Hydrogen-burning white dwarfs enjoy slow aging

The prevalent view of white dwarfs as inert, slowly cooling stars has been challenged by observations from the NASA/ESA Hubble Space Telescope. An international group of astronomers have discovered the first evidence that white dwarfs can slow down their rate of ageing by burning hydrogen on their surface.

"We have found the first observational evidence that white dwarfs can still undergo stable thermonuclear activity," explained Jianxing Chen of the Alma Mater Studiorum Università di Bologna and the Italian National Institute for Astrophysics, who led this research. "This was quite a surprise, as it is at odds with what is commonly believed."

White dwarfs are the slowly cooling stars which have cast off their outer layers during the last stages of their lives. They are common objects in the cosmos; roughly 98% of all the stars in the Universe will ultimately end up as white dwarfs, including our own Sun. Studying these cooling stages helps astronomers understand not only white dwarfs, but also their earlier stages as well.

To investigate the physics underpinning white dwarf evolution, astronomers compared cooling white dwarfs in two massive collections of stars: the globular clusters M3 and M13. These two clusters share many physical properties such as age and metallicity but the populations of stars which will eventually give rise to white dwarfs are different. In particular, the overall colour of stars at an evolutionary stage known as the Horizontal Branch are bluer in M13, indicating a population of hotter stars. This makes M3 and M13 together a perfect natural laboratory in which to test how different populations of white dwarfs cool.

"The superb quality of our Hubble observations provided us with a full view of the stellar populations of the two globular clusters," continued Chen. "This allowed us to really contrast how stars evolve in M3 and M13."

Using Hubble's Wide Field Camera 3 the team observed M3 and M13 at near-ultraviolet wavelengths, allowing them to compare more than 700 white dwarfs in the two clusters. They found that M3 contains standard white dwarfs which are simply cooling stellar cores. M13, on the other hand, contains two populations of white dwarfs: standard white dwarfs and those which have managed to hold on to an outer envelope of hydrogen, allowing them to burn for longer and hence cool more slowly.

Comparing their results with computer simulations of stellar evolution in M13, the researchers were able to show that roughly 70% of the white dwarfs in M13 are burning hydrogen on their surfaces, slowing down the rate at which they are cooling.

This discovery could have consequences for how astronomers measure the ages of stars in the Milky Way. The evolution of white dwarfs has previously been modelled as a predictable cooling process. This relatively straightforward relationship between age and temperature has led astronomers to use the white dwarf cooling rate as a natural clock to determine the ages of star clusters, particularly globular and open clusters. However, white dwarfs burning hydrogen could cause these age estimates to be inaccurate by as much as 1 billion years.

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The warming climate is causing animals to 'shapeshift'

Climate change is not only a human problem; animals have to adapt to it as well. Some "warm-blooded" animals are shapeshifting and getting larger beaks, legs, and ears to better regulate their body temperatures as the planet gets hotter. Bird researcher Sara Ryding of Deakin University in Australia describes these changes in a review published September 7th in the journal Trends in Ecology and Evolution.

"A lot of the time when climate change is discussed in mainstream media, people are asking 'can humans overcome this?', or 'what technology can solve this?'. It's high time we recognized that animals also have to adapt to these changes, but this is occurring over a far shorter timescale than would have occurred through most of evolutionary time," says Ryding (@zuuletc). "The climate change that we have created is heaping a whole lot of pressure on them, and while some species will adapt, others will not."

Ryding notes that climate change is a complex and multifaceted phenomenon that's been occurring progressively, so it is difficult to pinpoint just one cause of the shapeshifting. But these changes have been occurring across wide geographical regions and among a diverse array of species, so there is little in common apart from climate change.

Strong shapeshifting has particularly been reported in birds. Several species of Australian parrot have shown, on average, a 4%-10% increase in bill size since 1871, and this is positively correlated with the summer temperature each year. North American dark-eyed juncos, a type of small songbird, had a link between increased bill size and short-term temperature extremes in cold environments. There have also been reported changes in mammalian species. Researchers have reported tail length increases in wood mice and tail and leg size increases in masked shrews.

