Baculovirus synergism for improved management of false codling moth Thaumatotibia leucotreta Meyr. (Lepidoptera: Tortricidae)
- Authors: Taylor, David Graham
- Date: 2021-04
- Subjects: Baculoviruses , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Biological control , Biological pest control agents , Citrus -- Diseases and pests , Codling moth , Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV)
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/176942 , vital:42774
- Description: Baculoviruses are an environmentally friendly and effective agent for managing lepidopteran pests. This includes the management of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a serious pest of citrus in Southern Africa and a major threat to the South African citrus export industry. For more than 15 years, CrleGV-SA- based biopesticides have been used as part of an integrated pest management strategy for the control of T. leucotreta in citrus orchards in South Africa, under the names Cryptogran™ and Cryptex®. While these biopesticides have been effective during this period, there are some areas in which baculovirus use could potentially be improved. Baculoviruses are notoriously slow to kill in comparison to chemical-based pesticides, and lately, pest resistance to baculoviruses has become a major concern with the development of resistance by Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) to its granulovirus occurring in the field in Europe. The consistent use of CrleGV-SA for more than 15 years in the field has raised concern that T. leucotreta could develop resistance to this virus, and has made it necessary to alter baculovirus-based management strategies to prevent this from occurring. A second baculovirus, Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), has recently been isolated and was shown to be effective against T. leucotreta. However, the interactions between CrleGV-SA and CrpeNPV are not yet understood and so it is important to test these interactions before both viruses are applied on the same orchards. Not only is it important to know whether these viruses could negatively impact each other, but it is also important to test whether they could interact synergistically. A synergistic interaction could not only provide a potential tool for the management of resistance, but it could also be exploited to improve baculovirus-based management of T. leucotreta. In this study, a stock of CrleGV-SA was purified by glycerol gradient centrifugation from T. leucotreta cadavers, while a stock of CrpeNPV purified from Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae) cadavers was provided by River Bioscience (Pty) Ltd. These stocks were screened for purity by a multiplex polymerase chain reaction (mPCR) protocol designed to detect CrleGV-SA and CrpeNPV. The occlusion body (OB) density was then calculated using darkfield microscopy and a counting chamber. Both stocks were shown to be pure within the limits of the mPCR protocol, and the CrleGV-SA and CrpeNPV stocks were calculated to contain 3.08 × 1011 OBs/mL and 1.92 × 1011 OBs/mL respectively The first aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the dose mortality, in terms of lethal concentration. This was calculated using 7-day surface-dose biological assays for each virus and a 1:1 mixture of OBs of the two against T. leucotreta neonates. The lethal concentrations of each treatment required to kill 50 % of larvae (LC50) and 90 % of larvae (LC90) for each treatment were then calculated and compared using a probit regression. The mixed infection performed significantly better than either virus by itself, while each virus by itself did not differ significantly from the other. The LC50 for CrleGV-SA, CrpeNPV and the mixed infection were 1.53 × 104 OBs/mL, 1.15 × 104 OBs/mL and 4.38 × 103 OBs/mL respectively. The LC90 of CrleGV-SA, CrpeNPV and the mixed infection were calculated to be 4.10 × 105 OBs/mL, 1.05 × 105 OBs/mL, and 4.09 × 104 OBs/mL respectively. The second aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the speed of kill. A time-response biological assay protocol was created that allowed for effective observation of the larvae. This was then used to generate time-mortality data that were analysed by a logit regression function to calculate and compare the treatments at the time of 50 % larval mortality (LT50) and the time of 90 % mortality (LT90). Each virus by itself did not differ significantly from the other, while the mixed infection took significantly longer to kill 50 % and 90 % of the larvae, suggesting that there is competition for resources between viruses during the secondary, systemic phase of infection. The LT50 for CrleGV-SA, CrpeNPV and the mixed infection were 117.5 hours, 113.5 hours and 139.0 hours respectively. The LT90 for CrleGV-SA, CrpeNPV and the mixed infection were 153.2 hours, 159.3, and 193.4 hours respectively. Finally, the composition of OBs recovered from the cadavers produced by the time-response biological assays were investigated by mPCR. A method for extracting gDNA from OBs in neonate-sized T. leucotreta larvae is described. The presence of CrpeNPV along with CrleGV-SA was noted in 4 out of 9 larvae inoculated with only CrleGV-SA. The presence of CrleGV-SA as well as CrpeNPV was noted in all but one larva inoculated with only CrpeNPV, and both CrleGV-SA and CrpeNPV were noted in all but one larva inoculated with a 1:1 mixture of the two, with one larva only being positive for CrleGV-SA. This suggests either stock contamination or the presence of covert infections of CrleGV-SA and CrpeNPV in the T. leucotreta population used in this study. This is the second study to report an improved lethal concentration of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates, and the first study to report the slower speed of kill of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates. While the improved lethal concentration of the mixed infection is a promising step in the future improvement of baculovirus-based biopesticides, it is at the cost of a slower speed of kill. , Thesis (MSc) -- Faculty of Science, Department of Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Taylor, David Graham
- Date: 2021-04
- Subjects: Baculoviruses , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Biological control , Biological pest control agents , Citrus -- Diseases and pests , Codling moth , Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV)
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/176942 , vital:42774
- Description: Baculoviruses are an environmentally friendly and effective agent for managing lepidopteran pests. This includes the management of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a serious pest of citrus in Southern Africa and a major threat to the South African citrus export industry. For more than 15 years, CrleGV-SA- based biopesticides have been used as part of an integrated pest management strategy for the control of T. leucotreta in citrus orchards in South Africa, under the names Cryptogran™ and Cryptex®. While these biopesticides have been effective during this period, there are some areas in which baculovirus use could potentially be improved. Baculoviruses are notoriously slow to kill in comparison to chemical-based pesticides, and lately, pest resistance to baculoviruses has become a major concern with the development of resistance by Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) to its granulovirus occurring in the field in Europe. The consistent use of CrleGV-SA for more than 15 years in the field has raised concern that T. leucotreta could develop resistance to this virus, and has made it necessary to alter baculovirus-based management strategies to prevent this from occurring. A second baculovirus, Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), has recently been isolated and was shown to be effective against T. leucotreta. However, the interactions between CrleGV-SA and CrpeNPV are not yet understood and so it is important to test these interactions before both viruses are applied on the same orchards. Not only is it important to know whether these viruses could negatively impact each other, but it is also important to test whether they could interact synergistically. A synergistic interaction could not only provide a potential tool for the management of resistance, but it could also be exploited to improve baculovirus-based management of T. leucotreta. In this study, a stock of CrleGV-SA was purified by glycerol gradient centrifugation from T. leucotreta cadavers, while a stock of CrpeNPV purified from Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae) cadavers was provided by River Bioscience (Pty) Ltd. These stocks were screened for purity by a multiplex polymerase chain reaction (mPCR) protocol designed to detect CrleGV-SA and CrpeNPV. The occlusion body (OB) density was then calculated using darkfield microscopy and a counting chamber. Both stocks were shown to be pure within the limits of the mPCR protocol, and the CrleGV-SA and CrpeNPV stocks were calculated to contain 3.08 × 1011 OBs/mL and 1.92 × 1011 OBs/mL respectively The first aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the dose mortality, in terms of lethal concentration. This was calculated using 7-day surface-dose biological assays for each virus and a 1:1 mixture of OBs of the two against T. leucotreta neonates. The lethal concentrations of each treatment required to kill 50 % of larvae (LC50) and 90 % of larvae (LC90) for each treatment were then calculated and compared using a probit regression. The mixed infection performed significantly better than either virus by itself, while each virus by itself did not differ significantly from the other. The LC50 for CrleGV-SA, CrpeNPV and the mixed infection were 1.53 × 104 OBs/mL, 1.15 × 104 OBs/mL and 4.38 × 103 OBs/mL respectively. The LC90 of CrleGV-SA, CrpeNPV and the mixed infection were calculated to be 4.10 × 105 OBs/mL, 1.05 × 105 OBs/mL, and 4.09 × 104 OBs/mL respectively. The second aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the speed of kill. A time-response biological assay protocol was created that allowed for effective observation of the larvae. This was then used to generate time-mortality data that were analysed by a logit regression function to calculate and compare the treatments at the time of 50 % larval mortality (LT50) and the time of 90 % mortality (LT90). Each virus by itself did not differ significantly from the other, while the mixed infection took significantly longer to kill 50 % and 90 % of the larvae, suggesting that there is competition for resources between viruses during the secondary, systemic phase of infection. The LT50 for CrleGV-SA, CrpeNPV and the mixed infection were 117.5 hours, 113.5 hours and 139.0 hours respectively. The LT90 for CrleGV-SA, CrpeNPV and the mixed infection were 153.2 hours, 159.3, and 193.4 hours respectively. Finally, the composition of OBs recovered from the cadavers produced by the time-response biological assays were investigated by mPCR. A method for extracting gDNA from OBs in neonate-sized T. leucotreta larvae is described. The presence of CrpeNPV along with CrleGV-SA was noted in 4 out of 9 larvae inoculated with only CrleGV-SA. The presence of CrleGV-SA as well as CrpeNPV was noted in all but one larva inoculated with only CrpeNPV, and both CrleGV-SA and CrpeNPV were noted in all but one larva inoculated with a 1:1 mixture of the two, with one larva only being positive for CrleGV-SA. This suggests either stock contamination or the presence of covert infections of CrleGV-SA and CrpeNPV in the T. leucotreta population used in this study. This is the second study to report an improved lethal concentration of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates, and the first study to report the slower speed of kill of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates. While the improved lethal concentration of the mixed infection is a promising step in the future improvement of baculovirus-based biopesticides, it is at the cost of a slower speed of kill. , Thesis (MSc) -- Faculty of Science, Department of Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-04
