Faculty of Science (ETDs)

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Sex and age related distinctions in the feeding ecology of the African elephant
(2010-01-29T08:19:33Z) Greyling, Michelle Deborah
Control of serine dehydratase activity in rat liver
(University of the Witwatersrand, Johannesburg, 2015-02-24) Abed, Suliman; Manchester, K.L.
Gluconeogenesis from amino acids in the liver is enhanced when the utilisation of glucose is limited under various hormonal and dietary conditions, such as diabetes, starvation or administration of a carbohydrate free diet. Pyruvate is of great importance as a carbon source for gluconeogenesis, since the sequence of gluconeogenic reaction is initiated by carboxylation of pyruvate to oxaloacetate. From this point of view, an important physiological role is suggested for serine dehydratase, which catalyses the degradation of serine to pyruvate and ammonia. The relationship of serine dehydratase levels to gluconeogenic activities, however, is poorly understood, A study of the hormonal and dietary control of serine dehydratase activity was carried out in vivo and in vitro in rat liver. Serine dehydratase was assayed by the colorimetric method of Suda and Nakagawa (1971) and the enzymatic method of Wimhurst and Manchester (1973). Both these methods have been found to be suitable since they are in agreement with each other and also give results which compare favourably with other published values. Activities of serine dehydratase from fresh liver and in slices of liver cultured for various periods have been compared. Also a study of the activity of another soluble enzyme, lactic dehydrogenase, was undertaken and the in vivo and in vitro levels were compared.
Characterisation of a geothermal resource at Kwako Hills in Zambia using magnetic and natural source audio magnetotelluric methods
(University of the Witwatersrand, Johannesburg, 2019) Chinamora, Blessing; Dr Jones, Mike; Prof Webb, Susan
The announcement by the Zambian government that geothermal energy will be recognized as an energy source in the 2013 national budget drew a lot of attention to investors and scientists. Since the 1950s reconnaissance geoscientific surveys have been carried out on geothermal targets in Zambia by the Geological Survey of Zambia (GSZ). The GSZ, together with an Italian company (DAL, SpA), studied various hot springs (Legg, 1974) and as a result, various prospects have been considered for development or exploration. In this research, the Kwako Hills prospect which is located near Mumbwa district, about 150 km northwest of Lusaka, hosts two hot springs which are good surface manifestations for geothermal energy potential was investigated for its geothermal energy reservoir potential using magnetic and natural source audio-magnetotelluric (NSAMT) geophysical methods. The focus of these surveys was on examining the structural controls that govern the occurrence of the hot springs and the outcropping Hook Batholith just to the north of the east-west trending alluvium filled valley. The northern branch of the alluvium valley has a northwest–southeast trend which is the same as the minor fault controlling the two hot springs. These structural controls increase the vertical permeability in the area causing the thermal waters to circulate to depths where they acquire their heat. Permeability is high at intersections of faults and fracture zones, intersection of major and minor faults or intersection of faults and sedimentary aquifers. Major ENE and NE trending faults were mapped along the Mwembeshi Shear Zone and the boundary between the Hook Batholith and the Katanga sediments respectively. The area is underlain by foliated basement granitic gneiss, Hook Batholith granites and Katanga metasediments that are broken into fractures along the foliation trends that control the occurrence and flow of rivers and streams. Overlying the basement rocks are the recent Karoo and Kundelungu sediments which are also permeable along the bedding or cleavage planes. The vegetation pattern, flow and occurrence of rivers or streams reflect trends of zones of weakness in the basement. Fractured zones developed along these foliations and were mapped at outcropping scale using Google Earth, aeromagnetic and ground magnetic data interpretation. Interpretation of aeromagnetic data confirmed the foliation trends that were suggested by Abell (1970) and Naydenov et al. (2014). One dimensional (1D) and two dimensional (2D) magnetotelluric (MT) resistivity models were created on the basis of a 120 MT sounding data set. A dimensionality and distortion analysis of the NSAMT data was carried out based on the approach of Groom and Bailey (1989) and it was concluded that the data were collected almost perpendicular to strike, which is also supported by the geological mapping. MT smooth inversion models showed the lateral and vertical extent of the potential geothermal reservoir. Different 2D MT inversion approaches were applied to investigate the lateral continuity of the conductive sedimentary layer of the Kundelungu unit (slate, siltstone and shale). In order to map the subsurface structure of the area, a magnetic model was then produced using the acquired ground magnetic data and constrained using magnetic susceptibility measurements, MT data and geology mapped on the surface. Magnetic data interpretation confirmed an NW-SE fault controlling the hot springs, which was mapped using the NSAMT inversion results. The research shows that there is a lateral conductive, water saturated zone (reservoir) present between 150 m and 550 m depth and deeply seated faults in the basin. Along the deeply seated faults the conductive zones are vertical and continue with depth. The information shows that the thermal waters of the hot springs appear to circulate to depths more than 2.5 km along deep seated faults and foliation fractures penetrating the foliated rocks of the Hook Batholith and basement rocks. This water is heated by the regional geothermal gradient of 23ºC/km. Further exploration can be carried out on the study area to prove its potential for a geothermal resource.
A comparative analysis of classic Geometrical methods and sparse regression methods for linearly unmixing hyperspectral image data
(2019) Nicolae, Aurel
This research report presents an across-the-board comparative analysis on algorithms for linearly unmixing hyperspectral image data cubes. Convex geometry based endmember extraction algorithms (EEAs) such as the pixel purity index (PPI) algorithm and N-FINDR have been commonly used to derive the material spectral signatures called endmembers from the hyperspectral images. The estimation of their corresponding fractional abundances is done by solving the related inverse problem in a least squares sense. Semi-supervised sparse regression algorithms such as orthogonal matching pursuit (OMP) and sparse unmixing algorithm via variable splitting and augmented Lagrangian (SUnSAL) bypass the endmember extraction process by employing widely available spectral libraries a priori, automatically returning the fractional abundances and sparsity estimates. The main contribution of this work is to serve as a rich resource on hyperspectral image unmixing, providing end-to-end evaluation of a wide variety of algorithms using di erent arti cial data sets.
