Aspects of the thermal ecology of six species of carcass beetles in South Africa
- Authors: Midgley, John Mark
- Date: 2008
- Subjects: Forensic entomology , Diptera -- South Africa , Beetles -- South Africa , Burying beetles , Burying beetles -- South Africa , Beetles -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5643 , http://hdl.handle.net/10962/d1005325 , Forensic entomology , Diptera -- South Africa , Beetles -- South Africa , Burying beetles , Burying beetles -- South Africa , Beetles -- Effect of temperature on
- Description: The forensic application of entomology is well known, but it is generally a field which concentrates on Diptera. Many Coleoptera also have forensic application, but are generally neglected by forensic entomology researchers. Necrophilic Coleoptera are diverse and therefore have application in estimating Post-Mortem Interval (PMI) by community composition, but they are also valuable in estimating PMI by development. In addition, Coleoptera are more common in stored product cases. Six species of forensically important Coleoptera were studied, three from the family Dermestidae (Dermestes haemorrhoidalis, D. maculatus and D. peruvianus) and three from the family Silphidae (Silpha punctulata, Thanatophilus micans and T. mutilatus). The effect of killing method and storage time on larval length was investigated in T. micans. Coleopteran larvae were shown not to behave in the same way as dipteran larvae. In contrast to dipteran larvae, it is recommended that coleopteran larvae be killed using ethanol. A development model is presented for T. micans. This represents the first statistically robust development model for forensically important Coleoptera, and the first development model for forensically important Silphidae. The model offers a method of estimating PMI which can be used once Diptera are no longer present on a corpse. Upper lethal temperature limits for four species of carcass beetle were determined. A comparison between species shows distinct differentiation between families and species. This differentiation accounts for microhabitat differences which these species show on carcasses. Bioclimatic models for the six species showed contrasting distributions, with both widespread and localised species. These models allow forensic investigators to assess whether the absence of a species from a corpse is forensically significant, or a result of the species distributions. Moisture-related variables were shown to be more important in predicting species distributions than temperature at a regional scale. Forensic entomology standards can be adjusted based on the findings of this study. Length was again shown to be an inferior measurement of larval age. Coleopteran development has been shown to be useful, and should be given greater consideration in future work. T. micans has been shown to be capable of locating and ovipositing on carcasses promptly after death, making it a good forensic indicator. Further work is needed for the full potential of necrophilic Coleoptera to be realised.
- Full Text:
- Date Issued: 2008
- Authors: Midgley, John Mark
- Date: 2008
- Subjects: Forensic entomology , Diptera -- South Africa , Beetles -- South Africa , Burying beetles , Burying beetles -- South Africa , Beetles -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5643 , http://hdl.handle.net/10962/d1005325 , Forensic entomology , Diptera -- South Africa , Beetles -- South Africa , Burying beetles , Burying beetles -- South Africa , Beetles -- Effect of temperature on
- Description: The forensic application of entomology is well known, but it is generally a field which concentrates on Diptera. Many Coleoptera also have forensic application, but are generally neglected by forensic entomology researchers. Necrophilic Coleoptera are diverse and therefore have application in estimating Post-Mortem Interval (PMI) by community composition, but they are also valuable in estimating PMI by development. In addition, Coleoptera are more common in stored product cases. Six species of forensically important Coleoptera were studied, three from the family Dermestidae (Dermestes haemorrhoidalis, D. maculatus and D. peruvianus) and three from the family Silphidae (Silpha punctulata, Thanatophilus micans and T. mutilatus). The effect of killing method and storage time on larval length was investigated in T. micans. Coleopteran larvae were shown not to behave in the same way as dipteran larvae. In contrast to dipteran larvae, it is recommended that coleopteran larvae be killed using ethanol. A development model is presented for T. micans. This represents the first statistically robust development model for forensically important Coleoptera, and the first development model for forensically important Silphidae. The model offers a method of estimating PMI which can be used once Diptera are no longer present on a corpse. Upper lethal temperature limits for four species of carcass beetle were determined. A comparison between species shows distinct differentiation between families and species. This differentiation accounts for microhabitat differences which these species show on carcasses. Bioclimatic models for the six species showed contrasting distributions, with both widespread and localised species. These models allow forensic investigators to assess whether the absence of a species from a corpse is forensically significant, or a result of the species distributions. Moisture-related variables were shown to be more important in predicting species distributions than temperature at a regional scale. Forensic entomology standards can be adjusted based on the findings of this study. Length was again shown to be an inferior measurement of larval age. Coleopteran development has been shown to be useful, and should be given greater consideration in future work. T. micans has been shown to be capable of locating and ovipositing on carcasses promptly after death, making it a good forensic indicator. Further work is needed for the full potential of necrophilic Coleoptera to be realised.
- Full Text:
- Date Issued: 2008
Characterization of polarization dependent loss in optical fibres and optical components in the presence of polarization mode dispersion
- Authors: Pelaelo, Gaoboelwe
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10528 , http://hdl.handle.net/10948/695 , Fiber optics , Polarization (Light)
- Description: In this study, the Jones matrix eigenanalysis (JME), optical spectrum analyzer (OSA) and polarization scrambling methods were used to investigate polarization dependent loss (PDL) in the presence of polarization mode dispersion (PMD) in optical components and fibres. The PDL measurements were conducted both in the laboratory and in the field. For field measurements, a buried link (28.8 km) and an aerial fibre (7.1 km) were extensively studied. The findings obtained from these studies are very important for network operators who must assess the impact of PDL on the network reliability. The three different PDL measurement methods (JME, OSA and polarization scrambling) were compared and their PDL values were found to agree very well at the selected wavelength of 1550 nm. Concatenation of PDL components showed that as expected, PDL increase as the number of PDL components were added. The interactions between PMD and PDL measurements were analyzed. A PMD/PDL emulator was constructed. We observed that PMD decreased while PDL increased. The PMD decrease was a result of the PMD vector cancellation enhanced by the randomly distributed mode coupling angles while PDL increase was a result of each PM fibre segments contributing to the overall global PDL. It was observed that the presence of PMD in a link containing PDL, results in PDL being wavelength dependent and this resulted in the extraction of the PMD information from the PDL data. PDL was found to be Maxwellian distributed when considering low values of PMD. High PMD values resulted in the PDL distribution deviating from Maxwellian. Long-term PDL and PMD (average DGD) measurements indicated that the PDL and PMD varied slowly with time and wavelength for both the laboratory and field measurements. It was observed that the BER increase as both PDL and PMD increased for simulated optical link.
- Full Text:
- Date Issued: 2008
- Authors: Pelaelo, Gaoboelwe
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10528 , http://hdl.handle.net/10948/695 , Fiber optics , Polarization (Light)
- Description: In this study, the Jones matrix eigenanalysis (JME), optical spectrum analyzer (OSA) and polarization scrambling methods were used to investigate polarization dependent loss (PDL) in the presence of polarization mode dispersion (PMD) in optical components and fibres. The PDL measurements were conducted both in the laboratory and in the field. For field measurements, a buried link (28.8 km) and an aerial fibre (7.1 km) were extensively studied. The findings obtained from these studies are very important for network operators who must assess the impact of PDL on the network reliability. The three different PDL measurement methods (JME, OSA and polarization scrambling) were compared and their PDL values were found to agree very well at the selected wavelength of 1550 nm. Concatenation of PDL components showed that as expected, PDL increase as the number of PDL components were added. The interactions between PMD and PDL measurements were analyzed. A PMD/PDL emulator was constructed. We observed that PMD decreased while PDL increased. The PMD decrease was a result of the PMD vector cancellation enhanced by the randomly distributed mode coupling angles while PDL increase was a result of each PM fibre segments contributing to the overall global PDL. It was observed that the presence of PMD in a link containing PDL, results in PDL being wavelength dependent and this resulted in the extraction of the PMD information from the PDL data. PDL was found to be Maxwellian distributed when considering low values of PMD. High PMD values resulted in the PDL distribution deviating from Maxwellian. Long-term PDL and PMD (average DGD) measurements indicated that the PDL and PMD varied slowly with time and wavelength for both the laboratory and field measurements. It was observed that the BER increase as both PDL and PMD increased for simulated optical link.
