Electrocatalytic activity of ethynylbenzyl phthalocyanines when linked to quantum dots via click chemistry: Towards efficient oxygen reduction reaction and H2O2 oxidation
- Authors: Mpeta, Lekhetho S , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187037 , vital:44558 , xlink:href="https://doi.org/10.1016/j.jelechem.2019.03.064"
- Description: This work describes the conjugation of Co, Mn and Fe tetra ethynyl benzyl phthalocyanines to CdTe/ZnS quantum dots via click chemistry. The synthesized conjugates were then immobilised on glassy carbon electrode and their electrocatalytic activity towards hydrogen peroxide oxidation and oxygen reduction investigated. CoPc (1)-QDs showed superior electrocatalytic behaviour towards hydrogen peroxide catalysis with sensitivity of 2.8 × 105 μA/mM and limit of detection of 0.023 μM. On the other hand, FePc(3)-QDs showed the best oxygen reduction activity involving a direct 4-electron mechanism.
- Full Text:
- Date Issued: 2019
Employing the Processing Capability of Mixing Consoles and Audio Interfaces to Spatialize Sound:
- Authors: Foss, Richard
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426758 , vital:72389 , https://www.aes.org/e-lib/browse.cfm?elib=22211
- Description: Many audio interfaces and all mixing consoles have signal mixing capabilities. This paper describes an immersive sound system that employs these capabilities in order to spatialise sound sources, where these sources could be any of the inputs to these mix-capable devices. Graphic spatialisation control is provided on client devices, and 3D coordinates are sent to a server. The server uses these coordinates and speaker positions to render mix level and reverb parameter values. These values are sent to the mixer device using a control protocol. Advantages of this approach are that all inputs can be spatialised, and low-level processing is offloaded from the computer.
- Full Text:
- Date Issued: 2019
Encapsulation of isoniazid-conjugated phthalocyanine-In-cyclodextrin-in-liposomes using heating method
- Authors: Nkanga, Christian I , Krause, Rui W M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193999 , vital:45414 , xlink:href="https://doi.org/10.1038/s41598-019-47991-y"
- Description: Liposomes are reputed colloidal vehicles that hold the promise for targeted delivery of anti-tubercular drugs (ATBDs) to alveolar macrophages that host Mycobacterium tuberculosis. However, the costly status of liposome technology, particularly due to the use of special manufacture equipment and expensive lipid materials, may preclude wider developments of therapeutic liposomes. In this study, we report efficient encapsulation of a complex system, consisting of isoniazid-hydrazone-phthalocyanine conjugate (Pc-INH) in gamma-cyclodextrin (γ-CD), in liposomes using crude soybean lecithin by means of a simple organic solvent-free method, heating method (HM). Inclusion complexation was performed in solution and solid-state, and evaluated using UV-Vis, magnetic circular dichroism, 1H NMR, diffusion ordered spectroscopy and FT-IR. The HM-liposomes afforded good encapsulation efficiency (71%) for such a large Pc-INH/γ-CD complex (PCD) system. The stability and properties of the PCD-HM-liposomes look encouraging; with particle size 240 nm and Zeta potential −57 mV that remained unchanged upon storage at 4 °C for 5 weeks. The release study performed in different pH media revealed controlled release profiles that went up to 100% at pH 4.4, from about 40% at pH 7.4. This makes PCD-liposomes a promising system for site-specific ATBD delivery, and a good example of simple liposomal encapsulation of large hydrophobic compounds.
