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  • richardmitnick 5:10 pm on November 13, 2017 Permalink | Reply
    Tags: Elusive Atomic Deformations, , , Matter in Extreme Condition (MEC) experimental station at SLAC’s LCLS, , SLAC X-ray Laser Reveals How Extreme Shocks Deform a Metal’s Atomic Structure, The Tremendous Shock of a Tiny Recoil, , U York, When hit by a powerful shock wave materials can change their shape – a property known as plasticity – yet keep their lattice-like atomic structure   

    From SLAC: “SLAC X-ray Laser Reveals How Extreme Shocks Deform a Metal’s Atomic Structure” 


    SLAC Lab

    November 13, 2017
    Glennda Chui

    1
    This image depicts an experimental setup at SLAC’s Linac Coherent Light Source, where a tantalum sample is shocked by a laser and probed by an X-ray beam. The resulting diffraction patterns, collected by an array of detectors, show the material undergoes a particular type of plastic deformation called twinning. The background illustration shows a lattice structure that has created twins. (Ryan Chen/LLNL)

    SLAC/LCLS

    When hit by a powerful shock wave, materials can change their shape – a property known as plasticity – yet keep their lattice-like atomic structure. Now scientists have used the X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to see, for the first time, how a material’s atomic structure deforms when shocked by pressures nearly as extreme as the ones at the center of the Earth.

    The researchers said this new way of watching plastic deformation as it happens can help study a wide range of phenomena, such as meteor impacts, the effects of bullets and other penetrating projectiles and high-performance ceramics used in armor, as well as how to protect spacecraft from high-speed dust impacts and even how dust clouds form between the stars.

    The experiments took place at the Matter in Extreme Condition (MEC) experimental station at SLAC’s Linac Coherent Light Source (LCLS). They were led by Chris Wehrenberg, a physicist at the DOE’s Lawrence Livermore National Laboratory, and described in a recent paper in Nature.

    “People have been creating these really high-pressure states for decades, but what they didn’t know until MEC came online is exactly how these high pressures change materials – what drives the change and how the material deforms,” said SLAC staff scientist Bob Nagler, a co-author of the report.

    “LCLS is so powerful, with so many X-rays in such a short time, that it can interrogate how the material is changing while it is changing. The material changes in just one-tenth of a billionth of a second, and LCLS can deliver enough X-rays to capture information about those changes in a much shorter time that that.”

    Elusive Atomic Deformations

    The material they studied here was a thin foil made of tantalum, a blue-gray metallic element whose atoms are arranged in cubes. The team used a polycrystalline form of tantalum that is naturally textured so the orientation of these cubes varies little from place to place, making it easier to see certain types of disruptions from the shock.

    When this type of crystalline material is squeezed by a powerful shock, it can deform in two distinct ways: twinning, where small regions develop lattice structures that are the mirror images of the ones in surrounding areas, and slip deformation, where a section of the lattice shifts and the displacement spreads, like a propagating crack.

    But while these two mechanisms are fundamentally important in plasticity, it’s hard to observe them as a shock is happening. Previous research had studied shocked materials after the fact, as the material recovered, which introduced complications and led to conflicting interpretations.

    The Tremendous Shock of a Tiny Recoil

    In this experiment, the scientists shocked a piece of tantalum foil with a pulse from an optical laser. This vaporizes a small piece of the foil into a hot plasma that flies away from the surface. The recoil from this tiny plume creates tremendous pressures in the remaining foil – up to 300 gigapascals, which is three million times the atmospheric pressure around us and comparable to the 350-gigapascal pressure at the center of the Earth, Nagler said.

    While this was happening, researchers probed the state of the metal with X-ray laser pulses. The pulses are extremely short – only 50 femtoseconds, or millionths of a billionth of a second, long – and like a camera with a very fast shutter speed they can record the metal’s response in great detail.

    The X-rays bounce off the metal’s atoms and into a detector, where they create a “diffraction pattern” – a series of bright, concentric rings – that scientists analyze to determine the atomic structure of the sample. X-ray diffraction has been used for decades to discover the structures of materials, biomolecules and other samples and to observe how those structures change, but it’s only recently been used to study plasticity in shock-compressed materials, Wehrenberg said.

    And this time the researchers took the technique one step further: They analyzed not just the diffraction patterns, but also how the scattering signals were distributed inside individual diffraction rings and how their distribution changed over time. This deeper level of analysis revealed changes in the tantalum’s lattice orientation, or texture, taking place in about one-tenth of a billionth of a second. It also showed whether the lattice was undergoing twinning or slip over a wide range of shock pressures – right up to the point where the metal melts. The team discovered that as the pressure increased, the dominant type of deformation changed from twinning to slip deformation.

    Wehrenberg said the results of this study are directly applicable to Lawrence Livermore’s efforts to model both plasticity and tantalum at the molecular level.

    These experiments, he said, “are providing data that the models can be directly compared to for benchmarking or validation. In the future, we plan to coordinate these experimental efforts with related experiments on LLNL’s National Ignition Facility that study plasticity at even higher pressures.”

    In addition to LLNL and SLAC, researchers from the University of Oxford, the DOE’s Los Alamos National Laboratory and the University of York contributed to this study. Funding for the work at SLAC came from the DOE Office of Science. LCLS is a DOE Office of Science User Facility.

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 9:42 am on February 13, 2015 Permalink | Reply
    Tags: , , , , U York   

    From phys.org: “Scientists discover viral ‘Enigma machine'” 

    physdotorg
    phys.org

    Feb 04, 2015

    1
    A code hidden in the arrangement of the genetic information of single-stranded RNA viruses tells the virus how to pack itself within its outer shell of proteins.

