2,103 research outputs found
The Effects of Drought on Foraging Habitat Selection of Breeding Wood Storks in Coastal Georgia
Foraging habitat use by Wood Storks (Mycteria americana) during the breeding season was studied for three coastal colonies during a drought year and compared to habitat use during normal rainfall years. Information on the distribution of wetland habitat types was derived using U.S. Fish and Wildlife Service National Wetland In- ventory (NWI) data within a Geographic Information System (GIS). Foraging locations were obtained by following storks from their colonies in a fixed-winged aircraft. Differences in hydrologic condition and, the resulting prey availability in coastal zone freshwater wetlands greatly affected foraging habitat use and breeding success of the three stork colonies. In 1997 (dry), although the foraging range of each colony did not differ from wetter years, storks used estuarine foraging habitats much more extensively. Breeding success (fledged young/nest) in 1997 was less than half the success of the wetter years. Palustrine (freshwater) wetlands seem very important to storks breed- ing along the Georgia coast. During dry years, estuarine wetlands, by themselves, do not appear to be able to support the breeding population of storks in this region. Reasons why these productive wetlands do not provide sufficient resources for successful breeding are unclear, but could include limitations to only two foraging periods (low tides) in a 24-hr period
The Effects of Drought on Foraging Habitat Selection of Breeding Wood Storks in Coastal Georgia
Foraging habitat use by Wood Storks (Mycteria americana) during the breeding season was studied for three coastal colonies during a drought year and compared to habitat use during normal rainfall years. Information on the distribution of wetland habitat types was derived using U.S. Fish and Wildlife Service National Wetland In- ventory (NWI) data within a Geographic Information System (GIS). Foraging locations were obtained by following storks from their colonies in a fixed-winged aircraft. Differences in hydrologic condition and, the resulting prey availability in coastal zone freshwater wetlands greatly affected foraging habitat use and breeding success of the three stork colonies. In 1997 (dry), although the foraging range of each colony did not differ from wetter years, storks used estuarine foraging habitats much more extensively. Breeding success (fledged young/nest) in 1997 was less than half the success of the wetter years. Palustrine (freshwater) wetlands seem very important to storks breed- ing along the Georgia coast. During dry years, estuarine wetlands, by themselves, do not appear to be able to support the breeding population of storks in this region. Reasons why these productive wetlands do not provide sufficient resources for successful breeding are unclear, but could include limitations to only two foraging periods (low tides) in a 24-hr period
A Millisecond Interferometric Search for Fast Radio Bursts with the Very Large Array
We report on the first millisecond timescale radio interferometric search for
the new class of transient known as fast radio bursts (FRBs). We used the Very
Large Array (VLA) for a 166-hour, millisecond imaging campaign to detect and
precisely localize an FRB. We observed at 1.4 GHz and produced visibilities
with 5 ms time resolution over 256 MHz of bandwidth. Dedispersed images were
searched for transients with dispersion measures from 0 to 3000 pc/cm3. No
transients were detected in observations of high Galactic latitude fields taken
from September 2013 though October 2014. Observations of a known pulsar show
that images typically had a thermal-noise limited sensitivity of 120 mJy/beam
(8 sigma; Stokes I) in 5 ms and could detect and localize transients over a
wide field of view. Our nondetection limits the FRB rate to less than
7e4/sky/day (95% confidence) above a fluence limit of 1.2 Jy-ms. Assuming a
Euclidean flux distribution, the VLA rate limit is inconsistent with the
published rate of Thornton et al. We recalculate previously published rates
with a homogeneous consideration of the effects of primary beam attenuation,
dispersion, pulse width, and sky brightness. This revises the FRB rate downward
and shows that the VLA observations had a roughly 60% chance of detecting a
typical FRB and that a 95% confidence constraint would require roughly 500
hours of similar VLA observing. Our survey also limits the repetition rate of
an FRB to 2 times less than any known repeating millisecond radio transient.Comment: Submitted to ApJ. 13 pages, 9 figure
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MOLES3: implementing an ISO standards driven data catalogue
ISO19156 Observations and Measurements (O&M) provides a standardised framework for
organising information about the collection of information about the environment. Here
we describe the implementation of a specialisation of O&M for environmental data, the
Metadata Objects for Linking Environmental Sciences (MOLES3).
MOLES3 provides support for organising information about data, and for user navigation
around data holdings. The implementation described here, âCEDA-MOLESâ, also supports
data management functions for the Centre for Environmental Data Archival, CEDA.
The previous iteration of MOLES (MOLES2) saw active use over five years, being replaced
by CEDA-MOLES in late 2014. During that period important lessons were learnt
both about the information needed, as well as how to design and maintain the necessary
information systems. In this paper we review the problems encountered in MOLES2; how
and why CEDA-MOLES was developed and engineered; the migration of information
holdings from MOLES2 to CEDA-MOLES; and, finally, provide an early assessment of
MOLES3 (as implemented in CEDA-MOLES) and its limitations.
