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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Caltech and JPL Experts Discuss Climate Change

In today's installment of our Earth Week 2014 features, Caltech experts share their knowledge about climate change.


Caltech professor Jess Adkins, a geochemist and paleoclimatologist, offers insight into global warming in the video "Is There Hope for Planet Earth?" produced by Green Wish, a nonprofit organization that funds green initiatives at the local level. In the video, Adkins talks about the history of climate change, where we are today, and what we can do to mitigate its impact in the future.


On April 22—Earth Day—the Caltech Center for Teaching, Learning, & Outreach sponsored an "Ask A Scientist" panel on the Caltech campus to answer questions about climate change and earth sciences. Panel members included David Crisp, JPL senior research scientist and principal investigator of the NASA Earth System Science Pathfinder Orbiting Carbon Observatory mission; Joshua Fisher, JPL research scientist, Water and Carbon Cycles Group; science communicator and education specialist Laura Tenenbaum; and Caltech alumnus Julius Su (BS '98 and '99, PhD '07), cofounder of Su-Kam Intelligent Education Systems (SKIES). Su used the SKIES iPad app, an online learning and information crowdsourcing tool, to relay online and audience questions to the panelists. The video is a recording of the live event.


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Caltech Celebrates Earth Week

Events and online features honor Caltech's commitment to sustainability

Caltech joins the world in celebrating Earth Week, April 21–25, 2014, with events, news, and features highlighting our past, present, and future contributions to a healthier, cleaner, and greener planet.

Check out our homepage and Facebook, Twitter, and YouTube pages for daily Earth Week coverage, including features on Caltech's "Sustainability Heroes" and the centers where Caltech researchers are advancing sustainability, energy, and environmental science as well as highlights of our pioneering work to green the Caltech campus.

Through research and application, Caltech faculty, students, staff, and supporters/partners are actively engaged in protecting our earth and ensuring a sustainable future, not just on Earth Day but throughout the year.

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Airborne Over Iceland: Charting Glacier Dynamics

Mark Simons, professor of geophysics at Caltech, along with graduate student Brent Minchew, recently logged over 40 hours of flight time mapping the surface of Iceland's glaciers. Flying over two comparatively small ice caps, Hofsjökull and Langjökull, they traveled with NASA pilots and engineers in a retrofitted Gulfstream III business jet, crisscrossing the glaciers numerous times. Using a radar instrument designed at the Jet Propulsion Laboratory (JPL) and mounted on the underbelly of the plane, they imaged the surface of the glaciers, obtaining precise data on the velocity at which these rivers of ice flow downstream.

Following a set of test flights in Iceland in 2009, Simons and Minchew went to Iceland in June 2012 to systematically image the two ice caps at the beginning of the summer melt season. They have just returned from a February 2014 expedition aimed at setting a baseline for glacier velocity—during the winter freeze, meltwater should not play as significant a role in glacier dynamics. They sat down recently to discuss the science and the adventure of monitoring Iceland's glaciers.

Why go to Iceland to study glaciers?

Mark Simons: Iceland is an ideal natural laboratory. The glaciers there are small enough that you can do detailed measurements of them, and afterward you can process the data and analyze each ice cap in its entirety without needing overwhelming computer resources. This manageable scale lets us explore a wide range of models. Glaciers in Greenland or Antarctica are far too big for that. Logistics are also a lot easier in Iceland. We can drive up to the glaciers in just a few hours from downtown Reykjavik.

Most importantly, the Icelanders have a long history of studying these ice caps. In particular, they have nearly complete maps of the ice-bedrock interface. We can complement this information with continuous maps of the daily movement or strain of the glacier surface as well as maps of the topography of the glacier surface. These data are then combined to constrain models of glacier dynamics.

How can you map bedrock that is under hundreds of feet of ice?

Brent Minchew: Our collaborators at the University of Iceland have been doing this work for decades. Helgi Björnsson and Finnur Pálsson mapped the subglacial bedrock by dragging long radar antennas behind snowmobiles driven over the glaciers. They use long-wavelength radar that penetrates through the ice to the underlying bedrock. By looking at the reflection of the radar signals, they can estimate where the interface is between ice and bedrock. They are expert at studying the cryosphere—the earth's frozen regions, including ice caps, glaciers, and sea ice—as you might expect given their location so far north of the equator.

