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Search Results: 1 - 10 of 144623 matches for " B. Baugh "
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REFERQUAL: a pilot study of a new service quality assessment instrument in the GP exercise referral scheme setting
Don Cock, Iain C Adams, Adrian B Ibbetson, Phil Baugh
BMC Health Services Research , 2006, DOI: 10.1186/1472-6963-6-61
Abstract: A modified version of the SERVQUAL instrument was designed for use in the ERS setting and subsequently piloted amongst 27 ERS clients.Test re-test correlations were calculated via Pearson's 'r' or Spearman's 'rho', depending on whether the variables were Normally Distributed, to show a significant (mean r = 0.957, SD = 0.02, p < 0.05; mean rho = 0.934, SD = 0.03, p < 0.05) relationship between all items within the questionnaire. In addition, satisfactory internal consistency was demonstrated via Cronbach's 'α'. Furthermore, clients responded favourably towards the usability, wording and applicability of the instrument's items.REFERQUAL is considered to represent promise as a suitable tool for future evaluation of service quality within the ERS community. Future research should further assess the validity and reliability of this instrument through the use of a confirmatory factor analysis to scrutinise the proposed dimensional structure.Exercise Referral Schemes (ERSs) in the UK involve a recommendation from a clinician to a patient concerning the up-take of physical activity, based upon certain pre-determined criteria. The patient then attends a local exercise centre, where an advanced exercise instructor will create an appropriate individualised programme, usually designed to last around 12–15 weeks. The publication of 'Exercise Referral Systems: A National Quality Assurance Framework' [1] was, in part, aimed at improving standards among existing ERSs and aiding the development of new systems. However, many schemes both pre- and post-publication of this document suffered from and struggled with issues relating to poor levels of adherence [2,3]. Client perceptions of excellent service quality are highlighted as being crucial to the process of attracting new members and retaining existing members in the leisure management industry [4], a theme not uncommon within other service industries [5-7]. The development of a tool to accurately assess service quality within the
Refocussing off-resonant spin-1/2 evolution using spinor behavior
Jonathan Baugh
Physics , 2009,
Abstract: A systematic method is presented for constructing increasingly precise sequences to refocus off-resonant spin evolution with severely limited control amplitude. Sequences obtained should be readily applicable to the case of electron spin qubits in quantum dots with random nuclear fields, and other qubit systems with systematic qubit splitting errors comparable to control field amplitude.
A hybrid multi resolution scheme to efficiently model the structure of reionization on the largest scales
Han-Seek Kim,J. Stuart B. Wyithe,Jaehong Park,Gregory B. Poole,C. G. Lacey,C. M. Baugh
Physics , 2015, DOI: 10.1093/mnras/stv2623
Abstract: Redshifted 21cm measurements of the structure of ionised regions that grow during reionization promise to provide a new probe of early galaxy and structure formation. One of the challenges of modelling reionization is to account both for the sub-halo scale physics of galaxy formation and the regions of ionization on scales that are many orders of magnitude larger. To bridge this gap we first calculate the statistical relationship between ionizing luminosity and Mpc-scale overdensity using detailed models of galaxy formation computed using relatively small volume - ($\sim$100Mpc/$h$)$^{3}$, high resolution dark matter simulations. We then use a Monte-Carlo technique to apply this relationship to reionization of the intergalactic medium within large volume dark matter simulations - ($>$1Gpc/$h$)$^{3}$. The resulting simulations can be used to address the contribution of very large scale clustering of galaxies to the structure of reionization, and show that volumes larger than 500Mpc/$h$ are required to probe the largest reionization features mid-way through reionization. As an example application of our technique, we demonstrate that the predicted 21cm power spectrum amplitude and gradient could be used to determine the importance of supernovae feedback for early galaxy formation.
Predictions for the abundance and colours of galaxies in high redshift clusters in hierarchical models
Alexander I. Merson,Carlton M. Baugh,Filipe B. Abdalla,Violeta Gonzalez-Perez,Claudia del P. Lagos,Simona Mei
Physics , 2015,
Abstract: High redshift galaxy clusters allow us to examine galaxy formation in extreme environments. Here we compile data for $z>1$ galaxy clusters to test the predictions from one of the latest semi-analytical models of galaxy formation. The model gives a good match to the slope and zero-point of the cluster red sequence. The model is able to match the cluster galaxy luminosity function at faint and bright magnitudes, but under-estimates the number of galaxies around the break in the luminosity function. We find that simply assuming a weaker dust attenuation improves the model predictions for the cluster galaxy luminosity function, but worsens the predictions for the red sequence at bright magnitudes. Examination of the properties of the bright cluster galaxies suggests that the default dust attenuation is very large due to these galaxies having large reservoirs of cold gas as well as small radii. We find that matching the luminosity function and colours of high redshift cluster galaxies, whilst remaining consistent with local observations, poses a challenge for galaxy formation models. Our results highlight the need to consider observations beyond the local Universe, as well as for different environments, when calibrating the parameters of galaxy formation models.
