Space study offers clearest understanding yet of the life cycle of supermassive black holes

Black holes with varying light signatures but that were thought to be the same objects being viewed from different angles are actually in different stages of the life cycle, according to a study led by Dartmouth researchers.

The research on black holes known as "active galactic nuclei," or AGNs, says that it definitively shows the need to revise the widely used "unified model of AGN" that characterizes supermassive black holes as all having the same properties.

The study, published in The Astrophysical Journal, provides answers to a nagging space mystery and should allow researchers to create more precise models about the evolution of the universe and how black holes develop.

"These objects have mystified researchers for over a half-century," said Tonima Tasnim Ananna, a postdoctoral research associate at Dartmouth and lead author of the paper. "Over time, we've made many assumptions about the physics of these objects. Now we know that the properties of obscured black holes are significantly different from the properties of AGNs that are not as heavily hidden."

Supermassive black holes are believed to reside at the center of nearly all large galaxies, including the Milky Way. The objects devour galactic gas, dust and stars, and they can become heavier than small galaxies.

For decades, researchers have been interested in the light signatures of active galactic nuclei, a type of supermassive black hole that is "accreting," or in a rapid growth stage.

Beginning in the late 1980s, astronomers realized that light signatures coming from space ranging from radio wavelengths to X-rays could be attributed to AGNs. It was assumed that the objects usually had a doughnut-shaped ring -- or "torus" -- of gas and dust around them. The different brightness and colors associated with the objects were thought to be the result of the angle from which they were being observed and how much of the torus was obscuring the view.

From this, the unified theory of AGNs became the prevalent understanding. The theory guides that if a black hole is being viewed through its torus, it should appear faint. If it is being viewed from below or above the ring, it should appear bright. According to the current study, however, the past research relied too heavily on data from the less obscured objects and skewed research results.

The new study focuses on how quickly black holes are feeding on space matter, or their accretion rates. The research found that the accretion rate does not depend upon the mass of a black hole, it varies significantly depending on how obscured it is by the gas and dust ring.

"This provides support for the idea that the torus structures around black holes are not all the same," said Ryan Hickox, professor of physics and astronomy and a co-author of the study. "There is a relationship between the structure and how it is growing."

The result shows that the amount of dust and gas surrounding an AGN is directly related to how much it is feeding, confirming that there are differences beyond orientation between different populations of AGNs. When a black hole is accreting at a high rate, the energy blows away dust and gas. As a result, it is more likely to be unobscured and appear brighter. Conversely, a less active AGN is surrounded by a denser torus and appears fainter.

"In the past, it was uncertain how the obscured AGN population varied from their more easily observable, unobscured counterparts," said Ananna. "This new research definitively shows a fundamental difference between the two populations that goes beyond viewing angle."

The study stems from a decade-long analysis of nearby AGNs detected by Swift-BAT, a high-energy NASA X-ray telescope. The telescope allows researchers to scan the local universe to detect obscured and unobscured AGNs.

The research is the result of an international scientific collaboration -- the BAT AGN Spectroscopic Survey (BASS) -- that has been working over a decade to collect and analyze optical/infrared spectroscopy for AGN observed by Swift BAT.

"We have never had such a large sample of X-ray detected obscured local AGN before," said Ananna. "This is a big win for high-energy X-ray telescopes."

The paper builds on previous research from the research team analyzing AGNs. For the study, Ananna developed a computational technique to assess the effect of obscuring matter on observed properties of black holes, and analyzed data collected by the wider research team using this technique.

According to the paper, by knowing a black hole's mass and how fast it is feeding, researchers can determine when most supermassive black holes underwent most of their growth, thus providing valuable information about the evolution of black holes and the universe.

"One of the biggest questions in our field is where do supermassive black holes come from," said Hickox. "This research provides a critical piece that can help us answer that question and I expect it to become a touchstone reference for this research discipline."

Future research could include focusing on wavelengths that allow the team to search beyond the local universe. In the nearer term, the team would like to understand what triggers AGNs to go into high accretion mode, and how long it takes rapidly accreting AGNs to transition from heavily obscured to unobscured.

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Trilobites' growth may have resembled that of modern marine crustaceans

Trilobites -- extinct marine arthropods that roamed the world's oceans from about 520 million years ago until they went extinct 250 million years ago, at the end of the Permian period -- may have grown in a similar fashion and reached ages that match those of extant crustaceans, a new study has found.

