MIT News

Evaluating a new way to open clogged arteries

Tue, 21 May 2013 04:00:00 +0000

Over the past few decades, scientists have developed many devices that can reopen clogged arteries, including angioplasty balloons and metallic stents. While generally effective, each of these treatments has drawbacks, including the risk of side effects.

A new study from MIT analyzes the potential usefulness of a new treatment that combines the benefits of angioplasty balloons and drug-releasing stents, but may pose fewer risks. With this new approach, a balloon is inflated in the artery for only a brief period, during which it releases a drug that prevents cells from accumulating and clogging the arteries over time.

While approved for limited use in Europe, these drug-coated balloons are still in development in the United States and have not received FDA approval. The MIT study, which models the behavior of the balloons, should help scientists optimize their performance and aid regulators in evaluating their effectiveness and safety.

“Until now, people who evaluate such technology could not distinguish hype from promise,” says Elazer Edelman, the Thomas D. and Virginia W. Cabot Professor of Health Sciences and Technology and senior author of the paper describing the study, which appeared online recently in the journal Circulation.

Lead author of the paper is Vijaya Kolachalama, a former MIT postdoc who is now a principal member of the technical staff at the Charles Stark Draper Laboratory.

Evolution of technology

Until the late 1970s, the standard treatment for patients with blocked arteries near the heart was bypass surgery. Doctors then turned to the much less invasive process of reopening arteries with angioplasty balloons. Angioplasty quickly became the standard treatment for narrowed arteries, but it is not always a long-term solution because the arteries can eventually collapse again.

To prevent that, scientists developed stents — metal, cage-like structures that can hold an artery open indefinitely. However, these stents have problems of their own: When implanted, they provoke an immune response that can cause cells to accumulate near the stent and clog the artery again.

In 2003, the FDA approved the first drug-eluting stent for use in the United States, which releases drugs that prevent cells from clumping in the arteries. Drug-eluting stents are now the primary choice for treating blocked arteries, but they also have side effects: The drugs can cause blood to clot over time, which has led to death in some patients. Patients who receive these stents now need to take other medications, such as aspirin and Plavix, to counteract blood clotting.

Edelman’s lab is investigating a possible alternative to the current treatments: drug-coated balloons. “We’re trying to understand how and when this therapy could work and identify the conditions in which it may not,” Kolachalama says. “It has its merits; it has some disadvantages.”

Modeling drug release

The drug-coated balloons are delivered by a catheter and inflated at the narrowed artery for about 30 seconds, sometimes longer. During that time, the balloon coating, containing a drug such as Zotarolimus, is released from the balloon. The properties of the coating allow the drug to be absorbed in the body’s tissues. Once the drug is released, the balloon is removed.

In their new study, Kolachalama, Edelman and colleagues set out to rigorously characterize the properties of the drug-coated balloons. After performing experiments in tissue grown in the lab and in pigs, they developed a computer model that explains the dynamics of drug release and distribution. They found that factors such as the size of the balloon, the duration of delivery time, and the composition of the drug coating all influence how long the drug stays at the injury site and how effectively it clears the arteries.

One significant finding is that when the drug is released, some of it sticks to the lining of the blood vessels. Over time, that drug is slowly released back into the tissue, which explains why the drug’s effects last much longer than the initial 30-second release period.

“This is the first time we can explain the reasons why drug-coated balloons can work,” Kolachalama says. “The study also offers areas where people can consider thinking about optimizing drug transfer and delivery.”

Most previous efforts to develop drug-coated balloons have focused on a different drug, Paclitaxel. “For the first time, this study establishes a basis for drug-coated balloons based on Zotarolimus to work,” says Juan Granada, executive director of the Cardiovascular Research Foundation Skirball Research Center, who was not part of the research team. “It explains in a very elegant way the important implications for technology development based on these findings.”

In future studies, Edelman, Kolachalama and colleagues plan to further examine how blood flow affects drug delivery. They also plan to study a variety of different drugs and drug coating compositions, as well as how the balloons behave in different types of arteries.

The National Institutes of Health and Abbott Vascular funded the research.

Planes, trains and automobiles: faster, stronger, lighter

Mon, 20 May 2013 04:00:00 +0000

These days, aerospace engineering is all about the light stuff: building airplanes with lighter wings, fuselage and landing gear in an effort to reduce fuel costs.

Advanced carbon-fiber composites have been used in recent years to lighten planes’ loads. These materials can match aluminum and titanium in strength but at a fraction of the weight, and can be found in aircraft like the Boeing 787 and Airbus A380, reducing such jets’ weight by 20 percent.

For the next generation of commercial jets, researchers are looking to even stronger and lighter materials, such as composites made with carbon fibers coated with carbon nanotubes — tiny tubes of crystalline carbon. When arranged in certain configurations, nanotubes can be hundreds of times stronger than steel, but only one-sixth the weight, making such composites attractive for use in airplanes, as well as cars, trains, spacecraft and satellites.

But a significant hurdle to achieving such composites lies at the nanoscale: Scientists who have tried growing carbon nanotubes on carbon fibers have found that doing so significantly degrades the underlying fibers, stripping them of their inherent strength.

Postdoc Stephen Steiner (right) and graduate student Richard Li are part of the research team.Photo: David Castro-Olmedo/MIT

Now a team from MIT has identified the root cause of this fiber degradation, and devised techniques to preserve the fibers’ strength. Applying their discoveries, the researchers coated carbon fibers with nanotubes without causing fiber degradation, making the fibers twice as strong as previous nanotube-coated fibers — paving the way for carbon-fiber composites that are not only stronger, but also more electrically conductive. The researchers say the techniques can easily be integrated into current fiber-manufacturing processes.

