Chapter one: Founding and establishing an imperial university: the first twenty-five years
- Authors: Maylam, Paul
- Date: 2017
- Subjects: Rhodes University -- History , Rhodes Unviersity , Universities and colleges -- South Africa -- Grahamstown
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/59896 , vital:27689
- Description: Critics of South Africa's Truth and Reconciliation Commission (TRC) that sat in the late 1990s have sometimes pointed to its failure to examine the role of larger collectivities in colluding with or acquiescing in the apartheid system. Universities, for instance, have been singled out for their failure both to make submissions to the TRC and to acknowledge openly their past shortcomings during the apartheid era. The historically white, English-medium universities – among them Rhodes University – liked to project themselves as liberal institutions. This book puts this self-representation to the test by looking critically at the operation and functioning of Rhodes University during the segregation and apartheid eras. This study is one of very few that recounts and analyses the whole history of a South African university in a single volume. It covers the founding of Rhodes University College (as it was then called) in 1904, traces its development over the decades, through the attainment of independent status in 1951, ending with a full consideration of the transformation challenges that the university has faced in the post-apartheid era. This is a critical study that points to some of the university’s past failures. But there is also a celebratory dimension, as the book highlights some of the achievements and successes of those who have worked and studied at Rhodes University over the past 112 or so years. , Please note that only the first chapter of the book is available online. For further information, or should you wish to purchase a copy of this item, please contact Bulelani Mothlabane (b.mothlabaneATru.ac.za).
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- Date Issued: 2017
Characterisation and cryopreservation of semen from indigenous Namaqua Afrikaner sheep breed, in comparison with Dorper and Dohne Merino breeds
- Authors: Letsoalo, Phutiane Thomas
- Date: 2017
- Subjects: Merino sheep Dorper sheep Semen
- Language: English
- Type: Thesis , Masters , Animal Science
- Identifier: http://hdl.handle.net/10353/11707 , vital:39099
- Description: The aim of this study was to characterise and cryopreserve semen of the indigenous Namaqua Afrikaner breed, and to compare it to that of Dorper and Dohne Merino sheep, whose semen is commercially frozen on a large scale. The study was conducted between January and August 2015. September 2013-born Namaqua Afrikaner (12), Dohne Merino (12) and Dorper (9) rams were used in the study. The rams were kept under kraal conditions with adequate shade, and they received a high protein, high energy diet. Originally it was envisaged to collect semen samples using the artificial vagina (AV) method, which proved to be problematic with the Namaqua Afrikaner rams. Semen samples were subsequently collected twice a week by either AV (Dohne Merino and Dorper) or electro-ejaculation (EE; all three breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each semen sample was diluted with Triladyl® (1:3) and subsequently frozen in liquid nitrogen vapour in straws. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5 ml) from each thawed sample was assessed microscopically for post-thaw motility and percentage live sperm. Nigrosin-Eosin smears were prepared of fresh, diluted and frozen-thawed semen samples for determination of percentage live sperm. Data of all the traits were analysed with the GLM and CHI-SQUARE procedures of the SAS statistical package. Breed had a significant effect on ejaculate volume of fresh semen collected either via electro-ejaculation or artificial vagina. Dorper rams (1.37 ± 0.08 ml) and Dohne Merino rams (1.20 ± 0.08 ml) produced ejaculates with higher (P <0.05) semen volume than Namaqua Afrikaner rams (1.09 ± 0.08 ml) when using the EE. With the AV method, Dohne Merino rams (1.46 ± 0.08 ml) produced a higher (P <0.05) ejaculate volume than Dorper rams (1.22 ± 0.08 ml). Motility of the frozen-thawed semen samples was lower than that of the fresh and diluted samples for all breeds and collection methods. Furthermore, motility 3 hours after thawing was also lower than motility assessed immediately after thawing for all breeds and collection methods. Motility of frozen-thawed semen collected with an AV and evaluated at 7, 30 and 90 days after freezing was significantly higher than that collected via EE. Dorper rams had the lowest sperm concentration (1.10 ± 5.29x109 sperm/ml) and the Namaqua rams the highest sperm concentration (1.22 ± 5.20x109 sperm/ml) (P ˂0.05). The AV samples had a higher (P >0.05) sperm concentration (1.20 ± 3.68x109 sperm/ml) than the EE samples (1.11 ± 3.51x109 sperm/ml). The percentage live sperm in the fresh semen samples did not differ among Namaqua Afrikaner (67.76 ± 1.94percent), Dohne Merino (68.59 ± 1.94percent) and Dorper (72.82 ± 1.98percent) rams. The percentage live sperm for all three breeds dropped considerably after freezing to 17.76 ± 2.03percent, 17.86 ± 2.03percent and 22.72 ± 2.07percent respectively. It remained constant for all the breeds from 7 until 90 days after freezing, indicating that length of storage should not have an effect on percentage live sperm for semen collected via AV or EE. Percentage live sperm of the frozen-thawed semen of the Namaqua rams was lower than that of the Dorper rams, indicating that the Namaqua semen collected via EE did not freeze as well as that of the Dorper semen. In conclusion, neither fresh nor frozen-thawed Dorper and Dohne Merino semen collected via EE did differ significantly. Furthermore, except for semen volume, Dorper and Dohne Merino semen collected via AV did not differ significantly whether evaluated as fresh or frozen-thawed semen. However, both Dorper and Dohne Merino rams produced semen with higher motility and a higher percentage live sperm post-thaw when the semen samples were collected via an AV than via EE. From these results it can therefore be postulated that if Namaqua semen were collected via AV it could have a higher post-thaw percentage live sperm than if semen was collected via EE. Advanced further studies are necessary to investigate the reason for the lower post-thaw survival rate of sperm of the Namaqua Afrikaner rams. This is necessary as semen stored in a cryobank for breeding and conservation purposes for this endangered breed has to be of high quality. Such resources as cryobanks are expensive and funds cannot be wasted on preserving inferior samples that could not fertilize an ovum when needed. The low percentage of live sperm obtained with the frozen-thawed samples in this, as well as other studies on indigenous breeds, is an indication that further research is needed into more suitable freezing protocols. It can be concluded that Namaqua Afrikaner semen cannot be frozen successfully for the purpose of storage in a cryobank, when using a freezing protocol based on Triladyl® as extender. Furthermore, any increase in post-thaw survival rate of sperm will be beneficial and it is therefore suggested that all efforts be made to solve the problem of the Namaqua Afrikaner rams that do not want to ejaculate into an artificial vagina.
- Full Text:
- Date Issued: 2017
Characterisation and cryopreservation of semen from indigenous Namaqua Afrikaner sheep breed, in comparison with Dorper and Dohne Merino breeds
- Authors: Letsoalo, Phutiane Thomas
- Date: 2017
- Subjects: Cryopreservation of organs, tissues, etc Merino sheep Dorper sheep
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/4759 , vital:28510
- Description: The aim of this study was to characterise and cryopreserve semen of the indigenous Namaqua Afrikaner breed, and to compare it to that of Dorper and Dohne Merino sheep, whose semen is commercially frozen on a large scale. The study was conducted between January and August 2015. September 2013-born Namaqua Afrikaner (12), Dohne Merino (12) and Dorper (9) rams were used in the study. The rams were kept under kraal conditions with adequate shade, and they received a high protein, high energy diet. Originally it was envisaged to collect semen samples using the artificial vagina (AV) method, which proved to be problematic with the Namaqua Afrikaner rams. Semen samples were subsequently collected twice a week by either AV (Dohne Merino and Dorper) or electro-ejaculation (EE; all three breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each semen sample was diluted with Triladyl® (1:3) and subsequently frozen in liquid nitrogen vapour in straws. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5 ml) from each thawed sample was assessed microscopically for post-thaw motility and percentage live sperm..
