New heaviest exotic antimatter nucleus

Scientists studying the tracks of particles streaming from six billion collisions of atomic nuclei at the Relativistic Heavy Ion Collider (RHIC) -- an "atom smasher" that recreates the conditions of the early universe -- have discovered a new kind of antimatter nucleus, the heaviest ever detected. Composed of four antimatter particles -- an antiproton, two antineutrons, and one antihyperon -- these exotic antinuclei are known as antihyperhydrogen-4.

Members of RHIC's STAR Collaboration made the discovery by using their house-sized particle detector to analyze details of the collision debris. They report their results in the journal Nature and explain how they've already used these exotic antiparticles to look for differences between matter and antimatter.

"Our physics knowledge about matter and antimatter is that, except for having opposite electric charges, antimatter has the same properties as matter -- same mass, same lifetime before decaying, and same interactions," said STAR collaborator Junlin Wu, a graduate student at the Joint Department for Nuclear Physics, Lanzhou University and Institute of Modern Physics, China. But the reality is that our universe is made of matter rather than antimatter, even though both are believed to have been created in equal amounts at the time of the Big Bang some 14 billion years ago.

"Why our universe is dominated by matter is still a question, and we don't know the full answer," Wu said.

RHIC, a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at DOE's Brookhaven National Laboratory, is a good place to study antimatter. Its collisions of heavy ions -- atomic nuclei that have been stripped of their electrons and accelerated close to the speed of light -- melt the boundaries of the ions' individual protons and neutrons. The energy deposited in the resulting soup of free quarks and gluons, visible matter's most fundamental building blocks, generates thousands of new particles. And like the early universe, RHIC makes matter and antimatter in nearly equal amounts. Comparing characteristics of matter and antimatter particles generated in these particle smashups might offer clues to some asymmetry that tipped the balance to favor the existence of matter in today's world.

Detecting heavy antimatter

"To study the matter-antimatter asymmetry, the first step is to discover new antimatter particles," said STAR physicist Hao Qiu, Wu's advisor at IMP. "That's the basic logic behind this study."

STAR physicists had previously observed nuclei made of antimatter created in RHIC collisions. In 2010, they detected the antihypertriton. This was the first instance of an antimatter nucleus containing a hyperon, which is a particle containing at least one "strange" quark rather than just the lighter "up" and "down" quarks that make up ordinary protons and neutrons. Then, just a year later, STAR physicists toppled that heavyweight antimatter record by detecting the antimatter equivalent of the helium nucleus: antihelium-4.

A more recent analysis suggested that antihyperhydrogen-4 might also be within reach. But detecting this unstable antihypernucleus -- where the addition of an antihyperon (specifically an antilambda particle) in place of one of the protons in antihelium would edge out the heavyweight record holder once again -- would be a rare event. It would require all four components -- one antiproton, two antineutrons, and one antilambda -- to be emitted from the quark-gluon soup generated in RHIC collisions in just the right place, headed in the same direction, and at the right time to clump together into a temporarily bound state.

"It is only by chance that you have these four constituent particles emerge from the RHIC collisions close enough together that they can combine to form this antihypernucleus," said Brookhaven Lab physicist Lijuan Ruan, one of two co-spokespersons for the STAR Collaboration.

Needle in a "pi" stack

To find antihyperhydrogen-4, the STAR physicists looked at the tracks of the particles this unstable antihypernucleus decays into. One of those decay products is the previously detected antihelium-4 nucleus; the other is a simple positively charged particle called a pion (pi+).

"Since antihelium-4 was already discovered in STAR, we used the same method used previously to pick up those events and then reconstructed them with pi+ tracks to find these particles," Wu said.

By reconstruct, he means retracing the trajectories of the antihelium-4 and pi+ particles to see if they emerged from a single point. But RHIC smashups produce a lot of pions. And to find the rare antihypernuclei, the scientists were sifting through billions of collision events! Each antihelium-4 emerging from a collision could be paired with hundreds or even 1,000 pi+ particles.

"The key was to find the ones where the two particle tracks have a crossing point, or decay vertex, with particular characteristics," Ruan said. That is, the decay vertex has to be far enough from the collision point that the two particles could have originated from the decay of an antihypernucleus formed just after the collision from particles initially generated in the fireball.

The STAR team worked hard to rule out the background of all the other potential decay pair partners. In the end, their analysis turned up 22 candidate events with an estimated background count of 6.4.

"That means around six of the ones that look like decays from antihyperhydrogen-4 may just be random noise," said Emilie Duckworth, a doctoral student at Kent State University whose role was to ensure that the computer code used to sift through all those events and pick out the signals was written properly.

Subtracting that background from 22 gives the physicists confidence they've detected about 16 actual antihyperhydrogen-4 nuclei.

Matter-antimatter comparison

The result was significant enough for the STAR team to do some direct matter-antimatter comparisons.

They compared the lifetime of antihyperhydrogen-4 with that of hyperhydrogen-4, which is made of the ordinary-matter varieties of the same building blocks. They also compared lifetimes for another matter-antimatter pair: the antihypertriton and the hypertriton.

Neither showed a significant difference, which did not surprise the scientists.

The experiments, they explained, were a test of a particularly strong form of symmetry. Physicists generally agree that a violation of this symmetry would be extremely rare and will not hold the answer to the matter-antimatter imbalance in the universe.

"If we were to see a violation of [this particular] symmetry, basically we'd have to throw a lot of what we know about physics out the window," Duckworth said.

So, in this case, it was sort of comforting that the symmetry still works. The team agreed the results further confirmed that physicists' models are correct and are "a great step forward in the experimental research on antimatter."

The next step will be to measure the mass difference between the particles and antiparticles, which Duckworth, who was selected in 2022 to receive funding from the DOE Office of Science Graduate Student Research program, is pursuing.

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Antarctica vulnerable to invasive species hitching rides on plastic and organic debris

Antarctica's unique ecosystems could be threatened by the arrival of non-native marine species and marine pollution from Southern Hemisphere landmasses, new oceanographic modelling shows.

In a study published today in Global Change Biology, scientists from UNSW Sydney, ANU, University of Otago and the University of South Florida suggest that floating objects can reach Antarctic waters from more sources than previously thought.

"An increasing abundance of plastics and other human made debris in the oceans means there are potentially more opportunities for biota to reach Antarctica," says lead author Dr Hannah Dawson, who completed the study as part of her PhD at UNSW, and is now based at the University of Tasmania.

Non-native species -- including a range of small marine invertebrates -- can reach Antarctica by catching a ride on floating objects like kelp, driftwood, pumice, and plastic. Previously, scientists thought these species only drifted from remote and unpopulated islands in the Southern Ocean. However, this new research suggests they can reach the Antarctic coastline from all southern continents.

"We knew that kelp could raft to Antarctica from sub-Antarctic islands, such as Macquarie and Kerguelen Islands, but our study suggests that floating objects can reach Antarctica from much further north, including South America, New Zealand, Australia, and South Africa," says Dr Dawson.

Co-author Professor Crid Fraser from the University of Otago says that kelp could deal a potential double whammy blow to Antarctica's marine ecosystem.

"Southern bull kelp and giant kelp are very big -- often more than 10 m long -- and create forest-like habitat for a lot of small animals, which they can carry with them on the long rafting trips to Antarctica," she says.

"If they colonise Antarctica, marine ecosystems there could change dramatically."

Southern Ocean modelling

Using modelled surface current and wave data from 1997 to 2015, the team tracked the movement of floating debris from various Southern Hemisphere land sources toward Antarctica, providing valuable new insight into the frequency and pathways of marine dispersal.

"We were able to analyse how frequent these rafting connections are by simulating dispersal pathways across 19 years of differing oceanographic conditions," ANU co-author Dr Adele Morrison says.

"We found that rafting objects reached the Antarctic coastline in each of the years simulated. There seems to be a constant bombardment of anything that floats -- whether it's kelp or a plastic bottle."

Dr Dawson likens the computer modelling process to the game 'Poohsticks' from the children's classic Winnie the Pooh.

"Imagine dropping a stick into a river and then running downstream to see where it ends up -- that's essentially what we do with our modelling, using simulated ocean currents, instead of a river."

"We released millions of virtual particles -- representing drift objects -- from each of the source land masses and modelled their trajectories across 19 years of estimated surface ocean currents and surface waves. After running the simulations, we were able to see where they would likely end up.

