This thesis essentially reports an investigation of the behaviour of buried (0.12 to 0.25m diameter) single-walled PVC-U and vitrified clay pipes during installation in a uniform sand surround and when subjected to applied surface loading. An additional simple study of tail void displacements due to tunnelling in sand is also presented. Controlled laboratory tests were conducted in a glass-faced, steel-sided box. The buried pipes were installed perpendicular to the glass face and were subjected to static and cyclic loading, simulating increasing overburden stress and the passing of traffic over a shallow buried pipe respectively. The simulated shallow tunnel tests were also conducted perpendicular to the glass and involved withdrawal of the outer of two concentrically placed tubes. Photographs were taken of the sand particles and the buried structure in the plane of the cross section together with strain gauge readings on the pipe or tunnel wall throughout installation and loading/shield withdrawal. The resulting sand displacements are presented in the form of horizontal and vertical contour plots. Pipe deflections and volumetric and shear strain contours of the sand were also determined for the buried pipe tests. The shape of the deformed pipe and the imposed stress at the pipe springline were inferred from the pipe wall strains. During the PVC-U pipe tests, the deformation of the pipe caused the applied stress to be transferred to the sidefill via arching in the surrounding soil. This was associated with a reduction of applied stress reaching the pipe. Increasing the initial soil stiffness reduced the magnitude of the pipe and soil displacements and the stress carried by the pipe. Use of a vitrified clay pipe however, caused the soil surround to settle relative to the pipe. Soil shear strain contour plots are used to highlight the mechanisms of the transfer of applied stress onto, or away from, the buried pipes, and are related to the shape of the deformed pipe in the PVC-U pipe tests. The test data also allowed standard buried pipe design methods and installation procedures to be critically appraised. The soil movements recorded during the tunnel tests were shown to be similar to those recorded during the buried PVC-U pipe tests, indicating a similar soil loading transfer mechanism.

This thesis set out to improve our current understanding specifically of the role of permeability and carbon sources for the metabolic functioning of permeable sands.  Sampling of an intertidal sandy sediment in a shallow estuary over a 1-yr period revealed that permeability, being influenced by natural seasonal changes in biology and environmental conditions, varied temporally.  More specifically, the extracellular polymeric substances in the sediment were proven to substantially contribute to this temporal variability.  Sediment oxygen consumption also demonstrated seasonal variation and could be related to changes in temperature and total organic carbon, but, more importantly, also to permeability. Different carbon (C) sources were shown to influence the time series station but were also identified for other parts of the estuary.  A better understanding of the sedimentary C_org pool and the C_orgundergoing mineralization was furthermore obtained with the novel application of methods developed in the soil sciences comparing the δ¹³C of respired CO₂ to that of available source material and sedimentary C_org.  Overall, the results presented here demonstrate the crucial importance of permeability and carbon sources to metabolic processes and their mediation by biological factors. This thesis highlights the importance of continued research into the complexities of these permeable sands.

Machair is a habitat found predominantly in coastal areas of the north–west of Scotland and is characterised by a low-input, rotational arable system interspersed with semi-natural grasslands. Land management is an essential part of the machair system as both intensification and abandonment threaten its future. Little is known about this system in terms of its below ground communities. A survey was conducted over a three season, two year period for molecular determination of bacterial, AM fungal and nematode community structure. Cropped, fallow and undisturbed grassland were sampled; soil and roots associated with two commonly occurring species and composite soil samples were collected. In addition the effect of edaphic factors and vegetation composition on soil communities was assessed, both in the field and in greenhouse experiments. Results show that although all of the examined factors impacted the community structure of the three soil groups to some degree, the strength of this effect varied between groups. Bacterial communities were mainly affected by temporal factors, particularly year, possibly due to variation in soil moisture content. AM fungal community structure also varied considerably with season, but the mechanisms behind this were less obvious, with both abiotic and plant factors playing a role. AM fungal community structure varied with different plant hosts but also with soil moisture content. In contrast to both bacteria and AM fungi, nematode communities showed a strong response to land use although temporal factors and differences between locations were also observed. Grasslands harboured a distinctly different community structure from cropped and fallow, largely as a result of variation in bacterivores and carnivores. Vegetation composition and soil moisture content were also found to affect nematode community structure. This study has revealed that machair soil communities seem to be highly complex, dynamic and adapted to the changeable conditions that persist.

