Determination of nonlinear optical properties of phthalocyanine regioisomers using computational models
- Date: 2020
- Subjects: Electrochemistry , Phthalocyanines , Nanoparticles , Nonlinear optics , Nonlinear optical spectroscopy , Refraction
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166197 , vital:41337
- Description: This work investigates the effects of the nonlinear optical properties of four different constitutional isomers (C4h, C2v, Cs, and D2h) of a series of tetrasubstituted phthalocyanines (free-base 3-4-tert-butylphenoxyether phthalocyanines, free-base 4-4-tertbutylphenoxyether phthalocyanines, SnCl2 tetra substituted 3-4-tert-butylphenoxyether phthalocyanine, and SnCl2 tetra substituted 4-4-tert-butylphenoxyether phthalocyanine). The properties investigated were the real and imaginary components of the 3rd order hyperpolarizability, as well as the excited state absorption and refraction cross sections. The investigations were performed with a z-scan over a range of laser beam intensities. This work determined the imaginary component of the 3rd order hyperpolarizability for the free-base and SnCl2 3-4-tert-butylphenoxyether phthalocyanines and 4-4-tert-butylphenoxyether phthalocyanines to be highly dependent on the excited state cross sections. The refraction caused due to the real component of the 3rd order hyperpolarizability of the phthalocyanines was also investigated, however, the values found were strongly dependent on the laser beam intensity and the cause of this was investigated. A Five-level model was developed and run on GPGPU computing devices in order to isolate the absorption and refractive cross sections. Theeffects of the regio substitution on the excited state cross sections were also investigated, and the 1st singlet excited state and 1st triplet state absorption cross sections were calculated for all constitutional isomers. It was found that the symmetry of the constitutional isomers have a disproportionately large effect on the excited state absorption when compared to the ground state absorption. The nonlinear refractive properties of all constitutional isomers were also investigated, and the values of the parametric susceptibility are reported herein. The nonlinear refraction was found to have less effect than was seen in the nonlinear absorption. The 1st singlet excited state and 1st triplet state refractive cross sections of all constitutional isomer was determined. The results indicated that if more than one excited state was present and contributing to the nonlinear refraction, then more data than was collected here would be required. However, the 1st singlet excited state cross section were successfully determined for the free-base constitutional isomers. This work concluded that the region substitution affected the excited states more than the ground state.
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- Date Issued: 2020
Non-marital fertility in South Africa: trends, determinants and implications
- Authors: Kara, Reesha
- Date: 2020
- Subjects: Fertility, Human -- South Africa , Child rearing -- South Africa , Parenting -- South Africa , Motherhood -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/165620 , vital:41264
- Description: Background: Non-martial fertility is traditionally associated with teenage pregnancy however international and South African literature has detailed increases in the number of adult women who are having children outside of a marriage. South African literature on non-marital fertility is sparse as it lacks a national overview of the trends and determinants of non-marital fertility among women aged 30 and older. The aim of this study was to present a national overview of non-marital fertility among women aged 30 and older. South African’s attitudes to and opinions of non-marital fertility were also investigated, and the lived realities of older mothers were explored. Methods: A mixed-methods research design was employed where the General Household Survey, National Income Dynamics Study and the South African Social Attitudes Survey were the main data sources. Using these data sets, descriptive and inferential statistics were computed using Stata. Using purposive and snowball sampling, four never-married older mothers (NMOMs) from KwaZulu-Natal (Durban) were identified as research participants. The in-depth life histories of these women were collected through face-to- face semi-structured interviews. Results: The results show an 18.43% increase in never-married mothers aged 15- 49 between 2002 and 2017 and interestingly, this increase is not necessarily driven by older mothers (30-49). NMOMs belonged to households with a lower average per capita total monthly household income (R1873.91) compared to all mothers aged 30-49 (R3428.76). NMOMs were also more likely to live in female-headed households (89.52%), to be household heads (64.22%) and to live in traditional areas (35.72%). Between 2002 and 2017, there was a 76.76% increase in mothers (aged 30-49) who were never married and a 7.74% decrease in those who were married, indicating a change in the marital profile of mothers. Despite this national increase in non-marital fertility, South African’s believe that premarital sexual activity is wrong, and that childbearing should take place within a marriage. Similar sentiments were echoed in the in-depth life histories as being the sole breadwinner and primary caregiver, the research participants experienced challenges as single mothers. Conclusion and recommendations: The study has found that there has been an increase in non-marital fertility in South Africa between 2002 and 2017 and that there is an economic element to non-marital fertility in the country. Additional research into non-marital fertility at a national level is recommended with a focus on all women aged 15-49.
