The development of techniques for the identification of novel viruses associated with acute infantile gastroenteritis in South Africa
- Authors: Jaquet, Brittany J
- Date: 2017
- Subjects: Gastroenteritis in children -- Treatment , Gastroenteritis in children -- Treatment -- South Africa , Antiviral agents , Viral vaccines , Rotaviruses , Virus diseases in children
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/38013 , vital:24725
- Description: Gastroenteritis is a serious disease affecting both children and adults globally, but is more predominant in children with over half a million deaths reported each year. The leading cause of this disease is rotavirus, which accounts for 38% of all hospitalised cases. There has, however, been a significant decrease in the number of deaths associated with rotavirus worldwide since the introduction of the two vaccines, Rotarix® and RotaTeq®. A large number of cases are therefore either associated with other viruses, such as norovirus, Aichi virus (AiV) or Saffold virus (SAFV), or are of unknown aetiology. This study thus aims to develop techniques for the identification of viruses associated with gastroenteritis. Theiler’s murine encephalomyelitis virus (TMEV) was used to develop the sample preparation, transmission electron microscopy and RT-PCR techniques used in this study. This virus was chosen as a replication system using baby hamster kidney cells can be used to create high concentrations of viral particles from which RNA can be extracted preventing the waste of the limited samples. The virus particles are also similar in size and morphology to the viruses to be identified in this study, as it belongs to the same family. After sample preparation, TEM analysis showed the presence of small, round, non-enveloped virus particles in the TMEV sample. Due to the low concentration of virus particles, PEG precipitation was performed using both 0.15 M and 0.25 M NaCl and 8% (w/v) PEG 6000. TEM analysis then showed an increase in viral particle concentration, with the highest concentration observed at 0.25 M NaCl and 8% PEG 6000. RNA was successfully extracted and RT-PCR assays were performed for both the VP1 and 2B coding regions of TMEV. A method for creating a positive control for the RT-PCR assay was developed by the in vitro transcription of RNA from pTMEV, which contains the cDNA of TMEV. The RNA was then used as the template for the 2B two-step RT-PCR assay. A product of 412 bp was successfully amplified from the in vitro transcribed RNA and the sensitivity of the RT-PCR assay was determined. Using a Norovirus GII positive stool sample provided by Maureen Taylor, a nested RT-PCR assay was developed for the NoV GII N/S domain using a previously-published primer set and cycling parameters. A 342 bp product was successfully amplified from the RNA extracted from the stool sample and cloned into pGEM®-T Easy to produce pNoVGII. Using the plasmid containing the AiV 5’UTR and the PCR amplicon for AiV 3CD, RT-PCR assays were developed for AiV 5’UTR and partial 3CD. The RT-PCR assays produced a 1008 bp product for AiV 5’UTR and 266 bp for AiV 3CD, which were cloned into pGEM®-T Easy to produce pAiV5’UTR and pAiV3CD, respectively. Using in vitro transcribed RNA from pNoVGII, pAiV5’UTR, pAiV3CD and pSAFV, which contains the SAFV cDNA, positive controls were developed for the RT-PCR assays for NoV GII, AiV 5’UTR, AiV 3CD and SAFV 2C. The sensitivity of these assays was determined. The samples chosen for this study include wastewater collected from the Belmont Valley water treatment plant, oysters suspected to be infected with viruses collected from Port Elizabeth, South Africa and 30 stool samples from symptomatic patients. With the methods developed using TMEV, the wastewater, oysters and 30 stool samples were filter-sterilised, concentrated and screened by TEM. All samples showed the presence of virus particles. RNA was successfully extracted and the wastewater, oyster and 30 stool samples were screened for NoV GII using the NoV GII RT-PCR assay. The wastewater, oysters and 11 of the stool samples produced the 342 bp NoV GII PCR product and BLAST analysis determined the nucleotide sequences to be NoV GII.4. This shows that this study was able to develop sample preparation techniques and TEM analysis for selected samples and RT-PCR assays for NoV GII, AiV and SAFV. The NoV GII RT-PCR assay was successfully used for the screening of the wastewater, oysters and 30 stool samples for NoV GII. Due to the high number of gastroenteritis cases with unknown aetiology in South Africa, the development of techniques for the identification of NoV, AiV, SAFV and other viruses is very important. The identification of these viruses will allow for better surveillance, treatment and prevention of gastroenteritis in South Africa.
