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  • richardmitnick 10:32 am on August 18, 2019 Permalink | Reply
    Tags: "Totalitarian principle", Another hypothetical particle permitted by the laws of physics- the neutrino-did eventually turn up after nuclear reactors produced the particles copiously enough to enable their detection., , “Principle of plenitude”, “What is considered physically or genuinely possible” Kragh writes “depends on the best scientific knowledge at any given time.”, , Equations are precisely stated descriptions of nature’s behavior that enable scientists to make accurate predictions about how things happen in the world., Everything not forbidden is compulsory., Failure to find magnetic monopoles led to investigations that produced the theory of cosmic inflation- the best current explanation of the early history of the universe., Helge Kragh-confusions posed by the totalitarian principle., In science the official rulebook consists of the laws of nature., , One example of plenitude reasoning in physics (without naming it that) came from Paul Dirac the physicist who in 1931 predicted the existence of half magnets. He called them magnetic monopoles., , Plato believed that all possible ideal “forms” should actually exist in physical reality., Science News, Science’s unwritten rules aren’t strict. They are merely guidelines: suggestions for how best to play the game but without the totalitarian force of true natural law., Subsequent searches have failed to find monopoles., Whatever can exist does exist, Whatever the laws of nature allow must in fact exist or happen.   

    From Science News: “Murray Gell-Mann’s ‘totalitarian principle’ is the modern version of Plato’s plenitude’ 

    From Science News

    August 18, 2019
    Tom Siegfried

    Idea that whatever can exist does exist can guide scientific pursuits.

    1
    Plato’s principle of plenitude is reborn in the modern belief, credited to Murray Gell-Mann (right), that whatever can exist must exist. Left: © Marie-Lan Nguyen/Wikimedia Commons (CC-BY 2.5); Right: Joi/Wikimedia Commons (CC-BY 2.5)

    Science, like baseball, has a lot of unwritten rules.

    Every baseball player knows that you don’t flip your bat after hitting a home run, you never steal a base when you have a big lead, and you cover your mouth with your glove when having a conference on the mound. None of those regulations are codified in the official rules — it’s just how pros play the game.

    In science, the official rulebook consists of the laws of nature — equations or otherwise precisely stated descriptions of nature’s behavior that enable scientists to make accurate predictions about how things happen in the world. Science’s unwritten rules aren’t so strict. They are merely guidelines, suggestions for how best to play the game but without the totalitarian force of true natural law.

    One such less-than-totalitarian principle is known as the … totalitarian principle. It is commonly expressed as “whatever is not forbidden is compulsory.” In other words, whatever the laws of nature allow must, in fact, exist or happen.

    That sounds a little bit like the opposite of totalitarianism, which would seem to require doing only what is compulsory, with everything else forbidden. And that’s just one of the confusions posed by the totalitarian principle discussed in a new paper by the historian Helge Kragh.

    Kragh notes that the origin of the totalitarian principle in physics is usually attributed to Murray Gell-Mann, the Nobel laureate who died in May at the age of 89. But many sources, Kragh notes, claim that Gell-Mann borrowed the phrasing from T.H. White, author of the King Arthur story The Sword in the Stone.

    True enough, White used the phrase “everything not forbidden is compulsory” in The Sword in the Stone; it was on signs above tunnel entrances in an ant colony. But that ant colony appeared only in the 1958 edition of The Once and Future King, in which The Sword in the Stone was incorporated. Nothing like the totalitarian principle phrasing was found in previous versions, Kragh reports.

    Yet Gell-Mann first described the idea in 1956, two years earlier. In a paper concerned with new particles and the strong nuclear force, Gell-Mann asserted that for some particles “any process which is not forbidden by a conservation law actually does take place.” He called it an assumption that “is related to the state of affairs that is said to prevail in a perfect totalitarian state. Anything that is not compulsory is forbidden.”

    Kragh doesn’t think Gell-Mann articulated the principle very clearly. For one thing, he was talking only about the strong force. And though he described his idea as related to totalitarianism, he had inverted the phrasing. So Kragh suggests that Gell-Mann doesn’t really deserve credit for originating the idea. Nevertheless, subsequent physicists often attributed the principle to Gell-Mann and sometimes labeled it as totalitarian. A 1969 paper, for instance, mentioned “an unwritten precept in modern physics, often facetiously referred to as Gell-Mann’s totalitarian principle, which states that in physics ‘anything which is not prohibited is compulsory.’”

