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  • richardmitnick 7:41 am on April 18, 2014 Permalink | Reply
    Tags: , , , , , NASA SDO   

    From NASA: “Bright Points in Sun’s Atmosphere Mark Patterns Deep In Its Interior” 

    NASA Goddard Banner

    April 17, 2014
    Karen C. Fox
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    New research that uses data from NASA’s Solar Dynamics Observatory, or SDO, to track bright points in the solar atmosphere and magnetic signatures on the sun’s surface offers a way to probe the star’s depths faster than ever before. The technique opens the door for near real-time mapping of the sun’s roiling interior – movement that affects a wide range of events on the sun from its 22-year sunspot cycle to its frequent bursts of X-ray light called solar flares.

    sun
    Brightpoints in the sun’s atmosphere, left, correspond to magnetic parcels on the sun’s surface, seen in the processed data on the right. Green spots show smaller parcels, red and yellow much bigger ones. Images based on data from NASA’s SDO captured at 8 p.m. EDT on May 15, 2010. Image Credit: NASA/SDO

    “There are all sorts of things lurking below the surface,” said Scott McIntosh, first author of a paper on these results in the April 1, 2014, issue of The Astrophysical Journal Letters. “And we’ve found a marker for this deep rooted activity. This is kind of a gateway to the interior, and we don’t need months of data to get there.”

    One of the most common ways to probe the sun’s interior is through a technique called helioseismology in which scientists track the time it takes for waves – not unlike seismic waves on Earth — to travel from one side of the sun to the other. From helioseismology solar scientists have some sense of what’s happening inside the sun, which they believe to be made up of granules and super-granules of moving solar material. The material is constantly overturning like boiling water in a pot, but on a much grander scale: A granule is approximately the distance from Los Angeles to New York City; a super-granule is about twice the diameter of Earth.

    sdo
    SDO contains three instruments; Helioseismic and Magnetic Imager (HMI), Atmospheric Imaging Assembly (AIA), and Extreme Ultraviolet Variablity Experiment(EVE) — for observations leading to a more complete understanding of the solar dynamics that drive variability in the Earth’s environment.
    Image Credit: NASA/Goddard Space Flight Center

    NASA EVE Extreme Ultraviolet Variablity Experiment
    EVE

    NASA Helio Magnetic Imager
    Helioseismic and Magnetic Imager (HMI)

    Instead of tracking seismic waves, the new research probes the solar interior using the Helioseismic Magnetic Imager on NASA’s Solar Dynamics Observatory, or SDO, which can map the dynamic magnetic fields that thread through and around the sun. Since 2010, McIntosh has tracked the size of different magnetically-balanced areas on the sun, that is, areas where there are an even number of magnetic fields pointing down in toward the sun as pointing out. Think of it like looking down at a city from above with a technology that observed people, but not walls, and recording areas that have an even number of men and women. Even without seeing the buildings, you’d naturally get a sense for the size of rooms, houses, buildings, and whole city blocks – the structures in which people naturally group.

    The team found that the magnetic parcels they mapped corresponded to the size of granules and supergranules, but they also spotted areas much larger than those previously noted — about the diameter of Jupiter. It’s as if when searching for those pairs of men and women, one suddenly realized that the city itself and the sprawling suburbs was another scale worth paying attention to. The scientists believe these areas correlate to even larger cells of flowing material inside the sun.

    The researchers also looked at these regions in SDO imagery of the sun’s atmosphere, the corona, using the Atmospheric Imaging Assembly instrument. They noticed that ubiquitous spots of extreme ultraviolet and X-ray light, known as brightpoints, prefer to hover around the vertices of these large areas, dubbed g-nodes.

    NASA Atmospheric Imaging Assembly Instrument
    Atmospheric Imaging Assembly instrument

    “Imagine a bunch of helium balloons with weights on them,” said Robert Leamon, co-author on the paper at Montana State University in Bozeman and NASA Headquarters in Washington. “The weights get carried along by the motions at the bottom. We can track the motion of the helium balloons floating up high and that tells us what’s happening down below.”

