Of swords, stars and superconductors

Robert Cava weaves physicists’ dreams into exotic new materials

By Bennett McIntosh

ROBERT CAVA PULLS A LONG CURVED steel blade from its ornate sheath, revealing a rippling pattern of light and dark metal. The sword is a Japanese katana made from steel of such legendary strength and sharpness that it was said to be able to cut a hair as it fell to the ground.

In his office where the shelves are lined with mineral samples and crystal structures, Cava, Princeton’s Russell Wellman Moore Professor of Chemistry, recounts the sword’s role in his destiny. He’d entered the Massachusetts Institute of Technology (MIT) wanting to study applied physics. “Someone at MIT interpreted ‘applied physics’ as being about materials science,” he said. “So, I ended up in a freshman seminar about samurai swords.”

Samurai swords derive their mythic properties from distinctive arrangements of iron and carbon atoms, Cava learned. His fascination with the atomic structure of the ancient metal turned into a career arranging atoms into materials for a more modern age: batteries, superconductors and materials with strange and exotic properties that could become the basis for future electronic devices.

In the 1970s, when Cava was a student, these technologies were far off in the future. Captivated by the science of materials, Cava stayed at MIT to earn his Ph.D. in ceramics. “Now I know how to make toilet bowls,” Cava quipped. In fact, ceramics have a wide range of electrical properties that make them useful in computers, televisions and communications devices. After graduation and a postdoctoral fellowship at the National Bureau of Standards, Cava took a job at Bell Laboratories, the research arm of the then-dominant AT&T telephone company.

Renowned for hiring the best and giving its researchers intellectual freedom, Bell Labs was at the time brimming with new ideas. “Collaborations were built by sitting with random people in the cafeteria,” Cava recalled. One day in 1986, one of these collaborators invited Cava to a seminar on high temperature superconductors, which were newly discovered materials that conducted electricity with no energy loss, but required less of the expensive refrigeration conventional superconductors needed.

Sitting in the seminar, Cava contemplated how the atoms in the new materials could be arranged to improve their performance. “I went back to the lab and four days later I had made a better superconductor,” he said. He would co-author more than 30 papers on superconductors in 1987 alone. One former colleague, Bertram Batlogg, now at the Swiss Federal Institute of Technology in Zurich (ETH Zurich), recalled being so excited about one discovery that they wrote the paper in one night, fueled by “European-strength coffee and fresh home-baked cornbread.”

In 1996, as AT&T broke up and spun off Bell Labs, Cava moved to Princeton, where he established a reputation of being able to weave physicists’ dreams into exotic new materials. When his collaborators in the Department of Physics come to him with theoretical predictions, he can often make a material that exhibits the desired properties. Some of the new materials he has conjured are topological insulators, materials that act like superconductors on their surface but conduct no electricity at all under the surface. “It is dark magic,” said B. Andrei Bernevig, a Princeton professor of physics and a frequent collaborator of Cava’s.

Robert Cava

Chemistry professor Robert Cava can sometimes be spotted walking through Frick Chemistry Laboratory in one of the costumes he dons for his first-year general chemistry course. (Photo by Sameer A. Khan/Fotobuddy)

Cava is more understated in explaining what he calls his “chemical intuition.” The properties of a material depend as much upon the geometrical arrangement of its atoms as on the specific kinds of atoms. Cava approaches designing a new material first by finding the right geometry — how many other atoms of each kind should each atom connect to, and in which orientations — and then finding the right atoms to fit this geometry. All the while, he bounces ideas off his students and collaborators. “In the end, science is very personal,” Cava said.

The move to Princeton from Bell Labs brought more than new collaborators and projects. “At Princeton, I have to be more than a scientist,” Cava said. He had to become a teacher and, often, a performer, to engage the 100-plus students in his first-year general chemistry course.

To share the inspiration he has felt every day since his first materials-science class, Cava peppers his lessons with references to ancient alchemists and demonstrations of the power of their discoveries. Slicing a pumpkin — often adorned with a Harvard cap — with his Samurai sword is perhaps the tamest demonstration. “He’s always blowing something up, or lighting something on fire,” said Marisa Sanders, a Ph.D. student in Cava’s lab.

The antics cross over to his lab, where the lab rules encourage taking experimental risks, and where he can sometimes be spotted walking the lab in a Darth Vader costume, which he wears when he administers final exams, to, as he puts it, “relieve some of the students’ tension.” He is a patient teacher, willing to sit for hours with students to work through a difficult problem or an unexpected result.

