Aspect and slope as determinants of vegetation composition and soil properties in coastal forest backdunes of Eastern Cape, South Africa
- Ruwanza, Sheunesu, Shackleton, Charlie M
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180376 , vital:43358 , xlink:href="https://doi.org/10.1111/aje.12343"
- Description: Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass-dominated community on the middle slope and a tree- and shrub- dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.
- Full Text:
- Date Issued: 2017
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180376 , vital:43358 , xlink:href="https://doi.org/10.1111/aje.12343"
- Description: Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass-dominated community on the middle slope and a tree- and shrub- dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.
- Full Text:
- Date Issued: 2017
Assessing the potential role of microorganisms in the production of seedlings for the restoration of Albany Thicket
- Authors: Mpama, Nelisa
- Date: 2017
- Subjects: Vesicular-arbuscular mycorrhizas , Rhizobacteria , Restoration ecology South Africa Albany , Microorganisms
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/64555 , vital:28558
- Description: The role of microorganisms in restoration of the Albany Thicket has not been well documented, although the benefits to plants of these various interactions has been well documented. Microorganisms are chief ecological engineers and assist in resolving environmental problems and act to restore degraded ecosystem function by forming mutual relationships with the roots of the plants. The aim of this study was to assess the potential of microorganisms for the improved biomass production of selected woody and succulent seedlings used in mesic thicket restoration. Three tree species were selected for propagation in this study namely; Mystroxylon aethiopicum Scutia myrtina and Aloe ferox. Soil samples were collected from a degraded and intact thicket site from Bathurst, South Africa. Soils were evaluated for number of arbuscular mycorrhizal (AM) spores, mycorrhizal infectivity potential and nutrient availability both before and after seedling propagation. Pasteurized soil from the degraded site was used in a pot trial. Ten replicates seedling for plant species were planted and subjected to four treatments which included inoculation with AM fungi and the rhizobacterium, Enterobacter sp., alone and in combination; the fourth treatment was an un-inouclated control. Plant growth parameters were recorded at regular intervals where appropriate and seedlings were harvested after 24 weeks for biomass measurements and AM colonisation assessments. Although generally low (< 1 spore per gram) the density of AM fungal spores was significantly higher in soils from the intact site when compared with soils from the degraded site. The mycorrhizal potential of the soils was however not significantly different. Mystroxylon aethiopicum seedling shoot height, canopy diameter and shoot biomass showed a significant increase when inoculated with AM fungi while S. myrtina seedlings showed increased shoot height when inoculated with both AM fungi and Enterobacter sp. Aloe ferox seedlings did not respond to microbial inoculation. The concentration of soil P and Na increased in treatments with Enterobacter sp. alone and in combination with AM fungi. Mystroxylon aethiopicum and S. myrtina seedlings showed a dependency on microbial inoculants indicating the importance of inoculation in the nursery before planting out into the field. Overall AM fungal inoculants applied to seedlings can be used to compensate for nutrient deficiency in soils. Although the Enterobacter isolate used was known to have various plant growth promoting capabilities. It is recommended that other rhizobacterial isolates be investigated. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2017
- Full Text:
- Date Issued: 2017
- Authors: Mpama, Nelisa
- Date: 2017
- Subjects: Vesicular-arbuscular mycorrhizas , Rhizobacteria , Restoration ecology South Africa Albany , Microorganisms
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/64555 , vital:28558
