On the optical and electrical design of low concentrator photovoltaic modules
- Authors: Benecke, Mario Andrew
- Date: 2012
- Subjects: Photovoltaic cells -- Design and construction , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10543 , http://hdl.handle.net/10948/d1013102
- Description: The increasing interest in non-fossil fuel based electricity generation has caused a prominent boost for the renewable energy sector, especially the field of Photovoltaics (PV) with one of the main reasons being the decrease in cost of PV electricity generation. However, over the last few years a saturation in the efficiency of solar cells have been reached leading into a renewed search for other means to further reduce the cost of electricity generation from photovoltaic sources. One of the technologies that has attracted a lot of attention is low concentration photovoltaics (LCPV). LCPV investigates an alternative strategy to replace costly semiconductor material with relatively cheap optical materials by developing a Low Concentration Photovoltaic (LCPV) module. A LCPV module is divided into three subsystems, namely, the optical, electrical and thermal subsystem. This study focussed on the design, construction and characterisation of an optical subsystem accompanied by a thorough investigation into the design of an electrical subsystem. A facetted parabolic concentrator using a vertical receiver was modelled and a first prototype was constructed having a geometric concentration factor of 6.00 X. Upon electrical characterisation of this first vertical receiver LCPV prototype a concentration of only 4.53 X (receiver 1) and 4.71 X (receiver 2) was obtained. The first vertical receiver LCPV prototype did not reach the expected concentration factor due to optical losses and misalignment of optical elements. The illumination profile obtained from the reflector element was investigated and an undesirable non-uniform illumination profile was discovered. A second vertical receiver LCPV prototype was constructed in an attempt to improve on the first prototype, this second vertical receiver prototype had a geometrical concentration factor of 5.80 X. The results indicated a much improved illumination profile, yet still containing a number of non-uniformities. The second vertical receiver LCPV module yielded an operational concentration factor of 5.34 X. From the preliminary results obtained it was discovered that under concentrated illumination there was a limitation on the maximum power that could be obtained from the receiver. Upon further investigation it was discovered that this limitation was due to the higher current levels under concentrated illumination accompanied by a high series resistance of the receiver. This lead to the construction of new PV receivers, where this limitation could be minimised. 3 cell, 4 cell, 6 cell and 8 cell string configurations were constructed and used for the electrical characterisation of the prototypes. Due to non-uniformity of the illumination profile obtained from the second LCPV prototype a third vertical receiver LCPV prototype was constructed. This vertical receiver design illustrated more uniformity in the obtained illumination distribution and had a geometrical concentration factor of 4.61 X, although under operation only 4.26 X could be obtained. It is important to note that the geometric concentration factor does not account for reflective losses of the reflective material. One of the main reasons for the difficulty in obtaining a uniform illumination profile with the vertical receiver design is that the facetted reflector element is far away from the PV receiver. This enhances the effect of the slightest misalignment of any of the optical elements. This large distance also increases the effect of lensing from each facet. These factors lead to the consideration of a second design, which would counteract these factors. A horizontal receiver LCPV module design implementing a facetted parabolic reflector was considered to counteract these effects. From a mathematical model a horizontal receiver LCPV prototype was constructed having a geometrical concentration factor 5.3 X. The optical characterisation of the illumination profile showed a much improved illumination profile, which was much more uniform than the previous illumination profiles obtained from the other LCPV prototypes. The uniformity of the illumination profile could be seen in results obtained from the electrical characterisation where the concentrator reached operational concentration factor of 5.01 X. The reliability of the third vertical receiver LCPV prototype and the horizontal receiver LCPV prototype as well as the receivers were investigated by placing each receiver under stressed operational conditions for 60 sun hours. I-V characteristics were obtained after every five sun hours to investigate any signs of degradation. After 60 sun hours none of the receiver displayed any signs of degradation or reduction in electrical performance.
- Full Text:
- Date Issued: 2012
- Authors: Benecke, Mario Andrew
- Date: 2012
- Subjects: Photovoltaic cells -- Design and construction , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10543 , http://hdl.handle.net/10948/d1013102
- Description: The increasing interest in non-fossil fuel based electricity generation has caused a prominent boost for the renewable energy sector, especially the field of Photovoltaics (PV) with one of the main reasons being the decrease in cost of PV electricity generation. However, over the last few years a saturation in the efficiency of solar cells have been reached leading into a renewed search for other means to further reduce the cost of electricity generation from photovoltaic sources. One of the technologies that has attracted a lot of attention is low concentration photovoltaics (LCPV). LCPV investigates an alternative strategy to replace costly semiconductor material with relatively cheap optical materials by developing a Low Concentration Photovoltaic (LCPV) module. A LCPV module is divided into three subsystems, namely, the optical, electrical and thermal subsystem. This study focussed on the design, construction and characterisation of an optical subsystem accompanied by a thorough investigation into the design of an electrical subsystem. A facetted parabolic concentrator using a vertical receiver was modelled and a first prototype was constructed having a geometric concentration factor of 6.00 X. Upon electrical characterisation of this first vertical receiver LCPV prototype a concentration of only 4.53 X (receiver 1) and 4.71 X (receiver 2) was obtained. The first vertical receiver LCPV prototype did not reach the expected concentration factor due to optical losses and misalignment of optical elements. The illumination profile obtained from the reflector element was investigated and an undesirable non-uniform illumination profile was discovered. A second vertical receiver LCPV prototype was constructed in an attempt to improve on the first prototype, this second vertical receiver prototype had a geometrical concentration factor of 5.80 X. The results indicated a much improved illumination profile, yet still containing a number of non-uniformities. The second vertical receiver LCPV module yielded an operational concentration factor of 5.34 X. From the preliminary results obtained it was discovered that under concentrated illumination there was a limitation on the maximum power that could be obtained from the receiver. Upon further investigation it was discovered that this limitation was due to the higher current levels under concentrated illumination accompanied by a high series resistance of the receiver. This lead to the construction of new PV receivers, where this limitation could be minimised. 3 cell, 4 cell, 6 cell and 8 cell string configurations were constructed and used for the electrical characterisation of the prototypes. Due to non-uniformity of the illumination profile obtained from the second LCPV prototype a third vertical receiver LCPV prototype was constructed. This vertical receiver design illustrated more uniformity in the obtained illumination distribution and had a geometrical concentration factor of 4.61 X, although under operation only 4.26 X could be obtained. It is important to note that the geometric concentration factor does not account for reflective losses of the reflective material. One of the main reasons for the difficulty in obtaining a uniform illumination profile with the vertical receiver design is that the facetted reflector element is far away from the PV receiver. This enhances the effect of the slightest misalignment of any of the optical elements. This large distance also increases the effect of lensing from each facet. These factors lead to the consideration of a second design, which would counteract these factors. A horizontal receiver LCPV module design implementing a facetted parabolic reflector was considered to counteract these effects. From a mathematical model a horizontal receiver LCPV prototype was constructed having a geometrical concentration factor 5.3 X. The optical characterisation of the illumination profile showed a much improved illumination profile, which was much more uniform than the previous illumination profiles obtained from the other LCPV prototypes. The uniformity of the illumination profile could be seen in results obtained from the electrical characterisation where the concentrator reached operational concentration factor of 5.01 X. The reliability of the third vertical receiver LCPV prototype and the horizontal receiver LCPV prototype as well as the receivers were investigated by placing each receiver under stressed operational conditions for 60 sun hours. I-V characteristics were obtained after every five sun hours to investigate any signs of degradation. After 60 sun hours none of the receiver displayed any signs of degradation or reduction in electrical performance.
