Star clusters are only the tip of the iceberg

 Star clusters have been part of the Imaginarium of human civilization for millennia. The brightest star clusters to Earth, like the Pleiades, are readily visible to the naked eye. A team around astronomer has now revealed the existence of massive stellar halos, termed coronae, surrounding local star clusters.

"Clusters form big families of stars that can stay together for large parts of their lifetime. Today, we know of roughly a few thousand star clusters in the Milky Way, but we only recognize them because of their prominent appearance as rich and tight groups of stars. Given enough time, stars tend to leave their cradle and find themselves surrounded by countless strangers, thereby becoming indistinguishable from their neighbours and hard to identify" says Stefan Meingast, lead author of the paper published in Astronomy & Astrophysics. "Our Sun is thought to have formed in a star cluster but has left its siblings behind a long time ago" he adds.

Thanks to the ESA Gaia spacecraft's precise measurements, astronomers at the University of Vienna have now discovered that what we call a star cluster is only the tip of the iceberg of a much larger and often distinctly elongated distribution of stars.

"Our measurements reveal the vast numbers of sibling stars surrounding the well-known cores of the star clusters for the first time. It appears that star clusters are enclosed in rich halos, or coronae, more than 10 times as large as the original cluster, reaching far beyond our previous guesses. The tight groups of stars we see in the night sky are just a part of a much larger entity" says Alena Rottensteiner, co-author and master student at the University of Vienna. "There is plenty of work ahead revising what we thought were basic properties of star clusters, and trying to understand the origin of the newfound coronae."

To find the lost star siblings, the research team developed a new method that uses machine learning to trace groups of stars which were born together and move jointly across the sky. The team analyzed 10 star clusters and identified thousands of siblings far away from the center of the compact clusters, yet clearly belonging to the same family. An explanation for the origin of these coronae remains uncertain, yet the team is confident that their findings will redefine star clusters and aid our understanding of their history and evolution across cosmic time.

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Glitter litter could be damaging rivers

 New research indicates that glitter could be causing ecological damage to our rivers and lakes.

The study, led by Dr Dannielle Green of Anglia Ruskin University (ARU) and published in the Journal of Hazardous Materials, is the first to examine the impact of glitter on freshwater habitats.

The research found that after 36 days, the presence of glitter halved the root length of common duckweed (Lemna minor), while levels of chlorophyll in the water were three times lower than in control conditions, indicating reduced levels of phytoplankton, or microalgae.

Glitter is used in a variety of decorative ways, including on clothing, in arts and crafts, and in cosmetics and body paint. Traditional glitter is a form of microplastic consisting of a plastic core made of polyester PET film, which is coated with aluminium and then covered with another thin plastic layer.

Along with other forms of single use microplastics, such as microbeads, there have been efforts to phase out PET glitter with the introduction of more biodegradable alternatives.

One version has a core of modified regenerated cellulose (MRC), sourced mainly from eucalyptus trees, but this is still coated with aluminium for reflectivity and then topped with a thin plastic layer. Another form is mica glitter, which is increasingly used in cosmetics.

However, this new study found that the effects of MRC and mica glitters on root length and chlorophyll levels were almost identical to those of traditional glitter.

The only significant difference was a two-fold increase in the abundance of New Zealand mud snails (Potamopyrgus antipodarum) in water containing the biodegradable MRC glitter. These snails, commonly found in polluted waters, are an invasive species in the UK and an increase in numbers has the potential to disrupt ecosystems, as they can outcompete native species.

Dr Dannielle Green, Senior Lecturer in Biology at Anglia Ruskin University (ARU), said: "Many of the microplastics found in our rivers and oceans have taken years to form, as larger pieces of plastic are broken down over time, However, glitter is a ready-made microplastic that is commonly found in our homes and, particularly through cosmetics, is washed off in our sinks and into the water system.

"Our study is the first to look at the effects of glitter in a freshwater environment and we found that both conventional and alternative glitters can have a serious ecological impact on aquatic ecosystems within a short period of time.

"All types, including so-called biodegradable glitter, have a negative effect on important primary producers which are the base of the food web, while glitter with a biodegradable cellulose core has an additional impact of encouraging the growth of an invasive species.

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Breakthrough blood test developed for brain tumors

 Genetic mutations that promote the growth of the most common type of adult brain tumors can be accurately detected and monitored in blood samples using an enhanced form of liquid biopsy developed by researchers at Massachusetts General Hospital (MGH).

Comparing blood samples from patients with gliomas with tumor biopsy tissues from the same patients, Leonora Balaj, PhD, Bob S. Carter, MD, and other MGH investigators in the Department of Neurosurgery found that a novel digital droplet polymerase chain reaction (ddPCR) blood test they pioneered could accurately detect and monitor over time two mutations of the gene TERT. The mutations, labeled C228T and C250T, are known to promote cancer growth and are present in more than 60 percent of all gliomas, and in 80 percent of all high-grade gliomas, the most aggressive and life-threatening type.

Their discovery, which has the potential to substantially improve the diagnosis and monitoring of gliomas, is reported in the journal Clinical Cancer Research.

Gliomas are tumors of glia, central and peripheral nervous system cells that support and protect neurons, the cells that transmit electrical impulses.

Liquid biopsy is a method for detecting cancer by looking for fragments of tumor DNA that circulate in blood. The technique has been shown to be sensitive at detecting the presence of some forms of cancer, but brain tumors have until now posed a formidable barrier.

"Liquid biopsy is particularly challenging in brain tumors because mutant DNA is shed into the bloodstream at much lower level than any other types of tumors," Balaj says.

"By 'supercharging' our ddPCR assay with novel technical improvements, we showed for the first time that the most prevalent mutation in malignant gliomas can be detected in blood, opening a new landscape for detection and monitoring of the tumors," she says.

The researchers first tested the performance of the ddPCR assay in tumor tissue and found that the results were in perfect agreement with the results from an independently performed clinical laboratory assessment of TERT mutations in the tumor specimens.

They then looked at samples of blood plasma matched to patient tumors and found that the ddPCR assay could detect TERT mutations both in samples from MGH as well as from similarly matched plasma and tumor samples from collaborators at other institutions.

The ddPCR assay has an overall sensitivity (ability to detect the presence of a glioma) of 62.5 percent, which is a tenfold improvement over any prior assay for TERT mutations in the blood for brain tumors, compared to the standard of tissue-based detection of TERT mutations.

The test is easy to use, quick, and low cost, and could be performed in most laboratories, Balaj says. Importantly, the test can also be used to follow the course of disease. "We envision the future integration of tests like this one into the clinical care of our patients with brain tumors," says Carter, chief of Neurosurgery and co-director of the MGH Brain Tumor Center. "For example, if a patient has a suspected mass on MRI scanning, we can take a blood sample before the surgery and assess the presence of the tumor signature in the blood, and then use this signature as a baseline to monitor as the patient later receives treatment, both to gauge response to the treatment and gain early insight into any potential recurrence."

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Will the COVID-19 virus become endemic?

 A new article by Columbia Mailman School researchers Jeffrey Shaman and Marta Galanti explores the potential for the COVID-19 virus to become endemic, a regular feature producing recurring outbreaks in humans. They identify crucial contributing factors, including the risk for reinfection, vaccine availability and efficacy, as well as potential seasonality and interactions with other viral infections that may modulate the transmission of the virus. The article appears in the journal Science.

Shaman is a professor of environmental health sciences and director of the Columbia Mailman School Climate and Health program and a leading authority in modeling infectious disease outbreaks like SARS-CoV-2 and influenza. He was among the first to recognize the importance of asymptomatic spread and the effectiveness of lockdown measures and published highly cited estimations of the hypothetic lives saved had lockdown occurred sooner. He and Galanti, a post-doctoral research scientist in Shaman's research group, also published research finding reinfections with endemic coronaviruses are not uncommon, even within a year of prior infection.