In a paper published in the journal Paleobiology, researchers from the University of British Columbia and Uppsala University show that the Ordovician trilobite Triarthrus eatoni, some 450 million years ago, reached a length of just above 4 cm in about 10 years, with a growth curve very similar to that of small, slow-growing crustaceans.

"T. eatoni lived in low-oxygen environments and, similarly to extant crustaceans exposed to hypoxic conditions, exhibited low growth rates compared with growth under more oxygenated conditions," said Daniel Pauly, principal investigator of UBC's Sea Around Us initiative and lead author of the study. "Low-oxygen environments make is more difficult for water-breathers to grow, and add to the difficulties of breathing through gills, which, as 2D surfaces, cannot keep up with the growth of their 3D bodies. Thus, under hypoxic conditions, they must remain small if they are to maintain the rest of their body functions."

In the case of trilobites, their exopods -- external branches on the upper part of their limbs -- functioned as gills. Thus, these ancient animals had similar growth constraints to those of their modern counterparts.

To reach these conclusions, Pauly and his colleague from Uppsala University, paleontologist James Holmes, resorted to the analysis of length-frequency data, a method developed within fisheries science and marine biology for studying the growth of fish and invertebrates lacking the physical markings that indicate their age.

The information to perform their analysis was obtained from an earlier publication with information of the length frequency distribution of 295 exceptionally-preserved trilobite fossils collected at 'Beecher's Trilobite Bed' in New York State.

After estimating the parameters of a growth model widely used in fisheries science, the von Bertalanffy growth function, the researchers compared their results with published data on the growth of extant crustaceans. They found that the growth parameters they estimated for Triarthrus eatoni were well within the range of recent, slow-growing crustaceans.

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Researchers find why bat cells do not get infected by SARS-CoV-2

Bat cells have specific molecular barriers to deal with SARS-CoV-2 replication, according to a study published in the Journal of Virology -- a publication of the American Society of Microbiology -- which includes the participation of Jordi Serra-Cobo, lecturer of the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona and expert on ecoepidemiological studies.

The study was carried out on primary cells of bat species which had been little studied and which circulate around Europe and Asia (specifically, Rhinolopuhs ferrumequinum, Myotis myotis, Eptesicus serotinus, Tadarida brasiliensis and Nyctalus noctula). These cellular lines were obtained through small biopsies carried out on the wings of the bats -- for instance, in bat colonies of Myotis myotis in Majorca and other cell lines brought by some research teams that took part in the study. As stated in the conclusions, these cellular models defined in chiropterans are shaped as tools of scientific interest to study the evolutionary relationship between bats and coronaviruses.

The study, led by the experts Nolwenn Jouvenet and Laurent Dacheux, from the Institute Pasteur in Paris, includes the collaboration of experts from research institutions in France, the Czech Republic and Switzerland.

How do bats protect themselves from viral infections?

Coronaviruses are present in many animal species worldwide, such as bats (chiropteans). In this context, the scientific literature has described for years the great resistance of some chiropteran species towards the viral infection. In these flying mammals, the immune system is on a pre-alert stage, a condition that allows a faster response to viral infections. For most mammals, having an immune system on a constant pre-alert state would involve inflammation problems but this is not the case for bats, which is why they are the focus of many international epidemiological and immunological studies.

As part of the study, the team analysed the ability of primary cells from different bat species to support SARS-CoV-2 replication. "The results reveal that none of these cells was permissive to the infection, not even those expressing detectable levels of angiotensin-converting enzyme 2 (ACE2), a metallopeptidase that serves as a viral receptor in many mammal species," says Jordi Serra-Cobo, member of the Department of Evolutionary Biology, Ecology and Environmental Sciences of the UB and the only expert in Spain to take part in this study.

"The cells did not allow the infection in the species Rhinolophus ferrumequinum, a chiropteran from the same genus as the Asian bat in which the BANAL-52 virus was found, a potential ancestor of SARS-CoV-2. Specifically, the genetic sequences of the BANAL-52 virus is 96.8% similar to that of SARS-CoV-2," says Serra-Cobo, distinguished expert in studies with bats as natural reservoirs of infectious agents like coronaviruses.

Humans and chiropterans vs. SARS-CoV-2 infection

Regarding the human species, it is known that the SARS-CoV-2 spike protein binds to the cell membrane receptor ACE2 and then the virus infects the cell. "In the case of the chiropteran cells, either the amount of ACE2 enzyme is small and it no longer enters the cell or, if the virus binds to ACE2, it cannot infect the cell," highlights Serra-Cobo.

