Additional experimental evidence is presented in support of the recent hypothesis that a possible solar influence could explain fluctuations observed in the measured decay rates of some isotopes. These data were obtained during routine weekly calibrations of an instrument used for radiological safety at The Ohio State University Research Reactor using 36 Cl. The detector system used was based on a Geiger-Müller gas detector, which is a robust detector system with very low susceptibility to environmental changes. A clear annual variation is evident in the data, with a maximum relative count rate observed in January/February, and a minimum relative count rate observed in July/August, for seven successive years from July 2005 to June 2011. This annual variation is not likely to have arisen from changes in the detector surroundings, as we show here.

Hexavalent chromium [Cr(VI)] is a known carcinogen and mutagen; however, the actual mechanisms of Cr toxicity are unknown. Two approaches were used to isolate Cr(VI)-resistant bacteria from metal-contaminated river sediments. Diluted sediments were plated directly onto a peptone-yeast extract (PYE) medium containing 0 to 100 ,ug of Cr(VI) ml-'. Approximately 8.4 x 105 CFU g-1 were recovered on 0 ,ug of Cr(VI) ml-', whereas 4.0 x 102 CFU g-1 were recovered on PYE plus 100 ,ug of Cr(VI) ml-1. Alternatively, continuous culture enrichment techniques were employed using PYE and 100 ,ug Cr(VI) ml-' input at dilution rates of 0.02 and 0.10 h-1. After six residence periods, 109 CFU were recovered on PYE agar containing 0 p,g of Cr(VI) ml-1 and 107 CFU on PYE agar plus 100 jig of Cr(VI) ml-1. Of 89 isolates obtained by direct plating onto PYE, 47% were resistant to 100 ,ug of Cr(VI) ml-', and 29% were resistant to 250 ,ug of Cr(VI) ml-'. When the same isolates were plated onto PYE containing Cr(III), 88% were resistant to 100 ,ug ml-' but only 2% were resistant to 250 ,ug ml-'. Cr, Co, Sb, and Zn were found in significantly higher concentrations at an industry-related contaminated site than at a site 11 km downstream. Total Cr in the sediments at the contaminated site averaged 586 ,ug (dry weight) g-1, and the downstream site averaged 71 p.g (dry weight) g-1. The Cr recovered from acid-digested Ottawa River sediment samples was predominantly hexavalent. Five acid digestion procedures followed by atomic absorption spectroscopy were compared and found to be 30 to 70% efficient for recovery of Cr relative to neutron activation analysis. A population of aerobic, heterotrophic bacteria was recovered from sediments containing elevated levels of Cr. However, there was no apparent difference in the number of bacteria resistant to Cr(VI) at the contaminated site as compared to the downstream site. Recovery of Cr-resistant bacteria from river sediments was improved by using continuous culture enrichment as compared to direct plating.

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