The new paper explores one potential scenario in which immunity to SARS-CoV-2, either through infection or a vaccine, diminishes within a year -- a rate similar to that seen for the endemic betacoronavirus that causes mild respiratory illness. The result would be yearly outbreaks of COVID-19. On the other hand, if immunity to SARS-CoV-2 was longer, perhaps through protection provided by immune response to infection with other endemic coronaviruses, we might experience what would initially appear to be an elimination of COVID-19 followed by a resurgence after a few years. Other contributing factors include the availability and effectiveness of a vaccine and the innate seasonality of the virus.

"Should reinfection prove commonplace, and barring a highly effective vaccine delivered to most of the world's population, SARS-CoV-2 will likely settle into a pattern of endemicity," the authors write. "Whether reinfections will be commonplace, how often they will occur, how contagious re-infected individuals will be, and whether the risk of severe clinical outcomes changes with subsequent infection remain to be understood."

Reinfection

Among those who have been infected with COVID-19, serological studies indicate that most infections, regardless of severity, induce development of some SARS-CoV-2-specific antibodies. Yet it remains unclear whether those antibodies are themselves sufficient to provide long-term "sterilizing immunity" to prevent reinfection. For many viruses, insufficient immune response, waning immunity, or mutations that allow it to "escape" immune detection can undermine or circumvent immunity and allow subsequent reinfection, although a prior infection may provide partial immunity and reduce symptom severity.

Co-Infection

Immune response to SARS-CoV-2 may be affected by whether or not someone is currently or was recently infected with another virus. Many studies prior to the pandemic show that infection with one virus can provide short-term protection -- about a week -- against a second infection. Other studies confirm that simultaneous respiratory virus infections are not associated with increased disease severity. While some SARS-CoV-2 coinfections have been documented, including co-infections with influenza and respiratory syncytial virus, there is insufficient data to draw conclusions. At the population level, a significant seasonal influenza outbreak could strain hospitals already dealing with COVID-19.

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Scientists shed new light on viruses' role in coral bleaching

 Scientists at Oregon State University have shown that viral infection is involved in coral bleaching -- the breakdown of the symbiotic relationship between corals and the algae they rely on for energy.

Funded by the National Science Foundation, the research is important because understanding the factors behind coral health is crucial to efforts to save the Earth's embattled reefs -- between 2014 and 2017 alone, more than 75% experienced bleaching-level heat stress, and 30% suffered mortality-level stress.

The planet's largest and most significant structures of biological origin, coral reefs are found in less than 1% of the ocean but are home to nearly one-quarter of all known marine species. Reefs also help regulate the sea's carbon dioxide levels and are a vital hunting ground that scientists use in the search for new medicines.

Since their first appearance 425 million years ago, corals have branched into more than 1,500 species. A complex composition of dinoflagellates -- including the algae symbiont -- fungi, bacteria, archaea and viruses make up the coral microbiome, and shifts in microbiome composition are connected to changes in coral health.

The algae the corals need can be stressed by warming oceans to the point of dysbiosis -- a collapse of the host-symbiont partnership.

To better understand how viruses contribute to making corals healthy or unhealthy, Oregon State Ph.D. candidate Adriana Messyasz and microbiology researcher Rebecca Vega Thurber of the OSU College of Science led a project that compared the viral metagenomes of coral colony pairs during a minor 2016 bleaching event in Mo'orea, French Polynesia.

Also known as environmental genomics, metagenomics refers to studying genetic material recovered directly from environmental samples, in this case samples taken from a coral reef.

For this study, scientists collected bleached and non-bleached pairs of corals to determine if the mixes of viruses on them were similar or different. The bleached and non-bleached corals shared nearly identical environmental conditions.

"After analyzing the viral metagenomes of each pair, we found that bleached corals had a higher abundance of eukaryotic viral sequences, and non-bleached corals had a higher abundance of bacteriophage sequences," Messyasz said. "This gave us the first quantitative evidence of a shift in viral assemblages between coral bleaching states."

Bacteriophage viruses infect and replicate within bacteria. Eukaryotic viruses infect non-bacterial organisms like animals.

In addition to having a greater presence of eukaryotic viruses in general, bleached corals displayed an abundance of what are called giant viruses. Known scientifically as nucleocytoplasmic large DNA viruses, or NCLDV, they are complex, double-stranded DNA viruses that can be parasitic to organisms ranging from the single-celled to large animals, including humans.

"Giant viruses have been implicated in coral bleaching," Messyasz said. "We were able to generate the first draft genome of a giant virus that might be a factor in bleaching."

The researchers used an electron microscope to identify multiple viral particle types, all reminiscent of medium- to large-sized NCLDV, she said.

"Based on what we saw under the microscope and our taxonomic annotations of viral metagenome sequences, we think the draft genome represents a novel, phylogenetically distinct member of the NCLDVs," Messyasz said. "Its closest sequenced relative is a marine flagellate-associated virus."

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The mountains of Pluto are snowcapped, but not for the same reasons as on Earth

 In 2015, the New Horizons space probe discovered spectacular snowcapped mountains on Pluto, which are strikingly similar to mountains on Earth. Such a landscape had never before been observed elsewhere in the Solar System. However, as atmospheric temperatures on our planet decrease at altitude, on Pluto they heat up at altitude as a result of solar radiation.

So where does this ice come from? An international team led by CNRS scientists conducted this exploration. They first determined that the "snow" on Pluto's mountains actually consists of frozen methane, with traces of this gas being present in Pluto's atmosphere, just like water vapour on Earth.

Then, to understand how the same landscape could be produced in such different conditions, they used a climate model for the dwarf planet, which revealed that due to its particular dynamics, Pluto's atmosphere is rich in gaseous methane at altitudes. As a result, it is only at the peaks of mountains high enough to reach this enriched zone that the air contains enough methane for it to condense.

At lower altitudes the air is too low in methane for ice to form.

This research, published in Nature Communications, could also explain why the thick glaciers consisting of methane observed elsewhere on Pluto bristle with spectacular craggy ridges, unlike Earth's flat glaciers, which consist of water.

From Science Daily

Even minimal physical activity measurably boosts health

 More than 5 million people around the world die from causes associated with a lack of physical activity. Two research teams at UC San Diego School of Medicine sought to understand sedentary lifestyles, with one study finding that even light physical activity, including just standing, can benefit health, and the other that Americans are still sitting too much.

Stand up, your life may depend on it

It is well-documented that exercise and other moderate-to-vigorous physical activity (MVPA) reduces the risk of many age-related chronic diseases, such as heart disease, type 2 diabetes, numerous cancers, Alzheimer's disease and dementia. However, in the study published October 12, 2020 in Journals of Gerontology: Medical Sciences, researchers found that just standing still was associated with lower risk for mortality.

Led by Andrea LaCroix, PhD, chief of epidemiology at UC San Diego School of Medicine, the research team observed activity levels of nearly 6,000 American women, ages 63 to 97, in partnership with the Women's Health Initiative. Participants wore a research-grade accelerometer for seven days to get accurate measures of how much time they spent sitting, standing still or moving.

Participants who spent the most time standing had a 37 percent lower risk of death when compared to the group who didn't stand up as often. While the highest group was standing still almost 90 minutes per day, a lower risk of death was observed by standing still for as little as 30 minutes per day. The positive effects of standing were even stronger when participants were standing and moving around at the same time.

"Avoiding prolonged sedentary time and engaging in regular physical activity are key strategies for older Americans to improve their prospects for healthy aging," said first author Purva Jain, a doctoral candidate and research fellow. "Specifically low-intensity physical activities, such as standing, are important to study due to their feasibility and safety. During our research, we found that simply spending more time on your feet could have important health benefits, such as a decreased risk of mortality."

Adults in the United States aged 65 and older struggle to meet physical activity guidelines, which generally call for 150 minutes of activity per week. According to the researchers, many Americans spend up to 11 hours a day sitting. Women are specifically at an increased risk of having or developing health concerns associated with inactivity.