- Full Text:
- Date Issued: 2012
AC3P: an architecture using cloud computing for the provision of mathematical powerpoint content to feature phones
- Authors: Joubert, Jean-Pierre
- Date: 2012
- Subjects: Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10474 , http://hdl.handle.net/10948/d1011088 , Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Description: The Govan Mbeki Mathematics Development Unit (GMMDU) provides additional mathematics content to learners via mathematics workshops and DVDs. Mathematics is presented in PPT format. The prominence of feature phone usage has been confirmed amongst learners in socio-economic disadvantaged schools, specifically those learners participating in the GMMDU mathematics workshops. Feature phones typically contain limited device resources such as memory, battery power, and network resources. Distributed computing provides the potential to facilitate a new class of mobile applications with the provision of off-device resources. The objective of this research was the design of an architecture using Cloud Computing for the provision of mathematics in the form of PPT slides to feature phones. The capabilities of typical feature phones were reviewed as well as various distributed computing architectures that demonstrate potential benefit to the mobile environment. An Architecture using Cloud Computing for Content Provision (AC3P) was subsequently designed and applied as a proof of concept to facilitate the provision of mathematics in the form of PPT slides to feature phones. The application of AC3P was evaluated for efficiency and effectiveness. It was demonstrated that the application of AC3P provided efficient and effective provision of PPT to feature phones. The successful application of AC3P provided evidence that Cloud Computing may be used to facilitate the provision of mathematics content to feature phones. It is evident that AC3P may be applied in domains other than the provision of mathematics.
- Full Text:
- Date Issued: 2012
- Authors: Joubert, Jean-Pierre
- Date: 2012
- Subjects: Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10474 , http://hdl.handle.net/10948/d1011088 , Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Description: The Govan Mbeki Mathematics Development Unit (GMMDU) provides additional mathematics content to learners via mathematics workshops and DVDs. Mathematics is presented in PPT format. The prominence of feature phone usage has been confirmed amongst learners in socio-economic disadvantaged schools, specifically those learners participating in the GMMDU mathematics workshops. Feature phones typically contain limited device resources such as memory, battery power, and network resources. Distributed computing provides the potential to facilitate a new class of mobile applications with the provision of off-device resources. The objective of this research was the design of an architecture using Cloud Computing for the provision of mathematics in the form of PPT slides to feature phones. The capabilities of typical feature phones were reviewed as well as various distributed computing architectures that demonstrate potential benefit to the mobile environment. An Architecture using Cloud Computing for Content Provision (AC3P) was subsequently designed and applied as a proof of concept to facilitate the provision of mathematics in the form of PPT slides to feature phones. The application of AC3P was evaluated for efficiency and effectiveness. It was demonstrated that the application of AC3P provided efficient and effective provision of PPT to feature phones. The successful application of AC3P provided evidence that Cloud Computing may be used to facilitate the provision of mathematics content to feature phones. It is evident that AC3P may be applied in domains other than the provision of mathematics.
- Full Text:
- Date Issued: 2012
A spatial and temporal analysis of elephant induced thicket degradation in Addo Elephant National Park
- Authors: Smith, Janis
- Date: 2012
- Subjects: Soil degradation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10661 , http://hdl.handle.net/10948/d1012903
- Description: Thicket degradation within the Addo Elephant National Park (AENP), Eastern Cape, South Africa is a key issue of concern. The increasing elephant densities have over time threatened thicket vegetation, which is endemic to this area. The “elephant problem” within the Park has raised many concerns as to the vulnerability of thicket to elephant impacts. Remote sensing provides an environment in which temporal changes in thicket vegetation condition can be assessed. The main aim of this study was to assess temporal and spatial trends in thicket degradation within the AENP, using multi-temporal satellite imagery. Elephant induced thicket degradation was assessed using multi-temporal satellite imagery from between 1973 and 2010. Changes in thicket condition in relation to the AENP expansion were analysed using the Normalized Difference Vegetation Index (NDVI), post-classification and landscape metrics. The ‘per-pixel’ based classification approach was carried out and change detection of land cover classes was analysed by post-classification. Landscape spatial metrics were used in order to gain an understanding of vegetation fragmentation trends. Temporal changes in vegetation gradients in relation to water points and thicket condition within the botanical reserves were also assessed. Thicket condition was noted to deteriorate as the AENP expanded. An expansion of degraded vegetation away from the water points was identified during the study period. Thicket condition in botanical reserves 1 and 2 fluctuated over time, with a registered increase in intact thicket within botanical reserve 2, with botanical reserve 3 remaining constant. Landscape spatial metric analyses revealed evidence of increased vegetation fragmentation as new areas of the AENP were opened for elephant activity. A progressive decline in intact thicket and increase in degraded thicket were observed. Considering the current elephant densities, thicket degradation within AENP is set to continue, causing a continued threat to the thicket biome.