Is this similar to the radar you use in your airplane flights over Iceland's glaciers?

Simons: It's a similar principle. Radar is an active imaging system, so unlike optical observations, where you're just looking at the reflected light from the sun, we're actually illuminating the surface like a flashlight, but using radar instead.

Was this radar technology developed specifically for imaging glaciers?

Minchew: No. The technique we use, InSAR [Interferometric Synthetic Aperture Radar], has been available since the mid-1990s. It has revolutionized a number of disciplines in the earth sciences, including glaciology. The system we are using in Iceland is truly state-of-the-art. It enables complete control over where and when we collect data, and it returns images with millions of independent pixels. It's a very rich data source.

Simons: Actually, the exact same airplane we use in Iceland to study glaciers is also used to measure motion above restless volcanoes due to changes in magma pressure or along major seismically active faults such as the San Andreas fault. Repeated radar imaging can show us the parts of the fault that are stuck—those are the places that will generate earthquakes every so often—and the other parts that are steadily creeping year after year. Basically, we're bringing our experience from earthquake physics, both in terms of observation and modeling, to see if it can help us address important problems in glaciology.

Are there other methods besides radar for studying glacier dynamics?

Minchew: We can drill to the bed and take direct measurements, but a lot of effort is involved in this. Compared to Greenland, where the ice is close to a mile thick, or Antarctica, where it is even thicker, Iceland's glaciers are relatively thin. But they're still on average 300 meters thick. That's a long way to drill down for one data point.

Simons: Traditionally people measured velocities of glaciers by putting stakes in the glacier, and then returning to see how far downstream those stakes had moved by the end of the melting season. This approach can give an average velocity over the season. We still utilize this principle by installing GPS units at various spots on the glacier. These GPS units also help us calibrate our radar-based measurements and confirm that our velocity estimates are accurate.

What advantages does radar have over these other methods?

Simons: One of the wonderful things about radar imaging, unlike optical imaging, is that we can "see" the glacier whether it's day or night, whether it's cloudy or clear.

Minchew: Right. Another major advantage of radar technology is that we don't just see the average velocity for the season; we can detect short-term dynamics and variability over the entire glacier if the imaging is done sufficiently often.

How exactly does radar work to image the ice cap?

Simons: Radar images are usually taken at oblique angles to the surface of the earth, not straight down in a perpendicular line. Given two radar images taken from nearly identical positions but at different times, we can combine them in such a way as to measure changes in ground position that occurred in the intervening period along the oblique direction of the transmitted energy. We quantify these displacements in terms of fractions of a radar wavelength. This process is called repeat pass interferometry. We design the plane's flight path to make several interferometric measurements from different viewing angles, in order that the surface of the glacier is imaged at least three times and often as many as six times. We then combine these different perspectives to create accurate 3-D maps of the surface velocity of the glaciers, detecting its underlying east, north, and up components.

How can you be so precise in your measurements from that high up in the air?

Simons: The altitude itself isn't a problem. The trick is making certain the plane is at the same absolute position over consecutive flights. We owe this precision to engineers at NASA/JPL; it has nothing to do with us down here at Caltech. They have developed the technology to fly this plane at 40,000 feet, at 450 miles per hour, and then to come back an hour later, a day later, or a year later, and fly that exact same path in coordinates relative to the ground. Essentially they are flying in a "virtual tube" in the air that's less than 10 meters in diameter. That's how accurate it is.

Minchew: Of course even within this virtual tube, the plane moves around; that's what aircraft do. But aircraft motion has a characteristic appearance in the data, and it's possible for us to remove this effect. It never ceases to amaze me that we can get centimeter-scale, even millimeter-scale accuracy from an airplane. But we can do it, and it works beautifully.

What was the motivation for JPL and NASA to develop this radar technology in the first place?

Simons: Part of what NASA has been doing with airborne radar technology is prototyping what they want to do with radar from satellites, and to understand the characteristics of this kind of measurement for different scientific targets. The instrument is called UAVSAR, for Uninhabited Aerial Vehicle Synthetic Aperture Radar. Right now it's clearly not uninhabited because the radar is on a plane with pilots and engineers on board. But the idea is that eventually we could do these radar measurements from a drone that would stay aloft making observations for a day or a day and a half at a stretch. We can also use satellites to make the same type of measurements.