    By opening up a way to peer inside the sun quickly, these techniques could provide a straightforward way to map the sun’s interior and perhaps even improve our ability to forecast changes in magnetic fields that can lead to solar eruptions.

    SDO is the first mission in NASA’s Living with a Star program to explore aspects of the connected sun-Earth system that directly affect life and society. For more information about SDO and its mission, visit:

    http://www.nasa.gov/sdo

    See the full article here.

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA


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  • richardmitnick 5:55 pm on April 17, 2014 Permalink | Reply
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    Before you watch Particle Fever 

    I have put this video up before, but there is no time like the present. Released to theaters is Particle Fever, the story of the hunt for the Higgs boson. This movie will go to DVD pertty quickly, maybe to Netflix streaming, maybe to YouTube. Before you see it, be sure to see The Big Bang Machine with Dr. Sir Brian Cox, OBE

    You should also see The Atom Smashers, about the hunt at Fermilab. However, I cannot find a copy which WordPress will allow

     
  • richardmitnick 2:35 pm on April 17, 2014 Permalink | Reply
    Tags: , Cornell University, Heat Studies,   

    From Cornell: “Tiny tool measures heat at the nanoscale” 

    Cornell Bloc

    Cornell University

    Feb. 26, 2014
    Story Contacts
    Cornell Chronicle

    Anne Ju

    607- 255-9735

    amj8@cornell.edu
    Media Contact

    Syl Kacapyr

    607-255-7701

    vpk6@cornell.edu

    How heat flows at the nanoscale can be very different than at larger scales. Understanding how surfaces affect the transport of the fundamental units of heat, called phonons, could impact everything from thermoelectric materials to microelectronic cooling devices.

    heat
    Design of the spectrometer to probe phonon transmission through silicon nanosheet arrays.

    Cornell researchers have developed a new way to precisely measure the extremely subtle movement of heat in nanostructures. Recently published online in Nano Letters and highlighted in Physics Today, the study features the researchers’ phonon spectrometer, whose measurements are 10 times sharper than standard methods. This boosted sensitivity has uncovered never-before-seen effects of phonon transport.

    The scientists used the new instrument to directly measure the surface scattering of phonons in silicon nanosheets. They made nanosheets only 100 nanometers wide, which is 1,000 times thinner than a human hair, using special tools at the Cornell NanoScale Science and Technology Facility (CNF) – a key component in the success of their project, said senior author Richard Robinson, assistant professor of materials science and engineering.

    The scattering of phonons on surfaces influences how well heat can flow through a structure. Similar to how light bounces off a lake, if a surface is smooth, phonons reflect off it, but when surfaces are rough phonons scatter in random directions, called diffuse scattering.

    “If waters are calm you see a reflection, but in choppy waters you see diffuse scattering,” said Jared Hertzberg, the paper’s first author, a former postdoctoral associate. “This diffuse scattering slows down the transmission of phonons. This decrease in phonon transport becomes particularly important in nanoscale materials where surfaces play a larger role in the heat flow.”

    Precise experimental techniques for probing phonon surface interactions – which depend on surface roughness and phonon wavelength – are lacking, Robinson said.

    “The fundamental science of heat flow is not as well understood in nanostructures as it is in bulk materials,” Robinson said. “If we can precisely understand how this process works, then we can begin to engineer heat flow at the nanoscale, which can lead to more efficient alternate energy applications, such as thermoelectrics, or advanced phononic heat-logic circuits. We’ve just scratched the surface, so to speak, of how heat behaves at the nanoscale. There’s so much more to learn, and so much more that can be done with these phonons now that we know how to spectroscopically measure them.”

    The researchers fabricated silicon nanosheets and measured phonon transmission rates with their spectrometer, and gauged the nanosheets’ surface roughness using atomic force microscopy. By comparing transmission rates with those predicted by theory, they could assess the validity of a 50-year-old theory called the Casimir-Ziman theory, which determines the probability of phonon scattering based on surface roughness and the phonon’s wavelength. While a perfectly smooth surface will reflect phonons perfectly, and a perfectly rough surface randomly scatters phonons in all directions, real surfaces fall somewhere in between.

