6,388 research outputs found
Review of Conformally Flat Approximation for Binary Neutron Star Initial Conditions
The spatially conformally flat approximation (CFA) is a viable method to
deduce initial conditions for the subsequent evolution of binary neutron stars
employing the full Einstein equations. Here we review the status of the
original formulation of the CFA for the general relativistic hydrodynamic
initial conditions of binary neutron stars. We illustrate the stability of the
conformally flat condition on the hydrodynamics by numerically evolving ~100
quasi-circular orbits. We illustrate the use of this approximation for orbiting
neutron stars in the quasi-circular orbit approximation to demonstrate the
equation of state dependence of these initial conditions and how they might
affect the emergent gravitational wave frequency as the stars approach the
innermost stable circular orbit.Comment: 22 pages, 12 figures, revised as per referee recommendation
The spatial ecology of Mediterranean marine turtles: insights from stable isotope analysis, satellite telemetry, and environmental observations
Understanding the spatial and foraging ecology of marine migrants is challenging, due to the vast distances travelled and the numerous habitats occupied within a dynamic seascape. Mediterranean marine turtles migrate thousands of kilometers and face numerous threats, including bycatch, in their marine realm. To help inform targeted conservation, this complex marine ecology must be better understood. This thesis focuses on Mediterranean loggerhead (Caretta caretta) and green turtles (Chelonia mydas). By complementing stable isotope analysis (SIA), satellite telemetry, and environmental observations, this thesis aims to enhance our understanding of the complexities of marine turtle spatial and foraging ecology, as well as determine how future climate conditions may influence their habitat use. In Chapter 1, I introduce the importance of conserving marine migrants and discuss the current knowledge of marine turtle spatial and foraging ecology as well as threats faced, with particular emphasis on Mediterranean loggerhead and green turtles. By conducting an extensive review in Chapter 2, I demonstrate how SIA has been used to enhance our understanding of marine turtle ecology, as well as help inform conservation initiatives. I also highlight knowledge gaps (for example, bias in the species studied) and provide recommendations for future SIA studies (for example, following standardised protocols), and use this information to inform latter chapters. In Chapter 3, using SIA I highlight the ecological complexity of juvenile Mediterranean loggerhead turtles, demonstrating there are inter- and intra-population variations in ecology, and that region- and habitat-specific fisheries management is required. In Chapter 4, I identify the foraging grounds for two major Mediterranean loggerhead turtle populations, demonstrate foraging site fidelity over decades, show the proportion of females recruiting from each foraging region does not differ across the multi-decadal study, and suggest site-specific management would be beneficial. Finally, in Chapter 5, I show that migratory dive behaviours of loggerhead and green turtles are influenced by changes in environmental conditions (e.g. wave height and temperature) and that the species-specific migratory corridors used may be due to factors such as feeding preference and physiology, rather than species-specific environmental tolerances, suggesting dynamic and species-specific conservation is required. In Chapter 6, I summarise and discuss the findings from this thesis within the wider context. In conclusion, this thesis emphasises the complexities of marine turtle spatial ecology, shows that habitat use will likely differ under future climate scenarios, and suggests targeted and dynamic conservation is required for effective long term conservation
A simple formula for Bose-Einstein corrections
In analogy with the quantum field theory of free bosons a simple integral
representation is derived for recently proposed corrections describing the Bose
Einstein effect. The saddle point approximation to these integrals results in a
compact expression which sums effectively over all permutations of n particles
with accuracy better than 2 per cent for more than seven strongly correlated
bosons.Comment: 10 pages, LaTe
The Galactic disk mass-budget : II. Brown dwarf mass-function and density
In this paper, we extend the calculations conducted previously in the stellar
regime to determine the brown dwarf IMF in the Galactic disk. We perform Monte
Carlo calculations taking into account the brown dwarf formation rate, spatial
distribution and binary fraction. Comparison with existing surveys seems to
exclude a power-law MF as steep as the one determined in the stellar regime
below 1 \msol and tends to favor a more flatish behaviour. Comparison with
methane-dwarf detections tends to favor an eventually decreasing form like the
lognormal or the more general exponential distributions determined in the
previous paper. We calculate predicting brown dwarf counts in near-infrared
color diagrams and brown dwarf discovery functions. These calculations yield
the presently most accurate determination of the brown dwarf census in the
Galactic disk. The brown dwarf number density is comparable to the stellar one,
pc. The corresponding brown dwarf mass
density, however, represents only about 10% of the stellar contribution, i.e.
