Journeying home, exile and transnationalism in Noni Jabavu and Sisonke Msimang’s memoirs
- Authors: Masola, Athambile
- Date: 2020
- Subjects: Home in literature , Exile (Punishment) in literature , Women authors, Black -- South Africa -- History and criticism , Jabavu, Noni -- Criticism and interpretation , Msimang, Sisonke -- Criticism and interpretation
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166529 , vital:41376
- Description: This thesis examines the memoirs of two South Africa female writers: Noni Jabavu and Sisonke Msimang. In analysing their memoirs, this thesis sets out to contribute to the scholarship which centres the voices of Black women writers. It explores how both writers interrogate the concepts of home, exile and transnationalism. My focus is on the ways in which the writers theorise questions of belonging, and the extent to which their writing provides the opportunity to give voice to the complex nature of belonging. I read the narratives from these two writers alongside each other, as Noni Jabavu is Sisonke Msimang’s literary ancestor. By looking at their works alongside each other, this thesis becomes an intergenerational conversation between the past and the present. Using Black feminist thought and migratory subjectivity, this thesis examines the ways in which these writers connect the personal and the political. Noni and Sisonke navigate the private spaces of home in conversation with the political experience of exile and the nation. In the second chapter, I explore home as ekhaya, isizwe and an imaginary homeland. Ekhaya is the isiXhosa word denoting the family home, where there is a network of family rather than a nuclear family. Home is also isizwe: the isiXhosa word which evokes the nation state, which takes on layered meanings in the context of colonialism and apartheid. Home can also be an imaginary homeland, which is an imagined version of home after a long absence such as exile. In the third chapter, I examine three forms of exile: internal exile, estrangement and political exile. Finally, in chapter four, I analyse transnationalism: a border-crossing which raises questions of power, mobility and kinship. Looking at home, exile and transnationalism together allows for an exploration which challenges taken-for-granted ideas about place and identity. These memoirs illuminate the ways in which Black women constitute and reconstitute their identities according to the places which they access through travel.
- Full Text:
- Date Issued: 2020
- Authors: Masola, Athambile
- Date: 2020
- Subjects: Home in literature , Exile (Punishment) in literature , Women authors, Black -- South Africa -- History and criticism , Jabavu, Noni -- Criticism and interpretation , Msimang, Sisonke -- Criticism and interpretation
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166529 , vital:41376
- Description: This thesis examines the memoirs of two South Africa female writers: Noni Jabavu and Sisonke Msimang. In analysing their memoirs, this thesis sets out to contribute to the scholarship which centres the voices of Black women writers. It explores how both writers interrogate the concepts of home, exile and transnationalism. My focus is on the ways in which the writers theorise questions of belonging, and the extent to which their writing provides the opportunity to give voice to the complex nature of belonging. I read the narratives from these two writers alongside each other, as Noni Jabavu is Sisonke Msimang’s literary ancestor. By looking at their works alongside each other, this thesis becomes an intergenerational conversation between the past and the present. Using Black feminist thought and migratory subjectivity, this thesis examines the ways in which these writers connect the personal and the political. Noni and Sisonke navigate the private spaces of home in conversation with the political experience of exile and the nation. In the second chapter, I explore home as ekhaya, isizwe and an imaginary homeland. Ekhaya is the isiXhosa word denoting the family home, where there is a network of family rather than a nuclear family. Home is also isizwe: the isiXhosa word which evokes the nation state, which takes on layered meanings in the context of colonialism and apartheid. Home can also be an imaginary homeland, which is an imagined version of home after a long absence such as exile. In the third chapter, I examine three forms of exile: internal exile, estrangement and political exile. Finally, in chapter four, I analyse transnationalism: a border-crossing which raises questions of power, mobility and kinship. Looking at home, exile and transnationalism together allows for an exploration which challenges taken-for-granted ideas about place and identity. These memoirs illuminate the ways in which Black women constitute and reconstitute their identities according to the places which they access through travel.
