Towards a transnational feminist aesthetic: an analysis of selected prose writing by women of the South Asian diaspora
- Authors: Naidu, Samantha
- Date: 2007
- Subjects: South Asian literature -- Women authors , Women and literature -- Asia , English prose literature -- Women authors -- History and criticism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2307 , http://hdl.handle.net/10962/d1012941 , https://orcid.org/0000-0001-9456-8657
- Description: This thesis argues that women writers of the South Asian diaspora are inscribing a literary aesthetic which is recognisably feminist. In recent decades women of the South Asian diaspora have risen to the forefront of the global literary and publishing arena, winning acclaim for their endeavours. The scope of this literature is wide, in terms of themes, styles, genres, and geographic location. Prose works range from grave novelistic explorations of female subjectivity to short story collections intent on capturing historical injustices and the experiences of migration. The thesis demonstrates, through close readings and comparative frameworks, that an overarching pattern of common aesthetic elements is deployed in this literature. This deployment is regarded as a transnational feminist practice.
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- Date Issued: 2007
Towards a norm of compliance in recreational fisheries
- Authors: Bova, Christopher S
- Date: 2019
- Subjects: Fishing -- Management -- South Africa , Fishery law and legislation -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/95909 , vital:31213
- Description: The activity of fishing can be traced back to prehistoric times. However, only in the last century has there been a focus on the management of fisheries. Fishery regulations are tools used by resource managers with the aim of protecting the long-term sustainability of fishery resources. Although there is an overwhelming amount of evidence demonstrating the decline of fisheries, non-compliance with these regulations by fishers continues to manifest, which can exacerbate the negative ecological impacts of fisheries. Popular methods towards the measurement of noncompliance in fisheries derived from previous human dimensions literature may be flawed. Theories on improving compliance behaviour have typically relied on theory, which has at times proved paradoxical. Addressing the issues of non-compliance within a fishery of interest requires measuring the levels of non-compliance within the fishery and determining the relevant sociopsychological drivers behind the non-compliant behaviour. The data collection methods used during these assessments are limited in human dimensions research and are often case and context specific, requiring researchers to identify which approach is most practical for the specific fishery of interest. By identifying relevant behavioural drivers of non-compliance, a more effective approach aimed at improving compliance can be tailored. The recreational marine-based shore fishery (MBSF) in South Africa is not impervious to noncomplaint behaviour. In fact, it has been estimated to have relatively high rates of non-compliance. This high level of non-compliance makes the South African MBSF a unique and optimal context in which to undertake research that aims to formulate a framework towards compliance assessments and that develops a suitable approach for improving compliance rates. Using surveys to obtain compliance data can provide a range of details about violators, however they are susceptible to social desirability bias (SDB). Choosing the best method for controlling SDB required an assessment of existing methods for doing so. In this first part of the study, only fishers who were covertly observed breaking the rules were surveyed, using one of three methods for reducing SDB, to ground-truth the responses. Ground-truthing was done to determine which method would be most effective for a large-scale study within the same fishery. Of the methods used, which include the direct questioning method (DQM), the random response technique (RRT) and the ballot box method (BBM), all contained some level of SDB. However, the BBM provided a significantly higher level of response accuracy (79.6% ± 11.9) than the DQM (46.5% ± 14.9) and the RRT (44.3% ± 12.5). Random-stratified roving creel compliance surveys that employed the BBM were then undertaken at various locations along South Africa’s coastline to estimate current rates of non-compliance, and the face-to-face results were compared to results from an identical online survey to determine the suitability of online surveys as a replacement. The results indicated that online surveys only represent a subgroup of the fisher population within the MBSF, suggesting that face-to-face survey methods are required to obtain a more comprehensive sample and a more robust estimate of noncompliance. The results, based on 453 face-to-face surveys, showed a high level of overall self-reported noncompliance (48.3%) within the fishery. Responses to Likert scale survey questions on various aspects of the fishery, including angler motivations for fishing, were then modelled to test the relationship between the anglers’ responses and their compliance behaviour. In the South African MBSF context, the most significant behavioural drivers behind non-compliance related to normative concepts. Specifically, the poor perceptions of management and value-based legitimacy as well as low levels of moral obligation to adhere to the regulations appeared to contribute most to the observed non-compliant behaviour. Angler motivations for fishing also played a significant role in determining the compliance behaviour of anglers, with those fishing for food being more likely to violate regulations. In most countries, regardless of economic context, interventions to improve recreational fishery compliance have been developed around the instrumental concept. However, these findings suggest that for recreational fisheries, managers would do well to evaluate the impact of normative concepts on compliance and to design interventions aimed at addressing these. In the case of the South African MBSF, interventions that address angler perceptions of legitimacy and aim to correct misperceptions about social norms of compliance may provide a more practical and cost- effective method for improving poor compliance behaviour.