"The increases in appendage size we see so far are quite small -- less than 10% -- so the changes are unlikely to be immediately noticeable," says Ryding. "However, prominent appendages such as ears are predicted to increase -- so we might end up with a live-action Dumbo in the not-so-distant future."

Next, Ryding intends to investigate shapeshifting in Australian birds firsthand by 3D scanning museum bird specimens from the past 100 years. It will give her team a better understanding of which birds are changing appendage size due to climate change and why.

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Seven personality and behavior traits identified in cats

Researchers at the University of Helsinki have developed a new comprehensive questionnaire for surveying feline personality and behaviour. A dataset of more than 4,300 cats representing 26 breed groups revealed seven personality and behaviour traits, with significant differences observed between breeds.

Cats are our most common pets, and feline behaviour is increasingly being investigated due to a range of behavioural problems. Another topic of interest in addition to behaviour traits is personality since it can be connected to behavioural problems.

"Compared to dogs, less is known about the behaviour and personality of cats, and there is demand for identifying related problems and risk factors. We need more understanding and tools to weed out problematic behaviour and improve cat welfare. The most common behavioural challenges associated with cats relate to aggression and inappropriate elimination," says doctoral researcher Salla Mikkola from the University of Helsinki and the Folkhälsan Research Center.

Seven feline personality and behaviour traits

In a questionnaire designed by Professor Hannes Lohi's research group, personality and behaviour were surveyed through a total of 138 statements. The questionnaire included comprehensive sections on background and health-related information. By employing, among other means, factor analysis to process the data, seven personality and behaviour traits in all were identified.
 

• Activity/playfulness
• Fearfulness
• Aggression towards humans
• Sociability towards humans
• Sociability towards cats
• Litterbox issues (relieving themselves in inappropriate places, precision in terms of litterbox cleanliness and substrate material)
• Excessive grooming

"While the number of traits identified in prior research varies, activity/playfulness, fearfulness and aggression are the ones from among the traits identified in our study which occur the most often in prior studies. Litterbox issues and excessive grooming are not personality traits as such, but they can indicate something about the cat's sensitivity to stress," Mikkola adds.

Differences in the prevalence of traits seen between breeds

In addition to individuals, clear personality differences can be found between breeds. In other words, certain personality and behaviour traits are more common among certain cat breeds.

"The most fearful breed was the Russian Blue, while the Abyssinian was the least fearful. The Bengal was the most active breed, while the Persian and Exotic were the most passive. The breeds exhibiting the most excessive grooming were the Siamese and Balinese, while the Turkish Van breed scored considerably higher in aggression towards humans and lower in sociability towards cats. We had already observed the same phenomenon in a prior study," says Professor Hannes Lohi from the University of Helsinki and the Folkhälsan Research Center.

The researchers wish to emphasise that no pairwise comparisons between breeds were carried out at this juncture.

"We wanted to obtain a rough idea of whether there are differences in personality traits between breeds. In further studies, we will utilise more complex models to examine factors that affect traits and problematic behaviour. In these models, we will take into consideration, in addition to its breed, the cat's age, gender, health and a wide range of environmental factors," Mikkola says.

Assessing reliability and validity

Feline behaviour and personality can be studied, for example, through questionnaires aimed at cat owners. Such questionnaires can measure feline behaviour in the long term and in everyday circumstances, which is impossible in behavioural tests. Furthermore, cats do not necessarily behave in test settings in a way typical of themselves. Due to their subjective nature, the reliability of the questionnaires must be assessed before the data can be exploited further.

"Internationally speaking, our study is the most extensive and significant survey so far, and it provides excellent opportunities for further research. The reliability of prior feline behavioural questionnaires has not been measured in such a versatile manner, nor are they as comprehensive as this one. Establishing reliability is key to making further analyses worthwhile and enabling the reliable identification of various risk factors," says Lohi.

