3,936 research outputs found

    Interfacing citizen participation with planning and decision-making processes

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    The evolution of traditional and contemporary planning and decision-making models has given educational leaders several variations on a theme

    Barriers to Flow: The Effects of Experimental Cage Structures on Water Velocities in High-energy Subtidal and Intertidal Environments

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    For decades, marine ecologists have used cages as biological enclosure or exclosure devices to manipulate movement, growth, and survival of organisms. The ability to control the densities of focal organisms makes these structures a powerful tool. However, cages can often produce artifacts that influence the outcome of experiments. Although a subset of these artifacts have been examined previously, the effects of cages on water motion have not been adequately addressed from a quantitative standpoint, especially in high-flow environments. We targeted this data gap by explicitly measuring the fractional degree of velocity reduction inside a variety of experimental cage structures across flow conditions spanning those typical of wave-swept shallow subtidal and intertidal zones. Cages decreased velocities inside by up to 47% and reduced high-energy impact forces by more than 40%. Associated cage controls, employed to mimic physical effects of cages without interfering with organism movement, often had effects on water flow similar to those of cages. However, the nearly half an order of magnitude change in velocities inside cages and their controls reveals the need to be vigilant in considering potential artifacts, especially those tied to secondary biological interactions. These artifacts may be reduced by maximizing mesh size, employing large plot sizes and low profile structures, using cage controls that best mimic effects of the full cage, and monitoring cage controls to avoid the establishment of high-density “consumer hotels” within them. Using such approaches, researchers can minimize experimental biases and simplify the explanation of experimental results

    Near-infrared line identification in type Ia supernovae during the transitional phase

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    We present near-infrared synthetic spectra of a delayed-detonation hydrodynamical model and compare them to observed spectra of four normal type Ia supernovae ranging from day +56.5 to day +85. This is the epoch during which supernovae are believed to be undergoing the transition from the photospheric phase, where spectra are characterized by line scattering above an optically thick photosphere, to the nebular phase, where spectra consist of optically thin emission from forbidden lines. We find that most spectral features in the near-infrared can be accounted for by permitted lines of Fe II and Co II. In addition, we find that [Ni II] fits the emission feature near 1.98 {\mu}m, suggesting that a substantial mass of 58Ni exists near the center of the ejecta in these objects, arising from nuclear burning at high density. A tentative identification of Mn II at 1.15 {\mu}m may support this conclusion as well.Comment: accepted to Ap

    Investor Perceptions of Board Performance: Evidence From Uncontested Director Elections

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    This paper provides evidence that uncontested director elections provide informative polls of investor perceptions regarding board performance. We find that higher (lower) vote approval is associated with lower (higher) stock price reactions to subsequent announcements of management turnovers. In addition, firms with low vote approval are more likely to experience CEO turnover, greater board turnover, lower CEO compensation, fewer and better-received acquisitions, and more and better-received divestitures in the future. These findings hold after controlling for other variables reflecting or determining investor perceptions, suggesting that elections not only inform as a summary statistic, but incrementally inform as well
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