Extracellular digestion in two intertidal mussels and the role played by their gut bacteria
- Authors: Simon, Carol Anne
- Date: 1997
- Subjects: Perna -- Digestive organs , Mussels -- Digestive organs , Spirochaeta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5692 , http://hdl.handle.net/10962/d1005378 , Perna -- Digestive organs , Mussels -- Digestive organs , Spirochaeta
- Description: The intertidal mussels. Perna perna and Choromytilus meridionalis co-occur on the southern coast of South Africa. Mussels ingest mixtures of bacteria. phytoplankton. zooplankton and detritus. with proportions varying according to availability. These bivalves filter similar-sized particles. which might result in interspecific competition. Carbohydrate-digesting enzymes of the mussels and their enteric bacteria. and bacteriolytic enzymes of the mussels were therefore examined to elucidate feeding ecology in these animals at an enzymatic level. Style enzymes of both species digested the storage carbohydrates amylose glycogen and laminarin, and the structural carbohydrate carboxymethyl cellulose (CMC). Differential rates of digestion of these carbohydrates suggests that Perna perna relies more on plankton (and possibly bacteria) than on detritus for food while Choromytilus meridionalis relies equally on all components of the seston. There may therefore be some degree of resource partitioning of the seston. The styles of P.perna had a lower specific enzyme activity. but higher protein content than those of C.meridionalis. P.perna could therefore release more glucose from a given concentration of substrate than C.meridionalis. The gut contents and tissue were examined microscopically to determine where the bacterial colonisation sites were. Bacteria were associated primarily with the gut contents but not the gut walls. of both species. The styles housed spirochaete bacteria (Crislispira sp), Perna perna housed large numbers of one species. while Choromytilus meridionalis had lower numbers of two species. Levels of infection differed between species and localities. Enteric (but not style) bacteria of Perna perna and Choromytilus meridionalis always digested the same carbohydrates as the mussels as well as the structural carbohydrates mannan and fucoidan. Activity was erratic on the structural compounds, carageenin and xylan, and absent on alginic acid or inulin. Activity on the storage carbohydrates by enteric bacteria from C.meridionalis was higher than by those from P.perna. This is probably related to the larger bacterial populations housed by C.meridionalis than by P.perna. Bacteriolytic activity by the digestive enzymes of Pema perna was higher than for Choromytilus. In P.perna it was due to a combination of different enzymes one of which is a true lysozyme. C.meridionalis did not produce a true lysozyme. Enzymes produced by the mussels and their enteric bacteria allow the mussels to utilise all components of the seston. Low endogenous enzyme activity by Choromytilus meridionalis, coupled with the high activity by its enteric bacteria, suggests that they rely more on bacterial activity to meet their dietary requirements than does Perna perna. The ability of enteric bacteria to digest carbohydrates which the mussels cannot indicates that the bacteria are endosymbiotic, although the sporadic nature of activity of some of the enzymes, and the fact that bacteria are associated with the gut contents, indicates that the relationship is only incidental.
- Full Text:
- Date Issued: 1997
- Authors: Simon, Carol Anne
- Date: 1997
- Subjects: Perna -- Digestive organs , Mussels -- Digestive organs , Spirochaeta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5692 , http://hdl.handle.net/10962/d1005378 , Perna -- Digestive organs , Mussels -- Digestive organs , Spirochaeta
- Description: The intertidal mussels. Perna perna and Choromytilus meridionalis co-occur on the southern coast of South Africa. Mussels ingest mixtures of bacteria. phytoplankton. zooplankton and detritus. with proportions varying according to availability. These bivalves filter similar-sized particles. which might result in interspecific competition. Carbohydrate-digesting enzymes of the mussels and their enteric bacteria. and bacteriolytic enzymes of the mussels were therefore examined to elucidate feeding ecology in these animals at an enzymatic level. Style enzymes of both species digested the storage carbohydrates amylose glycogen and laminarin, and the structural carbohydrate carboxymethyl cellulose (CMC). Differential rates of digestion of these carbohydrates suggests that Perna perna relies more on plankton (and possibly bacteria) than on detritus for food while Choromytilus meridionalis relies equally on all components of the seston. There may therefore be some degree of resource partitioning of the seston. The styles of P.perna had a lower specific enzyme activity. but higher protein content than those of C.meridionalis. P.perna could therefore release more glucose from a given concentration of substrate than C.meridionalis. The gut contents and tissue were examined microscopically to determine where the bacterial colonisation sites were. Bacteria were associated primarily with the gut contents but not the gut walls. of both species. The styles housed spirochaete bacteria (Crislispira sp), Perna perna housed large numbers of one species. while Choromytilus meridionalis had lower numbers of two species. Levels of infection differed between species and localities. Enteric (but not style) bacteria of Perna perna and Choromytilus meridionalis always digested the same carbohydrates as the mussels as well as the structural carbohydrates mannan and fucoidan. Activity was erratic on the structural compounds, carageenin and xylan, and absent on alginic acid or inulin. Activity on the storage carbohydrates by enteric bacteria from C.meridionalis was higher than by those from P.perna. This is probably related to the larger bacterial populations housed by C.meridionalis than by P.perna. Bacteriolytic activity by the digestive enzymes of Pema perna was higher than for Choromytilus. In P.perna it was due to a combination of different enzymes one of which is a true lysozyme. C.meridionalis did not produce a true lysozyme. Enzymes produced by the mussels and their enteric bacteria allow the mussels to utilise all components of the seston. Low endogenous enzyme activity by Choromytilus meridionalis, coupled with the high activity by its enteric bacteria, suggests that they rely more on bacterial activity to meet their dietary requirements than does Perna perna. The ability of enteric bacteria to digest carbohydrates which the mussels cannot indicates that the bacteria are endosymbiotic, although the sporadic nature of activity of some of the enzymes, and the fact that bacteria are associated with the gut contents, indicates that the relationship is only incidental.
- Full Text:
- Date Issued: 1997
Fungal and substrate-associated factors affecting lignocellulolytic mushroom cultivation on wood sources available in South African [i.e. Africa]
- Authors: Da Serra, Maria Fatima
- Date: 1997
- Subjects: Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4020 , http://hdl.handle.net/10962/d1004080 , Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Description: Vast- quantities of lignocellulosic materials, representing potential substrates for the cultivation of speciality mushrooms, are produced annually in South Africa. A number of these materials are derived as waste products of the timber and agricultural industries, e.g. Maranti (Shorea spp.) and Port Jackson Willow (Acacia longifolia) respectively. The screening of various wood-degrading fungi, which are cultivated worldwide for their production of speciality mushrooms, indicated that under the environmental conditions considered, certain species were adapted to cultivation on these lignocellulosic wastes (Pleurotus species) whereas others were not (Lentinus edodes and Flammulina velutipes). Furthermore, intra- and interspecies specific differences in the growth and production potential of the various lignocellulolytic fungi investigated on synthetic and natural medium were discovered. Biochemical and genetical investigations of these strains indicated differences between and within species which were often significant. Species varied qualitatively and quantitatively in the lignocellulolytic enzymes produced, which was loosely correlated with productivity on the different media investigated. Genetical studies, using RAPD fingerprinting, indicated that the Pleurotus genus is highly variable which supports the observed differences in growth, yield and enzymatic activity between different strains and species.
- Full Text:
- Date Issued: 1997
- Authors: Da Serra, Maria Fatima
- Date: 1997
- Subjects: Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4020 , http://hdl.handle.net/10962/d1004080 , Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Description: Vast- quantities of lignocellulosic materials, representing potential substrates for the cultivation of speciality mushrooms, are produced annually in South Africa. A number of these materials are derived as waste products of the timber and agricultural industries, e.g. Maranti (Shorea spp.) and Port Jackson Willow (Acacia longifolia) respectively. The screening of various wood-degrading fungi, which are cultivated worldwide for their production of speciality mushrooms, indicated that under the environmental conditions considered, certain species were adapted to cultivation on these lignocellulosic wastes (Pleurotus species) whereas others were not (Lentinus edodes and Flammulina velutipes). Furthermore, intra- and interspecies specific differences in the growth and production potential of the various lignocellulolytic fungi investigated on synthetic and natural medium were discovered. Biochemical and genetical investigations of these strains indicated differences between and within species which were often significant. Species varied qualitatively and quantitatively in the lignocellulolytic enzymes produced, which was loosely correlated with productivity on the different media investigated. Genetical studies, using RAPD fingerprinting, indicated that the Pleurotus genus is highly variable which supports the observed differences in growth, yield and enzymatic activity between different strains and species.
- Full Text:
- Date Issued: 1997
Generalisations of filters and uniform spaces
- Authors: Muraleetharan, Murugiah
- Date: 1997
- Subjects: Filters (Mathematics) , Uniform spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5409 , http://hdl.handle.net/10962/d1005223 , Filters (Mathematics) , Uniform spaces
- Description: The notion of a filter F ∈ 2²x has been extended to that of a : prefilter: ƒ ∈ 1²x, generalised filter ƒ ∈ 2²x x and fuzzy filter ᵩ ∈ 1¹x. A uniformity is a filter with some other conditions and the notion of a uniformity D ∈ 2²xxx has been extended to that of a : fuzzy uniformity d ∈ 1²xxx , generalised uniformity ∈ 1²xxx and super uniformity b ∈ 1¹x. We establish categorical embeddings from the category of uniform spaces into the categories of fuzzy uniform spaces, generalised uniform spaces and super uniform spaces and also categorical embeddings into the category of super uniform spaces from the categories of fuzzy uniform spaces and generalised uniform spaces.
- Full Text:
- Date Issued: 1997
- Authors: Muraleetharan, Murugiah
- Date: 1997
- Subjects: Filters (Mathematics) , Uniform spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5409 , http://hdl.handle.net/10962/d1005223 , Filters (Mathematics) , Uniform spaces
- Description: The notion of a filter F ∈ 2²x has been extended to that of a : prefilter: ƒ ∈ 1²x, generalised filter ƒ ∈ 2²x x and fuzzy filter ᵩ ∈ 1¹x. A uniformity is a filter with some other conditions and the notion of a uniformity D ∈ 2²xxx has been extended to that of a : fuzzy uniformity d ∈ 1²xxx , generalised uniformity ∈ 1²xxx and super uniformity b ∈ 1¹x. We establish categorical embeddings from the category of uniform spaces into the categories of fuzzy uniform spaces, generalised uniform spaces and super uniform spaces and also categorical embeddings into the category of super uniform spaces from the categories of fuzzy uniform spaces and generalised uniform spaces.
- Full Text:
- Date Issued: 1997
Grouping complex systems for classification and parallel simulation
- Authors: Ikram, Ismail Mohamed
- Date: 1997
- Subjects: Digital computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4662 , http://hdl.handle.net/10962/d1006665
- Description: This thesis is concerned with grouping complex systems by means of concurrent model, in order to aid in (i) formulation of classifications and (ii) induction of parallel simulation programs. It observes, and seeks f~ furmalize _ and then exploit, the strong structural resemblance between complex systems and occam programs. The thesis hypothesizes that groups of complex systems may be discriminated according to shared structural and behavioural characteristics. Such an analysis of the complex systems domain may be performed in the abstract with the aid of a model for capturing interesting features of complex systems. The resulting groups would form a classification of complex systems. An additional hypothesis is that, insofar as the model is able to capture sufficient . programmatic information, these groups may be used to define, automatically, algorithmic skeletons for the concurrent simulation of complex systems. In order to test these hypotheses, a specification model and an accompanying formal notation are developed. The model expresses properties of complex systems in a mixture of object-oriented and process-oriented styles .. The model is then used as the basis for performing both classification and automatic induction of parallel simulation programs. The thesis takes the view that specification models should not be overly complex, especially if the specifications are meant to be executable. Therefore the requirement for explicit consideration of concurrency on the part of specifiers is minimized. The thesis formulates specifications of classes of cellular automata and neural networks according to the proposed model. Procedures for verificati6If - and induction of parallel simulation programs are also included.