But, especially in materials chemistry, such logical teaching only goes so far. The most harebrained ideas will either succeed or teach in their failure, according to Cava. “If he thinks something is not going to work, he won’t tell you not to do it,” said Elizabeth Seibel, a doctoral student in Cava’s lab. “But he might make a bet with you.”

When Cava isn’t conjuring crystals, he pursues his first scientific love, astronomy. Growing up on Long Island during the 1960s Space Race, Cava swapped his model-train set for another student’s home-built telescope just to get a good look at the moon. Now his students laugh at him for having so many telescopes in his garage that there is no room for a car. “I love to sit under the night sky and appreciate how beautiful the universe is,” he said. He shares this love with others, setting up a telescope outside the chemistry building to share eclipses and solar flares with colleagues and students. “It’s something that a bunch of us from the lab really look forward to,” Seibel said.

Beyond his passions for chemistry and astronomy, Cava hopes his mentorship and example help his students find something they love to do. “You have to be passionate about something,” he said. “In the end, you don’t want to look back and think, ‘I didn’t do anything with my life.’” He certainly will not have to worry about that.

CITIES: Resilient • Adaptable • Livable • Smart

Innovations in building materials, design, water systems and power grids are helping to make cities more livable, say researchers in Princeton’s School of Engineering and Applied Science

By Bennett McIntosh

Cities. They sprawl and tangle, juxtaposing ancient public squares and glistening skyscrapers. They provide homes for half of humanity, and economic and cultural centers for the rest.

It has taken us thousands of years to build today’s urban centers, and yet, they’re expected to double in land-area in just the next few decades. “Half the urban infrastructure we will be using in 2050 has not yet been built,” said Elie Bou-Zeid, a Princeton associate professor of civil and environmental engineering.

Though this growth is inevitable, the way these cities will expand is not. Rather than repeat the sprawling and uncoordinated development patterns of the past, researchers like Bou-Zeid and others in Princeton’s School of Engineering and Applied Science are exploring new ways to build urban infrastructures to serve our growing population, changing civilization and warming planet.

These intelligent cities will require buildings that heat and cool themselves on a limited energy budget. They’ll require bridges and other infrastructure built with the flexibility to adapt to a changing global climate and rising sea levels. And they’ll require innovations in the networks that supply cities with water and energy. These ideas — from new building materials to continent-spanning electrical grids — have the potential to shift urban development away from the present-day jumble of strip malls, suburbs and shantytowns toward the resilient cities of the future.

Clever buildings

The basic unit of these smarter, resilient cities is the intelligent building. Assistant Professor Forrest Meggers, who has a background in architecture and engineering, has a number of plans for making buildings smarter about how they heat and cool their indoor spaces. Often these heating and cooling systems involve water, which readily absorbs heat that is then shed through evaporation.

In one structure called the Thermoheliodome, the interior is coated with mirrors at odd angles to reflect heat toward water-cooled pipes. In another, the interior cools itself with evaporation through an external membrane that traps liquid water while allowing water vapor to escape. By demonstrating the effectiveness of these innovative ideas, Meggers, who has a joint appointment in the School of Architecture and the Andlinger Center for Energy and the Environment, hopes to show other architects that it is possible to make more effective and more attractive heating and cooling systems.

Meggers’ structures take advantage of two different ways heat is transferred: It can be carried by molecules of warm air or water, or it can radiate like light directly from surface to surface. Thermometers, which measure air temperature, don’t capture the effects that radiative heating and cooling can have on a building’s occupants, so Meggers developed a radiative heat-sensing camera. About the size of a thermostat, the camera captures a 360-degree view that researchers can use to build a 3-D model of the radiative surfaces in any room.

To investigate urban radiant-heat exchanges, Meggers’ students took similar devices to New York City, about 50 miles northeast of Princeton. The resulting thermal photographs enabled them to see how heat lingers in alleyways and clusters around window-mounted air conditioners. By seeing the heat, architects and engineers can improve their designs for optimal energy efficiency.

Optimal cooling is the goal of one project that Meggers collaborated on with Dorit Aviv, who earned her master’s degree in architecture in 2013 and is now a doctoral student at Princeton. The building is called the Cool Oculus and is designed to keep cool in the desert heat through a combination of evaporation and shifting shape. The researchers built the Cool Oculus as a prototype on the Princeton campus, and have secured a grant from the New York-based Tides Foundation to build a full-scale model and measure its capabilities.

