Seven hours of sleep is optimal in middle and old age, say researchers

Seven hours is the ideal amount of sleep for people in their middle age and upwards, with too little or too much little sleep associated with poorer cognitive performance and mental health, say researchers from the University of Cambridge and Fudan University.

Sleep plays an important role in enabling cognitive function and maintaining good psychological health. It also helps keep the brain healthy by removing waste products. As we get older, we often see alterations in our sleep patterns, including difficulty falling asleep and staying asleep, and decreased quantity and quality of sleep. It is thought that these sleep disturbances may contribute to cognitive decline and psychiatric disorders in the aging population.

In research published today in Nature Aging, scientists from the UK and China examined data from nearly 500,000 adults aged 38-73 years from the UK Biobank. Participants were asked about their sleeping patterns, mental health and wellbeing, and took part in a series of cognitive tests. Brain imaging and genetic data were available for almost 40,000 of the study participants.

By analysing these data, the team found that both insufficient and excessive sleep duration were associated with impaired cognitive performance, such as processing speed, visual attention, memory and problem-solving skills. Seven hours of sleep per night was the optimal amount of sleep for cognitive performance, but also for good mental health, with people experiencing more symptoms of anxiety and depression and worse overall wellbeing if they reported sleeping for longer or shorter durations.

The researchers say one possible reason for the association between insufficient sleep and cognitive decline may be due to the disruption of slow-wave -- 'deep' -- sleep. Disruption to this type of sleep has been shown to have a close link with memory consolidation as well as the build-up of amyloid -- a key protein which, when it misfolds, can cause 'tangles' in the brain characteristic of some forms of dementia. Additionally, lack of sleep may hamper the brain's ability to rid itself of toxins.

The team also found a link between the amount of sleep and differences in the structure of brain regions involved in cognitive processing and memory, again with greater changes associated with greater than or less than seven hours of sleep.

Having a consistent seven hours' sleep each night, without too much fluctuation in duration, was also important to cognitive performance and good mental health and wellbeing. Previous studies have also shown that interrupted sleep patterns are associated with increased inflammation, indicating a susceptibility to age-related diseases in older people.

Professor Jianfeng Feng from Fudan University in China said: "While we can't say conclusively that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a longer period of time appears to support this idea. But the reasons why older people have poorer sleep appear to be complex, influenced by a combination of our genetic makeup and the structure of our brains."

The researchers say the findings suggest that insufficient or excessive sleep duration may be a risk factor for cognitive decline in ageing. This is supported by previous studies that have reported a link between sleep duration and the risk of developing Alzheimer's disease and dementia, in which cognitive decline is a hallmark symptom.

Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge, one of the study's authors, said: "Getting a good night's sleep is important at all stages of life, but particularly as we age. Finding ways to improve sleep for older people could be crucial to helping them maintain good mental health and wellbeing and avoiding cognitive decline, particularly for patients with psychiatric disorders and dementias."

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New sleep molecule discovered: 'It shows just how complex the machinery of sleep is'

Researchers from the University of Copenhagen and Aalborg University presents a new study demonstrating that a small molecule in brain cells affects the level of hypocretin, which is responsible for making us feel awake during the day and tired at night. People with a genetic variation of this molecule have a higher risk of suffering from daytime sleepiness.

When brain scientist Birgitte Kornum from the Department of Neuroscience recently arrived in Rome for one of the largest sleep conferences in the world, she was completely taken aback. There were pharmaceutical companies everywhere -- with stands, information material and campaigns.

They all wanted to treat daytime sleepiness or to turn off the brain at night. And a lot of them focussed on hypocretin, which is a protein found in brain cells and which has recently attracted a lot of attention within sleep research.

This is because hypocretin is suspected to play a role in both insomnia, which is a decreased ability to fall asleep at night, and in narcolepsy, which is a decreased ability to stay awake during the day. People suffering from insomnia may have too much hypocretin in the brain, while people suffering from narcolepsy have too little. Researchers also suspect hypocretin to play a role in depression, ADHD and other mental disorders.

A lot is already known about the hypocretin system in the brain. There is even a new drug for insomnia countering the effect of hypocretin, latest introduced in Canada in 2018. According to Birgitte Kornum, though, the problem is that we know very little about how hypocretin is regulated inside the cells.

Therefore, Associate Professor Birgitte Kornum and her colleagues set out to shed light on the issue in a new study, which has recently been published in the reputed journal PNAS. The study combines tests on mice, zebrafish and human cells, and the researchers cooperated with their neighbours at the University of Copenhagen's Department of Cellular and Molecular Medicine, among others.

MicroRNA associated with sleep regulation

The team of researchers have spent several years studying one of the cellular mechanisms that affect hypocretin levels. Here they have focussed on a small molecule called microRNA-137 (miR-137).

"We discovered that miR-137 helps regulate hypocretin. To experience normal sleep, you need to have the right amount of hypocretin in the brain at the right time, and miR-137 helps with that. Though MiR-137 is also found in other parts of the body, it is especially pronounced in the brain," Birgitte Kornum says about the new study, which she has headed together with Assistant Professor Anja Holm from Aalborg University.

MicroRNA regulates various cellular processes, including hypocretin levels. Therefore, there is considerable research interest in microRNAs, as they could be targeted in order to regulate such processes.

Previously, the scientists knew very little about the role played by miR-137 in the brain, but now Birgitte Kornum's research team has demonstrated that it is associated with hypocretin regulation and thus with sleep.

"This is the first time a microRNA is associated with sleep regulation. Drawing on the UK Biobank, we discovered some genetic mutations in miR-137 which cause daytime sleepiness. The study demonstrates this connection in both mice and zebrafish, and we are able to prove the connection with hypocretin. Our discovery shows just how complex the machinery of sleep is. Imagine inheriting a variant of miR-137 that puts you at higher risk of feeling sleepy during the day," says Birgitte Kornum.

Hypocretin affects sleep stages

Hypocretin, which has caught the attention of the pharmaceutical companies, also affects the order of the sleep stages.

Our sleep is usually divided into four stages. The stages follow a specific order, and this order is vital to the quality of our sleep.

"Narcolepsy patients suffering from low levels of hypocretin experience muddled sleep stages. We know this from mice tests demonstrating that hypocretin affects the order of these stages," explains Anja Holm from Aalborg University, who is first author of the study and who did the tests together with Birgitte Kornum.

Existing research suggests that to solve the problem we need to gain more knowledge of hypocretin regulation. And here the Danish researchers point to a different, but equally important piece of the puzzle, namely the immune system.

"Most people know that when you are ill you often feel tired. And when you have a fever and the immune system is hard at work, you often suffer from poor sleep. So we know that something happens to the hypocretin level when the body is trying to fight off a virus infection, for example, and we are trying to understand this process," says Birgitte Kornum.

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Discovery of 30 exocomets in a young planetary system

For the past thirty years, the star β Pictoris has fascinated astronomers because it enables them to observe a planetary system in the process of formation. It is made up of at least two young planets, and also contains comets, which were detected as early as 1987. These were the first comets ever observed around a star other than the Sun.

Now, an international research team headed by Alain Lecavelier des Etangs, CNRS researcher at the Institut d'Astrophysique de Paris (CNRS/Sorbonne Université)1, has discovered 30 such exocomets and determined the size of their nuclei1, which vary between 3 and 14 kilometres in diameter. The scientists were also able to estimate the size distribution of the objects, i.e. the proportion of small comets to large ones. This is the first time this distribution has been measured outside our Solar System, and it is strikingly similar to that of comets orbiting the Sun. It shows that, just like the comets of the Solar System, the exocomets of β Pictoris were shaped by a series of collisions and breakups.

This work sheds new light on the origin and evolution of comets in planetary systems. Since a part of Earth's water probably originated in comets, scientists are seeking to understand their impact on the characteristics of planets. Their findings, published in Scientific Reports on April 28, 2022, are the outcome of 156 days of observation of the β Pictoris system using NASA's Transiting Exoplanet Survey Satellite (TESS).

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Sampling the deep graveyard of Earth's earliest crust

In an international collaboration, Earth scientists at the University of Cologne and Freie Universität Berlin discovered that some magmas on Earth, which made their way through the deep terrestrial mantle and erupted at Earth's surface, originate from mantle portions that contain remnants of Earth's earliest crust. This ancient material must have been buried in a 'graveyard' of old and cold crust more than 4 billion years ago and survived since then, maybe since the giant impact event forming the Moon.

This finding is unexpected because the plate tectonic regime of our planet progressively recycles crustal material via large-scale mantle convection at much smaller time scales. Therefore, it has been assumed that vestiges of early geological processes on Earth can only be found as analogues, on other terrestrial planets (Mercury, Venus, and Mars), asteroids, or the Moon. However, according to their study 'Long-term preservation of Hadean protocrust in Earth's mantle', which has recently appeared in the Proceedings of the National Academy of Sciences (PNAS), magmatic rocks that erupted throughout Earth's history can still carry signatures that provide detailed information about the nature of the first crust, its long-term preservation in a graveyard in the lower-most mantle, and its resurrection via younger volcanism.