“Up until now, people were basically improving one part of the material but degrading the underlying fiber, and it was a trade-off, you couldn’t get everything you wanted,” says Brian Wardle, an associate professor of aeronautics and astronautics at MIT. “With this contribution, you can now get everything you want.”

A paper detailing the results by Wardle and his colleagues is published in the journal ACS Applied Materials and Interfaces. Co-authors are postdoc Stephen Steiner, who contributed to the research as a graduate student, and Richard Li, a graduate student who was an undergraduate in Wardle’s lab.

Getting to the nitty-gritty of fiber degradation

To understand how carbon fibers are manufactured, the group visited carbon-fiber production plants in Japan, Germany and Tennessee. One aspect of the fiber-manufacturing process stood out: During manufacturing, fibers are stretched to near their breaking point as they are heated to high temperatures. In contrast, researchers who have tried to grow nanotubes on carbon fibers in the lab typically do not use tension in their fabrication processes.

To replicate the manufacturing process they witnessed, Li and Steiner engineered a small-scale apparatus made of graphite. The researchers strung individual carbon fibers — each 10 times thinner than a human hair — across the device, much like the strings of a guitar, and hung tiny weights on either end of each fiber, pulling them taut. The group then grew carbon nanotubes on the fibers, first covering the fibers with a special set of coatings, and then heating the fibers in a furnace. They then used chemical vapor deposition to grow a fuzzy layer of nanotubes along each fiber.

To get nanotubes to grow, the fiber typically needs to be coated with a metal catalyst like iron, but researchers have hypothesized that such catalysts might also be the source of fiber degradation. In their experiments, however, Steiner and Li found that the catalyst only contributed to about 15 percent of the fiber’s degradation.

“When we got to the nitty-gritty of it, we found that the metal catalyst, the perceived culprit, turned out to be more of an accomplice,” Steiner says. “We could see it did a little damage, but it wasn’t the thing really killing everything.”

Instead, the group found, after further experiments, that the majority of fiber degradation was due to a previously unidentified mechanochemical phenomenon arising from a lack of tension when carbon fibers are heated above a certain temperature.

Hair conditioner in reverse

After identifying the causes of fiber degradation, the researchers came up with two practical strategies for growing nanotubes on carbon fiber that preserve fiber strength.

First, the team coated the carbon fiber with a layer of alumina ceramic to “disguise” it, enabling the iron catalyst to stick to the fiber without degrading it. The solution, however, came with another challenge: the layer of alumina kept flaking off.

To keep the alumina in place, the team developed a polymer coating called K-PSMA — which, as Steiner describes it, works like hair conditioner in reverse. Hair conditioners have two seemingly opposite chemical features: a water-absorbent component that allows the conditioner to stick to hair, and a waterproof component that keeps hair from getting frizzy. Likewise, K-PSMA has hydrophilic and hydrophobic components, but its waterproof feature sticks to the carbon fiber, while the water-absorbent component attracts the alumina and the metal catalyst.

In their experiments, the researchers found the coating allowed the alumina and metal catalyst to stick, without having to add other processes, like pre-etching the fiber surface. The team placed the coated fibers under tension, and successfully grew nanotubes without damaging the fiber.

For the group’s second strategy, Steiner observed that it may be possible to eliminate the need for tension by reducing the temperature of nanotube growth. Using a recently discovered nanotube-growth process together with K-PSMA, the team demonstrated it is possible to grow nanotubes at a much lower temperature — nearly 300 degrees Celsius cooler than is typically used — avoiding damage to the underlying fiber,.

“This process reduces not only the amount of energy and volume of gas required, but the amount of extraneous substances you have to put on the fiber,” Steiner says. “It’s actually pretty simple and cost-effective.”

Milo Shaffer, a professor of materials chemistry at Imperial College, London, says the group’s carbon-fiber techniques may be useful in designing composites for use in electrodes and air filters. A next step toward this goal, he says, is to make sure the fiber’s various layers and coatings stay in place.

“This result indicates an important factor to be incorporated in future ‘hairy carbon fiber’ developments,” says Shaffer, who did not contribute to the research. “The effect of the various coating combinations on [nanotube] attachment, and the eventual — and critical — fiber-matrix adhesion in composites, remains to be explored.”

The researchers have filed a patent for the two strategies, and envision advanced fiber composites incorporating their techniques for a whole range of applications.

“There are not a lot of people innovating materials chemistry for advanced aerospace structural applications,” Steiner says. “I think this is particularly exciting, and has a very real possibility to make a large-scale impact on the environment, and on the performance of aerospace vehicles.”

Making quantum encryption practical

Mon, 20 May 2013 16:30:31 +0000

One of the many promising applications of quantum mechanics in the information sciences is quantum key distribution (QKD), in which the counterintuitive behavior of quantum particles guarantees that no one can eavesdrop on a private exchange of data without detection.

As its name implies, QKD is intended for the distribution of cryptographic keys that can be used for ordinary, nonquantum cryptography. That’s because it requires the transmission of a huge number of bits for each one that’s successfully received. That kind of inefficiency is tolerable for key distribution, but not for general-purpose communication.

Also, because QKD depends on the properties of individual light particles — photons — it’s very vulnerable to signal loss, which is inevitable over large enough distances. Although QKD systems have been built — some commercially — they generally work across distances of only 100 miles or so.

In a series of recent papers, researchers in the Optical and Quantum Communications Group at MIT’s Research Laboratory of Electronics described a new quantum communication protocol that could solve both of these problems. It’s much more resilient to signal loss than QKD, and it sends only one bit for every one received.

In the latest issue of Physical Review Letters, they describe the first experimental implementation of their system, which bore out all their theoretical predictions.

At present, the protocol does have one major caveat: It’s secure only against so-called passive eavesdroppers, who simply siphon light from an optical transmission, and not against active eavesdroppers, who maliciously inject their own light into a communication channel. Security against passive eavesdropping is probably adequate for some optical communication systems, but if the researchers can figure out how to thwart active eavesdroppers, too, their protocol could be used to secure optical data transmission over long distances.