- Full Text:
- Date Issued: 1997
- Authors: Ikram, Ismail Mohamed
- Date: 1997
- Subjects: Digital computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4662 , http://hdl.handle.net/10962/d1006665
- Description: This thesis is concerned with grouping complex systems by means of concurrent model, in order to aid in (i) formulation of classifications and (ii) induction of parallel simulation programs. It observes, and seeks f~ furmalize _ and then exploit, the strong structural resemblance between complex systems and occam programs. The thesis hypothesizes that groups of complex systems may be discriminated according to shared structural and behavioural characteristics. Such an analysis of the complex systems domain may be performed in the abstract with the aid of a model for capturing interesting features of complex systems. The resulting groups would form a classification of complex systems. An additional hypothesis is that, insofar as the model is able to capture sufficient . programmatic information, these groups may be used to define, automatically, algorithmic skeletons for the concurrent simulation of complex systems. In order to test these hypotheses, a specification model and an accompanying formal notation are developed. The model expresses properties of complex systems in a mixture of object-oriented and process-oriented styles .. The model is then used as the basis for performing both classification and automatic induction of parallel simulation programs. The thesis takes the view that specification models should not be overly complex, especially if the specifications are meant to be executable. Therefore the requirement for explicit consideration of concurrency on the part of specifiers is minimized. The thesis formulates specifications of classes of cellular automata and neural networks according to the proposed model. Procedures for verificati6If - and induction of parallel simulation programs are also included.
- Full Text:
- Date Issued: 1997
Guidelines for assessing single borehole yields in secondary aquifers
- Authors: Murray, Eric Charles
- Date: 1997
- Subjects: Aquifers -- Measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6026 , http://hdl.handle.net/10962/d1005512
- Description: The motivation for this research project arose from the realisation that many South African rural water supply schemes fail due to the over abstraction of groundwater from single boreholes. The main reason for this mis-management of groundwater is a result of inappropriate borehole yield recommendation methods. This research project set out to review existing borehole yield assessment methods and establish new methods which take the shortcomings of existing methods into account. The study is concerned with borehole yield assessment methods applicable to secondary aquifers, since these aquifers are by far the most common in South Africa. The yield assessment methods have been grouped into those that are based on aquifer yield analyses, and on the analysis of single borehole test pump data. In order to assess which methods give suitable yield recommendations, it was necessary to compare the yields obtained using the various methods, with established yields from production boreholes. The focus of the aquifer yield component of the study, was to develop a method for estimating the proportion of recharge that can be abstracted from a single borehole located in a relatively small aquifer. The method was developed by computer simulations of aquifers with different hydraulic properties, and by establishing a formula which describes the relationship between recharge and the abstractable proportion of recharge. Under specific hydrogeological conditions, the recharge based method proved to be reliable in relation to established yields from production boreholes. Of the borehole yield assessment methods based on the analysis of test pump data, none of the existing methods proved to be reliable. However, the yields obtained using the two newly developed methods compared favourably to the established yield of existing production boreholes. Both of these methods are based on the application of the Cooper-Jacob approximation of the Theis equation. This study reviews existing methods and presents newly developed methods for recommending borehole abstraction rates in secondary aquifers. While existing borehole yield assessment methods were found to be unreliable, some of the newly developed methods, if correctly applied, give acceptable yield recommendations.
- Full Text:
- Date Issued: 1997
- Authors: Murray, Eric Charles
- Date: 1997
- Subjects: Aquifers -- Measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6026 , http://hdl.handle.net/10962/d1005512
- Description: The motivation for this research project arose from the realisation that many South African rural water supply schemes fail due to the over abstraction of groundwater from single boreholes. The main reason for this mis-management of groundwater is a result of inappropriate borehole yield recommendation methods. This research project set out to review existing borehole yield assessment methods and establish new methods which take the shortcomings of existing methods into account. The study is concerned with borehole yield assessment methods applicable to secondary aquifers, since these aquifers are by far the most common in South Africa. The yield assessment methods have been grouped into those that are based on aquifer yield analyses, and on the analysis of single borehole test pump data. In order to assess which methods give suitable yield recommendations, it was necessary to compare the yields obtained using the various methods, with established yields from production boreholes. The focus of the aquifer yield component of the study, was to develop a method for estimating the proportion of recharge that can be abstracted from a single borehole located in a relatively small aquifer. The method was developed by computer simulations of aquifers with different hydraulic properties, and by establishing a formula which describes the relationship between recharge and the abstractable proportion of recharge. Under specific hydrogeological conditions, the recharge based method proved to be reliable in relation to established yields from production boreholes. Of the borehole yield assessment methods based on the analysis of test pump data, none of the existing methods proved to be reliable. However, the yields obtained using the two newly developed methods compared favourably to the established yield of existing production boreholes. Both of these methods are based on the application of the Cooper-Jacob approximation of the Theis equation. This study reviews existing methods and presents newly developed methods for recommending borehole abstraction rates in secondary aquifers. While existing borehole yield assessment methods were found to be unreliable, some of the newly developed methods, if correctly applied, give acceptable yield recommendations.
- Full Text:
- Date Issued: 1997
Healing stories of the unconscious: past-life imagery in transpersonal psychotherapy
- Authors: Knight, Zelda Gillian
- Date: 1997
- Subjects: Transpersonal psychotherapy Unconscious Reincarnation therapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3004 , http://hdl.handle.net/10962/d1002513
- Description: Theoretically this thesis was grounded in the discourse of transpersonal psychology and the related discourse of transpersonal feminism. The focus was on a particular category of transpersonal phenomena - past-life experiences. These experiences were viewed from a poetic and therapeutic perspective as being healing stories of the unconscious that served to articulate psychological and spiritual realities of the human psyche within both the personal and the collective unconscious. They were thus not questioned in regard to their literal occurrence. The central aims of this thesis were to (a) document and faithfully describe a participant's past-life experiences that occurred during selected psychotherapy sessions, (b) engage in a hermeneutic dialogue between the participant's past-life experiences and contemporary transpersonal literature, and, in so doing, to evaluate and extend existing theory, (c) uncover the archetypal significance of past-life experience and its relationship to the re-emerging Feminine within patriarchal culture and, finally, (d) show how the past-life stories and images contribute to the process of inner healing and transformation, a process termed 'spiritual emergence'. The research was a phenomenological-hermeneutic case study, comprising the selection of eight consecutive psychotherapy sessions in which nine past-life experiences were identified. These sessions were reduced to narrative synopses, and a hermeneutically grounded thematic analysis of a total of six past-life themes were explicated. Principle conclusions reached were that past-life stories and images contribute to the process of spiritual emergence and empowerment as well as to the re-emergence of the Feminine consciousness. Moreover, as healing stories of the unconscious, these past-life experiences can be understood as expressions of the collective struggle with unresolved archetypal forces within the collective psyche, as well as echoes of personal conflicts and dilemmas from the individual unconscious.
- Full Text:
- Date Issued: 1997
- Authors: Knight, Zelda Gillian
- Date: 1997
- Subjects: Transpersonal psychotherapy Unconscious Reincarnation therapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3004 , http://hdl.handle.net/10962/d1002513
- Description: Theoretically this thesis was grounded in the discourse of transpersonal psychology and the related discourse of transpersonal feminism. The focus was on a particular category of transpersonal phenomena - past-life experiences. These experiences were viewed from a poetic and therapeutic perspective as being healing stories of the unconscious that served to articulate psychological and spiritual realities of the human psyche within both the personal and the collective unconscious. They were thus not questioned in regard to their literal occurrence. The central aims of this thesis were to (a) document and faithfully describe a participant's past-life experiences that occurred during selected psychotherapy sessions, (b) engage in a hermeneutic dialogue between the participant's past-life experiences and contemporary transpersonal literature, and, in so doing, to evaluate and extend existing theory, (c) uncover the archetypal significance of past-life experience and its relationship to the re-emerging Feminine within patriarchal culture and, finally, (d) show how the past-life stories and images contribute to the process of inner healing and transformation, a process termed 'spiritual emergence'. The research was a phenomenological-hermeneutic case study, comprising the selection of eight consecutive psychotherapy sessions in which nine past-life experiences were identified. These sessions were reduced to narrative synopses, and a hermeneutically grounded thematic analysis of a total of six past-life themes were explicated. Principle conclusions reached were that past-life stories and images contribute to the process of spiritual emergence and empowerment as well as to the re-emergence of the Feminine consciousness. Moreover, as healing stories of the unconscious, these past-life experiences can be understood as expressions of the collective struggle with unresolved archetypal forces within the collective psyche, as well as echoes of personal conflicts and dilemmas from the individual unconscious.
