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Tag: California Institute of Technology

  • Quantum-Enhanced Microscope Doubles Resolution

    Quantum-Enhanced Microscope Doubles Resolution

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    Newswise — Using a “spooky” phenomenon of quantum physics, Caltech researchers have discovered a way to double the resolution of light microscopes.

    In a paper appearing in the journal Nature Communications, a team led by Lihong Wang, Bren Professor of Medical Engineering and Electrical Engineering, shows the achievement of a leap forward in microscopy through what is known as quantum entanglement. Quantum entanglement is a phenomenon in which two particles are linked such that the state of one particle is tied to the state of the other particle regardless of whether the particles are anywhere near each other. Albert Einstein famously referred to quantum entanglement as “spooky action at a distance” because it could not be explained by his relativity theory.

    According to quantum theory, any type of particle can be entangled. In the case of Wang’s new microscopy technique, dubbed quantum microscopy by coincidence (QMC), the entangled particles are photons. Collectively, two entangled photons are known as a biphoton, and, importantly for Wang’s microscopy, they behave in some ways as a single particle that has double the momentum of a single photon.

    Since quantum mechanics says that all particles are also waves, and that the wavelength of a wave is inversely related to the momentum of the particle, particles with larger momenta have smaller wavelengths. So, because a biphoton has double the momentum of a photon, its wavelength is half that of the individual photons.

    This is key to how QMC works. A microscope can only image the features of an object whose minimum size is half the wavelength of light used by the microscope. Reducing the wavelength of that light means the microscope can see even smaller things, which results in increased resolution.

    Quantum entanglement is not the only way to reduce the wavelength of light being used in a microscope. Green light has a shorter wavelength than red light, for example, and purple light has a shorter wavelength than green light. But due to another quirk of quantum physics, light with shorter wavelengths carries more energy. So, once you get down to light with a wavelength small enough to image tiny things, the light carries so much energy that it will damage the items being imaged, especially living things such as cells. This is why ultraviolet (UV) light, which has a very short wavelength, gives you a sunburn.

    QMC gets around this limit by using biphotons that carry the lower energy of longer-wavelength photons while having the shorter wavelength of higher-energy photons.

    “Cells don’t like UV light,” Wang says. “But if we can use 400-nanometer light to image the cell and achieve the effect of 200-nm light, which is UV, the cells will be happy, and we’re getting the resolution of UV.”

    To achieve that, Wang’s team built an optical apparatus that shines laser light into a special kind of crystal that converts some of the photons passing through it into biphotons. Even using this special crystal, the conversion is very rare and occurs in about one in a million photons. Using a series of mirrors, lenses, and prisms, each biphoton—which actually consists of two discrete photons—is split up and shuttled along two paths, so that one of the paired photons passes through the object being imaged and the other does not. The photon passing through the object is called the signal photon, and the one that does not is called the idler photon. These photons then continue along through more optics until they reach a detector connected to a computer that builds an image of the cell based on the information carried by the signal photon. Amazingly, the paired photons remain entangled as a biphoton behaving at half the wavelength despite the presence of the object and their separate pathways.

    Wang’s lab was not the first to work on this kind of biphoton imaging, but it was the first to create a viable system using the concept. “We developed what we believe a rigorous theory as well as a faster and more accurate entanglement-measurement method.  We reached microscopic resolution and imaged cells.”

    While there is no theoretical limit to the number of photons that can be entangled with each other, each additional photon would further increase the momentum of the resulting multiphoton while further decreasing its wavelength.

    Wang says future research could enable entanglement of even more photons, although he notes that each extra photon further reduces the probability of a successful entanglement, which, as mentioned above, is already as low as a one-in-a-million chance.

    The paper describing the work, “Quantum Microscopy of Cells at the Heisenberg Limit,” appears in the April 28 issue of Nature Communications. Co-authors are Zhe He and Yide Zhang, both postdoctoral scholar research associates in medical engineering; medical engineering graduate student Xin Tong (MS ’21); and Lei Li (PhD ’19), formerly a medical engineering postdoctoral scholar and now an assistant professor of electrical and computer engineering at Rice University.

    Funding for the research was provided by the Chan Zuckerberg Initiative and the National Institutes of Health.

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  • Form Habits in No Time: No Magic Number!

    Form Habits in No Time: No Magic Number!

