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  • richardmitnick 10:29 am on September 7, 2018 Permalink | Reply
    Tags: AIM-Adaptable Interpretable Machine Learning, , Black-box models, Duke University, , ,   

    From MIT News: “Taking machine thinking out of the black box” 

    MIT News
    MIT Widget

    From MIT News

    September 5, 2018
    Anne McGovern | Lincoln Laboratory

    1
    Members of a team developing Adaptable Interpretable Machine Learning at Lincoln Laboratory are: (l-r) Melva James, Stephanie Carnell, Jonathan Su, and Neela Kaushik. Photo: Glen Cooper.

    Adaptable Interpretable Machine Learning project is redesigning machine learning models so humans can understand what computers are thinking.

    Software applications provide people with many kinds of automated decisions, such as identifying what an individual’s credit risk is, informing a recruiter of which job candidate to hire, or determining whether someone is a threat to the public. In recent years, news headlines have warned of a future in which machines operate in the background of society, deciding the course of human lives while using untrustworthy logic.

    Part of this fear is derived from the obscure way in which many machine learning models operate. Known as black-box models, they are defined as systems in which the journey from input to output is next to impossible for even their developers to comprehend.

    “As machine learning becomes ubiquitous and is used for applications with more serious consequences, there’s a need for people to understand how it’s making predictions so they’ll trust it when it’s doing more than serving up an advertisement,” says Jonathan Su, a member of the technical staff in MIT Lincoln Laboratory’s Informatics and Decision Support Group.

    Currently, researchers either use post hoc techniques or an interpretable model such as a decision tree to explain how a black-box model reaches its conclusion. With post hoc techniques, researchers observe an algorithm’s inputs and outputs and then try to construct an approximate explanation for what happened inside the black box. The issue with this method is that researchers can only guess at the inner workings, and the explanations can often be wrong. Decision trees, which map choices and their potential consequences in a tree-like construction, work nicely for categorical data whose features are meaningful, but these trees are not interpretable in important domains, such as computer vision and other complex data problems.

    Su leads a team at the laboratory that is collaborating with Professor Cynthia Rudin at Duke University, along with Duke students Chaofan Chen, Oscar Li, and Alina Barnett, to research methods for replacing black-box models with prediction methods that are more transparent. Their project, called Adaptable Interpretable Machine Learning (AIM), focuses on two approaches: interpretable neural networks as well as adaptable and interpretable Bayesian rule lists (BRLs).

    A neural network is a computing system composed of many interconnected processing elements. These networks are typically used for image analysis and object recognition. For instance, an algorithm can be taught to recognize whether a photograph includes a dog by first being shown photos of dogs. Researchers say the problem with these neural networks is that their functions are nonlinear and recursive, as well as complicated and confusing to humans, and the end result is that it is difficult to pinpoint what exactly the network has defined as “dogness” within the photos and what led it to that conclusion.

    To address this problem, the team is developing what it calls “prototype neural networks.” These are different from traditional neural networks in that they naturally encode explanations for each of their predictions by creating prototypes, which are particularly representative parts of an input image. These networks make their predictions based on the similarity of parts of the input image to each prototype.

    As an example, if a network is tasked with identifying whether an image is a dog, cat, or horse, it would compare parts of the image to prototypes of important parts of each animal and use this information to make a prediction. A paper on this work: “This looks like that: deep learning for interpretable image recognition,” was recently featured in an episode of the “Data Science at Home” podcast. A previous paper, “Deep Learning for Case-Based Reasoning through Prototypes: A Neural Network that Explains Its Predictions,” used entire images as prototypes, rather than parts.

    The other area the research team is investigating is BRLs, which are less-complicated, one-sided decision trees that are suitable for tabular data and often as accurate as other models. BRLs are made of a sequence of conditional statements that naturally form an interpretable model. For example, if blood pressure is high, then risk of heart disease is high. Su and colleagues are using properties of BRLs to enable users to indicate which features are important for a prediction. They are also developing interactive BRLs, which can be adapted immediately when new data arrive rather than recalibrated from scratch on an ever-growing dataset.

    Stephanie Carnell, a graduate student from the University of Florida and a summer intern in the Informatics and Decision Support Group, is applying the interactive BRLs from the AIM program to a project to help medical students become better at interviewing and diagnosing patients. Currently, medical students practice these skills by interviewing virtual patients and receiving a score on how much important diagnostic information they were able to uncover. But the score does not include an explanation of what, precisely, in the interview the students did to achieve their score. The AIM project hopes to change this.

    “I can imagine that most medical students are pretty frustrated to receive a prediction regarding success without some concrete reason why,” Carnell says. “The rule lists generated by AIM should be an ideal method for giving the students data-driven, understandable feedback.”

    The AIM program is part of ongoing research at the laboratory in human-systems engineering — or the practice of designing systems that are more compatible with how people think and function, such as understandable, rather than obscure, algorithms.

    “The laboratory has the opportunity to be a global leader in bringing humans and technology together,” says Hayley Reynolds, assistant leader of the Informatics and Decision Support Group. “We’re on the cusp of huge advancements.”

    Melva James is another technical staff member in the Informatics and Decision Support Group involved in the AIM project. “We at the laboratory have developed Python implementations of both BRL and interactive BRLs,” she says. “[We] are concurrently testing the output of the BRL and interactive BRL implementations on different operating systems and hardware platforms to establish portability and reproducibility. We are also identifying additional practical applications of these algorithms.”

    Su explains: “We’re hoping to build a new strategic capability for the laboratory — machine learning algorithms that people trust because they understand them.”

    See the full article here .


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  • richardmitnick 11:01 am on September 5, 2018 Permalink | Reply
    Tags: Duke University, , , , ,   

    From Duke University via The News&Observer: “Look out, IBM. A Duke-led group is also a player in quantum computing” 

    Duke Bloc
    Duke Crest

    From Duke University

    via

    The News&Observer

    August 13, 2018
    Ray Gronberg

    1
    Duke University professors Iman Marvian, Jungsang Kim and Kenneth Brown, gathered here in Kim’s lab in the Chesterfield Building in downtown Durham, are working together to develop a quantum computer that relies on “trapped ion” technology. The National Science Foundation and the federal Intelligence Advanced Research Projects Activity are helping fund the project. Les Todd LKT Photography, Inc.

    There’s a group based at Duke University that thinks it can out-do IBM in the quantum-computing game, and it just got another $15 million in funding from the U.S. government.