The researchers reached out to cat owners who responded to the questionnaire one to three months ago, requesting them to fill out the questionnaire again or ask another adult living in the same household to respond to the questionnaire regarding the same cat. The goal was to assess the questionnaire's reliability both temporally and between respondents. Based on two additional datasets accumulated through this method, it was possible to evaluate the reliability of the questionnaire temporally and between respondents.

"By comparing the responses, we noted that the responses provided for the same cat were very similar, while the personality and behaviour traits were found to be reproducible and reliable. We also examined the validity of the questionnaire or whether it measures what it intended to measure. In these terms, too, the questionnaire functioned well," says Mikkola.

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Metabolic changes in plasma and immune cells associated with COVID-19 severity, can predict patient survival

COVID-19 patients have differing immune responses that lead to disease outcomes ranging from asymptomatic SARS-CoV-2 infection to death. After examining the blood samples from nearly 200 COVID-19 patients, researchers have uncovered underlying metabolic changes that regulate how immune cells react to the disease. These changes are associated with disease severity and could be used to predict patient survival. The findings were published in the journal Nature Biotechnology.

"We know that there are a range of immune responses to COVID-19, and the biological processes underlying those responses are not well understood," said co-first author Jihoon Lee, a graduate student at Fred Hutchinson Cancer Research Center. "We analyzed thousands of biological markers linked to metabolic pathways that underlie the immune system and found some clues as to what immune-metabolic changes may be pivotal in severe disease. Our hope is that these observations of immune function will help others piece together the body's response to COVID-19. The deeper understanding gained here may eventually lead to better therapies that can more precisely target the most problematic immune or metabolic changes."

The researchers collected 374 blood samples -- two draws per patient during the first week after being diagnosed with SARS-CoV-2 infection -- and analyzed their plasma and single immune cells. The analysis included 1,387 genes involved in metabolic pathways and 1,050 plasma metabolites.

In plasma samples, the team found that increased COVID-19 severity is associated with metabolite alterations, suggesting increased immune-related activity. Furthermore, through single-cell sequencing, researchers found that each major immune cell type has a distinct metabolic signature.

"We have found metabolic reprogramming that is highly specific to individual immune cell classes (e.g. "killer" CD8+ T cells, "helper" CD4+ T cells, antibody-secreting B cells, etc.) and even cell subtypes, and the complex metabolic reprogramming of the immune system is associated with the plasma global metabolome and are predictive of disease severity and even patient death," said co-first and co-corresponding author Dr. Yapeng Su, a research scientist at Institute for Systems Biology. "Such deep and clinically relevant insights on sophisticated metabolic reprogramming within our heterogeneous immune systems are otherwise impossible to gain without advanced single-cell multi-omic analysis."

"This work provides significant insights for developing more effective treatments against COVID-19. It also represents a major technological hurdle," said Dr. Jim Heath, president and professor of ISB and co-corresponding author on the paper. "Many of the data sets that are collected from these patients tend to measure very different aspects of the disease, and are analyzed in isolation. Of course, one would like these different views to contribute to an overall picture of the patient. The approach described here allows for the sum of the different data sets to be much greater than the parts, and provides for a much richer interpretation of the disease."

The research was conducted by scientists from ISB, Fred Hutchinson Cancer Research Center, Stanford University, Swedish Medical Center St. John's Cancer Institute at Saint John's Health Center, the University of Washington, the Howard Hughes Medical Institute.

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Astronomers explain origin of elusive ultradiffuse galaxies

As their name suggests, ultradiffuse galaxies, or UDGs, are dwarf galaxies whose stars are spread out over a vast region, resulting in extremely low surface brightness, making them very difficult to detect. Several questions about UDGs remain unanswered: How did these dwarfs end up so extended? Are their dark matter halos -- the halos of invisible matter surrounding the galaxies -- special?

Now an international team of astronomers, co-led by Laura Sales, an astronomer at the University of California, Riverside, reports in Nature Astronomythat it has used sophisticated simulations to detect a few "quenched" UDGs in low-density environments in the universe. A quenched galaxy is one that does not form stars.

