List of Titles

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NIR Absorbing AzaBODIPY Dyes for pH Sensing

- Kubheka, Gugu, Mack, John, Nyokong, Tebello, Zhen, Shen

Authors: Kubheka, Gugu , Mack, John , Nyokong, Tebello , Zhen, Shen
Date: 2020
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/186668 , vital:44523 , xlink:href="https://doi.org/10.3390/molecules25163689"
Description: Two near-infrared (NIR) absorbing di(thien-2-nyl)-di(dimethylanilino)azaBODIPY dyes 2a and 2b were synthesized and characterized that differ depending on whether the dimethylaniline substituents are introduced at the 3,5- or 1,7-positions of the azaBODIPY core. The main spectral bands lie at 824 and 790 nm, respectively, in CH2Cl2. The effect of substituent position on the photophysical and pH sensing properties was analyzed through a comparison of the optical properties with the results of time-dependent density functional theory (TD-DFT) calculations. Protonation of the dimethylamino nitrogen atoms eliminates the intramolecular charge transfer properties of these compounds, and this results in a marked blue-shift of the main absorption bands to 696 and 730 nm, respectively, in CH2Cl2, and a fluorescence “turn-on” effect in the NIR region. The pH dependence studies reveal that the pKa values of the non-protonated 2a and 2b molecules are ca. 6.9 (±0.05) and 7.3 (±0.05), respectively, while that of the monoprotonated species for both dyes is ca. 1.4 (±0.05) making them potentially suitable for use as colorimetric pH indicators under highly acidic conditions.
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Date Issued: 2020

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No evidence of genetic structure in a sky island endemic: implications for population persistence under a shrinking thermal niche

- Oswald, Krista N, Edwards, Shelley, Lee, Alan T K, Cunningham, Susan J, Smit, Ben

Authors: Oswald, Krista N , Edwards, Shelley , Lee, Alan T K , Cunningham, Susan J , Smit, Ben
Date: 2020
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/440558 , vital:73793 , https://www.authorea.com/doi/full/10.22541/au.157901262.24420308
Description: Mountain habitats physically isolated from one another (“sky islands”) represent a unique system for studying dispersal in seemingly isolated populations. The Cape Fold Belt of southwest South Africa forms a sky island archipelago of high-altitude mountain fynbos of which the Cape Rockjumper Chaetops frenatus is an avian-endemic. Continued contraction of habitat due to increasing temperatures may be causing further isolation of C. frenatus populations beyond their dispersal capacities, resulting in currently declining populations in warmer areas of their habitat. In this study, we sequenced two mitochondrial loci and one nuclear locus of 73 C. frenatus samples from 13 localities representing 8 mountain ranges. We found (1) low overall genetic diversity, (2) no evidence for geographically-based genetic structuring, and (3) no evidence for inbreeding within localities. While this may indicate birds are effectively dispersing, it may also indicate strong selective pressure is being placed on their specific genotype. Haplotype networks suggested that C. frenatus may have experienced a bottleneck or founder effect in their recent genetic past —- a result supported by a significantly negative Tajima’s D value. As the first avian genetic study to arise from a range-restricted species of the Cape Fold Belt sky islands, our results show no evidence that C. frenatus are unable to disperse across inhospitable lowland habitat, and thus may not experience isolation due to climate change. We thus potentially found further support that selective pressure in species with highly specialized habitat niches may have a stronger effect than dispersal limitations.
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Date Issued: 2020

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No evidence of genetic structure in a sky island endemic: implications for population persistence under a shrinking thermal niche

- Oswald, Krista N, Edwards, Shelley, Lee, Alan T K, Cunningham, Susan J, Smit, Ben

