Showing items 1081 - 1100 of 1292

Your selections:

Reeds as indicators of nutrient enrichment in the East Kleinemonde Estuary

  • Authors: Human, Lucienne Ryno Daniel
  • Date: 2009
  • Subjects: Estuaries -- South Africa -- Eastern Cape -- East Kleinemonde Estuary , Nutrient cycles -- South Africa -- Eastern Cape -- East Kleinemonde Estuary
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10615 , http://hdl.handle.net/10948/1252 , Estuaries -- South Africa -- Eastern Cape -- East Kleinemonde Estuary , Nutrient cycles -- South Africa -- Eastern Cape -- East Kleinemonde Estuary
  • Description: The release of nutrients (nitrogen and phosphorus) via land clearing, application of fertilisers, discharge of human waste and combustion of fossil fuels, is one of the most harmful effects of anthropogenic stresses on aquatic environments. This study investigated the use of reeds as indicators of nutrient input to estuaries. Small estuaries such as the oligotrophic East Kleinemonde where the research was mostly conducted are sensitive to nutrient enrichment from septic tanks, stormwater runoff and fertiliser application to lawns in close proximity to the estuary. Nutrient concentrations were sampled at different positions, in the groundwater, at the water’s edge, in the reed bed and in the main estuary channel at five sites in the East Kleinemonde Estuary. The NH4+ and SRP concentrations showed a definite trend as concentrations decreased from the groundwater or water’s edge into the main estuary channel. Groundwater introduced nutrients to the estuary which were then taken up by the fringing reeds (Phragmites australis (Cavinelles) Trinius ex Steudel). The water column nutrients were either below detectable limits or in very low concentrations. Low TOxN concentrations were consistently found at the different sites and probably resulted from P. australis assimilating N-TOxN for growth more efficiently than N- NH4+. The roots, rhizomes, stems and leaves of the reeds were measured for δ15N as an indicator of nutrient enrichment as nitrogen stable isotope analysis of plant tissue is an effective method for assessing and monitoring septic tank and other anthropogenic inputs. All plant parts for the three sampling sessions at Site 1 (mouth region) in the East Kleinemonde Estuary had significantly higher δ15N signatures (~20 percent) than the leaves at Site 5 (upper reaches). These differences were related to the surrounding land-use of the East Kleinemonde catchment, where the lower part of the estuary has moderate to low residential development and the upper reaches are utilized mainly for livestock farming. The high δ15N signatures at Site 1 were attributed to septic tank wastewater and stormwater run-off entering the estuary. Nutrient enrichment also influenced the morphology of the reeds. Reed biomass, height and stem density was significantly higher at Site 1 compared to Site 5. Similar studies were conducted in August 2008 in the Sundays Estuary and October 2008 in the nearby Mtati and Mpekweni estuaries to see if the results were similar. iii The same patterns were found where the groundwater NH4+ and SRP concentrations were higher than the estuary channel in the Mtati and Mpekweni estuaries. In the Mpekweni and Sundays estuaries Phragmites australis leaves had high δ15N signatures (10 and 11 percent) similar to that of Site 1 in the East Kleinemonde Estuary. Lower signatures (-2 to +4 percent) were found in the Mtati Estuary. This sampling site was sheltered by a bridge with a steep slope and the concentrations were similar to Site 3 and 5 in the East Kleinemonde Estuary where the derived nutrient was the result of stormwater runoff or fertilisers. Density and biomass of reeds in the Sundays and East Kleinemonde (Site 1) estuaries were similar and this could be related to different nutrient sources, agricultural return flow and septic tank input respectively. Reeds in the Sundays Estuary were significantly taller than in the other estuaries which showed that factors such as shelter and salinity also influence reed growth and therefore morphology alone would not be a good indicator of nutrient enrichment. Indicators of nutrient enrichment are important as the status of temporarily open / closed estuaries in South Africa is threatened by deteriorating water quality. Measurements of the water column may provide an inaccurate assessment of water quality whereas macrophytes are outstanding potential indicators of nutrient enrichment as they are widely distributed, abundant and long-lived. The findings from this study indicate that δ15N concentrations in reeds can be used to indicate nutrient loading.
  • Full Text:
  • Date Issued: 2009

Rhenium (I) and (V) complexes with potentially mulidentate ligands containing the Amino group

