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Research Highlights
 predicts economic, public health repercussions of lifting quarantine before COVID-19 vaccine<img alt="" src="/Profiles/PublishingImages/Nehorai_2017.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>​</p><p><img src="/news/PublishingImages/PBAF-8626%20Quarantine%20Scenarios%20Illustrative%20Chart%20for%20Media-01.png" alt="" style="margin: 5px;"/></p><p>COVID-19, the disease caused by the SARS-Cov-2 virus, was officially declared a pandemic on March 11 by the World Health Organization. Nearly two months later, many municipalities and states around the country have decided to relax some of the limitations put in place to prevent the disease from spreading at a pace that threatened to overwhelm the health care system.</p><p>New interdisciplinary research from Washington University in St. Louis — carried out by an electrical and systems engineer and a biomedical engineer from the McKelvey School of Engineering and a health care economist from the Olin Business School — outlines the effects on the economy and health outcomes of three distinct quarantine scenarios.</p><p>Their model indicates that, of the scenarios they consider, keeping a strict self-quarantine policy for seniors until the number of new infections is drastically reduced, while gradually loosening the policy for the rest of the population, will lead to the best economic and health outcomes.</p><p>One key result is the model’s prediction of the way in which different scenarios affect the number of people hospitalized. In two scenarios, the maximum number of simultaneous hospitalizations is about 189,000. In one, however, about 4.4 million people would need to be hospitalized at once.</p><p>Their work is<a href=""> published on MedRxiv</a> and is currently under review.</p><p>In general, the team sought to answer the question: “What is the most effective way to handle a country-wide quarantine for 76 weeks?” by which time the model assumes a vaccine is available. “The goal is to quantify and mitigate the impact of the current pandemic,” according to <a href="">Arye Nehorai</a>, the Eugene and Martha Lohman Professor of Electrical Engineering in the Preston M. Green Department of Electrical & Systems Engineering.<br/></p><p></p><p>The group — which also includes David Schwartzman, a business economics PhD candidate in the Olin School, and Uri Goldsztejn, a PhD candidate in biomedical engineering — started with a Susceptible, Exposed, Infectious, Recovered (SEIR) model, a commonly used mathematical tool for predicting the spread of infections. This dynamic model allows for people to be moved between groups known as compartments, and for each compartment to in turn influence the other.</p><p>At their most basic, these models divide the population into four compartments: Those who are susceptible, exposed, infectious and recovered.</p><p>Nehorai and his team used compartments with data sourced from peer-reviewed sources:</p> <ul> <li><p>Susceptible population</p></li><li><p>Quarantined susceptible population</p></li><li><p>Exposed population<br/></p></li><li><p>Quarantined exposed population</p></li><li><p>Infected hospitalized population</p></li><li><p>Infected asymptomatic population</p></li><li><p>Quarantined infected asymptomatic population</p></li><li><p>Dead population</p></li><li><p>Recovered population</p></li><li><p>Quarantined recovered population</p></li></ul><p>Beyond those 10 categories, each was subdivided into seniors, aged 60 and older, and non-seniors, as well as into those who are more able to work from home and those whose productivity is more damaged at home and who earn less to begin with.</p><p>“And then we added something very important,” said Goldsztejn. “A large fraction of the population is asymptomatic. These people move a lot and are contagious, as opposed to ebola, for instance, where the sick are easy to spot and isolate.”</p><p>The team’s model was able to incorporate these people, as well. They did so by varying the contagiousness of asymptomatic people to mirror public health measures and individual behavioral changes in responses to the severity of the pandemic. To account for improvements in health knowledge over time, they model better health outcomes for those getting sick later.