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The interaction between graphene quantum dots grafted with polyethyleneimine and Au@ Ag nanoparticles

  • Authors: Achadu, Ojodomo John , Uddin, Imran , Nyokong, Tebello
  • Date: 2016
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/188679 , vital:44775 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.03.016"
  • Description: Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
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  • Date Issued: 2016

Cloud computing adoption: Strategies for Sub-Saharan Africa SMEs for enhancing competitiveness

  • Authors: Adane, Martin
  • Date: 2018
  • Subjects: business intelligence small businesses business planning Article
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/11260/6862 , vital:51101 , xlink:href="https://doi.org/10.1080/20421338.2018.1439288"
  • Description: Small and medium-sized enterprises (SMEs) need to design and implement strategies for adopting new technologies as a competitive tool for maintaining their competitive advantage and cloud computing is at its peak. Since its emergence, there has been a surge in the adoption of cloud computing with research into its adoption primarily concentrated on bigger firms. However, a major characteristic of cloud computing is the anticipated possibilities it holds for SMEs. This paper primarily explores cloud computing adoption strategies for SMEs operating in Sub-Saharan Africa. Using a mixed method approach, a sample of 261 respondents and 11 SMEs was respectively used for the quantitative and qualitative stages of the research. The results reveal that, even though SMEs have their unique expectations for adopting cloud computing, they were of the consensus that elements of an adoption strategy should include adoption goals, a roadmap, and considerations. The paper makes specific recommendations to SMEs to develop adoption strategies that meet their specific needs if they expect cloud computing to play a stronger role to support more strategic initiatives to grow their businesses and improve customer experience.
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  • Date Issued: 2018

Synthesis and anti-parasitic activity of N-benzylated phosphoramidate Mg2+-chelating ligands

  • Authors: Adeyemi, Christiana M , Hoppe, Heinrich C , Isaacs, Michelle , Mnkandhla, Dumisani , Lobb, Kevin A , Klein, Rosalyn , Kaye, Perry T
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/451171 , vital:75025 , xlink:href="https://doi.org/10.1016/j.bioorg.2020.104280"
  • Description: A series of N-benzylated phosphoramidate esters, containing a 3,4-dihydroxyphenyl Mg2+-chelating group, has been synthesised in five steps as analogues of fosmidomycin, a Plasmodium falciparum 1-deoxy-1-D-xylulose-5- phosphate reductoisomerase (PfDXR) inhibitor. The 3,4-dihydroxyphenyl group effectively replaces the Mg2+- chelating hydroxamic acid group in fosmidomycin. The compounds showed very encouraging anti-parasitic activity with IC50 values of 5.6–16.4 µM against Plasmodium falciparum parasites and IC50 values of 5.2 – 10.2 µM against Trypanosoma brucei brucei (T.b.brucei). Data obtained from in silico docking of the ligands in the PfDXR receptor cavity (3AU9)5 support their potential as PfDXR inhibitors.
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  • Date Issued: 2020

Understanding foraging practices in Lagos metropolis to redesign urban greenspaces in support of human-nature interactions

  • Authors: Adeyemi, Opeyemi , Shackleton, Charlie M
  • Date: 2023
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/401353 , vital:69728 , xlink:href="https://doi.org/10.1016/j.ufug.2022.127805"
  • Description: Enhancing knowledge of urban foraging across different urban landscapes is an urgent matter given that about two-thirds of the world’s population is projected to live in urban areas by 2050, whilst 50 % of Africa’s population is expected to live in cities by 2030. This study was conducted in Lagos metropolis which is the economic hub of Africa’s most populous country. Data was collected using an in-person, semi-structured questionnaire from 347 persons who were 18 years or older to identify foragers and non-foragers, their sociodemographic profiles, and their foraging practices. Results revealed that about two out of three persons sampled forage to some degree. The collection happened more in domestic gardens (34 %) and streets (27 %) than in other foraging sites (such as unused lands, institutional grounds and lakes and riparian fringes). A total of 35 species were reportedly foraged within the metropolis, mostly for food (71 %) and medicine (26 %). Mango (Mangifera indica), pawpaw (Carica papaya), tropical almond (Terminalia catappa), fish (various species), bitter leaf (Vernonia amygdalina) and spinach (Spinacia oleracea) were the most gathered species. The distance travelled to foraging wild species ranged from 5 m to 25 km. The primary motivation for foraging was the acquisition of fresh and natural materials. However, some felt that foraging was a stressful activity. The unavailability of foraging sites and species was the major constraint to foraging in this megacity. Hence, efforts to increase the edible components of public green spaces and to provide free access could potentially allow more people to forage and make current foraging more secure. We suggest that making provisions for foraging in urban planning goals could contribute to the sustainable development of cities in Africa and elsewhere.
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  • Date Issued: 2023

