пятница, 17 января 2020 г.

Infectious disease defenses among ancient hominid contributions to adaptation of modern humans

During the past decade, our human evolutionary tree has turned into something more resembling an unwieldy bush. Scientists have discovered swapped segments of DNA that we shared from mating between two other hominids, Neanderthals and Denisovans, which were first sequenced in 2010 and 2014, respectively.

Infectious disease defenses among ancient hominid contributions to adaptation of modern humans
A reconstruction of a Neanderthal man (right) based on skull found at the La Ferrassie rock shelter in Dordogne Valley,
France. He's face to face with a male Homo sapien [Credit: Philippe Plailly & Atelier Daynes/Science Source]
How much of our hominid cousins remains in each of us today, and whether or not the presence of ancient hominid DNA has conferred any adaptation advantages or disadvantages has been a prime area of exploration.

Scientists have shown that single hominid genes can convey advantages, including a famous case of high-altitude adaption, which was the result of DNA swapping, otherwise known as genomic introgression, of a Denisovan for the gene EPAS1. That discovery may help explain why Tibetans are uniquely adapted to high-altitude living.

But since most diseases are likely are result of multiple genes and often exhibit complex traits, unpacking ancient hominid contributions to our genomes has been a difficult task.

Now, in a new study published in the advanced online edition of Molecular Biology and Evolution, scientists Alexandre Gouy and Laurent Excoffier have developed new computational tools to better analyze human genome datasets, and found more evidence of a legacy of ancient hominid adaptation, particularly to help fight off infectious diseases like malaria.

"Our results confirm that archaic introgression is widespread in immunity-related genes and that pathogens represent a strong selective pressure which could be one of the major causes of adaptive evolution in humans," said the authors. "Overall, our results suggest that archaic introgression has affected human metabolism and response to different types of pathogens (bacteria, virus and protists), which have been critically determinant during human adaptive history," said Excoffier.

In this study, the duo analyzed the latest archaic introgression maps that have been recently made available for 35 Melanesian individuals as well as samples from the 1000 Genomes project.

"Our results show not only that introgression is found at many genes involved in the same functions, but also that some of these interacting genes carrying archaic DNA have been co-selected," said Gouy.

Rather than analyze individual genes, they set about focusing on methods to detect patterns of introgression based on biological pathway analysis and data sets of connected genes and subnetworks.

They were able to identify highly introgressed subnetworks among three primary biological pathway databases (KEGG, NCI and Reactome), and among each of the three populations they looked at, including East Asians, Europeans and Papua New Guineans.

One of the more striking areas of evidence of possible resistance to malaria among the Papua New Guineans.

"One of the most striking areas of evidence of adaptive introgression is a possible resistance to malaria among Papua New Guineans," said Excoffier.

Also, beyond infectious disease, they also found evidence of introgression in genes related to porphyrins that are involved in energy metabolism (respiratory chain) and iron and oxygen binding in red blood cells (hemoglobin) and muscles (myoglobin), as well as in olfactory receptors showing signals of Neanderthal introgression among modern European populations.

One of the more strongly controversial areas is the development of modern human behavior and cognition. Though the authors caution the work is still very preliminary, they did find evidence of introgression among gene networks involved in such functions.

"These results suggest that archaic introgression might have also affected behavioral/neuronal traits, even though it is difficult to link these phenotypes to a precise selective pressure."

Their results build on other studies that have identified Neanderthal variants at two SLC loci (SLC6A11, SLC6A13) that have previously been associated with behavioral traits (depression, mood disorders, smoking behavior) and some gene variants that have been shown to be preferentially expressed in the brain.

"In Papuans, we also found genes showing a significant excess of introgression that have been respectively associated to autism susceptibility and attention deficit/hyperactivity disorder, e.g. SLC9A9," said Gouy. They also reported on other genes from the same family that have a brain-biased expression and show an excess of introgressed segments in East Asians and Europeans, including SLC6A1 (a GABA transporter), SLC6A5 (a neurotransmitter transporter) and SLC28A1, as well as in Papua New Guineans, with SLC4A10 (controlling intracellular pH of neurons and brain extracellular fluid).

Further explorations of these areas of influence will be needed to tease out their contributions to human health and disease.

Even though the overall amount of Neanderthal and Denisovan introgression is quite low in modern humans (typically 1-3%), their evidence continues to build the scientific case that the hominid DNA that remains has helped shaped modern human adaptation. It also suggests that these hominid windows into the past have a strong impact and continue to exert their influence on the present fitness of modern humans.

