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  • richardmitnick 9:26 am on September 24, 2016 Permalink | Reply
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    From Cornell: “Life ‘not as we know it’ possible on Saturn’s moon Titan” 

    Cornell Bloc

    Cornell University

    September 24, 2016
    Feb. 27, 2015
    Anne Ju
    amj8@cornell.edu

    1
    Graduate student James Stevenson, astronomer Jonathan Lunine and chemical engineer Paulette Clancy, with a Cassini image of Titan in the foreground of Saturn, and an azotosome, the theorized cell membrane on Titan. Jason Koski/University Photography

    Liquid water is a requirement for life on Earth. But in other, much colder worlds, life might exist beyond the bounds of water-based chemistry.

    Taking a simultaneously imaginative and rigidly scientific view, Cornell chemical engineers and astronomers offer a template for life that could thrive in a harsh, cold world – specifically Titan, the giant moon of Saturn. A planetary body awash with seas not of water, but of liquid methane, Titan could harbor methane-based, oxygen-free cells that metabolize, reproduce and do everything life on Earth does.

    Their theorized cell membrane, composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero, is published in Science Advances, Feb. 27. The work is led by chemical molecular dynamics expert Paulette Clancy, the Samuel W. and Diane M. Bodman Professor of Chemical and Biomolecular Engineering, with first author James Stevenson, a graduate student in chemical engineering. The paper’s co-author is Jonathan Lunine, the David C. Duncan Professor in the Physical Sciences in the College of Arts and Sciences’ Department of Astronomy.

    Lunine is an expert on Saturn’s moons and an interdisciplinary scientist on the Cassini-Huygens mission that discovered methane-ethane seas on Titan. Intrigued by the possibilities of methane-based life on Titan, and armed with a grant from the Templeton Foundation to study non-aqueous life, Lunine sought assistance about a year ago from Cornell faculty with expertise in chemical modeling. Clancy, who had never met Lunine, offered to help.

    “We’re not biologists, and we’re not astronomers, but we had the right tools,” Clancy said. “Perhaps it helped, because we didn’t come in with any preconceptions about what should be in a membrane and what shouldn’t. We just worked with the compounds that we knew were there and asked, ‘If this was your palette, what can you make out of that?’”

    On Earth, life is based on the phospholipid bilayer membrane, the strong, permeable, water-based vesicle that houses the organic matter of every cell. A vesicle made from such a membrane is called a liposome. Thus, many astronomers seek extraterrestrial life in what’s called the circumstellar habitable zone, the narrow band around the sun in which liquid water can exist. But what if cells weren’t based on water, but on methane, which has a much lower freezing point?

    2
    A representation of a 9-nanometer azotosome, about the size of a virus, with a piece of the membrane cut away to show the hollow interior. James Stevenson

    The engineers named their theorized cell membrane an “azotosome,” “azote” being the French word for nitrogen. “Liposome” comes from the Greek “lipos” and “soma” to mean “lipid body;” by analogy, “azotosome” means “nitrogen body.”

    The azotosome is made from nitrogen, carbon and hydrogen molecules known to exist in the cryogenic seas of Titan, but shows the same stability and flexibility that Earth’s analogous liposome does. This came as a surprise to chemists like Clancy and Stevenson, who had never thought about the mechanics of cell stability before; they usually study semiconductors, not cells.

    The engineers employed a molecular dynamics method that screened for candidate compounds from methane for self-assembly into membrane-like structures. The most promising compound they found is an acrylonitrile azotosome, which showed good stability, a strong barrier to decomposition, and a flexibility similar to that of phospholipid membranes on Earth. Acrylonitrile – a colorless, poisonous, liquid organic compound used in the manufacture of acrylic fibers, resins and thermoplastics – is present in Titan’s atmosphere.

    Excited by the initial proof of concept, Clancy said the next step is to try and demonstrate how these cells would behave in the methane environment – what might be the analogue to reproduction and metabolism in oxygen-free, methane-based cells.

    Lunine looks forward to the long-term prospect of testing these ideas on Titan itself, as he put it, by “someday sending a probe to float on the seas of this amazing moon and directly sampling the organics.”

    Stevenson said he was in part inspired by science fiction writer Isaac Asimov, who wrote about the concept of non-water-based life in a 1962 essay, “Not as We Know It.”

    Said Stevenson: “Ours is the first concrete blueprint of life not as we know it.”

    See the full article here .

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    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 9:04 am on September 24, 2016 Permalink | Reply
    Tags: , , , NGC 2440,   

    From Hubble: “Hubble Views a Colorful Demise of a Sun-like Star” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Sept. 23, 2016
    Editor: Karl Hille

    1
    Credits: NASA, ESA, and K. Noll (STScI), Acknowledgment: The Hubble Heritage Team (STScI/AURA)

    This image, taken by the NASA/ESA Hubble Space Telescope, shows the colorful “last hurrah” of a star like our sun. The star is ending its life by casting off its outer layers of gas, which formed a cocoon around the star’s remaining core. Ultraviolet light from the dying star makes the material glow. The burned-out star, called a white dwarf, is the white dot in the center. Our sun will eventually burn out and shroud itself with stellar debris, but not for another 5 billion years.

    Our Milky Way Galaxy is littered with these stellar relics, called planetary nebulae. The objects have nothing to do with planets. Eighteenth- and nineteenth-century astronomers called them the name because through small telescopes they resembled the disks of the distant planets Uranus and Neptune. The planetary nebula in this image is called NGC 2440. The white dwarf at the center of NGC 2440 is one of the hottest known, with a surface temperature of more than 360,000 degrees Fahrenheit (200,000 degrees Celsius). The nebula’s chaotic structure suggests that the star shed its mass episodically. During each outburst, the star expelled material in a different direction. This can be seen in the two bowtie-shaped lobes. The nebula also is rich in clouds of dust, some of which form long, dark streaks pointing away from the star. NGC 2440 lies about 4,000 light-years from Earth in the direction of the constellation Puppis.

