1,892 research outputs found
Standard spacecraft economic analysis. Volume 1: Executive summary
A study of the comparative program costs associated with use of various standardized spacecraft for Air Force space test program missions to be flown on the space shuttle during the 1980-1990 time period is reviewed. The first phase of the study considered a variety of procurement mixes composed of existing or programmed NASA standard spacecraft designs and a Air Force standard spacecraft design. The results were briefed to a joint NASA/Air Force audience on July 11, 1976. The second phase considered additional procurement options using an upgraded version of an existing NASA design. The results of both phases are summarized
Standard spacecraft economic analysis. Volume 2: Findings and conclusions
The comparative program costs associated with use of various standardized spacecraft for Air Force space test program missions to be flown on the space shuttle were studied in two phases. In the first phase, a variety of procurement mixes composed of existing or programmed NASA standard spacecraft designs and an Air Force standard spacecraft design were considered. The second phase dealt with additional procurement options using an upgraded version of an existing NASA design. The results of both phases are discussed
SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation
The Molonglo Observatory Synthesis Telescope, operating at 843 MHz with a 5
square degree field of view, is carrying out a radio imaging survey of the sky
south of declination -30 deg. This survey (the Sydney University Molonglo Sky
Survey, or SUMSS) produces images with a resolution of 43" x 43" cosec(Dec.)
and an rms noise level of about 1 mJy/beam. SUMSS is therefore similar in
sensitivity and resolution to the northern NRAO VLA Sky Survey (NVSS; Condon et
al. 1998). The survey is progressing at a rate of about 1000 square degrees per
year, yielding individual and statistical data for many thousands of weak radio
sources. This paper describes the main characteristics of the survey, and
presents sample images from the first year of observation.Comment: 27 pages, 12 figures (figures 2, 8, 10 in jpg format); AJ, in pres
The Molonglo Galactic Plane Survey: I. Overview and Images
The first epoch Molonglo Galactic Plane Survey (MGPS1) is a radio continuum
survey made using the Molonglo Observatory Synthesis Telescope (MOST) at 843
MHz with a resolution of 43" X 43" cosec |delta|. The region surveyed is 245
deg < l < 355 deg, |b| < 1.5 deg. The thirteen 9 deg X 3 deg mosaic images
presented here are the superposition of over 450 complete synthesis
observations, each taking 12 h and covering 70' X 70' cosec |delta|. The
root-mean-square sensitivity over much of the mosaiced survey is 1-2 mJy/beam
(1 sigma), and the positional accuracy is approximately 1" X 1" cosec |delta|
for sources brighter than 20 mJy. The dynamic range is no better than 250:1,
and this also constrains the sensitivity in some parts of the images. The
survey area of 330 sq deg contains well over 12,000 unresolved or barely
resolved objects, almost all of which are extra-galactic sources lying in the
Zone of Avoidance. In addition a significant fraction of this area is covered
by extended, diffuse emission associated with thermal complexes, discrete H II
regions, supernova remnants, and other structures in the Galactic interstellar
medium.Comment: Paper with 3 figures and 1 table + Table 2 + 7 jpg grayscales for Fig
4. Astrophysical Journal Supplement (in press) see also
http://www.astrop.physics.usyd.edu.au/MGP
Intrapancreatic delivery of human umbilical cord blood aldehyde dehydrogenase-producing cells promotes islet regeneration
Aims/hypothesis We sought to investigate the stimulation of islet regeneration by transplanted human umbilical cord blood (UCB) cells purified according to high aldehyde dehydrogenase (ALDH) activity (ALDHhi), a conserved characteristic of multiple progenitor lineages. We hypothesised that direct intrapancreatic (iPan) delivery of ALDHhi progenitors would augment islet regeneration via timely and localised exposure to islet-regenerative stimuli. Methods Cells were purified from UCB based on flow cytometry for low ALDH activity (ALDHlo) vs ALDHhi. UCB ALDHlo or ALDHhi cells were compared for surface marker expression, as well as haematopoietic, endothelial and multipotent stromal progenitor content in vitro. UCB ALDHlo or ALDHhi cells were i.v. or iPan injected into streptozotocin-treated non-obese diabetic/severe combined immune-deficient mice temporally monitored for blood glucose, serum insulin and glucose tolerance. Human cell recruitment and survival in the pancreas, insulin content, islet-associated cell proliferation and islet vascularisation were documented in situ. Results UCB-derived ALDHhi cells were highly enriched for haematopoietic and endothelial progenitor frequency, and showed increased expression of progenitor and myeloid cell surface markers. Although i.v. transplantation of ALDHhi cells demonstrated low pancreas engraftment and only transient blood glucose lowering capacity, iPan injected ALDHhi cells reversed established hyperglycaemia, increased serum insulin and improved the response to a glucose challenge. iPan injected ALDHhi cells surrounded damaged islets at early time points and increased islet-associated cell proliferation, resulting in the recovery of beta cell mass. Conclusions/interpretation iPan delivery of UCB ALDHhi cells potentiated islet-associated cell proliferation, insulin production and islet revascularisation, resulting in the recovery of host islet function. Elucidation of the progenitor-specific pathways stimulated during islet regeneration may provide new approaches to promote islet expansion during diabetes. © Springer-Verlag 2012
PKS 1018-42: A Powerful Kinetically Dominated Quasar
We have identified PKS 1018-42 as a radio galaxy with extraordinarily
powerful jets, over twice as powerful as any 3CR source of equal or lesser
redshift except for one (3C196). It is perhaps the most intrinsically powerful
extragalactic radio source in the, still poorly explored, Southern Hemisphere.