    Yet the scientists found, in fact, that the total diffusive scattering occurred at much lower frequencies than had been previously predicted by the Casmimir-Ziman theory.

    Since diffusive scattering effectively lowers phonon transmission, high phonon scattering rates have implications for thermal conductivity in nanostructures: The actual thermal conductance will be much lower than predicted using the standard Casimir-Ziman theory.

    The paper, Direct Measurements of Surface Scattering in Si Nanosheets using a Microscale Phonon Spectrometer: Implications for Casimir-Limit Predicted by Ziman Theory, also co-authored by graduate students Mahmut Aksit and Obafemi Otelaja and Derek Stewart, a CNF senior research associate, was supported by the National Science Foundation and the Department of Energy, Office of Basic Energy Science.

    See the full article here.

    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.


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  • richardmitnick 1:53 pm on April 17, 2014 Permalink | Reply
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    From Keck: “First Potentially Habitable Earth-Sized Planet Confirmed by Keck and Gemini Observatories” 

    Keck Observatory

    Keck Observatory

    Keck Observatory

    April 17, 2014
    Media Contact:
    Steve Jefferson
    Communications Officer
    W. M. Keck Observatory
    sjefferson@keck.hawaii.edu
    (808) 881-3827 (Desk)
    (808) 345-1319 (Cell)

    Science Contacts:
    Elisa Quintana
    SETI Institute
    elisa.quintana@nasa.gov
    650-604-2467 (Desk)
    415-730-1724 (Cell)

    Steve Howell
    Project Scientist, Kepler Mission
    NASA Ames Research Center, Moffett Field, CA
    steve.b.howell@nasa.gov
    (650) 604-4238 (Desk)(520) 461-6925 (Cell)

    The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by the Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes.

    NOAO Gemini North
    NOAO Gemini North Telescope

    NASA Kepler Telescope
    NASA/Kepler

    “What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form,” says Elisa Quintana of the SETI Institute and NASA Ames Research Center who led the paper published in the current issue of the journal Science. The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.

    Steve Howell, Kepler’s Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot an exoplanet of this size and proximity to its host star. “However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option.”

    With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected. To do this, the team obtained extremely high spatial resolution observations from the eight-meter Gemini North telescope on Mauna Kea in Hawai`i using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-meter Keck II telescope, Gemini’s neighbor on Mauna Kea. Together, these data allowed the team to rule out sources close enough to the star’s line-of-sight to confound the Kepler evidence, and conclude that Kepler’s detected signal has to be from a small planet transiting its host star.

    “The Keck and Gemini data are two key pieces of this puzzle,” says Quintana. “Without these complementary observations we wouldn’t have been able to confirm this Earth-sized planet.”

    The Gemini “speckle” data directly imaged the system to within about 400 million miles (about 4 AU, approximately equal to the orbit of Jupiter in our solar system) of the host star and confirmed that there were no other stellar size objects orbiting within this radius from the star. Augmenting this, the Keck AO observations probed a larger region around the star but to fainter limits. According to Quintana, “These Earth-sized planets are extremely hard to detect and confirm, and now that we’ve found one, we want to search for more. Gemini and Keck will no doubt play a large role in these endeavors.”

    The planet designated Kepler-186f is earth-sized and orbits within the star’s habitable zone. The host star, Kepler-186, is an M1-type dwarf star relatively close to our solar system, at about 500 light years and is in the constellation of Cygnus. The star is very dim, being over half a million times fainter than the faintest stars we can see with the naked eye. Five small planets have been found orbiting this star, four of which are in very short-period orbits and are very hot.

    The Kepler evidence for this planetary system comes from the detection of planetary transits. These transits can be thought of as tiny eclipses of the host star by a planet (or planets) as seen from the Earth. When such planets block part of the star’s light, its total brightness diminishes. Kepler detects that as a variation in the star’s total light output and evidence for planets. So far more than 2,500 possible planets have been detected by this technique with Kepler.

