A grid based approach for the control and recall of the properties of IEEE 1394 audio devices
- Authors: Foulkes, Philip James
- Date: 2009
- Subjects: IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4594 , http://hdl.handle.net/10962/d1004836 , IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Description: The control of modern audio studios is complex. Audio mixing desks have grown to the point where they contain thousands of parameters. The control surfaces of these devices do not reflect the routing and signal processing capabilities that the devices are capable of. Software audio mixing desk editors have been developed that allow for the remote control of these devices, but their graphical user interfaces retain the complexities of the audio mixing desk that they represent. In this thesis, we propose a grid approach to audio mixing. The developed grid audio mixing desk editor represents an audio mixing desk as a series of graphical routing matrices. These routing matrices expose the various signal processing points and signal flows that exist within an audio mixing desk. The routing matrices allow for audio signals to be routed within the device, and allow for the device’s parameters to be adjusted by selecting the appropriate signal processing points. With the use of the programming interfaces that are defined as part of the Studio Connections – Total Recall SDK, the audio mixing desk editor was integrated with compatible DAW applications to provide persistence of audio mixing desk parameter states. Many audio studios currently use digital networks to connect audio devices together. Audio and control signals are patched between devices through the use of software patchbays that run on computers. We propose a double grid-based FireWire patchbay aimed to simplify the patching of signals between audio devices on a FireWire network. The FireWire patchbay was implemented in such a way such that it can host software device editors that are Studio Connections compatible. This has allowed software device editors to be associated with the devices that are represented on the FireWire patchbay, thus allowing for studio wide control from a single application. The double grid-based patchbay was implemented such that it can be hosted by compatible DAW applications. Through this, the double grid-based patchbay application is able to provide the DAW application with the state of the parameters of the devices in a studio, as well as the connections between them. The DAW application may save this state data to its native song files. This state data may be passed back to the double grid-based patchbay when the song file is reloaded at a later stage. This state data may then be used by the patchbay to restore the parameters of the patchbay and its device editors to a previous state. This restored state may then be transferred to the hardware devices being represented by the patchbay.
- Full Text:
- Date Issued: 2009
- Authors: Foulkes, Philip James
- Date: 2009
- Subjects: IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4594 , http://hdl.handle.net/10962/d1004836 , IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Description: The control of modern audio studios is complex. Audio mixing desks have grown to the point where they contain thousands of parameters. The control surfaces of these devices do not reflect the routing and signal processing capabilities that the devices are capable of. Software audio mixing desk editors have been developed that allow for the remote control of these devices, but their graphical user interfaces retain the complexities of the audio mixing desk that they represent. In this thesis, we propose a grid approach to audio mixing. The developed grid audio mixing desk editor represents an audio mixing desk as a series of graphical routing matrices. These routing matrices expose the various signal processing points and signal flows that exist within an audio mixing desk. The routing matrices allow for audio signals to be routed within the device, and allow for the device’s parameters to be adjusted by selecting the appropriate signal processing points. With the use of the programming interfaces that are defined as part of the Studio Connections – Total Recall SDK, the audio mixing desk editor was integrated with compatible DAW applications to provide persistence of audio mixing desk parameter states. Many audio studios currently use digital networks to connect audio devices together. Audio and control signals are patched between devices through the use of software patchbays that run on computers. We propose a double grid-based FireWire patchbay aimed to simplify the patching of signals between audio devices on a FireWire network. The FireWire patchbay was implemented in such a way such that it can host software device editors that are Studio Connections compatible. This has allowed software device editors to be associated with the devices that are represented on the FireWire patchbay, thus allowing for studio wide control from a single application. The double grid-based patchbay was implemented such that it can be hosted by compatible DAW applications. Through this, the double grid-based patchbay application is able to provide the DAW application with the state of the parameters of the devices in a studio, as well as the connections between them. The DAW application may save this state data to its native song files. This state data may be passed back to the double grid-based patchbay when the song file is reloaded at a later stage. This state data may then be used by the patchbay to restore the parameters of the patchbay and its device editors to a previous state. This restored state may then be transferred to the hardware devices being represented by the patchbay.
- Full Text:
- Date Issued: 2009
A Hall-effect study of as-grown and hydrogenerated n-type ZnO layers grown by MOCVD
- Somhlahlo, Nomabali Nelisiwe
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
A hermeneutic description of a therapeutic interview using reader response concepts from literary theory
- Odendaal, Dirk Hermanus, 1954-
- Authors: Odendaal, Dirk Hermanus, 1954-
- Date: 2005
- Subjects: Psychotherapy , Hermeneutics , Narrative therapy , Reading, Psychology of , Reader-response criticism , Psychology and literature
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3168 , http://hdl.handle.net/10962/d1007749
- Description: Certain approaches in the discipline Psychology, use the term narrative to describe how they work. Upon investigation one finds that the term narrative is seldom informed from Literary Theory, the background from which it originated. Instead, other disciplines that were also influenced by Literary Theory are invariably used as a means of cross fertilisation, e.g. the work of Geertz from an anthropologist background. Therapists make use of techniques described in the theories in an attempt to come to an understanding of the interactions in the therapy session. Some of the later theories emanating from Literary Theory appear to very useful for opening new ways of research in psychology, especially because some of them already come from an interdisciplinary background. This research attempts to identify useful theories and then apply them within a hermeneutical background in a therapeutical session. Theoretical work on ambiguity, recent research on foregrounding and defamiliarization and also the research in psychonarratology appear to be eminently useful for coming to a deeper understanding of the processes that take place in a therapeutic environment. It is thought that these theories could be of use because they have been 'tested' against the experiences of real readers reading texts. As novels differ from reports and washing lists, therapeutic settings differ from discussions. A novel is a cultivated variant of a report, and a therapeutic conversation is a cultivated version of a chat. These theories then, were applied to a real therapeutic session. The therapists who participated were interviewed on the session and on their reactions to certain 'readings' made by them during the session. The purpose of the interview was to obtain an understanding of their interpretation of what had happened during that session. The questions, reactions, observations and reflections of the session constitute the text of this research. The generated text was then reread from the perspective of each of the theories. The data was collected and interpreted. The interpretation focusses on the therapists 'reading' or understanding of the session and in the process, leads the therapists and researcher to further levels of understanding. In conclusion, it was found that the theories were indeed useful as they were able to point out how certain stylistics of language and situation in the therapeutic session had led to hermeneutic or interpretive processes and also how these processes were perceived or experienced on reflection by the therapists.
- Full Text:
- Date Issued: 2005
- Authors: Odendaal, Dirk Hermanus, 1954-
- Date: 2005
- Subjects: Psychotherapy , Hermeneutics , Narrative therapy , Reading, Psychology of , Reader-response criticism , Psychology and literature
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3168 , http://hdl.handle.net/10962/d1007749
- Description: Certain approaches in the discipline Psychology, use the term narrative to describe how they work. Upon investigation one finds that the term narrative is seldom informed from Literary Theory, the background from which it originated. Instead, other disciplines that were also influenced by Literary Theory are invariably used as a means of cross fertilisation, e.g. the work of Geertz from an anthropologist background. Therapists make use of techniques described in the theories in an attempt to come to an understanding of the interactions in the therapy session. Some of the later theories emanating from Literary Theory appear to very useful for opening new ways of research in psychology, especially because some of them already come from an interdisciplinary background. This research attempts to identify useful theories and then apply them within a hermeneutical background in a therapeutical session. Theoretical work on ambiguity, recent research on foregrounding and defamiliarization and also the research in psychonarratology appear to be eminently useful for coming to a deeper understanding of the processes that take place in a therapeutic environment. It is thought that these theories could be of use because they have been 'tested' against the experiences of real readers reading texts. As novels differ from reports and washing lists, therapeutic settings differ from discussions. A novel is a cultivated variant of a report, and a therapeutic conversation is a cultivated version of a chat. These theories then, were applied to a real therapeutic session. The therapists who participated were interviewed on the session and on their reactions to certain 'readings' made by them during the session. The purpose of the interview was to obtain an understanding of their interpretation of what had happened during that session. The questions, reactions, observations and reflections of the session constitute the text of this research. The generated text was then reread from the perspective of each of the theories. The data was collected and interpreted. The interpretation focusses on the therapists 'reading' or understanding of the session and in the process, leads the therapists and researcher to further levels of understanding. In conclusion, it was found that the theories were indeed useful as they were able to point out how certain stylistics of language and situation in the therapeutic session had led to hermeneutic or interpretive processes and also how these processes were perceived or experienced on reflection by the therapists.