Source: Oxford University Press [January 14, 2020]

* This article was originally published here

How the Cat protected the Dog

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Channel: UFO Odessa  

Amazing dog behavior. He is very short, but cocky. Jumps to the neighboring dogs, a shepherd and a dog, and barks at them, they hide in the corners. I hardly managed to get him to return to the yard. And when he jumped home. That cat came, his friend, and began to hug him with his tail, to protect him from me, and I scolded him for leprosy, that he constantly runs away and scares huge dogs. Kitty felt sorry for his friend and he turned around until the owner became kind.October 24, 2019Задиристый низкого роста пёс, любит дразнить и пугать огромных соседских псов. Он перепрыгивает к ним во двор, и огромные псы трусливо жмутся по углам. Мне с трудом удалось его заставить вернуться во двор. Когда он перепрыгнул во двор дома, я начал его ругать за проказы, пришёл кот, его друг, и начал его обнимать хвостом, защищать от меня, кот вертелся и обнимал пса хвостом до тех пор, пока мне не стало смешно на это всё смотреть.

Video length: 7:22
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The interiors of stars

The interiors of stars are largely mysterious regions because they are so difficult to observe. Our lack of understanding about the physical processes there, like rotation and the mixing of hot gas, introduces considerable ambuguity about how stars shine and how they evolve. Stellar oscillations, detected through brightness fluctuations, offer one way to probe these subsurface regions.

The interiors of stars
An illustration of vibration modes in the Sun. Astronomers have used the TESS mission to study for the first time
stellar oscillations in intermeidate mass stars [Credit: Kosovichev et al., Structure and Rotation
of the Solar Interior: Initial Results from the MDI Medium-L Program]
In the Sun, these vibrations are due to pressure waves generated by turbulence in its outer layers (the layers dominated by convective gas motions). Helioseismology is the name given to the study of these oscillations in the Sun, and asteroseismology is the term used for the same study in other stars.

Astronomers have long detected strong brightness variations in other stars, for example the class of Cepheid variable stars used to calibrate the cosmic distance scale, but the small, solar-like oscillations driven by convection near the star’s surface are much harder to see.

Over the past few decades, space telescopes have successfully applied astroseismology to solar-type stars spanning many stages of stellar life. CfA astronomer Dave Latham was a member of a large team of astronomers who used the new TESS (Transiting Exoplanet Survey Satellite) datasets to study the interiors of the class of intermediate mass stars known as δ Sct and γ Dor stars.

These stars are more massive than the Sun but not large enough to burn through their hydrogen fuel very rapidly and die as supernovae. Pulsations generally arise principally from one of two processes, those dominated by pressure (where the gas pressure restores perturbations) or by gravity (where buoyancy does).

In these intermediate-mass stars both of these processes can be important, with pulsations having typical periods of roughly about six hours. The complexity of the combined processes, among other things, results in these intermediate-mass stars coming in a veritable zoo of variability types, and this variety offers astronomers more ways to test models of stellar interiors.

The astronomers analyzed TESS data on 117 of these stars using observations taken every two minutes; accurate distances to the stars (and hence accurate luminosities) were obtained from Gaia satellite measurements. The team was able for the first time to fully test and successfully refine models of pulsation for these stars.

They found, for example, that gas mixing in the outer envelope plays an important role. They also spotted many higher-frequency pulsators, thereby identifying promising targets for future studies. Not least, they showed that the TESS mission has enormous potential not just for studying exoplanets, but also for improving our understanding the interiors of intermediate mass stars.

The study appears in Monthly Notices of the Royal Astronomical Society.

Source: Harvard-Smithsonian Center for Astrophysics [January 11, 2020]

* This article was originally published here

Stars need a partner to spin universe's brightest explosions

When it comes to the biggest and brightest explosions seen in the Universe, University of Warwick astronomers have found that it takes two stars to make a gamma-ray burst.

Stars need a partner to spin universe's brightest explosions
Artist’s impression of gamma-ray burst with orbiting binary star
[Credit: University of Warwick/Mark Garlick]
New research solves the mystery of how stars spin fast enough to create conditions to launch a jet of highly energetic material into space, and has found that tidal effects like those between the Moon and the Earth are the answer.

The discovery, reported in Monthly Notices of the Royal Astronomical Society, has been made using simulated models of thousands of binary star systems, that is, solar systems that have two stars orbiting one another.

More than half of all stars are located in binary star systems and this new research has shown that they need to be in binary star systems in order for the massive explosions to be created.