- Full Text:
- Authors: Jaquet, Brittany J
- Date: 2017
- Subjects: Gastroenteritis in children -- Treatment , Gastroenteritis in children -- Treatment -- South Africa , Antiviral agents , Viral vaccines , Rotaviruses , Virus diseases in children
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/38013 , vital:24725
- Description: Gastroenteritis is a serious disease affecting both children and adults globally, but is more predominant in children with over half a million deaths reported each year. The leading cause of this disease is rotavirus, which accounts for 38% of all hospitalised cases. There has, however, been a significant decrease in the number of deaths associated with rotavirus worldwide since the introduction of the two vaccines, Rotarix® and RotaTeq®. A large number of cases are therefore either associated with other viruses, such as norovirus, Aichi virus (AiV) or Saffold virus (SAFV), or are of unknown aetiology. This study thus aims to develop techniques for the identification of viruses associated with gastroenteritis. Theiler’s murine encephalomyelitis virus (TMEV) was used to develop the sample preparation, transmission electron microscopy and RT-PCR techniques used in this study. This virus was chosen as a replication system using baby hamster kidney cells can be used to create high concentrations of viral particles from which RNA can be extracted preventing the waste of the limited samples. The virus particles are also similar in size and morphology to the viruses to be identified in this study, as it belongs to the same family. After sample preparation, TEM analysis showed the presence of small, round, non-enveloped virus particles in the TMEV sample. Due to the low concentration of virus particles, PEG precipitation was performed using both 0.15 M and 0.25 M NaCl and 8% (w/v) PEG 6000. TEM analysis then showed an increase in viral particle concentration, with the highest concentration observed at 0.25 M NaCl and 8% PEG 6000. RNA was successfully extracted and RT-PCR assays were performed for both the VP1 and 2B coding regions of TMEV. A method for creating a positive control for the RT-PCR assay was developed by the in vitro transcription of RNA from pTMEV, which contains the cDNA of TMEV. The RNA was then used as the template for the 2B two-step RT-PCR assay. A product of 412 bp was successfully amplified from the in vitro transcribed RNA and the sensitivity of the RT-PCR assay was determined. Using a Norovirus GII positive stool sample provided by Maureen Taylor, a nested RT-PCR assay was developed for the NoV GII N/S domain using a previously-published primer set and cycling parameters. A 342 bp product was successfully amplified from the RNA extracted from the stool sample and cloned into pGEM®-T Easy to produce pNoVGII. Using the plasmid containing the AiV 5’UTR and the PCR amplicon for AiV 3CD, RT-PCR assays were developed for AiV 5’UTR and partial 3CD. The RT-PCR assays produced a 1008 bp product for AiV 5’UTR and 266 bp for AiV 3CD, which were cloned into pGEM®-T Easy to produce pAiV5’UTR and pAiV3CD, respectively. Using in vitro transcribed RNA from pNoVGII, pAiV5’UTR, pAiV3CD and pSAFV, which contains the SAFV cDNA, positive controls were developed for the RT-PCR assays for NoV GII, AiV 5’UTR, AiV 3CD and SAFV 2C. The sensitivity of these assays was determined. The samples chosen for this study include wastewater collected from the Belmont Valley water treatment plant, oysters suspected to be infected with viruses collected from Port Elizabeth, South Africa and 30 stool samples from symptomatic patients. With the methods developed using TMEV, the wastewater, oysters and 30 stool samples were filter-sterilised, concentrated and screened by TEM. All samples showed the presence of virus particles. RNA was successfully extracted and the wastewater, oyster and 30 stool samples were screened for NoV GII using the NoV GII RT-PCR assay. The wastewater, oysters and 11 of the stool samples produced the 342 bp NoV GII PCR product and BLAST analysis determined the nucleotide sequences to be NoV GII.4. This shows that this study was able to develop sample preparation techniques and TEM analysis for selected samples and RT-PCR assays for NoV GII, AiV and SAFV. The NoV GII RT-PCR assay was successfully used for the screening of the wastewater, oysters and 30 stool samples for NoV GII. Due to the high number of gastroenteritis cases with unknown aetiology in South Africa, the development of techniques for the identification of NoV, AiV, SAFV and other viruses is very important. The identification of these viruses will allow for better surveillance, treatment and prevention of gastroenteritis in South Africa.
- Full Text:
The development, manufacture and characterisation of niosomes intended to deliver nevirapine to the brain
- Authors: Witika, Bwalya Angel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65257 , vital:28715
- Description: Expected release date-May 2019
- Full Text:
- Authors: Witika, Bwalya Angel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65257 , vital:28715
- Description: Expected release date-May 2019
- Full Text:
The ecological impacts of pollution on a river ecosystem: a community index and stable isotope approach
- Authors: Gininda, Simphiwe Linah
- Date: 2017
- Subjects: Water -- Pollution -- Bloukrans River , Water quality -- South Africa -- Makhanda , Stream ecology -- South Africa -- Makhanda , South African Scoring System , Sewage disposal in rivers, lakes, etc. -- South Africa -- Makhanda , Agricultural ecology -- South Africa -- Makhanda , Agricultural pollution -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7993 , vital:21331
- Description: For decades, urbanized rivers have been modified to meet the needs of constantly expanding human populations in many countries around the world. The Bloukrans River in Grahamstown is one of the polluted and structurally modified urban rivers in South Africa, and there is no published information regarding its water quality and ecological status. Water quality is threatened by human activities including the disposal of treated and raw sewage, livestock farming, and agriculture. This study was conducted to determine the ecological status of the river by assessing its biological, chemical, and physical components in relation to man-mediated activities. Biological responses of macroinvertebrates were used to assess changes in water quality through space and time based on the South African Scoring System version 5 and the Average Score per Taxon water quality indices. The results showed poor water quality due to high nitrate and ammonium concentrations derived from sewage, and channel modifications by agricultural activities and dumping of solid waste. Channel width, water depth, dissolved oxygen, nitrate, and ammonium concentrations were the main drivers of macroinvertebrate distribution patterns and had the most influence on the variability in macroinvertebrates taxa richness, diversity and abundance. Diatoms were also used to assess water quality, specifically to indicate the trophic status of the river based on changes in the Trophic Diatom Index. The results suggested that the Bloukrans River was eutrophic during the course of this study. However, the trophic status varied with freshwater input, resulting in mesotrophic conditions during flooding and eutrophication in dry seasons. Changes in pH, phosphate concentration, water velocity (current speed), and temperature influenced the distribution of diatoms in the Bloukrans River. However, only pH was important at the community level and significantly influenced diatom abundances. Stable nitrogen isotope ratios (S15N) of autotrophs and primary and secondary consumers revealed noticeable differences between tissues of organisms exposed to treated sewage and those without any exposure. The S15N values in biota occurring above the sewage treatment discharge point were low, and those collected below the sewage point were higher. Although fertilizer derived nitrogen is generally depleted in 15N, agriculture-derived nitrogen could not be excluded as a possible source since animals at the sample site that was most affected by agricultural activities had the highest S15N values. This study provided valuable information on the ecological status of the Bloukrans River and identified the major activities associated with reduced biodiversity and water quality.