- Full Text:
- Date Issued: 2008
Characterization of polarization effects on deployed aerial optical fibre in South Africa
- Authors: Mudau, Azwitamisi Eric
- Date: 2008
- Subjects: Polarization (Light) , Fiber optics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10521 , http://hdl.handle.net/10948/1060 , Polarization (Light) , Fiber optics
- Description: In this study, two polarization effects, namely the state of polarization (SOP) and polarization mode dispersion (PMD) in optical fibre cable are investigated. The change in polarization effects introduces errors in optical fibre communication system. We find that the SOP drifts slowly in buried cables, and rapidly in aerial cables. This is because buried cables are located in a static environment, whereas aerial cables are exposed directly to a dynamic environment. The SOP change in aerial cable shows significant correlation with its environment (the global radiation, temperature and wind). The autocorrelation function (ACF) was not performed in buried cable, since they do not satisfy the ACF assumption, whereas in aerial cable it is found that the ACF of the SOP decorrelates quite quickly during the day. The 50 percent decorrelation time during the day and night are 9.6 and 30.4 minutes, respectively. During the day the properties of the optical fibre change rapidly as a result of the rapidly changing environmental conditions, whereas at night the environmental conditions change relatively slowly. Fast Fourier Transform (FFT) of the SOP fluctuations show discrete peaks, which corresponds to the wind induced vibrational frequency of the cable. The PMD fluctuations for undeployed and deployed aerial optical fibre cable are monitored using the generalized interferometric technique (GINTY). It is found that the PMD measured with polarization scrambling is more scattered but more reliable than the PMD measured without polarization scrambling. This is because the PMD obtained with polarization scrambling is averaged over different input and output (I/O) SOP pairs. For deployed aerial cable, it is found that the PMD measured without polarization scrambling fluctuates rapidly during high wind speed conditions. Furthermore, there is a correlation between the measured PMD and the change in temperature. It is found that the change in temperature has a stronger influence than the wind on the PMD of the optical fibre link.
- Full Text:
- Date Issued: 2008
- Authors: Mudau, Azwitamisi Eric
- Date: 2008
- Subjects: Polarization (Light) , Fiber optics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10521 , http://hdl.handle.net/10948/1060 , Polarization (Light) , Fiber optics
- Description: In this study, two polarization effects, namely the state of polarization (SOP) and polarization mode dispersion (PMD) in optical fibre cable are investigated. The change in polarization effects introduces errors in optical fibre communication system. We find that the SOP drifts slowly in buried cables, and rapidly in aerial cables. This is because buried cables are located in a static environment, whereas aerial cables are exposed directly to a dynamic environment. The SOP change in aerial cable shows significant correlation with its environment (the global radiation, temperature and wind). The autocorrelation function (ACF) was not performed in buried cable, since they do not satisfy the ACF assumption, whereas in aerial cable it is found that the ACF of the SOP decorrelates quite quickly during the day. The 50 percent decorrelation time during the day and night are 9.6 and 30.4 minutes, respectively. During the day the properties of the optical fibre change rapidly as a result of the rapidly changing environmental conditions, whereas at night the environmental conditions change relatively slowly. Fast Fourier Transform (FFT) of the SOP fluctuations show discrete peaks, which corresponds to the wind induced vibrational frequency of the cable. The PMD fluctuations for undeployed and deployed aerial optical fibre cable are monitored using the generalized interferometric technique (GINTY). It is found that the PMD measured with polarization scrambling is more scattered but more reliable than the PMD measured without polarization scrambling. This is because the PMD obtained with polarization scrambling is averaged over different input and output (I/O) SOP pairs. For deployed aerial cable, it is found that the PMD measured without polarization scrambling fluctuates rapidly during high wind speed conditions. Furthermore, there is a correlation between the measured PMD and the change in temperature. It is found that the change in temperature has a stronger influence than the wind on the PMD of the optical fibre link.
- Full Text:
- Date Issued: 2008
Composition and phenology of insect pests of Capsicum (Solanaceae) cultivated in the Makana District, Eastern Cape Province, South Africa
- Authors: Hepburn, Colleen
- Date: 2008
- Subjects: Insects -- South Africa -- Eastern Cape -- Composition Insects -- South Africa -- Eastern Cape -- Phenology Agricultural pests -- South Africa -- Eastern Cape Peppers -- Diseases and pests -- South Africa -- Eastern Cape Solanaceae -- Diseases and pests -- South Africa -- Eastern Cape Insect pests -- South Africa -- Eastern Cape Insect pests -- Biological control -- South Africa -- Eastern Cape Insect pests -- Control -- Methods -- South Africa -- Eastern Cape Insects -- Host plants -- South Africa -- Eastern Cape Insect-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5656 , http://hdl.handle.net/10962/d1005339
- Description: Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.
- Full Text:
- Date Issued: 2008
- Authors: Hepburn, Colleen
- Date: 2008
- Subjects: Insects -- South Africa -- Eastern Cape -- Composition Insects -- South Africa -- Eastern Cape -- Phenology Agricultural pests -- South Africa -- Eastern Cape Peppers -- Diseases and pests -- South Africa -- Eastern Cape Solanaceae -- Diseases and pests -- South Africa -- Eastern Cape Insect pests -- South Africa -- Eastern Cape Insect pests -- Biological control -- South Africa -- Eastern Cape Insect pests -- Control -- Methods -- South Africa -- Eastern Cape Insects -- Host plants -- South Africa -- Eastern Cape Insect-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5656 , http://hdl.handle.net/10962/d1005339
- Description: Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.
- Full Text:
- Date Issued: 2008
Connection management applications for high-speed audio networking
- Authors: Sibanda, Phathisile
- Date: 2008 , 2008-03-12
- Subjects: Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4634 , http://hdl.handle.net/10962/d1006532 , Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Description: Traditionally, connection management applications (referred to as patchbays) for high-speed audio networking, are predominantly developed using third-generation languages such as C, C# and C++. Due to the rapid increase in distributed audio/video network usage in the world today, connection management applications that control signal routing over these networks have also evolved in complexity to accommodate more functionality. As the result, high-speed audio networking application developers require a tool that will enable them to develop complex connection management applications easily and within the shortest possible time. In addition, this tool should provide them with the reliability and flexibility required to develop applications controlling signal routing in networks carrying real-time data. High-speed audio networks are used for various purposes that include audio/video production and broadcasting. This investigation evaluates the possibility of using Adobe Flash Professional 8, using ActionScript 2.0, for developing connection management applications. Three patchbays, namely the Broadcast patchbay, the Project studio patchbay, and the Hospitality/Convention Centre patchbay were developed and tested for connection management in three sound installation networks, namely the Broadcast network, the Project studio network, and the Hospitality/Convention Centre network. Findings indicate that complex connection management applications can effectively be implemented using the Adobe Flash IDE and ActionScript 2.0.
- Full Text:
- Date Issued: 2008
- Authors: Sibanda, Phathisile
- Date: 2008 , 2008-03-12
- Subjects: Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4634 , http://hdl.handle.net/10962/d1006532 , Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Description: Traditionally, connection management applications (referred to as patchbays) for high-speed audio networking, are predominantly developed using third-generation languages such as C, C# and C++. Due to the rapid increase in distributed audio/video network usage in the world today, connection management applications that control signal routing over these networks have also evolved in complexity to accommodate more functionality. As the result, high-speed audio networking application developers require a tool that will enable them to develop complex connection management applications easily and within the shortest possible time. In addition, this tool should provide them with the reliability and flexibility required to develop applications controlling signal routing in networks carrying real-time data. High-speed audio networks are used for various purposes that include audio/video production and broadcasting. This investigation evaluates the possibility of using Adobe Flash Professional 8, using ActionScript 2.0, for developing connection management applications. Three patchbays, namely the Broadcast patchbay, the Project studio patchbay, and the Hospitality/Convention Centre patchbay were developed and tested for connection management in three sound installation networks, namely the Broadcast network, the Project studio network, and the Hospitality/Convention Centre network. Findings indicate that complex connection management applications can effectively be implemented using the Adobe Flash IDE and ActionScript 2.0.
- Full Text:
- Date Issued: 2008
Constructing confidence intervals for polarization mode dispersion
- Authors: Erlank, Warrick
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10571 , http://hdl.handle.net/10948/951 , Fiber optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) causes significant impairment in high bit-rate optical telecommunications systems. Knowledge of a fibre’s PMD mean value, and the relevant confidence interval, is essential for determining a fibre’s maximum allowable bit-rate. Various methods of confidence interval construction for time series data were tested in this dissertation using simulation. These included the autocovariance-matrix methods as suggested by Box and Jenkins, as well as the more practical and simpler batch means methods. Some of these methods were shown to be significantly better than the standard method of calculating confidence intervals for non time series data. The best of the tested methods were used on actual PMD data. The effect of using polarization scramblers was also tested.