Environmental drivers of the composition and distribution of larval fish assemblages off the south coast of South Africa
- Authors: Trassierra, Jaqueline Anne
- Date: 2019
- Subjects: Fishes -- Larvae -- South Africa -- Eastern Cape , Fishes -- Larvae -- Migration -- South Africa -- Eastern Cape , Fishes -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68154 , vital:29207
- Description: The species composition, distribution and patterns of vertical migration of larval fish assemblages were investigated in March and in September 2013 within two adjacent log spiral bays, Algoa Bay and St Francis Bay, on the south coast of South Africa. Fish larvae were collected by means of a boat towed bongo net (57 cm diameter; mesh aperture 500 μm). An onshore (2 km) and an offshore (3 km) station were each sampled twice during the daytime (06:00 – 18:00) with two horizontal tows: near the surface (0.5 m) and close to the bottom (12 m). Tows were repeated at night (18:00 – 23:00) for onshore sites. Larval catches included 16 fish families and 40 species. A multivariate analysis indicated that the species composition was significantly different between Algoa Bay and St Francis Bay, with Engraulidae, Blenniidae, Sparidae, Soleidae and Cynoglossidae making important contributions to the larval fish catch in Algoa Bay, while Blenniidae, Engraulidae, Tripterygiidae, Sparidae and Gobiesocidae contributed significantly in St Francis Bay. Differences in assemblage composition were noted between the Spring (September–October) and Autumn (March-April) months. The species composition of larval fish assemblages was related to wind speed, wave height, cloud cover, sea water temperature, depth, average current speed and direction. Wind speed, wave height, temperature and depth significantly contributed to the variation in larval fish densities. Abundances of larval fishes were greater offshore than onshore, larvae from pelagic eggs dominated catches offshore, while larvae from demersal eggs dominated onshore catches. Habitat structure strongly influenced the composition of larval fishes between the bays and abundances were significantly greater at night than during the day. Most larval fishes displayed a reverse diel vertical migration pattern and were most influenced by predators, wind speed and cloud cover. This study shows that larval fish assemblages are highly complex and patchy. Spawning mode, individual species behaviour, diel vertical migration, current structure, depth, temperature, wind speed, cloud cover and type of habitat substratum all influence larval fish composition and distribution in the nearshore waters of South Africa.
- Full Text:
- Date Issued: 2019
- Authors: Trassierra, Jaqueline Anne
- Date: 2019
- Subjects: Fishes -- Larvae -- South Africa -- Eastern Cape , Fishes -- Larvae -- Migration -- South Africa -- Eastern Cape , Fishes -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68154 , vital:29207
- Description: The species composition, distribution and patterns of vertical migration of larval fish assemblages were investigated in March and in September 2013 within two adjacent log spiral bays, Algoa Bay and St Francis Bay, on the south coast of South Africa. Fish larvae were collected by means of a boat towed bongo net (57 cm diameter; mesh aperture 500 μm). An onshore (2 km) and an offshore (3 km) station were each sampled twice during the daytime (06:00 – 18:00) with two horizontal tows: near the surface (0.5 m) and close to the bottom (12 m). Tows were repeated at night (18:00 – 23:00) for onshore sites. Larval catches included 16 fish families and 40 species. A multivariate analysis indicated that the species composition was significantly different between Algoa Bay and St Francis Bay, with Engraulidae, Blenniidae, Sparidae, Soleidae and Cynoglossidae making important contributions to the larval fish catch in Algoa Bay, while Blenniidae, Engraulidae, Tripterygiidae, Sparidae and Gobiesocidae contributed significantly in St Francis Bay. Differences in assemblage composition were noted between the Spring (September–October) and Autumn (March-April) months. The species composition of larval fish assemblages was related to wind speed, wave height, cloud cover, sea water temperature, depth, average current speed and direction. Wind speed, wave height, temperature and depth significantly contributed to the variation in larval fish densities. Abundances of larval fishes were greater offshore than onshore, larvae from pelagic eggs dominated catches offshore, while larvae from demersal eggs dominated onshore catches. Habitat structure strongly influenced the composition of larval fishes between the bays and abundances were significantly greater at night than during the day. Most larval fishes displayed a reverse diel vertical migration pattern and were most influenced by predators, wind speed and cloud cover. This study shows that larval fish assemblages are highly complex and patchy. Spawning mode, individual species behaviour, diel vertical migration, current structure, depth, temperature, wind speed, cloud cover and type of habitat substratum all influence larval fish composition and distribution in the nearshore waters of South Africa.
- Full Text:
- Date Issued: 2019
Interaction between the root-feeding beetle, Longitarsus bethae (Coleoptera: Chrysomelidae) and the root-knot nematode, Meloidogyne javanica (Nematoda: Heteroderidae): Implications for the biological control of Lantana camara L. (Verbenaceae) in South Africa
- Authors: Musedeli, Jufter
- Date: 2019
- Subjects: Insect-plant relationships , Insects -- Host plants , Flea beetles , Symbiosis , Longitarsus , Chrysomelidae , Lantana camara -- Biological control -- South Africa , Heteroderidae , Root-knot nematodes , Weeds -- Biological control -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/71130 , vital:29788
- Description: Plants often are simultaneously attacked by several herbivores that can affect each other’s performance, and their interaction may affect their host plant fitness. The current study was conducted to determine the interaction between the root-feeding beetle, Longitarsus bethae Savini & Escalona (Coleoptera: Chrysomelidae) and a root-knot nematode, Meloidogyne javanica (Treub) Chitwood (Tylenchida: Heteroderidae), with implications for the biological control of Lantana camara L. (Verbenaceae) in South Africa. The studies were conducted under quarantine conditions at the Agricultural Research Council-PHP, Roodeplaat, Pretoria, South Africa. Specifically, the study determined; (i) whether root damage by the flea beetle enhanced infection by M. javanica, (ii) whether L. camara roots infected with the nematode enhanced the performance of the beetle, (iii) whether single or combined effect of the two organisms (i.e. L. bethae and M. javanica) had an overall effect on the growth and biomass of their shared host, L. camara, and (iv) the susceptibility of 10 L. camara varieties that are commonly found in South Africa to M. javanica. The study found that galling on the roots of L. camara by the nematode occurs at the highest inoculation of 300 eggs of L. bethae per plant, and no galling occurred at inoculation of 200 eggs per plant and below. The findings also showed that L. bethae performed better on M. javanica-infected than on healthy L. camara roots, and that more L. bethae adult progeny with slightly bigger body size emerged from M. javanica-infected, than from healthy plants. Fresh weight (galls) of plant roots from treatments where both species (i.e., L. bethae and M. javanica) were combined was significantly higher than that from plants infected with the nematode only, suggesting that the combination of both species induces more galling than the nematode does alone. The above-ground dry biomass was significantly lower both in combined and M. javanica only treatments, than in L. bethae only treatment. The study also found that selected L. camara varieties were infected with M. javanica, albeit at varying degrees of infection. Among the 10 L. camara varieties, Orange Red OR 015 was the most susceptible. Other susceptible varieties included Light Pink 009 LP, Total Pink 021 TP and Dark Pink 018 DP, and these, together with variety Orange Red OR 015, constituted 40% of the L. camara varieties evaluated in the current study. Fifty percent of the varieties displayed slight to moderate susceptibility to M. javanica, while 10% displayed lack of susceptibility. The study concluded that the symbiotic relationship between L. bethae and M. javanica was mutual, resulting in increase in the fitness of the beetle. The combined herbivory by L. bethae and M. javanica was also found to be additive on one of the most common varieties of L. camara in South Africa, and therefore co-infestation by both species might enhance the biological control of this weed in South Africa. The study further concluded that the suitability of some invasive L. camara cultivars such as Light Pink 009 LP and Orange Red 015 OR for M. javanica, might also contribute towards biological control of this weed in South Africa, particularly in areas where the two herbivores species co-exist.
