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  • richardmitnick 2:23 pm on February 24, 2020 Permalink | Reply
    Tags: "ATLAS experiment searches for natural supersymmetry using novel techniques", , , , , , , phys.org   

    From CERN ATLAS via phys.org: “ATLAS experiment searches for natural supersymmetry using novel techniques” 

    CERN/ATLAS detector

    CERN ATLAS Higgs Event

    CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN


    From CERN ATLAS

    via


    phys.org

    February 24, 2020

    1
    Visualisation of the highest jet multiplicity event selected in a control region used to make predictions of the background from multijet production. This event was recorded by ATLAS on 18 July 2018, and contains 19 jets, illustrated by cones. Yellow blocks represent the calorimeter energy measured in in noise-suppressed clusters. Of the reconstructed jets, 16 (10) have transverse momenta above 50 GeV (80 GeV). Credit: ATLAS Collaboration/CERN

    In new results presented at CERN, the ATLAS Experiment’s search for supersymmetry (SUSY) reached new levels of sensitivity. The results examine a popular SUSY extension studied at the Large Hadron Collider (LHC): the “Minimal Supersymmetric Standard Model” (MSSM), which includes the minimum required number of new particles and interactions to make predictions at the LHC energies. However, even this minimal model introduces a large amount of new parameters (masses and other properties of the new particles), whose values are not predicted by the theory (free parameters).

    To frame their search, ATLAS physicists look for “natural” SUSY, which assumes the various corrections to the Higgs mass comparable in magnitude and their sum close to the electroweak scale (v ~ 246 GeV). Under this paradigm, the supersymmetric partners of the third-generation quarks (“top and bottom squarks”) and gluons (“gluinos”) could have masses close to the TeV scale, and would be produced through the strong interaction at rates large enough to be observed at the LHC.

    In a recent CERN LHC seminar, the ATLAS Collaboration presented new results in the search for natural SUSY, including searches for top squarks and gluinos using the full LHC Run-2 dataset collected between 2015 and 2018. The new results explore previously uncovered, challenging regions of the free parameter space. This is achieved thanks to new analysis techniques improving the identification of low-energy (“soft”) and high-energy (“boosted”) particles in the final state.

    ATLAS’ search for top squarks was performed by selecting proton–proton collisions containing up to one electron or muon. For top-squark masses less than the top-quark mass of 173 GeV (see Figure 1), the resulting decay products tend to be soft and therefore difficult to identify. Physicists developed new techniques based on charged-particle tracking to better identify these decay products, thus significantly improving the experimental sensitivity. For larger top-squark masses, the decay products are boosted, resulting in high-energy, close-by decay products. Physicists improved the search in this regime by using, among other techniques, more precise estimates of the statistical significance of the missing transverse momentum in a collision event.

    3
    Figure 1: Schematic representation of the various topologies of top-squark decays in the scenarios presented at today’s seminar (see link in footer). The region where the top-squark is lighter than the neutralino is not allowed in the models considered. Credit: ATLAS Collaboration/CERN

    The new search for gluinos looks at events containing eight or more “jets”—collimated sprays of hadrons—and missing transverse momentum generated by the production of stable neutralinos in the gluino decays, which, similar to neutrinos, are not directly detected by ATLAS. Physicists employed new reconstruction techniques to improve the energy resolution of the jets and the missing transverse momentum, allowing them to better separate the putative signal from background processes. These take advantage of “particle-flow” jet algorithms [https://arxiv.org/abs/1703.10485] that combine information from both the tracking detector and the calorimeter system.

    4
    Figure 2: Updated exclusion limits on (left) gluino and (right) top-squark production including the new results presented by ATLAS at the CERN LHC seminar today. Credit: ATLAS Collaboration/CERN

    ATLAS physicists also optimised their event-selection criteria to enhance the contribution of possible SUSY signals compared to the Standard Model background processes. No excess was observed in the data. The results were used to derive exclusion limits on MSSM-inspired simplified models in terms of gluino, top-squark and neutralino masses (see Figure 2).

    The new analyses significantly extend the sensitivity of the searches and further constrain the available parameter space for natural SUSY. The exclusion of heavy top squarks is extended from 1 to 1.25 TeV. The search continues.

    More information: CERN LHC Seminar: Constraining natural supersymmetry with the ATLAS detector by Jeanette Miriam Lorenz indico.cern.ch/event/868249/

    See the full article here .


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  • richardmitnick 1:41 pm on February 24, 2020 Permalink | Reply
    Tags: , , , , , , New binary millisecond pulsar discovered in NGC 6205", phys.org,   

    From Chinese Academy of Sciences via phys.org: “New binary millisecond pulsar discovered in NGC 6205 with FAST Radio Telescope” 

    From Chinese Academy of Sciences

    via


    phys.org

    February 24, 2020
    Tomasz Nowakowski

    1
    Positions of the six pulsars in the GC M13, marked with red circles with letters. Credit: Wang et al., 2020.

    Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), astronomers have detected a new binary millisecond pulsar (MSP) in the globular cluster NGC 6205. The newly found pulsar received designation PSR J1641+3627F. The finding is reported in a paper published February 14 on the arXiv pre-print repository.

    FAST [Five-hundred-meter Aperture Spherical Telescope] radio telescope, with phased arrays from CSIRO engineers Australia [located in the Dawodang depression in Pingtang County, Guizhou Province, south China

    Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation. The most rapidly rotating pulsars, with rotation periods below 30 milliseconds, are known as millisecond pulsars (MSPs).

