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Synthesis of a near infrared-actuated phthalocyanine-lipid vesicle system for augmented photodynamic therapy

  • Authors: Nwahara, Namdi , Managa, Muthumuni , Stoffels, Mihlali , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185395 , vital:44383 , xlink:href="https://doi.org/10.1016/j.synthmet.2021.116811"
  • Description: The efficacy of photodynamic therapy (PDT) is often limited by the poor bio-distributive properties of conventional photosensitizers and the local hypoxic microenvironment that characterises most solid tumours. Herein, a novel in situ oxygenic lipid formulation for photodynamic therapy (PDT) is reported. Such a hybrid was synthesized by adsorbing bimetallic nanozyme, MnO2@PtNPs (NPs = nanoparticles) onto graphene quantum dots (GQDs) – zinc (II) phthalocyanine conjugates, followed by liposomal encapsulation, affording it enhanced water solubility. The MnO2@PtNPs, which are is shown to possess excellent catalase-like properties surpassing that of MnO2 or PtNPs alone, serves to catalyze H2O2 to O2, while the zinc (II) phthalocyanine (1) serves to transform the formed oxygen to generate cytotoxic singlet oxygen immediately. We show that by combining each function of the respective building blocks, the as-synthesized 1-GQDs-MnO2@PtNPs-liposomes not only maintains the properties of oxygen supplementation through H2O2 catalysis but also displays cooperative properties for enhanced singlet oxygen production. Consequently, a remarkably improved PDT efficacy was observed for 1-GQDs-MnO2@PtNPs-liposomes in both normoxia and hypoxia. These results demonstrate the potential applicability of such nanozyme constituted 1-GQDs-MnO2@PtNPs-liposomes for achieving tumour treatment in hypoxic conditions by PDT.
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  • Date Issued: 2021

Synthesis, spectroscopic and nonlinear optical properties of asymmetric A3B type phthalocyanine complexes

  • Authors: Mugeza, Rhulani Donney
  • Date: 2021
  • Subjects: Spectrum analysis , Mass spectrometry , Phthalocyanines
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/171667 , vital:42108
  • Description: This work reports on the synthesis of symmetrical and asymmetrical A 3 B type metal free, cobalt and zinc Phthalocyanines (Pc) .A wide range of spectroscopic techniques such as Uv - visible absorption (UV), magnetic circular dichroism (MCD), mass spectrometry, elemental analysis, IR spectroscopy and time correlated single photo n counting spectroscopy (TCSPC) have been used to study the spectroscopic properties of the phthalocyanine complexes. The Z - scan technique was used to comparatively investigate the nonlinear absorption coefficient ( 휷 ) and the nonlinear refraction index ( 풏 ퟐ ) of the synthesized complexes. The following trend was obtained for the synthesized Pc’s in terms of the 휷 values 7.25 × 10 − 10 ( 4b ) > 3.76 × 10 − 10 ( 4a ) > 3.52 × 10 − 10 ( 4c ) > 2.29 × 10 − 10 ( 3c ) > 1.68 × 10 − 10 ( 3a ) > 1.65 × 10 − 10 ( 3b ) mW - 1 . The 휷 values trend of synthesized Pc complexes show that the asymmetrical A 3 B type metal free, cobalt and zinc Pc complexes ( 4a , 4b and 4c ) have larger 휷 values as compared to the octa - substituted symmetrical metal free, cobalt and zinc Pc complexes ( 3a , 3b and 3c ) which is attributed to the low symmetry of the Pc complexes. The five - level model rate equations were used to determine the two photon absorption, excited state absorption and ground state absorption cross sections of the synthesized complexes. The z inc A 3 B type asymmetrical Pc complexes gave the largest two photon absorption and 휎 푒 / 휎 푔 ratio values. This Pc complex could be used in future work to enhance the nonlinear response further by introducing nanomaterials and converting the Pc complex to a binuclear Pc. This work also reports on the density functional theory (DFT) calculations o f dipolar/octupolar contributions in order to study the first order hyperpolarizability of the synthesized Pc complexes.
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  • Date Issued: 2021

Synthesis, theoretical calculations and laser flash photolysis studies of selected amphiphilic porphyrin derivatives used as biofilm photodegradative materials

