Langmuir-Blodgett (LB) organic monomolecular (monolayer) films containing fatty acids and their perfluorinated counterparts separate into phases under certain conditions. These perfluorinated surfactant containing mixed-phase systems have been shown to exhibit many favourable attributes in comparison to non- perfluorinated surfactant monolayers. In this thesis project, two of these films were investigated. One film is a 2:1 ratio mixture of arachidic acid (C19H39COOH AA) to perfluorotetradecanoic acid (C13F27COOH PA), which phase-separates into hexagonal domains ~6 ìm large (2:1 ratio of AA to PA 2AA1PA). The other film is a 2:1 mixture of stearic acid (C17H35COOH - SA) to PA, which phase-separates into linear domains ~300 nm wide (2:1 ratio of SA to PA 2SA1PA).<p> Through the use of atomic force microscopy (AFM), and various synchrotron photoemission electron microscopy-based (PEEM) techniques, the films were characterized. As properties such as molecular organization, and dispersion of the molecules in the film, affect film function, it is necessary to use a variety of techniques to better understand order and composition in the films.<p> First, the well-known and previously-studied film, 2AA1PA, was used to better understand contrast mechanisms in the energy filtered x-ray photoemission electron microscope (X-PEEM) at the CLS. Through the use of techniques such as secondary electron emission microscopy (SEEM), ultraviolet photoelectron spectroscopy (UPS), and x-ray linear dichroism microscopy (XLDM), the effects of secondary electrons, valence character, and polarization dependence were studied so as to better understand their contribution to contrast in energy-filtered PEEM-based spectromicroscopy.<p> Second, the composition and organization of a novel system (2SA1PA), was characterized using traditional near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy. As the size of the domains in the 2SA1PA system are below the spatial resolution limit of PEEM spectromicroscopy, methods involving selective phase dissolution, and spectrum subtraction, were used to acquire phase composition and molecular order information.<p> The high lateral and vertical spatial resolution of AFM allowed physical imaging and confirmation of sample structure, as well as very accurate domain height determination. X-PEEM supplements this with chemical sensitivity using high spatial resolution spectromicroscopy. Therefore, using AFM and X-PEEM as complimentary techniques, it is possible to physically and chemically characterize phase-separated monolayer films.

Understanding the controls on fluid migration in reservoir rocks is becoming evermore important within the petroleum industry as significant hydrocarbon discoveries become less frequent and more emphasis is placed on enhanced oil recovery methods. To fully understand the factors controlling fluid migration in the subsurface, pore scale information is necessary. In this study, synchrotron-based X-ray computed microtomography (CMT) is being utilized to extract physically realistic images of carbonate rock cores for the evaluation of porosity and mineralogy in the Mississippian Midale beds of the Weyburn Oilfield in southeastern Saskatchewan. Non-destructive in-situ imaging by CMT is unique as it provides a detailed and novel approach for the description of pore space geometry, while preserving connectivity and spatial variation of pore-body and pore-throat sizes. Here, three-dimensional micron to sub-micron (0.3ìm-100ìm) resolution of CMT is coupled with, and compared against, conventional laboratory-based methods (liquid and gas permeametry, mercury injection porosimetry, electrical resistivity, backscattered electron (BSE) from electron probe micro-analysis (EPMA) and transmitted light microscopy). Petrophysical and mineralogical information obtained from both CMT and conventional methods will have direct implications for understanding the petrophysical mechanisms that control fluid movement in the subsurface of the Weyburn Oilfield.<p>At Weyburn, CO2 gas is being injected into producing horizons to enhance oil recovery and permanently sequester CO2 gas. Fundamental questions exist regarding: (1) The significance of pore geometry and connectivity to the movement of CO2 and other fluids in the subsurface, (2) the nature of the interactions between CO¬2 and pore lining minerals and their impact on petrophysical properties, and (3) the distribution and mineralogy of finely disseminated silicate and carbonate minerals adjacent to pore spaces as interaction among these phases and CO2 may result in permanent sequestration of CO2. <p>The two producing horizons within the Weyburn Reservoir, the Midale Marly and Midale Vuggy units, have variable porosities and permeabilities. Porosity in the Marly unit ranges from 16% to 38% while permeability ranges from 1mD to greater than 150 mD across the field. For the Vuggy unit, porosity ranges from 8% to 21% with permeability ranging from 0.3mD to 500mD. Using CMT, pore space is critically examined to highlight the controlling factors on permeability. Digital processing of CMT data indicates that pore space in the Marly unit is dominated by intercrystalline pores having diameters of approximately 4 ìm. From here, it is noted that the pore-throat radii are approximately ½ the radii of the pore-bodies, having profound implications to current oil recovery methods. Tortuosity values from CMT are also observed to have similar values in three orthogonal directions indicating an isotropic pore space distribution within the Marly unit. Alternatively, the Vuggy unit is found to possess greater pore-body and pore-throat sizes that are heterogeneous in distribution. Based on this, permeability in the Vuggy unit is strongly dependant on pore-length scales that vary drastically between localities.

