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The contributions of biological control to reduced plant size and biomass of water hyacinth populations

- Jones, Roy W, Hill, Jaclyn M, Coetzee, Julie A, Hill, Martin P

Authors: Jones, Roy W , Hill, Jaclyn M , Coetzee, Julie A , Hill, Martin P
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/68803 , vital:29326 , https://0-doi.org.wam.seals.ac.za/10.1007/s10750-017-3413-y
Description: Water hyacinth is invasive in many countries, where it reduces aquatic biodiversity and limits water resource utilisation. Biological control of water hyacinth has been successful in South Africa, but has suffered from a lack of empirical data to prove causation. Insect exclusion trials were conducted to quantify the contribution of Neochetina eichhorniae and N. bruchi to the integrated control of water hyacinth on the Nseleni River, South Africa. Insecticide was not expected to induce phytotoxicity, but would prevent weevil damage in water hyacinth plants; and weevil herbivory was predicted to reduce plant petiole length, and above/below surface biomass. Results showed that insecticide had no phytotoxic effects and excluded weevils for 3 weeks, providing a baseline for field applications. Biological control on the Nseleni River directly affected water hyacinth biomass and petiole length, but did not affect plant cover. Plants subject to weevil herbivory demonstrated reductions in above and below surface biomass and had shorter petioles compared to insect-free plants. Dead biomass was also higher in biological control treatments. Biological control strongly affects plant size, biomass and vigour; however, further integrated control is required to facilitate reduction in mat cover, which is the goalpost for successful control of floating aquatic plants.
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Date Issued: 2018

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The determination of CHARMM force field parameters for the Mg2+ containing HIV-1 integrase:

- Musyoka, Thommas, Tastan Bishop, Özlem, Lobb, Kevin A, Moses, Vuyani

Authors: Musyoka, Thommas , Tastan Bishop, Özlem , Lobb, Kevin A , Moses, Vuyani
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/148139 , vital:38713 , DOI: 10.1016/j.cplett.2018.09.019
Description: The HIV integrase enzyme is a validated drug target. However, its potential has remained largely unexploited until recently due to lack of structural and mechanistic information. Its catalytic core domain (CCD) is crucial for the viral-human DNA integration making integrase an ideal target for inhibitor design. However, in order to do so, force field parameters for the integrase magnesium ion need to be established. Quantum mechanical calculations were used to derive force field parameters which were validated through molecular dynamics studies. Our results show that the parameters determined accurately maintain the integrity of the metal pocket of the integrase CCD.
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Date Issued: 2018

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The development and implementation of a psychoeducational programme: a case study on mental toughness in a novice triathlete

- Coertzen, Marlé

Authors: Coertzen, Marlé
Date: 2018
Subjects: Sports -- Psychological aspects , Triathletes -- Mental health , Toughness (Personality trait) , Triathlon -- Psychological aspects , Achievement motivation , Mental discipline , Sport Mental Toughness Questionnaire (SMTQ)
Language: English
Type: text , Thesis , Masters , MA
Identifier: http://hdl.handle.net/10962/63010 , vital:28354
Description: As an academic and applied discipline, sport psychology is interested in identifying, understanding, measuring and developing the various mental constructs that interact with physical factors, aiming to produce optimum performance and enhance athletes’ experience of sport participation. The programmes developed within sport psychology are not only applicable to sport, but have applicability within other areas, such as the performing arts, business and professions that are considered high risk, such as the military. Using a mixed methods approach and a triangulation of qualitative and quantitative data collection and analysis techniques, the goal of this research was to document the process of developing and implementing a psychoeducational mental toughness programme and to evaluate the programme through exploring the participant’s subjective experience of such a programme. The aim of the research was to contribute to the existing literature on mental toughness programmes. This was attained through administering the Sport Mental Toughness Questionnaire (SMTQ) and a semi-structured interview, which informed the development and implementation of a psychoeducational mental toughness programme relative to the idiosyncrasies of the participant and grounded in strengths-based approaches to mental toughness development. Results were obtained based on post-implementation data collected through a second administration of the SMTQ and a semi-structured interview. The participant experienced the programme as positive and results were indicative of changes in his experiences of self-confidence and control, related to the global themes of mindset, flexibility and mindfulness.
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Date Issued: 2018

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The development, manufacture and evaluation of sustained release gastric-resistant isoniazid and gastroretentive microporous rifampicin microspheres

