The Progenitors of Recent Core-Collapse Supernovae

We present the results of our analysis of Hubble Space Telescope (HST) and deep ground-based images to isolate the massive progenitor stars of the two recent core-collapse supernovae 2008 bk and 2008 cn. The identification of the progenitors is facilitated in one of these two cases by high-precision astrometry based on our HST imaging of SNe at late times

Satisfaction with retention factors as predictors of the job embeddedness of medical and information technology services staff

The objective of the study was to determine whether employees’ satisfaction with retention factors (measured by the Retention Factors Scale) significantly predicted their job embeddedness (measured by the Job Embeddedness Scale). A quantitative survey was conducted on a purposive sample (n=206) of early career medical and information technology services staff, identified as scarce skills in a South African client services company. Retention factors such as training and development, career opportunities, supervisor support and the characteristics of the job (skills variety, challenge and autonomy) were shown to significantly predict the participants’ sense of job embeddedness. Satisfaction with training and development opportunities was the best predictor of organisational fit, while satisfaction with career opportunities was the best predictor of organisational sacrifice. The findings add valuable new knowledge that may be used to inform retention strategies for professional staff with scarce skills in the medical and information technology services sector.Key words: retention factors, perceived job embeddedness, training and development, career opportunities, job characteristics, supervisor suppor

On The Progenitor of the Type II-Plateau Supernova 2003gd in Messier 74

HST WFPC2 archival F606W and F300W images obtained within one year prior to the explosion of the nearby Type II supernova (SN) 2003gd in Messier 74 (NGC 628) have been analyzed to isolate the progenitor star. The SN site was located using precise astrometry applied to the HST images. Two plausible candidates are identified within 0.6" of the SN position in the F606W image. Neither candidate was detected in the F300W image. SN 2003gd appears to be of Type II-plateau (II-P), with age ~87 d on June 17 UT and with low reddening [E(B-V) = 0.13 mag]. The most likely of the two progenitor candidates has M_V_0 ~ -3.5 mag (for an extinction-corrected distance modulus of 29.3 mag) and, based on additional color information derived from a high-quality, archival ground-based I-band image, we estimate that this star was a red supergiant with initial mass M_ZAMS ~ 8 -- 9 Msun. This mass estimate is somewhat lower than, but relatively consistent with, recent limits placed on the progenitor masses of other SNe II-P, using HST data. Future HST imaging with the Advanced Camera for Surveys, when the SN has faded considerably, will be extremely useful in pinpointing the exact SN location and securing identification of the progenitor. If our proposed candidate is confirmed, it will be only the sixth SN progenitor ever directly identified.Comment: 10 pages, 6 figures, to appear now in PASP, 2003 Nov. This update includes more detailed light and color curves for the S

A BAYESIAN ANALYSIS OF THE AGES OF FOUR OPEN CLUSTERS

In this paper we apply a Bayesian technique to determine the best fit of stellar evolution models to find the main sequence turn off age and other cluster parameters of four intermediate-age open clusters: NGC 2360, NGC 2477, NGC 2660, and NGC 3960. Our algorithm utilizes a Markov chain Monte Carlo technique to fit these various parameters, objectively finding the best fit isochrone for each cluster. The result is a high precision isochrone fit. We compare these results with the those of traditional “by eye” isochrone fitting methods. By applying this Bayesian technique to NGC 2360, NGC 2477, NGC 2660, and NGC 3960 we determine the ages of these clusters to be 1.35 ± 0.05, 1.02 ± 0.02, 1.64 ± 0.04, and 0.860 ± 0.04 Gyr, respectively. The results of this paper continue our effort to determine cluster ages to higher precision than that offered by these traditional methods of isochrone fitting

Saved by the pump: Two successful resuscitations utilising emergency department-initiated extracorporeal cardiopulmonary resuscitation in South Africa

Extracorporeal life support is the utilisation of advanced techniques to sustain circulatory and/or ventilatory functions in critically ill patients when standard therapies fail. It is well established in developed countries. There is increasing literature supporting its application in refractory cardiac arrest with a potential reversible cause, a procedure also known as extracorporeal cardiopulmonary resuscitation (eCPR). Two cases where eCPR was successfully utilised in a busy (>30 000 visits per year) private South African emergency department are described here, the first such cases to be reported on the African continent. The first patient had a life-threatening cardiac arrhythmia due to toxin ingestion, and the second a refractory ventricular fibrillation due to acute myocardial infarction. In both these cases the cardiac arrest was witnessed, occurred in the emergency department, and failed to respond to standard advanced resuscitative measures. Both the patients were discharged neurologically intact. Although it is effective, the benefit of this advanced method of resuscitation in a low- to middle-income country is debated

BAYESIAN ANALYSIS OF TWO STELLAR POPULATIONS IN GALACTIC GLOBULAR CLUSTERS I: STATISTICAL AND COMPUTATIONAL METHODS

We develop a Bayesian model for globular clusters composed of multiple stellar populations, extending earlier statistical models for open clusters composed of simple (single) stellar populations (e.g., van Dyk et al. 2009; Stein et al. 2013). Specifically, we model globular clusters with two populations that differ in helium abundance. Our model assumes a hierarchical structuring of the parameters in which physical properties—age, metallicity, helium abundance, distance, absorption, and initial mass—are common to (i) the cluster as a whole or to (ii) individual populations within a cluster, or are unique to (iii) individual stars. An adaptive Markov chain Monte Carlo (MCMC) algorithm is devised for model fitting that greatly improves convergence relative to its precursor non-adaptive MCMC algorithm. Our model and computational tools are incorporated into an open-source software suite known as BASE-9. We use numerical studies to demonstrate that our method can recover parameters of two-population clusters, and also show model misspecification can potentially be identified. As a proof of concept, we analyze the two stellar populations of globular cluster NGC 5272 using our model and methods. (BASE-9 is available from GitHub: https://github.com/argiopetech/base/releases)

Barriers to Continuous Professional Development (CPD) participation for radiographers in Kenya

Abstract: Updating knowledge and skills on an ongoing basis is an important requirement if one is to remain professionally relevant. Formalized CPD is, therefore, essential in order to stay current in a dynamic work environment. The majority of radiographers in Kenya work in remote rural health facilities where CPD activities are limited. The question thus arose: “To what extent are radiographers participating in CPD activities and what constitute barriers to participation?” Objective: The aim of this article is to describe the challenges which affect diagnostic radiographers’ participation in CPD activities in Kenya. Methods: The study targeted radiographers who were registered with the Society of Radiographers in Kenya (SORK). Two hundred and fifty prospective participants were recruited from the SORK data base, using the fish bowl sampling method. Questionnaires with self-addressed stamped envelopes were posted by ordinary mail to facilitate ease of return, while telephone follow-ups improved the response rate. Results: The study revealed that 69% of diagnostic radiographers in Kenya were effectively participating in CPD activities. Barriers to CPD participation included time constraints (62%); financial constraints (66%); lack of information (54%); organizational culture (47%); paucity of resources (58%); and difficulty in being selected by their organisation to attend CPD activities (42%)