</p><p><span style="color: #666666; font-family: "open sans"; font-size: 1.15em; font-weight: 700;">Rushing to reopen worse in the end</span></p><p>In the end, the model shows three different possibilities of how quarantine might play out in the economy and in the health care system based on three different policy responses.</p><p>What they found, in short: “Rushing to reopen public spaces and businesses is great for a few weeks, but down the line, it’s very much worse,” Goldsztejn said.</p><p>In all three scenarios, there are three constants: 85% of non-seniors are quarantined; no restrictions are loosened for the first 40 weeks; a vaccine is available in 76 weeks; the majority of seniors remain quarantined until the vaccine is available.</p><p>In the first scenario, fairly restrictive quarantine measures are kept in place for 76 weeks. That leads to a sharp economic decline and about 200,000 deaths.</p><p>In the second, restrictive quarantine measures remain for 40 weeks, at which point the non-seniors go back to business as usual. This would lead to a rapid economic recovery followed by a second outbreak. Strict quarantine measures would need to be reestablished, which would undo any economic gain, and result in about 700,000 deaths.</p><p>The third scenario is similar to the second, but instead of going straight back to business as usual, the non-senior population leaves quarantine at a rate of 0.1% per day. Modeling shows this scenario to foster slow, steady economic improvement and about 220,000 deaths — with no second outbreak.</p><p>The addition of asymptomatic people had a profound effect, as well, suggesting that public health measures aimed at everyone — such as social distancing and limiting gatherings — will also help to limit the spread of the disease.</p><p>The scenarios considered by the model shared one outcome: No quarantine approach could bring economic and health outcomes back to pre-pandemic stages before a vaccine becomes available.</p><p>“Our research on modeling COVID-19 spread and the economy shows that it is critical to open the markets gradually while continuing the quarantine of seniors,” Nehorai said. In real-world terms, this means lifting restrictions at work several industries at a time, or gradually letting more low-risk people gather in one place.</p><p>However, he said, “If policymakers prioritize short-term economic productivity more, their quarantine policies may lead to many times more deaths and hospitalizations with minimal short-term economic gain.”</p><SPAN ID="__publishingReusableFragment"></SPAN><p><br/></p><span> <div class="cstm-section"><h3>Arye Nehorai</h3><div style="text-align: center;"> <img src="/Profiles/PublishingImages/Nehorai_2017.jpg?RenditionID=3" class="ms-rtePosition-4" alt="" style="margin: 5px;"/> <br/> </div><div style="text-align: left;"><ul style="padding-left: 20px; caret-color: #343434; color: #343434;"><li>The Eugene & Martha Lohman Professor of Electrical Engineering<br/></li><li>Research: Mathematical modeling of complex systems, statistical signal processing, machine learning, and imaging for information inference and decision making.<br/></li></ul></div><div style="text-align: center;"> <a href="/Profiles/Pages/Arye-Nehorai.aspx">>> ​View Bio</a><br/></div> </div></span>Brandie Jefferson avoid ‘worse’ outcome than past two months, model suggests seniors quarantined, measured reopening — under certain conditions<p>​To avoid ‘worse’ outcome than past two months, model suggests seniors quarantined, measured reopening — under certain conditions<br/></p> Engineering students, alumna win NSF Graduate Research Fellowships<img alt="" src="/news/PublishingImages/feb2020-east-end.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>Several McKelvey School of Engineering students have been offered the highly competitive National Science Foundation Graduate Research Fellowship.</p><p>The program recognizes and supports outstanding graduate students in NSF-supported science, technology, engineering and mathematics disciplines who are pursuing research-based master's and doctoral degrees at accredited U.S. institutions. The fellowship includes a three-year annual stipend of $34,000 along with a $12,000 cost of education allowance for tuition and fees, opportunities for international research and professional development, and the opportunity to conduct their own research.</p><p>In 2020, NSF made more than 2,000 fellowship offers to applicants. More than 1,700 applicants received honorable mentions, which is considered a significant academic achievement.