Studies on the Zoarcidae (Teleostei: Perciformes) of the Southern Hemisphere IV. New records and a new species from the Magellan Province of South America
- Authors: Anderson, M Eric , Gosztonyi, Atila E
- Date: 1991
- Language: English
- Type: Text
- Identifier: vital:14999 , http://hdl.handle.net/10962/d1019708 , ISSN 0073-4381 , Ichthyological Bulletin of the J.L.B. Smith Institute of Ichthyology; No. 55
- Description: New data on the eelpouts of the Magellan Province of South America are presented to include accounts of 10 of the 25 species presently known from the area. Aiakas zini, a second species for Aiakas Gosztonyi, 1977, is described as new. On the basis of material collected since the authors last published on the eelpouts of this region (1977 and 1988), enhanced descriptions are provided for Aiakas kreffti, Crossostomus chilensis, Lycenchelys bachmanni, Notolycodes schmidti, Oidiphoms brevis, Ophthalmolycus macrops and Pogonolycus marinae. Placed in synonymy are Crossostomus sobrali Lloris and Rucabado, 1987 with C. chilensis Regan, 1913, Iluocoetes facali Lloris and Rucabado, 1987 with I.fim- briatus Jenyns, 1842 and Haushia Lloris, 1988 with Pogonolycus Norman, 1937. Shorter accounts are provided for data from new specimens of Lycodonus malvinensis and Piedrabuenia ringueleti. A key to all of the species of Zoarcidae from the Magellan Province is included. , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1991
Synthesis and interaction of secondary N-nitrosamines with acetylcholinesterase
- Authors: Mmutle, Tsietso Bernard
- Date: 1991
- Subjects: Chemistry, Physical and theoretical , Enzyme kinetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4058 , http://hdl.handle.net/10962/d1004119 , Chemistry, Physical and theoretical , Enzyme kinetics
- Description: Secondary N-nitrosamines: diphenylnitrosamine (DPhNA), dimethylnitrosamine (DMNA), diethylnitrosamine (DENA), dipropylnitrosamine (DPNA), dibutylnitrosamine (DBNA), diethanolnitrosamine (DEtNA), methylnitrosoglycine (MNGly), nitrosopyrrolidine (NPyr), nitrosomorpholine (NMor) and nitrosopiperidine (NPip) were synthesised and their interaction with acetylcholinesterase (AChE) was investigated. Analyses of kinetic results show that DMNA (Ki=34.78 μM); DENA (Ki=54.24 μM); DPNA(Ki=60.36 μM); DBNA(Ki=95.54 μM); DEtNA(Ki=43.68 μM)MNGly (Ki=30.18 μM); NPip (Ki=123 μM); NPyr (Ki=66.07 μM), NMor (Ki=73.93 μM) and DPhNA (Ki=20.32 μM) are competitive and reversible inhibitors of acetylcholinesterase, with respect to the substrate, acetylthiocholine chloride, ATChCl. With time they act as irreversible covalent inhibitors with dipropy1nitrosamine producing 72% inactivation after 60 minutes. Scatchard analyses of f1uorometric titrations, (Kd=0.75mM-4.09mM); gel chromatography (Kd=O. 80mM-4. 60mM) and equilibrium dia1ysis (Kd=O. 71mM- 4.21mM) for MNG1y, DMNA, DEtNA, DENA, DPNA, NPyr, DSNA, NMor and NPip show that these compounds have weaker affinity for the enzyme, as compared to the much tightly binding aromatic DPhNA, Kd values (0.65mM, 0.68mM and 0.68mM) for fluorometric experiments, gel chromatography and equilibrium dialysis respectively. In all cases, the number of binding sites of acetylcholinesterase averaged to four.