A long gamma-ray burst (GRB), the type examined in this study, occurs when a massive star about ten times the size of our sun goes supernova, collapses into a neutron star or black hole and fires a relativistic jet of material into space. Instead of the star collapsing radially inwards, it flattens down into a disc to conserve angular momentum. As the material falls inwards, that angular momentum launches it in the form of a jet along the polar axis.

But in order to form that jet of material, the star has to be spinning fast enough to launch material along the axis. This presents a problem because stars usually lose any spin they acquire very quickly. By modelling the behaviour of these massive stars as they collapse, the researchers have been able to constrain the factors that cause a jet to be formed.

They found that the effects of tides from a close neighbour - the same effect that has the Moon and the Earth locked together in their spin - could be responsible for spinning these stars at the rate needed to create a gamma-ray burst.

Gamma-ray bursts are the most luminous events in the Universe and are observable from Earth when their jet of material is pointed directly at us. This means that we only see around 10-20% of the GRBs in our skies.

Lead author Ashley Chrimes, a PhD student in the University of Warwick Department of Physics, said: "We're predicting what kind of stars or systems produce gamma-ray bursts, which are the biggest explosions in the Universe. Until now it's been unclear what kind of stars or binary systems you need to produce that result.

"The question has been how a star starts spinning, or maintains its spin over time. We found that the effect of a star's tides on its partner is stopping them from slowing down and, in some cases, it is spinning them up. They are stealing rotational energy from their companion, a consequence of which is that they then drift further away.

"What we have determined is that the majority of stars are spinning fast precisely because they're in a binary system."

The study uses a collection of binary stellar evolution models created by researchers from the University of Warwick and Dr J J Eldridge from the University of Auckland. Using a technique called binary population synthesis, the scientists are able to simulate this mechanism in a population of thousands of star systems and so identify the rare examples where an explosion of this type can occur.

Dr Elizabeth Stanway, from the University of Warwick Department of Physics, said: "Scientists haven't modelled in detail for binary evolution in the past because it's a very complex calculation to do. This work has considered a physical mechanism within those models that we haven't examined before, that suggests that binaries can produce enough GRBs using this method to explain the number that we are observing.

"There has also been a big dilemma over the metallicity of stars that produce gamma-ray bursts. As astronomers, we measure the composition of stars and the dominant pathway for gamma-ray bursts requires very few iron atoms or other heavy elements in the stellar atmosphere. There's been a puzzle over why we see a variety of compositions in the stars producing gamma-ray bursts, and this model offers an explanation."

Ashley added: "This model allows us to predict what these systems should look like observationally in terms of their temperature and luminosity, and what the properties of the companion are likely to be. We are now interested in applying this analysis to explore different astrophysical transients, such as fast radio bursts, and can potentially model rarer events such as black holes spiralling into stars."

Author: Peter Thorley | Source: University of Warwick [January 13, 2020]

* This article was originally published here

2020 January 17 Apollo 17: A Stereo View from Lunar Orbit Gene...

2020 January 17

Apollo 17: A Stereo View from Lunar Orbit
Gene Cernan, Apollo 17, NASA; Anaglyph by Patrick Vantuyne

Explanation: Get out your red/blue glasses and check out this awesome stereo view of another world. The scene was recorded by Apollo 17 mission commander Eugene Cernan on December 11, 1972, one orbit before descending to land on the Moon. The stereo anaglyph was assembled from two photographs (AS17-147-22465, AS17-147-22466) captured from his vantage point on board the Lunar Module Challenger as he and Dr. Harrison Schmitt flew over Apollo 17’s landing site in the Taurus-Littrow Valley. The broad, sunlit face of the mountain dubbed South Massif rises near the center of the frame, above the dark floor of Taurus-Littrow to its left. Beyond the mountains, toward the lunar limb, lies the Moon’s Mare Serenitatis. Piloted by Ron Evans, the Command Module America is visible in orbit in the foreground against the South Massif’s peak.

∞ Source: apod.nasa.gov/apod/ap200117.html

* This article was originally published here

TESS dates an ancient collision with our galaxy

A single bright star in the constellation of Indus, visible from the southern hemisphere, has revealed new insights on an ancient collision that our galaxy the Milky Way underwent with another smaller galaxy called Gaia-Enceladus early in its history.