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    Newswise — Putting on your workout clothes and getting to the gym can feel like a slog at first. Eventually, you might get in the habit of going to the gym and readily pop over to your Zumba class or for a run on the treadmill. A new study from social scientists at Caltech now shows how long it takes to form the gym habit: an average of about six months.

    The same study also looked at how long it takes health care workers to get in the habit of washing their hands: an average of a few weeks.

    “There is no magic number for habit formation,” says Anastasia Buyalskaya (PhD ’21), now an assistant professor of marketing at HEC Paris. Other authors of the study, which appears in the journal Proceedings of the National Academy of Sciences, include Caltech’s Colin Camerer, Robert Kirby Professor of Behavioral Economics and director and leadership chair of the T&C Chen Center for Social and Decision Neuroscience, and researchers from the University of Chicago and the University of Pennsylvania. Xiaomin Li (MS ’17, PhD ’21), formerly a graduate student and postdoctoral scholar at Caltech, is also an author.

    “You may have heard that it takes about 21 days to form a habit, but that estimate was not based on any science,” Camerer says. “Our works supports the idea that the speed of habit formation differs according to the behavior in question and a variety of other factors.”

    The study is the first to use machine learning tools to study habit formation. The researchers employed machine learning to analyze large data sets of tens of thousands of people who were either swiping their badges to enter their gym or washing their hands during hospital shifts. For the gym research, the researchers partnered with 24 Hour Fitness, and for the hand-washing research, they partnered with a company that used radio frequency identification (RFID) technology to monitor hand-washing in hospitals. The data sets tracked more than 30,000 gymgoers over four years and more than 3,000 hospital workers over nearly 100 shifts.

    “With machine learning, we can observe hundreds of context variables that may be predictive of behavioral execution,” explains Buyalskaya. “You don’t necessarily have to start with a hypothesis about a specific variable, as the machine learning does the work for us to find the relevant ones.”

    Machine learning also let the researchers study people over time in their natural environments; most previous studies were limited to participants filling out surveys.

    The study found that certain variables had no effect on gym habit formation, such as time of day. Other factors, such as one’s past behavior, did come into play. For instance, for 76 percent of gymgoers, the amount of time that had passed since a previous gym visit was an important predicator of whether the person would go again. In other words, the longer it had been since a gymgoer last went to the gym, the less likely they were to make a habit of it. Sixty-nine percent of the gymgoers were more likely to go to the gym on the same days of the week, with Monday and Tuesday being the most well attended.

    For the hand-washing part of the study, the researchers looked at data from health care workers who were given new requirements to wear RFID badges that recorded their hand-washing activity. “It is possible that some health workers already had the habit prior to us observing them, however we treat the introduction of the RFID technology as a ‘shock’ and assume that they may need to rebuild their habit from the moment they use the technology,” Buyalskaya says.

    “Overall, we are seeing that machine learning is a powerful tool to study human habits outside the lab,” Buyalskayasays.

    The study titled “What can machine learning teach us about habit formation? Evidence from exercise and hygiene” was funded by the Behavior Change for Good Initiative, the Ronald and Maxine Linde Institute of Economics and Management Sciences at Caltech, and the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech. 

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  • ‘Smart’ bandages monitor wounds and provide targeted treatment

    ‘Smart’ bandages monitor wounds and provide targeted treatment

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    Newswise — Most of the time, when someone gets a cut, scrape, burn, or other wound, the body takes care of itself and heals on its own. But this is not always the case. Diabetes can interfere with the healing process and create wounds that will not go away and that could become infected and fester.

    These kinds of chronic wounds are not just debilitating for the people suffering from them. They are also a drain on healthcare systems, representing a $25 billion financial burden in the United States alone each year.

    A new kind of smart bandage developed at Caltech may make treatment of these wounds easier, more effective, and less expensive. These smart bandages were developed in the lab of Wei Gao, assistant professor of medical engineering, Heritage Medical Research Institute Investigator, and Ronald and JoAnne Willens Scholar.

    “There are many different types of chronic wounds, especially in diabetic ulcers and burns that last a long time and cause huge issues for the patient,” Gao says. “There is a demand for technology that can facilitate recovery.”

    Unlike a typical bandage, which might only consist of layers of absorbent material, the smart bandages are made from a flexible and stretchy polymer containing embedded electronics and medication. The electronics allow the sensor to monitor for molecules like uric acid or lactate and conditions like pH level or temperature in the wound that may be indicative of inflammation or bacterial infection.