- Full Text:
- Date Issued: 2019
Engagement in local social-ecological knowledge practices in a seasonal cycles approach for transitioning to future sustainability
- Authors: O'Donoghue, Rob B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387971 , vital:68294 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/186419"
- Description: This paper explores climate as variable natural forces driving seasonal cycles1 that many African cultures had adjusted themselves to within intergenerational knowledge practices of longue durée. The study points to the need to re-orientate and expand climate science education so that it is centred on the seasonal cycles and intergenerational learning to better align transitioning to future sustainability with these in our southern African contexts of climate change today. The narrative touches upon historical accounts of knowledge practices amongst the Krobo, Bemba, Shona, Zulu and Xhosa, briefly pointing to how each, as an African culture, is situated as a social-ecological entity within the climatic tapestries of our African landscapes. It takes note of how cultural articulation within the seasonal cycles of regional climate have a long history with adaptive change in some contexts in more recent times. The review suggests that our learning in relation to emerging climate change should be informed by these histories of intergenerational knowledge practice. It notes how a better grasp of these could be important drivers of a widening cultural response to the changing dynamics in our climatic surroundings today. The brief study suggests that southern Africa is a special place with many unique and interesting climatic processes and associated socio-ecological systems and practices. These can provide engaging perspectives for informing education to mitigate or adapt to climate change. Here, a situated exploration of seasonal cycles can draw on both the latest in modern climate science and the rich social-ecological heritage of Africa briefly touched upon in the study. A model of process is offered for how both can be used in a seasonal cycles approach climate change education. This better situated and more inclusive approach can enable us to contemplate how we might best adjust our social-ecological dispositions and practices in the changing world that we all share.
- Full Text:
- Date Issued: 2019
Environmental niche patterns of native and non-native fishes within an invaded African river system
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124407 , vital:35605 , https://doi.10.1111/jfb.13988
- Description: To test ecological niche theory, this study investigated the spatial patterns and the environmental niches of native and non-native fishes within the invaded Great Fish River system, South Africa. For the native fishes, there were contrasting environmental niche breadths that varied from being small to being large and overlapped for most species, except minnows that were restricted to headwater tributaries. In addition, there was high niche overlap in habitat association among fishes with similar distribution. It was therefore inferred that habitat filtering-driven spatial organization was important in explaining native species distribution patterns. In comparison, most non-native fishes were found to have broad environmental niches and these fishes showed high tolerance to environmental conditions, which generally supported the niche opportunity hypothesis. The proliferation of multiple non-native fishes in the mainstem section suggest that they form a functional assemblage that is probably facilitated by the anthropogenic modification of flow regimes through inter-basin water transfer. Based on the distribution patterns observed in the study, it was inferred that there was a likelihood of negative interactions between native and nonnative fishes. Such effects are likely to be exacerbated by altered flow regime that was likely to have negative implications for native ichthyofauna.
- Full Text:
- Date Issued: 2019
Establishing computational approaches towards identifying malarial allosteric modulators: a case study of plasmodium falciparum hsp70s
- Authors: Amusengeri, Arnold , Astl, Lindy , Lobb, Kevin A , Verkhivker, Gennady M , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163000 , vital:41003 , https://doi.org/10.3390/ijms20225574
- Description: Combating malaria is almost a never-ending battle, as Plasmodium parasites develop resistance to the drugs used against them, as observed recently in artemisinin-based combination therapies. The main concern now is if the resistant parasite strains spread from Southeast Asia to Africa, the continent hosting most malaria cases. To prevent catastrophic results, we need to find non-conventional approaches. Allosteric drug targeting sites and modulators might be a new hope for malarial treatments. Heat shock proteins (HSPs) are potential malarial drug targets and have complex allosteric control mechanisms. Yet, studies on designing allosteric modulators against them are limited. Here, we identified allosteric modulators (SANC190 and SANC651) against P. falciparum Hsp70-1 and Hsp70-x, affecting the conformational dynamics of the proteins, delicately balanced by the endogenous ligands. Previously, we established a pipeline to identify allosteric sites and modulators. This study also further investigated alternative approaches to speed up the process by comparing all atom molecular dynamics simulations and dynamic residue network analysis with the coarse-grained (CG) versions of the calculations. Betweenness centrality (BC) profiles for PfHsp70-1 and PfHsp70-x derived from CG simulations not only revealed similar trends but also pointed to the same functional regions and specific residues corresponding to BC profile peaks.
