Nutrient removal and biofuel potential of MaB-floc biomass from an integrated algal pond system treating domestic sewage
- Authors: Sibelo, Linda
- Date: 2020
- Subjects: Biomass energy , Waste products as fuel , Algal biofuels , Sewage -- Purification -- Nutrient removal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144955 , vital:38395
- Description: Integrated algal pond systems (IAPS) are a passive water treatment technology derived from the Oswald designed advanced integrated wastewater pond systems (AIWPS®) and effect wastewater treatment based on biological activity of microorganisms within the system, solar energy and gravity. The technology consists of an advanced facultative pond (AFP), a series of interconnected high rate algal oxidation ponds (HRAOP) and algal settling ponds. The symbiotic relationship between microalgae and bacteria facilitated by paddlewheel mixing of HRAOP results in the formation of biomass aggregates known as MaB-flocs. MaB-floc formation enhances nutrient abstraction, gravitational sedimentation and separation from water hence forming two product streams; recyclable water and biomass, both with valorisation potential. This work aimed to determine the suitability of MaB-floc biomass generated in the HRAOP of an IAPS treating domestic sewage as feedstock for biofuel production based on the content of carbohydrate and lipid. Nutrient removal efficiency, biomass productivity and bulk lipid and carbohydrate concentration were monitored for two consecutive three-month periods in the winter and summer seasons of 2018/19. Maximum removal efficiencies of nitrogen and phosphorus were determined as 71% and 75% respectively, demonstrating the efficiency of IAPS as a wastewater treatment technology. MaB-floc biomass productivity in winter and summer was 9.4 g/m2/d and 16.5 g/m2/d respectively indicating the heavy influence of seasonal temperature, possibly day length, and solar irradiation on biomass productivity in the HRAOP. Summer productivity was lower than the maximum theoretical productivity of 25 g/m2/d possibly due to photoinhibition of photosynthesis as well as grazing pressures caused by the proliferation of rotifers mainly of the Brachionus genus. MaB-floc biomass consistently contained higher amounts of carbohydrate than lipid despite the changes in species dominance from Scenedesmus sp. and Desmodesmus sp. in winter to Pediastrum sp. in summer. Variations in MaB-floc biomass carbohydrate content were linked to changes in nitrogen concentration, mainly in the form of nitrates. Lower nitrogen concentration significantly increased the carbohydrate content of MaB-floc biomass from 17.5 ± 0.15% to 33.5 ± 0.3 % recorded in summer. In winter, biomass carbohydrate increased from 18.3 ± 1.2% to 35.8 ± 0.3%.To induce accumulation of carbohydrates through nitrogen starvation, isolated microalgal species native to the HRAOPs of the IAPS at Institute for Environmental Biotechnology Rhodes University(EBRU) were used. The outcome from the laboratory studies showed that carbon partitioning within isolated strains could be altered from carbohydrate to lipid which is more energy-rich. Hence, exploring the biodiesel production option using HRAOP MaB-floc biomass, which had a lipid content ranging between 12.1 ± 0.64 % and 13.9 ± 0.5 %, would require a preconditioning step in the form of nitrogen starvation to enhance its lipid content. Overall, the outcome of outdoor monitoring studies on biomass biochemical composition indicated that HRAOPs operating under natural environmental conditions preferentially generated a biomass rich in carbohydrate. Therefore, anaerobic digestion may be a more viable option for HRAOP MaB-floc biomass because of the high carbohydrate levels ranging between 24.9 ± 0.6 % and 25.6 ± 1.3 % of the dry MaB-floc biomass weight. Despite the low biomass C/N ratio (7.1 to 7.8), the MaB-floc biomass can be anaerobically co-digested with a higher C/N ratio (24) substrate such as in-pond digester sludge, to improve methane yields calculated to be between 0.31 m3 CH4/ kg MaB-floc biomass and 0.33 m3 CH4/ kg MaB-floc biomass. Anaerobic digestion of biomass also produces CO2 which can be recovered and added to HRAOPs to enhance MaB-floc biomass productivity while lowering greenhouse gas emissions from a wastewater treatment plant. The digestate from the anaerobic process, which is rich in nitrogen and phosphorus can be used as a biofertiliser. Thus, a potential MaB-floc biomass biorefinery consisting of biogas and bio-fertiliser pathways can be established using IAPS treating sewage as the platform technology. IAPS is a system designed to operate in a way that is passive and without substantial environmental impact but technological innovations and a reduction in the size of the system are required to make the technology more acceptable.
- Full Text:
- Date Issued: 2020
Observations of diffuse radio emission in the Abell 773 galaxy cluster
- Authors: Sichone, Gift L
- Date: 2020
- Subjects: Galaxies -- Clusters -- Observations , Radio astronomy -- Observations , Astrophysics -- South Africa , Westerbork Radio Telescope , A773 galaxy cluster , Astronomy -- Observations , Radio sources (Astronomy
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144945 , vital:38394
- Description: In this thesis, we present 18 and 21 cm observations of the A773 galaxy cluster observed with the Westerbork radio telescope. The final 18 and 21 cm images achieve a noise level of 0.018 mJy beam‾ 1 and 0.025 mJy beam-1 respectively. After subtracting the compact sources, the low resolution images show evidence of a radio halo at 18 cm, whereas its presence is more uncertain in the low resolution 21 cm images due the presence of residual sidelobes from bright sources. In the joint analysis of both frequencies, the radio halo has a 5.37 arcmin2 area with a 6.76 mJy flux density. Further observations and analysis are, however, required to fully characterize its properties.