- Mwila, Chiluba

Authors: Mwila, Chiluba
Date: 2018
Subjects: Biodegradation , Microspheres (Pharmacy) , Drug delivery systems , Rifampin , Isoniazid
Language: English
Type: Doctoral theses , text
Identifier: http://hdl.handle.net/10962/63497 , vital:28421 , DOI 10.21504/10962/63497
Description: According to the World Health Organization Global Tuberculosis (TB) 2017 Report, there were an estimated 10.4 million new TB cases worldwide of which, in 2016, 65 % occurred in men, 28.1 % in women and 6.9 % in children. TB is the ninth leading cause of death globally and is the leading cause due to an infectious organism surpassing HIV/AIDS. Treatment is long-term and the use of a combination of medicines is required for success. The concern related to the use of fixed dose combination products for the treatment of TB is the issue of low bioavailability of rifampicin observed from a number of fixed dose combination (FDC) formulations. The hydrolysis of rifampicin, in acidic media, to form insoluble 3-formyl rifamycin SV contributes to poor bioavailability of rifampicin. The degradation of rifampicin to form this poorly absorbed compound is accelerated in the presence of isoniazid via the reversible formation of isonicotinyl hydrazone is a further factor contributing to the poor bioavailability of rifampicin. Therefore, the development of a novel drug delivery technology that prevents interactions between rifampicin and isoniazid in an acidic medium is required. A Box Behnken design was successfully used for the optimisation of a rapid and accurate stability-indicating gradient elution RP-HPLC method for the simultaneous analysis of isoniazid, pyrazinamide and rifampicin. The method was validated using ICH guidelines and the results indicate it can be used for the rapid analysis of commercially available TB FDC formulations containing the active pharmaceutical ingredients, API. The method is precise, sensitive and has the necessary selectivity for use during formulation development and optimisation studies for a combination of rifampicin, isoniazid and pyrazinamide. Initially formulation activities were undertaken with rifampicin and isoniazid for the development of an approach to enhance the effective delivery of these compounds. The characterisation of rifampicin and isoniazid was undertaken using spectroscopic, thermal and microscopic analysis. The studies revealed that the compounds are crystalline and exhibit distinct characteristic sharp peaks in X-ray diffractograms and Differential Scanning Calorimetry thermograms. The thermograms, 13C Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy results identified that rifampicin occurs as the form II polymorph however, as there are no significant biopharmaceutic differences between the polymorphic forms of rifampicin this information was used for identification purposes only. The results were used as baseline data for comparative purposes to monitor changes that may occur when rifampicin and isoniazid are used in formulation development, dosage form manufacture and characterisation activities for a FDC technology designed to deliver both compounds simultaneously. Hydroxypropylmethylcellulose acetate succinate (HPMC-AS) and Eudragit® L100 polymers were successfully used for manufacture of isoniazid loaded gastric-resistant sustained release microspheres using an o/o solvent emulsification and evaporation approach. A Hybrid experimental design was used to investigate the influence of input variables viz., homogenisation speed and amount of HPMC-AS and Eudragit® L100 on gastric-resistance, INH release and encapsulation efficiency. The approach of using coating polymers viz., HPMC-AS and Eudragit® L100, to manufacture gastric resistant sustained release microspheres of isoniazid is unique and was efficient for preventing the release of isoniazid in an acidic environment. Only 0.523 % isoniazid was released from the optimised formulation after 2 h exposure to pH 1.2 0.1 M HCl suggesting there is also the possibility of minimising the accelerated degradation of rifampicin that occurs in the presence of isoniazid in acidic media. The microspheres also exhibited sustained release properties without burst release in pH 6.8 0.1 M phosphate buffer as < 5 % isoniazid was released at 0.5 h and only 11 % isoniazid was released at 2 h. The release of isoniazid was sustained over the entire period of dissolution testing with > 85 % isoniazid released at 24 h, implying that the majority of encapsulated isoniazid would be available for absorption. The manufacturing process resulted in the production of hard spherical particles and particle size analysis revealed that the microspheres ranged between 415.76 ± 76.93 μm and 903.35 ± 197.10 μm in diameter. The microspheres exhibited excellent flow properties attributed to the spherical nature of particles. Carr‟s index (CI) was 4.934 ± 0.775 % and the Hausner ratio (HR) was 1.148 ± 0.033 indicating good packability of the microspheres that would help in achieving weight and content uniformity of capsule dosage units. The manufacturing process however produced a low % yield suggesting that scale up difficulties may be encountered. However the high encapsulation efficiency observed may counter the challenges associated with the low yield. The DSC thermograms and FT Raman spectra of 1:1 mixtures of isoniazid, excipients and the microspheres did not reveal any potential detrimental interactions. Microporous floating sustained release microspheres for the delivery of rifampicin in the stomach have been successfully manufactured using emulsification and a diffusion/evaporation process. A novel approach using solvent mixture of acetone and dichloromethane that has not been reported for the manufacture of rifampicin microspheres was successfully used and resulted in the formation of a stable emulsion and the manufacture of rifampicin-loaded microspheres with uniform characteristics. In addition the manufacturing process was shorter than most other reported methods. A Box-Behnken experimental design was successfully used to study the influence of ethylcellulose, Eudragit® RLPO and d-glucose content on the floating properties, encapsulation efficiency and % yield of microspheres. The optimised formulation did not yield desired floating characteristics as the % buoyancy was low and floating lag times were high. The optimised formulation was modified by addition of NaHCO3 to increase the % buoyancy and reduce the floating lag time. Rifampicin release from the microspheres of the modified batch was 87.10 % at 12 h and the microspheres exhibited a % buoyancy of 87.66 ± 1.28 % (n = 6) and floating lag time of 15 ± 3.2 (n = 6) seconds. The microspheres remained buoyant for up to 12 h and an encapsulation efficiency of 88.26 ± 1.25 % was achieved. SEM images of microspheres following exposure to dissolution fluid revealed that the microspheres had numerous pores on their surface. The mean particle size distribution ranged between 423.19 ± 121.86 μm to 620.07 ± 102.67 μm. The microspheres exhibited similar flow characteristics to isoniazid microspheres with a CI of 1.422 ± 0.074 %, and HR of 1.034 ± 0.002. The excellent flow characteristics indicate that filling of the microspheres into hard gelatin capsules was unlikely to pose a challenge in respect of producing a product with uniform content. Rifampicin-excipient compatibility studies did not reveal any potential or significant interactions suggesting that the excipients used for the manufacture of the microspheres were compatible, although long term stability studies would be required to ascertain this is, indeed the case. The microporous floating sustained release microspheres manufactured in these studies has the potential to increase the bioavailability of rifampicin as they may be retained in the stomach where the solubility of rifampicin is high and from which absorption is best achieved. The degradation of rifampicin after 12 h dissolution testing in pH 1.2 0.1 M HCl in the presence of isoniazid gastric-resistant sustained release microspheres was only 4.44%. These results indicate that the degradation of rifampicin in the presence of isoniazid in acidic media can be overcome by encapsulation of both active pharmaceutical ingredients in a manner that ensure release in different segments of the gastrointestinal tract. The use of sustained release microporous gastroretentive rifampicin microspheres in combination with sustained release isoniazid gastric-resistant microspheres revealed that accelerated degradation of rifampicin in the presence of isoniazid is reduced significantly when using this approach and a FDC of rifampicin and isoniazid microspheres has the potential to improve the bioavailability of rifampicin thereby enhancing therapeutic outcomes. In vivo studies would be required to confirm the potential benefits of using this approach to deliver rifampicin in combination with isoniazid. , Thesis (PhD) -- Faculty of Pharmacy, Pharmacy, 2018
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Date Issued: 2018