Authors: Oswald, Krista N , Edwards, Shelley , Lee, Alan T K , Cunningham, Susan J , Smit, Ben
Date: 2020
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/461528 , vital:76210 , xlink:href="https://www.authorea.com/doi/full/10.22541/au.157901262.24420308"
Description: Mountain habitats physically isolated from one another (“sky islands”) represent a unique system for studying dispersal in seemingly isolated populations. The Cape Fold Belt of southwest South Africa forms a sky island archipelago of high-altitude mountain fynbos of which the Cape Rockjumper Chaetops frenatus is an avian-endemic. Continued contraction of habitat due to increasing temperatures may be causing further isolation of C. frenatus populations beyond their dispersal capacities, resulting in currently declining populations in warmer areas of their habitat. In this study, we sequenced two mitochondrial loci and one nuclear locus of 73 C. frenatus samples from 13 localities representing 8 mountain ranges. We found (1) low overall genetic diversity, (2) no evidence for geographically-based genetic structuring, and (3) no evidence for inbreeding within localities. While this may indicate birds are effectively dispersing, it may also indicate strong selective pressure is being placed on their specific genotype. Haplotype networks suggested that C. frenatus may have experienced a bottleneck or founder effect in their recent genetic past —- a result supported by a significantly negative Tajima’s D value. As the first avian genetic study to arise from a range-restricted species of the Cape Fold Belt sky islands, our results show no evidence that C. frenatus are unable to disperse across inhospitable lowland habitat, and thus may not experience isolation due to climate change. We thus potentially found further support that selective pressure in species with highly specialized habitat niches may have a stronger effect than dispersal limitations.
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Date Issued: 2020

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Noise pollution at sea

- Karomo, Adelaide Aquiline

Authors: Karomo, Adelaide Aquiline
Date: 2020
Subjects: Marine pollution
Language: English
Type: Thesis , Masters , LLM
Identifier: http://hdl.handle.net/10948/48091 , vital:40470
Description: Marine species heavily rely on sound to perform day to day functions and, since the advent of industrialisation, anthropogenic noise in the marine environment has been on the increase and is expected to increase further as countries continue to develop. The impacts of anthropogenic noise on marine species have been deeply scrutinised especially by the international community and it has been established that this humaninduced noise at sea must be reduced to conserve marine biodiversity. A background of the major contributors to anthropogenic noise is discussed, as well as the international instruments regulating them. For instance the 1982 United Nations Convention on the Law of the Sea (hereinafter referred to as “the UNCLOS”),1 is discussed because it is the primary instrument regulating activities at sea and the protection of the marine environment and the species therein. South Africa has ratified the UNCLOS and is under a legal obligation to comply with its provisions by implementing them into domestic rules and regulations. Furthermore, the applicable global and regional instruments dealing with marine environmental protection from anthropogenic noise are weighed against the national South African legislation and this assessment serves the purpose of ascertaining the extent to which South Africa has complied with its international law obligation. The dissertation goes a step further by identifying and assessing the efforts made by foreign jurisdictions, specifically Australia, Greenland, the United Kingdom and the United States of America. This determination is meant to determine whether there are lessons South Africa can learn, if any, from these jurisdictions in order to improve its current marine environmental protection legislation in fulfilment of international law. The dissertation also shows that there is need to improve the South African environmental protection legislation by taking into account some of the developments made by international organisations, such as the International Maritime Organisation (hereinafter referred to as “the IMO”) and by foreign jurisdictions. These improvements to South African legislation would comprise of adopting activity-specific regulations, such as the IMO’s guidelines on minimising noise emitted by commercial shipping vessels and the United Kingdom’s Joint Nature Conservation Committee (hereinafter referred to as the “JNCC”) guidelines on seismic surveys. The regulations adopted by the international community are especially essential to fill the gap as far as the South African regulation of noise emitted by offshore renewable energy processes and naval operations are concerned.
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Date Issued: 2020

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Non-aggregated lipophilic water-soluble tin porphyrins as photosensitizers for photodynamic therapy and photodynamic antimicrobial chemotherapy:

- Babu, Balaji, Soy, Rodah C, Mack, John, Nyokong, Tebello

Authors: Babu, Balaji , Soy, Rodah C , Mack, John , Nyokong, Tebello
Date: 2020
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/158241 , vital:40165 , DOI: 10.1039/d0nj01564d
Description: Two readily synthesized water-soluble Sn(IV) porphyrins have been prepared with quaternized pyridyl nitrogens and 2-naphthalato trans-axial ligands. Methyl and hexyl groups were attached to the quaternized nitrogens to form lipophilic dyes with high singlet oxygen quantum yields (ca. 0.90) and unusually long triplet state lifetimes. The dyes exhibit good photodynamic activity against MCF-7 cells with IC50 values of 14.3 and 8.5 μM, respectively. The hexyl quaternized dye exhibited a 9.69 log reduction value (0.5 μM) towards S. aureus under illumination for 90 min (250 mW cm−2). The results demonstrate that this set of structural modification strategies for photosensitizer dyes merits further in depth study.
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Date Issued: 2020

