From stardust to pale blue dot: Carbon's interstellar journey to Earth

 We are made of stardust, the saying goes, and a pair of studies including University of Michigan research finds that may be more true than we previously thought.

The first study, led by U-M researcher Jie (Jackie) Li and published in Science Advances, finds that most of the carbon on Earth was likely delivered from the interstellar medium, the material that exists in space between stars in a galaxy. This likely happened well after the protoplanetary disk, the cloud of dust and gas that circled our young sun and contained the building blocks of the planets, formed and warmed up.

Carbon was also likely sequestered into solids within one million years of the sun's birth -- which means that carbon, the backbone of life on earth, survived an interstellar journey to our planet.

Previously, researchers thought carbon in the Earth came from molecules that were initially present in nebular gas, which then accreted into a rocky planet when the gases were cool enough for the molecules to precipitate. Li and her team, which includes U-M astronomer Edwin Bergin, Geoffrey Blake of the California Institute of Technology, Fred Ciesla of the University of Chicago and Marc Hirschmann of the University of Minnesota, point out in this study that the gas molecules that carry carbon wouldn't be available to build the Earth because once carbon vaporizes, it does not condense back into a solid.

"The condensation model has been widely used for decades. It assumes that during the formation of the sun, all of the planet's elements got vaporized, and as the disk cooled, some of these gases condensed and supplied chemical ingredients to solid bodies. But that doesn't work for carbon," said Li, a professor in the U-M Department of Earth and Environmental Sciences.

Much of carbon was delivered to the disk in the form of organic molecules. However, when carbon is vaporized, it produces much more volatile species that require very low temperatures to form solids. More importantly, carbon does not condense back again into an organic form. Because of this, Li and her team inferred most of Earth's carbon was likely inherited directly from the interstellar medium, avoiding vaporization entirely.

To better understand how Earth acquired its carbon, Li estimated the maximum amount of carbon Earth could contain. To do this, she compared how quickly a seismic wave travels through the core to the known sound velocities of the core. This told the researchers that carbon likely makes up less than half a percent of Earth's mass. Understanding the upper bounds of how much carbon the Earth might contain tells the researchers information about when the carbon might have been delivered here.

"We asked a different question: We asked how much carbon could you stuff in the Earth's core and still be consistent with all the constraints," Bergin said, professor and chair of the U-M Department of Astronomy. "There's uncertainty here. Let's embrace the uncertainty to ask what are the true upper bounds for how much carbon is very deep in the Earth, and that will tell us the true landscape we're within."

A planet's carbon must exist in the right proportion to support life as we know it. Too much carbon, and the Earth's atmosphere would be like Venus, trapping heat from the sun and maintaining a temperature of about 880 degrees Fahrenheit. Too little carbon, and Earth would resemble Mars: an inhospitable place unable to support water-based life, with temperatures around minus 60.

In a second study by the same group of authors, but led by Hirschmann of the University of Minnesota, the researchers looked at how carbon is processed when the small precursors of planets, known as planetesimals, retain carbon during their early formation. By examining the metallic cores of these bodies, now preserved as iron meteorites, they found that during this key step of planetary origin, much of the carbon must be lost as the planetesimals melt, form cores and lose gas. This upends previous thinking, Hirschmann says.

"Most models have the carbon and other life-essential materials such as water and nitrogen going from the nebula into primitive rocky bodies, and these are then delivered to growing planets such as Earth or Mars," said Hirschmann, professor of earth and environmental sciences. "But this skips a key step, in which the planetesimals lose much of their carbon before they accrete to the planets."

Hirschmann's study was recently published in Proceedings of the National Academy of Sciences.

"The planet needs carbon to regulate its climate and allow life to exist, but it's a very delicate thing," Bergin said. "You don't want to have too little, but you don't want to have too much."

Bergin says the two studies both describe two different aspects of carbon loss -- and suggest that carbon loss appears to be a central aspect in constructing the Earth as a habitable planet.

"Answering whether or not Earth-like planets exist elsewhere can only be achieved by working at the intersection of disciplines like astronomy and geochemistry," said Ciesla, a U. of C. professor of geophysical sciences. "While approaches and the specific questions that researchers work to answer differ across the fields, building a coherent story requires identifying topics of mutual interest and finding ways to bridge the intellectual gaps between them. Doing so is challenging, but the effort is both stimulating and rewarding."

