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Search Results: 1 - 10 of 220636 matches for " John G Hughes "
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RES - a Relative Method for Evidential Reasoning
Zhi An,David A. Bell,John G. Hughes
Computer Science , 2013,
Abstract: In this paper we describe a novel method for evidential reasoning [1]. It involves modelling the process of evidential reasoning in three steps, namely, evidence structure construction, evidence accumulation, and decision making. The proposed method, called RES, is novel in that evidence strength is associated with an evidential support relationship (an argument) between a pair of statements and such strength is carried by comparison between arguments. This is in contrast to the onventional approaches, where evidence strength is represented numerically and is associated with a statement.
Representing Heuristic Knowledge in D-S Theory
Weiru Liu,John G. Hughes,Michael F. McTear
Computer Science , 2013,
Abstract: The Dempster-Shafer theory of evidence has been used intensively to deal with uncertainty in knowledge-based systems. However the representation of uncertain relationships between evidence and hypothesis groups (heuristic knowledge) is still a major research problem. This paper presents an approach to representing such heuristic knowledge by evidential mappings which are defined on the basis of mass functions. The relationships between evidential mappings and multi valued mappings, as well as between evidential mappings and Bayesian multi- valued causal link models in Bayesian theory are discussed. Following this the detailed procedures for constructing evidential mappings for any set of heuristic rules are introduced. Several situations of belief propagation are discussed.
A Very Hot, High Redshift Cluster of Galaxies: More Trouble for Omega_0 = 1
Megan Donahue,G. Mark Voit,Isabella M. Gioia,Gerry Luppino,John P. Hughes,John T. Stocke
Physics , 1997, DOI: 10.1086/305923
Abstract: We have observed the most distant (z=0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey, with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3 +3.1/-2.2 keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members we have obtained at the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing signature. The X-ray temperature of this cluster implies a virial mass ~ 7.4 x 10^14 h^-1 solar masses, if the mean matter density in the universe equals the critical value, or larger if Omega_0 < 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an Omega_0 = 1 universe. Combining the assumptions that Omega_0 = 1 and that the intial perturbations were Gaussian with the observed X-ray temperature function at low redshift, we show that the probability of this cluster occurring in the volume sampled by the EMSS is less than a few times 10^{-5}. Nor is MS1054-0321 the only hot cluster at high redshift; the only two other $z > 0.5$ EMSS clusters already observed with ASCA also have temperatures exceeding 8 keV. Assuming again that the initial perturbations were Gaussian and Omega_0 = 1, we find that each one is improbable at the < 10^{-2} level. These observations, along with the fact that these luminosities and temperatures of the high-$z$ clusters all agree with the low-z L_X-T_X relation, argue strongly that Omega_0 < 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.
Considering the case for an antidepressant drug trial involving temporary deception: a qualitative enquiry of potential participants
Christopher F Dowrick, John G Hughes, Julia J Hiscock, Mark Wigglesworth, Thomas J Walley
BMC Health Services Research , 2007, DOI: 10.1186/1472-6963-7-64
Abstract: A qualitative approach was employed to explore the perspectives of general practitioners, psychiatrists, and patients with experience of depression. The doctors were chosen via purposive sampling, while patients were recruited through participating general practitioners. Three focus groups and 12 in-depth interviews were conducted. A vignette-based topic guide invited views on three deceptive strategies: post hoc, authorised and minimised deception. The focus groups and interviews were tape-recorded and transcribed. Transcripts were analysed thematically using Framework.Deception in non-research situations was typically perceived as acceptable within specific parameters. All participants could see the potential utility of introducing deception into trial designs, however views on the acceptability of deception within antidepressant drug trials varied substantially. Authorized deception was the most commonly accepted strategy, though some thought this would reduce the effectiveness of the design because participants would correctly guess the deceptive element. The major issues that affected views about the acceptability of deception studies were the welfare and capacity of patients, practicalities of trial design, and the question of trust.There is a trade-off between pragmatic and ethical responses to the question of whether, and under what circumstances, elements of deception could be introduced into antidepressant drug trials. Ensuring adequate ethical safeguards within balanced placebo designs is likely to diminish their ability to address the crucial issue of additivity. The balanced placebo designs considered in this study are unlikely to be feasible in future trials of antidepressant medication. However there remains an urgent need to improve the quality of antidepressant drug trials.There is considerable debate concerning the utility of antidepressant medication in the treatment of depressive disorders. The prevailing view amongst psychiatrists is that antide
