Gamma Group-The Pale Horse: A proposal in response to a commercial air transportation study ort study

A conventional remotely piloted vehicle (RPV) was designed to operate in a fictional 'Aeroworld' as a 30 passenger aircraft. The topics addressed include: economic/cost analysis, aerodynamics, weight and structures, propulsion, stability and control, and performance

Analysis of Predator Avoidance Behavior in California Valley Quail

Quail populations have been in decline across the United States, primarily due to habitat loss and climate. For remedy, landowners and game managers have attempted to restore populations by releasing captive-reared quail. These releases were largely unsuccessful, presumably due to high predation losses. Recently, there has been an increased interest in quail translocations, which tend to have lower mortality rates than captive-reared bird releases. Translocations are expensive and unpredictable, and require many person-hours; releasing captive-reared quail would be more efficient if the practice were successful. We compared predator avoidance behavior between captive-reared and wild-translocated California quail (Callipepla californica) in an aviary using simulated predator attacks (raptorial and mammalian). We recorded predator detection time, antipredator response time, and antipredator response type. Antipredator response type (run, flush, or freeze) frequencies were different, where captive-reared quail ran more frequently than wild-translocated quail when encountering a simulated predator. Predator detection time between captive-reared and wild-translocated quail was not different. However, antipredator response time was quicker for captive-reared quail than wild-translocated quail when subjected to simulated raptorial and mammalian attacks. The differences in antipredator response time and response type may be due to the lack of predator interaction experience of captive-reared birds and offer insight into observed differences in postrelease mortality between captive-reared and wild-trapped quail

NGC 2419, M92, and the Age Gradient in the Galactic Halo

The WFPC2 camera on HST has been used to obtain deep main sequence photometry of the low-metallicity ([Fe/H]=-2.14), outer-halo globular cluster NGC 2419. A differential fit of the NGC 2419 CMD to that of the similarly metal-poor \ standard cluster M92 shows that they have virtually identical principal sequences and thus the same age to well within 1 Gyr. Since other low-metallicity clusters throughout the Milky Way halo have this same age to within the 1-Gyr precision of the differential age technique, we conclude that the earliest star (or globular cluster) formation began at essentially the same time everywhere in the Galactic halo throughout a region now almost 200 kpc in diameter. Thus for the metal-poorest clusters in the halo there is no detectable age gradient with Galactocentric distance. To estimate the absolute age of NGC 2419 and M92, we fit newly computed isochrones transformed through model-atmosphere calculations to the (M_V,V-I) plane, with assumed distance scales that represent the range currently debated in the literature. Unconstrained isochrone fits give M_V(RR) = 0.55 \pm 0.06 and a resulting age of 14 to 15 Gyr. Incorporating the full effects of helium diffusion would further reduce this estimate by about 1 Gyr. A distance scale as bright as M_V(RR) = 0.15 for [Fe/H] = -2, as has recently been reported, would leave several serious problems which have no obvious solution in the context of current stellar models.Comment: 32 pages, aastex, 9 postscript figures; accepted for publication in AJ, September 1997. Also available by e-mail from [email protected]

Stress and Predation Impacts on North American Quail Translocations

Translocations have been used in attempts to bolster or restore native quail populations for \u3e150 years, often with little success. However, with some northeastern United States quail populations undetectable or extirpated, and others across the United States on the extreme decline, translocation as a tool for quail population restoration is becoming increasingly popular. Two factors contributing to translocation failure are physiological stress and predation. Chronic stress associated with translocations can result in weight loss, reduced immune system function, suppressed reproduction, and an altered fight-or-flight response. These stress-induced responses increase vulnerability to predation, the primary cause of quail mortality. Here, we review the relationship between quail translocations, stress, and predation, and recommend future research and best practices to mitigate the impacts of stress and predation on translocated quail. To improve future translocation outcomes, more research is needed on stress mitigation throughout the translocation process (capture, handling, transport, and release). While capture and handling are unavoidably stressful, there is greater potential to reduce stress levels during holding and transport. Recent validation of fecal corticosterone metabolites as a non-invasive method to quantify stress in quail offers a useful tool for testing stress reduction protocols. Preliminary experimental results regarding nutritional supplements and stress levels are inconclusive, but enrichment during temporary holding and access to travel rations may help improve survival in long-distance (\u3e800 km) translocations. We also recommend predator control at release sites, particularly for raccoons (Procyon lotor) and other mesomammals