From a global perspective, this study contributes to a better understanding of the fighting mechanisms against viral infections. This is a line of research that has been carried out for years by the team led by Serra-Cobo at the UB and IRBio and which is now gaining strength within the framework of the EvoDevo-Cat research group at the Faculty of Biology of the UB.

"Specifically, our team is working to understand the adaptations of the chiropterans regarding viral infections. An important number of zoonotic viruses circulate in chiropter populations without causing symptoms of the disease in the carriers," notes the researcher.

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Studies link COVID-19 to wildlife sales at Chinese market, find alternative scenarios extremely unlikely

An international team of researchers has confirmed that live animals sold at the Huanan Seafood Wholesale Market were the likely source of the COVID-19 pandemic that has claimed 6.4 million lives since it began nearly three years ago.

Led by University of Arizona virus evolution expert Michael Worobey, international teams of researchers have traced the start of the pandemic to the market in Wuhan, China, where foxes, raccoon dogs and other live mammals susceptible to the virus were sold live immediately before the pandemic began. Their findings were published Tuesday in two papers in the journal Science, after being previously released in pre-print versions in February.

The publications, which have since gone through peer review and include additional analyses and conclusions, virtually eliminate alternative scenarios that have been suggested as origins of the pandemic. Moreover, the authors conclude that the first spread to humans from animals likely occurred in two separate transmission events in the Huanan market in late November 2019.

One study scrutinized the locations of the first known COVID-19 cases, as well as swab samples taken from surfaces at various locations at the market. The other focused on genomic sequences of SARS-CoV-2 from samples collected from COVID-19 patients during the first weeks of the pandemic in China.

The first paper, led by Worobey and Kristian Andersen at Scripps Research Institute in San Diego, California, examined the geographic pattern of COVID-19 cases in the first month of the outbreak, December 2019. The team was able to determine the locations of almost all of the 174 COVID-19 cases identified by the World Health Organization that month, 155 of which were in Wuhan.

Analyses showed that these cases were clustered tightly around the Huanan market, whereas later cases were dispersed widely throughout Wuhan -- a city of 11 million people. Notably, the researchers found that a striking percentage of early COVID patients with no known connection to the market -- meaning they neither worked there nor shopped there -- turned out to live near the market. This supports the idea that the market was the epicenter of the epidemic, Worobey said, with vendors getting infected first and setting off a chain of infections among community members in the surrounding area.

"In a city covering more than 3,000 square miles, the area with the highest probability of containing the home of someone who had one of the earliest COVID-19 cases in the world was an area of a few city blocks, with the Huanan market smack dab inside it," said Worobey, who heads UArizona Department of Ecology and Evolutionary Biology.

This conclusion was supported by another finding: When the authors looked at the geographical distribution of later COVID cases, from January and February 2020, they found a "polar opposite" pattern, Worobey said. While the cases from December 2019 mapped "like a bullseye" on the market, the later cases coincided with areas of the highest population density in Wuhan.

"This tells us the virus was not circulating cryptically," Worobey said. "It really originated at that market and spread out from there."

In an important addition to their earlier findings, Worobey and his collaborators addressed the question of whether health authorities found cases around the market simply because that's where they looked.

"It is important to realize that all these cases were people who were identified because they were hospitalized," Worobey said. "None were mild cases that might have been identified by knocking on doors of people who lived near the market and asking if they felt ill. In other words, these patients were recorded because they were in the hospital, not because of where they lived."

To rule out any potentially lingering possibility of bias, Worobey's team took one further step: Starting at the market, they began removing cases from their analyses, going farther in distance from the market as they went, and ran the stats again. The result: Even when two-thirds of cases were removed, the findings were the same.

"Even in that scenario, with the majority of cases, removed, we found that the remaining ones lived closer to the market than what would be expected if there was no geographical correlation between these earliest COVID cases and the market," Worobey said.

The study also looked at swab samples taken from market surfaces like floors and cages after Huanan market was shuttered. Samples that tested positive for SARS-CoV-2 were significantly associated with stalls selling live wildlife.

The researchers determined that mammals now known to be susceptible to SARS-CoV-2, including red foxes, hog badgers and raccoon dogs, were sold live at the Huanan market in the weeks preceding the first recorded COVID-19 cases. The scientists developed a detailed map of the market and showed that SARS-CoV-2-positive samples reported by Chinese researchers in early 2020 showed a clear association with the western portion of the market, where live or freshly butchered animals were sold in late 2019.