"What we have detected is at odds with theories of galaxy formation since quenched dwarfs are required to be in clusters or group environments in order to get their gas removed and stop forming stars," said Sales, an associate professor of physics and astronomy. "But the quenched UDGs we detected are isolated. We were able to identify a few of these quenched UDGs in the field and trace their evolution backward in time to show they originated in backsplash orbits."

Here, "in the field" refers to galaxies isolated in quieter environments and not in a group or cluster environment. Sales explained that a backsplash galaxy is an object that looks like an isolated galaxy today but in the past was a satellite of a more massive system -- similar to a comet, which visits our sun periodically, but spends the bulk of its journey in isolation, far from most of the solar system.

"Isolated galaxies and satellite galaxies have different properties because the physics of their evolution is quite different," she said. "These backsplash galaxies are intriguing because they share properties with the population of satellites in the system to which they once belonged, but today they are observed to be isolated from the system."

Dwarf galaxies are small galaxies that contain anywhere from 100 million to a few billion stars. In contrast, the Milky Way has 200 billion to 400 billion stars. While all UDGs are dwarf galaxies, all dwarf galaxies are not UDGs. For example, at similar luminosity, dwarfs show a very large range of sizes, from compact to diffuse. UDGs are the tail end of most extended objects at a given luminosity. A UDG has the stellar content of a dwarf galaxy, 10-100 times smaller than the Milky Way. But its size is comparable to the Milky Way, giving it the extremely low surface brightness that makes it special.

Sales explained that the dark matter halo of a dwarf galaxy has a mass at least 10 times smaller than the Milky Way, and the size scales similarly. UDGs, however, break this rule and show a radial extension comparable to that of much larger galaxies.

"One of the popular theories to explain this was that UDGs are 'failed Milky Ways,' meaning they were destined to be galaxies like our own Milky Way but somehow failed to form stars," said José A. Benavides, a graduate student at the Institute of Theoretical and Experimental Astronomy in Argentina and the first author of the research paper. "We now know that this scenario cannot explain all UDGs. So theoretical models are arising where more than one formation mechanism may be able to form these ultradiffuse objects."

According to Sales, the value of the new work is twofold. First, the simulation used by the researchers, called TNG50, successfully predicted UDGs with characteristics similar to observed UDGs. Second, the researchers found a few rare quenched UDGs for which they have no formation mechanism.

"Using TNG50 as a 'time machine' to see how the UDGs got to where they are, we found these objects were satellites several billion years before but got expelled into a very elliptical orbit and look isolated today," she said.

The researchers also report that according to their simulations, quenched UDGs can commonly make up 25% of an ultradiffuse population of galaxies. In observations, however, this percentage is much smaller.

"This means a lot of dwarf galaxies lurking in the dark may have remained undetected to our telescopes," Sales said. "We hope our results will inspire new strategies for surveying the low-luminosity universe, which would allow for a complete census of this population of dwarf galaxies."

The study is the first to resolve the myriad of environments -- from isolated dwarfs to dwarfs in groups and clusters -- necessary to detect UDGs, and with high-enough resolution to study their morphology and structure.

Next, the research team will continue its study of UDGs in TNG50 simulations to better understand why these galaxies are so extended compared to other dwarf galaxies with the same stellar content. The researchers will use the Keck Telescope in Hawaii, one of the most powerful telescopes in the world, to measure the dark matter content of UDGs in the Virgo cluster, the closest galaxy cluster to Earth.

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Hummingbirds can smell their way out of danger

In less time than it takes to read this sentence, hummingbirds can catch a whiff of potential trouble. That's the result of new UC Riverside research showing, contrary to popular belief, the tiny birds do have an active sense of smell.

Researchers have known for some time that vultures have a highly sensitive sense of smell, with some species being compared to "airborne bloodhounds." This is due in part to their large olfactory bulbs -- tissue in the brain that controls smell.

However, hummingbirds' olfactory bulbs are, like the rest of their bodies, extremely small. Earlier studies were unable to demonstrate that hummingbirds showed a preference for the smell of flowers containing nectar. In addition, flowers pollinated by birds generally don't have strong odors, unlike those pollinated by insects. For these reasons, scientists did not previously believe the birds possessed the ability to smell things.

