'Life-like' lasers can self-organize, adapt their structure, and cooperate

While many artificial materials have advanced properties, they have a long way to go to combine the versatility and functionality of living materials that can adapt to their situation. For example, in the human body bone and muscle continuously reorganise their structure and composition to better sustain changing weight and level of activity.

Now, researchers from Imperial College London and University College London have demonstrated the first spontaneously self-organising laser device, which can reconfigure when conditions change.

The innovation, reported in Nature Physics, will help enable the development of smart photonic materials capable of better mimicking properties of biological matter, such as responsiveness, adaptation, self-healing, and collective behaviour.

Co-lead author Professor Riccardo Sapienza, from the Department of Physics at Imperial, said: "Lasers, which power most of our technologies, are designed from crystalline materials to have precise and static properties. We asked ourselves if we could create a laser with the ability to blend structure and functionality, to reconfigure itself and cooperate like biological materials do.

"Our laser system can reconfigure and cooperate, thus enabling a first step towards emulating the ever-evolving relationship between structure and functionality typical of living materials."

Lasers are devices that amplify light to produce a special form of light. The self-assembling lasers in the team's experiment consisted of microparticles dispersed in a liquid with high 'gain' -- the ability to amplify light. Once enough of these microparticles collect together, they can harness external energy to 'lase' -- produce laser light.

An external laser was used to heat up a 'Janus' particle (a particle coated on one side with light-absorbing material), around which the microparticles gathered. The lasing created by these microparticle clusters could be turned on and off by changing the intensity of the external laser, which in turn controlled the size and density of the cluster.

The team also showed how the lasing cluster could be transferred in space by heating different Janus particles, demonstrating the adaptability of the system. Janus particles can also collaborate, creating clusters that have properties beyond the simple adding of two clusters, such as changing their shape and boosting their lasing power.

Co-lead author Dr Giorgio Volpe, from the Department of Chemistry at UCL, said: "Nowadays, lasers are used as a matter of course in medicine, telecommunications, and also in industrial production. Embodying lasers with life-like properties will enable the development of robust, autonomous, and durable next-generation materials and devices for sensing applications, non-conventional computing, novel light sources and displays."

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Deep dive into the dusty Milky Way

An animated dive into the dusty Milky Way reveals the outlines of our galaxy taking shape as we look out further and further from Earth.

Based on new data from an interactive tool that exploits data from the European Space Agency's Gaia mission and other space science data sets, astronomers have created an animation to model dust in the Milky Way. The work was presented this week at the National Astronomy Meeting (NAM 2022) at the University of Warwick.

The animation shows the cumulative build-up of dust looking from Earth's local neighbourhood to ~13000 lightyears towards the galactic centre -- around 10% of the overall distance across the Milky Way. Close by, dust swirls all around but, further out, the concentration of dust along the galactic plane becomes clear. Two 'windows', one above and one below the galactic plane, are also revealed.

"Dust clouds are related to the formation and death of stars, so their distribution tells a story of how structures formed in the galaxy and how the galaxy evolves," said Nick Cox, coordinator of the EXPLORE project which is developing the tools. "The maps are also important for cosmologists in revealing regions where there is no dust and we can have a clear, unobstructed view out of the Milky Way to study the Universe beyond, such as to make Deep Field observations with Hubble or the new James Webb Space Telescope."

The tools used to create the animation combine data from the Gaia mission and the 2MASS All Sky Survey. The tools are part of a suite of applications designed to support studies of stars and galaxies, as well as lunar exploration, and have been developed through funding from the European Union's Horizon 2020 Programme.

"State-of-the-art machine learning and visual analytics have the power to greatly enhance scientific return and discovery for space science missions, but their use is still relatively novel in the field of astronomy," said Albert Zijlstra, of the University of Manchester and the EXPLORE project. "With a constant stream of new data, such as the recent third release of Gaia data in June 2022, we have an increasing wealth of information to mine -- beyond the scope of what humans could process in a lifetime. We need tools like the ones we are developing for EXPLORE to support scientific discovery, such as by helping us to characterise properties within the data, or to pick out the most interesting or unusual features and structures."

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Virtual reality app trial shown to reduce common phobias

Results from a University of Otago, Christchurch trial suggest fresh hope for the estimated one-in-twelve people worldwide suffering from a fear of flying, needles, heights, spiders and dogs.