Cascading correlations

Like all quantum information schemes, the new protocol exploits the central mystery of quantum physics: the ability of tiny particles of matter to inhabit mutually exclusive states at the same time. Electrons, for instance, have a property called spin, which describes how they act in a magnetic field. Spin can be either up or down, but it can also be in a strange quantum state known as superposition, in which it’s up and down simultaneously.

According to Jeffrey Shapiro, the Julius A. Stratton Professor of Electrical Engineering and one of the co-directors of the Optical and Quantum Communications Group, quantum particles are capable of a greater degree of correlation than objects described by classical physics. A coin, for instance, can be either face-up or face-down. If you glue a second coin to it, face-to-face, the states of the two coins are correlated: If one is up, the other is down, and vice versa.

In the same way, if two electrons are orbiting the nucleus of an atom at the same distance, their spins are correlated: If one is up, the other must be down. But there’s a third possibility: If one is up and down at the same time, so is the other.

This kind of mutual dependency, even in particles separated by great distances, is known as entanglement. But entanglement is very fragile: It begins to break down as soon as particles start interacting with their immediate environments. The key to the new protocol, Shapiro explains, is that even if the entanglement between two light beams breaks down, and their degree of correlation falls back within classical limits, it can still remain much higher than it would be if the beams had a merely classical correlation to begin with.

Bring the noise

Following cryptographic convention, the RLE researchers describe their protocol in terms of a secure communication between Alice and Bob, with an eavesdropper, named Eve, trying to listen in. Alice creates two entangled light beams and sends one of them to Bob, keeping the other one circulating locally.

“In classical physics, there’s a maximum amount of correlation you can get between two events,” Shapiro says. In the new protocol, however, the entangled beams “have a correlation that exceeds — by orders of magnitude — the classical limit.”

As one of those beams travels toward Bob, interactions with the environment begin to break the entanglement, introducing degradations of signal quality that engineers call “noise.” Bob then adds information to the beam, amplifies it — which adds much more noise — and sends it back. Alice uses the beam she kept circulating locally to decode Bob’s transmission.

Eve, on the other hand, extracts some of the signal that Alice sends Bob and uses that to decode Bob’s transmission. Because Bob’s transmission is so noisy, its correlation with Eve’s sample signal is much lower than it is with the signal Alice kept.

“My experiment can show for the communication between Alice and Bob, if Bob sends one megabit of information, about one bit gets flipped,” says Zheshen Zhang, a postdoc at RLE and first author on the new paper. “For the eavesdropper, about half of the bits get flipped.”

“The first distinction between this and what other people have done in the past is that Jeff’s protocol is a direct secure-communication protocol,” says Saikat Guha, a senior scientist at Raytheon subsidiary BBN Technologies who works on quantum optical communications and imaging. “This is not a key distribution protocol.”

As for whether the system will work over long distances, “we don’t have all the answers yet, but this does seem to have better promise than some of the standard QKD protocols,” Guha says. “In the standard QKD protocols, one big requirement is to have quantum repeaters, which are devices that are not yet available. People are working on it, but there aren’t any quantum repeaters. So you can’t do standard QKD over standard fiber for more than a couple hundred kilometers at the most.”

Guha observes that the RLE researchers’ protocol isn’t secure against active eavesdropping, but says, “I think it’s very promising that it will be adapted to active eavesdropping. It’s just that the analysis hasn’t been done.”

“We’re working on the theory for active eavesdropping,” Shapiro adds.

Complex brain function depends on flexibility

Sun, 19 May 2013 17:00:00 +0000

Over the past few decades, neuroscientists have made much progress in mapping the brain by deciphering the functions of individual neurons that perform very specific tasks, such as recognizing the location or color of an object.

However, there are many neurons, especially in brain regions that perform sophisticated functions such as thinking and planning, that don’t fit into this pattern. Instead of responding exclusively to one stimulus or task, these neurons react in different ways to a wide variety of things. MIT neuroscientist Earl Miller first noticed these unusual activity patterns about 20 years ago, while recording the electrical activity of neurons in animals that were trained to perform complex tasks.

“We started noticing early on that there are a whole bunch of neurons in the prefrontal cortex that can’t be classified in the traditional way of one message per neuron,” recalls Miller, the Picower Professor of Neuroscience at MIT and a member of MIT’s Picower Institute for Learning and Memory.

In a paper appearing in Nature on May 19, Miller and colleagues at Columbia University report that these neurons are essential for complex cognitive tasks, such as learning new behavior. The Columbia team, led by the study’s senior author, Stefano Fusi, developed a computer model showing that without these neurons, the brain can learn only a handful of behavioral tasks.

“You need a significant proportion of these neurons,” says Fusi, an associate professor of neuroscience at Columbia. “That gives the brain a huge computational advantage.”

Lead author of the paper is Mattia Rigotti, a former grad student in Fusi’s lab.

Multitasking neurons

Miller and other neuroscientists who first identified this neuronal activity observed that while the patterns were difficult to predict, they were not random. “In the same context, the neurons always behave the same way. It’s just that they may convey one message in one task, and a totally different message in another task,” Miller says.

For example, a neuron might distinguish between colors during one task, but issue a motor command under different conditions.

Miller and colleagues proposed that this type of neuronal flexibility is key to cognitive flexibility, including the brain’s ability to learn so many new things on the fly. “You have a bunch of neurons that can be recruited for a whole bunch of different things, and what they do just changes depending on the task demands,” he says.

At first, that theory encountered resistance “because it runs against the traditional idea that you can figure out the clockwork of the brain by figuring out the one thing each neuron does,” Miller says.