"The shortest time it took for particles to reach the Antarctic coastline was from Macquarie Island, south of New Zealand, some of which arrived in just under 9 months. On average, the longest journey was for objects released from South America," she says.

Warmer waters

The research also sheds light on which regions of the Antarctic coastline are most at risk to non-native species arrivals.

"Most of these rafting objects arrive at the tip of the Antarctic Peninsula, a region with relatively warm ocean temperatures and often ice-free conditions. These factors make it a likely area for non-native species to first establish," says UNSW Scientia Professor Matthew England, who is also a co-author.

The dramatic drop in Antarctic sea ice over the last couple of years makes these rafting connections particularly concerning.

"Sea ice is very abrasive and so acts as a barrier for many non-native species to successfully establish around Antarctica," Dr Dawson says.

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Placebos reduce stress, anxiety, depression -- even when people know they are placebos

A study out of Michigan State University found that nondeceptive placebos, or placebos given with people fully knowing they are placebos, effectively manage stress -- even when the placebos are administered remotely.

Researchers recruited participants experiencing prolonged stress from the COVID-19 pandemic for a two-week randomized controlled trial.

Half of the participants were randomly assigned to a nondeceptive placebo group and the other half to the control group that took no pills.

The participants interacted with a researcher online through four virtual sessions on Zoom.

Those in the nondeceptive placebo group received information on the placebo effect and were sent placebo pills in the mail along with and instructions on taking the pills.

The study, published in Applied Psychology: Health and Well-Being, found that the nondeceptive group showed a significant decrease in stress, anxiety and depression in just two weeks compared to the no-treatment control group.

Participants also reported that the nondeceptive placebos were easy to use, not burdensome and appropriate for the situation.

"Exposure to long-term stress can impair a person's ability to manage emotions and cause significant mental health problems long-term, so we're excited to see that an intervention that takes minimal effort can still lead to significant benefits," said Jason Moser, co-author of the study and professor in MSU's Department of Psychology.

"This minimal burden makes nondeceptive placebos an attractive intervention for those with significant stress, anxiety and depression."

The researchers are particularly hopeful in the ability to remotely administer the nondeceptive placebos by health care providers.

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Extraterrestrial chemistry with earthbound possibilities

Who are we? Why are we here? As the Crosby, Stills, Nash & Young song suggests, we are stardust, the result of chemistry occurring throughout vast clouds of interstellar gas and dust. To better understand how that chemistry could create prebiotic molecules -- the seeds of life on Earth and possibly elsewhere -- researchers investigated the role of low-energy electrons created as cosmic radiation traverses through ice particles. Their findings may also inform medical and environmental applications on our home planet.

Undergraduate student Kennedy Barnes will present the team's results at the fall meeting of the American Chemical Society (ACS).

"The first detection of molecules in space was made by Wellesley College alum Annie Jump Cannon more than a hundred years ago," says Barnes, who, with fellow undergraduate Rong Wu, led this study at Wellesley, mentored by chemistry professor Christopher Arumainayagam and physics professor James Battat. Since Cannon's discovery, scientists have been interested in finding out how extraterrestrial molecules form. "Our goal is to explore the relative importance of low-energy electrons versus photons in instigating the chemical reactions responsible for the extraterrestrial synthesis of these prebiotic molecules," Barnes explains.

The few studies that previously probed this question suggested that both electrons and photons can catalyze the same reactions. Studies by Barnes and colleagues, however, hint that the prebiotic molecule yield from low-energy electrons and photons could be significantly different in space. "Our calculations suggest that the number of cosmic-ray-induced electrons within cosmic ice could be much greater than the number of photons striking the ice," Barnes explains. "Therefore, electrons likely play a more significant role than photons in the extraterrestrial synthesis of prebiotic molecules."

Aside from cosmic ice, her research into low-energy electrons and radiation chemistry also has potential applications on Earth. Barnes and colleagues recently studied the radiolysis of water, finding evidence of electron-stimulated release of hydrogen peroxide and hydroperoxyl radicals, which destroy stratospheric ozone and act as damaging reactive oxygen species in cells.

"A lot of our water radiolysis research findings could be used in medical applications and medical simulations," Barnes shares, offering the example of using high-energy radiation to treat cancer. "I once had a biochemistry professor say that humans are basically bags of water. So, other scientists are investigating how low-energy electrons produced in water affect our DNA molecules."

She also says the team's findings are applicable to environmental remediation efforts where wastewater is being treated with high-energy radiation, which produces large numbers of low-energy electrons that are assumed to be responsible for the destruction of hazardous chemicals.

Back to space chemistry, in attempting to better understand prebiotic molecule synthesis, the researchers didn't limit their efforts to mathematical modeling; they also tested their hypothesis by mimicking the conditions of space in the lab. They use an ultrahigh-vacuum chamber containing an ultrapure copper substrate that they can cool to ultralow temperatures, along with an electron gun that produces low-energy electrons and a laser-driven plasma lamp that produces low-energy photons. The scientists then bombard nanoscale ice films with electrons or photons to see what molecules are produced.

"Although we have previously focused on how this research is applicable to interstellar submicron ice particles, it is also relevant to cosmic ice on a much larger scale, like that of Jupiter's moon Europa, which has a 20-mile-thick ice shell," says Barnes.

Thus, she suggests their research will help astronomers understand data from space exploration missions such as NASA's James Webb Space Telescope as well as the Europa Clipper, initially expected to launch in October 2024. Barnes hopes that their findings will inspire other researchers to incorporate low-energy electrons into their astrochemistry models that simulate what happens within cosmic ices.

Barnes and colleagues are also varying the molecular composition of ice films and exploring atom addition reactions to see if low-energy electrons can produce other prebiotic chemistries. This work is being performed in collaboration with researchers at the Laboratory for the Study of Radiation and Matter in Astrophysics and Atmospheres in France.

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New images reveal global air quality trends

The global concentrations of one of the main air pollutants known to affect human health have been graphically illustrated for the first time by a team of scientists.

The Air Quality Stripes which were created by the University of Leeds, the University of Edinburgh, North Carolina State University, and the UK Met Office, starkly contrast the significant improvements in air quality across much of Europe with the alarming deterioration in parts of Africa and Central Asia.

The project's findings highlight both the successes and ongoing challenges in tackling air pollution worldwide.

Dr Kirsty Pringle from EPCC at the University of Edinburgh and co-director of the project, said: "Air pollution is often called the 'invisible killer', but these images make the invisible visible, showing the changes in particulate matter pollution over the decades."

Dr Jim McQuaid, an Associate Professor of Atmospheric Composition in the Leeds' School of Earth and Environment who worked on the Air Quality Stripes project with Dr Pringle, said: "The bottom line is that air pollution is one of the world's leading risk factors for death, it is thought to contribute to one in ten deaths globally.

"Our Air Quality Stripes show the huge range in trends and concentrations around the world. The stripes demonstrate that there is still more work to be done to reduce people's exposure to poor air quality, and in some places a great deal more!"

Inspired by the world-famous climate warming stripes image, the researchers created their own illustration to plot the changing trends in outdoor concentrations of what is known as particulate matter air pollution, a mix of tiny liquid or solid particles such as dust, dirt, soot, or smoke, which are found throughout the atmosphere.

Dr Steven Turnock, a senior scientist from the UK Met Office who provided the data for the Air Quality Stripes project, said: "Presenting this scientific data as Air Quality stripes really brings into focus the stark contrast in air quality trends and people's exposure to poor air quality depending on where they live."

There are stripes for the capital city of every nation worldwide with two additional cities for China, India, and the United States. The research team also included their own cities of Leeds, Edinburgh, and Exeter.

The lightest blue stripes meet the World Health Organisation Air Quality Guidelines which were introduced in 2021, with all other colours exceeding the guideline values.

Data from computer simulations and satellite observations were combined to estimate the changing concentrations of particulate matter since the beginning of the industrial revolution, with the colour palette for the stripes devised by an artist who analysed over 200 online images of "air pollution" to identify the dominant colour palettes.