  • Authors: Openda, Yolande I , Ngoy, Bokolombe P , Muva, Jules T , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/190589 , vital:45008 , xlink:href="https://doi.org/10.1039/D1NJ02651H"
  • Description: Photodynamic antimicrobial activities of gallium and indium porphyrins as well as their quaternized derivatives have been investigated against S. aureus and E. coli biofilms, as well as on their planktonic (free floating) cells using a light emitting diode lamp at 415 nm. The studied photosensitizers show considerable ability to generate singlet oxygen and the quaternized molecules 2a and 3a are potential photodynamic antimicrobial chemotherapy (PACT) agents with log10 colony forming units >9 for E. coli and S. aureus planktonic cells. The quaternized derivatives are found to have higher ability to significantly suppress the biofilms of both S. aureus and E. coli in vitro. Therefore, this demonstrates that they are potentially suitable photosensitive agents for PACT use. The TD-B3LYP/LanL2DZ calculations were performed to evaluate the singlet excitation energies of quaternized and non-quaternized porphyrins in vacuo. Our study shows excellent agreement between time-dependent density-functional theory (TD-DFT) excited energies and experimental S1 > S0 excitation energies. The small deviation observed between the calculated and experimental spectra arises from the solvent effect. The excitation energies observed in these UV-visible spectra mostly originated from electron promotion between the highest occupied molecular orbital (HOMO) for the less intense band and the HOMO−1 for the most intense band of the ground states to the lower unoccupied molecular orbital (LUMO) of the excited states.
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  • Date Issued: 2021

T Kondo (Ed) law and investment in Africa: the fovernance of foreign direct investment in Zimbabwe

  • Authors: Zongwe, Dunia P
  • Date: 2021
  • Subjects: Investments, Foreign -- Africa, Sub-Saharan , Zimbabwe -- Economic conditions , Corporate governance
  • Language: English
  • Type: text , review , article
  • Identifier: http://hdl.handle.net/11260/6387 , vital:45443 , xlink:href="http://dx.doi.org/10.17159/2077-4907/2021/ldd.v25.16 "
  • Description: Tinashe Kondo’s book, Law and investment in Africa, narrates the efforts of a country to regain the trust [and the love] of foreign investors after several decades of argument and hostility. Encapsulated in the “Zimbabwe is open for business” slogan, these efforts show “how a country can move to regain credibility and commit to global rules despite its recent history”. This review of Kondo’s book concerns the manner in which readers can take advantage of this immensely useful publication. Particularly, this review looks into the book in order to advise law academics on possible strategies to integrate the book into their curricula in Zimbabwe and elsewhere on the continent.
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  • Date Issued: 2021

Terminaliamide, a new ceramide and other phytoconstituents from the roots of Terminalia mantaly H. Perrier and their biological activities

  • Authors: Mbosso, Emmanuel , Siwe-Noundou, Xavier , Fannang, Simon , Song, Achille M , Assob, Jules C N , Hoppe, Heinrich , Krause, Rui W M
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/191779 , vital:45163 , xlink:href="https://doi.org/10.1080/14786419.2019.1647425"
  • Description: Terminaliamide (1), a new ceramide was isolated from the roots of Terminalia mantaly H. Perrier (Combretaceae) along with 4 known compounds (2–5). The structures of the compounds were elucidated using 1D and 2D NMR spectroscopy analysis and mass spectrometry. Compound 1 exhibited moderated antibacterial activity towards Staphylococcus aureus with MIC value of 62.5 μg/mL. The crude MeOH extract (TMr) highly reduced Plasmodium falciparum growth with an IC50 value of 10.11 μg/mL, while hexane fraction (F1) highly reduced Trypanosoma brucei brucei growth with an IC50 value of 5.60 µg/mL. All tested samples presented little or no in vitro cytotoxicity on HeLa cell line. The present work confirms that T. mantaly is medicinally important and may be used effectively as an antimicrobial, an antiplasmodial and an antitrypanosomial with promising therapeutic index.
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  • Date Issued: 2021

Terminaliamide, a new ceramide and other phytoconstituents from the roots of Terminalia mantaly H. Perrier and their biological activities

  • Authors: Mbosso Teinkela, Jean E , Siwe-Noundou, Xavier , Fannang, Simone , Song, Achille M , Nguedia Assob, Jules C , Hoppe, Heinrich C , Krause, Rui W M
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/194095 , vital:45422 , xlink:href="https://doi.org/10.1080/14786419.2019.1647425"
  • Description: Terminaliamide (1), a new ceramide was isolated from the roots of Terminalia mantaly H. Perrier (Combretaceae) along with 4 known compounds (2–5). The structures of the compounds were elucidated using 1D and 2D NMR spectroscopy analysis and mass spectrometry. Compound 1 exhibited moderated antibacterial activity towards Staphylococcus aureus with MIC value of 62.5 μg/mL. The crude MeOH extract (TMr) highly reduced Plasmodium falciparum growth with an IC50 value of 10.11 μg/mL, while hexane fraction (F1) highly reduced Trypanosoma brucei brucei growth with an IC50 value of 5.60 µg/mL. All tested samples presented little or no in vitro cytotoxicity on HeLa cell line. The present work confirms that T. mantaly is medicinally important and may be used effectively as an antimicrobial, an antiplasmodial and an antitrypanosomial with promising therapeutic index.
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  • Date Issued: 2021