    The Gemini data utilized the Differential Speckle Survey Instrument (DSSI) on the Gemini North telescope. DSSI is a visiting instrument developed by a team led by Howell who adds, “DSSI on Gemini Rocks! With this combination, we can probe down into this star system to a distance of about 4 times that between the Earth and the Sun. It’s simply remarkable that we can look inside other solar systems.” DSSI works on a principle that utilizes multiple short exposures of an object to capture and remove the noise introduced by atmospheric turbulence producing images with extreme detail.

    “The observations from Keck and Gemini, combined with other data and numerical calculations, allowed us to be 99.98% confident that Kepler-186f is real,” says Thomas Barclay, a Kepler scientist and also a co-author on the paper. “Kepler started this story, and Gemini and Keck helped close it,” adds Barclay.

    Observations with the W.M. Keck Observatory used the Natural Guide Star Adaptive Optics system with the NIRC2 camera on the Keck II telescope. NIRC2 (the Near-Infrared Camera, second generation) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

    See the full article here.

    [I was unable to find graphic of Differential Speckle Survey Instrument (DSSI), or NIRC2 (the Near-Infrared Camera, second generation)

    Mission
    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
    Keck UCal

    Keck NASA

    Keck Caltech


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  • richardmitnick 1:23 pm on April 17, 2014 Permalink | Reply
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    From Duke Physics: “Another Outstanding Fermion Sign Problem Solved” 

    Duke Bloc
    Duke Crest

    Duke University

    Second year graduate student Emilie Huffman and Prof. Shailesh Chandrasekharan have recently solved an outstanding sign problem that had remained unsolved for almost 30 yrs.

    Sign problems arise when one tries to design Monte Carlo methods to compute quantum amplitudes in quantum many body physics. Although [Richard] Feynman taught us how one can compute such amplitudes by summing over an exponentially large number of classical paths, to perform such a sum exactly is almost always impossible in realistic physical systems. Most analytic calculations involve a “perturbative” expansion in which one argues that only a few diagrams contribute. Unfortunately, one needs to sum an incredibly large number of diagrams before an accurate answer can be found in many interesting strongly correlated quantum systems.

    In thermal equilibrium, the exponential sum can sometimes be viewed as a classical statistical mechanics problem and Monte Carlo methods can be used to perform the sum. However, the statistical Boltzmann weight can be negative or even complex due to quantum mechanics and in such cases the probability distribution to sample the classical configurations is unclear. A bad choice can lead to wrong results since one is sampling a non-representative set of configurations. This is the so called sign problem, which has hindered progress in our understanding of many strongly interacting fermionic quantum field theories.

    Prof. Chandrasekharan’s research focuses on solving sign problems. His research has shown that some sign problems are solvable if one is clever in grouping fermion world lines into what he calls fermion bags. If the fermions interact with bosons, the solution may also require the use of world line variables to represent bosons. Both relativistic and non-relativistic problems are solvable using this approach. The recent work is an extension of these ideas to a different class of problems.

    The new progress is based on an interesting compact formula in quantum many body physics, derived by Huffman. This formula seems to have remained unappreciated by the quantum Monte Carlo community. When combined with the fermion bag idea, the formula solves the sign problem in a class of lattice field theories involving massless fermions. Since electrons hopping on a honeycomb lattice produce such fermions at low energies, the progress will help us study quantum critical behavior in graphene inspired lattice models.

    The breakthrough achieved in the current work overcomes another important barrier. Traditionally, many sign problems are solvable when there is pairing between an even number of species of fermions. The recent work of Huffman and Chandrasekharan show that pairing can occur between particles and holes. This pairing is hidden in traditional formulations with an odd number of fermion species, but the fermion bag approach helps to uncover it. Hence we can now solve some models with an odd number of fermion species.

    See the full article here.