- Full Text:
- Date Issued: 2020
Observations of diffuse radio emission in the Perseus Galaxy Cluster
- Authors: Mungwariri, Clemence
- Date: 2020
- Subjects: Galaxies -- Clusters , Radio sources (Astronomy) , Radio interferometers , Perseus Galaxy Cluster , Diffuse radio emission
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143325 , vital:38233
- Description: In this thesis we analysed Westerbork observations of the Perseus Galaxy Cluster at 1380 MHz. Observations consist of two different pointings, covering a total of ∼ 0.5 square degrees, one including the known mini halo and the source 3C 84, the other centred on the source 3C 83.1 B. We obtained images with 83 μJy beam⁻¹ and 240 μJy beam⁻¹ noise rms for the two pointings respectively. We achieved a 60000 : 1 dynamic range in the image containing the bright 3C 84 source. We imaged the mini halo surrounding 3C 84 at high sensitivity, measuring its diameter to be ∼140 kpc and its power 4 x 10²⁴ W Hz⁻¹. Its morphology agrees quite well with that observed at 240 MHz (e.g. Gendron-Marsolais et al., 2017). We measured the flux density of 3C 84 to be 20.5 ± 0.4 Jy at the 2007 epoch, consistent with a factor of ∼2 increase since the 1960s.
- Full Text:
- Date Issued: 2020
Occurrence of early stage fishes associated with Anaulus australis in a temperate South African surf zone, with notes on feeding ecology and incidental microplastic consumption in a dominant species
- Authors: McGregor, Steven
- Date: 2020
- Subjects: Estuarine fishes -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48489 , vital:40881
- Description: Surf zones are important fish nursery areas, however, microhabitats and threats to fishes within them remain understudied. Diatom accumulations in surf zones are a worldwide phenomenon on certain beach types and discolour the water, offering refuge from visual predators and feeding opportunities for fishes, thus providing a microhabitat for early stage fishes. Surf diatom accumulations require long lasting rip current-entrained gyres to occur, which also entrap buoyant microplastics. These microplastics may then be consumed by filter feeding fishes such as the Southern mullet Chelon richardsonii. This work aimed to assess the extent of association of early stage fishes with diatom Anaulus australis accumulations and the feeding ecology and incidence of microplastic ingestion in the commercially important and dominant surf zone mugilid C. richardsonii. Early stage fishes were sampled within and outside of A. australis accumulations in the Sundays Beach surf zone on the southeast coast of South Africa, using a 4.5 x 1.5 m modified larval seine net with 500 µm mesh. Later developmental stage C. richardsonii were captured using a cast net. A total of 338 replicate larval fish seine hauls were done, capturing 1074 fishes including 33 taxa from 19 families. To assess ontogenetic shifts in diet of the dominant species C. richardsonii, stomach contents of 150 fish were categorised and assessed by prey abundance, frequency of occurrence, volume, index of relative importance and dietary niche breadth and compared across all developmental stages, excluding flexion and preflexion. Dominant families of early stage fishes were Sparidae, Soleidae, Mugilidae and Clupeidae that comprised 93 % of the catch, with dominant species including Heteromycteris capensis, Rhabdosargus holubi, Solea turbynei, Diplodus capensis and Chelon richardsonii. Species diversity and catch per unit effort (CPUE) were significantly higher within accumulations compared to outside, as was the CPUE of postflexion larvae and early juveniles. Generalized Linear Models showed that temperature, dissolved oxygen (mg l-1 ), turbidity and A. australis biomass (µg Chl a l -1 ) were the most significant factors affecting the overall CPUE and that of dominant species. It was suggested that after reaching the postflexion stage of development, fishes utilise diatom accumulations opportunistically when and where they are present. A diet study of the dominant species showed an ontogenetic dietary shift in C. richardsonii using A. australis accumulations as a feeding area, with postflexion larvae feeding mostly on copepods and microplastic fibres, while later developmental stages consumed predominantly A. australis cells and sand. Microplastic fibres were present in 40 % of fish sampled and microplastic fragments in 5 %, with both types found in all developmental stages assessed. It was suggested that C. richardsonii were unable to distinguish microplastics from their natural prey and incidentally ingested them. This presents a conservation concern, because chemicals associated with microplastics could bioaccumulate and biomagnify up the food chain if key baitfish species such as C. richardsonii are ingesting plastic. This study was the first to assess the association of early stage fishes with surf diatom accumulations, and the first to record microplastic ingestion in C. richardsonii. Understanding the function of microhabitats for early stage fishes and threats within them is needed to understand the life history strategies and survival of fishes in key coastal nursery and feeding areas.
- Full Text:
- Date Issued: 2020
Older people’s perspectives on the effectiveness of eye movement integration (emi) therapy as treatment intervention for their trauma symptoms
- Authors: Visagie, Andrea
- Date: 2020
- Subjects: Post-traumatic stress disorder in old age
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46389 , vital:39601
- Description: Many research studies propose that we have an ageing population with an increased number of people living past the age of 85 years. Ageing is accompanied by a gradual decline in physical, mental and sensory abilities. Older people may have experienced trauma throughout their lives, and very often, their symptoms of trauma are regarded as part of the ageing process rather than actual symptoms of trauma. In addition, older people often do not seek help throughout their lives for various reasons. While there is research available about older people and trauma, little is known about Eye Movement Integration(EMI)therapy as a treatment intervention in treating symptoms of trauma in older persons. The purpose of this research was an explorative and descriptive study of older people’s responses to EMI therapy as a treatment intervention for their symptoms of trauma. More specifically, the study was designed to determine how older people process their symptoms through EMI therapy and whether they view it as valuable. This qualitative study used an exploratory-descriptive research design with a non-probability, purposive sampling method. The EMI therapy sessions were offered to older adults in the Knysna area who presented with symptoms of trauma. From this group, only those who were able and willing to engage in therapeutic interviews formed part of the research. As part of the study, they consented to the use of their inventories from the EMI sessions as a qualitative document analysis and taking part in qualitative interviews to explore their views on the usefulness of EMI therapy to deal with their trauma. The findings emphasise that older people are not familiar with EMI. However, they view their experience of it in a positive light and regard it as a useful treatment intervention for treating their symptoms. Moreover, EMI seems to be a brief and cost-effective trauma intervention with practical benefits for older adults. The results from this study can assist social work professionals, specifically those working with older people, to address and improve the overall health and emotional wellbeing of older people. Data verification methods ensured the validity of this study
- Full Text:
- Date Issued: 2020
On the association of graphs to rings
- Authors: Mzulwini, Sboniso
- Date: 2020
- Subjects: Categories (Mathematics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47060 , vital:39779
- Description: Let R be a commutative ring with nonzero identity, and let Z (R) be the set of its zerodivisors. There exists an association between a simple graph (R) and the set Z(R) of nonzero zero-divisors of R. In this dissertation we investigate how the properties of R a⁄ect the properties of (R) and vice versa. There are other graphs that are associated with R. Some of these are shown to be special cases of the congruence-based zero-divisor graph.