- Description: The role of microorganisms in restoration of the Albany Thicket has not been well documented, although the benefits to plants of these various interactions has been well documented. Microorganisms are chief ecological engineers and assist in resolving environmental problems and act to restore degraded ecosystem function by forming mutual relationships with the roots of the plants. The aim of this study was to assess the potential of microorganisms for the improved biomass production of selected woody and succulent seedlings used in mesic thicket restoration. Three tree species were selected for propagation in this study namely; Mystroxylon aethiopicum Scutia myrtina and Aloe ferox. Soil samples were collected from a degraded and intact thicket site from Bathurst, South Africa. Soils were evaluated for number of arbuscular mycorrhizal (AM) spores, mycorrhizal infectivity potential and nutrient availability both before and after seedling propagation. Pasteurized soil from the degraded site was used in a pot trial. Ten replicates seedling for plant species were planted and subjected to four treatments which included inoculation with AM fungi and the rhizobacterium, Enterobacter sp., alone and in combination; the fourth treatment was an un-inouclated control. Plant growth parameters were recorded at regular intervals where appropriate and seedlings were harvested after 24 weeks for biomass measurements and AM colonisation assessments. Although generally low (< 1 spore per gram) the density of AM fungal spores was significantly higher in soils from the intact site when compared with soils from the degraded site. The mycorrhizal potential of the soils was however not significantly different. Mystroxylon aethiopicum seedling shoot height, canopy diameter and shoot biomass showed a significant increase when inoculated with AM fungi while S. myrtina seedlings showed increased shoot height when inoculated with both AM fungi and Enterobacter sp. Aloe ferox seedlings did not respond to microbial inoculation. The concentration of soil P and Na increased in treatments with Enterobacter sp. alone and in combination with AM fungi. Mystroxylon aethiopicum and S. myrtina seedlings showed a dependency on microbial inoculants indicating the importance of inoculation in the nursery before planting out into the field. Overall AM fungal inoculants applied to seedlings can be used to compensate for nutrient deficiency in soils. Although the Enterobacter isolate used was known to have various plant growth promoting capabilities. It is recommended that other rhizobacterial isolates be investigated. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2017
- Full Text:
- Date Issued: 2017
Aza boron-pyridyl-isoindoline analogues
- Zhang, Hui, Wu, Yanping, Fan, Minhui, Xiao, Xuqiong, Mack, John, Kubheka, Gugu, Nyokong, Tebello, Lu, Hua
- Authors: Zhang, Hui , Wu, Yanping , Fan, Minhui , Xiao, Xuqiong , Mack, John , Kubheka, Gugu , Nyokong, Tebello , Lu, Hua
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232912 , vital:50037 , xlink:href="https://doi.org/10.1039/C7NJ00707H"
- Description: Several aza boron-pyridyl-isoindoline analogues are synthesized through a facile and scale-up two step reaction using 1,2-naphthalenedicarbonitrile as a starting material. These analogues show broad envelopes of intense vibrational bands in the absorption spectra with moderate fluorescence quantum yields in solution and the solid-state. An analysis of the structure–property relationships is described based on X-ray crystallography, optical spectroscopy, and theoretical calculations.
- Full Text:
- Date Issued: 2017
- Authors: Zhang, Hui , Wu, Yanping , Fan, Minhui , Xiao, Xuqiong , Mack, John , Kubheka, Gugu , Nyokong, Tebello , Lu, Hua
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232912 , vital:50037 , xlink:href="https://doi.org/10.1039/C7NJ00707H"
- Description: Several aza boron-pyridyl-isoindoline analogues are synthesized through a facile and scale-up two step reaction using 1,2-naphthalenedicarbonitrile as a starting material. These analogues show broad envelopes of intense vibrational bands in the absorption spectra with moderate fluorescence quantum yields in solution and the solid-state. An analysis of the structure–property relationships is described based on X-ray crystallography, optical spectroscopy, and theoretical calculations.
- Full Text:
- Date Issued: 2017
Azide-derivatized gold nanosphere “clicked” to indium and zinc phthalocyanines for improved nonlinear optical limiting
- Bankole, Owolabi M, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188249 , vital:44738 , xlink:href="https://doi.org/10.1016/j.molstruc.2017.01.088"
- Description: We report on the conjugation of azide-derivatized gold nanoparticles (AuNPs) to alkyne moieties of ZnPc and InPc via azide-alkyne Huisgen cycloaddition reaction to form phthalocyanines-AuNPs (MPc-AuNPs) conjugates. The detailed structural characterizations of the composites were in good agreement with the expected results. The nonlinear absorption coefficients and other nonlinear optical limiting parameters were almost two times larger for the conjugates compared to free phthalocyanines. We established direct relationship between improved photophysical characterizations and enhanced nonlinear effects of reverse saturable absorption mechanisms favoured by excited triplet absorption of the phthalocyanines in the presence of AuNPs. The combination of InPc with AuNPs resulted in the lowest limiting intensity value of 0.06 J/cm2, hence the best performance in terms of optical limiting.
