A lama biliar em cães é considerada um achado incidental, sendo frequentemente identificada durante ultrassonografias abdominais como sedimento ecogênico de baixa amplitude sem sombra acústica e com mobilidade gravidade dependente. Em humanos, a presença de lama biliar é considerada anormal e está associada a diversas situações clínicas e complicações como cálculos biliares, colangite e pancreatite aguda. Em cães sua importância clínica ainda é desconhecida. Os objetivos deste estudo foram estimar a prevalência, avaliar fatores de risco, alterações encontradas ao exame de ultrassom e marcadores bioquímicos em cães com lama biliar diagnosticada por ultrassonografia. Determinou-se a prevalência e a influência das diferentes raças, sexo e idade na lama biliar, a partir de 1.021 cães submetidos à ultrassonografia abdominal, independente do estado de saúde. Desse total, foram selecionados por conveniência, 100 cães para avaliação das alterações encontradas na ultrassonografia, dos fatores de risco e dos marcadores bioquímicos perante a presença ou ausência de lama biliar. Os resultados mostraram que a prevalência de lama biliar é alta, sendo que cães com 10 anos ou mais estiveram mais predispostos. Machos e fêmeas foram acometidos em igual intensidade, havendo uma maior prevalência nas raças Beagle, Cocker Spaniel e Poodle. Nenhum dos marcadores bioquímicos estudados demonstrou correlação significativa com a lama e através da quantificação desse sedimento foi possível sugerir que o espessamento biliar raramente progride podendo acarretar complicações mais graves como a mucocele e colelitíase. Condição corporal e a castração não demonstraram relação com a presença de lama biliar e o tipo de dieta não foi considerado como o principal fator de risco, havendo apenas fraca associação da lama com o abuso da alimentação com petiscos veterinários. Já o uso de medicamentos demonstrou estar entre as possíveis causas para o desenvolvimento do espessamento biliar. Pacientes com doenças cardiovasculares encotraram-se no grupo de risco e a maior ocorrência de hepatomegalia nos cães acometidos pela lama foi associada à congestão hepática passiva, consequência das cardiopatias. Acredita-se que o fator idade também possa estar relacionado a esse fato, já que as cardiopatias são mais frequentes em cães mais velhos. / The biliary sludge in dogs is deemed to be an incidental finding, and is often identified during abdominal ultrasound as echogenic sediment of low amplitude without acoustic shadowing and gravity dependent mobility. In humans, the presence of biliary sludge is considered abnormal and it is associated with various medical conditions and complications such as gallstones, cholangitis and acute pancreatitis. In dogs their clinical importance is still unknown. The aims of this study were to estimate prevalence, evaluate risk factors, findings on ultrasound examination and biochemical markers in dogs with biliary sludge diagnosed by ultrasonography. It was determined the prevalence and influence of different breeds, gender and age in biliary sludge, from 1.021 dogs undergoing abdominal ultrasonography, regardless of their health status. Overall, it was selected for convenience, 100 dogs for evaluation of abnormalities found on ultrasound, the risk factors and biochemical markers before the presence or absence of biliary sludge. The results showed that the prevalence of biliary sludge is high, and dogs with 10 years old or more were more predisposed. Males and females were affected at the same intensity, with greater prevalence in breeds Beagle, Cocker Spaniel and Poodle. None of the biochemical markers studied showed a significant correlation with the sludge and through the quantification of sediment was possible to suggest that the thickened bile rarely progresses and may cause more serious complications such as mucocele and cholelithiasis. Body condition and castration showed no correlation with the presence of biliary sludge and the type of diet was not considered a major risk factor, with only a weak association of the sludge with the abuse with veterinarians’ snacks. But the use of medicines proved to be among the possible causes for the development of the thickened bile. Patients with cardiovascular diseases lay in the risk group and higher incidence of hepatomegaly in dogs affected by the mud was associated to passive hepatic congestion, as consequence of cardiopathies. It is believed that the age factor may also be related to this fact, since cardiopathies are more common in older dogs.