- Full Text:
- Date Issued: 1991
The alluvial diamond deposits of the lower Vaal river between Barkly West and the Vaal-Harts confluence in the Northern Cape province, South Africa
- Authors: Matheys, Fabrice Gilbert
- Date: 1991
- Subjects: Diamond deposits -- South Africa , Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4933 , http://hdl.handle.net/10962/d1005545 , Diamond deposits -- South Africa , Geology, Economic
- Description: The alluvial diamond deposits along the Vaal River, between Barkly West and the Vaal-Harts confluence, have been worked for more than one century by thousands of private diggers. The diamonds are recovered from two sedimentary units of Cenozoic age, the Older Gravels and the Younger Gravels. These rest on a basement of Ventersdorp Supergroup andesites and Karoo Sequence sediments, which have been intruded by Cretaceous kimberlites. The gravels are, in turn, overlain by the Riverton Formation and the Hutton Sand. On a large scale, tectonic setting, geomorphology and palaeoclimate have played a major role in the formation of diamondiferous placers in the area under investigation. A study of the sedimentology of the Younger Gravels was carried out with the aim of acquiring an understanding of the processes responsible for the economic concentration of high quality diamonds. An investigation of facies assemblages, clast composition, clast size, palaeocurrent directions external geometry, particle morphology and led to the conclusion that the Younger Gravels were deposited in a proximal braided stream environment during high discharge. A small-scale experiment was carried out to test the efficiency of different sedimentological trap sites in concentrating kimberlite indicator minerals. The results show that the concentration of indicator minerals is dependent on the size fraction chosen, bed roughness and gravel calibre. The examination of surface features on pyrope, picroilmenite and chrome diopside from kimberlite led to the conclusion that most of these minerals are locally derived. Diamond grade variations within the Younger Gravels are influenced by a combination of factors, including bed roughness, channel width and sorting process from the source. Alluvial diamond exploration programmes must take into account the tectonic setting, the palaeoclimate, the level of erosion, the stability of the drainage system in the area as well as the presence of local trap sites in the river profile. It is concluded that the diamonds are the product of a long and complex process of erosion, reworking and concentration and are derived from Cretaceous kimberlites in the area.
- Full Text:
- Date Issued: 1991
The Behaviour Of Palewinged Starlings And A Comparison With Other Onychognathvs Species
- Authors: Craig, Adrian J F K , Hulley, Patrick E , Walter, Grenville H
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447868 , vital:74680 , https://doi.org/10.1080/00306525.1991.9639648
- Description: Pairs of Palewinged Starlings associate throughout the year and roost at the nest sites. Flock sizes are generally small, even during the non-breeding season. Allofeeding and allopreening have not been recorded. Wing displays emphasize the white region of the primaries. The territory appears to be restricted to the nest site. Interspecific aggression occurred between Redwinged and Palewinged Starlings, and was also directed at other Ed species frequenting the cliff. A form of ceremonial gathering occurs re in Palewinged Starlings. A review of the literature suggests that on behavioural grounds the Palewinged Starling shows no close affinity to the Redwinged Starfng or to any other member of the genus.
- Full Text:
- Date Issued: 1991
The computer in secondary school mathematics : an analysis and classification of possible modes of application, with suggested implications for the mathematics curriculum in South Africa
- Authors: Marsh, Terence Anthony
- Date: 1991
- Subjects: Mathematics -- Computer-assisted instruction Mathematics -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1459 , http://hdl.handle.net/10962/d1003340
- Description: There is a variety of possible ways in which computers can be used to enhance mathematics education. This thesis attempts to identify, analyse and classify these possibilities, particularly at the secondary school level. It describes and exemplifies applications ranging from drill-and-practice through games and simulations to problem solving by computer programming. Software evaluation procedures are considered in some depth. Illuminative evaluations of various items of software and there classroom use are reported. The underlying methodology is small-scale action research. Insights gained during the process of investigating each class of software lead to the eventual formulation of a scheme for classifying mathematics education software by means of 'multidimensional attributes'. It is contended that this scheme will help mathematics teachers to make well informed and sound professional judgements regarding the evaluation and use of computer programs for teaching/learning purposes. Also, it is hoped that this scheme and the thesis as a whole will contribute towards the establishment of well founded standards and procedures for software development in the field of mathematics education. Several implications of the computer for the mathematics curriculum in South Africa are suggested. A note of caution is sounded regarding possible detrimental effects of the computer and several questions requiring further research are posed. A recommendation arising from the thesis is that in-service training courses concerning computer applications in mathematics education should be run for secondary school teachers.