"Standing is a feasible approach to interrupt long periods of time sitting that takes place throughout the day," said John Bellettiere, PhD, professor of epidemiology at UC San Diego School of Medicine. "We find this most beneficial for older adults who may not be able to partake in moderate-to-vigorous activities any more, but can still follow a healthy aging lifestyle safely just by replacing sitting with standing up more."

"This is the first study of its kind where we were able to decipher between the benefits of standing still versus standing and moving around," said senior author Andrea LaCroix, PhD, "In doing so, we were able to provide rigorous evidence that even standing still results in positive health benefits."

Modern technology and a sedentary life

In another study, published October 12, 2020 in BMJ Open Sport & Exercise Medicine, researchers with UC San Diego School of Medicine used physical activity data collected as part of a survey of farmers in rural Malawi, whose lives are minimally affected by technology, and compared it to lifestyles of Americans.

With this comparison, the team sought to investigate the potential impact of technology-dominated lifestyles on sedentary time and physical activity.

Their findings showed substantially higher levels of activity amongst the Malawi population versus participants in the United States. Specifically, Americans spend nearly two more hours of sedentary time each day compared to Malawians.

"Being able to compare our current activity levels in the United States to the lifestyle of famers in Malawi really puts an exclamation point on how inactive we are," said first author Michael Pratt, MD, director of the Institute for Public Health at UC San Diego. "We evolved to be active beings and we have left that behind for the luxury of certain modern advancements."

The study was conducted in Malawi, a country in Southeast Africa, where farmers in the Zomba and Ntcheu districts were recruited. Nearly all of the sampled farmers lacked electricity at home and did not own motorized vehicles. Conversely, computers, cell phones, TVs and cars dominate the daily lives of many Americans, resulting in increased sedentary time and less need for physical activity.

To quantify the difference in activity levels in these two samples with contrasting lifestyles, researchers asked 414 farmers in Malawi, ages 15 to 85, to wear an accelerometer every day for seven days. The data were then compared to a sample of 3,258 Americans in the same age range measured in previous studies for the same amount of time. Levels of MVPA and light activity in adults in Malawi were substantially higher and sedentary time were lower than those observed in the United States' sample. Researchers used near-identical data collection, scoring and analyses to make their conclusions.

The Malawian farmers met current physical activity guidelines 94 percent of the time, compared to only 55 percent of the United States sample. However, the results may have a different meaning in Malawi where hard work in predominantly subsistence and non-mechanized agriculture on family farms is essential for household food security.

Read more at Science Daily

Plastic bags could be 'eco-friendlier' than paper and cotton

 Scientists from Nanyang Technological University, Singapore (NTU Singapore) have modelled the cradle-to-grave environmental impact of using different types of shopping bags and report that in cities like Singapore, single-use plastic bags (made from high-density polyethylene plastic) have a lower environmental footprint than single-use paper and multi-use cotton bags.

Reusable plastic bags made from polypropylene non-woven plastic were the most eco-friendly option, followed by single-use plastic bags.

The model revealed that cotton and kraft paper bags have relatively bigger environmental footprints due to their greater contribution to global warming and eco-toxicity potential in their production.

However, the NTU team stressed that their model applied specifically to Singapore and might be applicable in cities such as Tokyo, Hong Kong, and Dubai. Reusable and single-use plastic bags would be a comparatively better environmental option only in these cities, due to the model's focus on densely populated metropolitan areas that have waste management structures with similar end-of-life incineration facilities.

The findings were published in the scientific Journal of Cleaner Production in August 2020.

Assistant Professor Grzegorz Lisak, Director of Residues & Resource Reclamation Centre at the Nanyang Environment and Water Institute (NEWRI), who led the research, said: "Our main message is that re-usable plastic bags are the best option, provided that they are re-used many times -- over 50 times to be precise. However, one surprising conclusion is that, in our model, in a single-use case, plastic bags, if treated properly afterwards, are less environmentally detrimental than the other types of bags in this study."

"It is essential to evaluate the implications case by case for dealing with plastic waste. In a well-structured closed metropolitan waste management system with incineration treatment, using plastic bags may be the best option that is currently available, provided that there is no significant leakage of waste into the environment."

To reach their conclusions, the team carried out a life cycle analysis of five types of bags to evaluate the environmental impacts associated with their production, distribution, transportation, waste collection, treatment, and end-of-life disposal.

The research team found that the global warming potential of a single-use kraft paper bag was the highest, over 80 times that of reusable plastic bags. Single-use plastic and reusable cotton bags (reused 50 times) were calculated to have over ten times the global warming potential of reusable plastic bags (reused 50 times).

To offset the emission equivalent to equal that of the creation of one single-use plastic bag, a reusable plastic bag would need to be reused four times.

The team also observed that the relative negative environmental impacts of cotton and kraft paper bags in the model are due to their production processes that consume immense amounts of water and natural resources. Hence, improving the production methods, optimizing resource usage, and following sustainable practices could in future favour the usage of bags made from cotton and paper.

Relevance to cities and their waste reduction goals

In the case of Singapore, the team recommends the usage of reusable plastic bags to the greatest extent possible to reduce consumption of single-use plastic bags. Reprocessing single-use plastic bags would be a good policy goal to cut down on their environmental impact.

Asst Prof Lisak said that based on 2018 statistics in Singapore, reducing the single-use plastic grocery bag consumption by half could prevent over 10 million kg-CO2 equivalent emissions in a year.

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Seeing evolution happening before your eyes

 Animal diversity and evolution are driven by changes in how our genetic code is expressed. Specific DNA sequences called enhancers control where, when and how strongly genes are expressed during development to create the respective organism. Studying enhancers and how they result in different patterns of gene expression therefore helps us to understand more about how evolution takes place. In addition to driving the evolution of species, enhancers are also relevant to disease: mutations in enhancers are associated with over 80% of all human diseases.

"What we see in terms of biodiversity in nature is caused, to a large degree, by changes in enhancers," explains Justin Crocker, group leader at EMBL Heidelberg. "Understanding -- and subsequently trying to predict -- evolution in the time of climate change, where many animals are under the pressure to adapt quickly to fast changing environments, is an important task."

Despite broad relevance to evolution and disease, researchers still struggle to understand how enhancers are coded in our genomes and how easy it is to reprogram them, for example to prevent or treat diseases. In an attempt to learn more about enhancers, the Crocker group from EMBL Heidelberg performed an extensive study, published in Nature, on a specific enhancer in the model organism Drosophila melanogaster, a species of fruit fly. The group discovered that this enhancer -- which controls the patterns where hair grows on flies -- contains a lot more information than expected.

"Whenever we changed a single letter of the enhancer DNA sequence, we created a significant change to the pattern of gene expression it drove," explains Timothy Fuqua, PhD student at EMBL and first author of the paper. "We also found that almost all mutations to the enhancer alter the gene expression pattern in multiple ways. For example, one mutation controls not only where the expression pattern is within the fly, but also when, and how much of the gene was expressed."

These results were surprising and contradict what had previously been known about enhancers. Researchers thought that these complex gene expression patterns were created by different proteins attaching to the enhancer. A first clue that this might not be true came when Crocker and his team discovered that artificially-produced enhancers did not work as designed. Their most recent results provide support for this idea. "The results showed that developmental enhancers encode a much higher level of information than previously appreciated," Crocker says. "When we received the data, I was honestly shocked! I couldn't believe it and we repeated everything, as we assumed that there has been a mistake."

Importantly, the density of information encoded within the enhancer also constrains how animals can evolve. The study also showed that each possible mutation has a certain possibility for happening. This gives scientists insights into where evolution could lead. "We can use this information to predict patterns in wild fruit flies. Something which has been incredibly difficult to do so far," Fuqua says. "Our results should encourage the community to reassess our assumption about how these regions contribute to human health."

While studying enhancers is a well-established field in molecular biology, this study is unique in the sheer number of mutations having been studied. The group created more than 700 unique, randomly generated mutations within a single enhancer. "Nobody ever has studied so many enhancer variants at this level of depth before. It was as if evolution was happening before our very eyes!" highlights Fuqua. To perform so many experiments, the team built -- assisted by the Janelia Research Campus and the Advanced Light Microscopy Facility at EMBL -- a robot to handle the fly embryos used in the study, and an automated microscope pipeline to take images of each mutated line.

