1,688 research outputs found

    Mapping X-ray heliometer for Orbiting Solar Observatory-8

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    An instrument combining mechanical collimators and proportional counter detectors was designed to record solar X-rays with energies of 2-30 keV with good temperal, spectral, and spatial resolution. The overall operation of the instrument is described to the degree needed by personnel who interact with the experimenter during SC/experiment interfacing, experiment testing, observatory integration and testing, and pre/post launch data processing. The general layout of the instrument is given along with a summary of the instrument characteristics

    Real-time observation of a coherent lattice transformation into a high-symmetry phase

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    Excursions far from their equilibrium structures can bring crystalline solids through collective transformations including transitions into new phases that may be transient or long-lived. Direct spectroscopic observation of far-from-equilibrium rearrangements provides fundamental mechanistic insight into chemical and structural transformations, and a potential route to practical applications, including ultrafast optical control over material structure and properties. However, in many cases photoinduced transitions are irreversible or only slowly reversible, or the light fluence required exceeds material damage thresholds. This precludes conventional ultrafast spectroscopy in which optical excitation and probe pulses irradiate the sample many times, each measurement providing information about the sample response at just one probe delay time following excitation, with each measurement at a high repetition rate and with the sample fully recovering its initial state in between measurements. Using a single-shot, real-time measurement method, we were able to observe the photoinduced phase transition from the semimetallic, low-symmetry phase of crystalline bismuth into a high-symmetry phase whose existence at high electronic excitation densities was predicted based on earlier measurements at moderate excitation densities below the damage threshold. Our observations indicate that coherent lattice vibrational motion launched upon photoexcitation with an incident fluence above 10 mJ/cm2 in bulk bismuth brings the lattice structure directly into the high-symmetry configuration for tens of picoseconds, after which carrier relaxation and diffusion restore the equilibrium lattice configuration.Comment: 22 pages, 4 figure

    The Lockheed OSO-8 program. Analysis of data from the mapping X-ray heliometer experiment

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    The final report describes the extent of the analysis effort, and other activities associated with the preservation and documentation of the data set are described. The main scientific results, which are related to the behavior of individual solar activity regions in the energy band 1.5 - 15 keV, are summarized, and a complete bibliography of publications and presentations is given. Copies of key articles are also provided

    Impact of neutron star oscillations on the accelerating electric field in the polar cap of pulsar: or could we see oscillations of the neutron star after the glitch in pulsar?

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    Pulsar "standard model", that considers a pulsar as a rotating magnetized conducting sphere surrounded by plasma, is generalized to the case of oscillating star. We developed an algorithm for calculation of the Goldreich-Julian charge density for this case. We consider distortion of the accelerating zone in the polar cap of pulsar by neutron star oscillations. It is shown that for oscillation modes with high harmonic numbers (l,m) changes in the Goldreich-Julian charge density caused by pulsations of neutron star could lead to significant altering of an accelerating electric field in the polar cap of pulsar. In the moderately optimistic scenario, that assumes excitation of the neutron star oscillations by glitches, it could be possible to detect altering of the pulsar radioemission due to modulation of the accelerating field.Comment: 7 pages, 8 figures. Presented at the conference "Isolated Neutron Stars: from the Interior to the Surface", London, April 24-28, 2006; to appear in Astrophysics and Space Scienc

    Federal Broadband Law

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    The authors of this book have brought together a vast and varied array of experience. Mr. Thorne is the Vice President & Associate General Counsel for Bell Atlantic; Mr. Huber is a Senior Fellow at the Manhattan Institute for Policy Research; and Mr. Kellogg is a Partner at Kellogg, Huber, Hansen & Todd. A reader will find the occasional use of technical jargon, such as domsats (domestic satellites), coax (coaxial cable), and syndex rules (syndicated exclusivity rules to protect syndicated, non-network programming) to be somewhat confusing. Telcos and cablecos are telephone and cable companies, respectively. Overall, however, technical jargon is well explained for such a comprehensive look at the hightech telecommunications field. After defining the telecosm as the universe of telecommunications and computers, the text moves into a comprehensive technical, regulatory, and legal analysis of the telecosm\u27s short- and long-term future

    Carrier confinement and bond softening in photoexcited bismuth films

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    Femtosecond pump-probe spectroscopy of bismuth thin films has revealed strong dependencies of reflectivity and phonon frequency on film thickness in the range of 25−40 nm. The reflectivity variations are ascribed to distinct electronic structures originating from strongly varying electronic temperatures and proximity of the film thickness to the optical penetration depth of visible light. The phonon frequency is redshifted by an amount that increases with decreasing film thickness under the same excitation fluence, indicating carrier density-dependent bond softening that increases due to suppressed diffusion of carriers away from the photoexcited region in thin films. The results have significant implications for nonthermal melting of bismuth as well as lattice heating due to inelastic electron-phonon scattering.United States. Office of Naval Research (Grant N00014-12-1-0530)National Science Foundation (U.S.) (Grant CHE-1111557

    Neural and Neurobehavioral Dysfunction in Children with Obstructive Sleep Apnea

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    Beebe discusses a new study that found that children with obstructive sleep apnea scored significantly lower than controls on tests of overall intelligence and executive function

    Exploring the Impacts of Predictor Variables on Success in a Mental Health Diversion Program

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    Since the first Mental Health Court (MHC) in 1997, there has been a steady increase of MHCs all over the country. With the introduction of these new specialty courts have also come to introduction of diversion programs. Diversion programs work to connect offenders who have mental illnesses to community-based mental health treatment services as an alternative to incarceration. Typically, with the completion of the program comes with the benefit of having their charges dropped. Diversion programs aim to reduce recidivism in offenders with mental illness and improve their access to treatment
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