    The material expelled by the star glows with different colors depending on its composition, its density and how close it is to the hot central star. Blue samples helium; blue-green oxygen, and red nitrogen and hydrogen.

    See the full article here .

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 8:28 am on September 24, 2016 Permalink | Reply
    Tags: CMS, , , Leptons,   

    From FNAL: “Lepton flavor violation: the search for mismatched Higgs boson decays at CMS” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    September 23, 2016
    Bo Jayatilaka

    1
    The Standard Model allows for the Higgs boson to decay to identically flavored pairs of , such as electrons and muons, but not to mixed pairings of lepton flavors. Evidence of the latter would be a sign of new physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    For a moment, forget everything you know about twins and imagine you were told “the only way two siblings could have been born on the same day is if they were identical twins.” You would go about life assuming that the only twins in the world were siblings who were the same age and looked exactly alike. Of course, in reality, there are fraternal twins, and the first time you encountered a pair of nonidentical siblings born on the same day, you’d have to assume that your initial information was at least incomplete. Physicists are trying to test a principle of the Standard Model by looking for a particle version of fraternal twins, or lepton flavor violation.

    The fundamental particles known as fermions that make up ordinary matter all seem to come in multiple flavors or generations. For example, the electron has a heavier cousin called the muon. Apart from its mass, a muon behaves much the same way as an electron in terms of having similar properties and interacting with the same forces. One key exception is the flavor itself, a quantity unique to a given flavor of particle. For example, an electron has an “electron number” of +1 while its antiparticle, the positron, has a corresponding number of -1. Muons, on the other hand, have an electron number of 0 but have corresponding “muon numbers.” The Standard Model requires that certain types of interactions, say the decay of a Higgs boson, always conserve lepton flavor. This means that a Higgs boson can decay into an electron and a positron (which would sum to an electron flavor of zero) or a muon and an antimuon (again, a muon flavor sum of zero), but not to an electron and an antimuon, the latter being an example of lepton flavor violation. In short, the Standard Model requires that identical twins of particles emerge from Higgs boson decays and expressly forbids fraternal twins.

    Thus, observing decays of Higgs boson into fraternal twins of lepton pairs, say an electron and a muon, would be a strong sign of physics beyond the Standard Model. CMS physicists searched for evidence of such decays, specifically for Higgs boson decays to electron-muon and electron-tau lepton pairs. The search, performed in the dataset accumulated by CMS in 2012 and reported in a paper submitted to Physics Letters B, yielded no evidence of either type of decay. The results did place the tightest bounds yet on the possible rates of such decays and allowed physicists to place constraints on some models of physics beyond the Standard Model.

    See the full article here .

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 7:52 am on September 24, 2016 Permalink | Reply
    Tags: , Austin Peay State University, , Clarksville online, , Quasar   

    From Clarksville online via FNAL: “APSU physics student Jacob Robertson discovers Quasar while visiting Fermilab” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    1

    Clarksville online

    2

    Austin Peay State University

    September 23, 2016
    No writer credit found

    Quasars—massive black holes that emit large amounts of radiation—are among the brightest objects in the universe, but that doesn’t mean they’re easy to identify.

    For centuries, they’ve been mistaken for other shining celestial objects, and in recent years, astronomers had yet to accurately identify a certain one of these brilliant specks in the southern sky.

    But earlier this summer, Austin Peay State University student Jacob Robertson took a look at this object and realized it wasn’t just another star.

    3
    Austin Peay physics student Jacob Robertson

    “My first thought was, ‘I know this is a quasar, I hope it hasn’t been discovered yet,’” Robertson, a physics major, said.

    It hadn’t. Now, Robertson is the second APSU student in recent years to make an important scientific discovery. In 2013, then-student Mees Fix also discovered a quasar while examining white dwarf stars.

    Like Fix three years ago, Robertson spent some of the summer of 2016 at Fermilab—the U.S. Department of Energy’s national laboratory—with Dr. Allyn Smith, APSU professor of physics and astronomy, assisting with the international Dark Energy Survey.

    Dark Energy Survey

    According to Fermilab’s website, the survey “is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision.”

    “It was my job to go through and reduce the data to confirm that the stars in this sample were white dwarfs,” Robertson said. “I had read (Fix’s) paper, so I knew what a quasar spectrum was supposed to look like. When I came across (the object), I immediately knew it was a quasar.”

    The APSU student will now be the lead author on an academic paper about the discovery. Smith and APSU physics student Deborah Gulledge, who also worked at Fermilab this summer, will be listed as co-authors.

    Robertson, only a junior, already has a strong resume as a physics and astronomy researcher. In addition to his work at Fermilab, he traveled to Arizona in early September to conduct research at Kitt Peak National Observatory, and in August, he accompanied a team of APSU students to Montana State University to participate in the NASA-funded Eclipse Ballooning Project.

    NOAO Kitt Peak National Observatory  on the Tohono O’odham reservation outside Tucson, AZ, USA
    NOAO Kitt Peak National Observatory on the Tohono O’odham reservation outside Tucson, AZ, USA

    Information on that project is available online at http://www.apsu.edu/news/apsu-students-launch-high-altitude-balloon-during-2017-eclipse

    “The unique thing about Austin Peay’s physics department is that there are so many opportunities to get involved in research,” Robertson said. “And the professors do push you to get involved in something.”

    For more information on the APSU Department of Physics and Astronomy, visit http://www.apsu.edu/physics

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 7:36 am on September 24, 2016 Permalink | Reply
    Tags: , , , Research at Princeton   

    From Research at Princeton: “New method identifies protein-protein interactions on basis of sequence alone (PNAS)” 

    Princeton University
    Princeton University

    September 23, 2016
    Catherine Zandonella, Office of the Dean for Research

    1
    Researchers can now identify which proteins will interact just by looking at their sequences. Pictured are surface representations of a histidine kinase dimer (HK, top) and a response regulator (RR, bottom), two proteins that interact with each other to carry out cellular signaling functions. (Image based on work by Casino, et. al. credit: Bitbol et. al 2016/PNAS.)

