Purification and characterization of an amyloglucosidase from an ericoid mycorrhizal fungus (Leohumicola incrustata)
- Authors: Adeoyo, Olusegun R , Pletschke, Brett I , Dames, Joanna F
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440405 , vital:73780 , https://doi.org/10.1186/s13568-018-0685-1
- Description: This study aimed to purify and characterize amyloglucosidase (AMG) from Leohumicola incrustata. AMG was purified to homogeneity from cell-free culture filtrate of an ERM fungus grown in a modified Melin–Norkrans liquid medium. The molecular mass of the AMG was estimated to be 101 kDa by combining the results of Sephadex G-100 gel filtration, sodium dodecyl sulphate–polyacrylamide gel electrophoresis, and zymography. The Km and kcat values were 0.38 mg mL−1 and 70 s−1, respectively, using soluble starch as a substrate. The enzyme was stable at 45 °C (pH 5.0), retaining over 65% activity after a pre-incubation period of 24 h. The metal inhibition profile of the AMG showed that Mn2+ and Ca2+ enhanced activity, while it was stable to metals ions, except a few (Al3+, Co2+, Hg2+ and Cd2+) that were inhibitory at a concentration higher than 5 mM. Thin layer chromatography revealed that only glucose was produced as the product of starch hydrolysis. The amylase from L. incrustata is a glucoamylase with promising characteristics such as temperature stability over an extended period, high substrate affinity and stability to a range of chemicals. Also, this study reports for the first time the possibility of using some culturable ERM fungi to produce enzymes for the bio-economy.
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Pyridone substituted phthalocyanines: Photophysico-chemical properties and TD-DFT calculations
- Authors: Abdurrahmanoğlu, Şaziye , Canlica, Mevlüde , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188216 , vital:44735 , xlink:href="https://doi.org/10.1142/S1088424617500730"
- Description: 4-(6-methyl-3-nitro-2-oxo-1,2-dihydropyridin-4-yloxy)phthalonitrile has been used to prepare a novel Zn(II) phthalocyanines with four peripheral pyridone substituents. The compound has been characterized by UV-visible absorption, FT-IR and 11H-NMR spectroscopy, elemental analysis and MALDI-TOF mass spectroscopy. The fluorescence, triplet quantum and singlet oxygen quantum yields have been determined and TD-DFT calculations have been used to identify trends in the electronic structure.
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Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis
- Authors: Yaripour, Saeid , Mohammadi, Ali , Esfanjani, Isa , Walker, Roderick B , Nojavan, Saeed
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184723 , vital:44266 , xlink:href="http://dx.doi.org/10.17179/excli2018-1140"
- Description: In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability (%RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %.
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Relational values about nature in protected area research
- Authors: de Vos, Alta , Bezerra, Joana C , Roux, Dirk
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416396 , vital:71345 , xlink:href="https://doi.org/10.1016/j.cosust.2018.10.018"
- Description: Protected areas are increasingly expected to justify their existence in terms of their importance to society. However, this importance, and the complex ways in which people relate to protected areas, cannot be captured by instrumental and intrinsic value framings alone. Rather, our understanding of the role of protected areas in society needs to take account of people’s relational values about nature. Here we review the literature on values associated with human-nature connection and related concepts to highlight which approaches are currently being used to understand expressions of relational values in empirical protected area research. Our results highlights seven ‘application domains’ for relational values research, highlighting expressions of relational values, and the stakeholder focus of each. Place-focused and psychological theories were most common across these domains. This work represents a first step in developing the foundations of a relational value research agenda in protected areas.