Synthesis and characterization of novel short antimicrobial peptides with wound healing properties
(University of the Witwatersrand, Johannesburg, 2019) Machumele, Khanani Peggy; Makatini, Maya Mellisa
In recent years, there has been an increasing health crisis due to multidrug-resistant microbes. These pathogens are strains of bacteria that have become resistant to antibiotic drugs. In the year 2016, the World Health Organisation (WHO) had appealed to the members of states in the USA to create a priority list of other bacteria that are resistant to antibiotics in order to support research and development of effective drugs. According to literature, antimicrobial peptides have the potential to be potent agents against pathogens that have multidrug-resistant properties. Despite these studies, there are still substantial limitations (toxicity and susceptibility to proteases) that have affected their clinical and commercial development. In this study, the focus was on bacteria that infect wounds. The lack of potent chronic wound treatment has resulted in an enormous financial and physical burden on patients and the health care system. The stress of multi-resistant microbes heighten the challenges plagued on a patient due to untreatable infected wounds. Peptides which are able to kill bacteria and promote the wound healing process would greatly benefit patients. For example, patients with diabetic foot ulcers are prone to chronic wounds because of their condition, which may lead to amputation. Wound healing antimicrobial peptides are able to kill bacteria in the wound and induce the formation of collagen which will result in fewer amputations. The aim of this proposed research is to develop novel wound healing and antimicrobial compounds by derivatizing bioactive peptides into selective and protease-stable peptidomimetics. Tigerinin RC1 is an antimicrobial peptide with wound healing properties. It was chosen as a starting point for the design of analogues with drug-like properties and it was also conjugated to silver nanoparticle (AgNPs) to improve its bactericidal activity. In this study, 16 Tigerinin RC1 peptide analogues were successfully synthesized using the solid phase peptide synthesis strategy. Peptides were purified using the semi prep-HPLC however, the desired purity of > 90% was only achieved after two or more purification runs. Thus only 4 of the peptide analogues had a purity great than 90% which were KM-PEP-carb, KM-PEP-cyc-amide, KM-PEP-ada and KM-PEP-CT. These peptides were tested for antimicrobial activity and KM-PEP-cyc-amide peptide showed promising results with the minimum inhibitory concentration of 128 μg/ml against P. aeruginosa. Cytotoxicity studies also revealed that conjugation of KM-PEP-carb to AgNPs improved cytotoxicity because when 25 μg/ml of KM-PEP-carb was tested against human T cells the cell viability was -1.48% and when conjugated to AgNPs the cell viability increased to 35.17.
Investigating 2-hydroxypropyl-β-cyclodextrin (HPβCD) as a novel therapeutic agent for breast cancer
(University of the Witwatersrand, Johannesburg, 2019) Saha, Sourav Taru; Kaur, Mandeep
Cancer cells have an increased need for cholesterol, which is required for cell membrane integrity. Cholesterol accumulation has been described in various malignancies including breast cancer. Cholesterol has also been known to be the precursor of estrogen and vitamin D, both of which play a key role in the histology of breast cancer. Elevated cholesterol levels have been linked to breast cancer therefore depleting cholesterol levels in cancer cells can be a viable strategy for treatment. 2-hydroxypropyl-β-cyclodextrin (HPβCD) is a cholesterol depleting compound which is a cyclic amylose oligomer composed of glucose units. It solubilizes cholesterol and is proven to be toxicologically benign in humans. This led us to hypothesise that it might deplete cholesterol from cancer cells and may prove to be a clinically useful compound. Our work provides experimental evidences to support this hypothesis. We identified the potency of HPβCD in vitro against two breast cancer cell lines: MCF7 (Estrogen positive, ER+), MDA-MB-231 [Triple negative breast cancer (TNBC)], and compared the results against two normal cell lines: MRC-5 (Normal Human Lung Fibroblasts) and HEK-293 (Human embryonic kidney) using cytotoxic, apoptosis and cholesterol based assays. HPβCD treatment reduced intracellular cholesterol resulting in significant breast cancer cell growth inhibition through apoptosis. The results hold true for both ER+ and TNBC. We have also tested HPβCD in vivo in MF-1 mice xenograft model and obtained 73.9%, 94% and 100% reduction in tumour size for late, intermediate and early stage TNBC. These data suggest that HPβCD can prevent cholesterol accumulation in breast cancer cells and is a promising anti- cancer agent
Application of integrated methods to assess and characterise the hydrogeology of coastal aquifers in parts of Lagos, Southwest, Nigeria
(2020) Yusuf, Mumeen Adebayo
The scope of this Thesis was to apply integrated methods to characterise the groundwater systems of the Lagos Coastal Basin. Like every coastal area in the world, saline intrusion has been the major challenge threatening the fresh groundwater aquifers of the study area over the last couple of decades, and thus, necessitating its assessment. Environmental isotopes, being a reliable and standard tool in hydrological investigation, was employed in combination with geophysical and hydrogeochemical methods to study the coastal aquifer systems. Geophysical probing of the subsurface revealed an alternating sequence of clay and sand, constituting the major lithological units in the study area. The basin aquifers are hosted essentially by sands and clayey sand, while the modes of aquifer occurrences are unconfined to semi-confined and confined for shallow and deep aquifers, respectively. Hydrochemical interpretation identified a surficial thin layer of fresh groundwater overlying the main zone of saline intrusion, which essentially comprises Ca-HCO3 and Ca-Mg-HCO3, Ca-Mg-HCO3 and Ca-Mg-Cl-SO4 hydrochemical facies for both dry and wet seasons, whereas the surface waters are characterised by Mg-Cl and Na-Cl water types for the lagoon and the ocean, respectively. The evaluation of the chemical processes revealed the dominance of carbonate weathering in the shallow aquifer. Hydrochemical, statistical and geochemical model analyses identified that the groundwater chemistry is significantly controlled by water–rock interaction and ion exchange processes as well as anthropogenic activities. Stable isotopes revealed precipitation as the main source of recharge into the basin aquifer systems. Analyses of the 3 H and 14 C activities were in agreement, revealing an interesting fact about the increase in the groundwater residence time from the surface through deeper depths deducible from 3H values range between 0.1 TU and 2.8TU; 0.0 TU and 0.3 TU; and 14 C age range from 4350±10 to 1050±10 years and between 12030±69 and 7400±50 years for the shallow and deep aquifers, respectively. The mean residence time was supported by the aquifer systems‟ recharge which took place in Holocene for the shallow aquifer and Late Pleistocene–early Holocene for the deep aquifers evident from the calculated ambient temperature, 18 O and 14 C plots. The hydrogeological conceptual models showed that saline incursion severely impacted the second aquifer from a depth ≥20m to 170m in the western and central parts of the study. However, the observed local saline occurrence in places <20m was attributed to groundwater overexploitation. Conclusively, the hydrological systems of the Lagos coastal basin is continually being modified by both anthropogenic and natural activities that constitute not only a major threat to the groundwater sustainability of the Lagos coastal basin but can also consume the entire study area
Remote sensing survey of archaeological sites in the Shashi- Limpopo Region
(2020) Thabeng, Olaotse Lokwalo