- Full Text:
- Date Issued: 1991
The concentration of economic power in South Africa
- Authors: TURP
- Date: 1991
- Subjects: TURP
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/160931 , vital:40568
- Description: Debate on a post-apartheid economy has once again raised the question of the concentration of economic power in South Africa. It is a known fact that the wealth of South Africa is concentrated in a few hands. For example, it is estimated that 5 % of the population owns 80% of the wealth in the country. At the same time, millions of our people live in poverty. Over half the population in South Africa live below the poverty datum lines (amounts needed for very basic subsistence).
- Full Text:
- Date Issued: 1991
The contribution of meditative experiences to personal growth : a case study
- Authors: Knight, Zelda Gillian
- Date: 1991
- Subjects: Meditation Self-actualization (Psychology)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1466 , http://hdl.handle.net/10962/d1003347
- Description: A three month meditation programme based on Joseph Goldstein's (1976) instructions and discourses given at a Vipassana meditation retreat was implemented among four 17 year old white English-speaking school girls at a private non-racial co-educational high school in South Africa. The meditation experiences of all four subjects were noted, hut only one subject's meditative experiences were documented and used as a case study to explore their use as a tool for personal growth within the framework of ego-psychology and transpersonal psychology. It is concluded that the subject, who meditated on a daily basis, experienced personal growth primarily from the ego-psychology perspective and, it is interesting to note, less so from the transpersonal perspective. Three bypotheses have been put forward for this. Firstly, the actual length of the meditation programme may have been too short, and secondly, the daily meditation sessions too brief to facilitate a process of personal growth and development from within the trans personal psychology framework. Thirdly, the subject was an adolescent school girl and thus may not have been developmentally ready in terms of reaching a level of cognitive, emotional, social and spiritual maturity necessary to experience identification to the transpersonal self.
- Full Text:
- Date Issued: 1991
The development of East London through four decades of municipal control, 1873-1914
- Authors: Tankard, Keith Peter Tempest
- Date: 1991
- Subjects: East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2560 , http://hdl.handle.net/10962/d1002413 , East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Description: This thesis is a study in Urban History which explores the development of East London, a port in the Border region of the Eastern Cape, South Africa, through four decades of municipal control from 1873 to 1914. The town had been established in 1847 as a supply route for the British forces during the War of the Axe (7th Frontier War) but the frontier nature of the port led to economic and physical stagnation during its initial 25 years of existence. Indeed, by the time that the municipality was established in 1873, there were still no streets beyond cart tracks, no established water supply, and sanitary conditions were medieval. The Town Council therefore had much to occupy its attention but lack of positive leadership resulted in failure to capitalise on prosperous economic conditions, while a depression in the 1880's led to a further truncation of growth. It was only in the 1890's that a combination of economic growth and vibrant leadership brought about rapid civic advance, with large-scale expenditure on street construction, as well as the establishment of electricity and a tramway system. The outbreak of the Anglo-Boer War in 1899 slowed progress, however, and a post-war depression placed renewed stress on the municipality. The thesis examines the progress of the town on a broad front, dealing with the issues of economic fluctuations, the growth of the harbour as the heart of the trading sector, the physical advance of the municipality, the search for a viable water supply, the evolution of public health and sanitation, and the establishment of the port as a coastal resort. In addition, it studies the conflict of social attitudes among the townspeople, the evolution of racial segregation, and the effects of the Anglo-Boer War on the town, with the influx of some 5 000 Uitlander refugees and the establishment of a Boer concentration camp. A final chapter attempts an analysis of the reasons behind the Town Council's inability to make the best use of its opportunities to foster the development of East London.
