36,127 research outputs found
MASSCLEAN - MASSive CLuster Evolution and ANalysis Package - Description, Tests, and Results
MASSCLEAN is a new, sophisticated and robust stellar cluster image and
photometry simulation package. This package is able to create color-magnitude
diagrams and standard FITS images in any of the traditional optical and
near-infrared bands based on cluster characteristics input by the user,
including but not limited to distance, age, mass, radius and extinction. At the
limit of very distant, unresolved clusters, we have checked the integrated
colors created in MASSCLEAN against those from other simple stellar population
(SSP) models with consistent results. Because the algorithm populates the
cluster with a discrete number of tenable stars, it can be used as part of a
Monte Carlo Method to derive the probabilistic range of characteristics
(integrated colors, for example) consistent with a given cluster mass and age.
We present the first ever mass dependent integrated colors as a function of
age, derived from over 100,000 Monte Carlo runs, which can be used to improve
the current age determination methods for stellar clusters.Comment: 4 pages, 5 figures, Proceedings International Astronomical Union
Symposium No. 266, Star Clusters - Basic Galactic Building Blocks throughout
Time and Space, Editors: Richard de Grijs & Jacques R. D. Lepin
Feasibility of Kevlar 49/PMR-15 Polyimide for High Temperature Applications
Kevlar 49 aramid organic fiber reinforced PMR-15 polyimide laminates were characterized to determine the applicability of the material to high temperature aerospace structures. Kevlar 49/3501-6 epoxy laminates were fabricated and characterized for comparison with the Kevlar 49/PMR-15 polyimide material. Flexural strengths and moduli and interlaminar shear strengths were determined from 75 F to 600 F for the PMR-15 and from 75 F to 450 F for the Kevlar/3501-6 epoxy material. The effects of hydrothermal and long-term elevated temperature exposures on the flexural strengths and moduli and the interlaminar shear strengths were also studied
Static and dynamic fatigue behavior of glass filament-wound pressure vessels at ambient and cryogenic temperatures
Static and dynamic fatigue behavior of glass filament-wound plastic pressure vessels at ambient and cryogenic temperature
Infrared spectroscopic variability of Cygnus X-3 in outburst and quiescence
We present four epochs of high-resolution infrared spectroscopy of the
peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small
flaring and outburst states of the system as defined by radio and X-ray
monitoring. The underlying infrared spectrum of the source, as observed during
radio and X-ray quiescence and small flaring states, is one of broad, weak HeII
and NV emission. Spectral variability in this state is dominated by modulation
at the 4.8 hr orbital period of the system. H-band spectra confirm the
significant hydrogen depletion of the mass donor. The closest spectral match to
the quiescent infrared spectrum of Cyg X-3 is an early-type WN Wolf-Rayet star.
In outburst, the infrared spectrum is dramatically different, with the
appearance of very strong twin-peaked HeI emission displaying both day-to-day
variability and V(iolet)/R(ed) variations with orbital phase. The most likely
explanation appears to be an enhanced stellar wind from the companion. Thus
X-ray and radio outbursts in this system are likely to originate in
mass-transfer, and not disc, instabilities, and the lengthening of the orbital
period will not be smooth but will be accelerated during these outbursts.
Furthermore, the appearance of these lines is suggestive of an asymmetric
emitting region. We propose that the wind in Cyg X-3 is significantly flattened
in the plane of the binary orbit. This may explain the observed twin-peaked HeI
features as well as reconciling a massive Wolf-Rayet secondary with the
relatively small optical depth to X-rays, if the disc wind is inclined at some
angle to the line of sight.Comment: 13 pages, 7 figures. Accepted for publication in MNRA
Surface protection of graphite fabric/PMR-15 composites subjected to thermal oxidation
Graphite fabric/PMR-15 laminates develop matrix cracks during long-term exposure in air at temperatures in the range of 500 to 600 F. This study was performed to demonstrate the effectiveness of incorporating graphite mat surface plies as a means of reducing the developing of matrix cracks. Celion 3000 graphite fabric/PMR-15 laminates were fabricated with graphite or graphite mat/325-mesh boron powder surface plies. Laminates without mat surface plies were also fabricated for control purposes. Composite flexural strength, flexural modulus, and interlaminar shear strength were determined at 288 C before and after long-term exposure (up to 1500 hr) in air at 316 C. The results of this study showed that the incorporation of graphite mat surface plies reduces matrix cracking and improves the elevated temperature mechanical property retention characteristics of the composites
Stoner-Wohlfart model applied to bicrystal magnetoresistance hysteresis
We calculate numerically the magnetization direction as function of magnetic
field in the Stoner-Wohlfart theory and are able to reproduce the shape of the
low-field magnetoresistance hysteresis observed in manganite grain boundary
junctions. Moreover, we show that it is necessary to include biaxial
magnetocrystalline anisotropy to fully describe the grain boundary
magnetoresistance in LaSrMnO/SrTiO bicrystal tunnel
junctions.Comment: 5 pages, 4 figure
The impact of information and communication technology on family carers of older people and professionals in Sweden
Government policy in Sweden, as in other developed countries, pays increasing attention as to how best to support the family carers of older people. New and innovative means of support, such as information and communication technology, are emerging. This paper explores the perceived benefits of, and barriers to, information technology as a means of supporting family carers of older people.
Following a brief overview of the care-giving literature, with particular reference to the Swedish context, interview and questionnaire data collected from 34 families who took part in the Swedish ACTION project are used to explore the role of user-friendly information and communication technology to inform and enable family carers of older people to exercise choice, to care more effectively and to work in partnership with professionals. Interview data from two groups of professionals that utilised ACTION are also examined to throw light on its potential benefits for both carers and professionals. Consideration is given to the barriers to using information technology, and to identifying those carers most likely to benefit. Areas for further development are the need for practitioners' education and a wider range of programmes to address carers' diverse needs. Clearly, lessons learned from the Swedish project have wider relevance, given that new forms of support are being developed in most technically advanced countries
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