  • Authors: Booysen, Irvin Noel
  • Date: 2009
  • Subjects: Rhenium , Ligands
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10386 , http://hdl.handle.net/10948/1270 , Rhenium , Ligands
  • Description: The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab = 1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only in a distorted octahedral coordination geometry around the metal ion. The complex trans- [Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The ‘2 + 1’ complex fac- [Re(CO)3(Hamp)(amp)] (Hamp = 2-aminophenol) was isolated from the reaction of a two molar ratio of Hamp with [Re(CO)5Br] in toluene. The reaction of a 1:1 molar ratio of [Re(CO)5Br] and H2ada led to the isolation of the Re(I) complex, fac- [Re(CO)3Br(H2ada)]. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of trans-[ReOCl3(PPh3)2] with N-(2-aminobenzylidene)-5-amino-1,3-dimethyl uracil (H3dua) in ethanol gave a mixed crystal which contains both the neutral oxorhenium(V) complex [ReOCl(Hdua)] and the imido rhenium(V) [Re(dua)Cl2(PPh3)] in an equimolar ratio in the asymmetric unit. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux led to the isolation of [C12H12N6O4] as only product. The [ReO4]- anion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination Abstract I.N. Booysen Nelson Mandela Metropolitan University vii of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of 2-(2-aminophenyl)benzothiazole (Habt) with [Re(CO)5Br] led to the isolation of the rhenium(I) complex fac-[Re(Habt)(CO)3Br]. With trans-[ReOCl3(PPh3)2], the ligand Habt decomposed to form the oxofree rhenium(V) complex [Re(itp)2Cl(PPh3)] (itp = 2-amidophenylthiolate). From the reaction of trans-[ReOBr3(PPh3)2] with 2-(2- hydroxyphenyl)benzothiazole (Hhpd) the complex [ReVOBr2(hpd)(PPh3)] was obtained. The reaction of a twofold molar excess of H2apb (2-(2-aminophenyl)-1-benzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonalbipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. A new nitrosylrhenium(II) complex salt, [Re(NO)BrL2(PPh3)2](ReO4) (H2L2 = 2-amino-5- (triphenylphosphino)phenol), is the first example of a complex containing the triphenylphosphonium-amidophenolate ligand L2, formed by the nucleophilic attack of a PPh3 on a coordinated amidophenolate ring. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps = N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The X-ray crystal structure show that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry, around the rhenium(V) centre, with the two chlorides in cis positions. A new oxofree rhenium(V) complex salt, [Re(bbd)2](ReO4) ( H2bbd = N-(2- Abstract I.N. Booysen Nelson Mandela Metropolitan University viii aminobenzylidene)benzene-1,2-diamine), has been synthesized and the chelates bbd are coordinated as dianionic tridentate N,N,N-donor diamidoimines. The rhenium(V) ion is centered in a distorted trigonal prism. The rhenium(I) compound fac-[Re(CO)3(daa)].Hpab.H2O (Hpab = N1,N2-(1,2- phenylene)bis(2-aminobenzamide); Hdaa = 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO)5Br] with a two equivalents of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. Daa is coordinated as a diaminoamide via three nitrogen-donor atoms. The reaction of a twofold molar excess of H2amben (H2amben = N1,N2-bis(2-aminobenzylidene)ethane-1,2-diamine) with trans- [ReOBr3(PPh3)2] gave the oxorhenium(V) cationic complex [ReO(amben)]X (X = Br-, PF6 -). The Re(V) oxo-bridged compound, {μ-O}[ReO(omben)]2.H2O (H2omben = N1,N2- bis(2-hydroxybenzylidene)ethane-1,2-diamine) was isolated from the reaction of a 2:1 molar ratio of H2omben and trans-[ReO2(py)4]Cl in methanol. The seven-coordinate rhenium(III) complex cation [ReIII(dhp)(PPh3)2]+ was isolated as the [ReO4]- salt from the reaction of cis-[ReVO2I(PPh3)2] with 2,6-bis(2- hydroxyphenyliminomethyl)pyridine (H2dhp) in ethanol. In the complex fac- [Re(CO)3(H2dhp)Br], prepared from [Re(CO)5Br] and H2dhp in toluene, the H2dhp ligand acts as a neutral bidentate N,N-donor chelate. An equimolar ratio reaction of 2-aminobenzaldehyde and 2-(2-aminophenyl)-1- benzimidazole in methanol led to 2-(5,6-dihydrobenzimidazolo[1,2-c]-quinazolin-6- yl)aniline. In an attempt to explore the template formation of this class of ligand with rhenium, the reaction of salicylaldehyde and 2-(2-aminophenyl)-1-benzimidazole in ethanol which was followed by the addition of trans-[ReOBr3(PPh3)2] led to the formation of the salt, 6-(2-hydroxyphenyl)-5,6-dihydrobenzimidazolo[1,2-c]quinazolin- 12-ium bromide. The compound 6-(2-methylthiophenyl)-5,6-dihydrobenzimidazolo[1,2- c]quinazolin-12-ium was synthesized via the reaction of 2-aminobenzaldehyde and 2- methylthiobenzaldehyde in methanol.
  • Full Text:
  • Date Issued: 2009

Seed dynamics and seedling survival in mainland thicket of the Eastern Cape

  • Authors: Weatherall-Thomas, Clayton Richard
  • Date: 2009
  • Subjects: Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10601 , http://hdl.handle.net/10948/1048 , Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
  • Description: Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.
  • Full Text:
  • Date Issued: 2009

Size prediction for plus-size women's intimate apparel using a 3D body scanner

  • Authors: Pandarum, Krishnavellie
  • Date: 2009
  • Subjects: Lingerie , Lingerie -- Design , Overweight women
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10450 , http://hdl.handle.net/10948/1153 , http://hdl.handle.net/10948/d1012020 , Lingerie , Lingerie -- Design , Overweight women
  • Description: Garment “fitting” from tailor-made to ready-to-wear clothing, has evolved over time. Ready to-wear and standardized sizes appeared in the middle 19th century. Today garment fitting is one of the most important criteria in the consumer buying decision making process. This is particularly so with “body hugging” garments, such as intimate apparel; or the bra that moulds the form of the wearer to produce “smooth” outer garment silhouettes. The South African bra retailer and manufacturers sizing charts are generally based upon body dimension data collected using traditional anthropometric methods. Professional measurers are not able to capture the hidden areas of the breast such as the inframmatory fold line, the volume, shape and contour of the breast using tape measures, calipers and other measuring devices. Traditional anthropometry also does not have the ability to systemically observe the bottom line of the breast base and extract accurate data on breast volume which are key factors in designing underwire bras and in the pattern making of the bra cup panels. Exploratory retail and consumer studies have indicated that consumers, notably plus size women, experience considerable problems and dissatisfaction with poorly fitting bras. There is therefore clearly a need in South Africa to conduct a 3D anthropometric study, focusing especially on the plus-sized women’s bra market segment, as there is very little or limited studies, to date, conduct for this market segment of the population. This pilot study collected 3D torso body measurement data from a convenient sample of 176 plus sized women, recruited from Playtex (Pty) Ltd. situated in Durban, KwaZulu Natal, South Africa. The study evaluates the 3D breast volume measurement data extraction process, using an expert system developed by [TC]2 integrated into the propriety NX12-3D full body scanner software and that taken using the traditional dress-makers tape-measure. The objective is to establish the relationship between the 3D torso and breast volume data measurement output as extracted by the expert system when compared to the South African bra manufacturers sizing chart, for use in pattern making for bra cup panel designs and in the designing of underwire bras for large breasted or plus size women. The results contained in this dissertation cannot be extrapolated to the larger population of South Africa and is limited to the 176 plus size women selected by Body Mass Index; recruited from KwaZulu Natal, South Africa.
  • Full Text:
  • Date Issued: 2009

Socio-economic and ecological correlates of leopard-stock farmer conflict in the Baviaanskloof mega-reserve, Eastern Cape