- Full Text:
- Date Issued: 1997
Idolatry and the artist's role with special reference to the work and thought of Andy Warhol
- Authors: Waterkeyn, Linda Catherine
- Date: 1997
- Subjects: Warhol, Andy, 1928-1987 -- Criticism and interpretation
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2425 , http://hdl.handle.net/10962/d1002221
- Description: This thesis uses Hirsch's dual notion of intention, i. e. conscious, intentional meaning and symptomatic, unconscious meaning, in order to avoid a dead end in the critical assessment of Warhol's work. T.S. Eliot's term "objective correlative" refers to a phenomenon whereby "an inner emotional reality" is evoked by its "external equivalent". (Benet, 1965). Thus, given that no work of art is purely self-referential (as distinct from its being autonomous),Hirsch's notion allows that viewerreconstruction of a painting involves shared values and concerns; that a painting reconstructed by a viewer acquires the status of an icon through which the viewer participates in the artist's sacred cosmos. Sociology of art tends on the whole to extrapolate from actual works to the alleged conditions that gave rise to them. That it cannot predict what specific works will arise from given conditions makes it unscientific. However, its usefulness lies in its ability to reveal what values and concerns are shared by artist and viewer. This is vital for an interpretation of Warhol's work. Warhol's biography leads directly into the meaning of his work. The sickly child of an immigrant steelworker, he grew up in Pittsburgh - an epitome of the technocratic-industrial environment - and was exposed from an early age to a violent and ugly world where the disparity between the super-wealthy and the struggling workers was deeply disturbing. That Warhol himself became a multi-millionaire artistic tycoon is significant, for it means that his works, his icons, were participatory in the very cultural myths and neuroses they appear to display or even despise. That his work has meaning and is open to interpretation there is no doubt. For example, a man-made soup can, as a manifestation and containment of the sacred, is coercive. Here the sacred becomes familiar, affordable and disposable. An electric chair, a man-made instrument of death, gives man supremacy over mortality and the divine prerogative of purging the world of all evil. The essay, however, does not attempt to answer the broader questions raised by Fromm and Roszak about the spiritual emptiness of the twentieth century and the existential crises experienced by those who hunger for meaning and fasten greedily onto anything that seems to proffer a glimpse of something beyond. The essay, nevertheless, strives within this context to elucidate the valid in Warhol's work
- Full Text:
- Date Issued: 1997
- Authors: Waterkeyn, Linda Catherine
- Date: 1997
- Subjects: Warhol, Andy, 1928-1987 -- Criticism and interpretation
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2425 , http://hdl.handle.net/10962/d1002221
- Description: This thesis uses Hirsch's dual notion of intention, i. e. conscious, intentional meaning and symptomatic, unconscious meaning, in order to avoid a dead end in the critical assessment of Warhol's work. T.S. Eliot's term "objective correlative" refers to a phenomenon whereby "an inner emotional reality" is evoked by its "external equivalent". (Benet, 1965). Thus, given that no work of art is purely self-referential (as distinct from its being autonomous),Hirsch's notion allows that viewerreconstruction of a painting involves shared values and concerns; that a painting reconstructed by a viewer acquires the status of an icon through which the viewer participates in the artist's sacred cosmos. Sociology of art tends on the whole to extrapolate from actual works to the alleged conditions that gave rise to them. That it cannot predict what specific works will arise from given conditions makes it unscientific. However, its usefulness lies in its ability to reveal what values and concerns are shared by artist and viewer. This is vital for an interpretation of Warhol's work. Warhol's biography leads directly into the meaning of his work. The sickly child of an immigrant steelworker, he grew up in Pittsburgh - an epitome of the technocratic-industrial environment - and was exposed from an early age to a violent and ugly world where the disparity between the super-wealthy and the struggling workers was deeply disturbing. That Warhol himself became a multi-millionaire artistic tycoon is significant, for it means that his works, his icons, were participatory in the very cultural myths and neuroses they appear to display or even despise. That his work has meaning and is open to interpretation there is no doubt. For example, a man-made soup can, as a manifestation and containment of the sacred, is coercive. Here the sacred becomes familiar, affordable and disposable. An electric chair, a man-made instrument of death, gives man supremacy over mortality and the divine prerogative of purging the world of all evil. The essay, however, does not attempt to answer the broader questions raised by Fromm and Roszak about the spiritual emptiness of the twentieth century and the existential crises experienced by those who hunger for meaning and fasten greedily onto anything that seems to proffer a glimpse of something beyond. The essay, nevertheless, strives within this context to elucidate the valid in Warhol's work
- Full Text:
- Date Issued: 1997
Investigations into the dietary protein requirements of juvenile spotted grunter, Pomadasys commersonnii (Haemulidae : Pisces)
- Authors: Irish, Abigail
- Date: 1997
- Subjects: Fishes -- Nutrition , Pomadasys -- Nutrition , Grunts (Fishes) -- Nutrition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5292 , http://hdl.handle.net/10962/d1005137 , Fishes -- Nutrition , Pomadasys -- Nutrition , Grunts (Fishes) -- Nutrition
- Description: The proximate composition of juvenile spotted grunter, Pomadasys commersonnii and their major prey items were analyzed to test the hypothesis that the dietary protein requirements would approximate the composition of the natural diet. The amino acid profile of juvenile P. commersonnii was analyzed to establish the pattern of limiting amino acids for this species. Juvenile P. commersonnii feed primarily on the mysid, Mesopodopsis slabberi, which has a protein content of 58.27±0.04% and a calorific value of 19.2kJ/g. The first-limiting essential amino acid for this fish was found to be lysine and it was predicted that the optimal dietary protein requirement would be between 50 and 60%. The optimal dietary protein inclusion level was investigated by feeding semi-purified diets containing graded levels of protein, ranging from 37-62%. Maximum growth was found to occur at dietary protein levels ranging from 40-51%. The best food conversion ratio was achieved at 56% dietary protein and the best protein efficiency ratio was obtained at a dietary protein inclusion level of 37-40%. The protein to energy ratio was defined by feeding 3 different protein levels at 3 different P:E levels. These semi-purified diets contained 35, 45 or 55% protein and 6, 8 or 12% dietary lipid, resulting in protein to energy ratios ranging from 21.1 to 42.3mg/kJ. The optimal P:E ratio for this species was found to be 26.7mg/kJ. This diet effected a low food conversion ratio (1.72±0.19), a low hepatosomatic index (4.01±0.23) and a high specific growth rate (5.96±0.36). The essential amino acid requirements of juvenile P. commersonnii were investigated. Semi-purified diets were formulated to contain graded levels of crystalline lysine based on the amino acid profile of the whole body and fed to the fish for a period of 60 days. Fish fed the "ideal protein" diet had significantly higher (p<0.05) specific growth rates (2.95±0.18), protein efficiency ratios (0.41±0.05) and significantly lower (p<0.05) food conversion ratios (3.02±0.29). Lysine levels in the whole body increased with increasing levels of supplemented lysine. The dietary requirement of lysine was found to be 4.30% of dietary protein. The crude protein digestibility of six protein sources was investigated. Diets were prepared with 1% chromic oxide as an internal marker. The tested protein sources included low temperature Danish fishmeal, steam dried Chilean fishmeal, blood meal, carcass meal, defatted soyabean meal and Spirulina meal. These potential fishmeal substitutes were selected due to their favourable amino acid profiles, and in particular their high levels of lysine, and their high protein content. Both the animal and the plant protein sources were highly digestible. Digestibility co-efficients ranged from 66.09% for Spirulina meal to 73.38% for low temperature Danish fishmeal. The results have shown that juvenile spotted grunter require a minimum of 40% crude protein in their diet, a P:E ratio of 26.7mg/kJ and a lysine concentration of 4.30% of the dietary protein. Long term growth trials are needed to confirm these results. The hypothesis that the proximate composition of the natural diet, and the proximate composition of the animal under investigation, provides a reliable indication of the animals' nutritional requirements was shown to be valid. Differences between the predicted, and the empirically determined optimal protein and protein:energy ratios were slight.
- Full Text:
- Date Issued: 1997
- Authors: Irish, Abigail
- Date: 1997
- Subjects: Fishes -- Nutrition , Pomadasys -- Nutrition , Grunts (Fishes) -- Nutrition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5292 , http://hdl.handle.net/10962/d1005137 , Fishes -- Nutrition , Pomadasys -- Nutrition , Grunts (Fishes) -- Nutrition
- Description: The proximate composition of juvenile spotted grunter, Pomadasys commersonnii and their major prey items were analyzed to test the hypothesis that the dietary protein requirements would approximate the composition of the natural diet. The amino acid profile of juvenile P. commersonnii was analyzed to establish the pattern of limiting amino acids for this species. Juvenile P. commersonnii feed primarily on the mysid, Mesopodopsis slabberi, which has a protein content of 58.27±0.04% and a calorific value of 19.2kJ/g. The first-limiting essential amino acid for this fish was found to be lysine and it was predicted that the optimal dietary protein requirement would be between 50 and 60%. The optimal dietary protein inclusion level was investigated by feeding semi-purified diets containing graded levels of protein, ranging from 37-62%. Maximum growth was found to occur at dietary protein levels ranging from 40-51%. The best food conversion ratio was achieved at 56% dietary protein and the best protein efficiency ratio was obtained at a dietary protein inclusion level of 37-40%. The protein to energy ratio was defined by feeding 3 different protein levels at 3 different P:E levels. These semi-purified diets contained 35, 45 or 55% protein and 6, 8 or 12% dietary lipid, resulting in protein to energy ratios ranging from 21.1 to 42.3mg/kJ. The optimal P:E ratio for this species was found to be 26.7mg/kJ. This diet effected a low food conversion ratio (1.72±0.19), a low hepatosomatic index (4.01±0.23) and a high specific growth rate (5.96±0.36). The essential amino acid requirements of juvenile P. commersonnii were investigated. Semi-purified diets were formulated to contain graded levels of crystalline lysine based on the amino acid profile of the whole body and fed to the fish for a period of 60 days. Fish fed the "ideal protein" diet had significantly higher (p<0.05) specific growth rates (2.95±0.18), protein efficiency ratios (0.41±0.05) and significantly lower (p<0.05) food conversion ratios (3.02±0.29). Lysine levels in the whole body increased with increasing levels of supplemented lysine. The dietary requirement of lysine was found to be 4.30% of dietary protein. The crude protein digestibility of six protein sources was investigated. Diets were prepared with 1% chromic oxide as an internal marker. The tested protein sources included low temperature Danish fishmeal, steam dried Chilean fishmeal, blood meal, carcass meal, defatted soyabean meal and Spirulina meal. These potential fishmeal substitutes were selected due to their favourable amino acid profiles, and in particular their high levels of lysine, and their high protein content. Both the animal and the plant protein sources were highly digestible. Digestibility co-efficients ranged from 66.09% for Spirulina meal to 73.38% for low temperature Danish fishmeal. The results have shown that juvenile spotted grunter require a minimum of 40% crude protein in their diet, a P:E ratio of 26.7mg/kJ and a lysine concentration of 4.30% of the dietary protein. Long term growth trials are needed to confirm these results. The hypothesis that the proximate composition of the natural diet, and the proximate composition of the animal under investigation, provides a reliable indication of the animals' nutritional requirements was shown to be valid. Differences between the predicted, and the empirically determined optimal protein and protein:energy ratios were slight.
- Full Text:
- Date Issued: 1997
Investigations into the larval rearing of two South African sparid species
- Authors: Davis, Jerome Adam
- Date: 1997
- Subjects: Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5293 , http://hdl.handle.net/10962/d1005138 , Sparidae
- Description: The most significant bottleneck to the development of marine finfish culture is a reliable production of juveniles for growout. This is due to the small size at hatch and delicate nature of the pelagic larvae produced by most commercially desirable species. However, over the last 30 years, improved larviculture techniques have been developed to the extent that many species are being successfully cultured worldwide. These techniques were applied to two endemic species as a preliminary step towards establishing marine finfish aquaculture in South Africa. Adult roman Chtysoblephus laticeps and carpenter Argyrozona argyrozona (Pisces: Sparidae) were caught in the Tsitsikamma National Park. Both species responded to injection with pituitary extract, HCG and LHRHa, and were succesfully stripped up to 48 hours after injection. Fish were stripped twice, the second stripping producing better quality eggs. Chyrysoblephus laticeps also spawned naturally after injection with LHRHa. The fertilised eggs were incubated and the larvae reared in a fully recirculating seawater system. One batch of A. argyrozona and three batches of C. laticeps were reared through metamorphosis on a diet of enriched rotifers and Anemia, and inert foods, following commonly used rearing procedures. Both species followed developmental patterns of other cultured larvae, displaying typical critical stages; high mortalities at first-feeding and cannibalism from 26-30 days after hatch resulted in survival rates ranging from 0.1-0.5%. Growth, survival, size of gape at first-feeding, and ease of weaning onto an inert diet of C. laticeps was comparable to other species being reared for the first time, indicating some potential as a candidate species. The numbers of A. argyrozona larvae reared were insufficient to make comparisons with other studies. The adults also proved to be susceptible to physical damage while in captivity and were, therefore, considered unsuitable for aquaculture. The thesis describes the spawning procedure, the systems developed and the larval rearing process. The critical stages of first-feeding, swim bladder inflation, settlement and cannibalism are discussed and the development of the larvae described. The ontogeny of both species is described in detail. Both species displayed typical sparid developmental patterns, but differed with respect to pigmentation, head spination and morphometrics.
- Full Text:
- Date Issued: 1997
- Authors: Davis, Jerome Adam
- Date: 1997
- Subjects: Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5293 , http://hdl.handle.net/10962/d1005138 , Sparidae
- Description: The most significant bottleneck to the development of marine finfish culture is a reliable production of juveniles for growout. This is due to the small size at hatch and delicate nature of the pelagic larvae produced by most commercially desirable species. However, over the last 30 years, improved larviculture techniques have been developed to the extent that many species are being successfully cultured worldwide. These techniques were applied to two endemic species as a preliminary step towards establishing marine finfish aquaculture in South Africa. Adult roman Chtysoblephus laticeps and carpenter Argyrozona argyrozona (Pisces: Sparidae) were caught in the Tsitsikamma National Park. Both species responded to injection with pituitary extract, HCG and LHRHa, and were succesfully stripped up to 48 hours after injection. Fish were stripped twice, the second stripping producing better quality eggs. Chyrysoblephus laticeps also spawned naturally after injection with LHRHa. The fertilised eggs were incubated and the larvae reared in a fully recirculating seawater system. One batch of A. argyrozona and three batches of C. laticeps were reared through metamorphosis on a diet of enriched rotifers and Anemia, and inert foods, following commonly used rearing procedures. Both species followed developmental patterns of other cultured larvae, displaying typical critical stages; high mortalities at first-feeding and cannibalism from 26-30 days after hatch resulted in survival rates ranging from 0.1-0.5%. Growth, survival, size of gape at first-feeding, and ease of weaning onto an inert diet of C. laticeps was comparable to other species being reared for the first time, indicating some potential as a candidate species. The numbers of A. argyrozona larvae reared were insufficient to make comparisons with other studies. The adults also proved to be susceptible to physical damage while in captivity and were, therefore, considered unsuitable for aquaculture. The thesis describes the spawning procedure, the systems developed and the larval rearing process. The critical stages of first-feeding, swim bladder inflation, settlement and cannibalism are discussed and the development of the larvae described. The ontogeny of both species is described in detail. Both species displayed typical sparid developmental patterns, but differed with respect to pigmentation, head spination and morphometrics.