For the new Nature study, Fusi and colleagues at Columbia created a computer model to determine more precisely what role these flexible neurons play in cognition, using experimental data gathered by Miller and his former grad student, Melissa Warden. That data came from one of the most complex tasks that Miller has ever trained a monkey to perform: The animals looked at a sequence of two pictures and had to remember the pictures and the order in which they appeared.

During this task, the flexible neurons, known as “mixed selectivity neurons,” exhibited a great deal of nonlinear activity — meaning that their responses to a combination of factors cannot be predicted based on their response to each individual factor (such as one image).

Expanding capacity

Fusi’s computer model revealed that these mixed selectivity neurons are critical to building a brain that can perform many complex tasks. When the computer model includes only neurons that perform one function, the brain can only learn very simple tasks. However, when the flexible neurons are added to the model, “everything becomes so much easier and you can create a neural system that can perform very complex tasks,” Fusi says.

The flexible neurons also greatly expand the brain’s capacity to perform tasks. In the computer model, neural networks without mixed selectivity neurons could learn about 100 tasks before running out of capacity. That capacity greatly expanded to tens of millions of tasks as mixed selectivity neurons were added to the model. When mixed selectivity neurons reached about 30 percent of the total, the network’s capacity became “virtually unlimited,” Miller says — just like a human brain.

Mixed selectivity neurons are especially dominant in the prefrontal cortex, where most thought, learning and planning takes place. This study demonstrates how these mixed selectivity neurons greatly increase the number of tasks that this kind of neural network can perform, says John Duncan, a professor of neuroscience at Cambridge University.

“Especially for higher-order regions, the data that have often been taken as a complicating nuisance may be critical in allowing the system actually to work,” says Duncan, who was not part of the research team.

Miller is now trying to figure out how the brain sorts through all of this activity to create coherent messages. There is some evidence suggesting that these neurons communicate with the correct targets by synchronizing their activity with oscillations of a particular brainwave frequency.

“The idea is that neurons can send different messages to different targets by virtue of which other neurons they are synchronized with,” Miller says. “It provides a way of essentially opening up these special channels of communications so the preferred message gets to the preferred neurons and doesn’t go to neurons that don’t need to hear it.”

The research was funded by the Gatsby Foundation, the Swartz Foundation and the Kavli Foundation.

A caring mind

Fri, 17 May 2013 04:00:00 +0000

At a health clinic in Guatemala, Paula Trepman watched as a visiting physician from the United States showed local workers how to properly administer a labor-inducing drug to pregnant women — a process that, if done at the wrong time, could have fatal consequences.

It was the summer after her sophomore year at MIT, and Trepman — now a senior — was helping to lead a global-health program for high school students. Yet the trip also solidified her own commitment to health care: “I saw firsthand how not having access to those services could have life or death consequences,” Trepman says.

Paula TrepmanPhoto: Allegra Boverman

A biological engineering major from Mercer Island, Wash., Trepman has conducted research on red blood cell development; traveled to Guatemala, Mexico and Kenya to work on public-service projects; and is currently developing a test for dengue fever that could be used in even the most resource-poor settings. In her free time, Trepman loves to run, do yoga, and engage in ballet, jazz and lyrical dance.

Trepman’s interest in medicine started at a young age, when she would tag along to the hospital with her mother, a physician who treats leukemia patients. Trepman saw the impact her mother had on patients’ lives, and she heard stories from her grandparents about the tragedies of inadequate medical care.

“Two of my grandparents were Holocaust survivors, and one of them almost died from typhoid because she did not have access to health care, nutritious food and water,” Trepman recounts. “Their history fuels my passion to do whatever I can to make sure that other people have access to those basic services.”

What’s in your blood?

In many parts of the world, health-care technologies are too costly or too difficult to use without extensive training. “In impoverished and remote areas, there may not be access to culturing facilities or other laboratory services that are needed to diagnose patients,” Trepman says.

Along with other researchers in the lab of Lee Gehrke, a professor of health sciences and technology at MIT, Trepman is working on a solution: a single strip of paper that, with a drop of a patient’s blood, would visibly signal whether or not the patient is ill.

“This test strip can be used to make a diagnosis by individuals with minimal training, so this technology can improve access to health care by empowering people at the local level,” Trepman says. These on-the-spot diagnosis tools are known as “point-of-care diagnostics.”

Trepman’s project targets dengue fever, a painful and debilitating disease spread by mosquitoes and prevalent in tropical areas. Early diagnosis could mean better care for patients and recognition of the epidemic outbreaks, potentially preventing further spread of the disease.

Using different antibodies — Y-shaped proteins that our bodies’ immune systems use to “tag” viruses or bacteria as foreign — and gold nanoparticles that appear red when dispersed, Trepman and the other researchers have created a strip that will show two red lines if a patient has dengue and one line otherwise.

It’s an inexpensive and simple technology. But dengue fever exists as four types, and it’s important to find out which kind a patient has. “When you’re co-infected with two or more different serotypes, you have a higher likelihood of getting hemorrhagic fever,” Trepman explains.

Currently, she’s working on a strip that could differentiate among the four types of dengue. “Ideally, the strip will show five different catch lines — a control line and a line to detect each type of dengue virus,” Trepman says.

Prior to her work in Gehrke’s lab, Trepman did three years of research on red blood cell development at the Whitehead Institute with professor of biology and bioengineering Harvey Lodish. She has drawn on her experiences there in designing the paper-strip test for dengue. “As a biological engineer, you need to understand basic biology to be able to then apply it to projects such as point-of-care diagnostics,” Trepman says.

Sowing change

Life-changing innovations don’t always come from labs, though. With MIT’s Global Poverty Initiative (GPI) during her sophomore and junior years, Trepman led two trips to rural Mexico, where students piloted a greenhouse project to generate a steady supply of fresh produce for surrounding communities.

