Investigation of the potency of topical corticosteroids using the vasoconstrictor assay
- Authors: Zvidzayi, Kudzayi Michael
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65279 , vital:28717
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Zvidzayi, Kudzayi Michael
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65279 , vital:28717
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Synthesis and evaluation of arylpyrrole-chalcone hybrids as antiplasmodial and antitrypanosomal agents
- Authors: Zulu, Ayanda Ignatia
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65268 , vital:28716
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Zulu, Ayanda Ignatia
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65268 , vital:28716
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Characterization of the distribution of platinum group elements in sulphide ores within the Merensky Reef at Modikwa and Two Rivers Platinum Mines, Eastern Bushveld Complex, South Africa
- Authors: Zilibokwe, Nosibulelo Julie
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7938 , vital:21326
- Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
- Full Text:
- Date Issued: 2017
- Authors: Zilibokwe, Nosibulelo Julie
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7938 , vital:21326
- Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
- Full Text:
- Date Issued: 2017
Computational design of a smart and efficient control system for a residential air source heat pump water heater
- Authors: Yongoua Nana Joel
- Date: 2017
- Subjects: Heat pumps -- Specifications Water heaters Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4582 , vital:28435
- Description: An air source heat pump (ASHP) water heater is a renewable and energy efficient hot water heating technology. ASHP water heaters are fast gaining maturity in the South African market and in Africa at large due to their low energy consumption (about 67 percent lower than conventional geysers), relatively low installation and operation cost, their environmental friendly nature and possibly the ease to retrofit with the old inefficient technologies. Furthermore, ASHP water heaters make use of some of the most recent advancement in refrigeration technologies enhancing their performance through a wide range of weather conditions. However, residential ASHP water heaters which come at the tail of a series of highly sophisticated models still harbour primitive control designs. One of such control system is the intermittent (on/off) control whereby the ASHP unit responds to a temperature differential threshold rather than instantaneous temperature fluctuations. Unfortunately, this control method contributes to a rapid deterioration of the compressor and other actuators due to high starting current during transient states and partial loading. Capacity control is a better alterative as it offers a more reliable system’s performance as well as a better protection for the system components. However, the drawbacks of implementing such a technology on residential ASHP water heaters is the initial purchasing cost. We use a systematic approach in this research to circumvent the purchasing cost and complete redesign hysteresis. The first step was centered around a hypothetical analysis of the performance of the heat exchangers in a bid to uncover the weakness during the operation of a residential ASHP water heater. It was observed that at ambient temperatures above 22°C notably during summer and winter afternoons, water only harnesses about 75 percent of the total heat rejected. Furthermore, the actuators keep doing work for about 15-20 minutes even after the heat transfer process has ceased completely. Following these observations, a sequential flow algorithm was developed aimed at matching the consumption point to weather variables like ambient temperature and secondly to most efficiently synchronize actuator components for a better energy management. This novel control method can save up to 58 percent of energy compared to the conventional on/off method during summer afternoons and averagely 20 percent during the rest of the day. It also has the merit to be cost effective as it barely requires no component retrofitting.
- Full Text:
- Date Issued: 2017
- Authors: Yongoua Nana Joel
- Date: 2017
- Subjects: Heat pumps -- Specifications Water heaters Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4582 , vital:28435
- Description: An air source heat pump (ASHP) water heater is a renewable and energy efficient hot water heating technology. ASHP water heaters are fast gaining maturity in the South African market and in Africa at large due to their low energy consumption (about 67 percent lower than conventional geysers), relatively low installation and operation cost, their environmental friendly nature and possibly the ease to retrofit with the old inefficient technologies. Furthermore, ASHP water heaters make use of some of the most recent advancement in refrigeration technologies enhancing their performance through a wide range of weather conditions. However, residential ASHP water heaters which come at the tail of a series of highly sophisticated models still harbour primitive control designs. One of such control system is the intermittent (on/off) control whereby the ASHP unit responds to a temperature differential threshold rather than instantaneous temperature fluctuations. Unfortunately, this control method contributes to a rapid deterioration of the compressor and other actuators due to high starting current during transient states and partial loading. Capacity control is a better alterative as it offers a more reliable system’s performance as well as a better protection for the system components. However, the drawbacks of implementing such a technology on residential ASHP water heaters is the initial purchasing cost. We use a systematic approach in this research to circumvent the purchasing cost and complete redesign hysteresis. The first step was centered around a hypothetical analysis of the performance of the heat exchangers in a bid to uncover the weakness during the operation of a residential ASHP water heater. It was observed that at ambient temperatures above 22°C notably during summer and winter afternoons, water only harnesses about 75 percent of the total heat rejected. Furthermore, the actuators keep doing work for about 15-20 minutes even after the heat transfer process has ceased completely. Following these observations, a sequential flow algorithm was developed aimed at matching the consumption point to weather variables like ambient temperature and secondly to most efficiently synchronize actuator components for a better energy management. This novel control method can save up to 58 percent of energy compared to the conventional on/off method during summer afternoons and averagely 20 percent during the rest of the day. It also has the merit to be cost effective as it barely requires no component retrofitting.