- Full Text:
- Date Issued: 2005
A hybrid approach to beach erosion mitigation and amenity enhancement, St Francis Bay, South Africa
- Authors: Anderson, Dylan Rory
- Date: 2008
- Subjects: Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10611 , http://hdl.handle.net/10948/d1008192 , Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Description: The St Francis Bay beach has experienced chronic erosion over the past three decades. This erosion can largely be attributed to the stabilisation of a large coastal dunefield which contributed +/- 80 percent of the sand supply to St Francis Bay. Stabilisation began in 1975 initially using plant cuttings and followed by the development of the Santareme holiday suburb resulting in complete stabilisation by 1985. Effects were felt from the late 1970‟s and since then the beach has retreated at between 0.5 - 3 m.yr-1. Erosion has encroached on beachfront properties since the early 1990‟s, leading to the placement of 3-4 m high unsightly rock revetments along much of the beach. Where properly maintained these structures have proved successful in protecting the properties behind, however exacerbated erosion of areas in front and adjacent to these structures is evident. Currently no dry beach is present at high tide for most of the year, leading to a significant reduction in beach amenity value. Several technical studies to investigate remediation of this beach erosion problem have been conducted since the early 1990‟s. This study includes investigations into the processes and dynamics of the existing environment and evaluation of the effectiveness and impacts of several elements of a hybrid approach to coastal protection and amenity enhancement for St Francis Bay beach. This proposal incorporated: Multi-Purpose Reefs (MPR‟s) offshore, for coastal protection and amenity enhancement in terms of surfing; beach nourishment with sand from the Kromme Estuary and dune rehabilitation with appropriate native sand binding species. Extensive fieldwork and data collection were conducted, this included: a series of bathymetric surveys; diving surveys and a helicopter flight; sediment sampling; beach profiling and deployment of a wave/current meter. Analysis of these data provided a greater understanding of the existing environment and dynamics of St Francis Bay and provided reliable inputs for numerical modelling. Numerical and physical modelling was conducted to assess the existing processes and conduct MPR design testing. In addition calibrated hydrodynamic modelling of the Kromme Estuary was conducted in order to assess the impacts of sand extraction from the large sand banks within the mouth of the Kromme Estuary for use as beach nourishment. Comparison of bathymetric survey data collected by the author in 2005/06 with survey data collected by the South African Navy Hydrographic Office (SANHO) in 1952 suggest a major loss of sand from the bay, with a volume difference of some 8.8 X 106 m3 calculated. Greater losses were measured between 10-15 m water depths, with shallow areas of +/- 5 m water depth, remaining more stable. This can be attributed to the presence of shallow reef and rocky substrate through much of the bay at this depth range. Monthly RTK GPS survey data from September 2006 to September 2007 indicates a total loss of 40 000 m3 over this period with the greatest losses measured along the northern part of the beach. The greatest losses were measured after large long period waves from a southerly to south-easterly direction occurred in conjunction with equinox tides in mid March 2007. Sediment sampling at over 100 locations within the bay indicated a high percentage of reef (26 percent) and fairly consistent grain size in the fine to medium size class throughout much of the beach, bay and large sand bank within the estuary. While the majority of the South African Coast is exposed to the predominant south westerly winds and waves, St Francis Bay‟s orientation means that waves from a south easterly to easterly direction dominate. The results of the detailed numerical modelling of the hydrodynamics agree with previous calculations and modelling results which concluded that strong unidirectional longshore currents occur along the headland due to the oblique angle of wave incidence and the close to parallel angle of wave incidence along the beach leads to weak longshore currents of variable direction. Erosion along St Francis Bay beach is a result of cross-shore erosion due to large waves from a southerly to easterly direction. Detached breakwaters are the most effective form of coastal protection in these environments and MPR‟s offer additional benefits over traditional breakwater structures. Results of empirical calculations and numerical modelling indicate that the MPR‟s will provide effective coastal protection through the processes of wave dissipation, wave rotation, salient formation and alteration of nearshore circulation. Physical modelling results allowed the MPR design to be assessed and refined in terms of surfing amenity enhancement and construction constraints. In addition numerical modelling results indicate that impacts due to the extraction of up to 600 000 m3 of sand from the lower Kromme Estuary result in highly localised velocity reduction, mainly limited to the extraction areas. The calculated rate of sediment influx into the lower Kromme Estuary indicates that limited extraction, in the order of 20 000 – 40 000 m3 per year, should be sustainable in the long term. Sedimentation of the lower estuary over recent years has had negative recreational and ecological impacts, through reduced navigability and water exchange respectively. Therefore both the estuary and beach systems prove to benefit from this approach. Although not investigated in detail as part of this study, evidence from numerous projects worldwide indicates that foredunes help to trap wind-blown sand on the beach and form a buffer to storm erosion, therefore dune rehabilitation with native sand-binding plant species was recommended as the third element of the proposed remediation of St Francis Bay beach.
- Full Text:
- Date Issued: 2008
- Authors: Anderson, Dylan Rory
- Date: 2008
- Subjects: Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10611 , http://hdl.handle.net/10948/d1008192 , Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Description: The St Francis Bay beach has experienced chronic erosion over the past three decades. This erosion can largely be attributed to the stabilisation of a large coastal dunefield which contributed +/- 80 percent of the sand supply to St Francis Bay. Stabilisation began in 1975 initially using plant cuttings and followed by the development of the Santareme holiday suburb resulting in complete stabilisation by 1985. Effects were felt from the late 1970‟s and since then the beach has retreated at between 0.5 - 3 m.yr-1. Erosion has encroached on beachfront properties since the early 1990‟s, leading to the placement of 3-4 m high unsightly rock revetments along much of the beach. Where properly maintained these structures have proved successful in protecting the properties behind, however exacerbated erosion of areas in front and adjacent to these structures is evident. Currently no dry beach is present at high tide for most of the year, leading to a significant reduction in beach amenity value. Several technical studies to investigate remediation of this beach erosion problem have been conducted since the early 1990‟s. This study includes investigations into the processes and dynamics of the existing environment and evaluation of the effectiveness and impacts of several elements of a hybrid approach to coastal protection and amenity enhancement for St Francis Bay beach. This proposal incorporated: Multi-Purpose Reefs (MPR‟s) offshore, for coastal protection and amenity enhancement in terms of surfing; beach nourishment with sand from the Kromme Estuary and dune rehabilitation with appropriate native sand binding species. Extensive fieldwork and data collection were conducted, this included: a series of bathymetric surveys; diving surveys and a helicopter flight; sediment sampling; beach profiling and deployment of a wave/current meter. Analysis of these data provided a greater understanding of the existing environment and dynamics of St Francis Bay and provided reliable inputs for numerical modelling. Numerical and physical modelling was conducted to assess the existing processes and conduct MPR design testing. In addition calibrated hydrodynamic modelling of the Kromme Estuary was conducted in order to assess the impacts of sand extraction from the large sand banks within the mouth of the Kromme Estuary for use as beach nourishment. Comparison of bathymetric survey data collected by the author in 2005/06 with survey data collected by the South African Navy Hydrographic Office (SANHO) in 1952 suggest a major loss of sand from the bay, with a volume difference of some 8.8 X 106 m3 calculated. Greater losses were measured between 10-15 m water depths, with shallow areas of +/- 5 m water depth, remaining more stable. This can be attributed to the presence of shallow reef and rocky substrate through much of the bay at this depth range. Monthly RTK GPS survey data from September 2006 to September 2007 indicates a total loss of 40 000 m3 over this period with the greatest losses measured along the northern part of the beach. The greatest losses were measured after large long period waves from a southerly to south-easterly direction occurred in conjunction with equinox tides in mid March 2007. Sediment sampling at over 100 locations within the bay indicated a high percentage of reef (26 percent) and fairly consistent grain size in the fine to medium size class throughout much of the beach, bay and large sand bank within the estuary. While the majority of the South African Coast is exposed to the predominant south westerly winds and waves, St Francis Bay‟s orientation means that waves from a south easterly to easterly direction dominate. The results of the detailed numerical modelling of the hydrodynamics agree with previous calculations and modelling results which concluded that strong unidirectional longshore currents occur along the headland due to the oblique angle of wave incidence and the close to parallel angle of wave incidence along the beach leads to weak longshore currents of variable direction. Erosion along St Francis Bay beach is a result of cross-shore erosion due to large waves from a southerly to easterly direction. Detached breakwaters are the most effective form of coastal protection in these environments and MPR‟s offer additional benefits over traditional breakwater structures. Results of empirical calculations and numerical modelling indicate that the MPR‟s will provide effective coastal protection through the processes of wave dissipation, wave rotation, salient formation and alteration of nearshore circulation. Physical modelling results allowed the MPR design to be assessed and refined in terms of surfing amenity enhancement and construction constraints. In addition numerical modelling results indicate that impacts due to the extraction of up to 600 000 m3 of sand from the lower Kromme Estuary result in highly localised velocity reduction, mainly limited to the extraction areas. The calculated rate of sediment influx into the lower Kromme Estuary indicates that limited extraction, in the order of 20 000 – 40 000 m3 per year, should be sustainable in the long term. Sedimentation of the lower estuary over recent years has had negative recreational and ecological impacts, through reduced navigability and water exchange respectively. Therefore both the estuary and beach systems prove to benefit from this approach. Although not investigated in detail as part of this study, evidence from numerous projects worldwide indicates that foredunes help to trap wind-blown sand on the beach and form a buffer to storm erosion, therefore dune rehabilitation with native sand-binding plant species was recommended as the third element of the proposed remediation of St Francis Bay beach.
- Full Text:
- Date Issued: 2008
A hybrid model for managing personal health records in South Africa
- Authors: Kyazze, Michael
- Date: 2014
- Subjects: Cloud computing -- South Africa , Information storage and retrieval systems -- Medical care -- South Africa , Medical records -- Management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3145 , vital:20403
- Description: Doctors can experience difficulty in accessing medical information of new patients. One reason for this is that the management of medical records is mostly institution-centred. The lack of access to medical information may negatively affect patients in several ways. These include new medical tests that may need to be carried out at a cost to the patient and doctors prescribing drugs to which the patient is allergic. This research investigates how patients can play an active role in sharing their personal health records (PHRs) with doctors located in geographically separate areas. In order to achieve the goal of this research, existing literature concerning medical health records and standards was reviewed. A literature review of techniques that can be used to ensure privacy of health information was also undertaken. Interview studies were carried out with three medical practices in Port Elizabeth with the aim of contextualising the findings from the literature study. The Design Science Research methodology was used for this research. A Hybrid Model for Managing Personal Health Records in South Africa is proposed. This model allows patients to view their PHRs on their mobile phones and medical practitioners to manage the patients’ PHRs using a web-based application. The patients’ PHR information is stored both on a cloud server and on mobile devices hence the hybrid nature. Two prototypes were developed as a proof of concept; a mobile application for the patients and a web-based application for the medical practitioners. A field study was carried out with the NMMU health services department and 12 participants over a period of two weeks. The results of the field study were highly positive. The successful evaluation of the prototypes provides empirical evidence that the proposed model brings us closer to the realisation of ubiquitous access to PHRS in South Africa.
