16,950 research outputs found
Chemical vapor deposition of high T sub c superconductors
The results are reported of an investigation into the synthesis and properties of high temperature superconducting materials. A chemical vapor deposition apparatus was designed and built which is suitable for the preparation of multicomponent metal films This apparatus was used to prepare a series of high T sub c A-15 structure superconducting films in the binary system Nb-Ge. The effect on T sub c of a variety of substrate materials was investigated. An extensive series of ternary alloys were also prepared. Conditions allowing the brittle high T sub c (approximately 18 K) A-15 structure superconductor Nb3A1 to be prepared in a low T sub c but ductile form were found. Some of the ways that the ductile (bcc) form can be cold worked or machined are described. Measurements of rate of transformation of cold worked bcc material to the high T sub c A-15 structure with low temperature annealing are given. Preliminary measurements indicate that this material has attractive high field critical current densities
Final data reduction and analysis of the AS and E OSO-4 grazing incidence X-ray telescope experiment
Final data analysis of grazing incidence of solar X ray telescope experiment of OSO- 4 satellit
Flow field prediction and analysis study for project RAM B3 Final report
Flow field properties in shock layer surrounding Ram B3 vehicl
The Australian Incident Monitoring Study in Intensive Care: AIMS-ICU. The development and evaluation of an incident reporting system in intensive care
Publisher's copy made available with the permission of the publisher © 1996 Australian Society of AnaesthetistsIntensive care units are complex, dynamic patient management environments. Incidents and accidents can be caused by human error, by problems inherent in complex systems, or by a combination of these. Study objectives were to develop and evaluate an incident reporting system. A report form was designed eliciting a description of the incident, contextual information and contributing factors. Staff group sessions using open-ended questions, observations in the workplace and a review of earlier narratives were used to develop the report form. Three intensive care units participated in a two-month evaluation study. Feedback questionnaires were used to assess staff attitudes and understanding, project design and organization. These demonstrated a positive attitude and good understanding by more than 90% participants. Errors in communication, technique, problem recognition and charting were the predisposing factors most commonly chosen in the 128 incidents reported. It was concluded that incident monitoring may be a suitable technique for improving patient safety in intensive care.U. Beckman, L.F. West, G.J. Groombridge, I. Baldwin, G.K. Hart, D.G. Clayton, R.K. Webb, W.B. Runcima
The Density Spike in Cosmic-Ray-Modified Shocks: Formation, Evolution, and Instability
We examine the formation and evolution of the density enhancement (density
spike) that appears downstream of strong, cosmic-ray-modified shocks. This
feature results from temporary overcompression of the flow by the combined
cosmic-ray shock precursor/gas subshock. Formation of the density spike is
expected whenever shock modification by cosmic-ray pressure increases strongly.
That occurence may be anticipated for newly generated strong shocks or for
cosmic-ray-modified shocks encountering a region of higher external density,
for example. The predicted mass density within the spike increases with the
shock Mach number and with shocks more dominated by cosmic-ray pressure. We
find this spike to be linearly unstable under a modified Rayleigh-Taylor
instability criterion at the early stage of its formation. We confirm this
instability numerically using two independent codes based on the two-fluid
model for cosmic-ray transport. These two-dimensional simulations show that the
instability grows impulsively at early stages and then slows down as the
gradients of total pressure and gas density decrease. Observational discovery
of this unstable density spike behind shocks, possibly through radio emission
enhanced by the amplified magnetic fields would provide evidence for the
existence of strongly cosmic-ray modified shock structures.Comment: 26 pages in Latex and 6 figures. Accepted to Ap
Unveiling Palomar 2: The Most Obscure Globular Cluster in the Outer Halo
We present the first color-magnitude study for Palomar 2, a distant and
heavily obscured globular cluster near the Galactic anticenter. Our (V,V-I)
color-magnitude diagram (CMD), obtained with the UH8K camera at the CFHT,
reaches V(lim) = 24 and clearly shows the principal sequences of the cluster,
though with substantial overall foreground absorption and differential
reddening. The CMD morphology shows a well populated red horizontal branch with
a sparser extension to the blue, similar to clusters such as NGC 1261, 1851, or
6229 with metallicities near [Fe/H] = -1.3, placing it about 34 kpc
from the Galactic center. We use starcounts of the bright stars to measure the
core radius, half-mass radius, and central concentration of the cluster. Its
integrated luminosity is M_V = -7.9, making it clearly brighter and more
massive than most other clusters in the outer halo.Comment: 25 pages, aastex, with 8 postscript figures; accepted for publication
in AJ, September 1997. Also available by e-mail from
[email protected]. Please consult Harris directly for (big)
postscript files of Figures 1a,b (the images of the cluster
Remotely tuneable optical filter based on polymer fibre Bragg grating
We propose a remotely tuneable optical Bragg grating filter written in polymer optical fibre (POF). Fibre optical pumping in the fibre's absorption bands increases the fibre temperature, which causes a negative wavelength change of the POF Bragg grating. By choosing a proper pumping wavelength remote tuning of the optical filter can be readily realized without changing the gain of the optical signal
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