For their study, the geologists investigated up to 3.55 billion years old rocks from southern Africa. The analysis of these rocks revealed small anomalies in the isotope composition of the element tungsten (W). The origin of these isotope anomalies, namely the relative abundance of 182W, relates to geological processes that must have occurred immediately after the formation of the Earth more than 4.5 billion years ago.

Model calculations by the authors show that the observed 182W isotope patterns are best explained by the recycling of Earth's earliest crust into mantle material that ascends via plumes from the lower mantle to generate lavas erupting at Earth's surface. Intriguingly, the study shows that similar isotope patterns can be observed in distinct types of modern volcanic rocks (ocean island basalts), which demonstrates that Earth's earliest crust is still buried in the lowermost mantle.

'We assume that the lower layers of the crust -- or the roots of the primordial continents -- became heavier than their surroundings due to a geological maturation process and therefore sank into the Earth's underlying mantle. Similar to a lava lamp,' geochemist Dr Jonas Tusch from the University of Cologne's Institute of Geology and Mineralogy remarked. 'This fascinating insight provides a geochemical fingerprint of the young Earth, allowing us to better understand how large continents formed over the history of our planet. It also explains how our current, oxygen-rich atmosphere evolved -- setting the stage for the origin of complex life,' Dr Elis Hoffmann of Freie Universität Berlin added.

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Large bodies helped extinct marine reptiles with long necks swim, new study finds

Scientists at the University of Bristol have discovered that body size is more important than body shape in determining the energy economy of swimming for aquatic animals.

This study, published today in Communications Biology, shows that big bodies help overcome the excess drag produced by extreme morphology, debunking a long-standing idea that there is an optimal body shape for low drag.

One important finding of this research is that the large necks of extinct elasmosaurs did add extra drag, but this was compensated by the evolution of large bodies.

Tetrapods or 'four-limbed vertebrates', have repeatedly returned to the oceans over the last 250 million years, and they come in many shapes and sizes, ranging from streamlined modern whales over 25 meters in length, to extinct plesiosaurs, with four flippers and extraordinarily long necks, and even extinct fish-shaped ichthyosaurs.

Dolphins and ichthyosaurs have similar body shapes, adapted for moving fast through water producing low resistance or drag. On the other hand, plesiosaurs, who lived side by side with the ichthyosaurs in the Mesozoic Era, had entirely different bodies. Their enormous four flippers which they used to fly underwater, and variable neck lengths, have no parallel amongst living animals. Some elasmosaurs had really extreme proportions, with necks up to 20 feet (6 metres) long. These necks likely helped them to snap up quick-moving fish, but were also believed to make them slower.

Until now, it has not been clear how shape and size influenced the energy demands of swimming in these diverse marine animals. Palaeobiologist Dr Susana Gutarra Díaz of Bristol's School of Earth Sciences and the National History Museum of London who led the research, explained: "To test our hypotheses, we created various 3D models and performed computer flow simulations of plesiosaurs, ichthyosaurs and cetaceans. These experiments are performed on the computer, but they are like water tank experiments."

Dr Colin Palmer, an engineer involved in the project said: "We showed that although plesiosaurs did experience more drag than ichthyosaurs or whales of equal mass because of their unique body shape, these differences were relatively minor. We found that when size is taken into account, the differences between groups became much less than the shape differences. We also show that the ratio of body length to diameter, which is widely used to classify these aquatic animals as more or less efficient, is not a good indicator of low drag."

Dr Gutarra Díaz said, "We were also particularly interested in the necks of elasmosaurs and so, we created hypothetical 3D models of plesiosaurs with various lengths of necks. Simulations of these models reveal that past a certain point, the neck adds extra drag, which potentially would make swimming costly. This 'optimal' neck limit lies around twice the length of the trunk of the animal."

Dr Benjamin Moon, another collaborator and expert on marine reptiles, continued: "When we examined a large sample of plesiosaurs modelled on really well preserved fossils at their real sizes, it turns out that most plesiosaurs had necks below this high-drag threshold, within which neck can get longer or shorter without increasing drag. But more interestingly, we showed that plesiosaurs with extremely long necks also had evolved very large torsos, and this compensated for the extra drag!"

Dr Tom Stubbs, another co-author summarised: "This study shows that, in contrast with prevailing popular knowledge, very long necked plesiosaurs were not necessarily slower swimmers than ichthyosaurs and whales, and this is in part thanks to their large bodies. We found that in elasmosaurs, neck proportions changed really fast. This confirms that long necks were advantageous for elasmosaurs in hunting, but they could not exploit this adaptation until they became large enough to offset the cost of high drag on their bodies."

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Bay Area storms get wetter in a warming world

The December 2014 North American Storm Complex was a powerful winter storm, referred to by some as California's "Storm of the Decade." Fueled by an atmospheric river originating over the tropical waters of the Pacific Ocean, the storm dropped 8 inches of rainfall in 24 hours, sported wind gusts of 139 miles per hour, and left 150,000 households without power across the San Francisco Bay Area.

Writing in Weather and Climate Extremes this week, researchers described the potential impacts of climate change on extreme storms in the San Francisco Bay area, among them the December 2014 North American Storm Complex.

Re-simulating five of the most powerful storms that have hit the area, they determined that under future conditions some of these extreme events would deliver 26-37% more rain, even more than is predicted simply by accounting for air's ability to carry more water in warmer conditions.

However, they found these increases would not occur with every storm, only those that include an atmospheric river accompanied by an extratropical cyclone.

The research -- funded by the City and County of San Francisco and in partnership with agencies including the San Francisco Public Utilities Commission, Port of San Francisco, and San Francisco International Airport -- will help the region plan its future infrastructure with mitigation and sustainability in mind.

"Having this level of detail is a game changer," said Dennis Herrera, General Manager of the San Francisco Public Utilities Commission, which was the lead City agency on the study. "This groundbreaking data will help us develop tools to allow our port, airport, utilities, and the City as a whole to adapt to our changing climate and increasingly extreme storms."

These first-of-their-kind forecasts for the city were made possible by the Stampede2 supercomputer at the Texas Advanced Computing Center (TACC) and the Cori system at the National Energy Research Scientific Computing Center (NERSC) -- two of the most powerful supercomputers in the world, supported by the National Science Foundation and Department of Energy respectively.

Hindcasting With the Future in Mind

Certain facets of our future climate are well established -- higher temperatures, rising seas, species loss. But how will greater greenhouse gas concentrations and warmer air and oceans effect extreme weather, like hurricanes, tornadoes, and heavy rainfall? And where precisely will these changes be the greatest and under what conditions?

Forecasting the natural hazards of the future is the mission of Christina Patricola, Assistant Professor of Geological and Atmospheric Sciences at Iowa State University and lead author on the Weather and Climate Extremes paper. Her research helps quantify and understand the risks we face from natural hazards in the future.

Using supercomputers allowed Patricola to model the region with 3 kilometer resolution. Scientists believe this level of detail is needed to capture the dynamics of storm systems like hurricanes and atmospheric rivers, and to predict their impact on an urban area.

For each of the historical storms, Patricola and her collaborators ran 10-member ensembles -- independent, slightly different simulations -- with 3 kilometer resolution, a process called 'hindcasting' (as opposed to forecasting). They then adjusted the greenhouse gas concentrations and sea-surface temperatures to predict how these historical storms would look in the projected future climates of 2050 and 2100.

Patricola calls these "storyline" experiments: computer models that are meant to be instructive for thinking about how historically-impactful storm events could look in a warmer world. Focusing on events that were known to be impactful to city operations provides a useful context for understanding the potential impacts of events if they occurred under future climate conditions.

The study doesn't address changes in the frequency of extreme storms in the future and therefore can't address how precipitation will change overall, she said. (Another pressing question for California planners.) But they can help decision-makers understand trends in the intensity of the worst-case-scenario storms and make informed choices.

On the West Coast, much of the precipitation that falls is associated with atmospheric rivers (ARs), which transport a substantial amount of moisture in a narrow band, Patricola explained. Some of the storms they looked at featured ARs alone. Others had ARs at the same time as low-pressure systems known as extratropical cyclones (ETCs).

"We found something very interesting," she said. "Precipitation increased substantially for events with an atmospheric river and a cyclone together, whereas precipitation changes were weak or negative when there was only an atmospheric river."

The difference, she believes, lies in the lifting mechanism. In general, heavy precipitation requires moist air to ascend. While the AR-only storms showed a future increase in atmospheric moisture, the storms with an AR and ETC showed a future increase in atmospheric moisture and rising air. Additional investigations will explore this relationship.

High Performance Climate Science

Patricola has used TACC supercomputers for climate and weather modeling since 2010, when she was a graduate student at Cornell University working with leading climate scientist, Kerry Cook (now at The University of Texas at Austin). She recalls that her first models had a horizontal resolution of 90 km -- 30 times less resolved than today -- and were considered state-of-the-art at the time.

"It was a very big help to have the resource from TACC and NERSC for these simulations," she said. "We're interested in extreme precipitation totals and hourly rainfall rates. We had to go to a high resolution of 3 km to make these predictions. And as we increase resolution, the computational expense goes up."