TESS dates an ancient collision with our galaxy
A snapshot from TESS of part of the southern sky showing the location of ν Indi (blue circle), the plane of the
Milky Way (bottom left) and the southern ecliptic pole (top). These snapshots come from data collected
in TESS observing sectors 1, 12 and 13 [Credit: J. T. Mackereth]
An international team of scientists led by the University of Birmingham adopted the novel approach of applying the forensic characterisation of a single ancient, bright star called ν Indi as a probe of the history of the Milky Way. Stars carry "fossilized records" of their histories and hence the environments in which they formed. The team used data from satellites and ground-based telescopes to unlock this information from ν Indi. Their results are published in the journal Nature Astronomy.

The star was aged using its natural oscillations (asteroseismology), detected in data collected by NASA's recently launched Transiting Exoplanet Survey Satellite (TESS). Launched in 2018, TESS is surveying stars across most of the sky to search for planets orbiting the stars and to study the stars themselves. When combined with data from the European Space Agency (ESA) Gaia Mission, the detective story revealed that this ancient star was born early in the life of the Milky Way, but the Gaia-Enceladus collision altered its motion through our Galaxy.

The animation shows a schematic of the orbits of three stars within our Galaxy the Milky Way – whose extent is marked by
 the dashed line -- as viewed from above (left) and side-on (right), projected over the next half a billion years. The three 
stars are: nu Indi, the subject of the Nature Astronomy paper; a star accreted from Gaia-Enceladus (after its collision 
with the Milky Way); and the Sun. The accreted star came from outside the Galaxy, as part of the Gaia-Enceladus 
collision, and so has a very elongated orbit. The collision affected the motion and orbit of nu Indi. 
Notice how its orbit is quite different to that of the Sun [Credit: J. T. Mackereth] 

Bill Chaplin, Professor of Astrophysics at the University of Birmingham and lead author of the study said: "Since the motion of ν Indi was affected by the Gaia-Enceladus collision, the collision must have happened once the star had formed. That is how we have been able to use the asteroseismically-determined age to place new limits on when the Gaia-Enceladus event occurred."

Co-author Dr Ted Mackereth, also from Birmingham, said: "Because we see so many stars from Gaia-Enceladus, we think it must have had a large impact on the evolution of our Galaxy. Understanding that is now a very hot topic in astronomy, and this study is an important step in understanding when this collision occurred."

Bill Chaplin added: "This study demonstrates the potential of asteroseismology with TESS, and what is possible when one has a variety of cutting-edge data available on a single, bright star"

The research clearly shows the strong potential of the TESS programme to draw together rich new insights about the stars that are our closest neighbours in the Milky Way. The research was funded by the Science and Technology Facilities Council and the European Research Council through the Asterochronometry project.

Source: University of Birmingham [January 13, 2020]

* This article was originally published here

How the solar system got its 'Great Divide,' and why it matters for life on Earth

Scientists, including those from the University of Colorado Boulder, have finally scaled the solar system's equivalent of the Rocky Mountain range.

How the solar system got its 'Great Divide,' and why it matters for life on Earth
An orrery, a type of device once used to track the movements of the planets, sitting above an infrared image
of a hypothetical "protoplanetary" disk that may have divided the solar system early in its history
[Credit: K. Ebert/Innovative Ideas & Methods]
In a study published in Nature Astronomy, researchers from the United States and Japan unveil the possible origins of our cosmic neighborhood's "Great Divide." This well-known schism may have separated the solar system just after the sun first formed.

The phenomenon is a bit like how the Rocky Mountains divide North America into east and west. On the one side are "terrestrial" planet, such as Earth and Mars. They are made up of fundamentally different types of materials than the more distant "jovians," such as Jupiter and Saturn.

"The question is: How do you create this compositional dichotomy?" said lead author Ramon Brasser, a researcher at the Earth-Life Science Institute (ELSI) at the Tokyo Institute of Technology in Japan. "How do you ensure that material from the inner and outer solar system didn't mix from very early on in its history?"

Brasser and coauthor Stephen Mojzsis, a professor in CU Boulder's Department of Geological Sciences, think they have the answer, and it may just shed new light on how life originated on Earth.

A sun disk holds vital clues

The duo suggests that the early solar system was partitioned into at least two regions by a ring-like structure that formed a disk around the young sun. This disk might have held major implications for the evolution of planets and asteroids, and even the history of life on Earth.

"The most likely explanation for that compositional difference is that it emerged from an intrinsic structure of this disk of gas and dust," Mojzsis said.

Mojzsis noted that the Great Divide, a term that he and Brasser coined, does not look like much today. It is a relatively empty stretch of space that sits near Jupiter, just beyond what astronomers call the asteroid belt.

