Synthesis, spectroscopic and nonlinear optical properties of asymmetric A3B type phthalocyanine complexes
- Authors: Mugeza, Rhulani Donney
- Date: 2021
- Subjects: Spectrum analysis , Mass spectrometry , Phthalocyanines
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/171667 , vital:42108
- Description: This work reports on the synthesis of symmetrical and asymmetrical A 3 B type metal free, cobalt and zinc Phthalocyanines (Pc) .A wide range of spectroscopic techniques such as Uv - visible absorption (UV), magnetic circular dichroism (MCD), mass spectrometry, elemental analysis, IR spectroscopy and time correlated single photo n counting spectroscopy (TCSPC) have been used to study the spectroscopic properties of the phthalocyanine complexes. The Z - scan technique was used to comparatively investigate the nonlinear absorption coefficient ( 휷 ) and the nonlinear refraction index ( 풏 ퟐ ) of the synthesized complexes. The following trend was obtained for the synthesized Pc’s in terms of the 휷 values 7.25 × 10 − 10 ( 4b ) > 3.76 × 10 − 10 ( 4a ) > 3.52 × 10 − 10 ( 4c ) > 2.29 × 10 − 10 ( 3c ) > 1.68 × 10 − 10 ( 3a ) > 1.65 × 10 − 10 ( 3b ) mW - 1 . The 휷 values trend of synthesized Pc complexes show that the asymmetrical A 3 B type metal free, cobalt and zinc Pc complexes ( 4a , 4b and 4c ) have larger 휷 values as compared to the octa - substituted symmetrical metal free, cobalt and zinc Pc complexes ( 3a , 3b and 3c ) which is attributed to the low symmetry of the Pc complexes. The five - level model rate equations were used to determine the two photon absorption, excited state absorption and ground state absorption cross sections of the synthesized complexes. The z inc A 3 B type asymmetrical Pc complexes gave the largest two photon absorption and 휎 푒 / 휎 푔 ratio values. This Pc complex could be used in future work to enhance the nonlinear response further by introducing nanomaterials and converting the Pc complex to a binuclear Pc. This work also reports on the density functional theory (DFT) calculations o f dipolar/octupolar contributions in order to study the first order hyperpolarizability of the synthesized Pc complexes.
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- Date Issued: 2021
The changing nature of work: understanding precarity and the gendered individualisation of risk in post-apartheid South Africa
- Authors: Mhlana, Siviwe
- Date: 2021
- Subjects: Precarious employment , Labor supply -- South Africa , Labor supply -- Statistics -- South Africa , Precarious employment -- South Africa , Informal sector (Economics) -- Employees -- South Africa , Women employees -- South Africa , Women temporary employees -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/172146 , vital:42170
- Description: Against the backdrop of workplace restructuring globally, post-Apartheid South Africa is experiencing consistently high levels of unemployment, the deterioration of employment security, and limited improvements in earnings. This trend in the proliferation of low-paid, unstable and otherwise insecure employment has given rise to a segment of the literature that is centred on the growing precariousness of work in a number of different contexts. This thesis reviews empirical work on the changing nature of labour-intensive production in the past two decades, with particular focus on the trends in non-standard, informal and precarious employment. Further, the thesis examines the shift in the gender structure of South Africa’s manufacturing sector and how it affects the share in the benefits of employment, particularly with regard to social reproduction. In so doing, the thesis expands the critical theoretical narrative about the challenges of labour under neoliberalism by providing an intersectional perspective of precarious work in post- Apartheid South Africa.