- Full Text:
- Date Issued: 2017
Characterisation of antibacterial compounds produced by Pseudomonas spp. isolated from Hogsback wetlands, Eastern Cape, South Africa
- Authors: Obi, Akudo Odochi
- Date: 2017
- Subjects: Bacteriology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15688 , vital:40507
- Description: With microbial pathogens developing resistance against currently existing antimicrobials, there is an earnest need to discover and develop new therapeutic compounds with unique and/or precise modes of action. Natural products have provided the inspiration for most of the active ingredients in medicines and thus are regarded as a potential screening resource lead for discovery of new drugs. Pseudomonads are ubiquitous, Gram-negative, motile bacteria that flourish and inhabit a diversity of environments. Literature has vastly revealed that some members of the genus Pseudomonas are capable of producing a plethora of biologically active metabolites and thus are regarded as “attractive” bacteria for testing as potential sources for new therapeutic compounds. In this regard, this study was undertaken with an aim to isolate and characterize antibacterial compounds produced by Pseudomonas species isolated from aquatic milieu of the Hogsback wetlands, Eastern Cape, South Africa. A total of 12 water samples were aseptically collected from Hogsback wetlands. To ascertain antimicrobial potential of the isolates, 9 test bacterial (sensitive) strains, namely Escherichia coli ATCC 3695, Vibrio fluvialis, Salmonella typhimurium, Salmonella enteritidis, Pseudomonas aeruginosa ATCC 27853, Escherichia coli (2), Listeria ivanovii, Listeria monocytogenes and Enterococcus faecalis ATCC 19433 were used for antimicrobial screening. A total of 500 presumptive Pseudomonas spp. were isolated and screened for the production of antibacterial compound through the Agar-well diffusion method. About 8percent of the presumptive Pseudomonas spp. produced compound with activity against the test bacteria and based on the levels of activity shown, three isolates coded as A53, Y55 and Y138 were selected and identified by 16S rDNA sequence analysis and The Basic Local Alignment Search Tool analysis revealed that the three isolates (A53, Y55 and Y138) belonged to the Pseudomonas genus. Using MEGA6 software, a molecular phylogenetic tree was constructed by Maximum Likelihood Method. The phylogenetic analysis by this method showed that all three isolate codes (A53, Y55 and Y138) formed the same clade with Pseudomonas viridiflava strain P3 (Accession number: AY972186) and Pseudomonas plecoglossicida strain P9 (Accession number: AY972231) at a high bootstrap value of 100percent. Isolate code A53 and Y55 also grouped together at a bootstrap value of 96percent. Factors affecting antibacterial compound production by the three isolates were elucidated. The effect of pH on the three isolates revealed that isolate code A53 and Y55 could produce antibacterial compounds over all pH ranges (pH 4-9), however, antibacterial production was produced optimally at acidic conditions (pH 4) and a less acidic-neutral condition (pH 6) respectively. Isolate Y138 showed optimal production at pH 5. The effect of temperature on all three isolates was studied at different temperatures ranging between 25°C-40°C. Study on effect of temperature variations on antibacterial production revealed that all three isolates are capable of growing and producing antibacterial compounds over all the different temperature ranges, however, maximum/optimum production was observed at temperature of 30°C. In order to establish the role of plasmids in antibacterial production, two curing agents; Sodium dodecyl sulfate (SDS) and Ethidium bromide under different sub-lethal concentrations (1 mg/ml -11mg/ml and 2.5 μg/ml- 125 μg/ml respectively) were used to cure the selected isolates. Plasmid DNA samples of A53, Y55 and Y138, were separated by electrophoresis on a 0.7percent (w/v) agarose. Agarose gel electrophoresis revealed that not all the concentrations used were effective in curing the plasmid. A Quick Load 1 kb Extend DNA ladder marker was used for determining the size of the plasmids. Isolate code A53 and Y138 had a plasmid size of 48.5 kb while isolate Y55 had a plasmid size of approximately 20 kb. Antibacterial activity by agar-well diffusion method after the curing process revealed that antibacterial production was not lost or prevented, but rather increased. Thus, it is suggested that the genes responsible for antibiotic production in this study were chromosomal-encoded and not plasmid-encoded. This study revealed that Hogsback wetlands may represent a previously unexplored environment/source of discovering novel and potent antibacterial compounds.
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- Date Issued: 2017
Characterisation of human pathogenic vibrios and methicillin-resistant staphylococcus aureus (MRSA) from wild and tank cultured dusky kob (agyrosomus japonicus) in the Eastern Cape Province, South Africa
- Authors: Justine, Fri
- Date: 2017
- Subjects: Marine microbiology Marine microbiology--South Africa--Eastern Cape Staphylococcus aureus infections--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Doctoral , Microbiology
- Identifier: http://hdl.handle.net/10353/16047 , vital:40607
- Description: Introduction: Marine finfish including dusky kob (Agyrosomus japonicus), in addition to its high protein value, is bestowed with numerous health benefits including being heart friendly due to high proportion of omega 3 fatty acids. They are therefore used as powerful preventive measures against cardiovaslcular diseases. They are also important in neurological development during gestation and infancy, thus a regular recommendation by nutritionists. However, fish and its environment may be contaminated by bacteria pathogens. Human infections caused by members of the genus Vibrio, and Staphylococcus especially Methicillin-resistant S. aureus (MRSA) are of increased concern worldwide especially with increased Vibrio disease outbreaks and rapid spread of MRSA in the community. Methicillin-resistant Staphylococcus aureus is regarded as an emerging zoonotic agent, therefore marine fish may be considered as a reservoir for infection. The emergence of multi-drug resistant organisms in both farm animals and humans has also been a challenge that hurdles chemotherapy worldwide. Methods: We enumerated the bacteria flora of skin, gill and gut of marine dusky kob (Agyrosomus japonicus) raised in a recirculatory aquaculture system using