- Full Text:
- Date Issued: 2014
- Authors: Kyazze, Michael
- Date: 2014
- Subjects: Cloud computing -- South Africa , Information storage and retrieval systems -- Medical care -- South Africa , Medical records -- Management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3145 , vital:20403
- Description: Doctors can experience difficulty in accessing medical information of new patients. One reason for this is that the management of medical records is mostly institution-centred. The lack of access to medical information may negatively affect patients in several ways. These include new medical tests that may need to be carried out at a cost to the patient and doctors prescribing drugs to which the patient is allergic. This research investigates how patients can play an active role in sharing their personal health records (PHRs) with doctors located in geographically separate areas. In order to achieve the goal of this research, existing literature concerning medical health records and standards was reviewed. A literature review of techniques that can be used to ensure privacy of health information was also undertaken. Interview studies were carried out with three medical practices in Port Elizabeth with the aim of contextualising the findings from the literature study. The Design Science Research methodology was used for this research. A Hybrid Model for Managing Personal Health Records in South Africa is proposed. This model allows patients to view their PHRs on their mobile phones and medical practitioners to manage the patients’ PHRs using a web-based application. The patients’ PHR information is stored both on a cloud server and on mobile devices hence the hybrid nature. Two prototypes were developed as a proof of concept; a mobile application for the patients and a web-based application for the medical practitioners. A field study was carried out with the NMMU health services department and 12 participants over a period of two weeks. The results of the field study were highly positive. The successful evaluation of the prototypes provides empirical evidence that the proposed model brings us closer to the realisation of ubiquitous access to PHRS in South Africa.
- Full Text:
- Date Issued: 2014
A hybridisation technique for game playing using the upper confidence for trees algorithm with artificial neural networks
- Authors: Burger, Clayton
- Date: 2014
- Subjects: Neural networks (Computer science) , Computer algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3957 , vital:20495
- Description: In the domain of strategic game playing, the use of statistical techniques such as the Upper Confidence for Trees (UCT) algorithm, has become the norm as they offer many benefits over classical algorithms. These benefits include requiring no game-specific strategic knowledge and time-scalable performance. UCT does not incorporate any strategic information specific to the game considered, but instead uses repeated sampling to effectively brute-force search through the game tree or search space. The lack of game-specific knowledge in UCT is thus both a benefit but also a strategic disadvantage. Pattern recognition techniques, specifically Neural Networks (NN), were identified as a means of addressing the lack of game-specific knowledge in UCT. Through a novel hybridisation technique which combines UCT and trained NNs for pruning, the UCTNN algorithm was derived. The NN component of UCT-NN was trained using a UCT self-play scheme to generate game-specific knowledge without the need to construct and manage game databases for training purposes. The UCT-NN algorithm is outlined for pruning in the game of Go-Moku as a candidate case-study for this research. The UCT-NN algorithm contained three major parameters which emerged from the UCT algorithm, the use of NNs and the pruning schemes considered. Suitable methods for finding candidate values for these three parameters were outlined and applied to the game of Go-Moku on a 5 by 5 board. An empirical investigation of the playing performance of UCT-NN was conducted in comparison to UCT through three benchmarks. The benchmarks comprise a common randomly moving opponent, a common UCTmax player which is given a large amount of playing time, and a pair-wise tournament between UCT-NN and UCT. The results of the performance evaluation for 5 by 5 Go-Moku were promising, which prompted an evaluation of a larger 9 by 9 Go-Moku board. The results of both evaluations indicate that the time allocated to the UCT-NN algorithm directly affects its performance when compared to UCT. The UCT-NN algorithm generally performs better than UCT in games with very limited time-constraints in all benchmarks considered except when playing against a randomly moving player in 9 by 9 Go-Moku. In real-time and near-real-time Go-Moku games, UCT-NN provides statistically significant improvements compared to UCT. The findings of this research contribute to the realisation of applying game-specific knowledge to the UCT algorithm.
- Full Text:
- Date Issued: 2014
- Authors: Burger, Clayton
- Date: 2014
- Subjects: Neural networks (Computer science) , Computer algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3957 , vital:20495
- Description: In the domain of strategic game playing, the use of statistical techniques such as the Upper Confidence for Trees (UCT) algorithm, has become the norm as they offer many benefits over classical algorithms. These benefits include requiring no game-specific strategic knowledge and time-scalable performance. UCT does not incorporate any strategic information specific to the game considered, but instead uses repeated sampling to effectively brute-force search through the game tree or search space. The lack of game-specific knowledge in UCT is thus both a benefit but also a strategic disadvantage. Pattern recognition techniques, specifically Neural Networks (NN), were identified as a means of addressing the lack of game-specific knowledge in UCT. Through a novel hybridisation technique which combines UCT and trained NNs for pruning, the UCTNN algorithm was derived. The NN component of UCT-NN was trained using a UCT self-play scheme to generate game-specific knowledge without the need to construct and manage game databases for training purposes. The UCT-NN algorithm is outlined for pruning in the game of Go-Moku as a candidate case-study for this research. The UCT-NN algorithm contained three major parameters which emerged from the UCT algorithm, the use of NNs and the pruning schemes considered. Suitable methods for finding candidate values for these three parameters were outlined and applied to the game of Go-Moku on a 5 by 5 board. An empirical investigation of the playing performance of UCT-NN was conducted in comparison to UCT through three benchmarks. The benchmarks comprise a common randomly moving opponent, a common UCTmax player which is given a large amount of playing time, and a pair-wise tournament between UCT-NN and UCT. The results of the performance evaluation for 5 by 5 Go-Moku were promising, which prompted an evaluation of a larger 9 by 9 Go-Moku board. The results of both evaluations indicate that the time allocated to the UCT-NN algorithm directly affects its performance when compared to UCT. The UCT-NN algorithm generally performs better than UCT in games with very limited time-constraints in all benchmarks considered except when playing against a randomly moving player in 9 by 9 Go-Moku. In real-time and near-real-time Go-Moku games, UCT-NN provides statistically significant improvements compared to UCT. The findings of this research contribute to the realisation of applying game-specific knowledge to the UCT algorithm.
- Full Text:
- Date Issued: 2014
A hydrogeological assessment of the Uitenhage-Coega artesian system
- Authors: Venables, Anthony John
- Date: 1985
- Subjects: Hydrogeology -- South Africa Aquifers -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4808 , http://hdl.handle.net/10962/d1003815
- Description: The Uitenhage artesian aquifer north-west of Port Elizabeth in South Africa, is one of the few artesian groundwater systems in Southern Africa. The Uitenhage - Coega, and Kruis River areas, are the most important portions of the Uitenhage Artesian System in terms of water abstraction and water use. This study concentrates on the Uitenhage - Coega area and in particular, on the Coega Ridge where the Table Mountain Sandstone (TNS) aquifer occurs at relatively shallow depths. The investigation is aimed at assessing the geological, hydrogeological and hydrochemical characteristics of the HIS and any other aquifers present, with the object of providing quantitative data for use in future decisions on the water resource management of the area. In order to achieve these objectives, field work, involving a hydrocensus, geological mapping, geophysical exploration, drilling, aquifer testing and hydrochemical sampling was carried out. Analysis of these data provided information on the extent of the aquifers, their hydrogeological characteristics and the chemical nature of the various groundwater types.
- Full Text:
- Date Issued: 1985
- Authors: Venables, Anthony John
- Date: 1985
- Subjects: Hydrogeology -- South Africa Aquifers -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4808 , http://hdl.handle.net/10962/d1003815
- Description: The Uitenhage artesian aquifer north-west of Port Elizabeth in South Africa, is one of the few artesian groundwater systems in Southern Africa. The Uitenhage - Coega, and Kruis River areas, are the most important portions of the Uitenhage Artesian System in terms of water abstraction and water use. This study concentrates on the Uitenhage - Coega area and in particular, on the Coega Ridge where the Table Mountain Sandstone (TNS) aquifer occurs at relatively shallow depths. The investigation is aimed at assessing the geological, hydrogeological and hydrochemical characteristics of the HIS and any other aquifers present, with the object of providing quantitative data for use in future decisions on the water resource management of the area. In order to achieve these objectives, field work, involving a hydrocensus, geological mapping, geophysical exploration, drilling, aquifer testing and hydrochemical sampling was carried out. Analysis of these data provided information on the extent of the aquifers, their hydrogeological characteristics and the chemical nature of the various groundwater types.
