A bulk and fraction-specific geochemical study of the origin of diverse high-grade hematitic iron ores from the Transvaal Supergroup, Northern Cape Province, South Africa
- Authors: Moloto, William
- Date: 2017
- Subjects: Iron ore -- South Africa -- Transvaal Supergroup , Hematite -- South Africa -- Transvaal Supergroup , Transvaal Supergroup (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50546 , vital:25998
- Description: The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade, Banded Iron Formation-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous studies suggest the origin of these iron ores to be ancient supergene, and that the ore forming process would have therefore pre-dated deposition of the basal Mapedi shales of the Olifansthoek Supergroup that unconformably overlies the Transvaal strata. The nature of the protolith to the ores has been suggested to be largely BIF of the Asbestos Hills Subgroup, and mainly the Kuruman BIF. The work presented in this thesis seeks to provide insights into the diversity of processes that are likely to have been involved during the genesis of these high-grade iron ores, in the context of constraining the pre-ore lithologies and the relative role of supergene-style, largely residual enrichment processes versus any possible metasomatic hydrothermal effects. This study had as primary focus the application of combined bulk and fraction-specific geochemical applications on representative iron-ore samples from four different localities in the Northern Cape Province, namely King/Khumani, Beeshoek, Heuninkranz and Hotazel. The collected samples show a variety of textures and also capture different pre-unconformity stratigraphic sections of BIF. The key objective was to assess whether the fraction-specific analytical results could provide any firm constraints for the origin of the ferrous and non-ferrous matrix fractions of the ores, namely whether they represent any combinations of protolith residue, allochtonously-introduced detritus or hydrothermally-derived material, and whether the results are comparable and consistent across all samples studied. In particular, constraints were sought as to whether the ore protolith was exclusively BIF or may potentially have contained at least a fraction of other lithologic types, such as shale; and whether there is sufficient evidence to support solely a supergene model for the ores or the data suggest other more epigenetic models of ore formation involving the action of hydrothermal fluids Bulk-rock geochemical analyses reveal the overwhelming dominance of Fe-oxide (as hematite) in all samples, at concentrations as high as 99 wt.% Fe2O3. Major and trace-element abundances of all samples were re-calculated assuming only iron addition from the postulated protolith (average BIF and shale), and the results revealed atypical enrichments in the iron ores by comparison to average BIF, and more shale-like relative abundances when normalised against the Post-Archaean Average Shale (PAAS). Specifically, BIF-normalised diagrams show relative enrichments by as much as 53-95% for Al2O3; 11-86% for TiO2; and 4-60% for P2O5. By contrast, PAAS-normalised values display enrichments of 1-3% for Al2O3, 0.2-3% for TiO2, and 3-13% for P2O5. Similar observations can be made for the greatest majority of trace elements when normalised against average BIF as compared to normalisation against PAAS. A suite of trace element that include alkali earths (e.g. Ba, Sr) and transition metals (e.g. Ni, Zn) show enrichments that are unrelated to the apparently detrital siliciclastic fraction of the ores, and are therefore linked to a possible hydrothermal input. Fraction-specific extractions were performed via the adaptation of existing dissolution protocols using oxalic acid (iron-oxide fraction) followed by HF digestion (silicate-fraction). The analyses of the produced aliquots using ICP-MS techniques, focused mainly on the REE abundances of the separated ferrous and non-ferrous matrix fractions and their comparisons to bulk-rock REE signatures. The results lend further support to the suggestion that the ore samples contain a predominant shale-like signal which does not directly compare to published REE signatures for supergene or hydrothermal BIF-hosted iron-ore deposits alike. The data therefore collectively point to a post-unconformity epigenetic hydrothermal event/s of iron ore-formation that would have exploited not only BIF but also shale as suitable pre-ore protolith.
- Full Text:
- Authors: Moloto, William
- Date: 2017
- Subjects: Iron ore -- South Africa -- Transvaal Supergroup , Hematite -- South Africa -- Transvaal Supergroup , Transvaal Supergroup (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50546 , vital:25998
- Description: The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade, Banded Iron Formation-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous studies suggest the origin of these iron ores to be ancient supergene, and that the ore forming process would have therefore pre-dated deposition of the basal Mapedi shales of the Olifansthoek Supergroup that unconformably overlies the Transvaal strata. The nature of the protolith to the ores has been suggested to be largely BIF of the Asbestos Hills Subgroup, and mainly the Kuruman BIF. The work presented in this thesis seeks to provide insights into the diversity of processes that are likely to have been involved during the genesis of these high-grade iron ores, in the context of constraining the pre-ore lithologies and the relative role of supergene-style, largely residual enrichment processes versus any possible metasomatic hydrothermal effects. This study had as primary focus the application of combined bulk and fraction-specific geochemical applications on representative iron-ore samples from four different localities in the Northern Cape Province, namely King/Khumani, Beeshoek, Heuninkranz and Hotazel. The collected samples show a variety of textures and also capture different pre-unconformity stratigraphic sections of BIF. The key objective was to assess whether the fraction-specific analytical results could provide any firm constraints for the origin of the ferrous and non-ferrous matrix fractions of the ores, namely whether they represent any combinations of protolith residue, allochtonously-introduced detritus or hydrothermally-derived material, and whether the results are comparable and consistent across all samples studied. In particular, constraints were sought as to whether the ore protolith was exclusively BIF or may potentially have contained at least a fraction of other lithologic types, such as shale; and whether there is sufficient evidence to support solely a supergene model for the ores or the data suggest other more epigenetic models of ore formation involving the action of hydrothermal fluids Bulk-rock geochemical analyses reveal the overwhelming dominance of Fe-oxide (as hematite) in all samples, at concentrations as high as 99 wt.% Fe2O3. Major and trace-element abundances of all samples were re-calculated assuming only iron addition from the postulated protolith (average BIF and shale), and the results revealed atypical enrichments in the iron ores by comparison to average BIF, and more shale-like relative abundances when normalised against the Post-Archaean Average Shale (PAAS). Specifically, BIF-normalised diagrams show relative enrichments by as much as 53-95% for Al2O3; 11-86% for TiO2; and 4-60% for P2O5. By contrast, PAAS-normalised values display enrichments of 1-3% for Al2O3, 0.2-3% for TiO2, and 3-13% for P2O5. Similar observations can be made for the greatest majority of trace elements when normalised against average BIF as compared to normalisation against PAAS. A suite of trace element that include alkali earths (e.g. Ba, Sr) and transition metals (e.g. Ni, Zn) show enrichments that are unrelated to the apparently detrital siliciclastic fraction of the ores, and are therefore linked to a possible hydrothermal input. Fraction-specific extractions were performed via the adaptation of existing dissolution protocols using oxalic acid (iron-oxide fraction) followed by HF digestion (silicate-fraction). The analyses of the produced aliquots using ICP-MS techniques, focused mainly on the REE abundances of the separated ferrous and non-ferrous matrix fractions and their comparisons to bulk-rock REE signatures. The results lend further support to the suggestion that the ore samples contain a predominant shale-like signal which does not directly compare to published REE signatures for supergene or hydrothermal BIF-hosted iron-ore deposits alike. The data therefore collectively point to a post-unconformity epigenetic hydrothermal event/s of iron ore-formation that would have exploited not only BIF but also shale as suitable pre-ore protolith.
- Full Text:
A case-control approach to assess variability in distribution of distance between transcription factor binding site and transcription start site
- Authors: Moos, Abdul Ragmaan
- Date: 2017
- Subjects: Transcription factors , Proteomics , Chromatin , Chromatin immunoprecipitation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5315 , vital:20808
- Description: Using the in-silico approach, with ENCODE ChIP-seq data for various transcription factors and different cell types; we systematically compared the distance between the transcription factor binding site (TFBS) and the transcription start (TSS). Our aim was to determine if the same transcription factor binds at a different position relative to the TSS in a normal and an abnormal cell type. We compare distribution of distance of binding sites from the TSS; to make description less verbose we call this “distance” where there is no possibility of confusion. We used a case-control methodology where the distance between the TFBS and the TSS in the normal, non-cancerous or untreated cell type is the control. The distance between the TFBS and the TSS in the cancerous or treated cell type is the case. We use the distance between the TFBS and the TSS in the control as the standard. We compared the distance between the TFBS and the TSS in the case and the control. If the distance between the TFBS and the TSS in the control was greater than the distance between the TFBS and the TSS in the case, we can infer the following. The transcription factor in the case binds closer to the TSS compared to the control. If the distance between the TFBS and the TSS in the control is smaller than the distance between the TFBS and the TSS in the case, we can infer the following. The TF in the case binds further away from the TSS compared to the control. Our method is a screening method whereby we compare ChIP-seq data to determine if there is a difference in the distribution distance between the TFBS and the TSS for normal and abnormal cell types. We used the R package ChIP-Enrich to compare the distribution of distance between ChIP-seq peak and the nearest TSS. ChIP-Enrich produces a histogram with the number of ChIP-seq peaks at a certain distance from the TSS. The results indicate for some transcription factors like GM12878-cMyc and K562-cMyc there is a difference between the distribution of distance between the TFBS and the nearest TSS. cMyc has more binding sites within a distance of 1kb from the TSS in GM12878 when compared to K562. GM12878-CTCF and K562-CTCF have slight differences when comparing their distribution of distance from the TSS. This means CTCF binds almost the same distance from the TSS in both GM12878 and K562. A549-gr treated with dexamethasone is interesting because with increase dose of dexamethasone the distribution of distance from the TSS changes as well.
- Full Text:
- Authors: Moos, Abdul Ragmaan
- Date: 2017
- Subjects: Transcription factors , Proteomics , Chromatin , Chromatin immunoprecipitation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5315 , vital:20808
- Description: Using the in-silico approach, with ENCODE ChIP-seq data for various transcription factors and different cell types; we systematically compared the distance between the transcription factor binding site (TFBS) and the transcription start (TSS). Our aim was to determine if the same transcription factor binds at a different position relative to the TSS in a normal and an abnormal cell type. We compare distribution of distance of binding sites from the TSS; to make description less verbose we call this “distance” where there is no possibility of confusion. We used a case-control methodology where the distance between the TFBS and the TSS in the normal, non-cancerous or untreated cell type is the control. The distance between the TFBS and the TSS in the cancerous or treated cell type is the case. We use the distance between the TFBS and the TSS in the control as the standard. We compared the distance between the TFBS and the TSS in the case and the control. If the distance between the TFBS and the TSS in the control was greater than the distance between the TFBS and the TSS in the case, we can infer the following. The transcription factor in the case binds closer to the TSS compared to the control. If the distance between the TFBS and the TSS in the control is smaller than the distance between the TFBS and the TSS in the case, we can infer the following. The TF in the case binds further away from the TSS compared to the control. Our method is a screening method whereby we compare ChIP-seq data to determine if there is a difference in the distribution distance between the TFBS and the TSS for normal and abnormal cell types. We used the R package ChIP-Enrich to compare the distribution of distance between ChIP-seq peak and the nearest TSS. ChIP-Enrich produces a histogram with the number of ChIP-seq peaks at a certain distance from the TSS. The results indicate for some transcription factors like GM12878-cMyc and K562-cMyc there is a difference between the distribution of distance between the TFBS and the nearest TSS. cMyc has more binding sites within a distance of 1kb from the TSS in GM12878 when compared to K562. GM12878-CTCF and K562-CTCF have slight differences when comparing their distribution of distance from the TSS. This means CTCF binds almost the same distance from the TSS in both GM12878 and K562. A549-gr treated with dexamethasone is interesting because with increase dose of dexamethasone the distribution of distance from the TSS changes as well.
