Sketch-based digital storyboards and floor plans for authoring computer-generated film pre-visuals
- Authors: Matthews, Timothy
- Date: 2012
- Subjects: Computer graphics , Computer vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10463 , http://hdl.handle.net/10948/d1008430 , Computer graphics , Computer vision
- Description: Pre-visualisation is an important tool for planning films during the pre-production phase of filmmaking. Existing pre-visualisation authoring tools do not effectively support the user in authoring pre-visualisations without impairing software usability. These tools require the user to either have programming skills, be experienced in modelling and animation, or use drag-and-drop style interfaces. These interaction methods do not intuitively fit with pre-production activities such as floor planning and storyboarding, and existing tools that apply a storyboarding metaphor do not automatically interpret user sketches. The goal of this research was to investigate how sketch-based user interfaces and methods from computer vision could be used for supporting pre-visualisation authoring using a storyboarding approach. The requirements for such a sketch-based storyboarding tool were determined from literature and an interview with Triggerfish Animation Studios. A framework was developed to support sketch-based pre-visualisation authoring using a storyboarding approach. Algorithms for describing user sketches, recognising objects and performing pose estimation were designed to automatically interpret user sketches. A proof of concept prototype implementation of this framework was evaluated in order to assess its usability benefit. It was found that the participants could author pre-visualisations effectively, efficiently and easily. The results of the usability evaluation also showed that the participants were satisfied with the overall design and usability of the prototype tool. The positive and negative findings of the evaluation were interpreted and combined with existing heuristics in order to create a set of guidelines for designing similar sketch-based pre-visualisation authoring tools that apply the storyboarding approach. The successful implementation of the proof of concept prototype tool provides practical evidence of the feasibility of sketch-based pre-visualisation authoring. The positive results from the usability evaluation established that sketch-based interfacing techniques can be used effectively with a storyboarding approach for authoring pre-visualisations without impairing software usability.
- Full Text:
- Date Issued: 2012
- Authors: Matthews, Timothy
- Date: 2012
- Subjects: Computer graphics , Computer vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10463 , http://hdl.handle.net/10948/d1008430 , Computer graphics , Computer vision
- Description: Pre-visualisation is an important tool for planning films during the pre-production phase of filmmaking. Existing pre-visualisation authoring tools do not effectively support the user in authoring pre-visualisations without impairing software usability. These tools require the user to either have programming skills, be experienced in modelling and animation, or use drag-and-drop style interfaces. These interaction methods do not intuitively fit with pre-production activities such as floor planning and storyboarding, and existing tools that apply a storyboarding metaphor do not automatically interpret user sketches. The goal of this research was to investigate how sketch-based user interfaces and methods from computer vision could be used for supporting pre-visualisation authoring using a storyboarding approach. The requirements for such a sketch-based storyboarding tool were determined from literature and an interview with Triggerfish Animation Studios. A framework was developed to support sketch-based pre-visualisation authoring using a storyboarding approach. Algorithms for describing user sketches, recognising objects and performing pose estimation were designed to automatically interpret user sketches. A proof of concept prototype implementation of this framework was evaluated in order to assess its usability benefit. It was found that the participants could author pre-visualisations effectively, efficiently and easily. The results of the usability evaluation also showed that the participants were satisfied with the overall design and usability of the prototype tool. The positive and negative findings of the evaluation were interpreted and combined with existing heuristics in order to create a set of guidelines for designing similar sketch-based pre-visualisation authoring tools that apply the storyboarding approach. The successful implementation of the proof of concept prototype tool provides practical evidence of the feasibility of sketch-based pre-visualisation authoring. The positive results from the usability evaluation established that sketch-based interfacing techniques can be used effectively with a storyboarding approach for authoring pre-visualisations without impairing software usability.
- Full Text:
- Date Issued: 2012
Small mammal communities at high altitude within the Sneeuberg Mountain complex, Eastern Cape Province, South Africa
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
Statistical tools for consolidation of energy demand forecasts
- Authors: Motsomi, Abel Pholo
- Date: 2012
- Subjects: Power resources -- Forecasting , Energy conservation -- Standards , Electric utilities
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10573 , http://hdl.handle.net/10948/d1011578 , Power resources -- Forecasting , Energy conservation -- Standards , Electric utilities
- Description: The electricity market in the South African economy uses specialised instruments in forecast-ing the energy load to be delivered. The current status quo operates with several forecasters from different offices, departments or businesses predicting for different purposes. This be-comes a challenge to derive a consolidated forecast. This study has attempted to develop a consolidating instrument that will merge all the forecasts from different offices, departments or businesses into one so-called ‘official forecast’. Such an instrument should be able to predict with accuracy the anticipated usage or demand. Article [18] examined patterns across G7 countries and forecasters to establish whether the present bias reflects the inefficient use of information, or whether it reflects a rational re- sponse to financial, reputation and other incentives operating for forecasters. This bias is particularly true for any electricity utility as forecasting is undertaken by different divisions; therefore each division has its own incentives. For instance, the generation division will tend to overstate their forecasts so as that there is no possibility of a shortage, whereas distri- bution (sales) might understate so as to give the impression of being profitable when more units are sold to consumers. Thus, the study attempts to rectify this bias by employing statistical tools in consolidating these forecasts. The results presented in this paper propose a newly developed procedure of consolidating energy demand forecasts from different users and accounting for different time horizons. Predicting for the short-term and long-term involves different measuring tools, which is one aspect of prediction this paper tackles.
- Full Text:
- Date Issued: 2012
- Authors: Motsomi, Abel Pholo
- Date: 2012
- Subjects: Power resources -- Forecasting , Energy conservation -- Standards , Electric utilities
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10573 , http://hdl.handle.net/10948/d1011578 , Power resources -- Forecasting , Energy conservation -- Standards , Electric utilities
- Description: The electricity market in the South African economy uses specialised instruments in forecast-ing the energy load to be delivered. The current status quo operates with several forecasters from different offices, departments or businesses predicting for different purposes. This be-comes a challenge to derive a consolidated forecast. This study has attempted to develop a consolidating instrument that will merge all the forecasts from different offices, departments or businesses into one so-called ‘official forecast’. Such an instrument should be able to predict with accuracy the anticipated usage or demand. Article [18] examined patterns across G7 countries and forecasters to establish whether the present bias reflects the inefficient use of information, or whether it reflects a rational re- sponse to financial, reputation and other incentives operating for forecasters. This bias is particularly true for any electricity utility as forecasting is undertaken by different divisions; therefore each division has its own incentives. For instance, the generation division will tend to overstate their forecasts so as that there is no possibility of a shortage, whereas distri- bution (sales) might understate so as to give the impression of being profitable when more units are sold to consumers. Thus, the study attempts to rectify this bias by employing statistical tools in consolidating these forecasts. The results presented in this paper propose a newly developed procedure of consolidating energy demand forecasts from different users and accounting for different time horizons. Predicting for the short-term and long-term involves different measuring tools, which is one aspect of prediction this paper tackles.
- Full Text:
- Date Issued: 2012
Statistical tools for wind energy generation
- Authors: Ndzukuma, Sibusiso
- Date: 2012
- Subjects: Wind power , Wind turbines , Winds -- Speed
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10580 , http://hdl.handle.net/10948/d1020627
- Description: In this study we conduct wind resource assessment to evaluate the annual energy production of a wind turbine. To estimate energy production of a wind turbine over a period of time, the power characteristics of the wind turbine are integrated with the probabilities of the wind speed expected at a chosen site. The first data set was obtained from a wind farm in Denmark. We propose several probability density functions to model the distribution of the wind speed. We use techniques from nonlinear regression analysis to model the power curve of a wind turbine. The best fit distribution model is assessed by performing numeric goodness–of–fit measures and graphical analyses. Johnson’s bounded (SB) distribution provides the best fit model with the smallest Kolmogorov–Smirnov (K-S) test statistic . 15. The four parameter logistic nonlinear regression (4PL) model is determined to provide the best fit to the power curve data, according to the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The estimated annual energy yield is compared to the actual production of the wind turbine. Our models underestimate the actual energy production by a 1 difference. In Chapter Six we conduct data processing, analyses and comparison of wind speed distributions using a data set obtained from a measuring wind mast mounted in Humansdorp, Eastern Cape. The expected annual energy production is estimated by using the certified power curve as provided by the manufacturer of the wind turbine under study. The commonly used Weibull distribution is determined to provide the best fit distribution model to our selected models. The annual energy yield is estimated at 7.33 GWh, with a capacity factor of 41.8 percent.
- Full Text:
- Date Issued: 2012
- Authors: Ndzukuma, Sibusiso
- Date: 2012
- Subjects: Wind power , Wind turbines , Winds -- Speed
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10580 , http://hdl.handle.net/10948/d1020627
- Description: In this study we conduct wind resource assessment to evaluate the annual energy production of a wind turbine. To estimate energy production of a wind turbine over a period of time, the power characteristics of the wind turbine are integrated with the probabilities of the wind speed expected at a chosen site. The first data set was obtained from a wind farm in Denmark. We propose several probability density functions to model the distribution of the wind speed. We use techniques from nonlinear regression analysis to model the power curve of a wind turbine. The best fit distribution model is assessed by performing numeric goodness–of–fit measures and graphical analyses. Johnson’s bounded (SB) distribution provides the best fit model with the smallest Kolmogorov–Smirnov (K-S) test statistic . 15. The four parameter logistic nonlinear regression (4PL) model is determined to provide the best fit to the power curve data, according to the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The estimated annual energy yield is compared to the actual production of the wind turbine. Our models underestimate the actual energy production by a 1 difference. In Chapter Six we conduct data processing, analyses and comparison of wind speed distributions using a data set obtained from a measuring wind mast mounted in Humansdorp, Eastern Cape. The expected annual energy production is estimated by using the certified power curve as provided by the manufacturer of the wind turbine under study. The commonly used Weibull distribution is determined to provide the best fit distribution model to our selected models. The annual energy yield is estimated at 7.33 GWh, with a capacity factor of 41.8 percent.