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- Date Issued: 2019
Towards a Mobile Bioethanol Unit for point of source conversion of sugar sources to bioethanol: design and feasibility study for South Africa
- Authors: Cech, Alexandra Louise
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/59141 , vital:27439
- Description: Restricted access-thesis embargoed for 5 years
- Full Text:
- Date Issued: 2015
Towards a framework to enhance entry-level national diploma students' learning of computer programming - effects of guided inquiry learning
- Authors: Lukose, Jose
- Date: 2018
- Subjects: Computer programming -- Study and teaching Computer science -- Study and teaching (Higher)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9522 , vital:34362
- Description: Research reports using global data show that the failure rates in introductory programming courses average about 32 percent. This study assessed the effect of elements of Guided Inquiry Learning (GIL) on enhancing academic performance of first year students in Introduction to Computer Programming course. As learners from schools join the university and enrol for different courses, they find the sudden transformation quite challenging. This makes it more challenging for first year university students, especially in difficult courses such as Introduction to Programming. As times change with advances in technology, the traditional ways of presenting information during teaching–learning interface may not address students’ needs. Lecturers and university stakeholders make efforts to address these challenges by proposing innovative teaching ways. One of the common approaches that have been used profitably in other science and engineering programmes is GIL. It is a form of inductive collaborative learning approach where students are presented with a challenge which challenges them to accomplish the desired learning outcomes in the process of responding to the posed challenge. The strategies in GIL include, among others, learning teams who participate in intra- and inter-learner interactions besides lecturer-learner interactions, linking theory and practical information cementing skills and problem solving strategies, scaffolding information, blended learning by integrating both traditional and technology-assisted learning, inquiry activities such as initiating investigations, gathering data, and critiquing evidence to come up with evidence-based solutions. The objective was to apply GIL to this module and observe if there were gains in students’ academic performance. This study was located in the pragmatic paradigm using action research design and a mixed method approach. The sample consisted offirst year students enrolled for Introduction to programming which was a year-long course (two semesters) at a South African university. The population consisted of the only 49 students who were registered for the module under focus. A group of 20 students were considered for the whole year in the GIL experiment. Although it would students were considered for the whole year in the GIL experiment. Although it would students were considered for the whole year in the GIL experiment. Although it would have been ideal to have experimental and control groups with same number of students, that was not possible in this study, because only 20 out of the 49 who were willing to be included in the experimental group. The present researcher employed willing to be included in the experimental group. The present researcher employed three of these GIL strategies in teaching the module Introduction to Programming to the experimental group while another colleague continued with traditional teaching in the control group. Care was taken to limit the insider outsider conflict. Both groups were assessed by the same assessment tools at the same times. Results from these assessments together with focus group interviews provided the core data for this study. Both quantitative and qualitative analyses were carried out on the data, statistical analysis (mainly, chi-Square and t-test) for the former and thematic analysis for the latter. Results indicated gains in the experimental group such as enhanced motivation, interaction, intra-group social cohesion, creativity and provided students the confidence to share knowledge and skills with their peers and keep everyone focused on the course contents. These gains are reflected in higher year marks and pass rates than those in the control group as the analysed data indicate. A study that will pilot the GIL framework in several universities with different teaching modes and large classes are recommended.
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- Date Issued: 2018
Towards a cost-efficient & standardised monitoring protocol for subtidal reef fish in the Agulhas ecoregion of South Africa
- Authors: Bernard, Anthony Thomas Firth
- Date: 2013
- Subjects: Reef fishes -- South Africa Reef fishes -- Monitoring--South Africa Fish stock assessment -- South Africa Coastal zone management -- South Africa Fish communities -- South Africa Marine parks and reserves -- South Africa Marine resources conservation -- South Africa Marine biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5585 , http://hdl.handle.net/10962/d1001674
- Description: Under the growing demand for marine fish resources, and the apparent and expected impacts of global climate change, there is a need to conduct long-term monitoring (LTM) to ensure effective management of resources and conservation of biodiversity. However LTM programmes often suffer from design deficiencies and fail to achieve their objectives. These deficiencies stem from the fact that insufficient consideration is afforded to the design phase, with programmes selecting methods that are not suitable to address the objectives, or are not cost-efficient, compromising the sustainability of the LTM. To facilitate the establishment of LTM programmes along the southern coast of South Africa, background research needed to be conducted to identify which methods were most appropriate for LTM of reef fish. This study presents a detailed field-based assessment of the suitability and cost-efficiency of monitoring methods for long-term monitoring of reef fish in the Agulhas Ecoregion of South Africa. The approach adopted to identify the method, or suite of methods most suited for LTM, involved (i) the selection of methods considered suitable for LTM, (ii) the individual assessment and optimisation of method performance, and (iii) the comparative assessment of the fish community sampled by the different methods. The most suited method(s) were then identified as those that provide the most comprehensive assessment of the fish community and had the highest cost-efficiency. The research was conducted between January 2008 and 2011 in the Tsitsikamma and Table Mountain National Park (TNP and TMNP, respectively) marine protected areas (MPAs) within the Agulhas Ecoregion. The methods selected included fish traps (FT), controlled angling (CA), underwater visual census (UVC), remote underwater video (RUV), baited RUV (BRUV) and remotely operated vehicles (ROV). The individual assessment and optimisation was conducted with the FT, UVC, RUV and BRUV methods. The assessment of the FT method aimed to identify the optimal soak time, and whether or not the size of the funnel entrance to the trap affected the catch. The results identified that larger funnel entrances caught more fish and soak times of 80 minutes produced the highest catches per unit effort. However the data were highly variable and the method detected few of the species typical of the region. Fish traps were also associated with high levels of mortality of fish post-release. The assessment of UVC strip transect method involved directly comparing the precision of data collected by researchers and volunteers using a novel double-observer technique (paired-transects). The results showed considerable error in both the volunteers and researchers data, however the researchers produced significantly higher precision data, compared to the volunteers. The distinction between researchers and volunteers was not evident in the data for the dominant species of fish. For all observers, the abundance of a species in the sample had a significant influence on its detectability, with locally scarce or rare species poorly detected. UVC was able to sample the majority of species typical of reefs in the region, however it appeared plagued by observer and detectability biases. The assessments of RUV and BRUV were conducted simultaneously which enabled the assessment of the effect of bait on the observed fish community. In addition the optimal deployment time for both methods to maximise species richness and abundance was determined. The results showed that BRUV, and to a lesser degree RUV, were able to effectively survey the reef fish community for the region with a 50 minute and 35 minute deployment time, respectively. Baited remote underwater video was especially good at detecting the invertebrate and generalist carnivores, and cartilaginous species. On the other hand, RUV was more effective at surveying the microinvertebrate carnivores. Remote underwater video was characterised by higher data variability, compared to BRUV, and was ultimately considered a less cost-efficient monitoring method. Comparative methods assessments were conducted during two field experiments with the FT, UVC and BRUV methods in the TMNP MPA, and the FT, CA, UVC, RUV, BRUV and ROV methods compared in the TNP MPA. The objectives of the comparison were to investigate differences in the fish communities observed with the different methods, and to determine the power of the data to detect an annual 10% growth in the fish populations over a period of five years. The results from the method comparison were in turn used to conduct the cost-benefit analysis to determine the efficiency of the different methods at achieving monitoring objectives requiring population data from multiple trophic and functional groups with the community, and from species of fisheries importance. The results indicated that FT, CA and ROV were ineffective at monitoring the reef fish community, although CA appeared to provide valuable data for the dominant fisheries species. Both CA and FT required minimal initial investment however, the variability in the data translated into high annual monitoring costs, as the required sampling effort was great. The ROV required the highest initial investment and was identified as the least cost-efficient method. Underwater visual census was able to adequately survey the bony fish within the community, however it did not detect the cartilaginous species. Underwater visual census required a large initial investment and was not cost-efficient, as a many samples were required to account for the variability in the data. Remote underwater video provided a comprehensive assessment of the reef fish community, however it too was associated with high levels of variability in the data, compared to BRUV, reducing its cost-efficiency. BRUV provided the most comprehensive assessment of the reef fish community and was associated with the highest cost-efficiency to address the community and fisheries species monitoring objectives. During the course of this research stereo-BRUV has gained considerable support as an effective reef fish monitoring method. Although not tested during this research, stereo-BRUV is preferred to BRUV as it provides accurate data on the size of fish. However, the initial investment of stereo-BRUV is over three times that required for the BRUV. Although it is recommended that a baited video technique be used for LTM in the Agulhas Ecoregion, the choice between BRUV and stereo-BRUV will depend on the specific objectives of the programme and the available budget at the implementing agency.
