Aurelia Butler

More stories

  • 113 Shares129 Views

    in Environment

    MIT engineering students take on the heat of Miami

    Think back to the last time you had to wait for a bus. How miserable were you? If you were in Boston, your experience might have included punishing wind and icy sleet — or, more recently, a punch of pollen straight to the sinuses. But in Florida’s Miami-Dade County, where the effects of climate change are both drastic and intensifying, commuters have to contend with an entirely different set of challenges: blistering temperatures and scorching humidity, making long stints waiting in the sun nearly unbearable.

    One of Miami’s most urgent transportation needs is shared by car-clogged Boston: coaxing citizens to use the municipal bus network, rather than the emissions-heavy individual vehicles currently contributing to climate change. But buses can be a tough sell in a sunny city where humidity hovers between 60 and 80 percent year-round. 

    Enter MIT’s Department of Electrical Engineering and Computer Science (EECS) and the MIT Priscilla King Gray (PKG) Public Service Center. The result of close collaboration between the two organizations, class 6.900 (Engineering For Impact) challenges EECS students to apply their engineering savvy to real-world problems beyond the MIT campus.

    This spring semester, the real-world problem was heat. 

    Miami-Dade County Department of Transportation and Public Works Chief Innovation Officer Carlos Cruz-Casas explains: “We often talk about the city we want to live in, about how the proper mix of public transportation, on-demand transit, and other mobility solutions, such as e-bikes and e-scooters, could help our community live a car-light life. However, none of this will be achievable if the riders are not comfortable when doing so.” 

    “When people think of South Florida and climate change, they often think of sea level rise,” says Juan Felipe Visser, deputy director of equity and engagement within the Office of the Mayor in Miami-Dade. “But heat really is the silent killer. So the focus of this class, on heat at bus stops, is very apt.” With little tree cover to give relief at some of the hottest stops, Miami-Dade commuters cluster in tiny patches of shade behind bus stops, sometimes giving up when the heat becomes unbearable. 

    A more conventional electrical engineering course might use temperature monitoring as an abstract example, building sample monitors in isolation and grading them as a merely academic exercise. But Professor Joel Volman, EECS faculty head of electrical engineering, and Joe Steinmeyer, senior lecturer in EECS, had something more impactful in mind.

    “Miami-Dade has a large population of people who are living in poverty, undocumented, or who are otherwise marginalized,” says Voldman. “Waiting, sometimes for a very long time, in scorching heat for the bus is just one aspect of how a city population can be underserved, but by measuring patterns in how many people are waiting for a bus, how long they wait, and in what conditions, we can begin to see where services are not keeping up with demand.”

    Only after that gap is quantified can the work of city and transportation planners begin, Cruz-Casas explains: “We needed to quantify the time riders are exposed to extreme heat and prioritize improvements, including on-time performance improvements, increasing service frequency, or looking to enhance the tree canopy near the bus stop.” 

    Quantifying that time — and the subjective experience of the wait — proved tricky, however. With over 7,500 bus stops along 101 bus routes, Miami-Dade’s transportation network presents a considerable data-collection challenge. A network of physical temperature monitors could be useful, but only if it were carefully calibrated to meet the budgetary, environmental, privacy, and implementation requirements of the city. But how do you work with city officials — not to mention all of bus-riding Miami — from over 2,000 miles away? 

    This is where the PKG Center comes in. “We are a hub and a connector and facilitator of best practices,” explains Jill Bassett, associate dean and director of the center, who worked with Voldman and Steinmeyer to find a municipal partner organization for the course. “We bring knowledge of current pedagogy around community-engaged learning, which includes: help with framing a partnership that centers community-identified concerns and is mutually beneficial; identifying and learning from a community partner; talking through ways to build in opportunities for student learners to reflect on power dynamics, reciprocity, systems thinking, long-term planning, continuity, ethics, all the types of things that come up with this kind of shared project.”

    Through a series of brainstorming conversations, Bassett helped Voldman and Steinmeyer structure a well-defined project plan, as Cruz-Casas weighed in on the county’s needed technical specifications (including affordability, privacy protection, and implementability).

    “This course brings together a lot of subject area experts,” says Voldman. “We brought in guest lecturers, including Abby Berenson from the Sloan Leadership Center, to talk about working in teams; engineers from BOSE to talk about product design, certification, and environmental resistance; the co-founder and head of engineering from MIT spinout Butlr to talk about their low-power occupancy sensor; Tony Hu from MIT IDM [Integrated Design and Management] to talk about industrial design; and Katrina LaCurts from EECS to talk about communications and networking.”

    With the support of two generous donations and a gift of software from Altium, 6.900 developed into a hands-on exercise in hardware/software product development with a tangible goal in sight: build a better bus monitor.

    The challenges involved in this undertaking became apparent as soon as the 6.900 students began designing their monitors. “The most challenging requirement to meet was that the monitor be able to count how many people were waiting — and for how long they’d been standing there — while still maintaining privacy,” says Fabian Velazquez ’23 a recent EECS graduate. The task was complicated by commuters’ natural tendency to stand where the shade goes — whether beneath a tree or awning or snaking against a nearby wall in a line — rather than directly next to the bus sign or inside the bus shelter. “Accurately measuring people count with a camera — the most straightforward choice — is already quite difficult since you have to incorporate machine learning to identify which objects in frame are people. Maintaining privacy added an extra layer of constraint … since there is no guarantee the collected data wouldn’t be vulnerable.”

    As the groups weighed various privacy-preserving options, including lidar, radar, and thermal imaging, the class realized that Wi-Fi “sniffers,” which count the number of Wi-Fi enabled signals in the immediate area, were their best option to count waiting passengers. “We were all excited and ready for this amazing, answer-to-all-our-problems radar sensor to count people,” says Velasquez. “That component was extremely complex, however, and the complexity would have ultimately made my team use a lot of time and resources to integrate with our system. We also had a short time-to-market for this system we developed. We made the trade-off of complexity for robustness.” 

    The weather also posed its own set of challenges. “Environmental conditions were big factors on the structure and design of our devices,” says Yong Yan (Crystal) Liang, a rising junior majoring in EECS. “We incorporated humidity and temperature sensors into our data to show the weather at individual stops. Additionally, we also considered how our enclosure may be affected by extreme heat or potential hurricanes.”