- Full Text:
- Date Issued: 2017
Species composition and seasonal population dynamics of free-living and engorged cattle ticks in three agro-ecological zones of the Eastern Cape Province, South Africa
- Authors: Yawa, Mandla
- Date: 2017
- Subjects: Ticks Boophilus microplus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9067 , vital:34224
- Description: This study was conducted to determine species composition and seasonal population dynamics of free-living and engorged cattle ticks in three agro-ecological zones (Bedford dry grassland, Kowie thicket and Bisho thornveld) of the Eastern Cape Province, South Africa. The occurrence of ticks on cattle was studied monthly from April 2016 and March 2017. Tick collections were performed on 360 selected cattle in each agro-ecological zones. During tick collections, 10 randomly selected cattle were sampled at each locality and more attention was given to African blue tick and the presence of Asian blue tick. A half body tick collection was performed from cattle and visible ticks were collected by means of fine-forceps after the animals had been restrained. Body regions that were examined includes the ear, head, neck, chest, abdomen, flank, front and hind leg and feet, tail, and peri-anal region. At each locality, six replicate drags of 100 m, approximately 50 m apart, were performed to collect ticks from vegetation. All ticks collected per cattle and from vegetation were stored in labelled sample tubes containing 70percent ethanol, subsequently counted and identified to genus and species level using a standard stereomicroscope. A total of 31425 ticks belonging to ten species were collected during the study. Rhipicephalus (Boophilus) decoloratus, was the most observed tick species (32.50percent), all other ticks like R. evertsi evertsi (18.84percent), R. appendiculatus (17.26percent), A. hebraeum (16.27percent), R. simus (7.69percent) were also commonly collected. Ixodes pilosus (3.84percent), H. rufipes (3.46percent), R. follis (0.08percent) together with Haemaphysalis silacea (0.02percent) were sporadic infestation. Haemaphysalis elliptica (0.04percent) was only found on the vegetation. No H. rufipes was collected in the thicket vegetation. Agro-ecological zones differ significantly (P<0.05) in tick species and distribution. Significantly more R. (B.) decoloratus were collected in thicket during summer compared to thornveld and dry grassland regions (P<0.05). Free-living ticks were widely distributed across different seasons but with of R. (B.) decoloratus larvae were significantly higher (P<0.05) in thornveld region during the spring season. In conclusion, agro-ecological differences and seasonal variations had an influence on ticks abundance and distribution. From this study, it is of interest to note the absence of R. (B.) microplus, whose trend to invade new areas previously colonised by R. (B.) decoloratus has been observed in Africa. In conclusion, agro-ecological differences and seasonal variations had an influence on ticks abundance and distribution. The aforementioned absence of R. (B.) microplus in this study highlights the importance of further research as this tick invades new areas previously colonised by R. (B.) decoloratus in the continent.
- Full Text:
- Date Issued: 2017
- Authors: Yawa, Mandla
- Date: 2017
- Subjects: Ticks Boophilus microplus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9067 , vital:34224
- Description: This study was conducted to determine species composition and seasonal population dynamics of free-living and engorged cattle ticks in three agro-ecological zones (Bedford dry grassland, Kowie thicket and Bisho thornveld) of the Eastern Cape Province, South Africa. The occurrence of ticks on cattle was studied monthly from April 2016 and March 2017. Tick collections were performed on 360 selected cattle in each agro-ecological zones. During tick collections, 10 randomly selected cattle were sampled at each locality and more attention was given to African blue tick and the presence of Asian blue tick. A half body tick collection was performed from cattle and visible ticks were collected by means of fine-forceps after the animals had been restrained. Body regions that were examined includes the ear, head, neck, chest, abdomen, flank, front and hind leg and feet, tail, and peri-anal region. At each locality, six replicate drags of 100 m, approximately 50 m apart, were performed to collect ticks from vegetation. All ticks collected per cattle and from vegetation were stored in labelled sample tubes containing 70percent ethanol, subsequently counted and identified to genus and species level using a standard stereomicroscope. A total of 31425 ticks belonging to ten species were collected during the study. Rhipicephalus (Boophilus) decoloratus, was the most observed tick species (32.50percent), all other ticks like R. evertsi evertsi (18.84percent), R. appendiculatus (17.26percent), A. hebraeum (16.27percent), R. simus (7.69percent) were also commonly collected. Ixodes pilosus (3.84percent), H. rufipes (3.46percent), R. follis (0.08percent) together with Haemaphysalis silacea (0.02percent) were sporadic infestation. Haemaphysalis elliptica (0.04percent) was only found on the vegetation. No H. rufipes was collected in the thicket vegetation. Agro-ecological zones differ significantly (P<0.05) in tick species and distribution. Significantly more R. (B.) decoloratus were collected in thicket during summer compared to thornveld and dry grassland regions (P<0.05). Free-living ticks were widely distributed across different seasons but with of R. (B.) decoloratus larvae were significantly higher (P<0.05) in thornveld region during the spring season. In conclusion, agro-ecological differences and seasonal variations had an influence on ticks abundance and distribution. From this study, it is of interest to note the absence of R. (B.) microplus, whose trend to invade new areas previously colonised by R. (B.) decoloratus has been observed in Africa. In conclusion, agro-ecological differences and seasonal variations had an influence on ticks abundance and distribution. The aforementioned absence of R. (B.) microplus in this study highlights the importance of further research as this tick invades new areas previously colonised by R. (B.) decoloratus in the continent.
- Full Text:
- Date Issued: 2017
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:
- Date Issued: 2017
- 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:
- Date Issued: 2017
Benthic algal communities of shallow reefs in the Eastern Cape: availability of abalone habitat
- Authors: Witte, Andrew Dennis
- Date: 2017
- Subjects: Reef ecology -- South Africa -- Eastern Cape Abalone fisheries -- Habitat -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12032 , vital:27021
- Description: Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.
- Full Text:
- Date Issued: 2017
- Authors: Witte, Andrew Dennis
- Date: 2017
- Subjects: Reef ecology -- South Africa -- Eastern Cape Abalone fisheries -- Habitat -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12032 , vital:27021
- Description: Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.
