Sulphide textures and compositions associated with the hydrothermal/magmatic system of the Twangiza gold deposit (South Kivu, DRC)
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
- Date Issued: 2019
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
- Date Issued: 2019
Mesoscale alongshore and cross-shore transport and settlement of invertebrate larvae on the south east coast of South Africa
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
Johannesburg as dystopia: South African science fiction as political criticism
- Authors: Kirsten, Ashton Lauren
- Date: 2020
- Subjects: Science fiction, South African -- History and criticism , Johannesburg (South Africa) -- Fiction , Science fiction films -- History and criticism , Dystopias in literature , Dystopian films , Politics in literature , Politics in motion pictures , Beukes, Lauren -- Zoo City , Blomkamp, Neill, 1979- -- Chappie , Miller, Andrew K., 1974 or 1975- -- Dub steps
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/147671 , vital:38659
- Description: This thesis will interrogate the spatial dynamics and configurations of one of the country’s most prominent cities: Johannesburg. Johannesburg has been, and continues to be, a central focus in the nation’s imaginary. There is a trend within South African science fiction (sf) – both literature and film – to portray Johannesburg as a dystopian, post-law, poverty-stricken space as a means of conceptualising the socioeconomic situation within the country. This study will isolate Johannesburg-based works of sf and interrogate why authors and filmmakers disproportionately return to this setting. Investigated are three contemporary works, namely, Zoo City (2010) by Lauren Beukes, Neill Blomkamp’s film, Chappie (2015), and Dub Steps (2015) by Andrew Miller. This study explores the ways in which South African works of sf serve as social and political critique in the post-apartheid era of financial disparity, the formation of new boundaries, divisions of space and privilege, and the dereliction of critical infrastructure. The primary methodology of this thesis is that of Marxist literary analysis (specifically with reference to Louis Althusser’s theoretical models), which will be conducted alongside discussions of authentic history of the country as well as political developments in order to illustrate how South African sf critically engages with, and succinctly critiques, its context. The aesthetics of African sf are inseparable from the politics of the past and the current moment and through the aesthetics of the future, South Africans can reimagine the politics of the now. This study therefore also revisits a selection of non-sf Johannesburg-set novels published post-1925 and argues that these texts can be studied as early examples of South African dystopian writing. In doing so, this study illustrates that dystopian writing about and in South Africa is not an advent of the 21st century, but an extension of a long history of critical engagement. This thesis suggests that the dystopian genre is helpful in reframing the issues of the present (and the past) so that some form of meaningful change is theorized. The underlying impulse of dystopian cultural production is ultimately hopeful: a worse context is imagined to warn society of its follies so that these shortcomings and issues can be corrected, thereby avoiding the disastrous world(s) portrayed in the fiction. In this way, this study contends that local sf should not be inextricably linked to the melancholia that thoughts of dystopia bring about. Rather, the nuanced criticism contained within these dystopian texts is testament to the country’s ever-enduring spirit of change and transformation.
- Full Text:
- Date Issued: 2020
- Authors: Kirsten, Ashton Lauren
- Date: 2020
- Subjects: Science fiction, South African -- History and criticism , Johannesburg (South Africa) -- Fiction , Science fiction films -- History and criticism , Dystopias in literature , Dystopian films , Politics in literature , Politics in motion pictures , Beukes, Lauren -- Zoo City , Blomkamp, Neill, 1979- -- Chappie , Miller, Andrew K., 1974 or 1975- -- Dub steps
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/147671 , vital:38659
- Description: This thesis will interrogate the spatial dynamics and configurations of one of the country’s most prominent cities: Johannesburg. Johannesburg has been, and continues to be, a central focus in the nation’s imaginary. There is a trend within South African science fiction (sf) – both literature and film – to portray Johannesburg as a dystopian, post-law, poverty-stricken space as a means of conceptualising the socioeconomic situation within the country. This study will isolate Johannesburg-based works of sf and interrogate why authors and filmmakers disproportionately return to this setting. Investigated are three contemporary works, namely, Zoo City (2010) by Lauren Beukes, Neill Blomkamp’s film, Chappie (2015), and Dub Steps (2015) by Andrew Miller. This study explores the ways in which South African works of sf serve as social and political critique in the post-apartheid era of financial disparity, the formation of new boundaries, divisions of space and privilege, and the dereliction of critical infrastructure. The primary methodology of this thesis is that of Marxist literary analysis (specifically with reference to Louis Althusser’s theoretical models), which will be conducted alongside discussions of authentic history of the country as well as political developments in order to illustrate how South African sf critically engages with, and succinctly critiques, its context. The aesthetics of African sf are inseparable from the politics of the past and the current moment and through the aesthetics of the future, South Africans can reimagine the politics of the now. This study therefore also revisits a selection of non-sf Johannesburg-set novels published post-1925 and argues that these texts can be studied as early examples of South African dystopian writing. In doing so, this study illustrates that dystopian writing about and in South Africa is not an advent of the 21st century, but an extension of a long history of critical engagement. This thesis suggests that the dystopian genre is helpful in reframing the issues of the present (and the past) so that some form of meaningful change is theorized. The underlying impulse of dystopian cultural production is ultimately hopeful: a worse context is imagined to warn society of its follies so that these shortcomings and issues can be corrected, thereby avoiding the disastrous world(s) portrayed in the fiction. In this way, this study contends that local sf should not be inextricably linked to the melancholia that thoughts of dystopia bring about. Rather, the nuanced criticism contained within these dystopian texts is testament to the country’s ever-enduring spirit of change and transformation.