How the solar system got its 'Great Divide,' and why it matters for life on Earth
How the solar system got its 'Great Divide,' and why it matters for life on Earth
Two so-called "ALMA disks" as seen in infrared light around distant stars
But you can still detect its presence throughout the solar system. Move sunward from that line, and most planets and asteroids tend to carry relatively low abundances of organic molecules. Go the other direction toward Jupiter and beyond, however, and a different picture emerges: Almost everything in this distant part of the solar system is made up of materials that are rich in carbon. This dichotomy "was really a surprise when it was first found," Mojzsis said.

Many scientists assumed that Jupiter was the agent responsible for that surprise. The thinking went that the planet is so massive that it may have acted as a gravitational barrier, preventing pebbles and dust from the outer solar system from spiraling toward the sun.

But Mojzsis and Brasser were not convinced. The scientists used a series of computer simulations to explore Jupiter's role in the evolving solar system. They found that while Jupiter is big, it was probably never big enough early in its formation to entirely block the flow of rocky material from moving sunward.

"We banged our head against the wall," Brasser said. "If Jupiter wasn't the agent responsible for creating and maintaining that compositional dichotomy, what else could be?"

A solution in plain sight

For years, scientists operating an observatory in Chile called the Atacama Large Millimeter/submillimeter Array (ALMA) had noticed something unusual around distant stars: Young stellar systems were often surrounded by disks of gas and dust that, in infrared light, looked a bit like a tiger's eye.

If a similar ring existed in our own solar system billions of years ago, Brasser and Mojzsis reasoned, it could theoretically be responsible for the Great Divide.

That's because such a ring would create alternating bands of high- and low-pressure gas and dust. Those bands, in turn, might pull the solar system's earliest building blocks into several distinct sinks--one that would have given rise to Jupiter and Saturn, and another Earth and Mars.

In the mountains, "the Great Divide causes water to drain one way or another," Mojzsis said. "It's similar to how this pressure bump would have divided material" in the solar system.

But, he added, there's a caveat: That barrier in space likely was not perfect. Some outer solar system material may still have climbed across the divide. And those fugitives could have been important for the evolution of our own world.

"Those materials that might go to the Earth would be those volatile, carbon-rich materials," Mojzsis said. "And that gives you water. It gives you organics."

The rest is Earth history.

Author: Daniel Strain | Source: University of Colorado at Boulder [January 13, 2020]

* This article was originally published here

Torhouse Prehistoric Stone Row, Dumfries and Galloway, Scotland, 12.1.20.

Torhouse Prehistoric Stone Row, Dumfries and Galloway, Scotland, 12.1.20.

* This article was originally published here

Meteorite contains the oldest material on Earth: 7-billion-year-old stardust

Stars have life cycles. They're born when bits of dust and gas floating through space find each other and collapse in on each other and heat up. They burn for millions to billions of years, and then they die. When they die, they pitch the particles that formed in their winds out into space, and those bits of stardust eventually form new stars, along with new planets and moons and meteorites. And in a meteorite that fell fifty years ago in Australia, scientists have now discovered stardust that formed 5 to 7 billion years ago-the oldest solid material ever found on Earth.

Meteorite contains the oldest material on Earth: 7-billion-year-old stardust
Dust-rich outflows of evolved stars similar to the pictured Egg Nebula are plausible sources of the large presolar silicon
carbide grains found in meteorites like Murchison [Credit: NASA, W. Sparks (STScI) and R. Sahai (JPL).
Inset: SiC grain with ~8 micrometers in its longest dimension, courtesy of Janaina N. Avila]
"This is one of the most exciting studies I've worked on," says Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and lead author of a paper describing the findings in Proceedings of the National Academy of Sciences. "These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy."

The materials Heck and his colleagues examined are called presolar grains-minerals formed before the Sun was born. "They're solid samples of stars, real stardust," says Heck. These bits of stardust became trapped in meteorites where they remained unchanged for billions of years, making them time capsules of the time before the solar system..

But presolar grains are hard to come by. They're rare, found only in about five percent of meteorites that have fallen to Earth, and they're tiny-a hundred of the biggest ones would fit on the period at the end of this sentence. But the Field Museum has the largest portion of the Murchison meteorite, a treasure trove of presolar grains that fell in Australia in 1969 and that the people of Murchison, Victoria, made available to science. Presolar grains for this study were isolated from the Murchison meteorite for this study about 30 years ago at the University of Chicago.

