977 research outputs found
The implications of a changing climate on agricultural land classification in England and Wales
The agricultural land classification (ALC) of England and Wales is a formal method of assessing the quality of agricultural land and guiding future land use. It assesses several soil, site and climate criteria and classifies land according to whichever is the most limiting. A common approach is required for calculating the necessary agroclimatic parameters over time in order to determine the effects of changes in the climate on land grading. In the present paper, climatic parameters required by the ALC classification have been re-calculated from a range of primary climate data, available from the Meteorological Office's UKCP09 historical dataset, provided as 5 km rasters for every month from 1914 to 2000. Thirty-year averages of the various agroclimatic properties were created for 1921–50, 1931–60, 1941–70, 1951–80, 1961–90 and 1971–2000. Soil records from the National Soil Inventory on a 5 km grid across England and Wales were used to determine the required soil and site parameters for determining ALC grade. Over the 80-year period it was shown that the overall climate was coolest during 1951–80. However, the area of land estimated in retrospect as ‘best and most versatile (BMV) land’ (Grades 1, 2 and 3a) probably peaked in the 1951–80 period as the cooler climate resulted in fewer droughty soils, more than offsetting the land which was downgraded by the climate being too cold. Overall there has been little change in the proportions of ALC grades among the six periods once all 10 factors (climate, gradient, flooding, texture, depth, stoniness, chemical, soil wetness, droughtiness and erosion) are taken into account. This is because it is rare for changes in climate variables all to point in the same direction in terms of ALC. Thus, a reduction in rainfall could result in higher grades in wetter areas but lead to lower classification in drier areas
Beyond the Bowen-York extrinsic curvature for spinning black holes
It is well-known that Bowen-York initial data contain spurious radiation.
Although this ``junk'' radiation has been seen to be small for non-spinning
black-hole binaries in circular orbit, its magnitude increases when the black
holes are given spin. It is possible to reduce the spurious radiation by
applying the puncture approach to multiple Kerr black holes, as we demonstrate
for examples of head-on collisions of equal-mass black-hole binaries.Comment: 10 pages, 2 figures, submitted to special "New Frontiers in Numerical
Relativity" issue of Classical and Quantum Gravit
Conformal thin-sandwich puncture initial data for boosted black holes
We apply the puncture approach to conformal thin-sandwich black-hole initial
data. We solve numerically the conformal thin-sandwich puncture (CTSP)
equations for a single black hole with non-zero linear momentum. We show that
conformally flat solutions for a boosted black hole have the same maximum
gravitational radiation content as the corresponding Bowen-York solution in the
conformal transverse-traceless decomposition. We find that the physical
properties of these data are independent of the free slicing parameter.Comment: 12 pages, 11 figure
Total recoil: the maximum kick from nonspinning black-hole binary inspiral
When unequal-mass black holes merge, the final black hole receives a ``kick''
due to the asymmetric loss of linear momentum in the gravitational radiation
emitted during the merger. The magnitude of this kick has important
astrophysical consequences. Recent breakthroughs in numerical relativity allow
us to perform the largest parameter study undertaken to date in numerical
simulations of binary black hole inspirals. We study non-spinning black-hole
binaries with mass ratios from to (
from 0.25 to 0.16). We accurately calculate the velocity of the kick to within
6%, and the final spin of the black holes to within 2%. A maximum kick of
km s is achieved for .Comment: 4 pages, 4 figures. Version accepted by PR
Supermassive recoil velocities for binary black-hole mergers with antialigned spins
Recent calculations of the recoil velocity in binary black hole mergers have
found the kick velocity to be of the order of a few hundred km/s in the case of
non-spinning binaries and about km/s in the case of spinning
configurations, and have lead to predictions of a maximum kick of up to km/s. We test these predictions and demonstrate that kick velocities of at
least km/s are possible for equal-mass binaries with anti-aligned spins
in the orbital plane. Kicks of that magnitude are likely to have significant
repercussions for models of black-hole formation, the population of
intergalactic black holes and the structure of host galaxies.Comment: Final version, published by Phys. Rev. Lett.; title changed according
to suggestion of PRL; note added after preparation of manuscrip
Exploring black hole superkicks
Recent calculations of the recoil velocity in black-hole binary mergers have
found kick velocities of km/s for equal-mass binaries with
anti-aligned initial spins in the orbital plane. In general the dynamics of
spinning black holes can be extremely complicated and are difficult to analyze
and understand. In contrast, the ``superkick'' configuration is an example with
a high degree of symmetry that also exhibits exciting physics. We exploit the
simplicity of this ``test case'' to study more closely the role of spin in
black-hole recoil and find that: the recoil is with good accuracy proportional
to the difference between the modes of , the major
contribution to the recoil occurs within before and after the merger, and
that this is after the time at which a standard post-Newtonian treatment breaks
down. We also discuss consequences of the asymmetry in the
gravitational wave signal for the angular dependence of the SNR and the
mismatch of the gravitational wave signals corresponding to the north and south
poles
An exploration of barriers and facilitators to older adults' participation in higher impact physical activity and bone health:a qualitative study
Where post-Newtonian and numerical-relativity waveforms meet
We analyze numerical-relativity (NR) waveforms that cover nine orbits (18
gravitational-wave cycles) before merger of an equal-mass system with low
eccentricity, with numerical uncertainties of 0.25 radians in the phase and
less than 2% in the amplitude; such accuracy allows a direct comparison with
post-Newtonian (PN) waveforms. We focus on one of the PN approximants that has
been proposed for use in gravitational-wave data analysis, the restricted 3.5PN
``TaylorT1'' waveforms, and compare these with a section of the numerical
waveform from the second to the eighth orbit, which is about one and a half
orbits before merger. This corresponds to a gravitational-wave frequency range
of to 0.1. Depending on the method of matching PN and NR
waveforms, the accumulated phase disagreement over this frequency range can be
within numerical uncertainty. Similar results are found in comparisons with an
alternative PN approximant, 3PN ``TaylorT3''. The amplitude disagreement, on
the other hand, is around 6%, but roughly constant for all 13 cycles that are
compared, suggesting that only 4.5 orbits need be simulated to match PN and NR
waves with the same accuracy as is possible with nine orbits. If, however, we
model the amplitude up to 2.5PN order, the amplitude disagreement is roughly
within numerical uncertainty up to about 11 cycles before merger.Comment: 14 pages, 18 figures. Modifications resulting from bug fixes in LAL,
and extended analysis of numerical errors and phase agreement with PN, now
including the 3PN TaylorT3 approximant. No change to main conclusion
An exploration of barriers and facilitators to older adults’ participation in higher impact physical activity and bone health:a qualitative study
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