A study of the geology of the Vaalbank and Lady Frere areas in the Karoo Basin of South Africa using gravity, magnetic and gamma-ray spectrometry data: implications of groundwater potential
- Authors: Khalimashe, Sinesihle , Gwavava, Oswald
- Date: 2020
- Subjects: Gamma ray astronomy
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/11983 , vital:39124
- Description: The Vaalbank and Lady Frere areas belong to the Elliot, Molteno and Burgersdorp Formations, that are part of the sedimentary succession of the Beaufort Group in the Karoo Basin of South Africa. There is Quaternary alluvium covering the mudstone, sandstone and shale rocks of the Beaufort Group. Dolerite and gabbro sills of the Karoo age have intruded the whole area. A number of investigations were carried out for the study namely field observations, petrographic, X-ray diffraction, airborne gamma-ray spectrometry, aeromagnetic and gravity analyses. Twenty four rock samples were collected in the field from fresh outcrops of the Karoo dolerites, Burgersdorp and Molteno formations. The measured densities and porosities show that the Karoo dolerite suite has the highest average dry density of 2.771 g/cm3 and the lowest average porosity of 3%. The Burgersdorp Formation has an intermediate average density of 2.458 g/cm3 and an intermediate average porosity of 5.4%. The Molteno Formation has the lowest average density of 2.190 g/cm3 and the highest average porosity of 14.5%. Petrographic and geochemical investigations were carried on 19 rocks samples collected in the field to determine the mineralogy character using microscopic and XRD analyses. Both petrographic and X-ray diffraction analyses revealed that the sandstones of the study area are composed of quartz as their primary mineral and feldspars as the secondary mineral. The dolerite consists of euhedral structured minerals such as magnetite, pyroxene, plagioclase and amphibole. The gamma ray maps show high spectrometric values are associated with the Burgersdorp Formation, alluvium cover and dolerite dykes. The low spectrometric values are associated with dolerite sills and ring complexes. The boundaries of the sill/ring complexes are clearly delineated by the K/U ratio and ternary maps. The magnetic maps show ring like patterns of magnetic high anomalies that are due to the sills/ring complexes whilst the numerous, narrow, linear magnetic highs are due to faults and dolerite dyke swarms. The majority of the dykes trend in a NW-SE direction and a few dykes are in a NE-SE direction. The magnetic power spectrum indicates four depths of the magnetic sources at average depths of 0.13 km, 1.60 km, 2.83 km and 12.40 km. The magnetic depth iii slices maps show that both the circular/ring like and linear anomalies extend from shallow to deeper depth of 12.4 km. The gravity map is dominated by a long wavelength gravity anomaly that increases from about -120 mGals in the northwestern corner of the study area to -110 mGals in the southeastern corner of the study area. Results from 2½D gravity modelling show that this long wavelength anomaly is due to a horizontal Moho at a depth of 47 km in the study area, which shallows outside the study area near the coast. Superimposed on it are short wavelength gravity anomalies due to low density sediments and high density dolerite intrusions. The simple 2½D models generated from five profiles traversing the study area reveal that the sediments of the Karoo Supergroup extend from the surface down to a depth 5 km below sea level attaining a maximum thickness of about 6½ km. These sediments are dykes, sills and ring complexes. The dykes and sills/ring complexes identified from gamma ray spectrometry, magnetic and gravity data results are likely to be associated with fractures, joints, cracks and fissures in the host rocks, which form preferential pathways for groundwater transmission. Hence, they could be suitable targets for groundwater.
- Full Text:
- Date Issued: 2020
Accessibility of agricultural information by smallholder farmers in Amatole District Municipality: Nexus between agricultural extension services and the library
- Authors: Sigigaba, Masimthembe
- Date: 2020
- Subjects: Farms, Small
- Language: English
- Type: Thesis , Masters , M Agric (Agric Extension)
- Identifier: http://hdl.handle.net/10353/18849 , vital:42870
- Description: Accessibility to relevant, accurate and timely information remains vital in farming. For farmers to improve their productivity they depend on access to pertinent agricultural information. Such information updated them about new agricultural technologies, climate change, new cultivars, access to market and access to financial assistance. These types of information help farmers in decision making regarding their farming. Agricultural extension officers remain a reliable source where farmers could obtain relevant agricultural information. Community libraries are also channels that could be used by agricultural extension officers to complement their work of providing farmers with information. Thus, the study sought to assess linkage between these two institutions to provide farmers with information. A positivism paradigm with quantitative research approach were adopted in the study. Smallholder farmers (169), agricultural extension officers (5) and librarians (15) were the unit of analysis. A semi-structured questionnaire was used for data collection and SPSS software for analysis. Findings revealed that, agricultural extension officers mostly utilise interpersonal channels that include demonstrations, group meetings and face-to-face interaction to provide farmers with information. Community libraries were found to be non-utilised by extension services and also by farmers. Farmers were of the perception that libraries are meant for educated people. It was also discovered that community libraries have information on agriculture that only targets learners who are taking agriculture in school as a subject. There was no existing linkage between agricultural extension services and community libraries working together to provide farmers with pertinent agricultural information that can help them improve productivity
- Full Text:
- Date Issued: 2020
Adol-Safety: A Framework for Empowering Parents to be Aware of Social Network Threats Affecting Adolescents
- Authors: Mjoli, Phumelela , Shibeshi, Z
- Date: 2020
- Subjects: Social networks Social media|
- Language: English
- Type: Thesis , Masters , MSc (Computer Science )
- Identifier: http://hdl.handle.net/10353/12016 , vital:39127
- Description: The use of social networks has grown so much that adolescents have become active members of various social networks such as Twitter, Facebook, and Instagram, etc. The gradual change in how people choose to communicate, socialize and share ideas today has influenced adolescents to an extent that they find themselves wanting to engage more on social networks than they really should due to peer pressure. Whenever a person joins social networks or browses the Internet, they by default are exposed and become vulnerable to many cyber threats. Cyber threats are driven by users that have negative intentions on the Internet or social networks. Adolescents are no exception to these cyber threats. The findings of this research reveal that threats such as cyberbullying, harassment, and online predators to name a few are often designed to abuse and affect adolescents). Therefore, this research aims to prevent such threats from prevailing by empowering parents to be aware of the threats that affect their adolescents in an online environment, which typically includes social networks. To achieve this, this research starts by investigating the cyber threats that affect adolescents and then explores ways that can be used to empower parents. A framework is developed to handle this. The framework includes strategies that parents can adopt and ways in which safety on social networks can be increased, as well as guidelines that can be followed in order to prevent cyber threats. The framework also aims to enhance a parent-child relationship that can help in preventing social network threats. Lastly, the framework is implemented as a knowledgesharing website that can be used by parents to receive and give an insight into social network threats that influence adolescents on social networks.