    Genomic sequencing has provided an enormous amount of new information, but researchers haven’t always been able to use that data to understand living systems.

    Now a group of researchers has used mathematical analysis to figure out whether two proteins interact with each other, just by looking at their sequences and without having to train their computer model using any known examples. The research, which was published online today in the journal Proceedings of the National Academy of Sciences, is a significant step forward because protein-protein interactions underlie a multitude of biological processes, from how bacteria sense their surroundings to how enzymes turn our food into cellular energy.

    “We hadn’t dreamed we’d be able to address this,” said Ned Wingreen, Princeton University‘s Howard A. Prior Professor in the Life Sciences, and a professor of molecular biology and the Lewis-Sigler Institute for Integrative Genomics, and a senior co-author of the study with Lucy Colwell of the University of Cambridge. “We can now figure out which protein families interact with which other protein families, just by looking at their sequences,” he said.

    Although researchers have been able to use genomic analysis to obtain the sequences of amino acids that make up proteins, until now there has been no way to use those sequences to accurately predict protein-protein interactions. The main roadblock was that each cell can contain many similar copies of the same protein, called paralogs, and it wasn’t possible to predict which paralog from one protein family would interact with which paralog from another protein family. Instead, scientists have had to conduct extensive laboratory experiments involving sorting through protein paralogs one by one to see which ones stick.

    In the current paper, the researchers use a mathematical procedure, or algorithm, to examine the possible interactions among paralogs and identify pairs of proteins that interact. The method was able to correctly predict 93% of the protein-protein paralog pairs that were present in a dataset of more than 20,000 known paired protein sequences, without being first provided any examples of correct pairs.

    Interactions between proteins happen when two proteins come into physical contact and stick together via weak bonds. They may do this to form part of a larger piece of machinery used in cellular metabolism. Or two proteins might interact to pass a signal from the exterior of the cell to the DNA, to enable a bacterial organism to react to its environment.

    When two proteins come together, some amino acids on one chain stick to the amino acids on the other chain. Each site on the chain contains one of 20 possible amino acids, yielding a very large number of possible amino-acid pairings. But not all such pairings are equally probable, because proteins that interact tend to evolve together over time, causing their sequences to be correlated.

    The algorithm takes advantage of this correlation. It starts with two protein families, each with multiple paralogs in any given organism. The algorithm then pairs protein paralogs randomly within each organism and asks, do particular pairs of amino acids, one on each of the proteins, occur much more or less frequently than chance? Then using this information it asks, given an amino acid in a particular location on the first protein, which amino acids are especially favored at a particular location on the second protein, a technique known as direct coupling analysis. The algorithm in turn uses this information to calculate the strengths of interactions, or “interaction energies,” for all possible protein paralog pairs, and ranks them. It eliminates the unlikely pairings and then runs again using only the top most likely protein pairs.

    The most challenging part of identifying protein-protein pairs arises from the fact that proteins fold and kink into complicated shapes that bring amino acids in proximity to others that are not close by in sequence, and that amino-acids may be correlated with each other via chains of interactions, not just when they are neighbors in 3D. The direct coupling analysis works surprisingly well at finding the true underlying couplings that occur between neighbors.

    The work on the algorithm was initiated by Wingreen and Robert Dwyer, who earned his Ph.D. in the Department of Molecular Biology at Princeton in 2014, and was continued by first author Anne-Florence Bitbol, who was a postdoctoral researcher in the Lewis-Sigler Institute for Integrative Genomics and the Department of Physics at Princeton and is now a CNRS researcher at Universite Pierre et Marie Curie – Paris 6. Bitbol was advised by Wingreen and Colwell, an expert in this kind of analysis who joined the collaboration while a member at the Institute for Advanced Study in Princeton, NJ, and is now a lecturer in chemistry at the University of Cambridge.

    The researchers thought that the algorithm would only work accurately if it first “learned” what makes a good protein-protein pair by studying ones discovered in experiments. This required that the researchers give the algorithm some known protein pairs, or “gold standards,” against which to compare new sequences. The team used two well-studied families of proteins, histidine kinases and response regulators, which interact as part of a signaling system in bacteria.

    But known examples are often scarce, and there are tens of millions of undiscovered protein-protein interactions in cells. So the team decided to see if they could reduce the amount of training they gave the algorithm. They gradually lowered the number of known histidine kinase-response regulator pairs that they fed into the algorithm, and were surprised to find that the algorithm continued to work. Finally, they ran the algorithm without giving it any such training pairs, and it still predicted new pairs with 93 percent accuracy.

    “The fact that we didn’t need a gold standard was a big surprise,” Wingreen said.

    Upon further exploration, Wingreen and colleagues figured out that their algorithm’s good performance was due to the fact that true protein-protein interactions are relatively rare. There are many pairings that simply don’t work, and the algorithm quickly learned not to include them in future attempts. In other words, there is only a small number of distinctive ways that protein-protein interactions can happen, and a vast number of ways that they cannot happen. Moreover, the few successful pairings were found to repeat with little variation across many organisms. This it turns out, makes it relatively easy for the algorithm to reliably sort interactions from non-interactions.

    Wingreen compared this observation – that correct pairs are more similar to one another than incorrect pairs are to each other – to the opening line of Leo Tolstoy’s Anna Karenina, which states, “All happy families are alike; each unhappy family is unhappy in its own way.”

    The work was done using protein sequences from bacteria, and the researchers are now extending the technique to other organisms.

    The approach has the potential to enhance the systematic study of biology, Wingreen said. “We know that living organisms are based on networks of interacting proteins,” he said. “Finally we can begin to use sequence data to explore these networks.”

    The research was supported in part by the National Institutes of Health (Grant R01-GM082938) and the National Science Foundation (Grant PHY–1305525).

