Urbanization: No fast lane to transformation

Accra, Ghana, “is a city I’ve come to know as well as any place in the U.S,” says Associate Professor Noah Nathan, who has conducted research there over the past 15 years. The booming capital of 4 million is an ideal laboratory for investigating the rapid urbanization of nations in Africa and beyond, believes Nathan, who joined the MIT Department of Political Science in July.

“Accra is vibrant and exciting, with gleaming glass office buildings, shopping centers, and an emerging middle class,” he says. “But at the same time there is enormous poverty, with slums and a mixing pot of ethnic groups.” Cities like Accra that have emerged in developing countries around the world are “hybrid spaces” that provoke a multitude of questions for Nathan.

“Rich and poor are in incredibly close proximity and I want to know how this dramatic inequality can be sustainable, and what politics looks like with such ethnic and class diversity living side-by-side,” he says.

With his singular approach to data collection and deep understanding of Accra, its neighborhoods, and increasingly, its built environment, Nathan is generating a body of scholarship on the political impacts of urbanization throughout the global South.

A trap in the urban transition

Nathan’s early studies of Accra challenged common expectations about how urbanization shifts political behavior.

“Modernization theory states that as people become more ‘modern’ and move to cities, ethnicity fades and class becomes the dominant dynamic in political behavior,” explains Nathan. “It predicts that the process of urbanization transforms the relationship between politicians and voters, and elections become more ideologically and policy oriented,” says Nathan.  

But in Accra, the heart of one of the fastest-growing economies in the developing world, Nathan found “a type of politics stuck in an old equilibrium, hard to dislodge, and not updated by newly wealthy voters,” he says. Using census data revealing the demographic composition of every neighborhood in Accra, Nathan determined that there were many enclaves in which forms of patronage politics and ethnic competition persist. He conducted sample surveys and collected polling-station level results on residents’ voting across the city. “I was able to merge spatial data on where people lived and their answers to survey questions, and determine how different neighborhoods voted,” says Nathan.

Among his findings: Ethnic politics were thriving in many parts of Accra, and many middle-class voters were withdrawing from politics entirely in reaction to the well-established practice of patronage rather than pressuring politicians to change their approach. “They decided it was better to look out for themselves,” he explains.

In Nathan’s 2019 book, “Electoral Politics and Africa's Urban Transition: Class and Ethnicity in Ghana,” he described this situation as a trap. “As the wealthy exit from the state, politicians double down on patronage politics with poor voters, which the middle class views as further evidence of corruption,” he explains. The wealthier citizens “want more public goods, and big policy reforms, such as changes in the health-care and tax systems, while poor voters focus on immediate needs such as jobs, homes, better schools in their communities.”

In Ghana and other developing countries where the state’s capacity is limited, politicians can’t deliver on the broad-scale changes desired by the middle class. Motivated by their own political survival, they continue dealing with poor voters as clients, trading services for votes. “I connect urban politics in Ghana to the early 20th-century urban machines in the United States, run by party bosses,” says Nathan.

This may prove sobering news for many engaged with the developing world. “There’s enormous enthusiasm among foreign aid organizations, in the popular press and policy circles, for the idea that urbanization will usher in big, radical political change,” notes Nathan. “But these kinds of transformations will only come about with structural change such as civil service reforms and nonpartisan welfare programs that can push politicians beyond just delivering targeted services to poor voters.”

Falling in love with Ghana

For most of his youth, Nathan was a committed jazz saxophonist, toying with going professional. But he had long cultivated another fascination as well. “I was a huge fan of ‘The West Wing’ in middle school” and got into American politics through that,” he says. He volunteered in Hillary Clinton’s 2008 primary campaign during college, but soon realized work in politics was “both more boring and not as idealistic” as he’d hoped.

As an undergraduate at Harvard University, where he concentrated in government, he “signed up for African history on a lark — because American high schools didn’t teach anything on the subject — and I loved it,” Nathan says. He took another African history course, and then found his way to classes taught by Harvard political scientist Robert H. Bates PhD ’69 that focused on the political economy of development, ethnic conflict, and state failure in Africa. In the summer before his senior year, he served as a research assistant for one of his professors in Ghana, and then stayed longer, hoping to map out a senior thesis on ethnic conflict.

