A study of the structural geology of the Witteberg Group and lowermost Karoo Supergroup, Darlington Dam, Jansenville District, Eastern Cape
- Authors: Goossens, Angelique Emily Maria
- Date: 2003
- Subjects: Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11071 , http://hdl.handle.net/10948/291 , Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Description: A number of outcrops of the Witteberg Group and lowermost Karoo Supergroup rocks were studied in the area south of the Darlington Dam, Jansenville District, with the aim of documenting structural characteristics of the area. All lithologies are folded with fold styles varying from gentle to near isoclinal (based on interlimb angle). Fold axes are either sub-horizontal or plunging at gentle to moderate angles whereas axial planes dip gently to vertically (predominantly steep to sub-vertical). Folds verge predominantly towards the north but where southward verging they are associated with faulting or strongly folded areas. Folds plunge gently to the east-southeast and west-northwest. The area consists of a large anticlinorium with both first and second order folds occurring. Eastwest striking faults occur in the study area and are classified as normal, reverse and thrust faults. A study of the joint sets shows that there are four dominant joint directions, namely 18o, 33o, 97o and 107o (in order from least to most important). An interpretation of the tectonic history is presented in which the relationships between faults and folds show that faults formed during and after folding. Folding, and reverse and thrust faulting, occurred during the compressional events that formed the Cape Fold Belt, whereas the normal faults formed during the relaxation of these compressional forces or during the break-up of Gondwana.
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- Date Issued: 2003
An assessment of bait availability, utilization and management guidelines in Eastern Cape estuaries
- Authors: Jooste, Jakobus Gerrit
- Date: 2003
- Subjects: Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11073 , http://hdl.handle.net/10948/334 , Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Description: Aspects around the management of benthic soft sediment bait organisms, with special focus on the mud prawn (Upogebia africana) of eastern Cape estuaries was investigated. The recreational linefishery of the Gamtoos estuary was described, and compared to previous studies. Target fish species was identified, and a large dependency on bait sourced from estuaries needed for the capture of these species was noted, especially for spotted grunter (Pomadasys commersonnii). A comparison between bait use, success and the natural diet of target fish species was also made. The structure and distribution of sediments in the old channel mud banks was described and compared with historical data. The influence of sediments on mud prawn distribution was investigated, but no significant interactions were found at the study site. The impacts of once-off pumping and digging events, and monthly trampling on the sediments and mud prawn population was studied over a 7-month period. Initial removal rates as well as recovery time varied significantly between the two collection methods, while the largest decline in prawn numbers (to zero) with no recovery visible after seven months was caused by trampling. All disturbances caused some alteration in sediment composition, but not to such an extent that the sediments became unfavorable for mud prawns. Trampling did, however, result in the compaction of sediments to such a degree that prawns could not construct burrows. Issues around current removal quotas of bait species as well as the creation of a small-scale commercial (SSC) bait selling operation at Swartkops estuary were critically evaluated, and suggestions for the future removal rates of mud prawns based on production export calculations were made. The distribution, size, sex ratios and number of gravid females occurring along a tidal gradient as well as along horizontal gradient of the mud bank during growth (January – March) and reproductive (September – October) periods was investigated. Changes in the distribution of females between the two study periods were significant, while the distribution of reproductively active females were closely linked to the low water mark (Lower tidal levels). Females occurring in this zone were also significantly larger than females occurring towards the back of the study site. Some minor changes along the horizontal gradient were also observed. The sediment compos ition of the mud bank was found not to play a role in this distribution, leading to the suggestion that exposure to ebb and flood tide currents could influence female prawn distributions. Management recommendations based on these observations were made.
