Photophysical properties of zinc phthalocyanine–uridine single walled carbon nanotube–conjugates
- Authors: Ogbodu, Rachael O , Amuhaya, Edith K , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193586 , vital:45350 , xlink:href="https://doi.org/10.1016/j.saa.2015.04.040"
- Description: The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.
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- Date Issued: 2015
Photophysical studies of newly derivatized mono substituted phthalocyanines grafted onto silica nanoparticles via click chemistry
- Authors: Fashina, Adedayo , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189537 , vital:44855 , xlink:href="https://doi.org/10.1016/j.saa.2014.12.070"
- Description: This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine–silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.
- Full Text:
- Date Issued: 2015
Photophysicochemical properties and in vitro cytotoxicity of zinc tetracarboxyphenoxy phthalocyanine–quantum dot nanocomposites
- Authors: Oluwole, David O , Tilbury, Chelsea M , Prinsloo, Earl , Limson, Janice L , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240846 , vital:50878 , xlink:href="https://doi.org/10.1016/j.poly.2015.12.060"
- Description: Cadmium based quantum dots (QDs) capped with two different ligands (thioglycolic acid, TGA, and glutathione, GSH) were synthesized. The QDs are: CdTe, CdTe/ZnO, CdTeSe, CdTeSe/ZnO and CdSe/ZnS (the last one for TGA only). Cytotoxicity of the QDs against MCF-7 epithelial breast cancer was evaluated. The TGA capped core QDs were found to be highly cytotoxic to the cell lines when compared to GSH capped ones. The glutathione capped QDs were covalently linked to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc). Cytotoxicity and photophysicochemical properties of the conjugates were investigated. The toxicity of the core QDs was reduced in the presence of ZnTCPPc. Enhanced triplet quantum yields and long triplet lifetimes were obtained for ZnTCPPc in the presence of all QDs.
- Full Text:
- Date Issued: 2015
Physicochemical and photodynamic antimicrobial chemotherapy studies of mono-and tetra-pyridyloxy substituted indium (III) phthalocyanines
- Authors: Osifeko, Olawale L , Durmus, Mahmut , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189547 , vital:44856 , xlink:href="https://doi.org/10.1016/j.jphotochem.2014.12.011"
- Description: The synthesis and photophysicochemical properties of mono- and tetra-pyridyloxy substituted indium(III) phthalocyanines (InPcs) are presented in this study. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of these compounds. The complexes exhibited high singlet oxygen quantum yields (ФΔ) ranging from 0.44 to 0.66 in DMF, and from 0.44 to 0.69 in DMSO and ФΔ = 0.31 for the quartenized tetra substituted InPc which is soluble in water. The triplet quantum yields (ФT) ranged from 0.77 to 0.95 in DMF and from 0.77 to 0.94) in DMSO. The tetra substituted photosensitizers do not differ in their inactivation of bacteria with over 8 log reduction of viable bacteria when compared with the mono substituted photosensitizer which could only manage a 1 log reduction.
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- Date Issued: 2015
Physicochemical behavior of nanohybrids of mono and tetra substituted carboxyphenoxy phthalocyanine covalently linked to GSH–CdTe/CdS/ZnS quantum dots
- Authors: Oluwole, David O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189480 , vital:44850 , xlink:href="https://doi.org/10.1016/j.poly.2014.10.024"
- Description: Zinc monocarboxyphenoxy and tetracarboxyphenoxy phthalocyanines were covalently linked with three different sizes of glutathione capped core/shell/shell {CdTe/CdS/ZnS(4.2), CdTe/CdS/ZnS(5.1) and CdTe/CdS/ZnS(6.7)}; a core shell {CdTe/CdS(3.1)} and core {CdTe(2.4)} quantum dots. The physicochemical behavior and Förster resonance energy transfer (FRET) processes of the nanohybrids were investigated. The highest FRET efficiency was observed with CdTe/CdS/ZnS(6.7) nanohybrids with 98% and the least efficiency was observed with CdTe(2.4) nanohybrids with 85%. The CdTe/CdS/ZnS(6.7) also showed the best physicochemical behavior. These good physicochemical properties make the synthesized nanohybrids viable photosensitizers.
