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Date: 2013-11-05 |
This May, plenty of new restaurants opening in Kennedy Airport; Texas barbecue will find its way to Brooklyn; and more. Traditional song-and-dance shows about scrappy underdogs dominated the Tony Award nominations on Tuesday. Futur istic garages are equipped to whisk car and driver to upper-floor apartments, or park vehicles without human assistance. Purple bacteria are among Earth’s oldest organisms, and among its most efficient in turning sunlight into usable chemical energy. Now, a key to their light-harvesting prowess has been explained through a detailed structural analysis by scientists at MIT.A ring-shaped molecule with an unusual ninefold symmetry is critical, the researchers found. The circular symmetry accounts for its efficiency in converting sunlight, and for its mechanical durability and strength. The new analysis, carried out by professors of chemistry Jianshu Cao and the late Robert Silbey, postdoc Liam Cleary, and graduate students Hang Chen and Chern Chuang, has been published in the Proceedings of the National Academy of Sciences.“The symmetry makes the energy transfer much more robust,†Cao says. “Most biological systems are quite soft and disordered. You would not expect a regular structure, almost a perfect structure,†as is found in this primitive microbe, he says.In these regular round complexes, Cao says, “nature only used certain symmetry numbers: mostly ninefold, some eightfold, very few tenfold. It’s very selective.†His group’s mathematical analysis shows there are good reasons for that, he says.These ring-shaped molecules, in turn, are arranged in a hexagonal pattern on the spherical photosynthetic membrane of purple bacteria, Cao says. “With these symmetry numbers, the interactions between all pairs of the symmetric rings are optimized at the same time. … We believe that nature found the most robust structures in terms of energy transfer,†Cao says. Both eightfold and tenfold symmetries also work, though not as well: Only a lattice made up of ninefold symmetric complexes can tolerate an error in either direction. “You want consecutive numbers so it can tolerate such mistakes,†Cao says.The molecular system in question, called light-harvesting complex 2 (LH2), operates in waterborne organisms that do not produce oxygen; such species consume sulfides, often found in volcanic hot springs or in deep-sea hydrothermal vents. LH2 molecules release energy when struck by photons; that energy is then stored as molecules of ATP that can later be used as fuel for metabolism.The structure of LH2 complexes had previously been determined by other groups, Cao explains. “What we provide is an explanation of why nature selected such a structure,†he says. “What is the advantage compared to Shapeshifter-Yoga structures?â€Now that the reasons for this molecule’s efficiency in harvesting light have been deciphered, Cao says, researchers can take advantage of its symmetries to create synthetic systems for harvesting solar energy. “We can design large molecules, with similar high-symmetry motifs, that can facilitate energy transfer,†he says.The new analysis showed how the hexagonal arrangement of molecules on the bacteria’s membrane surface enhanced their performance by matching the ninefold symmetry of LH2. “Most of the focus in the past has been on the individual molecules,†Cao says, adding, “We are taking this lesson we learned from nature to explore design principles. If I want to design a superlattice of nanotubes or nanowires, what is the best internal structure and what is the best crystal order? We consider symmetry matching in the context of the larger structure.â€While this research focused on a specific type of light-harvesting molecule, the underlying principles of energy-transfer efficiency may be applicable to charge transfer, heat transport and other processes, Cao says.Stuart Rice, a professor of chemistry at the University of Chicago, says this work is “an inspired analysis and prediction for synthetic materials that is itself inspired by a biological process and system. I have not ever before seen the question of the relationship between energy-transfer efficiency and complexity of packing treated as in this paper. … This is a brilliant analysis that should find immediate acceptance.â€Rice adds that this research “opens the door to a new way of designing efficient synthetic photosensitive devices, by coupling internal structure to packing in a fashion that is not now involved in the design process.