- Full Text:
- Date Issued: 2020
Parents’ perceptions of the content of pre-school lunch boxes following a nutritional programme in Nelson Mandela Bay
- Authors: Midigo, Odwour Erich
- Date: 2020
- Subjects: Children -- Nutrition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46429 , vital:39587
- Description: Rationale: Lunchboxes that parents prepare for preschool children have been noted to fall short of the recommended paediatrics dietary standards. No research has been done in Nelson Mandela Bay (NMB) to describe the perceptions of parents preparing the lunch boxes, particularly in underprivileged communities, and if nutrition education strategies can improve these practices. This study answered the following research question: How can nutrition education programmes play a role in parents’ perceptions about the content of the lunchboxes of children attending early childhood development centres (ECD) in underprivileged communities of NMB metropole? Aim: The research aimed at describing and exploring parents’ perceptions of the content of pre-school children’s lunch boxes following a nutrition programme.Methods: This descriptive, explorative study adopted a qualitative approach. Twenty-five participants were selected conveniently while five pre-schools were purposively sampled. Following the nutrition programme, data was collected through five Focus Group (FG) discussions and five interviews and was thematically analysed. The ethical principles that guided the study included justice, beneficence and autonomy. Results and Discussion: Five major themes and seventeen sub-themes emerged (1) Participants described the typical foodstuff in children’s lunch boxes which included both high quality and lower-quality foods and fluids; (2) Participants provided views (such as food preferences) on lunch box choices; (3) Principals appraised lunch box rules and the significance of revised rules to improve the lunch boxes;(4) Challenges such as poverty limited healthy food choices; (5) Participants commented on initiatives noted following the nutrition training; for instance, some schools commenced the cultivation of vegetable gardens. Conclusion and Recommendations: The study highlights that specific parent programmes helped to improve healthy lunch box choices in the study population. There is a need for parent programmes tailored to fathers. Dieticians and nutritionists in NMB can train practitioners as change agents in their respective schools.
- Full Text:
- Date Issued: 2020
Performance of an integrated algal pond for treatment of domestic sewage: a process audit
- Authors: Dube, Anele
- Date: 2020
- Subjects: Water -- Purification , Sewage -- Purification -- Anaerobic treatment , Algae -- Biotechnology , Waste disposal -- South Africa , Integrated algae pond systems (IAPS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167043 , vital:41432
- Description: Integrated algae pond systems (IAPS) are energy efficient, robust, passive systems that use the principles of fermentation, photosynthesis and microbial metabolism to remediate wastewater, producing a good quality effluent with reuse potential. In addition to the treatment of wastewater, IAPS have the ability to generate two additional product streams viz. biogas and biomass. The latter adds to the attractiveness of the system. However, the implementation of this technology, like many passive systems, has remained limited at a commercial scale, and the inclination is still towards grey technologies. The aim of this research was to investigate the capabilities and potential of a demonstration-scale IAPS and use results obtained to establish a process audit framework. The aspects considered for the audit included performance efficiency, effluent water quality, biomass composition, quantity and productivity within the ponds, and cost analysis of operation and maintenance over a 9-year period. Plant performance was closely monitored during the course of the study and this led to a review of previously adopted plant management strategies. Troubleshooting exercises were also carried out when plant performance declined. Results showed that IAPS efficiently reduced standard water parameters with the exception of pH, dissolved oxygen, and nitrate whose values increased from raw influent to final effluent. The following water quality parameters were established for the final effluent: total suspended solids 55 ± 7.1 mg. L-1 (n = 28); chemical oxygen demand 94.1 ± 10.6 mg. L-1 (n = 28) (after removal of algae); pH 9.9 ± 0.01 (n = 26); ammonium nitrogen 1.7 ± 0.3 mg. L-1 (n = 25); nitrate 3.3 ± 0.6 mg. L-1 (n = 25); ortho-phosphate 1.6 ± 0.2 mg. L-1 (n = 25); electrical conductivity 98.7 ± 2.0 mS m-1 (n = 26) and faecal coliforms (per 100 mL) 1482.6 ± 636.0 (n = 24). The final effluent measured consistently high chemical oxygen demand and total suspended solids, however close analysis showed that total suspended solids could be controlled by increasing the frequency of removal of settled biomass within the settling ponds. Biomass produced contained microalgae, bacteria, metazoa, and protozoa. The biomass productivity achieved was as high as 130.6 kg ha-1 d-1; however, about 33% was lost to the final effluent due to inadequate settling. Results obtained during the course of this study and outcomes of earlier work on IAPS are taken as the baseline to determine parameters needed for the development of the process audit framework. Techniques utilised to derive the blue print process audit protocol for IAPS included a turtle diagram, a flow diagram and a checklist. Attention to plant management proved vital in determining overall performance. Cost, including operating and maintenance, of treating water using the demonstration scale system on a per person equivalent per year basis was determined as ZAR 123.87 (where, ZAR to USD = 0.07).