Key Findings:

• Europe's Air Quality Gains: The images show substantial reductions in particulate matter levels across most of Europe (predominantly Western Europe). Stricter air quality regulations and technological advancements have successfully reduced particulate matter concentrations in most European cities (e.g. London, Brussels, Berlin).
• Worsening Conditions in Central Asia and parts of Africa: The visualisations reveal a concerning rise in particulate matter pollution in many cities in central Asia and Africa (e.g. Islamabad, Delhi, Nairobi). Rapid urbanisation, industrial growth, and limited regulatory frameworks are contributing to this troubling trend, which poses significant health risks to local populations.
• Global Disparities: The images highlight the stark disparities in air quality progress between different regions, emphasising the need for targeted international efforts to address the growing air pollution crisis in the most affected areas.
• The influence of natural sources was particularly notable in some locations, these sources include desert dust and wildfires, proximity to the coast was often quite noticeable with locations such as Jakarta having lower levels than might be expected.

A cocktail of pollutants

Particulate matter, or PM2.5, have a diameter less than a 30th of the width of a human hair and can penetrate deep into our lungs easily. The smallest particles cross into the bloodstream and affect our health, and some have even been detected in the blood of unborn children.

They can come from natural sources such as volcanoes and deserts but are also produced by human activities such as industry, cars, agriculture, domestic burning, and fires arising from climate change.

PM2.5 has been linked to a very wide range of health issues ranging from breathing problems like asthma, to reduced lung health, increased likelihood of developing cancer and heart disease, and an increased risk of developing many diseases including diabetes, Alzheimer's, and Parkinson's.

The World Health Organisation recommends that the annual average concentration of PM2.5 should not exceed a concentration of 5 micrograms per cubic meter air (5 ug/m³). This new guideline is a concentration which is generally classed as very good air quality. It is important to remember that there is NO safe level of PM2.5 recognised by medical science. At present, 99% of the world's population live with concentrations above this value, with the highest PM2.5 levels typically found in low- and middle-income countries.

TheAQ stripes use an annual average to take account of the ups and downs due to changes in weather patterns throughout the year, and to make comparison between locations simpler. However the researchers point out that even short-term exposure to very high levels can quickly have acute health effects requiring medical treatment.

Dr McQuaid added: "We created these to try to illustrate the complex data that computer models generate, into something that is much easier to understand.

"Strangely, one of the major headaches for us was the colour scheme. We finally went for blue to black, representing nice clean blue skies, through to black for extremely high levels of pollution.

"In the end we contacted a colleague in the US (Douglas Hamilton) and he worked with one of his team to create a colour scheme using an internet search of images tagged as 'air pollution' and they came up with what we finally went with. It was very similar to what we already had, but great to get external validation.

"To me it's all about that lightbulb moment when someone understands it; that sudden 'oh yeah now I get it!' I wanted it to be simple enough that non-experts could look at it and be able to understand it without having done science since leaving school. "

Dr Pringle added: "The images show that it is possible to reduce air pollution; the air in many cities in Europe is much cleaner now than it was 100 years ago, and this is improving our health. We really hope similar improvements can be achieved across the globe."

The Air Quality Stripes follow in the footsteps of the Climate Warming Stripes which were created by Professor Ed Hawkins at the National Centre for Atmospheric Science and University of Reading in 2018 and have since become very widely used as a visual representation of the Earth's warming climate.

Read more at Science Daily

Life from a drop of rain: New research suggests rainwater helped form the first protocell walls

One of the major unanswered questions about the origin of life is how droplets of RNA floating around the primordial soup turned into the membrane-protected packets of life we call cells.

A new paper by engineers from the University of Chicago's Pritzker School of Molecular Engineering (UChicago PME), the University of Houston's Chemical Engineering Department, and biologists from the UChicago Chemistry Department, have proposed a solution.

In the paper, published today in Science Advances, UChicago PME postdoctoral researcher Aman Agrawal and his co-authors -- including UChicago PME Dean Emeritus Matthew Tirrell and Nobel Prize-winning biologist Jack Szostak -- show how rainwater could have helped create a meshy wall around protocells 3.8 billion years ago, a critical step in the transition from tiny beads of RNA to every bacterium, plant, animal, and human that ever lived.

"This is a distinctive and novel observation," Tirrell said.

The research looks at "coacervate droplets" -- naturally occurring compartments of complex molecules like proteins, lipids, and RNA. The droplets, which behave like drops of cooking oil in water, have long been eyed as a candidate for the first protocells. But there was a problem. It wasn't that these droplets couldn't exchange molecules between each other, a key step in evolution, the problem was that they did it too well, and too fast.

Any droplet containing a new, potentially useful pre-life mutation of RNA would exchange this RNA with the other RNA droplets within minutes, meaning they would quickly all be the same. There would be no differentiation and no competition -- meaning no evolution.

And that means no life.

"If molecules continually exchange between droplets or between cells, then all the cells after a short while will look alike, and there will be no evolution because you are ending up with identical clones," Agrawal said.

Engineering a solution

Life is by nature interdisciplinary, so Szostak, the director of UChicago's Chicago Center for the Origins of Life, said it was natural to collaborate with both UChicago PME, UChicago's interdisciplinary school of molecular engineering, and the chemical engineering department at the University of Houston.

"Engineers have been studying the physical chemistry of these types of complexes -- and polymer chemistry more generally -- for a long time. It makes sense that there's expertise in the engineering school," Szostak said. "When we're looking at something like the origin of life, it's so complicated and there are so many parts that we need people to get involved who have any kind of relevant experience."

In the early 2000s, Szostak started looking at RNA as the first biological material to develop. It solved a problem that had long stymied researchers looking at DNA or proteins as the earliest molecules of life.

"It's like a chicken-egg problem. What came first?" Agrawal said. "DNA is the molecule which encodes information, but it cannot do any function. Proteins are the molecules which perform functions, but they don't encode any heritable information."

Researchers like Szostak theorized that RNA came first, "taking care of everything" in Agrawal's words, with proteins and DNA slowly evolving from it.

"RNA is a molecule which, like DNA, can encode information, but it also folds like proteins so that it can perform functions such as catalysis as well," Agrawal said.

RNA was a likely candidate for the first biological material. Coacervate droplets were likely candidates for the first protocells. Coacervate droplets containing early forms of RNA seemed a natural next step.

That is until Szostak poured cold water on this theory, publishing a paper in 2014 showing that RNA in coacervate droplets exchanged too rapidly.

"You can make all kinds of droplets of different types of coacervates, but they don't maintain their separate identity. They tend to exchange their RNA content too rapidly. That's been a long-standing problem," Szostak said. "What we showed in this new paper is that you can overcome at least part of that problem by transferring these coacervate droplets into distilled water -- for example, rainwater or freshwater of any type -- and they get a sort of tough skin around the droplets that restricts them from exchanging RNA content."

'A spontaneous combustion of ideas'

Agrawal started transferring coacervate droplets into distilled water during his PhD research at the University of Houston, studying their behavior under an electric field. At this point, the research had nothing to do with the origin of life, just studying the fascinating material from an engineering perspective.

"Engineers, particularly Chemical and Materials, have good knowledge of how to manipulate material properties such as interfacial tension, role of charged polymers, salt, pH control, etc.," said University of Houston Prof. Alamgir Karim, Agrawal's former thesis advisor and a senior co-author of the new paper. "These are all key aspects of the world popularly known as 'complex fluids' -- think shampoo and liquid soap."

Agrawal wanted to study other fundamental properties of coacervates during his PhD. It wasn't Karim's area of study, but Karim had worked decades earlier at the University of Minnesota under one of the world's top experts -- Tirrell, who later became founding dean of the UChicago Pritzker School of Molecular Engineering.

During a lunch with Agrawal and Karim, Tirrell brought up how the research into the effects of distilled water on coacervate droplets might relate to the origin of life on Earth. Tirrell asked where distilled water would have existed 3.8 billion years ago.

"I spontaneously said 'rainwater!' His eyes lit up and he was very excited at the suggestion," Karim said. "So, you can say it was a spontaneous combustion of ideas or ideation!"

Tirrell brought Agrawal's distilled water research to Szostak, who had recently joined the University of Chicago to lead what was then called the Origins of Life Initiative. He posed the same question he had asked Karim.

"I said to him, 'Where do you think distilled water could come from in a prebiotic world?'" Tirrell recalled. "And Jack said exactly what I hoped he would say, which was rain."

Working with RNA samples from Szostak, Agrawal found that transferring coacervate droplets into distilled water increased the time scale of RNA exchange -- from mere minutes to several days. This was long enough for mutation, competition, and evolution.

"If you have protocell populations that are unstable, they will exchange their genetic material with each other and become clones. There is no possibility of Darwinian evolution," Agrawal said. "But if they stabilize against exchange so that they store their genetic information well enough, at least for several days so that the mutations can happen in their genetic sequences, then a population can evolve."

