9,460 research outputs found
Modeling the effect of predicted sea-level rise on coastal conservation habitats using GIS
Global average temperatures have in
creased by about 0.6°C (± 0.2°C)
during the 20th century, and are project
ed to increase by 1.4 - 5.8°C by
2100 (IPCC, 2001a). The relationship
between atmospheric warming and
sea-level rise (SLR) is well understood,
and this change is predicted to lead
to SLR of up to 1m by 2100, cr
eating consequences for coastal
communities and environments
worldwide (IPCC, 2001b)
Dual-frequency GPS survey for validation of a regional DTM and for the generation of local DTM data for sea-level rise modelling in an estuarine salt marsh
Global average temperatures have risen by an average of 0.07°C per decade over the last
100 years, with a warming trend of 0.13°C per decade over the last 50 years.
Temperatures are predicted to rise by 2°C - 4.4°C by 2100 leading to global average sealevel
rise (SLR) of 2 – 6mm per year (20 – 60cms in total) up to 2100 (IPCC 2007) with
impacts for protected coastal habitats in Ireland.
Estuaries are predominantly sedimentary environments, and are characterised by shallow
coastal slope gradients, making them sensitive to even modest changes in sea-level. The
Shannon estuary is the largest river estuary in Ireland and is designated as a Special Area
of Conservation (SAC) under the EU Habitats Directive (EU 1992) providing protection
for listed habitats within it, including estuarine salt marsh.
Trends in Shannon estuary tidal data from 1877 – 2004 suggest an average upward SLR
trend of 4 - 5mm/yr over this period. A simple linear extension of this historical trend
would imply that local SLR will be in the region of 40 - 45cm by 2100. However, this
may underestimate actual SLR for the estuary by 2100, since it takes no account of
predicted climate-driven global SLR acceleration (IPCC 2007) up to 2100
The Kinematic Composition of MgII Absorbers
The study of galaxy evolution using quasar absorption lines requires an
understanding of what components of galaxies and their surroundings are
contributing to the absorption in various transitions. This paper considers the
kinematic composition of the class of 0.4 < z < 1.0 MgII absorbers,
particularly addressing the question of what fraction of this absorption is
produced in halos and what fraction arises from galaxy disks. We design models
with various fractional contributions from radial infall of halo material and
from a rotating thick disk component. We generate synthetic spectra from lines
of sight through model galaxies and compare the resulting ensembles of MgII
profiles with the 0.4 < z < 1.0 sample observed with HIRES/Keck. We apply a
battery of statistical tests and find that pure disk and pure halo models can
be ruled out, but that various models with rotating disk and infall/halo
contributions can produce an ensemble that is nearly consistent with the data.
A discrepancy in all models that we considered requires the existence of a
kinematic component intermediate between halo and thick disk. The variety of
MgII profiles can be explained by the gas in disks and halos of galaxies not
very much different than galaxies in the local Universe.
In any one case there is considerable ambiguity in diagnosing the kinematic
composition of an absorber from the low ionization high resolution spectra
alone. Future data will allow galaxy morphologies, impact parameters, and
orientations, FeII/MgII of clouds, and the distribution of high ionization gas
to be incorporated into the kinematic analysis. Combining all these data will
permit a more accurate diagnosis of the physical conditions along the line of
sight through the absorbing galaxy.Comment: 34 pages including 14 postscript figures; Accepted by the
Astrophysical Journal; URL http://www.astro.psu.edu/users/cwc/pubs.htm
Numerical analysis of suction embedded plate anchors in structured clay
As offshore energy developments move towards deeper water, moored floating production facilities are increasingly preferred to fixed structures. Anchoring systems are therefore of great interest to engineers working on deep water developments. Suction embedded plate anchors (SEPLAs) are rapidly becoming a popular solution, possessing a more accurate and predictable installation process compared to traditional alternatives. In this paper, finite element analysis has been conducted to evaluate the ultimate pullout capacity of SEPLAs in a range of post-keying configurations. Previous numerical studies of anchor pullout capacity have generally treated the soil as an elastic-perfectly plastic medium. However, the mechanical behaviour of natural clays is affected by inter-particle bonding, or structure, which cannot be accounted for using simple elasto-plastic models. Here, an advanced constitutive model formulated within the kinematic hardening framework is used to accurately predict the degradation of structure as an anchor embedded in a natural soft clay deposit is loaded to its pullout capacity. In comparison with an idealised, non-softening clay, the degradation of clay structure due to plastic strains in the soil mass results in a lower pullout capacity factor, a quantity commonly used in design, and a more complex load–displacement relationship. It can be concluded that clay structure has an important effect on the pullout behaviour of plate anchors.Peer ReviewedPostprint (author's final draft
Integrated waveguide and nanostructured sensor platform for surface-enhanced Raman spectroscopy
Limitations of current sensors include large dimensions, sometimes limited sensitivity and inherent single-parameter measurement capability. Surface-enhanced Raman spectroscopy can be utilized for environment and pharmaceutical applications with the intensity of the Raman scattering enhanced by a factor of 106. By fabricating and characterizing an integrated optical waveguide beneath a nanostructured precious metal coated surface a new surface-enhanced Raman spectroscopy sensing arrangement can be achieved. Nanostructured sensors can provide both multiparameter and high-resolution sensing. Using the slab waveguide core to interrogate the nanostructures at the base allows for the emission to reach discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Thin slab waveguide films of silicon oxynitride were etched and gold coated to create localized nanostructured sensing areas of various pitch, diameter, and shape. These were interrogated using a Ti:Sapphire laser tuned to 785-nm end coupled into the slab waveguide. The nanostructured sensors vertically projected a Raman signal, which was used to actively detect a thin layer of benzyl mercaptan attached to the sensors
The Elite Brain Drain
We collect data on the movement and productivity of elite scientists. Their mobility is remarkable: nearly half of the world's most-cited physicists work outside their country of birth. We show they migrate systematically towards nations with large R&D spending. Our study cannot adjudicate on whether migration improves scientists' productivity, but we find that movers and stayers have identical h-index citations scores. Immigrants in the UK and US now win Nobel Prizes proportionately less often than earlier. US residents' h-indexes are relatively high. We describe a framework where a key role is played by low mobility costs in the modern world.mobility, science, brain drain, citations
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