</p><h4>The new fellows from McKelvey Engineering include:</h4><ul style="list-style-type: disc;"><li>Anna Marie Powell Eddelbuettel, who will earn a bachelor's degree in biomedical engineering in May and will pursue graduate study at Princeton University;</li><li>Jacob Graham, who will earn a bachelor's degree in mechanical engineering in May and will pursue graduate study in mechanical engineering;<br/></li><li>Nicholas Matteucci, who will earn a bachelor's degree in chemical engineering in May and will pursue graduate study in chemical engineering;<br/></li><li> Alumna Sydney Katz, who earned bachelor's degrees in electrical engineering and in applied science from Engineering in 2018, is pursuing graduate study in aeronautical and aerospace engineering at Stanford University.<br/></li></ul><h4>Fellows who are studying at McKelvey Engineering include:</h4><ul style="list-style-type: disc;"><li>Elisabeth Anna Jones, who earned a bachelor's degree from SUNY College at Geneseo and is a doctoral student in systems science & mathematics at WashU;</li><li>Xiaohong Tan, who earned a bachelor's degree from Purdue University and is a doctoral student in biomedical engineering at WashU;</li><li>Hannah Maria Zmuda, who earned a bachelor's degree from Washington State University and is a doctoral student in biomedical engineering at WashU;</li></ul><h4>Those receiving honorable mentions include:<br/></h4><ul style="list-style-type: disc;"><li>Patrick Ryan Naughton, who will earn a bachelor's degree in electrical engineering and computer science from McKelvey Engineering in May, who will pursue robotics and computer vision;</li><li>Erin Newcomer, who earned a bachelor's degree from the University of Missouri, is a doctoral student in biomedical engineering at WashU;</li></ul><ul style="list-style-type: disc;"><li>Elizabeth Anne Sivriver, who will earn a degree in computer science and mathematics from Arts & Sciences in May and will pursue graduate study in the human-computer interface.</li></ul><p> </p><SPAN ID="__publishingReusableFragment"></SPAN><br/>Beth Miller 2020-04-02T05:00:00ZMcKelvey Engineering students and alumni win NSF Graduate Research Fellowships. the wire: Real-time imaging helps reveal active sites of photocatalysts<img alt="" src="/news/PublishingImages/shutterstock_613151393_760-760x507.jpg?RenditionID=1" style="BORDER:0px solid;" /><p>Nanoscale photocatalysts are small, man-made particles that harvest energy from sunlight to produce liquid fuels and other useful chemicals. But even within the same batch, the particles tend to vary widely in size, shape and surface composition. That makes it hard for researchers to tell what’s really doing the work.</p><p>A real-time imaging solution developed at Washington University in St. Louis could help, as reported in a new study in the journal <a href="">ACS Catalysis</a>.</p> <p>“The challenge in correlating single-molecule optical images with specific active sites in nanoscale catalysts is that the 10 to 25 nanometer spatial resolution provided by this technique still averages over many atoms on the surface of the catalyst — thus making it difficult to correlate reaction events with the structure of the catalyst,” said <a href="">Bryce Sadtler</a>, assistant professor of chemistry in Arts & Sciences and co-lead author of the new study.</p><p>Sadtler wanted to try imaging catalytic reactions using single-molecule fluorescence ever since he arrived at Washington University in 2014. The project got a jump-start after he was introduced to <a href="/Profiles/Pages/Matthew-Lew.aspx">Matthew Lew</a>, assistant professor in the <a href="">Preston M. Green Department of Electrical & Systems Engineering</a> in the <a href="/Pages/home.aspx">McKelvey School of Engineering</a>.</p><p>“After several discussions with Matt, we agreed that the microscopy hardware and image processing he was developing for super-resolution microscopy could provide a powerful tool to obtain structural information on the nature of the active sites in nanoscale catalysts that was previously unattainable,” Sadtler said.</p><p>For the new work reported in ACS Catalysis, the researchers imaged individual chemical reactions taking place on the surface of single tungsten oxide nanowires, a type of nanoscale photocatalyst that Sadtler’s group synthesized for the study.