Minchew: In ways, satellites are an easier platform for radar measurements. In space, there aren't a whole lot of dramatic perturbations to their motions; they fly a very steady path. But one advantage of an airborne platform is that we can collect data more frequently. We can sample the glacier surface every 24 hours if we wish. Satellites typically sample on the order of once a week to every several weeks.

What do you hope to learn from observing glacier dynamics in Iceland?

Simons: We want to use measurements of the ice cap to explore what is happening at the bottom of the glacier. We already know from the previous campaign in 2012 that over half of the movement measured in the early summer is associated with sliding at the bed rather than deformation of the ice. In the early part of the melt season, water gets down to the bottom of the glacier and doesn't have anywhere to go, so it increases the pressure at the bottom. It ends up reducing the friction so the glacier can flow faster over the bedrock. At some point there's so much water flow that it starts to make tunnels in the ice, and then the glacier drains more efficiently. But then the tunnels will collapse on themselves, and the whole glacier settles back down, compacting on itself. The glacier actually slides faster in the early part of the melt season than later in the melt season.

Minchew: The thing that propels glaciers is simply gravity. Ice is a viscous fluid, like honey. Very cold honey. Once it warms up and begins to melt slightly, the dynamics change tremendously. That's something we can observe in Iceland—unlike in Antarctica—where temperatures regularly go above the freezing point in summer. In Iceland, we think almost all the meltwater at the bed comes from surface melting. Geothermal heating from the earth and frictional heating from the sliding itself can also contribute to melting in Iceland's glaciers. These are the main sources of melting in Antarctica. But geothermal and frictional heating don't have anything to do with climate change nor should they vary with the seasons in the way that meltwater does.

Is climate change the major reason why you're studying glaciers?

Minchew: No, I just like cold and inhospitable places. Seriously, I was drawn to the field work aspect of geophysics, the opportunity to go to places in the world that are for the most part the way nature intends them to be. I'm also drawn to glaciers because they are fascinating and surprisingly complex physical systems. A number of fundamental problems in glaciology remain unsolved, so there is tremendous potential for discovery in this field. But helping to understand the potential effects of climate change is an obvious application of our work. People are much more interested in glaciers now as a result of climate change. One of the glaciologists at the University of Iceland likes to say, "We've turned a very cold subject into a hot one."

Simons: Iceland is actually a very good place to learn about how glaciers will react to climate change. We can watch these glaciers on a seasonal basis and see how they respond to temperature variation rather than trying to compare the behavior of those glaciers in Antarctica that have yet to experience surface melting to what we think their behavior might be 50 years from now. But for me, glaciology has always been interesting in itself. My job is to study the mechanics of the earth and how it deforms. And the cryosphere is just as much a part of that as the crust.


Simons's initial exploratory campaign on Iceland's glaciers was partially supported by the Terrestrial Hazard Observation and Reporting (THOR) Center at Caltech, funded by an endowed gift from Foster and Coco Stanback. Current efforts are supported by NASA.

Cynthia Eller
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Is Natural Gas a Solution to Mitigating Climate Change?

Methane, a key greenhouse gas, has more than doubled in volume in Earth's atmosphere since 1750. Its increase is believed to be a leading contributor to climate change. But where is the methane coming from? Research by atmospheric chemist Paul Wennberg of the California Institute of Technology (Caltech) suggests that losses of natural gas—our "cleanest" fossil fuel—into the atmosphere may be a larger source than previously recognized.

Radiation from the sun warms Earth's surface, which then radiates heat back into the atmosphere. Greenhouse gases trap some of this heat. It is this process that makes life on Earth possible for beings such as ourselves, who could not tolerate the lower temperatures Earth would have if not for its "blanket" of greenhouse gases. However, as Goldilocks would tell you, there is "too hot" as well as "too cold," and the precipitous increase in greenhouse gases since the beginning of the Industrial Revolution induces climate change, alters weather patterns, and has increased sea level. Carbon dioxide is the most prevalent greenhouse gas in Earth's atmosphere, but there are others as well, among them methane.

