6,942 research outputs found

    The Integrated Sachs-Wolfe Signal from BOSS Super-Structures

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    Cosmic structures leave an imprint on the microwave background radiation through the integrated Sachs-Wolfe effect. We construct a template map of the linear signal using the SDSS-III Baryon Acoustic Oscillation Survey at redshift 0.43 < z < 0.65. We verify the imprint of this map on the Planck CMB temperature map at the 97% confidence level and show consistency with the density-temperature cross-correlation measurement. Using this ISW reconstruction as a template we investigate the presence of ISW sources and further examine the properties of the Granett-Neyrinck-Szapudi supervoid and supercluster catalogue. We characterise the three-dimensional density profiles of these structures for the first time and demonstrate that they are significant structures. Model fits demonstrate that the supervoids are elongated along the line-of-sight and we suggest that this special orientation may be picked out by the void-finding algorithm in photometric redshift space. We measure the mean temperature profiles in Planck maps from public void and cluster catalogues. In an attempt to maximise the stacked ISW signal we construct a new catalogue of super-structures based upon local peaks and troughs of the gravitational potential. However, we do not find a significant correlation between these structures and the CMB temperature.Comment: Updated to match journal articl

    Relationship Between the Foveal Avascular Zone and Foveal Pit Morphology

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    Purpose.To assess the relationship between foveal pit morphology and size of the foveal avascular zone (FAZ). Methods. Forty-two subjects were recruited. Volumetric images of the macula were obtained using spectral domain optical coherence tomography. Images of the FAZ were obtained using either a modified fundus camera or an adaptive optics scanning light ophthalmoscope. Foveal pit metrics (depth, diameter, slope, volume, and area) were automatically extracted from retinal thickness data, whereas the FAZ was manually segmented by two observers to extract estimates of FAZ diameter and area. Results. Consistent with previous reports, the authors observed significant variation in foveal pit morphology. The average foveal pit volume was 0.081 mm3 (range, 0.022 to 0.190 mm3). The size of the FAZ was also highly variable between persons, with FAZ area ranging from 0.05 to 1.05 mm2 and FAZ diameter ranging from 0.20 to 1.08 mm. FAZ area was significantly correlated with foveal pit area, depth, and volume; deeper and broader foveal pits were associated with larger FAZs. Conclusions. Although these results are consistent with predictions from existing models of foveal development, more work is needed to confirm the developmental link between the size of the FAZ and the degree of foveal pit excavation. In addition, more work is needed to understand the relationship between these and other anatomic features of the human foveal region, including peak cone density, rod-free zone diameter, and Henle fiber layer

    Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia

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    The orbits of binary stars and planets, particularly eccentricities and inclinations, encode the angular momentum within these systems. Within stellar multiple systems, the magnitude and (mis)alignment of angular momentum vectors among stars, disks, and planets probes the complex dynamical processes guiding their formation and evolution. The accuracy of the \textit{Gaia} catalog can be exploited to enable comparison of binary orbits with known planet or disk inclinations without costly long-term astrometric campaigns. We show that \textit{Gaia} astrometry can place meaningful limits on orbital elements in cases with reliable astrometry, and discuss metrics for assessing the reliability of \textit{Gaia} DR2 solutions for orbit fitting. We demonstrate our method by determining orbital elements for three systems (DS Tuc AB, GK/GI Tau, and Kepler-25/KOI-1803) using \textit{Gaia} astrometry alone. We show that DS Tuc AB's orbit is nearly aligned with the orbit of DS Tuc Ab, GK/GI Tau's orbit might be misaligned with their respective protoplanetary disks, and the Kepler-25/KOI-1803 orbit is not aligned with either component's transiting planetary system. We also demonstrate cases where \textit{Gaia} astrometry alone fails to provide useful constraints on orbital elements. To enable broader application of this technique, we introduce the python tool \texttt{lofti\_gaiaDR2} to allow users to easily determine orbital element posteriors.Comment: 18 pages, 10 figures, accepted for publication in Ap

    A Study of the Hierarchical Culture Gaps Within Unionized Utilities Companies

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    The purpose of this study was to measure the culture gaps between hierarchical subgroups within unionized utilities companies. We conducted a mixed methods study. Using archival survey data, we compared hierarchically-defined subgroups’ perceptions of performance-linked culture traits within five unionized utilities companies. We later conducted interviews and focus groups, followed by qualitative coding and analysis. As compared to non-union employees, union employees viewed their companies as substantially less involving, consistent, adaptable, and clear about purpose and direction. Our qualitative analysis highlighted two prior management decisions as illustrative of the contrast between high and low levels of union involvement and clarity. Culture scholars and practitioners have suggested that leaders must align subcultures where they exist. Our study demonstrates large culture gaps between union employees and other subgroups and suggests that management’s involvement of the workforce in strategic decisions may have unique consequences for how subgroups perceive and interpret the culture

    Miami- Dade Urban Tree Canopy Analysis

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    Two of the Florida state universities, University of Florida (UF) and Florida International University (FIU), collaborated in assessing urban tree cover (UTC) for part of northwestern Miami-Dade County, covering an area of approximately 380 km2 (147 mi2). The analysis estimated the area with current tree canopy (existing UTC), the area of potential tree canopy (possible UTC), and various other land cover categories. The assessment used two methods to establish those estimates. The first method utilized the i-Tree canopy assessment tool provided by the USDA Forest Service. The second method used a combination of multispectral satellite data and airborne Light Detection and Ranging (LiDAR) datasets for detection and classification of land cover. Classification results were further analyzed in a Geographic Information System (GIS) to relate land cover distribution patterns (obtained from the second land cover classification method) to surface temperatures, land use patterns, and socioeconomic factors
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