NGC 2264 IRS1: The central engine and its cavity

We present a high-resolution study of NGC 2264 IRS1 in CS(2-1) and in the 3-mm continuum using the IRAM Plateau de Bure Interferometer. We complement these radio data with images taken at 2.2, 4.6, and 11.9 micron. The combined information allow a new interpretation of the closest environment of NGC 2264 IRS1. No disk around the B-type star IRS1 was found. IRS1 and its low-mass companions are located in a low-density cavity which is surrounded by the remaining dense cloud core which has a clumpy shell-like structure. Strong evidence for induced on-going star formation was found in the surroundings of IRS1. A deeply embedded very young stellar object 20 arcsec to the north of IRS1 is powering a highly collimated bipolar outflow. The object 8 in the closer environment of IRS1 is a binary surrounded by dusty circumbinary material and powering two bipolar outflows.Comment: 17 pages, 6 figures, The paper is accepted and will appear in the Astrophysical Journal, Vol 599, No 1 (issue December 10). A high-resolution postscript version of this paper is available here ( http://www.astro.uni-jena.de/Users/martin/publi.html). Furthermore, you can find a high resolution PDF file here ( http://www.tls-tautenburg.de/research/tls-research/pub2003.html

Miocene Shark and Batoid Fauna from Nosy Makamby (Mahajanga Basin, Northwestern Madagascar)

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Three-dimensional Continuum Radiative Transfer Images of a Molecular Cloud Core Evolution

We analyze a three-dimensional smoothed particle hydrodynamics simulation of an evolving and later collapsing pre-stellar core. Using a three-dimensional continuum radiative transfer program, we generate images at 7 micron, 15 micron, 175 micron, and 1.3 mm for different evolutionary times and viewing angles. We discuss the observability of the properties of pre-stellar cores for the different wavelengths. For examples of non-symmetric fragments, it is shown that, misleadingly, the density profiles derived from a one-dimensional analysis of the corresponding images are consistent with one-dimensional core evolution models. We conclude that one-dimensional modeling based on column density interpretation of images does not produce reliable structural information and that multidimensional modeling is required.Comment: accepted by ApJL, 4 pages, 4 figure

On chains in HH-closed topological pospaces

We study chains in an $H$-closed topological partially ordered space. We give sufficient conditions for a maximal chain $L$ in an $H$-closed topological partially ordered space such that $L$ contains a maximal (minimal) element. Also we give sufficient conditions for a linearly ordered topological partially ordered space to be $H$-closed. We prove that any $H$-closed topological semilattice contains a zero. We show that a linearly ordered $H$-closed topological semilattice is an $H$-closed topological pospace and show that in the general case this is not true. We construct an example an $H$-closed topological pospace with a non-$H$-closed maximal chain and give sufficient conditions that a maximal chain of an $H$-closed topological pospace is an $H$-closed topological pospace.Comment: We have rewritten and substantially expanded the manuscrip

Looking into the hearts of Bok globules: MM and submm continuum images of isolated star-forming cores

We present the results of a comprehensive infrared, submillimetre, and millimetre continuum emission study of isolated low-mass star-forming cores in 32 Bok globules, with the aim to investigate the process of star formation in these regions. The submillimetre and millimetre dust continuum emission maps together with the spectral energy distributions are used to model and derive the physical properties of the star-forming cores, such as luminosities, sizes, masses, densities, etc. Comparisons with ground-based near-infrared and space-based mid and far-infrared images from Spitzer are used to reveal the stellar content of the Bok globules, association of embedded young stellar objects with the submm dust cores, and the evolutionary stages of the individual sources. Submm dust continuum emission was detected in 26 out of the 32 globule cores observed. For 18 globules with detected (sub)mm cores we derive evolutionary stages and physical parameters of the embedded sources. We identify nine starless cores, most of which are presumably prestellar, nine Class 0 protostars, and twelve Class I YSOs. Specific source properties like bolometric temperature, core size, and central densities are discussed as function of evolutionary stage. We find that at least two thirds (16 out of 24) of the star-forming globules studied here show evidence of forming multiple stars on scales between 1,000 and 50,000 AU. However, we also find that most of these small prototstar and star groups are comprised of sources with different evolutionary stages, suggesting a picture of slow and sequential star formation in isolated globulesComment: 60 pages, 28 figures, accepted by The Astrophysical Journal Supplement Serie

Integral field spectroscopy of massive young stellar objects in the N113 H II region in the Large Magellanic Cloud

The Spitzer Surveying the Agents of Galaxy Evolution (SAGE) survey has allowed the identification and analysis of significant samples of Young Stellar Object (YSO) candidates in the Large Magellanic Cloud (LMC). However, the angular resolution of Spitzer is relatively poor meaning that at the distance of the LMC, it is likely that many of the Spitzer YSO candidates in fact contain multiple components. We present high-resolution K-band integral field spectroscopic observations of the three most prominent massive YSO candidates in the N113 H?II region using Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI). We have identified six K-band continuum sources within the three Spitzer sources and we have mapped the morphology and velocity fields of extended line emission around these sources. Br ?, He?I and H2 emission is found at the position of all six K-band sources; we discuss whether the emission is associated with the continuum sources or whether it is ambient emission. H2 emission appears to be mostly ambient emission and no evidence of CO emission arising in the discs of YSOs has been found. We have mapped the centroid velocities of extended Br ? emission and He?I emission and found evidence of two expanding compact H?II regions. One source shows compact and strong H2 emission suggestive of a molecular outflow. The diversity of spectroscopic properties observed is interpreted in the context of a range of evolutionary stages associated with massive star formation

