3,398 research outputs found

    TEXES Observations of Pure Rotational H_2 Emission from AB Aurigae

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    We present observations of pure rotational molecular hydrogen emission from the Herbig Ae star, AB Aur. Our observations were made using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility and the Gemini North Observatory. We searched for H_2 emission in the S(1), S(2), and S(4) lines at high spectral resolution and detected all three. By fitting a simple model for the emission in the three transitions, we derive T = 670 ± 40 K and M = 0.52 ± 0.15 M_⊙ for the emitting gas. On the basis of the 8.5 km s^(-1) FWHM of the S(2) line, assuming the emission comes from the circumstellar disk, and with an inclination estimate of the AB Aur system taken from the literature, we place the location for the emission near 18 AU. Comparison of our derived temperature to a disk structure model suggests that UV and X-ray heating are important in heating the disk atmosphere

    Leader-member Exchange (LMX) ambivalence and task performance: The cross-domain buffering role of social support.

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    Leader-member exchange (LMX) theory proposes that leaders develop different quality relationships with those they manage and this is predictive of work performance. While LMX quality has been viewed as univalent (ranging from low to high quality), this paper proposes that it can also be bivalent in nature (i.e., coexisting positive and negative thoughts towards the relationship), which we refer to as LMX ambivalence. A survey measure of LMX ambivalence is developed, and through three validation and two main studies, it is shown to have construct, discriminant, and incremental predictive validity beyond that of LMX quality. Hypotheses concerning LMX ambivalence and task performance are tested in two main studies and show that (1) LMX ambivalence is negatively related to performance regardless of LMX quality, (2) high levels of perceived support from the organization (Study 1) or coworkers (Study 2) nullify the negative association between LMX ambivalence and performance, and (3) high LMX ambivalence leads to more negative affect and in turn lower task performance, but only when coworker support is low (Study 2). These results show the importance of viewing LMX quality not only in terms of its absolute level (low vs. high quality) but also as a bivalent construct where both positive and negative cognitions can coexist. They also demonstrate the value of social support in buffering the negative effects of LMX ambivalence. Furthermore, our findings extend a central tenet of LMX theory by implying that LMX quality varies not only within groups (i.e., LMX differentiation) but also within leader-follower dyads

    Handbook of Field Methods for Monitoring Landbirds

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    This handbook is a compilation of methods that can be used to assay population size, demographics, and status of many species of birds occurring in a wide variety of habitats. The handbook will prove useful to field biologists, managers, and scientists anywhere in the New World from the arctic through the tropics. The methods include four types of censuses for determining population size and trends, mist-netting and nest searches to determine demographic parameters, and other methods that will be useful in operating a monitoring station, including habitat and weather observations, and suggestions for training personnel and possibilities for detailed studies. Suggestions of specific methods and data forms are included

    COLLECTIVE LEADERSHIP: A Case Study of the All Blacks

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    This case study evaluates the development of a formal collective leadership approach by the All Blacks (New Zealand’s national men’s rugby team) management. The All Blacks have an astonishing 75% winning record in test matches over a hundred year period. This winning ethos is part of their organizational culture, which has been developed, nurtured and sustained since the inception of the first national team in 1903 (Palenski, 2003; Tobin, 2005). In this qualitative research study, primary data was obtained through the analysis of semi-structured, in-depth interviews with past and present All Black captains and coaches (over a period of 60 years from 1950-2010). Stories which are narratives based on true events provide a rich description, which enhances the credibility and transferability of the findings. A key finding is the strong senior collective leadership that has been ever present. Originally led by senior players informally from ‘the back seat of the bus’ this internal leadership has been formalised by the most recent coaching team and has proved to be very effective with regards to maintaining a winning culture in an ever-changing organizational and socio-cultural environment. The learning culture and learning leadership demonstrated within the All Blacks collective leadership model instils a commitment to total honesty in self and team evaluation and reflection. It is anticipated that these findings will be transferable to other business and team sport contexts and assist in organizational development