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Rainforest model offers glimpse into future of the Amazon

 Tropical forests may be more resilient to predicted temperature increases under global climate change than previously thought, a study published in the journal Nature Plants suggests. The results could help make climate prediction models more accurate, according to the authors -- an international team led by scientists in the University of Arizona Department of Ecology and Evolutionary Biology.

The group studied data from the rainforest habitat at UArizona's Biosphere 2 and compared them to measurements taken at natural tropical forest sites. Due to being encased under a glass dome, the tropical forest at Biosphere 2 is possibly the hottest tropical forest in the world, with temperatures reaching up to 40 degrees Celsius, about 6 C higher than maximum temperatures currently experienced by natural tropical forests and in the range of what scientists expect them to experience in the year 2100, absent major climate change mitigation.

At Biosphere 2, when the effects of warming and drying were separated, the authors observed that, just as in natural forests, photosynthesis declined as the air dried, but when the air was wet, the trees continued to photosynthesize steadily at ever higher temperatures, right up to a forest-roasting 38 C.

"No previous studies of tropical forests looked at changes in temperature much beyond to what they experience today," said Scott Saleska, a professor in the UArizona Department of Ecology and Evolutionary Biology and senior author of the paper. "Biosphere 2 gave us a unique opportunity to look at what might happen when these forests get the full global warming treatment."

The paper's lead author, Marielle Smith -- a postdoctoral research associate at Michigan State University who pursued the research while she was a doctoral student in Saleska's lab at UArizona -- noted that "previous studies suggest that tropical forests are already approaching the limit of what they can tolerate in terms of temperature, provoking concern about the impacts of future warming."

"But when we looked at the rainforest in Biosphere 2, we saw that, under some conditions, the trees there were functioning well beyond temperatures currently deemed to be the limit, and even higher than those predicted for the Amazon basin by 2100," she said.

Smith and her co-authors wanted to know why. Biologists have long known that plants' ability to actively conduct photosynthesis, or turn carbon dioxide and water into biomolecules using sunlight, declines above a certain temperature threshold. However, the reason for this limit is not always clear.

That is because as temperature increases, the relative humidity goes down, and photosynthesis can decline due to the temperature increase, the decline in water content or both. Similar to an assembly line in a factory, where productivity could be affected by a shortage of supplies entering the production process or by an excessively hot working environment directly impacting the physical performance of workers, the productivity of forests could be limited by a shortage of raw materials -- in this case, atmospheric water vapor, or humidity -- or by high temperatures wreaking havoc with the biochemical machinery itself.

Understanding the reason for photosynthetic decline at higher temperatures is important because while the latter mechanism -- direct susceptibility to temperature -- would imply that tropical forests are highly vulnerable to future warming trends, the former would indicate some degree of resilience, especially under future elevated levels of carbon dioxide.

The problem is that in the natural world, higher temperatures and lower water content almost always go hand-in-hand, so their effects cannot easily be separated. In Biosphere 2, however, the climate can be adjusted in ways not possible in the natural world.

"The enclosed environment at Biosphere 2 allowed us to maintain high humidity despite high temperatures by adding water vapor via misters and trapping humidity inside the glass enclosure, which is something that would not happen in a natural tropical forest," Smith explained.

This finding can be understood in terms of basic plant behavior: When there is less moisture in the air, plants react by limiting the opening of their stomata -- microscopically small openings in their leaves -- to take in carbon dioxide, one of the raw materials for synthesis. The longer the stomata remain open, the more carbon dioxide can enter the leaf, but that comes at a price: The drier the air surrounding the plant, the more water escapes through the openings, forcing the plant to strike a balance between carbon uptake and water loss.

The reduction in photosynthetic productivity that previous studies had observed in the face of warmer temperatures, therefore, is likely due to plants limiting the time they keep their stomata open when confronted with drier air, in an effort to preserve water. This, in turn, limits how much carbon dioxide can enter the leaf, which may be behind the drop in photosynthetic productivity rather than the alternative scenario, in which heat damages the photosynthetic apparatus directly.

To assess the sensitivity of tropical forests to future warming, the authors compared the response of photosynthesis to high temperatures in the Biosphere 2 tropical forest to that of natural tropical forest sites in Mexico and in the Brazilian Amazon. So-called eddy flux towers reaching up to nearly 200 feet high, taller than the forest canopy, allow researchers to measure the exchange of carbon dioxide between the forests and the atmosphere.

"Flux towers allow us to measure the exchange of carbon dioxide between the forests and the atmosphere that we used to calculate total forest photosynthesis," Smith said. "When we looked very closely at the flux tower data, we could tell that it was the same mechanism that was causing declines in real-world photosynthesis during warm periods as in Biosphere 2; it was the decline in water vapor, not the increase in temperature."

"We interpret these findings such that in the presence of high humidity, the stomata in the leaves can remain open longer without losing as much water," said Tyeen Taylor, a co-author of the paper and postdoctoral research associate at the University of Michigan.

The authors discuss how heightened carbon dioxide in the atmosphere has the potential to have the same effect, because when more carbon dioxide is available, plants can keep their stomata opening times shorter, too, thereby limiting their water loss.

The authors point out that while their findings suggest that tropical forests may be more resilient to future warming than previously thought, that does not mean that tropical forests are not vulnerable to future climate change, as photosynthesis is not the only aspect of forest health.

"For example, reproduction could be affected independently, growth could be affected independently, herbivore and pathogen susceptibility could increase," Smith said. "There are many other reasons not to say, 'tropical forests are out of the woods.'"

The authors pointed out that Amazon forests are facing great threats from fires, deforestation and habitat destruction, and while the study may point to some resilience to coping with a warming world, "that hardly means these forests are safe, any more than slowing down as you run a red light is safe," Saleska said.

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Astronomers solve dark matter puzzle of strange galaxy

 At present, the formation of galaxies is difficult to understand without the presence of a ubiquitous, but mysterious component, termed dark matter. Astronomers have measure how much dark matter there is around galaxies, and have found that it varies between 10 and 300 times the quantity of visible matter. However, a few years ago, the discovery of a very diffuse object, named Dragonfly 44, changed this view. It was found that this galaxy has 10,000 times more dark matter than the stars. Taken back by this finding, astronomers have made efforts to see whether this object is really anomalous, or whether something went wrong in the analysis of the observations. Now we have the answer.

An international team led by the Kapteyn Institute of the University of Groningen (the Netherlands), with participation by the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), has found that the total number of globular clusters around Dragonfly 44 and, therefore, the dark matter content, is much less than earlier findings had suggested, which shows that this galaxy is neither unique nor anomalous. The result was recently published in Monthly Notices of the Royal Astronomical Society (MNRAS).

The galaxy Dragonfly 44 was discovered in a deep survey of the Coma cluster, a cluster with several thousand galaxies. From the start, the galaxy was considered remarkable by the researchers because the quantity of dark matter they inferred was almost as much as that in the Milky Way, the equivalent of a billion solar masses.

However, instead of containing around a hundred thousand million stars, as has the Milky Way, DF44 has only a hundred million stars, a thousand times fewer. This means that the amount of dark matter was ten thousand times greater than that of its stars. If this had been true, it would have been a unique object, with almost 100 times as much dark matter as that expected from the number of its stars.

Nevertheless, by an exhaustive analysis of the system of globular cluster around Dragonfly 44, the researchers have detected that the total number of globular clusters is only 20, and that the total quantity of dark matter is around 300 times that of the luminous matter, which means that it is not way outside the normal value for this type of galaxies.

"The fact that in our work we found only 20 globular clusters, compared with the 80 previously claimed, reduces drastically the amount of dark matter which the galaxy is believed to contain," explains Ignacio Trujillo, an IAC researcher and a co-author of the article. "Moreover, with the number of globular clusters we found, the amount of dark matter in Dragonfly 44 is in agreement with what is expected for this type of galaxies. The ratio of visible to dark matter is no longer 1 in 10,000 but one in 300," adds Trujillo.

