MIT Physics by Julia C. Keller | School Of Science - 1w ago
Seven MIT faculty members were among the more than 300 recipients of the 2019 Presidential Early Career Awards for Scientists and Engineers (PECASE), the highest honor bestowed by the U.S. government to science and engineering professionals in the early stages of their independent research careers.
Kwanghun Chung, associate professor in the departments of Brain and Cognitive Sciences and Chemical Engineering
James M. LeBeau, the John Chipman Associate Professor of Materials Science and Engineering;
Yen-Jie Lee, the Class of 1958 Career Development Associate Professor in the Department of Physics;
Benedetto Marelli, the Paul M. Cook Career Development Assistant Professor in the Department of Civil and Environmental Engineering;
Tracy Slatyer, the Jerrold R. Zacharias Career Development Associate Professor of Physics; and
Yogesh Surendranath, the Paul M. Cook Career Development Assistant Professor in the Department of Chemistry.
All of the 2019 MIT recipients were employed or funded by the following U.S. departments and agencies: Department of Defense, Department of Energy, and the Department of Health and Human Services.
These departments and agencies annually nominate the most meritorious scientists and engineers whose early accomplishments show exceptional promise for leadership in science and engineering and contributing to the awarding agencies' missions.
Established by President Bill Clinton in 1996, the PECASE awards are coordinated by the Office of Science and Technology Policy within the Executive Office of the President. Awardees are selected for their pursuit of innovative research at the frontiers of science and technology and their commitment to community service as demonstrated through scientific leadership, public education, or community outreach.
MIT granted tenure to eight School of Science faculty members in the departments of Biology; Chemistry; Earth, Atmospheric and Planetary Sciences; Mathematics; and Physics.
William Detmold’s research within the area of theoretical particle and nuclear physics incorporates analytical methods, as well as the power of the world’s largest supercomputers, to understand the structure, dynamics, and interactions of particles like protons and to look for evidence of new physical laws at the sub-femtometer scale probed in experiments such as those at the Large Hadron Collider. He joined the Department of Physics in 2012 from the College of William and Mary, where he was an assistant professor. Prior to that, he was a research assistant professor at the University of Washington. He received his BS and PhD from the University of Adelaide in Australia in 1996 and 2002, respectively. Detmold is a researcher in the Center for Theoretical Physics in the Laboratory for Nuclear Science.
Semyon Dyatlov explores scattering theory, quantum chaos, and general relativity by employing microlocal analytical and dynamical system methods. He came to the Department of Mathematics as a research fellow in 2013 and became an assistant professor in 2015. He completed his doctorate in mathematics at the University of California at Berkeley in 2013 after receiving a BS in mathematics at Novosibirsk State University in Russia in 2008. Dyatlov spent time after finishing his PhD as a postdoc at the Mathematical Sciences Research Institute before moving to MIT.
Mary Gehring studies plant epigenetics. By using a combination of genetic, genomic, and molecular biology, she explores how plants inherit and interpret information that is not encoded in their DNA to better understand plant growth and development. Her lab focuses primarily on Arabidopsis thaliana, a small flowering plant that is a model species for plant research. Gehring joined the Department of Biology in 2010 after performing postdoctoral research at the Fred Hutchinson Cancer Research Center. She received her BA in biology from Williams College in 1998 and her doctorate from the University of California at Berkeley in 2005. She is also a member of the Whitehead Institute for Biomedical Research.
David McGee performs research in the field of paleoclimate, merging information from stalagmites, lake deposits, and marine sediments with insights from models and theory to understand how precipitation patterns and atmospheric circulation varied in the past. He came to MIT in 2012, joining the Department of Earth, Atmospheric and Planetary Sciences after completing a NOAA Climate and Global Change Postdoctoral Fellowship at the University of Minnesota. Before that, he attended Carleton College for his BA in geology in 1993-97, Chatham College for an MA in teaching from 1999 to 2003, Tulane University for his MS from 2004 to 2006, and Columbia University for his PhD from 2006 to 2009. McGee is the director of the MIT Terrascope First-Year Learning Community, a role he has held for the past four years.
Ankur Moitra works at the interface between theoretical computer science and machine learning by developing algorithms with provable guarantees and foundations for reasoning about their behavior. He joined the Department of Mathematics in 2013. Prior to that, he received his BS in electrical and computer engineering from Cornell University in 2007, and his MS and PhD in computer science from MIT in 2009 and 2011, respectively. He was a National Science Foundation postdoc at the Institute for Advanced Study until 2013. Moitra was a 2018 recipient of a School of Science Teaching Prize. He is also a principal investigator in the Computer Science and Artificial Intelligence Laboratory (CSAIL) and a core member of the Center for Statistics.
Matthew Shoulders focuses on integrating biology and chemistry to understand how proteins function in the cellular setting, including proteins’ shape, quantity, and location within the body. This research area has important implications for genetic disorders and neurodegenerative diseases such as Alzheimer’s, diabetes, cancer, and viral infections. Shoulders’ lab works to elucidate, at the molecular level, how cells solve the protein-folding problem, and then uses that information to identify how diseases can develop and to provide insight into new targets for drug development. Shoulders joined the Department of Chemistry in 2012 after earning a BS in chemistry and minor in biochemistry from Virginia Tech in 2004 and a PhD in chemistry from the University of Wisconsin at Madison in 2009. He is also an associate member of the Broad Institute of MIT and Harvard, and a member of the MIT Center for Environmental Health Sciences.