- Full Text:
- Date Issued: 2013
Towards a community-based model for Agricultural development in Uganda : a case study of Kumi and Gomba districts
- Authors: Kiggundu, Joseph
- Date: 2020
- Subjects: Agricultural development projects -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48654 , vital:41056
- Description: This study intended to design a community-based model for agricultural development in Uganda, using Kumi and Gomba districts as case studies. The surge in attention towards community-based development is attributed to the growing challenges posed by the traditional approaches to community development, dominated by top-down mechanisms during the planning, implementation, management, monitoring, and evaluation phases of community development programmes. Driven by Robert Chambers and Conway’s theoretical perspectives, this study discusses that a community-based model is capable of filling knowledge gaps, not only in scientific research, but also in the community development process of many developing nations, such as Uganda. In this study particularly, a community-based approach has been identified as the better option in aiding and facilitating the current government efforts to transform the agricultural sector from its predominantly subsistence nature to commercial orientation. It has been acknowledged that the Ugandan government and its development partners do realise the significant role agriculture plays in directly or indirectly impacting the social welfare of Ugandans. The agricultural sector has been identified as a major source of livelihood for most rural Ugandans (over 95% depend on it for food, employment and income). Unfortunately, even with such recognition, coupled with many reforms initiated by government and supported by various development partners who have invested huge sums of money into the sector, agricultural productivity and profitability has remained extremely low. Most rural Ugandans still languish in abject poverty, hunger, malnutrition, vulnerability and powerlessness. This study has established that, while the agricultural sector in Uganda suffers from enormous institutional, technological, market, research and land-oriented challenges, if all these factors are kept constant, an effective community-based approach is capable of facilitating effective planning, implementation, management, monitoring, and evaluation of agricultural reforms, for increased agricultural productivity and profitability hence the improved quality of life of Ugandans. A qualitative elicitation interviewing technique involving in-depth discussions with agricultural extension workers, community development officers, representatives from NGOs, local farmers, farmers’ associations, local and religious leaders as well as key persons from the Ministry of Agriculture and other line ministries was conducted. The participants were selected through chain referrals until the level of theoretical saturation. In addition, directed field observations, document analysis and key informant interviews with other respondents selected through theoretical sampling enhanced the robustness of data acquisition methods. Group-based participatory data analysis and reflexive pragmatism also enhanced the rigour and quality of research findings intended to balance the knowledge generated from the recognised scientific audience and the views of the important but unknown “knowledge generators” (the local experts).The key findings indicate that, historically and currently, agriculture has been and is the predominant community development activity at household, community and national levels in Uganda. It is also anticipated that agriculture will remain a major contributor to the national economic development of Uganda even over the next hundred years. The efforts by government and its development partners to transform the sector are therefore justified by the sector’s strategic importance. It has been found out that although the sector faces huge challenges, there are numerous opportunities for the sector to become a driver of Uganda’s socio-economic development. A community-based model has been proposed as a viable option for facilitating faster agricultural development in Uganda, where technocratic developers tend to impose development reforms on local people. With the traditional approaches to planning and implementation, it was thought that local people do not know what they want, they are illiterate and ignorant and therefore incapable of driving government crafted programmes for effective change. From the proposed model, government technocratic development agents should engage local farmers who practically experience poverty, powerlessness, hunger, malnutrition and vulnerability, to jointly craft effective agricultural reforms that are not only life-changing, but also relevant and sustainable within the confines of community needs. Under this approach, the designers, planners, implementers, monitors, and evaluators, whether of government-initiated reforms, or initiatives from other development agencies, should learn to treat local people as subjects of the community development processes, as opposed to the traditional top-down mechanisms which view them as objects to be used and abused. The involvement of local experts during the planning, implementation, and management of development reforms, should cease to be applied as merely routine fulfilment of donor conditionality and requirements. Rather, the participation of local farmers during all phases of community programming should become intentional and consciously aimed at empowering local people to actively participate in the making of decisions critical to their own development.
- Full Text:
- Date Issued: 2020
Towards a collaborative approach to teacher professional development : a journey of negotiation
- Authors: Southwood, Sue
- Date: 2001
- Subjects: Teachers -- Training of -- South Africa Teachers -- In-service training -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1866 , http://hdl.handle.net/10962/d1004649
- Description: The research presented in this thesis is a case study, based on ethnographic principles, located in the interpretive paradigm of qualitative research. The focus is specifically on the development of a collaborative approach ro teacher professional development: an approach that recognises and celebrates teachers themselves as resources for their own and other teachers' professional development. The study was carried out over a period of four years with a group of twelve teachers who had recognised the need and expressed the desire to develop their teaching. The research evolved in two main phases. The initial phase was based on the implementation and evaluation of a project designed to encourage a collaborative approach to teacher development based on mutual peer support. This led to a second phase, the main focus of the research, aimed at gaining a greater understanding of the teachers' situation and situating their practice in the wider context generated by this understanding. Conversations with the teachers led to the identification of dimensions and tensions characterising their experience. The research presented here, represents an attempt to understand, interpret and make recommendations relating to the professional development of teachers. The understanding is linked to the teachers' educational biographies and experience of the culture in which they are situated. The interpretation is based on what may be viewed as a dynamic ongoing construction of meaning - a journey of negotiation. The text, described as a narrative collage, a tapestry of voices interwoven by threads of negotiation, represents a collaborative accomplishment. The teachers' words have been interpretively framed and these constructions validated in an interpersonal construction of social reality. The reader is invited to engage in an act of complicity, to collude with the text in the construction and negotiation of shared meaning, possibly finding resonance with their own situations. Reflections on the teachers' experience reveal journeys which resonate with that of the society in which the school is located - 'a case in transition' - situated between an environment characterised by constrained cooperation and an environment characterised by freer collaboration. The overall tension may be viewed metaphorically as a 'Tug o' War'. On one end of the rope is a cultural legacy of authority, isolation, social division and conservatism, while on the other end there is a pull towards greater autonomy and interaction, to adapt rather than conserve and to work together in mutual collegial support: a struggle between cooperating with what is and collaborating towards what could be. The main contention of this thesis is that we ought strongly to support and encourage collaborative approaches to professional development based on mutual peer support. We need to look towards a future of open professionalism where the teachers are regarded as key persons in the process. The attainment of such an ideal needs to be seen as part of systemic changes in management, policies and structure geared towards greater inclusivity and democratic practice; it necessitates a coherent approach that is based on relationships of mutual respect and appreciation.