- Full Text:
- Date Issued: 1985
A hydrogeological assessment of the Uitenhage-Kuils River area, Cape Province, South Africa
- Authors: Bush, Richard Alan
- Date: 1987
- Subjects: Aquifers -- South Africa , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4801 , http://hdl.handle.net/10962/d1001901 , Aquifers -- South Africa , Hydrogeology -- South Africa
- Full Text:
- Date Issued: 1987
- Authors: Bush, Richard Alan
- Date: 1987
- Subjects: Aquifers -- South Africa , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4801 , http://hdl.handle.net/10962/d1001901 , Aquifers -- South Africa , Hydrogeology -- South Africa
- Full Text:
- Date Issued: 1987
A hydrogeological investigation of Grahamstown, assessing both the dynamics and quality of the local groundwater system
- Authors: Smetherham, Kyle Norman
- Date: 2019
- Subjects: Hydrogeology -- South Africa -- Makhanda , Water quality -- South Africa -- Makhanda , Groundwater -- Quality -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94444 , vital:31045
- Description: In many parts of South Africa, complete allocation of surface water reservoirs together with current drought conditions has led to serious water shortages and subsequent awareness regarding the importance to save water. Grahamstown is no different, with water problems relating to low supply and high demand being compounded by insufficient treatment capacity and aging infrastructure. Groundwater is an alternative water resource that could potentially act as a supplementary and/or emergency supply to the town, reducing the reliability on surface reservoirs. Groundwater however, is a hidden resource and requires an understanding of various aquifer properties and continuous monitoring and modelling so not to permanently disrupt the natural system but rather achieve sustainable management. Grahamstown is situated towards the northern extent of the Cape Fold Belt (CFB) system, within a synclinal fold structure. The local geology forms two local aquifer systems beneath Grahamstown that directly influence both the dynamics and quality of the groundwater. These underground reservoirs are the Witpoort and Dwyka aquifers and can be described as a semi-confined, fractured, quartzitic sandstone aquifer and an unconfined, fractured, tillite aquifer, respectively. Separating these aquifer systems is a shale aquitard, although due to the fractured nature of the rocks in the region there is most likely some groundwater interaction between them. Evaluation of geological formations together with the monitoring of 31 local boreholes presented a valuable conceptualisation of the local system and allowed for the application of methods to estimate recharge. Recharge estimation is one of the most crucial factors when managing aquifer systems as it can be used to determine what proportion of rainfall contributes to the subsurface reservoir and therefore, the sustainable amount that can be extracted. Various methods have been developed to estimate recharge, however due to the uncertainty surrounding groundwater systems, especially fractured aquifers, it was important to apply multiple methods to validate results. The water-table fluctuation (WTF) and cumulative rainfall departure (CRD) are two methods that were used in the present study to determine recharge. These methods rely on water-table changes in boreholes and specifically how they respond to rainfall events. Along with the WTF and CRD methods, a modelling approach was also used to estimate recharge which focused on the dynamics of a natural groundwater outlet, termed the Fairview Spring. This natural spring system is located just outside the main town of Grahamstown, within the Witpoort aquifer system, and is an important water resource to many residents due to poor supply and quality of municipal water. Monitoring the discharge of this spring allowed for the development of a model which attempts to recreate the discharge conditions observed. Along with groundwater recharge, other processes added to the model include evapotranspiration, storage, interflow spring outflow and groundwater outflow. Several different model simulation scenarios provided valuable insight into the greater groundwater dynamics. In terms of groundwater quality, nine borehole samples and one spring sample were analysed for major ions (Ca, Na, K, Cl, Mg, SO4, HCO3), metals (Cu, Fe, Mn) as well as pH and electrical conductivity. Overall electrical conductivity levels and major ion concentrations were lower in the Witpoort aquifer indicating a better groundwater quality compared to that of the Dwyka aquifer. Of the three metals included in the analysis, Mn proved to be the most significant and the highest concentrations were produced for samples that intersected the shale aquitard unit, suggesting that Mn-containing groundwater is drawn from this geological layer. Development of a supplementary and/or emergency groundwater supply requires careful consideration of the geology, quantity, quality, and recharge in the study site. All these aspects were assessed as well as deliberation into the potential infrastructural costs involved. Through conceptualisation of the system; evidence gathered during basic monitoring; and a simple spring model, the current study aimed to explore certain management strategies and recommend potential options going forward. The hidden nature of the resource together with the heterogeneity of fracture networks creates an inevitable uncertainty surrounding the system. Proper development and management of the aquifer can only be achieved if the system is continually monitored, modelled and utilised sustainably.
- Full Text:
- Date Issued: 2019
- Authors: Smetherham, Kyle Norman
- Date: 2019
- Subjects: Hydrogeology -- South Africa -- Makhanda , Water quality -- South Africa -- Makhanda , Groundwater -- Quality -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94444 , vital:31045
- Description: In many parts of South Africa, complete allocation of surface water reservoirs together with current drought conditions has led to serious water shortages and subsequent awareness regarding the importance to save water. Grahamstown is no different, with water problems relating to low supply and high demand being compounded by insufficient treatment capacity and aging infrastructure. Groundwater is an alternative water resource that could potentially act as a supplementary and/or emergency supply to the town, reducing the reliability on surface reservoirs. Groundwater however, is a hidden resource and requires an understanding of various aquifer properties and continuous monitoring and modelling so not to permanently disrupt the natural system but rather achieve sustainable management. Grahamstown is situated towards the northern extent of the Cape Fold Belt (CFB) system, within a synclinal fold structure. The local geology forms two local aquifer systems beneath Grahamstown that directly influence both the dynamics and quality of the groundwater. These underground reservoirs are the Witpoort and Dwyka aquifers and can be described as a semi-confined, fractured, quartzitic sandstone aquifer and an unconfined, fractured, tillite aquifer, respectively. Separating these aquifer systems is a shale aquitard, although due to the fractured nature of the rocks in the region there is most likely some groundwater interaction between them. Evaluation of geological formations together with the monitoring of 31 local boreholes presented a valuable conceptualisation of the local system and allowed for the application of methods to estimate recharge. Recharge estimation is one of the most crucial factors when managing aquifer systems as it can be used to determine what proportion of rainfall contributes to the subsurface reservoir and therefore, the sustainable amount that can be extracted. Various methods have been developed to estimate recharge, however due to the uncertainty surrounding groundwater systems, especially fractured aquifers, it was important to apply multiple methods to validate results. The water-table fluctuation (WTF) and cumulative rainfall departure (CRD) are two methods that were used in the present study to determine recharge. These methods rely on water-table changes in boreholes and specifically how they respond to rainfall events. Along with the WTF and CRD methods, a modelling approach was also used to estimate recharge which focused on the dynamics of a natural groundwater outlet, termed the Fairview Spring. This natural spring system is located just outside the main town of Grahamstown, within the Witpoort aquifer system, and is an important water resource to many residents due to poor supply and quality of municipal water. Monitoring the discharge of this spring allowed for the development of a model which attempts to recreate the discharge conditions observed. Along with groundwater recharge, other processes added to the model include evapotranspiration, storage, interflow spring outflow and groundwater outflow. Several different model simulation scenarios provided valuable insight into the greater groundwater dynamics. In terms of groundwater quality, nine borehole samples and one spring sample were analysed for major ions (Ca, Na, K, Cl, Mg, SO4, HCO3), metals (Cu, Fe, Mn) as well as pH and electrical conductivity. Overall electrical conductivity levels and major ion concentrations were lower in the Witpoort aquifer indicating a better groundwater quality compared to that of the Dwyka aquifer. Of the three metals included in the analysis, Mn proved to be the most significant and the highest concentrations were produced for samples that intersected the shale aquitard unit, suggesting that Mn-containing groundwater is drawn from this geological layer. Development of a supplementary and/or emergency groundwater supply requires careful consideration of the geology, quantity, quality, and recharge in the study site. All these aspects were assessed as well as deliberation into the potential infrastructural costs involved. Through conceptualisation of the system; evidence gathered during basic monitoring; and a simple spring model, the current study aimed to explore certain management strategies and recommend potential options going forward. The hidden nature of the resource together with the heterogeneity of fracture networks creates an inevitable uncertainty surrounding the system. Proper development and management of the aquifer can only be achieved if the system is continually monitored, modelled and utilised sustainably.