- Full Text:
- Date Issued: 2020
An in silico analysis, purification and partial kinetic characterisation of a serine protease from Gelidium pristoides
- Authors: Ntsata, Zolani
- Date: 2020
- Subjects: Gelidium Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12076 , vital:39149
- Description: The aim of this study was to characterize the protease enzyme (s) from red algae. An in silico analysis of red algae genomes was used to identify gene coding for protease. Protease sequences identified from these genomes were examined for conserved domains, active site and structures. The domain search revealed that the identified sequences were from the five classes of protease enzymes. For function inference, the red algae sequences were aligned to identify the catalytic sites, and the tertiary structures were predicted using homology modelling. An in silico analysis provides an indication of the class and potential functions of the enzymes. However, it cannot predict whether the gene is constitutively expressed in the red algae or under which conditions it may be induced, and it cannot determine the kinetic efficiency of an enzyme against various substrate, or the optimum conditions for the protein activity. Attempts to clone and recombinantly express selected red algae proteases, proved unsuccessful, as the available genomes where from red algae species found mainly in Asia, and the designed primers, therefore, did not amplify a corresponding PCR product from the red algae harvested in South Africa. Crude extracts of red algae collected from Kenton-on-Sea, along the East Coast of South Africa, were screened for protease activity using Benzoyl-Arginine-pNitroAnilide (BApNA) as substrate. The proteases detected in the crude extract were purified using ammonium sulphate precipitation and HiPrep DEAE FF 16/10; CM FF 16/10, and HiPrep Q FF 16/10 columns for ion-exchange chromatography. The HiPrep Q FF 16/10 column yielded active protein, which revealed two bands of 11kDa and 17kDa on SDS-PAGE. It was assumed that these bands represented two subunits of the purified protease. Kinetic characterisation of the purified protease revealed a pH optimum of 9, using BApNA as substrate, a temperature optimum at 60ºC, and sensitivity to temperature when stored above 4ºC. The protease activity was inhibited by Ferric chloride (32%), induced by calcium chloride (156%), no inhibition by magnesium chloride (97%) and slight inhibition by potassium chloride (77%) and manganese chloride (70%). Phenylmethylsulfonyl fluoride (PMSF), a serine protease inhibitor, almost totally inhibited the protease activity, indicating that the protease from red algae was most likely a serine protease. The Km and kcat values were 1.96 µM, and 0.364 s -1 , respectively using BApNA as the substrate. This study revealed that the red algae genome contains numerous genes that encode for proteases from almost all the classes of proteases. A serine protease from the red algae Gelidium pristoides was partially purified and kinetically characterised, confirming that red algae found along the Eastern Coast of South Africa contain genes that express active proteases that may be of medical or industrial interest. Further studies, however, are required to recombinantly express, purify and characterise the numerous proteases encoded by the genes identified in the in silico analysis of this study.
- Full Text:
- Date Issued: 2020
Analysis of maximum power point tracking data for obtaining photovoltaic parameters
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
- Full Text:
- Date Issued: 2020
Beef quality, oxidative stability and fatty acid composition of Nguni heifers fed diets with incremental levels of Opuntia ficus-indica (cactus) cladodes
- Authors: Mkhosi, Silungile
- Date: 2020
- Subjects: Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc (Animal Science )
- Identifier: http://hdl.handle.net/10353/18732 , vital:42728
- Description: The objective of the study was to determine meat quality, fatty acid (FA) composition and shelf-life stability of longissimus muscle of Nguni heifers fed incremental levels of Opuntia ficus-indica (cactus) cladodes. A total of 32 heifers aged 36 months were allocated randomly to four dietary treatments: 10% cactus, 20% cactus, commercial and control diets for 90 days. The longissimus thoracis et lumborum (LTL) samples were taken from each carcass for the determination of meat quality, retail shelf-life stability and FA composition. Diet had no effect (P > 0.05) on pH and drip display, however, there was an increase in drip display with ageing time (P ≤ 0.05). Meat colour attributes (L* a* b* and C*) were influenced by diet, with 20% cactus diet having lower L* values compared to other diets (P ≤ 0.05). During a 14-day retail display, a diet day interaction was observed for hue angle with the cactus diets having the lowest values at day 14 of display compared to the other diets (P ≤ 0.05). Differences in meat from heifers fed different diets were observed with 20% cactus accounting for significantly (P ≤ 0.05) higher levels of deoxymyoglobin and the lowest levels of oxymyoglobin. Thawing loss and Warner Bratzler shear force decreased (P ≤ 0.05) with ageing period. Meat from heifers fed cactus diets had lower (P ≤ 0.05) proportions of oleic acid (C18:1n9c) and total MUFA, higher (P ≤ 0.05) proportions of total SFA, C15:1, C17:1, linoleic acid (C18:2n6c) and total PUFA. The control diet produced meat with the highest thiobarbituric acid reactive substances (TBARS) values compared to other diets (P ≤ 0.05) and with ageing TBARS values increased (P ≤ 0.05). Diet showed an effect (P ≤ 0.05) on sensory attributes such as overall tenderness and mouth feel with cactus diets accounting for lower scores. However, juiciness, overall tenderness, grassy and animal like attributes increased with ageing (P ≤ 0.05). Inclusion of cactus in the diet did not produce any adverse effects on meat quality, fatty acid composition, lipid oxidation and sensory quality. Therefore, it can be concluded that inclusion of cactus in Nguni heifer finisher diets up to 20% can improve meat quality.
- Full Text:
- Date Issued: 2020
Design of a Traffic Surveillance Application using iFogSim
- Authors: Sinqandu, Mluleki
- Date: 2020
- Subjects: Cloud computing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18676 , vital:42705
- Description: __iFogSim is a toolkit to model, simulate and evaluate networks of Fog computing, Edge computing and Internet of Things (IoT). This framework provides the capabilities of analysing and evaluating the performance of applications and resource management policies in Fog/IoT environments, based on which designers can model and test their applications. This thesis proposes a novel application model of a traffic surveillance vehicular network application through smart cameras using iFogSim, where the scenario of multiple vehicles tracking is considered. The effectiveness of the proposed application model is assessed and validated by simulations using a modified application model inherited from a case study of intelligent surveillance through distributed camera networks introduced. Simulations are conducted using the iFogSim tool and performance evaluation is done. The comparison between one vehicle and multiple vehicle tracking is done and the results demonstrate that the multiple vehicle application model achieves a better performance in terms of average latency and data transfer rate
- Full Text:
- Date Issued: 2020
Determinants of adaptation to climate variability:A case study of crop farming households in Tyhume Valley communities Eastern Cape,South Africa.