    The heat variable proved problematic in multiple ways. “People detection was especially difficult, for in the Miami heat, thermal cameras may not be able to distinguish human body temperature from the surrounding air temperature, and the glare of the sun off of other surfaces in the area makes most forms of imaging very buggy,” says Katherine Mohr ’23. “My team had considered using mmWave sensors to get around these constraints, but we found the processing to be too difficult, and (like the rest of the class), we decided to only move forward with Wi-Fi/BLE [Bluetooth Low Energy] sniffers.”

    The most valuable component of the new class may well have been the students’ exposure to real-world hardware/software engineering product development, where limitations on time and budget always exist, and where client requests must be carefully considered.  “Having an actual client to work with forced us to learn how to turn their wants into more specific technical specifications,” says Mohr. “We chose deliverables each week to complete by Friday, prioritizing tasks which would get us to a minimum viable product, as well as tasks that would require extra manufacturing time, like designing the printed-circuit board and enclosure.”

    Play video

    Joel Voldman, who co-designed 6.900 (Engineering For Impact) with Joe Steinmeyer and MIT’s Priscilla King Gray (PKG) Public Service Center, describes how the course allowed students help develop systems for the public good. Voldman is the winner of the 2023 Teaching with Digital Technology Award, which is co-sponsored by MIT Open Learning and the Office of the Vice Chancellor. Video: MIT Open Learning

    Crystal Liang counted her conversations with city representatives as among her most valuable 6.900 experiences. “We generated a lot of questions and were able to communicate with the community leaders of this project from Miami-Dade, who made time to answer all of them and gave us ideas from the goals they were trying to achieve,” she reports. “This project gave me a new perspective on problem-solving because it taught me to see things from the community members’ point of view.” Some of those community leaders, including Marta Viciedo, co-founder of Transit Alliance Miami, joined the class’s final session on May 16 to review the students’ proposed solutions. 

    The students’ thoughtful approach paid off when it was time to present the heat monitors to the class’s client. In a group conference call with Miami-Dade officials toward the end of the semester, the student teams shared their findings and the prototypes they’d created, along with videos of the devices at work. Juan Felipe Visser was among those in attendance. “This is a lot of work,” he told the students following their presentation. “So first of all, thank you for doing that, and for presenting to us. I love the concept. I took the bus this morning, as I do every morning, and was battered by the sun and the heat. So I personally appreciated the focus.” 

    Cruz-Casas agreed: “I am pleasantly surprised by the diverse approach the students are taking. We presented a challenge, and they have responded to it and managed to think beyond the problem at hand. I’m very optimistic about how the outcomes of this project will have a long-lasting impact for our community. At a minimum, I’m thinking that the more awareness we raise about this topic, the more opportunities we have to have the brightest minds seeking for a solution.”

    The creators of 6.900 agree, and hope that their class helps more MIT engineers to broaden their perspective on the meaning and application of their work. 

    “We are really excited about students applying their skills within a real-world, complex environment that will impact real people,” says Bassett. “We are excited that they are learning that it’s not just the design of technology that matters, but that climate; environment and built environment; and issues around socioeconomics, race, and equity, all come into play. There are layers and layers to the creation and deployment of technology in a demographically diverse multilingual community that is at the epicenter of climate change.” More

  • 138 Shares119 Views

    in Environment

    A clean alternative to one of the world’s most common ingredients

    Never underestimate the power of a time crunch.

    In 2016, MIT classmates David Heller ’18, Shara Ticku, and Harry McNamara PhD ’19 were less than two weeks away from the deadline to present a final business plan as part of their class MAS.883 (Revolutionary Ventures: How to Invent and Deploy Transformative Technologies). The students had connected over a shared passion for using biology to solve climate challenges, but their first few ideas didn’t pan out, so they went back to the drawing board.

    In a brainstorming session, Ticku began to reminisce about a trip to Singapore she’d taken where the burning of forests had cast a dark haze over the city. The story sparked a memory from halfway across the world in Costa Rica, where McNamara had traveled and noticed endless rows of palm plantations, which are used to harvest palm oil.

    “Besides Shara’s experience in Singapore and Harry’s in Costa Rica, palm was a material none of us had seriously thought about,” Heller recalls. “That conversation made us realize it was a big, big industry, and there’s major issues to the way that palm is produced.”

    The classmates decided to try using synthetic biology to create a sustainable alternative to palm oil. The idea was the beginning of C16 Biosciences. Today C16 is fulfilling that mission at scale with a palm oil alternative it harvests from oil-producing yeast, which ferment sugars in a process similar to brewing beer.

    The company’s product, which it sells to personal care brands and directly to consumers, holds enormous potential to improve the sustainability of the personal care and food industries because, as it turns out, the classmates had stumbled onto a massive problem.

    Palm oil is the most popular vegetable oil in the world. It’s used in everything from soaps and cosmetics to sauces, rolls, and crackers. But palm oil can only be harvested from palm trees near the equator, so producers often burn down tropical rainforests and swamps in those regions to make way for plantations, decimating wildlife habitats and producing a staggering amount of greenhouse gas emissions. One recent study found palm expansion in Southeast Asia could account for 0.75 percent of the world’s total greenhouse gas emissions. That’s not even including the palm expansion happening across west Africa and South America. Among familiar creatures threatened by palm oil deforestation are orangutans, all three species of which are now listed as “critically endangered” — the most urgent status on the IUCN Red List of Threatened Species, a global endangered species list.

    “To respond to increasing demand over the last few decades, large palm producers usually inappropriately seize land,” Heller explains. “They’ll literally slash and burn tropical rainforests to the ground, drive out indigenous people, they’ll kill or drive out local wildlife, and they’ll replace everything with hectares and hectares of palm oil plantations. That land conversion process has been emitting something like a gigaton of CO2 per year, just for the expansion of palm oil.”

    From milliliters to metric tons

    Heller took Revolutionary Ventures his junior year as one of the few undergraduates in the Media Lab-based class, which is also open to students from nearby colleges. On one of the first days, students were asked to stand in front of the class and explain their passions, or “what makes them tick,” as Heller recalls. He focused on climate tech.

    McNamara, who was a PhD candidate in the Harvard-MIT Program in Health Sciences and Technology at the time, talked about his interest in applying new technology to global challenges in biotech and biophysics. Ticku, who was attending Harvard Business School, discussed her experience working in fertility health and her passion for global health initiatives. The three decided to team up.

    “The core group is very, very passionate about using biology to solve major climate problems,” says Heller, who majored in biological engineering while at MIT.