A lama biliar em cães é considerada um achado incidental, sendo frequentemente identificada durante ultrassonografias abdominais como sedimento ecogênico de baixa amplitude sem sombra acústica e com mobilidade gravidade dependente. Em humanos, a presença de lama biliar é considerada anormal e está associada a diversas situações clínicas e complicações como cálculos biliares, colangite e pancreatite aguda. Em cães sua importância clínica ainda é desconhecida. Os objetivos deste estudo foram estimar a prevalência, avaliar fatores de risco, alterações encontradas ao exame de ultrassom e marcadores bioquímicos em cães com lama biliar diagnosticada por ultrassonografia. Determinou-se a prevalência e a influência das diferentes raças, sexo e idade na lama biliar, a partir de 1.021 cães submetidos à ultrassonografia abdominal, independente do estado de saúde. Desse total, foram selecionados por conveniência, 100 cães para avaliação das alterações encontradas na ultrassonografia, dos fatores de risco e dos marcadores bioquímicos perante a presença ou ausência de lama biliar. Os resultados mostraram que a prevalência de lama biliar é alta, sendo que cães com 10 anos ou mais estiveram mais predispostos. Machos e fêmeas foram acometidos em igual intensidade, havendo uma maior prevalência nas raças Beagle, Cocker Spaniel e Poodle. Nenhum dos marcadores bioquímicos estudados demonstrou correlação significativa com a lama e através da quantificação desse sedimento foi possível sugerir que o espessamento biliar raramente progride podendo acarretar complicações mais graves como a mucocele e colelitíase. Condição corporal e a castração não demonstraram relação com a presença de lama biliar e o tipo de dieta não foi considerado como o principal fator de risco, havendo apenas fraca associação da lama com o abuso da alimentação com petiscos veterinários. Já o uso de medicamentos demonstrou estar entre as possíveis causas para o desenvolvimento do espessamento biliar. Pacientes com doenças cardiovasculares encotraram-se no grupo de risco e a maior ocorrência de hepatomegalia nos cães acometidos pela lama foi associada à congestão hepática passiva, consequência das cardiopatias. Acredita-se que o fator idade também possa estar relacionado a esse fato, já que as cardiopatias são mais frequentes em cães mais velhos. / The biliary sludge in dogs is deemed to be an incidental finding, and is often identified during abdominal ultrasound as echogenic sediment of low amplitude without acoustic shadowing and gravity dependent mobility. In humans, the presence of biliary sludge is considered abnormal and it is associated with various medical conditions and complications such as gallstones, cholangitis and acute pancreatitis. In dogs their clinical importance is still unknown. The aims of this study were to estimate prevalence, evaluate risk factors, findings on ultrasound examination and biochemical markers in dogs with biliary sludge diagnosed by ultrasonography. It was determined the prevalence and influence of different breeds, gender and age in biliary sludge, from 1.021 dogs undergoing abdominal ultrasonography, regardless of their health status. Overall, it was selected for convenience, 100 dogs for evaluation of abnormalities found on ultrasound, the risk factors and biochemical markers before the presence or absence of biliary sludge. The results showed that the prevalence of biliary sludge is high, and dogs with 10 years old or more were more predisposed. Males and females were affected at the same intensity, with greater prevalence in breeds Beagle, Cocker Spaniel and Poodle. None of the biochemical markers studied showed a significant correlation with the sludge and through the quantification of sediment was possible to suggest that the thickened bile rarely progresses and may cause more serious complications such as mucocele and cholelithiasis. Body condition and castration showed no correlation with the presence of biliary sludge and the type of diet was not considered a major risk factor, with only a weak association of the sludge with the abuse with veterinarians’ snacks. But the use of medicines proved to be among the possible causes for the development of the thickened bile. Patients with cardiovascular diseases lay in the risk group and higher incidence of hepatomegaly in dogs affected by the mud was associated to passive hepatic congestion, as consequence of cardiopathies. It is believed that the age factor may also be related to this fact, since cardiopathies are more common in older dogs.