"Dragonfly 44 has been an anomaly all these years that could not be explained with the existing galaxy formation models. Now we know that the previous results were wrong and that DF44 is not extraordinary. It is time to move on," points out Teymoor Saifollahi, researcher at the Kapteyn Institute and the first author of the article.

"Our work shows that this galaxy is not so singular nor unexpected. That way the models of galaxy formation can explain it without the need for modification," says Michael A. Beasley, another IAC researcher, specialist in globular clusters, and a co-author of the article.

The total number of globular clusters is related to the total mass of a galaxy. So, if the number of globular clusters is measured, the quantity of dark matter can be found, especially if the quantity of visible matter is only a small fraction of the total.

Read more at Science Daily

Carnivores living near people feast on human food, threatening ecosystems

 Ecologists at the University of Wisconsin-Madison have found that carnivores living near people can get more than half of their diets from human food sources, a major lifestyle disruption that could put North America's carnivore-dominated ecosystems at risk. The researchers studied the diets of seven predator species across the Great Lakes region of the U.S. They gathered bone and fur samples for chemical analysis from areas as remote as national parks to major metropolitan regions like Albany, New York. They found that the closer carnivores lived to cities and farms, the more human food they ate.

While evolution has shaped these species to compete for different resources, their newfound reliance on a common food source could put them in conflict with one another. That conflict could be reordering the relationship between different carnivores and between predators and prey, with an unknown but likely detrimental impact on ecosystems that evolved under significant influence of strong predators.

Jon Pauli, a UW-Madison professor of forest and wildlife ecology, and his former graduate student Phil Manlick, published their findings this week in the Proceedings of the National Academy of Sciences. The study is the most comprehensive look yet at how most of the region's major carnivores -- like gray wolves, coyotes, and bobcats -- have changed their diets in response to people.

How much human food they ate varied considerably by location. On average, more than 25 percent of the carnivores' diets came from human sources in the most human-altered habitats.

It also varied by species. For instance, committed carnivores like bobcats ate a relatively small amount of human food. "But what you see is that the sort of generalist species that you might expect -- coyotes, foxes, fishers, martens -- in human-dominated landscapes, they're getting upwards of 50 percent of their diet from human foods," says Manlick, the lead author of the study who is now a postdoctoral researcher at the University of New Mexico. "That's a relatively shocking number, I think."

Pauli and Manlick found that relying on human food sources increased how much carnivores overlapped one another in their competition for food. Compared to when these predators vie for distinct prey, this increased competition could lead to more conflicts between animals. Their reliance on human food could also make the carnivores vulnerable to human attacks near towns, or even change how and when they hunt traditional prey, with potentially harmful ecological consequences.

The researchers studied the diets of almost 700 carnivores, including red and gray foxes, fishers, and American martens. They gathered bone and fur samples from Minnesota, Wisconsin, New York and the Upper Peninsula of Michigan with the help of state and federal researchers and citizen-science trappers. The researchers compared the carnivores' diets to the extent of human development in the region, which varied from essentially pristine wilderness to urban sprawl.

Thanks to quirks in how plants incorporate carbon as they grow, a sample of bone or fur is enough to get a snapshot of an animal's diet. Different weights, or isotopes, of carbon are common in different plants -- and in the animals who ultimately eat them.

"Isotopes are relatively intuitive: You are what you eat," says Manlick. "If you look at humans, we look like corn."

Human foods, heavy in corn and sugar, lend them distinctive carbon signatures. In contrast, the diets of prey species in the wild confer their own carbon signatures. The ratio of these two isotope fingerprints in a predator's bone can tell scientists what proportion of their diet came from human sources, either directly or from their prey that ate human food first.

The geographic extent of the study and the large number of species the ecologists examined demonstrate that the trend of human food subsidies in carnivore diets is not limited to a single location or species. The ultimate outcome of such widespread disruptions remains unclear.

"When you change the landscape so dramatically in terms of one of the most important attributes of a species -- their food -- that has unknown consequences for the overall community structure," says Pauli. "And so I think the onus is now on us as ecologists and conservation biologists to begin to understand these novel ecosystems and begin to predict who are the winners and who are the losers."

Read more at Science Daily

Act now on wildfires, global climate change, human health, study says

 Immediate actions are needed to limit the greenhouse gas emissions that are driving climate change that helps fuel wildfires, a Monash University study says.

A special report published in the New England Journal of Medicine, led by Professor Yuming Guo and Dr Shanshan Li from the Monash School of Public Health and Preventive Medicine, summarises the enormous impacts of climate change on wildfire seasons and the sequential increased morbidity, mortality, and mental health impacts.

The report, which analysed numerous studies on wildfires over the past 20 years, says global climate change is fueling the three essential conditions for wildfires -- fuel, oxygen and an ignition source. The world is seeing inconsistent rainfall, increased drought and hotter temperatures, leading to more flammable vegetation.

It says the global mean carbon dioxide (CO2) emissions from wildfires accounted for about 22 per cent of the carbon emission from burning fossil fuels between 1997-2016. The inconsistent approach to global forest management and the conversion of tropical savannas to agricultural lands is damaging the world's ability to absorb CO2 and cool the climate.

The report says projections suggest that if high greenhouse gas emissions continue, wildfire exposure could substantially increase to over 74 per cent of the global land mass by the end of the century.

However, if immediate climate mitigation efforts are taken to limit the global mean temperature increase to 2.0?C or 1.5?C, a corresponding 60 per cent and 80 per cent, respective increase in wildfire exposure could be avoided, the report says.

Reaching the 1.5°C target would require reducing global net CO2 emissions by about 45 per cent from 2010 levels by 2030 and reaching net zero around 2050. The 1.5°C target remains achievable if CO2 emissions decline by 7.6 per cent per year from 2020 to 2030.

The report says the devastating health impacts are illustrated by several large and -- in some cases -- unprecedented recent wildfires. These include the 2019-2020 Australian wildfires, the 2019 and 2020 Amazon fires in Brazil, the 2018 and 2020 wildfires in the western US, the 2017-2018 wildfires in British Columbia, Canada, and the ongoing record-breaking wildfires on the US West Coast.

Along with the increased eye irritation, corneal abrasions and respiratory impacts of the smoke, the psychological effects are equally as serious with post-traumatic stress disorder (PTSD), depression, and insomnia common. The psychological consequences of wildfire events can persist for years, with children and adolescents particularly vulnerable.

A 20-year study on adults exposed to an Australian bushfire disaster as children in 1983 found an increase in psychiatric morbidity in adulthood, with wildfire events associated with subsequent reductions in children's academic performance.

Read more at Science Daily

A tiny jaw from Greenland sheds light on the origin of complex teeth

 A team of scientists led from Uppsala University have described the earliest known example of dentary bone with two rows of cusps on molars and double-rooted teeth. The new findings offer insight into mammal tooth evolution, particularly the development of double-rooted teeth. The results are published in the scientific journal PNAS.

The first mammals originated in the latest Triassic period, around 205 million years ago. An ancestor to mammals were the therapsids, "mammal-like reptiles" referred to as stem mammals or proto-mammals, which originated about 320-300 million years ago. One unique characteristic of the lineage that included mammals and animals related to mammals (synapsids) was that they developed complex occlusion. Close ancestors to mammals, called mammaliaforms, developed rows of cusps on molar-like teeth adapted for more omnivorous feeding. The origin of this multicusped pattern and double-rooted tooth has thus far remained unclear.

A team of scientists led by Grzegorz Niedzwiedzki from Uppsala University have investigated the jaw anatomy and tooth structure of a recently described new mammaliaform species named Kalaallitkigun jenkinsi. It was discovered on the eastern coast of Greenland and was a very small, shrew-like animal, probably covered with fur. It would have been the size of a large mouse and lived during the Late Triassic, around 215 million years ago.