- Full Text:
- Date Issued: 2020
Petrographic and geochemical characterisation of the hangingwall and the footwall rocks (the Dipeta and R.A.T. stratigraphic units) to the Kinsevere and Nambulwa copper ore deposits of the Lufilian Arc, southern Democratic Republic of Congo
- Authors: Nkulu, Robert Kankomba
- Date: 2020
- Subjects: Petrogenesis -- Congo (Democratic Republic) , Analytical geochemistry -- Congo (Democratic Republic) , Copper ores -- Congo (Democratic Republic) , Ore deposits -- Congo (Democratic Republic) , Katangan Sequence , Geological mapping -- Congo (Democratic Republic) , Central African Copperbelt (Congo and Zambia) , Lufilian Arc , Neoproterozoic Katangan R.A.T. (Roches Argilo Talqueuse) Subgroup , Dipeta Subgroup
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/142772 , vital:38115
- Description: The Kinsevere and Nambulwa copper deposits in the Democratic Republic of Congo (D.R.C.) are set in the eastern side of the Neoproterozoic Katanga Supergroup, forming the Lufilian Arc, resulting from a cratonic collision between the Congo and the Kalahari Cratons (ca.620-570_Ma). The Katanga Supergroup was deposited in an extensional rift setting with a sedimentary thickness succession ranging between 7 to 10 km, sub-divided into: − the Roan, the Nguba and the Kundelungu Groups. The stratigraphic column of the Roan Group consists of the R.A.T. (Roche Argilo Talqueuse), the Mines, the Dipeta and the Mwashya Subgroups. Three major deformation phases have been described characterised by complex multiphase tectonics related to a curved superposition of folded, thrust and sheared blocks. The rocks of the R.A.T., Mines and Dipeta Subgroups are recognised as blocks that occur within a stratiform to discordant and diapiritic megabreccia. The blocks were rafted upward with salt tectonics, resulting in the juxtaposition with the hangingwall and the footwall terranes. Therefore, in that context it has been found that the Dipeta may appear overlying the R.A.T. Subgroup through the unconformity decollement surface of heterogeneous breccia. The petrographic observations made of the R.A.T. and Dipeta samples indicates in both units the presence of detrital quartz and feldspar that have been altered and replaced by sericite and muscovite minerals. Gypsum is intimately associated with magnesite, showing an evaporitic environment domain, while magnesite is common as alteration phase both in the R.A.T. and Dipeta Subgroups. Pyrophyllite has been observed in the Dipeta, resulting from reaction of silica with the Kaolinite at low temperature. Accessory detrital minerals include zircon, as well as xenotime intergrown with altered Fe-Ti-oxide hematite, forming complex textures with disseminated Ti-oxides both in R.A.T. and Dipeta units. Major and trace element geochemistry indicates that the Dipeta is more dolomitic and magnesite while the R.A.T. is clay-rich. The Ti2O value of Dipeta and R.A.T samples is relatively low, ranging between 0.36 and 0.69 wt.% respectively, which suggest highly evolved felsic material in the protolith. This is consistent with interpretation based on the Al2O3/TiO2 ratio, which ranges between 18 and 23 for the R.A.T. and Dipeta respectively, indicating an intermediate to felsic granitoids as the protolith of R.A.T. and Dipeta siltstones. The Ti/Zr ratio of R.A.T. and Dipeta samples of less than 10, while, the higher La/Sc ratio of between 2.6 and 5.5 (for the R.A.T. and Dipeta respectively) indicate that both the R.A.T. and Dipeta are active continental and passive margin tectonic setting. Based on the geochemical variation with depth across the R.A.T. and Dipeta and their contact zone, a geochemical fingerprinting suggests that the ratio TiO2/Al2O3 appears to be useful and could be considered as a stratigraphic geochemical maker able to discriminate the R.A.T. and the Dipeta Subgroups during the geological mapping.
- Full Text:
- Date Issued: 2020
Petrography, metamorphism, deformation and P-T conditions in the western arm of the Lufilian Arc - Zambezi, north-western Zambia
- Authors: Chilekwa, Mwango
- Date: 2020
- Subjects: Petrogenesis -- Zambia -- Zambezi District , Metamorphism (Geology) -- Zambia -- Zambezi District , Petrology -- Zambia -- Zambezi District , Formations (Geology) -- Zambia -- Zambezi District , Rock deformation -- Zambia -- Zambezi District , Lufilian Arc , Neoproterozoic Katangan R.A.T. (Roches Argilo Talqueuse) Subgroup
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/161971 , vital:40699
- Description: The Zambezi area in north-western Zambia is underlain by Neoproterozoic Katanga Supergroup and older, Archean to Mesoproterozoic Basement Supergroup rocks. The area lies within the Domes Region, which is a structural domain of the Lufilian Arc. The stratigraphic succession within Zambezi area is dominated by the Grand Conglomerate Formation (GC) and Mwashia Group which are the most extensive units, and the less abundant Lower and Upper Roan Groups of the Katanga Supergroup. They wrap around the domal Basement Supergroup units. The mineral assemblage of the Mwashia and the GC schists commonly contains garnet, anthophyllite and biotite. GC rocks show remnants of primary structures such as clasts and sedimentary features. Anthophyllite, garnet and biotite are the dominant Mg-Fe rich metamorphic minerals. However, these are iron rich for each mineral phase and has been attributed to iron rich protoliths. The earliest recognised deformation episode (D1) formed NE-SW S1 foliations within GC which is consistent with the regional structural trend in the western Lufilian Arc. S1 was later affected by D2 that generated downward facing F2 folds and S2 foliations. The other associated feature to D2 is garnet that grew as the result of pro-grade metamorphism. The D3 deformation fabric is not developed and did not affect much of the structural geometry of the Zambezi area. The peak assemblages of the Basement Supergroup and the Katanga Supergroup formed at mid-amphibolite facies conditions of 590 °C and 630 °C at an average pressure of 4.0 kbar. The Basement Supergroup has undergone retrograde metamorphism to greenschist facies condition indicated by presence of chlorite and also determined by biotite-anorthite isopleth in THERIAK DOMINO. At the eastern part of Zambezi area, the Katanga Supergroup rocks were retrogressed in the upper greenschist facies at about ~470°C and ~4.0 kbar due to isobaric cooling.