- Full Text:
- Date Issued: 1991
The development, pursuit and maintenance of a South African Antarctic policy : 1926-1988
- Authors: Laverde, René
- Date: 1991
- Subjects: Antarctic Treaty -- (1959) , Antarctica -- History , South Africa -- Foreign relations -- Antarctica
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2523 , http://hdl.handle.net/10962/d1001852
- Description: Connections between South Africa and Antarctica can be traced as far back as the 1700s when European expeditions in search of the southern continent used Cape Town (and later Simonstown) as a base of operation. This link expanded considerably after formal British acquisition of the Cape of Good Hope in 1815, yet it was not until 1926 that an actual South African policy towards the Antarctic began to materialize. Once this policy was established it continued to be characterized by procrastination as well as resistance both from within and without South Africa. The history of South Africa's Antarctic policy can be divided into five periods: first, the commencement of the policy (focusing primarily on economic interests), 1926-1939; second, the pursuit of interests through the policy (focusing on political interests), 1944- 1958; third, the entrenchment of South Africa's interests in the Antarctic (by securing South Africa's position within the Antarctic Treaty System), 1958-1960; fourth, the expansion of and foreign assault on the policy (under the auspices of the Antarctic Treaty System), 1960-1988; and fifth, the defence of and future prospects for the policy (from United Nation's calls for South Africa's exclusion from the Antarctic Treaty System), since 1982. While resistance from inside and outside the government during the first two periods resulted from inadequacies in the South African Antarctic policy itself, resistance in the final two periods has centred upon non-Antarctic issues. As South Africa has faced ever-increasing exclusion from international governmental organizations over opposition to Its apartheid policies, organizations such as the Antarctic Treaty Organization have inevitably been drawn into the debate. As a result, the Consultative Parties of the Antarctic Treaty (of which South Africa is one of the original twelve) have been forced to deal with the following question: to what extent will political issues outside the scope of the management policies of the Antarctic Treaty Organization be allowed to affect the functioning of the Antarctic Treaty System? While the Consultative Parties continue to ponder this and the fact that South Africa's Consultative Status has become the most divisive factor within the Antarctic Treaty System, no final solutions to these issues appear likely before 1991.
- Full Text:
- Date Issued: 1991
The digestive mechanisms of an intertidal grazer, the sea urchin Parechinus angulosus
- Authors: Sweijd, Neville Anthony
- Date: 1991
- Subjects: Sea urchins -- Nutrition , Sea urchins , Echinoida
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5662 , http://hdl.handle.net/10962/d1005346 , Sea urchins -- Nutrition , Sea urchins , Echinoida
- Description: Echinoids are important grazers in the near-shore ecosystem and can significantly effect their ecology. The sea urchin Parechinus angulosus occurs inter- and subtidally along the southern African coast. Within this range it consumes an extremely wide variety of algae. Since algal cell walls have an almost species specific chemical composition, the question arises as to how it can digest the algae that it consumes. In order to investigate the digestive mechanisms employed by P. angulosus, an ultrastructural study of the gut was undertaken to characterize the tissue and identify functional regions in the gut. Ten structural and storage polysaccharides commonly found in macroalgae were used as substrates to assay the digestive polysaccharidases of the sea urchin. The enteric bacteria of the sea urchin were isolated and tested separately for polysaccharidase activity using the same substrates. The results shown that the gut of Parechinus angulosus is regionally specialized, with the foregut primarily responsible for the production of hydrolytic enzymes, while the hindgut is primarily absorptive. The occurrence of lamellar bodies, heterolysosomes, cytoplasmic blebs and paddle cilia among other characteristic features of the digestive epithelium are described and discussed. Two levels of enzyme activity are apparent. Generally the urchin could hydrolyze the reserve polysaccharides, but only partially hydrolyze the structural polysaccharides, of red and green algae. P.angulosus was unable to digest alginic acid, the main structural polysaccharide of brown algae. Mixed cultures of bacteria utilized only the reserve polysaccharides of red and green algae. Significantly, the bacteria were able to hydrolyze alginic acid. Enteric bacteria also showed agarolytic activity. Parechinus angulosus has the ability to digest red and green algae. No lysozyme activity was detected. The enteric bacteria can digest the same algal reserve polysaccharides and so may compete for carbon in the gut. However, in the case of brown algae, bacteria have a potentially important endosymbiotic role as agents of digestion. These results correspond with food preference studies which have shown that, although P.angulosus consumes the kelp Ecklonia maxima, in the western Cape, it is amongst its least preferred food species. The reasons for this are its unpalatability and the urchin's inability to digest brown algae. The digestibility of algal material can be an important factor in determining algal-herbivore interactions.
