning environment that is rigorous but accessible. "No dumbing down of courses for popular consumption . . . no talking over people's heads either; at Caltech, we explain things well because we understand them well," adds Abu-Mostafa.

More information on Caltech's online learning opportunities is available on the Online Education website.

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Friday, October 4, 2013

Undergraduate Teaching Assistant Orientation

Thursday, October 17, 2013
Athenaeum – The Athenaeum


Made-to-Order Materials

Caltech engineers focus on the nano to create strong, lightweight materials

The lightweight skeletons of organisms such as sea sponges display a strength that far exceeds that of manmade products constructed from similar materials. Scientists have long suspected that the difference has to do with the hierarchical architecture of the biological materials—the way the silica-based skeletons are built up from different structural elements, some of which are measured on the scale of billionths of meters, or nanometers. Now engineers at the California Institute of Technology (Caltech) have mimicked such a structure by creating nanostructured, hollow ceramic scaffolds, and have found that the small building blocks, or unit cells, do indeed display remarkable strength and resistance to failure despite being more than 85 percent air.

"Inspired, in part, by hard biological materials and by earlier work by Toby Schaedler and a team from HRL Laboratories, Caltech, and UC Irvine on the fabrication of extremely lightweight microtrusses, we designed architectures with building blocks that are less than five microns long, meaning that they are not resolvable by the human eye," says Julia R. Greer, professor of materials science and mechanics at Caltech. "Constructing these architectures out of materials with nanometer dimensions has enabled us to decouple the materials' strength from their density and to fabricate so-called structural metamaterials which are very stiff yet extremely lightweight."

At the nanometer scale, solids have been shown to exhibit mechanical properties that differ substantially from those displayed by the same materials at larger scales. For example, Greer's group has shown previously that at the nanoscale, some metals are about 50 times stronger than usual, and some amorphous materials become ductile rather than brittle. "We are capitalizing on these size effects and using them to make real, three-dimensional structures," Greer says.

In an advance online publication of the journal Nature Materials, Greer and her students describe how the new structures were made and responded to applied forces.

The largest structure the team has fabricated thus far using the new method is a one-millimeter cube. Compression tests on the the entire structure indicate that not only the individual unit cells but also the complete architecture can be endowed with unusually high strength, depending on the material, which suggests that the general fabrication technique the researchers developed could be used to produce lightweight, mechanically robust small-scale components such as batteries, interfaces, catalysts, and implantable biomedical devices.

Greer says the work could fundamentally shift the way people think about the creation of materials. "With this approach, we can really start thinking about designing materials backward," she says. "I can start with a property and say that I want something that has this strength or this thermal conductivity, for example. Then I can design the optimal architecture with the optimal material at the relevant size and end up with the material I wanted."

The team first digitally designed a lattice structure featuring repeating octahedral unit cells—a design that mimics the type of periodic lattice structure seen in diatoms. Next, the researchers used a technique called two-photon lithography to turn that design into a three-dimensional polymer lattice. Then they uniformly coated that polymer lattice with thin layers of the ceramic material titanium nitride (TiN) and removed the polymer core, leaving a ceramic nanolattice. The lattice is constructed of hollow struts with walls no thicker than 75 nanometers.

"We are now able to design exactly the structure that we want to replicate and then process it in such a way that it's made out of almost any material class we'd like—for example, metals, ceramics, or semiconductors—at the right dimensions," Greer says.

In a second paper, scheduled for publication in the journal Advanced Engineering Materials, Greer's group demonstrates that similar nanostructured lattices could be made from gold rather than a ceramic. "Basically, once you've created the scaffold, you can use whatever technique will allow you to deposit a uniform layer of material on top of it," Greer says.

In the Nature Materials work, the team tested the individual octahedral cells of the final ceramic lattice and found that they had an unusually high tensile strength. Despite being repeatedly subjected to stress, the lattice cells did not break, whereas a much larger, solid piece of TiN would break at much lower stresses. Typical ceramics fail because of flaws—the imperfections, such as holes and voids, that they contain. "We believe the greater strength of these nanostructured materials comes from the fact that when samples become sufficiently small, their potential flaws also become very small, and the probability of finding a weak flaw within them becomes very low," Greer says. So although structural mechanics would predict that a cellular structure made of TiN would be weak because it has very thin walls, she says, "we can effectively trick this law by reducing the thickness or the size of the material and by tuning its microstructure, or atomic configurations."

Additional coauthors on the Nature Materials paper, "Fabrication and Deformation of Three-Dimensional Hollow Ceramic Nanostructures," are Dongchan Jang, who recently completed a postdoctoral fellowship in Greer's lab, Caltech graduate student Lucas Meza, and Frank Greer, formerly of the Jet Propulsion Laboratory (JPL). The work was supported by funding from the Dow-Resnick Innovation Fund at Caltech, DARPA's Materials with Controlled Microstructural Architecture program, and the Army Research Office through the Institute for Collaborative Biotechnologies at Caltech. Some of the work was carried out at JPL under a contract with NASA, and the Kavli Nanoscience Institute at Caltech provided support and infrastructure.

The lead author on the Advanced Engineering Materials paper, "Design and Fabrication of Hollow Rigid Nanolattices Via Two-Photon Lithography," is Caltech graduate student Lauren Montemayor. Meza is a coauthor. In addition to support from the Dow-Resnick Innovation Fund, this work received funding from an NSF Graduate Research Fellowship.

Kimm Fesenmaier
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