  • Authors: Minnie, Liaan
  • Date: 2009
  • Subjects: Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10702 , http://hdl.handle.net/10948/1044 , Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
  • Description: The leopard, Panthera pardus, is particularly threatened outside conservation areas in South Africa. This has been attributed to a reduction in natural habitat, decreasing natural prey populations, and commercial exploitation such as trophy hunting, and most importantly, persecution by stock farmers (Woodroffe 2001). The leopard population in the Baviaanskloof Mega-Reserve (BMR) has undergone a substantial decrease in range and numbers in the past 200 years, resulting in a highly fragmented population in the Baviaanskloof Mega-Reserve, and is regarded as being insecure. There is thus a need to investigate the nature and extent of leopard-stock farmer interactions to provide the foundation for an effective leopard conservation plan. Here I investigated the ecological and socio-economic factors influencing leopard-stock farmer conflict via landowner surveys and estimated potential leopard numbers using a prey-based density model. Leopards are not necessarily the most important causes of livestock mortality in the BMR. On average, leopards killed significantly less livestock (0.7 percent livestock per year) than black-backed jackals (4.7 percent per year) and caracal (2.5 percent per year), yet 67 percent of farmers had negative attitudes towards leopards. These negative attitudes were not significantly related to stock losses. However, most of the farmers that had negative attitudes towards leopards did not have any stock losses attributed to leopards. Thus if predator-stock conflict is not reduced it will result in the retaliatory killing of leopards. This will have severe consequences for this relatively small population (estimated at 59 – 104 individuals by the prey-based model), which may ultimately lead to the local extinction of these leopards (Woodroffe & Ginsberg 1998).
  • Full Text:
  • Date Issued: 2009

Solvent-free synthesis of bisferrocenylimines and their coordination to rhodium (I)

  • Authors: Kleyi, Phumelele Eldridge
  • Date: 2009
  • Subjects: Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10393 , http://hdl.handle.net/10948/1053 , Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
  • Description: Solvent-free reactions possess advantages compared to the solvent route, such as shorter reaction times, less use of energy, better yields, etc. Herein, the synthesis and characterization of bisferrocenylimines and arylbisamines are described. Reduction of the above compounds with LAH resulted in the formation of bisferrocenylamines and arylbisamines, respectively. The coordination chemistry of all the above compounds to rhodium(I) is also discussed in the prepared complexes [Rh(COD)(NN)]ClO4, where NN = bisferrocenylimines, and [Rh(COD)(NN)]BF4, where NN = bisferrocenylamines and arylbisamines. X-ray crystal structures of the complexes [Rh(COD)(NN)]ClO4 ([3.2] and [3.3]) have been obtained. Complexes of the type [Rh(COD)(NN)]BF4 were characterized with IR and UV-vis spectroscopy, cyclic voltammetry and conductometry. The catalytic activity of the complexes was also investigated: [Rh(COD)(NN)]ClO4 for the polymerization of phenylacetylene and [Rh(COD)(NN)]BF4 for the hydroformylation of styrene.
  • Full Text:
  • Date Issued: 2009

Statistical models for pricing weather derivatives for Port Elizabeth

  • Authors: Nasila, Mark Wopicho
  • Date: 2009
  • Subjects: Weather derivatives -- Prices -- South Africa -- Port Elizabeth
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10567 , http://hdl.handle.net/10948/1018 , Weather derivatives -- Prices -- South Africa -- Port Elizabeth
  • Description: Weather has a significant impact on business activities of many kinds. The list of economic activities subjected to the risk of the weather include: the energy producers and consumers, the industry of leisure, the insurance industry, the food industry and the agricultural industries but the primary industry, namely the energy industry, has given rise to the demand for weather derivatives and has caused the weather risk management industry to evolve actively. A derivative is a contract or security, whose payoffs depend upon the price of an underlying asset price, and is used to control the risks of naturally-arising exposures to such an asset price. Therefore weather derivatives are financial contracts with payouts that depend on weather in some form. It is a contract that provides a payoff in response to an index level based on weather phenomena (West, 2002).The underlying variable can be for example humidity, rain, snowfall, temperature, or even sunshine. The main players who take part in the weather derivatives markets industry can be grouped in to five main categories, namely: 1) End users who are also referred to as hedgers 2) Speculators 3) Market makers 4) Brokers 5) Insurance and re-insurance companies. Since the late 90’s when the first weather derivatives transactions were recorded, the underlying market has witnessed the development of a new derivative market in the United States, which is gradually expanding across Europe. However, the newly developed market for weather derivatives is not liquid in Africa and specifically South Africa mainly due to the following factors: 1) Many companies and business organisations have not yet established a hedging policy or even figured out how their businesses or industries are exposed to weather risks. 2 2) “Since many companies and industries depend on insurance companies to cover their risks, it is possible that the solutions suggested by these companies or industries looking for protection from weather risks differ according to the cover provided by these insurance organisations “(Micali, 2008). The main aim of this study is to review available statistical models for pricing derivatives, with temperature as the underlying which could enable industries, businesses and other organisations in South Africa to protect themselves against losses due to fluctuations in the weather and therefore hedge their risks.
  • Full Text:
  • Date Issued: 2009

Statistical relationship of customer behavioral characteristics in personal banking

  • Authors: Rasuba, Maanda
  • Date: 2009
  • Subjects: Customer relations -- South Africa -- Management , Consumer behavior -- South Africa , Banks and banking -- Customer services -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10566 , http://hdl.handle.net/10948/1165 , Customer relations -- South Africa -- Management , Consumer behavior -- South Africa , Banks and banking -- Customer services -- South Africa
  • Description: This study investigates the relationship of bank customers’ behavioural patterns based on the customers past transactions, with respect to their profile characteristics. The main aim of this study is to illustrate that different categories of customers (based on demographical variables such as race, gender and age) have statistically significant differences in behaviour, with respect to how they operate their accounts. A theoretical overview on the literature of customer relationship management in the banking sector emphasises the importance of understanding customers to ensure that a business is successful. Four null-hypotheses where formulated based on a general research hypothesis. The data base provided a major South African bank is used to achieve the objectives. Extensive cleaning of the data set was necessary to ensure the validity of the results. The data set had 7860 customer keys. The large data base used contributed to the reliability of the results. The following behavioural variables were used in the study namely, transaction data, average debit and credit transaction amounts and average number of transactions per month. The main results of study indicate that different customer categories have statistically significant differences in behaviour, with respect to how customers operate their accounts. This implies that it is important for the banking sector to consider customer gender differences, age differences and race group differences in the relationship strategies which they employ in their multicultural environment. Further research in the area may be necessary before generalisation can be made on all banking customers.
  • Full Text:
  • Date Issued: 2009

Synthesis and characterization of novel platinum complexes : their anticancer behaviour