"Upstream events are still obscure, but our analyses of available evidence clearly suggest that the pandemic arose from initial human infections from animals for sale at the Huanan Seafood Wholesale Market in late November 2019," said Andersen, who was a co-senior author of both studies and is a professor in the Department of Immunology and Microbiology at Scripps Research.

Virus likely jumped from animals to humans more than once

The second study, an analysis of SARS-CoV-2 genomic data from early cases, was co-led by Jonathan Pekar and Joel Wertheim at the University of California, San Diego and Marc Suchard of the University of California Los Angeles, as well as Andersen and Worobey.

The researchers combined epidemic modeling with analyses of the virus's early evolution based on the earliest sampled genomes. They determined that the pandemic, which initially involved two subtly distinct lineages of SARS-CoV-2, likely arose from at least two separate infections of humans from animals at the Huanan market in November 2019 and perhaps in December 2019. The analyses also suggested that, in this period, there were many other animal-to-human transmissions of the virus at the market that failed to manifest in recorded COVID-19 cases.

The authors used a technique known as molecular clock analysis, which relies on the natural pace with which genetic mutations occur over time, to establish a framework for the evolution of the SARS-CoV-2 virus lineages. They found that a scenario of a singular introduction of the virus into humans rather than multiple introductions would be inconsistent with molecular clock data. Earlier studies had suggested that one lineage of the virus -- named A and closely related to viral relatives in bats -- gave rise to a second lineage, named B. More likely, according to the new data, is a scenario in which the two lineages jumped from animals into humans on separate occasions, both at the Huanan market, Worobey said.

"Otherwise, lineage A would have had to have been evolving in slow motion compared to the lineage B virus, which just doesn't make biological sense," said Worobey.

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Explosive volcanic eruption produced rare mineral on Mars

Planetary scientists from Rice University, NASA's Johnson Space Center and the California Institute of Technology have an answer to a mystery that's puzzled the Mars research community since NASA's Curiosity rover discovered a mineral called tridymite in Gale Crater in 2016.

Tridymite is a high-temperature, low-pressure form of quartz that is extremely rare on Earth, and it wasn't immediately clear how a concentrated chunk of it ended up in the crater. GaleCrater was chosen as Curiosity's landing site due to the likelihood that it once held liquid water, and Curiosity found evidence that confirmed Gale Crater was a lake as recently as 1 billion years ago.

"The discovery of tridymite in a mudstone in Gale Crater is one of the most surprising observations that the Curiosity rover has made in 10 years of exploring Mars," said Rice's Kirsten Siebach, co-author of a study published online in Earth and Planetary Science Letters. "Tridymite is usually associated with quartz-forming, explosive, evolved volcanic systems on Earth, but we found it in the bottom of an ancient lake on Mars, where most of the volcanoes are very primitive."

Siebach, an assistant professor in Rice's Department of Earth, Environmental and Planetary Sciences, is a mission specialist on NASA's Curiosity team. To suss out the answer to the mystery, she partnered with two postdoctoral researchers in her Rice research group, Valerie Payré and Michael Thorpe, NASA's Elizabeth Rampe and Caltech's Paula Antoshechkina. Payré, the study's lead author, is now at Northern Arizona University and preparing to join the faculty of the University of Iowa in the fall.

Siebach and colleagues began by reevaluating data from every reported find of tridymite on Earth. They also reviewed volcanic materials from models of Mars volcanism and reexamined sedimentary evidence from the Gale Crater lake. They then came up with a new scenario that matched all the evidence: Martian magma sat for longer than usual in a chamber below a volcano, undergoing a process of partial cooling called fractional crystallization that concentrated silicon. In a massive eruption, the volcano spewed ash containing the extra silicon in the form of tridymite into the Gale Crater lake and surrounding rivers. Water helped break down the ash through natural processes of chemical weathering, and water also helped sort the minerals produced by weathering.

The scenario would have concentrated tridymite, producing minerals consistent with the 2016 find. It would also explain other geochemical evidence Curiosity found in the sample, including opaline silicates and reduced concentrations of aluminum oxide.

"It's actually a straightforward evolution of other volcanic rocks we found in the crater," Siebach said. "We argue that because we only saw this mineral once, and it was highly concentrated in a single layer, the volcano probably erupted at the same time the lake was there. Although the specific sample we analyzed was not exclusively volcanic ash, it was ash that had been weathered and sorted by water."

If a volcanic eruption like the one in the scenario did occur when Gale Crater contained a lake, it would mean explosive volcanism occurred more than 3 billion years ago, while Mars was transitioning from a wetter and perhaps warmer world to the dry and barren planet it is today.

