204 research outputs found
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Modelling the hydrological impacts of climate change on UK lowland wet grassland
Hydrological impacts of climate change upon the Elmley Marshes, southeast England, are simulated using a coupled hydrological/hydraulic model developed using MIKE SHE/MIKE 11 and calibrated to contemporary conditions. Predicted changes in precipitation, temperature, radiation and wind speed from the UK Climate Impacts Programme associated with four emissions scenarios for the 2050s are used to modify precipitation and potential evapotranspiration data. For each emissions scenario two sets of potential evapotranspiration data are derived, one using changes in temperature (PETtemp), the other incorporating changes in temperature, radiation and wind speed (PETtrws). Results indicate drier conditions through the progressively higher emissions scenarios when compared to contemporary conditions. Changes are particularly pronounced when using PETtrws. Summer water tables are lower (PETtemp 0.01�0.08 m; PETtrws 0.07�0.27 m) and the duration of high winter water tables is reduced. Although water tables still intercept the surface in winter when using PETtemp, this ceases when PETtrws is employed. Summer ditch water levels for the PETtemp scenarios are lower (0.01�0.21 m) and in dry winters they do not reach mean field level. Under the PETtrws scenarios summer and winter ditch water levels are lower by on average 0.21 and 0.30 m, respectively. Levels never reach the elevation of the marsh surface. Lower groundwater and ditch water levels result in declines in the magnitude and duration of surface inundation which is virtually eliminated with the PETtrws scenarios. The changes in hydrological conditions simulated by the model are of sufficiently fine resolution to infer ecological impacts which are likely to include the loss of some grassland species adapted to high water tables. Reductions in the extent of surface water in spring, especially for the PETtrws scenarios, are likely to reduce suitability for wading birds including lapwing (Vanellus vanellus) and redshank (Tringa totanus) for which the marshes are internationally renowned
Dissipation-assisted quantum gates with cold trapped ions
It is shown that a two-qubit phase gate and SWAP operation between ground
states of cold trapped ions can be realised in one step by simultaneously
applying two laser fields. Cooling during gate operations is possible without
perturbing the computation and the scheme does not require a second ion species
for sympathetic cooling. On the contrary, the cooling lasers even stabilise the
desired time evolution of the system. This affords gate operation times of
nearly the same order of magnitude as the inverse coupling constant of the ions
to a common vibrational mode.Comment: 4 pages, 5 figures, substantially revised versio
New Constraints on the Complex Mass Substructure in Abell 1689 from Gravitational Flexion
In a recent publication, the flexion aperture mass statistic was found to
provide a robust and effective method by which substructure in galaxy clusters
might be mapped. Moreover, we suggested that the masses and mass profile of
structures might be constrained using this method. In this paper, we apply the
flexion aperture mass technique to HST ACS images of Abell 1689. We demonstrate
that the flexion aperture mass statistic is sensitive to small-scale structures
in the central region of the cluster. While the central potential is not
constrained by our method, due largely to missing data in the central
0.5 of the cluster, we are able to place constraints on the masses and
mass profiles of prominent substructures. We identify 4 separate mass peaks,
and use the peak aperture mass signal and zero signal radius in each case to
constrain the masses and mass profiles of these substructures. The three most
massive peaks exhibit complex small-scale structure, and the masses indicated
by the flexion aperture mass statistic suggest that these three peaks represent
the dominant substructure component of the cluster (). Their complex structure indicates that the cluster --
far from being relaxed -- may have recently undergone a merger. The smaller,
subsidiary peak is located coincident with a group of galaxies within the
cluster, with mass . These results are in
excellent agreement with previous substructure studies of this cluster.Comment: 18 pages, 10 figures, MNRAS accepted (7 Dec 2010
Stability of Repulsive Bose-Einstein Condensates in a Periodic Potential
The cubic nonlinear Schr\"odinger equation with repulsive nonlinearity and an
elliptic function potential models a quasi-one-dimensional repulsive dilute gas
Bose-Einstein condensate trapped in a standing light wave. New families of
stationary solutions are presented. Some of these solutions have neither an
analog in the linear Schr\"odinger equation nor in the integrable nonlinear
Schr\"odinger equation. Their stability is examined using analytic and
numerical methods. All trivial-phase stable solutions are deformations of the
ground state of the linear Schr\"odinger equation. Our results show that a
large number of condensed atoms is sufficient to form a stable, periodic
condensate. Physically, this implies stability of states near the Thomas-Fermi
limit.Comment: 12 pages, 17 figure
The Health Impact Fund: How Might It Work for Novel Anticoagulants in Atrial Fibrillation?
Cardiovascular diseases represent the greatest burden of global disease. Spending on cardiovascular diseases is
higher than for other diseases, with the majority being spent on drugs. Therefore, these drugs and these
diseases are hugely important to health systems, society, and pharmaceutical companies. The Health Impact Fund represents a new mechanism by which pharmaceutical innovators would be rewarded on the basis of the health impact of their new drugs. This review illustrates the concept of the Health Impact Fund using the example of novel anticoagulants for prevention of stroke and thromboembolism in atrial fibrillation. By considering existing data and the current situation for novel anticoagulants, we suggest that epidemiologic data and modeling techniques can be used to predict future trends in disease and the health impact of new drugs. The Health Impact Fund may offer potential benefits to pharmaceutical companies, patients, and governments and warrants proper investigation
Exposure to aircraft and road traffic noise and associations with heart disease and stroke in six European countries: a cross-sectional study
This work was supported by the Economic and Social Research Council (grant ES/F038763/1) with additional funding from the European Network for Noise and Health (ENNAH, EU FP7 grant number 226442)
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