“Once I got to Ghana, I was fascinated by the place — the dynamism of this rapidly transforming society,” he recalls. “Growing up in the U.S., there are a lot of stereotypes about the developing world, and I quickly realized how much more complicated everything is.”

These initial experiences living in Ghana shaped Nathan’s ideas for what became his doctoral dissertation at Harvard and first book on the ethnic and class dynamics driving the nation’s politics. His frequent return visits to that country sparked a wealth of research that built on and branched out from this work.

One set of studies examines the historical development of Ghana’s rural north in its colonial and post-colonial periods, the center of ethnic conflict in the 1990s. These are communities “where the state delivers few resources, doesn’t seem to do much, yet figures as a central actor in people’s lives,” he says.

Part of this region had been a German colony, and the other part was originally under British rule, and Nathan compared the political trajectories of these two areas, focusing on differences in early state efforts to impose new forms of local political leadership and gradually build a formal education system.

“The colonial legacy in the British areas was elite families who came to dominate, entrenching themselves and creating political dynasties and economic inequality,” says Nathan. But similar ethnic groups exposed to different state policies in the original German colony were not riven with the same class inequalities, and enjoy better access to government services today. “This research is changing how we think about state weakness in the developing world, how we tend to see the emergence of inequality where societal elites come into power,” he says. The results of Nathan’s research will be published in a forthcoming book, “The Scarce State: Inequality and Political Power in the Hinterland.”

Politics of built spaces

At MIT, Nathan is pivoting to a fresh new framing for questions on urbanization. Wielding a public source map of cities around the world, he is scrutinizing the geometry of street grids in 1,000 of sub-Saharan Africa’s largest cities “to think about urban order,” he says. Digitizing historical street maps of African cities from the Library of Congress’s map collection, he can look at how these cities were built and evolved physically. “When cities emerge based on grids, rather than tangles, they are more legible to governments,” he says. “This means that it’s easier to find people, easier to govern, tax, repress, and politically mobilize them.”  

Nathan has begun to demonstrate that in the post-colonial period, “cities that were built under authoritarian regimes tend to be most legible, with even low-capacity regimes trying to impose control and make them gridded.” Democratic governments, he says, “lead to more tangled and chaotic built environments, with people doing what they want.” He also draws comparisons to how state policies shaped urban growth in the United States, with local and federal governments exerting control over neighborhood development, leading to redlining and segregation in many cities.

Nathan’s interests naturally pull him toward the MIT Governance Lab and Global Diversity Lab. “I’m hoping to dive into both,” he says. “One big attraction of the department is the really interesting research that’s being done on developing countries.”  He also plans to use the stature he has built over many years of research in Africa to help “open doors” to African researchers and students, who may not always get the same kind of access to institutions and data that he has had. “I’m hoping to build connections to researchers in the global South,” he says.

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An easier way to remove medical devices

By taking advantage of a phenomenon that leads to fractures in metal, MIT researchers have designed medical devices that could be used inside the body as stents, staples, or drug depots, then safely broken down on demand when they’re no longer needed.

The researchers showed that biomedical devices made from aluminum can be disintegrated by exposing them to a liquid metal known as eutectic gallium-indium (EGaIn). In practice, this might work by painting the liquid onto staples used to hold skin together, for example, or by administering EGaIn microparticles to patients.

Triggering the disintegration of such devices this way could eliminate the need for surgical or endoscopic procedures to remove them, the researchers say.

“It’s a really dramatic phenomenon that can be applied to several settings,” says Giovanni Traverso, the Karl van Tassel Career Development Assistant Professor of Mechanical Engineering at MIT and a gastroenterologist at Brigham and Women’s Hospital. “What this enables, potentially, is the ability to have systems that don’t require an intervention such as an endoscopy or surgical procedure for removal of devices.”

Traverso is the senior author of the study, which appears in Advanced Materials. Vivian Feig, an MIT postdoc, is the lead author of the paper.

Breaking down metals

For several years, Traverso’s lab has been working on ingestible devices that could remain in the digestive tract for days or weeks, releasing drugs on a specific schedule.

Most of those devices are made from polymers, but recently the researchers have been exploring the possibility of using metals, which are stronger and more durable. However, one of the challenges of delivering metal devices is finding a way to remove them once they’re no longer needed.

To create devices that could be broken down on demand inside the body, the MIT team drew inspiration from a phenomenon known as liquid metal embrittlement. This process has been well-studied as a source of failure in metal structures, including those made from zinc and stainless steel.

