59,563 research outputs found
Designer quantum states of matter created atom-by-atom
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
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
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
Deep NuSTAR observation of X-ray pulsar A 0535+262, performed at a very low
luminosity of erg s, 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 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
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
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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