3,924 research outputs found
Lateral Expansion of the Bridges of Cygnus A and other Powerful Radio Sources
Measurements of the width of the radio bridge at several locations along the
bridge for each of four powerful extended radio sources are presented. Adopting
a few simple assumptions, these measurements may be used to predict the radio
surface brightness as a function of position across the radio bridge. The
predicted and observed surface brightnesses across the bridges are compared and
found to agree fairly well. The results are consistent with a simple picture in
which the radio power and size of the radio lobe at the forward edge of the
radio bridge are roughly time-independent for a given source, and the expansion
of the bridge in the lateral direction is adiabatic. There is no indication
that reacceleration or energy transport is important in the bridges of these
sources. The rate of lateral expansion of the bridge just behind the radio lobe
and hotspot in terms of the rate of forward propagation is compared with that
predicted, and found to be in good agreement with the predicted value.Comment: 7 pages, uuencoded compressed postscript. To appear in the Proceding
of the Cygnus A workshop, May 1-4, Green Bank, W
Nano and Micro indentation studies of bulk zirconia and EB PVD TBCs
In order to model the erosion of a material it is necessary to know the material
properties of both the impacting particles as well as the target. In the case of
electron beam (EB) physical vapour deposited(PVD) thermal barrier coatings
(TBCs) the properties of the columns as opposed to the coating as a whole are
important. This is due to the fact that discrete erosion events are on a similar
scale as the size of the individual columns. Thus nano* and micro* indentation
were used to determine the hardness and the Young"s modulus of the
columns. However, care had to be taken to ensure that it was the hardness of the
columns that was being measured and not the coating as a whole. This paper
discusses the differences in the results obtained when using the two different
tests and relates them to the interactions between the indent and the columns of
the EB PVD TBC microstructure. It was found that individual columns had a
hardness of 14 GPa measured using nano indentation, while the hardness of the
coating, using micro indentation decreased from 13 to 2.4 GPa as the indentation
load increased from 0.1 to 3N. This decrease in hardness was attributed to the
interaction between the indenter and a number of adjacent columns and the
ability of the columns to move laterally under indentation
Viability of Nuerospora macroconidia after cryogenic storage by liquid nitrogen refrigeration
Viability of macroconidia after liquid nitrogen refrigeratio
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