- Full Text:
- Date Issued: 1997
Isolation and identification of Beta-Lactam Producing Microorganisms using PCR based methodologies
- Authors: Krallis, Myrsini
- Date: 1997
- Subjects: Polymerase chain reaction , Bacterial genetics , Fungi -- Genetics , Beta lactam antibiotics , Microbial enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4155 , http://hdl.handle.net/10962/d1018237
- Description: The polymerase chain reaction (PCR) was investigated as a potential tool in microbial screening for 13-lactam. producing organisms. Optimization of PCR conditions and the addition of acetamide to the PCR reaction allowed for the successful amplification of the isopenicillin N synthetase (lPNS) gene in S. clavuligerus, S. tanashiensis, S. griseus, S. olivaceus, S. lipmanii, and S. chartreusis. PCR was used to produce a radiolabelled probe from S. clavuligerus that was used to detect analogous genes in bacteria and fungi. Southern blot and dot blot analysis using the lPNS probe revealed the presence of IPNS-like sequences in seventeen organisms. Fourteen of these sequences belonged to known 13-lactam. producing organisms; one unidentified soil isolate; and two non-/3-lactam. producing organisms viz. S. venezuelae ATCC 10712 and S. hygroscopicus ATCC 21703. The lPNS gene was also detected in a 13-lactam producer (S. chartreusis) that had lost its ability to produce antibiotic. It would therefore have been overlooked in a conventional antibiotic screening program. The use of PCR, coupled with Southern hybridization and dot blot analysis, increased the sensitivity and specificity of the antibiotic screening procedures and allowed for the investigation of evolutionary relationships between the eukaryotes and the prokaryotes. A preliminary investigation into the potential use of RAPD PCR and protein fmgerprinting as tools for solving discrepancies in streptomycete identification was conducted. A variety of streptomycete species that were chosen as being representative of a number of numerical taxonomic classes were amplified using various RAPD primers. Streptomycetes appear to be genetically diverse organisms as was reflected by their RAPD and protein profiles. The application of PCR in an antibiotic screening program showed great potential as a specific and sensitive tool in the detection of /3-lactam producers and in the elimination of duplicate strains.
- Full Text:
- Date Issued: 1997
- Authors: Krallis, Myrsini
- Date: 1997
- Subjects: Polymerase chain reaction , Bacterial genetics , Fungi -- Genetics , Beta lactam antibiotics , Microbial enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4155 , http://hdl.handle.net/10962/d1018237
- Description: The polymerase chain reaction (PCR) was investigated as a potential tool in microbial screening for 13-lactam. producing organisms. Optimization of PCR conditions and the addition of acetamide to the PCR reaction allowed for the successful amplification of the isopenicillin N synthetase (lPNS) gene in S. clavuligerus, S. tanashiensis, S. griseus, S. olivaceus, S. lipmanii, and S. chartreusis. PCR was used to produce a radiolabelled probe from S. clavuligerus that was used to detect analogous genes in bacteria and fungi. Southern blot and dot blot analysis using the lPNS probe revealed the presence of IPNS-like sequences in seventeen organisms. Fourteen of these sequences belonged to known 13-lactam. producing organisms; one unidentified soil isolate; and two non-/3-lactam. producing organisms viz. S. venezuelae ATCC 10712 and S. hygroscopicus ATCC 21703. The lPNS gene was also detected in a 13-lactam producer (S. chartreusis) that had lost its ability to produce antibiotic. It would therefore have been overlooked in a conventional antibiotic screening program. The use of PCR, coupled with Southern hybridization and dot blot analysis, increased the sensitivity and specificity of the antibiotic screening procedures and allowed for the investigation of evolutionary relationships between the eukaryotes and the prokaryotes. A preliminary investigation into the potential use of RAPD PCR and protein fmgerprinting as tools for solving discrepancies in streptomycete identification was conducted. A variety of streptomycete species that were chosen as being representative of a number of numerical taxonomic classes were amplified using various RAPD primers. Streptomycetes appear to be genetically diverse organisms as was reflected by their RAPD and protein profiles. The application of PCR in an antibiotic screening program showed great potential as a specific and sensitive tool in the detection of /3-lactam producers and in the elimination of duplicate strains.
- Full Text:
- Date Issued: 1997
Juvenile diversion: keeping children out of prison
- Authors: Lewis, Sharon
- Date: 1997
- Subjects: Juvenile delinquents -- South Africa , Juvenile justice, Administration of -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3682 , http://hdl.handle.net/10962/d1003197 , Juvenile delinquents -- South Africa , Juvenile justice, Administration of -- South Africa
- Description: This thesis covers the topic of juvenile diversion with respect to keeping juveniles from progressing further into the justice system as well as keeping them out of prison. It deals with a number of areas. The first is diversion before an offence has been committed - prevention. Here a number of recommendations are made with respect to education of the child and the community in order to make prevention a priority when new diversion programmes are considered and introduced. The second area is that of diversion after the offence has taken place. This deals with diversion by the police at the moment of apprehension and recommends the introduction of cautions as a diversionary measure. The third aspect that is considered is diversion after the juvenile has been arrested and/or charged. The establishment of Reception and Assessment Centres and the setting up of Family Group Conferences are especially highlighted. The detention of the child until his/her trial is also investigated and it is concluded that this is an unnecessary measure except in extreme circumstances. The progression of the child's case to court is the fifth area considered. Here, recommendations are made as to the necessity for the proper training of court personnel and the need for the introduction of court imposed diversionary programmes before sentencing. With respect to diversion after the child has been found guilty, a number of suggestions are made as to the introduction of new sentencing options and new or improved institutions. Finally, recent reforms are discussed. The conclusion reached is that juveniles should not be imprisoned except in the most extreme cases, and that diversion programmes should be instituted as soon as possible as the basis of SouthAfrica's juvenile justice system. It is deemed essential that diversion begins with prevention and continues until sentencing is completed, and that all children are diverted unless this is not possible.
- Full Text:
- Date Issued: 1997
- Authors: Lewis, Sharon
- Date: 1997
- Subjects: Juvenile delinquents -- South Africa , Juvenile justice, Administration of -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3682 , http://hdl.handle.net/10962/d1003197 , Juvenile delinquents -- South Africa , Juvenile justice, Administration of -- South Africa
- Description: This thesis covers the topic of juvenile diversion with respect to keeping juveniles from progressing further into the justice system as well as keeping them out of prison. It deals with a number of areas. The first is diversion before an offence has been committed - prevention. Here a number of recommendations are made with respect to education of the child and the community in order to make prevention a priority when new diversion programmes are considered and introduced. The second area is that of diversion after the offence has taken place. This deals with diversion by the police at the moment of apprehension and recommends the introduction of cautions as a diversionary measure. The third aspect that is considered is diversion after the juvenile has been arrested and/or charged. The establishment of Reception and Assessment Centres and the setting up of Family Group Conferences are especially highlighted. The detention of the child until his/her trial is also investigated and it is concluded that this is an unnecessary measure except in extreme circumstances. The progression of the child's case to court is the fifth area considered. Here, recommendations are made as to the necessity for the proper training of court personnel and the need for the introduction of court imposed diversionary programmes before sentencing. With respect to diversion after the child has been found guilty, a number of suggestions are made as to the introduction of new sentencing options and new or improved institutions. Finally, recent reforms are discussed. The conclusion reached is that juveniles should not be imprisoned except in the most extreme cases, and that diversion programmes should be instituted as soon as possible as the basis of SouthAfrica's juvenile justice system. It is deemed essential that diversion begins with prevention and continues until sentencing is completed, and that all children are diverted unless this is not possible.
- Full Text:
- Date Issued: 1997
Knowledge of safe sex practices and HIV transmission, propensity for risk taking, and alcohol/drug use in the aetiology of unprotected sex
- Authors: Simpson, Malcolm Robert
- Date: 1997
- Subjects: HIV infections -- Prevention , Safe sex in AIDS prevention
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3146 , http://hdl.handle.net/10962/d1007421 , HIV infections -- Prevention , Safe sex in AIDS prevention
- Description: Second year psychology students (N=176) from Rhodes University were surveyed using an anonymous questionnaire to obtain information on sexual behaviour and knowledge of the acquired immunodeficiency syndrome (AIDS) among young people. The following information was obtained: Knowledge of safe sex practices and HIV transmission was high although a number of misconceptions were noted. Only fifty six percent of students viewed oral sex with a condom as safe and thirty one percent do not consider mutual masturbation with a condom safe. Thirteen percent and twenty five percent respectively identified insects and saliva as being routes of HIV transmission. Magazines (96%), informal discussions with friends (95%), public pamphlets (86%) and public television (79%) were preferred sources of information. The students' knowledge did not appear to significantly affect sexual behaviour. Eighty percent of respondents were intimately involved with another person during the past twelve months, and only fifteen percent always made use of a latex barrier when being sexually intimate. Despite high rates of alcohol and/or drug consumption (80% of students use such substances), and the belief by the majority of respondents that alcohol and/or drugs facilitate higher risk behaviours, no support for the alcohol/risky sex hypothesis was found. Students were found to score highly on proneness to psychological and behavioural risk taking, and no significant relationship between this and unprotected sex was found. It can be concluded that educational programmes need to focus on what constitutes safe sexual practices in order to equip young adults with the knowledge they need to make informed choices regarding the relative risks of various sexual activities.
- Full Text:
- Date Issued: 1997
- Authors: Simpson, Malcolm Robert
- Date: 1997
- Subjects: HIV infections -- Prevention , Safe sex in AIDS prevention
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3146 , http://hdl.handle.net/10962/d1007421 , HIV infections -- Prevention , Safe sex in AIDS prevention
- Description: Second year psychology students (N=176) from Rhodes University were surveyed using an anonymous questionnaire to obtain information on sexual behaviour and knowledge of the acquired immunodeficiency syndrome (AIDS) among young people. The following information was obtained: Knowledge of safe sex practices and HIV transmission was high although a number of misconceptions were noted. Only fifty six percent of students viewed oral sex with a condom as safe and thirty one percent do not consider mutual masturbation with a condom safe. Thirteen percent and twenty five percent respectively identified insects and saliva as being routes of HIV transmission. Magazines (96%), informal discussions with friends (95%), public pamphlets (86%) and public television (79%) were preferred sources of information. The students' knowledge did not appear to significantly affect sexual behaviour. Eighty percent of respondents were intimately involved with another person during the past twelve months, and only fifteen percent always made use of a latex barrier when being sexually intimate. Despite high rates of alcohol and/or drug consumption (80% of students use such substances), and the belief by the majority of respondents that alcohol and/or drugs facilitate higher risk behaviours, no support for the alcohol/risky sex hypothesis was found. Students were found to score highly on proneness to psychological and behavioural risk taking, and no significant relationship between this and unprotected sex was found. It can be concluded that educational programmes need to focus on what constitutes safe sexual practices in order to equip young adults with the knowledge they need to make informed choices regarding the relative risks of various sexual activities.