Tracy Slatyer researches fundamental aspects of theoretical physics, answering questions about both visible and dark matter by searching for potential indications of new physics in astrophysical and cosmological data. She has developed and adapted novel techniques for data analysis, modeling, and calculations in quantum field theory; her work has also inspired a range of experimental investigations. The Department of Physics welcomed Slatyer in 2013 after she completed a three-year postdoctoral fellowship at the Institute for Advanced Study. She majored in theoretical physics as an undergraduate at the Australian National University, receiving a BS in 2005, and completed her PhD in physics at Harvard University in 2010. In 2017, Slatyer received the School of Science Prize in Graduate Teaching and was also named the first recipient of the school’s Future of Science Award. She is a member of the Center for Theoretical Physics in the Laboratory for Nuclear Science.
Michael Williams uses novel experimental methods to improve our knowledge of fundamental particles, including searching for new particles and forces, such as dark matter. He also works on advancing the usage of machine learning within the domain of particle physics research. He joined the Department of Physics in 2012. He previously attended Saint Vincent College as an undergraduate, where he double majored in mathematics and physics. Graduating in 2001, Williams then pursued a doctorate at Carnegie Mellon University, which he completed in 2007. From 2008 to 2012 he was a postdoc at Imperial College London. He is a member of the Laboratory for Nuclear Science.
MIT Physics by David L. Chandler | Mit News Office - 2w ago
Self-assembling materials called block copolymers, which are known to form a variety of predictable, regular patterns, can now be made into much more complex patterns that may open up new areas of materials design, a team of MIT researchers say.
The new findings appear in the journal Nature Communications, in a paper by postdoc Yi Ding, professors of materials science and engineering Alfredo Alexander-Katz and Caroline Ross, and three others.
“This is a discovery that was in some sense fortuitous,” says Alexander-Katz. “Everyone thought this was not possible,” he says, describing the team’s discovery of a phenomenon that allows the polymers to self-assemble in patterns that deviate from regular symmetrical arrays.
Self-assembling block copolymers are materials whose chain-like molecules, which are initially disordered, will spontaneously arrange themselves into periodic structures. Researchers had found that if there was a repeating pattern of lines or pillars created on a substrate, and then a thin film of the block copolymer was formed on that surface, the patterns from the substrate would be duplicated in the self-assembled material. But this method could only produce simple patterns such as grids of dots or lines.
In the new method, there are two different, mismatched patterns. One is from a set of posts or lines etched on a substrate material, and the other is an inherent pattern that is created by the self-assembling copolymer. For example, there may be a rectangular pattern on the substrate and a hexagonal grid that the copolymer forms by itself. One would expect the resulting block copolymer arrangement to be poorly ordered, but that’s not what the team found. Instead, “it was forming something much more unexpected and complicated,” Ross says.
There turned out to be a subtle but complex kind of order — interlocking areas that formed slightly different but regular patterns, of a type similar to quasicrystals, which don’t quite repeat the way normal crystals do. In this case, the patterns do repeat, but over longer distances than in ordinary crystals. “We’re taking advantage of molecular processes to create these patterns on the surface” with the block copolymer material, Ross says.
This potentially opens the door to new ways of making devices with tailored characteristics for optical systems or for “plasmonic devices” in which electromagnetic radiation resonates with electrons in precisely tuned ways, the researchers say. Such devices require very exact positioning and symmetry of patterns with nanoscale dimensions, something this new method can achieve.
Katherine Mizrahi Rodriguez, who worked on the project as an undergraduate, explains that the team prepared many of these block copolymer samples and studied them under a scanning electron microscope. Yi Ding, who worked on this for his doctoral thesis, “started looking over and over to see if any interesting patterns came up,” she says. “That’s when all of these new findings sort of evolved.”
The resulting odd patterns are “a result of the frustration between the pattern the polymer would like to form, and the template,” explains Alexander-Katz. That frustration leads to a breaking of the original symmetries and the creation of new subregions with different kinds of symmetries within them, he says. “That’s the solution nature comes up with. Trying to fit in the relationship between these two patterns, it comes up with a third thing that breaks the patterns of both of them.” They describe the new patterns as a “superlattice.”
Having created these novel structures, the team went on to develop models to explain the process. Co-author Karim Gadelrab PhD ’19, says, “The modeling work showed that the emergent patterns are in fact thermodynamically stable, and revealed the conditions under which the new patterns would form.”
Ding says “We understand the system fully in terms of the thermodynamics,” and the self-assembling process “allows us to create fine patterns and to access some new symmetries that are otherwise hard to fabricate.”
He says this removes some existing limitations in the design of optical and plasmonic materials, and thus “creates a new path” for materials design.
So far, the work the team has done has been confined to two-dimensional surfaces, but in ongoing work they are hoping to extend the process into the third dimension, says Ross. “Three dimensional fabrication would be a game changer,” she says. Current fabrication techniques for microdevices build them up one layer at a time, she says, but “if you can build up entire objects in 3-D in one go,” that would potentially make the process much more efficient.
These findings “open new pathways to generate templates for nanofabrication with symmetries not achievable from the copolymer alone,” says Thomas P. Russell, the Silvio O. Conte Distinguished Professor of Polymer Science and Engineering at the University of Massachusetts, Amherst, who was not involved in this work. He adds that it “opens the possibility of exploring a large parameter space for uncovering other symmetries than those discussed in the manuscript.”
Russel says “The work is of the highest quality,” and adds “The pairing of theory and experiment is quite powerful and, as can be seen in the text, the agreement between the two is remarkably good.”