“It’s known that certain combinations of liquid metals can actually get into the grain boundaries of solid metals and cause them to dramatically weaken and fail,” Feig says. “We wanted to see if we could harness that known failure mechanism in a productive way to build these biomedical devices.”

One type of liquid metal that can induce embrittlement is gallium. For this study, the researchers used eutectic gallium-indium, an alloy of gallium that scientists have explored for a variety of applications in biomedicine as well as energy and flexible electronics.

For the devices themselves, the researchers chose to use aluminum, which is known to be susceptible to embrittlement when exposed to gallium.

Gallium weakens solid metals such as aluminum in two ways. First, it can diffuse through the grain boundaries of the metal — border lines between the crystals that make up the metal — causing pieces of the metal to break off. The MIT team showed that they could harness this phenomenon by designing metals with different types of grain structures, allowing the metals to break into small pieces or to fracture at a given point.

Gallium also prevents aluminum from forming a protective oxide layer on its surface, which increases the metal’s exposure to water and enhances its degradation.

The MIT team showed that after they painted gallium-indium onto aluminum devices, the metals would disintegrate within minutes. The researchers also created nanoparticles and microparticles of gallium-indium and showed that these particles, suspended in fluid, could also break down aluminum structures.

On-demand disintegration

While the researchers began this effort as a way to create devices that could be broken down in the gastrointestinal tract, they soon realized that it could also be applied to other biomedical devices such as staples and stents.

To demonstrate GI applications, the researchers designed a star-shaped device, with arms attached to a central elastomer by a hollow aluminum tube. Drugs can be carried in the arms, and the shape of the device helps it be retained in the GI tract for an extended period of time. In a study in animals, the researchers showed that this kind of device could be broken down in the GI tract upon treatment with gallium-indium.

The researchers then created aluminum staples and showed that they could be used to hold tissue together, then dissolved with a coating of gallium-indium.

“Right now, removing the staples can actually induce more tissue damage,” Feig says. “We showed that with our gallium formulation we can just paint it on the staples and get them to disintegrate on-demand instead.”

The researchers also showed that an aluminum stent they designed could be implanted in esophageal tissue, then broken down by gallium-indium.

Currently, esophageal stents are either left in the body permanently or endoscopically removed when no longer needed. Such stents are often made from metals such as nitinol, an alloy of nickel and titanium. The researchers are now working to see if they could create dissolvable devices from nitinol and other metals.

“An exciting thing to explore from a materials science perspective is: Can we take other metals that are more commonly used in the clinic and modify them so that they can become actively triggerable as well?” Feig says.

In this study, the researchers conducted initial toxicity studies in rodents and found that gallium-indium was non-toxic even at high doses. However, more study would be needed to ensure it would be safe to administer to patients, the researchers say.

The research was funded by the Bill and Melinda Gates Foundation, MIT’s Department of Mechanical Engineering, the Brigham and Women’s Hospital Division of Gastroenterology, the Schmidt Science Fellows Program, and the Rhodes Trust.

Other authors of the paper include Eva Remlova, Benjamin Muller, Johannes Kuosmanen, Nikhil Lal, Anna Ginzburg, Kewang Nan, Ashka Patel, Ahmad Mujtaba Jebran, Meghana Bantwal, Niora Fabian, Keiko Ishida, Joshua Jenkins, Jan-Georg Rosenboom, Sanghyun Park, Weema Madani, and Alison Hayward.

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A whole new world of learning via MIT OpenCourseWare videos

Like millions of others during the global Covid-19 lockdowns, Emmanuel Kasigazi, an entrepreneur from Uganda, turned to YouTube to pass the time. But he wasn’t following an influencer or watching music videos. A lifelong learner, Kasigazi was scouring the video-sharing platform for educational resources. Since 2013, when he got his first smartphone, Kasigazi has been charting his own learning journey through YouTube, educating himself on subjects as diverse as psychology and artificial intelligence. And it was while searching for the answer to an AI-related question that Kasigazi first discovered MIT OpenCourseWare (OCW).