    Quantum computing – IBM

    The National Science Foundation grant is helping underwrite a consortium led by professors Jungsang Kim and Ken Brown that’s previously received backing from the federal Intelligence Advanced Research Projects Activity.

    Kim said the group is developing a quantum computer that has “up to a couple dozen qubits” of computational power and reckons it’s a year or so from being operational. The world qubit is the quantum-computing world’s equivalent of normal computing’s “bit” when it comes to gauging processing ability, and each additional qubit represents a doubling of that power.

    “One of the goals of this [grant] is to establish the hardware so we can allow researchers to work on the software and systems optimization,” Kim said of the National Science Foundation grant the agency awarded on Aug. 6.

    Two or three dozen qubits might not sound like a lot when IBM says it has built and tested a 50-qubit machine. But the Duke-led research group is approaching the problem from an entirely different angle.

    The “trapped-ion” design it’s using could hold qubits steady in its internal memory for much longer than superconducting designs like those IBM is working on can manage, Brown said.

    Superconducting designs — which operate at extremely cold temperatures — “are a bit faster” than trapped-ion ones and are the focus of “a much larger industrial effort,” Brown said.

    That speed-versus-resilience tradeoff could matter because IBM says its machines can hold a qubit steady in memory for only up to about 90 microseconds. That means processing runs have to be short, on the order of no more than a couple of seconds total.

    “One thing that’s becoming clear in the community is, the thing we need to scale is not just the number of qubits but also the quality of operations,” said Brown, who in January traded a faculty post at Georgia Tech for a new one at Duke. “If you have a huge number of qubits but the operations are not very good, you effectively have a bad classical computer.”

    Kim added that designers working on quantum computers have to look for the same kind of breakthrough in thinking about the technology that the Wright brothers brought to the development of flight.

    Just as the Wrights and other people working in the field in the late 19th and early 20th centuries figured out that mimicking birds was a developmental dead end, the builders of quantum computers “have to start with something that’s fundamentally quantum and build the right technology to scale it,” Kim said. “You don’t build quantum computers by mimicking classical computers.”

    But for now, the government agencies that are subsidizing the field are backing different approaches and waiting to see what pans out.

    The Aug. 6 grant is the third big one Kim’s lab has secured, building on awards from IARPA in 2010 and 2016 that together brought it about $54.5 million in funding. But in both those rounds of funding, teams from IBM were also among those getting awards from the federal agency, which funds what it calls “high-risk/high-payoff” research for the intelligence community.

    The stakes are so high because quantum computing could become a breakthrough technology. It exploits the physics of subatomic particles in hopes of developing a machine that can process data that exists in multiple states at once, rather than the binary 1 or 0 of traditional computing.

    IBM and the government aren’t the only heavy hitters involved. Google has a quantum-computing project of its own that’s grown with help from IARPA funding.

    3
    Google’s Quantum Dream Machine

    Kim and other people involved in the Duke-led group have also formed a company called IonQ that’s received investment from Google and Amazon.

    The Duke-led group also includes teams from from the University of Maryland, the University of Chicago and Tufts University that are working on hardware, software and applications development, respectively, Duke officials say. Researchers from the University of New Mexico, MIT, the National Institute of Standards and Technology and the University of California-Berkeley are also involved.

    Duke doesn’t have quantum computing all to itself in the Triangle, as in the spring IBM made N.C. State University part of its Q Network, a group of businesses, universities and government agencies that can use IBM’s quantum machines via the cloud.

    But the big difference between the N.C. State and Duke efforts is that with State, the focus is on developing both the future workforce and beginning to push software development, while at Duke it’s more fundamentally about trying to develop the technology.

    Not that software is a side issue, mind.

    “If I had a quantum computer with 60 qubits, I know there are algorithms I can run on it that I can’t simulate with my regular computers,” Brown said, explaining that the technology requires new thinking there, too. “That’s a weird place to be.”

    The quantum project is important enough that Duke has backed it with faculty hires. Brown had been collaborating with Kim’s group for a while, but elected to move to Duke from Georgia Tech after Duke officials decided to conduct what Kim termed “a cluster hire” of quantum specialists.

    Brown joined Kim in the Pratt School of Engineering’s electrical and computer engineering department. A search for someone to fill an an endowed chair in physics continues.

    Another professor involved, Iman Marvian, also joined the Duke faculty at the start of 2018 thanks to the university’s previously announced “quantitative initiative.” A quantum information theorist, he got a joint appointment in physics and engineering. He came to Duke from MIT after a post-doc stint at the Boston school.

    See the full article here .

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    Please help promote STEM in your local schools.

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    Duke Campus

    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”

     
  • richardmitnick 8:24 am on March 21, 2018 Permalink | Reply
    Tags: Autonomously mapping the ocean floor, Blue Devil Ocean Engineering team, Duke Students Advance to Finals in $7 Million Ocean Discovery XPRIZE Competition, Duke University, Ocean Health XPRIZE, , Pratt School of Engineering   

    From Duke: “Duke Students Advance to Finals in $7 Million Ocean Discovery XPRIZE Competition” 

    Duke Bloc
    Duke Crest

    Duke University

    1

    March 7, 2018
    Ken Kingery

    After years of work from hundreds of students, the Duke Ocean XPRIZE team has qualified for the final round of competition aimed at autonomously mapping the ocean floor.

    2
    Duke Engineering students stand with their prototype heavy-lifting drone after a test flight for the Ocean Discovery XPRIZE competition. No image credit.

    Building on the research of more than two years of students in an innovative engineering course, a Duke University team is among the final nine teams left standing in the $7 million Shell Ocean Discovery XPRIZE that will conclude this fall.

    The Shell Ocean Discovery XPRIZE presents teams with the ambitious goal of mapping 250 square kilometers of ocean up to 4,000 meters deep within a half-meter resolution in less than 24 hours. The competition also requires teams to identify and image 10 archeological, biological or geological features. To make the task even harder, no boats or humans are allowed—the surveying must be completed with a system of autonomous drones that can all fit within a standard shipping container.

    “A lot of people who do this sort of work for a living didn’t even bother trying to compete,” said Martin Brooke, associate professor of electrical and computer engineering at Duke and leader of Duke’s team. “Most people viewed this challenge as completely and totally impossible. And they might be right.”

    The XPRIZE contests have a reputation for being challenging and audacious. The Google Lunar XPRIZE competition to send a robot to the moon ended this year without a winner. But the original Ansari XPRIZE to launch people into space with a reusable spacecraft found a winner, and the Wendy Schmidt Ocean Health XPRIZE aimed at developing ocean pH sensors found three.