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Non-marital fertility in South Africa: trends, determinants and implications

- Kara, Reesha

Authors: Kara, Reesha
Date: 2020
Subjects: Fertility, Human -- South Africa , Child rearing -- South Africa , Parenting -- South Africa , Motherhood -- South Africa
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/165620 , vital:41264
Description: Background: Non-martial fertility is traditionally associated with teenage pregnancy however international and South African literature has detailed increases in the number of adult women who are having children outside of a marriage. South African literature on non-marital fertility is sparse as it lacks a national overview of the trends and determinants of non-marital fertility among women aged 30 and older. The aim of this study was to present a national overview of non-marital fertility among women aged 30 and older. South African’s attitudes to and opinions of non-marital fertility were also investigated, and the lived realities of older mothers were explored. Methods: A mixed-methods research design was employed where the General Household Survey, National Income Dynamics Study and the South African Social Attitudes Survey were the main data sources. Using these data sets, descriptive and inferential statistics were computed using Stata. Using purposive and snowball sampling, four never-married older mothers (NMOMs) from KwaZulu-Natal (Durban) were identified as research participants. The in-depth life histories of these women were collected through face-to- face semi-structured interviews. Results: The results show an 18.43% increase in never-married mothers aged 15- 49 between 2002 and 2017 and interestingly, this increase is not necessarily driven by older mothers (30-49). NMOMs belonged to households with a lower average per capita total monthly household income (R1873.91) compared to all mothers aged 30-49 (R3428.76). NMOMs were also more likely to live in female-headed households (89.52%), to be household heads (64.22%) and to live in traditional areas (35.72%). Between 2002 and 2017, there was a 76.76% increase in mothers (aged 30-49) who were never married and a 7.74% decrease in those who were married, indicating a change in the marital profile of mothers. Despite this national increase in non-marital fertility, South African’s believe that premarital sexual activity is wrong, and that childbearing should take place within a marriage. Similar sentiments were echoed in the in-depth life histories as being the sole breadwinner and primary caregiver, the research participants experienced challenges as single mothers. Conclusion and recommendations: The study has found that there has been an increase in non-marital fertility in South Africa between 2002 and 2017 and that there is an economic element to non-marital fertility in the country. Additional research into non-marital fertility at a national level is recommended with a focus on all women aged 15-49.
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Date Issued: 2020

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Non-material costs of wildlife conservation to local people and their implications for conservation interventions:

- Thondhlana, Gladman, Redpath, Stephen Mark, Vedeld, Pål Olav, Van Eeden, Lily, Pascual, Unai, Sherren, Kate, Murata, Chenai

Authors: Thondhlana, Gladman , Redpath, Stephen Mark , Vedeld, Pål Olav , Van Eeden, Lily , Pascual, Unai , Sherren, Kate , Murata, Chenai
Date: 2020
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/150174 , vital:38946 , https://doi.org/10.1016/j.biocon.2020.108578
Description: In assessment of costs (and benefits) of wildlife conservation, conventional economic valuation frameworks may inadequately address various non-tangible values and neglect social, cultural and political contexts of resources and their use. Correspondingly, there seems to be much more focus on quantifying the economic, material benefits and costs of wildlife conservation than the non-material aspects that also affect human well-being. In addition, current research on the costs of wildlife conservation tends to be discipline-focused which constrains comparability, often causing conceptual ambiguity. This paper is an attempt to address this ambiguity. While there is growing acknowledgement of the material costs of wildlife conservation, we contend that employing a broader, composite social well-being approach may provide better conceptual insights on—and practical options for—managing various non-material impacts of wildlife conservation for local people.
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Date Issued: 2020