    The bandage can respond in one of three ways: First, it can transmit the gathered data from the wound wirelessly to a nearby computer, tablet, or smartphone for review by the patient or a medical professional. Second, it can deliver an antibiotic or other medication stored within the bandage directly to the wound site to treat the inflammation and infection. Third, it can apply a low-level electrical field to the wound to stimulate tissue growth resulting in faster healing.

    In animal models under laboratory conditions, the smart bandages showed the ability to provide real-time updates about wound conditions and the animals’ metabolic states to researchers, as well as offer speed healing of chronic infected wounds similar to those found in humans.

    Gao says the results are promising and adds that future research in collaboration with the Keck School of Medicine of USC will focus on improving the bandage technology and testing it on human patients, whose therapeutic needs may be different than those of lab animals.

    “We have showed this proof of concept in small animal models, but down the road, we would like to increase the stability of the device but also to test it on larger chronic wounds because the wound parameters and microenvironment may vary from site to site,” he says.

    The paper describing the research, “A stretchable wireless wearable bioelectronic system for multiplexed monitoring and combination treatment of infected chronic wounds,” appears in the March 24 issue of the journal Science Advances. Co-authors are postdoctoral scholar research associates in medical engineering Ehsan Shirzaei Sani and Yu Song; medical engineering graduate students Changhao Xu (MS ’20), Canran Wang, Jihong Min (MS ’19), Jiaobing Tu (MS ’20), Samuel A. Solomon, and Jiahong Li; and Jaminelli L. Banks and David G. Armstrong of the Keck School of Medicine of USC.

    Funding for the research was provided by the National Institutes of Health, the National Science Foundation, the Office of Naval Research, the Heritage Medical Research Institute, the Donna and Benjamin M. Rosen Bioengineering Center at Caltech, the Rothenberg Innovation Initiative at Caltech, and a Sloan Research Fellowship.

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  • What Does It Take to Be a ‘Minority-Serving Institution’?

    What Does It Take to Be a ‘Minority-Serving Institution’?

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    A group of researchers has recommended a new classification system for minority-serving institutions that they hope will ultimately direct more money to colleges that are serving minority students well, and not just enrolling them in large numbers.

    The MSI Data Project, the researchers said in a news release Sunday, is a response to “inaccurate and inconsistent data used to identify minority-serving institutions (MSIs) for funding and analysis.”

    “Our hope is … for MSI leaders, advocates, and policymakers to use this body of research, as well as our data dashboards, to make better informed decisions that promote equitable educational outcomes for students,” said Mike Hoa Nguyen, the principal investigator and an assistant professor of education at New York University.

    The data project, launched this month, examines 11 categories of minority-serving institutions. It includes dashboards that detail individual campuses’ eligibility for federal funds, institutional characteristics, enrollment, and graduation metrics over a five-year period, from 2017 to 2021.

    For instance, the dashboard shows, 219 Hispanic-serving institutions received funding from the U.S. Department of Education in 2021, but 462 were eligible for such money. Colleges still have to apply for competitive grants from a limited pool of money. Some applied and were denied, while other colleges may not have even known they were eligible.

    The researchers hope their recommendations will spur changes in how colleges are designated as MSIs and clear up confusion about who should be able to claim that status, and the federal money that can come with it.

    In an accompanying article in Educational Researcher, titled “What Counts as a Minority-Serving Institution?” Nguyen and two of the project’s co-creators raise the concern that federal money isn’t necessarily going to the most deserving institutions.

    “For example, perhaps an institution, not identified as an MSI under the federal statute, is found to serve students of color much better than those that are identified. Such findings could offer important suggestions for policy changes. Additionally, if institutions are receiving federal MSI funds but are not serving students of color well, this would be an important consideration to amend practices and policies so that federal funding is used in the manner in which it was intended.”

    “The MSI landscape is so unbelievably complex, in the way all 11 designations were created over a long period of time, using a patchwork legislative process,” Nguyen said in an interview. By getting everyone “speaking the same language” in how they examine minority-serving institutions, “our hope is that we can find out how well those students are being served” by the federal money set aside and where equity gaps exist.

    Nguyen’s fellow authors were Joseph J. Ramirez, an institutional research and assessment associate at the California Institute of Technology, and Sophia Laderman, an associate vice president at the State Higher Education Executive Officers Association (SHEEO).

