A comparison of open source and proprietary digital forensic software
- Authors: Sonnekus, Michael Hendrik
- Date: 2015
- Subjects: Computer crimes , Computer crimes -- Investigation , Electronic evidence , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4717 , http://hdl.handle.net/10962/d1017939
- Description: Scrutiny of the capabilities and accuracy of computer forensic tools is increasing as the number of incidents relying on digital evidence and the weight of that evidence increase. This thesis describes the capabilities of the leading proprietary and open source digital forensic tools. The capabilities of the tools were tested separately on digital media that had been formatted using Windows and Linux. Experiments were carried out with the intention of establishing whether the capabilities of open source computer forensics are similar to those of proprietary computer forensic tools, and whether these tools could complement one another. The tools were tested with regards to their capabilities to make and analyse digital forensic images in a forensically sound manner. The tests were carried out on each media type after deleting data from the media, and then repeated after formatting the media. The results of the experiments performed demonstrate that both proprietary and open source computer forensic tools have superior capabilities in different scenarios, and that the toolsets can be used to validate and complement one another. The implication of these findings is that investigators have an affordable means of validating their findings and are able to more effectively investigate digital media.
- Full Text:
- Date Issued: 2015
A comparison of the comfort properties, measured with a sweating manikin (WalterTM), of clothing containing different fibres
- Authors: Britz, Lizaan
- Date: 2017
- Subjects: Textile chemistry Cotton fabrics , Cotton textiles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14752 , vital:27842
- Description: The main objective of the present study was to determine the relative role and importance of worsted suiting fabric fibre blend vis-à-vis fabric structural parameters, on the comfort related properties of 12 clothing ensembles, each comprising a different man’s suit, but the same wool/nylon underwear and cotton shirt. To achieve the objective, the comfort related properties, namely thermal resistance (Rt) and water vapour resistance (Ret) and water vapour permeability index (Im), of the clothing ensembles, as determined by means of WalterTM, a thermal sweating fabric manikin, were subjected to multi-linear and multi-quadratic analysis, as dependent variables, with the various suiting fabric parameters, namely weight, thickness, density, porosity, air permeability and wool content, as independent variables. It was found that the multi-quadratic regression analysis was able to best explain the observed differences in the clothing ensemble comfort related properties, in terms of the differences in suiting fabric properties. The regression analyses were used to isolate and quantify the effects of the various fabric and fibre content variables on the above mentioned comfort related properties of the various clothing ensembles. This study indicated that the suiting fabric structural properties (notably air permeability), had a more significant influence than either fibre blend or suiting fabric, as measured on WalterTM, a thermal sweating fabric manikin.
- Full Text:
- Date Issued: 2017
A comparison of the legal environmental sustainability requirements of those engaging in the mining cycle, with actual practice in the Carolina X11B quaternary catchment, Mpumalanga, South Africa
- Authors: Thomson, Gareth Peter
- Date: 2018
- Subjects: Mineral industries Environmental aspects South Africa Mpumalanga , Acid mine drainage , Mineral industries Safety measures , Watersheds South Africa , South Africa. National Environmental Management Act, 1998 , Water-supply Law and legislation South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63481 , vital:28417
- Description: Mining is one of the most contentious water users. The mining sector has assumed that promises of economic growth and job creation will enable environmental concerns to be bypassed with as little interference as possible. More recently, the reality of legacy issues related to the inappropriate sign-off of mining sites has become increasingly clear, with acid mine drainage (AMD) being a prime example. There are also increasing concerns regarding uncontrolled prospecting. Climate change is one of the major issues faced in the 21st century, with predictions of heightened water stress for the Southern African region. This, coupled with increased population growth is putting a massive strain on the water resources currently available, making it vital to better protect and ensure the longevity of our water resources. The Carolina Crisis of 2012 highlighted the importance of protecting our water resources, and how easily they can be contaminated to a point where water is not usable. The Carolina crisis provided researchers with a suitable study site to better understand the role mining operations have in a catchment that has experienced a major pollution incident, and what changes have occurred since. In order to understand coal mining practice in relation to regulatory provisions, this project critically explored the processes involved within the mining sector, from ‘cradle-to-grave’, which is known as the coal mining life cycle. In addition, the composite suite of requirements of all the legislative provisions involved in the industry were investigated and the relationship between coal mining practice and environmental protection was explored. These elements were researched in the Upper Komati River Catchment specifically for catchment X11B, using Cultural Historical Activity Theory (CHAT), which gives a holistic understanding of mining as a human activity system. CHAT also sheds light on the issues, gaps and overlaps currently being experienced in the coal mining sector. The Thesis refers to case studies of where mining issues have caused environmental degradation. A complete mining lifecycle in terms of regulatory provisions was compiled, and major issues were uncovered with current legislation in the mining sector that can contribute to the degradation of water resources in South Africa. An integrated water resource quality management plan is needed in order to streamline conservation mandates, identify and reduce duplication of effort and specify roles and responsibilities of authorities involved with decision making process. A Decision Support System (DSS) has been proposed, which would involve adaptive, participatory and inclusive management.