Those who are concerned about greenhouse gases have a very special enemy to fear in atmospheric methane. Methane has a trifecta of effects on the atmosphere. First, like other greenhouse gases, methane works directly to trap Earth's radiation in the atmosphere. Second, when methane oxidizes in Earth's atmosphere, it is broken into components that are also greenhouse gases: carbon dioxide and ozone. Third, the breakdown of methane in the atmosphere produces water vapor, which also functions as a greenhouse gas. Increased humidity, especially in the otherwise arid stratosphere where approximately 10 percent of methane is oxidized, further increases greenhouse-gas induced climate change.

Fully one-third of the increase in radiative forcing (the ability of the atmosphere to retain radiation from the sun) since 1750 is estimated to be due to the presence and effects of methane. Because of the many potential sources of atmospheric methane, from landfills to wetlands to petroleum processing, it can be difficult to quantify which sources are making the greatest contribution. But according to Paul Wennberg, Caltech's R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering, and his colleagues, it is possible that a significant source of methane, at least in the Los Angeles basin, is fugitive emissions—leaks—from the natural-gas supply line.

"This was a surprise," Wennberg explains of the results of his research on methane in the Los Angeles atmosphere. In an initial study conducted in 2008, Wennberg's team analyzed measurements from the troposphere, the lowest portion of Earth's atmosphere, via an airplane flying less than a mile above the ground over the Los Angeles basin.

In analyzing chemical signatures of the preliminary samples, Wennberg's team made an intriguing discovery: the signatures bore a striking similarity to the chemical profile of natural gas. Normally, the methane from fossil fuel sources is accompanied by ethane gas—which is the second most common component of natural gas—while biogenic sources of methane (such as livestock and wastewater) are not. Indeed, the researchers found that the ratio of methane and ethane in the L.A. air samples was characteristic of the samples of natural gas provided by the Southern California Gas Company, which is the leading supplier of natural gas to the region.

Wennberg hesitates to pinpoint natural-gas leaks as the sole source of the L.A. methane, however. "Even though it looks like the methane/ethane could come from fugitive natural-gas emissions, it's certainly not all coming from this source," he says. "We're still drilling for oil in L.A., and that yields natural gas that includes ethane too."

The Southern California Gas Company reports very low losses in the delivery of natural gas (approximately 0.1 percent), and yet atmospheric data suggest that the source of methane from either the natural-gas infrastructure or petroleum production is closer to 2 percent of the total gas delivered to the basin. One possible way to reconcile these vastly different estimates is that significant losses of natural gas may occur after consumer metering in the homes, offices, and industrial plants that purchase natural gas. This loss of fuel is small enough to have no immediate negative impact on household users, but cumulatively it could be a major player in the concentration of methane in the atmosphere.

The findings of Wennberg and his colleagues have led to a more comprehensive study of greenhouse gases in urban settings, the Megacities Carbon Project, based at JPL. The goal of the project, which is focusing initially on ground-based measurements in Los Angeles and Paris, is to quantify greenhouse gases in the megacities of the world. Such cities—places like Hong Kong, Berlin, Jakarta, Johannesburg, Seoul, São Paulo, and Tokyo—are responsible for up to 75 percent of global carbon emissions, despite representing only 3 percent of the world's landmass. Documenting the types and sources of greenhouse gases in megacities will provide valuable baseline measurements that can be used in efforts to reduce greenhouse gas emissions.

If the findings of the Megacities Carbon Project are consistent with Wennberg's study of methane in Los Angeles, natural gas may be less of a panacea in the search for a "green" fuel. Natural gas has a cleaner emissions profile and a higher efficiency than coal (that is, it produces more power per molecule of carbon dioxide), but, as far as climate change goes, methods of extraction and distribution are key. "You have to dig it up, put it in the pipe, and burn it without losing more than a few percent," Wennberg says. "Otherwise, it's not nearly as helpful as you would think."

Wennberg's research was published in an article titled "On the Sources of Methane to the Los Angeles Atmosphere" in Environmental Science & Technology. Data for this study were provided by the Southern California Gas Company, NASA, NOAA, and the California Air Resources Board. The research was funded by NASA, the California Energy Commission's Public Interest Environmental Research program, the California Air Resources Board, and the U.S. Department of Energy.

