378 research outputs found
Nuclear Tracks from Cold Dark Matter Interactions in Mineral Crystals: A Computational Study
Recoiling nuclei from Cold Dark Matter (CDM) elastic scattering interactions
with the constituent elements of some minerals may produce etchable damage
tracks in the crystal structure. Present calculations show that in muscovite
mica, CDM tracks from recoiling potassium atoms could be readily distinguished
from others due to alpha-decays in the uranium and thorium chains. Under
favorable conditions, this technique could greatly improve the existing limits
on Weakly Interacting Massive Particles as the constituents of the galactic
halo.Comment: PostScript, 15 pages, 3 figure
Simulating Turbulence Using the Astrophysical Discontinuous Galerkin Code TENET
In astrophysics, the two main methods traditionally in use for solving the
Euler equations of ideal fluid dynamics are smoothed particle hydrodynamics and
finite volume discretization on a stationary mesh. However, the goal to
efficiently make use of future exascale machines with their ever higher degree
of parallel concurrency motivates the search for more efficient and more
accurate techniques for computing hydrodynamics. Discontinuous Galerkin (DG)
methods represent a promising class of methods in this regard, as they can be
straightforwardly extended to arbitrarily high order while requiring only small
stencils. Especially for applications involving comparatively smooth problems,
higher-order approaches promise significant gains in computational speed for
reaching a desired target accuracy. Here, we introduce our new astrophysical DG
code TENET designed for applications in cosmology, and discuss our first
results for 3D simulations of subsonic turbulence. We show that our new DG
implementation provides accurate results for subsonic turbulence, at
considerably reduced computational cost compared with traditional finite volume
methods. In particular, we find that DG needs about 1.8 times fewer degrees of
freedom to achieve the same accuracy and at the same time is more than 1.5
times faster, confirming its substantial promise for astrophysical
applications.Comment: 21 pages, 7 figures, to appear in Proceedings of the SPPEXA
symposium, Lecture Notes in Computational Science and Engineering (LNCSE),
Springe
Evaluating the real-life effect of MP-AzeFlu on asthma outcomes in patients with allergic rhinitis and asthma in UK primary care
This study was supported by funding from BGP Products Operations GmbH (A MylanCompany). BGP Products Operations GmbH was given the opportunity to review the manuscript for medical and scientific accuracy as well as for intellectual property considerations. The dataset supporting the conclusions of this article was derived from the Optimum Patient Care Research Database (www.opcrd.co.uk). The OPCRD has ethical approval from the National Health Service (NHS) Research Authority to hold and process anonymized research data (Research Ethics Committee reference: 15/EM/0150). This study was approved by the Anonymized Data Ethics Protocols and Transparency (ADEPT) committee â the independent scientific advisory committee for the OPCRD. The authors do not have permission to give public access to the study dataset; researchers may request access to OPCRD data for their own purposes. Access to OCPRD can be made via the OCPRD website (https://opcrd.co.uk/our-database/data-requests/) or via the enquiries email [email protected] reviewedPublisher PD
A closer look at the uncertainty relation of position and momentum
We consider particles prepared by the von Neumann-L\"uders projection. For
those particles the standard deviation of the momentum is discussed. We show
that infinite standard deviations are not exceptions but rather typical. A
necessary and sufficient condition for finite standard deviations is given.
Finally, a new uncertainty relation is derived and it is shown that the latter
cannot be improved.Comment: 3 pages, introduction shortened, content unchange
Muon Track Reconstruction and Data Selection Techniques in AMANDA
The Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy
neutrino telescope operating at the geographic South Pole. It is a lattice of
photo-multiplier tubes buried deep in the polar ice between 1500m and 2000m.