La toxicitat del mercuri depèn de la seva probabilitat d'exposició, factors geoquímics i ecològics, i en particular de l'espècie química en què es troba. No obstant això, el nombre i veracitat de tècniques analítiques d'especiació segueix sent molt limitat. En conseqüència, les tècniques espectroscòpiques d'absorció de raig-X (XAS) basades amb la radiació sincrotró, han esdevingut eines interessants i fàcilment disponibles per a superar la manca existent en aquest camp. Entre altres, les tècniques més comuns són XANES (X-ray Absorption Near Edge Spectroscopy) i EXAFS (Extended X-ray Absorption Fine Structure). Altres progressos en aquest camp es basen en la unió de les tècniques d'absorció amb a una alta resolució espacial a nivell de microescala, usant les tècniques µ-XRF (microscopic X-ray Fluorescence) o µ-XAS. La comprensió del perill per al medi ambient plantejat pel metilmercuri (CH3HgCl i CH3HgOH) adsorbit sobre típics components del sòl ha estat assolida per la combinació de les tècniques XAS i bacteris sensors luminiscents (Escherichia coli MC1061, pmerBRBSluc). La quantitat de Hg adsorbit ha resultat ser depenent del pH, mentre que el caràcter de l'enllaç independent del pH. En comparar la interacció entre el metilmercuri i les argiles o materials húmics, els primers han donat lloc a un caràcter iònic més alt i per tant a una possibilitat de mobilització del mercuri més gran. A més, aquesta interacció ha resultat ser més estable pel CH3HgOH que pel CH3HgCl.El districte d'Almadén a Ciudad Real ha donat lloc a un dels ambient més impactats pel Hg arreu del món. En aquest context, les tècniques XAS (juntament amb SES, XRD i SEM-EDS) s'han utilitzat per a estudiar el comportament del mercuri en aquesta regió. El cinabri s'ha trobat que és l'espècie principal en minerals i sòls, mentre que el metacinabri és l'espècie principal en les escòries. En totes les mostres, també s'han trobat sals més solubles de mercuri (HgCl2, HgSO4 i schuetteite). Les tècniques de microsonda també han revelat correlacions elementals entre el Hg i el Pb, Ni i S, indicant un possible acoblament geoquímic d'aquests elements. Les correlacions també s'han identificat entre el Hg i Fe/Mn, el qual s'ha atribuït a l'absorció del mercuri sobre els oxihidròxids de Fe i Mn. D'altra banda, les indústries clor-àlcali amb càtode de mercuri han estat un dels usos industrials més importants del mercuri a Europa occidental. El gravamen del comportament del mercuri en aquests ambients ha estat conduït per les tècniques XAS acoblades a SES. La informació d'especiació ha demostrat que els compostos inorgànics de mercuri dominen en totes les mostres de sòl considerades, sent cinabri i corderoite les principals espècies. No obstant això, també s'han identificat fases lleument solubles (HgO i HgSO4) en proporcions de menor importància. Per altra banda, l'anàlisi de µ-XRF ha demostrat una correlació geoquímica de Hg, Cu i Ni, que suggereixen la formació de possibles solucions sòlides d'aquests elements dintre de la mateixa estructura cristal·lina. Finalment, les tècniques de microsonda amb radiació sincrotró s'han proposat per a l'observació directa del mercuri i altres elements presents en dents humanes restaurades amb amalgames de mercuri. Les anàlisis han demostrat una difusió mínima del Hg a través de la dent, amb la identificació d'una correlació lineal entre el Hg i el Cu. Per altra banda, s'ha identificat una difusió significativa del Cu i el Zn de l'amalgama a la regió de la dentina, suggerint un possible intercanvi del Ca2+ amb el Cu2+/Zn2+ en els cristalls d'hidroxiapatita (Ca10(PO4)6(OH)2). Per altra banda, µ-EXAFS ha determinat que l'ambient molecular inicial del Hg en la regió de l'amalgama està limitat per la fase ?