The effectiveness of polyethylene glycol (PEG) and polyvinyl polypyrrolidone (PVPP) on removal of tannins from leaf extracts of selected medicinal plants in Limpopo Province

Five selected plant species (Balanites maughamii, Breonadia salicina, Dombeya rotundifolia, Hyperacanthus amoenus and Piliostigma thonningii) were extracted using 70 and 100% acetone and the presence of tannins were determined using radial diffusion assay. Our comparative assessment indicated that plant extracted with 100% acetone showed the highest levels of tannins as compared to 70% acetone. The highest tannin levels in both 70 and 100% acetone extracts were recorded for P. thonningii, while no tannins were detected in B. maughamii. However, addition of polyethylene glycol (PEG) and polyvinyl polypyrrolidone (PVPP) to the extraction media resulted in the reduction of tannins in all crude plant extracts, with PEG being more effective than PVPP. 1% PEG removed the highest quantity of tannins in all plant extracts, in comparison with 0.5% PEG (63.3%) and 0.5 and 1% PVPP (24.8 and 49.4%, respectively).Key words: Acetone, tannin, polyethylene glycol (PEG), polyvinyl polypyrrolidone (PVPP)

Secondary school teachers experiences of implementing a sexuality education programme in the life orientation learning area in Mpumalanga

The child needs to be introduced to all facets of being an adult, whether a woman or a man. For this to be done a planned and organised education should be done. If a child is inadequately educated in this regard life will remain alien and closed, and despite all the opportunities, she or he might never become fully actualised as a man or a woman. Sexuality Education is therefore aimed at helping learners at school to develop a positive view of sexuality, providing them with the necessary information, clarify values and the necessary social skills to make wise and to make wise and informed decisions about all matters relating to their sexuality. Promotion of a healthy personal life-style for learners, they are enabled to be morally independent, accountable, dedicated and responsible adults, all are learnt in Sexuality Education. Teachers and parents play an important role in guiding the learners towards adulthood, according to the values and norms of the society. Parental involvement in sexuality education is essential, but in the modern context parents are seemingly not able to cope with the responsibility due to a number of social and economic issues. Much of the education is left to the schools and responsibility is placed particularly on Life Orientation teachers to respond to this educational imperative. In-service teachers receive training in Sexuality Education in the Life Orientation learning area by way of in-service training workshops to support them in this role. It is, however documented that ”although Sexuality Education programmes have been around for many years, most programmes have not been as effective as hoped” (Edwards, 1998). This raises a question as to whether in-service teachers who are trained in a particular Sexuality Education programme in a certain region in Mpumalanga are indeed implementing it as was intended in the training. In order to partly answer this question, this study will therefore focus on secondary school teachers’ experiences of implementing this particular Sexuality Education programme.Dr. M.P. Van der Merw

Experiences of learning support teachers in the foundation phase, with reference to the implementation of inclusive education in Gauteng

The policy of Inclusive Education (IE) in White Paper 6 (2001) acknowledges that all children can learn with support. The aim of this study is to explore the experiences of Learning Support Teachers (LSTs) in supporting Foundation Phase teachers in implementing Inclusive Education (IE) in Gauteng Province, South Africa. A lack of support for teachers and learners in IE has dominated current discussions on education. According to the Department of Education (DoE, 2000:28), the establishment of an IE system in schools would require appropriate district as well as institution level support services, and more than just accepting learners with different learning needs in mainstream classrooms. Many teachers have not had the benefit of being trained to teach learners who experience barriers to learning, hence most find it difficult. Although specialist teachers in the form of Learning Support Teachers (LSTs) have been employed in the Foundation Phase to fill that gap and assist classroom teachers, the learners are not receiving the assistance hoped for. Based on an assumption that the failings may largely be systemic, this study therefore uses Bronfenbrenner’s ecological systems theory and a qualitative research design to examine the implementation of IE in selected schools, with seven LSTs being interviewed and observed, while documents pertaining to the support rendered were analysed. Seven principals and seven classroom teachers were also interviewed. The analysis employed Creswell’s method and the findings highlighted factors affecting the implementation of IE. The factors include inadequate district support, socio-cultural issues, classroom and management factors, lack of resources and inadequate collaboration between the stakeholders. The study makes recommendations and suggests further areas of research.Inclusive EducationD. Ed. (Inclusive Education