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- Date Issued: 2003
An evaluation of the Xenopus laevis liver slice model to study the toxic effects of microcystin
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
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- Date Issued: 2003
An investigation into the induction of oxidative stress and apoptosis by microcystin-LR in the CaCo2 cell line and intestinal tract of Balb/c mice
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
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- Date Issued: 2003
An investigation into the occurrence of major abscess causing bacteria at the law meat exporting abattoir in the Northern Cape province of South Africa
- Authors: Delport, Riëtte
- Date: 2003
- Subjects: Abscess , Meat -- Microbiology , Slaughtering and slaughter-houses -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10971 , http://hdl.handle.net/10948/249 , Abscess , Meat -- Microbiology , Slaughtering and slaughter-houses -- South Africa -- Northern Cape
- Description: The main objectives of this study can be divided into four categories: a) The determination of the presence of abscesses in carcasses. b) The determination whether the abscesses are area bound. c) The determination of the causative bacteria which is responsible for abscess formation. d) The determination of the economic impact due to carcass rejections and trimmings. The research area consists of the biggest part of the Northern Cape province, which can further be divided into three main production areas, namely Groblershoop, Gordonia and Hantam. The Groblershoop area includes Groblershoop and the surrounding districts. The Gordonia area includes Upington and the Kalahari. The Hantam area includes Calvinia, Springbok and the other districts bordering the areas. All the carcasses were slaughtered at an export abattoir, namely LAW, which is situated in Groblershoop. The Upington veterinary laboratory bacteriologically cultured the abscess material and the results were processed and noted. The following results were prominent: a) It was determined that abscesses did occur in carcasses. b) It was determined that in the Hantam main production area the prevalence of abscesses is the highest, although the slaughter numbers are the lowest. c) It was determined that the bacterium that was responsible for most of the abscesses was Escherichia coli. d) It was determined that the total occurrence of bacteria did not have a significant economic impact, because there were not many carcass rejections due to abscesses. The economic impact, however, of the value of the total rejections, might become a problem.
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- Date Issued: 2003
Aplousobranch ascidians (Tunicata: Ascidiacea) from Southern Africa
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
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- Date Issued: 2003
Effect of photoperiod on sexual development, growth and production of quail (coturnix coturnix japonica)
- Authors: De Jager, Pieter Herodes
- Date: 2003
- Subjects: Quails , Quails -- Growth , Quails -- Effect of light on , Photoperiodism
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10969 , http://hdl.handle.net/10948/227 , Quails , Quails -- Growth , Quails -- Effect of light on , Photoperiodism
- Description: The aim of the study was to determine the effect of photoperiod on production of quail in South Africa. Day old chicks were randomly divided into two groups. One group (n=74) received continuous light (LL) while the other group (n=77) received 13 h of light (LD) per day. Traits measured were sexual characteristics (age at sexual maturity and testis weight, egg production and egg weight) and growth (body weight) development in males and females respectively. Significant differences in growth existed between sexes; females were 171.44±17.15 and 182.91±17.75 g compared to the 151.77±13.20 and 155.00±16.86 g for males in both LL and LD groups respectively. Both males and females in the LL group initially outperformed the LD group in growth rate but, by day 72 the LD group had compensated and were 4.6% heavier than the LL group. A similar trend was observed for sexual maturity between the LL and LD groups. However, photoperiod did significantly influence initial egg production in favour of the LL group. The LL group had 80% of the females in production by day 44 compared to the 60% of the LD group. The initial egg weight of the LL group was 14 % higher than those of the LD group. Quail subjected to continuous light attained earlier sexual maturity and production with lower final weight compared to quail subjected to an intermediate photoperiod. The application of a longer photoperiod would therefore favour an egg production system.
