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Studies of the environmental and endocrine control of reproduction in the four striped field mouse, Rhabdomys pumilio

  • Authors: Jackson, Claire
  • Date: 2003
  • Subjects: Microtus Microtus -- South Africa -- Reproduction Mice -- Reproduction
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5777 , http://hdl.handle.net/10962/d1005465
  • Description: Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.
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  • Date Issued: 2003

The development and evaluation of Cryptophlebia Leucotreta granulovirus (CrleGV) as a biological control agent for the management of false codling moth, Cryptophlebia Leucotreta, on citrus

  • Authors: Moore, Sean Douglas
  • Date: 2003
  • Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- Control Pests -- Biological control Citrus -- Diseases and pests
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3942 , http://hdl.handle.net/10962/d1004001
  • Description: A granulovirus isolated from Cryptophlebia leucotreta larvae was shown through restriction endonuclease analysis to be a novel strain (CrleGV-SA). No more than one isolate could be identified from a laboratory culture of C. leucotreta. However, a preliminary examination of restricted DNA profiles of isolates from different geographical regions indicated some minor differences. In surface dose bioassays on artificial diet, LC50 and LC90 values with neonate larvae were estimated to be 4.095 x 103 OBs/ml and 1.185 x 105 OBs/ml respectively. LT50 and LT90 values with neonate larvae were estimated to be 4 days 22 h and 7 days 8 h, respectively. Detached fruit (navel orange) bioassays with neonate larvae indicated that virus concentrations that are likely to be effective in the field range from 1.08 x 107 to 3.819 x 1010 OBs/ml. In surface dose bioassays with fifth instar larvae LC50 and LC90 values were estimated to be 2.678 x 107 OBs/ml and 9.118 x 109 OBs/ml respectively. LT50 and LT90 values were estimated to be 7 days 17 h and 9 days 8 h, respectively. A new artificial diet for mass rearing the host was developed. Microbial contamination of diet was significantly reduced by adding nipagin and sorbic acid to the diet and by surface sterilising C. leucotreta eggs with Sporekill. Almost 20 % more eggs were produced from moths reared on the new diet compared to moths reared on the old diet. A further 9 % improvement in egg production and a reduction in the labour required to produce eggs, was made with the development of a new oviposition cage attached to the moth eclosion box. Virus was mass produced in fifth instar C. leucotreta larvae by surface inoculating diet with the LC90. When 300 individuals were placed onto inoculated diet, 56 % of them were recovered six to 11 days later as infected larvae. Mean larval equivalents was 1.158 x 1011 OBs/larva. When larvae and diet were harvested together, highest yields of virus were achieved at eight days after inoculation. Microbial contamination in semi-purified preparations of CrleGV ranged from 176211 to 433594 (OB:CFU ratio). Half-life of CrleGV in the field was estimated to be less than 1 day on the northern aspect of trees and between 3 - 6 days on the southern aspect. Original activity remaining (OAR) of the virus dropped below 50 % after 5 days on the northern aspect of trees and was still at 69 % on the southern aspect of trees after 3 weeks. In field trials, CrleGV reduced C. leucotreta infestation of navel oranges by up to 60 % for a period of 39 days. CrleGV in combination with augmentation of the C. leucotreta egg parasitoid, Trichogrammatoidea cryptophlebiae, reduced infestation by 70 %. The integration of CrleGV into an integrated pest management (IPM) system for the management of C. leucotreta on citrus is proposed.
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  • Date Issued: 2003

The diamondback moth, Plutella xylostella (L.), (Lepidoptera: Plutellidae) and its biological control in the Eastern Cape Province, South Africa

  • Authors: Smith, Tamara Jane
  • Date: 2003
  • Subjects: Plutellidae Plutellidae -- South Africa -- Eastern Cape Insect pests -- Biological control -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5626 , http://hdl.handle.net/10962/d1004742
  • Description: The diamondback moth, Plutella xylostella (L.), is a pest on crucifer crops worldwide, damaging the leaves, florets and seed pods of many crucifers including cabbage, cauliflower, broccoli and canola. It has been controlled using broad-spectrum insecticides, but this has led to a rapid build-up of insecticide resistance. In the Grahamstown area of the Eastern Cape Province, South Africa, diamondback moth showed resistance to cypermethrin (a pyrethroid) on commercially grown cabbages. Therefore it is imperative that other methods of control be adopted, including both cultural control and biological control using parasitoids, and that these are incorporated into an Integrated Pest Management (IPM) programme. The diamondback moth and its parasitoids were monitored weekly from April 1997 to November 1999 at three sites near Grahamstown. One site was a commercial farm with an active insecticide spraying program; the others were unsprayed. Infestation levels were highest during spring (September to November) and autumn (March to May). Nine species of parasitoids were associated with the diamondback moth, with abundances being highest over spring and early summer (September to December). Cotesia plutellae (Kurdjumov) dominated the sprayed site, while the unsprayed sites yielded a complex of parasitoids, including C. plutellae, Diadegma mollipla (Holmgren), Diadromus collaris Gravenhorst and Oomyzus sokolowsldi (Kurdjumov). Parasitism levels ranged between 10 and 90%. There was a large amount of site-to-site and year-to-year variation. Parasitoids were an effective mortality factor against the diamondback moth. The effects of temperature on development and mortality, and of field size and non-crop plants on the distribution of diamondback moth and its parasitoids, were investigated. The results show that high temperatures can depress pest populations, and that the size and surroundings of fields can be manipulated to improve cultural control of the diamondback moth. Suggestions for effective rPM in the Eastern Cape Province include a reduction in insecticide applications, the use of bioinsecticides, for example Bacillus thuringiensis Berliner (Bt) and the encouragement of indigenous parasitoids by planting suitable nectar sources. Cultural control methods are also important and involve removal of cabbage refuse after harvest, management of wild crucifers around cabbage fields, scouting and monitoring the moth population and determining the optimal field size to assist with control by parasitoids.
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  • 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.
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  • Date Issued: 2003

