4,420 research outputs found
Antarctic meteorite newsletter. Volume 4: Number 1, February 1981: Antarctic meteorite descriptions, 1976, 1977, 1978, 1979
This issue of the Newsletter is essentially a catalog of all antarctic meteorites in the collections of the Johnson Space Center Curation Facility and the Smithsonian except for 288 pebbles now being classed. It includes listings of all previously distributed data sheets plus a number of new ones for 1979. Indexes of samples include meteorite name/number, classification, and weathering category. Separate indexes list type 3 and 4 chondrites, all irons, all achondrites, and all carbonaceous chondrites
Antarctic meteorite descriptions 1976-1977-1978-1979
All previously distributed meteorite data sheets, plus a number of new ones for 1979 chondrites are included. A comprehensive sample index listing meteorite name/number, classification, and weathering category is also included. Separate indexes listing all petrologic type 3 and type 4 chondrites, all irons, all achondrites, and all carbonaceous chondrites in the collection is provided
LaRC Aerothermodynamic Ground Tests in Support of BOLT Flight Experiment
A review is provided of recent aerothermodynamic ground-test contributions by NASA Langley Research Center (LaRC) to the BOLT flight test program. Several test entries into the Langley Aerothermodynamic Laboratory 20-Inch Mach 6 Air Tunnel are discussed. These entries were intended to support the development and design of flight hardware and instrumentation. Some trends and observations from these entries are provided. Also, a comparison of two different global heat transfer test techniques is included and discussed
The accretion flow in the discless intermediate polar V2400 Ophiuchi
RXTE observations confirm that the X-ray lightcurve of V2400 Oph is pulsed at
the beat cycle, as expected in a discless intermediate polar. There are no
X-ray modulations at the orbital or spin cycles, but optical line profiles vary
with all three cycles. We construct a model for line-profile variations in a
discless accretor, based on the idea that the accretion stream flips from one
magnetic pole to the other, and show that this accounts for the observed
behaviour over the spin and beat cycles. The minimal variability over the
orbital cycle implies that 1) V2400 Oph is at an inclination of only ~10 deg,
and 2) much of the accretion flow is not in a coherent stream, but is circling
the white dwarf, possibly as a ring of denser, diamagnetic blobs. We discuss
the light this sheds on disc formation in intermediate polars.Comment: 10 pages, 12 figures, To appear in MNRAS, includes low-res figures to
reduce siz
Profitable and Sustainable Grazing Systems for Livestock Producers with Saline Land in Southern Australia
Dryland salinity affects over 2.5 M ha in Australia, mostly in southern states and is expanding at 3-5% per year (NLWRA, 2001). The prognosis is for considerable expansion of the area affected by salinity and waterlogging (1217 M ha at equilibrium), because groundwater levels continue to rise and only small-scale land management programmes have been implemented. In addition, many waterways are increasingly saline, especially in the Murray Darling Basin and in Western Australia (WA). Sustainable Grazing on Saline Land (SGSL) addresses the need to make productive use of saline land and water resources. Its research component operates at 12 sites across WA, South Australia (SA), Victoria and New South Wales (NSW) and consists of coordinated activities that have regional relevance and contribute nationally. The programme seeks to develop and demonstrate profitable and sustainable grazing systems on saline land that have positive environmental and social impacts. Whilst there are different priority research issues at each site, data collection is governed by common measurement protocols for salt and water movement, biodiversity, and pasture and animal performance in order to make comparisons and data sharing across sites practical
Profitable and Sustainable Grazing Systems for Livestock Producers with Saline Land in Southern Australia
Dryland salinity affects over 2.5 M ha in Australia, mostly in southern states and is expanding at 3-5% per year (NLWRA, 2001). The prognosis is for considerable expansion of the area affected by salinity and waterlogging (12–17 M ha at equilibrium), because groundwater levels continue to rise and only small-scale land management programmes have been implemented. In addition, many waterways are increasingly saline, especially in the Murray Darling Basin and in Western Australia (WA). Sustainable Grazing on Saline Land (SGSL) addresses the need to make productive use of saline land and water resources. Its research component operates at 12 sites across WA, South Australia (SA), Victoria and New South Wales (NSW) and consists of coordinated activities that have regional relevance and contribute nationally. The programme seeks to develop and demonstrate profitable and sustainable grazing systems on saline land that have positive environmental and social impacts. Whilst there are different priority research issues at each site, data collection is governed by common measurement protocols for salt and water movement, biodiversity, and pasture and animal performance in order to make comparisons and data sharing across sites practical
