Species prescriptions are developed for revegetating abandoned acidic coal overburden seepage sites in the Collie region of Western Australia. The research involved selecting appropriate plant species and determining successful methods of enhancing revegetation. Candidate species were screened for tolerance to acidic overburden materials, local climate conditions and metal toxicity. Methods tested included improving spoil conditions and trialing an alternative method for seeding.Twelve species of native plants were tested for tolerance in two acid overburden materials in pot and field trials. Eucalyptus robusta is the most tolerant, Eucalyptus camaldulensis and Eucalyptus cladocalyx are highly tolerant, Eucalyptus rudis and Melaleuca hamulosa demonstrate potential, provided adequate soil moisture is available.An important growth restriction factor in acid soils is the presence of free aluminium ions. A glasshouse trial performed on seven species for tolerance to aluminium toxicity revealed E. robusta as most tolerant and E. camaldulensis and Kunzea ericifolia a highly tolerant. E. rudis and M. hamulosa are moderately tolerant, but E. cladocalyx and Eucalyptus diversicolor are very sensitive to aluminium.Various methods were trialed to increase growth of seedlings transplanted on to acidic overburden sites. Both commercial cow manure and slow-release fertiliser tablets increase growth, whereas commercial potting mix and lime do not. Inoculation of plants with the ectomycorrhiza fungus Pisolithus tinctorius increases the amount of infection in roots but does not enhance plant growth.Supplementary fertilisation is necessary to maintain growth (nitrogen) and restore chlorophyll production (phosphorus) in fast growing eucalypt seedlings planted into typical acidic spoils. Poor levels of nutrient availability in such acidic sites appear to be the primary factor in ++ / retarding growth. In the absence of supplementation, foliage reddening is observed in several species.An alternative method of seeding dumps is fascining. Prepared dump surfaces may be covered with capsule-laden branchwood of myrtaceous species. Material of the locally available Kunzea ericifolia is effective in producing many seedlings. Subsequent seedling growth is enhanced with fertiliser and lime addition.

We explore efficient parallel radix sort for the AMD Fusion Accelerated Processing Unit (APU). Two challenges arise: efficiently partitioning data between the CPU and GPU and the allocation of data in memory regions. Our coarse-grained implementation utilizes both the GPU and CPU by sharing data at the begining and end of the sort. Our fine-grained implementation utilizes the APU’s integrated memory system to share data throughout the sort. Both these implementations outperform the current state of the art GPU radix sort from NVIDIA. We therefore demonstrate that the CPU can be efficiently used to speed up radix sort on the APU. Our fine-grained implementation slightly outperforms our coarse-grained implementation. This demonstrates the benefit of the APU’s integrated architecture. This performance benefit is hindered by limitations in the APU’s architecture and programming model. We believe that the performance benefits will increase once these limitations are addressed in future generations of the APU.

Der Siegeszug der Mikroelektronik ist faszinierend. In den vergangenen Jahrzehnten bestimmte die Mikroelektronik das Geschehen in der Informationstechnik: Immer leistungsstärkere Computer, vernetzte Systeme und das Internet sind ohne Mikroelektronik nicht denkbar. Weltweit haben Mikroelektronik-Firmen ihre strategischen Ziele im Rahmen einer in regelmäßigen Abständen aktualisierten “Roadmap” niedergelegt. Alle gehen davon aus, dass die bisher zu beobachtende Steigerung der Leistungsfähigkeit mikroelektronischer Produkte auch in den nächsten Jahrzehnten fortgesetzt werden wird. Das bedeutet konkret, dass an vielen Stellen – auch in der heutigen Massenfertigung der Mikroelektronik – die charakteristischen Abmessungen der Einzelelemente im Nanometerbereich liegen, also eigentlich schon als Nanoelektronik bezeichnet werden können. Hinzu kommt ein weiteres, ebenso spannendes Feld: die Mikrosystemtechnik.

We explore efficient parallel radix sort for the AMD Fusion Accelerated Processing Unit (APU). Two challenges arise: efficiently partitioning data between the CPU and GPU and the allocation of data in memory regions. Our coarse-grained implementation utilizes both the GPU and CPU by sharing data at the begining and end of the sort. Our fine-grained implementation utilizes the APU’s integrated memory system to share data throughout the sort. Both these implementations outperform the current state of the art GPU radix sort from NVIDIA. We therefore demonstrate that the CPU can be efficiently used to speed up radix sort on the APU. Our fine-grained implementation slightly outperforms our coarse-grained implementation. This demonstrates the benefit of the APU’s integrated architecture. This performance benefit is hindered by limitations in the APU’s architecture and programming model. We believe that the performance benefits will increase once these limitations are addressed in future generations of the APU.