    In any case, the underlying idea definitely did not originate with Gell-Mann. It rather descends from the philosophy of Plato, who believed that all possible ideal “forms” should actually exist in physical reality. In the 1930s, philosopher-historian Arthur Lovejoy referred to that idea as the “principle of plenitude” and discussed how it had been applied by other philosophers throughout history. But while the plenitude principle’s influence was widely recognized in biology, its use by physicists seems relatively recent. Kragh suggests that the totalitarian principle is in essence the successor of the plenitude principle “specially adapted to modern physics.”

    One example of plenitude reasoning in physics (without naming it that) came from Paul Dirac, the physicist who in 1931 predicted the existence of half magnets. (He called them magnetic monopoles — magnets with only a single pole, not both a north and a south.) Dirac’s quantum equations seemed to allow particles with a single magnetic pole to exist, and so, he decided, they probably did.

    Subsequent searches have failed to find monopoles. But another hypothetical particle permitted by the laws of physics, the neutrino, did eventually turn up after nuclear reactors produced the particles copiously enough to enable their detection.

    When Gell-Mann first mentioned the totalitarian principle, he recognized that depending on it posed a danger: Maybe there are laws you don’t know about. Thus the totalitarian principle offers physicists a two-sided blade. One, it suggests that if you discern that something is not forbidden, it’s a good idea to design an experiment to look for it. Two, if you look for it but don’t find it, then maybe that’s a sign that there’s some previously unknown law of nature that prevents it, and you should begin theoretical inquiries to look for the missing law. Kragh cites the discovery of baryon conservation in the 1950s as a consequence of failure to detect the decay of certain particles called baryons.

    Similarly, failure to find magnetic monopoles led to investigations that produced the theory of cosmic inflation, the best current explanation of the early history of the universe. (Inflation indicates that monopoles very well could exist but that the rapid expansion of space in the early universe diluted their concentration so much that we would be unlikely to encounter one in our neighborhood today.)

    In spite of such fruitful results from applying the totalitarian principle, it remains a mere guideline for scientific pursuits, not a guarantee of success. For one thing, it might not imply that anything that can exist does exist now — perhaps some possible things will come into existence only in the future. And saying that anything that’s possible must exist is inherently ambiguous because of the fuzzy meaning of the word possible. You never really know for sure what’s possible and what isn’t.

    “What is considered physically or genuinely possible,” Kragh writes, “depends on the best scientific knowledge at any given time.”

    See the full article here .


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  • richardmitnick 9:14 am on August 15, 2019 Permalink | Reply
    Tags: , , , , , , Science News   

    From Science News: “Astronomers just quintupled the number of known repeating fast radio bursts” 

    From Science News

    August 14, 2019
    Lisa Grossman

    The find could help reveal what causes these cryptic flashes of radio waves from deep space.

    1
    CONSTANT VIGILANCE A Canadian telescope called CHIME scans the sky each night for brief, bright bursts of cosmic radio waves. Now CHIME has spotted eight new bursts that flash over and over. Andre Renard/Dunlap Institute/University of Toronto/CHIME

    Astronomers have found eight new fast radio bursts that repeatedly flash on and off.

    That haul brings the total of known repeating fast radio bursts, or FRBs, to 10, compared with the 60 or so nonrepeating FRBs that have been spotted, researchers report August 9 at arXiv.org [Astrophysical Journal Letters]. Studying the cryptic bursts could reveal what phenomena cause these brief, brilliant flares of radio waves from deep space.

    The first nonrepeating burst was discovered only in 2007, so “FRBs are still quite new,” says astrophysicist Cherry Ng of the University of Toronto. But “the repeater population is larger than we might think. They’re not that unique,” she says.

    Ng and colleagues spotted the newly discovered repeating FRBs using the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, in British Columbia. The telescope also found the second known repeating FRB in August 2018 (SN: 2/2/19, p. 12).

    The new batch of repeat bursts could help astronomers start to figure out the sources of these flashes of radio energy, as well as how they might be different from their nonrepeating kin.

    For instance, radio waves from the first known repeat FRB, reported in 2016, were scrambled and tossed around by electrons on the way to Earth. That suggests the repeating FRB’s source is in a dense, turbulent environment, such as a supernova remnant or a neutron star orbiting a black hole (SN: 2/3/18, p. 6). But the energy from some of the new bursts seems to have had a less tumultuous journey, suggesting that these repeating FRBs hail from a calmer environment.

    Each burst from a repeat FRB also seems to last longer than an individual FRB, about 10 milliseconds per repeat burst versus one millisecond for a nonrepeater. That finding could support the idea that the two types of radio blasts have entirely different sources, although Ng thinks it’s too soon to be sure (SN: 8/3/19, p. 10). “Maybe don’t bet too much money on it,” she says.