- Full Text:
- Date Issued: 2008
- Authors: Erlank, Warrick
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10571 , http://hdl.handle.net/10948/951 , Fiber optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) causes significant impairment in high bit-rate optical telecommunications systems. Knowledge of a fibre’s PMD mean value, and the relevant confidence interval, is essential for determining a fibre’s maximum allowable bit-rate. Various methods of confidence interval construction for time series data were tested in this dissertation using simulation. These included the autocovariance-matrix methods as suggested by Box and Jenkins, as well as the more practical and simpler batch means methods. Some of these methods were shown to be significantly better than the standard method of calculating confidence intervals for non time series data. The best of the tested methods were used on actual PMD data. The effect of using polarization scramblers was also tested.
- Full Text:
- Date Issued: 2008
Cranial ontogeny of the sole, dagetichthys marginatus (soleidae), with considerations on the feeding ability of larvae and early juveniles
- Ende, Stephan Siegfried Werner
- Authors: Ende, Stephan Siegfried Werner
- Date: 2008
- Subjects: Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5250 , http://hdl.handle.net/10962/d1005093 , Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Description: The overall aim of this study was to gain a better understanding of the feeding mechanisms of the larvae and early juveniles of the sole, Dagetichthys marginatus (Soleidae), with which to assess the suitability of current feeding protocols and to facilitate the development of an appropriate pelleted feed. This was achieved by examining the ontogeny of the cranium of laboratory reared sole, with particular emphasis on those elements associated with feeding and by comparing the cranium of juvenile fish with that of adult fish. At 4 dah (days after hatch) Dagetichthys marginatus larvae develop the first rudimentary branchial arches that facilitates the capture and ingestion of food items. Subsequent development of cranial structures, such as the oral jaws, suspensorium, neurocranium, hyoid and branchial arches and the opercular apparatus enables the larvae, at 16 dah, to switch from ram feeding to suction feeding on live prey. The use of live Artemia nauplii from 4 to 16 dah is therefore appropriate. The first morphological asymmetries developed at 16 dah in the dentaries and at 22 dah the maxillae and the premaxillae began to show asymmetries. Teeth were present only on the blind side of the oral jaw elements and during this period (16 to 22 dah) the existing elements began to ossify. From 16 to 35 dah the standard feeding protocol consists of a combination of pelagic (Artemia metanauplii) and benthic prey (dead, frozen Artemia nauplii) and from 25 dah onwards a sinking pellet is provided. The time (dah) at which frozen Artemia and sinking pellets were provided, appropriately corresponded to the initiation of benthic feeding behaviour. However at this stage the use of pelagic Artemia metanauplii is inappropriate and unnecessary. At 31 dah the cranial morphology resembled that of adult fish. Adult D. marginatus display extreme asymmetries among the elements of the oral jaws, the suspensorium and certain elements of the neurocranium. Elements on the blind side are larger and more robust than those on the ocular side and are adapted for feeding, while those on the ocular side appear to have a respiratory function. From 31 dah the cranial elements are identical to those of adult fish, suggesting that no further feeding behavioural changes occurred and that a sinking pellet, of which the nutrient composition meets the requirements of the fish, would be appropriate for ongrowing.
- Full Text:
- Date Issued: 2008
- Authors: Ende, Stephan Siegfried Werner
- Date: 2008
- Subjects: Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5250 , http://hdl.handle.net/10962/d1005093 , Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Description: The overall aim of this study was to gain a better understanding of the feeding mechanisms of the larvae and early juveniles of the sole, Dagetichthys marginatus (Soleidae), with which to assess the suitability of current feeding protocols and to facilitate the development of an appropriate pelleted feed. This was achieved by examining the ontogeny of the cranium of laboratory reared sole, with particular emphasis on those elements associated with feeding and by comparing the cranium of juvenile fish with that of adult fish. At 4 dah (days after hatch) Dagetichthys marginatus larvae develop the first rudimentary branchial arches that facilitates the capture and ingestion of food items. Subsequent development of cranial structures, such as the oral jaws, suspensorium, neurocranium, hyoid and branchial arches and the opercular apparatus enables the larvae, at 16 dah, to switch from ram feeding to suction feeding on live prey. The use of live Artemia nauplii from 4 to 16 dah is therefore appropriate. The first morphological asymmetries developed at 16 dah in the dentaries and at 22 dah the maxillae and the premaxillae began to show asymmetries. Teeth were present only on the blind side of the oral jaw elements and during this period (16 to 22 dah) the existing elements began to ossify. From 16 to 35 dah the standard feeding protocol consists of a combination of pelagic (Artemia metanauplii) and benthic prey (dead, frozen Artemia nauplii) and from 25 dah onwards a sinking pellet is provided. The time (dah) at which frozen Artemia and sinking pellets were provided, appropriately corresponded to the initiation of benthic feeding behaviour. However at this stage the use of pelagic Artemia metanauplii is inappropriate and unnecessary. At 31 dah the cranial morphology resembled that of adult fish. Adult D. marginatus display extreme asymmetries among the elements of the oral jaws, the suspensorium and certain elements of the neurocranium. Elements on the blind side are larger and more robust than those on the ocular side and are adapted for feeding, while those on the ocular side appear to have a respiratory function. From 31 dah the cranial elements are identical to those of adult fish, suggesting that no further feeding behavioural changes occurred and that a sinking pellet, of which the nutrient composition meets the requirements of the fish, would be appropriate for ongrowing.
- Full Text:
- Date Issued: 2008
Designing and implementing a new pulsar timer for the Hartebeesthoek Radio Astronomy Observatory
- Authors: Youthed, Andrew David
- Date: 2008
- Subjects: Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5458 , http://hdl.handle.net/10962/d1005243 , Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Description: This thesis outlines the design and implementation of a single channel, dual polarization pulsar timing instrument for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The new timer is designed to be an improved, temporary replacement for the existing device which has been in operation for over 20 years. The existing device is no longer reliable and is di±cult to maintain. The new pulsar timer is designed to provide improved functional- ity, higher sampling speed, greater pulse resolution, more °exibility and easier maintenance over the existing device. The new device is also designed to keeping changes to the observation system to a minimum until a full de-dispersion timer can be implemented at theobservatory. The design makes use of an 8-bit Reduced Instruction Set Computer (RISC) micro-processor with external Random Access Memory (RAM). The instrument includes an IEEE-488 subsystem for interfacing the pulsar timer to the observation computer system. The microcontroller software is written in assembler code to ensure optimal loop execution speed and deterministic code execution for the system. The design path is discussed and problems encountered during the design process are highlighted. Final testing of the new instrument indicates an improvement in the sam- pling rate of 13.6 times and a significant reduction in 60Hz interference over the existing instrument.
- Full Text:
- Date Issued: 2008
- Authors: Youthed, Andrew David
- Date: 2008
- Subjects: Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5458 , http://hdl.handle.net/10962/d1005243 , Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Description: This thesis outlines the design and implementation of a single channel, dual polarization pulsar timing instrument for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The new timer is designed to be an improved, temporary replacement for the existing device which has been in operation for over 20 years. The existing device is no longer reliable and is di±cult to maintain. The new pulsar timer is designed to provide improved functional- ity, higher sampling speed, greater pulse resolution, more °exibility and easier maintenance over the existing device. The new device is also designed to keeping changes to the observation system to a minimum until a full de-dispersion timer can be implemented at theobservatory. The design makes use of an 8-bit Reduced Instruction Set Computer (RISC) micro-processor with external Random Access Memory (RAM). The instrument includes an IEEE-488 subsystem for interfacing the pulsar timer to the observation computer system. The microcontroller software is written in assembler code to ensure optimal loop execution speed and deterministic code execution for the system. The design path is discussed and problems encountered during the design process are highlighted. Final testing of the new instrument indicates an improvement in the sam- pling rate of 13.6 times and a significant reduction in 60Hz interference over the existing instrument.