- Full Text:
- Date Issued: 2018
A comparison of the performance of three conceptual mathematical models of the rainfall-runoff process in the Mareetsane Catchment
- Authors: Stickells Peter S
- Date: 1979
- Subjects: Rain and rainfall Mathematical models South Africa Runoff
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4793 , http://hdl.handle.net/10962/d1001893
- Description: The objective of the thesis is to make a critical assessment of the performance of three relatively simple deterministic models of the rainfall-runoff process. The need to evaluate and compare deterministic models arises because of the large number of models which are available in the literature. A number of the available models would appear to be equally suitable for a given situation whereas many models are found to be valid only under the specific range of conditions for which they were developed. Therefore there is a need for guidelines to allow the most judicious selection of a model for a particular set of circumstances. The models used in the study will be tested in a semi-arid catchment to determine their applicability under ephemeral flow conditions
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- Date Issued: 1979
A comparison of the reproductive strategies of key species of a prograding dune system in the Mlalazi Nature Reserve, Natal
- Authors: Todd, Colleen Barbara
- Date: 1995
- Subjects: Sand dune plants -- South Africa -- KwaZulu-Natal -- Mlalazi Nature Reserve , Sand dune plants Comparative studies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4231 , http://hdl.handle.net/10962/d1003800 , Sand dune plants -- South Africa -- KwaZulu-Natal -- Mlalazi Nature Reserve , Sand dune plants Comparative studies
- Description: The succession on the dunes of the Mlalazi Nature Reserve represents a classical example of primary succession. The reproductive strategies of eight key species were compared to determine some of the mechanisms affecting the community dynamics, at the population level, in the early stages of succession. There is a temporal separation in the flowering and fruiting phenologies. Passerina rigida, Stipagrostis zeyheri and Imperata cylindrica produced small seeds with a low fruit/seed mass ratio within a short cycle. The seeds are suitable for wind-dispersal. The animal-dispersed species; Eugenia capensis, Mimusops caffra and Scaevola plumieri, produced large fleshy seeds with a high fruit/seed mass ratio within cycles of six months and more. Chrysanthemoides monilifera, also an animal-dispersed species, produced a large quantity of small fleshy seeds throughout the year. The fern, Microsorium scolopendrium produced spores throughout the year. The staggered fruiting and flowering phenology ensures a year-round availability of fruit in the dunefield. The key species formed less than half of the species composition of the soil seed bank. The size and range of the soil seed bank differed between the species. P. rigida and S. plumieri formed a high proportion of the seeds in the soil with a wide distribution along the successional gradient. The other species had low soil seed densities with short distribution ranges, or were not present. P. rigida and S. plumieri are easily dispersed species, whereas the other species may have a more restricted and clumped distribution due to the effect of foragers. A high density of P. rigida and E. capensis seeds were found under the parent trees. Only seeds of P. rigida and S. zeyheri were found in the soil in the open. Seeds of P. rigida, S. zeyheri, E. capensis and M. caffra were found under the canopies of P. rigida, E. capensis and M. caffra. No seeds of C. monilifera and I. cylindrica were found in the soil, possibly due to predation. The period of the study (September 1991 to November 1992) was in a dry or drought cycle with only 56.8% of the mean annual rainfall falling. Seed germination and seedling survival of all the species were affected by these dry, warm climatic conditions. The species had seedling densities of less than 4 seeds/m². The environmental conditions along the successional gradient also had an effect on seed germination and seedling survival. Environmental factors of soil pH, light intensity and surface soil temperatures were higher in the open than under canopy. Soil pH and the understorey cover decreased as the light intensity decreased from under the canopy of P. rigida to M. caffra . Litter cover and plant height increased. E. capensis had measurements intermediate to the two species, but had higher surface soil temperatures and plant height than P. rigida. Seedlings of P. rigida in the open and under the canopy of the parent plants had died by the end of the monitoring period. 50% of the seedlings of S. zeyheri under the canopy of P. rigida and M. caffra died. The mortality rate of the seedlings of E. capensis was lower under M. caffra than under the parent plants. I. cylindrica may be propagated vegetatively. However, the mortality of the propagules was greater under the canopy of E. capensis than under P. rigida. M. caffra only germinated under the canopy of E. capensis with a 100% mortality of the seedlings. M. scolopendrium only produced propagules through vegetative propagation under the canopy of E. capensis and M. caffra. The mortality of the young ferns was less than 50% and less under M. caffra than under E. capensis. No seedlings of C. monilifera or S. plumieri were found. The seed distribution range, seed germination requirements and the effect of the environmental conditions on the germination of the seeds and seedling establishment of the species appear to important factors of the reproductive strategies regulating the size of the species populations along the successional gradient.