The trial, led by Associate Professor Cameron Lacey, from the Department of Psychological Medicine, studied phobia patients using a headset and a smartphone app treatment programme -- a combination of Virtual Reality (VR) 360-degree video exposure therapy and cognitive behavioural therapy (CBT).

Participants downloaded a fully self-guided smartphone app called "oVRcome," developed by Christchurch tech entrepreneur Adam Hutchinson, aimed at treating patients with phobia and anxiety.

The app was paired with a headset to immerse participants in virtual environments to help treat their phobia.

The results from the trial, just published in the Australian and New Zealand Journal of Psychiatry, showed a 75 per cent reduction in phobia symptoms after six weeks of the treatment programme.

"The improvements they reported suggests there's great potential for the use of VR and mobile phone apps as a means of self-guided treatment for people struggling with often-crippling phobias," Associate Professor Lacey says.

"Participants demonstrated a strong acceptability of the app, highlighting its potential for delivering easily accessible, cost-effective treatment at scale, of particular use for those unable to access in-person exposure therapy to treat their phobias."

A total of 129 people took part in the six-week randomised, controlled trial, between May 2021 and December 2021, with a 12-week follow-up. Participants needed to be aged between 18-64 years, have a fear of either flying, heights, needles, spiders and dogs. They were emailed weekly questionnaires to record their progress. Those experiencing adverse events could request contact from a clinical psychologist at any stage.

"Participants experiencing all five types of phobia showed comparable improvements in the Severity Measures for Specific Phobia scale over the course of the trial. The average severity score decreased from 28/40 (moderate to severe symptoms) to 7/40 (minimal symptoms) after six weeks. There were no participant withdrawals due to intervention-related adverse events.

"The oVRcome app involves what's called "exposure therapy," a form of CBT exposing participants to their specific phobias in short bursts, to build up their tolerance to the phobia in a clinically-approved and controlled way," Associate Professor Lacey says.

"Some participants reported significant progress in overcoming their phobias after the trial period, with one feeling confident enough to now book an overseas family holiday, another lining up for a Covid vaccine and another reporting they now felt confident not only knowing there was a spider in the house but that they could possibly remove it themselves."

The app programme consisted of standard CBT components including psychoeducation, relaxation, mindfulness, cognitive techniques, exposure through VR, and a relapse prevention model. Participants were able to select their own exposure levels to their particular phobia from a large library of VR videos.

"This means the levels of exposure therapy could be tailored to an individual's needs which is a particular strength. The more traditional in-person exposure treatment for specific phobias have a notoriously high dropout rate due to discomfort, inconvenience and a lack of motivation in people seeking out fears to expose themselves to. With this VR app treatment, triallists had increased control in exposure to their fears, as well as control over when and where exposure occurs," says Associate Professor Lacey.

The researchers say this trial was novel, due to the cost-effective availability of the app and headsets and the fact that multiple phobias were tested at once. They say most comparative VR studies to date have investigated high-end VR devices which are only available in research and limited clinical settings. One Dutch study examined a low-cost VR Dutch-language program using animated imagery that demonstrated improvement in fear-of-height symptoms, however this study only examined a single type of specific phobia.

Associate Professor Lacey says public demand to take part in the trial was unprecedented, demonstrating the increasing need and desire for phobia treatment in the community.

"An estimated ten per cent of New Zealanders have been hesitant to take part in the government's COVID-19 vaccination programme due to needle phobia. This hasn't been helped by a significant shortage of psychologists. A petition to Parliament last year claimed New Zealand is 1,000 psychologists short, causing ballooning wait times nationwide, making it difficult for people to access help if needed. We need to further research and explore the use of more cost-effective, easily-accessible, home-based solutions such as this oVRcome app, to provide people with the treatment and support they need."

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Link between air pollution and child brain development strengthened

Air pollution is not just a problem for lungs. Increasingly, research suggests air pollution can influence childhood behavioral problems and even IQ. A new study led by the University of Washington has added evidence showing that both prenatal and postnatal exposure to air pollution can harm kids.

The study, published in Environmental Health Perspectives, found that children whose mothers experienced higher nitrogen dioxide (NO2) exposure during pregnancy, particularly in the first and second trimester, were more likely to have behavioral problems.

Researchers also reported that higher exposures to small-particle air pollution (PM2.5) when children were 2 to 4 years old was associated with poorer child behavioral functioning and cognitive performance.

