'n Interdissiplinêre benadering tot die klasmusiekonderwys in Suid-Afrika
- Authors: Hendrikse, Salóme
- Date: 1993
- Subjects: School music -- Instruction and study -- South Africa Music -- Instruction and study -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2640 , http://hdl.handle.net/10962/d1002305
- Description: In hierdie tesis word 'n nuwe benadering tot klasmusiekonderwys in die R.S.A. bespreek. Die navorsing vervat in die tesis is vanaf 1984 tot 1992 gedoen. In 'n sekere sin verklaar die aanvangsdatum van die navorsing die feit dat die projek veral gerig is op die blanke onderwyssituasie aangesien die verskillende groepe se onderwysbelange volgens amptelike beleid grotendeels deur verskillende onderwysowerhede behartig is. Die blanke onderwysgerigtheid van die navorsingsontwerp ten spyt, is die uitgangspunte en die bevindings van die studie, veral ten opsigte van die rol en funksie van musiekopvoeding, sonder twyfel van toepassing op al die Suid-Afrikaanse gemeenskappe. In die opsig behoort die bevindings van die studie dus tot 'n groot mate ook die eise van musiekopvoeding veral vir 'n toekomsgerigte onderwys te kan ondervang juis omdat die vertrekpunt van die voorgestelde vemuwings en aanpassings in die musiekopvoeding die waardes en norme van gemeenskappe moet identiflseer en vertolk en terselfdertyd die beperkende effek daarvan moet teenwerk deur kulturele transenderings. Veral laasgenoemde is van groot belang in die multikulturele opset van die Suid-Afrikaanse gemeenskap waarin die musiekopvoeding juis 'n belangrike rol kan speel in die ontwikkeling van 'n onderlinge begrip en waardering tussen die verskillende kultuurgemeenskappe. In Afdeling A van die tesis word die huidige stand van klasmusiek bespreek en daar word op gewys dat, afgesien van 'n aantal sekondere faktore, die prirnere redes vir die nie-geslaagdheid van die vak, faktore soos die sillabusse, die opleiding van die onderwyser en die posisie van die vak in die kurrikulum is. Teenoor die huidige benadering van klasmusiek met al sy probleme word 'n ander benadering tot die onderwys in die a!gemeen en die klasmusiek in die besonder gestel, naamlik die interdissiplinere benadering met sy twee afdelings, naamlik die geesteswetenskappe en die kunstebenadering. Hierdie benaderings word bespreek soos wat dit in die V.SA. en Europa toegepas word, en daarna word 'n aangepaste benadering vir die R.S.A. ontwikkel ten opsigte van doelstellings,uitgangspunte, riglyne, metodiek en tegniek. In Afdeling B volg die empiriese navorsing wat ten opsigte van die interdissiplinere benadering in die R.S.A. gedoen is, en drie lesreekse, soos beplan vir Standerd 6 en 7; Standerd 8 en vir Standerd 9 en 10 word bespreek. As deel van elke lesreeks word die wordingstand van elke ouderdomsgroep bespreek en in gedagte gehou by die saamstel van hierdie lesreekse. Elke lesreeks bestaan uit 3-4 volledig uitgewerkte lesse wat insluit: hulpmiddels (kunsvoorbeelde, musiekvoorbeelde, gedigvoorbeelde ensomeer), beknopte aantekeninge vir die onderwyser, 'n bronnelys en 'n klankkasset met die nodige klankillustrasies soos waarna in die lesse verwys word. In Afdeling C word die resultate van 'n steekproef bespreek wat gedoen is in verskeie skole in die vier provinsies van die R.S.A. Met hierdie steekproef is beoog om die reaksies van leerlinge en onderwysers te toets ten opsigte van hierdie nuwe voorgestelde, en aangepaste interdissiplinêre benadering. Die lesreekse wat deel vorm van Afdeling B is as basis deur die onderwysers gebruik, maar hul was vry om eie idees te ontwikkel en te gebruik. Die reaksies van die leerlinge en die onderwysers word in die vorm van tabelle en besprekiogs aangedui, en aanbevelings van die leerlinge en die onderwysers word aangetoon. Die tesis word afgesluit met addendums tot die verskillende hoofstukke asook volledige bibliografiese besonderhede.
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- Date Issued: 1993
'n Perspektief op kommunikasie in 'n post-apartheidsera in Suid-Afrika met spesifieke verwysing na die rol van Afrikaans
- Authors: Van Rensburg, Nicolaas Gerhardus Lourens
- Date: 1993
- Subjects: Afrikaans language South Africa Languages
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3575 , http://hdl.handle.net/10962/d1002099
- Description: Chapter One is an historical review of the rejection of colonial domination in various states in Africa, before the spotlight was directed at the relationships between the "white" and "black" inhabitants of South Africa. The numerous problems which arise out of this inter-relationship can best be ascribed to the identity crisis which "white" and "black" experience in a multi-lingual country. The South African society needs to normalise its relations with cultural and language groups by means of communication. Chapter Two reviews the historical background, linguistic characteristics, the use, functions and the distribution of the ten most important languages of which the South African community consists. The diversity of these languages generates and complicates the debate which currently prevails concerning a language policy for a future non-racial South Africa. The geographical, social, historical and cultural factors which are conducive and non-conducive to language distribution are high-lighted in Chapter Three. In a changing South Africa, where affirmative actions are being insisted on, it is expected that the current privileged position of Afrikaans will be placed under political pressure. A painful process of self-examination by Afrikaans-speaking Afrikaners - one of the major role-players in the current controversy concerning the continued existence and status of Afrikaans in a "postApartheid era" - has been precipitated. Chapter Four looks at how the "white", "coloured", "black" and "Indian" Afrikaans-speaking Afrikaners' mother tongue has evolved to its present status. The arguments for and against, viewpoints of, and pleas for the re-unification of Afrikaans-speaking Afrikaners to a larger single power base is emphasized. The possible future status and functions of Afrikaans insofar as its present status, functions and attitudes are concerned, are extrapolated in Chapter Five. The viewpoint concerning a possible scenario for the above-mentioned matters as expressed by a wide spectrum of South African society - academics, cultural groupings, political leaders, non-mother-tongue speakers of Afrikaans - is evaluated. A scenario of the possible role of Afrikaans in a "post-Apartheid era" in South Africa is sketched in Chapter 6. The conclusion is that the Western culture as understood by the black man, differs in more than one way from the perception of the white man. First and foremost, the acceptance of and respect for the languages and cultures of all fellow South Africans is the first step towards seeing all South Africans as being Africans. , Opsomming: Hoofstuk Een is 'n historiese oorsig van hoe die verwerping van koloniale oorheersing elders in Afrika diekontaken verhouding tussen die "wit" en "swart" inwoners van Suid-Afrika onder die soeklig geplaas het. Die talle probleme wat uit die kontaksituasie spruit, kan gereduseer word tot die identiteitskrisis wat "wit" en "swart" in 'n multitalige land beleef. Die Suid-Afrikaanse gemeenskap het In dringende behoefte aan die normalisering van die verhoudings, vera! deur middel van kommunikasie, tussen die kulturele- en taleverskeidenheid. In Hoofstuk Twee word daar gekyk na die historiese agtergrond, linguistiese eienskappe, gebruik en funksies en die verspreiding van die tien vemaamste tale waaruit die Suid-Afrikaanse talegemeenskap bestaan. Die diversiteit van tale genereer en kompliseer die debat wat tans oor 'n taalbeleid vir 'n toekomstige nierassige Suid-Afrika gevoer word. Die geografiese, sosiale, historiese en kulturele faktore wat taalverspreiding bevorderof teenwerk, word in Hoofstuk Drie belig. In 'n veranderende Suid-Afrika, waar op regstellende aksies aangedring word, kan daar verwag word dat Afrikaans as gevolg van sy bevoorregte posisie onder politieke druk geplaas sal word. Vir die Afrikaanssprekende Afrikaners, as een van die hoofrolspelers in die polemiek oor die voortbestaan en status van Afrikaans in 'n "post-Apartheidsera", het dit 'n pynlike proses van selfondersoek gebring. In Hoofstuk Vier word daar gekyk hoe die "blanke", "anderskleurige", "swart" en "Asiatiese" Afrikaanssprekende Afrikaner sy moedertaal tot op hede ervaar het. Die argumente vir en teen, sienings van, en pleidooie vir 'n hereniging van Afrikaanssprekende Afrikaners tot 'n groter mags basis word belig. Die moontlike toekomstige status en funksies van Afrikaans word in Hoofstuk Vyfvanuit die huidige status, funksies en houdings geprojekteer. Die standpunte oor bogenoemde sake word vanuit 'n wye spektmm van akademici, kultuurgroeperinge, politieke leiers sowel as niemoedertaal-sprekers van Afrikaans van die talegemeenskap van die RSA op 'n moontlike scenario gefokus. ii 'n Scenario -oefening van die moontlike rol van Afrikaans in 'n "post-Apartheidsera" in Suid-Afrika word in Hoofstuk Ses geskets. Daar word tot die gevolgtrekking geraak. dat die Westerse kultuur, soos verinnerlik deur die swart man, in belangrike opsigte van die van die wit man verskil. Daarom is die aanvaarding van en respek vir aIle Afrikane as mede-Suid-Afrikaners die eerste stap om te verseker dat die Afrikaanssprekende Afrikaners se taal en kultuur gerespekteer sal word.