- Full Text:
- Date Issued: 2001
Towards a changing context and performance practice of mbira dzavadzimu music in Zimbabwe
- Authors: Chipendo, Claudio
- Date: 2015
- Subjects: Mbira music -- Zimbabwe Shona (African people) -- Music
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/6357 , vital:29588
- Description: Mbira dzavadzimu music and performance practice has been in existence since the pre-colonial era. It played a crucial role in ritual and non-ritual activities of the Shona people of Zimbabwe. However, political, social and global influences as well as technological advancement have resulted in change of context and performance practice. Unfortunately, these have not been recorded for future generations. The major aim of the study is therefore to examine the change of context and performance practice of mbira dzavadzimu in Zimbabwe. This was achieved by reviewing mbira dzavadzimu music and performance practice within the modern setting of dandaro. I looked at change from a theoretical lens of the theory of diffusion, syncretism and mediatisation. The study was in the qualitative form superimposed on some case studies. Unstructured interviews, participant and non-participant observations were the main instruments used to collect data from both traditional and modern mbira performances. Data was also collected from museums, archives, radio and television stations. The study established that the changes in context and performance practice of mbira dzavadzimu in Zimbabwe were to a larger extent due to foreign influences such as colonialism, the coming of missionaries, modernisation, urbanisation, commercialisation, mediatisation, the use of modern technology and institutionalisation. Due to the aforementioned influences, the environmental settings, the change of context from sacred to secular, the relationship with ancestral spirits, musical practices, performance situations and quality of sound, have been modified and adjusted in response to the influences of the globalised world’s ever changing audience and performance space. In short, this has resulted in a shift of mbira performances from its traditional to modern settings, from the village to the city and onto the international scene with a new performer-audience setting. Various innovations were carried out on the instrument and its music as a result of the advent of modern technology. The use of microphones, modern amplification systems, recording studios, radio and television broadcast, audio and video cassettes, CDs, DVD, teaching of the instrument using audio and video instructional models and the use of internet sites in learning how to play mbira dzavadzimu and other instruments have become a reality. It has been evident from the study that urban and rural areas take up change in different ways and that in the former change is more pronounced than in the latter. Urban area communities are more “developed” than their rural counterparts because the former are more exposed to technological influences and the commercialisation of music. The study has also established that Zimbabwean mbira music is a good example of modern transculturality. The instrument and its music have played a major role in breaking down cultural boundaries and bringing the people of the world together for purposes of performing on the instrument. From the findings of this study, I attribute most of the changes to technologisation, for most of the changes that have taken place on mbira dzavadzimu were a result of the highly technologised way of life Zimbabweans now lead.
- Full Text:
- Date Issued: 2015
Torn between skinship and kinship: the phenomenology of self-mutilation
- Authors: Malcolm, Charles F
- Date: 1994
- Subjects: Self-mutilation Case studies Borderline personality disorder
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3012 , http://hdl.handle.net/10962/d1002521
- Description: The aim of this study was to describe the female elf-mutilator's lived experience of cutting herself. A question which would elicit a description of the experience of this phenomenon was formulated. Five self-mutilators were interviewed. The four psychologically richest narratives were chosen for this study. Using the empirical phenomenological method. the four protocols were analysed in detail. Self-mutilation is conceptualized as a cycle wherein the mutilator experiences a diffuse bodily felt-sense that mounts to an unbearable point. She has an irresistible urge to alleviate the distress. She isolates herself and cuts herself with a sharp blade. Upon seeing the blood appear she is overcome with a deep sense of satisfaction. power, and ecstatic pleasure. The blood is perceived to carry the distressing contents out of the body. Concomitantly the self-mutilator recollects a sense of her feelings and her body as belonging to her. Her previously alienated body is felt to be a site of vitality. She also feels removed from further harm. encased in a cocoon of safety that renders her invulnerable to others. However. the cutting can never totally rid the body of distressing feelings. As a result the cycle of cutting wiII be re-enacted. The cutting cycle is conceptualized as a process whereby the self-mutilator suffers from a traumatization of the psyche such that the psychic container is fractured and rendered painfully porous. The act of cutting rids the psyche of unwanted contents such that a sense of going-on-being is restored. The cutting acts to temporarily shore up the rent fabric of the psychic envelope and thereby consolidate a sense of personal boundary. This is a temporary respite from the fracturing of the psychic container in that, once again confronted with interpersonal existence, the self-mutilator begins to feel vulnerable and defenceless. When it seems as if disintegration is again imminent, a cycle of cutting is reconstituted. The findings emergent from the interviews were dialogued with the literature on psychic containers, particularly that which addresses the role of the skin in the formation and functioning of psychic containers.