Seven months of the year are too cold to grow crops, and many of the soil’s nutrients have been depleted from years of growing corn, Trepman explains. “There is poor access to fruits and vegetables in this area of central Mexico. Most of the production is done in the northeast, and there is limited transportation in and out of those tiny communities,” she says. “They might have enough calories in their diet, but they are not necessarily getting the nutrients they need,” Trepman adds.

The students met with community members, who formed a committee to take charge of the project. “Although we helped by providing the technical knowledge and the building plans, local community members led the construction and taught the students how to use the greenhouses,” Trepman says.

Trepman and the other students helped to construct 14 family greenhouses and two school-based greenhouses that local residents tended once the students returned to MIT. When GPI returned to check on the project, its members found a number of new greenhouses and increased consumption of fruits and vegetables. “People who had extra vegetables were sharing them with their family members or selling them on the side, too,” Trepman recalls. “The project allowed people to take control of their own lives.”

The many faces of global health

Besides the strip to diagnose dengue and the greenhouse project, Trepman has worked on medical-record technology in Kenya and, last summer, at the World Bank in Washington, D.C. Her experiences have convinced her that improvements are necessary on many different levels: basic research, technologies and policies.

In the future, Trepman plans to focus on maternal and infant care and wants to engineer point-of-care diagnostics for expectant mothers. “When women become pregnant, they are at a higher risk for contracting many illnesses,” Trepman says. “For example, eclampsia is a disease associated with seizures during pregnancy and can be life-threatening.” She hopes to develop a multiplex test for pregnant women that would include a number of different tests in a single device.

In the face of the world’s problems, it can be hard to stay optimistic, Trepman says. But as she sees it, “The first step is to understand what is not working well, and then we can focus on developing a better solution.”

Using literature to understand violence against blacks

Fri, 17 May 2013 04:00:02 +0000

The grim history of lynching in the United States may be over, but it has been preserved through photographs, memoirs, novels and poetry.

To Sandy Alexandre, an associate professor of literature at MIT, those images and words help make clear, in retrospect, how closely lynching was related to the issue of property, in the form of bodies, possessions and land.

This is not the first thing usually associated with lynching; as many scholars and commentators have detailed, lynch mobs were often triggered by the suspicion, whether true or not, of physical relations between black men and white women.

Now Alexandre’s first book, “The Properties of Violence,” published by the University Press of Mississippi, explores the territorial aspects of lynching — including its capacity to uproot blacks and dispossess them of property, while also denying them access to particular places.

“Racial violence is a way to demarcate space, and it’s a way to demarcate people,” Alexandre says. “Blacks who were aspiring to, and achieving, middle-class status were effectively reined in through lynching violence — this became a mechanism to make sure that blacks stayed ‘in their place.’ And that place, as far as whites were concerned at the time, was certainly not the middle class.”

In the book, Alexandre examines this issue, in part, by studying lynching as a theme in the works of some famous 20th-century writers. The prominent midcentury writer Richard Wright, for instance, had an uncle who was lynched after becoming a relatively prosperous saloonkeeper.

A close reading of Wright’s work, as Alexandre makes clear, reveals how the young black protagonist in many of his works exists “in a state of awareness about his geographical, social, and political limits.”

Or, as Alexandre puts it, lynching “served as a kind of ‘No Trespassing’ sign, a ‘Whites Only’ sign” establishing physical boundaries over whole territories, not just, say, buildings and restaurants.

Originally looking at nature

Alexandre says she originally intended to write a book about literary representations of the relationship between black Americans and nature, but found greater focus after studying the images most often associated with the history of lynching violence in the United States.

“What ended up impinging upon that pastoral relationship of blacks and nature was history, particularly the visuals of lynching,” Alexandre says. “That very horrifying history has made the connection between blacks and nature necessarily complicated.” Indeed, the photographic record of lynching, as Alexandre notes, almost invariably juxtaposes bucolic rural settings with graphic, disturbing images of murder.

To be sure, Alexandre believes, the intent to prevent sexual relations between races was clearly a major impetus for lynching; it just isn’t the only issue to consider.

“The pretext for this extralegal form of violence was this desire to preserve white womanhood as something owned by the dominant culture,” Alexandre notes. “White women were considered a form of property that had to be rescued from ostensible black rapists.”

But following the pioneering black journalist and antilynching advocate Ida B. Wells, whose career began in the late 19th century, Alexandre believes American literature makes clear that lynching also was a tool of social control in economic terms.

Beyond that, a public lynching often served to stake out the site of the lynching as white territory for generations after the murder itself occurred.

“Violence itself was made into an event,” Alexandre observes. “Families would bring their children to view these gruesome murders, rendering the space an inviting picnic venue for whites and an off-putting place of death for blacks. The historical heft, atmosphere, and visual evidence of lynching violence ultimately shape discourses surrounding possession and dispossession.”

In American literature, an awareness of lynching continues in contemporary times; one of the chapters in Alexandre’s book, on Toni Morrison’s lauded 1987 novel “Beloved,” examines how violence against women — who were also sometimes lynched — has often been overlooked, creating heavily gender-influenced discussions of the subject. (Alexandre is currently teaching a seminar on Morrison’s writing.)

Other scholars have praised “The Properties of Violence.” Donald E. Pease, a professor of English at Dartmouth College, calls it a “remarkable monograph,” and particularly praises the way Alexandre sheds light on the impacts, tangible or intangible, that lynchings had on blacks.

“Professor Alexandre has unmoored the history of lynching from the white-supremacist discourse to which it was anchored so as to open its accounting to multiple interpretive possibilities and return psychological and politically empowered agency to its victims,” Pease says.