</p><p>They used two different chemical reporters that become fluorescent, or light up, in response to different types of reactions on the surface of the nanowires. By analyzing the spatial patterns of where these chemical reactions occur, they were able to elucidate the chemical structure of active sites on the surface of the nanowires.</p><p>The researchers found that clusters of oxygen vacancies along the nanowire surface activate adsorbed water molecules during the photocatalytic generation of hydroxyl radicals — an important intermediate in the production of chemical fuels, including hydrogen gas and methanol, from sunlight.</p> <figure class="wp-caption alignright" style="box-sizing: inherit; display: inline; margin: 0px 0px 1.5em 1.5em; float: right; max-width: 100%; padding: 0px; border: none; background-image: none; caret-color: #3c3d3d; color: #3c3d3d; font-family: "source sans pro", "helvetica neue", helvetica, arial, sans-serif; font-size: 19.200000762939453px;"><img data-attachment-id="381518" data-permalink="" data-orig-file="" data-orig-size="1806,945" data-comments-opened="0" data-image-meta="{"aperture":"0","credit":"","camera":"","caption":"ImageJ=1.52k","created_timestamp":"0","copyright":"","focal_length":"0","iso":"0","shutter_speed":"0","title":"ImageJ=1.52k","orientation":"1"}" data-image-title="ImageJ=1.52k" data-medium-file="" data-large-file="" class="size-full wp-image-381518" src="" alt="photocatalyst graphic" style="box-sizing: inherit; border-width: 0px; width: 627px; display: block; margin: 5px;"/><figcaption class="wp-caption-text" style="box-sizing: inherit; margin-bottom: 0px; font-size: 1rem; font-style: italic; line-height: 1.333; color: #626464; margin-top: 0.25em;">(Image courtesy ACS Catalysis)</figcaption></figure> <p>“While previous studies have focused on isolated oxygen vacancies, a type of defect common in metal oxides, the results reveal the significance of a structural feature — clusters of oxygen vacancies — in achieving high photocatalytic activity,” Sadtler said.</p><p>“This new insight provides a path toward designing photocatalysts with enhanced activity for sunlight-to-fuel conversion by controlling the distribution of oxygen vacancies.”</p><p>The results themselves — and the process used to uncover them — are both exciting to the researchers.</p><p>“It is always a dream to directly observe the single catalytic turnovers on the surface of solid catalysts while the catalytic transformation is going on,” said <a href="">Meikun Shen</a>, a graduate student in chemistry and first author of the new paper. “I can only speak for myself, this is my personal feeling!”</p><p>This particular imaging approach provides detailed spatial and temporal information on the catalytic process — something that is usually invisible to scientists like him, Shen explained.</p><p>“In this type of experiment, the chemical properties of the catalyst are usually hard to reveal,” Shen said. “We managed to overcome this difficulty by using two different molecules to probe either the activity or the chemical property of the same catalyst. The direct correlation we observed is unique in the research field of heterogeneous catalysis.”</p><hr style="height: 1px; background-color: #c8c8c8; border-top-width: 0px; margin-bottom: 1.5em; caret-color: #3c3d3d; color: #3c3d3d; font-family: "source sans pro", "helvetica neue", helvetica, arial, sans-serif; font-size: 19.200000762939453px;"/><p>Funding: This project received internal seed funding from Washington University’s <a href="">International Center for Energy, Environment and Sustainability</a> (InCEES).</p><p>Read more: Nanoscale Colocalization of Fluorogenic Probes Reveals the Role of Oxygen Vacancies in the Photocatalytic Activity of Tungsten Oxide Nanowires. ACS Catal. 2020, 10, 3, 2088-2099. January 8, 2020. <a href=""></a><br/></p><span> <div class="cstm-section"><h3>Matthew Lew<br/></h3><div><p style="text-align: center;"> <img src="/Profiles/PublishingImages/Lew_Matthew_5620.jpg?RenditionID=3" class="ms-rtePosition-4" alt="" style="margin: 5px;"/> </p><p></p><ul style="padding-left: 20px; caret-color: #343434; color: #343434;"><li>Electrical Systems Engineering - <span style="caret-color: #343434; color: #343434;">Assistant Professor</span><br/></li><li>Research: Builds advanced imaging systems to study biological and chemical systems at the nanoscale, leveraging innovations in applied optics, signal and image processing, design optimization, and physical chemistry.