- Full Text:
- Date Issued: 2008
Development of platinum metal specific separating agents
- Authors: Jonck, Heine
- Date: 2008
- Subjects: Platinum , Platinum -- Separation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10401 , http://hdl.handle.net/10948/712 , Platinum , Platinum -- Separation
- Description: In this dissertation, the aim was to develop a platinum specific resin to be utilized for the early removal of platinum from the industrial feed solution. Efforts were therefore directed towards the syntheses of silica based resins, with active centra, designed for platinum. The large chlorometallate ions present in the feed stream, were characterized in terms of physical parameters relevant to phase distribution, namely distortability (RD), charge density, softness (σ) etc. Matching cations for each of the types were investigated. In order to attempt the design of platinum specific resins, different structural amines were used to aminate the silicone precursor and to subsequently fix these onto the silica framework. Two different solvents namely alcohol and dmf were used in this process, resulting in two sets of resins, with different properties. The design was based on previous experience with these ions, with reference to their behaviour towards different types of cations. The platinum species, PtCl6 2- and PtCl4 2-, as well as the most important contaminants in the feed stream, were typified, bearing in mind size, charge, charge density and distortability. Different types of cationic centra, having differences in charge density, stereochemical crowding and extent of hydrophobicity, were synthesized and tested-both as solvent extractants (where possible) and silica based resins. The results indicated that, partly screened secondary ammonium cationic resin species, which could be regarded as “intermediate”, proved to be satisfactory both in their high percentage extraction for PtCl4 2- and rejection of contaminants like chlororhodates, chloroiridates(III) and FeCl4 -. It was however necessary, to work at a redox potential, where iridium(IV) in the form of IrCl6 2-, was absent. Various 2-aminoalkane resins were prepared, with variation in the length of alkane group and synthesised by the two different solvents. The latter resulted in two sets of resins with not only differing compactness, but also having significantly different properties with reference to platinum specificity, HCl effect and stripping potential. The 2-aminobutane and 2-aminoheptane resins in particular, proved to be very satisfactory platinum specific resins, both with respect to selectivity, platinum capacity and stripping potential. The various physical parameters could be applied to identify the chemical behaviour of anions and assist in the development of anion specificity for the relevant species.
- Full Text:
- Date Issued: 2008
- Authors: Jonck, Heine
- Date: 2008
- Subjects: Platinum , Platinum -- Separation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10401 , http://hdl.handle.net/10948/712 , Platinum , Platinum -- Separation
- Description: In this dissertation, the aim was to develop a platinum specific resin to be utilized for the early removal of platinum from the industrial feed solution. Efforts were therefore directed towards the syntheses of silica based resins, with active centra, designed for platinum. The large chlorometallate ions present in the feed stream, were characterized in terms of physical parameters relevant to phase distribution, namely distortability (RD), charge density, softness (σ) etc. Matching cations for each of the types were investigated. In order to attempt the design of platinum specific resins, different structural amines were used to aminate the silicone precursor and to subsequently fix these onto the silica framework. Two different solvents namely alcohol and dmf were used in this process, resulting in two sets of resins, with different properties. The design was based on previous experience with these ions, with reference to their behaviour towards different types of cations. The platinum species, PtCl6 2- and PtCl4 2-, as well as the most important contaminants in the feed stream, were typified, bearing in mind size, charge, charge density and distortability. Different types of cationic centra, having differences in charge density, stereochemical crowding and extent of hydrophobicity, were synthesized and tested-both as solvent extractants (where possible) and silica based resins. The results indicated that, partly screened secondary ammonium cationic resin species, which could be regarded as “intermediate”, proved to be satisfactory both in their high percentage extraction for PtCl4 2- and rejection of contaminants like chlororhodates, chloroiridates(III) and FeCl4 -. It was however necessary, to work at a redox potential, where iridium(IV) in the form of IrCl6 2-, was absent. Various 2-aminoalkane resins were prepared, with variation in the length of alkane group and synthesised by the two different solvents. The latter resulted in two sets of resins with not only differing compactness, but also having significantly different properties with reference to platinum specificity, HCl effect and stripping potential. The 2-aminobutane and 2-aminoheptane resins in particular, proved to be very satisfactory platinum specific resins, both with respect to selectivity, platinum capacity and stripping potential. The various physical parameters could be applied to identify the chemical behaviour of anions and assist in the development of anion specificity for the relevant species.
- Full Text:
- Date Issued: 2008
Diet and feeding effects of introduced giraffe in the Eastern Cape
- Authors: Jacobs, Evert Philippus
- Date: 2008
- Subjects: Giraffe -- Food -- South Africa -- Eastern Cape , Giraffe -- Ecology -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Introduced mammals -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10703 , http://hdl.handle.net/10948/964 , Giraffe -- Food -- South Africa -- Eastern Cape , Giraffe -- Ecology -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Introduced mammals -- Ecology -- South Africa -- Eastern Cape
- Description: This study presents the results of a study on introduced giraffe diet and feeding effects within the Eastern Cape Province of South Africa. Five sites were selected over a moisture gradient from the mesic east to the arid west of the Eastern Cape to describe giraffe diet and provide baseline data for feeding effect experiments. At each site faecal samples were collected seasonally and diet composition determined by microhistological analysis. Plant species availability was measured using the point intersect method in order to compare plant availability to plant consumption to determine diet preferences. Giraffe diet across the sites showed a unimodal response to rainfall by utilising fewer species in drier areas where plant availability is low and increasing the number of species consumed as the rainfall increases. In higher rainfall areas, giraffe reduced the number of plant species fed upon because of the high availability of important species that reduces the need for a varied diet. Across all sites, plant availability was dominated by woody plant species (more than 90 percent at each site). A total of 57 plants species were recorded as being eaten across the five sites. Several PDI (Principle Diet Items) plant species (Acacia karroo, Schotia afra, Pappea capensis and Euclea undulata) were eaten across sites. Over all the sites, significantly preferred species were Asparagus striatus, Schotia latifolia, Asparagus suaveolens, Commelina benghalensis, Viscum rotundifolium, and Acacia cyclops. Acacia karroo, Schotia afra, Pappea capensis, Rhus crenata, A. tetracantha, and Grewia robusta were utilised in proportion to their availability. Euclea undulata, Rhus longispina and Putterlickia pyracantha were avoided. Feeding effects were tested by erecting exclosures around trees, covering one half of each tree. Ten trees were selected for these manipulative experiments which ran from September 2003 to February 2005. The number of branches, number of leaves, branch orders, branch diameter, branch length, leaf length and leaf width were measured for ten samples per side (enclosed vs. exposed) and analysed using a Wilcoxon matched pairs test and tested for effect size using Cohen’s d. Although no significant differences were detected between the sides measured, the effect size indicated differences in all measurements between sides ranging from low to moderate. Leaf length was greater on the outside of exclosures and showed a moderate difference between the sides in terms of the d-value with the p-value (0.059) tending towards significance. Although leaf width was higher on the inside of exclosures, it only showed a moderate difference for d with no statistical significance. Leaf area was higher on the inside of exclosures and tended to significance (p = 0.059) and similarly the d value indicated moderate differences between the sides in terms of effect size. Similarly branch length was higher on the inside of exclosures although not significantly, the p-value (0.07) approached significance. The effect size for branch length also showed a moderate difference between the sides. The number of branches and the number of leaves showed no statistical differences between the sides although the p-value (0.059) for the number of branches, as well as number of leaves (p = 0.07) approached significance. For both these variables, effect size showed a moderate difference. Giraffe showed diversity in their diet selection across sites but mainly fed upon available species. Some preferred species were however less available and this preference could possibly result in increased pressure on the selected plant species Exclosure experiments showed no significant differences in leaf and shoot characteristics although all measurements showed differences in terms of effect size meriting further investigation. It is concluded that giraffe impact on sites may be reduced if populations are properly managed however, high densities of giraffe could lead to similar vegetation impacts as observed in other areas where giraffe have been introduced and potentially change vegetation structure and plant community composition.