Optimisation of Bioluminescent Reporters for Use with Mycobacteria

BACKGROUND: Mycobacterium tuberculosis, the causative agent of tuberculosis, still represents a major public health threat in many countries. Bioluminescence, the production of light by luciferase-catalyzed reactions, is a versatile reporter technology with multiple applications both in vitro and in vivo. In vivo bioluminescence imaging (BLI) represents one of its most outstanding uses by allowing the non-invasive localization of luciferase-expressing cells within a live animal. Despite the extensive use of luminescent reporters in mycobacteria, the resultant luminescent strains have not been fully applied to BLI. METHODOLOGY/PRINCIPAL FINDINGS: One of the main obstacles to the use of bioluminescence for in vivo imaging is the achievement of reporter protein expression levels high enough to obtain a signal that can be detected externally. Therefore, as a first step in the application of this technology to the study of mycobacterial infection in vivo, we have optimised the use of firefly, Gaussia and bacterial luciferases in mycobacteria using a combination of vectors, promoters, and codon-optimised genes. We report for the first time the functional expression of the whole bacterial lux operon in Mycobacterium tuberculosis and M. smegmatis thus allowing the development of auto-luminescent mycobacteria. We demonstrate that the Gaussia luciferase is secreted from bacterial cells and that this secretion does not require a signal sequence. Finally we prove that the signal produced by recombinant mycobacteria expressing either the firefly or bacterial luciferases can be non-invasively detected in the lungs of infected mice by bioluminescence imaging. CONCLUSIONS/SIGNIFICANCE: While much work remains to be done, the finding that both firefly and bacterial luciferases can be detected non-invasively in live mice is an important first step to using these reporters to study the pathogenesis of M. tuberculosis and other mycobacterial species in vivo. Furthermore, the development of auto-luminescent mycobacteria has enormous ramifications for high throughput mycobacterial drug screening assays which are currently carried out either in a destructive manner using LuxAB or the firefly luciferase

Trapping Solids at the Inner Edge of the Dead Zone: 3-D Global MHD Simulations

The poorly-ionized interior of the protoplanetary disk is the location where dust coagulation processes may be most efficient. However even here, planetesimal formation may be limited by the loss of solid material through radial drift, and by collisional fragmentation of the particles. Our aim is to investigate the possibility that solid particles are trapped at local pressure maxima in the dynamically evolving disk. We perform the first 3-D global non-ideal MHD calculations of the disk treating the turbulence driven by the magneto-rotational instability. The domain contains an inner MRI-active region near the young star and an outer midplane dead zone, with the transition between the two modeled by a sharp increase in the magnetic diffusivity. The azimuthal magnetic fields generated in the active zone oscillate over time, changing sign about every 150 years. We thus observe the radial structure of the `butterfly pattern' seen previously in local shearing-box simulations. The mean magnetic field diffuses from the active zone into the dead zone, where the Reynolds stress nevertheless dominates. The greater total accretion stress in the active zone leads to a net reduction in the surface density, so that after 800 years an approximate steady state is reached in which a local radial maximum in the midplane pressure lies near the transition radius. We also observe the formation of density ridges within the active zone. The dead zone in our models possesses a mean magnetic field, significant Reynolds stresses and a steady local pressure maximum at the inner edge, where the outward migration of planetary embryos and the efficient trapping of solid material are possible.Comment: 17 pages, 30 *.ps files for figures. Accepted 16 November 2009 in A&

Jejunal perforation caused by a feeding jejunostomy tube: a case report

<p>Abstract</p> <p>Introduction</p> <p>Percutaneous endoscopic gastrostomy and feeding jejunostomy are used for providing long-term nutritional support to patients with neurological disorders. Various mechanical complications of these procedures are described.</p> <p>Case presentation</p> <p>We report a case of a 17-year-old boy with cerebral injury who had a percutaneous endoscopic gastrostomy tube changed to a feeding jejunostomy tube. Twenty-four hours later he developed abdominal pain and became clinically septic. A contrast study through the feeding tube and a subsequent computed tomography scan did not reveal any intra-abdominal pathology. At laparotomy it was discovered that the tip of the feeding tube had perforated through the jejunal wall and was lying outside the lumen. This was successfully treated by re-inserting a feeding jejunostomy tube distally and closure of the perforation and previous FJ site</p> <p>Conclusion</p> <p>We suggest that the threshold for contrast studies and operative intervention should be low in neurologically impaired patients to avoid the delay in treatment of tube-related complications.</p