A lama biliar em cães é considerada um achado incidental, sendo frequentemente identificada durante ultrassonografias abdominais como sedimento ecogênico de baixa amplitude sem sombra acústica e com mobilidade gravidade dependente. Em humanos, a presença de lama biliar é considerada anormal e está associada a diversas situações clínicas e complicações como cálculos biliares, colangite e pancreatite aguda. Em cães sua importância clínica ainda é desconhecida. Os objetivos deste estudo foram estimar a prevalência, avaliar fatores de risco, alterações encontradas ao exame de ultrassom e marcadores bioquímicos em cães com lama biliar diagnosticada por ultrassonografia. Determinou-se a prevalência e a influência das diferentes raças, sexo e idade na lama biliar, a partir de 1.021 cães submetidos à ultrassonografia abdominal, independente do estado de saúde. Desse total, foram selecionados por conveniência, 100 cães para avaliação das alterações encontradas na ultrassonografia, dos fatores de risco e dos marcadores bioquímicos perante a presença ou ausência de lama biliar. Os resultados mostraram que a prevalência de lama biliar é alta, sendo que cães com 10 anos ou mais estiveram mais predispostos. Machos e fêmeas foram acometidos em igual intensidade, havendo uma maior prevalência nas raças Beagle, Cocker Spaniel e Poodle. Nenhum dos marcadores bioquímicos estudados demonstrou correlação significativa com a lama e através da quantificação desse sedimento foi possível sugerir que o espessamento biliar raramente progride podendo acarretar complicações mais graves como a mucocele e colelitíase. Condição corporal e a castração não demonstraram relação com a presença de lama biliar e o tipo de dieta não foi considerado como o principal fator de risco, havendo apenas fraca associação da lama com o abuso da alimentação com petiscos veterinários. Já o uso de medicamentos demonstrou estar entre as possíveis causas para o desenvolvimento do espessamento biliar. Pacientes com doenças cardiovasculares encotraram-se no grupo de risco e a maior ocorrência de hepatomegalia nos cães acometidos pela lama foi associada à congestão hepática passiva, consequência das cardiopatias. Acredita-se que o fator idade também possa estar relacionado a esse fato, já que as cardiopatias são mais frequentes em cães mais velhos. / The biliary sludge in dogs is deemed to be an incidental finding, and is often identified during abdominal ultrasound as echogenic sediment of low amplitude without acoustic shadowing and gravity dependent mobility. In humans, the presence of biliary sludge is considered abnormal and it is associated with various medical conditions and complications such as gallstones, cholangitis and acute pancreatitis. In dogs their clinical importance is still unknown. The aims of this study were to estimate prevalence, evaluate risk factors, findings on ultrasound examination and biochemical markers in dogs with biliary sludge diagnosed by ultrasonography. It was determined the prevalence and influence of different breeds, gender and age in biliary sludge, from 1.021 dogs undergoing abdominal ultrasonography, regardless of their health status. Overall, it was selected for convenience, 100 dogs for evaluation of abnormalities found on ultrasound, the risk factors and biochemical markers before the presence or absence of biliary sludge. The results showed that the prevalence of biliary sludge is high, and dogs with 10 years old or more were more predisposed. Males and females were affected at the same intensity, with greater prevalence in breeds Beagle, Cocker Spaniel and Poodle. None of the biochemical markers studied showed a significant correlation with the sludge and through the quantification of sediment was possible to suggest that the thickened bile rarely progresses and may cause more serious complications such as mucocele and cholelithiasis. Body condition and castration showed no correlation with the presence of biliary sludge and the type of diet was not considered a major risk factor, with only a weak association of the sludge with the abuse with veterinarians’ snacks. But the use of medicines proved to be among the possible causes for the development of the thickened bile. Patients with cardiovascular diseases lay in the risk group and higher incidence of hepatomegaly in dogs affected by the mud was associated to passive hepatic congestion, as consequence of cardiopathies. It is believed that the age factor may also be related to this fact, since cardiopathies are more common in older dogs.

L'objet de cette thèse est la construction d'objets géométriques sur une variété C paramétrant des courbes rationnelles dans l'espace des twisteurs d'une variété hyperkählérienne. On établira une correspondance entre la géométrie complexe de l'espace des twisteurs et des propriétés différentielles sur C (opérateurs différentiels et courbure de la structure riemanienne complexe héritée de la variété hyperkählérienne). Les premiers chapitres précisent le cadre et les résultats connus. Dans les chapitres 4, 5 et 6 on établit une équivalence de catégories entre fibrés triviaux en restriction à chaque droite de l'espace des twisteurs et les fibrés à connexion sur C satisfaisant une condition de courbure. Le chapitre 7 prolonge cette correspondance sur le plan cohomologique tandis que le chapitre 8 en fait l'étude infinitésimale en reliant la courbure de la connexion avec les épaississements infinitésimaux des fibrés le long des droites. / The purpose of this thesis is to construct geometric objects on a manifold C parametrizing rational curves in the twistor space of a hyperkähler manifold. We shall establish a correspondence between the complex geometry of the twistor space and some differential properties of C (differential operators and curvature of a complex riemannian structure inherited from the base hyperkähler manifold). The first chapters gather some classical results of the theory of hyperkähler manifolds and their twistor spaces. In the chapters 4, 5 and 6, we construct an equivalence of categories between bundles on the twistor space which are trivial on each line and bundles with a connexion of C satisfying certain curvature conditions. The chapter 7 extends this correspondence on the cohomological level whereas the chapter 8 explores its infinitesimal version ; it links curvature of the connexion with thickening (in the sense of LeBrun) of the bundle along the lines.