Cynthia Eller
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Nanoscale Materials and Big Solar Energy: An Interview with Harry Atwater

As a high school student during the oil crisis of the 1970s, Harry Atwater recognized firsthand the impact of energy supply issues. Inspired to contribute to renewable energies, his research at Caltech today works to develop better thin-film photovoltaics—cheaper, lighter, more efficient alternatives to the bulky cells now used in solar panels.

In addition to his individual research interests in photovoltaic cell development, Atwater is also part of a collaborative effort to advance solar energy research at the Joint Center for Artificial Photosynthesis (JCAP)—a U.S. Department of Energy (DOE) Energy Innovation Hub. JCAP, which is led by a team of researchers from Caltech and partner Lawrence Berkeley National Laboratory, aims to develop cost-effective fuel production methods that require only sunlight, water, and carbon dioxide.

Atwater, who serves as the project leader for the Membrane and Mesoscale Assembly Project at JCAP, recently chatted with us about his research, his background, and why he came to Caltech.

What originally drew you to Caltech?

It was the opportunity to pursue my area of research. I felt that Caltech was the best research environment I could [be in] for mixing fundamental science and engineering technology. Caltech is very developed in its orientation toward engineering and technology, and its connection to technology in many areas like aerospace, photonics, communications, semiconductors and chemistry. It is a great combination—an institutional focus on fundamentals but also a focus on applying those fundamentals to engineer new technologies.

What are your research interests?

My research is at the intersection of solar energy and nanophotonic materials. Nanophotonic materials are materials and structures in which the characteristic length scale of the material is less than the scale of the wavelength of light—meaning that they're so small that they must be visualized with something that has a wavelength much smaller than that of visual light. Half of my research group is focused on the fundamentals of nanophotonic materials. These materials could form the building blocks of a chip-based optical device technology for improved imaging in computing, communications, and for the detection of chemical and biological molecules.

The other half of my group is focused on improving solar energy. We are investigating several approaches to creating very low-cost and ultrahigh-efficiency thin-film photovoltaics, which are an alternative to, and the future of, today's solar cell panels. In our design, we use thin layers of semiconductors for absorbing sunlight. The Joint Center for Artificial Photosynthesis (JCAP) fundamentally focuses on using semiconductor photonic materials and devices to create fuel from solar energy, so it's a really good match for our work.

How do these semiconductors you're working with make thin-film photovoltaics cheaper, thinner, and more efficient?

Most materials cost nearly the same amount when you just think about them on a price-per-atom basis. What makes materials expensive or cheap is the cost of the synthesis and processing methods used to make them with sufficient purity and perfection to enable high performance. Much of what we do is aimed at either designing new syntheses that can yield high-performance materials in a scalable low-cost fashion or designing new structures and devices whose performance is robust against use of impure or defective materials.

How did you first get interested in your field?

I would say that my interest in solar energy dates back to the first big energy crisis in the 1970s, when I was a high school student. I grew up in Pennsylvania, and I remember my school was shut down for a few weeks in the wintertime because there literally was no oil to heat the burner. I thought then that addressing supplies of energy was an important problem. It made a big impression on me. But at that point, I hadn't really thought about how I could contribute to a solution.

But then in graduate school, I got interested in things at the intersection of physics and electrical engineering, which is really where my work lies. As a graduate student at MIT, I began to focus on developing new technologies for thin-film solar cells. At MIT, I worked in one of the first nanostructure fabrication labs in the country, where it became apparent to me that we could make nanostructures and characterize their properties.

You were among the first scientists to study these nanostructures. What was that like?

Nowadays "nano" is sort of pervasive in the ether—nanomaterials are not unusual. At that time, it was as invisible to the general public as the Internet. It became obvious to me that there was a lot of opportunity to use nanofabrication principles and techniques to make new optical materials. Later, around 2001, we ended up playing a pretty significant role in starting another new field called plasmonics, which studies the behavior of the excitations created by light in metals. This new field led to the first serious and widespread efforts to make these kinds of optical devices and optical materials out of metals.

Do you have any hobbies or interests outside of your research?