Leishmania development in their vectors is closely connected with bloodmeal digestion. This thesis focuses on factors affecting bloodmeal digestion, egg development and Leishmania infection within the sand fly gut. First, we compared the effect of mammalian (rabbit) and avian (chicken) blood on digestion and eggs development in Phlebotomus duboscqi. Sand flies fed on chickens had twice lower protein concentrations in the midgut and significantly lower trypsin activity compared to those fed on rabbits. The highest differences in the trypsin activity were observed during first 24 hours post bloodmeal. In addition, females fed on chickens had slower eggs development and their eggs were 10 % smaller compared to those fed on rabbits. In the second part of the thesis we tested the effect of mosquito hormone TMOF on the trypsin activity and eggs development of Lutzomyia longipalpis. Rabbit blood with TMOF (28 mg/ml) was presented to the females via a membrane feeding system. Sand flies fed on blood with TMOF had 15 - 35 % less trypsin activity than control females fed on only rabbit blood. In addition, females fed on blood with TMOF had developed 30 % less eggs and their eggs were 12 - 24 % smaller compared to control group. However the effect of TMOF we observed was lower than that described previously...

Doctor of Philosophy / Department of Entomology / Marcelo Ramalho-Ortigao / Kun Yan Zhu / Microbial communities residing within the midgut of insect vectors play a critical role in the response to various zoonotic and human pathogens, and can directly alter the development and survival of the insects. Sand flies are the primary vector of Leishmania, the causative pathogen of leishmaniasis, a neglected tropical disease. Sand flies acquire many microbes from the soil where immature stages develop until emergence as adults. Gram-negative Pantoea agglomerans and gram-positive Bacillus subtilis are two bacteria commonly associated with sand fly populations. Here, I demonstrated that an EGFP- and a GFP-expressing version of these two bacteria localize to different compartments of the midgut; a phenomenon that is achieved, in part, to pH differences found across the length of the gut. Additionally, P. agglomerans is able to selectively induce midgut epithelial apoptosis while B. subtilis does not. This is accompanied by differential immune and homeostasis responses to both bacteria highlighted by immune pathway suppression via the Poor Immune Response upon Knock-in (Pirk) gene. These effects may actually be representative of a broader type of response to bacterial infection that might be present across several insect species. Finally, I demonstrated that during metamorphosis the sand fly relies, at least in part, upon the activation of multiple genes from the autophagy pathway to aid in generating adult tissues. More specifically, I demonstrate, using microscopy, the presence of ATG6 in the cytoplasm of developing midgut epithelial cells of the sand fly pupae.

Folded map in pocket.

M.Sc. / The Mining of sand in South Africa is rapidly growing to sustain an increasing demand of sand for building purposes. Although mining of sand is regulated by environmental legislation, such as the National Environmental Management Act 107 of 1998, previous poor mining practices have left areas of land degraded and vulnerable to erosion. These areas need to be rehabilitated by restoring the vegetation and habitats to a natural state. This study was conducted in the Seringveld Conservancy, where the mining of sand has left the landscape with a degraded and unsightly appearance, and where little rehabilitation of the original vegetation has taken place. The aim of the study was to develop rehabilitation techniques for the degraded mined soils and to develop an overall strategy of revegetation by regenerating key plant species. Techniques for regenerating indigenous tree species cover, using modified mined sludge if topsoil is not available, were used to develop a practical and cost effective strategy to be used in revegetation. A comparative trial was used to cultivate indigenous tree species in different soil mixtures. Monitoring was done weekly to determine the growth performance and to ascertain which plant species would be most suitable and easy to cultivate. The study is important as it provides new information on the rehabilitation and revegetation of sand mined areas in the Seringveld Conservancy. This study will determine if alternatives could be used to replace topsoil on mined areas where none is available. The study is needed to determine whether revegetation of the mined areas would be possible using indigenous plant species that are often difficult to grow. The overall results indicate that replacing topsoil was successful for various modified soil mixtures that could sustain the growth of indigenous vegetation on the sand mines. Different indigenous tree species require different modified soil mixtures for successful propagation. A revegetation strategy was developed to complement and enable the rehabilitation of the mined in the Seringveld Conservancy. The revegetation initiative will benefit the restructuring of the degraded mined areas in the Seringveld Conservancy and will provide a benchmark for revegetation efforts in future in similar sand mining areas.