Patients with macular degeneration (MD) often fixate with a preferred retinal locus (PRL). Eye movements made while fixating with the PRL (in MD patients) has been observed to be maladaptive compared to those made while fixating with the fovea (normal sighted individuals). For example, in MD patients, PRL eye movements negatively affect fixation stability and re-fixation precision; consequently creating difficulty in reading and limits to their execution of other everyday activities. Abnormal eye movements from the PRL affect research on the physiological adaptations to MD. Specifically, previous research on cortical reorganization using functional magnetic resonance imaging (fMRI), indicates a critical need to accurately determine a MD patient's point of gaze in order to better infer existence of cortical reorganization. Unfortunately, standard MR compatible hardware eye-tracking systems do not work well with these patients. Their reduction in fixation stability often overwhelms the tracking algorithms used by these systems. This research investigates the use of an existing magnetic resonance imaging (MRI) based technique called Predictive Eye Estimation Regression (PEER) to determine the point of gaze of MD patients and thus control for fixation instability. PEER makes use of the fluctuations in the MR signal caused by eye movements to identify position of gaze. Engineering adaptations such as temporal resolution and brain coverage were applied to tailor PEER to MD patients. Also participants were evaluated on different fixation protocols and the results compared to that of the micro-perimeter MP-1 to test the efficacy of PEER. The fixation stability results obtained from PEER were similar to that obtained from the eye tracking results of the micro-perimeter MP-1. However, PEER's point of gaze estimations was different from the MP-1's in the fixation tests. The difference in this result cannot be concluded to be specific to PEER. In order to resolve this issue, advancements to PEER by the inclusion of an eye tracker in the scanner to run concurrently with PEER could provide more evidence of PEER's reliability. In addition, increasing the diversity of AMD patients in terms of the different scotoma types will help provide a better estimate of PEER flexibility and robustness.

Acid mine drainage (AMD) typically involves waters with low pH (pH 2-4) and high concentrations of Fe, SO4 and potentially toxic trace metals. Adsorption onto iron oxyhydroxides is the dominant mechanism controlling the transport and toxicity of trace metals in water bodies impacted by AMD. The purpose of this study was to apply the Diffuse Layer Model (DLM) to describe the adsorption of trace metals by iron oxyhydroxides from these systems, using synthetic iron oxyhydroxide minerals, ferrihydrite, pure acicular goethite, SO4-rich goethite prepared from FeSO4 oxidation and a synthetic schwertmannite. The ferrihydrite adsorption of the trace metals Cu, Zn, Cd and Co from single sorbate systems was accurately described using the DLM with two surface site types (type-1 and type-2) having site densities of 0.005 and 0.2 mol (mol Fe)-1 respectively. The ferrihydrite adsorption of SO4 from single sorbate systems was accurately described using the DLM with adsorption on the type-2 sites. However, the enhanced adsorption of Cu, Zn, Cd and Co in the presence of SO4 was not predicted using adsorption constants derived from single sorbate systems. By including a neutral ternary complex with stoichiometry Fe(2)OHMeSO4 (where Fe(2)OH is a type-2 surface site and Me is the trace metal) the effect of SO4 on metal adsorption was accurately described for the range of Me, Fe and SO4 concentrations studied. The adsorption of Cu and Zn onto schwertmannite at total metal to iron ratios (MeT:Fe) up to 8 x 10-3 was almost identical to that predicted for ferrihydrite in the presence of 0.01 mol kg-1 SO4. To model the ferrihydrite adsorption of Pb from single sorbate systems a third higher affinity site (type-0) with a site density of 0.00035 mol (mol Fe)-1 was required. The effect of SO4 on Pb adsorption could only be modelled by including a neutral ternary complex on both the type 1 and type 2 sites in the case of Pb. Metal adsorption onto a pure