Blake, a co-author on both studies and a Caltech professor of cosmochemistry and planetary science, and of chemistry, says this kind of interdisciplinary work is critical.

"Over the history of our galaxy alone, rocky planets like the Earth or a bit larger have been assembled hundreds of millions of times around stars like the Sun," he said. "Can we extend this work to examine carbon loss in planetary systems more broadly? Such research will take a diverse community of scholars."

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450-million-year-old sea creatures had a leg up on breathing

 A new study has found the first evidence of sophisticated breathing organs in 450-million-year-old sea creatures. Contrary to previous thought, trilobites were leg breathers, with structures resembling gills hanging off their thighs.

Trilobites were a group of marine animals with half-moon-like heads that resembled horseshoe crabs, and they were wildly successful in terms of evolution. Though they are now extinct, they survived for more than 250 million years -- longer than the dinosaurs.

Thanks to new technologies and an extremely rare set of fossils, scientists from UC Riverside can now show that trilobites breathed oxygen and explain how they did so. Published in the journal Science Advances, these findings help piece together the puzzle of early animal evolution.

"Up until now, scientists have compared the upper branch of the trilobite leg to the non-respiratory upper branch in crustaceans, but our paper shows, for the first time, that the upper branch functioned as a gill," said Jin-Bo Hou, a UCR paleontology doctoral student who led the research.

Among the oldest animals on earth, this work helps situate trilobites on the evolutionary tree more securely in between older arthropods, a large group of animals with exoskeletons, and crustaceans.

The research was possible, in part, because of unusually preserved fossil specimens. There are more than 22,000 trilobite species that have been discovered, but the soft parts of the animals are visible in only about two dozen.

"These were preserved in pyrite -- fool's gold -- but it's more important than gold to us, because it's key to understanding these ancient structures," said UCR geology professor and paper co-author Nigel Hughes.

A CT scanner was able to read the differences in density between the pyrite and the surrounding rock and helped create three-dimensional models of these rarely seen gill structures.

"It allowed us to see the fossil without having to do a lot of drilling and grinding away at the rock covering the specimen," said paleontologist Melanie Hopkins, a research team member at the American Museum of Natural History.

"This way we could get a view that would even be hard to see under a microscope -- really small trilobite anatomical structures on the order of 10 to 30 microns wide," she said. For comparison, a human hair is roughly 100 microns thick.

Though these specimens were first described in the late 1800s and others have used CT scans to examine them, this is the first study to use the technology to examine this part of the animal.

The researchers could see how blood would have filtered through chambers in these delicate structures, picking up oxygen along its way as it moved. They appear much the same as gills in modern marine arthropods like crabs and lobsters.

Comparing the specimens in pyrite to another trilobite species gave the team additional detail about how the filaments were arranged relative to one another, and to the legs.

Most trilobites scavenged the ocean floor, using spikes on their lower legs to catch and grind prey. Above those parts, on the upper branch of the limbs, were these additional structures that some believed were meant to help with swimming or digging.

"In the past, there was some debate about the purpose of these structures because the upper leg isn't a great location for breathing apparatus," Hopkins said. "You'd think it would be easy for those filaments to get clogged with sediment where they are. It's an open question why they evolved the structure in that place on their bodies."

The Hughes lab uses fossils to answer questions about how life developed in response to changes in Earth's atmosphere. Roughly 540 million years ago, there was an explosive diversification in the variety and complexity of animals living in the oceans.

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First-of-its-kind mechanical model simulates bending of mammalian whiskers

 Researchers have developed a new mechanical model that simulates how whiskers bend within a follicle in response to an external force, paving the way toward better understanding of how whiskers contribute to mammals' sense of touch. Yifu Luo and Mitra Hartmann of Northwestern University and colleagues present these findings in the open-access journal PLOS Computational Biology.

With the exception of some primates, most mammals use whiskers to explore their environment through the sense of touch. Whiskers have no sensors along their length, but when an external force bends a whisker, that deformation extends into the follicle at the base of the whisker, where the whisker pushes or pulls on sensor cells, triggering touch signals in the nervous system.