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Non-standard employment in terms of the labour relations act

- Tatchell, Veronique

Authors: Tatchell, Veronique
Date: 2020
Subjects: Labor laws and legislation -- South Africa , South Africa -- Labour Relations Act, 1995 , Flexible work arrangements -- South Africa
Language: English
Type: Thesis , Masters , LLM
Identifier: http://hdl.handle.net/10948/49027 , vital:41594
Description: Historically, employers utilised non-standard or atypical forms of employment in order to avoid statutory obligations in respect of these employees, and in turn justify differential treatment of said employees.1 As a result, non-standard employees were not on the same footing as their permanent counterparts. They were not remunerated on the same level, were not privy to advancement and training opportunities, and did not enjoy a sense of job security due to the ease at which their employment could be terminated, rendering them a vulnerable class of workers.2 There was pandemonium in the employment sphere of society due to the abusive practices faced by employees employed in terms of Temporary Employment Services, this was accompanied by a call to ban labour broking. The legislature, while acknowledging the important role that this form of employment plays in the labour market and broader economy, opted for increased regulation of this and other types of non-standard employment; instead of an outright ban. As a result thereof, the Labour Relations Act3 was amended by the Labour Relations Amendment Act,4 with a view of improving the regulation and protection of employees engaged in these forms of non-standard or atypical employment. This study seeks to determine whether the amendments have achieved the purpose of enhancing the job security of these employees.
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Date Issued: 2020

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Nonlinear optical response and electrocatalytic activity of cobalt phthalocyanine clicked zinc oxide nanoparticles

- Mpeta, Lekhetho S, Sekhosana, Kutloano E, Nyokong, Tebello

Authors: Mpeta, Lekhetho S , Sekhosana, Kutloano E , Nyokong, Tebello
Date: 2020
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/186179 , vital:44471 , xlink:href="https://doi.org/10.1016/j.ica.2020.119661"
Description: In this article, we report on the linking of cobalt tetrakis (4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.
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Date Issued: 2020

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Not Yet Uhuru! Attuning to, re-imagining and regenerating transgressive decolonial pedagogical praxis across times Khapa(ring) the rising cultures of change drivers in contemporary South Africa