The African continent is rich with archaeological heritage, which needs to be preserved for the current and future generations. The majority of archaeological heritage sites in Africa are facing disappearance due to a number of challenges including looting, destruction from developments, expansion of agricultural land and natural hazards. Documentation and monitoring of archaeological heritage sites, therefore, is of paramount importance for effective site management and preservation. However, archaeological heritage sites in the continent are poorly documented and monitored due to a number of factors including lack of funds by heritage management institutions, lack of trained personnel and inaccessibility of some areas due to conflicts or land ownership rights. Traditionally, the documentation and monitoring of archaeological heritage sites in Africa have been done through fieldwork, which is costly, time-consuming and difficult to carry out over large areas. Remote sensing offers a relatively fast, cheap, systematic and reproducible method of surveying and monitoring archaeological sites over large and/or restricted areas. Remote sensing techniques are used to identify earth surface features based on their spectral signature, which is the variation of reflection or emittance of materials’ electromagnetic energy. Spectral signatures for identifying archaeological sites are not universal, and an assessment of the applicability of remote sensing techniques in different archaeological landscapes is needed. The aim of this study, therefore, was to investigate the potential of using remote sensing techniques to document archaeological sites previously occupied by farming communities, which are traditionally associated with the Iron Age period in Southern Africa, using the Shashi-Limpopo case study. The first part of this study gives a review of the use of remote sensing in the African archaeological context. Despite it being a fast, cost-effective and systematic method of survey, the results of this study have demonstrated that remote sensing is not widely used in archaeological applications in Africa. The aforementioned situation calls for studies investigating the potential of using remote sensing techniques to fast track archaeological site survey, documentation and monitoring in the continent. The chemical composition of materials characterising different features have more or less subtle variations that, in turn influence the spectral behaviour of soil. This is an important principle that can be used for distinguishing archaeological soils from non-archaeological soils and can potentially help in discriminating different archaeological signatures. As such, the second part of this study investigated the possibility of using field spectrometer measurements to discriminate middens, non-vitrified dung, vitrified dung and non-sites (natural soils) characterising archaeological landscapes previously occupied by farming communities. It then investigated the presence of differences in the chemical composition of elements between middens, non-sites, vitrified dung and non-vitrified dung. The findings indicated that there is a statistically significant difference in the concentration of soil elements between non-sites, middens, vitrified dung and non-vitrified dung byres. They also indicated that some bands in the visible and shortwave infrared regions of the electromagnetic spectrum important bands for predicting the aforementioned archaeological sites and non-archaeological sites. In the third part of this study, the ability of multispectral sensors to discriminate archaeological and non-archaeological features in Shashi-Limpopo confluence area was investigated using field spectral data resampled to the spectral resolutions of common multispectral satellites namely GeoEye, Landsat 8 OLI, RapidEye, Sentinel-2, SPOT 5 and WorldView-2. This is because the spectral and spatial resolutions of various multispectral sensors determine the size and the type of archaeological data a sensor can detect. As such, another goal of this study was to identify multispectral sensors with the optimum spectral resolutions for detecting middens, non-vitrified dung, vitrified dung and non-sites. Additionally, the performance of advanced classification algorithms (random forest and support vector machines) in discriminating middens, non-vitrified dung, vitrified dung and non-sites was also investigated. The results proved the possibility of using multispectral satellites in mapping middens, non-sites, vitrified dung and non-vitrified dung sites. These results initiated the need to upscale the test to actual satellite images. The fourth part of this study assessed the possibility of prospecting for archaeological sites previously occupied by farming communities in the Shashi-Limpopo Confluence Area, using a very high-resolution satellite WorldView-2 image. The findings have shown that WorldView-2 satellite images and advanced classification algorithms can be used in prospecting for archaeological sites previously occupied by farming communities in Shashi-Limpopo Confluence Area. Finally, the ability of geographic object-based image analysis (GEOBIA) based on random forest and support vector machines, to discriminate archaeological and non-archaeological features on a very high-resolution satellite WorldView-2 image was investigated. The results of this study demonstrated the robust ability of the GEOBIA to integrate spatial attributes into the classification model improves the chances of separating materials with limited spectral contrast. Generally, this study has shown that remote sensing techniques can be used to map archaeological landscapes characterised by middens, non-vitrified dung, vitrified dung and non-sites. This will help archaeological heritage managers and researchers to document and monitor sites in archaeological landscapes characterised by the aforementioned features in a fast, systematic, reproducible and cost-effective manner
Resolvability of groups
(University of the Witwatersrand, Johannesburg, 2020) Ndhlalane, Mororiseng
A topological group is called resolvable if it can be partitioned into two dense subsets. A group is absolutely resolvable if it can be partitioned into two subsets dense in any nondescript group topology. The aim of this dissertation is to give a unified exposition of some major results about resolvability of groups. In particular, we show that; 1. Every countable nondescript topological group not containing an open Boolean subgroup is resolvable, 2. Every infinite Abelian group not containing an infinite Boolean subgroup is absolutely resolvable.
Climate change and heritage tourism: threats to Makgabeng in a regional context, Limpopo South Africa
(2020-11) Mcpherson, Fazlin Ahdielah
The Makgabeng area is situated in the north-west corner of the Limpopo province in South Africa. The Makgabeng area is an emerging tourist destination with a variety of activities to offer. The area is rich in ancient rock art sites and, as a result, has great potential for the development of heritage tourism. Extensive research has been conducted on the rock art in this region. However, the impact of climate change on heritage tourism has not yet been explored. The local community of the Makgabeng area is developing a heritage tourism destination within the region and it is important to determine whether the initiative will be sustainable, especially in the context of climate change threats to the region. In a region such as Makgabeng where the primary attraction is natural heritage tourism rather than cultural, this then poses a severe threat to tourism within the region, especially since most of these attractions are outdoors. Hence, this research project is primarily aimed at determining climate change threats to heritage tourism in the Makgabeng region, South Africa. The research has employed a mixed-method approach consisting of interviews done with various stakeholders within the tourism industry and community members in the Makgabeng region. The other methods used are hard-copy and online questionnaires, TripAdvisor reviews, and the Tourism Climatic Index (TCI). What the research has found is that people do not know that Makgabeng exists, and for those who are aware of its existence they have never visited the region. this is because the area is not being marketed effectively. The TCI scores show that winter is the best time of the year for tourism. Consequently, stakeholders and community members should market the area with this in mind. However, tourists have said they enjoy the weather in the region all year round.