- Full Text:
- Date Issued: 1995
A comparison of the vulcanisation of Polyisoprene by a range of Thiuram Diulfides
- Authors: Van Rooyen, Jason Leigh
- Date: 2007
- Subjects: Vulcanization , Vulcanization accelerators
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10399 , http://hdl.handle.net/10948/733 , Vulcanization , Vulcanization accelerators
- Description: This study was initiated in an attempt to investigate dithiocarbamic acid accelerated sulfur vulcanisation. This was, however, found impossible due to the innate instability of dithiocarbamic acids. The focus of the study was then shifted toward thiuram disulfide accelerated sulfur vulcanisation, with emphasis being placed on a rate comparison. Three groups of accelerators were investigated, namely the aromatic, linear aliphatic and cyclic aliphatic thiuram disulfide adducts. The analysis methods that were employed were conventional rubber (cis-1,4-polyisoprene) techniques coupled to model (squalene) compound investigations. The data that was collected consisted of rheometrical torque vs. time data in the rubber system while the data obtained in the model compound study consisted of sulfur and accelerator concentration data as determined by means of high performance liquid chromatography (HPLC). The aromatic accelerators were synthesised in our labs by means of an addition reaction between the aromatic amine and CS2 in basic medium and subsequent oxidation with K3Fe(CN)6, all in a 1:1 molar ratio. The reaction yield was low due to the instability of the dithiocarbamate intermediates and a sluggish oxidation reaction. In the rate constant determination a first order mathematical approach was used for the rubber system as crosslinking is considered to roughly obey first order kinetics. The model compound data was also found to more accurately fit the first order rate law, with an initial slopes method also being applied to the system to determine secondary rate constants and relative rates for the system. The determination of vulcanisation rate constants in the cis-1,4-polyisoprene system was a success, while the rate data determined by means of the squalene model was more related to the rate of accelerator and sulfur consumption as opposed to the rate of crosslinking as is the case with the rubber rate data. The sulfur first order rate data mirrored the rate data derived from the rubber system more closely than the corresponding accelerator rate data, the relative rate data determined by means of initial slopes method, proved that the homolytic cleavage of thiuram disulfides and the subsequent formation of accelerator polysulfides were not limiting steps. This is seen in the similar relative rate data derived from both the raw sulfur and accelerator data in systems that exhibit vastly different vulcanisation rates. Squalene was deemed a suitable model for the cis-1,4-polyisoprene system, although one should consider the extent of charring and solution effects in the individual systems to account for possible incongruities that may be observed between the rubber and simulated system. The lack of agreement between the rubber and model compound rate constant data lies in the fact that the rate of crosslinking is not simplistically related to the rate at which accelerator and sulfur is consumed, this being especially true for the rate at which the accelerator is consumed. Thus the discussion over the acceleratory rates in the various accelerator systems was limited to observations made in the rubber system, with the model compound data was used exclusively to elucidate mechanistic processes. It was discovered that the groups of accelerators examined, namely linear, cyclic and aromatic thiuram disulfide adducts, produced vastly varied rate data. The aromatic thiuram disulfide adducts had only a slight acceleratory effect on the rate of vulcanisation as compared to the unaccelerated sulfur system. The morpholine adduct had a moderately larger rate of acceleration followed by tetramethyl and tetrethylthiuram disulfide, with N’N-dicyclopentamethylenethiuram disulfide having the fastest rate of acceleration.