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 11:22 am on September 23, 2016 Permalink | Reply
    Tags: , Fermions, , ,   

    From Research at Princeton: “Unconventional quasiparticles predicted in conventional crystals” 

    Princeton University
    Princeton University

    July 22, 2016 [Just appeared in social media.]
    No writer credit found

    1
    Two electronic states known as Fermi arcs, localized on the surface of a material, stem out of the projection of a 3-fold degenerate bulk new fermion. This new fermion is a cousin of the Weyl fermion discovered last year in another class of topological semimetals. The new fermion has a spin-1, a reflection of the 3- fold degeneracy, unlike the spin-½ that the recently discovered Weyl fermions have. No image credit.

    An international team of researchers has predicted the existence of several previously unknown types of quantum particles in materials. The particles — which belong to the class of particles known as fermions — can be distinguished by several intrinsic properties, such as their responses to applied magnetic and electric fields. In several cases, fermions in the interior of the material show their presence on the surface via the appearance of electron states called Fermi arcs, which link the different types of fermion states in the material’s bulk.

    The research, published online this week in the journal Science, was conducted by a team at Princeton University in collaboration with researchers at the Donostia International Physics Center (DIPC) in Spain and the Max Planck Institute for Chemical Physics of Solids in Germany. The investigators propose that many of the materials hosting the new types of fermions are “protected metals,” which are metals that do not allow, in most circumstances, an insulating state to develop. This research represents the newest avenue in the physics of “topological materials,” an area of science that has already fundamentally changed the way researchers see and interpret states of matter.

    The team at Princeton included Barry Bradlyn and Jennifer Cano, both associate research scholars at the Princeton Center for Theoretical Science; Zhijun Wang, a postdoctoral research associate in the Department of Physics, Robert Cava, the Russell Wellman Moore Professor of Chemistry; and B. Andrei Bernevig, associate professor of physics. The research team also included Maia Vergniory, a postdoctoral research fellow at DIPC, and Claudia Felser, a professor of physics and chemistry and director of the Max Planck Institute for Chemical Physics of Solids.

    For the past century, gapless fermions, which are quantum particles with no energy gap between their highest filled and lowest unfilled states, were thought to come in three varieties: Dirac, Majorana and Weyl. Condensed matter physics, which pioneers the study of quantum phases of matter, has become fertile ground for the discovery of these fermions in different materials through experiments conducted in crystals. These experiments enable researchers to explore exotic particles using relatively inexpensive laboratory equipment rather than large particle accelerators.

    In the past four years, all three varieties of gapless fermions have been theoretically predicted and experimentally observed in different types of crystalline materials grown in laboratories around the world. The Weyl fermion was thought to be last of the group of predicted quasiparticles in nature. Research published earlier this year in the journal Nature (Wang et al., doi:10.1038/nature17410) has shown, however, that this is not the case, with the discovery of a bulk insulator which hosts an exotic surface fermion.

    In the current paper, the team predicted and classified the possible exotic fermions that can appear in the bulk of materials. The energy of these fermions can be characterized as a function of their momentum into so-called energy bands, or branches. Unlike the Weyl and Dirac fermions, which, roughly speaking, exhibit an energy spectrum with 2- and 4-fold branches of allowed energy states, the new fermions can exhibit 3-, 6- and 8-fold branches. The 3-, 6-, or 8-fold branches meet up at points – called degeneracy points – in the Brillouin zone, which is the parameter space where the fermion momentum takes its values.

    “Symmetries are essential to keep the fermions well-defined, as well as to uncover their physical properties,” Bradlyn said. “Locally, by inspecting the physics close to the degeneracy points, one can think of them as new particles, but this is only part of the story,” he said.

    Cano added, “The new fermions know about the global topology of the material. Crucially, they connect to other points in the Brillouin zone in nontrivial ways.”

    During the search for materials exhibiting the new fermions, the team uncovered a fundamentally new and systematic way of finding metals in nature. Until now, searching for metals involved performing detailed calculations of the electronic states of matter.

    “The presence of the new fermions allows for a much easier way to determine whether a given system is a protected metal or not, in some cases without the need to do a detailed calculation,” Wang said.

    Verginory added, “One can just count the number of electrons of a crystal, and figure out, based on symmetry, if a new fermion exists within observable range.”

    The researchers suggest that this is because the new fermions require multiple electronic states to meet in energy: The 8-branch fermion requires the presence of 8 electronic states. As such, a system with only 4 electrons can only occupy half of those states and cannot be insulating, thereby creating a protected metal.

    “The interplay between symmetry, topology and material science hinted by the presence of the new fermions is likely to play a more fundamental role in our future understanding of topological materials – both semimetals and insulators,” Cava said.

    Felser added, “We all envision a future for quantum physical chemistry where one can write down the formula of a material, look at both the symmetries of the crystal lattice and at the valence orbitals of each element, and, without a calculation, be able to tell whether the material is a topological insulator or a protected metal.”

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 10:57 am on September 23, 2016 Permalink | Reply
    Tags: , , , , , , Vox,   

    From Yale via Vox: “Why physicists really, really want to find a new subatomic particle” 

    Yale University bloc

    Yale University

    1

    Vox

    Sep 21, 2016
    Brian Resnick

    The latest search for a new particle has fizzled. Scientists are excited, and a bit scared.

    2
    Particle physicists are begging nature to reveal the secrets of the universe. The universe isn’t talking back. FABRICE COFFRINI/AFP/Getty Images

    Particle physicists are rather philosophical when describing their work.

    “Whatever we find out, that is what nature chose,” Kyle Cranmer, a physics professor at New York University, tells me. It’s a good attitude to have when your field yields great disappointments.

    For months, evidence was mounting that the Large Hadron Collider, the biggest and most powerful particle accelerator in the world, had found something extraordinary: a new subatomic particle, which would be a discovery surpassing even the LHC’s discovery of the Higgs boson in 2012, and perhaps the most significant advance since Einstein’s theory of relativity.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    And yet, nature had other plans.