- Full Text:
- Authors: Gininda, Simphiwe Linah
- Date: 2017
- Subjects: Water -- Pollution -- Bloukrans River , Water quality -- South Africa -- Makhanda , Stream ecology -- South Africa -- Makhanda , South African Scoring System , Sewage disposal in rivers, lakes, etc. -- South Africa -- Makhanda , Agricultural ecology -- South Africa -- Makhanda , Agricultural pollution -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7993 , vital:21331
- Description: For decades, urbanized rivers have been modified to meet the needs of constantly expanding human populations in many countries around the world. The Bloukrans River in Grahamstown is one of the polluted and structurally modified urban rivers in South Africa, and there is no published information regarding its water quality and ecological status. Water quality is threatened by human activities including the disposal of treated and raw sewage, livestock farming, and agriculture. This study was conducted to determine the ecological status of the river by assessing its biological, chemical, and physical components in relation to man-mediated activities. Biological responses of macroinvertebrates were used to assess changes in water quality through space and time based on the South African Scoring System version 5 and the Average Score per Taxon water quality indices. The results showed poor water quality due to high nitrate and ammonium concentrations derived from sewage, and channel modifications by agricultural activities and dumping of solid waste. Channel width, water depth, dissolved oxygen, nitrate, and ammonium concentrations were the main drivers of macroinvertebrate distribution patterns and had the most influence on the variability in macroinvertebrates taxa richness, diversity and abundance. Diatoms were also used to assess water quality, specifically to indicate the trophic status of the river based on changes in the Trophic Diatom Index. The results suggested that the Bloukrans River was eutrophic during the course of this study. However, the trophic status varied with freshwater input, resulting in mesotrophic conditions during flooding and eutrophication in dry seasons. Changes in pH, phosphate concentration, water velocity (current speed), and temperature influenced the distribution of diatoms in the Bloukrans River. However, only pH was important at the community level and significantly influenced diatom abundances. Stable nitrogen isotope ratios (S15N) of autotrophs and primary and secondary consumers revealed noticeable differences between tissues of organisms exposed to treated sewage and those without any exposure. The S15N values in biota occurring above the sewage treatment discharge point were low, and those collected below the sewage point were higher. Although fertilizer derived nitrogen is generally depleted in 15N, agriculture-derived nitrogen could not be excluded as a possible source since animals at the sample site that was most affected by agricultural activities had the highest S15N values. This study provided valuable information on the ecological status of the Bloukrans River and identified the major activities associated with reduced biodiversity and water quality.
- Full Text:
The effect of carbohydrate on dusky kob, Argyrosomus japonicus, fed pelleted diets
- Authors: Mabasa, Nyiko Charity
- Date: 2017
- Subjects: Carbohydrates in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44895 , vital:25450
- Description: The dusky kob, Argyrosomus japonicus, is an emerging commercial marine aquaculture species in South Africa. Attributes such as market acceptance, fast growth rates, tolerance to sibling density, acceptance of pelleted feed and adaptability to intensive aquaculture conditions make it a good candidate. Feed, the largest running cost in most aquaculture operations, is a limiting factor in dusky kob production as its nutritional requirements are not well understood. The present project formed part of a research program to develop a locally produced, least cost and sustainable feed that will support the growth and health of dusky kob. The approximate protein and energy requirements for kob fed formulated feeds have been established in earlier research, but the ability of kob to utilize carbohydrates as an energy source has not previously been investigated. The aim of this study was to determine the efficiency of dusky kob to utilize graded levels of carbohydrate (pregelatinized maize starch - PGMS) in pelleted diets. The research objectives were to determine the effect of dietary carbohydrate levels on:i) growth and feed utilization; ii) post prandial blood glucose levels; and iii) general fish health, gut bacterial composition and liver glycogen content of juvenile dusky kob. Hatchery reared juvenile dusky kob (5 g) were acclimatized in a recirculating experimental aquaculture system at the Department of Ichthyology and Fisheries Science at Rhodes University. They were fed trout crumble starter feed for three weeks before the start of the feeding experiment. Five diets containing 4.1, 8.2, 16.4 and 24.6% carbohydrate, hereafter referred to as 4.1C, 8.2C, 16.4C and 24.6C respectively, were formulated with pregelatinized maize starch as a carbohydrate source and fishmeal as the main protein source. Fish were fed these diets twice daily at 3.85% body weight per day for three months. Specific growth rates and feed conversion rations differed significantly between the four dietary treatments. Growth rate increased with increasing carbohydrate up to 16.4%, after which a significant decline was observed. Diet 16.4C produced the highest specific growth rate (SGR) of 1.84 ± 0.05% body weight/day, and the lowest feed conversion ratio of 1.28 ± 0.08. While the lowest specific growth rate and highest feed conversion ratio of 0.79 ± 0.05 and 2.14 ± 0.13 respectively, were found for diet 24.6C. A third order polynomial regression, using SGR, determined the optimum carbohydrate inclusion for dusky kob to be 16.72%. The general structure of the liver was similar between all fish fed the dietary treatments and all fish liver samples displayed a certain degree of lipid vacuolization of the hepatocytes. Evidence of starvation was observed in the livers of fish fed diet 24.6C. However, no differences in the amount of liver glycogen were observed. Gut bacterial composition did not differ among the different diets or between the different sections of the gut. Differences were however observed in the diversity of the bacterial community structure at the start (when they were fed commercial trout feed) and end of the experimental period (after being fed a fishmeal-maize diet). The rate at which glucose was cleared from the blood differed significantly between diets. The low carbohydrate diets (i.e. diet 4.1C and 8.2C) showed a steady rate of glucose removal from the blood over a 48 h experimental period. Sharp increases in blood glucose concentration were observed in diet 16.4C and diet 24.6C, with highest glucose concentrations of 7.18 ± 1.81 and 8.05 ± 2.35 mmol/l respectively, observed 24 h after feeding. The blood glucose concentration of the fish fed diet 16.4C however returned to resting glucose concentration after 48 h, while that of the fish fed diet 24.6C did not. The results demonstrated that the level of dietary carbohydrate inclusion has a significant effect on the growth and health of the fish. The optimum carbohydrate inclusion in dusky kob diets is indicated to be 16.7%, which gave the best growth rate and maximum protein sparing effect without adverse effects on fish health. These findings are important for diet formulation and producing ‘least-cost’ diets for dusky kob farming.
