A Wolf-Rayet-like progenitor of SN 2013cu from spectral observations of a stellar wind.

The explosive fate of massive Wolf-Rayet stars (WRSs) is a key open question in stellar physics. An appealing option is that hydrogen-deficient WRSs are the progenitors of some hydrogen-poor supernova explosions of types IIb, Ib and Ic (ref. 2). A blue object, having luminosity and colours consistent with those of some WRSs, has recently been identified in pre-explosion images at the location of a supernova of type Ib (ref. 3), but has not yet been conclusively determined to have been the progenitor. Similar work has so far only resulted in non-detections. Comparison of early photometric observations of type Ic supernovae with theoretical models suggests that the progenitor stars had radii of less than 10(12) centimetres, as expected for some WRSs. The signature of WRSs, their emission line spectra, cannot be probed by such studies. Here we report the detection of strong emission lines in a spectrum of type IIb supernova 2013cu (iPTF13ast) obtained approximately 15.5 hours after explosion (by 'flash spectroscopy', which captures the effects of the supernova explosion shock breakout flash on material surrounding the progenitor star). We identify Wolf-Rayet-like wind signatures, suggesting a progenitor of the WN(h) subclass (those WRSs with winds dominated by helium and nitrogen, with traces of hydrogen). The extent of this dense wind may indicate increased mass loss from the progenitor shortly before its explosion, consistent with recent theoretical predictions

National survey of outcomes and practices in acute respiratory distress syndrome in Singapore

The authors acknowledge the following as the total funding sources for this study: 1. SICM NICER grant: logistical, non-monetary, support from the Society of Intensive Care Medicine Singapore. This was in the form of Ngee Ann Polytechnic students (8) who collected the data for the study for one month. 2. NMRC (National medical research council) grant for Dr, Matthew Cove (partial support for this study): This was in the shape of salary support for all his research related activity. (NMRC/TA/0015/2013) (MEC)

Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star

Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining1. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability2,3,4,5. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required

Body composition analysis in critically ill survivors: A comparison of bioelectrical impedance spectroscopy devices

Background: Body composition is commonly altered in response to critical illness and can be estimated at the bedside with bioelectrical impedance spectroscopy (BIS). Different electrode configurations may be used to mitigate assumptions of the technique, but the reliability of tetra-polar and octo-polar arrangements has yet to be established. This study aimed to compare both configurations, in a prospective observational study of 17 critically ill survivors and 12 healthy controls. Methods: Weight, supine body length, and BIS on both tetra-polar and octo-polar configured devices were recorded, then repeated 2 days later. Bioelectrical impedance vector analysis was subsequently performed using data from the tetra-polar device at a frequency of 50 kHz. Results: Test-retest agreement was acceptable for the tetra-polar device (intraclass correlation coefficient range, patients: 0.876-0.988 vs controls: 0.983-0.998, P ≤ 0.001). However, lower and wider ranging test-retest intraclass correlation coefficients were obtained with the octo-polar instrument in both groups. Furthermore, there was a difference in the mass/volume of body compartments measured on each device in both patients (P ≤.017) and controls (P ≤.045). A change in the composition profile of critically ill males was evident between measurement occasions, which was reflected by a reduction in body weight of 1.6 (1.5) kg (P ≤ 0.001) across the sample over the same period. Conclusions: BIS devices should not be used interchangeably in the clinical setting. The reliability of the tetra-polar instrument was good, but daily fluctuations in body weight may have affected the results