This Doctoral thesis was carried out in 3 different Catalan aquatic ecosystems: The Flix reservoir and the lower part of Ebro river, the Camarasa reservoir (Pre-Pyrenees) and the Pyrenees lakes.The aim of this Doctoral Thesis in the Flix reservoir and the lower part of Ebro river part was to determine the Naturally Occurring Radioactivity waste materials (NORM) contained in Flix Reservoir sediments due to the dicalcium phosphate (DCP) production of a factory located in the reservoir vicinity, and evaluate the potential remobilization of the NORM waste materials downstream, along the 95 km of Ebro river until its river mouth delta (Ebro Delta). The results display an evident radiological impact in the waste materials dumped in Flix reservoir with maximum values of values 11723±198 Bq kg-1 238U, 9361± 181 Bq kg-1 226Ra, 3500±157 Bq kg-1 210Pb, 308 (238U), 92 (226Ra) and 38 (210Pb) times higher than the activity of these radionuclides in the Ebro sediments, that show an average activity of 20 Bq kg-1. In order to determine the mobilization of the radioactivity, 226Ra (dissolve) was studied. An enhancement of the 226Ra levels in water was detected in the Flix water (8.00.4 Bq m-3) and specially in the Flix meanders with a value of 37.5 ±1.2 Bq m-3, typical of the contaminated NORM rivers. However the rest of the lower part of the river water samples display non contaminated levels of 226Ra, with an average value of 5.9 ±1.6 Bq m-3.In Camarasa reservoir the aim of the research was to establish the sedimentation rates by 210Pb models (CFCS) and 137Cs dating mark, that allows us to date the last 100-150 years. The highest sedimentation rate in the central and lower part of the reservoir was 3.3 ± 0.2 cm yr-1 (14.1 kg m-2 a-1), close to the dam, due to the dam barrier effect that block the water stream. The central part of the reservoir displays a lower sedimentation rate of 1.370.14 cm yr-1. We have to take into account the effect of the flood events in the assessment of the sedimentation rates. In this study a punctual flood event in November 1982 was registered in the sediments depositing from 30 to 40 cm of material in 1 week, equivalent to 25 years of normal sedimentation in the central part of the reservoir. In the Pyrenees lake study, the distribution of 210Pb (0 to 5178 ± 1300 Bq·kg-1) and 137Cs (8 to 2970 ± 101 Bq·kg-1) displays a wide variation activity ranges, typical of remote lakes. 210Pb was used as a normalizer of the heavy metal (Zn and Cd) contaminations and some organochlorate compounds (Hexachlorobenzen and Hexachlorociclohexan) in order to detected contamination sources. The metal results display an evident Zn and Cd contamination in some lakes of Vall d'Aran area (Pica Palomera and Montoliu lakes) due to the mining activity during the period from 1740 to 1968. On the other hand, the normalized organochlorinate compounds display a source of contamination close to Sabiñanigo village (Aragon Pyrenees) probably due to the presence in the past of an Hexachlorociclohexan factory.

The Nuclear Waste Management Organization (NWMO) --- the crown corporation responsible for the long-term storage of nuclear fuel waste in Canada --- seeks to bury our nuclear fuel waste deep in the Canadian Shield, with the provisions that the waste is monitored and remains retrievable for possible future use. To ensure that its solution is ethically acceptable, the NWMO established a set of requirements which, if satisfied, would successfully discharge its ethical obligations to both present and future generations. Those requirements include the obligation to justify its practice, minimize risk, clearly identify all of the relevant costs and risks of harm, abide by the precautionary principle, obtain fully informed consent from potentially affected individuals, and distribute the risk fairly across multiple generations. In this document I show that the ethical principles, as formulated by the NWMO, are either (a) seriously vague and unhelpful; or (b), where substantial and helpful, the nature of the practice show that many of the principles cannot be satisfied. As a final result, it is deeply questionable whether nuclear power in general, and especially the current solution to nuclear waste in particular, can ever be deemed ethical in Canada.