- Full Text:
- Date Issued: 1991
The distribution patterns and community structure of the Tsitsikamma rocky littoral ichthyofauna
- Authors: Burger, Lynton Francois
- Date: 1991
- Subjects: Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5260 , http://hdl.handle.net/10962/d1005104 , Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Description: The results of a community survey of the rocky intertidal and subtidal reef ichthyofauna of the Tsitsikamma National Park and adjacent areas are presented. An updated species checklist is given, comprising 116 species of 46 families, including a new genus and species of Tripterygiid. Single species are shown to dominate, in terms of numbers, both the cryptic and subtidal components for all the areas sampled down the vertical profile. Species richness, evenness and diversity are found to increase with depth for both the cryptic and suprabenthic components. A community level feeding study shows an increase in trophic specialisation with depth and food availability is found to be an important factor delimiting littoral fish vertical distribution. The nursery function of the Tsitsikamma rocky littoral area is assessed and it is shown that shallow littoral areas as a whole are more important than intertidal pools alone in functioning as nurseries. The results of the study are found to fit into the existing trend of an increase in species richness and diversity, from west to east, along the South African coast. A significant difference is shown between the observed frequencies of species on exploited reefs outside the Park and unexploited reefs inside the Park. The density of the key reef predator Petrus rupestris is shown to be nine times more abundant on deep reef inside the park compared to deep reef outside the park (0.0045 fish/m² and 0.0005 fish/m² respectively) and a paucity of larger individuals of this species on exploited reefs is noted. Marked differences in the relative abundance of other species between exploited and unexploited reefs are evident and it is hypothesised that community disruption has occurred on exploited reefs, either directly or indirectly because of the removal of P. rupestris. These results are discussed in the context of marine reserves as a conservation strategy and a recommendation is made to extend the 5.6km seaward boundary of the Tsitsikamma National Park westwards to include the large concentration of presently exploited rocky reefs between the Blaaukrans river mouth and Natures Valley.
- Full Text:
- Date Issued: 1991
The ecology and culture of the rock catlet Chiloglanis pretoriae (Pisces : mochokidae)
- Authors: De Villiers, Pierre
- Date: 1991
- Subjects: Catfishes -- Africa , Catfishes -- Breeding -- Africa , Catfishes -- Ecology -- Africa , Fishes -- Cultural control -- Africa , Fishes -- Cultural control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5267 , http://hdl.handle.net/10962/d1005111 , Catfishes -- Africa , Catfishes -- Breeding -- Africa , Catfishes -- Ecology -- Africa , Fishes -- Cultural control -- Africa , Fishes -- Cultural control
- Description: Chiloglanis pretoriae is a rock catlet, indigenous to southern Africa. The aim of the study was to develop a technique to culture C. pretoriae as an alternative to harvesting and selling wild caught fish on the international aquarium trade. As nothing was known about the culture of African rock catlets an investigation into the biology and ecology of the species was necessary to develop the culture protocol. Chiloglanis pretoriae inhabits fast flowing rapids (current speeds over 0.6 metres per second). It is a serial interstitial gravel spawner, that spawns during the summer months. Chiloglanis pretoriae is a carnivorous fish species, feeding on aquatic insects. The natural growth rate is relatively fast in the first two years where after it levels off. Sexual maturity (50%) is attained within the first year (44mm total length). From the four cell stage, embryos took seven days to hatch, 16 days to first feeding and 75 days to reach the juvenile phase. The free embryos were well developed and readily accepted artificial feed at first feeding. The fish spawned readily, without hormone induction, in a continuous raceway. Spawning in the 801 retangular glass aquaria was irregular. The substrate within the raceway consisted of gravel and large rocks. The current was maintained at 0.6m/sec, temperature at 26± 0.6⁰C, dissolved oxygen concentrations at 7.1± 0.3mg/l, pH at 6.9± 0.2 and photoperiod at 16L:8D. Conductivity was monitored and remained within the acceptable range of C. pretoriae (84± 10uS/m).