- Full Text:
- Date Issued: 1997
Macroinvertebrate community and species responses to chlorinated sewage effluent in the Umsunduze and Umbilo rivers, Kwa Zulu-Natal, South Africa
- Authors: Williams, Margot Lluttrell
- Date: 1997
- Subjects: Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5727 , http://hdl.handle.net/10962/d1005413 , Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Description: Chlorine has a wide variety of applications in water treatment. Because of its disinfectant efficacy, it is used world wide for the treatment of potable water, sewage, swimming pools and for the control of nuisance organisms in cooling towers. A problem arises when such chlorinated water enters the natural environment, as chlorine's greatest advantage, i.e. its germicidal capacity, becomes its greatest disadvantage. In particular, the discharge of heated, chlorinated water from cooling towers and chlorinated, treated sewage into rivers have severe consequences for the riverine flora and fauna. This study focused on the effects of chlorinated, treated sewage effluent on the community structure of benthic macroinvertebrates in two rivers in KwaZulu-Natal viz. the Umsunduze River in the Pietermaritzburg area, and the Umbilo River in the Durban area. The study was conducted in three phases. The first two phases comprised a toxicological investigation of the effects of chlorine on a selected riverine macroinvertebrate, and the third phase comprised an ecotoxicological investigation of the effects of chlorinated treated sewage on benthic macroinvertebrate community structure. The first phase of the study involved the development of an artificial stream system which would be suitable for determining the response of a selected macroinvertebrate species to chlorine. Chlorine is both reactive and volatile, so this necessitated the development of a specialised flow-through system with apparatus which would allow continuous dosing of a sodium hypochlorite solution. The system was set up at the Process Evaluation Facility at Wiggins Waterworks, Durban, where raw water from lnanda Dam was used. The second phase involved the use of this artificial stream system to conduct acute 96 h toxicity tests. Baetid mayfly nymphs (Baetis harrisoni Barnard) were selected as the test organisms after a preliminary investigation found them to be suitable for survival under laboratory conditions. For comparative purposes, tests were run first on B. harrisoni from a relatively uncontaminated stream in a residential area of Westville, then on specimens from the severely impacted Umbilo River. The LC₅₀ of chlorine for organisms from both sources was found to be in the region of 0.004 mg/l (free chlorine). This value was well below the general effluent standard of 0.1 mg/l in effect at the time. The recommended acute environmental guideline is 0.001 mg/l. The third phase of the study involved field validation of the toxicity test results. It was hypothesised that since the LC₅₀ for free chlorine was 0.004 mg/l, B. harrisoni would not be found downstream from a point source of chlorinated effluent where the concentration of free chlorine ranged from 0.06 to 0.2 mg/l, and that the macroinvertebrate community structure would also be altered. In order to test these hypotheses, benthic macro invertebrate community structure was investigated at several sites up- and downstream from the outlets of the Darvill Wastewater Works in the Umsunduze River and the Umbilo Sewage Purification Works in the Umbilo River. In addition, in order to differentiate between the effects of chlorinated and unchlorinated treated sewage, a section of the Umbilo River (upstream from the chlorinated discharge) was exposed to unchlorinated, treated sewage. In this way, a limited "before and after" sewage and an "upstream and downstream" from sewage investigation could be carried out. Organisms were collected from riffles (and from pools in the Umbilo River) and the samples were then sorted and organisms were identified to species level, where possible, otherwise to genus or family. Changes in community composition were shown graphically as pie charts of relative proportions of organisms found at each site, graphs of the average number of taxa at each site; and graphs of the average number of individuals at each site; Data from the Umbilo River were also analysed using TWINSPAN (Two-way indicator species analysis). In both the Umsunduze and the Umbilo rivers, the deleterious effects of the chlorinated effluent were clearly evident. At Umsunduze Site 3 and Umbilo Site 5 (both immediately downstream from the chlorinated effluent) both the number of taxa and number of individuals were substantially reduced, sometimes to zero. Where organisms were found at the next sites downstream (Sites 4 and 6 respectively), the samples were dominated by Chironomus. In contrast, the unchlorinated effluent in the Umbilo River caused very little difference in community structure. As predicted, B. harrisoni was not found in downstream samples in which chlorine was present, yet appeared to be relatively unaffected by the unchlorinated effluent, suggesting that chlorine, rather than the effluent was responsible for its absence at downstream sites. In conclusion, it would appear that while treated sewage effluent certainly causes changes in macroinvertebrate community structure, chlorination of this effluent leads to large scale destruction of the riverine community. This in turn delays the recovery process of the river, rendering a longer stretch unfit for use. The consequences of this delayed recovery are that the failure to meet the water quality requirements of the natural environment results in those of the other water users (agriculture, industry, domestic and recreation) not being met. This reduces the natural capacity of the riverine community to process organic waste and recover from the discharge of sewage effluent. Chlorination increases the distance of impaired water quality and environmental integrity which result from organically enriched treated sewage effluent. The results of the study indicated that the draft water quality guidelines for aquatic ecosystems, derived from inadequate data, and calculated with a safety factor, were the correct order of magnitude. The approach followed in the study will be useful in the development and refinement of water quality guidelines for aquatic ecosystems.
- Full Text:
- Date Issued: 1997
- Authors: Williams, Margot Lluttrell
- Date: 1997
- Subjects: Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5727 , http://hdl.handle.net/10962/d1005413 , Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Description: Chlorine has a wide variety of applications in water treatment. Because of its disinfectant efficacy, it is used world wide for the treatment of potable water, sewage, swimming pools and for the control of nuisance organisms in cooling towers. A problem arises when such chlorinated water enters the natural environment, as chlorine's greatest advantage, i.e. its germicidal capacity, becomes its greatest disadvantage. In particular, the discharge of heated, chlorinated water from cooling towers and chlorinated, treated sewage into rivers have severe consequences for the riverine flora and fauna. This study focused on the effects of chlorinated, treated sewage effluent on the community structure of benthic macroinvertebrates in two rivers in KwaZulu-Natal viz. the Umsunduze River in the Pietermaritzburg area, and the Umbilo River in the Durban area. The study was conducted in three phases. The first two phases comprised a toxicological investigation of the effects of chlorine on a selected riverine macroinvertebrate, and the third phase comprised an ecotoxicological investigation of the effects of chlorinated treated sewage on benthic macroinvertebrate community structure. The first phase of the study involved the development of an artificial stream system which would be suitable for determining the response of a selected macroinvertebrate species to chlorine. Chlorine is both reactive and volatile, so this necessitated the development of a specialised flow-through system with apparatus which would allow continuous dosing of a sodium hypochlorite solution. The system was set up at the Process Evaluation Facility at Wiggins Waterworks, Durban, where raw water from lnanda Dam was used. The second phase involved the use of this artificial stream system to conduct acute 96 h toxicity tests. Baetid mayfly nymphs (Baetis harrisoni Barnard) were selected as the test organisms after a preliminary investigation found them to be suitable for survival under laboratory conditions. For comparative purposes, tests were run first on B. harrisoni from a relatively uncontaminated stream in a residential area of Westville, then on specimens from the severely impacted Umbilo River. The LC₅₀ of chlorine for organisms from both sources was found to be in the region of 0.004 mg/l (free chlorine). This value was well below the general effluent standard of 0.1 mg/l in effect at the time. The recommended acute environmental guideline is 0.001 mg/l. The third phase of the study involved field validation of the toxicity test results. It was hypothesised that since the LC₅₀ for free chlorine was 0.004 mg/l, B. harrisoni would not be found downstream from a point source of chlorinated effluent where the concentration of free chlorine ranged from 0.06 to 0.2 mg/l, and that the macroinvertebrate community structure would also be altered. In order to test these hypotheses, benthic macro invertebrate community structure was investigated at several sites up- and downstream from the outlets of the Darvill Wastewater Works in the Umsunduze River and the Umbilo Sewage Purification Works in the Umbilo River. In addition, in order to differentiate between the effects of chlorinated and unchlorinated treated sewage, a section of the Umbilo River (upstream from the chlorinated discharge) was exposed to unchlorinated, treated sewage. In this way, a limited "before and after" sewage and an "upstream and downstream" from sewage investigation could be carried out. Organisms were collected from riffles (and from pools in the Umbilo River) and the samples were then sorted and organisms were identified to species level, where possible, otherwise to genus or family. Changes in community composition were shown graphically as pie charts of relative proportions of organisms found at each site, graphs of the average number of taxa at each site; and graphs of the average number of individuals at each site; Data from the Umbilo River were also analysed using TWINSPAN (Two-way indicator species analysis). In both the Umsunduze and the Umbilo rivers, the deleterious effects of the chlorinated effluent were clearly evident. At Umsunduze Site 3 and Umbilo Site 5 (both immediately downstream from the chlorinated effluent) both the number of taxa and number of individuals were substantially reduced, sometimes to zero. Where organisms were found at the next sites downstream (Sites 4 and 6 respectively), the samples were dominated by Chironomus. In contrast, the unchlorinated effluent in the Umbilo River caused very little difference in community structure. As predicted, B. harrisoni was not found in downstream samples in which chlorine was present, yet appeared to be relatively unaffected by the unchlorinated effluent, suggesting that chlorine, rather than the effluent was responsible for its absence at downstream sites. In conclusion, it would appear that while treated sewage effluent certainly causes changes in macroinvertebrate community structure, chlorination of this effluent leads to large scale destruction of the riverine community. This in turn delays the recovery process of the river, rendering a longer stretch unfit for use. The consequences of this delayed recovery are that the failure to meet the water quality requirements of the natural environment results in those of the other water users (agriculture, industry, domestic and recreation) not being met. This reduces the natural capacity of the riverine community to process organic waste and recover from the discharge of sewage effluent. Chlorination increases the distance of impaired water quality and environmental integrity which result from organically enriched treated sewage effluent. The results of the study indicated that the draft water quality guidelines for aquatic ecosystems, derived from inadequate data, and calculated with a safety factor, were the correct order of magnitude. The approach followed in the study will be useful in the development and refinement of water quality guidelines for aquatic ecosystems.