- Full Text:
- Date Issued: 2012
Structural analysis of effects of mutations on HIV-1 subtype C protease active site
- Mathu, Alexander Muchugia Nganga
- Authors: Mathu, Alexander Muchugia Nganga
- Date: 2012
- Subjects: HIV (Viruses) -- Research , HIV infections -- Treatment -- Research , Protease inhibitors -- Research , Viruses -- Effect of drugs on -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4013 , http://hdl.handle.net/10962/d1004073 , HIV (Viruses) -- Research , HIV infections -- Treatment -- Research , Protease inhibitors -- Research , Viruses -- Effect of drugs on -- Research
- Description: HIV/AIDS is a global pandemic that poses a great threat especially in Sub-Saharan Africa where the highest population of those infected with the virus is found. It has far reaching medical, socio-economic and scientific implications. The HIV-1 protease enzyme is a prime therapeutic target that has been exploited in an effort to reduce morbidity and mortality. However problems arise from drug toxicity and drug-resistant mutations of the protease which is a motivation for research for new, safer and effective therapies. Evidence exists to show that there are significant genomic differences in Subtype B and C that have a negative effect on the intrinsic binding of inhibitors. It is imperative to look at all perspectives from epidemiological, molecular to the pharmacological ones so as to achieve rational design of therapeutic agents. This study involved the use of in silico structural analysis of the effects of mutations in the active site. The data was provided by the National Institute of Communicable Diseases consisting of HIV-1 Subtype C protease sequences of 29 infants exhibiting drug-resistance to ritonavir and lopinavir. The major active site mutations causing drug resistance identified in this study were M46I, I54V and V82A using the Stanford HIV database tool. Homology modeling without extra restraints produced models with improved quality in comparison to those with restraints. MetaMQAPII results differed when models were visualized as dimers giving erroneous modeled regions in comparison to monomers. A broader study with a larger dataset of HIV-1 subtype C protease sequences is required to increase statistical confidence and in order to identify the pattern of drug resistant mutations. Homology modeling without extra restraints is preferred for calculating homology models for the HIV-1 subtype C. Further investigations needs to be done to ascertain the accuracy of validation results for dimers from MetaMQAPII as it is designed for evaluation of monomers.
- Full Text:
- Date Issued: 2012
- Authors: Mathu, Alexander Muchugia Nganga
- Date: 2012
- Subjects: HIV (Viruses) -- Research , HIV infections -- Treatment -- Research , Protease inhibitors -- Research , Viruses -- Effect of drugs on -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4013 , http://hdl.handle.net/10962/d1004073 , HIV (Viruses) -- Research , HIV infections -- Treatment -- Research , Protease inhibitors -- Research , Viruses -- Effect of drugs on -- Research
- Description: HIV/AIDS is a global pandemic that poses a great threat especially in Sub-Saharan Africa where the highest population of those infected with the virus is found. It has far reaching medical, socio-economic and scientific implications. The HIV-1 protease enzyme is a prime therapeutic target that has been exploited in an effort to reduce morbidity and mortality. However problems arise from drug toxicity and drug-resistant mutations of the protease which is a motivation for research for new, safer and effective therapies. Evidence exists to show that there are significant genomic differences in Subtype B and C that have a negative effect on the intrinsic binding of inhibitors. It is imperative to look at all perspectives from epidemiological, molecular to the pharmacological ones so as to achieve rational design of therapeutic agents. This study involved the use of in silico structural analysis of the effects of mutations in the active site. The data was provided by the National Institute of Communicable Diseases consisting of HIV-1 Subtype C protease sequences of 29 infants exhibiting drug-resistance to ritonavir and lopinavir. The major active site mutations causing drug resistance identified in this study were M46I, I54V and V82A using the Stanford HIV database tool. Homology modeling without extra restraints produced models with improved quality in comparison to those with restraints. MetaMQAPII results differed when models were visualized as dimers giving erroneous modeled regions in comparison to monomers. A broader study with a larger dataset of HIV-1 subtype C protease sequences is required to increase statistical confidence and in order to identify the pattern of drug resistant mutations. Homology modeling without extra restraints is preferred for calculating homology models for the HIV-1 subtype C. Further investigations needs to be done to ascertain the accuracy of validation results for dimers from MetaMQAPII as it is designed for evaluation of monomers.
- Full Text:
- Date Issued: 2012
Structural analysis of prodomain inhibition of cysteine proteases in plasmodium species
- Authors: Njuguna, Joyce Njoki
- Date: 2012
- Subjects: Plasmodium , Cysteine proteinases , Proteolytic enzymes , Malaria -- Chemotherapy , Antimalarials , Plasmodium falciparum
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4021 , http://hdl.handle.net/10962/d1004081 , Plasmodium , Cysteine proteinases , Proteolytic enzymes , Malaria -- Chemotherapy , Antimalarials , Plasmodium falciparum
- Description: Plasmodium is a genus of parasites causing malaria, a virulent protozoan infection in humans resulting in over a million deaths annually. Treatment of malaria is increasingly limited by parasite resistance to available drugs. Hence, there is a need to identify new drug targets and authenticate antimalarial compounds that act on these targets. A relatively new therapeutic approach targets proteolytic enzymes responsible for parasite‟s invasion, rupture and hemoglobin degradation at the erythrocytic stage of infection. Cysteine proteases (CPs) are essential for these crucial roles in the intraerythrocytic parasite. CPs are a diverse group of enzymes subdivided into clans and further subdivided into families. Our interest is in Clan CA, papain family C1 proteases, whose members play numerous roles in human and parasitic metabolism. These proteases are produced as zymogens having an N-terminal extension known as the prodomain which regulates the protease activity by selectively inhibiting its active site, preventing substrate access. A Clan CA protease Falcipain-2 (FP-2) of Plasmodium falciparum is a validated drug target but little is known of its orthologs in other malarial Plasmodium species. This study uses various structural bioinformatics approaches to characterise the prodomain‟s regulatory effect in FP-2 and its orthologs in Plasmodium species (P. vivax, P. berghei, P. knowlesi, P. ovale, P. chabaudi and P. yoelii). This was in an effort to discover short peptides with essential residues to mimic the prodomain‟s inhibition of these proteases, as potential peptidomimetic therapeutic agents. Residues in the prodomain region that spans over the active site are most likely to interact with the subsite residues inhibiting the protease. Sequence analysis revealed conservation of residues in this region of Plasmodium proteases that differed significantly in human proteases. Further prediction of the 3D structure of these proteases by homology modelling allowed visualisation of these interactions revealing differences between parasite and human proteases which will lead to significant contribution in structure based malarial inhibitor design.
- Full Text:
- Date Issued: 2012
- Authors: Njuguna, Joyce Njoki
- Date: 2012
- Subjects: Plasmodium , Cysteine proteinases , Proteolytic enzymes , Malaria -- Chemotherapy , Antimalarials , Plasmodium falciparum
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4021 , http://hdl.handle.net/10962/d1004081 , Plasmodium , Cysteine proteinases , Proteolytic enzymes , Malaria -- Chemotherapy , Antimalarials , Plasmodium falciparum
- Description: Plasmodium is a genus of parasites causing malaria, a virulent protozoan infection in humans resulting in over a million deaths annually. Treatment of malaria is increasingly limited by parasite resistance to available drugs. Hence, there is a need to identify new drug targets and authenticate antimalarial compounds that act on these targets. A relatively new therapeutic approach targets proteolytic enzymes responsible for parasite‟s invasion, rupture and hemoglobin degradation at the erythrocytic stage of infection. Cysteine proteases (CPs) are essential for these crucial roles in the intraerythrocytic parasite. CPs are a diverse group of enzymes subdivided into clans and further subdivided into families. Our interest is in Clan CA, papain family C1 proteases, whose members play numerous roles in human and parasitic metabolism. These proteases are produced as zymogens having an N-terminal extension known as the prodomain which regulates the protease activity by selectively inhibiting its active site, preventing substrate access. A Clan CA protease Falcipain-2 (FP-2) of Plasmodium falciparum is a validated drug target but little is known of its orthologs in other malarial Plasmodium species. This study uses various structural bioinformatics approaches to characterise the prodomain‟s regulatory effect in FP-2 and its orthologs in Plasmodium species (P. vivax, P. berghei, P. knowlesi, P. ovale, P. chabaudi and P. yoelii). This was in an effort to discover short peptides with essential residues to mimic the prodomain‟s inhibition of these proteases, as potential peptidomimetic therapeutic agents. Residues in the prodomain region that spans over the active site are most likely to interact with the subsite residues inhibiting the protease. Sequence analysis revealed conservation of residues in this region of Plasmodium proteases that differed significantly in human proteases. Further prediction of the 3D structure of these proteases by homology modelling allowed visualisation of these interactions revealing differences between parasite and human proteases which will lead to significant contribution in structure based malarial inhibitor design.
- Full Text:
- Date Issued: 2012
Synthesis and characterisation of Pt-alloy oxygen reduction electrocatalysts for low temperature PEM fuel cells
- Authors: Mohamed, Rhiyaad
- Date: 2012
- Subjects: Electrochemical analysis , Proton exchange membrane fuel cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10428 , http://hdl.handle.net/10948/d1018586
- Description: This dissertation the syntheses of Pt-based binary and ternary alloy electrocatalysts using the transition metals of Co and Ni are presented. These electrocatalysts were synthesised by an impregnation-reduction procedure at high temperature whereby Pt supported on carbon, (Pt/C (40 percent), was impregnated with the various metal and mixtures thereof and reduced at high temperatures in a H2 atmosphere. The procedure was also designed in such a way so as to prevent the oxidation of the support material (carbon black) during the alloy formation. The resultant nanoparticles (9-12 nm) of Pt3Co/C, Pt3Ni/C and Pt3Co0.5Ni0.5/C were also subjected to a post treatment procedure by acid washing (denoted AW) to produce electrocatalysts of Pt3Co/C-AW, Pt3Ni/C-AW and Pt3Co0.5Ni0.5/C-AW to study the effect of acid treatment on these electrocatalysts. The synthesised electrocatalysts were then characterised by a number of physical and electrochemical techniques and compared to that of commercial Pt/C (Pt/C-JM, HiSpec 4000) as well as Pt/C catalysts (Pt/C-900 and Pt/C-900-AW) treated under the same conditions used for the alloy synthesis. The electrocatalysts were then used to fabricate MEAs that were loaded into commercial single test cells and characterised by means of polarisation curves and Electrochemical Impedance Spectroscopy (EIS). The extensive physical characterisation included Powder X-Ray Diffraction (PXRD) analysis, Transmission Electron Microscopy (TEM), elemental analysis by Energy Dispersive Spectroscopy (EDS) and metal loading by Thermo-Gravimetric Analysis (TGA). These studies showed that Pt-based alloy electrocatalysts were successfully synthesised with particle sizes ranging from 9 - 12 nm, within their respective atomic ratios and whereby no significant loss of carbon support occurred. This indicated that significant sintering or electrocatalyst particles occurred when compared to that of the starting Pt/C catalyst (3 – 4 nm). From the combined results of the physical characterisation procedures, it was also shown that leaching as a result of acid washing was catalyst dependent with Ni containing catalysts showing a significant degree of leaching compared to that of Co containing catalysts. Electrochemical characterisation in terms of Electrochemical Active Surface Area (ECSA) by Cyclic Voltammetry (CV) and ORR activity by Rotating Disc Electrode (RDE) analysis revealed that a significant decrease in the ECSA resulted from the increase in particle size and this had a major influence on the ORR activity. Furthermore it was found that a significant improvement in the ORR activity was achieved by the synthesis of Pt-based alloys. It was also found that catalytic properties of the acid washed electrocatalysts were substantially different from that of non-acid washed electrocatalysts. The experimental data confirmed that it was possibly to achieve better catalytic performance as compared to that of Pt/C at a lower material cost when Pt is alloyed with base transition metals. The trend observed from the ORR activity studies by RDE was successfully repeated in the in-situ fuel cell testing in terms of mass activity of the electrocatalysts. Of the electrocatalysts studied under „real‟ fuel cell conditions Pt/C-JM had the best performance compared to the others, with the ternary Pt3Co0.5Ni0.5/C showing better catalytic performance compared to the Pt3Co/C electrocatalyst. This was found to be due to a higher charge transfer resistance observed in Pt3Co/C as compared to that of Pt3Co0.5Ni0.5/C which was similar than that of the commercial Pt/C-JM catalyst with both Pt3Co/C and Pt3Co0.5Ni0.5/C-AW having similar but higher ohmic resistances than that of Pt/C-JM as determined by electrochemical impedance spectroscopy. The results showed that a great potential exist to improve the catalytic performance of low temperature PEM fuel electrocatalysts at a reduced cost as compared to that of pure Pt provided a method of controlling the particle size was established.