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- Date Issued: 2003
Evaluation of the large-scale trapping of blowflies (Lucilia spp.) for an integrated pest management program : the lucitrap
- Authors: Scholtz, Anna J
- Date: 2003
- Subjects: Blowflies -- Control , Insect trapping , Insect traps , Pests -- Control
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10972 , http://hdl.handle.net/10948/126 , Blowflies -- Control , Insect trapping , Insect traps , Pests -- Control
- Description: The results presented in this dissertation have been partially presented at scientific meetings. Chapter 2 is an exact copy of the technical contents of a paper submitted to a scientific journal. The format of this paper however has been changed to comply with the format used in this dissertation. The results of this paper were partially presented at the 36th National Congress of the South African Society of Animal Science, 5 – 8 April 1998 held in Stellenbosch. In this chapter errors occurred in the execution of the trial, but these were corrected in the follow-up trial after consulting with the manufacturers. It is discussed in the paper. Results of chapter 3 were partially presented at the 5th International Sheep Veterinary Congress 21 – 25 January 2001 held in Stellenbosch and at an International Congress (The FLICS (Flystrike & Lice IPM Control Strategies) Conference, 25 – 27 June 2001, Launceston) in Tasmania by Mr. S.W.P. Cloete in 2001. The updated results are given in this chapter. The results of chapter 4 were presented at a combined congress between the Grasslands and the Animal Production Societies of South Africa (The GSSA/SASAS Joint Congress 2002. 13 – 16 May) in Christiana in 2002. The results in this chapter represent the same experimental period as was reported upon at that congress, but additional statistical analyses were executed on the same data set. Copies of the abstracts of the contributions to these meetings are attached in chapter 6. The major objective of this study initially was to evaluate the Lucitrap® system under South African conditions. During the experimental period I had an opportunity to visit Australia and meet many role players. It came under my attention that the control of the blowfly is a rather complex problem with many facets. A current issue worldwide on the use of chemicals as a control method against insects and its hazardous influence on the environment is forcing producers to minimize chemical residues in textiles and other agricultural products. An Integrated Pest Management (IPM) approach seems to be the only option. This study has been executed to try and understand some aspects of the blowfly problem for future application in such a blowfly control program.
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- Date Issued: 2003
Investigations into the asymmetric reduction of ketones
- Authors: Bena, Luvuyo Clifford
- Date: 2003
- Subjects: Ketones , Asymmetric synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11065 , http://hdl.handle.net/10948/323 , Ketones , Asymmetric synthesis
- Description: A six-step synthesis of salbutamol from methyl salicylate with an overall yield of 17% has been completed, although the yield was not optimised. In the process, Zn(BH4)2 was found to selectively reduce a ketone carbonyl group in the presence of an ester unit. In contrast, borane was found to reduce both the ketone and ester carbonyl groups. Reduction of phenacyl bromide with borane in the presence of chiral catalysts based on (R)-alaninol and (R,S)-ephidrine resulted a measure of enantioselectivity in the product. However, the configuration of the alcohol obtained in the case of (R)-alaninol was contrary to expectations based both on experimental trends observed elsewhere as well as our own theoretical predictions. The asymmetric reduction of methyl 5-bromoacetyl-2-benzyloxybenzoate was accomplished with both borane and Zn(BH4)2 in the presence of a range of chiral catalysts. Optically active products were obtained in all cases, although the optical rotations were significantly smaller in the case of Zn(BH4)2. Unfortunately, we were not successful in determining the enantiomeric excesses of these reactions. The use of a NMR lanthanide shift reagent resulted in a complex spectrum that was impossible to interpret unambiguously. This presumably arises from the presence of several Lewis base sites in the product at which complexation with the shift reagent can take place. It was also not possible to determine the optical rotation of salbutamol itself owing to the relatively small amount of material obtained. A conformational analysis of salbutamol, where NMR data was correlated with molecular modelling results, was successfully carried out and revealed a strong preference for that conformer family characterised by O–C–C–N and Ar–C–C–N torsion angles of ca. 60º and 180º, respectively. Interestingly, these conformers are found to be stabilised by OH…N rather than NH…O hydrogen bonding. This study has also confirmed the effectiveness of the MMFF94 force field for conformational analysis studies in compounds of this kind. Lastly, a relatively simple method for modelling the BH3/oxazaborolidine reduction of ketones at the PM3 semiempirical MO level of approximation was devised. This approach has provided insights into the mechanism of the reaction and has furthermore enabled us to predict the enantioselectivities likely to result from various catalysts and ketones. In comparing our theoretical and experimental findings, an anomalous result was observed in the case of (R)-alaninol; this will have to be investigated further, particularly at the experimental level. However, we believe that our approach provides a sound basis for aiding the design and screening of new, potentially better catalysts.