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- Date Issued: 2021
A sociological analysis of the sex education of young adult white womxn and their understandings and practices of ‘Safe Sex’
- Authors: Guerra, Cassandra Gadelha
- Date: 2020
- Subjects: Sex instruction , Sex instruction for girls , Women, White -- Psychology , Women, White -- Sexual behavior
- Language: English
- Type: text , Thesis , Masters , MSocSci
- Identifier: http://hdl.handle.net/10962/147267 , vital:38610
- Description: This research sets out to examine the experiences and perspectives of young adult white womxn regarding their respective sex education. This is in terms of how sex education may shape and influence sexual practices. The relevance of exploring the sex education of this group is to gain an understanding of how constructions of sex education may facilitate the negotiation of sexual practices, particularly as these practices relate to the negotiation of ‘safe sex’. This involves an exploration of definitions of ‘safe sex’ as well as an examination of the various sources of sex education. This research argues that sex education has been socially constructed within a ‘heterosexual matrix’ where both gender identities and sexuality are constructed in heterosexual terms in accordance with compulsory heterosexuality. Furthermore, that sex education as well as understandings and practices of ‘safe sex’ intersect with other social categories such as race, gender and sexuality. Much of the sex-related research conducted in South Africa focuses on people of colour, as a result very little is known about the sexual behaviours and practices of the white demographic. This research accounts for the absence of analysis of sexual practices and behaviour among white people by examining the sex education and sexual practices of young adult white womxn between the ages of 19 and 24. The research observed key sources of sex education which included parents, schools, religious institutions and the internet. Findings indicate that the sex education of participants reflected ideals of heteronormativity and misogyny which were found to directly influence their understandings and practices of both sex and ‘safe sex’. Furthermore, that the sex education participants received has ultimately failed to promote ‘safe’ sexual practices.
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- 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.
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- Date Issued: 2020
“Ntombazana, ugayela bani?”: ubunzululwazi beentsimbi
- Authors: Silo, Tolakele Talitha
- Date: 2020
- Subjects: Beadwork, Xhosa , Xhosa (African people) -- Social life and customs , Beadwork, Tembu , Tembu (African people) -- Social life and customs
- Language: Xhosa
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/167487 , vital:41485
- Description: “ NTOMBAZANA, UGAYELA BANI?”: UBUNZULULWAZI BEENTSIMBI is a study on the culture of abaThembu, one of the amaXhosa subgroups. Focusing on beadwork as one of this group’s cultural aspects, this research is an initiative to ensure documentation of such indigenous knowledge as an influence on the lifestyle of abaThembu. It also strives to uplift the use of oral literature to present it a fair chance at being a driving force for change as it has previously been ousted with the acceptability of written literature. Of great surprise is to see that despite western civilization, which affected the people’s culture, beadwork remains a pillar of the abaThembu-amaXhosa culture. This craft has evolved and thus, shows no signs of regression. This thesis is an indigenous knowledge focused research.
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- Date Issued: 2020
Reproductive isolation mechanisms of two cryptic species of Eccritotarsus (Hemiptera: Miridae), biological control agents of water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae)
- Authors: Mnguni, Sandiso
- Date: 2019
- Subjects: Eccritotarsus , Meridae , Noxious weeds -- Biological control -- South Africa , Aquatic weeds -- Biological control -- South Africa , Water hyacinth -- Biological control -- South Africa , Biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68133 , vital:29202
- Description: Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), is one of the world’s worst alien invasive plants. It is indigenous to the Amazon basin in South America but has become a problematic alien invasive in other parts of the world. As such, several host-specific biological control agents have been sourced from the native distributions in South America and have been released to control this plant where it has become problematic. Two of these agents include the geographically and reproductively isolated cryptic species of Eccritotarsus (Hemiptera: Miridae). One of these species was collected in the upper reaches of the Amazon River in Peru, while the other was collected over 3500km away from that site, in Florianopolis, southern Brazil. These cryptic species were thought to be a single species until recently, when DNA barcoding indicated that they were likely to be two species, and the species status has now been