Tuesday, January 21st, 2014

Time	Event
3:00p	MIT and Harvard release working papers on open online courses MIT and Harvard University today announced the release of a series of working papers based on 17 online courses offered on the edX platform. Run in 2012 and 2013, the courses analyzed drew upon diverse topics — from ancient Greek poetry to electromagnetism — and an array of disciplines, from public health to engineering to law. The working paper series features detailed reports about individual courses; these reports reveal differences and commonalities among massive open online courses (MOOCs). In the coming weeks, data sets and interactive visualization tools will also be made available. Led by Isaac Chuang, a professor of electrical engineering and computer science at MIT, and Andrew Ho, an associate professor in Harvard’s Graduate School of Education, the collaborative research effort was in service of a mutual goal — “to research how students learn and how technologies can facilitate effective teaching both on-campus and online” — part of a mission statement established when MIT and Harvard joined to form edX, the not-for-profit online learning platform, in May 2012. The papers analyze an average of 20 gigabytes of data per course and draw on interviews with faculty and course teams as well as student metrics. Key takeaways Takeaway 1: Course completion rates, often seen as a bellwether for MOOCs, can be misleading and may at times be counterproductive indicators of the impact and potential of open online courses. The researchers found evidence of large numbers of registrants who may not have completed a course, but who still accessed substantial amounts of course content. Across the 17 MITx and HarvardX courses covered in the reports, 43,196 registrants earned certificates of completion. Additionally, another 35,937 registrants explored half or more of the units in a course without achieving certification. “We found students in the courses who engaged with every single piece of the courseware, students who only read text or viewed videos, students who only took assessments or completed problem sets, and students representing nearly every possible combination of these behaviors,” Chuang explains. “Experimentation is part of the learning process.” An additional 469,702 registrants viewed less than half of the units in a course and another 292,852 registrants never engaged with the online content. In total, the 17 online courses drew 841,687 registrations from 597,692 unique users. The reports note that many faculty encouraged learners to participate in the course experiences in whatever ways they found useful, whether or not that involved trying to earn a certificate. For such faculty, the participation of engaged auditors was just as important as the participation of those who completed the assessments of the course. “A fixation on completion rates limits our imagination of what might be possible with MOOCs. A better criterion for success might be for students to complete more of the course than they thought they would, or to learn more than they might have expected when they first clicked on a video or course forum,” Ho says. Takeaway 2: Most MOOC attrition happened after students first registered for a course. On average, 50 percent of people left within a week or two of enrolling. After that window, attrition rates decreased substantially. The average probability of a student ceasing to engage in the second week of the course declined to 16 percent. While the persistence rates in MOOCs look very different from those of conventional courses in higher education, they look very similar to how people interact with other Web-based media, such as video or social network sites. Many registrants briefly browse a MOOC, while only a smaller group persist and become more engaged over time. The asynchronous nature of the MITx and HarvardX courses also turned out to be an important factor related to engagement: Some students registered for courses months in advance of the start date, and other registered months after the course had launched. In some circumstances, students joined courses in the week before the final deadline for all graded materials, completing enough assessments to earn a certificate in the final week. In some courses, as many as one in five enrollments took place after the course certificate was no longer available. Takeaway 3: Given the “massive” scale of some MOOCs, small percentages are often still large numbers of students — and signify a potentially large impact. Demographic information about registrants can be misleading without context. The most typical course registrant in these initial courses was a male with a bachelor’s degree, age 26 or older. However, that profile describes fewer than one in three registrants (222,847, or 31 percent). A total of 234,463 registrants (33 percent) reported a high-school education or less; 45,884 (6.3 percent) reported that they were 50 or older; and 20,745 (2.7 percent) had IP or mailing addresses from countries on the United Nations’ list of Least Developed Countries. “While typical MOOC registrants have a college degree already, hundreds of thousands of our registrants do not. Many of our MOOC registrants are from the United States, but 72 percent are from abroad. These MOOCs are reaching many nontraditional and underserved communities of students, very different from typical students on campuses at traditional universities,” Chuang says. One interesting subpopulation is the group of people who enroll in and complete multiple courses. More than 4,000 registrants across MITx and HarvardX earned more than one certificate, including 1,912 who earned at least one certificate from each institution. Seventy-six registrants earned five or more certificates. “Context is so important to understanding these results,” Ho adds. “A graduate-level course in public health should attract different registrants, on