"Even in cities like Seattle or San Francisco, which have a lot of traffic but where the pollution levels are still relatively low, we found that children with higher prenatal NO2 exposure had more behavioral problems, especially with NO2exposure in the first and second trimester," said Yu Ni, lead author and a postdoctoral scholar in the Department of Environmental & Occupational Health Sciences.

The study involved data gathered from 1,967 mothers recruited during pregnancy from six cities: Memphis, Tennessee; Minneapolis; Rochester, N.Y.; San Francisco; and two in Washington, Seattle and Yakima. Originally, these participants were enrolled as part of three separate studies: CANDLE, GAPPS and TIDES. The three studies have been combined under a major NIH initiative called ECHO, which brings together multiple pregnancy cohorts to address key child health concerns. These three combined cohorts are known as the ECHO PATHWAYS consortium.

The study employed a state-of-the-art model of air pollution levels in the United States over time and space that was developed at the University of Washington. Using participant address information, the researchers were able to estimate each mother and child's exposures during the pregnancy period and early childhood.

Exposure to NO2 and PM2.5 pollution in early life is important to understand, Ni said, because "there are known biological mechanisms that can link a mother's inhalation of these pollutants to effects on placenta and fetal brain development."

Furthermore, once the child is born, the first few years are a critical time of ongoing brain development as the number of neural connections explodes and the brain reaches 90% of its future adult size, the researchers write. For young children, inhaled pollutants that invade deep in the lung and enter the central nervous system can cause damage in areas relevant for behavioral and cognitive function.

"This study reinforces the unique vulnerability of children to air pollution -- both in fetal life where major organ development and function occurs as well as into childhood when those processes continue. These early life perturbations can have lasting impacts on lifelong brain function. This study underscores the importance of air pollution as a preventable risk factor for healthy child neurodevelopment," said senior author Dr. Catherine Karr, a professor in the UW School of Public Health and School of Medicine.

More specifically, the researchers found that exposure to PM2.5 pollution was generally associated with more behavioral problems in girls than in boys, and that the adverse effect of PM2.5 exposure in the second trimester on IQ was stronger in boys.

"We hope the evidence from this study will contribute to informed policymaking in the future," Ni said. "In terms of reducing air pollution, the U.S. has gone a long way under the Clean Air Act, but there are threats to continued improvement in the nation's air quality. The evidence suggests there is reason to bring the level of air pollution down even further as we better understand the vulnerability of pregnant women and children."

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Loss of male sex chromosome leads to earlier death for men

The loss of the male sex chromosome as many men age causes the heart muscle to scar and can lead to deadly heart failure, new research from the University of Virginia School of Medicine shows. The finding may help explain why men die, on average, several years younger than women.

UVA researcher Kenneth Walsh, PhD, says the new discovery suggests that men who suffer Y chromosome loss -- estimated to include 40% of 70-year-olds -- may particularly benefit from an existing drug that targets dangerous tissue scarring. The drug, he suspects, may help counteract the harmful effects of the chromosome loss -- effects that may manifest not just in the heart but in other parts of the body as well.

On average, women live five years longer than men in the United States. The new finding, Walsh estimates, may explain nearly four of the five-year difference.

"Particularly past age 60, men die more rapidly than women. It's as if they biologically age more quickly," said Walsh, the director of UVA's Hematovascular Biology Center. "There are more than 160 million males in the United States alone. The years of life lost due to the survival disadvantage of maleness is staggering. This new research provides clues as to why men have shorter lifespans than women."

Chromosome Loss and Heart Health

While women have two X chromosomes, men have an X and a Y. But many men begin to lose their Y chromosome in a fraction of their cells as they age. This appears to be particularly true for smokers. The loss occurs predominantly in cells that undergo rapid turnover, such as blood cells. (Loss of the Y chromosome does not occur in male reproductive cells, so it is not inherited by the children of men who exhibit Y chromosome loss.) Scientists previously observed that men who suffer Y chromosome loss are more likely to die at a younger age and suffer age-associated maladies such as Alzheimer's disease. Walsh's new research, however, is believed to be the first hard evidence that the chromosome loss directly causes harmful effects on men's health.