    In August, the European Organization for Nuclear Research (CERN) reported that the evidence for the new particle had run thin. What looked like a promising “bump” in the data, indicating the presence of a particle with a unique mass, was just noise.

    But to Cranmer — who has analyzed LHC data in his work — the news did not equate failure. “You have to keep that in mind,” he says. “Because it can feel that way. It wasn’t there to be discovered. It’s like being mad that someone didn’t find an island when someone is sailing in the middle of the ocean.”

    What’s more, the LHC’s journey is far from over. The machine is expected to run for another 20 or so years. There will be more islands to look for.

    “We’re either going to discover a bunch of new particles or we will not,” Cranmer says. “If we find new particles, we can study them, and then we have a foothold to make progress. And if we don’t, then [we’ll be] staring at a flat wall in front figuring out how to climb it.”

    This is a dramatic moment, one that could provoke “a crisis at the edge of physics,” according to a New York Times op-ed. Because if the superlative LHC can’t find answers, it will cast doubt that answers can be found experimentally.

    From here, there are two broad scenarios that could play out, both of which will vastly increase our understanding of nature. One scenario will open up physics to a new world of understanding about the universe; the other could end particle physics as we know it.

    The physicists themselves can’t control the outcome. They’re waiting for nature to tell them the answers.

    Why do we care about new subatomic particles anyway?

    3
    A graphic showing traces of collision of particles at the Compact Muon Solenoid (CMS) experience is pictured with a slow speed experience at Universe of Particles exhibition of the the European Organization for Nuclear Research (CERN) on December 13, 2011, in Geneva. FABRICE COFFRINI/AFP/GettyImages

    The LHC works by smashing together atoms at incredibly high velocities. These particles fuse and can form any number of particles that were around in the universe from the Big Bang onward.

    When the Higgs boson was confirmed in 2012, it was a cause for celebration and unease.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    The Higgs was the last piece of a puzzle called the standard model, which is a theory that connects all the known components of nature (except gravity) together in a balanced, mathematical equation.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth

    The Higgs was the final piece that had been theorized to exist but never seen.

    After the Higgs discovery, the scientists at the LHC turned their hopes in a new direction. They hoped the accelerator could begin to find particles that had never been theorized nor ever seen. It was like going from a treasure hunt with a map to chartering a new ocean.

    They want to find these new subatomic particles because even though the standard model is now complete, it still can’t answer a lot of lingering questions about the universe. Let’s go through the two scenarios step by step.

    Scenario 1: There are more subatomic particles! Exciting!

    If the LHC finds new subatomic particles, it lend evidence to a theory known as supersymmetry. Supersymmetry posits that all the particles in the standard model must have a shadow “super partner” that spins in a slightly different direction.

    Standard model of Supersymmetry DESY
    Standard model of Supersymmetry DESY

    Scientists have never seen one of these supersymmetrical particles, but they’re keen to. Supersymmetry could neatly solve some of the biggest problems vexing physicists right now.

    Such as:

    1) No one knows what dark matter is

    One of these particles could be what scientists call “dark matter,” which is theorized to make up 27 percent of the universe. But we’ve never seen dark matter, and that leaves a huge gaping hole in our understanding of the how the universe formed and exists today.

    “It could be that one particle is responsible for dark matter,” Cranmer explains. Simple enough.

    2) The Higgs boson is much too light

    The Higgs discovery was an incredible triumph, but it also contained a mystery to solve. The boson — at 126 GeV (giga electron volts) — was much lighter than the standard model and the math of quantum mechanics suggests it should be.

    Why is that a problem? Because it’s a wrinkle to be ironed out in our understanding of the universe. It suggests the standard model can’t explain everything. And physicists want to know everything.

    “Either nature is sort of ugly, which is entirely conceivable, and we just have to live with the fact that the Higgs boson mass is light and we don’t know why,” Ray Brock, a Michigan State University physicist who has worked on the LHC, says, “or nature is trying to tell us something.”

    It could be that a yet-to-be-discovered subatomic particle interacts with the Higgs, making it lighter than it ought to be.

    3) The standard model doesn’t unify the forces of the universe

    There are four major forces that make the universe tick: the strong nuclear force (which holds atoms together), the weak nuclear force (what makes Geiger counters tick), electromagnetism (you’re using it right now, reading this article on an electronic screen), and gravity (don’t look down.)

    Scientists aren’t content with the four forces. They, for decades, have been trying to prove that the universe works more elegantly, that, deep down, all these forces are just manifestations of one great force that permeates the universe.

    Physicists call this unification, and the standard model doesn’t provide it.

    “If we find supersymmetry at the LHC, it is a huge boost to the dream that three of the fundamental forces we have [all of them except gravity] are all going to unify,” Cranmer says.

    4) Supersymmetry would lead to more particle hunting

    If scientists find one new particle, supersymmetry means they’ll find many more. That’s exciting. “It’s not going to be just one new particle that we discovered, and yay!” Cranmer says. “We’re going to be finding new forces, or learn something really deep about the nature of space and time. Whatever it is, it’s going to be huge.”

    Scenario 2: There are no new subatomic particles. Less exciting! But still interesting. And troubling.

    The LHC is going to run for around another 20 years, at least. There’s a lot of time left to find new particles, even if there is no supersymmetry. “This is what always blows my mind,” Brock says. “We’ve only taken about 5 percent of the total planned data that the LHC is going to deliver until the middle 2020s.”

    But the accelerator also might not find anything. If the new particles aren’t there to find, the LHC won’t find them. (Hence, the notion that physicists are looking for “what nature chose.”)

    But again, this doesn’t represent a failure. It will actually yield new insights about the universe.

    “It would be a profound discovery to find that we’re not going to see anything else,” Cranmer says.

    1) For one, it would suggest that supersymmetry isn’t the answer

    If supersymmetry is dead, then theoretical physicists will have to go back to the drawing board to figure out how to solve the mysteries left open by the standard model.