metagenomic sequencing of the 16S rRNA. We further screened 120 dusky kob fishes (skin, gill and gut) and 80 water samples from two fish farms and Kariega estuary collected over a 10 month period for human pathogenic vibrios, and MRSA using standard procedures. Vibrio species were further subjected to species specific PCRs delineating them into V. cholerae, V. parahaemolyticus, V. vulnificus, and V. fluvialis. This was followed by elucidation of the genotypic virulence determinants. The Reverse Fragment Length Polymorphism (RFLP) of the cytotoxin hemolysin (vvhA) gene of V. vulnificus strains was carried out to determine the associated biotypes. A total of 277 Vibrio strains consisting of 126 V. fluvialis, 45 Vibrio vulnificus, 30 V. parahaemolyticus and 76 vibrios belonging to other species were subjected to susceptibility testing to 15 antibiotics by the disc diffusion method and resistant strains were further evaluated for their genotypic antimicrobial resistant determinants by polymerase chain reaction followed by plasmid profiling. For MRSA screening, we evaluated the reliability of cefoxitin disc diffusion, oxacillin screen agar and BrillianceTM MRSA 2 agar tests, in detecting methicillin resistance from fish (environmental) samples using PCR detection of the mecA as the gold standard. A total of 33 mecA positive S. aureus strains (MRSA) were subjected to PCR detection of enterotoxins (Staphylococcal enterotoxin A-E) and Panton Valentine Leucocidin (PVL) encoding genes. The SCCmec types were also investigated by multiplex PCR targeting genes encoding type I-V. The antibiogram profiles of MRSA strains to 12 antibiotics by the disc diffusion method and to vancomycin by broth micro dilution method were elucidated. Polymerase chain reaction was employed to evaluate the presence of antibiotic resistant genes. The nucleotide sequences of the rpoB gene were analysed to determine mutations that could lead to rifampicin resistance. Results: A broad diversity of pathogenic and non-pathogenic bacterial species of different taxonomic groups was observed with Proteobacteria revealed as the most common bacteria phyla. Fifty one families were identified with Enterobacteriaceae the most frequently detected in all the anatomical sites and the gut showing the highest species diversity. A total of 606 (60.23 percent ) presumptive Vibrio isolates were confirmed by PCR of which V. fluvialis was the most predominant, 193 (31.85 percent ). This was followed by Vibrio vulnificus 74 (12.21 percent ), and V. parahaemolyticus 33 (5.45 percent ). No V. cholerae strain was detected. Only one of the V. parahaemolyticus strains possessed the trh virulent gene with no tdh detected. Virulence factors of V. fluvialis detected were stn (13.5 percent ), hupO (10.4 percent ), and vfpA (1.0 percent ). V. vulnificus biotype 3, formerly restricted to Isreal was identified. Generally, resistance among Vibrio isolates varied considerably with highest resistances recorded to amoxicillin (76.2 percent ), ampicillin (67.5 percent ), erythromycin (38.3 percent ), and doxycycline (35.0 percent ) while higher susceptibilities were revealed by gentamicin (100 percent ), norfloxacin (97.8 percent ), florfenicol (90.3 percent ), tetracycline (87.7 percent ), and chloramphenicol (87.4 percent ). Multiple antibiotic resistance (MAR) (resistance to ≥ 2 classes of antibiotics) was 58.5 percent . The MAR index did not vary significantly between sites (P>0.05) and values of >0.20 were recorded in 40 percent (108/277) of all the isolates. The resistant genes ampC, blaOXA, tetA, tetM, dfr1, sul1, sul2, ermB, nptII and strA were detected in two or more Vibrio isolates while the SXT intergrase was detected only in one isolate. Seven of the 18 extreme drug resistant isolates possessed 1–3 plasmids of 1.5–10 kb range. A total of 321 presumptive Staphylococcus aureus isolates were recovered by culture out of which 202 (62.9 percent ) were identified as S. aureus by PCR. Of these, 33 (16.3 percent ) strains were mecA positive while the rest, 169 (83.7 percent ) were mecA negative. The sensitivity and specificity of MRSA detection by use of cefoxitin disc (30 μg) test was 93.9 percent and 91.7 percent , that for oxacillin screen agar test (6 μg/mL) was 81.8 percent and 92.3 percent while that of BrillianceTM MRSATM 2 agar was 87.9 percent and 94.1 percent respectively. Staphylococcal enterotoxin SEE was detected in 12.1 percent (4/33) of total strains followed by SEA 3.0 percent (1/33), and SEC 3.0 percent (1/33). SEB and SED were absent. Six of the isolates had the PVL gene, giving a prevalence of 18.2 percent . The most frequently detected SCCmec type was SCCmec type III (17/33; 51.5 percent ), closely followed by SCCmec subtype IVc (10/33; 30.3 percent ) and the least were SCCmec types I and II with only 3.0 percent (1/33) each. The rest four (4/33; 12.1 percent ) did not belong to any of the above types and were therefore considered to belong to other subtypes of SCCmec type IV not tested in the study. For antibiogram patterns, 12 (36.4 percent ) strains were resistant to doxycyline, 10 (30.3 percent ) to trimethroprim-sulfamethoxazole, 9 (27.3 percent ) to tetracycline and only 1 (3.0 percent ) strain was resistant to ciprofloxacin. Nineteen (57.6 percent ) of the MRSA strains had vancomycin MIC of ≤ 2 μg/mL, 4 (12.1 percent ) with MIC range of 4-8 μg/mL, and 10 (30.3 percent ) with values ≥ 16 μg/mL. Overall, 27 (91.percent) isolates showed simultaneous resistance to 3 or more antibiotics. The resistant genes tetM, tetA, ermB, BlaZ femA were detected in two or more strains resistant to various antimicrobials. Resistance to rifampicin was not caused by mutations in the rpoB gene. Conclusions: To the best of our knowledge, this study is the first study reporting a broad, and diverse bacteria flora of skin, gill, and gut of the South African dusky kob as well as the first study on human pathogenic vibrios, and MRSA from marine finfish especially those from recirculatory aquaculture systems. Also, our study revealed that Vibrio species with pathogenic potential are present in marine dusky kob and its environs. Dusky kob is contaminated with CA- MRSA and HA- MRSA that may cause difficult to treat infections with regular antibiotics. Some of the MRSA strains contained toxins that can cause food-borne gastroeneteritis. The present study revealed that MRSA and Vibrio species are potential reservoirs for antibiotic resistant genes, which could be disseminated to other bacterial species probably through plasmids, a public health risk.