Rain, checked

Initially, Agrawal experimented with deionized water, which is purified under lab conditions. "This prompted the reviewers of the journal who then asked what would happen if the prebiotic rainwater was very acidic," he said.

Commercial lab water is free from all contaminants, has no salt, and lives with a neutral pH perfectly balanced between base and acid. In short, it's about as far from real-world conditions as a material can get. They needed to work with a material more like actual rain.

What's more like rain than rain?

"We simply collected water from rain in Houston and tested the stability of our droplets in it, just to make sure what we are reporting is accurate," Agrawal said.

In tests with the actual rainwater and with lab water modified to mimic the acidity of rainwater, they found the same results. The meshy walls formed, creating the conditions that could have led to life.

The chemical composition of the rain falling over Houston in the 2020s is not the rain that would have fallen 750 million years after the Earth formed, and the same can be said for the model protocell system Agrawal tested. The new paper proves that this approach of building a meshy wall around protocells is possible and can work together to compartmentalize the molecules of life, putting researchers closer than ever to finding the right set of chemical and environmental conditions that allow protocells to evolve.

Read more at Science Daily

Mitochondria are flinging their DNA into our brain cells

As direct descendants of ancient bacteria, mitochondria have always been a little alien.

Now a study shows that mitochondria are possibly even stranger than we thought.

Mitochondria in our brain cells frequently fling their DNA into the nucleus, the study found, where the DNA becomes integrated into the cells' chromosomes. And these insertions may be causing harm: Among the study's nearly 1,200 participants, those with more mitochondrial DNA insertions in their brain cells were more likely to die earlier than those with fewer insertions.

"We used to think that the transfer of DNA from mitochondria to the human genome was a rare occurrence," says Martin Picard, mitochondrial psychobiologist and associate professor of behavioral medicine at Columbia University Vagelos College of Physicians and Surgeons and in the Robert N. Butler Columbia Aging Center. Picard led the study with Ryan Mills of the University of Michigan.

"It's stunning that it appears to be happening several times during a person's lifetime, Picard adds. "We found lots of these insertions across different brain regions, but not in blood cells, explaining why dozens of earlier studies analyzing blood DNA missed this phenomenon."

Mitochondrial DNA behaves like a virus

Mitochondria live inside all our cells, but unlike other organelles, mitochondria have their own DNA, a small circular strand with about three dozen genes. Mitochondrial DNA is a remnant from the organelle's forebears: ancient bacteria that settled inside our single-celled ancestors about 1.5 billion years ago.

In the past few decades, researchers discovered that mitochondrial DNA has occasionally "jumped" out of the organelle and into human chromosomes.

"The mitochondrial DNA behaves similar to a virus in that it makes use of cuts in the genome and pastes itself in, or like jumping genes known as retrotransposons that move around the human genome," says Mills.

The insertions are called nuclear-mitochondrial segments -- NUMTs ("pronounced new-mites") -- and have been accumulating in our chromosomes for millions of years.

"As a result, all of us are walking around with hundreds of vestigial, mostly benign, mitochondrial DNA segments in our chromosomes that we inherited from our ancestors," Mills says.

Mitochondrial DNA insertions are common in the human brain

Research in just the past few years has shown that "NUMTogenesis" is still happening today.

"Jumping mitochondrial DNA is not something that only happened in the distant past," says Kalpita Karan, a postdoc in the Picard lab who conducted the research with Weichen Zhou, a research investigator in the Mills lab. "It's rare, but a new NUMT becomes integrated into the human genome about once in every 4,000 births. This is one of many ways, conserved from yeast to humans, by which mitochondria talk to nuclear genes."

The realization that new inherited NUMTs are still being created made Picard and Mills wonder if NUMTs could also arise in brain cells during our lifespan.

"Inherited NUMTs are mostly benign, probably because they arise early in development and the harmful ones are weeded out," says Zhou. But if a piece of mitochondrial DNA inserts itself within a gene or regulatory region, it could have important consequences on that person's health or lifespan. Neurons may be particularly susceptible to damage caused by NUMTs because when a neuron is damaged, the brain does not usually make a new brain cell to take its place.

To examine the extent and impact of new NUMTs in the brain, the team worked with Hans Klein, assistant professor in the Center for Translational and Computational Neuroimmunology at Columbia, who had access to DNA sequences from participants in the ROSMAP aging study (led by David Bennett at Rush University). The researchers looked for NUMTs in different regions of the brain using banked tissue samples from more than 1,000 older adults.

Their analysis showed that nuclear mitochondrial DNA insertion happens in the human brain -- mostly in the prefrontal cortex -- and likely several times over during a person's lifespan.

They also found that people with more NUMTs in their prefrontal cortex died earlier than individuals with fewer NUMTs. "This suggests for the first time that NUMTs may have functional consequences and possibly influence lifespan," Picard says. "NUMT accumulation can be added to the list of genome instability mechanisms that may contribute to aging, functional decline, and lifespan."

Stress accelerates NUMTogenesis

What causes NUMTs in the brain, and why do some regions accumulate more than others?

To get some clues, the researchers looked at a population of human skin cells that can be cultured and aged in a dish over several months, enabling exceptional longitudinal "lifespan" studies.

These cultured cells gradually accumulated several NUMTs per month, and when the cells' mitochondria were dysfunctional from stress, the cells accumulated NUMTs four to five times more rapidly.

"This shows a new way by which stress can affect the biology of our cells," Karan says. "Stress makes mitochondria more likely to release pieces of their DNA and these pieces can then 'infect' the nuclear genome," Zhou adds. It's just one way mitochondria shape our health beyond energy production.

Read more at Science Daily

New view of North Star reveals spotted surface

Researchers using Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array have identified new details about the size and appearance of the North Star, also known as Polaris. The new research is published in The Astrophysical Journal.

Earth's North Pole points to a direction in space marked by the North Star. Polaris is both a navigation aid and a remarkable star in its own right. It is the brightest member of a triple-star system and is a pulsating variable star. Polaris gets brighter and fainter periodically as the star's diameter grows and shrinks over a four-day cycle.

Polaris is a kind of star known as a Cepheid variable. Astronomers use these stars as "standard candles" because their true brightness depends on their period of pulsation: Brighter stars pulsate slower than fainter stars. How bright a star appears in the sky depends on the star's true brightness and the distance to the star. Because we know the true brightness of a Cepheid based on its pulsational period, astronomers can use them to measure the distances to their host galaxies and to infer the expansion rate of the universe.

A team of astronomers led by Nancy Evans at the Center for Astrophysics | Harvard & Smithsonian observed Polaris using the CHARA optical interferometric array of six telescopes at Mount Wilson, Calif. The goal of the investigation was to map the orbit of the close, faint companion that orbits Polaris every 30 years.

"The small separation and large contrast in brightness between the two stars makes it extremely challenging to resolve the binary system during their closest approach," Evans said.

The CHARA Array combines the light of six telescopes that are spread across the mountaintop at the historic Mount Wilson Observatory. By combining the light, the CHARA Array acted like a 330-meter telescope to detect the faint companion as it passed close to Polaris. The observations of Polaris were recorded using the MIRC-X camera which was built by astronomers at the University of Michigan and Exeter University in the U.K. The MIRC-X camera has the remarkable ability to capture details of stellar surfaces.

The team successfully tracked the orbit of the close companion and measured changes in the size of the Cepheid as it pulsated. The orbital motion showed that Polaris has a mass five times larger than that of the Sun. The images of Polaris showed that it has a diameter 46 times the size of the Sun.

The biggest surprise was the appearance of Polaris in close-up images. The CHARA observations provided the first glimpse of what the surface of a Cepheid variable looks like.

CHARA Array false-color image of Polaris from April 2021 that reveals large bright and dark spots on the surface. Polaris appears about 600,000 times smaller than the Full Moon in the sky.

"The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time," said Gail Schaefer, director of the CHARA Array. The presence of spots and the rotation of the star might be linked to a 120-day variation in measured velocity.

"We plan to continue imaging Polaris in the future," said John Monnier, an astronomy professor at the University of Michigan. "We hope to better understand the mechanism that generates the spots on the surface of Polaris."

The new observations of Polaris were made and recorded as part of the open access program at the CHARA Array, where astronomers from around the world can apply for time through the National Optical-Infrared Astronomy Research Laboratory (NOIRLab).