- Full Text:
- Date Issued: 2020
Photo-physicochemical characterization and in vitro Photodynamic Therapy Activity of Phthalocyanine-Graphene Quantum Dots Conjugates
- Authors: Nene, Lindokuhle Cindy
- Date: 2020
- Subjects: Photochemotherapy , Cancer -- Chemotherapy , Quantum dots , Graphene , Nanomedicine
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/140463 , vital:37891
- Description: This thesis reports on the preparation of several differently substituted Zn(II) phthalocyanine (Pc) complexes and their respective graphene quantum dots (GQDs) conjugates. In addition, Pc complexes substituted with biologically active molecules used in cancer therapeutics, namely: benzothiazole and morpholine, were also prepared and conjugated to GQDs. The photo-physicochemical properties were determined for both the complexes and their respective conjugates including the fluorescence/ triplet quantum yields and lifetimes as well as the singlet oxygen generating abilities. Upon conjugation to GQDs, the fluorescence of the Pc complexes decreased (insignificant decrease in some cases), with an increase in the triplet quantum yields. However, the singlet quantum yields of the Pcs in the conjugates did not show an increase with the increase in the triplet quantum yields. This is suspected to be due to the screening effect. The cytotoxicity of the complexes in vitro decreased upon conjugation, as a result of reduced actual number of Pc units provided in the conjugate for therapy. An increase in the efficacy upon quaternization was observed, and a relatively better performance was also observed for the cationic complex in combination with the biotin- functionalized GQDs, 7-GQDs-Biotin. Moreover, the cellular uptake of 7-GQDs-Biotin over 24 h was relatively high compared to complexes alone and other Pcs-GQDs conjugates.
- Full Text:
- Date Issued: 2020
Photocatalysis of 4-chloro and 4-nonylphenols using novel symmetric phthalocyanines and asymmetric porphyrin supported on polyacrylonitrite nanofibres
- Authors: Jones, Benjamin Martin
- Date: 2020
- Subjects: Nanoparticles , Phthalocyanines , Electrospinning , Porphyrins , Nanofibers , Photocatalysis , Photocatalysis -- Environmental aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164770 , vital:41163
- Description: This work explores the synthesis and characterisation of novel symmetrical phthalocyanines and novel asymmetric porphyrins that have been embedded or linked respectively,and electrospun into fibres for application in the photocatalysis of environmental pollutants. The phthalocyanines contain pyrrole moieties without hetero atom linkers to maintain a rigid structure. The porphyrin contains a carboxy moiety utilized to construct an amide bond between the complex and the polymer prior to the spinning process. The new compounds were characterized by elemental analyses, proton nuclear magnetic resonance (HNMR)Fourier-transform infrared spectroscopy (FTIR), MALDI-TOF and UV-vis spectroscopy. The general trends of fluorescence, triplet and singlet oxygen quantum yields are described as well as their appropriate lifetimes. The photocatalytic activity of phthalocyanine embedded fibres were compared against those that had been dyed. Unfortunately, during the degradation process, the dyed fibres leeched compound and the studies could not be continued. It was seen that the porphyrin fibres linked to the polymer showed the most efficient photocatalytic activity against 4-cholorphenol and 4-nonylphenol due to irradiation at lower wavelengths consequently having higher frequencies and transferring more energy.
- Full Text:
- Date Issued: 2020
Photocatalytic reduction of CO2 by cobalt doped TiO2 and ZnO micro/nanostructured materials
- Authors: Mgolombane, Mvano
- Date: 2020
- Subjects: Nanostructures , Catalysis , Nanotechnology , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49171 , vital:41607
- Description: Large emissions of carbon dioxide (CO2) in the atmosphere have caused many harmful effects on humans and the environment. Carbon dioxide is a good source C and is used in a number of applications such as synthesis of fossil fuels. Redox reaction of CO2 and H2O with photocatalysts such as TiO2 and ZnO to produce solar fuels is a promising approach in reducing the environmental impacts of greenhouse gasses. This dissertation describes an in-depth synthesis of four photochemical catalysts and their photocatalytic conversion of CO2 to methanol, thereby addressing the above-mentioned problems by applying synthesised nano-based catalysts. Prior to photocatalytic reduction studies, catalysts such as TiO2, Co-doped TiO2, Co-doped TiO2/rGO, ZnO, Co-doped ZnO and Co-doped ZnO/rGO were synthesized and characterized using various spectroscopic and imaging techniques such as Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Micrograph (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunner- Emmet- Teller measurement (BET), Thermogravimetry Analysis (TGA) and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The conversion yield of CO2 to methanol on TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of -18.12 KJ/mol. The photocatalytic activities of ZnO-based nanomaterials found that Co-doped ZnO/rGO with high ratio of Co, reduced graphene (rGO) and large surface area (10.62 m2g-1) possessed higher CH3OH (30.1 μmol/g) in comparison with Co-doped ZnO (27.3 μmol/g) and ZnO (7.5 μmol/g). The research will deepen the understanding that TiO2 based photocatalyst show higher activity and the mole ratio (Ti/Zn:Co) influences nanocomposites performance and provide new ideas for designing efficient photocatalysts.
- Full Text:
- Date Issued: 2020
Physical and thermal properties of binary and ternary blends of polypropylene, crumb rubber and wood flour
- Authors: Mosia, Lefika Ellen
- Date: 2020
- Subjects: Polypropylene , Polymers Materials science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49193 , vital:41609
- Description: The properties of binary and ternary blends of polypropylene (PP), crumb rubber (CR) and wood flour (WF), with and without ethylene-1-butene as a compatibiliser, were studied. The design of experiment (DoE) was used to determine the proportions of each component for various composites. The components were mixed using the Haake Thermo scientific Polylab QC internal mixer and the crumbs were then moulded into different shapes using the ARBURG 221-55-250 injection moulding machine. The properties of the blends were investigated using a scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanic analysis (DMA), tensile tester, water absorption and thickness swelling tests. The morphology of the blends showed the agglomeration of fillers (CR and WF) and more voids on untreated blends but on the treated blends fewer voids as well as improved distribution and dispersion were observed. PP bonded better with WF than with CR. The incorporation of both fillers improved the thermal stability, glass transition temperature, and melt temperature as well as crystallisation temperatures of the blends. Yet these fillers reduced the tensile strength and the yield strength of PP. The addition of WF increased the elongation at break and hardness of the blends but decreased the impact strength of the blends, whereas the addition of CR improved the elongation at break and impact strength of the blends and decreased the hardness of the blends. The blends with more WF absorbed more water and swelled more than the blends containing a high amount of CR. The incorporation of compatibiliser further decreased the tensile strength but improved the thermal stability and elongation at break of the blends. The water absorption and swelling of the blends seemed to decrease with the addition of the compatibiliser whereas the hardness increased. The impact strength of the blends containing more WF, increased after the addition of compatibiliser. The ternary blends showed better results than the binary blends.