- Full Text:
- Date Issued: 1997
Metabolic responses in melanoma cells to combined nutrient supplementation
- Authors: Midgley, Nicola-Ann
- Date: 1997
- Subjects: Melanoma Tumors -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4036 , http://hdl.handle.net/10962/d1004096
- Description: This thesis examined the effect and biochemical mechanism by which combined vitamin E and C supplementation may influence tumour cell growth. The study initially addressed the effect of combined vitamin E succinate and Asc supplementation over a nutritional concentration range (5- 20μg/ml) and (25-50μg/ml) respectively, on the in vitro growth of non-malignant LLCMK and malignant BL6 cells. Supplementation of BL6 and LLCMK cells with combined vitamin E succinate and ascorbic acid, resulted in no significant increasing or decreasing trend in LLCMK cell growth, while in BL6 cells a significant decrease in cell growth was observed at all combined vitamin concentrations. It has been suggested that these vitamins may act synergistically to inhibit tumour cell growth through their antioxidant properties in quenching free radicals and lipid peroxidation and furthermore through their modulation of the activities of various enzymes and metabolites in the eicosanoid pathway. This study consequently investigated the effects of combined vitamin E succinate and ascorbic acid supplementation on these parameters. Throughout this study, emphasis was placed on the BL6 melanoma cells, as combined vitamin E succinate and ascorbic acid supplementation did not significantly affect growth or levels of secondary metabolites in the non-malignant LLCMK cells. Combined vitamin E succinate and ascorbic acid supplementation of BL6 cells resulted in a marked but non significant increase in free radical and a significant increase in lipid peroxidation levels. This prooxidant effect was accompanied by a significant decrease in BL6 cell growth, suggesting that the growth inhibitory effects of combined vitainin E succinate and ascorbic acid on BL6 cells in vitro was not mediated through their synergistic antioxidant properties. Vitamin E succinate is a nonphysiological antioxidant in its esterified form, hence cleavage of the succinate group must occur in order for ascorbic acid to interact with the free alcohol, vitamin E. The inability of combined vitamin E succinate and ascorbic acid to reduce free radicals and lipid peroxidation levels within BL6 cells may not be due to their ineffectiveness as antioxidants but rather the presence of other contributing factors which influence the oxidation state within the BL6 cells. Vitamin E is believed to modulate membrane-bound enzymes through membrane stabilization. Furthermore, the stabilizing effect of vitamin E may be enhanced by the ascorbic acid-sparing effect of vitamin E. Hence, this study investigated the effect of combined vitamin E succinate and ascorbic acid in modulating the activity of various enzymes and secondary messengers in the eicosanoid pathway. Supplementation with combined vitamin E succinate (5-20μg/ml) and ascorbic acid (25-50μg/ml) resulted in significant increases in phospholipase A₂, 5-lipoxygenase, cyclooxygenase and adenyl ate cyclase activity, with a significant decrease in BL6 cell growth. The possible synergistic action of these vitamins in terms of modulating membrane-bound enzymes was further substantiated by uptake and cellular distribution studies. Vitamin E succinate and vitamin E in the membrane fraction increased significantly compared to control cultures, while ascorbic acid levels were significantly higher in the stroma fraction when compared to membrane fractions. Consequently, another factor accounting for increased activities of phospholipase A2, 5-lipoxygenase and adenylate cyclase activities as a result of vitamin supplementation in BL6 cells may be an increased availability of Ca²+. Supplementation of BL6 cells with combined vitamin E succinate and ascorbic acid resulted in significant increases in intracellular Ca²+ levels at all combined vitamin groups. Furthermore, this increase in intracellular Ca²+ was positively correlated with cl1anges of the above-mentioned enzyme activities. Within the eicosanoid pathway, the rate of prostaglandin synthesis is regulated by phospholipase A₂ activity and arachidonic acid release, and the net prostaglandin production is dependent on cyclooxygenase activity, hence the effects of combined vitamin E succinate and ascorbic acid on arachidonic acid composition and prostaglandin production within BL6 cells was determined. The percentage arachidonic acid composition of the BL6 cells was elevated and inversely related to cell growth following combined vitamin E succinate and ascorbic acid supplementation. Prostaglandin E₂ and prostaglandin I₂ levels increased significantly, while those of prostaglandin D2 and prostaglandin F₂α increased markedly following supplementation of combined vitamin E succinate and ascorbic acid. These increases in prostaglandin levels were inversely related to BL6 cell growth, suggesting that the prostaglandins were involved in negative regulation of BL6 cell growth. When comparing the levels of prostaglandins, prostaglandin E2 levels were significantly higher when compared to prostaglandin D₂, prostaglandin F₂α and prostaglandin I₂ suggesting that vitamin E₂ succinate and ascorbic acid effects were mediated primarily through an increase in prostaglandin E2. Hence, prostaglandin E2 levels in combined vitamin E succinate and ascorbic acid appeared to be dependent on the amount of precursor present and the activity of its synthetic enzymes. This was confirmed when BL6 cells were supplemented with arachidonic acid. Arachidonic acid had an inhibitory effect on BL6 cell growth and also stimulated prostaglandin E₂ production. Prostaglandin E₂ levels are in turn believed to modulate adenylate cyclase activity in BL6 cells, hence it is reasonable to conclude that adenylate cyclase activity is dependent on prostaglandin E₂ levels. Combined vitamin E succinate and Asc supplementation to BL6 cells resulted in significant increases in adenyl ate cyclase and cyclic adenosine monophosphate, which again correlated with a significant decrease in cell growth. As cyclic adenosine monophosphate has a regulatory role in the cell cycle this study suggested that the effect of combined vitamin E succinate and ascorbic acid supplementation was mediated through the final effect provided by the second messenger, cyclic adenosine monophosphate. This was confirmed when BL6 cells were supplemented with dexamethasone, a phospholipase A₂ inhibitor. This treatment rsulted in combined vitamin E succinate and ascorbic acid having no inhibitory effect on BL6 cell growth. Cyclooxygenase activity, prostaglandin E₂ levels, adenylate cyclase activity and cyclic adenosine monophosphate levels were significantly lower in dexamethasone-treated cells compared to non-treated dexamethasone cultures. The reason for the increased free radical and lipid peroxidation levels in BL6 cells was further investigated. Cyclooxygenase enzymes are believed to generate free radical species during catalytic activity. Analysis of free radical and lipid peroxidation levels following supplementation with dexamethasone revealed markedly lower free radical and significantly lower lipid peroxidation levels in comparison with control cultures and non dexamethasone-treated cultures. These results suggest that the observed increases in free radical and lipid peroxidation levels in BL6 cells supplemented with combined vitamin E succinate and ascorbic acid were indirectly due to the increase in cyclooxygenase activity in these cells.
- Full Text:
- Date Issued: 1997
- Authors: Midgley, Nicola-Ann
- Date: 1997
- Subjects: Melanoma Tumors -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4036 , http://hdl.handle.net/10962/d1004096
- Description: This thesis examined the effect and biochemical mechanism by which combined vitamin E and C supplementation may influence tumour cell growth. The study initially addressed the effect of combined vitamin E succinate and Asc supplementation over a nutritional concentration range (5- 20μg/ml) and (25-50μg/ml) respectively, on the in vitro growth of non-malignant LLCMK and malignant BL6 cells. Supplementation of BL6 and LLCMK cells with combined vitamin E succinate and ascorbic acid, resulted in no significant increasing or decreasing trend in LLCMK cell growth, while in BL6 cells a significant decrease in cell growth was observed at all combined vitamin concentrations. It has been suggested that these vitamins may act synergistically to inhibit tumour cell growth through their antioxidant properties in quenching free radicals and lipid peroxidation and furthermore through their modulation of the activities of various enzymes and metabolites in the eicosanoid pathway. This study consequently investigated the effects of combined vitamin E succinate and ascorbic acid supplementation on these parameters. Throughout this study, emphasis was placed on the BL6 melanoma cells, as combined vitamin E succinate and ascorbic acid supplementation did not significantly affect growth or levels of secondary metabolites in the non-malignant LLCMK cells. Combined vitamin E succinate and ascorbic acid supplementation of BL6 cells resulted in a marked but non significant increase in free radical and a significant increase in lipid peroxidation levels. This prooxidant effect was accompanied by a significant decrease in BL6 cell growth, suggesting that the growth inhibitory effects of combined vitainin E succinate and ascorbic acid on BL6 cells in vitro was not mediated through their synergistic antioxidant properties. Vitamin E succinate is a nonphysiological antioxidant in its esterified form, hence cleavage of the succinate group must occur in order for ascorbic acid to interact with the free alcohol, vitamin E. The inability of combined vitamin E succinate and ascorbic acid to reduce free radicals and lipid peroxidation levels within BL6 cells may not be due to their ineffectiveness as antioxidants but rather the presence of other contributing factors which influence the oxidation state within the BL6 cells. Vitamin E is believed to modulate membrane-bound enzymes through membrane stabilization. Furthermore, the stabilizing effect of vitamin E may be enhanced by the ascorbic acid-sparing effect of vitamin E. Hence, this study investigated the effect of combined vitamin E succinate and ascorbic acid in modulating the activity of various enzymes and secondary messengers in the eicosanoid pathway. Supplementation with combined vitamin E succinate (5-20μg/ml) and ascorbic acid (25-50μg/ml) resulted in significant increases in phospholipase A₂, 5-lipoxygenase, cyclooxygenase and adenyl ate cyclase activity, with a significant decrease in BL6 cell growth. The possible synergistic action of these vitamins in terms of modulating membrane-bound enzymes was further substantiated by uptake and cellular distribution studies. Vitamin E succinate and vitamin E in the membrane fraction increased significantly compared to control cultures, while ascorbic acid levels were significantly higher in the stroma fraction when compared to membrane fractions. Consequently, another factor accounting for increased activities of phospholipase A2, 5-lipoxygenase and adenylate cyclase activities as a result of vitamin supplementation in BL6 cells may be an increased availability of Ca²+. Supplementation of BL6 cells with combined vitamin E succinate and ascorbic acid resulted in significant increases in intracellular Ca²+ levels at all combined vitamin groups. Furthermore, this increase in intracellular Ca²+ was positively correlated with cl1anges of the above-mentioned enzyme activities. Within the eicosanoid pathway, the rate of prostaglandin synthesis is regulated by phospholipase A₂ activity and arachidonic acid release, and the net prostaglandin production is dependent on cyclooxygenase activity, hence the effects of combined vitamin E succinate and ascorbic acid on arachidonic acid composition and prostaglandin production within BL6 cells was determined. The percentage arachidonic acid composition of the BL6 cells was elevated and inversely related to cell growth following combined vitamin E succinate and ascorbic acid supplementation. Prostaglandin E₂ and prostaglandin I₂ levels increased significantly, while those of prostaglandin D2 and prostaglandin F₂α increased markedly following supplementation of combined vitamin E succinate and ascorbic acid. These increases in prostaglandin levels were inversely related to BL6 cell growth, suggesting that the prostaglandins were involved in negative regulation of BL6 cell growth. When comparing the levels of prostaglandins, prostaglandin E2 levels were significantly higher when compared to prostaglandin D₂, prostaglandin F₂α and prostaglandin I₂ suggesting that vitamin E₂ succinate and ascorbic acid effects were mediated primarily through an increase in prostaglandin E2. Hence, prostaglandin E2 levels in combined vitamin E succinate and ascorbic acid appeared to be dependent on the amount of precursor present and the activity of its synthetic enzymes. This was confirmed when BL6 cells were supplemented with arachidonic acid. Arachidonic acid had an inhibitory effect on BL6 cell growth and also stimulated prostaglandin E₂ production. Prostaglandin E₂ levels are in turn believed to modulate adenylate cyclase activity in BL6 cells, hence it is reasonable to conclude that adenylate cyclase activity is dependent on prostaglandin E₂ levels. Combined vitamin E succinate and Asc supplementation to BL6 cells resulted in significant increases in adenyl ate cyclase and cyclic adenosine monophosphate, which again correlated with a significant decrease in cell growth. As cyclic adenosine monophosphate has a regulatory role in the cell cycle this study suggested that the effect of combined vitamin E succinate and ascorbic acid supplementation was mediated through the final effect provided by the second messenger, cyclic adenosine monophosphate. This was confirmed when BL6 cells were supplemented with dexamethasone, a phospholipase A₂ inhibitor. This treatment rsulted in combined vitamin E succinate and ascorbic acid having no inhibitory effect on BL6 cell growth. Cyclooxygenase activity, prostaglandin E₂ levels, adenylate cyclase activity and cyclic adenosine monophosphate levels were significantly lower in dexamethasone-treated cells compared to non-treated dexamethasone cultures. The reason for the increased free radical and lipid peroxidation levels in BL6 cells was further investigated. Cyclooxygenase enzymes are believed to generate free radical species during catalytic activity. Analysis of free radical and lipid peroxidation levels following supplementation with dexamethasone revealed markedly lower free radical and significantly lower lipid peroxidation levels in comparison with control cultures and non dexamethasone-treated cultures. These results suggest that the observed increases in free radical and lipid peroxidation levels in BL6 cells supplemented with combined vitamin E succinate and ascorbic acid were indirectly due to the increase in cyclooxygenase activity in these cells.
- Full Text:
- Date Issued: 1997
Modelling parallel and distributed virtual reality systems for performance analysis and comparison
- Authors: Bangay, Shaun Douglas
- Date: 1997
- Subjects: Virtual reality Computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4657 , http://hdl.handle.net/10962/d1006656
- Description: Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems.
- Full Text:
- Date Issued: 1997
- Authors: Bangay, Shaun Douglas
- Date: 1997
- Subjects: Virtual reality Computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4657 , http://hdl.handle.net/10962/d1006656
- Description: Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems.