Writing the book has also helped spur more ongoing research for Alexandre: She is now working on her second book, on the relationship between slavery and material possession among black Americans, in the period after slavery formally ended. Alexandre is analyzing the ethical dilemmas and decisions blacks face regarding their relationship to material things, as a consequence of their prior participation in capitalism as owned property.

Stacking 2-D materials produces surprising results

Thu, 16 May 2013 18:00:00 +0000

Graphene has dazzled scientists, ever since its discovery more than a decade ago, with its unequalled electronic properties, its strength and its light weight. But one long-sought goal has proved elusive: how to engineer into graphene a property called a band gap, which would be necessary to use the material to make transistors and other electronic devices.

Now, new findings by researchers at MIT are a major step toward making graphene with this coveted property. The work could also lead to revisions in some theoretical predictions in graphene physics.

From left: Prof. Ray Ashoori, postdocs Andrea Young and Ben Hunt, graduate student Javier Sanchez-Yamagishi, and Prof. Pablo Jarillo-Herrero. Photo: Jarillo-Herrero and Ashoori groups

The new technique involves placing a sheet of graphene — a carbon-based material whose structure is just one atom thick — on top of hexagonal boron nitride, another one-atom-thick material with similar properties. The resulting material shares graphene’s amazing ability to conduct electrons, while adding the band gap necessary to form transistors and other semiconductor devices.

The work is described in a paper in the journal Science co-authored by Pablo Jarillo-Herrero, the Mitsui Career Development Assistant Professor of Physics at MIT, Professor of Physics Ray Ashoori, and 10 others.

“By combining two materials,” Jarillo-Herrero says, “we created a hybrid material that has different properties than either of the two.”

Graphene is an extremely good conductor of electrons, while boron nitride is a good insulator, blocking the passage of electrons. “We made a high-quality semiconductor by putting them together,” Jarillo-Herrero explains. Semiconductors, which can switch between conducting and insulating states, are the basis for all modern electronics.

To make the hybrid material work, the researchers had to align, with near perfection, the atomic lattices of the two materials, which both consist of a series of hexagons. The size of the hexagons (known as the lattice constant) in the two materials is almost the same, but not quite: Those in boron nitride are 1.8 percent larger. So while it is possible to line the hexagons up almost perfectly in one place, over a larger area the pattern goes in and out of register.

At this point, the researchers say they must rely on chance to get the angular alignment for the desired electronic properties in the resulting stack. However, the alignment turns out to be correct about one time out of 15, they say.

“The qualities of the boron nitride bleed over into the graphene,” Ashoori says. But what’s most “spectacular,” he adds, is that the properties of the resulting semiconductor can be “tuned” by just slightly rotating one sheet relative to the other, allowing for a spectrum of materials with varied electronic characteristics.

Others have made graphene into a semiconductor by etching the sheets into narrow ribbons, Ashoori says, but such an approach substantially degrades graphene’s electrical properties. By contrast, the new method appears to produce no such degradation.

The band gap created so far in the material is smaller than that needed for practical electronic devices; finding ways of increasing it will require further work, the researchers say.

“If … a large band gap could be engineered, it could have applications in all of digital electronics,” Jarillo-Herrero says. But even at its present level, he adds, this approach could be applied to some optoelectronic applications, such as photodetectors.

The results “surprised us pleasantly,” Ashoori says, and will require some explanation by theorists. Because of the difference in lattice constants of the two materials, the researchers had predicted that the hybrid’s properties would vary from place to place. Instead, they found a constant, and unexpectedly large, band gap across the whole surface.

In addition, Jarillo-Herrero says, the magnitude of the change in electrical properties produced by putting the two materials together “is much larger than theory predicts.”

The MIT team also observed an interesting new physical phenomenon. When exposed to a magnetic field, the material exhibits fractal properties — known as a Hofstadter butterfly energy spectrum — that were described decades ago by theorists, but thought impossible in the real world. There is intense research in this area; two other research groups also report on these Hofstadter butterfly effects this week in the journal Nature.

Eva Andrei, a professor of physics at Rutgers University who was not involved in this work, says that until recently, “decades-old theoretical predictions of novel and surprising physical phenomena, expected to occur in 2-D electron systems [such as graphene], have lain dormant.” But the MIT team’s work clearly demonstrates some of these phenomena, she says.

“Perhaps most significant is their observation of a band gap in zero magnetic field,” she says. “The ability to induce a zero-field band gap in graphene may one day allow its use as a switch in transistor applications, providing a viable and inexpensive alternative to silicon electronics.”

The research included postdocs Ben Hunt and Andrea Young and graduate student Javier Sanchez-Yamagishi, as well as six other researchers from the University of Arizona, the National Institute for Materials Science in Tsukuba, Japan, and Tohoku University in Japan. The work was funded by the U.S. Department of Energy, the Gordon and Betty Moore Foundation and the National Science Foundation.

3dim wins MIT $100K Entrepreneurship Competition

Thu, 16 May 2013 21:18:34 +0000

On Wednesday night, 3dim earned the grand prize at this year’s MIT $100K Entrepreneurship Competition after successfully pitching its business plan to merge two of today’s most popular, and profitable, technological phenomena: gesture-recognition and smart devices.

The startup was one of eight finalists that pitched business plans to a capacity crowd in Kresge Auditorium. While only one team walked away with the $100,000 top prize, finalists received startup funds totaling $257,000.

A panel of entrepreneurs, venture capitalists, scientists and industry professionals chose 3dim based on the strength of the team’s technology, business plan and presentation.

3dim, founded by a team of MIT engineers, has patented 3-D gesture-recognition technology — such as what’s used in the Nintendo Wii and Microsoft Kinect — to be implemented into devices such as smartphones, tablets or Google Glass. This would allow users to interact with their devices through thin air, rather than having to touch a screen.

