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Identification and characterization of novel oncology related platinum complexes using chromatographic and mass spectrometric techniques

  • Authors: Wentzel, Mauritz
  • Date: 2008
  • Subjects: Chromatographic analysis , Spectrum analysis
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10310 , http://hdl.handle.net/10948/715 , Chromatographic analysis , Spectrum analysis
  • Description: In this thesis mass spectral and chromatographic techniques were developed and applied to identify and characterise numerous novel platinum(II) and (IV) compounds designed as anticancer agents. In a novel method for the synthesis of cis-oxalato(trans- -1,2- cyclohexanediamine)platinum(II) or oxaliplatin these techniques could be applied to differentiate between the molecular complex and the autoionised analogue (viz. Ptdach2 2+Ptox2 2-). In another novel synthetic method for the same compound the ligand exchange reactions at various temperatures could be investigated and kinetic curves obtained served to illuminate the chemistry involved, indicating the role of small amounts of water in the essentially non-aqueous solvent systems dmf and isoamyl alcohol respectively. These allowed ligand exchange without resulting in hydrolyses even up to 85°C. The ionisation rate of divalent platinum halide complexes was determined for various amine ligands as well as N-S chelate ligands. A comparison of these could suggest why N-S complexes have poor anticancer action. Ionisation was not only studied for neutral molecular species but also for monocationic ones. Relationships could be found with stereochemical aspects of the chelates used. By investigating results of EV-CAD studies thermodynamic data could be obtained which indicated that bond strength decreases from chloro to iodo analogues although extent of ionisation in aqueous solution, i.e kinetic stability, is the reverse. Products formed by the reaction of NO2 gas with Platinum(II) compounds could be identified and separated which greatly contributed to the understanding of the chemistry involved in the formation of mononitro platinum(IV) complexes. Some of these proved to have exceptional anticancer properties. Studies of the interaction of thiol containing biomolecules were performed as a function of time. The results contributed to the understanding of the action of the anticancer agents.
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  • Date Issued: 2008

Integer optimization for the selection of a twenty20 cricket team

  • Authors: Lourens, Mark
  • Date: 2008
  • Subjects: Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10568 , http://hdl.handle.net/10948/1000 , http://hdl.handle.net/10948/d1009631 , Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
  • Description: During the last few years, much effort has been devoted to measuring the ability of sport teams, as well as that of the individual players. Much research has been on the game of cricket, and the comparison, or ranking, of players according to their abilities. This study continues preceding research using an optimization approach, namely, a binary integer programme, to select an SA domestic Pro20 cricket team.
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  • Date Issued: 2008

Investigation of polarization mode dispersion measurement perfomance in optical fibre with a focus on the fixed analyzer technique

  • Authors: Gamatham, Romeo Reginald Gunther
  • Date: 2008
  • Subjects: Fiber optics , Polarization (Light)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10524 , http://hdl.handle.net/10948/957 , Fiber optics , Polarization (Light)
  • Description: The work presented in this dissertation is a comparative study of polarization mode dispersion (PMD) measurement performance where the fixed analyzer (FA) technique was built and tested for the first time in South Africa. Techniques involved in the study are: the Jones matrix eigenanalysis (JME), generalised interferometric technique (GINTY) and the FA technique, with a particular focus on the FA technique. The FA PMD measurement technique determines the average differential group delay (DGD) from the transmitted intensity spectrum through a polarizer and has three analysis methods (extrema counting, mean level crossing and Fourier analysis) which were all evaluated. PMD measurements were performed in the laboratory on several different fibre types and in the field on buried deployed Telkom fibre links (28.8 km). The techniques showed good agreement in the measured PMD value, both in the laboratory and field measurements. In particular very good agreement was found between the JME average DGD and the extrema counting analysis PMD value. The GINTY and FA Fourier analysis method also gave very similar PMD values. It was found that the fibre birefringence and the mode coupling manifest in different ways on the intensity spectrum. By using the FA ratio method, the length regimes of the different fibre types were determined. Three characteristics of the FA technique were investigated, namely: wavelength window variation, sampling and input SOP scrambling. It was found that the wavelength window and the PMD are inversely proportional. Correct sampling plays a significant role in determining the correct measured PMD value. Lastly an average PMD value over the PMD values for different input SOPs serves as a better representation of the true PMD value. An additional study showed that the FA technique and a developed Poincaré sphere analysis method agree very well regarding the PMD value.
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  • Date Issued: 2008

Model selection for cointegrated relationships in small samples

  • Authors: He, Wei
  • Date: 2008
  • Subjects: Economics -- Statistical methods , Cointegration -- South Africa , Econometrics
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10570 , http://hdl.handle.net/10948/971 , Economics -- Statistical methods , Cointegration -- South Africa , Econometrics
  • Description: Vector autoregression models have become widely used research tools in the analysis of macroeconomic time series. Cointegrated techniques are an essential part of empirical macroeconomic research. They infer causal long-run relationships between nonstationary variables. In this study, six information criteria were reviewed and compared. The methods focused on determining the optimum information criteria for detecting the correct lag structure of a two-variable cointegrated process.
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  • Date Issued: 2008

Monitoring population trends of introduced rusa deer (Cervus timorensis russa) in New Caledonian sclerophyll forests : tests and relevance of methods for management programmes