- Full Text:
- Date Issued: 2017
The development, manufacture and characterisation of niosomes intended to deliver nevirapine to the brain
- Authors: Witika, Bwalya Angel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65257 , vital:28715
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Witika, Bwalya Angel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65257 , vital:28715
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Photophysical studies of conjugates of upconversion nanoparticles with aluminium phthalocyanines
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
Exploring feeding ecology and population growth rate responses of ungulates in Southern African arid biomes
- Authors: Vermeulen, Mika Margaret
- Date: 2017
- Subjects: Ungulates -- South Africa Arid regions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15237 , vital:28189
- Description: Limited resources, extreme temperatures and predators are some of the stresses that are faced by ungulates in arid biomes. Understanding how these stressors influence ungulate feeding ecology and population growth rates is important for managers, as these could influence the persistence of ungulates in protected areas. An understanding of these stressors is especially relevant given the significant population declines in ungulate species globally. The Nama Karoo biome and the arid Savanna, an arid form of the Savanna biome, are both arid, but have distinct rainfall seasonality and vegetation structure and represent unique characteristics that need to be properly considered in their own regard. The literature on African ungulate feeding ecology covers a range of species and biomes from southern and east Africa, however, very little is known about ungulate dietary preferences in the Nama Karoo. Unexplained population declines in springbok (Antidorcas marsupialis) and red hartebeest (Alcelaphus buselaphus caama) have occurred at local scales across the Nama Karoo and the arid Savanna, most notably springbok population declines at the Karoo National Park (Karoo NP). This study sought to improve the understanding of ungulate feeding ecology and population growth rate responses in two arid biomes of South Africa. To achieve this, ungulate dietary composition was characterised, in terms of the proportional seasonal contribution of C4 and C3 plant forms, of a range of ungulates in the Nama Karoo, at the Karoo NP and the arid Savanna, at the Tswalu Kalahari Reserve (Tswalu KR), using stable carbon isotope analysis. Fresh faecal samples of ungulate species were collected from both the biomes during the dry, early wet and late wet seasons. Species were categorised per biome into feeding guilds and the effects of season, biome and the interaction thereof on the diets of the ungulate species explored. Furthermore, the findings were interpreted against what is known about diets of the respective species elsewhere in southern and east Africa. Secondly, trends in ungulate population growth rates were assessed within the Karoo NP and the Tswalu KR over the past 12 and14 years respectively. Furthermore, the variables influencing ungulate population growth rates (and generality of trends), with emphasis on ungulate biomass and rainfall, were explored at biome and species level. Population size data were obtained from annual aerial censuses for the period 2002-2015 and used to calculate annual growth rates and biomass for each ungulate species. The contribution of C4 forage to the diets of ungulate species in the arid Savanna was generally higher than in the Nama Karoo,in line with greater relative abundance of C4 grasses in the former. During winter (dry season) C3 intake was higher in the Nama Karoo than in the arid Savanna, reflecting C3 plant growth (C3 grasses and shrubs) and rainfall during winter in the Nama Karoo. Mean population growth rates during the study period were negative in some of the threatened species considered, i.e. mountain reedbuck (Redunca fulvorufula fulvorufula), tsessebe (Damaliscus lunatus lunatus) and Hartmann’s mountain zebra (Equus zebra hartmannae). No evidence for negative density dependent regulation (~intra-/interspecific competition) of ungulate population growth rates was found, whereas bottom up (~rainfall) and positive density dependent (~biomass of the species under investigation) regulatory mechanisms were most influential. The rainfall and biomass variables influenced the population growth rates of smaller ungulate species more than those of larger bodied ungulate species. Knowledge of ungulate diets will enable managers of protected areas to better understand how climate change, and resultant changes in relative abundances of plant growth forms, will influence specific ungulate species. The finding that increased population biomass positively influenced certain ungulate species’ growth rates has potential implications for management intervention as ungulate biomass is a variable that can be manipulated in protected areas. The reinforcement of existing mountain reedbuck, springbok and red hartebeest populations, specifically, at the Karoo NP and the Tswalu KR may counter their current negative growth rates in these two protected areas. Finally, the influence of protected area size and fencing, on ungulate vulnerability to predators (~top down) and forage quality (~bottom up) mechanisms in arid biomes needs to be further explored.
- Full Text:
- Date Issued: 2017
- Authors: Vermeulen, Mika Margaret
- Date: 2017
- Subjects: Ungulates -- South Africa Arid regions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15237 , vital:28189
- Description: Limited resources, extreme temperatures and predators are some of the stresses that are faced by ungulates in arid biomes. Understanding how these stressors influence ungulate feeding ecology and population growth rates is important for managers, as these could influence the persistence of ungulates in protected areas. An understanding of these stressors is especially relevant given the significant population declines in ungulate species globally. The Nama Karoo biome and the arid Savanna, an arid form of the Savanna biome, are both arid, but have distinct rainfall seasonality and vegetation structure and represent unique characteristics that need to be properly considered in their own regard. The literature on African ungulate feeding ecology covers a range of species and biomes from southern and east Africa, however, very little is known about ungulate dietary preferences in the Nama Karoo. Unexplained population declines in springbok (Antidorcas marsupialis) and red hartebeest (Alcelaphus buselaphus caama) have occurred at local scales across the Nama Karoo and the arid Savanna, most notably springbok population declines at the Karoo National Park (Karoo NP). This study sought to improve the understanding of ungulate feeding ecology and population growth rate responses in two arid biomes of South Africa. To achieve this, ungulate dietary composition was characterised, in terms of the proportional seasonal contribution of C4 and C3 plant forms, of a range of ungulates in the Nama Karoo, at the Karoo NP and the arid Savanna, at the Tswalu Kalahari Reserve (Tswalu KR), using stable carbon isotope analysis. Fresh faecal samples of ungulate species were collected from both the biomes during the dry, early wet and late wet seasons. Species were categorised per biome into feeding guilds and the effects of season, biome and the interaction thereof on the diets of the ungulate species explored. Furthermore, the findings were interpreted against what is known about diets of the respective species elsewhere in southern and east Africa. Secondly, trends in ungulate population growth rates were assessed within the Karoo NP and the Tswalu KR over the past 12 and14 years respectively. Furthermore, the variables influencing ungulate population growth rates (and generality of trends), with emphasis on ungulate biomass and rainfall, were explored at biome and species level. Population size data were obtained from annual aerial censuses for the period 2002-2015 and used to calculate annual growth rates and biomass for each ungulate species. The contribution of C4 forage to the diets of ungulate species in the arid Savanna was generally higher than in the Nama Karoo,in line with greater relative abundance of C4 grasses in the former. During winter (dry season) C3 intake was higher in the Nama Karoo than in the arid Savanna, reflecting C3 plant growth (C3 grasses and shrubs) and rainfall during winter in the Nama Karoo. Mean population growth rates during the study period were negative in some of the threatened species considered, i.e. mountain reedbuck (Redunca fulvorufula fulvorufula), tsessebe (Damaliscus lunatus lunatus) and Hartmann’s mountain zebra (Equus zebra hartmannae). No evidence for negative density dependent regulation (~intra-/interspecific competition) of ungulate population growth rates was found, whereas bottom up (~rainfall) and positive density dependent (~biomass of the species under investigation) regulatory mechanisms were most influential. The rainfall and biomass variables influenced the population growth rates of smaller ungulate species more than those of larger bodied ungulate species. Knowledge of ungulate diets will enable managers of protected areas to better understand how climate change, and resultant changes in relative abundances of plant growth forms, will influence specific ungulate species. The finding that increased population biomass positively influenced certain ungulate species’ growth rates has potential implications for management intervention as ungulate biomass is a variable that can be manipulated in protected areas. The reinforcement of existing mountain reedbuck, springbok and red hartebeest populations, specifically, at the Karoo NP and the Tswalu KR may counter their current negative growth rates in these two protected areas. Finally, the influence of protected area size and fencing, on ungulate vulnerability to predators (~top down) and forage quality (~bottom up) mechanisms in arid biomes needs to be further explored.