The research was funded by the Office of General Sciences of the U.S. Department of Energy. The team also included graduate student Hejin Huang.
MIT Physics by Kelly Mcsweeney | Mit Open Learning - 2w ago
Seven MIT educators have received awards this year for their significant digital learning innovations and their contributions to teaching and learning at MIT and around the world.
Polina Anikeeva, Martin Bazant, and Jessica Sandland shared the third annual MITx Prize for Teaching and Learning in MOOCs — an award given to educators who have developed massive open online courses (MOOCs) that share the best of MIT knowledge and perspectives with learners around the world. Additionally, John Belcher, Amy Carleton, Jared Curhan, and Erik Demaine received Teaching with Digital Technology Awards, nominated by MIT students for their innovative use of digital technology to improve their teaching at MIT.
The MITx Prize for Teaching and Learning in MOOCs
This year’s MITx prize winners were honored at an MIT Open Learning event in May. Professor Polina Anikeeva of the Department of Materials Science and Engineering and Digital Learning Lab Scientist Jessica Sandland received the award for teaching 3.024x (Electronic, Optical and Magnetic Properties of Materials). The course was praised for not only its global impact, but also for the way in which it enhanced the residential experience. Increased flexibility from integrating the online content allowed for the addition of design reviews, which give MIT students firsthand experience working on complicated engineering problems.
3.024x is fast-paced and challenging. To bring some levity to the subject, the instructors designed problem sets around a series of superhero-themed comic strips that integrated the science and engineering concepts that students learned in class.
Martin Bazant, of the departments of Chemical Engineering and Mathematics, received the MITx prize for his course, 10.50.1x (Analysis of Transport Phenomena Mathematical Methods). Most problems in the course involve long calculations, which can be tricky to demonstrate online.
To solve this challenge, Bazant broke up problems into smaller parts that included tips and tutorials to help learners solve the problem while maintaining the rigorous intellectual challenge. Course participants included a diverse group of college students, industry professionals, and faculty from other universities in many science and engineering disciplines across the globe.
Teaching with Digital Technology Awards
Co-sponsored by MIT Open Learning and the Office of the Vice Chancellor, the Teaching with Digital Technology Awards are student-nominated awards for faculty and instructors who have improved teaching and learning at MIT with digital technology. MIT students nominated 117 faculty and instructors for this award this year, more than in any previous year. The winners were celebrated at an awards luncheon in early June. John Belcher, Erik Demaine, and Jared Curhan attended the awards luncheon, and — in the spirit of an award reception for digital innovation — Amy Carleton joined the event virtually, through video chat.
John Belcher was honored for his physics courses on electricity and magnetism. Students appreciated the way that Belcher incorporated videos with his lectures to help provide a physical representation of an abstract subject. He created the animated videos to show visualizations of fundamental physics concepts such as energy transfer and magnetic fields. Students remarked that the videos helped them learn about everything from solar flares and the solar cycle to the fundamentally relativistic nature of electromagnetism.
Erik Demaine of the Computer Science and Artificial Intelligence Lab received the award for his course 6.892 (Fun with Hardness Proofs). The course flipped the traditional classroom model. Instead of lecturing in person, all lectures were posted online and problems were done in class. This allowed the students to spend class time working together on collaborative problem solving through an online application that Demaine created, called Coauthor.
Jared Curhan received the award for his negotiation courses at the MIT Sloan School of Management, including 15.672 (Negotiation Analysis), which he designed for students across the Institute. Curhan used digital technology to provide feedback while students practiced their negotiating skills in class. A platform called iDecisionGames helped simulate negotiation exercises between students, and after each exercise it provided data about how each participant performed, both objectively and subjectively.
Amy Carleton received the award for her course on science writing and new media. During the course, students learned how to write about scientific and technical topics for a general audience. They put their skills to work by writing Wikipedia articles, where they used advanced editing techniques and wrote mathematical expressions in LaTEX. They also used Google Docs during class to edit articles in small groups, and developed PowerPoint presentations where they learned to incorporate sound and graphics to emphasize their ideas.
Both awards celebrate instructors who are using technology in innovative ways to help teach challenging courses to both traditional students and online learners.
“At MIT, there is no shortage of digital learning innovation, and this year’s winners reflect the Institute’s strong commitment to transforming teaching and learning at MIT and around the globe,” says MIT Professor Krishna Rajagopal, dean for digital learning. “They have set new standards for online and blended learning.”
In many materials, electrical resistance and voltage change in the presence of a magnetic field, usually varying smoothly as the magnetic field rotates. This simple magnetic response underlies many applications including contactless current sensing, motion sensing, and data storage. In a crystal, the way that the charge and spin of its electrons align and interact underlies these effects. Utilizing the nature of the alignment, called symmetry, is a key ingredient in designing a functional material for electronics and the emerging field of spin-based electronics (spintronics).
Recently a team of researchers from MIT, the French National Center for Scientific Research (CNRS) and École Normale Supérieure (ENS) de Lyon, University of California at Santa Barbara (UCSB), the Hong Kong University of Science and Technology (HKUST), and NIST Center for Neutron Research, led by Joseph G. Checkelsky, assistant professor of physics at MIT, has discovered a new type of magnetically driven electrical response in a crystal composed of cerium, aluminum, germanium, and silicon.