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- Date Issued: 1993
A comparative study of the life histories of the sister species, Pseudobarbus afer and Pseudobarbus asper, in the Gamtoos River system, South Africa
- Authors: Cambray, James Alfred
- Date: 1993
- Subjects: Barbus -- Life cycles , Barbus -- Ecology -- South Africa -- Gamtoos River , Cyprinidae -- Life cycles , Cyprinidae -- Ecology -- South Africa -- Gamtoos River , Minnows -- Life cycles , Minnows -- Ecology -- South Africa -- Gamtoos River
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5375 , http://hdl.handle.net/10962/d1015730
- Description: This thesis explores the biology, ecology, and life-history styles of two closely-related redfin minnows, Pseudobarbus afer and P. asper (pisces; Cyprinidae), which both occur in the Gamtoos River system of South Africa. Five of the seven species of flexible-rayed redfin minnows are in the South African Red Data Book - Fishes. This investigation was designed to provide the data which would enable conservation authorities to manage the remaining populations of the Pseudobarbus species. A thorough understanding of the Gamtoos River system was necessary to properly interpret the findings of this study. The palaeo river systems and the changing climates since the break-up of Gondwanaland are discussed so that the present day environments could be considered as well as the past environmental changes. P. afer and P. asper occur in the Gamtoos River system with no physical barrier separating the two species. P. afer only occurs in the clear mountain streams of the Cape Fold Mountain Belt whereas P. asper occurs in the highly saline and turbid Karoo section of the system. P. afer were found to be the more precocial form of the sister species. They had bigger eggs, lower relative fecundity, shorter breeding season, lower gonadosomatic indices, larger first feeding larval fish, matured later and had a longer life-span than did P. asper, which had more altricial life-history attributes. They differ in their tradeoffs with P. asper devoting more resources earlier to reproduction and having a shorter lifespan. The improvement in the one aspect of fitness (early maturity) leads to the deterioration in another, namely lifespan. Both species undertake breeding migrations to riffle areas where they spawn in mid-channel immediately above a pool after an increase in water flow. P. afer and P. asper are non-guarders of their non-adhesive eggs and young, open substrate spawners on coarse substrates (rocks) and have photophobic free embryos. The breeding season is shorter for P. afer whereas P. asper can spawn as late as April and impoundment releases can induce them to spawn. A study of comparative neuroecology revealed that of the four groups of fish analyzed (males and females of both species) male P. afer had the largest brains, especially the optic lobes and cerebellum. P. asper females had the smallest brains. No neural compensation in the external gustatory centre, the facial lobe, was found for P. asper inhabiting the turbid waters. P. afer also had significantly larger eyes and longer barbels. P. afer males were also found to have the highest density and largest nuptial tubercles as well as the most pronounced breeding colouration. It was concluded that P. asper is the more derived of the sister species pair with regard to life-history attributes. It is further suggested that investment per offspring is important in determining the life-history trajectories. Paedomorphosis has occurred and by this mechanism variability has been restored to the redfin minnows in the Groot River which enables them to survive in the highly variable, intermittent Karoo stream. The more precocial P. afer do not require this variability in the more constant and predictable environment of the Wit River.
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- Date Issued: 1993
A new approach to the Zulu land tenure system: an historical anthropological explanation of the development of an informal settlement
- Authors: Fourie, Clarissa Dorothy
- Date: 1993
- Subjects: Land tenure -- South Africa -- Kwazulu Kwazulu (South Africa) -- Economic conditions Zulu (African people) -- Social conditions Kwazulu (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2098 , http://hdl.handle.net/10962/d1002661
- Description: Mgaga, an informal settlement in KwaZulu, south of Durban, on Cele-Zulu polity land, had an indigenous, albeit urban, system of Zulu land tenure in 1980. Mgaga's transformation, from an area with scattered homesteads in 1959 to an informal settlement, was linked to local and external factors. The external factors were, regional industrialisation, urbanisation and apartheid policies which involved, the division of South Africa into ethnically based 'homelands'; controlled Black access to 'White' cities; an urban management system for 'homeland' townships, like Umlazi township which abutted Mgaga. Umlazi's development and urban management system involved, the resettlement of members of the polity; the removal of their office bearers from their posts; and the phased building of the township; which caused cumulative effects in Mgaga. I link these external factors to the behaviour of Mgaga's residents, who transformed the area's land tenure system, by using Comaroff's dialectical model (1982), where the internal dialectic interacts with external factors to shape behaviour at the local level. I analyze the Zulu ethnography to show that the internal dialectic in Zulu social organisation, and in Mgaga, is centred around fission and integration; and that the integrating hierarchy associated with Zulu social organisation and the Zulu land tenure system is composed of groups with opposed interests in the same land. Within this hierarchy entrepreneurship and coalition formation influence the transfer of land rights. Also, rather than rules determining the transfer of land in the land tenure system, processes associated with the interaction of external factors with the internal dialectic, within terms of the cultural repertoire associated with the system, shape local behaviour; and the system's rules are manipulated within this cultural repertoire by individuals striving for gain. This results in different manifestations of the internal dialectic in the Zulu land tenure system, i.e. a range of variations in the Zulu land tenure system, including different local level kinship groups; a variety of terminology and rights held by office bearers; and communal and individualised land rights. The external factor of urbanisation interacted with the internal dialectic in Mgaga, manifested in terms of an ongoing izigodi (wards) dispute -including its boundaries, to shape residents' behaviour, so that some introduced an informal settlement and others resisted its geographical spread. This informal settlement development, where eventually purely residential land rights were transferred for cash to strangers by strangers, with no role for polity officials, was an urban variation of the Zulu land tenure system, because of the continued existence of the internal dialectic in Zulu social organisation in the local system, with the integration side being expressed by the community overrights. Characteristics found in Mgaga, such as kinship diminution; the individualisation and sale of land rights; and the ongoing influence of polities; are found elsewhere in Africa where informal settlements have developed on indigenous land tenure systems. Therefore the transformation of Mgaga's land tenure system to urban forms is not an isolated phenomenon, and my dialectical ransactional approach may have an applicability beyond the context of the Zulu land tenure system.
