Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in young children. As the HI virus has been identified in cell-free and cell-associated compartments of breast milk, it is clear that breast milk is one of the ways in which mother-to-child transmission of HIV can take place in addition to in utero and intrapartum transmission. While breastfeeding carries the risk of HIV transmission, not breastfeeding carries significant health risks for infants and young children, such as an increased risk of diarrhoea and pneumonia, morbidity and mortality. When an HIV-positive mother decides to breastfeed her baby, pasteurisation of expressed breast milk (EBM) could be a possible infant-feeding option to limit transmission of the HI virus through breast milk, since this method has shown to effectively inactivate HIV type 1. Three methods of pasteurisation of human milk were investigated in this study: Holder pasteurisation, flash-heating and Pretoria pasteurisation. The systematic review is a helpful method to summarise the best-quality empirical evidence of the benefits and limitations of a specific method, such as heat treatment, and to provide recommendations for future research. Therefore, the aim of this study was to critically synthesise by means of a systematic review the best available existing evidence and to provide a clear overview of the effectiveness of heat treatment of EBM as an in-home procedure to inactivate the HI virus, and in so doing limit mother-to-child transmission of HIV. This study provides the clinical practitioner with accessible information on the effectiveness of heat treatment of EBM as an in-home procedure in terms of (1) safety, inactivation of the HI virus and retaining the protective and nutritional value of the EBM; (2) feasibility as an in-home procedure; and (3) acceptability by the mothers and their communities. This information could be used to improve clinical practitioners‟ knowledge and include it in their health education to contribute to the prevention of mother-to-child transmission. This study is based on the framework of the model for evidence-based clinical decisions of Haynes, Devereaux and Guyatt (2002). The search strategy was conducted in March/April 2009. The initial search resulted in 574 articles. After thorough screening of potentially relevant studies on heat treatment of EBM, the studies that met the inclusion criteria were critically appraised and scored based on their methodological qualities using standardised instruments. After 6 months, the search was updated. The search obtained 1 article. The final sample involved 12 articles. Conclusions were integrated and synthesised as a basis for developing a clear overview of the best available existing evidence. Finally, the findings of the study were synthesised and the research was evaluated, a conclusion was given, limitations were identified and recommendations were formulated for nursing practice, education and research. The bottom-line answer concluded that heat treatment of EBM should be emphasised as a safe alternative for feeding exposed infants (those of an HIV-positive mother, those of uncertain HIV status or during weaning if the mother cannot afford formula or cow‟s milk), but should be supported with appropriate information to the individual mother, her family and the community. Overall it can be concluded that existing evidence of the effectiveness (in terms of safety, feasibility and acceptability) of heat treatment of EBM, particularly Pretoria pasteurisation, used as a simple in-home procedure, is insufficient, and further research is required. / Thesis (M.Cur.)--North-West University, Potchefstroom Campus, 2010