An Opportunity for Diagonal Development in Global Surgery: Cleft Lip and Palate Care in Resource-Limited Settings
Pratik B. Patel,Marguerite Hoyler,Rebecca Maine,Christopher D. Hughes,Lars Hagander,John G. Meara
Plastic Surgery International , 2012, DOI: 10.1155/2012/892437
Abstract: Global cleft surgery missions have provided much-needed care to millions of poor patients worldwide. Still, surgical capacity in low- and middle-income countries is generally inadequate. Through surgical missions, global cleft care has largely ascribed to a vertical model of healthcare delivery, which is disease specific, and tends to deliver services parallel to, but not necessarily within, the local healthcare system. The vertical model has been used to address infectious diseases as well as humanitarian emergencies. By contrast, a horizontal model for healthcare delivery tends to focus on long-term investments in public health infrastructure and human capital and has less often been implemented by humanitarian groups for a variety of reasons. As surgical care is an integral component of basic healthcare, the plastic surgery community must challenge itself to address the burden of specific disease entities, such as cleft lip and palate, in a way that sustainably expands and enriches global surgical care as a whole. In this paper, we describe a diagonal care delivery model, whereby cleft missions can enrich surgical capacity through integration into sustainable, local care delivery systems. Furthermore, we examine the applications of diagonal development to cleft care specifically and global surgical care more broadly. 1. Introduction The inadequacy of surgical and anesthetic capacity in resource-limited settings is well demonstrated [1–5], as is the particular need for more robust pediatric surgical services [6–8]. Total surgical disease burden, estimated at 11–15% of disability-adjusted life years (DALYs) lost worldwide, disproportionately affects low- and middle-income countries (LMICs) [9–11]. Cleft lip and palate (CLP) and other congenital anomalies account for approximately 9% of this burden [9], and the consequences of untreated CLP range from social ostracism to death [12–14]. Although the economic burden of untreated CLP and the value and cost effectiveness of global cleft treatments have been proven [15–17], CLP treatment capacity remains insufficient in LMICs [18, 19]. Historically plastic surgeons’ efforts to address this need have focused on short-term, service-oriented commitments—a vertical approach to healthcare [20]. Narrowly focused, disease-specific, and vertical programs tend to operate outside the existing national and local healthcare structures, supplying their own facilities and delivery mechanisms [21–23]. By contrast, the horizontal approach focuses on developing and strengthening existing public infrastructure, with an
The Second Most Distant Cluster of Galaxies in the EMSS
Megan Donahue,G. Mark Voit,Caleb A. Scharf,Isabella M. Gioia,Christopher R. Mullis,John P. Hughes,John T. Stocke
Physics , 1999,
Abstract: We report on our ASCA, Keck, and ROSAT observations of MS1137.5+6625, the second most distant cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), at redshift 0.78. We now have X-ray temperatures, velocity dispersions, and X-ray images for a complete, high-redshift sample of EMSS clusters. ASCA observations of MS1137.5+6625 yield a temperature of 5.7 +2.1, -1.1 keV and a metallicity of 0.43 +0.40,-0.37 solar (90% confidence). Keck-II spectroscopy of 22 cluster members reveals a velocity dispersion of 884 +185, -124 km/s. ROSAT observations show that MS1137.5+6625 is regular and centrally concentrated. A beta-model fit yields a core radius of only 71 h^{-1} kpc (q_0=0.1) with beta=0.70 +0.45,-0.15. The gas fraction is 0.06 +/-0.04 h^{-3/2}. This is the highest redshift EMSS cluster with a possible cooling flow (~20-400 solar masses/yr). The velocity dispersion, temperature, gas fraction, and iron abundance of MS1137 are statistically the same as those properties in low-z clusters of similar luminosity. We derive a high-z temperature function for EMSS clusters with 0.5 < z < 0.9 and compare it with temperature functions at lower redshifts, showing that evolution of the temperature function is relatively modest. Supplementing our high-z sample with other data, we demonstrate that neither the cluster L-T relation, nor cluster metallicities, nor the cluster gas fraction has detectably evolved with redshift. The very modest degree of evolution in the L-T relation inferred from these data is inconsistent with the absence of evolution in the X-ray luminosity functions derived from ROSAT cluster surveys if a critical-density structure formation model is assumed.