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Astronomers believe that MSPs form in binary systems when the initially more massive component turns into a neutron star that is then spun-up due to accretion of matter from the secondary star. Observations conducted so far seem to support this theory, as more than a half of known MSPs have been found to have stellar companions.

    Now, a team of astronomers led by Lin Wang of CAS (Chinese Academy of Sciences) Key Laboratory of FAST in China, reports the detection of a new MSP in the bright globular cluster NGC 6205 (also known as M13), which is located some 23,150 light years away in the constellation of Hercules. The discovery was made as part of FAST observations of NGC 6205 that also monitored other pulsars in this cluster.

    “In this paper, we present the discovery of the binary pulsar PSR J1641+3627F (M13F) and timing solutions of all the known pulsars in the GC M13,” the astronomers wrote in the paper.

    According to the study, PSR J1641+3627F has a spin period of approximately 3.0 milliseconds and an orbital period of 1.38 days. This means that it has the second shortest spin period and the longest orbital period among the six pulsars that have been discovered in NGC 6205 (the other five are designated PSR J1641+3627A to E).

    FAST observations show that PSR J1641+3627F has a dispersion measure of around 30.4 parsecs/cm3. It was noted that this is close to the average dispersion measure value of other known pulsars in NGC 6205. The mass of the companion object is estimated to be around 0.16 solar masses, what suggests a white dwarf.

    The research also found that PSR J1641+3627F is located at the edge of the cluster core and its spin period derivative is typical for MSPs in globular clusters. However, the system’s eccentricity is, according to the astronomers, relatively small when compared to typical MSP-white dwarf systems.

    In general, the researchers concluded that all the discovered binary systems in NGC 6205 have relatively low eccentricities when compared to typical globular cluster pulsars and the eccentricities were found to decrease with distance from the cluster core.

    “This is consistent with what is expected as this cluster has a very low encounter rate per binary,” the authors of the paper underlined.

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    The Chinese Academy of Sciences is the linchpin of China’s drive to explore and harness high technology and the natural sciences for the benefit of China and the world. Comprising a comprehensive research and development network, a merit-based learned society and a system of higher education, CAS brings together scientists and engineers from China and around the world to address both theoretical and applied problems using world-class scientific and management approaches.

    Since its founding, CAS has fulfilled multiple roles — as a national team and a locomotive driving national technological innovation, a pioneer in supporting nationwide S&T development, a think tank delivering S&T advice and a community for training young S&T talent.

    Now, as it responds to a nationwide call to put innovation at the heart of China’s development, CAS has further defined its development strategy by emphasizing greater reliance on democratic management, openness and talent in the promotion of innovative research. With the adoption of its Innovation 2020 programme in 2011, the academy has committed to delivering breakthrough science and technology, higher caliber talent and superior scientific advice. As part of the programme, CAS has also requested that each of its institutes define its “strategic niche” — based on an overall analysis of the scientific progress and trends in their own fields both in China and abroad — in order to deploy resources more efficiently and innovate more collectively.

    As it builds on its proud record, CAS aims for a bright future as one of the world’s top S&T research and development organizations.

     
  • richardmitnick 12:42 pm on February 24, 2020 Permalink | Reply
    Tags: "First direct seismic measurements of Ьars reveal a geologically active planet", , , , , , phys.org,   

    From University of Maryland via phys.org: “First direct seismic measurements of Ьars reveal a geologically active planet” 


    From University of Maryland

    via


    phys.org

    February 24, 2020

    1
    NASA’s InSight lander deployed its seismometer on the Martian surface on Dec. 19, 2018. This image, captured on Feb. 2, 2019 (Martian Sol 66) by the deployment camera on the lander’s robotic arm shows the protective wind and thermal shield which covers the seismometer. Credit: NASA/JPL-Caltech

    NASA/Mars InSight Lander

    The first reports of seismic activity and ground vibrations on Mars are in. The red planet has a moderate level of seismic activity, intermediate between Earth and the Moon.

    An international team that includes University of Maryland geologists released preliminary results from the InSight mission, which landed a probe on Mars on November 26, 2018. Data from the mission’s Seismic Experiment for Interior Structure (SEIS) provided the first direct seismic measurements of the Martian subsurface and upper crust—the rocky outermost layer of the planet. The results were published in a special issue of the journal Nature Geoscience on February 24, 2020.

    “This is the first mission focused on taking direct geophysical measurements of any planet besides Earth, and it’s given us our first real understanding of Mars’ interior structure and geological processes,” said Nicholas Schmerr, an assistant professor of geology at UMD and a co-author of the study. “These data are helping us understand how the planet works, its rate of seismicity, how active it is and where it’s active.”

    The seismic data acquired over 235 Martian days showed 174 seismic events, or marsquakes. Of those, 150 were high-frequency events that produce ground shaking similar to that recorded on the Moon by the Apollo program. Their waveforms show that seismic waves bounce around as they travel through the heterogeneous and fractured Martian crust. The other 24 quakes observed by SEIS were predominantly low-frequency events. Three showed two distinct wave patterns similar to quakes on Earth caused by the movement of tectonic plates.

    “These low-frequency events were really exciting, because we know how to analyze them and extract information about subsurface structure,” said Vedran Lekic, an associate professor of geology at UMD and a co-author of the study. “Based on how the different waves propagate through the crust, we can identify geologic layers within the planet and determine the distance and location to the source of the quakes.”

    The researchers identified the source location and magnitude of three of the low-frequency marsquakes, and believe that 10 more are strong enough to reveal their source and magnitude once they are analyzed.