acicular goethite could be accurately described by the DLM with two surface site types. The type 2 site density that provided the best fit to the goethite adsorption data was 0.027 mol (mol Fe)-1 corresponding to 2.3 nm-2. The type-1 site density that provided the best fit to goethite adsorption of Cu, Pb and Cd was 0.00028 mol (mol Fe)-1 corresponding to 0.024 nm-2. For Zn adsorption on goethite the type-1 site density was significantly larger at 0.0015 mol (mol Fe)-1 corresponding to 0.13 nm-2. In all cases studied the presence of SO4 caused an increase in the extent of metal adsorption by goethite. This increased adsorption of metals in the presence of SO4 was accurately predicted by including ternary complex formation at both the high and low affinity adsorption sites. For both ferrihydrite and goethite the values of adsorption constants for ternary complex formation (logKxMeTC) were related to the adsorption constant for metal adsorption in the absence of SO4 (logKxMeINT). This was evident from a plot of logKxMeTC as a function of logKxMeINT for all metals, which showed a linear relationship with slope of 0.69 and intercept of 8.03. This relationship suggests that the enhancement of metal adsorption on both oxyhydroxides due to SO4 occurs by the same process. When comparing Cu, Zn and Cd adsorption onto ferrihydrite and acicular goethite the effect of the larger goethite adsorption constants are approximately compensated for by the lower goethite site densities. Therefore the Cu, Cd and Zn adsorption isotherms on ferrihydrite and acicular goethite are fairly similar at low adsorption densities. In the case of Pb, the site densities and adsorption constants are both larger on ferrihydrite and there is a large difference between the ferrihydrite and acicular goethite adsorption isotherms. Sulfate-rich goethite had considerably higher site densities, per mol of oxide, than the pure acicular goethite. Adsorption onto the sulfate-rich goethite could be modelled reasonably accurately using the parameters developed to model adsorption onto the pure acicular goethite but with a higher surface area and a higher ratio of type-1 to type 2 sites. In general, therefore, the parameters developed for pure goethite are apparently similar to those for the sulfate-rich goethite, but are not directly transferable. The difficulty in measuring the surface area of the highly aggregated sulfate-rich goethite makes comparisons between the two goethites more difficult. The adsorption of Cu, Zn and Cd onto the SO4-rich goethite exceeds that of ferrihydrite because the higher adsorption constants of goethite are combined with the considerably higher site densities of the SO4-rich goethite compared to the acicular goethite. In contrast the higher site densities of the SO4-rich goethite does not completely compensate for the low logKINT values of Pb adsorption on goethite. Therefore SO4-rich goethite adsorption of Pb is lower than that of ferrihydrite. When applied to literature data from AMD oxides the parameters derived in this thesis have significantly improved the ability of the DLM to predict trace metal adsorption in AMD systems, compared to using ferrihydrite as a proxy for all iron oxyhydroxides and adsorption data derived only from single sorbate systems.

Acid mine drainage (AMD) typically involves waters with low pH (pH 2-4) and high concentrations of Fe, SO4 and potentially toxic trace metals. Adsorption onto iron oxyhydroxides is the dominant mechanism controlling the transport and toxicity of trace metals in water bodies impacted by AMD. The purpose of this study was to apply the Diffuse Layer Model (DLM) to describe the adsorption of trace metals by iron oxyhydroxides from these systems, using synthetic iron oxyhydroxide minerals, ferrihydrite, pure acicular goethite, SO4-rich goethite prepared from FeSO4 oxidation and a synthetic schwertmannite. The ferrihydrite adsorption of the trace metals Cu, Zn, Cd and Co from single sorbate systems was accurately described using the DLM with two surface site types (type-1 and type-2) having site densities of 0.005 and 0.2 mol (mol Fe)-1 respectively. The ferrihydrite adsorption of SO4 from single sorbate systems was accurately described using the DLM with adsorption on