- Full Text:
- Date Issued: 2012
- Authors: Smith, Janis
- Date: 2012
- Subjects: Soil degradation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10661 , http://hdl.handle.net/10948/d1012903
- Description: Thicket degradation within the Addo Elephant National Park (AENP), Eastern Cape, South Africa is a key issue of concern. The increasing elephant densities have over time threatened thicket vegetation, which is endemic to this area. The “elephant problem” within the Park has raised many concerns as to the vulnerability of thicket to elephant impacts. Remote sensing provides an environment in which temporal changes in thicket vegetation condition can be assessed. The main aim of this study was to assess temporal and spatial trends in thicket degradation within the AENP, using multi-temporal satellite imagery. Elephant induced thicket degradation was assessed using multi-temporal satellite imagery from between 1973 and 2010. Changes in thicket condition in relation to the AENP expansion were analysed using the Normalized Difference Vegetation Index (NDVI), post-classification and landscape metrics. The ‘per-pixel’ based classification approach was carried out and change detection of land cover classes was analysed by post-classification. Landscape spatial metrics were used in order to gain an understanding of vegetation fragmentation trends. Temporal changes in vegetation gradients in relation to water points and thicket condition within the botanical reserves were also assessed. Thicket condition was noted to deteriorate as the AENP expanded. An expansion of degraded vegetation away from the water points was identified during the study period. Thicket condition in botanical reserves 1 and 2 fluctuated over time, with a registered increase in intact thicket within botanical reserve 2, with botanical reserve 3 remaining constant. Landscape spatial metric analyses revealed evidence of increased vegetation fragmentation as new areas of the AENP were opened for elephant activity. A progressive decline in intact thicket and increase in degraded thicket were observed. Considering the current elephant densities, thicket degradation within AENP is set to continue, causing a continued threat to the thicket biome.
- Full Text:
- Date Issued: 2012
The molecular analysis of the interation surface between sCD23 and the B2-integrins, CD11b & CD11c
- Authors: Pereira, Melanie Claire
- Date: 2012
- Subjects: CD23 antigen , Immune response -- Regulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10337 , http://hdl.handle.net/10948/d1014734
- Description: Both CD23 and the β2 integrins (also known as CD11/CD18) have very important immunological functions, especially during the allergic response where the binding of CD23 to β2 integrins contributes to various types of signalling in monocytes which can result in drastic sensitivities experienced by some allergic individuals. CD23, also known as the low affinity receptor for immunoglobulin E or (FcεRII), is a type II transmembrane glycoprotein which is synthesized by haematopoietic cells and has biological activity in both membrane-bound and freely soluble forms. It acts via a number of receptors, including the β2 integrins. β2 integrins are specifically found on leukocytes and they play important roles in cell–cell or cell–matrix adhesion via their ability to bind multiple ligands. These molecules occur as heterodimers consisting of an alpha (α) and beta (β) subunit. The α-subunits of β2 integrins contain an approximately 200-amino-acid inserted domain or I-domain which is implicated in ligand binding function. There are four different types of β2 integrins, namely CD11a, CD11b, CD11c and CD11d, all dimers with the common beta subunit, CD18. CD23 and CD11/18 are natural ligands of each other; however the interaction site for CD23 is unknown. It is postulated that the integrin recognizes a tripeptide motif in a small disulfide-bonded loop at the N-terminus of the lectin head region of CD23, which is focussed around Arg172, Lys173 and Cys174 (RKC). This study thus focused on the interaction between the I-domain of CD11 (b and c) and a recombinant 25kDa construct of sCD23. In order to understand the characteristics of ligand binding between the relevant proteins of interest, alanine substitutions on the RKC motif of CD23 were made via site-directed mutagenesis. Consequently, a recombinant form of the I-domain of CD11 (b and c) as well as a wild type (containing the RKC motif) and mutant form (containing an AAC motif) of sCD23 were expressed and purified. The CD11 recombinant proteins were purified via affinity chromatography and the CD23 recombinant proteins via gel filtration chromatography. In addition, synthetic (CD23 derived) peptides, one containing the RKC sequence and the other the AAC sequence, were designed and custom synthesized. The synthetic peptides as well as the recombinant CD23 proteins were then analyzed for their interaction with the CD11 I-domain via ELISA. Subsequent ELISA analyses showed that the native sCD23 and the RKC peptide were able to bind to the integrin α I-domain whereas the mutant sCD23 and the corresponding synthetic AAC peptide failed to bind. This interaction was also analysed via flow cytometry using differentiated U937 cells, yielding similar results. ELISA analyses for the sCD23-CD11b I-domain interaction showed a Kd of 0.36 ± 0.14 μM whereas the RKC-CD11b I-domain interaction yielded a Kd of 1.75 ± 0.58 μM. Similarly, the sCD23-CD11c I-domain interaction yielded a Kd of 0.39 ± 0.09 μM and 1.53 ± 0.72 μM for the RKC-CD11c I-domain interaction. Peptide inhibitory analysis, analysed via ELISA and flow cytometry, reinforced the fact that the RKC motif on sCD23 is a prerequisite for ligand binding of the CD11b/c I-domain.