During a hot day, mist flows into the Oculus’ central chimney and evaporates to cool the air within, which sinks as a refreshing breeze into the building. Meanwhile, the structure’s foundation absorbs excess heat, which it releases at night when the chimney widens to expose the foundation to the cool night sky. Combined, these effects can turn 100-degree desert heat into a comfortable 75 degrees.

Inspired by nature

The Oculus moves on a daily cycle, but Sigrid Adriaenssens, an associate professor of civil and environmental engineering, has designed structures whose real-time response to heat is built into the material itself. In a transparent case above her desk, Adriaenssens displays three structures that could pass for the leaves of a cyborg Venus flytrap. They each are made of white translucent shells curving off a central metallic strut.

The resemblance to a flytrap is not coincidental. Adriaenssens designed the structures with inspiration from the waterwheel plant, an aquatic cousin of the flytrap. This shape allows the entire structure to open or close in response to a small movement of the central strut. The strut, in turn, is made of two metals that expand differently when heated, so the shell expands significantly with a small increase in temperature. Adriaenssens envisions that these shells, which were developed with funding from the Andlinger Center for Energy and the Environment, could cover a building’s entire façade. On hot days, the shells would expand and block heat from streaming in through the windows.

Structures like these, which make clever use of materials and their form, will be the key to affordable and efficient structures in future cities, according to Adriaenssens. To make these structures, Adriaenssens and her team use computer simulations to calculate the structure’s optimal form. Like optimized forms in nature, Adriaenssens’ structures often show striking curves, from spiraling earthen garden walls and arching steel footbridges, to shell-shaped pavilions with slats to keep out direct sunlight while allowing in scattered light and breezes. Nor are the spreading leaves Adriaenssens’ only dynamic structure: To protect coastlines from storm surges while keeping them visually uncluttered, she has designed thick elastic spherical membranes that will inflate and press together to hold off the waves.

Water world

Where does the water that surges around Adriaenssens’ barriers go? Where does the water that cools Meggers’ buildings come from? To plan something as complex as a future city’s water system requires not just understanding the interactions between structures like these, but understanding how the structures and the people affect each other. Such an undertaking requires cooperation between researchers from many different fields, and an understanding of the successes and failings of many different cities, according to Bou-Zeid.

Bou-Zeid first grew interested in cities when he was a mechanical engineering undergraduate at the American University of Beirut in Lebanon. “I thought I would be designing racecars or airplanes, but environmental problems that involve the interaction of humans with their surroundings are more interesting,” he said. During his graduate and postdoctoral studies, Bou-Zeid investigated how cities — with their skyscraper-created wind canyons and their innumerable sources of heat and steam — fundamentally alter the movement of air around them.

Bou-Zeid is interested in how this airflow affects an invisible but critical part of cities’ water systems: evaporation. Before a city is built, water evaporates out of plants and earth, cooling the area. But in built-up areas, dark asphalt absorbs heat. Water flows off impermeable pavement into storm systems before it has the chance to evaporate and take heat away with it, trapping heat in the buildings and the streets. This trapped heat can warm cities by 10 to 15 degrees Fahrenheit higher than the surrounding countryside. The so-called urban heat island raises energy consumption and contributes to climate change as we burn fossil fuels to cool ourselves.

Parks, greenbelts and green roofs covered in plants can solve this problem by encouraging cooling through evaporation, Bou-Zeid said. But it is not as simple as planting trees: While Baltimore’s greenbelts have cooled it significantly, drier cities like Denver and Phoenix may be better off saving water by cooling with traditional air conditioning. “How do you compare the value of a gallon of water and a kilowatt-hour of energy in different cities?” Bou-Zeid asked.

Bou-Zeid’s attempts to answer this question, and similar studies by other researchers in every aspect of the water cycle, led to the formation of the Urban Water Innovation Network. The Network, supported by a five-year grant from the National Science Foundation, includes engineers, architects and social scientists from 14 institutions who are studying how six American cities interact with water. Bou-Zeid, Princeton’s team lead for the network, is working with colleagues at the University of Maryland and Arizona State University to create software that will model everything water can do in a city. Such software could be used to predict the benefit of new water projects while accounting for local climate and geology.