The fundamental right to just administrative action: judicial review of administrative action in the democratic South Africa

  • Authors: Plasket, Clive
  • Date: 2003
  • Subjects: Judicial review of administrative acts -- South Africa Administrative acts -- South Africa Administrative law -- South Africa Public administration -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3693 , http://hdl.handle.net/10962/d1003208
  • Description: For most of its existence South African administrative law has been shaped by the doctrine of parliamentary sovereignty – the heart of the constitutional order from 1910 to 1994 – and a racist political system that favoured the white minority at the expense of the black majority. In these circumstances, the rules of administrative law were of limited use in protecting the individual from exercises of administrative power that infringed fundamental human rights, often on a grand scale. On 27 April 1994, however, a new political and constitutional order came into existence that swept away the very foundations of the old order: parliamentary sovereignty was replaced by constitutional supremacy and the racial exclusivity of the old order was replaced by a commitment to equality, freedom and dignity in a democratic state. A justiciable Bill of Rights was at centre stage in this new order. That Bill of Rights includes a fundamental right to just administrative action. It is both the new constitutional order and this rather unusual fundamental right that have changed the nature of South African administrative law. This thesis examines the effect of the fundamental right to just administrative action on the law and practice of the judicial review of administrative action. It does so principally by examining the legal position before and after 27 April 1994 with particular reference to: what is meant by administrative action; the exercise of administrative power by private bodies regulated by the rules of administrative law, on the one hand, and exercises of private power regulated by rules of private law, on the other; the rules of standing, the notion of justiciability and the constitutionality of rules that seek to limit the right of the individual to approach a court to review administrative action; the meaning and scope of the right to lawful, reasonable and procedurally fair administrative action, in terms of the common law, the Constitution and the Promotion of Administrative Justice Act 3 of 2000; the meaning, scope and efficacy of the rights to reasons for administrative actions and of access to information; the procedure of judicial review and remedies that may be granted for the infringement of a person’s right to just administrative action; and conclusions and recommendations with regard to progress made in the construction of South Africa’s new, democratically based, administrative law.
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  • Date Issued: 2003

The geochemistry of ore fluids and control of gold mineralization in banded iron-formation at the Kalahari Goldridge deposit, Kraaipan greenstone belt, South Africa

  • Authors: Hammond, Napoleon Quaye
  • Date: 2003
  • Subjects: Gold ores -- Geology -- South Africa -- North-West Greenstone belts -- South Africa -- North-West Ore deposits -- South Africa -- North-West Geochemistry -- South Africa -- North-West
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5048 , http://hdl.handle.net/10962/d1008370
  • Description: The Kalahari Goldridge mine is located within the Archaean Kraaipan Greenstone Belt about 60 km SW of Mafikeng in the Northwestern Province, South Africa. Several gold deposits are located within approximately north - south-striking banded iron-formation (BIF). Current opencast mining operations are focused on the largest of these (D Zone). The orebody is stratabound and hosted primarily in the BIF, which consists of alternating chert and magnetite-chloritestilpnomelane-sulphide-carbonate bands ranging from mm to cm scale. The ore body varies in thickness from 15 to 45 m along a strike length of about 1.5 km. The BlF is sandwiched between a sericite-carbonate-chlorite schist at the immediate footwall and carbonaceous meta-pelites in the hanging-wall. Further west in the footwall, the schists are underlain by mafic meta-volcanic amphibolite. Overlying the hanging-wall carbonaceous metapeiites are schist units and meta-greywackes that become increasingly conglomeratic up the stratigraphy. Stilpnomelane-, chlorite- and minnesotaite-bearing assemblages in the BlFs indicate metamorphic temperatures of 300 - 450°C and pressures of less than 5 kbars. The BIF generally strikes approximately 3400 and dips from 60 to 75°E. Brittle-ductile deformation is evidenced by small-scale isoclinal folds, brecciation, extension fractures and boudinaging of cherty BIF units. Fold axial planes are sub-parallel to the foliation orientation with sub-vertical plunges parallel to prominent rodding and mineral lineation in the footwall. Gold mineralization at the Kalahari Goldridge deposit is associated with two generations of subhorizontal quartz-carbonate veins dips approximately 20 to 40°W. The first generation consists of ladder vein sets (Group lIA) preferentially developed in Fe-rich meso bands, whilst the second generation consists of large quartz-carbonate veins (Group lIB), which crosscut the entire ore body extending into the footwall and hanging-wall in places. Major structures that control the ore body are related to meso-scale isoclinal folds with fold axes subparallel to mineral elongation lineations, which plunge approximately 067°E. These linear structures form orthogonal orientation with the plane of the mineralized shallowdipping veins indicating stretching and development of fluid - focusing conduits. A second-order controlling feature corresponds to the intersection of the mineralized veins and foliation planes of host rock, plunging approximately 008°N and trending 341°. G0ld is closely associated with sulphides, mainly pyrite and pyrrhotite and to a lesser extent with bismuth tellurides, and carbonate gangue. The ore fluid responsible for the gold deposition is in the C-O-H system with increased CH₄ contents attributed to localized hydrolysis reaction between interbedded carbonaceous sediment and ore fluid. The fluid is characterized by significant C0₂ contents and low salinities below 7.0 wt % NaCl equivalent (averages of 3.5 and 3.0 wt % NaCl equivalent for the first and second episodes of the mineralization respectively) . Calculated values of f0₂. ranging from 10⁻²⁹·⁹⁸ to 10⁻³²·⁹⁶ bars, bracket the C0₂-CH₄ and pyrite-pyrrhotite-magnetite buffer boundaries and reveal the reducing nature of the ore fluid at deposition. Calculated total sulphur content in the ore fluid (mΣs), ranges from 0.011 to 0.018M and is consistent with the range (10⁻³·⁵ to 10⁻¹M) reported for subamphibolite facies ore fluids. The close association of sulphides with the Au and nature of the fluid also give credence that the Au was carried in solution by the Au(HS)₂ - complex. Extensive epigenetic replacement of magnetite and chlorite in BIF and other meta-pelitic sediments in the deposit by sulphides and carbonates, both on meso scopic and microscopic scales gives evidence of an interaction by a CO₂- and H₂S-bearing fluid with the Fe-rich host rocks in the deposit. This facilitated Au precipitation due to changes in the physico-chemical conditions of the ore fluid such as a decrease in the mΣs and pH leading to the destabilization of the reduced sulphur complexes. Local gradients in f0₂ may account for gold precipitation in places within carbonaceous sediments. The fineness of the gold grams (1000*Au/(Au + Ag) ranges from 823 to 921. This compares favourably with the fineness reported for some Archaean BIFhosced deposits (851 - 970). Mass balance transfer calculations indicate that major chemical changes associated with the hydrothermal alteration of BIF include enrichment of Au, Ag, Bi, Te, volatiles (S and CO₂), MgO, Ba, K and Rb but significant depletion of SiO₂ and minor losses of Fe₂O₃. In addition, anomalous enrichment of Sc (average, 1247%) suggests its possible use as an exploration tool in the ferruginous sediments in the Kraaipan greenstone terrane. Evidence from light stable isotopes and fluid inclusions suggests that the mineralized veins crystallized from a single homogeneous fluid source during the two episodes of mineralization under the similar physicochemical conditions. Deposition occurred at temperatures rangmg from 350 to 400°C and fluid pressures ranging from 0.7 to 2.0kbars. Stable isotope constraints indicate the following range for the hydrothermal fluid; θ¹⁸H₂O = 6.65 to 10.48%0, 8¹³CΣc = -6.0 to -8.0 %0 and 8³⁴SΣs = + 1.69 to + 4.0%0 . These data do not offer conclusive evidence for the source of fluid associated with the mineralization at the Kalahari Goldridge deposit as they overlap the range prescribed for fluid derived from devolatization of deep-seated volcano-sedimentary piles near the brittle-ductile transition in greenstone belts during prograde metamorphism, and magmatic hydrothermal fluids. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2003