<br/></li></ul><div style="text-align: center;"> <a href="/Profiles/Pages/Matthew-Lew.aspx">View Bio</a><br/></div></div><br/></div></span>An imaging solution developed in collaboration between chemists in Arts & Sciences and engineers at the McKelvey School of Engineering reveals the role of oxygen vacancies in the photocatalytic activity of tungsten oxide nanowires. (Photo: Shutterstock)Talia Ogliore research has implications for harvesting energy from sunlight<p>​InCEES-funded research has implications for harvesting energy from sunlight<br/></p> optical resonators gives researchers control over transparency<img alt="" src="/news/PublishingImages/EITUpdate.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>In the quantum realm, under some circumstances and with the right interference patterns, light can pass through opaque media.</p><p>This feature of light is more than a mathematical trick; optical quantum memory, optical storage and other systems that depend on interactions of just a few photons at a time rely on the process, called electromagnetically induced transparency, also known as EIT.  </p><p>Because of its usefulness in existing and emerging quantum and optical technologies, researchers are interested in the ability to manipulate EIT without the introduction of an outside influence, such as additional photons that could perturb the already delicate system. Now, researchers at the McKelvey School of Engineering at Washington University in St. Louis have devised a fully contained optical resonator system that can be used to turn transparency on and off, allowing for a measure of control that has implications across a wide variety of applications.<br/></p><p>The group published the results of the research, conducted in the lab of Lan Yang, the Edwin H. & Florence G. Skinner Professor in the Preston M. Green Department of Electrical & Systems Engineering, in a paper titled <a href="">Electromagnetically Induced Transparency at a Chiral Exceptional Point</a> in the Jan. 13 issue of <em>Nature Physics</em>.</p><p>An optical resonator system is analogous to an electronic resonant circuit but uses photons instead of electrons. Resonators come in different shapes, but they all involve reflective material that captures light for a period of time as it bounces back and forth between or around its surface. These components are found in anything from lasers to high precision measuring devices.</p><p>For their research, Yang’s team used a type of resonator known as a whispering gallery mode resonator (WGMR). It operates in a manner similar to the whispering gallery at St. Paul’s Cathedral, where a person on one side of the room can hear a person whispering on the other side. What the cathedral does with sound, however, WGMRs do with light — trapping light as it reflects and bounces along the curved perimeter.</p><p>In an idealized system, a fiber optic line intersects with a resonator, a ring made of silica, at a tangent. When a photon in the line meets the resonator, it swoops in, reflecting and propagating along the ring, exiting into the fiber in the same direction it was initially headed.</p><p>Reality, however, is rarely so neat.</p><p>“Fabrication in high quality resonators is not perfect,” Yang said. “There is always some defect, or dust, that scatters the light.” What actually happens is some of the scattered light changes direction, leaving the resonator and travelling back in the direction whence it came. The scattering effects disperse the light, and it doesn’t exit the system.</p><p>Imagine a box around the system: If the light entered the box from the left, then exited out the right side, the box would appear transparent. But if the light that entered was scattered and didn’t make it out, the box would seem opaque.</p><p>Because manufacturing imperfections in resonators are inconsistent and unpredictable, so too was transparency. Light that enters such systems scatters and ultimately loses its strength; it is absorbed into the resonator, rendering the system opaque.</p><p>In the system devised by co-first authors Changqing Wang, a PhD candidate, and Xuefeng Jiang, a researcher in Yang’s lab, there are two WGMRs indirectly coupled by a fiber optic line. The first resonator is higher in quality, having just one imperfection. Wang added a tiny pointed material that acts like a nanoparticle to the high-quality resonator. By moving the makeshift particle, Wang was able to “tune” it, controlling the way the light inside scatters.