- Full Text:
- Date Issued: 2019
A hydrogeological investigation of the Grootegeluk mine
- Authors: Johnstone, Andrew Clifford
- Date: 1989
- Subjects: Hydrogeology -- South Africa Coal mines and mining -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4795 , http://hdl.handle.net/10962/d1001895
- Description: The study concerns an assessment of the hydrogeological impact of an open cast coal mine in the North Western Transvaal Province of South Africa. The hydrogeological impact of the mine is assessed in terms of groundwater quality and levels. A monitoring system was installed to enable the present and future impact of mining operations on the hydrogeological regime to be assessed. Grootegeluk Mine is situated in the Waterberg Coal Field of South Africa and began production in 1980. The mine extracts fifteen million tons of mine material annually from a single open pit. Forty percent of the mined material is saleable product and the remaining sixty percent is stacked on discard dumps. The Daarby fault forms the northern boundary of the open pit and serves to bring the younger Letaba and Clarens Formations into contact with the older Beaufort and Ecca Groups. The mine discards are deposited north of the fault on a different hydrogeological environment from which they are mined. Dewatering of the mine open pit has resulted in a steady decline in water levels in the Ecca Group, south of the Daarby fault. In contrast, water levels north of the Daarby fault in the Letaba and Clarens Formations have risen. The short term hydrochemical impact of the mine discard dumps and slimes dams have resulted in a rise in the calcium, sulphate, chloride, fluoride and nitrate concentrations of the ambient groundwater . The longer term hydrochemical impact from the waste dumps, acid mine drainage, is not evident at present in the groundwater below the waste dumps. However, it is expected to manifest itself during the next ten years. A monitoring system was installed at the mine to allow groundwater levels and quality to be monitored. By measuring groundwater quality and levels the impact of the mine on the regional hydrogeology can be monitored and assessed presently, and during the next forty years of production. Monitoring will also enable the timeous implementation of remedial measures at an early stage and eliminate the need for large late stage "clean up" operations. Future monitoring of both water levels and quality will be crucial in evaluating the mine's impact on the regional groundwater regimes over the next forty years of production. The remedial measures recommended for leachate presently emanating from the waste dumps and slimes dams north of the Daarby fault, are a number of collector wells drilled into the basalts and sandstone north of the Daarby fault. The proposed positions of the wells (boreholes) are as close as possible to the dumps and slimes dams with expansion taken into consideration. The boreholes should be designed to lower the water level in the vicinity of the dumps in order to create a nett groundwater gradient towards the dumps and as a result, halt the spread of leachate away from the dumps. Grootegeluk plans to backfill the open pit with plant discards on completion of the mining of zone 2. The backfilled material will consist of the currently produced plant waste and will be covered with overburden and topsoil. It is expected that the backfilling will have a major impact on groundwater quantity if no remedial measures are implemented. The two remedial measures discussed are chemical treatment of the discard material before backfilling or the continual abstraction of water from the pit resulting in a nett groundwater inflow into the pit. No material from the present waste dumps and slimes dams will be transported into the open pit as backfill material
- Full Text:
- Date Issued: 1989
- Authors: Johnstone, Andrew Clifford
- Date: 1989
- Subjects: Hydrogeology -- South Africa Coal mines and mining -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4795 , http://hdl.handle.net/10962/d1001895
- Description: The study concerns an assessment of the hydrogeological impact of an open cast coal mine in the North Western Transvaal Province of South Africa. The hydrogeological impact of the mine is assessed in terms of groundwater quality and levels. A monitoring system was installed to enable the present and future impact of mining operations on the hydrogeological regime to be assessed. Grootegeluk Mine is situated in the Waterberg Coal Field of South Africa and began production in 1980. The mine extracts fifteen million tons of mine material annually from a single open pit. Forty percent of the mined material is saleable product and the remaining sixty percent is stacked on discard dumps. The Daarby fault forms the northern boundary of the open pit and serves to bring the younger Letaba and Clarens Formations into contact with the older Beaufort and Ecca Groups. The mine discards are deposited north of the fault on a different hydrogeological environment from which they are mined. Dewatering of the mine open pit has resulted in a steady decline in water levels in the Ecca Group, south of the Daarby fault. In contrast, water levels north of the Daarby fault in the Letaba and Clarens Formations have risen. The short term hydrochemical impact of the mine discard dumps and slimes dams have resulted in a rise in the calcium, sulphate, chloride, fluoride and nitrate concentrations of the ambient groundwater . The longer term hydrochemical impact from the waste dumps, acid mine drainage, is not evident at present in the groundwater below the waste dumps. However, it is expected to manifest itself during the next ten years. A monitoring system was installed at the mine to allow groundwater levels and quality to be monitored. By measuring groundwater quality and levels the impact of the mine on the regional hydrogeology can be monitored and assessed presently, and during the next forty years of production. Monitoring will also enable the timeous implementation of remedial measures at an early stage and eliminate the need for large late stage "clean up" operations. Future monitoring of both water levels and quality will be crucial in evaluating the mine's impact on the regional groundwater regimes over the next forty years of production. The remedial measures recommended for leachate presently emanating from the waste dumps and slimes dams north of the Daarby fault, are a number of collector wells drilled into the basalts and sandstone north of the Daarby fault. The proposed positions of the wells (boreholes) are as close as possible to the dumps and slimes dams with expansion taken into consideration. The boreholes should be designed to lower the water level in the vicinity of the dumps in order to create a nett groundwater gradient towards the dumps and as a result, halt the spread of leachate away from the dumps. Grootegeluk plans to backfill the open pit with plant discards on completion of the mining of zone 2. The backfilled material will consist of the currently produced plant waste and will be covered with overburden and topsoil. It is expected that the backfilling will have a major impact on groundwater quantity if no remedial measures are implemented. The two remedial measures discussed are chemical treatment of the discard material before backfilling or the continual abstraction of water from the pit resulting in a nett groundwater inflow into the pit. No material from the present waste dumps and slimes dams will be transported into the open pit as backfill material
- Full Text:
- Date Issued: 1989
A life-history approach to the biology of Oreochromis mossambicus (Pisces : Cichlidae) in the Eastern Cape, South Africa
- Authors: James, Nick, 1955-
- Date: 1990
- Subjects: Cichlids -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5187 , http://hdl.handle.net/10962/d1001963
- Description: The phenotypic plasticity of the cichlid Oreochromis mossambicus was examined in fresh and brackish water populations living in the eastern Cape near the southern extremity of the natural range. The primary goal of the study was to examine the wide variety of life-history styles which were expressed in relation to the varying environmental conditions. Four natural populations were studied during 1986 and 1987, and some experimental work under artificial conditions was carried out at the Rhodes University fishfarm during 1988. This comparative approach gave insights into the complex interactions between biotic and abiotic factors which are exploited by this hardy species. O. mossambicus displayed a wide variety of life-history tactics under harsh environmental conditions. The growth of juvenile fish was rapid and mortality of the young-of-the-year was high. Age at first onset of sexual maturity ranged from one to three years. Under harsh conditions growth rate was markedly reduced after maturity, which occurred during the second or third summer and growth disparity between the sexes was more pronounced. Longevity was found to vary from five to ten years for different populations. Under more favourable conditions (resembling the typical "floodplain" habitats of this species at lower latitudes) very rapid juvenile growth, and a high maximum mass of over 2300 g for both sexes was iii achieved. Sexual maturity under these conditions could be delayed until the third or fourth summer of life. O. mossambicus demonstrated an ability to withstand and even benefit from fluctuating water levels, and adjusted its life style according to the prevailing conditions: at times of high water level recruitment was low and sexual maturity delayed. During low water periods reproductive rates increased. Q. mossambicus showed a distinct preference for gentle gradients and well-vegetated habitats for feeding, nesting and refuge. During the study winter temperatures were near and at some times below the generally accepted lower limits for this species. This implies that these indigenous populations have a degree of cold tolerance. A further implication is that Q. mossambicus has the ability to thrive under adverse conditions which may partially explain its wide and successful colonisation of water bodies far from its natural range, and its obvious fisheries potential.
- Full Text:
- Date Issued: 1990
- Authors: James, Nick, 1955-
- Date: 1990
- Subjects: Cichlids -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5187 , http://hdl.handle.net/10962/d1001963
- Description: The phenotypic plasticity of the cichlid Oreochromis mossambicus was examined in fresh and brackish water populations living in the eastern Cape near the southern extremity of the natural range. The primary goal of the study was to examine the wide variety of life-history styles which were expressed in relation to the varying environmental conditions. Four natural populations were studied during 1986 and 1987, and some experimental work under artificial conditions was carried out at the Rhodes University fishfarm during 1988. This comparative approach gave insights into the complex interactions between biotic and abiotic factors which are exploited by this hardy species. O. mossambicus displayed a wide variety of life-history tactics under harsh environmental conditions. The growth of juvenile fish was rapid and mortality of the young-of-the-year was high. Age at first onset of sexual maturity ranged from one to three years. Under harsh conditions growth rate was markedly reduced after maturity, which occurred during the second or third summer and growth disparity between the sexes was more pronounced. Longevity was found to vary from five to ten years for different populations. Under more favourable conditions (resembling the typical "floodplain" habitats of this species at lower latitudes) very rapid juvenile growth, and a high maximum mass of over 2300 g for both sexes was iii achieved. Sexual maturity under these conditions could be delayed until the third or fourth summer of life. O. mossambicus demonstrated an ability to withstand and even benefit from fluctuating water levels, and adjusted its life style according to the prevailing conditions: at times of high water level recruitment was low and sexual maturity delayed. During low water periods reproductive rates increased. Q. mossambicus showed a distinct preference for gentle gradients and well-vegetated habitats for feeding, nesting and refuge. During the study winter temperatures were near and at some times below the generally accepted lower limits for this species. This implies that these indigenous populations have a degree of cold tolerance. A further implication is that Q. mossambicus has the ability to thrive under adverse conditions which may partially explain its wide and successful colonisation of water bodies far from its natural range, and its obvious fisheries potential.