The primary goal of this detector is to discover astrophysical sources of high
energy neutrinos. A high-energy muon neutrino coming through the earth from the
Northern Hemisphere can be identified by the secondary muon moving upward
through the detector. The muon tracks are reconstructed with a maximum
likelihood method. It models the arrival times and amplitudes of Cherenkov
photons registered by the photo-multipliers. This paper describes the different
methods of reconstruction, which have been successfully implemented within
AMANDA. Strategies for optimizing the reconstruction performance and rejecting
background are presented. For a typical analysis procedure the direction of
tracks are reconstructed with about 2 degree accuracy.Comment: 40 pages, 16 Postscript figures, uses elsart.st
Results from the Antarctic Muon and Neutrino Detector Array (AMANDA)
We show new results from both the older and newer incarnations of AMANDA
(AMANDA-B10 and AMANDA-II, respectively). These results demonstrate that AMANDA
is a functioning, multipurpose detector with significant physics and
astrophysics reach. They include a new higher-statistics measurement of the
atmospheric muon neutrino flux and preliminary results from searches for a
variety of sources of ultrahigh energy neutrinos: generic point sources,
gamma-ray bursters and diffuse sources producing muons in the detector, and
diffuse sources producing electromagnetic or hadronic showers in or near the
detector.Comment: Invited talk at the XXth International Conference on Neutrino Physics
and Astrophysics (Neutrino 2002), Munich, Germany, May 25-30, 200
IceCube - the next generation neutrino telescope at the South Pole
IceCube is a large neutrino telescope of the next generation to be
constructed in the Antarctic Ice Sheet near the South Pole. We present the
conceptual design and the sensitivity of the IceCube detector to predicted
fluxes of neutrinos, both atmospheric and extra-terrestrial. A complete
simulation of the detector design has been used to study the detector's
capability to search for neutrinos from sources such as active galaxies, and
gamma-ray bursts.Comment: 8 pages, to be published with the proceedings of the XXth
International Conference on Neutrino Physics and Astrophysics, Munich 200
Gravitational radiation from gamma-ray bursts as observational opportunities for LIGO and VIRGO
Gamma-ray bursts are believed to originate in core-collapse of massive stars.
This produces an active nucleus containing a rapidly rotating Kerr black hole
surrounded by a uniformly magnetized torus represented by two counter-oriented
current rings. We quantify black hole spin-interactions with the torus and
charged particles along open magnetic flux-tubes subtended by the event
horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of
frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with
GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii)
aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich
et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al.
2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating
LIGO/Virgo detectors enables searches for nearby events and their spectral
closure density 6e-9 around 250Hz in the stochastic background radiation in
gravitational waves. At current sensitivity, LIGO-Hanford may place an upper
bound around 150MSolar in GRB030329. Detection of Egw thus provides a method
for identifying Kerr black holes by calorimetry.Comment: to appear in PRD, 49
Sensitivity of the IceCube Detector to Astrophysical Sources of High Energy Muon Neutrinos
We present the results of a Monte-Carlo study of the sensitivity of the
planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV
energies. A complete simulation of the detector and data analysis is used to
study the detector's capability to search for muon neutrinos from sources such
as active galaxies and gamma-ray bursts. We study the effective area and the
angular resolution of the detector as a function of muon energy and angle of
incidence. We present detailed calculations of the sensitivity of the detector
to both diffuse and pointlike neutrino emissions, including an assessment of
the sensitivity to neutrinos detected in coincidence with gamma-ray burst
observations. After three years of datataking, IceCube will have been able to
detect a point source flux of E^2*dN/dE = 7*10^-9 cm^-2s^-1GeV at a 5-sigma
significance, or, in the absence of a signal, place a 90% c.l. limit at a level
E^2*dN/dE = 2*10^-9 cm^-2s^-1GeV. A diffuse E-2 flux would be detectable at a
minimum strength of E^2*dN/dE = 1*10^-8 cm^-2s^-1sr^-1GeV. A gamma-ray burst
model following the formulation of Waxman and Bahcall would result in a 5-sigma
effect after the observation of 200 bursts in coincidence with satellite
observations of the gamma-rays.Comment: 33 pages, 13 figures, 6 table
Projected impacts of increased uptake of source control mitigation measures on agricultural diffuse pollution emissions to water and air
The authors gratefully acknowledge the funding provided by Defra project LM0304; Phase 2 of the Avon Demonstration Test Catchment. The DTC farm survey data were collected in conjunction with the Avon (Defra project WQ0211), Wensum (Defra project WQ0212) and Eden (Defra project WQ02010) DTC programmes. The Environment Agency kindly provided access to national GIS layers. The authors thank the experts included in the elicitation exercise for current implementation of source control measures
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