    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”


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  • richardmitnick 12:41 pm on April 17, 2014 Permalink | Reply
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    From LC Newsline: “The ILC design evolves” 

    Linear Collider Collaboration header

    17 April 2014
    Mike Harrison

    The ILC baseline design as described in the Technical Design Report and its associated cost estimate was finalised in 2012. Since that time the design has been relatively static while the global high-energy physics community absorbed and responded to this information. During the past 12 months, significant progress in Japan has resulted in the choice of a preferred site together with a proposal to consider implementing the ILC project in a series of discrete energy stages rather than an initial 500- gigaelectronvolt (GeV) centre-of-mass energy. Thus the time is fitting to evolve the TDR baseline in response to these new eventualities. An initial step in this direction was taken recently in a three-day meeting at the University of Tokyo, which involved a joint team from the conventional facilities and accelerator design and integration groups.

    LC Linnear Collider
    Projected design of the Linear Collider

    The goals of the meeting were described thus: “This meeting will examine the scope of the pre-project CFS work, the schedule, and necessary resources. The detector hall concept at the proposed site, and the impact of energy phasing will also be addressed. The pre-project CFS timeline will likely drive many aspects of the accelerator design work in the next few years thus it is important to understand these constraints. In order to derive a site dependent ILC design and address long lead-time CFS activities then we need to assess what design information needs to be available to the CFS group and when. The ILC technical design in the TDR relied on a generic site description which is inadequate to proceed much further in the site specific design.”

    During the LCWS13 meeting last November, it became apparent that in order to be consistent with a construction project which can start in 2018, a multi-year pre-construction programme centred around the conventional facilities work in Japan needed to start soon. In turn, this programme would need timely input from the site-specific accelerator design. Although three days is insufficient time to finalise anything, a consensus was achieved on many items which provides the necessary framework for how to proceed during the next few years. Next month’s Americas Workshop on Linear Collider to be held at Fermilab will build on this work.

    Conventional facilities preparation for a construction project covers not only the detailed design of the tunnel, associated enclosures and the interaction region/damping ring complex but also such green-field related topics as land acquisition, environmental impact, geological and topographical studies. The schedule for this work depends to a certain degree on the available resources but it will require a minimum of several years. The meeting discussed the work scope and how best to proceed but there was little dissent from the conclusion that we need to start soon to remain consistent with a construction start in 2018 or thereabouts. This topic will provide the basis of a funding request for the long lead-time elements.

    Intermediate energy operation at values less than 500 GeV is based on a partial installation of the main linac and has ramifications on many aspects of the project execution including such programme aspects as the cryomodule production rate, funding profiles and minor design changes to best accommodate lower energies. The exact details depend on the desired energy points and the associated integrated luminosity at these values. These specifications are currently under study by the parameters working group, but one critical conclusion from the meeting was the recognition that all the major convention construction needs to be completed as part of the first phase of any project. This result will now be used as input for subsequent planning.

    A partial linac can be implemented in several ways. The basic variants consist of “missing” cryomodules at the upstream end, the downstream end or interspersed along the length. All of these approaches require the full injector complex, the complete beam delivery system and transport sections in the main tunnel. Emittance growth minimisation requires an initial accelerating section of at least 50 Ge,V which argues against a missing linac on the upstream end. Most discussions involved a solution which has the location of the accelerating sections determined by the baseline cryogenic infrastructure which satisfies the beam dynamics requirements and allows for some operational flexibility. This approach will be used for the future energy scaling discussions.

    The preferred site has re-opened debate on the possibility of a vertical access shaft (or shafts) for the detector hall as opposed to, or in addition to, the baseline design which involved a horizontal access tunnel. This is complicated issue involving the detector construction technique, personnel safety, and exact location of interaction point as well as old favourites such as cost and schedule. More work is necessary before an optimal decision can be made but in order to start to restrict the potential phase space of solutions we decided to use the TDR baseline (horizontal) and the so-called Hybrid A (CMS
    -like) as the models for further study. The goal in this area is to converge on a solution by the end of this calendar year.

    Several other topics such as the role of the central campus, safety issues arising from the tunnel design, and short-term activities were also part of the meeting. The looming LC NewsLine deadline suggests that these items be left for a later date – the talks are posted on the aforementioned web site for those of you who can’t bear to wait. The upcoming Fermilab workshop will provide the next forum for further face-to-face dialogue.