Walsh, of UVA's Division of Cardiovascular Medicine and the Robert M. Berne Cardiovascular Research Center, and his team used cutting-edge CRISPR gene-editing technology to develop a special mouse model to better understand the effects of Y chromosome loss in the blood. They found that the loss accelerated age-related diseases, made the mice more prone to heart scarring and led to earlier death. This wasn't the result of just inflammation, the scientists determined. Instead, the mice suffered a complex series of responses in the immune system, leading to a process referred to as fibrosis throughout the body. This tug-of-war within the immune system, the researchers believe, may accelerate disease development.

The scientists also looked at the effects of Y chromosome loss in human men. They conducted three analyses of data compiled from the UK Biobank, a massive biomedical database, and found that Y chromosome loss was associated with cardiovascular disease and heart failure. As chromosome loss increased, the scientists found, so did the risk of death.

Potential Treatment

The findings suggest that targeting the effects of Y chromosome loss could help men live longer, healthier lives. Walsh notes that one potential treatment option might be a drug, pirfenidone, that has already been approved by the federal Food and Drug Administration for the treatment of idiopathic pulmonary fibrosis, a form of lung scarring. The drug is also being tested for the treatment of heart failure and chronic kidney disease, two conditions for which tissue scarring is a hallmark. Based on his research, Walsh believes that men with Y chromosome loss could respond particularly well to this drug, and other classes of antifibrotic drugs that are being developed, though more research will be needed to determine that.

At the moment, doctors have no easy way to determine which men suffer Y chromosome loss. Walsh's collaborator Lars A. Forsberg, of Uppsala University in Sweden, has developed an inexpensive polymerase chain reaction (PCR) test, like those used for COVID-19 testing, that can detect Y chromosome loss, but the test is largely confined to his and Walsh's labs. Walsh, however, can foresee that changing: "If interest in this continues and it's shown to have utility in terms of being prognostic for men's disease and can lead to personalized therapy, maybe this becomes a routine diagnostic test," he said.

"The DNA of all our cells inevitably accumulate mutations as we age. This includes the loss of the entire Y chromosome within a subset of cells within men. Understanding that the body is a mosaic of acquired mutations provides clues about age-related diseases and the aging process itself," said Walsh, a member of UVA's Department of Biochemistry and Molecular Genetics. "Studies that examine Y chromosome loss and other acquired mutations have great promise for the development of personalized medicines that are tailored to these specific mutations."

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What a Martian meteorite can teach us about Earth's origins

What do Mars and Iceland have in common?

These days, not so much. But more than 4.5 billion years ago, it's possible the Red Planet had a crust comparable to Iceland today. This discovery, hidden in the oldest martian fragments found on Earth, could provide information about our planet that was lost over billions of years of geological movement and could help explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.

These insights into Earth's past came out of a new study, published today in Nature Communications, by an international team that includes an NAU researcher. The study details how they found the likely martian origin of the 4.48-billion-year-old meteorite, informally named Black Beauty. Its origin is one of the oldest regions of Mars.

"This meteorite recorded the first stage of the evolution of Mars and, by extension, of all terrestrial planets, including the Earth," said Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science. "As the Earth lost its old surface mainly due to plate tectonics, observing such settings in extremely ancient terrains on Mars is a rare window into the ancient Earth surface that we lost a long time ago."

What Mars can tell us about Earth

The team, led by Anthony Lagain from Curtin University in Australia, searched for the location of origin of a martian meteorite (officially named NWA -- Northwest Africa -- 7034 for where it was found on Earth). This meteorite, the chemistry of which indicates that Mars had volcanic activity to that found on Earth, recorded the first stage of Mars' evolution. Although it was ejected from the surface of Mars five to 10 million years ago after an asteroid impact, its source region and geological context has remained a mystery.

This team studied chemical and physical properties of Black Beauty to pinpoint where it came from; they determined it was from Terra Cimmeria-Sirenum, one of the most ancient regions of Mars. It may have a surface similar to Earth's continents. Planetary bodies like Mars have impacts craters all over their surface, so finding the right one is challenging. In a previous study, Lagain's team developed a crater detection algorithm that uses high-resolution images of the surface of Mars to identify small impact craters, finding about 90 million as small as 50 meters in diameter. In this study, they were able to isolate the most plausible ejection site -- the Karratha crater that excavated ejecta of an older crater named Khujirt.

