290 research outputs found
Opportunities to utilize traditional phenological knowledge to support adaptive management of social-ecological systems vulnerable to changes in climate and fire regimes
The field of adaptive management has been embraced by researchers and managers in the United States as an approach to improve natural resource stewardship in the face of uncertainty and complex environmental problems. Integrating multiple knowledge sources and feedback mechanisms is an important step in this approach. Our objective is to contribute to the limited literature that describes the benefits of better integrating indigenous knowledge (IK) with other sources of knowledge in making adaptive-management decisions. Specifically, we advocate the integration of traditional phenological knowledge (TPK), a subset of IK, and highlight opportunities for this knowledge to support policy and practice of adaptive management with reference to policy and practice of adapting to uncharacteristic fire regimes and climate change in the western United States
Exposure to Novel Parainfluenza Virus and Clinical Relevance in 2 Bottlenose Dolphin (Tursiops truncatus) Populations
Evidence of PIV exposure was detected in free-ranging and managed dolphin populations living along 2 US coastlines
The planetary system host HR\,8799: On its Bootis nature
HR\,8799 is a Bootis, Doradus star hosting a planetary
system and a debris disk with two rings. This makes this system a very
interesting target for asteroseismic studies. This work is devoted to the
determination of the internal metallicity of this star, linked with its
Bootis nature (i.e., solar surface abundances of light elements, and
subsolar surface abundances of heavy elements), taking advantage of its
Doradus pulsations. This is the most accurate way to obtain this
information, and this is the first time such a study is performed for a
planetary-system-host star. We have used the equilibrium code CESAM and the
non-adiabatic pulsational code GraCo. We have applied the Frequency Ratio
Method (FRM) and the Time Dependent Convection theory (TDC) to estimate the
mode identification, the Brunt-Va\"is\"al\"a frequency integral and the mode
instability, making the selection of the possible models. When the
non-seismological constraints (i.e its position in the HR diagram) are used,
the solar abundance models are discarded. This result contradicts one of the
main hypothesis for explaining the Bootis nature, namely the
accretion/diffusion of gas by a star with solar abundance. Therefore, according
to these results, a revision of this hypothesis is needed. The inclusion of
accurate internal chemical mixing processes seems to be necessary to explain
the peculiar abundances observed in the surface of stars with internal subsolar
metallicities. The use of the asteroseismological constraints, like those
provided by the FRM or the instability analysis, provides a very accurate
determination of the physical characteristics of HR 8799. However, a dependence
of the results on the inclination angle still remains. The determination of
this angle, more accurate multicolour photometric observations, and high
resolution spectroscopy can definitively fix the mass and metallicity of this
star.Comment: 11 pages, 10 figures. Accepted for publication in MNRA
Abundance analysis of prime B-type targets for asteroseismology I. Nitrogen excess in slowly-rotating beta Cephei stars
We present the results of a detailed NLTE abundance study of nine beta Cephei
stars, all of them being prime targets for theoretical modelling: gamma Peg,
delta Cet, nu Eri, beta CMa, xi1 CMa, V836 Cen, V2052 Oph, beta Cep and DD (12)
Lac. The following chemical elements are considered: He, C, N, O, Mg, Al, Si, S
and Fe. Our abundance analysis is based on a large number of time-resolved,
high-resolution optical spectra covering in most cases the entire oscillation
cycle of the stars. Nitrogen is found to be enhanced by up to 0.6 dex in four
stars, three of which have severe constraints on their equatorial rotational
velocity, \Omega R, from seismic or line-profile variation studies: beta Cep
(\Omega R~26 km/s), V2052 Oph (\Omega R~56 km/s), delta Cet (\Omega R < 28
km/s) and xi1 CMa (\Omega R sin i < 10 km/s). The existence of core-processed
material at the surface of such largely unevolved, slowly-rotating objects is
not predicted by current evolutionary models including rotation. We draw
attention to the fact that three stars in this subsample have a detected
magnetic field and briefly discuss recent theoretical work pointing to the
occurrence of diffusion effects in beta Cephei stars possibly capable of
altering the nitrogen surface abundance. On the other hand, the abundances of
all the other chemical elements considered are, within the errors,
indistinguishable from the values found for OB dwarfs in the solar
neighbourhood. Despite the mild nitrogen excess observed in some objects, we
thus find no evidence for a significantly higher photospheric metal content in
the studied beta Cephei stars compared to non-pulsating B-type stars of similar
characteristics.Comment: Accepted for publication in A&A, 21 pages, 7 figure
Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope
SS433, located at the center of the supernova remnant W50, is a close
proximity binary system consisting of a compact star and a normal star. Jets of
material are directed outwards from the vicinity of the compact star
symmetrically to the east and west. Non-thermal hard X-ray emission is detected
from lobes lying on both sides. Shock accelerated electrons are expected to
generate sub-TeV gamma rays through the inverse-Compton process in the lobes.