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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:
- 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:
A risk-based framework for new products: a South African telecommunication’s study
- Authors: Jeffries, Michael
- Date: 2017
- Subjects: Telephone companies -- Risk management -- South Africa , Telephone companies -- South Africa -- Case studies , Telecommunication -- Security measures -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4765 , vital:20722
- Description: The integrated reports of Vodacom, Telkom and MTN — telecommunication organisations in South Africa — show that they are diversifying their product offerings from traditional voice and data services. These organisations are including new offerings covering the financial, health, insurance and mobile education services. The potential exists for these organisations to launch products that are substandard and which either do not take into account customer needs or do not comply with current legislations or regulations. Most telecommunication organisations have a well-defined enterprise risk management program, to ensure compliance to King III, however risk management processes specifically for new products and services might be lacking. The responsibility usually resides with the product managers for the implementation of robust products; however they do not always have the correct skillset to ensure adherence to governance requirements and therefore might not be aware of which laws they might not be adhering to, or understand the customers’ requirements. More complex products, additional competition, changes to technology and new business ventures have reinforced the need to manage risk on telecommunication products. Failure to take risk requirements into account could lead to potential fines, damage the organisation’s reputation which could lead to customers churning from these service providers. This research analyses three periods of data captured from a mobile telecommunication organisation to assess the current status quo of risk management maturity within the organisation’s product and service environment. Based on the analysis as well as industry best practices, a risk management framework for products is proposed that can assist product managers analyse concepts to ensure adherence to governance requirements. This could assist new product or service offerings in the marketplace do not create a perception of distrust by consumers.
- Full Text:
- Authors: Jeffries, Michael
- Date: 2017
- Subjects: Telephone companies -- Risk management -- South Africa , Telephone companies -- South Africa -- Case studies , Telecommunication -- Security measures -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4765 , vital:20722
- Description: The integrated reports of Vodacom, Telkom and MTN — telecommunication organisations in South Africa — show that they are diversifying their product offerings from traditional voice and data services. These organisations are including new offerings covering the financial, health, insurance and mobile education services. The potential exists for these organisations to launch products that are substandard and which either do not take into account customer needs or do not comply with current legislations or regulations. Most telecommunication organisations have a well-defined enterprise risk management program, to ensure compliance to King III, however risk management processes specifically for new products and services might be lacking. The responsibility usually resides with the product managers for the implementation of robust products; however they do not always have the correct skillset to ensure adherence to governance requirements and therefore might not be aware of which laws they might not be adhering to, or understand the customers’ requirements. More complex products, additional competition, changes to technology and new business ventures have reinforced the need to manage risk on telecommunication products. Failure to take risk requirements into account could lead to potential fines, damage the organisation’s reputation which could lead to customers churning from these service providers. This research analyses three periods of data captured from a mobile telecommunication organisation to assess the current status quo of risk management maturity within the organisation’s product and service environment. Based on the analysis as well as industry best practices, a risk management framework for products is proposed that can assist product managers analyse concepts to ensure adherence to governance requirements. This could assist new product or service offerings in the marketplace do not create a perception of distrust by consumers.
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A stratigraphic, petrographic and geochemical study of the gamagara formation at the maremane dome, Northern Cape province, South Africa
- Authors: Cousins, David Patrick
- Date: 2017
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape , Mineralogy -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4679 , vital:20711
- Description: Between 80 and 90 percent of the potential iron ore reserves in the Griqualand West basin in the Northern Cape province of South Africa is situated in the Asbesheuwels Iron-formation immediately below an unconformity that separates it from the Gamagara Formation of the Olifantshoek Supergroup. This extensive regional unconformity marks a lengthy period of non-deposition and erosion which preceded the deposition of the Gamagara Formation. Due to the nature of the intimate relationship between the shales and iron ore body, specifically on the Maremane dome, new insights into the Gamagara Formation were required. The thesis provides a renewed stratigraphic, petrographic and geochemical study on the Gamagara Formation and relates it to previous studies done on the lateral correlative Mapedi Formation, some 70 km north of the Maremane dome. The use of 10 newly available drill-cores selected from across the Maremane Dome allows for regional correlations to be made in a study which employs petrographic/mineralogical investigations using transmitted/reflected light microscopy, XRD and EPMA, complimented by traditional whole-rock geochemical analysis of majors, traces, rare earth elements and Nd isotopes. At the base of the Gamagara lie conglomerates representing an alluvial fan deposit, overlying this, shale and quartzite successions represent progradational delta lobes. The deltas are interpreted to be tide- dominated as indicated by a combination of features including: microbial mat growth, intertidal deposition in the delta top, sand bars and flaser laminations in the upward coarsening quartzite units of the delta front. Transgression is indicated by periodic transgressive lag deposits. A variety of sedimentary structures and textural features are described that can be interpreted as the results of microbial mat colonization on the sediment surface. Although in none of the described features can it irrefutably be proven that they are microbial mat deposits, the observed features are consistent with such an interpretation and should be considered indicators of possible microbial mat presence in the Gamagara Formation. Hydrothermal modifications are identified in various units of the Gamagara Formation and seem to occur as separate events. Basal white shales show mobility of Al and slight HFSE enrichments, while overlying red shales record HFSE, K and Fe enrichments. K-metasomatism has been known to occur in the underlying paleoweathering profile of the Transvaal Supergroup (Ongeluk lavas) a unit which is interpreted as the most likely provenance for the mid-to-upper shale lithofacies of the Gamagara Formation. Highly alkaline F-bearing brines had the ability to mobilize titania and fluorapatite, reset Nd isotope systematics and ultimately enriched HFSE concentrations in the red shales of the Gamagara Formation. As the same enrichment is evident in the Mapedi Formation, the event possibly represents unconformity related fluid flow on a regional scale (~140 km). Nd-isotopes record an isotopic disturbance concurrent with the HFSE enrichment and Tdm model ages suggest disruption (and enrichment) occurred between 1.73 and 1.86 Ga. Following this, Fe-addition occurred by epigenetic mechanisms similar to those of MVT-type deposits. Although gaps in the current understanding of the modifications of the Gamagara Formation exist, such events may have far reaching implications for the underlying iron ore bodies and the possibility arises that the genesis and/or epigenetic modification of the ore bodies of the Transvaal Supergroup may be casually linked to the same fluid-migration event/s.
- Full Text:
- Authors: Cousins, David Patrick
- Date: 2017
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape , Mineralogy -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4679 , vital:20711
- Description: Between 80 and 90 percent of the potential iron ore reserves in the Griqualand West basin in the Northern Cape province of South Africa is situated in the Asbesheuwels Iron-formation immediately below an unconformity that separates it from the Gamagara Formation of the Olifantshoek Supergroup. This extensive regional unconformity marks a lengthy period of non-deposition and erosion which preceded the deposition of the Gamagara Formation. Due to the nature of the intimate relationship between the shales and iron ore body, specifically on the Maremane dome, new insights into the Gamagara Formation were required. The thesis provides a renewed stratigraphic, petrographic and geochemical study on the Gamagara Formation and relates it to previous studies done on the lateral correlative Mapedi Formation, some 70 km north of the Maremane dome. The use of 10 newly available drill-cores selected from across the Maremane Dome allows for regional correlations to be made in a study which employs petrographic/mineralogical investigations using transmitted/reflected light microscopy, XRD and EPMA, complimented by traditional whole-rock geochemical analysis of majors, traces, rare earth elements and Nd isotopes. At the base of the Gamagara lie conglomerates representing an alluvial fan deposit, overlying this, shale and quartzite successions represent progradational delta lobes. The deltas are interpreted to be tide- dominated as indicated by a combination of features including: microbial mat growth, intertidal deposition in the delta top, sand bars and flaser laminations in the upward coarsening quartzite units of the delta front. Transgression is indicated by periodic transgressive lag deposits. A variety of sedimentary structures and textural features are described that can be interpreted as the results of microbial mat colonization on the sediment surface. Although in none of the described features can it irrefutably be proven that they are microbial mat deposits, the observed features are consistent with such an interpretation and should be considered indicators of possible microbial mat presence in the Gamagara Formation. Hydrothermal modifications are identified in various units of the Gamagara Formation and seem to occur as separate events. Basal white shales show mobility of Al and slight HFSE enrichments, while overlying red shales record HFSE, K and Fe enrichments. K-metasomatism has been known to occur in the underlying paleoweathering profile of the Transvaal Supergroup (Ongeluk lavas) a unit which is interpreted as the most likely provenance for the mid-to-upper shale lithofacies of the Gamagara Formation. Highly alkaline F-bearing brines had the ability to mobilize titania and fluorapatite, reset Nd isotope systematics and ultimately enriched HFSE concentrations in the red shales of the Gamagara Formation. As the same enrichment is evident in the Mapedi Formation, the event possibly represents unconformity related fluid flow on a regional scale (~140 km). Nd-isotopes record an isotopic disturbance concurrent with the HFSE enrichment and Tdm model ages suggest disruption (and enrichment) occurred between 1.73 and 1.86 Ga. Following this, Fe-addition occurred by epigenetic mechanisms similar to those of MVT-type deposits. Although gaps in the current understanding of the modifications of the Gamagara Formation exist, such events may have far reaching implications for the underlying iron ore bodies and the possibility arises that the genesis and/or epigenetic modification of the ore bodies of the Transvaal Supergroup may be casually linked to the same fluid-migration event/s.
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A unified data repository for rich communication services
- Authors: Sogunle, Oluwasegun Francis
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5777 , vital:20974
- Description: Rich Communication Services (RCS) is a framework that defines a set of IP-based services for the delivery of multimedia communications to mobile network subscribers. The framework unifies a set of pre-existing communication services under a single name, and permits network operators to re-use investments in existing network infrastructure, especially the IP Multimedia Subsystem (IMS), which is a core part of a mobile network and also acts as a docking station for RCS services. RCS generates and utilises disparate subscriber data sets during execution, however, it lacks a harmonised repository for the management of such data sets, thus making it difficult to obtain a unified view of heterogeneous subscriber data. This thesis proposes the creation of a unified data repository for RCS which is based on the User Data Convergence (UDC) standard. The standard was proposed by the 3rd Generation Partnership Project (3GPP), a major telecommunications standardisation group. UDC provides an approach for consolidating subscriber data into a single logical repository without adversely affecting existing network infrastructure, such as the IMS. Thus, this thesis details the design and development of a prototypical implementation of a unified repository, named Converged Subscriber Data Repository (CSDR). It adopts a polyglot persistence model for the underlying data store and exposes heterogeneous data through the Open Data Protocol (OData), which is a candidate implementation of the Ud interface defined in the UDC architecture. With the introduction of polyglot persistence, multiple data stores can be used within the CSDR and disparate network data sources can access heterogeneous data sets using OData as a standard communications protocol. As the CSDR persistence model becomes more complex due to the inclusion of more storage technologies, polyglot persistence ensures a consistent conceptual view of these data sets through OData. Importantly, the CSDR prototype was integrated into a popular open-source implementation of the core part of an IMS network known as the Open IMS Core. The successful integration of the prototype demonstrates its ability to manage and expose a consolidated view of heterogeneous subscriber data, which are generated and used by different RCS services deployed within IMS.
- Full Text:
- Authors: Sogunle, Oluwasegun Francis
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5777 , vital:20974
- Description: Rich Communication Services (RCS) is a framework that defines a set of IP-based services for the delivery of multimedia communications to mobile network subscribers. The framework unifies a set of pre-existing communication services under a single name, and permits network operators to re-use investments in existing network infrastructure, especially the IP Multimedia Subsystem (IMS), which is a core part of a mobile network and also acts as a docking station for RCS services. RCS generates and utilises disparate subscriber data sets during execution, however, it lacks a harmonised repository for the management of such data sets, thus making it difficult to obtain a unified view of heterogeneous subscriber data. This thesis proposes the creation of a unified data repository for RCS which is based on the User Data Convergence (UDC) standard. The standard was proposed by the 3rd Generation Partnership Project (3GPP), a major telecommunications standardisation group. UDC provides an approach for consolidating subscriber data into a single logical repository without adversely affecting existing network infrastructure, such as the IMS. Thus, this thesis details the design and development of a prototypical implementation of a unified repository, named Converged Subscriber Data Repository (CSDR). It adopts a polyglot persistence model for the underlying data store and exposes heterogeneous data through the Open Data Protocol (OData), which is a candidate implementation of the Ud interface defined in the UDC architecture. With the introduction of polyglot persistence, multiple data stores can be used within the CSDR and disparate network data sources can access heterogeneous data sets using OData as a standard communications protocol. As the CSDR persistence model becomes more complex due to the inclusion of more storage technologies, polyglot persistence ensures a consistent conceptual view of these data sets through OData. Importantly, the CSDR prototype was integrated into a popular open-source implementation of the core part of an IMS network known as the Open IMS Core. The successful integration of the prototype demonstrates its ability to manage and expose a consolidated view of heterogeneous subscriber data, which are generated and used by different RCS services deployed within IMS.