The loss of ecosystem resilience and rangeland (often referred to as veld in South Africa) productivity is a major problem in the semi-arid Savanna environments of southern Africa. The over-utilization of rangelands in the Molopo region of the North- West Province in South Africa has resulted in profound habitat transformations. A common regional indicator of rangeland degradation is the imbalance in the grasswoody ratio, characterized by a loss of grass cover and density with increased shrub or tree density. This can result in major reductions of rangeland productivity for the grazing animal, forcing land users to apply active or passive restoration actions to improve rangeland condition, control the thickening of woody species (bush thickening), mitigate economic losses and restoring the aesthetical value of the Savanna environment for ecotourism and game hunting aspects. This study formed part of the multinational EU-funded PRACTICE project (“Prevention and restoration actions to combat desertification: an integrated assessment”). The first aim of the study was to evaluate locally applied restoration actions using a participatory approach, followed by interviews with certain stakeholders that formed part of a multi-stakeholder platform (MSP) related to the livestock and game farming community in the Molopo. Participants of the MSP ranked indicators according to their relative importance regarding the restoration actions on an individual basis. The individual ranking results were combined with quantitative bio-physical and qualitative socio-economic measurements for each indicator in a multi-criteria decision analysis (MCDA), whereby the alternative actions were ranked according to their relevancy and performance. The results were then shared with members of the MSP in order to stimulate discussion among the members and contribute to the social learning of the project outcome. The overall positive response and acceptance of results by members of the MSP changed the perceptions and objectives of the land users regarding rangeland management. This type of participatory assessment was therefore found to be very promising in helping to identify more sustainable actions to mitigate rangeland degradation in the Molopo Savanna region. There is, however, still an urgent need to create legal policy frameworks and institution-building, to support local-level implementation in all socio-ecological and economic settings, particularly in communal areas. The second aim was to evaluate the effect of two chemical bush control actions (chemical hand- (HC) and aeroplane control (AC)) as well as rotational grazing (RGM) on the Molopo Savanna vegetation. Results show that rangeland productivity, i.e. forage production and grazing capacity, was found to be negatively related to the woody phytomass in the savanna system studied. Bush thickening influenced grass species composition which was commonly associated with a decline in the abundance of sub-climax to climax grasses, respectively. All three actions (HC, AC & RGM) significantly reduced the woody phytomass and increased forage production and grazing capacity. Although AC resulted in the highest reduction of woody phytomass, the highest forage production and grazing capacity was found under RGM. The second highest grazing capacity was found in HC sites, which was due to a high abundance of perennial, palatable climax grass species. Results from this study also show that the patterns and compositions of grass species, grass functional groups (GFGs) and woody densities indicated by RGM and chemical HC, best resemble a productive and stable savanna system that provides important key resources to support both grazing and browsing herbivores. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

För att kunna möta framtidens striktare reningskrav för avloppsvatten och en ökad belastning på grund av befolkningstillväxt bygger Stockholm Vatten och Avfall (SVOA) om Henriksdals reningsverk inom projektet Stockholms Framtida Avloppsvattenrening (SFA). En av de större förändringarna i det framtida Henriksdals reningsverk är införandet av MBR-teknik, där slam och vatten avskiljs genom membranfiltrering. Separationen medför förändrade egenskaper hos slammet då en större andel av partiklarna kan avskiljas från utgående vatten jämfört med avskiljning från konventionella sedimentationsbassänger. På Hammarby Sjöstadsverk drivs en pilotanläggning där MBR-teknik undersöks inför implementering i framtida Henriksdals reningsverk. Denna studie har undersökt skillnader i mängd partiklar, organiskt innehåll, filtrerbarhet, sedimenteringsegenskaper och