UCR scientists have now shown for the first time that not only can hummingbirds smell insects, but also that scent may help them stay out of danger while looking for nectar to eat. A paper describing their experiments has now been published in the journal Behavioral Ecology and Sociobiology.

"This is pretty exciting, as it is the first clear demonstration of hummingbirds using their sense of smell alone to make foraging decisions and avoid contact with potentially dangerous insects at a flower or feeder," said Erin Wilson Rankin, associate entomology professor and study co-author.

For their experiments, the researchers allowed more than 100 hummingbirds to choose between two feeders, either sugar water alone, or sugar water plus one of several chemicals whose scent signaled the presence of an insect. There were no visual differences between the two feeders offered in each of the experiments.

Tests included the scent deposited on flowers by European honeybees, an attraction chemical secreted by Argentine ants, and formic acid, a defensive compound produced by some Formica ants which is known to harm birds as well as mammals.

"If a bird has any exposed skin on their legs, formic acid can hurt, and if they get it in their eyes, it isn't pleasant," Rankin said. "It's also extremely volatile."

The hummingbirds avoided both of the ant-derived chemicals, especially the formic acid. However, they had no reaction at all to the honeybee scent, which is known to deter other bees from visiting flowers.

To ensure it was the chemical itself the birds were reacting to, and not simply a fear of new smells, the researchers did an additional test with ethyl butyrate, a common additive in human food.

"It smells like Juicy Fruit gum, which is not a smell known in nature," Rankin said. "I did not enjoy it. The birds did not care about it though and didn't go out of their way to avoid it."

Rankin said the study raises new questions about the underrated importance that scent plays in birds' foraging decisions and specifically, hummingbird foraging.

Ashley Kim, first author on the paper and current ecology doctoral student at UC San Diego, was based in the Rankin Lab at UCR while participating in this project.

"This research made me understand the importance of studying the basic biology and natural history of animals that are commonly overlooked," she said.

Kim's participation was supported by the National Science Foundation, through its Research Experiences for Undergraduates program, which helps undergraduates get hands-on experience conducting research.

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Struggling to learn a new language? Blame it on your stable brain

A study in patients with epilepsy is helping researchers understand how the brain manages the task of learning a new language while retaining our mother tongue. The study, by neuroscientists at UC San Francisco, sheds light on the age-old question of why it's so difficult to learn a second language as an adult.

The somewhat surprising results gave the team a window into how the brain navigates the tradeoff between neuroplasticity -- the ability to grow new connections between neurons when learning new things -- and stability, which allows us to maintain the integrated networks of things we've already learned. The findings appear in the Aug. 30, 2021, issue of Proceedings of the National Academy of Sciences.

"When learning a new language, our brains are somehow accommodating both of these forces as they're competing against each other," said Matt Leonard, PhD, assistant professor of neurological surgery and a member of the UCSF Weill Institute for Neurosciences.

By using electrodes on the surface of the brain to follow high-resolution neural signals, the team found that clusters of neurons scattered throughout the speech cortex appear to fine-tune themselves as a listener gains familiarity with foreign sounds.

"These are our first insights into what's changing in the brain between first hearing the sounds of a foreign language and being able to recognize them," said Leonard, who is a principal investigator on the study.

"That in-between stage is a crucial step in language learning but has been difficult to tackle, because the process is dynamic and unique to the individual," he said. "With this study, we were able to see what's actually happening in the brain regions involved in differentiating sounds during this initial phase of learning."

Brain Activity Shifts as Foreign Sounds Become Familiar

Learning the sounds of a new language is the first step in learning to use that language, said Leonard. So for this study, Leonard and lead author and postdoctoral scholar Han Yi, PhD, investigated how the activity in the dispersed brain regions associated with language shifted as the listener became more familiar with the foreign sounds.

The team worked with 10 patient volunteers, aged 19 to 59, whose native language is English, and asked them to recognize speech sounds in Mandarin. Mandarin is a tonal language in which the meaning of the word relies not only on the vowel and consonant sounds but also on subtle changes in the pitch of the voice, known as tones. Speakers of non-tonal languages like English often find it very challenging to discern these unfamiliar sounds.