"I knew it was important from the moment I took this 20 mm specimen off the ground," says Niedzwiedzki, researcher at Uppsala University and the corresponding author of the publication.

Kalaallitkigun jenkinsi exhibits the earliest known dentary with two rows of cusps on molars and double-rooted teeth. The anatomical features place Kalaallitkigun jenkinsi as an intermediate between the mammals and the insectivorous morganucodontans, another type of mammaliaform.

The researchers believe that the structural changes in the teeth are related to changed feeding habits. In this case study, the animals were switching to a more omnivorous/herbivorous diet and the tooth crown was expanding laterally. Broader teeth with "basins" on the top surface are better for grinding food. This development also forced changes in the structure of the base of the tooth.

The biomechanical analysis that was carried out within the study found that multi-rooted teeth are better able to withstand mechanical stresses, including those of upper and lower tooth contact during biting, compared to single-rooted teeth. Human teeth, for instance, have this characteristic. The results suggest that the development of molar-like teeth with complex crowns may have developed together with biomechanically optimised dual roots.

"The early evolution of mammals is a particularly interesting topic in evolutionary studies. This tiny jaw from Greenland shows us how complex mammalian teeth arose and why they appeared," says Niedzwiedzki.

"Our discovery of the oldest mammalian ancestor with double-rooted molars shows how important the role of teeth was in the origin of mammals. I had this idea to look at the biomechanics and the collaboration with the engineers turned out great," says Tomasz Sulej, researcher at the Polish Academy of Sciences, first author of the publication.

Read more at Science Daily

Central Asian horse riders played ball games 3,000 years ago

 Researchers have investigated ancient leather balls discovered in the graves of horse riders in northwest China. According to the international research team, they are around 3,000 years old, making them the oldest balls in Eurasia. The find suggests amongst others that the mounted warriors of Central Asia played ball games to keep themselves fit.

Today, ball games are one of the most popular leisure activities in the world, an important form of mass entertainment and big business. But who invented balls, where and when? The oldest balls that are currently known about were made in Egypt about 4,500 years ago using linen. Central Americans have been playing ball games for at least 3,700 years, as evidenced through monumental ball courts made of stone and depictions of ball players. Their oldest balls were made of rubber. Until now, it was believed that ball games in Europe and Asia followed much later: In Greece about 2,500 years ago and in China about 300 years after that.

Eurasia's oldest known balls

Researchers from the University of Zurich, together with German and Chinese researchers, have now examined in more detail three leather balls found in graves in the old Yanghai cemetery near the city of Turfan in northwest China. The balls, measuring between 7.4 and 9.2cm in diameter, have been dated at around 2,900 to 3,200 years old. "This makes these balls about five centuries older than the previously known ancient balls and depictions of ball games in Eurasia," says first author Patrick Wertmann of the Institute of Asian and Oriental Studies of the University of Zurich. "Unfortunately, however, the associated archaeological information is not sufficient to answer the question of exactly how these balls were played."

The earliest illustrations from Greece show ball players running, and depictions from China show riders using sticks. Comparable curved sticks were also found in Yanghai, but there was no apparent direct connection with the balls. Moreover, they are dated to a more recent period. "Therefore, the leather balls from Yanghai are not connected to early forms of field hockey or polo, even though two of the balls were found in the graves of horsemen," says Wertmann.

New era of Central Asian equestrian warfare

In one of the riders' graves, the preserved remains of a composite bow and a pair of trousers (1) were found, which were made in the region at that time and are among the oldest in the world. Both are signs of a new era of horse riding, equestrian warfare and fundamental societal transformations which accompanied increasing environmental changes and a rising mobility in eastern Central Asia. The current study shows that balls and ball games were part of physical exercise and military training from the very beginning. In addition, just like today, sport also played a central role in society and was a widespread leisure activity. The study's findings once again highlight that this region was a center of innovation within Eurasia several millennia ago.

Read more at Science Daily

Ancient tiny teeth reveal first mammals lived more like reptiles

 Pioneering analysis of 200 million-year-old teeth belonging to the earliest mammals suggests they functioned like their cold-blooded counterparts -- reptiles, leading less active but much longer lives.

The research, led by the University of Bristol, UK and University of Helsinki, Finland, published today in Nature Communications, is the first time palaeontologists have been able to study the physiologies of early fossil mammals directly, and turns on its head what was previously believed about our earliest ancestors.

Fossils of teeth, the size of a pinhead, from two of the earliest mammals, Morganucodon and Kuehneotherium, were scanned for the first time using powerful X-rays, shedding new light on the lifespan and evolution of these small mammals, which roamed the earth alongside early dinosaurs and were believed to be warm-blooded by many scientists. This allowed the team to study growth rings in their tooth sockets, deposited every year like tree rings, which could be counted to tell us how long these animals lived. The results indicated a maximum lifespan of up to 14 years -- much older than their similarly sized furry successors such as mice and shrews, which tend to only survive a year or two in the wild.

"We made some amazing and very surprising discoveries. It was thought the key characteristics of mammals, including their warm-bloodedness, evolved at around the same time," said lead author Dr Elis Newham, Research Associate at the University of Bristol, and previously PhD student at the University of Southampton during the time when this study was conducted.

"By contrast, our findings clearly show that, although they had bigger brains and more advanced behaviour, they didn't live fast and die young but led a slower-paced, longer life akin to those of small reptiles, like lizards."

Using advanced imaging technology in this way was the brainchild of Dr Newham's supervisor Dr Pam Gill, Senior Research Associate at the University of Bristol and Scientific Associate at the Natural History Museum London, who was determined to get to the root of its potential.

"A colleague, one of the co-authors, had a tooth removed and told me they wanted to get it X-rayed, because it can tell all sorts of things about your life history. That got me wondering whether we could do the same to learn more about ancient mammals," Dr Gill said.

By scanning the fossilised cementum, the material which locks the tooth roots into their socket in the gum and continues growing throughout life, Dr Gill hoped the preservation would be clear enough to determine the mammal's lifespan.

To test the theory, an ancient tooth specimen belonging to Morganucodon was sent to Dr Ian Corfe, from the University of Helsinki and the Geological Survey of Finland, who scanned it using high-powered Synchrotron X-ray radiation.

"To our delight, although the cementum is only a fraction of a millimetre thick, the image from the scan was so clear the rings could literally be counted," Dr Corfe said.

It marked the start of a six-year international study, which focused on these first mammals, Morganucodon and Kuehneotherium, known from Jurassic rocks in South Wales, UK, dating back nearly 200 million years.

"The little mammals fell into caves and holes in the rock, where their skeletons, including their teeth, fossilised. Thanks to the incredible preservation of these tiny fragments, we were able to examine hundreds of individuals of a species, giving greater confidence in the results than might be expected from fossils so old," Dr Corfe added.

The journey saw the researchers take some 200 teeth specimens, provided by the Natural History Museum London and University Museum of Zoology Cambridge, to be scanned at the European Synchrotron Radiation Facility and the Swiss Light Source, among the world's brightest X-ray light sources, in France and Switzerland, respectively.

In search of an exciting project, Dr Newham took this up for the MSc in Palaeobiology at the University of Bristol, and then a PhD at the University of Southampton.

"I was looking for something big to get my teeth into and this more than fitted the bill. The scanning alone took over a week and we ran 24-hour shifts to get it all done. It was an extraordinary experience, and when the images started coming through, we knew we were onto something," Dr Newham said.

Dr Newham was the first to analyse the cementum layers and pick up on their huge significance.

"We digitally reconstructed the tooth roots in 3-D and these showed that Morganucodon lived for up to 14 years, and Kuehneotherium for up to nine years. I was dumbfounded as these lifespans were much longer than the one to three years we anticipated for tiny mammals of the same size," Dr Newham said.