  • Authors: Myburgh, Jolanda
  • Date: 2009
  • Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
  • Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
  • Full Text:
  • Date Issued: 2009

The coordination chemistry of Rhenium(V) with multidentate no-donor ligands

  • Authors: Abrahams, Abubak'r
  • Date: 2009
  • Subjects: Rhenium , Ligands
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10370 , http://hdl.handle.net/10948/912 , Rhenium , Ligands
  • Description: The neutral distorted octahedral complexes [ReOCl(L)] {H2L = N,N-bis(2- hydroxybenzyl)-2-(2-aminoethyl)dimethylamine (H2had), N,N-bis(2-hydroxybenzyl) aminomethylpyridine (H2hap); N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)pyridine (H2hae)} were prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H2L in ethanol. The X-ray structure determinations of [ReOCl(had)] and [ReOCl(hap)] were performed, and in both complexes the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen. Treatment of trans-[ReO2(py)4]I with two equivalents and one equivalent each of H2had in acetone afforded the iodide salts of the oxypyridinium-ammonium zwitterions N1-(2-hydroxybenzyl)-N2,N2- dimethyl-N1-((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [Hhpd]+ and N2,N2- dimethyl-N1-bis((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [dod]+ respectively. In [Hhpd]I, one of the 2-hydroxyphenyl groups of H2had is substituted by an oxypyridinium group, and in [dod]I, both 2-hydroxyphenyl groups are converted. The X-ray crystal structure determination of the starting material H2had, [Hhpd]I and [dod]I reveals trigonal pyramidal geometries around the central amino nitrogen. The complex salt [ReO(bsa)]PF6 (H2bsa=bis(N-methylsalicylicylideneiminopropyl) amine) was prepared from the reaction of cis-[ReO2I(PPh3)2] with H2bsa in toluene. The dianionic pentadentate ligand bsa is coordinated to the ReO3+ moiety via one secondary amino and two imino nitrogens, and two anionic phenolate oxygens. The complex was characterized by spectroscopy and analytical data, and the structure has been determined by single-crystal X-ray diffraction analysis. The complex exhibits a distorted octahedral geometry around the central rhenium(V) ion, with the basal plane being defined by a phenolate oxygen, two imino nitrogens and the secondary amino. ix A. Abrahams Nelson Mandela Metropolitan University The reaction of a two-fold molar excess of the potentially NN-donor ligand 2,2’- dipyridylamine (dpa) with trans-[ReO(OEt)Cl2(PPh3)2] in ethanol led to the isolation of [ReOCl2(OEt)(dpa)]. The X-ray crystal structure shows that the NN-chelated dpa is coordinated in the equatorial plane cis to the oxo and ethoxo groups, which are in trans positions relative to each other. The treatment of trans- [ReOCl3(PPh3)2] with a tenfold molar excess of dpa in ethanol at the refluxing temperature yielded the trans-dioxo complex [ReO2(dpa)2]Cl, but with a twofold molar excess only (μ-O)[{ReOCl2(dpa)}2] was isolated. Repeating the latter reaction with (n-Bu4N)[ReOCl4] as starting material in ethanol at room temperature a dark green product, also with the formulation (μ-O)[{ReOCl2(dpa)}2], was isolated. The reaction of equimolar quantities of bis(pyridin-2-yl)methyl)amine (HBPA) with (n-Bu4N)[ReOCl4] in acetone at room temperature led to the isolation of the sixcoordinate rhenium(V) complex [ReOCl(H2O)(BPA)]Cl. IR, NMR and X-ray crystallographic results indicate that BPA is coordinated as a tridentate uninegative chelate, with deprotonation of the amine nitrogen. The water molecule is coordinated trans to the oxo group, with the Re=O and Re-OH2 bond distances equal to 1.663(9) and 2.21(1) Å respectively. Complexes of the general formula [ReOX2{(C5H4N)CH(O)CH2(C5H4N)}] (X = Cl, I) were prepared by the reactions of trans-[ReOCl3(PPh3)2] and trans- [ReOI2(OEt)(PPh3)2] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. Experimental evidence shows that the coordinated DPE ligand has undergone addition of water at the ethylenic carbons, and that the (C5H4N)CH(O)CH2(C5H4N) moiety acts as a uninegative tridentate NON-donor ligand. The X-ray crystal structures of both complexes show a distorted octahedral geometry around the rhenium(V) centre. The treatment of trans-[ReOCl3(PPh3)2] with H2dbd in a 2:1 molar ratio in acetonitrile led to the isolation of the ligand-bridged dimer (μ-dbd)[ReOCl2(PPh3)]2. The X-ray crystal structure of the complex reveals a dinuclear structure in which two rhenium(V) ions are bridged by the dbd ligand. Each rhenium ion is in a x A. Abrahams Nelson Mandela Metropolitan University distorted octahedral geometry. The basal plane is defined by a phosphorus atom of the PPh3 group, two chlorides cis to each other, and a pyridyl nitrogen atom of dbd. The oxo group and alcoholate oxygen of dbd lie in trans axial positions. The complexes cis-[ReOX2(msa)(PPh3)] (X = Cl, Br, I) were prepared from trans- [ReOCl3(PPh3)2], trans-[ReOBr3(PPh3)2] or trans-[ReOI2(OEt)(PPh3)2] with 2-(1- iminoethyl)phenol (Hmsa) in acetonitrile. An X-ray crystallographic study shows that the bonding distances and angles in the comlexes are nearly identical, and that the two halides in each complex are coordinated cis to each other in the equatorial plane cis to the oxo group. The oxo-bridged dinuclear rhenium(V) complex [(μ-O){ReOCl(amp)}2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] and 6-amino-3-methyl-1-phenyl- 4-azahept-2-ene-1-one (Hamp) in acetone. The characterization of the complex by elemental analysis, infrared and 1H NMR spectroscopy and X-ray crystallography shows that amp is coordinated as a monoanionic NNO-donor chelate as an amino-amido ketone. However, the reaction of the similar ligand 7- amino-4,7-dimethyl-5-aza-3-octen-2-one (Hada) with [Re(CO)5Br] produced the product fac-[Re(CO)3Br(Hada)], with Hada coordinated as a neutral NN-donor amino-imino-ketone.
  • Full Text:
  • Date Issued: 2009

