549 research outputs found
Rotational Structure and Outflow in the Infrared Dark Cloud 18223-3
We examine an Infrared Dark Cloud (IRDC) at high spatial resolution as a
means to study rotation, outflow, and infall at the onset of massive star
formation. Submillimeter Array observations combined with IRAM 30 meter data in
12CO(2--1) reveal the outflow orientation in the IRDC 18223-3 region, and PdBI
3 mm observations confirm this orientation in other molecular species. The
implication of the outflow's presence is that an accretion disk is feeding it,
so using high density tracers such as C18O, N2H+, and CH3OH, we looked for
indications of a velocity gradient perpendicular to the outflow direction.
Surprisingly, this gradient turns out to be most apparent in CH3OH. The large
size (28,000 AU) of the flattened rotating object detected indicates that this
velocity gradient cannot be due solely to a disk, but rather from inward
spiraling gas within which a Keplerian disk likely exists. From the outflow
parameters, we derive properties of the source such as an outflow dynamical age
of ~37,000 years, outflow mass of ~13 M_sun, and outflow energy of ~1.7 x 10^46
erg. While the outflow mass and energy are clearly consistent with a high-mass
star forming region, the outflow dynamical age indicates a slightly more
evolved evolutionary stage than previous spectral energy distribution (SED)
modeling indicates. The calculated outflow properties reveal that this is truly
a massive star in the making. We also present a model of the observed methanol
velocity gradient. The rotational signatures can be modeled via rotationally
infalling gas. These data present evidence for one of the youngest known
outflow/infall/disk systems in massive star formation. A tentative evolutionary
picture for massive disks is discussed.Comment: 11 pages, 9 figures. Accepted for publication in A&A. Figures 2,3,6,
and 9 are available at higher resolution by email or in the journal
publicatio
The Supernova Triggered Formation and Enrichment of Our Solar System
We investigate the enrichment of the pre-solar cloud core with short lived
radionuclides (SLRs), especially 26Al. The homogeneity and the surprisingly
small spread in the ratio 26Al/27Al observed in the overwhelming majority of
calcium-aluminium-rich inclusions (CAIs) in a vast variety of primitive
chondritic meteorites places strong constraints on the formation of the the
solar system. Freshly synthesized radioactive 26Al has to be included and well
mixed within 20kyr. After discussing various scenarios including X-winds, AGB
stars and Wolf-Rayet stars, we come to the conclusion that triggering the
collapse of a cold cloud core by a nearby supernova is the most promising
scenario. We then narrow down the vast parameter space by considering the
pre-explosion survivability of such a clump as well as the cross-section
necessary for sufficient enrichment. We employ numerical simulations to address
the mixing of the radioactively enriched SN gas with the pre-existing gas and
the forced collapse within 20kyr. We show that a cold clump of 10Msun at a
distance of 5pc can be sufficiently enriched in 26Al and triggered into
collapse fast enough - within 18kyr after encountering the supernova shock -
for a range of different metallicities and progenitor masses, even if the
enriched material is assumed to be distributed homogeneously in the entire
supernova bubble. In summary, we envision an environment for the birth place of
the Solar System 4.567Gyr ago similar to the situation of the pillars in M16
nowadays, where molecular cloud cores adjacent to an HII region will be hit by
a supernova explosion in the future. We show that the triggered collapse and
formation of the Solar System as well as the required enrichment with
radioactive 26Al are possible in this scenario.Comment: 12 pages, 8 figures, accepted for publication in ApJ. Resolution of
most figures degraded to fit within arXiv size limits. A full resolution
version is available at
http://www.usm.uni-muenchen.de/~gritschm/Gritschneder_2011_sun.pd
'Education, education, education' : legal, moral and clinical
This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students
Identification of Equid herpesvirus 2 in tissue-engineered equine tendon
Background: Incidental findings of virus-like particles were identified following electron microscopy of tissue-engineered tendon constructs (TETC) derived from equine tenocytes. We set out to determine the nature of these particles, as there are few studies which identify virus in tendons per se, and their presence could have implications for tissue-engineering using allogenic grafts. Methods: Virus particles were identified in electron microscopy of TETCs. Virion morphology was used to initially hypothesise the virus identity. Next generation sequencing was implemented to identify the virus. A pan herpesvirus PCR was used to validate the RNASeq findings using an independent platform. Histological analysis and biochemical analysis was undertaken on the TETCs. Results: Morphological features suggested the virus to be either a retrovirus or herpesvirus. Subsequent next generation sequencing mapped reads to Equid herpesvirus 2 (EHV2). Histological examination and biochemical testing for collagen content revealed no significant differences between virally affected TETCs and non-affected TETCs. An independent set of equine superficial digital flexor tendon tissue (n=10) examined using designed primers for specific EHV2 contigs identified at sequencing were negative. These data suggest that EHV is resident in some equine tendon. Conclusions: EHV2 was demonstrated in equine tenocytes for the first time; likely from in vivo infection. The presence of EHV2 could have implications to both tissue-engineering and tendinopathy
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
- …