Pre-main-sequence isochrones -- I. The Pleiades benchmark

We present a critical assessment of commonly used pre-main-sequence isochrones by comparing their predictions to a set of well-calibrated colour-magnitude diagrams of the Pleiades in the wavelength range 0.4 to 2.5 microns. Our analysis shows that for temperatures less than 4000 K the models systematically overestimate the flux by a factor two at 0.5 microns, though this decreases with wavelength, becoming negligible at 2.2 microns. In optical colours this will result in the ages for stars younger than 10 Myr being underestimated by factors between two and three. We show that using observations of standard stars to transform the data into a standard system can introduce significant errors in the positioning of pre-main-sequences in colour-magnitude diagrams. Therefore we have compared the models to the data in the natural photometric system in which the observations were taken. Thus we have constructed and tested a model of the system responses for the Wide-Field Camera on the Isaac Newton Telescope. As a benchmark test for the development of pre-main-sequence models we provide both our system responses and the Pleiades sequence.Comment: 15 pages, 12 figures, 7 tables, accepted for publication in MNRAS. All tables are available online at the Cluster Collaboration homepage http://www.astro.ex.ac.uk/people/timn/Catalogues

Bilateral pneumothoraces, pneumomediastinum, pneumoperitoneum, pneumoretroperitoneum, and subcutaneous emphysema after percutaneous tracheostomy -A case report-

We report a rare case of a 72-year-old female who developed extensive subcutaneous emphysema, bilateral pneumothoraces, pneumomediastinum, pneumoperitoneum, and pneumoretroperitoneum after a percutaneous dilatational tracheostomy. The patient's T-cannula was accidentally connected to the oxygen line with a non-perforated connector. The patient rapidly developed respiratory insufficiency and subcutaneous emphysema in the neck and both shoulders. The bilateral pneumothoraces were managed using a chest tube. CT scans of the chest, abdomen, and pelvis revealed an extensive distribution of air throughout the chest and abdomen. The patient was treated successfully with supportive care. This case illustrates the rare occurrence of air passing into multiple body compartments, highlighting the potentially serious complications of a tracheostomy and the importance of intensive care during the recovery period