Princeton Research Day highlights student and early-career work


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MORE THAN 150 undergraduates, graduate students and postdoctoral researchers presented their work at the first Princeton Research Day held May 5, 2016.

The event highlighted research from the natural sciences, engineering, social sciences, humanities and the arts in formats including talks, poster presentations, performances, art exhibitions and digital presentations — all designed with the general public in mind.

“It’s a wonderful cross section of the research enterprise at Princeton,” said Dean for Research Pablo Debenedetti, the Class of 1950 Professor in Engineering and Applied Science, and professor of chemical and biological engineering.

In all, Princeton Research Day presented an important opportunity for undergraduates, said Dean of the College Jill Dolan, the Annan Professor in English and professor of theater in the Lewis Center for the Arts.

“Princeton is one of the very few universities in the world where undergraduate students are encouraged to do the kind of original research that every single undergraduate on this campus does,” Dolan said. “So taking the opportunity at the end of the year to do a major public event in which students can present that work is groundbreaking.”

Princeton Research Day was a collaborative initiative between the offices of the dean of the college, dean of the faculty, dean of the graduate school and the dean for research. The second Princeton Research Day is scheduled for May 11, 2017. –By Michael Hotchkiss

Bright future: Princeton researchers unlock the potential of light to perform previously impossible feats

By Bennett McIntosh

One hundred years ago, Italian chemist Giacomo Ciamician predicted a future society that would run on sunlight.

In a paper presented in 1912 to an international meeting of chemists in New York City, he foresaw a future of vibrant desert communities under “a forest of glass tubes and greenhouses of all sizes” where light-driven chemical reactions would produce not just energy but also wondrous medicines and materials.

Ciamician’s vision has not yet arrived, but a handful of Princeton researchers have succeeded with one part of his legacy: they are harnessing light to perform previously impossible feats of chemistry. In Princeton’s Frick Chemistry Laboratory, blue LED lamps cast light on flask after flask of gently stirring chemicals that are reacting in ways they never have before to create tomorrow’s medicines, solvents, dyes and other industrial chemicals.

The leader in this emerging field is David MacMillan, who arrived in Princeton’s chemistry department in 2006. He was intrigued by the potential for using light to coax new chemical reactions. Like most chemists, he’d spent years learning the rules that govern the interactions of elements such as carbon, oxygen and hydrogen, and then using those rules to fashion new molecules. Could light help change these rules and catalyze reactions that have resisted previous attempts at manipulation?

Changing the rules

The idea for using light as a catalyst had been explored since Ciamician’s time with limited success. Light can excite a molecule to kick loose one or more of its electrons, creating free radicals that are extremely reactive and readily form new bonds with one another. However, most chemists did not think this process could be controlled precisely enough to make a wide variety of precision molecules.

But that changed in the summer of 2007.

MacMillan and postdoctoral researcher David Nicewicz were working on a tough problem. The two scientists wanted to create chemical bonds between one group of atoms, called bromocarbonyls, and another group, known as aldehydes. “It was one of those longstanding challenges in the field,” MacMillan said. “It was one of those reactions that was really useful for making new medicines, but nobody knew how to do it.”

Nicewicz had found a recipe that worked, but it involved using ultraviolet (UV) light. This high-energy form of light causes sunburn by damaging the molecules in the skin, and it also damaged the molecules in the reaction mixture, making the recipe Nicewicz had discovered less useful. MacMillan, who is Princeton’s James S. McDonnell Distinguished University Professor of Chemistry, asked Nicewicz to investigate how to do the transformation without UV light.

Nicewicz recalled some experiments that he’d seen as a graduate student at the University of North Carolina-Chapel Hill. Researchers led by chemistry professor Malcom Forbes had split water into oxygen and hydrogen fuel using visible light and a special molecule, a catalyst containing a metal called ruthenium. The approach was known as “photoredox catalysis” because particles of light, or photons, propel the exchange of electrons in a process called oxidation-reduction, or “redox” for short.

David MacMillan

David MacMillan is a leader in developing the use of light to catalyze chemical reactions — a technique called photoredox catalysis. (Photo by Sameer A. Khan/Fotobuddy)

Visible light is lower in energy than ultraviolet light, so Nicewicz and MacMillan reasoned that the approach might work without damaging the molecules. Indeed, when the researchers added a ruthenium catalyst to the reaction mixture and placed the flask under an ordinary household fluorescent lightbulb, the two scientists were astounded to see the reaction work almost perfectly the first time. “More times than not, the reaction you draw on the board never works,” Nicewicz said. Instead, the reaction produced astonishing amounts of linked molecules with high purity. “I knew right away it was a fantastic result,” he said.

With support from the National Institutes of Health, MacMillan and Nicewicz spent the next year showing that the reaction was useful for many different types of bromocarbonyls and aldehydes, results that the team published in Science in October 2008. Research in the lab quickly expanded beyond this single reaction, and each new reaction hinted at a powerful shift in the rules of organic chemistry. “It just took off like gangbusters,” MacMillan said. “As time goes on you start to realize that there are nine or 10 different things that it can do that you didn’t think of.”

Old catalysts, new tricks

At the time that Nicewicz and MacMillan were making their discovery, chemistry professor Tehshik Yoon and his team at the University of Wisconsin-Madison found that combining the ruthenium catalyst with light produced a different chemical reaction. They published their work in 2008 in the Journal of the American Chemical Society the same day MacMillan’s paper appeared in Science. Within a year of MacMillan publishing his paper, Corey Stephenson, a University of Michigan chemistry professor, and his team found yet another photoredox-based reaction.

With these demonstrations of the versatility of photoredox catalysts, other chemists quickly joined the search for new reactions. About 20 photoredox catalysts were already available for purchase from chemical catalogs due to previous research on watersplitting and energy storage, so researchers could skip the months-long process of building catalysts. However, by designing and tailoring new catalysts, the chemists unlocked the potential to use light to drive numerous new reactions, and today there are more than 400 photoredox catalysts available.

The secret to these catalysts’ ability to drive specific reactions lies in their design. The catalysts consist of a central atom, often a metal atom such as ruthenium or iridium, surrounded by a halo of other atoms. Light frees an electron from the central atom, and the atoms surrounding the center act as a sort of channel that ushers the freed electrons toward the specific atoms that the chemists want to join.

One scientist who became intrigued with the power of photoredox catalysts was Abigail Doyle, a Princeton associate professor of chemistry. Doyle, whose work is funded by the National Institutes of Health, uses nickel to help join two molecules. In 2014, she was searching for a way to conduct a reaction that had long eluded other scientists. She wanted to find a catalyst that could make perhaps the most common bond in organic chemistry — between carbon and hydrogen — reactive enough to couple to another molecule. Perhaps a photocatalyst could make a reactive free radical, allowing her to then bring in a nickel catalyst to attach the carbon-carbon bond.

Abigail Doyle

Abigail Doyle is one of a handful of Princeton professors to quickly adapt the use of blue LED light and photoredox catalysis to rewrite the rules of organic chemistry. Drug companies have taken notice. (Photo by Sameer A. Khan/Fotobuddy)

Unbeknownst to Doyle, the MacMillan lab had recently turned their attention to combining photoredox and nickel catalysts on a similar reaction, coupling molecules at the site of a carboxylate group, a common arrangement of atoms found in biological molecules from vinegar to proteins.

Given the similarities in their findings, the MacMillan and Doyle labs decided to combine their respective expertise in nickel and photoredox chemistry. Together, the teams found a photocatalyst based on the metal iridium that worked with nickel to carry out both coupling reactions — at the carbon-hydrogen bond and at the carboxylate group. Their collaborative paper, published in Science July 25, 2014, showed the extent of photoredox catalysis’ power to couple molecules with these common features.

The ability to combine molecules using natural features such as the carbon-hydrogen bond or the carboxylate group makes photoredox chemistry extremely useful. Often, chemists have to significantly modify a natural molecule to make it reactive enough to easily link to another molecule. One popular reaction — which earned a Nobel Prize in 2010 — requires several steps before two molecules can be linked. Skipping all these steps means a far easier and cheaper reaction — and one that is rapidly being applied.

