A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904

Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z approximately 20, and therefore to be powerful probes of the early Universe. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39 - 0.12 + 0.11 (refs 5-7). Subsequently, it was measured spectroscopically to be z = 6.29 +/- 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe.     

New stochastic model for geomagnetic reversals

A non-stationary model for geomagnetic reversals is proposed. From the model, a mean length of all polarity intervals of 1.6 m.y. is predicted.     

Spontaneous contractions and bioelectric activity after differentiation in culture of presumptive neuromuscular tissues of the early frog embryo

Zusammenfassung Gewebekulturen vonFroschneurula mit zugehörigen Muskelprimordien differenzieren in vitro und zeigen charakteristische Serien von Muskelkontraktionen. Elektrophysiologisch wurde nachgewiesen, dass die Muskelzuckungen durch endogene, komplexe, rhythmische Nervenaktivität hervorgerufen werden können.

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Supported in part by award from the National Multiple Sclerosis Society (USA). Thanks are due to Dr.Margaret R. Murray and to the staff of her tissue culture laboratory for their hospitality and assistance during this period.

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Supported in part by grants NB-03814 and NB-K3-2904 from the National Institute of Neurological Diseases and Blindness.