- Full Text:
Abalone stock enhancement at Cape Recife, Eastern Cape Province of South Africa
- Authors: Witte, Warren
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45695 , vital:25532
- Description: The potential for restocking depleted natural reefs with hatchery abalone, Haliotis midae, to support a commercial ranching venture in the Eastern Cape Province of South Africa was investigated. A baseline stock assessment and analysis of historical fishery data provided compelling evidence of significant declines in the abalone stock, attributed to uncontrolled illegal fishing over the last 20 years at the study site. A ranching pilot study was undertaken where small-scale replicated seeding experiments were set up which quantified the effect of seed size, density and habitat on survival and growth of hatchery-reared abalone. Thirty-six experimental plots were seeded with 8400 abalone spread evenly over two broad habitats. Mean retrievals of seeded abalone were 17% ranging from 4 - 42% after a minimum of eight months at large. Release density and large-scale habitat had no significant effect on seed survival, but smaller seed size (40.0 ±3.7mm shell length) achieved higher (F1, 22 = 4.64, p = 0.042) retrievals than larger seed size (53 ±3.7mm). Growth rates were an average of 30% higher in the shallow sites compared deeper sites (t1, 1091 = -2.79, p = 0.005). There was seasonal component in growth with a 0.55 ± 0.04 mm per month higher rate in summer than during winter (t1, 1091 = -12.45, p < 0.001). Abalone seed releases were also conducted on a larger scale, which focused on the economic potential for commercial-scale ranching. Over 160 sites were seeded with 1.4 million hatchery reared abalone or 30 metric tonnes. Seventeen sites underwent long-term monitoring of survival with repeated sampling events on sites over a period of up to 666 days. Nine of these sites were seeded with 140800 small abalone (29 – 40 mm), three sites with 25100 medium abalone (30 – 46 mm) and five sites with 14700 large abalone (60 – 84 mm). There was a significant difference in survival between the seed sizes (F4,6329 = 304.3, P < 0.001). The Generalized Linear Mixed Model (GLMM) calculation estimated the instantaneous apparent mortality rate for small, medium and large abalone at 1.19 yr-1 , -0.9 yr-1 and -0.67 yr-1 , which equated to a survival rate of 21%, 28% and 36% per year respectively. The weighted mortality rate calculated according to the seed size differential mortality and the number of seed released for those sizes was 1 yr-1 or 25% survival. In conjunction with a conservative somatic growth rate of 1.2mm.m-1 and plausible emigration rates, a range of biomass harvesting estimates were obtained. Movement and mortality were investigated using video analysis which showed that hatchery seed had the ability to move considerably once released onto natural reefs and confirmed that mortality immediately following releases was due to the heavy predation pressure as confirmed by shell collections. This project has demonstrated that potential exists for ranching in South Africa and highlights critical factors that need to be addressed if ranching is to be an economically viable operation.
- Full Text:
- Authors: Witte, Warren
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45695 , vital:25532
- Description: The potential for restocking depleted natural reefs with hatchery abalone, Haliotis midae, to support a commercial ranching venture in the Eastern Cape Province of South Africa was investigated. A baseline stock assessment and analysis of historical fishery data provided compelling evidence of significant declines in the abalone stock, attributed to uncontrolled illegal fishing over the last 20 years at the study site. A ranching pilot study was undertaken where small-scale replicated seeding experiments were set up which quantified the effect of seed size, density and habitat on survival and growth of hatchery-reared abalone. Thirty-six experimental plots were seeded with 8400 abalone spread evenly over two broad habitats. Mean retrievals of seeded abalone were 17% ranging from 4 - 42% after a minimum of eight months at large. Release density and large-scale habitat had no significant effect on seed survival, but smaller seed size (40.0 ±3.7mm shell length) achieved higher (F1, 22 = 4.64, p = 0.042) retrievals than larger seed size (53 ±3.7mm). Growth rates were an average of 30% higher in the shallow sites compared deeper sites (t1, 1091 = -2.79, p = 0.005). There was seasonal component in growth with a 0.55 ± 0.04 mm per month higher rate in summer than during winter (t1, 1091 = -12.45, p < 0.001). Abalone seed releases were also conducted on a larger scale, which focused on the economic potential for commercial-scale ranching. Over 160 sites were seeded with 1.4 million hatchery reared abalone or 30 metric tonnes. Seventeen sites underwent long-term monitoring of survival with repeated sampling events on sites over a period of up to 666 days. Nine of these sites were seeded with 140800 small abalone (29 – 40 mm), three sites with 25100 medium abalone (30 – 46 mm) and five sites with 14700 large abalone (60 – 84 mm). There was a significant difference in survival between the seed sizes (F4,6329 = 304.3, P < 0.001). The Generalized Linear Mixed Model (GLMM) calculation estimated the instantaneous apparent mortality rate for small, medium and large abalone at 1.19 yr-1 , -0.9 yr-1 and -0.67 yr-1 , which equated to a survival rate of 21%, 28% and 36% per year respectively. The weighted mortality rate calculated according to the seed size differential mortality and the number of seed released for those sizes was 1 yr-1 or 25% survival. In conjunction with a conservative somatic growth rate of 1.2mm.m-1 and plausible emigration rates, a range of biomass harvesting estimates were obtained. Movement and mortality were investigated using video analysis which showed that hatchery seed had the ability to move considerably once released onto natural reefs and confirmed that mortality immediately following releases was due to the heavy predation pressure as confirmed by shell collections. This project has demonstrated that potential exists for ranching in South Africa and highlights critical factors that need to be addressed if ranching is to be an economically viable operation.
- Full Text:
An analysis of flood activity over the past century based on the sedimentary deposits in the Mfolozi floodplain
- Authors: Mbao, Chabala
- Date: 2017
- Subjects: Floodplain morphology -- South Africa -- Mfolozi River , Floodplains -- South Africa -- Kwazulu-Natal , Sedimentation and deposition -- South Africa -- Kwazulu-Natal , Floods -- South Africa -- Kwazulu-Natal -- Measurement , Hydrology -- Research -- South Africa -- Kwazulu-Natal , Stream measurements -- South Africa -- Kwazulu-Natal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53711 , vital:26312
- Description: Floods are natural phenomena that are of widespread interest to the scientific community, particularly in the context of understanding the impact of climate change as well as changing land use patterns and the security of infrastructure such as towns and roads. In northern KwaZulu-Natal, large flood events have been a reoccurring feature over the past century. The geographical position and extent of the region means that is affected by both inland and coastal weather phenomena, each with the potential to cause large flood events. While information pertaining to large floods in the region in the form of flow data is readily available, flow data is often incomplete and limited in terms of how far back in time the records extend. The Mfolozi River floodplain itself also houses a record of flood activity in the region in the form of sedimentary deposits, which have the potential to reveal flood activity over a much longer timescale, even when monitoring of flood activity in the region was not present. Establishing a link between the hydrological and sedimentary features of floods may be useful in establishing a record of flood activity extending beyond the limits of historical records. The aim of this project was to construct a record of major flood events on the Mfolozi River floodplain over the last century and determine their source. The first objective involved establishing the history of flood events in the Mfolozi River catchment utilising hydrological data recorded throughout the catchment. Thirty nine different large floods (defined as being over 800 m3.s-1) were recorded on the floodplain over the past century. The data also highlighted differences in the extent of known coastal and inland systems (tropical cyclones and cut-off lows respectively), allowing for inferences to be made about the area of the catchment most likely affected by each event; some flood events were identified as having mostly affected the upper reaches of the catchment, while others mostly affected the lower reaches, closer to the coast. The second objective was to identify the various physical, mineralogical and geochemical features of the sediment deposited on the Mfolozi floodplain. Multiple individual flood deposits were identified in the sedimentary record, with sediment tracing analysis providing insight into the source of the deposits within the catchment; no traces of igneous or metamorphic material could be found within the sediment. The source rocks were identified as mostly quartzite, with minor shale and sandstone deposits as well. This put the source of the sediment in the upper to middle reaches of the catchment. The sedimentary analysis was combined with the hydrological records to establish a chronology of flood events extending back to the 1960's. Unfortunately, this record could not be extended further due to the limited amount of sediment collected as well the limits of readily available analytical techniques; radionuclide dating methods were unsuccessful due to the low amounts of fallout radionuclides present in the sediment. The study has however successfully established a history of flood events in the region, as well as providing a link between the hydrological and sedimentary features of flood events that could potentially be useful for current and future research.
- Full Text:
- Authors: Mbao, Chabala
- Date: 2017
- Subjects: Floodplain morphology -- South Africa -- Mfolozi River , Floodplains -- South Africa -- Kwazulu-Natal , Sedimentation and deposition -- South Africa -- Kwazulu-Natal , Floods -- South Africa -- Kwazulu-Natal -- Measurement , Hydrology -- Research -- South Africa -- Kwazulu-Natal , Stream measurements -- South Africa -- Kwazulu-Natal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53711 , vital:26312
- Description: Floods are natural phenomena that are of widespread interest to the scientific community, particularly in the context of understanding the impact of climate change as well as changing land use patterns and the security of infrastructure such as towns and roads. In northern KwaZulu-Natal, large flood events have been a reoccurring feature over the past century. The geographical position and extent of the region means that is affected by both inland and coastal weather phenomena, each with the potential to cause large flood events. While information pertaining to large floods in the region in the form of flow data is readily available, flow data is often incomplete and limited in terms of how far back in time the records extend. The Mfolozi River floodplain itself also houses a record of flood activity in the region in the form of sedimentary deposits, which have the potential to reveal flood activity over a much longer timescale, even when monitoring of flood activity in the region was not present. Establishing a link between the hydrological and sedimentary features of floods may be useful in establishing a record of flood activity extending beyond the limits of historical records. The aim of this project was to construct a record of major flood events on the Mfolozi River floodplain over the last century and determine their source. The first objective involved establishing the history of flood events in the Mfolozi River catchment utilising hydrological data recorded throughout the catchment. Thirty nine different large floods (defined as being over 800 m3.s-1) were recorded on the floodplain over the past century. The data also highlighted differences in the extent of known coastal and inland systems (tropical cyclones and cut-off lows respectively), allowing for inferences to be made about the area of the catchment most likely affected by each event; some flood events were identified as having mostly affected the upper reaches of the catchment, while others mostly affected the lower reaches, closer to the coast. The second objective was to identify the various physical, mineralogical and geochemical features of the sediment deposited on the Mfolozi floodplain. Multiple individual flood deposits were identified in the sedimentary record, with sediment tracing analysis providing insight into the source of the deposits within the catchment; no traces of igneous or metamorphic material could be found within the sediment. The source rocks were identified as mostly quartzite, with minor shale and sandstone deposits as well. This put the source of the sediment in the upper to middle reaches of the catchment. The sedimentary analysis was combined with the hydrological records to establish a chronology of flood events extending back to the 1960's. Unfortunately, this record could not be extended further due to the limited amount of sediment collected as well the limits of readily available analytical techniques; radionuclide dating methods were unsuccessful due to the low amounts of fallout radionuclides present in the sediment. The study has however successfully established a history of flood events in the region, as well as providing a link between the hydrological and sedimentary features of flood events that could potentially be useful for current and future research.