“It’s one of the fastest-adopted chemistries I’ve seen,” Doyle said. “A couple of months after we published, we were visiting pharmaceutical companies and many of them were using this chemistry.”

The search for new drugs often involves testing vast libraries of molecules for ones that interact with a biological target, like trying thousands of keys to see which ones open a door. Pharmaceutical companies leapt at the chance to quickly and cheaply make many more kinds of molecules for their libraries.

Merck & Co., Inc., a pharmaceutical company with research labs in the Princeton area, was one of the first companies to become interested in using the new approach — and in funding MacMillan’s research.The company donated $5 million to start Princeton’s Merck Center for Catalysis in 2006, and recently announced another $5 million in continued research funding.

In addition to aiding drug discovery, photoredoxcatalyzed reactions can produce new or less expensive fine chemicals for flavorings, perfumes and pesticides, as well as plastic-like polymer materials. And the techniques keep getting cheaper. MacMillan published a paper June 23, 2016, in Science showing that with the aid of a photoredox catalyst, a widely used reaction to make carbon-nitrogen bonds can be carried out with nickel instead of palladium. Because nickel is thousands of times cheaper than palladium, companies hoping to use the reaction were contacting MacMillan before the paper was even published.

Spreading the light

Doyle has continued to explore photoredox chemistry, as have other Princeton faculty members, including two new assistant professors, Robert Knowles and Todd Hyster.

Hyster combines photoredox catalysis with reactions inspired by biology. Drugs often function by fitting in a protein like a hand fits in a glove. But just as placing a left hand in a right glove results in a poor fit, inserting a left-handed molecule into a protein designed for a right-handed molecule will give poor results. Many catalysts produce both the intended product and its mirror image, but by combining photoredox catalysts with artificial proteins, Hyster is finding reactions that can make that distinction.

Hyster, who arrived at Princeton in summer 2015, was drawn to Princeton’s chemistry department in part because of the opportunities to share knowledge and experience with other groups researching photoredox catalysis. “The department is quite collegial, so there’s no barrier when talking to colleagues about projects that are broadly similar,” he said.

Students from different labs chat about their work over lunch, teaching and learning informally — and  formally, as the labs encourage collaboration and sharing expertise, said Emily Corcoran, a postdoctoral researcher who works with MacMillan. When Corcoran was trying to determine exactly how one of her reactions  worked, she was able to consult with students in Knowles’ lab who had experience using sensitive magnetic measurements to find free radicals in the reaction mixture.

“If you have a question, you can just walk down the hall and ask,” Corcoran said. “That really pushes all the labs forward at a faster pace.”

A bright future

After the graduate students go home at night, the blue LEDs continue to drive new chemical reactions and new discoveries. “This is really just the beginning,” Doyle said.

Hyster thinks that within a few years, manufacturers may take advantage of photoredox chemistry to produce biological chemicals — such as insulin and the malaria drug artemisinin — to meet human needs. For his part, MacMillan envisions zero-waste chemical plants in the Nevada desert, driven not by fossil fuels but by the sun.

MacMillan’s vision echoes that of the original photochemist, Ciamician. The Italian’s optimistic vision of a sunlit future is brighter than ever.

Wild birds: A trip to the market reveals species imperiled

Wild Birds

“Wild birds are being vacuumed out of the forests, gardens and fields of Indonesia, and we have to quickly figure out which species are in danger of extinction.” –David Wilcove, professor of ecology and evolutionary biology and public affairs in the Woodrow Wilson School

THE SIGHT OF A SOUTHEAST ASIAN BIRD market rivals the din of one for being overwhelming. Thousands of wild-caught birds are packed into cages that hang from eaves and fill market stalls to the ceiling, lining the paths trod by prospective buyers like a living wall. Taken from fields and forests, these birds are prized for their song, their colors, their spiritual significance or their long-time association with status and wealth. For the people who come to these markets, the birds — young and old, endangered and common — have meaning and value.

But to scientists, conservationists and governments, the wild-pet trade is a destructive yet unmonitored and elusive force on wildlife populations.

Princeton University researchers went deep into the wild-bird markets and trapping operations on the Indonesian island of Sumatra to document the draining of species by the pet trade. They found there a new and interesting weapon in the struggle to gauge — and halt — the devastation of the wildlife trade on animal populations: the very markets where the animals are bought and sold.

Species that are disappearing as a result of the pet trade can be identified by changes in their market prices and trade volumes, a study led by the Princeton researchers found. The researchers studied open-air pet markets on Sumatra from 1987 to 2013 and found that bird species that increased in price but decreased in availability exhibited plummeting populations in the wild.

The researchers concluded in the journal Biological Conservation in July 2015 that a prolonged rise in price coupled with a slide in availability could indicate that a species is being wiped out by its popularity in the pet trade. Through regular pet-market monitoring, conservationists and governments could use this information as an early indicator that a particular species is in trouble, the researchers reported.

Lead author Bert Harris, who was a postdoctoral fellow in the Program in Science, Technology and Environmental Policy in Princeton’s Woodrow Wilson School of Public and International Affairs when the work was conducted, said that market monitoring can be done far more quickly and cheaply than field-based monitoring of wild populations.

birds

Birds such as the Oriental white-eye (top photo ) are packed into tight cages where they are at risk of disease. Many Asian and African countries host a startling number of species yet have lax-to-nonexistent monitoring and conservation programs. The Princeton researchers’ market-monitoring method can be done far more quickly and cheaply than field-based monitoring of wild populations. PHOTO COURTESY OF DAVID WILCOVE

One important function of the study is to highlight the pet trade as an emerging threat facing many birds and other wildlife, one that can act independently from other drivers of extinction such as habitat loss, said senior author David Wilcove, a professor of ecology and evolutionary biology and public affairs in the Wilson School.

He and Harris worked with co-authors Jonathan Green, who was a Princeton postdoctoral researcher in the Wilson School and is now at the University of Cambridge; Xingli Giam, who earned his Ph.D. at Princeton in 2014 and is now at the University of Washington; and researchers from the Wildlife Conservation Society and the Indonesian Institute of Sciences.

“Wild birds are being vacuumed out of the forests, gardens and fields of Indonesia and we have to quickly figure out which species are in danger of extinction,” Wilcove said. “We’ve got to change how we tackle this problem.”

Carter Roberts, president and CEO of the World Wildlife Fund, said that the researchers’ use of wildlife-trade market data to identify endangered species is a “potentially breakthrough idea.”

“What I think makes this paper so exciting is that it suggests a two-pronged approach to addressing the threat to biodiversity posed by the wildlife trade: using market data to identify the species that are likely being severely overexploited, and then targeted research and conservation efforts at those species,” Roberts said.

The researchers found that 14 birds popular in Sumatran pet markets were identified by local experts as declining or severely declining — yet, only two are officially recognized as imperiled. In addition, only two species are restricted to old growth forests, meaning that deforestation alone could not explain the declines. The pet trade was clearly a culprit, too. Furthermore, the researchers found that six species that are not popular as pets exhibited population increases. The researchers confirmed their method by studying the cases of two birds that are critically endangered by the pet trade — the yellow-crested cockatoo and the Bali myna.

Existing studies have explored wildlife markets, but only documented a species’ market volume, or availability, Harris said. The Princeton-led study, which was supported by the High Meadows Foundation, is the first to consider price and market volume. Market availability alone can fluctuate for reasons unrelated to a species’ wild population, such as a decrease in popularity, he said.

During the course of the research, Harris visited bird markets to gather price and availability data. They are chaotic places where Westerners asking about prices are viewed with suspicion.

“The markets are the dirty part of conservation,” Harris said. “They’re noisy and smelly. And after someone who looks like me asks about prices two or three weeks in a row, sellers just stop responding.”