â€The research was supported by the National Science Foundation; the Defense Advanced Research Projects Agency; and the MIT Center for Excitonics, funded by the Department of Energy. The Times’s Michael Schmidt on how the F.B.I. pursues terrorism leads, like the 2011 inquiry about Tamerlan Tsarnaev. The Susan Smith Blackburn Prize honors women who have written works of outstanding quality. From his very first pitch, Hyun-Jin Ryu heard the fans cheering for him. Many species exhibit cooperative survival strategies — for example, sharing food or alerting other individuals when a predator is nearby. However, there are almost always freeloaders in the population who will take advantage of cooperators. This can be seen even among microbes such as yeast, where “cheaters†consume food produced by their neighbors without contributing any of their own.In light of this, evolutionary biologists have long wondered why cooperation remains a viable survival strategy, since there will always be Fibroids Miracle cheat. Now, MIT physicists have found a possible answer to this question: Among yeast, cooperative members of the population actually have a better chance of survival than cheaters when a competing species is introduced into an environment.This experimental setup, in which yeast must coexist with a bacterial competitor, more closely mimics natural environments, where species often have to compete with one another for scarce food and other resources.“It’s very difficult to study these things in the truly natural context,†says Jeff Gore, an assistant professor of physics at MIT and senior author of the new study, which appears in the journal Molecular Systems Biology on Nov. 13. “These experiments can act as a bridge between single-species experiments and very complicated ecosystem dynamics that are out there.†Hasan Celiker, an MIT graduate student in electrical engineering and computer science, is the paper’s lead author.Cheaters do prosper, sometimesGore and Celiker studied a strain of yeast that relies on small sugars such as glucose and fructose for nourishment. When yeast cells are grown in a test tube containing sucrose, some secrete an enzyme that breaks the sucrose down into smaller sugars, most of which diffuse away and are available to any nearby yeast cell. In 2009, Gore and colleagues published a study showing that in a stable population of these yeast, freeloaders dominate. Only 14 percent of the yeast cells cooperate by secreting metabolic enzymes, while the rest enjoy the bounty of others’ work.  In the new study, the researchers wanted to bring their experimental system closer to the complexity of natural environments. “Our approach is to start with the most simple system you can,†Gore says. “Then we’d like to try to understand these more complicated interactions between different species, so as a baby step in that direction, we added a bacterial competitor.â€This bacterial competitor consumes much of the sugar produced by the cooperative yeast, and also competes for other resources, such as nutrients. After these bacteria were added, the percentage of cooperators in the yeast population increased to about 45 percent. This isn’t because the yeast “decide†to become more cooperative, as humans might when faced with an external threat, Gore says. It’s determined purely by genetics. “That’s the point of doing experiments with microbial populations: There should be a mechanism that we can understand,†he says.Extra competitionIn this case, the researchers found two mechanisms at work. First, in the face of extra competition for sugars, the cooperators have a slight advantage over cheaters because they natural vitiligo treatment easier access to the sugar they produce themselves.A related mechanism involves population density. When bacteria are present, the overall yeast population stays smaller and is forced to spread out more, making it harder for the freeloaders to find food.“The cheater cells can really spread when there are a lot of other yeast, because there’s a lot of sugar out there for them. If there aren’t very many yeast, then it’s challenging for cheaters to spread,†Gore says.The study represents an important step toward integrating interactions between species into scientists’ understanding of the evolution of cooperation, says Michael Brockhurst, a professor of biology at the University of York.“This suggests that the effects of species interactions on social traits in natural communities could be highly dynamic and complex, and thus provide an area ripe for future research,†says Brockhurst, who was not part of the research team.Though the experiment does not precisely replicate natural conditions, it does show that it is important to try to get as close to those conditions as possible, Gore says. “If you just study something in isolation, such as yeast in a test tube, you might conclude that cooperation is very unstable,†he says. “But if you look at these populations in the wild, where their densities are limited and they have to interact with all these other species, you might come to very different conclusions for how difficult it is for the cooperative behavior to survive.