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- Date Issued: 2015
Phytochemical analyses, synthesis of silver nanoparticles from Filipendula ulmaria (L.) Maxin and Agathosma betulina (Berg.) Pillans and their bioassays
- Authors: Herbert, Chiguvare
- Date: 2015
- Subjects: Phytochemicals , Analgesics , Anti-inflammatory agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/29289 , vital:77847
- Description: Agathosma betulina (Buchu) and Filipendula ulmaria (Meadowsweet) are popular herbal plants used in South Africa. These plants have been used as herbal medicines for the treatment of several diseases for years but without scientific analysis to validate their claims as herbal remedies. Hydrodistillation was carried out for the two plants and 2.3 g were obtained from buchu representing a yield of 0.8 percent while 0.73 g was obtained from A. betulina representing a yield of 0.73 percent. The two oils were analysed using GC/MS and 41 oil components were obtained from F. ulmaria and 11 oil components were obtained from A. betulina. The major oil components of F. ulmaria oil were found to be Methyl salicylate (17.2 percent), salicaldehyde (10.6 percent), menthol (8.6 percent), Anisaldehyde (8.2 percent), menthone (8.1 percent) Isomenthone (6.3 percent) and A. betulina oil comprised majorly of Isomenthone (26.1 percent), Diosphenol (17.9 percent), Menthone (12.1 percent), p-Diosphenol (12.8 percent) and pulegone (10.5 percent). Diosphenol with its two isomers constitute the biggest component of 30.7 percent of A betulina oil. The ethanolic crude extract of F. ulmaria was subjected to isolation through chromatographic methods. One isolate was obtained and fully elucidated by 2D NMR analysis to be Lupeol. The two plants were further used as agents in plant mediated silver nanoparticle synthesis. Use of medicinal plants for the synthesis of silver nanoparticles is a green synthesis approach because of the use of non hazardous reacting materials, less aggressive reaction conditions such as very low energy requirements, harmless solvents systems among others. F. ulmaria mediated Ag-NPs synthesis was not successful and thus yielded inconclusive results. A. betulina plant mediated biosynthesis of silver nanoparticles using the chemical reduction of silver nitrate method was completed in 24 hours at 40 °C, 60⁰C and 75⁰C. UV-Vis spectroscopy, FTIR spectroscopy and TEM were used to confirm the reduction of silver ions and formation of silver nanoparticles. F. ulmaria mediated synthesis of silver nanoparticles yielded inconclusive results. Polydispersed spherical, oblong and irregularly shaped silver nanoparticles ranging from 5-60 nm were produced from the A. betulina extract at synthesised at 60⁰C. This is the first report on the synthesis of silver nanoparticles using A. betulina and F. ulmaria. The Formalin assay, a chemical model for stimulation of pain and the egg albumin paw oedema model were used for testing analgesic and anti-inflammatory activity respectively. The oils, ethanolic crude extracts and the silver nano particles were tested against standard drugs. The oils, ethanolic crude extracts and the silver nano particles were found to have significant ability to inhibit pain and inflammation. Results obtained gave scientific validation for the uses of A. betulina and F.ulmaria extracts in the management of pain and inflammation in traditional medicine. , Thesis (PhD) -- Faculty of Science and Agriculture, 2015
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- Date Issued: 2015
Plasmodium falciparum Hop (PfHop) interacts with the Hsp70 chaperone in a nucleotide-dependent fashion and exhibits ligand selectivity
- Authors: Zininga, Tawanda , Makumire, Stanley , Gitau, Grace W , Njunge, James M , Pooe, Ofentse J , Klimek, Hanna , Scheurr, Robina , Raifer, Hartmann , Prinsloo, Earl , Przyborski, Jude M , Hoppe, Heinrich C , Shonhai, Addmore
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431752 , vital:72801 , xlink:href=" https://doi.org/10.1371/journal.pone.0135326"
- Description: Heat shock proteins (Hsps) play an important role in the development and pathogenicity of malaria parasites. One of the most prominent functions of Hsps is to facilitate the folding of other proteins. Hsps are thought to play a crucial role when malaria parasites invade their host cells and during their subsequent development in hepatocytes and red blood cells. It is thought that Hsps maintain proteostasis under the unfavourable conditions that malaria parasites encounter in the host environment. Although heat shock protein 70 (Hsp70) is capable of independent folding of some proteins, its functional cooperation with heat shock protein 90 (Hsp90) facilitates folding of some proteins such as kinases and steroid hormone receptors into their fully functional forms. The cooperation of Hsp70 and Hsp90 occurs through an adaptor protein called Hsp70-Hsp90 organising protein (Hop). We previously characterised the Hop protein from Plasmodium falciparum (PfHop). We observed that the protein co-localised with the cytosol-localised chaperones, PfHsp70-1 and PfHsp90 at the blood stages of the malaria parasite. In the current study, we demonstrated that PfHop is a stress-inducible protein. We further explored the direct interaction between PfHop and PfHsp70-1 using far Western and surface plasmon resonance (SPR) analyses.