Wilcove was inspired to conduct the current research after a trip to Sumatra when he noticed a prevalence of wild-caught pet birds. Research has found that 22 percent of Indonesian households own birds.

One bird the researchers identified as declining in the wild, the white-rumped shama, which is prized for its song, can be raised in captivity. Yet people seem to prefer the wild individuals, Wilcove said. He and Harris want to explore how governments and conservation groups can convince people to keep captive-raised birds.

“It’s time for some new approaches,” Wilcove said.

–By Morgan Kelly

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RESILIENT SHORES: After Sandy, climate scientists and architects explore how to co-exist with rising tides

Coastal Resilience
AFTER THE WIND, RAIN AND WAVES of Hurricane Sandy subsided, many of the modest homes in the Chelsea Heights section of Atlantic City, New Jersey, were filled to their windows with murky water. Residents returned to find roads inundated by the storm surge. Some maneuvered through the streets by boat.

This mode of transport could become more common in neighborhoods like Chelsea Heights as coastal planners rethink how to cope with the increasing risk of hurricane-induced flooding over the coming decades. Rather than seeking to defend buildings and infrastructure from storm surges, a team of architects and climate scientists is exploring a new vision, with an emphasis on living with rising waters. “Every house will be a waterfront house,” said Princeton Associate Professor of Architecture Paul Lewis. “We’re trying to find a way that canals can work their way through and connect each house, so that kayaks and other small boats are able to navigate through the water.”

The researchers aim for no less than a reinvention of flood hazard planning for the East Coast. A new approach, led by Princeton Professor of Architecture Guy Nordenson, rejects the strict dividing line between land and water that coastal planners historically have imposed, favoring the development of “amphibious suburbs” and landscapes that can tolerate periodic floods. These resilient designs can be readily modified as technologies, conditions and climate predictions change.

Discovery2014_CR_textbox1To plan for future flood risks, Princeton climate scientists are using mathematical models of hurricanes to predict storm surge levels over the next century, taking into account the effects of sea level rise at different locations. Four design teams — from Princeton, Harvard University, the City College of New York and the University of Pennsylvania — are using these projections to guide resilience plans for specific sites along the coast: Atlantic City; Narragansett Bay in Rhode Island; New York City’s Jamaica Bay; and Norfolk, Virginia. [See Planning for resilience up and down the coast.]

The designs will serve as a guide for the U.S. Army Corps of Engineers’ North Atlantic Coast Comprehensive Study, a plan to reduce the risk of flood damage to coastal communities, which is due to Congress in January 2015. “The Army Corps understands that they have to revisit what it means to make structures that are resilient,” said Enrique Ramirez, a postdoctoral research associate in architecture at Princeton and the project’s manager. He serves as a liaison between the design teams and Army Corps officials in regional districts.

The idea for the project grew out of Nordenson’s work on a pre-Sandy project to develop creative proposals for adaptation to rising sea levels in New York Harbor. The project culminated in a book, On the Water: Palisade Bay, and a 2010 exhibition, Rising Currents, at the New York City Museum of Modern Art. The proposals included repairing and lengthening existing piers, as well as planting wetlands and building up small islands inside the harbor. “It was forward thinking because we showed that there are benefits to building things in the water,” Nordenson said. Other Princeton contributors to On the Water were engineering professors James Smith and Ning Lin (then a graduate student) and climate scientist Michael Oppenheimer of the Woodrow Wilson School of Public and International Affairs.

Hurricane Sandy heightened the urgency of long-term coastal planning. While advising a New York State commission on future land use strategies, Nordenson began discussing a broader plan for the East Coast with Joseph Vietri of the U.S. Army Corps of Engineers and Nancy Kete of the Rockefeller Foundation. This discussion led to the Structures of Coastal Resilience project, which is funded by the Rockefeller Foundation and began in October 2013. The project is managed by Princeton’s Andlinger Center for Energy and the Environment and will extend resilient design concepts to other coastal regions, as well as integrate hurricane storm surge predictions with projections of local sea level rise.

One of the project’s goals is to encourage a reconsideration of the absolute flood zone boundaries on maps produced by the Federal Emergency Management Agency (FEMA), which determine building code requirements and insurance rates. Climate science shows that the geographical borders of flood risk should be based on the probabilities and outcomes of different storm events, not the placements of artificial levees that may be overtopped by high storm surges. Indeed, many of the homes and businesses ravaged by Hurricane Sandy were not located in flood hazard zones on FEMA’s maps. “Sandy really brought home the message that we have to do a lot better in the future,” said Oppenheimer, the Albert G. Milbank Professor of Geosciences and International Affairs. “Because while we sit here thinking about it, the risk is only increasing.”

Click to enlarge. The low-lying barrier island that is home to Atlantic City is particularly vulnerable to storm surges, especially in parts of the city, such as residential Chelsea Heights, that were built on wetlands. Researchers are exploring ways to make existing neighborhoods (Panel A) more resilient in the face of occasional storm surges. By raising houses, using roads as low levees and letting abandoned lots return to wetland conditions, these neighborhoods can become “amphibious suburbs” (Panel B). A similar approach can be applied to existing canal neighborhoods (Panel C), making them more resilient and tolerant of flooding (Panel D).

Click to enlarge. The low-lying barrier island that is home to Atlantic City is particularly vulnerable to storm surges, especially in parts of the city, such as residential Chelsea Heights, that were built on wetlands. Researchers are exploring ways to make existing neighborhoods (Panel A) more resilient in the face of occasional storm surges. By raising houses, using roads as low levees and letting abandoned lots return to wetland conditions, these neighborhoods can become “amphibious suburbs” (Panel B). A similar approach can be applied to existing canal neighborhoods (Panel C), making them more resilient and tolerant of flooding (Panel D).

Smarter building codes are also needed, according to Lin, an assistant professor of civil and environmental engineering, who heads the effort to predict storm surge levels. Current building code books primarily address earthquake risks. “A tiny few chapters are for wind, and very few pages are for flooding,” Lin said. Large-scale, long-term projects such as levees and seawalls have been the standard approach to coastal protection. But the Coastal Resilience team puts forth a different view, one of coping with occasional flooding rather than fighting it. “We will never be able to prevent such hazards. We can only be prepared to reduce their impact,” Lin said.

Resilient designs call for supporting, revitalizing and in some cases reengineering natural features such as wetlands and beach dunes. This so-called “soft infrastructure” can reduce the impact of waves, improve water quality and create new recreational spaces for coastal residents and visitors. Rather than the exclusive construction of barriers, the project’s plans include “layered systems of natural and engineered structures that will respond in different ways to different hazards,” Nordenson said. “It is a more nuanced and more resilient approach.”

Flexible design is also an important component of the project. Ideally, the sizes and arrangements of structures will be adaptable as predictive models improve. Scientists continue to debate how climate change will affect the strength and frequency of storms. “But we are trying to take what we know right now and do the best job we can in accounting for the uncertainties in what we know, and use that to explore how we should be thinking about adaptation,” said Smith, the William and Edna Macaleer Professor of Engineering and Applied Science and chair of the Department of Civil and Environmental Engineering at Princeton.

Meteorological measurements show that the extreme winds of a swirling hurricane transfer energy to the ocean surface. The winds and the storm’s low air pressure cause a dome of water to rise, generating a surge of high water when the storm makes landfall. “When you think of the storm, you think of the wind and the rain. That’s what seems scary,” said Talea Mayo, a postdoctoral research associate who is working with Lin to model storm surges. But the coastal storm surge was the main cause of deaths and property damages from Hurricane Sandy.

To predict future storm surges, Lin and Mayo are using thousands of synthetic hurricanes modeled by Kerry Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology. “Anytime you’re studying hurricanes, especially so far north, your historical data are really limited because there just aren’t enough events,” Mayo said. “So instead of basing our risk analysis on historical data, we use synthetic data.”