- Full Text:
- Date Issued: 2019
- Authors: Musedeli, Jufter
- Date: 2019
- Subjects: Insect-plant relationships , Insects -- Host plants , Flea beetles , Symbiosis , Longitarsus , Chrysomelidae , Lantana camara -- Biological control -- South Africa , Heteroderidae , Root-knot nematodes , Weeds -- Biological control -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/71130 , vital:29788
- Description: Plants often are simultaneously attacked by several herbivores that can affect each other’s performance, and their interaction may affect their host plant fitness. The current study was conducted to determine the interaction between the root-feeding beetle, Longitarsus bethae Savini & Escalona (Coleoptera: Chrysomelidae) and a root-knot nematode, Meloidogyne javanica (Treub) Chitwood (Tylenchida: Heteroderidae), with implications for the biological control of Lantana camara L. (Verbenaceae) in South Africa. The studies were conducted under quarantine conditions at the Agricultural Research Council-PHP, Roodeplaat, Pretoria, South Africa. Specifically, the study determined; (i) whether root damage by the flea beetle enhanced infection by M. javanica, (ii) whether L. camara roots infected with the nematode enhanced the performance of the beetle, (iii) whether single or combined effect of the two organisms (i.e. L. bethae and M. javanica) had an overall effect on the growth and biomass of their shared host, L. camara, and (iv) the susceptibility of 10 L. camara varieties that are commonly found in South Africa to M. javanica. The study found that galling on the roots of L. camara by the nematode occurs at the highest inoculation of 300 eggs of L. bethae per plant, and no galling occurred at inoculation of 200 eggs per plant and below. The findings also showed that L. bethae performed better on M. javanica-infected than on healthy L. camara roots, and that more L. bethae adult progeny with slightly bigger body size emerged from M. javanica-infected, than from healthy plants. Fresh weight (galls) of plant roots from treatments where both species (i.e., L. bethae and M. javanica) were combined was significantly higher than that from plants infected with the nematode only, suggesting that the combination of both species induces more galling than the nematode does alone. The above-ground dry biomass was significantly lower both in combined and M. javanica only treatments, than in L. bethae only treatment. The study also found that selected L. camara varieties were infected with M. javanica, albeit at varying degrees of infection. Among the 10 L. camara varieties, Orange Red OR 015 was the most susceptible. Other susceptible varieties included Light Pink 009 LP, Total Pink 021 TP and Dark Pink 018 DP, and these, together with variety Orange Red OR 015, constituted 40% of the L. camara varieties evaluated in the current study. Fifty percent of the varieties displayed slight to moderate susceptibility to M. javanica, while 10% displayed lack of susceptibility. The study concluded that the symbiotic relationship between L. bethae and M. javanica was mutual, resulting in increase in the fitness of the beetle. The combined herbivory by L. bethae and M. javanica was also found to be additive on one of the most common varieties of L. camara in South Africa, and therefore co-infestation by both species might enhance the biological control of this weed in South Africa. The study further concluded that the suitability of some invasive L. camara cultivars such as Light Pink 009 LP and Orange Red 015 OR for M. javanica, might also contribute towards biological control of this weed in South Africa, particularly in areas where the two herbivores species co-exist.
- Full Text:
- Date Issued: 2019
An analysis of fusing advanced malware email protection logs, malware intelligence and active directory attributes as an instrument for threat intelligence
- Authors: Vermeulen, Japie
- Date: 2018
- Subjects: Malware (Computer software) , Computer networks Security measures , Data mining , Phishing , Data logging , Quantitative research
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63922 , vital:28506
- Description: After more than four decades email is still the most widely used electronic communication medium today. This electronic communication medium has evolved into an electronic weapon of choice for cyber criminals ranging from the novice to the elite. As cyber criminals evolve with tools, tactics and procedures, so too are technology vendors coming forward with a variety of advanced malware protection systems. However, even if an organization adopts such a system, there is still the daily challenge of interpreting the log data and understanding the type of malicious email attack, including who the target was and what the payload was. This research examines a six month data set obtained from an advanced malware email protection system from a bank in South Africa. Extensive data fusion techniques are used to provide deeper insight into the data by blending these with malware intelligence and business context. The primary data set is fused with malware intelligence to identify the different malware families associated with the samples. Active Directory attributes such as the business cluster, department and job title of users targeted by malware are also fused into the combined data. This study provides insight into malware attacks experienced in the South African financial services sector. For example, most of the malware samples identified belonged to different types of ransomware families distributed by known botnets. However, indicators of targeted attacks were observed based on particular employees targeted with exploit code and specific strains of malware. Furthermore, a short time span between newly discovered vulnerabilities and the use of malicious code to exploit such vulnerabilities through email were observed in this study. The fused data set provided the context to answer the “who”, “what”, “where” and “when”. The proposed methodology can be applied to any organization to provide insight into the malware threats identified by advanced malware email protection systems. In addition, the fused data set provides threat intelligence that could be used to strengthen the cyber defences of an organization against cyber threats.
- Full Text:
- Date Issued: 2018
- Authors: Vermeulen, Japie
- Date: 2018
- Subjects: Malware (Computer software) , Computer networks Security measures , Data mining , Phishing , Data logging , Quantitative research
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63922 , vital:28506
- Description: After more than four decades email is still the most widely used electronic communication medium today. This electronic communication medium has evolved into an electronic weapon of choice for cyber criminals ranging from the novice to the elite. As cyber criminals evolve with tools, tactics and procedures, so too are technology vendors coming forward with a variety of advanced malware protection systems. However, even if an organization adopts such a system, there is still the daily challenge of interpreting the log data and understanding the type of malicious email attack, including who the target was and what the payload was. This research examines a six month data set obtained from an advanced malware email protection system from a bank in South Africa. Extensive data fusion techniques are used to provide deeper insight into the data by blending these with malware intelligence and business context. The primary data set is fused with malware intelligence to identify the different malware families associated with the samples. Active Directory attributes such as the business cluster, department and job title of users targeted by malware are also fused into the combined data. This study provides insight into malware attacks experienced in the South African financial services sector. For example, most of the malware samples identified belonged to different types of ransomware families distributed by known botnets. However, indicators of targeted attacks were observed based on particular employees targeted with exploit code and specific strains of malware. Furthermore, a short time span between newly discovered vulnerabilities and the use of malicious code to exploit such vulnerabilities through email were observed in this study. The fused data set provided the context to answer the “who”, “what”, “where” and “when”. The proposed methodology can be applied to any organization to provide insight into the malware threats identified by advanced malware email protection systems. In addition, the fused data set provides threat intelligence that could be used to strengthen the cyber defences of an organization against cyber threats.
- Full Text:
- Date Issued: 2018
Health and fitness of young, healthy adult females and the effect of an eight week pilates intervention
- Authors: Eaton, Lara Lee
- Date: 2018
- Subjects: Physical fitness for women -- South Africa -- Makhanda , Pilates method , Exercise for women -- South Africa -- Makhanda , Exercise -- Health aspects -- South Africa -- Makhanda , Exercise -- Physiological aspects -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58267 , vital:27112
- Description: Purpose: The first phase of this study aimed to investigate the health and fitness status of young adult females in the local community. The second phase of this study investigated the impact of an eight week progressive Pilates intervention on selected health and fitness parameters in this cohort. Methods: Healthy young adult females aged 18-26 years (n=96), from the local community, partook in once-off tests including anthropometric measures (stature, body mass, Body Mass Index and waist circumference) as well as fitness parameters including balance, flexibility, muscular strength and endurance, and lastly lumbo-pelvic stability. Health measures investigated included blood pressure and spirometry. Where possible, results were compared to those of similar populations from national surveys or published normative data. Sedentary volunteers from this cohort were then randomised into a Pilates Exercise (PEx, n=12) or an inactive Control (Con, n=11) group, with their results from Phase 1 serving as baseline measures. Pilates classes were held twice weekly (60 minutes per session). All the measures from phase 1 were repeated at weeks 4 and 8. An additional intervention test included Transversus abdominis recruitment. Participants maintained habitual dietary intake and energy expenditure throughout. Nine PEx group and eight Con group participants completed the intervention. Results: The current sample (phase 1) was found to be healthier than comparative populations from national surveys, and significant differences (p<0.05) were found for all comparisons except Forced Expiratory Volume (FEV1), (p=0.64). Physical activity levels (230 min.week-1) exceeded that of the recommend weekly threshold (150 min.week-1). BMI, waist circumference, blood pressure and spirometry measures were all found to be within suggested healthy normal ranges. Pilates significantly improved lumbo-pelvic stability in the PEx group at weeks 4 (p<0.005) and 8 (p<0.002). Similarly, abdominal (p=0.00, d=1.1), upper limb (p=0.037, d=0.9) and lower limb endurance (p=0.02, d=1.0, between group d=0.73 for PEx) also improved with no changes in the Con group. PEx energy expenditure significantly increased from baseline to weeks 4 (p=0.007, d=10.7) and 8 (p=0.027, d=0.64), however body mass was maintained throughout. Conversely, Minute Ventilation decreased in the PEx cohort (p=0.010, d=0.95) from weeks 4 to 8. The Con group showed significant increases in body mass (p=0.018), leg strength (within-group Cohen’s d=-1.08 between weeks 0-8; d=-2 between weeks 4-8) and dynamic balance (p=0.01, d=-0.5). While no within-group changes were observed, Protein intake was significantly greater (p=0.036, d>0.8 at baseline and week 8) in the PEx group throughout the intervention. Medium between-group effect sizes (d>0.5) were noted for PEx BMI and waist circumference measures at all time points. Further, although not significant, the large within-group effect size (d=-0.84) between baseline and week 8 for PEx systolic blood pressure, suggested the 9 mm Hg was meaningful. The same time period also indicated a large within-group effect size (d=-0.8) for PEx dynamic balance, and a medium Cohen’s d for (d=0.57) PEx static balance. Conclusion: The local population of young adult females was found to be significantly healthier than those of comparable national samples. Further, Pilates participation significantly improved lumbo-pelvic stability and muscular endurance with meaningful changes in systolic blood pressure, and balance in previously sedentary young, adult females. Body mass was also maintained.