The wildest possible experiments

To ensure that the urban landscape is accurately represented in such simulations, professor James Smith is leading a team of researchers from five universities in the network to produce extremely accurate maps of the rainfall and flooding in each of the cities. For Smith, the William and Edna Macaleer Professor of Engineering and Applied Science and professor of civil and environmental engineering, such studies of real cities are the only way to understand urbanization’s present and future effects.

“In cities,” he said, “the wildest possible experiments are being carried out for you.” Rivers are rerouted. Vast tracts of land are paved over. Artificial shorelines and skylines change the flow of water and air. It is up to researchers to watch and learn from these unprecedented alterations to the land and environment.

Collaboration within the network leads in surprising directions. Meggers, also a member of the network, found a way to combine his interest in efficient heat transfer with the water systems. With Sybil Sharvelle, a professor at Colorado State University, he is designing wastewater systems that recapture the heat from showers and other uses of hot water.

When the project ends in 2020, the network will release a report detailing its findings and recommendations for the cities under study. The research covers an environmentally diverse collection of cities so that the suggestions can be useful to cities across the country and, in some cases, around the world. In the meantime, the network connects researchers and government officials to craft individual recommendations on short-term projects. “We ask the policymakers what they need to know, and try to understand their constraints so that our recommendations can be implemented,” Bou-Zeid said.

It’s not the first time Bou-Zeid has worked to make small, efficient changes to cities. Simply painting black roofs white so that they reflect more light keeps buildings cooler and saves energy and money.

New York City has implemented this idea via their °CoolRoofs program, through which thousands of volunteers have painted roofs white since 2009. These efforts provided Bou-Zeid with more data than he could ever have achieved in a laboratory. He is using data from this experiment in conjunction with his models of urban air and heat flow to determine the cost and energy savings of painting roofs white.

Networks and grids

Painting roofs white is a relatively easy modification to make to a city, but other modifications require a new way of thinking. Our cities are already in need of upgrades to electricity supply and delivery systems. Going forward, our electricity will increasingly come from renewable sources such as solar and wind power, which, while better for the environment, can vary due to wind shifts and cloud cover.

With renewable energy making up only about 10 percent of power production in the United States, this variability is not yet an issue, said Warren Powell, a professor of operations research and financial engineering who studies networks such as electrical grids and transportation systems. “But I see us hitting problems at about 20 percent renewables,” Powell said.

This variability makes it hard to fully replace coal, the traditional workhorse of electricity generation, and natural-gas turbines, which can be ramped up quickly. “When the dust clears in 40 years, we’re still going to have some fossil energy,” Powell said. While large, efficient batteries could store wind and solar power and release it as needed, the marginal cost of battery storage increases as more batteries are added to the grid. “It is going to be hard to fight this curve,” he said.

Changes in how the power grid operates could help. Powell recently began a project in Brazil, where a drought has cut into Brazil’s heavy dependence on hydroelectric power. Powell has begun working with a group of Brazilian power companies to study strategies for managing the variability from the influx of wind power. Because of wind’s variability, this is not simply a matter of replacing one power source with another. Instead, Powell will be supervising the development of Brazil’s first grid model that can closely simulate the variability of wind. This model will be used to develop robust management policies and energy portfolios that would help Brazil optimize an energy system that depends heavily on  wind and solar.

New technologies deployed smartly will help, Powell said. For example, self-driving electrical vehicles can decrease congestion in dense cities and lend their batteries to the electrical grid, selling power when the city needs it most and recharging overnight from the grid’s excess capacity.

Ultimately, these changes in technologies and policy must work within the economic and social constraints of existing cities. Failing to understand and anticipate urban changes and growth leads to not just bad policy, but unenforceable policy, Bou-Zeid said. If a city tries to prevent urban growth, for example, by limiting new housing, the city will often still grow, but in unregulated and unhealthy shantytowns on the periphery. “You must accept urban expansion — you have to work with it,” Bou-Zeid said.

But the size and inertia of cities is an opportunity, too, Meggers said. “Cities have the power to make a change.”

If researchers and policymakers at Princeton and in cities around the world can collaborate, making clever use of form, physics and interacting components as a part of urban planning, then that change will be a positive one.

Better living through behavioral science

How the psychology of human behavior is helping tackle society’s biggest problems

By Wendy Plump

SUPPOSE someone approaches you on the street with the following proposition: You can receive either cash on the spot or a much larger contribution to your retirement account that likely will yield far more in the future. Do you choose the instant cash, or go with the retirement account?

The answer tells a lot about how people think, and about how public policymakers think people think.