- Full Text:
- Date Issued: 2017
The effect of quantitative feed restriction on growth performance, carcass characteristics and selected meat quality parameters in broiler chickens
- Authors: Velele, Siphelo
- Date: 2017
- Subjects: Broilers (Chickens) Poultry -- Breeding Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8888 , vital:33907
- Description: The study investigated the effects of quantitative feed restriction on growth performance, carcass characteristics, internal organs, breast muscle pH and meat colour in broiler chickens. A total of 90, un-sexed, day-old broiler chicks were procured from an accredited supplier and were used for the current trial. For the first 14 days, all birds were brooded in one house and subjected to a uniform day-to-day management. Water was supplied throughout the trial, whereas, feed was only supplied ad libitum between days 1-14 and 29-35 days in feed restricted birds. Feed phases included starter (1-14 days), grower (15-28) and finisher (29-35), respectively. On day 15, birds were randomly allocated to three treatments; each treatment was replicated three times with 10 birds per replicate. The first treatment (T1) group, which acted as control group, was ad libitum feeding for the whole trial duration (1-35 days). For treatments 2 (T2) and 3(T3), 85 percent and 70 percent of the Cobb 500 broiler feed intake standards were applied for a period of 14 days (days 15-28), respectively. Average daily feed intake (ADFI) was determined daily and then average body weight (ABW) was determined weekly. Feed conversion ratio and average daily weight gain was thus computed for each experimental unit (replicate). On day 35, broiler birds were electrically stunned and slaughtered by a sharp knife and then hung for complete bleeding. Data collected included slaughter, carcass, breast, thigh, wing, drumstick, feet, head, spleen, heart, gizzard, intestines (small & large) and liver weights. Breast muscle was further used for the determination of colour (L*, b* and a*), initial (pHi) and ultimate breast pH (pHu) measurements. Although, quantitative feed restriction (T2 & T3) significantly affected growth performance in weeks 3 and 4, birds submitted to T2 performed similar (P>0.05) to control in the final stage, whilst birds in T3 was the poorest (P<0.05). Furthermore, birds subjected to T2 showed no differences of edible carcass portions to the control, however, T3 group showed lower (P<0.05) slaughter and wing weights. Breast ultimate pH values of birds under T2 were similar to control, but birds in T3 had significantly higher (P<0.05) values. Birds under T2 had less (P<0.05) reddish breast meat colour than control at 45 minutes. At 24 hours post-mortem, birds in T3 had lower (P<0.05) lightness values and birds submitted to T2 had higher (P<0.05) yellowness values. Liver weight was significantly lower in birds under T3 and higher (P<0.05) gizzard weights were found in birds subjected to T2. Birds under T2 performed similar to control and were able to compensate for the weight loss when high plane of feed was re-introduced. It can be concluded from the results that restricting 15 percent of feed from Cobb 500 standard feed intake had moderately affected broiler performance. Moreover, restricting 15percent of feed significantly reduced feed intake in broiler chicken.
- Full Text:
- Date Issued: 2017
- Authors: Velele, Siphelo
- Date: 2017
- Subjects: Broilers (Chickens) Poultry -- Breeding Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8888 , vital:33907
- Description: The study investigated the effects of quantitative feed restriction on growth performance, carcass characteristics, internal organs, breast muscle pH and meat colour in broiler chickens. A total of 90, un-sexed, day-old broiler chicks were procured from an accredited supplier and were used for the current trial. For the first 14 days, all birds were brooded in one house and subjected to a uniform day-to-day management. Water was supplied throughout the trial, whereas, feed was only supplied ad libitum between days 1-14 and 29-35 days in feed restricted birds. Feed phases included starter (1-14 days), grower (15-28) and finisher (29-35), respectively. On day 15, birds were randomly allocated to three treatments; each treatment was replicated three times with 10 birds per replicate. The first treatment (T1) group, which acted as control group, was ad libitum feeding for the whole trial duration (1-35 days). For treatments 2 (T2) and 3(T3), 85 percent and 70 percent of the Cobb 500 broiler feed intake standards were applied for a period of 14 days (days 15-28), respectively. Average daily feed intake (ADFI) was determined daily and then average body weight (ABW) was determined weekly. Feed conversion ratio and average daily weight gain was thus computed for each experimental unit (replicate). On day 35, broiler birds were electrically stunned and slaughtered by a sharp knife and then hung for complete bleeding. Data collected included slaughter, carcass, breast, thigh, wing, drumstick, feet, head, spleen, heart, gizzard, intestines (small & large) and liver weights. Breast muscle was further used for the determination of colour (L*, b* and a*), initial (pHi) and ultimate breast pH (pHu) measurements. Although, quantitative feed restriction (T2 & T3) significantly affected growth performance in weeks 3 and 4, birds submitted to T2 performed similar (P>0.05) to control in the final stage, whilst birds in T3 was the poorest (P<0.05). Furthermore, birds subjected to T2 showed no differences of edible carcass portions to the control, however, T3 group showed lower (P<0.05) slaughter and wing weights. Breast ultimate pH values of birds under T2 were similar to control, but birds in T3 had significantly higher (P<0.05) values. Birds under T2 had less (P<0.05) reddish breast meat colour than control at 45 minutes. At 24 hours post-mortem, birds in T3 had lower (P<0.05) lightness values and birds submitted to T2 had higher (P<0.05) yellowness values. Liver weight was significantly lower in birds under T3 and higher (P<0.05) gizzard weights were found in birds subjected to T2. Birds under T2 performed similar to control and were able to compensate for the weight loss when high plane of feed was re-introduced. It can be concluded from the results that restricting 15 percent of feed from Cobb 500 standard feed intake had moderately affected broiler performance. Moreover, restricting 15percent of feed significantly reduced feed intake in broiler chicken.
- Full Text:
- Date Issued: 2017
Dinoflagellate communities in Algoa Bay: abundance and dynamics
- Authors: Van Zyl, Hendrik Francois
- Date: 2017
- Subjects: Marine microbiology , Microbiology Marine biology -- Indian Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21218 , vital:29457
- Description: The contribution of dinoflagellates to the phytoplankton of Algoa Bay is largely unknown. This study aimed to address this, but additionally considered seasonal and spatial variation in the dinoflagellate communities of Algoa Bay. Phytoplankton abundance and the inorganic nutrients ammonium, total oxidized nitrogen, soluble reactive phosphorus and silicate were analysed. Diatoms dominated the phytoplankton community in most samples, with dinoflagellates only occasionally dominating the community. No seasonality could be detected in dinoflagellate abundance. Furthermore, no significant spatial patterns could be distinguished in dinoflagellate abundance, with the only exception being that the Port Elizabeth harbour waters contained significantly fewer dinoflagellate cells than the younger Ngqura harbour. Total phytoplankton abundance was correlated with inorganic nitrogen concentrations, but this was due to diatoms – dinoflagellate abundance did not correlate significantly with any nutrient measured. Both the common, historically bloom-forming Noctiluca scintilans, as well as the recently red tide-forming Lingulodinium polyhedra were recorded during the study, the latter almost exclusively from the harbours, which can be considered repositories of these toxic and harmful algal cells. The findings suggest that dinoflagellates in Algoa Bay are a robust phytoplankton group able to survive, and often thrive, in wide range of environmental conditions.
