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Wednesday, February 26th, 2014
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| 4:30p |
In praise of the Institute’s unsung heroes
People who regularly go above and beyond the requirements of their jobs — providing exceptional service, help, and encouragement to their colleagues and community — often receive little formal recognition for their outstanding efforts.
MIT annually presents a series of Excellence Awards to honor such dedicated work; this year, for the first time, the awards expanded to include the Collier Medal, in memory of MIT Police Officer Sean Collier, who was killed in the line of duty last April 18. This award will be given annually to an individual or group that embodies the character and qualities that Collier exhibited as a member of the MIT community.
Fittingly, the first Collier Medal went to the 56 volunteers, mostly students, who operate MIT Emergency Medical Services (MIT EMS), a student-run ambulance service. Many MIT EMS members were close friends of Collier, and some were called upon to transport the wounded officer to Massachusetts General Hospital after last year’s shooting.
“Last year, through circumstances none of us will ever forget, Officer Collier gave his life protecting our community,” MIT President L. Rafael Reif said yesterday in presenting the Collier Medal. “So that his spirit will live on at MIT, this is a fresh opportunity to express our gratitude that he lived and worked among us.”
MIT EMS, Reif said, exemplifies “a distinct MIT blend of leadership and problem-solving. The time, energy and expertise they make available goes far beyond what is expected of a student group. … They even designed a new ambulance, which is one of the safest in the country.”
Collier, Reif said, had worked closely with MIT EMS volunteers, and “wrote a letter praising them, months before his death.” He added, “It is with full hearts and the deepest appreciation that the members of MIT EMS are receiving the recognition they deserve.”
The annual awards ceremony, held yesterday in Kresge Auditorium, presented a variety of awards to members of the staffs of MIT and Lincoln Laboratories, in six different categories. Twelve members of MIT Medical received “Sustaining MIT” awards in recognition of the highly efficient flu clinics they mounted, which succeeded this winter in getting 25 percent of the MIT community vaccinated.
Four individuals and three teams were recognized as “Unsung Heroes,” and five others received awards for “Serving the Client.” Senior admissions counselor Chris Peterson received an award for “Innovative Solutions,” in recognition of a creative video production he led. Three others received awards for “Bringing Out the Best,” and 12 others were recognized for “Advancing Inclusion and Global Perspectives.”
A surprise award was added at the end, in recognition of MIT’s outgoing vice president for human resources, Alison Alden, who is retiring after seven years at the Institute.
Excellence Award recipients are nominated by their peers, and selected following careful evaluation by a committee of MIT staffers. Recipients receive a cash award of $2,000 and a snow globe containing a replica of MIT’s Building 10 — and often a cheering, pompom-waving ovation from colleagues in the audience.
| | 10:00p |
Need a water filter? Peel a tree branch
If you’ve run out of drinking water during a lakeside camping trip, there’s a simple solution: Break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water.
In fact, an MIT team has discovered that this low-tech filtration system can produce up to four liters of drinking water a day — enough to quench the thirst of a typical person.
In a paper published this week in the journal PLoS ONE, the researchers demonstrate that a small piece of sapwood can filter out more than 99 percent of the bacteria E. coli from water. They say the size of the pores in sapwood — which contains xylem tissue evolved to transport sap up the length of a tree — also allows water through while blocking most types of bacteria.
Co-author Rohit Karnik, an associate professor of mechanical engineering at MIT, says sapwood is a promising, low-cost, and efficient material for water filtration, particularly for rural communities where more advanced filtration systems are not readily accessible.
“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily,” Karnik says. “The idea here is that we don’t need to fabricate a membrane, because it’s easily available. You can just take a piece of wood and make a filter out of it.”
The paper’s co-authors include Michael Boutilier and Jongho Lee from MIT, Valerie Chambers from Fletcher-Maynard Academy in Cambridge, Mass., and Varsha Venkatesh from Jericho High School in Jericho, N.Y.
Tapping the flow of sap
There are a number of water-purification technologies on the market today, although many come with drawbacks: Systems that rely on chlorine treatment work well at large scales, but are expensive. Boiling water to remove contaminants requires a great deal of fuel to heat the water. Membrane-based filters, while able to remove microbes, are expensive, require a pump, and can become easily clogged.
Sapwood may offer a low-cost, small-scale alternative. The wood is comprised of xylem, porous tissue that conducts sap from a tree’s roots to its crown through a system of vessels and pores. Each vessel wall is pockmarked with tiny pores called pit membranes, through which sap can essentially hopscotch, flowing from one vessel to another as it feeds structures along a tree’s length. The pores also limit cavitation, a process by which air bubbles can grow and spread in xylem, eventually killing a tree. The xylem’s tiny pores can trap bubbles, preventing them from spreading in the wood.
“Plants have had to figure out how to filter out bubbles but allow easy flow of sap,” Karnik observes. “It’s the same problem with water filtration where we want to filter out microbes but maintain a high flow rate. So it’s a nice coincidence that the problems are similar.”
Seeing red
To study sapwood’s water-filtering potential, the researchers collected branches of white pine and stripped off the outer bark. They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps.