- Full Text:
- Authors: Mabasa, Nyiko Charity
- Date: 2017
- Subjects: Carbohydrates in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44895 , vital:25450
- Description: The dusky kob, Argyrosomus japonicus, is an emerging commercial marine aquaculture species in South Africa. Attributes such as market acceptance, fast growth rates, tolerance to sibling density, acceptance of pelleted feed and adaptability to intensive aquaculture conditions make it a good candidate. Feed, the largest running cost in most aquaculture operations, is a limiting factor in dusky kob production as its nutritional requirements are not well understood. The present project formed part of a research program to develop a locally produced, least cost and sustainable feed that will support the growth and health of dusky kob. The approximate protein and energy requirements for kob fed formulated feeds have been established in earlier research, but the ability of kob to utilize carbohydrates as an energy source has not previously been investigated. The aim of this study was to determine the efficiency of dusky kob to utilize graded levels of carbohydrate (pregelatinized maize starch - PGMS) in pelleted diets. The research objectives were to determine the effect of dietary carbohydrate levels on:i) growth and feed utilization; ii) post prandial blood glucose levels; and iii) general fish health, gut bacterial composition and liver glycogen content of juvenile dusky kob. Hatchery reared juvenile dusky kob (5 g) were acclimatized in a recirculating experimental aquaculture system at the Department of Ichthyology and Fisheries Science at Rhodes University. They were fed trout crumble starter feed for three weeks before the start of the feeding experiment. Five diets containing 4.1, 8.2, 16.4 and 24.6% carbohydrate, hereafter referred to as 4.1C, 8.2C, 16.4C and 24.6C respectively, were formulated with pregelatinized maize starch as a carbohydrate source and fishmeal as the main protein source. Fish were fed these diets twice daily at 3.85% body weight per day for three months. Specific growth rates and feed conversion rations differed significantly between the four dietary treatments. Growth rate increased with increasing carbohydrate up to 16.4%, after which a significant decline was observed. Diet 16.4C produced the highest specific growth rate (SGR) of 1.84 ± 0.05% body weight/day, and the lowest feed conversion ratio of 1.28 ± 0.08. While the lowest specific growth rate and highest feed conversion ratio of 0.79 ± 0.05 and 2.14 ± 0.13 respectively, were found for diet 24.6C. A third order polynomial regression, using SGR, determined the optimum carbohydrate inclusion for dusky kob to be 16.72%. The general structure of the liver was similar between all fish fed the dietary treatments and all fish liver samples displayed a certain degree of lipid vacuolization of the hepatocytes. Evidence of starvation was observed in the livers of fish fed diet 24.6C. However, no differences in the amount of liver glycogen were observed. Gut bacterial composition did not differ among the different diets or between the different sections of the gut. Differences were however observed in the diversity of the bacterial community structure at the start (when they were fed commercial trout feed) and end of the experimental period (after being fed a fishmeal-maize diet). The rate at which glucose was cleared from the blood differed significantly between diets. The low carbohydrate diets (i.e. diet 4.1C and 8.2C) showed a steady rate of glucose removal from the blood over a 48 h experimental period. Sharp increases in blood glucose concentration were observed in diet 16.4C and diet 24.6C, with highest glucose concentrations of 7.18 ± 1.81 and 8.05 ± 2.35 mmol/l respectively, observed 24 h after feeding. The blood glucose concentration of the fish fed diet 16.4C however returned to resting glucose concentration after 48 h, while that of the fish fed diet 24.6C did not. The results demonstrated that the level of dietary carbohydrate inclusion has a significant effect on the growth and health of the fish. The optimum carbohydrate inclusion in dusky kob diets is indicated to be 16.7%, which gave the best growth rate and maximum protein sparing effect without adverse effects on fish health. These findings are important for diet formulation and producing ‘least-cost’ diets for dusky kob farming.
- Full Text:
The effect of different seating conditions, in aircrafts, on passenger comfort and the use of cabin space
- Authors: Olley, Emma-Jane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19734 , vital:22479
- Description: Although aircraft cabin design has improved over the years, passengers continue to complain about sitting discomfort whilst flying. These complaints are often centred on the cramped and restricted seating conditions. Whilst passenger comfort is important, in order for airline companies to attract and retain customers, it is also important to design for cabin space needs. Denel Aviation intends to build a South African Regional Aircraft (SARA) that will fly point-to-point, linking regional centres and intends to design aircraft seats that not only optimise passenger comfort, but which also save cabin space. The aim of this investigation was two-fold. The first aim was to determine how aircraft backrest angle affected passenger comfort, ease of seat access, perceived restriction and legroom, with different seat pan angles and seat heights. The second aim was to determine whether passenger comfort was affected with the most preferred backrest angle for each seat pan angle and seat height. Determining how seat pan angle and seat height affect the preferred angle of the backrest was considered important as Denel intend to use aircraft seats with a non-adjustable backrest angle. For this study, 80 participants were recruited from Rhodes University and the general Grahamstown population. The participants consisted of 40 males and 40 females and were not limited by race, ethnicity or culture. The participants were classified into two age groups; 18-30 years of age and 31-60 years of age. Participant stature, body mass, BMI and lower leg length was recorded to determine the effect these factors had on sitting comfort when the participants were seated in different seating conditions. From the results obtained, it was found that, by altering seat height, seat pan angle, and backrest angle, passenger comfort can be optimised. Furthermore, it was found that certain combinations of seat height, seat pan angle and backrest angle are more beneficial with regards to saving aircraft cabin space. However, this means that a compromise needs to be found for SARA as passenger comfort needs to be optimised, whilst decreasing the use of cabin space to reduce costs.