Most people, it turns out, would choose the instant cash. Most policymakers, at least until somewhat recently, would have said that people would select the higher long-term payout of the retirement account.

Over the past two decades, policy planners from the Oval Office to the middle-school principal’s office have become aware that people often do not behave rationally, nor even in their own best interests. Understanding why people act as they do is the basis of the growing discipline of behavioral science, which is helping shape policies that tackle society’s biggest problems, from financial planning to public health.

“It is remarkable how little effort has been made to understand human behavior in policy circles,” said Eldar Shafir, the Class of 1987 Professor in Behavioral Science and Public Policy and a leader in this field of research. “Policy depends upon people doing things that the policymakers expect them to do. Yet, there has been almost no attempt to understand what people actually do, what they can do and what they want to do.”

Shafir has been working to change that along with colleagues at Princeton’s Woodrow Wilson School of Public and International Affairs. Wilson School researchers are exploring the behavioral aspects of policies that combat poverty, school bullying, discrimination and many other issues.

The idea that psychology is essential for good public policy can be traced back 100 years to American economist John Maurice Clark at Columbia University, according to Shafir. “Clark pointed out that any time you design policy, you have to understand psychology,” Shafir said. “If you don’t, your policy design and implementation will often be flawed.”

This may sound like common sense, but in the past, psychology rarely had a place at the policy table, said Daniel Kahneman, Princeton’s Eugene Higgins Professor of Psychology, Emeritus, and professor of psychology and public affairs, emeritus, and a pioneer in the field. Instead, two disciplines — economics and law — were the wells from which policymakers drew almost exclusively.

Kahneman’s work is credited with improving economic analyses by including insights from psychology, especially on human judgment and decision making under uncertainty. The citation for his 2002 Nobel Prize in Economic Sciences lauds him for “laying the foundation for a new field of research.”

Yet, Kahneman is uncomfortable taking credit for the field’s progress. Instead, he cites economist Richard Thaler of the University of Chicago. Thaler and Harvard University Law School’s Cass Sunstein co-authored a 2008 book titled, Nudge: Improving Decisions about Health, Wealth and Happiness, that ushered applied behavioral science into the public consciousness.

The book brought attention to concepts such as how to present choices to people in ways that provide a gentle prod toward making good decisions. For example, automatically enrolling new employees in a retirement-savings program and allowing them to opt out, rather than encouraging employees to opt in to the program, dramatically increases the number of people who save for retirement.

These and other insights are backed up by extensive studies of how people actually behave and make decisions in given situations. A number of Princeton researchers are involved in research in behavioral science that has direct implications for public policy:

Stopping schoolyard conflict

Early in her career, Elizabeth Levy Paluck became interested in how social norms can influence people’s behavior. In post-genocide Rwanda, she found that a media campaign to help reduce prejudice and violence drew much of its success from its emphasis on changing people’s definition of acceptable and desired behavior.

“I study social norms — informal laws that are created and enforced by people,” said Paluck, professor of psychology and public affairs in the Wilson School. “How do people in a community figure out what these laws are, and how to follow them? One theory is that we look to the behavior of certain peers for cues as to what we should be doing.”

Paluck and colleagues wondered whether highly influential students could have an outsized impact on the social norms and behaviors of other students in a school setting. They designed an intervention called the Roots program that was aimed at reducing school bullying and conflict by convincing influential students to practice positive behaviors, with the goal of reaching wider networks of peers.

With colleagues at Rutgers and Yale universities, Paluck tested this approach in a study conducted at 56 middle schools throughout New Jersey. The researchers asked students to report who they socialized with on a regular basis — both in person and online — and then used the data to identify the most connected students.

The analysis identified students who were leaders among their specific peer groups, not just those who were the most popular overall. The researchers encouraged this small set of students to take a public stand against bullying at their schools. Would these “social referents” be able to spread social change?

Paluck and her collaborators found that middle schools that instituted Roots experienced a 30 percent reduction in reported “conflict incidents,” a finding the researchers published Jan. 4, 2016, in the journal Proceedings of the National Academy of Sciences. The results suggest that behavior-change campaigns may be made more effective when they harness networks of influence to change societal norms.

Funding for the project came from the William T. Grant Foundation’s Scholars Program, the Canadian Institute for Advanced Research, Princeton’s Educational Research Section, the Russell Sage Foundation, the National Science Foundation and the Spencer Foundation.