- Full Text:
An investigation into the origin and evolution of the Tierkloof Wetland, a peatland dominated by Prionium serratum, in the Western Cape
- Authors: Bekker, Debra Jane
- Date: 2017
- Subjects: Prionium serratum , Tierkloof Wetland (Western Cape, South Africa) , Wetlands -- South Africa -- Western Cape , Aquatic plants -- South Africa -- Western Cape Cape , Peatland ecology -- South Africa -- Western Cape , Kromme River (Eastern Cape, South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53689 , vital:26311
- Description: The Tierkloof Wetland in the Western Cape has been damaged through erosion down to bedrock with gullies that are up to 50 m wide and 7 m deep. The purpose of this study was to investigate the origin and evolution of the Tierkloof Wetland and consider the role both natural and human-induced processes have played in its degradation. The main methods used were digital mapping using GIS software, satellite and aerial photographic interpretation of past and current land use, detailed topographic surveying, coring to bedrock, stratigraphic analysis of valley-fill sediments, and radio carbon dating of peat samples. Nine GIS-produced topographic profiles across the valley were plotted to analyse downstream changes in valley width and morphology along the length of the Tierkloof valley. Detailed cross sections of the stream channel were produced using topographic survey data. Depth to bedrock analysis indicated that there is evidence of a degree of planing of bedrock over geological time periods. Survey data indicates that the longitudinal slope of the former wetland surface is remarkably uniform over most of its length and there is an overall thinning of the valley fill from the head to the toe of the wetland. The stratigraphy and associated organic matter content of the wetland soils showed that the sedimentary fill varies considerably. There are appreciable accumulations of organic sediment, including sandy peat and peat layers with organic content of up to 50 %. The two radio carbon dates obtained from the gully wall midway down the Tierkloof Wetland suggest that peat accumulation started following the last glacial maximum. The peat has accumulated consistently and is mostly associated with the growth of the palmiet, Prionium serratum. Evidence from past and current land-use activities from aerial photographic interpretation show that natural vegetation in the Tierkloof Wetland has been severely degraded, alien plants are extremely common, and road-building and artificial drainage in the wetland have influenced fluvial processes. It is likely that these activities, exacerbated by the high rainfall events in the early 2000s, have triggered the erosional phase that was initiated a few decades ago. However, longer term processes (thousands to tens-of-thousands of years), such as the planing of the bedrock, also indicate that erosional processes have been a natural part of the Tierkloof Wetland development. A conceptual model of wetland development is thus proposed, based on long-term erosional and depositional processes that are linked with climate change and the current aggradation phase of peat formation that is being driven by the ecosystem engineering processes of palmiet plant growth. It is further suggested that relatively recent land-use activities have resulted in an already vulnerable wetland, in geomorphological terms, to cross a threshold to become a severely degraded, gulley- dominated wetland.
- Full Text:
- Authors: Bekker, Debra Jane
- Date: 2017
- Subjects: Prionium serratum , Tierkloof Wetland (Western Cape, South Africa) , Wetlands -- South Africa -- Western Cape , Aquatic plants -- South Africa -- Western Cape Cape , Peatland ecology -- South Africa -- Western Cape , Kromme River (Eastern Cape, South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53689 , vital:26311
- Description: The Tierkloof Wetland in the Western Cape has been damaged through erosion down to bedrock with gullies that are up to 50 m wide and 7 m deep. The purpose of this study was to investigate the origin and evolution of the Tierkloof Wetland and consider the role both natural and human-induced processes have played in its degradation. The main methods used were digital mapping using GIS software, satellite and aerial photographic interpretation of past and current land use, detailed topographic surveying, coring to bedrock, stratigraphic analysis of valley-fill sediments, and radio carbon dating of peat samples. Nine GIS-produced topographic profiles across the valley were plotted to analyse downstream changes in valley width and morphology along the length of the Tierkloof valley. Detailed cross sections of the stream channel were produced using topographic survey data. Depth to bedrock analysis indicated that there is evidence of a degree of planing of bedrock over geological time periods. Survey data indicates that the longitudinal slope of the former wetland surface is remarkably uniform over most of its length and there is an overall thinning of the valley fill from the head to the toe of the wetland. The stratigraphy and associated organic matter content of the wetland soils showed that the sedimentary fill varies considerably. There are appreciable accumulations of organic sediment, including sandy peat and peat layers with organic content of up to 50 %. The two radio carbon dates obtained from the gully wall midway down the Tierkloof Wetland suggest that peat accumulation started following the last glacial maximum. The peat has accumulated consistently and is mostly associated with the growth of the palmiet, Prionium serratum. Evidence from past and current land-use activities from aerial photographic interpretation show that natural vegetation in the Tierkloof Wetland has been severely degraded, alien plants are extremely common, and road-building and artificial drainage in the wetland have influenced fluvial processes. It is likely that these activities, exacerbated by the high rainfall events in the early 2000s, have triggered the erosional phase that was initiated a few decades ago. However, longer term processes (thousands to tens-of-thousands of years), such as the planing of the bedrock, also indicate that erosional processes have been a natural part of the Tierkloof Wetland development. A conceptual model of wetland development is thus proposed, based on long-term erosional and depositional processes that are linked with climate change and the current aggradation phase of peat formation that is being driven by the ecosystem engineering processes of palmiet plant growth. It is further suggested that relatively recent land-use activities have resulted in an already vulnerable wetland, in geomorphological terms, to cross a threshold to become a severely degraded, gulley- dominated wetland.
- Full Text:
Antimalarial secondary metabolites from Morinda lucida
- Authors: Chithambo, Bertha
- Date: 2017
- Subjects: Botanical chemistry , Anthraquinones , Antimalarials , Rubiaceae -- Therapeutic use , Malaria -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45730 , vital:25535
- Description: Antimalarial activities of secondary metabolites from Morinda lucida (Rubiaceae), were investigated. Even though M. lucida is traditionally used to treat malaria, diabetes, jaundice, hypertension, dysentery and many other diseases, the compounds in this plant have not yet been fully investigated and characterised. Most of the studies that have been done on this plant focused on the medicinal properties of the crude extracts but have not gone further to isolate and characterise the compounds. In this study, the methanol - dichloromethane crude extract from the bark of M. lucida was fractionated into fractions 1-8. Fractions 2-5 were purified in order to isolate active secondary metabolites. The isolated pure compounds were characterised and identified. An in vitro antimalarial assay was carried out on the crude extract, fractions, pure compounds and solutions made from different combinations of pure compounds using the parasite lactate dehydrogenase (pLDH) assay. An IC50 done on the methanolic crude extract gave a value of 25 µg/mL. The % cell viability for the crude extract in cell toxicity assay remained at 100%. Each of the pure compounds tested had very little activity. Their activities were increased when samples from the different compounds were mixed. One of these mixtures reduced malaria viability to about 22 % at 20 µM and gave an IC50 value of 17 µM. Antibacterial assays were also carried out on the crude extract and fractions. Fractions 2 and 3 were relatively active (MIC values ranging between 125-1000 µg/mL) against M. cattarhalis and E. faecalis. Fraction 2 was also the most active on S. typhimurium and S. aureus (MIC value of 1000 µg/mL) compared with the other fractions. This same fraction also showed some activity against M. tuberculosis with MIC90 and MIC99 values of 40.9 and 46.3 µg/mL respectively in an anti-tuberculosis assay.The following compounds, comprising of iridoids (asperuloside and asperulosidic acid), terpenoids (stigmasterol, P-sitosterol, campesterol, lanosterol and cycloartenol) and anthraquinones [5,15-O-dimethylmorindol, 1,7-dihydroxy-2-methoxy-5-(methoxymethyl) anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone], were isolated. All these compounds have been isolated from different plants before with the exception of 1,7-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone which were tentatively assigned the structures due to insufficient data. To the best of our knowledge, this is the first report on the identification of all of the mentioned compounds, with the exception of ß-sitosterol and stigmasterol, from M. lucida. Molecular docking was performed on one of the isolated anthraquinones (5,15-O- dimethylmorindol) to check if it can bind to cytochrome bci, a known target for atovaquone. This compound interacted with the same amino acids that atovaquone, a well known antimalarial agent, interacted with on cytochrome bc1 indicating a possible similar mode of action.
- Full Text:
- Authors: Chithambo, Bertha
- Date: 2017
- Subjects: Botanical chemistry , Anthraquinones , Antimalarials , Rubiaceae -- Therapeutic use , Malaria -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/45730 , vital:25535
- Description: Antimalarial activities of secondary metabolites from Morinda lucida (Rubiaceae), were investigated. Even though M. lucida is traditionally used to treat malaria, diabetes, jaundice, hypertension, dysentery and many other diseases, the compounds in this plant have not yet been fully investigated and characterised. Most of the studies that have been done on this plant focused on the medicinal properties of the crude extracts but have not gone further to isolate and characterise the compounds. In this study, the methanol - dichloromethane crude extract from the bark of M. lucida was fractionated into fractions 1-8. Fractions 2-5 were purified in order to isolate active secondary metabolites. The isolated pure compounds were characterised and identified. An in vitro antimalarial assay was carried out on the crude extract, fractions, pure compounds and solutions made from different combinations of pure compounds using the parasite lactate dehydrogenase (pLDH) assay. An IC50 done on the methanolic crude extract gave a value of 25 µg/mL. The % cell viability for the crude extract in cell toxicity assay remained at 100%. Each of the pure compounds tested had very little activity. Their activities were increased when samples from the different compounds were mixed. One of these mixtures reduced malaria viability to about 22 % at 20 µM and gave an IC50 value of 17 µM. Antibacterial assays were also carried out on the crude extract and fractions. Fractions 2 and 3 were relatively active (MIC values ranging between 125-1000 µg/mL) against M. cattarhalis and E. faecalis. Fraction 2 was also the most active on S. typhimurium and S. aureus (MIC value of 1000 µg/mL) compared with the other fractions. This same fraction also showed some activity against M. tuberculosis with MIC90 and MIC99 values of 40.9 and 46.3 µg/mL respectively in an anti-tuberculosis assay.The following compounds, comprising of iridoids (asperuloside and asperulosidic acid), terpenoids (stigmasterol, P-sitosterol, campesterol, lanosterol and cycloartenol) and anthraquinones [5,15-O-dimethylmorindol, 1,7-dihydroxy-2-methoxy-5-(methoxymethyl) anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone], were isolated. All these compounds have been isolated from different plants before with the exception of 1,7-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone and 1,6-dihydroxy-2-methoxy-5-(methoxymethyl)anthraquinone which were tentatively assigned the structures due to insufficient data. To the best of our knowledge, this is the first report on the identification of all of the mentioned compounds, with the exception of ß-sitosterol and stigmasterol, from M. lucida. Molecular docking was performed on one of the isolated anthraquinones (5,15-O- dimethylmorindol) to check if it can bind to cytochrome bci, a known target for atovaquone. This compound interacted with the same amino acids that atovaquone, a well known antimalarial agent, interacted with on cytochrome bc1 indicating a possible similar mode of action.
- Full Text:
Appropriate integration of workers with physical limitations into a manual workplace – development of an assessment tool
- Authors: Pearson, Jessie T
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8209 , vital:21368
- Description: Background: People with physical limitations can contribute significantly to society and the economy, however, barriers to full and effective participation in the labour market often hinder decent employment. In light of this, placement decisions of impaired workers should be based on detailed information of the nature of the jobs available, as well as individual capabilities of the worker. An ergonomics approach to design attempts to achieve an appropriate balance between the capabilities of the worker and the requirements of the task and uses this balance to improve productivity and encourage physical and mental well-being, job satisfaction and safety. A specific analysis tool which can be applied to various workplaces and jobs, and provide information for decisions regarding placement of physically limited workers, will help to increase the percentage of correct placement in an appropriate workplace, resulting in optimum productivity and worker safety. Methods: An assessment tool which allows matching of job requirements and worker capabilities was developed based on a theoretical framework from Mattison and Goebel (2007), as well as principles defined by Almgren and Schaurig (2012) and Demura and Nakada (2010). The tool assesses range of motion, force and time components of the physical requirements of different tasks involved in the job, as well as movement capabilities and limitations of the worker. The tool was pilot tested in a case study with an above the knee amputee working at a research facility. Results: The tool successfully provided information regarding the matching of the work to the identified job. The output of the tool highlighted two tasks which would place the worker at risk due to physical requirements of the tasks being greater than movement capabilities of the worker. These tasks need to be further investigated to determine if accommodations can be made to assist the worker in safely performing the task, or if the job is not suitable for the worker. Conclusions: The tool developed was useful in providing information to inform appropriate placement of the physically limited worker. Further research needs to be done to validate and determine reliability of the tool.