"They were otherwise quite mammal-like in their skeletons, skulls and teeth. They had specialised chewing teeth, relatively large brains and probably had hair, but their long lifespan shows they were living life at more of a reptilian pace than a mammalian one. There is good evidence that the ancestors of mammals began to become increasingly warm-blooded from the Late Permian, more than 270 million years ago, but, even 70 million years later, our ancestors were still functioning more like modern reptiles than mammals"

While their pace-of-life remained reptilian, evidence for an intermediate ability for sustained exercise was found in the bone tissue of these early mammals. As a living tissue, bone contains fat and blood vessels. The diameter of these blood vessels can reveal the maximum possible blood flow available to an animal, critical for activities such as foraging and hunting.

Read more at Science Daily

Studying the sun as a star to understand stellar flares and exoplanets

 New research shows that sunspots and other active regions can change the overall solar emissions. The sunspots cause some emissions to dim and others to brighten; the timing of the changes also varies between different types of emissions. This knowledge will help astronomers characterize the conditions of stars, which has important implications for finding exoplanets around those stars.

An international research team led by Shin Toriumi at the Japan Aerospace Exploration Agency added up the different types of emissions observed by a fleet of satellites including "Hinode" and the "Solar Dynamics Observatory" to see what the Sun would look like if observed from far away as a single dot of light like other stars.

The team investigated how features like sunspots change the overall picture. They found that when a sunspot is near the middle of the side of the Sun facing us, it causes the total amount of visible light to dim. In contrast, when the sunspots are near the edge of the Sun the total visible light brightens because at that viewing angle bright structures known as faculae surrounding the sunspots are more visible than the dark centers.

In addition, X-rays which are produced in the corona above the solar surface grow brighter when a sunspot is visible. The coronal loops extending above the sunspots are magnetically heated, so this brightening appears before the sunspot itself rotates into view and persists even after the sunspot has rotated out of view.

Because the changes in the overall solar emissions and their timings carry information about the location and structure of features on the surface of the Sun, astronomers hope to be able to deduce the surface features of other stars such as starspots and magnetic fields. This will help astronomers to better recognize dimming caused by the shadow of an exoplanet. With better knowledge about the effects of starspots, we can estimate the parameters, such as the radii and orbits, of exoplanets more accurately.

As in-depth investigations into the Sun proceed, a better understanding of the detailed mechanisms of atmospheric heating and flare eruptions will be gained. Toriumi comments, "To this end, the next-generation solar-observing satellite Solar-C(EUVST), being developed by Japan in close collaboration with US and European partners, aims to observe the Sun in emissions that probe the chromosphere, transition region, and corona as a single system."

From Science Daily

Scientists find neurochemicals have unexpectedly profound roles in the human brain

 In first-of-their-kind observations in the human brain, an international team of researchers has revealed two well-known neurochemicals -- dopamine and serotonin -- are at work at sub-second speeds to shape how people perceive the world and take action based on their perception.

The discovery shows researchers can continually and simultaneously measure the activity of both dopamine and serotonin -- whose receptor and uptake sites are therapeutic targets for disorders ranging from depression to Parkinson's disease -- in the human brain.

Furthermore, the neurochemicals appear to integrate people's perceptions of the world with their actions, indicating dopamine and serotonin have far more expansive roles in the human nervous system than previously known.

Known as neuromodulators, dopamine and serotonin have traditionally been linked to reward processing -- how good or how bad people perceive an outcome to be after taking an action.

The study online today in the journal Neuron opens the door to a deeper understanding of an expanded role for these systems and their roles in human health.

"An enormous number of people throughout the world are taking pharmaceutical compounds to perturb the dopamine and serotonin transmitter systems to change their behavior and mental health," said P. Read Montague, senior author of the study and a professor and director of the Center for Human Neuroscience Research and the Human Neuroimaging Laboratory at the Fralin Biomedical Research Institute at Virginia Tech Carilion. "For the first time, moment-to-moment activity in these systems has been measured and determined to be involved in perception and cognitive capacities. These neurotransmitters are simultaneously acting and integrating activity across vastly different time and space scales than anyone expected."

Better understanding of the underlying actions of dopamine and serotonin during perception and decision-making could deliver important insight into psychiatric and neurological disorders, the researchers said.

"Every choice that someone executes involves taking in information, interpreting that information, and making decisions about what they perceived," said Kenneth Kishida, a corresponding author of the study and an assistant professor of physiology and pharmacology, and neurosurgery, at Wake Forest School of Medicine. "There's a whole host of psychiatric conditions and neurological disorders where that process is altered in the patients, and dopamine and serotonin are prime suspects."

Lack of chemically specific methods to study neuromodulation in humans at fast time scales has impeded understanding of these systems, according to Montague, who is an honorary professor at the Wellcome Center for Human Neuroimaging at University College London and a professor of physics at the Virginia Tech College of Science.

But now, in first-ever measurements, scientists used an electrochemical method called "fast scan cyclic voltammetry," which employs a small carbon fiber microelectrode that has low voltages ramped across it for real-time detection of dopamine and serotonin activity.

In the study, researchers recorded fluctuations in dopamine and serotonin using specially designed electrodes in five patients undergoing deep brain stimulation electrode implantation surgery to treat essential tremor or Parkinson's disease. Patients were awake during surgery, playing a computer game designed to quantify aspects of thought and behavior while the measurements were taken.

On each round of the game, patients briefly viewed a cloud of dots and were asked to judge the direction they were moving. The method, designed by corresponding author Dan Bang, a Sir Henry Wellcome Postdoctoral Fellow, and Steve Fleming, a Sir Henry Dale/Royal Society Fellow, both at the Wellcome Center for Human Neuroimaging at University College London, helped indicate that dopamine and serotonin were involved in simple perceptual decisions, outside of the traditional context of rewards and losses.

"These neuromodulators play a much broader role in supporting human behavior and thought, and in particular they are involved in how we process the outside world," Bang said. "For example, if you move through a room and the lights are off, you move differently because you're uncertain about where objects are. Our work suggests these neuromodulators -- serotonin in particular -- are playing a role in signaling how uncertain we are about the outside environment."

Montague and Kishida, along with Terry Lohrenz, a research assistant professor, and Jason White, a senior research associate, now both at the Fralin Biomedical Research Institute, started working on a new statistical approach to identify dopamine and serotonin signals while still at the Baylor College of Medicine in Houston, Texas.

"Ken rose to the challenge of doing fast neurochemistry in human beings during active cognition," Montague said. "A lot of other good groups of scientists were not able to do it. Aside from the computation of enormous amounts of data, there are complicated issues to solve, including great, fundamental algorithmic tasks."

Until recently, only slow methodologies such as PET scanning could measure the impact of neurotransmitters, but they were nowhere near the frequency or volume of the second-to-second measurements of fast scan cyclic voltammetry.

The measurements in the new study were taken at the Wake Forest Baptist Medical Center, and involved neurosurgical teams led by Adrian W. Laxton and Stephen B. Tatter.

"The enthusiasm the neurosurgeons have for this research is derived from the same reasons that drove them to be doctors -- first and foremost, they want to do the best for their patients, and they have a real passion for understanding how the brain works to improve patient outcomes," said Kishida, who oversaw the data collection in the operating room during the surgeries. "Both are collaborative scientists along with Charles Branch, the chair of the neurosurgery department at Wake Forest, who has been an amazing advocate for this work."

Likewise, Montague said, "You can't do it without the surgeons being real, shoulder-to-shoulder partners, and certainly not without the people who let you make recordings from their brains while they are having electrodes implanted to alleviate the symptoms of a neurological disorder."

Montague had read a study in the Proceedings of the National Academy of Sciences that prompted him to approach colleagues Bang and Fleming at University College London to tailor a task for patients to perform during surgery that would reveal sub-second dopamine and serotonin signaling in real-time inference about the external world -- separate from their often-reported roles in reward-related processes.

"I said I have this new method to measure dopamine and serotonin, but I need you to help with the task," Montague said. "They ended up in the study. The research really took a lot of hard work and an integrated a constellation of people to obtain these results."