The need for power-hungry, specialized hardware has kept such technology from mobile devices — problems that 3dim has now rectified, co-founder Andrea Colaco, a PhD student at the MIT Media Lab, said during the winning pitch.

“What is the next interface [for mobile devices]? … The answer is gesture recognition,” Colaco said. “Every mobile-device manufacturer is scrambling to bring gesture-recognition into their devices. This is an immediate and unaddressed market.”

After the competition, Colaco, surrounded by elated teammates and well-wishers, said the victory felt “surreal.” “It took a lot of work,” she said. “Just a year ago, we were technologists at MIT with an idea. Now, we’re here.”

With the prize money, 3dim will go “full steam ahead,” Colaco said, further developing the technology for customers — namely, smart-device manufacturers — who have already expressed interest in the product.

But no one walked away empty-handed. Each of the eight finalists — out of a pool of 215 entrants this year — received $15,000 for winning its respective track: life sciences, products and services, mobile, web/IT, energy, the Segal Family Foundation’s emerging markets track, and two wildcard entries.

The contest also hosted several offshoots: a $10,000 Thomson Reuters Data Prize for the team with the most innovative data-centric business plan; the first-ever $10,000 Creative Arts Prize for the innovative use of art in a business plan; an AARP Prize for $10,000; and a $2,000 Audience Choice Award.

Since its debut in 1989, the competition has helped launch more than 160 companies, which have gone on to collectively raise $1.3 billion in venture capital, employ 4,600 people and build $16 billion in market capital.

Health, energy and infrastructure solutions

Other finalists’ innovations aim to prevent and diagnosis debilitating diseases, deliver clean energy and fix infrastructure issues.

Several teams — NoMos, QuikCatheter, SympSolutions and eyeMITRA — are developing health-care innovations. NoMos, winner of the Audience Choice Award, aims to stop the spread of mosquito-borne diseases, such as malaria, by distributing a natural, nontoxic, environmentally friendly extract that prevents mosquito-human contact.

QuikCatheter plans to manufacture modified microcatheters doctors could use to help improve patient outcomes in time-sensitive emergencies, such as stroke and arterial bleeding, and improve efficiency in a variety of non-urgent or outpatient procedures. SympSolutions is developing a cost-effective and noninvasive way to treat the carotid body — a small organ known to contribute to high blood pressure — in hypertensive patients who no longer respond to oral medications alone.

Finally, eyeMITRA is developing mobile technology that collects valuable information about a person’s well-being — such as eyesight complications associated with diabetes — via retina monitoring. “It may seem like science fiction, but this is MIT,” said eyeMITRA team member Everett Lawson, a postdoc in the MIT Media Lab.

Other teams developed infrastructure and clean-energy innovations. UPower, which won MIT’s Clean Energy Prize last week, is developing a nuclear generator for places off the power grid, such as U.S. Army bases in Afghanistan, that could replace diesel generators — reducing energy costs and, in theory, providing power for up to 12 years without a recharge.

Ant Intelligence aims to collect and interpret data from buildings and infrastructure — such as bridges, dams and excavation sites — and generate structural data to be used for remote monitoring and preventive maintenance, disaster management and big-data analytics, among other things.

Finally, C2Sense has several patents and published academic articles backing its technology: low-cost “sensors on a chip” that can be used for detecting and measuring a range of chemical substances in food, or for safety monitoring and environmental protection.

Three other teams — AugMI Labs, Kiwi and Mediuum — won the Data Prize, the AARP Prize and the Creative Arts Prize, respectively.

‘Am I making a difference?’

Keynote speaker Yoky Matsuoka SM ’95, PhD ’98 has extensive experience with life-altering technologies — from designing robotic limbs to working at Google to her current role as vice president of technology at an innovative thermostat company, Nest Labs.

Through all her endeavors, Matsuoka said she always sought to change the world — an ideal she wished to impart upon the audience. “One of the things that I like to go back and think about is this picture,” Matsuoka said, presenting a large photo of Earth. “Sometimes I ask, ‘Am I contributing to society?’ ‘Am I making a difference?’ As long as my answer is ‘yes,’ I’ll be fine.”

As a tennis player at MIT, Matsuoka sought to create a robotic “tennis buddy”: an advanced robot for players to practice against. This led to a detour into robotics and neuroscience — a field she later dubbed neurobotics — that ultimately fed her desire to help society. “I learned there were a lot of people with neurological disorders who could use this technology,” she said.

From there, she entered academia, setting out to create artificial limbs controlled by human thought. Along the way, she became director of the University of Washington’s Neurobotics Lab and the National Science Foundation’s Center for Sensorimotor Neural Engineering, and then head of innovation at Google. She’s now settled on creating Nest Lab’s programmable thermometers that aim to save people thousands of dollars on heating.

Matsuoka said this human-technology integration is her passion — and the future of our technologically advanced society. “That’s what just really gets me going: building these beautiful devices,” she said. “Am I doing something that’s really helping society? I think so.”

Nanotechnology could help fight diabetes

Thu, 16 May 2013 04:00:00 +0000

Injectable nanoparticles developed at MIT may someday eliminate the need for patients with Type 1 diabetes to constantly monitor their blood-sugar levels and inject themselves with insulin.

The nanoparticles were designed to sense glucose levels in the body and respond by secreting the appropriate amount of insulin, thereby replacing the function of pancreatic islet cells, which are destroyed in patients with Type 1 diabetes. Ultimately, this type of system could ensure that blood-sugar levels remain balanced and improve patients’ quality of life, according to the researchers.

“Insulin really works, but the problem is people don’t always get the right amount of it. With this system of extended release, the amount of drug secreted is proportional to the needs of the body,” says Daniel Anderson, an associate professor of chemical engineering and member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Anderson is the senior author of a paper describing the new system in a recent issue of the journal ACS Nano. Lead author of the paper is Zhen Gu, a former postdoc in Anderson’s lab. The research team also includes Robert Langer, the David H. Koch Institute Professor at MIT, and researchers from the Department of Anesthesiology at Boston Children’s Hospital.