    CHIME also has found many more nonrepeating FRBs in the last year, Ng says. That research is yet to be published, but “it will be a game changer,” she says.

    See the full article here .


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  • richardmitnick 11:40 am on August 2, 2019 Permalink | Reply
    Tags: "Stars may keep spinning fast, , , , , long into old age", , Science News   

    From Science News: “Stars may keep spinning fast, long into old age” 

    From Science News

    August 2, 2019
    Lisa Grossman

    The idea that older stars continually slow their rotation may be wrong.

    1
    SLOWDOWN Sunlike stars start as fast-spinning balls of gas (illustrated at left). As this type of star ages, its spin slows and it puffs up, before dying as a nebula (middle and right). But the spin of these aging stars might not slow as much as thought. S. Steinhöfel/ESO

    Stars may keep some of their youthful vigor as they age. Astronomers have spotted a star in its twilight years that spins much faster than expected. The discovery supports a new idea that, rather than continually slowing with age, some stars may have a magnetic midlife crisis that keeps them on a roll.

    “This process of slowing rotation … that we assumed happened indefinitely over the lifetime of a star may be interrupted in the middle of a star’s life,” says astronomer Travis Metcalfe of the Space Science Institute in Boulder, Colo. He presented new measurements of the star’s age July 30 at the first TESS Science Conference.

    The star, 94 Aquarii Aa, is a member of a triple-star system in the constellation Aquarius about 69 light-years from Earth. Its color and brightness suggest that it’s in the part of a star’s life cycle called the subgiant stage, which happens near the end of a sunlike star’s life as it starts running out of fuel.

    But it’s difficult to pinpoint a star’s age. Theories of stellar evolution predict that young stars rotate quickly but slow as they age and lose angular momentum, a process called spinning down. So astronomers often use a star’s spin rate to estimate age.

    Recently, though, data have emerged that raise questions about whether that aging scenario is correct.

    NASA’s Kepler space telescope, which watched distant stars for signs of orbiting planets from 2009 to 2018 (SN Online: 10/30/18), tracked how oscillations, or “starquakes,” ripple through a star’s interior, a technique called asteroseismology.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    Those ripples’ speeds are closely linked to the star’s mass and interior structure. Structure changes over the course of a star’s life, so asteroseismology is a good way to estimate a star’s age. In 2016, Metcalfe and colleagues reported in Nature that Kepler was finding old stars that rotated too fast for their ages. Young stars followed the spin-down trends, but around middle age, stars’ spin speed leveled off.

    As an aging subgiant, 94 Aquarii Aa made a good test case, Metcalfe said. He used NASA’s Transiting Exoplanet Survey Satellite, or TESS, the successor to Kepler, to estimate the star’s age and mass using asteroseismology. It’s about 6.2 billion years old, he found, and 1.2 times the mass of the sun. (In comparison, the sun is 4.5 billion years old.)

    If it had been spinning down its whole life, a star of that mass should now be rotating once every 78 days. But previous measurements made from ground-based telescopes had shown that the star rotates once every 47 days.

    “The only way to explain a star of that age having that rotation period is that this stalled rotation has to kick in around middle age,” Metcalfe says. “It’s a smoking gun.” He hopes to repeat the experiment with hundreds of more stars over the course of the TESS mission.

    Stars might stop slowing their rotation because of a midlife change in their magnetic field. A star’s magnetic field drives its stellar wind, which carries mass and angular momentum away from the star, contributing to its slowdown (SN Online: 7/29/19). But if the magnetic field changes its geometry around the middle of a star’s life, shifting from dominating the entire star to a more small-scale field, that could weaken the magnetic field’s control over the star’s rotation, Metcalfe says.

    “This is the first time we’ve seen convincing evidence that you have to invoke [the stalled slowdown] to explain the rotation of a subgiant,” says Jason Curtis, an astronomer at Columbia University. Astronomers had a lot of skepticism about Metcalfe and colleagues’ previous work using Kepler data, he says, but “every time they look at it from a different angle, it becomes more convincing.”

    Unfortunately, the result might mean that astronomers can’t use stars’ spin speeds to guess ages anymore. “If that stops working in old stars, that’s a bummer,” Curtis says.

    See the full article here .