- Full Text:
- Date Issued: 1997
Negotiating a comprehensive long-term relationship between South Africa and the European Union: from free trade to trade and development
- Authors: Cross, Peter John
- Date: 1997
- Subjects: Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2768 , http://hdl.handle.net/10962/d1002978 , Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Description: On 10 May 1994 the European Union offeredSouth Africa a package of measures to ... send a strong political signal to the incoming govemment and to the South African population, thus proving its firm determination to support the transition towards democracy and its willingness to contribute to the reconstruction and economic development of South Africa after the elections. This package consisted of two parts: 1. A series of short term implementations to take place with immediate effect to help South Africa's development and transition, and 2. An offer to negotiate a comprehensive long-term relationship with South Africa should the new government so request. South Africa accepted the European Union's offer to negotiate a long-term relationship, and in response requested membership of the structure governing the Union's relations with the rest of the countries in Sub-Saharan Africa and some countries in the Caribbean and Pacific, namely the Lomé Convention. Due to various incompatibilities South Africa was not allowed to join this organisation. In its place the European Union offered to negotiate an agreement with South Africa that would lead to a Free Trade Area. This agreement was in keeping with the rules as laid down by the World Trade Organisation. It envisaged the lowering of tariffs and trade barriers between the Union and South Africa over a period not exceeding 12 years, allowing for asymmetry in terms of time constraints in implementation only. South Africa saw this type of agreement as inconsistent with the desire expressed by the European Union to support the countries development and the integration of the Southern African region. In its place South Africa proposed a new concept in trade agreement, this concept, known as the Trade and Development Agreement, embodied both trade liberalisation and support for development. This agreement would introduce a new paradigm of thought to govern trade between developed countries and developing countries within the World Trade Organisation's rules. This paper explores the events that unfolded in these negotiations. It attempts to discover whether, in the current global environment, it is possible, or beneficial, for the developed world to act in an altruistic manner towards another state in order to assist its development.
- Full Text:
- Date Issued: 1997
- Authors: Cross, Peter John
- Date: 1997
- Subjects: Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2768 , http://hdl.handle.net/10962/d1002978 , Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Description: On 10 May 1994 the European Union offeredSouth Africa a package of measures to ... send a strong political signal to the incoming govemment and to the South African population, thus proving its firm determination to support the transition towards democracy and its willingness to contribute to the reconstruction and economic development of South Africa after the elections. This package consisted of two parts: 1. A series of short term implementations to take place with immediate effect to help South Africa's development and transition, and 2. An offer to negotiate a comprehensive long-term relationship with South Africa should the new government so request. South Africa accepted the European Union's offer to negotiate a long-term relationship, and in response requested membership of the structure governing the Union's relations with the rest of the countries in Sub-Saharan Africa and some countries in the Caribbean and Pacific, namely the Lomé Convention. Due to various incompatibilities South Africa was not allowed to join this organisation. In its place the European Union offered to negotiate an agreement with South Africa that would lead to a Free Trade Area. This agreement was in keeping with the rules as laid down by the World Trade Organisation. It envisaged the lowering of tariffs and trade barriers between the Union and South Africa over a period not exceeding 12 years, allowing for asymmetry in terms of time constraints in implementation only. South Africa saw this type of agreement as inconsistent with the desire expressed by the European Union to support the countries development and the integration of the Southern African region. In its place South Africa proposed a new concept in trade agreement, this concept, known as the Trade and Development Agreement, embodied both trade liberalisation and support for development. This agreement would introduce a new paradigm of thought to govern trade between developed countries and developing countries within the World Trade Organisation's rules. This paper explores the events that unfolded in these negotiations. It attempts to discover whether, in the current global environment, it is possible, or beneficial, for the developed world to act in an altruistic manner towards another state in order to assist its development.
- Full Text:
- Date Issued: 1997
Newspapers in education programmes and South African youth: a survey of the relationship between South African school-goers and newspapers in Esikhawini, Kwazulu-Natal
- Authors: McComb, Roslin Vanessa
- Date: 1997
- Subjects: Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3465 , http://hdl.handle.net/10962/d1002920 , Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Description: This study examines the relationship which scholars have with newspapers against the background of a Newspapers in Education (NIE) programme in two black South African primary schools. Considering the presence of newspapers in the class as a medium of instruction, a number of factors are found to influence the -relationship which scholars have with newspapers. These factors are: scholars' access to newspapers; the nature of lessons using the newspaper; the character of the newspaper used in NIE and the context of education at the particular schools, including the attitudes and organisational abilities of both teachers and the principal. A description and analysis of this relationship is conducted in terms of the knowledge, attitudes and behaviour which scholars had -in te1ation to newspapers. This research is qualitative, undertaken from a constructivist-interpretative approach, and is set within international and South African contexts. The findings are relevant to understanding NIE programmes' interface with scholars' educational performance and with newspaper marketing objectives, as well as to the theorisation of NIE practices.
- Full Text:
- Date Issued: 1997
- Authors: McComb, Roslin Vanessa
- Date: 1997
- Subjects: Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3465 , http://hdl.handle.net/10962/d1002920 , Newspapers in education -- South Africa , School children -- South Africa -- KwaZulu-Natal -- esikhawini , Newspapers in education
- Description: This study examines the relationship which scholars have with newspapers against the background of a Newspapers in Education (NIE) programme in two black South African primary schools. Considering the presence of newspapers in the class as a medium of instruction, a number of factors are found to influence the -relationship which scholars have with newspapers. These factors are: scholars' access to newspapers; the nature of lessons using the newspaper; the character of the newspaper used in NIE and the context of education at the particular schools, including the attitudes and organisational abilities of both teachers and the principal. A description and analysis of this relationship is conducted in terms of the knowledge, attitudes and behaviour which scholars had -in te1ation to newspapers. This research is qualitative, undertaken from a constructivist-interpretative approach, and is set within international and South African contexts. The findings are relevant to understanding NIE programmes' interface with scholars' educational performance and with newspaper marketing objectives, as well as to the theorisation of NIE practices.
- Full Text:
- Date Issued: 1997
Parasitism and invasive species : an ecological study of mussel populations
- Calvo Ugarteburu, Miren Gurutze
- Authors: Calvo Ugarteburu, Miren Gurutze
- Date: 1997
- Subjects: Perna -- Parasites Mytilidae -- Parasites Perna -- Ecology Mytilidae -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5736 , http://hdl.handle.net/10962/d1005422
- Description: The Mediterranean mussel Mytilus galloprovincialis, was introduced accidentally to South Africa and has since become invasive. One possible explanation for the success of this species is that it has been released from the effects of parasites which affect the indigenous species of mussels. The aim of this work was to examine the parasitic load of different mussel populations along the southern African coast and to assess the effects of parasites on their hosts. A survey was done to quantify the levels of parasitism in indigenous populations of Perna perna from Southern Africa and of Mytilus galloprovincialis from South Africa (where it is exotic) and Spain (where it is indigenous). This survey was carried out at three different geographic scales: small scale (metres), studying the incidence of parasites within a mussel bed; medium scale (kilometres to tens of kilometres), comparing prevalences of infection among different localities; and large scale (hundreds to thousands of kilometres), examining infection rates along the Southern African coast, as well as the coast of the Basque Country (North Spain). During this survey metazoan parasites other than trematodes were rare. Four species of trematodes were commonly found infecting the indigenous mussel Perna perna. These were metacercariae of the genus Proctoeces, bucephalid sporocysts, encysted metacercariae on the labial palps and gelatinous cysts with metacercariae inside. A detailed description of Proctoeces is given; the other parasites are described elsewhere. No parasites were found in M. galloprovincialis either in South Africa or in Spain. This thesis concentrates on the study of prevalences of Proctoeces and bucephalid sporocysts and their effects on Perna perna. Infection rates with Proctoeces are highly dependent on the sex of the host, with more females than males being infected, and are also size dependent, though only for females. Identification of the sex of mussels infected with bucephalid sporocysts is often not possible since the sporocysts spread over the gonad and replace it. Prevalence of infection with this parasite also increases with the size of the host. To study the influence of Proctoeces and bucephalid sporocysts on the ecological fitness of Perna perna, their effects on survival and competitive ability were tested. The results showed significant negative effects. Both parasites significantly depressed condition but only after spawning, when the mussels were already stressed. In order to check for effects on host survival, the effects of both parasites on mortality rates, gaping behaviour and water loss of mussels exposed to air were also examined. Neither parasite affected mortality rate or gaping behaviour of Perna perna. Proctoeces did not affect the amount of water lost by mussels, but the bucephalid sporocysts did. Mussels infected with sporocysts lost significantly more water than non-infected individuals. This increase in water loss was not related to the gaping behaviour, but a test of the strength of the adductor muscles showed that less force was needed to open mussels with bucephalid sporocysts than non-infected mussels. This was not the case for mussels infected by Proctoeces. Weaker mussels will fail to seal the valves properly, resulting in an increase of water loss on exposure to air by evaporation. Another factor that will have an obvious effect on a population is the reproductive output of the animals. Histological sections of the gonad of infected and non-infected females were cut to study the effects of both parasites on reproduction. Statistical tests comparing the numbers and sizes of oocytes in females infected with Proctoeces and non-infected females showed no significant differences. However, bucephalid sporocysts have a dramatic effect on reproduction by castrating the host, leaving no trace of sex products. One of the major factors shaping the composition of a mussel bed is competition for space and food, with smaller mussels being at a competitive disadvantage. Thus, in order to examine effects of both parasites on the competitive ability of Perna perna, summer and winter growth rates were compared for infected and non-infected mussels. Proctoeces reduced growth both in summer and in winter whilst bucephalid sporocysts had no significant effect. Both growth and reproduction are important components of the energy budget of an animal, and each is affected by either Proctoeces or the bucephalid sporocysts. In an attempt to test if Perna perna compensates energetically for these negative effects, filtration rates and oxygen consumption of mussels with and without parasites were measured. Neither parasite had a significant effect on filtration rates or oxygen consumption of the host. All these results indicate that both Proctoeces and the bucephalid sporocysts have a detrimental effect on their host, and that the mussels do not compensate for these negative effects. There is neither an increase in filtration, nor a decrease in respiration to balance the energy lost to the parasite. The two parasites studied affect the host in different but complementary ways. The effects of both parasites are concentrated on those size classes of mussel which channel most energy into the portion of the energy budget affected by the parasite. Proctoeces affects growth only in the smaller individuals, which under normal conditions would put most energy into growth; and the bucephalid sporocysts castrate the bigger mussels, which would expend most energy on reproduction. By reducing growth rates of small mussels or castrating large mussels, these parasites effectively remove them from the breeding population and reduce their competitive abilities. These negative effects, together with the high prevalence of both parasites in Perna perna along the South African coast and their absence in Mytilus galloprovincialis, suggest that parasites may be an important reason for the success of Mytilus.