    “Understanding these processes is part of a bigger question about the planet itself,” Schmerr said. “Can it support life, or did it ever? Life exists at the edge, where the equilibrium is off. Think of areas on Earth such as the thermal vents at the deep ocean ridges where chemistry provides the energy for life rather than the sun. If it turns out there is liquid magma on Mars, and if we can pinpoint where the planet is most geologically active, it might guide future missions searching for the potential for life.”

    Detecting signs of life was the primary mission of the earlier Mars probes, Viking 1 and Viking 2.

    NASA/Viking 1 Lander

    NASA Viking 2 Lander

    Each carried seismometers, but they were mounted directly on the landers and provided no useful data. The Viking 1 instrument did not unlock properly, and Viking 2 only picked up noise from wind buffeting the lander but no convincing marsquake signals.

    The InSight mission is dedicated specifically to geophysical exploration, so engineers worked to solve previous noise problems. A robotic arm on the lander placed the SEIS seismometer directly on the Martian ground some distance away to isolate it from the lander. The instrument is also housed in a vacuum chamber and covered by the aptly named Wind and Thermal Shield. The SEIS seismometer is sensitive enough to discern very faint ground vibrations, which on Mars are 500 times quieter than ground vibrations found in quietest locations on Earth.

    In addition, the seismometer provided important information about Martian weather. Low-pressure systems and swirling columns of wind and dust called dust devils lift the ground enough for the seismometer to register a tilt in the substrate. High winds flowing across the surface of the ground also create a distinct seismic signature. Combined with data from meteorological instruments, SEIS data help paint a picture of the daily cycles of surface activity near the InSight lander.

    The researchers found that the winds pick up from about midnight through early morning, as cooler air rolls down from highlands in the Southern Hemisphere onto the Elysium Planitia plains in the Northern Hemisphere where the lander is located. During the day, heating from the sun causes convective winds to build. Winds reach their peak in late afternoon when atmospheric pressure drops and dust devil activity occurs. By evening, the winds die down, and conditions around the lander become quiet. From late evening until about midnight, atmospheric conditions are so quiet, the seismometer is able to detect the rumblings from deeper inside the planet.

    All of the marsquakes have been detected during these quiet periods at night, but the geologic activity likely persists throughout the day.

    “What is so spectacular about this data is that it gives us this beautifully poetic picture of what a day is actually like on another planet,” Lekic said.

    The InSight mission is scheduled to continue collecting data through 2020.

    The research papers, “Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data,” P.Lognonné et al., and “Initial results from the InSight mission on Mars” by W. Banerdt et al., were published as part of a special issue of the journal Nature Geoscience released on February 24, 2020.

    See the full article here .

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    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    U Maryland Campus

    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 3:25 pm on February 21, 2020 Permalink | Reply
    Tags: "Scientists predict state of matter that can conduct both electricity and energy perfectly", , phys.org, ,   

    From University of Chicago via phys.org: “Scientists predict state of matter that can conduct both electricity and energy perfectly” 

    U Chicago bloc

    From University of Chicago

    via


    phys.org

    February 21, 2020

    1
    From left: Shiva Safaei, David Mazziotti, and LeeAnn Sager discuss their finding that a dual state of matter with both fermion and exciton condensates could exist. Credit: University of Chicago

    Three scientists from the University of Chicago have run the numbers, and they believe there may be a way to make a material that could conduct both electricity and energy with 100% efficiency—never losing any to heat or friction.

    The breakthrough, published Feb. 18 in Physical Review B, suggests a framework for an entirely new type of matter, which could have very useful technological applications in the real world. Though the prediction is based on theory, efforts are underway to test it experimentally.

    “We started out trying to answer a really basic question, to see if it was even possible—we thought these two properties might be incompatible in one material,” said co-author and research adviser David Mazziotti, a professor of Chemistry and the James Franck Institute and an expert in molecular electronic structure. “But to our surprise, we found the two states actually become entangled at a quantum level, and so reinforce each other.”

    Since an untold amount of energy is lost off power lines, engines and machinery every year, scientists are eager to find more efficient alternatives. “In many ways, this is the most important question of the 21st century—how to generate and move energy with minimal loss,” Mazziotti said.

    We’ve known about superconductors—a kind of material that can conduct electricity forever with nearly zero loss—for more than a century. But it was only in the last few years that scientists managed to make a similar material in the laboratory which can conduct energy with nearly zero loss, called an exciton condensate.

    But both superconductors and exciton condensates are tricky materials to make and to keep functioning—partly because scientists don’t fully understand how they work and the theory behind them is incomplete. We do know, however, that both involve the action of quantum physics.

    UChicago graduate student LeeAnn Sager began to wonder how the two states could be generated in the same material. Mazziotti’s group specializes in exploring the properties and structures of materials and chemicals using computation, so she began plugging different combinations into a computer model. “We scanned through many possibilities, and then to our surprise, found a region where both states could exist together,” she said.

    It appears that in the right configuration, the two states actually become entangled—a quantum phenomenon in which systems become intangibly linked together. This challenges the conventional notion that the two states are unrelated, and may open a new field of dual exciton and fermion pair condensates.

    Using some advanced mathematics, they showed that thanks to the quantum entanglement, the dual condensates should theoretically exist even at the macroscopic size—that is, visible to the human eye.

    “This implies that such condensates may be realizable in novel materials, such as a double layer of superconductors,” Sager said.

    The scientists are working with experimental groups to see if the prediction can be achieved in real materials.

    “Being able to combine superconductivity and exciton condensates would be amazing for lots of applications—electronics, spintronics, quantum computing,” said Shiva Safaei, a postdoctoral researcher and the third author on the paper. “Though this is a first step, it looks extremely promising.”