    “If we’re all coming up empty, we would have to question our fundamental assumptions,” Sarah Demers, a Yale physicist, tells me. “Which is something we’re trying to do all the time, but that would really force us.”

    2) The answers exist, but they exist in a different universe

    If the LHC can’t find answers to questions like “why is the Higgs so light?” scientists might grow to accept a more out-of-the-box idea: the multiverse.

    That’s the idea where there are tons of universes all existing parallel to one another. It could be that “in most of [the universes], the Higgs boson is really heavy, and in only in very unusual universes [like our own] is the Higgs boson so light that life can form,” Cranmer says.

    Basically: On the scale of our single universe, it might not make sense for the Higgs to be light. But if you put it together with all the other possible universes, the math might check out.

    There’s a problem with this theory, however: If heavier Higgs bosons exist in different universes, there’s no possible way to observe them. They’re in different universes!

    “Which is why a lot of people hate it, because they consider it to be anti-science,” Cranmer says. “It might be impossible to test.”

    3) The new subatomic particles do exist, but the LHC isn’t powerful enough to find them

    In 20 years, if the LHC doesn’t find any new particles, there might be a simple reason: These particles are too heavy for the LHC to detect.

    This is basic E=mc2 Einstein: The more energy in the particle accelerator, the heavier the particles it can create. The LHC is the most powerful particle accelerator in the history of man, but even it has its limits.

    So what will physicists do? Build an even bigger, even smashier particle collider? That’s an option. There are currently preliminary plans in China for a collider double the size of the LHC.

    Building a bigger collider might be a harder sell for international funding agencies. The LHC was funded in part because of the quest to confirm the Higgs. Will governments really spend billions on a machine that may not yield epic insights?

    “Maybe we were blessed as a field that we always had a target or two to shoot for. We don’t have that anymore,” says Markus Klute, an MIT physicist stationed at CERN in Europe. “It’s easier to explain to the funding agencies specifically that there’s a specific endpoint.”

    The LHC will keep running for the foreseeable future. But it could prove a harder task to make the case to build a new collider.

    Either way, these are exciting times for physics

    4
    Dean Mouhtaropoulos/Getty Images

    “I think we have had a tendency to be prematurely depressed,” Demers says. “It’s never a step backward to learn something new,” even if the news is negative. “Ruling out ideas teaches us an incredible amount.”

    And she says that even if the LHC can never find another particle, it can still produce meaningful insights. Already, her colleagues are using it to help determine why there’s so much more matter than antimatter in the universe. And she reminds me the LHC can still teach us more about the mysterious Higgs. We will be able to measure it to a more precise degree.

    Brock, the MSU physicist, notes that since the 1960s, physicists have been chasing the standard model. Now they don’t quite know what they’re chasing. But they know it will change the world.

    “I can’t honestly say in all those 40 years, I’ve been exploring,” Brock says. “I’ve been testing the standard model. The Higgs boson was the last missing piece. Now, we have to explore.”

    See the full article here .

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    Yale University Campus

    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 10:28 am on September 23, 2016 Permalink | Reply
    Tags: , , , , , PTOLEMY laboratory, Tritium   

    From PPPL: “Intern helped get robotic arm on PPPL’s PTOLEMY experiment up and running” 


    PPPL

    September 22, 2016
    Jeanne Jackson DeVoe

    1
    PPPL intern Mark Thom with a device containing a robotic arm that will be used with PPPL’s PTOLEMY experiment, behind him. (Photo by Elle Starkman/PPPL Office of Communications)

    Deep in a laboratory tucked away in the basement of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), intern Mark Thom punched commands into a computer as two other students checked a chamber where a silver robotic arm extended from a small port.

    The arm will allow scientists studying neutrinos that originated at the beginning of the universe to load a tiny amount of nuclear material into the device while still maintaining a vacuum in the PTOLEMY laboratory.

    Thom, along with high school interns Xaymara Rivera and Willma Arias de la Rosa, worked closely with Princeton University physicist Chris Tully and PPPL engineers to get the robotic arm moving again. The crucial device will load tritium, a radioactive isotope of hydrogen, into PTOLEMY, the Princeton Tritium Observatory for Light, Early Universe Massive Neutrino Yield.

    Tritium can capture Big Bang neutrinos and release them with electrons in radioactive decay. The neutrinos can provide a tiny boost of energy to the electrons, which PTOLEMY is designed to precisely measure in the darkest, coldest conditions possible. It is funded by the Mark Simons Foundation and the John Templeton Foundation.

    “For me it was just amazing that I actually got onto that project,” Thom said. “It’s exactly the kind of thing I thought I would like to do, being an engineer working on a high-energy physics project.”

    The robotic arm, together with the portable container and the computer program to operate it, were recycled from another experiment when Thom and fellow interns Rivera and Arias de la Rosa began the project. Thom was responsible for making the arm operational and altering it so it would fit PTOLEMY.

    Handling delicate materials

    Tully said the device can safely handle very delicate radioactive materials from DOE’s Savannah River National Laboratory. Without the device, scientists would have to shut down PTOLEMY completely twice a day to change the tritium sample, he said. Maintaining a vacuum in PTOLEMY is also necessary for the extremely sensitive sensors that measure the energy spectrum of the electrons emitted from the tritium to function properly.

    To make the robotic arm function again, Thom had to analyze why the coding was failing, which meant learning the code for the machine. He had to learn an unfamiliar program and then rewrite it to redirect the arm to handle tritium samples, without having worked on a device of that kind before, Tully said.

    The students encountered a setback when the arm stopped working. At first, they thought the device would need a new motor, which would cost $20,000. It turned out that the culprit was a circuit that would cost just a few dollars to replace. While Tully fixed the computer, Thom took the arm apart and researched how to install magnetic shielding around the motors and sketched a design for that shielding, Tully said. “Mark was quite amazing,” he said. “I was very impressed with him.”

