37,384 research outputs found
Dense molecular clumps in the envelope of the yellow hypergiant IRC+10420
The circumstellar envelope of the hypergiant star IRC+10420 has been traced
as far out in SiO J=2-1 as in CO J = 1-0 and CO J = 2-1, in dramatic contrast
with the centrally condensed (thermal) SiO- but extended CO-emitting envelopes
of giant and supergiant stars. Here, we present an observation of the
circumstellar envelope in SiO J=1-0 that, when combined with the previous
observation in {\sioii}, provide more stringent constraints on the density of
the SiO-emitting gas than hitherto possible. The emission in SiO peaks at a
radius of 2\arcsec\ whereas that in SiO J=2-1 emission peaks at a smaller
radius of 1\arcsec, giving rise to their ring-like appearances. The ratio
in brightness temperature between SiO J=1-0 and SiO J=2-1 decreases from a
value well above unity at the innermost measurable radius to about unity at
radius of 2\arcsec, beyond which this ratio remains approximately
constant. Dividing the envelope into three zones as in models for the CO J =
1-0 and CO J = 2-1 emission, we show that the density of the SiO-emitting gas
is comparable with that of the CO-emitting gas in the inner zone, but at least
an order of magnitude higher by comparison in both the middle and outer zones.
The SiO-emitting gas therefore originates from dense clumps, likely associated
with the dust clumps seen in scattered optical light, surrounded by more
diffuse CO-emitting interclump gas. We suggest that SiO molecules are released
from dust grains due to shock interactions between the dense SiO-emitting
clumps and the diffuse CO-emitting interclump gas.Comment: Accepted for publication in Ap
Myocardial fibrosis in stroke survivors
Stroke survivors are most likely to die of cardiac death, yet few undergo comprehensive cardiac assessment to look for reversible causes. Myocardial fibrosis (MF) is not only the hallmark of cardiomyopathy, but also a substrate for sudden cardiac death, ventricular tachyarrhythmia and heart failure. Procollagen carboxyl-terminal telopeptide (PICP) was found to be a marker of MF. The relationship between PICP and cardiac abnormalities in stroke survivors is unknown. We recently showed that MF in stroke survivors can be treated by spironolactone and amiloride in a randomised placebo-controlled cross-over study with reduction in PICP levels and QTc [1]
Anomalous Soft Photons in Hadron Production
Anomalous soft photons in excess of what is expected from electromagnetic
bremsstrahlung have been observed in association with the production of
hadrons, mostly mesons, in high-energy (K+)p, (pi+)p, (pi-)p, pp, and (e+)(e-)
collisions. We propose a model for the simultaneous production of anomalous
soft photons and mesons in quantum field theory, in which the meson production
arises from the oscillation of color charge densities of the quarks of the
underlying vacuum in the flux tube. As a quark carries both a color charge and
an electric charge, the oscillation of the color charge densities will be
accompanied by the oscillation of electric charge densities, which will in turn
lead to the simultaneous production of soft photons during the meson production
process. How the production of these soft photons may explain the anomalous
soft photon data will be discussed. Further experimental measurements to test
the model will be proposed.Comment: 19 pages, 2 figures, to be published in Physical Review
Effect of cloud on UVA and exposure to humans
The daily autumn and winter UVA exposures and 6-minute UVA irradiance data for a Southern Hemisphere, subtropical site (Toowoomba, Australia, 27.6 S, 151.9 E) are presented. This data is used to quantify the effect of cloud on UVA using an integrated sky-camera and radiation system. Additionally, an estimate of the effect of enhanced UVA exposure on humans is made. The measurement system consisted of broadband visible-infrared and UVA sensors together with a sun tracking, wide-angle video camera. The mean daily June exposure was found to be 409 kJm-2. Under the constraints of the uncertainty of both the UVA measurement system and clear-sky model, one case of enhanced UVA irradiance was found. Three cases of cloud enhancement of daily UVA exposure, approaching clear-sky levels, were also determined using a calculated clear-sky envelope. It was also determined that for a fulltime outdoor worker, the additional UVA exposure could approach approximately that of one third of a full winter's day. For indoor workers with an outside lunch break of noon to 1 pm, the additional UVA exposure was on average 6.9 kJm-2 over three cloud enhanced days. To the authors' knowledge this is the first paper to present some evidence of cloud enhanced UVA human exposure
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