At temperatures below 5.6 kelvins (corresponding to -449.6 degrees Fahrenheit), these crystals show a sharp enhancement of electrical resistivity when the magnetic field is precisely aligned within an angle of 1 degree along the high symmetry direction of the crystal. This effect, which the researchers have named “singular angular magnetoresistance,” can be attributed to the symmetry — in particular, the ordering of the cerium atoms’ magnetic moments. Their results are published today in the journal Science.
Novel response and symmetry
Like an old-fashioned clock designed to chime at 12:00 and at no other position of the hands, the newly discovered magnetoresistance only occurs when the direction, or vector, of the magnetic field is pointed straight in line with the high-symmetry axis in the material’s crystal structure. Turn the magnetic field more than a degree away from that axis and the resistance drops precipitously.
"Rather than responding to the individual components of the magnetic field like a traditional material, here the material responds to the absolute vector direction," says Takehito Suzuki, a research scientist in the Checkelsky group who synthesized these materials and discovered the effect. "The observed sharp enhancement, which we call singular angular magnetoresistance, implies a distinct state realized only under those conditions."
Magnetoresistance is a change in the electrical resistance of a material in response to an applied magnetic field. A related effect known as giant magnetoresistance is the basis for modern computer hard drives and its discoverers were awarded the Nobel Prize in 2007.
"The observed enhancement is so highly confined with the magnetic field along the crystalline axis in this material that it strongly suggests symmetry plays a critical role,” Lucile Savary, permanent CNRS researcher at ENS de Lyon, adds. Savary was a Betty and Gordon Moore Postdoctoral Fellow at MIT from 2014-17, when the team started collaborating.
To elucidate the role of the symmetry, it is crucial to see the alignment of the magnetic moments, for which Suzuki and Jeffrey Lynn, NIST fellow, performed powder neutron diffraction studies on the BT-7 triple axis spectrometer at the NIST Center for Neutron Research (NCNR). The research team used the NCNR’s neutron diffraction capabilities to determine the material’s magnetic structure, which plays an essential role in understanding its topological properties and nature of the magnetic domains. A "topological state" is one that is protected from ordinary disorder. This was a key factor in unraveling the mechanism of the singular response.
Based on the observed ordering pattern, Savary and Leon Balents, professor and permanent member of Kavli Institute of Theoretical Physics at UCSB, constructed a theoretical model where the spontaneous symmetry-breaking caused by the magnetic-moment ordering couples to the magnetic field and the topological electronic structure. As a consequence of the coupling, switching between the uniformly ordered low- and high-resistivity states can be manipulated by the precise control of the magnetic field direction.
“The agreement of the model with the experimental results is outstanding and was the key to understanding what was a mysterious experimental observation,” says Checkelsky, the paper’s senior author.
Universality of the phenomenon
"The interesting question here is whether or not the singular angular magnetoresistance can be widely observed in magnetic materials and, if this feature can be ubiquitously observed, what is the key ingredient for engineering the materials with this effect," Suzuki says.
The theoretical model indicates that the singular response may indeed be found in other materials and predicts material properties beneficial for realizing this feature. One of the important ingredients is an electronic structure with a small number of free charges, which occurs in a point-like electronic structure referred to as nodal. The material in this study has so-called Weyl points that achieve this. In such materials, the allowed electron momenta depends on the configuration of the magnetic order. Such control of the momenta of these charges by the magnetic degree of freedom allows the system to support switchable interface regions where the momenta are mismatched between domains of different magnetic order. This mismatch also leads to the large increase in resistance observed in this study.
This analysis is further supported by the first-principles electronic structure calculation performed by Jianpeng Liu, research assistant professor at the HKUST, and Balents. Using more traditional magnetic elements such as iron or cobalt, rather than rare-earth cerium, may offer a potential path to higher temperature observation of the singular angular magnetoresistance effect. The study also ruled out a change in the arrangement of the atoms, called a structural phase transition, as a cause of the change in resistivity of the cerium-based material.
Kenneth Burch, graduate program director and associate professor of physics at Boston College, whose lab investigates Weyl materials, notes: “The discovery of remarkable sensitivity to magnetic angle is a completely unexpected phenomena in this new class of materials. This result suggests not only new applications of Weyl semimetals in magnetic sensing, but the unique coupling of electronic transport, chirality and magnetism.” Chirality is an aspect of electrons related to their spin that gives them either a left-handed or right-handed orientation.
The discovery of this sharp but narrowly confined resistance peak could eventually be used by engineers as a new paradigm for magnetic sensors. Notes Checkelsky, “One of the exciting things about fundamental discoveries in magnetism is the potential for rapid adoptions for new technologies. With the design principles now in hand, we are casting a wide net to find this phenomena in more robust systems to unlock this potential.”
This research was supported in part by the Gordon and Betty Moore Foundation and the National Science Foundation.
With a new telescope situated on a scenic plateau in Tenerife, Spain, MIT planetary scientists now have an added way to search for Earth-sized exoplanets. Artemis, the first ground-based telescope of the SPECULOOS Northern Observatory (SNO), joins a network of 1-meter-class robotic telescopes as part of the SPECULOOS project (Search for habitable Planets EClipsing ULtra-cOOl Stars), which is led by Michael Gillon at the University of Liège in Belgium and carried out in collaboration with MIT and several other institutions and financial supporters. Artemis is the latest product of a collaboration with MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). The other network telescopes that make up the SPECULOOS Southern Observatory — named Io, Europa, Ganymede, and Callisto after the four Galilean moons of Jupiter — are up and running at the Paranal Observatory in Chile, busily scanning the skies for exoplanets in the Southern Hemisphere.
