1,720,963 research outputs found
Fate and behaviour of WO3 nanoparticles in wastewater treatment plant
Get PDFM.Sc. (Chemistry)Abstract: With the widespread use of nanoparticles, a concern has been raised to understand their behaviour in the actual environment. Monoclinic tungsten trioxide nanoparticles (m-WO3) have gained considerate interest as a photocatalyst particularly in the photodegradation of organic pollutants and oxidation of water resulting in the evolution of oxygen. As a result, the increased application will inherently lead to large amounts of m-WO3 being found in wastewater effluent. Wastewater effluent is a confluence of several chemicals; molecules such as natural organic matter, surfactants and amino acids to name a few. Natural organic matter present in wastewater include substances like humic acid and fulvic acid. Thus this study aimed to understand the fate and behaviour of m-WO3 nanoparticles in a wastewater treatment system. This research involved investigation of solution chemistry and its effects on the stability and aggregation kinetics of m-WO3. Thus, accurate characterization of the physicochemical properties was paramount as they could be extrapolated to their toxicological effects. The physicochemical properties measured included size distribution, aggregation/agglomeration, surface area, crystal structure, and surface charge..
Aluminium triflate-mediated reactions of glycals: towards chiral multicyclic products
Get PDFPh.D. (Chemistry)The bridged chiral benzopyrans were strategically ring opened via acetolysis to yield either galactose based chromenes or chromans, depending on the reaction conditions. A proposal relating to the mechanism of this selective ring opening acetolysis is discussed. The benzopyrans (chromenes, chromans and bridged chiral benzopyrans) were de-acetylated via triethyl amine catalysed transesterification. Interestingly, the chromenes did not yield the anticipated hydrolysis product (triol) but a new class of bridged chiral benzopyrans which were a result of intramolecular oxa-Michael addition. A chromene that formed during the selective ring opening of the bridged chiral benzopyrans was employed to develop a method for the synthesis of a carbohydrate derived oxepane. The oxepane synthesis was achieved, albeit in the face of numerous challenges from side reactions. The difficulties encountered in the synthesis are discussed..
Aluminium triflate mediated reactions of cyclic enol ethers
Get PDFM.Sc.The objective of the project described in this dissertation was to develop environmentally benign organic transformations using aluminium triflate as a Lewis acid catalyst. The activity of aluminium triflate had already been investigated in our labs in other reactions. The present project was directed towards protection and deprotection of hydroxyl functions and glycosidation of differently protected glycal substrates. A range of alcohols and phenols was successfully protected to their corresponding tetrahydropyranyl (THP) and tetrahydrofuranyl (THF) ethers using 3,4-Dihydro-2H-pyran (DHP) and 2,3-Dihydrofuran (DHF) respectively. Catalytic amounts of Al(OTf)3 were employed to drive the reaction through in the presence of dichloromethane (DCM) as a solvent. This process allowed the preparation of a structural variety of these protected ethers, including those of a protected D-ribose derivative. The THP and THF ethers so generated were hydrolysed back to their corresponding alcohols using Al(OTf)3 in the presence of methanol. In all cases, the free alcohols were isolated in excellent yields. Importantly, other acid-sensitive groups (e.g. the ring acetal and acetonide on the ribose derivative) were retained on the more complex systems. Aluminium triflate was also employed to catalyse the O-glycosidation of 3,4,6-tri-O-acetyl-Dglucal, 3,4,6-tri-O-acetyl-D-galactal and 3,4,6-tri-O-benzyl-D-glucal. Different alkyl and aromatic nucleophiles were used as glycosyl acceptors in these reactions. This aspect of the study allowed a focus on O-glycosidation leading to the synthesis of 2,3-unsaturated glycosides via Ferrier rearrangement and 2-deoxy glycosides by direct addition of alcohol nucleophiles. Interestingly, the work discovered a temperature-switched selective Ferrier rearrangement or direct addition with alcohols in certain instances. This important innovation led to the idea that this protocol may be employed in the synthesis of unsymmetrical glycal based bolaforms. Progress in this direction shall also be detailed
Poverty in post -apartheid South Africa: Measurement, trends and the demography of the poor
No full textThe dissertation comprises two major parts. The first reviews major theories of poverty and measures its extent in South Africa using four datasets (the 1996 and the 2001 censuses, the 1999 OHS and the 2004 GHS). The second part applies demographic, statistical and spatial techniques to study differentials in under-5-mortality by poverty status of households and selected socioeconomic variables using only the censuses. The dissertation conceptualizes poverty as a multidimensional phenomenon that can be proxied by the socioeconomic variables that are commonly collected in African datasets. Following on Filmer and Pritchett (1998, 2001) an index of living standards is created by combining different dimensions of wellbeing, bringing together the concepts of absolute, relative and capabilities deprivation. The resulting index—the assets and capabilities poverty—demonstrates that poverty can be measured in the absence of income or expenditure data. The index is a complement, not a replacement of income measures of poverty. In addition to profiling the poor, the study shows its trend over time. Results show huge but declining inequality in living standards. Relative poverty declined from 50% in 1996 to 40% in 2004. The