Can Gamma Ray Bursts Produce the Observed Cosmic Rays Above 102010^{20} eV?

It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux and spectrum of cosmic rays at the highest energies. However, recent observations indicate that the redshift distribution of GRBs most likely follows that of the star formation rate in the universe, a rate which was much higher at redshifts 1.5-2 than it is today. Thus, most GRBs are at high redshifts. As a consequence, any cosmic rays emitted by these GRBs at energies above 2-3 X 10^{19} eV would be strongly attenuated by interactions with the 3K background radiation. If one assumes rough equality between the energy released in 10^{-2} to 1 MeV photons and that released in 10^{20} eV cosmic rays, then less than 10 per cent of the cosmic rays observed above 10^{20} eV can be accounted for by GRBs.Comment: 7 tex pages, no figures, one reference added to previous version, Astroparticle Physics, in pres

Magmatic and hydrothermal inclusions in carbonatite of the Magnet Cove Complex, Arkansas

The carbonatite at Magnet Cove, Arkansas, USA contains a great variety and abundance of magmatic and hydrothermal inclusions that provide an informative, though fragmentary, record of the original carbonatite melt and of late hydrothermal solutions which permeated the complex in postmagmatic time. These inclusions were studied by optical and scanning electron microscopy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47322/1/410_2004_Article_BF00375576.pd