- Full Text:
- Date Issued: 1994
Tomographic imaging of East African equatorial ionosphere and study of equatorial plasma bubbles
- Authors: Giday, Nigussie Mezgebe
- Date: 2018
- Subjects: Ionosphere -- Africa, Central , Tomography -- Africa, Central , Global Positioning System , Neural networks (Computer science) , Space environment , Multi-Instrument Data Analysis System (MIDAS) , Equatorial plasma bubbles
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63980 , vital:28516
- Description: In spite of the fact that the African ionospheric equatorial region has the largest ground footprint along the geomagnetic equator, it has not been well studied due to the absence of adequate ground-based instruments. This thesis presents research on both tomographic imaging of the African equatorial ionosphere and the study of the ionospheric irregularities/equatorial plasma bubbles (EPBs) under varying geomagnetic conditions. The Multi-Instrument Data Analysis System (MIDAS), an inversion algorithm, was investigated for its validity and ability as a tool to reconstruct multi-scaled ionospheric structures for different geomagnetic conditions. This was done for the narrow East African longitude sector with data from the available ground Global Positioning Sys-tem (GPS) receivers. The MIDAS results were compared to the results of two models, namely the IRI and GIM. MIDAS results compared more favourably with the observation vertical total electron content (VTEC), with a computed maximum correlation coefficient (r) of 0.99 and minimum root-mean-square error (RMSE) of 2.91 TECU, than did the results of the IRI-2012 and GIM models with maximum r of 0.93 and 0.99, and minimum RMSE of 13.03 TECU and 6.52 TECU, respectively, over all the test stations and validation days. The ability of MIDAS to reconstruct storm-time TEC was also compared with the results produced by the use of a Artificial Neural Net-work (ANN) for the African low- and mid-latitude regions. In terms of latitude, on average,MIDAS performed 13.44 % better than ANN in the African mid-latitudes, while MIDAS under performed in low-latitudes. This thesis also reports on the effects of moderate geomagnetic conditions on the evolution of EPBs and/or ionospheric irregularities during their season of occurrence using data from (or measurements by) space- and ground-based instruments for the east African equatorial sector. The study showed that the strength of daytime equatorial electrojet (EEJ), the steepness of the TEC peak-to-trough gradient and/or the meridional/transequatorial thermospheric winds sometimes have collective/interwoven effects, while at other times one mechanism dominates. In summary, this research offered tomographic results that outperform the results of the commonly used (“standard”) global models (i.e. IRI and GIM) for a longitude sector of importance to space weather, which has not been adequately studied due to a lack of sufficient instrumentation.
- Full Text:
- Date Issued: 2018
Time series models for paired comparisons
- Authors: Sjolander, Morne Rowan
- Date: 2011
- Subjects: Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10577 , http://hdl.handle.net/10948/d1012858
- Description: The method of paired comparisons is seen as a technique used to rank a set of objects with respect to an abstract or immeasurable property. To do this, the objects get to be compared two at a time. The results are input into a model, resulting in numbers known as weights being assigned to the objects. The weights are then used to rank the objects. The method of paired comparisons was first used for psychometric investigations. Various other applications of the method are also present, for example economic applications, and applications in sports statistics. This study involves taking paired comparison models and making them time-dependent. Not much research has been done in this area. Three new time series models for paired comparisons are created. Simulations are done to support the evidence obtained, and theoretical as well as practical examples are given to illustrate the results and to verify the efficiency of the new models. A literature study is given on the method of paired comparisons, as well as on the areas in which we apply our models. Our first two time series models for paired comparisons are the Linear-Trend Bradley- Terry Model and the Sinusoidal Bradley-Terry Model. We use the maximum likelihood approach to solve these models. We test our models using exact and randomly simulated data for various time periods and various numbers of objects. We adapt the Linear-Trend Bradley-Terry Model and received our third time series model for paired comparisons, the Log Linear-Trend Bradley-Terry Model. The daily maximum and minimum temperatures were received for Port Elizabeth, Uitenhage and Coega for 2005 until 2009. To evaluate the performance of the Linear-Trend Bradley-Terry Model and the Sinusoidal Bradley-Terry Model on estimating missing temperature data, we artificially remove observations of temperature from Coega’s temperature dataset for 2006 until 2008, and use various forms of these models to estimate the missing data points. The exchange rates for 2005 until 2008 between the following currencies: the Rand, Dollar, Euro, Pound and Yen, were obtained and various forms of our Log Linear-Trend Bradley-Terry Model are used to forecast the exchange rate for one day ahead for each month in 2006 until 2008. One of the features of this study is that we apply our time series models for paired comparisons to areas which comprise non-standard paired comparisons; and we want to encourage the use of the method of paired comparisons in a broader sense than what it is traditionally used for. The results of this study can be used in various other areas, like for example, in sports statistics, to rank the strength of sports players and predict their future scores; in Physics, to calculate weather risks of electricity generation, particularly risks related to nuclear power plants, and so forth, as well as in many other areas. It is hoped that this research will open the door to much more research in combining time series analysis with the method of paired comparisons.