the type-2 sites. However, the enhanced adsorption of Cu, Zn, Cd and Co in the presence of SO4 was not predicted using adsorption constants derived from single sorbate systems. By including a neutral ternary complex with stoichiometry Fe(2)OHMeSO4 (where Fe(2)OH is a type-2 surface site and Me is the trace metal) the effect of SO4 on metal adsorption was accurately described for the range of Me, Fe and SO4 concentrations studied. The adsorption of Cu and Zn onto schwertmannite at total metal to iron ratios (MeT:Fe) up to 8 x 10-3 was almost identical to that predicted for ferrihydrite in the presence of 0.01 mol kg-1 SO4. To model the ferrihydrite adsorption of Pb from single sorbate systems a third higher affinity site (type-0) with a site density of 0.00035 mol (mol Fe)-1 was required. The effect of SO4 on Pb adsorption could only be modelled by including a neutral ternary complex on both the type 1 and type 2 sites in the case of Pb. Metal adsorption onto a pure acicular goethite could be accurately described by the DLM with two surface site types. The type 2 site density that provided the best fit to the goethite adsorption data was 0.027 mol (mol Fe)-1 corresponding to 2.3 nm-2. The type-1 site density that provided the best fit to goethite adsorption of Cu, Pb and Cd was 0.00028 mol (mol Fe)-1 corresponding to 0.024 nm-2. For Zn adsorption on goethite the type-1 site density was significantly larger at 0.0015 mol (mol Fe)-1 corresponding to 0.13 nm-2. In all cases studied the presence of SO4 caused an increase in the extent of metal adsorption by goethite. This increased adsorption of metals in the presence of SO4 was accurately predicted by including ternary complex formation at both the high and low affinity adsorption sites. For both ferrihydrite and goethite the values of adsorption constants for ternary complex formation (logKxMeTC) were related to the adsorption constant for metal adsorption in the absence of SO4 (logKxMeINT). This was evident from a plot of logKxMeTC as a function of logKxMeINT for all metals, which showed a linear relationship with slope of 0.69 and intercept of 8.03. This relationship suggests that the enhancement of metal adsorption on both oxyhydroxides due to SO4 occurs by the same process. When comparing Cu, Zn and Cd adsorption onto ferrihydrite and acicular goethite the effect of the larger goethite adsorption constants are approximately compensated for by the lower goethite site densities. Therefore the Cu, Cd and Zn adsorption isotherms on ferrihydrite and acicular goethite are fairly similar at low adsorption densities. In the case of Pb, the site densities and adsorption constants are both larger on ferrihydrite and there is a large difference between the ferrihydrite and acicular goethite adsorption isotherms. Sulfate-rich goethite had considerably higher site densities, per mol of oxide, than the pure acicular goethite. Adsorption onto the sulfate-rich goethite could be modelled reasonably accurately using the parameters developed to model adsorption onto the pure acicular goethite but with a higher surface area and a higher ratio of type-1 to type 2 sites. In general, therefore, the parameters developed for pure goethite are apparently similar to those for the sulfate-rich goethite, but are not directly transferable. The difficulty in measuring the surface area of the highly aggregated sulfate-rich goethite makes comparisons between the two goethites more difficult. The adsorption of Cu, Zn and Cd onto the SO4-rich goethite exceeds that of ferrihydrite because the higher adsorption constants of goethite are combined with the considerably higher site densities of the SO4-rich goethite compared to the acicular goethite. In contrast the higher site densities of the SO4-rich goethite does not completely compensate for the low logKINT values of Pb adsorption on goethite. Therefore SO4-rich goethite adsorption of Pb is lower than that of ferrihydrite. When applied to literature data from AMD oxides the parameters derived in this thesis have significantly improved the ability of the DLM to predict trace metal adsorption in AMD systems, compared to using ferrihydrite as a proxy for all iron oxyhydroxides and adsorption data derived only from single sorbate systems.

