1,031 research outputs found

    Distribution of soft drinks in the greater Boston area.

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    Thesis (M.B.A.)--Boston Universit

    School Leadership and Equity : an examination of policy response in Scotland

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    In this paper we adopt a critical perspective on the implementation of policy on school leadership and equity in Scotland, viewing policy as both an attempt to solve problems and an attempt to persuade social actors to subscribe to particular beliefs that delineate action. We begin by offering a definition of “policy response”, and then examine how policy “conversations” establish consensus around such things as school leadership and equity. We examine Scottish policy on school leadership and equity and consider what practices this policy does, and does not permit. In so doing, our examination of the implementation of policy on school leadership and equity in Scotland acknowledges that such policy is in part extemporized, and in part the attempt to make inevitable a “de-stated” account of governance. We conclude by contextualising our forthcoming empirical study of the Leadership Standards for Social Justice in Scotlan

    Laser-only adaptive optics achieves significant image quality gains compared to seeing-limited observations over the entire sky

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    Adaptive optics laser guide star systems perform atmospheric correction of stellar wavefronts in two parts: stellar tip-tilt and high-spatial-order laser-correction. The requirement of a sufficiently bright guide star in the field-of-view to correct tip-tilt limits sky coverage. Here we show an improvement to effective seeing without the need for nearby bright stars, enabling full sky coverage by performing only laser-assisted wavefront correction. We used Robo-AO, the first robotic AO system, to comprehensively demonstrate this laser-only correction. We analyze observations from four years of efficient robotic operation covering 15,000 targets and 42,000 observations, each realizing different seeing conditions. Using an autoguider (or a post-processing software equivalent) and the laser to improve effective seeing independent of the brightness of a target, Robo-AO observations show a 39+/-19% improvement to effective FWHM, without any tip-tilt correction. We also demonstrate that 50% encircled-energy performance without tip-tilt correction remains comparable to diffraction-limited, standard Robo-AO performance. Faint-target science programs primarily limited by 50% encircled-energy (e.g. those employing integral field spectrographs placed behind the AO system) may see significant benefits to sky coverage from employing laser-only AO.Comment: Accepted for publication in The Astronomical Journal. 7 pages, 6 figure

    Network operations support plan for Apollo Lunar Surface Experiments Package

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    The purpose of this Network Operations Support Plan (NOSP) is to provide operational configurations and procedures applicable to the Apollo Lunar Surface Experiments Packages (ALSEP). Some information on the Particles and Fields Subsatellite (P&FS) has been retained for historical purposes. The provisions of this document take precedence over procedures contained in other documents.Carl O. Roberts, Michael T. Ward.Mission operations -- Telemetry -- Unified S-band -- Station computer systems -- command -- Computer support -- Data management -- Station communications system -- NOCC/station interface -- Network testing and simulations -- 12-meter (40-foot) tracking antenna system -- 26-meter (85-foot) tracking antenna system -- ALSEP sunrise/sunset predictionsRevision

    The Predictability of Commodity Trading Advisor Returns

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    This study investigates the performance and predictability of returns generated by advisors to Commodity Trading Funds from 1979 through 1989. Rates of return and Sharpe Ratios show evidence of predictability from one year to the next for all Commodity Trading Advisors (CTAs). Returns for the top one-third and top 5 performing CTAs show more predictability than for all CTAs

    Matrix Pencils and Entanglement Classification

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    In this paper, we study pure state entanglement in systems of dimension 2⊗m⊗n2\otimes m\otimes n. Two states are considered equivalent if they can be reversibly converted from one to the other with a nonzero probability using only local quantum resources and classical communication (SLOCC). We introduce a connection between entanglement manipulations in these systems and the well-studied theory of matrix pencils. All previous attempts to study general SLOCC equivalence in such systems have relied on somewhat contrived techniques which fail to reveal the elegant structure of the problem that can be seen from the matrix pencil approach. Based on this method, we report the first polynomial-time algorithm for deciding when two 2⊗m⊗n2\otimes m\otimes n states are SLOCC equivalent. Besides recovering the previously known 26 distinct SLOCC equivalence classes in 2⊗3⊗n2\otimes 3\otimes n systems, we also determine the hierarchy between these classes

    Robo-AO Kepler Survey IV: the effect of nearby stars on 3857 planetary candidate systems

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    We present the overall statistical results from the Robo-AO Kepler planetary candidate survey, comprising of 3857 high-angular resolution observations of planetary candidate systems with Robo-AO, an automated laser adaptive optics system. These observations reveal previously unknown nearby stars blended with the planetary candidate host star which alter the derived planetary radii or may be the source of an astrophysical false positive transit signal. In the first three papers in the survey, we detected 440 nearby stars around 3313 planetary candidate host stars. In this paper, we present observations of 532 planetary candidate host stars, detecting 94 companions around 88 stars; 84 of these companions have not previously been observed in high-resolution. We also report 50 more-widely-separated companions near 715 targets previously observed by Robo-AO. We derive corrected planetary radius estimates for the 814 planetary candidates in systems with a detected nearby star. If planetary candidates are equally likely to orbit the primary or secondary star, the radius estimates for planetary candidates in systems with likely bound nearby stars increase by a factor of 1.54, on average. We find that 35 previously-believed rocky planet candidates are likely not rocky due to the presence of nearby stars. From the combined data sets from the complete Robo-AO KOI survey, we find that 14.5\pm0.5% of planetary candidate hosts have a nearby star with 4", while 1.2% have two nearby stars and 0.08% have three. We find that 16% of Earth-sized, 13% of Neptune-sized, 14% of Saturn-sized, and 19% of Jupiter-sized planet candidates have detected nearby stars.Comment: Accepted to the Astronomical Journa

    Robo-AO Kepler Survey V: The effect of physically associated stellar companions on planetary systems

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    The Kepler light curves used to detect thousands of planetary candidates are susceptible to dilution due to blending with previously unknown nearby stars. With the automated laser adaptive optics instrument, Robo-AO, we have observed 620 nearby stars around 3857 planetary candidates host stars. Many of the nearby stars, however, are not bound to the KOI. In this paper, we quantify the association probability between each KOI and detected nearby stars through several methods. Galactic stellar models and the observed stellar density are used to estimate the number and properties of unbound stars. We estimate the spectral type and distance to 145 KOIs with nearby stars using multi-band observations from Robo-AO and Keck-AO. We find most nearby stars within 1" of a Kepler planetary candidate are likely bound, in agreement with past studies. We use likely bound stars as well as the precise stellar parameters from the California Kepler Survey to search for correlations between stellar binarity and planetary properties. No significant difference between the binarity fraction of single and multiple planet systems is found, and planet hosting stars follow similar binarity trends as field stars, many of which likely host their own non-aligned planets. We find that hot Jupiters are ~4x more likely than other planets to reside in a binary star system. We correct the radius estimates of the planet candidates in characterized systems and find that for likely bound systems, the estimated planetary candidate radii will increase on average by a factor of 1.77, if either star is equally likely to host the planet. We find that the planetary radius gap is robust to the impact of dilution, and find an intriguing 95%-confidence discrepancy between the radius distribution of small planets in single and binary systems.Comment: 19 pages, 12 figures, submitted to AAS Journal
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