- Full Text:
- Date Issued: 2020
Prediction of mass spectra for natural products using an ab initio approach
- Authors: Novokoza, Yolanda
- Date: 2020
- Subjects: Molecular dynamics , Molecular dynamics -- Computer simulation , Mass spectroscopy , Electron impact ionization
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167166 , vital:41443
- Description: Mass spectrometry (MS) is a technique that measures the fragmentation of molecules, dependent on the molecule’s chemical composition and structure, by first introducing a charge on the molecules. The instrument records the mass to charge ratio, but the energy from the ionization process causes the molecule to fragment. The resultant mass spectrum is highly indicative of not only the molecule analyzed, but also its chemical composition. MS is used in research and industry for both routine and research purposes. One such way to ionize molecules for MS is by bombarding the molecule with electrons which is the basis of electron impact mass spectrometry (EIMS). Although EIMS is widely used, prediction of electron impact mass spectra from first principles is a challenging problem due to a need to accurately determine the probability of different fragmentation pathways of a molecule. Ab initio molecular dynamics based methods are able to explore in an automatic fashion the energetically available fragmentation paths thus give reaction mechanisms in an unbiased way. The mass spectra of five molecules have been explored in work-flows leading to the prediction of mass spectra. These molecules include three natural products alpha-hispanolol, PFB oxime derivative and boronolide (for which experimental mass spectra were not available) and two compounds from the NIST database (for which experimental mass spectra were available). For each of these systems many random conformations were generated using the RDKit library. To all conformations random velocities were applied to each atom. Ab initio molecular dynamics was performed on each conformer, using these initial random velocities using CP2K software, at DFTB+ level at a variety of highly raised temperatures (to accelerate the formation of fragments) Fragmentation was monitored by iterating through all bonds, and identifying bond breakages during dynamics. Graph theoretical packages were used then to track distinct fragments generated. For each of these fragments, charges were determined from Mulliken analysis for all atoms on the fragment from the QM calculations and sum of atomic spin densities per fragment was also plotted. The fragment with the greatest charge (corresponding to the formation of a cation fragment) was taken for plotting on the mass spectrum. Finally, from the mass of the fragment and its elemental composition, the isotopic distribution for the fragment was determined, and this distribution was included by addition in to the mass spectrum. For all trajectories, the sum of all isotopic distributions determined the final mass spectrum.
- Full Text:
- Date Issued: 2020
Profitable day-neutral strawberry variety and planting date combination for year-round strawberry fruit production in the Southern Cape
- Authors: Parehwa, Patience
- Date: 2020
- Subjects: Strawberries -- Fertilizers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48599 , vital:40894
- Description: South Africa’s strawberry production is currently limited to winter and spring production. Strawberry growers have not been able to extend the growing season for year-round strawberry production primarily due to variety- and climatic limitations. Consumers world-wide, however, demand year-round supply of strawberries on their markets. Delayed planting and robust day-neutral varieties may allow growers to extend the marketing season. To investigate the most profitable variety and planting date combination for season extension in the Southern Cape, trials were conducted at Groeneweide Farm, George. Day-neutral strawberry varieties Monterey, San Andreas and Albion were planted at 30-day intervals from April to September for 3 seasons. They were planted in single layer, standard coir grow-bags at a density of 75 000/ha. Analyses of variance (ANOVA) were performed on vegetative growth stages (crown and runner formation), yield (flowering and fruit yield), fruit quality (fruit mass and total soluble solids content) and gross income. The analysis encompassed variety, month and planting month × variety interaction. ‘Monterey’ significantly outperformed ‘San Andreas’ which in turn significantly (p<0.05) outperformed ‘Albion’ for crown number, flower number, yield, fruit size and margin above cost. ‘San Andreas’ produced significantly fewer runners than ‘Monterey’ and ‘Albion’. ‘Albion’ produced significantly higher TSS followed by ‘Monterey’ and ‘San Andreas’. Over all, the three day-neutral varieties had no significant differences in yield within all planting dates. However, August and September planting dates produced significantly more runners, flowers and higher margin above cost, but significantly smaller fruit and lower total soluble solids (TSS). ‘Monterey’ planted in April and May produced the highest margin above cost and brought earliness to the production window. Together with ‘San Andreas’ planted in August, which extended the harvest season and gave similar margin above cost, it is possible to maximise profitability, extend both ends of the harvest season and also minimise hygiene costs associated with weekly runner removal. Since the strawberry price is very responsive, to quantity supplied, an oversupply out of the normal season, may however lead to lower prices affecting gross income.