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- Date Issued: 2017
Characterisation of photovoltaic devices using large area light beam induced current measurements
- Authors: Okullo, Michael , Van Dyk, Ernes , Okullo, W
- Date: 2017
- Subjects: Photovoltaic cells Photovoltaic power generation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20526 , vital:29314
- Description: Photovoltaic (PV) modules are made by connecting PV cells in series in order to generate a reasonable voltage that can be used for any productive work. Inaccuracy in cell sorting during crystalline silicon module construction, or non-uniform deposition of PV material and laser scribing during thin _lm module construction, may introduce current mismatch in the module. Current mismatch is a consequence of connecting module cells which have non-identical electrical characteristics. When current mismatch occurs in a module, it is the cell generating the lowest current that determines the module output current and this leads to a decrease in the output power and lifespan of the module. Investigation of current uniformity and the different current reducing features in PV modules, which are potential sources of current mismatch, is therefore critical in optimising the performance of PV modules. In this study, a large area light beam induced current (LA-LBIC) measurement system was developed. This non-destructive technique was used to characterise crystalline silicon PV modules (mono-crystalline and multi-crystalline), thin _lm PV modules (amorphous silicon and copper indium diselenide) and a combined concentrator photovoltaic (CPV) module. A light source mounted onto a motorised x-y scanning stage was used to illuminate a PV module, or the Fresnel lens of a CPV module, point-by-point, while measuring the module output current. The measured current was mapped as a function of position and presented as an LBIC image. The point-illuminated circuit model of a PV module was designed and used to explain the variation in current between and within module cells in the LA-LBIC maps. Application of the model to crystalline silicon modules attributes the variation in photo-generated current between cells mainly to current mismatch between series connected cells. Current variation within cells is attributed to individual cell shunts. In the thin _lm modules, the model attributes the variation in photo-generated current mainly to differences in local cell shunts and series resistances originating from the scribing procedure during cell formation in the manufacturing process. In the PV modules studied, variation in photo-generated current was found to exist both between and within cells. The variation was more pronounced between cells than within cells. Module point I-V curves at different points of the module were measured in order to extract short circuit current, to quantify the variations between and within cells. A striation ring defect, causing a drop in short circuit current of 38%, was detected in the mono-crystalline module. Investigation of the striation ring defect indicated that the defect is active in the bulk (p-type) but inactive in the top (n-type) layer. Further characterisation of the defect revealed that a higher percentage loss in short circuit current occurs at lower light intensities. In the multi-crystalline silicon module, cracks were detected and found to electrically isolate the module cells into two parts, causing them to operate in parallel and consequently introducing current mismatch in the module. The I-V curve of the module at standard test condition (STC) revealed a step below the knee, which is a manifestation of current mismatch in the module. High currents, as a consequence of diffuse reflection, leading to multiple reflections by the top glass were also observed at localised points on the bus bar and cell separations. In the a-Si module, the variation in photo-current within some cells, was found to be substantial. In the copper indium diselenide (CIS) module, an electrical disconnection across the module cells was identified. A disconnection in the form of a triangular shape was also identified in this module, which completely disconnected the front contact of this area from the module. This unique disconnection feature caused current in the module to follow in a reverse direction when the light spot was incident within the boundary of the disconnection. Scans performed under different forward voltage biases were useful in identifying severely shunted module cells. A severely shunted cell was found to generate a higher photo-current than a good cell at the same forward bias voltage. This unique observation was explored further using point-illuminated module I-V measurements, and was found to be due to the crossing over of the I-V curves of the two cells. In order to explore the relationship between cell photo-current and cell shunt resistance, a method to determine the shunt resistances of the cells in an encapsulated module was devised. The method involves measuring the I-V curves of a fully illuminated module and a partially illuminated module when one of its cells is shaded and the I-V curves used to determine the short circuit current and the shunt resistance of the shaded cell. A strong correlation was found to exist between the short circuit current of the shaded cell and the cell shunt resistance, as well as between the short circuit current of the shaded cell and dark LBIC. The LA-LBIC technique was further applied to characterise a combine CPV module. Results showed that the Fresnel lens facets close to the centre generate a higher photo-current at the receiver than those towards the edges. The reduced photo-current towards the edges was attributed to losses due to di_raction, dielectric reflection and internal re_ection. About 65% of the area of the Fresnel lenses were found to be e_ective in light collection in terms of the photo-current generated at the receiver. Abrasions and scratches on the Fresnel lenses were identi_ed as some of the current limiting features in a CPV module. The LA-LBIC technique used in this study has demonstrated the potential to investigate current mismatch, current limiting and current enhancing features in PV modules. The capacity to further characterise current limiting features in order to investigate their effects on photo-current under different wavelengths and light intensities was also demonstrated. Extending the LA-LBIC technique to characterise a combined CPV module is a great achievement of this work.
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- Date Issued: 2017
Characterisation, antimalarial and biological activities of secondary metabolites from leaves of anonidium mannii
- Authors: Makoni, Pfungwa Gervase
- Date: 2017
- Subjects: Anonidium mannii -- Therapeutic use , Botanical chemistry , Annonaceae -- Therapeutic use , Apocynaceae -- Therapeutic use , Malaria -- Chemotherapy , Tuberculosis -- Chemotherapy , Bacterial diseases -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4797 , vital:20725
- Description: Anonidium mannii is a plant of the Annonaceae genus which is used traditionally in Africa for the treatment of gonorrhoea, malaria, cancer, skin inflammation and dysentery. In this study we will evaluate antimalarial, antifungal, anti - tuberculosis, antibacterial activities and cytotoxicity of different fractions in order to provide a scientific rationale for the traditional use of Anonidium mannii as well as provide possible novel drugs in the treatment of multi drug resistant strains of parasites and bacteria. Extracts from dried leaves were obtained by using solvent extraction and different fractions obtained using column chromatography eluted with solvents of varying polarities to obtain a wide range of metabolites. The antimalarial activity of the various fractions and some pure compounds was evaluated using plasmodium lactate dehydrogenase (pLDH) assay. Cytotoxicity was evaluated using HeLa cells while anti – tuberculosis assay was evaluated using the green fluorescent protein. Antibacterial activity of the extracts was evaluated using micro-dilution assay against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria and Gram-negative (Escherichia coli and Salmonella typhi) bacteria. Antifungal activity was evaluated against Candida albicans. The antimalarial assays yielded some fractions with promising IC50 values. The selected fractions yielded activities ranging between 0.73 μg/mL and 20.23 μg/mL. The fraction with the best activity was obtained from a hexane/ethyl acetate fraction. AM1C, a cholestane, showed the best activity from the pure metabolites that were screened. AM3C, stigmasterol, a pure compound gave the best antifungal activity with an MIC of 0.063 μg/mL. AM9C another pure compound (sterol) showed the best activity against S. typhi with a value of 0.031 μg/mL. AM2C a pure compound showed an activity of 0.063 μg/mL against E. faecalis. The best cytotoxicity was demonstrated by the fraction C2AM3P with a cell viability of 7.1 ± 0.2 % while AM1C had a viability of 20.2 ± 1.2 %. Several pure metabolites were isolated and four of these were positively identified as steroids. Of these steroids the structure of three novel metabolites from A. mannii was deduced. The study showed promising antibacterial, antifungal, anti – tuberculosis, antimalarial and anticancer activity of A. mannii. These results validate the use of A. manni against cancer, skin inflammation which is caused by fungus, malaria and bacterial diseases.
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- Date Issued: 2017
Characterization and physicochemical studies of the conjugates of graphene quantum dots with differently charged zinc phthalocyanines
- Authors: Matshitse, Refilwe , Sekhosana, Kutloana E , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189227 , vital:44829 , xlink:href="https://doi.org/10.1080/00958972.2017.1387652"
- Description: Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.
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- Date Issued: 2017
Characterization of a glycated gelatin model to explore the therapeutic properties of macrofungi in diabetic wound healing: an in vitro study
- Authors: Pringle, Nadine Alex
- Date: 2017
- Subjects: Diabetes -- Animal models Chronic diseases -- Age factors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11992 , vital:27017
- Description: Diabetic wounds frequently undergo impaired and prolonged wound healing due to a multitude of factors including hypoxia, impaired angiogenesis, hyperglycaemia, formation of ROS and AGEs, and infection - all of which may lead to cellular dysfunction. To date, however, treatment options for individuals suffering from impaired diabetic wound healing are limited, non-specific, and generally unsuccessful. The search for new and effective treatment strategies is severely hampered by the availability of adequately characterized screening models which comprehensively mimic the complexity of the diabetic wound healing process. In order to explore natural products as potential therapeutics to treat diabetic wounds and to encourage more research on this topic, this study sought out to develop and characterize a more convenient and cost effective in vitro screening assay which mimics the effects of protein glycation on the healing process of diabetic wounds. As proof of principal, this model was subsequently used to screen the potential of five wild mushroom species (P. tinctorius, R. capensis, B. badius, P. ostreatus and G. lucidum) as suitable diabetic wound healing therapies. The glycated gelatin model developed during this study was found to suitably mimic the diabetic state as it successfully simulated the major cellular dysfunctions in macrophages (NO production, phagocytosis, macrophage polarization, NF-ĸB translocation and COX-2 expression) and fibroblasts (proliferation and migration) documented during diabetic wound healing. Together these findings provide confidence that the model may serve as a valuable tool to study the poorly understood mechanisms which characterize cellular dysfunction in response to AGE accumulation and also to aid the identification of novel therapeutic agents to treat this pathology. Screening a number of mushroom extracts revealed that the ethanol extracts of R. capensis and P. ostreatus had the greatest potential for attenuating chronic inflammation due to their ability to promote macrophage phagocytosis, increased M2 activation (R. capensis) and decreased M1 activation (P. ostreatus) as well as reduced COX-2 expression while the water extract of G. lucidum proved to be the most promising candidate for stimulating fibroplasia as it was the most successful at promoting both fibroblast proliferation and migration. Different mushroom species were thus shown to promote different stages of the wound healing process providing sufficient evidence to support further studies related to the use of macrofungi as therapeutic agents in the search for more cost-effective and efficient treatment strategies for impaired diabetic wound healing.