Patricola has used the methodology she developed to understand other phenomena, like how tropical cyclones may change in the future. She and collaborator Michael Wehner reported on these changes in a 2018 Nature paper. "If a hurricane like Katrina happened at the end of the 21st century, what could it be like? More rainfall, higher winds? Our method can be used for any type of weather system that can be hindcasted."

In the next phase of the San Francisco project, Patricola will work with city staff and their collaborators to understand what the weather changes mean in terms of city operations.

Read more at Science Daily

Earth's atmosphere may be source of some lunar water

Hydrogen and oxygen ions escaping from Earth's upper atmosphere and combining on the moon could be one of the sources of the known lunar water and ice, according to new research by University of Alaska Fairbanks Geophysical Institute scientists.

The work led by UAF Geophysical Institute associate research professor Gunther Kletetschka adds to a growing body of research about water at the moon's north and south poles.

Finding water is key to NASA's Artemis project, the planned long-term human presence on the moon. NASA plans to send humans back to the moon this decade.

"As NASA's Artemis team plans to build a base camp on the moon's south pole, the water ions that originated many eons ago on Earth can be used in the astronauts' life support system," Kletetschka said.

The new research estimates the moon's polar regions could hold up to 3,500 cubic kilometers -- 840 cubic miles -- or more of surface permafrost or subsurface liquid water created from ions that escaped Earth's atmosphere. That's a volume comparable to North America's Lake Huron, the world's eighth-largest lake.

Researchers based that total on the lowest volume model calculation -- 1% of Earth's atmospheric escape reaching the moon.

A majority of the lunar water is generally believed to have been deposited by asteroids and comets that collided with the moon. Most was during a period known as the Late Heavy Bombardment. In that period, about 3.5 billion years ago when the solar system was about 1 billion years old, it is argued that the early inner planets and Earth's moon sustained unusually heavy impact from asteroids.

Scientists also hypothesize that the solar wind is a source. The solar wind carries oxygen and hydrogen ions, which may have combined and been deposited on the moon as water molecules.

Now there's an additional way to explain how water accumulates on the moon.

The research was published March 16 in the journal Scientific Reports in a paper authored by Kletetschka and co-authored by Ph.D. student Nicholas Hasson of the Geophysical Institute and UAF Water and Environmental Research Center at the Institute for Northern Engineering. Several colleagues from the Czech Republic are also among the co-authors.

Kletetschka and his colleagues suggest hydrogen and oxygen ions are driven into the moon when it passes through the tail of the Earth's magnetosphere, which it does on five days of the moon's monthly trip around the planet. The magnetosphere is the teardrop-shaped bubble created by Earth's magnetic field that shields the planet from much of the continual stream of charged solar particles.

Recent measurements from multiple space agencies -- NASA, European Space Agency, Japan Aerospace Exploration Agency and Indian Space Research Organization -- revealed significant numbers of water-forming ions present during the moon's transit through this part of the magnetosphere.

These ions have slowly accumulated since the Late Heavy Bombardment.

The presence of the moon in the magnetosphere's tail, called the magnetotail, temporarily affects some of Earth's magnetic field lines -- those that are broken and which simply trail off into space for many thousands of miles. Not all of Earth's field lines are attached to the planet at both ends; some have only one attachment point. Think of each of these as a thread tethered to a pole on a windy day.

The moon's presence in the magnetotail causes some of these broken field lines to reconnect with their opposing broken counterpart. When that happens, hydrogen and oxygen ions that had escaped Earth rush to those reconnected field lines and are accelerated back toward Earth.

The paper's authors suggest many of those returning ions hit the passing moon, which has no magnetosphere of its own to repel them.

"It is like the moon is in the shower -- a shower of water ions coming back to Earth, falling on the moon's surface," Kletetschka said.

The ions then combine to form the lunar permafrost. Some of that, through geologic and other processes such as asteroid impacts, is driven below the surface, where it can become liquid water.

Read more at Science Daily

In Einstein's footsteps and beyond

In physics, as in life, it's always good to look at things from different perspectives.

Since the beginning of quantum physics, how light moves and interacts with matter around it has mostly been described and understood mathematically through the lens of its energy. In 1900, Max Planck used energy to explain how light is emitted by heated objects, a seminal study in the foundation of quantum mechanics. In 1905, Albert Einstein used energy when he introduced the concept of photon.

But light has another, equally important quality known as momentum. And, as it turns out, when you take momentum away, light starts behaving in really interesting ways.

An international team of physicists led by Michaël Lobet, a research associate at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Eric Mazur, the Balkanski Professor of Physics and Applied Physics at SEAS, are re-examining the foundations of quantum physics from the perspective of momentum and exploring what happens when the momentum of light is reduced to zero.

The research is published in Nature Light Science & Applications.

Any object with mass and velocity has momentum -- from atoms to bullets to asteroids -- and momentum can be transferred from one object to another. A gun recoils when a bullet is fired because the momentum of the bullet is transferred to the gun. At the microscopic scale, an atom recoils when it emits light because of the acquired momentum of the photon. Atomic recoil, first described by Einstein when he was writing the quantum theory of radiation, is a fundamental phenomenon which governs light emission.

But a century after Planck and Einstein, a new class of metamaterials is raising questions regarding these fundamental phenomena. These metamaterials have a refractive index close to zero, meaning that when light travels through them, it doesn't travel like a wave in phases of crests and troughs. Instead, the wave is stretched out to infinity, creating a constant phase. When that happens, many of the typical processes of quantum mechanics disappear, including atomic recoil.

Why? It all goes back to momentum. In these so-called near-zero index materials, the wave momentum of light becomes zero and when the wave momentum is zero, odd things happen.

"Fundamental radiative processes are inhibited in three dimensional near-zero index materials," says Lobet, who is currently a lecturer at the University of Namur in Belgium. "We realized that the momentum recoil of an atom is forbidden in near-zero index materials and that no momentum transfer is allowed between the electromagnetic field and the atom."

If breaking one of Einstein's rules wasn't enough, the researchers also broke perhaps the most well-known experiment in quantum physics -- Young's double-slit experiment. This experiment is used in classrooms across the globe to demonstrate the particle-wave duality in quantum physics -- showing that light can display characteristics of both waves and particles.

In a typical material, light passing through two slits produces two coherent sources of waves that interfere to form a bright spot in the center of the screen with a pattern of light and dark fringes on either side, known as diffraction fringes.

"When we modelled and numerically computed Young's double-slit experiment, it turned out that the diffraction fringes vanished when the refractive index was lowered," said co-author Larissa Vertchenko, of the Technical University of Denmark.

"As it can be seen, this work interrogates fundamental laws of quantum mechanics and probes the limits of wave-corpuscle duality," said co-author Iñigo Liberal, of the Public University of Navarre in Pamplona, Spain.

While some fundamental processes are inhibited in near-zero refractive index materials, others are enhanced. Take another famous quantum phenomenon -- Heisenberg's uncertainty principle, more accurately known in physics as the Heisenberg inequality. This principle states that you cannot know both the position and speed of a particle with perfect accuracy and the more you know about one, the less you know about the other. But, in near-zero index materials, you know with 100% certainty that the momentum of a particle is zero, which means you have absolutely no idea where in the material the particle is at any given moment.

"This material would make a really poor microscope, but it does enable to cloak objects quite perfectly," Lobet said. "In some way, objects become invisible."

"These new theoretical results shed new light on near-zero refractive index photonics from a momentum perspective," said Mazur. "It provides insights in the understanding of light-matter interactions in systems with a low- refraction index, which can be useful for lasing and quantum optics applications."

The research could also shed light on other applications, including quantum computing, light sources that emit a single photon at a time, the lossless propagation of light through a waveguide and more.

The team next aims to revisit other foundational quantum experiments in these materials from a momentum perspective. Afterall, even though Einstein didn't predict near-zero refractive index materials, he did stress the importance of momentum. In his seminal 1916 paper on fundamental radiative processes, Einstein insisted that, from a theoretical point of view, energy and momentum "should be considered on a completely equal footing since energy and momentum are linked in the closest possible way."

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Loneliness leads to higher risk of future unemployment

Experiencing loneliness appears to lead to a higher risk of future unemployment, according to new research.

Previous research has established that being unemployed can cause loneliness, however the new study from the University of Exeter is the first to directly explore whether the opposite also applies across the working age population. Published in BMC Public Health, the study found that people who reported "feeling lonely often" were significantly more likely to encounter unemployment later. Their analysis also confirmed previous findings that the reverse is true -- people who were unemployed were more likely to experience loneliness later.

Lead author Nia Morrish, of the University of Exeter, said: "Given the persisting and potentially scarring effects of both loneliness and unemployment on health and the economy, prevention of both experiences is key. Decreased loneliness could mitigate unemployment, and employment abate loneliness, which may in turn relate positively to other factors including health and quality of life. Thus, particular attention should be paid to loneliness with additional support from employers and government to improve health and wellbeing. Our research was largely conducted pre-pandemic, however we suspect this issue may be even more pressing, with more people working from home and potentially experiencing isolation because of anxieties around covid."