Together, these SPECULOOS telescopes will look for terrestrial planets circling very faint, nearby stars, called ultra-cool dwarfs, and the new Artemis telescope will allow the research group to expand the search into the Northern Hemisphere skies. Artemis was unveiled today at an inauguration event attended by scientists and dignitaries from MIT, the University of Liège, and the Instituto de Astrofísica de Canarias (IAC) in Tenerife. Artemis was funded by MIT donors Peter A. Gilman, the Heising-Simons Foundation, and Colin and Leslie Masson, with additional support from the Ministry of Higher Education of the Federation Wallonie-Bruxelles, and the Balzan Foundation.
Before the SPECULOOS telescopes were conceived, researchers had already established the proof of concept for this technique with a project using a small, ground-based telescope located in La Silla, Chile, known as TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope). With the TRAPPIST telescope, researchers looked at a limited sample of 50 target stars and discovered the TRAPPIST-1 system, which consists of seven terrestrial planets orbiting their cool, ultra-dwarf star. To date, these are the only known planets that are nearby, Earth-sized, temperate, and amenable for future atmospheric characterization, setting them apart from previous exoplanet findings. The SPECULOOS group is building on this earlier project with its new telescope network to scan more of the sky for similar Earth-sized exoplanets, and deliver more targets that can be assessed for habitability and potentially signs of life in the future.
Julien de Wit is an EAPS assistant professor, SPECULOOS collaborator, Artemis principal investigator, and SNO co-principal investigator with Gillon. As a postdoc in the group of MIT Professor Sara Seager, he worked with Gillon and the TRAPPIST team to identify and characterize the TRAPPIST-1 system. Later he spearheaded the expansion of the SPECULOOS venture into the Northern Hemisphere. EAPS recently spoke with de Wit about the capabilities of Artemis and what we can expect to find with the SPECULOOS project.
Q: Tell us about the new Artemis telescope. Why is it particularly exciting?
A: The first telescope of the SPECULOOS Northern Observatory is named Artemis, built and owned by MIT, after the Greek goddess of the hunt, the wilderness, the moon, which seemed appropriate as we are hunting for planets and signs of life.
Artemis is located on the Spanish Canary Island of Tenerife about 150 miles off the coast of Morocco. The SNO is built within the Teide Observatory, which is an astronomical observatory by the Teide Volcano, 2,400 meters above sea level and operated by the Insituto de Astrofisica de Canarias. The location, which hosts one of the first major international observatories, boasts excellent astronomical conditions for viewing.
As far as the telescope itself, it measures about 4 meters high, with an optical quality of less than 0.8 arcsec and a field of view, 12 arcmin by 12 arcmin. Artemis, which was built by the German company ASTELCO, has a robot mount, and its detectors are very sensitive to the near-infrared wavelengths that we find emanating from these ultra-cool dwarf stars. We will be operating it remotely from MIT or any other collaborating institutes.
With TRAPPIST, we demonstrated a proof of concept — confirming that ultra-cool dwarf stars have the capacity to host planets — and are investigating the atmospheres of these TRAPPIST-1 planets with the Hubble Space Telescope. To date, there are no other temperate Earth-sized planets that would be such exquisite targets for atmospheric study. This justified fully scaling up with the SPECULOOS project.
Telescopes like this provide two important observational advantages. One, due to similar planet-to-star area ratios, the signal we’ll get from an Earth-sized planet transiting an ultra-cool dwarf star will be similar to a Jupiter-sized planet crossing in front of a sun-like star. Two, the vicinity of their habitable zone, due to their small size and temperature, means that habitable planets will have small transit periodicities, similar to gas giants, which are in close orbit around solar-type stars. This means that each star will require less monitoring time, and that the transit search targeting the roughly 1,200 nearest ultra-cool stars could be done in about 10 years with four telescopes scanning each hemisphere.
Q: What is the goal of Artemis, and how many exoplanets do you estimate can be evaluated by MIT’s new SPECULOOS Northern Observatory?
A: Over each night, we will be gathering pictures of a specific section of the sky, focused on our target stars in order to search for a brightness drop characteristic of a planetary transit.
The goal of the Artemis telescope is to look at the roughly 800 nearest ultra-cool dwarf stars located in the northern skies (and a sliver of the southern skies) to find Earth-sized planets that may have a temperate climate and be amenable for further in-depth characterization with the next generation of observatories, such as the James Webb Space Telescope (JWST) and the Extremely Large Telescopes. These will be able to tell us more about their atmosphere, climate, and what molecules might be present on them. We are confidently expecting to identify about 15 temperate planets with the SPECULOOS network, and doing so on a relevant timeline, which will allow for their atmospheres to be studied with the JWST, which is expected to launch in 2021 and last for 10 years.
Additionally, we’ll expand Artemis’s scope of work. We plan to do a follow-up of some of the trickiest planet candidates (terrestrial planets around small M-dwarfs) identified by the MIT-led TESS [Transiting Exoplanet Survey Satellite] NASA mission, since Artemis has 100 times larger viewing areas. We’ll also be able to study asteroids, comets, and other objects, such as observations of the Quaoar occultation, with other scientists at MIT and outside of the Institute.
Q: You mentioned that Artemis is the first telescope for the SPECULOOS Northern Observatory. Does that mean more telescopes might be added to the SPECULOOS network in the future?
