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

Analysis of Global Radiotherapy Needs and Costs by Geographic Region and Income Level.

Recent years have seen various reviews on the lack of access to radiotherapy often based on geographic regions of the world such as Africa, Asia Pacific, Europe, Latin America and North America. Countries are often defined by their national income per capita levels based on World Bank definitions of high income, upper middle income, lower middle income and low income. Within the world regions, there are significant variations in gross national income (GNI) per capita among the different countries, and even within similar income levels, large variations exist. This report presents the actual status of radiotherapy and analyses the current needs and costs to provide full access in the different regions of the world. Actual coverage of the needs ranges from 34% in Africa to over 92% in Europe to about double the needs in North America. In line with this, proportional additional investments and operational costs are as high as more than 200% in Africa to almost none in North America. Two world regions face substantial challenges: Africa, based on the important demands to build new capacity and subsequently to maintain operational capability; and Asia Pacific, due to its high population density, translating into large absolute needs in radiotherapy treatments and resources, and hence in associated costs. With the data highlighting a large variability of GNI/capita even within similar income levels in the various world regions, it is expected that additional investment in resources and costs may be more dependent on income level of the country than on the GNI group or the geographic region of the world

Radio Detection of SN 1986E in NGC 4302

Radio observations of SN 1986E have shown a clear detection of emission at 6 cm wavelength about 8 months after optical discovery. Combined with a number of new upper limits and a study of the possible models, it appears that SN 1986E was probably a fairly normal Type IIL supernova, somewhat similar to SN 1980K, with radio emission at roughly expected levels. This detection continues the correlation between radio detection and late time optical emission.Comment: 14 pages, LaTeX (AASTeX), 2 PostScript figures, to appear in ApJ (Letters

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)

Possible Recovery of SN 1961V In Hubble Space Telescope Archival Images

SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type V'' supernova. However, it has been argued that SN 1961V was not a genuine supernova, but instead the superoutburst of an eta Carinae-like luminous blue variable star. In particular, Filippenko et al. (1995, AJ, 110, 2261) used pre-refurbishment HST WFPC images and the known radio position of SN 1961V to conclude that the star survived the eruption and is likely coincident with a V \~ 25.6 mag, V-I ~ 1.9 mag object. Recently, Stockdale et al. (2001, AJ, 122, 283) recovered the fading SN 1961V at radio wavelengths and argue that its behavior is similar that of some Type II supernovae. We have analyzed post-refurbishment archival HST WFPC2 data and find that the new radio position is still consistent with the Filippenko et al. object, which has not changed in brightness or color, but is also consistent with an adjacent, fainter (I ~ 24.3 mag) and very red (V-I > 1.0 mag) object. We suggest that this fainter object could be the survivor of SN 1961V. Forthcoming HST observations may settle this issue.Comment: 8 pages, 6 figures, to appear in the PASP (2002 July issue

Ultrasound comparison of the effects of prehabilitation exercises and the scapular assistance test on the acromiohumeral distance

Abstract: Background: Prolonged participation in overhead sports creates shoulder muscle imbalances which eventually alter the efficacy of the shoulder stabiliser muscles and heighten injury risk, such as subacromial impingement syndrome. Objectives: The aim of this study was to determine if ultrasound is effective to measure the acromiohumeral distance (AHD) to compare the effect of the scapular assistance test (SAT) on the AHD with a prehabilitative exercise intervention programme in asymptomatic cricket players. Methods: Baseline testing on cricket players from the North- West University cricket squad (N=34) included AHD measurements performed by a sonographer at 0°, 30° and 60° humeral abduction angles respectively, with and without the SAT application. Players were then randomly assigned to an intervention and control group..

Ultrasound comparison of the effects of prehabilitation exercises and the scapular assistance test on the acromiohumeral distance

Abstract: Background: Prolonged participation in overhead sports creates shoulder muscle imbalances which eventually alter the efficacy of the shoulder stabiliser muscles and heighten injury risk, such as subacromial impingement syndrome. Objectives: The aim of this study was to determine if ultrasound is effective to measure the acromiohumeral distance (AHD) to compare the effect of the scapular assistance test (SAT) on the AHD with a prehabilitative exercise intervention programme in asymptomatic cricket players. Methods: Baseline testing on cricket players from the North- West University cricket squad (N=34) included AHD measurements performed by a sonographer at 0°, 30° and 60° humeral abduction angles respectively, with and without the SAT application. Players were then randomly assigned to an intervention and control group..

Constraints on the Binary Companion to the SN Ic 1994I Progenitor

Core-collapse supernovae (SNe), which mark the deaths of massive stars, are among the most powerful explosions in the universe and are responsible, e.g., for a predominant synthesis of chemical elements in their host galaxies. The majority of massive stars are thought to be born in close binary systems. To date, putative binary companions to the progenitors of SNe may have been detected in only two cases, SNe 1993J and 2011dh. We report on the search for a companion of the progenitor of the Type Ic SN 1994I, long considered to have been the result of binary interaction. Twenty years after explosion, we used the Hubble Space Telescope to observe the SN site in the ultraviolet (F275W and F336W bands), resulting in deep upper limits on the expected companion: F275W > 26.1 mag and F336W > 24.7 mag. These allow us to exclude the presence of a main sequence companion with a mass ≳ 10 M_⊙. Through comparison with theoretical simulations of possible progenitor populations, we show that the upper limits to a companion detection exclude interacting binaries with semi-conservative (late Case A or early Case B) mass transfer. These limits tend to favor systems with non-conservative, late Case B mass transfer with intermediate initial orbital periods and mass ratios. The most likely mass range for a putative main sequence companion would be ~5–12 M_⊙, the upper end of which corresponds to the inferred upper detection limit

Psychological debriefing (PD) of trauma : a proposed model for Africa

CITATION: Van Dyk, E. L. & Van Dyk, G. A. J. 2010. Psychological debriefing (PD) of trauma : a proposed model for Africa. Journal for Transdisciplinary Research in Southern Africa, 6(2):a270, doi:10.4102/td.v6i2.270.The original publication is available at https://td-sa.netAfrica is a continent with severe trauma. Traumatic events include experiences of child soldiers, people living in war and conflict zones, and people struggling with the HIV/AIDS pandemic. These events cause high levels of trauma. The trauma causes psychological disorders like post traumatic stress disorder, acute stress disorder and combat stress reaction, specific in the military environment. This article focuses on a better understanding of the implications of trauma for military people and civilians. It discusses the different theories and models of psychological debriefing. Lastly the article discusses psychological debriefing models for military forces and the civil ian population to prevent severe psychopathology after traumatic incidents in Africa.https://td-sa.net/index.php/td/article/view/270Publisher's versio