Combating scarcity

For his research on poverty, Shafir studies the impact that deprivation has on an individual’s ability to focus intellectual energy on life tasks. His work touches on the age-old question regarding the causes and effects of poverty: Are people poor because they are not capable, or are they are not capable because they are poor?

Shafir and his team have found that poor people are often quite good at making short-term decisions about how to spend money. But the continual pressure to make ends meet can create an oppressive cognitive load on the individual, leaving little bandwidth for other tasks, including long-term planning.

This situation is compounded by the fact that small but unexpected expenses, such as a car-repair bill, can have much larger consequences for poor people than for middle-class individuals who have some slack in their monthly budget. Shafir and co-author Sendhil Mullainathan of Harvard explored research on poverty in their 2013 book, Scarcity: Why Having Too Little Means So Much. They challenge the common societal perception that poverty is the result of personal failings and recast it as the outcome of a chronic lack of resources, be it money, transportation and housing, or even time.

Understanding the drivers of behavior among the poor can guide policies that help reduce the stresses and challenges associated with poverty, Shafir said. For example, if a fast-food company were to hand out employee work schedules further in advance — as opposed to the 48-hour timeframe it typically uses — then parents would be able to dedicate fewer cognitive resources to the constant management of childcare concerns, leaving them with more resources to devote to other aspects in their lives, including their job performance.

Counteracting stereotypes

Since she came to Princeton 16 years ago, Susan Fiske, the Eugene Higgins Professor of Psychology and professor of psychology and public affairs, has been researching issues of bias, discrimination and stereotypes.

One area of study involves exploring our perceptions of people as “warm and trustworthy” and “competent” at what they do. Middle-class individuals get high ratings on both counts, while homeless people and undocumented immigrants score low on both counts. Older people are seen as trustworthy but not competent, and rich people are seen as competent but not trustworthy.

In a study published earlier this year, Fiske and graduate student Jillian Swencionis reported that people in the workplace try to appear more competent by acting cold when dealing with their superiors, while superiors play up their warmth when dealing with subordinates. Supervisors and subordinates engage in these behaviors both to disprove stereotypes about themselves and to match what they think about the other person.

Recognizing these warmth-competence tradeoffs in interactions between employees of different ranks could help improve communications within organizations. The study was published in the Journal of Experimental Social Psychology in May 2016. Swencionis was funded in part by the National Science Foundation.

“People automatically categorize other people by race and gender and age,” Fiske said. “They do this without intention, so it’s not about evil motivation when people act on these associations. It’s kind of a default. As a result, people and organizations have to engage in extraordinary efforts to counteract that proclivity.”

No matter how groundbreaking the research, it is useless to public policy unless it is available to people in a position to implement it. So, Fiske started the journal Policy Insights from the Behavioral and Brain Sciences a few years ago. The journal is affiliated with the Federation of Associations in Behavioral & Brain Sciences, which does education and advocacy work. Fiske has been the federation’s president and serves on its executive committee.

Bringing policy into the 21st century

In September 2015, President Barack Obama signed an executive order directing federal agencies to draw on emerging research from the field of behavioral science when crafting policies. Obama described the directive as a way to “bring our government into the 21st century.”

Researchers at the Wilson School and in Princeton’s Department of Psychology are helping lead the application of behavioral science to policymaking through their work in government, at think tanks and nongovernmental organizations, and at schools and institutions. The growing demand for these skills led Shafir and several colleagues to cofound ideas42, a nonprofit company devoted to creating behaviorally informed solutions to societal problems.

The Wilson School also is home to a new center launched in spring 2015 and led by Shafir that is focused on applied behavioral science research. In the fall of 2016, the Kahneman-Treisman Center for Behavioral Science & Public Policy launched its inaugural symposium. The center has more than 45 affiliated faculty members, including Alin Coman and Johannes Haushofer, both assistant professors of psychology and public affairs in the Wilson School. The center also has members from 11 departments across campus, including such diverse fields as geosciences, human values, philosophy and African American studies.

“It’s an exciting time,” Fiske said. “I’m a child of the ’60s and ’70s. So for me to be able to have an influence with data on policy is really a dream come true. We wanted to make the world a better place. It’s not so clear that we did, but there’s progress on several fronts.”

Race for profits

Research on the 1970s urban housing crisis exposes a familiar history

By Catherine Zandonella

PREDATORY LENDERS. Subprime and no-doc loans. Mortgage-backed securities. Mass foreclosures that disproportionately impacted minority homeowners. Sound like 2008? It was 1972.

