Dissecting Massive YSOs with Mid-Infrared Interferometry

The very inner structure of massive YSOs is difficult to trace. With conventional observational methods we often identify structures still several hundreds of AU in size. But we also need information about the innermost regions where the actual mass transfer onto the forming high-mass star occurs. An innovative way to probe these scales is to utilise mid-infrared interferometry. Here, we present first results of our MIDI GTO programme at the VLTI. We observed 10 well-known massive YSOs down to scales of 20 mas. We clearly resolve these objects which results in low visibilities and sizes in the order of 30 - 50 mas. Thus, with MIDI we can for the first time quantify the extent of the thermal emission from the warm circumstellar dust and thus calibrate existing concepts regarding the compactness of such emission in the pre-UCHII region phase. Special emphasis will be given to the BN-type object M8E-IR where our modelling is most advanced and where there is indirect evidence for a strongly bloated central star.Comment: 8 pages, 6 figures, proceedings contribution for the conference "Massive Star Formation: Observations confront Theory", held in September 2007 in Heidelberg, Germany; to appear in ASP Conf. Ser. 387, H. Beuther et al. (eds.

Detecting Extrasolar Planets with Integral Field Spectroscopy

Observations of extrasolar planets using Integral Field Spectroscopy (IFS), if coupled with an extreme Adaptive Optics system and analyzed with a Simultaneous Differential Imaging technique (SDI), are a powerful tool to detect and characterize extrasolar planets directly; they enhance the signal of the planet and, at the same time, reduces the impact of stellar light and consequently important noise sources like speckles. In order to verify the efficiency of such a technique, we developed a simulation code able to test the capabilities of this IFS-SDI technique for different kinds of planets and telescopes, modelling the atmospheric and instrumental noise sources. The first results obtained by the simulations show that many significant extrasolar planet detections are indeed possible using the present 8m-class telescopes within a few hours of exposure time. The procedure adopted to simulate IFS observations is presented here in detail, explaining in particular how we obtain estimates of the speckle noise, Adaptive Optics corrections, specific instrumental features, and how we test the efficiency of the SDI technique to increase the signal-to-noise ratio of the planet detection. The most important results achieved by simulations of various objects, from 1 M_J to brown dwarfs of 30 M_J, for observations with an 8 meter telescope, are then presented and discussed.Comment: 60 pages, 37 figures, accepted in PASP, 4 Tables adde

VLTI observations of IRS~3: The brightest compact MIR source at the Galactic Centre

The dust enshrouded star IRS~3 in the central light year of our galaxy was partially resolved in a recent VLTI experiment. The presented observation is the first step in investigating both IRS~3 in particular and the stellar population of the Galactic Centre in general with the VLTI at highest angular resolution. We will outline which scientific issues can be addressed by a complete MIDI dataset on IRS~3 in the mid infrared.Comment: 4 pages, 3 figures, published in: The ESO Messenge

Test Set Diameter: Quantifying the Diversity of Sets of Test Cases

A common and natural intuition among software testers is that test cases need to differ if a software system is to be tested properly and its quality ensured. Consequently, much research has gone into formulating distance measures for how test cases, their inputs and/or their outputs differ. However, common to these proposals is that they are data type specific and/or calculate the diversity only between pairs of test inputs, traces or outputs. We propose a new metric to measure the diversity of sets of tests: the test set diameter (TSDm). It extends our earlier, pairwise test diversity metrics based on recent advances in information theory regarding the calculation of the normalized compression distance (NCD) for multisets. A key advantage is that TSDm is a universal measure of diversity and so can be applied to any test set regardless of data type of the test inputs (and, moreover, to other test-related data such as execution traces). But this universality comes at the cost of greater computational effort compared to competing approaches. Our experiments on four different systems show that the test set diameter can help select test sets with higher structural and fault coverage than random selection even when only applied to test inputs. This can enable early test design and selection, prior to even having a software system to test, and complement other types of test automation and analysis. We argue that this quantification of test set diversity creates a number of opportunities to better understand software quality and provides practical ways to increase it

Prehospital anaesthesia by a physician and paramedic critical care team in Southwest England

OBJECTIVES: Prehospital anaesthesia using rapid sequence induction (RSI) is carried out internationally and in the UK despite equivocal evidence of clinical benefit. It is a core skill of the prehospital critical care service established by the Great Western Ambulance Service NHS Trust (GWAS) in 2008. This retrospective analysis of the service's first 150 prehospital RSIs describes intubation success rates and complications, thereby contributing towards the ongoing debate on its role and safety. METHODS: Within the GWAS critical care team, RSI is only carried out in the presence of a qualified physician and critical care paramedic (CCP). The role of the intubating practitioner is interchangeable between physician and CCP. Data were collected retrospectively from RSI audit forms and electronic patient monitor printouts. RESULTS: GWAS physician and CCP teams undertook 150 prehospital RSIs between June 2008 and August 2011. The intubation success rate was 82, 91 and 97% for the first, second and third attempts, respectively. Successful intubation on the first attempt was achieved in 58 (85%) and 64 (78%) patients for physicians and CCPs, respectively. RSI complications included hypoxaemia (10.2%), hypotension (9.7%) and bradycardia (1.3%). CONCLUSION: Prehospital RSI can be carried out safely, with intubation success rates and complications comparable with RSI in the emergency department. The variation in the intubation success rates between individual practitioners highlights the importance of ongoing performance monitoring, coupled with high standards of clinical governance and training. © 2013 Wolters Kluwer Health Lippincott Williams & Wilkins