- Full Text:
- Date Issued: 1990
A life-history approach to the early ontogeny of Oreochromis Mossambicus (Peters)
- Authors: Holden, Kathleen Karen
- Date: 1991
- Subjects: Cichlids -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5298 , http://hdl.handle.net/10962/d1005143 , Cichlids -- Research
- Description: The adult ecophenotype of an animal is the result of interactive events which occur during its early ontogeny through a series of sequential steps of increasing morphological complexity. At the step boundaries, there are qualitative and quantitative changes in the structures present which will allow the developing animal to successfully cope with new trophic features of its internal and external environment. There is some controversy as to whether the shifts that occur at these step boundaries are gradual or saltatory. Environmental parameters, early life-history plasticity and genetic instructions are the interactive events which produce the ecophenotype. The early ontogeny of Oreochromis mossambicus was followed from the time of egg activation until juvenilization. The eggs, embryos and larvae were artificially incubated at 25±0.5ºC. The descriptive text and the figures are composites derived from drawings, photomicrographs and observational notes of live and preserved individuals. It was found that the early ontogeny of O. mossambicus consists of an embryonic period of approximately 11 days and a truncated larval period of about 4-5 days. The embryonic period can be further divided into a cleavage, an embryonic and a free-embryonic phase. Comparisons of the early development of three other mouthbrooding and one substrate-spawning cichlid done by other researchers, revealed that the early ontogeny of O. mossambicus closely resembles that of Sarotherodon melanotheron (also a mouthbrooding species). Embryo length and yolksac area changed gradually in the cleavage and embryonic phases, showed little or no change in the free-embryonic phase, and changed rapidly in the larval period. Heart rate increased gradually in the embryonic phase and peaked just before the shift into the free-embryonic phase. Gradual decrease in heart rate occurred in the free-embryonic phase followed by a second peak at the boundary between the embryonic and larval periods. In the larval period, heart rate levelled off. Although distinctive boundaries were not clearly evident at all steps, it was concluded that there are three definite ontogenetic steps which occur at the boundaries between the embryonic phase, the free-embryonic phase and the larval period. These thresholds occur at a point where shifts in the trophic features of the external environment are expected. Regression analysis revealed that two regimes exist for changes in embryo length and yolksac area and that a breakpoint occurs just prior to the boundary between the embryonic and larval periods. It appears that ontogeny is saltatory at points where a change in the trophic features of the environment requires a new set of interactions to occur between the environment and the ecomorphological and eco-ethological features of the animal.
- Full Text:
- Date Issued: 1991
- Authors: Holden, Kathleen Karen
- Date: 1991
- Subjects: Cichlids -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5298 , http://hdl.handle.net/10962/d1005143 , Cichlids -- Research
- Description: The adult ecophenotype of an animal is the result of interactive events which occur during its early ontogeny through a series of sequential steps of increasing morphological complexity. At the step boundaries, there are qualitative and quantitative changes in the structures present which will allow the developing animal to successfully cope with new trophic features of its internal and external environment. There is some controversy as to whether the shifts that occur at these step boundaries are gradual or saltatory. Environmental parameters, early life-history plasticity and genetic instructions are the interactive events which produce the ecophenotype. The early ontogeny of Oreochromis mossambicus was followed from the time of egg activation until juvenilization. The eggs, embryos and larvae were artificially incubated at 25±0.5ºC. The descriptive text and the figures are composites derived from drawings, photomicrographs and observational notes of live and preserved individuals. It was found that the early ontogeny of O. mossambicus consists of an embryonic period of approximately 11 days and a truncated larval period of about 4-5 days. The embryonic period can be further divided into a cleavage, an embryonic and a free-embryonic phase. Comparisons of the early development of three other mouthbrooding and one substrate-spawning cichlid done by other researchers, revealed that the early ontogeny of O. mossambicus closely resembles that of Sarotherodon melanotheron (also a mouthbrooding species). Embryo length and yolksac area changed gradually in the cleavage and embryonic phases, showed little or no change in the free-embryonic phase, and changed rapidly in the larval period. Heart rate increased gradually in the embryonic phase and peaked just before the shift into the free-embryonic phase. Gradual decrease in heart rate occurred in the free-embryonic phase followed by a second peak at the boundary between the embryonic and larval periods. In the larval period, heart rate levelled off. Although distinctive boundaries were not clearly evident at all steps, it was concluded that there are three definite ontogenetic steps which occur at the boundaries between the embryonic phase, the free-embryonic phase and the larval period. These thresholds occur at a point where shifts in the trophic features of the external environment are expected. Regression analysis revealed that two regimes exist for changes in embryo length and yolksac area and that a breakpoint occurs just prior to the boundary between the embryonic and larval periods. It appears that ontogeny is saltatory at points where a change in the trophic features of the environment requires a new set of interactions to occur between the environment and the ecomorphological and eco-ethological features of the animal.
- Full Text:
- Date Issued: 1991
A light-emitting-diode pulsing system for measurement of time-resolved luminescence
- Authors: Uriri, Solomon Akpore
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:20976 , http://hdl.handle.net/10962/5788
- Description: A new light-emitting-diode based pulsing system for measurement of time-resolved luminescence has been developed. The light-emitting-diodes are pulsed at various pulse-widths by a 555-timer operated as a monostable multivibrator. The light-emitting-diodes are arranged in a dural holder connected in parallel in sets of four, each containing four diodes in series. The output pulse from the 555-timer is fed into an 2N7000 MOSFET to produce a pulse-current of 500 mA to drive the set of 16 light-emitting-diodes. This size of current is sufficient to drive the diodes with each driven at a pulse-current of 90 mA with a possible maximum of 110 mA per diode. A multichannel scaler is used to trigger the pulsing system and to record data at selectable dwell times. The system is capable of generating pulse-widths in the range of microseconds upwards.
- Full Text:
- Date Issued: 2015
- Authors: Uriri, Solomon Akpore
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:20976 , http://hdl.handle.net/10962/5788
- Description: A new light-emitting-diode based pulsing system for measurement of time-resolved luminescence has been developed. The light-emitting-diodes are pulsed at various pulse-widths by a 555-timer operated as a monostable multivibrator. The light-emitting-diodes are arranged in a dural holder connected in parallel in sets of four, each containing four diodes in series. The output pulse from the 555-timer is fed into an 2N7000 MOSFET to produce a pulse-current of 500 mA to drive the set of 16 light-emitting-diodes. This size of current is sufficient to drive the diodes with each driven at a pulse-current of 90 mA with a possible maximum of 110 mA per diode. A multichannel scaler is used to trigger the pulsing system and to record data at selectable dwell times. The system is capable of generating pulse-widths in the range of microseconds upwards.
- Full Text:
- Date Issued: 2015
A linear model for valuating preferences of freshwater inflows into forty selected estuaries along the South African coastline
- Authors: Smith, Melnick Jurgen
- Subjects: Estuaries -- South Africa -- Eastern Cape , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10581 , http://hdl.handle.net/10948/d1020916
- Description: According to the National Water Act of 1998, an estuary is an enclosed body of water that is either periodically or permanently open to the ocean. Within an estuary, the seawater is diluted to a measurable degree, creating a unique aquatic environment for animals and plants. Estuaries are environmental and economic assets to the population. The health status of our local estuaries, however, is being compromized due to a steady decrease in the freshwater inflow and supply. Tides and climatic conditions do have an impact upon the dynamics of an estuary, but these factors remain relatively constant throughout each year. The freshwater inflow and supply, however, are highly variable and are directly influenced by human involvement. Upstream abstraction for industrial and domestic use, for example, could lead to mouth closure where the ocean meets the river. The National Water Act of 1998 was established to address the lack of research and predominant mismanagement of freshwater inflow into South Africa’s estuaries (Allanson and Baird, 1999). To ensure proper water resource management, different water allocation costs and benefits need to be compared and analyzed to secure an optimum solution (Mlangeni, 2007). Like many environmental services yielded to man, estuary services are not traded in any markets. Alternative markets are thus sought to allow the estimation of the values of such services. Among the available valuation techniques are the Contingent Valuation Method (CVM), Travel Cost Method (TCM) and Hedonic Pricing Method (HPM). The involved benefits of water allocations are predicted in this study by use of the CVM which elicits respondents’ willingness to pay (WTP) towards predetermined changes in freshwater inflow into estuaries. The CVM was applied throughout the Water Research Commission’s (WRC) Project K5/1413 from 2000 to 2008 (Hosking, 2010). Each individual study employed specialized surveys which ideally created a close correspondence between the answers provided by respondents to the supposed scenarios and their voluntary exchanges in markets should money actually have been handled (Mlangeni, 2007). Much criticism has been directed towards the CVM, but careful use and application of the method has been shown to produce significant and satisfactory results (Hosking, 2010). The primary aim of this study was to collectively analyze the collated data provided by the WRC and compare the results with the findings of previous studies. Each variable was analyzed separately in order to reveal any discrepancies between the respective findings. A supplementary objective of this study was to add to the body of knowledge pertaining to South Africa’s estuaries and guide management in the distribution of freshwater towards proficient levels (Du Preez and Hosking, 2010). The associated change in the cumulative consumer surplus with an increased freshwater supply into forty selected estuaries was therefore investigated. The subsequent benefits due to a superior freshwater supply are therefore reflected (Du Preez and Hosking, 2010). The data gathered by each of the individual researchers throughout their studies (supported by the WRC) were combined to form a single dataset including all recorded information supplied by the corresponding respondents. As the investigation progressed, improvements were made upon the questionnaires posed to the considered estuary populations. Consequently, some of the data in the combined dataset were “missing”, since previous studies did not include certain questions, while later studies omitted others. Data imputation was employed to create an imputed dataset, enabling the modeling of the public’s WTP through regression techniques. A linear model was utilized in this study, also incorporating interaction between the predictor variables. The double-log functional form was implemented to estimate the public’s WTP. The population’s total willingness to pay (TWTP) was further estimated by aggregation. A summary of the respective results is displayed in in Table 1.