A: Yes, we hope to build out the SPECULOOS Northern Observatory and add telescopes to accompany Artemis. As a matter of fact, we have already built an additional platform ready to host a twin to Artemis, as soon as we have found additional funding. Our agreement with the Teide Observatory reserves space to accommodate up to three additional telescopes. Doing so will allow us to thoroughly study all the nearest ultra-cool dwarf stars and complete the Northern Hemisphere survey in time to perform the atmospheric characterization of their transiting planets with the JWST.
With SPECULOOS, we are giving it our best shot at enabling the identification of habitats beyond Earth within the next decade. Our team is looking forward to sharing “first light” with our donors and the public, and it is a privilege for MIT to be working with our international partners on this exciting venture.
MIT has again been named the world’s top university by the QS World University Rankings, which were announced today. This is the eighth year in a row MIT has received this distinction.
The full 2019-20 rankings — published by Quacquarelli Symonds, an organization specializing in education and study abroad — can be found at topuniversities.com. The QS rankings were based on academic reputation, employer reputation, citations per faculty, student-to-faculty ratio, proportion of international faculty, and proportion of international students. MIT earned a perfect overall score of 100.
MIT received a No. 1 ranking in the following QS subject areas: Chemistry; Computer Science and Information Systems; Chemical Engineering; Civil and Structural Engineering; Electrical and Electronic Engineering; Mechanical, Aeronautical and Manufacturing Engineering; Linguistics; Materials Science; Mathematics; Physics and Astronomy; and Statistics and Operational Research.
MIT also placed second in six subject areas: Accounting and Finance; Architecture/Built Environment; Biological Sciences; Earth and Marine Sciences; Economics and Econometrics; and Environmental Sciences.
MIT Physics by David L. Chandler | Mit News Office - 1M ago
The formation of air bubbles in a liquid appears very similar to its inverse process, the formation of liquid droplets from, say, a dripping water faucet. But the physics involved is actually quite different, and while those water droplets are uniform in their size and spacing, bubble formation is typically a much more random process.
Now, a study by researchers at MIT and Princeton University shows that under certain conditions, bubbles can also be coaxed to form spheres as perfectly matched as droplets.
The new findings could have implications for the development of microfluidic devices for biomedical research and for understanding the way natural gas interacts with petroleum in the tiny pore spaces of underground rock formations, the researchers say. The findings are published today in the journal PNAS, in a paper by MIT graduate Amir Pahlavan PhD ’18, Professor Howard Stone of Princeton, MIT School of Engineering Professor of Teaching Innovation Gareth McKinley, and MIT Professor Ruben Juanes.
The key to producing uniformly sized and spaced bubbles lies in confining them to a narrow space, Juanes explains. When air or gas is released into a large container of liquid, the dispersal of bubbles is scattershot. When released into liquid that is confined in a relatively narrow tube, however, the gas will produce a stream of bubbles perfectly matched in size, and forming at even intervals. This uniform and predictable behavior, independent of specific starting conditions, is known as universality.
The process of formation of droplets or bubbles is very similar, beginning with an elongation of the flowing material (whether it’s air or water), and eventually a thinning and pinch-off of the “neck” connecting the droplet or bubble to the flowing material. That pinch-off then allows the droplet or bubble to collapse into a spherical shape. Picture blowing soap bubbles: As you blow through the ring, a tube of soap film gradually extends outward in a long pouch before pinching off to form a round bubble that floats away.
Motion of a microbubble in the vicinity of the bubble neck. The microbubble here acts as a tracer showing the flow direction.
“The process of a droplet dripping from a faucet is known to be universal,” says Juanes, who has a joint appointment in the departments of Civil and Environmental Engineering and Earth, Atmospheric and Planetary Sciences. If the dripping liquid has a different viscosity or surface tension, or if the opening of the faucet is a different size, “it doesn’t matter. You can find relationships that allow you to determine a master curve or a master behavior for describing that process,” he says.
But when it comes to what is, in a sense, the opposite process to a dripping faucet — the injection of air through an opening into a large tank of liquid such as a Jacuzzi tub — the process is not universal. “So if you have irregularities in the orifice, or if the orifice is larger or smaller, or if you inject with some pulsation, all of that will lead to a different pinch-off of the bubbles,” Juanes says.
The new experiments involved gas percolating onto viscous liquids such as oil. In an unconfined space, the sizes of the bubbles are unpredictable, but the situation changes when they bubble into liquid in a tube instead. Up to a certain point, the size and shape of the tube doesn’t matter, nor do the characteristics of the orifice the gas comes through. Instead the bubbles, like the droplets from a faucet, are uniformly sized and spaced.
Evolution of the dewetting rim and the ultimate breakup of the bubble in a capillary tube. Courtesy of the researchers
Pahlavan says, “Our work is really a tale of two surprising observations; the first surprising observation came around 15 years ago, when another group investigating formation of bubbles in large liquid tanks observed that the pinch-off process is nonuniversal” and depends on the details of the experimental setup. “The second surprise now comes in our work, which shows that confining the bubble inside a capillary tube makes the pinch-off insensitive to the details of the experiment and therefore universal.”
This observation is “surprising,” he says, because intuitively it might seem that bubbles able to move freely through the liquid would be less affected by their initial conditions than those that are hemmed in. But the opposite turned out to be true. It turns out that interactions between the tube and the forming bubble, as a line of contact between the air and the liquid advances along the inside of the tube, play an important role. This “effectively erases the memory of the system, of the details of the initial conditions, and therefore restores the universality to the pinch-off of a bubble,” he says.