    Thom also designed a cover for one of the ports that would need to be sealed for the robotic arm to work. Rivera and Arias de la Rosa helped him operate and test the robotic arm and wrote procedures for running it. Thom and the other interns also worked with PPPL engineers Charles Gentile and Mike Mardenfeld, along with senior mechanical technician Andy Carpe and lead technician Jim Taylor.

    Gentile, who supervised Thom and other engineering interns, said Thom was one of the best interns he has seen in 25 years of supervising more than 200 interns. “He’s an excellent mechanical engineer,” Gentile said. “He was a hard worker and he came up with innovative solutions to problems.”

    The arm connects to PTOLEMY through two ports equipped with valves. One valve connects to the experiment. The other connects to a loading chamber where scientists can insert a tiny sample of tritium on a graphene base.

    Researchers would create a vacuum in the loading chamber and attach it to the vacuum chamber of PTOLEMY. The robotic arm could then collect the tritium and graphene sample and deposit it into PTOLEMY. Researchers would next retract the arm and close the valve connecting it to PTOLEMY.

    Following parents’ footsteps

    Thom, who is in his final year of master’s degree work at Howard University, is from Trinidad. The son of two engineers, he considered becoming a physician and briefly flirted with the idea of being an actor or music producer before choosing to follow in his parents’ footsteps.

    Thom studied engineering as an undergraduate at Howard. He learned about the internship when Andrea Moten, PPPL acting director of human resources, and engineer Atiba Brereton met him at National Laboratory Day at Howard University in February. The two passed Thom’s resume along to Gentile as a candidate for the engineering apprenticeship program.

    The graduate student recently celebrated his one-year anniversary with his wife, Sydney, who is also an engineer and is currently teaching at a Kipp DC Middle School in Washington, D.C. Thom commuted to Washington every weekend on Friday nights to see her and then headed back to New Jersey on Monday mornings. “It was challenging at first,” he said. “But after a while I got accustomed to it and I actually began to appreciate those drives because it gave me some time to think.”

    Thom said he enjoyed the laid-back atmosphere at PPPL. He was surprised when Gentile told him he was overdressed on his first day. But he most enjoyed talking to researchers about their work. “I met some really cool people – a bunch of physicists whom I was able to have certain conversations with, just talking about abstract theories. That’s the kind of conversation I enjoy,” Thom said. “Being able to interact with people like that in that atmosphere was really enjoyable.”

    The internship gave him a better idea of possible careers as he prepares to graduate, Thom said. “I had a limited view of the engineering world prior to going into this work,” he said. “But now I have a better idea of the kind of environment I’d like to be in, so it gives me idea of what I should do to prepare for that environment.”

    See the full article here .

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    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

     
  • richardmitnick 10:15 am on September 23, 2016 Permalink | Reply
    Tags: , , , Science | Business, ,   

    From SKA via Science Business: “Square Kilometre Array prepares for the ultimate big data challenge” 

    SKA Square Kilometer Array

    SKA

    1

    Science | Business

    22 September 2016
    Éanna Kelly

    The world’s most powerful radio telescope will collect more information each day than the entire internet. Major advances in computing are required to handle this data, but it can be done, says Bernie Fanaroff, strategic advisor for the SKA

    The Square Kilometre Array (SKA), the world’s most powerful telescope, will be ready from day one to gather an unprecedented volume of data from the sky, even if the supporting technical infrastructure is yet to be built.

    “We’ll be ready – the technology is getting there,” Bernie Fanaroff, strategic advisor for the most expensive and sensitive radio astronomy project in the world, told Science|Business.

    Construction of the SKA is due to begin in 2018 and finish sometime in the middle of the next decade. Data acquisition will begin in 2020, requiring a level of processing power and data management know-how that outstretches current capabilities.

    Astronomers estimate that the project will generate 35,000-DVDs-worth of data every second. This is equivalent to “the whole world wide web every day,” said Fanaroff.

    The project is investing in machine learning and artificial intelligence software tools to enable the data analysis. In advance of construction of the vast telescope – which will consist of some 250,000 radio antennas split between sites in Australia and South Africa – SKA already employs more than 400 engineers and technicians in infrastructure, fibre optics and data collection.

    The project is also working with IBM, which recently opened a new R&D centre in Johannesburg, on a new supercomputer. SKA will have two supercomputers to process its data, one based in Cape Town and one in Perth, Australia.

    Recently, elements of the software under development were tested on the world’s second fastest supercomputer, the Tianhe-2, located in the National Supercomputer Centre in Guangzhou, China. It is estimated a supercomputer with three times the power of Tianhe-2 will need to be built in the next decade to cope with all the SKA data.

    In addition to the analysis, the project requires large off-site data warehouses. These will house storage devices custom-built in South Africa. “There were too many bells and whistles with the stuff commercial providers were offering us. It was far too expensive, so we’ve designed our own servers which are cheaper,” said Fanaroff.

    Fanaroff was formerly director of SKA, retiring at the end of 2015, but remaining as a strategic advisor to the project. He was in Brussels this week to explore how African institutions could gain access to the European Commission’s new Europe-wide science cloud, tentatively scheduled to go live in 2020.

    Ten countries are members of the SKA, which has its headquarters at Manchester University’s Jodrell Bank Observatory, home of the world’s third largest fully-steerable radio telescope. The bulk of SKA’s funding has come from South Africa, Australia and the UK.

    Currently its legal status is as a British registered company, but Fanaroff says the plan is to create an intergovernmental arrangement similar to CERN. “The project needs a treaty to lock in funding,” he said.

    Early success

    On SKA’s website is a list of five untold secrets of the cosmos, which the telescope will explore. These include how the very first stars and galaxies formed just after the Big Bang.

    However, Fanaroff, believes the Eureka moment will be something nobody could have imagined. “It’ll make its name, like every telescope does, by discovering an unknown, unknown,” he said.

