116 research outputs found

    Unsteady flow over bluff bodies

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    SIGLEAvailable from British Library Document Supply Centre- DSC:D67654/86 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

    Interferometric Studies of the extreme binary, ϵ\epsilon Aurigae: Pre-eclipse Observations

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    We report new and archival K-band interferometric uniform disk diameters obtained with the Palomar Testbed Interferometer for the eclipsing binary star ϵ\epsilon Aurigae, in advance of the start of its eclipse in 2009. The observations were inteded to test whether low amplitude variations in the system are connected with the F supergiant star (primary), or with the intersystem material connecting the star with the enormous dark disk (secondary) inferred to cause the eclipses. Cepheid-like radial pulsations of the F star are not detected, nor do we find evidence for proposed 6% per decade shrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K band diameter is consistent with a 300 times solar radius F supergiant star at the Hipparcos distance of 625 pc. These results provide an improved context for observations during the 2009-2011 eclipse.Comment: Accepted for Ap.J. Letters, Oct. 200

    Investor Competition Over Information and the Pricing of Information Asymmetry

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    Whether the information environment affects the cost of capital is a fundamental question in accounting and finance research. Relying on theories about competition between informed investors as well as the pricing of information asymmetry, we hypothesize a cross-sectional variation in the pricing of information asymmetry that is conditional on competition. We develop and validate empirical proxies for competition using the number and concentration of institutional investor ownership. Using these proxies, we find a lower pricing of information asymmetry when there is more competition. Overall, our results suggest that competition between informed investors has an important effect on how the information environment affects the cost of capital.Deloitte Foundatio

    Solar System Objects Observed in the SDSS Commissioning Data

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    We discuss measurements of the properties of about 10,000 asteroids detected in 500 deg2 of sky in the Sloan Digital Sky Survey (SDSS) commissioning data. The moving objects are detected in the magnitude range 14 < r < 21.5, with a baseline of 5 minutes. Extensive tests show that the sample is at least 98% complete, with the contamination rate of less than 3%. We find that the size distribution of asteroids resembles a broken power-law, independent of the heliocentric distance: D^{-2.3} for 0.4 km < D < 5 km, and D^{-4} for 5 km < D < 40 km. As a consequence of this break, the number of asteroids with r < 21.5 is ten times smaller than predicted by extrapolating the power-law relation observed for brighter asteroids (r < 18). The observed counts imply that there are about 530,000 objects with D>1 km in the asteroid belt, or about four times less than previous estimates. The distribution of main belt asteroids in the 4-dimensional SDSS color space is bimodal, and the two groups can be associated with S (rocky) and C (carbonaceous) asteroids. A strong bimodality is also seen in the heliocentric distribution of asteroids and suggests the existence of two distinct belts: the inner rocky belt, about 1 AU wide (FWHM) and centered at R~2.8 AU, and the outer carbonaceous belt, about 0.5 AU wide and centered at R~3.2 AU. The colors of Hungarias, Mars crossers, and near-Earth objects are more similar to the C-type than to S-type asteroids, suggesting that they originate in the outer belt. (abridged).Comment: 89 pages, 31 figures, submitted to A

    LSST: from Science Drivers to Reference Design and Anticipated Data Products

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    (Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2^2 field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5σ\sigma point-source depth in a single visit in rr will be 24.5\sim 24.5 (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg2^2 with δ<+34.5\delta<+34.5^\circ, and will be imaged multiple times in six bands, ugrizyugrizy, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg2^2 region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r27.5r\sim27.5. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

    Breast cancer risk variants at 6q25 display different phenotype associations and regulate ESR1, RMND1 and CCDC170.

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    We analyzed 3,872 common genetic variants across the ESR1 locus (encoding estrogen receptor α) in 118,816 subjects from three international consortia. We found evidence for at least five independent causal variants, each associated with different phenotype sets, including estrogen receptor (ER(+) or ER(-)) and human ERBB2 (HER2(+) or HER2(-)) tumor subtypes, mammographic density and tumor grade. The best candidate causal variants for ER(-) tumors lie in four separate enhancer elements, and their risk alleles reduce expression of ESR1, RMND1 and CCDC170, whereas the risk alleles of the strongest candidates for the remaining independent causal variant disrupt a silencer element and putatively increase ESR1 and RMND1 expression.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/ng.352
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