Hurricane damage 1944

Storms have caused significant damage to Atlantic City’s iconic boardwalk throughout its existence. Shown here is South Inlet during the Great Atlantic Hurricane of 1944. Image from the archive of the Coastal and Hydraulics Laboratory, Engineer Research and Development Center, Vicksburg.

Emanuel’s team uses existing models of global climate circulation patterns to generate 3,000 synthetic, physically possible storms for nine different climate change scenarios at each of the four study sites — a total of more than 100,000 storms. These hurricanes exist only in computer code, but their wind speeds, air pressure levels and patterns of movement are based on physical laws and information from recorded storms. Mayo and Lin plug these parameters into algorithms that work like sophisticated versions of high school physics problems: solve the equations for conservation of mass and momentum to estimate maximum water levels at each site. Variations in tide levels, coastline shapes and seafloor topographies add additional layers of complexity.

To make reasonable projections of future flood hazards, the models must also account for sea level rise. According to geoscientist Chris Little, an associate research scholar working with Oppenheimer, storm surges are a short-term version of sea level rise. “They both contribute to coastal flooding,” Little said. “Climate change will be felt through the superposition of changes in long- and short-term variations in sea level.”

And when it comes to sea level rise, local projections are crucial for planning efforts. A constellation of factors influence regional differences in sea levels, including the vertical movement of the Earth’s surface, changes in ocean circulation and the melting of glacial ice. Little and Oppenheimer were among the authors of a study published in June 2014 in the journal Earth’s Future, which used model-based and historical tide gauge data for sites around the globe to project local sea levels over the next two centuries.

“We live in a hotspot, where the local sea level rise has been higher in the past than the global mean, and we expect it to continue to be higher in the future,” Oppenheimer said — as much as 40 percent higher than the worldwide average. One reason for this is that the land along the East Coast is slowly sinking (by a millimeter or two each year), a legacy of the ice sheet that covered much of North America until about 12,000 years ago. The ice sheet depressed Earth’s crust over present-day Canada, causing the liquid mantle beneath to bulge southward. Now that the glaciers have melted, the mantle is being gradually redistributed, flowing out from under the East Coast of the United States.

Sea levels respond slowly to changes in climate, including the current warming trend, caused in part by increased carbon dioxide levels from human activity. Because future carbon emissions depend on human decisions, predictions of sea level rise come with built-in uncertainty. This project attempts to meet this challenge head-on: “A major purpose of the project is to think about doing a more thorough job of assessing the uncertainty in these flood zones,” Little said. “I think it’s difficult but worthwhile.”

Resilient designs call for planning and reengineering natural features such as salt marshes, submerged aquatic vegetation and wetlands, as in this imagined coastline for Staten Island, south of Manhattan.

Resilient designs call for planning and reengineering natural features such as salt marshes, submerged aquatic vegetation and wetlands, as in this imagined coastline for Staten Island, south of Manhattan.

Because of this uncertainty, climate scientists deal in probabilities. The Princeton team has projected flood levels for storms with return periods of 100, 500 and 2,500 years. A return period of 100 years is akin to a “100-year flood” — this means that in any given year there is a 1 percent chance of that flood level occurring. These forecasted flood risks are key to making smart building and design decisions in the face of climate change. “Every decision-maker is going to look and decide what risk is tolerable for their region in the context of how much it would cost to defend against that risk,” Oppenheimer said.

The design teams are beginning to test their plans against the climate scientists’ predictions. Simulated local water levels will reveal which structures may be inundated by future storms and at what probabilities. These analyses may prompt the designers to adjust the heights of buildings, roads or beach dunes in their blueprints. And as the science improves, this process will repeat itself. “Over time, others can start to add things that we haven’t been able to include, like the relationship of the wind and the flood,” Nordenson said.

True resilience necessitates a change in outlook. In Atlantic City, the focus area for Lewis and the Princeton group, a narrow channel of water separates the Chelsea Heights neighborhood from the city’s famous boardwalk and high-rise casinos, where many residents work. “You have extensive areas of suburban neighborhoods that are built on wetlands,” said Lewis. “Two binary positions are retreat, where you return these to wetlands, and fortification, which is the seawall approach. And both of them are problematic.”

The team recognizes the social and economic importance of maintaining the neighborhood. But barricading it behind a seawall may be prohibitively expensive, not to mention unattractive. More important, metal or concrete seawalls can actually exacerbate flooding when areas behind them are inundated by heavy rain. Lewis and his team have a fundamentally different vision for places like Chelsea Heights: “We’re looking at developing an amphibious suburb,” he said. “We want water to come in. If there are berms [earthen seawalls] that are put in, they should be built with a series of valves.”

The plans for Chelsea Heights include raised homes and roads interspersed with canals and revitalized wetlands. Lewis hopes these ideas will be useful to policymakers and to the Army Corps of Engineers, which may apply the Princeton team’s concepts to Chelsea Heights and other similar communities along the New Jersey shore. By the end of this century, grassy suburban lawns may be transformed into salt marshes.

PLANNING FOR RESILIENCE UP AND DOWN THE COAST

Natural features play a pivotal role in the designs for two of the project’s other focal regions, New York’s Jamaica Bay and Rhode Island’s Narragansett Bay.

  • The plan for Jamaica Bay includes the use of local dredged materials to build up land for marsh terraces, which can serve to reduce wind fetch as well as improve water quality and encourage sediment deposition, according to Catherine Seavitt, an associate professor of landscape architecture at the City College of New York. In particular, her team hopes to expand the restoration of a native wetland grass, Spartina alterniflora, an effective attenuator of wind and waves that also provides valuable ecological habitat.
  • Michael Van Valkenburgh and Rosetta Elkin lead the Harvard design effort for Narragansett Bay. One of their plans involves relocating two critical reservoirs that supply drinking water to the city of Newport. The reservoirs are currently vulnerable to coastal flooding; the proposed project would use dredged material from the original reservoir to fill in and extend the existing maritime forest, now a rare ecosystem along the New England coast. The larger forest, designed by the team, would mitigate coastal erosion, attenuate wave action, and become a valuable recreational area for surrounding communities.
  • The project’s other site, the Norfolk, Virginia, area of Chesapeake Bay, calls for a more extensive reshuffling of settlement and infrastructure, according to Dilip da Cunha, an adjunct professor of landscape architecture at the University of Pennsylvania. Of the four sites, Norfolk is expected to see the most dramatic sea level rise, and is home to the world’s largest naval station and a vital commercial port. The UPenn team’s designs stem from the natural network of fractal-like interfaces where land and water meet. The plan seeks to bolster “fingers of higher ground” that will be more robust to gradual sea level rise as well as storm surges. “The higher grounds could be for housing, schools and other facilities, and the low grounds could accommodate various things, from marsh grasses to football fields,” da Cunha said. “Things that can take water in the case of a storm event, but will not endanger lives.”

-By Molly Sharlach

Computer visions: A selection of research projects in Computer Science

Princeton’s Department of Computer Science has strong groups in theory, networks/systems, graphics/vision, programming languages, security/policy, machine learning, and computational biology. Find out what the researchers have been up to lately in these stories:

Computer VisionsArmchair victory: Computers that recognize everyday objects

JIANXIONG XIAO TYPES “CHAIR” INTO GOOGLE’S search engine and watches as hundreds of images populate his screen. He isn’t shopping — he is using the images to…

 

 

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A NEW SOFTWARE PROGRAM MAKES IT EASY for novices to create computer-based 3-D models using simple instructions such as “make it look scarier.” The software could be useful for…

 

 

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Wetlands provide solutions for agricultural runoff

Wetlands

When a dry spell made their intended experiments impossible, researchers made a serendipitous discovery: a novel biochemical reaction that could help clean up wastewater and remediate wetlands. (Photo by Peter Jaffe)

A PATCHWORK OF SMALL LAKES, forests and marshes surrounded by farms and suburbs, the Assunpink Wildlife Management Area in central New Jersey is an ideal place to track the effects of agricultural nitrogen runoff on wetland soil chemistry. Princeton professor Peter Jaffe and his students arrived at the study site in 2004, along with an ecology research group from Rutgers University.