The interest in superhydrophobic coatings have increased exponentially in the recentdecades due to their potential and versatility in their applications. The use forsuperhydrophobic surfaces range from water repellent fabric, to self cleaning surfacesand numerous applications in industry. In this project the durability of 6 differentsuperhydrophobic coatings have been examined. The durability was tested bydropping sand on the surfaces from a set hight of 10 cm and a flow of 40 g/min. Thesurfaces were mounted on a 45° angle. The surfaces were abraded for 30 seconds ata time and the static, receding, and advancing contact angles along with the roll-ofangle was measured. Five of the surfaces were built up with nano particles and onewas sand blasted and anodized to create a superhydrophobic structure. The surfacesthat withstood the most abrasion was the surface that had been calcined to improveadhesion and the surface that had been sand blasted and anodized. Measurementsshowed that the roll-off angle and the receding contact angle were the two bestindicators of the deterioration of a surface, while the static contact angle and theadvancing contact angle varied little with abrasion. The project was done at thecompany Technical Research Institute of Sweden (SP) at their chemistry, surfaces andmaterials department in Stockholm. All coatings and equipment was supplied by SP.

Abrasive blasting process optimization is aimed at establishing relationships between applied feed rates and resulting productivity and consumption rates. It is clear that the high costs of disposal of the multimedia wastes generated by the dry abrasive blasting processes are of increasing concern in the future of shipbuilding industry. In such circumstances essential care has to be given to all components of the process to enhance productivity and decrease consumption rates. This study discusses most of the process components and their respective effects on blasting productivity and consumption rates briefly and concentrates on two important process parameters, nozzle pressure and abrasive feed rate. Feed rate is a vital process parameter that contributes to the productivity and consumption rates of the process. Subsequently feed rates also can significantly impact the costs bore by Shipbuilding Industry in the form of disposal and environmental costs. Most commonly used abrasives were identified through a rigorous survey and were opted to be used in this study. The approach adopted to develop the relationships consists of a mass balance equation between the expended abrasives and disposed wastes to clean a predetermined area of a plate. The obtained data was further analysed to develop productivity rates and consumption rates for each sample runs. The data was then evaluated to formulate relationships that would enable the derivation of optimum feed rates for desirable productivity and reduced waste generation.