Mid-infrared interferometry of massive young stellar objects. I. VLTI and Subaru observations of the enigmatic object M8E-IR

[abridged] Our knowledge of the inner structure of embedded massive young stellar objects is still quite limited. We attempt here to overcome the spatial resolution limitations of conventional thermal infrared imaging. We employed mid-infrared interferometry using the MIDI instrument on the ESO/VLTI facility to investigate M8E-IR, a well-known massive young stellar object suspected of containing a circumstellar disk. Spectrally dispersed visibilities in the 8-13 micron range were obtained at seven interferometric baselines. We resolve the mid-infrared emission of M8E-IR and find typical sizes of the emission regions of the order of 30 milli-arcseconds (~45 AU). Radiative transfer simulations have been performed to interpret the data. The fitting of the spectral energy distribution, in combination with the measured visibilities, does not provide evidence for an extended circumstellar disk with sizes > 100 AU but requires the presence of an extended envelope. The data are not able to constrain the presence of a small-scale disk in addition to an envelope. In either case, the interferometry measurements indicate the existence of a strongly bloated, relatively cool central object, possibly tracing the recent accretion history of M8E-IR. In addition, we present 24.5 micron images that clearly distinguish between M8E-IR and the neighbouring ultracompact HII region and which show the cometary-shaped infrared morphology of the latter source. Our results show that IR interferometry, combined with radiative transfer modelling, can be a viable tool to reveal crucial structure information on embedded massive young stellar objects and to resolve ambiguities arising from fitting the SED.Comment: 7 pages, 5 figures, accepted for publication in A&A, new version after language editing, one important reference added, conclusions unchange

A rigorous evaluation of crossover and mutation in genetic programming

The role of crossover and mutation in Genetic Programming (GP) has been the subject of much debate since the emergence of the field. In this paper, we contribute new empirical evidence to this argument using a rigorous and principled experimental method applied to six problems common in the GP literature. The approach tunes the algorithm parameters to enable a fair and objective comparison of two different GP algorithms, the first using a combination of crossover and reproduction, and secondly using a combination of mutation and reproduction. We find that crossover does not significantly outperform mutation on most of the problems examined. In addition, we demonstrate that the use of a straightforward Design of Experiments methodology is effective at tuning GP algorithm parameters

Subarcsecond Submillimeter Imaging of the Ultracompact HII Region G5.89-0.39

We present the first subarcsecond submillimeter images of the enigmatic ultracompact HII region (UCHII) G5.89-0.39. Observed with the SMA, the 875 micron continuum emission exhibits a shell-like morphology similar to longer wavelengths. By using images with comparable angular resolution at five frequencies obtained from the VLA archive and CARMA, we have removed the free-free component from the 875 micron image. We find five sources of dust emission: two compact warm objects (SMA1 and SMA2) along the periphery of the shell, and three additional regions further out. There is no dust emission inside the shell, supporting the picture of a dust-free cavity surrounded by high density gas. At subarcsecond resolution, most of the molecular gas tracers encircle the UCHII region and appear to constrain its expansion. We also find G5.89-0.39 to be almost completely lacking in organic molecular line emission. The dust cores SMA1 and SMA2 exhibit compact spatial peaks in optically-thin gas tracers (e.g. 34SO2), while SMA1 also coincides with 11.9 micron emission. In CO(3-2), we find a high-velocity north/south bipolar outflow centered on SMA1, aligned with infrared H2 knots, and responsible for much of the maser activity. We conclude that SMA1 is an embedded intermediate mass protostar with an estimated luminosity of 3000 Lsun and a circumstellar mass of ~1 Msun. Finally, we have discovered an NH3 (3,3) maser 12 arcsec northwest of the UCHII region, coincident with a 44 GHz CH3OH maser, and possibly associated with the Br gamma outflow source identified by Puga et al. (2006).Comment: 41 pages, 11 figures, published in The Astrophysical Journal (2008) Volume 680, Issue 2, pp. 1271-1288. An error in the registration of the marker positions in Figure 11 has been corrected in this versio

Ground truth deficiencies in software engineering: when codifying the past can be counterproductive

Many software engineering tools build and evaluate their models based on historical data to support development and process decisions. These models help us answer numerous interesting questions, but have their own caveats. In a real-life setting, the objective function of human decision-makers for a given task might be influenced by a whole host of factors that stem from their cognitive biases, subverting the ideal objective function required for an optimally functioning system. Relying on this data as ground truth may give rise to systems that end up automating software engineering decisions by mimicking past sub-optimal behaviour. We illustrate this phenomenon and suggest mitigation strategies to raise awareness