956 research outputs found
The environmental context of the Neolithic monuments on the Brodgar Isthmus, Mainland, Orkney
This work was funded in part by Historic Environment Scotland.The World Heritage Sites of Orkney, Scotland contain iconic examples of Neolithic monumentality that have provided significant information about this period of British prehistory. However, currently, a complete understanding of the sites remains to be achieved. This is, in part, because the monuments lack an adequate context within the broader palaeolandscape. Recent investigations (seismic geophysical survey, microfossil analysis and 14C dating) in and around the Brodgar Isthmus, both onshore and offshore, are used to reconstruct the landscapes at a time when sea-level, climate and vegetation were different to that experienced today. Results show that in the early Neolithic the isthmus between the Ring of Brodgar and Stones of Stenness was broader with a smaller loch to the west. Furthermore this landscape contained sandstone outcrops that would have provided a potential source of stone for monument construction. Microfossil analysis and radiocarbon dates demonstrate that the Loch of Stenness was transformed from freshwater to brackish during the early Neolithic, perhaps immediately preceding construction of the major monuments. Finally, the analysis of our data suggests that sediment influx to the loch shows a tenfold increase coincident with widespread vegetation change that straddles the Mesolithic/Neolithic transition at c. 8 ka cal. B.P. These results provide, for the first time, a landscape context for the Neolithic sites on the isthmus.PostprintPeer reviewe
Semiconductor disk lasers: the future's bright; the colour's flexible
Presentation describing semiconductor disk lasers, their use and how they work
Dynamic Front Transitions and Spiral-Vortex Nucleation
This is a study of front dynamics in reaction diffusion systems near
Nonequilibrium Ising-Bloch bifurcations. We find that the relation between
front velocity and perturbative factors, such as external fields and curvature,
is typically multivalued. This unusual form allows small perturbations to
induce dynamic transitions between counter-propagating fronts and nucleate
spiral vortices. We use these findings to propose explanations for a few
numerical and experimental observations including spiral breakup driven by
advective fields, and spot splitting
Measurements of Scintillation Efficiency and Pulse-Shape for Low Energy Recoils in Liquid Xenon
Results of observations of low energy nuclear and electron recoil events in
liquid xenon scintillator detectors are given. The relative scintillation
efficiency for nuclear recoils is 0.22 +/- 0.01 in the recoil energy range 40
keV - 70 keV. Under the assumption of a single dominant decay component to the
scintillation pulse-shape the log-normal mean parameter T0 of the maximum
likelihood estimator of the decay time constant for 6 keV < Eee < 30 keV
nuclear recoil events is equal to 21.0 ns +/- 0.5 ns. It is observed that for
electron recoils T0 rises slowly with energy, having a value ~ 30 ns at Eee ~
15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by
single exponential functions although some evidence is found for a double
exponential form for the nuclear recoil pulse-shape.Comment: 11 pages, including 5 encapsulated postscript figure
Statistical Effects in the Multistream Model for Quantum Plasmas
A statistical multistream description of quantum plasmas is formulated, using
the Wigner-Poisson system as dynamical equations. A linear stability analysis
of this system is carried out, and it is shown that a Landau-like damping of
plane wave perturbations occurs due to the broadening of the background Wigner
function that arises as a consequence of statistical variations of the wave
function phase. The Landau-like damping is shown to suppress instabilities of
the one- and two-stream type.Comment: 5 page
Magnetic fields and Sunyaev-Zel'dovich effect in galaxy clusters
In this work we study the contribution of magnetic fields to the Sunyaev
Zeldovich (SZ) effect in the intracluster medium. In particular we calculate
the SZ angular power spectrum and the central temperature decrement. The effect
of magnetic fields is included in the hydrostatic equilibrium equation by
splitting the Lorentz force into two terms one being the force due to magnetic
pressure which acts outwards and the other being magnetic tension which acts
inwards. A perturbative approach is adopted to solve for the gas density
profile for weak magnetic fields (< 4 micro G}). This leads to an enhancement
of the gas density in the central regions for nearly radial magnetic field
configurations. Previous works had considered the force due to magnetic
pressure alone which is the case only for a special set of field
configurations. However, we see that there exists possible sets of
configurations of ICM magnetic fields where the force due to magnetic tension
will dominate. Subsequently, this effect is extrapolated for typical field
strengths (~ 10 micro G) and scaling arguments are used to estimate the angular
power due to secondary anisotropies at cluster scales. In particular we find
that it is possible to explain the excess power reported by CMB experiments
like CBI, BIMA, ACBAR at l > 2000 with sigma_8 ~ 0.8 (WMAP 5 year data) for
typical cluster magnetic fields. In addition we also see that the magnetic
field effect on the SZ temperature decrement is more pronounced for low mass
clusters ( ~ 2 keV). Future SZ detections of low mass clusters at few arc
second resolution will be able to probe this effect more precisely. Thus, it
will be instructive to explore the implications of this model in greater detail
in future works.Comment: 20 pages, 8 figure
Changing practices: The specialised domestic violence court process
Specialised domestic violence courts, initially developed in the United States of America, have been recognised by other jurisdictions including Canada, Australia and the United Kingdom. This article presents a case study of K Court in Toronto, drawing upon documentary evidence, direct observations and interviews with key informants. It is argued that the specialised domestic violence court process includes changing practices of some of the key stakeholders. Learning lessons from abroad can offer jurisdictions insights that can steer implementation of appropriate practices in the field
The ZEPLIN II dark matter detector: data acquisition system and data reduction
ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching
for WIMP-nucleon interactions. In this paper we describe the data acquisition
system used to record the data from ZEPLIN-II and the reduction procedures
which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure
Tradeoffs and synergies in wetland multifunctionality: A scaling issue
Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale
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