- Full Text:
- Date Issued: 2017
- Authors: Bankole, Owolabi M , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188249 , vital:44738 , xlink:href="https://doi.org/10.1016/j.molstruc.2017.01.088"
- Description: We report on the conjugation of azide-derivatized gold nanoparticles (AuNPs) to alkyne moieties of ZnPc and InPc via azide-alkyne Huisgen cycloaddition reaction to form phthalocyanines-AuNPs (MPc-AuNPs) conjugates. The detailed structural characterizations of the composites were in good agreement with the expected results. The nonlinear absorption coefficients and other nonlinear optical limiting parameters were almost two times larger for the conjugates compared to free phthalocyanines. We established direct relationship between improved photophysical characterizations and enhanced nonlinear effects of reverse saturable absorption mechanisms favoured by excited triplet absorption of the phthalocyanines in the presence of AuNPs. The combination of InPc with AuNPs resulted in the lowest limiting intensity value of 0.06 J/cm2, hence the best performance in terms of optical limiting.
- Full Text:
- Date Issued: 2017
Beyond benefit sharing: Place attachment and the importance of access to protected areas for surrounding communities
- Cundill, Georgina, Bezerra, Joana C, de Vos, Alta, Ntingana, Nokuthula
- Authors: Cundill, Georgina , Bezerra, Joana C , de Vos, Alta , Ntingana, Nokuthula
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416265 , vital:71334 , xlink:href="https://doi.org/10.1016/j.ecoser.2017.03.011"
- Description: The concept of place attachment can assist to integrate relational values into ecosystem service research, and assist us to rethink the notion of benefits in contemporary protected area thinking. We present a case study from South Africa, where the concept of two-dimensional place attachment was used to understand the relationship between a protected area and a land claimant community that now owns part of this protected area but does not have physical access to the land. A place attachment lens helps refocus access to protected areas as cornerstone to long term sustainability of such areas. Such access must be considered in the context of spatially and economically differentiated users, including a focus on trade-offs between such users. Our findings highlight that when communities previously displaced from protected areas respond to offers of ‘benefit sharing’ with demands for access and recognition as land owners, they are asking for a recognition of relational values, and identity, based on close interaction with nature. A place attachment and relational values perspective raises questions about the extent to which traditional conservation practice can accommodate such values, and therefore meet local people’s expectations and remain viable in the long term.
- Full Text:
- Date Issued: 2017
- Authors: Cundill, Georgina , Bezerra, Joana C , de Vos, Alta , Ntingana, Nokuthula
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416265 , vital:71334 , xlink:href="https://doi.org/10.1016/j.ecoser.2017.03.011"
- Description: The concept of place attachment can assist to integrate relational values into ecosystem service research, and assist us to rethink the notion of benefits in contemporary protected area thinking. We present a case study from South Africa, where the concept of two-dimensional place attachment was used to understand the relationship between a protected area and a land claimant community that now owns part of this protected area but does not have physical access to the land. A place attachment lens helps refocus access to protected areas as cornerstone to long term sustainability of such areas. Such access must be considered in the context of spatially and economically differentiated users, including a focus on trade-offs between such users. Our findings highlight that when communities previously displaced from protected areas respond to offers of ‘benefit sharing’ with demands for access and recognition as land owners, they are asking for a recognition of relational values, and identity, based on close interaction with nature. A place attachment and relational values perspective raises questions about the extent to which traditional conservation practice can accommodate such values, and therefore meet local people’s expectations and remain viable in the long term.