Acid mine drainage (AMD) typically involves waters with low pH (pH 2-4) and high concentrations of Fe, SO4 and potentially toxic trace metals. Adsorption onto iron oxyhydroxides is the dominant mechanism controlling the transport and toxicity of trace metals in water bodies impacted by AMD. The purpose of this study was to apply the Diffuse Layer Model (DLM) to describe the adsorption of trace metals by iron oxyhydroxides from these systems, using synthetic iron oxyhydroxide minerals, ferrihydrite, pure acicular goethite, SO4-rich goethite prepared from FeSO4 oxidation and a synthetic schwertmannite. The ferrihydrite adsorption of the trace metals Cu, Zn, Cd and Co from single sorbate systems was accurately described using the DLM with two surface site types (type-1 and type-2) having site densities of 0.005 and 0.2 mol (mol Fe)-1 respectively. The ferrihydrite adsorption of SO4 from single sorbate systems was accurately described using the DLM with adsorption on the type-2 sites. However, the enhanced adsorption of Cu, Zn, Cd and Co in the presence of SO4 was not predicted using adsorption constants derived from single sorbate systems. By including a neutral ternary complex with stoichiometry Fe(2)OHMeSO4 (where Fe(2)OH is a type-2 surface site and Me is the trace metal) the effect of SO4 on metal adsorption was accurately described for the range of Me, Fe and SO4 concentrations studied. The adsorption of Cu and Zn onto schwertmannite at total metal to iron ratios (MeT:Fe) up to 8 x 10-3 was almost identical to that predicted for ferrihydrite in the presence of 0.01 mol kg-1 SO4. To model the ferrihydrite adsorption of Pb from single sorbate systems a third higher affinity site (type-0) with a site density of 0.00035 mol (mol Fe)-1 was required. The effect of SO4 on Pb adsorption could only be modelled by including a neutral ternary complex on both the type 1 and type 2 sites in the case of Pb. Metal adsorption onto a pure acicular goethite could be accurately described by the DLM with two surface site types. The type 2 site density that provided the best fit to the goethite adsorption data was 0.027 mol (mol Fe)-1 corresponding to 2.3 nm-2. The type-1 site density that provided the best fit to goethite adsorption of Cu, Pb and Cd was 0.00028 mol (mol Fe)-1 corresponding to 0.024 nm-2. For Zn adsorption on goethite the type-1 site density was significantly larger at 0.0015 mol (mol Fe)-1 corresponding to 0.13 nm-2. In all cases studied the presence of SO4 caused an increase in the extent of metal adsorption by goethite. This increased adsorption of metals in the presence of SO4 was accurately predicted by including ternary complex formation at both the high and low affinity adsorption sites. For both ferrihydrite and goethite the values of adsorption constants for ternary complex formation (logKxMeTC) were related to the adsorption constant for metal adsorption in the absence of SO4 (logKxMeINT). This was evident from a plot of logKxMeTC as a function of logKxMeINT for all metals, which showed a linear relationship with slope of 0.69 and intercept of 8.03. This relationship suggests that the enhancement of metal adsorption on both oxyhydroxides due to SO4 occurs by the same process. When comparing Cu, Zn and Cd adsorption onto ferrihydrite and acicular goethite the effect of the larger goethite adsorption constants are approximately compensated for by the lower goethite site densities. Therefore the Cu, Cd and Zn adsorption isotherms on ferrihydrite and acicular goethite are fairly similar at low adsorption densities. In the case of Pb, the site densities and adsorption constants are both larger on ferrihydrite and there is a large difference between the ferrihydrite and acicular goethite adsorption isotherms. Sulfate-rich goethite had considerably higher site densities, per mol of oxide, than the pure acicular goethite. Adsorption onto the sulfate-rich goethite could be modelled reasonably accurately using the parameters developed to model adsorption onto the pure acicular goethite but with a higher surface area and a higher ratio of type-1 to type 2 sites. In general, therefore, the parameters developed for pure goethite are apparently similar to those for the sulfate-rich goethite, but are not directly transferable. The difficulty in measuring the surface area of the highly aggregated sulfate-rich goethite makes comparisons between the two goethites more difficult. The adsorption of Cu, Zn and Cd onto the SO4-rich goethite exceeds that of ferrihydrite because the higher adsorption constants of goethite are combined with the considerably higher site densities of the SO4-rich goethite compared to the acicular goethite. In contrast the higher site densities of the SO4-rich goethite does not completely compensate for the low logKINT values of Pb adsorption on goethite. Therefore SO4-rich goethite adsorption of Pb is lower than that of ferrihydrite. When applied to literature data from AMD oxides the parameters derived in this thesis have significantly improved the ability of the DLM to predict trace metal adsorption in AMD systems, compared to using ferrihydrite as a proxy for all iron oxyhydroxides and adsorption data derived only from single sorbate systems.