I'm an avid soccer player, and I play weekly with the graduate students. Until my kids got to an age when I started embarrassing them, I was coaching them every week. That's what I like to do for fun.

Atwater joined the Caltech faculty as an assistant professor of applied physics in 1988, becoming an associate professor in 1994 and a professor in 1999. Now the Howard Hughes Professor of Applied Physics and Materials Science, Atwater has many roles on campus and beyond. These include serving as the director of the Resnick Sustainability Institute, the director of the Department of Energy's "Light-Material Interactions in Energy Conversion" Energy Frontier Research Center (LMI-EFRC), and most recently as the editor-in-chief of a new research journal, ACS Photonics.

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Bacterial "Syringe" Necessary for Marine Animal Development

If you've ever slipped on a slimy wet rock at the beach, you have bacteria to thank. Those bacteria, nestled in a supportive extracellular matrix, form bacterial biofilms—often slimy substances that cling to wet surfaces. For some marine organisms—like corals, sea urchins, and tubeworms—these biofilms serve a vital purpose, flagging suitable homes for such organisms and actually aiding the transformation of larvae to adults.

A new study at the California Institute of Technology (Caltech) is the first to describe a mechanism for this phenomenon, providing one explanation for the relationship between bacterial biofilms and the metamorphosis of marine invertebrates. The results were published online in the January 9 issue of Science Express.

The study focused on a marine invertebrate that has become a nuisance to the shipping industry since its arrival in U.S. waters during the last half century: the tubeworm Hydroides elegans. The larvae of the invasive pest swim free in the ocean until they come into contact with a biofilm-covered surface, such as a rock or a buoy—or the hull of a ship. After the tubeworm larvae come in contact with the biofilm, they develop into adult worms that anchor to the surface, creating hard, mineralized "tubes" around their bodies. These tubes, which often cover the bottoms of ships, create extra drag in the water, dramatically increasing the ship's fuel consumption.

The tubeworms' unwanted and destructive presence on ships, called biofouling, is a "really bad problem," says Dianne Newman, a professor of biology and geobiology and Howard Hughes Medical Institute (HHMI) investigator at Caltech. "For example, biofouling costs the U.S. Navy millions of dollars every year in excess fuel costs," says Newman, who is also a coauthor of the study. And although researchers have known for decades that biofilms are necessary for tubeworm development, says Nicholas Shikuma, one of the two first authors on the study and a postdoctoral scholar in Newman's laboratory, "there was no mechanistic explanation for how bacteria can actually induce that process to happen. We wanted to provide that explanation."

Shikuma began by investigating Pseudoalteromonas luteoviolacea, a bacterial species known to induce metamorphosis in the tubeworm and other marine invertebrates. In earlier work, Michael G. Hadfield of the University of Hawai'i at Mānoa, a coauthor of the Science Express paper, had identified a group of P. luteoviolacea genes that were necessary for tubeworm metamorphosis. Near those genes, Shikuma found a set of genes that produced a structure similar to the tail of bacteriophage viruses.

The tails of these phage viruses contain three main components: a projectile tube, a contractile sheath that deploys the tube, and an anchoring baseplate. Together, the phage uses these tail components as a syringe, injecting their genetic material into host bacteria cells, infecting—and ultimately killing—them. To determine if the phage tail-like structures in P. luteoviolacea played a role in tubeworm metamorphosis, the researchers systematically deleted the genes encoding each of these three components.

Electron microscope images of the bacteria confirmed that syringe-like structures were present in "normal" P. luteoviolacea cells but were absent in cells in which the genes encoding the three structural components had been deleted; these genes are known as metamorphosis-associated contractile structure (mac) genes. The researchers also discovered that the bacterial cells lacking mac genes were unable to induce metamorphosis in tubeworm larvae. Previously, the syringe-like structures had been found in other species of bacteria, but in these species, the tails were deployed to kill other bacteria or insects. The new study provides the first evidence of such structures benefitting another organism, Shikuma says.

In order to view the three-dimensional arrangement of these unique structures within intact bacteria, the researchers collaborated with the laboratory of Grant Jensen, professor of biology and HHMI investigator at Caltech. Utilizing a technique called electron cryotomography, the researchers flash-froze the bacterial cells at very low temperatures. This allowed them to view the cells and their internal structures in their natural, "near-native" states.

