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No description available.

No description available.

The applicability of the technique of inductively coupled plasma mass spectrometry to the analysis of geological samples was investigated using a variety of sample introduction techniques including: solution nebulisation; slurry nebulisation; flow injection; electrothermal vaporisation; and laser ablation, Solution sample introduction is limited by the amount of time required to prepare the sample, and the relative intolerance of the technique to high concentrations of sample matrix. The maximum level of dissolved solids for a refractory matrix such as a digested igneous rock was found to be 0.2% w/v. Good accuracy and precision are achievable. Acceptable results can be obtained using slurry nebulisation. However, standardisation is a problem due to the difference in response for aqueous and slurried analytes. Calibration against aqueous standards and the use of an internal standard is therefore precluded. In addition, the preparation of stable slurries is a highly skilled and time consuming task. Flow injection analysis offers the most benefit to the geochemical analyst. Flow injection was found to increase sample throughput and, more important, to improve matrix tolerance by a factor of l0x, thus allowing the direct determination of the platinum group elements and gold in geological samples without pretreatment. Small samples, such as fluid inclusion leachates can also be analysed without dilution and the matrix effects experienced when analysing samples containing high salt concentrations can be reduced by careful control of dispersion. The potential for increased detection limits by electrothermal vaporisation was not proved for geological materials due to the same matrix tolerance problems which limit detection limits in solution work. Laser ablation sampling allows direct analysis of the solid but quantitation requires matrix matched standards or independent variable internal standardisation, limiting the applicability of the technique for bulk screening. The use of laser ablation to analyse trace element concentrations in individual mineral grains has been investigated and partition coefficients for trace elements, including the rare earths in a large zoned pyroxene crystal, were determined.

As ~ 50% of global photosynthesis occurs in marine environments, the factors regulating this process e.g. trace metal availability, have an impact on the global carbon cycle. The key cyanobacteria genera Prochlorococcus and Synechococcus have an absolute requirement for Co. Dissolved cobalt (dCo) concentrations in the open ocean are extremely low (5–120 pM). A sensitive flow injection technique using chemiluminescence detection (FI-CL) was developed (detection limit 4.5 pM dCo, RSD ≤ 4%). Seawater samples must be UV-irradiated prior to analysis, in order to liberate organically-bound Co. A field study in the Sargasso Sea, demonstrated that aerosol Co was significantly more soluble than aerosol Fe over a range of aerosol dust deposition fluxes (1–1040 μg Fe m-2 d-1) (8-100% for Co versus 0.44-45% for Fe). The dry deposition flux of aerosol Co was of the same order of magnitude as the advective upwelling flux (47-1540 pmol m-2 d-1 and 1.7-1430 pmol m-2 d-1 respectively). Wet deposition, dominated the total aerosol flux (~ 85%). The vertical distribution of dCo influenced Prochlorococcus abundance. A regional study in the eastern North Atlantic gyre demonstrated that the highest rates of N2 fixation occurred with the highest dFe concentrations (9.8 nM N L-1 h-1, 0.6 nM respectively). No increase in primary production following additions of trace metals (Co, Cu, Fe, Zn) was observed. The addition of N resulted in an increase in primary production. However, there was no synergistic effect of trace metal plus N addition, suggesting that alleviation of N-limitation shifted the system to P-limitation. On a meridional transect from ~ 50°N–50°S in the Atlantic Ocean, the highest concentrations of dCo (> 80 pM) coincided with low-O2 (< 150 μM) upwelled water. The lowest dCo (< 20 pM) was observed in the eastern North Atlantic gyre. Lateral advection of continental Co and upwelling were identified as important sources of Co. The highly efficient recycling of Co in the euphotic zone is an important additional source.

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Central fuelling is a fundamental issue in the neat generation tokamak ITER (International Thermonuclear Experimental Reactor). It is essential for optimization of the bootstrap current which is proportional to the pressure gradient of trapped particles. The conventional tokamak fuelling techniques, such as gas puffing and cryogenic pellet injection, are considered to be inadequate to fulfill this goal due to premature ionization caused by high plasma temperature and density. Fuelling by injecting a compact torus (CT) may be the only viable method suitable for a reactor-grade tokamak. CTs can be injected at different angles with respect to the tokamak toroidal magnetic field, either horizontally or vertically. In vertical injection, deeper CT penetration is expected due to the absence of the gradient of tokamak toroidal magnetic field in that direction. This thesis contributes to experimental investigation of vertical compact torus injection into the STOR-M tokamak. <p>To perform vertical injection, the original injector- USCTI (University of Saskatchewan Compact Torus Injector) was modified by attaching a segment of 90˚ curved drift tube to bend the CT trajectory from horizontal to vertical. Bench tests have shown that a CT injected horizontally can be deflected effectively to the vertical direction. The velocity of 130 kms^{-1}has been achieved while the CT passes through the 90˚ curved drift tube. It was found that the CT magnetic field structure kept intact as a typical structure of compact torus plasma. By further optimization of the USCTI configuration, the velocity has been increased to 270 kms^{-1}. Based on the encouraging bench test results, actual vertical CT injection experiments have been performed in the STOR-M tokamak. Experimental results demonstrated, for the first time, vertical CT injection into a tokamak. Prompt increases both in line averaged electron density and in soft X-ray emission (central cord) are observed following vertical injection. Some H-mode phenomena, characterized by suppression of the m =2 Mirnov oscillation level and drop in Hα radiation level, have also been observed following the vertical injection. Fuelling effects caused by vertical injection and by tangential injection are discussed. The experimental results suggest that vertical CT injection is a feasible tokamak fuelling technique.

Despite thirty published evaluation reports citing the effectiveness of Vancouver’s safe injection site (Small 2008), the Canadian federal government refuses to endorse safe injection sites as a health service option available to injection drug users (IDUs). Insite’ s evaluation results are undergoing debate, because two communicative spheres of knowledge, each with a unique authoritative language, are conflicting as each is attempting to gain moral authority over the right to recontextualize drug users. Drawing on a literature review of two harm reduction programs in Vancouver, Insite and Sheway, and expert interviews with evaluators, I show that what constitutes “evidence” is in fact subjective, determined by spheres of communicability that are built upon social, professional and political contexts. To confront the problematic nature of this issue, I suggest that evaluators and overseers need to treat program evaluation as a process of negotiation, best approached in a fluid manner. By obscuring multiple user experiences in the evaluation of harm reduction programs, evaluators and overseers risk imposing their communicative ideologies on what it means to be a drug user.