Excitons observed in action for the first time (MIT News)

Insights generated by this new imaging technique could lead to significant advances in electronics, and deeper understanding about energy-transfer processes like photosynthesis.

Excitons observed in action for the first time
Technique developed at MIT reveals the motion of energy-carrying quasiparticles in solid material.

David L. Chandler | MIT News Office
April 16, 2014

A quasiparticle called an exciton — responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits — has been understood theoretically for decades. But exciton movement within materials has never been directly observed.

Now scientists at MIT and the City College of New York have achieved that feat, imaging excitons’ motions directly. This could enable research leading to significant advances in electronics, they say, as well as a better understanding of natural energy-transfer processes, such as photosynthesis.

The research is described this week in the journal Nature Communications, in a paper co-authored by MIT postdocs Gleb Akselrod and Parag Deotare, professors Vladimir Bulovic and Marc Baldo, and four others.

“This is the first direct observation of exciton diffusion processes,” Bulovic says, “showing that crystal structure can dramatically affect the diffusion process.”

“Excitons are at the heart of devices that are relevant to modern technology,” Akselrod explains: The particles determine how energy moves at the nanoscale. “The efficiency of devices such as photovoltaics and LEDs depends on how well excitons move within the material,” he adds. Read more…

Learn more about the exciton and related phenomena in these OCW courses:

A molecular approach to solar power (MIT News)

Diagram of molecules going through solar-induced charge-discharge cycle, with heat released.

The working cycle of a solar thermal fuel, using azobenzene as an example. (Courtesy of Jeff Grossman.)

A molecular approach to solar power
Switchable material could harness the power of the sun — even when it’s not shining.

David L. Chandler | MIT News Office
April 13, 2014

It’s an obvious truism, but one that may soon be outdated: The problem with solar power is that sometimes the sun doesn’t shine.

Now a team at MIT and Harvard University has come up with an ingenious workaround — a material that can absorb the sun’s heat and store that energy in chemical form, ready to be released again on demand.

This solution is no solar-energy panacea: While it could produce electricity, it would be inefficient at doing so. But for applications where heat is the desired output — whether for heating buildings, cooking, or powering heat-based industrial processes — this could provide an opportunity for the expansion of solar power into new realms.

“It could change the game, since it makes the sun’s energy, in the form of heat, storable and distributable,” says Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering at MIT, who is a co-author of a paper describing the new process in the journal Nature Chemistry. Timothy Kucharski, a postdoc at MIT and Harvard, is the paper’s lead author.

The principle is simple: Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle. Exposing them to sunlight causes them to absorb energy and jump from one configuration to the other, which is then stable for long periods of time.

But these photoswitches can be triggered to return to the other configuration by applying a small jolt of heat, light, or electricity — and when they relax, they give off heat. In effect, they behave as rechargeable thermal batteries: taking in energy from the sun, storing it indefinitely, and then releasing it on demand.

Read more…

See Prof. Grossman teach about this new class of solar materials, in this lecture video from his OCW course 3.021J Introduction to Modeling and Simulation:

Winners of 2014 Site, Course, and Project Awards for OpenCourseWare Excellence (OCW Consortium)

The OpenCourseWare Consortium has announced the 2014 winners of Site, Course, and Project Awards for OpenCourseWare Excellence (ACE).  Congratulations to all!

Site and Course Awards

This year’s Site and Course awards fall into three categories: Outstanding Site, Outstanding Course, and Open MOOC.

Outstanding Site Winners

Outstanding Course Winners

Open MOOC Winners

  • Solar Energy (Delft University of Technology; Dr. Arno Smets)
  • Introduction to Water Treatment (Delft University of Technology; Prof.Dr.Ir. Jules B. van Lier)
  • Pre-Algebra CCC 2013 (Cuyahoga Community College; Professor Idrissa Aidara, Professor Don Gabriel, Professor Curtis Kaschube, Professor Cathleen Rossman, Professor Michael Wilkins, Dr. Belinda Miles, Dr. Charles Dull, Sash Thackaberry, and Cheryl Knight)

Read the full press release on Site and Course Awards.

Project Awards

The Project awards are a new category aiming to recognize efforts that support the production, use and/or promotion of OCW/OER in ways other than the creation and use of material resource, and fall into two categories: Creative Innovation and Open Research..