inequities manifest in differentials by race, urban/rural residence, province and between magisterial districts. Gauteng and Western Cape provinces are the wealthiest whilst the Eastern Cape, Limpopo and KwaZulu-Natal provinces are the poorest. This pattern is statistically significant. The district-level analysis underscores the magnitude of disparities in living conditions. Some districts have more than 95% of their households lacking even the most basic necessities of life. Data quality problems in the 2001 census prevent inferences about trends in under-5-mortality. Further analysis, however, shows that the data could still be used to show differentials in childhood mortality. Despite being one of the poorest provinces, Limpopo was found to have relatively low child mortality. Poor children experience more than twice the likelihood of dying before age five as compared to non-poor children. Lastly, a spatial analysis of the data showed that child mortality is not randomly distributed. Thus, we can learn more about demographic phenomena if we incorporate spatial dimensions of the data into our analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Spatial Differentials in Childhood Mortality in South Africa: Evidence from the 2001 Census
Get PDFThis study examines spatial differentials in childhood mortality in
South Africa using data from the 2001 population census. Of the complex
routes of geographical area hierarchy maintained by South Africa, one
route links provinces to Magisterial Districts (MDs). There are in all
354 MDs and nine provinces. Our analyses are conducted mainly at the
level of MDs. The results show that provincial level indicators mask
huge disparities in child health experienced by certain segments of the
population. Children born in MDs such as Tabankulu, Lusikisiki, Bizana,
Flagstaff, Libode and in the Eastern Cape Province in general are the
most threatened early in life. Under prevailing mortality conditions,
more than 10% of the children born in these districts are unlikely to
celebrate their fifth anniversary. Most of the high mortality MDs form
clusters that sometimes cut across provincial boundary. As it is to be
expected, most of these high risk districts are among the poorest in
the country as measured by average monthly expenditure. However, the
worse-off districts, health-wise, are not necessarily the poorest and
similarly, the best child health achievers are not necessarily the most
economically well-off. On the basis of these findings, implementing
policies targeting such high risk districts would seem a more rational
way to help close the within-country disparities in child mortality and
thereby speed up progress toward the MDGs target
Spatial Differentials in Childhood Mortality in South Africa: Evidence from the 2001 Census
No full textThis study examines spatial differentials in childhood mortality in
South Africa using data from the 2001 population census. Of the complex
routes of geographical area hierarchy maintained by South Africa, one
route links provinces to Magisterial Districts (MDs). There are in all
354 MDs and nine provinces. Our analyses are conducted mainly at the
level of MDs. The results show that provincial level indicators mask
huge disparities in child health experienced by certain segments of the
population. Children born in MDs such as Tabankulu, Lusikisiki, Bizana,
Flagstaff, Libode and in the Eastern Cape Province in general are the
most threatened early in life. Under prevailing mortality conditions,
more than 10% of the children born in these districts are unlikely to
celebrate their fifth anniversary. Most of the high mortality MDs form
clusters that sometimes cut across provincial boundary. As it is to be
expected, most of these high risk districts are among the poorest in
the country as measured by average monthly expenditure. However, the
worse-off districts, health-wise, are not necessarily the poorest and
similarly, the best child health achievers are not necessarily the most
economically well-off. On the basis of these findings, implementing
policies targeting such high risk districts would seem a more rational
way to help close the within-country disparities in child mortality and
thereby speed up progress toward the MDGs target
Spatial Differentials in Childhood Mortality in South Africa: Evidence from the 2001 Census
Get PDFThis study examines spatial differentials in childhood mortality in South Africa using data from the 2001 population census. Of the complex routes of geographical area hierarchy maintained by South Africa, one route links provinces to Magisterial Districts (MDs). There are in all 354 MDs and nine provinces. Our analyses are conducted mainly at the level of MDs. The results show that provincial level indicators mask huge disparities in child health experienced by certain segments of the population. Children born in MDs such as Tabankulu, Lusikisiki, Bizana, Flagstaff, Libode and in the Eastern Cape Province in general are the most threatened early in life. Under prevailing mortality conditions, more than 10% of the children born in these districts are unlikely to celebrate their fifth anniversary. Most of the high mortality MDs form clusters that sometimes cut across provincial boundary. As it is to be expected, most of these high risk districts are among the poorest in the country as measured by average monthly expenditure. However, the worse-off districts, health-wise, are not necessarily the poorest and similarly, the best child health achievers are not necessarily the most economically well-off. On the basis of these findings, implementing policies targeting such high risk districts would seem a more rational way to help close the within country disparities in child mortality and thereby speed up progress toward the MDGs targe
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