- Full Text:
- Authors: Olley, Emma-Jane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19734 , vital:22479
- Description: Although aircraft cabin design has improved over the years, passengers continue to complain about sitting discomfort whilst flying. These complaints are often centred on the cramped and restricted seating conditions. Whilst passenger comfort is important, in order for airline companies to attract and retain customers, it is also important to design for cabin space needs. Denel Aviation intends to build a South African Regional Aircraft (SARA) that will fly point-to-point, linking regional centres and intends to design aircraft seats that not only optimise passenger comfort, but which also save cabin space. The aim of this investigation was two-fold. The first aim was to determine how aircraft backrest angle affected passenger comfort, ease of seat access, perceived restriction and legroom, with different seat pan angles and seat heights. The second aim was to determine whether passenger comfort was affected with the most preferred backrest angle for each seat pan angle and seat height. Determining how seat pan angle and seat height affect the preferred angle of the backrest was considered important as Denel intend to use aircraft seats with a non-adjustable backrest angle. For this study, 80 participants were recruited from Rhodes University and the general Grahamstown population. The participants consisted of 40 males and 40 females and were not limited by race, ethnicity or culture. The participants were classified into two age groups; 18-30 years of age and 31-60 years of age. Participant stature, body mass, BMI and lower leg length was recorded to determine the effect these factors had on sitting comfort when the participants were seated in different seating conditions. From the results obtained, it was found that, by altering seat height, seat pan angle, and backrest angle, passenger comfort can be optimised. Furthermore, it was found that certain combinations of seat height, seat pan angle and backrest angle are more beneficial with regards to saving aircraft cabin space. However, this means that a compromise needs to be found for SARA as passenger comfort needs to be optimised, whilst decreasing the use of cabin space to reduce costs.
- Full Text:
The effect of shade on the biological control of Salvinia molesta D.S. Mitchell [Salviniaceae] by the weevil, Cyrtobagous salviniae Calder and Sands [Curculionidae]
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
The effect of submersion in water and breathing modality (assisted breathing and apnea) on different stages of the information processing chain
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
The effect of total standing duration during sit-stand regimes on cognitive performance, rating of perceived exertion and heart rate frequency
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
The effects of a lion (Panthera Leo) re-introduction on a resident cheetah (Acinonyx Jubatus) population In Mountain Zebra National Park, Eastern Cape, South Africa
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
The effects of the type of rest breaks on return-to-task performance in semi-automated tasks with varying complexities
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
- Full Text:
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
- Full Text:
The identification of key vulnerability components within Solomon Islands coastal communities
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
- Full Text:
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
- Full Text:
The influence of environmental variability on the catch of chokka, Loligo reynaudii, off the coast of South Africa
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
The interaction of selected bacteria with tailored electrospun fibres: towards future applications in bioremediation, bacterial inactivation and electricity generation
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
The pest status and integrated management programme of carob moth, Ectomyelois ceratoniae Zeller, attacking citrus in South Africa
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
The potential of hydrellia egeriae rodrigues (diptera: ephydridae) as a biocontrol agent for egeria densa planch. (hydrocharitaceae) in South Africa
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
The relationship between OCT4 and an aggressive phenotype in triple negative breast cancer (TNBC)
- Authors: Jackson, Hayley Claire
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59209 , vital:27477
- Description: Expected release date-April 2019
- Full Text:
- Authors: Jackson, Hayley Claire
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59209 , vital:27477
- Description: Expected release date-April 2019
- Full Text:
The response of microalgal biomass and community composition to the chemical and physical dynamics of two Eastern Cape estuaries
- Authors: Cotiyane, Phumlile L
- Date: 2017
- Subjects: Estuarine plants -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Phytoplankton -- South Africa -- Eastern Cape , Algal blooms -- South Africa -- Eastern Cape , Algal blooms -- Monitoring-- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4999 , vital:20751
- Description: Water quality characteristics of estuaries are influenced by both natural and anthropogenic activities. Estuaries situated in coastal urban areas are exposed to more perturbations than those in rural settings. This study determined the drivers of phytoplankton biomass and community composition in two Eastern Cape estuaries and evaluated the anthropogenic activities that influence the overall health of each estuary. The estuaries were sampled in summer and winter (2014, 2015). The water quality of the estuaries was determined by measuring the variability in physico-chemical parameters (salinity, temperature, dissolved oxygen and pH), nutrients, phytoplankton biomass and composition and faecal bacteria. Results show that both Mngazana and Nahoon are well oxygenated (~ 6.0 mg l-¹) and are saline systems (~ 35 ppt) due to low freshwater inputs into both estuaries. Mngazana Estuary exhibited low nutrient inputs along the length of the estuary including Creeks 1 and 2 with low chlorophyll a (4.0 ± 0.2 µg Chl-a r¹) being recorded during this study while Nahoon Estuary had an overall chlorophyll a of 3.5 ± 0.3 µg Chl-a r¹. The two estuaries were dominated by flagellates with phytoplankton blooms recorded seasonally. Possible eutrophic conditions were evident along the upper reaches of Nahoon indicated by nutrient accumulation and by the presence of cyanobacteria. This also this reflected the possible anthropogenic nutrient inputs originating from the Nahoon catchment despite the low freshwater inflow. The presence of faecal bacteria counts along both estuaries indicates the need for further investigation into the source of faecal contamination. The use of nutrient analyses and phytoplankton composition during this study enabled a clear description of the water characteristics of the investigated estuaries. Furthermore, the need for the adherence to freshwater flow requirements of estuaries to limit the dominance of marine waters was clearly illustrated. Urban runoff due to impervious surfaces increases nutrient inputs into estuaries while rural use of estuarine waters introduces contaminants into the system; coupled with low freshwater inputs and eutrophic conditions, the deterioration of estuarine water quality over time demonstrates the need for effective monitoring of these systems.