- Full Text:
- Date Issued: 1997
- Authors: Calvo Ugarteburu, Miren Gurutze
- Date: 1997
- Subjects: Perna -- Parasites Mytilidae -- Parasites Perna -- Ecology Mytilidae -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5736 , http://hdl.handle.net/10962/d1005422
- Description: The Mediterranean mussel Mytilus galloprovincialis, was introduced accidentally to South Africa and has since become invasive. One possible explanation for the success of this species is that it has been released from the effects of parasites which affect the indigenous species of mussels. The aim of this work was to examine the parasitic load of different mussel populations along the southern African coast and to assess the effects of parasites on their hosts. A survey was done to quantify the levels of parasitism in indigenous populations of Perna perna from Southern Africa and of Mytilus galloprovincialis from South Africa (where it is exotic) and Spain (where it is indigenous). This survey was carried out at three different geographic scales: small scale (metres), studying the incidence of parasites within a mussel bed; medium scale (kilometres to tens of kilometres), comparing prevalences of infection among different localities; and large scale (hundreds to thousands of kilometres), examining infection rates along the Southern African coast, as well as the coast of the Basque Country (North Spain). During this survey metazoan parasites other than trematodes were rare. Four species of trematodes were commonly found infecting the indigenous mussel Perna perna. These were metacercariae of the genus Proctoeces, bucephalid sporocysts, encysted metacercariae on the labial palps and gelatinous cysts with metacercariae inside. A detailed description of Proctoeces is given; the other parasites are described elsewhere. No parasites were found in M. galloprovincialis either in South Africa or in Spain. This thesis concentrates on the study of prevalences of Proctoeces and bucephalid sporocysts and their effects on Perna perna. Infection rates with Proctoeces are highly dependent on the sex of the host, with more females than males being infected, and are also size dependent, though only for females. Identification of the sex of mussels infected with bucephalid sporocysts is often not possible since the sporocysts spread over the gonad and replace it. Prevalence of infection with this parasite also increases with the size of the host. To study the influence of Proctoeces and bucephalid sporocysts on the ecological fitness of Perna perna, their effects on survival and competitive ability were tested. The results showed significant negative effects. Both parasites significantly depressed condition but only after spawning, when the mussels were already stressed. In order to check for effects on host survival, the effects of both parasites on mortality rates, gaping behaviour and water loss of mussels exposed to air were also examined. Neither parasite affected mortality rate or gaping behaviour of Perna perna. Proctoeces did not affect the amount of water lost by mussels, but the bucephalid sporocysts did. Mussels infected with sporocysts lost significantly more water than non-infected individuals. This increase in water loss was not related to the gaping behaviour, but a test of the strength of the adductor muscles showed that less force was needed to open mussels with bucephalid sporocysts than non-infected mussels. This was not the case for mussels infected by Proctoeces. Weaker mussels will fail to seal the valves properly, resulting in an increase of water loss on exposure to air by evaporation. Another factor that will have an obvious effect on a population is the reproductive output of the animals. Histological sections of the gonad of infected and non-infected females were cut to study the effects of both parasites on reproduction. Statistical tests comparing the numbers and sizes of oocytes in females infected with Proctoeces and non-infected females showed no significant differences. However, bucephalid sporocysts have a dramatic effect on reproduction by castrating the host, leaving no trace of sex products. One of the major factors shaping the composition of a mussel bed is competition for space and food, with smaller mussels being at a competitive disadvantage. Thus, in order to examine effects of both parasites on the competitive ability of Perna perna, summer and winter growth rates were compared for infected and non-infected mussels. Proctoeces reduced growth both in summer and in winter whilst bucephalid sporocysts had no significant effect. Both growth and reproduction are important components of the energy budget of an animal, and each is affected by either Proctoeces or the bucephalid sporocysts. In an attempt to test if Perna perna compensates energetically for these negative effects, filtration rates and oxygen consumption of mussels with and without parasites were measured. Neither parasite had a significant effect on filtration rates or oxygen consumption of the host. All these results indicate that both Proctoeces and the bucephalid sporocysts have a detrimental effect on their host, and that the mussels do not compensate for these negative effects. There is neither an increase in filtration, nor a decrease in respiration to balance the energy lost to the parasite. The two parasites studied affect the host in different but complementary ways. The effects of both parasites are concentrated on those size classes of mussel which channel most energy into the portion of the energy budget affected by the parasite. Proctoeces affects growth only in the smaller individuals, which under normal conditions would put most energy into growth; and the bucephalid sporocysts castrate the bigger mussels, which would expend most energy on reproduction. By reducing growth rates of small mussels or castrating large mussels, these parasites effectively remove them from the breeding population and reduce their competitive abilities. These negative effects, together with the high prevalence of both parasites in Perna perna along the South African coast and their absence in Mytilus galloprovincialis, suggest that parasites may be an important reason for the success of Mytilus.
- Full Text:
- Date Issued: 1997
Participatory programme development at an environmental education centre through action research involving secondary school teachers
- Authors: Klein, Charmain Phillida
- Date: 1997
- Subjects: Environmental education -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1690 , http://hdl.handle.net/10962/d1003573
- Description: This mini-thesis documents and analyses an action research project which I conducted with secohdary school teachers. The teachers wished to learn more about environmental education so that they could run their own programmes. I, on the other hand, wanted to improve environmental education programmes offered at the centre where I worked. I hoped that through encouraging teacher participation and involvement, I could begin a process through which the teachers themselves could contribute to, and be in greater control of, their own learning in environmental education. As an introduction to this mini-thesis, I provide some background information on the centre, and state the reasons for having embarked on this project. In addition, I outline the literature and various research findings pertinent to this study. For the purpose of this study, I have selected emancipatory action research as a mode of research, since I believe that emancipatory action research, which embodies processes of reflection and informed action, constitutes the possibility for authentic, emancipatory change in the practice of teachers. The bulk of this thesis, therefore, documents the first two cycles of the action research process and the experiences of those involved in the process. I also briefly comment on some of the claims of action research as a method for research. An important feature of this thesis is that it addresses the possibilities of and constraints to implementing education for the environment in the teachers' practices. The existence of the latter is acknowledged and discussed from my perspective and those of the participating teachers. The study, furthermore, documents teachers' understandings of environmental education, and how this determines the kind of environmental education activities in which they engage. In the final analysis, I argue that the education system we inherited from the apartheid regime has had the effect of producing passive, disempowered and highly demotivated teachers with extremely low levels of self confidence and assertiveness. Despite this fact, I have not only had the opportunity to wltness some positive attitudinal changes occurring in teachers as the study progressed; the project has also enhanced my own understanding of environmental education and the effect the apartheid education system had in shaping my own thoughts and life.
- Full Text:
- Date Issued: 1997
- Authors: Klein, Charmain Phillida
- Date: 1997
- Subjects: Environmental education -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1690 , http://hdl.handle.net/10962/d1003573
- Description: This mini-thesis documents and analyses an action research project which I conducted with secohdary school teachers. The teachers wished to learn more about environmental education so that they could run their own programmes. I, on the other hand, wanted to improve environmental education programmes offered at the centre where I worked. I hoped that through encouraging teacher participation and involvement, I could begin a process through which the teachers themselves could contribute to, and be in greater control of, their own learning in environmental education. As an introduction to this mini-thesis, I provide some background information on the centre, and state the reasons for having embarked on this project. In addition, I outline the literature and various research findings pertinent to this study. For the purpose of this study, I have selected emancipatory action research as a mode of research, since I believe that emancipatory action research, which embodies processes of reflection and informed action, constitutes the possibility for authentic, emancipatory change in the practice of teachers. The bulk of this thesis, therefore, documents the first two cycles of the action research process and the experiences of those involved in the process. I also briefly comment on some of the claims of action research as a method for research. An important feature of this thesis is that it addresses the possibilities of and constraints to implementing education for the environment in the teachers' practices. The existence of the latter is acknowledged and discussed from my perspective and those of the participating teachers. The study, furthermore, documents teachers' understandings of environmental education, and how this determines the kind of environmental education activities in which they engage. In the final analysis, I argue that the education system we inherited from the apartheid regime has had the effect of producing passive, disempowered and highly demotivated teachers with extremely low levels of self confidence and assertiveness. Despite this fact, I have not only had the opportunity to wltness some positive attitudinal changes occurring in teachers as the study progressed; the project has also enhanced my own understanding of environmental education and the effect the apartheid education system had in shaping my own thoughts and life.
- Full Text:
- Date Issued: 1997
Periglacial features in the vicinity of Tiffindell Ski Resort, North East Cape Drakensberg, South Africa, and their implications for the development of the resort
- Authors: Kück, Karen Melody
- Date: 1997
- Subjects: Tiffindell Ski Resort (South Africa) , Slopes (Physical geography) -- South Africa -- Eastern Cape , Landforms -- South Africa -- Eastern Cape , Climatic geomorphology -- South Africa -- Eastern Cape , Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4844 , http://hdl.handle.net/10962/d1005520 , Tiffindell Ski Resort (South Africa) , Slopes (Physical geography) -- South Africa -- Eastern Cape , Landforms -- South Africa -- Eastern Cape , Climatic geomorphology -- South Africa -- Eastern Cape , Drakensberg Mountains
- Description: This thesis provides a description of the periglacial environment and features in the vicinity of Tiffindell Ski resort, on the slopes of Ben MacDhui (3001.2m.), the highest point of the East Cape Drakensberg, South Africa. Active and inactive periglacial features were located, mapped and described. Of particular interest were periglaciar slope deposits including gelifluction turf-banked lobes and stone lobes, and cryoturbation features including polygons and thufur. Local environmental factors, such as aspect, moisture, topography, soil texture and depth of freezing, appear to act as important controls on the spatial distribution of the periglacial features. Identification and quantification of periglacial processes in the regolith was investigated using temperature and soil moisture sensors coupled to dataloggers. Research was undertaken over a 16 month period from June 1995 to September 1996 so that comparisons between the winter conditions of 1995 and 1996 could be drawn. The Tiffindell area was observed to be characterised in the winter months by 'diurnal freezethaw days', as well as by 'ice days', 1996 experiencing colder temperatures than 1995. With more than 78% of the days from May to September 1996 being 'ice days', and simultaneously experiencing high soil moisture contents, freezing penetration to a depth of greater than 0.2m was observed to occur in the Tiffindell area, causing frost heave and gelifluction. The summer thaw of ice lenses that developed in the cold winter months caused surface movement downslope of gelifluction lobes of up to 39mm over an 18 month period, although movement declined rapidly with depth and was essentially restricted to the uppermost 130mm of the regolith. Other features such as sorted and non-sorted polygons and thufur were identified and found to be active under the present climatic conditions and depth of frost penetration at Tiffindell. Stone lobes were identified on the south and southeast-facing slopes at Tiffindell, but are apparently inactive under present climatic conditions. Their existence suggests the presence of severe seasonal frost in the past. The implications of the air and ground surface temperatures, and of seasonal frost penetration for the development of Tiffindell Ski resort were considered, and suggestions regarding their economic significance are presented.
- Full Text:
- Date Issued: 1997
- Authors: Kück, Karen Melody
- Date: 1997
- Subjects: Tiffindell Ski Resort (South Africa) , Slopes (Physical geography) -- South Africa -- Eastern Cape , Landforms -- South Africa -- Eastern Cape , Climatic geomorphology -- South Africa -- Eastern Cape , Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4844 , http://hdl.handle.net/10962/d1005520 , Tiffindell Ski Resort (South Africa) , Slopes (Physical geography) -- South Africa -- Eastern Cape , Landforms -- South Africa -- Eastern Cape , Climatic geomorphology -- South Africa -- Eastern Cape , Drakensberg Mountains
- Description: This thesis provides a description of the periglacial environment and features in the vicinity of Tiffindell Ski resort, on the slopes of Ben MacDhui (3001.2m.), the highest point of the East Cape Drakensberg, South Africa. Active and inactive periglacial features were located, mapped and described. Of particular interest were periglaciar slope deposits including gelifluction turf-banked lobes and stone lobes, and cryoturbation features including polygons and thufur. Local environmental factors, such as aspect, moisture, topography, soil texture and depth of freezing, appear to act as important controls on the spatial distribution of the periglacial features. Identification and quantification of periglacial processes in the regolith was investigated using temperature and soil moisture sensors coupled to dataloggers. Research was undertaken over a 16 month period from June 1995 to September 1996 so that comparisons between the winter conditions of 1995 and 1996 could be drawn. The Tiffindell area was observed to be characterised in the winter months by 'diurnal freezethaw days', as well as by 'ice days', 1996 experiencing colder temperatures than 1995. With more than 78% of the days from May to September 1996 being 'ice days', and simultaneously experiencing high soil moisture contents, freezing penetration to a depth of greater than 0.2m was observed to occur in the Tiffindell area, causing frost heave and gelifluction. The summer thaw of ice lenses that developed in the cold winter months caused surface movement downslope of gelifluction lobes of up to 39mm over an 18 month period, although movement declined rapidly with depth and was essentially restricted to the uppermost 130mm of the regolith. Other features such as sorted and non-sorted polygons and thufur were identified and found to be active under the present climatic conditions and depth of frost penetration at Tiffindell. Stone lobes were identified on the south and southeast-facing slopes at Tiffindell, but are apparently inactive under present climatic conditions. Their existence suggests the presence of severe seasonal frost in the past. The implications of the air and ground surface temperatures, and of seasonal frost penetration for the development of Tiffindell Ski resort were considered, and suggestions regarding their economic significance are presented.
- Full Text:
- Date Issued: 1997