- Authors: Mtintsilana, Olona
- Date: 2020
- Subjects: Climatic changes Sustainable agriculture Climatic changes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18789 , vital:42733
- Description: Climate variability affects rural households and agricultural productivity, yet it is just one of many stresses that vulnerable rural households have to cope with. Climate variability is not as noticeable as weather variability, because it happens over seasons and years. It is the manner in which climate fluctuates above or below a long-term average value. Without measures at local and national level to adapt to climate variability, risk of food insecurity will continue to increase at household level. The objective of the study was to determine factors affecting adaptation to climate variability. Purposive sampling was used to identify households who participated because of un-availability of sampling frame. Information was elicited from the selected households with the aid of a semi-structured questionnaire. The study utilised a cross-sectional survey of 205 farming households in Tyhume Valley communities. Data gathered was subjected to descriptive statistics, Cross tabulations and Binary logit model. The results indicate that rural households from Tyhume Valley communities practiced coping adaptation through use of the following adaptation strategies; crop rotation, planted drought resistant crops, changed planting dates and used indigenous strategies such as using ash to kill mule (intuku). Most of the households used irrigation as the coping strategy to adapt to climate variability. However, heatwave, high winds, employment status, cell phones, age and gender of the rural households’ heads have effects on households’ adaptation to climate variability in Tyhume Valley. In view of the research findings, a large number of farming households are old and are females, there is a need for development of labour saving technologies and extension services to increase the likelihood of adaptation of climate variability by vulnerable farmers such as women and elderly farmers.The study also recommends that there must be a development of infrastructure for farmers as they are negatively affect by high winds due to low infrastructural development.The study also shows that farming households who have access to cellphones are more likely to adapt to climate variability, therefore the study recommends that communication of farming households must be improved.Adapting to climate variability is an increasingly important issue in agriculture and one that is likely to persist for many years.
- Full Text:
- Date Issued: 2020
Developing a Machine Learning Algorithm for Outdoor Scene Image Segmentation
- Authors: Zangwa, Yamkela
- Date: 2020
- Subjects: Computational intelligence Computer science
- Language: English
- Type: Thesis , Masters , MSc (Computer Science )
- Identifier: http://hdl.handle.net/10353/12087 , vital:39150
- Description: Image segmentation is one of the major problems in image processing, computer vision and machine learning fields. The main reason for image segmentation existence is to reduce the gap between computer vision and human vision by training computers with different data. Outdoor image segmentation and classification has become very important in the field of computer vision with its applications in woodland-surveillance, defence and security. The task of assigning an input image to one class from a fixed set of categories seem to be a major problem in image segmentation. The main question that has been addressed in this research is how outdoor image classification algorithms can be improved using Region-based Convolutional Neural Network (R-CNN) architecture. There has been no one segmentation method that works best on any given problem. To determine the best segmentation method for a certain dataset, various tests have to be done in order to achieve the best performance. However deep learning models have often achieved increasing success due to the availability of massive datasets and the expanding model depth and parameterisation. In this research Convolutional Neural Network architecture is used in trying to improve the implementation of outdoor scene image segmentation algorithms, empirical research method was used to answer questions about existing image segmentation algorithms and the techniques used to achieve the best performance. Outdoor scene images were trained on a pre-trained region-based convolutional neural network with Visual Geometric Group-16 (VGG-16) architecture. A pre-trained R-CNN model was retrained on five different sample data, the samples had different sizes. Sample size increased from sample one to five, to increase the size on the last two samples the data was duplicated. 21 test images were used to evaluate all the models. Researchers has shown that deep learning methods perform better in image segmentation because of the increase and availability of datasets. The duplication of images did not yield the best results; however, the model performed well on the first three samples.
- Full Text:
- Date Issued: 2020
Effect of increasing fossil shell flour levels on digestive and metabolic utilization, health, body weight change and wool production, and quality in Dohne-Merino wethers
- Authors: Ikusika, Olusegun Oyebade
- Date: 2020
- Subjects: Merino sheep Sheep -- Quality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/18465 , vital:42542
- Description: The study's broad objective was to assess growth performance, blood and parasitic profiles, wool parameters, methane emission, and nutritional status of Dohne-Merino wethers fed diets supplemented with varying levels of fossil shell flour. Twenty-four Dohne-Merino wethers, averagely weighing 20.0±1.50 kg, were divided into four groups and used in this study. The effects of varying inclusion levels of fossil shell flour (FSF) (0, 2, 4, and 6 %) on feed intake, water intake, nutrient digestibility, N-retention, hematobiochemical and parasitic profiles, body condition scores, feed preference, wool parameters and methane output were determined. The influence of FSF's varying inclusion levels on fermentation parameters, in vitro true digestibility, and relative feed values were also determined. Wethers fed with 4% FSF inclusion level diet showed the highest (P<0.05) values for dry matter intake, average daily weight gain, N retention, (Nitrogen retention) and apparent digestibility of crude protein (CP), Ether Extract (EE) and Ash 6 % (P < 0.05). The urinary N and fecal N were lowest in wethers fed 4% FSF inclusion level and highest in those fed on diets without FSF (P < 0.05). Water intake was highest in wethers fed 0% FSF diet, followed by those fed on 4% and lowest in 6% FSF (P< 0.05). There was a significant increase in white blood cell counts in wethers fed on a diet with 4% and 6% FSF inclusion levels from day 10 to 100 compared to wethers fed on a diet with 0% and 2% FSF (P <0.05). Red blood cell counts also increased significantly in wethers fed on a diet containing 4% FSF, but a slight increase in wethers with 6 % FSF diet, throughout the experimental period (P < 0.05). Blood urea was highest in wethers fed 0% FSF inclusion level and lowest in 6% at day 30 to day 100. Wethers on 4% FSF diet showed an increase in blood urea from day 30 to day 100 (P < 0.05) while wethers on 0% and 2% remained unchanged (P<0.05) during this period and not different (P > 0.05) from wethers on 4% FSF as well. The total protein concentration, albumin, total bilirubin, Na, K, glucose, cholesterol, and liver enzymes were normal for wethers. However, serum creatinine level was lower in wethers fed on 4% FSF than those on 0% FSF (P < 0.01). Haemonchus and Coccidian fecal egg counts were low in wethers fed diets with 2%, 4%, and 6 % FSF (P < 0.01) compared 11 with wethers fed with 0% FSF inclusion level during the same period. The body condition score of wethers fed on diets with 2%, 4%, and 6% FSF inclusion levels were higher than those on 0% (P < 0.05). Wool yield, staple length, the coefficient variation of the fibre diameter, and fibre of wethers fed on diets with FSF were higher than those without FSF (P < 0.05). The fibre diameter of the wethers fed on FSF supplemented diets was the same as those on 0 % FSF (P > 0.05). The wethers spent more time on FSF supplemented diets and consumed more feed compared to that without FSF supplemented (P < 0.05). The levels of FSF inclusion in the diet affected the enteric methane output (ppm-m), where 4 % FSF had the highest enteric methane output while wethers on 2 % FSF had the lowest methane output (P < 0.05). Resting wethers produced more methane (g/day) than those feeding or standing (P < 0.05). Increasing levels of FSF did not affect ruminal temperature and pH. Ammonia-N increased with increasing FSF except in wethers fed on a diet with 4% FSF (P < 0.01). The total molar concentrations of the wethers' volatile fatty acids decreased with increasing FSF levels (P > 0.05). The acetic propionic ratio of the wethers also decreased except at a 4% inclusion level. The in vitro true digestibility dry matter (IVTDDM), in vitro true digestibility neutral detergent fibre (IVTDNDF), and in vitro true digestibility acid detergent fibre (IVTDADF) of the wethers decreased up to 4% FSF inclusion but tended to increase at 6% inclusion. This study's result as one of the pioneer studies in Dohne-Marino wethers showed that FSF treatment has the potential to improve the nutritional status of the animal and the animal performance and wool quality. Health-wise, FSF decrease nematode population and boost animal immunity as seen in RBC and WBC counts. It also can play a major role in protecting the environment, as seen in its reduction in feacal and urinary nitrogen, which is heavily involved in environmental pollution. Result also confirmed that the best period to target for methane mitigation in ruminants is the resting period. In conclusion, the inclusion of FSF in the diet of Dohne-Merino wethers has the potential to improve the overall performance, with a 4% FSF inclusion level having optimal productivity. However, future research is required to investigate FSF's effect on meat quality, rumen microbial community, in-vivo digestibility, and milk production.