    Whether teams are able to complete the challenge or not, the lofty goals of the XPRIZE competitions serve to push science forward, catalyze new markets and provide incentives for talented, intelligent people to innovate and make significant impacts.

    More than 30 teams submitted proposals at the start of the competition, and 19 were chosen as semi-finalists based on their technical merits in early 2017. These teams included more than 350 people from 25 countries, ranging from undergraduate students to industry professionals. The Duke team is joined in the finals by just one other university-based team, from Texas A&M. Both student teams will be competing against teams formed by industry professionals in Germany, Switzerland, Japan, Portugal, England and the United States.

    The Blue Devil Ocean Engineering team has taken an unusual tactic—several undergraduate classes were formed at the start of the competition to begin work on the project. While a handful of graduate students and undergraduate students working through independent studies have been able to stick with the project since its inception, most of the work being done each year is by an entirely new set of students. This means that few of the students finishing the competition this fall will have been the ones who started it in 2016.

    “Each year there’s a bit of a slowdown as the new students come up to speed on the project. But at the same time, they come in with fresh ideas and a lot of energy,” said Doug Nowacek, the Randolph K. Repass and Sally-Christine Rodgers University Associate Professor of Conservation Technology in Duke’s Nicholas School of the Environment and Pratt School of Engineering.

    3
    A computer-generated rendering of the initial prototype for the heavy-lifting drone designed to compete in the Ocean Discovery XPRIZE.

    Duke’s approach is to use giant heavy-lifting drones to deploy and retrieve a series of sonar-equipped sensors that are lowered from floating platforms at the ocean’s surface. This is much more difficult than it sounds.

    The drones must autonomously navigate gusting winds and waves that average six meters in height while dropping off and retrieving the sensors. The floating sensor platforms must carry at least 3,500 meters of cable to lower and then pull up the sensor pods, making them extremely heavy for the drones to carry. The sensor pods themselves must withstand the pressure, temperature and salinity of the ocean’s depths. And to successfully map the area required, the team must deploy multiple drones making multiple drop-offs and pick-ups, and then seamlessly analyze all of the data.

    To advance to the final round, the semifinalist teams had to pass a Round 1 Technology Readiness Test, which comprised site visits to each team by XPRIZE staff and judges. The teams were tested against 11 measurement criteria to show their technological solutions were capable of meeting the operational requirements necessary for rapid, unmanned and high-resolution ocean mapping and discovery.

    When the judges visited Duke, they saw a team with all of its components in place. The team has built and flown a heavy-lift drone in Duke Forest. They have sensor pods that have been tested at the Duke University Marine Laboratory in Beaufort, North Carolina. They have software to analyze the resulting data. The combination was enough to move them into the final round of competition.

    As the school year draws to a close, more than 50 students are now working to finalize their design. More rotors are being added to the drone to make sure it can lift the heavy sensor pods. Control software is being smoothed so that the drone can pick up the pods while using as little energy as possible. And the sensor pods themselves are receiving upgrades to increase their range so that fewer drops are needed to cover the area required in the final stage of competition.

    4
    Students test a prototype floating launching pad for their sonar pods. No image credit.

    “Our goal is to get this project to the point where all the next group of students need to do is build more of the drones and sensors that we’ve already completed,” said William Willis, a junior studying mechanical engineering who plans to continue participating during his senior year.

    “We want to demonstrate a full cycle of dropping off a sensor, mapping an area and picking it up before graduation in May,” added Nick Lockett, a senior studying electrical engineering.

    The team hopes to get some help assembling more units over the summer from high school students brought in by Tyler Bletsch, assistant professor of the practice of electrical and computer engineering at Duke, who has also been instrumental to the project. Whether or not they are successful in either their short-term goals or the final competition, the massive, long-term project has been valuable for everyone involved.

    “This project has given us a chance to work on electrical engineering problems in a real-world setting,” said Krista Opsahl-Ong, also a senior studying electrical engineering. “And I don’t mean just from a science perspective. We’ve had to work with a huge team with a lot of moving parts. It’s forced us to segment our work and keep track of a lot of parallel projects. And of course it’s been a ton of fun to actually get our hands dirty.”

    The nine finalist teams will be formally recognized and awarded at Oceanology International’s Catch the Next Wave conference in London on March 15. Attending the event for the Duke University team will be Brooke and graduating senior Sam Kelly—one of the few undergraduate students who has worked on the project since its inception. The final Round 2 testing will take place during October and November of 2018.

    See the full article here .

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    Duke Campus

    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”

     
  • richardmitnick 11:05 am on July 12, 2017 Permalink | Reply
    Tags: An Out of Body Experience, , Duke University, , , The Ice Age May Be Over   

    From Duke: “An Out of Body Experience” 

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    Duke University

    Jul 11, 2017
    Scott Behm

    Each day, tens of thousands of patients on waiting lists across the United States await a simple phone call: one that says a match has been found and an organ is available for transplant. Despite a growing demand for donors, organ shortages continue to hinder many patients’ chances in receiving their potentially life-saving call.

    The organ shortage has impacted several transplant teams at Duke. Carmelo Milano, MD, Professor, Division of Cardiovascular and Thoracic Surgery, says part of the reason for the shortage is the method used to preserve organs while in transit from donor to recipient.

    “Duke has performed over 1,000 heart transplants using cold static storage,” says Dr. Milano, Heart Transplant Surgical Director. (That’s a fancy term for a bag of ice.) “With this method, the heart is removed from the donor and cooled with a solution before it is transported, but lack of oxygen to the organ can cause graft failure.”

    Cold storage has been a staple of the transplant procedure for over 50 years. While this method is serviceable, it is far from ideal. Vital organs are sensitive to cold ischemia while stored on ice, as irreparable damage from a lack of oxygenated blood flow rapidly occurs. When a heart stops beating, or lungs stop breathing, the organ slowly dies.

    Cold storage slows down the deterioration process but not entirely, and this race against the clock severely limits organ availability. The heart is particularly sensitive to cold ischemia. Consequently, Duke’s range of potential donors for heart transplants has been limited to those east of the Mississippi, according to Dr. Milano.

    The lung transplant team faces similar obstacles, says Matthew Hartwig, MD, Associate Professor, Division of Cardiovascular and Thoracic Surgery. Though the team has successfully transplanted lungs held in cold storage for longer than the conservative 4-hour window, Dr. Hartwig says doing so can create more complications. With such a small window of time, organ matches found a considerable distance away often go unused.