"There's ample evidence of basaltic volcanic eruptions on Mars, but this is a more evolved chemistry," she said. "This work suggests that Mars may have a more complex and intriguing volcanic history than we would have imagined before Curiosity."

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New study finds lowest risk of death was among adults who exercised 150-600 minutes/week

An analysis of more than 100,000 participants over a 30-year follow-up period found that adults who perform two to four times the currently recommended amount of moderate or vigorous physical activity per week have a significantly reduced risk of mortality, according to new research published today in the American Heart Association's flagship, peer-reviewed journal Circulation. The reduction was 21-23% for people who engaged in two to four times the recommended amount of vigorous physical activity, and 26-31% for people who engaged in two to four times the recommended amount of moderate physical activity each week.

It is well documented that regular physical activity is associated with reduced risk of cardiovascular disease and premature death. In 2018, the United States Department of Health and Human Services' Physical Activity Guidelines for Americans recommended that adults engage in at least 150-300 minutes/week of moderate physical activity or 75-150 minutes/week of vigorous physical activity, or an equivalent combination of both intensities. The American Heart Association's current recommendations, which are based on HHS's Physical Activity Guidelines, are for at least 150 minutes per week of moderate-intensity aerobic exercise or 75 minutes per week or vigorous aerobic exercise, or a combination of both.

"The potential impact of physical activity on health is great, yet it remains unclear whether engaging in high levels of prolonged, vigorous or moderate intensity physical activity above the recommended levels provides any additional benefits or harmful effects on cardiovascular health," said Dong Hoon Lee, Sc.D., M.S., a research associate in the department of nutrition at the Harvard T.H. Chan School of Public Health in Boston. "Our study leveraged repeated measures of self-reported physical activity over decades to examine the association between long-term physical activity during middle and late adulthood and mortality."

Researchers analyzed mortality data and medical records for more than 100,000 adults gathered from two large prospective studies: the all-female Nurses' Health Study and the all-male Health Professionals Follow-up Study from 1988-2018. Participants whose data were examined were 63% female, and more than 96% were white adults. They had an average age of 66 years and an average body mass index (BMI) of 26 kg/m2 over the 30-year follow-up period.

Participants self-reported their leisure-time physical activity by completing a validated questionnaire for either the Nurses' Health Study or Health Professionals Follow-Up Study every two years. The publicly available questionnaires, which were updated and expanded every two years, included questions about health information, physician-diagnosed illnesses, family medical histories and personal habits such as cigarette and alcohol consumption and frequency of exercise. Exercise data was reported as the average time spent per week on various physical activities over the past year. Moderate activity was defined as walking, lower-intensity exercise, weightlifting and calisthenics. Vigorous activity included jogging, running, swimming, bicycling and other aerobic exercises.

The analysis found that adults who performed double the currently recommended range of either moderate or vigorous physical activity each week had the lowest long-term risk of mortality.

The analysis also found:

• Participants who met the guidelines for vigorous physical activity had an observed 31% lower risk of CVD mortality and 15% lower risk of non-CVD mortality, for an overall 19% lower risk of death from all causes.
• Participants who met the guidelines for moderate physical activity had an observed 22-25% lower risk of CVD mortality and 19-20% lower risk of non-CVD mortality, for an overall 20-21% lower risk of death from all causes.
• Participants who performed two to four times above the recommended amount of long-term vigorous physical activity (150-300 min/week) had an observed 27-33% lower risk of CVD mortality and 19% non-CVD mortality, for an overall 21-23% lower risk of death from all causes.
• Participants who performed two to four times above the recommended amount of moderate physical activity (300-600 min/week) had an observed 28-38% lower risk of CVD mortality and 25-27% non-CVD mortality, for an overall 26-31% lower risk of mortality from all causes.

In addition, no harmful cardiovascular health effects were found among the adults who reported engaging in more than four times the recommended minimum activity levels. Previous studies have found evidence that long-term, high-intensity, endurance exercise, such as marathons, triathlons and long-distance bicycle races, may increase the risk of adverse cardiovascular events, including myocardial fibrosis, coronary artery calcification, atrial fibrillation and sudden cardiac death.

"This finding may reduce the concerns around the potential harmful effect of engaging in high levels of physical activity observed in several previous studies," Lee noted.

However, engaging in long-term, high intensity physical activity (?300 minutes/week) or moderate intensity physical activity (?600 minutes/week) at levels more than four times the recommended weekly minimum did not provide any additional reduction in risk of death.