But a drought made their intended experiments impossible; they couldn’t study the wetlands when they had dried out. Instead, Jaffe, a professor of civil and environmental engineering, asked his students to take soil samples back to the lab, where they added different sources of nitrogen to the samples and analyzed changes in their chemistry.

In some of the samples, the researchers observed something unexpected: in the absence of oxygen, a polluting form of nitrogen called ammonium was transformed into harmless nitrogen gas. In these samples, electrons — charged particles — were moving from ammonium, which comes from fertilizer runoff, to iron, a plentiful metal in the soil. Jaffe’s group documented this reaction for the first time.

Although Jaffe’s original goal was to examine how nitrogen runoff from fertilizer affects metal transport in wetland ecosystems, he wondered if this newly discovered natural phenomenon could be useful for cleaning up nitrogen pollution. To investigate it further, he secured funding from the National Science Foundation and Princeton’s Project X, a program that funds risky but promising projects, and returned to the site in 2011 with postdoctoral research associate Shan Huang. “My first fear was that we wouldn’t see anything,” Jaffe said. “But our findings were reproducible.”

Huang and Jaffe brought fresh soil samples back to the lab. To mimic the underground environment at the field site, Huang placed the small bottles of mud in a chamber without oxygen and bathed them in water spiked with ammonium. She monitored levels of ammonium and forms of iron in the samples and found that the ammonium was indeed being converted into nitrite, a precursor of nitrogen gas.

As Huang monitored the reaction, she noticed something intriguing. “After six months, the reaction became more and more efficient,” she said. “We thought there should be some bacteria responsible for the reaction.” When Huang sterilized the soil by heating it under high pressure, the ammonium removal stopped, suggesting that microorganisms were the force behind the chemical transformations.

Those microorganisms were carrying out a reaction, now known as Feammox, that oxidizes ammonium — takes the electrons from it — and transfers the electrons to iron (Fe is the symbol for the element iron). The oxidized ammonium became nitrite, and other bacteria converted the nitrite to nitrogen gas.

Since the Jaffe team’s initial discovery of Feammox, two other groups have observed the process, in a laboratory sewage treatment reactor and in soil from a Puerto Rican rainforest. But Jaffe and Huang were the first to identify the bacterium that carries out the reaction. Huang isolated this bacterial species from the others present in the soil. “We tried hundreds of different growth conditions, and finally got a pure culture,” she said. “It was 50 percent hard work and 50 percent luck.” The winning recipe had an acidic pH, similar to the soil environment where the bacteria were found.

The bug, which belongs to a family of soil microbes called Acidimicrobiaceae, functions without oxygen and at a relatively low temperature — about 68 degrees Fahrenheit, compared with 86 degrees for other microbes that oxidize ammonium in the absence of oxygen. “This is really good when you think about applying this in wastewater treatment plants,” said Melany Ruiz-Urigüen, a graduate student who is working to optimize the Feammox reaction. “It means you wouldn’t have to heat the water, and that saves a lot of energy.”

Ruiz-Urigüen is also testing whether the bacteria can use inexpensive sources of iron, such as scrap metal. The Feammox reaction requires iron oxide, which is found on rusty steel — a plentiful industrial waste. For Ruiz-Urigüen’s latest experiments, she uses steel wool pads purchased from a home improvement store. She sprays the metal mesh with a salty solution and lets it rust for two weeks before adding it to a reactor.

In the wetland environment, Feammox bacteria likely depend on plants to supply oxidized iron for the reaction. Oxygen leaks out of plant roots, forming orange nodules where it reacts with iron in the soil; this natural rust can seep into areas without oxygen, where Feammox bacteria thrive. To investigate how the Feammox process might work in an engineered wetland, graduate student Zheyun Zhang is monitoring the reaction in greenhouse pots planted with cattails and bulrushes. “We want to use the plants to recycle the iron,” Zhang said. “Plants are very cheap. And it’s a natural process.”

Jaffe and his team hope to improve the Feammox process and harness it to clean up pollution — not only of nitrogen runoff, but perhaps also of certain toxic metals that may act as stand-ins for iron. The success of this fortuitous discovery gives the researchers confidence as they strive to turn Feammox into a useful technology.

–By Molly Sharlach

Emotional map illuminates an iconic rock song

Gilad Cohen

Gilad Cohen, a graduate student in music composition, analyzed the songs of the English rock band Pink Floyd. (Photo by David Kelly Crow)

IN A TYPICAL ROCK SONG, a few chords and a simple rhythm form the foundation for catchy lyrics that carry the listener along for three or four minutes. Expand these elements into a 20-minute song, and the result should be boring.

Yet songs of this length were common for progressive rock bands in the late 1960s and 1970s. Most of these extra-long songs were actually collections of “sub-songs” — sequences of disparate musical ideas, according to Gilad Cohen, a graduate student in music composition. As part of his dissertation research, Cohen analyzed the expanded songs of the ever-popular English rock band Pink Floyd.

The 1975 Pink Floyd song “Shine On You Crazy Diamond” is 26 minutes long. “And it’s all in the same key,” Cohen said. “The rhythm is very simple. You have a few chord progressions, and they just repeat themselves again and again.”

But the song is anything but boring. “There’s a very clever, detailed arrangement process that makes this music interesting, and allows it to maintain momentum throughout a long stretch of time,” Cohen said. The arrangement includes motivic development — the alteration or repetition of a motif throughout a piece of music — and the layering of instruments, in addition to the use of studio effects such as reverb and delay, innovative tools at the time.

“Shine On You Crazy Diamond” is a tribute to Syd Barrett, Pink Floyd’s former leader. Barrett left the band in 1968 due to mental illness, which was likely exacerbated by his use of LSD and the intense pressure he felt to create hits. Cohen views the song as an emotional journey through the stages of grief, an expression of the band’s sense of loss.

A "bereavement map" for Pink Floyd's "Shine On You Crazy Diamond" reveals which parts of the song express each of the five stages of grief - numbness, yearning, anger, mourning and acceptance.

A “bereavement map” for Pink Floyd’s “Shine On You Crazy Diamond” reveals which parts of the song express each of the five stages of grief – numbness, yearning, anger, mourning and acceptance.

To better understand how the sounds reflect these emotions, Cohen created a “bereavement map” showing which parts of the song express each of the five stages of grief — numbness, yearning, anger, mourning and acceptance. Like the real grieving process, the progression is not exactly linear.

Numbness, for example, is represented by drawn-out, improvised keyboard and guitar solos built around a single chord. Then, the guitar plays the song’s famous four-note “yearning motif,” in which the last note doesn’t quite belong with the rest. “It sounds like it wants to go somewhere,” Cohen said. “Pink Floyd is amazing at creating this tension.” Later, the same melody is played in two different rhythms, which alternately impart feelings of yearning and anger.

“Rock music is starting to have its day in the sun in musicological scholarship,” said Scott Burnham, the Scheide Professor of Music History and Cohen’s dissertation adviser. “Gilad’s work is timely, and it’s coming from a really great place — namely, his work as a musician and composer.”

Cohen shared his passion for Pink Floyd by organizing the first academic conference on the band’s music, “Pink Floyd: Sound, Sight and Structure,” which was held at Princeton in April 2014, and was co-organized by Dave Molk, a fellow graduate student in composition. The event’s keynote speaker was James Guthrie, Pink Floyd’s producer and engineer.

Cohen said he was inspired by the reactions of students, scholars and “hardcore fans” who attended the conference. “They’re really starved for this kind of knowledge. They listen differently to the music now,” Cohen said. “If I can expand someone’s enjoyment of music they’ve listened to throughout their lives, that’s a big thrill.”