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

    We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

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    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
  • richardmitnick 4:57 pm on February 20, 2020 Permalink | Reply
    Tags: "Huge stores of Arctic sea ice likely contributed to past climate cooling", Experiments show that there was enough cold fresh water to disrupt ocean salt-temperature circulation patterns and trigger abrupt climate cooling such as the Younger Dryas., phys.org, ,   

    From UMass Amherst and Woods Hole Oceanographic Institution via phys.org: “Huge stores of Arctic sea ice likely contributed to past climate cooling” 

    U Mass Amherst

    From UMass Amherst

    and

    Woods Hole Oceanographic Institution

    via


    phys.org

    February 20, 2020
    Raymond Bradley

    1
    One of the last remains of the formerly extensive ice off the coast of Ellesmere Island, Arctic Canada, pictured in July 2002. At the end of the last Ice Age, ice such as this would have covered large parts of the Arctic Ocean and been up to 164 feet (50 meters) thick in places, creating an enormous reservoir of fresh water independent from land-based lakes and ice sheets, say Raymond Bradley of UMass Amherst and Alan Condron of Woods Hole Oceanographic Institute in a new paper on past climate. Credit: Woods Hole Oceanographic Institution/Alan Condron

    In a new paper, climate scientists at the University of Massachusetts Amherst and Woods Hole Oceanographic Institution propose that massive amounts of melting sea ice in the Arctic drained into the North Atlantic and disrupted climate-steering currents, thus playing an important role in causing past abrupt climate change after the last Ice Age, from about 8,000 to 13,000 years ago. Details of how they tested this idea for the first time are online now in Geology.

    Raymond Bradley, director of UMass Amherst’s Climate Systems Research Center, and lead author Alan Condron, research scientist at Woods Hole, explain that geologists have considered many theories about abrupt temperature plunges into “glacier-like” conditions since the last glaciers retreated, notably a very cold period about 12,900 years ago, known as the Younger Dryas. Meteorite impact and volcanic eruptions were proposed to explain these episodes, but evidence has been unconvincing, they add.

    Now Condron and Bradley, with Ph.D student Anthony Joyce, say they have new evidence that periodic break-up of thick Arctic sea ice greatly affected climate. Melting of this ice led to freshwater flooding into the seas near Greenland, Norway and Iceland between 13,000 and 8,000 years ago, slowing the strength of the Atlantic Meridional Overturning Circulation (AMOC). They say their experiments show that there was enough cold, fresh water to disrupt ocean salt-temperature circulation patterns and trigger abrupt climate cooling such as the Younger Dryas.

    Bradley explains, “Understanding the past helps us understand how the Arctic system works.”

    Condron says researchers once thought this cold period was triggered by the draining of Lake Agassiz, an enormous glacial lake at the edge of the massive ice sheet that once extended from the Arctic south into modern New York. “But although the lake was big by modern standards, it has been difficult in the climate modeling community to trigger a 1,000-year cold period with the water it contained, because the volume of water is not large enough to weaken the Atlantic circulation over a long period,” he notes.

    “However, the volumes of water we find stored as sea ice in the Arctic vastly exceed the volume of Lake Agassiz, making sea ice break-up a really good candidate for triggering the Younger Dryas cooling,” he adds.

    To establish that there was enough ice in the Arctic to disrupt the sea circulation pattern, the researchers used numerical climate model experiments to estimate past Arctic sea ice extent and thickness. They also examined diaries and journals of early 19th and 20th century Arctic expeditions to see if those explorers, whose explorations came at the end of a “Little Ice Age,” encountered unusually thick sea ice.

    Condron and Bradley cite the impressions of Vice-Admiral Sir George Nares, who led the 1875 British Arctic Expedition to the North Pole. He was so struck by the extensive, thick ice his expedition encountered that he introduced the term “palaeocrystic ice” to describe “floes… of gigantic thickness with a most uneven surface and covered with deep snow.”

    They note, “It seems from these, and other accounts kept by early Arctic explorers, that the Arctic Ocean was covered by ice considerably thicker than has been observed over the past 30-40 years. While recent climate warming in the Arctic has caused much of this old and thick ice to break up and melt, large pieces of it were also still being reported in the early 20th century.” including floes used as scientific research stations by both the U.S. and Russia as late as the Cold War.

    They say their numerical ocean/sea-ice model of the volume of freshwater stored as sea ice and changes in ice export at the end of the Ice Age show these were large enough to slow the AMOC and cool climate. Thick ice over the Arctic Ocean created “an enormous reservoir of freshwater, independent of terrestrial sourc¬es.” As ice sheets retreated and sea level rose, changes in atmospheric circulation and land-based floods caused this ice to flow to the sea through Fram Strait east of Greenland, where it melted and freshened Nordic Seas enough to weaken Atlantic circulation.

    As both the volume of ice stored in the Arctic Basin and the magnitude of these export events far exceed the volume of meltwater discharged from Lake Agassiz, they report, “our results show that ice from the Arctic Ocean itself may have played an important role in causing abrupt climate change in the past.” This work was supported by the National Science Foundation and its Extreme Science and Engineering Discovery Environment. Also, numerical simulations were carried out using MITgcm.

