Monday, October 28th, 2019

Time	Event
11:15a	Nature can help solve optimization problems Today's best digital computers still struggle to solve, in a practical time frame, a certain class of problem: combinatorial optimization problems, or those that involve combing through large sets of possibilities to find the best solution. Quantum computers hold potential to take on these problems, but scaling up the number of quantum bits in these systems remains a hurdle.  Now, MIT Lincoln Laboratory researchers have demonstrated an alternative, analog-based way to accelerate the computing of these problems. "Our computer works by 'computing with physics' and uses nature itself to help solve these tough optimization problems," says Jeffrey Chou, co-lead author of a paper about this work published in Nature's Scientific Reports. "It's made of standard electronic components, allowing us to scale our computer quickly and cheaply by leveraging the existing microchip industry." Perhaps the most well-known combinatorial optimization problem is that of the traveling salesperson. The problem asks to find the shortest route a salesperson can take through a number of cities, starting and ending at the same one. It may seem simple with only a few cities, but the problem becomes exponentially difficult to solve as the number of cities grows, bogging down even the best supercomputers. Yet optimization problems need to be solved in the real world daily; the solutions are used to schedule shifts, minimize financial risk, discover drugs, plan shipments, reduce interference on wireless networks, and much more. "It has been known for a very long time that digital computers are fundamentally bad at solving these types of problems," says Suraj Bramhavar, also a co-lead author. "Many of the algorithms that have been devised to find solutions have to trade off solution quality for time. Finding the absolute optimum solution winds up taking an unreasonably long time when the problem sizes grow." Finding better solutions and doing so in dramatically less time could save industries billions of dollars. Thus, researchers have been searching for new ways to build systems designed specifically for optimization. Finding the beat   Nature likes to optimize energy, or achieve goals in the most efficient and distributed manner. This principle can be witnessed in the synchrony of nature, like heart cells beating together or schools of fish moving as one. Similarly, if you set two pendulum clocks on the same surface, no matter when the individual pendula are set into motion, they will eventually be lulled into a synchronized rhythm, reaching their apex at the same time but moving in opposite directions (or out of phase). This phenomenon was first observed in 1665 by the Dutch scientist Christiaan Huygens. These clocks are an example of coupled oscillators, set up in such a way that energy can be transferred between them.  "We've essentially built an electronic, programmable version of this [clock setup] using coupled nonlinear oscillators," Chou says, showing a YouTube video of metronomes displaying a similar phenomenon. "The idea is that if you set up a system that encodes your problem's energy landscape, then the system will naturally try to minimize the energy by synchronizing, and in doing so, will settle on the best solution. We can then read out this solution." The laboratory's prototype is a type of Ising machine, a computer based on a model in physics that describes a network of magnets, each of which have a magnetic "spin" orientation that can point only up or down. Each spin's final orientation depends on its interaction with every other spin. The individual spin-to-spin interactions are defined with a specific coupling weight, which denotes the strength of their connection. The goal of an Ising machine is to find, given a specific coupling strength network, the correct configuration of each spin, up or down, that minimizes the overall system energy. But how does an Ising machine solve an optimization problem? It turns out that optimization problems can be mapped directly onto the Ising model, so that a set of a spins with certain coupling weights can represent each city and the distances between them in the traveling salesperson problem. Thus, finding the lowest-energy configuration of spins in the Ising model translates directly into the solution for the seller's fastest route. However, solving this problem by individually checking each of the possible configurations becomes prohibitively difficult when the problems grow to even modest sizes.  