- Full Text:
- Date Issued: 2020
Extraction, Isolation and Biological studies of Pentanisia prunelloides and Hippobromus pauciflorus
- Authors: Ngcetane , Lazola Luyolo
- Date: 2020
- Subjects: Medicinal plants Antioxidants
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: http://hdl.handle.net/10353/18766 , vital:42731
- Description: Enormous amounts of drugs or drug components have been found with the use and help of ethnobotanical knowledge of plants by the indigenous civilisation of that region. The primary reason that plants are chosen as a potential source of new medicines is that they are readily available to researcher and the public either free of charge or at a low and affordable cost in the rural majority community in the developing world. The aim of this study was to evaluate the chemical content of two commonly used medicinal plants of the Eastern Cape Province of South Africa and to explore their antioxidant potential. Crude extracts of Hippobromus pauciflorus and Pentanisia prunelloides were obtained by means of sequential solvent extraction followed by evaluation of the phenolic and flavonoid content of extracts and the anti-oxidant ability of the both plant samples and also their ability to hinder lipid peroxidation. For the H.pauciflorus sample, different masses of crude extracts were obtained with Dichloromethane (0.817 g) yielding the smallest mass and the 70% Ethanol (120.196 g) extract yielding the largest mass. The total phenolic content of the plant sample extracts were measured using the Folin-Ciocalteau reagent. The Methanol extract (133.019 ± 0.003 μgGAE/mL) exhibited the largest content while the EtOH extract (13.981 ± 0.001 μgGAE/mL) exhibited the least content. The MeOH extract exhibited the highest flavonoid content (46.005 ± 0.001 μgQE/mg extract) while the Hexane extract (19.000 ± 0.008 μgQE/mg extract) exhibited the least. 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper Frap assay was performed with the Ethyl Acetate extract displaying the least anti-oxidant ability (10.284 ± 0.014 AAE/mL) while the Hex extract (204.705 ± 0.119 AAE/mL) displayed the highest anti-oxidant ability. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay was performed with the hexane, methanol and ethanol extracts exhibiting an anti-oxidant property with IC50 values of 3.594x10-3 ± 0.133 mg/mL, 0.185 ± 0.019 mg/mL and 0.011 ± 0.002 mg/mL respectively. Inhibition of lipid peroxidation at 150 μg/mL was performed where the Dichloromethane extract showed the highest inhibition percentage (-75.000 ± 0.119%) while the Hex extract (-41.667 ± 0.021005%) showed the lowest inhibition percentage at 300 μg/mL; only the DCM extract (-3.051 ± 0.018%) displayed inhibition ability. For the P.prunelloides sample, different masses of crude extracts were obtained with EA extract (0.348 g) yielding the smallest mass and the MeOH (47.941 g) extract yielding the largest mass. Phenolic content was evaluated with the DCM extract (122.827 ± 0.010 μgGAE/mL) exhibited the largest content while the MeOH extract (48.788 ± 0.001 μgGAE/mL) exhibited the least content. Flavonoid content was evaluated with the DCM extract (88.543 ± 0.005 μgQE/mg extract) exhibited the largest content while the EtOH extract (19.254 ± 0.001 μgQE/mg extract) exhibited the least content. FRAP assay was performed with the DCM extract (13.021 ± 0.008 AAE/mL) displaying the least anti-oxidant ability while the MeOH extract (217.758 ± 0.025 AAE/mL) displaying the highest anti-oxidant ability. DPPH assay was conducted with EA and methanol extracts exhibiting antianti-oxidant ability and having IC50 values of 0.579 ± 0.021 mg/mL and 0.006± 0.001 mg/mL respectively. Inhibition of lipid peroxidation at 150 μg/mL was performed with the n-Hex extract (-36.395 ± 0.015%) showing the highest inhibition percentage while the DCM extract (-17.647 ± 0.005%) the lowest and at 300μg/mL the EA (- 12.881 ± 0.018%) and DCM (-0.847 ± 0.009%) extracts displayed inhibition. An attempt was made to isolate and elucidate the compounds in the extracts but unsuccessful, although the TLC results indicated several compounds that can be elucidated in future study
- Full Text:
- Date Issued: 2020
Fabrication of a photocatalytic PAN supported C-TiO2-CFA nanocomposite for use in water treatment
- Authors: Mpelane, Amkelwa
- Date: 2020
- Subjects: Photocatalysis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: http://hdl.handle.net/10353/18744 , vital:42729
- Description: The goal of this study was to fabricate a visible light responsive composite of C-TiO2-CFA. The prepared nanocomposite (C-TiO2-CFA) was immobilized on poly(acrylonitrile) membrane to address the drawback of recovering the nanosized photocatalyst from water after photodegradation experiments. The C-TiO2-CFA nanocomposites were fabricated using a modified sol-gel method, while the C-TiO2-CFA/PAN membranes were prepared via the phase inversion technique. The nanocomposites were fully characterized using FTIR, XRD, SEM-EDX, TEM, DRS, and BET surface area analysis. The prepared C-TiO2-CFA/PAN membranes were evaluated in the photodegradation of methyl orange and the golden yellow dyes, as well as the photoreduction of lead and cadmium heavy metals in synthetic wastewater. UV-Visible spectroscopy was used to follow the changes in the concentration of organic dyes, while inductively coupled plasma optical emission spectroscopy was used to follow changes in the concentration of the heavy metals. FTIR analysis confirmed the presence of functional groups expected on the prepared C-TiO2- CFA/PAN membranes and EDX analysis accounted for the elements expected. The prepared membranes all exhibited an asymmetric structure as depicted by cross-sectional view study via SEM analysis. TEM and SEM analyses revealed that the prepared C-TiO2-CFA nanocomposite was roughly spherical in shape with an estimate particle size of 10.94 nm according to TEM and 11.62 nm according to XRD using Scherrer equation. The incorporation of carbon into the lattice structure of titanium dioxide resulted in a reduction in bandgap from 3.19 eV to 2.78 eV through introduction of mid-band states, allowing visible light utilization. The best nanocomposite was obtained by doping TiO2 with 4% carbon and having a C-TiO2 to CFA ratio of 4:1 respectively. The C-TiO2-CFA nanocomposite exhibits a crystalline structure with a mixture of rutile and anatase phases. The parameters investigated in the evaluation of photocatalytic performance of C-TiO2- CFA/PAN were effect of photocatalyst load on PAN membrane, initial dye concentration, pH and light source in the activation of photocatalyst. For both dyes (methyl arrange and golden yellow), it was observed that photodegradation efficiencies increased with an increase in catalyst load. In the photodegradation of MO and GY using the membrane with 1% C-TiO2- CFA, removal efficiencies of 73.3% and 59.99% were attained respectively, while the membrane