Prevalence and molecular analysis of multidrug-resistant Acinetobacter baumannii in the extra-hospital environment in Mthatha, South Africa

  • Authors: Adjei, Anane Yaw , Apalata, Teke , Vasaikar, Sandeep , Okuthe, Grace Emily , Songca, Sandile
  • Date: 2019
  • Subjects: Acinetobacter baumannii , Carbapenemase-encoding genes , Multidrug-resistance , ISAba1 , intI1
  • Language: English
  • Type: article , text
  • Identifier: http://hdl.handle.net/11260/2409 , vital:41457 , https://doi.org/10.1016/j.bjid.2019.09.004
  • Description: The presence of Acinetobacter baumannii outside hospitals remains unclear. This study aimed to determine the prevalence of multidrug-resistance (MDR) A. baumannii in the extra-hospital environment in Mthatha, South Africa and to investigate the frequency of carbapenemase-encoding genes. Material and Methods: From August 2016 to July 2017 a total of 598 abattoir samples and 689 aquatic samples were collected and analyzed presumptively by cultural methods for the presence of A. baumannii using CHROMagarTM Acinetobacter medium. Species identification was performed by autoSCAN-4 (Dade Behring Inc., IL) and confirmed by the detection of their intrinsic blaOXA-51 gene. Confirmed MDR A. baumannii isolates were screened for the presence of carbapenemase-encoding genes, ISAba1 insertion sequence and integrase intI1. Results: In total, 248 (19.3%) Acinetobacter species were isolated. Acinetobacter. baumannii was detected in 183 (73.8%) of which 85 (46.4%) and 98 (53.6%) were recovered from abattoir and aquatic respectively. MDR A. baumannii was detected in 56.5% (48/85) abattoir isolates and 53.1% (52/98) aquatic isolates. Isolates showed high resistance to antimicrobials most frequently used to treat Acinetobacter infections such as piperacillin/tazobactam; abattoir (98% of isolates resistant), aquatic (94% of isolates resistant), ceftazidime (84%, 83%), ciprofloxacin (71%, 70%), amikacin (41%, 42%), imipenem (75%, 73%), and meropenem (74%, 71%). All the isolates were susceptible to tigecycline and colistin. All the isolates carried blaOXA-51-like. The blaOXA-23 was detected in 32 (66.7%) abattoir isolates and 11 (21.2%) aquatic isolates. The blaOXA-58-like was positive in 7 (14.6%) and 4 (7.7%) abattoir and aquatic isolates, respectively. Both groups of isolates lacked blaOXA-24-like, blaIMP-type, blaVIM-type, blaNDM-1, blaSIM, blaAmpC, ISAba1 and inI1. Isolates showed high level of Multiple Antibiotic Resistance Index (MARI) ranging from 0.20-0.52. Conclusion: Extra-hospital sources such as abattoir and aquatic environments may be a vehicle of spread of MDR A. baumannii strains in the community and hospital settings.
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  • Date Issued: 2019

Photodynamic therapy activities of phthalocyanine-based macromolecular photosensitizers on MCF-7 breast cancer cells

  • Authors: Ahmetali, Erem , Sen, Pinar , Süer, N Ceren , Nyokong, Tebello , Erin, Tarik , Sener, M Kasim
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/185655 , vital:44407 , xlink:href="https://doi.org/10.1080/10601325.2021.1934012"
  • Description: Poly(oxanorbornene)s with zinc(II) phthalocyanine side chains have been synthesized by ring-opening metathesis polymerization. The incorporation of zinc(II) phthalocyanine into cationic polymer has given poly(oxanorbornene)s noteworthy photophysicochemical properties and the capacity to generate singlet oxygen under light irradiation. To investigate photosensitizer’s properties of the newly synthesized polymers P6 and P7: fluorescence (ΦF), singlet oxygen (ΦΔ) and triplet (ΦT) quantum yields of polymers have been measured in dimethyl sulfoxide and aqueous medium. Singlet oxygen quantum yields of P6 and P7 have been found to be 0.22 and 0.20 in dimethyl sulfoxide, respectively. Then, photodynamic therapy activities of polymers (P1-P7) against human breast adenocarcinoma cell line (MCF-7 cells) have been investigated. The copolymer P5 bearing pendant zinc(II) phthalocyanine and triethyl phosphonium functionalities has showed enhanced PDT activity with less than 10% viable cells at 60 μg/mL.
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  • Date Issued: 2021