Sixth Scale Model Studies of Masonry Arch Rib Behaviour at Different Eccentricities  [PDF]
Abbagana Mohammed, T. G. Hughes
Open Journal of Civil Engineering (OJCE) , 2018, DOI: 10.4236/ojce.2018.84038
Abstract: This paper reports a validation study involving sixth scale masonry model to replicate prototype tests carried out on five unit high masonry prisms. In order to test the applicability of small masonry models to real life problems, an investigation into masonry behaviour relevant to the serviceability requirement of masonry arch bridges was chosen as prototype test to validate the small scale masonry tests. Only representative masonry specimens were considered in the study; this corresponded to parts of an arch ring in a complete masonry arch. Two mortar designations; designation iv and designation v were used. These weak mortars tend to conform better to existing old structures. Loads were applied at four eccentricities of 0, 5, 9, and 14 mm from the centre of the specimens. This corresponds to e/d ratios of 0, 0.14, 0.25, and 0.39, where e is the eccentricity of the load and d the length of the transverse section of the specimens. The result shows that validation study corresponds with prototype study for low eccentricities; therefore, strength enhancement is seen over the concentric compressive strength. However, this does not apply at higher eccentricities as specimens were noticed to fail by elastic instability characterised by tension debonding of the top mortar joint.
Polarization engineering in photonic crystal waveguides for spin-photon entanglers
Andrew B. Young,Arthur Thijssen,Daryl M. Beggs,Petros Androvitsaneas,L. Kuipers,John G. Rarity,Stephen Hughes,Ruth Oulton
Physics , 2014, DOI: 10.1103/PhysRevLett.115.153901
Abstract: By performing a full analysis of the projected local density of states (LDOS) in a photonic crystal waveguide, we show that phase plays a crucial role in the symmetry of the light-matter interaction. By considering a quantum dot (QD) spin coupled to a photonic crystal waveguide (PCW) mode, we demonstrate that the light-matter interaction can be asymmetric, leading to unidirectional emission and a deterministic entangled photon source. Further we show that understanding the phase associated with both the LDOS and the QD spin is essential for a range of devices that that can be realised with a QD in a PCW. We also show how quantum entanglement can completely reverse photon propagation direction, and highlight a fundamental breakdown of the semiclassical dipole approximation for describing light-matter interactions in these spin dependent systems.
Revisiting the Mass of the Coma Cluster from X-Ray Observations
John P. Hughes
Physics , 1997,
Abstract: I re-examine mass estimates of the Coma cluster from pre-ASCA X-ray spectral observations. A large range of model dark matter distributions are examined, under the assumptions of hydrostatic equilibrium and spherical symmetry, to determine the widest possible allowed range on the total mass of the cluster. Within a radius of 1 Mpc, the total cluster mass is tightly constrained to be (6.2 +/- 0.9) x 10**14 solar masses and the ratio of luminous baryonic matter to total matter lies between 13% and 17%. Within a radius of 3 Mpc the total mass is (1.3 +/- 0.5) x 10**15 solar masses and the luminous matter fraction is 20%-40%. I find that the ``universal'' dark matter density profile proposed by Navarro, Frenk, and White, based on N-body simulations of a standard cold-dark-matter dominated Universe, predicts a steep temperature gradient within the core of the cluster that is a poor fit to the Coma data and can be rejected at greater than 99% confidence.
Hot Electrons and Cold Photons: Galaxy Clusters and the Sunyaev-Zel'dovich Effect
John P. Hughes
Physics , 1997,
Abstract: The hot gas in clusters of galaxies emits thermal bremsstrahlung emission that can be probed directly through measurements in the X-ray band with satellites like ROSAT and ASCA. Another probe of this gas comes from its effect on the cosmic microwave background radiation (CMBR): the hot cluster electrons inverse Compton scatter the CMBR photons and thereby distort the background radiation from its blackbody spectral form. In the last few years, the development of sensitive new instruments for measuring this distortion, called the Sunyaev-Zel'dovich (SZ) effect, has sparked a revolution in the field. Current radio interferometric arrays can now detect and map the SZ effect in even distant (z ~ 1) clusters. It is well known that one of the purposes of conducting such measurements is to determine the Hubble constant. In this review I report on the progress that has been made in this area, quote the current best estimate of Ho from the SZ effect of 8 galaxy clusters (44 - 64 km/s/Mpc +/- 17%), discuss important systematic uncertainties, and highlight what else has been learned about galaxy clusters from these investigations.
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