"Our study provides evidence to guide individuals to choose the right amount and intensity of physical activity over their lifetime to maintain their overall health," Lee said. "Our findings support the current national physical activity guidelines and further suggest that the maximum benefits may be achieved by performing medium to high levels of either moderate or vigorous activity or a combination."

He also noted that people who perform less than 75 minutes of vigorous activity or less than 150 minutes of moderate activity per week may have greater benefits on mortality reduction by consistently performing approximately 75-150 minutes of vigorous activity or 150-300 minutes of moderate exercise per week, or an equivalent combination of both, over the long term.

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Study shows link between frequent naps and high blood pressure

Napping on a regular basis is associated with higher risks for high blood pressure and stroke, according to new research published today in Hypertension, an American Heart Association journal.

Researchers in China examined whether frequent naps could be a potential causal risk factor for high blood pressure and/or stroke. This is the first study to use both observational analysis of participants over a long period of time and Mendelian randomization -- a genetic risk validation to investigate whether frequent napping was associated with high blood pressure and ischemic stroke.

"These results are especially interesting since millions of people might enjoy a regular, or even daily nap," says E Wang, Ph.D., M.D., a professor and chair of the Department of Anesthesiology at Xiangya Hospital Central South University, and the study's corresponding author.

Researchers used information from UK Biobank, a large biomedical database and research resource containing anonymized genetic, lifestyle and health information from half a million UK participants. UK Biobank recruited more than 500,000 participants between the ages of 40 and 69 who lived in the United Kingdom between 2006 and 2010. They regularly provided blood, urine and saliva samples, as well as detailed information about their lifestyle. The daytime napping frequency survey occurred 4 times from 2006 -- 2019 in a small proportion of UK Biobank participants.

Wang's group excluded records of people who had already had a stroke or had high blood pressure before the start of the study. This left about 360,000 participants to analyze the association between napping and first-time reports of stroke or high blood pressure, with an average follow-up of about 11 years. Participants were divided into groups based on self-reported napping frequency: "never/rarely," "sometimes," or "usually."

The study found:

• A higher percentage of usual-nappers were men, had lower education and income levels, and reported cigarette smoking, daily drinking, insomnia, snoring and being an evening person compared to never- or sometimes-nappers;
• When compared to people who reported never taking a nap, people who usually nap had a 12% higher likelihood of developing high blood pressure and 24% higher likelihood of having a stroke;
• Participants younger than age 60 who usually napped had a 20% higher risk of developing high blood pressure compared to people the same age who never napped. After age 60, usual napping was associated with 10% higher risk of high blood pressure compared to those who reported never napping;
• About three-fourths of participants remained in the same napping category throughout the study;
• The Mendelian randomization result showed that If napping frequency increased by one category (from never to sometimes or sometimes to usually) high blood pressure risk increased 40%. Higher napping frequency was related to the genetic propensity for high blood pressure risk.

"This may be because, although taking a nap itself is not harmful, many people who take naps may do so because of poor sleep at night. Poor sleep at night is associated with poorer health, and naps are not enough to make up for that," said Michael A. Grandner, Ph.D., MTR, a sleep expert and co-author of the American Heart Association's new Life's Essential 8 cardiovascular health score, which added sleep duration in June 2022 as the 8th metric for measuring optimal heart and brain health. "This study echoes other findings that generally show that taking more naps seems to reflect increased risk for problems with heart health and other issues." Grander is director of the Sleep Health Research Program and the Behavioral Sleep Medicine Clinic and associate professor of psychiatry at the University of Arizona in Tucson.

The authors recommend further examination of the associations between a healthy sleep pattern, including daytime napping, and heart health.

The study has several important limitations to consider. Researchers only collected daytime napping frequency, not duration, so there is no information how or whether the length of nap affects blood pressure or stroke risks. Additionally, nap frequency was self-reported without any objective measurements, making estimates nonquantifiable. The study's participants were mostly middle-aged and elderly with European ancestry, so the results may not be generalizable. Finally, researchers have not yet discovered the biological mechanism for the effect of daytime napping on blood pressure regulation or stroke.

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Pre-teen children believe 'brilliance' is a male trait, and this stereotype increases in strength up to the age of twelve

Children hold stereotypical views that 'brilliance' is a male trait, and this belief strengthens as they grow up to the age of twelve, researchers from Singapore and the United States have reported.