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, David D , 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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  • Date Issued: 2018

Ephemeroptera, Plecoptera and Trichoptera (EPT) functional feeding group responses to fine grain sediment stress in a river in the Eastern Cape, South Africa

  • Authors: Akamagwuna, Frank C , Odume, Oghenekaro N
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/486426 , vital:79504 , xlink:href="https://doi.org/10.1007/s10661-020-8187-4"
  • Description: Sedimentation arising from agricultural run-offs, riparian habitat fragmentation and channel bank erosion has long been known to impair the structure and ecological functioning of stream and river ecosystems. This study examined the effects of fine sediment grain sizes on the functional feeding group structure of Ephemeroptera, Plecoptera and Trichoptera (EPT) in the Tsitsa River catchment in the Eastern Cape Province of South Africa. Fine sediments and EPT were sampled between August 2016 and April 2017 from eight selected sampling sites. The eight sites were classified into four groups in terms of fine sediments and turbidity to represent a gradient of sediment stress, with site groups 4 and 3 being less influenced and groups 2 and 1 as the highly influenced groups. EPT genera/species were assigned to five functional feeding groups (FFGs) and their responses to sediment stress assessed.
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  • Date Issued: 2020

Physical-biological coupling in the waters surrounding the Prince Edward Islands (Southern Ocean)

Perceptions of Cultural and Heritage Tourism Entrepreneurship among Students at a Higher Educational Institution in Cape Town

  • Authors: Asoba, Samson Nambei , Patricia, Nteboheng Mefi
  • Date: 2021
  • Subjects: Heritage Tourism Entrepreneurship Article
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/11260/8085 , vital:61394 , xlink:href="https://www.abacademies.org/articles/perceptions-of-cultural-and-heritage-tourism-entrepreneurship-among-students-at-a-higher-educational-institution-in-cape-town-13940.html"
  • Description: This study was inspired by the need to increase entrepreneurial opportunities in South Africa. It analysed the opportunity presented by tourism as a possible entrepreneurial field for you entrepreneurs from Universities. The study was based on the position that despite the attacks on colonial heritage sites, they can present possible entrepreneurial opportunities. The study adopted the quantitative approach to collect and analyse the perceptions of entrepreneurship students at a Higher Education Institution. Evidence was found that there were many benefits of heritage entrepreneurship which included creating financial viability, creation of employment and improving the environment and infrastructure in communities. It was also found that most of the students held a positive impression of the role of tourist and tourism entrepreneurship in the communities. They held a good image of the tourist and felt that they did not offer any threat to locals. Youth are recommended to adopt heritage tourism entrepreneurship as employment opportunity.
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  • Date Issued: 2021

The Profit motive and the enabling environment for Growth of Survivalist Township Entrepreneurship: A Study at a Township in Cape Town

  • Authors: Asoba, Samson Nambei , Patricia, Nteboheng Mefi
  • Date: 2021
  • Subjects: Small Business Entrepreneurship Article
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/11260/8141 , vital:61398 , "https://www.abacademies.org/articles/the-profit-motive-and-the-enabling-environment-for-growth-of-survivalist-township-entrepreneurship-a-study-at-a-township-in-cape-t-10396.html"
  • Description: The paper draws attention to the profit motive in respect of survivalist entrepreneurship at a township environment in Cape Town. Survivalist entrepreneurs have received little specific focus yet they represent a significant portion of economic activities in South Africa townships. Essentially the study considers the problem of failure to grow among survivalist entrepreneurs as reported in related literature. Many survivalist entrepreneurs fail to grow beyond the survivalist phase and there is no consensus on the underlying cause for such a phenomenon. With the Covid-19 pandemic, there is an expectation that survivalist entrepreneurs are likely to multiply owing to the collapse of many small businesses as well as the loss of employment arising from the pandemic. Two specific objective were formulated for the study: (1) to inquire into the business motives of survivalist entrepreneurs and (2) to assess the perception of the survivalist entrepreneurs on the degree to which the small business environment in supportive of motive attainment. The study adopted a quantitative research design based on the selection of respondents using a convenience sampling strategy. The evidence established from this study suggest that survivalist entrepreneurs do not pursue the profit motive significantly but they faced inhibitions presented by the economic environment in which they operate. Government and other stakeholders in the national economy are recommended to develop a suitable legal and institutional framework with strong structures to ensure the growth of survivalist entrepreneurs Keywords: Survivalist Entrepreneur, Township Entrepreneurship, Profit Motive, Small Businesses.
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  • Date Issued: 2021