    1
    Transplant surgeon Matthew Hartwig examines a set of donor lungs,
    transported to Duke in the time-honored bag of ice. (Photo: Shawn Rocco)

    The most logical answer to the cold storage problem is also the most challenging: keep a transplanted organ in a near-physiologic state while outside of the body, perfused with blood, and limit the amount of time the organ is kept on ice.

    Though the ability to keep an organ alive outside of the body may sound like something out of science fiction, perfusion systems make this a reality. The devices keep an organ as functional as possible after surgical removal, during a process known as “ex vivo perfusion.” Rather than using ice, the device stores the organ at close to body temperature, causing less injury. Nutrient-rich blood taken from the donor filters through the organ, and the system allows close monitoring while the donated organ remains in a living state: beating, breathing, or producing bile, metabolizing glucose and balancing the blood’s chemistry.

    Several Duke teams are at the forefront of national clinical studies to examine the effectiveness of these devices in transplant procedures.

    Duke’s cardiac transplant team has partnered with TransMedics, whose portable Organ Care System™ (OCS) allows the heart to be perfused while in transit from donor to recipient. Dubbed the “heart in a box,” the device is sent with the procurement team to retrieve the heart, which is transported back to the transplant center.

    The first successful surgery at Duke using an organ transported via the OCS was performed in July 2016. The surgery would not have been possible without the new system due to the distance the organ had to travel, says Dr. Milano. Since then, surgeons have performed eight more successful transplants using the OCS.

    The lung transplant team has also had success using a device developed by XVIVO Perfusion, completing 25 successful transplants and enrolling more patients than any other center in the United States for the trial. Lungs are fragile organs at high risk for infection due to their role as a main filter of our outside environment. This fragility comes at a cost: the Organ Procurement and Transplantation Network reports only 1 in 4 donated lungs is viable for transplant.

    Duke’s trial with the XVIVO system focused specifically on lungs that initially would not have been accepted for transplant. Using a perfusion device allows the lungs to breathe without straining, making the organ stronger and healthier outside of the body.

    The liver transplant team formed a third partnership with OrganOx. The manufacturer’s metra device allows the donor’s liver to be preserved for up to 24 hours prior to transplant. This clinical trial began in February of 2017.

    “There are several benefits to using the device,” explains Andrew Barbas, MD, Assistant Professor, Division of Abdominal Transplant Surgery. “We can access the metabolic activity of the liver and restore energy levels in liver cells. We can also assess which organs will function better after transplant.”

    This evaluation period prior to the transplant procedure can be critical to success, and perfusion devices offer the surgeon more breathing room to examine the organ fully before surgery begins.

    Expanding the Donor Pool

    Duke’s transplant surgeons all say perfusion systems can increase the number of organs available. Longer preservation times allow organs to travel greater distances, offering a larger geographic area to search for matches.

    But more important than geography is the ability to use “extended criteria organs,” says Jacob Schroder, MD, Assistant Professor, Division of Cardiovascular and Thoracic Surgery.

    “Extended criteria hearts have some feature that makes them imperfect—ventricular hypertrophy, minor coronary disease, advanced age of the donor, certain causes of death, or a long estimated ischemic time,” says Dr. Schroder. “The success rate for these hearts has traditionally been very low, but the OCS™ device allows us to take the ischemic time out of the question.”

    Whether heart, lung, or liver, when the threat of damage from cold storage is minimized, more organs become viable options for patients in need. To put it simply, Dr. Schroder explains that utilizing the OCS is the equivalent of transplanting an organ from a donor found in Raleigh, rather than farther away. It entails less risk, and more positive outcomes.

    The Future of Ex Vivo Perfusion

    3
    A Duke liver transplant team poses with the OrganOx system. The donor liver
    is in the clear box at the lower right, sustained by donor blood, saline and a pump.

    Perfusion also raises an interesting question about the ability to rehabilitate organs while outside of the body: Is it possible to transplant an organ in a better condition than when it was procured?

    Dawn Bowles, PhD, Assistant Professor, Division of Surgical Sciences, believes this may be a possibility. She has conducted biological therapy studies using pig hearts perfused in the TransMedics OCS.

    “These devices answer questions about whether or not a heart can be rehabilitated while it is stored,” says Bowles. “It is possible that we could fix some things that need fixing in a heart before it is transplanted.”

    While this type of therapy is still on the horizon, it highlights the potential of the new technology. Through a grant from the American Society of Transplant Surgeons, Dr. Barbas is using animal models to test the possibility of repairing damaged livers through perfusion.

    Repairing organs ex vivo may be another solution to the organ shortage problem.

    This potential application may already be a reality for lung transplants. Duke’s next trial with United Therapeutics will test the use of what Dr. Hartwig calls an “organ hospital” — a centralized location where organs are rehabilitated before transplantation.

    “This technology is still in its infancy, but I can see our program being able to use the devices to not only stabilize lungs while outside of the body, but to intervene and improve them,” says Dr. Hartwig.

    Healthier organs available in greater numbers means more patients could receive the life-saving operations they need. For many patients awaiting a transplant, the wait for their phone call may become shorter.

    See the full article here .

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    Duke Campus

    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”

     
  • richardmitnick 12:21 pm on June 7, 2017 Permalink | Reply
    Tags: , , Duke University, Research the world with drones   

    From Duke: “Research from a New Point of View” 

    Duke Bloc
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    Duke University

    April 17, 2017 [Where have yo been hiding, Duke?]

    Karl Bates
    Laura Brinn
    Eric Ferreri

    Drone technology provides new opportunities for Duke research—both within the university and out in the field.

    To get some overhead images while doing archaeology field work several years ago, members of Katherine McCusker’s archaeology research team rigged a camera to a weather balloon attached to a really long rope. They let the balloon drift upward, holding tight to the rope while hoping the camera was programmed properly to snap some photos.

    “You hope the wind isn’t too strong and the camera is at the right angle,” McCusker, now a doctoral student at Duke, recalls. “That was our low-tech solution. We got some really nice photos – but they weren’t useful for research.”

    McCusker remembers those makeshift camerawork days often now as she pilots drones over the Italian countryside, watching in real time as it records digital data.

    “…The use of drones is really changing how research is done….”
    — Lawrence Carin, Vice Provost for Research

    McCusker works in Duke’s Dig@Lab, where professor Maurizio Forte leads a team that uses drones and other high-tech resources to efficiently examine Italian landscapes in search of clues to ancient civilizations. In Forte’s lab and across the university – and in higher education more generally – researchers are finding myriad uses for these relatively inexpensive new tools that provide a valuable new vantage point for examination of everything from ancient Roman ruins to the eating habits of whales to the migratory patterns of turtles.