    After a successful final presentation in the class, the founders received a small amount of funding by participating in the MIT $100K Pitch Competition and from the MIT Sandbox Innovation Fund.

    “MIT Sandbox was one of our first bits of financial support,” Heller says. “We also received great mentorship. We learned from other startups at MIT and made connections with professors whom we learned a lot from.”

    By the time Heller graduated in 2018, the team had experimented with different yeast strains and produced a few milliliters of oil. The process has gradually been optimized and scaled up from there. Today C16 is producing metric tons of oil in 50,000-liter tanks and has launched a consumer cosmetic brand called Palmless.

    Heller says C16 started its own brand as a way to spread the word about the harms associated with palm oil and to show larger companies it was ready to be a partner.

    “The oil palm tree is amazing in terms of the yields it generates, but the location needed for the crop is in conflict with what’s essential in our ecosystem: tropical rainforests,” Heller says. “There’s a lot of excitement when it comes to microbial palm alternatives. A lot of brands have been under pressure from consumers and even governments who are feeling the urgency around climate and are feeling the urgency from consumers to make changes to get away from an oil ingredient that is incredibly destructive.”

    Scaling with biology

    C16’s first offering, which it calls Torula Oil, is a premium product compared to traditional palm oil, but Heller notes the cost of palm oil today is deflated because companies don’t factor in its costs to the planet and society. He also notes that C16 has a number of advantages in its quest to upend the $60 billion palm oil industry: It’s far easier to improve the productivity of C16’s precision fermentation process than it is to improve agricultural processes. C16 also expects its costs to plummet as it continues to grow.

    “What’s exciting for us is we have these economies of scale,” Heller says. “We have the opportunity to expand vertically, in large stainless steel tanks, as opposed to horizontally on land, so we can drive down our cost curve by increasing the size of the infrastructure and improving the optimization of our strain. The timelines for improvement in a precision fermentation process are a fraction of the time it takes in an agricultural context.”

    Heller says C16 is currently focused on partnering with large personal care brands and expects to announce some important deals in coming months. Further down the line, C16 also hopes to use its product to replace the palm oil in food products, although additional regulations mean that dream is still a few years away.

    With all of its efforts, C16 tries to shine a light on the problems associated with the palm industry, which the company feels are underappreciated despite palm oil’s ubiquitous presence in our society.

    “We need to find a way to reduce our reliance on deforestation products,” Heller says. “We do a lot of work to help educate people on the palm oil industry. Just because something has palm oil in it doesn’t mean you should stop using it, but you should understand what that means for the world.” More

  • 100 Shares179 Views

    in Environment

    Preparing Colombia’s cities for life amid changing forests

    It was an uncharacteristically sunny morning as Marcela Angel MCP ’18, flanked by a drone pilot from the Boston engineering firm AirWorks and a data collection team from the Colombian regional environmental agency Corpoamazonia, climbed a hill in the Andes Mountains of southwest Colombia. The area’s usual mountain cloud cover — one of the major challenges to working with satellite imagery or flying UAVs (unpiloted aerial vehicles, or drones) in the Pacific highlands of the Amazon — would roll through in the hours to come. But for now, her team had chosen a good day to hike out for their first flight. Angel is used to long travel for her research. Raised in Bogotá, she maintained strong ties to Colombia throughout her master’s program in the MIT Department of Urban Studies and Planning (DUSP). Her graduate thesis, examining Bogotá’s management of its public green space, took her regularly back to her hometown, exploring how the city could offer residents more equal access to the clean air, flood protection and day-to-day health and social benefits provided by parks and trees. But the hill she was hiking this morning, outside the remote city of Mocoa, had taken an especially long time to climb: five years building relationships with the community of Mocoa and the Colombian government, recruiting project partners, and navigating the bureaucracy of bringing UAVs into the country. Now, her team finally unwrapped their first, knee-high drone from its tarp and set it carefully in the grass. Under the gathering gray clouds, the buzz of its rotors joined the hum of insects in the trees, and the machine at last took to the skies.

    From Colombia to Cambridge

    “I actually grew up on the last street before the eastern mountains reserve,” Angel says of her childhood in Bogotá. “I’ve always been at that border between city and nature.” This idea, that urban areas are married to the ecosystems around them, would inform Angel’s whole education and career. Before coming to MIT, she studied architecture at Bogotá’s Los Andes University; for her graduation project she proposed a plan to resettle an informal neighborhood on Bogotá’s outskirts to minimize environmental risks to its residents. Among her projects at MIT was an initiative to spatially analyze Bogotá’s tree canopy, providing data for the city to plan a tree-planting program as a strategy to give vulnerable populations in the city more access to nature. And she was naturally intrigued when Colombia’s former minister of environment and sustainable development came to MIT in 2017 to give a guest presentation to the DUSP master’s program. The minister, Luis Gilberto Murillo (now the Colombian ambassador to the United States), introduced the students to the challenges triggered by a recent disaster in the city of Mocoa, on the border between the lowland Amazon and the Andes Mountains. Unprecedented rainstorms had destabilized the surrounding forests, and that April a devastating flood and landslide had killed hundreds of people and destroyed entire neighborhoods. And as climate change contributed to growing rainfall in the region, the risks of more landslide events were rising. Murillo provided useful insights into how city planning decisions had contributed to the crisis. But he also asked for MIT’s support addressing future landslide risks in the area. Angel and Juan Camilo Osorio, a PhD candidate at DUSP, decided to take up the challenge, and in January 2018 and 2019, a research delegation from MIT traveled to Colombia for a newly-created graduate course. Returning once again to Bogotá, Angel interviewed government agencies and nonprofits to understand the state of landslide monitoring and public policy. In Mocoa, further interviews and a series of workshops helped clarify what locals needed most and what MIT could provide: better information on where and when landslides might strike, and a process to increase risk awareness and involve traditionally marginalized groups in decision-making processes around that risk. Over the coming year, a core team formed to put the insights from this trip into action, including Angel, Osorio, postdoc Norhan Bayomi of the MIT Environmental Solutions Initiative (ESI) and MIT Professor John Fernández, director of the ESI and one of Angel’s mentors at DUSP. After a second visit to Mocoa that brought into the fold Indigenous groups, environmental agencies, and the national army, a plan was formed: MIT would partner with Corpoamazonia and build a network of community researchers to deploy and test drone technology and machine learning models to monitor the mountain forests for both landslide risks and signs of forest health, while implementing a participatory planning process with residents. “What our projects aim to do is give the communities new tools to continue protecting and restoring the forest,” says Angel, “and support new and inclusive development models, even in the face of new challenges.”