- Full Text:
- Date Issued: 2017
- Authors: Van Zyl, Hendrik Francois
- Date: 2017
- Subjects: Marine microbiology , Microbiology Marine biology -- Indian Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21218 , vital:29457
- Description: The contribution of dinoflagellates to the phytoplankton of Algoa Bay is largely unknown. This study aimed to address this, but additionally considered seasonal and spatial variation in the dinoflagellate communities of Algoa Bay. Phytoplankton abundance and the inorganic nutrients ammonium, total oxidized nitrogen, soluble reactive phosphorus and silicate were analysed. Diatoms dominated the phytoplankton community in most samples, with dinoflagellates only occasionally dominating the community. No seasonality could be detected in dinoflagellate abundance. Furthermore, no significant spatial patterns could be distinguished in dinoflagellate abundance, with the only exception being that the Port Elizabeth harbour waters contained significantly fewer dinoflagellate cells than the younger Ngqura harbour. Total phytoplankton abundance was correlated with inorganic nitrogen concentrations, but this was due to diatoms – dinoflagellate abundance did not correlate significantly with any nutrient measured. Both the common, historically bloom-forming Noctiluca scintilans, as well as the recently red tide-forming Lingulodinium polyhedra were recorded during the study, the latter almost exclusively from the harbours, which can be considered repositories of these toxic and harmful algal cells. The findings suggest that dinoflagellates in Algoa Bay are a robust phytoplankton group able to survive, and often thrive, in wide range of environmental conditions.
- Full Text:
- Date Issued: 2017
Mineralogical variation in the basal Upper Zone, Bushveld Igneous Complex, South Africa: implications for ore genesis and mineral extraction
- Van Huyssteen, Darryn Ashley
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017
The effects of a lion (Panthera Leo) re-introduction on a resident cheetah (Acinonyx Jubatus) population In Mountain Zebra National Park, Eastern Cape, South Africa
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Date Issued: 2017
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Date Issued: 2017
Missing values: a closer look
- Authors: Thorpe, Kerri
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/d1017827 , vital:20798
- Description: Problem: In today’s world, missing values are more present than ever. Due to the ever-changing and fast paced global society in which we live, most business and research data produced around the world contain missing data. This means that locating data which is meticulously precise can be a hard task in itself, but at times may prove essential as the consequences of making use of incomplete data could be disastrous. The reasons for missing data cropping up in almost all forms of work are numerous and shall be discussed in this dissertation. For example, those being interviewed or polled may choose to simply ignore questions which are posed to them, recording equipment may malfunction or be misplaced, or organisers may not be able to locate the respondent in order to rectify the missing data. Whatever the reasons for data being incomplete, it is necessary to avoid having to use inefficient and incomplete data as a result from the above problems. Therefore, various strategies or methods have been developed in order to handle these missing values. It is important, however, that these strategies or methods are utilised effectively as missing data treatment can introduce bias into the analysis. This dissertation shall look at these and other problems in more detail by using a data set which consists of records for 581 children who were interviewed in 1990 as part of the National Longitudinal Survey of Youth (NLSY). Approach: As mentioned above, many strategies or methods have been developed in order to deal with missing values. More specifically, traditional methods such as complete case analysis, available case analysis or single imputation are widely used by researchers and shall be discussed herein. Although these methods are simple and easy to implement, they require assumptions about the data that are not often satisfied in practice. Over the years, more up to date and relevant methods, such as multiple imputation and maximum likelihood have been developed. These methods rely on weaker assumptions and contain superior statistical properties when compared to the traditional techniques. In this dissertation, these traditional methods shall be reviewed and assessed in SAS and shall be compared to the more modern techniques. Results: The ad hoc techniques for handling missing data such as complete case and available case methods produce biased parameter estimates when the data is not missing completely at random (MCAR). Single imputation techniques likewise produce biased estimates as well as result in the underestimation of standard errors. Although the expectation maximisation (EM) algorithm yields unbiased parameter estimates, the lack of convenient standard errors suggests that using this algorithm for hypothesis testing is not a good idea. Multiple imputation, however, yields unbiased parameter estimates and correctly estimates standard errors. Conclusion: Ignoring missing data in any analysis produces biased parameter estimates. Using single imputation to handle missing values is not recommended, as using a single value to replace missing values does not account for the variation that would have been present if the variables were observed. As a result, the variance will be greatly underestimated. The more modern missing data methods such as the EM algorithm and multiple imputation are preferred over the traditional techniques as they require less stringent assumptions and they also mitigate the downsides of the older methods.