Acid mine drainage (AMD) typically involves waters with low pH (pH 2-4) and high concentrations of Fe, SO4 and potentially toxic trace metals. Adsorption onto iron oxyhydroxides is the dominant mechanism controlling the transport and toxicity of trace metals in water bodies impacted by AMD. The purpose of this study was to apply the Diffuse Layer Model (DLM) to describe the adsorption of trace metals by iron oxyhydroxides from these systems, using synthetic iron oxyhydroxide minerals, ferrihydrite, pure acicular goethite, SO4-rich goethite prepared from FeSO4 oxidation and a synthetic schwertmannite. The ferrihydrite adsorption of the trace metals Cu, Zn, Cd and Co from single sorbate systems was accurately described using the DLM with two surface site types (type-1 and type-2) having site densities of 0.005 and 0.2 mol (mol Fe)-1 respectively. The ferrihydrite adsorption of SO4 from single sorbate systems was accurately described using the DLM with adsorption on the type-2 sites. However, the enhanced adsorption of Cu, Zn, Cd and Co in the presence of SO4 was not predicted using adsorption constants derived from single sorbate systems. By including a neutral ternary complex with stoichiometry Fe(2)OHMeSO4 (where Fe(2)OH is a type-2 surface site and Me is the trace metal) the effect of SO4 on metal adsorption was accurately described for the range of Me, Fe and SO4 concentrations studied. The adsorption of Cu and Zn onto schwertmannite at total metal to iron ratios (MeT:Fe) up to 8 x 10-3 was almost identical to that predicted for ferrihydrite in the presence of 0.01 mol kg-1 SO4. To model the ferrihydrite adsorption of Pb from single sorbate systems a third higher affinity site (type-0) with a site density of 0.00035 mol (mol Fe)-1 was required. The effect of SO4 on Pb adsorption could only be modelled by including a neutral ternary complex on both the type 1 and type 2 sites in the case of Pb. Metal adsorption onto a pure acicular goethite could be accurately described by the DLM with two surface site types. The type 2 site density that provided the best fit to the goethite adsorption data was 0.027 mol (mol Fe)-1 corresponding to 2.3 nm-2. The type-1 site density that provided the best fit to goethite adsorption of Cu, Pb and Cd was 0.00028 mol (mol Fe)-1 corresponding to 0.024 nm-2. For Zn adsorption on goethite the type-1 site density was significantly larger at 0.0015 mol (mol Fe)-1 corresponding to 0.13 nm-2. In all cases studied the presence of SO4 caused an increase in the extent of metal adsorption by goethite. This increased adsorption of metals in the presence of SO4 was accurately predicted by including ternary complex formation at both the high and low affinity adsorption sites. For both ferrihydrite and goethite the values of adsorption constants for ternary complex formation (logKxMeTC) were related to the adsorption constant for metal adsorption in the absence of SO4 (logKxMeINT). This was evident from a plot of logKxMeTC as a function of logKxMeINT for all metals, which showed a linear relationship with slope of 0.69 and intercept of 8.03. This relationship suggests that the enhancement of metal adsorption on both oxyhydroxides due to SO4 occurs by the same process. When comparing Cu, Zn and Cd adsorption onto ferrihydrite and acicular goethite the effect of the larger goethite adsorption constants are approximately compensated for by the lower goethite site densities. Therefore the Cu, Cd and Zn adsorption isotherms on ferrihydrite and acicular goethite are fairly similar at low adsorption densities. In the case of Pb, the site densities and adsorption constants are both larger on ferrihydrite and there is a large difference between the ferrihydrite and acicular goethite adsorption isotherms. Sulfate-rich goethite had considerably higher site densities, per mol of oxide, than the pure acicular goethite. Adsorption onto the sulfate-rich goethite could be modelled reasonably accurately using the parameters developed to model adsorption onto the pure acicular goethite but with a higher surface area and a higher ratio of type-1 to type 2 sites. In general, therefore, the parameters developed for pure goethite are apparently similar to those for the sulfate-rich goethite, but are not directly transferable. The difficulty in measuring the surface area of the highly aggregated sulfate-rich goethite makes comparisons between the two goethites more difficult. The adsorption of Cu, Zn and Cd onto the SO4-rich goethite exceeds that of ferrihydrite because the higher adsorption constants of goethite are combined with the considerably higher site densities of the SO4-rich goethite compared to the acicular goethite. In contrast the higher site densities of the SO4-rich goethite does not completely compensate for the low logKINT values of Pb adsorption on goethite. Therefore SO4-rich goethite adsorption of Pb is lower than that of ferrihydrite. When applied to literature data from AMD oxides the parameters derived in this thesis have significantly improved the ability of the DLM to predict trace metal adsorption in AMD systems, compared to using ferrihydrite as a proxy for all iron oxyhydroxides and adsorption data derived only from single sorbate systems.

