1,514 research outputs found
High-density lipoprotein: does it have a dark side?
There are proven pleiotropic anti-atherogenic actions of high-density lipoprotein (HDL). However, in systemic inflammation, HDL can have pro-inflammatory properties that may contribute to accelerated atherosclerosis, likely mediated by a change in the structure of HDL to pro-inflammatory HDL (PiHDL). Validation of the technically challenging assay for PiHDL, and confirmation of an association of PiHDL in multiple populations with known risk for atherosclerosis will eventually provide a useful biomarker. Identification of PiHDL in patients with rheumatic disease may help identify patients at risk of accelerated atherosclerosis, and focus our therapeutic interventions
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
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
High-Resolution Infrared Imaging of Herschel 36 SE: A Showcase for the Influence of Massive Stars in Cluster Environments
We present high-resolution infrared imaging of the massive star-forming region around the O-star Herschel 36. Special emphasis is given to a compact infrared source at 0".25 southeast of the star. The infrared source, hereafter Her 36 SE, is extended in the broad-band images, but features spatially unresolved Br gamma line emission. The line-emission source coincides in position with the previous HST detections in H alpha and the 2 cm radio continuum emission detected by VLA interferometry. We propose that the infrared source Her 36 SE harbors an early B-type star, deeply embedded in a dusty cloud. The fan shape of the cloud with Herschel 36 at its apex, though, manifests direct and ongoing destructive influence of the O7V star on Her 36 SE
Wireless capsule endoscopy for the detection of small bowel diseases in HIV-1-infected patients
<p>Abstract</p> <p>Background and Aims</p> <p>In HIV-infected patients, manifestations of the disease are common in the gastrointestinal tract. The objective of our study was to evaluate the diagnostic yield of the Given<sup>® </sup>Video Capsule System (Given Imaging, Yoqneam, Israel) in these patients.</p> <p>Methods</p> <p>After exclusion of GI-tract stenosis by anamnestic exploration, 49 patients were included into the study. Stratification: Group A (n = 19): HIV-positive, CD<sub>4 </sub>cell count < 200/μl, gastrointestinal symptoms present. Group B: HIV-positive, CD<sub>4 </sub>< 200/μl, without gastrointestinal symptoms (n = 19 Group) C: healthy volunteers (n = 11).</p> <p>Results</p> <p>In group A there was a total of 30 pathological findings, 15 of which with therapeutic implications. In group B, there was a total of 22 pathological findings, 5 relevant for therapy. In group C there was a total of 13 pathological findings, 3 with therapeutic relevance. In 89% (group A) vs. 26% (group B), pathological findings were detected distal the ligament of Treitz (p = 0.001). All capsules were recovered without complications after 12 to 96 h from the stool.</p> <p>Conclusion</p> <p>Wireless capsule endoscopy of the small intestine should be considered for HIV-infected patients with marked immunosuppression and gastrointestinal symptoms.</p
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
The VLTI/MIDI survey of massive young stellar objects - Sounding the inner regions around intermediate- and high-mass young stars using mid-infrared interferometry
We aim to characterize the distribution and composition of circumstellar
material around young massive stars, and to investigate exactly which physical
structures in these objects are probed by long-baseline mid-infrared
interferometric observations. We used the two-telescope interferometric
instrument MIDI of the Very Large Telescope Interferometer of the European
Southern Observatory to observe a sample of 24 intermediate- and high-mass
young stellar objects in the N band (8-13 micron). We had successful fringe
detections for 20 objects, and present spectrally-resolved correlated fluxes
and visibility levels for projected baselines of up to 128 m. We fit the
visibilities with geometric models to derive the sizes of the emitting regions,
as well as the orientation and elongation of the circumstellar material.
Fourteen objects in the sample show the 10 micron silicate feature in
absorption in the total and correlated flux spectra. For 13 of these objects,
we were able to fit the correlated flux spectra with a simple absorption model,
allowing us to constrain the composition and absorptive properties of the
circumstellar material. Nearly all of the massive young stellar objects
observed show significant deviations from spherical symmetry at mid-infrared
wavelengths. In general, the mid-infrared emission can trace both disks and
outflows, and in many cases it may be difficult to disentangle these components
on the basis of interferometric data alone, because of the sparse spatial
frequency coverage normally provided by current long-baseline interferometers.
For the majority of the objects in this sample, the absorption occurs on
spatial scales larger than those probed by MIDI. Finally, the physical extent
of the mid-infrared emission around these sources is correlated with the total
luminosity, albeit with significant scatter.Comment: 36 pages, 22 figures. Accepted to Astronomy and Astrophysic
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
- …