The antibacterial and antifungal properties of neutral, octacationic and hexadecacationic Zn phthalocyanines when conjugated to silver nanoparticles

  • Authors: Mapukata, Sibusisiwe , Sen, Pinar , Osifeko, Olawale L , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185667 , vital:44408 , xlink:href="https://doi.org/10.1016/j.pdpdt.2021.102361"
  • Description: The syntheses and characterization of novel octacationic and hexadecacationic Pcs is reported. With the aim of enhancing singlet oxygen generation efficiencies and hence antimicrobial activities, these Pcs (including their neutral counterpart) are conjugated to Ag nanoparticles (AgNPs). The obtained results show that the conjugate composed of the neutral Pc has a higher loading of Pcs as well as a greater singlet oxygen quantum yield enhancement (in the presence of AgNPs) in DMSO. The antimicrobial efficiencies of the Pcs and their conjugates were evaluated and compared on S. aureus, E. coli and C. albicans. The cationic Pcs possess better activity than the neutral Pc against all the microorganisms with the hexadecacationic Pc being the best. This work therefore demonstrates that increase in the number of cationic charges on the reported Pcs results in enhanced antimicrobial activities, which is maintained even when conjugated to Ag nanoparticles. The high activity and lack of selectivity of the cationic Pcs when conjugated to Ag NPs against different microorganisms make them good candidates for real life antimicrobial treatments.
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  • Date Issued: 2021

The antibody assisted detection of HER2 on a cobalt porphyrin binuclear framework and gold functionalized graphene quantum dots modified electrode

  • Authors: Centane, Sixole , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185931 , vital:44449 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.114908"
  • Description: In this work a novel simple, inexpensive and highly sensitive approach for the antibody assisted detection of the human epidermal growth factor receptor 2 (HER2) is presented. Three sensors using carboxylic group containing gold functionalized graphene quantum dots (SNGQDs@AuNPs), CoP-BNF (cobalt porphyrin binuclear framework) and CoP-BNF/SNGQDs@AuNPs (the conjugate) nanocomposites on a GCE were designed. The sensors were fabricated by covalent immobilization of the antibody to the GCE via an amide bond. The modified GCE was characterized using cyclic voltammetry and impedance spectroscopy. The performance of the sensors was assessed using electrochemical impedance spectroscopy. The selective recognition of the antibody towards HER2 on the electrode led to an increase of the electron transfer resistance (Rct). The different modified electrodes had low detection limit values: 0.0327 ng/mL, 0.0454 ng/mL and 0.1072 ng/mL towards the detection of HER2. The sensors showed good stability and reproducibility. The sensors showed promising potential in clinical applicability, in the detection of HER2 protein in human serum.
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  • Date Issued: 2021

The application of human factors and ergonomics (HFE) to community-sport organisations in resource scarce contexts: a case study of grassroots football in Makana, Eastern Cape