    Lifelines for the climate

    The goal of tropical forest conservation is an urgent one. As forests are cut down, their trees and soils release carbon they have stored over millennia, adding huge amounts of heat-trapping carbon dioxide to the atmosphere. Deforestation, mainly in the tropics, is now estimated to contribute more to climate change than any country besides the United States and China — and once lost, tropical forests are exceptionally hard to restore. “Tropical forests should be a natural way to slow and reverse climate change,” says Angel. “And they can be. But today, we are reaching critical tipping points where it is just the opposite.” This became the motivating force for Angel’s career after her graduation. In 2019, Fernández invited her to join the ESI and lead a new Natural Climate Solutions Program, with the Mocoa project as its first centerpiece. She quickly mobilized the partners to raise funding for the project from the Global Environmental Facility and the CAF Development Bank of Latin America and the Caribbean, and recruited additional partners including MIT Lincoln Laboratories, AirWorks, and the Pratt Institute, where Osorio had become an assistant professor. She hired machine learning specialists from MIT to begin design on UAVs’ data processing, and helped assemble a local research network in Mocoa to increase risk awareness, promote community participation, and better understand what information city officials and community groups needed for city planning and conservation. “This is the amazing thing about MIT,” she says. “When you study a problem here, you’re not just playing in a sandbox. Everyone I’ve worked with is motivated by the complexity of the technical challenge and the opportunity for meaningful engagement in Mocoa, and hopefully in many more places besides.” At the same time, Angel created opportunities for the next generation of MIT graduate students to follow in her footsteps. With Fernández and Bayomi, she created a new course, 4.S23 (Biodiversity and Cities), in which students traveled to Colombia to develop urban planning strategies for the cities of Quidbó and Leticia, located in carbon-rich and biodiverse areas. The course has been taught twice, with Professor Gabriella Carolini joining the teaching team for spring 2023, and has already led to a student report to city officials in Quidbó recommending ways to enhance biodiversity and adapt to climate change as the city grows, a multi-stakeholder partnership to train local youth and implement a citizen-led biodiversity survey, and a seed grant from the MIT Climate and Sustainability Consortium to begin providing both cities detailed data on their tree cover derived from satellite images. “These regions face serious threats, especially on a warming planet, but many of the solutions for climate change, biodiversity conservation, and environmental equity in the region go hand-in-hand,” Angel says. “When you design a city to use fewer resources, to contribute less to climate change, it also causes less pressure on the environment around it. When you design a city for equity and quality of life, you’re giving attention to its green spaces and what they can provide for people and as habitat for other species. When you protect and restore forests, you’re protecting local bioeconomies.”

    Bringing the data home

    Meanwhile, in Mocoa, Angel’s original vision is taking flight. With the team’s test flights behind them, they can now begin creating digital models of the surrounding area. Regular drone flights and soil samples will fill in changing information about trees, water, and local geology, allowing the project’s machine learning specialists to identify warning signs for future landslides and extreme weather events. More importantly, there is now an established network of local community researchers and leaders ready to make use of this information. With feedback from their Mocoan partners, Angel’s team has built a prototype of the online platform they will use to share their UAV data; they’re now letting Mocoa residents take it for a test drive and suggest how it can be made more user-friendly. Her visit this January also paved the way for new projects that will tie the Environmental Solutions Initiative more tightly to Mocoa. With her project partners, Angel is exploring developing a course to teach local students how to use UAVs like the ones her team is flying. She is also considering expanded efforts to collect the kind of informal knowledge of Mocoa, on the local ecology and culture, that people everywhere use in making their city planning and emergency response decisions, but that is rarely codified and included in scientific risk analyses. It’s a great deal of work to offer this one community the tools to adapt successfully to climate change. But even with all the robotics and machine learning models in the world, this close, slow-unfolding engagement, grounded in trust and community inclusion, is what it takes to truly prepare people to confront profound changes in their city and environment. “Protecting natural carbon sinks is a global socio-environmental challenge, and one where it is not enough for MIT to just contribute to the knowledge base or develop a new technology,” says Angel. “But we can help mobilize decision-makers and nontraditional actors, and design more inclusive and technology-enhanced processes, to make this easier for the people who have lifelong stakes in these ecosystems. That is the vision.” More

  • 113 Shares139 Views

    in Environment

    Advancing material innovation to address the polymer waste crisis

    Products made from polymers — ranging from plastic bags to clothing to cookware to electronics — provide many comforts and support today’s standard of living, but since they do not decompose easily, they pose long-term environmental challenges. Developing polymers, a large class of materials, with a more sustainable life cycle is a critical step in making progress toward a green economy and addressing this piece of the global climate change crisis. The development of biodegradable polymers, however, remains limited by current biodegradation testing methods.

    To address this limitation, a team of MIT researchers led by Bradley D. Olsen, the Alexander and I. Michael Kasser (1960) Professor in the Department of Chemical Engineering, has developed an expansive biodegradation dataset to help determine whether or not a polymer is biodegradable.

    Their findings were recently published in The Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS), in a paper titled “High-Throughput Experimentation for Discovery of Biodegradable Polyesters.” The MIT team is led by Olsen and PhD candidates Katharina A. Fransen and Sarah H. M. Av-Ron, and also includes postdoc Dylan J. Walsh and undergraduate students Tess R. Buchanan, Dechen T. Rota, and Lana Van Note.

    “Despite polymer waste being a known and significant contributor to the climate crisis, the study of polymer biodegradation has been limited to a small number of polymers because current biodegradation testing methods are time- and resource-intensive,” says Olsen. “This limited scope slows new material innovation, so we are working to open that up to a much broader portfolio of materials.”

    Unique high-throughput approach

    The dataset Olsen’s team has developed, with support from the MIT Climate and Sustainability Consortium (MCSC), the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), and DIC Corporation, includes more than 600 distinct polyester chemistries.