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  • richardmitnick 5:20 pm on July 29, 2019 Permalink | Reply
    Tags: “We’re not re-creating the sun because that’s impossible” says plasma physicist Ethan Peterson of the University of Wisconsin–Madison. “But we’re re-creating some of the fundamental phys, , NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker, Parker spiral named after solar physicist Eugene Parker who predicted the existence of the solar wind in 1958., , , Science News, , The magnet in the center of the ball mimics the sun’s magnetic field and carefully applied electric currents send the plasma spinning and a wind streaming., The sun spews a constant stream of charged particles-called the solar wind out into space - though scientists aren’t sure exactly how., The team used a 3-meter-wide aluminum vacuum chamber called the Big Red Ball heated to 100000° Celsius at the Wisconsin Plasma Physics Laboratory.,   

    From University of Wisconsin Madison via Science News: “In a first, physicists re-created the sun’s spiraling solar wind in a lab” 

    U Wisconsin

    From University of Wisconsin Madison

    via

    Science News

    July 29, 2019
    Lisa Grossman

    Some of the sun’s fundamental physics have been re-created with plasma inside a vacuum chamber.

    1
    SUN IN A BALL This view shows the inside of the Big Red Ball, a 3-meter-wide aluminum sphere at the University of Wisconsin–Madison that can mimic properties of the sun. Carefully applied magnets and electric currents make the plasma spin and send out streams of charged particles, like the solar wind. Univ. of Wisconsin-Madison

    Physicists have created mini gusts of solar wind in the lab, with hopes that the charged particle streams can help to resolve some mysteries about our nearest star [Nature Physics].

    “We’re not re-creating the sun, because that’s impossible,” says plasma physicist Ethan Peterson of the University of Wisconsin–Madison, who reports the new work July 29 in Nature Physics. “But we’re re-creating some of the fundamental physics that happens near the sun.”

    The sun spews a constant stream of charged particles, called the solar wind, out into space — though scientists aren’t sure exactly how (SN Online: 8/18/17). As the sun rotates, its magnetic field twists the wind into a helical shape called the Parker spiral, named after solar physicist Eugene Parker, who predicted the existence of the solar wind in 1958.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    NASA last year launched its Parker Solar Probe to directly investigate the source of the solar wind (SN: 7/21/18, p. 12). But Peterson and colleagues found a way to mimic the Parker spiral much closer to home.

    The team used a 3-meter-wide aluminum vacuum chamber called the Big Red Ball at the Wisconsin Plasma Physics Laboratory to confine a ball of plasma heated to 100,000° Celsius. A magnet in the center of the ball mimics the sun’s magnetic field, and carefully applied electric currents send the plasma spinning and a wind streaming.

    There are some unavoidable differences between the Big Red Ball and the sun, including size, gravity and temperature. Even so, the wind organized itself into a clear Parker spiral, as expected. The wind also occasionally ejected little blobs of plasma, each about 10 centimeters across. The sun ejects similar blobs, called plasmoids, but no one is sure why. The Big Red Ball could help provide an answer, Peterson says.


    BALLERINA SKIRT The Parker spiral, which has also been described as a “ballerina skirt,” is the shape that the solar wind takes on as the sun rotates, twisting the wind into a helix as seen in a NASA simulation. Scientists mimicked this spiral in plasma in the lab. This video shows a smaller Parker spiral appearing in a ball of hot, spinning plasma inside a vacuum chamber. The bright spiraling structures follow the plasma’s magnetic field.

    See the full article here .

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    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 9:59 am on July 28, 2019 Permalink | Reply
    Tags: , Among the leading candidates are weakly interacting massive particles- WIMPs, Among the leading candidates are weakly interacting massive particles- WIMPs but scientists have hunted for them for decades with no success., , Dark Matter Macros, EVERY AXION HAS ITS DAY Physicist Gray Rybka of the University of Washington in Seattle and colleagues have created a detector sensitive enough to potentially find hypothetical dark matter particles c, , Physicists think the invisible dark matter must exist because they can see its gravitational effects on visible matter throughout the cosmos. But no one knows what it’s actually made of., Science News, So physicists are turning to other theoretical candidates.   

    From Science News: “Dark matter particles won’t kill you. If they could, they would have already” 

    From Science News

    July 25, 2019
    Lisa Grossman

    A lack of mysterious deaths from hypothetical ‘macros’ suggests dark matter is small and light.

    1
    STRIKETHROUGH Hypothetical dark matter particles called “macros” could stream through space and constantly bombard Earth. Some could seriously injure any unlucky humans they pass through, but a lack of mysterious deaths suggests the biggest potential macros don’t exist. NASA JPL-Caltech

    The fact that no one seems to have been killed by speeding blobs of dark matter puts limits on how large and deadly these particles can be, a study posted July 18 at arXiv.org suggests.