The CHARA Array is located at the Mount Wilson Observatory in the San Gabriel Mountains of southern California. The six telescopes of the CHARA Array are arranged along three arms. The light from each telescope is transported through vacuum pipes to the central beam combining lab. All the beams converge on the MIRC-X camera in the lab.

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Action plan to help patients with lung disease cope with wildfire smoke

A multidisciplinary team of UC Davis Health experts are calling on health systems to create wildfire preparedness action plans to support patients with preexisting respiratory diseases. They are urging providers to proactively put in place interventions to mitigate the effects of poor air quality from smoke.

Their article, published in the Journal of the COPD Foundation, identifies the needs of high-risk populations when affected by wildfire smoke. It outlines an action plan for health systems to help these groups with the burdens of poor air quality from wildfires.

"Patients being treated for respiratory conditions are at high-risk of exacerbations of symptoms when they are exposed to wildfire smoke," said Reshma Gupta, chief of population health and accountable care at UC Davis Health and co-author of the article. "Unfortunately, wildfire frequency and severity are increasing in the United States and negatively affecting these clinically at-risk and underserved communities. So, there is a significant need for us to install interventions to mitigate the health threat posed by wildfires."

Health impacts of poor air quality

Many components of wildfire smoke can have adverse impacts on health, especially for those with preexisting respiratory diseases.

Currently more than 34 million people living in the United States live with a chronic lung disease like asthma, chronic obstructive pulmonary disease (COPD) or Alpha-1 antitrypsin deficiency (AATD) according to the American Lung Association.

Exposure to wildfire-related air pollutants has been shown to cause and exacerbate diseases of the lungs, heart, brain and nervous system, skin and other major organs.

For patients being treated for preexisting respiratory conditions, poor air quality causes inflammation in the lungs. This can exacerbate symptoms and lead to emergency department visits and hospitalizations.

"Poor air quality can trigger exacerbations -- acute increase in shortness of breath, cough, dyspnea -- even leading to hospitalization," explained Brooks Kuhn, co-director of the Comprehensive COPD Clinic at UC Davis Health and co-author of the article. "The impact is not just transient: Respiratory exacerbations lead to persistent and accelerated worsening of lung function."

And adults are not the only ones at risk for these complications.

"Children also see these impacts when they are exposed to poor air quality from wildfires," said Kiran Nandalike, chief of pediatric pulmonology at UC Davis Children's Hospital. "As we see more wildfires impacting our communities each year, the urgency for health systems to outline a response to support patients is pressing."

Wildfire population health approach

The targeted wildfire preparedness action plan adopted by UC Davis Health uses a population health approach. This means care teams with providers from different specialties proactively work with patients who are at higher risk of developing symptoms from poor air quality.

"A population health approach zeroes in on targeted interventions tailored to specific communities or population groups," Gupta explained. "This approach considers a range of determinants, including social, economic, environmental and behavioral factors, which affect the health of these groups."

The team's wildfire preparedness action plan includes:

• Identifying clinically at-risk and underserved patient populations using well-validated, condition-targeted registries
• Assembling multidisciplinary care teams to understand the needs of these communities and patients
• Creating custom analytics and wildfire-risk stratification
• Developing care pathways based on wildfire-risk tiers by disease, risk of exposure and health care access
• Identifying outcome measures tailored to interventions with a commitment to continuous, iterative improvement efforts

"We have seen population health approaches be successfully implemented to support patients with dementia, chronic kidney disease, and cancer," Gupta said. "Using this model, we can adapt to the threat of poor air quality from wildfires and adopt a proactive approach to meet the needs of clinically at-risk and underserved patients."

UC Davis Health experience with wildfires

As the regional academic health system in Northern California, UC Davis Health has been at the epicenter of recent wildfires -- including the recent Park Fire, the fourth largest in California history. Because of this experience, the health system team has experience caring for patients in the most affected areas.

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Searching old stem cells that stay young forever

The sea anemone Nematostella vectensis is potentially immortal. Using molecular genetic methods, developmental biologists led by Ulrich Technau from the University of Vienna have now identified possible candidates for multipotent stem cells in the sea anemone for the first time. These stem cells are regulated by evolutionary highly conserved genes, which in humans are usually only active in the formation of egg and sperm cells, but give ancient animal phyla such as cnidarians a high degree of regenerative capacity to even escape ageing. The results are currently being published in Science Advances and could also provide insights into the human ageing process in the future.

"We live as long as our stem cells" is a somewhat bold but essentially accurate statement.

Stem cells contribute to the constant renewal of various cells and tissues in humans, e.g. blood cells, skin or hair.

If stem cells lose this ability or their number decreases in the course of life, the body ages or develops diseases.

Stem cells are therefore of great interest for biomedical research.

While humans and most vertebrates can only regenerate parts of certain organs or limbs, other animal groups have far stronger regeneration mechanisms.

This ability is made possible by pluripotent or multipotent stem cells, which can form (differentiate) almost all cell types of the body.

The sea anemone Nematostella vectensis is also highly regenerative: it can reproduce asexually by budding and also shows no signs of ageing, which makes it an interesting subject for stem cell research.

However, researchers have not yet been able to identify any stem cells in these animals.

Using the new "Single Cell Genomics" method, Technau and his team could identify cells of a complex organism based on their specific transcriptome profiles and determine from which stem cells they have developed.

"By combining single-cell gene expression analyses and transgenesis, we have now been able to identify a large population of cells in the sea anemone that form differentiated cells such as nerve cells and glandular cells and are therefore candidates for multipotent stem cells," explains first author Andreas Denner from the University of Vienna.

They have remained undiscovered until now due to their tiny size.

These potential stem cells express the evolutionarily highly conserved genes nanos and piwi, which enable the development of germ cells (sperm and egg cells) in all animals, including humans.

By specifically mutating the nanos2 gene using the CRISPR gene scissors, the scientists were also able to prove that the gene is necessary for the formation of germ cells in sea anemones.

It has also been shown in other animals that this gene is essential for the production of gametes.

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Using AI to find the polymers of the future

Nylon, Teflon, Kevlar. These are just a few familiar polymers -- large-molecule chemical compounds -- that have changed the world. From Teflon-coated frying pans to 3D printing, polymers are vital to creating the systems that make the world function better.

Finding the next groundbreaking polymer is always a challenge, but now Georgia Tech researchers are using artificial intelligence (AI) to shape and transform the future of the field. Rampi Ramprasad's group develops and adapts AI algorithms to accelerate materials discovery.

This summer, two papers published in the Nature family of journals highlight the significant advancements and success stories emerging from years of AI-driven polymer informatics research. The first, featured in Nature Reviews Materials, showcases recent breakthroughs in polymer design across critical and contemporary application domains: energy storage, filtration technologies, and recyclable plastics. The second, published in Nature Communications, focuses on the use of AI algorithms to discover a subclass of polymers for electrostatic energy storage, with the designed materials undergoing successful laboratory synthesis and testing.

"In the early days of AI in materials science, propelled by the White House's Materials Genome Initiative over a decade ago, research in this field was largely curiosity-driven," said Ramprasad, a professor in the School of Materials Science and Engineering. "Only in recent years have we begun to see tangible, real-world success stories in AI-driven accelerated polymer discovery. These successes are now inspiring significant transformations in the industrial materials R&D landscape. That's what makes this review so significant and timely."

AI Opportunities

Ramprasad's team has developed groundbreaking algorithms that can instantly predict polymer properties and formulations before they are physically created. The process begins by defining application-specific target property or performance criteria. Machine learning (ML) models train on existing material-property data to predict these desired outcomes. Additionally, the team can generate new polymers, whose properties are forecasted with ML models. The top candidates that meet the target property criteria are then selected for real-world validation through laboratory synthesis and testing. The results from these new experiments are integrated with the original data, further refining the predictive models in a continuous, iterative process.

While AI can accelerate the discovery of new polymers, it also presents unique challenges. The accuracy of AI predictions depends on the availability of rich, diverse, extensive initial data sets, making quality data paramount. Additionally, designing algorithms capable of generating chemically realistic and synthesizable polymers is a complex task.

The real challenge begins after the algorithms make their predictions: proving that the designed materials can be made in the lab and function as expected and then demonstrating their scalability beyond the lab for real-world use. Ramprasad's group designs these materials, while their fabrication, processing, and testing are carried out by collaborators at various institutions, including Georgia Tech. Professor Ryan Lively from the School of Chemical and Biomolecular Engineering frequently collaborates with Ramprasad's group and is a co-author of the paper published in Nature Reviews Materials.