- Full Text:
- Authors: Cotiyane, Phumlile L
- Date: 2017
- Subjects: Estuarine plants -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Phytoplankton -- South Africa -- Eastern Cape , Algal blooms -- South Africa -- Eastern Cape , Algal blooms -- Monitoring-- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4999 , vital:20751
- Description: Water quality characteristics of estuaries are influenced by both natural and anthropogenic activities. Estuaries situated in coastal urban areas are exposed to more perturbations than those in rural settings. This study determined the drivers of phytoplankton biomass and community composition in two Eastern Cape estuaries and evaluated the anthropogenic activities that influence the overall health of each estuary. The estuaries were sampled in summer and winter (2014, 2015). The water quality of the estuaries was determined by measuring the variability in physico-chemical parameters (salinity, temperature, dissolved oxygen and pH), nutrients, phytoplankton biomass and composition and faecal bacteria. Results show that both Mngazana and Nahoon are well oxygenated (~ 6.0 mg l-¹) and are saline systems (~ 35 ppt) due to low freshwater inputs into both estuaries. Mngazana Estuary exhibited low nutrient inputs along the length of the estuary including Creeks 1 and 2 with low chlorophyll a (4.0 ± 0.2 µg Chl-a r¹) being recorded during this study while Nahoon Estuary had an overall chlorophyll a of 3.5 ± 0.3 µg Chl-a r¹. The two estuaries were dominated by flagellates with phytoplankton blooms recorded seasonally. Possible eutrophic conditions were evident along the upper reaches of Nahoon indicated by nutrient accumulation and by the presence of cyanobacteria. This also this reflected the possible anthropogenic nutrient inputs originating from the Nahoon catchment despite the low freshwater inflow. The presence of faecal bacteria counts along both estuaries indicates the need for further investigation into the source of faecal contamination. The use of nutrient analyses and phytoplankton composition during this study enabled a clear description of the water characteristics of the investigated estuaries. Furthermore, the need for the adherence to freshwater flow requirements of estuaries to limit the dominance of marine waters was clearly illustrated. Urban runoff due to impervious surfaces increases nutrient inputs into estuaries while rural use of estuarine waters introduces contaminants into the system; coupled with low freshwater inputs and eutrophic conditions, the deterioration of estuarine water quality over time demonstrates the need for effective monitoring of these systems.
- Full Text:
The role of protected areas in the conservation and management of fisheries in the Chobe District of Botswana
- Authors: Bakane, Modiegi
- Date: 2017
- Subjects: Cichlids Botswana Chobe District , Protected areas Botswana Chobe District , Fishery management Botswana Chobe District
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7459 , vital:21262
- Description: This study was aimed at better understanding the function of protected areas as a management strategy for the Chobe District fishery in Botswana, by first investigating the relative abundance in fish communities in and outside protected areas and secondly, by performing an assessment of the biology of commercially important large cichlid species viz threespot tilapia Oreochromis andersonii, greenhead tilapia Oreochromis macrochir and redbreast tilapia Coptodon rendalli. In this study, data and specimens were collected during seasonal surveys between September 2014 and April 2015, using the standard graded fleets of gillnets employed in other programmes in the region, together with D-nets, angling and electro-fishing. The study demonstrated that fish communities in the floodplain ecosystems in the Chobe District of Botswana were representative of the region, containing some 70 species in 14 families. This study also demonstrated that for all the species collected, the mean Catch Per Unit Effort (CPUE) by weight for all the species was significantly higher in protected areas (Kruskal Wallis Test; P<0.05) namely, Zibadianja Lagoon (38 ± 31 kg/net.night"1 and Savuti River/marsh 25 ± 19 kg/net.night"1) than in the fished Chobe River floodplains CPUE (6 ± 3 kg/net.night-1). Biological contributions were estimates of longevity, growth and maturity for O. andersonii, O. macrochir and C. rendalli. Age and growth were estimated using sectioned sagittal otoliths. The Von Bertalanffy growth equation from otolith derived length at age was Lt(mm) =298 (1-e-0 59(t=- 098)) for O. andersonii and Lt(mm) = 337 (1-e-0'20(t=-235)) for C. rendalli. The results indicated that protected areas enhanced fish longevity, and fish in protected areas were larger and older than those in exploited areas. Maturity estimates for the large cichlids were consistent with other research in the region and the length-at-50% maturity was estimated as 250mm Lt for O. andersonii, 225 mm Lt for O. macrochir and 210 mm Lt for C. rendalli. Management recommendations are therefore to retain gill net mesh size regulations that ensure that these fish reach maturity and can breed before being harvested and to assess the possibility of increasing the number of protected areas in the district.