- Full Text:
- Authors: Pearson, Jessie T
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8209 , vital:21368
- Description: Background: People with physical limitations can contribute significantly to society and the economy, however, barriers to full and effective participation in the labour market often hinder decent employment. In light of this, placement decisions of impaired workers should be based on detailed information of the nature of the jobs available, as well as individual capabilities of the worker. An ergonomics approach to design attempts to achieve an appropriate balance between the capabilities of the worker and the requirements of the task and uses this balance to improve productivity and encourage physical and mental well-being, job satisfaction and safety. A specific analysis tool which can be applied to various workplaces and jobs, and provide information for decisions regarding placement of physically limited workers, will help to increase the percentage of correct placement in an appropriate workplace, resulting in optimum productivity and worker safety. Methods: An assessment tool which allows matching of job requirements and worker capabilities was developed based on a theoretical framework from Mattison and Goebel (2007), as well as principles defined by Almgren and Schaurig (2012) and Demura and Nakada (2010). The tool assesses range of motion, force and time components of the physical requirements of different tasks involved in the job, as well as movement capabilities and limitations of the worker. The tool was pilot tested in a case study with an above the knee amputee working at a research facility. Results: The tool successfully provided information regarding the matching of the work to the identified job. The output of the tool highlighted two tasks which would place the worker at risk due to physical requirements of the tasks being greater than movement capabilities of the worker. These tasks need to be further investigated to determine if accommodations can be made to assist the worker in safely performing the task, or if the job is not suitable for the worker. Conclusions: The tool developed was useful in providing information to inform appropriate placement of the physically limited worker. Further research needs to be done to validate and determine reliability of the tool.
- Full Text:
Assessing MODIS evapotranspiration data for hydrological modelling in South Africa
- Mazibuko, Sbongiseni Christian
- Authors: Mazibuko, Sbongiseni Christian
- Date: 2017
- Subjects: Evapotranspiration , Evapotranspiration -- Measurement , Hydrologic models , Hydrologic models -- South Africa , MODIS (Spectroradiometer)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8009 , vital:21334
- Description: Evapotranspiration as a major component of the water balance has been identified as a key factor in hydrological modelling. Water management can be improved by means of increased use of reliable methods for estimating evapotranspiration. The limited availability of measured climate and discharge data sets, particularly in the developing world, restricts the reliability of hydrological models in these regions. Furthermore, rapid changes in hydrological systems with increasing development mean uncertainties in water resource estimation are growing. These changes are related to the modification of catchment hydrological processes with increasing human activity. Dealing with data uncertainty and quantifying the impacts of catchment activities are significant challenges that scientists in the field of hydrology face today. Uncertainties in hydrometeorological data are associated with poor observation networks that provide data at point scales which are not adequately representative of the inherent heterogeneity within catchment processes. Using uncertain data in model applications reduces the predictive power of hydrological models as well as the ability to validate the model outcomes. This study examines the potential of using remote sensing-based evapotranspiration data to reduce uncertainty in the climatic forcing data and constraining the output of a rainfall-runoff hydrological model. It is common to use fixed seasonally variable potential evapotranspiration (PET) instead of temporally varying PET data as inputs to standard rainfall-runoff models. Part of the reason is that there are relatively few stations available to measure a variety of meteorological input data needed to compute PET, as well as the apparent lack of sensitivity of rainfall-runoff models to different types of PET inputs. As hydrometeorological data become more readily available through the use of earth observation systems, it is important to determine whether rainfall-runoff models are sensitive to time-varying PET derived from these earth observations systems. Further potential includes the use of actual evapotranspiration (ETa) from this type of data to constrain model outputs and improve model realism. It is assumed that a better representation of evapotranspiration demands could improve the efficiency of models, and this study explores some of these issues. The study used evapotranspiration estimates (PET and ETa) from the MOD16 global product with one of the most widely used hydrological models in South Africa. The investigation included applying the Pitman model in a number of case study catchments located in different climatic regions of the country. The main objectives of the study included (i) the establishment of behavioural model parameter sets that generate acceptable hydrological response under both naturalised and present-day conditions, (ii) the use of time-varying PET estimates derived from MOD16 data to force the model, and (iii) the use of MOD16 ETa estimates to constrain model-simulated ETa. Before examining the use of different PET forcing data in the model, a two-step modelling approached was employed both a single-run and an uncertainty version of the Pitman model. During the first step (using a single-run version), available information on catchment physical properties and regionalised groundwater recharge together with model calibration principles were used to develop model functionality understanding and establish initial parameter sets. The outcomes from the first step were used to define uncertain parameter ranges for the use in the uncertainty version of the Pitman model (second step). Further, catchment water uses were quantified to ensure comparability with present-day flow conditions represented by the stream flow records. The effects of forcing the Pitman model with MOD16-based time-varying PET data inputs were evaluated using static and dynamic sensitivity analysis approaches. In the static approach, parameter sets calibrated using fixed seasonal distributions of PET data remain unchanged when forcing the model with other forms of PET, whereas in the dynamic method, the model is recalibrated with changing PET inputs. In both approaches, model sensitivity was assessed by comparing objective function statistics of reference flow simulations with those simulations incorporating changing PET data inputs. The use of the MOD16 ETa data to constrain model- simulated evapotranspiration losses was conducted by calibrating the parameters such that the simulated-ETa matched the evapotranspiration loss estimated from the MOD16 data. Despite issues around model equifinality and significant uncertainty within water use information, the Pitman model simulations were generally satisfactory and compared with observed stream flow data where available. The use of time-varying PET data does not improve the efficiency of the model when both static and dynamic sensitivity approaches are used. This was highly expected with the static approach where fixed model parameter sets do not account for the changes in evapotranspiration demands. However, with the dynamic approach, it was difficult to conclude why the model efficiency did not improve given the flexibility of the model to achieve appropriate parameter sets to different forms of PET. The study noted that the insensitivity of the model to changes in PET demands could be due to uncertainties in the model structure and MOD16 data. Attempts to constrain the model-simulated actual evapotranspiration with MOD16 ETa estimates were hampered by large errors in the MOD16 data and resulted in the non-closure of the catchment annual water balance, even when likely errors in the other components of the water balance were accounted for. There is still a great deal of work that needs to be done to reduce uncertainties associated with the use of earth observation data in hydrological modelling. This study has identified some of the specific gaps within the application of evapotranspiration data from earth observation information. While the MOD16 data applied with the Pitman model did not achieve improved simulations, the study has demonstrated the enormous potential of the data product in the future should the identified uncertainties be resolved. Lastly, the investigation highlighted some of the possible model structural uncertainties specifically associated with the simplified soil-moisture accounting routines within the model. It is possible that amending the model structure through investigating the dynamics of the relationship between soil moisture and evapotranspiration losses would assist in the improved utilisation of earth observation products related to the MOD16 ET data.
- Full Text:
- Authors: Mazibuko, Sbongiseni Christian
- Date: 2017
- Subjects: Evapotranspiration , Evapotranspiration -- Measurement , Hydrologic models , Hydrologic models -- South Africa , MODIS (Spectroradiometer)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8009 , vital:21334
- Description: Evapotranspiration as a major component of the water balance has been identified as a key factor in hydrological modelling. Water management can be improved by means of increased use of reliable methods for estimating evapotranspiration. The limited availability of measured climate and discharge data sets, particularly in the developing world, restricts the reliability of hydrological models in these regions. Furthermore, rapid changes in hydrological systems with increasing development mean uncertainties in water resource estimation are growing. These changes are related to the modification of catchment hydrological processes with increasing human activity. Dealing with data uncertainty and quantifying the impacts of catchment activities are significant challenges that scientists in the field of hydrology face today. Uncertainties in hydrometeorological data are associated with poor observation networks that provide data at point scales which are not adequately representative of the inherent heterogeneity within catchment processes. Using uncertain data in model applications reduces the predictive power of hydrological models as well as the ability to validate the model outcomes. This study examines the potential of using remote sensing-based evapotranspiration data to reduce uncertainty in the climatic forcing data and constraining the output of a rainfall-runoff hydrological model. It is common to use fixed seasonally variable potential evapotranspiration (PET) instead of temporally varying PET data as inputs to standard rainfall-runoff models. Part of the reason is that there are relatively few stations available to measure a variety of meteorological input data needed to compute PET, as well as the apparent lack of sensitivity of rainfall-runoff models to different types of PET inputs. As hydrometeorological data become more readily available through the use of earth observation systems, it is important to determine whether rainfall-runoff models are sensitive to time-varying PET derived from these earth observations systems. Further potential includes the use of actual evapotranspiration (ETa) from this type of data to constrain model outputs and improve model realism. It is assumed that a better representation of evapotranspiration demands could improve the efficiency of models, and this study explores some of these issues. The study used evapotranspiration estimates (PET and ETa) from the MOD16 global product with one of the most widely used hydrological models in South Africa. The investigation included applying the Pitman model in a number of case study catchments located in different climatic regions of the country. The main objectives of the study included (i) the establishment of behavioural model parameter sets that generate acceptable hydrological response under both naturalised and present-day conditions, (ii) the use of time-varying PET estimates derived from MOD16 data to force the model, and (iii) the use of MOD16 ETa estimates to constrain model-simulated ETa. Before examining the use of different PET forcing data in the model, a two-step modelling approached was employed both a single-run and an uncertainty version of the Pitman model. During the first step (using a single-run version), available information on catchment physical properties and regionalised groundwater recharge together with model calibration principles were used to develop model functionality understanding and establish initial parameter sets. The outcomes from the first step were used to define uncertain parameter ranges for the use in the uncertainty version of the Pitman model (second step). Further, catchment water uses were quantified to ensure comparability with present-day flow conditions represented by the stream flow records. The effects of forcing the Pitman model with MOD16-based time-varying PET data inputs were evaluated using static and dynamic sensitivity analysis approaches. In the static approach, parameter sets calibrated using fixed seasonal distributions of PET data remain unchanged when forcing the model with other forms of PET, whereas in the dynamic method, the model is recalibrated with changing PET inputs. In both approaches, model sensitivity was assessed by comparing objective function statistics of reference flow simulations with those simulations incorporating changing PET data inputs. The use of the MOD16 ETa data to constrain model- simulated evapotranspiration losses was conducted by calibrating the parameters such that the simulated-ETa matched the evapotranspiration loss estimated from the MOD16 data. Despite issues around model equifinality and significant uncertainty within water use information, the Pitman model simulations were generally satisfactory and compared with observed stream flow data where available. The use of time-varying PET data does not improve the efficiency of the model when both static and dynamic sensitivity approaches are used. This was highly expected with the static approach where fixed model parameter sets do not account for the changes in evapotranspiration demands. However, with the dynamic approach, it was difficult to conclude why the model efficiency did not improve given the flexibility of the model to achieve appropriate parameter sets to different forms of PET. The study noted that the insensitivity of the model to changes in PET demands could be due to uncertainties in the model structure and MOD16 data. Attempts to constrain the model-simulated actual evapotranspiration with MOD16 ETa estimates were hampered by large errors in the MOD16 data and resulted in the non-closure of the catchment annual water balance, even when likely errors in the other components of the water balance were accounted for. There is still a great deal of work that needs to be done to reduce uncertainties associated with the use of earth observation data in hydrological modelling. This study has identified some of the specific gaps within the application of evapotranspiration data from earth observation information. While the MOD16 data applied with the Pitman model did not achieve improved simulations, the study has demonstrated the enormous potential of the data product in the future should the identified uncertainties be resolved. Lastly, the investigation highlighted some of the possible model structural uncertainties specifically associated with the simplified soil-moisture accounting routines within the model. It is possible that amending the model structure through investigating the dynamics of the relationship between soil moisture and evapotranspiration losses would assist in the improved utilisation of earth observation products related to the MOD16 ET data.