- Full Text:
- Date Issued: 2017
- Authors: Thorpe, Kerri
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/d1017827 , vital:20798
- Description: Problem: In today’s world, missing values are more present than ever. Due to the ever-changing and fast paced global society in which we live, most business and research data produced around the world contain missing data. This means that locating data which is meticulously precise can be a hard task in itself, but at times may prove essential as the consequences of making use of incomplete data could be disastrous. The reasons for missing data cropping up in almost all forms of work are numerous and shall be discussed in this dissertation. For example, those being interviewed or polled may choose to simply ignore questions which are posed to them, recording equipment may malfunction or be misplaced, or organisers may not be able to locate the respondent in order to rectify the missing data. Whatever the reasons for data being incomplete, it is necessary to avoid having to use inefficient and incomplete data as a result from the above problems. Therefore, various strategies or methods have been developed in order to handle these missing values. It is important, however, that these strategies or methods are utilised effectively as missing data treatment can introduce bias into the analysis. This dissertation shall look at these and other problems in more detail by using a data set which consists of records for 581 children who were interviewed in 1990 as part of the National Longitudinal Survey of Youth (NLSY). Approach: As mentioned above, many strategies or methods have been developed in order to deal with missing values. More specifically, traditional methods such as complete case analysis, available case analysis or single imputation are widely used by researchers and shall be discussed herein. Although these methods are simple and easy to implement, they require assumptions about the data that are not often satisfied in practice. Over the years, more up to date and relevant methods, such as multiple imputation and maximum likelihood have been developed. These methods rely on weaker assumptions and contain superior statistical properties when compared to the traditional techniques. In this dissertation, these traditional methods shall be reviewed and assessed in SAS and shall be compared to the more modern techniques. Results: The ad hoc techniques for handling missing data such as complete case and available case methods produce biased parameter estimates when the data is not missing completely at random (MCAR). Single imputation techniques likewise produce biased estimates as well as result in the underestimation of standard errors. Although the expectation maximisation (EM) algorithm yields unbiased parameter estimates, the lack of convenient standard errors suggests that using this algorithm for hypothesis testing is not a good idea. Multiple imputation, however, yields unbiased parameter estimates and correctly estimates standard errors. Conclusion: Ignoring missing data in any analysis produces biased parameter estimates. Using single imputation to handle missing values is not recommended, as using a single value to replace missing values does not account for the variation that would have been present if the variables were observed. As a result, the variance will be greatly underestimated. The more modern missing data methods such as the EM algorithm and multiple imputation are preferred over the traditional techniques as they require less stringent assumptions and they also mitigate the downsides of the older methods.
- Full Text:
- Date Issued: 2017
The pest status and integrated management programme of carob moth, Ectomyelois ceratoniae Zeller, attacking citrus in South Africa
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Date Issued: 2017
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Date Issued: 2017
Incidence of norovirus from pig faecal samples in the Eastern Cape South Africa
- Authors: Taku, Ongeziwe
- Date: 2017
- Subjects: Viral gastroenteritis Virus diseases Swine -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12374 , vital:39257
- Description: Norovirus is one of the causative agents of gastroenteritis in humans and belongs to the Caliciviridae family. Gastroenteritis is a common disease which has emerged as a worldwide health problem and it induces high number of diarrheal episodes in children and adults. Communal location such as schools, homes, day-care, cruise ships and hospitals have high risk of Norovirus infection. Besides humans, Norovirus have been found in farm animals including pigs; porcine Norovirus has been reported to be genetically related to human Norovirus which raise concerns about potential zoonotic spread and pigs may serve as reservoirs of human Norovirus strains. This current study assessed the occurrence of Norovirus infection amongst pigs in selected commercial pig farms in the Eastern Cape, South Africa. One hundred and twenty (120) RNA samples isolated from faecal samples of pigs were amplified using the RT-PCR and Nested PCR assay targeting the RdRp gene. Out of the one hundred and twenty RNA samples analysed, only five (4.2 percent) were positive for Norovirus. All positive isolates were sequenced (ABI 310 prism sequencer), edited and analysed phylogenetically using the Geneious version 9.1.5 software. Phylogenetic analysis of the generated sequences from the positive samples was performed with reference sequences obtained from the GenBank. Out of the five positive isolates analysed, four nucleotide sequences (FH14, FH20, FH13 and TS05) showed high similarity with Caliciviruses (non-human) and FHO5 showed high similarity to human Norovirus and clustered with human Norovirus GII. These findings revealed low prevalence of Norovirus in the Eastern Cape Province. Notwithstanding the low prevalence of Norovirus in the study communities, it is still of serious health concern.
- Full Text:
- Date Issued: 2017
- Authors: Taku, Ongeziwe
- Date: 2017
- Subjects: Viral gastroenteritis Virus diseases Swine -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12374 , vital:39257
- Description: Norovirus is one of the causative agents of gastroenteritis in humans and belongs to the Caliciviridae family. Gastroenteritis is a common disease which has emerged as a worldwide health problem and it induces high number of diarrheal episodes in children and adults. Communal location such as schools, homes, day-care, cruise ships and hospitals have high risk of Norovirus infection. Besides humans, Norovirus have been found in farm animals including pigs; porcine Norovirus has been reported to be genetically related to human Norovirus which raise concerns about potential zoonotic spread and pigs may serve as reservoirs of human Norovirus strains. This current study assessed the occurrence of Norovirus infection amongst pigs in selected commercial pig farms in the Eastern Cape, South Africa. One hundred and twenty (120) RNA samples isolated from faecal samples of pigs were amplified using the RT-PCR and Nested PCR assay targeting the RdRp gene. Out of the one hundred and twenty RNA samples analysed, only five (4.2 percent) were positive for Norovirus. All positive isolates were sequenced (ABI 310 prism sequencer), edited and analysed phylogenetically using the Geneious version 9.1.5 software. Phylogenetic analysis of the generated sequences from the positive samples was performed with reference sequences obtained from the GenBank. Out of the five positive isolates analysed, four nucleotide sequences (FH14, FH20, FH13 and TS05) showed high similarity with Caliciviruses (non-human) and FHO5 showed high similarity to human Norovirus and clustered with human Norovirus GII. These findings revealed low prevalence of Norovirus in the Eastern Cape Province. Notwithstanding the low prevalence of Norovirus in the study communities, it is still of serious health concern.