The development and evaluation of gaze selection techniques

  • Authors: Van Tonder, Martin Stephen
  • Date: 2009
  • Subjects: Human-computer interaction , User interfaces (Computer systems) , Gaze
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10469 , http://hdl.handle.net/10948/882 , Human-computer interaction , User interfaces (Computer systems) , Gaze
  • Description: Eye gaze interaction enables users to interact with computers using their eyes. A wide variety of eye gaze interaction techniques have been developed to support this type of interaction. Gaze selection techniques, a class of eye gaze interaction techniques which support target selection, are the subject of this research. Researchers developing these techniques face a number of challenges. The most significant challenge is the limited accuracy of eye tracking equipment (due to the properties of the human eye). The design of gaze selection techniques is dominated by this constraint. Despite decades of research, existing techniques are still significantly less accurate than the mouse. A recently developed technique, EyePoint, represents the state of the art in gaze selection techniques. EyePoint combines gaze input with keyboard input. Evaluation results for this technique are encouraging, but accuracy is still a concern. Early trigger errors, resulting from users triggering a selection before looking at the intended target, were found to be the most commonly occurring errors for this technique. The primary goal of this research was to improve the usability of gaze selection techniques. In order to achieve this goal, novel gaze selection techniques were developed. New techniques were developed by combining elements of existing techniques in novel ways. Seven novel gaze selection techniques were developed. Three of these techniques were selected for evaluation. A software framework was developed for implementing and evaluating gaze selection techniques. This framework was used to implement the gaze selection techniques developed during this research. Implementing and evaluating all of the techniques using a common framework ensured consistency when comparing the techniques. The novel techniques which were developed were evaluated against EyePoint and the mouse using the framework. The three novel techniques evaluated were named TargetPoint, StaggerPoint and ScanPoint. TargetPoint combines motor space expansion with a visual feedback highlight whereas the StaggerPoint and TargetPoint designs explore novel approaches to target selection disambiguation. A usability evaluation of the three novel techniques alongside EyePoint and the mouse revealed some interesting trends. TargetPoint was found to be more usable and accurate than EyePoint. This novel technique also proved more popular with test participants. One aspect of TargetPoint which proved particularly popular was the visual feedback highlight, a feature which was found to be a more effective method of combating early trigger errors than existing approaches. StaggerPoint was more efficient than EyePoint, but was less effective and satisfying. ScanPoint was the least popular technique. The benefits of providing a visual feedback highlight and test participants' positive views thereof contradict views expressed in existing research regarding the usability of visual feedback. These results have implications for the design of future gaze selection techniques. A set of design principles was developed for designing new gaze selection techniques. The designers of gaze selection techniques can benefit from these design principles by applying them to their techniques
  • Full Text:
  • Date Issued: 2009

The development of a commercial production process for p-menthane-3,8-diol

  • Authors: Rust, Nico
  • Date: 2009
  • Subjects: Insect pests -- Control , Repellents
  • Language: English
  • Type: Thesis , Doctoral , DTech
  • Identifier: vital:10427 , http://hdl.handle.net/10948/d1018273
  • Description: The synthesis of p-menthane-3,8-diol via the acid-catalyzed cyclization of citronellal in a dilute aqueous sulphuric acid medium was investigated using conventional batch and continuous systems in order to develop a commercial production process for said p-menthane-3,8-diol (PMD). The batch studies conducted during the first part of this study showed that the formation of PMD from citronellal occurs via an intra-molecular Prins reaction that results in the formation of both the desired PMD product, as well as the partially hydrated isopulegol. It was shown that the formationof the by- product, PMD-acetal, results from the reaction between an intermediate, 5-methyl-2- isopropylcyclohexanol, and the citronellal starting material, and not from the reaction between PMD and citronellal as previously reported. Kinetic studies confirmed the existence of a complicated kinetic model. The formation of PMD from citronellal displayed typical pseudo first order kinetics up to conversions of 70 after which the kinetic model becomes complicated as the result of the establishment of quasi equilibrium reactions between PMD and isopulegol (dehydration of PMD and hydration of isopulegol) and between PMD the PMD-acetal, both systems being acid catalysed. The PMD-acetal formation reaction appears to be second order with respect to PMD. Scale-up studies of the batch process to 30L and 50L scales showed that it would be extremely difficult to limit the level of PMD-acetal formation below the desired level of 1 percent, even if citronellal conversions are restricted to about 50 percent. During studies conducted on a commercially availablemicro-structured organic synthesis plant (OSP) it was shown that it is possible to perform the PMD reaction as a continuous process. The results obtained showed that the use of a micro-mixer such as the caterpillar micro-mixer did not provide enough residence time in order for desirable conversions (- 40 percent) to be obtained. By combining themicro-mixer with delay-loops of different thicknesses and lengths, and using increasing reaction temperatures, it was shown that the conversion of citronellal could be improved to some extent, but compared poorly to the expected conversions for a well-stirred batch reactor. By packing selected delay loops with inert SiC particles, improved mass transfer was observed between the organic and aqueous phases as reflected in the increased conversion of citronellal. Using the observations that were made during the use of the OSP, a continuous-flow, tubular reactor system was designed and constructed. Advanced statistical techniques were used to investigate the effect of variables such as temperature, acid concentration, reactor length, flow rate and the organic to aqueous ratio on the rate and selectivity of the reaction. Mathematical models were derived for citronellal conversion, yield of PMD and yield of PMD- acetals, and used to predict the concentrations of citronellal, PMD and PMD-acetals at set experimental conditions. The results obtained showed that it was possible to obtain a product which approached desired specifications.Downstream processing of the PMD reaction mixture as it exits the reactor requires phase separation and neutralization of the acid catalyst solution, followed by further work-up to recover unreacted starting material and intermediates for recycle back to the synthesis reactor, followed by purification of crude PMD to the desired specification. The study showed that neutralization, prior or after phase separation, does not affect the selectivity of the PMD to such a great extent, but does influence the relative conversion due to extended contact of the catalyst with the organic phase after the reaction is terminated. Recovery of unreacted citronellal and isopulegol could be achieved by a simple vacuum evaporation step, which may either be carried out in a batch manner using traditional distillation equipment, or in a continuous process using wiped-film (short path) techniques. It was also shown that selective crystallization of PMD from the crude product mixture by addition of a solvent, such as heptanes or hexane proved to be the best way of achieving the desired product specification.
  • Full Text:
  • Date Issued: 2009

The ecophysiology of Gelidium Pristoides (Turner) Kuetzing : towards commercial cultivation