XMM-Newton observations of AM CVn binaries : V396 Hya and SDSS J1240–01
We present the results of XMM-Newton observations of two AM CVn systems - V396 Hya and SDSS J1240-01. Both systems are detected in X-rays and in the UV: neither shows coherent variability in their light curves. We compare the rms variability of the X-ray and UV power spectra of these sources with other AM CVn systems. Apart from ES Cet, AM CVn sources are not strongly variable in X-rays, while in the UV the degree of variability is related to the systems apparent brightness. The X-ray spectra of V396 Hya and SDSS J1240-01 show highly non-solar abundances, requiring enhanced nitrogen to obtain good fits. We compare the UV and X-ray luminosities for 7 AM CVn systems using recent distances. We find that the X-ray luminosity is not strongly dependent upon orbital period. However, the UV luminosity is highly correlated with orbital period with the UV luminosity decreasing with increasing orbital period. We expect that this is due to the accretion disk making an increasingly strong contribution to the UV emission at shorter periods. The implied luminosities are in remarkably good agreement with predictions
Leveraging Information Technology to Support Agents of World Benefit
There is much debate about social responsibility in the context of business and industry but not much in the context of information technology. We address this void by examining developments and innovations at the interface between information technologies and positive social change. In particular, the paper explores the role of information technology in three critical domains: connectivity, education, and economic development. The underlying premise of the authors is that information and communication technologies can serve agents of social innovation in underserved communities and that their consideration is vital to the success of many efforts that pursue global and sustainable change. We also submit that such issues ought to be integrated more centrally into the practice and scholarly mission of the IS discipline
The Three Dimensional Structure of EUV Accretion Regions in AM Herculis Stars: Modeling of EUV Photometric and Spectroscopic Observations
We have developed a model of the high-energy accretion region for magnetic
cataclysmic variables and applied it to {\it Extreme Ultraviolet Explorer}
observations of 10 AM Herculis type systems. The major features of the EUV
light curves are well described by the model. The light curves exhibit a large
variety of features such as eclipses of the accretion region by the secondary
star and the accretion stream, and dips caused by material very close to the
accretion region. While all the observed features of the light curves are
highly dependent on viewing geometry, none of the light curves are consistent
with a flat, circular accretion spot whose lightcurve would vary solely from
projection effects. The accretion region immediately above the WD surface is a
source of EUV radiation caused by either a vertical extent to the accretion
spot, or Compton scattering off electrons in the accretion column, or, very
likely, both. Our model yields spot sizes averaging 0.06 R, or the WD surface area, and average spot heights of 0.023
R. Spectra extracted during broad dip phases are softer than spectra
during the out-of-dip phases. This spectral ratio measurement leads to the
conclusion that Compton scattering, some absorption by a warm absorber,
geometric effects, an asymmetric temperature structure in the accretion region
and an asymmetric density structure of the accretion columnare all important
components needed to fully explain the data. Spectra extracted at phases where
the accretion spot is hidden behind the limb of the WD, but with the accretion
column immediately above the spot still visible, show no evidence of emission
features characteristic of a hot plasma.Comment: 30 Pages, 11 Figure
XHIP-II: Clusters and associations
Context. In the absence of complete kinematic data it has not previously been
possible to furnish accurate lists of member stars for all moving groups. There
has been an unresolved dispute concerning the apparent inconsistency of the
Hipparcos parallax distance to the Pleiades.
Aims. To find improved candidate lists for clusters and associations
represented among Hipparcos stars, to establish distances, and to cast light on
the Pleiades distance anomaly.
Methods. We use a six dimensional fitting procedure to identify candidates,
and plot CMDs for 20 of the nearest groups. We calculate the mean parallax
distance for all groups.
Results. We identify lists of candidates and calculated parallax distances
for 42 clusters and 45 associations represented within the Hipparcos catalogue.
We find agreement between parallax distance and photometric distances for the
most important clusters. For single stars in the Pleiades we find mean parallax
distance 125.6 \pm 4.2 pc and photometric distance 132 \pm 3 pc calibrated to
nearby groups of similar in age and composition. This gives no reason to doubt
either the Hipparcos database or stellar evolutionary theory.Comment: Accepted for publication in Astronomy Letters, 10 pages, 2 fig
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