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The distribution and abundance of the stem-galling fly, Cecidochares connexa (Macquart)(Diptera: Tephritidae), a biological control agent of Chromolaena odorata (L.)(Asteraceae), in Ghana

- Aigbedion-Atalor, Pascal O, Wilson, DD, Eziah, Vincent Y, Day, M, Paterson, Iain D

Authors: Aigbedion-Atalor, Pascal O , Wilson, DD , Eziah, Vincent Y , Day, M , Paterson, Iain D
Date: 2018
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/407074 , vital:70334 , xlink:href="https://hdl.handle.net/10520/EJC-113112d1da"
Description: Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae: Eupatorieae) is one of the worst invasive weeds in West Africa, and a serious biotic threat to food security. The stem-galling fly, Cecidochares connexa (Macquart) (Diptera: Tephritidae), a biological control agent for C. odorata, was released in the Ivory Coast in 2003 and first detected in Ghana in 2014. The spatiotemporal distribution and abundance of C. connexa in Ghana was determined by country-wide surveys from 2015 to 2016. Galls were found in varying densities across Ghana but gall densities were consistently low east of Lake Volta. A limited survey conducted in the extreme west of Togo in 2016, found the gall fly also in low numbers. There was a significant correlation between C. connexa gall densities and the distance from the release sites in the Ivory Coast. The distribution and abundance of the gall fly in Ghana could be explained by its spread from the original release sites over time and/or the much drier conditions east of Lake Volta. Cecidochares connexa has dispersed a distance of about 1000 km over a 10-year period and, while there is some evidence that the gall fly is still dispersing towards the east, its range and population size could be limited by the dry climatic conditions in the east of Ghana and in Togo. Actively redistributing the agent over this dry corridor to the more humid and higher rainfall areas of Nigeria, may result in the spread of this agent through the rest of West and Central Africa, thereby aiding the control of C. odorata in the region.
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Date Issued: 2018

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The ecological risk of acid mine drainage in a salinising landscape