PKS 1018-42 belongs to the class of FR II objects that are kinetically
dominated, the jet kinetic luminosity, (calculated at 151 MHz), is 3.4 times larger than the
total thermal luminosity (IR to X-ray) of the accretion flow, . It is the fourth most kinetically dominated
quasar that we could verify from existing radio data. From a review of the
literature, we find that kinetically dominated sources such as PKS 1018-42 are
rare, and list the 5 most kinetically dominated sources found from our review.
Our results for PKS 1018-42 are based on new observations from the Australia
Telescope Compact Array.Comment: To appear in ApJ Letter
Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps
The contribution from the residuals of the foreground can have a significant
impact on the temperature maps of the Cosmic Microwave Background (CMB).
Mostly, the focus has been on the galactic plane, when foreground cleaning has
taken place. However, in this paper, we will investigate the possible
foreground contamination, from sources outside the galactic plane in the CMB
maps. We will analyze the correlation between the Faraday rotation map and the
CMB temperature map. The Faraday rotation map is dependent on the galactic
magnetic field, as well as the thermal electron density, and both may
contribute to the CMB temperature. We find that the standard deviation for the
mean cross correlation deviate from that of simulations at the 99.9% level.
Additionally, a comparison between the CMB temperature extrema and the extremum
points of the Faraday rotation is also performed, showing a general overlap
between the two. Also we find that the CMB Cold Spot is located at an area of
strong negative cross correlation, meaning that it may be explained by a
galactic origin. Further, we investigate nearby supernova remnants in the
galaxy, traced by the galactic radio loops. These super nova remnants are
located at high and low galactic latitude, and thus well outside the galactic
plane. We find some correlation between the Faraday Rotation and the CMB
temperature, at select radio loops. This indicate, that the galactic
foregrounds may affect the CMB, at high galactic latitudesComment: 13 pages, 22 figures, 6 table
A high-resolution radio survey of the Vela supernova remnant
This paper presents a high-resolution radio continuum (843 MHz) survey of the
Vela supernova remnant. The contrast between the structures in the central
pulsar-powered nebula of the remnant and the synchrotron radiation shell allows
the remnant to be identified morphologically as a member of the composite
class. The data are the first of a composite remnant at spatial scales
comparable with those available for the Cygnus Loop and the Crab Nebula, and
make possible a comparison of radio, optical and soft X-ray emission from the
resolved shell filaments. The survey, made with the Molonglo Observatory
Synthesis Telescope, covers an area of 50 square degrees at a resolution of
43'' x 60'', while imaging structures on scales up to 30'.Comment: 18 pages, 7 jpg figures (version with ps figures at
http://astro.berkeley.edu/~dbock/papers/); AJ, in pres
The final two redshifts for radio sources from the equatorial BRL sample
Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful
radio sources from the Molonglo Reference Catalogue, for which redshifts were
compiled or measured for 177 of the 178 objects. For the final object,
MRC1059-010 (3C249), the host galaxy is here identified using near-infrared
imaging, and the redshift is determined from VLT spectroscopy. For one other
object in the sample, MRC0320+053 (4C05.14), the literature redshift has been
questioned: new spectroscopic observations of this object are presented,
deriving a corrected redshift. With these two results, the spectroscopic
completeness of this sample is now 100%.
New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7
GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10
shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission
profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA
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