- Full Text:
- Date Issued: 2011
Tidal exchanges of carbon, nitrogen and phosphorus between a Sarcocornia salt-marsh and the Kariega estuary, and the role of salt-marsh brachyura in this transfer
- Authors: Taylor, David Ian
- Date: 1988
- Subjects: Salt marsh ecology -- South Africa -- Eastern Cape Salt marsh animals -- South Africa -- Eastern Cape Kariega River
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5623 , http://hdl.handle.net/10962/d1004524
- Description: Tidal exchanges of organic carbon, nitrogen and phosphorus between a south temperate Sarcocornia marsh and its associated estuary are examined. Subterranean water flow was small, and the hydraulic exchange between the two systems largely surficial. The dominant tidal signal was semi-diurnal, and the extent of inundation of the marsh varied considerably as a consequence of interactions of semi-lunar tidal cycles with changes in daily mean sea level. Annual net fluxes of organic carbon were directed from the marsh to the estuary, but amounted to less than 2% of marsh aerial net primary productivity. This indicates the incompatibility of E.P. Odum's outwelling hypothesis to this marsh-estuarine system. The direction of net flux of organic carbon switched on a time-scale of days. These directions were largely correlated with mesoscale oceanic events, which materially altered the extent of marsh inundation, and which provided evidence of the mutual exclusivity of outwelling of DOC from the marsh and oceanic upwelling. Laboratory mesocosm experiments using intact marsh blocks of sediment from the marsh were conducted to identify the proximate processes and interactions at the marsh-water interface responsible for the variability of marsh-estuarine exchanges. Patterns of fluxes of organic carbon, total nitrogen and phosphorus were markedly different in the structurally contrasted tidal creek and Sarcocornia Zone regions of the marsh. Both regions exported these components, but the fluxes of organic carbon and total phosphorus were significantly larger from the tidal creek than from the Sarcocornia zone, and the opposite applied to nitrogen. The presence of brachyuran crabs . the most numerous macrofauna on the marsh enhanced the flux of carbon, nitrogen and phosphorus from the marsh biocoenosis, largely as a result of the effect of their bioturbation. Evidence is examined which suggests that differential mobilization of nutrients in the two zones by crabs is responsible for biogeochemical coupling of these two regions , which may account for the elevated productivity of salt- marsh systems
- Full Text:
- Date Issued: 1988
Three dimensional kinetic analysis of asymmetrical lifting
- Authors: Li, Jian-Chuan
- Date: 1996
- Subjects: Lifting and carrying , Human engineering , Materials handling , Manual work
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5174 , http://hdl.handle.net/10962/d1018240
- Description: Manual lifting is dynamic in nature and involves asymmetrical loading of the human body. This study investigated kinematic and kinetic characteristics of asymmetrical lifting in three dimensions, and then constructed a 3-D biomechanical force model of the lower back which is capable of quantifying torsional stress on the human spine. Eleven healthy adult male manual workers were recruited as subjects and lifted a 1 Okg load placed at the sagittal plane (0°) and at 30°, 60° and 90° lateral planes to the right, from 150mm and 500mm initial lift heights, respectively, to an 800mm high bench in the sagittal plane. Subjects' spinal motions and the trajectorial movements of the load in three-dimensional space were monitored simultaneously by a Lumbar Motion Monitor and a V-scope Motion Analyzer. Generally, the spinal motion factors increased as a function of increasing task asymmetry and differed (p < 0.05) between the lower (150mm) and higher (500mm) levels in the sagittal plane. In all asymmetrical conditions the motion factors showed a dramatic increase at the 500mm level compared to the increase at the 150mm level. The rates of increase in the horizontal and frontal planes were greater than those in the sagittal plane. Task asymmetry had a significant effect on the spinal kinematic parameters in the frontal plane at the two lift heights, and only at the high level (500mm) in the horizontal plane, with exception of average acceleration . Initial lift height exerted a significant effect on peak velocity and acceleration in both frontal and horizontal planes and on range of motion in the horizontal plane. Kinetic characteristics of the object being lifted in three-dimensions increased with an increase in task asymmetry. The increase was more dramatic in the lateral direction in the horizontal plane. However, motion factors in the vertical direction dominated the full range of the lift, irrespective of task asymmetry and lift height. The kinetic measures differed (p < 0.05) between the lower ( 1 50mm) and the higher (500mm) levels in the vertical direction except for average force. Task asymmetry had a significant effect on dynamic measures in the anterior-posterior direction. Both task asymmetry and lift height had a significant effect on dynamic motion factors in the lateral direction. From insights gained in the empirical study a three-dimensional biomechanical force model of the lower back was constructed based on a mechanism of muscle force re-orientation in the lumbar region. Acknowledging that the lower back is designed to be able to rotate around its longitudinal axis, the proposed model accounts for compression and shear forces and a torsional moment. The model has similar predictability to Schultz and Andersson's (1981) model when the human trunk exerts only a flexion-extension moment in the sagittal plane, but additionally predicts dramatic increases in shear forces, oblique muscle forces and torsional moment under asymmetrical lifting conditions which the Schultz-Andersson model does not. The increase rates in these forces and moment are not linearly related over task asymmetric angle.
- Full Text:
- Date Issued: 1996
Third sector intervention and sustainable development : an evaluation of selected non-governmental organization supported projects in the Eastern Cape, South Africa
- Authors: Moyo, Thokozani Patience
- Date: 2017
- Subjects: Non-governmental organizations -- South Africa -- Eastern Cape Economic development projects -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/5774 , vital:29389
- Description: This study evaluates the impact of Third Sector- supported rural development projects in three rural communities of the Eastern Cape, South Africa. It focusses on how interventions driven by this sector – denoted by, among others, local and international non-governmental organisations (NGOs) - impact the lives and livelihoods of the rural poor. This is against the background of an established discourse that views NGOs as effective agents in the alleviation of poverty. The thesis contends that praise for the Third Sector is driven mostly by advocacy than based on systematic scientific evidence of the real impact of NGO-sponsored rural development interventions. Rural agricultural development projects supported by two Eastern Cape-based NGOs (the one a local NGO, and the other international) were selected for the study. A mini survey was conducted in the communities where the projects are located. Survey data were complemented by qualitative data obtained through focus groups, semi-structured and in-depth interviews as well as key informant interviews. The study found that whereas the projects had been established by the state later went moribund, they were resuscitated by the NGOs through a largely ‘bottom-up’ model of rural development intermediation. In other words, the interventions were resuscitated through a relatively robust prior engagement with project beneficiaries. As a result, while originally lacking a meaningful sense of local empowerment, ownership, and commitment, the projects had become revived and now played an important role in the livelihoods of some community members – even though social grants remained the primary and main source of income for those community members. Even so, the narratives of community members revealed what may be termed a ‘transformation paradox’ in the way the projects were implemented. The NGOs seemed to have replaced one kind of lop-sidedness in rural development (the exclusion of women) with another (the exclusion of men), by focussing on community projects that were ‘culturally’ deemed as ’women jobs’. In this way, the interventions appeared like a systematic attempt to do away with the ‘feminisation of rural poverty’ and entrench the ‘feminisation of rural development interventions’. The study concludes from these and other findings, that the key to understanding the significance and impact of Third Sector-supported development interventions in the rural arena – especially in the Eastern Cape context – is to go beyond the proliferation of NGOs and NGO-supported projects – and the broad sweep of advocacy that underpins it – and pay equally robust attention to systematically studying how these projects resonate at the grassroots, especially from a beneficiary perspective.