Each of the volunteers had previously had brain surgery, during which electrodes were implanted in their brains to locate the source of their seizures. The study included seven patients at the UCSF Epilepsy Center, and three in the Epilepsy Center at the University of Iowa Hospitals and Clinics. The volunteers agreed to allow Leonard and his team to gather data from high-density, 256-channel electrodes placed on the surface of the brain regions that process speech sounds.

Over the course of the next few days, Leonard and Yi worked with the volunteers individually, playing recordings of several native Mandarin speakers of different ages, both male and female, pronouncing syllables like "ma" and "di" using each of the four tones. After each sound, the patient indicated whether they thought the tone was going up, down, up and then down, or staying flat, and received feedback on whether they were correct. Patients repeated this task about 200 times, over several 5- to 10-minute sessions.

After that brief amount of time, Leonard said, people had gotten through the initial learning phase and had become somewhat adept at categorizing the sounds.

"We also saw a lot of variability," he added. "Some people will get a bunch of trials right and then they'll start getting them wrong and then they'll get it right again in this kind of up-and-down that seems to be part of the learning process."

Learning New Sounds Involves Fine-Tuning Neural "Knobs"

When Leonard and Yi looked at the neural signals generated by the language learners, they saw a pattern that both surprised them and explained the performance curve they'd observed.

Data from other published studies suggested that activity across the speech cortex might increase as a person becomes more familiar with the language. What the researchers discovered instead was a spectrum of changes distributed throughout that speech cortex; with activity increasing in some areas but decreasing in others, maintaining a careful balance.

Those changes might be related to a brain area becoming tuned in to a particular tone, said Yi.

"We could see some groups of cells would respond more to the falling tone, and just keep ramping up their response, while right next to it another group of cells would increasingly engage when the person heard the dipping tone," Yi said. "It's as if these small clumps of neurons took on different roles."

In addition, which brain regions were more activated by which tone varied across individuals.

"It's more like each person's brain has a unique set of knobs that are getting fine-tuned while they're becoming familiar with these sounds," Leonard said.

Leonard and Yi think this may explain why some people pick up the sounds much more easily than others, as each unique brain strikes its own balance between maintaining the stability of the native language while calling on the plasticity required to learn a new one.

"The volunteers were able to learn the tones in Mandarin without affecting their ability to perceive pitch in English or in music," said Leonard. "These little neural knobs were all communicating with each other to reach the point where they can do the task correctly by working together."

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Over 200 health journals call on world leaders to address 'catastrophic harm to health' from climate change

Over 200 health journals across the world have come together to simultaneously publish an editorial calling on world leaders to take emergency action to limit global temperature increases, halt the destruction of nature, and protect health.

While recent targets to reduce emissions and conserve biodiversity are welcome, they are not enough and are yet to be matched with credible short and longer term plans, it warns.

The editorial is published in leading titles from every continent including The BMJ, The Lancet, the New England Journal of Medicine, the East African Medical Journal, the Chinese Science Bulletin, the National Medical Journal of India, the Medical Journal of Australia, and 50 BMJ specialist journals including BMJ Global Health and Thorax.

Never have so many journals come together to make the same statement, reflecting the severity of the climate change emergency now facing the world.

The editorial is being published ahead of the UN General Assembly next week, one of the last international meetings taking place before the (COP26) climate conference in Glasgow, UK in November. This is a crucial moment to urge all countries to deliver enhanced and ambitious climate plans to honour the goals of the Paris Agreement, the international treaty on climate change adopted by 195 countries in 2015.

For decades, health professionals and health journals have been warning of the severe and growing impacts on health from climate change and the destruction of nature .

The impact on health and survival of extreme temperatures, destructive weather events, and the widespread degradation of essential ecosystems are just some of the impacts that we are seeing more of due to a changing climate.

They disproportionately affect the most vulnerable, including children and the elderly, ethnic minorities, poorer communities and those with underlying health conditions.