The phosphorylation and nuclear localization of the co-chaperone murine stress-inducible protein 1

  • Authors: Longshaw, Victoria Mary
  • Date: 2003
  • Subjects: Phosphorylation Proteins Heat shock proteins
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3979 , http://hdl.handle.net/10962/d1004038
  • Description: The co-chaperone murine stress-inducible protein 1 (mSTI1), a heat shock protein 70 (Hsp70)/ heat shock protein 90 (Hsp90) organizing protein (Hop) homologue, mediates the assembly of the Hsp70/Hsp90 chaperone heterocomplex. mSTI1 is phosphorylated in vitro by cell cycle kinases, proximal to a putative nuclear localization signal (NLS), substantiating a predicted CKII-cdc2-NLS (CcN) motif at position 189-239. Stable transfectants of NIH 3T3 fibroblasts that expressed mSTI1-EGFP, NLSmSTI1-EGFP and EGFP, were prepared. Fluorescence microscopy revealed mSTI1 was cytoplasmically localized, and that this localization was not affected by the fusion of mSTI1 with the EGFP moiety. NLSmSTI1-EGFP was targeted to the nucleus compared to EGFP, suggesting that the NLSmSTI1 was a functional NLS. The localization of mSTI1 was determined under normal and heat shock conditions, inhibition of nuclear export (leptomycin B), inhibition of CKII 5,6-dichlorobenzimidazole riboside, DRB), inhibition of cdc2 kinase (olomoucine), and G1/S phase arrest (hydroxyurea). mSTI1-EGFP and mSTI1 were excluded from the nucleus in the majority of resting cells, but accumulated in the nucleus following leptomycin B treatment, implying that mSTI1 possibly undergoes a functional import process, and export via the chromosomal region maintenance 1 (CRM-1)-mediated export pathway. Hydroxyurea and olomoucine (but not DRB or heat shock) treatment increased the proportion of cells in which mSTI1-EGFP exhibited cytoplasmic and nuclear localization. 2D gel electrophoresis detected three endogenous mSTI1 isoforms, which changed following hydroxyurea treatment. Furthermore, point inactivation and mimicking of phosphorylatable residues in mSTI1 altered the translocation of the protein and the isoform composition. Modification of mSTI1 at S189 and T198 decreased the number of isoforms of mSTI1-EGFP, suggesting that the protein is modified at these sites in vivo. The removal of the in vitro cdc2 kinase site at T198 promoted a nuclear localization during G1/S phase arrest. Therefore active cdc2 kinase, but not CKII, may be required for cytoplasmic localization of mSTI1. The CKII site appears to have no regulatory role under heat shock conditions or during the cell cycle. In vitro phosphorylation studies on untagged mSTI1 further supported the prediction that S189 is the only site recognised by CKII. The cdc2 kinase site at T198, however, although the major site, was not the only site phosphorylated in vitro. However, mSTI1 and cdc2 kinase did not interact in a detectable stable complex. Bioinformatic analysis of mSTI1 revealed NLS residues were conserved in STI1 proteins, and the NLS and TPR2A motifs were in close proximity. This may have mechanistic implications for the formation of the Hsp90-mSTI1 heterocomplex. The cytoplasmic or nuclear localization of mSTI1 is predicted to be the result of a dynamic equilibrium between nuclear import and nuclear export, the fulcrum of which may be shifted under different cell cycle conditions. These data provide the first evidence of regulated nuclear import/export of a major Hsp70/Hsp90 co-chaperone, and the regulation of this nuclear import by cell cycle status and cell cycle kinases.
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  • Date Issued: 2003