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- Date Issued: 1993
A phenomenological investigation into the psychoanalytic psychotherapist's experience of identifying, differentiating and processing the patient's transference-based and reality-oriented reactions
- Authors: Danilewitz, Larry Mark
- Date: 1993
- Subjects: Reality therapy Transference (Psychology) -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2960 , http://hdl.handle.net/10962/d1002469
- Description: The aim of this study was to describe the psychoanalytically-oriented therapist's experience of identifying, differentiating and processing the patient's transference-based and reality-oriented reactions. In order to investigate the therapist's lived experience of being receptive to the total communication of the patient in the analytic situation, the researcher adopted the empirical phenomenological method. This descriptive and intuitive method grounded the researcher in the concreteness of the everyday life-world of the therapist, and enabled him to explicate the therapist's immediate, pre-theoretical experiences of his patient. The appropriate central research question, formulated to elicit the experience of this phenomenon, emerged through the process of enquiry during the pilot study. Thirteen experienced, psychoanalytically-oriented psychotherapists were interviewed and the five protocols considered most revelatory of the phenomenon under investigation were analyzed in detail. The remaining eight protocols were used to illuminate central themes and to clarify areas of uncertainty during the phase of formal explication. The central findings revealed that the oscillating process of the therapist as he shifts from being immersed in the world of his patient to being in a position of observation and self reflection is the fulcrum around which he evaluates the nature of his patient's communications. During this ongoing process of discrimination, living in duality, the therapist comes to experience himself as a patient scrutinized by his own and his patient's confrontations. His journey of disentanglement, the endeavour to differentiate his responses from his patient's actions, is dependent on his ability to engage in honest selfreflection and to access his pre-theoretical and articulated cognitions of his patient. This allows him to acknowledge his own role in what has unfolded interpersonally and to appropriate his previously denied feelings for and attitudes towards his patient, a prerequisite for the accurate and full appraisal of the nature of his patient's communications. Forsaking fixed judgements, the therapist becomes open to the confluence between the reality-oriented responses and transference-based reactions of his patient. This salient discovery, when dialogued with the literature, reinforced the theories of Greenson and Langs that not all the interactions between the patient and the analyst/therapist are transference-based and that it is therefore imperative that the analyst/therapist reflect on his participation in the analytic situation.
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- Date Issued: 1993
Aspects of the symplectic and metric geometry of classical and quantum physics
- Authors: Russell, Neil Eric
- Date: 1993
- Subjects: Symplectic manifolds Geometry, Differential Geometric quantization Quantum theory Clifford algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5452 , http://hdl.handle.net/10962/d1005237
- Description: I investigate some algebras and calculi naturally associated with the symplectic and metric Clifford algebras. In particular, I reformulate the well known Lepage decomposition for the symplectic exterior algebra in geometrical form and present some new results relating to the simple subspaces of the decomposition. I then present an analogous decomposition for the symmetric exterior algebra with a metric. Finally, I extend this symmetric exterior algebra into a new calculus for the symmetric differential forms on a pseudo-Riemannian manifold. The importance of this calculus lies in its potential for the description of bosonic systems in Quantum Theory.
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- Date Issued: 1993
Bioaccumulation of metal cations by yeast and yeast cell components
- Authors: Brady, Dean
- Date: 1993
- Subjects: Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4046 , http://hdl.handle.net/10962/d1004107 , Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Description: The aim of the project was to determine whether a by-product of industrial fermentations, Saccharomyces cerevisiae, could be utilized to bioaccumulate heavy metal cations and to partially define the mechanism of accumulation. S. cerevisiae cells were found to be capable of accumulating Cu²⁺in a manner that was proportional to the external Cu²⁺ concentration and inversely proportional to the concentration of biomass. The accumulation process was only minimally affected by temperature variations between 5 and 40°C or high ambient concentrations of sodium chloride. The accumulation process was however considerably affected by variations in pH, bioaccumulation being most efficient at pH 5 - 9 but becoming rapidly less so at either extreme of pH. Selection for copper resistant or tolerant yeast diminished the yeast's capacity for Cu²⁺ accumulation. For this and other reasons the development of heavy metal tolerance in yeasts was deemed to be generally counterproductive to heavy metal bioaccumulation. The yeast biomass was also capable of accumulating other heavy metal cations such as c0²⁺ or Cd²⁺. The yeast biomass could be harvested after bioaccumulation by tangential filtration methods, or alternatively could be packed into hollow fibre microfilter membrane cartridges and used as a fixed-bed bioaccumulator. By immobilizing the yeast in polyacrylamide gel and packing this material into columns, cu²⁺, C0²⁺ or Cd²⁺ could be removed from influent aqueous solutions yielding effluents with no detectable heavy metal, until breakthrough point was reached. This capacity was hypothesized to be a function of numerous "theoretical plates of equilibrium" within the column. The immobilized biomass could be eluted with EDTA and recycled for further bioaccumulation processes with minor loss of bioaccumulation capacity. Yeast cells were fractionated to permit identification of the major cell fractions and molecular components responsible for metal binding. Isolation of the yeast cell walls permitted investigation of their role in heavy metal accumulation. Although the amino groups of chitosan and proteins, the carboxyl groups of proteins, and the phosphate groups of phosphomannans were found to be efficient groups for the accumulation of copper, the less effective hydroxyl groups of the carbohydrate polymers (glucans and mannans) had a similar overall capacity for copper accumulation owing to their predominance in the yeast cell wall. The outer (protein-mannan) layer of the yeast cell wall was found to be a better Cu²⁺ chelator than the inner (chitinglucan) layer. It appeared that the physical condition of the cell wall may be more important than the individual macromolecular components of the cell wall in metal accumulation. It was apparent that the cell wall was the major, if not the sole contributor to heavy metal accumulation at low ambient heavy metal concentrations. At higher ambient metal concentrations the cytosol and vacuole become involved in bioaccumulation. Copper and other metals caused rapid loss of 70% of the intracellular potassium, implying permeation of the plasma membrane. This was followed by a slower "leakage" of magnesium from the vacuole which paralleled Cu²⁺ accumulation, suggesting that it may represent some form of ion-exchange. An intracellular copper chelating agent of approximately 2 kDalton molecular mass was isolated from copper tolerant yeast. This chelator was not a metallothionein and bound relatively low molar equivalents of copper compared to those reported for metallothionein. Treatment of the biomass with hot alkali yielded two biosorbents, one soluble (which could be used as a heavy metal flocculent), and an insoluble biosorbent which could be formed into a granular product to be used in fixed-bed biosorption columns. The granular biosorbent could accumulate a wide range of heavy metal cations in a semispecific manner and could be stored in a dehydrated form indefinitely, and rehydrated when required. Bioaccumulation by live algae was investigated as an alternative to yeast based processes. Various strains of algae, of which Scenedesmus and Selenastrum were the most effective, were found to be capable of accumulating heavy metals such as Cu²⁺, Pb²⁺ and Cr³⁺.