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- Date Issued: 2020
The Transformative Power of Language: From Postcolonial to Knowledge Societies in Africa
- Authors: Kaschula, Russell H , Wolff, H Ekkehard
- Date: 2020
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/174514 , vital:42484 , ISBN 9781108498821
- Description: Language has played a pivotal role in societal transformation in postcolonial Africa towards the creation of globally competitive knowledge societies; however so far, this role has been under-researched and under-estimated. This volume addresses this gap in the literature, by bringing together a team of globally-recognised scholars to explore the effect of language on African postcolonial societies, and how it has contributed to achieving 'mental decolonisation'. A range of languages are explored, both imported (ex-colonial) and indigenous African, and case studies from different spheres of public discourse are investigated, from universities to legal settings. Demonstrating that multilingualism is a resource for, rather than barrier to, successful transformation, this book brings the intellectualisation and institutionalisation of African languages to the forefront of development discourse, and provides an insightful snap-shot of how current academic research, public discourse, political activism and social community engagement have contributed to societal transformation in South Africa.
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- Date Issued: 2020
Atlas of Southern African freshwater fishes
- Authors: Scott, L E P , Skelton, P H , Booth, A J , Verheust, L , Dooley, J , Harris, R
- Date: 2006
- Subjects: Freshwater fishes -- South Africa , Freshwater fishes -- Africa, Southern , Freshwater fishes -- Africa, Southern -- Identification
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/199097 , vital:46068
- Description: Worldwide concern over the loss of biological diversity during the past decade has provided the impetus for the development of biodiversity databases and biological atlas projects in order to make information accessible. This Geographic Information Systems-based Atlas of Southern African Freshwater Fishes is the first of its kind for fishes in Africa and, as such, can be seen as contributing towards this global trend of consolidation and refining of biodiversity information. The technological advances made in computing systems over the past decade have facilitated the extraction and utilisation of much of the untapped information in museum collections. The size of most natural history collections had tended to prohibit any comprehensive applied use of the specimens on a large scale, but the computerisation of these collections has proved to be an invaluable tool to systematists, taxonomists and ecologists, by allowing faster and more efficient access to specimen record data of interest. With the automation of many biological databases, public attention has been brought to their potential contribution to biodiversity studies and conservation efforts around the world. The application of Geographic Information Systems (GIS) in the field of southern African ichthyology and freshwater fisheries management has been limited, until now, by the lack of good-quality, comprehensive data sets, adequate budgets and GIS skills. Sophisticated investigations of fish distributions for conservation and management purposes need a powerful computing platform. This is realised in the Atlas of Southern African Freshwater Fishes, which has been tested and used for biogeographic analysis in the southern African region. The atlas was established using specimen records from nineteen museum collections, and currently contains 35145 geo-referenced specimen records, collected between 1885 and 2000 in eleven countries of southern Africa, which represent 254 fish species from 37 families. The Atlas of Southern African Freshwater Fishes was developed with the objective of being a dynamic, powerful information system. It has been constructed to allow the import of additional information at any stage, and it is designed to be as accessible and as user-friendly as current technology allows. This Atlas is the product of the successful integration of fish distributional information with other spatial data layers to provide a new tool for the study of freshwater fish in southern Africa.
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- Date Issued: 2006