Versions of confinement: Melville's bodies and the psychology of conquest

  • Authors: Goddard, Kevin Graham
  • Date: 2003
  • Subjects: Melville, Herman, 1819-1891 -- Criticism and interpretation Human body in literature
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2216 , http://hdl.handle.net/10962/d1002259
  • Description: This thesis explores aspects of Melville’s presentation of both the whale and the human bodies in Moby-Dick and human bodies in other important novels. It argues that Melville uses his presentation of bodies to explore some of the versions of confinement those bodies experience, and by doing so, analyses the psychology which subtends that confinement. Throughout Melville’s works bodies are confined, both within literal spatial limits and by the psychology which creates and/or accepts these spatial limits. The thesis argues that perhaps the most important version of bodily confinement Melville addresses is the impulse to conquer bodies, both that of the other and one’s own. It adopts a largely psychoanalytic approach to interpreting bodies and their impulse to conquer, so that the body is seen to figure both in its actions and its external appearance the operations of the inner psyche. The figure of the body is equally prevalent in Melville’s exploration of nationalist conquest, where, as with Manifest Destiny and antebellum expansionism, the psychological and physical lack experienced by characters can be read as motivating factors in the ideology of conquest. A final important strand of the thesis is its argument in favour of a gradual shift in Melville’s interpretation of the value and possibility of genuine communion between human beings and between humans and the whale. One may read Typee as an attempt by Melville to explore the possibility of a this-worldly utopia in which human beings can return to a version of primitive interconnectedness. This exploration may be seen to be extended in Moby-Dick, particularly in Ishmael’s attempts to find communion with others and in some moments of encounter with the whales. The thesis uses phenomenology as a theory to interpret what Melville is trying to suggest in these moments of encounter. However, it argues, finally, that such encounter, or ‘intersubjectivity’ is eventually jettisoned, especially in the works after Moby-Dick. By the end of Melville’s life and work, any hope of an intersubjective utopia he may have harboured as a younger man have been removed in favour of a refusal actually to assert any final ‘truth’ about social, political or even religious experience. Billy Budd, his last body, is hanged, and his final word is silence.
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  • Date Issued: 2003

Where the global meets the local : South African youth and their experience of global media

  • Authors: Strelitz, Larry Nathan
  • Date: 2003
  • Subjects: Mass media and youth -- South Africa Mass media -- Sociological aspects Mass media and culture -- South Africa Youth -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3290 , http://hdl.handle.net/10962/d1003078
  • Description: Within the context of debates concerning the impact of global media on local youth, this study explores how a sample of South African youth responds to texts which were produced internationally, but distributed locally. Recognising the profound rootedness of media consumption in everyday life, the research examines the way these youth, differentially embedded in the South African economic and ideological formation, use these texts as part of their ongoing attempts to make sense of their lives. The study rejects the 'either/or' formulations that often accompany competing structuralist and culturalist approaches to text/audience relationships. Instead, using a combination of quantitative and qualitative research methods, it seeks to highlight the interplay between agency and structure, between individual choice and the structuring of experience by wider social and historical factors. The findings of the study point to the complex individual and social reasons that lie behind media consumption choices, and the diverse (and socially patterned) reasons why local audiences are either attracted to, or reject, global media. These and other findings, the study argues, highlight the deficiencies of the media imperialism thesis with its definitive claims for cultural homogenisation, seen as the primary, or most politically significant, effect of the globalisation of media. As such, this study should be read as a dialogue with those schools of thought that take a more unequivocal point of view on the impact of globalised media culture.
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  • Date Issued: 2003

A comparative study of atmospheric dynamics in the mesosphere and lower thermosphere (MLT) near Grahamstown (South Africa) and Adelaide (Australia)

  • Authors: Malinga, Sandile Bethuel
  • Date: 2002
  • Subjects: Atmospheric physics Atmospheric physics -- South Africa -- Eastern Cape Atmospheric physics -- Australia Dynamic meteorology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5506 , http://hdl.handle.net/10962/d1007307
  • Description: The observations made near Grahamstown (33 .3°S, 26.5°E), South Africa and Adelaide (34.5°S, 138.5°E), Australia over the years 1987 to 1994 are used to study the dynamics of the mesosphere and lower thermosphere (ML T) region with a focus on ∼ 90 km altitude. In particular this thesis deals with on the atmospheric mean flow and the solar diurnal and semi diurnal oscillations with a view to (i) deducing their patterns at the two sites, (ii) comparing the dynamic structures observed at the two sites with special emphases on longitudinal variations, and (iii) putting these observations in a global context by comparing with other ground-based observations, satellite observations and numerical simulations. The main findings are summarised below. The mean flow and the tides at Grahamstown and Adelaide are characteristically variable at planetary time scales. Wavelet spectral and multiresolution analyses reveal that the dominant planetary oscillation is the quasi-16-day oscillation. However, no apparent correlation in the 16-day waves of the mean flow, the diurnal tide and the semidiurnal tide was found. The short-term fluctuations were also investigated using complex demodulation and bispectral techniques and it was found that some of the observed variations in tides could be due to non-linear wave-wave interactions. The long-term trends of the mean flow and tides show patterns that are in broad agreement with theory, results from elsewhere (ground-based and satellite) and the results of the Global-Scale Wave Model and various models by Portnyagin and others. In general the mean flow, the amplitudes and phases of both tides were found to exhibit seasonal and interannual variations which are thought to be related to various factors including (i) changes in the atmospheric mean environment, (ii) thermotidal forcing (iii) gravity wave effects, (iv) planetary scale influence, (v) long-term (e.g. quasi-biennial oscillation) modulation, and (vi) solar activity. There are significant longitudinal differences in the dynamic structure between Grahamstown and Adelaide. More especially, Grahamstown tends to have stronger mean flow and tidal activity than Adelaide. For tides, these differences are thought to be partly due to nonmigrating tidal modes but, in general, migrating modes were found to be dominant.
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  • Date Issued: 2002

A historical study of John Graham Lake and South African/United States pentecostalism