- Full Text:
- Date Issued: 2018
- Authors: Eaton, Lara Lee
- Date: 2018
- Subjects: Physical fitness for women -- South Africa -- Makhanda , Pilates method , Exercise for women -- South Africa -- Makhanda , Exercise -- Health aspects -- South Africa -- Makhanda , Exercise -- Physiological aspects -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58267 , vital:27112
- Description: Purpose: The first phase of this study aimed to investigate the health and fitness status of young adult females in the local community. The second phase of this study investigated the impact of an eight week progressive Pilates intervention on selected health and fitness parameters in this cohort. Methods: Healthy young adult females aged 18-26 years (n=96), from the local community, partook in once-off tests including anthropometric measures (stature, body mass, Body Mass Index and waist circumference) as well as fitness parameters including balance, flexibility, muscular strength and endurance, and lastly lumbo-pelvic stability. Health measures investigated included blood pressure and spirometry. Where possible, results were compared to those of similar populations from national surveys or published normative data. Sedentary volunteers from this cohort were then randomised into a Pilates Exercise (PEx, n=12) or an inactive Control (Con, n=11) group, with their results from Phase 1 serving as baseline measures. Pilates classes were held twice weekly (60 minutes per session). All the measures from phase 1 were repeated at weeks 4 and 8. An additional intervention test included Transversus abdominis recruitment. Participants maintained habitual dietary intake and energy expenditure throughout. Nine PEx group and eight Con group participants completed the intervention. Results: The current sample (phase 1) was found to be healthier than comparative populations from national surveys, and significant differences (p<0.05) were found for all comparisons except Forced Expiratory Volume (FEV1), (p=0.64). Physical activity levels (230 min.week-1) exceeded that of the recommend weekly threshold (150 min.week-1). BMI, waist circumference, blood pressure and spirometry measures were all found to be within suggested healthy normal ranges. Pilates significantly improved lumbo-pelvic stability in the PEx group at weeks 4 (p<0.005) and 8 (p<0.002). Similarly, abdominal (p=0.00, d=1.1), upper limb (p=0.037, d=0.9) and lower limb endurance (p=0.02, d=1.0, between group d=0.73 for PEx) also improved with no changes in the Con group. PEx energy expenditure significantly increased from baseline to weeks 4 (p=0.007, d=10.7) and 8 (p=0.027, d=0.64), however body mass was maintained throughout. Conversely, Minute Ventilation decreased in the PEx cohort (p=0.010, d=0.95) from weeks 4 to 8. The Con group showed significant increases in body mass (p=0.018), leg strength (within-group Cohen’s d=-1.08 between weeks 0-8; d=-2 between weeks 4-8) and dynamic balance (p=0.01, d=-0.5). While no within-group changes were observed, Protein intake was significantly greater (p=0.036, d>0.8 at baseline and week 8) in the PEx group throughout the intervention. Medium between-group effect sizes (d>0.5) were noted for PEx BMI and waist circumference measures at all time points. Further, although not significant, the large within-group effect size (d=-0.84) between baseline and week 8 for PEx systolic blood pressure, suggested the 9 mm Hg was meaningful. The same time period also indicated a large within-group effect size (d=-0.8) for PEx dynamic balance, and a medium Cohen’s d for (d=0.57) PEx static balance. Conclusion: The local population of young adult females was found to be significantly healthier than those of comparable national samples. Further, Pilates participation significantly improved lumbo-pelvic stability and muscular endurance with meaningful changes in systolic blood pressure, and balance in previously sedentary young, adult females. Body mass was also maintained.
- Full Text:
- Date Issued: 2018
A study of why some physic concepts in the South African Physical Science curriculum are poorly understood in order to develop a targeted action-research intervention for Newton’s second law
- Authors: Cobbing, Kathleen Margaret
- Date: 2020
- Subjects: Physics -- Study and teaching (Secondary) -- South Africa , Physics -- Examinations, questions, etc. -- South Africa , Motion -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146903 , vital:38575
- Description: Globally, many students show a poor understanding of concepts in high school physics and lack the necessary problem-solving skills that the course demands. The application of Newton’s second law was found to be particularly problematic through document analysis of South African examination feedback reports, as well as from an analysis of the physics examinations at a pair of well-resourced South African independent schools that follow the Independent Examination Board curriculum. Through an action-research approach, a resource for use by students was designed and modified to improve students’ understanding of this concept, while modelling problemsolving methods. The resource consisted of brief revision notes, worked examples and scaffolded exercises. The design of the resource was influenced by the theory of cognitive apprenticeship, cognitive load theory and conceptual change theory. One of the aims of the resource was to encourage students to translate between the different representations of a problem situation: symbolic, abstract, model and concrete. The impact of this resource was evaluated at a pair of schools using a mixed methods approach. This incorporated pre- and post-tests for a quantitative assessment, qualitative student evaluations and the analysis of examination scripts. There was an improvement from pre- to post-test for all four iterations of the intervention and these improvements were shown to be significant. The use of the resource led to an increase in the quality and quantity of diagrams drawn by students in subsequent assessments.
- Full Text:
- Date Issued: 2020
- Authors: Cobbing, Kathleen Margaret
- Date: 2020
- Subjects: Physics -- Study and teaching (Secondary) -- South Africa , Physics -- Examinations, questions, etc. -- South Africa , Motion -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146903 , vital:38575
- Description: Globally, many students show a poor understanding of concepts in high school physics and lack the necessary problem-solving skills that the course demands. The application of Newton’s second law was found to be particularly problematic through document analysis of South African examination feedback reports, as well as from an analysis of the physics examinations at a pair of well-resourced South African independent schools that follow the Independent Examination Board curriculum. Through an action-research approach, a resource for use by students was designed and modified to improve students’ understanding of this concept, while modelling problemsolving methods. The resource consisted of brief revision notes, worked examples and scaffolded exercises. The design of the resource was influenced by the theory of cognitive apprenticeship, cognitive load theory and conceptual change theory. One of the aims of the resource was to encourage students to translate between the different representations of a problem situation: symbolic, abstract, model and concrete. The impact of this resource was evaluated at a pair of schools using a mixed methods approach. This incorporated pre- and post-tests for a quantitative assessment, qualitative student evaluations and the analysis of examination scripts. There was an improvement from pre- to post-test for all four iterations of the intervention and these improvements were shown to be significant. The use of the resource led to an increase in the quality and quantity of diagrams drawn by students in subsequent assessments.
- Full Text:
- Date Issued: 2020
Statistical study of traveling ionospheric disturbances over South Africa
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
- Date Issued: 2019
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
- Date Issued: 2019
Recombinant expression, purification and in vitro interaction analysis of HOP and RhoC
- Vaaltyn, Michaelone Chantelle
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2016
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2016
Identification of SANCDB compounds against G2019S and I2020T variants of leucine-rich repeat Kinase 2 (LRRK2) for the development of drugs against Parkinson’s Disease
- Authors: Baye, Bertha Cinthia
- Date: 2020
- Subjects: Antiparkinsonian agents , Parkinson's disease -- Treatment , Protein kinases , Parkinson's disease -- Chemotherapy , Molecules -- Models
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138764 , vital:37671
- Description: Parkinson’s disease is a type of movement disorder that occurs when nerve cells in the brain stop producing dopamine. It is the second neurodegenerative disease affecting 1-2% of people above the ages of 65 years old. There is a worldwide prevalence of 7 to 10 million affected people of all cultures and race. Studies have shown that mutation that causes Parkinson’s disease result in increased kinase activity. The c.6055 G > A in exon 41 is the most prevalent LRRK2 variation which causes a substitution of glycine to serine in G2019S in the highly activated loop of its MAP kinase domain. The LRRK2 G2019S variant is the most common genetic determinant of Parkinson’s disease identified to date. This work focused on building accurate 3D models of the LRRK2 kinase domain, that were used for large-scale in silico docking against South African natural compounds from the South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/). Molecular docking was performed to identify compounds that formed interactions with the active site of the protein and had the lowest binding energy scores. Molecular dynamics simulations showed different movements of the protein-ligand complexes and behavioural difference of the wildtype and the variants, all three structures proved to be compact. Network analysis was done to study residue interactions, contact maps, dynamic cross correlations, average BC and average L were used to study the residue interactions and general residue contribution to the functioning of the protein..
