Sink or ecological trap for tree swallows in Central Minnesota?

Background: An ecological trap is typically defined as a low-quality habitat, incapable of sustaining a population, which is preferred over a high quality habitat. Ecological traps may lead to species extinction in populations with 1) strict habitat requirements 2) minimal information about the habitat, and 3) low population size. Tree Swallows (Tachycineta bicolor) meet the former two of these criteria. Methods: We monitored Tree Swallow (TS) nest boxes (n=90) at two ecologically similar sites A and B with similar occupancy rates. Site B has lower reproductive fitness —suggestive of an ecological trap. Binary logistic regression was used to identify whether TS in better condition preferred site A or B and what environmental characteristics predicted nest box occupancy. Results: Site A’s Tree Swallows were in significantly better condition and laid eggs earlier than site B’s TS. Significant predictors of nest box occupancy include distance from nearest box (p=0.000), DBH of largest stem in adjacent wooded area (p=0.026). Conclusion: Tree Swallows seemingly recognized site A to be a superior breeding habitat over site B, suggesting that site B is a sink rather than an ecological trap. Distance from an adjacent box was an important predictor of occupancy, possibly to reduce extra-pair mating or depredation. TS favored nest boxes adjacent to an edge with smaller stems which may lessen competition by birds a nesting in naturally occurring cavities along hardwood edges. Although not a significant predictor of occupation, the average distance from the edge was greater at Site A (p = 0.012). It is possible that distance from the edge is a habitat cue utilized by Tree Swallows, independent of whether hetero- or conspecifics might be nesting in nearby natural cavities

Exoplanets or Dynamic Atmospheres? The Radial Velocity and Line Shape Variations of 51 Pegasi and Tau Bootis

Because of our relatively low spectral resolution, we compare our observations with Gray's line bisector data by fitting observed line profiles to an expansion in terms of orthogonal (Hermite) functions. To obtain an accurate comparison, we model the emergent line profiles from rotating and pulsating stars, taking the instrumental point spread function into account. We describe this modeling process in detail. We find no evidence for line profile or strength variations at the radial velocity period in either 51 Peg or in Tau Boo. For 51 Peg, our upper limit for line shape variations with 4.23-day periodicity is small enough to exclude with 10 sigma confidence the bisector curvature signal reported by Gray & Hatzes; the bisector span and relative line depth signals reported by Gray (1997) are also not seen, but in this case with marginal (2 sigma) confidence. We cannot, however, exclude pulsations as the source of 51 Peg's radial velocity variation, because our models imply that line shape variations associated with pulsations should be much smaller than those computed by Gray & Hatzes; these smaller signals are below the detection limits both for Gray & Hatzes' data and for our own. Tau Boo's large radial velocity amplitude and v*sin(i) make it easier to test for pulsations in this star. Again we find no evidence for periodic line-shape changes, at a level that rules out pulsations as the source of the radial velocity variability. We conclude that the planet hypothesis remains the most likely explanation for the existing data.Comment: 44 pages, 19 figures, plain TeX, accepted to ApJS (companion to letter astro-ph/9712279

Personality traits and motivations of medical voluntourists

Tourism is a critical component to many developing countries\u27 economies. As tourism grows worldwide many individuals seek new opportunity in search of authentic experiences. In some cases these individuals want this new experience to include a component of helping others in the communities that they visit. This has caused a growth in multiple types of volunteer driven tourism called voluntourism. Previously, a group of Creative Inquire students addressed the personality traits and motivation of surf voluntourists. This study extends that research to medical voluntourists. As the name implies, these individuals contribute medical care in communities that are in need of said services while also experiencing what the community has to offer as a tourist. This study utilizes both quantitative and qualitative data to identify personality traits and motivations of medical voluntourists. The information is designed to help organizations better recruit future volunteers

HAT-P-55b: A Hot Jupiter Transiting a Sun-like Star

We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The planet orbits a V = 13.207 +/- 0.039 sun-like star with a mass of 1.013 +/- 0.037 solar masses, a radius of 1.011 +/- 0.036 solar radii and a metallicity of -0.03 +/- 0.08. The planet itself is a typical hot Jupiter with a period of 3.5852467 +/- 0.0000064 days, a mass of 0.582 +/- 0.056 Jupiter masses and a radius of 1.182 +/- 0.055 Jupiter radii. This discovery adds to the increasing sample of transiting planets with measured bulk densities, which is needed to put constraints on models of planetary structure and formation theories.Comment: 7 pages, 4 figures, accepted for publication in PAS