Observations of the western X-ray lobe region of SS433/W50 system have been
performed to detect sub-TeV gamma-rays using the 10m CANGAROO-II telescope in
August and September, 2001, and July and September, 2002. The total observation
times are 85.2 hours for ON source, and 80.8 hours for OFF source data. No
significant excess of sub-TeV gamma rays has been found at 3 regions of the
western X-ray lobe of SS433/W50 system. We have derived 99% confidence level
upper limits to the fluxes of gamma rays and have set constraints on the
strengths of the magnetic fields assuming the synchrotron/inverse-Compton model
for the wide energy range of photon spectrum from radio to TeV. The derived
lower limits are 4.3 microgauss for the center of the brightest X-ray emission
region and 6.3 microgauss for the far end from SS433 in the western X-ray lobe.
In addition, we suggest that the spot-like X-ray emission may provide a major
contribution to the hardest X-ray spectrum in the lobe.Comment: 7 pages, 8 figures, to be published in Astroparticle Physic
Identification of metal-poor stars using the artificial neural network
Context. Identification of metal-poor stars among field stars is
extremely useful for studying the structure and evolution of the Galaxy and of external
galaxies.
Aims. We search for metal-poor stars using the artificial neural network
(ANN) and extend its usage to determine absolute magnitudes.
Methods. We have constructed a library of 167 medium-resolution stellar
spectra (R ~ 1200) covering the stellar temperature range of 4200 to
8000 K, log g range of 0.5 to 5.0, and [Fe/H] range of −3.0 to +0.3 dex.
This empirical spectral library was used to train ANNs, yielding an accuracy of 0.3 dex in
[Fe/H] , 200 K in temperature, and 0.3 dex in log g. We found that the
independent calibrations of near-solar metallicity stars and metal-poor stars decreases
the errors in Teff and log g by nearly a
factor of two.
Results. We calculated Teff, log
g, and [Fe/H] on a consistent scale for a large number of field stars
and candidate metal-poor stars. We extended the application of this method to the
calibration of absolute magnitudes using nearby stars with well-estimated parallaxes. A
better calibration accuracy for MV could be
obtained by training separate ANNs for cool, warm, and metal-poor stars. The current
accuracy of MV calibration is ±0.3 mag.
Conclusions. A list of newly identified metal-poor stars is presented.
The MV calibration procedure developed here
is reddening-independent and hence may serve as a powerful tool in studying galactic
structure
The R-Process Alliance: Discovery of a Low-α, r-process-enhanced Metal-poor Star in the Galactic Halo
A new moderately r-process-enhanced metal-poor star, RAVE J093730.5−062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937−0626 is likely a horizontal branch star. At [Fe/H] = −1.86, J0937−0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ~0.6 dex excess of Fe; J0937−0626 is therefore similar to the subclass of "iron-enhanced" metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = −2.5 suggests that J0937−0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937−0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937−0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937−0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment
Contemporary contestations over working time: time for health to weigh in
Non-communicable disease (NCD) incidence and prevalence is of central concern to most nations, along with international agencies such as the UN, OECD, IMF and World Bank. As a result, the search has begun for ‘causes of the cause’ behind health risks and behaviours responsible for the major NCDs. As part of this effort, researchers are turning their attention to charting the temporal nature of societal changes that might be associated with the rapid rise in NCDs. From this, the experience of time and its allocation are increasingly understood to be key individual and societal resources for health (7–9). The interdisciplinary study outlined in this paper will produce a systematic analysis of the behavioural health dimensions, or ‘health time economies’ (quantity and quality of time necessary for the practice of health behaviours), that have accompanied labour market transitions of the last 30 years - the period in which so many NCDs have risen sharply
Water Contamination Reduces the Tolerance of Coral Larvae to Thermal Stress
Coral reefs are highly susceptible to climate change, with elevated sea surface temperatures (SST) posing one of the main threats to coral survival. Successful recruitment of new colonies is important for the recovery of degraded reefs following mortality events. Coral larvae require relatively uncontaminated substratum on which to metamorphose into sessile polyps, and the increasing pollution of coastal waters therefore constitutes an additional threat to reef resilience. Here we develop and analyse a model of larval metamorphosis success for two common coral species to quantify the interactive effects of water pollution (copper contamination) and SST. We identify thresholds of temperature and pollution that prevent larval metamorphosis, and evaluate synergistic interactions between these stressors. Our analyses show that halving the concentration of Cu can protect corals from the negative effects of a 2–3°C increase in SST. These results demonstrate that effective mitigation of local impacts can reduce negative effects of global stressors
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