BODIPY dyes for singlet oxygen and optical limiting applications
- Authors: Harris, Jessica
- Date: 2018
- Subjects: Photosensitizing compounds , Active oxygen -- Physiological effect , Photochemotherapy , Cancer -- Treatment , Nonlinear optics , BODIPY (Boron-dipyrromethene)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58002 , vital:27014
- Description: A series of structurally related BODIPY dyes were synthesised and characterised. Their photophysical properties were studied in order to determine whether they would be suitable candidates for use as photosensitisers in the photodynamic therapy (PDT) treatment of cancer. The synthesis of two highly fluorescent BODIPY cores was achieved via the acid-catalysed condensation of a pyrrole and a functionalised aldehyde. In order to promote intersystem crossing, and hence improve the singlet oxygen generation of these dyes, bromine atoms were added at the 2,6-positions of the BODIPY core. These dibrominated analogues showed good singlet oxygen quantum yields, and excellent photostability in ethanol. In order to red-shift the main spectral bands of the BODIPY dyes towards the therapeutic window, vinyl/ styryl groups were introduced at the 3-, 5-, and 7-positions via a modified Knoevengal condensation reaction. The addition of vinyl/ styryl groups to the BODIPY core caused an increase in fluorescence quantum yield as well as a decrease in singlet oxygen quantum yield with respect to the dibrominated analogues. However, two of the red-shifted BODIPY dyes still showed moderate singlet oxygen quantum yields. The use of BODIPY dyes in nonlinear optics (NLO) was explored. The nonlinear optical characterisations and optical limiting properties of a series of 3,5-dithienylenevinylene BODIPY dyes were studied, both in dimethylformamide (DMF) solution and when embedded in poly(bisphenol A carbonate) (PBC) as thin films. The 3,5-dithienylenevinylene BODIPY dyes showed typical nonlinear absorption behaviour, with reverse saturable absorption (RSA) profiles, indicating that they have potential as optical limiters. The second-order hyperpolarizability (Y), and third-order nonlinear susceptibility (/m[/(3)]) values are also reported for these dyes. The optical limiting values of one of the BODIPY dyes in solution, and two of the BODIPY-embedded PBC films, were below the maximum threshold of 0.95 J-cm-2. The effect of addition of substituents on the electronic structure of the BODIPY dyes was investigated using TD-DFT calculations. The calculated trends closely followed those determined experimentally.
- Full Text:
- Date Issued: 2018
- Authors: Harris, Jessica
- Date: 2018
- Subjects: Photosensitizing compounds , Active oxygen -- Physiological effect , Photochemotherapy , Cancer -- Treatment , Nonlinear optics , BODIPY (Boron-dipyrromethene)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58002 , vital:27014
- Description: A series of structurally related BODIPY dyes were synthesised and characterised. Their photophysical properties were studied in order to determine whether they would be suitable candidates for use as photosensitisers in the photodynamic therapy (PDT) treatment of cancer. The synthesis of two highly fluorescent BODIPY cores was achieved via the acid-catalysed condensation of a pyrrole and a functionalised aldehyde. In order to promote intersystem crossing, and hence improve the singlet oxygen generation of these dyes, bromine atoms were added at the 2,6-positions of the BODIPY core. These dibrominated analogues showed good singlet oxygen quantum yields, and excellent photostability in ethanol. In order to red-shift the main spectral bands of the BODIPY dyes towards the therapeutic window, vinyl/ styryl groups were introduced at the 3-, 5-, and 7-positions via a modified Knoevengal condensation reaction. The addition of vinyl/ styryl groups to the BODIPY core caused an increase in fluorescence quantum yield as well as a decrease in singlet oxygen quantum yield with respect to the dibrominated analogues. However, two of the red-shifted BODIPY dyes still showed moderate singlet oxygen quantum yields. The use of BODIPY dyes in nonlinear optics (NLO) was explored. The nonlinear optical characterisations and optical limiting properties of a series of 3,5-dithienylenevinylene BODIPY dyes were studied, both in dimethylformamide (DMF) solution and when embedded in poly(bisphenol A carbonate) (PBC) as thin films. The 3,5-dithienylenevinylene BODIPY dyes showed typical nonlinear absorption behaviour, with reverse saturable absorption (RSA) profiles, indicating that they have potential as optical limiters. The second-order hyperpolarizability (Y), and third-order nonlinear susceptibility (/m[/(3)]) values are also reported for these dyes. The optical limiting values of one of the BODIPY dyes in solution, and two of the BODIPY-embedded PBC films, were below the maximum threshold of 0.95 J-cm-2. The effect of addition of substituents on the electronic structure of the BODIPY dyes was investigated using TD-DFT calculations. The calculated trends closely followed those determined experimentally.
- Full Text:
- Date Issued: 2018
Procurement challenges faced by Eskom contractors during the tender stage
- Authors: Hlalutye, Thandiwe
- Date: 2018
- Subjects: Management -- Procurement -- South Africa -- Northern Cape , Project management -- South Africa -- Northern Cape Contractors' operation -- South Africa -- Northern Cape -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30260 , vital:30913
- Description: The procurement process within South Africa has become an increasing focus in open market access for local economic development. The government introduced Preferential Procurement Policy Frame Act 5 of 2000 (PPPFA) which must be followed by all government owned organisations, including parastatals. Eskom, therefore, has to abide to this regulation and, since it started utilising the Act in its tendering process, there has been a challenge to getting contractors who are commercially and technically approved to be able to execute work or projects. The aim of this study is to examine challenges faced by Eskom Northern Cape Operating Unit contractors during the tender stage in terms of tender requirements, whereby they fail to submit all required tender returnables and fail to meet a set threshold in order to be successful and being awarded with the contract. This study undertook an empirical study using a case study of Eskom after a literature review. A questionnaire was used to collect data from all the active contractors on the Eskom Northern Cape Operating Unit data base. The key findings included that; contractors agreed that they still lack understanding of a quality management system. However they disagreed that they are not complying with safety health and environment and that they lack knowledge of technical requirements which leads them to not submitting objective evidence. The study concluded that contracting firms still do not comply with procurement requirements during the tender stage.
- Full Text:
- Date Issued: 2018
- Authors: Hlalutye, Thandiwe
- Date: 2018
- Subjects: Management -- Procurement -- South Africa -- Northern Cape , Project management -- South Africa -- Northern Cape Contractors' operation -- South Africa -- Northern Cape -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30260 , vital:30913
- Description: The procurement process within South Africa has become an increasing focus in open market access for local economic development. The government introduced Preferential Procurement Policy Frame Act 5 of 2000 (PPPFA) which must be followed by all government owned organisations, including parastatals. Eskom, therefore, has to abide to this regulation and, since it started utilising the Act in its tendering process, there has been a challenge to getting contractors who are commercially and technically approved to be able to execute work or projects. The aim of this study is to examine challenges faced by Eskom Northern Cape Operating Unit contractors during the tender stage in terms of tender requirements, whereby they fail to submit all required tender returnables and fail to meet a set threshold in order to be successful and being awarded with the contract. This study undertook an empirical study using a case study of Eskom after a literature review. A questionnaire was used to collect data from all the active contractors on the Eskom Northern Cape Operating Unit data base. The key findings included that; contractors agreed that they still lack understanding of a quality management system. However they disagreed that they are not complying with safety health and environment and that they lack knowledge of technical requirements which leads them to not submitting objective evidence. The study concluded that contracting firms still do not comply with procurement requirements during the tender stage.
- Full Text:
- Date Issued: 2018
Passive acoustic monitoring of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay: temporal patterns and group dynamics
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
Donor-acceptor effects on the optical limiting properties of BODIPY dyes
- Authors: Hlatshwayo, Zweli Thabiso
- Date: 2018
- Subjects: Dyes and dyeing -- Chemistry , Photosensitizing compounds -- Therapeutic use , Cancer -- Photochemotherapy , Upconversion nanoparticles (UCNPs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63368 , vital:28397
- Description: The main objectives of the research described in this thesis were firstly to synthesize and characterize a series of structurally related BODIPY dyes that are potentially suitable for use in applications, secondly to conjugate a carboxylic acid substituted BODIPY dye to amine-functionalized upconversion nanoparticles (UCNPs) through an amide bond to enable singlet oxygen production upon irradiation at 978 nm in the biological window for tissue penetration for biomedical applications, and thirdly to compare the nonlinear optical (NLO) properties of various BODIPY dyes to determine whether push-pull effects enhance their utility for optical limiting (OL) applications. Halogenated BODIPY cores with high singlet oxygen quantum yields were prepared, which absorb in the green portion of the visible region and making it difficult to treat deeper skin tumors in the context of photodynamic therapy (PDT) applications. UCNPs generally absorb in the near-infrared (NIR) region (978 nm), and this is advantageous because, this is where absorption by water, cells and tissues is minimized. NaYF4: Yb/Er/Gd UCNPs were synthesized, amine functionalized and successfully conjugated to a halogenated carboxylic acid functionalized BODIPY. This allowed for favorable Förster resonance energy transfer (FRET) since one of the emission wavelengths of the NaYF4: Yb/Er/Gd UCNPs overlaps with the main absorption band of the BODIPY at 540 nm. The conjugate was irradiated at 978 nm, but instability of the BODIPY dye was observed, which made singlet oxygen quantum yield determination impossible. An enhanced singlet oxygen quantum yield value was observed upon irradiation of the conjugate at 540 nm, suggesting that further studies of this system are warranted. The OL properties of BODIPY cores and dyes, which are π-extended at the 3,5-positions with styryl groups, were studied in a series of different organic solvents at 532 nm by using the z-scan technique on a nanosecond timescale. Many of the dyes were used to compare the effects of introducing electron donor and acceptor groups on the OL properties of the dyes. The dipole moments of these dyes were found to correlate with the OL response. The OL results indicate that BODIPY dyes with push-pull properties, which are π-extended at the 3,5-positions with styryl groups, can be considered as viable candidates for use in OL applications. The studies sought to establish the effect of ESA in the triplet manifold as compared to the singlet manifold in as far as the OL response is concerned. The most promising dyes were embedded in polystyrene thin films, and this was found to significantly enhance their OL properties.