- Full Text:
- Date Issued: 2012
- Authors: Mohamed, Rhiyaad
- Date: 2012
- Subjects: Electrochemical analysis , Proton exchange membrane fuel cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10428 , http://hdl.handle.net/10948/d1018586
- Description: This dissertation the syntheses of Pt-based binary and ternary alloy electrocatalysts using the transition metals of Co and Ni are presented. These electrocatalysts were synthesised by an impregnation-reduction procedure at high temperature whereby Pt supported on carbon, (Pt/C (40 percent), was impregnated with the various metal and mixtures thereof and reduced at high temperatures in a H2 atmosphere. The procedure was also designed in such a way so as to prevent the oxidation of the support material (carbon black) during the alloy formation. The resultant nanoparticles (9-12 nm) of Pt3Co/C, Pt3Ni/C and Pt3Co0.5Ni0.5/C were also subjected to a post treatment procedure by acid washing (denoted AW) to produce electrocatalysts of Pt3Co/C-AW, Pt3Ni/C-AW and Pt3Co0.5Ni0.5/C-AW to study the effect of acid treatment on these electrocatalysts. The synthesised electrocatalysts were then characterised by a number of physical and electrochemical techniques and compared to that of commercial Pt/C (Pt/C-JM, HiSpec 4000) as well as Pt/C catalysts (Pt/C-900 and Pt/C-900-AW) treated under the same conditions used for the alloy synthesis. The electrocatalysts were then used to fabricate MEAs that were loaded into commercial single test cells and characterised by means of polarisation curves and Electrochemical Impedance Spectroscopy (EIS). The extensive physical characterisation included Powder X-Ray Diffraction (PXRD) analysis, Transmission Electron Microscopy (TEM), elemental analysis by Energy Dispersive Spectroscopy (EDS) and metal loading by Thermo-Gravimetric Analysis (TGA). These studies showed that Pt-based alloy electrocatalysts were successfully synthesised with particle sizes ranging from 9 - 12 nm, within their respective atomic ratios and whereby no significant loss of carbon support occurred. This indicated that significant sintering or electrocatalyst particles occurred when compared to that of the starting Pt/C catalyst (3 – 4 nm). From the combined results of the physical characterisation procedures, it was also shown that leaching as a result of acid washing was catalyst dependent with Ni containing catalysts showing a significant degree of leaching compared to that of Co containing catalysts. Electrochemical characterisation in terms of Electrochemical Active Surface Area (ECSA) by Cyclic Voltammetry (CV) and ORR activity by Rotating Disc Electrode (RDE) analysis revealed that a significant decrease in the ECSA resulted from the increase in particle size and this had a major influence on the ORR activity. Furthermore it was found that a significant improvement in the ORR activity was achieved by the synthesis of Pt-based alloys. It was also found that catalytic properties of the acid washed electrocatalysts were substantially different from that of non-acid washed electrocatalysts. The experimental data confirmed that it was possibly to achieve better catalytic performance as compared to that of Pt/C at a lower material cost when Pt is alloyed with base transition metals. The trend observed from the ORR activity studies by RDE was successfully repeated in the in-situ fuel cell testing in terms of mass activity of the electrocatalysts. Of the electrocatalysts studied under „real‟ fuel cell conditions Pt/C-JM had the best performance compared to the others, with the ternary Pt3Co0.5Ni0.5/C showing better catalytic performance compared to the Pt3Co/C electrocatalyst. This was found to be due to a higher charge transfer resistance observed in Pt3Co/C as compared to that of Pt3Co0.5Ni0.5/C which was similar than that of the commercial Pt/C-JM catalyst with both Pt3Co/C and Pt3Co0.5Ni0.5/C-AW having similar but higher ohmic resistances than that of Pt/C-JM as determined by electrochemical impedance spectroscopy. The results showed that a great potential exist to improve the catalytic performance of low temperature PEM fuel electrocatalysts at a reduced cost as compared to that of pure Pt provided a method of controlling the particle size was established.
- Full Text:
- Date Issued: 2012
The accelerated life cycle testing and modelling of Li-ion cells used in electric vehicle applications
- Authors: Rossouw, Claire Angela
- Date: 2012
- Subjects: Lithium Ions , Electric batteries , Energy storage , Electric vehicles -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10417 , http://hdl.handle.net/10948/d1012709 , Lithium Ions , Electric batteries , Energy storage , Electric vehicles -- Power supply
- Description: Li-ion batteries have become one of the chosen energy storage devices that are used in applications such as power tools, cellular phones and electric vehicles (EV). With the demand for portable high energy density devices, the rechargeable Li-ion battery has become one of the more viable energy storage systems for large scale commercial EVs because of their higher energy density to weight or volume ratio when compared to other current commercial battery energy storage systems. Various safety procedures for the use of Li-ion batteries in both consumer and EV applications have been developed by the international associations. The test procedures studied in this dissertation demonstrated the importance of determining the true capacity of a cell at various discharge rates. For this, the well known Peukert test was demonstrated. The study also showed that cells with different battery geometries and chemistries would demonstrate different thermal heating during discharge and slightly different Ragone results if different test methods were used as reported in the literature. Accelerated ageing tests were done on different cells at different Depth-of-Discharge (DoD) regions. The different DoD regions were determined according to expected stresses the electrode material in a cell would experience when discharged to specific DoD that follows the discharge voltage profile. Electrochemical Impedance Spectroscopy (EIS) was used to measure various electrochemical changes within these cells. The EIS results showed that certain observed modelled parameters would change similarly to the ageing of the cell as it aged due to the accelerated testing. EIS was also done on cells at different State-of-Charge (SoC) and temperatures. The results showed that EIS can be used as an effective technique to observe changes within a Li-ion cell as the SoC or temperature changed. For automotive vehicles that are powered by a fuel cell or battery, a supercapacitor can be coupled to a battery in order to increase and optimize the energy and power densities of the drive systems. A test procedure in the literature that evaluated the use of capacitors with Pb-acid batteries was applied to Li-ion type cells in order to quantify the increased power due to the use of a supercapacitor with a Li-ion cell. Both a cylindrical LiCoO2 cell and a VRLA Pb-acid cell showed some additional charge acceptance and delivery when connected to the supercapacitors. A LiMn2O4 pouch cell showed significant charge acceptance and delivery when connected to supercapacitors. The amount of additional charge acceptance and delivery of the different combinations could be explained by EIS, in particular, the resistance and capacitance of the cell in comparison to the combination of the cell and supercapacitor. A large capacity LiCoO2 cell showed high charge acceptance and delivery without connection with a supercapacitor. The study proved that EIS can be used to model the changes within cells under the different conditions and using different test procedures.
- Full Text:
- Date Issued: 2012
- Authors: Rossouw, Claire Angela
- Date: 2012
- Subjects: Lithium Ions , Electric batteries , Energy storage , Electric vehicles -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10417 , http://hdl.handle.net/10948/d1012709 , Lithium Ions , Electric batteries , Energy storage , Electric vehicles -- Power supply
- Description: Li-ion batteries have become one of the chosen energy storage devices that are used in applications such as power tools, cellular phones and electric vehicles (EV). With the demand for portable high energy density devices, the rechargeable Li-ion battery has become one of the more viable energy storage systems for large scale commercial EVs because of their higher energy density to weight or volume ratio when compared to other current commercial battery energy storage systems. Various safety procedures for the use of Li-ion batteries in both consumer and EV applications have been developed by the international associations. The test procedures studied in this dissertation demonstrated the importance of determining the true capacity of a cell at various discharge rates. For this, the well known Peukert test was demonstrated. The study also showed that cells with different battery geometries and chemistries would demonstrate different thermal heating during discharge and slightly different Ragone results if different test methods were used as reported in the literature. Accelerated ageing tests were done on different cells at different Depth-of-Discharge (DoD) regions. The different DoD regions were determined according to expected stresses the electrode material in a cell would experience when discharged to specific DoD that follows the discharge voltage profile. Electrochemical Impedance Spectroscopy (EIS) was used to measure various electrochemical changes within these cells. The EIS results showed that certain observed modelled parameters would change similarly to the ageing of the cell as it aged due to the accelerated testing. EIS was also done on cells at different State-of-Charge (SoC) and temperatures. The results showed that EIS can be used as an effective technique to observe changes within a Li-ion cell as the SoC or temperature changed. For automotive vehicles that are powered by a fuel cell or battery, a supercapacitor can be coupled to a battery in order to increase and optimize the energy and power densities of the drive systems. A test procedure in the literature that evaluated the use of capacitors with Pb-acid batteries was applied to Li-ion type cells in order to quantify the increased power due to the use of a supercapacitor with a Li-ion cell. Both a cylindrical LiCoO2 cell and a VRLA Pb-acid cell showed some additional charge acceptance and delivery when connected to the supercapacitors. A LiMn2O4 pouch cell showed significant charge acceptance and delivery when connected to supercapacitors. The amount of additional charge acceptance and delivery of the different combinations could be explained by EIS, in particular, the resistance and capacitance of the cell in comparison to the combination of the cell and supercapacitor. A large capacity LiCoO2 cell showed high charge acceptance and delivery without connection with a supercapacitor. The study proved that EIS can be used to model the changes within cells under the different conditions and using different test procedures.