The research analysed largely pre-pandemic data from more than 15,000 people in the Understanding Society Household Longitudinal Study. The team analysed responses from the participants during 2017-2019, then from 2018-2020, controlling for factors including age, gender, ethnicity, education, marital status, household composition, number of own children in household and region.

Senior author Professor Antonieta Medina-Lara said: "Loneliness is an incredibly important societal problem, which is often thought about in terms of the impact on mental health and wellbeing only. Our findings indicate that there may also be wider implications, which could have negative impacts for individuals and the economy. We need to explore this further, and it could lay the foundations for employers or policy makers to tackle loneliness with a view to keeping more people in work."

Read more at Science Daily

Climate change could spark the next pandemic, new study finds

As Earth's climate continues to warm, researchers predict wild animals will be forced to relocate their habitats -- likely to regions with large human populations -- dramatically increasing the risk of a viral jump to humans that could lead to the next pandemic.

This link between climate change and viral transmission is described by an international research team led by scientists at Georgetown University and is published April 28 in Nature.

In their study, the scientists conducted the first comprehensive assessment of how climate change will restructure the global mammalian virome. The work focuses on geographic range shifts -- the journeys that species will undertake as they follow their habitats into new areas. As they encounter other mammals for the first time, the study projects they will share thousands of viruses.

They say these shifts bring greater opportunities for viruses like Ebola or coronaviruses to emerge in new areas, making them harder to track, and into new types of animals, making it easier for viruses to jump across a "stepping stone" species into humans.

"The closest analogy is actually the risks we see in the wildlife trade," says the study's lead author Colin Carlson, PhD, an assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center. "We worry about markets because bringing unhealthy animals together in unnatural combinations creates opportunities for this stepwise process of emergence -- like how SARS jumped from bats to civets, then civets to people. But markets aren't special anymore; in a changing climate, that kind of process will be the reality in nature just about everywhere."

Of concern is that animal habitats will move disproportionately in the same places as human settlements, creating new hotspots of spillover risk. Much of this process may already be underway in today's 1.2 degrees warmer world, and efforts to reduce greenhouse gas emissions may not stop these events from unfolding.

An additional important finding is the impact rising temperatures will have on bats, which account for the majority of novel viral sharing. Their ability to fly will allow them to travel long distances, and share the most viruses. Because of their central role in viral emergence, the greatest impacts are projected in southeast Asia, a global hotspot of bat diversity.

"At every step," said Carlson, "our simulations have taken us by surprise. We've spent years double-checking those results, with different data and different assumptions, but the models always lead us to these conclusions. It's a really stunning example of just how well we can, actually, predict the future if we try."

As viruses start to jump between host species at unprecedented rates, the authors say that the impacts on conservation and human health could be stunning.

"This mechanism adds yet another layer to how climate change will threaten human and animal health," says the study's co-lead author Gregory Albery, PhD, a postdoctoral fellow in the Department of Biology in the Georgetown University College of Arts and Sciences.

"It's unclear exactly how these new viruses might affect the species involved, but it's likely that many of them will translate to new conservation risks and fuel the emergence of novel outbreaks in humans."

Altogether, the study suggests that climate change will become the biggest upstream risk factor for disease emergence -- exceeding higher-profile issues like deforestation, wildlife trade, and industrial agriculture. The authors say the solution is to pair wildlife disease surveillance with real-time studies of environmental change.

"When a Brazilian free-tailed bat makes it all the way to Appalachia, we should be invested in knowing what viruses are tagging along," says Carlson. "Trying to spot these host jumps in real-time is the only way we'll be able to prevent this process from leading to more spillovers and more pandemics."

"We're closer to predicting and preventing the next pandemic than ever," says Carlson. "This is a big step towards prediction -- now we have to start working on the harder half of the problem."

"The COVID-19 pandemic, and the previous spread of SARS, Ebola, and Zika, show how a virus jumping from animals to humans can have massive effects. To predict their jump to humans, we need to know about their spread among other animals," said Sam Scheiner, a program director with the U.S. National Science Foundation (NSF), which funded the research. "This research shows how animal movements and interactions due to a warming climate might increase the number of viruses jumping between species."

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Supernova reveals secrets to astronomers

An international group of astronomers led by Benjamin Thomas of The University of Texas at Austin has used observations from the Hobby-Eberly Telescope (HET) at the university's McDonald Observatory to unlock a puzzling mystery about a stellar explosion discovered several years ago and evolving even now. The results, published in today's issue of The Astrophysical Journal, will help astronomers better understand the process of how massive stars live and die.

When an exploding star is first detected, astronomers around the world begin to follow it with telescopes as the light it gives off changes rapidly over time. They see the light from a supernova get brighter, eventually peak, and then start to dim. By noting the times of these peaks and valleys in the light's brightness, called a "light curve," as well as the characteristic wavelengths of light emitted at different times, they can deduce the physical characteristics of the system.

"I think what's really cool about this kind of science is that we're looking at the emission that's coming from matter that's been cast off from the progenitor system before it exploded as a supernova," Thomas said. "And so this makes a sort of time machine."

In the case of supernova 2014C, the progenitor was a binary star, a system in which two stars were orbiting each other. The more massive star evolved more quickly, expanded, and lost its outer blanket of hydrogen to the companion star. The first star's inner core continued burning lighter chemical elements into heavier ones, until it ran out of fuel. When that happened, the outward pressure from the core that had held up the star's great weight dropped. The star's core collapsed, triggering a gigantic explosion.

This makes it a type of supernova astronomers call a "Type Ib." In particular, Type Ib supernovae are characterized by not showing any hydrogen in their ejected material, at least at first.

Thomas and his team have been following SN 2014C from telescopes at McDonald Observatory since its discovery that year. Many other teams around the world also have studied it with telescopes on the ground and in space, and in different types of light, including radio waves from the ground-based Very Large Array, infrared light, and X-rays from the space-based Chandra Observatory.

But the studies of SN 2014C from all of the various telescopes did not add up into a cohesive picture of how astronomers thought a Type Ib supernova should behave.

For one thing, the optical signature from the Hobby-Eberly Telescope (HET) showed SN 2014C contained hydrogen -- a surprising finding that also was discovered independently by another team using a different telescope.

"For a Type Ib supernova to begin showing hydrogen is completely weird," Thomas said. "There's just a handful of events that have been shown to be similar."

For a second thing, the optical brightness (light curve) of that hydrogen was behaving strangely.

Most of the light curves from SN 2014C -- radio, infrared, and X-rays -- followed the expected pattern: they got brighter, peaked, and started to fall. But the optical light from the hydrogen stayed steady.

"The mystery that we've wrestled with has been 'How do we fit our Texas HET observations of hydrogen and its characteristics into that [Type Ib] picture?'," said UT Austin professor and team member J. Craig Wheeler.

The problem, the team realized, was that previous models of this system assumed that the supernova had exploded and sent out its shockwave in a spherical manner. The data from HET showed that this hypothesis was impossible -- something else must have happened.

"It just would not fit into a spherically symmetric picture," Wheeler said.

The team proposes a model where the hydrogen envelopes of the two stars in the progenitor binary system merged to form a "common-envelope configuration," where both were contained within a single envelope of gas. The pair then expelled that envelope in an expanding, disk-like structure surrounding the two stars. When one of the stars exploded, its fast-moving ejecta collided with the slow-moving disk, and also slid along the disk surface at a "boundary layer" of intermediate velocity.

The team suggests that this boundary layer is the origin of the hydrogen they detected and then studied for seven years with HET.

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News from the climate history of the Dead Sea

The lake level of the Dead Sea is currently dropping by more than one metre every year -- mainly because of the heavy water consumption in the catchment area. However, very strong lake level drops due to climate changes are also known from earlier times. At the end of the last ice age, for example, the water level dropped by almost 250 metres within a few millennia. A study published today in the journal Scientific Reports now provides new insights into the exact course of this process. Daniela Müller and Achim Brauer from the German Research Centre for Geosciences (GFZ) in Potsdam, together with colleagues from the Hebrew University of Jerusalem, studied 15,000-year-old sediments from the Dead Sea and the surrounding area using newly developed methods. With unprecedented accuracy, they show that the long period of drought was interrupted by wet periods lasting ten to a hundred years. This also offers new insights into the settlement history of this region, which is significant for human development, and enables better assessments of current and future developments driven by climate change.

The water cycle at the Dead Sea -- then and now

In highly sensitive regions such as the Eastern Mediterranean, where water availability is an important factor for socio-economic and political development, it is crucial to understand how the water cycle is changing in response to climate change. Geologists can achieve this by assessing strong hydroclimatic changes that occurred several millennia back in time. For example, during the transition from the last ice age to the Holocene, the water level of Lake Lisan dropped by about 240 metres in the period 24-11 thousand years ago, which eventually led to its transition into today's Dead Sea.

