20,385 research outputs found
Verification tests of durable TPS concepts
Titanium multiwall, superalloy honeycomb, and Advanced Carbon-carbon (ACC) multipost Thermal Protection System (TPS) concepts are being developed to provide durable protection for surfaces of future space transportation systems. Verification tests including thermal, vibration, acoustic, water absorption, lightning strike, and aerothermal tests are described. Preliminary results indicate that the three TPS concepts are viable up to a surface temperature in excess of 2300 F
Notes on some chalicothere remains from Makapansgat
Main articleThis paper deals with the South African chalicothere remains from Makapansgat, Potgietersrus, with mention of those from Serengeti described by Dietrich. From Makapansgat there are 12 post-cranial remains comprising 2 terminal phalanges, 1 intermediate phalanx, 1 co-ossified phalanx, 1 carpal or tarsal bone, 2 metacarpals, 2 tibiae, 2 innominates and 1 scapula: and 74 cranial remains . This latter figure is made up of 45 isolated teeth, of which 36 are upper teeth and 9 are lower teeth, 7 maxillary fragments and 22 mandibular fragments.
The South African form, classified as Metaschizotherium transvaalensis is compared with the American forms Moropus elatus and Moropus petersoni and is found to resemble more closely in size M. elatus .
The reasons for retaining the classification of M. transvaalensis are given and discussed. Finally the relationship of the Makapansgat specimens to the osteodontokeratic culture is
discussed.Non
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
The first high-amplitude delta Scuti star in an eclipsing binary system
We report the discovery of the first high-amplitude delta Scuti star in an
eclipsing binary, which we have designated UNSW-V-500. The system is an
Algol-type semi-detached eclipsing binary of maximum brightness V = 12.52 mag.
A best-fitting solution to the binary light curve and two radial velocity
curves is derived using the Wilson-Devinney code. We identify a late A spectral
type primary component of mass 1.49+/-0.02 M_sun and a late K spectral type
secondary of mass 0.33+/-0.02 M_sun, with an inclination of 86.5+/-1.0 degrees,
and a period of 5.3504751+/-0.0000006 d. A Fourier analysis of the residuals
from this solution is performed using PERIOD04 to investigate the delta Scuti
pulsations. We detect a single pulsation frequency of f_1 = 13.621+/-0.015 c/d,
and it appears this is the first overtone radial mode frequency. This system
provides the first opportunity to measure the dynamical mass for a star of this
variable type; previously, masses have been derived from stellar evolution and
pulsation models.Comment: 7 pages, 6 figures, 2 tables, for submission to MNRAS, v2: paper size
change, small typographical changes to abstrac
An introductory guide to fluid models with anisotropic temperatures Part 1 -- CGL description and collisionless fluid hierarchy
We present a detailed guide to advanced collisionless fluid models that
incorporate kinetic effects into the fluid framework, and that are much closer
to the collisionless kinetic description than traditional magnetohydrodynamics.
Such fluid models are directly applicable to modeling turbulent evolution of a
vast array of astrophysical plasmas, such as the solar corona and the solar
wind, the interstellar medium, as well as accretion disks and galaxy clusters.
The text can be viewed as a detailed guide to Landau fluid models and it is
divided into two parts. Part 1 is dedicated to fluid models that are obtained
by closing the fluid hierarchy with simple (non Landau fluid) closures. Part 2
is dedicated to Landau fluid closures. Here in Part 1, we discuss the CGL fluid
model in great detail, together with fluid models that contain dispersive
effects introduced by the Hall term and by the finite Larmor radius (FLR)
corrections to the pressure tensor. We consider dispersive effects introduced
by the non-gyrotropic heat flux vectors. We investigate the parallel and
oblique firehose instability, and show that the non-gyrotropic heat flux
strongly influences the maximum growth rate of these instabilities.
Furthermore, we discuss fluid models that contain evolution equations for the
gyrotropic heat flux fluctuations and that are closed at the 4th-moment level
by prescribing a specific form for the distribution function. For the
bi-Maxwellian distribution, such a closure is known as the "normal" closure. We
also discuss a fluid closure for the bi-kappa distribution. Finally, by
considering one-dimensional Maxwellian fluid closures at higher-order moments,
we show that such fluid models are always unstable. The last possible non
Landau fluid closure is therefore the "normal" closure, and beyond the
4th-order moment, Landau fluid closures are required.Comment: Improved version, accepted to JPP Lecture Notes. Some parts were
shortened and some parts were expanded. The text now contains Conclusion
Decoherence and Quantum Fluctuations
We show that the zero-point fluctuations of the intrinsic electromagnetic
environment limit the phase coherence time in all mesoscopic systems at low
temperatures. We derive this quantum noise limited dephasing time and its
temperature dependence in the crossover to the thermal regime. Our results
agree well with most experiments in 1D systems.Comment: 4 pages & 1 figur
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