-Ag2Hg3 formada durant el procés d'amalgamació / Toxicity of mercury is determined by the likelihood of exposure, geochemical and ecological factors, and in particular by the chemical species in which it is found. Chemical speciation become of an utmost importance when assessing the risk associated to mercury impacted environments. Despite this, the number and reliability of analytical techniques able to recognise different mercury species is still very limited, even more when dealing with solid samples. Hence, synchrotron-based x-ray absorption spectroscopic (XAS) techniques have risen as an interesting and readily available tool to overcome the existing speciation gap. Among others, the most common techniques dealing with speciation are XANES (X-ray Absorption Near Edge Spectroscopy) and EXAFS (Extended X-ray Absorption Fine Structure). Further developments in this field focus on the coupling of x-ray absorption techniques to a spatial resolution at a micro-scale level, by using µ-XRF (microscopic X-ray Fluorescence) or µ-XAS techniques.The understanding of the environmental hazard posed by methylmercury (CH3HgCl and CH3HgOH) adsorbed onto a number of key soil materials has been accomplished by the combination of XAS techniques and luminisent sensor bacteria (Escherichia coli MC1061, pmerBRBSluc). The amount of Hg adsorbed was observed to be pH-dependent, whereas the bond character was found to be pH-independent. When comparing interaction between methylmercury and clays or humic materials, the former resulted in a higher ionic character and consequently in a larger possibility of mercury mobilisation. Additionally, this interaction was observed to be more stable for CH3HgOH than for CH3HgCl, due to the higher reactivity of the hydroxyl group. The Almadén district in Ciudad Real has lead to one of the most Hg-impacted environments found around the world. In this context, XAS techniques (complemented with SES, XRD and SEM-EDS analyses) have been utilised to study the mercury behaviour in this region. Cinnabar has been found to be the main species in ores and soils, whereas metacinnabar was the main species in slag. In all samples, slightly soluble mercury salts (HgCl2, HgSO4 and schuetteite) have been also found. Microprobe techniques have also revealed elemental correlations between Hg and Pb, Ni and S, indicating a possible geochemical linkage of these elements. Correlations were also identified between Hg and Fe/Mn, which have been attributed to sorption of mercury onto oxy-hydroxides of Fe and Mn. Chlor-alkali industries with mercury cathode remain as one of the most important industrial applications of mercury in Western Europe, which become one of the most important point-sources for mercury contamination. The assessment of mercury behaviour in these environments has been conducted by XAS techniques coupled to SES. Speciation information showed that inorganic mercury compounds dominate in all soil samples considered, being cinnabar and corderoite the main species. However, slightly soluble phases (HgO and HgSO4) have been also identified in minor proportions. On the other hand, µ-XRF analysis has shown a geochemical correlation of Hg, Cu and Ni, which suggest the possible formation of solid solutions of these elements within the same crystalline structure.Finally, synchrotron X-ray microprobe techniques have been proposed for the direct observation of mercury and other elements present in human teeth restored with dental amalgams. Microprobe analyses showed a minimum diffusion of Hg throughout the tooth, with the identification of a linear correlation between Hg and Cu. On the other hand, a significant diffusion of Cu and Zn from the amalgam to the dentine region was identified, which suggested the possible exchange of Ca2+ by Cu2+/Zn2+ in hydroxiapatite crystals (Ca10(PO4)6(OH)2). On the other hand, µ-EXAFS has determined that the initial molecular environment of Hg in the amalgam region is limited to the ?-Ag2Hg3 phase formed during the amalgamation process.