“The search results showed MIT lectures, and I thought, 'Which MIT is this?’” recalls Kasigazi, who admits he was initially skeptical as he opened the OCW YouTube channel. To his amazement, he found hundreds of courses there — not only clips, but complete lectures that he could follow alongside the students in MIT classrooms. He searched for more information on OCW and tried the channel on different browsers to triple-check its credibility. “Here they were, all these courses by one of the best — if not the best — schools in tech in the world, and they were free. For a long time I couldn’t believe it. I told everyone I knew,” he remembers.

For Kasigazi, the channel became a gateway to other open education resources, including the OpenCourseWare website and MITx courses, both part of MIT Open Learning. “I always had the questions — I grew up on science cartoons like 'Dexter’s Laboratory' and 'Pinky and the Brain' — so I would go on YouTube to try to find answers to these questions, and I found this whole other world,” he says.

OCW launched its YouTube channel in 2008, and this August passed 4 million subscribers. While introductory computer science, math, and physics are the most-visited courses on the OCW website, the most popular YouTube videos reflect a more diverse range of interests, including a lecture about piloting a fighter jet aircraft, an introduction to the human brain, and an introduction to financial terms and concepts.

Through this extensive collection, Kasigazi explains that he’s been able to explore “the things I love,” while also studying cloud computing, data science, and AI — fields that he plans to pursue in graduate studies. He says, “This is what OpenCourseWare has enabled me to do: I get the chance to not only watch the future happen, but I can actually be a part of it and create it.”  

Understanding humanity through the liberal arts

When Kasigazi was young, a beloved aunt recognized his natural curiosity and steered him toward the best schools. “I owe her everything,” he says, “everything I am is because of her.” Thanks to his excellent grades he received an academic scholarship from the Ugandan government to attend Makerere University, one of the top universities in sub-Saharan Africa, where he earned a degree in information systems. Having pursued IT for its practical applications, Kasigazi admits that he was initially more interested in the science and theory behind computers than “the coding bits of it.”

“I love the concept of it — how we are trying to make these machines,” he says, explaining that he’s long been drawn to the social sciences and humanities, particularly psychology and philosophy.

“I’m interested in how we work as human beings, because everything we do is for, with, and around human beings,” says Kasigazi, who considers psychology to be foundational to almost every field. “Whatever it is you’re teaching these kids, they’re going to be dealing with people. So first teach them what people think, how they act — that was my drive to love psychology.”

Kasigazi has also turned to OCW to brush up on his coding skills, watching 6.0001 (Introduction to Computer Science and Programming Using Python) lectures with Professor Ana Bell and reviewing the instructor-paced version with Professor Eric Grimson now on MITx. “I am proud to say MIT OCW has made me fall in love with coding … it makes sense like it never has before,” he says.

Nurturing a worldview

In 2014 Kasigazi moved to South Sudan, which had only recently emerged from a civil war as an independent nation. Fresh out of university, he was there to teach computer skills and graphic design — some of his students included members of the new country’s government — but his time in South Sudan quickly became a learning experience for him, too. “When you grow up in your community, you have this bubble. We all experience it — it’s a human thing,” he reflects. “For the first time, I realized that everything I knew is not a given. Everything I grew up knowing is not universal.”

With his worldview newly broadened, he began to nurture his interest in psychology, philosophy, and the sciences, watching crash courses, explainer videos, and other content on the subject. “It’s entertainment, to me, at the same time that it’s a passion,” he says. Today Kasigazi runs his own company, which he started in 2012 with friends and resumed when he returned to Uganda seven years ago.

Since coming across the OCW YouTube channel, Kasigazi has worked through all of the freely available MIT psychology courses. Professor John Gabrieli’s 9.00SC (Introduction to Psychology) have particularly resonated with him, even prompting him to reach out to Gabrieli. “As much as I’d been getting some knowledge on psychology over the years online, it wasn’t as deep and as interesting or captivating as your classes were,” he wrote. “From your teaching style, to the explanations, to the topics, to how you make people understand a topic, to the experiments mentioned and referenced, to how you approach questions and later make one think deeper about them.”

“The message from Emmanuel is deeply touching about the joy of learning,” says Gabrieli. “I am so grateful to OCW for making this course on psychology open to the world, and to Emmanuel for so delightfully sharing what this course meant to him.”

New courses are added regularly to both the OCW website and YouTube channel. Kasigazi, who’s currently enjoying Professor Nancy Kanwisher’s 9.13 (Introduction to the Human Brain), looks forward to discovering what new worlds of knowledge they’ll open.