- Full Text:
- Date Issued: 2019
Evaluation of the photosensitizing properties of zinc and indium tetra cinnamic acid phthalocyanines linked to magnetic nanoparticles on human breast adenocarcinoma cells
- Authors: Matlou, Gauta G , Oluwole, David O , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187582 , vital:44673 , xlink:href="https://doi.org/10.1016/j.jlumin.2018.09.054"
- Description: This work reports on the synthesis, photophysico-chemical properties and photodynamic therapy activity of novel zinc (1) and indium (2) tetra substituted cinnamic acid phthalocyanine (Pc) complexes linked to amino functionalized magnetic nanoparticles (AMNPs) through an amide bond. Asymmetric ZnPc complex (3) showed better triplet and singlet oxygen quantum yields as compared to its symmetrical analogues (1 and 2). The AMNPs (1-AMNPs and 2-AMNPs) linked conjugates depicted increased triplet quantum yields in comparison to their unlinked Pcs, while 3-AMNPs showed a decrease compared to 3. The complexes showed increased in-vitro photo-cytotoxic effect against MCF-7 cells with an increase in drug concentration. At 80 µg/mL, 2 and 3, 2-AMNPs and 3-AMNPs with higher singlet oxygen quantum yields caused more cytotoxic effect on the cancer cells in the presence of light as compared to 1 and 1-AMNPs respectively.
- Full Text:
- Date Issued: 2019
Excavating the South African teacher leadership archive
- Authors: Grant, Carolyn
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281051 , vital:55687 , xlink:href="https://doi.org/10.1177/1741143217717274"
- Description: In established democracies, the notion of ‘singular’ school leadership practised by the principal has been challenged and a more expansive approach to leadership which includes the practice of teacher leadership is now widely accepted by practitioners and researchers alike. In contrast, in emerging democracies the practice of teacher leadership is less obvious, despite the embeddedness of the concept in policy discourse. This article takes South Africa as its case and reviews literature on teacher leadership in this emerging African democracy. It draws on published articles and unpublished postgraduate theses with a specific teacher leadership focus and loosely adopts the format of two previously published comprehensive literature reviews in organising its findings. Similar to the findings of these two literature reviews, this South African archive also shows that the majority of research in this domain is conspicuously descriptive rather than explanatory, largely atheoretical and overly reliant on small case study design. In response, this article argues that teacher leadership research must continue to be undertaken in emerging democracies but with far greater use made of critical methodologies underpinned by relevant social theory.
- Full Text:
- Date Issued: 2019
Exhibition review: Site of memory: Berni Searle’s-aplace-in-the-sun
- Authors: Muvhuti, Barnabas , Zhang, Lifang
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/146937 , vital:38578 , https://artthrob.co.za/2019/07/31/site-of-memory-berni-searles-a-place-in-the-sun/
- Description: Commissioned by the National Arts Festival, Berni Searle created a four-screen multi-channel video installation, A Place in the Sun, which cooperated perfectly with the four wall compartments of the rotunda-shaped Gallery in the Round in the basement of the 1820 Settlers Monument. With the shifting of lights, the video symbolically indicates a full day at a drained swimming pool, from morning to sunset until the whole scene turns into ashes and darkness.