- Full Text:
- Date Issued: 2008
- Authors: Jacobs, Evert Philippus
- Date: 2008
- Subjects: Giraffe -- Food -- South Africa -- Eastern Cape , Giraffe -- Ecology -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Introduced mammals -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10703 , http://hdl.handle.net/10948/964 , Giraffe -- Food -- South Africa -- Eastern Cape , Giraffe -- Ecology -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Introduced mammals -- Ecology -- South Africa -- Eastern Cape
- Description: This study presents the results of a study on introduced giraffe diet and feeding effects within the Eastern Cape Province of South Africa. Five sites were selected over a moisture gradient from the mesic east to the arid west of the Eastern Cape to describe giraffe diet and provide baseline data for feeding effect experiments. At each site faecal samples were collected seasonally and diet composition determined by microhistological analysis. Plant species availability was measured using the point intersect method in order to compare plant availability to plant consumption to determine diet preferences. Giraffe diet across the sites showed a unimodal response to rainfall by utilising fewer species in drier areas where plant availability is low and increasing the number of species consumed as the rainfall increases. In higher rainfall areas, giraffe reduced the number of plant species fed upon because of the high availability of important species that reduces the need for a varied diet. Across all sites, plant availability was dominated by woody plant species (more than 90 percent at each site). A total of 57 plants species were recorded as being eaten across the five sites. Several PDI (Principle Diet Items) plant species (Acacia karroo, Schotia afra, Pappea capensis and Euclea undulata) were eaten across sites. Over all the sites, significantly preferred species were Asparagus striatus, Schotia latifolia, Asparagus suaveolens, Commelina benghalensis, Viscum rotundifolium, and Acacia cyclops. Acacia karroo, Schotia afra, Pappea capensis, Rhus crenata, A. tetracantha, and Grewia robusta were utilised in proportion to their availability. Euclea undulata, Rhus longispina and Putterlickia pyracantha were avoided. Feeding effects were tested by erecting exclosures around trees, covering one half of each tree. Ten trees were selected for these manipulative experiments which ran from September 2003 to February 2005. The number of branches, number of leaves, branch orders, branch diameter, branch length, leaf length and leaf width were measured for ten samples per side (enclosed vs. exposed) and analysed using a Wilcoxon matched pairs test and tested for effect size using Cohen’s d. Although no significant differences were detected between the sides measured, the effect size indicated differences in all measurements between sides ranging from low to moderate. Leaf length was greater on the outside of exclosures and showed a moderate difference between the sides in terms of the d-value with the p-value (0.059) tending towards significance. Although leaf width was higher on the inside of exclosures, it only showed a moderate difference for d with no statistical significance. Leaf area was higher on the inside of exclosures and tended to significance (p = 0.059) and similarly the d value indicated moderate differences between the sides in terms of effect size. Similarly branch length was higher on the inside of exclosures although not significantly, the p-value (0.07) approached significance. The effect size for branch length also showed a moderate difference between the sides. The number of branches and the number of leaves showed no statistical differences between the sides although the p-value (0.059) for the number of branches, as well as number of leaves (p = 0.07) approached significance. For both these variables, effect size showed a moderate difference. Giraffe showed diversity in their diet selection across sites but mainly fed upon available species. Some preferred species were however less available and this preference could possibly result in increased pressure on the selected plant species Exclosure experiments showed no significant differences in leaf and shoot characteristics although all measurements showed differences in terms of effect size meriting further investigation. It is concluded that giraffe impact on sites may be reduced if populations are properly managed however, high densities of giraffe could lead to similar vegetation impacts as observed in other areas where giraffe have been introduced and potentially change vegetation structure and plant community composition.
- Full Text:
- Date Issued: 2008
Drought responses of C3 and C4 (NADP-ME) Panicoid grasses
- Authors: Frole, Kristen Marie
- Date: 2008
- Subjects: Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4193 , http://hdl.handle.net/10962/d1003762 , Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Description: The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.
- Full Text:
- Date Issued: 2008
- Authors: Frole, Kristen Marie
- Date: 2008
- Subjects: Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4193 , http://hdl.handle.net/10962/d1003762 , Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Description: The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.
- Full Text:
- Date Issued: 2008
Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa
- Authors: Allan, Elizabeth Louise
- Date: 2008
- Subjects: Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5666 , http://hdl.handle.net/10962/d1005351 , Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Description: The main aim of this study was to assess the “top-down” and “bottom-up” control of bacterial production in the small temporarily open/closed East Kleinemonde Estuary, situated on the south-eastern coastline of southern Africa. Spatial and temporal patterns in bacterial abundance, biomass and production and the importance of abiotic and biotic factors were investigated over the period May 2006 to April 2007. The trophic interactions between bacteria, phytoplankton, nanoflagellates (< 20 μm), microzooplankton (< 200 μm) and mesozooplankton (< 2 000 μm) were investigated during winter and summer. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells 1⁻¹, 32.4 and 109 μg C 1⁻¹ and 0.01 and 1.99 μg C 1⁻¹ h⁻¹, respectively. With a few exceptions there were no spatial patterns in the values. Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Nanoflagellate and bacterial abundances were significantly correlated to one another (lower reaches: r = 0.818, p < 0.001; middle reaches: r = 0.628, p < 0.001; upper reaches: r = 0.484, p < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the mean number of virus particles within each bacterial cell during this study demonstrated no temporal or spatial patterns and ranged from 0.5 to 6.1 % and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% of the total which suggests that viral lysis represented a very important source of bacterial mortality during this study. The biological interactions between the selected components of the plankton community demonstrated that among the heterotrophic components of the plankton, the nanoflagellates were identified as the most important consumers of bacteria and small phytoplankton cells (< 20 μm). In the presence of microzooplankton the impact of the nanoflagellates on both the bacteria and phytoplankton was reduced, indicating that larger heterotrophs were preying upon the nanoflagellates. Mesozooplankton, however, appeared to exert the greatest impact on nanoflagellates. In the cascading experiments, the data suggest that mesozooplankton consume nanoflagellates, which resulted in a decrease in the predation impact of these organisms on the bacteria. This result is consistent with predator-prey cascades. The presence of the larger heterotrophs therefore, mediates the interactions between the primary bacterivores, the nanoflagellates, and the bacteria within the temporarily open/closed East Kleinemonde Estuary.
- Full Text:
- Date Issued: 2008
- Authors: Allan, Elizabeth Louise
- Date: 2008
- Subjects: Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5666 , http://hdl.handle.net/10962/d1005351 , Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Description: The main aim of this study was to assess the “top-down” and “bottom-up” control of bacterial production in the small temporarily open/closed East Kleinemonde Estuary, situated on the south-eastern coastline of southern Africa. Spatial and temporal patterns in bacterial abundance, biomass and production and the importance of abiotic and biotic factors were investigated over the period May 2006 to April 2007. The trophic interactions between bacteria, phytoplankton, nanoflagellates (< 20 μm), microzooplankton (< 200 μm) and mesozooplankton (< 2 000 μm) were investigated during winter and summer. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells 1⁻¹, 32.4 and 109 μg C 1⁻¹ and 0.01 and 1.99 μg C 1⁻¹ h⁻¹, respectively. With a few exceptions there were no spatial patterns in the values. Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Nanoflagellate and bacterial abundances were significantly correlated to one another (lower reaches: r = 0.818, p < 0.001; middle reaches: r = 0.628, p < 0.001; upper reaches: r = 0.484, p < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the mean number of virus particles within each bacterial cell during this study demonstrated no temporal or spatial patterns and ranged from 0.5 to 6.1 % and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% of the total which suggests that viral lysis represented a very important source of bacterial mortality during this study. The biological interactions between the selected components of the plankton community demonstrated that among the heterotrophic components of the plankton, the nanoflagellates were identified as the most important consumers of bacteria and small phytoplankton cells (< 20 μm). In the presence of microzooplankton the impact of the nanoflagellates on both the bacteria and phytoplankton was reduced, indicating that larger heterotrophs were preying upon the nanoflagellates. Mesozooplankton, however, appeared to exert the greatest impact on nanoflagellates. In the cascading experiments, the data suggest that mesozooplankton consume nanoflagellates, which resulted in a decrease in the predation impact of these organisms on the bacteria. This result is consistent with predator-prey cascades. The presence of the larger heterotrophs therefore, mediates the interactions between the primary bacterivores, the nanoflagellates, and the bacteria within the temporarily open/closed East Kleinemonde Estuary.
- Full Text:
- Date Issued: 2008
Effect of salinity on oxygen consumption and growth of juvenile white steenbras, litohognathus lithognathus
- Authors: Kandjou, Kaunahama
- Date: 2008
- Subjects: Lithognathus -- Growth , Salinity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5275 , http://hdl.handle.net/10962/d1005119 , Lithognathus -- Growth , Salinity
- Description: A stress-induced increase in metabolic rate of fish consumes energy within the metabolic scope of a fish that could otherwise be used for such functions as growth and reproduction. By estimating the degree of the metabolic response under given salinity levels and sudden changes thereof, it could be tested whether growth under given culture conditions could be predicted. Using intermittent respirometers, this study investigated the metabolic response of juvenile Lithognathus lithognathus following gradual acclimation to 5, 25 and 35‰ and, as a result of abrupt change from 35‰ to 5‰ or from 35‰ to 25‰ at 20˚C. The main aim of the study was to establish whether the magnitude of such responses could be used to predict growth of juvenile L. lithognathus under culture conditions. Hence, in addition to the respirometry study, two growth studies were conducted at 5, 10, 25 and 35‰ salinities. The baseline metabolic rates of juvenile L. lithognathus were also determined. Oxygen consumption measurements over 24-hours showed that most fish exhibited a diurnal peak in metabolic rates. The standard and active metabolic rates calculated from juvenile L. lithognathus with a diurnal peak in oxygen consumption were 0.06±0.001mgO₂g⁻¹h⁻¹ (mean±SEM, n = 5), and 0.11±0.01mg O₂g⁻¹h⁻¹, respectively. The standard and active metabolic rates of juvenile L lithognathus showing a nocturnal peak in metabolic activities were 0.04±0.001mgO₂g-1h-1 (n = 1), and 0.12±0.003 mg O₂g⁻¹ h⁻¹, respectively. Routine metabolic rate of these fish calculated over a 3-h measurement period was 0.09±0.005mgO₂g⁻¹h⁻¹ (n = 6). Juvenile L. lithognathus showed a relationship between metabolic rate (mo₂) and body weight (W) following the equation: mo₂ = 0.62 W⁻°·⁵³.