Before experimenting with contaminated water, the group used water mixed with red ink particles ranging from 70 to 500 nanometers in size. After all the liquid passed through, the researchers sliced the sapwood in half lengthwise, and observed that much of the red dye was contained within the very top layers of the wood, while the filtrate, or filtered water, was clear. This experiment showed that sapwood is naturally able to filter out particles bigger than about 70 nanometers.
However, in another experiment, the team found that sapwood was unable to separate out 20-nanometer particles from water, suggesting that there is a limit to the size of particles coniferous sapwood can filter.
Picking the right plant
Finally, the team flowed inactivated, E. coli-contaminated water through the wood filter. When they examined the xylem under a fluorescent microscope, they saw that bacteria had accumulated around pit membranes in the first few millimeters of the wood. Counting the bacterial cells in the filtered water, the researchers found that the sapwood was able to filter out more than 99 percent of E. coli from water.
Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size.
Karnik says his group now plans to evaluate the filtering potential of other types of sapwood. In general, flowering trees have smaller pores than coniferous trees, suggesting that they may be able to filter out even smaller particles. However, vessels in flowering trees tend to be much longer, which may be less practical for designing a compact water filter.
Designers interested in using sapwood as a filtering material will also have to find ways to keep the wood damp, or to dry it while retaining the xylem function. In other experiments with dried sapwood, Karnik found that water either did not flow through well, or flowed through cracks, but did not filter out contaminants.
“There’s huge variation between plants,” Karnik says. “There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away and replace at almost no cost. It’s orders of magnitude cheaper than the high-end membranes on the market today.”
While the pores in sapwood are too big to filter out salts, Saurya Prakash, an assistant professor of mechanical engineering at Ohio State University, says the design could be useful in parts of the world where people collect surface water, which can be polluted with fine dust and particles of decaying plant and animal matter. Most of this detritus, Prakash says, could easily be filtered out by the group’s design.
“The xylem tissue acts as a natural filter, similar to a manmade membrane,” says Prakash, who was not involved in the research. “The study by the Karnik group shows that use of abundant, naturally occurring materials could pave the way for a new generation of water filters that are potentially low-cost enough to be disposable.”
This research was supported by the James H. Ferry Jr. Fund for Innovation in Research Education. | | 10:00p |
Social media’s ‘law’ of short messages
In the last year or two, you may have had some moments — during elections, sporting events, or weather incidents — when you found yourself sending out a flurry of messages on social media sites such as Twitter.
You are not alone, of course: Such events generate a huge volume of social-media activity. Now a new study published by researchers in MIT’s Senseable City Lab shows that social-media messages grow shorter as the volume of activity rises at these particular times.
“This helps us better understand what is going on — the way we respond to things becomes faster and more impulsive,” says Carlo Ratti, director of the Senseable City Lab and an associate professor of the practice in MIT’s Department of Urban Studies and Planning.
Take Twitter, where individual messages have a 140-character limit. The study found that at times of lower activity, the most popular length of tweets ranges from about 70 to 120 characters. But at moments of much greater traffic — when messages are sent up to 200 times as frequently — the highest concentration of tweets is only around 25 characters in length, and declines sharply to a low at about the 130-character mark.
“If you plot the rate of the messages versus the length, then you can find a mathematical relation between these two things during [major] events,” adds Michael Szell, a researcher at the Senseable City Lab.
Ratti, Szell, and Senseable City researcher Sebastian Grauwin are co-authors of a new paper about the study, “Contraction of online response to major events,” published today in the journal PLoS ONE.
Three words for golf fans: You the man!
To conduct the study, the researchers looked at data from several social-media sources at a variety of moments. The Twitter data, for example, comes from April 2012 and involves tweets on the subject of The Masters, one of golf’s four major tournaments. That year, golfer Bubba Watson won the tournament in a dramatic playoff against Louis Oosthuizen, prompting a flurry of shorter tweets.
As the paper drolly notes, a “large part of these tweets contain the name ‘Bubba’ followed by a varying number of exclamation marks.’”
Other data used in the study includes social media activity during election night in the U.S. in November 2012, and during a major snowstorm in February 2013.
“We wanted to see if this was Twitter-specific or if it happens in other media as well,” Szell says. “Basically we found this effect every time there was an event going on. And when there was no event, we did not find this effect.”
Renaud Lambiotte, a mathematician at the University of Namur in Belgium who has read the study, calls it “an interesting piece of research” that may lead to fruitful follow-up work, “in particular for the modeling of the relation between behavioral response and emotional stimuli.” Lambiotte suggests that well-designed online social experiments may yield further insight about behavior on social media.
The Senseable City Lab conducts large-scale data projects, often based on mobile technology or social media, to evaluate patterns of activity in urban environments or among technologically connected networks of people.
“It’s all about detecting specific signatures of how people behave, in any kind of aspect of their life, whether it’s tweeting, commenting, or moving around,” says Grauwin, who is working in the Senseable City Lab via a fellowship with the technology firm Ericsson.
The current study also revealed what Grauwin calls an “index of frustration” among some social-media users: namely, during major events, a small minority of users run up against the 140-limit on Twitter.
Ratti suggests that further studies of message length will continue to uncover more data that could be useful in the design of social-media platforms. He also thinks more research can shed light on the behavioral mechanisms that lead people to send shorter messages: Are people doing this independently, or in response to seeing other short messages?
“You get this kind of herd effect,” Ratti says. “The paper suggests this is an interesting problem to look at.”
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