    About one in five postsecondary institutions are eligible for federal money as MSIs, but more than half of all undergraduate students of color attend these colleges, the authors wrote. President Biden has pledged significant increases in the amount of money directed toward minority-serving institutions.

    Researchers, including Gina Ann Garcia, an associate professor of educational foundations, organizations, and policy at the University of Pittsburgh, have pointed out that the nation’s demographic changes have resulted in hundreds of campuses being designated as Hispanic serving based on numbers alone. The data-project researchers acknowledge that some colleges engage in “the strategic manipulation of enrollment trends in order to meet eligibility requirements.”

    Hispanic-serving institutions, which were first designated by the federal government in 1994, are among the minority-serving institutions that get that designation based on share of enrollment. For HSIs, the threshold is 25 percent of the undergraduate population.

    By contrast, Historically Black and Tribal-Serving colleges achieve that designation based on their histories and missions. Colleges that weren’t designated in those categories can’t join their ranks, regardless of their own changing demographics. That has caused longstanding tensions between Historically Black and predominantly Black institutions over who should have access to the federal money set aside for minority-serving institutions.

    Among the minority-serving institutions the database tracks are those representing Hispanic students, Asian American and Pacific Islanders, both tribal and non-tribally-controlled Native American colleges, and colleges that are either Historically Black or predominantly Black.

    Many colleges are designated in more than one category, but they may only be able to receive funding under one. Designating their multiple identities is important, the authors write, because it “recognizes the diversity and complexity of the institution, and does not render invisible the students of color who attend that institution.”

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  • Knots smaller than human hair make materials unusually tough

    Knots smaller than human hair make materials unusually tough

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    Newswise — In the latest advance in nano- and micro-architected materials, engineers at Caltech have developed a new material made from numerous interconnected microscale knots.

    The knots make the material far tougher than identically structured but unknotted materials: they absorb more energy and are able to deform more while still being able to return to their original shape undamaged. These new knotted materials may find applications in biomedicine as well as in aerospace applications due to their durability, possible biocompatibility, and extreme deformability.
     
    “The capability to overcome the general trade-off between material deformability and tensile toughness [the ability to be stretched without breaking] offers new ways to design devices that are extremely flexible, durable, and can operate in extreme conditions,” says former Caltech graduate student Widianto P. Moestopo (MS ‘ 19, PhD ’22), now at Lawrence Livermore National Laboratory. Moestopo is the lead author of a paper on the nanoscale knots that was published on March 8 in Science Advances.

    Moestopo helped develop the material in the lab of Julia R. Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering; Fletcher Jones Foundation director of the Kavli Nanoscience Institute; and senior author of the Science Advances paper. Greer is at the forefront of the creation of such nano-architected materials, or materials whose structure is designed and organized at a nanometer scale and that consequently exhibit unusual, often surprising properties.
     
    “Embarking on understanding how the knots would affect the mechanical response of micro-architected materials was a new out-of-the-box idea,” Greer says. “We had done extensive research on studying the mechanical deformation of many other types of micro-textiles, for example, lattices and woven materials. Venturing into the world of knots allowed us to gain deeper insights into the role of friction and energy dissipation, and proved to be meaningful.”
     
    Each knot is around 70 micrometers in height and width, and each fiber has a radius of around 1.7 micrometers (around one-hundredth the radius of a human hair). While these are not the smallest knots ever made—in 2017 chemists tied a knot made from an individual strand of atoms—this does represent the first time that a material composed of numerous knots at this scale has ever been created. Further, it demonstrates the potential value of including these nanoscale knots in a material—for example, for suturing or tethering in biomedicine. 
     
    The knotted materials, which were created out of polymers, exhibit a tensile toughness that far surpasses materials that are unknotted but otherwise structurally identical, including ones where individual strands are interwoven instead of knotted. When compared to their unknotted counterparts, the knotted materials absorb 92 percent more energy and require more than twice the amount of strain to snap when pulled. 
     
    The knots were not tied but rather manufactured in a knotted state by using advanced high-resolution 3D lithography capable of producing structures in the nanoscale. The samples detailed in the Science Advancespaper contain simple knots—an overhand knot with an extra twist that provides additional friction to absorb additional energy while the material is stretched. In the future, the team plans to explore materials constructed from more complex knots.
     