  • Authors: Roques-Rogery, Guillaume
  • Date: 2008
  • Subjects: Cervus timorensis -- Caledon , Deer -- Management
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10750 , http://hdl.handle.net/10948/727 , Cervus timorensis -- Caledon , Deer -- Management
  • Description: New Caledonia, an archipelago situated in the South-West Pacific Ocean has a very high biodiversity of which many flora and fauna species are endemic, and is therefore considered as one of the world hotspots for the biodiversity conservation. Sclerophyll forests, one of the five main vegetation types occurring on the island are mainly threatened by anthropogenic activities. Rusa deer (Cervus timorensis russa) were introduced into New Caledonia from Java in 1870. They have colonised all the biotopes of the main island, and represent one of the major threats to the New Caledonian sclerophyll forests. Currently, there is a lack of management tools to monitor the trends of rusa deer in New Caledonian sclerophyll forests. To test monitoring methods for use as management tools, six sclerophyll forests study sites were studied using direct census methods (i.e. spotlight count and drive count), indirect census methods (i.e. faecal standing crop method) and three indices (i.e. the faecal pellet groups index, the browsing index and the antler rubbing index). The faecal pellet groups index is based on sampling pellet groups in plots along transects. To ensure reliable data collection with a coefficient of variation of the mean number of intact faecal pellet groups per plot per transect of less than 20 percent, my study indicated that 15 plots per transect and 20 transects per sites should be sampled in New Caledonian sclerophyll forests whereas previous studies conducted in New Zealand indicated that a minimum of 25 plots per transect and of 18 transects per site should be sampled. The advantages of reducing the number of plots per transect and of transects per site is that it reduces the expenses (e.g. time, finance) and the bias due to data collection (e.g. fatigue, boredom and visual activity) which will improve the precision of the data recorded. Estimates of rusa deer density obtained from the census methods were not correlated (r = - 0.425, df = 4, P = 0.401) due to my small sample size. The reliability of these estimates is questionable because of biases. Previous publications have shown that biases are difficult to avoid when using direct census methods and that it is difficult to estimate the size of animal populations with accuracy and precision. The faecal standing crop method was subjected to bias because the estimation of the decay rate and the defecation rate were unreliable. These methods were not recommended for rusa deer management in New Caledonian sclerophyll forests. Of the three indices tested, the faecal pellet groups index and the browsing index based on unpalatable browse species were the most reliable as the confidence intervals of these two indices were small (i.e. from ±0.08 to ±0.11 for the faecal pellet groups index; from ±0.04 to ±0.27 for the browsing index of unpalatable browse species), and they also showed significant correlations with a subjective ranking of the rusa deer density based on expert knowledge (rs = 0.829, df = 4, P = 0.042 and rs = 0.829, df = 4, P = 0.042 respectively). These two indices appear to show the most promise for use as management tools, as they could reliably track local variations of rusa deer densities on the sclerophyll forests. These two indices could be used by wildlife technicians in New Caledonia to establish management plans of rusa deer populations which rely on participative management involving the stakeholders (e.g. hunters, forest managers, local communities). We believe that the faecal pellet groups index and the browsing index could be useful to monitor rusa deer populations in New Caledonian sclerophyll forests, and meet conservation and hunting objectives of the local population and authorities. Management tools such as culling and hunting operations will be implemented in New Caledonian sclerophyll forests where monitoring of indices I recommended show an increase in the deer population. Stakeholders will be involved in the implementation of the monitoring tools (i.e. indices) and of the management tools (e.g. culling and hunting operations, fencing) but also in decision making for the management of the rusa deer in New Caledonian sclerophyll forests.
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  • Date Issued: 2008

Novel aspects of platinum-amine coordination compounds: their chemistry and anticancer application

  • Authors: Bouwer, Yolanda
  • Date: 2008
  • Subjects: Coordination compounds , Platinum compounds , Antineoplastic agents
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10444 , http://hdl.handle.net/10948/d1021052
  • Description: The aim in this thesis, was to synthesize novel platinum coordination compounds, in order to develop compounds with improved anticancer action which could lead to an improved understanding of the mechanism by which they operate and at the same time, improve synthetic methods for their products. The initial work included the development of a novel synthetic method for 1R,2R-diaminocyclohexaneoxalato-platinum(II) (oxaliplatin), by using an essentially non-aqueous solvent medium and direct ligand exchange at elevated temperatures. This was done by a study of the kinetics of the reaction in a variety of conditions; such as relative reagent concentrations and ratios as well as solvent mixtures. An effective method was developed which could be applied industrially. An international patent was taken out on this method. Various amine complexes of platinum(II) were synthesized using chloro, bromo and oxalato groups as leaving groups. The non-leaving groups were selected having certain specific characteristics in mind. Novel mononitroplatinum(IV) complexes were synthesized, mostly with oxalato leaving groups. One of these in particular, had excellent anticancer behaviour. Another trichloromononitro complex was also synthesized with very good anticancer properties. Two international patents were filed for the latter two compounds. As far as possible, all compounds were studied by spectrometric, chromatographic and thermal methods. They were also tested against 3 cancer cell lines namely cervical (Hela), Colon (HT29) and Breast (MCF7) cancer cells.
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  • Date Issued: 2008