    “The ingenuity of our work is pushing the screening to be high-throughput, which accelerates the pace of discovery,” says Av-Ron. High-throughput synthesis methods enable large quantities of samples to be screened rapidly, identifying products with the desired property or function you are looking for. In this case, the high-throughput approach was conducted using a method called clear-zone assay, which detects polymer biofragmentation and identifies polymer degrading bacteria. The biodegradation dataset can then lead to structure-property relationships, a concept central to materials science and engineering, where relationships between the chemical detail and property can be established, and used to build a biodegradation prediction model. When developing these models to predict biodegradation, the researchers were interested in looking into the potential linearity and nonlinearity of the relationships between structure and biodegradability.

    “We consider our scientific breakthrough to be having this large dataset, and the qualitative relationships and predictive models such a substantial  amount of data enabled,” adds Av-Ron. “It was captivating to figure out how to integrate the high complexity of polymer chemical representation with predictive machine-learning models. I was very excited to get a validation accuracy of 82 percent for one representation/model combination. With additional data we might be able to improve our predictions even more.”

    The team’s work focuses largely on polyesters; the development of biodegradable polyesters presents a key opportunity for addressing the polymer sustainability crisis and reducing the environmental burden of the polymer life cycle.

    One strain of bacteria, many chemistries

    The biodegradation test that these data create is accessible and cost-effective to put in place; initial industry feedback has been positive. The datasets are also more reproducible than many other standards in this space.

    “With our method, there is one strain of bacteria, so you know exactly what you’re testing,” says Av-Ron. This speaks to the uniqueness of the team’s approach.

    “When polymers are developed, normally the strength of the material is examined first, and then once the material is developed, whether or not it biodegrades comes second,” says Fransen.

    Olsen and his team are examining the opposite — developing the biodegradability screen first, to help filter and focus what to look for in a material. This way, the team’s infrastructure can assess a lot of different options, quickly.

    “There has been big movement recently in developing sustainable polymers,” concludes Fransen, “and having something like this that is quick, tangible, and relatively inexpensive, could add a lot of value to that community.”

    Fransen received a 2022 J-WAFS Fellowship for this work, and she and Av-Ron together won second place in the 2022 J-WAFS World Food Day Student Video Competition, as this research can be applied to creating more sustainable food packaging. More

  • 88 Shares149 Views

    in Environment

    Q&A: Are far-reaching fires the new normal?

    Where there’s smoke, there is fire. But with climate change, larger and longer-burning wildfires are sending smoke farther from their source, often to places that are unaccustomed to the exposure. That’s been the case this week, as smoke continues to drift south from massive wildfires in Canada, prompting warnings of hazardous air quality, and poor visibility in states across New England, the mid-Atlantic, and the Midwest.

    As wildfire season is just getting going, many may be wondering: Are the air-polluting effects of wildfires a new normal?

    MIT News spoke with Professor Colette Heald of the Department of Civil and Environmental Engineering and the Department of Earth, Atmospheric and Planetary Sciences, and Professor Noelle Selin of the Institute for Data, Systems and Society and the Department of Earth, Atmospheric and Planetary Sciences. Heald specializes in atmospheric chemistry and has studied the climate and health effects associated with recent wildfires, while Selin works with atmospheric models to track air pollutants around the world, which she uses to inform policy decisions on mitigating  pollution and climate change. The researchers shared some of their insights on the immediate impacts of Canada’s current wildfires and what downwind regions may expect in the coming months, as the wildfire season stretches into summer.  

    Q: What role has climate change and human activity played in the wildfires we’ve seen so far this year?

    Heald: Unusually warm and dry conditions have dramatically increased fire susceptibility in Canada this year. Human-induced climate change makes such dry and warm conditions more likely. Smoke from fires in Alberta and Nova Scotia in May, and Quebec in early June, has led to some of the worst air quality conditions measured locally in Canada. This same smoke has been transported into the United States and degraded air quality here as well. Local officials have determined that ignitions have been associated with lightning strikes, but human activity has also played a role igniting some of the fires in Alberta.

    Q: What can we expect for the coming months in terms of the pattern of wildfires and their associated air pollution across the United States?

    Heald: The Government of Canada is projecting higher-than-normal fire activity throughout the 2023 fire season. Fire susceptibility will continue to respond to changing weather conditions, and whether the U.S. is impacted will depend on the winds and how air is transported across those regions. So far, the fire season in the United States has been below average, but fire risk is expected to increase modestly through the summer, so we may see local smoke influences as well.

    Q: How has air pollution from wildfires affected human health in the U.S. this year so far?

    Selin: The pollutant of most concern in wildfire smoke is fine particulate matter (PM2.5) – fine particles in the atmosphere that can be inhaled deep into the lungs, causing health damages. Exposure to PM2.5 causes respiratory and cardiovascular damage, including heart attacks and premature deaths. It can also cause symptoms like coughing and difficulty breathing. In New England this week, people have been breathing much higher concentrations of PM2.5 than usual. People who are particularly vulnerable to the effects are likely experiencing more severe impacts, such as older people and people with underlying conditions. But PM2.5 affects everyone. While the number and impact of wildfires varies from year to year, the associated air pollution from them generally lead to tens of thousands of premature deaths in the U.S. overall annually. There is also some evidence that PM2.5 from fires could be particularly damaging to health.

    While we in New England usually have relatively lower levels of pollution, it’s important also to note that some cities around the globe experience very high PM2.5 on a regular basis, not only from wildfires, but other sources such as power plants and industry. So, while we’re feeling the effects over the past few days, we should remember the broader importance of reducing PM2.5 levels overall for human health everywhere.

    Q: While firefighters battle fires directly this wildfire season, what can we do to reduce the effects of associated air pollution? And what can we do in the long-term, to prevent or reduce wildfire impacts?

    Selin: In the short term, protecting yourself from the impacts of PM2.5 is important. Limiting time outdoors, avoiding outdoor exercise, and wearing a high-quality mask are some strategies that can minimize exposure. Air filters can help reduce the concentrations of particles in indoor air. Taking measures to avoid exposure is particularly important for vulnerable groups. It’s also important to note that these strategies aren’t equally possible for everyone (for example, people who work outside) — stressing the importance of developing new strategies to address the underlying causes of increasing wildfires.

    Over the long term, mitigating climate change is important — because warm and dry conditions lead to wildfires, warming increases fire risk. Preventing the fires that are ignited by people or human activities can help.  Another way that damages can be mitigated in the longer term is by exploring land management strategies that could help manage fire intensity. More

  • 138 Shares129 Views

    in Environment

    Megawatt electrical motor designed by MIT engineers could help electrify aviation

    Aviation’s huge carbon footprint could shrink significantly with electrification. To date, however, only small all-electric planes have gotten off the ground. Their electric motors generate hundreds of kilowatts of power. To electrify larger, heavier jets, such as commercial airliners, megawatt-scale motors are required. These would be propelled by hybrid or turbo-electric propulsion systems where an electrical machine is coupled with a gas turbine aero-engine.