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- Date Issued: 2015
Problem-solving ability of first year CS students: A case study and intervention
- Authors: Marais, Craig , Bradshaw, Karen L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/475235 , vital:77787
- Description: This paper reports the findings of computational thinking research undertaken to develop problem-solving skills in first year computer science students. Through the use of pre-and post-tests, statistical results are presented showing the definite acquisition of problem-solving skills by the students after completing the introductory first year computer science course. These skills are argued to be both innate in some students and acquired in others. By identifying the component skills required and presenting a step-by-step approach to teaching problem solving, this research aims to provide a method for actively instilling these skills in learners who lack them.
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- Date Issued: 2015
Resemiotising concerns from constituencies in the South African parliament
- Authors: Siebörger, Ian , Adendorff, Ralph D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/385362 , vital:68011 , xlink:href="https://doi.org/10.2989/16073614.2015.1061892"
- Description: Members of Parliament (MPs) in South Africa represent different constituencies across the country. In this article, we report on how MPs resemiotise concerns from their constituencies in spoken discourse in a parliamentary committee, and on the effectiveness with which this informa- tion is in turn resemiotised into a written committee report. Both resemiotisations form part of a genre chain which we investigated while conducting a linguistic ethnography of the communica- tion difficulties which occur in parliament's committee process. We use a multi-stranded theoretical foundation, including tools from Systemic Functional Linguistics, Interactional Sociolinguistics and Legitimation Code Theory to analyse MPs’ ability to communicate concerns from their constituen- cies in parliamentary discourse. We conclude that the success of MPs’ resemiotisations of these concerns depends on their ability to rescale them as relevant on a national level, and on their ability to negotiate the power relations at play in parliament.
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- Date Issued: 2015
Service learning based environmental health promotion activities for pharmacy students: educating young on the safe disposal of medicines and used sharps
- Authors: Srinivas, Sunitha C , Paphitis, Sharli , Ncomanzi, A.S , Tandlich, Roman , Bradshaw, Karen L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/475255 , vital:77788
- Description: The objective of this study was to investigate the effects of a service-learning based environmental health promotion exhibit in raising awareness of safe disposal of medicines and used sharps during the 2014 National Science Festival in South Africa. The study design utilised a computer-based quiz, an information poster, an interactive model and a take-home information leaflet on the safe disposal of medicines and used sharps which were developed by students and staff in the faculty of pharmacy at Rhodes University. Predominantly school students attended the exhibit and took part in a quiz. 413 participants took part in the environmental health promotion activity, with 91% of the participating learners attending schools in the Eastern Cape Province. significant improvement (p is less than 0.001). Moreover, the results show significant gender differences for both the pre- and post-intervention mean scores. The environmental health promotion project was successful in raising awareness of the safe and appropriate disposal of medicines and used sharps by highlighting the dangers associated with their incorrect disposal, both to the environment and eventually to humans. Similar continuous health promotion activities are essential for sustainable effectiveness in the transformation of individual and communal actions in South Africa for the safe disposal of medicines and used sharps.
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- Date Issued: 2015
Socio-spatial dynamics in the use of wild natural resources: Evidence from six rapidly growing medium-sized cities in Africa
- Authors: Schlesinger, Johannes , Drescher, Axel W , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180897 , vital:43668 , xlink:href="https://doi.org/10.1016/j.apgeog.2014.11.013"
- Description: Increasing urbanisation in sub-Saharan Africa transforms spatial configurations in and around towns and cities. At the same time wild natural resources play an important role in African livelihoods. Yet, little is known about the impact of urbanisation on the socio-spatial dynamics of the use of wild natural resources. Here we examined the importance of these resources for livelihoods, differences in their use between different locations along the urban-rural continuum, and the respective temporal dynamics. A total of 1158 households were interviewed in six medium-sized cities distributed across five African countries using a standardised questionnaire supplemented by expert interviews and spatial analyses employing Geographic Information Systems. Overall, even though periurban and rural households were more likely to use wild natural resources than those in the urban areas, the use of these resources was generally high along the entire urban-rural continuum. Despite the increasing urban pressure on these resources, they remain an integral part for most households, not only for those lacking access to productive resources, but also for those with a higher standard of living. This trend was found across all study towns, despite the marked differences in their respective socio-spatial as well as environmental settings.