- Full Text:
- Date Issued: 2020
A Bayesian approach to tilted-ring modelling of galaxies
- Authors: Maina, Eric Kamau
- Date: 2020
- Subjects: Bayesian statistical decision theory , Galaxies , Radio astronomy , TiRiFiC (Tilted Ring Fitting Code) , Neutral hydrogen , Spectroscopic data cubes , Galaxy parametrisation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145783 , vital:38466
- Description: The orbits of neutral hydrogen (H I) gas found in most disk galaxies are circular and also exhibit long-lived warps at large radii where the restoring gravitational forces of the inner disk become weak (Spekkens and Giovanelli 2006). These warps make the tilted-ring model an ideal choice for galaxy parametrisation. Analysis software utilizing the tilted-ring-model can be grouped into two and three-dimensional based software. Józsa et al. (2007b) demonstrated that three dimensional based software is better suited for galaxy parametrisation because it is affected by the effect of beam smearing only by increasing the uncertainty of parameters but not with the notorious systematic effects observed for two-dimensional fitting techniques. TiRiFiC, The Tilted Ring Fitting Code (Józsa et al. 2007b), is a software to construct parameterised models of high-resolution data cubes of rotating galaxies. It uses the tilted-ring model, and with that, a combination of some parameters such as surface brightness, position angle, rotation velocity and inclination, to describe galaxies. TiRiFiC works by directly fitting tilted-ring models to spectroscopic data cubes and hence is not affected by beam smearing or line-of-site-effects, e.g. strong warps. Because of that, the method is unavoidable as an analytic method in future Hi surveys. In the current implementation, though, there are several drawbacks. The implemented optimisers search for local solutions in parameter space only, do not quantify correlations between parameters and cannot find errors of single parameters. In theory, these drawbacks can be overcome by using Bayesian statistics, implemented in Multinest (Feroz et al. 2008), as it allows for sampling a posterior distribution irrespective of its multimodal nature resulting in parameter samples that correspond to the maximum in the posterior distribution. These parameter samples can be used as well to quantify correlations and find errors of single parameters. Since this method employs Bayesian statistics, it also allows the user to leverage any prior information they may have on parameter values.
- Full Text:
- Date Issued: 2020
- Authors: Maina, Eric Kamau
- Date: 2020
- Subjects: Bayesian statistical decision theory , Galaxies , Radio astronomy , TiRiFiC (Tilted Ring Fitting Code) , Neutral hydrogen , Spectroscopic data cubes , Galaxy parametrisation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145783 , vital:38466
- Description: The orbits of neutral hydrogen (H I) gas found in most disk galaxies are circular and also exhibit long-lived warps at large radii where the restoring gravitational forces of the inner disk become weak (Spekkens and Giovanelli 2006). These warps make the tilted-ring model an ideal choice for galaxy parametrisation. Analysis software utilizing the tilted-ring-model can be grouped into two and three-dimensional based software. Józsa et al. (2007b) demonstrated that three dimensional based software is better suited for galaxy parametrisation because it is affected by the effect of beam smearing only by increasing the uncertainty of parameters but not with the notorious systematic effects observed for two-dimensional fitting techniques. TiRiFiC, The Tilted Ring Fitting Code (Józsa et al. 2007b), is a software to construct parameterised models of high-resolution data cubes of rotating galaxies. It uses the tilted-ring model, and with that, a combination of some parameters such as surface brightness, position angle, rotation velocity and inclination, to describe galaxies. TiRiFiC works by directly fitting tilted-ring models to spectroscopic data cubes and hence is not affected by beam smearing or line-of-site-effects, e.g. strong warps. Because of that, the method is unavoidable as an analytic method in future Hi surveys. In the current implementation, though, there are several drawbacks. The implemented optimisers search for local solutions in parameter space only, do not quantify correlations between parameters and cannot find errors of single parameters. In theory, these drawbacks can be overcome by using Bayesian statistics, implemented in Multinest (Feroz et al. 2008), as it allows for sampling a posterior distribution irrespective of its multimodal nature resulting in parameter samples that correspond to the maximum in the posterior distribution. These parameter samples can be used as well to quantify correlations and find errors of single parameters. Since this method employs Bayesian statistics, it also allows the user to leverage any prior information they may have on parameter values.