No description available.

No description available.

The stabilization of electron beam in the Storage Ring (SR) is an important task in the 3rd generation synchrotron facility worldwide. Deviations in the position and angle of electron beam with respect to a desired orbit must be below 10% of the beam size. This requirement corresponds to about 3 μm deviations at the Canadian Light Source (CLS). Further, the higher the correction bandwidth, the better in the stabilization process. The correction bandwidth at CLS was expected to increase to be 45 Hz or higher from the current operating rate at 18 Hz. In addition, there is requirement to control the beam deviation at specific positions on the orbit. To meet these requirements, a comparative study of the existing methods for the stabilization of electron beam in the SR is thus necessary, which is the main motivation of this thesis study. The overall objective of this thesis study was to find the most suitable method for CLS so that the correction bandwidth can be 45 Hz or higher. The study was primarily conducted by simulation due to the restriction in performing experiments on the whole beamline. The transfer functions of three important devices at the storage ring, which are Beam Position Monitor (BPM), Orbit Correction Magnets (OCM) and Vacuum Chamber (VC), were identified. Noises on the storage ring were also identified to improve the reliability of the simulation study. The existing methods for beam orbit correction, such as (1) Singular Value Decomposition (SVD), (2) Eigen Vector method with Constraints (EVC) and (3) SVD plus Proportional integral derivative (PID), were compared based on the simulation technique. Several conclusions can be drawn from this study: (1) there is no significant difference between the EVC method and SVD method in terms of overall orbit correction performance, and they both can meet the correction bandwidth of 45 Hz. The EVC method is however much better than the SVD method in terms of the beam orbit correction performance at specific positions; (2) the SVD plus PID method is much better than the SVD method as well as EVC method in terms of the overall orbit correction performance, and its performance for specific position orbit correction is comparable with the performance of EVC. Therefore, the SVD plus PID method is recommended for CLS. This study has made the following contributions on the problem of beam stabilization the storage ring in the synchrotron technology: (1) provision of the models of BPM and OCM and the PID controller tailored to specific BPM and OCM devices, which is useful to other synchrotron facilities in the world; (2) generation of the knowledge regarding the performances of SVD, EVC and SVD plus PID methods on one synchrotron facility is valuable, and this knowledge is useful to other synchrotron facilities in selection of the best methods for electron orbit correction.

The development of X-ray Beam Position Monitors (XBPM) used on the Canadian Light Source front ends is described in this thesis, from the design concepts to the practical implementation and commissioning. Surveyed into position to provide a fiducialized point of origin for incoming synchrotron radiation, the primary purpose of the XBPM is to provide a measure of synchrotron beam motion. Currently XBPMs have been installed on three beamlines at the Canadian Light Source, a 2.9 GeV third generation synchrotron radiation source. Two of the XBPMs are comprised of chemical vapour deposition synthetic diamond blades coated with gold and installed on insertion device beamlines, while the third makes use of molybdenum blades for a dipole beamline. By incrementally scanning the blades of the XBPM through the synchrotron beam it is possible to determine the monitors� spatial resolution to beam motion. For the commissioned XBPM a typical spatial resolution of +/- 1 micron of beam motion was achieved; and the thermal power loading capacity has been tested to the 2/5 of maximum value. An independent white beam profiler, comprised of a converter crystal and image acquisition software, was constructed to corroborate the functionality of the XBPM.

Understanding the controls on fluid migration in reservoir rocks is becoming evermore important within the petroleum industry as significant hydrocarbon discoveries become less frequent and more emphasis is placed on enhanced oil recovery methods. To fully understand the factors controlling fluid migration in the subsurface, pore scale information is necessary. In this study, synchrotron-based X-ray computed microtomography (CMT) is being utilized to extract physically realistic images of carbonate rock cores for the evaluation of porosity and mineralogy in the Mississippian Midale beds of the Weyburn Oilfield in southeastern Saskatchewan. Non-destructive in-situ imaging by CMT is unique as it provides a detailed and novel approach for the description of pore space geometry, while preserving connectivity and spatial variation of pore-body and pore-throat sizes. Here, three-dimensional micron to sub-micron (0.3ìm-100ìm) resolution of CMT is coupled with, and compared against, conventional laboratory-based methods (liquid and gas permeametry, mercury injection porosimetry, electrical resistivity, backscattered electron (BSE) from electron probe micro-analysis (EPMA) and transmitted light microscopy). Petrophysical and mineralogical information obtained from both CMT and conventional methods will have direct implications for understanding the petrophysical mechanisms that control fluid movement in the subsurface of the Weyburn Oilfield.<p>At Weyburn, CO2 gas is being injected into producing horizons to enhance oil recovery and permanently sequester CO2 gas. Fundamental questions exist regarding: (1) The significance of pore geometry and connectivity to the movement of CO2 and other fluids in the subsurface, (2) the nature of the interactions between CO¬2 and pore lining minerals and their impact on petrophysical properties, and (3) the distribution and mineralogy of finely disseminated silicate and carbonate minerals adjacent to pore spaces as interaction among these phases and CO2 may result in permanent sequestration of CO2. <p>The two producing horizons within the Weyburn Reservoir, the Midale Marly and Midale Vuggy units, have variable porosities and permeabilities. Porosity in the Marly unit ranges from 16% to 38% while permeability ranges from 1mD to greater than 150 mD across the field. For the Vuggy unit, porosity ranges from 8% to 21% with permeability ranging from 0.3mD to 500mD. Using CMT, pore space is critically examined to highlight the controlling factors on permeability. Digital processing of CMT data indicates that pore space in the Marly unit is dominated by intercrystalline pores having diameters of approximately 4 ìm. From here, it is noted that the pore-throat radii are approximately ½ the radii of the pore-bodies, having profound implications to current oil recovery methods. Tortuosity values from CMT are also observed to have similar values in three orthogonal directions indicating an isotropic pore space distribution within the Marly unit. Alternatively, the Vuggy unit is found to possess greater pore-body and pore-throat sizes that are heterogeneous in distribution. Based on this, permeability in the Vuggy unit is strongly dependant on pore-length scales that vary drastically between localities.

