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Melatonin generates singlet oxygen on laser irradiation but acts as a quencher when irradiated by lamp photolysis

- Maharaj, Deepa S, Molell, H, Antunes, Edith M, Maharaj, Hiren, Maree, D M, Nyokong, Tebello, Glass, Beverley D, Daya, Santy

  • Authors: Maharaj, Deepa S , Molell, H , Antunes, Edith M , Maharaj, Hiren , Maree, D M , Nyokong, Tebello , Glass, Beverley D , Daya, Santy
  • Date: 2005
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/300335 , vital:57917 , xlink:href="https://doi.org/10.1111/j.1600-079X.2004.00185.x"
  • Description: Melatonin, a naturally occurring chemical mediator, although assigned a diverse range of functions, has attracted interest in recent years because of its ability to function as a free radical scavenger. Because of the implications of singlet oxygen in neurotoxicity, the objective of the study was to investigate the ability of melatonin to quench singlet oxygen generated using laser irradiation or lamp photolysis. The results show that melatonin produces radicals upon laser irradation while the lamp photolysis studies show that melatonin is able to scavenge singlet oxygen produced by naphthalene. While melatonin is a free radical scavenger under biological conditions, it acts as a generator of singlet oxygen and or radicals (as ΦΔ is 1.41) when irradiated with laser light, implying that it has the potential to be used in photodynamic therapy in the destruction of tumors.
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  • Date Issued: 2005

Menemene ndini lomdlezana

- Preformer not specified, Composer not specified, Dargie, Dave

Metalorganic vapour phase epitaxial growth and characterisation of Sb-based semiconductors

- Vankova, Viera

  • Authors: Vankova, Viera
  • Date: 2005
  • Subjects: Compound semiconductors , Epitaxy , Organometallic compounds , Metal organic chemical vapor deposition
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10548 , http://hdl.handle.net/10948/d1019678
  • Description: This study focuses on the growth and characterization of epitaxial InAs and InAs1-xSbx. Layers are grown on InAs, GaAs and GaSb substrates by metalorganic vapour phase epitaxy, using trimethylindium, trimethylantimony and arsine as precursors. The growth parameters (V/III ratio, Sb vapour phase compositions) are varied in the temperature range from 500 ºC to 700 ºC, in order to study the influence of these parameters on the structural, optical and electrical properties of the materials. The layers were assessed by X-ray diffraction, electron and optical microscopy, photoluminescence and Hall measurements. Furthermore, the influence of hydrogenation and annealing on the electrical and optical properties of GaSb was investigated. It is shown that the growth temperature and the V/III ratio play a vital role in the resulting surface morphology of homoepitaxial and heteroepitaxial InAs layers. Growth at low temperatures is found to promote three-dimensional growth in both cases, with improvements in the surface morphologies observed for higher growth temperatures. All the investigated epilayers are n-type. It is shown that the electrical properties of heteroepitaxial InAs epilayers are complicated by a competition between bulk conduction and conduction due to a surface accumulation and an interface layer. The low temperature photoluminescence spectra of homoepitaxial InAs are dominated by two transitions. These are identified as band-to-band/excitonic and donor-acceptor recombination. The incorporation efficiency of antimony (Sb) into InAs1-xSbx is dependent on the growth temperature and the V/III ratio. Under the growth conditions used in this study, the incorporation efficiency of Sb is controlled by the thermal stability of the two constituent binaries (i.e. InAs and InSb). Changes in the low temperature photoluminescence spectra are detected with increasing x. From temperature and laser power dependent measurements, the highest energy line is attributed to band-to-band/excitonic recombination, while the peak appearing approximately 15 meV below this line is assigned to donor-acceptor recombination. The origin of an additional “moving” peak observed for higher Sb mole fraction x is tentatively attributed to quasi-donor-acceptor-recombination, arising from increased impurity/defect concentrations and a higher compensation ratio in the material. However, the unusual behaviour of this peak may also be ascribed to the presence of some degree of ordering in InAsSb. The exposure of a semiconductor to a hydrogen plasma usually leads to the passivation of shallow and deep centres, thereby removing their electrical and optical activity. In this study, the passivation and thermal stability of the native acceptor in p-type GaSb is also investigated. It is shown that this acceptor can be passivated, where after improvements in the electrical and optical properties of GaSb are observed. Upon annealing the passivated samples above 300 °C, the acceptor is reactivated.
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  • Date Issued: 2005