Sediments as witnesses of time

The sediments at the edge of lake Lisan near the archaeological site of Masada and from the bottom of what is now the Dead Sea are unique witnesses to this development. In their new study, researchers led by Achim Brauer, head of Section 4.3 "Climate Dynamics and Landscape Evolution" at the German Research Centre for Geosciences Potsdam, and doctoral student Daniela Müller together with colleagues from the Geological Survey Israel and the Hebrew University of Jerusalem, analysed these sediments with unprecedented precision. The investigations took place within the framework of the PALEX project 'Paleohydrology and Extreme Floods from the Dead Sea ICDP Core', which is funded by the German Research Foundation (DFG).

New high-resolution methods for sediment analysis

For this study, new high-resolution analytical methods were developed at the GFZ to gain precise information from the stratification of the sediments and their geochemical composition, even about seasonal deposition processes and thus about the type, duration and course of climatic phases.

In particular, the combination of light microscopic methods with so-called 2D element mapping using X-ray fluorescence scanners is new. This enables the precise identification and localisation of elements in the sediments. Important and challenging for this is the preparation of the sediments for this analysis: The moisture must be removed from them by freeze-drying -- not easy given the high salt content of the Dead Sea and its affinity for water. Then the sediments are impregnated in synthetic resin and thin sections are made from them. In all this, the microstructure must not be altered.

Pause in climate change: humid phases interrupted long dry periods

The researchers found out that the dramatic long-term drop in the lake level due to increasing dryness was interrupted several times by wetter phases when climate change took breaks. "In this study, we were able for the first time to precisely determine the duration of these phases with several decades and in one case up to centuries by counting annual layers in the sediment," says Daniela Müller, lead author of the study. The exact reason for these pauses in the climate change of this region still remain elusive. Possible links to North Atlantic climate are suspected.

"What was particularly surprising was that during these wetter phases, in some cases over several decades, there we even did not find any traces of extreme floods, which are typical for this region even today and during wetter times in the past," Müller explains.

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New cocoa processing method produces fruitier, more 'flowery' dark chocolate

Producing chocolate, one of the world's most beloved sweets, is a multistep process beginning with freshly harvested cocoa beans. People have been experimenting with chocolate-making for millennia, and even today, new methods are still being introduced. Now, researchers reporting in ACS' Journal of Agricultural and Food Chemistry have found that an alternative processing step called "moist incubation" results in a fruitier, more flowery-tasting dark chocolate than the conventional fermentation process.

After cocoa beans are harvested, they are traditionally covered in banana leaves and left for a few days to ferment. During this time, microbes in the environment degrade the pulp surrounding the beans, heating and acidifying them. This causes biochemical changes in the beans that reduce bitterness and astringency, while developing the pleasing flavors and aromas associated with chocolate. Recently, scientists developed an alternative, non-microbial approach called moist incubation, in which dried, unfermented cocoa nibs are rehydrated in an acidic solution, heated for 72 hours and then re-dried. The method, which is faster and more easily controlled than fermentation, produced similar aromas in beans as fermentation, with some differences. Irene Chetschik, Ansgar Schlüter and colleagues wanted to find out how the taste and aroma of the final product -- chocolate -- compared when using moist incubation versus traditional fermentation.

The researchers made chocolate bars using moist incubated or fermented dried cocoa beans, as well as unfermented beans as a control. Sensory panelists said the moist incubated sample had higher intensities of fruity, flowery, malty and caramel-like aromas, whereas the fermented one had higher roasty aroma notes, and the bar made from unfermented beans had a primarily green aroma. The panelists rated the moist incubated sample as the sweetest-tasting, while the unfermented chocolate was the most bitter and astringent. Identification of aroma compounds by gas chromatography (GC)-olfactometry and their subsequent quantitation by GC-mass spectrometry revealed higher levels of malty compounds called Strecker aldehydes and lower amounts of roasty compounds called pyrazines in the moist incubated chocolate compared with the fermented one. The researchers concluded that moist incubation produces a chocolate with a pleasant aroma and taste and could, therefore, serve as an alternative postharvest treatment.

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Neuronal plasticity in chronic pain-induced anxiety revealed

Hokkaido University researchers have shown how chronic pain leads to maladaptive anxiety in mice, with implications for treatment of chronic pain-related psychiatric disorders in humans.

Chronic pain is persistent and inescapable, and can lead to maladaptive emotional states. It is often comorbid with psychiatric disorders, such as depression and anxiety disorders. It is thought that chronic pain causes changes in neural circuits, and gives rise to depression and anxiety.

Researchers at Hokkaido University have identified the neuronal circuit involved in chronic pain-induced anxiety in mice. Their research, which was recently published in Science Advances, could lead to the development of new treatments for chronic pain and psychiatric disorders such as anxiety disorders and major depressive disorder.

"Clinicians have known for a long time that chronic pain often leads to anxiety and depression, however the brain mechanism for this was unclear," said Professor Masabumi Minami of the Faculty of Pharmaceutical Sciences at Hokkaido University, the corresponding author of the paper.

The researchers looked at how neuronal circuits were affected by chronic pain in mice. They used an electrophysiological technique to measure the activities of neurons after four weeks of chronic pain. They found that chronic pain caused the neuroplastic change which suppressed the neuronal pathway projecting from the brain region called bed nucleus of the stria terminalis (BNST) to the region called lateral hypothalamus (LH).

Using chemogenetics, an advanced technique to manipulate neuronal activity, they showed that restoration of the suppressed activity of this neuronal pathway attenuated the chronic pain-induced anxiety. These findings indicate that chronic pain-induced functional changes in the neuronal circuits within the BNST leads to maladaptive anxiety.

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Classifying exoplanet atmospheres opens new field of study

An international team of researchers examined data for 25 exoplanets and found some links among the properties of the atmospheres, including the thermal profiles and chemical abundances in them. This marks the first time exoplanet atmospheres have been studied as populations, rather than individually. These findings will help establish a generalized theory of planet formation which will improve our understanding of all planets, including the Earth.

Today there are more than 3000 confirmed exoplanets, planets orbiting stars other than the Sun. Because they are far away from Earth, it is difficult to study them in detail. Determining the characteristics of even one exoplanet has been a noteworthy accomplishment.

In this research, astronomers used archival data for 25 hot Jupiters, gas giant planets that orbit close to their host stars. The data included 600 hours of observations from the Hubble Space Telescope and more than 400 hours of observations from the Spitzer Space Telescope.

One of the characteristics investigated by the team was the presence or absence of a "thermal inversion." Planetary atmospheres trap heat, so in general the temperature increases as you probe deeper into the atmosphere. But some planets show a thermal inversion where an upper layer of the atmosphere is warmer than the layer beneath it. On Earth, the presence of ozone causes a thermal inversion. The team found that almost all of the hot Jupiters with a thermal inversion also showed evidence for hydrogen anion (H-) and metallic species such as titanium oxide (TiO), vanadium oxide (VO), or iron hydride (FeH). Conversely, exoplanets without these chemicals almost never had thermal inversions. It is difficult to draw conclusions based on correlation alone, but since these metallic species are efficient absorbers of stellar light, one theory holds that when these chemicals are present in the upper atmosphere, they absorb light from the host star and cause the temperature to increase.

Masahiro Ikoma at the National Astronomical Observatory of Japan, a co-investigator in this study, explains, "The theory of gas giant formation proposed by my students and I predicted diversity in the composition of hot Jupiter atmospheres, and helped to motivate this systematic survey of atmospheric characteristics."

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Beetle in the coconut: Fossil find sheds new light on Neotropical rainforests

Tiny beetles that feed on fruit from the palm family may have developed their taste for coconuts long ago, according to a Penn State-led team of scientists studying suspected insect damage in a 60-million-year-old fossil.

"We found this remarkable fossil coconut that has clear signs of insect tunneling," said L. Alejandro Giraldo, a graduate student in geosciences at Penn State. "After studying the damage in detail, we were able to pinpoint the insect culprit: a group of beetles commonly referred to as palm bruchines that today still eat lots of palm fruit -- coconuts included."

The findings represent the earliest fossil evidence of seed beetles feeding on palm fruit and shed new light on the Neotropical rainforests that emerged in modern day South America following the Cretaceous-Paleogene extinction event 66 million years ago that wiped out the dinosaurs and reshaped life on Earth, the scientists said.

"These were the first Neotropical forests as we know them today," said Giraldo, whose adviser is Peter Wilf, professor of geosciences at Penn State. "We know these forests had similar plants compared to today, and the next step is knowing what was happening to these forests -- for example how insects were interacting with the plants."

Previous studies have focused on insect damage to fossil leaves, the most abundant plant parts found in the fossil record, the scientists said. Examples of insect damage to fruit and seeds are less common, but scientists found six suspected insect holes on a coconut fossil from a site in modern day Colombia.

The fossil contained damage to the outer and inner layers of the fruit, revealing a three-dimensional path that suggests the holes had a biological origin -- like from larvae eating their way through the coconut, the scientists said.

The team analyzed the number, position and size of the holes and the scar tissue left behind and compared that with damaged caused by modern insects, especially those that feed on plants from the palm family. The damage was consistent with a sub-group of modern beetles called palm bruchines, the scientists reported in the journal Review of Palaeobotany and Palynology.