- Full Text:
- Date Issued: 2018
- Authors: Hlatshwayo, Zweli Thabiso
- Date: 2018
- Subjects: Dyes and dyeing -- Chemistry , Photosensitizing compounds -- Therapeutic use , Cancer -- Photochemotherapy , Upconversion nanoparticles (UCNPs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63368 , vital:28397
- Description: The main objectives of the research described in this thesis were firstly to synthesize and characterize a series of structurally related BODIPY dyes that are potentially suitable for use in applications, secondly to conjugate a carboxylic acid substituted BODIPY dye to amine-functionalized upconversion nanoparticles (UCNPs) through an amide bond to enable singlet oxygen production upon irradiation at 978 nm in the biological window for tissue penetration for biomedical applications, and thirdly to compare the nonlinear optical (NLO) properties of various BODIPY dyes to determine whether push-pull effects enhance their utility for optical limiting (OL) applications. Halogenated BODIPY cores with high singlet oxygen quantum yields were prepared, which absorb in the green portion of the visible region and making it difficult to treat deeper skin tumors in the context of photodynamic therapy (PDT) applications. UCNPs generally absorb in the near-infrared (NIR) region (978 nm), and this is advantageous because, this is where absorption by water, cells and tissues is minimized. NaYF4: Yb/Er/Gd UCNPs were synthesized, amine functionalized and successfully conjugated to a halogenated carboxylic acid functionalized BODIPY. This allowed for favorable Förster resonance energy transfer (FRET) since one of the emission wavelengths of the NaYF4: Yb/Er/Gd UCNPs overlaps with the main absorption band of the BODIPY at 540 nm. The conjugate was irradiated at 978 nm, but instability of the BODIPY dye was observed, which made singlet oxygen quantum yield determination impossible. An enhanced singlet oxygen quantum yield value was observed upon irradiation of the conjugate at 540 nm, suggesting that further studies of this system are warranted. The OL properties of BODIPY cores and dyes, which are π-extended at the 3,5-positions with styryl groups, were studied in a series of different organic solvents at 532 nm by using the z-scan technique on a nanosecond timescale. Many of the dyes were used to compare the effects of introducing electron donor and acceptor groups on the OL properties of the dyes. The dipole moments of these dyes were found to correlate with the OL response. The OL results indicate that BODIPY dyes with push-pull properties, which are π-extended at the 3,5-positions with styryl groups, can be considered as viable candidates for use in OL applications. The studies sought to establish the effect of ESA in the triplet manifold as compared to the singlet manifold in as far as the OL response is concerned. The most promising dyes were embedded in polystyrene thin films, and this was found to significantly enhance their OL properties.
- Full Text:
- Date Issued: 2018
Demographic change in the Upper Tsitsa Catchment: the integration of census and land cover data for 2001 and 2011
- Authors: Hodgson, Danuta Lorina
- Date: 2018
- Subjects: Land use -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Thematic maps -- South Africa -- Eastern Cape , Population density -- South Africa -- Eastern Cape , Mzimvubu River Watershed (South Africa) -- Census , Upper Tsitsa Catchment (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57296 , vital:26870
- Description: The purpose of this research was to determine if the integration of census and land cover data could provide evidence of spatial patterns and temporal change for the Upper Tsitsa Catchment. This thesis contributed to academic literature with regards to dasymetric mapping and provided a database for the Ntabelanga and Laleni Ecological Infrastructure Project. The study took place in the Upper Tsitsa Catchment which is located in the north-eastern region of the Eastern Cape and falls within the uMzimvubu Catchment. South Africa National Population Censuses for 2001 and 2011 and the National Land Cover data sets for 2000 and 2013/14 were used to create dasymetric maps depicting demographic changes over time for the catchment area. Spatial statistics were performed on the dasymetric and choropleth map to determine the accuracy of the data that was created. From the results, it was found that although the statistics were skewed, the method was more accurate in displaying the population densities, which was noted during the sampling process of the spatial analysis. It was found that there had been a decrease in the population density within the catchment. This affected the density of several other variables such as population race group, language and employment status statistics as decreases in these values could be due to individuals migrating out of the catchment as well as socio-economic upliftment, such as having better access to services. The use of dasymetric mapping allowed an accurate representation of the population density from the census data to be created. The results of the dasymetric mapping were more accurate as they depicted where the population within the enumeration areas were located, and recognised that some areas were populated while some areas were not. To conclude, it was found that using dasymetric mapping provided reliable and useful data about population density and enables comparison over time.
- Full Text:
- Date Issued: 2018
- Authors: Hodgson, Danuta Lorina
- Date: 2018
- Subjects: Land use -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Thematic maps -- South Africa -- Eastern Cape , Population density -- South Africa -- Eastern Cape , Mzimvubu River Watershed (South Africa) -- Census , Upper Tsitsa Catchment (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57296 , vital:26870
- Description: The purpose of this research was to determine if the integration of census and land cover data could provide evidence of spatial patterns and temporal change for the Upper Tsitsa Catchment. This thesis contributed to academic literature with regards to dasymetric mapping and provided a database for the Ntabelanga and Laleni Ecological Infrastructure Project. The study took place in the Upper Tsitsa Catchment which is located in the north-eastern region of the Eastern Cape and falls within the uMzimvubu Catchment. South Africa National Population Censuses for 2001 and 2011 and the National Land Cover data sets for 2000 and 2013/14 were used to create dasymetric maps depicting demographic changes over time for the catchment area. Spatial statistics were performed on the dasymetric and choropleth map to determine the accuracy of the data that was created. From the results, it was found that although the statistics were skewed, the method was more accurate in displaying the population densities, which was noted during the sampling process of the spatial analysis. It was found that there had been a decrease in the population density within the catchment. This affected the density of several other variables such as population race group, language and employment status statistics as decreases in these values could be due to individuals migrating out of the catchment as well as socio-economic upliftment, such as having better access to services. The use of dasymetric mapping allowed an accurate representation of the population density from the census data to be created. The results of the dasymetric mapping were more accurate as they depicted where the population within the enumeration areas were located, and recognised that some areas were populated while some areas were not. To conclude, it was found that using dasymetric mapping provided reliable and useful data about population density and enables comparison over time.
- Full Text:
- Date Issued: 2018
Development of a low-cost bioprinting system for the fabrication of cell-laden sodium alginate hydrogels
- Authors: Honiball, John Robert
- Date: 2018
- Subjects: Regenerative medicine , Tissue engineering , Alginates , Colloids , Three-dimensional printing
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59204 , vital:27470
- Description: Bioprinting is a rapidly expanding technology with the ability to fabricate in vitro 3D tissues in a layer-by-layer manner to ultimately produce a living tissue which physiologically resembles native in vivo tissue functionality. Unfortunately, large costs associated with commercially available bioprinters severely limit the amount of people/research groups with access to the technology. Here, we investigated the potential for modifying a commercially available RepRap Prusa iteration 3 (i3) three-dimensional (3D) printer, by replacing the traditional plastic-based print-head with various open-source syringe-housed microextrusion print-head units, such that deposition of composite bioinks consisting of cells, biopolymer scaffolds and/or biomolecules may be achieved at a relatively low cost. Using adipose-derived human mesenchymal stromal stem cells (ad-HMSC) induced for adipogenic differentiation, as well as human umbilical vein endothelial cells (HUVEC), the potential for fabricating vascularised adipose tissue was investigated. The non-toxic, inexpensive algal polysaccharide, sodium alginate, was used to test the printability of the system, as well as for investigating the functionality unmodified sodium alginate has for use as a potential bioink in adipose tissue engineering. Cell viability assays, namely WST-1 and fluorescein diacetate (FDA)/propidium iodide (PI) live/dead cell staining, revealed that ad-HMSC were viable after 7 days of culture. However, viability of HUVEC encapsulated hydrogels revealed significantly lower cell viability. Live/dead cell staining revealed that the modified printing system was able to print ad-HMSC/HUVEC co-cocultures with a large degree of cell viability after 1 day of culture. However, after 7 days of culture, the majority of cells were revealed to be dead. Furthermore, due to the lack of mechanical integrity possessed by alginate in a liquid-like state, printing sodium alginate hydrogels in air consistently resulted in deformation of printed constructs. The newly developed 3D printing technique termed freeform reversible embedding of suspended hydrogels (FRESH) was therefore investigated as a means for achieving 3D spatial control of printed hydrogels using the modified system. Printing cell-free sodium alginate hydrogels within gelatin sacrificial support baths allowed for fabricating constructs in a spatially defined manner. However, overprinting and swelling of alginate hydrogels negatively affected the overall printing accuracy. The present study aimed to pave the way for further system modifications and refinements, such that the ultimate goal of low-cost bioprinting may be achieved. Further optimisation of printing parameters, hydrogel characteristics and sterilisation techniques may allow for fabricating viable, physiologically relevant tissues using the modified system developed.