- Vellemu, Emmanuel Captain

Authors: Vellemu, Emmanuel Captain
Date: 2018
Subjects: Acid mine drainage Environmental aspects South Africa Mpumalanga , Salinization South Africa Mpumalanga , Water salinization South Africa Mpumalanga , Water quality South Africa Mpumalanga , Aquatic animals Effect of water quality on South Africa Mpumalanga , Freshwater ecology South Africa Mpumalanga
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/60563 , vital:27797
Description: Acid mine drainage (AMD) and increasing salinity of freshwater ecosystems pose serious threats to water quality in water-stressed South Africa. These threats are exacerbated by mining activities, mainly gold and coal from both active and abandoned mines that continue to release acidic water that is rich in toxic metals and high sulphate concentrations. Therefore, the overarching hypothesis for this study was that “the combination of AMD and sulphate salts confers high ecological risk to the aquatic biota”. The study employed both laboratory and field investigations to test this hypothesis and provide appropriate tools to protect freshwater ecosystems from increasing anthropogenic impacts. Firstly, a laboratory investigation was carried out to develop risk-based water quality guidelines (WQGs) for sulphates and treated AMD (TAMD) using the species sensitivity distributions (SSDs) technique. Five South African freshwater species belonging to five different taxonomic groupings, including Adenophlebia auriculata (insect), Burnupia stenochorias (mollusc), Caridina nilotica (crustacea), Pseudokirchneriella subcapitata (algae) and Oreochromis mossambicus (fish) were exposed to varying concentrations of sodium sulphate (Na2SO4), magnesium sulphate (MgSO4) and calcium sulphate (CaSO4), as well as TAMD in separate ecotoxicological experiments, applying short-term (96 h) non-renewal and long-term (240 h) renewal exposure test methods. Secondly, a novel trait-based approach (TBA) was also used to predict the vulnerability of taxa to treated acid mine drainage (TAMD). The TBA used a combination of carefully selected traits of organisms that are mechanistically linked to TAMD for their potential vulnerability predictions. Leptoceridae (caddisflies) and Leptophlebiidae (mayflies) were selected taxa for evaluation of the trait-based vulnerability predictions to TAMD for laboratory toxicity exposures. This was followed by a field investigation to assess macroinvertebrates assemblage responses, abundance and richness to a TAMD-impacted stream using the South African Scoring System version 5 (SASS5) protocol. Outcomes form the above three sources were combined in a multi-criteria analysis (MCA) to develop an appropriate water quality management strategy in a form of a trait-based decision-making support tool. Results of the risk-based WQGs revealed that Na2SO4 was the most toxic of the tested salts. A concentration of 0.020 g/L Na2SO4, 0.055 g/L CaSO4, and 0.108 g/L MgSO4 or a combined sulphate salts limit of 0.067 g/L were derived as long-term WQGs to protect over 95% of the population species in a natural environment considered as relatively pristine. This means that the generic 0.25 g/L sulphate compliance limit for South African freshwater systems is under-protective. Burnupia stenochorias was the most sensitive to AMD after long-term exposures, and it was adjudged as a good indicator of AMD along with P. subcapitata. Long-term scenario-specific WQG for AMD for the protection of over 95% of the population species was derived as 0.014%. Results of the TBA revealed that the relative abundance and diversity of taxa at a site that received direct impact from TAMD generally corresponded to trait-based predictions. The site that received direct TAMD was largely dominated by members of the Corixidae and Naucoridae families. However, Leptoceridae was more vulnerable to TAMD than Leptophlebidae contrary to predictions. Its assemblage did not match the predictions although Leptophlebiidae corresponded to predictions in terms of its assemblage and diversity. As water quality improved further downstream of the TAMD source, macroinvertebrates assemblage and diversity also improved as predicted. However, it is important to note that other equally important traits that were not studied might influence the response of organisms during toxicity test exposures. The MCA findings suggest that the trait-based decision-making support tool is a useful management strategy for the predicting vulnerability of taxa aquatic stressors including AMD and increasing salinity. Overall, the outcome of this study suggests that AMD poses an ecological risk to aquatic biota, but this becomes riskier in the presence of excess sulphate salts. Albeit, the WQGs for sulphate salts and AMD as well as the developed trait-based decision support tool all contribute novel sound scientific knowledge basis for managing the AMD and increasing salinity in freshwater ecosystems. The study recommends incorporating different life stages of indigenous species tested to determine if their sensitivity to AMD and sulphate would correspond to current findings because early life stages could be more sensitive to aquatic stressors than juveniles or adults. This is important for the derivation of strong and relevant WQGs. The TBA requires further refinement for its incorporation in ecotoxicology on a wide scale.
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Date Issued: 2018

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The effect of annealing and beta irradiation on thermoluminescence spectra of α-Al2O3: C, Mg