    “In the last 30 years, if someone had died of this, we would have heard of it,” says physicist Glenn Starkman of Case Western Reserve University in Cleveland.

    Physicists think the invisible dark matter must exist because they can see its gravitational effects on visible matter throughout the cosmos. But no one knows what it’s actually made of. Among the leading candidates are weakly interacting massive particles, or WIMPs, but scientists have hunted for them for decades with no success (SN: 6/23/18, p. 13).

    2
    WIMPING OUT The XENON1T experiment (contained inside the large tank above, at left) reports no hint of any interactions from particles of dark matter within, despite a yearlong search.

    So physicists are turning to other theoretical candidates (SN Online: 4/9/18).

    4
    EVERY AXION HAS ITS DAY Physicist Gray Rybka of the University of Washington in Seattle and colleagues have created a detector sensitive enough to potentially find hypothetical dark matter particles called axions.

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    Starkman and colleagues focused on macroscopic dark matter, or macros, first proposed by physicist Edward Witten in the 1980s (SN Online: 10/7/13). If they exist, macros would be made up of subatomic particles called quarks, just like ordinary matter, but combined in a way never before observed.

    Theoretically, macros could have almost any size and mass. And because dark matter doesn’t interact with regular matter, there would be nothing to stop these particles from zipping around unimpeded. So Starkman — along with Case Western physicist Jagjit Singh Sidhu and physicist Robert Scherrer of Vanderbilt University in Nashville — decided to do a gut check using human flesh as a dark matter detector.

    If a macro as small as a square micrometer zipped through your body at hypersonic speed, it would deposit about as much energy in your body as a typical metal bullet, the team calculated. But the damage it caused would be different from that of a bullet: A macro would heat the cylinder of tissue in its wake to about 10,000,000° Celsius — vaporizing the tissue and leaving a path of plasma.

    “It’s like if you were in Star Wars, and a Jedi hit you with their lightsaber, or someone shot you with their phaser [gun],” Starkman says.

    There would be nothing you could do to shield yourself from such a macro strike. Still, there’s no reason to worry, Starkman says. Considering there have been no reports of anyone suddenly suffering a mysterious lightsaber wound, the researchers concluded that if macros exist, they have to be smaller than a micrometer and heavier than about 50 kilograms.

    “The odds of dying from this are less than 1 in 100 million,” Starkman says.

    As wacky as this might sound, physicist Katherine Freese thought these calculations were worth doing. “This study is fun,” says Freese of the University of Michigan in Ann Arbor. “Looking for macros in already existing detectors, such as the human body, is a good idea.” Though she wasn’t involved in the macro research, she and colleagues did a similar thought experiment with WIMPs in 2012 [Physics Letters B]. “But weak interactions are so weak as to be harmless” to human bodies.

    Next, Starkman and Sidhu plan to look for macro tracks in slabs of granite, which would appear as cylinders of black obsidian running straight through the rock. They’re starting with a cemetery near the Case Western campus.

    See the full article here .


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  • richardmitnick 12:40 pm on July 22, 2019 Permalink | Reply
    Tags: "Increased control over ions’ motions may help improve quantum computers", Science News,   

    From University of Washington via Science News: “Increased control over ions’ motions may help improve quantum computers” 

    U Washington

    From University of Washington

    via

    Science News

    July 22, 2019
    Emily Conover

    A single ion was put into quantum states with up to 100 quanta of energy.

    1
    ION MANEUVERS Physicist Katie McCormick (shown manipulating a mirror that directs a laser beam) and colleagues coaxed a beryllium ion to go through the motions. The ion exhibited precise quantum movements within an electromagnetic field. Burrus/NIST

    Physicists are taking their quantum powers to the next level — the next energy level, that is.

    Researchers have controlled the motion of a trapped ion, an electrically charged atom, better than ever possible before, manipulating the energy level of its oscillation within an electromagnetic field. A single ion of beryllium, trapped by electromagnetic fields, was made to oscillate according to scientists’ bidding, the team reports July 22 in Nature.

    In quantum mechanics, energy comes in discrete amounts, packets known as quanta. Using lasers to tweak the ion, the researchers were able to set it oscillating within the electromagnetic field that confined it, with any number of quanta up to 100, breaking previously published records of about 17 quanta.

    The team also put the ion in a superposition — a weird situation in which the ion is simultaneously in two energy states at once, making it ultrasensitive to any stray electromagnetic fields. The larger the difference in the two energy levels in superposition, the more sensitive the ion is. The researchers put the ion in a superposition between a state with no quanta of energy and one with 18. Such ions could be used as precise sensors to locate electromagnetic fields.

