3,531 research outputs found
An X-Ray Spectroscopic Study of the SMC X-1/Sk 160 System
We have investigated the composition and distribution of the wind of Sk 160,
the supergiant companion of the X-ray star SMC X-1, by comparing an X-ray
spectrum of the source, obtained with the ASCA observatory, during an eclipse
with the computed spectra of reprocessed radiation from circumstellar matter
with various density distributions. We show that the metal abundance in the
wind of Sk 160 is no greater than a few tenths of solar, as has been determined
for other objects in the Magellanic Clouds. We also show that the observed
X-ray spectrum is not consistent with the density distributions of
circumstellar matter of the spherically symmetric form derived for line-driven
winds, nor with the density distribution derived from a hydrodynamic simulation
of the X-ray perturbed and line-driven wind by Blondin & Woo (1995).Comment: 35 pages including 16 figures, uses AASTeX v5.0.2, accepted to Ap
X-ray Signatures of an Ionized Reprocessor in the Seyfert galaxy Ton S 180
We discuss the hard X-ray properties of the Seyfert galaxy Ton S 180, based
upon the analysis of ASCA data. We find the X-ray flux varied by a factor ~2 on
a time scale of a few thousand seconds. The source showed significantly higher
amplitude of variability in the 0.5-2 keV band than in the 2-10 keV band. The
continuum is adequately parameterized as a Gamma ~ 2.5 power-law across the
0.6--10 keV band . We confirm the recent discovery of an emission line of high
equivalent width, due to Fe K-shell emission from highly-ionized material.
These ASCA data show the Fe line profile to be broad and asymmetric and
tentatively suggest it is stronger during the X-ray flares, consistent with an
origin from the inner parts of an accretion disk. The X-ray spectrum is complex
below 2 keV, possibly due to emission from a blend of soft X-ray lines, which
would support the existence of an ionized reprocessor, most likely due to a
relatively high accretion rate in this source.Comment: 24 pages, 8 figures. LaTeX with encapsulated postscript. To appear in
the Astrophysical Journa
Results of investigations into the groundwater response and productivity of high water use agricultural systems 1990-1997 4. TKK Engineering\u27s Catchment (Williams)
High water use vegetation systems for salinity control were trialed on a 70 ha catchment located about 15 km north of Williams, Western Australia. The catchment receives about 545 mm annual rainfall and 1870 mm annual evaporation. Development of salinity is characterised by passive discharge upslope from a dolerite dyke. Because recharge exceeds the discharge capacity of current seeps, there is potential for new seeps to develop in the mid to lower slopes
Results of investigations into the groundwater response and productivity of high water use agricultural systems 1990-1997 1. Wooldridge/Wright\u27s Catchment (Kojonup)
High water use vegetation systems for salinity control were trialed on a 170 ha catchment located 13 km north of Kojonup, Western Australia. The catchment receives about 470 mm annual rainfall and 1825 mm annual evaporation
Results of investigations into the groundwater response and productivity of high water use agricultural systems 1990-1997 5 White/Beattys\u27 Catchment (Dinninup)
High water use vegetation systems for salinity control were trialed on a 250 ha catchment located three km north-west of Dinninup, Western Australia. The catchment receives about 620 mm annual rainfall and 1500 mm annual evaporation. The catchment is characterised by slopes with gradients in excess of 5%, deep weathering (15-25 m to bedrock), active seepage in the valley (piezometric heads 204 m above ground surface) and high recharge (water table fluctuations of 1-4 m)
Results of investigations into the groundwater response and productivity of high water use agricultural systems 1990-1997 3 Hunts\u27 Catchment (Frankland)
High water use vegetation systems for salinity control were trialed on an 80 ha catchment located 12 km east of Frankland, Western Australia. The catchment receives about 510 mm annual rainfall and 1525 mm annual evaporation. Development of salinity in the catchment is concentrated in the valley floor. Here the groundwater is extremely saline (3000-4000 mS/m) and piezometric levels are between 1 m below and 1 m above the surface
Results of investigations into the groundwater response and productivity of high water use agricultural systems 1990-1997. 2. Souths\u27 Catchment (Darkan)
High water use vegetation systems for salinity control were trialed on a 90 ha catchment located 12 km north north-west of Darkan, Western Australia. The catchment receives about 560 mm annual rainfall and 1895 mm annual evaporation. The catchment is characterised by a number of actively expanding seeps which are developing under the strong geological control of quartz and dolerite dykes. Development of salinity is also influenced by high recharge rates in the free draining gravel soils of the upper slope
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Transcriptional profiling of inductive mesenchyme to identify molecules involved in prostate development and disease
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background The mesenchymal compartment plays a key role in organogenesis, and cells within the mesenchyme/stroma are a source of potent molecules that control epithelia during development and tumorigenesis. We used serial analysis of gene expression (SAGE) to profile a key subset of prostatic mesenchyme that regulates prostate development and is enriched for growth-regulatory molecules. Results SAGE libraries were constructed from prostatic inductive mesenchyme and from the complete prostatic rudiment (including inductive mesenchyme, epithelium, and smooth muscle). By comparing these two SAGE libraries, we generated a list of 219 transcripts that were enriched or specific to inductive mesenchyme and that may act as mesenchymal regulators of organogenesis and tumorigenesis. We identified Scube1 as enriched in inductive mesenchyme from the list of 219 transcripts; also, quantitative RT-PCR and whole-mount in situ hybridization revealed Scube1 to exhibit a highly restricted expression pattern. The expression of Scube1 in a subset of mesenchymal cells suggests a role in prostatic induction and branching morphogenesis. Additionally, Scube1 transcripts were expressed in prostate cancer stromal cells, and were less abundant in cancer associated fibroblasts relative to matched normal prostate fibroblasts. Conclusion The use of a precisely defined subset of cells and a back-comparison approach allowed us to identify rare mRNAs that could be overlooked using other approaches. We propose that Scube1 encodes a novel stromal molecule that is involved in prostate development and tumorigenesis.Published versio
First Constraints on Iron Abundance versus Reflection Fraction from the Seyfert~1 Galaxy MCG--6-30-15
We report on a joint ASCA and RXTE observation spanning an 400~ks time
interval of the bright Seyfert~1 galaxy MCG--6-30-15. The data clearly confirm
the presence of a broad skewed iron line ( 266 eV) and
Compton reflection continuum at higher energies reported in our previous paper.
We also investigate whether the gravitational and Doppler effects that affect
the iron line may also be manifest in the reflected continuum. The uniqueness
of this data set is underlined by the extremely good statistics that we obtain
from the approximately four million photons that make up the 2-20 keV RXTE PCA
spectrum alone. This, coupled with the high energy coverage of HEXTE and the
spectral resolution of ASCA in the iron line regime has allowed us to constrain
the relationship between abundance and reflection fraction for the first time
at the 99 per cent confidence level. The reflection fraction is entirely
consistent with a flat disk, i.e. the cold material subtends sr at
the source, to an accuracy of 20 per cent. Monte Carlo simulations show that
the observed strong iron line intensity is explained by an overabundance of
iron by a factor of 2 and an underabundance of the lower-Z elements by a
similar factor. By considering non-standard abundances, a clear and consistent
picture can be made in which both the iron line and reflection continuum come
from the same material such as e.g. an accretion disk.Comment: 8 pages, 8 figures, accepted for publication MNRAS 7/9
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