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    Woods Hole Oceanographic Institute

    Vision & Mission

    The ocean is a defining feature of our planet and crucial to life on Earth, yet it remains one of the planet’s last unexplored frontiers. For this reason, WHOI scientists and engineers are committed to understanding all facets of the ocean as well as its complex connections with Earth’s atmosphere, land, ice, seafloor, and life—including humanity. This is essential not only to advance knowledge about our planet, but also to ensure society’s long-term welfare and to help guide human stewardship of the environment. WHOI researchers are also dedicated to training future generations of ocean science leaders, to providing unbiased information that informs public policy and decision-making, and to expanding public awareness about the importance of the global ocean and its resources.
    Mission Statement

    The Woods Hole Oceanographic Institution is dedicated to advancing knowledge of the ocean and its connection with the Earth system through a sustained commitment to excellence in science, engineering, and education, and to the application of this knowledge to problems facing society.

    U Mass Amherst campus

    UMass Amherst, the Commonwealth’s flagship campus, is a nationally ranked public research university offering a full range of undergraduate, graduate and professional degrees.

    As the flagship campus of America’s education stateUniversity of Massachusetts Amherst is the leader of the public higher education system of the Commonwealth, making a profound, transformative impact to the common good. Founded in 1863, we are the largest public research university in New England, distinguished by the excellence and breadth of our academic, research and community outreach programs. We rank 29th among the nation’s top public universities, moving up 11 spots in the past two years in the U.S. News & World Report’s annual college guide.

     
  • richardmitnick 4:59 pm on February 19, 2020 Permalink | Reply
    Tags: "What if we could teach photons to behave like electrons?", phys.org, , The researchers tricked the photons—which are intrinsically non-magnetic—into behaving like charged electrons.   

    From Stanford University via phys.org: “What if we could teach photons to behave like electrons?” 

    Stanford University Name
    From Stanford University

    via


    phys.org

    1
    Credit: CC0 Public Domain

    To develop futuristic technologies like quantum computers, scientists will need to find ways to control photons, the basic particles of light, just as precisely as they can already control electrons, the basic particles in electronic computing. Unfortunately, photons are far more difficult to manipulate than electrons, which respond to forces as simple as the sort of magnetism that even children understand.

    But now, for the first time, a Stanford-led team has created a pseudo-magnetic force that can precisely control photons. In the short term, this control mechanism could be used to send more internet data through fiber optic cables. In the future, this discovery could lead to the creation of light-based chips that would deliver far greater computational power than electronic chips. “What we’ve done is so novel that the possibilities are only just beginning to materialize,” said postdoctoral scholar Avik Dutt, first author of an article describing the discovery in Science.

    Essentially, the researchers tricked the photons—which are intrinsically non-magnetic—into behaving like charged electrons. They accomplished this by sending the photons through carefully designed mazes in a way that caused the light particles to behave as if they were being acted upon by what the scientists called a “synthetic” or “artificial” magnetic field.

    “We designed structures that created magnetic forces capable of pushing photons in predictable and useful ways,” said Shanhui Fan, a professor of electrical engineering and senior scientist behind the research effort.

    Although still in the experimental stage, these structures represent an advance on the existing mode of computing. Storing information is all about controlling the variable states of particles, and today, scientists do so by switching electrons in a chip on and off to create digital zeroes and ones. A chip that uses magnetism to control the interplay between the photon’s color (or energy level) and spin (whether it is traveling in a clockwise or counterclockwise direction) creates more variable states than is possible with simple on-off electrons. Those possibilities will enable scientists to process, store and transmit far more data on photon-based devices than is possible with electronic chips today.

    To bring photons into the proximities required to create these magnetic effects, the Stanford researchers used lasers, fiber optic cables and other off-the-shelf scientific equipment. Building these tabletop structures enabled the scientists to deduce the design principles behind the effects they discovered. Eventually they’ll have to create nanoscale structures that embody these same principles to build the chip. In the meantime, says Fan, “we’ve found a relatively simple new mechanism to control light, and that’s exciting.”

    See the full article here .


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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 4:23 pm on February 19, 2020 Permalink | Reply
    Tags: "Cryo-chip overcomes obstacle to large-scale quantum computers", Horse Ridge, phys.org, QuTech   

    From QuTech via phys.org: “Cryo-chip overcomes obstacle to large-scale quantum computers” 

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    From Qutech

    via


    phys.org

    1
    Horse Ridge mounted on the board ready to be installed in the cryogenic refrigerator. Credit: QuTech.

    QuTech has resolved a major issue on the road toward a working large-scale quantum computer. QuTech, a collaboration of TU Delft and TNO, and Intel have designed and fabricated an integrated circuit that can controlling qubits at extremely low temperatures. This paves the way for the crucial integration of qubits and their controlling electronics in the same chip. The scientists have presented their research during the ISSCC Conference in San Francisco.

    Quantum computers

    “This result brings us closer to a large-scale quantum computer which can solve problems that are intractable by even the most powerful supercomputers. Solutions to those problems can make a strong impact on everyday life, for instance in the fields of medicine and energy,” said team lead Fabio Sebastiano from QuTech and the Faculty of Electrical Engineering, Mathematics and Computer Science.

    Extreme temperatures

    “There are many issues to be resolved before we have a working large-scale quantum computer,” said Sebastiano. “The quantum information stored in qubits can rapidly degrade and become unusable unless qubits are cooled down to temperatures very close to absolute zero (-273 degrees Celsius, or 0 Kelvin). For this reason, qubits typically operate inside special refrigerators at temperatures as low as 0.01 K, controlled by conventional electronics working at room temperature.”

    Scaling up

    One wire is required to connect each qubit to the control electronics. While this is feasible for the small number of qubits now in operation, the approach will become impractical for the millions of qubits required in useful quantum computers. “It would be equivalent to taking the 12-megapixel camera on your mobile phone and trying to individually wire each of the million pixels to a separate electronic circuit,” said Sebastiano. “A more viable solution is to operate the electronics controlling the qubits at extremely low (cryogenic) temperatures, so they can be placed as close as possible to the qubits.”