In recent years, there have been efforts to build quantum machines that map to the Ising model, the most notable of which is one from the Canadian company D-Wave Systems. These machines may offer an efficient way to search the large solution space and find the correct answer, although they operate at cryogenic temperatures. The laboratory's system runs a similar search, but does so using simple electronic oscillators. Each oscillator represents a spin in the Ising model, and similarly takes on a binarized phase, where oscillators that are synchronized, or in phase, represent the "spin up" configuration and those that are out of phase represent the "spin down" configuration. To set the system up to solve an optimization problem, the problem is first mapped to the Ising model, translating it into programmable coupling weights connecting each oscillator. With the coupling weights programmed, the oscillators are allowed to run, like the pendulum arm of each clock being released. The system then naturally relaxes to its overall minimum energy state. Electronically reading out each oscillator's final phase, representing "spin up" or "spin down," presents the answer to the posed question. When the system ran against more than 2,000 random optimization problems, it came to the correct solution 98 percent of the time. Previously, researchers at Stanford University demonstrated an Ising machine that uses lasers and electronics to solve optimization problems. That work revealed the potential for a significant speedup over digital computing although, according to Chou, the system may be difficult and costly to scale to larger sizes. The goal of finding a simpler alternative ignited the laboratory's research.  Scaling up The individual oscillator circuit the team used in their demonstration is similar to circuitry found inside cellphones or Wi-Fi routers. One addition they've made is a crossbar architecture that allows all of the oscillators in the circuit to be directly coupled to each other. "We have found an architecture that is both scalable to manufacture and can enable full connectivity to thousands of oscillators," Chou says. A fully connected system allows it to easily be mapped to a wide variety of optimization problems.  "This work from Lincoln Laboratory makes innovative use of a crossbar architecture in its construction of an analog-electronic Ising machine," says Peter McMahon, an assistant professor of applied and engineering physics at Cornell University who was not involved in this research. "It will be interesting to see how future developments of this architecture and platform perform."   The laboratory's prototype Ising machine uses four oscillators. The team is now working out a plan to scale the prototype to larger numbers of oscillators, or "nodes," and fabricate it on a printed circuit board. "If we can get to, say, 500 nodes, there is a chance we can start to compete with existing computers, and at 1,000 nodes we might be able to beat them," Bramhavar says. The team sees a clear path forward to scaling up because the technology is based on standard electronic components. It's also extremely cheap. All the parts for their prototype can be found in a typical undergraduate electrical engineering lab and were bought online for about $20. "What excites me is the simplicity," Bramhavar adds. "Quantum computers are expected to demonstrate amazing performance, but the scientific and engineering challenges required to scale them up are quite hard. Demonstrating even a small fraction of the performance gains envisioned with quantum computers, but doing so using hardware from the existing electronics industry, would be a huge leap forward. Exploiting the natural behavior of these circuits to solve real problems presents a very compelling alternative for what the next era of computing could be." (Comment on this)
11:40a	Collision course: a geological mystery in the Himalayas According to Craig Martin, deciphering Earth’s geologic past is like an ant climbing over a car crash. “You’ve got to work out how the car crash happened, how fast the cars were going, at what angle they impacted,” explains Martin, a graduate student at MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “You’re just a tiny ant wandering over this massive chaos,” he adds. The crash site Martin is investigating is the Himalayas, a 1,400-mile mountain range that rose when the Indian and Eurasian tectonic plates scrunched together. “The mainstream idea is: There was Eurasia; there was India; and they collided 50 million years ago,” says Oliver Jagoutz, an associate professor in EAPS and Martin’s advisor. “We think it was much more complicated than that, because it’s always more complicated.” Detective work at 11,000 feet Eighty million years ago, India and Eurasia were 4,000 miles apart, separated by an ancient body of water that geologists call the Neotethys Ocean, but Jagoutz believes there was more than just seawater between the two. He’s not alone. Many geologists agree on the existence of an arc of volcanic islands that formed on the boundary of a smaller tectonic plate, similar to the Mariana Islands in the Pacific Ocean. However, there is debate on whether these islands first collided with the Eurasian plate to the north or the Indian plate to the south. Jagoutz’s hypothesis is the