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Wednesday, March 21st, 2018

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    1:59p
    Soft robotic fish swims alongside real ones in coral reefs

    This month scientists published rare footage of one of the Arctic’s most elusive sharks. The findings demonstrate that, even with many technological advances in recent years, it remains a challenging task to document marine life up close.

    But MIT computer scientists believe they have a possible solution: using robots.

    In a paper out today, a team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) unveiled “SoFi,” a soft robotic fish that can independently swim alongside real fish in the ocean.

    During test dives in the Rainbow Reef in Fiji, SoFi swam at depths of more than 50 feet for up to 40 minutes at once, nimbly handling currents and taking high-resolution photos and videos using (what else?) a fisheye lens.

    Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down. The team also used a waterproofed Super Nintendo controller and developed a custom acoustic communications system that enabled them to change SoFi’s speed and have it make specific moves and turns.

    “To our knowledge, this is the first robotic fish that can swim untethered in three dimensions for extended periods of time,” says CSAIL PhD candidate Robert Katzschmann, lead author of the new journal article published today in Science Robotics. “We are excited about the possibility of being able to use a system like this to get closer to marine life than humans can get on their own.”

    Katzschmann worked on the project and wrote the paper with CSAIL director Daniela Rus, graduate student Joseph DelPreto and former postdoc Robert MacCurdy, who is now an assistant professor at the University of Colorado at Boulder.

    How it works

    Existing autonomous underwater vehicles (AUVs) have traditionally been tethered to boats or powered by bulky and expensive propellers.

    In contrast, SoFi has a much simpler and more lightweight setup, with a single camera, a motor, and the same lithium polymer battery that’s found in consumer smartphones. To make the robot swim, the motor pumps water into two balloon-like chambers in the fish’s tail that operate like a set of pistons in an engine. As one chamber expands, it bends and flexes to one side; when the actuators push water to the other channel, that one bends and flexes in the other direction.

    These alternating actions create a side-to-side motion that mimics the movement of a real fish. By changing its flow patterns, the hydraulic system enables different tail maneuvers that result in a range of swimming speeds, with an average speed of about half a body length per second.

    “The authors show a number of technical achievements in fabrication, powering, and water resistance that allow the robot to move underwater without a tether,” says Cecilia Laschi, a professor of biorobotics at the Sant'Anna School of Advanced Studies in Pisa, Italy. “A robot like this can help explore the reef more closely than current robots, both because it can get closer more safely for the reef and because it can be better accepted by the marine species.”

    The entire back half of the fish is made of silicone rubber and flexible plastic, and several components are 3-D-printed, including the head, which holds all of the electronics. To reduce the chance of water leaking into the machinery, the team filled the head with a small amount of baby oil, since it’s a fluid that will not compress from pressure changes during dives.

    Indeed, one of the team’s biggest challenges was to get SoFi to swim at different depths. The robot has two fins on its side that adjust the pitch of the fish for up and down diving. To adjust its position vertically, the robot has an adjustable weight compartment and a “buoyancy control unit” that can change its density by compressing and decompressing air.

    Katzschmann says that the team developed SoFi with the goal of being as nondisruptive as possible in its environment, from the minimal noise of the motor to the ultrasonic emissions of the team’s communications system, which sends commands using wavelengths of 30 to 36 kilohertz.

    “The robot is capable of close observations and interactions with marine life and appears to not be disturbing to real fish,” says Rus.

    The project is part of a larger body of work at CSAIL focused on soft robots, which have the potential to be safer, sturdier, and more nimble than their hard-bodied counterparts. Soft robots are in many ways easier to control than rigid robots, since researchers don’t have to worry quite as much about having to avoid collisions.

    “Collision avoidance often leads to inefficient motion, since the robot has to settle for a collision-free trajectory,” says Rus, the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science at MIT. “In contrast, a soft robot is not just more likely to survive a collision, but could use it as information to inform a more efficient motion plan next time around.”

    As next steps the team will be working on several improvements on SoFi. Katzschmann plans to increase the fish’s speed by improving the pump system and tweaking the design of its body and tail.

    He says that they also plan to soon use the on-board camera to enable SoFi to automatically follow real fish, and to build additional SoFis for biologists to study how fish respond to different changes in their environment.

    “We view SoFi as a first step toward developing almost an underwater observatory of sorts,” says Rus. “It has the potential to be a new type of tool for ocean exploration and to open up new avenues for uncovering the mysteries of marine life.”

    This project was supported by the National Science Foundation.

    4:59p
    How often do medical problems lead to bankruptcy?