- Full Text:
- Date Issued: 2008
- Authors: Kandjou, Kaunahama
- Date: 2008
- Subjects: Lithognathus -- Growth , Salinity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5275 , http://hdl.handle.net/10962/d1005119 , Lithognathus -- Growth , Salinity
- Description: A stress-induced increase in metabolic rate of fish consumes energy within the metabolic scope of a fish that could otherwise be used for such functions as growth and reproduction. By estimating the degree of the metabolic response under given salinity levels and sudden changes thereof, it could be tested whether growth under given culture conditions could be predicted. Using intermittent respirometers, this study investigated the metabolic response of juvenile Lithognathus lithognathus following gradual acclimation to 5, 25 and 35‰ and, as a result of abrupt change from 35‰ to 5‰ or from 35‰ to 25‰ at 20˚C. The main aim of the study was to establish whether the magnitude of such responses could be used to predict growth of juvenile L. lithognathus under culture conditions. Hence, in addition to the respirometry study, two growth studies were conducted at 5, 10, 25 and 35‰ salinities. The baseline metabolic rates of juvenile L. lithognathus were also determined. Oxygen consumption measurements over 24-hours showed that most fish exhibited a diurnal peak in metabolic rates. The standard and active metabolic rates calculated from juvenile L. lithognathus with a diurnal peak in oxygen consumption were 0.06±0.001mgO₂g⁻¹h⁻¹ (mean±SEM, n = 5), and 0.11±0.01mg O₂g⁻¹h⁻¹, respectively. The standard and active metabolic rates of juvenile L lithognathus showing a nocturnal peak in metabolic activities were 0.04±0.001mgO₂g-1h-1 (n = 1), and 0.12±0.003 mg O₂g⁻¹ h⁻¹, respectively. Routine metabolic rate of these fish calculated over a 3-h measurement period was 0.09±0.005mgO₂g⁻¹h⁻¹ (n = 6). Juvenile L. lithognathus showed a relationship between metabolic rate (mo₂) and body weight (W) following the equation: mo₂ = 0.62 W⁻°·⁵³.
- Full Text:
- Date Issued: 2008
Equiprime near-rings
- Authors: Mogae, Kabelo
- Date: 2008
- Subjects: Near-rings
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10505 , http://hdl.handle.net/10948/1028 , Near-rings
- Description: Prior to 1990, the only well known ideal-hereditary Kurosh-Amitsur radicals in the variety of zero-symmetric near-rings were the Jacobson type radicals Iv(N) , where ∨∈{2,3} and the Brown-McCoy radical. In 1990, Booth, Groenewald and Veldsman introduced the concept of an equiprime near-ring which leads to an ideal-hereditary Kurosh-Amitsur radical in N∘. The concept of an equiprime near-ring generalizes the concept of a prime ring to near-rings. Although the search for more ideal-hereditary radicals of near-rings was apparently the original motivation for the introduction of equiprime near-rings, it became clear that these near-rings are interesting in their own right. It is our aim in this treatise to give an exposition of the many interesting properties of equiprime near-rings. We begin with a brief reminder of near-ring rudiments; giving basic definitions and elementary results which are necessary for understanding and development of subsequent chapters. With the basics out of the way, our main task begins with a consideration of equiprime, strongly and completely equiprime left ideals. It is noted that any zero-symmetric near-ring can be embedded in an equiprime near-ring. Moreover, the class of equiprime near-rings is shown to be hereditary. Open questions arising out of the study of equiprime near-rings are highlighted along the way. In Chapter 3 we consider well known examples of near-rings and determine when such near-rings are equiprime. This provides more insight into the nature of equiprime near-rings and is a fertile ground for the birth of examples and counterexamples which may be used to close or solve some open question within the literature. We also prove some results which generalize some results of Booth and Hall [10] and Veldsman [29]. These results have not been previously presented elsewhere to the best of our knowledge. vii In Chapter 4, the equiprime near-rings are shown to yield an ideal-hereditary radical in N∘. It is shown that a special radical theory can be built on the equiprime nearrings in much the same way prime rings are used in ring theory to define special radical classes of rings.
- Full Text:
- Date Issued: 2008
- Authors: Mogae, Kabelo
- Date: 2008
- Subjects: Near-rings
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10505 , http://hdl.handle.net/10948/1028 , Near-rings
- Description: Prior to 1990, the only well known ideal-hereditary Kurosh-Amitsur radicals in the variety of zero-symmetric near-rings were the Jacobson type radicals Iv(N) , where ∨∈{2,3} and the Brown-McCoy radical. In 1990, Booth, Groenewald and Veldsman introduced the concept of an equiprime near-ring which leads to an ideal-hereditary Kurosh-Amitsur radical in N∘. The concept of an equiprime near-ring generalizes the concept of a prime ring to near-rings. Although the search for more ideal-hereditary radicals of near-rings was apparently the original motivation for the introduction of equiprime near-rings, it became clear that these near-rings are interesting in their own right. It is our aim in this treatise to give an exposition of the many interesting properties of equiprime near-rings. We begin with a brief reminder of near-ring rudiments; giving basic definitions and elementary results which are necessary for understanding and development of subsequent chapters. With the basics out of the way, our main task begins with a consideration of equiprime, strongly and completely equiprime left ideals. It is noted that any zero-symmetric near-ring can be embedded in an equiprime near-ring. Moreover, the class of equiprime near-rings is shown to be hereditary. Open questions arising out of the study of equiprime near-rings are highlighted along the way. In Chapter 3 we consider well known examples of near-rings and determine when such near-rings are equiprime. This provides more insight into the nature of equiprime near-rings and is a fertile ground for the birth of examples and counterexamples which may be used to close or solve some open question within the literature. We also prove some results which generalize some results of Booth and Hall [10] and Veldsman [29]. These results have not been previously presented elsewhere to the best of our knowledge. vii In Chapter 4, the equiprime near-rings are shown to yield an ideal-hereditary radical in N∘. It is shown that a special radical theory can be built on the equiprime nearrings in much the same way prime rings are used in ring theory to define special radical classes of rings.
- Full Text:
- Date Issued: 2008
Growth of the South African abalone (Haliotis Midae) on three diets, under commercial conditions
- Authors: Makhande, Emmanuel Denis
- Date: 2008
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10706 , http://hdl.handle.net/10948/755 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Description: Haliotis midae is the cornerstone of the South African abalone fishery. For more than a decade, the wild abalone stock of South Africa has suffered decline due to over-exploitation and illegal activities such as poaching. Prior to 1970, no regulations were in place concerning the annual landings. As a result the fishery was exploited as if it were an infinite resource. It is this initial uncontrolled harvesting (regardless of age) and poaching that has driven the abalone resource decline. Due to the slow growth rate exhibited by abalone as a species, natural replenishment of wild stock following exploitation and poaching was far below the rate of exploitation of this resource. Studies on the growth of abalone have mainly been conducted under laboratory conditions. The purpose of this study was to measure the growth of abalone, fed different diets, under commercial culture conditions. Three food types were used namely; commercial pellets, seaweed (Ulva spp.) and dried kelp bars (Ecklonia maxima). Four diets were obtained from the three food types namely; combination of commercial pellets and seaweed (Diet A), commercial pellets only (Diet B), seaweed only (Diet C) and dried kelp bars only (Diet D). The food types used in this study represent both artificial (Commercial pellets) and natural feeds (seaweed and kelp) used in commercial abalone culture. The growth of two cohorts (40-50 mm and 50-60 mm) was followed over a 426 day period, with data for the first 183 days being used for statistical analysis to determine performance of a given diet. The best growth rates were found in abalone fed Diet A (40-50 mm: 2.64 mm.month-1; 50-60 mm 2.78: mm.month-1) and B (40-50 mm: 2.20 mm.month-1; 50-60 mm: 2.35: mm.month-1). These (Diets A and B) gave higher growth rates when compared to Diets C and D (natural diets), whose growth rates ranged between 0.50 mm.month-1 and 1.71 mm.month-1 for both cohorts. Also observed in this study was that, the mixture of formulated diet and seaweed gave better growth than formulated diet given exclusively.
