139 research outputs found
Infrared Excess and Molecular Gas in the Galactic Worm GW46.4+5.5
We have carried out high-resolution (~3') HI and CO line observations along
one-dimensional cuts through the Galactic worm GW46.4+5.5. By comparing the HI
data with IRAS data, we have derived the distributions of I_100 excess and
tau_100 excess, which are respectively the 100 mum intensity and 100 mum
optical depth in excess of what would be expected from HI emission. In two
observed regions, we were able to make a detailed comparison of the infrared
excess and the CO emission. We have found that tau_100 excess has a very good
correlation with the integrated intensity of CO emission, W_CO, but I_100
excess does not. There are two reasons for the poor correlation between I_100
excess and W_CO: firstly, there are regions with enhanced infrared emissivity
without CO, and secondly, dust grains associated with molecular gas have a low
infrared emissivity. In one region, these two factors completely hide the
presence of molecular gas in the infrared. In the second region, we could
identify the area with molecular gas, but I_100 excess significantly
underestimates the column density of molecular hydrogen because of the second
factor mentioned above. We therefore conclude that tau_100 excess, rather than
I_100 excess, is an accurate indicator of molecular content along the line of
sight. We derive tau_100/N(H)=(1.00+-0.02)*10^-5~(10^20 cm^-2)^-1, and
X=N(H_2)/W_CO=~0.7*10^20 cm^-2 (K km s^-1)^-1. Our results suggest that I_100
excess could still be used to estimate the molecular content if the result is
multiplied by a correction factor xi_c=_HI/_H_2 (~2 in
the second region), which accounts for the different infrared emissivities of
atomic and molecular gas. We also discuss some limitations of this work.Comment: 10 pages, 9 postscript figures, uses aas2pp4.sty to be published in
Astrophyslcal Journa
Dense Iron Ejecta and Core-collapse Supernova Explosion in the Young Supernova Remnant G11.2-0.3
We present the results of near-infrared spectroscopic observations of dense
(\simgt 10 cm) iron ejecta in the young core-collapse supernova
remnant G11.2-0.3. Five ejecta knots projected to be close to its center show a
large dispersion in their Doppler shifts: two knots in the east are blueshifted
by more than 1,000 \kms, while three western knots have relatively small
blueshifts of 20-60 \kms. This velocity discrepancy may indicate that the
western knots have been significantly decelerated or that there exists a
systematic velocity difference among the knots. One ejecta filament in the
northwestern boundary, on the other hand, is redshifted by \simgt 200 \kms,
while opposite filament in the southeastern boundary shows a negligible radial
motion. Some of the knots and filaments have secondary velocity components, and
one knot shows a bow shock-like feature in the velocity structure. The iron
ejecta appear to be devoid of strong emission from other heavy elements, such
as S, which may attest to the alpha-rich freezeout process in the explosive
nucleosynthesis of the core-collapse supernova explosion close to its center.
The prominent bipolar distribution of the Fe ejecta in the northwestern and
southeastern direction, along with the elongation of the central pulsar wind
nebula in the perpendicular direction, is consistent with the interpretation
that the supernova exploded primarily along the northwestern and southeastern
direction.Comment: To appear in ApJ Letter
Multiple cerebral infarction and paradoxical air embolism during hepatectomy using the Cavitron Ultrasonic Surgical Aspirator -A case report-
A venous air embolism and paradoxical air embolism (PAE) are serious complications in patients undergoing a hepatectomy. We report a case of PAE and cerebral infarctions in a patient undergoing a hepatic resection using a Cavitron Ultrasonic Surgical Aspirator (CUSA®). A 65-year-old woman underwent a left lobe hepatectomy. During the middle phase of the liver resection with CUSA®, there was a sudden decrease in arterial blood pressure, end-tidal carbon dioxide and SpO2. With resuscitation, intraoperative ultrasonography revealed massive air emboli in both her left and right heart, which lasted for 40 min. The hepatectomy was completed after the disappearance of the air emboli from her heart. After surgery, her mental status was stuporous. The brain CT and MRI revealed multiple acute cerebral infarctions. Finally, she died from septic shock. This case highlights the need for anesthetists and surgeons to be aware of the potential for CUSA®-related massive PAE
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