  • Authors: Bennett, Ryan
  • Date: 2021
  • Subjects: Makana Local Football Association (South Africa) , Human engineering , Soccer teams -- South Africa -- Makhanda -- Management , Soccer -- Management -- South Africa
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/172412 , vital:42198 , 10.21504/10962/172412
  • Description: Background: Modern Human Factors and Ergonomics (HFE) focuses on the optimisation of complex socio-technical systems and has been challenged to contribute to broader societal issues. An example is within grassroots football organisations in resource-scarce areas such as Makana, South Africa. Through embedded participatory approaches, the research problem was co-constructed: To investigate the socio-technical system of the Makana Local Football Association (LFA). Method: A useful complex system modelling tool is that of Cognitive Work Analysis (CWA), with its 5 phases used to identify constraints and affordances. Three perspectives were adopted for the application of an adapted (to suit participant characteristics) CWA to the Makana LFA: 1) how work is prescribed by the governing body SAFA, 2) how subject matter experts (SME) disclose its current functioning, and 3) how SMEs imagine it could function. Five SMEs attended 12 three-hour workshops to complete the latter two perspectives. Results: The composite work domain analysis between work as prescribed and work as disclosed identified significant mismatches between how policymakers envision the system and how SMEs report its functioning. Key differences in perspectives included the fundamental purpose of the Makana LFA, while only four of 22 functions operate within the Makana LFA. Participants also identified key affordances for the LFA such as reorientation as a community sports organisation. Discussion: Comparison between perspectives indicated four mismatches. 1) SAFA views the LFA as the foundation of the talent identification and development infrastructure of South African football. SMEs view it as a community centred organisation. 2) A lack of human capacity is evident at the community level of Makana football. 3) Funding and assets are absent at this grassroots level. 4) The LFA relies on other stakeholders, but these relationships are not formalised. Policymakers, therefore, have a lack of knowledge of the contextual challenges faced by LFA administrators. It is recommended that SAFA view the LFA as a community sport organisation, focusing on improving human capacity, increasing funding, and formalising stakeholder networks. Furthermore, conceptual models from CWA provide explicit socio-technical system redesign recommendations. Conclusion: Large mismatches between the organising body SAFA and the actual functioning of the LFA significantly hinder the effective management and running of football at a grassroots level in resource-scarce contexts in South Africa. The perspectives approach to CWA was useful in elucidating the constraints and affordances of the Makana LFA socio-technical system and informing redesign opportunities. Systems HFE methodology is therefore well placed to contribute to broader societal issues within resources scarce contexts such as football in Makana. Furthermore, the philosophical underpinnings of systems based HFE were successful in the development of sustainable participatory research within the South African grassroots football context.
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  • Date Issued: 2021

The changing nature of work: understanding precarity and the gendered individualisation of risk in post-apartheid South Africa

  • Authors: Mhlana, Siviwe
  • Date: 2021
  • Subjects: Precarious employment , Labor supply -- South Africa , Labor supply -- Statistics -- South Africa , Precarious employment -- South Africa , Informal sector (Economics) -- Employees -- South Africa , Women employees -- South Africa , Women temporary employees -- South Africa
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10962/172146 , vital:42170
  • Description: Against the backdrop of workplace restructuring globally, post-Apartheid South Africa is experiencing consistently high levels of unemployment, the deterioration of employment security, and limited improvements in earnings. This trend in the proliferation of low-paid, unstable and otherwise insecure employment has given rise to a segment of the literature that is centred on the growing precariousness of work in a number of different contexts. This thesis reviews empirical work on the changing nature of labour-intensive production in the past two decades, with particular focus on the trends in non-standard, informal and precarious employment. Further, the thesis examines the shift in the gender structure of South Africa’s manufacturing sector and how it affects the share in the benefits of employment, particularly with regard to social reproduction. In so doing, the thesis expands the critical theoretical narrative about the challenges of labour under neoliberalism by providing an intersectional perspective of precarious work in post- Apartheid South Africa.
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  • Date Issued: 2021

The complex relationship between asset wealth, adaptation, and diversification in tropical fisheries

  • Authors: Taylor, Sarah F , Aswani, Shankar , Jiddawi, Narriman , Coupland, Jack , James, Phillip , Kelly, Stephen , Kizenga, Hellen , Roberts, Michael , Popova, Ekaterina
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/403475 , vital:69964 , xlink:href="https://doi.org/10.1016/j.ocecoaman.2021.105808"
  • Description: Marine small-scale fisheries are complex social and ecological systems that are currently pressurised by climate change, increasing demand for food, and expectation to sustain livelihoods. Species diversification and occupational diversification are often offered as adaptation strategies to increase the resilience of these fisheries to natural and economic shocks. However, little is known about the nature of species diversification within marine tropical fisheries. Based on 293 interviews with artisanal fishers from six coastal communities located at the isles of Zanzibar, Pemba, Mafia, and Mainland Tanga in Tanzania - we assess if fishers with the highest level of species diversification are the most financially secure and able to adapt to changes in the fishing industry. By creating an Asset Wealth Index (AWI) based on a Multiple Correspondence Approach (MCA), we investigate the relative levels of adaptive capacity and fishery connectivity within the different regional wealth quartiles. We find that less wealthy fishers target fewer species, making them less able to absorb changes in management measures focused on species, area, and closures. Likewise, fishers with higher wealth scores and higher adaptive capacity are able to better absorb the short-term losses of fisheries closures when compared to those with lower wealth and adaptive scores reliant on higher levels of fishery connectivity.
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  • Date Issued: 2021

The cultural significance of plant-fiber crafts in Southern Africa: a comparative study of Eswatini, Malawi, and Zimbabwe