- Full Text:
- Date Issued: 2019
Expansive Social Learning, Morphogenesis and Reflexive Action in an Organization Responding to Wetland Degradation
- Authors: Lindley, David S , Lotz-Sisitka, Heila
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182450 , vital:43831 , xlink:href="https://doi.org/10.3390/su11154230"
- Description: This study (conducted as PhD research at Rhodes University, South Africa) describes a formative interventionist research project conducted to explore factors inhibiting improved wetland management within a corporate plantation forestry context and determine if, and how, expansive social learning processes could strengthen organizational learning and development to overcome these factors. A series of formative interventionist workshops and feedback meetings took place over three years; developing new knowledge amongst staff of Company X, and improved wetland management practices. Through the expansive learning process, the tensions and contradictions that emerged became generative, supporting expansive learning that was reflectively engaged with throughout the research period. The study was== supported by an epistemological framework of cultural historical activity theory and expansive learning. Realist social theory, emerging from critical realism, with its methodological compliment the morphogenetic framework gave the research the depth of detail required to explain how the expansive learning, organizational social change, and boundary crossings that are necessary for assembling the collective were taking place. This provided ontological depth to the research. The research found that expansive learning processes, which are also social learning processes (hence we use the term ‘expansive social learning’, supported organizational learning and development for improved wetland management. Five types of changes emerged from the research: (1) Changes in structure, (2) changes in practice, (3) changes in approach, (4) changes in discourse, and (5) changes in knowledge, values, and thinking. The study was able to explain how these changes occurred via the interaction of structural emergent properties and powers; cultural emergent properties and powers; and personal emergent properties and powers of agents. It was concluded that expansive learning could provide an environmental education platform to proactively work with the sociological potential of morphogenesis to bring about future change via an open-ended participatory and reflexive expansive learning process.
- Full Text:
- Date Issued: 2019
Explaining people's perceptions of invasive alien species: A conceptual framework
- Authors: Shackleton, Ross T , Richardson, David M , Shackleton, Charlie M , Bennett, Brett , Crowley, Sarah L , Dehnen-Schmutz, Katharina , Estévez, Rodrigo A , Fischer, Anke , Kueffer, Christoph , Kull, Christian , Marchante, Elizabete , Novoa, Ana , Potgieter, Luke J , Vass, Jetske , Vas, Anna S , Larson, Brendon
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181356 , vital:43726 , xlink:href="https://doi.org/10.1016/j.jenvman.2018.04.045"
- Description: Human perceptions of nature and the environment are increasingly being recognised as important for environmental management and conservation. Understanding people's perceptions is crucial for understanding behaviour and developing effective management strategies to maintain, preserve and improve biodiversity, ecosystem services and human well-being. As an interdisciplinary team, we produced a synthesis of the key factors that influence people's perceptions of invasive alien species, and ordered them in a conceptual framework. In a context of considerable complexity and variation across time and space, we identified six broad-scale dimensions: (1) attributes of the individual perceiving the invasive alien species; (2) characteristics of the invasive alien species itself; (3) effects of the invasion (including negative and positive impacts, i.e. benefits and costs); (4) socio-cultural context; (5) landscape context; and (6) institutional and policy context. A number of underlying and facilitating aspects for each of these six overarching dimensions are also identified and discussed. Synthesising and understanding the main factors that influence people's perceptions is useful to guide future research, to facilitate dialogue and negotiation between actors, and to aid management and policy formulation and governance of invasive alien species. This can help to circumvent and mitigate conflicts, support prioritisation plans, improve stakeholder engagement platforms, and implement control measures.
- Full Text:
- Date Issued: 2019
Exploring and expanding transdisciplinary research for sustainable and just natural resource management
- Authors: Finca, Andiswa , Wolff, Margaret G , Cockburn, Jessica J , de Wet, Christopher J , Bezerra, Joana C , Weaver, Matthew J T , de Vos, Alta , Ralekhetla, Mateboho M , Libala, Notiswa , Mkabile, Qawekazi B , Odume, Nelson O , Palmer, Carolyn G
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416307 , vital:71337 , xlink:href="https://doi.org/10.5751/ES-11077-240414"
- Description: Transdisciplinarity is gaining acceptance in sustainability science research as an approach to work across disparate types of knowledge and practices in order to tackle complex social-ecological problems. On paper, transdisciplinarity appears to be substantially helpful, but in practice, participants may remain voiceless and disadvantaged. In this paper, we retrospectively investigate four case studies using recent design principles for transdisciplinary research, to explore a deeper understanding of the practical successes and failures of transdisciplinary research engagement. We show that the transdisciplinary way of working is time consuming, challenging, and insists that researchers and participants contribute reflexively. Careful attention to research design and methodology is central. The acceptance that complexity renders knowledge provisional, and complete honesty about the purpose of the research are critical to building relationships between researchers and participants. Gaining an understanding of the values people hold influences the research process and the possible outcomes toward sustainable and just natural resource management. We suggest that in order to enable sustainable and just natural resource management, transdisciplinary research should include values and ethics in the design, implementation, and reporting of projects.