förtjockningskapacitet hos överskottslam från MBR-linjen på Hammarby Sjöstadsverk (ÖS-MBR) och Henriksdals reningsverk (ÖS-CAS). Detta för att ge underlag till optimering av framtida slambehandling på Henriksdals reningsverk. Därutöver har massbalans för förtjockningsförsöken beräknats. Resultatet av studien visar att egenskaperna hos ÖS-MBR och ÖS-CAS skiljer sig tydligt för torrsubstans (TS), totalt suspenderade partiklar (TSS) och filtrerbarhet (TTF). Ingen skillnad i slamvolymindex (SVI) kunde verifieras i studien. Efter förtjockning av slammen i en trumsil, med olika polymertillsats, uppvisade ÖS-MBR högre TSS i rejektvattnet än ÖS-CAS. Denna skillnad indikerar att partiklar i ÖS-MBR har mindre benägenhet att binda till polymeren som användes, än partiklar i ÖS-CAS. Det är därför av betydelse att pröva ut rätt typ av polymer vid förtjockning av ÖS-MBR, för att nå målet på en TSS under 1000 mg/L i rejektvattnet. Därtill uppvisade ÖS-MBR högre TS i det förtjockade slammet än ÖS-CAS. Detta skulle kunna indikera att ÖS-MBR är lättare att förtjocka än ÖSCAS, men det kunde dock inte bekräftas av massbalanserna. Slutligen kunde denna studie inte samstämmigt visa på en skillnad i potentialen att förtjocka de båda slammen då fördelningen av partiklar mellan förtjockat slam och rejektvatten varierade i varje försök. Däremot minskade TSS i rejektvattnet med högre dos av polymer medan samma samband inte gällde för TS i det förtjockade slammet där dosen polymer, efter en viss mängd, hade en begränsad påverkan på TS. En viktig aspekt som påverkade förtjockningskapaciteten i denna studie var igensättning av trumsilen. Centrifuger, som kommer att användas i framtida Henriksdals reningsverk, kommer inte uppvisa samma typ av störningar i driften. / To comply with future stricter regulations on treated wastewater and an increasing load on the system due to a growing population, the Stockholm Vatten och Avfall Company (SVOA) is upgrading the Henriksdal wastewater treatment plant within the project Stockholm’s Future Wastewater Treatment (SFA). One of the main changes in the future plant is the introduction of MBR-treatment, where sludge and water will be separated through the use of membranes. This separation will change the composition of the sludge by removing a larger fraction of particles from the effluent than what can be achieved in conventional sedimentation basins. Hammarby Sjöstadsverk operates a pilot plant with a MBR-process, where the technology is evaluated before the implementation in the future Henriksdal wastewater treatment plant. This study examines the difference in the sludge characteristics, i.e. sedimentation, filterability, and the potential for thickening of excess sludge from the MBR-process in Hammarby Sjöstadsverk (ÖS-MBR) and from the activated sludge process in the current Henriksdal wastewater treatment plant (ÖS-CAS). Furthermore, a mass balance and a sensitivity analysis has been used within this study. The study aimed at providing decision support for optimisation of the sludge treatment at the future Henriksdal wastewater treatment plant once the MBR process is implemented. The results of this study show that the characteristics of ÖS-MBR and ÖS-CAS differ considerably in total solids (TS), total suspended solids (TSS) and filterability (TTF). No difference in sludge volume index (SVI) could be verified between the two types of sludges. After thickening in a rotary drum screen with different doses of polymer, the TSS in the reject water was higher for the ÖS-MBR than the ÖS-CAS. This difference indicates that particles in ÖS-MBR are less attracted to the particular thickening polymer used, than the particles in ÖS-CAS. Therefore, it is important to select the correct type of polymer when thickening ÖS-MBR in order to reach the target TSS of 1000 mg/L in the reject water. In addition, the thickened ÖS-MBR showed higher TS than ÖS-CAS. This could indicate that ÖS-MBR would be easier to thicken; however, this is not confirmed by the mass balances. In the end, this study could not conclusively show any trend in the level of thickening between the two types of sludges because the distribution of particles varied in each trial. Nevertheless, while a higher dosage of polymer evidently reduced the TSS in the reject water, the same was not true for the TS in the thickened sludge, which seems to be less affected by the dose of polymer after a certain level. An important consideration in this study was the clogging of the drum screen. However, centrifuges, which will be used in the future Henriksdal wastewater treatment plant, do not have the same operational problems.