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Reproductive phenology of two Mimusops species in relation to climate, tree diameter and canopy position in Benin (West Africa)
- Authors: Sinasson Sanni, Giséle K , Shackleton, Charlie M , Sinsin, Brian
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180337 , vital:43354 , xlink:href=" https://doi.org/10.1111/aje.12457"
- Description: Assessing species phenology provides useful understanding about their autecology, to contribute to management strategies. We monitored reproductive phenology of Mimusops andongensis and Mimusops kummel, and its relationship with climate, tree diameter and canopy position. We sampled trees in six diameter classes and noted their canopy position. For both species flowering began in the dry season through to the rainy season, but peaked in the dry season, whilst fruiting occurred in the rainy season and peaked during the most humid period. Flowering was positively correlated with temperature. Conversely, fruiting was negatively correlated with temperature and positively with rainfall, only in the Guineo-Sudanian zone. For M. andongensis, flowering and fruiting prevalences were positively linked to stem diameter, while only flowering was significantly related to canopy position. For M. kummel, the relationship with stem diameter was significant for flowering prevalence only and in the Guineo-Sudanian zone. Results suggest that phylogenetic membership is an important factor restricting Mimusops species phenology. Flowering and fruiting of both species are influenced by climate, and consequently climate change might shift their phenological patterns. Long-term investigations, considering flowering and fruiting abortion, will help to better understand the species phenology and perhaps predict demographic dynamics.
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Rethinking urban green infrastructure and ecosystem services from the perspective of sub-Saharan African cities
- Authors: Lindley, Sarah , Pauleit, Stephan , Yeshitela, Kumelachew , Cilliers, Sarel , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398357 , vital:69403 , xlink:href="https://doi.org/10.1016/j.landurbplan.2018.08.016"
- Description: Urban green infrastructure and its ecosystem services are often conceptualised in terms of a predominantly western perspective of cities and their wider social, economic and environmental challenges. However, the benefits which are derived from urban ecosystems are equally – if not more – important in the cities of the developing world. Cities in sub-Saharan Africa are well known to be facing severe pressures. Nevertheless, despite the challenges of rapid population change, high levels of poverty and seemingly chaotic urban development processes, there are also tremendous opportunities. Realising the opportunities around urban green infrastructure and its benefits requires harnessing the inherent local knowledge and community innovation associated with a multitude of inter-connected urban social-ecological systems. Such systems are a powerful driving force shaping urban realities. Associated planning regimes are frequently lambasted as being either absent, weakly enforced, corrupt or wholly inappropriate. Much of this criticism is justified. However, it must also be recognised that decision-makers are frequently working in contexts which lack the scientific foundations through which their decision-making might be made more effective and complementary to bottom-up initiatives. The paucity of research into urban ecosystems in sub-Saharan Africa and the lack of development of context-specific conceptual, theoretical and empirical foundations is a problem which must be addressed. Drawing on papers from a Special Issue centred on urban green infrastructure and urban ecosystem services in sub-Saharan Africa, we consider what concepts and frameworks are in use and what needs to be considered when framing future research. We also synthesise key messages from the Special Issue and draw together themes to help create a new research agenda for the international research community.
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Revolutionary trends at the National Arts Festival 2017 (an overview)
- Authors: Krueger, Anton
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225563 , vital:49235 , xlink:href="https://doi.org/10.1080/10137548.2017.1407025"
- Description: My 2017 Fest Everybody's festival is different. Each individual charts their own course in navigating this vast, unwieldy, multidisciplinary festival of festivals that happens every year in the Eastern Cape. Since the long running print version of the festival paper, Cue went under this year when Standard Bank withdrew funding, I wasn't officially reviewing and this freed me up to play a bit more and to see things that appealed to me, rather than having to attend shows from a sense of obligation.
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Satisfaction with family life in South Africa: The role of socioeconomic status
- Authors: Botha, Ferdi , Booysen, Frikkie
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396115 , vital:69151 , xlink:href="https://doi.org/10.1007/s10902-017-9929-z"
- Description: This paper investigates the determinants of self-reported satisfaction with family life, applied to the South African context, with socioeconomic status (SES) as the main covariate and family functioning as the secondary covariate of interest. An individual-, household-, and subjective SES index is constructed via multiple correspondence analysis. Structural equation modelling (SEM) and multiple-group SEM (MGSEM) are used to analyse the role of SES in explaining satisfaction with family life. Higher levels of SES, especially household SES and subjective SES, are related to greater satisfaction with family life. Family functioning, in terms of better family flexibility, is associated with higher satisfaction with family life. The MGSEM results indicate that the role of family flexibility in explaining satisfaction with family life is similar across SES quartiles; family flexibility is an important predictor of family-life satisfaction, regardless of SES quartile.
