29,398 research outputs found
Solar cell radiation flight experiment Quarterly progress report, 2 Dec. 1968 - 14 Mar. 1969
Design and test data of solar cells selected for flight on ATS-E for radiation effect
Rocket propulsion research at Lewis Research Center
A small contingent of engineers at NASA LeRC pioneered the basic research on liquid propellants for rockets shortly after World War 2. Carried on through the 1950s, this work influenced the important early decisions made by Abe Silverstein when he took charge of the Office of Space Flight Programs for NASA. He strongly supported the development of liquid hydrogen as a propulsion fuel in the face of resistance from Wernher von Braun. Members of the LeRC staff played an important role in bringing liquid hydrogen technology to the point of reliability through their management of the Centaur Program. This paper demonstrates how the personality and engineering intuition of Abe Silverstein shaped the Centaur program and left a lasting imprint on the laboratory research tradition. Many of the current leaders of LeRC received their first hands-on engineering experience when they worked on the Centaur program in the 1960s
The British Geological Survey's new Geomagnetic Data Web Service
Increasing demand within the geomagnetism community for high quality real-time or near-real-time observatory data means there is a requirement for data producers to have a robust and scalable data processing infrastructure capable of delivering geomagnetic data products over the Internet in a variety of formats. We describe a new software system, developed at BGS, which will allow access to our geomagnetic data products both within our organisation's intranet and over the Internet. We demonstrate how the system is designed to afford easy access to the data by a wide range of software clients and allow rapid development of software utilizing our observatory data
Exact Solution of a Jamming Transition: Closed Equations for a Bootstrap Percolation Problem
Jamming, or dynamical arrest, is a transition at which many particles stop
moving in a collective manner. In nature it is brought about by, for example,
increasing the packing density, changing the interactions between particles, or
otherwise restricting the local motion of the elements of the system. The onset
of collectivity occurs because, when one particle is blocked, it may lead to
the blocking of a neighbor. That particle may then block one of its neighbors,
these effects propagating across some typical domain of size named the
dynamical correlation length. When this length diverges, the system becomes
immobile. Even where it is finite but large the dynamics is dramatically
slowed. Such phenomena lead to glasses, gels, and other very long-lived
nonequilibrium solids. The bootstrap percolation models are the simplest
examples describing these spatio-temporal correlations. We have been able to
solve one such model in two dimensions exactly, exhibiting the precise
evolution of the jamming correlations on approach to arrest. We believe that
the nature of these correlations and the method we devise to solve the problem
are quite general. Both should be of considerable help in further developing
this field.Comment: 17 pages, 4 figure
A marker suitable for sex-typing birds from degraded samples
A new primer set was developed for sex-typing
birds, Z37B. This primer set was designed to amplify alleles
of small size to render it suitable for sex-typing degraded
samples, including shed feathers. This marker
successfully sex-typed 50 % of the species tested, including
passerines, shorebirds, rails, seabirds, eagles and the
brown kiwi Apteryx australis (allele size range
=81–103 bp), and is therefore expected to be suitable for
sex-typing a wide range of species. Z37B sex-typed nondegraded
samples (blood), degraded tissue (dead unhatched
embryos, dead nestlings and museum specimens) and
samples of low quantity DNA (plucked feathers and buccal
swabs). The small amplicon sizes in birds suggest that this
marker will be of utility for sex-typing feathers, swabs and
degraded samples from a wide range of avian species
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