Classic grounded theory: Identifying the main concern

Grounded theory comprises a family of research approaches designed to support the generation of a theory explaining a phenomenon experienced by a group of participants. One style of grounded theory, Classic grounded theory, is used less often than other types of grounded theory. The less frequent use of Classic grounded theory may be attributed to the limited availability of clearly articulated processes for conducting this method. Particularly important within Classic grounded theory, and not used in other forms of grounded theory, is identifying the participants\u27 main concern. Identifying the participants\u27 main concern is a signature feature of Classic grounded theory and is a prerequisite for ascertaining the core category and subsequent discovery of theory. In this article we provide a detailed explanation of how to identify the participants\u27 main concern, and in so doing, we offer an exemplar to illustrate the process involved

Evaluation of a Coping Kit of Items to Support Children with Developmental Disorders in the Hospital Setting

This study attempted to answer the question, Do nurses perceive coping kits to be effective at meeting the needs of hospitalized children with developmental disabilities who are at increased risk for challenging behaviors? A cross-sectional post-test survey study design was used, with a convenience sample of 24 registered nurses at a Midwestern free-standing children\u27s hospital. A coping kit with simple communication cards, social script book, and distraction items (toys) was developed to enhance communication and distract children with developmental disabilities (including autism spectrum disorder) undergoing procedures in the hospital. A modified version of Hudson\u27s (2006) intervention effectiveness survey was used to measure the nurse\u27s perception of the effectiveness of the coping kit. Nurses perceived the coping kits to be effective for decreasing their patient\u27s anxiety, calming the child\u27s behavior, and increasing cooperation during procedures. The nurse can develop a plan of care that includes a coping kit to help gain cooperation with the hospitalized child with challenging behaviors

Student evaluation of teaching: Reactions of Australian academics to anonymous non-constructive student commentary.

Within Australian higher education, student evaluation of teaching (SET) is regularly conducted and data are utilised for quality control and staff appraisal. Within current methodologies, students can anonymously provide further feedback as written commentary. There is now growing evidence that, once this narrative becomes derogatory or abusive, it may have the potential to create harm. To investigate staff reactions to receiving anonymous non-constructive commentary, a one group point in time design was constructed, and a survey conducted. Participants (N = 741) from a broad cross-section of Australian universities responded to Likert questions asking about their reactions. A significant impact was revealed according to age for mental health, stress and professional confidence, with younger and tenured academics indicating the most vulnerability. There were no differences across gender. Non-health disciplines with teaching loads greater than 50% reported an impact of anonymous SET on mental health and professional confidence. Being casually or seasonally employed or from an ethnic background was shown to have a significant effect on professional confidence. Findings suggest that the potential for higher education academics to be harmed via this process is a continued risk and highlights the need for review and reform of SET systems and protocols

Estimate of dark halo ellipticity by lensing flexion

Aims. The predictions of the ellipticity of the dark matter halos from models of structure formation are notoriously difficult to test with observations. A direct measurement would give important constraints on the formation of galaxies, and its effect on the dark matter distribution in their halos. Here we show that galaxy-galaxy flexion provides a direct and potentially powerful method for determining the ellipticity of (an ensemble of) elliptical lenses. Methods. We decompose the spin-1 flexion into a radial and a tangential component. Using the ratio of tangential-to- radial flexion, which is independent of the radial mass profile, the mass ellipticity can be estimated. Results. An estimator for the ellipticity of the mass distribution is derived and tested with simulations. We show that the estimator is slightly biased. We quantify this bias, and provide a method to reduce it. Furthermore, a parametric fitting of the flexion ratio and orientation provides another estimate for the dark halo ellipticity, which is more accurate for individual lenses Overall, galaxy-galaxy flexion appears as a powerful tool for constraining the ellipticity of mass distributions.Comment: 6 pages,5 figures, submitted to AA, comments welcom

Multi-scale cluster lens mass mapping I. Strong Lensing modelling

We propose a novel technique to refine the modelling of galaxy clusters mass distribution using gravitational lensing. The idea is to combine the strengths of both "parametric" and "non-parametric" methods to improve the quality of the fit. We develop a multi-scale model that allows sharper contrast in regions of higher density where the number of constraints is generally higher. Our model consists of (i) a multi-scale grid of radial basis functions with physically motivated profiles and (ii) a list of galaxy-scale potentials at the location of the cluster member galaxies. This arrangement of potentials of different sizes allows to reach a high resolution for the model with a minimum number of parameters. We apply our model to the well studied cluster Abell 1689. We estimate the quality of our mass reconstruction with a Bayesian MCMC sampler. For a selected subset of multiple images, we manage to halve the errors between the predicted and observed image positions compared to previous studies. This owes to the flexibility of multi-scale models at intermediate scale between cluster and galaxy scale. The software developed for this paper is part of the public lenstool package which can be found at www.oamp.fr/cosmology/lenstool.Comment: 15 pages, 17 figures, accepted for publication in MNRA