Observation and Spectral Measurements of the Crab Nebula with Milagro

The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is believed to be caused by inverse-Compton up-scattering scattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fit. The fit is consistent with values measured by IACTs between 1 and 20 TeV. Fixing the spectral index to values that have been measured below 1 TeV by IACT experiments (2.4 to 2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20 to 40 TeV.Comment: Submitted to Astrophysical Journa

Search for very high energy gamma-rays from WIMP annihilations near the Sun with the Milagro Detector

The neutralino, the lightest stable supersymmetric particle, is a strong theoretical candidate for the missing astronomical ``dark matter''. A profusion of such neutralinos can accumulate near the Sun when they lose energy upon scattering and are gravitationally captured. Pair-annihilations of those neutralinos may produce very high energy (VHE, above $100 GeV$) gamma-rays. Milagro is an air shower array which uses the water Cherenkov technique to detect extensive air showers and is capable of observing VHE gamma-rays from the direction of the Sun with an angular resolution of $0.75^{\circ}$. Analysis of Milagro data with an exposure to the Sun of 1165 hours presents the first attempt to detect TeV gamma-rays produced by annihilating neutralinos captured by the Solar system and shows no statistically significant signal. Resulting limits that can be set on gamma-ray flux due to near-Solar neutralino annihilations and on neutralino cross-section are presented

Milagro Constraints on Very High Energy Emission from Short Duration Gamma-Ray Bursts

Recent rapid localizations of short, hard gamma-ray bursts (GRBs) by the Swift and HETE satellites have led to the observation of the first afterglows and the measurement of the first redshifts from this type of burst. Detection of >100 GeV counterparts would place powerful constraints on GRB mechanisms. Seventeen short duration (< 5 s) GRBs detected by satellites occurred within the field of view of the Milagro gamma-ray observatory between 2000 January and 2006 December. We have searched the Milagro data for >100 GeV counterparts to these GRBs and find no significant emission correlated with these bursts. Due to the absorption of high-energy gamma rays by the extragalactic background light (EBL), detections are only expected for redshifts less than ~0.5. While most long duration GRBs occur at redshifts higher than 0.5, the opposite is thought to be true of short GRBs. Lack of a detected VHE signal thus allows setting meaningful fluence limits. One GRB in the sample (050509b) has a likely association with a galaxy at a redshift of 0.225, while another (051103) has been tentatively linked to the nearby galaxy M81. Fluence limits are corrected for EBL absorption, either using the known measured redshift, or computing the corresponding absorption for a redshift of 0.1 and 0.5, as well as for the case of z=0.Comment: Accepted for publication in the Astrophysical Journa

Observation of TeV Gamma Rays from the Crab Nebula with Milagro Using a New Background Rejection Technique

The recent advances in TeV gamma-ray astronomy are largely the result of the ability to differentiate between extensive air showers generated by gamma rays and hadronic cosmic rays. Air Cherenkov telescopes have developed and perfected the "imaging" technique over the past several decades. However until now no background rejection method has been successfully used in an air shower array to detect a source of TeV gamma rays. We report on a method to differentiate hadronic air showers from electromagnetic air showers in the Milagro gamma ray observatory, based on the ability to detect the energetic particles in an extensive air shower. The technique is used to detect TeV emission from the Crab nebula. The flux from the Crab is estimated to be 2.68(+-0.42stat +- 1.4sys) x10^{-7} (E/1TeV)^{-2.59} m^{-2} s^{-1} TeV^{-1}, where the spectral index is assumed to be as given by the HEGRA collaboration.Comment: 22 pages, 11 figures, submitted to Astrophysical Journa

Self-related consequences of death fear and death denial

This study explores self-related outcomes (e.g., esteem, self-concept clarity, existential well-being) as a function of the interaction between self-reported levels of death fear and death denial. Consistent with the idea that positive existential growth can come from individuals facing, rather than denying, their mortality (Cozzolino, 2006), the authors observed that not fearing and denying death can bolster important positive components of the self. That is, individuals low in death denial and death fear evidenced an enhanced self that is valued, clearly conceived, efficacious, and that has meaning and purpose