57,641 research outputs found

    Designer quantum states of matter created atom-by-atom

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    With the advances in high resolution and spin-resolved scanning tunneling microscopy as well as atomic-scale manipulation, it has become possible to create and characterize quantum states of matter bottom-up, atom-by-atom. This is largely based on controlling the particle- or wave-like nature of electrons, as well as the interactions between spins, electrons, and orbitals and their interplay with structure and dimensionality. We review the recent advances in creating artificial electronic and spin lattices that lead to various exotic quantum phases of matter, ranging from topological Dirac dispersion to complex magnetic order. We also project future perspectives in non-equilibrium dynamics, prototype technologies, engineered quantum phase transitions and topology, as well as the evolution of complexity from simplicity in this newly developing field

    Air Force construction automation/robotics

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    The Air Force has several missions which generate unique requirements that are being met through the development of construction robotic technology. One especially important mission will be the conduct of Department of Defense (DOD) space activities. Space operations and other missions place construction/repair equipment operators in dangerous environments and potentially harmful situations. Additionally, force reductions require that human resources be leveraged to the maximum extent possible, and more stringent construction repair requirements push for increased automation. To solve these problems, the U.S. Air Force is undertaking a research and development effort at Tyndall AFB, FL, to develop robotic construction/repair equipment. This development effort involves the following technologies: teleoperation, telerobotics, construction operations (excavation, grading, leveling, tool change), robotic vehicle communications, vehicle navigation, mission/vehicle task control architecture, and associated computing environment. The ultimate goal is the fielding of a robotic repair capability operating at the level of supervised autonomy. This paper will discuss current and planned efforts in space construction/repair, explosive ordnance disposal, hazardous waste cleanup, and fire fighting

    Composition Conditions for Classes of Analytic Functions

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    We prove that for classes of analytic functions tree composition condition and composition condition coincide.Comment: 13 page

    Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262

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    Deep NuSTAR observation of X-ray pulsar A 0535+262, performed at a very low luminosity of ∼7×1034\sim7\times10^{34} erg s−1^{-1}, revealed the presence of two spectral components. We argue that the high-energy component is associated with cyclotron emission from recombination of electrons collisionally excited to the upper Landau levels. The cyclotron line energy of Ecyc=47.7±0.8E_{\rm cyc}=47.7\pm0.8 keV was measured at the luminosity of almost an order of magnitude lower than what was achieved before. The data firmly exclude a positive correlation of the cyclotron energy with the mass accretion rate in this source.Comment: 5 pages, 3 figures, accepted by MNRAS Letter

    Archimedes' law and its corrections for an active particle in a granular sea

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    We study the origin of buoyancy forces acting on a larger particle moving in a granular medium subject to horizontal shaking and its corrections before fluidization. In the fluid limit Archimedes' law is verified; before the limit memory effects counteract buoyancy, as also found experimentally. The origin of the friction is an excluded volume effect between active particles, which we study more exactly for a random walker in a random environment. The same excluded volume effect is also responsible for the mutual attraction between bodies moving in the granular medium. Our theoretical modeling proceeds via an asymmetric exclusion process, i.e., via a dissipative lattice gas dynamics simulating the position degrees of freedom of a low density granular sea.Comment: 22 pages,5 figure

    Measuring 10-1000 GeV Cosmic Ray Electrons with GLAST/LAT

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    We present here the capabilities of the GLAST Large Area Telescope to detect cosmic ray high-energy (HE) electrons in the energy range from 10 GeV to 1 TeV. We also discuss the science topics that can be investigated with HE electron data and quantify the results with LAT instrument simulations. The science topics include CR propagation, calibration of the IC gamma-ray model, testing hypotheses regarding the origin of HE energy cosmic-ray electrons, searching for any signature of Kaluza Klein Dark Matter annihilation, and measuring the HE electron anisotropy. We expect to detect ~ 107 electrons above 20 GeV per year of LAT operation.Comment: 5 pages, 5 figures, 1 tabl
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