"There are thousands of different insect species that can feed on seeds, but not many of them feed on palm seeds, so that was the way to start," Giraldo said. "After that it was doing a lot of detective work, really digging into the literature and studying different morphological features in terms of how this damage occurs. And it paid off."

This kind of relationship between specific plants and insects -- called specialized interactions -- plays an important role in creating and maintaining plant diversity in modern Neotropical rainforests. By eating and destroying seeds, these highly specialized insects help prevent any one group of plants from dominating the landscape.

The findings suggest that palm bruchines have consistently eaten palm fruits for at least 60 million years and that the specialized interactions that define modern-day Neotropical rainforests have occurred through geological time, the scientists said.

"This is something that we see 60 million years ago, and it's something that is still occurring today," Giraldo said. "Our contribution is that we pinpoint this specific group of insects as the culprit, and that group is still living today and attacks the same coconuts and same palms as it did in the past."

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Ecotourism is having a negative effect on primate's behavior

New research shows that the increase in primate ecotourism is having a negative effect on monkey's behaviour.

The study, led by the University of Portsmouth, found that this fast-growing tourism sector where tourists can conveniently reach primates via motor boats is causing stress-related behaviours in monkeys.

The research looked at the impact of a single engine motor boat approaching a community of proboscis monkeys, an endangered species living in a remote riparian area (strips of vegetation that border rivers, streams and lakes) in Sabah, Malaysia. Proboscis monkeys are unusual looking with their very long noses, which adds to making them appealing to tourists.

Many of these boats, carrying multiple tourists, approach the primates quickly and loudly, often reaching the river banks just a few metres away from the wildlife.

The researchers found that frequent visits by such groups, which often involve an unusually high level of noise, caused stress-related behaviours in the primates such as self-scratching, an increased vigilant state, increased levels of aggression and reduced feeding.

Lead author of the study, Dr Marina Davila-Ross, Reader in Comparative Psychology at the University of Portsmouth, said: "Our evidence shows that even a single motor boat moving slowly, with humans behaving calmly, can negatively affect the primate's behaviour and induce stress -- an impact that is likely to be larger with tourist boats.

"The riparian area is an important habitat that has become increasingly popular to primate ecotourism, because it enables tourists to conveniently reach primates via motor boats."

The researchers conducted the experiment by approaching the monkeys in a motor boat with different speeds and travel distances -- fast-close (approaching the monkeys for 10 seconds when 40 metres away at a speed of 14.4 km/hr), slow-close (approaching the monkey for 40 seconds when 40 metres away at a speed of 3.6 km/hr), and slow-far conditions (approaching the monkeys for 20 seconds when 100 metres away, at a speed of 3.6 km/hr). For each condition, they compared stress-related behaviours before the boat approached with after the boat started its approach.

The results showed that the monkeys displayed stress-related behaviours for longer in the fast-close and slow-close conditions and also reduced feeding as a result of the boat approaching in the fast-close condition. They also found that male proboscis monkeys displayed more vigilant behaviour than females.

Once the boat started to approach, the proboscis monkeys gazed at the boat for longer than before the boat approached, showed repeated scratching, and often moved quickly backwards to hide in the trees. This could potentially cause the monkeys to leave their safe sleeping sites and to retreat deep into the forest as it gets dark, where they could face a higher risk of predation.

Dr Davila-Ross said: "Collectively, our findings suggest that the approach of a single motor boat induces stress in proboscis monkeys when approaching them as closely as 60 metres from the other side of the river, regardless of the speed of approach. The findings match those obtained in studies on sea mammals and birds, suggesting that stress is a universal response across animals when a boat approaches -- a large, loud, and artificial object moving toward them is likely to be threatening."

The researchers propose that guidelines for primate tourism in the riparian areas, which are largely unregulated, should include an approach speed of no more than 4 km/hr within 100 metres of the proboscis monkeys. They suggest it is also important to keep a distance, preferably no closer than 60 metres away, from the monkeys.

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Being in nature: Good for mind, body and nutrition

In late 2020, Canadian doctors made headlines for "prescribing nature," or recommended time outdoors based on research that suggests people who spent two or more hours in nature per week improved their health and wellbeing. Knowing this, transdisciplinary researchers from Drexel University investigated how nature relatedness -- simply feeling connected with the natural world -- benefits dietary diversity and fruit and vegetable intake, in a study recently published the American Journal of Health Promotion.

"Nature relatedness has been associated with better cognitive, psychological and physical health and greater levels of environmental stewardship. Our findings extend this list of benefits to include dietary intake," said Brandy-Joe Milliron, PhD, an associate professor in Drexel's College of Nursing and Health Professions and lead author of the publication. "We found people with higher nature relatedness were more likely to report healthful dietary intake, including greater dietary variety and higher fruit and vegetable consumption."

The research team surveyed over 300 adults in Philadelphia to measure their self-reported connection to nature, including their experience with and perspective of nature, and the foods and beverages they had consumed the previous day to assess their dietary diversity and estimate their daily fruit and vegetable consumption. Survey participants mirrored demographic characteristics (gender, income, education and race) of Philadelphia, as of the 2010 census. The data were collected between May and August 2017. The results of the survey showed that participants with a stronger connection to nature reported a more varied diet and ate more fruits and vegetables.

"This work can impact health promotion practices in two ways," said Milliron. "First, nature-based health promotion interventions may increase nature relatedness across the lifespan and potentially improve dietary intake. And second, augmenting dietary interventions with nature-based activities may lead to greater improvements in dietary quality."

The research team added that these findings highlight the potential for leveraging nature-based experiences or interventions such as incorporating green spaces or urban greening into city planning, integrating nature- and park-prescription programs into healthcare practices (similar to the Canadian model) and promoting nature-based experiences in the classroom settings, among many others.

But, the researchers noted, while improving dietary intake through nature-based interventions may be valuable, it is also complex.

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Scientists find elusive gas from post-starburst galaxies hiding in plain sight

Post-starburst galaxies were previously thought to scatter all of their gas and dust -- the fuel required for creating new stars -- in violent bursts of energy, and with extraordinary speed. Now, new data from the Atacama Large Millimeter/submillimeter Array (ALMA) reveals that these galaxies don't scatter all of their star-forming fuel after all. Instead, after their supposed end, these dormant galaxies hold onto and compress large amounts of highly-concentrated, turbulent gas. But contrary to expectation, they're not using it to form stars.

In most galaxies, scientists expect gas to be distributed in a way similar to starlight. But for post-starburst galaxies, or PSBs, this isn't the case. PSBs are different from other galaxies because they are born in the aftermath of violent collisions, or mergers between galaxies. Galaxy mergers typically trigger massive bursts of star formation, but in PSBs, this outburst slows down and near-completely stops almost as soon as it begins. As a result, scientists previously believed that little or no star-forming fuel was left in these galaxies' central star-forming factories. And until now, the belief was that the molecular gases had been redistributed to radii well beyond the galaxies, either through stellar processes or by the effects of black holes. The new results challenge this theory.

"We've known for some time that large amounts of molecular gas remains in the vicinity of PSBs but haven't been able to say where, which in turn, has prevented us from understanding why these galaxies stopped forming stars. Now, we have discovered a considerable amount of remaining gas within the galaxies and that remaining gas is very compact," said Adam Smercina, an astronomer at the University of Washington and the principal investigator of the study. "While this compact gas should be forming stars efficiently, it isn't. In fact, it is less than 10-percent as efficient as similarly compact gas is expected to be."

In addition to being compact enough to make stars, the gas in the observed dormant -- or quiescent -- galaxies had another surprise in store for the team: it was often centrally-located, though not always, and was surprisingly turbulent. Combined, these two characteristics led to more questions than answers for researchers.

"The rates of star formation in the PSBs we observed are much lower than in other galaxies, even though there appears to be plenty of fuel to sustain the process," said Smercina. "In this case, star formation may be suppressed due to turbulence in the gas, much like a strong wind can suppress a fire. However, star formation can also be enhanced by turbulence, just like wind can fan flames, so understanding what is generating this turbulent energy, and how exactly it is contributing to dormancy, is a remaining question of this work."

Decker French, an astronomer at the University of Illinois, and a co-author of the research added, "These results raise the question of what energy sources are present in these galaxies to drive turbulence and prevent the gas from forming new stars. One possibility is energy from the accretion disk of the central supermassive black holes in these galaxies."

A clear understanding of the processes that govern the formation of stars and galaxies is key to providing context to the Universe and our place in it. The discovery of turbulent, compact gas in otherwise dormant galaxies gives researchers one more clue to solving the mystery of how galaxies in particular live, evolve and die over the course of billions of years. And that means additional future research with the help of ALMA's 1.3mm receiver, which sees the otherwise invisible with stark clarity.

J.D. Smith, an astronomer at the University of Toledo, and a co-author of the research said, "There is much about the evolution of a typical galaxy we don't understand, and the transition from their vibrant star-forming lives into quiescence is one of the least understood periods. Although post-starbursts were very common in the early Universe, today they are quite rare. This means the nearest examples are still hundreds of millions of light-years away, but these events foreshadow the potential outcome of a collision, or merger, between the Milky Way Galaxy and the Andromeda Galaxy several billion years from now. Only with the incredible resolving power of ALMA could we peer deep into the molecular reservoirs left behind 'after the fall.'"