"For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before the NASA's Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater," said Lagain, a research fellow in the School of Earth and Planetary Sciences at Curtin. "This research paved the way to locate the ejection site of other Martian meteorites, in order to create the most exhaustive view of the Red Planet's geological history."

Payré studies the nature and formation of Mars' crust to determine if Earth and Mars share a common past that include both a continent-like and ocean-like crust. She uses orbital observations captured in this region to investigate whether traces of volcanism similar to Iceland exist on Mars.

"As of today, Mars' crust complexity is not understood, and knowing about the origin of these amazing ancient fragments could lead future rover and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of Mars' evolution, and perhaps the Earth's," she said. "This work paves the road to locate the ejection site of other martian meteorites that will provide the most exhaustive view of the geological history of Mars and will answer one of the most intriguing questions: why Mars, now dry and cold, evolved so differently from Earth, a flourishing planet for life?"

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An ocean of galaxies awaits

Sometime around 400 million years after the birth of our universe, the first stars began to form. The universe's so-called dark ages came to an end and a new light-filled era began. More and more galaxies began to take shape and served as factories for churning out new stars, a process that reached a peak about 4 billion years after the Big Bang.

Luckily for astronomers, this bygone era can be observed. Distant light takes time to reach us, and our telescopes can pick up light emitted by galaxies and stars billions of years ago (our universe is 13.8 billion years old). But the details of this chapter in our universe's history are murky since most of the stars being formed are faint and hidden by dust.

A new Caltech project, called COMAP (CO Mapping Array Project), will offer us a new glimpse into this epoch of galaxy assembly, helping to answer questions about what really caused the universe's rapid increase in the production of stars.

"Most instruments might see the tip of an iceberg when looking at galaxies from this period," says Kieran Cleary, the project's principal investigator and the associate director of Caltech's Owens Valley Radio Observatory (OVRO). "But COMAP will see what lies underneath, hidden from view."

The current phase of the project uses a 10.4-meter "Leighton" radio dish at OVRO to study the most common kinds of star-forming galaxies spread across space and time, including those that are too difficult to view in other ways because they are too faint or hidden by dust. The radio observations trace the raw material from which stars are made: cold hydrogen gas. This gas is not easy to pinpoint directly, so instead COMAP measures bright radio signals from carbon monoxide (CO) gas, which is always present along with the hydrogen. COMAP's radio camera is the most powerful ever built to detect these radio signals.

The first science results from the project have just been published in seven papers in The Astrophysical Journal. Based on observations taken one year into a planned five-year survey, COMAP set upper limits on how much cold gas must be present in galaxies at the epoch being studied, including the ones that are normally too faint and dusty to see. While the project has not yet made a direct detection of the CO signal, these early results demonstrate that it is on track to do so by the end of the initial five-year survey and ultimately will paint the most comprehensive picture yet of the universe's history of star formation.

"Looking to the future of the project, we aim to use this technique to successively look further and further back in time," Cleary says. "Starting 4 billion years after the Big Bang, we will keep pushing back in time until we reach the epoch of the first stars and galaxies, a couple of billion years earlier."

Anthony Readhead, the co-principal investigator and the Robinson Professor of Astronomy, Emeritus, says that COMAP will see the not only the first epoch of stars and galaxies, but also their epic decline. "We will observe star formation rising and falling like an ocean tide," he says.

COMAP works by capturing blurry radio images of clusters of galaxies over cosmic time rather than sharp images of individual galaxies. This blurriness enables the astronomers to efficiently catch all the radio light coming from a larger pool of galaxies, even the faintest and dustiest ones that have never been seen.

"In this way, we can find the average properties of typical, faint galaxies without needing to know very precisely where any individual galaxy is located," explains Cleary. "This is like finding the temperature of a large volume of water using a thermometer rather than analyzing the motions of the individual water molecules."

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Researchers use quantum-inspired approach to increase lidar resolution

Researchers have shown that a quantum-inspired technique can be used to perform lidar imaging with a much higher depth resolution than is possible with conventional approaches. Lidar, which uses laser pulses to acquire 3D information about a scene or object, is usually best suited for imaging large objects such as topographical features or built structures due to its limited depth resolution.

"Although lidar can be used to image the overall shape of a person, it typically doesn't capture finer details such as facial features," said research team leader Ashley Lyons from the University of Glasgow in the United Kingdom. "By adding extra depth resolution, our approach could capture enough detail to not only see facial features but even someone's fingerprints."