Using this visualization technique, Martin Pilhofer, a postdoctoral scholar in Jensen's lab and the paper's other first author, discovered something unique about the phage tail-like structures within P. luteoviolacea; instead of existing as individual appendages, the structures were linked together to create a spiny array. "In these arrays, about 100 tails are stuck together in a hexagonal lattice to form a complex with a porcupine-like appearance," Shikuma says. "They're all facing outward, poised to fire," he adds. "We believe this is the first observation of arrays of phage tail-like structures."

Initially, the array is compacted within each bacterium; however, the cells eventually burst—killing the microbes—and the array unfolds. The researchers hypothesize that, at this point, the individual spines of the array fire outward into the tubeworm larva. Following this assault, the larvae begin their developmental transition to adulthood.

"It was a tremendous surprise that the agent that drives metamorphosis is such an elaborate, well-organized injection machine," says coauthor Jensen. "Who would have guessed that the signal is delivered by an apparatus that is almost as large as the bacterial cell itself? It is simply a marvelous structure, synthesized in a 'loaded' but tightly collapsed state within the cell, which then expands like an umbrella, opening up into a much larger web of syringes that are ready to inject," he says.

Although the study confirms that the phage tail-like structures can cause tubeworm metamorphosis, the nature of the interaction between the tail and the tubeworm is still unknown, Shikuma says. "Our next step is to determine whether metamorphosis is caused by an injection into the tubeworm larva tissue, and, then, if the mechanical action is the trigger, or if the bacterium is injecting a chemical morphogen," he says. He and his colleagues would also like to determine if mac genes and the tail-like structures they encode might influence other marine invertebrates, such as corals and sea urchins, that also rely on P. luteoviolacea biofilms for metamorphosis.

Understanding this process might one day help reduce the financial losses from P. luteoviolacea biofilm fouling on ship hulls, for example. While applications are a long way off, Newman says, it is also interesting to speculate on the possibility of leveraging metamorphosis induction in beneficial marine invertebrates to improve yields in aquaculture and promote coral reef growth.

The study, the researchers emphasize, is an example of the collaborative research that is nurtured at Caltech. For his part, Shikuma was inspired to utilize electron cryotomography after hearing a talk by Martin Pilhofer at the Center for Environmental Microbiology Interactions (CEMI) at Caltech. "Martin gave a presentation on another type of phage tail-like structures in the monthly CEMI seminar. I saw his talk and I thought that the mac genes I was working with might somehow be related," Shikuma says. Their subsequent collaboration, Newman says, made the current study possible.

The paper is titled "Marine tubeworm metamorphosis induced by arrays of bacterial phage tail-like structures." Gregor L. Weiss, a Summer Undergraduate Research Fellowship student in Jensen's laboratory at Caltech, was an additional coauthor on the study. The published work was funded by a Caltech Division of Biology Postdoctoral Fellowship (to N. Shikuma), the Caltech CEMI, the Howard Hughes Medical Institute, the Office of Naval Research, the National Institutes of Health, and the Gordon and Betty Moore Foundation.

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Saturday, November 9, 2013
Cahill, Hameetman Auditorium – Cahill Center for Astronomy and Astrophysics

Beyond Rhetoric: Real Solutions for the Climate Change Crisis

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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Meet DALE: Solar Decathlon 2013 Construction is Under Way

Trading in their textbooks for power tools this summer, a group of nine Caltech students and recent graduates have had a unique opportunity to apply their classroom knowledge to real-world challenges. Along with students in architectural design from the Southern California Institute of Architecture (SCI-Arc), the Caltech students have spent their summer building the Dynamic Augmented Living Environment (DALE), a joint SCI-Arc/Caltech entry in the 2013 Solar Decathlon competition. DALE marks Caltech's second collaboration with SCI-Arc, following their Compact Hyper-Insulated Prototype (CHIP), the partnership's first Solar Decathlon entry, in 2011.

Sponsored by the Department of Energy, the biennial Solar Decathlon competition challenges collegiate teams to "design, build, and operate solar-powered houses that are cost-effective, energy-efficient, and attractive." Contest rules state that each entry must be a net-zero home, meaning that its solar panels must produce at least as much energy as the home uses.