with 2% C-TiO2-CFA achieved MO and GY photodegradation efficiencies of 99.8% and 99.2% respectively. Photodegradation efficiencies of MO and GY were observed to decrease with an increase in dye concentration. Low pH (3) was observed to favour the photodegradation of MO and GY azo dyes. Photodegradation efficiencies of 99.8% and 99.2% were attained where obtained at lower MO and GY initial concentration. The modified photocatalyst (C-TiO2-CFA/PAN) exhibited better photoactivity under sunlight irradiation compared to strict UV light irradiation. Evidently, the C-TiO2-CFA/PAN membranes can be 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper utilized as a sustainable and stable photocatalyst to efficiently eliminate methyl orange and golden yellow dyes. A PAN membrane with 2 wt% C-TiO2-CFA revealed enhanced cadmium and lead removal efficiencies in comparison to PAN membranes with 1 wt% and 1.5% C-TiO2-CFA. A Cd2+ removal efficiency of 95% was obtained using 2 wt% C-TiO2-CFA/PAN nanocomposite membranes. Cadmium removal efficiencies of 92.5% and 91% were obtained using the 1.5 wt% and 1 wt% C-TiO2-CFA/PAN nanocomposite membranes. A lead removal efficiency of 97% was obtained using PAN membrane with 2 wt% C-TiO2-CFA. Pb2+ removal efficiencies of 90.9% and 94.6% were obtained using the 1.5 wt% and 1 wt% C-TiO2-CFA/PAN nanocomposite membranes. The photoreduction activity was observed to decrease with an increase in cadmium and lead initial concentrations. A cadmium and lead removal efficiencies of 95% and 97% were observed at lower Cd2+ and Pb2+ initial concentrations (20 ppm), respectively. The removal efficiencies varied marginally with changes in pH values. The fouling activity of the C-TiO2 modified PAN asymmetric membranes and pure PAN was investigated by carrying out pure water filtration tests as well as bovine serum albumin (BSA) filtration tests. A bovine serum albumin rejection of 98% was obtained utilizing the 2 wt% CTiO2-CFA/PAN membrane.
- Full Text:
- Date Issued: 2020
Geological and geophysical investigations of groundwater resource in the area of Ndlambe Municipality, Eastern Cape Province, South Africa.
- Authors: Mpofu, Mthulisi
- Date: 2020
- Subjects: Groundwater Geophysical surveys
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18755 , vital:42730
- Description: Groundwater is an essential resource contributing extensively to overall total annual supply. However, overexploitation has depleted groundwater availability significantly and also brought about land subsidence at some places. The evaluation of groundwater potential zones is essential in protecting the quality of water and managing of groundwater structures. The Eastern Cape Province is one of the provinces faced with the challenge of supplying clean fresh water to the communities residing in it. Ndlambe municipality is a case in point where people rely on groundwater for agriculture and domestic activities. Few studies have been undertaken to evaluate groundwater resource in the study area. This study aims to assess groundwater resources as a way of achieving the goal of water sustainability. In the southeast of the Cape Fold Belt (CBF), is the Ndlambe municipality underneath folded Cape and Karoo Supergroup rocks. The rock sequence in the region reflects the geological history over a considerable period. In general, the area of study comprises of the Bokkeveld and Witteberg groups. The Bokkeveld comprises of shale along with sandstone whilst the Witteberg Group consists predominantly of quartzites with minor interbedded shales. The aims of the study were to target potential zones for groundwater exploration, analyse zones of lineaments, investigate the networks of fractures and the mineralogy of the area of study. In line with studies for groundwater exploration, a number of methods were undertaken for obtaining the results. These included literature review, remote sensing and geographic information system, thin section analysis, scanning electron microscope (SEM), X-ray fluorescence (XRF), structural analysis and geophysical investigations (magnetic and vertical electrical sounding). Potential zones for groundwater were identified using remote sensing techniques and geographical information systems (GIS). Maps were generated using GIS tools. Geology, slope, lineaments and Normalised Difference Vegetation Index (NDVI) were considered as parameters for determining groundwater potential zones. A geological and geophysical study was conducted in the Ndlambe municipality. Twelve samples for thin sections, 12 samples for XRF analysis and 4 samples for SEM analysis were collected at different locations in the area of study and were analysed. Thin section analysis revealed that quartz arenite has been metamorphosed to quartzite due to high pressure and temperatures and the cracks in the quartz grains are due to pressure and brittle deformation that has in turn enhanced secondary porosity resulting in joints and fractures which are good for groundwater movement. Scanning electron microscopy complemented the findings from optical microscopy by revealing splatter pores which are due to intense fracturing and these contribute to increasing permeability of the rock structures. XRF revealed the chemical composition of various rock types in the area of study. The analysed samples were dominated by silica reflecting their source from weathering of silicate rocks. The Chemical Index of Alteration (CIA) and Al2O3 values of the analysed samples reflected moderate to intensive weathering. In the study area, three main hydrogeologically important structures were taken into account. These included primary structures (bedding), contacts (geological) and secondary structures like fractures and folds. The study area comprises of several faults that are an important factor for porosity and permeability. The study area is dominated by blocky quartz veins that have been crushed due to compression hence higher permeability of groundwater. The Syscal Pro multichannel resistivity equipment was used to conduct the survey using the Schlumberger- Dipole-dipole array on three lines of varying length (350 m, 530 m and 340 m). Data collected were processed using RES2DINV software, producing a subsurface 2-D geoelectrical model from the pseudosections of apparent resistivity. Low resistivities in the study area were inferred to be weathered moist sandstone while low resistivities with depth indicated an overlying zone of fractured sandstone and quartzite which may be hosting some groundwater. An area of low resistivity zones between two large bodies suggests that the massive rock bodies are being weathered and fractured and fractures act as conduits for groundwater. High resistivity values indicate hard rock bodies that are unweathered hence low potential zone for groundwater localisation. The ground magnetic survey was used to delineate the subsurface structures as these control groundwater potential.