Novel camphor derivatives as potential asymmetric alkylation auxiliaries

  • Authors: Skiti-Mama, Neliswa
  • Date: 2008
  • Subjects: Alkylation , Chemistry, Organic
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10372 , http://hdl.handle.net/10948/1077 , Alkylation , Chemistry, Organic
  • Description: The investigation has been focussed on the synthesis and characterisation of camphor-derived chiral auxiliaries that incorporate two camphor skeletons and an evaluation of their stereodirecting potential in ester α-benzylation reactions. Two regioisomeric camphorquinone-derived monoketals were synthesised and identified by 1D- and 2D-NMR, and X-ray crystallography. The stereo-directing potential of the alcohols that resulted from reduction of these ketones as chiral auxiliaries in the alkylation of carboxylate ester derivatives has been studied. The diastereoselectivities shown by NMR spectroscopy range from 14- 30 % d.e. for (1R,2 S, 3R) -2 ,2-[ (1R, 2 S, 3R) -bornane-2,3-dioxy] - bornan-3-ol and 68-74 % d.e. for (1R, 2S ,3R) -3 ,3-[ (1R, 2S ,3R) - bornane-2, 3 -dioxy]bornan-2-ol with selectivities that correlate with the size of the alkyl group in the ester moiety. Trapping of the enolates generated from (1R, 2S ,3R)-2, 2 -[(1R,2 S, 3R) -bornane- 2,3-dioxy]bornan-3-yl propanoate afforded both E- and Z-silyl ketene acetal derivatives in the ratio of 64:36 confirming the formation of both possible enolate structures during enolization. Chiral auxiliaries containing a hemiaminal ether blocking group as well as two chiral alcohols containing monothio-ketal blocking groups have also been synthesised. α-Benzylation of their corresponding propanoate esters afforded the alkylated product with disappointingly low diastereos electivities. Asymmetric reduction of α-keto esters attached to (1R, 2 S, 3R) - 2,2- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-3-ol and (1R, 2S ,3R) - 3,3- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-2-ol with metal hydrides proceeded with selectivities of up to 30 % d.e. Modelling of the keto ester derivatives at DFT levels provided useful insights into possible conformations adopted by the two α-keto esters and hence the preferred face of attack by metal hydride during reduction.
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  • Date Issued: 2008

On the optical characterization of photovoltaic devices

  • Authors: Gxasheka, Andile Richman
  • Date: 2008
  • Subjects: Photovoltaic power systems -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10529 , http://hdl.handle.net/10948/692 , Photovoltaic power systems -- South Africa
  • Description: Semiconductor materials used for making photovoltaic (PV) cells have defects and impurities due to constraints of keeping production costs low. Electrically active defects that are distributed over the bulk material lead to reduced overall performance of a photovoltaic (PV) cell. In this study an adaptable Light Beam Induced Current (LBIC) system was designed in order to characterize the local performance of PV cells. The system uses a laser source and objective lens mounted vertically above the sample on the X-Y stage. Two current pre-amplifiers are used for converting the photo-generated current from the PV cell and the signal from the reflection detector cell into a voltage that can be measured by the data acquisition board. Two configurations for measuring the photo-current maps of either bare cells or encapsulated PV mini-modules can be used. To add flexibility it was envisaged that the system would be built in such a way that it allows easy integration of carrier lifetime mapping capabilities while keeping costs to a minimum. The carrier lifetime measurement technique integrated into the LBIC system is based on the optical Open-Circuit Voltage-Decay (OCVD) method. In a single-crystalline silicon PV cell that was tested, photo-current and opencircuit voltage LBIC scans revealed shunting behaviour due to scratch marks on the front surface. The marks are believed to have been caused by poor handling during manufacturing process. Reduced photo-current due to edge shunting was observed towards the edges of the PV cell. In another sample of single crystalline silicon cell an edge shunt resulted in a 30 percent drop in photo-current measured. LBIC measurements performed on multi-crystalline cells revealed nonuniformities such as enhanced photo-current on one side of grain boundaries. These asymmetric enhancements of local photo-current are attributed to the incline of the grain boundary into the bulk of the material. LBIC results obtained from mini modules showed a high degree of mismatching from cell to cell. It is well known that mismatching can degrade the performance of a PV module with series connected cells. The LBIC measurements presented also illustrated the negative effects of delamination on the photo-current of PV modules. The LBIC measurements performed on mini PV modules highlight some of the benefits of using an LBIC technique as a tool for investigating PV cell’s local photo-current response. The effective lifetime maps obtained highlight the importance of optical OCVD method as a tool that can be used in conjunction with conventional LBIC technique. Effective minority carrier lifetimes around 40 ms were measured on a single crystalline silicon cell of 2.5 x 2.5 cm2. Local features such as cracks and lifetime degrading defects were revealed by LBIC maps and were also confirmed on effective lifetime maps. The results presented demonstrate the importance of using effective carrier lifetime maps to complement photocurrent maps of PV cells and identification of areas where defects are located.
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  • Date Issued: 2008