    A first taste of the SKA’s potential arrived in July through the MeerKAT telescope, which will form part of the SKA. MeerKAT will eventually consist of 64 dishes, but the power of the 16 already installed has surpassed Fanaroff’s expectations.

    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA
    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA

    The telescope revealed over a thousand previously unknown galaxies. “Two things were remarkable: when we switched it on, people told us it was going to take a long time to work. But it collected very good images from day one. Also, our radio receivers worked four times better than specified,” he said. Some 500 scientists have already booked time on the array.

    Researchers with the Breakthrough Listen project, a search for intelligent life funded by Russian billionaire Yuri Milner, would also like a slot, Fanaroff said. Their hunt is exciting and a good example of the sort of bold mission for which SKA will be built. “It’s high-risk, high-reward territory. If you search for aliens and you find nothing, you end your career with no publications. But on the other hand you could be involved in one of the biggest discoveries ever,” said Fanaroff.

    Golden age

    SKA has helped put South Africa’s scientific establishment in the shop window says Fanaroff, referring to the recent Nature Index, which indicates the country’s scientists are publishing record levels of high-quality research, mostly in astronomy. “It’s the start of a golden age,” Fanaroff predicted.

    Not that the SKA does not have its critics. With so much public funding going to the telescope, “Some scientists were a little bit bitter at the beginning,” Fanaroff said. “But that has faded with the global interest from science and industry we’re attracting. The SKA can go on to be a platform for all science in Africa, not just astronomy.”

    See the full article here .

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    SKA CSIRO  Pathfinder Telescope
    SKA ASKAP Pathefinder Telescope

    SKA Meerkat telescope
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    SKA Murchison Widefield Array
    SKA Murchison Wide Field Array

    About SKA

    The Square Kilometre Array will be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, led by SKA Organisation. The SKA will conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.

    Already supported by 10 member countries – Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom – SKA Organisation has brought together some of the world’s finest scientists, engineers and policy makers and more than 100 companies and research institutions across 20 countries in the design and development of the telescope. Construction of the SKA is set to start in 2018, with early science observations in 2020.

     
  • richardmitnick 9:53 am on September 23, 2016 Permalink | Reply
    Tags: 000 years, , Ice cores reveal a slow decline in atmospheric oxygen over the last 800,   

    From Research at Princeton: “Ice cores reveal a slow decline in atmospheric oxygen over the last 800,000 years” 

    Princeton University
    Princeton University

    September 23, 2016
    Morgan Kelly

    1
    No image credit

    Princeton University researchers have compiled 30 years of data to construct the first ice core-based record of atmospheric oxygen concentrations spanning the past 800,000 years, according to a paper published today in the journal Science.

    The record shows that atmospheric oxygen has declined 0.7 percent relative to current atmospheric-oxygen concentrations, a reasonable pace by geological standards, the researchers said. During the past 100 years, however, atmospheric oxygen has declined by a comparatively speedy 0.1 percent because of the burning of fossil fuels, which consumes oxygen and produces carbon dioxide.

    Curiously, the decline in atmospheric oxygen over the past 800,000 years was not accompanied by any significant increase in the average amount of carbon dioxide in the atmosphere, though carbon dioxide concentrations do vary over individual ice age cycles. To explain this apparent paradox, the researchers called upon a theory for how the global carbon cycle, atmospheric carbon dioxide and Earth’s temperature are linked on geologic timescales.

    “The planet has various processes that can keep carbon dioxide levels in check,” said first author Daniel Stolper, a postdoctoral research associate in Princeton’s Department of Geosciences. The researchers discuss a process known as silicate weathering in particular, wherein carbon dioxide reacts with exposed rock to produce, eventually, calcium carbonate minerals, which trap carbon dioxide in a solid form. As temperatures rise due to higher carbon dioxide in the atmosphere, silicate-weathering rates are hypothesized to increase and remove carbon dioxide from the atmosphere faster.

    2
    Researchers at Princeton University analyzed ice cores collected in Greenland and Antarctica to determine levels of atmospheric oxygen over the last 800,000 years. (Image: Stolper, et al.)

    Stolper and his co-authors suggest that the extra carbon dioxide emitted due to declining oxygen concentrations in the atmosphere stimulated silicate weathering, which stabilized carbon dioxide but allowed oxygen to continue to decline.

    “The oxygen record is telling us there’s also a change in the amount of carbon dioxide [that was created when oxygen was removed] entering the atmosphere and ocean,” said co-author John Higgins, Princeton assistant professor of geosciences. “However, atmospheric carbon dioxide levels aren’t changing because the Earth has had time to respond via increased silicate-weathering rates.

    “The Earth can take care of extra carbon dioxide when it has hundreds of thousands or millions of years to get its act together. In contrast, humankind is releasing carbon dioxide today so quickly that silicate weathering can’t possibly respond fast enough,” Higgins continued. “The Earth has these long processes that humankind has short-circuited.”

    The researchers built their history of atmospheric oxygen using measured ratios of oxygen-to-nitrogen found in air trapped in Antarctic ice. This method was established by co-author Michael Bender, professor of geosciences, emeritus, at Princeton.

    Because oxygen is critical to many forms of life and geochemical processes, numerous models and indirect proxies for the oxygen content in the atmosphere have been developed over the years, but there was no consensus on whether oxygen concentrations were rising, falling or flat during the past million years (and before fossil fuel burning). The Princeton team analyzed the ice-core data to create a single account of how atmospheric oxygen has changed during the past 800,000 years.

    “This record represents an important benchmark for the study of the history of atmospheric oxygen,” Higgins said. “Understanding the history of oxygen in Earth’s atmosphere is intimately connected to understanding the evolution of complex life. It’s one of these big, fundamental ongoing questions in Earth science.”

    Read the abstract

    Daniel A. Stolper, Michael L. Bender, Gabrielle B. Dreyfus, Yuzhen Yan, and John A. Higgins. 2016. A Pleistocene ice core record of atmospheric oxygen concentrations. Science. Arti­cle pub­lished Sept. 22, 2016.

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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