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    Synthesis and Fabrication of Alpha Phase Iron Oxide (α-Fe2O3) Nanostructured doped with Ruthenium for Highly Sensitive and Selective Flammable and Toxic Gas Sensor
    (2022) Cebekhulu, Ntokozo God-Knowledge
    The increase in the number of manufacturing industries in recent times had both positive and negative impacts on our environment and human health. The use of heavy-duty machines in manufacturing industries causes the release of flammable and hazardous gases, which affect human health, into the atmosphere. Many research efforts have been focused on detecting and monitoring these gases using metal oxide semiconductor materials. This study investigates the gas sensing performance of ruthenium-doped alpha iron oxide towards flammable and hazardous gases. The chemical precipitation method synthesised the alpha iron oxide doped with a different weight percentage of ruthenium. The samples underwent some characterisation techniques, such as X-ray diffractometry, thermogravimetric analysis, x-ray photoelectron spectroscopy, Brunauer-emmett-teller surface area analysis, scanning electron microscopy, and high-resolution transmission electron microscopy, to study certain properties of the material. The sensors were fabricated by using the drop casting method, and the sensors were tested for gas sensing performance at 225 ⁰C operating temperature, towards liquefied petroleum gas (LPG), ethanol, propanol, ammonium (NH3), and hydrogen sulphide (H2S). The pure sample alpha iron oxide (α Fe2O3) was more sensitive to the target gases with the response being 26.01 towards the ammonia gas. The selectivity shift towards LPG while the response decreases upon the addition of different weight percentage of the ruthenium to alpha iron oxide ruthenium was found to be unsuitable as a dopant material in alpha iron oxide for gas sensing applications.
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    Investigation of co1-2xnixmnxceyfe2-yo4 double-substitution spinel for highly efficient detection of flammable and hazardous liquefied petroleum gas: sensing performance
    (2022) Ogundipe, Sunday Ayodeji
    The presence of high concentrations of flammable gases and volatile organic compounds in the atmosphere has recently been reported to be detrimental to human survival. A lot of research effort has been directed towards finding an efficient means of quick detection of these gases below their ‘immediately dangerous to life or health’ concentrations. Also, detecting these gases in an oxygen-deficient environment is a crucial task to consider. In this research, double substitution spinels with chemical formula Co1-2xNixMnxFe2-yCeyO4, where 0 ≤ x = y ≤ 0.3, were prepared via the glycol thermal technique. The final products following the appropriate substitution were CoFe2O4 (dried naturally), CoFe2O4 (dried with Infrared lamp), Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4, Co0.6Ni0.2Mn0.2Fe1.8Ce0.2O4, and Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4 spinel ferrites. X-ray diffractometry (XRD), high resolution transmission electron micrographs (HRTEM), and X-ray photoelectron spectroscopy (XPS) of the samples confirm the formation of the spinels. The gas sensing performance of these samples was tested at an operating temperature of 225 ºC towards liquefied petroleum gas (LPG), ammonia, ethanol and propanol using nitrogen, argon, helium, and dry air, each at different times as carrier gases. The Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4-based sensor was selective to LPG, with a high response of 116.43 towards 0.6 vol % of LPG, using helium as carrier gas. The response and recovery times of this sensor were 2.68 minutes and 3.01 minutes respectively. The sensor proved to be a potential tool for LPG detection in an oxygen-deficient environment.
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    Assessment of selenium supplementation on the attainment of puberty in Merino ram lambs
    (2023) Makhado, Ngelekanyo Elaine
    In small ruminants, the attainment of puberty is influenced by different factors, such as season of birth, photoperiod, nutrition, breed type, management, genetics, endocrine regulation, body weight and the development of the reproductive system. This study was conducted to evaluate the effect of selenium (Se) supplementation on the attainment of puberty in South African Merino ram lambs. Forty South African Merino ram lambs were divided into two groups, Se-supplemented (n = 20) and control (n = 20). The treatment group received a dosage of 0.34 mg Se per kg in the form of sodium selenite at two-week intervals for an experimental period of 130 days. The phenotypic parameters were evaluated weekly. Semen was collected each week using an electroejaculator and was analysed for volume, pH, appearance, motility, viability, morphology and concentration. Blood samples were collected bi-weekly to determine the concentration of glutathione peroxidase (GSH-Px), cortisol and reproductive hormones. Collected data were analysed using analysis of variance, and the means were separated through the Student’s t-test. At 6 months, motile spermatozoa were collected from 80% of the supplemented group compared to 60% of the control. The Se treated group showed significantly higher semen quality in the form of improved spermatozoa motility, concentration, increased percentage of live spermatozoa, decreased percentage of dead spermatozoa and fewer spermatozoa abnormalities compared to the control group. Supplementation with Se had no effect (P > 0.05) on body weight and scrotum circumference. Selenium supplementation significantly (P < 0.05) improved testicular measurements and decreased the age to attain puberty. Supplementation with Se also increased luteinising hormone and testosterone concentrations (P < 0.05). However, Se supplementation did not affect glutathione peroxidase and cortisol concentrations (P > 0.05). The control group attained puberty at 6.5 months based on ejaculated semen with viable spermatozoa. Therefore, it was concluded that Se supplementation hastened the attainment of South African Merino ram lambs’ puberty to 6 months. Treatment also improved testicular measurements, semen quality and reproductive hormones concentration of South African Merino ram lambs.