Methodological Decisions in Context: The dilemmas and challenges of novice African scholars

- Lupele, Justin, Mwingi, Mweru, Kinyanjui, Felistus, Kimani, Joyce, Kisamba, Christine

  • Authors: Lupele, Justin , Mwingi, Mweru , Kinyanjui, Felistus , Kimani, Joyce , Kisamba, Christine
  • Date: 2005
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/373734 , vital:66717 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122698"
  • Description: This paper emerges out of a panel discussion during a PhD week and subsequent 8th International Environmental Education Invitation Seminar held at Rhodes University in 2004 and 2005 respectively. It illuminates some insights into our struggles (as novice African researchers) in trying to respond to contextual realities as we research education and social change in African contexts, seeking insight into what counts as legitimate research in this context. The paper considers our struggles at conceptual, methodological, analytical and data generation levels, and in a politics of research. This is done by means of examples drawn from five current doctoral research projects being undertaken in east and southern African regions, using a review framework that represents fairly common dimensions of PhD research. We conclude that research, when defined rigidly within research disciplines/paradigms (as have been defined in some – primarily Western – research trajectories) may fail to take into account African social and contextual realities when applied uncritically. We argue that there is need for researchers in Africa to consider a multiplicity of approaches if research is to be meaningful in, and responsive to, social and contextual realities. In particular, we argue for taking account of socio historical and socio-cultural contexts in creating African epistemology in and through research.
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  • Date Issued: 2005

Military strategy and it's [i.e.] its use in competitive strategy with reference to the Nelson Mandela Metropole automotive industry

- Fouché, Craig

  • Authors: Fouché, Craig
  • Date: 2005
  • Subjects: Strategic planning -- South Africa -- Nelson Mandela Metropole , Automobile industry and trade -- South Africa -- Nelson Mandela Metropole , Competition
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: vital:8542 , http://hdl.handle.net/10948/177 , Strategic planning -- South Africa -- Nelson Mandela Metropole , Automobile industry and trade -- South Africa -- Nelson Mandela Metropole , Competition
  • Description: Presently in the South African automotive industry competition is becoming more fierce. It is becoming more important for companies to concentrate on thier competitive strategies to ensure that they remain competitive in this industry. Military strategy techniques have always been successful in defeating an anemy opponent. An enemy in a military sense could be considered as a competitor in a business sense. There is currently a potential for an improvement of the competitive strategies that South African organisations, in particular the South African automotive industry uses to remain competitive. Military strategists such as Sun Tzu and Carl von Clausewitz have provided valuable strategy theories and philosophies to many military institutions. Military strategies such as Attrition and Maneuver have long been used by these institutions in battle to defeat the enemy. Military strategies could provide the edge that companies ranging from manufacturers, suppliers of components and dealerships need, to remain competitive in the automotive industry.
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  • Date Issued: 2005

Modeling and measurement of torqued procession in radio pulsars

- Tiplady, Adrian John

  • Authors: Tiplady, Adrian John
  • Date: 2005
  • Subjects: Pulsars , Radio telescopes , Radio astronomy , Precession , Hartebeeshoek Radio Astronomy Observatory (HartRAO)
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5475 , http://hdl.handle.net/10962/d1005260
  • Description: The long term isolated pulsar monitoring program, which commenced in 1984 using the 26 m radio telescope at the Hartebeeshoek Radio Astronomy Observatory (HartRAO), has produced high resolution timing residual data over long timespans. This has enabled the analysis of observed spin down behaviour for 27 braking pulsars, most of which have dataspans longer than 14 years. The phenomenology of observed timing residuals of certain pulsars can be explained by pseudo periodic effects such as precession. Analytic and numerical models are developed to study the kinematic and dynamic behaviour of isolated but torqued precessing pulsars. The predicted timing residual behaviour of the models is characterised, and confronted with timing data from selected pulsars. Cyclic variations in the observed timing residuals of PSR B1642-03, PSR B1323-58 and PSR B1557-50 are fitted with a torqued precession model. The phenomenology of the observed timing behaviour of these pulsars can be explained by the precession models, but precise model fitting was not possible. This is not surprising given that the complexity of the pulsar systems is not completely described by the model. The extension of the pulsar monitoring program at HartRAO is used as motivation for the design and development of a new low cost, multi-purpose digital pulsar receiver. The instrument is implemented using a hybrid filterbank architecture, consisting of an analogue frontend and digital backend, to perform incoherent dedispersion. The design of a polyphase filtering system, which will consolidate multiple processing units into a single filtering solution, is discussed for future implementation.
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  • Date Issued: 2005