average, than an introductory physics course, or a course on global poverty. In this light, it’s wonderful that so many students are engaging so deeply in courses across topics and institutions.” Future directions Looking ahead, Chuang and Ho view the publication of the working papers, and the open sharing of such data, as a key activity in a broad, positive dialogue in higher education. Specifically, they emphasize that the rise of MOOCs has sparked and encouraged experimentation in teaching and in pedagogical research, benefiting both teachers and students. New tools, they contend, give faculty more flexibility and offer novel opportunities to run experiments and gather data. Likewise, online learning platforms put students in the driver’s seat, allowing an individual to engage in a manner that best suits his or her needs. “This isn’t just about MOOCs,” Ho says. “This is about the democratization of learning: Learners are in control. We are at the beginning of an exciting effort to understand how people learn and how to educate well and effectively at scale.” Finally, the researchers expect the working papers and data to serve as one benchmark for future studies on MOOCs and support further work in the science of learning. “The story hidden underneath this series of reports may be this: Institutions like ours are coming to appreciate how cross-institutional educational collaborations involving many students and many courses can open new routes to understand and improve student learning — making a difference around the world and back here on campus,” Chuang says. The lead authors of the MITx and HarvardX course reports were Daniel T. Seaton, a postdoc in MIT’s Office of Digital Learning, and Justin Reich, a HarvardX research fellow. (Comment on this)
4:00p	Seeing things: A new transparent display system could provide heads-up data Transparent displays have a variety of potential applications — such as the ability to see navigation or dashboard information while looking through the windshield of a car or plane, or to project video onto a window or a pair of eyeglasses. A number of technologies have been developed for such displays, but all have limitations. Now, researchers at MIT have come up with a new approach that can have significant advantages over existing systems, at least for certain kinds of applications: a wide viewing angle, simplicity of manufacture, and potentially low cost and scalability. The innovative system is described in a paper published this week in the journal Nature Communications, co-authored by MIT professors Marin Soljačić and John Joannopoulos, graduate student Chia Wei Hsu, and four others. Many current “heads-up” display systems use a mirror or beam-splitter to project an image directly into the user’s eyes, making it appear that the display is hovering in space somewhere in front of him. But such systems are extremely limited in their angle of view: The eyes must be in exactly the right position in order to see the image at all. With the new system, the image appears on the glass itself, and can be seen from a wide array of angles. Other transparent displays use electronics directly integrated into the glass: organic light-emitting diodes for the display, and transparent electronics to control them. But such systems are complex and expensive, and their transparency is limited. The secret to the new system: Nanoparticles are embedded in the transparent material. These tiny particles can be tuned to scatter only certain wavelengths, or colors, or light, while letting all the rest pass right through. That means the glass remains transparent enough to see colors and shapes clearly through it, while a single-color display is clearly visible on the glass. To demonstrate the system, the team projected a blue image in front of a scene containing cups of several colors, all of which can clearly be seen through the projected image. While the team’s demonstration used silver nanoparticles — each about 60 nanometers across — that produce a blue image, they say it should be possible to create full-color display images using the same technique. Three colors (red, green, and blue) are enough to produce what we perceive as full-color, and each of the three colors would still show only a very narrow spectral band, allowing all other hues to pass through freely. “The glass will look almost perfectly transparent,” Soljačić says, “because most light is not of that precise wavelength” that the nanoparticles are designed to scatter. That scattering allows the projected image to be seen in much the same way that smoke in the air can reveal the presence of a laser beam passing through it. Such displays might be used, for example, to project images onto store windows while still allowing passersby to see clearly the merchandise on display inside, or to provide heads-up windshield displays for drivers or pilots, regardless of viewing angle. Soljačić says that his group’s demonstration is just a proof-of-concept, and that much work remains to optimize the performance of the system. Silver nanoparticles, which are commercially available, were selected for the initial testing because it was “something we could do very simply and cheaply,” Soljačić says. The team’s promising results, even without any attempt to optimize the materials, “gives us encouragement that you could make this work better,” he says. The particles could be incorporated in a thin, inexpensive plastic coating applied to the glass, much as tinting is applied to car windows. This would work with commercially available laser projectors or conventional projectors that produce the specified color. “This is a very clever idea using the spectrally selective scattering properties of nanoparticles to create a transparent display,” says Shanhui Fan, a professor of electrical engineering at Stanford University who was not involved in this work. “I think it is a beautiful demonstration.” The work, which also included MIT graduate student Bo Zhen, recent PhD recipient Wenjun Qiu, MIT affiliate Ofer Shapira, and Brendan Lacey of the U.S. Army Edgewood Chemical Biological Center, was supported by the Army Research Office and the National Science Foundation. (Comment on this)
