Phytoplankton associated with mesoscale eddies in the Mozambique Channel
- Authors: O'Reilly, Bevan James
- Date: 2012
- Subjects: Mozambique Channel. , Phytoplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10622 , http://hdl.handle.net/10948/d1010967 , Mozambique Channel. , Phytoplankton
- Description: The study undertaken was an attempt to provide information on the effect that oceanographic features common in the Mozambique Channel have on primary production. Oligotrophic conditions dominated the Mozambique Channel at the time of sampling and the introduction of nutrients into the euphotic zone by upwelling processes were identified as cyclonic eddies. Differences in physico-chemical variables between surface and F-max across all sites proved to be stronger than the physico-chemical variables between 4 grouped oceanographic features. This was revealed by stronger variations in phytoplankton community structure and chlorophyll a concentration between surface and F-max compared to oceanographic features sampled. One of the hypotheses presented for the study was that diatoms would dominate phytoplankton communities within a cyclonic eddy. This was not the case as the coccolithophorid, Emiliania huxleyi Lohmann (Hay and Mohler 1967) dominated F-max and surface water in the cyclonic eddies and most other sites. Phytoplankton community structure did not differ significantly between the oceanographic features sampled which contradicted another one of hypotheses presented in the study. Chlorophyll a concentration in surface water of the cyclonic eddies was significantly higher than in surface waters within the anti-cyclonic eddy. F-max was not significantly different in phytoplankton biomass between these two system types. The cyclonic eddies and anti-cyclone had similar phytoplankton diversity which did not verify the hypothesis that there would be less phytoplankton species diversity within cyclonic eddies compared to the anti-cyclonic eddy. Phytoplankton community structure differed between F-max (depth at which maximum chlorophyll a is found) and the surface. This phytoplankton community difference was linked to differences in physico-chemical variables between the two depths. The diatoms Thalassionema nitzschioides, Pseudo-nitzschia sp.A, Pseudo-nitzschia sp.B, Thalassiosira sp.C, Thalassiosira sp.E, Bacteriastrum furcatum, Guinardia cylindrus, Nitzschia closterium, Hemiaulus hauckii, and Nitzschia braarudii revealed the only discernible ecological similarity amongst phytoplankton species across all sites and depths. This is important as it revealed that these species were regularly found occupying similar depths and potentially similar physico-chemical ranges in the water column which suggest these diatom species responded to a dominant source of variation. Distribution patterns of species and of ecologically defined groups support the hypothesis that diatom species and assemblages are good indicators of the changing character of an upwelling system. These statements lead to the assumption that the diatom grouping found in this study indicates areas of upwelling where water temperatures are reduced and nutrients are more readily available. One must keep in mind that ordination techniques are only descriptive and no significance is tested. The coccolithophorid D. anthos and the dinoflagellate Phalacroma spp. were noted as being most dissimilar to all other phytoplankton species with regards to their position in the water column and their response to physico-chemical variables. Finally, the dominance of E. huxleyi in the Mozambique Channel during November/December of 2009 reveals the potential vulnerability of phytoplankton in the channel to ocean acidification.