- Kalita, Jitumani M, Chithambo, Makaiko L

Authors: Kalita, Jitumani M , Chithambo, Makaiko L
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/112875 , vital:33669 , https://doi.org/10.1016/j.jlumin.2017.12.036
Description: The effect of annealing on thermoluminescence spectra of beta irradiated α-Al2O3:C,Mg has been studied. Measurements were made on an un-annealed sample and samples annealed at 600, 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy shows a high intensity peak at 163 °C and six secondary peaks of weaker intensity at 43, 73, 195, 280, 329 and 370 °C. When the samples are annealed at 700 or 900 °C, an additional secondary peak appears at 100 °C. The thermoluminescence spectrum of an un-annealed sample measured at 1 °C/s between 300 and 700 nm shows the main emission band at ~ 410 nm and subsidiary emission bands at ~ 325 and 485 nm. The emission from samples annealed at 700 and 900 °C show similar bands except for a decrease in intensity of the emission at 485 nm. The emission bands at 325, 410 and 485 nm are attributed to F+, F and F22+(2Mg) -centres respectively. The decrease of the emission band at 485 nm is deduced to be due to the destruction of the F22+(2Mg) centre at 700 °C. The emission bands are unaffected by irradiation dose between 10 and 320 Gy. However, when the sample is annealed at or beyond 700 °C, any effects on the F+ and F centres emission can be easier distinguished particularly for doses greater than 10 Gy.
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Date Issued: 2018

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The effect of human resources management practices on employee commitment: the case of Mnquma Local Municipality

- Fihla, Siphenathi https://orcid.org/0000-0001-9632-2650

Authors: Fihla, Siphenathi https://orcid.org/0000-0001-9632-2650
Date: 2018
Subjects: Personnel management--South Africa , Municipal government--South Africa
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10353/24431 , vital:62790
Description: This study evaluated the relationship between the Human Resource Management Practices (HRMP) and employee commitment. Results based on a sample from Mnquma Local Municipality indicate that these practices have a significant impact on employee commitment. This project will help to advance research on exploring the influence of organisational variables on commitment. Research purpose: The purpose of the study was to investigate the effects of human resources management practices on employee commitment at Mnquma Local Municipality. Motivation for the study: The study examines HRMP and employee commitment in the public sector. The relationship between the two may be of value to the municipality’s success. Research approach, design and method: A quantitative research approach was followed to carry out this study. Data were collected from a sample of 137 respondents in a selected municipality (Mnquma Local Municipality). A self-administered questionnaire was sent to respondents. Main findings: A significant relationship was found between HRMP and employee commitment. Practical or managerial implications: Findings may be relevant to practitioners, including strategic management researchers, policy-makers, directors, managers, and supervisors. The study could assist various practitioners directly or indirectly involved in private and public organisations to develop HRMP that improves employee commitment. Contribution or value-add: The study adds to the literature on HRMP and employee commitment among the public service. , Thesis (MCom) -- Faculty of Management and Commerce, 2018
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Date Issued: 2018

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The effect of pre-dose on thermally and optically stimulated luminescence from α-Al2O3C, Mg and α-Al2O3: C

- Kalita, Jitumani M, Chithambo, Makaiko L

Authors: Kalita, Jitumani M , Chithambo, Makaiko L
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
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Date Issued: 2018

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The effect of the cobalt and manganese central metal ions on the nonlinear optical properties of tetra (4-propargyloxyphenoxy) phthalocyanines

- Mwanza, Daniel, Louzada, Marcel, Britton, Jonathan, Sekhosana, Kutloano E, Khene, Samson M, Nyokong, Tebello, Mashazi, Philani N

Authors: Mwanza, Daniel , Louzada, Marcel , Britton, Jonathan , Sekhosana, Kutloano E , Khene, Samson M , Nyokong, Tebello , Mashazi, Philani N
Date: 2018
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/233357 , vital:50083 , xlink:href="https://doi.org/10.1039/C8NJ00748A"
Description: The metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (Mn(OAc)TPrOPhOPc) tetra propargyloxyphenoxy phthalocyanines were evaluated for their potential as optical limiting materials. The effect of the substituents and the central metal ions on the nonlinear optical properties was evaluated. The metal-free phthalocyanine exhibited better nonlinear optical properties when compared to the cobalt and manganese complexes owing to the metal ions quenching the excited state due to their half-filled d-orbitals. The nonlinear absorption coefficient (βeff, ×10−5 m MW−1) followed the trend of H2TPrOPhOPc > CoTPrOPhOPc > Mn(OAc)TPrOPhOPc. The values βeff (×10−5 m MW−1) using 532 nm Nd:YAG (560 nm monochromatic Ekspla) laser sources were 23.5 > 14.3 > 9.20 (14.4). The second-order nonlinear coefficient obtained using density functional theory calculations, the theoretical hyper-Rayleigh scattering (βHRS, ×10−28 esu), showed the decreasing trend for H2TPrOPhOPc (2.28) > CoTPrOPhOPc (2.10) > Mn(OAc)TPrOPhOPc (1.86). The 4-(propargyloxy)phenoxy substituents enhanced the optical limiting properties of the synthesized phthalocyanines.
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Date Issued: 2018