  • Authors: Burpeau, Kemp Pendleton
  • Date: 2002
  • Subjects: Lake, John G , Pentecostalism -- South Africa , Pentecostalism -- United States , Pentecostals , Christianity and politics -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2587 , http://hdl.handle.net/10962/d1006484 , Lake, John G , Pentecostalism -- South Africa , Pentecostalism -- United States , Pentecostals , Christianity and politics -- South Africa
  • Description: American minister John Graham Lake (1870-1935) was a pivotal participant in an era of profound religious and political transition. Surprisingly, Lake's often provocative life had previously been largely neglected as a field of academic inquiry. In the U.S. Lake associated with key Holiness, Wesleyan and Apostolic Faith charismatics like John Alexander Dowie of the Zion City, Illinois Utopia, Charles Parham of the Topeka Revival and William Seymour of the Azusa Street Revival. Lake served as an important intermediary between Parham's often reactionary, white orientation that was unreceptive to an enthusiastic black liturgy and Seymour's expansive African-American egalitarianism expressed through exuberant spirit manifestations. Lake's South African ministry was shaped by his middle class white business background, Azusa Street message and American perspectives. He brought together the faith healing movement inspired by Dutch Reformed minister Andrew Murray, P. Ie Roux's black and white Zion charismatic adherents affiliated with Dowie and the new U.S. Pentecostalism of Parham and Seymour. Lake's African-American influenced Pentecostalism was compatible with indigenous African worship. His emphasis on the spiritual needs of the disempowered found a receptive audience in talented black evangelists Elias Letwaba and Edward Lion. Even though acquainted with Mohandas Gandhi, Lake did not undertake a South African social gospel-type civil protest against societal injustice. In fact, Lake's participation with Afrikaner politicians like Louis Botha in fashioning a segregationist land use law was most troubling. Lake was ambivalent about racial integration. His belief in an egalitarian status for all Christians, his Populist/Progressive ethics and his enthusiastic promotion of women's rights were complicated by his advocacy, or at least tolerance, of some disparate racial treatment in his Apostolic Faith Mission and South African society at large. Lake's paternalism and notion of Westem cultural superiority conflicted with his love of all persons. Lake's otherworldly prioritization of individual spiritualism over a socioeconomic agenda usually stymied activism. His uncharacteristic use of nonviolent protest to protect faith healing formed a remarkable contrast with his reluctance to actively campaign against unequal racial treatment in Africa and America. Historiographical perspectives on Lake range from the saintly pioneer charismatic missionary to the Elmer Gantry type charlatan acting only for personal benefit. Lake was a unique personality with his flamboyant rhetoric, strong convictions and feelings of personal worth. His distinctive Jesus as healing and suffering God theology evidenced both consistency with precedent as well as creative anticipation. Shortcomings resulting from his preference to address social concerns on an individual spiritual rather than societal level, his liberties with truth and his bad business judgments resulting in litigation. Nevertheless, Lake's life demonstrated that a gifted but imperfect instrument could accomplish a meaningful ministry. , Adobe Acrobat Pro 9.5.4 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2002

Biological generation of reactive alkaline species and their application in a sustainable bioprocess for the remediation of acid and metal contaminated wastewaters

  • Authors: Van Hille, Robert Paul
  • Date: 2002
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:21049 , http://hdl.handle.net/10962/6129
  • Description: This project focused on the development of an integrated biological system for the treatment of acidic and metal-laden effluents, based on the sustainable biological generation of reactive alkaline species. Initial studies concentrated on the binding and accumulation of heavy metals by biomass of the cyanobacteria, Spirulina sp. Metal binding was rapid, with saturation reached in 30 minutes, and followed an affinity series of Pb > Cu > Zn >>Fe. The binding capacity of the Spirulina for each of the metals was relatively low when compared to a range of other biosorbents. The toxicity thresholds of the algae was determined for copper and zinc. These were low (10umoles/g) and as such, the algae were not suitable for application in a treatment system in which they came into direct contact with the toxic metals. The algae were able to increase the pH of the surrounding medium. This occurred as a result of the accumulation of inorganic carbon, from bicarbonate, as a response to low concentrations of carbon dioxide in the medium. The resulting release of a hydroxide ion into solution led to the increase in pH. The increase in pH was shown to be due to a reduction in acidity, rather than an increase in alkalinity. The enzyme carbonic anhydrase was shown to be pivotal in this system. Attempts to determine the enzyme activity directly were unsuccessful, due to the inherent inaccuracy of the assay system. An indirect method of determining enzyme activity, by measuring changes in the carbonate species equilibrium, was developed. Under optimal conditions Spirulina was able to reduce the acidity by an amount equivalent to the addition of 3670umoles NaOH g·' h·'. Predictive modelling showed that this enhanced the potential of the medium to effect metal precipitation. For the algal system to be sustainable, a readily available source of bicarbonate was needed. This was achieved by the oxidation of organic carbon, under sulphidogenic conditions, by a bacterial consortium isolated from the anaerobic component of a facultative pond. The consortium was shown to consist of sulphate reducing (most likely Desulvovibrio and Desulfotomaculum)and acetogenic bacteria. Sulphate removal rates of 500mg 1·' day·' and 135mg 1·' day·' were achieved in a 21 agitated and 281 upflow reactor respectively. The bicarbonate generation rate in the 281 reactor was calculated as 4033umoles 1·' day·', which proved sufficient to act as a feed for the algal system. Sparging the anaerobic digester overflow with air and nitrogen resulted in a reduction in the aqueous sulphide concentration. Using nitrogen, a 70% recovery of sulphide, as H2S gas, was achieved in 60 minutes, while with air, this dropped to 40%, due to the oxidation of the aqueous sulphide. The stripping ofH2S resulted in an increase in pH. The H2S gas was used for the selective precipitation of copper and lead in the integrated system. The dynamics of metal precipitation was investigated. For simple reactions, between individual IV metal and base species, it was possible to generate an accurate predictive model and confirm the precipitating species using wavelength dispersive X-ray spectroscopy (WDS). In more complex systems, where precipitation of the artificial acid mine drainage was examined, the predictive modelling and WDS could not accurately describe the system. The addition of aqueous sulphide to copper and iron resulted in the formation of metastable, amorphous precipitates, which remained in suspension. Ageing of the copper precipitate resulted in the evolution of a stable crystalline structure (covellite) and the aggregation and settling of the precipitate. In the case of iron, the amorphous precipitate underwent oxidation before a stable iron sulphide could evolve and the settled precipitate was an iron oxide or oxyhydroxide. The artificial acid mine drainage was treated with sulphide, hydroxide, anaerobic digester overflow and algal overflow. The best metal removal was achieved with the sulphide and hydroxide, while the algal overflow outperformed the anaerobic digester overflow. The precipitate generated by the addition of sulphide was the most compact, followed by the algal overflow, the anaerobic digester overflow and the hydroxide. Efficient precipitation of all the heavy metals, except manganese, was achieved using the algal overflow at an acidity to alkalinity ratio of 1 :2. This ratio was selected for use in the pilot system. The Spirulina based pilot system was effectively used to treat an effluent from the Black Mountain base metal mine. The necessity to maintain the algae in suspension and avoid biomass washout were practical considerations which counted against this system. The replacement of the Spirulina by Oscillatoria, which adhered to a solid support, overcame these problems. The integrated biological system was able to effectively treat an artificial acid mine drainage for 90 days, reducing the concentration of all metals, except manganese, to below the acceptable environmental risk levels. The treatment of the final effluent in a second anaerobic digester reduced the manganese concentration to 4.5uM and proved that the sulphate reducing bacteria could be cultivated on enriched, partially treated acid mine drainage. The integrated biological treatment system performed well, effectively treating an effluent modelled closely on the quality of the water being discharged from the East Rand Basin. The cost of such a system would be considerably less than a "high tech" physico-chemical system. This, coupled with the potential long term sustainability of a biological system, would make it a potentially attractive option for the treatment of future acid mine drainage discharges.
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  • Date Issued: 2002