    To meet this need, a team of MIT engineers is now creating a 1-megawatt motor that could be a key stepping stone toward electrifying larger aircraft. The team has designed and tested the major components of the motor, and shown through detailed computations that the coupled components can work as a whole to generate one megawatt of power, at a weight and size competitive with current small aero-engines.

    For all-electric applications, the team envisions the motor could be paired with a source of electricity such as a battery or a fuel cell. The motor could then turn the electrical energy into mechanical work to power a plane’s propellers. The electrical machine could also be paired with a traditional turbofan jet engine to run as a hybrid propulsion system, providing electric propulsion during certain phases of a flight.

    “No matter what we use as an energy carrier — batteries, hydrogen, ammonia, or sustainable aviation fuel — independent of all that, megawatt-class motors will be a key enabler for greening aviation,” says Zoltan Spakovszky, the T. Wilson Professor in Aeronautics and the Director of the Gas Turbine Laboratory (GTL) at MIT, who leads the project.

    Spakovszky and members of his team, along with industry collaborators, will present their work at a special session of the American Institute of Aeronautics and Astronautics – Electric Aircraft Technologies Symposium (EATS) at the Aviation conference in June.

    The MIT team is composed of faculty, students, and research staff from GTL and the MIT Laboratory for Electromagnetic and Electronic Systems: Henry Andersen Yuankang Chen, Zachary Cordero, David Cuadrado,  Edward Greitzer, Charlotte Gump, James Kirtley, Jr., Jeffrey Lang, David Otten, David Perreault, and Mohammad Qasim,  along with Marc Amato of Innova-Logic LLC. The project is sponsored by Mitsubishi Heavy Industries (MHI).

    Heavy stuff

    To prevent the worst impacts from human-induced climate change, scientists have determined that global emissions of carbon dioxide must reach net zero by 2050. Meeting this target for aviation, Spakovszky says, will require “step-change achievements” in the design of unconventional aircraft, smart and flexible fuel systems, advanced materials, and safe and efficient electrified propulsion. Multiple aerospace companies are focused on electrified propulsion and the design of megawatt-scale electric machines that are powerful and light enough to propel passenger aircraft.

    “There is no silver bullet to make this happen, and the devil is in the details,” Spakovszky says. “This is hard engineering, in terms of co-optimizing individual components and making them compatible with each other while maximizing overall performance. To do this means we have to push the boundaries in materials, manufacturing, thermal management, structures and rotordynamics, and power electronics”

    Broadly speaking, an electric motor uses electromagnetic force to generate motion. Electric motors, such as those that power the fan in your laptop, use electrical energy — from a battery or power supply — to generate a magnetic field, typically through copper coils. In response, a magnet, set near the coils, then spins in the direction of the generated field and can then drive a fan or propeller.

    Electric machines have been around for over 150 years, with the understanding that, the bigger the appliance or vehicle, the larger the copper coils  and the magnetic rotor, making the machine heavier. The more power the electrical machine generates, the more heat it produces, which requires additional elements to keep the components cool — all of which can take up space and add significant weight to the system, making it challenging for airplane applications.

    “Heavy stuff doesn’t go on airplanes,” Spakovszky says. “So we had to come up with a compact, lightweight, and powerful architecture.”

    Good trajectory

    As designed, the MIT electric motor and power electronics are each about the size of a checked suitcase weighing less than an adult passenger.

    The motor’s main components are: a high-speed rotor, lined with an array of magnets with varying orientation of polarity; a compact low-loss stator that fits inside the rotor and contains an intricate array of copper windings; an advanced heat exchanger that keeps the components cool while transmitting the torque of the machine; and a distributed power electronics system, made from 30 custom-built circuit boards, that precisely change the currents running through each of the stator’s copper windings, at high frequency.

    “I believe this is the first truly co-optimized integrated design,” Spakovszky says. “Which means we did a very extensive design space exploration where all considerations from thermal management, to rotor dynamics, to power electronics and electrical machine architecture were assessed in an integrated way to find out what is the best possible combination to get the required specific power at one megawatt.”

    As a whole system, the motor is designed such that the distributed circuit boards are close coupled with the electrical machine to minimize transmission loss and to allow effective air cooling through the integrated heat exchanger.

    “This is a high-speed machine, and to keep it rotating while creating torque, the magnetic fields have to be traveling very quickly, which we can do through our circuit boards switching at high frequency,” Spakovszky says.

    To mitigate risk, the team has built and tested each of the major components individually, and shown that they can operate as designed and at conditions exceeding normal operational demands. The researchers plan to assemble the first fully working electric motor, and start testing it in the fall.

    “The electrification of aircraft has been on a steady rise,” says Phillip Ansell, director of the Center for Sustainable Aviation at the University of Illinois Urbana-Champaign, who was not involved in the project. “This group’s design uses a wonderful combination of conventional and cutting-edge methods for electric machine development, allowing it to offer both robustness and efficiency to meet the practical needs of aircraft of the future.”

    Once the MIT team can demonstrate the electric motor as a whole, they say the design could power regional aircraft and could also be a companion to conventional jet engines, to enable hybrid-electric propulsion systems. The team also envision that multiple one-megawatt motors could power multiple fans distributed along the wing on future aircraft configurations. Looking ahead, the foundations of the one-megawatt electrical machine design could potentially be scaled up to multi-megawatt motors, to power larger passenger planes.

    “I think we’re on a good trajectory,” says Spakovszky, whose group and research have focused on more than just gas turbines. “We are not electrical engineers by training, but addressing the 2050 climate grand challenge is of utmost importance; working with electrical engineering faculty, staff and students for this goal can draw on MIT’s breadth of technologies so the whole is greater than the sum of the parts. So we are reinventing ourselves in new areas. And MIT gives you the opportunity to do that.” More

  • 175 Shares159 Views

    in Environment

    Q&A: Gabriela Sá Pessoa on Brazilian politics, human rights in the Amazon, and AI

    Gabriela Sá Pessoa is a journalist passionate about the intersection of human rights and climate change. She came to MIT from The Washington Post, where she worked from her home country of Brazil as a news researcher reporting on the Amazon, human rights violations, and environmental crimes. Before that, she held roles at two of the most influential media outlets in Brazil: Folha de S.Paulo, covering local and national politics, and UOL, where she was assigned to coronavirus coverage and later joined the investigative desk.