- Full Text:
- Date Issued: 2020
- Authors: Baye, Bertha Cinthia
- Date: 2020
- Subjects: Antiparkinsonian agents , Parkinson's disease -- Treatment , Protein kinases , Parkinson's disease -- Chemotherapy , Molecules -- Models
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138764 , vital:37671
- Description: Parkinson’s disease is a type of movement disorder that occurs when nerve cells in the brain stop producing dopamine. It is the second neurodegenerative disease affecting 1-2% of people above the ages of 65 years old. There is a worldwide prevalence of 7 to 10 million affected people of all cultures and race. Studies have shown that mutation that causes Parkinson’s disease result in increased kinase activity. The c.6055 G > A in exon 41 is the most prevalent LRRK2 variation which causes a substitution of glycine to serine in G2019S in the highly activated loop of its MAP kinase domain. The LRRK2 G2019S variant is the most common genetic determinant of Parkinson’s disease identified to date. This work focused on building accurate 3D models of the LRRK2 kinase domain, that were used for large-scale in silico docking against South African natural compounds from the South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/). Molecular docking was performed to identify compounds that formed interactions with the active site of the protein and had the lowest binding energy scores. Molecular dynamics simulations showed different movements of the protein-ligand complexes and behavioural difference of the wildtype and the variants, all three structures proved to be compact. Network analysis was done to study residue interactions, contact maps, dynamic cross correlations, average BC and average L were used to study the residue interactions and general residue contribution to the functioning of the protein..
- Full Text:
- Date Issued: 2020
A study of four-dimensional oscillator groups and the associated left-invariant control affine systems
- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
- Full Text:
- Date Issued: 2012
- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
- Full Text:
- Date Issued: 2012
Targeted attack detection by means of free and open source solutions
- Authors: Bernardo, Louis F
- Date: 2019
- Subjects: Computer networks -- Security measures , Information technology -- Security measures , Computer security -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92269 , vital:30703
- Description: Compliance requirements are part of everyday business requirements for various areas, such as retail and medical services. As part of compliance it may be required to have infrastructure in place to monitor the activities in the environment to ensure that the relevant data and environment is sufficiently protected. At the core of such monitoring solutions one would find some type of data repository, or database, to store and ultimately correlate the captured events. Such solutions are commonly called Security Information and Event Management, or SIEM for short. Larger companies have been known to use commercial solutions such as IBM's Qradar, Logrythm, or Splunk. However, these come at significant cost and arent suitable for smaller businesses with limited budgets. These solutions require manual configuration of event correlation for detection of activities that place the environment in danger. This usually requires vendor implementation assistance that also would come at a cost. Alternatively, there are open source solutions that provide the required functionality. This research will demonstrate building an open source solution, with minimal to no cost for hardware or software, while still maintaining the capability of detecting targeted attacks. The solution presented in this research includes Wazuh, which is a combination of OSSEC and the ELK stack, integrated with an Network Intrusion Detection System (NIDS). The success of the integration, is determined by measuring postive attack detection based on each different configuration options. To perform the testing, a deliberately vulnerable platform named Metasploitable will be used as a victim host. The victim host vulnerabilities were created specifically to serve as target for Metasploit. The attacks were generated by utilising Metasploit Framework on a prebuilt Kali Linux host.
- Full Text:
- Date Issued: 2019
- Authors: Bernardo, Louis F
- Date: 2019
- Subjects: Computer networks -- Security measures , Information technology -- Security measures , Computer security -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92269 , vital:30703
- Description: Compliance requirements are part of everyday business requirements for various areas, such as retail and medical services. As part of compliance it may be required to have infrastructure in place to monitor the activities in the environment to ensure that the relevant data and environment is sufficiently protected. At the core of such monitoring solutions one would find some type of data repository, or database, to store and ultimately correlate the captured events. Such solutions are commonly called Security Information and Event Management, or SIEM for short. Larger companies have been known to use commercial solutions such as IBM's Qradar, Logrythm, or Splunk. However, these come at significant cost and arent suitable for smaller businesses with limited budgets. These solutions require manual configuration of event correlation for detection of activities that place the environment in danger. This usually requires vendor implementation assistance that also would come at a cost. Alternatively, there are open source solutions that provide the required functionality. This research will demonstrate building an open source solution, with minimal to no cost for hardware or software, while still maintaining the capability of detecting targeted attacks. The solution presented in this research includes Wazuh, which is a combination of OSSEC and the ELK stack, integrated with an Network Intrusion Detection System (NIDS). The success of the integration, is determined by measuring postive attack detection based on each different configuration options. To perform the testing, a deliberately vulnerable platform named Metasploitable will be used as a victim host. The victim host vulnerabilities were created specifically to serve as target for Metasploit. The attacks were generated by utilising Metasploit Framework on a prebuilt Kali Linux host.
- Full Text:
- Date Issued: 2019
Photocatalysis of 4-chloro and 4-nonylphenols using novel symmetric phthalocyanines and asymmetric porphyrin supported on polyacrylonitrite nanofibres
- Authors: Jones, Benjamin Martin
- Date: 2020
- Subjects: Nanoparticles , Phthalocyanines , Electrospinning , Porphyrins , Nanofibers , Photocatalysis , Photocatalysis -- Environmental aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164770 , vital:41163
- Description: This work explores the synthesis and characterisation of novel symmetrical phthalocyanines and novel asymmetric porphyrins that have been embedded or linked respectively,and electrospun into fibres for application in the photocatalysis of environmental pollutants. The phthalocyanines contain pyrrole moieties without hetero atom linkers to maintain a rigid structure. The porphyrin contains a carboxy moiety utilized to construct an amide bond between the complex and the polymer prior to the spinning process. The new compounds were characterized by elemental analyses, proton nuclear magnetic resonance (HNMR)Fourier-transform infrared spectroscopy (FTIR), MALDI-TOF and UV-vis spectroscopy. The general trends of fluorescence, triplet and singlet oxygen quantum yields are described as well as their appropriate lifetimes. The photocatalytic activity of phthalocyanine embedded fibres were compared against those that had been dyed. Unfortunately, during the degradation process, the dyed fibres leeched compound and the studies could not be continued. It was seen that the porphyrin fibres linked to the polymer showed the most efficient photocatalytic activity against 4-cholorphenol and 4-nonylphenol due to irradiation at lower wavelengths consequently having higher frequencies and transferring more energy.
- Full Text:
- Date Issued: 2020
- Authors: Jones, Benjamin Martin
- Date: 2020
- Subjects: Nanoparticles , Phthalocyanines , Electrospinning , Porphyrins , Nanofibers , Photocatalysis , Photocatalysis -- Environmental aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164770 , vital:41163
- Description: This work explores the synthesis and characterisation of novel symmetrical phthalocyanines and novel asymmetric porphyrins that have been embedded or linked respectively,and electrospun into fibres for application in the photocatalysis of environmental pollutants. The phthalocyanines contain pyrrole moieties without hetero atom linkers to maintain a rigid structure. The porphyrin contains a carboxy moiety utilized to construct an amide bond between the complex and the polymer prior to the spinning process. The new compounds were characterized by elemental analyses, proton nuclear magnetic resonance (HNMR)Fourier-transform infrared spectroscopy (FTIR), MALDI-TOF and UV-vis spectroscopy. The general trends of fluorescence, triplet and singlet oxygen quantum yields are described as well as their appropriate lifetimes. The photocatalytic activity of phthalocyanine embedded fibres were compared against those that had been dyed. Unfortunately, during the degradation process, the dyed fibres leeched compound and the studies could not be continued. It was seen that the porphyrin fibres linked to the polymer showed the most efficient photocatalytic activity against 4-cholorphenol and 4-nonylphenol due to irradiation at lower wavelengths consequently having higher frequencies and transferring more energy.
- Full Text:
- Date Issued: 2020
Synthesis, photophysicochemical properties and photodynamic therapy activities of indium and zinc phthalocyanines when incorporated into Pluronic polymer micelles
- Authors: Motloung, Banele Mike
- Date: 2020
- Subjects: Indium , Zinc , Phthalocyanines , Polymers , Photochemotherapy , Micelles
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167529 , vital:41489
- Description: This thesis reports on the syntheses, photophysicochemical properties and photodynamic therapy activities of symmetrical metallophthalocyanines (MPcs) when alone or when incorporated into Pluronic polymer micelles. The Pcs contain either zinc or indium as central metals and have phenyldiazenylphenoxy, pyridine-2-yloxy and benzo[d]thiazol-2-ylthio as ring substituents. Spectroscopic and microscopic techniques were used to confirm the formation MPcs with micelles. The photophysics and photochemistry of the Pcs were assessed when alone and with micelles. All the studied Pcs showed good photophysicochemical behavior with relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yields. The Pcs with indium in their central cavity exhibited higher triplet and singlet oxygen quantum yields in comparison to their zinc counterparts due to the heavy atom effect obtained from the former. The in vitro dark cytotoxicity and photodynamic therapy of the Pc complexes and conjugates against MCF7 cells was tested. All studied Pc complexes alone and with micelles showed minimum dark toxicity making them applicable for PDT. All complexes displayed good phototoxicity < 50% cell viability (except for complex 2 > 50% cell viability) at concentrations ≤100 μg/mL, however the conjugates showed < 45% cell viability at concentrations ≤ 100 μg/mL, probably due to the small micellar size and EPR effect. The findings from this work show the importance of incorporating photosensitizers such as phthalocyanines into Pluronic polymers micelles and making them water soluble and ultimately improving their photodynamic effect.