    “Drones are certainly introducing new opportunities for research in some important areas,” said Lawrence Carin, Duke’s Vice Provost for Research. “Especially in the environmental sector, the use of drones is really changing how research is done.”

    At Duke, researchers from across the academic spectrum are finding uses for drones and other high-tech tools that speed their work.

    McCusker has spent the last three summers in Vulci, an Etruscan archaeological site in the Viterbo province in Italy.

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    Vulci. http://www.etruriaoggi.it/il-parco-di-vulci-come-non-lo-avete-mai-visto/

    With images recorded by drones, she’s able to examine the development of civilizations – first the Etruscans, and later the Romans – over a period of roughly seven centuries. Vulci is a treasure trove of history, and drones have helped McCusker and others with the Duke lab narrow their searches, create 3D models that suggest how communities looked way back then. With drone images as a key tool, the team discovered hundreds of new archaeological sites and tombs as well as a Roman forum, and was able to create a virtual model of the archaeological landscape.

    “Drones and other tools have completely changed the speed and quality of research,” said Forte, a professor of both classics and art, art history and visual studies at Duke who has worked in Vulci since 2014. “It has had such a deep impact in so short a time. The research template is different now.”

    Carin, the research vice provost, said he’s seeing a steady increase in the number of faculty expressing interest in using drones in their own research – drawn by the relatively low cost and promise of a literal new view of their scholarly landscape.

    There have been hurdles. Drones are still a new enough that regulators have scrambled to keep up with them. But there are now federal policies in place that Duke and other research universities follow. And Duke has developed its own drone use guidelines for researchers to follow, Carin said.

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    Ahmedabad, India. No image credits

    On the outskirts of Ahmedabad, India, a drone helped Duke students and researchers sample trash-burning emissions from a municipal dump site that stood several stories tall. In a setting where it wouldn’t be safe for researchers to climb up high enough to collect the samples, the drone allowed the team to safely and efficiently measure a common source of air pollution over a large spatial area.

    The team attached a small sensor—designed at Professor Mike Bergin’s lab at Duke—to its drone, turning it into a flying air quality monitoring station. Although some research applications require specialized drones, in this case the team used a recreational drone, given that it was easy to use and fly, and stable enough to manage the additional weight of the sensor while in flight.

    Video taken by the drone also improves the researchers’ ability to understand fluctuations in the data.

    “If we see a sudden spike or change in the emissions while we’re analyzing the data, we can check the corresponding point on the video to look for an explanation, such as a passing vehicle or somebody smoking a cigarette,” explained graduate student Heidi Vreeland. “When we look only at the sensor data, we can’t know what source caused the fluctuations—but drones allow us to find out.”

    Bergin, Vreeland and their team acknowledge the limitations of using drones. Drones might not be universally applicable to the type of work they do, due to the risk of potentially interfering with the research process.

    “Drones do attract a lot of attention,” said Vreeland. “We try to be careful that bringing in something like a drone doesn’t inadvertently cause people to change their behavior because they assume the drone is watching or measuring their activity.”

    5
    Weddell Sea. https://cherihunston.wordpress.com/2011/12/02/

    In the Weddell Sea along the coast of Antarctica, drones allow researchers to collect valuable data in the most inhospitable conditions.

    The sea and its shores are notoriously difficult environments to study, but a relatively unobtrusive drone that looks like nothing more than an odd-sounding seabird gives marine scientists some remarkable new abilities.

    With it, scholars with the Duke Marine Lab can accurately count marine turtles as they lay eggs on a Costa Rican beach; differentiate juvenile seals and penguins from their parents using a heat-sensitive camera; map and measure barrier islands before and after storms to see how much sand is moved; and monitor how humpback whales feed on krill in Antarctica’s Weddell Sea.

    And a drone will go where no human would ever want to – through a shower of airborne whale snot to capture precious DNA.

    “We can collect huge volumes of data from even the most remote or extreme locations,” said David Johnston, executive director of the new facility and assistant professor of the practice of marine conservation ecology at Duke’s Nicholas School of the Environment. “ are transforming how we study and learn about the marine environment.”

    Duke’s is the first marine lab to win FAA certification to operate scientific drones and provide training. And these drones aren’t just those octo-copters you can buy at your local big-box store. They also have fixed wing airplanes that can stay aloft for 45 minutes, beaming VR video back to the operator’s headset.

    Their biggest drone is an amphibious plane with a 9-foot wingspan that can fly for 90 minutes at a time. Like several of their other drones, this one can fly itself back and forth within a pre-defined area, like “mowing the lawn” for data.

    The Duke drone workshop, just steps from the water in a former boathouse at the Beaufort, NC lab, is strewn with wings, wires and tiny propellers in various states of disassembly. The program manager, AKA jack of all trades, is retired Col. Everette Newton, who flew F-15s in the Air Force. Newton also trained the Duke archaeologists now using drones in Italy.

    The training covers flight planning, flying drones, data management and analysis and provides a working knowledge of federal and state airspace restrictions and rules. It is intended to prepare more scientists for FAA certification and some participants also get the chance to build and fly their own unmanned craft.

    And what teacher and student each learn is that this new flying technology is a pretty good research aid.

    “As much as it hurts me as a pilot, the drone flies a lot more accurately than me,” Newton told Duke Magazine.

    See the full article here .

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  • richardmitnick 4:13 pm on June 4, 2017 Permalink | Reply
    Tags: 30 Pages of Calculations Settle a 30-Year Debate over a Mysterious New Phase of Matter, Algebraic calculations all done by hand, , “Moments like these are the reason why I do science” Yaida said, , Breaking Glass in Infinite Dimensions, Duke University, Frank Gehry, Highly-ordered nature of crystals, , Sho Yaida   

    From Duke: “Breaking Glass in Infinite Dimensions” 

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    Duke University

    May 30, 2017
    Kara Manke

    30 Pages of Calculations Settle a 30-Year Debate over a Mysterious New Phase of Matter.

    1
    With 30 pages of handwritten calculations, Duke postdoctoral fellow Sho Yaida has laid to rest a 30-year-old mystery about the nature of glass and “disordered” materials at low temperatures. They may in fact be a new state of matter. Credit: Irem Altan

    Zoom in on a crystal and you will find an ordered array of atoms, evenly spaced like the windows on the Empire State Building. But zoom in on a piece of glass, and the picture looks a bit messier — more like a random pile of sand, or perhaps the windows on a Frank Gehry building.