Analytical shear and flexion of Einasto dark matter haloes

N-body simulations predict that dark matter haloes are described by specific density profiles on both galactic- and cluster-sized scales. Weak gravitational lensing through the measurements of their first and second order properties, shear and flexion, is a powerful observational tool for investigating the true shape of these profiles. One of the three-parameter density profiles recently favoured in the description of dark matter haloes is the Einasto profile. We present exact expressions for the shear and the first and second flexions of Einasto dark matter haloes derived using a Mellin-transform formalism in terms of the Fox H and Meijer G functions, that are valid for general values of the Einasto index. The resulting expressions can be written as series expansions that permit us to investigate the asymptotic behaviour of these quantities. Moreover, we compare the shear and flexion of the Einasto profile with those of different mass profiles including the singular isothermal sphere, the Navarro-Frenk-White profile, and the S\'ersic profile. We investigate the concentration and index dependences of the Einasto profile, finding that the shear and second flexion could be used to determine the halo concentration, whilst for the Einasto index the shear and first and second flexions may be employed. We also provide simplified expressions for the weak lensing properties and other lensing quantities in terms of the generalized hypergeometric function.Comment: 14 pages, 3 figures. Accepted for publication in Astronomy and Astrophysic

Strong-Lensing Analysis of a Complete Sample of 12 MACS Clusters at z>0.5: Mass Models and Einstein Radii

We present the results of a strong-lensing analysis of a complete sample of 12 very luminous X-ray clusters at $z>0.5$ using HST/ACS images. Our modelling technique has uncovered some of the largest known critical curves outlined by many accurately-predicted sets of multiple images. The distribution of Einstein radii has a median value of \simeq28\arcsec (for a source redshift of $z_{s}\sim2$), twice as large as other lower-$z$ samples, and extends to 55\arcsec for MACS J0717.5+3745, with an impressive enclosed Einstein mass of $7.4\times10^{14} M_{\odot}$. We find that 9 clusters cover a very large area (>2.5 \sq \arcmin) of high magnification ($\mu > \times10$) for a source redshift of $z_{s}\sim8$, providing primary targets for accessing the first stars and galaxies. We compare our results with theoretical predictions of the standard $\Lambda$CDM model which we show systematically fall short of our measured Einstein radii by a factor of $\simeq1.4$, after accounting for the effect of lensing projection. Nevertheless, a revised analysis once arc redshifts become available, and similar analyses of larger samples, are needed in order to establish more precisely the level of discrepancy with $\Lambda$CDM predictions.Comment: Accepted for publication in MNRAS, 19 pages, 35 figures, 2 tables. V2 includes several changes, mainly additional discussion of the results. A higher resolution version is available at ftp://wise-ftp.tau.ac.il/pub/adiz/macs1

Cluster Lenses

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author

Halo Shapes From Weak Lensing: The Impact of Galaxy--Halo Misalignment

We analyse the impact of galaxy--halo misalignment on the ability of weak lensing studies to constrain the shape of dark matter haloes, using a combination of the Millennium dark matter N-body simulation and different semi-analytic galaxy formation models, as well as simpler Monte Carlo tests. Since the distribution of galaxy--halo alignments is not known in detail, we test various alignment models, together with different methods of determining the halo shape. In addition to alignment, we examine the interplay of halo mass and shape, and galaxy colour and morphology with the resulting stacked projected halo shape. We find that only in the case where significant numbers of galaxy and halo minor axes are parallel does the stacked, projected halo axis ratio fall below 0.95. When using broader misalignment distributions, such as those found in recent simulations of galaxy formation, the halo ellipticity signal is washed out and would be extremely difficult to measure observationally. It is important to note that the spread in stacked halo axis ratio due to theoretical unknowns (differences between semi-analytic models, and between alignment models) are much bigger than any statistical uncertainty: It is naive to assume that, simply because LCDM predicts aspherical haloes, the stacked projected shape will be elliptical. In fact, there is no robust LCDM prediction yet for this procedure, and the interpretation of any such elliptical halo signal from lensing in terms of physical halo properties will be extremely difficult.Comment: 22 pages, 19 figures, accepted for publication in MNRAS. Minor changes for clarification and correcting typeo