\rho_{BD}\simle 5.0\times 10^{-3} \mvol. Adding up the local stellar density
determined previously yields the density of star-like objects, stars and brown
dwarfs, in the solar neighborhood \rho_\odot \approx 5.0\times 10^{-2} \mvol.Comment: 39 pages, Latex file, uses aasms4.sty, to be published in ApJ,
corrected version with correct figure
Composting paper and grass clippings with anaerobically treated palm oil mill effluent
Purpose The purpose of this study is to investigate the composting performance of anaerobically treated palm oil mill effluent (AnPOME) mixed with paper and grass clippings. Methods Composting was conducted using a laboratory scale system for 40 days. Several parameters were determined: temperature, mass reduction, pH, electrical conductivity, colour, zeta potential, phytotoxicity and final compost nutrients. Results The moisture content and compost mass were reduced by 24 and 18 %, respectively. Both final compost pH value and electrical conductivity were found to increase in value. Colour (measured as PtCo) was not suitable as a maturity indicator. The negative zeta potential values decreased from â12.25 to â21.80 mV. The phytotoxicity of the compost mixture was found to decrease in value during the process and the final nutrient value of the compost indicates its suitability as a soil conditioner. Conclusions From this study, we conclude that the addition of paper and grass clippings can be a potential substrate to be composted with anaerobically treated palm oil mill effluent (AnPOME). The final compost produced is suitable for soil conditioner
An experimental synthetic aperture SONAR
Aperture synthesis is a mature technique that has been used with success in a number
of remote sensing fields. Sonars can also potentially benefit from the technique,
though to date the limitations of slow acoustic propagation and difficulty in
maintaining a stable platform has hindered investigation.
This thesis investigates aperture synthesis for high resolution underwater imaging. A
prototype sonar is designed and fabricated for the study. The performance of the sonar
is assessed in both tank and sea trials and the results presented in this thesis
A latest Cretaceous to earliest Paleogene dinoflagellate cyst zonation of Antarctica, and implications for phytoprovincialism in the high southern latitudes
The thickest uppermost Cretaceous to lowermost Paleogene (Maastrichtian to Danian) sedimentary succession in the world is exposed on southern Seymour Island (65° South) in the James Ross Basin, Antarctic Peninsula. This fossiliferous shallow marine sequence, which spans the CretaceousâPaleogene boundary, has allowed a high-resolution analysis of well-preserved marine palynomorphs. Previous correlation of CretaceousâPaleogene marine palynomorph assemblages in the south polar region relied on dinoflagellate cyst biozonations from New Zealand and southern Australia. The age model of the southern Seymour Island succession is refined and placed within the stratigraphical context of the mid to high southern palaeolatitudes. Quantitative palynological analysis of a new 1102 m continuous stratigraphical section comprising the uppermost Snow Hill Island Formation and the LĂłpez de Bertodano Formation (Marambio Group) across southern Seymour Island was undertaken. We propose the first formal late Maastrichtian to early Danian dinoflagellate cyst zonation scheme for the Antarctic based on this exceptional succession. Two new late Maastrichtian zones, including three subzones, and one new early Danian zone are defined. The oldest beds correlate well with the late Maastrichtian of New Zealand. In a wider context, a new South Polar Province based on Maastrichtian to Danian dinoflagellate cysts is proposed, which excludes most southern South American marine palynofloras. This interpretation is supported by models of ocean currents around Antarctica and implies an unrestricted oceanic connection across Antarctica between southern South America and the Tasman Sea
Saharan dust and biomass burning aerosols during ex-hurricane Ophelia: Observations from the new UK lidar and sun-photometer network
This is the final version. Available from European Geosciences Union (EGU) / Copernicus Publications via the DOI in this record.âŻOn 15-16 October 2017, ex-hurricane Ophelia passed to the west of the British Isles, bringing dust from the Sahara and smoke from Portuguese forest fires that was observable to the naked eye and reported in the UK's national press. We report here detailed observations of this event using the UK operational lidar and sun-photometer network, established for the early detection of aviation hazards, including volcanic ash. We also use ECMWF ERA5 wind field data and MODIS imagery to examine the aerosol transport. The observations, taken continuously over a period of 30 h, show a complex picture, dominated by several different aerosol layers at different times and clearly correlated with the passage of different air masses associated with the intense cyclonic system. A similar evolution was observed at several sites, with a time delay between them explained by their different location with respect to the storm and associated meteorological features. The event commenced with a shallow dust layer at 1-2 km in altitude and culminated in a deep and complex structure that lasted âŒ12 h at each site over the UK, correlated with the storm's warm sector. For most of the time, the aerosol detected was dominated by mineral dust mixtures, as highlighted by depolarisation measurements, but an intense biomass burning aerosol (BBA) layer was observed towards the end of the event, lasting around 3 h at each site. The aerosol optical depth at 355 nm (AOD355) during the whole event ranged from 0.2 to 2.9, with the larger AOD correlated to the intense BBA layer. Such a large AOD is unprecedented in the UK according to AERONET records for the last 20 years. The Raman lidars permitted the measurement of the aerosol extinction coefficient at 355 nm, the particle linear depolarisation ratio (PLDR), and the lidar ratio (LR) and made the separation of the dust (depolarising) aerosol from other aerosol types possible. A specific extinction has also been computed to provide an estimate of the atmospheric concentration of both aerosol types separately, which peaked at 420±200 ÎŒgm-3 for the dust and 558±232 ÎŒgm-3 for the biomass burning aerosols. Back trajectories computed using the Numerical Atmospheric-dispersion Modelling Environment (NAME) were used to identify the sources and strengthen the conclusions drawn from the observations. The UK network represents a significant expansion of the observing capability in northern Europe, with instruments evenly distributed across Great Britain, from Camborne in Cornwall to Lerwick in the Shetland Islands, and this study represents the first attempt to demonstrate its capability and validate the methods in use. Its ultimate purpose will be the detection and quantification of volcanic plumes, but the present study clearly demonstrates the advanced capabilities of the network.Natural Environment Research CouncilUniversity of Exete
Patient perspectives in geographic atrophy (GA) : exploratory qualitative research to understand the impact of GA for patients and their families
Background
Age-related macular degeneration (AMD) is the major cause of blindness for the older population in the developed world. Geographic atrophy (GA) is an advanced form of AMD. This progressive degenerative disease causes loss of visual function but unlike exudative AMD there are currently no approved therapeutic treatments for GA. Instead management of the condition is through supportive care. The aim of this study was to conduct exploratory qualitative research to develop a further understanding specifically of the impact of geographic atrophy (GA) on the quality of life for both patients and their families, and to explore the resources GA patients most frequently access.
Methods
Two focus groups were conducted where participants were assigned to âbetterâ or âworseâ group based upon their level of visual acuity. The data were analysed using the principles of thematic analysis. Transcripts were coded using an a priori framework. Emerging themes and subthemes were added, and transcripts recoded to reflect this. Transcripts were coded by one researcher, and the emerging themes and subthemes discussed and agreed prior to transcript recoding.
Results
Nine participants were recruited to the study (n=5 âbetter groupâ and n=4 âworse groupâ). Six overarching themes were identified. These are: experience of symptoms and understanding of GA; impact on activities; feelings and emotions; relationships and informal support; accessing formal support; and information needs.
Conclusion
Key findings indicated that: participants had little knowledge of the mechanisms of GA, but were aware of their prognosis; activities impacted by GA were management of daily activities and reading; emotions experienced included fear and frustration, and these frequently crossed over into their relationships with others; and access to formal support was mainly practical and information needs were largely unmet, with peer support being identified as important. Management of GA should include signposting to appropriate support agencies, such as low vision services and charities
The contrasting climate response to tropical and extratropical energy perturbations
This is the final version of the article. Available from Springer Verlag via the DOI in this record.The link between cross-equatorial energy transport, the double-intertropical convergence zone (DI) problem and biases in tropical and extratropical albedo and energy budgets in climate models have been investigated in multiple studies, though DI biases persist in many models. Here, a coupled climate model, HadGEM2-ES, is used to investigate the response to idealised energy perturbations in the tropics and extratropics, in both the northern and southern hemispheres, through the imposition of stratospheric aerosols that reflect incoming radiation. The impact on the tropical climate of high and low latitude forcing strongly contrasts, with large changes in tropical precipitation and modulation of the DI bias when the tropics are cooled as precipitation moves away from the cooled hemisphere. These responses are muted when the extratropics are cooled, as the meridional energy transport anomalies that are excited by these energy budget anomalies are partitioned between the atmosphere and ocean. The results here highlight the persistence of the DI bias in HadGEM2-ES, indicating why little progress has been made in rectifying these problems through many generations of climate models. A highly linear relationship between cross-equatorial atmospheric energy transport, tropical precipitation asymmetry and tropical sea surface temperature biases is also demonstrated, giving some suggestion as to where improvements in these large scale, persistent biases may be achieved.MKH, MC and JMH were supported by the Natural Environment Research Council/Department for International Development via the Future Climates for Africa (FCFA) funded project âImproving Model Processes for African Climateâ (IMPALA, NE/M017265/1). JMH and AJ were supported by the Joint UK BEIS/Defra Met Office Hadley Centre Climate Programme (GA01101)
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