    2
    Frank Gehry IAC Building Manhattan

    The highly-ordered nature of crystals makes them fairly simple to understand mathematically, and physicists have developed theories that capture all sorts of crystal properties, from how they absorb heat to what happens when they break.

    But the same can’t be said of glassy, amorphous or otherwise “disordered” materials such as the glass in our windows and vases, frozen food, and certain plastics. There are no widely agreed-upon theories to explain their physical behavior.

    For nearly 30 years, physicists have debated whether a mysterious phase transition, present in theoretical models of disordered materials, might also exist in real-life glasses. With the help of some mathematical wizardry borrowed from particle physics — plus dozens of pages of algebraic calculations, all done by hand — Duke University postdoctoral fellow Sho Yaida has laid this mystery to rest.

    Yaida’s insights open up the possibility that some types of glass may exist in a new state of matter at low temperatures, influencing how they respond to heat, sound and stress, and how and when they break.

    “We found hints of the transition that we didn’t dare say was evidence of the transition because part of the community said that it could not exist,” said Patrick Charbonneau, associate professor of chemistry at Duke and Yaida’s advisor. “What Sho shows is that it can exist.”

    3
    Earlier calculations failed to find a “fixed point” in three dimensions, or a spot where the lines overlap (left). By taking the calculations one more step, Yaida found a fixed point (right), showing that a phase transition might exist. Credit: Sho Yaida

    Mind-boggling as it may seem, Charbonneau said, the mathematics behind glasses and other disordered systems is actually much easier to solve by assuming that these materials exist in a hypothetical infinite-dimensional universe. In infinite dimensions, their properties can be calculated relatively easily — much like how the properties of crystals can be calculated for our three-dimensional universe.

    “The question is whether this model has any relevance to the real world.” Charbonneau said. For researchers who carried out these calculations, “the gamble was that, as you change dimension, things change slowly enough that you can see how they morph as you go from an infinite number of dimensions to three,” he said.

    One feature of these infinite dimensional calculations is the existence of a phase transition — called the “Gardner transition” after pioneering physicist Elizabeth Gardner — which, if present in glasses, could significantly change their properties at low temperatures.

    But did this phase transition, clearly present in infinite dimensions, also exist in three? Back in the 1980s, a team of physicists produced mathematical calculations showing that no, it could not. For three decades, the prevailing viewpoint remained that this transition, while theoretically interesting, was irrelevant to the real world.

    That is, until recent experiments and simulations by Charbonneau and others started showing hints of it in three-dimensional glasses.

    “The new drive to look at this is that, when attacking the problem of glass formation, they found a transition very much like the one that appeared in these studies,” Charbonneau said. “And in this context it can have significant materials applications.”

    Yaida, who has a background in particle physics, took a second look at the old mathematical proofs. These calculations had failed to find a “fixed point” in three dimensions, a prerequisite for the existence of a phase transition. But if he took the calculation one more step, he thought, the answer might change.

    One month and 30 pages of calculations later, he had it.

    “Moments like these are the reason why I do science,” Yaida said. “It is just a point, but it means a lot to people in this field. It shows that this exotic thing that people found in the seventies and eighties does have a physical relevance to this three-dimensional world.”

    After a year of checks and re-checks, plus another 60-odd pages of supporting calculations, the results were published May 26 in Physical Review Letters.

    “The fact that this transition might actually exist in three dimensions means that we can start looking for it seriously,” Charbonneau said. “It affects how sound propagates, how much heat can be absorbed, the transport of information through it. And if you start shearing the glass, how it will yield, how it will break.”

    “It changes profoundly how we understand amorphous materials in general, whether they be amorphous plastics or piles of sand or window glasses,” he said.

    This research was supported by a grant from the Simons Foundation (#454937).

    See the full article here .

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  • richardmitnick 2:45 pm on May 22, 2017 Permalink | Reply
    Tags: Duke University, Lily Zerihun, ,   

    From Duke via The News&Observer: Women in STEM -“Duke grad, a daughter of immigrants, admitted to 11 medical schools” Lily Zerihun 

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    1

    The News&Observer

    2
    Lily Zerihun Courtesy of Lily Zerihun

    May 11, 2017
    Abbie Bennett

    Lily Zerihun knows that health care is a privilege not many can afford – and she wants to dedicate her life to changing that.

    Being admitted to 11 medical schools gets her off to a great start.

    Zerihun, 23, of Greensboro, graduated from Duke University in 2016. Her parents emigrated to the United States from Ethiopia, and Zerihun was born soon after. She was raised with a keen understanding of how different her life was from the life she might have led if she had been born in her parents’ home country.

    “Growing up I was always very aware of health-care issues in my own family, including people who had to come to the U.S. for treatment from Ethiopia,” she said. “Or people who, if they lived in the U.S., could have been treated, but had to go without.”

    In the back of her mind, Zerihun wanted to have a role in alleviating the imbalance in global health.

    And it’s not just the difference between health care in the United States and in countries such as Ethiopia. It’s also the disparities right here in the United States.

    “I want to work in some service capacity,” she said. “Being able to directly impact communities in the U.S. and around the world that don’t have access to health care – I want to be someone who makes a difference in that.”

    Zerihun is already on her way to accomplishing that with her 11 medical school offers.

    The application process is long and arduous, and each decision was heart-stopping. When Zerihun got her very first decision – from Wake Forest University – she even made a friend open the email for her.

    “I was too afraid,” she said, laughing. “It didn’t really sink in … I just thought, ‘I’m really going to be a doctor.’”

    As more and more decisions rolled in – from George Washington University, Yale, Duke, North Carolina, East Carolina, Northwestern, Mount Sinai, Emory, NYU and Columbia – Zerihun said it was a “surreal experience.”

    She decided on Columbia.

    Most medical school applicants are fortunate to be admitted to two schools – let alone 11. And many are rejected from every school they apply to. Most medical schools accept less than 10 percent of all applicants.

    But Zerihun says she was raised to work hard and be appreciative, especially given her parents’ background.

    Her father came to the United States to further his education and give his family greater opportunities. He’s a chemist and has been a professor at North Carolina A&T; he’s one of Zerihun’s biggest inspirations.

    3

    “He’s given me the motivation to do well in school, and it’s been really valuable,” she said. “Understanding the struggles that he overcame for his education – finishing his undergrad degree during a time in Ethiopia when scholars were being killed by the government – that journey my father took and the emphasis he put on education has really made a difference for me.”