    On behalf of the meeting participants I would like to thank the University of Tokyo and the support staff for arranging the meeting, the facilities, the excellent weather, the cherry blossom in bloom, and a damn good meal which appeared to materialise in a mysterious and spontaneous fashion courtesy of the physics department.

    See the full article here.

    The Linear Collider Collaboration is an organisation that brings the two most likely candidates, the Compact Linear Collider Study (CLIC) and the International Liner Collider (ILC), together under one roof. Headed by former LHC Project Manager Lyn Evans, it strives to coordinate the research and development work that is being done for accelerators and detectors around the world and to take the project linear collider to the next step: a decision that it will be built, and where.

    Some 2000 scientists – particle physicists, accelerator physicists, engineers – are involved in the ILC or in CLIC, and often in both projects. They work on state-of-the-art detector technologies, new acceleration techniques, the civil engineering aspect of building a straight tunnel of at least 30 kilometres in length, a reliable cost estimate and many more aspects that projects of this scale require. The Linear Collider Collaboration ensures that synergies between the two friendly competitors are used to the maximum.

    Linear Collider Colaboration Banner


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  • richardmitnick 12:20 pm on April 17, 2014 Permalink | Reply
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    From Fermilab- “Frontier Science Result: DZero Most precise single measurement of the top quark mass” 


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

    Thursday, April 17, 2014
    Mark Williams

    Just four weeks ago in this column we featured the world combination of top quark mass measurements, which used as ingredients the set of best measurements from both Tevatron and LHC experiments available in February 2014. Far from indicating that we’ve reached the end of top quark analyses at DZero and CDF, this represents just a single snapshot of a continually developing program. As a perfect illustration, the DZero experiment this week released a new measurement of the top quark mass in the lepton-plus-jets channel, which is the most precise single measurement ever made and which is actually competitive with the world average itself.

    Fermilab Tevatron
    Tevatron at Fermilab

    CERN LHC New
    LHC at CERN

    The lepton-plus-jets channel is probably familiar to regular readers. The analysis reconstructs top quark-antiquark pairs in their decays into four quark jets, a charged lepton (an electron or muon) and missing momentum consistent with an undetected neutrino. This signature is distinctive enough to be distinguished from most backgrounds, but it also provides a sufficiently large sample with which to reach the required statistical precision on the top mass. Effectively, once the sample composition has been determined, the mass of the top (or antitop) quark can be extracted by appropriately adding the energies of the six decay products, which of course is much easier said than done.

    Reaching the desired precision requires pushing our understanding of the DZero detector to its limit. In particular, with four quark jets in the final state, it is crucial to understand the correspondence between the measured signals and the true jet energies. This analysis uses some advanced techniques to help achieve this goal. Since all the top quark decays involve an intermediate W boson, we can use the existing precise measurements of the W boson mass to constrain the properties of the final jets, lepton and neutrino. Doing this provides enough additional information to make an independent jet energy calibration in situ, rather than relying on the existing calibrations, which relate the measured and true jet energies.

    top
    The DZero experiment this week released the single most precise measurement of the top quark mass ever made. This plot shows the favored region for the top mass (the x-axis) and an important experimental parameter kJES (the y-axis) which is extracted simultaneously to improve the overall precision.

    Using this method, the final analysis reports a two-dimensional measurement of the top quark mass and a jet energy scale factor kJES, as shown in the figure above. This method allows every last drop of information to be squeezed from the data and significantly reduces the dominant source of systematic uncertainty on the final measurement.

    The upshot of this two-dimensional approach is a measured top quark mass of 174.98 GeV, with a total uncertainty of just 0.76 GeV, or less than half a percent. For reference, the world combination of the top mass, which does not include this new measurement, also has an uncertainty of 0.76 GeV. It is an impressive achievement that this single measurement can achieve the same precision as the recent worldwide combination and gives a taste of things to come. The era of high-precision top quark measurements is well and truly here.

    See the full article here.

    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.