- Full Text:
- Date Issued: 2018
- Authors: Honiball, John Robert
- Date: 2018
- Subjects: Regenerative medicine , Tissue engineering , Alginates , Colloids , Three-dimensional printing
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59204 , vital:27470
- Description: Bioprinting is a rapidly expanding technology with the ability to fabricate in vitro 3D tissues in a layer-by-layer manner to ultimately produce a living tissue which physiologically resembles native in vivo tissue functionality. Unfortunately, large costs associated with commercially available bioprinters severely limit the amount of people/research groups with access to the technology. Here, we investigated the potential for modifying a commercially available RepRap Prusa iteration 3 (i3) three-dimensional (3D) printer, by replacing the traditional plastic-based print-head with various open-source syringe-housed microextrusion print-head units, such that deposition of composite bioinks consisting of cells, biopolymer scaffolds and/or biomolecules may be achieved at a relatively low cost. Using adipose-derived human mesenchymal stromal stem cells (ad-HMSC) induced for adipogenic differentiation, as well as human umbilical vein endothelial cells (HUVEC), the potential for fabricating vascularised adipose tissue was investigated. The non-toxic, inexpensive algal polysaccharide, sodium alginate, was used to test the printability of the system, as well as for investigating the functionality unmodified sodium alginate has for use as a potential bioink in adipose tissue engineering. Cell viability assays, namely WST-1 and fluorescein diacetate (FDA)/propidium iodide (PI) live/dead cell staining, revealed that ad-HMSC were viable after 7 days of culture. However, viability of HUVEC encapsulated hydrogels revealed significantly lower cell viability. Live/dead cell staining revealed that the modified printing system was able to print ad-HMSC/HUVEC co-cocultures with a large degree of cell viability after 1 day of culture. However, after 7 days of culture, the majority of cells were revealed to be dead. Furthermore, due to the lack of mechanical integrity possessed by alginate in a liquid-like state, printing sodium alginate hydrogels in air consistently resulted in deformation of printed constructs. The newly developed 3D printing technique termed freeform reversible embedding of suspended hydrogels (FRESH) was therefore investigated as a means for achieving 3D spatial control of printed hydrogels using the modified system. Printing cell-free sodium alginate hydrogels within gelatin sacrificial support baths allowed for fabricating constructs in a spatially defined manner. However, overprinting and swelling of alginate hydrogels negatively affected the overall printing accuracy. The present study aimed to pave the way for further system modifications and refinements, such that the ultimate goal of low-cost bioprinting may be achieved. Further optimisation of printing parameters, hydrogel characteristics and sterilisation techniques may allow for fabricating viable, physiologically relevant tissues using the modified system developed.
- Full Text:
- Date Issued: 2018
An investigation of mitochondrial dynamics and networks observed within human undifferentiated and differentiated cell lines
- Authors: Houseman, Pascalené Shannon
- Date: 2018
- Subjects: Mitochondria , Mitochondrial pathology , Degeneration (Pathology) , Mesenchymal stem cells , Neural stem cells , Cell lines , Reactive oxygen species (ROS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60687 , vital:27816
- Description: Mitochondrial dynamics refers to a series of constant division and fusion cycles that form interconnecting networks within healthy cells. Reactive oxygen species (ROS) are the byproducts of cellular redox reactions, and, when in excess, have been linked to degenerative diseases and aging. Mesenchymal stem cells (MSCs) require a niche that presents with low levels of ROS; this enables the stem cell to maintain its “sternness”, the stem cell population, as well as the ability to adhere, migrate, and proliferate. If ROS levels increase within the MSC niche, inhibition of cellular adhesion and migration occurs. In contrast, neural stem cells require a niche that presents with a high level of ROS, aiding in their proliferative, self- renewing capacities. Investigations into what constitutes a healthy mitochondrial network versus the disease state of the network are required in order to determine what promotes degeneration and aging within stem cells. It was hypothesized that increased levels of ROS would stunt the ability of MSCs to attach and migrate, and hinder their abilities of proliferation and differentiation. In contrast, neuronal differentiation would present with an increased proliferation. This led to the investigation into the effects of ROS and oxidative stress, and the resulting mitochondrial dynamics, have on undifferentiated and differentiated mesenchymal stem and SH-SY5Y cells. Upon the addition of non-lethal S3I-201 (STAT3 has been linked to a reduction in ROS) to MSCs, an increase in ROS was observed. Higher concentrations of STAT3 inhibitor resulted in a decrease in MSC attachment and proliferation. When exposed to similar conditions, the SH-SY5Y cells underwent an increased proliferation; due to multiple restrictions, they were not used any further within the study. Mitochondrial dynamics were observed using a fusion promoter (M1) and a fission inhibitor (Mdivi-1); the MSCs were dosed with varying concentrations in order to determine the effects that mitochondrial dysfunction may have on the established networks, and cell survival. The mitochondria within MSCs migrated to the extensions of the cell, and displayed an alteration in morphology, or were clustered around the nucleus and/or the lipid deposits. These high density clusters correlated with a high intensity of fluorescence using 2’,7’- dichlorofluorescein diacetate. In conclusion, varying concentrations of ROS have different effects on MSCs in terms of overall maintenance and function; mitochondrial dynamics play an important role in cell survivability and the fate of stem cell differentiation. Further investigation into the mitochondrial dynamics and networks of these cell lines and their differentiated progeny is required.
- Full Text:
- Date Issued: 2018
- Authors: Houseman, Pascalené Shannon
- Date: 2018
- Subjects: Mitochondria , Mitochondrial pathology , Degeneration (Pathology) , Mesenchymal stem cells , Neural stem cells , Cell lines , Reactive oxygen species (ROS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60687 , vital:27816
- Description: Mitochondrial dynamics refers to a series of constant division and fusion cycles that form interconnecting networks within healthy cells. Reactive oxygen species (ROS) are the byproducts of cellular redox reactions, and, when in excess, have been linked to degenerative diseases and aging. Mesenchymal stem cells (MSCs) require a niche that presents with low levels of ROS; this enables the stem cell to maintain its “sternness”, the stem cell population, as well as the ability to adhere, migrate, and proliferate. If ROS levels increase within the MSC niche, inhibition of cellular adhesion and migration occurs. In contrast, neural stem cells require a niche that presents with a high level of ROS, aiding in their proliferative, self- renewing capacities. Investigations into what constitutes a healthy mitochondrial network versus the disease state of the network are required in order to determine what promotes degeneration and aging within stem cells. It was hypothesized that increased levels of ROS would stunt the ability of MSCs to attach and migrate, and hinder their abilities of proliferation and differentiation. In contrast, neuronal differentiation would present with an increased proliferation. This led to the investigation into the effects of ROS and oxidative stress, and the resulting mitochondrial dynamics, have on undifferentiated and differentiated mesenchymal stem and SH-SY5Y cells. Upon the addition of non-lethal S3I-201 (STAT3 has been linked to a reduction in ROS) to MSCs, an increase in ROS was observed. Higher concentrations of STAT3 inhibitor resulted in a decrease in MSC attachment and proliferation. When exposed to similar conditions, the SH-SY5Y cells underwent an increased proliferation; due to multiple restrictions, they were not used any further within the study. Mitochondrial dynamics were observed using a fusion promoter (M1) and a fission inhibitor (Mdivi-1); the MSCs were dosed with varying concentrations in order to determine the effects that mitochondrial dysfunction may have on the established networks, and cell survival. The mitochondria within MSCs migrated to the extensions of the cell, and displayed an alteration in morphology, or were clustered around the nucleus and/or the lipid deposits. These high density clusters correlated with a high intensity of fluorescence using 2’,7’- dichlorofluorescein diacetate. In conclusion, varying concentrations of ROS have different effects on MSCs in terms of overall maintenance and function; mitochondrial dynamics play an important role in cell survivability and the fate of stem cell differentiation. Further investigation into the mitochondrial dynamics and networks of these cell lines and their differentiated progeny is required.
- Full Text:
- Date Issued: 2018
A baseline survey of channel geomorphology with particular reference to the effects of sediment characteristics on ecosystem health in the Tsitsa River, Eastern Cape, South Africa
- Huchzermeyer, Nicholaus Heinrich
- Authors: Huchzermeyer, Nicholaus Heinrich
- Date: 2018
- Subjects: Fluvial geomorphology -- South Africa -- Eastern Cape , Stream health -- South Africa -- Eastern Cape , River sediments -- South Africa -- Eastern Cape , Watershed management -- South Africa -- Eastern Cape , Dams -- Environmental aspects -- South Africa -- Eastern Cape , Tsitsa River (South Africa) , Ntabelanga Dam (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58056 , vital:27040
- Description: Fluvial systems are dynamic systems in which variables in a catchment and river channel affect the morphology of river reaches. South African rivers are increasingly being exposed to stresses from a combination of factors, one of the most prevalent being the impacts of damming rivers which result in varying downstream sediment fluxes and flow regimes. The sediment load combined with flow characteristics for respective river channels provides the physical habitat for aquatic ecosystems. The damming of the Tsitsa River, through the construction of the Ntabelanga Dam, will change the overall downstream geomorphology. This creates an opportunity for research in the preconstruction window. The current condition of the Tsitsa River was monitored by completing a baseline survey of the channel geomorphology with specific reference to the influence of sediment on river habitats and ecosystem health. Five sites were established in variable reaches of the Tsitsa River, with Site 1 located above the proposed Ntabelanga Dam inundation and Sites 2-5 below the proposed dam wall. Each site included a range of features that can be monitored for their response to the dam. Physical variables, water quality and biota were monitored seasonally to note changes in habitat quality. A baseline survey of the present geomorphology and associated instream habitats of the selected reaches was set up by conducting cross-sectional surveys of channel topography, water slope surveys, discharge measurements and visual and quantitative assessments of substrate. Level loggers were installed at each site to collect continuous data on variations in depth and temperature. Monitoring surveys, in terms of fine sediment accumulation, were conducted to characterise dynamic habitat arrangements and macroinvertebrate community composition. A taxa related physical habitat score for the Tsitsa River was created. The relationship between water quality, physical and ecological characteristics of the Tsitsa River will aid further research in the area as well as create a better understanding of the influence of sediment on river habitats and ecosystem health. Monitoring sites can be used to monitor the impact of catchment-wide rehabilitation on river health prior to the dam being built. After dam construction, the top site above the dam inundation can still be used as a point to monitor the impact of catchment rehabilitation on ecosystem health in terms of fine sediment accumulation.