"In our day-to-day research, we extensively use the machine learning models Rampi's team has developed," Lively said. "These tools accelerate our work and allow us to rapidly explore new ideas. This embodies the promise of ML and AI because we can make model-guided decisions before we commit time and resources to explore the concepts in the laboratory."

Using AI, Ramprasad's team and their collaborators have made significant advancements in diverse fields, including energy storage, filtration technologies, additive manufacturing, and recyclable materials.

Polymer Progress

One notable success, described in the Nature Communications paper, involves the design of new polymers for capacitors, which store electrostatic energy. These devices are vital components in electric and hybrid vehicles, among other applications. Ramprasad's group worked with researchers from the University of Connecticut.

Current capacitor polymers offer either high energy density or thermal stability, but not both. By leveraging AI tools, the researchers determined that insulating materials made from polynorbornene and polyimide polymers can simultaneously achieve high energy density and high thermal stability. The polymers can be further enhanced to function in demanding environments, such as aerospace applications, while maintaining environmental sustainability.

"The new class of polymers with high energy density and high thermal stability is one of the most concrete examples of how AI can guide materials discovery," said Ramprasad. "It is also the result of years of multidisciplinary collaborative work with Greg Sotzing and Yang Cao at the University of Connecticut and sustained sponsorship by the Office of Naval Research."

Industry Potential

The potential for real-world translation of AI-assisted materials development is underscored by industry participation in the Nature Reviews Materials article. Co-authors of this paper also include scientists from Toyota Research Institute and General Electric. To further accelerate the adoption of AI-driven materials development in industry, Ramprasad co-founded Matmerize Inc., a software startup company recently spun out of Georgia Tech. Their cloud-based polymer informatics software is already being used by companies across various sectors, including energy, electronics, consumer products, chemical processing, and sustainable materials.

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New research shows unprecedented atmospheric changes during May's geomagnetic superstorm

On May 11, a gorgeous aurora surprised stargazers across the southern United States. That same weekend, a tractor guided by GPS missed its mark.

What do the visibility of the northern lights have in common with compromised farming equipment in the Midwest?

A uniquely powerful geomagnetic storm, according to two newly published papers co-authored by Virginia Tech's Scott England.

"The northern lights are caused by energetic, charged particles hitting our upper atmosphere, which are impacted by numerous factors in space, including the sun," said England, associate professor in the Kevin T. Crofton Department of Aerospace and Ocean Engineering. "During solar geomagnetic storms, there's a lot more of these energetic charged particles in the space around Earth, so we see a brightening of the northern lights and the region over which you can see them spreads out to include places like the lower 48 states that usually don't see this display."

England and a team of university and industry collaborators tracked the upper atmospheric event on May 11 using NASA's GOLD instrument. It turned out to be the strongest geomagnetic storm captured in the last 20 years. Their findings were recently published in Geophysical Research Letters in two studies, both co-authored by England. The first study, by first author Deepak Karan, from the University of Colorado, Boulder, showed unprecedented changes in location and spread of particles in the upper atmosphere. The second study, by first author and Virginia Tech alumnus J. Scott Evans '88, documented composition and temperature changes.

Among the collected data, England noted witnessing some "delightful swirly patterns" for the first time, and a dramatic motion of the air away from the aurora causing the formation of enormous vortices that moved air in a spiral larger than a hurricane. Specific observations included:

• Unpredictable movement of low energy charged particles from around the equator toward the aurora
• Charged particles that can be divided into two buckets: low energy and high energy, the latter of which can hurt humans working in space and damage electronics
• Changes in temperature and pressure that likely lead to the swirls and vortices seen
• Changes in locations and spread of low energy particles, which can negatively impact GPS, satellites, and even the electrical grid

"As the aurora intensifies, you see more lights, but along with that, there's more energy entering the atmosphere, so it makes the atmosphere near the poles very hot, which starts to push air away from the poles and towards the equator," England said. "This data poses a lot of questions like, did something really different happen during this geomagnetic storm than has happened previously, or do we just have better instruments to measure the changes?"

Furthermore, what could those changes mean for the human-made technology that orbits that region of the atmosphere?

More than a northern lights show

Earth's upper atmosphere, spanning from about 60 to 400 miles above us, borders space and is the hang-out zone for satellites and the International Space Station. The upper atmosphere is made up of some of the same particles as the lower atmosphere, where we live and breathe. But it also has another side, the ionosphere that can be thought of almost like an electric blanket -- highly charged and constantly fluctuating. These charged particles in the ionosphere are one thing that makes this region of space so dynamic. It's common for the temperature and composition of the upper atmosphere and ionosphere to change. In fact, it does so predictably during the day and night and even changes overtime with seasons.

England said the particles in earth's atmosphere are impacted by numerous factors in space, including the sun's activity. During a solar geomagnetic storm flare, an intense burst of radiation from the sun changes the composition and speed of the particles within the earth's atmosphere. So why in recent months all over the globe the northern lights have been visible in places where they've not been seen before now?

"The number of sunspots, flares, and storms changes with an 11-year cycle that we call the solar cycle," England said. "The number of flares we are seeing has been increasing gradually for the last couple of years as we move toward the peak of the solar cycle."

In addition to the visibility of the northern lights, geomagnetic storms have a range of impacts on our technology. Because radio and GPS signals travel through this constantly fluctuating "electric blanket," changes in this layer of the atmosphere can disrupt signals and impede navigation and communication systems such as GPS. Various factors from both earth's weather and space weather can impact this crucial layer, but there's much to be learned about why changes in the upper and lower atmosphere occur and how they might impact life as we know it.

"These storms can also increase electrical currents that flow around the Earth, which can impact technological devices that use very long wires. In recent years, there have been impacts to the power grid when too much current was flowing through the wires. During the largest geomagnetic storm ever recorded, the Carrington Event in 1859, these caused telegraph systems -- peak technology at that time -- to catch on fire," England said.

Scientists suspect that a storm similar to the 1859 Carrington Event, if it happened today, could cause an internet apocalypse, sending large numbers of people and businesses offline. While the May 11 storm did not cause drastic disruptions, with the peak of the solar cycle expected to reach in July 2025, we are still about a year away from knowing those potential effects.

Read more at Science Daily

Preservation of organic carbon in the ocean floor

On geological timescales, the burial rate of sedimentary organic carbon exerts major control on the concentrations of atmospheric oxygen and carbon dioxide and thus substantially influences Earth's environmental conditions. In marine sediments, about 20 percent of the organic carbon is directly bound to reactive iron oxides (FeR). However, the fate of reactive iron-bound organic carbon (FeR-OC) in subseafloor sediments and its availability to microorganisms, remain undetermined.

To study this, the team reconstructed continuous FeR-OC records in two sediment cores of the northern South China Sea encompassing the suboxic to methanic biogeochemical zones and reaching a maximum age of around 100,000 years.

The study reveals that in sulfate-methane transition zone (SMTZ) with high microbial activities, FeR-OC is remobilized during microbial-mediated iron reduction processes, and consequently remineralized by microorganisms.

The energy produced is able to support a substantial fraction of microbial life in the SMTZ, which is around one meter thick.

With the exception of the SMTZ, a relatively stable proportion of the total organic carbon survives the microbial degradation processes as FeR-OC and is stored in marine sediments over geological time periods.

"This means," says Dr. Yunru Chen, first author of the study and now a postdoctoral researcher at the Cluster of Excellence 'The Ocean Floor -- Uncharted Interface of the Earth, "that the estimated global reservoir of FeR-OC in microbially active Quaternary marine sediments could be 18 to 45 times larger than the atmospheric carbon pool."

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Tracking down the asteroid that sealed the fate of the dinosaurs

Geoscientists from the University of Cologne have led an international study to determine the origin of the huge piece of rock that hit the Earth around 66 million years ago and permanently changed the climate. The scientists analysed samples of the rock layer that marks the boundary between the Cretaceous and Paleogene periods. This period also saw the last major mass extinction event on Earth, in which around 70 percent of all animal species became extinct. The results of the study published in Science indicate that the asteroid formed outside Jupiter's orbit during the early development of our solar system.

According to a widely accepted theory, the mass extinction at the Cretaceous-Paleogene boundary was triggered by the impact of an asteroid at least 10 kilometres in diameter near Chicxulub on the Yucatán Peninsula in Mexico.

On impact, the asteroid and large quantities of earth rock vaporized.

