ABSTRACT Significant effort has been put into the development of cost-effective abalone (Haliotis midae; Gastropoda) cultivation systems in South Africa, but the limited availability of suitable seaweed for abalone food is an obstacle to future development. The aim of this study was to investigate whether a land-based recirculating seaweed-abalone integrated aquaculture system using Ulva lactuca was feasible as well as to test the differences between a commercial gravel bed recirculation syst...
ABSTRACT A new liquid scintillation counting technique to resolve mixtures of two pure beta-emitting radionuclides Winifred Margaret van Wyngaardt Submitted November 2007 Methods currently available for the accurate activity resolution of dual-label solutions of pure β-emitting radionuclides are mostly time consuming and involve much effort. The goal of this thesis was therefore to devise a simpler method to achieve the same objective. The technique developed is based on elements of two liqu...
ABSTRACT Survival analysis is a method for analysing the occurrence of a given event. This research seeks to evaluate the survival of HIVIAIDS, TB and co-infected patients and to identify the major prognostic factors that influence their survival. In this study, survival data for HIV/AIDS, TB and HIVITB co infection patients were obtained from St. Mathias Hospital in Yeji, Pru District of Brong Ahafo Region of Ghana. The data was fitted using both the Cox model and accelerated failure time mo...
Toxicity of ammonia, which can reach toxic levels in aquaculture systems, was investigated for Haliotis midae. Toxic FAN (free un-ionized ammonia) was estimated from TAN (total ammonia nitrogen) measurements. It was found that commonly used Nesslers and Palintest methods underestimated TAN. Tolerance of H midae to ammonia increased with increasing size, as indicated by 36 h LC50 values; farmed juvenile abalone (1 - 2.5 cm shell length) had the smallest LC50 of 9.8 f,lg rl FAN, whereas LC50 wa...
ABSTRACT This thesis addresses the recruitment patterns of barnacles and mussels at a range of spatial and temporal scales and attempts to relate them to larval and adult abundance, as well as to local productivity and oceanographic conditions that would influence larval transport and the connectivity of adult populations. In Chapter 1, I investigated the spatial and temporal patterns of mussel recruitment and adult bed dynamics offour mussel species (Aulacomya ater, Mytilus galloprovincialis...
Abstract The marine bacterium Vibrio cholerae produces pyomelanin through the catabolism of L-tyrosine to homogentisic acid. Various types of melanins are used by microbes as defense mechanisms against a variety of environmental stresses. This thesis investigated the defensive role of V. cholerae pyomelanin against exogenous stresses, particularly hydrogen-peroxide (HzOz). A V. cholerae 569B melanin-deficient mutant was created by insertional inactivation of ppdA, which encodes for p-hydroxyp...
ABSTRACT This thesis explores the relationships between commercial data and those obtained from research surveys in an attempt to broaden the database available for management, and to cover seasonal and inter-annual changes in density estimates of Cape hake (Merluccius capensis). It also attempts to explain hake variability of in terms of environmental indices based on satellite remote sensing, carefully chosen to reflect underlying oceanographic processes. The influence of various factors on...
Abstract Fires are often used as a management tool in both game reserves and rangelands to manipulate food availability for grazing animals. After fires, large areas of the landscape are quickly covered with nutritious new regrowth, which grazers move into and utilise as a food resource. The effect of this change in animal grazing patterns on the grass communities is not yet well understood. Certain grass communities depend on heavy, continuous grazing for their persistence: they are out-comp...
ABSTRACT Unsteady heat and mass transfers are important transport phenomena that are found in many engineering and industrial applications. In such systems, the variations in the fluid flow result in variations in the heat flux for fluid-solid temperature difference. In this study, analytical and theoretical investigations of some non-linear problems arising from unsteady heat and mass transfer through porous media are considered. Analytical models are developed. These are non-linear mathem...
The primary focus of this thesis was to investigate the movement patterns of the South African West Coast rock lobster, Jasus lalandii, using a diverse range of techniques. These were (1) an examination of long-term data from an ongoing tag-recapture program, (2) observations on rock lobsters in a mesocosm aquarium, (3) surveys that monitored the seasonal fluxes in activities and abundance of rock lobsters in the field, (4) video recordings of movement behaviour in small aquaria and (5) acous...
ABSTRACT This thesis is divided into 2 parts. The first part (Chapters 1-5) concentrates on unravelling the . Precambrian geological history of the high-grade poly-metamorphic and poly-deformed basement of southernmost India, using field geology and U-Pb geochronology. Because Peninsular India occupied a central position in Gondwana, this work bears on reconstruction models of central Gondwana between circa 600 Ma and 200 :f,a. The second part of the thesis (Chapter 6) tests the use of organ...
ABSTRACT The synthesis, characterization, spectroscopic and biological evaluation of 2-benzoylpyridine-s-methyldithiocarbazate (HL1 ) and di-2-pyradylketone-s-methyldithiocarbazate (HL2 ) with selected metal ions of copper (II), zinc (II), cadmium (II), nickel (II), iron (II) and cobalt (II). The ligands, HL1 and HL2 were synthesized by an acid catalyzed condensation reaction of s-methyldithiocarbazate with 2-benzoylpyradine and di-2-pyradylketone respectively. The reaction of metal salts wi...
ABSTRA.CT The studies in this thesis recognise the key role of fire as a factor which has shaped the life-histories of plants in fire-prone mediterranean shrublands. Fire regimes are not simply products of the abiotic elements of climate and ignition sources. The biotic component makes a significant contribution because community structure and processes like litter fall determine fuel loads, and fuel distribution, and will determine properties such as fire recurrence intervals and shapes and ...
Abstract By utilizing some basic analytical techniques, the authors establish some new Gamma function inequalities occurring in the study of Probability Theory.
ABSTRACT BACKGROUND: Developing countries including Namibia are experiencing a rapid increase in non-communicable diseases. Blood pressure is estimated to instigate round about 60 percent of deaths around the world, of which 80 percent occur in developing countries.