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UpNano joins MIT.nano Consortium

MIT.nano has announced that UpNano US Inc., a company that manufactures and supplies high-precision and high-resolution 3D printing instruments for academia and industry, has joined the MIT.nano Consortium. This engagement, initially planned for two years, will include locating one of UpNano’s NanoOne 1000 instruments in MIT.nano.

“We’re thrilled to welcome UpNano to the MIT.nano Consortium,” says Vladimir Bulović, the founding faculty director of MIT.nano and the Fariborz Maseeh (1990) Professor of Emerging Technology. “Not only is UpNano’s 3D printing technology an exciting addition to MIT.nano’s growing toolsets, but the company brings a global perspective on academic research and industry application that will be immensely valuable to the MIT.nano community and our consortium members.”

UpNano US Inc. is the Boston-based U.S. subsidiary of UpNano GmbH. Headquartered in Vienna, Austria, the company is a global distributor of 2-photon polymerization-based (2PP) 3D printers.

The NanoOne platform includes a compact multiphoton lithography device with custom control software that supports a range of photopolymer materials. This system combines the high precision of 2PP with the possibility to dynamically change the dimensions of the focal point on demand. The result is a printer that is both high resolution (producing feature sizes from 150 nanometers to 40 millimeters) and quick (up to 100 times more rapid than other 2PP systems). The speed of the system supports faster prototyping, shorter development cycles, and even small-scale serial production.

Additionally, an UpNano application scientist will be stationed at MIT.nano this fall to support research activities, including training, use of the NanoOne 1000, and collaboration with MIT researchers.

“UpNano is very excited to provide support to the important scientific mission of MIT.nano and affiliated researchers,” says Bernhard Küenburg, co-founder and CEO of UpNano. “From next-generation display materials, and micro-scale systems for biological study, to new material and design options for microelectronic devices, MIT researchers are at the forefront of many of the world’s most urgent challenges. We look forward to working with them to extend this research to even smaller dimensions and enable them to continue to push the boundaries of what is possible.”

In MIT.nano’s quarterly industry consortium meetings, UpNano will provide advice to help guide and advance nanoscale innovations at MIT alongside the 10 other consortium companies:

• Analog Devices
• Draper
• Edwards
• Fujikura
• IBM Research
• Lam Research
• NC
• NEC
• Oxford Instruments/Asylum Research
• Raith

MIT.nano continues to welcome new companies as sustaining members. For more details, visit the MIT.nano Consortium page.

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MIT engineers develop a low-cost terahertz camera

Terahertz radiation, whose wavelengths lie between those of microwaves and visible light, can penetrate many nonmetallic materials and detect signatures of certain molecules. These handy qualities could lend themselves to a wide array of applications, including airport security scanning, industrial quality control, astrophysical observations, nondestructive characterization of materials, and wireless communications with higher bandwidth than current cellphone bands.

However, designing devices to detect and make images from terahertz waves has been challenging, and most existing terahertz devices are expensive, slow, bulky, and require vacuum systems and extremely low temperatures.

Now, researchers at MIT, the University of Minnesota, and Samsung have developed a new kind of camera that can detect terahertz pulses rapidly, with high sensitivity, and at room temperature and pressure. What’s more, it can simultaneously capture information about the orientation, or “polarization,” of the waves in real-time, which existing devices cannot. This information can be used to characterize materials that have asymmetrical molecules or to determine the surface topography of materials.

The new system uses particles called quantum dots, which, it has recently been found, can emit visible light when stimulated by terahertz waves. The visible light can then be recorded by a device that is similar to a standard electronic camera’s detector and can even be seen with the naked eye. The device is described in a paper published today in the journal Nature Nanotechnology, by MIT doctoral student Jiaojian Shi, professor of chemistry Keith Nelson, and 12 others.

The team produced two different devices that can operate at room temperature: One uses the quantum dot’s ability to convert terahertz pulses to visible light, enabling the device to produce images of materials; the other produces images showing the polarization state of the terahertz waves.

The new “camera” consists of several layers, made with standard manufacturing techniques like those used for microchips. An array of nanoscale parallel lines of gold, separated by narrow slits, lies on the substrate; above that is a layer of the light-emitting quantum dot material; and above that is a CMOS chip used to form an image. The polarization detector, called a polarimeter, uses a similar structure, but with nanoscale ring-shaped slits, which allows it to detect the polarization of the incoming beams.