- Full Text:
- Date Issued: 2007
A comparison of web-based technologies to serve images from an Oracle9i database
- Authors: Swales, Dylan
- Date: 2004 , 2013-06-18
- Subjects: Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4583 , http://hdl.handle.net/10962/d1004380 , Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Description: The nature of Internet and Intranet Web applications has changed from a static content-distribution medium into an interactive, dynamic medium, often used to serve multimedia from back-end object-relational databases to Web-enabled clients. Consequently, developers need to make an informed technological choice for developing software that supports a Web-based application for distributing multimedia over networks. This decision is based on several factors. Among the factors are ease of programming, richness of features, scalability, and performance. The research focuses on these key factors when distributing images from an Oracle9i database using Java Servlets, JSP, ASP, and ASP.NET as the server-side development technologies. Prototype applications are developed and tested within each technology: one for single image serving and the other for multiple image serving. A matrix of recommendations is provided to distinguish which technology, or combination of technologies, provides the best performance and development platform for image serving within the studied envirorunent. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2004
A comprehensive evaluation framework for system modernization : a case study using data services
- Authors: Barnes, Meredith Anne
- Date: 2011
- Subjects: Computer architecture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10460 , http://hdl.handle.net/10948/1499 , Computer architecture
- Description: Modernization is a solution to migrate cumbersome existing systems to a new architecture for improved longevity of business processes. Three modernization approaches exist. White-box and black-box modernization are distinct from one another. Grey-box modernization is a hybrid of the white-box and black-box approaches. Modernization can be utilised to create data services for a Service Oriented Architecture. Since it is unclear which modernization approach is more suitable for the development of data services, a comprehensive evaluation framework is proposed to evaluate which of the white- or black-box approaches is more suitable. The comprehensive framework consists of three evaluation components. Firstly, developer effort to modernize existing code is measured by acknowledged software metrics. Secondly, the quality of the data services is measured against identified Quality of Service criteria for data services in particular. Thirdly, the effectiveness of the modernized data services is measured through usability evaluations. By inspection of the combination of application of each of the evaluation components, a recommended approach is identified for the modernization of data services. The comprehensive framework was successfully employed to compare the white-box and black-box modernization approaches applied to a case study. Results indicated that had only a single evaluation component been used, inconclusive results of the more suitable approach may have been obtained. The findings of this research contribute a comprehensive evaluation framework which can be applied to compare modernization approaches and measure modernization success.
- Full Text:
- Date Issued: 2011
A computer analysis of some of the Harrison metrics
- Authors: Sadler, Christopher John
- Date: 1975
- Subjects: Computer science -- Mathematics , Software measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5427 , http://hdl.handle.net/10962/d1013151
- Description: In his paper B.K.Harrison concludes with the observation that his "solutions ... are presented as raw material for further research in General Relativity". In the same spirit, the present work started out as an attempt to process that raw material in a production-line powered by a computer. Harrison's solutions uould be fed in at one end, and the finished product, as yet undecided, would appear at the other. In the event, however, the project became more like an exercise in quality control, to continue the analogy. A search was made for algebraic criteria which would distinguish between those solutions which were acceptable for further analysis with particular regard to Gravitational radiation, and those which were not. Regrettably, no criteria could be found which characterised radiative solutions unequivocally, and, at the same time, lent themselves to a computer approach. The result is that the discussion of radiative solutions has had to be relegated to an appendix (Appendix 1), while the main body of the work is concerned with the determination of those quantities (the Newman-Penrose scalars) which would seem to be the foundation of any future computer-based analysis of gravitational radiation. Chapter 1 is an account of the underlying mathematical formulation, defining the terms, concepts and processes involved. In Chapter 2 the transformation of some of the ideas of Chapter 1 into computer software is presented. Chapter 3 is concerned with the specific metrics (the Harrison metrics) and the extent to which they have heen processed. The project has leaned heavily on papers by Harrison for the "raw material", by D' Inverno and Russell Clark, who pioneered the techniques and classified the Harrison metrics, and by Sachs for the treatment of gravitational radiation. However, the analysis of diagonal metrics, the special tetrad of Chapter 2 and the results in Appendix 2 are new.
- Full Text:
- Date Issued: 1975
A computer-controlled tracking system
- Authors: Oberem, Graham Edmund
- Date: 1979
- Subjects: Artificial satellites -- Tracking
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5437 , http://hdl.handle.net/10962/d1001990
- Description: A computer-controlled tracking system has been designed and constructed for the two metre antenna of the 22 GHz radio telescope at Rhodes University. The control system has been tested and its step response has been analysed with a view to response time optimization. Computer programs for tracking the sun and the moon have been written. Initial results of tracking the sun have revealed linearity and temperature stability problems. These problems have been investigated and suggestions have been made as to how they might be removed
- Full Text:
- Date Issued: 1979
A congestion aware ant colony optimisation-based routing and wavelength assignment algorithm for transparent flexi-grid optical burst switched networks
- Authors: Oladipo, Joshua Femi
- Date: 2018
- Subjects: Ants -- Behavior -- Mathematical models , Distributed algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34733 , vital:33432
- Description: Optical Burst Switching (OBS) over transparent exi-grid optical networks, is considered a potential solution to the increasing pressure on backbone networks due to the increase in internet use and widespread adoption of various high bandwidth applications. Both technologies allow for more e cient usage of a networks resources. However, transmissions over exi-grid networks are more susceptible to optical impairments than transmissions made over xed-grid networks, and OBS suers from high burst loss due to contention. These issues need to be solved in order to reap the full benets of both technologies. An open issue for OBS whose solution would mitigate both issues is the Routing and Wavelength Assignment (RWA) algorithm. Ant Colony Optimisation (ACO) is a method of interest for solving the RWA problem on OBS networks. This study aims to improve on current dynamic ACO-based solutions to the Routing and Wavelength Assignment problem on transparent exi-grid Optical Burst Switched networks.