    Researchers have cracked a code that governs infections by a major group of viruses including the common cold and polio.

    Until now, scientists had not noticed the code, which had been hidden in plain sight in the sequence of the ribonucleic acid (RNA) that makes up this type of viral genome.

    But a paper published in the Proceedings of the National Academy of Sciences (PNAS) Early Edition by a group from the University of Leeds and University of York unlocks its meaning and demonstrates that jamming the code can disrupt virus assembly. Stopping a virus assembling can stop it functioning and therefore prevent disease.

    Professor Peter Stockley, Professor of Biological Chemistry in the University of Leeds’ Faculty of Biological Sciences, who led the study, said: “If you think of this as molecular warfare, these are the encrypted signals that allow a virus to deploy itself effectively.”

    “Now, for this whole class of viruses, we have found the ‘Enigma machine’—the coding system that was hiding these signals from us. We have shown that not only can we read these messages but we can jam them and stop the virus’ deployment.”

    Single-stranded RNA viruses are the simplest type of virus and were probably one of the earliest to evolve. However, they are still among the most potent and damaging of infectious pathogens.

    Rhinovirus (which causes the common cold) accounts for more infections every year than all other infectious agents put together (about 1 billion cases), while emergent infections such as chikungunya and tick-borne encephalitis are from the same ancient family.

    Other single-stranded RNA viruses include the hepatitis C virus, HIV and the winter vomiting bug norovirus.

    This breakthrough was the result of three stages of research

    •In 2012, researchers at the University of Leeds published the first observations at a single-molecule level of how the core of a single-stranded RNA virus packs itself into its outer shell—a remarkable process because the core must first be correctly folded to fit into the protective viral protein coat. The viruses solve this fiendish problem in milliseconds. The next challenge for researchers was to find out how the viruses did this.
    •University of York mathematicians Dr Eric Dykeman and Professor Reidun Twarock, working with the Leeds group, then devised mathematical algorithms to crack the code governing the process and built computer-based models of the coding system.
    •In this latest study, the two groups have unlocked the code. The group used single-molecule fluorescence spectroscopy to watch the codes being used by the satellite tobacco necrosis virus, a single stranded RNA plant virus.

    Dr Roman Tuma, Reader in Biophysics at the University of Leeds, said: “We have understood for decades that the RNA carries the genetic messages that create viral proteins, but we didn’t know that, hidden within the stream of letters we use to denote the genetic information, is a second code governing virus assembly. It is like finding a secret message within an ordinary news report and then being able to crack the whole coding system behind it.

    “This paper goes further: it also demonstrates that we could design molecules to interfere with the code, making it uninterpretable and effectively stopping the virus in its tracks.”

    Professor Reidun Twarock, of the University of York’s Department of Mathematics, said: “The Enigma machine metaphor is apt. The first observations pointed to the existence of some sort of a coding system, so we set about deciphering the cryptic patterns underpinning it using novel, purpose designed computational approaches. We found multiple dispersed patterns working together in an incredibly intricate mechanism and we were eventually able to unpick those messages. We have now proved that those computer models work in real viral messages.”

    The next step will be to widen the study into animal viruses. The researchers believe that their combination of single-molecule detection capabilities and their computational models offers a novel route for drug discovery.

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) 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, Phys.org’s readership has grown steadily to include 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 6:14 pm on January 26, 2015 Permalink | Reply
    Tags: , , U York   

    From UK Space Agency: “Does human space flight influence the uptake of STEM subjects?” 

    UK Space Agency

    UK Space Agency

    26 January 2015

    UK Space Agency funds new research project.

    Science Education researchers at University of York are to work with leading space scientist and The Sky at Night presenter Dr Maggie Aderin-Pocock MBE to investigate if human spaceflight inspires school students to study science, technology, engineering and maths (STEM) subjects.

    1

    The £348,000 three-year project, funded by the UK Space Agency and the Economic and Social Research Council (ESRC), will focus on British astronaut Tim Peake’s mission to the International Space Station (ISS), to be launched at the end of November 2015.

    Tim Peake is the first British member of the European Space Agency’s astronaut corps, and he will become the first Briton to visit the ISS. As well as delivering invaluable scientific research and cutting edge technology, it is hoped that the programme will boost participation and interest in STEM subjects among school children.

    The research will involve gathering views from pupils and teachers from a sample of 30 primary and 30 secondary schools. In addition, perspectives will be gained from space scientists on areas of the industry that may influence students. Participants will be asked their advice on space science resources for use with school students, leading to the production of an overview of space science resources. The study, starting in January 2015, will also involve the design of a new instrument to assess school students’ attitudes to STEM subjects and to space science.

    Principal Investigator Professor Judith Bennett, from the Department of Education, University of York, said:

    “There is anecdotal evidence to suggest that space and space travel increase the interest of young people in science, technology, engineering and maths (STEM) subjects. We have a golden opportunity to gauge this hypothesis as we prepare to send a British astronaut into space at the end of next year.”

    Dr Maggie Aderin-Pocock added:

    “It is important that we help students to see the correlation between what they are studying in the classroom and what people do outside as scientists. The University of York’s study will help to find out more about what inspires young people to participate in and gain a life-long passion in STEM subjects.”

    Dr David Parker, Chief Executive of the UK Space Agency said:

    “The UK Space Agency is committed to supporting UK space activities. This research will allow us to better understand the ways in which our programmes affect society. The excitement of space gives an excellent context for STEM education, and we’re keen to make sure that the benefits of space – for education, for society, for growth – are properly assessed and understood.”

    Co-Investigators on the project are Dr Jeremy Airey and Dr Lynda Dunlop from the Department of Education, University of York.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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