The photons of terahertz radiation have extremely low energy, Nelson explains, which makes them hard to detect. “So, what this device is doing is converting that little tiny photon energy into something visible that’s easy to detect with a regular camera,” he says. In the team’s experiments, the device was able to detect terahertz pulses at low intensity levels that surpassed the capability of today’s large and expensive systems.

The researchers demonstrated the capabilities of the detector by taking terahertz-illuminated pictures of some of the structures used in their devices, such as the nano-spaced gold lines and the ring-shaped slits used for the polarized detector, proving the sensitivity and resolution of the system.

Developing a practical terahertz camera requires a component that produces terahertz waves to illuminate a subject, and another that detects them. On the latter point, current terahertz detectors are either very slow, because they rely on detecting heat generated by the waves striking a material, and heat propagates slowly, or they use photodetectors that are relatively fast, but have very low sensitivity. In addition, until now, most approaches have required a whole array of terahertz detectors, each producing one pixel of the image. “Each one is quite expensive,” Shi says, so “once they start to make a camera, the cost of the detectors starts to scale up really, really quickly.”

While the researchers say they have cracked the terahertz pulse detection problem with their new work, the lack of good sources remains — and is being worked on by many research groups around the world. The terahertz source used in the new study is a large and cumbersome array of lasers and optical devices that cannot easily be scaled to practical applications, Nelson says, but new sources based microelectronic techniques are well under development.

“I think that’s really the rate-limiting step: Can you make the [terahertz] signals in a facile way that isn’t expensive?” he says. “But there’s no question that’s coming.”

Sang-Hyun Oh, a co-author of the paper and a McKnight Professor of Electrical and Computer Engineering at the University of Minnesota, adds that while present versions of terahertz cameras cost tens of thousands of dollars, the inexpensive nature of CMOS cameras used for this system makes it “a big step forward toward building a practical terahertz camera.” The potential for commercialization led Samsung, which makes CMOS camera chips and quantum dot devices, to collaborate on this research.

Traditional detectors for such wavelengths operate at liquid helium temperatures (-452 degrees Fahrenheit), Nelson says, which is necessary to pick out the extremely low energy of the terahertz photons from background noise. The fact that this new device can detect and produce images of these wavelengths with a conventional visible-light camera at room temperature has been unexpected to those working in the terahertz field. “People are like, ‘What?’ It’s kind of unheard of, and people get very surprised,” says Oh.

There are many avenues for further improving the sensitivity of the new camera, the researchers say, including further miniaturization of the components and ways of protecting the quantum dots. Even at the present detection levels, the device could have some potential applications, they say.

In terms of commercialization potential for the new device, Nelson says that quantum dots are now inexpensive and readily available, currently being used in consumer products such as television screens. The actual fabrication of the camera devices is more complex, he says, but is also based on existing microelectronics technology. In fact, unlike existing terahertz detectors, the entire terahertz camera chip can be manufactured using today’s standard microchip production systems, meaning that ultimately mass production of the devices should be possible and relatively inexpensive.

Already, even though the camera system is still far from commercialization, researchers at MIT have been using the new lab device when they need a quick way to detect terahertz radiation. “We don’t own one of those expensive cameras,” Nelson says, “but we have lots of these little devices. People will just stick one of these in the beam and look by eye at the visible light emission so they know when the terahertz beam is on. … People found it really handy.”

While terahertz waves could in principle be used to detect some astrophysical phenomena, those sources would be extremely weak and the new device is not able to capture such weak signals, Nelson says, although the team is working on improving its sensitivity. “The next generation lies in making everything smaller, so it will be much more sensitive,” he says.

The research team included Daehan Yoo at the University of Minnesota; Ferran Vidal-Codina, Ngoc-Cuong Nguyen, Hendrik Utzat, Jinchi Han, Vladimir Bulović, Moungi Bawendi, and Jaime Peraire at MIT; Chan-Wook Baik and Kyung-Sang Cho at Samsung Advanced Institute of Technology; and Aaron Lindenberg at Stanford University. The work was supported by the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies, the Samsung Global Research Outreach Program, and the Center for Energy Efficient Research Science.