- Full Text:
- Date Issued: 2012
The analysis of the strain level and the predicted human error probability for critical hospital tasks
- Authors: Burford, Eva-Maria
- Date: 2012
- Subjects: Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5104 , http://hdl.handle.net/10962/d1005182 , Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Description: South African hospitals, as a result of numerous factors, have the problem of an increasing workload for nursing staff, which in turn may affect patient treatment quality. This project aimed at addressing patient treatment quality specifically from the perspective of worker capabilities by investigating the strain level and predicted human error probability associated with specific patient-centered tasks in the South African health care sector. This was achieved through two independent yet interlinked studies which focused on seven patient-centred tasks. The tasks analysed were the tasks of setting up and changing intravenous medication, administering injection and pill medication, measuring blood glucose, temperature and heart rate and blood pressure. In the first study, work environment and task characteristics, task structure and execution were analysed. In addition to the task execution, the resulting strain levels, in the form of heart rate measures and subjective ratings of workload, were studied. The second study determined the error protocols and predictive error probability within the healthcare environment for the seven pre-defined tasks. The results for the first study established that different organizational and environment factors could affect task complexity and workload. The individual task components and information processing requirements for each task was also established. For the strain analysis, significant results for the tasks were determined for heart rate frequency and the heart rate variability measures, but some of these were contradictory. For the second study, specific error protocols and error reporting data were determined for the hospital where this research was conducted. Additionally the predictive error probability for the pre-defined tasks was determined. This combined approach and collective results indicate that strain and predictive error probability as a result of task workload can be determined in the field as well as being able to identify which factors have an effect on task strain and error probability. The value of this research lies in the foundation that the gathered information provides and the numerous potential applications of this data. These applications include providing recommendations aimed at improving nursing work environment with regards to workload, improving patient treatment as a result of a reduction in errors and the potential foundation these results provide for future research
- Full Text:
- Date Issued: 2012
- Authors: Burford, Eva-Maria
- Date: 2012
- Subjects: Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5104 , http://hdl.handle.net/10962/d1005182 , Nursing errors -- South Africa -- Prevention , Nursing -- South Africa -- Psychological aspects , Hospitals -- Employees -- Health and hygiene -- South Africa , Nursing -- Job stress -- South Africa
- Description: South African hospitals, as a result of numerous factors, have the problem of an increasing workload for nursing staff, which in turn may affect patient treatment quality. This project aimed at addressing patient treatment quality specifically from the perspective of worker capabilities by investigating the strain level and predicted human error probability associated with specific patient-centered tasks in the South African health care sector. This was achieved through two independent yet interlinked studies which focused on seven patient-centred tasks. The tasks analysed were the tasks of setting up and changing intravenous medication, administering injection and pill medication, measuring blood glucose, temperature and heart rate and blood pressure. In the first study, work environment and task characteristics, task structure and execution were analysed. In addition to the task execution, the resulting strain levels, in the form of heart rate measures and subjective ratings of workload, were studied. The second study determined the error protocols and predictive error probability within the healthcare environment for the seven pre-defined tasks. The results for the first study established that different organizational and environment factors could affect task complexity and workload. The individual task components and information processing requirements for each task was also established. For the strain analysis, significant results for the tasks were determined for heart rate frequency and the heart rate variability measures, but some of these were contradictory. For the second study, specific error protocols and error reporting data were determined for the hospital where this research was conducted. Additionally the predictive error probability for the pre-defined tasks was determined. This combined approach and collective results indicate that strain and predictive error probability as a result of task workload can be determined in the field as well as being able to identify which factors have an effect on task strain and error probability. The value of this research lies in the foundation that the gathered information provides and the numerous potential applications of this data. These applications include providing recommendations aimed at improving nursing work environment with regards to workload, improving patient treatment as a result of a reduction in errors and the potential foundation these results provide for future research
- Full Text:
- Date Issued: 2012
The biota of the Swartkops Solar Saltworks and their potential for producing biofuels
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
The contribution of the trade in medicinal plants to urban livelihoods: a case study of the informal markets in Nelson Mandela Bay Municipality, Eastern Cape
- Ah Goo, Delia Felecia Stephanie
- Authors: Ah Goo, Delia Felecia Stephanie
- Date: 2012
- Subjects: Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10654 , http://hdl.handle.net/10948/d1011601 , Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Description: The commercialisation of natural resources such as medicinal plants is a strategy that is increasingly being employed by poor people in developing countries such as South Africa, as a means of generating an income. Increasing economic hardship and a lack of employment opportunities in the formal sector of the economy has led to many urban dwellers seeking alternative means of meeting their everyday livelihood needs. Although the contribution of natural resources to subsistence economies is widely recognised, there are few studies that have examined the significance of the trade in medicinal plants to the livelihoods of poor and marginalised people. Thirty informal street traders were interviewed to investigate the role of the medicinal plant trade in sustaining the livelihoods of the traders who operate in the informal sector of the Nelson Mandela Bay Municipality, South Africa. The findings of the research indicate that the sale and collection of medicinal plants is an activity which is exploited by people with limited resources, few skills, little or no education and often without any other source of household income. Middle-aged women from impoverished, single income households dominated the trade. Although income from the trade is modest, it contributed substantially to the total household cash income of the traders. Other benefits of the trade included independence and having a sense of purpose in life, as the traders felt that they were not only helping their families but also the wider community. However, without the income from the trade, many of the traders and their families would be destitute and thus the medicinal plant trade is vital to the wellbeing of these people.
- Full Text:
- Date Issued: 2012
- Authors: Ah Goo, Delia Felecia Stephanie
- Date: 2012
- Subjects: Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10654 , http://hdl.handle.net/10948/d1011601 , Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Description: The commercialisation of natural resources such as medicinal plants is a strategy that is increasingly being employed by poor people in developing countries such as South Africa, as a means of generating an income. Increasing economic hardship and a lack of employment opportunities in the formal sector of the economy has led to many urban dwellers seeking alternative means of meeting their everyday livelihood needs. Although the contribution of natural resources to subsistence economies is widely recognised, there are few studies that have examined the significance of the trade in medicinal plants to the livelihoods of poor and marginalised people. Thirty informal street traders were interviewed to investigate the role of the medicinal plant trade in sustaining the livelihoods of the traders who operate in the informal sector of the Nelson Mandela Bay Municipality, South Africa. The findings of the research indicate that the sale and collection of medicinal plants is an activity which is exploited by people with limited resources, few skills, little or no education and often without any other source of household income. Middle-aged women from impoverished, single income households dominated the trade. Although income from the trade is modest, it contributed substantially to the total household cash income of the traders. Other benefits of the trade included independence and having a sense of purpose in life, as the traders felt that they were not only helping their families but also the wider community. However, without the income from the trade, many of the traders and their families would be destitute and thus the medicinal plant trade is vital to the wellbeing of these people.
- 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
The development of an orodispersible sildenafil citrate tablet intended for paediatric use
- Authors: Dagnolo, Bianca
- Date: 2012
- Subjects: Drug development -- Children -- Research -- South Africa , Pulmonary hypertension -- Children -- Research , Tablets (Medicine) -- Development , Pharmaceutical chemistry -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3751 , http://hdl.handle.net/10962/d1003229 , Drug development -- Children -- Research -- South Africa , Pulmonary hypertension -- Children -- Research , Tablets (Medicine) -- Development , Pharmaceutical chemistry -- Research
- Description: Sildenafil citrate (SC) is a phosphodiesterase-5 inhibitor that is used to treat pulmonary hypertension (PH) in paediatric patients. The purpose of these studies was to develop a formulation and manufacture an orodispersible tablet (ODT) that can be easily administered to neonates and children with PH. The advantages of ODT dosage forms include ease of administration, rapid dissolution of the API, SC. Furthermore the dosage form can be taken without water which is beneficial to patients without immediate access to potable fluids. A simple, rapid, accurate, precise and selective reversed-phase HPLC method was developed and validated in accordance with International Conference on Harmonization (ICH) guidelines and was successfully used for the analysis of SC as raw material and in SC containing pharmaceutical dosage forms. Preformulation studies were performed on SC, alone and in combination with potential excipients that could be used to make tablets. Investigations into potential interactions between SC and the excipients were performed using Differential Scanning Calorimetry (DSC) and Infrared Spectroscopy (IR). DSC results revealed that SC was compatible with all potential excipients except mannitol and magnesium stearate. However these interactions were not observed with IR and therefore it was concluded that the interactions were induced by the high temperatures that DSC operates at. Particle size and shape was also established by use of Scanning Electron Microscopy (SEM) and flow properties were monitored by calculating Carr’s Index (CI) and the Hausner Ratio (HR). Direct compression was used as the method of manufacture for SC tablets as this approach is simple and the most economic production approach. The powder blends were assessed for bulk and tapped density and the CI and HR were used to determine the flowability of the blends. The quality attributes of the resultant tablets that were monitored included uniformity of weight, friability, crushing strength, tensile strength, disintegration, wetting and in vitro dispersion times. Design of Experiments is an efficient statistical approach that has become a popular tool used in the pharmaceutical industry to optimize formulation compositions, as it allows for the investigation of several input factors at the same time whilst not using the tedious and traditional “ modification of one variable at a time” approach. A Central composite experimental design was chosen as the most appropriate means to optimize the formulation as it produces more accurate results as opposed to other experimental designs approaches as input factors are investigated at five different levels. Through the use of mathematical modelling, optimum concentrations of disintegrant(s) and an appropriate blending time were established. Analysis of the data from the experimental design and mathematical modelling studies reveal that no changes in disintegrant concentration or blending time altered the disintegration time of the formulation to any significant extent. This result is most likely due to the fact that the critical disintegrant concentration has been reached and increasing the disintegrant concentration further has no effect on disintegration time. It was also established that a change in the concentration of CMS and CRP altered the wetting time of the tablet significantly. Finally it was noted that there was a linear relationship between blending time and the uniformity of content of the tablets produced in these studies. The optimized product was a white tablet with a diameter of 7.31 mm with a thickness of 2.80mm.The dosage form had no visible cracks or evidence of picking or sticking. The tablet exhibits suitable friability and tensile strength while exhibiting a disintegration time of only 8s. Therefore an orodispersible tablet containing SC intended for paediatric use has been successfully developed, manufactured and optimized through the use of preformulation studies, appropriate quality control monitoring and mathematical modelling. These formulations require further optimization in respect of addition of flavours and or additional sweetening agents.