- Full Text:
- Date Issued: 2020
- Authors: Motloung, Banele Mike
- Date: 2020
- Subjects: Indium , Zinc , Phthalocyanines , Polymers , Photochemotherapy , Micelles
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167529 , vital:41489
- Description: This thesis reports on the syntheses, photophysicochemical properties and photodynamic therapy activities of symmetrical metallophthalocyanines (MPcs) when alone or when incorporated into Pluronic polymer micelles. The Pcs contain either zinc or indium as central metals and have phenyldiazenylphenoxy, pyridine-2-yloxy and benzo[d]thiazol-2-ylthio as ring substituents. Spectroscopic and microscopic techniques were used to confirm the formation MPcs with micelles. The photophysics and photochemistry of the Pcs were assessed when alone and with micelles. All the studied Pcs showed good photophysicochemical behavior with relatively high triplet and singlet oxygen quantum yields corresponding to their low fluorescence quantum yields. The Pcs with indium in their central cavity exhibited higher triplet and singlet oxygen quantum yields in comparison to their zinc counterparts due to the heavy atom effect obtained from the former. The in vitro dark cytotoxicity and photodynamic therapy of the Pc complexes and conjugates against MCF7 cells was tested. All studied Pc complexes alone and with micelles showed minimum dark toxicity making them applicable for PDT. All complexes displayed good phototoxicity < 50% cell viability (except for complex 2 > 50% cell viability) at concentrations ≤100 μg/mL, however the conjugates showed < 45% cell viability at concentrations ≤ 100 μg/mL, probably due to the small micellar size and EPR effect. The findings from this work show the importance of incorporating photosensitizers such as phthalocyanines into Pluronic polymers micelles and making them water soluble and ultimately improving their photodynamic effect.
- Full Text:
- Date Issued: 2020
Investigating the relationship between Heat Shock Proteins and HIV Transactivator of Transcription
- Authors: Flax, Lili Marie
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163307 , vital:41027
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Biochemistry and Microbiology, 2020.
- Full Text:
- Date Issued: 2020
- Authors: Flax, Lili Marie
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163307 , vital:41027
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Biochemistry and Microbiology, 2020.
- Full Text:
- Date Issued: 2020
In silico study of Plasmodium 1-deoxy-dxylulose 5-phosphate reductoisomerase (DXR) for identification of novel inhibitors from SANCDB
- Authors: Diallo, Bakary N'tji
- Date: 2018
- Subjects: Plasmodium 1-deoxy-dxylulose 5-phosphate reductoisomerase , Isoprenoids , Plasmodium , Antimalarials , Malaria -- Chemotherapy , Molecules -- Models , Molecular dynamics , South African Natural Compounds Database
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64012 , vital:28523
- Description: Malaria remains a major health concern with a complex parasite constantly developing resistance to the different drugs introduced to treat it, threatening the efficacy of the current ACT treatment recommended by WHO (World Health Organization). Different antimalarial compounds with different mechanisms of action are ideal as this decreases chances of resistance occurring. Inhibiting DXR and consequently the MEP pathway is a good strategy to find a new antimalarial with a novel mode of action. From literature, all the enzymes of the MEP pathway have also been shown to be indispensable for the synthesis of isoprenoids. They have been validated as drug targets and the X-ray structure of each of the enzymes has been solved. DXR is a protein which catalyses the second step of the MEP pathway. There are currently 255 DXR inhibitors in the Binding Database (accessed November 2017) generally based on the fosmidomycin structural scaffold and thus often showing poor drug likeness properties. This study aims to research new DXR inhibitors using in silico techniques. We analysed the protein sequence and built 3D models in close and open conformations for the different Plasmodium sequences. Then SANCDB compounds were screened to identify new potential DXR inhibitors with new chemical scaffolds. Finally, the identified hits were submitted to molecular dynamics studies, preceded by a parameterization of the manganese atom in the protein active site.
- Full Text:
- Date Issued: 2018
- Authors: Diallo, Bakary N'tji
- Date: 2018
- Subjects: Plasmodium 1-deoxy-dxylulose 5-phosphate reductoisomerase , Isoprenoids , Plasmodium , Antimalarials , Malaria -- Chemotherapy , Molecules -- Models , Molecular dynamics , South African Natural Compounds Database
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64012 , vital:28523
- Description: Malaria remains a major health concern with a complex parasite constantly developing resistance to the different drugs introduced to treat it, threatening the efficacy of the current ACT treatment recommended by WHO (World Health Organization). Different antimalarial compounds with different mechanisms of action are ideal as this decreases chances of resistance occurring. Inhibiting DXR and consequently the MEP pathway is a good strategy to find a new antimalarial with a novel mode of action. From literature, all the enzymes of the MEP pathway have also been shown to be indispensable for the synthesis of isoprenoids. They have been validated as drug targets and the X-ray structure of each of the enzymes has been solved. DXR is a protein which catalyses the second step of the MEP pathway. There are currently 255 DXR inhibitors in the Binding Database (accessed November 2017) generally based on the fosmidomycin structural scaffold and thus often showing poor drug likeness properties. This study aims to research new DXR inhibitors using in silico techniques. We analysed the protein sequence and built 3D models in close and open conformations for the different Plasmodium sequences. Then SANCDB compounds were screened to identify new potential DXR inhibitors with new chemical scaffolds. Finally, the identified hits were submitted to molecular dynamics studies, preceded by a parameterization of the manganese atom in the protein active site.
- Full Text:
- Date Issued: 2018
The effect of age and maturation on anthropometric characteristics and physical abilities of youth South African footballers
- Authors: De Beer, Ashley
- Date: 2020
- Subjects: Soccer -- Physiologial aspects , Soccer players -- South Africa -- Makhanda -- Physiology , Soccer players -- South Africa -- Makhanda -- Psychophysiology , Makana Local Football Association (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/141222 , vital:37954
- Description: Currently there is limited research investigating the football related abilities of youth South African individuals. Populations from North and South America, Europe and Asia have been extensively covered in terms of their anthropometric characteristics, physical abilities, technical competency, tactical understanding as well as various personality traits. In describing these details, and especially how each is affected during the ageing and pubertal process, a more informed understanding of the talent development systems is created. A holistic approach to talent development is required to effectively and efficiently produce elite level footballers. An important consideration is the unique socio-economic environment many youth footballers experience which may impact on the talent development process. The present study therefore sought to quantify the anthropometric characteristics and the physical ability level of youth South African footballers from Local Football Association in Makhanda in the Sarah Baartman Region of the Eastern Cape province. In order to achieve this a two-factorial design was used with age and maturity status as independent variables. Anthropometric characteristics were tested by finding the height, weight, body mass index and total fat percentage of participants. Physical ability was determined by results for aerobic capacity, power, acceleration, speed and agility. All tests were football specific and had been widely used in a variety of footballing studies. Additional demographic and socio-economic information was also recorded. A total of 136 participants were placed in their respective Under 11, 13, 15 or Under 19 age groups, while the maturity status of 96 participants were stratified into five distinct categories. Statistical analyses was conducted using p-value significance, with appropriate Tukey post-hoc tests administered when necessary, while effect sizes were calculated using Cohen’s d. Significant changes and practical effect sizes were present for nearly all dependent variables when either stratified by age or by maturity. Total fat percentage was the only dependent variable which was not influenced by either age or maturity. Age and maturity effect sizes for total body fat percentage indicated practical changes present which did not occur during statistical analysis. The present results indicate poor values when compared to normative data or that of other football playing study populations. Further longitudinal research is required to better understand individual growth rates for youth South African footballers, particularly from the Makana region. Implications of the thesis may determine long term development pathways, while the delayed maturity rate is a critical finding which needs to be further researched.