VLBI observations of the Crab nebula pulsar

Observations were made at meter wave-lengths using very long base-line interferometry techniques. At 196.5 MHz no resolution of the pulsar are observed; all the pulse shapes observed with the interferometers are similar to single dish profiles, and all the power pulsates. At 111.5 MHz besides the pulsing power there is always a steady component, presumably due to interstellar scattering. The pulsar is slightly resolved at 111.5 MHz with an apparent angular diameter of 0.07 sec ? 0.01 sec. A 50 percent linear polarization of the time-averaged power is noted at 196.5 MHz; at 111.5 MHz, 20 percent of the total time-averaged power is polarized, 35 percent of the pulsing power is polarized, and the steady component is unpolarized

Pea-Wheat Rotation Affects Soil Microbiota Diversity, Community Structure, and Soilborne Pathogens

Intensive cultivation based on monocultures has a significant impact on ecosystem function, and sustainable agriculture must rely on alternative methods, including crop rotation. On the Canadian prairies, the use of pulse crops is a common practice, but few studies have investigated the impact on soil microorganisms. Here, we studied the effect of pea, wheat, pea–wheat rotation, and fallow in bulk soil bacterial and fungal communities. We characterized soil microbiota by high-throughput sequencing of 16S and 18S rRNA genes for bacteria and eukaryotes. Different crop rotations and fallow significantly modified soil community composition, as well as bacterial and fungal diversity. Pea alone caused a strong reduction of bacterial and fungal richness and diversity compared to wheat, pea–wheat rotation, and fallow. Notably, pea–wheat rotation increased the abundance of Fusarium graminearum compared to other management practices. The bacterial community was less responsive to crop rotation identity compared to the fungal microbiota, and we found minor differences at the phylum level, with an increase in Actinobacteria in fallow and Firmicutes in wheat. In summary, our study demonstrated that rotations alter bulk soil microbial community diversity and composition in Canadian prairies. The frequent use of pea in rotation with wheat should be carefully evaluated, balancing their ecological effects on nitrogen mineralization, water conservation, and impact on beneficial, as well as pathotrophic, fungi

On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models

Stellar models have been computed for stars having [Fe/H] = 0.0 and -2.0 to determine the effects of using boundary conditions derived from the latest MARCS model atmospheres. The latter were fitted to the interior models at both the photosphere and at tau = 100, and at least for the 0.8-1.0 solar mass stars considered here, the resultant evolutionary tracks were found to be nearly independent of the chosen fitting point. Particular care was taken to treat the entire star as consistently as possible; i.e., both the interior and atmosphere codes assumed the same abundances and the same treatment of convection. Tracks were also computed using either the classical gray T(tau,T_eff) relation or that derived by Krishna Swamy (1966) to derive the boundary pressure. The latter predict warmer giant branches (by ~150 K) at solar abundances than those based on gray or MARCS atmospheres, which happens to be in good agreement with the inferred temperatures of giants in the open cluster M67 from the latest (V-K)-T_eff relations. Most of the calculations assumed Z=0.0125 (Asplund et al.), though a few models were computed for Z=0.0165 (Grevesse & Sauval) to determine the dependence of the tracks on Z_\odot. Grids of "scaled solar, differentially corrected" (SDC) atmospheres were also computed to try to improve upon theoretical MARCS models. When they were used as boundary conditions, the resultant tracks agreed very well with those based on a standard scaled-solar (e.g., Krishna Swamy) T(tau,T_eff) relation, independently of the assumed metal abundance. Fits of isochrones to the C-M diagram of the [Fe/H] = -2 globular cluster M68 were examined, as was the possibility that the mixing-length parameter varies with stellar parameters.Comment: 54 pages, including 20 figures and 3 tables; accepted (July 2007) for publication in the Astrophysical Journa