In the Optica Publishing Group journal Optics Express, Lyons and first author Robbie Murray describe the new technique, which they call imaging two-photon interference lidar. They show that it can distinguish reflective surfaces less than 2 millimeters apart and create high-resolution 3D images with micron-scale resolution.

"This work could lead to much higher resolution 3D imaging than is possible now, which could be useful for facial recognition and tracking applications that involve small features," said Lyons. "For practical use, conventional lidar could be used to get a rough idea of where an object might be and then the object could be carefully measured with our method."

Using classically entangled light

The new technique uses "quantum inspired" interferometry, which extracts information from the way that two light beams interfere with each other. Entangled pairs of photons -- or quantum light -- are often used for this type of interferometry, but approaches based on photon entanglement tend to perform poorly in situations with high levels of light loss, which is almost always the case for lidar. To overcome this problem, the researchers applied what they've learned from quantum sensing to classical (non-quantum) light.

"With quantum entangled photons, only so many photon pairs per unit time can be generated before the setup becomes very technically demanding," said Lyons. "These problems don't exist with classical light, and it is possible to get around the high losses by turning up the laser power."

When two identical photons meet at a beam splitter at the same time they will always stick together, or become entangled, and leave in the same direction. Classical light shows the same behavior but to a lesser degree -- most of the time classical photons go in the same direction. The researchers used this property of classical light to very precisely time the arrival of one photon by looking at when two photons simultaneously arrive at detectors.

Enhancing depth resolution

"The time information gives us the ability to perform depth ranging by sending one of those photons out onto the 3D scene and then timing how long it takes for that photon to come back," said Lyons. "Thus, two-photon interference lidar works much like conventional lidar but allows us to more precisely time how long it takes for that photon to reach the detector, which directly translates into greater depth resolution."

The researchers demonstrated the high depth resolution of two-photon interference lidar by using it to detect the two reflective surfaces of a piece of glass about 2 millimeters thick. Traditional lidar wouldn't be able to distinguish these two surfaces, but the researchers were able to clearly measure the two surfaces. They also used the new method to create a detailed 3D map of a 20-pence coin with 7-micron depth resolution. This shows that the method could capture the level of detail necessary to differentiate key facial features or other differences between people.

Two-photon interference lidar also works very well at the single-photon level, which could enhance more complex imaging approaches used for non-line-of-sight imaging or imaging through highly scattering media.

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Study confirms lead-in-water causes adverse fetal health outcomes

Lehigh University and Bentley University health economics researchers have published the first study to confirm a causal relationship between lead-in-water and adverse fetal health outcomes. Although many studies have found a correlation between lead exposure and health, a causal link had been lacking in the literature -- until now.

The study has recently been published in the Journal of Health Economics in an article titled: Lead in Drinking Water and Birth Outcomes: A Tale of Two Water Treatment Plants.

The researchers,Muzhe Yang, professor of economics at Lehigh University and Dhaval M. Dave of Bentley University, used data on the exact home addresses of pregnant women living in the City of Newark together with information on the spatial boundary separating areas within the city serviced by two water treatment plants. Their study exploits an exogenous, or external, change in the water's pH level that caused lead to leach into the drinking water of one plant's service area, but not the other's, to identify the causal effect of prenatal lead exposure on fetal health.

Yang and his colleague found robust evidence of adverse health impacts. Among the findings: prenatal lead exposure increased the chance of low-birth-weight by 18% and increased the probability of preterm birth by 19%.

"These findings have important policy implications," says Yang, "especially in light of the substantial number of lead water pipes that remain in use as part of the aging infrastructure and the cost-benefit calculus of lead abatement interventions."

Yang notes that the crisis in Newark is not singular, but rather emblematic of the nation's aging water infrastructure.

According to the American Academy of Pediatrics, there is no safe threshold for lead exposure that has been identified for children. Lead collects over time in the human body through repeated exposure and is stored in the bones alongside calcium. In utero exposure is of particular concern as lead in the mother's bones can be mobilized during pregnancy and released as a calcium substitute to aid in the formation of the bones of the fetus, and lead in a mother's blood can also cross the placenta, exposing the fetus to lead poisoning. Prenatal lead exposure has been associated with impaired neural development putting children at risk for cognitive impairment later.

The Environmental Protection Agency (EPA) estimates that drinking water may account for more than 20 percent of total lead exposure for adults and 40 to 60 percent for infants.