    A team of researchers led by an MIT economist has found that medical expenses account for roughly 4 percent of bankruptcy filings among nonelderly adults in the U.S.

    The scholars combined medical records and financial data for hundreds of thousands of people to pinpoint the percentage of bankruptcies caused by medical costs, thus giving new empirical precision to a topic of considerable policy importance.

    The 4 percent figure is lower than some commonly cited estimates, but the new statistic comes with a twist: It is part of a larger research project that found multiple negative economic consequences of having medical problems, including a 20 percent drop in earnings and an 11 percent drop in employment for adults between ages 50 and 59 who had been hospitalized.

    This combination of effects — fewer medically rooted bankruptcies but pervasive workplace troubles for people with health issues — underscores the need to understand the full range of financial challenges people face due to their medical needs, the researchers say.  

    “It doesn’t mean there aren’t really adverse economic consequences from adverse health,” says MIT economist Amy Finkelstein, co-author of a new paper outlining the findings. “It just turns out they’re not [strictly] about bankruptcy. They’re much more about lost employment and earnings.”

    The article, “Myth and Measurement — The Case of Medical Bankruptcies,” appears today in the New England Journal of Medicine. The co-authors are Finkelstein, who is the John and Jennie S. MacDonald Professor of Economics at MIT; Carlos Dobkin, a professor of economics at the University of California at Santa Cruz; Raymond Kluender, a PhD student in economics at MIT; and Matthew Notowidigdo, an associate professor of economics at Northwestern University.

    The study’s main source of data consists of hospitalization records from the years 2003–2007 and credit reports from 2002–2011, from the state of California, for people over age 25. The study included about 780,000 people with health insurance and roughly 150,000 people without health insurance. That information was available to the research team only under particular conditions that preserved the anonymity of the people being studied.

    By examining cases where previously healthy people were hospitalized, then tracking the finances of those people in subsequent years, the researchers were able to study the issue in a way that delivers a solid link between cause and effect — namely, how often medical events themselves are the principal cause of changes in financial status.  

    Some of the previous research on the frequency of medically caused bankruptcies used survey data to produce estimates; one commonly cited figure is that 60 percent of bankruptcies have medical causes. However, those estimates used self-reported data about health issues, among those who filed for bankruptcy, without establishing that medical costs were the principal cause of those bankruptcies.

    “The approach of the prior literature was just conceptually not right,” Finkelstein says.

    The current study found that poor health has a larger impact on the uninsured than the insured: For instance, as a related, recently published paper by the research team shows, four years after being admitted to the hospital, people with insurance owe $300 more in unpaid medical bills, on average, while people without insurance have an average increase of $6,000 in unpaid medical bills.

    The researchers also found that medically caused bankruptcies are minimal among the elderly — those over age 64 — who are likely to have Medicare and who tend to be retired, thus not suffering the earnings reductions that ill people in the workforce experience.

    “We suspect what’s driving the [level of] bankruptcy we find is the fact that some people lose their job because of adverse health, and in turn that causes them to go bankrupt,” Finkelstein says. “That’s just not going to [apply to] the elderly, because they’re not working, so they don’t have the labor market risk from poor health.”

    To be sure, Finkelstein acknowledges, the current study has some aspects that may need additional scrutiny. By focusing on examples involving hospitalization, the researchers could be missing some cases in which accumulated medical costs of other kinds drive people to bankruptcy — including medical costs incurred by children, parents, or other relatives.

    “We’re not going to go to the mat over the idea that [the rate of medically caused bankruptcies] is always going to be 4 percent in every context and by every measurement,” Finkelstein says. Still, she notes, the accurate figure is likely to be much lower than other recent estimates imply.

    To Finkelstein, the findings also have a clear upshot for policymakers and legislators. Grasping the full breadth of the economic consequences of poor health might affect the priorities of lawmakers, directing them to seek solutions for the lost income that many people endure after a serious medical event.

    “Focusing on bankruptcy might lead you to think about bankruptcy protection reform,” Finkelstein says, “and while that may or may not be useful in its own right, if you’re interested in the economic consequences of poor health, you’re missing a main issue and potential policy responses — thinking about how we might want to structure sick pay and disability insurance.”

    Some of the research data pertaining to job outcomes, covering the years 1992–2012 for nearly 10,000 people, was obtained from the Health and Retirement Study (HRS), a biannual U.S. national survey supported by the National Institute on Aging and the Social Security Administration, and directed by the University of Michigan.

    Support for the study came in part from the National Institute on Aging and the National Science Foundation.

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