Creative Innovation Winners

The Creative Innovation Award recognizes outstanding innovations that bring a new approach to Open Education. These may be ideas or solutions presented as sites, courses or projects that substantially improve the discoverability, presentation, usability, accessibility or availability of course materials.

  • Sésamath (SESAMATH)
  • Slidewiki (Rheinische Friedrich-Wilhelms-Universität Bonn; Darya Tarasowa, Ali Khalili, Sören Auer)

Open Research Winners

The Open Research Award recognizes excellence in research studies about open education and/or related areas. These may be studies that help advance our understanding and demonstrate effectiveness related to challenges in discoverability, presentation, usability, accessibility or availability of OCW/OER.

Read the full press release on Project Awards.

Shorter Videos are More Engaging (and other insights from an edX study)

You’ve just pressed play on a video lecture for a new MOOC; how long before your attention starts to wander? As it turns out, only about six minutes!

By analyzing the viewing habits of more than 100,000 MOOC learners on the edX platform, researchers now know what aspects of video production affect student engagement. The most important factor is video length: shorter videos are much more engaging.

Based on their findings, the researchers have recommendations for MOOC video producers and professors that will help them create the most engaging content in future videos. For example, videos should be kept shorter than six minutes, so spend time in pre-production breaking the content into small chunks.

You can read the entire paper here, or read Philip Guo’s blog post that summarizes the paper and lists their most important findings and recommendations.

Celebrate National Poetry Month with OCW

MIT is best known for science and engineering, but the Institute is also home to a thriving School of Humanities, Arts, and Social Sciences (SHASS). In honor of National Poetry Month, here are some poetry-related courses on OCW:

Learn more about SHASS and the HASS requirements for MIT students.

Robert Talbert – Getting student buy-in for the inverted calculus class (Chronicle of Higher Ed)

Here’s an excerpt from the fifth post in from Robert Talbert’s excellent series on flipping his calculus class:

Getting student buy-in for the inverted calculus class

So far, regarding the inverted/flipped calculus course, we’ve discussed why I flipped the calculus class in the first place, the role of self-regulated learning as a framework and organizing principle for the class, how to design pre-class activities that support self-regulated learning, and how to make learning objectives that get pre-class activities started on a good note. This is all “design thinking”. Now it’s time to focus on the hard part: Students, and getting them to buy into this notion of a flipped classroom.

I certainly do not have a perfect track record with getting students on board with an inverted/flipped classroom structure. In fact the first time I did it, it was a miserable flop among my students (even though they learned a lot). It took that failure to make me start thinking that getting student buy-in has to be as organized, systematic, and well-planned as the course itself.

Here are three big “don’ts” and “dos” that I’ve learned about getting students to buy in to the flipped classroom, mostly through cringe-worthy teaching performances of my own in the past, along with some examples of how we built these into the calculus course. Read more.

Anant Agarwal on MOOC Learners: Who They Are, What Motivates Them (HuffPost Education)

Imagine a MOOC learner: Who is she? How old is she? Where does she live? Anant Agarwal, the CEO of edX, recently wrote a blog post on HuffPost Education that highlighted the diversity of MOOC learners and their goals:

MOOC learners are diverse, coming from many cultures across the globe and all ages and backgrounds. For instance, edX learners, who now number two million, range in ages from eight to 95, come from every country in the world and have varying levels of education. We see learners from elementary schoolers to Ph.D.s. Despite this diversity, three main attributes unite them: A desire to learn, a desire to connect to a global community and a desire to experience and consume content online.

The goals of our learners are as diverse as they are. When they first enroll in a course, some may be interested in engaging with homework or other interactive labs, or in completing the coursework to earn a certificate (we call these “active learners”). Others may simply want to browse and view a few of the videos. Data collected from edX shows that approximately 56 percent of learners rated “gaining understanding of the subject matter for lifelong learning,” as an extremely important reason for taking an edX course, and another 57 percent cite “learning from the best professors in the world.” However, only 27 percent rated “earning a certificate of mastery to add to my professional credentials,” as an extremely important reason for enrolling in a course. Read the entire post here.

Browse the listings on edX and enroll in a MOOC yourself. And if your goal is to earn a certificate, we have courseware related to MITx MOOCs to help you study.