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- Date Issued: 1993
Coastal dune ecology and management in the Eastern Cape
- Authors: Avis, Anthony Mark
- Date: 1993
- Subjects: Sand dune ecology -- South Africa Shore protection -- South Africa Coastal zone management -- South Africa Sand dunes -- South Africa Sand dune plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4185 , http://hdl.handle.net/10962/d1003753
- Description: The importance of understanding the ecological functioning of coastal dune systems is emphasized as being fundamental to the correct management of the dune landscape. Dune vegetation along the Eastern Cape coastline, from Cape St Francis in the west to Kei Mouth in the east was described in terms of the distribution and phytochorological affinities of the taxa. At a regional scale species distribution was strongly influenced by both the climate, particularly rainfall, and the phytochorological affinities of the taxa. Seven communities were defined using TWINSPAN, and the interrelationships between these communities in anyone area appeared to be linked to a successional gradient. Dune Slacks are thought to play a key role in this successional sequence, and a temporal study of this community led to a conceptual model of plant succession in these dunefields. Climate, particularly rainfall and wind, are major factors influencing plant succession. Wind-borne sand causes the slacks to migrate in an easterly direction under the influence of the predominantly westerly winds, although easterly winds, mainly in summer months may reverse these trends. Autogenic changes appeared to be important in this succession, and a comparative study of a good example of a primary succession at Mtunzini in Natal was undertaken to elucidate the main mechanism of change. Eight communities that were identified here were concluded to be distnbuted along a gradient of increasing age, with successional changes predictable, linear and directional. Species were grouped in distinct zones along the continuum and edaphic changes (decrease in soil pH, increase in organic matter and exchangeable bases) were related to the community based changes in species composition. The mechanism of change supported the facilitation model of plant succession which is a modification of the original Clementsian concept. Similar results were found in the Eastern Cape, but due to the harsh environment, multiple pathways of succession exist. Data from this study lent support to the model of plant succession developed earlier, and confinned that the dune slacks played an important role in this facilitation by acting as centres of diversity. The foredunes were found to have an indirect role in protecting these slacks from salt spray and sand movement. The central theme of the management studies was to investigate the ecological consequences of recreational pressure within the dune environment. Current levels of beach utilization at East London were lower than other beaches in South Africa, but a general trend of increasing utilization due to sociopolitical changes can be expected. The suitability of questionnaire surveys to assess aspects such as the adequacy of facilities, perceptual carrying capacity and the beach users opinion of natural vegetation and preference for particular beaches was demonstrated. The dune vegetation was found to be sensitive to human trampling, but at current levels, the ecological carrying capacity will not be exceeded since results of the aerial census counts and questionnaire survey revealed that few people entered sensitive zones such as the coastal forest. More detailed long term studies on the susceptibility of dune vegetation to both trampling and off-road vehicle impacts revealed a low resilience of dune plant communities to these effects. Although susceptibility differed between the three communities tested, generally the greatest amount of damage occurred after the first few passages, and vehicles caused a more significant decrease in height when compared to trampling. Recovery rates were slow and low levels of repeated damage were sufficient to retard or prevent the recovery of the plants. Stricter control of vehicle use on beaches is therefore required, and in high use zones the ecological carrying capacity should be increased by providing access tracks if possible, or if not possible, by restricting access. A historical account of the process of dune stabilization showed that although first initiated in 1845, indigenous species were only used in the past three decades. The use of alien species has resulted in problems such as a reduction in the ecological integrity and aesthetic appeal of coastal systems. The techniques applied in the stabilization of drift sands with indigenous vegetation have been successful, as revealed by a quantitative survey of 17 sites in the Eastern Cape. Sites were grouped by multivariate analysis on the basis of their species composition, and variability between sites was dependent on the types of species planted. Selection of suitable species is therefore important and is discussed with respect to their natural distribution along the coast. The long term objective of stabilization should be the creation of functional, diverse, aesthetic ecosystems, since the intrinsic and economic value of the dune landscape for tourism lies therein. However, detailed studies should be undertaken prior to implementing a manipulative process such as dune stabilization, since ecological processes may be disrupted. An understanding of such processes is therefore important if one wishes to effectively manage the dune landscape.
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- Date Issued: 1993
Contemporary pollen spectra from the Natal Drakensberg and their relation to associated vegetation communities
- Authors: Hill, Trevor Raymond
- Date: 1993
- Subjects: Pollen -- South Africa -- KwaZulu-Natal Palynology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4199 , http://hdl.handle.net/10962/d1003768
- Description: The research focuses on the contemporary pollen rain-vegetation relationship for vegetation communities within the Natal Drakensberg, a region which is recognized as having the potential for extensive palynological investigations. The objective was to investigate the fundamental assumption underlying palynology, viz: that the pollen rain of a particular region is indicative or representative of the existing vegetation of that region. If the modern pollen rain is indicative of and/or distinctive for a particular vegetation community then the principle of methodological uniformitarianism can be applied, which states that the present day patterns and relationships can provide a factual basis for the reconstruction of the past through the extrapolation of modern analogues backwards in time. A vegetation survey was conducted in thirteen communities identified as pertinent to the research and a two-year modern pollen rain sampling programme was carried out, using both surface soil and pollen trap samples as a means of recording and quantifying the pollen rain. Once the necessary sample preparation and pollen counts had been performed, descriptive and numerical/statistical methods were employed to determine and describe the existing pollen-vegetation relationship. Descriptive analysis of the data sets was carried out with the aid of spectra depicted as rotated bar graphs and representing the relative percentage frequencies of the collected/counted taxa. Annual and seasonal pollen influx values were calculated and presented. Analysis of variance was applied to test various hypotheses related to sampling strategy and pollen influx variation. Statistical methods employed were two-way indicator species analysis (a classification analysis technique), detrended correspondence analysis and principal components analysis (ordination techniques), canonical correlation analysis (for data set association) and multiple discriminant analysis (for determination of vegetation zonal indices). The latter technique allowed for the probability of modern analogues to be assessed which are necessary for accurate interpretation of fossil pollen assemblages if the assumption under investigation is correct. The findings of the study were that the modern pollen rain-vegetation assumption holds true. Recommendations are put forward regarding future contemporary pollen studies with regards to the number of soil and pollen trap samples required, the magnitude of the pollen count and the numerical/statistical techniques most appropriate to clearly interpret the results. The conclusions are that future fossil pollen spectra can be expected to provide a good indication of former regional vegetation patterns for the study region. The study has extended the limited understanding of the contemporary pollen rain-vegetation relationship in South Africa and enables the interpretation of fossil pollen spectra to be carried out with greater confidence. This in turn lends greater credibility to possible Quaternary environmental change models required to help understand present and possible future environmental change.