The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc

We use photometric and spectroscopic observations of the eclipsing binary V69-47 Tuc to derive the masses, radii, and luminosities of the component stars. Based on measured systemic velocity, distance, and proper motion, the system is a member of the globular cluster 47 Tuc. The system has an orbital period of 29.5 d and the orbit is slightly eccentric with e=0.056. We obtain Mp=0.8762 +- 0.0048 M(Sun), Rp=1.3148 +-0.0051 R(Sun), Lp=1.94 +- 0.21 L(Sun) for the primary and Ms=0.8588 +- 0.0060 M(Sun), Rs=1.1616 +- 0.0062 R(Sun), Ls=1.53 +- 0.17 L(Sun) for the secondary. These components of V69 are the first Population II stars with masses and radii derived directly and with an accuracy of better than 1%. We measure an apparent distance modulus of (m-M)v=13.35 +- 0.08 to V69. We compare the absolute parameters of V69 with five sets of stellar evolution models and estimate the age of V69 using mass-luminosity-age, mass-radius-age, and turnoff mass - age relations. The masses, radii, and luminosities of the component stars are determined well enough that the measurement of ages is dominated by systematic differences between the evolutionary models, in particular, the adopted helium abundance. By comparing the observations to Dartmouth model isochrones we estimate the age of V69 to be 11.25 +- 0.21(random) +- 0.85(systematic) Gyr assuming [Fe/H]=-0.70, [alpha/Fe]=0.4, and Y=0.255. The determination of the distance to V69, and hence to 47Tuc, can be further improved when infrared eclipse photometry is obtained for the variable.Comment: 49 pages, 15 figures, submitted to A

A Homogenous Set of Globular Cluster Relative Distances and Reddenings

We present distance modulus and reddening determinations for 72 Galactic globular clusters from the homogeneous photometric database of Piotto et al. (2002), calibrated to the HST flight F439W and F555W bands. The distances have been determined by comparison with theoretical absolute magnitudes of the ZAHB. For low and intermediate metallicity clusters, we have estimated the apparent Zero Age Horizontal Branch (ZAHB) magnitude from the RR Lyrae level. For metal rich clusters, the ZAHB magnitude was obtained from the fainter envelope of the red HB. Reddenings have been estimated by comparison of the HST colour-magnitude diagrams (CMD) with ground CMDs of low reddening template clusters. The homogeneity of both the photometric data and the adopted methodological approach allowed us to obtain highly accurate relative cluster distances and reddenings. Our results are also compared with recent compilations in the literature.Comment: 12 pages, 6 figures, accepted for publication in Astronomy & Astrophysic

A Study of the B-V Colour Temperature Relation

We attempt to construct a B-V colour temperature relation for stars in the least model dependent way employing the best modern data. The fit we obtained with the form Teff = Teff((B-V)0,[Fe/H],log g) is well constrained and a number of tests show the consistency of the procedures for the fit. Our relation covers from F0 to K5 stars with metallicity [Fe/H] = -1.5 to +0.3 for both dwarfs and giants. The residual of the fit is 66 K, which is consistent with what are expected from the quality of the present data. Metallicity and surface gravity effects are well separated from the colour dependence. Dwarfs and giants match well in a single family of fit, differing only in log g. The fit also detects the Galactic extinction correction for nearby stars with the amount E(B-V) = 0.26 +/-0.03 mag/kpc. Taking the newly obtained relation as a reference we examine a number of B-V colour temperature relations and atmosphere models available in the literature. We show the presence of a systematic error in the colour temperature relation from synthetic calculations of model atmospheres; the systematic error across K0 to K5 dwarfs is 0.04-0.05 mag in B-V, which means 0.25-0.3 mag in Mv for the K star range. We also argue for the error in the temperature scale used in currently popular stellar population synthesis models; synthetic colours from these models are somewhat too blue for aged elliptical galaxies. We derive the colour index of the sun (B-V)sun = 0.627 +/-0.018, and discuss that redder colours (e.g., 0.66-0.67) often quoted in the literature are incompatible with the colour-temperature relation.Comment: AASLaTeX (aaspp4.sty),36 pages (13 figures included), submitted to Astronomical Journal, replaced (typo in author name