Few previous studies have examined how whiskers deform within follicles in order to impinge on the sensor cells -- mechanoreceptors -- inside. To better understand this process, Luo and colleagues drew on data from experimental studies of whisker follicles to create the first mechanical model capable of simulating whisker deformation within follicles.

The simulations suggest that whisker deformation within follicles most likely occurs in an "S" shape, although future experimental data may show that the deformation is "C" shaped. The researchers demonstrate that these shape estimates can be used to predict how whiskers push and pull on different kinds of mechanoreceptors located in different parts of the follicle, influencing touch signals sent to the brain.

The new model applies to both passive touch and active "whisking," when an animal uses muscles to move its whiskers. The simulations suggest that, during active whisking, the tactile sensitivity of the whisker system is enhanced by increased blood pressure in the follicle and by increased stiffness of follicular muscle and tissue structures.

"It is exciting to use simulations, constrained by anatomical observations, to gain insights into biological processes that cannot be directly measured experimentally," Hartmann says. "The work also underscores just how important mechanics are to understanding the sensory signals that the brain has evolved to process."

Future research will be needed to refine the model, both computationally and by incorporating new experimental data.

From Science Daily

Distant, spiralling stars give clues to the forces that bind sub-atomic particles

Space scientists at the University of Bath in the UK have found a new way to probe the internal structure of neutron stars, giving nuclear physicists a novel tool for studying the structures that make up matter at an atomic level.

Neutron stars are dead stars that have been compressed by gravity to the size of small cities. They contain the most extreme matter in the universe, meaning they are the densest objects in existence (for comparison, if Earth were compressed to the density of a neutron star, it would measure just a few hundred meters in diameter, and all humans would fit in a teaspoon). This makes neutron stars unique natural laboratories for nuclear physicists, whose understanding of the force that binds sub-atomic particles is limited to their work on Earth-bound atomic nuclei. Studying how this force behaves under more extreme conditions offers a way to deepen their knowledge.

Step in astrophysicists, who look to distant galaxies to unravel the mysteries of physics.

In a study described in the Monthly Notices of the Royal Astronomical Society, Bath astrophysicists have found that the action of two neutron stars moving ever faster as they spiral towards a violent collision gives a clue to the composition of neutron-star material. From this information, nuclear physicists will be in a stronger position to calculate the forces that determine the structure of all matter.

RESONANCE

It is through the phenomenon of resonance that the Bath team has made its discovery. Resonance occurs when force is applied to an object at its natural frequency, generating a large, often catastrophic, vibrational motion. A well-known example of resonance is found when an opera singer shatters a glass by singing loudly enough at a frequency that matches the oscillation modes of the glass.

When a pair of in-spiralling neutron stars reach a state of resonance, their solid crust -- which is thought to be 10-billion times stronger than steel -- shatters. This results in the release of a bright burst of gamma-rays (called a Resonant Shattering Flare) that can be seen by satellites. The in-spiralling stars also release gravitational waves that can be detected by instruments on Earth. The Bath researchers found that by measuring both the flare and the gravitational-wave signal, they can calculate the 'symmetry energy' of the neutron star.

Symmetry energy is one of the properties of nuclear matter. It controls the ratio of the sub-atomic particles (protons and neutrons) that make up a nucleus, and how this ratio changes when subjected to the extreme densities found in neutron stars. A reading for symmetry energy would therefore give a strong indication of the makeup of neutron stars, and by extension, the processes by which all protons and neutrons couple, and the forces that determine the structure of all matter.

The researchers stress that measurements obtained by studying the resonance of neutron stars using a combination of gamma-rays and gravitational-waves would be complementary to, rather than a replacement for, the lab experiments of nuclear physicists.

"By studying neutron stars, and the cataclysmic final motions of these massive objects, we're able to understand something about the tiny, tiny nuclei that make up extremely dense matter," said Bath astrophysicist Dr David Tsang. "The enormous difference in scale makes this fascinating."