- Full Text:
- Date Issued: 2019
Exploring group solidarity for insights into qualities of T-learning
- Authors: Mudokwani, Kuda , Mukute, Mutizwa
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/390612 , vital:68568 , xlink:href="https://doi.org/10.3390/su11236825"
- Description: Across the world, organised groups of farmers participating in just and sustainability transformations encounter multiple obstacles. Through solidarity manifested in iterative processes of questioning, co-learning, collective action and reflection, and value creation for themselves and for others, some succeed in overcoming them. This article investigates how a district organic farmer association in Zimbabwe is encountering and handling group solidarity challenges arising from shifting from local to district level coordinated organic production and marketing. Based on the use of change laboratory, this paper explores solidarity at the local niche and networked district level to seek insights into the qualities of T-learning.
- Full Text:
- Date Issued: 2019
Fabrication of efficient nonlinear optical absorber using Zn phthalocyanine-semiconductor quantum dots conjugates
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187496 , vital:44663 , xlink:href="https://doi.org/10.1016/j.poly.2018.11.024"
- Description: In this paper, we report on the synthesis of Zn(II) phthalocyanine derivatives and their conjugates with core/shell and core/shell/shell semiconductor quantum dots (SQDs). Zn(II) mono amino-carboxyethylphenoxy phthalocyanine (1), Zn(II) mono 3-carboxyphenoxy-tris(pyridin-2-yloxy) phthalocyanine (2) and Zn(II) mono aminophenoxy-tris(benzothiazole) phthalocyanine (3) were synthesized. The photophysical and optical limiting properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs were investigated in dimethyl sulfoxide. The optical limiting behaviour of the Pc complexes and their conjugates were measured by the open aperture Z-scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. The conjugates outperformed the Pc complexes alone with the conjugates of 2-SQDs affording highest nonlinear absorption coefficient (βeff) value of ∼80 cm/GW and lowest limiting threshold (Ilim) value of ∼0.27 J·cm−2 as compared to other samples while complex 1 gave low βeff and high Ilim values of 42.2 cm/GW and 1.39 J·cm−2, respectively.