  • Authors: Steyn, Paul-Pierre
  • Date: 2009
  • Subjects: Marine algae -- South Africa , Marine algae -- Ecophysiology , Red algae -- South Africa , Gelidium -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10617 , http://hdl.handle.net/10948/1117 , Marine algae -- South Africa , Marine algae -- Ecophysiology , Red algae -- South Africa , Gelidium -- South Africa
  • Description: The ecophysiology of the red alga Gelidium pristoides (Turner) Kuetzing was investigated in an effort to establish a technique for commercial cultivation. The seaweed is of commercial importance in South Africa where it is harvested from the intertidal zone rocky shores along the coast. It is dried and exported abroad for the extraction of agar. Yields and quality could be improved by cultivation in commercial systems. However, attempts at growing the seaweed in experimental systems have all ended in failure. This study aimed to describe the conditions in which the seaweed grows naturally; and investigate its physiological response to selected physical conditions in the laboratory in order to determine suitable conditions for mariculture. Ecological studies showed that G. pristoides grew above the spring low tide water level. The upper limit of the seaweed’s vertical distribution range, as well as its abundance, was largely dependent on wave exposure. The zone normally inhabited by G. pristoides was dominated by coralline turf in sheltered areas, while the abundance of G. pristoides increased towards more exposed rocky shore sites. The seaweed occurred among species such as Pattelid limpets and barnacles, but was usually the dominant macroalga in this zone, with coralline turf and encrusting algae being the only others. Physical conditions in the part of the intertidal zone inhabited by G. pristoides were highly variable. During low tide temperatures could vary by as much as 10°C within the three hours between tidal inundation of the seaweed population, while salinity varied by up to 9 ppt, and light intensity by as much as 800 μmol m-2 s-1. During these exposure periods the seaweed suffered up to 20% moisture loss. Laboratory experiments on the seaweed’s response to these conditions indicated that it was well adapted to such fluctuations. It had a broad salinity (20 and 40 ppt), and temperature tolerance range (18 to 24°C), with an o ptimum of temperature of 21°C for photosynthesis, while there was no difference in the photosynthetic rate of the alga within the 20 to 40 ppt salinity range. The alga had a low saturating irradiance (ca. 45 – 80 μmol m-2 s-1) equipping it well for photosynthesis in turbulent environments, with high light attenuation, but poorly to unattenuated light conditions. Exposure resulted in an initial increase in photosynthetic rate followed by a gradual decrease thereafter. pH drift experiments showed that low seawater pH, and associated increased carbon dioxide availability, resulted in an increase in photosynthetic rate. This response suggests that the seaweed has a high affinity for carbon dioxide, while the reduction in photosynthetic rate in response to bicarbonate use inhibition indicates that it also has the capacity for bicarbonate use. The high affinity of Gelidium pristoides for carbon dioxide as an inorganic carbon source appears to be the primary reason for the low abundance of the alga on sheltered rocky shore areas, and also explains the failure of the alga to grow in tank or open-water mariculture systems. Exposed rocky shores have experience heavy wave action, and the resultant aeration and mixing of nearshore waters increases the availability of carbon dioxide, which is considered a limiting resource. The absence of such mixing and aeration at sheltered site makes this less suitable habitat for G. pristoides. Periodic exposure also makes high levels of atmospheric carbon dioxide available from which the seaweed benefits. The traditional mariculture systems in which attempts have been made to cultivate the seaweed failed to satisfy either of the above conditions.
  • Full Text:
  • Date Issued: 2009

The effect of temperature and turbidity on spawning chokka squid, loligo reynaudii, in Eastern Cape waters

  • Authors: Downey, Nicola Jean
  • Date: 2009
  • Subjects: Squids -- Effect of temperature on -- South Africa , Squids -- Effect of turbidity on -- South Africa , Squids -- Spawning -- South Africa , Loliginidae -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10719 , http://hdl.handle.net/10948/945 , http://hdl.handle.net/10948/d1012895 , Squids -- Effect of temperature on -- South Africa , Squids -- Effect of turbidity on -- South Africa , Squids -- Spawning -- South Africa , Loliginidae -- South Africa
  • Description: Several studies suggest the environment influences chokka squid catches which are mostly based on the successful formation of inshore spawning aggregations. None of the evidence, however, is direct observation. Acoustic telemetry offers a means to determine the response of spawners to changes in the environment and insight into the behaviour of spawning squid. A hexagonal array of VR2 receivers deployed 500 m apart was deemed to be ideal to monitor the movement patterns of squid on the spawning sites. In isothermic conditions, an area up to 1.28 km2 could be monitored as there was an approximate 50 m overlap in individual VR2 receiver range. In thermocline conditions however, “acoustic dead zones” as wide as 350 m may have existed between VR2 receivers, limiting the performance of this configuration. Similarly benthic turbidity events would also decrease detection range and limit performance. A hexagonal array of VR2 receivers was moored in Kromme Bay on and around active spawning aggregations during the squid fishery closed seasons of November 2003, 2004, 2005 and 2006. Squid were caught on jigs and tagged with V9 acoustic pressure telemetry transmitters. A total of 45 animals were tagged. Presence-absence analysis identified three general behaviours: (1) arrival at dawn and departure after dusk, (2) a continuous and uninterrupted presence for a number of days and (3) presence interrupted by frequent but short periods of absence. Overall, the data suggests frequent migrations between spawning aggregations and offshore feeding grounds. The pressure sensor data showed both males and females stayed persistently near the seabed during the day, but at night, this pattern was broken with common activity higher up in the water column. The squid did not remain exclusively in the water column and regularly made excursions to the seabed. CTD and temperature data indicated the intrusion of a cold bottom layer due to upwelling at the monitored spawning sites on a number of occasions. The formation of spawning aggregations appears to be triggered by upwelling events and spawning behaviour, once initiated, disrupted by upwelling events with a rapid onset, possibly due to an inability to adapt physiologically over such a short time period.
  • Full Text:
  • Date Issued: 2009

The effect of tulbaghia violacea plant extract on the growth of aspergillus species