- Kulundu-Bolus, Injairu M

Authors: Kulundu-Bolus, Injairu M
Date: 2020
Subjects: Not Yet Uhuru (Arts Project) , Anti-imperialist movements -- South Africa , Education -- Social aspects -- South Africa , Social change -- South Africa , Education -- Philosophy -- South Africa , Arts and society -- South Africa
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/166081 , vital:41327 , 10.21504/10962/166081
Description: The “Not yet Uhuru!” project positions itself as emancipatory African research in motion. It is a regenerative project that responds to the concern that whilst dominant discourses can articulate what African states, societies and economies are not, we still know very little about what they actually are. This is a particularly important gap in how research on Africa is conceptualised, especially as it pertains to apprehending the futures that the majority of young people on the continent are instinctively leading themselves to (Mbembe, 2001, p.9). The project seeks to forgo youth development strategies that act as a form of containment by prescribing normative aspects of citizenship on young leaders in ways that stifle the transgressive impulses they have reason to value (Kelley in Tuck and Yang, 2014, p.89). The study traces rising cultures in transgressive decolonial pedagogical praxis across times, as a way of “khapa(ring)” or accompanying the contemporary questions that Change Drivers in South Africa hold at the edge of their praxis. The study co-conspired with 21 Change Drivers in South Africa who were interested in regenerating and re-imagining what transgressive decolonial praxis could be in these times based on their experiences and learnings. Residential art-based workshops that explored each co-conspirator’s offerings on the subject were distilled through the medium of film. These in turn were analysed using an “ethics of attunement” that produced songs as a reflexive pedagogical tool (Lispari, 2014, p.176). Sharing the resonate echoes of their praxis through song created another iterative reflection on their praxis two years after their initial offerings. As a way of weaving together the findings with a historical perspective, the resonant praxis of Change Drivers was put into conversation with three unconventional reviews that trace impulses around transgressive decolonial pedagogical praxis through fictional texts, political theory, poetry and intergenerational analysis, in order to surface resonant themes in praxis that echo across different times in history. This methodology sought to engage the question of the archive in pluriversal ways that appealed to different sensibilities, including the imaginative and hermeneutical, the traditionally analytical as well as the gifts of the lyrical and the erotic as different conceptual threads needed to resource the study. The reviews additionally spanned periods in the history of the continent that hold questions around precolonial and nascent colonial encounters, efforts to transgress within the liberatory movements and the intergenerational transmissions embedded in women and queer people’s struggles. The themes that coalesced across times were leveraged into capsules of rising cultures that form an experimental nexus for the practice of transgressive decolonial pedagogical praxis that is already underway. These rising cultures were conceptualised as meditations on what it means to live into a vision of home built on the explorations of a paradigm of peace, humanness, pluriversality and decolonial love for those like and unlike us that strive for freedom on this continent (Dlala, 2017, p.52; Ndlovu- Gatsheni, 2013, p.142; Gqola, 2017, pp.197, 199). The rising ultures were reconciled through the creation of a litany that chronicles different refrains in transgressive decolonial pedagogical praxis in contemporary times. The litany is a tool that charts particular experiences that are surfacing as symptomatic. It seeks to generously surface the contradictions that we are collectively starting to see past, whilst acknowledging the tensions that we need to straddle, integrate and navigate towards greater synthesis. The litany is an honest way of acknowledging the glimpses gained of who we are in this present moment, while we continually challenge ourselves to open up to questions about what it means to grapple towards decolonial futures. This stance has influenced my role as an educator to unconditionally embrace movements that already underway, and reflect these back to those that I am conspiring with in ways that promote an ethic of care, solidarity and critical engagement. The study celebrates what is possible when we do not theorise ourselves away from the questions embedded in our current praxis. This is an ethic that chooses to stay close to the phenomena arriving at present, whilst acknowledging the historical experiences that echo it as a collective pulse for meaningful experimentation and praxis. The study believes by being faithful to ways of amplifying, integrating and reflecting what has been emerging for us over time, we build our capacity to better respond with an ethic centred on transgressive decolonial pedagogical praxis. This is the kind of accompaniment and care that Change Drivers across the continent deserve as they make the way towards a future worthy of their longing (Rushdie, 1999).
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Date Issued: 2020

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Now that we have the land: analysing the experiences of land reform beneficiaries in the Makana Municipal District of the Eastern Cape, South Africa

- Msuthu, Simela Thuleka

Authors: Msuthu, Simela Thuleka
Date: 2020
Subjects: Land reform , Sustainable development , Land reform -- South Africa -- Eastern Cape , Land tenure -- South Africa -- Eastern Cape , Land settlement -- Government policy -- South Africa -- Eastern Cape , Restitution -- South Africa -- Eastern Cape , Local government -- South Africa -- Eastern Cape , Municipal government -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape
Language: English
Type: text , Thesis , Masters , MA
Identifier: http://hdl.handle.net/10962/167551 , vital:41491
Description: The “land question” in South Africa goes back more than a century to the 1913 Natives Land Act which facilitated the dispossession of African people from fertile land to arid homelands and congested townships. This mass dispossession of Africans from their land was accompanied by an array of legislation aimed at restricting their upward mobility, thus laying the foundations of structural inequality in South Africa. The advent of democracy in 1994 brought about a number of legislative reforms aimed at addressing the injustices that were imposed by the colonial and apartheid governments on the African people. At the forefront of these legislative efforts was the restoration of land to the original inhabitants of the country. Research indicates that, since 1994, the South African government has issued out land to different individuals and communities around the country in an attempt to address structural unemployment and poverty that plague the country. Using the Sustainable Livelihoods Theoretical framework, this study sought to examine the experiences of land reform beneficiaries in the Makana Municipal district of the Eastern Cape, in order to determine the extent to which the transfer of land to landless people has met the governments’ agenda to alleviate poverty and unemployment in the rural regions of South Africa. The findings in this study show that, successful land reform in South Africa is hindered mostly by two factors. Firstly, the inability of land beneficiaries to access quality education, skills training, finances and formal agricultural value chains. Secondly, land beneficiaries are further placed at a disadvantage by the poor quality of public services in their local municipalities and inconsistent post-settlement support from the state. The conclusion made in this study, is that the government has to be cognizant of the aforementioned structural barriers, when designing and rolling out land reform projects throughout the country. Failure to address these glaring structural barriers, will result in the creation of a peasant class of people living on underutilized land.
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Date Issued: 2020