Read more at Science Daily

ESO telescopes record last moments of star devoured by a black hole

 

ESO's Very Large Telescope complex in Paranal, Chile

Using telescopes from the European Southern Observatory (ESO) and other organisations around the world, astronomers have spotted a rare blast of light from a star being ripped apart by a supermassive black hole. The phenomenon, known as a tidal disruption event, is the closest such flare recorded to date at just over 215 million light-years from Earth, and has been studied in unprecedented detail. The research is published today in Monthly Notices of the Royal Astronomical Society.

"The idea of a black hole 'sucking in' a nearby star sounds like science fiction. But this is exactly what happens in a tidal disruption event," says Matt Nicholl, a lecturer and Royal Astronomical Society research fellow at the University of Birmingham, UK, and the lead author of the new study. But these tidal disruption events, where a star experiences what's known as spaghettification as it's sucked in by a black hole, are rare and not always easy to study. The team of researchers pointed ESO's Very Large Telescope (VLT) and ESO's New Technology Telescope (NTT) at a new flash of light that occurred last year close to a supermassive black hole, to investigate in detail what happens when a star is devoured by such a monster.

Astronomers know what should happen in theory. "When an unlucky star wanders too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole shreds the star into thin streams of material," explains study author Thomas Wevers, an ESO Fellow in Santiago, Chile, who was at the Institute of Astronomy, University of Cambridge, UK, when he conducted the work. As some of the thin strands of stellar material fall into the black hole during this spaghettification process, a bright flare of energy is released, which astronomers can detect.

Although powerful and bright, up to now astronomers have had trouble investigating this burst of light, which is often obscured by a curtain of dust and debris. Only now have astronomers been able to shed light on the origin of this curtain.

"We found that, when a black hole devours a star, it can launch a powerful blast of material outwards that obstructs our view," explains Samantha Oates, also at the University of Birmingham. This happens because the energy released as the black hole eats up stellar material propels the star's debris outwards.

The discovery was possible because the tidal disruption event the team studied, AT2019qiz, was found just a short time after the star was ripped apart. "Because we caught it early, we could actually see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10,000 km/s," says Kate Alexander, NASA Einstein Fellow at Northwestern University in the US. "This unique 'peek behind the curtain' provided the first opportunity to pinpoint the origin of the obscuring material and follow in real time how it engulfs the black hole."

The team carried out observations of AT2019qiz, located in a spiral galaxy in the constellation of Eridanus, over a 6-month period as the flare grew in luminosity and then faded away. "Several sky surveys discovered emission from the new tidal disruption event very quickly after the star was ripped apart," says Wevers. "We immediately pointed a suite of ground-based and space telescopes in that direction to see how the light was produced."

Multiple observations of the event were taken over the following months with facilities that included X-shooter and EFOSC2, powerful instruments on ESO's VLT and ESO's NTT, which are situated in Chile. The prompt and extensive observations in ultraviolet, optical, X-ray and radio light revealed, for the first time, a direct connection between the material flowing out from the star and the bright flare emitted as it is devoured by the black hole. "The observations showed that the star had roughly the same mass as our own Sun, and that it lost about half of that to the monster black hole, which is over a million times more massive," says Nicholl, who is also a visiting researcher at the University of Edinburgh.

Read more at Science Daily

Researchers find 'missing link' between magnetars and rotation-powered pulsars

 Researchers from the RIKEN Cluster for Pioneering Research have made observations of a new magnetar, called Swift J1818.0-1607, which challenges current knowledge about two types of extreme stars, known as magnetars and pulsars. The research, just published in The Astrophysical Journal, was done using the Neutron star Interior Composition Explorer (NICER), an X-ray instrument aboard the International Space Station. Magnetars are a subtype of pulsars, which are neutron stars -- degenerate stars that failed to become black holes but instead became extremely dense bodies composed mostly of neutrons. Magnetars as well as some young rotation-powered pulsars -- another type of pulsar -- emit powerful X-ray beams, but the mechanism is believed to be different. With magnetars, the beams are believed to be powered by extremely strong magnetic fields, whereas in canonical pulsars they are powered by the rapid rotation of the star. However, there is much that is not well understood about these phenomena. Recently, several magnetars have been shown to emit radio waves -- a property that was formerly thought to be limited to canonical rotation-powered pulsars -- blurring the boundary between the two.

For the current study, work done by Chin-Ping Hu, a visiting researcher at the Extreme Natural Phenomena RIKEN Hakubi Research Team in the RIKEN Cluster for Pioneering Research and colleagues, has revealed a missing link between the two types of pulsar.

On March 12, a new gamma-ray burst was detected by the Burst Alert Telescope (BAT) aboard the Neil Gehrels Swift Observatory, a space-based gamma ray observatory. The object, believed to be a magnetar, was dubbed Swift J1818.0-1607. The RIKEN group and NICER team quickly moved into action. Four hours after the alert, they began making X-ray follow-up observations with NICER.

They found that the magnetar had a pulsation period of 1.36 seconds, the shortest among magnetars observed until now. Their observations showed that it was showing spin-down behavior -- suggesting that the emissions were to some extent being powered by rotations -- and that it had a magnetar-level surface magnetic field of 2.7×1014 Gauss, indicating that it is a young magnetar, formed about 420 years earlier. Studies of "glitches" -- sudden changes in the rotational frequency that are important of understanding neutron stars -- as well as the noisy timing behavior of its stellar rotation showed that it is indeed young. However, its X-ray emission was found to be lower than that of other magnetars, indicating that the star has attributes of both magnetars and rotation powered pulsars.

According to Hu, "Our study has given us new understanding of the neutron stars with high magnetic fields. Recent radio observations suggest that magnetars may be a cause of mysterious phenomena called fast radio bursts, so we look forward to investigating further."

Read more at Science Daily

Scientists find upper limit for the speed of sound

 A research collaboration between Queen Mary University of London, the University of Cambridge and the Institute for High Pressure Physics in Troitsk has discovered the fastest possible speed of sound.

The result- about 36 km per second -- is around twice as fast as the speed of sound in diamond, the hardest known material in the world.

Waves, such as sound or light waves, are disturbances that move energy from one place to another. Sound waves can travel through different mediums, such as air or water, and move at different speeds depending on what they're travelling through. For example, they move through solids much faster than they would through liquids or gases, which is why you're able to hear an approaching train much faster if you listen to the sound propagating in the rail track rather than through the air.

Einstein's theory of special relativity sets the absolute speed limit at which a wave can travel which is the speed of light, and is equal to about 300,000 km per second. However until now it was not known whether sound waves also have an upper speed limit when travelling through solids or liquids.

The study, published in the journal Science Advances, shows that predicting the upper limit of the speed of sound is dependent on two dimensionless fundamental constants: the fine structure constant and the proton-to-electron mass ratio.

These two numbers are already known to play an important role in understanding our Universe. Their finely-tuned values govern nuclear reactions such as proton decay and nuclear synthesis in stars and the balance between the two numbers provides a narrow 'habitable zone' where stars and planets can form and life-supporting molecular structures can emerge. However, the new findings suggest that these two fundamental constants can also influence other scientific fields, such as materials science and condensed matter physics, by setting limits to specific material properties such as the speed of sound.

The scientists tested their theoretical prediction on a wide range of materials and addressed one specific prediction of their theory that the speed of sound should decrease with the mass of the atom. This prediction implies that the sound is the fastest in solid atomic hydrogen. However, hydrogen is an atomic solid at very high pressure above 1 million atmospheres only, pressure comparable to those in the core of gas giants like Jupiter. At those pressures, hydrogen becomes a fascinating metallic solid conducting electricity just like copper and is predicted to be a room temperature superconductor. Therefore, researchers performed state-of-the-art quantum mechanical calculations to test this prediction and found that the speed of sound in solid atomic hydrogen is close to the theoretical fundamental limit.

Professor Chris Pickard, Professor of Materials Science at the University of Cambridge, said: "Soundwaves in solids are already hugely important across many scientific fields. For example, seismologists use sound waves initiated by earthquakes deep in the Earth interior to understand the nature of seismic events and the properties of Earth composition. They're also of interest to materials scientists because sound waves are related to important elastic properties including the ability to resist stress."

From Science Daily