    Horse Ridge

    QuTech teamed up with Intel to address this precise challenge. The result is called Horse Ridge—an integrated circuit named after one of the coldest spots in Oregon. Sebastiano: “We have designed and fabricated a CMOS integrated circuit able to control up to 128 qubits, which can operate at 3 K (-270 °C) and can therefore be described as a cryo-CMOS circuit.”

    CMOS (complementary metal oxide semiconductor) is the same technology employed for standard microprocessors. Using CMOS therefore enables the reliable fabrication of very complex circuits comprising billions of electrical components, as required for large-scale quantum computers.

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    The team in the lab next to the cryogenic refrigerator hosting the qubit and Horse Ridge. The Horse Ridge output is visible on the screen on the bottom right. From top to bottom, from left to right: Bishnu Patra, Jeroen van Dijk, Xiao Xue, Fabio Sebastiano (holding the qubits), Lieven Vandersypen, Masoud Babaie (holding Horse Ridge). Credit: Ernst de Groot for QuTech.

    Integrated circuit and qubit

    The researchers demonstrated experimentally both proper operation of the integrated circuit and an ability to drive a real spin qubit. Spin qubits are among the promising qubit candidates for a large-scale quantum computer. Sebastiano: “This is the most complex cryo-CMOS circuit ever demonstrated, and the first capable of driving a spin qubit.”

    One chip

    The next challenge is to close the remaining temperature gap. “Spin qubits are expected to function at slightly higher temperatures than is achieved now, say above 1,5 K,” said Sebastiano. “Our cryo-CMOS circuit now works at 3 K. If we can bridge this temperature gap, we could integrate both qubits and their controlling electronics into the same package or chip, thus achieving an extremely compact system.”

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 3:54 pm on February 19, 2020 Permalink | Reply
    Tags: "Keeping it simple—Synthesizing useful organic compounds now made easier and cheaper", , , he Suzuki-Miyaura reaction, phys.org, The scientists knew that the process required a palladium catalyst.,   

    From Tokyo University of Science via phys.org: “Keeping it simple—Synthesizing useful organic compounds now made easier and cheaper” 

    From Tokyo University of Science

    1
    Credit: CC0 Public Domain

    The Suzuki-Miyaura reaction is a well-known chemical process in which a reaction between organic boronic acids and aryl halides leads to the synthesis of “biaryl” compounds, which are important components of various drugs and chemical products. This is also called cross-coupling, as two aryl molecules are combined, or cross-coupled, in this process. Because the organic aromatic molecules—which are formed as a result of this reaction—have various applications, such as in solvents and drugs, finding a way of optimizing the existing cross-coupling reactions is crucial. This is why, in a new study published in ACS Catalysts, a team of scientists from Japan, including Junior Assoc Prof Yuichiro Mutoh and Prof Shinichi Saito of Tokyo University of Science, wanted to check if this reaction can be made more efficient.

    “Protected” organic boronic acid, which is an organic boronic acid with a ‘masking group,’ is frequently used as a precursor for boronic acid in the Suzuki-Miyaura reaction. Because the reactivity of the protected boronic acid is low, it does not take part in this reaction. Thus, the masking group needs to be removed for the reaction to proceed, which adds another step to the process. This made these scientists wonder: what if the masked molecules were directly used in the reaction? It would lead us to a much faster, cheaper technique!

    Prof Saito explains, “Because the removal of the masking group is necessary to provide the latent boronic acids that engage in subsequent Suzuki-Miyaura reactions, the direct use of the protected boronic acid in a Suzuki-Miyaura reaction would be highly desirable in terms number of steps and atom economy. This would help streamline the synthesis of complex molecules.” The only challenge was that until now, there was no known way to directly use protected boronic acids without removing the masking group first, and thus, the scientists set out to find ways to do this.

    The scientists knew that the process required a palladium catalyst (a molecule or compound that can speed up a reaction), a base, and two starting aryl molecules. They proceeded to check if the reaction takes place with a protected molecule. To begin with, they examined the impact of various bases on the reaction. They saw that when a particular potassium base, called KOτ-Bu, was used, it resulted in a high yield of products, and this effect as not seen with other bases. Then, they tested various palladium-based catalysts and saw that all catalysts produced a similar yield, indicating that common palladium-based catalyst systems can be used for the cross-coupling. This led them to conclude that the KOτ-Bu base played a crucial role if one was to use protected boronic acid directly.

    After over a dozen successful Suzuki-Miyaura reactions with high yield for different biaryl compounds, the team conducted ‘control’ experiments to check for other variables and to gain insight into the underlying mechanisms of the KOτ-Bu base. Specifically, they checked if the chemical species were present in the reaction mixture before the reaction was complete, which uncovered an intermediate compound involving the KOτ-Bu base and the boronic acid reagent. Using techniques like NMR spectroscopy and single-crystal X-ray diffraction analysis, the scientists confirmed that the key to the success of these cross-coupling reactions is the use of KOτ-Bu as the base, as it enables the formation of an active borate, essential for the reaction.

    The methodology discovered in this study provides insight into the Suzuki-Miyaura reaction and proposes a novel way in which the required steps to use protected boronic acids can be minimized. The entire process to obtain biaryl molecules was carried in one single pot, which is advantageous in terms of space and cost. Prof Saito concludes, “We developed a way for the reaction to be step- and pot-economic, features that have received considerable attention in recent years. Thus, this study opens up new possibilities for the use of protected boronic acids in various coupling reactions.”