Fine dust particles spread into the stratosphere and obscured the sun.

This led to dramatic changes in the living conditions on the planet and brought photosynthetic activity to a halt for several years.

The dust particles released by the impact formed a layer of sediment around the entire globe.

This is why the Cretaceous-Paleogene boundary can be identified and sampled in many places on Earth.

It contains high concentrations of platinum-group metals, which come from the asteroid and are otherwise extremely rare in the rock that forms the Earth's crust.

By analysing the isotopic composition of the platinum metal ruthenium in the cleanroom laboratory of the University of Cologne's Institute of Geology and Mineralogy, the scientists discovered that the asteroid originally came from the outer solar system.

"The asteroid's composition is consistent with that of carbonaceous asteroids that formed outside of Jupiter's orbit during the formation of the solar system," said Dr Mario Fischer-Gödde, first author of the study.

The ruthenium isotope compositions were also determined for other craters and impact structures of different ages on Earth for comparison. This data shows that within the last 500 million years, almost exclusively fragments of S-type asteroids have hit the Earth. In contrast to the impact at the Cretaceous-Paleogene boundary, these asteroids originate from the inner solar system. Well over 80 percent of all asteroid fragments that hit the Earth in the form of meteorites come from the inner solar system. Professor Dr Carsten Münker, co-author of the study, added: "We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in geological time. The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system."

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New insights on how bird flu crosses the species barrier

In recent years, public health measures, surveillance, and vaccination have helped bring about significant progress in reducing the impact of seasonal flu epidemics, caused by human influenza viruses A and B. However, a possible outbreak of avian influenza A (commonly known as 'bird flu') in mammals, including humans, poses a significant threat to public health.

The Cusack group at EMBL Grenoble studies the replication process of influenza viruses. A new study from this group sheds light on the different mutations that the avian influenza virus can undergo to be able to replicate in mammalian cells.

Some avian influenza strains can cause severe disease and mortality. Fortunately, significant biological differences between birds and mammals normally prevent avian influenza from spreading from birds to other species. To infect mammals, the avian influenza virus must mutate to overcome two main barriers: the ability to enter the cell and to replicate within that cell. To cause an epidemic or pandemic, it must also acquire the ability to be transmitted between humans.

However, sporadic contamination of wild and domestic mammals by bird flu is becoming increasingly common. Of particular concern is the recent unexpected infection of dairy cows in the USA by an avian H5N1 strain, which risks becoming endemic in cattle. This might facilitate adaptation to humans, and indeed, a few cases of transmission to humans have been reported, so far resulting in only mild symptoms.

At the heart of this process is the polymerase, an enzyme that orchestrates the virus's replication inside host cells. This flexible protein can rearrange itself according to the different functions it performs during infection. These include transcription -- copying the viral RNA into messenger RNA to make viral proteins -- and replication -- making copies of the viral RNA to package into new viruses.

Viral replication is a complex process to study because it involves two viral polymerases and a host cell protein -- ANP32. Together, these three proteins form the replication complex, a molecular machine that carries out replication. ANP32 is known as a 'chaperone', meaning that it acts as a stabiliser for certain cellular proteins. It can do this thanks to a key structure -- its long acidic tail. In 2015, it was discovered that ANP32 is critical for influenza virus replication, but its function was not fully understood.

The results of the new study, published in the journal Nature Communications, show that ANP32 acts as a bridge between the two viral polymerases -- called replicase and encapsidase. The names reflect the two distinct conformations taken up by the polymerases to perform two different functions -- creating copies of the viral RNA (replicase) and packaging the copy inside a protective coating with ANP32's help (encapsidase).

Through its tail, ANP32 acts as a stabiliser for the replication complex, allowing it to form within the host cell. Interestingly, the ANP32 tail differs between birds and mammals, although the core of the protein remains very similar. This biological difference explains why the avian influenza virus does not replicate easily in mammals and humans.

"The key difference between avian and human ANP32 is a 33-amino-acid insertion in the avian tail, and the polymerase has to adapt to this difference," explained Benoît Arragain, a postdoctoral fellow in the Cusack group and first author of the publication. "For the avian-adapted polymerase to replicate in human cells, it must acquire certain mutations to be able to use human ANP32."

To better understand this process, Arragain and his collaborators obtained the structure of the replicase and encapsidase conformations of a human-adapted avian influenza polymerase (from strain H7N9) while they were interacting with human ANP32. This structure gives detailed information about which amino acids are important in forming the replication complex and which mutations could allow the avian influenza polymerase to adapt to mammalian cells.

To obtain these results, Arragain carried out in vitro experiments at EMBL Grenoble, using the Eukaryotic Expression Facility, the ISBG biophysical platform, and the cryo-electron microscopy platform available through the Partnership for Structural Biology. "We also collaborated with the Naffakh group at the Institut Pasteur, who carried out cellularexperiments," added Arragain. "In addition, we obtained the structure of the human type B influenza replication complex, which is similar to that of influenza A. The cellular experiments confirmed our structural data."

These new insights into the influenza replication complex can be used to study polymerase mutations in other similar strains of the avian influenza virus. It is therefore possible to use the structure obtained from the H7N9 strain and adapt it to other strains such as H5N1.

"The threat of a new pandemic caused by highly pathogenic, human-adapted avian influenza strains with a high mortality rate needs to be taken seriously," said Stephen Cusack, EMBL Grenoble Senior Scientist who led the study and has been studying influenza viruses for 30 years. "One of the key responses to this threat includes monitoring mutations in the virus in the field. Knowing this structure allows us to interpret these mutations and assess if a strain is on the path of adaptation to infect and transmit between mammals."

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Scientists find oceans of water on Mars: It's just too deep to tap

Using seismic activity to probe the interior of Mars, geophysicists have found evidence for a large underground reservoir of liquid water -- enough to fill oceans on the planet's surface.

The data from NASA's Insight lander allowed the scientists to estimate that the amount of groundwater could cover the entire planet to a depth of between 1 and 2 kilometers, or about a mile.

While that's good news for those tracking the fate of water on the planet after its oceans disappeared more than 3 billion years ago, the reservoir won't be of much use to anyone trying to tap into it to supply a future Mars colony. It's located in tiny cracks and pores in rock in the middle of the Martian crust, between 11.5 and 20 kilometers below the surface. Even on Earth, drilling a hole a kilometer deep is a challenge.

The finding does pinpoint another promising place to look for life on Mars, however, if the reservoir can be accessed. For the moment, it helps answer questions about the geological history of the planet.

"Understanding the Martian water cycle is critical for understanding the evolution of the climate, surface and interior," said Vashan Wright, a former UC Berkeley postdoctoral fellow who is now an assistant professor at UC San Diego's Scripps Institution of Oceanography. "A useful starting point is to identify where water is and how much is there."

Wright, alongside colleagues Michael Manga of UC Berkeley and Matthias Morzfeld of Scripps Oceanography, detailed their analysis in a paper that will appear this week in the journal Proceedings of the National Academy of Sciences.

The scientists employed a mathematical model of rock physics, identical to models used on Earth to map underground aquifers and oil fields, to conclude that the seismic data from Insight are best explained by a deep layer of fractured igneous rock saturated with liquid water. Igneous rocks are cooled hot magma, like the granite of the Sierra Nevada.

"Establishing that there is a big reservoir of liquid water provides some window into what the climate was like or could be like," said Manga, a UC Berkeley professor of earth and planetary science. "And water is necessary for life as we know it. I don't see why [the underground reservoir] is not a habitable environment. It's certainly true on Earth -- deep, deep mines host life, the bottom of the ocean hosts life. We haven't found any evidence for life on Mars, but at least we have identified a place that should, in principle, be able to sustain life."

Manga was Wright's postdoctoral adviser. Morzfeld was a former postdoctoral fellow in UC Berkeley's mathematics department and is now an associate professor of geophysics at Scripps Oceanography.

Manga noted that lots of evidence -- river channels, deltas and lake deposits, as well as water-altered rock -- supports the hypothesis that water once flowed on the planet's surface. But that wet period ended more than 3 billion years ago, after Mars lost its atmosphere. Planetary scientists on Earth have sent many probes and landers to the planet to find out what happened to that water -- the water frozen in Mars' polar ice caps can't account for it all -- as well as when it happened, and whether life exists or used to exist on the planet.

The new findings are an indication that much of the water did not escape into space but filtered down into the crust.