–By Molly Sharlach

Captured on video: Virus-sized particle trying to enter cell

Virus video

Researchers captured video of a virus-like particle trying to enter a cell (Image courtesy of Kevin Welsher)

RESEARCHERS AT PRINCETON UNIVERSITY achieved an unprecedented look at a virus-like particle as it tries to break into and infect a cell. The video reveals the particle zipping around in a rapid, erratic manner until it encounters a cell, bounces and skids along the surface, and either lifts off again or, in much less time than it takes to blink an eye, slips into the cell’s interior. The work, conducted by Professor of Chemistry Haw Yang and postdoctoral researcher Kevin Welsher, was supported by the U.S. Department of Energy and published in the Feb. 23, 2014, issue of Nature Nanotechnology.

–By Catherine Zandonella

The Planet Hunters

Milky way

The Milky Way as seen from a telescope in the Namibian desert. (Photo courtesy of Gáspár Bakos)

From Gáspár Bakos’ desk at Princeton, he can see everything that happens at his telescopes on three continents. He can see wild burros nuzzle at the cables in Chile, warthogs wander by in Namibia, and kangaroos come a bit too close for comfort in Australia.

Despite the risks to his equipment, managing telescopes in three time zones across the Southern Hemisphere has a major advantage: it is always nighttime somewhere, so Bakos’ telescope network can search around the clock for planets outside our solar system, or exoplanets.

Bakos, an assistant professor of astrophysical sciences, is one of several Princeton faculty members involved in finding and studying exoplanets. Some researchers, like Bakos, are searching for the faint dimming of starlight that happens when a planet transits in front of a star. Others are trying to achieve what some have called the Holy Grail of planet hunting: direct imaging of an exoplanet. But detecting a planet is just the beginning. Researchers hope that by studying other solar systems they can confirm theories about how planets form and perhaps even learn whether life exists on these other worlds.

“Princeton is making contributions to the search for exoplanets in a number of areas,” said David Spergel, the Charles A. Young Professor of Astronomy on the Class of 1897 Foundation and chair of the Department of Astrophysical Sciences.

Discover and characterize

Just 20 years ago, finding planets around stars other than our sun was thought to be impossible — they were too far away, too dim and too close to the glare of their star. But today, due to creative strategies and new telescopes, about 1,000 planets have been detected and confirmed, with thousands of candidates awaiting confirmation.

The vast majority of the confirmed planets are quite unlike our own, however. Some are gas giants larger than Jupiter that orbit very close to their star — so close, in fact, that they can make an entire circuit around the star in a few days. Contrast this to our solar system, where Mercury, the closest planet to the sun, has an orbital period of 88 days — that is, it takes 88 days to orbit the sun. Earth makes the journey in 365 days.

The reason we’ve found so many of these large planets, which astronomers have nicknamed hot-Jupiters, is because they are relatively easy to detect with current methods. The two most successful ways of finding planets to date are to look for the periodic dimming of starlight when the planet crosses in front of the star, as Bakos’ telescopes do, or to look for the episodic wobbling of the star in response to the planet’s gravitational pull.

Professor Gáspár Bakos

Professor Gáspár Bakos (Photo by Pal Sari)

Through findings from a space-based NASA telescope known as Kepler, which hunted planets from 2009 until earlier this year, we now know that hot-Jupiters are the exception rather than the norm. “We can detect these hot-Jupiters because they pass in front of their stars fairly often and they block a significant fraction of the starlight,” said Bakos, “not because there are more of them than there are other kinds of planets.”

These other kinds of planets could include ones with conditions capable of supporting life. These planets lie in the “habitable zone” not too close and not too far from their star, and are capable of having liquid water on their surfaces.

One of Bakos’ telescope networks, HATSouth, is looking for exoplanets, including possibly habitable ones. HATSouth can detect planets with orbital periods of 15 to 20 days, which may not seem like much, but for certain classes of stars, namely the mid- to late-M dwarf stars, planets with 15-day periods lie in the habitable zone.       Bakos started building his first HAT — Hungarian made Automated Telescope — in 1999 while a student at Eötvös Loránd University in Budapest. The automated telescopes are relatively small — close in size to amateur models — but the lower costs allow more of them to be deployed. An earlier network Bakos built, HATNet, which came online in 2003 and consists of telescopes at sites belonging to the Smithsonian Astrophysical Observatory (SAO) in Arizona and Hawaii, has discovered 43 candidate planets.

HATSouth became operational in 2009 and is a collaboration between Princeton University, the Max Planck Institute for Astronomy, Australian National University and Pontificia Universidad Católica de Chile. Originally funded by the National Science Foundation and SAO, the network consists of six robotic instruments located at Las Campanas Observatory in Chile, the High Energy Stereoscopic System site in Namibia and Siding Springs Observatory in Australia. To date, HATSouth has detected a handful of planets, and has a dozen candidates awaiting confirmation. So far, all of the planets have fairly short orbital periods — they orbit their stars in one to three days — but Bakos is optimistic about HATSouth and his new project, HATPI, for which he has received funding from the David and Lucile Packard Foundation. HATPI is a wide-field camera system that will continuously image the entire night sky at high resolution and precision for five years, with the goal of identifying planets with longer orbital periods. Bakos’ team includes Joel Hartman and Kaloyan Penev, both associate research scholars; Zoltan Csubry, an astronomical software specialist; Waqas Bhatti and Miguel de Val-Borro, both postdoctoral research associates; and Xu (Chelsea) Huang, a graduate student.

Direct imaging

While HATSouth looks for dips in starlight that indicate the presence of a planet, other researchers at Princeton are aiming to directly image exoplanets. Such imaging is possible, for example, when the planet appears on the right or left side of the star rather than directly in front of it. To date, only a handful of exoplanets have been observed this way, because the star’s light is so bright that seeing a nearby planet is like trying to see a speck of dust in the glare of a headlight.

Kasdin

Professor Jeremy Kasdin (Photo by Alexandra Kasdin)

Jeremy Kasdin’s group is working to develop instrumentation for direct imaging. “The idea is to block out the star’s light so that it is possible to see the planet,” said Kasdin, a professor of mechanical and aerospace engineering.

Astronomers have used this concept to study the sun since the 1930s: they place a black disc, called a coronagraph, at the center of the telescope’s image to block light from the sun so they can study solar flares on its surface.

For planet-watching however, this light must be blocked with great precision. Because light acts as a wave, it diffracts around the edge of the telescope and, without a coronagraph, creates concentric patterns on the resulting image (see illustration, page 27), just as water makes ripples in a pond when it flows past an obstacle. These patterns obscure the planet.

To eliminate or change these patterns, researchers at Princeton’s High Contrast Imaging Laboratory, led by Kasdin, are developing a coronagraph with a distinctive shape and arrangement of slits that alter the patterns in ways that can permit detection of planets. This “shaped-pupil coronagraph” is being developed by Kasdin and his collaborators Spergel, Edwin Turner, a professor of astrophysical sciences, Michael Littman, a professor of mechanical and aerospace engineering, and Robert Vanderbei, a professor of operations research and financial engineering, along with postdoctoral research associates Tyler Groff and Alexis Carlotti and graduate students Elizabeth Jensen and A.J. Eldorado Riggs. The coronagraph could be sent up in a space-based telescope mission under consideration for later in the decade.

Pupil diagramThe Kasdin lab is also working on another light-blocking idea called an occulter. This is a giant sail that could fly in space, ahead of a space-based telescope, to block out light from a star. “It is sort of like holding your hand up to block the sun while you watch a bird in the sky,” said Kasdin. The occulter would be launched folded-up, like a flower bud with petals that would unfold in space to create a shield with a diameter of about 40 meters (131 feet) that would fly about 11,000 kilometers — or roughly 6,800 miles — ahead of the telescope to block the star’s light.

Occulter diagramAt Princeton’s Forrestal Campus three miles from the main campus, graduate student Daniel Sirbu is testing four-inch high models of occulters. The team collaborates closely with NASA’s Jet Propulsion Laboratory at the California Institute of Technology where an occulter is being built and tested with the help of engineers at Northrop Grumman and Lockheed Martin.