- Full Text:
- Date Issued: 2012
- Authors: Dagnolo, Bianca
- Date: 2012
- Subjects: Drug development -- Children -- Research -- South Africa , Pulmonary hypertension -- Children -- Research , Tablets (Medicine) -- Development , Pharmaceutical chemistry -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3751 , http://hdl.handle.net/10962/d1003229 , Drug development -- Children -- Research -- South Africa , Pulmonary hypertension -- Children -- Research , Tablets (Medicine) -- Development , Pharmaceutical chemistry -- Research
- Description: Sildenafil citrate (SC) is a phosphodiesterase-5 inhibitor that is used to treat pulmonary hypertension (PH) in paediatric patients. The purpose of these studies was to develop a formulation and manufacture an orodispersible tablet (ODT) that can be easily administered to neonates and children with PH. The advantages of ODT dosage forms include ease of administration, rapid dissolution of the API, SC. Furthermore the dosage form can be taken without water which is beneficial to patients without immediate access to potable fluids. A simple, rapid, accurate, precise and selective reversed-phase HPLC method was developed and validated in accordance with International Conference on Harmonization (ICH) guidelines and was successfully used for the analysis of SC as raw material and in SC containing pharmaceutical dosage forms. Preformulation studies were performed on SC, alone and in combination with potential excipients that could be used to make tablets. Investigations into potential interactions between SC and the excipients were performed using Differential Scanning Calorimetry (DSC) and Infrared Spectroscopy (IR). DSC results revealed that SC was compatible with all potential excipients except mannitol and magnesium stearate. However these interactions were not observed with IR and therefore it was concluded that the interactions were induced by the high temperatures that DSC operates at. Particle size and shape was also established by use of Scanning Electron Microscopy (SEM) and flow properties were monitored by calculating Carr’s Index (CI) and the Hausner Ratio (HR). Direct compression was used as the method of manufacture for SC tablets as this approach is simple and the most economic production approach. The powder blends were assessed for bulk and tapped density and the CI and HR were used to determine the flowability of the blends. The quality attributes of the resultant tablets that were monitored included uniformity of weight, friability, crushing strength, tensile strength, disintegration, wetting and in vitro dispersion times. Design of Experiments is an efficient statistical approach that has become a popular tool used in the pharmaceutical industry to optimize formulation compositions, as it allows for the investigation of several input factors at the same time whilst not using the tedious and traditional “ modification of one variable at a time” approach. A Central composite experimental design was chosen as the most appropriate means to optimize the formulation as it produces more accurate results as opposed to other experimental designs approaches as input factors are investigated at five different levels. Through the use of mathematical modelling, optimum concentrations of disintegrant(s) and an appropriate blending time were established. Analysis of the data from the experimental design and mathematical modelling studies reveal that no changes in disintegrant concentration or blending time altered the disintegration time of the formulation to any significant extent. This result is most likely due to the fact that the critical disintegrant concentration has been reached and increasing the disintegrant concentration further has no effect on disintegration time. It was also established that a change in the concentration of CMS and CRP altered the wetting time of the tablet significantly. Finally it was noted that there was a linear relationship between blending time and the uniformity of content of the tablets produced in these studies. The optimized product was a white tablet with a diameter of 7.31 mm with a thickness of 2.80mm.The dosage form had no visible cracks or evidence of picking or sticking. The tablet exhibits suitable friability and tensile strength while exhibiting a disintegration time of only 8s. Therefore an orodispersible tablet containing SC intended for paediatric use has been successfully developed, manufactured and optimized through the use of preformulation studies, appropriate quality control monitoring and mathematical modelling. These formulations require further optimization in respect of addition of flavours and or additional sweetening agents.
- Full Text:
- Date Issued: 2012
The diet and ecological role of black-backed jackals, Canis Mesomelas, in two conservation areas in the Eastern Cape Province, South Africa
- Authors: Brassine, Mathilde Chloé
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5660 , http://hdl.handle.net/10962/d1005344 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Description: Mammalian predators are keystone species and can have disproportionately large impacts, relative to their abundance, on the communities and ecosystems they inhabit. In addition, predator-prey interactions (including bottom-up and top-down effects) are the fundamental linkage among species in food webs. Thus, understanding the food requirements of predators is imperative. There have been no comprehensive studies on the diet of black-backed jackals (Canis mesomelas) across a full seasonal cycle in the Albany Thicket Biome of the Eastern Cape Province. This biome is rich in plant diversity, is highly nutritious for herbivores and supports a large number of mammalian species, yet it is poorly conserved. The aim of the present study was to establish the diet of black-backed jackals on two conservation areas where thicket vegetation dominates (Great Fish River Reserve and Kwandwe Private Game Reserve). The diet was assessed using scats collected monthly from June 2009 to May 2010 and a sample of 25 stomachs over the same period. At both sites and across all seasons, mammalian hair was encountered most often (93% of all scats) and a total of 23 mammal species were consumed. Of the mammals recorded in the scats, hair from several ungulate species was encountered most frequently and these were mostly hider species (offspring hidden in tall vegetation just after birth). On a seasonal basis, the proportion of mammalian hair was lowest in autumn. However, the contribution of fruits (Carissa haematocarpa, Diospyros lycioides and Grewia robusta) to the diet was significantly higher during this season. This suggests that black-backed jackals may employ diet switching in the Eastern Cape as a mechanism to capitalise on seasonally abundant food sources. Based on the stomach content analysis, invertebrates were consumed as frequently as mammalian prey throughout the year but mammalian prey was recorded in greater quantity (i.e. volume and mass). Thus, scat analysis may have overestimated mammalian prey and fruits and underestimated the importance of invertebrates, particularly highly digestible species (e.g. termites). In spite of these differences, scat analysis demonstrated similar general and seasonal trends as the stomach content analysis. Thus, scat analysis can provide an efficient and relatively accurate source of information on the diet of blackbacked jackals in the Eastern Cape. Both stomach content and scat collection methods depicted the black-backed jackal as a generalist and opportunistic predator, mainly relying on mammals and invertebrates. Although the results of my study suggest that black-backed jackal may be important predators of certain ungulate species, further study on their prey preferences, actual biomass ingested and the effects on the population viability of prey species is required in order to develop a robust management plan for the species in the protected areas of the Eastern Cape.
- Full Text:
- Date Issued: 2012
- Authors: Brassine, Mathilde Chloé
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5660 , http://hdl.handle.net/10962/d1005344 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Description: Mammalian predators are keystone species and can have disproportionately large impacts, relative to their abundance, on the communities and ecosystems they inhabit. In addition, predator-prey interactions (including bottom-up and top-down effects) are the fundamental linkage among species in food webs. Thus, understanding the food requirements of predators is imperative. There have been no comprehensive studies on the diet of black-backed jackals (Canis mesomelas) across a full seasonal cycle in the Albany Thicket Biome of the Eastern Cape Province. This biome is rich in plant diversity, is highly nutritious for herbivores and supports a large number of mammalian species, yet it is poorly conserved. The aim of the present study was to establish the diet of black-backed jackals on two conservation areas where thicket vegetation dominates (Great Fish River Reserve and Kwandwe Private Game Reserve). The diet was assessed using scats collected monthly from June 2009 to May 2010 and a sample of 25 stomachs over the same period. At both sites and across all seasons, mammalian hair was encountered most often (93% of all scats) and a total of 23 mammal species were consumed. Of the mammals recorded in the scats, hair from several ungulate species was encountered most frequently and these were mostly hider species (offspring hidden in tall vegetation just after birth). On a seasonal basis, the proportion of mammalian hair was lowest in autumn. However, the contribution of fruits (Carissa haematocarpa, Diospyros lycioides and Grewia robusta) to the diet was significantly higher during this season. This suggests that black-backed jackals may employ diet switching in the Eastern Cape as a mechanism to capitalise on seasonally abundant food sources. Based on the stomach content analysis, invertebrates were consumed as frequently as mammalian prey throughout the year but mammalian prey was recorded in greater quantity (i.e. volume and mass). Thus, scat analysis may have overestimated mammalian prey and fruits and underestimated the importance of invertebrates, particularly highly digestible species (e.g. termites). In spite of these differences, scat analysis demonstrated similar general and seasonal trends as the stomach content analysis. Thus, scat analysis can provide an efficient and relatively accurate source of information on the diet of blackbacked jackals in the Eastern Cape. Both stomach content and scat collection methods depicted the black-backed jackal as a generalist and opportunistic predator, mainly relying on mammals and invertebrates. Although the results of my study suggest that black-backed jackal may be important predators of certain ungulate species, further study on their prey preferences, actual biomass ingested and the effects on the population viability of prey species is required in order to develop a robust management plan for the species in the protected areas of the Eastern Cape.