- Full Text:
- Date Issued: 2020
Physicochemical properties and photodynamic therapy activities of indium and zinc phthalocyanine-nanoparticle conjugates
- Authors: Dube, Edith
- Date: 2019
- Subjects: Indium , Zinc , Phthalocyanines , Breast -- Cancer -- Photochemotherapy , Nanoparticles
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76506 , vital:30589
- Description: The syntheses and characterization of symmetric and asymmetric Pcs functionalized at the peripheral position are reported. The Pcs contain either zinc or indium as central metals and have carboxyphenoxy, phenoxy propanoic acid, benzothiazole phenoxy, thiophine ethoxy or di-O-isopropylidene-α-D-glucopyranose as ring substituents. The Pcs were linked to NPs via an amide bond or through self-assembly. The photophysics and photochemistry of the Pcs were assessed when alone and with conjugates. All the studied Pcs showed good photophysicochemical behaviour with relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yield. The Pcs with indium in their central cavity exhibited higher triplet and singlet oxygen quantum yields in comparison to their zinc counterparts due to the heavy–atom effect obtained from the former. Asymmetrical Pcs displayed higher triplet and singlet oxygen quantum yields than their symmetrical counterparts. The triplet quantum yield, generally increased on linkage to nanoparticles (NPs) due to the heavy–atom effect of gold and silver in NPs. The conjugates to gold nanospheres yielded higher triplet and singlet quantum yields than their gold nanotriangles counterparts due to the higher loading by the former probably encouraged by their relatively small particle size. The in vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates against MCF-7 cells was tested. All studied Pc complexes and conjugates showed minimum dark toxicity making them applicable for PDT. All complexes displayed poor phototoxicity with >50Îll viability at concentrations≤ 160μg/mL, however the conjugates showed<50% cell viabilityatconcentrations≤ 160μg/mLprobably due to the enhanced singlet oxygen quantum yield. The findings from this work show the importance of linking photosensitises such as phthalocyanines to metal nanoparticles for the enhancement ofsinglet oxygen quantum yield and ultimately the photodynamic effect.
- Full Text:
- Date Issued: 2019
- Authors: Dube, Edith
- Date: 2019
- Subjects: Indium , Zinc , Phthalocyanines , Breast -- Cancer -- Photochemotherapy , Nanoparticles
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76506 , vital:30589
- Description: The syntheses and characterization of symmetric and asymmetric Pcs functionalized at the peripheral position are reported. The Pcs contain either zinc or indium as central metals and have carboxyphenoxy, phenoxy propanoic acid, benzothiazole phenoxy, thiophine ethoxy or di-O-isopropylidene-α-D-glucopyranose as ring substituents. The Pcs were linked to NPs via an amide bond or through self-assembly. The photophysics and photochemistry of the Pcs were assessed when alone and with conjugates. All the studied Pcs showed good photophysicochemical behaviour with relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yield. The Pcs with indium in their central cavity exhibited higher triplet and singlet oxygen quantum yields in comparison to their zinc counterparts due to the heavy–atom effect obtained from the former. Asymmetrical Pcs displayed higher triplet and singlet oxygen quantum yields than their symmetrical counterparts. The triplet quantum yield, generally increased on linkage to nanoparticles (NPs) due to the heavy–atom effect of gold and silver in NPs. The conjugates to gold nanospheres yielded higher triplet and singlet quantum yields than their gold nanotriangles counterparts due to the higher loading by the former probably encouraged by their relatively small particle size. The in vitro dark cytotoxicity and photodynamic therapy of selected Pc complexes and conjugates against MCF-7 cells was tested. All studied Pc complexes and conjugates showed minimum dark toxicity making them applicable for PDT. All complexes displayed poor phototoxicity with >50Îll viability at concentrations≤ 160μg/mL, however the conjugates showed<50% cell viabilityatconcentrations≤ 160μg/mLprobably due to the enhanced singlet oxygen quantum yield. The findings from this work show the importance of linking photosensitises such as phthalocyanines to metal nanoparticles for the enhancement ofsinglet oxygen quantum yield and ultimately the photodynamic effect.
- Full Text:
- Date Issued: 2019
The predictors of student performance in a blended learning environment at Higher Education Institutions (HEIs) in Tanzania: a case study conducted at the University of Dar-es-Salaam
- Authors: Kabudi, Tumaini John
- Date: 2019
- Subjects: Prediction of scholastic success -- Tanzania -- Case studies , Motivation in education -- Tanzania -- Case studies , Academic achievement -- Tanzania -- Case studies , Blended learning -- Tanzania -- Case studies , Chuo Kikuu cha Dar es Salaam -- Students
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68358 , vital:29242
- Description: Blended Learning is an important technological platform which has the potential to enhance the efficiency and efficacy of educational provision, especially in Tanzania universities. Despite a high level of investment into Blended learning, students face various challenges that have impeded them performing well in Blended learning courses. The purpose of this research is to examine and explore how student’s performance in a Blended learning environment is influenced by motivation and learning strategies; using the University of Dar es Salaam as a case study. This is a pragmatic research that utilises a mixed research design. The research design includes both qualitative design (in-depth single case study) and quantitative design (survey). The target population for this study is students participating in Blended learning modules. Primary data will be collected by means of Motivational Strategies for Learning Questionnaire and observation. It was found that motivation and learning strategies are significant predictors of student performance in a Blended learning environment. In terms of the motivation categories, Intrinsic Goal Orientation and Self-efficacy have statistically significant effect on student performance. With learning strategies sub factors, it was found out that Rehearsal, Effort Regulation and Peer Learning have significance effect on student performance. Moreover, age and gender significantly influence performance. The findings obtained are significant in building a better understanding of the influence that the mentioned predictors have on predicting the performance of students in Blended learning courses in Tanzania.