- Full Text:
- Date Issued: 2018
A contribution to a generic revision of Simochromis and Tropheus (Pisces : Cichlidae) - from Lake Tanganyika, with special reference to the Pharyngeal Apophysis and its taxonomic importance
- Authors: Axelrod, Glen S
- Date: 1978
- Subjects: Cichlids -- Tanganyika, Lake
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5349 , http://hdl.handle.net/10962/d1007510 , Cichlids -- Tanganyika, Lake
- Description: The purpose of this thesis is to investigate the taxonomic status of Simochromis and Tropheue. Material for the study wae collected during three visits to Lake Tanganyika in 1976-1977. Tropheus polli G. S . Axelrod 1977, was found and described, and a new species of Simochromis was found and will be described in a forthcoming paper. Nine colour varieties of Tropheus maorii and three colour varieties of Tropheus duboisi were found and described. A diagnosis and description, with colour photographs, is given using morphometries and meristics of the five species of Simochromis and four species of Tropheus. A dissection and cleaning technique tor the pharyngeal apophysis and lower pharyngeal bone is explained, together with a method for the interpretation of relative bone composition of the pharyngeal apophysis. Photographs are included. The dentition is examined, evaluated and figured. Doubt has been cast upon the taxonomic validity of the composition of the pharyngeal apophysis as an indicator of affinity at the sub familial level. This is shown by its seeming lack of functional relationship, apparent arbitrary variation, interspecific variability in Simochromis and Tropheus, and intraspecific variability in S. diagramma and T. duboisi. Thus, the apophysis cannot be considered a reliable cichlid taxonomic characteristic at any level of classification, unless its validity is Substantiated in each instance. Furthermore, it is considered very probable that the Tropheus-Simochromis species complex is a monophyletic assemblage at the genus level, on the basis of similar dentition and mouth form, which is unique in Lake Tanganyika. It is proposed on phyletic grounds that Simochromis and Tropheus be united into the one genus Tropheus, and that Tropheus be divided into the subgenera , Tropheus (Tropheus) and Tropheus (Simochromis), along the lines of its previous division in two separate genera. Characteristics supporting this division include differences in the anal and dorsal fin meristic counts noted in the original descriptions of the genera. In addition, two modifications of the dentition were found during the course of this study which are not mentioned in any previous literature. It is considered probable, that Tropheus (Tropheus) and Tropheus (Simochromis) are monophyletic sister groups within the Tropheus complex. Pseudosimochromis Nelissen 1977 is not considered to be a taxonomically valid genus on either phyletic or gradistic grounds, and is included within Tropheus (Simochromis). The lower pharyngeal bone of T . (S.) diagramma is considered to be plesiomorphic in tooth arrangement, size and shape. A preliminary worKing hypothesis is established on the basis of the conjectures made and other available information which supports the phyletic relationship suggested by Fryer and lIes (1972). An illustration is given.