- Full Text:
- Date Issued: 2012
The diet of black-backed jackal (Canis Mesomelas) on two contrasting land-use types in the Eastern Cape Province, South Africa and the validation of a new analytical method of mammalian hair identification
- Authors: Forbes, Ross William
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5661 , http://hdl.handle.net/10962/d1005345 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Description: Diet assessments are critical for understanding the foraging behaviour, habitat use and trophic separation of mammalian predators and are vital for gaining insight into how predators influence prey populations. The aim of this research was to qualitatively describe the diet of black-backed jackals (Canis mesomelas, Schreber 1775) using scat analysis on two contrasting land-use types in the Eastern Cape Province, South Africa. Scats were collected on a monthly basis from November 2009 to October 2010 from two game reserves (Great Fish River Reserve and Shamwari Private Game Reserve) and two neighbouring livestock farms. The relative frequency of occurrence of mammal hair (33 – 47 %) and vegetation (32 – 45%)dominated jackal diet throughout the year across the four study sites. Other important prey items included invertebrates (8 – 21 %) and fruit and seeds (3 – 11 %). Birds and reptiles constituted ≤ 2 % of the diet and were only recorded on the game reserves. Significant seasonal dietary shifts were observed on the game reserves but not on the farms. Fruit and seeds were significantly more frequent in the diet during autumn at Great Fish River Reserve and invertebrates were significantly less common in the diet during winter on both reserves. In addition, vegetation was significantly more common in the diet during winter at Shamwari Private Game Reserve. The significant temporal variation of certain prey items is testament to black-backed jackals being opportunistic generalists, foraging on those food items which are most abundant, accessible and energetically beneficial. Land-use type also influenced the diet of black-backed jackals with significantly more invertebrates and, fruit and seeds being recorded on the game reserves than on the farms. By contrast, significantly more mammal hair and vegetation were present in the diet on the farms compared with the game reserves. The mammalian component of the diet was dominated by ruminants and rodents on the game reserves and by ruminants and livestock on the farms. The presence of livestock in the diet of black-backed jackals on the farms highlights their potential impact on the livestock industry in the region and may assist farmers in determining which predators are responsible for stock loss. Previous approaches for identifying mammalian hairs from predator scats have utilised dichotomous keys and reference collections but these are often time-consuming and require a trained individual to carry out the identification. Thus, I also tested the efficacy of an automated pattern recognition programme (HairSnap) for identifying mammalian hairs from black-backed jackal scats. The overall accuracy of the programme was 38 % with black-backed jackal, Greater kudu (Tragelaphus strepsiceros) and striped polecat (Ictonyx striatus) hairs being accurately identified more often (70 – 80 %) than any other species tested. It is likely that both the size and species composition of the sample resulted in the poor accuracy of the programme. However, with the implementation of several improvement measures (e.g. adjustment of the algorithm) the programme may offer a superior, bias-free method of mammalian hair identification. The dietary information gathered here furthers our knowledge of the biology of the blackbacked jackals, especially in the locally important thicket biome. Moreover, understanding their foraging habits allows for more effective management of the species on both game reserves and farmlands. I recommend that future research should focus on quantitatively assessing the diet of black-backed jackals in the Eastern Cape Province and elsewhere. This will compliment the dietary description provided in this study and may offer a biologically more meaningful indication of the relative importance of the prey items.
- Full Text:
- Date Issued: 2012
- Authors: Forbes, Ross William
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5661 , http://hdl.handle.net/10962/d1005345 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Description: Diet assessments are critical for understanding the foraging behaviour, habitat use and trophic separation of mammalian predators and are vital for gaining insight into how predators influence prey populations. The aim of this research was to qualitatively describe the diet of black-backed jackals (Canis mesomelas, Schreber 1775) using scat analysis on two contrasting land-use types in the Eastern Cape Province, South Africa. Scats were collected on a monthly basis from November 2009 to October 2010 from two game reserves (Great Fish River Reserve and Shamwari Private Game Reserve) and two neighbouring livestock farms. The relative frequency of occurrence of mammal hair (33 – 47 %) and vegetation (32 – 45%)dominated jackal diet throughout the year across the four study sites. Other important prey items included invertebrates (8 – 21 %) and fruit and seeds (3 – 11 %). Birds and reptiles constituted ≤ 2 % of the diet and were only recorded on the game reserves. Significant seasonal dietary shifts were observed on the game reserves but not on the farms. Fruit and seeds were significantly more frequent in the diet during autumn at Great Fish River Reserve and invertebrates were significantly less common in the diet during winter on both reserves. In addition, vegetation was significantly more common in the diet during winter at Shamwari Private Game Reserve. The significant temporal variation of certain prey items is testament to black-backed jackals being opportunistic generalists, foraging on those food items which are most abundant, accessible and energetically beneficial. Land-use type also influenced the diet of black-backed jackals with significantly more invertebrates and, fruit and seeds being recorded on the game reserves than on the farms. By contrast, significantly more mammal hair and vegetation were present in the diet on the farms compared with the game reserves. The mammalian component of the diet was dominated by ruminants and rodents on the game reserves and by ruminants and livestock on the farms. The presence of livestock in the diet of black-backed jackals on the farms highlights their potential impact on the livestock industry in the region and may assist farmers in determining which predators are responsible for stock loss. Previous approaches for identifying mammalian hairs from predator scats have utilised dichotomous keys and reference collections but these are often time-consuming and require a trained individual to carry out the identification. Thus, I also tested the efficacy of an automated pattern recognition programme (HairSnap) for identifying mammalian hairs from black-backed jackal scats. The overall accuracy of the programme was 38 % with black-backed jackal, Greater kudu (Tragelaphus strepsiceros) and striped polecat (Ictonyx striatus) hairs being accurately identified more often (70 – 80 %) than any other species tested. It is likely that both the size and species composition of the sample resulted in the poor accuracy of the programme. However, with the implementation of several improvement measures (e.g. adjustment of the algorithm) the programme may offer a superior, bias-free method of mammalian hair identification. The dietary information gathered here furthers our knowledge of the biology of the blackbacked jackals, especially in the locally important thicket biome. Moreover, understanding their foraging habits allows for more effective management of the species on both game reserves and farmlands. I recommend that future research should focus on quantitatively assessing the diet of black-backed jackals in the Eastern Cape Province and elsewhere. This will compliment the dietary description provided in this study and may offer a biologically more meaningful indication of the relative importance of the prey items.
- Full Text:
- Date Issued: 2012
The dispersal of African wild dogs (Lycaon Pictus) from protected areas in the Northern KwaZulu‐Natal Province, South Africa.
- Whittington‐Jones, Brendan Mark
- Authors: Whittington‐Jones, Brendan Mark
- Date: 2012
- Subjects: African wild dog , African wild dog -- Conservation -- South Africa -- KwazuluNatal , African wild dog -- Dispersal -- South Africa -- KwaZulu-Natal , African wild dog -- Effect of human beings on -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5893 , http://hdl.handle.net/10962/d1013414
- Description: The number of African wild dogs Lycaon pictus in Northern KwaZulu‐Natal, South Africa has increased substantially over the last six years. This is largely due to a managed metapopulation approach of introductions onto protected areas and private game reserves since 1998. Because of the increasing wild dog population, the likelihood of rural communities surrounding protected areas encountering dispersing wild dogs in northern KwaZulu‐Natal has also increased. Resident wild dog populations currently occur in Hluhluwe‐iMfolozi Park (HiP), Mkhuze Game Reserve (MGR) of Isimangaliso Wetland Park and Thanda Private Game Reserve (TPGR) all of which are bordered by a matrix of natural habitats and human settlements. Thus, land outside these protected areas could be utilized to expand wild dog distribution and provide connectivity between existing resident populations of wild dogs within KwaZulu‐Natal. To investigate the viability of such an approach, Maximum Entropy Modelling (Maxent) was used to characterize habitat niche selection of dispersing wild dogs, and to identify potential dispersal linkages between current wild dog metapopulation reserves. The model was calibrated using 132 location points collected from 2006 until 2009. From 2008 to 2009 I also conducted a survey of 247 community members in tribal authorities bordering HiP and MGR, to understand factors influencing attitudes towards wild dogs. A habitat suitability model with seven predictor variables had an AUC of 0.96 (SD = 0.02) and indicated four variables which best predicted probability of presence for dispersing wild dogs: elevation, road density, land cover and human density. The results suggest that elevation and land cover may be of greater influence for dispersing wild dogs than human density or activity. Elevation was the single most effective variable indicating a higher probability of presence for dispersing wild dogs in lower lying locations; peaking at approximately 200 – 300m a.s.l. Wild dogs also showed a preference for Woodland and Bushland habitats which in KwaZulu‐Natal tend to be found on lower lying topography. A preference for areas of lower human density and a highest probability of presence at road densities of approximately 0.7km/km2 or less would suggest that while wild dogs may show a tendency to avoid areas of high human activity, they can coexist in close proximity to humans. Respondent’s attitudes, knowledge of wild dogs and livestock husbandry were interpreted by the development of a set of indices. Attitudes were positively related to formal education levels and wild dog‐specific education, but were not influenced by demographic factors such as gender, age and employment status. Eighty three percent of respondents believed efforts to protect wild dogs should continue. Respondents with higher numbers of livestock tended to have more positive attitudes towards wild dogs despite generally incurring higher losses to carnivore depredation than those with less livestock. This appears to be because the financial burden of livestock losses to those with fewer livestock is perceived to be a loss of a greater proportion of total financial wealth. The study highlighted the substantial scope for improvement in livestock management. Theft (34 percent), drought (30 percent) and disease (14 percent) were ranked as the greatest problems facing livestock owners while predators were ranked as the greatest problem by only 4 percent of respondents. My findings suggest that wild dogs are generally viewed positively or with ambivalence. Concerns over the potentially increasing threat to livestock, as natural prey numbers outside protected areas decline and wild dogs disperse from natal packs, are likely to be manageable. However, wild dog population expansion within KwaZulu‐Natal will continue to rely on managed core populations on perimeter‐fenced metapopulation reserves with tolerant communities and landowners contributing to the connectivity of isolated reserves. Generation of tolerance can be instilled through continued advocacy and education, supported by conflict mitigation initiatives and rapid response to conflict reports. The implementation of incentive schemes for adjoining private landowners to co‐manage wild dog populations will need to be addressed in conjunction with managed metapopulation practices and law enforcement, to promote range expansion, and reduce potentially lethal edge effects and wild dog‐human conflict.