- Full Text:
- Date Issued: 2020
- Authors: De Beer, Ashley
- Date: 2020
- Subjects: Soccer -- Physiologial aspects , Soccer players -- South Africa -- Makhanda -- Physiology , Soccer players -- South Africa -- Makhanda -- Psychophysiology , Makana Local Football Association (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/141222 , vital:37954
- Description: Currently there is limited research investigating the football related abilities of youth South African individuals. Populations from North and South America, Europe and Asia have been extensively covered in terms of their anthropometric characteristics, physical abilities, technical competency, tactical understanding as well as various personality traits. In describing these details, and especially how each is affected during the ageing and pubertal process, a more informed understanding of the talent development systems is created. A holistic approach to talent development is required to effectively and efficiently produce elite level footballers. An important consideration is the unique socio-economic environment many youth footballers experience which may impact on the talent development process. The present study therefore sought to quantify the anthropometric characteristics and the physical ability level of youth South African footballers from Local Football Association in Makhanda in the Sarah Baartman Region of the Eastern Cape province. In order to achieve this a two-factorial design was used with age and maturity status as independent variables. Anthropometric characteristics were tested by finding the height, weight, body mass index and total fat percentage of participants. Physical ability was determined by results for aerobic capacity, power, acceleration, speed and agility. All tests were football specific and had been widely used in a variety of footballing studies. Additional demographic and socio-economic information was also recorded. A total of 136 participants were placed in their respective Under 11, 13, 15 or Under 19 age groups, while the maturity status of 96 participants were stratified into five distinct categories. Statistical analyses was conducted using p-value significance, with appropriate Tukey post-hoc tests administered when necessary, while effect sizes were calculated using Cohen’s d. Significant changes and practical effect sizes were present for nearly all dependent variables when either stratified by age or by maturity. Total fat percentage was the only dependent variable which was not influenced by either age or maturity. Age and maturity effect sizes for total body fat percentage indicated practical changes present which did not occur during statistical analysis. The present results indicate poor values when compared to normative data or that of other football playing study populations. Further longitudinal research is required to better understand individual growth rates for youth South African footballers, particularly from the Makana region. Implications of the thesis may determine long term development pathways, while the delayed maturity rate is a critical finding which needs to be further researched.
- Full Text:
- Date Issued: 2020
Detection and effects of selected pharmaceutical compounds from selected water bodies in the Eastern Cape Province, South Africa
- Authors: Setshedi, Koketso Josinah
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177074 , vital:42788
- Description: Theses embargoed. Release date March 2023. , Thesis (MSc) -- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Setshedi, Koketso Josinah
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177074 , vital:42788
- Description: Theses embargoed. Release date March 2023. , Thesis (MSc) -- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
A study of malicious software on the macOS operating system
- Authors: Regensberg, Mark Alan
- Date: 2019
- Subjects: Malware (Computer software) , Computer security , Computer viruses , Mac OS
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92302 , vital:30701
- Description: Much of the published malware research begins with a common refrain: the cost, quantum and complexity of threats are increasing, and research and practice should prioritise efforts to automate and reduce times to detect and prevent malware, while improving the consistency of categories and taxonomies applied to modern malware. Existing work related to malware targeting Apple's macOS platform has not been spared this approach, although limited research has been conducted on the true nature of threats faced by users of the operating system. While macOS focused research available consistently notes an increase in macOS users, devices and ultimately in threats, an opportunity exists to understand the real nature of threats faced by macOS users and suggest potential avenues for future work. This research provides a view of the current state of macOS malware by analysing and exploring a dataset of malware detections on macOS endpoints captured over a period of eleven months by an anti-malware software vendor. The dataset is augmented with malware information provided by the widely used Virus. Total service, as well as the application of prior automated malware categorisation work, AVClass to categorise and SSDeep to cluster and report on observed data. With Windows and Android platforms frequently in the spotlight as targets for highly disruptive malware like botnets, ransomware and cryptominers, research and intuition seem to suggest the threat of malware on this increasingly popular platform should be growing and evolving accordingly. Findings suggests that the direction and nature of growth and evolution may not be entirely as clear as industry reports suggest. Adware and Potentially Unwanted Applications (PUAs) make up the vast majority of the detected threats, with remote access trojans (RATs), ransomware and cryptocurrency miners comprising a relatively small proportion of the detected malware. This provides a number of avenues for potential future work to compare and contrast with research on other platforms, as well as identification of key factors that may influence its growth in the future.
- Full Text:
- Date Issued: 2019
- Authors: Regensberg, Mark Alan
- Date: 2019
- Subjects: Malware (Computer software) , Computer security , Computer viruses , Mac OS
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92302 , vital:30701
- Description: Much of the published malware research begins with a common refrain: the cost, quantum and complexity of threats are increasing, and research and practice should prioritise efforts to automate and reduce times to detect and prevent malware, while improving the consistency of categories and taxonomies applied to modern malware. Existing work related to malware targeting Apple's macOS platform has not been spared this approach, although limited research has been conducted on the true nature of threats faced by users of the operating system. While macOS focused research available consistently notes an increase in macOS users, devices and ultimately in threats, an opportunity exists to understand the real nature of threats faced by macOS users and suggest potential avenues for future work. This research provides a view of the current state of macOS malware by analysing and exploring a dataset of malware detections on macOS endpoints captured over a period of eleven months by an anti-malware software vendor. The dataset is augmented with malware information provided by the widely used Virus. Total service, as well as the application of prior automated malware categorisation work, AVClass to categorise and SSDeep to cluster and report on observed data. With Windows and Android platforms frequently in the spotlight as targets for highly disruptive malware like botnets, ransomware and cryptominers, research and intuition seem to suggest the threat of malware on this increasingly popular platform should be growing and evolving accordingly. Findings suggests that the direction and nature of growth and evolution may not be entirely as clear as industry reports suggest. Adware and Potentially Unwanted Applications (PUAs) make up the vast majority of the detected threats, with remote access trojans (RATs), ransomware and cryptocurrency miners comprising a relatively small proportion of the detected malware. This provides a number of avenues for potential future work to compare and contrast with research on other platforms, as well as identification of key factors that may influence its growth in the future.
- Full Text:
- Date Issued: 2019
Ecological engineering: an assessment of the ecological impact of Reno mattress structures used in erosion control in the Keurbooms Estuary, South Africa
- Authors: De Villiers, Nina
- Date: 2020
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Keurboomstrand , Coast changes -- South Africa -- Keurboomstrand , Shore protection -- South Africa -- Keurboomstrand , Coastal engineering-- South Africa -- Keurboomstrand , Coastal zone management-- South Africa -- Keurboomstrand , Estuarine ecology-- South Africa -- Keurboomstrand , Eelgrass -- South Africa -- Keurboomstrand , Reno Mattresses
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166138 , vital:41332
- Description: Global climate changes have been associated with ocean warming and sea-level rise. Armouring of coastlines has become common practice with the increasing threat of coastal erosion. The transformation of soft sediment habitats to hard, artificial habitats because of coastline armouring can lead to changes in species diversity, composition and distribution. It is, therefore, essential to assess changes to habitats from coastal development as well as the ecological impact erosion control structures have within coastal systems. Ecological engineering attempts to combine engineering principals and ecological processes to reduce environmental impacts from coastal development and the implementation of artificial structures. Estuaries are particularly vulnerable to anthropogenic impacts through development, and are extremely important systems offering nursery and foraging grounds for many species. These systems are, however, particularly vulnerable to anthropogenic impacts from urbanisation and development. Within South Africa many estuaries are being transformed by the addition of artificial structures to combat erosion, one such structure is the Reno mattress (a flattened wire box filled with rocks). This study compared the fish diversity and abundances of existing Reno mattress structures and natural eelgrass (Zostera capensis) habitat in the Keurbooms Estuary, South Africa. Benthic invertebrates were sampled using standard core sampling and an adapted suction sampling approach within the two habitats. The non-destructive method of mini Baited Remote Underwater Video Systems (BRUVs) was used to sample fish. Seasonal benthic invertebrate and fish abundances and assemblages were assessed from winter 2018 to spring 2019 with greater abundances of both recorded in summer. Significantly greater abundances, diversity, and richness of fish were found in the Reno mattress habitat compared to Z. capensis. Invertebrate taxa displayed some overlap between habitats, however, three higher taxonomic groups were only recorded within Reno mattress habitat and one only within the eelgrass habitat. Fish assemblages differed significantly between the two established habitats. A Before-After-Control-Impact (BACI) investigation was used to assess the ecological impact of newly installed Reno mattresses in the Keurbooms Estuary. Zostera capensis extent was sampled by determining the percentage cover of 0.5 m X 0.5 m quadrats and measurements of eelgrass blades. Percentage cover and blade length decreased during the installation of Reno mattress, but then recovered shortly after completion of the installation. Abundances, richness and diversity of invertebrates and fish were found to be similar before and after the installation which suggests that the installation had no net negative impact on the site. The Reno mattresses were found to attract fauna typical of rocky shore environments as well as a few invasive alien invertebrate species. This study noted that a hybrid habitat of Reno mattress and eelgrass was created and may in fact provide the positives of both to a system. In any coastal development it will be important to balance the demands of a growing population and the protection of natural habitats. The results of this study suggest that complex artificial structures such as Reno mattresses do provide habitat for fish and invertebrates. However, the use of these structures should be in combination with natural vegetation (e.g. as a hybrid habitat) and not one that replaces intertidal and subtidal natural habitat especially eelgrass. There is limited information regarding the ecological impacts of using Reno mattresses in estuaries and this study provides new information on their ecological efficacy that should be valuable for future coastal erosion control practices.