- Full Text:
- Date Issued: 2012
- Authors: O'Reilly, Bevan James
- Date: 2012
- Subjects: Mozambique Channel. , Phytoplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10622 , http://hdl.handle.net/10948/d1010967 , Mozambique Channel. , Phytoplankton
- Description: The study undertaken was an attempt to provide information on the effect that oceanographic features common in the Mozambique Channel have on primary production. Oligotrophic conditions dominated the Mozambique Channel at the time of sampling and the introduction of nutrients into the euphotic zone by upwelling processes were identified as cyclonic eddies. Differences in physico-chemical variables between surface and F-max across all sites proved to be stronger than the physico-chemical variables between 4 grouped oceanographic features. This was revealed by stronger variations in phytoplankton community structure and chlorophyll a concentration between surface and F-max compared to oceanographic features sampled. One of the hypotheses presented for the study was that diatoms would dominate phytoplankton communities within a cyclonic eddy. This was not the case as the coccolithophorid, Emiliania huxleyi Lohmann (Hay and Mohler 1967) dominated F-max and surface water in the cyclonic eddies and most other sites. Phytoplankton community structure did not differ significantly between the oceanographic features sampled which contradicted another one of hypotheses presented in the study. Chlorophyll a concentration in surface water of the cyclonic eddies was significantly higher than in surface waters within the anti-cyclonic eddy. F-max was not significantly different in phytoplankton biomass between these two system types. The cyclonic eddies and anti-cyclone had similar phytoplankton diversity which did not verify the hypothesis that there would be less phytoplankton species diversity within cyclonic eddies compared to the anti-cyclonic eddy. Phytoplankton community structure differed between F-max (depth at which maximum chlorophyll a is found) and the surface. This phytoplankton community difference was linked to differences in physico-chemical variables between the two depths. The diatoms Thalassionema nitzschioides, Pseudo-nitzschia sp.A, Pseudo-nitzschia sp.B, Thalassiosira sp.C, Thalassiosira sp.E, Bacteriastrum furcatum, Guinardia cylindrus, Nitzschia closterium, Hemiaulus hauckii, and Nitzschia braarudii revealed the only discernible ecological similarity amongst phytoplankton species across all sites and depths. This is important as it revealed that these species were regularly found occupying similar depths and potentially similar physico-chemical ranges in the water column which suggest these diatom species responded to a dominant source of variation. Distribution patterns of species and of ecologically defined groups support the hypothesis that diatom species and assemblages are good indicators of the changing character of an upwelling system. These statements lead to the assumption that the diatom grouping found in this study indicates areas of upwelling where water temperatures are reduced and nutrients are more readily available. One must keep in mind that ordination techniques are only descriptive and no significance is tested. The coccolithophorid D. anthos and the dinoflagellate Phalacroma spp. were noted as being most dissimilar to all other phytoplankton species with regards to their position in the water column and their response to physico-chemical variables. Finally, the dominance of E. huxleyi in the Mozambique Channel during November/December of 2009 reveals the potential vulnerability of phytoplankton in the channel to ocean acidification.
- Full Text:
- Date Issued: 2012
Retrospective analysis of birth HIV PCR testing and follow-up of positive HIV PCR results in Nelson Mandela Bay Health District
- Authors: Makubalo, Nomlindo Princess
- Date: 2020
- Subjects: HIV infections -- South Africa -- Nelson Mandela Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46351 , vital:39580
- Description: BACKGROUND HIV infection contributes significantly to infant morbidity and mortality, especially in high-prevalence, low-income countries. In view of this evidence-based knowledge, South Africa’s National Department of Health, in April 2015, released the National Consolidated Guidelines of Human Immunodeficiency Virus (HIV) stipulating that all HIV-exposed babies should have a HIV Polymer Chain Reaction (PCR) test performed at birth. Early infant diagnosis (EID) means early initiation of combined antiretroviral treatment (cART) and a reduction in the incidence of early infant HIV-related mortality. However, these guidelines can only be successful if implemented properly across all public sector healthcare institutions. Thus,the research question was,“How well has the Nelson Mandela Bay Health District implemented the EID?”AIM The aim of the study was to review the impact of the consolidated HIV guidelines on birth HIV-PCR testing and initiation of treatment in the Nelson Mandela Bay Health District. METHOD A retrospective quantitative longitudinal non-experimental design was used.The study consisted of two components,namely,analysis of NHLS databases, particularly HIV birth PCR results of infants over a three-year period (June 2015 to June 2018),and analysis of feedback received from the primary health care clinics. The feedback focused on infants with a positive-birth PCR