- Full Text:
- Date Issued: 2019
- Authors: Kabudi, Tumaini John
- Date: 2019
- Subjects: Prediction of scholastic success -- Tanzania -- Case studies , Motivation in education -- Tanzania -- Case studies , Academic achievement -- Tanzania -- Case studies , Blended learning -- Tanzania -- Case studies , Chuo Kikuu cha Dar es Salaam -- Students
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68358 , vital:29242
- Description: Blended Learning is an important technological platform which has the potential to enhance the efficiency and efficacy of educational provision, especially in Tanzania universities. Despite a high level of investment into Blended learning, students face various challenges that have impeded them performing well in Blended learning courses. The purpose of this research is to examine and explore how student’s performance in a Blended learning environment is influenced by motivation and learning strategies; using the University of Dar es Salaam as a case study. This is a pragmatic research that utilises a mixed research design. The research design includes both qualitative design (in-depth single case study) and quantitative design (survey). The target population for this study is students participating in Blended learning modules. Primary data will be collected by means of Motivational Strategies for Learning Questionnaire and observation. It was found that motivation and learning strategies are significant predictors of student performance in a Blended learning environment. In terms of the motivation categories, Intrinsic Goal Orientation and Self-efficacy have statistically significant effect on student performance. With learning strategies sub factors, it was found out that Rehearsal, Effort Regulation and Peer Learning have significance effect on student performance. Moreover, age and gender significantly influence performance. The findings obtained are significant in building a better understanding of the influence that the mentioned predictors have on predicting the performance of students in Blended learning courses in Tanzania.
- Full Text:
- Date Issued: 2019
Invariant optimal control on the three-dimensional semi-Euclidean group: control affine and quadratic Hamilton-Poisson systems
- Authors: Barrett, Dennis Ian
- Date: 2014
- Subjects: Automorphisms , Symmetry (Mathematics) , Lyapunov stability , Geometry, Riemannian , Geometry, Affine , Elliptic functions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64805 , vital:28605
- Description: In this thesis we consider invariant control systems and Hamilton-Poisson systems on the three dimensional semi-Euclidean group SE(1,1). We first classify the left-invariant control affine systems (under detached feedback equivalence). We provide a complete list of normal forms, as well as classifying conditions. As a corollary to this classification, we derive controllability criteria for control affine systems on SE(1,1). Secondly, we consider quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space se(1,1)*. These systems are classified up to an affine isomorphism. Six normal forms are identified for the homogeneous case, whereas sixteen representatives (including several infinite families) are obtained for the inhomogeneous systems. Thereafter we consider the stability and integration of the normal forms obtained. For all homogeneous systems, and a subclass of inhomogeneous systems, we perform a complete stability analysis and derive explicit expressions for all integral curves. (The extremal controls of a large class of optimal control problems on SE(1,1) are linearly related to these integral curves.) Lastly, we discuss the Riemannian and sub-Riemannian problems. The (left-invariant) Riemannian and sub-Riemannian structures on SE(1,1) are classified, up to isometric group automorphisms and scaling. Explicit expressions for the geodesics of the normalised structures are found.
- Full Text:
- Date Issued: 2014
- Authors: Barrett, Dennis Ian
- Date: 2014
- Subjects: Automorphisms , Symmetry (Mathematics) , Lyapunov stability , Geometry, Riemannian , Geometry, Affine , Elliptic functions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64805 , vital:28605
- Description: In this thesis we consider invariant control systems and Hamilton-Poisson systems on the three dimensional semi-Euclidean group SE(1,1). We first classify the left-invariant control affine systems (under detached feedback equivalence). We provide a complete list of normal forms, as well as classifying conditions. As a corollary to this classification, we derive controllability criteria for control affine systems on SE(1,1). Secondly, we consider quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space se(1,1)*. These systems are classified up to an affine isomorphism. Six normal forms are identified for the homogeneous case, whereas sixteen representatives (including several infinite families) are obtained for the inhomogeneous systems. Thereafter we consider the stability and integration of the normal forms obtained. For all homogeneous systems, and a subclass of inhomogeneous systems, we perform a complete stability analysis and derive explicit expressions for all integral curves. (The extremal controls of a large class of optimal control problems on SE(1,1) are linearly related to these integral curves.) Lastly, we discuss the Riemannian and sub-Riemannian problems. The (left-invariant) Riemannian and sub-Riemannian structures on SE(1,1) are classified, up to isometric group automorphisms and scaling. Explicit expressions for the geodesics of the normalised structures are found.