"It starts with crushing fragments of the meteorite down into a powder ," explains Jennika Greer, a graduate student at the Field Museum and the University of Chicago and co-author of the study. "Once all the pieces are segregated, it's a kind of paste, and it has a pungent characteristic-it smells like rotten peanut butter."

This "rotten-peanut-butter-meteorite paste" was then dissolved with acid, until only the presolar grains remained. "It's like burning down the haystack to find the needle," says Heck.

Once the presolar grains were isolated, the researchers figured out from what types of stars they came and how old they were. "We used exposure age data, which basically measures their exposure to cosmic rays, which are high-energy particles that fly through our galaxy and penetrate solid matter," explains Heck. "Some of these cosmic rays interact with the matter and form new elements. And the longer they get exposed, the more those elements form.

"I compare this with putting out a bucket in a rainstorm. Assuming the rainfall is constant, the amount of water that accumulates in the bucket tells you how long it was exposed," he adds. By measuring how many of these new cosmic-ray produced elements are present in a presolar grain, we can tell how long it was exposed to cosmic rays, which tells us how old it is.

Meteorite contains the oldest material on Earth: 7-billion-year-old stardust
Scanning electron micrograph of a dated presolar silicon carbide grain. The grain is ~8 micrometers
 in its longest dimension [Credit: Janaina N. Avila]
The researchers learned that some of the presolar grains in their sample were the oldest ever discovered-based on how many cosmic rays they'd soaked up, most of the grains had to be 4.6 to 4.9 billion years old, and some grains were even older than 5.5 billion years. For context, our Sun is 4.6 billion years old, and the Earth is 4.5 billion.

But the age of the presolar grains wasn't the end of the discovery. Since presolar grains are formed when a star dies, they can tell us about the history of stars. And 7 billion years ago, there was apparently a bumper crop of new stars forming-a sort of astral baby boom.

"We have more young grains that we expected," says Heck. "Our hypothesis is that the majority of those grains, which are 4.9 to 4.6 billion years old, formed in an episode of enhanced star formation. There was a time before the start of the Solar System when more stars formed than normal."

This finding is ammo in a debate between scientists about whether or not new stars form at a steady rate, or if there are highs and lows in the number of new stars over time. "Some people think that the star formation rate of the galaxy is constant," says Heck. "But thanks to these grains, we now have direct evidence for a period of enhanced star formation in our galaxy seven billion years ago with samples from meteorites. This is one of the key findings of our study."

Heck notes that this isn't the only unexpected thing his team found. As almost a side note to the main research questions, in examining the way that the minerals in the grains interacted with cosmic rays, the researchers also learned that presolar grains often float through space stuck together in large clusters, "like granola," says Heck. "No one thought this was possible at that scale."

Heck and his colleagues look forward to all of these discoveries furthering our knowledge of our galaxy. "With this study, we have directly determined the lifetimes of stardust. We hope this will be picked up and studied so that people can use this as input for models of the whole galactic life cycle," he says.

Heck notes that there are lifetimes' worth of questions left to answer about presolar grains and the early Solar System. "I wish we had more people working on it to learn more about our home galaxy, the Milky Way," he says.

"Once learning about this, how do you want to study anything else?" says Greer. "It's awesome, it's the most interesting thing in the world."

"I always wanted to do astronomy with geological samples I can hold in my hand," says Heck. "It's so exciting to look at the history of our galaxy. Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the Sun."

"It's the next best thing to being able to take a sample directly from a star," says Greer.

Source: Field Museum [January 13, 2020]

* This article was originally published here

Grange Burn Stone Circle, Isle of Whithorn, Dumfries and Galloway, Scotland, 12.1.20.Like the Grange...

Grange Burn Stone Circle, Isle of Whithorn, Dumfries and Galloway, Scotland, 12.1.20.

Like the Grange Burn Cairn I temporarily named earlier this week, this small stone circle is to be located in the corner of the same field. If anyone can offer further information it would be appreciated.

* This article was originally published here

High temperatures due to global warming will be dramatic even for tardigrades

Global warming, a major aspect of climate change, is already causing a wide range of negative impacts on many habitats of our planet. It is thus of the utmost importance to understand how rising temperatures may affect animal health and welfare.

High temperatures due to global warming will be dramatic even for tardigrades
A research group from Department of Biology, University of Copenhagen has just shown that tardigrades are very
vulnerable to long-term high temperature exposures. Animals, which in their desiccated state are best known
 for their extraordinary tolerance to extreme environments [Credit: Ricardo Neves]
A research group from Department of Biology, University of Copenhagen has just shown that tardigrades are very vulnerable to long-term high temperature exposures. The tiny animals, in their desiccated state, are best known for their extraordinary tolerance to extreme environments.