- Full Text:
- Date Issued: 2020
- Authors: De Villiers, Nina
- Date: 2020
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Keurboomstrand , Coast changes -- South Africa -- Keurboomstrand , Shore protection -- South Africa -- Keurboomstrand , Coastal engineering-- South Africa -- Keurboomstrand , Coastal zone management-- South Africa -- Keurboomstrand , Estuarine ecology-- South Africa -- Keurboomstrand , Eelgrass -- South Africa -- Keurboomstrand , Reno Mattresses
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166138 , vital:41332
- Description: Global climate changes have been associated with ocean warming and sea-level rise. Armouring of coastlines has become common practice with the increasing threat of coastal erosion. The transformation of soft sediment habitats to hard, artificial habitats because of coastline armouring can lead to changes in species diversity, composition and distribution. It is, therefore, essential to assess changes to habitats from coastal development as well as the ecological impact erosion control structures have within coastal systems. Ecological engineering attempts to combine engineering principals and ecological processes to reduce environmental impacts from coastal development and the implementation of artificial structures. Estuaries are particularly vulnerable to anthropogenic impacts through development, and are extremely important systems offering nursery and foraging grounds for many species. These systems are, however, particularly vulnerable to anthropogenic impacts from urbanisation and development. Within South Africa many estuaries are being transformed by the addition of artificial structures to combat erosion, one such structure is the Reno mattress (a flattened wire box filled with rocks). This study compared the fish diversity and abundances of existing Reno mattress structures and natural eelgrass (Zostera capensis) habitat in the Keurbooms Estuary, South Africa. Benthic invertebrates were sampled using standard core sampling and an adapted suction sampling approach within the two habitats. The non-destructive method of mini Baited Remote Underwater Video Systems (BRUVs) was used to sample fish. Seasonal benthic invertebrate and fish abundances and assemblages were assessed from winter 2018 to spring 2019 with greater abundances of both recorded in summer. Significantly greater abundances, diversity, and richness of fish were found in the Reno mattress habitat compared to Z. capensis. Invertebrate taxa displayed some overlap between habitats, however, three higher taxonomic groups were only recorded within Reno mattress habitat and one only within the eelgrass habitat. Fish assemblages differed significantly between the two established habitats. A Before-After-Control-Impact (BACI) investigation was used to assess the ecological impact of newly installed Reno mattresses in the Keurbooms Estuary. Zostera capensis extent was sampled by determining the percentage cover of 0.5 m X 0.5 m quadrats and measurements of eelgrass blades. Percentage cover and blade length decreased during the installation of Reno mattress, but then recovered shortly after completion of the installation. Abundances, richness and diversity of invertebrates and fish were found to be similar before and after the installation which suggests that the installation had no net negative impact on the site. The Reno mattresses were found to attract fauna typical of rocky shore environments as well as a few invasive alien invertebrate species. This study noted that a hybrid habitat of Reno mattress and eelgrass was created and may in fact provide the positives of both to a system. In any coastal development it will be important to balance the demands of a growing population and the protection of natural habitats. The results of this study suggest that complex artificial structures such as Reno mattresses do provide habitat for fish and invertebrates. However, the use of these structures should be in combination with natural vegetation (e.g. as a hybrid habitat) and not one that replaces intertidal and subtidal natural habitat especially eelgrass. There is limited information regarding the ecological impacts of using Reno mattresses in estuaries and this study provides new information on their ecological efficacy that should be valuable for future coastal erosion control practices.
- Full Text:
- Date Issued: 2020
Using action cameras to assess habitat use by Pseudobarbus afer and Sandelia capensis in the Swartkops River, Eastern Cape, South Africa
- Authors: Hannweg, Bianca
- Date: 2018
- Subjects: Freshwater biodiversity -- South Africa -- Eastern Cape , Freshwater biodiversity conservation -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Freshwater fishes -- South Africa -- Eastern Cape , Freshwater fishes -- Behavior -- South Africa -- Eastern Cape , Freshwater fishes -- Habitat -- South Africa -- Eastern Cape , Underwater videography , Anabantidae -- South Africa -- Eastern Cape , Cyprinidae -- South Africa -- Eastern Cape , Pseudobarbus afer , Sandelia capensis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62039 , vital:28098
- Description: Currently, freshwater systems are facing various threats, freshwater biota are declining and there is an increased need to monitor freshwater fauna and flora using non-invasive methods. This thesis aimed to evaluate the potential of using action cameras as a tool for the monitoring of freshwater fish populations and the collection of habitat utilisation data. This evaluation was conducted in headwater tributaries of the Swartkops River in South Africa, using two threatened species that have not been extensively studied, Pseudobarbus afer (Peters, 1864) and Sandelia capensis (Cuvier, 1831). The aims of this study were to: (1) assess the use of underwater video analysis (UWVA) using action cameras (videos and still photographs) in comparison to estimates derived from snorkel surveys, to estimate the abundance of P. afer in headwater streams; (2) use estimates derived from UWVA (videos and photographs) to assess the habitat use of two imperilled species, P. afer and S. capensis; and (3) assess habitat use by these two species in the presence of an artificial habitat. This work demonstrated that: (1) estimates derived from videos and photographs were strongly correlated to estimates derived from snorkel surveys, provided multiple cameras were used; (2) estimates derived from videos and photographs were not significantly different to estimates derived from snorkel surveys; (3) a filming period of 15 minutes was sufficient at detecting 0.9 of the cumulative mMaxN (mean MaxN) within one of the five habitats; and (4) still photographs, which are less time consuming to process than videos, could be used in preference to videos. Based on these findings, techniques using action cameras to assess habitat utilisation and behaviour in situ of the two-focal species, were developed using six habitat types (inflow, outflow, woody debris, fern root, middle and artificial) in four pools. It was demonstrated that: (1) there was a significant difference in proportional occupancies across habitats for both P. afer and S. capensis; (2) Pseudobarbus afer were mainly observed schooling in the middle of the pool and feeding on detritus material in fern root, woody debris and off the artificial structure; and (3) Sandelia capensis rapidly colonised the artificial structure and were observed utilising it for refuge. In conclusion, this work demonstrated that still photographs from action cameras can be used in place of videos to estimate the abundance of freshwater fishes and assess their habitat use and behaviour in clear headwater streams. This work also demonstrated how action cameras could be used to evaluate the effect of the introduction of artificial habitat as a restoration measure for headwater fish communities.
- Full Text:
- Date Issued: 2018
- Authors: Hannweg, Bianca
- Date: 2018
- Subjects: Freshwater biodiversity -- South Africa -- Eastern Cape , Freshwater biodiversity conservation -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Freshwater fishes -- South Africa -- Eastern Cape , Freshwater fishes -- Behavior -- South Africa -- Eastern Cape , Freshwater fishes -- Habitat -- South Africa -- Eastern Cape , Underwater videography , Anabantidae -- South Africa -- Eastern Cape , Cyprinidae -- South Africa -- Eastern Cape , Pseudobarbus afer , Sandelia capensis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62039 , vital:28098
- Description: Currently, freshwater systems are facing various threats, freshwater biota are declining and there is an increased need to monitor freshwater fauna and flora using non-invasive methods. This thesis aimed to evaluate the potential of using action cameras as a tool for the monitoring of freshwater fish populations and the collection of habitat utilisation data. This evaluation was conducted in headwater tributaries of the Swartkops River in South Africa, using two threatened species that have not been extensively studied, Pseudobarbus afer (Peters, 1864) and Sandelia capensis (Cuvier, 1831). The aims of this study were to: (1) assess the use of underwater video analysis (UWVA) using action cameras (videos and still photographs) in comparison to estimates derived from snorkel surveys, to estimate the abundance of P. afer in headwater streams; (2) use estimates derived from UWVA (videos and photographs) to assess the habitat use of two imperilled species, P. afer and S. capensis; and (3) assess habitat use by these two species in the presence of an artificial habitat. This work demonstrated that: (1) estimates derived from videos and photographs were strongly correlated to estimates derived from snorkel surveys, provided multiple cameras were used; (2) estimates derived from videos and photographs were not significantly different to estimates derived from snorkel surveys; (3) a filming period of 15 minutes was sufficient at detecting 0.9 of the cumulative mMaxN (mean MaxN) within one of the five habitats; and (4) still photographs, which are less time consuming to process than videos, could be used in preference to videos. Based on these findings, techniques using action cameras to assess habitat utilisation and behaviour in situ of the two-focal species, were developed using six habitat types (inflow, outflow, woody debris, fern root, middle and artificial) in four pools. It was demonstrated that: (1) there was a significant difference in proportional occupancies across habitats for both P. afer and S. capensis; (2) Pseudobarbus afer were mainly observed schooling in the middle of the pool and feeding on detritus material in fern root, woody debris and off the artificial structure; and (3) Sandelia capensis rapidly colonised the artificial structure and were observed utilising it for refuge. In conclusion, this work demonstrated that still photographs from action cameras can be used in place of videos to estimate the abundance of freshwater fishes and assess their habitat use and behaviour in clear headwater streams. This work also demonstrated how action cameras could be used to evaluate the effect of the introduction of artificial habitat as a restoration measure for headwater fish communities.
- Full Text:
- Date Issued: 2018