- Full Text:
- Date Issued: 2014
Rhodes University Research Report 2011
- Rhodes University, Rhodes University Research Office, Roberts, Jaine, Connan, Verna, Dore, Sally
- Authors: Rhodes University , Rhodes University Research Office , Roberts, Jaine , Connan, Verna , Dore, Sally
- Date: 2011
- Language: English
- Type: Text
- Identifier: vital:566 , http://hdl.handle.net/10962/d1011981
- Description: [From Introduction] Rhodes University continued to show a gratifying and steady increase in overall accredited research outputs in 2011, and individual increases were experienced in all categories of output. Overall accredited units increased to 639.6 (a 12.7% increase on 2010), with a similar percentage increase in the DHET per capita output figure, which kept Rhodes in the position of third most productive university in South Africa in terms of accredited research. 51% of the outputs were due to publications, 25% to PhD graduations, and 24% to Masters graduations by thesis. The PhD contribution represented a record year, and a 30% increase over the number graduating in the preceding year. Our journal output, (which accounts for 86% of our total accredited publishing output for higher education subsidy purposes) grew by 5.9% from the 2010 level (to 309.61 units in 2011). The previous year had seen a 3% decline in this category. Coupled with Rhodes’ high volume of accredited journal outputs in relation to its size, a very pleasing quality measure was that 90% of journal outputs (by far the highest proportion of universities in the sector) appeared in international accredited journals. Our output from accredited conference proceedings, (which in 2011 amounted to 7% of our total accredited publishing output) grew by 3.5% to 24.22 units - from a small base where year-on-year variance in either direction is common. The book outputs (which in 2011 amounted to 7% of our total accredited publishing output) increased by 162% - again from a small base (moving up to 25.02 units), where year-on-year variance is expected. This category had seen a negative growth of 60.6% in the previous year. add my warm thanks and congratulations to all of our researchers, funders, collaborators, partners and students who contributed to the excellent accredited research results of 2011, as well as generated the many forms of scholarship that are not counted in the accreditation exercise, but which contribute much to the rich intellectual space that is Rhodes. I also thank all of the administrators who played a critical role in preparing the university’s meticulous audited submission. , A publication of the Rhodes Research Office, compiled and edited by Jaine Roberts and Verna Connan. Design and Layout: Sally Dore.
- Full Text:
- Date Issued: 2011
- Authors: Rhodes University , Rhodes University Research Office , Roberts, Jaine , Connan, Verna , Dore, Sally
- Date: 2011
- Language: English
- Type: Text
- Identifier: vital:566 , http://hdl.handle.net/10962/d1011981
- Description: [From Introduction] Rhodes University continued to show a gratifying and steady increase in overall accredited research outputs in 2011, and individual increases were experienced in all categories of output. Overall accredited units increased to 639.6 (a 12.7% increase on 2010), with a similar percentage increase in the DHET per capita output figure, which kept Rhodes in the position of third most productive university in South Africa in terms of accredited research. 51% of the outputs were due to publications, 25% to PhD graduations, and 24% to Masters graduations by thesis. The PhD contribution represented a record year, and a 30% increase over the number graduating in the preceding year. Our journal output, (which accounts for 86% of our total accredited publishing output for higher education subsidy purposes) grew by 5.9% from the 2010 level (to 309.61 units in 2011). The previous year had seen a 3% decline in this category. Coupled with Rhodes’ high volume of accredited journal outputs in relation to its size, a very pleasing quality measure was that 90% of journal outputs (by far the highest proportion of universities in the sector) appeared in international accredited journals. Our output from accredited conference proceedings, (which in 2011 amounted to 7% of our total accredited publishing output) grew by 3.5% to 24.22 units - from a small base where year-on-year variance in either direction is common. The book outputs (which in 2011 amounted to 7% of our total accredited publishing output) increased by 162% - again from a small base (moving up to 25.02 units), where year-on-year variance is expected. This category had seen a negative growth of 60.6% in the previous year. add my warm thanks and congratulations to all of our researchers, funders, collaborators, partners and students who contributed to the excellent accredited research results of 2011, as well as generated the many forms of scholarship that are not counted in the accreditation exercise, but which contribute much to the rich intellectual space that is Rhodes. I also thank all of the administrators who played a critical role in preparing the university’s meticulous audited submission. , A publication of the Rhodes Research Office, compiled and edited by Jaine Roberts and Verna Connan. Design and Layout: Sally Dore.