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- Date Issued: 2003
Observed metabolic changes in male Wistar rats after treatment with an antidepressant implied in undesirable weight gain, or Sutherlandia frutescens for Type II diabetes
- Authors: Chadwick, Wayne
- Date: 2003
- Subjects: Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11068 , http://hdl.handle.net/10948/313 , Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Description: Type II diabetes is fast becoming a growing problem in developed countries worldwide. Traditionally the median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve has shifted to the left. Western countries boast the worst statistics in which type II diabetes is being reported in children under the age of ten. At such a young age the disease often goes undiagnosed for long periods of time allowing considerable damage to occur. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with a characteristically unhealthy western diet. Type II diabetes is an extremely expensive disease to manage, and with the rapid growth of this pandemic our country will soon feel the economic burden of this disease. It is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight or appetite thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of the S. frutescens, metformin (a well known type II diabetes medication) and amitriptyline (a common tricyclic antidepressant) was administered to three groups of ten male Wistar rats. The control group received water without any medication. The rat’s weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after four months of medicinal compliance and glucose uptake, in the presence and absence of insulin, was tested in epididymal fat, liver and muscle. Fasting plasma glucose levels, lipoprotein, cholesterol and triglyceride concentrations were also determined.
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- Date Issued: 2003
Sandy beach morphodynamics and macrobenthic communities in temperate, subtropical and tropical regions : a macroecological approach
- Authors: Soares, Alexandre Goulart
- Date: 2003
- Subjects: Seashore ecology , Intertidal ecology , Benthos
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11077 , http://hdl.handle.net/10948/293 , Seashore ecology , Intertidal ecology , Benthos
- Description: A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.
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- Date Issued: 2003
The effect of human soluble FceRII on the RPMI 8866 B-Lymphoblastoid and the U937 Monocyte cell lines
- Authors: Daniels, Brodie Belinda
- Date: 2003
- Subjects: Developmental inmmunology , Cellular control mechanisms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11084 , http://hdl.handle.net/10948/322 , Developmental inmmunology , Cellular control mechanisms
- Description: Due to the diverse functions of Fc eRII, such as its roles in cellular adhesion, growth and differentiation of B and T lymphocytes, rescue of B cells from apoptosis and release of cytotoxic mediators, it is clear why it is believed to be a central molecule in allergic response. Because of its important role in the regulation of IgE production, FceRII may be the primary cause of certain allergic conditions. This study attempted to express and purify a recombinant human soluble FceRII to test its effect on a B-lymphoblastoid (RPMI 8866) and a monocytic (U937) cell line. The protein was expressed in Escherichia coli inclusion bodies, before being refolded and purified in a single gel chromatography step. This pure protein was then tested for biological activity by testing its IgE binding func tion. Once proven functional, it was used to test its effect on the cell lines at three concentrations for its apoptotic rescue properties and its cytokine effects. The recombinant protein did not seem to have any significant effect on the apoptotic rescue of either cell line. While the recombinant sFceRII appeared to have a slight effect on the stimulation of IL-1ß and TNFa in the RPMI 8866 cells, there was no apparent effect on the production of NF?B. In U937 cells, the protein did not seem to have any effect on the stimulation of IL-1ß, TNFa or NF?B. However, the cytokine effects of the recombinant protein were tested on isolated PBMCs from a healthy individual and a hyper-IgE syndrome patient. The recombinant protein was able to stimulate the production of cytokines in both individuals’ PBMCs, proving that it has the same effect as the natural protein. The upregulation of these cytokines indicates that the recombinant protein is able to stimulate the immune system. Therefore, this recombinant soluble FceRII protein could possibly be used for immune therapy.