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The effect of water temperature on the distribution of the Eastern Cape redfin minnow, Pseudobarbus afer (Peters, 1864)

- Bloy, Lesley Elizabeth

Authors: Bloy, Lesley Elizabeth
Date: 2018
Subjects: Minnows -- South Africa -- Eastern Cape , Cyprinidae -- South Africa -- Eastern Cape , Minnows -- Effect of temperature on -- South Africa -- Eastern Cape , Minnows -- Effect of exotic animals on -- South Africa -- Eastern Cape , Introduced organisms -- South Africa -- Eastern Cape
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/62017 , vital:28096
Description: The main objective of this MSc study was to disentangle whether temperature or the presence of non-native fish was limiting the distribution of Pseudobarbus afer (Peters, 1864) in the Blindekloof stream, Eastern Cape, South Africa. The aims were to: i) describe the thermal regime of the Blindekloof stream; ii) conduct experiments to determine the preferred and critical temperatures of P. afer and; iii) use snorkel surveys to contextualise the distribution of both native and non-native fishes in the Blindekloof stream to assess whether the downstream distribution of P. afer was likely to be influenced by temperature or by the presence of non-native, predatory fishes. To describe the thermal regime, year-long temperature data from four long term monitoring sites in the Blindekloof stream were collected using Hobo temperature loggers and analysed in order to better understand the thermal profile, the thermal variation and the rate of temperature change in the stream. The warmest temperatures were recorded in late December 2015 (absolute maximum of 29.4 °C). The coolest water temperatures were recorded in early August 2015 (absolute minimum of 9.5 °C). There is both seasonal and diel variation in temperature with mean, minimum, maximum, 7 day mean, 7 day maximum and temperature ranges differing significantly between sites. With knowledge of the thermal regime of a monitored reach of the Blindekloof stream, the thermal tolerance and preference of P. afer were investigated. The thermal tolerance of P. afer was investigated using the Critical Thermal Method (CTM) which uses non-lethal endpoints (the loss of equilibrium). At low acclimatization temperatures (11.9 ± 0.7 °C), the mean CTmax of P. afer was found to be 29.9 ± 0.7 °C, while at a higher acclimatization temperature (19.9 ± 0.1 °C), the mean CTmax was 35.1 ± 0.6°C. Custom-built thermal choice tanks were used to investigate the thermal preference of P. afer in both summer and winter. The preferred median temperatures for the summer experiments ranged from 22.4 - 29.3 °C while the winter preferred median temperatures ranged from 18.5 - 23.1 °C. The thermal tolerance of P. afer was compared to the thermal regime of the stream and the results suggest that temperature is not limiting the distribution of P. afer. Snorkel surveys were used to determine the distribution of fishes in the Blindekloof stream. Analysis of the distribution data suggests that, in the absence of non-native predatory species, native fishes have the potential to inhabit pools throughout the system right to the confluence, thus predatory fishes and not temperature was limiting P. afer distributions.
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Date Issued: 2018

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The effects of intermittent task parameters on muscle fatigue development during submaximal dynamic exertions

- King, Josephine Claire

Authors: King, Josephine Claire
Date: 2018
Subjects: Muscles -- Physiology , Muscles -- Wounds and injuries , Fatigue , Human engineering , Occupational diseases
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/63855 , vital:28498
Description: The negative effects of localised muscle fatigue on accidents, injuries and poor work performance are well known, as is the realisation that modifying task characteristics can minimise fatigue development. A large amount of literature has investigated the effects of task-dependent factors on localised muscle fatigue, most studies have focussed on prolonged or intermittent static (isometric) exertions. Few studies have investigated muscle fatigue development during more complex tasks, namely those which resemble common work activities and which tend to be intermittent and dynamic in nature. More specifically, the interactions between the main intermittent parameters - duty cycle, force level, and cycle time - during dynamic exertions are poorly understood. The purpose of this study was to investigate the effects of cycle time and combinations of duty cycles and force levels on the development of muscle fatigue during submaximal dynamic exertions while the overall mean muscle load was kept constant. A two-factorial repeated-measures experiment was developed for this study. Nine experimental conditions, each lasting 16 minutes, aimed at inducing muscle fatigue in the middle deltoid muscle via intermittent dynamic shoulder abduction and adduction motions at three cycle times (30, 60, and 120 seconds) and three combinations of duty cycles and force levels. The percentage of muscle activation during one cycle (i.e. the duty cycle) varied depending on the exertion intensity (force level) so that the overall mean muscle load remained consistent throughout all experimental conditions, namely at 20% of maximum force exertion. As a result, the three duty cycle/force level combinations were: 0.8/25% of maximum voluntary force (MVF), 0.5/40%MVF, and 0.4/50%MVF. Muscle fatigue development was inferred by changes in peak torque, total work, average power, local Ratings of Perceived Exertion (RPE), and surface electromyographical (EMG) activity (time domain and frequency domain).Two-factorial analyses of variance with Tukey post-hoc tests were used to identify significant condition effects at p<0.05. All dependent measures showed that muscle fatigue was induced by the 16-minute fatigue protocol. Peak torque, total work, average power, and EMG percentage of maximum showed that cycle time and the duty cycle/force level combination had no effect on the development of muscle fatigue, whereas the measures evaluated during the 16-minute fatigue protocol did. The cycle time of 120 seconds induced the greatest change in six of the eight variables, while the duty cycle/force level combination (0.8/25%) also resulted in the greatest effect in six of the measures. Fatigue was also found to be dependent on the interaction of cycle time and duty cycle/force level combination. The conclusion draws from this study is that shorter cycles and activities with short activation periods, and proportionally longer rest breaks result in the lowest fatigue developments.
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Date Issued: 2018