- Full Text:
- Date Issued: 2020
Retrospective analysis of birth HIV PCR testing and follow-up of positive HIV PCR results in Nelson Mandela Bay Health District
- Authors: Makubalo, Nomlindo Princess
- Date: 2020
- Subjects: HIV infections -- South Africa -- Nelson Mandela Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46351 , vital:39580
- Description: BACKGROUND HIV infection contributes significantly to infant morbidity and mortality, especially in high-prevalence, low-income countries. In view of this evidence-based knowledge, South Africa’s National Department of Health, in April 2015, released the National Consolidated Guidelines of Human Immunodeficiency Virus (HIV) stipulating that all HIV-exposed babies should have a HIV Polymer Chain Reaction (PCR) test performed at birth. Early infant diagnosis (EID) means early initiation of combined antiretroviral treatment (cART) and a reduction in the incidence of early infant HIV-related mortality. However, these guidelines can only be successful if implemented properly across all public sector healthcare institutions. Thus,the research question was,“How well has the Nelson Mandela Bay Health District implemented the EID?”AIM The aim of the study was to review the impact of the consolidated HIV guidelines on birth HIV-PCR testing and initiation of treatment in the Nelson Mandela Bay Health District. METHOD A retrospective quantitative longitudinal non-experimental design was used.The study consisted of two components,namely,analysis of NHLS databases, particularly HIV birth PCR results of infants over a three-year period (June 2015 to June 2018),and analysis of feedback received from the primary health care clinics. The feedback focused on infants with a positive-birth PCR test, using a purpose-designed data collection tool that was used by the clinics for the duration of the same three-year period. The paper-based tool documented antenatal care attendance, enrolment into the prevention of mother-to-child transmission (PMTCT) programme and initiation of ART. RESULTS Over the three-year period, there were approximately 13,096 live births to HIV-positive women in the study area, and a total of 11,066 HIV birth PCR tests were done over xiiithe three-year study period (84.5% of HIV-exposed infants). The birth HIV PCR was negative in 10,909 (98.6%) neonates, while 130 (1.2%) of neonates had positive-birth HIV PCR tests,and a further 27 (0.2%) had indeterminate results. The birth HIV PCR positivity rate reduced from 1.4%(2015)to 1%(2018)over the three-year study period. Of the 130 infants with positive-birth HIV PCR, the files of 42 children were excluded, and further analysis conducted on the files of 88 infants. cART was initiated within seven days in only nine of the 88 infants (10.2%). ARV initiation was delayed for 58 infants (65.9%) and 21 neonates (23.9%) were never initiated on cART. Among the 88 mothers of infants, more than one-third (38.6%) of pregnant women did not attend antenatal care, thus,compromising their opportunity to be enrolled on the PMTCT programme. Of those who attended antenatal care, only 39.1% were reported to attend antenatal care before 20 weeks CONCLUSION AND RECOMMENDATIONS The incidence of positive-birth HIV PCR has reduced from 1.4% in 2015 to 1% in 2018 whilst there has been an increase in birth HIV PCR testing. However, initiation of cART within seven days was achieved in only 10.2% of infants with positive-birth HIV PCR test results. Implementation of point-of-care birth HIV PCR testing would ensure that results are immediately available resulting in increasing the proportion of infants initiated on cART within seven days.
- Full Text:
- Date Issued: 2020
Seasonal trends of rainfall intensity, ground cover and sediment dynamics in the Little Pot River and Gqukunqa River catchments, South Africa
- Authors: Herd-Hoare, Sean
- Date: 2020
- Subjects: Land degradation -- Control -- South Africa -- Eastern Cape , Vegetation mapping -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Gqukunqa River catchment (South Africa) , Little Pot River catchment (South Africa) , Tsitsa River catchment (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146288 , vital:38512
- Description: Natural rangelands provide a variety of ecosystem services including livestock production which occurs on land under freehold land tenure and on land under communal tenure. There is an ongoing debate around the extent to which land degradation is occurring on these rangelands under different land management and land tenure systems and what the main degradation drivers are. Over-grazing, rainfall and soil type are key drivers of rangeland dynamics and the resultant sediment yield in the river systems, however, over-grazing is an outcome of land management while rainfall and soil type are natural drivers. This study explores the relationship between rainfall and daily sediment flux as well as the seasonal trends of vegetation cover and the study is part of a greater research effort called the Tsitsa Project which is based in the Tsitsa River catchment (near Maclear, Eastern Cape, South Africa). The Tsitsa Project aims at developing and managing both land and water in a sustainable way by improving the land, water and lives of people living in the Tsitsa River catchment. The restoration efforts of the Tstisa Project will aid in extending the lifespan of both the proposed dams on the Tsitsa River. The Tsitsa River catchment is characterised by grasslands, steep topography, highly erodible soils with many large gullies present and a very high sediment yield in the Tsitsa River which allowed for the exploration of some of the system drivers of sediment yield in this catchment. The study involved two sub-catchments of the Upper Tsitsa River catchment of different land management strategies: one dominated by commercial livestock farms (Little Pot River catchment) and one dominated by communal rangelands (Gqukunqa River catchment). The aim of this study was to determine the seasonal trends of rainfall intensity, ground cover and sediment dynamics in the Little Pot River and Gqukunqa River catchments. The purpose of the findings was to improve management strategies in degraded areas and catchments. In order to achieve this aim a variety of field and desktop methods were used. Field methods involved measuring variables including: vegetation biomass, vegetation cover, soil surface hardness, biocrust cover and slope angle for a range of Normalized Difference Vegetation Index (NDVI) values from the Sentinel-2A sensor. The study assessed the system response of the field variables in both catchments over one rainfall season (2018-2019). Desktop methods included various NDVI analyses as well as analyses of trends and relationships between vegetation dynamics, rainfall and sediment. The relationship between erosive rainfall events, daily rainfall, antecedent rainfall and daily sediment flux was explored over the time period of January 2016 to January 2019 and October 2015 to January 2019 for the Little Pot River catchment and the Gqukunqa River catchment respectively. NDVI was explored as a proxy for vegetation cover to extrapolate across the catchments and monitoring period. NDVI was found to have a weak positive relationship with vegetation cover and biomass (R2 values ranged from 0,04 to 0,525). Mean monthly catchment NDVI values, biomass and vegetation cover increased throughout the wet season of 2018-2019 in both catchments. Mean monthly NDVI values increased from 0,26 to 0,55 in the Little Pot River catchment and from 0,29 to 0,53 in the Gqukunqa River catchment over the course of the 2018-2019 wet season. NDVI, biomass and vegetation cover was found to be higher on south-facing slopes than north-facing slopes in both catchments for the majority of the wet season. The Gqukunqa River has significantly higher daily sediment fluxes than the Little Pot River despite similar NDVI and rainfall intensities which is owed to the dispersive soils in the Gqukunqa River catchment. Soil surface hardness results were inconclusive due to rainfall before or during every field trip which changed the properties of the soil. The largest erosive rainfall, daily rainfall and daily sediment events occurred from January to March each wet season in both catchments. Rainfall intensity and sediment fluxes were found to have a weak relationship, however, there was a stronger relationship found between antecedent rainfall and sediment flux. The larger daily sediment fluxes in each catchment often did not result from an erosive rainfall event on the same day but rather from multiple days of rainfall which can result in saturated soils and runoff leading to surface and sub-surface erosion. The possibility of sub-surface erosion via chemical processes contributing to the larger sediment events was also explored to explain the stronger relationship between antecedent rainfall and daily sediment flux.