- Full Text:
- Date Issued: 1991
The ecology and management of the fishes of the Okavango Delta, Botswana, with particular reference to the role of the seasonal floods
- Authors: Merron, Glen Steven
- Date: 1991
- Subjects: Fishes -- Ecology -- Botswana Fishes -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5268 , http://hdl.handle.net/10962/d1005112
- Description: The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
- Full Text:
- Date Issued: 1991
The effect of teaching text organisation on reading in English as a second language
- Authors: Silburn, Gail Deirdre
- Date: 1991
- Subjects: English language -- Study and teaching -- Foreign speakers
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: vital:1372 , http://hdl.handle.net/10962/d1001438
- Description: This research investigated the effect of teaching text organisation on reading in English second language to schoolgirls. All subjects underwent a training programme of five one-hour sessions on consecutive school days. The experimental group were trained in the use and recognition of top-level organisation as a reading strategy, based on work done by Bartlett (1978) and Carrell (1985). The control group were trained in unrelated grammar exercises. A pre-test was administered to each group before their programme began. Post-test 1 was administered immediately after the training was completed, and Post-test 2, three weeks later. These tests required a written recall of two passages once they had been read, and an answer to a question on their organisation. The null hypotheses stated that the experimental group's training in the use and recognition of top-level organisation as a reading strategy would make no difference in their ability to read and recall information or to recognise and use top-level organisation in their recalls. For the quantity of information recalled, no differences were found in the Pre-test and Post-test 1; a statistically significant difference was found in Post-test 2 in favour of the experimental group. For the quality of information recalled, the control group remembered more top-level idea units in the Pre-test; there was no difference in Post-test 1; the experimental group did better in three out of five levels in Post-test 2. There was no difference in the Pretest in either group's use of the passage's top-level organisation to structure recalls, but the experimental group did better in both post-tests. The control group did better in the Pre-test in recognising the passage's top-level organisation, but the experimental group did better in both post-tests. The null hypotheses were rejected as the experimental training made a difference, although this difference only became apparent three weeks later, and not immediately after the training. The experimental group's nullifying the control group's Pre-test advantage in Post-test 1 and surpassing it in Post-test 2, powerfully supports Bartlett's and Carrell's findings that teaching the strategy did make a difference and that this effect could be maintained over three weeks
- Full Text:
- Date Issued: 1991
The genesis and controls of gold mineralization south of Rehoboth, Namibia
- Authors: Whitfield, Derek
- Date: 1991
- Subjects: Gold ores -- Geology -- Namibia , Gold ores -- Geology -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4948 , http://hdl.handle.net/10962/d1005560 , Gold ores -- Geology -- Namibia , Gold ores -- Geology -- Africa, Southern
- Description: Gold mineralization is hosted within gossanous quartz-haematite veins in volcano-sedimentary lithologies of the Klein Aub - Rehoboth basin of the Irumide Belt, Namibia. Mineralization and hydrothermal alteration are restricted to deformed lithologies particularly the metasediments. Lithological relationships, geochemistry and metallogenic characteristics of the Irumide Belt suggest an intra-continental rift setting. Copper mineralization is well known along the length of the belt, from Klein Aub in the southwest to Ghanzi in the northeast, whereas gold mineralization appears restricted to the Klein Aub Rehoboth basin. The gold is envisaged as having being leached initially from graben fill sequences during rift closure and basin dewatering. Location of the mineralization is strongly controlled by structure and lithological contact zones. Such zones are percieved as having acted as conduit zones for escaping mineralized fluids during basin closure and deformation. Apart from the lack of an effective mineralizing trap, all features consistent with the development of an ore deposit are present. The largest mineralization traps within the area studied are shear zones followed by lithological contact zones. The Mebi and Blanks gold mines are developed over large shear zones while the Swartmodder and Neuras gold mines are situated over mineralized lithological contacts. The Swartmodder copper mine yielded ore from a mineralized schist enclave within granite. Copper and gold occurrences are attributed to two contrasting styles of mineralization. Copper mineralization is suggested to have developed during initial rifting of the belt (ie. stratabound sedimentary exhalative type), while the gold and minor copper resulted from rift closure and basin dewatering. Although no economical orebody was realized during the course of this study a model is proposed for the development of mineralization within the Irumide basement lithologies as a working hypothesis for future exploration.
- Full Text:
- Date Issued: 1991
The genesis of ilmenite-rich heavy mineral deposits in the Bothaville/Delmas area, and an economic analysis of titanium, with particular reference to the Dwarsfontein deposit, Delmas district
- Authors: Brennan, Michael Brendan
- Date: 1991
- Subjects: Heavy minerals -- South Africa -- Transvaal , Titanium , Geology -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4949 , http://hdl.handle.net/10962/d1005561 , Heavy minerals -- South Africa -- Transvaal , Titanium , Geology -- South Africa -- Transvaal
- Description: A number of ilmenite-rich heavy mineral deposits occur along the northern margin of the intracratonic Karoo basin, and are hosted by the fluvio-deltaic Middle Ecca Group. Coastal reworking of delta front sands within a regressive, microtidal shoreline may be considered as a depositional model for the development of the heavy mineral deposits. An economic analysis of titanium suggests long term positive demand, and sustained high prices for this commodity. An evaluation of the Dwarsfontein ilmenite-rich heavy mineral deposit, using available data, indicates how important it is for deposits of this type to be situated close to an upgrading plant or export harbour.