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Nuruddin Farah: variations on the theme of return

- Naicker, Kamil

Authors: Naicker, Kamil
Date: 2020
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/149643 , vital:38871 , https://www.ajol.info/index.php/tvl/article/view/196356
Description: This article explores the role of the returnee protagonist in selected works of Nuruddin Farah. Nadine Gordimer described Farah as “one of the real interpreters” of Africa and this article argues that Farah’s returnees operate as interpreters themselves, their liminality working to mediate between international readers and “local” subject matter. However, it also observes that Farah, who spent decades in exile, is often as preoccupied with writing non-belonging as he is with rendering Somalia itself. Farah’s returnee narratives are, broadly, novels of redress, in which characters enact their return in an attempt to seek out the missing, rebuild the lost or reclaim the stolen, with imperfect results. In exploring these variations on homecoming, the paper investigates the ways in which Farah’s body of work reflects shifts in identity politics over time, and the unique pressures these shifts exert on the homecoming arc.
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Date Issued: 2020

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Nutrient patchiness, phytoplankton surge-uptake, and turbulent history: a theoretical approach and its experimental validation

- Schapira, Mathilde, Seuront, Laurent

Authors: Schapira, Mathilde , Seuront, Laurent
Date: 2020
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/149774 , vital:38883 , https://doi.org/10.3390/fluids5020080
Description: Despite ample evidence of micro- and small-scale (i.e., millimeter- to meter-scale) phytoplankton and zooplankton patchiness in the ocean, direct observations of nutrient distributions and the ecological importance of this phenomenon are still relatively scarce. In this context, we first describe a simple procedure to continuously sample nutrients in surface waters, and subsequently provide evidence of the existence of microscale distribution of ammonium in the ocean. We further show that ammonium is never homogeneously distributed, even under very high conditions of turbulence. Instead, turbulence intensity appears to control nutrient patchiness, with a more homogeneous or a more heterogeneous distribution observed under high and low turbulence intensities, respectively, under the same concentration in nutrient. Based on a modelling procedure taking into account the stochastic properties of intermittent nutrient distributions and observations carried out on natural phytoplankton communities, we introduce and verify the hypothesis that under nutrient limitation, the “turbulent history” of phytoplankton cells, i.e., the turbulent conditions they experienced in their natural environments, conditions their efficiency to uptake ephemeral inorganic nitrogen patches of different concentrations.
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Date Issued: 2020

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Nutrient release dynamics associated with native and invasive leaf litter decomposition: a Mesocosm Experiment

- Mutshekwa, Thendo, Cuthbert, Ross N, Wasserman, Ryan J, Murungweni, Florence M, Dalu, Tatenda

Authors: Mutshekwa, Thendo , Cuthbert, Ross N , Wasserman, Ryan J , Murungweni, Florence M , Dalu, Tatenda
Date: 2020
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/160467 , vital:40448 , https://doi.org/10.3390/w12092350
Description: Leaf litter contributes to the functioning of aquatic ecosystems through allochthonous inputs of carbon, nitrogen, and other elements. Here, we examine leaf litter nutrient inputs and decomposition associated with four plant species using a mesocosm approach. Native sycamore fig Ficus sycomorus L., and silver cluster–leaf Terminalia sericea Burch. ex DC. decomposition dynamics were compared to invasive tickberry Lantana camara L. and guava Psidium guajava L., whereby phosphate, nitrate, nitrite, silicate, and ammonium releases were quantified over time. Leaf inputs significantly reduced pH, with reductions most marked by invasive L. camara. Conductivity was heightened by all leaf input treatments, except native T. sericea.
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Date Issued: 2020

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Nutrient removal and biofuel potential of MaB-floc biomass from an integrated algal pond system treating domestic sewage