Trimetallic nanoparticles immobilised on polymeric membranes for the degradation of organic pollutants in water
(University of the Witwatersrand, Johannesburg, 2021) Kgatle, Masaku; Moloto, Nosipho; Sikhwivhilu, Keneiloe; Ndlovu, Gebhu
Water is one of the most essential resources in the world, but its scarcity has become an issue of global concern. The scarcity of water is largely the result of climate change, water pollution and increasing population growth which limits the availability of water resources. Moreover, South Africa has been making headlines since 2010 due to water shortages experienced. It is, therefore crucial to find cost-effective ways to expand the water supply and address the issue of water pollution. This study seeks to tackle the problem of water pollution emanating from textile industries. Over the last few years, nanotechnology and membrane technology have appeared as some of the most widely used methods for the mitigation of water pollution problems. Particularly, nanoscale zerovalent iron (nZVI) has emerged as one of the most broadly used nanoparticles in wastewater treatment and remediation owing to its low-cost and high effectiveness. However, because of its ease of aggregation and consequent loss of reactivity, nZVI is coupled with one or more transition metals to produce multimetallic systems. Nanoparticles alone quickly agglomerate and form large micro-scale particles owing to the magnetic forces thus losing their mobility and chemical reactivity. To avoid these issues, the nanoparticles are stabilized on polymeric membranes. In this study, two trimetallic nanoparticle systems were synthesized, characterized and tested for catalytic activity. The polyvinylpyrrolidone (PVP)-stabilized Fe/Cu/Ag nanoparticles were synthesized by the sodium borohydride chemical reduction method. These nanoparticles were characterized using XRD, XPS, EDX and TEM. The XRD, EDX and XPS techniques showed the presence of all three metals, including iron oxides due to the oxidation of iron in air. The obtained TEM images showed the characteristic core-shell morphology of the nZVI-based nanoparticles. The evaluation of the catalytic activity of the nanoparticles was conducted using methyl orange (MO) dye as the model pollutant and this showed a remarkable degradation efficiency within few minutes. The effect of parameters such as MO solution pH, initial MO dye concentration and nanoparticle dosage in MO degradation was investigated. The nanoparticles were found to have performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The degradation of MO dye was monitored using UV-Vis analysis and occurred within 1 min. The degradation was found to follow a pseudo first-order kinetic model and was vastly influenced by the studied parameters. The analysis of by-products and reaction pathway were done using LC-MS and this further confirmed that the degradation of MO was indeed rapid. The Fe/Cu/Ag trimetallic nanoparticles were demonstrated as suitable and effectual alternative for the remediation of textile dye wastewater. For the second trimetallic system, three different trimetallic nanoparticles (Fe/(Zn/Ag), Fe/Zn/Ag and Fe/ Ag/Zn) with different metal addition sequences were synthesized. The prepared nanoparticles were characterized using XRD, EDX and TEM analyses. The techniques proved successful synthesis of the nanoparticles and XRD and EDX showed the presence of the three metals together with the oxides. The evaluation of the catalytic reactivity of the nanoparticles was conducted in a series of batch experiments using MO dye as the model pollutant. About 100% of the MO dye was degraded by Fe/ Ag/Zn trimetallic nanoparticles within 1 min and the second-order rate constant obtained was 0.0744 ppm- 1min-\ the rate of reaction was higher than that of the other trimetallic systems. Using Fe/ Ag/Zn trimetallic nanoparticles, parametric tests were conducted at different MO solution pH, initial MO concentration and nanoparticle dosage. The results showed that the reactivity of the Fe/Ag/Zn trimetallic nanoparticles was highly dependent on the aforementioned parameters. Like the Fe/Cu/Ag system, the Fe/Ag/Zn performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The overall kinetic study showed the removal of MO using Fe/Ag/Zn system to follow a second-order kinetic model. The elucidation of the degradation pathway and MO by-products identification were done using LC-MS and the mechanism of degradation displayed the degradation of methyl orange to proceed via azo-bond cleavage. Moreover, the Fe/ Ag/Zn nanoparticles proved to be effective at degrading methyl orange dye and can be used to treat azo-dye wastewater from textile industries. The Fe/Cu/ Ag trimetallic nanoparticle system was immobilized on a polymethacrylic acid grafted polyethersulfone (PMAA-g-PES) membrane to minimize the issue of recoverability and nanoparticle agglomeration. The nanocomposite membranes were prepared by loading different quantities of Fe/Cu/Ag trimetallic nanoparticles onto the PMAA-g-PES membrane for optimization purposes. Characterization was performed using FTIR, NMR, XPS, SEM/EDS and AFM analyses. The PMAA g-PES and nanocomposite membranes were found to have a porous top layer and a rough surface. Moreover, the addition of nanoparticles did not cause any significant changes in the membrane structure, however, further addition of nano particles led to the blockage of pores. The performance of the synthesized membranes was tested using pure water flux and MO (anionic dye) and methylene blue (MB) (cationic dye) dye removal capacity. The negatively charged membranes were found to have more affinity for MB dye than the MO dye and this was ascribed to the charge interaction between the membrane surface and the dyes. The nanocomposite with 5% Fe/Cu/Ag trimetallic nanoparticle loading on PMAA-g-PES membrane (M4-5% membrane) was found to have the best adsorption capacity with about 60% MB dye removal efficiency. Furthermore, the effect of process parameters such as pH, temperature and H2O2 concentration on the removal of MB was studied. The removal efficiency was found to be higher at higher pH and lower temperature. About 100% removal efficiency was obtained when the process was performed at pH 9 in the presence of H2O2 via adsorption and Fenton degradation. This showed that a hybrid of processes was convenient for the removal of MB dye by adsorption (primarily) and degradation using the nanocomposite membrane. Adsorption equilibrium data were assessed using the Langmuir, Freundlich and Temkin models; the Temkin model was the most convenient to explain the adsorption of MB onto M4-5% membrane. Moreover, lcinetic studies were performed on four kinetic models: pseudo first-order, pseudo second order, intraparticle diffusion and elovich models. The pseudo second-order was found to be the best suitable to explain the adsorption of MB onto M4-5% membrane. Thus, the adsorption of MB onto the nanocomposite membrane is an exothermic chemical process that occurs on a heterogeneous surface. Therefore, the nanocomposite membrane has the prospective to be applied in the removal of cationic textile dyes in the presence of an oxidiser.