Synthesis and characterization of ZnO nanoparticle synthesized by a microwave-assisted combustion method and catalytic activity for the removal of ortho-nitrophenol

  • Authors: Assi, Navid , Mohammadi, Ali , Sadr Manuchehri, Q , Walker, Roderick B
  • Date: 2015
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/183850 , vital:44075 , xlink:href="https://doi.org/10.1080/19443994.2014.891083"
  • Description: ZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.
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  • Date Issued: 2015

Detecting change in local ecological knowledge: An application of an index of taxonomic distinctness to an ethnoichthyological classification in the Solomon Islands

  • Authors: Aswani, Shankar , Ferse, Sebastien C A , Stäbler, Moritz , Chong-Montenegro, Carolina
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/406521 , vital:70282 , xlink:href="https://doi.org/10.1016/j.ecolind.2020.106865"
  • Description: The global accelerating loss of biodiversity is having immediate repercussions for ecosystems and human wellbeing, particularly in areas where people depend intimately on their natural environment for their livelihoods. Dovetailing this loss is the demise of local/traditional knowledge systems resulting from factors such as changing lifestyle and the transformation of local belief systems. While the importance of local ecological knowledge (LEK) for documentation of biodiversity and environmental change and development of management responses is well established, quantitative tools to analyze and systematically compare LEK are scarce. In this research, we analyze the complexity of local ecological knowledge used by respondents to classify locally-recognized marine species. We do so by applying a modified index of taxonomic distinctness to an ethnoichthyological classification in coastal communities in the Solomon Islands. In addition, we assess simple taxonomic diversity (richness in locally-recognized species names) by comparing taxonomies collected in 1992–1995 and 2014–2015. Results indicate that both endogenous (gender, age) and exogenous (proximity to market) factors have discernible effects on folk taxonomic knowledge in the region, with younger respondents and communities closer to a regional market center displaying a significantly lower richness of local species names. Folk taxonomic distinctness was significantly reduced closer to the regional market. The modified index of taxonomic distinctness applied in this research provides a useful tool to explore facets of local ecological knowledge in addition to simple richness of terms, and to compare across different regions and cultural backgrounds. Understanding changes in LEK is important because such knowledge enables communities who are highly dependent on living natural resources to harvest and manage resources more efficiently and also to detect and react to environmental change.
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  • Date Issued: 2020

Synthesis and photodynamic potential of tetra-and octa-triethyleneoxysulfonyl substituted zinc phthalocyanines

  • Authors: Atilla, Devrim , Savdan, Nil , Durmus, Mahmut , Gürek, Ayşe Gül , Khan, Tania , Rück, Angelika , Walt, Heinrich , Nyokong, Tebello , Ahsen, Vefa
  • Date: 2007
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/281342 , vital:55715 , xlink:href="https://doi.org/10.1016/j.jphotochem.2006.08.022"
  • Description: Synthesis of the water soluble zinc phthalocyanines (3, 4) obtained from the phthalonitriles substituted with oligo(ethyleneoxy)thia groups are described. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, including HSQC, HMBC and COSY bidimensional correlation techniques, electronic spectroscopy and mass spectra. The aggregation behaviour of the phthalocyanine compounds (3, 4) was investigated using UV–vis spectroscopy in dimethylsulphoxide. Photochemical and photophysical measurements were conducted on oligo(ethyleneoxy)thia appended zinc phthalocyanines. General trends are described for quantum yields of photodegredation, fluorescence yields, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds. The phototoxicity against cancer cells of the new compounds was investigated during several in vitro experiments. The dye-sensitized photooxidation of 1,3-diphenylisobenzofurane via 1O2 was studied in dimethylsulphoxide.
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  • Date Issued: 2007