- Full Text:
- Date Issued: 1978
A contribution to cabbage pest management by subsistence and small-scale farmers in the Eastern Cape, South Africa
- Authors: Mkize, Nolwazi
- Date: 2004
- Subjects: Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5659 , http://hdl.handle.net/10962/d1005342 , Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Description: The interaction between farmers, agricultural scientists and extension workers is sometimes overlooked in agricultural entomology. In an attempt to respond to this reality this study examines some foundation of this interaction in relation to the pest management practices of subsistence and small-scale farmers and also highlights the problems that might arise in the implementation of IPM. Problems involving pests occurrence; language barriers; beliefs, knowledge and perception about insects, and visual literacy are examined. The thesis has a two-fold focus, firstly the study of pests on cabbages of subsistence farmers in Grahamstown and secondly a broader focus on other aspects such as cultural entomology, perception of insects and visual literacy specifically in relation to Xhosa speaking people in the Eastern Cape. The most important crop for emergent farmers in the Eastern Cape are cabbages, which have a variety of pests of which diamondback moths and are the most important. Traditional pest management practices tend to influence the development of IPM programmes adopted by these farmers. Eastern Cape farmers apply periodic cropping systems, which had an effect on the population densities of diamondback moth (DBM), other lepidopteran pests and their parasitoids. Considering the maximum population densities of DBM, which were 0.2 - 2.9 larvae/plant, there were no major pest problems. The availability of parasitoids, even in highly disturbed and patchy environments, showed good potential for biological control. Since some extension officers cannot speak the local farmers’ language, a dictionary of insect names was formulated in their language (isiXhosa) to assist communication. Response-frequency distribution analysis showed that the dictionary is essentially complete. The literal translations of some names show that isiXhosa speakers often relate insects to people, or to their habitat or classify them according to their behaviour. Farmers from eight sites in the Eastern Cape were interviewed regarding their knowledge and perception of insect pests and their control thereof. To some extent, farmers still rely on cultural control and have beliefs about insects that reflected both reality and superstition. There is no difference between the Ciskei and Transkei regions regarding insect-related beliefs. Farmers generally lack an understanding of insect ecology. There is a need for farmers to be taught about insects to assist with the implementation of IPM. Leftover pesticides from commercial farms or detergents are sometimes used to manage the pests. When training illiterate or semi-literate farmers, it is important to understand their media literacy so as to design useful graphic and object training media. Generally farmers showed that they either understand graphic or object media depending on the features of the insects being looked at. These findings are discussed with regard to the potential development of IPM training material for subsistence and small-scale farmers in a community.
- Full Text:
- Date Issued: 2004
A contribution to the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa
- Authors: Bruton, Michael N
- Date: 1973
- Subjects: Cichlids , Tilapia , Mozambique tilapia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5839 , http://hdl.handle.net/10962/d1009950 , Cichlids , Tilapia , Mozambique tilapia
- Description: An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Previous work on Tilapia in Lake Sibaya is reviewed. Apart from brief gillnet surveys, which recorded the species' presence, no research on T. mossambica had been performed at Lake Sibaya before the two-year study of Minshull who collected data on food preferences, depth distribution of juveniles and breeding biology of adults. The main physiographical features of the lake are outlined. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1-7 m deep. Adult fishes (over 8 cm SL) are usually absent from water deeper than 12 m and shallower than 0.5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral in the warm and transition periods (August to April) but moves into deep water in the cool season (May to July). Exposed and sheltered shallow areas are utilised for different purposes by adult fishes, the former for nesting, and the latter for feeding and mouth-brooding. Habitat selection by males was governed by nest site selection. Habitat Nests were most common in sheltered, sparsely vegetated littoral and sublittoral areas, but also present in well-vegetated sheltered areas. Breeding females preferred sheltered littoral areas but ventured onto the terrace to release the young. Juvenile and fry T. mossambica inhabited shallow exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour of T. mossambica is described, and integrated with data on T. mossambica from other systems. The breeding season spans seven months. Shoaling takes place in shallow water probably as a means of protection. T. mossambica is an omnivorous feeder relying largely on diatoms. The main predator is probably the barbel Clarias gariepinus, but avian predators may be more important. A method whereby the time of formation of rings on the scales of T. mossambica is described. The fishes were found to reach maturity after one year at a length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 14 cm (females) and 17 cm (males). The maximum final size was about 24 cm SL. An estimate of the standing crop for fishes in the littoral and subiittoral areas of the eastern and southern shores of the south basin is given. The data were derived from a mark and recapture The biology of T. mossambica in Lake Sibaya as revealed by the present study is discussed with reference to data on the same and similar species in other systems. The utilis ation of the available resources in the lake by T. mossambica is commented upon, and reference is made to the significance of stunting, and the import ance of the retention of generalised characters for the successful habitation of the cyclically-renewed habitat of the littoral. Precocious breeding in T. mossambica is regarded as a functional adaptation which increases the proportion of fishes small enough to utilise the rich food resources in shallow water.