    Owing to its novel findings, this study was even selected to be on the cover of the January 2020 issue of ACS Catalysis. These findings will hopefully help simplify the synthesis of important complex molecules, including pharmaceutical drugs, so that more people can benefit from advances in the chemical sciences.

    See the full article here .

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    Tokyo University of Science was founded in 1881 as The Tokyo Academy of Physics by 21 graduates of the Department of Physics in the Faculty of Science, University of Tokyo (then the Imperial University). In 1883, it was renamed the Tokyo College of Science, and in 1949, it attained university status and became the Tokyo University of Science. The leading character appearing in Japanese novelist Soseki Natsume’s novel Botchan graduated from Tokyo University of Science.

    As of 2016, it is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

     
  • richardmitnick 6:16 pm on February 18, 2020 Permalink | Reply
    Tags: "Researchers combine lasers and terahertz waves in camera that sees 'unseen' detail", , , , phys.org, University of Sussex   

    From University of Sussex via phys.org: “Researchers combine lasers and terahertz waves in camera that sees ‘unseen’ detail” 

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    From University of Sussex

    via


    phys.org

    February 18, 2020

    2
    The time-resolved nonlinear ghost imaging camera uses a nonlinear crystal to convert standard laser light to terahertz patterns, allowing the reconstruction of complex samples using a single terahertz pixel. Credit: University of Sussex

    A team of physicists at the University of Sussex has successfully developed the first nonlinear camera capable of capturing high-resolution images of the interior of solid objects using terahertz (THz) radiation.

    Led by Professor Marco Peccianti of the Emergent Photonics (EPic) Lab, Luana Olivieri, Dr. Juan S. Totero Gongora and a team of research students built a new type of THz camera capable of detecting THz electromagnetic waves with unprecedented accuracy.

    Images produced using THz radiation are called ‘hyperspectral’ because the image consists of pixels, each one containing the electromagnetic signature of the object in that point.

    Lying between microwaves and infrared in the electromagnetic spectrum, THz radiation easily penetrates materials like paper, clothes and plastic in the same way X-rays do, but without being harmful. It is safe to use with even the most delicate biological samples. THz imaging makes it possible to ‘see’ the molecular composition of objects and distinguish between different materials—such as sugar and cocaine, for example.

    Explaining the significance of their achievement, Prof Peccianti said: “The core challenge in THz cameras is not about collecting an image, but it is about preserving the objects spectral fingerprint that can be easily corrupted by your technique. This is where the importance of our achievement lies. The fingerprint of all the details of the image is preserved in such a way that we can investigate the nature of the object in full detail. ”

    3
    Artistic rendering of the terahertz field transmitted by an abstract object. Credit: University of Sussex

    Until now, cameras capable of capturing a hyperspectral image preserving all the fine details revealed by THz radiation had not been considered possible.

    The EPic Lab team used a single-pixel camera to image sample objects with patterns of THz light. The prototype they built can detect how the object alters different patterns of THz light. By combining this information with the shape of each original pattern, the camera reveals the image of an object as well as its chemical composition.

    Sources of THz radiation are very faint and hyperspectral imaging had, until now, limited fidelity. To overcome this, The Sussex team shone a standard laser onto a unique non-linear material capable of converting visible light to THz. The prototype camera creates THz electromagnetic waves very close to the sample, similar to how a microscope works. As THz waves can travel right through an object without affecting it, the resulting images reveal the shape and composition of objects in three dimensions.

    Dr. Totero Gongora said: “This is a major step forward because we have demonstrated that all the possibilities explored in our previous theoretical research are not only feasible, but our camera works even better than we expected. While building our device, we discovered several ways to optimise the imaging process and now the technology is stable and works well. The next phase of our research will be in speeding up the image reconstruction process and taking us closer to applying THz cameras to real-world applications; like airport security, intelligent car sensors, quality control in manufacturing and even scanners to detect health problems like skin cancer.”

    Science paper:
    Luana Olivieri et al. Hyperspectral terahertz microscopy via nonlinear ghost imaging, Optica (2020)

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

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    The University of Sussex is a public research university located in Falmer, Sussex, England. Its campus is surrounded by the South Downs National Park and it is a short distance away from central Brighton. The University received its Royal Charter in August 1961, the first of the plate glass university generation, and was a founding member of the 1994 Group of research-intensive universities.

    More than a third of its students are enrolled in postgraduate programs and approximately a third of staff are from outside the United Kingdom. Sussex has a diverse community of over 17,000 students, with around one in three being foreign students, and over 1000 academics, representing over 140 different nationalities. The annual income of the institution for 2016–17 was £286.1 million with an expenditure of £270.4 million. In 2017, over 32,000 students applied to the University of Sussex, with around 5,000 joining the institution.

    The Times Higher Education World University Rankings 2018 placed Sussex 147th in the world overall, 39th in the world for Social Sciences and 49th globally for Business and Law studies. Sussex is particularly known for its Humanities and Social Sciences departments, with its Development studies program being placed at number 1 globally in the QS World University Ranking.

    Sussex counts 5 Nobel Prize winners, 15 Fellows of the Royal Society, 9 Fellows of the British Academy, 24 fellows of the Academy of Social Sciences and a winner of the Crafoord Prize among its faculty. By 2011, many of its faculty members had also received the Royal Society of Literature Prize, the Order of the British Empire and the Bancroft Prize. Alumni include heads of states, diplomats, politicians, eminent scientists and activists.

