301 research outputs found
Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy
A renewed attempt to detect radio recombination lines from external galaxies
has resulted in the measurement of lines from several bright starburst
galaxies. The lines are produced by hydrogen ionized by young, high-mass stars
and are diagnostic of the conditions and gas dynamics in the starburst regions
without problems of dust obscuration. We present here detections of the lines
H91alpha and H92alpha near 8.6 GHz from the starburst nuclei in NGC 3256, NGC
4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line
emitting region as a collection of H II regions, we derive the required number
of H II regions, their temperature, density, and distribution.Comment: 6 pages, to appear in "Proc 331. Heraeus Seminar: The Evolution of
Starbursts", Bad Honnef, Germany, Aug 16 - 20, 2004, Eds: S. Huettemeister,
S. Aalto, D.J. Bomans, and E. Manthe
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September 1965
Massachusetts Lawn and Turf Grass CouncilBetter Grass Through Research and Educatio
Oral-facial tissue reconstruction in the regenerative axolotl
Absence of large amounts of orofacial tissues caused by cancerous resections, congenital
defects or trauma result in sequelae such as dysphagia and noticeable scars. Oral-neck tissue
regeneration was studied in the axolotl (regenerative amphibian) following a 2.5mm punch
biopsy that simultaneously removed skin, connective tissue, muscle, and cartilage in the tongue
and intermandibular region. The untreated wound was studied macroscopically and histologically
at 17 different time points ranging from 0-180d (N= 120 axolotls). At 12h the wound’s surface
was smoothened and within 1mm, internal lingual muscular modifications occurred; at the same
distance, between days 4-7 lingual muscle degradation was complete. Immunofluorescence
indicates complete keratinocytes migration by 48h. These cells with epidermal Leydig cells,
appearing yellow, lead the chin’s deep tissue outgrowth until its closure on the 14th day.
Regeneration speeds varied and peaked in time for each tissue, 1) deep Immunofluorescence to
Col IV showed basement membrane reconnected between days 30-45 coinciding with the chin’s
dermal tissue’s surface area recovery. New muscle appeared at 21d and was always preceded by
the formation of a collagen bed. Both chin tissues regain all surface area and practically all
components while the lingual structure lacks some content but is generally similar to the original.
The methodology and high-resolution observations described here are the first of its kind for this
animal model and could serve as a basis for future studies in oral and facial regenerative research
Tiny scale opacity fluctuations from VLBA, MERLIN and VLA observations of HI absorption toward 3C 138
The structure function of opacity fluctuations is a useful statistical tool
to study tiny scale structures of neutral hydrogen. Here we present high
resolution observation of HI absorption towards 3C 138, and estimate the
structure function of opacity fluctuations from the combined VLA, MERLIN and
VLBA data. The angular scales probed in this work are ~ 10-200 milliarcsec
(about 5-100 AU). The structure function in this range is found to be well
represented by a power law S_tau(x) ~ x^{beta} with index beta ~ 0.33 +/- 0.07
corresponding to a power spectrum P_tau(U) ~ U^{-2.33}. This is slightly
shallower than the earlier reported power law index of ~ 2.5-3.0 at ~ 1000 AU
to few pc scales. The amplitude of the derived structure function is a factor
of ~ 20-60 times higher than the extrapolated amplitude from observation of Cas
A at larger scales. On the other hand, extrapolating the AU scale structure
function for 3C 138 predicts the observed structure function for Cas A at the
pc scale correctly. These results clearly establish that the atomic gas has
significantly more structures in AU scales than expected from earlier pc scale
observations. Some plausible reasons are identified and discussed here to
explain these results. The observational evidence of a shallower slope and the
presence of rich small scale structures may have implications for the current
understanding of the interstellar turbulence.Comment: 6 pages, 5 figures. Accepted for publication in ApJ. The definitive
version will be available at http://iopscience.iop.org
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July 1965
Massachusetts Turf and Lawn Grass CouncilBetter Turf Through Research and Educatio
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Experimental cross-correlation Nitrogen Q-branch CARS Thermometry in a Spark Ignition Engine
A purely experimental technique was employed to derive temperatures from nitrogen Q-branch Coherent Anti-Stokes Raman Scattering (CARS) spectra, obtained in a high pressure, high temperature environment (spark ignition Otto engine). This was in order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch CARS spectra at high pressure. The spectra obtained in the engine were compared with spectra obtained in a calibrated high pressure, high temperature cell, using direct cross-correlation in place of the minimisation of sums of squares of residuals. The technique is demonstrated through the measurement of air temperature as a function of crankshaft angle inside the cylinder of a motored single-cylinder Ricardo E6 research engine, followed by the measurement of fuel-air mixture temperatures obtained during the compression stroke in a knocking Ricardo E6 engine. A standard CARS program (SANDIA’s CARSFIT) was employed to calibrate the altered non-resonant background contribution to the CARS spectra that was caused by the alteration to the mole fraction of nitrogen in the unburned fuel-air mixture. The compression temperature profiles were extrapolated in order to predict the auto-ignition temperatures
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Fall 1983
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