On the Geometry of Lightlike Hypersurfaces
(University of the Witwatersrand, Johannesburg, 2022) Khoza, Jabulile; Ssekajja, Samuel
The study of lightlike geometry in semi-Riemannian manifolds was introduced by A. Bejancu and K. L. Duggal in their book [3]. The book laid a foundation for the study of lightlike submanifolds by providing some constructions on such subspaces. In this research, we focus on the study of lightlike hypersurfaces of semi-Riemannian manifolds, i.e. submanifolds of codimension one. In this line, we prove necessary and sufficient conditions for a lightlike hypersurface of a semi-Riemannian space form to be totally umbilical, screen conformal and screen almost conformal (see Theorem 2.5.2, 2.5.4 and 2.5.5)
Water quality assessment at Vaalkop Dam in North-West Province using multispectral remote sensing data
(University of the Witwatersrand, Johannesburg, 2022) Mthimkulu, Lindy Ndzumbululo; Adam, Elhadi
Water is a life-sustaining resource for all organisms. As much as nature share the value of water with human being it cannot supersede how human have become dependent on water for drinking, sanitation, farming, mining, and other industrial purposes such as power generation. Water is perceived as a vital component in the fight against poverty, the foundation of any successfully growing and developed country is also measured on water and sanitation provision (Basson et al., 1997). The water law in South Africa stresses that essential human and ecological necessities must be given (DWAF, 1998) and that the misuse of water from all perspectives should be feasible (New, 2002).
The reporting of the sustainability goals and the Sustainable Development Goals (SDGs) in the context of the private sector in South Africa
(University of the Witwatersrand, Johannesburg, 2022) Mosi, Tumelo
Sustainability challenges continue to mount and the fate of this planet lies in a precarious position. In response, the United Nations has introduced a global agreement known as the Sustainable Development Goals (SDGs). These are 17 goals underpinned by 169 targets for addressing social, economic and environmental issues on a global scale. The SDGs seek to do so by unlocking the potential that lies within the private sector and more. The aim of my research was to assess the sustainability goals disclosed by the top 25 Johannesburg Stock Exchange (JSE) listed companies against that of five other countries in 2017. Furthermore, I compared the environmental SDG disclosure of five companies from the metals and mining sector as well as the consumer products sector respectively, within the same period. The sample was selected from the original sample of the top 25 JSE listed companies. Comparisons were done by analysing sustainability/annual/integrated reports of the top 25 JSE listed companies. The results for the sample showed South Africa to be lagging behind the other countries with regards to disclosing sustainability goals in the corporate sustainability reporting for 2017. From 2017 to 2019, the number of reports addressing environmental SDGs from the selected sectors showed an increase. Furthermore, the study companies from the metal and mining sector performed better than those from the consumer products sector with regards to environmental SDG disclosure. However, the environmental SDG score of the study companies from the consumer products sector increased relatively more within the three years of assessment (2017-2019). Variation was also found between the study companies from the two sectors with regards to preference for specific environmental SDGs which included Responsible Consumption and Production (SDG 12), Climate Action (SDG 13), Life Below Water (SDG 14) and Life on Land (SDG 15). Moreover, the iii interviews conducted with the relevant participants revealed that SDG awareness has improved overtime, however internalisation of the SDGs remains the biggest challenge.
A comparative analysis of mining environmental management programme reports following a change to the one environmental system
(University of the Witwatersrand, Johannesburg, 2022) Mathe, Lebogang; Watson, I.
The mining fraternity has recently seen a shift in terms of environmental requirements under the ambit of the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) to the National Environmental Management Act 107 of 1998 (NEMA). The objective was to ensure a streamlined environmental compliance and to put emphasis on integrated environmental management. The One Environmental System (OES) was introduced which denotes that all environmental related projects or activities, including mining, are regulated through an ambit of one system. NEMA is recognised as an overarching law which provides for co-operative environmental governance; therefore, all environmental related activities are regulated under its ambit and EIA regulations. In this research report, the Environmental Management Programme (EMP) reports and Environmental Authorisations that were issued under the MPRDA and the 2014 NEMA regulations respectively, were analysed using the respective regulations to compare the environmental management measures outlined in the reports to achieve better environmental results. The aim of the research was to assess whether the Environmental Authorisations granted in terms of NEMA reflect better environmental results as compared to those issued under the MPRDA. Better environmental results mean improved management plans with clearer assessment of impacts, more detailed mitigation measures with specific, achievable, relevant and time bound actions that do not pose harmful effects on the environment and communities. A mixed method of analysis was implemented which included a review and comparison of legislation, evaluation and scoring of 20 EMPs (10 submitted under MPRDA and 10 submitted under NEMA) and interviews with key informants, namely competent authorities and the Environmental Assessment Practitioners (EAPs) were conducted to support the findings of the reports. In conclusion, the reports analysed presented a significant improvement and better environmental results under NEMA. The interviews conducted with authorities and the EAPs have also substantiated the observations made in terms of Environmental Management Programme reports and Environmental Authorisations submitted. The findings indicated that there were similarities in the MPRDA and NEMA regulations as 4 | P a g e regards some environmental requirements. However, the MPRDA lacked to outline a detailed description of environmental requirements needed to manage environmental impacts. Thus, applicants provided limited information in terms of the management of impacts. NEMA has provided additional requirements, including baseline environmental information, specialist reports and public participation amongst others; these contributed to improved environmental results. The study revealed that the reports submitted under NEMA provided better environmental management measures as compared to the reports submitted under MPRDA.