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Professor Emeritus Louis Braida, speech and hearing scientist and hearing aid innovator, dies at 79

Louis Braida, the Henry Ellis Warren (1894) Professor Emeritus in the MIT Department of Electrical Engineering and Computer Science (EECS), died Sept. 2. He was 79.

Braida was a principal researcher in the Research Laboratory of Electronics, and a faculty member in the Harvard-MIT Program in Health Sciences and Technology (HST), which is housed in the Institute for Medical Engineering and Science (IMES) at MIT.

Born in the Bronx to Louis Braida and Elvina Tonelli Braida, Braida received a BEE from The Cooper Union in 1964, and an SM and PhD in electrical engineering from MIT in 1965 and 1969, respectively. During the course of his career at MIT, he was for many years the director of the Speech and Hearing Sciences training program within HST.

Braida was internationally known for his research in the areas of intensity perception, the characterization of hearing impairments, and aids for the deaf. Using modern communication theory and computational techniques, he worked to develop improved hearing aids for people suffering from sensorineural hearing impairments, and cochlear implants for the deaf, addressing many of the field’s knottiest problems in the pursuit of improved performance.

His work strongly enhanced the research community’s analytical understanding of both the benefits and limitations of compression amplification in hearing aids. Additionally, Braida sought to develop tactile aids for people who are profoundly deaf or deaf-blind, serving as a substitute for hearing in the reception of speech and environmental sounds.

“Lou Braida was, in many respects, the father of speech and hearing sciences within HST,” says Collin Stultz, Nina T. and Robert H. Rubin Professor in Medical Engineering and Science, associate director of IMES, and co-director of HST. “His contributions to the field will endure in perpetuity. He was a scholar, a cherished mentor, and a dedicated educator.”

Charlotte Reed, a principal investigator and senior research scientist in the Research Laboratory of Electronics and longtime friend and colleague of Braida, notes that “Lou applied a rigorous quantitative approach to the study of a wide range of topics in speech and hearing science. Among his lasting contributions to the field are his comprehensive modeling work on the auditory perception of intensity and loudness and on the multimodal perception of speech.”

Beyond Braida’s contributions to the world of auditory science, he was known throughout EECS for his community-minded and collegial approach to work. Taking time from his intense research schedule, he volunteered to mentor new faculty members and orient them to MIT’s largest department. Elazer R. Edelman, Edward J. Poitras Professor in Medical Engineering and Science and the director of IMES, was one of the many influenced by Braida: “Lou was the consummate educator and mentor, a citizen of MIT and a dedicated member of HST whose engineering and programmatic innovations made life better for all in our community and the world at large.”

Jae Lim, professor post-tenure of electrical engineering, remembers his friend as a kindly influence on all who entered his sphere. “Lou influenced the lives of many students at MIT. He supervised my bachelor’s and master’s theses. I learnt from him what research is and how exciting and satisfying research can be. As a floor tutor of Burton-Conner House, he helped many students, including me, not only with academic issues, but personal matters. He will be remembered and missed by many whose lives he touched.”

Braida’s devotion to his community was recognized in 2001, when he was awarded the Thomas A. McMahon Mentoring Award by HST. His friend Charlotte Reed aptly sums up his legacy of care, saying, “Lou will be remembered by his many students and colleagues as an intellectual force who had an enormous impact on our personal and professional growth, and he will be greatly missed.”

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Ocean microbes get their diet through a surprising mix of sources, study finds

One of the smallest and mightiest organisms on the planet is a plant-like bacterium known to marine biologists as Prochlorococcus. The green-tinted microbe measures less than a micron across, and its populations suffuse through the upper layers of the ocean, where a single teaspoon of seawater can hold millions of the tiny organisms.

Prochlorococcus grows through photosynthesis, using sunlight to convert the atmosphere’s carbon dioxide into organic carbon molecules. The microbe is responsible for 5 percent of the world’s photosynthesizing activity, and scientists have assumed that photosynthesis is the microbe’s go-to strategy for acquiring the carbon it needs to grow.

But a new MIT study in Nature Microbiology today has found that Prochlorococcus relies on another carbon-feeding strategy, more than previously thought.

Organisms that use a mix of strategies to provide carbon are known as mixotrophs. Most marine plankton are mixotrophs. And while Prochlorococcus is known to occasionally dabble in mixotrophy, scientists have assumed the microbe primarily lives a phototrophic lifestyle.