The HI mass function as a probe of photoionisation feedback on low mass galaxy formation
Han-Seek Kim,J. Stuart. B. Wyithe,C. Power,Jaehong Park,C. d. P. Lagos,C. M. Baugh
Physics , 2015, DOI: 10.1093/mnras/stv1822
Abstract: We explore the galaxy formation physics governing the low mass end of the HI mass function in the local Universe. Specifically, we predict the effects on the HI mass function of varying i) the strength of photoionisation feedback and the redshift of the end of the epoch of reionization, ii) the cosmology, iii) the supernovae feedback prescription, and iv) the efficiency of star formation. We find that the shape of the low-mass end of the HI mass function is most affected by the critical halo mass below which galaxy formation is suppressed by photoionisation heating of the intergalactic medium. We model the redshift dependence of this critical dark matter halo mass by requiring a match to the low-mass end of the HI mass function. The best fitting critical dark matter halo mass decreases as redshift increases in this model, corresponding to a circular velocity of $\sim 50 \, {\rm km \,s}^{-1}$ at $z=0$, $\sim 30 \, {\rm km\, s}^{-1}$ at $z \sim 1$ and $\sim 12 \, {\rm km \, s}^{-1}$ at $z=6$. We find that an evolving critical halo mass is required to explain both the shape and abundance of galaxies in the HI mass function below $M_{\rm HI} \sim 10^{8} h^{-2} {\rm M_{\odot}}$. The model makes specific predictions for the clustering strength of HI-selected galaxies with HI masses > $10^{6} h^{-2} {\rm M_{\odot}}$ and $> 10^{7} h^{-2} {\rm M_{\odot}}$ and for the relation between the HI and stellar mass contents of galaxies which will be testable with upcoming surveys with the Square Kilometre Array and its pathfinders. We conclude that measurements of the HI mass function at $z \ge 0$ will lead to an improvement in our understanding of the net effect of photoionisation feedback on galaxy formation and evolution.
Incorporating Morphological Types into Semi-analytic Schemes for Galaxy Formation
C. M. Baugh
Physics , 1995,
Abstract: We test the hypothesis that elliptical galaxies are formed by violent mergers in a universe with hierarchical structure formation. Within the framework of a semi-analytic scheme for galaxy formation, we predict the distribution of morphological types with redshift and compare the colours of elliptical galaxies in different environments.
Large scale fluctuations in the distribution of galaxies
C. M. Baugh
Physics , 1996, DOI: 10.1093/mnras/282.4.1413
Abstract: The null hypothesis that the three dimensional power spectrum measured from the APM Survey is consistent with the one dimensional power spectrum measured from the pencil beams surveys of Broadhurst et al and of Szalay et al is tested. The external estimates of the mean power that we make are sensitive to details of the model for the survey geometry and to the assumed level of the distortion of the pattern of galaxy clustering caused by peculiar motions. We find that the measured 3D clustering of galaxies can account for the presence of peaks in the one dimensional power spectrum, but is less successful in recovering the detailed appearence of the observations. We find no strong evidence for any additional large scale structure in the deep pencil beams beyond that recovered from the APM Survey. We conclude therefore that it is unlikey that large scale structure can be responsible for the steep local number counts of bright galaxies.
The Real Space Correlation Function Measured from the APM Galaxy Survey
C. M. Baugh
Physics , 1995, DOI: 10.1093/mnras/280.1.267
Abstract: We present a determination of the real space correlation function for galaxies in the APM Survey, with magnitudes in the range $17 < b_J < 20$. We recover a power law form for the correlation function $\xi(r) = (r/4.5)^{-1.7}$ on scales $r < 4 Mpc/h$, for a flat universe and clustering that is fixed in comoving coordinates.If we assume that clustering evolves according to linear perturbation theory, we obtain $\xi(r) = (r/5.25)^{-1.7}$. We recover a shoulder feature in $\xi(r)$ for scales $4 < r < 25 Mpc/h$, with the correlation function rising above the power law, before becoming consistent with zero around $r > 40 Mpc/h$. The form we obtain for $\xi(r)$ is smooth on large scales, allowing a determination of the distortions in the correlation function in redshift space, caused by the peculiar motions of galaxies to be made. Comparing the real space correlation function with the measurement of the redshift space correlation function by Loveday et al (1995), we find that a value for $omega^{0.6}/b$ (where $\omega$ is the density parameter of the universe and b is the bias factor between the density of light and mass) of unity is ruled out at the 2 sigma level.
Luminosity bias: from haloes to galaxies
C. M. Baugh
Physics , 2013, DOI: 10.1017/pas.2013.007
Abstract: Large surveys of the local Universe have shown that galaxies with different intrinsic properties, such as colour, luminosity and morphological type display a range of clustering amplitudes. Galaxies are therefore not faithful tracers of the underlying matter distribution. This modulation of galaxy clustering, called bias, contains information about the physics behind galaxy formation. It is also a systematic to be overcome before the large-scale structure of the Universe can be used as a cosmological probe. Two types of approaches have been developed to model the clustering of galaxies. The first class is empirical and filters or weights the distribution of dark matter to reproduce the measured clustering. In the second approach an attempt is made to model the physics which governs fate of baryons in order to predict the number of galaxies in dark matter haloes. I will review the development of both approaches and summarize what we have learnt about galaxy bias.
Orbital Josephson Interference in a Nanowire Proximity Effect Junction
Kaveh Gharavi,Jonathan Baugh
Physics , 2014, DOI: 10.1103/PhysRevB.91.245436
Abstract: A semiconductor nanowire based superconductor-normal-superconductor (SNS) junction is modeled theoretically. A magnetic field is applied along the nanowire axis, parallel to the current. The Bogoliubov-de Gennes equations for Andreev bound states are solved while considering the electronic subbands due to radial confinement in the N-section. The energy-versus-phase curves of the Andreev bound states shift in phase as the N-section quasiparticles with orbital angular momentum couple to the axial field. A similar phase shift is observed in the continuum current of the junction. The quantum mechanical result is shown to reduce to an intuitive, semi-classical model when the Andreev approximation holds. Numerical calculations of the critical current versus axial field reveal flux-aperiodic oscillations that we identify as a novel form of Josephson interference due to this orbital subband effect. This behavior is studied as a function of junction length and chemical potential. Finally, we discuss extensions to the model that may be useful for describing realistic devices.
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