    Literacy rates in Ethiopia for women are markedly lower than in the United States, and while the number of female, minority and minority female doctors in the United States is low, Zerihun knows she had far greater opportunities here.

    “I knew I had to focus on my education to give back to the women in my community,” she said. “It’s a real motivating force for me.”

    Zerihun said she wants her success to show women and minority students that they can achieve their dreams and enter the field of medicine, regardless of the obstacles.

    “I feel like that’s what my calling is,” she said. “There’s a definite lack of representation in the field, but I’ve managed to find mentors already and that’s really inspiring for me. I hope one day I can be that for someone, too.”

    Zerihun said she hoped to share her story for the next generation of students, because she knows how tough it was for her.

    “Especially in the black community with such an under-representation of black doctors, I’m hoping my story can be an inspiration for people who want to go to medical school.”

    Not only will Zerihun undoubtedly serve as an inspiration for U.S. students who want to follow in her footsteps, she also hopes to give back in her parents’ home country.

    “That’s definitely a strong aspect of my commitment to global health,” she said. “My mother taught me the language and my cultural heritage, and I’m really thankful for that because it gives me a foundation that would allow me to go back to Ethiopia and hopefully contribute.

    “I feel really strongly about giving back. I think Ethiopia could be a strong hub for health care across the African continent and on an international scale, and I’m excited to see how I can be part of bringing that vision for Ethiopia and African health care for that undeserved population.”

    See the full article here .

    Please help promote STEM in your local schools.

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  • richardmitnick 8:52 am on April 5, 2017 Permalink | Reply
    Tags: , Duke University, Jumping Droplets Whisk Away Hotspots in Electronics,   

    From Duke: “Jumping Droplets Whisk Away Hotspots in Electronics” 

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    April 3, 2017
    Ken Kingery

    New technology adds a third dimension to cooling modern electronics.

    Engineers have developed a technology to cool hotspots in high-performance electronics using the same physical phenomenon that cleans the wings of cicadas.

    When water droplets merge, the reduction in surface area causes the release of a small amount of energy. So long as the surface beneath is hydrophobic enough to repel water, this energy is sufficient to make the merged droplet jump away.

    On the wings of cicadas, this phenomenon drives droplets to catch and remove particles of dirt and debris. In the new cooling technology created by engineers at Duke University and Intel Corporation, droplets jump toward hotspots to bring cooling where the electronics need it most.

    The results appear online on April 3, 2017, in the journal Applied Physics Letters.

    “Hotspot cooling is very important for high-performance technologies,” said Chuan-Hua Chen, associate professor of mechanical engineering and materials science at Duke. “Computer processors and power electronics don’t perform as well if waste heat cannot be removed. A better cooling system will enable faster computers, longer-lasting electronics and more powerful electric vehicles.”

    2
    When droplets merge on a super hydrophobic surface, the loss in surface area releases enough energy to make them jump up off the surface.

    The new technology relies on a vapor chamber made of a super-hydrophobic floor with a sponge-like ceiling. When placed beneath operating electronics, moisture trapped in the ceiling vaporizes beneath emerging hotspots. The vapor escapes toward the floor, taking heat away from the electronics along with it.

    Passive cooling structures integrated into the floor of the device then carry away the heat, causing the water vapor to condense into droplets. As the growing droplets merge, they naturally jump off the hydrophobic floor and back up into the ceiling beneath the hotspot, and the process repeats itself. This happens independent of gravity and regardless of orientation, even if the device is upside-down.

    The technology has many advantages over existing cooling techniques. Thermoelectric coolers that act as tiny refrigerators cannot target random hotspot locations, making them inefficient for use over large areas. Other approaches can target moving hotspots, but require additional power inputs, which also leads to inefficiencies.

    3
    A schematic of how the new jumping droplets electronics cooling system works. No image credit.

    The jumping-droplet cooling technology also has a built-in mechanism for vertical heat escape, which is a major advantage over today’s heat spreaders that mostly dissipate heat in a single plane.

    “As an analogy, to avoid flooding, it is useful to spread the rain over a large area. But if the ground is soaked, the water has no vertical pathway to escape, and flooding is inevitable,” said Chen. “Flat-plate heat pipes are remarkable in their horizontal spreading, but lack a vertical mechanism to dissipate heat. Our jumping-droplet technology addresses this technological void with a vertical heat spreading mechanism, opening a pathway to beat the best existing heat spreaders in all directions.”

    There is still much work to be done before Chen’s jumping droplets can compete with today’s cooling technologies. The main challenge is to find suitable materials that work with high-heat vapor over the long term. But Chen remains optimistic.

    “It has taken us a few years to work the system to a point where it’s at least comparable to a copper heat spreader, the most popular cooling solution,” said Chen. “But now, for the first time, I see a pathway to beating the industry standards.”

    This work was supported by Intel Corporation and the National Science Foundation (CBET-12-36373, DMR-11-21107, DGF-11-06401).

    See the full article here .

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  • richardmitnick 12:05 pm on March 1, 2017 Permalink | Reply
    Tags: A Mind—And an Ear—For Big Data, , Data Expeditions, Duke University   

    From Duke: “A Mind—And an Ear—For Big Data” 

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    February 23, 2017
    Ken Kingery

    At Duke, engineering doctoral student Chris Tralie discovered a passion for analyzing the topology of music—and for teaching undergraduates about the power of data science.

    1
    Chris Tralie with advisors John Harer (Math) and Guillermo Sapiro (ECE)

    Chris Tralie wasn’t even working with big data when he came to Duke as a graduate student. But a movement gaining steam here in 2013 helped him realize he had the technical skillset to reveal structures and patterns where others saw chaos—or nothing.

    “There were people working on Big Data problems in various departments when I first got to campus,” said Tralie, a doctoral candidate in electrical & computer engineering (ECE) and a National Science Foundation Graduate Research Fellow. “Then the Information Initiative at Duke launched. It was brilliant because it brought everyone together and let them learn from each other’s work. There was real and sudden excitement in the air.”

    Tralie found his niche while learning about topology with John Harer, a professor of mathematics with a secondary appointment in ECE. The class boiled down to understanding the “shape” of data. Tralie thought, “Why can’t we do this with music?”

    Tralie designed a program that analyzes many different musical parameters of a song and mathematically reduces each time point into 3D space. The resulting shape can help determine which genre of music a song belongs to and can even recognize covers of songs by other bands.

    “Nobody thought you could do that, because of the differences in vocals and instruments,” said Tralie.