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- Date Issued: 1993
Data reduction techniques for Very Long Baseline Interferometric spectropolarimetry
- Authors: Kemball, Athol James
- Date: 1993
- Subjects: Very long baseline interferometry Radio interferometers Data reduction -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5457 , http://hdl.handle.net/10962/d1005242
- Description: This thesis reports the results of an investigation into techniques for the calibration and imaging of spectral line polarization observations in Very Long Baseline Interferometry (VLBI). A review is given of the instrumental and propagation effects which need to be removed in the course of calibrating such obervations, with particular reference to their polarization dependence. The removal of amplitude and phase errors and the determination of the instrumental feed response is described. The polarization imaging of such data is discussed with particular reference to the case of poorly sampled cross-polarization data. The software implementation of the algorithms within the Astronomical Image Processing System (AlPS) is discussed and the specific case of spectral line polarization reduction for data observed using the MK3 VLBI system is considered in detail. VLBI observations at two separate epochs of the 1612 MHz OH masers towards the source IRC+ 10420 are reduced as part of this work. Spectral line polarization maps of the source structure are presented, including a discussion of source morphology and variability. The source is sigmficantly circularly polarized at VLBI resolution, but does not display appreciable linear polarization. A proper motion study of the circumstellar envelope is presented, which supports an ellipsoidal kinematic model with anisotropic radial outflow. Kinematic modelling of the measured proper motions suggests a distance to the source of ~ 3 kpc. The cirumstellar magnetic field strength in the masing regions is determined as 1-3 mG, assuming Zeeman splitting as the polarization mechanism.
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- Date Issued: 1993
Ecology and natural history of the Masarid wasps of the world with an assessment of their role as pollinators in southern Africa (Hymenoptera : Vespoidea : Masaridae)
- Authors: Gess, Sarah Kathleen
- Date: 1993
- Subjects: Wasps -- Ecology Pollen wasps -- Ecology Vespidae -- Ecology Pollination by insects -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5669 , http://hdl.handle.net/10962/d1005354
- Description: The worldwide knowledge of the ecology and natural history of the masarid wasps, those wasps which bee-like provision their nest cells with pollen and nectar, is synthesized and discussed putting into context the investigations concerning nesting and flower visiting by southern African masarids conducted by the present author. Masarids are found mostly to favour warm to hot areas with relatively low rainfall and open scrubby vegetation. At the generic level the masarids of the Nearctic, Neotropical and Australian regions are distinct from each other and from those of the Palaearctic and Afrotropical regions combined. No species are shared between regions. Southern Africa is apparently the area of greatest species diversity. In this region, at least, there is a high incidence of narrow endemism. Masarids are associated with a relatively small range of plant families. Where sufficient records are available distinct major preferences are shown between zoogeographical regions. Relatedness of plant preferences between zoogeographical regions is apparent when relatedness of plant taxa is considered. Within a region there is marked overlap in masarid generic preferences for flower families. At the specific level there is marked oligolecty and narrow polylecty. The majority of nesting studies indicate that nest construction, egg laying and provisioning are performed by a single female per nest, however, nest sharing has been alledged for two species. No parasitic masarids have been recorded. Egg laying precedes provisioning. Mass provisioning is the rule. According to species, nests are sited in the ground, in non-friable soil or friable soil, in earthen vertical banks, on stones or on plants. Seven nest types are defined. Three bonding agents, water, nectar and self-generated silk are used. Masarids are evaluated as potential pollinators of their forage plants in southern Africa. The "masarid pollination syndrome", though less broad is shown to fall within that designated melittophily. The case studies considered make it clear that, whereas the masarids visiting some flower groups are members of a guild of potential pollinators, the masarids visiting others are probably their most important pollinators. Increasing land utilization is shown to threaten the existence of narrowly endmic masarid species.
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- Date Issued: 1993
Interactions between figs (Ficus spp., Moraceae) and fig wasps (Chalcidoidea, Agaonidae)
- Authors: Ware, Anthony Brian
- Date: 1993
- Subjects: Fig -- South Africa Fig wasp -- South Africa Pollination Agaonidae Chalcid wasps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5719 , http://hdl.handle.net/10962/d1005405
- Description: Fig trees (Ficus spp., Moraceae) and fig wasps (Chalcidoidea, Agaonidae) are uniquely associated. In one fig wasp group, the pollinators (Agaoninae), each species is generally host species-specific. The relationship is one of obligate mutualism where the wasps provide pollination services and in return utilises some of the ovules for larval development. Non-pollinating fig wasps (generally belonging to subfamilies other than the Agaoninae) may be gallers or parasitoids, and can also be host species-specific. In the accompanying studies we examined the factors governing the interactions between fig wasps and their host trees. Surveys of fig trees and their associated pollinating fig wasps conducted in southern Africa, Madagascar and The Comores generally confirmed their specific relationships. An examination of F. sycomorlls in Madagascar resulted in the reclassification of F. sakalavarum as a distinct species with its own specific pollinator species. Biological and chemical evidence is presented demonstrating that the pollinators were able to distinguish their hosts through volatiles which emanated from the figs when they were ready to be pollinated. Environmental factors were found to influence wasp behaviour. Ambient temperature governed the timing of wasp emergence from their natal figs. When dispersing from their natal figs, the fig wasps flew upwards and then were blown downwind. Once nearing trees bearing figs ready to be pollinated, the wasps lost height and flew upwind towards the trees. E. baijnathi females apparently avoided figs which already contained a conspecific foundress. Scanning electron microscope studies of pollinating female fig wasp antennae showed that while all the species possessed multiporous plate sensilla, in only a few species were these sensilla elongated. Multiporous plate sensilla elongation is rare or absent among other female chalcids and may have evolved within the Agaoninae in order to facilitate their location on receptive host figs. Pollinator choice specificity appears to break down in a number of cases. In the first case examined, two pollinator species were recorded from the figs of African F. sycomorus. One. C. arabicus, pollinates the figs while the other, C. galili, acts as a 'cuckoo' by utilising some of ovules for oviposition without providing pollen. In the second case three pollinating fig wasp species were recorded from the rigs of F. lutea. Two were found to be incidental visitors and were not specifically attracted to the tree. The hybrid seeds from these crosses were successfully germinated but the seedlings did not grow passed the cotyledon stage of their development. In the concluding study the consequences of Ficus phenology and the structure of the fig's unusual inflorescence on the nonpollinating fig wasp community were examined. Various factors affecting the population levels and species richness were also examined. Future possible research directions were discussed.
