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Search Results: 1 - 10 of 325307 matches for " S. Paling "
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Converting a controlled vocabulary into an ontology: the case of GEM
Jian Qin,Stephen Paling
Information Research: an international electronic journal , 2001,
Abstract: The prevelance of digital information raised issues regarding the suitability of conventional library tools for organizing information. The multi-dimensionality of digital resources requires a more versatile and flexible representation to accommodate intelligent information representation and retrieval. Ontologies are used as a solution to such issues in many application domains, mainly due to their ability to explicitly specify the semantics and relations and to express them in a computer understandable language. Conventional knowledge organization tools such as classifications and thesauri resemble ontologies in a way that they define concepts and relationships in a systematic manner, but they are less expressive than ontologies when it comes to machine language. This paper used the controlled vocabulary at the Gateway to Educational Materials (GEM) as an example to address the issues in representing digital resouces. The theoretical and methodological framework in this paper serves as the rationale and guideline for converting the GEM controlled vocabulary into an ontology. Compared to the original semantic model of GEM controlled vocabulary, the major difference between the two models lies in the values added through deeper semantics in describing digital objects, both conceptually and relationally.
First measurement of low intensity fast neutron background from rock at the Boulby Underground Laboratory
E. Tziaferi,M. J. Carson,V. A. Kudryavtsev,R. Lerner,P. K. Lightfoot,S. M. Paling,M. Robinson,N. J. C. Spooner
Physics , 2006, DOI: 10.1016/j.astropartphys.2006.12.005
Abstract: A technique to measure low intensity fast neutron flux has been developed. The design, calibrations, procedure for data analysis and interpretation of the results are discussed in detail. The technique has been applied to measure the neutron background from rock at the Boulby Underground Laboratory, a site used for dark matter and other experiments, requiring shielding from cosmic ray muons. The experiment was performed using a liquid scintillation detector. A 6.1 litre volume stainless steel cell was filled with an in-house made liquid scintillator loaded with Gd to enhance neutron capture. A two-pulse signature (proton recoils followed by gammas from neutron capture) was used to identify the neutron events from much larger gamma background from PMTs. Suppression of gammas from the rock was achieved by surrounding the detector with high-purity lead and copper. Calibrations of the detector were performed with various gamma and neutron sources. Special care was taken to eliminate PMT afterpulses and correlated background events from the delayed coincidences of two pulses in the Bi-Po decay chain. A four month run revealed a neutron-induced event rate of 1.84 +- 0.65 (stat.) events/day. Monte Carlo simulations based on the GEANT4 toolkit were carried out to estimate the efficiency of the detector and the energy spectra of the expected proton recoils. From comparison of the measured rate with Monte Carlo simulations the flux of fast neutrons from rock was estimated as (1.72 +- 0.61 (stat.) +- 0.38 (syst.))*10^(-6) cm^(-2) s^(-1) above 0.5 MeV.
Simulation of muon radiography for monitoring CO$_2$ stored in a geological reservoir
J. Klinger,S. J. Clark,M. Coleman,J. G. Gluyas,V. A. Kudryavtsev,D. L. Lincoln,S. Pal,S. M. Paling,N. J. C. Spooner,S. Telfer,L. F. Thompson,D. Woodward
Physics , 2015, DOI: 10.1016/j.ijggc.2015.09.010
Abstract: Current methods of monitoring subsurface CO$_2$, such as repeat seismic surveys, are episodic and require highly skilled personnel to acquire the data. Simulations based on simplified models have previously shown that muon radiography could be automated to continuously monitor CO$_2$ injection and migration, in addition to reducing the overall cost of monitoring. In this paper, we present a simulation of the monitoring of CO$_2$ plume evolution in a geological reservoir using muon radiography. The stratigraphy in the vicinity of a nominal test facility is modelled using geological data, and a numerical fluid flow model is used to describe the time evolution of the CO$_2$ plume. A planar detection region with a surface area of 1000 m$^2$ is considered, at a vertical depth of 776 m below the seabed. We find that one year of constant CO$_2$ injection leads to changes in the column density of $\lesssim 1\%$, and that the CO$_2$ plume is already resolvable with an exposure time of less than 50 days.
Neutron background in large-scale xenon detectors for dark matter searches
M. J. Carson,J. C. Davies,E. Daw,R. J. Hollingworth,V. A. Kudryavtsev,T. B. Lawson,P. K. Lightfoot,J. E. McMillan,B. Morgan,S. M. Paling,M. Robinson,N. J. C. Spooner,D. R. Tovey
Physics , 2004, DOI: 10.1016/j.astropartphys.2004.05.001
Abstract: Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (alpha,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of $10^{-9}-10^{-10}$ pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector.