- Sibelo, Linda

Authors: Sibelo, Linda
Date: 2020
Subjects: Biomass energy , Waste products as fuel , Algal biofuels , Sewage -- Purification -- Nutrient removal
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/144955 , vital:38395
Description: Integrated algal pond systems (IAPS) are a passive water treatment technology derived from the Oswald designed advanced integrated wastewater pond systems (AIWPS®) and effect wastewater treatment based on biological activity of microorganisms within the system, solar energy and gravity. The technology consists of an advanced facultative pond (AFP), a series of interconnected high rate algal oxidation ponds (HRAOP) and algal settling ponds. The symbiotic relationship between microalgae and bacteria facilitated by paddlewheel mixing of HRAOP results in the formation of biomass aggregates known as MaB-flocs. MaB-floc formation enhances nutrient abstraction, gravitational sedimentation and separation from water hence forming two product streams; recyclable water and biomass, both with valorisation potential. This work aimed to determine the suitability of MaB-floc biomass generated in the HRAOP of an IAPS treating domestic sewage as feedstock for biofuel production based on the content of carbohydrate and lipid. Nutrient removal efficiency, biomass productivity and bulk lipid and carbohydrate concentration were monitored for two consecutive three-month periods in the winter and summer seasons of 2018/19. Maximum removal efficiencies of nitrogen and phosphorus were determined as 71% and 75% respectively, demonstrating the efficiency of IAPS as a wastewater treatment technology. MaB-floc biomass productivity in winter and summer was 9.4 g/m2/d and 16.5 g/m2/d respectively indicating the heavy influence of seasonal temperature, possibly day length, and solar irradiation on biomass productivity in the HRAOP. Summer productivity was lower than the maximum theoretical productivity of 25 g/m2/d possibly due to photoinhibition of photosynthesis as well as grazing pressures caused by the proliferation of rotifers mainly of the Brachionus genus. MaB-floc biomass consistently contained higher amounts of carbohydrate than lipid despite the changes in species dominance from Scenedesmus sp. and Desmodesmus sp. in winter to Pediastrum sp. in summer. Variations in MaB-floc biomass carbohydrate content were linked to changes in nitrogen concentration, mainly in the form of nitrates. Lower nitrogen concentration significantly increased the carbohydrate content of MaB-floc biomass from 17.5 ± 0.15% to 33.5 ± 0.3 % recorded in summer. In winter, biomass carbohydrate increased from 18.3 ± 1.2% to 35.8 ± 0.3%.To induce accumulation of carbohydrates through nitrogen starvation, isolated microalgal species native to the HRAOPs of the IAPS at Institute for Environmental Biotechnology Rhodes University(EBRU) were used. The outcome from the laboratory studies showed that carbon partitioning within isolated strains could be altered from carbohydrate to lipid which is more energy-rich. Hence, exploring the biodiesel production option using HRAOP MaB-floc biomass, which had a lipid content ranging between 12.1 ± 0.64 % and 13.9 ± 0.5 %, would require a preconditioning step in the form of nitrogen starvation to enhance its lipid content. Overall, the outcome of outdoor monitoring studies on biomass biochemical composition indicated that HRAOPs operating under natural environmental conditions preferentially generated a biomass rich in carbohydrate. Therefore, anaerobic digestion may be a more viable option for HRAOP MaB-floc biomass because of the high carbohydrate levels ranging between 24.9 ± 0.6 % and 25.6 ± 1.3 % of the dry MaB-floc biomass weight. Despite the low biomass C/N ratio (7.1 to 7.8), the MaB-floc biomass can be anaerobically co-digested with a higher C/N ratio (24) substrate such as in-pond digester sludge, to improve methane yields calculated to be between 0.31 m3 CH4/ kg MaB-floc biomass and 0.33 m3 CH4/ kg MaB-floc biomass. Anaerobic digestion of biomass also produces CO2 which can be recovered and added to HRAOPs to enhance MaB-floc biomass productivity while lowering greenhouse gas emissions from a wastewater treatment plant. The digestate from the anaerobic process, which is rich in nitrogen and phosphorus can be used as a biofertiliser. Thus, a potential MaB-floc biomass biorefinery consisting of biogas and bio-fertiliser pathways can be established using IAPS treating sewage as the platform technology. IAPS is a system designed to operate in a way that is passive and without substantial environmental impact but technological innovations and a reduction in the size of the system are required to make the technology more acceptable.
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Date Issued: 2020