    Scientists’ newly demonstrated prowess with ions could also be used to build better quantum computers. Some quantum computers store and process information via ions confined in traps, with lasers used to perform operations on the quantum data. Though quantum computers are still in their early stages, scientists predict the machines will be able to perform calculations more complex than what’s currently possible (SN: 7/8/17, p. 28).

    “It’s an unprecedented level of control,” says Katie McCormick, a physicist at the University of Washington in Seattle. “We’ve generated quantum states at a level that nobody has before.”

    See the full article here .


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    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.
    So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 10:23 am on July 8, 2019 Permalink | Reply
    Tags: 7 Tesla MRI, , , , , Science News   

    From Science News: “A 100-hour MRI scan captured the most detailed look yet at a whole human brain” 

    From Science News

    July 8, 2019
    Laura Sanders

    A device recently approved by the U.S. FDA made extremely precise images of a postmortem sample.

    1
    CLOSE-UP A 3-D view of the entire human brain, taken with a powerful 7 Tesla MRI and shown here from two angles, could reveal new details on structures in the mysterious organ.

    Over 100 hours of scanning has yielded a 3-D picture of the whole human brain that’s more detailed than ever before. The new view, enabled by a powerful MRI, has the resolution potentially to spot objects that are smaller than 0.1 millimeters wide.

    “We haven’t seen an entire brain like this,” says electrical engineer Priti Balchandani of the Icahn School of Medicine at Mount Sinai in New York City, who was not involved in the study. “It’s definitely unprecedented.”

    The scan shows brain structures such as the amygdala in vivid detail, a picture that might lead to a deeper understanding of how subtle changes in anatomy could relate to disorders such as post-traumatic stress disorder.

    To get this new look, researchers at Massachusetts General Hospital in Boston and elsewhere studied a brain from a 58-year-old woman who died of viral pneumonia. Her donated brain, presumed to be healthy, was preserved and stored for nearly three years.

    Before the scan began, researchers built a custom spheroid case of urethane that held the brain still and allowed interfering air bubbles to escape. Sturdily encased, the brain then went into a powerful MRI machine called a 7 Tesla, or 7T, and stayed there for almost five days of scanning.

    The strength of the 7T, the length of the scanning time and the fact that the brain was perfectly still led to the high-resolution images, which are described May 31 at bioRxiv.org. Associated videos of the brain, as well as the underlying dataset, are publicly available.


    ZOOM IN This video moves from the outer wrinkles to the inner structures and then back out to the wrinkles of a complete human brain at extremely high resolution.

    Researchers can’t get the same kind of resolution on brains of living people. For starters, people couldn’t tolerate a 100-hour scan. And even tiny movements, such as those that come from breathing and blood flow, would blur the images.

    But pushing the technology further in postmortem samples “gives us an idea of what’s possible,” Balchandani says. The U.S. Food and Drug Administration approved the first 7T scanner for clinical imaging in 2017, and large medical centers are increasingly using them to diagnose and study illnesses.

    These detailed brain images could hold clues for researchers trying to pinpoint hard-to-see brain abnormalities involved in disorders such as comas and psychiatric conditions such as depression. The images “have the potential to advance understanding of human brain anatomy in health and disease,” the authors write.

    See the full article here .


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  • richardmitnick 8:16 am on June 25, 2019 Permalink | Reply
    Tags: "The highest-energy photons ever seen hail from the Crab Nebula", , , , , , , Science News, , The Tibet AS-gamma experiment, When a high-energy photon hits Earth’s atmosphere it creates a shower of other subatomic particles that can be detected on the ground.   

    From Science News: “The highest-energy photons ever seen hail from the Crab Nebula” 

    From Science News

    June 24, 2019
    Emily Conover

    Some of the supernova remnant’s gamma rays have more than 100 trillion electron volts of energy.

    1
    CRAB FISHING Scientists hunting for high-energy photons raining down on Earth from space have found the most energetic light yet detected. It’s from the Crab Nebula, a remnant of an exploded star (shown in an image combining light seen by multiple telescopes).

    Physicists have spotted the highest-energy light ever seen. It emanated from the roiling remains left behind when a star exploded.

    This light made its way to Earth from the Crab Nebula, a remnant of a stellar explosion, or supernova, about 6,500 light-years away in the Milky Way. The Tibet AS-gamma experiment caught multiple particles of light — or photons — from the nebula with energies higher than 100 trillion electron volts, researchers report in a study accepted in Physical Review Letters. Visible light, for comparison, has just a few electron volts of energy.