The subprime-mortgage crisis is nothing new, at least for America’s poor urban communities. In the late 1960s, the United States government, reeling from violent civil-rights protests, enacted a plan to encourage homeownership among poor and low-income residents, most of whom were African American. But the program, a partnership between public agencies and private enterprise, quickly became rife with corruption. The result was eerily prescient of the recent housing crisis.

Keeanga-Yamahtta Taylor, a Princeton assistant professor of African American studies, became fascinated by this little-remembered era as a graduate student. She was living in Chicago and was already a fierce proponent of social justice — she attended her first demonstration at age 16, in support of women’s reproductive rights. She has brought that tradition of activism to her position at Princeton where, within a year of being hired, she wrote her first book, touching on how structural inequalities embedded in American society and its institutions have fueled the Black Lives Matter movement. The book, From #BlackLivesMatter to Black Liberation (Haymarket Books, 2016), received the 2016 Lannan Foundation Freedom Award for an Especially Notable Book.

The fact that inequality continues to permeate society some 60 years after the dismantling of discriminatory laws comes as no surprise to Taylor. As a student in the 1990s at a predominantly black high school in Buffalo, New York, she recalls being told by a white teacher that the students “would all be on welfare” if they didn’t learn to respect authority. During a parent-teacher conference, the teacher threatened to call the police to remove her father, who was a university professor.

Although she enrolled in college directly after high school, Taylor was restless, and after a year, she dropped out and moved to New York City to pursue writing. She continued to demonstrate against social injustice, protesting police brutality in the city. A relationship led her to move to Chicago where she and her partner joined efforts to repeal the death penalty.

A turning point for Taylor came in 2000 when these efforts paid off: Illinois’ governor placed a moratorium on executions. “It was an important moment for me because I saw the results that can happen when people advocate for change,” she said. At 29, she decided to finish her undergraduate degree and enrolled at Northeastern Illinois University in a program for returning adult students.

Taylor already knew she wanted to study housing disparities and race when she entered graduate school at Northwestern University. “I was fascinated by how rigidly segregated Chicago is,” Taylor said. “The black areas stretch for miles, and you can walk for blocks without seeing a white person.”

Through her work as a community organizer, Taylor had learned about the housing policies that shaped segregation in Chicago and the nation. The government’s post-World War II emphasis on homeownership favored purchases in newly built suburbs. Many black families could not afford to buy in the new suburbs, and those that could endured blatant discrimination from realtors. The government considered urban areas to be “high-risk,” so these areas didn’t qualify for federally insured loans, a policy Taylor described in her doctoral dissertation as “racial judgments cloaked in the garb of objective economic analysis.”

The civil unrest of the 1960s brought attention to the crisis of dilapidated and unsafe housing in urban America. In response, President Lyndon B. Johnson in 1968 announced that the government would extend its pro-home buying policy — including federally insured loans — to low-income purchasers. The hope was that a new cadre of urban residents, spurred by the pride of homeownership, would fix up neglected dwellings and catalyze urban renewal from within.

The new program would accomplish this through the creation of a “federally chartered private, profitmaking housing partnership.” Under the program, called Section 235, the private sector would provide the real estate agents, appraisers, mortgage brokers and financing, while the Department of Housing and Urban Development (HUD) would oversee the process.

Flaws emerged almost from the outset. One was that the responsibility for vetting a potential homeowner’s creditworthiness fell to parties that had little stake in making sure people could afford the loans. Traditional banks and savings-and-loans stayed away from the new borrowers — they were considered too risky. Instead, a new type of lender, the mortgage broker, stepped in and began to pool loans that were resold as investments known as mortgage-backed securities.

By 1971, new infractions had surfaced. Owners found that the homes had more than cosmetic problems, including “faulty plumbing, leaky roofs, cracked plaster, faulty and inadequate wiring, rotten wood in the floors, staircases and porches, lack of insulation and faulty heating units,” according to a HUD report. “About one-quarter were in such poor condition that investigators concluded that they should have never been insured,” wrote Taylor in her dissertation.

It emerged that real estate speculators were buying cheap and uninhabitable properties and quickly “flipping” them for sale under the Section 235 program. A HUD internal report found that real estate agents, property appraisers and mortgage brokers colluded to artificially inflate prices for buyers. “No-doc” loans — issued without checking income statements and other documents — were common because, due to the federal insurance payout, lenders stood to make more money when a borrower defaulted. The report called attention to the biased attitudes of HUD officials toward the potential homeowners, suggesting that race played a role in letting the abuse happen.