    Moestopo’s interest in knots grew out of research he was conducting in 2020 during the COVID-19 lockdowns. “I came across some works from researchers who are studying the mechanics of physical knots as opposed to knots in a purely mathematical sense. I do not consider myself a climber, a sailor, or a mathematician, but I have tied knots throughout my life, so I thought it was worth trying to insert knots into my designs,” he says.
     
    The paper has a tongue-in-cheek title—“Knots are Not for Naught: Design, Properties, and Topology of Hierarchical Intertwined Microarchitected Materials.” Co-authors include Caltech graduate students Sammy Shaker and Weiting Deng. This research was funded by the National Science Foundation through Moestopo’s Graduate Research Fellowship Program, Caltech’s Clinard Innovation Fund, Greer’s Vannevar Bush Faculty Fellowship, and the Office of Naval Research.

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  • Making engineered cells dance to ultrasound

    Making engineered cells dance to ultrasound

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    Newswise — Let’s say you needed to move an individual cell from one place to another. How would you do it? Maybe some special tweezers? A really tiny shovel?

    The fact is that manipulating individual cells is a difficult task. Some work has been done on so-called optical tweezers that can push cells around with beams of light, but while they are good at moving a single cell around, they are not intended for manipulating larger numbers of cells.

    New research conducted at Caltech has created an alternative: air-filled proteins, produced by genetically engineered cells, that can be pushed around—along with the cells containing them—by ultrasound waves. A paper describing the work appears in the journal Science Advances.

    The work builds on previous work conducted in the lab of Mikhail Shapiro, professor of chemical engineering and medical engineering and investigator with the Howard Hughes Medical Institute.

    Shapiro has for years worked with gas vesicles derived from bacteria as an acoustic tag. These vesicles, which are air-filled capsules of protein, provide buoyancy to some species of aquatic bacteria. But they also have another useful quality: Because of their air-filled interiors, they show up quite strongly in ultrasound imagery. Shapiro’s discovery of this quality has led his lab to develop gas vesicles as a genetic marker for tracking the location of individual bacterial cells, and for observing gene-expression activity in mammalian cells deep inside the body.

    Now, Shapiro and his colleagues have shown that these vesicles can push and pull cells into specific locations under the influence of ultrasound. The phenomenon is very similar to how ultrasound in air can be used to suspend and/or move small, light objects. This is due to the fact that sound waves create pressure zones that act on objects in their vicinity. The physical properties of an object or material determine whether it will be attracted to a high-pressure zone or repulsed by it. Normal cells are pushed away from areas of higher pressure, but cells containing gas vesicles are attracted to them.

    “We’ve used these vesicles for imaging previously, and this time we’ve shown that we can actually use them as actuators so we can apply force to these objects using ultrasound,” says Di Wu (MS ’16, PhD ’21), a research scientist in Shapiro’s lab and the study’s lead author. “What this allows us to do is to move cells around in space using ultrasound and to be able to do so in a very selective manner.”

    Shapiro and Wu say there a few reasons you might want to be able to move cells around. For one, tissue engineering—the creation of artificial tissues for research or medical purposes—requires cells of specific types to be arranged in complex patterns. An artificial muscle might need multiple layers of muscle cells, cells that create tendons, and nerve cells, for example.

    Another case in which you might want to move cells around is in cell-based therapy, a field of medicine in which cells with desirable properties are introduced into the body.

    “You’re introducing engineered cells into the body, and they go all over the place to find their target,” Di says. “But with this technology, we potentially have a way to guide them to the desired location into the body.”

    As a demonstration, the team showed that cells containing gas vesicles can be forced to clump into a small ball, or arranged as thin bands, or pushed to the edges of a container. When they changed the ultrasound pattern, the cells “danced” to take up new positions. They also developed an ultrasound pattern that pushed the cells into the shape of the letter “R” in a gel that held them in that shape after it solidified. They call the resulting figure an “acoustic hologram.”

    Wu says one area where their research has the potential for immediate impact is in cell sorting, a process necessary for various kinds of biological and medical research.

    “A common way people sort cells now is to engineer them to express a fluorescent protein and then use a fluorescent-activated cell sorter (FACS),” he says. “That is a $300,000 piece of equipment that is bulky, often lives in a biosafety cabinet, and doesn’t sort cells very fast.”