  • Authors: Belewa, Xoliswa Vuyokazi
  • Date: 2009
  • Subjects: Plant products , Plant extracts , Traditional medicine
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10315 , http://hdl.handle.net/10948/d1008186 , Plant products , Plant extracts , Traditional medicine
  • Description: Traditional medicine has become an important part of healthcare worldwide. It is estimated that about 25 percent of prescribed medicines contain plant products or active compounds derived from plants. In South Africa, traditional medicine forms part of the culture and tradition of most communities. Garlic compounds have been shown to have a variety of antimicrobial properties. Amongst these are antifungal, antibacterial, antiviral and anti protozoal activities. Allicin and its breakdown products have been shown to be the main active compounds which possess these properties. Tulbaghia violacea has been used for the treatment of a variety of illnesses including asthma, fever, oesophageal cancer, constipation and hypertension. This study investigated the antifungal nature of T.violacea on the morphology, spore germination and lipid synthesis of Aspergillus flavus and Aspergillus parasiticus. The results of this study showed that the plant extract inhibited A. flavus growth at a minimal inhibitory concentration of 15mg/ml and was fungicidal at 20mg/ml and above. A. parasiticus was not inhibited at 25mg/ml indicating resistance to the inhibitory component of the plant extract. A measure of metabolic activity using the XTT assay showed reduced metabolic activity in the presence of increasing concentrations of the plant extract. Higher extract concentrations resulted in higher percentage inhibition of fungal growth for both fungal species with up to 98 percent inhibition being observed for the highest extract concentrations for both fungi. Germination was also delayed in the presence of 15mg/ml plant extract concentration by up to 60hr for A. flavus and 48hr for A. parasititcus. The TEM results showed increased thickening of the cell wall with higher extract concentrations. The thickening was greater for A. flavus than for A. parasiticus. Cell wall thickening may be the reason for the delay in germination in both species. Lipid production was reduced in the presence of plant extracts when compared to the control. The plant extracts inhibited triglyceride production at 15mg/ml for both A. flavus and A. parasiticus. The results therefore indicate that T. violacea extracts are antifungal and probably affect germination through interactions with the cell wall. It is possible that the extract affects lipid production in Aspergillus species.
  • Full Text:
  • Date Issued: 2009

The effects of a Kenyan antidiabetic plant on insulin homeostasis

  • Authors: Suleiman, Khairunisa Yahya
  • Date: 2009
  • Subjects: Medicinal plants -- Kenya , Insulin resistance
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10326 , http://hdl.handle.net/10948/1055 , Medicinal plants -- Kenya , Insulin resistance
  • Description: The metabolic disorder diabetes; is a global epidemic affecting people in developed countries and increasingly in developing countries. In two decades time, 350 million people will be diabetic at the current rate of prevalence. In a preliminary study, insulin resistant rats were treated with Prunus Africana (plant A) for 28 days. Plasma samples obtained from P. africana treated rats had increased insulin levels compared to normal and untreated insulin resistant rats (Karachi, 2009). The treatment of insulin resistant rats with P. africana also showed increased glucose uptake in rat adipose tissue (Karachi, 2009), suggesting that P. africana had anti-diabetic properties. The aim of the study was to investigate the mechanism of the anti-diabetic properties of P africana extract. Increased insulin secretion was confirmed by the increased Cpeptide concentration in plasma samples of rats treated with P. africana. In order to explain the high insulin levels, several hypothesis’ were investigated: (1) P. africana may increase insulin secretion in β cells, hence the effect of P. africana on insulin secretion by INS-1 cells was investigated; (2) P. africana may increase insulin secretion by prolonging the half-life of glucagon like peptide-1 (GLP-1) by decreasing dipeptidyl peptidase IV (DPP IV) activity; the effect of P. africana on DPP IV activity was determined spectrophotometrically, (3) P. africana may increase the half-life of insulin in the plasma by decreasing the activity of insulin degrading enzyme (IDE); the effect of P. africana on IDE in rat muscle and spleen samples was investigated. To explain the increased glucose uptake in adipose tissue observed in the previous study two parameters were investigated: (1) increased GLUT4 expression in P. africana treated rats; the effect of P. africana treatment on the expression of glucose transporter 4 (GLUT4) was determined using real-time polymerase chain reaction (RT-PCR), (2) P. africana may increase glucose utilization; the effect of P. africana on glucose utilization was determined in 3T3-L1 cells. The plant extract did not significantly increase insulin secretion by INS-1 cells in the absence of glucose. P. africana decreased DPP IV activity in rat plasma when compared to the untreated insulin resistant rats and this could be a mechanism by which insulin secretion is increased during plant treatment. P. africana decreased IDE activity (however not significantly) when compared to the untreated insulin resistant The effects of a Kenyan antidiabetic plant on insulin homeostasis KY Suleiman VII rats. P. africana appeared to have no effect on GLUT4 expression. The plant appeared to increase glucose utilization in 3T3-L1 cells in the absence of insulin suggesting that P. africana may have insulin like activity. In summary, this study indicates that P. africana is indirectly involved in inhibiting DDPIV. This in turn can increase the half life of GLP-1, which in turn can enhance the secretion of insulin. P. africana increases glucose utilization although there was no evidence that the GLUT 4 transporter has a higher expression in the plant treated rats. Further studies should be conducted to investigate the expression of GLUT1 under the same conditons.
  • Full Text:
  • Date Issued: 2009

The integration of GIS technology into demographic and quality of life surveying of informal settlements : Nelson Mandela Bay, South Africa

  • Authors: Van Niekerk, Susan
  • Date: 2009
  • Subjects: Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10659 , http://hdl.handle.net/10948/881 , http://hdl.handle.net/10948/d1012888 , Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
  • Description: A number of mostly informal areas in Nelson Mandela Bay have experienced rapid expansion over the past decade or so. Census data available for these areas is outdated and does not provide enough information for local authorities to accurately plan for tasks such as service delivery management and resource allocation. In this dissertation, a GIS based demographic and Quality of Life study of informal settlements and previously disadvantaged areas within Nelson Mandela Bay is undertaken to address this issue. The study aims to integrate GIS technology into a demographic and Quality of Life survey to significantly improve the collection, analysis, interpretation, display and management of survey data and to provide the accurate and necessary updates required between census collections. Data relating to informal settlements were captured from aerial photographs and satellite imagery and demographic and Quality of Life data were collected from field surveys. The results demonstrated that the use of GIS technology provided more accurate information for demographic variables, including the number of dwellings, dwelling type, size of the population and population dynamics. A specific demographic trend observed through spatial analysis included the identification of backyard shacks predating formal structures in settlements. The analysis and representation of the Quality of Life field survey data in GIS demonstrated how residents' perceptions of problems and issues in their neighbourhoods are better interpreted, understood and managed when analyzed within a spatial context. This research concluded that GIS based demographic and QOL studies are vital for providing accurate social and spatial information for municipalities, particularly in urban environments of developing countries, and for providing the necessary updates to censuses occurring every ten years.
  • Full Text:
  • Date Issued: 2009