The study led by Nanyang Technological University, Singapore (NTU Singapore) in collaboration with New York University, was published in the scientific journal Child Development in May 2022. It involved 389 Chinese Singaporean parents and 342 of their children aged 8 to 12.

Tests were carried out to measure the extent to which parents and their children associate the notion of brilliance with men, and to probe the relationship between parents and their children's views.

The study defined brilliance as an exceptional level of intellectual ability and results showed that children are as likely to associate brilliance with men, as their parents are.

This belief was stronger among older children and stronger among those children whose parents held the same view.

While previous research on gender stereotypes has found the idea that giftedness is a male trait can emerge at around the age of six, it was not known whether and how this stereotype changes over the course of childhood, until now.

Lead author of the study, Associate Professor Setoh Peipei from NTU Singapore's School of Social Sciences, said the Singapore-based study is the first to identify that the tendency to associate brilliance with men (also known as the 'brilliance equals to men' stereotype) increases in strength through the primary school years, and reaches the level of belief seen in adults by the age of 13.

"Stereotypical views about how boys are smarter than girls can take root in childhood and become a self-fulfilling prophecy," said Prof Setoh. "For girls, this may lead them to doubt their abilities, thus limiting their ideas about their interests and what they can achieve in life."

"Our research work shows parents must also be included in policies and school programmes to effectively combat children's gender stereotypes from a young age," she added.

For example, as previous studies have found that parents use different explanation styles for daughters and for sons, the research team said programmes to train parents and teachers to be mindful of balancing their behaviour during interactions with children -- especially with girls -- could be introduced.

The authors say the study offers evidence to support Singapore's push to close the gender gap in the Science, Technology, Engineering, and Mathematics (STEM) sectors.

While Singapore has the second highest in the world OECD PISA scores in mathematics, science and reading, a recent study by the Promotion of Women in Engineering, Research, and Science (POWERS) programme at NTU Singapore found that women in Singapore are less confident in their math and science abilities compared to men. Women are also more likely than men to perceive gender barriers to STEM career entry and career progress.

How the study was conducted

The researchers used the Implicit Association Test (IAT) -- a commonly-used implicit measure of stereotyping -- to evaluate parents' and children's behaviour. During the test, participants were asked to categorise photographs of men and women, along with two sets of words. One set of 'genius words' referred to the notion of brilliance and included words such as "super-smart" and "genius," while the other set of words referred to creativity (control attribute).

During the first half of the trials, participants had to press a key to categorise the male photographs with the genius words. This process was repeated in the second half of the trials with female photographs and genius words. Participants with an implicit association of men being brilliant will react faster to the task of categorising genius words with the male photographs than the same task with female photographs.

Results revealed an average D score (a metric of the strength of the stereotypical 'intellectual brilliance = men' association) of 0.16, indicating that Singaporean children associate brilliance with men more than women and that this stereotypical belief increased in strength with age among the child sample and reached stereotype levels comparable to those of adults by age 12. Thereafter, there was little change in their perspective.

In the second part of the study, the researchers investigated scores from parent-child pairs who took the tests separately but at the same time and found that children's scores were correlated to their parents' test scores. This finding suggests that during the earlier years of primary school, parents may play a role in their children's acquisition of the 'brilliance equals to men' stereotype.

Further analysis revealed that as the age of the boys that were tested got older, they were less likely to hold the same stereotypical views of males as more brilliant as their parents. However, for girls, their stereotypes remained closely linked to their parents' stereotypes throughout the primary school years.

Co-author Andrei Cimpian, Professor of Psychology at New York University said, "This study adds to the evidence that the gender imbalances observed in many prestigious careers are not a function of differences between women and men in their inherent aptitudes or interests. Rather, these imbalances are the product of the messages that young people are getting from those around them about what women and men are supposedly -- and supposed to be -- like. As a society, we have a responsibility to work toward addressing this issue."

Moving forward, the research team is studying whether this gender stereotype about brilliance may differently impact primary and secondary school girls' and boys' outcomes in math -- a core STEM subject that is typically believed to require intellectual brilliance to excel in.

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Measuring the universe with star-shattering explosions

An international team of 23 researchers led by Maria Dainotti, Assistant Professor at the National Astronomical Observatory of Japan (NAOJ), has analyzed archive data for powerful cosmic explosions from the deaths of stars and found a new way to measure distances in the distant Universe.