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The energy transition patterns of low-income households in South Africa: an evaluation of energy programme and policy

- Israel-Akinbo, Sylvia O, Snowball, Jeanette D, Fraser, Gavin C G

Authors: Israel-Akinbo, Sylvia O , Snowball, Jeanette D , Fraser, Gavin C G
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/69397 , vital:29518 , https://doi.org/10.17159/2413-3051/2018/v29i3a3310
Description: The transition to modern energy carriers like electricity is an important way to achieve to eradicate energy poverty. This study investigated energy transition patterns and trends in low-income South African households. The marginal effects of the different determinants on the probability of choosing a specific energy carrier were computed and the influence of some endogenous characteristics in transitioning to modern energy carriers was explored. It was found that energy ladder behaviour exists for cooking while energy stacking was most likely for space heating and the pattern for lighting tended towards energy stacking. Dwelling type, household size and geographical location were among the key determinants of the energy transition pattern. Policies to reduce energy poverty need a multi-pronged approach and not only a focus on electricity access.
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Date Issued: 2018

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The English East India Company and the British Crown: c. 1795-1803, the first occupation at the Cape of Good Hope

- Jordan, Calvin

Authors: Jordan, Calvin
Date: 2018
Subjects: East India Company , East India Company -- Influence , Cape of Good Hope (Colony) , Cape of Good Hope (South Africa) -- History -- 1795-1872 , Cape of Good Hope (South Africa) -- Politics and government -- 1795-1872 , British -- South Africa -- History -- 19th century , Great Britain -- Colonies -- Commerce , Great Britain -- Colonies -- Administration -- History -- 19th century , Merchant marine -- Great Britain -- History
Language: English
Type: text , Thesis , Masters , MA
Identifier: http://hdl.handle.net/10962/63164 , vital:28369
Description: My thesis aims to investigate the relationship between the English East India Company (EEIC) and the British colonial administration at the Cape of Good Hope during the first British occupation (1795 to 1803). Studies and literature that concern the EEIC have rarely gone beyond the surface, detailing the presence of the EEIC at the Cape, and neglecting the Company’s involvement in the administration thereof. My thesis draws on prior works but attempts to address both temporal and spatial gaps in this literature on the Atlantic and Indian Ocean, and the history of the EEIC. This study takes note of the seaborne related activity around the ports, bays and islands at the Cape – including the regulation of these spaces and issues related to securing British trade and colonial possessions more generally. I question the framing of the Cape primarily as a constituent of a national unit by locating the colony within a broader global and maritime context. A key interest is to determine the degree to which the EEIC influenced and participated in the British governance of the Cape, particularly by exploring the maritime dimensions of the relationship between the EEIC and colonial governance during this particular period. This involves understanding the embeddedness of the Cape in British (Crown and Company) networks and the constitution of a ‘British maritime zone’. This study uses archival sources drawn from the British colonial government records, Company records, and the private diaries and letters of Lady Anne Barnard that relate to the Cape. It is shown that a uniquely configured governance convention was constituted to secure the mutual commercial and imperial interests of both Crown and Company. By keeping the Cape secure, the British sought to keep their greater seaborne Empire secure. This study reveals that the EEIC was significantly involved in and influenced the way the British administration governed the Cape.
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Date Issued: 2018

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The environmental imagination in Arthur Nortje’s poetry