The invasion of pteronia incana (blue bush) along a range of gradients in the Eastern Cape Province : it's spectral chacteristics and implications for soil moisture

  • Authors: Odindi, John Odhiambo
  • Date: 2009
  • Subjects: Invasive plants -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:10650 , http://hdl.handle.net/10948/1052 , Invasive plants -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape
  • Description: Extensive areas of the Eastern Cape Province have been invaded by Pteronia incana (Blue bush), a non-palatable patchy invader shrub that is associated with soil degradation. This study sought to establish the relationship between the invasion and a range of eco-physical and land use gradients. The impact of the invader on soil moisture flux was investigated by comparing soil moisture variations under grass, bare and P. incana invaded surfaces. Field based and laboratory spectroscopy was used to validate P. incana spectral characteristics identified from multi-temporal High Resolution Imagery (HRI). A belt transect was surveyed to gain an understanding of the occurrence of the invasion across land use, isohyetic, geologic, vegetation, pedologic and altitudinal gradients. Soil moisture sensors were calibrated and installed under the respective surfaces in order to determine soil moisture trends over a period of six months. To classify the surfaces using HRI, the pixel and sub-pixel based Perpendicular Vegetation Index (PVI) and Spectral Mixture Analysis (SMA) respectively were used. There was no clear trend established between the underlying geology and P. incana invasion. Land disturbance in general was strongly associated with the invasion, as the endemic zone for the invasion mainly comprised abandoned cultivated and overgrazed land. Isohyetic gradients emerged as the major limiting factor of the invasion; a distinct zone below 619mm of mean annual rainfall was identified as the apparent boundary for the invasion. Low organic matter content identified under invaded areas was attributed to the patchy nature of the invader, leading to loss of the top soil in the bare inter-patch areas. The area covered by grass had consistently higher moisture values than P. incana and bare surfaces. The difference in post-rainfall moisture retention between grass and P. incana surfaces was significant up to about six days, after which a near parallel trend was noticed towards the ensuing rainfall episode. Whereas a higher amount of moisture was recorded on grass, the surface experienced moisture loss faster than the invaded and bare surfaces after each rainfall episode. ii There was consistency in multi-temporal Digital Number (DN) values for the surfaces investigated. The typically low P. incana reflectance in the Near Infrared band, identified from the multi-temporal HRI was validated by field and laboratory spectroscopy. The PVI showed clear spectral separability between all the land surfaces in the respective multi-temporal HRI. The consistence of the PVI with the unmixed surface image fractions from the SMA illustrates that using HRI, the effectiveness of the PVI is not impeded by the mixed pixel problem. Results of the laboratory spectroscopy that validated HRI analyses showed that P. incana’s typically low reflectance is a function of its leaf canopy, as higher proportions of leaves gave a higher reflectance. Future research directions could focus on comparisons between P. incana and typical green vegetation internal leaf structures as potential causes of spectral differences. Collection of spectra for P incana and other invader vegetation types, some of which have similar characteristics, with a view to assembling a spectral library for delineating invaded environments using imagery, is another research direction.
  • Full Text:
  • Date Issued: 2009

The kinetics and associated reactions of ruthenium(VIII)

  • Authors: Van Aswegen, Werner
  • Date: 2009
  • Subjects: Ruthenium , Ruthenium compounds , Alcohols
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10392 , http://hdl.handle.net/10948/1130 , http://hdl.handle.net/10948/d1008611 , Ruthenium , Ruthenium compounds , Alcohols
  • Description: This study investigated the reduction reaction of ruthenium tetroxide by various aliphatic alcohols in acidic medium. UV-Vis spectroscopy still plays an essential role in the analysis and study of volatile ruthenium tetroxide and was used in this study to collect kinetic data. This data was analyzed using graphical and computational methods, such as Mauser diagrams and kinetic simulation software. From the results obtained it is proposed that the reaction occurs by the following two-step reaction model: Ru(VIII) k1 Ru(VI) Ru(VI) k2 k-2 Ru(III) Molar extinction coefficients and conditional rate constants were calculated using kinetic simulating software and a hydride transfer mechanism was proposed. The temperature dependence of this reduction reaction was also investigated and thermodynamic parameters calculated. Ruthenium concentrations were determined using a method employing UV-Vis spectroscopy. The method proved to be a reliable, sensitive and simple technique.
  • Full Text:
  • Date Issued: 2009

The reactions of osmium (VIII) in hydroxide medium

  • Authors: Geswindt, Theodore Earl
  • Date: 2009
  • Subjects: Osmium , Spectrophotometry
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10395 , http://hdl.handle.net/10948/960 , Osmium , Spectrophotometry
  • Description: Spectrophotometric techniques were used to elucidate the discrepancies surrounding the reduction of osmium tetroxide by several primary alcohols in a hydroxide matrix. In contrast to the documented literature, this reaction was observed to occur in two consecutive reaction steps. Geometrical and computational analysis of kinetic data revealed that the reaction proceeds by the following reaction model: Os(VIII) + RCH2OH Os(VI) + RCHO Os(VIII) + Os(VI) Os2(VII) k1 k+2 k-2 The conditional rate constants and molar extinction coefficients were calculated using custom written software. A hydride transfer mechanism, coupled with the synchronous removal of the hydroxyl proton of the alcohol, was postulated. The complexation between osmium(VIII) and osmium(VI) was investigated. Mole ratio titrations and mole fraction plots show that at pH 14.3 a 1:1 complexation occurs between osmium(VIII) and osmium(VI). The equilibrium constants and molar extinction coefficients calculated by these methods were found to be consistent with the parameters obtained from the reduction of osmium tetroxide by primary alcohols at pH 14.3. The formation of a mixed oxidation state dimeric osmium complex (denoted Os2(VII)) has been proposed. Key words: Spectrophotometric techniques, osmium tetroxide, osmium(VIII), primary alcohols, osmium(VI).
  • Full Text:
  • Date Issued: 2009
  • Disclaimer
  • Privacy
  • Copyright
  • Contact