- Full Text:
- Date Issued: 2018
- Authors: Huchzermeyer, Nicholaus Heinrich
- Date: 2018
- Subjects: Fluvial geomorphology -- South Africa -- Eastern Cape , Stream health -- South Africa -- Eastern Cape , River sediments -- South Africa -- Eastern Cape , Watershed management -- South Africa -- Eastern Cape , Dams -- Environmental aspects -- South Africa -- Eastern Cape , Tsitsa River (South Africa) , Ntabelanga Dam (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58056 , vital:27040
- Description: Fluvial systems are dynamic systems in which variables in a catchment and river channel affect the morphology of river reaches. South African rivers are increasingly being exposed to stresses from a combination of factors, one of the most prevalent being the impacts of damming rivers which result in varying downstream sediment fluxes and flow regimes. The sediment load combined with flow characteristics for respective river channels provides the physical habitat for aquatic ecosystems. The damming of the Tsitsa River, through the construction of the Ntabelanga Dam, will change the overall downstream geomorphology. This creates an opportunity for research in the preconstruction window. The current condition of the Tsitsa River was monitored by completing a baseline survey of the channel geomorphology with specific reference to the influence of sediment on river habitats and ecosystem health. Five sites were established in variable reaches of the Tsitsa River, with Site 1 located above the proposed Ntabelanga Dam inundation and Sites 2-5 below the proposed dam wall. Each site included a range of features that can be monitored for their response to the dam. Physical variables, water quality and biota were monitored seasonally to note changes in habitat quality. A baseline survey of the present geomorphology and associated instream habitats of the selected reaches was set up by conducting cross-sectional surveys of channel topography, water slope surveys, discharge measurements and visual and quantitative assessments of substrate. Level loggers were installed at each site to collect continuous data on variations in depth and temperature. Monitoring surveys, in terms of fine sediment accumulation, were conducted to characterise dynamic habitat arrangements and macroinvertebrate community composition. A taxa related physical habitat score for the Tsitsa River was created. The relationship between water quality, physical and ecological characteristics of the Tsitsa River will aid further research in the area as well as create a better understanding of the influence of sediment on river habitats and ecosystem health. Monitoring sites can be used to monitor the impact of catchment-wide rehabilitation on river health prior to the dam being built. After dam construction, the top site above the dam inundation can still be used as a point to monitor the impact of catchment rehabilitation on ecosystem health in terms of fine sediment accumulation.
- Full Text:
- Date Issued: 2018
Guest inclusion behaviour of zirconium(IV)- based polycarboxylate complexes: a study of metal-organic frameworks
- Hulushe, Siyabonga Theophillus
- Authors: Hulushe, Siyabonga Theophillus
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63710 , vital:28474
- Description: Expected release date-April 2019
- Full Text:
- Date Issued: 2018
- Authors: Hulushe, Siyabonga Theophillus
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63710 , vital:28474
- Description: Expected release date-April 2019
- Full Text:
- Date Issued: 2018
Impact of dietary factors on drug adherence and the nutritional status of tuberculosis patients in the Nelson Mandela Bay Health District
- Authors: Human, Wieda
- Date: 2018
- Subjects: Patients -- Nutritional aspects -- South Africa -- Nelson Mandela Bay Municipality , Tuberculosis -- Patients -- Nutritional aspects -- South Africa -- Nelson Mandela Bay Municipality Drug-nutrient interactions Appetite -- Effect of drugs on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22265 , vital:29929
- Description: The prevalence of poor adherence by Tuberculosis (TB) patients to their drug regimens poses a major public health problem in South Africa. Many South Africans are the victims of poverty and unemployment and, as a result, may face food insecurity, hunger and have diets lacking diversity. Malnutrition is commonly noted in patients with TB. Poor immunity as a result of TB further compromises the nutritional status of the patient and thus the prognosis. Chronic hunger together with food insecurity and inadequate dietary diversity can lead to poor drug adherence amongst patients. This highlights the fact that dietary factors may pose a threat to TB drug adherence. There is limited information available regarding the impact of dietary factors on drug adherence and the nutritional status in patients with TB, especially in the Eastern Cape. This emphasises the need for more research focusing on the impact that dietary factors have on drug adherence and nutritional status of patients with TB from underprivileged areas. The aim of the study was to describe the impact of dietary factors on drug adherence and the nutritional status of patients with TB from underprivileged areas in the Nelson Mandela Bay Health District (NMBHD) in order to revise current guidelines to standardise the nutrition management in patients with TB who are initiated on treatment. A descriptive, cross-sectional study was conducted using a quantitative approach. Ethical approval was obtained from the Research Ethics Committee (NMU) and the Eastern Cape Department of Health Provincial Research Committee. All participants provided written, informed consent prior to participation. A representative sample was drawn from each of the three sub-districts in the NMBHD to include a total of 256 participants. The following clinics were randomly selected: Max Madlingozi, Tshangana, Soweto clinic (sub-district A), Laetitia Bam, Middle Street, Rosedale (sub-district B) while clinics in sub-district C included Korsten, Walmer, Gelvandale and Helenvale. The population for the study included patients with TB older than 18 years treated at these specific clinics. Patients with Drug- Resistant TB were excluded. A structured interview was conducted by the researcher and three fieldworkers to obtain information on socio-demographics, drug adherence, food insecurity and dietary diversity. Anthropometric measurements (weight and height) were also obtained to determine the nutritional status of participants. The majority of participants were male (59%; n=150). The mean age of participants was 35,03 years (SD=11.97). Of the total sample, 70% (n=179) reported being currently unemployed, while 59% of the total sample were also unemployed prior to TB diagnosis. Fifty percent of participants (n=127) were HIV co-infected, while only a marginal percentage (3%; n=7) had Diabetes Mellitus. Treatment adherence was considered 'good' as 94% (n=240) reported taking their TB treatment daily while 92% (n=121) reported taking their antiretroviral therapy (ART) daily. About a third (32%; n=81) of the total sample experienced low appetite, followed by nausea (21%; n=53) and vomiting (20%; n=50). A large percentage (48%; n=123) of participants experienced severe hunger. The mean individual dietary diversity score (DDS) for this sample was below 3 (2.81/9) and could be classified as being moderately diverse. Forty-three percent (n=110) had a low DDS of 2 or less food groups. Only 2% (n=5) had a high DDS of more than 7 food groups. A statistically significant association was found between employment status and food insecurity and poor DDS. Previous TB infection was also significantly associated with food insecurity and poor DDS. Although so many participants were food insecure, 74% (n=188) reported taking their TB treatment with food. Regarding substance use, 24% (n=88) consumed alcohol weekly, whereas 31% (n=80) of participants smoked cigarettes. The mean BMI value for males was 20.93 kg/m2 (SD=4.19) and for females at 20.91 kg/m2 (SD=5.10). However, 30% (n=76) had BMI values below 18.5 kg/m2 and 16% (n=40) had BMI values above 25 kg/m2. Majority of the participants (91%; n=233) had lost weight prior to data collection. Furthermore, 75% (n=175) reported having experienced involuntary weight loss in the preceding 3 months, while 17% (n=43) reported having lost more than 10% of their body weight in the last 3 months. Almost all participants reported taking their TB treatment as prescribed. However, the study results echo the findings of other studies that a large cohort of participants are currently unemployed and food insecure. Many participants were consuming monotonous diets, consisting primarily of starch with little vegetables and fruits. As a result, the nutritional status of the sample population was compromised. This sample also reflected unhealthy lifestyle habits which included substance use (alcohol and cigarette smoking). As so many participants self-reported adhering to TB treatment, it was challenging to determine the impact that dietary factors have on TB drug adherence. Government, NGO's and other private stakeholders should make nutrition a priority especially in vulnerable groups such as patients with TB. Dietitians and nutritionists should be involved in the care of all patients with TB by providing relevant nutrition counselling. Although malnourished patients with TB are currently receiving nutrition supplementation, the amount and sustainability thereof should be revised. Food gardens may further be a safety net against food insecurity, hunger and inadequate dietary diversity.
- Full Text:
- Date Issued: 2018
- Authors: Human, Wieda
- Date: 2018
- Subjects: Patients -- Nutritional aspects -- South Africa -- Nelson Mandela Bay Municipality , Tuberculosis -- Patients -- Nutritional aspects -- South Africa -- Nelson Mandela Bay Municipality Drug-nutrient interactions Appetite -- Effect of drugs on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22265 , vital:29929
- Description: The prevalence of poor adherence by Tuberculosis (TB) patients to their drug regimens poses a major public health problem in South Africa. Many South Africans are the victims of poverty and unemployment and, as a result, may face food insecurity, hunger and have diets lacking diversity. Malnutrition is commonly noted in patients with TB. Poor immunity as a result of TB further compromises the nutritional status of the patient and thus the prognosis. Chronic hunger together with food insecurity and inadequate dietary diversity can lead to poor drug adherence amongst patients. This highlights the fact that dietary factors may pose a threat to TB drug adherence. There is limited information available regarding the impact of dietary factors on drug adherence and the nutritional status in patients with TB, especially in the Eastern Cape. This emphasises the need for more research focusing on the impact that dietary factors have on drug adherence and nutritional status of patients with TB from underprivileged areas. The aim of the study was to describe the impact of dietary factors on drug adherence and the nutritional status of patients with TB from underprivileged areas in the Nelson Mandela Bay Health District (NMBHD) in order to revise current guidelines to standardise the nutrition management in patients with TB who are initiated on treatment. A descriptive, cross-sectional study was conducted using a quantitative approach. Ethical approval was obtained from the Research Ethics Committee (NMU) and the Eastern Cape Department of Health Provincial Research Committee. All participants provided written, informed consent prior to participation. A representative sample was drawn from each of the three sub-districts in the NMBHD to include a total of 256 participants. The following clinics were randomly selected: Max Madlingozi, Tshangana, Soweto clinic (sub-district A), Laetitia Bam, Middle Street, Rosedale (sub-district B) while clinics in sub-district C included Korsten, Walmer, Gelvandale and Helenvale. The population for the study included patients with TB older than 18 years treated at these specific clinics. Patients with Drug- Resistant TB were excluded. A structured interview was conducted by the researcher and three fieldworkers to obtain information on socio-demographics, drug adherence, food insecurity and dietary diversity. Anthropometric measurements (weight and height) were also obtained to determine the nutritional status of participants. The majority of participants were male (59%; n=150). The mean age of participants was 35,03 years (SD=11.97). Of the total sample, 70% (n=179) reported being currently unemployed, while 59% of the total sample were also unemployed prior to TB diagnosis. Fifty percent of participants (n=127) were HIV co-infected, while only a marginal percentage (3%; n=7) had Diabetes Mellitus. Treatment adherence was considered 'good' as 94% (n=240) reported taking their TB treatment daily while 92% (n=121) reported taking their antiretroviral therapy (ART) daily. About a third (32%; n=81) of the total sample experienced low appetite, followed by nausea (21%; n=53) and vomiting (20%; n=50). A large percentage (48%; n=123) of participants experienced severe hunger. The mean individual dietary diversity score (DDS) for this sample was below 3 (2.81/9) and could be classified as being moderately diverse. Forty-three percent (n=110) had a low DDS of 2 or less food groups. Only 2% (n=5) had a high DDS of more than 7 food groups. A statistically significant association was found between employment status and food insecurity and poor DDS. Previous TB infection was also significantly associated with food insecurity and poor DDS. Although so many participants were food insecure, 74% (n=188) reported taking their TB treatment with food. Regarding substance use, 24% (n=88) consumed alcohol weekly, whereas 31% (n=80) of participants smoked cigarettes. The mean BMI value for males was 20.93 kg/m2 (SD=4.19) and for females at 20.91 kg/m2 (SD=5.10). However, 30% (n=76) had BMI values below 18.5 kg/m2 and 16% (n=40) had BMI values above 25 kg/m2. Majority of the participants (91%; n=233) had lost weight prior to data collection. Furthermore, 75% (n=175) reported having experienced involuntary weight loss in the preceding 3 months, while 17% (n=43) reported having lost more than 10% of their body weight in the last 3 months. Almost all participants reported taking their TB treatment as prescribed. However, the study results echo the findings of other studies that a large cohort of participants are currently unemployed and food insecure. Many participants were consuming monotonous diets, consisting primarily of starch with little vegetables and fruits. As a result, the nutritional status of the sample population was compromised. This sample also reflected unhealthy lifestyle habits which included substance use (alcohol and cigarette smoking). As so many participants self-reported adhering to TB treatment, it was challenging to determine the impact that dietary factors have on TB drug adherence. Government, NGO's and other private stakeholders should make nutrition a priority especially in vulnerable groups such as patients with TB. Dietitians and nutritionists should be involved in the care of all patients with TB by providing relevant nutrition counselling. Although malnourished patients with TB are currently receiving nutrition supplementation, the amount and sustainability thereof should be revised. Food gardens may further be a safety net against food insecurity, hunger and inadequate dietary diversity.