Biosulphidogenic hydrolysis of lignin and lignin model compounds

  • Authors: Madikane, Mzekelo
  • Date: 2002
  • Subjects: Lignin Lignin -- Biodegradation
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3917 , http://hdl.handle.net/10962/d1003976
  • Description: Lignin degradation under biosulphidogenic conditions has not been extensively reported in the literature. Although aerobic degradation of lignin is well documented, anaerobic biodegradation has focused mainly on methanogenic systems with biosulphidogenic systems receiving less attention. Sulphate reducing bacteria are known to generate moderately high levels of both sulphide and alkalinity at room temperatures, and these conditions draw some comparison with the Kraft pulping process. In the Kraft pulping process, lignin is degraded chemically at ±170°C under high sulphide and alkaline conditions and may provide a model for understanding biosulphidogenic lignin degrading activity. The aim of this study was to investigate the biosulphidogenic hydrolysis of lignin within the context of the chemical and biological conditions generated by a mixed sulphate reducing bacteria consortia. Bioreactor studies with a mixed sulphate reducing consortia and pine wood powder (both untreated and depectinated) resulted in the generation of comparable levels of sulphide and alkalinity used in the chemical hydrolysis studies. Aromatic compound yields were between 20 to 50% of the chemical hydrolysis studies. This fluctuation may have been due to the utilization of these aromatic compounds as electron donors by the sulphate reducing consortia as evidenced by the high rate of sulphate reduction in both the untreated and depectinated wood bioreactors. Biodegradation of lignin model compounds was investigated in order to elucidate lignin degradation mechanisms. Both mono-aromatic and dimeric lignin model compounds were used as electron donors and carbon sources for the mixed sulphate reducing consortia. Biodegradation and mass spectrometer analysis of mono-aromatic compounds, ferulic acid and ferulic acid ethyl ester resulted in the production of intermediates such as catechol, cyclohexane carboxylic acid and adipic acid. These intermediates were also observed in the degradation of dimeric ferulic acid. Biodegradation of salicin resulted in the production of salicyl alcohol, ortho-cresol and acetate. Biodegradation of benzylic ether resulted in the production of vanillin and acetate as end products. The results of these studies provide evidence for a biosulphidogenic hydrolysis of lignin, and also the utilisation of lignin-derived aromatic compounds as electron donor sources, by a mixed sulphate reducing consortia.
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  • Date Issued: 2002

Catalytic behaviour of metallophthalocyanines towards the detection of nitric oxide

  • Authors: Vilakazi, Lea Sibulelo
  • Date: 2002
  • Subjects: Electrochemistry Nitric oxide
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4418 , http://hdl.handle.net/10962/d1006852
  • Description: Electrocatalytic reduction and oxidation of nitric oxide (NO) using cobalt phthalocyanine complexes have been studied and compared to vitamin B₁₂ and other metallophthalocyanine (MPc) complexes. Modifying a glassy carbon electrode with these complexes resulted in improved sensitivity of the electrode allowing detection of NO to 10⁻⁹ mol dm⁻³. The mechanisms of catalysis were studied. Electrocatalysis of NO involves coordination of NO to the MPc complex. Hence catalytic activity is affected by the nature of the metal center. However coordination of NO to the MPc complex has to be reversible to eliminate poisoning of the electrode. Though FePc gave the best sensitivity and lowered the reduction potential more than CoPc, the strong Fe-NO bond resulted in the poisoning of the electrode hence, rendering the electrode unstable. Rate constants for NO coordination to the MPc complexes were studied. These rates were smaller than the studied NO porphyrin coordination rates. Electrocatalytic reduction of NO using MPc complexes involves a transfer of an electron from the metal center to the NO ligand. Hence, substitution of electron-donating grohps on the cobalt pthalocyanine complex resulted in improved sensitivity and catalytic activity. A CoPc modified microelectrode (11μm) was used to monitor NO in human blood components and to detect NO in a rat brain. Detections of NO were also done in aqueous solutions in the presence of interfering species such as dopamine and serotonin. An interaction between NO and serotonin was observed.
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  • Date Issued: 2002