- Full Text:
- Date Issued: 2020
Household and business recycling programs as green strategies for waste management in East London, South Africa
- Authors: Fotoyi, Tenjiwe
- Date: 2020
- Subjects: Refuse and refuse disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18687 , vital:42706
- Description: Municipalities in South Africa generate enormous waste which is disposed of in a few landfill sites which, in turn, have a limited life span. Household recycling is one important mechanism that can be used to reduce the amount of waste that reaches overfilled landfill sites. The city of East London is running out of land to dispose waste, and their landfill sites, in particular, are filing up fast. Most of the waste generated, is recyclable, however recycling in the city remains fragmented, and is moving very slowly. This is because of the lack of a co-ordinated approach between the BCMM and the local communities, across the many suburbs of East London. Considering that urban areas have limited space, effective and efficient use of current landfills is of strategic importance. This research therefore will examine ways of improving recycling in East London, addressing challenges facing current recycling. Data for this study was collected from the random administration of 100 questionnaires on different categories of respondents in the study area. The study revealed that by the introduction of the “Hand-on-waste” programme, the waste management personnel have taken the first step towards household waste recycling. However, the level of awareness and knowledge of the public on domestic recycling was quite poor, if residents are given the necessary encouragement, motivation and recycling infrastructure waste minimisation would be achieved
- Full Text:
- Date Issued: 2020
Identification of differentially expressed proteins involved in wheat (Triticum aestivum) resistance against Russian Wheat Aphid (Diuraphis noxia) SA2 using SWATH-MS analysis
- Authors: Ntlokwana, Sitha Emmanuel
- Date: 2020
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18872 , vital:42888
- Description: Wheat (Triticum aestivum) is the second most-consumed cereal crop in the world, second only to maize. In South Africa it is mainly produced in three provinces; the Free State, Western Cape, and the Northen Cape. The average total land area used for wheat cultivation in these three Provinces, is 533 000 hectares, with a resultant annual production of between 1.3 to 2 million tons. The total wheat requirement in South Africa is currently 2.7 million tons according to the production of wheat guidelines published by the Department of Agriculture, Forestry and Fisheries, which is higher than the total annual production. One of the primary reasons that contribute to the lower production levels is insect and pest infestation, in particular, the Russian wheat aphid (Diurophis noxis), which can result in crop loss of up to sixty percent. Russian wheat aphids (RWA) are invasive insects that feed on the phloem of the plant through their specialised thin stylet-like mouthparts and release toxic agents contained in their saliva during feeding, which disrupt cellular functions inside the host plant. This damage leads to symptoms like; chlorosis, necrosis, wilting, stunting and curling of leaves, also known as leaf rolling. This study aimed to identify differentially expressed proteins in resistant and susceptible wheat (Triticum aestivum) cultivars during Russian wheat aphid Biotype South African 2 (RWA-SA2) infestation, in order to identify proteins involved in the wheat resistant mechanism against RWA-SA2. Two wheat cultivars SST398 (resistant to RWA-SA2) and SST356 (susceptible to RWA-SA2) were used, and a total number of 126 plants were planted and divided according to four different harvest times (Control day 0; day 5; day 7 and day 12). The wheat plants were infested with approximately 10 aphids per plant at the three-leaf stage, and placed within an insect cage inside a growth chamber (Conviron, Winnipeg, Canada) set at 24ºC, light intensity of 352 µmol.m-2.sec-1, ambient CO2 levels (410 ppm) and humidity of 60% with a 16h/8h day/night cycle. Wheat leaves were harvested at various time frames, and total protein extraction was performed. The protein samples were reduced with 10 mM dithiothreitol (DTT) and alkylated with 30 mM iodoacetamide (IAA). Sample clean-up and on-bead trypsin digest were performed on megReSyn Hilic columns, over four hours. The resultant peptides were vacuum dried and resuspended in 2% acetonitrile (ACN) before submitting them to LC-MS/MS (SWATH) for analysis. A total number of 611 proteins were differentially expressed, of which 19 were identified to be involved in the resistance response of wheat, and an additional 20 involved in biotic stress responses. This study showed that reactive oxidative species (ROS) such as hydrogen peroxide and hydroxyl radicals (OH-) play a significant role in the early stages of wheat resistance against RWA-SA2 infestation. They are involved in cell wall strengthening, activation of defence genes, involvement of phytohormone signals such as salicylic and jasmonic acid, which also mediates the systemic defences such as, systemic acquired resistance (SAR), leading to the expression of pathogen-related proteins such as (thaumatin-like proteins, oxalate oxidase, defensin, chitinase, and thionins). Although up-regulation of photosynthesis proteins such as (chlorophyll a/b binding protein, photosystem I and II, rubisco and divinyl chlorophyllide a, and 8 vinyl-reductase) were seen on both infested cultivars (susceptible and resistance), higher numbers of these classes of proteins were identified in the resistance cultivar, suggesting that they also play a critical role in resistance. In conclusion, the SWATH analysis used in this study was able to identify numerous proteins involved in the wheat resistance mechanism against RWA-SA2, most of which have not yet been reported to be involved in either biotic stress or RWA-SA2 resistance responses. Future studies are required to biochemically confirm the involvement of these enzymes and proteins the specific metabolic pathways where they are found, in the wheat resistance mechanism against Russian wheat aphid Biotype 2
- Full Text:
- Date Issued: 2020
Influence of Tamarix species on soil physicochemical properties and mapping its distribution and density using GIS in Western Cape, South Africa
- Authors: Mlahlwa, Asiphe
- Date: 2020
- Subjects: Tamarisks
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18588 , vital:42611
- Description: Tamarix ramosissima invasion is unarguably one of the worst ecological disasters in South Africa and is classified under category 1b by the National Environmental Management: Biodiversity Act 2014 (NEM: BA). The exotic Tamarix species was introduced in South Africa during the early 1900s as an ornamental or phytoremediating plant. This study was conducted to assess Tamarix distribution and evaluate its impact on soil physicochemical properties in two sites at Leeu River and Olifant River in Western Cape, South Africa. Samples were collected from Leeu River (which consists both the exotic and native Tamarix species) and Olifant River (only exotic Tamarix species). Three transects were laid from the water point outwards, with exotic Tamarix invading the river bank (first transect), the control on the open land (second transect) and the native Tamarix at the far end of the study site (third transect) in Leeu River. In Olifant, transects were laid according to the degree of invasion, low Tamarix density transect was referred to as T1, the medium as T2 and the high density as T3. Soil samples from each transect were taken from three points, at three soil depths (0-10, 10-20 and 20-30 cm) during winter and summer. Soil physiochemical properties such as soil pH, electro-conductivity (EC), total nitrogen (TN), total carbon (TC), soil organic carbon (SOC), sodium (Na+ ), potassium (K+ ), Calcium (Ca2+), Magnesium (Mg2+), bulk density, soil texture and sodium adsorption ratio (SAR) were determined. Soil chemicals properties including EC, Na+ , SAR, K+ and Mg2+ were found significantly higher under the native and the exotic Tamarix species when compared to Tamarix free soils. In general, salinity of surface soils (0–10 cm) was greater than those in the deeper soils with 5.05 mS/cm and 4.73 mS/cm observed under exotic and native Tamarix species, respectively. High levels of EC, K+ , Ca2+, Na+ , SAR, TN, TC and SOC were observed under T3, followed by T2 with the lowest being recorded in T1 at 0-10 cm. Unlike the soil EC, the effect of Tamarix density on soil pH at 0-10 cm soil profile was not significant. Alterations of soil physicochemical properties were more pronounced under the high Tamarix density as compared to the low invasion. Increased in distance from the river was related to a higher density of the invasive species and also topography had a major role in the change of species density. An increase in Tamarix density, results in high leaf litter which in turn results in salinity and soil nutrient at 0-10 cm. Soil salinity was dramatically increased under Tamarix species. Tamarix species are capable of altering the soil properties making it conducive for their growth.