Modelling the sustainable harvest of Sclerocarya birrea subsp. caffra fruits in the South African lowveld

- Emanuel, P L, Shackleton, Charlie M, Baxter, Jeremy

  • Authors: Emanuel, P L , Shackleton, Charlie M , Baxter, Jeremy
  • Date: 2005
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181312 , vital:43718 , xlink:href="https://doi.org/10.1016/j.foreco.2005.03.066"
  • Description: Levels of commercialization, size class profile and fruit production of Sclerocarya birrea (marula) trees were studied in the Bushbuckridge region of South Africa. A stage-based population matrix model was used to estimate the sustainable yield for S. birrea fruit. The trees begin to bear fruit at an average size of 42.8 cm in circumference and this relates to an approximate age of 19 years. For a stable size class profile, the population growth rate, λ, was 1.1828758. The observed size class profile did not conform to the stable stage size class profile, obtained from the model. Thus, it was not possible to predict the state of the observed population. Using the model, it was estimated that 92% of fruit could be removed without impacting the current population profile. The management of other more destructive forms of S. birrea resource use (such as bark or firewood harvesting), however, do need to be monitored to limit negative impacts on the population that may reduce fruit availability for regeneration or cropping.
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  • Date Issued: 2005

Monetary valuation of livelihoods for understanding the composition and complexity of rural households

- Dovie, Delali B K, Witkowski, Ed T F, Shackleton, Charlie M

  • Authors: Dovie, Delali B K , Witkowski, Ed T F , Shackleton, Charlie M
  • Date: 2005
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181346 , vital:43721 , xlink:href="https://doi.org/10.1007/s10460-004-7233-0"
  • Description: There is, at present, little precise understanding of the relative contributions of the various income streams used by impoverished rural households in southern Africa. The impact of household profiles on overall income also is not well understood. There is, therefore, little consideration of these factors in national economic accounting. This paper is an attempt to reduce this gap in knowledge by reflecting on the relative contribution of agro-pastoralism, secondary woodland resources, and formal and informal cash income streams to households in the semi-arid rural village of Thorndale, Limpopo Province, South Africa. In the absence of jobs and confronted with high migrant labor, households with open access to natural resources derived more benefits from land-based livelihoods than cash income streams (i.e., 57.5 % vs. 42.5 %). Total livelihood income was valued at US$2887 per household per annum. A significant correlation between monetary values derived from crops and formal wages was established, and it was found that households with high cash incomes tended to invest more in crop production. Over 80 of households were male-headed. Of these heads of household, more than 60 were long-term migrants to urban areas, leaving household decision-making to the women. The low literacy rates of women have deprived them of paid jobs outside the area and, therefore, have increased their dependence on crops (62%) and secondary woodlands resources (60%). This was further reflected in the proportion of households in which females were the main contributors of cash income (9.7%), or joint contributors with men (24.4%). Various positive correlations were established between the number of women per household and the three land-based livelihoods. This implied that women’s total control over such activities was mostly a result of the absence of men and not a typical phenomenon. In spite of this control, it was not positively reflected in the lives of majority of the women. Households differed in their participation in livelihood activities. Household size influenced the level of production and was positively correlated with the value of secondary woodland resources and crops. The study shows the interdependence of land-based livelihood sources and the impact of household features on production and consumption. Policies that focus on livelihood options need to recognize and accommodate associated household dynamics.
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  • Date Issued: 2005

Monitoring the oceanic flow between Africa and Antarctica: report of the first Good Hope cruise

- Ansorge, Isabelle J, Speich, S, Lutjeharms, Johan R E, Goni, G J, Rautenbach, C J de W, Froneman, P William, Rouault, M, Garzoli, S