While such research may seem esoteric, its findings have potential applications in a variety of practical settings, Pahlavan says. “Controlled generation of drops and bubbles is very desirable in microfluidics, with many applications in mind. A few examples are inkjet printing, medical imaging, and making particulate materials.”
The new understanding is also important for some natural processes. “In geophysical applications, we often see fluid flows in very tight and confined spaces,” he says. These interactions between the fluids and the surrounding grains are often neglected in analyzing such processes. But the behavior of such geological systems is often determined by processes at the grain-scale, which means that the kind of microscale analysis done in this work could be helpful in understanding even such very large-scale situations.
The bubble formation in such geological formations can be a blessing or a curse, depending on the context, Juanes says, but either way it’s important to understand. For carbon sequestration, for example, the hope is to pump carbon dioxide, separated out from power plant emissions, into deep formations to prevent the gas from getting out into the atmosphere. In this case, the formation of bubbles in tiny pore spaces in the rock is an advantage, because the bubbles tend to block the flow and keep the gas anchored in position, preventing it from leaking back out.
But for the same reason, bubble formation in a natural gas well can be a problem, because it can also block the flow, inhibiting the ability to extract the desired natural gas. “It can be immobilized in the pore space,” he says. “It would take a much greater pressure to be able to move that bubble.”
“This is a very nice and careful piece of work,” says Jens Eggers, a professor of applied mathematics at the University of Bristol, in the U.K., who was not involved in this research. “It almost goes without saying that a large part of the success of this paper is that it is backed up by careful and quantitative experiments.”
These findings, he says, reflect the fact that “there is a lot more complexity
to problems like pinch-off than previously thought.” Eggers adds that “Of course, understanding this complexity is crucial for applications, where one does not have a choice to pick a particularly simple part of the problem, but has to face all the complications.”
MIT Physics by Julia Mongo | Office Of Distinguish.. - 1M ago
This article has been updated to include a scholar who was promoted from alternate to winner in June 2019.
Twelve MIT graduating seniors and current graduate students have been named winners in the 2019-2020 Fulbright U.S. Student Fellowship Program. In addition to the 12 students accepting their awards, three applicants from MIT were selected as finalists but decided to decline their grants.
MIT’s newest Fulbright students will engage in independent research and English teaching assignments in Brazil, France, the Netherlands, Spain, Russia, Taiwan, and Senegal.
Sponsored by the U.S. Department of State’s Bureau of Educational and Cultural Affairs, the mission of Fulbright is to promote cultural exchange, increase mutual understanding, and build lasting relationships among people of the world. The Fulbright U.S. Student Program offers grants in over 140 countries.
The MIT students were supported in the application process by the Presidential Committee on Distinguished Fellowships, chaired by professors Rebecca Saxe and Will Broadhead, and by MIT’s Distinguished Fellowships Office within Career Advising and Professional Development. The MIT winners are:
Annamarie "Anna" Bair ’18 earned a bachelor of science in computer science and engineering in June 2018 and will receive her master of engineering degree in computer science later this year. In Barcelona, Spain, Bair will engage in complex systems research.
Abigail "Abby" Bertics will graduate in June with a bachelor of science in electrical engineering and computer science. Her research in Yekaterinburg, Russia, will focus on natural language processing methods for understanding English second language acquisition by Russian speakers.
Hope Chen is a senior graduating with a bachelor of science in mechanical engineering. She will be going to Taiwan as an English Teaching Assistant in primary school classrooms. After completing her Fulbright program and returning to the U.S., Chen will matriculate in medical school.
Dariel Cobb is a doctoral student in the History, Theory and Criticism program within the MIT School of Architecture and Planning. In France, she will conduct archival research on architect Henri Chomette’s projects in Francophone West Africa in the years surrounding independence, and the influence of the Négritude movement on modern architecture.
Alexis D’Alessandro will graduate this spring with a bachelor of science in mechanical engineering. For her research in Aracaju, Brazil, she will develop an educational program and chemical sensing tool to promote water safety awareness among children.
Sarah DiIorio will earn her bachelor of science in biological engineering in June. She is headed to Eindhoven, the Netherlands, to conduct medical research related to cartilage regeneration for osteoarthritis.
Katie Fisher is a senior in MIT’s Scheller Teaching Education Program graduating with a bachelor of science in urban studies and planning with a concentration in education. As an English teaching assistant in the Netherlands, Fisher will work with students at a vocational college in Amsterdam.
Miranda McClellan ’18 received a bachelor of science in computer science and engineering in June 2018 and will earn her master of engineering degree in computer science this spring. McClellan will research automated scaling of 5G computer network resources in Barcelona, Spain.
Samira Okudo will graduate in June with a joint bachelor of science in computer science and comparative media studies. As an English teaching assistant in Brazil, she will work with university students training to be English-language instructors.
James Pelletier is a PhD candidate in physics. For his Fulbright research in Madrid, Spain, he will develop biophysical models to investigate how plants process information for cellular resource allocation and agricultural efficiency.
Jonars Spielberg is a third-year doctoral student in the Department of Urban Studies and Planning’s international development program. In Senegal, he will examine how the personal interactions of bureaucrats and farmers shape agricultural policy implementation in the country's main irrigated regions.
Catherine Wu will graduate in June with a bachelor of science in biology. She will be working with university students in Brazil as a Fulbright English Teaching Assistant.
MIT students interested in applying to the Fulbright U.S. Student Program should contact Julia Mongo in Distinguished Fellowships.
