Arboreal twig-nesting ants form dominance hierarchies over nesting resources.

Interspecific dominance hierarchies have been widely reported across animal systems. High-ranking species are expected to monopolize more resources than low-ranking species via resource monopolization. In some ant species, dominance hierarchies have been used to explain species coexistence and community structure. However, it remains unclear whether or in what contexts dominance hierarchies occur in tropical ant communities. This study seeks to examine whether arboreal twig-nesting ants competing for nesting resources in a Mexican coffee agricultural ecosystem are arranged in a linear dominance hierarchy. We described the dominance relationships among 10 species of ants and measured the uncertainty and steepness of the inferred dominance hierarchy. We also assessed the orderliness of the hierarchy by considering species interactions at the network level. Based on the randomized Elo-rating method, we found that the twig-nesting ant species Myrmelachista mexicana ranked highest in the ranking, while Pseudomyrmex ejectus was ranked as the lowest in the hierarchy. Our results show that the hierarchy was intermediate in its steepness, suggesting that the probability of higher ranked species winning contests against lower ranked species was fairly high. Motif analysis and significant excess of triads further revealed that the species networks were largely transitive. This study highlights that some tropical arboreal ant communities organize into dominance hierarchies

Response of Waterbirds to Salt Pond Enhancements and Island Creation in the San Francisco Bay

Historically, San Francisco Bay supported the largest salt pond complex on the Pacific coast of North America, and these areas have been used by large numbers of migrating and wintering waterbirds for more than a century. In 2003, salt ponds in the South San Francisco Bay were purchased with a goal of restoring 50-90% of the 6100 ha of former salt ponds to replace lost tidal marsh habitats. However, a major challenge for the restoration project has been maintaining the abundance of non-breeding waterbirds in a smaller footprint of managed ponds. Thus, in 2009-2010, Pond SF2 was enhanced with 30 islands of two different shapes and water control structures that provided muted tidal flows with shallow water depths predicted to benefit waterbirds. To assess how non-breeding waterbirds responded to these enhancements, a spatial grid (50 m x 50 m) was used to survey SF2 weekly from October to May 2010-2012, and examine waterbird use. Of the 262,932 non-breeding waterbirds observed, only 12-15% used the islands depending on tide. Island size, shape, or both predicted the presence or relative abundance of some foraging guilds, whereas island slope, perimeter, and distance to mudflat did not improve the model\u27s predictions of relative guild abundances. Results indicated that waterbirds were attracted to areas with shallow water depths; however, the constructed islands were not used by a large number of waterbirds

Bruxism and autonomic activity

not applicabl

Fitting the radial acceleration relation to individual SPARC galaxies

Galaxies follow a tight radial acceleration relation (RAR): the acceleration observed at every radius correlates with that expected from the distribution of baryons. We use the Markov Chain Monte Carlo method to fit the mean RAR to 175 individual galaxies in the SPARC database, marginalizing over stellar mass-to-light ratio ($\Upsilon_{\star}$), galaxy distance, and disk inclination. Acceptable fits with astrophysically reasonable parameters are found for the vast majority of galaxies. The residuals around these fits have an rms scatter of only 0.057 dex ($\sim$13$\%$). This is in agreement with the predictions of modified Newtonian dynamics (MOND). We further consider a generalized version of the RAR that, unlike MOND, permits galaxy-to-galaxy variation in the critical acceleration scale. The fits are not improved with this additional freedom: there is no credible indication of variation in the critical acceleration scale. The data are consistent with the action of a single effective force law. The apparent universality of the acceleration scale and the small residual scatter are key to understanding galaxies.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in A&A. The same as the first version with typos corrected. A set of 175 figures is available at http://astroweb.cwru.edu/SPARC

Polarization and Extent of Maser Emission from Late-Type Stars: Support for a Plasma Turbulence Model of Maser Production

The integrated spectrum of OH emission from late-type stars is often circularly polarized, by as much as 50% in some cases. While the spectra are partially polarized, the individual maser components revealed by VLBI are much more so. Using VLBI observations of late-type stars from the literature, we show that the difference in circular polarization between main lines correlates with a difference in angular extent for a given object. This is a natural result if turbulent magnetic fields are causing the masers to be polarized via the Cook mechanism, and might serve as a good diagnostic for determining which objects should be investigated in the search for magnetic fields around evolved stars.Comment: 5 pages, 2 figs ApJL, accepte

Do Management Changes Matter? An Empirical Investigation of REIT Performance

Management’s (board of directors or executive officers) contribution to a firm is difficult to directly observe, although stock return performance can be a source of information. This study addresses this issue by extending the work of McIntosh, Rogers, Sirmans and Liang (1994) by analyzing management changes within REITs from 1984 to 2002. The findings indicate a significant relationship between negative performance and a management change from a period three months prior to the change in management. Logit and probit analysis are used to determine whether negative firm performance (measured by its relationship to market returns) can predict the likelihood of a management change. No predictive ability is found.