In the introduction to their paper, Yang and Dave write: "Drinking water contamination is becoming an increasingly important and widespread source of prenatal exposure to environmental pollution. Between 2018 and 2020, nearly 30 million people received their drinking water from community water systems that were in violation of the EPA's Lead and Copper Rule, which sets maximum enforceable levels of these metals in drinking water…"

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Astronomers detect a radio 'heartbeat' billions of light-years from Earth

Astronomers at MIT and elsewhere have detected a strange and persistent radio signal from a far-off galaxy that appears to be flashing with surprising regularity.

The signal is classified as a fast radio burst, or FRB -- an intensely strong burst of radio waves of unknown astrophysical origin, that typically lasts for a few milliseconds at most. However, this new signal persists for up to three seconds, about 1,000 times longer than the average FRB. Within this window, the team detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to a beating heart.

The researchers have labeled the signal FRB 20191221A, and it is currently the longest-lasting FRB, with the clearest periodic pattern, detected to date.

The source of the signal lies in a distant galaxy, several billion light-years from Earth. Exactly what that source might be remains a mystery, though astronomers suspect the signal could emanate from either a radio pulsar or a magnetar, both of which are types of neutron stars -- extremely dense, rapidly spinning collapsed cores of giant stars.

"There are not many things in the universe that emit strictly periodic signals," says Daniele Michilli, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research. "Examples that we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beamed emission similar to a lighthouse. And we think this new signal could be a magnetar or pulsar on steroids."

The team hopes to detect more periodic signals from this source, which could then be used as an astrophysical clock. For instance, the frequency of the bursts, and how they change as the source moves away from Earth, could be used to measure the rate at which the universe is expanding.

The discovery is reported today in the journal Nature, and is authored by members of the CHIME/FRB Collaboration, including MIT co-authors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin, and Kiyoshi Masui at MIT, along with Michilli, who led the discovery first as a researcher at McGill University, and then as a postdoc at MIT.

"Boom, boom, boom"

Since the first FRB was discovered in 2007, hundreds of similar radio flashes have been detected across the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, an interferometric radio telescope consisting of four large parabolic reflectors that is located at the Dominion Radio Astrophysical Observatory in British Columbia, Canada.

CHIME continuously observes the sky as the Earth rotates, and is designed to pick up radio waves emitted by hydrogen in the very earliest stages of the universe. The telescope also happens to be sensitive to fast radio bursts, and since it began observing the sky in 2018, CHIME has detected hundreds of FRBs emanating from different parts of the sky.

The vast majority of FRBs observed to date are one-offs -- ultrabright bursts of radio waves that last for a few milliseconds before blinking off. Recently, researchers discovered the first periodic FRB that appeared to emit a regular pattern of radio waves. This signal consisted of a four-day window of random bursts that then repeated every 16 days. This 16-day cycle indicated a periodic pattern of activity, though the signal of the actual radio bursts was random rather than periodic.

On Dec. 21, 2019, CHIME picked up a signal of a potential FRB, which immediately drew the attention of Michilli, who was scanning the incoming data.

"It was unusual," he recalls. "Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second -- boom, boom, boom -- like a heartbeat. This is the first time the signal itself is periodic."

Brilliant bursts

In analyzing the pattern of FRB 20191221A's radio bursts, Michilli and his colleagues found similarities with emissions from radio pulsars and magnetars in our own galaxy. Radio pulsars are neutron stars that emit beams of radio waves, appearing to pulse as the star rotates, while a similar emission is produced by magnetars due to their extreme magnetic fields.

The main difference between the new signal and radio emissions from our own galactic pulsars and magnetars is that FRB 20191221A appears to be more than a million times brighter. Michilli says the luminous flashes may originate from a distant radio pulsar or magnetar that is normally less bright as it rotates and for some unknown reason ejected a train of brilliant bursts, in a rare three-second window that CHIME was luckily positioned to catch.

"CHIME has now detected many FRBs with different properties," Michilli says. "We've seen some that live inside clouds that are very turbulent, while others look like they're in clean environments. From the properties of this new signal, we can say that around this source, there's a cloud of plasma that must be extremely turbulent."

The astronomers hope to catch additional bursts from the periodic FRB 20191221A, which can help to refine their understanding of its source, and of neutron stars in general.

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