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- Date Issued: 1993
Prodigality, liberality and meanness in the parable of the prodigal son : Greco-Roman perspective on Luke 15:11-32
- Authors: Holgate, David A
- Date: 1993
- Subjects: Bible. Luke XV, 11-32 -- Criticism, interpretation, etc. , Prodigal son (Parable) , Ethics in the Bible
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1244 , http://hdl.handle.net/10962/d1009701
- Description: This dissertation consists of an interpretation of the Parable of the Prodigal Son (Luke 15: 11-32) from the perspective of Greco-Roman moral philosophy. It is divided into three parts. Part 1 traces the history of relating the New Testament to Greco-Roman literature and philosophy. Despite the importance of this perspective for the study of Luke-Acts, the relationship between Luke 15: 11-32 and Greco-Roman moral philosophy has not been investigated before. The legitimacy of this approach is demonstrated by a literary analysis of the parable, which demonstrates the formal emphasis placed upon the liberal and compassionate words and actions of the father. The strong moral orientation of the parable is further illustrated by the formal, linguistic and thematic features which it shares with the other L parables. Part 2 consists of a study of the Greco-Roman moral topos On Covetousness. The use of the Greco-Roman topos as a critical tool for the study of the New Testament is evaluated, the term is defined, and the influence of the topos On Covetousness upon representative works of moral philosophy is studied. This part ends with a summary of the characteristic features of the topos and its use by writers with differing philosophical affiliations. Part 3 reads the whole parable in terms of the topos On Covetousness,with the emphasis being placed on the relationship between the Lukan text and works of Greco-Roman moral philosophy. The parable is seen to be structured according to the influential Peripatetic doctrine of the mean, with the father representing the virtue of liberality, and his two sons the opposing vices of prodigality and meanness. The comparison with the topos reveals Luke's strong rejection of the two vices, and his endorsement of the Greco-Roman virtue of liberality, which is modified by his emphasis upon the Christian virtue of compassion. The approach affirms and demonstrates the internal unity of the parable and its close relationship to the Lukan theme of the correct use of possessions.
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- Date Issued: 1993
Seasonal changes in pituitary and plasma prolactin concentrations, and the role of Prolactin in the control of delayed implantation in female Miniopterus schreibersii
- Authors: Bojarski, Christina
- Date: 1993
- Subjects: Bats -- Reproduction Prolactin -- Research Pituitary hormones Zoology, Experimental
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5764 , http://hdl.handle.net/10962/d1005452
- Description: Mammotropes were successfully identified in the anterior pituitary gland of Miniopterus schreibersii using immunocytochemical (ICC) staining at the light and electron microscopy level. Mammotropes were distributed throughout the gland, were polygonal in shape and during secretory activity contained numerous large secretory granules (350 - 800nm). Using double ICC labelling, prolactin and growth hormone were never co-localiszed and found in individual cells only. Plasma prolactin levels were successfully measured on a monthly basis using radioimmunoassay and monthly pituitary prolactin levels were quantified using morphometric analysis of immunogold ICC staining and densitometry with polyacrylamide gels. Seasonal changes in the ultrastructure of mammotropes, and pituitary and plasma prolactin concentrations in female Miniopterus schreibersii indicated that there was an increase in prolactin secretion during the second half of the period of delayed implantation and that prolactin secretion remained elevated during normal embryonic development and lactation. This suggests that prolactin may be part of the luteotropic and lactogenic complex, and that the hormone might be responsible for terminating the period of delayed implantation. The latter is supported by experiments, where exogenous prolactin initiated precocious implantation during early delayed implantation, and treatment with bromocryptine (which inhibits prolactin synthesis) retarded implantation. Activation of mammotropes to synthesise prolactin and an increase of plasma prolactin levels occurred shortly after the winter solstice (21 June), suggesting that increasing daylength may be the environmental cue, which terminates the period of delayed implantation in Miniopterus schreibersii.
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- Date Issued: 1993
Studies in fuzzy groups
- Authors: Makamba, B B
- Date: 1993
- Subjects: Mathematics Fuzzy sets Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5415 , http://hdl.handle.net/10962/d1005229
- Description: In this thesis we first extend the notion of fuzzy normality to the notion of normality of a fuzzy subgroup in another fuzzy group. This leads to the study of normal series of fuzzy subgroups, and this study includes solvable and nilpotent fuzzy groups, and the fuzzy version of the Jordan-Hõlder Theorem. Furthermore we use the notion of normality to study products and direct products of fuzzy subgroups. We present a notion of fuzzy isomorphism which enables us to state and prove the three well-known isomorphism theorems and the fact that the internal direct product of two normal fuzzy subgroups is isomorphic to the external direct product of the same fuzzy subgroups. A brief discussion on fuzzy subgroups generated by fuzzy subsets is also presented, and this leads to the fuzzy version of the Basis Theorem. Finally, the notion of direct product enables us to study decomposable and indecomposable fuzzy subgroups, and this study includes the fuzzy version of the Remak-Krull-Schmidt Theorem.
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- Date Issued: 1993
The ecology of the South African citrus thrips, Scirtothrips aurantii Faure and its economic implications
- Authors: Gilbert, Martin Jeffray
- Date: 1993
- Subjects: Thrips -- Control -- South Africa Citrus -- Diseases and pests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5673 , http://hdl.handle.net/10962/d1005358
- Description: The South African Citrus Thrips, Scirtothrips aurantii Faure (Thysanoptera: Thripidae) has been a serious pest of the citrus industry of Southern Africa for over 70 years. It is indigenous to Africa and has no recorded parasitoids and, in most citrus-growing regions, predators are not economically effective. Firstly, in this study, the general ecology of thrips was reviewed along with the recorded history of S. aurantii and its control. Host plant relationships of S. aurantii were then examined and wild hosts were not found to be important in promoting citrus thrips outbreaks in the orchard after flowering. In addition, Scirtothrips dorsalis Hood, which attacks citrus in Asia, was collected for the first time in Africa, but from Castor Oil plant. It is therefore a potential pest of citrus here. Notes on its appearance compared to that of S. aurantii were prepared. Weekly sampling of S. aurantii adults was carried out from June 1984 to May 1990. Population fluctuations were then correlated with phenology of the citrus trees and the direct and indirect effects of weather. Temperature and rainfall were not found to be significantly directly correlated with thrips numbers recorded. However, the indirect effects of rainfall were important in promoting a large winter thrips population in certain years. Relatively high rainfall during March and April compared to that of the previous January and February stimulated atypical flushing of the citrus trees during autumn and the setting of out-of-season fruit. S. aurantii then exploited this unusual food source and high numbers were subsequently recorded in the following winter; as well as in spring. Thus the mild winter climate alone could not suppress thrips numbers at Letaba. Dispersal/Emergence traps, which are used in the U.S.A. for the monitoring of Scirtothrips citri, were evaluated over 24 months, and were effective in recording population peaks of S. aurantii. The emergence rate of adults in relation to second instar larvae trapped was 43.7%. 35.7% of adults caught after emerging from the soil were males and 64.3 were females. In contrast, yellow traps had recorded 59.1% males and 40.9% females over the same period. The yellow traps were subsequently found to be biased towards male catches when young fruit and/or soft flush was present on the citrus trees. Relative inhibition of female flight activity during times of food abundance is known in other thrips species. During times of food scarcity, the bias in the yellow trap results disappeared. At Letaba Estates, availability of food rather than the direct effects of weather was seen to be the most important factor in governing S. aurantii numbers. Because of the importance of soft flush in the promotion of S. aurantii population increase, it is recommended that more attention should be given to the control of thrips on, as well as conducting surveys for, this food source. As the climate at Letaba is so favourable for citrus thrips, even during winter, it is further recommended that trapping for S. aurantii is carried out throughout the year. Furthermore, males and females should be recorded separately in trapping results as the sex ratio gives an indication of the phenological state of the tree.