- Full Text:
- Date Issued: 2018
A comparison of exact string search algorithms for deep packet inspection
- Authors: Hunt, Kieran
- Date: 2018
- Subjects: Algorithms , Firewalls (Computer security) , Computer networks -- Security measures , Intrusion detection systems (Computer security) , Deep Packet Inspection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60629 , vital:27807
- Description: Every day, computer networks throughout the world face a constant onslaught of attacks. To combat these, network administrators are forced to employ a multitude of mitigating measures. Devices such as firewalls and Intrusion Detection Systems are prevalent today and employ extensive Deep Packet Inspection to scrutinise each piece of network traffic. Systems such as these usually require specialised hardware to meet the demand imposed by high throughput networks. Hardware like this is extremely expensive and singular in its function. It is with this in mind that the string search algorithms are introduced. These algorithms have been proven to perform well when searching through large volumes of text and may be able to perform equally well in the context of Deep Packet Inspection. String search algorithms are designed to match a single pattern to a substring of a given piece of text. This is not unlike the heuristics employed by traditional Deep Packet Inspection systems. This research compares the performance of a large number of string search algorithms during packet processing. Deep Packet Inspection places stringent restrictions on the reliability and speed of the algorithms due to increased performance pressures. A test system had to be designed in order to properly test the string search algorithms in the context of Deep Packet Inspection. The system allowed for precise and repeatable tests of each algorithm and then for their comparison. Of the algorithms tested, the Horspool and Quick Search algorithms posted the best results for both speed and reliability. The Not So Naive and Rabin-Karp algorithms were slowest overall.
- Full Text:
- Date Issued: 2018
- Authors: Hunt, Kieran
- Date: 2018
- Subjects: Algorithms , Firewalls (Computer security) , Computer networks -- Security measures , Intrusion detection systems (Computer security) , Deep Packet Inspection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60629 , vital:27807
- Description: Every day, computer networks throughout the world face a constant onslaught of attacks. To combat these, network administrators are forced to employ a multitude of mitigating measures. Devices such as firewalls and Intrusion Detection Systems are prevalent today and employ extensive Deep Packet Inspection to scrutinise each piece of network traffic. Systems such as these usually require specialised hardware to meet the demand imposed by high throughput networks. Hardware like this is extremely expensive and singular in its function. It is with this in mind that the string search algorithms are introduced. These algorithms have been proven to perform well when searching through large volumes of text and may be able to perform equally well in the context of Deep Packet Inspection. String search algorithms are designed to match a single pattern to a substring of a given piece of text. This is not unlike the heuristics employed by traditional Deep Packet Inspection systems. This research compares the performance of a large number of string search algorithms during packet processing. Deep Packet Inspection places stringent restrictions on the reliability and speed of the algorithms due to increased performance pressures. A test system had to be designed in order to properly test the string search algorithms in the context of Deep Packet Inspection. The system allowed for precise and repeatable tests of each algorithm and then for their comparison. Of the algorithms tested, the Horspool and Quick Search algorithms posted the best results for both speed and reliability. The Not So Naive and Rabin-Karp algorithms were slowest overall.
- Full Text:
- Date Issued: 2018
A framework for malicious host fingerprinting using distributed network sensors
- Authors: Hunter, Samuel Oswald
- Date: 2018
- Subjects: Computer networks -- Security measures , Malware (Computer software) , Multisensor data fusion , Distributed Sensor Networks , Automated Reconnaissance Framework , Latency Based Multilateration
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60653 , vital:27811
- Description: Numerous software agents exist and are responsible for increasing volumes of malicious traffic that is observed on the Internet today. From a technical perspective the existing techniques for monitoring malicious agents and traffic were not developed to allow for the interrogation of the source of malicious traffic. This interrogation or reconnaissance would be considered active analysis as opposed to existing, mostly passive analysis. Unlike passive analysis, the active techniques are time-sensitive and their results become increasingly inaccurate as time delta between observation and interrogation increases. In addition to this, some studies had shown that the geographic separation of hosts on the Internet have resulted in pockets of different malicious agents and traffic targeting victims. As such it would be important to perform any kind of data collection over various source and in distributed IP address space. The data gathering and exposure capabilities of sensors such as honeypots and network telescopes were extended through the development of near-realtime Distributed Sensor Network modules that allowed for the near-realtime analysis of malicious traffic from distributed, heterogeneous monitoring sensors. In order to utilise the data exposed by the near-realtime Distributed Sensor Network modules an Automated Reconnaissance Framework was created, this framework was tasked with active and passive information collection and analysis of data in near-realtime and was designed from an adapted Multi Sensor Data Fusion model. The hypothesis was made that if sufficiently different characteristics of a host could be identified; combined they could act as a unique fingerprint for that host, potentially allowing for the re-identification of that host, even if its IP address had changed. To this end the concept of Latency Based Multilateration was introduced, acting as an additional metric for remote host fingerprinting. The vast amount of information gathered by the AR-Framework required the development of visualisation tools which could illustrate this data in near-realtime and also provided various degrees of interaction to accommodate human interpretation of such data. Ultimately the data collected through the application of the near-realtime Distributed Sensor Network and AR-Framework provided a unique perspective of a malicious host demographic. Allowing for new correlations to be drawn between attributes such as common open ports and operating systems, location, and inferred intent of these malicious hosts. The result of which expands our current understanding of malicious hosts on the Internet and enables further research in the area.
- Full Text:
- Date Issued: 2018
- Authors: Hunter, Samuel Oswald
- Date: 2018
- Subjects: Computer networks -- Security measures , Malware (Computer software) , Multisensor data fusion , Distributed Sensor Networks , Automated Reconnaissance Framework , Latency Based Multilateration
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60653 , vital:27811
- Description: Numerous software agents exist and are responsible for increasing volumes of malicious traffic that is observed on the Internet today. From a technical perspective the existing techniques for monitoring malicious agents and traffic were not developed to allow for the interrogation of the source of malicious traffic. This interrogation or reconnaissance would be considered active analysis as opposed to existing, mostly passive analysis. Unlike passive analysis, the active techniques are time-sensitive and their results become increasingly inaccurate as time delta between observation and interrogation increases. In addition to this, some studies had shown that the geographic separation of hosts on the Internet have resulted in pockets of different malicious agents and traffic targeting victims. As such it would be important to perform any kind of data collection over various source and in distributed IP address space. The data gathering and exposure capabilities of sensors such as honeypots and network telescopes were extended through the development of near-realtime Distributed Sensor Network modules that allowed for the near-realtime analysis of malicious traffic from distributed, heterogeneous monitoring sensors. In order to utilise the data exposed by the near-realtime Distributed Sensor Network modules an Automated Reconnaissance Framework was created, this framework was tasked with active and passive information collection and analysis of data in near-realtime and was designed from an adapted Multi Sensor Data Fusion model. The hypothesis was made that if sufficiently different characteristics of a host could be identified; combined they could act as a unique fingerprint for that host, potentially allowing for the re-identification of that host, even if its IP address had changed. To this end the concept of Latency Based Multilateration was introduced, acting as an additional metric for remote host fingerprinting. The vast amount of information gathered by the AR-Framework required the development of visualisation tools which could illustrate this data in near-realtime and also provided various degrees of interaction to accommodate human interpretation of such data. Ultimately the data collected through the application of the near-realtime Distributed Sensor Network and AR-Framework provided a unique perspective of a malicious host demographic. Allowing for new correlations to be drawn between attributes such as common open ports and operating systems, location, and inferred intent of these malicious hosts. The result of which expands our current understanding of malicious hosts on the Internet and enables further research in the area.
- Full Text:
- Date Issued: 2018
Effects of polymerisation conditions on the mechanism and properties of furfuryl alcohol resin
- Authors: Iroegbu, Austine Ofondu
- Date: 2018
- Subjects: Polymerization , Polyethylene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30386 , vital:30937
- Description: The purpose of this study was to do a comparative investigation on the acid- and heat catalysed polymerisation and resinification of furfuryl alcohol and the effects of these polymerisation conditions on the mechanism, morphology, molecular weight and thermal properties of the polyfurfuryl alcohol resins. The formation of furfuryl alcohol polymers was confirmed using size exclusion chromatography (SEC); the synthesised polymer resins were investigated using Fourier transform infrared spectroscopy (FTIR,), scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA). The effects of polymerisation conditions on the mechanism of polyfurfuryl alcohol polymerisation was a major focus of this study. The obtained results confirm that the surface topology, mechanism of polymerisation, thermal behaviour and molecular weights of polyfurfuryl alcohol polymer resins are dependent on the polymerisation condition. The acid and heat catalysed polyfurfuryl alcohol resin polymers presented interesting and promising results.