test, using a purpose-designed data collection tool that was used by the clinics for the duration of the same three-year period. The paper-based tool documented antenatal care attendance, enrolment into the prevention of mother-to-child transmission (PMTCT) programme and initiation of ART. RESULTS Over the three-year period, there were approximately 13,096 live births to HIV-positive women in the study area, and a total of 11,066 HIV birth PCR tests were done over xiiithe three-year study period (84.5% of HIV-exposed infants). The birth HIV PCR was negative in 10,909 (98.6%) neonates, while 130 (1.2%) of neonates had positive-birth HIV PCR tests,and a further 27 (0.2%) had indeterminate results. The birth HIV PCR positivity rate reduced from 1.4%(2015)to 1%(2018)over the three-year study period. Of the 130 infants with positive-birth HIV PCR, the files of 42 children were excluded, and further analysis conducted on the files of 88 infants. cART was initiated within seven days in only nine of the 88 infants (10.2%). ARV initiation was delayed for 58 infants (65.9%) and 21 neonates (23.9%) were never initiated on cART. Among the 88 mothers of infants, more than one-third (38.6%) of pregnant women did not attend antenatal care, thus,compromising their opportunity to be enrolled on the PMTCT programme. Of those who attended antenatal care, only 39.1% were reported to attend antenatal care before 20 weeks CONCLUSION AND RECOMMENDATIONS The incidence of positive-birth HIV PCR has reduced from 1.4% in 2015 to 1% in 2018 whilst there has been an increase in birth HIV PCR testing. However, initiation of cART within seven days was achieved in only 10.2% of infants with positive-birth HIV PCR test results. Implementation of point-of-care birth HIV PCR testing would ensure that results are immediately available resulting in increasing the proportion of infants initiated on cART within seven days.
- Full Text:
- Date Issued: 2020
- Authors: Makubalo, Nomlindo Princess
- Date: 2020
- Subjects: HIV infections -- South Africa -- Nelson Mandela Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46351 , vital:39580
- Description: BACKGROUND HIV infection contributes significantly to infant morbidity and mortality, especially in high-prevalence, low-income countries. In view of this evidence-based knowledge, South Africa’s National Department of Health, in April 2015, released the National Consolidated Guidelines of Human Immunodeficiency Virus (HIV) stipulating that all HIV-exposed babies should have a HIV Polymer Chain Reaction (PCR) test performed at birth. Early infant diagnosis (EID) means early initiation of combined antiretroviral treatment (cART) and a reduction in the incidence of early infant HIV-related mortality. However, these guidelines can only be successful if implemented properly across all public sector healthcare institutions. Thus,the research question was,“How well has the Nelson Mandela Bay Health District implemented the EID?”AIM The aim of the study was to review the impact of the consolidated HIV guidelines on birth HIV-PCR testing and initiation of treatment in the Nelson Mandela Bay Health District. METHOD A retrospective quantitative longitudinal non-experimental design was used.The study consisted of two components,namely,analysis of NHLS databases, particularly HIV birth PCR results of infants over a three-year period (June 2015 to June 2018),and analysis of feedback received from the primary health care clinics. The feedback focused on infants with a positive-birth PCR test, using a purpose-designed data collection tool that was used by the clinics for the duration of the same three-year period. The paper-based tool documented antenatal care attendance, enrolment into the prevention of mother-to-child transmission (PMTCT) programme and initiation of ART. RESULTS Over the three-year period, there were approximately 13,096 live births to HIV-positive women in the study area, and a total of 11,066 HIV birth PCR tests were done over xiiithe three-year study period (84.5% of HIV-exposed infants). The birth HIV PCR was negative in 10,909 (98.6%) neonates, while 130 (1.2%) of neonates had positive-birth HIV PCR tests,and a further 27 (0.2%) had indeterminate results. The birth HIV PCR positivity rate reduced from 1.4%(2015)to 1%(2018)over the three-year study period. Of the 130 infants with positive-birth HIV PCR, the files of 42 children were excluded, and further analysis conducted on the files of 88 infants. cART was initiated within seven days in only nine of the 88 infants (10.2%). ARV initiation was delayed for 58 infants (65.9%) and 21 neonates (23.9%) were never initiated on cART. Among the 88 mothers of infants, more than one-third (38.6%) of pregnant women did not attend antenatal care, thus,compromising their opportunity to be enrolled on the PMTCT programme. Of those who attended antenatal care, only 39.1% were reported to attend antenatal care before 20 weeks CONCLUSION AND RECOMMENDATIONS The incidence of positive-birth HIV PCR has reduced from 1.4% in 2015 to 1% in 2018 whilst there has been an increase in birth HIV PCR testing. However, initiation of cART within seven days was achieved in only 10.2% of infants with positive-birth HIV PCR test results. Implementation of point-of-care birth HIV PCR testing would ensure that results are immediately available resulting in increasing the proportion of infants initiated on cART within seven days.