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  • richardmitnick 11:56 am on April 17, 2014 Permalink | Reply
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    From NASA/ESA Hubble: “A cross-section of the Universe” 

    NASA Hubble Telescope

    17 April 2014
    Georgia Bladon
    Hubble/ESA
    Garching, Germany
    Tel: +49-89-3200-6855
    Email: gbladon@partner.eso.org

    An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range from cosmic near neighbours to objects seen in the early years of the Universe. The 14-hour exposure shows objects around a billion times fainter than can be seen with the naked eye.

    uni

    This new Hubble image showcases a remarkable variety of objects at different distances from us, extending back over halfway to the edge of the observable Universe. The galaxies in this image mostly lie about five billion light-years from Earth but the field also contains other objects, both significantly closer and far more distant.

    Studies of this region of the sky have shown that many of the objects that appear to lie close together may actually be billions of light-years apart. This is because several groups of galaxies lie along our line of sight, creating something of an optical illusion. Hubble’s cross-section of the Universe is completed by distorted images of galaxies in the very distant background.

    These objects are sometimes distorted due to a process called gravitational lensing, an extremely valuable technique in astronomy for studying very distant objects. This lensing is caused by the bending of the space-time continuum by massive galaxies lying close to our line of sight to distant objects.

    One of the lens systems visible here is called CLASS B1608+656, which appears as a small loop in the centre of the image. It features two foreground galaxies distorting and amplifying the light of a distant quasar the known as QSO-160913+653228. The light from this bright disc of matter, which is currently falling into a black hole, has taken nine billion years to reach us — two thirds of the age of the Universe.

    As well as CLASS B1608+656, astronomers have identified two other gravitational lenses within this image. Two galaxies, dubbed Fred and Ginger by the researchers who studied them, contain enough mass to visibly distort the light from objects behind them. Fred, also known more prosaically as [FMK2006] ACS J160919+6532, lies near the lens galaxies in CLASS B1608+656, while Ginger ([FMK2006] ACS J160910+6532) is markedly closer to us. Despite their different distances from us, both can be seen near to CLASS B1608+656 in the central region of this Hubble image.

    To capture distant and dim objects like these, Hubble required a long exposure. The image is made up of visible and infrared observations with a total exposure time of 14 hours.

    See the full article, with note, here.

    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 8:23 am on April 17, 2014 Permalink | Reply
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    From Caltech: “Made-to-Order Materials” 

    Caltech Logo
    Caltech

    09/05/2013
    Kimm Fesenmaier

    Caltech engineers focus on the nano to create strong, lightweight materials

    The lightweight skeletons of organisms such as sea sponges display a strength that far exceeds that of manmade products constructed from similar materials. Scientists have long suspected that the difference has to do with the hierarchical architecture of the biological materials—the way the silica-based skeletons are built up from different structural elements, some of which are measured on the scale of billionths of meters, or nanometers. Now engineers at the California Institute of Technology (Caltech) have mimicked such a structure by creating nanostructured, hollow ceramic scaffolds, and have found that the small building blocks, or unit cells, do indeed display remarkable strength and resistance to failure despite being more than 85 percent air.

    mat
    Three-dimensional, hollow titanium nitride nanotruss with tessellated octahedral geometry. Each unit cell is on the order of 10 microns, each strut length within the unit cell is about three to five microns, the diameter of each strut is less than one micron, and the thickness of titanium nitride is roughly 75 nanometers.Credit: Dongchan Jang and Lucas Meza

    “Inspired, in part, by hard biological materials and by earlier work by Toby Schaedler and a team from HRL Laboratories, Caltech, and UC Irvine on the fabrication of extremely lightweight microtrusses, we designed architectures with building blocks that are less than five microns long, meaning that they are not resolvable by the human eye,” says Julia R. Greer, professor of materials science and mechanics at Caltech. “Constructing these architectures out of materials with nanometer dimensions has enabled us to decouple the materials’ strength from their density and to fabricate so-called structural metamaterials which are very stiff yet extremely lightweight.

    “At the nanometer scale, solids have been shown to exhibit mechanical properties that differ substantially from those displayed by the same materials at larger scales. For example, Greer’s group has shown previously that at the nanoscale, some metals are about 50 times stronger than usual, and some amorphous materials become ductile rather than brittle. “We are capitalizing on these size effects and using them to make real, three-dimensional structures,” Greer says.