- Full Text:
- Date Issued: 2018
- Authors: Iroegbu, Austine Ofondu
- Date: 2018
- Subjects: Polymerization , Polyethylene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30386 , vital:30937
- Description: The purpose of this study was to do a comparative investigation on the acid- and heat catalysed polymerisation and resinification of furfuryl alcohol and the effects of these polymerisation conditions on the mechanism, morphology, molecular weight and thermal properties of the polyfurfuryl alcohol resins. The formation of furfuryl alcohol polymers was confirmed using size exclusion chromatography (SEC); the synthesised polymer resins were investigated using Fourier transform infrared spectroscopy (FTIR,), scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA). The effects of polymerisation conditions on the mechanism of polyfurfuryl alcohol polymerisation was a major focus of this study. The obtained results confirm that the surface topology, mechanism of polymerisation, thermal behaviour and molecular weights of polyfurfuryl alcohol polymer resins are dependent on the polymerisation condition. The acid and heat catalysed polyfurfuryl alcohol resin polymers presented interesting and promising results.
- Full Text:
- Date Issued: 2018
The effect of ER stress in INS-1E cells using IL-1β under hyperglycaemic conditions
- Authors: Jackson, Simon
- Date: 2018
- Subjects: Diabetes -- Pathogenesis , Endoplasmic reticulum -- Pathophysiology Endoplasmic reticulum Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30397 , vital:30938
- Description: Diabetes afflicts millions of individuals worldwide, and the statistics rise each year. It is associated with various ailments which reduce the quality of life and has been shown to be associated with seemingly unrelated diseases or conditions. One aspect of the pathogenesis of diabetes is endoplasmic reticulum (ER) stress, which is an imbalance in the protein loading and protein folding capacities of the ER of a cell. Under chronic hyperglycaemic conditions associated with the development of diabetes, excessive insulin production disrupts the ER homeostasis, leading to ER stress. If the ER stress is severe or chronic, cell death of pancreatic β-cells may occur, leading to the onset of diabetes. There is currently a gap in available models that closely resemble the pathogenesis of diabetes in insulinoma-1E (INS-1E) pancreatic β-cells to study ER stress under hyperglycaemic conditions. This study optimised various ER stress-inducing models and tested terpenoid treatments to investigate their potential in modulating ER stress. Using various cell viability assays, five models to induce ER stress were optimised (hyperglycaemic, interleukin-1β (IL-1β), tunicamycin (Tm), brefeldin-A (BFA) and thapsigargin (Tg)). The five models were shown to induce ER stress through the expression of the downstream ER stress marker CCAAT-enhancer binding protein (C/EBP) homologous protein (CHOP). The various models induced ER stress under different mechanisms. Insulin secretion analysis using enzyme-linked immunosorbent assays (ELISAs) demonstrated that low concentrations of IL-1β promoted insulin secretion. Several of the terpenoid treatments showed potential in alleviating different aspects of either ER stress or inflammation.
- Full Text:
- Date Issued: 2018
- Authors: Jackson, Simon
- Date: 2018
- Subjects: Diabetes -- Pathogenesis , Endoplasmic reticulum -- Pathophysiology Endoplasmic reticulum Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30397 , vital:30938
- Description: Diabetes afflicts millions of individuals worldwide, and the statistics rise each year. It is associated with various ailments which reduce the quality of life and has been shown to be associated with seemingly unrelated diseases or conditions. One aspect of the pathogenesis of diabetes is endoplasmic reticulum (ER) stress, which is an imbalance in the protein loading and protein folding capacities of the ER of a cell. Under chronic hyperglycaemic conditions associated with the development of diabetes, excessive insulin production disrupts the ER homeostasis, leading to ER stress. If the ER stress is severe or chronic, cell death of pancreatic β-cells may occur, leading to the onset of diabetes. There is currently a gap in available models that closely resemble the pathogenesis of diabetes in insulinoma-1E (INS-1E) pancreatic β-cells to study ER stress under hyperglycaemic conditions. This study optimised various ER stress-inducing models and tested terpenoid treatments to investigate their potential in modulating ER stress. Using various cell viability assays, five models to induce ER stress were optimised (hyperglycaemic, interleukin-1β (IL-1β), tunicamycin (Tm), brefeldin-A (BFA) and thapsigargin (Tg)). The five models were shown to induce ER stress through the expression of the downstream ER stress marker CCAAT-enhancer binding protein (C/EBP) homologous protein (CHOP). The various models induced ER stress under different mechanisms. Insulin secretion analysis using enzyme-linked immunosorbent assays (ELISAs) demonstrated that low concentrations of IL-1β promoted insulin secretion. Several of the terpenoid treatments showed potential in alleviating different aspects of either ER stress or inflammation.
- Full Text:
- Date Issued: 2018
Water quality, biomass and extracellular polymeric substances in an integrated algae pond system
- Authors: Jimoh, Taobat Adekilekun
- Date: 2018
- Subjects: Water -- Purification , Sewage -- Purification -- Anaerobic treatment , Sewage lagoons , Sewage disposal plants , ASPAM model (Acid mine drainage) , Integrated algae pond systems (IAPS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57307 , vital:26871
- Description: Integrated algae pond systems (IAPS) combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Although, IAPS as a technology process offers many advantages including efficient and simultaneous N and P removal, no requirement for additional chemicals, O2 generation, CO2 mitigation, and a biomass with potential for valorization, a lack of technological advancement and the need for large land area, has limited the reach of this technology at industrial scale. In mitigation, peroxonation was introduced as a tertiary treatment unit and its effect on COD and TSS of IAPS treated water investigated. An effort was made to characterize the soluble but persistent COD in IAPS treated water and, productivity of the HRAOP mixed liquor was investigated to gain insight into the potential use of this biomass. Results show that peroxone treatment effectively reduced COD, TSS, and nutrient load of IAPS water without any significant impact on land area requirement. Indeed, summary data describing the effect of peroxone on quality of IAPS-treated water confirmed that it complies with the general limit values for either irrigation or discharge into a water resource that is not a listed water resource for volumes up to 2 ML of treated wastewater on any given day. Extraction followed by FT-IR spectroscopy was used to confirm albeit tentatively, the identity of the soluble but persistent COD in IAPS treated water as MaB-floc EPS. Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. A relationship between photosynthesis and EPS production was established by quantification of the EPS following exposure of MaB-flocs to either continuous light or darkness. Several novel strains of bacteria were isolated from HRAOP mixed liquor and 16S ribosomal genomic sequence analysis resulted in the molecular characterization of Planococcus maitriensis strain ECCN 45b. This is the first report of Planococcus maitriensis from a wastewater treatment process. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning and evening were monitored and revealed that MLSS is composed of microalgae and bacteria but not fungi. Concentration varied from 77 mg L-1 in September (winter) to 285 mg L-1 in November (spring); pond productivity increased from 5.8 g m-2 d-1 (winter) to 21.5 g m-2 d-1 (spring); and, irrespective of MLSS concentration in late afternoon, approximately 39% was lost overnight, which presumably occurred due to passive removal by the algae settling pond. The outcomes of this research are discussed in terms of the quality of treated water, and the further development of IAPS as a platform technology for establishing a biorefinery within the wastewater treatment sector.
- Full Text:
- Date Issued: 2018
- Authors: Jimoh, Taobat Adekilekun
- Date: 2018
- Subjects: Water -- Purification , Sewage -- Purification -- Anaerobic treatment , Sewage lagoons , Sewage disposal plants , ASPAM model (Acid mine drainage) , Integrated algae pond systems (IAPS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57307 , vital:26871
- Description: Integrated algae pond systems (IAPS) combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Although, IAPS as a technology process offers many advantages including efficient and simultaneous N and P removal, no requirement for additional chemicals, O2 generation, CO2 mitigation, and a biomass with potential for valorization, a lack of technological advancement and the need for large land area, has limited the reach of this technology at industrial scale. In mitigation, peroxonation was introduced as a tertiary treatment unit and its effect on COD and TSS of IAPS treated water investigated. An effort was made to characterize the soluble but persistent COD in IAPS treated water and, productivity of the HRAOP mixed liquor was investigated to gain insight into the potential use of this biomass. Results show that peroxone treatment effectively reduced COD, TSS, and nutrient load of IAPS water without any significant impact on land area requirement. Indeed, summary data describing the effect of peroxone on quality of IAPS-treated water confirmed that it complies with the general limit values for either irrigation or discharge into a water resource that is not a listed water resource for volumes up to 2 ML of treated wastewater on any given day. Extraction followed by FT-IR spectroscopy was used to confirm albeit tentatively, the identity of the soluble but persistent COD in IAPS treated water as MaB-floc EPS. Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. A relationship between photosynthesis and EPS production was established by quantification of the EPS following exposure of MaB-flocs to either continuous light or darkness. Several novel strains of bacteria were isolated from HRAOP mixed liquor and 16S ribosomal genomic sequence analysis resulted in the molecular characterization of Planococcus maitriensis strain ECCN 45b. This is the first report of Planococcus maitriensis from a wastewater treatment process. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning and evening were monitored and revealed that MLSS is composed of microalgae and bacteria but not fungi. Concentration varied from 77 mg L-1 in September (winter) to 285 mg L-1 in November (spring); pond productivity increased from 5.8 g m-2 d-1 (winter) to 21.5 g m-2 d-1 (spring); and, irrespective of MLSS concentration in late afternoon, approximately 39% was lost overnight, which presumably occurred due to passive removal by the algae settling pond. The outcomes of this research are discussed in terms of the quality of treated water, and the further development of IAPS as a platform technology for establishing a biorefinery within the wastewater treatment sector.