With no landmarks in space, it is very difficult to get a sense of depth. One technique astronomers use is to look for "standard candles," objects or events where the underlying physics dictate that the absolute brightness (what you would see if you were right next to it) is always the same. By comparing this calculated absolute brightness to the apparent brightness (what is actually observed from Earth), it is possible to determine the distance to the standard candle, and by extension other objects in the same area. The lack of standard candles bright enough to be seen more than 11 billion light-years away has hindered research on the distance Universe. Gamma-Ray bursts (GRBs), bursts of radiation produced by the deaths of massive stars, are bright enough, but their brightness depends on the characteristics of the explosion.

Embracing the challenge of attempting to use these bright events as standard candles, the team analyzed archive data for the visible light observations of 500 GRBs taken by world-leading telescopes such as the Subaru Telescope (owned and operated by NAOJ), RATIR, and satellites such as the Neil Gehrels Swift Observatory. Studying the light curve's pattern of how the GRB brightens and dims over time, the team identified a class of 179 GRBs which have common features and have likely been caused by similar phenomena. From the characteristics of the light curves, the team was able to calculate a unique brightness and distance for each GRB which can be used as a cosmological tool.

These findings will provide new insights into the mechanics behind this class of GRBs, and provide a new standard candle for observing the distant Universe. Lead author Dainotti had previously found a similar pattern in X-ray observations of GRBs, but visible light observations have been revealed to be more accurate in determining cosmological parameters.

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Study finds why many IVF embryos fail to develop

In humans, a fertilized egg is no guarantee of reproductive success. Most embryos stop developing and perish within days of fertilization, usually because they have an abnormal number of chromosomes. Now, researchers at Columbia University Vagelos College of Physicians and Surgeons have found that most of these mistakes are due to spontaneous errors in DNA replication in the earliest phase of cell division.

The findings provide new insights into the basic biology of human reproduction and in the long term could lead to improvements in the success rate of in vitro fertilization (IVF). The study was published online July 19 in the journal Cell.

Challenging task for early embryos

Approximately 24 hours after a human egg is fertilized, the process of cell division begins. During cell division, the entire genome -- 46 chromosomes containing more than 3 billion base pairs of DNA -- must be faithfully duplicated. The duplicate sets of chromosomes must then be separated so that each daughter cell receives a complete set.

In many human embryos created for IVF, something goes wrong and some cells within the embryo have too few or too many chromosomes.

"Duplicating the genome is a challenging task for the early embryo," says study leader Dieter Egli, PhD, the Maimonides Assistant Professor of Developmental Cell Biology (in pediatrics) at Columbia University Vagelos College of Physicians and Surgeons.

Researchers have long theorized that errors occur during the final phase of cell division, when the duplicate sets of chromosomes separate into two identical daughter cells. Most of these failures were attributed to issues with the microtubule spindle, the apparatus that pulls the two sets of chromosomes apart.

But Egli's studies found that chromosomal abnormalities stem from errors that occur much earlier in the process of cell division when the genome's DNA is duplicated. If the DNA is not copied precisely, his studies found, the spindle malfunctions and places the wrong number of chromosomes into each daughter cell. When DNA duplication is abnormal, the spindle does not function normally. "This has largely been overlooked in previous studies -- because why would the embryo allow the integrity of the genome to be compromised when this is such a critical requirement for normal development?" Egli says.

Though the studies were conducted with embryos created in a petri dish -- including from individuals undergoing IVF and egg donors who were not seeking fertility treatment -- the same problems may contribute to the failure of embryos created in natural human reproduction.

Clues to source of DNA errors

The source of DNA copying errors in embryos appears to spring from obstacles within the DNA's double helix. Though the precise reason for these obstacles is not yet known, they cause duplication of the DNA to pause, or even stop, which results in DNA breakage and an abnormal number of chromosomes.

Spontaneous DNA errors can occur as early as the first cycle of cell division in human embryos, the researchers found, as well as in subsequent cell divisions. If too many cells in the early embryo are affected by chromosomal abnormalities, the embryo cannot develop further.

IVF

Most human embryos created for IVF stop developing within days after fertilization. This inefficiency of human development is an obstacle to successful fertility treatments.

"Many women undergoing fertility treatment require multiple IVF cycles in order to get pregnant, and some never get pregnant at all. Not only is this enormously expensive, it's emotionally taxing," says Jenna Turocy, MD, a fertility specialist at Columbia University Fertility Center and a co-author of the study.

The researchers are planning additional studies looking at DNA damage during replication in the hope of understanding normal and disease-causing variations in the human germ line. In the long term, these studies may lead to methods to reduce the risk of genetic abnormalities and embryo attrition for patients undergoing IVF.

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