The new MIT study shows that in fact, Prochlorococcus may be more of a mixotroph than it lets on. The microbe may get as much as one-third of its carbon through a second strategy: consuming the dissolved remains of other dead microbes.

The new estimate may have implications for climate models, as the microbe is a significant force in capturing and “fixing” carbon in the Earth’s atmosphere and ocean.

“If we wish to predict what will happen to carbon fixation in a different climate, or predict where Prochlorococcus will or will not live in the future, we probably won’t get it right if we’re missing a process that accounts for one-third of the population’s carbon supply,” says Mick Follows, a professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), and its Department of Civil and Environmental Engineering.

The study’s co-authors include first author and MIT postdoc Zhen Wu, along with collaborators from the University of Haifa, the Leibniz-Institute for Baltic Sea Research, the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, and Potsdam University.

Persistent plankton

Since Prochlorococcus was first discovered in the Sargasso Sea in 1986, by MIT Institute Professor Sallie “Penny” Chisholm and others, the microbe has been observed throughout the world’s oceans, inhabiting the upper sunlit layers ranging from the surface down to about 160 meters. Within this range, light levels vary, and the microbe has evolved a number of ways to photosynthesize carbon in even low-lit regions.

The organism has also evolved ways to consume organic compounds including glucose and certain amino acids, which could help the microbe survive for limited periods of time in dark ocean regions. But surviving on organic compounds alone is a bit like only eating junk food, and there is evidence that Prochlorococcus will die after a week in regions where photosynthesis is not an option.

And yet, researchers including Daniel Sher of the University of Haifa, who is a co-author of the new study, have observed healthy populations of Prochlorococcus that persist deep in the sunlit zone, where the light intensity should be too low to maintain a population. This suggests that the microbes must be switching to a non-photosynthesizing, mixotrophic lifestyle in order to consume other organic sources of carbon.

“It seems that at least some Prochlorococcus are using existing organic carbon in a mixotrophic way,” Follows says. “That stimulated the question: How much?”

What light cannot explain

In their new paper, Follows, Wu, Sher, and their colleagues looked to quantify the amount of carbon that Prochlorococcus is consuming through processes other than photosynthesis.

The team looked first to measurements taken by Sher’s team, which previously took ocean samples at various depths in the Mediterranean Sea and measured the concentration of phytoplankton, including Prochlorococcus, along with the associated intensity of light and the concentration of nitrogen — an essential nutrient that is richly available in deeper layers of the ocean and that plankton can assimilate to make proteins.

Wu and Follows used this data, and similar information from the Pacific Ocean, along with previous work from Chisholm’s lab, which established the rate of photosynthesis that Prochlorococcus could carry out in a given intensity of light.

“We converted that light intensity profile into a potential growth rate — how fast the population of Prochlorococcus could grow if it was acquiring all it’s carbon by photosynthesis, and light is the limiting factor,” Follows explains.

The team then compared this calculated rate to growth rates that were previously observed in the Pacific Ocean by several other research teams.

“This data showed that, below a certain depth, there’s a lot of growth happening that photosynthesis simply cannot explain,” Follows says. “Some other process must be at work to make up the difference in carbon supply.”

The researchers inferred that, in deeper, darker regions of the ocean, Prochlorococcus populations are able to survive and thrive by resorting to mixotrophy, including consuming organic carbon from detritus. Specifically, the microbe may be carrying out osmotrophy — a process by which an organism passively absorbs organic carbon molecules via osmosis.

Judging by how fast the microbe is estimated to be growing below the sunlit zone, the team calculates that Prochlorococcus obtains up to one-third of its carbon diet through mixotrophic strategies.

“It’s kind of like going from a specialist to a generalist lifestyle,” Follows says. “If I only eat pizza, then if I’m 20 miles from a pizza place, I’m in trouble, whereas if I eat burgers as well, I could go to the nearby McDonald’s. People had thought of Prochlorococcus as a specialist, where they do this one thing (photosynthesis) really well. But it turns out they may have more of a generalist lifestyle than we previously thought.”

Chisholm, who has both literally and figuratively written the book on Prochlorococcus, says the group’s findings “expand the range of conditions under which their populations can not only survive, but also thrive. This study changes the way we think about the role of Prochlorococcus in the microbial food web.”

This research was supported, in part, by the Israel Science Foundation, the U.S. National Science Foundation, and the Simons Foundation.

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