Direct-fired heat pump for multi-pass water heating using microchannel heat and mass exchangers

Absorption heat pump water heaters offer improved performance compared to conventional direct-fired water heaters, with the potential for coefficients of performance well in excess of 1. A primary energy usage comparison with electric heat pumps shows that absorption systems can be competitive with current technology. However, the implementation of these systems in the residential and light commercial market has not been practical for several reasons, including a limited knowledgebase on absorption systems for this application and the lack of compact and economically viable heat and mass exchangers. An improved understanding of the coupled heat and mass transfer processes in thermally driven absorption systems to be used as heat pump water heaters was obtained over the course of this study. In addition, microchannel heat and mass exchangers that enable such compact gas-fired heat pump water heaters were developed and tested. Performance at design and off-design conditions over a range of water and ambient temperatures was simulated in detail with a system-level model developed for this purpose. The system-level model was coupled with a water-tank model to investigate several water heating scenarios including a cold start, response to a medium sized draw and response to stand-by losses. Heat and mass exchangers were designed using component-level heat and mass transfer models. The heat and mass exchangers were first installed and evaluated on a breadboard test facility. Insights from these experiments were then used to design and fabricate a monolithic unit integrating several of the microchannel heat and mass exchangers, coupled with a gas-fired desorber heat exchanger to yield a stand-alone water heater prototype. The performance of the prototype was investigated over a range of water and ambient temperatures. A comparison of results was performed to investigate the deviation between model predictions and experimental values. A refined model was developed that more accurately predicted experimental results. Energy-use and cost analyses were performed and showed the potentially significant energy savings of thermally driven heat pump water heaters.Ph.D

Characterization and biological activity of antifungal compounds present in Breonadia salicina (Rubiaceae) leaves