- Full Text:
- Date Issued: 2012
- Authors: Pereira, Melanie Claire
- Date: 2012
- Subjects: CD23 antigen , Immune response -- Regulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10337 , http://hdl.handle.net/10948/d1014734
- Description: Both CD23 and the β2 integrins (also known as CD11/CD18) have very important immunological functions, especially during the allergic response where the binding of CD23 to β2 integrins contributes to various types of signalling in monocytes which can result in drastic sensitivities experienced by some allergic individuals. CD23, also known as the low affinity receptor for immunoglobulin E or (FcεRII), is a type II transmembrane glycoprotein which is synthesized by haematopoietic cells and has biological activity in both membrane-bound and freely soluble forms. It acts via a number of receptors, including the β2 integrins. β2 integrins are specifically found on leukocytes and they play important roles in cell–cell or cell–matrix adhesion via their ability to bind multiple ligands. These molecules occur as heterodimers consisting of an alpha (α) and beta (β) subunit. The α-subunits of β2 integrins contain an approximately 200-amino-acid inserted domain or I-domain which is implicated in ligand binding function. There are four different types of β2 integrins, namely CD11a, CD11b, CD11c and CD11d, all dimers with the common beta subunit, CD18. CD23 and CD11/18 are natural ligands of each other; however the interaction site for CD23 is unknown. It is postulated that the integrin recognizes a tripeptide motif in a small disulfide-bonded loop at the N-terminus of the lectin head region of CD23, which is focussed around Arg172, Lys173 and Cys174 (RKC). This study thus focused on the interaction between the I-domain of CD11 (b and c) and a recombinant 25kDa construct of sCD23. In order to understand the characteristics of ligand binding between the relevant proteins of interest, alanine substitutions on the RKC motif of CD23 were made via site-directed mutagenesis. Consequently, a recombinant form of the I-domain of CD11 (b and c) as well as a wild type (containing the RKC motif) and mutant form (containing an AAC motif) of sCD23 were expressed and purified. The CD11 recombinant proteins were purified via affinity chromatography and the CD23 recombinant proteins via gel filtration chromatography. In addition, synthetic (CD23 derived) peptides, one containing the RKC sequence and the other the AAC sequence, were designed and custom synthesized. The synthetic peptides as well as the recombinant CD23 proteins were then analyzed for their interaction with the CD11 I-domain via ELISA. Subsequent ELISA analyses showed that the native sCD23 and the RKC peptide were able to bind to the integrin α I-domain whereas the mutant sCD23 and the corresponding synthetic AAC peptide failed to bind. This interaction was also analysed via flow cytometry using differentiated U937 cells, yielding similar results. ELISA analyses for the sCD23-CD11b I-domain interaction showed a Kd of 0.36 ± 0.14 μM whereas the RKC-CD11b I-domain interaction yielded a Kd of 1.75 ± 0.58 μM. Similarly, the sCD23-CD11c I-domain interaction yielded a Kd of 0.39 ± 0.09 μM and 1.53 ± 0.72 μM for the RKC-CD11c I-domain interaction. Peptide inhibitory analysis, analysed via ELISA and flow cytometry, reinforced the fact that the RKC motif on sCD23 is a prerequisite for ligand binding of the CD11b/c I-domain.
- Full Text:
- Date Issued: 2012
Microstructural and analytical characterization of plasma dissociated zircon
- Authors: Minnaar, Ettiénne Gerald
- Date: 2012
- Subjects: Zircon , Zirconium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10547 , http://hdl.handle.net/10948/d1015972
- Description: This dissertation focuses on the microstructural and analytical characterization of plasma dissociated zircon (PDZ) which was produced by the South African Nuclear Energy Corporation (NECSA). The techniques used in the analysis of the material include scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy and wavelength dispersive X-ray spectrometry (EDS and WDS), infrared spectroscopy, Raman spectroscopy and X-ray diffraction (XRD). The differences in morphology of the zirconia (ZrO2) crystals observed in the PDZ are related to the thermal history of the material. Large zirconia crystals grow in a spherulitic manner and have the monoclinic crystal structure. Some smaller crystals formed via a rapid cooling process appear to retain the tetragonal or cubic crystal structures rather than relaxing to the monoclinic structure, and this may be because such nanocrystals are stabilised by small surface area or constraints from surrounding materials. Impurity distribution analysis of the PDZ showed that majority of the impurities present in zircon segregates to the silica phase during the dissociation process. The infrared and Raman spectroscopy analysis of the PDZ material indicated that the zirconia is present in the monoclinic and tetragonal polymorphs. X-ray diffraction revealed the presence of monoclinic, tetragonal and cubic zirconia phases. Rietveld refinement of the XRD patterns revealed zirconia to be predominantly found in the monoclinic polymorph followed by the tetragonal and cubic polymorphs. A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) cell proved to be a viable method for determining the percentage dissociated zircon in PDZ.
- Full Text:
- Date Issued: 2012
- Authors: Minnaar, Ettiénne Gerald
- Date: 2012
- Subjects: Zircon , Zirconium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10547 , http://hdl.handle.net/10948/d1015972
- Description: This dissertation focuses on the microstructural and analytical characterization of plasma dissociated zircon (PDZ) which was produced by the South African Nuclear Energy Corporation (NECSA). The techniques used in the analysis of the material include scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy and wavelength dispersive X-ray spectrometry (EDS and WDS), infrared spectroscopy, Raman spectroscopy and X-ray diffraction (XRD). The differences in morphology of the zirconia (ZrO2) crystals observed in the PDZ are related to the thermal history of the material. Large zirconia crystals grow in a spherulitic manner and have the monoclinic crystal structure. Some smaller crystals formed via a rapid cooling process appear to retain the tetragonal or cubic crystal structures rather than relaxing to the monoclinic structure, and this may be because such nanocrystals are stabilised by small surface area or constraints from surrounding materials. Impurity distribution analysis of the PDZ showed that majority of the impurities present in zircon segregates to the silica phase during the dissociation process. The infrared and Raman spectroscopy analysis of the PDZ material indicated that the zirconia is present in the monoclinic and tetragonal polymorphs. X-ray diffraction revealed the presence of monoclinic, tetragonal and cubic zirconia phases. Rietveld refinement of the XRD patterns revealed zirconia to be predominantly found in the monoclinic polymorph followed by the tetragonal and cubic polymorphs. A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) cell proved to be a viable method for determining the percentage dissociated zircon in PDZ.
- Full Text:
- Date Issued: 2012
Creation of clay flameless burner for vaporizing an insect repellent containing pmd as an active ingredient
- Authors: Akwi, Faith Mary
- Date: 2012
- Subjects: Insect baits and repellents , Montmorillonite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10383 , http://hdl.handle.net/10948/d1008406 , Insect baits and repellents , Montmorillonite
- Description: Insecticide treated mosquito bed nets, insecticide aerosol sprays, repellent lotions and creams, repellent candles, vaporizable repellent essential oils, mosquito mats and coils are some of the many malaria personal protection tools that are in use. The latter of these measures are the most accessible and affordable options for the rural population in sub-Saharan Africa. It is therefore important to determine how effective these personal protection measures are by determining their ability to efficiently disperse an active ingredient when the protection measure is in use. In this study, a copper II oxide montmorillonite clay burner (CuOMontmorillonite clay burner) was created to vaporize repellent formulations containing various concentrations of p-menthane-3,8-diol (PMD) as the active ingredient with the aim of determining the percentage of the active ingredient that is released into the air and the rate of release. The performance of the CuO-Montmorillonite clay burner was also compared to that of the Lampe Berger fragrance burner (LBFB). In addition to this, the percentage of PMD released from 6 percentage wt PMD candles of diameters 40mm, 69mm and 83mm was determined and compared to that released when the CuO-Montmorillonite clay burner and Lampe Berger Fragrance burner where used to vaporize PMD repellent formulations. It was found that the rate of vaporization of the various PMD repellent formulations vaporized using the Lampe Berger fragrance burner is affected by the mass of PMD present in the repellent formulations. The 6 percentage wt PMD repellent candles released the least percentage of PMD as compared to that released when the CuO-Montmorillonite clay burner and the Lampe Berger fragrance burner were used to vaporize the PMD repellent formulations.