- Full Text:
- Date Issued: 2003
The effects of goat browsing on ecosystem patterns and processes in succulent thicket, South Africa
- Authors: Lechmere-Oertel, Richard Geoffrey
- Date: 2003
- Subjects: Succulent plants -- South Africa -- Eastern Cape , Landscape ecology -- South Africa -- Eastern Cape , Goats -- Feeding and feeds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11074 , http://hdl.handle.net/10948/309 , Succulent plants -- South Africa -- Eastern Cape , Landscape ecology -- South Africa -- Eastern Cape , Goats -- Feeding and feeds
- Description: Transformation in the arid succulent thicket of the Eastern Cape of South Africa in response to unsustainable livestock production has been widespread, with less than 10 percent remaining intact. Transformation in succulent thicket has resulted in large areas of dense thicket (comprising a two-phase mosaic of perennial-vegetated patches separated by animal paths and bare patches) being replaced with a ‘pseudo-savanna’ of remnant canopy trees with a structurally simple field layer of ephemeral and short- lived perennial grasses and forbs. There is an extensive literature describing the transformation of succulent thicket, with many speculative statements about the underlying mechanisms of transformation. The central focus of this study was to improve our mechanistic understanding of transformation in succulent thicket using field experiments. Hopefully these results will set another foundation upon which future management of succulent thicket can be improved and large-scale restoration initiated. This study comprises four themes that are linked to the concept of landscape function. The central premise of landscape function is that functional landscapes have mechanisms that capture and retain scarce resources. Conversely, as landscapes become increasingly dysfunctional, so these mechanisms become disrupted. In succulent thicket, dysfunctio n appears to be linked to the reduced ability to harvest water, cycle carbon and a loss of organic carbon. In this thesis I examined some of the key processes that influence water and organic carbon fluxes: perennial vegetation cover, soil fertility, litter fall and decomposition, and runoff and soil erosion. The experimental design that was used for all this work was a factorial ANOVA based on replicated fenceline contrasts that reflect differences in long-term management history. The main objectives of this thesis were to: quantify the patterns of transformation in an arid form of succulent thicket, including changes in the biomass, cover and structure of the dominant vegetation guilds; test the stability of the transformed succulent thicket ecosystem to show whether it is a new stable state or an intermediate stage in a trajectory towards a highly desertified state where only the ephemeral grasses and forbs persist; describe and compare soil fertility across transformation contrasts, concentrating on changes in the spatial patterns of soil resources and the ability of the soil to harvest precipitation; to compare litter fall and decomposition of leaf material from the dominant plants in intact and transformed succulent thicket; to quantify and compare run-off and erosion from run-off plots in intact and transformed succulent thicket. Transformation and stability I quantified the changes in plant diversity, physiognomy and biomass that occur across transformation contrasts. Thicket transformation results in a significant loss of plant diversity and functional types. There is also a significant reduction in the biomass (c. 80 t.ha-1) and structural complexity of the vegetation, both vertically and horizontally. These results were interpreted in terms of their implications for ecosystem functioning and stability. To test the stability of the transformed succulent thicket I used aerial photographs and ground-truthing to track the survivorship of canopy trees over 60 years in pseudo-savanna landscapes. I also measured seedling establishment in different habitats. I show that the pseudo-savanna is not a stable state owing to ongoing adult mortality and no recruitment of canopy trees. Soil fertility and water status I hypothesised that the above-ground changes in ve getation would be accompanied by similar trends in the pattern and levels of soil nutrient resources and the ability of the landscape to harvest precipitation. I compared soil fertility (organic carbon, available nitrogen and phosphorus), texture, matric potential, and surface micro-topography in the two main micro- habitats on either side of the replicated fenceline contrasts. The results show that intact spekboom thicket has a distinct spatial pattern of soil fertility where nutrients and organic carbon are concentrated under the patches of perennial shrubs, compared to under canopy trees and open spaces. Transformation results in a significant homogenisation out of this pattern and an overall reduction in the fertility of the landscape. The proportion of the landscape surface that would promote infiltration of water decreases from 60 – 0.6 percent. Soil moisture retention (matric potential) also decreases with transformation. I interpreted these patterns in terms of the ability of the landscape to harvest and release water after rainfall events. Litter fall and decomposition Surface litter and soil organic matter are critical components to wooded ecosystems; contributing to several ecosystem functions. The rates of litter fall and decomposition are ratelimiting steps in nutrient cycling and incorporation of organic matter into the soil. The ecological mechanisms behind the collapse of succulent thicket in the face of domestic herbivory are not fully understood, but are believed to include the breakdown of several ecosystem processes, including litter fall and decomposition. I quantified the changes in litter fall and litter decomposition of four of the dominant perennial woody plants (Euclea undulata, Pappea