7,335 research outputs found

    Extensometer automatically measures elongation in elastomers

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    Extensometer, with a calibrated shaft, measures the elongation of elastomers and automatically records this distance on a chart. It is adaptable to almost any tensile testing machine and is fabricated at a relatively low cost

    Development of a bedrest muscle stress apparatus

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    In attempting further to define the deleterious effects of spaceflight on the human body, measurement systems and techniques were devised to determine the loss of skeletal muscle strength and tone as a result of spaceflight exposure. In order to determine how the muscle degradation process progresses with time during nonuse, a system for measuring muscle stress during bedrest was developed. The Bedrest Muscle Stress Apparatus is configured to slip snugly over the foot board of a standard hospital bed. Data collected with this device correlated well with pre- and post-bedrest data collected with the original skeletal muscle stress apparatus

    Detecting Axion-Like Particles With Gamma Ray Telescopes

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    We propose that axion-like particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the "Hillas criterion", such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground based gamma ray telescopes in the TeV range.Comment: corrected typos, one plot modified, material rearranged for clarification. Conclusions unchanged. Matches version published in Phys. Rev. Let

    Low-temperature elastic behavior of fourteen compounded elastomers

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    Low temperature elastic properties of elastomers - modulus of rigidity, brittle temperature, and youngs modulus

    Probing Exotic Physics With Cosmic Neutrinos

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    Traditionally, collider experiments have been the primary tool used in searching for particle physics beyond the Standard Model. In this talk, I will discuss alternative approaches for exploring exotic physics scenarios using high energy and ultra-high energy cosmic neutrinos. Such neutrinos can be used to study interactions at energies higher, and over baselines longer, than those accessible to colliders. In this way, neutrino astronomy can provide a window into fundamental physics which is highly complementary to collider techniques. I will discuss the role of neutrino astronomy in fundamental physics, considering the use of such techniques in studying several specific scenarios including low scale gravity models, Standard Model electroweak instanton induced interactions, decaying neutrinos and quantum decoherence.Comment: 11 pages, 6 figures; For the proceedings of From Colliders To Cosmic Rays, Prague, Czech Republic, September 7-13, 200

    Primordial Black Holes, Hawking Radiation and the Early Universe

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    The 511 keV gamma emission from the galactic core may originate from a high concentration (∼1022\sim 10^{22}) of primordial black holes (PBHs) in the core each of whose Hawking radiation includes ∼1021\sim 10^{21} positrons per second. The PBHs we consider are taken as near the lightest with longevity greater than the age of the universe (mass ∼1012\sim 10^{12} kg; Schwarzschild radius ∼1\sim 1 fm). These PBHs contribute only a small fraction of cold dark matter, ΩPBH∼10−8\Omega_{PBH} \sim 10^{-8}. This speculative hypothesis, if confirmed implies the simultaneous discovery of Hawking radiation and an early universe phase transition.Comment: 4 Page

    The Indirect Search for Dark Matter with IceCube

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    We revisit the prospects for IceCube and similar kilometer-scale telescopes to detect neutrinos produced by the annihilation of weakly interacting massive dark matter particles (WIMPs) in the Sun. We emphasize that the astrophysics of the problem is understood; models can be observed or, alternatively, ruled out. In searching for a WIMP with spin-independent interactions with ordinary matter, IceCube is only competitive with direct detection experiments if the WIMP mass is sufficiently large. For spin-dependent interactions IceCube already has improved the best limits on spin-dependent WIMP cross sections by two orders of magnitude. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while being within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes have the opportunity to play an important as well as complementary role in the search for particle dark matter.Comment: 17 pages, 10 figures, published in the New Journal of Physics 11 105019 http://www.iop.org/EJ/abstract/1367-2630/11/10/105019, new version submitted to correct Abstract in origina
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