latter. “If I’m right, the arc sits near the equator. If the others are right, the fragments should be 30 degrees north,” he explains. “That’s how simple it is.” But it can mean a world of difference in terms of explaining the paleoclimate — not just in the Himalayas, but globally as well. To confirm this idea, Jagoutz and Martin turned to paleomagnetism. Some rock minerals, such as magnetite, contain iron and orient themselves along Earth’s magnetic field. At the equator, magnetite in newly formed rocks will be parallel to the ground, but the further north or south it is, the more inclined it will be. “We can measure, essentially, the latitude that a rock was formed at,” explains Martin. If you were to take a slice of the Kohistan-Ladakh region of the Himalayas in northern India, you would see a succession of rock layers representing the India plate and the Eurasia plate, with the volcanic island arc sandwiched in between. “That’s why Ladakh is a really cool place to go to, because you can walk though this whole collision,” says Martin. In summer 2018, Martin and Jade Fischer, a junior double-majoring in EAPS and physics, spent six weeks in Ladakh collecting samples from the volcanic rocks. Back at MIT, Martin measured the paleomagnetic signature of these rocks, and his results placed the Kohistan-Ladakh arc right at the equator, in agreement with Jagoutz’s theory. A magnetic collaboration Megan Guenther, a junior in EAPS, first heard about the opportunity to do field work in Ladakh when Martin gave a presentation about his research in her structural geology class last fall. “At the end, he told us he was probably going again and to let him know if we were interested,” Guenther explains. “I emailed him an hour later.” Guenther had been looking for a chance to gain more field experience. She works on the compositions of lunar glasses with Tim Grove, the Robert R. Shrock Professor of Earth and Planetary Sciences, where the research takes place entirely in the lab. “You can’t really do field work on the moon,” she jokes. This past summer, Guenther and Martin spent six weeks in Ladakh collecting rock samples from the Eurasia plate to prove that this was not also further south, mapping the region and doing structural analyses. Both Guenther and Martin were supported by MIT International Science and Technology Initiatives (MISTI) and the MISTI Global Seed Fund. MISTI and Jagoutz go back a long time, with MISTI funding class excursions, department field trips, and a number of Jagoutz’s students. “MISTI-India has been good to us,” he says. “They financed the workshop where we came up with the whole concept of this work.” And, says Jagoutz, the students really love the experience. “They get influenced by it, and a lot of people chose their career paths after it,” says Jagoutz. “Ultimately, that’s what MISTI is all about: an experience that tells students they want to get into science.” For Guenther, the trip was an essential part of her education as a geologist. “I feel much more confident as a field geologist, which is exactly what I wanted,” she says. It also impressed on her the titanic scale of geology. “The scale of everything is so crazy,” says Guenther. “You’re already at 11,000 feet, minimum, the whole time, and then these huge mountains tower above that.” By solving the story of the collision that resulted in the Himalayas, Jagoutz and his team also shed light on its global implications. Large-scale collisions, Jagoutz explains, don’t just have local effects, and in the case of the Himalayas they can also explain some of Earth’s past glaciation events. “That’s the good thing about geology: the dimensions,” says Jagoutz. “You look at a magnetite crystal in a rock, and it tells you how global cooling works.” (Comment on this)
12:00p	New synthesis method yields degradable polymers MIT chemists have devised a way to synthesize polymers that can break down more readily in the body and in the environment. A chemical reaction called ring-opening metathesis polymerization, or ROMP, is handy for building novel polymers for various uses such as nanofabrication, high-performance resins, and delivering drugs or imaging agents. However, one downside to this synthesis method is that the resulting polymers do not naturally break down in natural environments, such as inside the body. The MIT research team has come up with a way to make those polymers more degradable by adding a novel type of building block to the backbone of the polymer. This new building block, or monomer, forms chemical bonds that can be broken down by weak acids, bases, and ions such as fluoride. “We believe that this is the first general way to produce ROMP polymers with facile degradability under biologically relevant conditions,” says Jeremiah Johnson, an associate professor of chemistry at MIT and the senior author of the study. “The nice part is that it works using the standard ROMP workflow; you just need to sprinkle in the new