capensis, Portulacaria afra and Rhus longispina) across the replicated fenceline. Litter fall was measured over 14 months using mesh traps. Decomposition was measured over 15 months using a combination of litterbags and unprotected leaf packs. I also quantified soil microclimate during the experimental period; hypothesising that transformation would lead to soil conditions less amenable for biotic activity. Litter fall in succulent thicket was very high for a semi-arid system, comparing more to temperate forests. The leaf-succulent P. afra contributed the largest single component of the total litter production at a landscape scale. The effect of transformation on litter fall was species specific. Deep-rooted or drought-adapted species showed no change in litter yield with transformation; shallow-rooted species showed a significant decrease. There were few significant differences in decomposition rates across the transformation gradient and between litter types. Portulacaria afra litter had the steepest rate of mass loss, and was most affected by transformation. The more recalcitrant (high C:N ratio) leaves of P. capensis remained largely unaffected by transformation. These results indicate the critical role of the perennial vegetation in incorporating organic carbon into the soil. Transformation of succulent thicket leads to a disruption of the flow of carbon into the soil, reinforcing the cycle of transformation through reduced fertility. Rehabilitation of this ecosystem will require the active establishment of species, such as P. afra, that will restart the flow of carbon into the soil. Run-off & Erosion The landscape function model predicts that functional semi-arid shrublands efficiently conserve limiting resources such as water and water-bourn sediments (soil and organic matter). As these rangelands become transformed through unsustainable livestock production, so their ability to conserve resources decreases. The primary determinant of landscape function and conservation of resources appears to be the proportional cover of perennial vegetation. I hypothesised that the switch from a two-phase mosaic dominated by perennial succulent and woody shrubs to a single phase system dominated by an ephemeral field layer would be accompanied by disruption of the mechanisms that conserve resources. Specifically, I tested the hypothesis that transformation of succulent thicket increases runoff volume, sediment concentration of runoff, soil erosion and loss of organic matter at a patch scale (c. 100 m2). Runoff and water-borne sediment were measured from runoff plots established across replicated fenceline contrasts. Data were collected from eight extreme weather events over two years. There were no significant differences between runoff and erosion across the transformation contrast, as each extreme weather event was unique in terms of its runoff response. The transformed runoff plots alone also gave inconsistent results, largely due to differences in the cover of ephemeral forbs and weakly perennial grasses. Runoff and erosion were not predictable from the data across the transformation gradient due to complex interactions between the nature of the above-ground vegetation, soil micro-topography and land use history. The results highlighted the need for longer-term catchment experiments to generate a predictive understanding of the effect of transformation on runoff and erosion in succulent thicket.
- Full Text:
- Date Issued: 2003
The evaluation of potential improvements of barton pot oxides for lead acid batteries
- Authors: Geyer, Laurence Thomas
- Date: 2003
- Subjects: Lead oxides -- South Africa , Lead acid batteries -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10982 , http://hdl.handle.net/10948/233 , Lead oxides -- South Africa , Lead acid batteries -- South Africa
- Description: Lead Oxide (PbO) is the main material used for the preparation of the active material for the positive and negative electrodes in the lead acid battery where the electrochemical reaction that provides the electrical energy of the battery takes place. The particle size distribution and surface area characteristics of the lead oxide play a major role in the electrical performance of the completed battery. The two most commonly used processes to manufacture PbO in the lead acid battery industry are the Barton pot and the Ball mill processes. These two processes produce oxides that differ in particle size distribution, particle shape and surface area. It is generally accepted that the Ball mill process produces an oxide with a smaller mean particle size with a higher surface area and better initial electrical performance than the Barton pot process to the detriment of an initial higher capital and running cost. The study showed that it is possible to improve the surface area and particle size distribution characteristics of Barton pot oxide, by subsequently hammer milling the oxide particles before the paste manufacturing process. The results showed that there was an initial reduction in the particle size with an increase in the surface area. This increased the electrochemical performance in terms of the high rate discharge. However, further hammering of the oxide reduced the average particle size only slightly with little change in the surface area and a reduction in the electrochemical performance. The study showed that an improvement in Barton pot oxide can be achieved with a hammering of the oxide in order to obtain a uniform particle size with improved surface area and an improved high rate performance of the electrochemical cells made with such an oxide. As a comparison, the particle size and surface area characteristics of Ball mill lead oxide subjected to the hammer milling process was also studied. The results showed a similar effect to the Barton pot oxide on the particle size distribution. However, there was no appreciable change in the surface area due to the hammer milling process.