- Full Text:
- Date Issued: 2012
- Authors: Akwi, Faith Mary
- Date: 2012
- Subjects: Insect baits and repellents , Montmorillonite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10383 , http://hdl.handle.net/10948/d1008406 , Insect baits and repellents , Montmorillonite
- Description: Insecticide treated mosquito bed nets, insecticide aerosol sprays, repellent lotions and creams, repellent candles, vaporizable repellent essential oils, mosquito mats and coils are some of the many malaria personal protection tools that are in use. The latter of these measures are the most accessible and affordable options for the rural population in sub-Saharan Africa. It is therefore important to determine how effective these personal protection measures are by determining their ability to efficiently disperse an active ingredient when the protection measure is in use. In this study, a copper II oxide montmorillonite clay burner (CuOMontmorillonite clay burner) was created to vaporize repellent formulations containing various concentrations of p-menthane-3,8-diol (PMD) as the active ingredient with the aim of determining the percentage of the active ingredient that is released into the air and the rate of release. The performance of the CuO-Montmorillonite clay burner was also compared to that of the Lampe Berger fragrance burner (LBFB). In addition to this, the percentage of PMD released from 6 percentage wt PMD candles of diameters 40mm, 69mm and 83mm was determined and compared to that released when the CuO-Montmorillonite clay burner and Lampe Berger Fragrance burner where used to vaporize PMD repellent formulations. It was found that the rate of vaporization of the various PMD repellent formulations vaporized using the Lampe Berger fragrance burner is affected by the mass of PMD present in the repellent formulations. The 6 percentage wt PMD repellent candles released the least percentage of PMD as compared to that released when the CuO-Montmorillonite clay burner and the Lampe Berger fragrance burner were used to vaporize the PMD repellent formulations.
- Full Text:
- Date Issued: 2012
Curcumin analogues as ligands for Re (I) and (V)
- Authors: Schmitt, Bonell
- Date: 2012
- Subjects: Rhenium , Ligands , Chemistry, Inorganic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10443 , http://hdl.handle.net/10948/d1020975
- Description: Coordination properties of 4-bromo-N-(diethylcarbamothioyl)benzamide (Hbeb) and 4-bromo-N-(diphenylcarbamothioyl)benzamide (Hbpb) with oxorhenium(V) and rhenium(I) are reported and discussed. Transition metal complexes of these ligands were studied due to the wide range of applications of thiourea derivatives in biological fields. N-[Di(alkyl/aryl)carbamothioyl]benzamide derivatives readily coordinate to metal ions as O,S-donors and the catalytic property of the complexes can be altered by these ligands, due to steric and electronic properties provided by various substituents. The coordination possibilities of curcumin with rhenium(V) are discussed, as well as the difficulties encountered. Analogues of curcumin have been made, which also contains a seven-spacer unit between the phenyl rings, which would be more reactive and more effective in bonding to rhenium and which have greater or a similar biological activity to curcumin. This was done by assessing the coordination properties of 1,5-bis(salicylidene)thiocarbohydrazide (H4salt) and 2,4-bis(vanilidene)thiocarbohydrazide (H4vant) with oxorhenium(V) and rhenium(I) starting materials. Two rhenium(V) complex salts of the core [ReX(PPh3)2]4+ (X = Br, I), containing a coordinated imido nitrogen, are reported. One is a ‘2+1’ complex, coordinating bi- and monodentately, with the other a similar ‘3+0’ complex containing a tridentate imido-coordinated Schiff base. Selected compounds were tested against oesophageal cancer cell lines in order to evaluate and compare their effectiveness in eliminating or reducing the cancer cells in the test medium during biological testing.
- Full Text:
- Date Issued: 2012
- Authors: Schmitt, Bonell
- Date: 2012
- Subjects: Rhenium , Ligands , Chemistry, Inorganic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10443 , http://hdl.handle.net/10948/d1020975
- Description: Coordination properties of 4-bromo-N-(diethylcarbamothioyl)benzamide (Hbeb) and 4-bromo-N-(diphenylcarbamothioyl)benzamide (Hbpb) with oxorhenium(V) and rhenium(I) are reported and discussed. Transition metal complexes of these ligands were studied due to the wide range of applications of thiourea derivatives in biological fields. N-[Di(alkyl/aryl)carbamothioyl]benzamide derivatives readily coordinate to metal ions as O,S-donors and the catalytic property of the complexes can be altered by these ligands, due to steric and electronic properties provided by various substituents. The coordination possibilities of curcumin with rhenium(V) are discussed, as well as the difficulties encountered. Analogues of curcumin have been made, which also contains a seven-spacer unit between the phenyl rings, which would be more reactive and more effective in bonding to rhenium and which have greater or a similar biological activity to curcumin. This was done by assessing the coordination properties of 1,5-bis(salicylidene)thiocarbohydrazide (H4salt) and 2,4-bis(vanilidene)thiocarbohydrazide (H4vant) with oxorhenium(V) and rhenium(I) starting materials. Two rhenium(V) complex salts of the core [ReX(PPh3)2]4+ (X = Br, I), containing a coordinated imido nitrogen, are reported. One is a ‘2+1’ complex, coordinating bi- and monodentately, with the other a similar ‘3+0’ complex containing a tridentate imido-coordinated Schiff base. Selected compounds were tested against oesophageal cancer cell lines in order to evaluate and compare their effectiveness in eliminating or reducing the cancer cells in the test medium during biological testing.