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- Date Issued: 1993
The fishes of Tristan Da Cunha and Gough Island (South Atlantic), and the effects of environmental seasonality on the biology of selected species
- Authors: Andrew, Timothy Gilbert
- Date: 1993
- Subjects: Fishes -- Tristan da Cunha Fishes -- Gough Island Fishes -- Conservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5284 , http://hdl.handle.net/10962/d1005128
- Description: This study focuses on the taxonomy, biogeography and biological aspects of the fishes of Tristan da Cunha and Gough Island in the cental South Atlantic Ocean. Oceanographic measurements were undertaken to determine the position and nature of the Subtropical Convergence (STC) in the vicinity of the islands. The Tristan da Cunha group is thought to be situated on the northern edge of the STC while Gough Island is situated on the southern edge of the front. The seasonal environmental cycle at the islands is characterised by an annual sea surface temperature fluctuation of approximately 5 °C and an annual change in stratification of the water column. It is suggested that this increase in stratification at the STC, brought about in the summer by insolation warming the surface layers of the ocean, enhances primary production. The STC is identified as a unique habitat for fishes and as an important barrier to dispersal of species in the Southern Ocean. The present study has produced 18 new distributional records from the shelf waters of Tristan da Cunha and Gough Island. The fish fauna known from the shelf waters of these islands is reviewed, and a diagnosis, synonymy, and in some cases an illustration are provided. For certain species, brief notes on their biology, relative abundance and seasonal distribution are included. An analysis of the ichthyofaunal relationships between shallow water areas in the vicinity of the STC has resulted in the identification of a characteristic neritic STC ichthyofauna. The circumglobal distribution of many of these species is thought to be a consequence of a dispersive pelagic phase in their life-cycles. Biological processes in fishes at these islands are temporally and spatially affected by seasonal changes in oceanographic conditions. Seasonal sea temperature variation was identified as being an indicator of other oceanographic phenomena that may affect processes such as growth, reproduction and feeding in fishes at the islands. Most species have a summer spawning season and growth rate increased during the summer months. It was hypothesised that enhanced primary production and a related increase in food quality and availability during the summer were the major factors temporally regulating the growth and reproduction of fishes at the islands. Twenty families of neritic fishes have been recorded in the shelf waters of Tristan da Cunhaand Gough Island. Most families are represented by only one species. Because of this a wide range of life-history strategies are apparent in the fauna. Nevertheless, there are a number of common life-history characteristics shared by most of the neritic species. Firstly, the early lifehistory of many species included an extended pelagic phase which might have facilitated colonisation throughout the STC zone in the past, thereby regulating extant species diversity in this region. Secondly, the common occurrence of an extended summer breeding season and iteroparity suggested that these characters also contributed to survival in what is considered to be an unpredictable environment. It would appear that these common characteristics hold the key to the success of many fishes in the STC zone. This study has contributed to our understanding of oceanic island ecosystems and has revealed distributional patterns of fishes that were unknown previously. By focusing on the biological processes of selected species the regulatory role played by local environmental conditions became apparent. The results of this study are also relevant to proposed conservation measures for Tristan da Cunha and Gough Island.
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- Date Issued: 1993
The influence of contrasting freshwater inflows on the feeding ecology and food resources of zooplankton in two eastern Cape estuaries, South Africa
- Authors: Grange, Neil
- Date: 1993
- Subjects: Freshwater zooplankton -- Ecology -- South Africa Aquatic ecology -- Research -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5714 , http://hdl.handle.net/10962/d1005400
- Description: The trophodynamic implications of reduced freshwater inflow on the zooplankton of eastern Cape estuaries was investigated by a comparison of the community composition and standing stocks, grazing rates and food resources of zooplankton in two systems, the Kariega and the Great Fish estuaries, which are subject to contrasting freshwater inflow. The climate of South Africa is semi-arid, and the low rainfall, coupled with high evaporative loss, result in the region having one of the lowest conversions of rainfall to run-off in the world. In addition, many of the major rivers are extensively impounded, consequently, estuaries often experience prolonged periods of zero or reduced freshwater inflow. The amount of freshwater available for estuarine management in the future is expected to decline as the demand for domestic, agricultural and industrial use increases. The influence of climate, tidal amplitude and wave action are essentially constant, consequently, the individual characteristics of an estuary are determined largely by the indirect influences of catchment size and regulation. Estuaries along the eastern Cape coast range from negative hypersaline systems, to positive systems in which a salinity gradient is well established. The Kariega estuary is a homogeneous marine estuary as a result of minimal freshwater inflow, whereas the Great Fish estuary receives sustained freshwater inflow and is partially-stratified. The quality and quantity of particulate food resources for suspension-feeders depended to a large extent on the allochthonous import of material associated with freshwater inflow. Nutrients, rather than light penetration of the watercolumn are the major factor limiting phytoplankton standing stocks. In the Kariega estuary, phytoplankton standing stocks were low (up to 1.0 μg l⁻¹) and the estuary is classified as oligotrophic. Correlation analyses indicated that lower quality detritus, originating from fringing macrophytes, may contribute substantially to suspended particulate organic material. Phytoplankton food resources were considerably higher in the Great Fish estuary (up to 21.8 μg ⁻¹) which is classified as mesotrophic/eutrophic, and correlation analyses indicated that phytoplankton comprised the dominant fraction of the particulate organic material. Although this suggested that the organic material was of a higher quality, the seston was "masked" by a higher suspended inorganic load. Consequently, the organic fraction comprised between 13 and 22% of total particulate material in the Great Fish estuary, compared with between 20 and 39% in the Kariega estuary. Food resources demonstrated a fairly uniform distribution along the length of the Kariega estuary and exhibited a slight seasonal increase during warmer months. By contrast, the point source influence of freshwater inflow resulted in a spatial gradient of food resources in the Great Fish estuary with higher values recorded towards the upper reaches. There was evidence that higher concentrations of particulate material in the upper reaches are also a consequence of hydrodynamic trapping. There was no marked seasonal pattern in the availability of food resources which were generally elevated in response to sporadic pulses of freshwater inflow. Tidal currents were responsible for elevating suspended food resources by re-suspension of material from the sediments. This