- Full Text:
- Date Issued: 1973
A contribution to the ecology and systematics of the genus Petrotilapia (Pisces : Cichlidae) in Lake Malawi
- Authors: Marsh, Alan Clive
- Date: 2013-03-20
- Subjects: Cichlids -- Nyasa, Lake , Petrotilapia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5355 , http://hdl.handle.net/10962/d1009513 , Cichlids -- Nyasa, Lake , Petrotilapia
- Description: The nominal species Petrotilapia tridentiger Trewavas, a rock-frequenting fish from Lake Malawi, occurs in three distinct male and female colour forms at Monkey Bay. Field observations on courtship and aggression indicate that the three colour forms are distinct species. The taxonomy of the three species of Petrotilapia that occur at Monkey Bay is revised. R. tridentiger is redescribed and two new species, P. genalutea and P. nigra, are described. The three species are very similar morphologically and are considered to be sibling species. The only morphological character which reliably separates the three sibling species is live coloration: Live coloration is considered to be an important component of the specific mate recognition systems in Petrotilapia species. The coloration of a further fourteen forms of Petrotilapia is described and it is suggested that these forms are valid species. Space resource partitioning plays an important role in facilitating the coexistence of Petrotilapia sibling species. Space is partially partitioned in terms of depth range. In shallow water, where all three species are sympatric, there are differences in the feeding sites used by the various Petrotilapia forms. Changes in niche breadth and overlap, which are associated with changes in the abundance of epilithic algae, indicate that competition for feeding space occurs between the three Petrotilapia species. The Petrotilapia species partition their resources according to a social dominance hierarchy. Dominant forms, such as territorial males, R. tridentiger females and schooling R. genalutea females, have access to rich food supplies which occur within the territories of certain highly aggressive Pseudotronheus species. are facultative and opportunistic .feeders. Petrotilapia species Speciation in allopatry is considered to be the mechanism which adequately explains the current diversity of the genus Petrotilapia. The importance of an integrative approach to future systematic and ecological research on Lake Malawi cichlids is stressed. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
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A contribution to the oceanology of the Prince Edward Islands
- Authors: Parker, Llewellyn Derek
- Date: 1985
- Subjects: Oceanography -- Prince Edward Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5605 , http://hdl.handle.net/10962/d1002055
- Description: While the terrestrial ecosystem of the Prince Edward Island Group has been subject to intensive research, the marine ecosystem has to a large extent been neglected. This together with the possible existence of an "island effect" at these islands, as was first proposed after the visit to these islands of the French vessel Marion Dufresne, led to the initiation of a programme to determine the distribution of standing stocks and the productivity of phytoplankton and zooplankton in the neritic seas of these islands. To do this and before a detailed biological survey could be attempted, it was first necessary to define the physical and chemical properties of the circuminsular waters. This dissertation discusses the results of several surveys to these islands in the light of a possible "island effect" and comments upon processes likely to influence such an effect
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- Date Issued: 1985
A contribution to the petrology of kimberlites
- Authors: Kruger, Floris Johan
- Date: 1978 , 2013-10-17
- Subjects: Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5024 , http://hdl.handle.net/10962/d1006886 , Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Description: The petrogenetic relationships of the different varieties of kimberlite in the De Beers Mine and Letseng-Ia-terai composite diatremes have been investigated using petrographic and chemical methods. Kimberlites in the Letseng-Ia-terai diatreme were found to be strongly contaminated by crustal material, mainly basalt. A method to correct for the effects of the contamination has been developed and applied to these kimberlites. Using the corrected data, the four kimberlite types in each group appear to be related to each other by crystal/liquid fractionation models. However the two groups cannot be related to each other. The De Beer Mine has two varieties of kimberlite, a monticellite apatite and calcite rich variety which intruded first, and a phlogopite rich type forming a discrete cylindrical body within the earlier kimberlite. These two kimberlites do not appear to be related by any of the fractionation models discussed. An examination of the data from this work and published sources, suggests that kimberlites are derived from below the low velocity zone by small degrees of partial melting involving garnet lherzolite with subordinate phlogopite and carbonate. Diamonds are probably incorporated as xenocrysts in the magma. Upward movement and emplacement of kimberlite appears to have been very rapid. The diatremes were probably eroded and shaped by gas, derived from the kimberlite magma, escaping to surface along weak zones in the earth's crust. Xenoliths of crustal material incorporated in the kimberlite on intrusion have also been studied and various features due to alteration by the magma are described, including the formation of natrolite and cebollite. The latter is a rare mineral that has not been described from kimberlite before. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Date Issued: 1978
A contribution to the respiratory physiology of three South African freshwater pulmonate snails, Bulinus (Physopsis) Africanus (Krauss), Bulinus (Bulinus) Tropicus (Krauss), and Lymnaea Natalensis Krauss
- Authors: Alberts, I E
- Date: 1966
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:20965 , http://hdl.handle.net/10962/5696
- Description: From Introduction: The use of chemical molluscicides in the control of schistosome transmitting snails has been largely based on empirical studies of toxicity, rather than on a clear understanding of basic physiology and biochemistry of snail hosts. It is therefore possible that purely physiological studies may in themselves provide information which could be of value in the development of more effective mollucicides. In this investigation an attempt has been made to understand some aspects of the respiratory physiology of three species of fresh-water pulmonate snails, all of which are of medical and veterinary importance in the Republic of South Africa. Bulinus (Physopsis) africanus (Krauss) is the intermediate host of Schistosoma haematobium, the causative organism of human schistosomiasis (Bilharziasis). Bulinus (Bulinus) tropicus (Krauss) is the intermediate host of the conical flukes Calicophoron calicophorum and Paramphistomum microbothrium and of the liver fluke Fasciola hepatica, while Lymnaea natalensis Krauss is the intermediate host of the liver fluke Fasciola gigantica.