- Full Text:
- Date Issued: 2020
Investigating carcass characteristics, meat quality and ageing effects on physicochemical attributes, lipid oxidation, and degradation of muscle proteins in mature beef and dairy cull cows
- Authors: Mpala, Bukhosi
- Date: 2020
- Subjects: Meat -- Quality Dairy cattle
- Language: English
- Type: Thesis , Masters , MSc (Animal Science )
- Identifier: http://hdl.handle.net/10353/18777 , vital:42732
- Description: This study aimed to examine carcass characteristics, meat quality and postmortem ageing effects on physicochemical properties, lipid oxidation and muscle protein degradation in dairy and beef cull cows. Three cattle genotypes representing dairy {Holstein-Friesian (HF)}, beef {Bonsmara (BON)}, and a mixed purpose genotype {South Devon × Aberdeen Angus crossbreed (SD × AA)} were selected at a commercial abattoir lairage and used for this study. From each genotype, mature cows falling into the C-age class were then randomly chosen consisting of 24 HF, 31 BON and 26 SD × AA. The South African red meat classification system was used to evaluate carcass parameters, while objective measurements associated with meat quality {i.e., pH, colour (CIE L*, a*, b*), water holding capacity (WHC) and Warner-Bratzler shear force (WBSF)} were assessed in the M. longissimus thoracis et lumborum (LTL) muscle. Also, six cows were selected from each genotype within a carcass weight range of 290 ± 5 kg and fat score (FS) and conformation score (CS) of 2 and 3 respectively, and their meat was aged in a 4 ℃ chiller for 1, 7 or 14 days. At each ageing period, steaks were evaluated for pH, colour, WHC, WBSF and lipid oxidation. Furthermore, sub-samples were cut from each aged steak, vacuum-sealed, and stored in a freezer at -20 ℃ until needed for the determination of protein solubility and degradation of myofibrillar and sarcoplasmic proteins. Study results showed that the HF had a significantly (P < 0.05) lower dressing percentage than the BON and SD × AA. A total of 59% of the cull cows yielded lean carcasses, while 33% and 4% had a medium and fat subcutaneous fat score, respectively. The Holstein-Friesian recorded carcasses that had a fat score of 0 (2%) and a fat score of 1 (4%) while the Bonsmara had 20% C2, 16% C3 and 2% C4 carcasses, respectively. Most of the carcasses (78%) had a medium CS with the BON and SD × AA making up to 37% and 30%, respectively. All the measured meat quality attributes showed significant differences (P < 0.05) among the three cattle genotypes, except b*, hue angle and thawing loss. Notably, the HF recorded higher (P < 0.05) L*, a* and drip loss values but had a lower WBSF than the BON. The findings of the present study also showed that meat pH, colour traits, purge loss, lipid oxidation, cooking loss and WBSF were significantly (P < 0.05) influenced by post-mortem ageing and genotype. Except for SD × AA, WBSF only showed a significant decrease after 14 days of ageing. Moreover, significant (P < 0.05) ageing and genotype effects were observed on protein solubility and degradation of sarcoplasmic and myofibrillar proteins. One dimensional gel electrophoresis revealed the presence of several protein bands 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper with molecular weights ranges of 16 - 250 kDa and 12.5 – 166.6 kDa in the myofibrillar and sarcoplasmic protein extracts, respectively. The staining intensities of some the protein bands were significantly (P < 0.05) influenced by ageing and cattle genotype. In conclusion, the present study observed that carcass characteristics and meat quality traits vary among cattle genotypes with different production use. The data also revealed that physicochemical characteristics and degradation of muscle proteins is related to both cattle genotype and postmortem ageing. It is recommended that the meat of mature cull cows be aged under vacuum conditions for up to 14 days to improve its tenderness.