effect was probably of greater importance in the Kariega estuary where food resources were generally limiting. In the Kariega estuary, the zooplankton community was dominated by calanoid copepods of the genera Acartia and Pseudodiaptomus. However, in the Great Fish estuary, the community was dominated by the mysid Mesopodopsis siabberi, and the calanoid P. hessei. Community biomass generally reflected the trophic status of the estuary. The mean seasonal biomass recorded in the Kariega estuary was 38 mg m⁻³ compared with 1597 mg m⁻³ in the Great Fish estuary. Greater spatial variability in community biomass was evident in the Great Fish estuary, partly in response to the food resource gradient, but also due to the inability of the mysid shrimps, which dominated the community biomass, to penetrate the lower salinity water of the upper reaches. Zooplankton in the Kariega estuary demonstrated a seasonal pattern of abundance whereas in the Great Fish estuary, community biomass was elevated in response to sporadic pulses of freshwater inflow. Grazing rates, measured in situ using a modified Gliwicz-Haney chamber, indicated that the zooplankton communities were capable of "clearing" substantial proportions of the watercolumn at certain times of the year. The pattern of grazing pressure over a diel cycle was examined in relation to the diel vertical migration movements of the zooplankton. Higher nighttime grazing rates were generally associated with the greater abundance of zooplankton resulting from the movement of zooplankton into the watercolumn after dusk, and their return to the sediments at dawn. Seasonal estimates of diel grazing pressure, extrapolated from daytime and nighttime feeding rates, indicated that the zooplankton "cleared" up to 40% of the watercolumn in a day in the Kariega estuary, and up to 120% d⁻¹ in the Great Fish estuary. However, values of around 25% d⁻¹ in the Kariega estuary, and 50 to 80% d⁻¹ in the Great Fish estuary, were not uncommon. Multiple regression analyses were used in an attempt to explain the influence of environmental factors on the variation in in situ grazing rates. These attempts were largely unsuccessful and the possible reasons, as well as recommended improvements to the methods used, are discussed. Seston concentration in the estuaries was highly variable as a result of the effects of tidal re-suspension and freshwater inflow. Consequently, further laboratory-based experiments were carried out to examine the influence of seston concentration on the filtration rates of the dominant calanoid copepods. Results indicated that some of the unexplained variability in the community filtration rates may be attributed to differences in species-specific response to changes in seston concentration.
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- Date Issued: 1993
The microbial production of polyphenol oxidase enzyme systems and their application in the treatment of phenolic wastewaters
- Authors: Goetsch, Patricia-Ann
- Date: 1993
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21060 , http://hdl.handle.net/10962/6190
- Description: Phenolic compounds are a group of organic chemicals present in the wastewaters of many synthetic industrial processes. Due to their extreme toxicity to man and animals, and deleterious impact on the environment, a range of techniques exist for the effective treatment and disposal of these pollutants. Biological degradation using microbial enzymes presents a valuable alternative to conventional wastewater treatment systems. This research was therefore initiated to investigate the polyphenol oxidase enzyme system and the feasibility of its application for effluent treatment and studies in organic solvents. The enzyme system is widely distributed in nature, with Agaricus bisporus (the common mushroom) being the best known producer. Biochemical investigations of the enzyme system were therefore carried out using this extract. A screening programme was initiated to identify microbial polyphenol oxidase producers which could be cultured in liquid media, thereby enabling the production of large quantities of enzyme in fermentation systems. Extensive growth optimization and enzyme induction and optimization studies were carried out on selected cultures. A number of good producers were isolated, namely a bacterial culture designated AECI culture no. 26, Streptomyces antibioticus, Streptomyces glaucescens and a manipulated strain, Streptomyces lividans (pIJ702). Enzyme production by Agaricus bisporus mycelia was optimized in deep-liquid culture; enzyme extracts showed high phenol removal efficiencies. Streptomyces antibioticus, Streptomyces glaucescens, Streptomyces lividans (pIJ702) and AECI culture no. 26 whole cells were also investigated for phenol-removing ability in simulated phenolic effluents. The use of whole cells reduces enzyme inactivation and instability due to the protection of the enzyme system within the cell. All cultures showed improved removal efficiencies in phenolic growth media. These results strongly suggest their use for phenol removal in continuous systems.
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- Date Issued: 1993
The regulation of Serotonin N-acetyltransferase in the rat pineal gland
- Authors: Olivieri, Gianfranco
- Date: 1993
- Subjects: Serotonin -- Research Pineal gland Acetyltransferases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4051 , http://hdl.handle.net/10962/d1004112
- Description: The synthesis of the pineal hormone, melatonin, is finely regulated by the pineal enzyme serotonin N-acetyltransferase (NAT). In the absence of light, the activity of NAT is markedly enhanced by the release of nor-adrenaline from sympathetic nerve endings in the pineal. Exposure of animals to light during darkness causes a sudden and dramatic reduction in the activity of NAT. The present study investigated a possible mechanism for this sudden decline in NAT activity. These investigations included the determination of the effects of S-adenosylmethionine (SAM), adenosine nucleotides and calcium on NAT activity. In vitro experiments using SAM showed that pineals pre-incubated with SAM prior to adrenergic stimulation did not significantly alter NAT activity or pineal indoleamine metabolism. However, measurement of pineal cyclic AMP showed that SAM exposure reduced the adrenergic-induced rise in pineal cyclic AMP. Experiments using adenosine 5'-monophosphate (5'-AMP) showed that this nucleotide enhanced both dark- and isoproterenol-induced NAT activity. Adenosine 5'-triphosphate (A TP), on the other hand, reduced NAT activity with a concomitant reduction in pineal indoleamine metabolism. Exposure of isoproterenol-stimulated pineals in organ culture to propranolol resulted in a marked rise in ATP and adenosine 5'-diphosphate (ADP) synthesis accompanied by a decline in 5'-AMP levels as compared with pineals treated with isoproterenol alone. This then implies that exposure of animals to light could cause a change in pineal nucleotide levels. Since nucleotide levels are also controlled by calcium, experiments were carried out to determine the effect of calcium on pineal NAT activity. These experiments showed that ethyleneglycol-bis-N,N,N,N,-tetraacetic acid (EGTA) enhanced NAT activity whilst calcium reduced the activity in pineal homogenates, implying that calcium may act directly on NAT to regulate its activity. Exposure of pineal glands in organ culture to the calmodulin antagonist R24571 caused a rise in pineal cyclic AMP levels with a concomitant decrease in cAMP-phosphodiesterase activity. This was, however, accompanied by a decline in Nacetyl serotonin and melatonin synthesis. These findings implicate a number of factors in the regulation of pineal NAT activity. A mechanism for the regulation of pineal NAT is proposed.
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- Date Issued: 1993