- Full Text:
- Date Issued: 2020
A critical appraisal of Saule’s portrayal of women as Amadelakufa (resilient)
- Authors: Molubo, Rendani
- Date: 2020
- Subjects: Women in literature , Feminism -- Africa , Saule, N -- Vuleka Mhlaba , Saule, N -- Inkululeko Isentabeni , Saule, N -- Libambe Lingatshoni , Xhosa fiction -- History and criticism
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/143982 , vital:38300
- Description: This study seeks to explore how Professor Ncedile Saule’s works Vuleka Mhlaba (2006), Inkululeko Isentabeni (2010) and Libambe Lingatshoni (2017), depict female characters to reveal the inner resilience women embody. It is important to portray females as bold, intelligent and courageous beings as African women are subjected to major patriarchal myths. South Africa prides itself with a progressive Constitution and Bill of Rights that speaks of gender equality and the liberation of all persons. However, in practice women still live under patriarchal bondages and their efforts are side-lined, thus, the essentiality of writings that contributes towards the empowerment of women through displaying their resilience. Women in literature are mostly depicted as subordinate, submissive and emotional. At times they are portrayed as victims. They are very seldom portrayed as heroes or independent beings. They are constantly placed behind a man instead of in front of a man. This research aims to display women as heroes in their own capacity, without having to be dimmed by a man. The researcher decided to utilise writings of a male author so as to provide a different perspective from the norm that most male authors are known to write about in issues pertaining female characters. This is also deliberately done to encourage more male writers to change the mythical narration about women and start admiring their contributions without having them shadow any man. The projection of female resilience through the gaze of a male author gives hope that there are men who see and admire women’s efforts. It also indicates that men realise now that African feminisms are not against men and instead advocate for equality between men and women and recognise the greatness that could come out of a partnership between the two genders. Women’s behaviour and characteristics are mostly socially constructed, hence the need to exhibit the boldness that black women possess, instead of them only being utilised as nurturing sources and household caretakers. One of the purposes of this research study is to illustrate the resilience that women possess and analyse the forms of torment that women in Saule’s chosen novels have experienced and how their experience engenders resilience and a determination to succeed. The women in Saule’s three novels selected for this study break the traditional status quo. The approach that this paper will utilize is that of African Feminisms, focusing on Walker’s Womanism, Ogunyemi’s Africana Womanism, and Stiwanism as the theoretical approaches. This is because African Feminisms concentrates on the issues related to gender, race and class that African women across spectrums face.
- Full Text:
- Date Issued: 2020
- Authors: Molubo, Rendani
- Date: 2020
- Subjects: Women in literature , Feminism -- Africa , Saule, N -- Vuleka Mhlaba , Saule, N -- Inkululeko Isentabeni , Saule, N -- Libambe Lingatshoni , Xhosa fiction -- History and criticism
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/143982 , vital:38300
- Description: This study seeks to explore how Professor Ncedile Saule’s works Vuleka Mhlaba (2006), Inkululeko Isentabeni (2010) and Libambe Lingatshoni (2017), depict female characters to reveal the inner resilience women embody. It is important to portray females as bold, intelligent and courageous beings as African women are subjected to major patriarchal myths. South Africa prides itself with a progressive Constitution and Bill of Rights that speaks of gender equality and the liberation of all persons. However, in practice women still live under patriarchal bondages and their efforts are side-lined, thus, the essentiality of writings that contributes towards the empowerment of women through displaying their resilience. Women in literature are mostly depicted as subordinate, submissive and emotional. At times they are portrayed as victims. They are very seldom portrayed as heroes or independent beings. They are constantly placed behind a man instead of in front of a man. This research aims to display women as heroes in their own capacity, without having to be dimmed by a man. The researcher decided to utilise writings of a male author so as to provide a different perspective from the norm that most male authors are known to write about in issues pertaining female characters. This is also deliberately done to encourage more male writers to change the mythical narration about women and start admiring their contributions without having them shadow any man. The projection of female resilience through the gaze of a male author gives hope that there are men who see and admire women’s efforts. It also indicates that men realise now that African feminisms are not against men and instead advocate for equality between men and women and recognise the greatness that could come out of a partnership between the two genders. Women’s behaviour and characteristics are mostly socially constructed, hence the need to exhibit the boldness that black women possess, instead of them only being utilised as nurturing sources and household caretakers. One of the purposes of this research study is to illustrate the resilience that women possess and analyse the forms of torment that women in Saule’s chosen novels have experienced and how their experience engenders resilience and a determination to succeed. The women in Saule’s three novels selected for this study break the traditional status quo. The approach that this paper will utilize is that of African Feminisms, focusing on Walker’s Womanism, Ogunyemi’s Africana Womanism, and Stiwanism as the theoretical approaches. This is because African Feminisms concentrates on the issues related to gender, race and class that African women across spectrums face.
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- Date Issued: 2020
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