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Seasonal physiological responses to heat in an alpine range-restricted bird: the Cape Rockjumper (Chaetops frenatus)
- Authors: Oswald, Krista N , Lee, Alan T K , Smit, Ben
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441655 , vital:73904 , https://doi.org/10.1007/s10336-018-1582-8
- Description: Hot, dry summer conditions impose physiological stress on endotherms, yet we have a poor understanding of how endotherms seasonally adjust their costs of thermoregulation under hot conditions. We determined whether seasonal phenotypic plasticity in evaporative cooling capacity at high temperatures explained how the range-restricted Cape Rockjumper (Chaetops frenatus; hereafter ‘Rockjumper’), copes with hot and dry summer temperatures of the temperate mountain peaks of southwest South Africa. We measured evaporative water loss (EWL), resting metabolic rate (RMR), and body temperature at high air temperatures (30–42 °C) of individuals from a wild population of Rockjumpers during winter and summer (n = 11 winter, 4 females, 7 males; n = 10 summer, 6 females, 4 males). We found Rockjumper evaporative cooling in summer imposes higher EWL (i.e. greater water costs) compared to winter, although an accompanying lack of change in RMR resulted in increased summer cooling efficiency. These patterns are similar to those observed in species that inhabit regions where summer temperatures are routinely high but the species are not water stressed. Our findings indicate that avian seasonal physiological adjustments to heat can be diverse. Further seasonal studies on thermoregulation in response to heat will greatly improve our knowledge of the functional value of traits such as evaporative cooling efficiency and heat tolerance and how they contribute to the physiological stress organisms experience in heterogenous environments.
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Seed extract of Psoralea corylifolia and its constituent bakuchiol impairs AHL-based quorum sensing and biofilm formation in food-and human-related pathogens
- Authors: Husain, Fohad M , Ahmad, Iqbal , Khan, Faez I , Al-Shabib, Nasser A , Baig, Mohammad H , Hussain, Afzal , Rehman, Md T , Alajmi, Mohamed F , Lobb, Kevin A
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447182 , vital:74590 , xlink:href="https://doi.org/10.3389/fcimb.2018.00351"
- Description: The emergence of multi-drug resistance in pathogenic bacteria in clinical settings as well as food-borne infections has become a serious health concern. The problem of drug resistance necessitates the need for alternative novel therapeutic strategies to combat this menace. One such approach is targeting the quorum-sensing (QS) controlled virulence and biofilm formation. In this study, we first screened different fractions of Psoralea corylifolia (seed) for their anti-QS property in the Chromobacterium violaceum 12472 strain.
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Singlet oxygen generating properties of different sizes of charged Graphene quantum dot Nanoconjugates with a positively charged Phthalocyanine
- Authors: Matshitse, Refilwe , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187614 , vital:44680 , xlink:href="https://doi.org/10.1007/s10895-018-2247-y"
- Description: Various sizes of graphene quantum dots (GQDs) denoted as GQD2, GQD6 and GQD10 (increasing in size) were non-covalently attached to 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) to form GQDs-ZnTPPcQ nanoconjugates. X-ray photoelectron spectroscopy (XPS) showed that increasing sizes of GQDs decreases the atomic concentrations of oxygen, which leads to blue shift in spectra of the GQDs. Relative to Pcs alone (0.03), the presence of GQDs improved the singlet oxygen quantum yields with the following values: GQD2-ZnTPPcQ (0.17), GQD6-ZnTPPcQ (0.27) and GQD10-ZnTPPcQ (0.11). GQD2-ZnTPPcQ nanoconjugate system had the most ZnTPPcQ loading, but did not generate the most singlet oxygen species due to aggregation. This study shows that, the quantity of oxygen, size and quality of GQDs as well as amount of Pc loading are amongst the vital properties to consider when constructing GQD-nanoconjugate systems with optimal singlet oxygen quantum yields.