  • Authors: Pullanikkatil, Deepa , Thondhlana, Gladman , Shackleton, Charlie M
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/399860 , vital:69564 , xlink:href="https://doi.org/10.1080/14728028.2021.1998797"
  • Description: Traditional handicrafts made from various plant materials are produced by most cultures around the world. Many originated through symbolic and utilitarian needs that became ritualized through time, thereby gradually attaining greater value as cultural items or symbols rather than solely functional ones. Here we report on a survey of 343 crafters across Eswatini, Malawi, and Zimbabwe in southern Africa regarding the cultural uses and significance of the items they make from wild plant fibers and sell to local communities or tourists. The plant materials used were largely dictated by tradition and local availability and were crafted into a diverse range of products including baskets, mats, brooms, storage containers, hats, fish traps, ornaments, and furniture. Many products had uses and cultural significance at major ceremonies or rituals, such as weddings, funerals, initiation, and divination. The preparation and design of the different crafts were influenced by tradition as well as market demand as indicated by tourist fashions and advice provided by government or non-government agencies to boost income generation from crafts. Although the crafting of cultural objects is increasingly commercialized and subject to the tastes and fashions of tourist markets in the region, the traditional and cultural significance of such artifacts remains widely recognized and valued.
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  • Date Issued: 2021

The distribution of selected woody invasive alien species in small towns in the Eastern Cape, South Africa

  • Authors: Mabusela, A , Shackleton, Charlie M , Gewdla, Nanamhla
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/401289 , vital:69723 , xlink:href="https://doi.org/10.1016/j.sajb.2021.05.019"
  • Description: The potential and real negative and positive effects of invasive alien species (IAS) are increasingly recognised by researchers, land managers and decision-makers. However, most of the research and knowledge stems from understandings developed from rural and natural landscapes, with relatively little derived from studies in urban settings. Small towns in particular pose a novel suite of conditions that make the study and mangment of IAS particularly pressing. Here we examined the distribution of seven woody IAS (Acacia mearnsii, Cestrum laevigatum, Eucalyptus spp., Lantana camara, Melia azedarach, Senna didymobotrya and Solanaum mauritianum) within and between five small towns in the Eastern Cape via means of drive-by road surveys of every street in each town. Across the five towns and seven IAS 4,307 individuals were recorded, with the highest densities found in the two more coastal towns. Almost two-thirds (63%) of the IAS were located in residential properties, 24 % in public spaces and 13 % on road verges, closely mirroring the proportional area of these landuses. Within the residential landuse zone specifically, the townships had between 41 % and 61 % of all the recorded IAS plants per town, followed by the affluent neighbourhoods (22 – 41 %) and lastly, the RDP neighbourhoods (6 – 32 %). Cestrum laevigatum was the most abundant woody IAS across the five towns as a whole (1,783 inviduals). The second-most abundant species was M. azedarach (914 stems) and the least recorded was S. mauritianum (44). Additionally, there were differences in the general distribution of the seven species across residential neighbourhoods, with C. laevigatum (71.2 %), M. azedarach (49.3 %) and S. mauritianum (60.0 %) concentrated in township neighbourhoods, whilst A. mearnsii (66.4 %), L. camara (64.1 %) and Eucalyptus spp. (48.6 %) were most common in the affluent neighbourhoods. This study confirms that woody IAS are widespread in small towns of the region, but that they are unevenly distributed between towns and landuses within towns, indicating the need for local-scale inventories and management.
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  • Date Issued: 2021

The effect of habitat and spatial management on reef fish in an established marine protected area