- Full Text:
- Authors: Smith, Melnick Jurgen
- Subjects: Estuaries -- South Africa -- Eastern Cape , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10581 , http://hdl.handle.net/10948/d1020916
- Description: According to the National Water Act of 1998, an estuary is an enclosed body of water that is either periodically or permanently open to the ocean. Within an estuary, the seawater is diluted to a measurable degree, creating a unique aquatic environment for animals and plants. Estuaries are environmental and economic assets to the population. The health status of our local estuaries, however, is being compromized due to a steady decrease in the freshwater inflow and supply. Tides and climatic conditions do have an impact upon the dynamics of an estuary, but these factors remain relatively constant throughout each year. The freshwater inflow and supply, however, are highly variable and are directly influenced by human involvement. Upstream abstraction for industrial and domestic use, for example, could lead to mouth closure where the ocean meets the river. The National Water Act of 1998 was established to address the lack of research and predominant mismanagement of freshwater inflow into South Africa’s estuaries (Allanson and Baird, 1999). To ensure proper water resource management, different water allocation costs and benefits need to be compared and analyzed to secure an optimum solution (Mlangeni, 2007). Like many environmental services yielded to man, estuary services are not traded in any markets. Alternative markets are thus sought to allow the estimation of the values of such services. Among the available valuation techniques are the Contingent Valuation Method (CVM), Travel Cost Method (TCM) and Hedonic Pricing Method (HPM). The involved benefits of water allocations are predicted in this study by use of the CVM which elicits respondents’ willingness to pay (WTP) towards predetermined changes in freshwater inflow into estuaries. The CVM was applied throughout the Water Research Commission’s (WRC) Project K5/1413 from 2000 to 2008 (Hosking, 2010). Each individual study employed specialized surveys which ideally created a close correspondence between the answers provided by respondents to the supposed scenarios and their voluntary exchanges in markets should money actually have been handled (Mlangeni, 2007). Much criticism has been directed towards the CVM, but careful use and application of the method has been shown to produce significant and satisfactory results (Hosking, 2010). The primary aim of this study was to collectively analyze the collated data provided by the WRC and compare the results with the findings of previous studies. Each variable was analyzed separately in order to reveal any discrepancies between the respective findings. A supplementary objective of this study was to add to the body of knowledge pertaining to South Africa’s estuaries and guide management in the distribution of freshwater towards proficient levels (Du Preez and Hosking, 2010). The associated change in the cumulative consumer surplus with an increased freshwater supply into forty selected estuaries was therefore investigated. The subsequent benefits due to a superior freshwater supply are therefore reflected (Du Preez and Hosking, 2010). The data gathered by each of the individual researchers throughout their studies (supported by the WRC) were combined to form a single dataset including all recorded information supplied by the corresponding respondents. As the investigation progressed, improvements were made upon the questionnaires posed to the considered estuary populations. Consequently, some of the data in the combined dataset were “missing”, since previous studies did not include certain questions, while later studies omitted others. Data imputation was employed to create an imputed dataset, enabling the modeling of the public’s WTP through regression techniques. A linear model was utilized in this study, also incorporating interaction between the predictor variables. The double-log functional form was implemented to estimate the public’s WTP. The population’s total willingness to pay (TWTP) was further estimated by aggregation. A summary of the respective results is displayed in in Table 1.
- Full Text:
A longitudinal study of DNS traffic: understanding current DNS practice and abuse
- Authors: Van Zyl, Ignus
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3707 , vital:20537
- Description: This thesis examines a dataset spanning 21 months, containing 3,5 billion DNS packets. Traffic on TCP and UDP port 53, was captured on a production /24 IP block. The purpose of this thesis is twofold. The first is to create an understanding of current practice and behavior within the DNS infrastructure, the second to explore current threats faced by the DNS and the various systems that implement it. This is achieved by drawing on analysis and observations from the captured data. Aspects of the operation of DNS on the greater Internet are considered in this research with reference to the observed trends in the dataset, A thorough analysis of current DNS TTL implementation is made with respect to all response traffic, as well as sections looking at observed DNS TTL values for ,za domain replies and NX DOMAIN flagged replies. This thesis found that TTL values implemented are much lower than has been recommended in previous years, and that the TTL decrease is prevalent in most, but not all EE TTL implementation. With respect to the nature of DNS operations, this thesis also concerns itself with an analysis of the geoloeation of authoritative servers for local (,za) domains, and offers further observations towards the latency generated by the choice of authoritative server location for a given ,za domain. It was found that the majority of ,za domain authoritative servers are international, which results in latency generation that is multiple times greater than observed latencies for local authoritative servers. Further analysis is done with respect to NX DOM AIN behavior captured across the dataset. These findings outlined the cost of DNS miseonfiguration as well as highlighting instances of NXDOMAIN generation through malicious practice. With respect to DNS abuses, original research with respect to long-term scanning generated as a result of amplification attack activity on the greater Internet is presented. Many instances of amplification domain scans were captured during the packet capture, and an attempt is made to correlate that activity temporally with known amplification attack reports. The final area that this thesis deals with is the relatively new field of Bitflipping and Bitsquatting, delivering results on bitflip detection and evaluation over the course of the entire dataset. The detection methodology is outlined, and the final results are compared to findings given in recent bitflip literature.
- Full Text:
- Date Issued: 2016
- Authors: Van Zyl, Ignus
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3707 , vital:20537
- Description: This thesis examines a dataset spanning 21 months, containing 3,5 billion DNS packets. Traffic on TCP and UDP port 53, was captured on a production /24 IP block. The purpose of this thesis is twofold. The first is to create an understanding of current practice and behavior within the DNS infrastructure, the second to explore current threats faced by the DNS and the various systems that implement it. This is achieved by drawing on analysis and observations from the captured data. Aspects of the operation of DNS on the greater Internet are considered in this research with reference to the observed trends in the dataset, A thorough analysis of current DNS TTL implementation is made with respect to all response traffic, as well as sections looking at observed DNS TTL values for ,za domain replies and NX DOMAIN flagged replies. This thesis found that TTL values implemented are much lower than has been recommended in previous years, and that the TTL decrease is prevalent in most, but not all EE TTL implementation. With respect to the nature of DNS operations, this thesis also concerns itself with an analysis of the geoloeation of authoritative servers for local (,za) domains, and offers further observations towards the latency generated by the choice of authoritative server location for a given ,za domain. It was found that the majority of ,za domain authoritative servers are international, which results in latency generation that is multiple times greater than observed latencies for local authoritative servers. Further analysis is done with respect to NX DOM AIN behavior captured across the dataset. These findings outlined the cost of DNS miseonfiguration as well as highlighting instances of NXDOMAIN generation through malicious practice. With respect to DNS abuses, original research with respect to long-term scanning generated as a result of amplification attack activity on the greater Internet is presented. Many instances of amplification domain scans were captured during the packet capture, and an attempt is made to correlate that activity temporally with known amplification attack reports. The final area that this thesis deals with is the relatively new field of Bitflipping and Bitsquatting, delivering results on bitflip detection and evaluation over the course of the entire dataset. The detection methodology is outlined, and the final results are compared to findings given in recent bitflip literature.
- Full Text:
- Date Issued: 2016
A machine-independent microprogram development system
- Authors: Ward, Michael John
- Date: 1987 , 2013-03-11
- Subjects: Microprogramming
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4581 , http://hdl.handle.net/10962/d1003738 , Microprogramming
- Description: The aims of this project are twofold. They are firstly, to implement a microprogram development system that allows the programmer to write microcode for any microprogrammable machine, and secondly, to build a microprogrammable machine, incorporating the user friendliness of a simulator, while still providing the 'hands on' experience obtained actual hardware. Microprogram development involves a two stage process. The first step is to describe the target machine, using format descriptions and mnemonic-based template definitions. The second stage involves using the defined mnemonics to write the microcodes for the target machine. This includes an assembly phase to translate the mnemonics into the binary microinstructions. Three main components constitute the microprogrammable machine. The Arithmetic and Logic Unit (ALU) is built using chips from Advanced Micro Devices' Am29ØØ bit-slice family, the action of the Microprogram Control Unit (MCU) is simulated by software running on an IBM Personal Computer, and a section of the IBM PC's main memory acts as the Control Store (CS) for the system. The ALU is built on a prototyping card that plugs into one of the slots on the IBM PC's mother board. A hardware simulator program, that produces the effect of the ALU, has also been developed. A small assembly language has been developed using the system, to test the various functions of the system. A mini-assembler has also been written to facilitate assembly of the above language. A group of honours students at Rhodes University tested the microprogram development system. Their ideas and suggestions have been tabulated in this report and some of them have been used to enhance the system's performance. The concept of allowing 'inline' microinstructions in the macroprogram is also investigated in this report and a method of implementing this is shown.
- Full Text:
- Date Issued: 1987
- Authors: Ward, Michael John
- Date: 1987 , 2013-03-11
- Subjects: Microprogramming
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4581 , http://hdl.handle.net/10962/d1003738 , Microprogramming
- Description: The aims of this project are twofold. They are firstly, to implement a microprogram development system that allows the programmer to write microcode for any microprogrammable machine, and secondly, to build a microprogrammable machine, incorporating the user friendliness of a simulator, while still providing the 'hands on' experience obtained actual hardware. Microprogram development involves a two stage process. The first step is to describe the target machine, using format descriptions and mnemonic-based template definitions. The second stage involves using the defined mnemonics to write the microcodes for the target machine. This includes an assembly phase to translate the mnemonics into the binary microinstructions. Three main components constitute the microprogrammable machine. The Arithmetic and Logic Unit (ALU) is built using chips from Advanced Micro Devices' Am29ØØ bit-slice family, the action of the Microprogram Control Unit (MCU) is simulated by software running on an IBM Personal Computer, and a section of the IBM PC's main memory acts as the Control Store (CS) for the system. The ALU is built on a prototyping card that plugs into one of the slots on the IBM PC's mother board. A hardware simulator program, that produces the effect of the ALU, has also been developed. A small assembly language has been developed using the system, to test the various functions of the system. A mini-assembler has also been written to facilitate assembly of the above language. A group of honours students at Rhodes University tested the microprogram development system. Their ideas and suggestions have been tabulated in this report and some of them have been used to enhance the system's performance. The concept of allowing 'inline' microinstructions in the macroprogram is also investigated in this report and a method of implementing this is shown.