Chemical studies of selected chromone derivatives

  • Authors: Nchinda, Aloysius Tchangwe
  • Date: 2002
  • Subjects: Heterocyclic compounds
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4434 , http://hdl.handle.net/10962/d1007442
  • Description: This investigation has been geared towards several aspects of chromone chemistry. Selected 2-(N,N-dimethylarnino)chromones have been synthesized via 2-hydroxyacetophenone boron difluoride complex intermediates, and potentiometric analysis of these compounds in ethanolwater has been used to determine the influence of substituents on their basicity. The pKa values have been found to lie within a narrow range (1.92 - 2.52), and the observed substituent effects have been rationalized with the aid of semi-empirical and ab initio molecular orbital calculations. An efficient route has been developed for the synthesis of the naturally-occurring chromone, "granulosin" [7,8-(methylenedioxy)-2-propylchromone], and several C-2 side chain analogues in good yields, by condensing 2'-hydroxy-3',4'-(methylenedioxy)acetophenone with a range of ethyl carboxylate esters. These compounds show significant cytotoxic activity against the brine shrimp, Artemia salina, and two of them, the 2-ethyl and 2-benzyl derivatives also show 100% activity as pesticides on Beet army worms (BAW). Another naturally-occurring chromone derivative, 5-hydroxy-2-isopropyl-7-methoxychromone, and four C-2 side chain analogues have been prepared in moderate yields. These compounds also show significant cytotoxic activity against the brine shrimp, Artemia salina, and it is apparent that the presence of the hydroxyl group at C-5 is critical for such activity. The electronimpact mass spectra of both series of chromone derivatives have been investigated, permitting the elucidation of characteristic fragmentation patterns. In work directed towards the synthesis of potential HIV -1 protease inhibitors, five novel chromone-containing analogues of the clinically useful drug, ritonavir, have been synthesized. The design strategy has involved the coupling of substituted chromone-2- carboxylic acids with a specially prepared, hydroxyethylene dipeptide isostere to afford ritonavir analogues containing chromone termini. An interactive docking procedure has been used to explore the docking of ritonavir and the novel chromone-containing analogues into ' the active site of the enzyme, and has indicated the capacity of the ritonavir analogues to form hydrogen-bonds with the HJV-l enzyme receptor. Various substituted cbromone-3-carbaldehydes, which have been synthesized from the corresponding o-hyclroxyacetophenones using Vilsmeier-Haack methodology, have been examined as substrates for Morita-Baylis-Hillman reactions, using 3-hyclroxyquinuclidine as the catalyst and arcylonitrile and methyl acrylate as the activated alkenes. Optimization of the reaction conditions has permitted efficient conversion of the cbromone-3-carbaldehydes to the Morita-Baylis-Hillman products and, in some cases, dimeric products, within 24 h. Heating of the Morita-Baylis-Hillman products, arising from reactions with methyl acrylate, at 80 ºC for 3 h in the presence of DABCO as catalyst, has been shown to effect transformation to the corresponding dimers in good yield.
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  • Date Issued: 2002

Continuity and generalized continuity in dynamics and other applications

  • Authors: Mimna, Roy Allan
  • Date: 2002
  • Subjects: Topological dynamics -- Research Dynamics -- Mathematical models -- Research Perturbation (Mathematics) Attractors (Mathematics) Baire classes Mathematics -- Research
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5404 , http://hdl.handle.net/10962/d1005218
  • Description: The topological dynamics of continuous and noncontinuous dynamical systems are investigated. Various definitions of chaos are studied, as well as notions of stability. Results are obtained on asymptotically stable sets and the perturbation stability of such sets. The primary focus is on the traditional point sets of topological dynamics, including the chain recurrent set, omega-limit sets and attractors. The basic setting is that of a continuous function on a compact metric space, sometimes with additional properties on the space. The investigation includes results on the dynamical properties of typical continuous functions in the sense of Baire category. Results are also developed concerning dynamical systems involving quasi-continuous functions. An invariance property for the omega-limit sets of such functions is given. Omega-limit sets are characterized for Riemann integrable derivatives and derivatiyes which are continuous almost everywhere. Techniques used in the investigation and formulation of results include finding theorems which relate the rather disparate notions of dynamical properties and generalized continuity. In addition to dynamical systems, numerous other applications of generalized continuity are imoestigated. Techniques used include application of the Baire Category Theorem and the notion of semi-closure. For example, results are formulated concerning functions determined by dense sets, including separately continuous functions, thus generalizing the classical result for continuous functions on dense subsets of the domain. The uniform boundedness theorem is extended to functions which are not necessarily continuous, including various derivatives. The closed graph theorem is strictly generalized in two separate ways, and applications are presented using these generalizations. An invariance property of separately continuous functions is given. Cluster sets are studied in connection with separate continuity, and various results are presented concerning locally bounded functions.
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  • Date Issued: 2002

Detection of neurotransmitters using metallophthalocyanines as electrocatalysts

  • Authors: Oni, Joshua Idowu
  • Date: 2002
  • Subjects: Neurotransmitters Electrochemistry
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4435 , http://hdl.handle.net/10962/d1007470
  • Description: Some metallophthalocyanine complexes were synthesized and their catalytic activities towards the detection and quantification of the neurotransmitters dopamine, serotonin and histamine were investigated. The study of the possible interaction between these transmitter substances and the metallophthalocyanine complexes was undertaken. Dopamine, serotonin and histamine formed complexes with Iron (II) tetrasulfophthalocyanine. The rate and equilibrium constants obtained for the coordination are in the range of values reported in the literature for ligand coordination to iron phthalocyanine complexes. Carbon paste electrodes of millimetric diameters modified with Iron (II) tetrasulfophthalocyanine exhibited good electro catalytic activity towards the detection and analysis of dopamine and serotonin while at the same time eliminated the problem of interference posed by ascorbic acid in the electrochemical analysis of neurotransmitters. A detection limit of the order of 10-6 mol dm-3 was obtained for both dopamine and serotonin at the modified electrodes. Carbon paste ultra micro electrodes modified with iron (II) tetrasulfophthalocyanine were also used for the detection of dopamine and serotonin as well as the simultaneous determination of dopamine and ascorbic acid in a mixture. The detection limit obtained for dopamine at the ultra microelectrode was 4.2xlO-7 mol dm-3 The electrode kinetics of vitamin BI as well as the stability of the electrode towards its determination was improved upon by modifying carbon paste electrodes with manganese phthalocyanine. The modified electrodes were used for the analysis of vitamin BI in tablets.
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  • Date Issued: 2002