The development of a burn-in test station for the ATLAS Tile Calorimeter Low Voltage Power Supplies for phase II upgrades
(University of the Witwatersrand, Johannesburg, 2022) Lepota, Thabo James; Mellado, Bruce
It is planned that the High Luminosity (HL) function of the Large Hadron Collider (LHC) will begin operation in 2027 with an integrated luminosity of 4000 fb−1.By using the HL-LHC scientists will be able to investigate new physics beyond the Standard Model (SM), examine electroweak symmetry in more detail, and examine the characteristics of the Higgs boson. The ATLAS Tile Calorimeter’s on and off detector electronics will be completely redesigned during phase II upgrade, run 3. Due to the high radiation levels, trigger rates, and high pile-up conditions associated with the HL-LHC era, it will be necessary to accommodate its acquisition system. The Institute of Collider Particle Physics is responsible for developing and manufacturing over a thousand transformer-coupled buck converters, known as Bricks, for the Low Voltage Power Supply (LVPS) system. The LVPS is critical to the TileCAL on detector electronics as it powers them by converting 200 V high voltage to 10 V. The Bricks are located within the inner barrel, they can only be accessed once a year. If an LVPS box fails, it can be down for up to a year, causing the Front-End electronics it supports to remain offline for the same amount of time. As a result, the Bricks’ reliability is of critical concern that must be addressed throughout their manufacturing process. In addition to the burn-in test station, the Bricks that pass the quality assurance tests are sent to the European Organization for Nuclear Research (CERN), to be installed in the ATLAS detector. In this manuscript, we show how we programmed the Peripheral Interface Controller (PIC) firmware, which is an integral part of the Brick Interface board functionality in the burn-in test station. We further give detail as to how the software framework (LabVIEW) used as a control program was modified and used to operate the burn-in test station during the burn-in process. The purpose of the test results discussed is to demonstrate the burn-in test station is functional according to the preliminary protocols prescribed for Bricks
The reproductive system of Campuloclinium macrocephalum and its implications for biocontrol implementation
(University of the Witwatersrand, Johannesburg, 2022) Moodley, Saness; Glennon, Kelsey; Goodman-Cron, Glynis
Invasive species are a threat to biodiversity therefore it is imperative to determine the factors that facilitate the invasion potential of a species. Campuloclinium macrocephalum Less. (DC), the ‘pompom weed’, is an alien invasive species in South Africa and is currently threatening the persistence of the grassland, wetland, and savanna biomes. The species is also significantly contributing to a decline in plant diversity by outcompeting native vegetation in these areas. Various integrated approaches using combinations of chemical, mechanical and biocontrol management programs have been developed to manage the spread of the species in its invaded range, however the species has still been able to persist. The persistence of the species was hypothesised to be a consequence of the co-occurrence of apomixis and polyploidy, however despite the identification of triploid and tetraploid cytotypes in South African populations of the pompom weed, the reproductive strategy of the species has not yet been determined. The aim of this study was therefore to infer whether populations of C. macrocephalum (pompom weed) reproduces via vector-mediated crosses, self-pollination or apomixis (either facultative or obligate) and examine the relationship of the mode of reproduction with ploidy level. Male fertility was also assessed to ascertain if interploidy gene flow was possible. The collated information was then used to infer the potential impact of reproductive strategies and polyploidy on biocontrol. All examined populations were shown to have high mean pollen viability percentages of 90% and 98% with no significant differences in pollen viability amongst the four populations. The high pollen viability percentages were supported by prolific pollen grain germination on the stigmatic surfaces (margins of style at base of style branches) and the sides of the style. This suggested that the pollen grains can fertilize and interploidy mating is likely possible in South African populations of the pompom weed. It is plausible that the high pollen viability is enabling triploids to act as a ‘triploid bridge’. However, the high pollen viability was confounded by the pollen tube analyses revealing that pollen tube growth is being arrested on the stigmatic surface suggesting that overall male fertility is low. The arrested pollen tube growth is typically associated with a ‘triploid block’. Nevertheless, the production of viable gametes can reduce the triploid block and facilitate gene flow between populations. The predominant mode of reproduction was determined by assessing the contribution of insects to pollen transfer, pollinator exclusion experiments, germination trials, pollen tube growth to the ovules and genetic analyses. We found that the African Monarch butterfly (Danaus chrysippus) and the honeybee (Apis mellifera) contributed most to pollen transfer in comparison to the other insects visiting C. macrocephalum. A pollinator exclusion experiment showed that the pompom weed can set seed in the absence of pollinators, albeit at lower quantities than in the open treatments. Nevertheless, germination percentages showed that reproductive success was similar between open and bagged treatments in each population. The Modderfontein population showed lower reproductive success and seedling establishment in comparison to the other populations, presumably due to the severity of the biocontrol infestation on this population. Genetic analyses revealed low genetic variation within and amongst populations. Pollen tube analyses showed no pollen tube growth to the ovules in all samples, which suggests that seed set is independent of fertilization. The lack of pollen tube growth is a strong indicator of obligate autonomous apomixis which is further corroborated by the low genetic differentiation between maternal plants and their respective offspring. The co-occurrence of apomixis and polyploidy made it difficult to discern which factor contributes more to the invasiveness of the species, however, we hypothesise that autonomous apomixis provides the pompom weed with the competitive advantage to persist in its invaded range. However, further studies on the reproductive strategies of tetraploid cytotypes are needed to confirm this hypothesis. The low genetic variation suggests that all populations should be equally susceptible to biocontrol agents, however that this may be affected by other factors such as environmental conditions or phenotypic plasticity. Phenotype plasticity refers to a single genotype producing different phenotypes in response to environmental conditions. This could reduce the efficacy of biocontrol agents as they may exhibit differential responses on different phenotypes
The impact of fly ash on the growth rate of maize (Zea mays L.) and the potential for fly ash to be used commercially in agriculture
(University of the Witwatersrand, Johannesburg, 2022) Riba, Mpho Mahlatse; Scholes, Mary
South Africa’s coal-fired power plants (CFPPs) produce about 34.4 million tons of fly ash (FA) per annum, as a by-product of the coal combustion process, which is stockpiled adjacent to these CFPPs. This FA contains traces of heavy metals (HMs), as a result it is a potential environmental hazard. The purpose of this study was, therefore, to establish the effects of (‘FA’) on the growth of maize (Zea mays L.), as well as its potential commercial use in agriculture due to its nutrient content, instead of maintaining the status quo. Another aim of the study was also to determine the phytoextraction abilities of the HMs (Mn, Cr, Ba and Mo) from contaminated soils by the maize plants. The study was conducted by planting maize seeds in five soil substrates with 0 %, 20 %, 40 %, 55 % and 60 % FA treatment, on mass basis. The ANOVA indicated that there were significant differences when comparing most of the mean stem length, number of leaves, root length and the mean mass of total plant dry biomass, across all the FA treatments, after 122 days of growth. The mean stem lengths after 122 days of growth were 86.67  20.55 cm, 148.33  13.87 cm, 154.17  18.10 cm, 121.17  14.99 cm and 149.50  24.20 cm for maize plants grown in 0 % , 20 %, 40 %, 55 % and 60 % FA treatments, respectively. The mean number of leaves were 12  1.87, 16  2.34, 18  2.83, 12  1.87 and 14  1.79 across all treatments, respectively. The key finding was that the growth of these plants improved with the amount of FA in the soil, with the plants that were grown in the 40 % FA treatment yielding the best results. The same observation was made with the root length and the mean masses of total plant biomass (roots, stems and leaves). Another important finding was that the accumulation of the HMs (Mn and Cr) in the plants increased, across the FA treatments, while their concentrations in the soil decreased across the FA treatments. The accumulation of Ba and Mo in the plants also increased, across the FA treatments, while Ba remained slightly constant and Mo increased in the soil. This indicated that the maize plants can potentially remediate Mn and Cr contaminated soils, through phytoextration, but are retained in the root system.