- Full Text:
Assessing selected ecosystem services in urban green spaces in Bulawayo, Zimbabwe
- Ngulani, Thembelihle Tshandapiwa
- Authors: Ngulani, Thembelihle Tshandapiwa
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5856 , vital:20982
- Description: Urbanization has resulted in the building of numerous structures such as buildings and roads which reduces the amount of natural land. Urban space planning has taken this into consideration resulting in planned urban green spaces and remnant land within urban areas. Urban green spaces provide a number of ecosystem services which are beneficial to urban residents. This study sought to determine residents’ use and perception of urban green spaces in Bulawayo, the second largest city in Zimbabwe, and to quantify and value four selected ecosystem services, i.e. carbon sequestration by urban trees, urban heat island amelioration, spiritual services and firewood provision. All ecosystem services were valued using local a variety of direct or substitutive methods. Questionnaires were administered at green spaces to green space users to capture responses on reasons why they use green spaces and their perception of green spaces. Residents’ responses showed that they appreciate green spaces as multidimensional spaces which provide a number of benefits for cultural and provisioning services. The role of the green spaces in providing regulating services was not well appreciated by the residents as they did not directly experience these benefits. An association was revealed between primary purpose of visit to urban green spaces and household income. Residents in areas of medium and high density housing visited green spaces on a daily basis, whereas those in more affluent, low density housing areas visited green spaces less often, i.e. a few times a month Carbon sequestration rate was determined by measuring tree diameter within one year to determine increase in carbon sequestered. Bulawayo’s urban green spaces sequester 3 290 t/C/yr valued at approximately $13 000/yr. There was a significant difference in carbon sequestration by urban trees between formal and informal green spaces with formal green spaces sequestering more carbon. Indigenous trees were shown to sequester more carbon than exotic trees and trees with bigger stem diameter were determined sequester more carbon than trees with small diameter. The effect of urban green spaces on ambient temperature was determined by measuring ambient air temperature in green spaces and built up areas over six months. Urban green spaces in Bulawayo play a role in urban micro-climate regulation by reducing the ambient temperature in the green spaces as well as is built up areas. The mean difference between green spaces and surrounding urban areas was up to 60C, with larger green spaces generally showing larger differences. The green spaces extend their cooling effect to surrounding areas thus reducing the temperatures in surrounding residential areas thus reducing the energy demand used for indoor cooling. To determine why residents worship in green spaces, questionnaires were administered to congregation members to capture reasons why and how often they worship in green spaces, challenges faced by the congregants as well as assistance that can be given by the Bulawayo city council to improve the outdoor worship experience. Green spaces offer ideal places for worship in natural areas for congregants to be in touch with nature. The green spaces are also used by some congregations who ordinarily would worship in buildings but fail to do so due to lack of funds for rent or to purchase or construct a church building to use. The value of Bulawayo’s green spaces spiritual services was determined to be $92.50/ha/yr. Firewood provision was also determined by measuring tree diameter within one year to determine increase in fuelwood. The green spaces showed a significant difference in firewood production among sites. Formal green spaces were shown to produce more firewood as compared to informal green spaces and no difference was determined in growth rates between exotic and indigenous tree species. Bulawayo’s green spaces produce 1.9t/ha/yr of firewood with an ecosystem service value of $340 to $490 /ha/yr. These findings indicate the importance of urban green spaces in Bulawayo. They are multifunctional spaces, providing multiple ecosystem services. The local appreciation of the services provided by urban green spaces differs according to the type of service and location in the city. The value of services provided by green spaces is high, albeit not taken into account in planning decisions.
- Full Text:
- Authors: Ngulani, Thembelihle Tshandapiwa
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5856 , vital:20982
- Description: Urbanization has resulted in the building of numerous structures such as buildings and roads which reduces the amount of natural land. Urban space planning has taken this into consideration resulting in planned urban green spaces and remnant land within urban areas. Urban green spaces provide a number of ecosystem services which are beneficial to urban residents. This study sought to determine residents’ use and perception of urban green spaces in Bulawayo, the second largest city in Zimbabwe, and to quantify and value four selected ecosystem services, i.e. carbon sequestration by urban trees, urban heat island amelioration, spiritual services and firewood provision. All ecosystem services were valued using local a variety of direct or substitutive methods. Questionnaires were administered at green spaces to green space users to capture responses on reasons why they use green spaces and their perception of green spaces. Residents’ responses showed that they appreciate green spaces as multidimensional spaces which provide a number of benefits for cultural and provisioning services. The role of the green spaces in providing regulating services was not well appreciated by the residents as they did not directly experience these benefits. An association was revealed between primary purpose of visit to urban green spaces and household income. Residents in areas of medium and high density housing visited green spaces on a daily basis, whereas those in more affluent, low density housing areas visited green spaces less often, i.e. a few times a month Carbon sequestration rate was determined by measuring tree diameter within one year to determine increase in carbon sequestered. Bulawayo’s urban green spaces sequester 3 290 t/C/yr valued at approximately $13 000/yr. There was a significant difference in carbon sequestration by urban trees between formal and informal green spaces with formal green spaces sequestering more carbon. Indigenous trees were shown to sequester more carbon than exotic trees and trees with bigger stem diameter were determined sequester more carbon than trees with small diameter. The effect of urban green spaces on ambient temperature was determined by measuring ambient air temperature in green spaces and built up areas over six months. Urban green spaces in Bulawayo play a role in urban micro-climate regulation by reducing the ambient temperature in the green spaces as well as is built up areas. The mean difference between green spaces and surrounding urban areas was up to 60C, with larger green spaces generally showing larger differences. The green spaces extend their cooling effect to surrounding areas thus reducing the temperatures in surrounding residential areas thus reducing the energy demand used for indoor cooling. To determine why residents worship in green spaces, questionnaires were administered to congregation members to capture reasons why and how often they worship in green spaces, challenges faced by the congregants as well as assistance that can be given by the Bulawayo city council to improve the outdoor worship experience. Green spaces offer ideal places for worship in natural areas for congregants to be in touch with nature. The green spaces are also used by some congregations who ordinarily would worship in buildings but fail to do so due to lack of funds for rent or to purchase or construct a church building to use. The value of Bulawayo’s green spaces spiritual services was determined to be $92.50/ha/yr. Firewood provision was also determined by measuring tree diameter within one year to determine increase in fuelwood. The green spaces showed a significant difference in firewood production among sites. Formal green spaces were shown to produce more firewood as compared to informal green spaces and no difference was determined in growth rates between exotic and indigenous tree species. Bulawayo’s green spaces produce 1.9t/ha/yr of firewood with an ecosystem service value of $340 to $490 /ha/yr. These findings indicate the importance of urban green spaces in Bulawayo. They are multifunctional spaces, providing multiple ecosystem services. The local appreciation of the services provided by urban green spaces differs according to the type of service and location in the city. The value of services provided by green spaces is high, albeit not taken into account in planning decisions.
- Full Text:
Assessing the physical fitness level of children with intellectual disability in the Grahamstown region of the Eastern Cape, and subsequently designing, implementing and evaluating the efficacy of an exercise intervention
- Authors: Parsons, Samantha Lee
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19723 , vital:22478
- Description: Background: Extensive research has addressed physical fitness as an agent in promoting health and well-being; however, there is little research on this topic for special populations, such as individuals with intellectual disability and even less relating to the South African context. Children with intellectual disability attending special need schools in disadvantaged communities in the Eastern Cape have lacked the opportunity to participate in structured physical education programs. Implementing a solution to this problem was seen to be a challenge, due to the lack of informative research and available data. Aims: The purpose of this research was two-fold; firstly, it aimed to identify the physical fitness levels of the intellectually disabled children in the Grahamstown region of the Eastern Cape province of South Africa; and secondly, it aimed to implement and evaluate the efficacy of an exercise intervention programme on physical fitness in a local school for children with intellectual disability. Phase 1: The descriptive study compared basic anthropometric as well as physical fitness measures from a sample of participants with intellectual disability (n=29) with a comparable sample of typically developed children (n=25). There were 15 males and 14 females in the intellectually disabled sample group, with an average age of 10.69 ± 1.26 years, and the typically developed sample had 13 males and 12 females, with an average age of 10.51 ± 0.74 years. The anthropometric measures included stature and mass; while the health-related physical fitness components included cardiorespiratory endurance, muscular endurance, strength, body composition, and flexibility; and the skill-related physical fitness components were balance, agility, speed, power, coordination and reaction time. The results revealed that the children with intellectual disability were significantly shorter in stature and lighter in mass (p <0.001) compared to their typically developed peers. Muscular endurance and strength, balance, speed, power, coordination and reaction time were poorer among those with intellectual disabilities (p <0.05). Cardiorespiratory endurance, flexibility and agility were similar between groups. Results of the correlation analyses determined significant (p <0.05) relationships between certain health-related and/or skill-related physical fitness components, which were instrumental for selecting measures for Phase 2. The physical fitness components that had the most significant (p <0.05) correlations were speed with five significant correlations, both muscular endurance and balance with six, coordination with seven, and power with eight significant correlations of the eleven physical fitness components. The comparative results, in conjunction with the correlations, determined that the most suitable physical fitness components to be implemented in the exercise intervention for Phase 2 were muscular endurance, balance, and power. Phase 2: The intervention study was a case-control study (intervention group: n = 16; control group: n = 15), whereby the intervention group was exposed to an 8-week multi-modal exercise intervention training muscular endurance, balance and power. Pre-and post-intervention measures were performed using the same eleven physical fitness tests as in Phase 1. The interaction effects and effect sizes were determined and the results showed significant improvements and large effect sizes for the intervention group’s performance of muscular endurance (p=0.026; d=0.617) and power (p<0.000; d=0.999), whereas no significant changes were found for balance. Furthermore, the exercise intervention also impacted the overall level of physical fitness, as significant changes were found for cardiorespiratory endurance (p<0.001; d=0.98), strength (p=0.021; d=0.654) and flexibility (p=0.032; d=586). In conclusion, the exercise intervention was effective for improving the intellectually disabled participants’ muscular endurance and power but not found effective for balance.
- Full Text:
- Authors: Parsons, Samantha Lee
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19723 , vital:22478
- Description: Background: Extensive research has addressed physical fitness as an agent in promoting health and well-being; however, there is little research on this topic for special populations, such as individuals with intellectual disability and even less relating to the South African context. Children with intellectual disability attending special need schools in disadvantaged communities in the Eastern Cape have lacked the opportunity to participate in structured physical education programs. Implementing a solution to this problem was seen to be a challenge, due to the lack of informative research and available data. Aims: The purpose of this research was two-fold; firstly, it aimed to identify the physical fitness levels of the intellectually disabled children in the Grahamstown region of the Eastern Cape province of South Africa; and secondly, it aimed to implement and evaluate the efficacy of an exercise intervention programme on physical fitness in a local school for children with intellectual disability. Phase 1: The descriptive study compared basic anthropometric as well as physical fitness measures from a sample of participants with intellectual disability (n=29) with a comparable sample of typically developed children (n=25). There were 15 males and 14 females in the intellectually disabled sample group, with an average age of 10.69 ± 1.26 years, and the typically developed sample had 13 males and 12 females, with an average age of 10.51 ± 0.74 years. The anthropometric measures included stature and mass; while the health-related physical fitness components included cardiorespiratory endurance, muscular endurance, strength, body composition, and flexibility; and the skill-related physical fitness components were balance, agility, speed, power, coordination and reaction time. The results revealed that the children with intellectual disability were significantly shorter in stature and lighter in mass (p <0.001) compared to their typically developed peers. Muscular endurance and strength, balance, speed, power, coordination and reaction time were poorer among those with intellectual disabilities (p <0.05). Cardiorespiratory endurance, flexibility and agility were similar between groups. Results of the correlation analyses determined significant (p <0.05) relationships between certain health-related and/or skill-related physical fitness components, which were instrumental for selecting measures for Phase 2. The physical fitness components that had the most significant (p <0.05) correlations were speed with five significant correlations, both muscular endurance and balance with six, coordination with seven, and power with eight significant correlations of the eleven physical fitness components. The comparative results, in conjunction with the correlations, determined that the most suitable physical fitness components to be implemented in the exercise intervention for Phase 2 were muscular endurance, balance, and power. Phase 2: The intervention study was a case-control study (intervention group: n = 16; control group: n = 15), whereby the intervention group was exposed to an 8-week multi-modal exercise intervention training muscular endurance, balance and power. Pre-and post-intervention measures were performed using the same eleven physical fitness tests as in Phase 1. The interaction effects and effect sizes were determined and the results showed significant improvements and large effect sizes for the intervention group’s performance of muscular endurance (p=0.026; d=0.617) and power (p<0.000; d=0.999), whereas no significant changes were found for balance. Furthermore, the exercise intervention also impacted the overall level of physical fitness, as significant changes were found for cardiorespiratory endurance (p<0.001; d=0.98), strength (p=0.021; d=0.654) and flexibility (p=0.032; d=586). In conclusion, the exercise intervention was effective for improving the intellectually disabled participants’ muscular endurance and power but not found effective for balance.