On the Processing of InAsSb/GaSb photodiodes for infrared detection

  • Authors: Odendaal, Vicky
  • Date: 2008
  • Subjects: Gallium arsenide semiconductors , Photovoltaic cells , Infrared detectors , Gas-detectors
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10523 , http://hdl.handle.net/10948/980 , Gallium arsenide semiconductors , Photovoltaic cells , Infrared detectors , Gas-detectors
  • Description: The objective of this dissertation is the development of the necessary processing steps needed to manufacture infrared photodiodes on InAs1-xSbx material. Preliminary surface preparation steps were performed on both InAs and InSb material, thus covering both possible extremes of the antimony mole fraction. The first experiments endeavoured to characterise the effect of several possible etchants with regards to etch rate, repeatability, limitations for photolithographic patterning and the resultant surface roughness. The etchants investigated include a lactic acid based etchant, a sulphuric acid based etchant, an acetic acid based etchant, an ammonium based etchant, a hydrochloric acid based etchant as well as an organic rinse procedure. These cleaning and etching steps were evaluated at several temperatures. Measurements were performed on an Alpha Step stylus profiler as well as an atomic force microscope. Metal-insulator-semiconductor capacitor devices were manufactured, on both InAs and InSb material, in order to investigate the effects of the above-mentioned etchants combined with surface passivation techniques in terms of surface state densities. Capacitance-versus-bias voltage measurements were done to determine the resultant surface state densities and to compare these to the surface state density of an untreated reference sample. The surface passivation techniques included KOH, Na2S as well as (NH4)2S anodisation. Auger electron spectroscopy measurements were done on InAs and InSb material in order to examine possible surface contamination due to the etchants as well as combinations of these etching and anodisation procedures. The extent of surface coverage by contaminants as well as by the intrinsic elements was measured. The results of the cleaning and etching as well as the surface passivation studies were used to manufacture photovoltaic infrared diodes on an MOCVD (metal oxide chemical vapour deposition) grown p-InAs0.91Sb0.09/i- InAs0.91Sb0.09/n-GaSb structure. Current-versus-voltage and electro-optical measurements were performed on the these diodes in order to evaluate the effect of sulphuric acid based etching combined with KOH, Na2S or (NH4)2S anodisation on the detector performance. The results of surface passivated structures were compared to those of an unpassivated reference detector.
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  • Date Issued: 2008

Phytoplankton chlorophyll a concentration and community structure in two temporarily open/closed estuaries in the Eastern Cape, South Africa

  • Authors: Gama, Phumelele Thuthuka
  • Date: 2008
  • Subjects: Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10621 , http://hdl.handle.net/10948/707 , Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
  • Description: River flow is important in controlling phytoplankton distribution in estuaries. Data on the effect of river inflow on phytoplankton distribution patterns in temporarily open/closed estuaries is lacking. This study investigated the influence of river inflow on size-fractionated phytoplankton biomass (Chl a), community composition and environmental parameters measured monthly over three years in two temporarily open/closed estuaries in the Eastern Cape, South Africa. A once-off primary production study over an annual cycle was completed in the Van Stadens and Maitland estuaries. The study monitored physical, chemical and biological characteristics in both estuaries to examine the effects of changes in environmental factors and river inflow. Daily sampling of physico-chemical and biological variables from river to sea was carried out in the Van Stadens to investigate short-time scale effects of changes in environmental factors and river inflow on the phytoplankton biomass. Five and three stations in the main channel of the Van Stadens and Maitland estuaries respectively were sampled at 0.5 m below the water surface and 0.5 m above the sediment surface for biological and chemical variables and at the surface, 0.25 m and every 0.5 m thereafter for physical parameters. Five stations adjacent to the main channel along the estuary were monitored for groundwater macronutrient concentrations and five additional sites located within the upper catchment of the Van Stadens River were sampled on a quarterly basis over two years. Both estuaries were characterised by distinct hydrological conditions, an overwash, an open, a closed and a semi-closed mouth phase. Flooding in the Maitland and Van Stadens estuaries in 2001 and 2002 caused sediment scour, altered channel morphology and brought about breaching of the mouth. Flood driven mouth-breaching events occurred three and four times in each of the estuaries during the study. The mouth stayed open 20 – 25 percent and was closed 60 – 65 percent of the time. In the Van Stadens the closed overwash mouth condition occurred approximately 10 – 20 percent of the time while in the Maitland it occurred less with the semi-closed mouth condition occurring 10 – 20 percent of the time. Incidents related to mouth opening not associated with strong river floods occurred approximately 10 – 15 percent of the time, although in the Maitland a semi-closed mouth state persisted more frequently than in the Van Stadens Estuary. During flooding events salinity dropped to low levels (< 5 psu) but soon recovered to brackish conditions when river flow was reduced and marine water penetrated deep upstream. Reduction in river flow combined with marine sediment deposition resulted in the closure of the mouth. During closed mouth conditions strong onshore storm surges and spring high tides introduced marine water through overwash that kept salinity high. In both estuaries salinity showed a negative correlation with rainfall (R2 = 0.12), indicative of the strong influence of marine overwash that kept salinity high thus masking the influence of freshwater. High rainfall in the Van Stadens Estuary caused high levels of turbidity that reduced light penetration at depth. Light attenuation was positively correlated with the high rainfall (R 2 = 0.26) suggesting that increased turbidity was linked to rainfall induced discharge. In contrast, in the Maitland Estuary light attenuation did not show any correlation with increased rainfall possibly because of the reduced water depth and increased euphotic zone following the floods in 2002. High river inflow introduced macronutrients in both estuaries such that dissolved inorganic phosphates (DIP) and dissolved inorganic nitrogen (DIN) concentrations in the Van Stadens Estuary were strongly correlated with rainfall (R2 = 0.78 and 0.57 respectively). In the Maitland Estuary DIP and DIN concentrations remained significantly higher (p < 0.05) compared to that in the Van Stadens suggesting that the Maitland catchment contributed greater nutrient input into the estuary and may be associated with farming activities. Phytoplankton chlorophyll a (Chl a) ranged from 0.8 – 13.9 μg L-1 in the Van Stadens and in the Maitland Estuary from 5.3 – 138 μg L-1 during the 3-year study. During the open mouth condition Chl a biomass and primary production ranged from 5.4 – 52.9 μg Chl a L-1 and 1.2 – 11.7 mg C m-2 d-1 in the Maitland and in the Van Stadens from 1.6 – 9.8 μg Chl a L-1 and 1.2 - 14 mg C m-2 d-1 respectively. Maximum annual primary production in the Maitland and Van Stadens estuaries was 8.8 and 5.1 g C m-2 y-1 respectively. When the mouth was open in the Van Stadens Estuary the microphytoplankton (> 20 μm) accounted for > 65 percent of the Chl a, whereas during closed mouth conditions they accounted for about 55 percent of the Chl a biomass. Chlorophytes became the dominant taxon in the dry summer months but were replaced by cryptophytes and dinoflagellates during the wet season. When nutrient concentrations were low during low flow conditions in the Van Stadens Estuary mixotrophic microphytoplankton became an important fraction of the water column together with phototrophic dinoflagellates and cryptophytes. In the Maitland large sized chlorophytes were the dominant taxa in late spring and summer seasons and made up more than 80 percent of the cell numbers. In the Maitland before the floods in 2002 cyanophytes were the dominant group in late spring contributing more than 75 percent in cell abundance. Data from the short-term study in the Van Stadens Estuary showed similarities and differences in the Chl a response to increased river inflow. High river inflow initially reduced Chl a biomass followed by a recovery period of a couple of days compared to a 8 – 10 week recovery period in studies monitored over seasonal and annual temporal scales. The responses may be dissimilar but help to illustrate that there are similar response patterns to environmental forcing necessary to support phytoplankton biomass at different temporal scales. This study has demonstrated that flooding events caused by strong river flow cause breaching of the mouth, a reduction in salinity and marked nutrient input. Although the causes of flooding can be similar in both estuaries the resultant effects are varied and can alter the ability of the estuary to retain water. This study was able to demonstrate that the supply of macronutrients from the catchment was strongly correlated with rainfall (R2 = 0.67) and that phytoplankton growth mainly depended on an allochthonous source of macronutrients although internal supplies could be critical at times in controlling microalgal biomass.
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  • Date Issued: 2008

