2,749 research outputs found
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 75.Comment: Accepted for publication in MNRAS, 16 pages, 8 figure
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