L'analyse visuelle de scènes débute par l'extraction en parallèle de différentes caractéristiques visuelles élémentaires à différentes fréquences spatiales. L'objectif de cette thèse a été de préciser les mécanismes et les bases cérébrales du traitement des fréquences spatiales lors de la catégorisation de scènes et leur évolution au cours du vieillissement normal et pathologique. Nous avons tout d'abord mené deux études en Imagerie par Résonance Magnétique fonctionnelle (IRMf) sur des adultes jeunes avec une vision normale afin de proposer un outil de cartographie rétinotopique des aires visuelles permettant une localisation fine des activations cérébrales qui soit à la fois rapide et précis (Expériences 1 et 2). Dans un second temps, nous avons étudié via IRMf les bases cérébrales du traitement des fréquences spatiales lors de la catégorisation de scènes chez de jeunes adultes avec vision normale(Expérience 3). Nous avons également étudié l'influence de la normalisation RMS (« root mean square ») du contraste de luminance des scènes filtrées. Au sein du cortex occipital, nous avons montré une organisation rétinotopique du traitement des fréquences spatiales contenues dans de larges scènes visuelles. Au sein du cortex occipito-temporal, nous avons montré que les régions sélectives aux scènes (la « parahippocampal place area », le cortex retrosplenial et l'« occipital place area ») participent de façon distincte au traitement des fréquences spatiales. Enfin, nous avons montré que la normalisation du contraste de luminance modifiait l'intensité et l'étendue des activations cérébrales. Dans un dernier temps, nous avons ensuite étudié le traitement des fréquences spatiales au cours du vieillissement normal et pathologique. Nous avons tout d'abord montré, dans le cas du vieillissement normal (Expérience 4), un déficit spécifique de la catégorisation de scènes en hautes fréquences spatiales (HFS), associé à une hypo activation du cortex occipital et des régions sélectives aux scènes. Dans le cas de la perte de la vision centrale consécutive à une dégénérescence maculaire liée à l'âge (patients DMLA, Expériences 5 et 6), nous avons mis en évidence un déficit du traitement des HFS encore plus marqué que celui observé au cours du vieillissement normal. De façon intéressante pour l'aide aux patients DMLA, l'augmentation du contraste de luminance des scènes en HFS améliorait significativement leur catégorisation des scènes en HFS. Les résultats de ces travaux nous permettent de mieux comprendre les mécanismes neuro-fonctionnels impliqués dans la perception visuelle de scènes et de différencier les changements au niveau cortical liés au vieillissement normal de ceux résultant d'une pathologie visuelle.Mots clés : Scènes visuelles, Fréquences spatiales, IRMf, Cortex visuel, Rétinotopie, Régions sélectives aux scènes, Vieillissement normal, DMLA. / Visual analysis begins with the parallel extraction of different attributes at different spatial frequencies. The aim of this thesis was to investigatethe mechanisms and the cerebral basis of spatial frequencies processing during scene categorization and their evolution during normal and pathological aging. As a first step, we performed two functional Magnetic Resonance Imaging (fMRI) studies on young adults with normal vision in order to design a retinotopic mapping tool that allows to localize cerebral activations, which is both fast and accurate (studies 1 and 2). As a second step, we studied via fMRI (study 3) the cerebral basis involved in spatial frequencies processing during scenes categorization in young adults with normal vision (study 3). We also assessedthe influence of RMS luminance contrast (“root mean square”) normalization of filtered scenes. Within the occipital cortex, we showed a retinotopic organization of spatial frequencies processing for large visual scenes. Within the occipito-temporal cortex, we showed that scenes-selective regions (the parahippocampal place area, retrosplenial cortex and occipital place area) are specifically involved in spatial frequencies processing. Also, we highlighted the factthat luminance contrast normalization changesboth the intensity and the size of cerebral activations. As a last step, we studiedspatial frequencies processing in normal and pathological aging. We first highlighted in normal aging (study 4) a specific deficit in the ability to categorize scenes with high spatial frequencies (HSF); this deficit was associated with a decrease of activation within the occipital cortex and scenes selective regions. In patients suffering from a loss in central vision due to Age-Related Macular Degeneration (AMD patients, studies 5 and 6), we showed an even more pronounced deficit of HSF processing than observed in normal aging. Interestingly, with respect to the assistance of AMD patients, we observed that increasing the contrast luminance of HSF scenes significantly improved their ability to categorize such scenes. In the end, these results allow us to better understand the neurofunctional mechanisms involved in the visual perception of scenes and to distinguish the cortical changes related to normal aging from those resulting from a visual pathology.Keywords: Visual scenes, Spatial frequencies, fMRI, Visual cortex, Retinotopy, Scene-selective regions, Normal aging, AMD.