- Full Text:
- Date Issued: 2020
Joint Modelling Inference for Longitudinal and Time To Event Data with Application to Biomarkers in Medical and Clinical Studies
- Authors: Azeez, Adeboye Nurudeen
- Date: 2020
- Subjects: Biochemical markers Bayesian statistical decision theory
- Language: English
- Type: Thesis , Doctoral , PhD (Biostatistics)
- Identifier: http://hdl.handle.net/10353/18476 , vital:42543
- Description: In the past couple of decades, longitudinal and survival data analysis have emerged as important and popular concepts of biostatistics and statistics for disease modelling. In recent years, these two statistics concepts have been combined to develop a joint model for longitudinal and survival data analysis. The Joint model is a simultaneous modelling application of longitudinal and survival data while taking into account a possible association between them. In this thesis, three sub-topics (Conditional score approach, estimating equation approach, and modified Cholesky decomposition approach) are utilised to model the association if the independence assumption is violated. Using the conditional score approach, the study investigated the association between longitudinal covariates and the time-to-event process to examine the within-subject measurement error that could influence estimation when the assumption of normality and mutual independence is violated. Given the assumption violation, I proposed an estimating equation approach based on the conditional score to relax parametric distributional assumptions for repeated measures of random effects. I jointly modelled the time-dependent biomarkers and event times using the Cox model with intermittent time-dependent covariates measure, in which the longitudinal model was used to characterize the biomarker underlying (unobservable) trajectory and incorporated as a latent time-dependent covariate in the survival model to predict failure times. Estimates of the parameters were obtained by a restricted maximum likelihood estimate (REML). A modified Cholesky decomposition method was used to capture the within-subject covariance for a positive definite and symmetric matrix, with the assumption that the observed data from different subjects are independent. I illustrated the proposed method by a real data set from a lung study and simulation. An extension to the joint model of longitudinal-survival data was also proposed, in which the longitudinal data has a cumulative and weighted effect on the hazard event function. Using a Bayesian parametric method, I proposed a skewed weighted probability density function to estimate the parameters. The weighted cumulative effect used enabled different longitudinal profiles to be incorporated over time in calculating the hazard ratio between the subjects. The proposed functions provide greater flexibility for modelling the association structure of different longitudinal and survival sub-model. The focus was on the association between the biomarker (serum creatinine, sCr) and the development of end-stage renal disease (ESRD). Since the effect of sCr biomarker is anticipated to be a cumulative effect, with the development of sCr biomarker over time leading to progressively higher damage of the kidney. The approach was applied a simulation for validation of the proposed method
- Full Text:
- Date Issued: 2020
Laypersons’ perceptions and livelihood uses of invasive alien species (Opuntia ficus-indica) in the Eastern Cape Province, South Africa
- Authors: Mdweshu, Luleka
- Date: 2020
- Subjects: Opuntia ficus-indica
- Language: English
- Type: Thesis , Masters , MSc (Botany)
- Identifier: http://hdl.handle.net/10353/18720 , vital:42727
- Description: Opuntia ficus-indica is a succulent plant species that originated from Mexico and parts of neighbouring middle-America and introduced in South Africa by white settlers in the eighteenth century. The species is now categorized as invasive in South Africa but has both commercial and non-market uses. This study evaluated the livelihood uses and local perceptions of O. ficus-indica of rural residents in Makana, Ngqushwa and Raymond Mhlaba Local Municipalities in the Eastern Cape province in South Africa. Data on the livelihood uses and local perceptions on the species in the study area were gathered through community focus group discussions and household surveys using semi-structured questionnaires between June 2018 and August 2019. A sample of 150 participants selected via snowball-sampling technique provided detailed accounts on utilization of O. ficus-indica in the study area. The importance of O. ficus-indica as a useful plant species was ubiquitously perceived, with all respondents reporting its contribution towards their livelihood needs and more than three quarters (88.0%) using the species on a regular basis. Majority of the respondents (41.0%) regarded O. ficus-indica as an important source of cash income while about a third (33.0%) regarded the species as an important source of food products and nutrition. Interviews with respondents revealed that O. ficusindica is currently being harvested from the wild with 73.3% of the respondents reporting that the abundance of the species was decreasing. The positive socioeconomic contributions of O. ficus-indica need to be taken into account when assessing the costs resulting from invasions caused by alien plant species. This study is a crucial starting point in trying to understand and initiate the management of alien invasive species such as O. ficus-indica. Results of this study are also important for understanding local peoples’ perceptions of new introductions and management of existing alien plants in the province.
- Full Text:
- Date Issued: 2020
Mineralogy, geochemistry and pebble morphology of the Katberg Formation around Graaff Reinet and East London, Eastern Cape province of South Africa
- Authors: Ndlazi, Nondumiso Zandile
- Date: 2020
- Subjects: Mineralogy|
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18631 , vital:42615
- Description: The Katberg Formation forms the upper part of the Tarkastad Subgroup in the Beaufort Group of the main Karoo Supergroup. The Katberg Formation consists of siliciclastic sedimentary rocks mostly dominated by greyish sandstone, red mudstone with minor siltstone occurrences. The Katberg Formation also consists of calcareous and ferruginous concretions that formed during diagenesis. Braided streams deposited the Katberg Formation with a predominantly sand bed load. The Katberg Formation sandstones contain pebbles with no true conglomerates identified in the study area. This study was conducted in the Katberg Formation to understand the mineralogy, geochemistry, and pebble morphology around Graaff Reinet and East London areas. The major and trace elements were analyzed through X-Ray Fluorescence (XRF) to deduce the source rock provenance, tectonic setting, paleo-weathering conditions, climatic conditions, and sediment maturity. The X-Ray Diffraction (XRD) was used to highlight a detailed distribution and variation of mineralogical polymorphs of the minerals present in sandstones and mudstones. The pebble morphology was used to confirm the depositional environment of the Katberg Formation. The use of The bivariate plots of the Maximum Projection Sphericity Index (MPSI) and the Oblate-Prolate Index (OPI) showed that 79 % of pebbles fall in the fluvial environment, whereas 21 % of pebbles fall in the beach environment. A small proportion of beach pebbles within the Katberg Formation suggests that the river reached the marginal marine environment during its flow. The majority of the pebbles yielded a bladed shape with a dominating Sphericity Index symptomatic of fluvial sediments. All the bivariate plots illustrate the fluvial depositional environment for the sediments of the Katberg Formation. Petrographic studies based on the prepared 15 thin sections indicated that the Katberg Formation rocks are dominated by quartz, feldspar, and clay minerals. However, they show more plagioclase feldspar than k-feldspars. The grains are poorly sorted and immature, with irregular grain sizes and shapes. The angularity of clasts indicates that the grains have travelled shorter distances. The abundance of feldspar minerals suggests that the arkose sandstone was derived either from situ or from a short distance. The albitization of plagioclase to illite and the replacement of plagioclase feldspars by calcite and laumontite is very common in the Katberg Formation, which points out deep burial diagenesis. The XRD analysis revealed the occurrence of 14 minerals in the siliciclastic rocks of the Katberg Formation, namely: quartz, albite, clinochlore, muscovite, phlogopite, annite, illite, orthoclase, anorthoclase, laumontite, calcite, and ankerite. Amongst these minerals, albite, clinochlore, muscovite, and phlogopite show variation in crystal forms known as polymorphs. Geochemical analysis of the Katberg Formation sandstones and mudrocks revealed that all samples show a high concentration of SiO2, Al2O3, Fe2O3, K2O, Na2O, CaO, and MgO. The trace elements: TiO2, MnO, P2O5, BaO, SrO, ZrO2, and V2O5 are depleted with values ranging below 1 wt %. The geochemical classification of the Katberg Formation sandstones revealed the origin from wacke and arkose sources. The geochemical diagrams and indices of paleoweathering conditions suggested that the Katberg Formation underwent a moderate degree of chemical weathering. The geochemistry revealed that the sediments were 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper deposited during the arid climate conditions. The studied sandstone and mudstone samples pointed an active continental margin and passive margin tectonic setting of the Katberg Formation.
- Full Text:
- Date Issued: 2020