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Nutrient-mediated silica uptake from agricultural runoff in invasive floating macrophytes: implications for biological control

- Baso, Nompumelelo C, Delport, Garyn A, Coetzee, Julie A

Authors: Baso, Nompumelelo C , Delport, Garyn A , Coetzee, Julie A
Date: 2020
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/424803 , vital:72185 , xlink:href="https://doi.org/10.1007/s10750-020-04344-5"
Description: Silica (Si) plays a significant role in alleviating the effects of biotic and abiotic stressors in many plants, especially in an agricultural context. With increased use of Si-based fertilisers, understanding plant responses to the addition of Si to their environment, particularly aquatic environments, is important. We investigated how two invasive macrophytes, Eichhornia crassipes and Pistia stratiotes, responded to different nutrient and Si concentrations, in the presence and absence of herbivory. Both species incorporated Si into their foliage, but uptake of Si did not increase under high nutrient availability but rather decreased, especially in P. stratiotes. Plant quality (i.e. C:N) for both weed species was affected more by nutrient concentrations than Si content, and the addition of Si had a negative effect on plant growth. Eichhornia crassipes increased daughter plant production under high Si conditions, while P. stratiotes plants showed no reproductive response to increased Si except in low nutrient conditions where reproduction was reduced. The addition of Si resulted in increased biomass of E. crassipes, while P. stratiotes was unaffected. These results highlight that runoff of Si from fertiliser alter aquatic plant–insect interactions, which has consequences for biological control.
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Date Issued: 2020

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Observations of diffuse radio emission in the Abell 773 galaxy cluster

- Sichone, Gift L

Authors: Sichone, Gift L
Date: 2020
Subjects: Galaxies -- Clusters -- Observations , Radio astronomy -- Observations , Astrophysics -- South Africa , Westerbork Radio Telescope , A773 galaxy cluster , Astronomy -- Observations , Radio sources (Astronomy
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/144945 , vital:38394
Description: In this thesis, we present 18 and 21 cm observations of the A773 galaxy cluster observed with the Westerbork radio telescope. The final 18 and 21 cm images achieve a noise level of 0.018 mJy beam‾ 1 and 0.025 mJy beam-1 respectively. After subtracting the compact sources, the low resolution images show evidence of a radio halo at 18 cm, whereas its presence is more uncertain in the low resolution 21 cm images due the presence of residual sidelobes from bright sources. In the joint analysis of both frequencies, the radio halo has a 5.37 arcmin2 area with a 6.76 mJy flux density. Further observations and analysis are, however, required to fully characterize its properties.
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Date Issued: 2020

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Observations of diffuse radio emission in the Perseus Galaxy Cluster

- Mungwariri, Clemence

Authors: Mungwariri, Clemence
Date: 2020
Subjects: Galaxies -- Clusters , Radio sources (Astronomy) , Radio interferometers , Perseus Galaxy Cluster , Diffuse radio emission
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/143325 , vital:38233
Description: In this thesis we analysed Westerbork observations of the Perseus Galaxy Cluster at 1380 MHz. Observations consist of two different pointings, covering a total of ∼ 0.5 square degrees, one including the known mini halo and the source 3C 84, the other centred on the source 3C 83.1 B. We obtained images with 83 μJy beam⁻¹ and 240 μJy beam⁻¹ noise rms for the two pointings respectively. We achieved a 60000 : 1 dynamic range in the image containing the bright 3C 84 source. We imaged the mini halo surrounding 3C 84 at high sensitivity, measuring its diameter to be ∼140 kpc and its power 4 x 10²⁴ W Hz⁻¹. Its morphology agrees quite well with that observed at 240 MHz (e.g. Gendron-Marsolais et al., 2017). We measured the flux density of 3C 84 to be 20.5 ± 0.4 Jy at the 2007 epoch, consistent with a factor of ∼2 increase since the 1960s.
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Date Issued: 2020

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