    “In contrast, acousto-fluidic sorting can be done with a tiny little chip that costs maybe $10. The reason for this difference is that in fluorescent sorting, you have to separately measure the gene expression of the cells and then move them. This is done one cell at a time. With gas vesicle expression, the cell’s genetics are directly linked to the force that’s being applied to the cell. If they express gas vesicles, they will experience a different force, so we don’t need to separately check if they’re expressing gas vesicles and then move them; we can move them all at once. That greatly simplifies things.”

    The paper describing the research, titled “Biomolecular actuators for genetically selective acoustic manipulation of cells,” appears in the February 22 of Science Advances. Additional co-authors are former Caltech medical engineering PhD students Colin Cook (MS ’16, PhD ’19), who is now a staff scientist at City of Hope; and David R. Mittelstein (MS ’16, PhD ’20), who is now a resident physician at Scripps Health; former postdoctoral fellow David Maresca, who is now an assistant professor at Delft University of Technology, Netherlands; Caltech chemical engineering graduate student Maria Abundo and bioengineering graduate students Mengtong Duan, Justin Lee, and Shirin Shivaei; Dina Malounda of the Howard Hughes Medical Institute, Diego Baresch of the University of Bordeaux in France; Zhichao Ma of the Max Planck Institute for Intelligent Systems in Stuttgart, Germany; Tian Qiu of the University of Stuttgart, Germany; and Peer Fischer of the Max Planck Institute for Medical Research and Heidelberg University in Heidelberg, Germany.

    Funding for the research was provided by the National Institutes of Health, the U.S. Army’s Institute for Collaborative Biotechnologies, the David and Lucile Packard Foundation, and the Pew Charitable Trust. Mikhail Shapiro is an affiliated faculty member with the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech.

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  • ZTF makes first discovery of a rare cosmic “lunch”

    ZTF makes first discovery of a rare cosmic “lunch”

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    Newswise — The universe can be a violent place. Stars die or collide with each other and black holes devour everything that gets too close. These and other events produce flashes of light in the night sky that astronomers call transients. The Zwicky Transient Facility is currently one of the largest transient surveys astronomers use to study the ever-changing universe. The survey is also a treasure trove of rare, strange, and unusual events that often astronomers discover by chance. 

    “Our new search technique helps us to quickly identify rare cosmic events in the ZTF survey data. And since ZTF and upcoming larger surveys such as Vera Rubin’s LSST scan the sky so frequently, we can now expect to uncover a wealth of rare, or previously undiscovered cosmic events and study them in detail”, says Igor Andreoni, a postdoctoral associate in the Department of Astronomy at UMD and NASA Goddard Space Flight Center. 

    AT2022cmc is a peculiar case of what is known as a tidal-disruption event or TDE. TDEs happen with a star approaching a black hole is violently ripped apart by the black hole’s gravitational tidal forces—similar to how the Moon pulls tides on Earth but with greater strength. Then, pieces of the star are captured into a swiftly spinning disk orbiting the black hole. Finally, the black hole consumes what remains of the doomed star in the disk. 

    In some extremely rare cases such as AT2022cmc, the supermassive black hole launches “relativistic jets”—beams of matter traveling close to the speed of light—after destroying a star. Discovered in Feb 2022, astronomers led by Andreoni followed up AT2022cmc and observed it with multiple facilities at multiple wavelengths. The analysis is now published in the journal Nature. 

    “The last time scientists discovered one of these jets was well over a decade ago,” said Michael Coughlin, an assistant professor of astronomy at the University of Minnesota Twin Cities and co-lead on the paper. “From the data we have, we can estimate that relativistic jets are launched in only 1% of these destructive events, making AT2022cmc an extremely rare occurrence. In fact, the luminous flash from the event is among the brightest ever observed.”

    The novel data-crunching method – equivalent to searching through a million pages of information every night –  allowed Andreoni and colleagues to conduct a rapid analysis of the ZTF data and identify the AT2022cmc TDE with relativistic jets. They quickly started follow-up observations that revealed an exceptionally bright event across the electromagnetic spectrum, from the X-rays to the millimeter and radio.

    ESO’s Very Large Telescope revealed that AT2022cmc was at a cosmological distance of 8.5 billion light years away. The Hubble Space Telescope optical/infrared images and radio observations from the Very Large Array pinpointed the location of AT2022cmc with extreme precision. 

    The researchers believe that AT2022cmc was at the center of a galaxy that is not yet visible because the light from AT2022cmc outshone it, but future space observations with Hubble or James Webb Space Telescopes may unveil the galaxy when the transient eventually disappears.

