61,077 research outputs found
Apollo experience report: Problem reporting and corrective action system
The Apollo spacecraft Problem Reporting and Corrective Action System is presented. The evolution from the early system to the present day system is described. The deficiencies and the actions taken to correct them are noted, as are management controls for both the contractor and NASA. Significant experience gained from the Apollo Problem Reporting and Corrective Action System that may be applicable to future manned spacecraft is presented
Asymmetric Avalanches in the Condensate of a Zeeman-limited Superconductor
We report the non-equilibrium behavior of disordered superconducting Al films
in high Zeeman fields. We have measured the tunneling density of states of the
films through the first-order Zeeman critical field transition. We find that
films with sheet resistances of a few hundred ohms exhibit large avalanche-like
collapses of the condensate on the superheating branch of the critical field
hysteresis loop. In contrast, the transition back into the superconducting
phase (i.e., along the supercooling branch) is always continuous. The fact that
the condensate follows an unstable trajectory to the normal state suggests that
the order parameter in the hysteretic regime is not homogeneous.Comment: 5 pages, 5 figures, to appear in PR
A procedure for furnace brazing butt joints in tungsten-uranium dioxide cermet cylinders at 3000 deg C
Furnace brazing butt joints in tungsten-uranium dioxide cermet cylinders at 3000 deg
Fluctuation Results from PHENIX
The PHENIX Experiment at the Relativistic Heavy Ion Collider has made
measurements of event-by-event fluctuations in the net charge, the mean
transverse momentum, and the charged particle multiplicity as a function of
collision energy, centrality, and transverse momentum in heavy ion collisions.
The results of these measurements will be reviewed and discussed.Comment: Proceedings for the Workshop on Correlations and Fluctuations in
Relativistic Nuclear Collisions, April 21-23, 2005; 10 pages, 17 figure
Growth, age and size of the Jurassic pachycormid Leedsichthys problematicus (Osteichthyes: Actinopterygii)
The Jurassic pachycormid osteichthyan Leedsichthys problematicus is renowned for having been able to achieve
prodigious size for a bony fish. Building on work of MARTILL (1986a), a thorough examination of all known
material was conducted in order to constrain estimates of the size of this animal and examine its rate of growth.
Important specimens of Leedsichthys are described for the first time. The histology of Leedsichthys is reviewed, and
the presence of growth annuli is used to establish ages for five specimens. Age and growth data were obtained
from gill rakers (n = 4) and lepidotrichia (n = 2). Lepidotrichia show upward curvilinear growth profiles and
ages ranging from 21 to 40 annuli, which are assumed to represent years. Both growth profiles start at a small
size (0.26 and 0.33 mm radial distance), which is assumed to represent age 1. However, annuli can be lost near
the margins of the elements. Gill rakers exhibit a sigmoidal growth profile. Age of gill rakers was estimated by
adjusting the alignment of the inflection points of the growth profiles thereby giving adjusted ages. Gill rakers
ranged in age from 19–38 annuli, but all show evidence of reabsorption of annuli near the focal points and at the
margins of most elements. Sizes for the five individuals range from 8.0-16.5 m for ages of 19-40 years. Growth
rate (0.01-0.05 K) was relatively slow as expected for a large, long-lived fish. At age 1, individuals were 1.6 m in
length. Estimates for the length of L. problematicus compare well with published lengths of other large suspension
feeders such as those for basking and whale sharks
Transverse Momentum Correlations in Relativistic Nuclear Collisions
From the correlation structure of transverse momentum in relativistic
nuclear collisions we observe for the first time temperature/velocity structure
resulting from low- partons. Our novel analysis technique does not invoke
an {\em a priori} jet hypothesis. autocorrelations derived from the scale
dependence of fluctuations reveal a complex parton dissipation process
in RHIC heavy ion collisions. We also observe structure which may result from
collective bulk-medium recoil in response to parton stopping.Comment: 10 pages, 10 figures, proceedings, MIT workshop on fluctuations and
correlations in relativistic nuclear collision
Elliptic flow of the dilute Fermi gas: From kinetics to hydrodynamics
We use the Boltzmann equation in the relaxation time approximation to study
the expansion of a dilute Fermi gas at unitarity. We focus, in particular, on
the approach to the hydrodynamic limit. Our main finding are: i) In the regime
that has been studied experimentally hydrodynamic effects beyond the
Navier-Stokes approximation are small, ii) mean field corrections to the
Boltzmann equation are not important, iii) experimental data imply that
freezeout occurs very late, that means that the relaxation time remains smaller
than the expansion time during the entire evolution of the system, iv) the
experimental results also imply that the bulk viscosity is significantly
smaller than the shear viscosity of the system.Comment: 18 pages, 6 figure
Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films
We present a study of the proximity effect between a ferromagnet and a
paramagnetic metal of varying disorder. Thin beryllium films are deposited onto
a 5 nm-thick layer of the ferromagnetic insulator EuS. This bilayer arrangement
induces an exchange field, , of a few tesla in low resistance Be films
with sheet resistance , where is the quantum resistance.
We show that survives in very high resistance films and, in fact,
appears to be relatively insensitive to the Be disorder. We exploit this fact
to produce a giant low-field magnetoresistance in the correlated insulator
phase of Be films with .Comment: To be published in Physical Review Letter
First Direct Measurement of Jets in GeV Heavy Ion Collisions by STAR
We present the first measurement of reconstructed jets in ultra-relativistic
heavy ion collisions. Utilizing the large coverage of the STAR Time Projection
Chamber and Electromagnetic Calorimeter, we apply several modern jet
reconstruction algorithms and background subtraction techniques and explore
their systematic uncertainties in heavy ion events. The differential spectrum
for inclusive jet production in central Au+Au collisions at GeV is presented. In order to assess the jet reconstruction biases, this
spectrum is compared with the jet cross section measured in GeV
p+p collisions scaled by the number of binary N-N collisions to account for
nuclear geometric effects.Comment: Proceedings of the 3rd International Conference on Hard and Electro-
Magnetic Probes of High-Energy Nuclear Collisions 8-14 June 2008, Illa da
Toxa (Galicia-Spain
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