When a raindrop falls through a thundercloud, it is subject to strong electric fields that pull and tug on the droplet, like a soap bubble in the wind. If the electric field is strong enough, it can cause the droplet to burst apart, creating a fine, electrified mist.
Scientists began taking notice of how droplets behave in electric fields in the early 1900s, amid concerns over lightning strikes that were damaging newly erected power lines. They soon realized that the power lines’ own electric fields were causing raindrops to burst around them, providing a conductive path for lightning to strike. This revelation led engineers to design thicker coverings around power lines to limit lightning strikes.
Today, scientists understand that the stronger the electric field, the more likely it is that a droplet within it will burst. But, calculating the exact field strength that will burst a particular droplet has always been an involved mathematical task.
Now, MIT researchers have found that the conditions for which a droplet bursts in an electric field all boil down to one simple formula, which the team has derived for the first time.
With this simple new equation, the researchers can predict the exact strength an electric field should be to burst a droplet or keep it stable. The formula applies to three cases previously analyzed separately: a droplet pinned on a surface, sliding on a surface, or free-floating in the air.
Their results, published today in the journal Physical Review Letters, may help engineers tune the electric field or the size of droplets for a range of applications that depend on electrifying droplets. These include technologies for air or water purification, space propulsion, and molecular analysis.
“Before our result, engineers and scientists had to perform computationally intensive simulations to assess the stability of an electrified droplet,” says lead author Justin Beroz, a graduate student in MIT’s departments of Mechanical Engineering and Physics. “With our equation, one can predict this behavior immediately, with a simple paper-and-pencil calculation. This is of great practical benefit to engineers working with, or trying to design, any system that involves liquids and electricity.”
Beroz’ co-authors are A. John Hart, associate professor of mechanical engineering, and John Bush, professor of mathematics.
“Something unexpectedly simple”
Droplets tend to form as perfect little spheres due to surface tension, the cohesive force that binds water molecules at a droplet’s surface and pulls the molecules inward. The droplet may distort from its spherical shape in the presence of other forces, such as the force from an electric field. While surface tension acts to hold a droplet together, the electric field acts as an opposing force, pulling outward on the droplet as charge builds on its surface.
“At some point, if the electric field is strong enough, the droplet can’t find a shape that balances the electrical force, and at that point, it becomes unstable and bursts,” Beroz explains.
He and his team were interested in the moment just before bursting, when the droplet has been distorted to its critically stable shape. The team set up an experiment in which they slowly dispensed water droplets onto a metal plate that was electrified to produce an electric field, and used a high-speed camera to record the distorted shapes of each droplet.
“The experiment is really boring at first — you’re watching the droplet slowly change shape, and then all of a sudden it just bursts,” Beroz says.
After experimenting on droplets of different sizes and under various electric field strengths, Beroz isolated the video frame just before each droplet burst, then outlined its critically stable shape and calculated several parameters such as the droplet’s volume, height, and radius. He plotted the data from each droplet and found, to his surprise, that they all fell along an unmistakably straight line.
“From a theoretical point of view, it was an unexpectedly simple result given the mathematical complexity of the problem,” Beroz says. “It suggested that there might be an overlooked, yet simple, way to calculate the burst criterion for the droplets.”
A water droplet, subject to an electric field of slowly increasing strength, suddenly bursts by emitting a fine, electrified mist from its apex.
Volume above height
Physicists have long known that a liquid droplet in an electric field can be represented by a set of coupled nonlinear differential equations. These equations, however, are incredibly difficult to solve. To find a solution requires determining the configuration of the electric field, the shape of the droplet, and the pressure inside the droplet, simultaneously.
“This is commonly the case in physics: It’s easy to write down the governing equations but very hard to actually solve them,” Beroz says. “But for the droplets, it turns out that if you choose a particular combination of physical parameters to define the problem from the start, a solution can be derived in a few lines. Otherwise, it’s impossible.”
Physicists who attempted to solve these equations in the past did so by factoring in, among other parameters, a droplet’s height — an easy and natural choice for characterizing a droplet’s shape. But Beroz made a different choice, reframing the equations in terms of a droplet’s volume rather than its height. This was the key insight for reformulating the problem into an easy-to-solve formula.
“For the last 100 years, the convention was to choose height,” Beroz says. “But as a droplet deforms, its height changes, and therefore the mathematical complexity of the problem is inherent in the height. On the other hand, a droplet’s volume remains fixed regardless of how it deforms in the electric field.”
By formulating the equations using only parameters that are “fixed” in the same sense as a droplet’s volume, “the complicated, unsolvable parts of the equation cancel out, leaving a simple equation that matches the experimental results,” Beroz says.
Specifically, the new formula the team derived relates five parameters: a droplet’s surface tension, radius, volume, electric field strength, and the electric permittivity of the air surrounding the droplet. Plugging any four of these parameters into the formula will calculate the fifth.
Beroz says engineers can use the formula to develop techniques such as electrospraying, which involves the bursting of a droplet maintained at the orifice of an electrified nozzle to produce a fine spray. Electrospraying is commonly used to aerosolize biomolecules from a solution, so that they can pass through a spectrometer for detailed analysis. The technique is also used to produce thrust and propel satellites in space.
“If you’re designing a system that involves liquids and electricity, it’s very practical to have an equation like this, that you can use every day,” Beroz says.
This research was funded in part by the MIT Deshpande Center for Technological Innovation, BAE Systems, the Assistant Secretary of Defense for Research and Engineering via MIT Lincoln Laboratory, the National Science Foundation, and a Department of Defense National Defence Science and Engineering Graduate Fellowship.