The editorial urges governments to intervene to transform societies and economies, for example, by supporting the redesign of transport systems, cities, production and distribution of food, markets for financial investments, and health systems.

Substantial investment will be needed, but this will have huge positive health and economic benefits, including high quality jobs, reduced air pollution, increased physical activity, and improved housing and diet, explain the authors.

Crucially, cooperation hinges on wealthy nations doing more, they say. In particular, countries that have disproportionately created the environmental crisis must do more to support low and middle income countries to build cleaner, healthier, and more resilient societies.

"As health professionals, we must do all we can to aid the transition to a sustainable, fairer, resilient, and healthier world," they write. "We, as editors of health journals, call for governments and other leaders to act, marking 2021 as the year that the world finally changes course."

Dr Fiona Godlee, Editor-in-Chief of The BMJ, and one of the co-authors of the editorial, said: "Health professionals have been on the frontline of the covid-19 crisis and they are united in warning that going above 1.5C and allowing the continued destruction of nature will bring the next, far deadlier crisis. Wealthier nations must act faster and do more to support those countries already suffering under higher temperatures. 2021 has to be the year the world changes course -- our health depends on it."

Seye Abimbola, Editor-in-Chief of BMJ Global Health, said: "What we must do to tackle pandemics, health inequities, and climate change is the same - global solidarity and action that recognise that, within and across nations our destinies are inextricably linked, just as human health is inextricably linked to the health of the planet."

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Astronomers create 3D-printed stellar nurseries

Astronomers can't touch the stars they study, but astrophysicist Nia Imara is using 3-dimensional models that fit in the palm of her hand to unravel the structural complexities of stellar nurseries, the vast clouds of gas and dust where star formation occurs.

Imara and her collaborators created the models using data from simulations of star-forming clouds and a sophisticated 3D printing process in which the fine-scale densities and gradients of the turbulent clouds are embedded in a transparent resin. The resulting models -- the first 3D-printed stellar nurseries -- are highly polished spheres about the size of a baseball (8 centimeters in diameter), in which the star-forming material appears as swirling clumps and filaments.

"We wanted an interactive object to help us visualize those structures where stars form so we can better understand the physical processes," said Imara, an assistant professor of astronomy and astrophysics at UC Santa Cruz and first author of a paper describing this novel approach published August 25 in Astrophysical Journal Letters.

An artist as well as an astrophysicist, Imara said the idea is an example of science imitating art. "Years ago, I sketched a portrait of myself touching a star. Later, the idea just clicked. Star formation within molecular clouds is my area of expertise, so why not try to build one?" she said.

She worked with coauthor John Forbes at the Flatiron Institute's Center for Computational Astrophysics to develop a suite of nine simulations representing different physical conditions within molecular clouds. The collaboration also included coauthor James Weaver at Harvard University's School of Engineering and Applied Sciences, who helped to turn the data from the astronomical simulations into physical objects using high-resolution and photo-realistic multi-material 3D printing.

The results are both visually striking and scientifically illuminating. "Just aesthetically they are really amazing to look at, and then you begin to notice the complex structures that are incredibly difficult to see with the usual techniques for visualizing these simulations," Forbes said.

For example, sheet-like or pancake-shaped structures are hard to distinguish in two-dimensional slices or projections, because a section through a sheet looks like a filament.

"Within the spheres, you can clearly see a two-dimensional sheet, and inside it are little filaments, and that's mind boggling from the perspective of someone who is trying to understand what's going on in these simulations," Forbes said.

The models also reveal structures that are more continuous than they would appear in 2D projections, Imara said. "If you have something winding around through space, you might not realize that two regions are connected by the same structure, so having an interactive object you can rotate in your hand allows us to detect these continuities more easily," she said.

The nine simulations on which the models are based were designed to investigate the effects of three fundamental physical processes that govern the evolution of molecular clouds: turbulence, gravity, and magnetic fields. By changing different variables, such as the strength of the magnetic fields or how fast the gas is moving, the simulations show how different physical environments affect the morphology of substructures related to star formation.