Construction on the SCI-Arc/Caltech collaboration began in March, when DALE's cement foundation was poured. In April, the home's steel frames were dropped in, allowing the students (guided by a few construction professionals) to begin nailing the lumber into place.

As of August, the home is starting to take shape; the bathroom has been framed out, the kitchen cabinets are set for installation, and soon the house will be sporting a vinyl exterior and a set of moving canopies that will hold its solar panels.

Although construction work only began a few months ago, the Caltech students began planning for DALE last fall in an engineering project course called Introduction to Multidisciplinary Systems Engineering, taught by Melany Hunt, Dotty and Dick Hayman Professor of Mechanical Engineering and a vice provost.

"I really like this project because it's very hands-on," says DALE team member Zeke Millikan (BS '13, mechanical engineering). "A lot of classes at Caltech are very theoretical, and I'm more of a hands-on type of person. It's really satisfying to actually build something and see it come together."

"Prior to this summer," says DALE team member Sheila Lo ('16), "I didn't really have a lot of experience in construction, so I spent a lot of time learning the terminology and how to use which tools in certain situations. As one of the youngest members of the team, it's been a great privilege to work with upperclassmen and recent graduates because they've taught me a lot about dedication to a project and what it means to apply the skills you learn at Caltech."

And this dedication will be important in the coming weeks, as there is still plenty of work to be done for the early-October competition. Unlike the five previous Solar Decathlons, which were held in Washington, D.C., this year's event will take place in nearby Irvine, California. "Having the competition just right down the road from us inspired the design," says DALE team member Ella Seal (BS '13, mechanical engineering).

To capitalize on Southern California's mild climate, DALE is made up of two moving modules that can glide apart on warm sunny days, creating an open indoor courtyard that can triple the home's available living space. During inclement weather—and for enhanced safety and privacy—DALE's modules can also move together, creating an enclosed home of about 600 square feet.

The home's untraditional moving design—conceived by SCI-Arc team members—is more than just eye-catching. "It also will actually save energy and money over the course of the year," says Seal. By varying the configurations of DALE's modules and shade canopies—the same ones that will hold DALE's solar panels—the Caltech students were able to optimize energy efficiency during different times of the day without sacrificing comfort. "During the summer, the air-conditioning energy consumption drops by at least half when you are able to open up the house and adjust the shading depending on the weather outside," says Millikan.

But a moving house also presents several engineering challenges, says Seal. Wires for electricity and pipes for plumbing had to be specially designed for their moving platform. Seal and Millikan were also tasked with creating a foolproof safety mechanism for DALE's movement systems. Applying their backgrounds in mechanical engineering, they created a system of laser beams, light curtains, and pressure sensors that acts "basically like a garage door sensor on steroids," says Millikan. "We think we've addressed pretty much every scenario where someone could get seriously hurt."

In addition to the movement systems, students from Caltech are responsible for designing the home's heating, ventilation, and air-conditioning system; hot water system; photovoltaic arrays; and other engineering aspects of the solar-powered home. As well as their technical contributions, the Caltech students will collaborate with their SCI-Arc teammates on publicity and fund-raising efforts and the compilation of a final written report.

"I appreciate the fact that it's not just engineering," says Seal. "I really like the fact that we have to write an engineering narrative, describing all of the really cool innovations that we've built into the house. It's not necessarily something that I would get to do if I took a different project class at Caltech."

This type of multidisciplinary and collaborative experience is important for Caltech students, notes Hunt. "Engineering students need experiences in which they design, create, build, and test," she says. "They also should have opportunities in which they work as part of a team. Most engineering projects require multiple perspectives with input coming from a range of individuals with different expertise and vision."

In addition to Millikan, Seal, and Lo, the DALE team includes current Caltech students Brynan Qui ('15), Do Hee Kim ('15), Sharon Wang ('16), as well as recent graduates Tony Wu (BS '13, mechanical engineering and business economics and management) and Christine Viveiros (BS '13, mechanical engineering), and project manager Andrew Gong (BS '12, chemical engineering [materials]). The SCI-Arc/Caltech project, along with other entries for this year's Solar Decathlon competition, will be open to the public October 3–6 and 10–13 at the Orange County Great Park in Irvine, California.

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