  • Authors: Ansorge, Isabelle J , Speich, S , Lutjeharms, Johan R E , Goni, G J , Rautenbach, C J de W , Froneman, P William , Rouault, M , Garzoli, S
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6832 , http://hdl.handle.net/10962/d1007568
  • Description: The Southern Ocean plays a major role in the global oceanic circulation, as a component of the Meridional Overturning Circulation, and it is postulated that it has a great influence on present-day climate. However, our understanding of its complex three-dimensional dynamics and of the impact of its variability on the climate system is rudimentary. The newly constituted, international GoodHope research venture aims to address this knowledge gap by establishing a programme of regular observations across the Southern Ocean between the African and Antarctic continents. The objectives of this programme are fivefold: (1) to improve understanding of Indo-Atlantic inter-ocean exchanges and their impact on the global thermohaline circulation and thus on global climate change; (2) to understand in more detail the influence these exchanges have on the climate variability of the southern African subcontinent; (3) to monitor the variability of the main Southern Ocean frontal systems associated with the Antarctic Circumpolar Current; (4) to study air-sea exchanges and their role on the global heat budget, with particular emphasis on the intense exchanges occurring within the Agulhas Retroflection region south of South Africa, and (5) to examine the role of major frontal systems as areas of elevated biological activity and as biogeographical barriers to the distribution of plankton. We present here preliminary results on the physical and biological structure of the frontal systems using the first GoodHope transect that was completed during February-March 2004.
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  • Date Issued: 2005

Motopomo: the historical-theoretical background to contemporary graphic design practices

- Economou, Inge

  • Authors: Economou, Inge
  • Date: 2005
  • Subjects: Graphic arts , Graphic arts -- 20th century , Modernism (Art)
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10764 , http://hdl.handle.net/10948/179 , Graphic arts , Graphic arts -- 20th century , Modernism (Art)
  • Description: This study proposes to illustrate that the twentieth century passage from modernity to postmodernity, with its induction of socio-cultural development and attitudinal change, exists as a fundamental means of informing the character of contemporary graphic design practice1. Today, in contrast to the intentions of this study, many appraisals of graphic design work would seem to place too much emphasis on the analyses and evaluation of the stylistic character of creative practices and not enough on the theoretical, historical and attitudinal issues surrounding them. As such, this study attempts to reveal the meaning and moreover the relevance of philosophical, social, cultural and critical theory for contemporary, postmodern graphic design practices. This is done in order to provide graphic designers with a reflective awareness of the structure of the cultural context within which they work, and takes into account twentieth century cultural theory and twentieth century, western graphic design practice, within the framework of the passage from modernity to postmodernity.
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  • Date Issued: 2005

Msawawa

- Preformer not specified, Composer not specified, Dargie, Dave

Multivariate morphometric analysis of Apis cerana of southern mainland Asia

- Hepburn, H Randall, Radloff, Sarah E, Hepburn, Colleen, Fuchs, S, Otis, G W, Sein, M M, Aung, H L, Pham, H T, Tam, D Q, Nuru, A M, Ken, T

  • Authors: Hepburn, H Randall , Radloff, Sarah E , Hepburn, Colleen , Fuchs, S , Otis, G W , Sein, M M , Aung, H L , Pham, H T , Tam, D Q , Nuru, A M , Ken, T
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6906 , http://hdl.handle.net/10962/d1011859
  • Description: Multivariate morphometric analyses were performed on a series of worker honeybees, Apis cerana, representing 557 colonies from all of southern mainland Asia extending from Afghanistan to Vietnam south of the Himalayas. Scores from the principal components analysis revealed five statistically separable but not entirely distinct morphoclusters of bees: (1) the Hindu Kush, Kashmir, N. Myanmar, N. Vietnam and S. China; (2) Himachal Pradesh region of N. India; (3) N. India, Nepal; (4) central and S. Myanmar and Vietnam, Cambodia, Thailand, S. China and peninsular Malaysia; (5) central and S. India. The major morphoclusters are distributed coherently with the different climatic zones of the region. While populations are definable, nomenclatural adjustments remain for the future.
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  • Date Issued: 2005

Ndihamba ndodwa

- Preformer not specified, Composer not specified, Dargie, Dave

Ndiyahamba mna

- Preformer not specified, Composer not specified, Dargie, Dave

Ndiyathakatha ngemfene katata

- Preformer not specified, Composer not specified, Dargie, Dave

Ndiyathakatha ngemfene katata

- Preformer not specified, Composer not specified, Dargie, Dave

Ndiyathakatha ngemfene katata

- Preformer not specified, Composer not specified, Dargie, Dave

Ndiyawoyik' amapolisa

- Preformer not specified, Composer not specified, Dargie, Dave

Nomathotholo

- Preformer not specified, Composer not specified, Dargie, Dave

Nomutile ndikwenzeni

- Preformer not specified, Composer not specified, Dargie, Dave

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