Keele University

About: Keele University is a education organization based out in Newcastle-under-Lyme, United Kingdom. It is known for research contribution in the topics: Population & Stars. The organization has 11318 authors who have published 26323 publications receiving 894671 citations. The organization is also known as: Keele University.

Can sample size in qualitative research be determined a priori

Abstract: There has been considerable recent interest in methods of determining sample size for qualitative research a priori, rather than through an adaptive approach such as saturation. Extending previous literature in this area, we identify four distinct approaches to determining sample size in this way: rules of thumb, conceptual models, numerical guidelines derived from empirical studies, and statistical formulae. Through critical discussion of these approaches, we argue that each embodies one or more questionable philosophical or methodological assumptions, namely: a naive realist ontology; a focus on themes as enumerable ‘instances’, rather than in more conceptual terms; an incompatibility with an inductive approach to analysis; inappropriate statistical assumptions in the use of formulae; and an unwarranted assumption of generality across qualitative methods. We conclude that, whilst meeting certain practical demands, determining qualitative sample size a priori is an inherently problematic approach...

A Longitudinal Study of Psychological Burnout in Teachers

Abstract: This longitudinal study examined antecedents and consequences of psychological burnout among human service professionals. Antecedents of psychological burnout included individual and situational characteristics, work stressors, and measures of social support. Consequences of psychological burnout emphasized satisfaction and emotional and physical well-being variables. Participants in the study were 362 school-based educators (teachers and administrators) employed by the same school board. Respondents completed questionnaires sent to them at their schools at two points in time, 1 year apart. Regression analyses of time-lagged data replicated many empirical findings from cross-sectional studies.

Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes

Abstract: All ten LIGO/Virgo binary black hole (BH-BH) coalescences reported following the O1/O2 runs have near-zero effective spins. There are only three potential explanations for this. If the BH spin magnitudes are large, then: (i) either both BH spin vectors must be nearly in the orbital plane or (ii) the spin angular momenta of the BHs must be oppositely directed and similar in magnitude. Then there is also the possibility that (iii) the BH spin magnitudes are small. We consider the third hypothesis within the framework of the classical isolated binary evolution scenario of the BH-BH merger formation. We test three models of angular momentum transport in massive stars: A mildly efficient transport by meridional currents (as employed in the Geneva code), an efficient transport by the Tayler-Spruit magnetic dynamo (as implemented in the MESA code), and a very-efficient transport (as proposed by Fuller et al.) to calculate natal BH spins. We allow for binary evolution to increase the BH spins through accretion and account for the potential spin-up of stars through tidal interactions. Additionally, we update the calculations of the stellar-origin BH masses, including revisions to the history of star formation and to the chemical evolution across cosmic time. We find that we can simultaneously match the observed BH-BH merger rate density and BH masses and BH-BH effective spins. Models with efficient angular momentum transport are favored. The updated stellar-mass weighted gas-phase metallicity evolution now used in our models appears to be key for obtaining an improved reproduction of the LIGO/Virgo merger rate estimate. Mass losses during the pair-instability pulsation supernova phase are likely to be overestimated if the merger GW170729 hosts a BH more massive than 50âMâS. We also estimate rates of black hole-neutron star (BH-NS) mergers from recent LIGO/Virgo observations. If, in fact. angular momentum transport in massive stars is efficient, then any (electromagnetic or gravitational wave) observation of a rapidly spinning BH would indicate either a very effective tidal spin up of the progenitor star (homogeneous evolution, high-mass X-ray binary formation through case A mass transfer, or a spin-up of a Wolf-Rayet star in a close binary by a close companion), significant mass accretion by the hole, or a BH formation through the merger of two or more BHs (in a dense stellar cluster). (Less)

The VMC Survey - I. Strategy and First Data

Abstract: Context. The new VISual and Infrared Telescope for Astronomy (VISTA) has started operations. Over its first five years it will be col lecting data for six Public Surveys, one of which is the near-infrared Y JKs VISTA survey of the Magellanic Clouds system (VMC). This survey comprises the Large Magellanic Cloud (LMC), the Small Magellanic Cloud, the Magellanic Bridge connecting the two galaxies and two fields in the Magellanic Stream. Aims. This paper provides an overview of the VMC survey strategy and presents first science results. The main goals of the VMC sur vey are the determination of the spatially-resolved star-form ation history and the three-dimensional structure of the Magellanic system. The VMC survey is therefore designed to reach stars as faint as the ol dest main sequence turn-off point and to constrain the mean magnitude of pulsating variables such as RR Lyrae stars and Cepheids. This paper focuses on observations of VMC fields in the LMC obtained between November 2009 and March 2010. These observations correspond to a completeness of 7% of the planned LMC fields. Methods. The VMC data are comprised of multi-epoch observations which are executed following specific time constraints. The data were reduced using the VISTA Data Flow System pipeline with source catalogues, including astrometric and photometric corrections, produced and made available via the VISTA Science Archive. The VMC data will be released to the astronomical community following the European Southern Observatory’s Public Survey policy. The analysis of the data shows that the sensitivity in each wave band agrees with expectations. Uncertainties and completeness of the data are also derived. Results. The first science results, aimed at assessing the scientific q uality of the VMC data, include an overview of the distribution of stars in colour-magnitude and colour-colour diagrams, the detection of planetary nebulae and stellar clusters, and the Ks band light-curves of variable stars. Conclusions. The VMC survey represents a tremendous improvement, in spatial resolution and sensitivity, on previous panoramic observations of the Magellanic system in the near-infrared, providing a powerful complement to deep observations at other wavelengths.

A comparison between the time-management skills and academic performance of mature and traditional-entry university students

Abstract: Time-management skills are acknowledged to be important but there has been little actual research on this topic with students. In this study we examined the scores obtained from 293 first-year students of psychology on a British version of an American time-management scale. The students were divided into three age groups: traditional-entry students - aged less than 21 years (N = 172); borderline mature students - aged 21–25 years (N = 50) and older mature students - aged more than 25 years (N = 71). Our analyses indicated (i) that women students in general reported significantly greater time-management skills than did men students, and (ii) that our older mature students reported significantly better time-management skills than did the other two groups. Academic performance, however, was only modestly predicted by age and scores on one component of the time-management scale.