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    Assessment of minor ions and trace element chemistry in groundwater in Luvuvhu catchment, Limpopo province, South Africa.
    (Univeristy of Zululand, 2022) Madondo, Takalani Patience
    Agricultural activities are often associated with contamination of water, which resulted in high concentration of nutrients and trace metals in the shallow aquifer. Occurrence and distribution of nutrients and trace metals in the groundwater of intensively irrigated region of Luvuvhu catchment was carried out to determine the status of groundwater quality and its suitability for drinking. Groundwater samples were collected and analysed for physiochemical parameters. The results suggest that the concentration of nutrients and trace metals in the groundwater are below the permissible limit of drinking water standards recommended by the World Health Organization and South African standards except pH, K and Pb. Low pH (51%), potassium (31%) and lead (100%) restrict the groundwater usage for drinking. Relation between groundwater flow direction and EC, sulphate, nitrate, and ammonium contents indicate that it is mostly constant towards the centre of the study area, but sudden enrichment is noticed in the downstream. Silica and fluoride has increased along with the direction of groundwater flow. Trace metals (B, Pb and Zn) show decreasing trend in the flow direction. However, pH, K, Li, Cr, and phosphate concentrations do not show significant variation along the flow direction. Positive relation between nitrate, EC, sulphate, and ammonium implies that groundwater quality is affected by the surface contamination sources, and mostly from irrigation return flow, through the application of fertilizers and organic manures. However, groundwater with high silica and fluoride also has high nitrate, which justifies that wastewater infiltration from the surface has triggered the mineral dissolution in the vadose. Trace metals does not correlate with nitrate. High concentrations of trace metals are recorded with low nitrate, which implies that metals are derived from mineral weathering. However, boron concentrations in a few wells show positive relation with nitrate, which justified the impact of natural sources and irrigational activities.
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    Participatory selection of traditional leafy vegetables and variation in morphology and mineral content of colchicine-treated Corchorus olitorius plants in northern KwaZulu-Natal, South Africa
    (University of Zululand, 2019) Mncwango, Ngcebo Colile
    Traditional leafy vegetables (TLVs) are mostly wild-collected, nutrient-rich herbaceous plants whose leaves, shoot tips, flowers and fruits are consumed as vegetables. They are well-adapted to harsh environmental conditions and grow in soils with limited fertility. This study focused on TLVs that are utilized by a rural community of the KwaMbonambi area of northern KwaZulu-Natal, South-Africa. A survey was conducted to identify the most preferred TLV’s in this study area and to determine factors affecting their consumption and cultivation. In a total of 19 recorded TLV species, Amaranthus hybridus, A. spinosus, A. thunbergii, Bidens biternata and Corchorus olitorius, were the most preferred in the area based primarily on their appealing taste. Most TLVs were collected from the wild mainly by females, during the rainy summer season, and were consumed only once a week depending on their availability. The cultivation of TLVs was very rare because poor seed quality restricted their cultivation. Participatory variety selection was done with the KwaMbonambi community of the study to evaluate 15 Amaranthus genotypes. Amaranthus was selected because of its popularity as a TLV in the area. During the participatory variety selection, mild-tasting and high-yielding genotypes were the most preferred. Genotypes ACAT seed fair, Tanzania and AMES-22680 were the most preferred in terms of the above traits. Induced mutation through colchicine has been successful in many crop species but least applied in traditional leafy vegetables. The effect of colchicine treatment on 15 morphological traits and 19 leaf minerals were therefore investigated in Corchorus olitorious. The evaluated colchicine treatments showed significant (P < 0.05) differences among them in both morphological and nutritional traits evaluated. Of all morphological traits measured, only the leaf chlorophyll content (LCC) of the 0.025 g l-1 colchicine treatment for two hours was significantly higher than the control. The trend for mineral nutrient content was similar with the highest values for most nutrients corresponding with 0.025 g l-1 of colchicine for two hours treatment.