- Full Text:
- Date Issued: 2008
- Authors: Makhande, Emmanuel Denis
- Date: 2008
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10706 , http://hdl.handle.net/10948/755 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Description: Haliotis midae is the cornerstone of the South African abalone fishery. For more than a decade, the wild abalone stock of South Africa has suffered decline due to over-exploitation and illegal activities such as poaching. Prior to 1970, no regulations were in place concerning the annual landings. As a result the fishery was exploited as if it were an infinite resource. It is this initial uncontrolled harvesting (regardless of age) and poaching that has driven the abalone resource decline. Due to the slow growth rate exhibited by abalone as a species, natural replenishment of wild stock following exploitation and poaching was far below the rate of exploitation of this resource. Studies on the growth of abalone have mainly been conducted under laboratory conditions. The purpose of this study was to measure the growth of abalone, fed different diets, under commercial culture conditions. Three food types were used namely; commercial pellets, seaweed (Ulva spp.) and dried kelp bars (Ecklonia maxima). Four diets were obtained from the three food types namely; combination of commercial pellets and seaweed (Diet A), commercial pellets only (Diet B), seaweed only (Diet C) and dried kelp bars only (Diet D). The food types used in this study represent both artificial (Commercial pellets) and natural feeds (seaweed and kelp) used in commercial abalone culture. The growth of two cohorts (40-50 mm and 50-60 mm) was followed over a 426 day period, with data for the first 183 days being used for statistical analysis to determine performance of a given diet. The best growth rates were found in abalone fed Diet A (40-50 mm: 2.64 mm.month-1; 50-60 mm 2.78: mm.month-1) and B (40-50 mm: 2.20 mm.month-1; 50-60 mm: 2.35: mm.month-1). These (Diets A and B) gave higher growth rates when compared to Diets C and D (natural diets), whose growth rates ranged between 0.50 mm.month-1 and 1.71 mm.month-1 for both cohorts. Also observed in this study was that, the mixture of formulated diet and seaweed gave better growth than formulated diet given exclusively.
- Full Text:
- Date Issued: 2008
Home range dynamics of spotted grunter, pomadasys commersonnii, in a South African intermittently open estuary
- Authors: O'Connell, Bronwyn Anne
- Date: 2008
- Subjects: Grunts (Fishes) -- South Africa -- Eastern Cape , Pomadasys -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Fishes -- Home range , Fishes -- Home range -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5286 , http://hdl.handle.net/10962/d1005130 , Grunts (Fishes) -- South Africa -- Eastern Cape , Pomadasys -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Fishes -- Home range , Fishes -- Home range -- South Africa -- Eastern Cape
- Description: The spotted grunter (Pomadasys commersonnii) is an important, estuarine-dependent, fishery species in southern Africa. Since estuaries are essential habitats in the life history of this species, the quantification of area use patterns and movements is important for fisheries management. In this study, acoustic telemetry was used to investigate movements, use of habitat and home range dynamics of spotted grunter in the small intermittently open East Kleinemonde Estuary on the Eastern Cape coast of South Africa. Nine spotted grunter (range: 326-489mm TL) were surgically equipped with uniquely coded acoustic transmitters. Positional fixes were obtained by manual tracking tagged individuals on six days and six nights during five tracking sessions from March to November 2004. In addition, five stationary data-logging receivers, moored at specific locations from the mouth to the top of the estuary provided additional long-term monitoring. Kernel home ranges (95% UD) varied in size (26 296-165 321m²) but were all located in a common high use area situated between 300-1 300m from the estuary mouth, which coincided with the highest abundance of prey items. There was no significant variation in home range size [C² (N = 9, df = 4) = 4.18; p = 0.38] between the temporally segregated tracking sessions (over nine months). The persistence of these home range estimates were confirmed by the long-term data-logging receivers. There was no significant diel variation in home range size [F(4, 64) = 0.05, p = 0.99] or core area size [F(4, 64) = 1.40, p = 0.25]. Fish length showed negative, although not significant, relationships between home range size (p = 0.225); number of home range areas (p = 0.065); core area size (p = 0.512) and home range length (p = 0.320). Use of habitat and home range dynamics of spotted grunter in the East Kleinemonde Estuary were consistent over the nine month study period, and they appeared to be influenced more by biotic than abiotic factors. However, when the mouth opened at the end of the study, most tagged fish vacated their home ranges and emigrated to sea.
- Full Text:
- Date Issued: 2008
- Authors: O'Connell, Bronwyn Anne
- Date: 2008
- Subjects: Grunts (Fishes) -- South Africa -- Eastern Cape , Pomadasys -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Fishes -- Home range , Fishes -- Home range -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5286 , http://hdl.handle.net/10962/d1005130 , Grunts (Fishes) -- South Africa -- Eastern Cape , Pomadasys -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Fishes -- Home range , Fishes -- Home range -- South Africa -- Eastern Cape
- Description: The spotted grunter (Pomadasys commersonnii) is an important, estuarine-dependent, fishery species in southern Africa. Since estuaries are essential habitats in the life history of this species, the quantification of area use patterns and movements is important for fisheries management. In this study, acoustic telemetry was used to investigate movements, use of habitat and home range dynamics of spotted grunter in the small intermittently open East Kleinemonde Estuary on the Eastern Cape coast of South Africa. Nine spotted grunter (range: 326-489mm TL) were surgically equipped with uniquely coded acoustic transmitters. Positional fixes were obtained by manual tracking tagged individuals on six days and six nights during five tracking sessions from March to November 2004. In addition, five stationary data-logging receivers, moored at specific locations from the mouth to the top of the estuary provided additional long-term monitoring. Kernel home ranges (95% UD) varied in size (26 296-165 321m²) but were all located in a common high use area situated between 300-1 300m from the estuary mouth, which coincided with the highest abundance of prey items. There was no significant variation in home range size [C² (N = 9, df = 4) = 4.18; p = 0.38] between the temporally segregated tracking sessions (over nine months). The persistence of these home range estimates were confirmed by the long-term data-logging receivers. There was no significant diel variation in home range size [F(4, 64) = 0.05, p = 0.99] or core area size [F(4, 64) = 1.40, p = 0.25]. Fish length showed negative, although not significant, relationships between home range size (p = 0.225); number of home range areas (p = 0.065); core area size (p = 0.512) and home range length (p = 0.320). Use of habitat and home range dynamics of spotted grunter in the East Kleinemonde Estuary were consistent over the nine month study period, and they appeared to be influenced more by biotic than abiotic factors. However, when the mouth opened at the end of the study, most tagged fish vacated their home ranges and emigrated to sea.
- Full Text:
- Date Issued: 2008
Importance of various data sources in deterministic stock assessment models
- Authors: Northrop, Amanda Rosalind
- Date: 2008
- Subjects: Fish stock assessment -- Mathematical models , Fishery management -- Mathematical models , Fish populations -- Mathematical models , Error analysis (Mathematics) , Fishery management -- Statistical methods , Fish stock assessment -- Statistical methods
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5571 , http://hdl.handle.net/10962/d1002811 , Fish stock assessment -- Mathematical models , Fishery management -- Mathematical models , Fish populations -- Mathematical models , Error analysis (Mathematics) , Fishery management -- Statistical methods , Fish stock assessment -- Statistical methods
- Description: In fisheries, advice for the management of fish populations is based upon management quantities that are estimated by stock assessment models. Fisheries stock assessment is a process in which data collected from a fish population are used to generate a model which enables the effects of fishing on a stock to be quantified. This study determined the effects of various data sources, assumptions, error scenarios and sample sizes on the accuracy with which the age-structured production model and the Schaefer model (assessment models) were able to estimate key management quantities for a fish resource similar to the Cape hakes (Merluccius capensis and M. paradoxus). An age-structured production model was used as the operating model to simulate hypothetical fish resource population dynamics for which management quantities could be determined by the assessment models. Different stocks were simulated with various harvest rate histories. These harvest rates produced Downhill trip data, where harvest rates increase over time until the resource is close to collapse, and Good contrast data, where the harvest rate increases over time until the resource is at less than half of it’s exploitable biomass, and then it decreases allowing the resource to rebuild. The accuracy of the assessment models were determined when data were drawn from the operating model with various combinations of error. The age-structured production model was more accurate at estimating maximum sustainable yield, maximum sustainable yield level and the maximum sustainable yield ratio. The Schaefer model gave more accurate estimates of Depletion and Total Allowable Catch. While the assessment models were able to estimate management quantities using Downhill trip data, the estimates improved significantly when the models were tuned with Good contrast data. When autocorrelation in the spawner-recruit curve was not accounted for by the deterministic assessment model, inaccuracy in parameter estimates were high. The assessment model management quantities were not greatly affected by multinomial ageing error in the catch-at-age matrices at a sample size of 5000 otoliths. Assessment model estimates were closer to their true values when log-normal error were assumed in the catch-at-age matrix, even when the true underlying error were multinomial. However, the multinomial had smaller coefficients of variation at all sample sizes, between 1000 and 10000, of otoliths aged. It was recommended that the assessment model is chosen based on the management quantity of interest. When the underlying error is multinomial, the weighted log-normal likelihood function should be used in the catch-at-age matrix to obtain accurate parameter estimates. However, the multinomial likelihood should be used to minimise the coefficient of variation. Investigation into correcting for autocorrelation in the stock-recruitment relationship should be carried out, as it had a large effect on the accuracy of management quantities.