The Insight lander was sent by NASA to Mars in 2018 to investigate the crust, mantle, core and atmosphere, and it recorded invaluable information about Mars' interior before the mission ended in 2022.

"The mission greatly exceeded my expectations," Manga said. "From looking at all the seismic data that Insight collected, they've figured out the thickness of the crust, the depth of the core, the composition of the core, even a little bit about the temperature within the mantle."

Insight detected Mars quakes up to about a magnitude of 5, meteor impacts and rumblings from volcanic areas, all of which produced seismic waves that allowed geophysicists to probe the interior.

An earlier paper reported that above a depth of about 5 kilometers, the upper crust did not contain water ice, as Manga and others suspected. That may mean that there's little accessible frozen groundwater outside the polar regions.

The new paper analyzed the deeper crust and concluded that the "available data are best explained by a water-saturated mid-crust" below Insight's location. Assuming the crust is similar throughout the planet, the team argued, there should be more water in this mid-crust zone than the "volumes proposed to have filled hypothesized ancient Martian oceans."

Read more at Science Daily

Decoding mysterious seismic signals

For the decades since their discovery, seismic signals known as PKP precursors have challenged scientists. Regions of Earth's lower mantle scatter incoming seismic waves, which return to the surface as PKP waves at differing speeds.

The origin the precursor signals, which arrive ahead of the main seismic waves that travel through Earth's core, has remained unclear, but research led by University of Utah geophysicists sheds new light on this mysterious seismic energy.

PKP precursors appear to propagate from places deep below North America and the western Pacific and possibly bear an association with "ultra-low velocity zones," thin layers in the mantle where seismic waves significantly slow down, according to research published in AGU Advances, the American Geophysical Union's lead journal. (The AGU highlighted the research in its magazine Eos.)

"These are some of the most extreme features discovered on the planet. We legitimately do not know what they are," said lead author Michael Thorne, a U associate professor of geology and geophysics. "But one thing we know is they seem to end up accumulating underneath hotspot volcanoes. They seem like they may be the root of whole mantle plumes giving rise to hotspot volcanoes."

These plumes are responsible for the volcanism observed at Yellowstone, the Hawaiian Islands, Samoa, Iceland and the Galapagos Islands.

"These really, really big volcanoes seem to persist for hundreds of millions of years in roughly the same spot," Thorne said. In previous work, he also found one of the world's largest known ultra-low velocity zones.

"It sits right beneath Samoa, and Samoa is one of the biggest hotspot volcanoes," Thorne noted.

For nearly a century, geoscientists have used seismic waves to probe Earth's interior, leading to numerous discoveries that would not be otherwise possible. Other researchers at the U, for example, have characterized the structure of Earth's solid inner core and tracked its movement by analyzing seismic waves.

When an earthquake rattles Earth's surface, seismic waves shoot through the mantle -- the 2,900-kilometer-thick dynamic layer of hot rock between Earth's crust and metal core. Thorne's team is interested in those that get "scattered" when they pass through irregular features that pose changes in material composition in the mantle. Some of those scattered waves become PKP precursors.

Thorne sought to determine exactly where this scattering happens, especially since the waves travel through Earth's mantle twice, that is, before and after passing through Earth's liquid outer core. Because of that double journey through the mantle, it has been nearly impossible to distinguish whether the precursors originated on the source-side or receiver-side of the ray path.

Thorne's team, which included research assistant professor Surya Pachhai, devised a way to model waveforms to detect crucial effects that previously went unnoticed.

Using a cutting-edge seismic array method and new theoretical observations from earthquake simulations, the researchers developed, they analyzed data from 58 earthquakes that occurred around New Guinea and were recorded in North America after passing through the planet.

"I can put virtual receivers anywhere on the surface of the earth, and this tells me what the seismogram should look like from an earthquake at that location. And we can compare that to the real recordings that we have," Thorne said. "We're able to now back project where this energy's coming from."

Their new method allowed them to pinpoint where the scattering occurred along the boundary between the liquid metal outer core and the mantle, known as the core-mantle boundary, located 2,900 kilometers below Earth's surface.

Their findings indicate that the PKP precursors likely come from regions that are home to ultra-low velocity zones. Thorne suspects these layers, which are only 20 to 40 kilometers thick, are formed where subducted tectonic plates impinge on the core-mantle boundary in oceanic crust.

"What we've now found is that these ultra-low velocity zones do not just exist beneath the hotspots. They're spread out all across the core-mantle boundary beneath North America," Thorne said. "It really looks like these ULVZs are getting actively generated. We don't know how. But because we're seeing them near subduction, we think mid-ocean ridge basalts are getting melted, and that is how it's getting generated. And then the dynamics is pushing these things all across Earth, and ultimately they're going to accumulate beneath the hotspots."

"What we've now found is that these ultra-low velocity zones do not just exist beneath the hotspots. They're spread out all across the core-mantle boundary beneath North America," Thorne said. "It really looks like these ULVZs are getting actively generated. We don't know how. But because we're seeing them near subduction, we think mid-ocean ridge basalts are getting melted, and that may be how they're getting generated."

The dynamics is pushing these things all across Earth, and ultimately, they're going to accumulate against the boundaries of Large Low Velocity Provinces, which are compositionally distinct continent scale features beneath the Pacific and Africa, according to Thorne.

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Beige fat cells with a 'Sisyphus mechanism'

Fat cells come in three colours: white, brown, and beige. White fat cells store fat in our body as an energy reserve. We need these cells, but having too many creates health problems. Brown fat cells are particularly active in infants. They produce heat and thus maintain the baby's body temperature. However, the amount of brown adipose tissue decreases over a person's lifetime; adults have very little of it. Then, finally, the beige fat cells. These can also produce heat, albeit somewhat less well than brown fat cells. Beige fat cells occur in adults as well: scattered throughout the white fatty tissue, especially in the neck and shoulder area, they help in using up excess energy.

Now an international research team has discovered and described a new type of beige fat cells, which differ from the ones that were already known. "Fat cells of this new beige type play an important role in energy metabolism in the human body and have a positive effect on metabolic diseases and obesity," says Anand Sharma, a postdoc in ETH Professor Christian Wolfrum's group and coauthor of the study. "That's why it's so important to understand in detail how they work." The study was led by ETH Zurich, the University of Basel, the University of Leipzig Medical Center and the Dana-Farber Cancer Institute in Boston. Numerous other hospitals and research institutions around the world were involved in the project.

Independent of a known protein

The beige fat cells that researchers were already familiar with generate heat in the same way as brown fat cells: via a protein called UCP1. This protein is located in the inner of two membranes that surround the mitochondria, the structural units often referred to as the powerhouse of the cell. As part of their normal function, mitochondria pump protons into the space between the two membranes. Protons are electrically charged elementary particles that generally play an important role in energy conversion processes in cells. Bown fat cells and the classic beige fat cells described earlier have the protein UCP1. It forms a very narrow channel in the inner membrane through which the protons flow back into the mitochondria, thereby generating heat from friction.

In recent years, scientists have discovered that there are also beige fat cells without the UCP1 protein, and that these also consume energy and thus produce heat. The research team from ETH Zurich and the participating institutions has now precisely characterised the new class of beige fat cells and shown how they do this: by means of a "Sisyphus mechanism."

Here's how it works: All biochemical processes that take place in cells always generate some heat. The new class of beige fat cells takes advantage of this and allows individual processes to run back and forth, seemingly without purpose. This primarily involves two conversion processes. In one, the cells break fats down into their components (fatty acids) at full speed and then assemble them into new fats just as quickly. In the other, they apply an enzyme to convert molecules of creatine into creatine phosphate, a related molecule, only to immediately convert it back into creatine. Scientists call these back-and-forth processes "futile cycles." They don't add anything to the biochemical budget overall, but they consume energy and generate heat.

Preventing diabetes and obesity

The research team first described the new type of beige fat cells in mice. They then examined human adipose tissue and were able to show that these fat cells occur there, too. While less than half the population has the previously known type of classical beige fat cells, almost all humans have the new futile-cycle type, albeit in differing amounts.

As the researchers were able to show, people with a high number of beige fat cells -- of either the previously known type or this new type -- are slimmer and tend to have better metabolic health. That makes them less prone to obesity and metabolic disorders such as diabetes. "Because beige fat cells convert energy into heat, they help to break down excess fat," explains Tongtong Wang, an ETH doctoral student in ETH Professor Wolfrum's group and lead author of the study.

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