- Full Text:
- Date Issued: 2011
Collaborative monitoring in ecosystem management in South Africa's communal lands
- Authors: Bolus, Cosman
- Date: 2010
- Subjects: Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4743 , http://hdl.handle.net/10962/d1006948 , Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Description: Internationally there is an increasing focus on involving local communities in natural resource management and monitoring. Monitoring methods which are professionally driven appear to be inadequate to deal with the monitoring of natural resource use and biodiversity conservation, globally. This is especially evident in areas such as South African rural communal land. Two community based natural resource management (CBNRM) programmes in areas which are communally governed in the Eastern Cape, South Africa, namely Nqabara and Machubeni, were used as part of this research study. This thesis identified and tested potentially simple and cost effective monitoring methods related to the utilization of the local rangelands and indigenous forests. The criteria that were tested include 1) appropriateness and effectiveness in measuring change, and 2) contribution to building adaptive capacity among local land managers through learning. The criteria were assessed using a scoring system for each monitoring method in order to evaluate their strengths and weaknesses . This was done by using both quantitative and qualitative data. Contribution to building adaptive capacity was assessed by evaluating technical capacity gained, local ecological knowledge contributed and learning by participants. This was done using qualitative data. The results show that the monitoring methods had different strengths and weaknesses in relation to the criteria, making them more appropriate for different priorities such as effectively measuring change or building adaptive capacity. It is argued that an adaptive approach is a useful component in the participatory monitoring process. An adaptive framework was developed from lessons learnt in this study for collaborative monitoring. Challenges such as low literacy levels and adequate training still need to be addressed to strengthen efforts towards participatory monitoring. Factors such as incentives, conflict and local values may negatively affect the legitimacy and sustainability of participatory monitoring and therefore also need to be addressed.
- Full Text:
- Date Issued: 2010
- Authors: Bolus, Cosman
- Date: 2010
- Subjects: Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4743 , http://hdl.handle.net/10962/d1006948 , Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Description: Internationally there is an increasing focus on involving local communities in natural resource management and monitoring. Monitoring methods which are professionally driven appear to be inadequate to deal with the monitoring of natural resource use and biodiversity conservation, globally. This is especially evident in areas such as South African rural communal land. Two community based natural resource management (CBNRM) programmes in areas which are communally governed in the Eastern Cape, South Africa, namely Nqabara and Machubeni, were used as part of this research study. This thesis identified and tested potentially simple and cost effective monitoring methods related to the utilization of the local rangelands and indigenous forests. The criteria that were tested include 1) appropriateness and effectiveness in measuring change, and 2) contribution to building adaptive capacity among local land managers through learning. The criteria were assessed using a scoring system for each monitoring method in order to evaluate their strengths and weaknesses . This was done by using both quantitative and qualitative data. Contribution to building adaptive capacity was assessed by evaluating technical capacity gained, local ecological knowledge contributed and learning by participants. This was done using qualitative data. The results show that the monitoring methods had different strengths and weaknesses in relation to the criteria, making them more appropriate for different priorities such as effectively measuring change or building adaptive capacity. It is argued that an adaptive approach is a useful component in the participatory monitoring process. An adaptive framework was developed from lessons learnt in this study for collaborative monitoring. Challenges such as low literacy levels and adequate training still need to be addressed to strengthen efforts towards participatory monitoring. Factors such as incentives, conflict and local values may negatively affect the legitimacy and sustainability of participatory monitoring and therefore also need to be addressed.
- Full Text:
- Date Issued: 2010
On the growth and characterisation of AIGaN alloys for optoelectronic applications
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
South African anti-apartheid documentaries 1977-1987: some theoretical excursions
- Authors: Steenveld, Lynette Noreen
- Date: 1991
- Subjects: Documentary films -- South Africa -- History and criticism , Apartheid -- South Africa , Anti-apartheid movements -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3484 , http://hdl.handle.net/10962/d1002939 , Documentary films -- South Africa -- History and criticism , Apartheid -- South Africa , Anti-apartheid movements -- South Africa
- Description: This study examines anti-apartheid documentary production in South Africa between 1977 and 1987. These documentaries were produced by a variety of producers in order to record aspects of South Africa's contemporary social history, and as a means of contributing - in some way - to changing the conditions described. While the 'content' of the documentaries is historical and social, and their intention political, this study is aimed at elucidating how a documentary, as a representational system, produces meaning. The study is therefore located within the discourse of film studies. My study is based on the theory that a documentary is the embodiment of several relationships: the relationship between social reality and documentary producers; the social relationships engaged in, in the production of the text; the relationship between the text and its audience 1, and the relationship between the audience and its social context. This informs my methodological approach in which analysis appropriate to each area of study is used. Using secondary sources obtained through standard library research, I pursue social and historical analysis of the 1970s and 1980s in order to contextualise both the producers of the documentaries, and their audience. The social relations of production of a text are examined using material gathered through extensive interviews with the producers and published secondary material. How this impinges on the documentary is ascertained through detailed textual analysis of 30 documentaries. For analytical clarity each chapter focuses on a specific aspect of documentary - although I do show how the various relationships impinge on each other. This research finds that the documentaries faithfully reflect the anti-apartheid ideology dominant in the extra-parliamentary opposition in the period under discussion - to the extent that all forms of consciousness are framed by this discourse. An examination of the textual strategies used shows that they are bound by the conventions of broadcast television. They therefore construct a spectator-text relationship which is not consistent with the political concern that democratic relationships be established as the basis of a post-apartheid society. In other words, there is an inconsistency between the ideology espoused, and the way in which film- and videomakers, in their specialised field of production, practise their politics. This can be attributed to the over-riding political intention of the documentarists 'to record' what is happening, and to establish a popular archive which can be used by extra-parliamentary opposition groups in their struggle against apartheid.