- Full Text:
- Date Issued: 2017
Thermoluminescence and phototransferred phermoluminescence of synthetic quartz
- Authors: Dawam, Robert Rangmou
- Date: 2020
- Subjects: Thermoluminescence , Quartz
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/145849 , vital:38472
- Description: The main aim of this investigation is on thermoluminescence and phototransferred thermoluminescence of synthetic quartz. Thermoluminescence was one of the tools used in characterising the electron traps parameters. The samples of quartz annealed at various temperatures up to 900̊C and the unannealed were used. The thermoluminescence glow curve was measured at 1̊C s~ 1 following beta irradiation to 40 Gy from the samples annealed at 500̊C and the unannealed consist of main peak at 70̊C and secondary peaks at 110, 180 and 310̊C. In comparison, the thermoluminescence glow curve for the sample annealed at 900̊C have main peak at 86̊C and the secondary ones at 170 and 310̊C. The kinetic analysis was carried out only on the main peak in each case. The activation energy was found to be decreasing with increase in annealing temperatures. The samples annealed at 500̊C and the unannealed were found to be affected by thermal quenching while sample annealed at 900̊C shows an inverse quenching for irradiation dose of 40 Gy. However, when the dose was reduce to 3 Gy the effects of thermal quenching was manifested. The activation energy of thermal quenching was also found to decrease with increase in annealing temperature. Thermally assisted optically stimulated luminescence measurement was carried out using continuous wave optical stimulated luminescence (CW-OSL). The samples studied were those annealed at 500̊C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The CW-OSL is stimulated using 470 nm blue LEDs at sample temperatures between 30 and 200̊C. It is measured after preheating to either 300 and 500̊C. When the integrated OSL intensity is plotted as a function of measurement temperature, the intensity goes through a peak. The increase in OSL intensity as a function of temperature is associated to thermal assistance and the decrease to thermal quenching. The kinetic parameters were evaluated by fitting the experimental data. The values of activation energies of thermal quenching are the same within experimental uncertainties for all the experimental conditions. This shows that annealing temperature, duration of annealing and irradiation dose have a negligible influence on the recombination site of luminescence using OSL. Phototransferred thermoluminescence (PTTL) induced from annealed samples using 470 nm blue light was also investigated. The quartz were annealed at 500 _C for 10 minutes, 900̊C for 10, 30, 60 minutes and 1000̊C for 10 minutes prior to use. The glow curves of conventional TL measured at 1 _C s1 following irradiation to 200 Gy shows six peaks in each case labelled I-VI for ease of reference whereas peaks observed under PTTL are referred to as A1 onwards. Only the first three peaks were reproduced under phototransfer for the sample annealed at 900̊C for 60 minutes and 1000̊C C for 10 minutes. Interestingly, for the intermediate duration of annealing of 30 minutes, the only peak that appears under phototransfer is the A1. For quartz annealed at 900̊C for 10 minutes, the PTTL appears as long as the preheating temperature does not exceed 560̊C. All other annealing temperatures, PTTL only appears for preheating to 450 and below. This shows that the occupancy of deep electron traps at temperatures beyond 450̊C or 560̊C is low. The activation energy for peaks A1, A2 and A3 were calculated. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were found to be affected. The activation energies for thermal quenching were determined as 0.62 ± 0.04 eV and 0.65 ± 0.02 eV for peaks A1 and A3 respectively. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature.
- Full Text:
- Date Issued: 2020
Thermal, spectroscopic and x-ray diffraction studies of copper(II) 1,2,4,5-Benzenetetracarboxylates and copper(II) oxalate a study of metal-organic frameworks
- Authors: Lamprecht, Emmanuel
- Date: 2008
- Subjects: Organometallic compounds Copper Oxalates -- Thermal properties Organic compounds -- Synthesis Spectrum analysis X-rays -- Diffraction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4389 , http://hdl.handle.net/10962/d1005054
- Description: Novel and known metal organic frameworks with copper(II), sodium and 1,2,4,5-benzenetetracarboxylate were prepared by ambient precipitation, solvothermal and gel-synthesis methods, and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetry with FTIR evolved-gas analysis. Some of these complexes were investigated for guest inclusion properties with water (the original guest species), methanol, ethanol and pyridine. The gel-synthesis products were the most interesting. The novel threedimensional metal-organic framework complex Cu₂ Na(OH)L·7H₂O (where L=1,2,4,5-benzenetetracarboxylate) -formed by gel-synthesis- is a covalent three-dimensional metal organic framework polymer with open channels containing both guest water molecules and water molecules coordinated to sodium. The structure collapsed on dehydration, but was essentially restored to the original structure on rehydration in moist air. On exposure of the dehydrated material to methanol and ethanol vapour, significant uptake of these solvents was observed, and the resolvated structures closely resembled that of the parent material. On heating in dry nitrogen, small amounts of methanol and ethanol remained until about 280 °C, when loss of the remaining guest triggered decomposition of the framework. The related complex, Cu₂¼(OH)½ L·7½H₂O (or possibly Cu₂⅓ (OH)⅔L·8H₂O) -formed by gel-synthesis- had a different physical appearance to Cu₂Na(OH)L·7H₂O above, but had nearly identical X-ray diffraction pattern, mid-infrared spectrum and thermal behaviour. The novel complex Cu₄Na₄L₃·14H₂O -formed by gel-synthesis- is a covalent three-dimensional metal-organic framework with small channels containing both guest water molecules and water coordinated to sodium and copper. Upon dehydration the structure collapsed, but on rehydration in moist air the original structure was partly restored. The dehydrated material did not absorb methanol. Known two-dimensional polymeric complexes [Cu₂L·6H₂O]·4H₂O and [Cu₂L·4H₂O]·2H₂O were also obtained by gel-synthesis, and were characterized and investigated for guest inclusion properties. The structures of these complexes collapsed on dehydration, and were only partly restored on rehydration in saturated water vapour. The dehydrated materials did not absorb methanol. The two-dimensional polymeric mixed-ligand complex Cu₂(pyridine)₄·6H₂O -formed very slowly by gel-synthesis- was characterized by TG-FTIR, and was shown to undergo a complicated decomposition involving the loss of water and pyridine, carbon dioxide and carbon monoxide in various stages. Solvothermal synthesis did not yield materials suitable for single-crystal X-ray diffraction studies or inclusion studies, producing only an anhydrous or hemihydrate complex with the formula Cu₂L·0.65H2O. Ambient precipitation syntheses did not yield materials suitable for singlecrystal diffraction studies, forming products approximately equivalent to the complexes [Cu₂L·6H₂O]·4H₂O and Cu₂¼(OH)½L·7 ½H₂O above. During the course of the above study it was discovered that, on changing the DSC purge from nitrogen to argon, the normally exothermic carboxylate decompositions appeared to become endothermic. The effects of the supposedly inert atmospheres of argon and nitrogen on the decomposition-mechanism of copper(II) oxalate -a well-studied copper carboxylate- were therefore studied by DSC, TG, TG-FTIR and XRPD. DSC experiments were performed in nitrogen and argon at different flow-rates, in various mixtures of nitrogen and argon, and at various heating rates. Regardless of the proportions of nitrogen and argon, the DSC residues consisted mainly of copper metal, a small amount of copper(I) oxide (cuprite) and, in some circumstances, traces of copper(II) oxide (tenorite). Also, regardless of whether TG-FTIR experiments were performed under argon or nitrogen, the gaseous decomposition products consisted mainly of carbon dioxide, with traces of carbon monoxide being detected over part of the decomposition period. Various explanations for the thermal behaviour are discussed, and it is possible that small amounts of O2 or monatomic oxygen were given off during the decomposition under argon. The design and implementation of a low-cost prototype X-ray proportional counter detector system, consisting of a hybrid analog-digital computer built using commonly available electronic components, is presented. This system was designed to replace ageing discrete-transistor designs still in use in earlier X-ray diffractometers. The prototype performs the functions of pulse-shaping, pulseheight discrimination, counting and scaling, and provides both digital and scaled analog outputs.