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- Date Issued: 1966
A contribution towards an understanding of the intensive tank culture of an ornamental Cichlid, Aulonocara Baenschi, from Chipoka, Lake Malawi
- Authors: Impson, N D (Neville Dean)
- Date: 1988
- Subjects: Cichlids -- Nysas, Lake , Cichlids -- Nyasa, Lake -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5208 , http://hdl.handle.net/10962/d1004596 , Cichlids -- Nysas, Lake , Cichlids -- Nyasa, Lake -- Physiology
- Description: The intensive tank culture of ornamental mouthbrooding cichlids poses several problems which limit their aquaculture potential. This project addressed some of these problems for Aulonocara baenschi. The production of juveniles in 2501 aquaria was accelerated when: a) aquaria were equipped with refuges, b) females of less than 70mm in standard length were used as broodstock, c) mouthbrooding females were replaced with gravid females at seven day intervals, and d) embryos were removed from the mouths of females at replacement times for artificial incubation. Two sex ratios also accelerated juvenile production. The sex ratio (male:females) 1:30 yielded the highest spawning returns per tank, and therefore represented the most effective utilization of aquarium space (a critical consideration for the small-scale culturist). Contrastingly, the sex ratio 1:12 yielded the highest clutch sizes and a high percentage female spawning return, and therefore represented the most effective utilization of broodstock (an important consideration for culturists inhibited by financial constraints or having an abundance of culture vessels). The reproductive behaviour of A. baenschi was described. Emphasis was given to aspects of reproduction of relevance to culture, for example; spawning times and seasons, clutch size and its relationship with female size, age and size of sexes at first spawning, embryo development rate and size of first swimming juveniles. The slow growth rate of juveniles, combined with a late attainment of marketable size (± seven months) was a major limitation affecting the cuIture potential of A. baenschi. Two factors favouring the cuIture of this species was the high survival rate recorded for both adults and juveniles, and the comparatively high prices fetched by fish on domestic wholesale markets (R4,00 per fish). It is recommended that A. baenschi should not be cultured exclusively for the relatively small South African ornamental fish market. A more profitable strategy for domestic culturists should involve a major production effort with A. baenschi and other desirable species of Aulonocara (e.g . A. ethelwynnae; A. hansbaenschi; A. stuartgranti & A. maylandi) for foreign markets (in particular, the U.S.A.; Western Europe & Japan). Not only are these markets massive, but prevailing exchange rates of the Rand with these currencies favour such a strategy.
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- Date Issued: 1988
A convenient approach to the deterministic routing of MIDI messages
- Authors: Shaw, Brent Roy
- Date: 2018
- Subjects: MIDI (Standard) , Microcontrollers , XMOS Limited , Computer architecture , Embedded computer systems
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63256 , vital:28387
- Description: This research investigates the design and development of a Wireless MIDI Connection Management solution in order to create a deterministic MIDI transmission system. A investigation of the MIDI protocol show it to have certain limitation that can be overcome through the use of transmission solutions. These solutions can be used to improve on the versatility of MIDI while overcoming the MIDI's notorious cable length limitation. XMOS's deterministic XS1 microcontrollers are used to enable the design of a real-time system. The MIDINet system is investigated to identify both the strengths and weaknesses of such a connection management system, while other systems for network transmission of MIDI messages are reviewed. These investigations lead to a design concept for a new network MIDI transmission system that allows for the remote management of connections. The design and subsequent implementation of both the transmission system and the connection management system are then detailed. A testing methodology is then devised to allow for the newly created connection management system to be compared to the MIDINet system. The findings show the deterministic system to have lower latency than that of the MIDINet system, while utilising more compact and power efficient hardware.
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- Date Issued: 2018