- Full Text:
- Date Issued: 1991
- Authors: Steenveld, Lynette Noreen
- Date: 1991
- Subjects: Documentary films -- South Africa -- History and criticism , Apartheid -- South Africa , Anti-apartheid movements -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3484 , http://hdl.handle.net/10962/d1002939 , Documentary films -- South Africa -- History and criticism , Apartheid -- South Africa , Anti-apartheid movements -- South Africa
- Description: This study examines anti-apartheid documentary production in South Africa between 1977 and 1987. These documentaries were produced by a variety of producers in order to record aspects of South Africa's contemporary social history, and as a means of contributing - in some way - to changing the conditions described. While the 'content' of the documentaries is historical and social, and their intention political, this study is aimed at elucidating how a documentary, as a representational system, produces meaning. The study is therefore located within the discourse of film studies. My study is based on the theory that a documentary is the embodiment of several relationships: the relationship between social reality and documentary producers; the social relationships engaged in, in the production of the text; the relationship between the text and its audience 1, and the relationship between the audience and its social context. This informs my methodological approach in which analysis appropriate to each area of study is used. Using secondary sources obtained through standard library research, I pursue social and historical analysis of the 1970s and 1980s in order to contextualise both the producers of the documentaries, and their audience. The social relations of production of a text are examined using material gathered through extensive interviews with the producers and published secondary material. How this impinges on the documentary is ascertained through detailed textual analysis of 30 documentaries. For analytical clarity each chapter focuses on a specific aspect of documentary - although I do show how the various relationships impinge on each other. This research finds that the documentaries faithfully reflect the anti-apartheid ideology dominant in the extra-parliamentary opposition in the period under discussion - to the extent that all forms of consciousness are framed by this discourse. An examination of the textual strategies used shows that they are bound by the conventions of broadcast television. They therefore construct a spectator-text relationship which is not consistent with the political concern that democratic relationships be established as the basis of a post-apartheid society. In other words, there is an inconsistency between the ideology espoused, and the way in which film- and videomakers, in their specialised field of production, practise their politics. This can be attributed to the over-riding political intention of the documentarists 'to record' what is happening, and to establish a popular archive which can be used by extra-parliamentary opposition groups in their struggle against apartheid.
- Full Text:
- Date Issued: 1991
A cross cultural study of eidetic imagery and short term memory
- Authors: Lewis, William Michael
- Date: 1974
- Subjects: Cross-cultural studies , Eidetic imagery , Short-term memory
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3141 , http://hdl.handle.net/10962/d1007182 , Cross-cultural studies , Eidetic imagery , Short-term memory
- Description: The complexity of behaviour necessitates a clear and concise approach in order to comprehend its functioning. An example of such an approach is highlighted by the field of cybernetics. Cybernetic models have been used extensively throughout the various fields of Psychology but perhaps never more so as in the case of short term memory (STM). This particular field abounds with behavioural models and research workers are constantly developing new models or testing the universality of existing models. Universal validity is essential to the strength of the behavioural principles inherent in any model but unfortunately such validity tends to be neglected. The present study attempts to reconcile this position with reference to specific models of STM, with relation to the phenomena of eidetic imagery (EI). Certain studies concerning the incidence of EI in illiterate Africans have produced results which are contradictory to those obtained in the Western culture. Two of the most important contradictions concern the fact that the illiterate Africans experienced the absence of an age parameter on the occurrence of such imagery and the fact that the incidence of imagery was more extensive in the African culture. A reason for these contradictions was sought and it was reasoned that as eidetic images have been closely linked with memory images, it may, therefore, be assumed that these particular cultures may use EI as an aid to memory in the absence of written material. Further, it would not be unreasonable to assume that this visual imagery may tend to dominate the STM process and thereby challenge the universality of those memory models that proposed acoustic domination of this process. No work has been done in investigating the memory process of the Africans. Thus, a study which did so would not only test the universality of specific memory models but would also possibly throw more light on the memory process itself. In this particular study there were three specific aims; (a) to ascertain the relative incidence of EI on a cross-cultural level, (b) to