  • Authors: Dames, Vivienne Abigail
  • Date: 2021
  • Subjects: iSimangaliso Wetland Park (South Africa) -- Management , Reef fishes -- South Africa -- KwaZulu-Natal , Baited remote underwater stereo-video systems (stereo-BRUVs) , Marine parks and reserves -- Monitoring -- South Africa -- KwaZulu-Natal , Fish populations -- Measurement
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/171150 , vital:42024
  • Description: The persistence of harvested fish populations in the Anthropocene will be determined, above all, by how they respond to the interacting effects of climate change and fisheries exploitation. Predicting how populations will respond to both these threats is essential for any adaptive and sustainable management strategy. The response of fish populations to climate change is underpinned by physiological rates and tolerances, and emerging evidence suggests there may be physiological-based selection in capture fisheries. By quantifying important physiological rates of a model species, the endemic seabream, Chrysoblephus laticeps, across ecologically relevant thermal gradients and from populations subjected to varying intensities of commercial exploitation, this thesis aimed to 1) provide the first physiologically grounded climate resilience assessment for a South African linefish species, and 2) elucidate whether exploitation can drive populations to less physiologically resilient states in response to climate change. To identify physiologically limiting sea temperatures and to determine if exploitation alters physiological trait distributions, an intermittent flow respirometry experiment was used to test the metabolic response of spatially protected and exploited populations of C. laticeps to acute thermal variability. Exploited populations showed reduced metabolic phenotype diversity, fewer high-performance aerobic scope phenotypes, and a significantly lower aerobic scope curve across all test temperatures. Although both populations maintained a relatively high aerobic scope across a wide thermal range, their metabolic rates were compromised when extreme cold events were simulated (8 °C), suggesting that predicted future increases in upwelling frequency and intensity may be the primary limiting factor in a more thermally variable future ocean. The increment widths of annuli in the otoliths of C. laticeps from contemporary and historic collections were measured, as a proxy for the annual growth rate of exploited and protected populations. Hierarchical mixed models were used to partition growth variation within and among individuals and ascribe growth to intrinsic and extrinsic effects. The best model for the protected population indicated that the growth response of C. laticeps was poorer during years characterised by a high cumulative upwelling intensity, and better during years characterised by higher mean autumn sea surface temperatures. The exploited population growth chronology was too short to identify an extrinsic growth driver. The growth results again highlight the role of thermal variability in modulating the response of C. laticeps to its ambient environment and indicate that the predicted increases in upwelling frequency and intensity may constrain future growth rates of this species. A metabolic index (ϕ), representing the ratio of O2 supply to demand at various temperatures and oxygen concentrations, was estimated for exploited and protected populations of C. laticeps and used to predict future distribution responses. There was no difference in the laboratory calibrations of ϕ between populations, and all data was subsequently combined into a single piecewise (12 °C) calibrated ϕ model. To predict the distribution of C. laticeps, ϕ was projected across a high-resolution ocean model of the South African coastal zone, and a species distribution model implemented using the random forest algorithm and C. laticeps occurrence points. The future distribution of C. laticeps was estimated by predicting trained models across ocean model projections up to 2100. The best predictor of C. laticeps’ current distribution was minimum monthly ϕ and future predictions indicated only a slight range contraction on either edge of C. laticeps’ distribution by 2100. In order to provide policy makers, currently developing climate change management frameworks for South Africa’s ocean, with a usable output, the results of all research chapters were combined into a marine spatial model. The spatial model identified areas where C. laticeps is predicted to be resilient to climate change in terms of physiology, growth and distribution responses, which can then be prioritised for adaptation measures, such as spatial protection from exploitation. While these results are specific to C. laticeps, the methodology developed to identify areas of climate resilience has broad applications across taxa. From a global perspective, perhaps the most salient points to consider from this case study are the evidence of selective exploitation on physiological traits and the importance of environmental variability, rather than long-term mean climate changes, in affecting organism performance. These ideas are congruent with the current paradigm shift in how we think of the ocean, selective fisheries, and how they relate to organism climate resilience.
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  • Date Issued: 2021

The effects of elevated atmospheric CO2 concentration on the biological control of invasive aquatic weeds

  • Authors: Baso, Nompumelelo C , Coetzee, Julie A , Ripley, Brad S , Hill, Martin P
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/419423 , vital:71643 , xlink:href="https://doi.org/10.1016/j.aquabot.2020.103348"
  • Description: There has been a rapid increase in atmospheric CO2 concentration, from pre-industrial values of 280 ppm to more than 400 ppm currently, and this is expected to double by the end of the 21st century. Studies have shown that plants grown at elevated CO2 concentrations have increased growth rates and invest more in carbon-based defences. This has important implications for the management of invasive alien plants, especially using biological control which is mostly dependent on herbivorous insects. The aim of this study was to investigate the effects of elevated atmospheric CO2 on the biological control of four invasive aquatic weeds (Azolla filiculoides, Salvinia molesta, Pistia stratiotes and Myriophyllum aquaticum). These species are currently under successful control by their respective biological control agents (Stenopelmus rufinasus, Cyrtobagous salviniae, Neohydronomus affinis, and Lysathia sp.) in South Africa. The plant species were grown in a two factorial design experiment, where atmospheric CO2 concentrations were set at ambient (400 ppm) or elevated (800 ppm), and plants were either subjected to or not subjected to herbivory by their target biological control agents. There was an overall increase in biomass production and C:N across all species at elevated CO2, both in the absence and presence of biological control, although C:N of M. aquaticum and biomass of A. filiculoides with herbivory were not constant with this trend. Insect feeding damage was reduced by elevated CO2, except for S. molesta. Thus, we can expect that plants will respond differently to CO2 increase, but the general trend suggests that these species will become more challenging to manage through biological control in future.
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  • Date Issued: 2021