In a study published recently in Scientific Reports, Ricardo Neves and Nadja Mobjerg and colleagues at Department of Biology, University of Copenhagen present results on the tolerance to high temperatures of a tardigrade species.

Tardigrades, commonly known as water bears or moss piglets, are microscopic invertebrates distributed worldwide in marine, freshwater and terrestrial microhabitats.

Ricardo Neves, Nadja Mobjerg and colleagues investigated the tolerance to high temperatures of Ramazzottius varieornatus, a tardigrade frequently found in transient freshwater habitats.

"The specimens used in this study were obtained from roof gutters of a house located in Niva, Denmark. We evaluated the effect of exposures to high temperature in active and desiccated tardigrades, and we also investigated the effect of a brief acclimation period on active animals," explains postdoc Ricardo Neves.

Rather surprisingly the researchers estimated that for non-acclimated active tardigrades the median lethal temperature is 37.1°C, though a short acclimation periods leads to a small but significant increase of the median lethal temperature to 37.6°C. Interestingly, this temperature is not far from the currently measured maximum temperature in Denmark, i.e. 36.4°C. As for the desiccated specimens, the authors observed that the estimated 50% mortality temperature is 82.7°C following 1 hour exposures, though a significant decrease to 63.1°C following 24 hour exposures was registered.

The research group used logistic models to estimate the median lethal temperature (at which 50% mortality is achieved) both for active and desiccated tardigrades.

Approximately 1300 tardigrade species have been described so far. The body of these minute animals is barrel-shaped (or dorsoventrally compressed) and divided into a head and a trunk with four pairs of legs. Their body length varies between 50 micrometers and 1.2 millimeters. Apart from their impressive ability to tolerate extreme environments, tardigrades are also very interesting because of their close evolutionary relationship with arthropods (e.g., insects, crustaceans, spiders).

As aquatic animals, tardigrades need to be surrounded in a film of water to be in their active state (i.e., feeding and reproducing). However, these critters are able to endure periods of desiccation (anhydrobiosis) by entering cryptobiosis, i.e., a reversible ametabolic state common especially among limno-terrestrial species. Succinctly, tardigrades enter the so-called "tun" state by contracting their anterior-posterior body axis, retracting their legs and rearranging the internal organs. This provides them with the capacity to tolerate severe environmental conditions including oxygen depletion (anoxybiosis), high toxicant concentrations (chemobiosis), high solute concentration (osmobiosis) and extremely low temperatures (cryobiosis).

The extraordinary tolerance of tardigrades to extreme environments includes also high temperature endurance. Some tardigrade species were reported to tolerate temperatures as high as 151°C. However, the exposure time was only of 30 minutes. Other studies on thermotolerance of desiccated (anhydrobiotic) tardigrades revealed that exposures higher than 80°C for 1 hour resulted in high mortality, with almost all specimens dying at temperatures above 103°C. It remained, yet, unknown how anhydrobiotic tardigrades handle exposures to high temperatures for long periods, i.e., exceeding 1 hour.

"From this study, we can conclude that active tardigrades are vulnerable to high temperatures, though it seems that these critters would be able to acclimatize to increasing temperatures in their natural habitat. Desiccated tardigrades are much more resilient and can endure temperatures much higher than those endured by active tardigrades. However, exposure-time is clearly a limiting factor that constrains their tolerance to high temperatures," says Ricardo Neves.

Indeed, although tardigrades are able to tolerate a diverse set of severe environmental conditions, their endurance to high temperatures is noticeably limited and this might actually be the Achilles heel of these otherwise super-resistant animals.

Source: Faculty of Science - University of Copenhagen [January 13, 2020]

* This article was originally published here

Cairnholy II Prehistoric Chambered Cairn, Creetown, Dumfries and Galloway, Scotland, 12.1.20.

Cairnholy II Prehistoric Chambered Cairn, Creetown, Dumfries and Galloway, Scotland, 12.1.20.

* This article was originally published here

Iodine may slow ozone layer recovery

A new paper quantifying small levels of iodine in Earth's stratosphere could help explain why some of the planet's protective ozone layer isn't healing as fast as expected.