The benefits of breastfeeding are well known. It has been shown that HIV is transmitted through breast milk. The HIV epidemic is threatening exclusive breastfeeding in South Africa. It is important that mothers make the right infant feeding choice. There are three basic infant feeding methods available for HIV infected mothers namely; breastfeeding, replacement feeding or formula feeding and heat treatment of breast milk. There are many risk factors for the transmission of HIV through breast milk. Exclusive breastfeeding may reduce the risk of mother-to-child-transmission, compared with mixed feeding. This can only take place when breastfeeding is done safely and not mixed with other food or drinks. There are many factors that influence a mother's decision to breastfeed, for example personal, social, cultural factors, facilities, environmental factors, knowledge about breastfeeding, mass media and friends. There are also many sources of information about infant feeding methods. The aim of this study was to determine which factors influence the decision on the early infant feeding choice of women who delivered at the Lower Umfolozi District War Memorial Hospital in Empangeni, KwaZulu-Natal. This may help to understand what factors health professionals should focus on in promoting appropriate infant feeding methods. A structured questionnaire was completed by a 100 women and focus group discussions were held with 22 women who delivered at the Lower Umfolozi District War Memorial Hospital. Most of the mothers (72%) did choose breastfeeding, and 58% of these mothers intended to breastfeed for only six months. The majority of the women (97%) received counseling about their infant feeding method, mostly from a health care worker at the clinic. One-third of the women (33%) were influenced by health care professionals on deciding on their infant feeding method and 44% of the participants indicated that no-one influenced them and that they decided themselves. In the focus group discussions the fear of transmission of HIV through breast milk was stated as an important reason why mothers should choose replacement feeding. In conclusion the most important results are that significantly more HIV-infected mothers chose replacement feeding as infant feeding method, and mothers who chose breastfeeding were significantly older than mothers who selected replacement feeding and they made their infant feeding decision significantly earlier than those who chose replacement feeding. According to the focus group discussion results the communities also felt that the HIV-infected mothers should not breastfeed their infants due to the fact that the virus can be transmitted through breast milk. Health professionals should still provide all the necessary information about exclusive breastfeeding for the first six months, even where the prevalence of HIV is high. In most of these areas replacement feeding will not be acceptable, feasible, affordable, sustainable and safe, due to lack of safe water, sanitation and the poor socio-economic status of these people. The dangers of mixed feeding should be emphasized. Most of the women in this study received information from health care workers and family. It is important that family members are included when information is given to women of child-bearing age. Health care workers need appropriate training to ensure that they give the right messages about safe infant feeding to the mothers. / Thesis (M.Sc. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in young children. As the HI virus has been identified in cell-free and cell-associated compartments of breast milk, it is clear that breast milk is one of the ways in which mother-to-child transmission of HIV can take place in addition to in utero and intrapartum transmission. While breastfeeding carries the risk of HIV transmission, not breastfeeding carries significant health risks for infants and young children, such as an increased risk of diarrhoea and pneumonia, morbidity and mortality. When an HIV-positive mother decides to breastfeed her baby, pasteurisation of expressed breast milk (EBM) could be a possible infant-feeding option to limit transmission of the HI virus through breast milk, since this method has shown to effectively inactivate HIV type 1. Three methods of pasteurisation of human milk were investigated in this study: Holder pasteurisation, flash-heating and Pretoria pasteurisation. The systematic review is a helpful method to summarise the best-quality empirical evidence of the benefits and limitations of a specific method, such as heat treatment, and to provide recommendations for future research. Therefore, the aim of this study was to critically synthesise by means of a systematic review the best available existing evidence and to provide a clear overview of the effectiveness of heat treatment of EBM as an in-home procedure to inactivate the HI virus, and in so doing limit mother-to-child transmission of HIV. This study provides the clinical practitioner with accessible information on the effectiveness of heat treatment of EBM as an in-home procedure in terms of (1) safety, inactivation of the HI virus and retaining the protective and nutritional value of the EBM; (2) feasibility as an in-home procedure; and (3) acceptability by the mothers and their communities. This information could be used to improve clinical practitioners‟ knowledge and include it in their health education to contribute to the prevention of mother-to-child transmission. This study is based on the framework of the model for evidence-based clinical decisions of Haynes, Devereaux and Guyatt (2002). The search strategy was conducted in March/April 2009. The initial search resulted in 574 articles. After thorough screening of potentially relevant studies on heat treatment of EBM, the studies that met the inclusion criteria were critically appraised and scored based on their methodological qualities using standardised instruments. After 6 months, the search was updated. The search obtained 1 article. The final sample involved 12 articles. Conclusions were integrated and synthesised as a basis for developing a clear overview of the best available existing evidence. Finally, the findings of the study were synthesised and the research was evaluated, a conclusion was given, limitations were identified and recommendations were formulated for nursing practice, education and research. The bottom-line answer concluded that heat treatment of EBM should be emphasised as a safe alternative for feeding exposed infants (those of an HIV-positive mother, those of uncertain HIV status or during weaning if the mother cannot afford formula or cow‟s milk), but should be supported with appropriate information to the individual mother, her family and the community. Overall it can be concluded that existing evidence of the effectiveness (in terms of safety, feasibility and acceptability) of heat treatment of EBM, particularly Pretoria pasteurisation, used as a simple in-home procedure, is insufficient, and further research is required. / Thesis (M.Cur.)--North-West University, Potchefstroom Campus, 2010