    It is still a mystery why some TDEs launch jets while others may not. From their observations, Andreoni and his team concluded that the black holes in AT2022cmc and other similarly jetted TDEs are likely spinning rapidly so as to power the extremely luminous jets. This suggests that a rapid black hole spin may be one necessary ingredient for jet launching—an idea that brings researchers closer to understanding the physics of supermassive black holes at the center of galaxies billions of light years away.

    Before AT2022cmc, only a couple of possible jetted TDEs were known, primarily discovered by gamma-ray space missions, which detect the highest-energy forms of radiation produced by these jets. With their new method, astronomers can now search for such rare events in ground-based optical surveys. 

    “Astronomy is changing rapidly,” Andreoni said. “More optical and infrared all-sky surveys are now active or will soon come online. Scientists can use AT2022cmc as a model for what to look for and find more disruptive events from distant black holes. This means that more than ever, big data mining is an important tool to advance our knowledge of the universe.”

    The paper, “A very luminous jet from the disruption of a star by a massive black hole,” is published in Nature on November 30, 2022.
    DOI: DOI : 10.1038/s41586-022-05465-8

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  • Brain-machine interface device predicts internal speech

    Brain-machine interface device predicts internal speech

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    Newswise — New Caltech research is showing how devices implanted into people’s brains, called brain-machine interfaces (BMIs), could one day help patients who have lost their ability to speak. In a new study presented at the 2022 Society for Neuroscience conference in San Diego, the researchers demonstrated that they could use a BMI to accurately predict which words a tetraplegic participant was simply thinking and not speaking or miming.

    “You may already have seen videos of people with tetraplegia using BMIs to control robotic arms and hands, for example to grab a bottle and to drink from it or to eat a piece of chocolate,” says Sarah Wandelt, a Caltech graduate student in the lab of Richard Andersen, James G. Boswell Professor of Neuroscience and director of the Tianqiao and Chrissy Chen Brain-Machine Interface Center at Caltech. 

    “These new results are promising in the areas of language and communication. We used a BMI to reconstruct speech,” says Wandelt, who presented the results at the conference on November 13. 

    Previous studies have had some success at predicting participants’ speech by analyzing brain signals recorded from motor areas when a participant whispered or mimed words. But predicting what somebody is thinking, internal dialogue, is much more difficult, as it does not involve any movement, explains Wandelt. “In the past, algorithms that tried to predict internal speech have only been able to predict three or four words and with low accuracy or not in real time,” Wandelt says.

    The new research is the most accurate yet at predicting internal words. In this case, brain signals were recorded from single neurons in a brain area called the supramarginal gyrus, located in the posterior parietal cortex. The researchers had found in a previous study that this brain area represents spoken words. 

    Now, the team has extended its findings to internal speech. In the study, the researchers first trained the BMI device to recognize the brain patterns produced when certain words were spoken internally, or thought, by the tetraplegic participant. This training period took about 15 minutes. They then flashed a word on a screen and asked the participant to say the word internally. The results showed that the BMI algorithms were able to predict eight words with an accuracy up to 91 percent.

    The work is still preliminary but could help patients with brain injuries, paralysis, or diseases such as amyotrophic lateral sclerosis (ALS) that affect speech. “Neurological disorders can lead to complete paralysis of voluntary muscles, resulting in patients being unable to speak or move, but they are still able to think and reason. For that population, an internal speech BMI would be incredibly helpful,” Wandelt says.  

    “We have previously shown that we can decode imagined hand shapes for grasping from the human supramarginal gyrus,” says Andersen. “Being able to also decode speech from this area suggests that one implant can recover two important human abilities: grasping and speech.”

    The researchers also point out that the BMIs cannot be used to read people’s minds; the device would need to be trained in each person’s brain separately, and they only work when a person focuses on the word. 

    The study, which is in the process of journal submission but is not yet peer reviewed, is titled “Online internal speech decoding from single neurons in a human participant.” It was funded by the National Institutes of Health, the Tianqiao and Chrissy Chen Brain-Machine Interface Center, and the Boswell Foundation. Other Caltech authors besides Wandelt and Andersen include David Bjanes, Kelsie Pejsa, Brian Lee (PhD ’06), and Charles Liu. Lee and Liu are Caltech visiting associates who are on the faculty of the Keck School of Medicine at USC.
     

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    California Institute of Technology

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