Pneumocystis jiroveci and respiratorey bacterial pathogens in cases of pneumonia at hospitals in Port Elizabeth

  • Authors: Du Plessis, Sarah Jane
  • Date: 2008
  • Subjects: Pneumocystis carinii pneumonia , Tuberculosis -- pathogenesis , Opportunistic infections
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10328 , http://hdl.handle.net/10948/946 , Pneumocystis carinii pneumonia , Tuberculosis -- pathogenesis , Opportunistic infections
  • Description: Pneumocystis jiroveci, Mycoplasma pneumoniae and Mycobacterium tuberculosis are respiratory pathogens associated with pneumonia, with increasing prevalence of Pneumocystis pneumonia (PcP) and tuberculosis (TB) in AIDS patients. Increased resistance of M. tuberculosis has emphasized the need for rapid susceptibility testing, such as flow cytometry. Sputum specimens (102) were assessed by PCR employing primers directed at the following genes: P. jiroveci: mitochondrial large subunit ribosomal RNA (mtLSUrRNA), dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR), and for M. pneumoniae: 16S rRNA and P1 adhesin. Positive P. jiroveci samples were genotyped by PCR-SSCP (single-strand conformation polymorphism) targeting the: internal transcribed spacer region (ITS), intron of the nuclear 26S rRNA gene (26S), variable region of the mitochondrial 26S rRNA gene (mt26S) and β-tubulin gene (β-tub). Multi-drug resistant (MDR-TB) cultures grown in the presence and absence of four antibiotics (rifampicin, isoniazid, ethambutol and ofloxacin) were heat killed, stained with SYTO16 and Propidium Iodide and analysed using flow cytometry. Rifampicin resistance gene mutations were screened by PCR and DNA sequencing. Details of patient’s gender, age, HIV and M. tuberculosis status were provided by the hospitals. Women were seen to be at high risk for community-acquired P. jiroveci colonisation. Overall, prevalence of P. jiroveci was 55.1 percent (54/102 patients). P. jiroveci was mainly associated with HIV (25/102 P. jiroveci positive patients for which clinical data was available) and co-colonisation with M. tuberculosis was observed in 11 cases. Sequence analysis of DHPS and DHFR products found no resistance associated mutations. M. pneumoniae was detected in one patient. Four simple SSCP patterns were identified and there were no co-infections with other P. jiroveci strains. Nine M. tuberculosis samples [8 MDR-TB isolates (NHLS) and M. tuberculosis ATCC® 27294TM] were tested. There was a 53 percent (19 out of 36 tests) agreement of flow cytometry with the BACTEC MGIT 960. Mutations (at two specific codons, namely 516 and 531) in the rifampicin resistance-determining region (RRDR) of the rpoB gene were observed in eight M. tuberculosis isolates. Evaluation of methods for genotyping and drug susceptibility testing of PcP and TB are imperative for epidemiology and drug resistance studies, and impact on treatment protocols.
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  • Date Issued: 2008

Practical and scalable synthesis of N-Alkyl-N,N'Diacylhydrazines

  • Authors: Gouws, Melissa Claire
  • Date: 2008
  • Subjects: Chemistry, Organic , Acylation , Insecticides
  • Language: English
  • Type: Thesis , Doctoral , DTech
  • Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
  • Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
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  • Date Issued: 2008

Process for the preparation of cis- AND trans-3,7-Dimethyl 2,6-Octadiene-1-OL from crude sulphated turpentine stream