confirmed by interbreeding experiments and detailed morphological studies. The Brazilian population remains Eccritotarsus catarinensis (Carvalho), while the Peruvian population is now known as Eccritotarsus eichhorniae (Henry). The aim of this project was to investigate the mating behaviour and other behavioural traits of the two species that have resulted in reproductive isolation, and which could have led to speciation. In addition, investigations involving analysis of chemical compound compositions of the two species aimed to determine the extent to which the compounds played a role in the development and maintenance of reproductive isolation. To achieve the aims, behavioural-observation experiments were conducted in the form of no-choice, bi-choice and multi-choice tests in 1:1, 2:1 and 3:1 sex ratio assessments, both within and between species. Chemical compound compositions of E. catarinensis and E. eichhorniae were also assessed using Nuclear Magnetic Resonance (NMR), Solid-phase micro-extraction (SPME) and Gas-Chromatography Mass-Spectrometry (GC-MS) techniques. In no-choice experiments, the highest number of single and multiple copula incidences, and average total copula duration was found within species while copulation between species was much rarer. In bi-choice experiments, E. eichhorniae females and E. catarinensis males only chose to mate with their respective conspecifics, and within species copulations continued to have higher average total copula duration. In multi-choice experiments, the highest number of single and multiple copula incidences and average total copula duration was also found within species. GC-MS analysis suggested that E. catarinensis females and E. eichhorniae males have unique chemical compounds missing in their conspecifics and same sex of the other species. Further analysis suggested that E. catarinensis females and E. eichhorniae males have similar chemical compound compositions, whereas as E. eichhorniae females and E. catarinensis males have similar chemical compound compositions. These results suggest that there are behavioural differences that led to the development and maintenance of prezygotic reproductive isolation mechanisms, and that this is probably driven by pheromones in chemical compound compositions. These two species were geographically isolated in the native range and the populations have diverged to the point that they are now reproductively incompatible and therefore, distinct species. The main driver of the speciation is most likely mate recognition and attraction, as only reproductively important traits such as pheromones, genitalia, the scent glands and antennae have changed, while other traits, including host range and morphology, have remained remarkably stable. This provides evidence that differences in sexual selection in isolated populations may be important drivers of speciation and reproductive isolation in cryptic species.
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- Date Issued: 2019
Synthesis of indium phthalocyanines for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Sindelo, Azole
- Date: 2019
- Subjects: Phthalocyanines , Azo dyes , Indium compounds , Photochemotherapy , Nanoparticles , Photodegradation , Pollutants , Water -- Purification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67581 , vital:29116
- Description: Indium (III) octacarboxyl phthalocyanine (ClInOCPc) alone and when conjugated to magnetic nanoparticles (MNP-ClInOCPc), 2(3),9(10),16(17),23(24)-octapyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOPyPc) and its quaternized derivative 2(3),9(10),16(17),23(24)-octamethylpyridylsulfanyl phthalocyaninato chloroindium (III) (ClInOMePyPc) were synthesized. All Pcs were tested for both photodynamic antimicrobial chemotherapy (PACT) of an unknown water sample and photo-degradation of methyl red (MR). The singlet quantum yield (ΦΔ) for the ClInOCPc and MNP-ClInOCPc in PAN polymer fibers were 0.36 and 0.20 respectively using ADMA as a quencher in water. The photo-inactivation of bacteria in a water sample with unknown microbes was tested, with the MNP-ClInOCPc inactivating 90.6 % of the microbes and the ClInOCPc with 84.8 %. When embedded to the polymer, there was 48% bacterial clearance for ClInOCPc and 64% clearance for the MNP-ClInOCPc. The rate of degradation of MR increased with decrease of the MR concentration, with the MNP-ClInOCPc having the fastest rate. For ClInOPyPc and ClInOMePyPc, the singlet quantum yields were 0.46 and 0.33 in dimethylformamide (DMF), respectively. The PACT activity of ClInOMePyPc (containing 8 positive charges) was compared to those of 9(10),16(17),23(24)-tri-N-methyl-4-pyridylsulfanyl-2(3)-(4-aminophenoxy) phthalocyaninato chloro indium (III) triiodide (1) (containing 3 positive charges) and 2-[4-(N-methylpyridyloxy) phthalocyaninato] chloroindium (III) iodide (2) (containing 4 positive charges). When comparing ClInOMePyPc, 1 and 2, the largest log reduction for E. coli were obtained for complex 2 containing four positive charges hence showing it is not always the charge that determines the PACT activity, but the bridging atom in the phthalocyanine plays a role.