- Full Text:
- Date Issued: 2008
- Authors: Northrop, Amanda Rosalind
- Date: 2008
- Subjects: Fish stock assessment -- Mathematical models , Fishery management -- Mathematical models , Fish populations -- Mathematical models , Error analysis (Mathematics) , Fishery management -- Statistical methods , Fish stock assessment -- Statistical methods
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5571 , http://hdl.handle.net/10962/d1002811 , Fish stock assessment -- Mathematical models , Fishery management -- Mathematical models , Fish populations -- Mathematical models , Error analysis (Mathematics) , Fishery management -- Statistical methods , Fish stock assessment -- Statistical methods
- Description: In fisheries, advice for the management of fish populations is based upon management quantities that are estimated by stock assessment models. Fisheries stock assessment is a process in which data collected from a fish population are used to generate a model which enables the effects of fishing on a stock to be quantified. This study determined the effects of various data sources, assumptions, error scenarios and sample sizes on the accuracy with which the age-structured production model and the Schaefer model (assessment models) were able to estimate key management quantities for a fish resource similar to the Cape hakes (Merluccius capensis and M. paradoxus). An age-structured production model was used as the operating model to simulate hypothetical fish resource population dynamics for which management quantities could be determined by the assessment models. Different stocks were simulated with various harvest rate histories. These harvest rates produced Downhill trip data, where harvest rates increase over time until the resource is close to collapse, and Good contrast data, where the harvest rate increases over time until the resource is at less than half of it’s exploitable biomass, and then it decreases allowing the resource to rebuild. The accuracy of the assessment models were determined when data were drawn from the operating model with various combinations of error. The age-structured production model was more accurate at estimating maximum sustainable yield, maximum sustainable yield level and the maximum sustainable yield ratio. The Schaefer model gave more accurate estimates of Depletion and Total Allowable Catch. While the assessment models were able to estimate management quantities using Downhill trip data, the estimates improved significantly when the models were tuned with Good contrast data. When autocorrelation in the spawner-recruit curve was not accounted for by the deterministic assessment model, inaccuracy in parameter estimates were high. The assessment model management quantities were not greatly affected by multinomial ageing error in the catch-at-age matrices at a sample size of 5000 otoliths. Assessment model estimates were closer to their true values when log-normal error were assumed in the catch-at-age matrix, even when the true underlying error were multinomial. However, the multinomial had smaller coefficients of variation at all sample sizes, between 1000 and 10000, of otoliths aged. It was recommended that the assessment model is chosen based on the management quantity of interest. When the underlying error is multinomial, the weighted log-normal likelihood function should be used in the catch-at-age matrix to obtain accurate parameter estimates. However, the multinomial likelihood should be used to minimise the coefficient of variation. Investigation into correcting for autocorrelation in the stock-recruitment relationship should be carried out, as it had a large effect on the accuracy of management quantities.
- Full Text:
- Date Issued: 2008
Integer optimization for the selection of a twenty20 cricket team
- Authors: Lourens, Mark
- Date: 2008
- Subjects: Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10568 , http://hdl.handle.net/10948/1000 , http://hdl.handle.net/10948/d1009631 , Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Description: During the last few years, much effort has been devoted to measuring the ability of sport teams, as well as that of the individual players. Much research has been on the game of cricket, and the comparison, or ranking, of players according to their abilities. This study continues preceding research using an optimization approach, namely, a binary integer programme, to select an SA domestic Pro20 cricket team.
- Full Text:
- Date Issued: 2008
- Authors: Lourens, Mark
- Date: 2008
- Subjects: Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10568 , http://hdl.handle.net/10948/1000 , http://hdl.handle.net/10948/d1009631 , Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Description: During the last few years, much effort has been devoted to measuring the ability of sport teams, as well as that of the individual players. Much research has been on the game of cricket, and the comparison, or ranking, of players according to their abilities. This study continues preceding research using an optimization approach, namely, a binary integer programme, to select an SA domestic Pro20 cricket team.
- Full Text:
- Date Issued: 2008
Interaction between arbuscular mycorrhizal fungi and soil microbial populations in the rhizosphere
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
Investigation of polarization mode dispersion measurement perfomance in optical fibre with a focus on the fixed analyzer technique
- Gamatham, Romeo Reginald Gunther
- Authors: Gamatham, Romeo Reginald Gunther
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10524 , http://hdl.handle.net/10948/957 , Fiber optics , Polarization (Light)
- Description: The work presented in this dissertation is a comparative study of polarization mode dispersion (PMD) measurement performance where the fixed analyzer (FA) technique was built and tested for the first time in South Africa. Techniques involved in the study are: the Jones matrix eigenanalysis (JME), generalised interferometric technique (GINTY) and the FA technique, with a particular focus on the FA technique. The FA PMD measurement technique determines the average differential group delay (DGD) from the transmitted intensity spectrum through a polarizer and has three analysis methods (extrema counting, mean level crossing and Fourier analysis) which were all evaluated. PMD measurements were performed in the laboratory on several different fibre types and in the field on buried deployed Telkom fibre links (28.8 km). The techniques showed good agreement in the measured PMD value, both in the laboratory and field measurements. In particular very good agreement was found between the JME average DGD and the extrema counting analysis PMD value. The GINTY and FA Fourier analysis method also gave very similar PMD values. It was found that the fibre birefringence and the mode coupling manifest in different ways on the intensity spectrum. By using the FA ratio method, the length regimes of the different fibre types were determined. Three characteristics of the FA technique were investigated, namely: wavelength window variation, sampling and input SOP scrambling. It was found that the wavelength window and the PMD are inversely proportional. Correct sampling plays a significant role in determining the correct measured PMD value. Lastly an average PMD value over the PMD values for different input SOPs serves as a better representation of the true PMD value. An additional study showed that the FA technique and a developed Poincaré sphere analysis method agree very well regarding the PMD value.
- Full Text:
- Date Issued: 2008
- Authors: Gamatham, Romeo Reginald Gunther
- Date: 2008
- Subjects: Fiber optics , Polarization (Light)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10524 , http://hdl.handle.net/10948/957 , Fiber optics , Polarization (Light)
- Description: The work presented in this dissertation is a comparative study of polarization mode dispersion (PMD) measurement performance where the fixed analyzer (FA) technique was built and tested for the first time in South Africa. Techniques involved in the study are: the Jones matrix eigenanalysis (JME), generalised interferometric technique (GINTY) and the FA technique, with a particular focus on the FA technique. The FA PMD measurement technique determines the average differential group delay (DGD) from the transmitted intensity spectrum through a polarizer and has three analysis methods (extrema counting, mean level crossing and Fourier analysis) which were all evaluated. PMD measurements were performed in the laboratory on several different fibre types and in the field on buried deployed Telkom fibre links (28.8 km). The techniques showed good agreement in the measured PMD value, both in the laboratory and field measurements. In particular very good agreement was found between the JME average DGD and the extrema counting analysis PMD value. The GINTY and FA Fourier analysis method also gave very similar PMD values. It was found that the fibre birefringence and the mode coupling manifest in different ways on the intensity spectrum. By using the FA ratio method, the length regimes of the different fibre types were determined. Three characteristics of the FA technique were investigated, namely: wavelength window variation, sampling and input SOP scrambling. It was found that the wavelength window and the PMD are inversely proportional. Correct sampling plays a significant role in determining the correct measured PMD value. Lastly an average PMD value over the PMD values for different input SOPs serves as a better representation of the true PMD value. An additional study showed that the FA technique and a developed Poincaré sphere analysis method agree very well regarding the PMD value.
- Full Text:
- Date Issued: 2008