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Social-ecological systems as complex adaptive systems
- Authors: Preiser, Rika , Biggs, Reinette , de Vos, Alta , Folke, Carl
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416410 , vital:71346 , xlink:href="https://doi.org/10.5751/ES-10558-230446"
- Description: The study of social-ecological systems (SES) has been significantly shaped by insights from research on complex adaptive systems (CAS). We offer a brief overview of the conceptual integration of CAS research and its implications for the advancement of SES studies and methods. We propose a conceptual typology of six organizing principles of CAS based on a comparison of leading scholars’ classifications of CAS features and properties. This typology clusters together similar underlying organizing principles of the features and attributes of CAS, and serves as a heuristic framework for identifying methods and approaches that account for the key features of SES. These principles can help identify appropriate methods and approaches for studying SES. We discuss three main implications of studying and engaging with SES as CAS. First, there needs to be a shift in focus when studying the dynamics and interactions in SES, to better capture the nature of the organizing principles that characterize SES behavior. Second, realizing that the nature of the intertwined social-ecological relations is complex has real consequences for how we choose methods and practical approaches for observing and studying SES interactions. Third, engagement with SES as CAS poses normative challenges for problemoriented researchers and practitioners taking on real-world challenges.
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Special section on urbanisation and ecosystem services in sub-Saharan Africa: Current status and scenarios
- Authors: Pauleit, Stephan , Lindley, Sarah , Lotz-Sisitka, Heila , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183082 , vital:43910 , xlink:href="https://doi.org/10.1016/j.landurbplan.2018.09.008"
- Description: The African continent is facing unprecedented population growth in the 21st century. Most of this growth will be absorbed by urban areas where the overall population is projected to triple from presently appr. 400 people to 1.3 billion people in 2050 (UN-Habitat, 2014). In sub-Saharan Africa, which is the focus of this Special Issue, not only the number of megacities with more than 10 million such as Lagos will rise, but smaller or medium sized cities will attract most of this growth (UN-Habitat, 2014). The majority of this increase is taking place in the form of informal settlements where people are living in poverty and where basic facilities and services such as a secure supply of clean drinking water and safe waste water disposal are missing.
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Synthesis and photophysical properties of BODIPY-decorated graphene quantum dot–phthalocyanine conjugates
- Authors: Nwahara, Nnamdi , Nkhahle, Reitumetse , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233409 , vital:50088 , xlink:href="https://doi.org/10.1039/C8NJ00758F"
- Description: This work reports on the synthesis and characterisation of novel supramolecular hybrids containing BODIPY-decorated graphene quantum dots (BODIPY@GQDs) and zinc phthalocyanine. Graphene quantum dots (GQDs) were functionalized with L-glutathione (GSH) in order to assist coupling to the BODIPY dye. {2,9(10)16(17)23(24)-Tetrakis-[3-(diethylamino)phenoxy]phthalocyaninato}zinc(II) (1) was immobilized via π–π stacking interaction on the BODIPY-decorated GQDs and pristine GQDs to form the supramolecular hybrids 1-BODIPY@GQDs and 1-GQDs, respectively. The photophysical and photochemical properties of these conjugates were investigated. Energy transfer occurred from the (i) GQDs to BODIPY, (ii) GQDs to 1, and (iii) BODIPY@GQDs to 1via fluorescence resonance energy transfer (FRET). The highest FRET efficiency was observed for the BODIPY@GQDs (0.93). The introduction of the BODIPY core to the GQD structure resulted in higher triplet, and singlet oxygen quantum yields for the resultant Pc/GQD hybrid (1-BODIPY@GQDs). The zeta potential values obtained imply a high colloidal stability for the supramolecular hybrids. The results suggest that such hybrids may be applied in fields such as photodynamic therapy (PDT), where a high singlet oxygen quantum yield is desired.