Astrophysics PhD student Duncan Neill, who led the research, added: "I like that this work looks at the same thing being studied by nuclear physicists. They look at tiny particles and we astrophysicists look at objects and events from many millions of light years away. We are looking at the same thing in a completely different way."

Dr Will Newton, astrophysicist at the Texas A&M University-Commerce and project collaborator, said: "Though the force that binds quarks into neutrons and protons is known, how it actually works when large numbers of neutrons and protons come together is not well understood. The quest to improve this understanding is helped by experimental nuclear physics data, but all the nuclei we probe on Earth have similar numbers of neutrons and protons bound together at roughly the same density.

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Sugar not so nice for your child's brain development

 Sugar practically screams from the shelves of your grocery store, especially those products marketed to kids.

Children are the highest consumers of added sugar, even as high-sugar diets have been linked to health effects like obesity and heart disease and even impaired memory function.

However, less is known about how high sugar consumption during childhood affects the development of the brain, specifically a region known to be critically important for learning and memory called the hippocampus.

New research led by a University of Georgia faculty member in collaboration with a University of Southern California research group has shown in a rodent model that daily consumption of sugar-sweetened beverages during adolescence impairs performance on a learning and memory task during adulthood. The group further showed that changes in the bacteria in the gut may be the key to the sugar-induced memory impairment.

Supporting this possibility, they found that similar memory deficits were observed even when the bacteria, called Parabacteroides, were experimentally enriched in the guts of animals that had never consumed sugar.

"Early life sugar increased Parabacteroides levels, and the higher the levels of Parabacteroides, the worse the animals did in the task," said Emily Noble, assistant professor in the UGA College of Family and Consumer Sciences who served as first author on the paper. "We found that the bacteria alone was sufficient to impair memory in the same way as sugar, but it also impaired other types of memory functions as well."

Guidelines recommend limiting sugar

The Dietary Guidelines for Americans, a joint publication of the U.S. Departments of Agriculture and of Health and Human Services, recommends limiting added sugars to less than 10 percent of calories per day.

Data from the Centers for Disease Control and Prevention show Americans between the ages 9-18 exceed that recommendation, the bulk of the calories coming from sugar-sweetened beverages.

Considering the role the hippocampus plays in a variety of cognitive functions and the fact the area is still developing into late adolescence, researchers sought to understand more about its vulnerability to a high-sugar diet via gut microbiota.

Juvenile rats were given their normal chow and an 11% sugar solution, which is comparable to commercially available sugar-sweetened beverages.

Researchers then had the rats perform a hippocampus-dependent memory task designed to measure episodic contextual memory, or remembering the context where they had seen a familiar object before.

"We found that rats that consumed sugar in early life had an impaired capacity to discriminate that an object was novel to a specific context, a task the rats that were not given sugar were able to do," Noble said.

A second memory task measured basic recognition memory, a hippocampal-independent memory function that involves the animals' ability to recognize something they had seen previously.

In this task, sugar had no effect on the animals' recognition memory.

"Early life sugar consumption seems to selectively impair their hippocampal learning and memory," Noble said.

Additional analyses determined that high sugar consumption led to elevated levels of Parabacteroides in the gut microbiome, the more than 100 trillion microorganisms in the gastrointestinal tract that play a role in human health and disease.

To better identify the mechanism by which the bacteria impacted memory and learning, researchers experimentally increased levels of Parabacteroides in the microbiome of rats that had never consumed sugar. Those animals showed impairments in both hippocampal dependent and hippocampal-independent memory tasks.

"(The bacteria) induced some cognitive deficits on its own," Noble said.

Noble said future research is needed to better identify specific pathways by which this gut-brain signaling operates.

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Toddler TV time not to blame for attention problems

A comprehensive review published in the journal Psychological Science re-examines previous work that claimed to show a direct link between early screen time and attention problems in children. Although other studies do not reflect these findings, the earlier research continues to be widely reported by the media.

"The findings from the original study, upon further scrutiny, are not borne out. We found that there is still no evidence that TV, by itself, causes ADHD or any kind of attention problems in young children," said Wallace E. Dixon, Jr., a professor of psychology and department head at East Tennessee State University and coauthor of the study. "Our research also tells us that it's important to be skeptical of earth-shattering findings that come in the form of 'something that everybody is doing harms our children.' Extraordinary claims require extraordinary evidence.