     
  • richardmitnick 3:10 pm on February 17, 2020 Permalink | Reply
    Tags: , , , , , , phys.org, , Shedding new light on the internal structure of atomic nuclei.   

    From KTH Royal Institute of Technology via phys.org: “Exotic atomic nuclei reveal traces of new form of superfluidity” 

    1

    From KTH Royal Institute of Technology

    via


    phys.org

    Published Feb 17, 2020
    David Callahan

    2
    The team behind the discovery of the new form of superfluidity: from left, Bo Cederwall, professor of physics at KTH Royal Institute of Technology, Xiaoyu Liu, Wei Zhang, Aysegül Ertoprak, Farnaz Ghazi Moradi and Özge Aktas.Published Feb 17, 2020

    Recent observations of the internal structure of the rare isotope ruthenium-88 shed new light on the internal structure of atomic nuclei, a breakthrough which could also lead to further insights into how some chemical elements in nature and their isotopes are formed.

    Led by Bo Cederwall, Professor of Experimental Nuclear Physics at KTH Royal Institute of Technology, an international research team identified new rotational states in the extremely neutron-deficient, deformed, atomic nucleus 88Ru. The results suggest that the structure of this exotic nuclear system is heavily influenced by the presence of strongly-coupled neutron-proton pairs.

    “Such a structure is fundamentally different from the normal conditions observed in atomic nuclei, where neutrons and protons interact in pairs in separate systems, forming a near-superfluid state,” Cederwall says.

    The results may also suggest alternative explanations for how the production of different chemical elements, and in particular their most neutron-poor isotopes, proceeds in the nucleosynthesis reactions in certain stellar environments such as neutron star-red giant binaries, he says.

    The discovery, which was published February 12 in the journal, Physical Review Letters, results from an experiment at the Grand Accélérateur National d’Ions Lourds (GANIL), France, using the Advanced Gamma Tracking Array (AGATA) [below].

    The researchers used nuclear collisions to create highly unstable atomic nuclei with equal numbers of neutrons and protons. Their structure was studied by using sensitive instruments, including AGATA, detecting the radiation they emit in the form of high-energy photons, neutrons, protons and other particles.

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    The Advanced Gamma Tracking Array (AGATA), which researchers from KTH used to study unstable atomic nuclei generated at the Grand Accélérateur National d’Ions Lourds.

    According to the Standard Model of particle physics describing the elementary particles and their interactions, there are two general types of particles in nature; bosons and fermions, which have integer and half-integer spins, respectively. Examples of fermions are fundamental particles like the electron and the electron neutrino but also composite particles like the proton and the neutron and their fundamental building blocks, the quarks. Examples of bosons are the fundamental force carriers; the photon, the intermediate vector bosons, the gluons and the graviton.

    The properties of a system of particles differ considerably depending on whether it is based on fermions or bosons. As a result of the Pauli principle of quantum mechanics, in a system of fermions (such as an atomic nucleus) only one particle can hold a certain quantum state at a certain point in space and time. For several fermions to appear together, at least one property of each fermion, such as its spin, must be different. At low temperature systems of many fermions can exhibit condensates of paired particles manifested as superfluidity for uncharged particles (for example, the superfluid 3He), and superconductivity for charged particles, such as electrons in a superconductor below the critical temperature. Bosons, on the other hand, can condense individually with an unlimited number of particles in the same state, so-called Bose-Einstein condensates.

    In most atomic nuclei that are close to the line of beta stability and in their ground state, or excited to an energy not too high above it, the basic structure appears to be based on pair-correlated condensates of particles with the same isospin quantum number but with opposite spins. This means that neutrons and protons are paired separately from each other. These isovector pair correlations give rise to properties similar to superfluidity and superconductivity. In deformed nuclei, this structure is for example revealed as discontinuities in the rotational frequency when the rotational excitation energy of the nucleus is increased.

    Such discontinuities, which were discovered already in the early 1970s by KTH Professor emeritus Arne Johnson, have been labeled “backbending”. The backbending frequency is a measure of the energy required to break a neutron or proton pair and therefore also reflects the energy released by the formation of a pair of nucleons in the nucleus. There are long-standing theoretical predictions that systems of neutron-proton pairs can be mixed with, or even replace, the standard isovector pair correlations in exotic atomic nuclei with equal numbers of protons and neutrons. The nuclear structure resulting from the isoscalar component of such pair correlations is different from that found in “ordinary” atomic nuclei close to stability. Among different possible experimental observables, the backbending frequency in deformed nuclei is predicted to increase significantly compared with nuclei with different numbers of neutrons and protons.

    The KTH research group has previously observed evidence of strong neutron-proton correlations in the spherical nuclear nucleus 92Pd, which was published in the journal Nature (B. Cederwall et al., Nature, volume 469, p 68-71 (2011)). The ruthenium isotope 88Ru, with 44 neutrons and 44 protons, is deformed and exhibits a rotation-like structure that has now been observed up to higher spin, or rotational frequency, than previously possible. The new measurement provides a different angle on nuclear pair correlations compared with the previous work. By confirming the theoretical predictions of a shift towards higher backbending frequency it provides complementary evidence for the occurrence of strong isoscalar pair correlations in the heaviest nuclear systems with equal numbers of neutrons and protons.

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

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    An innovative European technical university

    Since its founding in 1827, KTH Royal Institute of Technology in Stockholm has grown to become one of Europe’s leading technical and engineering universities, as well as a key centre of intellectual talent and innovation. We are Sweden’s largest technical research and learning institution and home to students, researchers and faculty from around the world dedicated to advancing knowledge.

     
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