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- Date Issued: 2019
A comparative study of tax incentives for small businesses and investors in small businesses in South Africa, Australia, New Zealand, Singapore and Ireland
- Authors: Horn, Edward Bennet
- Date: 2018
- Subjects: Small business -- Taxation -- South Africa , Small business -- South Africa -- Finance , Job creation -- South Africa , Government aid to small business -- South Africa , Tax incentives -- South Africa , Tax incentives -- Australia , Tax incentives -- New Zealand , Tax incentives -- Singapore , Tax incentives -- Ireland
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/61669 , vital:28047
- Description: In the South African context, it is accepted that small businesses will be the vehicle for job creation and changing the current business ownership patterns. This is to be achieved by creating access to finance, exploring the role of venture capital and simplifying the tax obligations and the compliance burden. The literature indicates that the current South African tax incentives for small businesses are perceived as unfair and fundamentally ineffective. The objective of this thesis was to compare the tax incentives available to small businesses and investors in small businesses in South Africa to those available in Australia, New Zealand, Singapore and Ireland, in order to identify possible measures that could be introduced in South Africa. In addressing the objective, the research set out to provide, in terms of South African tax legislation, a definition of a small business for tax purposes and document the tax incentives available for start-up and existing small businesses, as well as the tax incentives available for investors in small businesses, either through a venture capital company or a direct investment in small business. It was found that South Africa has a complex and onerous multi-layered approach to classifying a taxpayer as either a “micro business” or a “small business corporation” for the purpose of applying tax incentives. The international jurisdictions included in this research follow a single requirement approach, based on either one or a combination of turnover, balance sheet total or staff headcount. The international jurisdictions provide a wide range of tax incentives to small businesses and investors in small businesses, aimed at reducing taxable income to enable the small businesses to grow and access equity finance. By identifying differences and similarities, a number of possible tax relief measures were recommended that could be introduced in South Africa.
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- Date Issued: 2018
Teacher-in-role as a problem-posing method for learners in a special needs school in South Africa
- Authors: Hellemann, Phemelo Cordelia
- Date: 2018
- Subjects: Special education -- Activity programs -- South Africa , Special education -- South Africa , Drama in education -- South Africa , Drama -- Therapeutic use -- South Africa , Children with mental disabilities -- Life skills guides , Kuyasa School (South Africa)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/62549 , vital:28205
- Description: Paulo Freire’s problem-posing pedagogy urges for a creative and collaborative educational environment between learners and teachers that encourages critical thinking and engagement. This research explores how special needs pedagogical approaches in South Africa can transform their classroom practices to embrace creative and collaborative teaching methods such as drama. Drama-in-education (D-i-E) is an area where the learner and teacher relationship is characterised by creativity and engagement. This qualitative study considers the uses of drama as a teaching and learning method for learners in the Skills Phase class at Kuyasa Special School, Grahamstown. The research aimed to provide learners with intellectual barriers to learning with access to D-i-E. This was done through a series of practical drama lessons, which broadly aimed to enhance life skills and work environment competencies such as communication, problem-solving and interpersonal relations. The lessons followed a cross- curricular approach that integrated aspects of the Life Orientation (Grade 10-12) curriculum and the Drama (Creative Arts Grade 7-9) curriculum. This practice-led study reflects on how Dorothy Heathcote’s teacher-in-role (t-i-r) drama technique was implemented to teach topics and themes extracted and adapted from the Life Orientation learning area. This drama-based pedagogy employs three elements of Freire’s problem-posing education model, which are learner-centred, problem-posing and liberated pedagogy. The study discusses how these elements manifested in the lessons conducted, and how this approach benefited and improved the learners’ critical thinking skills, self-esteem and confidence. This study therefore provides a broad understanding of the possibilities of a drama-based pedagogy within a South Africa context of learning disability, proposing an alternative pedagogical approach in South African special schools. The findings contribute to the academic literature on D-i-E in South Africa and advocate for the inclusion of learners with learning disabilities within the performing arts education.
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- Date Issued: 2018