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- Date Issued: 2003
The long term effects of fire frequency and season on the colophospermum mopane shrubveld of the Kruger National Park
- Authors: Lombard, Pieter Jacobus Lategan
- Date: 2003
- Subjects: Mopane tree -- Effect of fires on -- South Africa -- Kruger National Park
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10970 , http://hdl.handle.net/10948/257 , Mopane tree -- Effect of fires on -- South Africa -- Kruger National Park
- Description: Background : The recorded history of veld burning in the Kruger National Park (KNP) started with the appointment of Colonel James Stevenson-Hamilton as warden of the Park (then the Sabie Game Reserve) in July 1912 and can be divided into five periods: From 1912 to 1926, a haphazard, and indecisive burning policy was practiced, mainly due to the perception that fire was unfavourable for the environment and because the means to combat veld fires were very meagre. From 1926 to 1948, in which period it was realized that fire was not only unavoidable over a large area such as the KNP, but also actually desirable, necessary and beneficial when applied with circumspection. During this period the capability to successfully introduce and apply a definite fire policy did not exist. From 1948 to 1956, prescribed burning was not practiced, but a network of graded firebreaks was being established (to create burning blocks), and wild fires were actively combated. From 1957 to 1993, during which period a definite prescribed burning policy was practiced, amended several times, but basically consisting of a triennial rotational system where blocks were burned by management. All fires of non-management ignition sources were combated. From 1993 to the present, when a policy of allowing lightning-ignited fires to burn freely was introduced, and fires of human origin were suppressed. The shift away from a rigid prescribed burning programme was because of the concern that the dominance of grass species characteristic of over utilised veld was a result of too frequent burning (Potgieter, 2001). Lightning fires probably played just as an important role in shaping African savanna in pre-industrial times as anthropogenic fires caused by preindustrial man. The role of post-industrial man as far as its influence on the creation of savanna is concerned is probably negligible, but significantly important in the role of maintaining savanna, although probably not more so than that of lighting fires. Fires caused by postindustrial man becomes suspect as far as the creation of savanna is concerned, because instead of the mere burning of the veld for the pure reasons of survival as practiced by pre-industrial man, a measure of commercialism crept in (Potgieter, 2001). Fire management of the KNP in pre-industrial times can be regarded in the same light as that of post-industrial times. Although the motive for burning the veld in the KNP was beyond reproach, the underlying reasoning was not. Managers’ thinking was geared towards preventing so called “devastating fires”, laying to waste large areas of the Park, not realising that this was in actual fact nature going about its business in this ecosystem. They therefore devised a system of firebreak roads, which was gradually extended to the extent that we now have more than 4000 km roads that must be maintained. This was all in the cause of preventing or managing lightning and arson fires. Given the above, a revision of the veld fire policy was extremely necessary. The mission statement hammered out during the revising process in 1993 underscored and supported the proposal put forward in 1992, that lightning fires should be recognised as a legitimate and completely natural phenomenon in the Lowveld ecosystem. This had to be weighed against the prevailing practice of combating all fires caused by lightning and non-management anthropogenic sources of fire. The essence of this policy would therefore be to allow lightning-fires to burn to their full extent i.e. if vegetation conditions (available biomass) are such that large areas will burn, then such burns will be permitted to proceed to their full extent with the provision that no more than 50% of the management unit will be allowed to burn out (no matter what the ignition source) in a specific fire season (Potgieter, 2001).