"What excites us about the research is that we can ease up on blaming parents or making them feel guilty for letting their children watch television when they are very young," said Dixon.

The newly reported research involved looking at the same data as the 2004 study and using multiverse analyses -- a technique that involves asking a research question hundreds of different ways to determine if the answers are similar each time. This method was used to create 848 analyses to find out if early TV viewing causes later attention problems. A vast majority of results showed no link between the two. The few that did, the authors believe, reflect some oddities in the data set that are not likely to represent the real world.

From Science Daily

First X-rays from Uranus discovered

Astronomers have detected X-rays from Uranus for the first time, using NASA's Chandra X-ray Observatory. This result may help scientists learn more about this enigmatic ice giant planet in our solar system.

Uranus is the seventh planet from the Sun and has two sets of rings around its equator. The planet, which has four times the diameter of Earth, rotates on its side, making it different from all other planets in the solar system. Since Voyager 2 was the only spacecraft to ever fly by Uranus, astronomers currently rely on telescopes much closer to Earth, like Chandra and the Hubble Space Telescope, to learn about this distant and cold planet that is made up almost entirely of hydrogen and helium.

In the new study, researchers used Chandra observations taken in Uranus in 2002 and then again in 2017. They saw a clear detection of X-rays from the first observation, just analyzed recently, and a possible flare of X-rays in those obtained fifteen years later. The main graphic shows a Chandra X-ray image of Uranus from 2002 (in pink) superimposed on an optical image from the Keck-I Telescope obtained in a separate study in 2004. The latter shows the planet at approximately the same orientation as it was during the 2002 Chandra observations.

What could cause Uranus to emit X-rays? The answer: mainly the Sun. Astronomers have observed that both Jupiter and Saturn scatter X-ray light given off by the Sun, similar to how Earth's atmosphere scatters the Sun's light. While the authors of the new Uranus study initially expected that most of the X-rays detected would also be from scattering, there are tantalizing hints that at least one other source of X-rays is present. If further observations confirm this, it could have intriguing implications for understanding Uranus.

One possibility is that the rings of Uranus are producing X-rays themselves, which is the case for Saturn's rings. Uranus is surrounded by charged particles such as electrons and protons in its nearby space environment. If these energetic particles collide with the rings, they could cause the rings to glow in X-rays. Another possibility is that at least some of the X-rays come from auroras on Uranus, a phenomenon that has previously been observed on this planet at other wavelengths.

On Earth, we can see colorful light shows in the sky called auroras, which happen when high-energy particles interact with the atmosphere. X-rays are emitted in Earth's auroras, produced by energetic electrons after they travel down the planet's magnetic field lines to its poles and are slowed down by the atmosphere. Jupiter has auroras, too. The X-rays from auroras on Jupiter come from two sources: electrons traveling down magnetic field lines, as on Earth, and positively charged atoms and molecules raining down at Jupiter's polar regions. However, scientists are less certain about what causes auroras on Uranus. Chandra's observations may help figure out this mystery.

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Ancient meteoritic impact over Antarctica 430,000 years ago

 A research team of international space scientists, led by Dr Matthias van Ginneken from the University of Kent's School of Physical Sciences, has found new evidence of a low-altitude meteoritic touchdown event reaching the Antarctic ice sheet 430,000 years ago.

Extra-terrestrial particles (condensation spherules) recovered on the summit of Walnumfjellet (WN) within the Sør Rondane Mountains, Queen Maud Land, East Antarctica, indicate an unusual touchdown event where a jet of melted and vaporised meteoritic material resulting from the atmospheric entry of an asteroid at least 100 m in size reached the surface at high velocity.

This type of explosion caused by a single-asteroid impact is described as intermediate, as it is larger than an airburst, but smaller than an impact cratering event.

The chondritic bulk major, trace element chemistry and high nickel content of the debris demonstrate the extra-terrestrial nature of the recovered particles. Their unique oxygen isotopic signatures indicate that their interacted with oxygen derived from the Antarctic ice sheet during their formation in the impact plume.

The findings indicate an impact much more hazardous that the Tunguska and Chelyabinsk events over Russia in 1908 and 2013, respectively.