â€In future studies, Gore hopes to add further complexity to the experimental microbial ecosystems, including varying the size of the yeast habitat.The research was funded by the National Institutes of Health, the National Science Foundation, a Pew Fellowship, a Foundational Questions in Evolutionary Biology grant, a Sloan Foundation Fellowship, and a Siebel Scholarship. Filed under: In The News, Special Needs, Bullying A soldier bent on revenge tracks down his target in “Killing Season.†; When the Arlington Partnership for Affordable Housing renovated the Fisher House apartments last year, the developer took care to see that the property\'s lush old linden trees survived the construction. The Oxford police chief says Mississippi guard Marshall Henderson appeared to be in possession of a small amount of marijuana and cocaine during a traffic stop in May. Since at least the late 19th century, when John Dewey opened his experimental Laboratory School at the University of Chicago, experiential learning — learning by doing — has had strong proponents among educational theorists. In MIT’s Department of Electrical Engineering and Computer Science (EECS), the Pregnancy Miracle experiential-learning theory can be seen in several courses in which each student spends the entire semester working on a single programming project.Even such project-based classes, however, miss aspects of the experience of commercial software development. “If you go to work at Microsoft, for example, you’re going to be handed code with 30 years of history, and you have to be able to quickly get up to speed, navigate hundreds of thousands of lines of code and then build on top of it, often without access to the people who originally wrote it,†says Ted Benson, a PhD student in EECS, who before coming to MIT worked for three years as a commercial software developer. “And then you need to make your contributions in a way where, 30 years later, other people can do the same.â€This spring, Benson and his thesis advisor, professor of computer science and engineering David Karger, created a new course in which rather than developing small projects from scratch, students participate in large, ongoing, open-source-software development initiatives, mentored by industry professionals. And as is the case with much modern commercial software development, they collaborate online with geographically dispersed colleagues — in this case, their fellow students at some 15 universities around the world.The consortium of universities, and their joint open-source development projects, were the brainchild of Jay Borenstein, a lecturer in computer science at Stanford University. Borenstein got funding from Facebook, convened a working group of educators — including Karger — to design courses and other educational initiatives around development projects, worked with members of the open-source-software community to identify outstanding problems, and recruited the industry mentors.Baptism of fireNot only does working on real development projects impart practical skills that are difficult to acquire in a conventional classroom setting, Benson says, but it also engages the students in a way that readings and problem sets rarely do.“There’s this age-old question for any teacher, which is how do you motivate the students to really buy into what they’re learning,†Benson says. “They’re fixing bugs and adding features to software that will touch millions of users. And when that’s your homework, it’s completely different. I’ve had students give me high-fives when they come in to report that they’ve finished something.â€One group of students, for instance, is helping repair a deep-rooted problem with the popular web-development framework Ruby on Rails. Frequently, tasks executed by commercial sites need to be processed as “transactions,†meaning that either all the aspects of the task are executed or none ex girlfriend guru wouldn’t want, say, a travel site charging you for one leg of a trip when it couldn’t find a return flight. Ruby on Rails had a bug, however, that meant that sometimes, failed transactions left program code out of sync with the database. MIT students are helping fix it. Another group is helping to develop a monitoring tool for the open-source database application MongoDB, so that application users can tell what types of queries the database is receiving and which servers are processing them.Software studioThe design of the course — the Open Source Software Project Lab, or 6.S194 in MIT’s course-numbering scheme — borrows elements from both the studio critiques typical of architecture courses and the residency model used in medical schools, Benson says. At the beginning of the semester, students were presented with the nine projects identified by Borenstein. On the basis of their personal preferences, they were sorted into five teams, with each assigned to a different project with a different mentor.On Mondays, Benson lectures, often tailoring his subject matter to questions raised by the students’ recent work. Every Wednesday, teams present their ongoing work to the rest of the class, explaining their approaches, inviting criticism and prompting general discussion of programming principles and philosophies.Otherwise, the students work chiefly with each other, with their collaborators at the other schools, and with their mentors. Every week, each team meets with Benson for 20 minutes to describe the next stage of its project and report its progress on the previous stage. “They learn that a very valid thing to accomplish in a week is thoroughly understanding a particular technology and coming up with a plan for how you might use it,†Benson says. “Sometimes learning is their assignment.