The aim of this study was to investigate plant species to develop a product with the potential of protecting plants or plant products against plant fungal pathogens. Hexane, dichloromethane, acetone, and methanol leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were evaluated for antifungal activity against seven plant fungal pathogens (Aspergillus niger, A. parasiticus, Colletotrichum gloeosporioides, Penicillium janthinellum, P. expansum, Trichoderma harzianum and Fusarium oxysporum). These plant species were selected from more than 400 plant species evaluated in the Phytomedicine Programme that had good activity against two animal fungal pathogens. All the leaf extracts were active against at least one or more of the phytopathogenic fungi in a serial microdilution assay. Of the six plant species, B. buceras had the best antifungal activity against four of the fungi, with MIC values as low as 0.02 mg/ml and 0.08 mg/ml against Penicillium expansum, P. janthinellum, Trichoderma harzianum and Fusarium oxysporum. The number of active compounds in the plant extracts was determined using bioautography with the above-mentioned plant pathogens. No active compounds were observed in some plant extracts against the fungal plant pathogens indicating possible synergism between metabolites responsible for the antifungal activity of the extract. B. salicina and O. ventosa were the most promising plant species, with at least three antifungal compounds. The antioxidant activities of plant extracts were determined using the qualitative method by spraying TLC chromatograms developed in three eluent systems BEA, CEF and EMW with 1, l-diphenyl -2 picrylhydrazyl (DPPH). The plant extracts of five of these species did not have a strong antioxidant activity. The methanol extract of X. kraussiana was the most active radical scavenger in the DPPH assay amongst the six medicinal plants screened. Based on good activity against Aspergillus niger and A. parasiticus, leaf extracts of the six plant species were also tested for antifungal activity against A. fumigatus, a very important animal fungal pathogen. The acetone extracts of B. buceras, B. salicina, V. infausta and X. kraussina had good antifungal activity against the animal pathogens, with MIC values ranging between 0.02 and 0.08 mg/ml. This indicates that crude extracts of these species may be more valuable in combating Aspergillus infections in animals than in humans. Based on the results discussed above, B. salicina was selected for in-depth study. Serial exhaustive extraction was used to extract plant material with solvents of increasing polarities namely, hexane, chloroform, acetone and MeOH. Amongst the four extractants, MeOH extracted the largest quantity of plant material 12.3% (61.5g), followed by acetone 5.6% (27.8 g), hexane 2.6% (12.8 g) and chloroform 2.1% (10.3 g). The chloroform fraction was selected for further work because it had the best antifungal activity against A. niger, C. gloeosporioides, P. janthinellum and T. harzianum and the bioautography assay showed the presence of several antifungal compounds in the chloroform fraction. Column chromatography was used in a bio-assay guided fractionation and led to isolation of four compounds. The antimicrobial activity was determined against seven plant pathogenic fungi and three bacteria, including the Gram-positive Staphylococcus aureus (ATCC 29213) and the Gram-negative Escherichia coli (ATCC 25922) and Pseudomonas aureus (ATCC 27853). The isolated compounds had good antifungal activity against A. parasiticus with an MIC of 10 μg/ml, while in other cases it ranged from 20 to 250 μg/ml. Amongst the four compounds tested, only three had a clear band, indicating that the growth of the pathogenic fungi was inhibited in the bioautography assay. Nuclear magnetic resonance spectroscopy (NMR) and mass spectroscopy (MS) were used for identification of isolated compounds. Only one compound was identified as the triterpenoid ursolic acid. Ursolic acid has been isolated from several plant species and has antifungal activity against Candida albicans (Shai et al. 2008). This is the first report on the isolation of antifungal compounds from leaves of Breonadia salicina. The other compounds isolated appeared to be mixtures of fatty acids based on mass spectroscopy and the structures were not elucidated. The cytotoxicity of acetone extracts and the four isolated compounds were determined against Vero cells using a tetrazolium-based colorimetric (MTT) assay. The acetone extract was selected based on good in vitro antifungal activity and was used in an in vivo fruit experiment. The acetone extract was less toxic toward the Vero cells with an LC50 of 82 μg/ml than ursolic acid and compound 4 which had LC50 values of 25 and 36 μg/ml respectively. Compounds 2 and 3 had low toxicity against the cells with LC50 values greater than 200 μg/ml. The potential use of the extract or isolated compound(s) against three plant fungal pathogens Penicillium expansum and P. janthinellum as well as P. digitatum (isolated from infected oranges) were tested after treating the oranges with the extract and ursolic acid. The model used gave good reproducible results. The concentration that inhibited growth correlated reasonably well with MIC values determined by serial microplate dilution. There were substantial differences in the susceptibility of the different isolates tested. The activity of ursolic acid was in the same order as that of the crude acetone leaf extract of B. salicina. The LC50 of the extract varied from 1 to 1.8 mg/ml. Penicillium digitatum was more resistant to amphotericin B in comparison to other Penicillium species. It has been reported that the fungus was resistant to the three fungicides: sodium ï-phenylphenate (ï-phenylphenol), imazalil, and thiabendazole used commercially in the fruit industry to reduce postharvest decay (Holmes and Eckert 1999). The toxicity of the extract to Vero cells was in the order of 10 times lower than the LC50 of the extracts to the fungal pathogens. Although much work still has to be done, there is good potential that a commercial product can be developed from an acetone leaf extract of B.salicina leaves, especially if the activity of this extract can be improved by removing inactive compounds. The results confirm the traditional use of B. salicina and demonstrate the potential value of developing biopesticides from plants.Thesis (PhD)--University of Pretoria, 2009.Paraclinical Sciencesunrestricte

Тепловая экономичность привода питательных насосов электростанций

In the production of micro devices the surface properties become more and more important for chemistry, biotechnology and medical technology with respect to wetting properties and chemical composition of the surface. Typical applications are implants as well as micro fluidic systems or miniaturized devices for DNA- and proteome analysis (biochips). In this paper newly designed laser technologies based on UV-laser treatment of polymers for surface processing are described to manipulate wetting properties, cell growth and immobilization of functional molecules with high spatial resolution. Depending on the processing parameters and used polymers either hydrophobic or hydrophilic properties can be enhanced (i.e. laser induced lotus/anti-lotus effect). Enhanced roughness and changes of the chemical composition have also influence on cell growth on polymer surfaces. Thus guiding aids for cells e.g. on medical implants can be generated by laser irradiation. Due to photo oxidation processes while UV-treatment in air, functional groups are created that are suited for covalent bonding of (bio)moelcules onto the surfaces. A second process for the locally selective immobilization of anchor molecules based on azide functionalized templates suitable for further modification steps is presented by means of irradiating polymers under solutions of these linkers