- Full Text:
- Date Issued: 2012
Using an intelligent self-service solution to support telecommunication service provisioning
- Authors: Barlow, Sherwin Riaan
- Date: 2012
- Subjects: Telecommunication systems -- Management , Electronic commerce -- Computer programs , Web applications
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10484 , http://hdl.handle.net/10948/d1013417
- Description: The increasing competition between telecommunication service providers (TSPs) and the large amounts of human resource costs incurred to provision telecommunication services to small, medium and micro enterprises (SMMEs), highlight the need for effective self-service provisioning methods to reduce costs. Existing service provisioning methods do not effectively support SMMEs in the service provisioning process. The current methods used are manual and Web-based. The manual service provisioning method is labour and time-intensive. TSPs are being forced to cut human resource costs as the profit margins for provisioning services are narrow due to competition. The current web-based systems do not allow SMMEs to effectively purchase services as they provide long textual lists to consult and limited information about services. The objective of this research was to develop an intelligent web-based self-service system to support SMMEs in telecommunication service provisioning, using a Design Science Research methodology. A constraint-based, knowledge-based recommender system was selected as the most appropriate intelligent system to support telecommunication service provisioning. A prototype called SelPro was developed as a solution to address the shortcomings of the current ineffective service provisioning methods available for SMMEs. SelPro incorporates an interactive wizard-style user interface with dynamic recommendations to support novice users as well as an expert interface which provides less user support. An expert review and a user study were conducted to determine if SelPro was usable, useful and effective. SelPro was perceived as being usable for SMMEs wishing to purchase telecommunication services. Expert participants were satisfied with the usability of SelPro and perceived it as being useful, easy to use and easy to learn. SelPro was considered effective because of the high task success ratings provided by the participants using the two interfaces. The research determined that intelligent web-based self-service provisioning can be used to effectively support SMMEs in telecommunication service provisioning. General design recommendations for similar systems were proposed and future work will involve using intelligent systems to support large enterprises in telecommunication service provisioning.
- Full Text:
- Date Issued: 2012
- Authors: Barlow, Sherwin Riaan
- Date: 2012
- Subjects: Telecommunication systems -- Management , Electronic commerce -- Computer programs , Web applications
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10484 , http://hdl.handle.net/10948/d1013417
- Description: The increasing competition between telecommunication service providers (TSPs) and the large amounts of human resource costs incurred to provision telecommunication services to small, medium and micro enterprises (SMMEs), highlight the need for effective self-service provisioning methods to reduce costs. Existing service provisioning methods do not effectively support SMMEs in the service provisioning process. The current methods used are manual and Web-based. The manual service provisioning method is labour and time-intensive. TSPs are being forced to cut human resource costs as the profit margins for provisioning services are narrow due to competition. The current web-based systems do not allow SMMEs to effectively purchase services as they provide long textual lists to consult and limited information about services. The objective of this research was to develop an intelligent web-based self-service system to support SMMEs in telecommunication service provisioning, using a Design Science Research methodology. A constraint-based, knowledge-based recommender system was selected as the most appropriate intelligent system to support telecommunication service provisioning. A prototype called SelPro was developed as a solution to address the shortcomings of the current ineffective service provisioning methods available for SMMEs. SelPro incorporates an interactive wizard-style user interface with dynamic recommendations to support novice users as well as an expert interface which provides less user support. An expert review and a user study were conducted to determine if SelPro was usable, useful and effective. SelPro was perceived as being usable for SMMEs wishing to purchase telecommunication services. Expert participants were satisfied with the usability of SelPro and perceived it as being useful, easy to use and easy to learn. SelPro was considered effective because of the high task success ratings provided by the participants using the two interfaces. The research determined that intelligent web-based self-service provisioning can be used to effectively support SMMEs in telecommunication service provisioning. General design recommendations for similar systems were proposed and future work will involve using intelligent systems to support large enterprises in telecommunication service provisioning.
- Full Text:
- Date Issued: 2012
Population dynamics of the Zuurberg Cycad and the predicted impact of climate change
- Authors: Singh, Karishma
- Date: 2012
- Subjects: Cycads -- South Africa -- Eastern Cape , Encephalartos -- South Africa -- Eastern Cape , Climate change -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10633 , http://hdl.handle.net/10948/d1012857
- Description: Cycads first appeared about 300 million years ago and historical data indicates that they survived fluctuations of global temperature and carbon dioxide concentrations and reached peak abundance during periods where temperature and carbon dioxide concentrations were much higher than the present conditions as well as the predicted increased levels. With Africa being one of the most vulnerable regions to climate change and in the absence of an evaluation of predicted impacts of climate change on cycads, this study aims to contribute to our understanding of responses of Encephalartos longifolius to increased temperature. Encephalartos longifolius (Jacq.) Lehm is an Eastern Cape endemic and like most cycads has been around for millions of years with very little change to its basic structure. Photosynthetic rates showed E.longifolius seedlings have C3 photosynthesis and even under stress they do not switch over to CAM photosynthesis. The photosynthetic rates of seedlings showed a typical C3 -plant type response under elevated carbon dioxide levels. Increased temperatures could be detrimental to the species but coupled with elevated carbon dioxide levels the growth of Encephalartos longifolius are postulated to outweigh the negative impacts of increased temperatures. Whilst climatic conditions in the Eastern Cape might not impact the abundance of Encephalartos longifolius, the species however is declining rapidly to the present near-threatened status. Demographic studies revealed a high percentage of juvenile numbers in the wild; however juvenile plants are impacted on by animals thereby jeopardizing their survival. Adult plants are heavily impacted on by animals; this reduces the probability of new offspring being produced. Cycads are also very slow - growing which is the primary cause of their ruin in the wild. Encephalartos longifolius grows at just over approximately 1 cm per year with growth being more rapid in the juvenile plants. Once juvenile plants reach approximately 60 cm they stop growing in diameter but only get taller. Seed germination is also a very slow process with an optimum temperature of 28°C and a growth medium of at least 50 percent moisture. Regardless of the Eastern Cape predicted to become the hottest province in South Africa as a result of climate change, cycads will be able to adapt to the changing environment and conservation plans should focus on animal and human impacts that are the major force causing decreasing abundance of Encephalartos longifolius in the wild.