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Scientists model landscape formation on Titan, revealing an Earth-like alien world

Saturn's moon Titan looks very much like Earth from space, with rivers, lakes, and seas filled by rain tumbling through a thick atmosphere. While these landscapes may look familiar, they are composed of materials that are undoubtedly different -- liquid methane streams streak Titan's icy surface and nitrogen winds build hydrocarbon sand dunes.

The presence of these materials -- whose mechanical properties are vastly different from those of silicate-based substances that make up other known sedimentary bodies in our solar system -- makes Titan's landscape formation enigmatic. By identifying a process that would allow for hydrocarbon-based substances to form sand grains or bedrock depending on how often winds blow and streams flow, Stanford University geologist Mathieu Lapôtre and his colleagues have shown how Titan's distinct dunes, plains, and labyrinth terrains could be formed.

Titan, which is a target for space exploration because of its potential habitability, is the only other body in our solar system known to have an Earth-like, seasonal liquid transport cycle today. The new model, published in Geophysical Research Letters April 25, shows how that seasonal cycle drives the movement of grains over the moon's surface.

"Our model adds a unifying framework that allows us to understand how all of these sedimentary environments work together," said Lapôtre, an assistant professor of geological sciences at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "If we understand how the different pieces of the puzzle fit together and their mechanics, then we can start using the landforms left behind by those sedimentary processes to say something about the climate or the geological history of Titan -- and how they could impact the prospect for life on Titan."

A missing mechanism

In order to build a model that could simulate the formation of Titan's distinct landscapes, Lapôtre and his colleagues first had to solve one of the biggest mysteries about sediment on the planetary body: How can its basic organic compounds -- which are thought to be much more fragile than inorganic silicate grains on Earth -- transform into grains that form distinct structures rather than just wearing down and blowing away as dust?

On Earth, silicate rocks and minerals on the surface erode into sediment grains over time, moving through winds and streams to be deposited in layers of sediments that eventually -- with the help of pressure, groundwater, and sometimes heat -- turn back into rocks. Those rocks then continue through the erosion process and the materials are recycled through Earth's layers over geologic time.

On Titan, researchers think similar processes formed the dunes, plains, and labyrinth terrains seen from space. But unlike on Earth, Mars, and Venus, where silicate-derived rocks are the dominant geological material from which sediments are derived, Titan's sediments are thought to be composed of solid organic compounds. Scientists haven't been able to demonstrate how these organic compounds may grow into sediment grains that can be transported across the moon's landscapes and over geologic time.

"As winds transport grains, the grains collide with each other and with the surface. These collisions tend to decrease grain size through time. What we were missing was the growth mechanism that could counterbalance that and enable sand grains to maintain a stable size through time," Lapôtre said.

An alien analog

The research team found an answer by looking at sediments on Earth called ooids, which are small, spherical grains most often found in shallow tropical seas, such as around the Bahamas. Ooids form when calcium carbonate is pulled from the water column and attaches in layers around a grain, such as quartz.

What makes ooids unique is their formation through chemical precipitation, which allows ooids to grow, while the simultaneous process of erosion slows the growth as the grains are smashed into each other by waves and storms. These two competing mechanisms balance each other out through time to form a constant grain size -- a process the researchers suggest could also be happening on Titan.

"We were able to resolve the paradox of why there could have been sand dunes on Titan for so long even though the materials are very weak, Lapôtre said. "We hypothesized that sintering -- which involves neighboring grains fusing together into one piece -- could counterbalance abrasion when winds transport the grains."

Global landscapes

Armed with a hypothesis for sediment formation, Lapôtre and the study co-authors used existing data about Titan's climate and the direction of wind-driven sediment transport to explain its distinct parallel bands of geological formations: dunes near the equator, plains at the mid-latitudes, and labyrinth terrains near the poles.

Atmospheric modeling and data from the Cassini mission reveal that winds are common near the equator, supporting the idea that less sintering and therefore fine sand grains could be created there -- a critical component of dunes. The study authors predict a lull in sediment transport at mid-latitudes on either side of the equator, where sintering could dominate and create coarser and coarser grains, eventually turning into bedrock that makes up Titan's plains.

Sand grains are also necessary for the formation of the moon's labyrinth terrains near the poles. Researchers think these distinct crags could be like karsts in limestone on Earth -- but on Titan, they would be collapsed features made of dissolved organic sandstones. River flow and rainstorms occur much more frequently near the poles, making sediments more likely to be transported by rivers than winds. A similar process of sintering and abrasion during river transport could provide a local supply of coarse sand grains -- the source for the sandstones thought to make up labyrinth terrains.

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Friendship ornaments from the Stone Age

Roughly 6,000 years ago, hunter-gatherer communities in northeast Europe produced skillfully manufactured slate ring ornaments in great numbers. While these ornaments are commonly referred to as 'slate rings', they were rarely used as intact rings. Instead, the ornaments were fragmented on purpose, using pieces of rings as tokens. These fragments were further processed into pendants.

The fragments have most likely served as symbols of the social relations of Stone Age hunter-gatherers.

Purposeful fragmentation of ornaments

As most archaeological material is found in a fragmented state, the phenomenon has been considered a natural consequence of objects' having been long buried underground. However, according to Postdoctoral Researcher Marja Ahola from the University of Helsinki, not all objects have necessarily been broken by accident. Instead, it is possible some were fragmented on purpose as part of maintaining social relations, bartering or ritual activities. The research now completed has demonstrated that a substantial number of ornaments have been found in extensive and central locations. As some of the ornaments originate in Lake Onega region and have been transported to Finland through a widespread exchange network, it is possible that they symbolise the connections established within the network.

By matching pieces of slate ring ornaments, analysing their geochemical composition and investigating traces of use and manufacture in the objects, a research group at the University of Helsinki and the University of Turku demonstrated that the ornaments had not only been worn, but also intentionally broken. Because fragments from the same ornament were found in two different locations, it is possible that they were worn by two different individuals. Another indication of this is the fact that one of the fragments had been worked on more finely than the other.

"These fragments of the same object may show the handprint and preferences of two individuals. Perhaps they wore the ornaments as a symbol of a connection established," Ahola muses.

A similar link was found in slate ring ornaments created during the same manufacturing process, one of which was found in a settlement-site context and the other in a burial site investigated near the settlement.

"What we see here may be one way of maintaining connection between the living and the dead. This is also the first clear material connection between a certain place of residence and a burial site. In other words, the people who lived there most likely buried their dead in a site close to them," Ahola explains.

An X-ray fluorescence analysis (XRF) of a little over 50 slate ring ornaments demonstrated that some of the ornaments or fragments thereof had been imported from Lake Onega region, Russia, hundreds of kilometres from the site where they were found. XRF analyses can be used to determine the element concentrations and raw materials of inorganic archaeological materials with a very high precision. The technique can be applied as an entirely non-invasive surface analysis, which makes it perfectly suited to the study of archaeological objects.

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'I know this song!' Evolutionary keys to musical perception

How do we perceive music and sounds? This question is the basis of the research by the Language and Comparative Cognition Group (LCC) of the UPF Center for Brain and Cognition (CBC) published recently in the journal Animal Cognition.

Humans share characteristics that for the time being appear to be unique in the animal kingdom: language and music. "Our group is dedicated to understanding how these skills have evolved in humans and to what extent some of their components are shared with other species," explains Juan Manuel Toro, director of the LCC and one of the authors of the study, together with Paola Crespo Bojorque and Alexandre Celma Miralles.

When we hear a song that we already know, we can identify it even if it is not an exact version of the original. If it sounds higher or lower, faster or slower, or if the instruments are different from the known version, humans can identify it even if there are these superficial changes to the melody. The study by the LLC explores the extent to which this skill is based on skills that are also present in other animals, i.e., not unique to humans.

Hence, they studied 40 laboratory rats (Rattus norvegicus, commonly known as Long-Evans rats), trained to identify a melody, in this case using the second half of the song "Happy Birthday." "It is a thirteen-tone melody that includes all the entire range of pitches of the Western major scales," they explain in the article.

The experiment began with a familiarization phase followed by three test sessions. Twenty familiarization sessions were held, each session lasting 10 minutes per day. At each session, the rats were placed individually in a response box and presented with 40 repetitions of the familiarization melody while being given a sucrose pill as food.

The results suggest that the ability to recognize patterns over changes in pitch and tempo present in humans might emerge from pre-existing abilities in other species

After the familiarization phase, three sessions were held in which modified versions of the song were used. Responses to the following physical changes in the melody were analysed:
 

• Fundamental frequency (pitch): the song was played one eighth above or below the original.
• Speed (tempo)
• Timbre. The original song was played on a piano and the variant on a violin.

"Our results show that the rats recognized the song even when there were changes in frequency and tempo," Toro explains, "but when we changed the timbre they were no longer able to recognize the song. The results suggest that the ability to recognize patterns over changes in pitch and tempo present in humans might emerge from pre-existing abilities in other species."

