Browsing by Author "Louw, Jeanne"
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- ItemHIV transmission from mother to child : HAART compared with dual therapy(Health and Medical Publishing Group (HMPG), 2009-10) Theron, Gerhard; Nellensteijn, Myrthe; Theron, Anneke; Louw, JeanneThere are increasing calls for the use of highly active antiretroviral therapy (HAART) for the prevention of perinatal mother-to-child transmission (PMTCT) of HIV.1 This approach does not recognise the weaknesses in health systems to implement complex treatment protocols. In addition, the safety of HAART during pregnancy is uncertain and the consequences of stopping HAART if not required outside pregnancy are unknown. If the same PMTCT of HIV could be attained with a simple regimen with proven safety and known adverse drug effects, this would be a better option in most under-resourced countries.2 The superiority of HAART compared with dual therapy according to World Health Organization (WHO) recommendations for immune-competent women to reduce PMTCT has not been proven.3 We aimed to determine whether there is a difference in perinatal HIV transmission on HAART therapy compared with the national dual-therapy regimen. In addition, the relation between CD4 counts and transmission in the dual-therapy group was investigated.
- Itemn Literatuuroorsig : die rol van irrasionele kognisies en lokus van kontrole by godsdiens(Stellenbosch : Stellenbosch University, 1990) Louw, Jeanne; Stellenbosch University. Faculty of . Dept. of .
- ItemSupercritical water gasification of wood-related products: a thermodynamic and experimental study(Stellenbosch : Stellenbosch University, 2016-12) Louw, Jeanne; Burger, A. J.; Schwarz, C. E.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Supercritical water gasification (SCWG) is a method through which energy can be harvested, allowing high-‐energy gases such as hydrogen and methane to be generated from wet organic materials without prior energy-‐intensive drying. This thesis provides new insight into and an improved understanding of both the thermodynamic equilibrium and practical kinetic behaviour during SCWG of three wood-‐derived products, namely wood chips, primary paper sludge and wood-‐based pyrolysis char. A method, based on thermodynamic equilibrium calculations and the feedstock composition (molar H/C and O/C ratio) was developed to aid in the selection of suitable feed material and operating conditions for SCWG1. It was shown that, thermodynamically, feed material containing less oxygen, such as pyrolysis char, might be a promising feed material to achieve high H2 and CH4 yields as well as a gas product with a high calorific value. Experimental and theoretical thermodynamic equilibrium results are presented for SCWG of primary paper waste sludge (PWS)2, E.grandis wood chips and various related pyrolysis chars3. The effect of various parameters that may influence the kinetic behaviour were assessed, including catalyst type, catalyst loading, reaction time and feedstock composition (specifically O/C ratio and volatile matter content). A gas product relatively close to the calculated thermodynamic composition was produced during SCWG of PWS and E.grandis using a high loading of heterogeneous catalyst (0.5 – 1 g/gfeed,dry Ni/Al2O3-‐SiO2) and longer reaction times (60 – 120 min). Furthermore, significantly higher conversion of carbon to the gas phase was achieved with Ni/Al2O3-‐SiO2 than with a homogeneous catalyst (K2CO3). While feed material with lower O/C ratios typically resulted in higher thermodynamic equilibrium CH4 yields and gasification efficiencies, these feed material resulted in the lowest experimental CH4 yields and gasification efficiencies. Furthermore, a linear relationship between the carbon efficiency (CE) and both the volatile matter content and O/C ratio of the feed material was found to hold true in both catalytic and non-‐catalytic experiments. The results suggest that, although thermodynamic calculations disregard the volatile matter content of the feed material, very useful predictive information can still be obtained from such calculations. It should therefore not be disregarded when considering a specific material as possible feedstock for SCWG. To summarise, this dissertation provides more insight into both the thermodynamic equilibrium and possible kinetic effects associated with SCWG for various wood-‐related products. The major contributions are encapsulated in three peer reviewed journal publications.