Sand ramps have been (and still are) neglected in geomorphological research. Only recently any awareness of their potential of being a major source of palaeoenvironmental information, thanks to their multi-process character, has been developed. In Namibia, sand ramps were terra incognita. This study defines, classifies and systematizes sand ramps, investigates the formative processes and examines their palaeoenvironmental significance. The study region is located between the coastal Namib desert and the Great Escarpment, between the Tiras Mountains to the north and the Aus area to the south. Two lines of work were followed: geomorphological and sedimentological investigations in the field, assisted by interpretation of satellite images, aerial photographs and topographic maps, and palaeopedological and sedimentological analytical work in the laboratory. Two generations of sand ramps could be identified. The older generation, represented by a single sand ramp within the study region, is characterized by the presence of old basal sediments. The bulk of the sand ramps is assigned to the young generation, which is divided into three morpho-types: in windward positions voluminous ramps are found, in leeward positions low-volume ramps exist, either of very high or very low slope angle. The most distinct characteristic of sand ramp sediments is their formation by interacting aeolian deposition and fluvial slope wash. The last period of deposition, which shaped all the entire young sand ramps, but also the upper part of the old ramp, is suggested to have occurred after c. 40 ka BP, implying a highly dynamic climatic system during that time, with seasonal aridity and low-frequency, but high-intensity rainfall. A phase of environmental stability followed, most likely around 25 ka BP, supporting growth of vegetation, stabilization and consolidation of the sediments as well as soil formation. Subsequently, the profile was truncated and a desert pavement formed, under climatic conditions comparable to those of the present semi-desert. The ramps were then largely cut off from the bedrock slopes, implying a change towards higher ecosystem variability. As the final major process, recent and modern aeolian sands accumulated on the upper ramp slopes. A luminescence date for the recent sand places their deposition at about 16 ka BP, close to the Last Glacial Maximum. Regarding the source of the sands, a local origin is proposed. For the sand ramp of the old generation the "basic cycle" of initial deposition, stabilization and denudation occurred twelve times, including a phase of calcrete and/or root-cast formation in each of them, adding up to around 60 changes in morphodynamics altogether. At least nine of these cycles took place between 105 ka BP and the LGM, indicating that the general cooling trend during the Late Pleistocene was subject to a high number of oscillations of the environmental conditions not identified before for southern Namibia. Due to the high resolution obtained by the study of sand ramp sediments, but also due to the very special situation of the study area in a desert margin, 100 km from the South Atlantic and in the transition zone between summer and winter rainfall, correlation with stratigraphies (of mostly lower resolution) established for different regions in southern Africa did not appear promising. In conclusion, sand ramps generally serve as a valuable tool for detailed deciphering of past morphodynamics and thereby palaeoenvironmental conditions. For south-west Namibia, sand ramps shed some more light on the Late Quaternary landscape evolution. / In der geomorphologischen Forschung haben Sandrampen bislang wenig Beachtung gefunden, erst in jüngster Zeit ist auf ihr Potential als Speicher von Paläoumweltbedingungen hingewiesen worden. In Namibia waren Sandrampen terra incognita. Die vorliegende Studie definiert, klassifiziert und systematisiert Sandrampen in Südwest-Namibia, sie entschlüsselt ihre Bildungsprozesse und untersucht ihre paläoklimatische Bedeutung. Das Arbeitsgebiet liegt zwischen der küstenparallelen Namib und der Großen Randstufe, zwischen den Tirasbergen im Norden und der Gegend um Aus im Süden. Methodisch standen geomorphologische und sedimentologische Untersuchungen im Gelände im Vordergrund, unterstützt durch die Interpretation von Satellitenbildern, Luftbildern und topographischen Karten. Zahlreiche Substratproben wurden im Labor paläopedologisch und sedimentologisch analysiert. Es konnten zwei Sandrampen-Generationen identifiziert werden. Die ältere Generation, im Arbeitsgebiet durch nur eine Rampe vertreten, zeichnet sich durch das Vorkommen alter basaler Sedimente aus. Alle anderen Rampen sind der jüngeren Generation zuzuordnen und lassen sich in drei Morpho-Typen unterteilen: In Luv-Positionen finden sich voluminöse Rampen, während im Lee geringmächtige Rampen von entweder extrem steiler oder sehr geringer Hangneigung ausgebildet sind. Das auffälligste Merkmal der Sandrampen ist ihre Bildung durch die Interaktion von äolischer Deposition und Hangspülung. Die letzte Depositionsphase, in der die gesamten Körper der jungen Sandrampen abgelagert und die basalen Sedimente der alten Generation überlagert wurden, hat vermutlich nach 40 ka BP stattgefunden. Dies impliziert ein hochdynamisches klimatisches System zu dieser Zeit, mit saisonaler Aridität und seltenen, aber intensiven Regenfällen. Es folgte eine Phase der Ökosystemstabilität, vermutlich um 25 ka BP, in der es zu Vegetationsentwicklung und Bodenbildung sowie zu Stabilisierung und Konsolidierung der Sedimente kam. Eine anschließende Profilkappung mit Wüstenpflasterbildung geschah dann unter ähnlichen klimatischen Bedingungen wie in der heutigen Halbwüste. Danach wurden die Sandrampen fast überall von den Hängen abgeschnitten, was einer Änderung zu höherer Variabilität im Ökosystem zuzusprechen wäre. Die jüngste wesentliche Überprägung bestand in der Ablagerung subrezenter und moderner äolischer Sande in den obersten Bereichen der Sandrampen. Lumineszenzdatierungen stellen die subrezenten Sande ins letzte Hochglazial (~ 16 ka BP). Dem Sandrampensand wird eine lokale Herkunft zugesprochen. Für die Sandrampe der älteren Generation wiederholte sich der Zyklus von Deposition, Stabilisierung und Denudation insgesamt zwölfmal, inklusive je einer Phase von Kalkkrusten- und/oder Wurzelpseudomorphosenbildung. Insgesamt sind rund 60 Prozesswechsel dokumentiert. Mindestens neun dieser Zyklen verliefen zwischen 105 ka BP und dem letzten Hochglazial. Der generelle Abkühlungstrend während des Spätpleistozäns war also einer bedeutenden Anzahl von Schwankungen unterworfen, die bislang für Südnamibia nicht bekannt waren. Aufgrund der hohen zeitlichen Auflösung, die sich aus den Sandrampensedimenten erschließt, aber auch durch die besondere Lage des Arbeitsgebietes in einer Wüstenrandregion, 100 km vom Südatlantik entfernt und in der Übergangszone von Sommer- und Winterniederschlag, wurden Korrelationen mit Stratigraphien (von meist geringerer Auflösung), die für andere Regionen im südlichen Afrika aufgestellt worden sind, als wenig sinnvoll erachtet. Die vorliegende Arbeit zeigt, dass sich Sandrampen generell sehr gut zur Entschlüsselung paläomorphodynamischer Prozesse eignen und damit wesentlich zur Rekonstruktion von Paläoumweltbedingungen beitragen. Für Südwest-Namibia liefern Sandrampen neue, detaillierte Informationen zur spätquartären Landschaftsgeschichte.