â€When students have completed work on a particular section of code, they log it into the open-source project’s online code repository, where Benson can, if he chooses, review it to see if it accords with the weekly progress report. Sometimes, indeed, he has found that it doesn’t — but in an unexpected way. “I have had to go to some students and say, ‘Give yourself credit for this!’†Benson says. “You did far more work than I would have expected you to this week.â€Scaling upThat kind of individual attention, Benson acknowledges, is possible mainly because the MIT class, in its inaugural session, is intentionally small — only 11 students. One of the questions that he and Karger spend a lot of time discussing is how to preserve its tinnitusmiracle increasing its size. One possibility is to assign the students to more homogeneous projects — to have them all, for instance, work on different aspects of a single open-source application, such as Mozilla’s Firefox. Another possibility is to introduce tiers of instruction, where some of the regular evaluation and feedback is provided by upperclassmen who have already taken the course. A peer mentorship program, Benson says, could be modeled on MIT’s celebrated Undergraduate Research Opportunity Program, in which undergraduates perform original research for either course credit or stipends. Or Benson and Karger might use some other recruitment mechanism altogether. “Some of the students seem to enjoy this so much that I wouldn’t be surprised if they would volunteer to do it,†Benson says.Aaron Patterson, a senior software architect at AT&T and one of the student mentors, says that he would definitely participate in the course again, but that he could use some more help. “It\'s a lot of work,†he says. “Next time, I would try to involve more people as mentors or reduce the number of students I have.â€Patterson doesn’t believe that programs like the Open Source Software Project Lab will supplant the conventional computer science curriculum, but he does think that they complement it. “The textbook background is important for long-term development, but I don’t think textbooks prepare you for how to apply those techniques to real-world software,†he says. “Techniques I learned in school were extremely helpful, but didn’t prepare me for dealing with — frankly — bad code from the real world.â€And with the Open Source Software Project Lab, he says, the students have more to show for their work than a stack of graded problem sets. “Overall, the students are making extremely valuable contributions,†he says. “The work being accomplished via the students I’m working with is greater than I could accomplish on my own.†Russian Deputy Foreign Minister Sergey Ryabkov, who daily oversees relations between Moscow and the United States, last week provided interesting insight on issues such as Iran, Afghanistan and arms control in an appearance at the Nixon Center in Washington. Swedish House Mafia — the disc jockeys and producers Axwell, Sebastian Ingrosso and Steve Angello, of Stockholm — came to the Barclays Center on their “One Last Tour.†ALONG-DORMANT battle over the Department of Homeland Security\'s labor practices resurfaced last week in the Senate. The White House threatened to veto a generally sensible homeland security bill that was based on the Sept. 11 commission\'s recommendations, because directory of ezine provision that would allow Transportation Security Administration employees to engage in collective bargaining. In the Senate, 36 Republicans are promising to sustain that decision by President Bush.... \"Who is your local Congressman?