assess the influence of EI on the memory process, and (c) to ascertain the extent to which principles of STM developed in the West applied to the African groups. The groups concerned in the study comprised two Xhosa groups and a European group. The European group (WS) was drawn from a White Student population at Rhodes University and was regarded as a control group. The equivalent literate Xhosa group (BS) was drawn from a Black Student population at the University of Fort Hare. The illiterate Xhosa group (RX) was drawn from a population of Red Xhosa people in the Transkei. Four tasks were administered to the groups with the cross-cultural variable carefully controlled as much as possible. The following comprised the four tasks; (a) eidetic imagery (b) auditory serial recall (c) visual serial recall and (d) an acoustic confusable task. Each subject commenced with the eidetic imagery task and was then confronted with a random presentation of the other three tasks. The EI task began with an after image task which was foIlowed by three selected pictures which comprised the EI task. After each picture presentation the subject was closely questioned as to the presence of imagery. Scoring was of a subjective nature. The visual and acoustic confusion tasks constituted serial presentation of ten items over six randomized trials. Each item was presented for 0,75 seconds with a negligible inter-item interval. The presentation order of the items was randomized throughout the trials. Presentation was by means of a preprogrammed 16mm colour film. Items were scored for correct serial position. The auditory task consisted of the serial presentation of ten items over six randomized trials. The items were once again randomized throughout the trials with regards to presentation order. The presentation speed was one word per second. The presentation was by means of a pre-programmed tape. Items were scored for correct serial position. The visual task was common to both language groups whilst the other two tasks correlated with the language group. Thus, the items in the auditory and acoustic confusion tasks were different for each language but an attempt was made to control this variable. The tasks were conducted in the subjects home language which was either Xhosa or English. It was assumed that the RX group would demonstrate a greater incidence of EI, irrespective of the age of the subject, and that imagery would be reflected in the recall performance of the memory tasks. It was suggested that imagery may determine or encourage the mode of storage that the subject employed, which, in this case, would be the visual modality. If so then it would be expected that visual storage would circumvent the detrimental influence of acoustic confusability. The Xhosa university group (BS ) was an unknown quantity but was included to ascertain whether there were any marked differences between the group and the other two. The results revealed that imagery was in fact more prevalent in the Xhosa groups whilst the WS group demonstrated a complete lack of EI but did report the presence of pictorial imagery (PI). However, imagery did not appear to function as an aid to memory. It seemed, however, that in certain instances it correlated with visual encoding. Generally the Xhosa subjects, especially with regards to the visual tasks, tended to encode visually whilst the WS group encoded auditorily. With reference to recall performance, it was found that in all instances the WS group demonstrated superior recall followed by the BS and RX groups in that order. There was a significant difference in the strength of recall between each of the groups. The results of the auditory and visual tasks were interpreted within the STM principles developed in the West. It was found that the WS group adhered to these principles thereby justifying its position as a central group. The BS group followed a similar pattern with exception to the recency effect which was much weaker in their case. The RX group reported the absence of any storage and rehearsal strategies and this was reflected in their poor recall performance. They too were characterized by a very weak recency effect. The interesting point arose, however, when the auditory and visual recency effects were compared. According to Crawder and Norton (1969) the influence or the precategorical acoustic store (PAS) on recall should be reflected by a comparatively stronger auditory recency effect. This trend was observed in relation to the WS group but not to the Xhosa groups who tended to demonstrate a stronger visual recency effect. It was therefore, suspected that PAS did not operate with the same effectiveness with the Xhosa subjects. In fact it was suggested that in the case of the Xhosa subjects the visual peripheral store may be stronger than PAS. Contrary to expectation all three groups exhibited acoustic confusion. This was expected of the WS group as the subjects preferred auditory storage , but not of the Xhosa subjects who preferred visual storage. It was suggested however, that in the case of the Xhosa subjects the visual storage technique would have to be abandoned immediately prior to or during recall as recall was necessarily in the auditory modality. The outcome of the experiment generally confirmed Doab's conclusions as to the incidence of imagery and its relation with memory. However, due to the Xhosa preference for visual storage and their stronger visual recency effect, Sperling's model was slightly modified. Conrad 's findings were, of course, substantiated.