    Tralie took his own academic journey and used it to turn other Duke students on to big data—creating a “Data Expedition” using his method for visualizing songs as a fun and approachable way to teach undergraduates how to design data-crunching algorithms.

    Data Expeditions are projects proposed and taught by graduate students within the context of an existing undergraduate course. “Data Expeditions and Data+ both benefit our undergraduates by making technical subjects more relevant and exciting, but they’re also professional development opportunities for our graduate students,” said Robert Calderbank, director of iiD, which sponsors both programs. “Industry and academia both need people who can lead projects and manage multidisciplinary teams, so these experiences can provide a competitive advantage for Duke graduates.”

    “The Data Expeditions were really useful for me growing as a mentor,” said Tralie. “I got to work with really talented students who were still learning the basics and yet had amazing new ideas that I could learn from too. Those skills will translate to my future career, where I hope to be a faculty member advising graduate students of my own someday in engineering or applied math.”

    He also developed a new course for graduate students about using data analytics on video recognition challenges, like tracking heartbeats from video clips. Tralie’s own promising work in that arena can potentially add another element to an app developed to recognize signs of autism by another of his advisors, Guillermo Sapiro, the Edmund T. Pratt, Jr. School Professor of Electrical and Computer Engineering.

    After defending his dissertation this spring, Tralie plans to stay in academia, at least in part because he loves the teaching experiences he has had while at Duke.

    “Mentoring and teaching forces me to explain my work in simple terms, which raises my own understanding of it,” said Tralie. “Plus the students all end up going out and doing their own interesting things, which they can later teach me about in return. They’re like my eyes and ears out there in the fast developing world of Big Data.”

    See the full article here .

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  • richardmitnick 9:02 am on February 23, 2017 Permalink | Reply
    Tags: , , Duke University, Light-driven reaction converts carbon dioxide into fuel, , , Rhodium nanoparticles   

    From Duke via phys.org: “Light-driven reaction converts carbon dioxide into fuel” 

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    phys.org

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    February 23, 2017

    1
    Duke University researchers have engineered rhodium nanoparticles (blue) that can harness the energy in ultraviolet light and use it to catalyze the conversion of carbon dioxide to methane, a key building block for many types of fuels. Credit: Chad Scales

    Duke University researchers have developed tiny nanoparticles that help convert carbon dioxide into methane using only ultraviolet light as an energy source.

    Having found a catalyst that can do this important chemistry using ultraviolet light, the team now hopes to develop a version that would run on natural sunlight, a potential boon to alternative energy.

    Chemists have long sought an efficient, light-driven catalyst to power this reaction, which could help reduce the growing levels of carbon dioxide in our atmosphere by converting it into methane, a key building block for many types of fuels.

    Not only are the rhodium nanoparticles made more efficient when illuminated by light, they have the advantage of strongly favoring the formation of methane rather than an equal mix of methane and undesirable side-products like carbon monoxide. This strong “selectivity” of the light-driven catalysis may also extend to other important chemical reactions, the researchers say.

    “The fact that you can use light to influence a specific reaction pathway is very exciting,” said Jie Liu, the George B. Geller professor of chemistry at Duke University. “This discovery will really advance the understanding of catalysis.”

    The paper appears online Feb. 23 in Nature Communications.

    Despite being one of the rarest elements on Earth, rhodium plays a surprisingly important role in our everyday lives. Small amounts of the silvery grey metal are used to speed up or “catalyze” a number of key industrial processes, including those that make drugs, detergents and nitrogen fertilizer, and they even play a major role breaking down toxic pollutants in the catalytic converters of our cars.

    Rhodium accelerates these reactions with an added boost of energy, which usually comes in the form of heat because it is easily produced and absorbed. However, high temperatures also cause problems, like shortened catalyst lifetimes and the unwanted synthesis of undesired products.

    2
    Rhodium nanocubes were observed under a transmission electron microscope. Credit: Xiao Zhang

    In the past two decades, scientists have explored new and useful ways that light can be used to add energy to bits of metal shrunk down to the nanoscale, a field called plasmonics.

    “Effectively, plasmonic metal nanoparticles act like little antennas that absorb visible or ultraviolet light very efficiently and can do a number of things like generate strong electric fields,” said Henry Everitt, an adjunct professor of physics at Duke and senior research scientist at the Army’s Aviation and Missile RD&E Center at Redstone Arsenal, AL. “For the last few years there has been a recognition that this property might be applied to catalysis.”

    Xiao Zhang, a graduate student in Jie Liu’s lab, synthesized rhodium nanocubes that were the optimal size for absorbing near-ultraviolet light. He then placed small amounts of the charcoal-colored nanoparticles into a reaction chamber and passed mixtures of carbon dioxide and hydrogen through the powdery material.

    When Zhang heated the nanoparticles to 300 degrees Celsius, the reaction generated an equal mix of methane and carbon monoxide, a poisonous gas. When he turned off the heat and instead illuminated them with a high-powered ultraviolet LED lamp, Zhang was not only surprised to find that carbon dioxide and hydrogen reacted at room temperature, but that the reaction almost exclusively produced methane.

    “We discovered that when we shine light on rhodium nanostructures, we can force the chemical reaction to go in one direction more than another,” Everitt said. “So we get to choose how the reaction goes with light in a way that we can’t do with heat.”

    This selectivity—the ability to control the chemical reaction so that it generates the desired product with little or no side-products—is an important factor in determining the cost and feasibility of industrial-scale reactions, Zhang says.

    “If the reaction has only 50 percent selectivity, then the cost will be double what it would be if the selectively is nearly 100 percent,” Zhang said. “And if the selectivity is very high, you can also save time and energy by not having to purify the product.”

    Now the team plans to test whether their light-powered technique might drive other reactions that are currently catalyzed with heated rhodium metal. By tweaking the size of the rhodium nanoparticles, they also hope to develop a version of the catalyst that is powered by sunlight, creating a solar-powered reaction that could be integrated into renewable energy systems.

    “Our discovery of the unique way light can efficiently, selectively influence catalysis came as a result of an on-going collaboration between experimentalists and theorists,” Liu said. “Professor Weitao Yang’s group in the Duke chemistry department provided critical theoretical insights that helped us understand what was happening. This sort of analysis can be applied to many important chemical reactions, and we have only just begun to explore this exciting new approach to catalysis.”

    Read more at: https://phys.org/news/2017-02-light-driven-reaction-carbon-dioxide-fuel.html#jCp

    See the full article here .

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    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”

     
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