Valuing South Africa's savannas: Methodological Issues

  • Authors: Ballance, A , Shackleton, Charlie M , Shackleton, Sheona E , Geach, B S , Crookes, D , De Wit, M , Evans, J , von Maltitz, Graham P , Willis, C B , Kelatwang, S , Havemann, J
  • Date: 2001
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/182262 , vital:43816 , xlink:href="https://hdl.handle.net/10520/EJC33860"
  • Description: Natural resource valuation techniques have been applied in recent years to savannas and savanna resources in South and southern Africa. Results from these studies have been used to demonstrate the importance of savannas, and to assist in resource-use planning. Because these studies have been conducted to meet different research objectives a large number of disparities exist between studies. This makes comparison of results difficult and identification of underlying drivers of value is problematic. This paper discusses issues which can lead to differences in estimates of resource value, and makes recommendations for future studies to reduce incompatibilities. In particular, this paper recommends that future studies make full descriptions of the objectives of the study, the background characteristics of the study area (including the social, political, economic, cultural, and biophysical characteristics), the methods used, and assumptions made. In this way, the values reported from case studies may be used in other research and decision-making exercises.
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  • Date Issued: 2001

Nonlinear optical response of a low symmetry phthalocyanine in the presence of gold nanoparticles when in solution or embedded in poly acrylic acid polymer thin films

  • Authors: Bankole, Owolabi M , Nyokong, Tebello
  • Date: 2016
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/188719 , vital:44779 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.12.014"
  • Description: In this article, we explored the photophysical and nonlinear optical (NLO) characterizations of low symmetry phthalocyanine (ZnPc-NH2) covalently linked to MPA-capped AuNPs (ZnPc-NH2-AuNPs) and poly acrylic acid (ZnPc-NH2-PAA). Nonlinear optical (NLO) properties of the samples were evaluated using Z-scan technique at 532 nm and 10 ns pulsed duration. We observed enhanced photophysical and nonlinear optical behaviour for the ZnPc-NH2 in presence of AuNPs. By virtue of the magnitude of absorption coefficients and other NLO optical parameters estimated in this work, ZnPc-NH2-AuNPs was found to exhibit improved nonlinear optical response compared to the ZnPc-NH2 and ZnPc-NH2-PAA. Both ZnPc-NH2-AuNPs and ZnPc-NH2 doped in PAA possess strong nonlinear absorption coefficients and very low limiting thresholds than when measured in solution.
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  • Date Issued: 2016

Understanding spatial variation in the drivers of nature-based tourism and their influence on the sustainability of private land conservation

  • Authors: Baum, Julia , Cumming, Graeme S , de Vos, Alta
  • Date: 2017
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/416481 , vital:71352 , xlink:href="https://doi.org/10.1016/j.ecolecon.2017.05.005"
  • Description: Protected areas connect socio-economic and ecological systems through their provision of ecosystem goods and services. Analysis of ecosystem services allows the expression of ecological benefits in economic terms. However, cultural services, such as recreation opportunities, have proved difficult to quantify. An important challenge for the analysis of cultural services is to understand the geography of service provision in relation to both human and ecological system elements. We used data on visitation rates and measures of context, content, connectivity, and location for 64 private land conservation areas (PLCAs) to better understand geographic influences on cultural service provision. Visitation to PLCAs was influenced by a combination of ecological and socio-economic drivers. Variance partitioning analysis showed that ecology explained the largest proportion of overall variation in visitation rates (26%), followed by location (22%). In tests using generalized linear mixed models, individual factors that significantly explained visitation rates included the number of mammal species, the number of Big 5-species (ecological variables), the number of facilities provided (infrastructure) and average accommodation charges (affordability). Our analysis has important implications for the economic sustainability of PLCAs and more generally for understanding the relevance of spatial variation for analyses of cultural services.
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  • Date Issued: 2017

Entrainment of Antarctic euphausiids across the Antarctic Polar Front by a cold eddy