The effects of supply chain cooperation on humanitarian relief operations: A case of Cyclone Idai in Zimbabwe

  • Authors: Chari, Felix , Muzinda, Ozwell , Novukela, Cawe , Ngcamu, Bethuel S.
  • Date: 2021
  • Subjects: Cyclone damage Business logistics Article
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/11260/7155 , vital:53076 , xlink:href="https://doi.org/10.4102/jtscm.v15i0.532"
  • Description: Background: The increased frequency of occurrence and complexity of disasters, the world over, have called for increased cooperation amongst stakeholders to deliver humanitarian aid. Objectives: This study came as a result of the growing interest focussed on creating and implementing cooperation to facilitate management of supply chain-related activities in the humanitarian sector. This study therefore sought to gain a better understanding of the effectiveness of supply chain cooperation in aid delivery performance variables, specifically in the context of Cyclone Idai humanitarian relief operations in Zimbabwe. Method: A pragmatic research paradigm was adopted, where the researchers took a mixed approach informed by both quantitative and qualitative research tools. Results: Findings of this study show a significant and positive impact of humanitarian supply chain (HSC) cooperation in achieving output, resource and flexibility performance in the delivery of aid. These findings will change the shape of humanitarian response to have more cooperation amongst organisations rather than responding as single entities. Conclusion: This study will therefore contribute to how humanitarian organisations improve their approach to future disasters through cooperation in their supply chain activities. Theoretically, the study will show how supply chain cooperation is key to humanitarian responses, thus improving effectiveness of HSC when put into practice. Policymakers can use these findings to develop a standard framework of how humanitarian organisations should collectively respond to disasters. Keywords: cyclone; humanitarian logistics; relief operations; supply chain; supply chain cooperation.
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  • Date Issued: 2021

The effects of the composition and structure of quantum dots combined with cobalt phthalocyanine and an aptamer on the electrochemical detection of prostate specific antigen

  • Authors: Nxele, Siphesihle R , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185002 , vital:44315 , xlink:href="https://doi.org/10.1016/j.dyepig.2021.109407"
  • Description: The ability to functionalize and modify graphene-based quantum dots has also allowed for the tuning of their activity in different applications. A comparative study is carried out in this work where a prostate specific aptamer (PSA) and cobalt phthalocyanine molecule are combined with graphene quantum dots (GQDs), nitrogen doped graphene quantum dots (NGQDs) and graphitic carbon nitride quantum dots (gCNQDs) in order to determine the effects of quantum dots type (and therefore composition) on the electrocatalytic ability of the sensor to detect the analyte of interest. For the detection of prostate-specific antigen, electrochemical impedance spectroscopy (EIS) is employed to determine detection limits as well as sensitivity and selectivity of the aptasensors. Results showed a good performance of all sensors fabricated with the NGQDs based aptasensor showing the best performance with a detection limit of 1.54 pM in EIS as well as negligible interference in mixed samples. This electrode was further verified in spiked human serum samples and good recovery and low detection limits were determined, putting this aptasensor in good stead as a reliable, efficient PSA aptasensor.
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  • Date Issued: 2021

The electrocatalytic response of metallophthalocyanines when clicked to electrodes and to nanomaterials