Video: How an occulter would unfold in space:

In addition to blocking light, Kasdin’s group is working to improve the technology for correcting faulty imaging caused by the Earth’s atmosphere, as well as heat, vibrations and imperfections in the telescopes themselves. All ground-based telescopes suffer from poor imaging quality due to atmospheric water vapor that is present even on cloudless nights, causing turbulence that makes stars appear to twinkle. Astronomers can correct these distortions using a technology known as adaptive optics which involves bendable mirrors. The Kasdin lab is working on improvements to these systems.

Coronagraphs and adaptive optics already are in use in a handful of telescopes, including the Subaru Telescope, operated by the National Astronomical Observatory of Japan (NAOJ), in Hawaii. Princeton researchers, including Kasdin and his colleagues, as well as Turner; astrophysical sciences professor Gillian Knapp; Timothy Brandt, a 2013 Ph.D. in astrophysical sciences; and others, are part of an international collaboration led by NAOJ scientist Motohide Tamura that is known as SEEDS (Strategic Explorations of Exoplanets and Disks with Subaru).

Kasdin’s group is working on designing an instrument, the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), to add to the Subaru Telescope to look at the different kinds of light, or spectra, emitted by a planet. Just as a prism splits white light into its rainbow of colors, CHARIS contains prisms and special filters that allow researchers to see the different wavelengths of light. These wavelengths provide signatures that can reveal the planet’s temperature and hint at which atoms and molecules are present around the planet. Graduate student Mary Anne Peters and Groff are working on CHARIS.

“The instrument makes it possible to look at the spectrum at each point in the image,” said Groff, “so you can distinguish the planet light from the star and see whether the planet’s atmosphere is uniform or cloudy, and you can get an idea of age because as the planet gets older, it cools.”

Beyond detection

Detecting exoplanets, whether by watching for their transits or by direct imaging, is just the first step in developing an understanding of these objects, said Adam Burrows, a professor of astrophysics who uses data gathered from these campaigns to construct theories about the characteristics of exoplanets and planetary systems. “Once we’ve detected planets, how do we figure out their makeup, their atmospheric compositions and temperatures, and their climates? These are the kinds of questions we are interested in answering,” Burrows said.

These questions can be addressed only by detecting and interpreting the spectral emissions that will be detected by instruments such as CHARIS, but so far these are only available for large exoplanets. “As larger ground-based telescopes and space-based missions like the James Webb Space Telescope come online,” Burrows said, “we will have data from planets that are closer in size to the Earth. The objects being studied now are but stepping stones toward the broader characterization of the planets in general in the galaxy and in the universe.”

This broader characterization includes ongoing studies by a number of other Princeton researchers, including Markus Janson, a NASA Hubble Postdoctoral Research Fellow in astrophysical sciences, who studies how planets are formed from dust and debris that orbits the star. Other researchers studying planet formation include Roman Rafikov, assistant professor in astrophysical sciences, and Ruobing Dong, who earned his Ph.D. in 2013 while working on the SEEDS project and is now a NASA fellow at the University of California-Berkeley. Emily Rauscher, a NASA Sagan Postdoctoral Fellow in astrophysical sciences, is studying the climate on these faraway worlds.

Many researchers hope that studying exoplanets will help us learn more not only about planetary formation and solar systems but also about whether other planets exist that could support life. The instruments and telescope networks being developed at Princeton could lead the way. And if a wild burro chews on a cable now and then, well, it is part of the cost of learning what lies outside our solar system.

Box: Data mining for planets

Xu (Chelsea) Huang

Xu (Chelsea) Huang (Photo by Keren Fedida)

Data mining for planets Xu (Chelsea) Huang remembers the thrill of finding her first planet. “It was exciting,” said the graduate student in astrophysical sciences. Huang found that planet and many more in 2012 while looking through a publicly available data set from NASA’s space-based Kepler mission, which scans for dips in starlight as the planet crosses in front of the star. Using techniques developed for analyzing HATNet findings under the guidance of Associate Research Scholar Joel Hartman and Assistant Professor Gáspár Bakos, Huang found 150 potential planets — many of which were hot “super-Earths” that are slightly large than Earth but orbiting their host stars much more closely — that the Kepler team and others had missed. The paper was published earlier this year in the journal Monthly Notices of the Royal Astronomy Society. When the Kepler mission later released an updated list of possible planets, about half the ones that Huang had found were on it.

Box: Forecasting the climate on other worlds

Emily Rauscher

Emily Rauscher, a NASA Sagan Postdoctoral Fellow at Princeton’s Department of Astrophysical Sciences, is modeling the climate on exoplanets. (Photo by Andrew Howard)

Emily Rauscher, a NASA Sagan Postdoctoral Fellow in the Department of Astrophysical Sciences, said that new acquaintances don’t believe her when she says she does climate modeling for exoplanets. Rauscher uses what is known about our solar system, plus the laws of fluid dynamics and the exoplanets’ orbital period and mass, to try to understand the climate on these faraway worlds. “If you watch a planet throughout its orbit, you can see the change in the amount of light emitted from the planet’s night side versus from its day side,” Rauscher said. “Because it is very hot in the day and very cold at night, we expect winds to blow around the planet, and by measuring the difference in brightness coming from the planet, we can detect how the wind affects the planet’s temperature.” Rauscher is fascinated by the idea of life on other planets but said that there is plenty to discover even on uninhabitable hot-Jupiters. “There is a big push to discover Earth-like planets,” she said, “but there is a lot we can learn from studying the planets we know about already.”

Box: Exploring how planets are formed

Studying exoplanets also could help researchers learn more about how planets are formed from dust and debris that orbits the star, said Markus Janson, a NASA Hubble Postdoctoral Research Fellow in the Department of Astrophysical Sciences. Some of the material that doesn’t end up in planets is collected in rings called debris disks, he explained. Our solar system has two such debris disks: an asteroid belt between Mars and Jupiter and the Kuiper Belt beyond Neptune.

“Our conventional theory of how planets form— that dust sticks together and forms into planets like Earth, and that sometimes large amounts of gas accumulate onto a rocky core to form gas giants like Jupiter — is based on what we’ve observed in our solar system.” Janson said. “Now we can study other solar systems, so we can test this theory.” A recent study by Janson and colleagues, accepted for publication by The Astrophysical Journal, indicates that the majority of exoplanetary systems probably did form in this manner.

-By Catherine Zandonella

Inventions Bridge the Gap between lab and marketplace

Road trip

A road trip offered Mark Zondlo and his team the opportunity to test their new air quality sensors. (Photo by Lei Tao)

The college experience often involves at least one road trip, but most students do not bring along their faculty adviser. But last spring, two graduate students crammed into a rented Chevy Impala with Professor Mark Zondlo and a postdoctoral researcher to drive eight hours a day across California’s Central Valley, testing their new air-quality sensors, which were strapped to a rooftop ski rack.

The sensors are an example of technologies being developed at Princeton that have the potential to improve quality of life as commercial products or services. Although teaching and research are Princeton’s core missions, the campus is home to a vibrant entrepreneurial spirit, one that can be found among faculty members who are making discoveries that could lead to better medicines as well as students working to turn a dorm-room dream into the next big startup.

“Princeton has a number of initiatives aimed at supporting innovation and technology transfer,” said John Ritter, director of Princeton’s Office of Technology Licensing, which works with University researchers to file invention disclosures and patent applications, and with businesses and investment capitalists to find partners for commercialization. “Our goal is to accelerate the transfer and development of Princeton’s basic research so that society can benefit from these innovations,” he said.

Crossing the valley

One of the ways that Princeton supports this transfer is with programs that help bridge the gap between research and commercialization, a gap that some call the Valley of Death because many promising technologies never make it to the product stage. One such program is the Intellectual Property Accelerator Fund, which provides financial resources for building a prototype or conducting additional testing with the goal of attracting corporate interest or investor financing.