Tolerance, uptake, and translocation of platinum (Pt), nickel (Ni), and cobalt (Co) by Tamarix usneoides E. Mey. ex Bunge
(University of the Witwatersrand, Johannesburg, 2022) Mader, Anthony E.; Weiersbye, Isabel M.; Mycock David J.
The intensification of platinum (Pt), cobalt (Co) and nickel (Ni) mining and processing results in the release of salts and metals into the environment. This calls for the identification of halophytes with an ability to tolerate and desalinate metal-contaminated sites while simultaneously allocating metals (Pt, Ni, and Co) into harvestable biomass. Tamarix usneoides E. Mey ex Bunge is an indigenous exo-recretohalophyte that has been used for erosion control and for the desalination and allocation of metals from gold and uranium mine tailings and land contaminated by metallurgical effluent. The aim of this study was to investigate the uptake, translocation, and tolerance of Pt, Ni, and Co by T. usneoides from liquid medium (in vitro) and soil contaminated by base metal refinery effluent spillages and previous overspray from the enhanced evaporation spray system (in situ). More specifically, the in situ study investigated the utility of mature T. usneoides trees in the desalination of soil contaminated by previous metallurgical spillages and overspray emissions through the extraction of sulphur and metals Pt, Ni, and Co into harvestable biomass. Four T. usneoides trees were categorised into different size classes based on tree measurements and allometric equations. Seven soil pits (four “planted” and three “unplanted” – control) were excavated and opposite faces of the soil profile were sampled at 20 different intervals (0 – 340 cm). Soil samples were freeze-dried and analysed for total element concentrations. Root systems were harvested by excavating soil pits (maximum depth of 3.5 meters) using a mechanical excavator. Trees were harvested and immediately separated into above (leaves, twigs, wood, and flowers) and belowground (coarse and fine roots) plant organs. Tree biomass was further separated into different above (outer bark, inner bark, and sapwood and heartwood) and belowground (epidermis, cortex, and stele) tissue types. Plant material was rinsed three times in tap water to remove unbound residual metals and residual substrate from root and shoot surfaces. It must be noted that the determined metal concentrations are a combined measure of metals adsorbed on the root surface, assimilated in planta, and excreted on the plant surface from the foliar salt glands. Metals were allocated in trees (across plant organs and tissue types) in the order: Ni (59.46 ± 4.67 mg/kg) > Co (2.65 ± 0.34 mg/kg) > Pt (50 ± 6 µg/kg) whereas sulphur (S) was hyperaccumulated in tree leaves [39 900 ± 861 mg/kg (3.9% ± 0.7 %)]. Platinum was bioaccumulated [bioconcentration factor (BCF) > 1.5] and translocated [translocation factor (TF) > 1] in the leafy shoots of one individual tree, Ni in one (BCF = 1.03), and Co in another replicate (BCF = 1.02). Soil chemical properties (pH, electrical conductivity, and redox potential) differed between planted and unplanted pits whereby pH and EC were lower in planted pits [pH 6.0; EC = 3 499 µS/cm (34.99 mM NaCl)] compared with unplanted [pH 7.6; EC = 9 644 µS/cm (96.44 mM NaCl)] (ANOVA, p < 0.01). The lower EC, along with S hyperaccumulation (BCF > 20; TF > 1), supports the potential use of T. usneoides for phytoextraction of S and Ni in shoot tissues and Co and Pt in roots. At a spacing of 1333 trees / ha, T. usneoides trees could remove an estimated 2.23 ± 0.30 mg Pt/ha, 3.02 ± 0.83 kg Ni/ha, 1.28 ± 0.90 kg Co/ha, and 1.28 ± 0.09 tons S/ha, excluding excreted salts. Excreted salts were visible but could not be quantified without confounding surface dust contamination. The first in vitro study determined factors influencing the rhizogenesis of T. usneoides in order to develop a mass propagation protocol. Explant establishment in vitro was influenced by various donor plant factors, viz. growing conditions (contaminated < non-contaminated; Kruskal-Wallis (KW), p < 0.05), physiological age (younger > older donor plants; ANOVA, p < 0.05), genotype (KW, p < 0.001), season of culturing (higher establishment in winter; KW, p < 0.05), length of explant (40 mm > 25 mm; KW, p < 0.05), and volume of growth vial (50 mL > 15 mL; KW, p < 0.05) but not pH, chronological age, strength of plant growth medium, or auxin pulse treatments. This study indicates that propagation protocols can be developed by controlling factors influencing explant establishment. A standardised and rapid in vitro protocol was developed for the mass propagation of T. usneoides explants. This in vitro protocol was used for the metal uptake studies whereby established explants were exposed to 25 % Murashige and Skoog standard plant growth medium supplemented with Pt, Co, or Ni (as sulphate complexes) at 0, 25, 50, or 100 mg/L at pH 5.5 or 7.5 over a 14-day exposure period. On completion of the metal exposure period, plantlets were harvested, separated into roots and shoots, freeze-dried, and analysed for metal concentrations. Higher metal concentrations (Ni > Co >> Pt) were accumulated in roots (combined measure of metals adsorbed on the root surface and assimilated in planta) compared with shoots whereby BCF > 1 (excluding Pt) and TF < 1. Metal BCF (Ni > Co >> Pt; KW, p < 0.05) and TF (Co > Ni >> Pt; KW, p < 0.05) increased in a dose-dependent fashion and were not influenced by pH level. Cobalt and Ni (≤ 50 mg/L) uptake dynamics did not v differ suggesting similar uptake dynamics, when treated separately. Platinum (defined in this study as Pt > 1 – 4 mg/kg), Ni (> 1 000 mg/kg), and Co (> 300 mg/kg) were hyperaccumulated in roots (“rhizo-hyperaccumulation”) across treatments with possible Co-hyperaccumulation in shoots by two genotypes. Genotype influenced Co allocation in shoots but not Ni or Pt. Tolerance indices did not differ [Co (97 %) > Pt (82 %) > Ni (77 %)] between pH, metal, treatment concentration, or the interplay between these factors. Metal treatments did not impact measured morphological parameters (excluding Ni treatments which promoted shoot length increment) (KW, p < 0.05). Plantlet survival differed between pH and metals [Pt (90 %) > Ni (81 %) > Co (62 %)] (KW, p < 0.05). Variability in Co accumulation capacity between genotypes indicated that selective breeding, using the developed in vitro mass propagation protocol, for improved rhizofiltration and phytoextraction traits is feasible. Results demonstrate that T. usneoides has the potential for recovery of Ni and Co (and Pt to a lesser degree) from effluents, exhibiting a tolerance to Ni, Co, and Pt at 1, 10, and 10,000 times the average soil crustal abundance, respectively, under moderately acidic (pH 5.5) and alkaline (pH 7.5) conditions and across a wide metal concentration range. Results from the in situ study indicate that 9- year-old T. usneoides trees can be used for the decontamination of sulphate-contaminated soils under study site conditions which are more conducive to the survival of glycophytes. Tamarix usneoides is thus able to assimilate, translocate, and tolerate Ni, Co, and Pt (to a lesser degree) when exposed to metals across a wide pH and metal concentration range, under different (in situ and in vitro) experimental conditions. This opens the possibility for the species to be used in a range of phytotechnologies.