  • Authors: Mpeta, Lekhetho Simon
  • Date: 2021
  • Subjects: Phthalocyanines , Nanostructured materials , Electrocatalysis , Nanoparticles , Environmental chemistry , Electrodes , Organic wastes -- Purification
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/172191 , vital:42174 , 10.21504/10962/172191
  • Description: Conjugates of nanomaterials and metallophthalocyanines (MPcs) have been prepared and their electrocatalytic activity studied. The prepared nanomaterials are zinc oxide and silver nanoparticles, reduced graphene oxide nanosheets and semiconductor quantum dots. The MPcs used in this work are cobalt (II) (1a), manganese(III) (1b) and iron (II) (1c) 2,9(10),16(17),23(24)- tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyaninato, 2,9(10),16(17),23(24)- tetrakis(5-pentyn-oxy) cobalt (II) phthalocyaninato (2), 9(10),16(17),23(24)- tris-[4-tert-butylphenoxy)-2- (4-ethylbezyl-oxy) cobalt (II) phthalocyaninato (3), 9(10),16(17),23(24)- tris-[4-tertbutylphenoxy)-2-(pent-4yn-yloxy)] cobalt (II) phthalocyaninato (4), cobalt (II) (5a) and manganese (III) (5b) 2,9(10),16(17),23(24)- tetrakis [4-(4-(5-chloro-1H-benzo [d]imidazol-2-yl)phenoxy] phthalocyaninato and 9(10),16(17),23(24)- tris tert butyl phenoxy- 2- [4-(4-(5-chloro-1H-benzo[d]imidazole-2-yl)phenoxy] cobalt (II) phthalocyaninato (6). Some of these MPcs (1a, 3 and 4) were directly clicked on azide grafted electrode, while some (1b, 1c, 2, 5a and 5b) were clicked to azide functionalised nanomaterials and then drop-dried on the electrodes. One phthalocyanine (5b) was drop-dried on the electrode then silver nanoparticles were electrodeposited on it taking advantage of metal-N bond. Scanning electrochemical microscopy, voltammetry, chronoamperometry, electrochemical impedance spectroscopy are among electrochemical methods used to characterise modified electrodes. Transmission electron microscopy, X-ray photoelectron spectroscopy, Xray diffractometry, Raman spectroscopy and infrared spectroscopy were employed to study surface functionalities, morphology and topography of the nanomaterials and complexes. Electrocatalytic activity of the developed materials were studied towards oxidation of 2-mercaptoethanol, hydrazine and hydrogen peroxide while the reduction study was based on oxygen and hydrogen peroxide. In general, the conjugates displayed superior catalytic activity when compared to individual materials. Complex 2 alone and when conjugated to zinc oxide nanoparticles were studied for their nonlinear optical behaviour. And the same materials were explored for their hydrazine detection capability. The aim of this study was to develop sensitive, selective and affordable sensors for selected organic waste pollutants. Conjugates were found to achieve the aim of the study compared to when individual materials were employed.
  • Full Text:
  • Date Issued: 2021

The electrochemical detection of prostate specific antigen on glassy carbon electrode modified with combinations of graphene quantum dots, cobalt phthalocyanine and an aptamer

  • Authors: Nxele, Siphesihle R , Nyokong, Tebello
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185013 , vital:44316 , xlink:href="https://doi.org/10.1016/j.jinorgbio.2021.111462"
  • Description: Herein, a novel aptasensor is developed for the electrochemical detection of prostate specific antigen (PSA) on electrode surfaces modified using various combinations of a Cobalt phthalocyanine (CoPc), an aptamer and graphene quantum dots (GQDs). Electrochemical impedance spectroscopy (EIS) as well as differential pulse voltammetry (DPV) are employed for the detection of PSA. In both analytical techniques, linear calibration curves were observed at a concentration range of 1.2–2.0 pM. The glassy carbon electrode where CoPc and GQDs are placed on the electrode when non-covalently linked followed by addition of the aptamer (GQDs-CoPc(ππ)-aptamer (sequential)) showed the best performance with a limit of detection (LoD) as low as 0.66 pM when using DPV. The detection limits were much lower than the dangerous levels reported for PSA in males tested for prostate cancer. This electrode showed selectivity for PSA in the presence of bovine serum albumin, glucose and L-cysteine. The aptasensor showed good stability, reproducibility and repeatability, deeming it a promising early detection device for prostate cancer.
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  • Date Issued: 2021

The hermeneutics of recovery

  • Authors: Kong, Camillia , Campbell, Megan , Kpobi, Lily , Swartz, Leslie , Atuire, Caesar
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/302554 , vital:58207 , xlink:href="https://doi.org/10.1177/13634615211000549"
  • Description: The widespread use of faith-based and traditional healing for mental disorders within African contexts is well known. However, normative responses tend to fall within two camps: on one hand, those oriented towards the biomedical model of psychiatry stress the abuses and superstition of such healing, whilst critics adopting a more ‘local’ perspective have fundamentally challenged the universalist claims of biomedical diagnostic categories and psychiatric treatments. What seemingly emerges is a dichotomy between those who endorse more ‘universalist’ or ‘relativist’ approaches as an analytical lens to the challenges of the diverse healing strands within African contexts. In this article, we draw upon the resources of philosophy and existing empirical work to challenge the notion that constructive dialogue cannot be had between seemingly incommensurable healing practices in global mental health. First, we suggest the need for much-needed conceptual clarity to explore the hermeneutics of meaning, practice, and understanding, in order to forge constructive normative pathways of dialogue between seemingly incommensurable values and conceptual schemas around mental disorder and healing. Second, we contextualise the complex motives to emphasise difference amongst health practitioners within a competitive healing economy. Finally, we appeal to the notion of recovery as discovery as a fruitful conceptual framework which incorporates dialogue, comparative evaluation, and cross-cultural enrichment across divergent conceptualisations of mental health.
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  • Date Issued: 2021
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