7:12p	New surface treatment stops scale buildup You’ve probably seen it in your kitchen cookware, or inside old plumbing pipes: scaly deposits left over time by hard, mineral-laden water. It happens not only in pipes and cooking pots in the home, but also in pipelines and valves that deliver oil and gas, and pipes that carry cooling water inside power plants. Scale, as these deposits are known, causes inefficiencies, downtime, and maintenance issues. In the oil and gas industry, scale has sometimes led to the complete shutdown, at least temporarily, of operating wells. So addressing this problem could have a big payoff. Now a team of researchers at MIT has come up with a potential solution to this huge but little-recognized problem. A new kind of surface treatment — involving nanoscale texturing of the surface, which is then coated with a lubricating liquid — can reduce the rate of scale formation at least tenfold, they have found. The findings are reported this week in a paper in the journal Advanced Materials Interfaces written by graduate student Srinivas Subramanyam, postdoc Gisele Azimi, and Kripa Varanasi, the Doherty Associate Professor of Ocean Utilization in MIT’s Department of Mechanical Engineering. “You can see [scale] pretty much everywhere,” Varanasi says. In the home, these deposits are mostly an annoyance, but in industry they can cause “lost productivity, and the ways of removing [them] can be environmentally harmful,” typically involving the use of harsh chemicals. And in power plants and desalination plants, scale can cause significant efficiency losses, because it acts as a thermal barrier that impairs cooling or condensing in heat exchangers. The problem arises because water often contains large amounts of dissolved salts and minerals. The ability of water to dissolve these materials depends on solubility, so if the water cools or evaporates, the solution may become supersaturated: It contains more of the dissolved material than it can accommodate, so some begins to precipitate out. It’s the same principle that causes fogging on a cold glass when warm, moist air cools suddenly as it meets a cooler surface. For the most part, engineers have dealt with the problem by overdesigning systems, Varanasi says: using pipes that are much larger than needed, for example, in anticipation of the partial blockages that scaling will cause, or a larger surface area, in the case of heat exchangers. The problem is far from new, Subramanyam points out: “Cooking pots from ancient times have this buildup,” he says. “We don’t have good solutions yet.” Though it remains to be proven on an industrial scale, the new approach developed by the MIT team could make a significant difference in the rate of scale formation, and in many situations may prevent it altogether. Their approach sounds deceptively simple: effective nanotexturing of the surface and filling the resulting textures with a lubricant. The texturing depends mostly on the scale of the bumps and grooves produced; the precise shapes don’t seem to matter. So a variety of techniques can be used to create that texture — including applying a textured coating to the surface, or chemically etching it in place. The researchers also describe a process for selecting appropriate lubricants that can not only increase the energy barrier for scale formation, but also spread on the textured solid, making the surface “smooth” and reducing the nucleation sites available for scale formation. Previous attempts to prevent or reduce scale formation have typically involved adding a coating (such as Teflon) to a surface to prevent minerals from bonding to it. The problem with that approach, Varanasi explains, is that these coatings can wear out, just as the coating on a nonstick frying pan often degrades with use. And if there’s even a pinprick of a hole in that coating, he says, that provides a place for scale to begin forming. With the new method, once the nanotexture has been created on the surface, oil or another lubricating liquid is applied to that surface. The tiny nanoscale grooves capture this liquid, holding it firmly in place through capillary action, Varanasi says. Unlike a solid nonstick coating, the liquid can flow to fill any gaps, spread on the surface textures, and can be replenished continually if some is washed away. “Even if there’s mechanical damage, the lubricant can return to that surface,” Subramanyam says. “It can maintain its smoothness for an extended period of time.” Because this lubricant layer is vanishingly thin — just a few hundred nanometers in thickness — protecting a surface for decades would require only a tiny amount of lubricant. Reservoirs built into a section of pipe could supply lubrication for the lifetime of the equipment, Varanasi says. In the case of oil pipelines, “the lubricant is already there,” and oil captured by the surface texturing could protect the pipe surfaces. Jurgen Rühe, head of the Laboratory for Chemistry and Physics of Interfaces at the University of Freiburg, who was not involved in this research, says this represents a “very significant finding and an important scientific advancement.” He calls the team’s approach to reducing scale formation “novel and creative,” and says it “could have potential impact in all areas where water is heated and steam is generated.” After further laboratory testing to determine the best lubricants and texturing methods for particular applications, this system could be ready for commercial applications in as little as three years, the researchers say. The work was supported by the MIT Energy Initiative. (Comment on this)

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