    Sá Pessoa was awarded the 2023 Elizabeth Neuffer Fellowship by the International Women’s Media Foundation, which supports its recipient with research opportunities at MIT and further training at The Boston Globe and The New York Times. She is currently based at the MIT Center for International Studies. Recently, she sat down to talk about her work on the Amazon, recent changes in Brazilian politics, and her experience at MIT.

    Q: One focus of your reporting is human rights and environmental issues in the Amazon. As part of your fellowship, you contributed to a recent editorial in The Boston Globe on fighting deforestation in the region. Why is reporting on this topic important?

    A: For many Brazilians, the Amazon is a remote and distant territory, and people living in other parts of the country aren’t fully aware of all of its problems and all of its potential. This is similar to the United States — like many people here, they don’t see how they could be related to the human rights violations and the destruction of the rainforest that are happening.

    But, we are all complicit in the destruction in some ways because the economic forces driving the deforestation of the rainforest all have a market, and these markets are everywhere, in Brazil and here in the U.S. I think it is part of journalism to show people in the U.S., Brazil, and elsewhere that we are part of the problem, and as part of the problem, we should be part of the solution by being aware of it, caring about it, and taking actions that are within our power.

    In the U.S., for example, voters can influence policy like the current negotiations for financial support for fighting deforestation in the Amazon. And as consumers, we can be more aware — is the beef we are consuming related to deforestation? Is the timber on our construction sites coming from the Amazon?

    Truth is, in Brazil, we have turned our backs to the Amazon for so long. It’s our duty to protect it for the sake of climate change. If we don’t take care of it, there will be serious consequences to our local climate, our local communities, and for the whole world. It’s a huge matter of human rights because our living depends on that, both locally and globally.

    Q: Before coming to MIT, you were at The Washington Post in São Paulo, where you contributed to reporting on the recent presidential election. What changes do you expect to see with the new Lula administration?

    A: To climate and environment, the first signs were positive. But the optimism did not last a semester, as politics is imposing itself. Lula is facing increasing difficulty building a majority in a conservative Congress, over which agribusiness holds tremendous power and influence. As we speak, environmental policy is under Congress’s attack. A committee in the House has just passed a ruling drowning power from the environmental minister, Marina Silva, and from the recently created National Indigenous People Ministry, led by Sonia Guajajara. Both Marina and Sonia are global ecological and human rights champions, and I wonder what the impact would be if Congress ratifies these changes. It is still unclear how it would impact the efforts to fight deforestation.

    In addition, there is an internal dispute in the government between environmentalists and those in favor of mining and big infrastructure projects. Petrobras, the state-run oil company, is trying to get authorization to research and drill offshore oil reserves in the mouth of the Amazon River. The federal environmental protection agency did a conclusive report suspending the operation, saying it is critical and threatens the region’s sensitive environment and indigenous communities. And, of course, it would be another source of greenhouse gas emissions. ​

    That said, it’s not a denialist government. I should mention the quick response from the administration to the Yanomami genocide earlier this year. In January, an independent media organization named Sumaúma reported on the deaths of over five hundred indigenous children from the Yanomami community in the Amazon over the past four years. This was a huge shock in Brazil, and the administration responded immediately. They sent task forces to the region and are now expelling the illegal miners that were bringing diseases and were ultimately responsible for these humanitarian tragedies. To be clear: It is still a problem. It’s not solved. But this is already a good example of positive action.

    Fighting deforestation in the Amazon and the Cerrado, another biome critical to climate regulation in Brazil, will not be easy. Rebuilding the environmental policy will take time, and the agencies responsible for enforcement are understaffed. In addition, environmental crime has become more sophisticated, connecting with other major criminal organizations in the country. In April, for the first time, there was a reduction in deforestation in the Amazon after two consecutive months of higher numbers. These are still preliminary data, and it is still too early to confirm whether they signal a turning point and may indicate a tendency for deforestation to decrease. On the other hand, the Cerrado registered record deforestation in April.

    There are problems everywhere in the economy and politics that Lula will have to face. In the first week of the new term, on Jan. 8, we saw an insurrection in Brasília, the country’s capital, from Bolsonaro voters who wouldn’t accept the election results. The events resembled what Americans saw in the Capitol attacks in 2021. We also seem to have imported problems from the United States, like mass killings in schools. We never used to have them in Brazil, but we are seeing them now. I’m curious to see how the country will address those problems and if the U.S. can also inspire solutions to that. That’s something I’m thinking about, being here: Are there solutions here? What are they?

    Q: What have you learned so far from MIT and your fellowship?

    A: It’s hard to put everything into words! I’m mostly taking courses and attending lectures on pressing issues to humanity, like existential threats such as climate change, artificial intelligence, biosecurity, and more.

    I’m learning about all these issues, but also, as a journalist, I think that I’m learning more about how I can incorporate the scientific approach into my work; for example, being more pro-positive. I am already a rigorous journalist, but I am thinking about how I can be more rigorous and more transparent about my methods. Being in the academic and scientific environment is inspiring that way.

    I am also learning a lot about how to cover scientific topics and thinking about how technology can offer us solutions (and problems). I’m learning so much that I think I will need some time to digest and fully understand what this period means for me!

    Q: You mentioned artificial intelligence. Would you like to weigh in on this subject and what you have been learning?

    A: It has been a particularly good semester to be at MIT. Generative artificial intelligence, which became more popular after ChatGPT, has been a topic of intense discussion this semester, and I was able to attend many classes, seminars, and events about AI here, especially from a policy perspective.

    Algorithms have influenced the economy, society, and public health for many years. It has had great outcomes, but also injustice. Popular systems like ChatGPT have made this technology incredibly popular and accessible, even for those with no computer knowledge. This is scary and, at the same time, very exciting. Here, I learned that we need guardrails for artificial intelligence, just like other technologies. Think of the pharmaceutical or automobile industries, which have to meet safety criteria before putting a new product on the market. But with artificial intelligence, it’s going to be different; supply chains are very complex and sometimes not very transparent, and the speed at which new resources develop is so fast that it challenges the policymaker’s ability to respond.