monomer, making it very convenient.” This building block could be incorporated into polymers for a wide variety of uses, including not only medical applications but also synthesis of industrial polymers that would break down more rapidly after use, the researchers say. The lead author of the paper, which appears in Nature Chemistry today, is MIT postdoc Peyton Shieh. Postdoc Hung VanThanh Nguyen is also an author of the study. Powerful polymerization The most common building blocks of ROMP-generated polymers are molecules called norbornenes, which contain a ring structure that can be easily opened up and strung together to form polymers. Molecules such as drugs or imaging agents can be added to norbornenes before the polymerization occurs. Johnson’s lab has used this synthesis approach to create polymers with many different structures, including linear polymers, bottlebrush polymers, and star-shaped polymers. These novel materials could be used for delivering many cancer drugs at once, or carrying imaging agents for magnetic resonance imaging (MRI) and other types of imaging. “It’s a very robust and powerful polymerization reaction,” Johnson says. “But one of the big downsides is that the backbone of the polymers produced entirely consists of carbon-carbon bonds, and as a result, the polymers are not readily degradable. That’s always been something we’ve kept in the backs of our minds when thinking about making polymers for the biomaterials space.” To circumvent that issue, Johnson’s lab has focused on developing small polymers, on the order of about 10 nanometers in diameter, which could be cleared from the body more easily than larger particles. Other chemists have tried to make the polymers degradable by using building blocks other than norbornenes, but these building blocks don’t polymerize as efficiently. It’s also more difficult to attach drugs or other molecules to them, and they often require harsh conditions to degrade. “We prefer to continue to use norbornene as the molecule that enables us to polymerize these complex monomers,” Johnson says. “The dream has been to identify another type of monomer and add it as a co-monomer into a polymerization that already uses norbornene.” The researchers came upon a possible solution through work Shieh was doing on another project. He was looking for new ways to trigger drug release from polymers, when he synthesized a ring-containing molecule that is similar to norbornene but contains an oxygen-silicon-oxygen bond. The researchers discovered that this kind of ring, called a silyl ether, can also be opened up and polymerized with the ROMP reaction, leading to polymers with oxygen-silicon-oxygen bonds that degrade more easily. Thus, instead of using it for drug release, the researchers decided to try to incorporate it into the polymer backbone to make it degradable. They found that by simply adding the silyl-ether monomer in a 1:1 ratio with norbornene monomers, they could create similar polymer structures to what they have previously made, with the new monomer incorporated fairly uniformly throughout the backbone. But now, when exposed to a slightly acidic pH, around 6.5, the polymer chain begins to break apart. “It’s quite simple,” Johnson says. “It’s a monomer we can add to widely used polymers to make them degradable. But as simple as that is, examples of such an approach are surprisingly rare.” Faster breakdown In tests in mice, the researchers found that during the first week or two, the degradable polymers showed the same distribution through the body as the original polymers, but they began to break down soon after that. After six weeks, the concentrations of the new polymers in the body were between three and 10 times less than the concentrations of the original polymers, depending on the exact chemical composition of the silyl-ether monomers that the researchers used. The findings suggest that adding this monomer to polymers for drug delivery or imaging could help them get cleared from the body more quickly. “We are excited about the prospect of using this technology to precisely tune the breakdown of ROMP-based polymers in biological tissues, which we believe could be leveraged to control biodistribution, drug release kinetics, and many other features,” Johnson says. The researchers have also started working on adding the new monomers to industrial resins, such as plastics or adhesives. They believe it would be economically feasible to incorporate these monomers into the manufacturing processes of industrial polymers, to make them more degradable, and they are working with Millipore-Sigma to commercialize this family of monomers and make them available for research. The research was funded by the National Institutes of Health, the American Cancer Society, and the National Science Foundation. (Comment on this)