  • Authors: Sathikge, Ndavheleseni David
  • Date: 2008
  • Subjects: Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10398 , http://hdl.handle.net/10948/734 , Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
  • Description: As part of CSIR Biosciences’ interest in aroma chemicals, the processing of crude sulphated turpentine (CST) into high value aroma products was investigated. The primary target product, linalool, was obtained from a mixture of α- and β-pinene in four steps. It can be transformed into a wide range of high value added aroma chemicals. Isomerisation of linalool in the presence of a transition metal catalyst furnishes geraniol and nerol. The scientific work described in this report was part of a bigger project aimed at developing innovative processes to manufacture aroma, flavour & fragrance chemicals through beneficiation of industrial waste streams and other raw materials, available locally from the Forestry, Paper & Pulp industries. The evaluation of a process for the preparation of precursor aroma, flavour & fragrance compounds, in particular geraniol and nerol, from locally available raw materials and industrial waste streams, was investigated. Preparation of geraniol and nerol from linalool (ex α-pinene stream) was investigated using acids or organometallic complexes as catalysts for the corresponding isomerisation reaction. The investigation was conducted in an effort to find a less costly process utilising milder conditions than via the conventional cleavage of β-pinene to myrcene under extreme pyrolysis conditions (>650°C). The transformation of linalool to geraniol/nerol using mineral acids was found to be dominated by secondary reactions such as dehydration and cyclisation, resulting in poor product selectivities and yields. On the other hand, organometallic complexes, in particular vanadium-based complexes (e.g. (OV(OBu)3) produced satisfactory results in the preliminary assessment (conversion of 79.8 percent and selectivity of 98.3 percent). A set of statistically designed experiments was carried out on the (VO(BuO)3 + [(Bu)4N+]OH¯) catalyst system where three variables were tested, i.e. substrate concentration, temperature, and catalyst loading. The selected model for conversion was significant with the “Probability > F” being < 0.0001. The most important contributing variable to the model for conversion was temperature i.e. 83.9 percent. Temperature was still the most important variable for the selectivity response at 65.0 percent contribution level. The response surface generated for the selectivity response was flat indicating a robust method within the parameter range selected.
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  • Date Issued: 2008

Purification and partial characterization of a Myofibril-Bound Serine Protease and its endogenous inhibitor from skeletal muscle of the ostrich

  • Authors: Tshidino, Shonisani Cathphonia
  • Date: 2008
  • Subjects: Proteolytic enzymes , Ostrich products industry
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10330 , http://hdl.handle.net/10948/703 , Proteolytic enzymes , Ostrich products industry
  • Description: The ostrich is becoming an important source of meat for humans in developed and developing countries. This study was conducted to purify and characterize myofibrilbound serine protease (MBSP) and its endogenous inhibitor (MBSPI) from skeletal muscle of the ostrich. It is well documented that MBSP is tightly bound to myofibrils and its endogenous inhibitor has been purified from the same tissue of other studied mammalian species. Literature supports an association of MBSP and its endogenous inhibitor with the degradation of myofribrillar proteins, resulting in the softening of muscle that lead to the conversion of muscle into meat with the control of the inhibitor. MBSP was successfully dissociated from washed myofibrils by 40 percent ethylene glycol at pH 8.5. Following centrifugation, MBSP was partially purified in two chromatographic steps, namely Toyopearl Super Q 650S and p-aminobenzamidine-Agarose. On the other hand, MBSPI was fractionated from the sarcoplasmic fraction using 75 percent ammonium sulfate saturation, followed by centrifugation and partially purified by three chromatographic steps, namely Toyopearl Super Q 650S, Superdex 200 and HiTrap SP HR. Ostrich MBSP was physicochemically and kinetically characterized, while MBSPI was only physicochemically characterized. Ostrich MBSP revealed an Mr of 21 kDa, cleaving synthetic fluorogenic substrates specifically at the carboxyl side of arginine residues. Optimum pH and temperature of ostrich MBSP were 8.0 and 40˚C, respectively. Kinetic parameters (Km and Vmax values) were calculated from Lineweaver-Burk plots. The characteristics of ostrich MBSP were compared to the values obtained for commercial bovine trypsin in this study, as well as that obtained for MBSP from various fish species and mouse. The results suggest that ostrich MBSP is a trypsin-like serine protease, thereby confirming the existence of MBSP in ostrich skeletal muscle. Partially purified ostrich MBSPI (Mr 17 kDa) (one form) shares 100 percent identity to myoglobin from the same species, while 2 other forms of MBSPI (Mr values of 35 and 36 kDa) exhibited high sequence identity to glyceraldehyde 3- phosphate dehydrogenase (GAPDH) (76 percent) from human and rat.
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  • Date Issued: 2008