- Full Text:
- Date Issued: 2012
- Authors: Whittington‐Jones, Brendan Mark
- Date: 2012
- Subjects: African wild dog , African wild dog -- Conservation -- South Africa -- KwazuluNatal , African wild dog -- Dispersal -- South Africa -- KwaZulu-Natal , African wild dog -- Effect of human beings on -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5893 , http://hdl.handle.net/10962/d1013414
- Description: The number of African wild dogs Lycaon pictus in Northern KwaZulu‐Natal, South Africa has increased substantially over the last six years. This is largely due to a managed metapopulation approach of introductions onto protected areas and private game reserves since 1998. Because of the increasing wild dog population, the likelihood of rural communities surrounding protected areas encountering dispersing wild dogs in northern KwaZulu‐Natal has also increased. Resident wild dog populations currently occur in Hluhluwe‐iMfolozi Park (HiP), Mkhuze Game Reserve (MGR) of Isimangaliso Wetland Park and Thanda Private Game Reserve (TPGR) all of which are bordered by a matrix of natural habitats and human settlements. Thus, land outside these protected areas could be utilized to expand wild dog distribution and provide connectivity between existing resident populations of wild dogs within KwaZulu‐Natal. To investigate the viability of such an approach, Maximum Entropy Modelling (Maxent) was used to characterize habitat niche selection of dispersing wild dogs, and to identify potential dispersal linkages between current wild dog metapopulation reserves. The model was calibrated using 132 location points collected from 2006 until 2009. From 2008 to 2009 I also conducted a survey of 247 community members in tribal authorities bordering HiP and MGR, to understand factors influencing attitudes towards wild dogs. A habitat suitability model with seven predictor variables had an AUC of 0.96 (SD = 0.02) and indicated four variables which best predicted probability of presence for dispersing wild dogs: elevation, road density, land cover and human density. The results suggest that elevation and land cover may be of greater influence for dispersing wild dogs than human density or activity. Elevation was the single most effective variable indicating a higher probability of presence for dispersing wild dogs in lower lying locations; peaking at approximately 200 – 300m a.s.l. Wild dogs also showed a preference for Woodland and Bushland habitats which in KwaZulu‐Natal tend to be found on lower lying topography. A preference for areas of lower human density and a highest probability of presence at road densities of approximately 0.7km/km2 or less would suggest that while wild dogs may show a tendency to avoid areas of high human activity, they can coexist in close proximity to humans. Respondent’s attitudes, knowledge of wild dogs and livestock husbandry were interpreted by the development of a set of indices. Attitudes were positively related to formal education levels and wild dog‐specific education, but were not influenced by demographic factors such as gender, age and employment status. Eighty three percent of respondents believed efforts to protect wild dogs should continue. Respondents with higher numbers of livestock tended to have more positive attitudes towards wild dogs despite generally incurring higher losses to carnivore depredation than those with less livestock. This appears to be because the financial burden of livestock losses to those with fewer livestock is perceived to be a loss of a greater proportion of total financial wealth. The study highlighted the substantial scope for improvement in livestock management. Theft (34 percent), drought (30 percent) and disease (14 percent) were ranked as the greatest problems facing livestock owners while predators were ranked as the greatest problem by only 4 percent of respondents. My findings suggest that wild dogs are generally viewed positively or with ambivalence. Concerns over the potentially increasing threat to livestock, as natural prey numbers outside protected areas decline and wild dogs disperse from natal packs, are likely to be manageable. However, wild dog population expansion within KwaZulu‐Natal will continue to rely on managed core populations on perimeter‐fenced metapopulation reserves with tolerant communities and landowners contributing to the connectivity of isolated reserves. Generation of tolerance can be instilled through continued advocacy and education, supported by conflict mitigation initiatives and rapid response to conflict reports. The implementation of incentive schemes for adjoining private landowners to co‐manage wild dog populations will need to be addressed in conjunction with managed metapopulation practices and law enforcement, to promote range expansion, and reduce potentially lethal edge effects and wild dog‐human conflict.
- Full Text:
- Date Issued: 2012
The distribution and diversity of macroalgae in selected estuaries along the Eastern Cape coast of South Africa
- Authors: Prinsloo, Shireen
- Date: 2012
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10631 , http://hdl.handle.net/10948/d1012314 , Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Description: The growth and accumulation of macroalgae in estuaries are a common sight throughout the world (Boyer and Fong, 2005). Because macroalgae establish such complex but important links with other components within an estuary, it is essential to know which variables control and regulate their occurrences. The type of algae that will occur in an estuary depends however, on the physical and chemical features of the particular estuary (Lobban and Harrison, 1994). The focus of this study was to document and provide a listing of algae from estuaries around the Eastern Cape coast of South Africa and describe the communities which form within each estuarine habitat. The questions posed were: Do algae assemblages differ in estuaries with different environmental conditions? Are different plant communities inhabited by different algae communities? Also, are algae diverse in estuaries that are in a pristine condition? The estuaries were Mngazana, Ngqusi/Nxaxo, Mtati, Mpekweni, East Kleinemonde, West Kleinemonde, Kariega, Bushmans, Kowie and the Sundays estuary. Percentage cover surveys were conducted and environmental parameters recorded to determine community structure of algae and their environmental tolerances. A total of 49 different macroalgal species were identified from 11 estuaries, which were dominated by Chlorophytes (23 species) and Rhodophytes (17 species). The Ochrophytes consisted of 10 species. The highest number of species recorded was 29 at the Bushmans estuary (March 2009), while the lowest number (4 species) was recorded at Mtati (October 2008). Common Chlorophytes found included Ulva prolifera, Chaetomorpha linum and Codium tenue. In the Division Ochrophyta, species from the Genus Ectocarpus were the most common. Of the red algae filamentous reds, Polysiphonia incompta and Polysiphonia kowiensis were the common algae found at estuaries. Salinity (p= 0.029861; n= 49) and temperature (p= 0.037641; n= 49) were the driving environmental parameters of estuaries and significantly influenced richness of species. In ordination analyses, patterns of biogeographic distribution were noticeable and were described by salinity. Four gradients caused by salinity were therefore found – which is inversely correlated to water clarity. Moreover, a clear split between temporarily open/closed and the permanently open estuaries was observed. Samples grouped into four communities presumably based on the similarity in conditions of estuaries. Within each estuarine community and major type of estuary there was a range of environmental conditions. However, the macroalgae within each community may not have been colonists of or found in greatest abundances in the estuaries of these communities per se, but may have grouped together in this manner based on the optimum growing conditions for them. Also, specific algal groups were not directly determined by the type of estuary they were found in; they were driven by environmental ranges rather. The results therefore support hypothesis one which states species distribution and diversity differ and are influenced by environmental gradients of the estuary. Although close species and habitat relationships were apparent from the ordination analyses, providing support for hypothesis two which states “Different plant communities in estuaries will be inhabited by different macroalgae communities”, the evidence was not substantial enough to provide sufficient support for the hypothesis. Lastly, the hypothesis “Macroalgae are diverse in estuaries that are in a pristine condition” was not accepted as highest species numbers were found in estuaries of greatest anthropogenic disturbance (e.g. Bushmans estuary) and not in estuaries which where ecologically more natural (e.g. Mtati estuary). By doing monthly macroalgal sampling over a period of one year for example one would obtain greater information of biodiversity, and patterns of macroalgal seasonality may be uncovered as well. This is an area of reasearch which needs to be investigated in the future as it would greatly add to the understanding of the role macroalge have in an estuarine environment.
- Full Text:
- Date Issued: 2012
- Authors: Prinsloo, Shireen
- Date: 2012
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10631 , http://hdl.handle.net/10948/d1012314 , Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Description: The growth and accumulation of macroalgae in estuaries are a common sight throughout the world (Boyer and Fong, 2005). Because macroalgae establish such complex but important links with other components within an estuary, it is essential to know which variables control and regulate their occurrences. The type of algae that will occur in an estuary depends however, on the physical and chemical features of the particular estuary (Lobban and Harrison, 1994). The focus of this study was to document and provide a listing of algae from estuaries around the Eastern Cape coast of South Africa and describe the communities which form within each estuarine habitat. The questions posed were: Do algae assemblages differ in estuaries with different environmental conditions? Are different plant communities inhabited by different algae communities? Also, are algae diverse in estuaries that are in a pristine condition? The estuaries were Mngazana, Ngqusi/Nxaxo, Mtati, Mpekweni, East Kleinemonde, West Kleinemonde, Kariega, Bushmans, Kowie and the Sundays estuary. Percentage cover surveys were conducted and environmental parameters recorded to determine community structure of algae and their environmental tolerances. A total of 49 different macroalgal species were identified from 11 estuaries, which were dominated by Chlorophytes (23 species) and Rhodophytes (17 species). The Ochrophytes consisted of 10 species. The highest number of species recorded was 29 at the Bushmans estuary (March 2009), while the lowest number (4 species) was recorded at Mtati (October 2008). Common Chlorophytes found included Ulva prolifera, Chaetomorpha linum and Codium tenue. In the Division Ochrophyta, species from the Genus Ectocarpus were the most common. Of the red algae filamentous reds, Polysiphonia incompta and Polysiphonia kowiensis were the common algae found at estuaries. Salinity (p= 0.029861; n= 49) and temperature (p= 0.037641; n= 49) were the driving environmental parameters of estuaries and significantly influenced richness of species. In ordination analyses, patterns of biogeographic distribution were noticeable and were described by salinity. Four gradients caused by salinity were therefore found – which is inversely correlated to water clarity. Moreover, a clear split between temporarily open/closed and the permanently open estuaries was observed. Samples grouped into four communities presumably based on the similarity in conditions of estuaries. Within each estuarine community and major type of estuary there was a range of environmental conditions. However, the macroalgae within each community may not have been colonists of or found in greatest abundances in the estuaries of these communities per se, but may have grouped together in this manner based on the optimum growing conditions for them. Also, specific algal groups were not directly determined by the type of estuary they were found in; they were driven by environmental ranges rather. The results therefore support hypothesis one which states species distribution and diversity differ and are influenced by environmental gradients of the estuary. Although close species and habitat relationships were apparent from the ordination analyses, providing support for hypothesis two which states “Different plant communities in estuaries will be inhabited by different macroalgae communities”, the evidence was not substantial enough to provide sufficient support for the hypothesis. Lastly, the hypothesis “Macroalgae are diverse in estuaries that are in a pristine condition” was not accepted as highest species numbers were found in estuaries of greatest anthropogenic disturbance (e.g. Bushmans estuary) and not in estuaries which where ecologically more natural (e.g. Mtati estuary). By doing monthly macroalgal sampling over a period of one year for example one would obtain greater information of biodiversity, and patterns of macroalgal seasonality may be uncovered as well. This is an area of reasearch which needs to be investigated in the future as it would greatly add to the understanding of the role macroalge have in an estuarine environment.