12:00p	J-PAL North America announces five new partnerships with state and local governments J-PAL North America, a research center in MIT’s Department of Economics, announced new partnerships with five state and local governments across the United States. The California Department of State Hospitals, Minnesota Board of Pharmacy, Minnesota State Court Administrator’s Office, Shasta County Superior Court, and Virginia Department of Social Services were selected to partner with J-PAL North America and its network of leading academic researchers through the J-PAL State and Local Innovation Initiative. These partnerships will develop randomized evaluations, also known as randomized controlled trials (RCTs), which have the potential to yield rigorous evidence about which programs and policies are most effective.  “We are thrilled to partner with these five state and local governments to address pressing policy problems across the country through rigorous evaluation,” says Mary Ann Bates, J-PAL North America executive director and co-chair of the State and Local Innovation Initiative. “We are particularly excited about how many of these projects will build on evidence from prior randomized evaluations to test if similar interventions can be effective in different settings.” These proposals will examine a wide variety of topics and intervention methods, including reducing over-prescription of opioids, reducing failures to appear for arraignment, addressing homelessness and housing instability, and increasing the take-up of federal tax credits for low-income families. In California, individuals with serious mental illness who face felony charges and are likely to be found incompetent to stand trial are directed to the Department of State Hospitals (DSH) to receive treatments to regain competency. DSH has launched a new Pre-trial Felony Mental Health Diversion program, through which approximately 20 counties will receive funding to divert individuals who are incompetent to stand trial out of the criminal justice system and into wrap-around community treatment services. DSH is partnering with J-PAL North America to evaluate the effects of the Pre-Trial Felony Mental Health Diversion program. This evaluation will contribute significant insight into how diverting those found to be incompetent to stand trial due to mental health reasons to community mental health services may impact their individual well-being, as well as broader outcomes in the criminal justice and behavioral health systems. “The California Department of State Hospitals is pleased to partner with J-PAL to evaluate how Felony Mental Health Diversion impacts individuals living with serious mental illness in California,” says Stephanie Clendenin, director of the California Department of State Hospitals. “The Felony Mental Health Diversion program seeks to provide long-term community mental health treatment and other services for individuals with serious mental illness so that they avoid criminalization and institutionalization and receive the critical mental health care and supportive services they need.” While the opioid prescribing rate among physicians has declined in recent years, the number of opioids prescribed per person remains three times higher than in 1999. Many states are testing interventions to reduce the overprescription of opioids among physicians. The Minnesota Board of Pharmacy and Minnesota Management and Budget will partner with J-PAL North America to identify ways to increase the use of Minnesota’s prescription monitoring program (PMP) and measure the impact of that increased use on prescribers’ rate of controlled-substance prescriptions. The PMP database maintains a secure record of all controlled-substance prescriptions, and more frequent use of the database may help avoid prescribing to individuals misusing opioids and, instead, allow prescribers to make referrals to treatment services. "We are excited about this innovative partnership that will help Minnesota use data to increase the use of Prescription Monitoring Programs and reduce overprescribing of opioids,” says Myron Frans, commissioner of Minnesota Management and Budget. “The opioid crisis has caused tremendous damage to our families and communities. To achieve better results, we will continue to collaborate and use evidence-based governing principles to combat this crisis.” “The Minnesota Board of Pharmacy looks forward to working with Minnesota Management and Budget and J-PAL to evaluate our PMP, with the aim to increase use of the PMP and to analyze its impact on controlled substance prescription rates,” says Cody Wiberg, executive director of the Minnesota Board of Pharmacy. In 2017, Minnesota’s largest county piloted a text reminder program for individuals with court hearings; after promising results suggested the reminders increased court appearances, the Minnesota Judicial Branch decided to make these e-reminders available statewide. The Minnesota State Court Administrator’s Office is now working with Minnesota Management and Budget and J-PAL North America to test