- Full Text:
- Date Issued: 1987
A marine chemical ecology study of the sea hare, Bursatella leachii in South Africa
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
A mathematical investigation of the effects of sexual orientation and HIV status on HPV transmission and vaccination
- Authors: Holtzhausen, Tresia Louisa
- Date: 2013
- Subjects: Virus diseases -- Mathematical models , Cervix uteri -- Cancer -- Treatment , Sexual orientation , Immune response -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3946 , vital:20494
- Description: The effect of the inclusion of sexual behaviour, particularly three sexual orientation classes, on the transmission dynamics of HPV and cervical cancer incidence was investigated. A comprehensive literature review of mathematical models of HPV transmission and the natural history of cervical cancer was concluded. A mathematical model using ordinary differential equations was developed, which incorporated the three sexual orientation classes, and a sexual mixing algorithm for modelling the transmission dynamics. Reproduction numbers, determined through a simplified version of the developed model, indicated that the bisexual population could form a bridge between the heterosexual and homosexual population. The level of interaction is determined by the selection preferences of a bisexual individual to form a partnership with an individual of the same or opposite sex. The model was simulated, with parameters based on a South African population and HPV type 16/18, to investigate the effects of HIV status, sexual orientation and various vaccination strategies on HPV transmission and cervical cancer incidence. The results indicated that HIV status is a significant factor when determining cervical cancer incidence. The results regarding vaccination strategies agreed with results from the literature review with a two sex before sexual debut and catch up program the most effective, noting that with increased vaccination coverage of females the marginal impact on cervical cancer incidence of this approach diminished.
- Full Text:
- Date Issued: 2013
- Authors: Holtzhausen, Tresia Louisa
- Date: 2013
- Subjects: Virus diseases -- Mathematical models , Cervix uteri -- Cancer -- Treatment , Sexual orientation , Immune response -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3946 , vital:20494
- Description: The effect of the inclusion of sexual behaviour, particularly three sexual orientation classes, on the transmission dynamics of HPV and cervical cancer incidence was investigated. A comprehensive literature review of mathematical models of HPV transmission and the natural history of cervical cancer was concluded. A mathematical model using ordinary differential equations was developed, which incorporated the three sexual orientation classes, and a sexual mixing algorithm for modelling the transmission dynamics. Reproduction numbers, determined through a simplified version of the developed model, indicated that the bisexual population could form a bridge between the heterosexual and homosexual population. The level of interaction is determined by the selection preferences of a bisexual individual to form a partnership with an individual of the same or opposite sex. The model was simulated, with parameters based on a South African population and HPV type 16/18, to investigate the effects of HIV status, sexual orientation and various vaccination strategies on HPV transmission and cervical cancer incidence. The results indicated that HIV status is a significant factor when determining cervical cancer incidence. The results regarding vaccination strategies agreed with results from the literature review with a two sex before sexual debut and catch up program the most effective, noting that with increased vaccination coverage of females the marginal impact on cervical cancer incidence of this approach diminished.
- Full Text:
- Date Issued: 2013
A mathematical study on optimal prevention and control strategies for tuberculosis: case study for Port Elizabeth, South Africa
- Authors: Zembe, Pumelela Vincent
- Date: 2016
- Subjects: Tuberculosis -- South Africa -- Port Elizabeth -- Prevention Tuberculosis -- Mathematical models , Tuberculosis -- Case studies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12823 , vital:27124
- Description: In this treatise a SEIR model for the transmission of tuberculosis was proposed. It assumes that the latent infected individuals progress to active tuberculosis through endogenous reactivation and exogenous re-infection and that the individuals who have recovered from the disease through treatment are not immune to tuberculosis re-infection. While most features of the original model were kept, the model was modified to incorporate two control measures in the form of post-exposure tuberculosis prophylaxis for the treatment of latent individuals and tuberculosis therapeutics for the treatmentof individuals with active tuberculosis. Mathematical analysis of the modelwas done under the assumption that the two control measures are positiveconstants. The disease-free equilibrium point was locally asymptotically stable when the basic reproduction number was less than unity and unstable when this epidemic threshold exceeds unity. An optimal control problem was formulated and the necessary conditions for optimality were derived.The numerical results based on data from Port Elizabeth suggest that using both forms of control measures simultaneously is more effective in reducing the total number of infected individuals than applying single controls separately.
- Full Text:
- Date Issued: 2016
- Authors: Zembe, Pumelela Vincent
- Date: 2016
- Subjects: Tuberculosis -- South Africa -- Port Elizabeth -- Prevention Tuberculosis -- Mathematical models , Tuberculosis -- Case studies
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12823 , vital:27124
- Description: In this treatise a SEIR model for the transmission of tuberculosis was proposed. It assumes that the latent infected individuals progress to active tuberculosis through endogenous reactivation and exogenous re-infection and that the individuals who have recovered from the disease through treatment are not immune to tuberculosis re-infection. While most features of the original model were kept, the model was modified to incorporate two control measures in the form of post-exposure tuberculosis prophylaxis for the treatment of latent individuals and tuberculosis therapeutics for the treatmentof individuals with active tuberculosis. Mathematical analysis of the modelwas done under the assumption that the two control measures are positiveconstants. The disease-free equilibrium point was locally asymptotically stable when the basic reproduction number was less than unity and unstable when this epidemic threshold exceeds unity. An optimal control problem was formulated and the necessary conditions for optimality were derived.The numerical results based on data from Port Elizabeth suggest that using both forms of control measures simultaneously is more effective in reducing the total number of infected individuals than applying single controls separately.
- Full Text:
- Date Issued: 2016
A meteorological analysis of extreme flood events in the southern parts of the Eastern Cape, South Africa
- Authors: Jacobs, Tennielle Lindsay
- Date: 2017
- Subjects: Floods -- South Africa -- Eastern Cape , Floods -- South Africa -- Eastern Cape -- Cast studies , Lows (Meteorology) -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Rainfall anomalies -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50525 , vital:25996
- Description: Extreme flood events have been found to occur in the Eastern Cape Province of South Africa. The southern and south-eastern coastal regions are particularly susceptible to floods with daily rainfall records of up to 490 mm having been recorded here. In order to gain a better understanding of these floods, historical floods in the southern parts of the Eastern Cape have been analysed in this study. This study aimed to investigate the most extreme flood events in the history of the area and to analyse the surface observational data during the heavy rainfall events found, to contribute to the understanding of these heavy rainfall events. Seven case studies were investigated using NCEP/NCAR Reanalysis 1 data and surface observational data, to analysis the synoptic circulation and surface data tendencies during heavy rainfall events. All of the case studies that had synoptic data available showed to have a COL system present with the upper air low lying westward of the flood area. The surface synoptic situation presented an intense high pressure system lying south west or south of the country in the Atlantic Ocean between 35-45°S. Another key factor was a surface trough over the interior of the country, due to the COL, extending southwards to protrude off of the south or south eastern coastline east of the flood areas. The combination of these three systems colloquially referred to as a “Black South-Easter”, produced dangerous rainfall intensities when the winds were perpendicular to the coast. The results of the surface observations revealed temperatures increasing at night (against diurnal cycles) with increasing relative humidity preceding the heavy rainfall events. The pressure showed both increasing and decreasing trends during heavy rainfall events however in five of six cases a tight pressure gradient was present producing an influx of moist air into the flood area. Onshore winds were found to be of high importance in heavy rainfall events to bring moist air into the area. Wind speeds greater than 5m/s occurred during times of high rainfall intensities.
- Full Text:
- Date Issued: 2017
- Authors: Jacobs, Tennielle Lindsay
- Date: 2017
- Subjects: Floods -- South Africa -- Eastern Cape , Floods -- South Africa -- Eastern Cape -- Cast studies , Lows (Meteorology) -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Rainfall anomalies -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50525 , vital:25996
- Description: Extreme flood events have been found to occur in the Eastern Cape Province of South Africa. The southern and south-eastern coastal regions are particularly susceptible to floods with daily rainfall records of up to 490 mm having been recorded here. In order to gain a better understanding of these floods, historical floods in the southern parts of the Eastern Cape have been analysed in this study. This study aimed to investigate the most extreme flood events in the history of the area and to analyse the surface observational data during the heavy rainfall events found, to contribute to the understanding of these heavy rainfall events. Seven case studies were investigated using NCEP/NCAR Reanalysis 1 data and surface observational data, to analysis the synoptic circulation and surface data tendencies during heavy rainfall events. All of the case studies that had synoptic data available showed to have a COL system present with the upper air low lying westward of the flood area. The surface synoptic situation presented an intense high pressure system lying south west or south of the country in the Atlantic Ocean between 35-45°S. Another key factor was a surface trough over the interior of the country, due to the COL, extending southwards to protrude off of the south or south eastern coastline east of the flood areas. The combination of these three systems colloquially referred to as a “Black South-Easter”, produced dangerous rainfall intensities when the winds were perpendicular to the coast. The results of the surface observations revealed temperatures increasing at night (against diurnal cycles) with increasing relative humidity preceding the heavy rainfall events. The pressure showed both increasing and decreasing trends during heavy rainfall events however in five of six cases a tight pressure gradient was present producing an influx of moist air into the flood area. Onshore winds were found to be of high importance in heavy rainfall events to bring moist air into the area. Wind speeds greater than 5m/s occurred during times of high rainfall intensities.
- Full Text:
- Date Issued: 2017