- Full Text:
Assessing the potential impact of climate change in the south-eastern Great Escarpment, Southern Africa
- Authors: Bentley, Luke Kinross
- Date: 2017
- Subjects: Mountain plants -- Climatic factors -- Drakensberg Mountains , Mountain biodiversity -- Drakensberg Mountains , Climatic changes -- Drakensberg Mountains , Rain and rainfall -- Drakensberg Mountains , Plant diversity -- Climatic factors -- Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4657 , vital:20709
- Description: Rapid, anthropogenic climate change is a contemporary phenomenon which is threatening natural ecosystems. Mountains are globally important, housing high levels of plant and animal biodiversity, as well as being important suppliers of water with 50% of mountainous regions being essential for the provision of water to downstream inhabitants. Owing to their importance, an assessment of the historical, current and potential impacts of climate change on the south-eastern Great Escarpment encompassing South Africa and Lesotho is necessary and is the primary aim of this thesis. In order to assess the historical and current impacts of climate change, historical rainfall records were collected from 78 sites throughout the Eastern Cape. These records were used to determine rainfall trends and trends in the frequency of daily extreme events. Climate change projections predict increasing trends in summer and annual rainfall, and a marginal increase to a slightly decreasing trend in winter rainfall, depending on if statistically downscaled or dynamically downscaled projections are examined. Extreme events are also predicted to increase in frequency. Results showed trends which generally agree with the predictions, except for extreme events for which there was insufficient data to support the projections. This has implications for farmers in the area and validates the downscaled Regional Climate Models (RCMs) to be used for the predictive analysis determining the potential future impacts of climate change on plant species' distributions in the south-eastern Great Escarpment. In order to assess montane plant species to future climate predictions, occurrence records of 46 species were correlated to rainfall and temperature predictor variables and predictions for species richness and beta diversity were made for current and future climates. This predictive analysis used and compared two correlative species distribution modelling methods - one method used one correlating algorithm in a nuanced manner and the other method used five correlating algorithms in an ensemble. A trend of range restriction to higher elevations for the 46 species analysed was as expected from a warming climate. The nuanced, single algorithm modelling method produced less conservative models. The predicted trend of an elevational increase in montane vegetation in this region points to Lesotho and the Drakensberg highlands as being an important refugium for montane plant taxa of the southeastern Great Escarpment. The Maloti Drakensberg Transfrontier Conservation Area hence needs to be expanded and its mandate properly enforced to protect this region adequately.
- Full Text:
- Authors: Bentley, Luke Kinross
- Date: 2017
- Subjects: Mountain plants -- Climatic factors -- Drakensberg Mountains , Mountain biodiversity -- Drakensberg Mountains , Climatic changes -- Drakensberg Mountains , Rain and rainfall -- Drakensberg Mountains , Plant diversity -- Climatic factors -- Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4657 , vital:20709
- Description: Rapid, anthropogenic climate change is a contemporary phenomenon which is threatening natural ecosystems. Mountains are globally important, housing high levels of plant and animal biodiversity, as well as being important suppliers of water with 50% of mountainous regions being essential for the provision of water to downstream inhabitants. Owing to their importance, an assessment of the historical, current and potential impacts of climate change on the south-eastern Great Escarpment encompassing South Africa and Lesotho is necessary and is the primary aim of this thesis. In order to assess the historical and current impacts of climate change, historical rainfall records were collected from 78 sites throughout the Eastern Cape. These records were used to determine rainfall trends and trends in the frequency of daily extreme events. Climate change projections predict increasing trends in summer and annual rainfall, and a marginal increase to a slightly decreasing trend in winter rainfall, depending on if statistically downscaled or dynamically downscaled projections are examined. Extreme events are also predicted to increase in frequency. Results showed trends which generally agree with the predictions, except for extreme events for which there was insufficient data to support the projections. This has implications for farmers in the area and validates the downscaled Regional Climate Models (RCMs) to be used for the predictive analysis determining the potential future impacts of climate change on plant species' distributions in the south-eastern Great Escarpment. In order to assess montane plant species to future climate predictions, occurrence records of 46 species were correlated to rainfall and temperature predictor variables and predictions for species richness and beta diversity were made for current and future climates. This predictive analysis used and compared two correlative species distribution modelling methods - one method used one correlating algorithm in a nuanced manner and the other method used five correlating algorithms in an ensemble. A trend of range restriction to higher elevations for the 46 species analysed was as expected from a warming climate. The nuanced, single algorithm modelling method produced less conservative models. The predicted trend of an elevational increase in montane vegetation in this region points to Lesotho and the Drakensberg highlands as being an important refugium for montane plant taxa of the southeastern Great Escarpment. The Maloti Drakensberg Transfrontier Conservation Area hence needs to be expanded and its mandate properly enforced to protect this region adequately.
- Full Text:
Automation of source-artefact classification
- Sebokolodi, Makhuduga Lerato Lydia
- Authors: Sebokolodi, Makhuduga Lerato Lydia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4920 , vital:20743
- Description: The high sensitivities of modern radio telescopes will enable the detection of very faint astrophysical sources in the distant Universe. However, these high sensitivities also imply that calibration artefacts, which were below the noise for less sensitive instruments, will emerge above the noise and may limit the dynamic range capabilities of these instruments. Detecting faint emission will require detection thresholds close to the noise and this may cause some of the artefacts to be incorrectly detected as real emission. The current approach is to manually remove the artefacts, or set high detection thresholds in order to avoid them. The former will not be possible given the large quantities of data that these instruments will produce, and the latter results in very shallow and incomplete catalogues. This work uses the negative detection method developed by Serra et al. (2012) to distinguish artefacts from astrophysical emission in radio images. We also present a technique that automates the identification of sources subject to severe direction-dependent (DD) effects and thus allows them to be flagged for DD calibration. The negative detection approach is shown to provide high reliability and high completeness catalogues for simulated data, as well as a JVLA observation of the 3C147 field (Mitra et al., 2015). We also show that our technique correctly identifies sources that require DD calibration for datasets from the KAT-7, LOFAR, JVLA and GMRT instruments.
- Full Text:
- Authors: Sebokolodi, Makhuduga Lerato Lydia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4920 , vital:20743
- Description: The high sensitivities of modern radio telescopes will enable the detection of very faint astrophysical sources in the distant Universe. However, these high sensitivities also imply that calibration artefacts, which were below the noise for less sensitive instruments, will emerge above the noise and may limit the dynamic range capabilities of these instruments. Detecting faint emission will require detection thresholds close to the noise and this may cause some of the artefacts to be incorrectly detected as real emission. The current approach is to manually remove the artefacts, or set high detection thresholds in order to avoid them. The former will not be possible given the large quantities of data that these instruments will produce, and the latter results in very shallow and incomplete catalogues. This work uses the negative detection method developed by Serra et al. (2012) to distinguish artefacts from astrophysical emission in radio images. We also present a technique that automates the identification of sources subject to severe direction-dependent (DD) effects and thus allows them to be flagged for DD calibration. The negative detection approach is shown to provide high reliability and high completeness catalogues for simulated data, as well as a JVLA observation of the 3C147 field (Mitra et al., 2015). We also show that our technique correctly identifies sources that require DD calibration for datasets from the KAT-7, LOFAR, JVLA and GMRT instruments.
- Full Text:
Biogeomorphic aspects of lichen colonisation in part of western Dronning Maud Land, Antarctica
- Authors: Ayres, Gabrielle Alexzena
- Date: 2017
- Subjects: Lichen communities -- Queen Maud Land , Lichens -- Ecology -- Queen Maud Land , Polar regions , Ecology -- Polar regions , Antarctica , Ecology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19713 , vital:22477
- Description: Ice-free regions in Antarctica provide natural laboratories for investigating and modelling change in landscapes and ecosystems. The terrestrial ecosystems in western Dronning Maud Land are potentially critical to improve current understanding of polar ecosystems, however, they remain poorly represented and under-protected. Lichen habitats were used to elucidate geomorphic-biological feedbacks that shape the landscape’s topography and biodiversity, which in turn promote environmental heterogeneity. Environmental parameters acting on two landforms were measured to determine the colonisation and growth of lichens in niche habitats. The habitats were identified and characterised, and topographic heterogeneity was found to control lichen colonisation. Micro-topographical niches provide the most stable environments for colonisation, and are preferred habitats. Lichen-habitat interactions were species specific, and closely related to insolation and moisture availability. The bidirectional relationships between rock weathering and lichen colonisation was ascertained. Results showed that lichens are good indicators of landform heterogeneity, but also promote landform heterogeneity. Given the habitat preferences of specific lichen species, they provide proxy to evaluating environmental responses, especially environmental change. The findings of this research are to be used as baseline data for future studies exploring ecosystem development in emerging landforms.
- Full Text:
- Authors: Ayres, Gabrielle Alexzena
- Date: 2017
- Subjects: Lichen communities -- Queen Maud Land , Lichens -- Ecology -- Queen Maud Land , Polar regions , Ecology -- Polar regions , Antarctica , Ecology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19713 , vital:22477
- Description: Ice-free regions in Antarctica provide natural laboratories for investigating and modelling change in landscapes and ecosystems. The terrestrial ecosystems in western Dronning Maud Land are potentially critical to improve current understanding of polar ecosystems, however, they remain poorly represented and under-protected. Lichen habitats were used to elucidate geomorphic-biological feedbacks that shape the landscape’s topography and biodiversity, which in turn promote environmental heterogeneity. Environmental parameters acting on two landforms were measured to determine the colonisation and growth of lichens in niche habitats. The habitats were identified and characterised, and topographic heterogeneity was found to control lichen colonisation. Micro-topographical niches provide the most stable environments for colonisation, and are preferred habitats. Lichen-habitat interactions were species specific, and closely related to insolation and moisture availability. The bidirectional relationships between rock weathering and lichen colonisation was ascertained. Results showed that lichens are good indicators of landform heterogeneity, but also promote landform heterogeneity. Given the habitat preferences of specific lichen species, they provide proxy to evaluating environmental responses, especially environmental change. The findings of this research are to be used as baseline data for future studies exploring ecosystem development in emerging landforms.
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Browsing as a demographic bottleneck in a semi-arid savanna: the effect of size and age on compensatory responses of Vachellia karroo seedlings after simulated herbivory
- Authors: Perumal, Lavinia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4899 , vital:20741
- Description: Savannas are characterised by a continuous grass layer with scattered trees at varying densities. This vegetation structure is determined by several interacting factors, including fire, herbivory, resource competition and atmospheric CO2 concentration. The preservation of savanna biomes is important and a shift towards a woody biome threatens savanna globally. Bush encroachment which describes the shift towards domination of savannas by C3 woody plants, is especially acute in southern Africa. In semi-arid rangelands, encroachment progresses to dense thickets dominated by thorny and unpalatable bushes and trees. There is evidence that bush encroachment is driven by a reduction in fire and browsing events as well as their interaction. Despite browsing having strong effects on African savannas its isolated role in maintaining tree-grass coexistence has not received as much attention as the role of fire. Therefore the overall aim of this study was to examine the effects of browsing on seedlings of a commonly encroaching species, Vachellia karroo. Browsing was hypothesized to be a demographic release bottleneck for bush encroachment in a semiarid (MAP ~550mm) savanna in the Eastern Cape of South Africa, where fire has been historically rare. In a single study I explored the fate of V. karroo seedlings (less than a year old) following browsing in sub canopy and inter canopy microhabitats. Additionally, I explored how the fate of a seedling changed under high and low tree cover. Firstly, I investigated the type, intensity and frequency of herbivory, from both small and large herbivores, which seedlings were subjected to. Results revealed that browsing was severe and frequent with the majority of seedlings browsed more than twice over a 12 month period. Large browsers such as kudu and impala caused high seedling mortality (46%) while smaller browsers such as invertebrates were more effective at suppressing growth. Microhabitat had little impact on seedling survival, but significantly influenced plant compensatory growth. Reduced seedling growth following browsing was observed in the sub-canopy in comparison to seedling growth in full sunlight in the intercanopy, suggesting V.karroo may be shade intolerant. Secondly, the effect of tree cover on browsed seedlings was determined by quantifying browsing frequency and intensity at high and low tree cover. No differences in browsing intensity and frequency were observed between high and low tree cover. However, high tree cover due to bush encroachment limited seedling above ground growth. The aim of the second study was to investigate how V.karroo survival and growth were influenced by its age and size following simulated browsing. I explored this aim through field and greenhouse experiments. I was particularly interested in testing how plant sensitivity to varying defoliation intensities of repeated browsing varied with plant age (known ages of 6, 12, 16 and 30 weeks). There were large differences in mortality between the different age groups. Furthermore, age interacted with repeated browsing and negatively influenced seedling survival and regrowth. Older seedlings (16 and 30 week old) had greater survival and higher browsing frequencies resulted in greater mortality and reduced growth. The threshold age after which seedlings become more tolerant to herbivory occurs at an age of 28 weeks. Seedlings less than six weeks old experiencing intense (100 % defoliation)browsing had a very low probability (33%) of survival following just a single defoliation. Interestingly, all 16 week old seedlings regrew most of their foliage following a moderate (50%) defoliation with some plants overcompensating for leaf loss. The field study revealed two distinct demographic stages based on age and size (seedlings< 9 mm and saplings >9 mm in stem basal diameter (SBD)). Browsing had a strong negative effect on seedlings, resulting in reduced investment in leaf biomass. These findings suggest plant size and age can be used as robust predictors of a plants vulnerability to browsing. An increase in tree cover requires successful transitions of seedlings to saplings (also known as release). The results of this study suggest that in semi-arid savannas, browsing can impact tree cover through imposing a release bottleneck for tree seedlings and to lesser extent saplings. By limiting tree growth plants are kept in a disturbance trap and will therefore be exposed to not only browsers but fire. These findings also have important implications for tree-grass coexistence dynamics, suggesting that specific size and browsing thresholds should be considered in savanna management.