This research, published by Science Advances, guides an important discovery for the geological record where evidence of such events in scarce. This is primarily due to the difficult in identifying and characterising impact particles.

The study highlights the importance of reassessing the threat of medium-sized asteroids, as it likely that similar touchdown events will produce similar particles. Such an event would be entirely destructive over a large area, corresponding to the area of interaction between the hot jet and the ground.

Dr van Ginneken said: 'To complete Earth's asteroid impact record, we recommend that future studies should focus on the identification of similar events on different targets, such as rocky or shallow oceanic basements, as the Antarctic ice sheet only covers 9% of Earth's land surface. Our research may also prove useful for the identification of these events in deep sea sediment cores and, if plume expansion reaches landmasses, the sedimentary record.

'While touchdown events may not threaten human activity if occurring over Antarctica, if it was to take place above a densely populated area, it would result in millions of casualties and severe damages over distances of up to hundreds of kilometres.'

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Multilingual people have an advantage over those fluent in only two languages

 Multilingual people have trained their brains to learn languages, making it easier to acquire more new languages after mastering a second or third. In addition to demystifying the seemingly herculean genius of multilinguals, researchers say these results provide some of the first neuroscientific evidence that language skills are additive, a theory known as the cumulative?enhancement model of language acquisition.

"The traditional idea is, if you understand bilinguals, you can use those same details to understand multilinguals. We rigorously checked that possibility with this research and saw multilinguals' language acquisition skills are not equivalent, but superior to those of bilinguals," said Professor Kuniyoshi L. Sakai from the University of Tokyo, an expert in the neuroscience of language and last author of the research study recently published in Scientific Reports. This joint research project includes collaboration with Professor Suzanne Flynn from the Massachusetts Institute of Technology (MIT), a specialist in linguistics and multilanguage acquisition, who first proposed the cumulative?enhancement model.

Neuroscientists measured brain activity while 21 bilingual and 28 multilingual adult volunteers tried to identify words and sentences in Kazakh, a language brand new to them.

All participants were native speakers of Japanese whose second language was English. Most of the multilingual participants had learned Spanish as a third language, but others had learned Chinese, Korean, Russian or German. Some knew up to five languages.

Fluency in multiple languages requires command of different sounds, vocabularies, sentence structures and grammar rules. Sentences in English and Spanish are usually structured with the noun or verb at the start of a phrase, but Japanese and Kazakh consistently place nouns or verbs at the end of a phrase. English, Spanish and Kazakh grammars require subject-verb agreement (she walks, they walk), but Japanese grammar does not.

Instead of grammar drills or conversation skills in a classroom, researchers simulated a more natural language learning environment where volunteers had to figure out the fundamentals of a new language purely by listening. Volunteers listened to recordings of individual Kazakh words or short sentences including those words while watching a screen with plus or minus symbols to signal if the sentence was grammatically correct or not. Volunteers were given a series of four increasingly difficult listening tests while researchers measured their brain activity using functional magnetic resonance imaging (fMRI).

In the simplest test, volunteers had to determine if they were hearing a word from the earlier learning session or if it was a grammatically different version of the same word; for example: run/ran or take/takes. In the next test levels, volunteers listened to example sentences and were asked if the sentences were grammatically correct and to decipher sentence structures by identifying noun-verb pairs. For example, "We understood that John thought," is translated in Kazakh as "Biz John oyladï dep tu?sindik." The sentence would be grammatically incorrect if volunteers heard tu?sindi instead of tu?sindik. The correct noun-verb pairs are we understood (Biz tu?sindik) and John thought (John oyladï).

Volunteers could retake the learning session and repeat the test an unlimited number of times until they passed and progressed to the next level of difficulty.

Multilingual participants who were more fluent in their second and third languages were able to pass the Kazakh tests with fewer repeated learning sessions than their less-fluent multilingual peers. More-fluent multilinguals also became faster at choosing an answer as they progressed from the third to fourth test level, a sign of increased confidence and that knowledge acquired during easier tests was successfully transferred to higher levels.

"For multilinguals, in Kazakh, the pattern of brain activation is similar to that for bilinguals, but the activation is much more sensitive, and much faster," said Sakai.