Made available in DSpace on 2014-12-17T15:41:41Z (GMT). No. of bitstreams: 1 GuymmannCS.pdf: 1754712 bytes, checksum: 731ccc6c9bb4f783f3a118094959297b (MD5) Previous issue date: 2008-02-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Latices based on acrylic acid and ethyl methacrylate, crosslinked with 1,6‐propoxylate‐hexanodiol diacrylate were synthesized via emulsion polymerization with different monomeric compositions. The resultant latices were thickened with different NaOH/(acrylic acid) molar ratios and were characterized by titrimetry, zeta potential measurements, turbidimetry, and capillary viscometry. Intrinsic viscosity was determined for an uncrosslinked copolymer, using toluene as solvent. All the latices were coagulated with NaCl and washed with water at 60?C analyzed by FTIR spectrophotometry, in order to characterize functional groups from the copolymer and crosslinking agent. / L?tices ? base de ?cido acr?lico e metacrilato de etila, reticulados com 1,6‐diacrilato de propoxilato hexanodiol, foram sintetizados via polimeriza??o em emuls?o, com diferentes composi??es monom?ricas. Os l?tices sintetizados foram espessados com diferentes raz?es molares NaOH/(?cido acr?lico) e caracterizados por titrimetria, medidas de potencial zeta, turbidimetria e viscometria capilar. Todos os l?tices foram coagulados com NaCl, lavados com ?gua destilada e em seguida secos a 60 0C, para a an?lise de FTIR. A viscosidade intr?nseca do l?tex n?o reticulado foi determinada utilizando tolueno como solvente. O potencial zeta foi usado para determinar a carga superficial das part?culas e o FTIR para caracterizar os grupos funcionais dos comon?meros.

Made available in DSpace on 2014-12-17T15:41:43Z (GMT). No. of bitstreams: 1 ZilvanMS.pdf: 850138 bytes, checksum: 377846a49fcf47805db83b68c5e1b5f7 (MD5) Previous issue date: 2007-07-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Latexes based on acrylic acid, acrylamide, ethyl methacrylate, and ethyl acrylate were synthesized via emulsion polymerization with different monomer compositions. The resultant latices were thickened with different molar ratios of NaOH to acrylic acid and were analyzed in terms of acid‐basis titrimetry, turbidimetry, rheology, and tensiometry. Titrimetry, turbidimetry, and rheometry were used to analyze factors such as carboxyl group availability and particle solubilization, tensiometry monitoring the influence of carboxyl neutralization on polymer‐surfactant interactions. For the acrylic acid content used in this work (20 wt%), the results indicated that as carboxyl groups distribution became more homogeneous, the process of latex thickening became more effective / L?tices baseados em ?cido acr?lico, acrilamida, acrilato de etila e metacrilato de etila foram sintetizados via polimeriza??o em emuls?o com diferentes composi??es monom?ricas. Os l?tices resultantes foram espessados a diferentes raz?es molares de NaOH/?cido acr?lico. Titrimetria ?cido‐base, turbidimetria, reometria e tensiometria foram usados para analisar fatores tais como a disponibilidade de grupos carboxila e a solubiliza??o de part?culas, a tensiometria sendo usada para monitorar a influ?ncia da neutraliza??o de grupos carboxilas nas intera??es pol?mero‐surfactante. Para o teor de ?cido acr?lico usado neste trabalho (20 m/m%), os resultados indicaram que, a medida em que a distribui??o de grupos carboxilas torna‐se mais homog?nea, o processo de espessamento tornou‐se mais efetivo

Les suspensions non browniennes présentent un comportement rhéologique très différent en fonction de leur concentration. L'écoulement de suspensions semi-diluées est newtonien et montre une migration des particules provoquant des hétérogénéités de concentration. Au contraire, les suspensions concentrées présentent un large éventail de phénomènes rhéologiques non linéaire. Ce travail cherche à mieux comprendre les écoulements de suspensions dans différente gamme de concentration. A basse concentration,une étude de la migration est réalisée afin de quantifier les forces responsables de ce phénomène. Pour cela, les forces de migration sont comparées aux forces de sédimentation,grâce à un écoulement unidirectionnel et confiné. Des techniques de suivi de particules avancées et la microscopie confocale, permettent une mesure systématiquement à la fois des profils de fraction volumique et des profils de vitesse. Plusieurs systèmes sont comparés afin de mettre en évidence que les forces hydrodynamiques jouent un rôle important dans la migration. La seconde partie de ce travail consiste à caractériser l'écoulement d'un système rhéoépaississant. Des techniques de rhéologie locale, tel que la vélocimétrie ultrasonore et la tomographie RX sont utilisées dans différentes cellules de Couette. Ces techniques permettent de mesurer les profils de fraction volumique et les profils de vitesse. Nous soulevons que les propriétés rhéologiques dépendent fortement du confinement et de la rugosité, et parfois, nous avons observé instabilités dues aux interfaces. / Flows of non-Brownian suspensions are present