- Kaze, Douglas Eric

Authors: Kaze, Douglas Eric
Date: 2018
Subjects: Nortje, Arthur, 1942-1970 -- Criticism and interpretation , Ecology in literature , Race awareness in literature , South African poetry (English) -- History and criticism , Nature in literature , Transversal postcolonial environmental criticism
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/58024 , vital:27033
Description: This thesis seeks to contribute to the conversations in the humanities about the treatment of the physical environment in the context of a global ecological fragility and increased scholarly interest in the poetry of Arthur Nortje, a South African poet who wrote in the 1960s. While previous studies on Nortje concentrate on the political, psychic and technical aspects of his poetry, this study particularly explores the representations of the environment in Nortje’s poetic imagination. Writing in the dark period of apartheid in South Africa’s history, Nortje’s poetry articulates a strong interest in the physical environment against the backdrop of official racialization of space and his personal nomadic life and exile. The poetry abounds with constant intersections of nature and culture (industrialism, urbanity and the quotidian), a sense of place and a deep sense of dislocation. The poems, therefore, present a platform from which to reevaluate conventional ecocritical ideas about nature, place-attachment and environmental consciousness. Drawing mainly on Felix Guattari’s ideas of three ecologies and transversality along with other theories, I conduct the study through what I call a transversal postcolonial environmental criticism, which considers the ecological value of the kind of assemblages that Nortje’s works represent. The first chapter focuses on conceptualizing a postcolonial approach to the environment based on Guattari’s concept of transversality to lay the theoretical foundation for the whole work. The second chapter analyses Nortje’s poetic imagination of place and displacement through his treatment of the private-public tension and the motif of exile. While the third chapter examines Nortje’s depiction of nature as both an everyday and urban phenomenon, the fourth chapter turns to his direct treatment of environmental crises handled through his imagination of the Canadian urban spaces, exile memory of apartheid geography, war and ecocide and the human body as a subject of environmental degradation. The fifth chapter, which is the conclusion, takes a brief look at the implication of Nortje’s complex treatment of the environment on postcolonial environmentalism.
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Date Issued: 2018

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The evaluation of potential dietary media, measurement parameters and storage techniques for use in forensic entomotoxicology

- Mbatha, Erica Isabel Tavares Da Silva

Authors: Mbatha, Erica Isabel Tavares Da Silva
Date: 2018
Subjects: Blowflies -- Feeding and feeds , Blowflies -- Larvae , Blowflies -- Physiology , Blowflies -- Collection and preservation , Poisons -- Analysis , Death -- Causes , Forensic pathology , Forensic entomology , Forensic entomotoxicology
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/63323 , vital:28393
Description: The term forensic entomotoxicology was coined by Pounder and is used to describe the process of using insects to determine the presence or absence of toxicants in decomposing corpses. Forensic entomotoxicology is most applicable when the orthodox sources of evidence (i.e. blood and urine) are no longer available for testing due to the degree of putrefaction as a result of the decomposition process. As the field is relatively new, various authors have conducted studies to determine the effects of different toxicants on different insects. These studies have all been conducted in the absence of a standardised protocol and we hypothesise that this has led to conflicting results (i.e. two different authors will conduct a study using the same toxicant and model insect and the effects on the insects will differ significantly). The aim of this thesis was to identify the areas which might have led to the artefacts in the results and identify ways in which to standardise them. The three areas selected were the feeding substrates and the measures taken to quantify growth rate, as well as the preservation techniques that should be used for preserving larval flies. The recommendation from the literature review was that artificial diets would be the most appropriate dietary media to use for entomotoxicological studies. An artificial diet was selected and modified for potential used in entomotoxicological studies. Four different diets (no meat treatment, fish, beef and pork artificial diets) were used to rear Chrysomya chloropyga larvae and their growth rates were measured using length and width. The fly larvae reared on the fish and no meat treatment diets did not reach pupation stage. The beef and pork diets produced the largest larvae and the flies in these treatments reached adult stage. The recommendation was that the beef and pork treatments be tested with various toxicants to establish their stability in the matrix and the diet that provides the toxicants with the most stability should be used for future entomotoxicological studies. The two other factors selected for standardisation were the parameters used to quantify growth rate, as well as the preservation techniques used to store empty Chrysomya chloropyga pupal casings and Calliphora croceipalpis third instar larvae. Previous authors have suggested that width be used as an alternative to length to quantify growth rate. The results from this thesis show that length should continue to be used as the standard parameter because the incremental change in length is much larger than the change in width, and these larger increments allow for greater resolution when estimating the age of the larvae. Various authors have also suggested that pupal casings should be stored without any preservative, whereas fly larvae should be stored in concentrations of ethanol >70%. The results in this thesis have shown that the concentration of ethanol does not make any significant difference to the proportional change of length and width of the empty pupal casings and the third instar larvae. The recommendation is that when selecting the preservation technique, the integrity of the specimen for examination of other evidence (i.e. DNA or toxicological extraction) should take precedence. Although this thesis has not completely standardised the protocol for forensic entomotoxicology, it has indicated the areas that need to be focused on in order for standardisation to occur. Future studies should focus on standardisation, as this makes studies more comparable and ultimately makes entomotoxicological evidence admissible in the court of law.
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Date Issued: 2018

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