- Full Text:
- Date Issued: 2012
- Authors: Singh, Karishma
- Date: 2012
- Subjects: Cycads -- South Africa -- Eastern Cape , Encephalartos -- South Africa -- Eastern Cape , Climate change -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10633 , http://hdl.handle.net/10948/d1012857
- Description: Cycads first appeared about 300 million years ago and historical data indicates that they survived fluctuations of global temperature and carbon dioxide concentrations and reached peak abundance during periods where temperature and carbon dioxide concentrations were much higher than the present conditions as well as the predicted increased levels. With Africa being one of the most vulnerable regions to climate change and in the absence of an evaluation of predicted impacts of climate change on cycads, this study aims to contribute to our understanding of responses of Encephalartos longifolius to increased temperature. Encephalartos longifolius (Jacq.) Lehm is an Eastern Cape endemic and like most cycads has been around for millions of years with very little change to its basic structure. Photosynthetic rates showed E.longifolius seedlings have C3 photosynthesis and even under stress they do not switch over to CAM photosynthesis. The photosynthetic rates of seedlings showed a typical C3 -plant type response under elevated carbon dioxide levels. Increased temperatures could be detrimental to the species but coupled with elevated carbon dioxide levels the growth of Encephalartos longifolius are postulated to outweigh the negative impacts of increased temperatures. Whilst climatic conditions in the Eastern Cape might not impact the abundance of Encephalartos longifolius, the species however is declining rapidly to the present near-threatened status. Demographic studies revealed a high percentage of juvenile numbers in the wild; however juvenile plants are impacted on by animals thereby jeopardizing their survival. Adult plants are heavily impacted on by animals; this reduces the probability of new offspring being produced. Cycads are also very slow - growing which is the primary cause of their ruin in the wild. Encephalartos longifolius grows at just over approximately 1 cm per year with growth being more rapid in the juvenile plants. Once juvenile plants reach approximately 60 cm they stop growing in diameter but only get taller. Seed germination is also a very slow process with an optimum temperature of 28°C and a growth medium of at least 50 percent moisture. Regardless of the Eastern Cape predicted to become the hottest province in South Africa as a result of climate change, cycads will be able to adapt to the changing environment and conservation plans should focus on animal and human impacts that are the major force causing decreasing abundance of Encephalartos longifolius in the wild.
- Full Text:
- Date Issued: 2012
Using mobile information visualisation to support the analysis of telecommunication service ultilisation
- Authors: Twigg, Gianni Gurshwin
- Date: 2012
- Subjects: Telecommunication , Visualization , Technology -- Social aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10497 , http://hdl.handle.net/10948/d1020831
- Description: Telecommunication service utilisation (TSU) focuses on how customers make use of telecommunication services and can provide valuable information for decision making for improved customer service delivery. When a telecommunication service provider consults with customers, large amounts of static documentation on TSU data are compiled. Compiling this documentation for in-field investigation is manually intensive and the documentation does not effectively support decision making. Existing systems for visualising TSU data do not efficiently support in-field investigation of TSU and lack dynamic interaction. This highlights the need to investigate a solution to better support in-field investigation of TSU. This research followed a Design Science Research methodology to develop and evaluate a solution to solve the problem identified. The use of tablet devices for in-field investigation of TSU was identified as a suitable solution. Mobile information visualisation (MIV) techniques were investigated to determine appropriate display and interaction techniques for the visualisation of TSU data on a tablet device. An existing visualisation framework for TSU was identified and extended to incorporate touch-based interactions. Three service usage views were identified for visualising TSU, namely a Trend, Network and Detail Usage View. A Dashboard View was also identified to provide a quick reference view of the different views. A prototype called MobiTel was developed on a tablet device. MobiTel incorporated the identified information visualisation techniques. MobiTel was evaluated using an expert review and a user study to determine its usability and usefulness. The results indicated that MobiTel was perceived as being useful for in-field investigation and that the participants perceived the prototype to be easy to use and learn. The user study also indicated that the participants were satisfied with MobiTel. This research has determined that MIV techniques can be used for in-field investigation of TSU. Design recommendations were devised for designing an interactive mobile prototype for visualising service usage information. Future work will involve using map-based visualisation for visualising TSU data on different customer sites.
- Full Text:
- Date Issued: 2012
- Authors: Twigg, Gianni Gurshwin
- Date: 2012
- Subjects: Telecommunication , Visualization , Technology -- Social aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10497 , http://hdl.handle.net/10948/d1020831
- Description: Telecommunication service utilisation (TSU) focuses on how customers make use of telecommunication services and can provide valuable information for decision making for improved customer service delivery. When a telecommunication service provider consults with customers, large amounts of static documentation on TSU data are compiled. Compiling this documentation for in-field investigation is manually intensive and the documentation does not effectively support decision making. Existing systems for visualising TSU data do not efficiently support in-field investigation of TSU and lack dynamic interaction. This highlights the need to investigate a solution to better support in-field investigation of TSU. This research followed a Design Science Research methodology to develop and evaluate a solution to solve the problem identified. The use of tablet devices for in-field investigation of TSU was identified as a suitable solution. Mobile information visualisation (MIV) techniques were investigated to determine appropriate display and interaction techniques for the visualisation of TSU data on a tablet device. An existing visualisation framework for TSU was identified and extended to incorporate touch-based interactions. Three service usage views were identified for visualising TSU, namely a Trend, Network and Detail Usage View. A Dashboard View was also identified to provide a quick reference view of the different views. A prototype called MobiTel was developed on a tablet device. MobiTel incorporated the identified information visualisation techniques. MobiTel was evaluated using an expert review and a user study to determine its usability and usefulness. The results indicated that MobiTel was perceived as being useful for in-field investigation and that the participants perceived the prototype to be easy to use and learn. The user study also indicated that the participants were satisfied with MobiTel. This research has determined that MIV techniques can be used for in-field investigation of TSU. Design recommendations were devised for designing an interactive mobile prototype for visualising service usage information. Future work will involve using map-based visualisation for visualising TSU data on different customer sites.