- Full Text:
- Date Issued: 2008
Thermal tolerance and the potential effects of climate change on coastal intertidal and estuarine organisms in the Kariega Estuary and adjacent intertitdal coastline, Eastern Cape, South Africa
- Authors: Van der Walt, Kerry-Ann
- Date: 2020
- Subjects: Ectotherms -- Climatic factors , Ectotherms -- Effect of temperature on , Fishes -- Climatic factors , Fishes -- Effect of temperature on , Climatic changes -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/148459 , vital:38741
- Description: Temperature changes due to the effects of climate change are evident on all continents and oceans. As a result, there is a growing concern over how marine ectotherms will respond to extreme or fluctuating environmental temperatures. Temperature changes have strong direct and indirect effects on individual, population, and ecosystem functioning traits. A multi-scale approach determining the thermal tolerance and performance of several marine ectotherms belonging to different coastal habitats is rarely considered in thermal physiology studies but is effective for an integrated ecosystem assessment. As such, for this thesis, I aimed to quantify and compare the thermal tolerance and performance of a range of coastal marine ectotherms (fish and macro-invertebrates) with different biogeographical distributions from estuarine, subtidal and rocky intertidal habitats to available and projected in situ temperature data. This was also undertaken to gauge the local vulnerability of each species across summer and winter in a warm-temperate region of South Africa. This was done using a multi-method physiological approach, which included the dynamic method (CTmax and CTmin), static respirometry and maximum heart rate fHmax). Results of the dynamic method on several fish and macro-invertebrate species indicated that there are differences in thermal tolerance according to taxonomy, biogeography and habitat for both summer and winter. Macro-invertebrate species generally had higher CTmax endpoints, lower CTmin endpoints, higher upper and lower breadths in tolerance, higher upper and lower thermal safety margins and higher thermal scopes than the fish species. This could be a result of the macro-invertebrate species studied being less mobile compared with fish species (which are able to move to more favourable conditions) as well as having broader geographical distributions. In addition, macro-invertebrates from the intertidal rock pool habitat (Palaemon peringueyi; Pernaperna) were more tolerant of high and low temperatures compared with the macro-invertebrates from the estuarine habitat (Clibanarius virescens; Parasesarma catenatum; Upogebia africana). Overall, macro-invertebrates, with the exception of Parechinus angulosus, investigated in this study indicated that current temperatures and projected climate change scenarios across seasons would not have a significant impact on them and that they are highly adaptable to changing temperature regimes. This sign of high tolerance was further supported by the heart rates of P. perna and P. catenatum under an acute increase in temperature (1.0 °C.h-1) which showed individuals of each species physiologically depressing their metabolism until a final Arrhenius breakpoint temperature was reached (TAB). Among the fish species investigated in this study, tropical species (Chaetodon marleyi; Kuhlia mugil) had the highest CTmax and CTmin endpoints when compared with the temperate (Diplodus capensis; Sarpa salpa), warm-water endemic (Chelon dumerili; Rhabdosargus holubi) and cool-water endemic (Chelon richardsonii) fishes. This suggests that due to their lower breadths in tolerance and thermal safety margins being small, tropical species may be less tolerant of cold temperatures and thermal variability, especially in the form of summer upwelling events which are expected to increase in intensity and frequency in this region as a result of anthropogenic climate change effects. On the other hand, however, if a temperature increase of 2.0 - 4.0 °C takes place at the end of the century as predicted by the Intergovernmental Panel on Climate Change (IPCC), it is likely that tropical species such as C. marleyi will become more common. Temperate species such as D. capensis and S. salpa were able to tolerate a wide range of temperatures (wide thermal scope) compared with the other fish species. These findings may suggest that D. capensis and S. salpa are thermally resilient and may be the least vulnerable to climate change effects and temperature variability. When evaluating the different life stages of D. capensis, however, using the dynamic method (juveniles and adults), static respirometry (juveniles) and maximum heart rate (adults), results suggested that juveniles of this temperate species will be more resilient to increases in ocean temperatures compared with the adults because they have a higher thermal tolerance (CTmax/TCRIT) and a greater metabolic scope (TOPT) at higher temperatures. For both juveniles and adults, temperatures beyond 28.0 °C (upper Tpej; Tarr) will have a significant impact on their physiology. Using a multi-scale and multi-method approach thus helped to identify which species or community may be vulnerable to the effects of climate change within shallow coastal environments in this warm-temperate climate change hotspot. Adopting this type of approach will assist policy makers in developing comprehensive climate change management frameworks for coastal ecosystems globally and around South Africa.
- Full Text:
- Date Issued: 2020
Thermal physiology and behavioural ecology of the white shark, carcharodon carcharias
- Authors: Gennari, Enrico
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64002 , vital:28522
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2015
Thermal degradation of diamond compacts: a TEM investigation
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
Thermal decomposition of ammonium metavanadate
- Authors: Stewart, Brian Victor
- Date: 1972
- Subjects: Decomposition (Chemistry) , Solids -- Thermal properties , Ammonia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4503 , http://hdl.handle.net/10962/d1013274
- Description: The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.
- Full Text:
- Date Issued: 1972