    The K2 Mission: Characterization and Early results

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    The K2 mission will make use of the Kepler spacecraft and its assets to expand upon Kepler's groundbreaking discoveries in the fields of exoplanets and astrophysics through new and exciting observations. K2 will use an innovative way of operating the spacecraft to observe target fields along the ecliptic for the next 2-3 years. Early science commissioning observations have shown an estimated photometric precision near 400 ppm in a single 30 minute observation, and a 6-hour photometric precision of 80 ppm (both at V=12). The K2 mission offers long-term, simultaneous optical observation of thousands of objects at a precision far better than is achievable from ground-based telescopes. Ecliptic fields will be observed for approximately 75-days enabling a unique exoplanet survey which fills the gaps in duration and sensitivity between the Kepler and TESS missions, and offers pre-launch exoplanet target identification for JWST transit spectroscopy. Astrophysics observations with K2 will include studies of young open clusters, bright stars, galaxies, supernovae, and asteroseismology.Comment: 25 pages, 11 figures, Accepted to PAS

    PySilSub: An open-source Python toolbox for implementing the method of silent substitution in vision and nonvisual photoreception research

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    The normal human retina contains several classes of photosensitive cell—rods for low-light vision, three cone classes for daylight vision, and intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing melanopsin for non-image-forming functions, including pupil control, melatonin suppression, and circadian photoentrainment. The spectral sensitivities of the photoreceptors overlap significantly, which means that most lights will stimulate all photoreceptors to varying degrees. The method of silent substitution is a powerful tool for stimulating individual photoreceptor classes selectively and has found much use in research and clinical settings. The main hardware requirement for silent substitution is a spectrally calibrated light stimulation system with at least as many primaries as there are photoreceptors under consideration. Device settings that will produce lights to selectively stimulate the photoreceptor(s) of interest can be found using a variety of analytic and algorithmic approaches. Here we present PySilSub (https://github.com/PySilentSubstitution/pysilsub), a novel Python package for silent substitution featuring flexible support for individual colorimetric observer models (including human and mouse observers), multiprimary stimulation devices, and solving silent substitution problems with linear algebra and constrained numerical optimization. The toolbox is registered with the Python Package Index and includes example data sets from various multiprimary systems. We hope that PySilSub will facilitate the application of silent substitution in research and clinical settings

    FiberGLAST: a scintillating fiber approach to the GLAST mission

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    FiberGLAST is a scintillating fiber gamma-ray detector designed for the GLAST mission. The system described below provides superior effective area and field of view for modest cost and risk. An overview of the FiberGLAST instrument is presented, as well as a more detailed description of the principle elements of the primary detector volume. The triggering and readout electronics are described, and Monte Carlo Simulations of the instrument performance are presented

    Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems

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    The Kepler mission has discovered over 2500 exoplanet candidates in the first two years of spacecraft data, with approximately 40% of them in candidate multi-planet systems. The high rate of multiplicity combined with the low rate of identified false-positives indicates that the multiplanet systems contain very few false-positive signals due to other systems not gravitationally bound to the target star (Lissauer, J. J., et al., 2012, ApJ 750, 131). False positives in the multi- planet systems are identified and removed, leaving behind a residual population of candidate multi-planet transiting systems expected to have a false-positive rate less than 1%. We present a sample of 340 planetary systems that contain 851 planets that are validated to substantially better than the 99% confidence level; the vast majority of these have not been previously verified as planets. We expect ~2 unidentified false-positives making our sample of planet very reliable. We present fundamental planetary properties of our sample based on a comprehensive analysis of Kepler light curves and ground-based spectroscopy and high-resolution imaging. Since we do not require spectroscopy or high-resolution imaging for validation, some of our derived parameters for a planetary system may be systematically incorrect due to dilution from light due to additional stars in the photometric aperture. None the less, our result nearly doubles the number of verified exoplanets.Comment: 138 pages, 8 Figures, 5 Tables. Accepted for publications in the Astrophysical Journa
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