- Full Text:
- Date Issued: 2012
The development and optimization of a cosmetic formulation that facilitates the process of detangling braids from African hair
- Authors: Mkentane, Kwezikazi
- Date: 2012
- Subjects: Cosmetics--Patents , Hairdressing of Blacks , Braids (Hairdressing)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10366 , http://hdl.handle.net/10948/1662 , Cosmetics--Patents , Hairdressing of Blacks , Braids (Hairdressing)
- Description: A large number of people throughout the world have naturally kinky hair that may be very difficult to manage. These people often subject their hair to vigorous and harsh treatment processes in order to straighten it and hence make it more manageable. Hair braiding is a popular and fashionable trend amongst many people, in particular people of African descent. Braided hairstyles serve to preserve hair and protect it, and to give it time to rejuvenate after a period of harsh treatment. During the braiding process synthetic hair is attached to natural hair by weaving a length of the natural hair into one end of each braid. Other materials like wool or cotton may be use used to achieve different hairstyles and textures. Several strands of natural hair are used to secure each braid. The braids are normally left intact for a number of weeks or even months. Although braiding is a helpful African hair grooming practice, the process of taking down or detangling the braids is labor intensive and entails each braid being cut just below where the natural hair ceases and the natural hair being untangled from the braid using a safety pin, a needle or a fine toothed comb. The labor and long hours required to detangle braided hairstyles often results in braid wearers frustratingly pulling on their braided hair. This behavior inevitably destroys the hair follicle and leaves the hair damaged. According to a study conducted by the University of Cape Town’s dermatology department, braiding may be the root cause of traction alopecia (TA) amongst braid wearers. Traction alopecia is a form of alopecia, or gradual hair loss that is caused primarily by excessive pulling forces applied to the hair. The purpose of this current study was to investigate the factors, other than braid tightness, that affect the way and ease with which braids are detangled from the human hair. The study hypothesized that frictional forces present in braided hair were amongst these factors. It was hypothesized that introducing a lubricating formulation in the braids would allow for easier braid detangling. In order to decrease the prevalence of traction alopecia from braided hair, two hair strengthening actives were included in the test formulation. The study investigated the effects of the test formulations on braid detangling, hair friction and on the tensile strength of human hair. The study found that the method used did not pick up any significant differences between the braid detangling forces of treated braids when compared to the braid vi detangling forces of untreated hair. The same method used to measure braid detangling forces was able to show that there are variations in the braid detangling forces of different sections along the braid length. The method to measure braid detangling was based on the principles of hair combability measurements. The study also found that although the method used to measure braid detangling forces was unsuccessful in picking up significant differences in braid detangling forces of treated hair and untreated hair, the method used to measure the frictional forces of human hair showed that the frictional forces of hair treated with test formulations were significantly different than that of untreated hair. The method used to measure frictional forces was based on the capstan approach. The Capstan method measures the forces required to slide a weighted hair fibre over a curved surface of reference material. The interaction between the weighted fibre and the reference material simulates the movement of hair out of a braid ensemble in the braid detangling process. The optimum mixture with the minimum coefficient of friction, predicted a coefficient of friction of 0.61 ± 0.04. The optimum formulation was found to be one that contained 30% Cyclopentasiloxane , 0% PEG-12 Dimethicone, 10% 18-MEA, 29% water, 10% hair strengthening actives, 12.86% emulsifier combination and 8% other oils. The study also showed that including hair strengthening actives, such as hydrolysed proteins had significant effects in the tensile strength properties of chemically treated African hair.
- Full Text:
- Date Issued: 2012
- Authors: Mkentane, Kwezikazi
- Date: 2012
- Subjects: Cosmetics--Patents , Hairdressing of Blacks , Braids (Hairdressing)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10366 , http://hdl.handle.net/10948/1662 , Cosmetics--Patents , Hairdressing of Blacks , Braids (Hairdressing)
- Description: A large number of people throughout the world have naturally kinky hair that may be very difficult to manage. These people often subject their hair to vigorous and harsh treatment processes in order to straighten it and hence make it more manageable. Hair braiding is a popular and fashionable trend amongst many people, in particular people of African descent. Braided hairstyles serve to preserve hair and protect it, and to give it time to rejuvenate after a period of harsh treatment. During the braiding process synthetic hair is attached to natural hair by weaving a length of the natural hair into one end of each braid. Other materials like wool or cotton may be use used to achieve different hairstyles and textures. Several strands of natural hair are used to secure each braid. The braids are normally left intact for a number of weeks or even months. Although braiding is a helpful African hair grooming practice, the process of taking down or detangling the braids is labor intensive and entails each braid being cut just below where the natural hair ceases and the natural hair being untangled from the braid using a safety pin, a needle or a fine toothed comb. The labor and long hours required to detangle braided hairstyles often results in braid wearers frustratingly pulling on their braided hair. This behavior inevitably destroys the hair follicle and leaves the hair damaged. According to a study conducted by the University of Cape Town’s dermatology department, braiding may be the root cause of traction alopecia (TA) amongst braid wearers. Traction alopecia is a form of alopecia, or gradual hair loss that is caused primarily by excessive pulling forces applied to the hair. The purpose of this current study was to investigate the factors, other than braid tightness, that affect the way and ease with which braids are detangled from the human hair. The study hypothesized that frictional forces present in braided hair were amongst these factors. It was hypothesized that introducing a lubricating formulation in the braids would allow for easier braid detangling. In order to decrease the prevalence of traction alopecia from braided hair, two hair strengthening actives were included in the test formulation. The study investigated the effects of the test formulations on braid detangling, hair friction and on the tensile strength of human hair. The study found that the method used did not pick up any significant differences between the braid detangling forces of treated braids when compared to the braid vi detangling forces of untreated hair. The same method used to measure braid detangling forces was able to show that there are variations in the braid detangling forces of different sections along the braid length. The method to measure braid detangling was based on the principles of hair combability measurements. The study also found that although the method used to measure braid detangling forces was unsuccessful in picking up significant differences in braid detangling forces of treated hair and untreated hair, the method used to measure the frictional forces of human hair showed that the frictional forces of hair treated with test formulations were significantly different than that of untreated hair. The method used to measure frictional forces was based on the capstan approach. The Capstan method measures the forces required to slide a weighted hair fibre over a curved surface of reference material. The interaction between the weighted fibre and the reference material simulates the movement of hair out of a braid ensemble in the braid detangling process. The optimum mixture with the minimum coefficient of friction, predicted a coefficient of friction of 0.61 ± 0.04. The optimum formulation was found to be one that contained 30% Cyclopentasiloxane , 0% PEG-12 Dimethicone, 10% 18-MEA, 29% water, 10% hair strengthening actives, 12.86% emulsifier combination and 8% other oils. The study also showed that including hair strengthening actives, such as hydrolysed proteins had significant effects in the tensile strength properties of chemically treated African hair.
- Full Text:
- Date Issued: 2012