- Full Text:
- Date Issued: 2017
Template-assisted sol-gel synthesis of carbon doped titanium dioxide nanotubes and their characterization
- Authors: Takata, Nwabisa
- Date: 2017
- Subjects: Nanotechnology Titanium dioxide Nanostructures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13194 , vital:39473
- Description: This study reveals the effects of doping on the morphological, structural and optical properties of titanium dioxide (TiO2) nanotubes (TNTs), synthesized by sol-gel template-assisted sol-gel technique. The nanotubes (TNTs) were prepared in anodic alumina membranes (AAM) with a pore diameter range of 110-210 nm by using titanium tetra butoxide as a sol-gel precursor and oxalic acid dihydrate as a dopant source. The synthesized nanotubes were evaluated using scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), confocal Raman spectroscopy (CRS) and photoluminescence spectroscopy (PL). SEM analysis has revealed the presence of closely-packed TNTs, with a modal external tube diameters of 150, 170, 210,190 and 210 nm for the un-doped TNTs, 9 mM carbon doped-TNTs (C-TNTs), 27 mM C-TNTs, 45 mM C-TNTs and 75 mM C-TNTs respectively. The diameters are consistent with the AAM diameter range. EDX spectra revealed the presence of Ti peaks at 0.45 and 4.9 keV corresponding to Kα1 and Kβ1 emission lines respectively. Oxygen exhibits a signal at 0.5 keV corresponding to Kα1 emission line. The occurrence of these peaks in the EDX spectra endorses the existence of Ti and O atoms in the prepared titanium dioxide nanotubes. FTIR spectroscopy has revealed the presence of vibration modes at 580-660 cm-1 indicating the presence of Ti-O bonds and additional vibration modes at 2324 cm-1 resulting from C-O stretching in the C-TNTs. The XRD analysis has revealed the presence of a mixed anatase-brookite phase with diffraction peaks at 2θ angles of 25.49⁰, 38.11⁰, 40.60º, 48.14⁰, 54.58⁰, 63.00⁰, 70.11⁰ and 75.66⁰. Additionally, XRD analysis has revealed elongation of lattice parameter “c” from 9.143 to 9.830 Å with carbon concentration increase. Lattice expansion indicates the possibility of carbon substituting oxygen sites. Raman large area scan has revealed the presence of rutile, brookite and anatase for the undoped samples. On doping the rutile phase of TiO2 has shown to be suppressed by the presence of carbon atoms such that the doped samples consist of brookite and anatase phases only. The Eg1 mode of anatase of the undoped TNTs at 153. 78 cm-1 was red shifted by Δ9.78 cm-1 relative to the bulk anatase TiO2. This was attributed to decrease in particle size, presence of brookite and phonon confinement. Upon doping, the 9 mM C-TNTs, 27 mM TNTs and 75 mM TNTs have shown a red shift of Δ0. 09 cm-1, Δ1. 39 cm-1 and 1.81 cm-1 respectively, suggesting the incorporation of carbon in the TiO2 matrix. CRS depth profiling in the XZ direction has also validated the presence of a mixed anatase-brookite phase at Raman active modes 153.19 cm-1, 208.87 cm-1, 404.55 cm-1, 523.26 cm-1 and 648.55 cm-1. Photoluminescence spectra of carbon doped TiO2 showed two emission peaks at 398 nm attributed to annihilation of excitons while the broad peak at 400-460 nm was attributed to the presence of oxygen vacancies. The peak intensity of the 45 mM C-TNTs has shown a lower PL intensity suggesting that efficiency of charge separation was higher and recombination rate was lower than other carbon containing samples.
- Full Text:
- Date Issued: 2017
- Authors: Takata, Nwabisa
- Date: 2017
- Subjects: Nanotechnology Titanium dioxide Nanostructures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13194 , vital:39473
- Description: This study reveals the effects of doping on the morphological, structural and optical properties of titanium dioxide (TiO2) nanotubes (TNTs), synthesized by sol-gel template-assisted sol-gel technique. The nanotubes (TNTs) were prepared in anodic alumina membranes (AAM) with a pore diameter range of 110-210 nm by using titanium tetra butoxide as a sol-gel precursor and oxalic acid dihydrate as a dopant source. The synthesized nanotubes were evaluated using scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), confocal Raman spectroscopy (CRS) and photoluminescence spectroscopy (PL). SEM analysis has revealed the presence of closely-packed TNTs, with a modal external tube diameters of 150, 170, 210,190 and 210 nm for the un-doped TNTs, 9 mM carbon doped-TNTs (C-TNTs), 27 mM C-TNTs, 45 mM C-TNTs and 75 mM C-TNTs respectively. The diameters are consistent with the AAM diameter range. EDX spectra revealed the presence of Ti peaks at 0.45 and 4.9 keV corresponding to Kα1 and Kβ1 emission lines respectively. Oxygen exhibits a signal at 0.5 keV corresponding to Kα1 emission line. The occurrence of these peaks in the EDX spectra endorses the existence of Ti and O atoms in the prepared titanium dioxide nanotubes. FTIR spectroscopy has revealed the presence of vibration modes at 580-660 cm-1 indicating the presence of Ti-O bonds and additional vibration modes at 2324 cm-1 resulting from C-O stretching in the C-TNTs. The XRD analysis has revealed the presence of a mixed anatase-brookite phase with diffraction peaks at 2θ angles of 25.49⁰, 38.11⁰, 40.60º, 48.14⁰, 54.58⁰, 63.00⁰, 70.11⁰ and 75.66⁰. Additionally, XRD analysis has revealed elongation of lattice parameter “c” from 9.143 to 9.830 Å with carbon concentration increase. Lattice expansion indicates the possibility of carbon substituting oxygen sites. Raman large area scan has revealed the presence of rutile, brookite and anatase for the undoped samples. On doping the rutile phase of TiO2 has shown to be suppressed by the presence of carbon atoms such that the doped samples consist of brookite and anatase phases only. The Eg1 mode of anatase of the undoped TNTs at 153. 78 cm-1 was red shifted by Δ9.78 cm-1 relative to the bulk anatase TiO2. This was attributed to decrease in particle size, presence of brookite and phonon confinement. Upon doping, the 9 mM C-TNTs, 27 mM TNTs and 75 mM TNTs have shown a red shift of Δ0. 09 cm-1, Δ1. 39 cm-1 and 1.81 cm-1 respectively, suggesting the incorporation of carbon in the TiO2 matrix. CRS depth profiling in the XZ direction has also validated the presence of a mixed anatase-brookite phase at Raman active modes 153.19 cm-1, 208.87 cm-1, 404.55 cm-1, 523.26 cm-1 and 648.55 cm-1. Photoluminescence spectra of carbon doped TiO2 showed two emission peaks at 398 nm attributed to annihilation of excitons while the broad peak at 400-460 nm was attributed to the presence of oxygen vacancies. The peak intensity of the 45 mM C-TNTs has shown a lower PL intensity suggesting that efficiency of charge separation was higher and recombination rate was lower than other carbon containing samples.