  • Authors: Bernard, Anthony T F , Ansorge, Isabelle J , Froneman, P William , Lutjeharms, Johan R E , Bernard, Kim S , Swart, NC
  • Date: 2016
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/490466 , vital:80363 , xlink:href="https://doi.org/10.1016/j.dsr.2007.06.007"
  • Description: An unusual region of high meso-scale turbulence has been identified in the Indian Ocean sector of the Southern Ocean. It has been shown that this is the result of eddy shedding from the Antarctic Polar Front. These eddies may dramatically affect the local distribution of marine organisms. To investigate this, the euphausiid community structure and species composition in the region of a cold eddy within the Antarctic Polar Frontal Zone (APFZ) was investigated during April 2005. Water masses within the core of the eddy were typically Antarctic, showing they had come from south of the Antarctic Polar Front. Results of numerical analyses indicate that the euphausiid community within the survey area consisted of three distinct groups: those in APFZ waters, those at the edge of the eddy and those in the core of the eddy. These results indicate that eddies generated by the interaction of the Antarctic Circumpolar Current with the South-West Indian Ridge play an important role in transporting Antarctic euphausiid species equatorward, thus contributing to the spatial heterogeneity of the zooplankton community within the region.
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  • Date Issued: 2016

Exploring DOXP-reductoisomerase binding limits using phosphonated N-aryl and N-heteroarylcarboxamides as DXR inhibitors

  • Authors: Bodill, Taryn , Conibear, Anne C , Mutorwa, Marius K , Goble, Jessica L , Blatch, Gregory L , Lobb, Kevin A , Klein, Rosalyn , Kaye, Perry T
  • Date: 2013
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/448912 , vital:74770 , xlink:href=""
  • Description: DOXP-reductoisomerase (DXR) is a validated target for the development of antimalarial drugs to address the increase in resistant strains of Plasmodium falciparum. Series of aryl- and heteroarylcarbamoylphosphonic acids, their diethyl esters and disodium salts have been prepared as analogues of the potent DXR inhibitor fosmidomycin. The effects of the carboxamide N-substituents and the length of the methylene linker have been explored using in silico docking studies, saturation transfer difference NMR spectroscopy and enzyme inhibition assays using both EcDXR and PfDXR. These studies indicate an optimal linker length of two methylene units and have confirmed the importance of an additional binding pocket in the PfDXR active site. Insights into the constraints of the PfDXR binding site provide additional scope for the rational design of DXR inhibitors with increased ligand–receptor interactions.
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  • Date Issued: 2013

A comparison of anthropogenic and elephant disturbance on Acacia xanthophloea (fever tree) populations in the Lowveld, South Africa

  • Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
  • Date: 2002
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181629 , vital:43753 , xlink:href="https://doi.org/10.4102/koedoe.v45i1.10"
  • Description: Acacia xanthophloea (the ‘fever tree’) is a popular medicinal species that is traded widely in South Africa. Although it occurs throughout southern Africa, there is increasing pressure on its riverine and marshy habitats. This study compares the impact of harvesting on an A. xanthophloea population located on private land near Komatipoort, Mpumalanga, with two protected populations situated within the Kruger National Park. The densities of the harvested and protected populations were similar (84±8 trees/ha and 85±20 trees/ha, respectively). There were fluctuations in the quotients between frequencies of trees in successive diameter classes, which is common in savanna where high levels of fire, mega-herbivore and anthropogenic disturbance are experienced. The extent of stem damage (stripping of bark and breakage) by elephants in the protected area was significantly higher than the extent of harvesting on private land, although the degree of damage was relatively low, with only 7 % of the populations having been damaged at rates >26 %. The degree of harvesting on private land was relatively low, with the majority of trees having been harvested at rates of less than 10 % of the stem below 2 m. Despite this, ringbarking had occurred (4 %). The basal diameters and heights were significantly lower in the protected population than in the harvested one, suggesting that over time elephant impact was the more severe disturbance. Acacia xanthophloea exhibited high resilience to disturbance, with all the elephant damaged trees and harvested individuals surviving. However, the mean bark thickness measured in local markets (6.3±1.4 mm) was significantly lower than that measured in either the harvested (12.4±1.0 mm) or the KNP (10.3±0.8 mm) populations. As harvesters tend to select the largest individuals in a population to maximise their financial returns, this could mean that smaller individuals are being harvested, and/or bark is not being given sufficient time to grow back after harvesting. Acacia xanthophloea outside protected areas thus need to be monitored and the management improved, preferably in conjunction with the resource users. In addition, traditional healers, those selling medicinal plants and other members of the community need to continue to be encouraged to cultivate this fast growing species.
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  • Date Issued: 2002
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