- Full Text:
- Authors: Bakane, Modiegi
- Date: 2017
- Subjects: Cichlids Botswana Chobe District , Protected areas Botswana Chobe District , Fishery management Botswana Chobe District
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7459 , vital:21262
- Description: This study was aimed at better understanding the function of protected areas as a management strategy for the Chobe District fishery in Botswana, by first investigating the relative abundance in fish communities in and outside protected areas and secondly, by performing an assessment of the biology of commercially important large cichlid species viz threespot tilapia Oreochromis andersonii, greenhead tilapia Oreochromis macrochir and redbreast tilapia Coptodon rendalli. In this study, data and specimens were collected during seasonal surveys between September 2014 and April 2015, using the standard graded fleets of gillnets employed in other programmes in the region, together with D-nets, angling and electro-fishing. The study demonstrated that fish communities in the floodplain ecosystems in the Chobe District of Botswana were representative of the region, containing some 70 species in 14 families. This study also demonstrated that for all the species collected, the mean Catch Per Unit Effort (CPUE) by weight for all the species was significantly higher in protected areas (Kruskal Wallis Test; P<0.05) namely, Zibadianja Lagoon (38 ± 31 kg/net.night"1 and Savuti River/marsh 25 ± 19 kg/net.night"1) than in the fished Chobe River floodplains CPUE (6 ± 3 kg/net.night-1). Biological contributions were estimates of longevity, growth and maturity for O. andersonii, O. macrochir and C. rendalli. Age and growth were estimated using sectioned sagittal otoliths. The Von Bertalanffy growth equation from otolith derived length at age was Lt(mm) =298 (1-e-0 59(t=- 098)) for O. andersonii and Lt(mm) = 337 (1-e-0'20(t=-235)) for C. rendalli. The results indicated that protected areas enhanced fish longevity, and fish in protected areas were larger and older than those in exploited areas. Maturity estimates for the large cichlids were consistent with other research in the region and the length-at-50% maturity was estimated as 250mm Lt for O. andersonii, 225 mm Lt for O. macrochir and 210 mm Lt for C. rendalli. Management recommendations are therefore to retain gill net mesh size regulations that ensure that these fish reach maturity and can breed before being harvested and to assess the possibility of increasing the number of protected areas in the district.
- Full Text:
The sedimentology and depositional model of VS5 reef at Beatrix mine and surrounding areas of the Freestate Goldfield, South Africa
- Authors: Shivambu, Steven
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4942 , vital:20745
- Description: Historically, placers of economic importance at Sibanye Gold's Beatrix No. 3 Shaft were Beatrix Reef, Aandenk Reef and Composite of the two reefs. Recently, the VS5 placer has emerged to be a significant contributor of ore tonnages mined on the Shaft as mining advances into deeper levels towards the northern portion of the mine lease area. Gold concentration in the VS5 Reef is highly variable from uneconomic, through marginal to economic gold values. A good knowledge of the sedimentological framework of the VS5 Reef was considered necessary in order to interpret the variable distribution of the gold within the VS5 placer. The aim of this study was to determine the depositional environments that played a major role during the formation of the VS5 placer by means of investigating the macroscopic sedimentological parameters of this particular reef. These sedimentological parameters were used as the basis for the subdivision of VS5 Reef into different facies recognized in the mine and surrounding areas. It was recognized that the VS5 placer was formed in a distal, braided fluvial environment by the reworking of the pre-existing Aandenk Reef by new materials containing significant amount of nondurable materials (see definition on page xii) such as shale detritus. Where there is no evidence of reworking of the older Aandenk Reef, the VS5 Reef occurs as poorly sorted, polymictic conglomerate with abundance of non-durable detritus. This is referred to as the Immature (IV) VS5 facies and occurs in the northern portion of the study area. The degree of reworking of the gravel bars by waves and current action resulted in the formation of well sorted, oligomictic conglomerates of the Beatrix facies in the southern portion of the mine. At the boundaries between the Immature VS5 and Beatrix facies occurs the Transitional (Sub-mature) VS5 facies, characterized by reef comprising a polymictic upper portion and a basal more mature oligomictic unit. The Transitional VS5 facies extends across the current central northern mining faces of Beatrix No. 3 Shaft with a northwest-southeast trend. There is a strong correlation between the VS5 lithofacies and distribution of gold mineralization. The Immature VS5 facies is poorly mineralized, with gold values averaging 200 c.m.g/t and lower. The Transitional (Sub-mature) VS5 facies has elevated gold values, ranging from 300 c.m.g/t to 1500 cm.g/t. Mineralization in this unit tend to be bottom loaded as well as at the base of each cyclic unit. The Beatrix facies records the highest grades averaging >1500 cmg/t. The improved understanding of the VS5 lithofacies made it possible to predict gold mineralization and aid planning to mine into viable VS5 areas.