- Full Text:
- Date Issued: 2017
Characterization of conjugates of NaYF4
- Authors: Watkins, Zane , Uddin, Imran , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238132 , vital:50589 , xlink:href="https://doi.org/10.1016/j.molstruc.2016.10.011"
- Description: NaYF4:Er/Yb/Gd upconversion nanoparticles (UCNP) capped with amino groups were covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). There was a decrease in the intensity of fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to Förster resonance energy transfer (FRET). FRET efficiencies of 18% and 21% for ClAlTSPc and ClAlTCPc, respectively, were obtained. Oxygen generation by ClAlTSPc following FRET was proved.
- Full Text:
- Date Issued: 2017
Characterization of livestock manures biochar and their effect on soil chemical properties and crop growth under glasshouse conditions
- Authors: Dzvene, Admire Rukudzo
- Date: 2017
- Subjects: Biochar Soil fertility
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9863 , vital:35091
- Description: Biochar is being promoted as an amendment to improve soil properties, crop productivity, and carbon sequestration. In Africa, biochar adoption is hindered by production systems which include technology and feedstocks availability. However, little research has been published on the influence of biochar incorporation on soil chemical properties and early crop establishment. The aim of this study was to characterize biochar from cattle, goat, sheep and poultry kraal manures and their effect on soil properties and crop growth. This was guided by the following specific objectives, (i) to explore the mixed-farming system of Raymond Mhlaba Municipality on availability and utilization of livestock kraal manures (ii) to characterize biochar samples produced from cattle, goat, sheep and poultry kraal manures (iii) to determine the nutrient release patterns of biochars amended in a degraded soil (iv) to determine the effectiveness of converting manure to biochar and cattle manure on maize early development and, (v) to determine the effects of biochar type and application rate on early maize development. The farming system was surveyed to identify quantities of livestock manure, its availability and utilization for soil fertility amendment in cropping in the Raymond Mhlaba Municipality. The emerging results across all the villages revealed that, the mean livestock numbers were, 9.24±8.21 sheep, 9.37±8.15 goats, 7.95±7.66 cattle and 9.02±9.47 chickens. The findings revealed that 94 (82.4percent) of the respondents had access to cropland allocations in the form of outfields and homegardens. However, only 55 (48.2percent) of the respondents were currently cropping their fields. Maize was the most common crop grown followed by butternuts and potatoes. The application of manure by the respondents currently cropping their lands was only 40 (35.1percent) and the quantities used ranged from 210-1450 kg ha-1. The results further showed that the estimated total manure production was 2.9 t year-1, 0.82 t year-1, 0.04 t year-1, and 0.8 t year-1 from cattle, goats, chicken, and sheeps respectively. Drum retort method of slow pyrolysis at a temperature of 400°C was used to produce biochar from cattle, goat, sheep and poultry manure feedstocks. The biochar yields were 63percent, 72percent, 61percent and 83percent on a weight basis for the different feedstocks. The chemical properties of the biochar were significantly different from those of the manure from which they were made. Biochars that were high in Ca and K such as poultry manure biochar and sheep manure biochar indicated higher pH and electrical conductivity values. For instance, sheep manure biochar was (8.1 mS cm-1) and poultry manure biochar was (9.2 mS cm-1). The scanning electron microscopy (SEM) revealed that, the biochars had porous structures ranging from 1.23um to 5.23um in diameter which are important for water conductance and holding capacity. The target soil carbon level to determine the effects of biochar soil incorporation was 2percent and the soil had 0.7percent. Therefore, it was treated with four livestock manure biochars at application rates of 0; 53.2 t ha-1 (CMB); 48.1 t ha-1 (GMB); 50.7 t ha-1 (SMB); and 40.2 t ha-1 (PMB) based on their carbon content to supplement the soil carbon difference. The effect on soil pH was such that SMB increased to 6.44, PMB (6.45), CMB (6.54), and GMB (6.53) relative to the control which did not show any changes. An increase was also observed on Olsen P concentrations (mg P kg-1) which varied with biochar treatments: PMB (6.22), GMB (6.37), SMB (6.44) and CMB (6.44) and were significantly higher than the control. Ammonium-N(NH4+) concentrations (mg NH4+-N) were increased in biochar treatments but, no significant differences were obtained with sampling time. SMB released 7.95 mg kg-1, CMB 7.50 mg kg- 1, PMB 7.46 mg kg-1 and GMB 7.05 mg kg-1, compared to the control 3.23 mg kg-1. Maize growth in soil sampled from farmers fields in cultivation and abandoned treated with biochar without application of inorganic fertilizer did not differ with control (soil only) treatments. However, maize growth in soil treated with biochar and inorganic fertilizer was comparative to manure treatments. This resulted in a follow up study to elucidate the effects of biochar alone and was carried out with cattle, goat, sheep and poultry biochars at five application rates (0, 100, 200, 300, and 400 kg C ha-1) applied to a sandy loam and a clayey loam soil of the Oakleaf and Tukulu soil forms respectively. Post-harvest soil pH, electrical conductivity and Olsen P showed improvements in biochar treatments relative to the control. Improvements in the chemical parameters and plant growth increased simultaneously with biochar application rate. Maize growth was not affected by biochar application at different rates.