the content and timing of different messages to determine which behavioral strategies are most effective in reducing failures to appear for court hearings. Previous research suggests that behavioral nudges, like text messages and redesigned summons, can reduce failure-to-appears for criminal hearings. This evaluation will measure the effectiveness of different message content and whether these reminders can also be effective for increasing court appearances among tenants facing eviction proceedings. “Hearing eReminders are about keeping the justice system, and those within it, from incurring additional costs. We are focused on keeping the court process moving efficiently, because we know that justice delayed is justice denied,” says Minnesota State Court Administrator Jeff Shorba. “We have already seen from the 18-month pilot that parties who received some form of Hearing eReminder were 35 percent more likely to appear for their hearing. Rigorous evaluation of Hearing eReminder messages and sequencing will ensure we are delivering the most effective messages on the most impactful schedule.” Similarly, in Shasta County, California, individuals who commit low-level offenses receive court summonses that require offenders to appear in court. Failure to appear in court results in the issuance of an arrest warrant, which is costly for the criminal justice system and recipients. The Shasta County Superior Court will partner with J-PAL North America to evaluate behavioral interventions to reduce defendants’ failure to appear at arraignments. This evaluation will expand the previous literature on reducing failures to appear and provide insight into the effectiveness of these interventions in a different setting. “The Shasta County Superior Court is excited to join with J-PAL to analyze strategies that could help reduce the incidence of homeless individuals failing to appear to in court,” says Melissa Fowler-Bradley, court executive officer of the Shasta County Superior Court. “In Shasta County, about one-third of the people who fail to appear for their court cases are homeless, and similar statistics exist throughout the country. Unfortunately, a failure to appear has an added impact on those who are economically challenged. The Shasta County Superior Court’s goal is to reduce those failures to appear among the homeless population as much as possible using strategies that are proven effective through the rigorous evaluation made possible by J-PAL. A successful project created under this state and local initiative could have nationwide impact, improve the plight of the impoverished, and increase the efficiency of the criminal justice system.” Millions of dollars of the Earned Income Tax Credit (EITC), a federal tax credit for low-income households, go unclaimed every year. Previous research suggests that behavioral interventions, like messages and simplified materials, can increase the uptake of the EITC. The Virginia Department of Social Services will partner with J-PAL North America to develop an evaluation of a text-messaging intervention to generate higher rates of tax filing and EITC claims. This evaluation will add to the growing body of literature on behavioral interventions to increase EITC claims. “This new partnership with J-PAL is an opportunity to transform how we pursue our mission of triumphing over poverty, abuse, and neglect,” says Duke Storen, commissioner of the Virginia Department of Social Services. “We will gain valuable insight from the RCT about how to more effectively encourage eligible Virginians to claim the EITC, which has been found to be one of the most effective federal antipoverty programs. We anticipate the results of this work will not only improve how we communicate with our customers as it relates to the EITC and the full-spectrum of our programs and services, but will prove to benefit other states as well.”  The California Department of State Hospitals, Minnesota Board of Pharmacy, Minnesota State Court Administrator’s Office, Shasta County Superior Court, and Virginia Department of Social Services join 13 state and local governments selected through previous rounds of the J-PAL State and Local Innovation Initiative: Baltimore, Maryland; King County, Washington; Minneapolis, Minnesota; Philadelphia, Pennsylvania; Rochester, New York; Santa Clara, California; and Washington; the states of California, Washington, Massachusetts, Pennsylvania, New Mexico, and South Carolina; and the U.S. territory of Puerto Rico. These state and local governments are part of a growing movement to use evidence to improve the effectiveness of policies and programs and ultimately the lives of people experiencing poverty. Anyone wishing to learn more about the initiative or to receive updates about its progress is invited to visit online. The J-PAL contact for more information is Initiative Manager Rohit Naimpally. (Comment on this)

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