Langmuir-Blodgett (LB) organic monomolecular (monolayer) films containing fatty acids and their perfluorinated counterparts separate into phases under certain conditions. These perfluorinated surfactant containing mixed-phase systems have been shown to exhibit many favourable attributes in comparison to non- perfluorinated surfactant monolayers. In this thesis project, two of these films were investigated. One film is a 2:1 ratio mixture of arachidic acid (C19H39COOH AA) to perfluorotetradecanoic acid (C13F27COOH PA), which phase-separates into hexagonal domains ~6 ìm large (2:1 ratio of AA to PA 2AA1PA). The other film is a 2:1 mixture of stearic acid (C17H35COOH - SA) to PA, which phase-separates into linear domains ~300 nm wide (2:1 ratio of SA to PA 2SA1PA).<p> Through the use of atomic force microscopy (AFM), and various synchrotron photoemission electron microscopy-based (PEEM) techniques, the films were characterized. As properties such as molecular organization, and dispersion of the molecules in the film, affect film function, it is necessary to use a variety of techniques to better understand order and composition in the films.<p> First, the well-known and previously-studied film, 2AA1PA, was used to better understand contrast mechanisms in the energy filtered x-ray photoemission electron microscope (X-PEEM) at the CLS. Through the use of techniques such as secondary electron emission microscopy (SEEM), ultraviolet photoelectron spectroscopy (UPS), and x-ray linear dichroism microscopy (XLDM), the effects of secondary electrons, valence character, and polarization dependence were studied so as to better understand their contribution to contrast in energy-filtered PEEM-based spectromicroscopy.<p> Second, the composition and organization of a novel system (2SA1PA), was characterized using traditional near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy. As the size of the domains in the 2SA1PA system are below the spatial resolution limit of PEEM spectromicroscopy, methods involving selective phase dissolution, and spectrum subtraction, were used to acquire phase composition and molecular order information.<p> The high lateral and vertical spatial resolution of AFM allowed physical imaging and confirmation of sample structure, as well as very accurate domain height determination. X-PEEM supplements this with chemical sensitivity using high spatial resolution spectromicroscopy. Therefore, using AFM and X-PEEM as complimentary techniques, it is possible to physically and chemically characterize phase-separated monolayer films.

In this thesis, two aspects of research in soft X-ray absorption spectroscopy chemistry are explored. The first objective was to measure the natural circular dichroism of small chiral organic molecules at soft X-ray wavelengths. The second objective was to characterize the electronic structure and spectra of a series of organometallic polymers. <p>The goal of the first part of this thesis was to enhance the sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to the intrinsic handedness of chiral organic molecules. The phenomenon of X-ray natural circular dichroism (XNCD) has been well described by theoreticians; however, there have been few successful measurements reported, mainly due to the weakness of the effect and the difficulty of preparing suitable samples. The fourth chapter of this thesis outlines the requirements for XNCD experiments and the efforts made to prepare appropriate samples. <p>The goal of the second part was to use NEXAFS spectroscopy as an analytical technique for the elemental and chemical characterization of innovative materials based on organoiron compounds. The interpretation of transition metal compounds by NEXAFS spectroscopy is difficult due to complex interactions between the metal and its surroundings. Two approaches are commonly used; an atomic multiplet model and a covalent bonding model, which lead to conflicting spectral assignments. Earlier NEXAFS studies of metallocene complexes were found to be lacking as these two models were not adequately rationalized. Owing in part to greatly improved instrumental sensitivity and to efficient theoretical calculations, the interpretation of NEXAFS spectra for a series of metallocene and metal arene complexes was refined. Enhanced understanding of the spectroscopy of these compounds eventually contributed to the characterization of a series of organometallic polymeric materials.<p>Underlining these studies is the remarkable complementarity of NEXAFS spectroscopy and chemistry. A comprehensive understanding of the chemistry of the samples examined in the measurement of XNCD is shown to be crucial for a successful advancement of this spectroscopy. In return, optimization of soft X-ray spectroscopy of metallocenes is demonstrated to remarkably benefit the understanding of the organometallic polymers.