Key drivers for the MOLES3 development included the necessity for improved data provenance,
for further structured information to support ISO19115 discovery metadata export
(for EU INSPIRE compliance), and to provide appropriate fixed landing pages for Digital
Object Identifiers (DOIs) in the presence of evolving datasets. Key lessons learned
included the importance of minimising information structure in free text fields, and the
necessity to support as much agility in the information infrastructure as possible without
compromising on maintainability both by those using the systems internally and externally
(e.g. citing in to the information infrastructure), and those responsible for the systems
themselves. The migration itself needed to ensure continuity of service and traceability of
archived assets
Trophic dynamics of U, Ni, Hg and other contaminants of potential concern on the Department of Energyâs Savannah River Site
The Department of Energyâs Savannah River Site is a former nuclear weapon material production and current research facility located in South Carolina, USA. Wastewater discharges from a fuel and nuclear reactor target manufacturing facility released depleted and natural U, as well as other metals into the Tims Branch- Steed Pond water system. We investigated the current dynamics of this system for the purposes of environmental monitoring and assessment by examining metal concentrations, bioavailability, and trophic transfer of contaminants in seven ponds. Biofilm, detritus, and Anuran and Anisopteran larvae were collected and analyzed for stable isotopes (ÎŽ15N, ÎŽ13C) and contaminants of potential concern (COPC) with a focus on Ni, U, and Hg, to examine metal mobility. Highest levels of Ni and U were found in biofilms U (147 and 332 mg kgâ1 DW, respectively), while highest Hg levels were found in tadpoles (1.1 mg kgâ1 DW). We found intraspecific biomagnification of COPCs as expressed through stable isotope analysis. Biofilms were the best indicators for contamination and Anuran larvae with the digestive tract removed were the best indicators of the specific bioavailability of the focal metals. Monitoring data showed that baseline ÎŽ15N values differed between ponds, but within a pond, values were stable throughout tadpole Gosner stage, strengthening the case to use this species for monitoring purposes. It is likely that there still is risk to ecosystem integrity as COPC metals are being assimilated into lower trophic organisms and even low levels of this mixture has shown to produce deleterious effects to some wildlife species
SKA Deep Polarization and Cosmic Magnetism
Deep surveys with the SKA1-MID array offer for the first time the opportunity
to systematically explore the polarization properties of the microJy source
population. Our knowledge of the polarized sky approaching these levels is
still very limited. In total intensity the population will be dominated by
star-forming and normal galaxies to intermediate redshifts (), and
low-luminosity AGN to high redshift. The polarized emission from these objects
is a powerful probe of their intrinsic magnetic fields and of their magnetic
environments. For redshift of order 1 and above the broad bandwidth of the
mid-bands span the Faraday thick and thin regimes allowing study of the
intrinsic polarization properties of these objects as well as depolarization
from embedded and foreground plasmas. The deep field polarization images will
provide Rotation Measures data with very high solid angle density allowing a
sensitive statistical analysis of the angular variation of RM on critical
arc-minute scales from a magnetic component of Large Scale Structure of the
Universe.Comment: 9 pages, 3 figures; to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)11
Pterodactyl: Trade Study for an Integrated Control System Design of a Mechanically Deployable Entry Vehicle
This paper presents the trade study method used to evaluate and downselect from a set of guidance and control (G&C) system designs for a mechanically Deployable Entry Vehicle (DEV). The Pterodactyl project was prompted by the challenge to develop an effective G&C system for a vehicle without a backshell, which is the case for DEVs. For the DEV, the project assumed a specific aeroshell geometry pertaining to an Adaptable, Deployable Entry and Placement Technology (ADEPT) vehicle, which was successfully developed by NASAs Space Technology Mission Directorate (STMD) prior to this study. The Pterodactyl project designed three different entry G&C systems for precision targeting. This paper details the Figures of Merit (FOMs) and metrics used during the course of the projects G&C system assessment. The relative importance of the FOMs was determined from the Analytic Hierarchy Process (AHP), which was used to develop weights that were combined with quantitative design metrics and engineering judgement to rank the G&C systems against one another. This systematic method takes into consideration the projects input while simultaneously reducing unintentional judgement bias and ultimately was used to select a single G&C design for the project to pursue in the next design phase
Elective affinities of the Protestant ethic : Weber and the chemistry of capitalism
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Validation of the GRAPE single view aerosol retrieval for ATSR-2 and insights into the long term global AOD trend over the ocean
The Global Retrieval of ATSR Cloud Parameters and Evaluation (GRAPE) project has produced a global data-set of cloud and aerosol properties from the Along Track Scanning Radiometer-2 (ATSR-2) instrument, covering the time period 1995Ăąïżœïżœ2001. This paper presents the validation of aerosol optical depths (AODs) over the ocean from this product against AERONET sun-photometer measurements, as well as a comparison to the Advanced Very High Resolution Radiometer (AVHRR) optical depth product produced by the Global Aerosol Climatology Project (GACP).
The GRAPE AOD over ocean is found to be in good agreement with AERONET measurements, with a Pearson's correlation coefficient of 0.79 and a best-fit slope of 1.0ñ0.1, but with a positive bias of 0.08ñ0.04. Although the GRAPE and GACP datasets show reasonable agreement, there are significant differences. These discrepancies are explored, and suggest that the downward trend in AOD reported by GACP may arise from changes in sampling due to the orbital drift of the AVHRR instruments
Development and exploitation of a controlled vocabulary in support of climate modelling
There are three key components for developing a metadata system: a container structure laying out the key semantic issues of interest and their relationships; an extensible controlled vocabulary providing possible content; and tools to create and manipulate that content. While metadata systems must allow users to enter their own information, the use of a controlled vocabulary both imposes consistency of definition and ensures comparability of the objects described. Here we describe the controlled vocabulary (CV) and metadata creation tool built by the METAFOR project for use in the context of describing the climate models, simulations and experiments of the fifth Coupled Model Intercomparison Project (CMIP5). The CV and resulting tool chain introduced here is designed for extensibility and reuse and should find applicability in many more projects
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