20,088 research outputs found
Analysis of ancient sediments and extra-terrestrial materials Semiannual report, 1 Jun. - 30 Nov. 1966
Isolation and identification of organic components of meteorites, and ancient sediment
Thermal alteration of organic matter in recent marine sediments. 1: Pigments
Sediment from Tanner Basin, the outer continental shelf off Southern California, was analyzed for photosynthetic pigments and their derivatives, namely carotenes and chlorins. Samples of the sediment were also exposed to raised temperatures (65, 100, 150 C) for various periods of time (1 week, 1 month, 2 months). Analysis of the heat-treated sediment revealed the presence of alpha-ionene and 2,6-dimethylnapthalene, thermal degradation products of Betacarotente. Chlorins were converted to nickel porphyrins of both DPEP and etio series. Possible mechanisms of these transformations are presented
New Limits on Radio Emission from X-ray Dim Isolated Neutron Stars
We have carried out a search for radio emission at 820 MHz from six X-ray dim
isolated neutron stars with the Robert C. Byrd Green Bank Radio Telescope. No
transient or pulsed emission was found using fast folding, fast Fourier
transform, and single-pulse searches. The corresponding flux limits are about
0.01 mJy for pulsed emission, depending on the integration time for the
particular source and assuming a duty cycle of 2%, and 20 mJy for single
dispersed pulses. These are the most sensitive limits to date on radio emission
from X-ray dim isolated neutron stars. There is no evidence for isolated radio
pulses, as seen in a class of neutron stars known as rotating radio transients.
Our results imply that either the radio luminosities of these objects are lower
than those of any known radio pulsars, or they could simply be long-period
nearby radio pulsars with high magnetic fields beaming away from the Earth. To
test the latter possibility, we would need around 40 similar sources to provide
a 1 sigma probability of at least one of them beaming toward us. We also give a
detailed description of our implementation of the Fast Folding Algorithm.Comment: 16 pages, 8 figures, 3 tables, accepted to Ap
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