The chest x-ray in congenital heart disease 5

This paper is the fourth of the series focusing on the chest x-ray (CXR). The patient in question was a woman aged 56 years who was sent to a cardiologist with left chest pain that was of non-cardiac origin.peer-reviewe

The chest x-ray in congenital heart disease 7

This paper is the seventh of the series focusing on the chest x-ray (CXR). This CXR shows a normal vascular pedicle with a left aortic knuckle and normal pulmonary vascularity. There is some prominence of the apex to the left with a rounded contour suggestive of left ventricular enlargement. There is no evidence of either atria being abnormally placed or distorted. An interesting point is that the patient has an aortic valve replacement and the disk valve prosthesis lies in an unusual and high horizontal position. This suggests that aortic valve is in unusual position such as in transposition of great arteries following an arterial switch procedure. This is the case in this patient wherein aortic valve replacement was carried out for aortic regurgitation.peer-reviewe

Needs Assessment for the Topsfield Council on Aging

The Town of Topsfield’s older population grew substantially during the last decade. Increases are expected to continue as the number of seniors increase moving forward, as well as the share of the Topsfield population they represent. In response to these demographic changes, a study was undertaken to generate and organize information on the older residents of Topsfield and the community organizations supporting their well-being. Special focus was placed on needs of older residents along with the capacity of the Topsfield COA to meet those needs. Methods used included description of existing data, key informant interviews, and focus groups aimed at identifying concerns related to aging in Topsfield, with an emphasis on services and amenities that facilitate aging in place. Assessment methods were designed to identify areas of concern with respect to aging in Topsfield, and to provide a context for planning to address future aging-related needs of the Town’s population

Total anomalous pulmonary venous drainage and coarctation of the aorta

The chest x-ray (CXR) is a useful investigation in congenital heart disease, and has been probably ignored in recent years as echocardiography and other exotic and expensive imaging techniques can show anatomy and physiology. The CXR is a simple, quick and cheap test that yields useful diagnostic information, heart size, lung pathology as well as providing a readily available documentation of these facts for serial comparison. Such information is useful and even vital for the paediatric and the grown up congenital heart population. The echocardiogram gives little or no information on lung pathology or secondary pulmonary effects. The CXR readily demonstrates the classic heart shapes of congenital heart disease and supplies an easily seen record of heart size with low radiation levels. For young clinicians to find teaching about this cheap investigation is hard. This article is the first of a series of articles that highlight the use and the value of the CXR in congenital heart disease.peer-reviewe

Estimating photometric redshifts with artificial neural networks

A new approach to estimating photometric redshifts - using Artificial Neural Networks (ANNs) - is investigated. Unlike the standard template-fitting photometric redshift technique, a large spectroscopically-identified training set is required but, where one is available, ANNs produce photometric redshift accuracies at least as good as and often better than the template-fitting method. The Bayesian priors on the underlying redshift distribution are automatically taken into account. Furthermore, inputs other than galaxy colours - such as morphology, angular size and surface brightness - may be easily incorporated, and their utility assessed. Different ANN architectures are tested on a semi-analytic model galaxy catalogue and the results are compared with the template-fitting method. Finally the method is tested on a sample of ~ 20000 galaxies from the Sloan Digital Sky Survey. The r.m.s. redshift error in the range z < 0.35 is ~ 0.021.Comment: Submitted to MNRAS, 9 pages, 9 figures, substantial improvements to paper structur

Hierarchical Bayesian inference of the Initial Mass Function in Composite Stellar Populations

The initial mass function (IMF) is a key ingredient in many studies of galaxy formation and evolution. Although the IMF is often assumed to be universal, there is continuing evidence that it is not universal. Spectroscopic studies that derive the IMF of the unresolved stellar populations of a galaxy often assume that this spectrum can be described by a single stellar population (SSP). To alleviate these limitations, in this paper we have developed a unique hierarchical Bayesian framework for modelling composite stellar populations (CSPs). Within this framework we use a parameterized IMF prior to regulate a direct inference of the IMF. We use this new framework to determine the number of SSPs that is required to fit a set of realistic CSP mock spectra. The CSP mock spectra that we use are based on semi-analytic models and have an IMF that varies as a function of stellar velocity dispersion of the galaxy. Our results suggest that using a single SSP biases the determination of the IMF slope to a higher value than the true slope, although the trend with stellar velocity dispersion is overall recovered. If we include more SSPs in the fit, the Bayesian evidence increases significantly and the inferred IMF slopes of our mock spectra converge, within the errors, to their true values. Most of the bias is already removed by using two SSPs instead of one. We show that we can reconstruct the variable IMF of our mock spectra for signal-to-noise ratios exceeding $\sim$75.Comment: Accepted for publication in MNRAS, 16 pages, 8 figure