- Full Text:
- Date Issued: 2020
Synthesis of fluorescent polymers with coumarin backbones by "click" polymerization
- Authors: Okerio, Jaspher Mosomi
- Date: 2013
- Subjects: Polymerization , Fluorescent polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10431 , http://hdl.handle.net/10948/d1020132
- Description: Click chemistry is one of the growing areas of research which is applied in the design and synthesis of a wide range of polymeric architectures. This investigation focuses on the synthesis of fluorescent coumarin based polymers by “click” A-B step growth polymerization process and evaluation of their photophysical properties. Non-fluorescent azide-alkyne functionalized coumarin-based monomers were synthesized in multiple steps from 2,4-dihydroxybenzaldehyde in reasonable yields. Polymers with coumarin backbone were synthesized from azide-alkyne functionalized coumarin monomers via the Cu(I) catalyzed 1,3-dipolar cycloaddition reaction between azides and alkynes, a typical click reaction, to form polymers whose repeating units are connected by a 1,2,3-triazole ring. The structures of the synthesized polymers were confirmed by NMR and FT-IR spectroscopy. Finally, the photophysical properties of the synthesized monomers and polymers were evaluated in DMF. All coumarin based monomers showed reduced fluorescent properties due to the quenching effect from the azido group. Although all polymers absorbed at maximum wavelength of 340 nm, a characteristic for coumarin chromophore, the homo-polymers emitted at a shorter wavelength of 413 nm as compared to the co-polymers which emitted at 421 nm.
- Full Text:
- Date Issued: 2013
- Authors: Okerio, Jaspher Mosomi
- Date: 2013
- Subjects: Polymerization , Fluorescent polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10431 , http://hdl.handle.net/10948/d1020132
- Description: Click chemistry is one of the growing areas of research which is applied in the design and synthesis of a wide range of polymeric architectures. This investigation focuses on the synthesis of fluorescent coumarin based polymers by “click” A-B step growth polymerization process and evaluation of their photophysical properties. Non-fluorescent azide-alkyne functionalized coumarin-based monomers were synthesized in multiple steps from 2,4-dihydroxybenzaldehyde in reasonable yields. Polymers with coumarin backbone were synthesized from azide-alkyne functionalized coumarin monomers via the Cu(I) catalyzed 1,3-dipolar cycloaddition reaction between azides and alkynes, a typical click reaction, to form polymers whose repeating units are connected by a 1,2,3-triazole ring. The structures of the synthesized polymers were confirmed by NMR and FT-IR spectroscopy. Finally, the photophysical properties of the synthesized monomers and polymers were evaluated in DMF. All coumarin based monomers showed reduced fluorescent properties due to the quenching effect from the azido group. Although all polymers absorbed at maximum wavelength of 340 nm, a characteristic for coumarin chromophore, the homo-polymers emitted at a shorter wavelength of 413 nm as compared to the co-polymers which emitted at 421 nm.
- Full Text:
- Date Issued: 2013
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