- Full Text:
- Date Issued: 2012
The effect of dietary fish oil replacement with soybean oil on growth and health of dusky kob, Argyrosomus japonicus (Pisces: Sciaenidae)
- Authors: Rossetti, Nani Adami
- Date: 2012
- Subjects: Sciaenidae , Fish culture , Argyrosomus -- Growth , Argyrosomus -- Feeding and feeds , Argyrosomus -- Health , Fish oils as feed , Soy oil , Lipids , Eicosapentaenoic acid , Docosahexaenoic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5272 , http://hdl.handle.net/10962/d1005116 , Sciaenidae , Fish culture , Argyrosomus -- Growth , Argyrosomus -- Feeding and feeds , Argyrosomus -- Health , Fish oils as feed , Soy oil , Lipids , Eicosapentaenoic acid , Docosahexaenoic acid
- Description: Lipids are essential components for fish because they contain fatty acids that are vital for regular growth and health. Fish oil is rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are essential fatty acids for carnivorous fish, and therefore this product has traditionally been used as the main source of lipids in fish feeds. However, with declining fisheries resources worldwide and the rapid expansion of the aquaculture industry pressuring this finite resource, such ingredients are becoming less available and more expensive. It is therefore necessary to explore the utilization of ingredients that are sustainable and competitive alternatives to fish oil in marine finfish feeds. This work investigated the effects of the substitution of fish oil with soybean oil on the growth performance, feed efficiency, fatty acid composition of the liver tissue and some health parameters in juvenile dusky kob, Argyrosomus japonicus; an increasingly popular sciaenid marine aquaculture species in South Africa. Six diets (18 % total lipid and 46 % protein) with increasing percentage substitution of fish oil with soybean oil (1, 14, 28, 42, 56 and 70 %) were fed to juvenile kob. After 84 days of feeding these diets to the fish, no significant differences in fish length and weight between treatments were observed. However, there was a significant trend of a decrease in specific growth rate, ranging from (± standard error) 0.87 ± 0.06 to 0.72 ± 0.04 % body weight day⁻¹, and condition factor, ranging from 1.59 ± 0.03 to 1.54 ± 0.02, with increasing vegetable oil replacement in the diets between days 56 and 84. There were no differences in red blood cell count, haematocrit and haemoglobin concentration after 206 days of feeding. However, visceral fat index (VFI) increased significantly from 1.08 ± 0.17 % for fish fed diets with 28 % soybean oil, to 2.24 ± 0.15 % for fish fed diets with 70 % soybean oil. Similarly, hepatosomatic index (HSI) increased significantly from 0.84 ± 0.08 % to 1.80 ± 0.12 % in the control diet and the 56 % soybean oil diet, respectively. After 206 days of feeding, fish fed diets with 42 to 70 % soybean oil showed greater number of lipid vacuoles in the liver, which were also larger in size, and hepatocytes nuclei were displaced to the cell periphery. The fatty acid composition of the liver tissue strongly corresponded to the fatty acid composition of the diets. Linoleic acid accumulated in the liver of the fish fed increasing soybean oil in the diets. In contrast, EPA and DHA decreased from 13.63 to 1.97 %, and 14.34 to 3.28 %, respectively, in the liver tissue of fish fed diets with increasing soybean oil content; consequently the n-3/n-6 ratio was also significantly reduced with inclusion of vegetable oil in the diets. The trend of decreasing growth rate with increasing oil replacement towards the end of the trial corresponds with increases in VFI, HSI, as well as the fatty acid accumulation and lipid vacuoles in the liver. This suggests that dusky kob is less able to metabolise soybean oil at increased substitution levels which would account for the poorer growth at higher levels. The dependence of fish on dietary marine oil decreased significantly with each inclusion of soybean oil in the diets. Nonetheless, the calculations based on the nutrient ratio presented positive outcomes for all treatments, that is, values of marine oil dependency ratio were below one for all treatments. It is concluded that soybean oil can replace fish oil in formulated diets for dusky kob up to a level of 28 % of total dietary lipids, as evidenced by the good growth and feed efficiency, and no apparent negative health effects observed up to this level.
- Full Text:
- Date Issued: 2012
- Authors: Rossetti, Nani Adami
- Date: 2012
- Subjects: Sciaenidae , Fish culture , Argyrosomus -- Growth , Argyrosomus -- Feeding and feeds , Argyrosomus -- Health , Fish oils as feed , Soy oil , Lipids , Eicosapentaenoic acid , Docosahexaenoic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5272 , http://hdl.handle.net/10962/d1005116 , Sciaenidae , Fish culture , Argyrosomus -- Growth , Argyrosomus -- Feeding and feeds , Argyrosomus -- Health , Fish oils as feed , Soy oil , Lipids , Eicosapentaenoic acid , Docosahexaenoic acid
- Description: Lipids are essential components for fish because they contain fatty acids that are vital for regular growth and health. Fish oil is rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are essential fatty acids for carnivorous fish, and therefore this product has traditionally been used as the main source of lipids in fish feeds. However, with declining fisheries resources worldwide and the rapid expansion of the aquaculture industry pressuring this finite resource, such ingredients are becoming less available and more expensive. It is therefore necessary to explore the utilization of ingredients that are sustainable and competitive alternatives to fish oil in marine finfish feeds. This work investigated the effects of the substitution of fish oil with soybean oil on the growth performance, feed efficiency, fatty acid composition of the liver tissue and some health parameters in juvenile dusky kob, Argyrosomus japonicus; an increasingly popular sciaenid marine aquaculture species in South Africa. Six diets (18 % total lipid and 46 % protein) with increasing percentage substitution of fish oil with soybean oil (1, 14, 28, 42, 56 and 70 %) were fed to juvenile kob. After 84 days of feeding these diets to the fish, no significant differences in fish length and weight between treatments were observed. However, there was a significant trend of a decrease in specific growth rate, ranging from (± standard error) 0.87 ± 0.06 to 0.72 ± 0.04 % body weight day⁻¹, and condition factor, ranging from 1.59 ± 0.03 to 1.54 ± 0.02, with increasing vegetable oil replacement in the diets between days 56 and 84. There were no differences in red blood cell count, haematocrit and haemoglobin concentration after 206 days of feeding. However, visceral fat index (VFI) increased significantly from 1.08 ± 0.17 % for fish fed diets with 28 % soybean oil, to 2.24 ± 0.15 % for fish fed diets with 70 % soybean oil. Similarly, hepatosomatic index (HSI) increased significantly from 0.84 ± 0.08 % to 1.80 ± 0.12 % in the control diet and the 56 % soybean oil diet, respectively. After 206 days of feeding, fish fed diets with 42 to 70 % soybean oil showed greater number of lipid vacuoles in the liver, which were also larger in size, and hepatocytes nuclei were displaced to the cell periphery. The fatty acid composition of the liver tissue strongly corresponded to the fatty acid composition of the diets. Linoleic acid accumulated in the liver of the fish fed increasing soybean oil in the diets. In contrast, EPA and DHA decreased from 13.63 to 1.97 %, and 14.34 to 3.28 %, respectively, in the liver tissue of fish fed diets with increasing soybean oil content; consequently the n-3/n-6 ratio was also significantly reduced with inclusion of vegetable oil in the diets. The trend of decreasing growth rate with increasing oil replacement towards the end of the trial corresponds with increases in VFI, HSI, as well as the fatty acid accumulation and lipid vacuoles in the liver. This suggests that dusky kob is less able to metabolise soybean oil at increased substitution levels which would account for the poorer growth at higher levels. The dependence of fish on dietary marine oil decreased significantly with each inclusion of soybean oil in the diets. Nonetheless, the calculations based on the nutrient ratio presented positive outcomes for all treatments, that is, values of marine oil dependency ratio were below one for all treatments. It is concluded that soybean oil can replace fish oil in formulated diets for dusky kob up to a level of 28 % of total dietary lipids, as evidenced by the good growth and feed efficiency, and no apparent negative health effects observed up to this level.
- Full Text:
- Date Issued: 2012
The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
The feeding and spatial ecology of cheetahs (Acinonyx jubatus) and lions (Panthera leo) in the Little Karoo, South Africa
- Authors: Vorster, Paul Hendrik
- Date: 2012
- Subjects: Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5693 , http://hdl.handle.net/10962/d1005379 , Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Description: The re-introduction of large carnivores into relatively small conservation areas that fall within the historic distribution range of the species is becoming an increasingly common occurrence. The success of such re-introductions depends very much on the quality of the information that is available to guide management decisions, but in many cases, little information is available. The re-introduction of lions and cheetahs to Sanbona created the opportunity to monitor the behaviour of re-introduced predators to a relatively large system that was characterised by a low ungulate stocking density and little standing water. The broad aims were to study the feeding and spatial ecologies of the lions and cheetahs, to collect standard base-line data, and to examine the effects of the low prey density and limited standing water on habitat selection, range size and diet. The diet (data collected from direct observation and faecal analysis) was similar to that reported in previous studies, and lions and cheetahs preferred greater kudu, black wildebeest and springbok. Lions preferred medium to large prey items, and cheetahs preferred medium to small prey items. The hilly and mountainous terrain of much of the reserve meant that only 50% of the total space was available to the predators. Home ranges of most of the predators were focused around the single large body of standing water. This is likely to have been a response to the water, the vegetation, and the prey that was attracted to these. Habitat selection was also influenced by inter and intra-specific interactions at least for a solitary male lion and female cheetahs. Range sizes were larger than on some other reserves and it is suggested that this was a result of the low prey density. These results form the basis for management recommendations including the importance of continuing to monitor the system and opening up additional parts of the reserve to the predators.
- Full Text:
- Date Issued: 2012
- Authors: Vorster, Paul Hendrik
- Date: 2012
- Subjects: Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5693 , http://hdl.handle.net/10962/d1005379 , Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Description: The re-introduction of large carnivores into relatively small conservation areas that fall within the historic distribution range of the species is becoming an increasingly common occurrence. The success of such re-introductions depends very much on the quality of the information that is available to guide management decisions, but in many cases, little information is available. The re-introduction of lions and cheetahs to Sanbona created the opportunity to monitor the behaviour of re-introduced predators to a relatively large system that was characterised by a low ungulate stocking density and little standing water. The broad aims were to study the feeding and spatial ecologies of the lions and cheetahs, to collect standard base-line data, and to examine the effects of the low prey density and limited standing water on habitat selection, range size and diet. The diet (data collected from direct observation and faecal analysis) was similar to that reported in previous studies, and lions and cheetahs preferred greater kudu, black wildebeest and springbok. Lions preferred medium to large prey items, and cheetahs preferred medium to small prey items. The hilly and mountainous terrain of much of the reserve meant that only 50% of the total space was available to the predators. Home ranges of most of the predators were focused around the single large body of standing water. This is likely to have been a response to the water, the vegetation, and the prey that was attracted to these. Habitat selection was also influenced by inter and intra-specific interactions at least for a solitary male lion and female cheetahs. Range sizes were larger than on some other reserves and it is suggested that this was a result of the low prey density. These results form the basis for management recommendations including the importance of continuing to monitor the system and opening up additional parts of the reserve to the predators.
- Full Text:
- Date Issued: 2012