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Synthesis, characterization and DPPH scavenging activity of some benzimidazole derivatives
- Authors: Odame, Felix , Krause, Jason , Hosten, Eric C , Betz, Richard , Lobb, Kevin A , Tshentu, Zenixole R , Frost, Carminita L
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447209 , vital:74592 , xlink:href="https://dx.doi.org/10.4314/bcse.v32i2.8 "
- Description: A base-catalyzed conversion of aldehydes to benzimidazoles has been achieved. The compounds have been characterized by IR, NMR, micoranalysis, and GC-MS. The reaction for the formation of benzimidazoles has been monitored with 1 H NMR and IR. The crystal structures of two derivatives, 2-(2- chlorophenyl)-1H-benzimidazole and 2-(1H-benzimidazol-2-yl)-4-nitrophenol, are presented. A study of the DPPH scavenging activity of these compounds showed that 2-(1H-benzimidazol-2-yl)phenol (2), 2-p-tolyl-1Hbenzimidazole (3) and 2-(4-methoxyphenyl)-1H-benzimidazole (7) gave IC50 values 1974, 773 and 800 µM.
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Synthesis, photophysicochemical and photodynamic antimicrobial chemotherapy studies of indium pyridyl phthalocyanines: Charge versus bridging atom
- Authors: Sindelo, Azole , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187650 , vital:44683 , xlink:href="https://doi.org/10.1016/j.ica.2018.02.020"
- Description: 2(3), 9(10), 16(17), 23(24)-Octapyridylsulfanyl phthalocyaninato chloroindium(III) (complex 1a) and its quaternized derivative 2(3), 9(10), 16(17), 23(24)-octamethylpyridylsulfanyl phthalocyaninato chloroindium (III) (complex 1b) were synthesised. The triplet quantum yields were 0.53 and 0.48 while the singlet oxygen quantum yields were 0.46 and 0.33 in DMF for 1a and 1b, respectively. The photodynamic antimicrobial chemotherapy (PACT) activity of 1b (containing 8 positive charges) was compared to those of 9(10),16(17),23(24)-tri-N-methyl-4-pyridylsulfanyl-2(3)-(4-aminophenoxy) phthalocyaninato chloro indium(III) triiodide (2) (containing 3 positive charges) and 2-[4-(N-Methylpyridyloxy) phthalocyaninato] chloroindium (III) iodide (3) (containing 4 positive charges). Complex 1b gave log reductions of 4.21, 8.30 and 3.21 for Gram(−) E. coli, Gram(+) S. aureus and C. albicans, respectively. When comparing 1b, 2 and 3, the largest log reductions for E. coli were obtained for complex 3 containing four positive charges hence showing it is not always the charge that determines the PACT activity, but the bridging atom in the phthalocyanine plays a role.
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Temporal dynamics and motivations for urban community food gardens in medium-sized towns of the Eastern Cape, South Africa
- Authors: Roberts, Sky , Shackleton, Charlie M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179768 , vital:43178 , xlink:href="https://doi.org/10.3390/land7040146"
- Description: Urban agriculture is said to be increasing with global urbanization. However, there is little examination of the temporal or spatial dynamics of urban agriculture. We investigated the benefits and challenges experienced by community gardeners in four towns in South Africa, along with GIS analysis of the number, area, and location of urban food community gardens over the last three decades. Common reasons for practicing community gardening were cash poverty (37%) and the need to grow food (34%). The most common benefits reported by respondents were a healthy lifestyle (58%) and consumption of the food produced (54%). Theft of garden infrastructure or produce was a noteworthy challenge to continued motivation and engagement in urban community gardening. There were declines in the number and area of urban community gardens, and more central location over the last three decades. Only 16% of the gardens present in the 1980s were still operating in the 2000s. Clearly community gardening is temporally and spatially dynamic, which requires context-sensitive policy initiatives.