- Full Text:
- Date Issued: 2019
Factors associated with consistent condom use: a cross-sectional survey of two Nigerian universities
- Authors: Ajayi, Anthony Idowu , Ismail , Kafayat Olanike , Akpan, Wilson
- Date: 2019
- Subjects: Nigeria Condom Use Computer File
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5834 , vital:44650 , https://DOI:10.1186/s12889-019-7543-1
- Description: Background: Consistent condom use is central to the prevention of transmission of human immunodeficiency virus (HIV) and other sexually transmitted diseases (STDs), especially among young adults. This study drew from a cross-sectional survey of two Nigerian universities to determine the level of consistent condom use, explored the determinants of condom use consistency and reasons for inconsistent condom use. Methods: We adopted a descriptive cross-sectional design, which involves the recruitment of 800 male and female students using stratified random sampling. Adjusted and unadjusted logistic regression models were used to examine the factors associated with consistent condom use among a final sample of 498 students who engaged in sex in the last year preceding the study. Results: Only 38.6% of sexually active participants (n = 498) used condoms consistently in the previous year. High condom self-efficacy score (AOR: 2.40; 95% CI: 1.58–3.64), discussion of HIV/STIs with sexual partner (AOR: 1.91; 95%CI: 1.29–2.83), knowing partner’s HIV status (AOR: 1.48; 95% CI: 1.02–2.16), being students of university located in a high HIV prevalence area (AOR: 2.86; 95% CI: 1.92–4.28) and engaging in sex with only steady partner (AOR: 1.74; 95% CI: 1.17–2.60) were associated with a higher odds of consistent condom use. Trust, unavailability of condoms, dislike of condoms and a perception that condoms reduced sexual pleasure were the main reasons for inconsistent use of condoms. Conclusion: The study found a low level of consistent condom use among study participants. Counselling young adults in Nigeria on condom self-efficacy, providing condoms on campuses and encouraging the discussion of sexually transmitted infections with sexual partners are central to improving the level of consistent condom use among Nigerian university students. Keywords: Condoms, Self-efficacy, Consistent condom use, HIV, Drug use, Alcohol use, Nigeria, University students
- Full Text:
- Date Issued: 2019
Factors influencing the spatial patterns of vertebrate roadkill in South Africa: The Greater Mapungubwe Transfrontier Conservation Area as a case study
- Authors: Collinson, Wendy J , Parker, Daniel M , Bernard, Ric T F , Reilly, Brian K , Davies-Mostert, Harriet T
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158320 , vital:40172 , https://0-doi.org.wam.seals.ac.za/10.1111/aje.12628
- Description: Few studies have investigated the factors that influence roadkill occurrence in developing countries. In 2013, we monitored a 100‐km section of the road (comprising the R572 and R521 regional highways and the D2662) that pass through the Greater Mapungubwe Transfrontier Conservation Area in South Africa, to assess the possible factors influencing roadkill. Over a period of 120 days, and across the three ecological seasons, we recorded 981 roadkills (rate = 0.08 roadkill/km/day) from four vertebrate taxonomic groups. We generated predictive models of roadkill from one combined data set that considered eight variables identified from the literature as potential correlates of roadkill. The model that included the distance of the fence from the road, habitat type adjacent to the road, and the presence of a hill in the road (i.e., elevation) or a bank on the side of the road best explained roadkill occurrence.
- Full Text:
- Date Issued: 2019
Feminine sexual desire and shame in the classroom: an educator’s constructions of and investments in sexuality education
- Authors: Saville Young, Lisa , Moodley, Dale , Macleod, Catriona I
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444302 , vital:74215 , xlink:href="https://doi.org/10.1080/14681811.2018.1511974"
- Description: Within the growing body of literature on sexuality education in South Africa, researchers have highlighted how teachers may face, or themselves be, barriers to the implementation of rights-based comprehensive sexuality education. Important issues with regard to educators are: firstly, the social and discursive space within which educators are located; and secondly, the complex emotional and psychic investments that educators take up within particular discourses and practices. This paper explores, through a psychosocial reading of an interview extract with a particular educator based in the Eastern Cape of South Africa, how discursive and psychic concerns are sutured within the complex subjectivity of the educator as the medium for sexual education in schools. Specifically, it highlights the numerous ways in which feminine sexuality and desire may be avoided, denied and silenced. Even when feminine desire is specifically evoked as in this case, it is done so in a way that ensures social and cultural respectability, thereby reproducing shame narratives that form and maintain traditional gender discourses. Our analysis demonstrates how engaging with educators as subjects with their own sexual history and psychic dynamics, and as individuals with raced, gendered and classed identities, is a potentially transformative perspective for effective sexuality education.