A study of the support effect of carbon dots-derived graphene-like sheets on the autoreduction of cobalt nanoparticles for Fischer–Tropsch synthesis
(2022) Mokoloko, Lerato Lydia
The aim of this study was to synthesize and characterize carbon dots (CDs) and to use them as a support material for cobalt (Co) based Fischer-Tropsch synthesis (FTS) reactions. The CDs were chosen for this study due to their small size (< 10 nm), easy surface functionalization and synthesis. The small size of the CDs was required for the study of inverse catalyst support effects. An inverse supported catalyst (in this case, the Co/CDs catalyst) refers to the dispersion of a support material that has a small size (d < 5 nm) onto the surface of a metal catalyst with a similar small size (d > 8 nm). The synthesis of this proposed catalyst was successful. FTS studies on the Co ‘supported’ CDs were attempted. Extremely poor FT activity was observed. Post analysis of the catalyst revealed that the CDs did not retain their quasi-spherical and small particle size morphology under the FTS reaction conditions (temperature 220 °C, 10 bar P; H2:CO ratio = 2:1). Instead, upon exposure to a heat treatment, the CDs were transformed into layered structures with a unique resemblance to graphene-based nanosheets (GNSs). This transformation impacted on the use of these catalysts in the FTS reaction. However, this result indicated an unusual transformation of the CDs into another carbon shape. In light of the fascinating transformation phenomenon, annealing studies were then conducted to investigate the effect of annealing temperatures on the CDs structural changes. The CDs (average d= ~ 2.5 nm) used in this study were obtained from the microwave-assisted carbonization of L-ascorbic acid and subjected to a heat treatment (i.e. annealing) at temperatures between 200 and 700 ℃ in a horizontal CVD apparatus under an inert nitrogen gas. It was observed that annealing transformed the CDs from 0-D qausi-spherical nanoparticles to 3- D multi-layered carbons (at 300-600 ℃) and finally 2-D layered materials (at 700 ℃). Furthermore, annealing at 700 ℃ yielded a 2-D single-layered material with comparable properties to traditionally reduced graphene oxide (rGO). A wide range of characterization techniques were used to gain an insight into the physicochemical properties of these novel CDs-derived allotropes as well as to rationalize their mechanism of formation. After evaluating the properties of these materials, it was clear that the surface oxygen functional groups, observed from XPS, 13C NMR and other studies, were responsible for the CDs to rGO transformation. It was proposed that the CDs are assembled to form rGO (and other CDs-rGO derivatives) by either the Ostwald ripening (in which the carbons agglomerated via a gas phase) or a solid phase reaction (involving reaction of CD edges). To further investigate the effect of annealing on the evolution of CDs to layered carbon structures, N-doped CDs (or NCDs) were also studied. The method used to make the pristine CDs was modified by incorporating urea as a nitrogen source to make the NCDs. Annealing the NCDs at temperatures between 200 and 700 ℃ also transformed the quasi-spherical NCDs (average d = ~ 4.1 nm) to multi-layered carbon sheets at temperature as low as 200 ℃. The CD transformation was also associated with the loss of surface functional groups, with % O and N contents of ca. 17 and 16 % (pristine NCDs) being reduced to ca. 8 and 7 % for NCDs annealed at 700 ℃. A similar mechanism for the formation of these N-doped layered carbon structures by annealing was also proposed here. For these samples, it was also observed that the N-bonds, especially the sp3 type nitrogen bonds found on the edges of the NCDs, also took part in the coalescence of the NCDs to give the layered materials. XPS data suggested that in the process, these sp3 type nitrogen bonds were transformed into sp2 pyrrolic-N, pyridinic-N and GraphiticN groups. The annealed CDs products were used to support Co (called Co3O4/T250, Co3O4/T400 and Co3O4/T700 where T is the temperature at which the CDs were annealed) for use in FT studies. Studies were conducted to evaluate the effect Co hydrogen reduction temperatures verses autoreduction temperature, catalyst thermal stability and performance in the FTS reaction at 220 °C (10 bar P; H2:CO ratio = 2:1). Upon investigation of the reduction behaviour of the Co/CDs derivative catalysts using in situ PXRD, it was found that these materials can successfully facilitate autoreduction of Co3O4 to Co face-centered-cubic (fcc) at temperatures > 400 ℃ by a reduction pathway similar to that observed using conventional H2 reduction conditions. As expected, the reduction under H2 took place at a lower activation temperature (> 250 ℃) than the autoreduction process. It was also noted that these novel carbon support derived from CDs gave reduced FTS performance compared to the unsupported Co, especially towards C5+ yields (< 30 % for all Co supported catalysts). These novel CDs-derived allotropes were found to have limited use as supports in Co-based FTS, due to Co agglomeration. These NCDs-derived allotropes (annealed at 200 ℃, 400 ℃ and 700 ℃) were incorporated as active layers in the fabrication of chemoresistive sensing device detection of volatile organic compounds (VOCs). These layered showed enhanced chemical vapour sensing properties, especially for methanol and ethanol detection at room temperature. Therefore, although there are great limitations for applications of these CDs-derived layered allotropes in FTS reaction, these materials show a much better potential for applications in facile and cost effective VOC sensors. Further studies on this will be conducted.