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- Date Issued: 2015
SPACES Project ARS AfricaE–Adaptive Resilience of Southern African ecosystems
- Authors: Falge, E M , Brümmer, Christian , Schmullius, Christiane , Hüttich, C , Scholes, Robert J , Midgley, Guy F , Hickler, Thomas , Scheiter, Simon , Twine, Wayne , Bradshaw, Karen L , Lück, W , Lenfers, Ulfia A , Thiel-Clemen, T , Mafukute, Mukelabai , Kutsch, Werner L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/475274 , vital:77791
- Description: Nowadays, many semi-arid ecosystems are affected by at least two different kinds of disturbances: land use (change) and climate change. Based on this, it can be hypothesized that even very resilient ecosystems may not return to their initial state after disturbance, but will rather adapt to a new steady-state. We name this phenomenon "Adaptive Resilience of Ecosystems" and use it as base for the research concept of ARS AfricaE. This project wants to go beyond older approaches that only describe structural changes in savannas and their drivers. It employs functional aspects, such as the investigation of biogeochemical cycles, but also targets a deeper understanding of the functional consequences of ecosystem changes caused by multiple disturbances, and defines "degradation" as a sustained loss in the broad set of ecosystem services, i.e. a decrease in natural capital. To achieve this goal, the project will • create a network of research clusters (with natural and altered vegetation) along an aridity gradient in the Greater Karoo, Kruger National Park in South Africa, and Kataba Forest Reserve in Zambia • link biogeochemical functions with ecosystem structure, diversity of species and eco-physiological properties • describe ecosystem disturbance (and recovery) in terms of ecosystem function such as carbon balance components and water use efficiency • build an individual-based model to predict ecosystem dynamics under (post) disturbance managements • combine this model with long-term landscape dynamic information derived from remote sensing and aerial photography • develop sustainable management strategies for disturbed ecosystems and land use change.
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- Date Issued: 2015
Spatial and temporal changes in estuarine food web structure: differential contributions of marsh grass detritus
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457295 , vital:75623 , xlink:href="https://doi.org/10.1007/s12237-014-9814-5"
- Description: We measured stable isotope signatures and fatty acid profiles in dominant consumers and basal food sources to assess spatial and temporal changes in the trophic structure within an estuarine ecosystem. The consumers analyzed included zooplankton, benthic invertebrates and fishes from the upper, middle and lower reaches of the estuary collected over four seasons. The contributions of different food sources to the consumers were assessed using the isotopic mixing model stable isotope analysis in R (SIAR). Our stable isotope and fatty acid data indicated that the food webs differed significantly among reaches and seasons within the estuary. Benthic invertebrates exhibited lower carbon isotopic (δ13C) values in the upper reaches of the estuary during all seasons, with lowest values occurring during autumn. In contrast, nitrogen isotopic (δ15N) values of consumers were higher in the upper reaches of the estuary and were highest during summer and spring. SIAR models and fatty acid compositional data both indicated greater utilization of marsh grass by consumers inhabiting the lower reaches of the estuary, particularly during autumn and winter. Our data indicated that differential inputs of detritus contributed to spatial changes in the benthic estuarine food web structure and that the trends changed throughout the year.
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- Date Issued: 2015
Spectroscopic and nonlinear optical properties of the four positional isomers of 4α-(4-tert-butylphenoxy) phthalocyanine
- Authors: Ngubeni, Grace N , Britton, Jonathan , Mack, John , New, Edward , Hancox, Ian , Walker, Marc , Nyokong, Tebello , Jones, Tim S , Khene,Samson M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241448 , vital:50940 , xlink:href="https://doi.org/10.1039/C5TC01601K"
- Description: The spectroscopic and nonlinear optical properties of the positional isomers of metal free 4α-(4-tert-butylphenoxy) phthalocyanine are presented. Second order nonlinear polarizability (β), imaginary hyperpolarizability (Im(γ)) and imaginary susceptibility (Im[χ(3)]) values were determined for the four positional isomers. The measured β values of the four isomers displayed the following trend, C4h (34.0 × 10−5 m MW−1) > D2h (28.8 × 10−5 m MW−1) > C2v (22.8 × 10−5 m MW−1) > Cs (13.7 × 10−5 m MW−1).