What do we know about communicating risk? A brief review and suggestion for contextualising serious, but rare, risk, and the example of cox-2 selective and non-selective NSAIDs
R Andrew Moore, Sheena Derry, Henry J McQuay, John Paling
Arthritis Research & Therapy , 2008, DOI: 10.1186/ar2373
Abstract: We identified observational studies (primarily in the form of meta-analyses) with information on individual non-steroidal anti-inflammatory drug (NSAID) or selective cyclooxygenase-2 inhibitor (coxib) use and relative risk of gastrointestinal bleed or cardiovascular event, the background rate of events in the absence of NSAID or coxib, and the likelihood of death from an event. Using this information we present the outcome of additional risk of death from gastrointestinal bleed and cardiovascular event for individual NSAIDs and coxibs alongside information about death from other causes in a series of perspective scales.The literature on communicating risk to patients is limited. There are problems with literacy, numeracy and the human tendency to overestimate rare risk and underestimate common risk. There is inconsistency in how people translate between numbers and words. We present a method of communicating information about serious risks using the common outcome of death, using pictures, numbers and words, and contextualising the information. The use of this method for gastrointestinal and cardiovascular harm with NSAIDs and coxibs shows differences between individual NSAIDs and coxibs.Although contextualised risk information can be provided on two possible adverse events, many other possible adverse events with potential serious consequences were omitted. Patients and professionals want much information about risks of medical interventions but we do not know how best to meet expectations. The impact of contextualised information remains to be tested.Many factors contribute to an incomplete understanding and evidence base for risk and risk presentation. We should not be surprised when both patients and professionals are confused about risk, about competing risks, and about comparing risks with benefits. Decisions are based on facts and emotions, both of which may be manipulated, and it may well be that emotions dominate the facts. This is important in the framewor
Track Reconstruction and Performance of DRIFT Directional Dark Matter Detectors using Alpha Particles
S. Burgos,J. Forbes,C. Ghag,M. Gold,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,J. E. McMillan,D. Muna,A. StJ. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,N. J. T. Smith,D. P. Snowden-Ifft,N. J. C. Spooner,T. J. Sumner,J. Turk,T. Tziaferi
Physics , 2007, DOI: 10.1016/j.nima.2007.10.013
Abstract: First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to characterise detector performance--an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was [59.3 +/- 0.2 (stat) +/- 7.5 (sys)] m/s based on an analysis of naturally-occurring alpha-emitting background. The drift velocity in DRIFT-IIb was [57 +/- 1 (stat) +/- 3 (sys)] m/s determined by the analysis of alpha particle tracks from a Po-210 source. 3D range reconstruction and energy spectra were used to identify alpha particles from the decay of Rn-222, Po-218, Rn-220 and Po-216. This study found that (22 +/- 2)% of Po-218 progeny (from Rn-222 decay) are produced with no net charge in 40 Torr CS2. For Po-216 progeny (from Rn-220 decay) the uncharged fraction is (100 +0 -35)%.
Measurement of the Range Component Directional Signature in a DRIFT-II Detector using 252Cf Neutrons
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2008, DOI: 10.1016/j.nima.2008.11.147
Abstract: The DRIFT collaboration utilizes low pressure gaseous detectors to search for WIMP dark matter with directional signatures. A 252Cf neutron source was placed on each of the principal axes of a DRIFT detector in order to test its ability to measure directional signatures from the three components of very low energy (~keV/amu) recoil ranges. A high trigger threshold and the event selection procedure ensured that only sulfur recoils were analyzed. Sulfur recoils produced in the CS2 target gas by the 252Cf source closely match those expected from massive WIMP induced sulfur recoils. For each orientation of the source a directional signal from the range components was observed, indicating that the detector is directional along all 3 axes. An analysis of these results yields an optimal orientation for DRIFT detectors when searching for a directional signature from WIMPs. Additional energy dependent information is provided to aid in understanding this effect.
Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches
S. Burgos,E. Daw,J. Forbes,C. Ghag,M. Gold,C. Hagemann,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. St. J. Murphy,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,D. P. Snowden-Ifft,N. J. C. Spooner,J. Turk,E. Tziaferi
Physics , 2009, DOI: 10.1088/1748-0221/4/04/P04014
Abstract: Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.
First Results from the DRIFT-IIa Dark Matter Detector
S. Burgos,J. Forbes,C. Ghag,M. Gold,V. A. Kudryavtsev,T. B. Lawson,D. Loomba,P. Majewski,D. Muna,A. StJ. Murphy,G. G. Nicklin,S. M. Paling,A. Petkov,S. J. S. Plank,M. Robinson,N. Sanghi,N. J. T. Smith,D. P. Snowden-Ifft,N. J. C. Spooner,T. J. Sumner,J. Turk,E. Tziaferi
Statistics , 2007, DOI: 10.1016/j.astropartphys.2007.08.007
Abstract: Data from the DRIFT-IIa directional dark matter experiment are presented, collected during a near continuous 6 month running period. A detailed calibration analysis comparing data from gamma-ray, x-ray and neutron sources to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%. Software-based cuts, designed to remove non-nuclear recoil events, are shown to reject 60Co gamma-rays with a rejection factor of better than 8x10-6 for all energies above threshold. An unexpected event population has been discovered and is shown here to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the central cathode. A limit on the flux of neutrons in the Boulby Underground Laboratory is derived from analysis of unshielded and shielded data.
First data from DM-Ice17
DM-Ice Collaboration,:,J. Cherwinka,D. Grant,F. Halzen,K. M. Heeger,L. Hsu,A. J. F. Hubbard,A. Karle,M. Kauer,V. A. Kudryavtsev,C. Macdonald,R. H. Maruyama,S. Paling,W. Pettus,Z. P. Pierpoint,B. N. Reilly,M. Robinson,P. Sandstrom,N. J. C. Spooner,S. Telfer,L. Yang
Physics , 2014, DOI: 10.1103/PhysRevD.90.092005
Abstract: We report the first analysis of background data from DM-Ice17, a direct-detection dark matter experiment consisting of 17 kg of NaI(Tl) target material. It was codeployed with IceCube 2457 m deep in the South Pole glacial ice in December 2010 and is the first such detector operating in the Southern Hemisphere. The background rate in the 6.5 - 8.0 keVee region is measured to be 7.9 +/- 0.4 counts/day/keV/kg. This is consistent with the expected background from the detector assemblies with negligible contributions from the surrounding ice. The successful deployment and operation of DM-Ice17 establishes the South Pole ice as a viable location for future underground, low-background experiments in the Southern Hemisphere. The detector assembly and deployment are described here, as well as the analysis of the DM-Ice17 backgrounds based on data from the first two years of operation after commissioning, July 2011 - June 2013.
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