Dynamics of early stage fishes associated with selected warm temperate estuaries in South Africa

  • Authors: Strydom, Nadine Amelia
  • Date: 2002
  • Subjects: Estuarine fishes -- South Africa Fishes -- Infancy -- South Africa Estuarine ecology -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5262 , http://hdl.handle.net/10962/d1005106
  • Description: Early stage fishes, namely larvae and early juveniles, were collected from 12 estuaries and associated habitats in the warm temperate region of South Africa between July 1998 and December 2000. This study served to provide new information and expand on existing knowledge of early stage fish assemblages associated with various types of Eastern Cape estuaries. A total of 65 536 predominantly postflexion fish larvae were collected. Together with early juveniles, taxa comprised 72 species from 25 teleost fish families. Surf zones associated with two intermittently open estuaries showed that estuary-dependent marine species predominated in this zone. Early stage fishes responded positively during natural estuary opening events and concentrated along the estuary outflow plume, suggesting that cueing from estuary and/or river water may be taking place. A habitat study in the Swartkops Estuary, using light traps, showed that newly recruited larval fishes concentrated along the margins of the estuary and unlike their older juvenile counterparts, were poorly represented in eelgrass beds. A multi-estuary comparison, including seven permanently open and five intermittently open estuaries, indicated that early stage fish assemblages were more diverse than indicated by past investigations. Early stage fishes were also shown to concentrate in the mesohaline regions of these estuaries. Studies of estuaries with altered freshwater flow regimes were also included in the research. A regulated release of dam water in the euhaline Kromme Estuary failed to induce a cueing response from estuary-dependent marine fish larvae. This project showed that large amounts of freshwater are required to reverse the negative effects of river impoundments. The release study did show that estuary-resident fishes were sensitive to small natural pulses of freshwater and responded by spawning. However, excessive river supply through an inter-basin water transfer scheme was shown to have a flushing effect on the larvae and early juveniles of the estuary-resident Gilchristella aestuaria in the upper reaches of the Great Fish Estuary. This effect was evident in comparisons with the freshwater starved Kariega Estuary where concentrations of G. aestuaria, a species usually more abundant in freshwater rich estuaries, were considerably higher. This finding suggests that freshwater minima and maxima be considered when assessing and managing estuarine systems.
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  • Date Issued: 2002

Effects of Axial Ligands on the Photosensitising Properties of Silicon Octaphenoxyphthalocyanines

  • Authors: Maree, Machiel David
  • Date: 2002
  • Subjects: Ligands , Photochemotherapy , Phthalocyanines
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4553 , http://hdl.handle.net/10962/d1018246
  • Description: Various axially substituted Silicon octaphenoxyphthalocyanines were synthesised as potential photosensitisers in the photodynamic therapy of cancer. Conventional reflux reactions were used for synthesis as well as new microwave irradiation reactions, wherein the reaction times were decreased tenfold with a marginal increase in reaction yield and product purity. An interesting series of oligomeric (dimer to a nonamer) silicon octaphenoxyphthalocyanines were also successfully synthesised in a reaction similar to polymerisation reactions. These compounds were found to undergo an axial ligand transformation upon irradiation with red light (> 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.
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  • Date Issued: 2002

Effects of substituents on the photosensitizing and electrocatalytic properties of phthalocyanines

  • Authors: Maree, Suzanne Elizabeth
  • Date: 2002
  • Subjects: Phthalocyanines
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4554 , http://hdl.handle.net/10962/d1018247
  • Description: In this work a selection of octasubstituted phthalocyaninato Zinc, Ge(IV) and Sn(IV) complexes were synthesized for possible use in photodynamic therapy and their photochemistry, photophysics and electrochemistry studied. Third-generation complexes containing steroids, e.g. cholesterol and estrone, were synthesized to improve tumour selectivity. The zinc phthalocyanine complexes (ZnPc) showed that complexes containing electron-donating groups have higher photostability. Germanium phthalocyanine complexes (GePc) undergo phototransformation rather than direct photobleaching and the tin phthalocyanine complexes (SnPc) undergo photobleaching mediated by photoreduction of the phthalocyanine ring. Singlet oxygen production showed increased in the following order: GePc>SnPc>ZnPc. Triplet lifetimes of the GePc (168-340μs) are very similar to that of the ZnPc (197 - 366μs), but the triplet lifetimes of the SnPc are ten fold shorter (10 - 32μs ). Triplet quantum yields are higher for the GePc (0.20 - 0.50) and SnPc (0.08 - 0.45) than for the ZnPc (0.02 - 0.25). Fluorescence lifetimes of GePc ( 4.0 - 5.1 ns) are significantly longer than that of ZnPc (1.9 - 3.0 ns) and SnPc (0.2 - 0.4 ns). Fluorescence quantum yields decrease in the following order: GePc(0.21-0.31)>ZnPc(0.02-0.21)>SnPc(0.02- 0.06). Ring-substituted cobalt phthalocyanine complexes of the form CoPc(R)4 (R= NH2, N02, C(CH3)3, S03H and COOH) are compared for their catalytic activities towards the oxidation of cysteine. The potential for the electrocatalytic oxidation of cysteine is closely related to the Com/Co11 couple of the CoPc(R)4 complexes in acidic media and to the Con/Co1 couple in basic media. The catalytic current and the oxidation potential for cysteine are dependent on the pH of the solution, the potential becoming less positive and the currents increasing with increase in pH.
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  • Date Issued: 2002
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