- Full Text:
- Date Issued: 2017
Farm level cost-benefit analysis of conservation agriculture for maize smallholder farners in Okhahlamba Municipality in Kwa-Zulu Natal Province, South Africa
- Authors: Tafa, Sanelise
- Date: 2017
- Subjects: Agriculture -- South Africa -- Cost effectiveness Agricultural conservation -- South Africa -- Kwa-Zulu Natal Land use -- Economic aspects -- South Africa , Sustainable agriculture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2809 , vital:28094
- Description: Land degradation is a serious problem that many poor communities face and this worsens their vulnerability and therefore, poses a threat to food security, as it reduces yield, forces farmers to use more inputs, and disproportionately affect the smallholder farmers in remote communities that also suffer diverse infrastructure disadvantages. In response to that, the international development agencies, donors, and Non-Governmental Organizations (NGOs), especially faith-based organizations have turned towards sustainable farming approaches. Much attention has been paid to a combination of sustainable farming measures which are packaged under the “Conservation Agriculture” (CA) banner. The previous work in the KZN Province and elsewhere has demonstrated that CA has the potential to improve the soil structure, thereby reversing the effect of soil degradation. Consequently, many of the farmers in the areas in which these demonstrations have been conducted appreciate the ecological and economic value of adopting CA. However, the on-farm financial benefits of adopting a CA specific tillage practice are not as well known or thought to be as pronounced. By means of integrating field survey, reviewed literature, and econometric analysis, this study assessed the farm level cost-benefit analysis of conservation agriculture for smallholder maize farmers in OLM, specifically in one demonstration village of Bergville town. The analysis is based on the case study of the NGO’s work in which they had selected a community and participating households who received assistance in a number of ways such as maize seed, soil preparation, and CA planters. To analyse the farm level cost-benefit analysis, descriptive, linear regression, gross margin (GM) and appraisal indicators such as Net Present Value (NPV), Benefit Cost Ratio (BCR) and Internal Rate of Return (IRR) were used. The descriptive analysis, used to analyse the factors affecting the extent of adoption of CA revealed that socio-economic characteristics have the influence on the level to which a farmer responds to incentives. Linear regression model used in this study showed that years in farming, involvement in joint farmer’s group, and use of cover crops have the significant effect on the extent of adoption of CA. Moreover, the calculated gross margins of the two tillage systems were different, revealing higher Gross Margins for CA plots than for conventional plots. The major cause of the difference was found to be differences in the variable costs. When using appraisal indicators (NPV, BCR, and IRR) the study projected a 10-year period at 8% and 10.5% discount rates. The study also revealed positive NPVs for both CA and conventional agriculture. The positive sign implies that there are positive pay-offs for investing in both trial and control plots. However, trial plots have larger NPVs compared to control plots, meaning that there are less additional returns for investing in control plots compared to trial plots. Results also reveal that with 10.5% discount rate, the NPVs are lower than with 8% discount rate, showing that lower discount rates are consistent with higher performance over the long term. This therefore means that at lower discount rate, it is more viable to produce maize using CA than using conventional tillage system. In the case of BRC presented in the study, it was revealed that at both low and high discount rates, the trial plots were more viable than the control plots. Finally, the IRR presented in the study reveal that the trial plots would be able to pay their way much faster than the control plots. Overall, the study found that there are incentives to adoption of CA compared to conventional farming. The message from the different results arising from the use of different discount rates is that farmers should receive assistance at low cost of capital in order for their operations to be viable and this works out well over the long term as shown by the 10-year period projections.
- Full Text:
- Date Issued: 2017
- Authors: Tafa, Sanelise
- Date: 2017
- Subjects: Agriculture -- South Africa -- Cost effectiveness Agricultural conservation -- South Africa -- Kwa-Zulu Natal Land use -- Economic aspects -- South Africa , Sustainable agriculture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2809 , vital:28094
- Description: Land degradation is a serious problem that many poor communities face and this worsens their vulnerability and therefore, poses a threat to food security, as it reduces yield, forces farmers to use more inputs, and disproportionately affect the smallholder farmers in remote communities that also suffer diverse infrastructure disadvantages. In response to that, the international development agencies, donors, and Non-Governmental Organizations (NGOs), especially faith-based organizations have turned towards sustainable farming approaches. Much attention has been paid to a combination of sustainable farming measures which are packaged under the “Conservation Agriculture” (CA) banner. The previous work in the KZN Province and elsewhere has demonstrated that CA has the potential to improve the soil structure, thereby reversing the effect of soil degradation. Consequently, many of the farmers in the areas in which these demonstrations have been conducted appreciate the ecological and economic value of adopting CA. However, the on-farm financial benefits of adopting a CA specific tillage practice are not as well known or thought to be as pronounced. By means of integrating field survey, reviewed literature, and econometric analysis, this study assessed the farm level cost-benefit analysis of conservation agriculture for smallholder maize farmers in OLM, specifically in one demonstration village of Bergville town. The analysis is based on the case study of the NGO’s work in which they had selected a community and participating households who received assistance in a number of ways such as maize seed, soil preparation, and CA planters. To analyse the farm level cost-benefit analysis, descriptive, linear regression, gross margin (GM) and appraisal indicators such as Net Present Value (NPV), Benefit Cost Ratio (BCR) and Internal Rate of Return (IRR) were used. The descriptive analysis, used to analyse the factors affecting the extent of adoption of CA revealed that socio-economic characteristics have the influence on the level to which a farmer responds to incentives. Linear regression model used in this study showed that years in farming, involvement in joint farmer’s group, and use of cover crops have the significant effect on the extent of adoption of CA. Moreover, the calculated gross margins of the two tillage systems were different, revealing higher Gross Margins for CA plots than for conventional plots. The major cause of the difference was found to be differences in the variable costs. When using appraisal indicators (NPV, BCR, and IRR) the study projected a 10-year period at 8% and 10.5% discount rates. The study also revealed positive NPVs for both CA and conventional agriculture. The positive sign implies that there are positive pay-offs for investing in both trial and control plots. However, trial plots have larger NPVs compared to control plots, meaning that there are less additional returns for investing in control plots compared to trial plots. Results also reveal that with 10.5% discount rate, the NPVs are lower than with 8% discount rate, showing that lower discount rates are consistent with higher performance over the long term. This therefore means that at lower discount rate, it is more viable to produce maize using CA than using conventional tillage system. In the case of BRC presented in the study, it was revealed that at both low and high discount rates, the trial plots were more viable than the control plots. Finally, the IRR presented in the study reveal that the trial plots would be able to pay their way much faster than the control plots. Overall, the study found that there are incentives to adoption of CA compared to conventional farming. The message from the different results arising from the use of different discount rates is that farmers should receive assistance at low cost of capital in order for their operations to be viable and this works out well over the long term as shown by the 10-year period projections.
- Full Text:
- Date Issued: 2017
Comparative localization studies of P.falciparum ADP-ribosylation factor proteins in P.falciparum parasites and hela cells using GFP tagged constructs
- Authors: Swart, Tarryn
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3537 , vital:20519
- Description: Expected release date-December 2018
- Full Text:
- Date Issued: 2017
- Authors: Swart, Tarryn
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3537 , vital:20519
- Description: Expected release date-December 2018
- Full Text:
- Date Issued: 2017