- Full Text:
- Date Issued: 1974
- Authors: Lewis, William Michael
- Date: 1974
- Subjects: Cross-cultural studies , Eidetic imagery , Short-term memory
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3141 , http://hdl.handle.net/10962/d1007182 , Cross-cultural studies , Eidetic imagery , Short-term memory
- Description: The complexity of behaviour necessitates a clear and concise approach in order to comprehend its functioning. An example of such an approach is highlighted by the field of cybernetics. Cybernetic models have been used extensively throughout the various fields of Psychology but perhaps never more so as in the case of short term memory (STM). This particular field abounds with behavioural models and research workers are constantly developing new models or testing the universality of existing models. Universal validity is essential to the strength of the behavioural principles inherent in any model but unfortunately such validity tends to be neglected. The present study attempts to reconcile this position with reference to specific models of STM, with relation to the phenomena of eidetic imagery (EI). Certain studies concerning the incidence of EI in illiterate Africans have produced results which are contradictory to those obtained in the Western culture. Two of the most important contradictions concern the fact that the illiterate Africans experienced the absence of an age parameter on the occurrence of such imagery and the fact that the incidence of imagery was more extensive in the African culture. A reason for these contradictions was sought and it was reasoned that as eidetic images have been closely linked with memory images, it may, therefore, be assumed that these particular cultures may use EI as an aid to memory in the absence of written material. Further, it would not be unreasonable to assume that this visual imagery may tend to dominate the STM process and thereby challenge the universality of those memory models that proposed acoustic domination of this process. No work has been done in investigating the memory process of the Africans. Thus, a study which did so would not only test the universality of specific memory models but would also possibly throw more light on the memory process itself. In this particular study there were three specific aims; (a) to ascertain the relative incidence of EI on a cross-cultural level, (b) to assess the influence of EI on the memory process, and (c) to ascertain the extent to which principles of STM developed in the West applied to the African groups. The groups concerned in the study comprised two Xhosa groups and a European group. The European group (WS) was drawn from a White Student population at Rhodes University and was regarded as a control group. The equivalent literate Xhosa group (BS) was drawn from a Black Student population at the University of Fort Hare. The illiterate Xhosa group (RX) was drawn from a population of Red Xhosa people in the Transkei. Four tasks were administered to the groups with the cross-cultural variable carefully controlled as much as possible. The following comprised the four tasks; (a) eidetic imagery (b) auditory serial recall (c) visual serial recall and (d) an acoustic confusable task. Each subject commenced with the eidetic imagery task and was then confronted with a random presentation of the other three tasks. The EI task began with an after image task which was foIlowed by three selected pictures which comprised the EI task. After each picture presentation the subject was closely questioned as to the presence of imagery. Scoring was of a subjective nature. The visual and acoustic confusion tasks constituted serial presentation of ten items over six randomized trials. Each item was presented for 0,75 seconds with a negligible inter-item interval. The presentation order of the items was randomized throughout the trials. Presentation was by means of a preprogrammed 16mm colour film. Items were scored for correct serial position. The auditory task consisted of the serial presentation of ten items over six randomized trials. The items were once again randomized throughout the trials with regards to presentation order. The presentation speed was one word per second. The presentation was by means of a pre-programmed tape. Items were scored for correct serial position. The visual task was common to both language groups whilst the other two tasks correlated with the language group. Thus, the items in the auditory and acoustic confusion tasks were different for each language but an attempt was made to control this variable. The tasks were conducted in the subjects home language which was either Xhosa or English. It was assumed that the RX group would demonstrate a greater incidence of EI, irrespective of the age of the subject, and that imagery would be reflected in the recall performance of the memory tasks. It was suggested that imagery may determine or encourage the mode of storage that the subject employed, which, in this case, would be the visual modality. If so then it would be expected that visual storage would circumvent the detrimental influence of acoustic confusability. The Xhosa university group (BS ) was an unknown quantity but was included to ascertain whether there were any marked differences between the group and the other two. The results revealed that imagery was in fact more prevalent in the Xhosa groups whilst the WS group demonstrated a complete lack of EI but did report the presence of pictorial imagery (PI). However, imagery did not appear to function as an aid to memory. It seemed, however, that in certain instances it correlated with visual encoding. Generally the Xhosa subjects, especially with regards to the visual tasks, tended to encode visually whilst the WS group encoded auditorily. With reference to recall performance, it was found that in all instances the WS group demonstrated superior recall followed by the BS and RX groups in that order. There was a significant difference in the strength of recall between each of the groups. The results of the auditory and visual tasks were interpreted within the STM principles developed in the West. It was found that the WS group adhered to these principles thereby justifying its position as a central group. The BS group followed a similar pattern with exception to the recency effect which was much weaker in their case. The RX group reported the absence of any storage and rehearsal strategies and this was reflected in their poor recall performance. They too were characterized by a very weak recency effect. The interesting point arose, however, when the auditory and visual recency effects were compared. According to Crawder and Norton (1969) the influence or the precategorical acoustic store (PAS) on recall should be reflected by a comparatively stronger auditory recency effect. This trend was observed in relation to the WS group but not to the Xhosa groups who tended to demonstrate a stronger visual recency effect. It was therefore, suspected that PAS did not operate with the same effectiveness with the Xhosa subjects. In fact it was suggested that in the case of the Xhosa subjects the visual peripheral store may be stronger than PAS. Contrary to expectation all three groups exhibited acoustic confusion. This was expected of the WS group as the subjects preferred auditory storage , but not of the Xhosa subjects who preferred visual storage. It was suggested however, that in the case of the Xhosa subjects the visual storage technique would have to be abandoned immediately prior to or during recall as recall was necessarily in the auditory modality. The outcome of the experiment generally confirmed Doab's conclusions as to the incidence of imagery and its relation with memory. However, due to the Xhosa preference for visual storage and their stronger visual recency effect, Sperling's model was slightly modified. Conrad 's findings were, of course, substantiated.
- Full Text:
- Date Issued: 1974
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