- Full Text:
- Date Issued: 1991
The geology, petrology and geochemistry of the mineralization and hydrothermal alteration at Ongeama, Ongombo and Matchless West Extension, Namibia
- Authors: Moroni, Marilena
- Date: 1991
- Subjects: Geology -- Namibia , Petrology -- Namibia , Geochemistry -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5045 , http://hdl.handle.net/10962/d1007693 , Geology -- Namibia , Petrology -- Namibia , Geochemistry -- Namibia
- Description: The Matchless Amphibolite Belt (Damara Orogen, Namibia) hosts several volcanogenic-exhalative, sediment-hosted stratiform cupriferous pyrite deposits. These are thought to be related to submarine volcanism during the early evolutionary stages of a narrow Damaran ocean, the Matchless Trough. The mineralized bodies examined (Ongeama, Ongombo and Matchless West Extension) are deformed and metamorphosed to low-medium grade (greenschist-amphibolite facies). They are associated with metapelite and amphibolite country rocks, and crop out as prominent limonite-rich gossans. The elongated shape of the sulphide bodies suggests a structural control. The mineralization normally consists of a variably developed massive sulphide portion, either quartz-, talc- or amphibole-bearing, and a stratigraphically overlying, extensive horizon of sulphide- and baryte-bearing exhalite (magnetite quartzite and less common talc- and actinolite-bearing schists). Lateral and vertical mineralogical changes within the mineralization match with significant variations in the element distribution. A metamorphosed and deformed alteration pipe, indicating the position of the fluid conduit, can be recognized in association with some ore bodies. The formation of quartz-muscovite and chlorite alteration envelopes (Ongeama, Matchless West Extension) and the presence of subtle mineralogical changes (Ongombo) in the immediate wallrocks, accompanied by extensive redistribution, leaching and introduction of elements from outside, suggest the hydrothermal metasomatic origin of the alteration zones. Element zoning within the mineralized bodies can be related to the original position of the vent, possibly coinciding with the intersection of the axis of the alteration pipe with the sulphide body. Cu, Zn, Au (pro parte) and Mo are enriched proximal to the vent, whereas Pb, Ba, Mn, Ag, Au, Sn, Bi and W enrichment characterizes the distal facies of the mineralization. In spite of the obliterating and disrupting effects of the regional dynamo-metamorphism, the element distribution within the mineralization and alteration zones examined is comparable with the geochemical trends observed in present-day mineralizing systems in early- stage oceanic environments (e.g. Guaymas Basin). During exploration for blind volcanogenic mineralization, the detection of hydrothermally altered rocks is fundamental in indicating the proximity to the mineralization. The localization of the alteration zone is also important in the interpretation of the regional geology of the explored area: in deformed terrains the assessment of the stratigraphic position of the alteration zone, relative to the mineralization, helps in establishing the polarity of the sequence.