Selective para-funtionalization of phenol

  • Authors: Indurkar, Jayant R
  • Date: 2008
  • Subjects: Phenol
  • Language: English
  • Type: Thesis , Doctoral , DTech
  • Identifier: vital:10402 , http://hdl.handle.net/10948/710 , Phenol
  • Description: In previous work done in our laboratories, a method was discovered to produce phenolic mono-ethers from 4-hydroxyacetophenone and other 4-hydroxyketones by treating with ammonium peroxy-disulfate in an alcohol as a reaction solvent and in the presence of concentrated sulphuric acid or other strong protonic acids. Since this method of producing 4-alkoxyphenol ethers provides a very convenient way to modify hydroquinone and substituted hydroquinones to produce a variety of phenol mono-ethers, it was of interest to study the general scope of this reaction, including a more detailed investigation of the reaction mechanism. In previous studies, it was suggested that interaction between the aromatic pi-system of hydroquinone and the cyclohexa-2,5-diene structure of benzoquinone plays a significant role during the reaction. It was therefore of interest to investigate whether other compounds that are also capable of forming the cyclohexa-2,5-diene structure, will interact in a manner analogous to the hydroquinone/benzoquinone couple. Two specific compounds were selected for this purpose, namely 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one . The scope of etherification reactions of hydroquinone-benzoquinone or hydroquinone/benzoquinone like substrates such as 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one in the presence of acid catalyst and alcohols was investigated. These studies showed that hydroquinone, 4- nitrosophenol and 4-(diphenylmethylene)cyclohexa-2,5-dien-1-one successfully affords the phenolic ethers in good to excellent yield. For example, quantitative yield of 4-methoxyphenol could be obtained from a 1:1 mixture of hydroquinone and benzoquinone at the reflux temperature of methanol. In order to study the reaction mechanism, the cross-over reaction between tertbutylhydroquinone and benzoquinone (or hydroquinone and tertbutylbenzoquinone) was studied in detail. The results of these cross-over reactions were used to propose a mechanistic pathway that could explain the requirement for pi-interaction between the hydroquinone and benzoquinone molecules, the role of the acid catalyst, as well as the relative rates of hydroquinone and benzoquinone consumption during these reactions. The mechanism was also capable of explaining all the reaction products observed during these reactions. The work was then extended to reactions of 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one with methanol in the presence of either hydroquinone or benzoquinone. The results of these investigations strongly suggest the presence of similar interactions between these molecules that also influence the outcome of the reactions. The exploitation of pi-interactions between two molecules of these types investigated during this work opens an interesting field of chemistry. Clearly, the level of understanding developed during this work is only beginning to address this interesting field of chemistry and much work will need to be done to gain a fuller understanding of the chemistry involved as well as the potential synthetic value of these interactions.
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  • Date Issued: 2008

The effect of different management practices on the feed intake and growth rate of ostrich chicks

  • Authors: Kruger, Anna Christina Magdalena
  • Date: 2008
  • Subjects: Ostriches -- South Africa -- Growth
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10589 , http://hdl.handle.net/10948/834 , Ostriches -- South Africa -- Growth
  • Description: Different management techniques were studied, at the Kromme Rhee Experimental Farm near Stellenbosch, in order to stimulate feed intake of ostrich chicks and to determine the effect on their growth rate. A first experiment was conducted to determine the effect of different dietary flavourants on the feed intake of ostrich chicks. Ostrich chicks (1-28 days of age), with no previous exposure to flavourants showed a strong preference for salty feed. Another experiment determined the effect of different colourants on the feed intake of ostrich chicks. Exposure of chicks to feed coloured artificially in different colours (green, red, blue and yellow) had no impact on the feed intake of ostrich chicks (1-28 days of age). Throughout the study the dry matter intake was the highest for the control diet, indicating that the provision of coloured feed to ostriches, as practised in this study, will not stimulate feed intake. The effect of feed processing and restriction of water availability for ostrich chicks was also examined. Extrusion reduced microbial counts in feed by 99.7 percent. Feed intake as well as average daily gain of chicks were lowered by both the pelleting and the extrusion process practised in this study. Processing did not have a positive influence on the production of ostrich chicks 6-15 weeks of age. Dry matter intake for chicks subjected to water restriction were the same as for birds receiving water ad libitum. Similarly growth rate as well as feed conversion ratio was not effected by restriction of water, as practised in this study. Another technique studied was to determine the effect of 24h artificial light on feed intake, growth and the behaviour of ostrich chicks (1-28 days of age). A Timeactivity budget revealed that chicks subjected to 24 hours of light spent more time eating (14.7 percent) than those subjected to normal day and night cycles (11.4 percent). In spite of this, no significant difference in feed intake, growth rate and feed conversion ratio was observed for ostrich chicks subjected to different light regimes. The effect of different dietary salt levels on the production of ostrich chicks (8-12 weeks of age) was also determined. The performance of chicks was the best on a diet with a salt inclusion of 1.4 percent.
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  • Date Issued: 2008

The effects of thicket transformation on the diet and body condition of Angora goats