- Full Text:
- Authors: Shivambu, Steven
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4942 , vital:20745
- Description: Historically, placers of economic importance at Sibanye Gold's Beatrix No. 3 Shaft were Beatrix Reef, Aandenk Reef and Composite of the two reefs. Recently, the VS5 placer has emerged to be a significant contributor of ore tonnages mined on the Shaft as mining advances into deeper levels towards the northern portion of the mine lease area. Gold concentration in the VS5 Reef is highly variable from uneconomic, through marginal to economic gold values. A good knowledge of the sedimentological framework of the VS5 Reef was considered necessary in order to interpret the variable distribution of the gold within the VS5 placer. The aim of this study was to determine the depositional environments that played a major role during the formation of the VS5 placer by means of investigating the macroscopic sedimentological parameters of this particular reef. These sedimentological parameters were used as the basis for the subdivision of VS5 Reef into different facies recognized in the mine and surrounding areas. It was recognized that the VS5 placer was formed in a distal, braided fluvial environment by the reworking of the pre-existing Aandenk Reef by new materials containing significant amount of nondurable materials (see definition on page xii) such as shale detritus. Where there is no evidence of reworking of the older Aandenk Reef, the VS5 Reef occurs as poorly sorted, polymictic conglomerate with abundance of non-durable detritus. This is referred to as the Immature (IV) VS5 facies and occurs in the northern portion of the study area. The degree of reworking of the gravel bars by waves and current action resulted in the formation of well sorted, oligomictic conglomerates of the Beatrix facies in the southern portion of the mine. At the boundaries between the Immature VS5 and Beatrix facies occurs the Transitional (Sub-mature) VS5 facies, characterized by reef comprising a polymictic upper portion and a basal more mature oligomictic unit. The Transitional VS5 facies extends across the current central northern mining faces of Beatrix No. 3 Shaft with a northwest-southeast trend. There is a strong correlation between the VS5 lithofacies and distribution of gold mineralization. The Immature VS5 facies is poorly mineralized, with gold values averaging 200 c.m.g/t and lower. The Transitional (Sub-mature) VS5 facies has elevated gold values, ranging from 300 c.m.g/t to 1500 cm.g/t. Mineralization in this unit tend to be bottom loaded as well as at the base of each cyclic unit. The Beatrix facies records the highest grades averaging >1500 cmg/t. The improved understanding of the VS5 lithofacies made it possible to predict gold mineralization and aid planning to mine into viable VS5 areas.
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The socio-economic contribution of non-timber forest product trade to households in four villages in Zomba and Machinga Districts, Malawi
- Authors: Mahonya, Sophie Manchichi
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4787 , vital:20724
- Description: The principal aim of this study was to assess the socio-economic contribution of nontimber forest product (NTFP) trade to households in Zomba and Machinga, southern Malawi. Quantitative and qualitative data were collected through several methods, including a household survey using questionnaire interviews, focus group discussions, key informant interviews with individual traders, direct observations, and literature review. The quantitative data were analysed statistically using SPPS version 16.0 while the qualitative data were analysed thematically. NTFP trade was the third important source of cash income for 15% of the households, although the level of use, buying and selling of NTFPs varied across the four study villages. All households in all the study villages used firewood (100%), and most used thatch grass (94%), bamboo (96%), wood for building (92%), largely as construction materials. However, the percentage of households buying NTFPs was lower, with the maximum percentage of households being 50%. The percent of households engaged in selling at least one NTFP was lower still at 39%. Substantial cash incomes were generated from firewood and edible orchids sales which provided up to a maximum of Mk180,000, equivalent to US$456, per year. Households joined the trade mostly for an alternative source of cash income due to poverty and to meet basic needs when other options were not available or feasible. Cash income generated from NTFP trade acted as a safety net and a coping strategy when other avenues supporting livelihoods were not accessible. The socio-economic benefits derived from NTFP trade were associated with the quantities collected, sold, market forces influenced by the law of demand and supply. The small amounts of cash income generated by most households were important as they supplemented household cash needs. There was a strong association between NTFP trade as one of the important sources of cash income and the number of months a household had food from their own garden in a year. There was a significant relationship though weak between ranking of NTFP trade and livestock ownership by households. Value chain analysis was used as an analytical tool to understand the processes involved in NTFP trade. The value chains for the products under study were short, dominated by traders and some intermediaries. Most of the products were sold in local markets with little value addition. This study recommends that policy makers should integrate NTFPs into their development plans, emphasizing the establishment of management strategies that will enhance availability and sustainability of the resource. NTFPs contributed to the livelihoods of the households socially and economically through provision of food, cash income, energy for cooking, medicine and construction materials.
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- Authors: Mahonya, Sophie Manchichi
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4787 , vital:20724
- Description: The principal aim of this study was to assess the socio-economic contribution of nontimber forest product (NTFP) trade to households in Zomba and Machinga, southern Malawi. Quantitative and qualitative data were collected through several methods, including a household survey using questionnaire interviews, focus group discussions, key informant interviews with individual traders, direct observations, and literature review. The quantitative data were analysed statistically using SPPS version 16.0 while the qualitative data were analysed thematically. NTFP trade was the third important source of cash income for 15% of the households, although the level of use, buying and selling of NTFPs varied across the four study villages. All households in all the study villages used firewood (100%), and most used thatch grass (94%), bamboo (96%), wood for building (92%), largely as construction materials. However, the percentage of households buying NTFPs was lower, with the maximum percentage of households being 50%. The percent of households engaged in selling at least one NTFP was lower still at 39%. Substantial cash incomes were generated from firewood and edible orchids sales which provided up to a maximum of Mk180,000, equivalent to US$456, per year. Households joined the trade mostly for an alternative source of cash income due to poverty and to meet basic needs when other options were not available or feasible. Cash income generated from NTFP trade acted as a safety net and a coping strategy when other avenues supporting livelihoods were not accessible. The socio-economic benefits derived from NTFP trade were associated with the quantities collected, sold, market forces influenced by the law of demand and supply. The small amounts of cash income generated by most households were important as they supplemented household cash needs. There was a strong association between NTFP trade as one of the important sources of cash income and the number of months a household had food from their own garden in a year. There was a significant relationship though weak between ranking of NTFP trade and livestock ownership by households. Value chain analysis was used as an analytical tool to understand the processes involved in NTFP trade. The value chains for the products under study were short, dominated by traders and some intermediaries. Most of the products were sold in local markets with little value addition. This study recommends that policy makers should integrate NTFPs into their development plans, emphasizing the establishment of management strategies that will enhance availability and sustainability of the resource. NTFPs contributed to the livelihoods of the households socially and economically through provision of food, cash income, energy for cooking, medicine and construction materials.
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