- Full Text:
- Date Issued: 2018
Best simultaneous approximation in normed linear spaces
- Authors: Johnson, Solomon Nathan
- Date: 2018
- Subjects: Normed linear spaces , Approximation theory , Mathematical analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58985 , vital:27400
- Description: In this thesis we consider the problem of simultaneously approximating elements of a set B C X by a single element of a set K C X. This type of a problem arises when the element to be approximated is not known precisely but is known to belong to a set.Thus, best simultaneous approximation is a natural generalization of best approximation which has been studied extensively. The theory of best simultaneous approximation has been studied by many authors, see for example [4], [8], [25], [28], [26] and [12] to name but a few.
- Full Text:
- Date Issued: 2018
- Authors: Johnson, Solomon Nathan
- Date: 2018
- Subjects: Normed linear spaces , Approximation theory , Mathematical analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58985 , vital:27400
- Description: In this thesis we consider the problem of simultaneously approximating elements of a set B C X by a single element of a set K C X. This type of a problem arises when the element to be approximated is not known precisely but is known to belong to a set.Thus, best simultaneous approximation is a natural generalization of best approximation which has been studied extensively. The theory of best simultaneous approximation has been studied by many authors, see for example [4], [8], [25], [28], [26] and [12] to name but a few.
- Full Text:
- Date Issued: 2018
The development of rhenium(III) oxide nanoradiopharmaceuticals
- Authors: Joseph, Sinelizwi Veronica
- Date: 2018
- Subjects: Radiopharmaceuticals , Radiopharmaceuticals Rhenium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30507 , vital:30955
- Description: The study details the experimental work on the development of rhenium(III) oxide nanoradiopharmaceuticals for imaging and therapy of disease states. The nanoparticles (NPs) were capped with covalently linked tetraaminophthalocyanine-folate and ethylenediamine-folate to enhance their targeting ability. The capping agents were successfully synthesised and structurally characterised using Ultraviolet-Visible Spectroscopy (UV-Vis), Fourier Transform-Infrared Spectroscopy (FT-IR), Proton Nuclear Magnetic Resonance (1H-NMR), and Liquid Chromatography-Mass Spectroscopy (LC-MS). The nanoparticles were characterised using UV-Vis, spectrofluorimetry, Transmission Electron Microscopy (TEM), dynamic light scattering (DLS) and Zeta potential. Nanoparticles of sizes between 10 and 100 nm size were envisaged to be suitable for applications in biological systems. The preferred surface charge for the uptake of NPs must be between -30 and +30 mV, Re2O3 NPs capped with ethylenediamine were found to have a surface charge of -49 mV as compared with NPs capped with ethylenediamine-folate which gave -18.6 mV. The cytotoxicity studies of the nanoparticles were tested against four different cell lines: MDA-MB-468, MDA-MB-231, MCF-7, and MCF-10A. The cell survival rate after treatment was done with different capped rhenium(III) oxide nanoparticles obtained at a 10 μM concentration showed more than 80% cell viability. A comparison was conducted based on different nanoparticle sizes of capping agents across the four cell lines of varying folate receptor. All the cell lines were compared, and it was observed that MCF-7 had high percentage of cell viability especially with the cells treated with folate conjugated nanoparticles. Further investigation was done on the effects of folate conjugates and the effects of size. It was observed that the tetraaminophthalocyanine-folate favoured the MCF-7, for large-sized nanoparticles. However, further work is required to test the cancer cell internalisation of the nanoparticles using TEM as well as the correct size for endocytosis. Thereafter, the mice model study will be carried out for investigation of biodistribution of particles in tumour tissue using hot isotopes (186/188Re) and this will be done in a radiophamarceutical laboratory.
- Full Text:
- Date Issued: 2018
- Authors: Joseph, Sinelizwi Veronica
- Date: 2018
- Subjects: Radiopharmaceuticals , Radiopharmaceuticals Rhenium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30507 , vital:30955
- Description: The study details the experimental work on the development of rhenium(III) oxide nanoradiopharmaceuticals for imaging and therapy of disease states. The nanoparticles (NPs) were capped with covalently linked tetraaminophthalocyanine-folate and ethylenediamine-folate to enhance their targeting ability. The capping agents were successfully synthesised and structurally characterised using Ultraviolet-Visible Spectroscopy (UV-Vis), Fourier Transform-Infrared Spectroscopy (FT-IR), Proton Nuclear Magnetic Resonance (1H-NMR), and Liquid Chromatography-Mass Spectroscopy (LC-MS). The nanoparticles were characterised using UV-Vis, spectrofluorimetry, Transmission Electron Microscopy (TEM), dynamic light scattering (DLS) and Zeta potential. Nanoparticles of sizes between 10 and 100 nm size were envisaged to be suitable for applications in biological systems. The preferred surface charge for the uptake of NPs must be between -30 and +30 mV, Re2O3 NPs capped with ethylenediamine were found to have a surface charge of -49 mV as compared with NPs capped with ethylenediamine-folate which gave -18.6 mV. The cytotoxicity studies of the nanoparticles were tested against four different cell lines: MDA-MB-468, MDA-MB-231, MCF-7, and MCF-10A. The cell survival rate after treatment was done with different capped rhenium(III) oxide nanoparticles obtained at a 10 μM concentration showed more than 80% cell viability. A comparison was conducted based on different nanoparticle sizes of capping agents across the four cell lines of varying folate receptor. All the cell lines were compared, and it was observed that MCF-7 had high percentage of cell viability especially with the cells treated with folate conjugated nanoparticles. Further investigation was done on the effects of folate conjugates and the effects of size. It was observed that the tetraaminophthalocyanine-folate favoured the MCF-7, for large-sized nanoparticles. However, further work is required to test the cancer cell internalisation of the nanoparticles using TEM as well as the correct size for endocytosis. Thereafter, the mice model study will be carried out for investigation of biodistribution of particles in tumour tissue using hot isotopes (186/188Re) and this will be done in a radiophamarceutical laboratory.
- Full Text:
- Date Issued: 2018
Assessment of pheromone specificity in Thaumatotibia leucotreta (Meyrick) populations with focus on pest monitoring and the regional rollout of the sterile insect technique in citrus
- Authors: Joubert, Francois D
- Date: 2018
- Subjects: Cryptophlebia leucotreta , Pheromone traps , Citrus -- Diseases and pests -- South Africa , Cryptophlebia leucotreta -- Contol , Cryptophlebia leucotreta -- Biological control
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60665 , vital:27812
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. It is recognized by several markets as a phytosanitary organism and the efficient control of this pest is now more important than ever. The pheromone communication between the male and female moths has been exploited in order to control FCM through the sterile insect technique (SIT). The sterilized males used for all SIT programmes across South Africa come from a colony that originates from wild material collected from the Citrusdal area of the Western Cape Province. The aim of this study was to determine if any differences in attractiveness of females to males exist between different geographical populations of FCM and if so what impact this would have on the male’s ability to locate females from other populations via the volatile sex pheromone released by the female. Laboratory trials with Y-tube olfactometers and flight tunnels tested the attraction of male moths to virgin females, but did not yield any consistent results. Field experiments were conducted with sterile male Citrusdal moths released and recaptured in yellow delta traps in two separate trials. For one trial, the traps were baited with live virgin females from five different geographical populations including Addo, Nelspruit, Marble Hall, Citrusdal and the Old colony, which is a mixture of several populations. For the other trial traps were baited with various synthetic pheromone blends including three regional blends which included South Africa, Ivory Coast and Malawi and three commercial blends including Pherolure, Isomate and Checkmate. For the virgin female trial the Citrusdal males showed a significant preference for females from their own population. There was also a significant difference in the recaptures from the different synthetic pheromones. The South African blend was the most attractive of all the regional and commercial blends. A cross-mating trial was also conducted under laboratory conditions in petri dishes with five different FCM populations including Citrusdal, Addo, Marble Hall, Nelspruit and Old (mixed origin). Females produced more eggs when mated with males from the same population for the Addo, Marble Hall, Nelspruit and Old (mixed origin) populations. The only case in which this was statistically significant was for the Marble Hall population. All the crosses produced viable eggs and the origin of the male or female did not influence egg hatch. The results from this study may lead to improvements in both the control and monitoring of FCM populations. The control methods include mating disruption, attract-and-kill and SIT. Tailoring these methods for a specific growing area with a pheromone blend originating from the area or releasing sterile moths from a colony that originates from the area may optimize the available monitoring and control options.
- Full Text:
- Date Issued: 2018
- Authors: Joubert, Francois D
- Date: 2018
- Subjects: Cryptophlebia leucotreta , Pheromone traps , Citrus -- Diseases and pests -- South Africa , Cryptophlebia leucotreta -- Contol , Cryptophlebia leucotreta -- Biological control
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60665 , vital:27812
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. It is recognized by several markets as a phytosanitary organism and the efficient control of this pest is now more important than ever. The pheromone communication between the male and female moths has been exploited in order to control FCM through the sterile insect technique (SIT). The sterilized males used for all SIT programmes across South Africa come from a colony that originates from wild material collected from the Citrusdal area of the Western Cape Province. The aim of this study was to determine if any differences in attractiveness of females to males exist between different geographical populations of FCM and if so what impact this would have on the male’s ability to locate females from other populations via the volatile sex pheromone released by the female. Laboratory trials with Y-tube olfactometers and flight tunnels tested the attraction of male moths to virgin females, but did not yield any consistent results. Field experiments were conducted with sterile male Citrusdal moths released and recaptured in yellow delta traps in two separate trials. For one trial, the traps were baited with live virgin females from five different geographical populations including Addo, Nelspruit, Marble Hall, Citrusdal and the Old colony, which is a mixture of several populations. For the other trial traps were baited with various synthetic pheromone blends including three regional blends which included South Africa, Ivory Coast and Malawi and three commercial blends including Pherolure, Isomate and Checkmate. For the virgin female trial the Citrusdal males showed a significant preference for females from their own population. There was also a significant difference in the recaptures from the different synthetic pheromones. The South African blend was the most attractive of all the regional and commercial blends. A cross-mating trial was also conducted under laboratory conditions in petri dishes with five different FCM populations including Citrusdal, Addo, Marble Hall, Nelspruit and Old (mixed origin). Females produced more eggs when mated with males from the same population for the Addo, Marble Hall, Nelspruit and Old (mixed origin) populations. The only case in which this was statistically significant was for the Marble Hall population. All the crosses produced viable eggs and the origin of the male or female did not influence egg hatch. The results from this study may lead to improvements in both the control and monitoring of FCM populations. The control methods include mating disruption, attract-and-kill and SIT. Tailoring these methods for a specific growing area with a pheromone blend originating from the area or releasing sterile moths from a colony that originates from the area may optimize the available monitoring and control options.