Iodine may slow ozone layer recovery
Tropical convection (seen in these towering clouds) can redistribute ocean emissions of inorganic
iodine into the lower stratosphere, where the iodine contributes to ozone depletion
[Credit: Rainer Volkamer, CIRES and CU Boulder]
The paper posits a set of connections that link air pollution near Earth's surface to ozone destruction much higher in the atmosphere. That higher-level ozone protects the planet's surface from radiation that can cause skin cancer and damage crops.

"The impact is maybe 1.5 to 2 percent less ozone," said lead author Theodore Koenig, a postdoctoral researcher at CIRES and the University of Colorado Boulder, referring to ozone in the lower part of the ozone layer, around Earth's tropics and temperate zones. "That may sound small, but it's important," he said.

A slightly thinner ozone layer means more UVB radiation can get through to Earth's surface.

Koenig's paper, the first "quantitative detection" of iodine in the stratosphere, is published in the Proceedings of the National Academy of Sciences, with co-authors from CIRES, CU Boulder and other institutions.

Chemicals once used widely in refrigeration, spray cans and solvents can eat away at Earth's ozone layer. After scientists discovered the stratospheric "ozone hole" in the 1980s, nations around the world signed the international Montreal Protocol agreement to protect the ozone layer, limiting the emission of ozone-depleting chemicals.

"The ozone layer is starting to show early signs of recovery in the upper stratosphere, but ozone in the lower stratosphere continues to decline for unclear reasons," said Rainer Volkamer, a CIRES Fellow, CU Boulder professor of chemistry and corresponding author of the new assessment.

"Before now, the decline was thought to be due to changes in how air mixes between the troposphere and stratosphere. Our measurements show there is also a chemical explanation, due to iodine from oceans. What I find exciting is that iodine changes ozone by just enough to provide a plausible explanation for why ozone in the lower stratosphere continues to decline."

For the new work, Volkamer and his colleagues pored through data from several recent atmospheric research campaigns involving U.S. National Science Foundation (NSF) and NASA research aircraft, and which included instruments that could pick up tiny amounts of iodine and other so-called halogens in the lower stratosphere during the daytime. Halogens, which also include chlorine and bromine, are key to ozone destruction.

It's been tricky to get data from this part of the atmosphere, Koenig said. "We knew there was some iodine there, but we couldn't pin numbers on it until now... This is a result of technological advancement: Our instruments just kept getting a little bit better and eventually, it was enough to make measurements."

The amount of iodine they picked up in the lower stratosphere is tiny, similar to adding a few bottles of water to the Great Salt Lake. But iodine is extremely effective at destroying ozone, and, generally speaking, the amount the scientists measured is enough to explain the level of ozone destruction in the lower stratosphere.

So where did the iodine come from? Strangely it seems to be a result of air pollution down here at the surface of the planet, the new assessment reports.

Ozone at Earth's surface is a pollutant, one that is regulated in the United States and elsewhere because it can harm people's lungs. And when ozone pollution interacts chemically with the surface of oceans, it can "pull" naturally occurring iodine up into the atmosphere. Other studies have shown that in the lower atmosphere, iodine levels have roughly tripled in concentration since 1950.

Some of that iodine is apparently making it up into the stratosphere, where it can trigger ozone depletion, Koenig said. "This should not diminish the success story of the Montreal Protocol, but still, it is important. The lower stratosphere should have improved already, not gotten worse."

"There's something going on resulting in deterioration. Our hypothesis is that ozone at the surface is destroying ozone in the stratosphere," Koenig added.

It will be important to study the hypothesis in greater detail, Koenig and his coauthors said. If ozone pollution at Earth's surface increases, for example, could it trigger even more lower-stratosphere ozone layer destruction?

Coauthor Pedro Campuzano-Jost, a CIRES research associate, said the success of the research project is partly due to the unique scope of NASA's ATom (Atmospheric Tomography) mission, which flew a research aircraft across the globe; and NSF's CONTRAST (Convective Transport of Active Species in the Tropics) mission, which detected iodine oxide radicals in the stratosphere.

"Half of the places we went had never been sampled before for aerosols," Campuzano-Jost said, and that is the kind of opportunity that leads to new discoveries.

Volkamer and his colleagues hope to successfully pitch a new mission to study iodine chemistry in greater detail, to better understand the future of Earth's protective ozone layer.

Source: University of Colorado at Boulder [January 13, 2020]

* This article was originally published here


https://t.co/hvL60wwELQ — XissUFOtoday Space (@xufospace) August 3, 2021 Жаждущий ежик наслаждается пресной водой после нескольких дней в о...