Mimicking the pancreas

Currently, people with Type 1 diabetes typically prick their fingers several times a day to draw blood for testing their blood-sugar levels. When levels are high, these patients inject themselves with insulin, which breaks down the excess sugar.

In recent years, many researchers have sought to develop insulin-delivery systems that could act as an “artificial pancreas,” automatically detecting glucose levels and secreting insulin. One approach uses hydrogels to measure and react to glucose levels, but those gels are slow to respond or lack mechanical strength, allowing insulin to leak out.

The MIT team set out to create a sturdy, biocompatible system that would respond more quickly to changes in glucose levels and would be easy to administer.

Their system consists of an injectable gel-like structure with a texture similar to toothpaste, says Gu, who is now an assistant professor of biomedical engineering and molecular pharmaceutics at the University of North Carolina at Chapel Hill and North Carolina State University. The gel contains a mixture of oppositely charged nanoparticles that attract each other, keeping the gel intact and preventing the particles from drifting away once inside the body.

Using a modified polysaccharide known as dextran, the researchers designed the gel to be sensitive to acidity. Each nanoparticle contains spheres of dextran loaded with an enzyme that converts glucose into gluconic acid. Glucose can diffuse freely through the gel, so when sugar levels are high, the enzyme produces large quantities of gluconic acid, making the local environment slightly more acidic.

That acidic environment causes the dextran spheres to disintegrate, releasing insulin. Insulin then performs its normal function, converting the glucose in the bloodstream into glycogen, which is absorbed into the liver for storage.

Long-term control

In tests with mice that have Type 1 diabetes, the researchers found that a single injection of the gel maintained normal blood-sugar levels for an average of 10 days. Because the particles are mostly composed of polysaccharides, they are biocompatible and eventually degrade in the body.

The researchers are now trying to modify the particles so they can respond to changes in glucose levels faster, at the speed of pancreas islet cells. “Islet cells are very smart. They can release insulin very quickly once they sense high sugar levels,” Gu says.

Before testing the particles in humans, the researchers plan to further develop the system’s delivery properties and to work on optimizing the dosage that would be needed for use in humans.

“Clearly longer-term studies are warranted, but from a closed-loop perspective, this is a very clever approach to normalizing blood-glucose levels in individuals with diabetes, achieved by integrating the glucose sensing with the insulin delivery, much like a natural pancreatic beta cell,” says Frank Doyle, a professor of chemical engineering at the University of California at Santa Barbara who was not part of the research team.

The research was funded by the Leona M. and Harry B. Helmsley Charitable Trust and the Tayebati Family Foundation.

Stephen Lippard wins faculty’s Killian Award

Thu, 16 May 2013 17:37:23 +0000

Stephen J. Lippard, who is widely acknowledged as one of the founders of the field of bioinorganic chemistry, is this year’s recipient of MIT’s James R. Killian Jr. Faculty Achievement Award.

Established in 1971 to honor MIT’s 10th president, the Killian Award recognizes extraordinary professional achievements by an MIT faculty member.

In announcing this year’s award at the May 15 faculty meeting, the award committee noted that Lippard’s “groundbreaking work has pushed back the frontiers of inorganic chemistry, while simultaneously paving the way for improvements in human health and the conquering of disease.”

Lippard, the Arthur Amos Noyes Professor of Chemistry, has spent his career studying the role of inorganic molecules, especially metal ions and their complexes, in critical processes of biological systems. He has made pioneering contributions in understanding the mechanism of the cancer drug cisplatin and in designing new variants to combat drug resistance and side effects.

His research achievements include the preparation of synthetic models for metalloproteins; structural and mechanistic studies of iron-containing bacterial monooxygenases including soluble methane monooxygenase; and the invention of probes to elucidate the roles of mobile zinc and nitric oxide in biological signaling and disease.

“It’s humbling,” Lippard said of receiving the award. “Many of my MIT heroes are on the list of previous recipients, and it’s really an honor to join them.”

“I am indebted to my wonderful group of students, both graduate and undergraduate, as well as many talented postdoctoral associates who have worked in my lab over the years to produce the research results that are recognized by this award,” he added. “I also thank my wife Judy for her love and support.”

Lippard earned his PhD in chemistry from MIT in 1965 and spent a year at the Institute as a postdoc before joining the faculty of Columbia University in 1966. He returned to MIT as a professor in 1983 and served as the head of the Department of Chemistry from 1995 to 2005. He has published more than 800 scientific papers and recorded nearly 30 patents. With Jeremy Berg, he published “Principles of Bioinorganic Chemistry,” which is regarded as the definitive text in the field.

The award citation noted that in addition to his exceptional work as a scientist, “Professor Lippard has excelled as a teacher and mentor, fostering the training of a generation of leading young scientists in the field of bioinorganic chemistry.” He has trained more than 100 PhD students and an even greater number of postdocs.

“After years of great science, scholarship, and service, Professor Lippard still projects a wonderful youthful enthusiasm when discussing new research results, or when teaching freshman chemistry to new MIT undergraduates,” according to the award citation, read at the May 15 faculty meeting by Michel Goemans, chair of the Killian Award selection committee and a professor of mathematics.

Lippard’s many other awards include the Linus Pauling Medal, the UK Royal Society of Chemistry Centenary Medal, the Ronald Breslow Award for Achievement in Biomimetic Chemistry, the Alfred Bader Award in Bioinorganic or Bioorganic Chemistry, and the National Medal of Science. He has been elected to the National Academy of Sciences, the National Institute of Medicine and the American Academy of Arts and Sciences.