The Nuclear Waste Management Organization (NWMO) --- the crown corporation responsible for the long-term storage of nuclear fuel waste in Canada --- seeks to bury our nuclear fuel waste deep in the Canadian Shield, with the provisions that the waste is monitored and remains retrievable for possible future use. To ensure that its solution is ethically acceptable, the NWMO established a set of requirements which, if satisfied, would successfully discharge its ethical obligations to both present and future generations. Those requirements include the obligation to justify its practice, minimize risk, clearly identify all of the relevant costs and risks of harm, abide by the precautionary principle, obtain fully informed consent from potentially affected individuals, and distribute the risk fairly across multiple generations. In this document I show that the ethical principles, as formulated by the NWMO, are either (a) seriously vague and unhelpful; or (b), where substantial and helpful, the nature of the practice show that many of the principles cannot be satisfied. As a final result, it is deeply questionable whether nuclear power in general, and especially the current solution to nuclear waste in particular, can ever be deemed ethical in Canada.

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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Roy F. Schwitters. Vita. Includes bibliographical references.

Thesis--University of California, Berkeley, 1959. / Includes bibliographical references (p. 81-84).

No description available.

In this thesis, new acquisition and analysis methods are described for multinuclear magnetic resonance spectroscopy (MRS) for the quantification of brain metabolites at ultra high magnetic field strengths (7T). An analytical model was derived for the optimisation of the stimulated echo acquisition mode (STEAM) sequence timing parameters for lactate detection. The effects of the chemical shift displacement artefact on the J-modulated signal for a weakly-coupled spin system were considered in the three applied directions of field gradients and the product operator formalism was used to obtain expressions for the signal modulation in each compartment of the excited volume. The validity of this model was demonstrated experimentally in a phantom and acquisitions with optimised parameters were performed on a healthy volunteer. The spectra acquired with an echo time (TE) of 144 ms and with an optimised mixing time and TE of 288 ms showed easily detectable lactate peaks in the normal human brain. Additionally, the acquisition with the longer TE resulted in a spectrum with less lipid/macromolecular (MM) contamination. The simulations demonstrated that the proposed analytical model is suitable for correctly predicting the resulting lactate signal. With the optimised parameters, it was possible to use a simple sequence with sufficient signal-to-noise ratio (SNR) to reliably distinguish lactate from overlapping resonances in a healthy brain at ultra high-field. Estimation of metabolic changes during neuronal activation represents a challenge for in vivo MRS, especially for metabolites with low concentration and signal overlap, such as lactate. This thesis also includes work focused on the reliable quantification of lactate during a paradigm with 15 minutes of visual stimulation. The lipid and MM signals were significantly reduced by using a long TE (144 ms) sequence and the remaining MM signals in the vicinity of the lactate peak were individually fitted with simulated Lorentzian peaks, to ensure a good fit of the inverted lactate doublet. Statistically significant changes in lactate (~10%) and glutamate (~3%) levels during stimulation were detected in the visual cortex and agree with previous measurements. Furthermore, the use of a prolonged stimulation period unveiled a distinctive metabolic response pattern, which can provide further insight into brain activation mechanisms. 13C MRS combined with the infusion of labelled substrates is able to provide unique information on the relationship between neuroenergetics and brain function. However, the lack of sensitivity associated with the general complexity of 13C experiments has hampered its widespread use for research into human brain disease. In this study, a new methodology for acquisition and analysis of 13C signal is presented for the study of neuroenergetics and neurotransmission in a deep brain structure - anterior cingulate cortex - that is thought to play a major role in the processing of sensory information and can be impaired in patients with schizophrenia. In vitro testing was performed to evaluate the performance of the implemented sequence for signal localisation and polarisation transfer, both proving adequate for the intended purpose. In vivo data were acquired in four subjects, one diagnosed with early schizophrenia, with a protocol which involved 60 minutes of infusion of [1-13C]glucose. Turnover curves for the labelled products were generated from the dynamic 13C spectra with a temporal resolution of 10 minutes and were in agreement with the ones obtained from rodent experiments. Therefore, the feasibility of 13C experiments for the study of psychosis was here demonstrated, taking advantage of the increase in SNR at ultra high-field for determination of metabolic fluxes.