    In an advance online publication of the journal Nature Materials, Greer and her students describe how the new structures were made and responded to applied forces.

    The largest structure the team has fabricated thus far using the new method is a one-millimeter cube. Compression tests on the the entire structure indicate that not only the individual unit cells but also the complete architecture can be endowed with unusually high strength, depending on the material, which suggests that the general fabrication technique the researchers developed could be used to produce lightweight, mechanically robust small-scale components such as batteries, interfaces, catalysts, and implantable biomedical devices.

    Greer says the work could fundamentally shift the way people think about the creation of materials. “With this approach, we can really start thinking about designing materials backward,” she says. “I can start with a property and say that I want something that has this strength or this thermal conductivity, for example. Then I can design the optimal architecture with the optimal material at the relevant size and end up with the material I wanted.”

    The team first digitally designed a lattice structure featuring repeating octahedral unit cells—a design that mimics the type of periodic lattice structure seen in diatoms. Next, the researchers used a technique called two-photon lithography to turn that design into a three-dimensional polymer lattice. Then they uniformly coated that polymer lattice with thin layers of the ceramic material titanium nitride (TiN) and removed the polymer core, leaving a ceramic nanolattice. The lattice is constructed of hollow struts with walls no thicker than 75 nanometers.

    “We are now able to design exactly the structure that we want to replicate and then process it in such a way that it’s made out of almost any material class we’d like—for example, metals, ceramics, or semiconductors—at the right dimensions,” Greer says.

    In a second paper, scheduled for publication in the journal Advanced Engineering Materials, Greer’s group demonstrates that similar nanostructured lattices could be made from gold rather than a ceramic. “Basically, once you’ve created the scaffold, you can use whatever technique will allow you to deposit a uniform layer of material on top of it,” Greer says.

    In the Nature Materials work, the team tested the individual octahedral cells of the final ceramic lattice and found that they had an unusually high tensile strength. Despite being repeatedly subjected to stress, the lattice cells did not break, whereas a much larger, solid piece of TiN would break at much lower stresses. Typical ceramics fail because of flaws—the imperfections, such as holes and voids, that they contain. “We believe the greater strength of these nanostructured materials comes from the fact that when samples become sufficiently small, their potential flaws also become very small, and the probability of finding a weak flaw within them becomes very low,” Greer says. So although structural mechanics would predict that a cellular structure made of TiN would be weak because it has very thin walls, she says, “we can effectively trick this law by reducing the thickness or the size of the material and by tuning its microstructure, or atomic configurations.”

    Additional coauthors on the Nature Materials paper, Fabrication and Deformation of Three-Dimensional Hollow Ceramic Nanostructures, are Dongchan Jang, who recently completed a postdoctoral fellowship in Greer’s lab, Caltech graduate student Lucas Meza, and Frank Greer, formerly of the Jet Propulsion Laboratory (JPL). The work was supported by funding from the Dow-Resnick Innovation Fund at Caltech, DARPA’s Materials with Controlled Microstructural Architecture program, and the Army Research Office through the Institute for Collaborative Biotechnologies at Caltech. Some of the work was carried out at JPL under a contract with NASA, and the Kavli Nanoscience Institute at Caltech provided support and infrastructure.

    The lead author on the Advanced Engineering Materials paper, Design and Fabrication of Hollow Rigid Nanolattices Via Two-Photon Lithography, is Caltech graduate student Lauren Montemayor. Meza is a coauthor. In addition to support from the Dow-Resnick Innovation Fund, this work received funding from an NSF Graduate Research Fellowship.

    See the full article here.

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”


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  • richardmitnick 10:22 pm on April 16, 2014 Permalink | Reply
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    From Don Lincoln at Fermilab: Dark Energy, a New Video 


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

    Fermilab Don Lincoln
    Dr. Don Lincoln

    Dr. Don Lincoln brings us a new video on Dark Energy. I hope that you enjoy the video.

    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.


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