Some mammalian and bird species can perceive changes in fundamental frequency (rhesus monkeys -Macaca mulatta), tempo (California sea lion -Zalophus californianus- or cockatoo -Cacatua galerita eleonora) and timbre (chimpanzees -- Pa troglodytes). However, Toro explains that humans process music perceiving musical structures in a relative rather than an absolute way; that is, independently of surface changes along features such as pitch, tempo and timbre. It is thus important to understand the extent to which this ability is based on sensitivities already present in other species."

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Prehistoric people created art by firelight, new research reveals

Our early ancestors probably created intricate artwork by firelight, an examination of 50 engraved stones unearthed in France has revealed.

The stones were incised with artistic designs around 15,000 years ago and have patterns of heat damage which suggests they were carved close to the flickering light of a fire, the new study has found.

The study, by researchers at the Universities of York and Durham, looked at the collection of engraved stones, known as plaquettes, which are now held in the British Museum. They are likely to have been made using stone tools by Magdalenian people, an early hunter-gatherer culture dating from between 23,000 and 14,000 years ago.

The researchers identified patterns of pink heat damage around the edges of some of the stones, providing evidence that they had been placed in close proximity to a fire.

Following their discovery, the researchers have experimented with replicating the stones themselves and used 3D models and virtual reality software to recreate the plaquettes as prehistoric artists would have seen them: under fireside light conditions and with the fresh white lines engravers would have made as they first cut into the rock thousands of years ago.

Lead author of the study, Dr Andy Needham from the Department of Archaeology at the University of York and Co-Director of the York Experimental Archaeology Research Centre said: "It has previously been assumed that the heat damage visible on some plaquettes was likely to have been caused by accident, but experiments with replica plaquettes showed the damage was more consistent with being purposefully positioned close to a fire.

"In the modern day, we might think of art as being created on a blank canvas in daylight or with a fixed light source; but we now know that people 15,000 years ago were creating art around a fire at night, with flickering shapes and shadows."

Working under these conditions would have had a dramatic effect on the way prehistoric people experienced the creation of art, the researchers say. It may have activated an evolutionary capacity designed to protect us from predators called "Pareidolia," where perception imposes a meaningful interpretation such as the form of an animal, a face or a pattern where there is none.

Dr Needham added: "Creating art by firelight would have been a very visceral experience, activating different parts of the human brain. We know that flickering shadows and light enhance our evolutionary capacity to see forms and faces in inanimate objects and this might help explain why it's common to see plaquette designs that have used or integrated natural features in the rock to draw animals or artistic forms."

The Magdalenian era saw a flourishing of early art, from cave art and the decoration of tools and weapons to the engraving of stones and bones.

Co-author of the study, PhD student Izzy Wisher from the Department of Archaeology at the University of Durham, said: "During the Magdalenian period conditions were very cold and the landscape was more exposed. While people were well-adapted to the cold, wearing warm clothing made from animal hides and fur, fire was still really important for keeping warm. Our findings reinforce the theory that the warm glow of the fire would have made it the hub of the community for social gatherings, telling stories and making art.

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A roadmap for deepening understanding of a puzzling universal process

A puzzling process called magnetic reconnection triggers explosive phenomena throughout the universe, creating solar flares and space storms that can take down mobile phone service and electrical power grids. Now scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have detailed a roadmap for untangling a key aspect of this puzzle that could deepen insight into the workings of the cosmos.

Reconnection converts the magnetic field energy to particle eruptions in astrophysical plasmas by snapping apart and explosively reconnecting the magnetic field lines -- a process that occurs within what are called dissipation regions that are often enormously smaller than the regions they impact.

Stressed magnetic field

"Plasma doesn't like reconnection," said Hantao Ji, a PPPL physicist and Princeton University professor who is first author of a paper that details the roadmap in Nature Reviews Physics. "However, reconnection does happen when the magnetic field is sufficiently stressed," he said.

"Dissipation scales are tiny whereas astrophysical scales are very large and can extend for millions of miles. Finding a way to bridge these scales through a multiscale mechanism is a key to solving the reconnection puzzle."

The roadmap outlines the role of developing technologies with multiscale capabilities such as the Facility for Laboratory Reconnection Experiment (FLARE), a recently installed collaborative facility that is being upgraded and will probe facets of magnetic reconnection never before accessible to laboratory experiments. Complementing these experiments will be simulations on coming exascale supercomputers that will be 10 times faster than current computers. "The hope is for FLARE and exascale computing to go hand-in-hand," Ji said.

The working theory the PPPL roadmap proposes is that multiple plasmoids, or magnetic islands, that arise from reconnection along lengthy plasma current sheets could bridge the vast range of scales. Such plasmoids would correspond more closely to the affected reconnection region, with multiscale laboratory experiments planned to provide the first tests of this theory and to evaluate competing hypotheses.

"Exascale will allow us to do more credible simulations based on high-fidelity FLARE experiments," said PPPL physicist Jongsoo Yoo, a coauthor of the paper. The increased size and power of the new machine -- its diameter will be twice that of the sports-utility-vehicle-sized Magnetic Reconnection Experiment (MRX), PPPL's long-standing laboratory experiment -- and will enable scientists to replicate reconnection in nature more faithfully.

"FLARE can access wider astrophysical regimes than MRX with multiple reconnection points and measure the field geometry during reconnection," said William Daughton, a computational scientist at Los Alamos National Laboratory and a coauthor of the paper. "Understanding this physics is important for predicting how reconnection proceeds in solar flares," he said.

Key challenge

A key challenge to the coming experiments will be innovating new high-resolution diagnostic systems free from restrictive assumptions. Once developed these systems will enable FLARE to build upon satellite sightings such as those produced by the Magnetospheric Multiscale mission, a fleet of four spacecraft launched in 2015 to study reconnection in the magnetosphere, the magnetic field that surrounds the Earth.

"Progress in understanding multiscale physics critically depends on innovation and efficient implementation of such diagnostics systems in the coming decade," the paper said. The new findings will address open questions that include:

• How exactly does reconnection start?
• How are explosive plasma particles heated and accelerated?
• What role does reconnection play in related processes such as turbulence and space shocks?

Overall, "The paper lays out plans to provide the entire space physics and astrophysics communities with methods to solve the multiscale problem," Yoo said. Such a solution would mark a major step toward a more complete understanding of magnetic reconnection in large systems throughout the universe.

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Got food cravings? What's living in your gut may be responsible

Eggs or yogurt, veggies or potato chips? We make decisions about what to eat every day, but those choices may not be fully our own. New University of Pittsburgh research on mice shows for the first time that the microbes in animals' guts influence what they choose to eat, making substances that prompt cravings for different kinds of foods.

"We all have those urges -- like if you ever you just feel like you need to eat a salad or you really need to eat meat," said Kevin Kohl, an assistant professor in the Department of Biology in the Kenneth P. Dietrich School of Arts and Sciences. "Our work shows that animals with different compositions of gut microbes choose different kinds of diets."

Despite decades of speculation by scientists about whether microbes could influence our preferred diets, the idea has never been directly tested in animals bigger than a fruit fly. To explore the question, Kohl and his postdoc Brian Trevelline (A&S '08), now at Cornell University, gave 30 mice that lacked gut microbes a cocktail of microorganisms from three species of wild rodents with very different natural diets.

The duo found that mice in each group chose food rich in different nutrients, showing that their microbiome changed their preferred diet. The researchers published their work today in the Proceedings of the National Academy of Sciences.

While the idea of the microbiome affecting your behavior may sound far-fetched, it's no surprise for scientists. Your gut and your brain are in constant conversation, with certain kinds of molecules acting as go-betweens. These byproducts of digestion signal that you've eaten enough food or maybe that you need certain kinds of nutrients. But microbes in the gut can produce some of those same molecules, potentially hijacking that line of communication and changing the meaning of the message to benefit themselves.

One such messenger will be familiar to anyone who's had to take a nap after a turkey dinner: tryptophan.

"Tryptophan is an essential amino acid that's common in turkey but is also produced by gut microbes. When it makes its way to the brain, it's transformed into serotonin, which is a signal that's important for feeling satiated after a meal," Trevelline said. "Eventually that gets converted into melatonin, and then you feel sleepy."

In their study, Trevelline and Kohl also showed that mice with different microbiomes had different levels of tryptophan in their blood, even before they were given the option to choose different diets -- and those with more of the molecule in their blood also had more bacteria that can produce it in their gut.

It's a convincing smoking gun, but tryptophan is just one thread of a complicated web of chemical communication, according to Trevelline. "There are likely dozens of signals that are influencing feeding behavior on a day-to-day basis. Tryptophan produced by microbes could just be one aspect of that," he said. It does, however, establish a plausible way that microscopic organisms could alter what we want to eat -- it's one of just a few rigorous experiments to show such a link between the gut and the brain despite years of theorizing by scientists.

There's still more science to do before you should start distrusting your food cravings, though. Along with not having a way to test the idea in humans, the team didn't measure the importance of microbes in determining diet compared to anything else.

"It could be that what you've eaten the day before is more important than just the microbes you have," Kohl said. "Humans have way more going on that we ignore in our experiment. But it's an interesting idea to think about."

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