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  • Author or Editor: R. Durham x
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Abstract  

Radionuclide concentrations in digester sludge and effluent samples from Hamilton and Dundas sewage treatment plants, located at the western tip of Lake Ontario, have been determined by high-resolution γ-ray spectrometry. The radionuclides51Cr,75Se and131I, which are used in nuclear medicine procedures, were found in sludge samples. Very low concentrations of51Cr, entering Lake Ontario through the Hamilton plant effluent discharge, have little effect on lake water quality.

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Abstract  

A method is described for the determination of228Th,230Th, and232Th in environmental samples from uranium mining and milling operations. The analytical procedure is based on the direct determination of228Th in the sample by high resolution γ-spectrometry followed by extraction and purification of the thorium fraction using high molecular weight amines and an anion-exchange technique, respectively, prior to α-spectrometry to determine isotopic ratios. The lowest level of detection for each thorium isotope is 0.01 pCi/g for solid samples and 20 pCi/l for aqueous samples. Replicate analyses of a typical mine waste stream gave a standard deviation of ±3% for228Th. Standard deviations of the230Th and232Th increased to ±11% apparently due to traces of210Po interfering in the α-spectrometry.

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Abstract  

Cosmic ray neutron interactions with indium, used as electrical contact within a Ge diode, the diode itself and the surrounding materials can give rise to a large number of photopeaks in the 50 to 1300 keV region of background spectra of Ge spectrometers with a passive shield. The nuclear processes and decays involved in the production of these photopeaks are discussed. These cosmic ray produced photopeaks are compared with those due to primordial radionuclides. Some useful information can be drawn from these measurements on the contribution of the cosmic rays on the background of Ge detectors with a passive shield.

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The central nervous system (CNS) of a metamorphically competent larva of the caenogastropod Ilyanassa obsoleta contains a medial, unpaired apical ganglion (AG) of approximately 25 neurons that lies above the commissure connecting the paired cerebral ganglia. The AG, also known as the cephalic or apical sensory organ (ASO), contains numerous sensory neurons and innervates the ciliated velar lobes, the larval swimming and feeding structures. Before metamorphosis, the AG contains 5 serotonergic neurons and exogenous serotonin can induce metamorphosis in competent larvae. The AG appears to be a purely larval structure as it disappears within 3 days of metamorphic induction. In competent larvae, most neurons of the AG display nitric oxide synthase (NOS)-like immunoreactivity and inhibition of NOS activity can induce larval metamorphose. Because nitric oxide (NO) can prevent cells from undergoing apoptosis, a form of programmed cell death (PCD), we hypothesize that inhibition of NOS activity triggers the loss of the AG at the beginning of the metamorphic process. Within 24 hours of metamorphic induction, cellular changes that are typical of the early stages of PCD are visible in histological sections and results of a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in metamorphosing larvae show AG nuclei containing fragmented DNA, supporting our hypothesis.

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