- Full Text:
- Date Issued: 2019
First record of an indigenous South African parasitoid wasp on an imported biological control agent, the water hyacinth hopper
- Authors: Kraus, Emily C , Coetzee, Julie A , van Noort, Simon , Olmi, Massimo
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417462 , vital:71455 , xlink:href="https://doi.org/10.1080/09583157.2019.1660306"
- Description: Water hyacinth, Pontederia crassipes (Martius) [≡Eichhornia crassip es (Martius) Solms-Laubach] (Pontederiaceae), is native to South America, but has expanded its range to many other regions of the world including South Africa. Megamelus scutellaris Berg (Hemiptera: Delphacidae) was released as a biological control agent and has established in several regions. Recently, the indigenous species Echthrodelphax migratorius Benoit, (Hymenoptera: Dryinidae) was discovered in South Africa parasitising M. scutellaris. This newly discovered relationship might have repercussions for the efficacy of biological control of water hyacinth by the delphacid. The wasp may negatively impact M. scutellaris populations making it difficult for the agent to successfully manage the invasive weed. Contrarily, the parasitoid may be beneficial by keeping the M. scutellaris populations stable, serving as a natural enemy.
- Full Text:
- Date Issued: 2019
Fluorescence “turn-ON” nanosensor for cyanide ion using supramolecular hybrid of graphene quantum dots and cobalt pyrene-derivatized phthalocyanine
- Authors: Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187594 , vital:44674 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.08.038"
- Description: A functional hybrid of graphene quantum dots (GQDs) and cobalt pyrene-derivatized phthalocyanine (CoPc) used as a sensitive nanoprobe for the recognition of cyanide ion (CN−) is described in this work. The fluorescence of GQDs was quenched upon non-covalent (π-π stacking) hybrid formation with CoPc via a possible energy transfer pathway. However, in the presence of CN−, the interaction between GQDs and CoPc was perturbed, such that the fluorescence of GQDs initially quenched by CoPc was found to be efficiently recovered in the presence of CN−. Amongst the molecules and anions tested to ascertain their effects on the fluorescence behaviour of the hybrid, only CN− ion induced the tunable “off-on” restoration of the fluorescence of GQDs, which demonstrates the selectivity of the hybrid towards CN−. The restored fluorescence signals of the GQDs were linearly modulated by different concentrations of CN− and were used for the quantitative assay of CN− with high sensitivity coupled with rapid detection time. The detection was in the linear range of 1.0–50.0 nM with limits of detection (LOD) of 0.5 nM. The analysis of spiked samples for the recovery of CN− further demonstrated the applicability of the hybrid for the satisfactory detection of the target analyte.
- Full Text:
- Date Issued: 2019
Food insecurity in South Africa: To what extent can social grants and consumption of wild foods eradicate hunger?
- Authors: Chakona, Gamuchirai , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179541 , vital:43081 , xlink:href="https://doi.org/10.1016/j.wdp.2019.02.001"
- Description: As the world continues to face widespread food insecurity, achieving food security for all at all times is increasingly complicated. In South Africa, social grants and the use of wild foods have been reported as some ways to improve household food insecurity and reduce poverty. The study examined if social grants and consumption of wild foods alleviate food insecurity in South Africa. Household surveys and focus group discussions were conducted along the rural-urban continuum in three South African towns situated along an agro-ecological gradient. We explored the differences in household food security indicators, mean monthly food expenditure and wealth index between households receiving social grants, households consuming wild foods, and those who did not. Households receiving social grants were more food insecure with lower mean monthly food expenditure and wealth index than those who did not. Overall all towns, the use of wild foods improved household food security which was not true within towns where wild foods were mostly consumed by low income and more food insecure households. Social grants alone cannot eradicate food insecurity as the money is not enough to cater for all household needs whilst wild foods can potentially alleviate household food insecurity. As food prices continue to increase gradually and worsening household food insecurity, ways to shift ‘income circumstances’ of households and promote the use and consumption of wild foods which may increase dietary diversity and diversifying food access. Focus should be placed on capacity building, employment creation and promoting awareness on own food production which is one way to improve food security of poor households rather than depending on purchases from the grant money alone.
- Full Text:
- Date Issued: 2019