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- Date Issued: 2017
Characterization of maize biochars, their effects on soils, early maize growth and effectiveness of fertilizers
- Authors: Pinkson, Sibusisiwe
- Date: 2017
- Subjects: Soil fertility Crops and soils Biochar
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9974 , vital:35211
- Description: The use of maize biochar in smallholder cropping systems of the Eastern Cape (EC) Province could be a strategy that helps mitigate a common challenge such as poor soil fertility in maize productivity. The current study investigated the following: a) comparison of maize biochars derived from the drum and pit kiln pyrolytic systems as soil amendments; b) effects of maize biochars on soil acidity and extractable nutrients of three arable soil types of the EC Province; c) effects of maize biochars on early maize growth and nutrient uptake; d) effect of maize biochars on the effectiveness of organic and inorganic fertilizers for improved soil quality and maize growth. Maize biochars were produced from two pyrolytic systems namely the pit and drum kiln, each maize biochar type was analyzed with respect to its chemical and physical characteristics to investigate its potential as a soil amendment. Both pyrolytic systems were monitored to identify optimum pyrolytic temperatures reached by each process. Observed peak pyrolytic temperature were 300 °C and 500 °C for the pit and drum pyrolytic systems respectively. Both maize biochar types were alkaline in nature with pH values of 8.36 (H2O) and 7.45 (KCl) and 8.95 (H2O) and 7.82 (KCl) for pit and drum biochar respectively. Electrical conductivity (Ec) of drum biochar was 199 mS /m and that of pit biochar 186 mS /m. Generally, there were no differences in the chemical compositions of the two biochar types. However, in most analysis drum biochar gave higher values in nutrient composition compared to the pit biochar. Moreover, according to SEM analysis both biochar materials consisted of an increase in pore size distribution compared to the original feedstock material. In addition, an increase in nutrient composition in the two biochar types compared to the original feedstock was also observed. In an incubation experiment, potential effects of the two maize biochar types derived from the pit and drum kiln pyrolytic systems on soil acidity and nutrients were investigated on three arable soil types of the EC Province. Three soil types investigated were obtained from the University of Fort Hare (UFH), Phandulwazi (PND) and Msobomvu (MSV). The UFH soil was a sandy loam of the Oakleaf form or Eutric Cambisol, the PND soil was a sandy loam over sandy clay a Haplic Luvisol, while the MSV soil was a clay loam of Westleigh form a Ferric luvisol. Both maize biochar types significantly (p< 0.05) increased soil pH of the three soil types in the incubation study from an average of 4.68- 7.5. Soil pH improvement was in the following order pit biochar> drum biochar> control. Also, the two maize biochar types significantly (p< 0.05) increased the release of cations namely Ca, Mg and Na however, some decrease in nutrient concentrations were observed due to increase in pH levels at the later stage of the study. Biochar incorporation increased extractable P release from 30- 40 mg P/kg to an average range of between 120- 160 mg P/kg across all soil types. A glasshouse study was also conducted investigating the effect of different biochar rates of the two maize biochar types used in the previous studies on early maize growth and nutrient uptake, same soil types were used as those in the incubation study. Biochar was applied at application rates of 0, 100, 200 and 300 kg C/ha of biochar. The glasshouse experiment consisted of two cycles, each with a six week period of monitoring maize seedling growth development. Generally, a significant increase in maize growth parameters such as plant height, stem girth, number of leaves and leaf area increased after biochar additions compared to the control. Both biochars significantly improved maize seedling growth at an application rate of 200 kg C/haHowever, the two biochar types displayed varying impacts on maize growth due to influence of soil type and biochar application rates. Nutrient- uptake of Ca, P, Na and Mg showed to improve at an application rate of 200 kg C/ha for both biochar types showing a 50 percent increase compared to the control. Nutrient- uptake patterns for P, Ca, Mg and Na differed across all soil types, mainly due to changes in pH and Na levels which were influenced by increased biochar concentrations resulting in nutrient deficiency. Another glasshouse experiment aimed at investigating the effects on the two maize biochar types on influencing the effectiveness of both organic and inorganic fertilizers for improved early maize growth and soil productivity. Biochar was applied at an application rate of 400 kg C/ha of biochar, fertilizer was applied at application rates of 0, 10, 20, 30 and 40 kg N/ha and manure at 0, 10, 20, 30 and 40 t/ha respectively. The glasshouse experiment consisted of two cycles, each with a six week period of monitoring maize seedling growth development. In the 1st cycle, manure rate of 40 t/ha resulted in the highest plant height of maize seedlings grown in the glasshouse, biochar type also showed to influence plant height. After the 1st harvest Mg, K and P levels improved at 30 t/ha, Na at 20 t/ha and Ca 40 t/ha of manure. Plant height and stem girth improved at 30 kg N/ha of fertilizer, however, nutrient levels for Ca, K and Mg decreased after the 1st harvest, while Na levels increased. Nutrient uptake was the highest for Mg and Na at 40 kg N/ha while for Ca at 30 kg N/ha of fertilizer. During the 2nd cycle plant height was the highest at 30 t/ha of manure, and effect of manure rate was significant (p<0.05) for number of leaves, plant height and biomass. Whereas, manure rate and biochar type effect were insignificant (p>0.05) for pH, Ec and nutrient uptake changes. Maize seedling showed significant response to fertilizer 40 kg N/ha for most of the growth parameters measured (P<0.05), except for germination percentage. All treatments investigated had no effect on germination percentage. The two biochar types showed significant (p<0.05) effects on soil pH and Ec. Drum biochar was slightly better performing than pit biochar. Results obtained from the various studies suggests that maize biochars derived from the pit and drum pyrolytic systems are potential soil amendments in correcting soil acidity and nutrient deficiency in the EC Province. Both biochar types have shown abilities to improve early maize growth and effectiveness of fertilizers in maize based systems of the EC Province. However, some variations in soil fertility and early maize growth were observed as a result of the soil type response towards the two biochar applications. This could also have risen as a result of a number of factors such as the nutritional composition of biochar material, initial soil type chemical composition, biochar and fertilizer application rates and time taken or period to complete each study. Therefore, further experiments should be conducted to validate these results, preferable having longer periods of study, moreover, field experiments. In addition, investigations on potential feedstock materials such as animal wastes used as biochar in the EC Province can be conducted.
- Full Text:
- Date Issued: 2017
Characterization of phthalocyanine functionalized quantum dots by dynamic light scattering, laser Doppler, and capillary electrophoresis
- Authors: Ramírez-García, Gonzalo , Oluwole, David O , Nxele, Siphesihle Robin , d’Orlyé, Fanny , Nyokong, Tebello , Bedioui, Fethi , Varenne, Anne
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238184 , vital:50595 , xlink:href="https://doi.org/10.1007/s00216-016-0120-x"
- Description: In this work, we characterized different phtalocyanine-capped core/shell/shell quantum dots (QDs) in terms of stability, ζ-potential, and size at various pH and ionic strengths, by means of capillary electrophoresis (CE), and compared these results to the ones obtained by laser Doppler electrophoresis (LDE) and dynamic light scattering (DLS). The effect of the phthalocyanine metallic center (Zn, Al, or In), the number (one or four), and nature of substituents (carboxyphenoxy- or sulfonated-) of functionalization on the phthalocyanine physicochemical properties were evaluated. Whereas QDs capped with zinc mono-carboxyphenoxy-phtalocyanine (ZnMCPPc-QDs) remained aggregated in the whole analyzed pH range, even at low ionic strength, QDs capped with zinc tetracarboxyphenoxy phtalocyanine (ZnTPPc-QDs) were easily dispersed in buffers at pH equal to or higher than 7.4. QDs capped with aluminum tetrasulfonated phthalocyanine (AlTSPPc-QDs) and indium tetracarboxyphenoxy phthalocyanines (InTCPPc-QDs) were stable in aqueous suspension only at pH higher than 9.0 due to the presence of functional groups bound to the metallic center of the phthalocyanine. The ζ-potential values determined by CE for all the samples decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiological relevant solutions and thereby, its usefulness for improving their design and applications for photodynamic therapy.