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- Date Issued: 2015
Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
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- Date Issued: 2015
Study of the biotransformations and microbiological properties of cymbopogon citratus
- Authors: Ajayi, Emmanuel Olusegun https://orcid.org/0000-0002-0838-4948
- Date: 2015
- Subjects: Lemongras , Essences and essential oils
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19737 , vital:43197
- Description: Variations in the essential oil yield, chemical composition and kinetics of chemical transformation, antibacterial, and antioxidant properties of the Cymbopogon citratus cultivated in Alice, Eastern Cape of South Africa, over a period of 12 months using the solvent-free microwave extraction and the modified forms of conventional hydrodistillation methods have been evaluated. The modified forms involve variation in the pH medium to effect extraction and to obtain the whole leaf extracts of Cymbopogon citratus (lemongrass). The GC-MS analyses of the essential oils revealed the presence of 10, 11, 13, and 9 principal compounds in the microwave, extraction, hydrodistillation (water-distilled), hydrodistillation (aciddistilled and hydrodistillation (base-distilled), respectively with citral being the prominent compound in all the various extraction methods, with the water-distilled method having the highest cumulative citral content under the period specified. Each of the components of the oils varied in quantity and quality of yield at different points of the year. Different extraction methods produce different compounds. Increase in the amount of citral content was observed during the maturation stage of Cymbopogon citratus in all the extraction methods. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration (MIC) values were determined on the oils and extracts of Cymbopogon citratus using agar dilution method. The essential oils obtained using all the methods of extraction showed activity against all the tested bacteria at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the acid-distilled varied between 1.25 and 5.0 mg mL-1, while those obtained by both water- and base-distilled showed equal activity on the microorganisms with the MIC ranging between 2.5 and 10 mg mL-1. The microwave extraction showed the least activity with the MIC of 10 mg mL-1. This however suggested that the oils obtained through acid-distillation showed the greatest activity than all other methods of extraction. Activity of the various extracts on bacteria showed that the ethanol extract had the highest activity on the tested organisms with MIC ranging between 0.625 and 1.25 mg mL-1. This was closely followed by the acid-extract (1.25 and 5.0 mg mL-1), methanol extract (1.25 and 10 mg mL-1), acetone extract (2.5 and 5.0 mg mL-1), and base extract (5.0 mg mL-1). Both cold water and hot water extracts showed the least activity of MIC, >10 mg mL-1. The antioxidant and free-radical scavenging activity of the obtained oils and extracts were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay, [(2,2ˊ-azino bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS), nitric oxide and ferric reducing power assays. The oils and extracts showed DPPH radical scavenging ability, but not as high as the standard drugs. The base extract showed a higher reducing power than the standard drug, rutin. There were significant differences in the phytochemicals contents of the various leaf extracts. The acetone extract has the highest flavonol, proanthocyanidin, and alkaloid contents. The ethanol extract showed the highest amount of phenolic content with the acid extract, having the least. Thin layer chromatography (TLC) and column chromatography was employed to obtain different fractions of extracts using four eluent solvent systems of varying polarities: toluene, petroleum ether, hexane and ethyl acetate and sprayed with anisaldehyde. A single, visible spot of B-fraction was developed, collected and analyzed as 1-methyl-2,4,5- trinitroimidazole with renown valuable properties. , Thesis (PhD) -- Faculty of Science and Agriculture, 2015
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- Date Issued: 2015
Study South Africa
- Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
- Date: 2015
- Subjects: Education, Higher -- South Africa , Education and globalization -- South Africa Student mobility -- Africa International education -- South Africa Education, Higher -- International cooperation , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/64911 , vital:28636 , ISBN 9780620672306
- Description: [Editor's Letter]: This, the 15th edition of Study South Africa, continues to provide a platform for South African universities to profile themselves. It also provides highlights from the South African Higher Education system for the past year. This edition will focus on research and the internationalisation of research in the South African context. Study South Africa has established itself as the international mouthpiece for South African universities and without missing a beat has been produced by volunteers who, with enthusiasm, have dedicated their time and intellect to promote Higher Education Internationalisation as well as to promote South Africa as a knowledge destination for students, academics and professional staff. It is a special privilege and honour to write the introductory message for this 15th edition of Study South Africa as President of IEASA and Editor of the publication. In an era where global re-organisation is dominating the Higher Education scene and new alliances are formed to emulate the new geopolitical landscape, we need to take note of all the challenges facing Higher Education Internationalisation. A