2,227 research outputs found
Molecular Hydrogen in the Lagoon: H2 line emission from Messier 8
The 2.12 micron v=1-0 S(1) line of molecular hydrogen has been imaged in the
Hourglass region of M8. The line is emitted from a roughly bipolar region,
centred around the O7 star Herschel 36. The peak H2 1-0 S(1) line intensity is
8.2 x 10E-15 erg s-1 cm-2 arcsec-2. The line centre emission velocity varies
from -25 kms in the SE lobe to +45 kms in the NW lobe. The distribution is
similar to that of the CO J=3-2 line. The H2 line appears to be shock-excited
when a bipolar outflow from Herschel 36 interacts with the ambient molecular
cloud. The total luminosity of all H2 lines is estimated to be ~ 16 Lsun and
the mass of the hot molecular gas ~9 x 10E-4 Msun (without any correction for
extinction).Comment: 11 pages, 4 figures (1 in colour). Submitted to Publications of the
Astronomical Society of Australia, December 200
Shocked H2 and Fe+ Dynamics in the Orion Bullets
Observations of H2 velocity profiles in the two most clearly defined Orion
bullets are extremely difficult to reconcile with existing steady-state shock
models. We have observed [FeII] 1.644um velocity profiles of selected bullets
and H2 1-0 S(1) 2.122um velocity profiles for a series of positions along and
across the corresponding bow-shaped shock fronts driven into the surrounding
molecular cloud. Integrated [FeII] velocity profiles of the brightest bullets
are consistent with theoretical bow shock predictions. However, observations of
broad, singly-peaked H2 1-0 S(1) profiles at a range of positions within the
most clearly resolved bullet wakes are not consistent with molecular shock
modelling. A uniform, collisionally broadened background component which
pervades the region in both tracers is inconsistent with fluorescence due to
the ionizing radiation of the Trapezium stars alone.Comment: 20 pages including 18 figures, published in MNRA
The elite variable in democratic transitions and breakdowns (1989)
"Stable democratic regimes depend heavily on the 'consensual unity' of national elites. So Jong as elites remain disunified, political regimes are unstable, a condition which makes democratic transitions and democratic breakdowns merely temporary oscillations in the forms unstable regimes take. Disunity appears to be the generic condition of national elites, and disunity strongly tends to persist regardless of socioeconomic development and other changes in mass populations. The consensually unified elites that are necessary to stable democracies are created in only a few ways, two of the most important of which involve distinctive elite transformations. After elaborating this argument, we examine the relationship between elites and regimes in Western nation-states since they began to consolidate after 1500. We show that our approach makes good sense of the Western political record, that it does much to clarify prospects for stable democracies in developing societies today, and that it makes the increasingly elite-centered analysis of democratic transitions and breakdowns more systematic." (author's abstract
Systematic Floral Anatomy of Pontederiaceae
Twenty species of Pontederiaceae and six species of the outgroup families Haemodoraceae and Philydraceae were investigated with regard to floral anatomy, using standard histological methods and graphic reconstructions. Variation is described in several features, including functional carpel number, the distribution of floral aerenchyma, the presence of unusual floral epithelial cells, the presence, type, and distribution of tannin cells, crystal type and distribution, aspects of placentation, ovule number, number of ovule rows per carpel, and septal nectary presence. In order to better assess character homology, one of these features, placentation, was divided into three discrete characters: septal fusion, placenta position, and placenta evagination. Several of the floral characters were optimized onto a most parsimonious cladogram from a relatively recent study using combined chloroplast DNA data. Associations of character states with specific clades were observed in functional carpel number, aerenchyma distribution, epithelial cell presence, tannin cell distribution, septal nectary presence, and the three redefined aspects of placentation: septal fusion, placenta position, and placenta evagination. These floral data will be valuable in further elucidating relationships in Pontederiaceae in future studies of the group
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