- Full Text:
- Date Issued: 2017
Characterization of Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA) in selected recreational marine waters and beach sand in the Eastern Cape Province, South Africa
- Authors: Ankabi, Olufemi Emmanuel
- Date: 2017
- Subjects: Marine microbiology -- South Africa -- Eastern Cape Staphylococcus aureus infections -- South Africa -- Eastern Cape Pathogenic microorganisms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4992 , vital:28915
- Description: Staphylococcus aureus is a Gram-positive bacterium predominantly found on human skin and in nasal passages with 20 to 40 percent of the population carrying this organism. Although S. aureus is an unspectacular, non-motile coccoid bacterium, it is a perilous human pathogen associated with both nosocomial and community-acquired infections and it is increasingly becoming virulent and resistant to most antibiotics. It is responsible for several infections such as osteomyelitis, toxin-mediated diseases and bacteraemia, with severe infections arising from strains harbouring antibiotic resistance genes together with virulence genes. S. aureus has been largely confined to hospitals and long-term care facilities, but it is now emerging in the community in places such as recreational beach waters, and occurring in healthy individuals with no associated risk factors. This organism has been reported to be released by swimmers in beaches, suggesting that recreational waters are a potential source of community-acquired S. aureus infections. It is possibly the pathogen of greatest concern due to its intrinsic virulence, its capacity to cause various life-threatening infections, and its ability to adapt to varying environmental conditions. This study was aimed at characterizing S. aureus and methicillin-resistant S. aureus (MRSA) in Port Elizabeth, Port Alfred, Kenton-on-sea and East London beaches of the Eastern Cape Province of South Africa. This was done by investigating the occurrence, antibiotic susceptibilities, antibiotic-resistant genes and virulence genes profiles of S. aureus in the selected beaches. To achieve this aim, 249 beach sand and water samples were obtained from the beaches during the period of April 2015 to April 2016. Physico-chemical parameters of beach water was investigated on site using a multi-parameter ion specific meter during sample collection. Samples were filtered and inoculated on m-Endo agar, m-FC agar and bile aesculin azide agar for total and faecal coliform as well as Enterococci respectively. For isolation of S. aureus and MRSA, samples were cultured on Mannitol salt agar and Staph 24 agar. S. aureus was identified using morphological, Gram staining and molecular (PCR) methods. The isolates were further characterized by determining their antimicrobial resistance profiles, antibiotic resistant genes (mecA, rpoB, blaZ, ermB and tetK genes) and detection of virulent genes encoding intracellular adhesion (icaA), enterotoxin (seaA) and cytolytic toxins (PVL). The majority of study sites passed the directives of physico-chemical standards levels set by WHO during the study period. A total of 143 presumptive isolates were obtained of which 30 (30 percent) were confirmed as S. aureus with 22 (73.3 percent) of these confirmed isolates from marine water and 8 (26.7 percent) from marine sand. Upon culturing on MRSA 2 agar, 15 (50 percent) of isolates showed phonotypic resistance to methicillin. Based on Antimicrobial susceptibility tests, (22/30) 73.3 percent of the isolates showed phonotypic resistance to oxacillin. Out of the 30 isolates, 16 (53.3 percent) were mecA positive and were considered methicillin-resistant S. aureus. S. aureus showed high susceptibility to gentamycin, cefoxithin, levofloxacin, ciprofloxacin, imipenem, and chloramphenicol. A large proportion (36.67 percent to 96.7 percent) of the S. aureus isolates was resistant to penicillin G, ampicillin, oxacillin, tetracycline, clindamycin, rifampicin, vancomycin, sulfamethoxazole-Trimethoprim and erythromycin. Multiple antibiotic resistance (MAR) phenotypes were generated from 7 S. aureus isolates showing resistance to three or more antibiotics. The mecA, rpoB, blaZ, ermB and tetM genes coding for methicillin, rifampicin, βeta-lactam, erythromycin and tetracycline antibiotics resistance was detected in 5 (22.7 percent), 11 (45.8 percent), 16 (55.2 percent), 15 (71.4 percent) and 8 (72.7 percent) respectively. The PVL, icaA and seaA genes coding for virulent determinants were detected in 50, 20 and 13.3 percent of the confirmed isolates respectively. Physico-chemical and faecal indicator bacteria results obtained from this study can assist municipal authorities in developing appropriate management strategies for beaches in the study area. The findings of this study showed that the investigated beaches were contaminated with toxigenic and multi-drug resistant S. aureus strains. This emphasizes the need for the implementation of better control measures to reduce the occurrence of antibiotic resistant S. aureus and of virulent S. aureus strains in recreational waters. In our study it was established that the potential of recreational waters to be reservoirs of S. aureus should not be taken for granted, and it is important that beach goers be educated about this organism as well as other related pathogens that could affect human health, especially immuno-compromised individuals. The community should be educated on antibiotic stewardship and the detrimental effects of antibiotics abuse.
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- Date Issued: 2017
Characterization of the distribution of platinum group elements in sulphide ores within the Merensky Reef at Modikwa and Two Rivers Platinum Mines, Eastern Bushveld Complex, South Africa
- Authors: Zilibokwe, Nosibulelo Julie
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7938 , vital:21326
- Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
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- Date Issued: 2017
Characterization of the Mitochondrial Plasmodium falciparum heat shock protein 70
- Authors: Nyakundi, David Onchong’a
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44449 , vital:25408 , https://doi.org/10.21504/10962/44448
- Description: Malaria remains a global health problem and accounts for many deaths and illnesses in subSaharan Africa. Plasmodium falciparum, the causative agent of the most fatal form of malaria, expresses a repertoire of heat shock proteins for cytoprotection, survival and pathogenesis. The parasite genome encodes six Hsp70 proteins found in various cell compartments. However, the putative parasite mitochondrial Hsp70 (PfHsp70-3) has not been investigated. The J-proteins, Pfj1 and PFF1415c, were proposed to function as co-chaperones of PfHsp70-3. The biochemical characterization of PfHsp70-3 was initially complicated by the fact that the protein was insoluble when expressed in E. coli cells. Various approaches to solubilize it resulted in inactive protein. A general characteristic of eukaryotic mitochondrial Hsp70s is their insolubility and their reliance on an Hsp70 escort protein (Hep) for solubility and ultimate functions. In this study, a putative Hep protein was identified in the genome of P. falciparum that is referred to as PfHep1. Coexpression of PfHep1 with PfHsp70-3 resulted in soluble and biochemically active PfHsp70-3. Size exclusion chromatography was employed to separate PfHsp70-3 from PfHep1 after coexpression. PfHep1 suppressed thermally induced aggregation of PfHsp70-3 but not the aggregation of malate dehydrogenase or citrate synthase, thus showing specificity for PfHsp70-3. Zinc ions were also found to be essential for maintaining the functions of PfHep1, as EDTA chelation abrogated its abilities to suppress the aggregation of PfHsp70-3. Furthermore, PfHep1 did not stimulate the basal ATPase or increase refoldase activities of PfHsp70-3 hence displaying no co-chaperone roles. The full-length putative mitochondrial type I J protein, Pfj1, could not be produced in E.coli but a truncated protein containing the J-domain was produced which stimulated both the ATPase and refoldase activities of PfHsp70-3. Further, this study demonstrated that both PfHep1 and PfHsp70-3 localized to the mitochondrion in the erythrocytic stage of P. falciparum development thus confirming in silico predictions of their localization. Besides, PfHsp70-3 was expressed during all stages of the intraerythrocytic cycle of parasite development and was heat inducible. Generally, the data obtained in this study will enhance the existing knowledge on the biology of the parasite mitochondrial chaperone functions and open the possible avenue of drug targeting considering the specificity of PfHsp70- 3 and PfHep1 partnerships.