    Tibet AS Gamma Expeiment

    “This energy regime has not been accessible before,” says astrophysicist Petra Huentemeyer of Michigan Technological University in Houghton, who was not involved with the research. For physicists who study this high-energy light, known as gamma rays, “it’s an exciting time,” she says.

    In space, supernova remnants and other cosmic accelerators can boost subatomic particles such as electrons, photons and protons to extreme energies, much higher than those achieved in the most powerful earthly particle accelerators (SN: 10/1/05, p. 213). Protons in the Large Hadron Collider in Geneva, for example, reach a comparatively wimpy 6.5 trillion electron volts. Somehow, the cosmic accelerators vastly outperform humankind’s most advanced machines.

    “The question is: How does nature do it?” says physicist David Hanna of McGill University in Montreal.

    In the Crab Nebula, the initial explosion set up the conditions for acceleration, with magnetic fields and shock waves plowing through space, giving an energy boost to charged particles such as electrons. Low-energy photons in the vicinity get kicked to high energies when they collide with the speedy electrons, and ultimately, some of those photons make their way to Earth.

    When a high-energy photon hits Earth’s atmosphere, it creates a shower of other subatomic particles that can be detected on the ground. To capture that resulting deluge, Tibet AS-gamma uses nearly 600 particle detectors spread across an area of more than 65,000 square meters in Tibet. From the information recorded by the detectors, researchers can calculate the energy of the initial photon.

    But other kinds of spacefaring particles known as cosmic rays create particle showers that are much more plentiful. To select photons, cosmic rays, which are mainly composed of protons and atomic nuclei, need to be weeded out. So the researchers used underground detectors to look for muons — heavier relatives of electrons that are created in cosmic ray showers, but not in showers created by photons.

    Previous experiments have glimpsed photons with nearly 100 TeV, or trillion electron volts. Now, after about three years of gathering data, the researchers found 24 seemingly photon-initiated showers above 100 TeV, and some with energies as high as 450 TeV. Because the weeding out process isn’t perfect, the researchers estimate that around six of those showers could have come from cosmic rays mimicking photons, but the rest are the real deal.

    Researchers with Tibet AS-gamma declined to comment for this story, as the study has not yet been published.

    Looking for photons of ever higher energies could help scientists nail down the details of how the particles are accelerated. “There has to be a limit to how high the energy of the photons can go,” Hanna says. If scientists can pinpoint that maximum energy, that could help distinguish between various theoretical tweaks to how the particles get their oomph.

    See the full article here .


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  • richardmitnick 9:42 am on June 22, 2019 Permalink | Reply
    Tags: "The cosmic ‘Cow’ may be a strange supernova", , , , , Science News   

    From Science News: “The cosmic ‘Cow’ may be a strange supernova” 

    From Science News

    June 21, 2019
    Lisa Grossman

    1
    HOLY COW The cosmic oddity called the Cow may be a supernova that exploded in a dense environment. This image from the Sloan Digital Sky Survey shows the Cow’s host galaxy 200 million light-years away. The Cow itself is a bright spot at about 4 o’clock in the galaxy’s disk. R. Margutti/W. M. Keck Observatory

    The cosmic oddity known as the Cow may have been a dying star that shed its skin like a snake before it exploded.

    Newly released observations support the idea that the burst occurred in a dense environment with strong magnetic fields, astronomer Kuiyun Huang and colleagues report in The Astrophysical Journal Letters June 12.

    These new measurements “for the mysterious transient … provide one of the strong hints of its nature,” says Huang, of the Chung Yuan Christian University in Taoyuan City, Taiwan.

    Since the Cow appeared in June 2018 as a brief burst of light in a galaxy about 200 million light-years away, astronomers haven’t been sure what to think of it. The initial glow flared more quickly and seemed 10 times brighter than an ordinary supernova, the violent explosion that marks the death of a massive star (SN: 2/18/17, p. 20).

    Follow-up observations of the Cow — which got its nickname from the randomly assigned name “AT2018cow” — left two main theories for what it could be: a strange sort of supernova, or an exotic star being shredded by a black hole (SN: 2/2/19, p. 13). But neither theory alone could explain all the Cow’s weird features.

    Astronomer Anna Ho of Caltech and colleagues published work in April at arXiv.org that analyzed light from the Cow in a range of wavelengths, from short gamma rays to long radio waves. That work suggested that the light was getting distorted on its journey. So if the Cow is a supernova, it must have exploded in a very dense environment that squashed some of the light emerging from the dying star. But to come to that conclusion, the team had to simplify assumptions about how the explosion’s energy was released.