- Full Text:
- Date Issued: 1991
The healer's art : Cape Nguni diviners in the townships of Grahamstown
- Authors: Hirst, Manton Myatt
- Date: 1991
- Subjects: Healers -- South Africa , Nguni (African people) -- Social life and customs , Divination -- South Africa , Medicine, Magic, mystic, and spagiric -- South Africa , Nguni (African people) -- Religion
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:2084 , http://hdl.handle.net/10962/d1001601
- Description: This is a study of Cape Nguni diviners practising in the townships of Grahamstown where, during the 1970s, there was a large and active concentration of diviners treating clients from the locality, the rural areas and even the large urban centres further afield. The study situates local diviners in the socio-economic, cultural and religious context of contemporary township Iife during the 1970s (see chapter 1 and section 2.1). The personalities and socio-economic circumstances of diviners (and herbalists) are described as well as their case-loads, the various problems they treat, the relations between them and their clients, the economics of healing and the ethics pertaining to the profession (see chapter 2) . Chapter three focuses on the various problems and afflictions - which are largely of an interpersonal nature - suffered by those who are eventually inducted as diviners and the ritual therapy this necessarily entails. Here we see how the diviner, what Lewis (1971) terms a 'wounded healer', becomes an expert in interpersonal and social relations as a result of suffering problems - largely connected to the family but not necessarily limited to it - in interpersonal relations and that require a ritual, and thus social, prophylaxis. The main theoretical argument is that the diviner, qua healer, functions as a hybrid of Levi-Strauss' s bricoleur and Castaneda's 'man of knowledge' artfully combining the ability of the former to invert, mirror or utilise analogies from linguistics to make everything meaningful and the ability of the latter to creatively bend reality . The diviner's cosmology is described in terms of a 'handy', limited but extensive cultural code/repertoire of signs, symbols and metaphors that is utilised in getting the message across to others and in which animals bear the main symbolic load (see chapter 4). This leads logically to a reappraisal of Hammond-Tooke's (1975b) well-known model of Cape Nguni symbolic structure particularly in so far as it pertains to the way in which diviners classify animals, both wild and domestic (see section 4.6). A striking evocation and confirmation of the view argued here, namely of the diviner as bricoleur/'man of knowledge', is contained in chapter five dealing with an analysis of the diviner's 'river' myth and the context, form and content of the divinatory consultation itself. Finally, the conclusions, arising out of this study of contemporary Cape Nguni diviners in town, are evaluated in the ligrht of Lewis's (1966, 1971, 1986) deprivation hypothesis of spirit possession (see chapter 6)
- Full Text:
- Date Issued: 1991
The hermeneutic value of the Daseinsanalytic approach to dream interpretation in psychotherapy: a case study
- Authors: Oberholzer, Sofia Adriana
- Date: 1991
- Subjects: Boss, Medard, 1903-1990 , Dreams -- Psychological aspects -- Case studies , Dream interpretation -- Case studies , Psychotherapy -- Case studies
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3222 , http://hdl.handle.net/10962/d1012988
- Description: The purpose of this study was to investigate the hermeneutic value of the Daseinsanalytic approach to dream interpretation in the process of psychotherapy. After delineating the Daseinsanalytic view on dream interpretation, with emphasis on the conceptualization of Medard Boss, the study explores the usefulness and validity of the case study as a method of investigating the content and process of psychotherapy. A psychodynamic formulation of the presenting problem is based on the conceptualization of the nature and etiology of neurosis as delineated by Andras Angyal, with particular reference to the pattern of noncommitment. The dreams included in the case material are then examined to determine to what degree they facilitated insight into the subjective experience and phenomenological existence of the dreamer, and what effect the dream interpretation based on the Daseinsanalytic approach had on the process of therapy. It is established that a phenomenological understanding of the client's dreams corresponds with his subjective experience of his emotional and existential condition, and that positive changes in the content of the dreams during the course of therapy correspond with overt, observable changes in his behaviour, ideation and mood. Based on these findings, the case study leads to the conclusion that the Daseinsanalytic approach to dream interpretation has hermeneutic value in the process of psychotherapy.
- Full Text:
- Date Issued: 1991
The human skin-blanching assay for comparing topical corticosteroid availability
- Authors: Smith, Eric W , Meyer, Eric , Haigh, John M , Maibach, Harold I
- Date: 1991
- Language: English
- Type: Article
- Identifier: vital:6433 , http://hdl.handle.net/10962/d1006604
- Description: The human skin blanching assay remains in widespread use as a reliable, qualitative, comparative indicator of topical corticosteroid availability and potency. The experimental refinements promulgated by certain researchers in this field have yielded a versatile bioassay for the accurate assessment of new drugs or delivery vehicles. With the increasing appearance of generic topical corticosteroid formulations which compete with trade-name equivalents, the vital importance of this assay in regulatory affairs and assessing bioequivalence has been re-emphasized. It is stressed that if the blanching assay is to be used in this sphere, then multiple-reading trials must be conducted; important registration or clinical decisions cannot be made with any validity from short-term assessments.
- Full Text:
- Date Issued: 1991