- Full Text:
- Date Issued: 2017
Chemical composition of leaf essential oils of Lantana camara varieties in South Africa and their effect on the behavioural preference of Falconia intermedia
- Authors: Ngxande-Koza, Samella W
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4877 , vital:20739
- Description: Lantana camara L. (Verbenaceae) is one the most problematic invaders in South Africa invading forest edges, sand dunes, and shorelines by forming impenetrable thickets. Lantana camara invasions degrade natural biodiversity, reduce the value of land and consequently it has been a target for biological control, over the last 50 years in South Africa. Studies that have reported on chemical profile of Lantana camara have been conducted around the world but not in South Africa. Hence, the first aim of the current study was to identify the chemical baseline of L. camara varieties in the Eastern Cape, South Africa. Recent studies have shown that feeding by one of the agents released against L. camara, Falconia intermedia (Distant) (Hemiptera: Miridae), induces anti-herbivory response through increased leaf toughness and trichome density. A preliminary study conducted also reported the production of volatile chemicals by one variety, Whitney Farm, due to feeding by the mirids. Therefore, the second aim was to determine the induced changes in chemical compounds of L. camara varieties after feeding by F. intermedia. A third aim was to determine the effect these chemical compounds have on the behaviour of F. intermedia. To identify the chemical baseline of L. camara varieties, the essential oils of four L. camara varieties (East London, Port Alfred, Whitney Farm and Heather Glen) were analysed using gas chromatography mass spectrometry (GC-MS) and that resulted to the identification of 163 constitutive and 75 induced chemicals across the varieties tested. Lantana camara varieties showed different chemical classes but were highly dominated by terpenes. A great variation in the number of constitutive chemical compounds was found in all the varieties. There were 56 constitutive chemical compounds in the Whitney Farm variety, 41 in the East London variety, 36 in the Heather Glen variety and 30 in the Port Alfred variety. The Whitney Farm variety had the highest number (22) of unique constitutive chemicals identified when compared with other varieties. This indicates the chemical distinctiveness of the Whitney Farm variety from the other varieties. In the varieties tested, there were common chemical compounds identified in constitutive and induced (discussed below) states of the plants such as caryophyllene, hexane, naphthalene, copaene and a-caryophyllene. Besides naphthalene, the majority of chemical compounds in South African L. camara varieties were similar to compounds that have been identified across the world, suggesting that they are closely related. The expression of naphthalene in these varieties may be due to changes in the chemicals expressed over evolutionary time as predicted by the Novel Weapons Hypothesis. Amongst the varieties, a great variation in chemical compounds and their concentrations was shown in the induced states of the plants. The concentration of constitutive caryophyllene ranged from (3.13 - 15.7) %, to (4.02 - 11.10) % after feeding. The concentration of constitutive hexane ranged from (6.13 - 71.19) %, to (33.3 - 75.8) % after feeding. The concentration of constitutive naphthalene ranged from (0.21 - 4.79) %, to (0.92 - 2.11) % after feeding. The concentration of constitutive copaene ranged from (0.57 - 1.57) %, to (1.20 - 2.72) %. Lastly, the concentration of constitutive a-caryophyllene ranged from (1.18 - 9.03) %, to (0.78 - 5.48) % after feeding. The changes in chemical concentrations in lantana varieties indicated that feeding by the mirid on L. camara varieties causes an induction by either reducing or increasing the chemical concentrations. To determine the effect of the identified compounds on the behaviour of F. intermedia adults, olfactometer bioassays were conducted using a Y-tube technique. A significantly higher proportion of F. intermedia were attracted to undamaged leaves over damaged leaves and purified air. Undamaged leaves attracted 52 % of F. intermedia from the East London variety, 62.5 % from the Port Alfred variety, 56 % from the Whitney Farm variety, 58 % from the Lyndhurst variety and 54.5 % from the Heather Glen variety in dual choice trials versus damaged leaves. Furthermore, a significantly higher proportion of F. intermedia were attracted to damaged leaves over purified air. Damaged leaves attracted 67 % of F. intermedia from the East London variety, 67 % from the Port Alfred variety, 65.9 % from the Whitney Farm variety, 65.3 % from the Heather Glen variety and 64.5 % from the Lyndhurst variety. Olfactometer bioassays were also conducted using purified standard compounds of four chemical compounds identified from essential oils, hexane was used as a positive control as it is reported to be an insect attractant in literature. Hexane was highly attractive to the mirids compared to three standard compounds caryophyllene, caryophyllene oxide and naphthalene at the rate of 80 %, 73 % and 80 %, respectively. The standard compounds tested against F. intermedia are major compounds contained by L. camara varieties and they have proven to have a repellent effect. This may indicate that after feeding by F. intermedia, the major compounds expressed by the plant varieties repel F. intermedia contributing to the invasiveness of this weed. The increased expression of hexane and caryophyllene after feeding may also indicate increased attraction to some insects, opening up the potential for third trophic level interactions in varieties where this is the case. This is the first study on the chemical composition of essential oils of L. camara in South Africa. Therefore, we recommend that where appropriate chemical profile studies of the invasive alien plants should be considered during host specificity testing, and the vital role of chemical compounds on agent-weed interactions must be taken into consideration with other factors before and after the biological control agents are released.
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- Date Issued: 2017
Children and wild foods in the context of deforestation in rural Malawi
- Authors: Maseko, Heather N , Shackleton, Charlie M , Nagoli, J , Pullanikkatil, Deepa
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182101 , vital:43800 , xlink:href="https://doi.org/10.1007/s10745-017-9956-8"
- Description: There is growing recognition of the contribution of wild foods to local diets, nutrition, and culture. Yet disaggregation of understanding of wild food use by gender and age is limited. We used a mixed methods approach to determine the types, frequencies, and perceptions of wild foods used and sold by children in four villages in southern Malawi that have different levels of deforestation. Household and individual dietary diversity scores are low at all sites. All households consume one or more wild foods. Across the four sites, children listed 119 wild foods, with a wider variety at the least deforested sites than the most deforested ones. Older children can name more wild foods than younger ones. More children from poor households sell wild foods than from well-off households. Several reasons were provided for the consumption or avoidance of wild foods (most commonly taste, contribution to health, limited alternatives, hunger, availability, local taboos).
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- Date Issued: 2017
Chinese aid and African agency since 2000: examining the cases of Zimbabwe, Angola and Ghana
- Authors: Chipaike, Ronald
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/59151 , vital:27442
- Description: Restricted access-thesis embargoed for 2 years
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- Date Issued: 2017
Chinese Cabbage:
- Authors: Mwaba, Stary
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/146699 , vital:38549 , https://www.ru.ac.za/artsofafrica/latestnews/rhodesparticipatesintheafrica-chinasymposiumatthegoetheinstitute.html
- Description: Stary Mwaba, an MFA candidate in the Arts of Africa and the Global South research team in the Fine Art Department, presented a paper on his installation, Chinese Cabbage, which was first displayed in his solo exhibition, Life on Mars, at the Künstlerhaus Bethanien in Germany in 2015. At the Africa–China symposium, Mwaba talked about his personal inroad into the Zambia–China debate, which draws from a family history of living along the Tazara Railway that was built by the Chinese in the 1960s, as well as the experience of his daughter attending a Chinese-run international school in Lusaka. Mwaba is currently expanding this research as part of his MFA studies at Rhodes by collecting oral narratives along the line of rail in Zambia and by addressing, through his painting practice, issues pertinent to the controversial copper slug known as Black Mountain in Kitwe.
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- Date Issued: 2017