    Now, Huang and colleagues have released new radio wave observations that back up the findings by Ho’s team, without relying on those assumptions. In June and July 2018, Huang’s group used the Atacama Large Millimeter-submillimeter Array in Chile to look at the way the Cow’s light was polarized, a measurement of the light’s preferred direction.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Imagine holding a jump rope: If you swing your arm up and down, the jump rope will take on an up-down wave pattern. Swinging left to right gives the rope a side-to-side wave.

    The radio waves emitted in the wreckage of a supernova should do the same thing, Ho explains. But if the waves travel through an environment filled with gas, charged particles and magnetic fields, the waves’ preferred direction can get rotated or smeared out. “By the time it all gets out at the end, it can look like a blurred mess,” Ho says.

    That’s what Huang and colleagues saw from the Cow: The radio waves essentially had no polarization by the time they reached Earth, suggesting the waves had been tossed about in a dense and turbulent environment.

    That environment probably came from the Cow itself, Ho says. Toward the end of the star’s life, it started shedding outer layers of gas, similar to a snake shedding its skin. Those discarded layers were still nearby when the star finally ran out of fuel and exploded, so the light and material from the explosion plowed through the debris from the star’s death throes.

    “That might actually be a common thing that stars do,” Ho says. She and her colleagues observed another stellar explosion in September, SN2018gep, that first appeared to be a Cow-like event. It ended up looking more like a straightforward supernova, with ordinary speed and brightness — but one that was also surrounded by the dense layers the star tossed off before it died.

    The new polarization observations by Huang’s team aren’t the final word on the Cow’s identity, though, says astronomer Daniel Perley of Liverpool John Moores University in England. “It supports one argument,” he says, “but doesn’t overall change the balance of the somewhat contradictory evidence pointing in different directions for this event.” More work on the shredded star theory could help break the tie, he says.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

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  • richardmitnick 11:55 am on June 13, 2019 Permalink | Reply
    Tags: "Astronomers may have spotted the ghost galaxy that hit the Milky Way long ago", , , , , Science News, The dim galaxy Antlia 2   

    From Science News: “Astronomers may have spotted the ghost galaxy that hit the Milky Way long ago” 

    From Science News

    June 12, 2019
    Lisa Grossman

    Discovered in Gaia data, Antlia 2 could be the star system scientists have been looking for.

    The Milky Way survived a galactic hit and run millions of years ago — and astronomers may have finally found the culprit.

    2
    The Large Magellanic Cloud, the Milky Way Galaxy and Antlia 2 (from left to right). Image credit: V. Belokurov / Marcus and Gail Davies / Robert Gendler.
    GHOSTLY GALAXY The dim galaxy Antlia 2 (faint glow shown at right in this illustration) was found orbiting the Milky Way (center) in 2018. It’s a bit bigger than the Large Magellanic Cloud, another satellite galaxy (left), but contains far fewer stars. V. Belokurov/Univ. of Cambridge/CCA, based on the images by Marcus and Gail Davies and Robert Gendler

    Ten years ago, astrophysicists Sukanya Chakrabarti and Leo Blitz of the University of California, Berkeley, suggested that ripples in the outer gas disk of the Milky Way were caused by a collision with a dwarf galaxy that shook the Milky Way’s gas like a pebble dropped in a pond. The pair made predictions for how massive and distant the galaxy had to be, as well as roughly where it should be found. But none of the known dwarf galaxies that orbit the Milky Way fit the bill (SN: 4/4/15, p. 6).

    Now, Chakrabarti thinks she’s found her quarry, she reported June 12 in St. Louis at the American Astronomical Society meeting and in a study posted on arXiv.org.

    Last year, astronomers using data from the Gaia space telescope discovered a new dwarf galaxy called Antlia 2, which has so few visible stars that its discoverers called it a hidden giant (SN Online: 5/9/18). Antlia 2’s location is “stupidly close” to where Chakrabarti, now at the Rochester Institute of Technology in N.Y., and Blitz predicted that the offending dwarf galaxy should be today, she says.

    Its mass is also close to what the surviving remnant of the colliding galaxy’s mass would be, she estimates. And the collision could even explain why Antlia 2 has so few stars — the encounter with the Milky Way could have stripped many of them away.

    To make sure Antlia 2 is the culprit, Chakrabarti and her colleagues have predicted where its stars should be in the next set of Gaia data, due out in 2020 or 2021. “If this is what’s observed a year from now, I’d say it’s indisputable really that Antlia 2 is the dwarf galaxy that we predicted,” she says.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
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