\" Read full article >> A few rookie mistakes and some grand discoveries while traveling in China on a budget. Far beneath Manhattan, and out of sight it\'s 8 million residents, the largest transportation project in the country is churning away day and night hollowing out granite to create six miles of new tunnels. -- --- Home sales fell 9.6 pct. in February WASHINGTON (AP) - Fewer Americans bought previously occupied homes in February and those who did purchased them at steep discounts. The weak sales and rise in foreclosures pushed home prices down to their lowest level in nearly nine years. A group of former lawmakers and government officials gathered this week in the capital to discuss what they said was secrecy surrounding aliens and unidentified flying objects. This easy combination makes a great dessert or snack. Four MIT professors have been named 2013 MacVicar Faculty Fellows for their outstanding undergraduate teaching, mentoring and educational innovation. This year’s honorees are Linda Griffith, the School of Engineering Teaching Innovation Professor of Biological and Mechanical Engineering; Rob Miller, an associate professor of computer science and engineering; Laura Schulz, the Class of 1943 Career Development Associate Professor of Cognitive Science; and Emma Teng, an associate professor of China studies and the T.T. and Wei Fong Chao Professor of Asian Civilizations.These professors bring to 45 the number of current MacVicar Faculty Fellows, part of a program established in 1992 to honor the life and devotion to teaching excellence of Margaret MacVicar ‘64, ScD ‘67, MIT’s first dean for undergraduate education and founder of the Undergraduate Research Opportunities Program (UROP). The 10-year fellowship provides an annual allowance in support of undergraduate teaching.Provost Chris A. Kaiser selected the fellows in conjunction with an advisory committee of faculty and students chaired by Daniel Hastings, dean for undergraduate education.To celebrate undergraduate education on this MacVicar Day, the Institute will host a symposium this afternoon featuring five MIT faculty members speaking on “Reimagining the MIT Classroom: Experiments with Digital Learning.†Hastings will introduce the new MacVicar Fellows and then moderate the symposium. Speakers will include Teng; Jesus del Alamo, the Donner Professor of Science in the Department of Electrical Engineering and Computer Science; Anette Hosoi, an associate professor of mechanical engineering and applied mathematics; Anne E. C. McCants, a vision-without glasses history; and Troy Van Voorhis, a professor of chemistry. Today’s program will run from 2 to 4 p.m. in Bartos Theater (E15-070). A reception honoring the new MacVicar Fellows will follow from 4 to 5 p.m. in Bartos Lobby. The symposium and reception are open to the entire MIT community.Linda GriffithLinda Griffith received her BS in chemical engineering from the Georgia Institute of Technology in 1982, and her PhD in chemical engineering from the University of California at Berkeley in 1988. She was a postdoc in MIT’s Department of Chemical Engineering from 1988 to 1990, becoming an assistant professor in that department in 1991, an associate professor in 1996, and a full professor in 2002. Griffith joined the faculty of the Department of Biological Engineering in 1998, and the faculty of the Department of Mechanical Engineering in 2003.Students view Griffith as a “rockstar†and a “dynamic forceâ€; a colleague described her lectures as “extraordinary, flawlessly moving from engineering calculations to cell biology to medicine.†“She entered the classroom each day a blur of energy and enthusiasm … ready to fill chalkboard after chalkboard with equations, stopping only to entertain us with colorful anecdotes,†one student wrote. “No matter how complex the topic, Linda made it look easy and interesting.†“She would often ask us questions in class,†another student added, “and where possible, she would weave in the impact of what we do. … For me personally, making the relationship between core engineering principles and the impact that engineers could — and should — have on society was paramount.â€Griffith and Miller are among the Institute’s most dedicated researchers and educators, says Ian A. Waitz, dean of the School of Engineering and a MacVicar Faculty Fellow. “Along with Linda’s remarkable research in biological and tissue engineering,†Waitz says, “she was a driving force behind the creation of MIT’s newest undergraduate major, biological engineering, which has served as a model for similar curricula around the world. Working with colleagues from across the Institute, she oversaw the creation of nine new subjects for the major, creating two of them herself from scratch. And while working toward the broad impacts that come with such innovations, Linda has throughout her career remained a trusted and dedicated advisor and advocate to her many students.â€Â Rob MillerRob Miller received his SB and MEng from MIT in 1995, and his PhD from Carnegie Mellon University in 2002. He joined MIT as an assistant professor in 2002, becoming an associate professor in 2006.One colleague trademiner as “a fabulous teacher in all respects: in course development, in course management and organization, in hands-on pedagogy and engagement with students, and in inventing new ways to use technology to enhance education.â€Another wrote: “I think Rob embodies the ideal of an MIT teacher — caring, engaging, tirelessly working on behalf of the students, eliciting respect, admiration, and joy from the students.