in different fields, and exhibitdifferent behavior in function of concentration. Flows of semi-dilute suspensions aremainly governed by the spatial repartition of the particles. At low Reynolds numbers,it is indeed generally non-uniform due to cross-stream migration towards low shearedregions of the flow. In this work we aim at testing the idea that interactions betweenparticles could also be involved in the shear induced migration phenomenon. In orderto quantify the strength of shear induced migration, we take advantage of horizontalflow of buoyant particles in slits, where viscous resuspension is in competitionwith buoyancy.Using advanced particle imaging velocimetrie techniques and confocalmicroscopy, we measure systematically both volume fraction and velocity profiles.We compare two systems with and without interaction and any different was found.Concentrated suspensions exhibit a wide range of non linear rheological phenomena.This work characterizes the local rheology of a continuous shear thickening. We areused ultrasonic rheology and tomography RX in Couette cell for measured the volumefraction profile and velocity profile. We report that the rheological properties dependstrongly of the confinement and roughness, and sometimes we observed instabilitiesdue to the interface.

The loss of ecosystem resilience and rangeland (often referred to as veld in South Africa) productivity is a major problem in the semi-arid Savanna environments of southern Africa. The over-utilization of rangelands in the Molopo region of the North- West Province in South Africa has resulted in profound habitat transformations. A common regional indicator of rangeland degradation is the imbalance in the grasswoody ratio, characterized by a loss of grass cover and density with increased shrub or tree density. This can result in major reductions of rangeland productivity for the grazing animal, forcing land users to apply active or passive restoration actions to improve rangeland condition, control the thickening of woody species (bush thickening), mitigate economic losses and restoring the aesthetical value of the Savanna environment for ecotourism and game hunting aspects. This study formed part of the multinational EU-funded PRACTICE project (“Prevention and restoration actions to combat desertification: an integrated assessment”). The first aim of the study was to evaluate locally applied restoration actions using a participatory approach, followed by interviews with certain stakeholders that formed part of a multi-stakeholder platform (MSP) related to the livestock and game farming community in the Molopo. Participants of the MSP ranked indicators according to their relative importance regarding the restoration actions on an individual basis. The individual ranking results were combined with quantitative bio-physical and qualitative socio-economic measurements for each indicator in a multi-criteria decision analysis (MCDA), whereby the alternative actions were ranked according to their relevancy and performance. The results were then shared with members of the MSP in order to stimulate discussion among the members and contribute to the social learning of the project outcome. The overall positive response and acceptance of results by members of the MSP changed the perceptions and objectives of the land users regarding rangeland management. This type of participatory assessment was therefore found to be very promising in helping to identify more sustainable actions to mitigate rangeland degradation in the Molopo Savanna region. There is, however, still an urgent need to create legal policy frameworks and institution-building, to support local-level implementation in all socio-ecological and economic settings, particularly in communal areas. The second aim was to evaluate the effect of two chemical bush control actions (chemical hand- (HC) and aeroplane control (AC)) as well as rotational grazing (RGM) on the Molopo Savanna vegetation. Results show that rangeland productivity, i.e. forage production and grazing capacity, was found to be negatively related to the woody phytomass in the savanna system studied. Bush thickening influenced grass species composition which was commonly associated with a decline in the abundance of sub-climax to climax grasses, respectively. All three actions (HC, AC & RGM) significantly reduced the woody phytomass and increased forage production and grazing capacity. Although AC resulted in the highest reduction of woody phytomass, the highest forage production and grazing capacity was found under RGM. The second highest grazing capacity was found in HC sites, which was due to a high abundance of perennial, palatable climax grass species. Results from this study also show that the patterns and compositions of grass species, grass functional groups (GFGs) and woody densities indicated by RGM and chemical HC, best resemble a productive and stable savanna system that provides important key resources to support both grazing and browsing herbivores. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014