number of trends can be identified as major influences on Higher Education on a global scale. I will focus on some of those trends affecting Higher Education in emerging economies and the developing world. The first of these trends is the focus on regional and south-south cooperation. South African universities indicated their intent to further develop closer relationships with universities in Africa through their participation in the re-thinking of Africa’s future during the African Higher Education Summit on the Revitalisation of Higher Education for Africa’s future, in Dakar, Senegal during March 2015. The vision agreed upon during the summit is to ‘develop a high quality, massive, vibrant, diverse, differentiated, innovative, autonomous and socially responsible Higher Education sector. This sector will be a driving force to achieving the vision outlined in the Agenda 2063 by the African Union with a commitment to a shared strategic framework for the inclusive growth, sustainable development and global strategy to optimise the use of Africa’s resources for the benefit of all Africans’. The role of universities would be to develop closer cooperation as well as to advance research with a focus on innovation and sustainable economic growth that will integrate African economies as equal partners in the world economy. It is clear from the vision that although the emphasis should be on inter-African collaboration, collaboration with institutions outside the African continent should not be excluded to achieve the knowledge creation needed to achieve Agenda 2063. Another Higher Education Internationalisation trend in South Africa is the development of closer cooperation within the BRICS countries. The agreements reached and strategies agreed to during the BRICS Summit in Ufa, and included in the Ufa Declaration of 17 June 2015, open doors to future collaborations between BRICS universities. It is envisaged that in the next year the constituent meeting of the BRICS University Network and the establishment of the BRICS Universities League will provide the necessary framework for future collaboration amongst universities from the BRICS member countries. It is imperative that organisations like IEASA and the Brazilian FAUBAI play a key role in the establishment and function of the above mentioned networks. We can provide the necessary support and leadership to other member countries where Higher Education Internationalisation is still at the early stages of conceptualisation and organisation. It will be important to make effective use of the occasion of the Global Conference on Higher Education Internationalisation, scheduled to take place in South Africa in August 2016, to debate and set the future agenda for the BRICS University Network in relation to the rest of the world. It is also vital that the BRICS universities as well as the universities in Africa integrate fully with the rest of the world instead of developing a separate grouping. , 15th Edition
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- Date Issued: 2015
Surface modification of silica-coated gadolinium oxide nanoparticles with zinc tetracarboxyphenoxy phthalocyanine for the photodegradation of Orange G
- Authors: Ledwaba, Mpho , Masilela, Nkosiphile , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193621 , vital:45353 , xlink:href="https://doi.org/10.1016/j.molcata.2015.03.023"
- Description: Zinc tetracarboxyphenoxy phthalocyanine was covalently linked to Gd2O3 nanoparticles for the photocatalytic degradation of Orange G. Characterization of the composite was carried out using XRD, TEM, XPS, UV–vis spectroscopy and FT-IR spectroscopy. The composite showed improved photophysical properties over the phthalocyanine alone and the catalyst was found to be reusable. Analyses of the photodegradation rates of the azo dye indicated pseudo first-order kinetics.
- Full Text:
- Date Issued: 2015
Synthesis and characterization of Na (Y, Gd) F4 upconversion nanoparticles and an investigation of their effects on the photophysical properties of an unsubstituted tetrathiophenoxy phthalocyanine
- Authors: Taylor, Jessica M , Litwinski, Christian , Nyokong, Tebello , Antunes, Edith M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241437 , vital:50939 , xlink:href="https://doi.org/10.1007/s11051-015-2889-5"
- Description: Sphere- and star-shaped Na(Y,Gd)F4:Yb/Er(Tm)upconversion nanoparticles (UCNP) were successfully synthesized utilizing a methanol-assisted thermal decomposition approach and their spectroscopic (absorption, emission and luminescence lifetime) properties fully characterized. The factors affecting the size and shape of the UCNPs were studied and discussed in detail. The size of the nanoparticles was determined using TEM primarily and found to be approximately 19 and 30 nm for the Er and Tm spheres, respectively, while the Er and Tm “stars” were found to be much larger with sizes ranging from 110 to 240 nm, respectively (as determined along the width of the nanoparticle). In addition, their influence on the spectroscopic properties of an unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) was investigated. The UCNP were found to produce characteristic upconversion luminescence emissions in the blue, green, red and NIR regions. Simple mixing with an H2Pc in toluene was found to exert no obvious changes in the spectroscopic properties of the Pc, although a considerable increase in the radiative lifetimes is observed for the Pc in the presence of the UCNPs. The singlet oxygen generation mediated by the red light excitation of the H2Pc mixed with UCNP was found to decrease in the presence of the NPs.
- Full Text:
- Date Issued: 2015
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.
- Full Text:
- Date Issued: 2015