The pattern of brain activation in bilingual and multilingual volunteers fits current understanding of how the brain understands language, specifically that portions of the left frontal lobe become more active when understanding both the content and meaning of a sentence. When learning a second language, it is normal for the corresponding areas on the right side of the brain to become active and assist in efforts to understand.

Multilingual volunteers had no detectable right-side activation during the initial, simple Kazakh grammar test level, but brain scans showed strong activity in those assisting areas of bilingual volunteers' brains.

Researchers also detected differences in the basal ganglia, often considered a more fundamental area of the brain. Bilingual volunteers' basal ganglia had low levels of activation that spiked as they progressed through the test and then returned to a low level at the start of the next test. Multilingual volunteers began the first test level with similarly low basal ganglia activity that spiked and then remained high throughout the subsequent test levels.

The UTokyo-MIT research team says this activation pattern in the basal ganglia shows that multilingual people can make generalizations and build on prior knowledge, rather than approach each new grammar rule as a separate idea to understand from scratch.

Prior studies by Sakai and others have found a three-part timeline of changes in brain activation while learning a new language: an initial increase, a high plateau and a decline to the same low level of activation required to understand the native language.

These new results confirm that pattern in multilinguals and support the possibility that prior experience progressing through those stages of language learning makes it easier to do again, supporting the cumulative-enhancement model of language acquisition.

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Undetected coronavirus variant was in at least 15 countries before its discovery, study finds

 A highly contagious SARS-CoV-2 variant was unknowingly spreading for months in the United States by October 2020, according to a new study from researchers with The University of Texas at Austin COVID-19 Modeling Consortium. Scientists first discovered it in early December in the United Kingdom, where the highly contagious and more lethal variant is thought to have originated. The journal Emerging Infectious Diseases, which has published an early-release version of the study, provides evidence that the coronavirus variant B117 (501Y) had spread across the globe undetected for months when scientists discovered it.

"By the time we learned about the U.K. variant in December, it was already silently spreading across the globe," said Lauren Ancel Meyers, the director of the COVID-19 Modeling Consortium at The University of Texas at Austin and a professor of integrative biology. "We estimate that the B117 variant probably arrived in the U.S. by October of 2020, two months before we knew it existed."

Analyzing data from 15 countries, researchers estimated the chance that travelers from the U.K. introduced the variant into 15 countries between Sept. 22 and Dec. 7, 2020. They found that the virus variant had almost certainly arrived in all 15 countries by mid-November. In the U.S., the variant probably had arrived by mid-October.

"This study highlights the importance of laboratory surveillance," Meyers said. "Rapid and extensive sequencing of virus samples is critical for early detection and tracking of new variants of concern."

In conjunction with the paper's publication, consortium members developed a new tool that decision-makers anywhere in the United States can use in planning for genetic sequencing that helps to detect the presence of variants. To help the U.S. expand national surveillance of variants, the new online calculator indicates the number of virus samples that must be sequenced in order to detect new variants when they first emerge. For example, if the goal is to detect an emerging variant by the time it is causing 1 out of every 1,000 new COVID-19 infections, approximately 3,000 SARS-CoV-2 positive specimens per week need to be sequenced.

"Health officials are looking for better ways to manage the unpredictability of this virus and future variants," said Spencer Woody, a postdoctoral fellow at the UT COVID-19 Modeling Consortium. "Our new calculator determines how many positive SARS-CoV-2 specimens must be sequenced to ensure that new threats are identified as soon as they start spreading."

He explained that the calculator has a second feature. "It also helps labs figure out how quickly they will detect new variants, given their current sequencing capacity."

"We created this tool to support federal, state and local health officials in building credible early warning systems for this and future pandemic threats," Meyers said.

In addition to Meyers, authors of the Emerging Infectious Disease paper are Zhanwei Du, Bingyi Yang, Sheikh Taslim Ali, Tim K. Tsang, Songwei Shan, Peng Wu, Eric H.Y. Lau and Benjamin J. Cowling of the WHO Collaborating Centre for Infectious Disease Epidemiology and Control in Hong Kong and Lin Wang of the University of Cambridge.

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