â€Students in Miller’s courses agree that his lectures are exceptional.“In my six years at MIT,†one wrote, “Rob’s course was the only one whose lectures I felt could not be missed. I was absent for exactly one lecture due to travel for a job interview, and I still remember how genuinely disappointed I felt … his lectures always prompted such interesting discussion and the material was presented so well, I felt as though I had missed something.â€â€œRob’s research projects — including a revolutionary crowd-based system for text editing and programming-code evaluation — may also have significant educational applications, with the potential to impact the lives and learning of students around the world as they are implemented on MITx,†Waitz says. “Similarly, the course he developed on user interface and design has been extremely successful with an entire generation of students who are now in industry shaping our interactive experiences on a daily basis.†Laura SchulzLaura Schulz earned a BA in philosophy from the University of Michigan in 1992, and an MA and PhD, both in developmental psychology from the University of California at Berkeley, in 2002 and 2004, respectively. She joined MIT as an assistant professor in the Department of Brain and Cognitive Science in 2005, becoming an associate professor in 2010.Schulz’s colleagues call her “a brilliant, passionate, innovative and enthusiastic teacher†and “a caring and committed educator who is deeply engaged in undergraduate education at all levels.â€â€œShe knows her undergraduates well, has them over to her house and welcomes them warmly into her life, meets with them about their work and takes them seriously as junior colleagues and human beings,†one wrote. “She has more undergraduate office hours than anyone else I know, and is regularly meeting with undergraduates outside her normally scheduled hours … she sets the highest example for MIT undergraduates on how to be a scientist, an educator and a person who is deeply committed to helping others develop themselves and their potential.â€â€œDr. Schulz was undoubtedly the one professor who made the most lasting impact on my life,†one student wrote. “I felt like Dr. Schulz became one of my forex growth bot review supporters and advocates. We discussed my interests and goals, and together figured out a plan to help me get there.â€Marc Kastner, dean of the School of Science, cites Schulz’s teaching of 9.85 (Early Childhood Cognition), a key part of the undergraduate curriculum in the Department of Brain and Cognitive Science (BCS), as an example of her devotion to students. “Her high expectations for students in this Communication Intensive (CI-M) course and her dedication to excellence in teaching have provided essential training in critical writing and analysis for BCS undergraduates,†Kastner says. “As of last spring, she had mentored an astounding 68 UROP [Undergraduate Research Opportunities Program] students, who were able to participate in her groundbreaking research into how children learn.â€Emma TengEmma Teng holds three degrees from Harvard University: an AB, received in 1989; an AM, received in 1992, and a PhD, received in 1997. She became an assistant professor in MIT’s Foreign Languages and Literatures section in 1998, and an associate professor in 2002. In 2012, she began a second appointment in the Institute’s History section.Teng’s students describe her as “simultaneously … an instructor, a mentor, and a confidante.â€â€œI know of no other faculty member who appears always to be with a student — in her office, in the copying room, or just walking down the hallway,†one colleague wrote. “Professor Teng attracts students like a magnet. She is a mentor to many formally, and to many more informally.†“Emma is a brilliant scholar whose energy, enthusiasm and talent for bringing scholars together enables her to inspire students and faculty to move beyond what is usually expected,†another colleague observed. “Her creativity gives others a model of how to think across disciplines, and her high standards keep us rigorous in our efforts.†“Emma Teng embodies the best combination of qualities — top-notch research on Asian and Asian-American identities and histories with hands-on, deeply effective teaching and mentoring of students,†says Deborah K. Fitzgerald, Kenan Sahin Dean of the School of Humanities, Arts, and Social Sciences. “Whether in History, Foreign Languages and Literatures, or Women’s and Gender Studies, Emma puts it all together for MIT students. Her dedication to students and impact in the field make her an excellent MacVicar Fellow.†NEW DELHI - India and Pakistan agreed Thursday to resume formal peace talks that were broken off after the 2008 terrorist attacks in Mumbai, which were blamed on Pakistan-based militants. The decision could ease tensions between the nuclear-armed rivals and was welcomed by the Obama |