</p><p>Importantly, he was also able to tune the resonator to what’s known as an “exceptional point,” a point at which one and only one state can exist. In this case, the state is the direction of light in the resonator: clockwise or counter clockwise.</p><p>For the experiment, researchers directed light toward a pair of indirectly coupled resonators from the left (see illustration). The lightwave entered the first resonator, which was “tuned” to ensure light traveled clockwise. The light bounced around the perimeter, then exited, continuing along the fiber to the second, lower-quality resonator. </p><p>There, the light was scattered by the resonator’s imperfections and some of it began traveling counter clockwise along the perimeter. The light wave then returned to the fiber, but headed back toward the first resonator.</p><p>Critically, researchers not only used the nanoparticle in the first resonator to make the lightwaves move clockwise, they also tuned it in a way that, as the light waves propagated back and forth between resonators, a special interference pattern would form. As a result of that pattern, the light in the resonators was cancelled out, so to speak, allowing the light traveling along the fiber to eek by, rendering the system transparent. </p><p>It would be as if someone shined a light on a brick wall — no light would get through. But then another person with another flashlight shined it in the same spot and, all of a sudden, that spot in the wall became transparent.</p><p>One of the more important — and interesting — functions of EIT is its ability to create “slow light.” The speed of light is always constant, but the actual value of that speed can change based on the properties of the medium through which it moves. In a vacuum, light always travels at 300,000,000 meters per second.</p><p>With EIT, people have slowed light down to less than eight meters per second, Wang said. “That can have significant influence on the storage of light information. If light is slowed down, we have enough time to use the encoded information for optical quantum computing or optical communication.” If engineers can better control EIT, they can more reliably depend on slow light for these applications.</p><p>Manipulating EIT could also be used in the development of long distance communication. A tuning resonator can be indirectly coupled to another resonator kilometers away along the same fiber optic cable. “You could change the transmitted light down the line,” Yang said.</p><p>This could be critical for, among other things, quantum encryption.</p><p>The research team also included collaborators at Yale University, University of Chicago and the University of Southern California.<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><br/><div><div class="cstm-section"><h3>Lan Yang<br/></h3><div style="text-align: center;"> <strong><a href="/Profiles/Pages/Lan-Yang.aspx"><img src="/Profiles/PublishingImages/Yang_Lan.jpg?RenditionID=3" alt="Lan Yang" style="margin: 5px;"/></a> <br/></strong></div><ul style="text-align: left;"><li>Edwin H. & Florence G. Skinner Professor</li><li>Expertise: Photonics, optical sensing, microresonators, lasers, non-Hermitian physics, parity-time symmetry in photonics<br/></li></ul><p style="text-align: center;"> <a href="/Profiles/Pages/Lan-Yang.aspx">>> View Bio</a><br/></p></div></div><div class="cstm-section"><h3>Media Coverage<br/></h3><div> <strong>Photonics Media: </strong> <a href="">Tuned Resonators Allow Control of Electromagnetically Induced Transparency</a></div></div> <br/>Electromagnetically induced transparency (EIT) is "tuned" by two particles on the optical resonator. (Image: Yang Lab)Brandie Jefferson has ramifications for quantum computing, communications and more<p>​Method has ramifications for quantum computing, communications and more<br/></p>

Research Areas

Applied Physics
  • Nano-photonics
  • Quantum Optics
  • Engineered Materials
  • Electrodynamics
Devices & Circuits
  • Computer Engineering
  • Integrated Circuits
  • Radiofrequency Circuits
  • Sensors
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  • Optimization
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