    Artificial intelligence is changing the world radically. It’s exciting to have the privilege of being here and seeing these discussions take place. After all, I have a future to report on. At least, I hope so!

    Q: What are you working on going forward?

    A: After MIT, I am going to New York, where I’ll be working with The New York Times in their internship program. I’m really excited about that because it will be a different pace from MIT. I am also doing research on carbon credit markets and hope to continue that project, either in a reporting or academic environment. 

    Honestly, I feel inspired to keep studying. I would love to spend more time here at MIT. I would love to do a master’s or join any program here. I’m going to work on coming back to academia because I think that I need to learn more from the academic environment. I hope that it’s at MIT because honestly, it’s the most exciting environment that I’ve ever been in, with all the people here from different fields and different backgrounds. I’m not a scientist, but it’s inspiring to be with them, and if there’s a way that I could contribute to their work in a way that they’re contributing to my work, I’ll be thrilled to spend more time here. More

  • 100 Shares99 Views

    in Environment

    River erosion can shape fish evolution, study suggests

    If we could rewind the tape of species evolution around the world and play it forward over hundreds of millions of years to the present day, we would see biodiversity clustering around regions of tectonic turmoil. Tectonically active regions such as the Himalayan and Andean mountains are especially rich in flora and fauna due to their shifting landscapes, which act to divide and diversify species over time.

    But biodiversity can also flourish in some geologically quieter regions, where tectonics hasn’t shaken up the land for millennia. The Appalachian Mountains are a prime example: The range has not seen much tectonic activity in hundreds of millions of years, and yet the region is a notable hotspot of freshwater biodiversity.

    Now, an MIT study identifies a geological process that may shape the diversity of species in tectonically inactive regions. In a paper appearing today in Science, the researchers report that river erosion can be a driver of biodiversity in these older, quieter environments.

    They make their case in the southern Appalachians, and specifically the Tennessee River Basin, a region known for its huge diversity of freshwater fishes. The team found that as rivers eroded through different rock types in the region, the changing landscape pushed a species of fish known as the greenfin darter into different tributaries of the river network. Over time, these separated populations developed into their own distinct lineages.

    The team speculates that erosion likely drove the greenfin darter to diversify. Although the separated populations appear outwardly similar, with the greenfin darter’s characteristic green-tinged fins, they differ substantially in their genetic makeup. For now, the separated populations are classified as one single species. 

    “Give this process of erosion more time, and I think these separate lineages will become different species,” says Maya Stokes PhD ’21, who carried out part of the work as a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

    The greenfin darter may not be the only species to diversify as a consequence of river erosion. The researchers suspect that erosion may have driven many other species to diversify throughout the basin, and possibly other tectonically inactive regions around the world.

    “If we can understand the geologic factors that contribute to biodiversity, we can do a better job of conserving it,” says Taylor Perron, the Cecil and Ida Green Professor of Earth, Atmospheric, and Planetary Sciences at MIT.

    The study’s co-authors include collaborators at Yale University, Colorado State University, the University of Tennessee, the University of Massachusetts at Amherst, and the Tennessee Valley Authority (TVA). Stokes is currently an assistant professor at Florida State University.

    Fish in trees

    The new study grew out of Stokes’ PhD work at MIT, where she and Perron were exploring connections between geomorphology (the study of how landscapes evolve) and biology. They came across work at Yale by Thomas Near, who studies lineages of North American freshwater fishes. Near uses DNA sequence data collected from freshwater fishes across various regions of North America to show how and when certain species evolved and diverged in relation to each other.

    Near brought a curious observation to the team: a habitat distribution map of the greenfin darter showing that the fish was found in the Tennessee River Basin — but only in the southern half. What’s more, Near had mitochondrial DNA sequence data showing that the fish’s populations appeared to be different in their genetic makeup depending on the tributary in which they were found.

    To investigate the reasons for this pattern, Stokes gathered greenfin darter tissue samples from Near’s extensive collection at Yale, as well as from the field with help from TVA colleagues. She then analyzed DNA sequences from across the entire genome, and compared the genes of each individual fish to every other fish in the dataset. The team then created a phylogenetic tree of the greenfin darter, based on the genetic similarity between fish.

    From this tree, they observed that fish within a tributary were more related to each other than to fish in other tributaries. What’s more, fish within neighboring tributaries were more similar to each other than fish from more distant tributaries.

    “Our question was, could there have been a geological mechanism that, over time, took this single species, and splintered it into different, genetically distinct groups?” Perron says.

    A changing landscape

    Stokes and Perron started to observe a “tight correlation” between greenfin darter habitats and the type of rock where they are found. In particular, much of the southern half of the Tennessee River Basin, where the species abounds, is made of metamorphic rock, whereas the northern half consists of sedimentary rock, where the fish are not found.

    They also observed that the rivers running through metamorphic rock are steeper and more narrow, which generally creates more turbulence, a characteristic greenfin darters seem to prefer. The team wondered: Could the distribution of greenfin darter habitat have been shaped by a changing landscape of rock type, as rivers eroded into the land over time?

    To check this idea, the researchers developed a model to simulate how a landscape evolves as rivers erode through various rock types. They fed the model information about the rock types in the Tennessee River Basin today, then ran the simulation back to see how the same region may have looked millions of years ago, when more metamorphic rock was exposed.

    They then ran the model forward and observed how the exposure of metamorphic rock shrank over time. They took special note of where and when connections between tributaries crossed into non-metamorphic rock, blocking fish from passing between those tributaries. They drew up a simple timeline of these blocking events and compared this to the phylogenetic tree of diverging greenfin darters. The two were remarkably similar: The fish seemed to form separate lineages in the same order as when their respective tributaries became separated from the others.

    “It means it’s plausible that erosion through different rock layers caused isolation between different populations of the greenfin darter and caused lineages to diversify,” Stokes says.

    “This study is highly compelling because it reveals a much more subtle but powerful mechanism for speciation in passive margins,” says Josh Roering, professor of Earth sciences at the University of Oregon, who was not involved in the study. “Stokes and Perron have revealed some of the intimate connections between aquatic species and geology that may be much more common than we realize.”

    This research was supported, in part, by the mTerra Catalyst Fund and the U.S. National Science Foundation through the AGeS Geochronology Program and the Graduate Research Fellowship Program. While at MIT, Stokes received support through the Martin Fellowship for Sustainability and the Hugh Hampton Young Fellowship. More