The program came to an end in 1973 when President Richard M. Nixon declared a moratorium on subsidized housing programs, citing the corruption and disarray. A new narrative emerged that enabled the government to distance itself from programs to help provide homeownership in the inner cities: Poor people were too irresponsible to own homes and to revitalize their own communities.

This new narrative ignored the evidence — documented in HUD reports, hearings before Congress and major newspapers — that property speculators, real estate agents, appraisers and mortgage brokers lured poor and predominantly African American people into buying homes they could not afford. By mid-1975, the foreclosures were mounting. Foreclosure rates were seven times higher in the low-income housing programs than they were in the conventional home-lending market. According to newspaper reports, the government had paid more than $4 billion in insurance claims since the start of the program.

Yet, few people were indicted or censured for these failings, Taylor found. One reason was the close relationship between the private sector and HUD. According to a government report, the president of the Mortgage Bankers Association had personally helped write HUD regulations.

In archives held at the Hoover Institution at Stanford University, Taylor found the personal correspondence of Carla Hills, HUD director during the mid-1970s. The files were a treasure trove — an insight into what HUD officials were thinking during the height of the scandal. What Taylor found surprised her.

“There was a reluctance to discipline lenders and private-sector companies because of the fear that too much regulation would discourage participation in HUD programs,” Taylor said. “There also was a discussion of HUD employees’ concerns that they would be risking their ability to get jobs in the private sector. It was a surprise to me to find an open, written discussion of these issues.”

This and other evidence has helped inform Taylor’s viewpoint that private enterprise has no business shaping or implementing public policies. “In my opinion, those two spheres are very different,” she said. “Private enterprise is about making profits, while the public sector was created to protect the public’s welfare. As my work shows, public-private partnerships have a history, and this history should be included in the discussion about the best approaches to providing necessities such as water, healthcare, education or housing.”

Taylor earned her doctorate and published her dissertation, “Race for Profit: Black Housing and the Urban Crisis in the 1970s,” in 2013. She began as a faculty member at Princeton the following year, and she continues her work as an activist through her writing, lectures and community involvement. She is now writing a book about her housing research.

Her combination of high-quality research and her drive to bring her findings to the broader public are needed to make sure past policy mistakes are not repeated, said Taylor’s Ph.D. adviser, Martha Biondi, a professor of African American studies and history at Northwestern University.

“Questions around finance and lending have been critically important in our own recent recession, and Keeanga brings a sharp historical lens to an issue that has been forgotten and neglected in most histories of the 1970s,” Biondi said. “In a society that celebrates homeownership, Keeanga’s work is a cautionary tale about the ways in which homeownership can be used to exploit poor and working-class communities.”

Taylor’s work underscores the importance of research in shaping public policy, said Eddie Glaude Jr., Princeton’s William S. Tod Professor of Religion and African American Studies and the chair of the Department of African American Studies.

“Keeanga’s work reveals in really powerful ways the unintended consequences of these public-private partnerships to solve the crisis of housing for low- and moderate-income families,” Glaude said. “You come away from reading her work with not only a sense of the disaster that that decision was, but also the importance of understanding its social and historical overtones.”

Taylor’s research on structural discrimination in housing, combined with her ongoing work as an activist, led her to consider how Americans can move beyond inequality to build a society where people are treated fairly and not on the basis of racial stereotypes, a topic she tackles in From #BlackLivesMatter to Black Liberation.

“The Civil Rights Movement addressed legal discrimination, but it also revealed that the problems confronting African Americans were not just Jim Crow laws — they were the practices and customs of racial discrimination that weren’t written in law, that were found in real estate or banking or employment,” Taylor said. “The outcome has been that African Americans suffer disproportionately in the areas that determine the quality of one’s life.”

The Black Lives Matter movement has brought much-needed awareness to the structural and institutional forms of racism in American society, she said. “We’ve become accustomed to thinking of racism as acts by individuals. But putting the blame on the individual suggests that racism can be overcome by education alone.”

Instead, Taylor reminds us that throughout history racism has been used as a way for the powerful to control others for material gain — and it is still used that way. “Unless you address the way society is organized, you won’t dismantle that power structure,” Taylor said. “Patterns, unless actively undone, replicate themselves.

“Knowledge alone will not reverse this.”

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.