  • Authors: Milne, Tracey Anne
  • Date: 2008
  • Subjects: Angora goat -- Feeding and feeds -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10720 , http://hdl.handle.net/10948/700 , http://hdl.handle.net/10948/d1012896 , Angora goat -- Feeding and feeds -- South Africa -- Eastern Cape
  • Description: Climate change is predicted to have a negative effect on the rangelands of sub-Saharan Africa, affecting the distribution, productivity and extent of these rangelands. Similarly, Subtropical Thicket vegetation in the Eastern Cape, South Africa is expected to experience a reduction in plant growth with conditions becoming similar to those experienced under desertification. The transformation of thicket results in a decrease in perennial plant species cover and richness, which is replaced by an ephemeral layer of grasses and forbs. Assessing the responses of herbivores to this transformation thus allows the testing of the hypothesis that climate change and desertification will lead to a broadening of diet and a decline in secondary productivity. In this study, the diet and productivity of Angora goats in intact and transformed thicket in adjacent paddocks was investigated from August 2005 to July 2006. Faecal analysis was used to compare the diets of the Angora goats in the intact and transformed thicket treatments. Goats in the transformed treatment consumed a higher diversity of plant species (94 species) compared to those in the intact thicket (42 species). The higher species richness per faecal sample and the larger seasonal variation in plant species utilized by the goats in the transformed treatment reflected the variability of this treatment in response to rainfall. Dietary shifts to include less palatable species not found in the intact treatment diet were clear, but due to the high rainfall year an abundant ephemeral layer, comprising grasses and forbs, was available in the transformed treatment. The diet quality of the transformed treatment goats was higher, as indexed by faecal lignin, than the intact treatment goats, although there was no statistical difference in the NDF and ash levels between the treatments. There was however, more variation in the nutritional quality of the transformed thicket diet, as indexed by dietary phosphorous, showing that intact thicket retains a more constant nutritional level. There was no difference in the body condition and mohair production of the goats in the two treatments. The hypothesis of broadening of the diet was thus supported, but there was no evidence for the predicted decline in secondary productivity. This study was undertaken during an above average rainfall period and large quantities of nutritious ephemeral grasses were available in the transformed treatment. This resource would not be available in a drought; therefore goats in the intact thicket will likely perform better over longer periods; providing stocking rates are realistic. This is the first study to measure the response of domestic herbivores to transformation either in terms of resource use or production.
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  • Date Issued: 2008

The feasibility of artificial recharge of the Bushmans River Mouth Aquifer

  • Authors: Nickall, Enéz Sarah-Leigh
  • Date: 2008
  • Subjects: Artificial groundwater recharge -- South Africa -- Bushmans River Estuary , Water conservation -- South Africa , Aquifer storage recovery -- South Africa -- Bushmans River Estuary
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10657 , http://hdl.handle.net/10948/704 , http://hdl.handle.net/10948/d1012886 , Artificial groundwater recharge -- South Africa -- Bushmans River Estuary , Water conservation -- South Africa , Aquifer storage recovery -- South Africa -- Bushmans River Estuary
  • Description: The main aim of the project is to investigate the feasibility of artificial recharge of the Bushmans River Mouth Aquifer in the Eastern Cape. The suggested method of recharge is through natural infiltration through a series of wetlands in the back dune area. The proposed site was the Klipfontein Vlei which is located just north of the Bushmans River Mouth. Artificial recharge is defined as augmenting the natural movement of surface water into underground formations by some method of construction, the spreading of water, or by artificially changing natural conditions. A variety of methods have been developed, including water spreading, recharging through pits and wells, and pumping to induce recharge from surface water bodies. The choice of a specific method is controlled by local topography, geology and soil conditions, and the quantity of water to be recharged and ultimate water usage. In special circumstances, land value, water quality, and climate play an important role. Artificial recharge is not a foreign concept to South Africa and this project is to test its feasibility in a back dune wetland area. Augering done in the study area revealed the dominance of sandy loam in the upper layers of the pans, loamy sand in the middle levels and the presence of some sand lenses in the lower reaches. Particle size analysis done by sieving and hydrometer test, showed a dominant 3f fraction. There was variation in modes in pan 1 from unimodal to bimodal to trimodal. Pan 2 showed no variation as all samples were unimodal and moderately well sorted. Infiltration tests were done by a double ring infiltrometer. These results showed that the infiltration rates of the pans became stable after 15 to 20 minutes, thus indicating that the soil had reached its saturation point. The resistivity surveys revealed a stepped water table. The inclination of the water is controlled by the predominately argillaceous horizons of the Bokkeveld Group. Based on the above results, it is recommended that the Klipfontein Vlei be used as an artificial recharge site.
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  • Date Issued: 2008

The identification of criteria to be utilised in mathematical diagnostic tests

  • Authors: Wagner-Welsh, Shirley Joy
  • Date: 2008
  • Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , DPhil
  • Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
  • Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
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  • Date Issued: 2008

The impact of an in-depth code comprehension tool in an introductory programming module

  • Authors: Leppan, Ronald George
  • Date: 2008
  • Subjects: Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10471 , http://hdl.handle.net/10948/847 , Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
  • Description: Reading and understanding algorithms is not an easy task and often neglected by educators in an introductory programming course. One proposed solution to this problem is the incorporation of a technological support tool to aid program comprehension in introductory programming. Many researchers advocate the identification of beacons and the use of chunking as support for code comprehension. Beacon recognition and chunking can also be used as support in the teaching model of introductory programming. Educators use a variety of different support tools to facilitate program comprehension in introductory programming. Review of a variety of support tools fails to deliver an existing tool to support a teaching model that incorporates chunking and the identification of beacons. The experimental support tool in this dissertation (BeReT) is primarily designed to encourage a student to correctly identify beacons within provided program extracts. BeReT can also be used to allow students to group together related statements and to learn about plans implemented in any semantically and syntactically correct algorithm uploaded by an instructor. While these requirements are evident in the design and implementation of BeReT, data is required to measure the effect BeReT has on the indepth comprehension of introductory programming algorithms. A between-groups experiment is described which compares the program comprehension of students that used BeReT to study various introductory algorithms, with students that relied solely on traditional lecturing materials. The use of an eye tracker was incorporated into the empirical study to visualise the results of controlled experiments. The results indicate that a technological support tool like BeReT can have a significantly positive effect on student comprehension of algorithms traditionally taught in introductory programming. This research provides educators with an alternative way for the incorporation of in-depth code comprehension skills in introductory programming.
  • Full Text:
  • Date Issued: 2008
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