Zondlo, an assistant professor of civil and environmental engineering, is one of the researchers using the fund to cross the valley — in this case literally as well as figuratively. Earlier this year, Zondlo and his research team, which consisted of graduate students Kang Sun and David Miller and postdoctoral researcher Lei Tao, tested their air-quality sensor in California’s Central Valley, a major agricultural center that is home to some of the worst air pollution in the nation.

Their goal was to compare the new portable sensors to existing stationary sensors as well as to measurements taken by plane and satellite as part of a larger NASA-funded air-quality monitoring project, DISCOVER-AQ.

One of the new sensors measures nitrous oxide, the worst greenhouse gas after carbon dioxide and methane. Nitrous oxide escapes into the air when fertilizers are spread on farm fields. Currently, to measure this gas, workers must collect samples of air in bottles and then take them to a lab for analysis using equipment the size of refrigerators.

Zondlo’s sensor, which is bundled with two others that measure ammonia and carbon monoxide, is portable and can be held in one hand, or strapped to a car roof. “The portability allows measurements to be taken quickly and frequently, which could greatly expand the understanding of how nitrous oxide and other gases are released and how their release can be controlled,” Zondlo said.

The sensors involve firing a type of battery-powered laser, called a quantum cascade laser, through a sample of air, while a detector measures the light absorption to deduce the amount of gas in the air. The researchers replaced bulky calibration equipment, necessary to ensure accurate measurements in the field, with a finger-sized chamber of reference gas against which the sensor’s accuracy can be routinely tested.

The decision to commercialize the sensor arose from the desire to make the device available to air-quality regulators and researchers, Zondlo said. “Our sensor has precision and stability similar to the best sensors on the market today, but at a fraction of the size and power requirements,” said Zondlo, a member of the Mid-Infrared Technologies for Health and the Environment (MIRTHE) center, a multi-institution center funded by the National Science Foundation (NSF) and headquartered at Princeton. “We are already getting phone calls from people who want to buy it.”

Lighting up the brain — with help from a synthetic liver

Far from the dusty farm roads of California, Princeton faculty member John (Jay) Groves sits in his office in the glass-enclosed Frick Chemistry Laboratory, thinking about the potential uses for a new synthetic enzyme. Modeled on an enzyme isolated from the liver, the synthetic version can carry out reactions that human chemists find difficult to pull off.

One of these reactions involves attaching radioactive fluorine tags to drugs to make them visible using a brain-imaging method known as positron emission tomography (PET) scanning.

PET scans of the radiolabeled drugs could help investigators track experimental medicines in the brain, to see if they are reaching their targets, and could aid in the development of drugs to treat disorders such as Alzheimer’s disease and stroke, according to Groves, Princeton’s Hugh Stott Taylor Chair of Chemistry. The synthetic enzyme adds fluorine tags without the toxic and corrosive agents used with radioactive fluorine today.

Groves’ initial work was supported by the NSF, but to develop the technology for use in pharmaceutical research, the Groves team, which includes graduate students Wei Liu and Xiongyi Huang, is receiving funding from a Princeton program aimed at supporting concepts that are risky but have potential for broad impact. The Eric and Wendy Schmidt Transformative Technology Fund was created with a $25 million endowment from Google executive chairman Eric Schmidt, a 1976 alumnus and former trustee, and his wife, Wendy.

“The Schmidt funding is enabling us to explore ways to optimize the chemical reaction and create a prototype of an automated system,” Groves said. “This will allow us to create a rapid and noninvasive way to evaluate drug candidates and observe important metabolites within the human brain.”

Aiding the search for planets

Tyler Groff

Postdoctoral researcher Tyler Groff is creating an improved system for adjusting the blurry images seen through telescopes due to atmospheric turbulence, heat and vibrations. (Photo by Denise Applewhite)

Inspired by the search for planets outside our solar system, Princeton postdoctoral researcher Tyler Groff conceived of a technology that could enhance the quality of images from telescopes. Groff received Schmidt funding to develop a device for controlling the mirrors that telescopes use to correct blurring and distortion caused by atmospheric turbulence, heat and vibrations.

This technology, known as adaptive optics, involves measuring disturbances in the light coming into the telescope and making small deformations to the surface of a mirror in precise ways to correct the image. These deformations are made using an array of mechanical devices, known as actuators, each capable of moving a small area of the flexible reflective surface up or down. But existing actuators are limited in the amount of correction they can provide, and the spaces between the actuators create dimples in the mirror, producing a visible pattern in the resulting images that astronomers call “quilting.”

Groff envisioned replacing the array of rigidly attached actuators with flexible ones made from packets containing iron particles suspended in a liquid, or ferrofluid. Just as iron filings can be moved by waving a magnet over them, applying varying magnetic fields to the ferrofluid changes the shape of the fluid in ways that deform the mirror.

The ferrofluid mirror enables highquality images while being more resistant to vibrations and potentially more power efficient, which will be important for future satellite-based telescopes, said Groff, who works in the laboratory of Jeremy Kasdin, professor of mechanical and aerospace engineering. A ferrofluid mirror can also achieve something that a rigid actuator mirror cannot: it can assume a concave or bowl-like shape that aids the focusing of the telescope on objects in space. “A telescope that uses ferrofluid mirrors would be able to see dim objects better,” Groff said, “which would greatly enhance our ability to probe other solar systems.”

From drug discovery to space exploration, Princeton’s dedication to supporting technology transfer and potentially disruptive but high-risk research ideas is yielding tremendous benefits for the advancement of science and the improvement of people’s lives.

Box: From student project to startup

Carlee Joe-Wong (Photo by Steve Schultz)

Carlee Joe-Wong (Photo by Steve Schultz)

In 2009 when Princeton undergraduate Carlee Joe-Wong started working on the technology that would become the DataMi company, she didn’t even own a smartphone. Today, the startup company co-founded by Joe-Wong provides mobile traffic management solutions to wireless Internet providers, and also helps consumers manage their data usage through an app, DataWiz, that has been downloaded by more than 200,000 Apple and Android users.

Joe-Wong became involved in the study of mobile data usage in the spring of her junior year when Professor Mung Chiang challenged her to explore ways that wireless providers could reduce congestion by adjusting their prices based on the variations in network supply and demand. “I mostly just worked on the project in my dorm room,” Joe-Wong said. “I thought it would be cool if it was adopted but I didn’t think that I would be the one helping to make that happen.” After graduation, Joe-Wong became a graduate student working with Chiang on mathematical algorithms that predict the most effective methods for balancing network use across “peak” minutes and “valley” minutes.

“With companies charging $10 per gigabyte, mobile consumers today need to intelligently manage their data,” said Chiang, the Arthur LeGrand Doty Professor of Electrical Engineering. “What the DataWiz app does is tell you when, where and what app used how much of your quota.”

In May 2013 the team, under the engineering leadership of associate research scholar Sangtae Ha, opened an office for DataMi one block off campus. Needless to say, Joe-Wong now has a smartphone.

Taking it to the streets with help from Princeton’s eLab

ELab students

From left: Nathan Haley, Christine Odabashian, Luke Amber and Leif Amber. (Photo by Denise Applewhite)

A love of motorcycles brought them together: three Princeton undergraduates decided to explore building and marketing an electric motorcycle to provide a superior riding experience at significantly lower emissions than gasoline powered models.

The team was one of nine groups selected to participate in the 10-week eLab Summer Accelerator Program, an initiative of the Keller Center in the School of Engineering and Applied Science, which teaches entrepreneurship by offering resources, mentoring and working space.

Throughout the summer, the team members worked on ways to market the bike while simultaneously building a prototype. “We geared the product toward people who enjoy taking weekend trips,” said Nathan Haley, Class of 2014, an economics major.

Haley was joined by Luke Amber, Class of 2015, and Christine Odabashian, Class of 2014, both majors in mechanical and aerospace engineering. The team also included Luke’s older brother, Leif Amber, a graduate student in electrical engineering at Clarkson University.

-By Catherine Zandonella