Stars tend to form in clumps and cores located at the intersection of filaments, where the density of gas and dust becomes high enough for gravity to take over. "We think that the spins of these newborn stars will depend on the structures in which they form -- stars in the same filament will 'know' about each other's spins," Imara said.

With the physical models, it doesn't take an astrophysicist with expertise in these processes to see the differences between the simulations. "When I looked at 2D projections of the simulation data, it was often challenging to see their subtle differences, whereas with the 3D-printed models, it was obvious," said Weaver, who has a background in biology and materials science and routinely uses 3D printing to investigate the structural details of a wide range of biological and synthetic materials.

"I'm very interested in exploring the interface between science, art, and education, and I'm passionate about using 3D printing as a tool for the presentation of complex structures and processes in an easily understandable fashion," Weaver said. "Traditional extrusion-based 3D printing can only produce solid objects with a continuous outer surface, and that's problematic when trying to depict, gases, clouds, or other diffuse forms. Our approach uses an inkjet-like 3D printing process to deposit tiny individual droplets of opaque resin at precise locations within a surrounding volume of transparent resin to define the cloud's form in exquisite detail."

He noted that in the future the models could also incorporate additional information through the use of different colors to increase their scientific value. The researchers are also interested in exploring the use of 3D printing to represent observational data from nearby molecular clouds, such as those in the constellation Orion.

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Gut bacteria influence brain development

Extremely premature infants are at a high risk for brain damage. Researchers have now found possible targets for the early treatment of such damage outside the brain: Bacteria in the gut of premature infants may play a key role. The research team found that the overgrowth of the gastrointestinal tract with the bacterium Klebsiella is associated with an increased presence of certain immune cells and the development of neurological damage in premature babies.

Complex interplay: the gut-immune-brain axis

The early development of the gut, the brain and the immune system are closely interrelated. Researchers refer to this as the gut-immune-brain axis. Bacteria in the gut cooperate with the immune system, which in turn monitors gut microbes and develops appropriate responses to them. In addition, the gut is in contact with the brain via the vagus nerve as well as via the immune system. "We investigated the role this axis plays in the brain development of extreme preterm infants," says the first author of the study, David Seki. "The microorganisms of the gut microbiome -- which is a vital collection of hundreds of species of bacteria, fungi, viruses and other microbes -- are in equilibrium in healthy people. However, especially in premature babies, whose immune system and microbiome have not been able to develop fully, shifts are quite likely to occur. These shifts may result in negative effects on the brain," explains the microbiologist and immunologist.

Patterns in the microbiome provide clues to brain damage

"In fact, we have been able to identify certain patterns in the microbiome and immune response that are clearly linked to the progression and severity of brain injury," adds David Berry, microbiologist and head of the research group at the Centre for Microbiology and Environmental Systems Science (CMESS) at the University of Vienna as well as Operational Director of the Joint Microbiome Facility of the Medical University of Vienna and University of Vienna. "Crucially, such patterns often show up prior to changes in the brain. This suggests a critical time window during which brain damage of extremely premature infants may be prevented from worsening or even avoided."

Comprehensive study of the development of extremely premature infants

Starting points for the development of appropriate therapies are provided by the biomarkers that the interdisciplinary team was able to identify. "Our data show that excessive growth of the bacterium Klebsiella and the associated elevated ??-T-cell levels can apparently exacerbate brain damage," explains Lukas Wisgrill, Neonatologist from the Division of Neonatology, Pediatric Intensive Care Medicine and Neuropediatrics at the Department of Pediatric and Adolescent Medicine at the Medical University of Vienna. "We were able to track down these patterns because, for a very specific group of newborns, for the first time we explored in detail how the gut microbiome, the immune system and the brain develop and how they interact in this process," he adds. The study monitored a total of 60 premature infants, born before 28 weeks gestation and weighing less than 1 kilogram, for several weeks or even months. Using state-of-the-art methods -- the team examined the microbiome using 16S rRNA gene sequencing, among other methods -- the researchers analysed blood and stool samples, brain wave recordings (e.g. aEEG) and MRI images of the infants' brains.

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