- Full Text:
- Date Issued: 2020
Securing software development using developer access control
- Authors: Ongers, Grant
- Date: 2020
- Subjects: Computer software -- Development , Computers -- Access control , Computer security -- Software , Computer networks -- Security measures , Source code (Computer science) , Plug-ins (Computer programs) , Data encryption (Computer science) , Network Access Control , Data Loss Prevention , Google’s BeyondCorp , Confidentiality, Integrity and Availability (CIA) triad
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/149022 , vital:38796
- Description: This research is aimed at software development companies and highlights the unique information security concerns in the context of a non-malicious software developer’s work environment; and furthermore explores an application driven solution which focuses specifically on providing developer environments with access control for source code repositories. In order to achieve that, five goals were defined as discussed in section 1.3. The application designed to provide the developer environment with access control to source code repositories was modelled on lessons taken from the principles of Network Access Control (NAC), Data Loss Prevention (DLP), and Google’s BeyondCorp (GBC) for zero-trust end-user computing. The intention of this research is to provide software developers with maximum access to source code without compromising Confidentiality, as per the Confidentiality, Integrity and Availability (CIA) triad. Employing data gleaned from examining the characteristics of DLP, NAC, and Beyond- Corp—proof-of-concept code was developed to regulate access to the developer’s environment and source code. The system required sufficient flexibility to support the diversity of software development environments. In order to achieve this, a modular design was selected. The system comprised a client side agent and a plug-in-ready server component. The client side agent mounts and dismounts encrypted volumes containing source code. Furthermore, it provides the server with information of the client that is demanded by plug-ins. The server side service provided encryption keys to facilitate the mounting of the volumes and, through plug-ins, asked questions of the client agent to determine whether access should be granted. The solution was then tested with integration and system testing. There were plans to have it used by development teams who were then to be surveyed as to their view on the proof of concept but this proved impossible. The conclusion provides a basis by which organisations that develop software can better balance the two corners of the CIA triad most often in conflict: Confidentiality in terms of their source code against the Availability of the same to developers.
- Full Text:
- Date Issued: 2020
Sexual attraction and mating compatibility between Thaumatotibia leucotreta populations and implications for semiochemical dependent technologies
- Authors: Upfold, Jennifer Kate
- Date: 2020
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction , Citrus -- Disease and pests -- Control -- South Africa , Insect sterilization -- South Africa , Pheromones , Pheromone traps
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/148526 , vital:38747
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick), is the most important pest for the cultivation of citrus in South Africa. False codling moth is indigenous to southern Africa and is a regulated pest of many international markets for phytosanitary concerns. Considerable research efforts have been invested in the past decades to develop semiochemcial technologies, such as monitoring with sex pheromones, attract-and-kill, mating disruption and the sterile insect technique. One of the potential obstacles identified with semiochemical control is the differences in the ratio of the compounds comprising the sex pheromone at different geographical locations, resulting in what is known as regional attraction. This has been identified in FCM populations from three different countries, however, regional attraction within South African FCM populations was unknown. Therefore, the study assessed the genetic integrity of five laboratory-reared FCM populations originating from geographically isolated populations in South Africa using the AFLP technique in order to assess regional attractiveness within the country. The results found isolated populations from Addo, Citrusdal, Marble Hall, Nelspruit and a fifth group found to be closely related to Addo and Citrusdal called the ‘Old’ colony. These five genetically isolated populations as well as a population from Xsit (Pty) Ltd, used for the sterile insect technique (SIT), were used in regional attractiveness trials. Males were significantly (P = <0.05) more attracted to females originating from the same population. No significant attraction could be determined from the sterile males, as the recapture rates in the trap were too low. Furthermore, regional attractiveness was assessed through choice/ no-choice mating compatibility trials. Significant sexual isolation (ISI) occurred between mating combinations Addo × Nelspruit (ISI = 0,13; t2 = 6.23; p = 0.02), Addo × Marble Hall (ISI = 0,11; t2 = 4.72; p = 0.04), Citrusdal × Nelspruit (ISI = 0,11; t2 = 4.95; p = 0.04), and Citrusdal × Marble Hall (ISI = 0,12; t2 = 4.31; p = 0.04). In these combinations, Addo and Citrusdal males were found to have outcompeted Nelspruit and Marble Hall males for more mating events. Significant sexual isolation was also recorded for Sterile × Marble Hall (ISI = 0.12; t2 = 4.98; p =0.01) and Sterile × Citrusdal (ISI = 0.13; t2 = 3.96; p = 0.01) populations. The male relative performance index was significant in both combinations, indicating that non-sterile laboratory males outcompeted the sterile males in these two combinations. When given no choice, evaluated as spermatophore transfer/ female/ 48h, all males (including sterile) were successful in transferring spermatophores to all FCM populations, with no significant differences. These results indicate that there may be incipient pre-isolation mechanisms affected by local natural selection, resulting in localised sexual attraction via differences in the sex pheromone ratios. These findings provide important information for semiochemical technologies and the implication of these results with regard to monitoring with sex pheromones, attract-and-kill, mating disruption and sterile insect technique are discussed.
- Full Text:
- Date Issued: 2020