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- Date Issued: 2003
The specification and design of a prototype 2-D MPEG-4 authoring tool
- Authors: Viljoen, Deon Walter
- Date: 2003
- Subjects: MPEG (Video coding standard) , Digital video -- Standards , Multimedia systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11092 , http://hdl.handle.net/10948/d1015741 , MPEG (Video coding standard) , Digital video -- Standards , Multimedia systems
- Description: The purpose of this project was the specification, design and implementation of a prototype 2-D MPEG-4 authoring tool. A literature study was conducted of the MPEG-4 standard and multimedia authoring tools to determine the specification and design of a prototype 2- D MPEG-4 authoring tool. The specification and design was used as a basis for the implementation of a prototype 2-D MPEG-4 authoring tool that complies with the Complete 2-D Scene Graph Profile. The need for research into MPEG-4 authoring tools arose from the reported lack of knowledge of the MPEG-4 standard and the limited implementations of MPEG-4 authoring tools available to content authors. In order for MPEG-4 to reach its full potential, it will require authoring tools and content players that satisfy the needs of its users. The theoretical component of this dissertation included a literature study of the MPEG-4 standard and an investigation of relevant multimedia authoring systems. MPEG-4 was introduced as a standard that allows for the creation and streaming of interactive multimedia content at variable bit rates over high and low bandwidth connections. The requirements for the prototype 2-D MPEG-4 authoring system were documented and a prototype system satisfying the requirements was designed, implemented and evaluated. The evaluation of the prototype system showed that the system successfully satisfied all its requirements and that it provides the user with an easy to use and intuitive authoring tool. MPEG-4 has the potential to satisfy the increasing demand for innovative multimedia content on low bandwidth networks, including the Internet and mobile networks, as well as the need expressed by users to interact with multimedia content. This dissertation makes an important contribution to the understanding of the MPEG-4 standard, its functionality and the design of a 2-D MPEG-4 Authoring tool. Keywords: MPEG-4; MPEG-4 authoring; Binary Format for Scenes.
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- Date Issued: 2003
Using E-learning to support IT education in a university environment a case study approach
- Authors: Taljaard, Marinda
- Date: 2003
- Subjects: Education, Higher -- South Africa -- Port Elizabeth -- Computer-assisted instruction , Internet in education , Information technology -- Study and teaching (Higher) -- South Africa -- Port Elizabeth , College teaching -- South Africa -- Port Elizabeth -- Computer network resources , University of Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11091 , http://hdl.handle.net/10948/d1015740 , Education, Higher -- South Africa -- Port Elizabeth -- Computer-assisted instruction , Internet in education , Information technology -- Study and teaching (Higher) -- South Africa -- Port Elizabeth , College teaching -- South Africa -- Port Elizabeth -- Computer network resources , University of Port Elizabeth
- Description: At the University of Port Elizabeth (UPE), the End User Computing course (EUC) acts as a service course for many departments. This implies that many students are forced by their curricula to register for this course. The ever-increasing numbers in EUC place a considerable load on existing human and physical resources. In lecture groups of 120 –160, students rarely get the attention they need, and the pace at which the content is delivered (too slow or too fast) may also inhibit the learning process. During an initial investigation into E-learning at UPE in 1999, a prototype virtual classroom was developed. There were, however, a number of problems with this prototype. Firstly, it was implemented using a number of different technologies, which made it difficult to extend and maintain. Secondly, it only addressed some aspects of an E-learning environment, which proved insufficient for the EUC course. In the existing EUC course at UPE, the students are already exposed to some E-learning concepts, as a section of their skills training component is handled by using multimedia software in a simulated environment. The objective of this project was to extend the E-learning component further to determine the advantages and disadvantages of using E-learning to support information technology (IT) education in a contact-university environment. This project included a literature search and survey of existing E-learning environments at other universities. This research was used to develop a draft framework for an E-learning environment. The framework was used to select a tool to create an E-learning environment at UPE. An experiment was designed using this E-learning environment to support two IT courses at different year levels. The results of the experiment were analysed using qualitative and quantitative methods to determine the impact of using E-learning to support IT education at UPE. The results of this research show that E-learning can be used to support IT education at UPE. More success, however, was achieved at postgraduate level than at first-year level. Making use of Elearning increased student satisfaction and promoted active learning, while providing benefits like convenience, communication, flexibility and scaffolding. We conclude, therefore, that E-learning can provide a flexible approach to IT education in a university environment in the future.
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- Date Issued: 2003