The benefits of breastfeeding are well known. It has been shown that HIV is transmitted through breast milk. The HIV epidemic is threatening exclusive breastfeeding in South Africa. It is important that mothers make the right infant feeding choice. There are three basic infant feeding methods available for HIV infected mothers namely; breastfeeding, replacement feeding or formula feeding and heat treatment of breast milk. There are many risk factors for the transmission of HIV through breast milk. Exclusive breastfeeding may reduce the risk of mother-to-child-transmission, compared with mixed feeding. This can only take place when breastfeeding is done safely and not mixed with other food or drinks. There are many factors that influence a mother's decision to breastfeed, for example personal, social, cultural factors, facilities, environmental factors, knowledge about breastfeeding, mass media and friends. There are also many sources of information about infant feeding methods. The aim of this study was to determine which factors influence the decision on the early infant feeding choice of women who delivered at the Lower Umfolozi District War Memorial Hospital in Empangeni, KwaZulu-Natal. This may help to understand what factors health professionals should focus on in promoting appropriate infant feeding methods. A structured questionnaire was completed by a 100 women and focus group discussions were held with 22 women who delivered at the Lower Umfolozi District War Memorial Hospital. Most of the mothers (72%) did choose breastfeeding, and 58% of these mothers intended to breastfeed for only six months. The majority of the women (97%) received counseling about their infant feeding method, mostly from a health care worker at the clinic. One-third of the women (33%) were influenced by health care professionals on deciding on their infant feeding method and 44% of the participants indicated that no-one influenced them and that they decided themselves. In the focus group discussions the fear of transmission of HIV through breast milk was stated as an important reason why mothers should choose replacement feeding. In conclusion the most important results are that significantly more HIV-infected mothers chose replacement feeding as infant feeding method, and mothers who chose breastfeeding were significantly older than mothers who selected replacement feeding and they made their infant feeding decision significantly earlier than those who chose replacement feeding. According to the focus group discussion results the communities also felt that the HIV-infected mothers should not breastfeed their infants due to the fact that the virus can be transmitted through breast milk. Health professionals should still provide all the necessary information about exclusive breastfeeding for the first six months, even where the prevalence of HIV is high. In most of these areas replacement feeding will not be acceptable, feasible, affordable, sustainable and safe, due to lack of safe water, sanitation and the poor socio-economic status of these people. The dangers of mixed feeding should be emphasized. Most of the women in this study received information from health care workers and family. It is important that family members are included when information is given to women of child-bearing age. Health care workers need appropriate training to ensure that they give the right messages about safe infant feeding to the mothers. / Thesis (M.Sc. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

Aluminum alloys are a suitable substitution for heavy ferrous alloys in automobile structures. The purpose of this study was to investigate the flow stress behavior of as-cast and homogenized A535 aluminum alloy under various deformation conditions. A hot compression test of A535 alloy was performed in the temperature range of 473-673 K (200-400˚C) and strain rate range of 0.005-5 s-1 using a GleebleTM machine. Experimental data were fitted to Arrhenius-type constitutive equations to find material constants such as n, nʹ, β, A and activation energy (Q). Flow stress curves for as-cast and homogenized A535 alloy were predicted using an extended form of the Arrhenius constitutive equations. The dynamic shock load response of the alloy was studied using a split Hopkinson pressure bar (SHPB) test apparatus. The strain rate used ranged from 1400 s-1 to 2400 s-1 for as-cast and homogenized A535 alloy. The microstructures of the deformed specimens under different deformation conditions were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). Obtained true stress-true strain curves at elevated temperatures showed that the flow stress of the alloy increased by increasing the strain rate and decreasing the temperature for both as-cast and homogenized specimens. The homogenization heat treatment showed no effect on the mechanical behavior of the A535 alloy under hot deformation conditions. Hot deformation activation energy for both as-cast and homogenized A535 alloy was calculated to be 193 kJ/mol, which is higher than that for self-diffusion of pure aluminum (142 kJ/mol). The calculated stress values were compared with the measured ones and they showed good agreement by the correlation coefficient (R) of 0.997 and the average absolute relative error (AARE) of 6.5 %. The peak stress and the critical strain at the onset of thermal softening increased with strain rate for both the as-cast and homogenized A535 alloy. Homogenization heat treatment affected the high strain-rate deformation of the alloy, by increasing the peak stress and the thermal softening onset strain compared to those obtained for as-cast specimens. Deformed shear bands (DSBs) were formed in both the as-cast and homogenized A535 alloy in the strain rate range of 2000-2400 s-1.

In this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot &ndash / wire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that&nbsp / hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties.<br /> <br /> We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced. <br /> <br /> This work explores the optical, structural and electronic properties of this promising material whose study &ndash / samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape.

Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects. Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation. The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed. Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Licentiatavhandling (sammanfattning) Luleå : Luleå tekniska univ., 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.