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- Authors: Perumal, Lavinia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4899 , vital:20741
- Description: Savannas are characterised by a continuous grass layer with scattered trees at varying densities. This vegetation structure is determined by several interacting factors, including fire, herbivory, resource competition and atmospheric CO2 concentration. The preservation of savanna biomes is important and a shift towards a woody biome threatens savanna globally. Bush encroachment which describes the shift towards domination of savannas by C3 woody plants, is especially acute in southern Africa. In semi-arid rangelands, encroachment progresses to dense thickets dominated by thorny and unpalatable bushes and trees. There is evidence that bush encroachment is driven by a reduction in fire and browsing events as well as their interaction. Despite browsing having strong effects on African savannas its isolated role in maintaining tree-grass coexistence has not received as much attention as the role of fire. Therefore the overall aim of this study was to examine the effects of browsing on seedlings of a commonly encroaching species, Vachellia karroo. Browsing was hypothesized to be a demographic release bottleneck for bush encroachment in a semiarid (MAP ~550mm) savanna in the Eastern Cape of South Africa, where fire has been historically rare. In a single study I explored the fate of V. karroo seedlings (less than a year old) following browsing in sub canopy and inter canopy microhabitats. Additionally, I explored how the fate of a seedling changed under high and low tree cover. Firstly, I investigated the type, intensity and frequency of herbivory, from both small and large herbivores, which seedlings were subjected to. Results revealed that browsing was severe and frequent with the majority of seedlings browsed more than twice over a 12 month period. Large browsers such as kudu and impala caused high seedling mortality (46%) while smaller browsers such as invertebrates were more effective at suppressing growth. Microhabitat had little impact on seedling survival, but significantly influenced plant compensatory growth. Reduced seedling growth following browsing was observed in the sub-canopy in comparison to seedling growth in full sunlight in the intercanopy, suggesting V.karroo may be shade intolerant. Secondly, the effect of tree cover on browsed seedlings was determined by quantifying browsing frequency and intensity at high and low tree cover. No differences in browsing intensity and frequency were observed between high and low tree cover. However, high tree cover due to bush encroachment limited seedling above ground growth. The aim of the second study was to investigate how V.karroo survival and growth were influenced by its age and size following simulated browsing. I explored this aim through field and greenhouse experiments. I was particularly interested in testing how plant sensitivity to varying defoliation intensities of repeated browsing varied with plant age (known ages of 6, 12, 16 and 30 weeks). There were large differences in mortality between the different age groups. Furthermore, age interacted with repeated browsing and negatively influenced seedling survival and regrowth. Older seedlings (16 and 30 week old) had greater survival and higher browsing frequencies resulted in greater mortality and reduced growth. The threshold age after which seedlings become more tolerant to herbivory occurs at an age of 28 weeks. Seedlings less than six weeks old experiencing intense (100 % defoliation)browsing had a very low probability (33%) of survival following just a single defoliation. Interestingly, all 16 week old seedlings regrew most of their foliage following a moderate (50%) defoliation with some plants overcompensating for leaf loss. The field study revealed two distinct demographic stages based on age and size (seedlings< 9 mm and saplings >9 mm in stem basal diameter (SBD)). Browsing had a strong negative effect on seedlings, resulting in reduced investment in leaf biomass. These findings suggest plant size and age can be used as robust predictors of a plants vulnerability to browsing. An increase in tree cover requires successful transitions of seedlings to saplings (also known as release). The results of this study suggest that in semi-arid savannas, browsing can impact tree cover through imposing a release bottleneck for tree seedlings and to lesser extent saplings. By limiting tree growth plants are kept in a disturbance trap and will therefore be exposed to not only browsers but fire. These findings also have important implications for tree-grass coexistence dynamics, suggesting that specific size and browsing thresholds should be considered in savanna management.
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Calibration and imaging with variable radio sources
- Authors: Mbou Sob, Ulrich Armel
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37977 , vital:24721
- Description: Calibration of radio interferometric data is one of the most important steps that are required to produce high dynamic range radio maps with high fidelity. However, naive calibration (inaccurate knowledge of the sky and instruments) leads to the formation of calibration artefacts: the generation of spurious sources and the deformations in the structure of extended sources. A particular class of calibration artefacts, called ghost sources, which results from calibration with incomplete sky models has been extensively studied by Grobler et al. (2014, 2016) and Wijnholds et al. (2016). They developed a framework which can be used to predict the fluxes and positions of ghost sources. This work uses the approach initiated by these authors to study the calibration artefacts and ghost sources that are produced when variable sources are not considered in sky models during calibration. This work investigates both long-term and short-term variability and uses the root mean square (rms) and power spectrum as metrics to evaluate the “quality” of the residual visibilities obtained through calibration. We show that the overestimation and underestimation of source flux density during calibration produces similar but symmetrically opposite results. We show that calibration artefacts from sky model errors are not normally distributed. This prevents them from being removed by employing advanced techniques, such as stacking. The power spectrums measured from the residuals with a variable source was significantly higher than those from residuals without a variable source. This implies advanced calibration techniques and sky model completeness will be required for studies such as probing the Epoch of Reoinization, where we seek to detect faint signals below thermal noise.
- Full Text:
- Authors: Mbou Sob, Ulrich Armel
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37977 , vital:24721
- Description: Calibration of radio interferometric data is one of the most important steps that are required to produce high dynamic range radio maps with high fidelity. However, naive calibration (inaccurate knowledge of the sky and instruments) leads to the formation of calibration artefacts: the generation of spurious sources and the deformations in the structure of extended sources. A particular class of calibration artefacts, called ghost sources, which results from calibration with incomplete sky models has been extensively studied by Grobler et al. (2014, 2016) and Wijnholds et al. (2016). They developed a framework which can be used to predict the fluxes and positions of ghost sources. This work uses the approach initiated by these authors to study the calibration artefacts and ghost sources that are produced when variable sources are not considered in sky models during calibration. This work investigates both long-term and short-term variability and uses the root mean square (rms) and power spectrum as metrics to evaluate the “quality” of the residual visibilities obtained through calibration. We show that the overestimation and underestimation of source flux density during calibration produces similar but symmetrically opposite results. We show that calibration artefacts from sky model errors are not normally distributed. This prevents them from being removed by employing advanced techniques, such as stacking. The power spectrums measured from the residuals with a variable source was significantly higher than those from residuals without a variable source. This implies advanced calibration techniques and sky model completeness will be required for studies such as probing the Epoch of Reoinization, where we seek to detect faint signals below thermal noise.
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Cardiovascular disease risk in Black and Caucasian females: an Eastern Cape sample
- Authors: Remsing, Sandra Claudia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/40737 , vital:25021
- Description: The purpose of this study was to investigate cardiovascular disease risk in Black and Caucasian urban working females of the Makana region of the Eastern Cape. One- hundred and sixty six age-matched urban-working individuals (Black n = 88; Caucasian n = 78) voluntarily participated in this cross-sectional study. Cardiovascular disease risk was assessed in four categories: 1) obesity, classified as ‘morphological risk’, 2) blood pressure, classified as ‘cardiovascular risk’, 3) diet, physical activity, smoking, and alcohol consumption, classified as ‘lifestyle risk’, and 4) education and income, classified as ‘socioeconomic factors’. Results showed that Black females were significantly (p<0.01) heavier than Caucasian females and categorized as ‘obese’ according to BMI classifications (31.19 ± 8.09 kg.m2 and 25.90 ±4.67 kg.m2, respectively). Black females also presented with significantly (p<0.01) higher waist circumferences and waist-to-stature ratios, further confirming the obesity prevalence in this group. When accounting for those who were on anti-hypertensive mediation, Black females additionally presented with significantly (p<0.05) higher blood pressure, categorizing them as ‘pre-hypertensive’ (MAP = 98 ± 16 mmHg and 85 ± 11 mmHg, respectively). These results therefore placed Black females at increased cardiovascular disease risk compared to Caucasian females. With respect to lifestyle factors, Black females consumed significantly (p<0.05) more kilojoules carbohydrates, and total sugar than Caucasian females, and expended more physical activity MET- minutes per week (2688.86 ± 1486.56 MET-minutes and 1828.27 ± 2238.10 MET- minutes, respectively). However, reduced validity of physical activity data as well as poor dietary recall limited the interpretations of these findings. In addition, despite significant differences between smoking and alcohol consumption between groups, the majority of both Black and Caucasian females reported being non-smokers and consumed alcohol minimally. Thus, these were concluded to be unlikely contributors to cardiovascular disease risk in these samples. Socioeconomic results nevertheless expectedly showed that Black females were significantly (p<0.05) less educated, and subsequently earned lower incomes. It was thus concluded that this may be a likely contributor to higher cardiovascular risk in Black females. Future recommendations include the incorporation of exercise intensity measures as well as objective measures of habitual diet. This is in order to get a clearer understanding of the impact of these lifestyle factors on cardiovascular disease risk.
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- Authors: Remsing, Sandra Claudia
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/40737 , vital:25021
- Description: The purpose of this study was to investigate cardiovascular disease risk in Black and Caucasian urban working females of the Makana region of the Eastern Cape. One- hundred and sixty six age-matched urban-working individuals (Black n = 88; Caucasian n = 78) voluntarily participated in this cross-sectional study. Cardiovascular disease risk was assessed in four categories: 1) obesity, classified as ‘morphological risk’, 2) blood pressure, classified as ‘cardiovascular risk’, 3) diet, physical activity, smoking, and alcohol consumption, classified as ‘lifestyle risk’, and 4) education and income, classified as ‘socioeconomic factors’. Results showed that Black females were significantly (p<0.01) heavier than Caucasian females and categorized as ‘obese’ according to BMI classifications (31.19 ± 8.09 kg.m2 and 25.90 ±4.67 kg.m2, respectively). Black females also presented with significantly (p<0.01) higher waist circumferences and waist-to-stature ratios, further confirming the obesity prevalence in this group. When accounting for those who were on anti-hypertensive mediation, Black females additionally presented with significantly (p<0.05) higher blood pressure, categorizing them as ‘pre-hypertensive’ (MAP = 98 ± 16 mmHg and 85 ± 11 mmHg, respectively). These results therefore placed Black females at increased cardiovascular disease risk compared to Caucasian females. With respect to lifestyle factors, Black females consumed significantly (p<0.05) more kilojoules carbohydrates, and total sugar than Caucasian females, and expended more physical activity MET- minutes per week (2688.86 ± 1486.56 MET-minutes and 1828.27 ± 2238.10 MET- minutes, respectively). However, reduced validity of physical activity data as well as poor dietary recall limited the interpretations of these findings. In addition, despite significant differences between smoking and alcohol consumption between groups, the majority of both Black and Caucasian females reported being non-smokers and consumed alcohol minimally. Thus, these were concluded to be unlikely contributors to cardiovascular disease risk in these samples. Socioeconomic results nevertheless expectedly showed that Black females were significantly (p<0.05) less educated, and subsequently earned lower incomes. It was thus concluded that this may be a likely contributor to higher cardiovascular risk in Black females. Future recommendations include the incorporation of exercise intensity measures as well as objective measures of habitual diet. This is in order to get a clearer understanding of the impact of these lifestyle factors on cardiovascular disease risk.
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