1,895 research outputs found
Effects of temperature and the presence of benthic predators on the vertical distribution of the ctenophore Pleurobrachia pileus
Advanced detectors and signal processing
Continued progress is reported toward development of a silicon on garnet technology which would allow fabrication of advanced detection and signal processing circuits on bubble memories. The first integrated detectors and propagation patterns have been designed and incorporated on a new mask set. In addition, annealing studies on spacer layers are performed. Based on those studies, a new double layer spacer is proposed which should reduce contamination of the silicon originating in the substrate. Finally, the magnetic sensitivity of uncontaminated detectors from the last lot of wafers is measured. The measured sensitivity is lower than anticipated but still higher than present magnetoresistive detectors
Increasing prevalence of the marine cladoceran Penilia avirostris (Dana, 1852) in the North Sea
Rising sea surface temperatures in the North
Sea have had consequential effects on not only indigenous
plankton species, but also on the possibility of
successful colonisation of the area by invasive plankton
species. Previous studies have noted the introduction
and integration into the plankton community of various
phytoplankton species, but establishment of zooplankton
organisms in the North Sea is less well-documented.
Examining continuous plankton recorder (CPR) survey
data and zooplankton results from the Helgoland Roads
study, the autumn of 1999 witnessed the occurrence of
the marine cladoceran Penilia avirostris in large numbers
in the North Sea. The rapid appearance of the species
corresponded with exceptionally warm sea surface temperatures
(SSTs). Since 1999, the species has become a
regular feature of the autumnal zooplankton community
of the North Sea. In 2002 and 2003, the species occurred
in greater abundance than recorded before. It is suggested
that increased autumn SSTs have proved
favourable to P. avirostris, with warmer conditions
contributing to the success of the species’ resting eggs
and aiding colonisation
Paragonimiasis In Iowa
The presence of the lung fluke, Paragonimus kelliocotti, was first recorded in the United States in a cat in 1894. It was first recognized in domesticated animals in Iowa in a dog from Blackhawk County in 1948. Subsequently, paragonimiasis has been diagnosed in dogs from Polk and Dallas counties. An additional case was found in a dog from an unrecorded county. Also, one cat from Story County has been found to harbor P. kellicotti
Evaluation of the ALMA Prototype Antennas
The ALMA North American and European prototype antennas have been evaluated
by a variety of measurement systems to quantify the major performance
specifications. Nearfield holography was used to set the reflector surfaces to
17 microns RMS. Pointing and fast switching performance was determined with an
optical telescope and by millimeter wavelength radiometry, yielding 2 arcsec
absolute and 0.6 arcsec offset pointing accuracies. Path length stability was
measured to be less than or approximately equal to 20 microns over 10 minute
time periods using optical measurement devices. Dynamical performance was
studied with a set of accelerometers, providing data on wind induced tracking
errors and structural deformation. Considering all measurements made during
this evaluation, both prototype antennas meet the major ALMA antenna
performance specifications.Comment: 83 pages, 36 figures, AASTex format, to appear in PASP September 2006
issu
Millimetre-VLBI Monitoring of AGN with Sub-milliarcsecond Resolution
Global millimetre VLBI allows detailed studies of the most central jet
regions of AGN with unprecedent spatial resolution of a few 100-1000
Schwartzschild radii to be made. Study of these regions will help to answer the
question how the highly relativistic AGN jets are launched and collimated.
Since the early 1990s, bright mm-sources have been observed with global 3 mm
VLBI. Here we present new images from an ongoing systematic analysis of the
available observations. In particular, we focus on the structure and structural
evolution of the best observed AGN jets, taking 3C 454.3 as a characteristic
example. This core-dominated and highly variable quasar shows a complex
morphology with individual jet components accelerating superluminally towards
the outer structure. We briefly discuss the X-ray properties of 3C 454.3 and
present its radio- to X-ray large-scale brightness distribution.Comment: 4 pages, 4 figures, Proceedings of the 7th EVN Symposium held in
Toledo, Spain in October 2004, needs evn2004.cl
Heterogeneity of resting and hyperemic myocardial blood flow in healthy volunteers: a quantitative CMR perfusion pixel-map study
Effects of hydrogen on the morphology and electrical properties of GaN grown by plasma-assisted molecular-beam epitaxy
We study the effect of introducing hydrogen gas through the rf-plasma source during plasma-assisted molecular-beam epitaxy of GaN(0001). The well-known smooth-to-rough transition that occurs for this surface as a function of decreasing Ga flux in the absence of H is found to persist even with H present, although the critical Ga flux for this transition increases. Under Ga-rich conditions, the presence of hydrogen is found to induce step bunching (facetting) on the surface. Conductive atomic force microscopy reveals that leakage current through dislocation cores is significantly reduced when hydrogen is present during the growth
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