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The case for collation to inform debate and transform practice in decolonising Psychology
- Authors: Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444397 , vital:74225 , xlink:href="https://doi.org/10.1177/0081246318784508"
- Description: Critiques of the ‘relevance’ of Psychology in South Africa and Africa have been raging for a number of decades now. Recent debates about decolonising Psychology and what is meant by African Psychology have been rigorous and necessary. In this commentary, I argue that in order for Psychology to move beyond Euro-American-centric epistemology and practice, these efforts need to be supplemented with the grounded praxis of research and literature collation. The epistemological, empirical, and conceptual knowledges that have been generated within the South African, African, and Global South contexts need to be brought together in coherent forms. As with other analytical processes, the grounded praxis of collating knowledges around a particular topic or approach allows for fresh insights and for the transfer of knowledges generated in context. Gaps in current research may be identified, debates on particular issues strengthened, and practice potentially improved. Drawing on two examples – textbooks and systematic literature reviews – and from my and colleagues’ work in conducting these kinds of collation work, I argue that: textbook writers should use grounded methodologies to generate texts based on South African, African, and Global South research, with reference to research conducted in the Global North being peripheral at best; and systematic reviews enable the cross-fertilisation of ideas from other social science research where psychological research is sparse. Funders should consider funding collation efforts.
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The distribution and abundance of the stem-galling fly, Cecidochares connexa (Macquart)(Diptera: Tephritidae), a biological control agent of Chromolaena odorata (L.)(Asteraceae), in Ghana
- Authors: Aigbedion-Atalor, Pascal O , Wilson, DD , Eziah, Vincent Y , Day, Michael D , Paterson, Iain D
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407074 , vital:70334 , xlink:href="https://hdl.handle.net/10520/EJC-113112d1da"
- Description: Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae: Eupatorieae) is one of the worst invasive weeds in West Africa, and a serious biotic threat to food security. The stem-galling fly, Cecidochares connexa (Macquart) (Diptera: Tephritidae), a biological control agent for C. odorata, was released in the Ivory Coast in 2003 and first detected in Ghana in 2014. The spatiotemporal distribution and abundance of C. connexa in Ghana was determined by country-wide surveys from 2015 to 2016. Galls were found in varying densities across Ghana but gall densities were consistently low east of Lake Volta. A limited survey conducted in the extreme west of Togo in 2016, found the gall fly also in low numbers. There was a significant correlation between C. connexa gall densities and the distance from the release sites in the Ivory Coast. The distribution and abundance of the gall fly in Ghana could be explained by its spread from the original release sites over time and/or the much drier conditions east of Lake Volta. Cecidochares connexa has dispersed a distance of about 1000 km over a 10-year period and, while there is some evidence that the gall fly is still dispersing towards the east, its range and population size could be limited by the dry climatic conditions in the east of Ghana and in Togo. Actively redistributing the agent over this dry corridor to the more humid and higher rainfall areas of Nigeria, may result in the spread of this agent through the rest of West and Central Africa, thereby aiding the control of C. odorata in the region.
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The effect of the cobalt and manganese central metal ions on the nonlinear optical properties of tetra (4-propargyloxyphenoxy) phthalocyanines
- Authors: Mwanza, Daniel , Louzada, Marcel , Britton, Jonathan , Sekhosana, Kutloano E , Khene, Samson M , Nyokong, Tebello , Mashazi, Philani N
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233357 , vital:50083 , xlink:href="https://doi.org/10.1039/C8NJ00748A"
- Description: The metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (Mn(OAc)TPrOPhOPc) tetra propargyloxyphenoxy phthalocyanines were evaluated for their potential as optical limiting materials. The effect of the substituents and the central metal ions on the nonlinear optical properties was evaluated. The metal-free phthalocyanine exhibited better nonlinear optical properties when compared to the cobalt and manganese complexes owing to the metal ions quenching the excited state due to their half-filled d-orbitals. The nonlinear absorption coefficient (βeff, ×10−5 m MW−1) followed the trend of H2TPrOPhOPc > CoTPrOPhOPc > Mn(OAc)TPrOPhOPc. The values βeff (×10−5 m MW−1) using 532 nm Nd:YAG (560 nm monochromatic Ekspla) laser sources were 23.5 > 14.3 > 9.20 (14.4). The second-order nonlinear coefficient obtained using density functional theory calculations, the theoretical hyper-Rayleigh scattering (βHRS, ×10−28 esu), showed the decreasing trend for H2TPrOPhOPc (2.28) > CoTPrOPhOPc (2.10) > Mn(OAc)TPrOPhOPc (1.86). The 4-(propargyloxy)phenoxy substituents enhanced the optical limiting properties of the synthesized phthalocyanines.
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