- Full Text:
- Date Issued: 2018
Farmers' perceptions of insect pests in the Eastern Cape maize-based cropping systems and the effects of crop residue management on insect pest populations
- Authors: Kadango, Tendayi Lovemore
- Date: 2018
- Subjects: Cropping systems Crop residue management Corn -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6202 , vital:29507
- Description: Maize (Zea mays L.) is one of the most important crops in South Africa that is cultivated for food, feed and as a cash crop. Maize in the Eastern Cape is typically grown for consumption and the Province is one of the least producers owing to small landholdings, poor production conditions and pests. This study investigated: (i) the different maize cropping systems smallholder farmers practice in the Eastern Cape (EC), (ii) the major maize insect pests within the identified cropping systems, (iii) the perceptions of Eastern Cape smallholder maize farmers on the effects of insect pests, and (iv) the effects of crop residues on insect pests’ population dynamics. Four major cropping systems namely: maize sole cropping without rotations by government sponsored farmers (GCP) (94 percent), maize intercropping without rotations by independent farmers (IF) (79 percent), maize sole cropping without rotations by IF (67 percent) and maize intercropping without rotations by GCP (61 percent) were identified. The choice of a cropping system by the smallholder farmers was significantly influenced by source of sponsorship, the difference in their district localities, tenure system, availability of inputs and farming equipment, percentage of farmland farmers allocate to maize, maize varieties, farming experience, fallow operations and access to irrigation facilities. The major constraints faced by the farmers in maize production are the attack by insect pests, weeds competition, drought, the lack of fencing around the fields and destruction by mammals. The major insect pests identified were stalk borers (Busseola fusca, Chilo partellus), cutworms (Agrotis spp.), aphids (Rhopalosiphum maidis), bollworms (Helicoverpa armigera) and weevils (Sitophylus spp.). The most popular control measures employed were the use of GM maize and pesticides. Results from the field trial showed that field crickets were the major ground dwelling insect pests observed followed by bollworms and cutworms. However, there were no significant influence of residue retention on the insects’ diversity indices, richness, and evenness. Above ground insects sampling revealed the domination by four major insects namely, cutworms, maize stalk borer, bollworms, and spotted stalk borer. Residue management significantly influenced the infestation by spotted stalk borer only on maize plots. However, the general trend was that there was less infestation by the insects in plots where residues were retained than the ones with residue removed. Results from the study indicate that government sponsorship is significantly influencing the maize cropping systems of the smallholder farmers of the Eastern Cape.
- Full Text:
- Date Issued: 2018
- Authors: Kadango, Tendayi Lovemore
- Date: 2018
- Subjects: Cropping systems Crop residue management Corn -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6202 , vital:29507
- Description: Maize (Zea mays L.) is one of the most important crops in South Africa that is cultivated for food, feed and as a cash crop. Maize in the Eastern Cape is typically grown for consumption and the Province is one of the least producers owing to small landholdings, poor production conditions and pests. This study investigated: (i) the different maize cropping systems smallholder farmers practice in the Eastern Cape (EC), (ii) the major maize insect pests within the identified cropping systems, (iii) the perceptions of Eastern Cape smallholder maize farmers on the effects of insect pests, and (iv) the effects of crop residues on insect pests’ population dynamics. Four major cropping systems namely: maize sole cropping without rotations by government sponsored farmers (GCP) (94 percent), maize intercropping without rotations by independent farmers (IF) (79 percent), maize sole cropping without rotations by IF (67 percent) and maize intercropping without rotations by GCP (61 percent) were identified. The choice of a cropping system by the smallholder farmers was significantly influenced by source of sponsorship, the difference in their district localities, tenure system, availability of inputs and farming equipment, percentage of farmland farmers allocate to maize, maize varieties, farming experience, fallow operations and access to irrigation facilities. The major constraints faced by the farmers in maize production are the attack by insect pests, weeds competition, drought, the lack of fencing around the fields and destruction by mammals. The major insect pests identified were stalk borers (Busseola fusca, Chilo partellus), cutworms (Agrotis spp.), aphids (Rhopalosiphum maidis), bollworms (Helicoverpa armigera) and weevils (Sitophylus spp.). The most popular control measures employed were the use of GM maize and pesticides. Results from the field trial showed that field crickets were the major ground dwelling insect pests observed followed by bollworms and cutworms. However, there were no significant influence of residue retention on the insects’ diversity indices, richness, and evenness. Above ground insects sampling revealed the domination by four major insects namely, cutworms, maize stalk borer, bollworms, and spotted stalk borer. Residue management significantly influenced the infestation by spotted stalk borer only on maize plots. However, the general trend was that there was less infestation by the insects in plots where residues were retained than the ones with residue removed. Results from the study indicate that government sponsorship is significantly influencing the maize cropping systems of the smallholder farmers of the Eastern Cape.
- Full Text:
- Date Issued: 2018
Productivity and profitability of different maize varieties and cropping systems used in the smallholder sector of the Eastern Cape Province of South Africa : implication on food security
- Authors: Kambanje, Ardinesh
- Date: 2018
- Subjects: Crop yields Crops and climate Cropping systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6237 , vital:29528
- Description: Low maize yields in the midst of abundant arable land, favourable climatic conditions, input and financial support programs, plagues smallholder maize farming in Eastern Cape Province. These scenarios have led the province to be a net importer of maize. In essence, low production may signify a mis-match between maize varieties being promoted amongst smallholder farmers and their farming system. Thus, the main objective of the study was to investigate the productivity and profitability of different maize varieties and cropping system under smallholder agriculture in selected villages of the Eastern Cape Province of South Africa as well as, the implications posed on the household food security. The study sought to assess: (i) the productivity of different maize varieties and cropping systems, (ii) the effect of GM maize adoption on food security among smallholder farmers, (iii) the profitability of GM, conventional hybrids and OPV maize varieties produced by farmers under different agro-ecological conditions and (iv) the impact of different maize varieties and cropping systems on food security in the smallholder agriculture. A cross sectional quantitative-based survey study was carried out to obtain information from a total of 650 small holder farmers. The study was conducted in three local municipalities in Oliver Reginald (OR) Tambo District Municipality of the Eastern Cape Province of South Africa. Descriptive statistics, partial factor productivity, gross margin analysis, household food insecurity access score (HFIAS), ordinal logistic and linear regression were the analytical techniques used in establishing correlations among variables. Results obtained from the survey indicated that under mono-cropping system, Genetically Modified (GM) maize variety was highly productive with an average yield of 1.9 t/ha whilst, improved OPV maize variety was productive (with an average yield of 1.6 t/ha) under mixed cropping system. Furthermore, GM maize (GM = -R418.10), and landrace (GM = -R1 140.29) maize varieties had negative gross margins whilst, conventional hybrids (GM = R5 181.21) and improved OPV (GM = R1 457.41) were profitable. There was a significant and negative correlation between use of GM maize variety and reduction of household food insecurity. GM maize varieties, improved OPV, white maize, white as well as yellow GM maize varieties had a significant impact in reducing household food insecurity; whilst using more than one variety of maize (landraces and GMO) positively influenced household food insecurity. In light of these research findings, it is recommended that, there is need to address household food security by growing improved OPVs under a mixed cropping system and GM maize under monocropping system.
- Full Text:
- Date Issued: 2018
- Authors: Kambanje, Ardinesh
- Date: 2018
- Subjects: Crop yields Crops and climate Cropping systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6237 , vital:29528
- Description: Low maize yields in the midst of abundant arable land, favourable climatic conditions, input and financial support programs, plagues smallholder maize farming in Eastern Cape Province. These scenarios have led the province to be a net importer of maize. In essence, low production may signify a mis-match between maize varieties being promoted amongst smallholder farmers and their farming system. Thus, the main objective of the study was to investigate the productivity and profitability of different maize varieties and cropping system under smallholder agriculture in selected villages of the Eastern Cape Province of South Africa as well as, the implications posed on the household food security. The study sought to assess: (i) the productivity of different maize varieties and cropping systems, (ii) the effect of GM maize adoption on food security among smallholder farmers, (iii) the profitability of GM, conventional hybrids and OPV maize varieties produced by farmers under different agro-ecological conditions and (iv) the impact of different maize varieties and cropping systems on food security in the smallholder agriculture. A cross sectional quantitative-based survey study was carried out to obtain information from a total of 650 small holder farmers. The study was conducted in three local municipalities in Oliver Reginald (OR) Tambo District Municipality of the Eastern Cape Province of South Africa. Descriptive statistics, partial factor productivity, gross margin analysis, household food insecurity access score (HFIAS), ordinal logistic and linear regression were the analytical techniques used in establishing correlations among variables. Results obtained from the survey indicated that under mono-cropping system, Genetically Modified (GM) maize variety was highly productive with an average yield of 1.9 t/ha whilst, improved OPV maize variety was productive (with an average yield of 1.6 t/ha) under mixed cropping system. Furthermore, GM maize (GM = -R418.10), and landrace (GM = -R1 140.29) maize varieties had negative gross margins whilst, conventional hybrids (GM = R5 181.21) and improved OPV (GM = R1 457.41) were profitable. There was a significant and negative correlation between use of GM maize variety and reduction of household food insecurity. GM maize varieties, improved OPV, white maize, white as well as yellow GM maize varieties had a significant impact in reducing household food insecurity; whilst using more than one variety of maize (landraces and GMO) positively influenced household food insecurity. In light of these research findings, it is recommended that, there is need to address household food security by growing improved OPVs under a mixed cropping system and GM maize under monocropping system.
- Full Text:
- Date Issued: 2018