- Full Text:
- Date Issued: 2017
Biogeographical comparison of the emergent macrophyte, Sagittaria platyphylla in its native and introduced ranges
- Kwong, Raelene M, Sagliocco, Jean L, Harms, Nathan E, Butler, Kym L, Green, Peter T, Martin, Grant D
- Authors: Kwong, Raelene M , Sagliocco, Jean L , Harms, Nathan E , Butler, Kym L , Green, Peter T , Martin, Grant D
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419287 , vital:71631 , xlink:href="https://doi.org/10.1016/j.aquabot.2017.05.001"
- Description: Understanding why some plant species become invasive is important to predict and prevent future weed threats and identify appropriate management strategies. Many hypotheses have been proposed to explain why plants become invasive, yet few studies have quantitatively compared plant and population parameters between native and introduced range populations to gain an objective perspective on the causes of plant invasion. The present study uses a biogeographical field survey to compare morphological and reproductive traits and abundance between the native range (USA) and two introduced ranges (Australia and South Africa) of Sagittaria platyphylla (Engelm.) J.G. Sm (Alismataceae), a highly invasive freshwater macrophyte. Introduced and native populations differed in sexual reproductive output with the number of achenes per fruiting head and individual achene weight found to be 40% and 50% greater in introduced populations respectively. However, no other morphological traits were found to be consistently different between the native and both introduced ranges, especially after taking into account differences in environmental conditions between the three ranges. Although populations in introduced regions were larger and occupied greater percentage cover, no differences in plant density were evident. Our results suggest that, apart from sexual reproduction, many of the trait patterns observed in S. platyphylla are influenced by environmental and habitat conditions within the native and invaded ranges. We conclude that the enemy release hypothesis best explains the results observed for sexual reproduction. In particular, we hypothesise that a release from natural enemies, specifically a pre-dispersal seed predator, may induce reproductive plasticity in S. platyphylla.
- Full Text:
- Date Issued: 2017
- Authors: Kwong, Raelene M , Sagliocco, Jean L , Harms, Nathan E , Butler, Kym L , Green, Peter T , Martin, Grant D
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419287 , vital:71631 , xlink:href="https://doi.org/10.1016/j.aquabot.2017.05.001"
- Description: Understanding why some plant species become invasive is important to predict and prevent future weed threats and identify appropriate management strategies. Many hypotheses have been proposed to explain why plants become invasive, yet few studies have quantitatively compared plant and population parameters between native and introduced range populations to gain an objective perspective on the causes of plant invasion. The present study uses a biogeographical field survey to compare morphological and reproductive traits and abundance between the native range (USA) and two introduced ranges (Australia and South Africa) of Sagittaria platyphylla (Engelm.) J.G. Sm (Alismataceae), a highly invasive freshwater macrophyte. Introduced and native populations differed in sexual reproductive output with the number of achenes per fruiting head and individual achene weight found to be 40% and 50% greater in introduced populations respectively. However, no other morphological traits were found to be consistently different between the native and both introduced ranges, especially after taking into account differences in environmental conditions between the three ranges. Although populations in introduced regions were larger and occupied greater percentage cover, no differences in plant density were evident. Our results suggest that, apart from sexual reproduction, many of the trait patterns observed in S. platyphylla are influenced by environmental and habitat conditions within the native and invaded ranges. We conclude that the enemy release hypothesis best explains the results observed for sexual reproduction. In particular, we hypothesise that a release from natural enemies, specifically a pre-dispersal seed predator, may induce reproductive plasticity in S. platyphylla.
- Full Text:
- Date Issued: 2017
Biosynthesis of silver nanoparticles from Acacia mearnsii De Wild stem bark and its antinociceptive properties
- Avoseh, Opeyemi N, Oyedeji, Opeoluwa O, Aremu, Olukayode, Nkeh-Chungag, Benedicta N, Songca, Sandile P, Oyedeji, Adebola Omowunmi, Mohan, Sneha, Oluwafemi, Oluwatobi S
- Authors: Avoseh, Opeyemi N , Oyedeji, Opeoluwa O , Aremu, Olukayode , Nkeh-Chungag, Benedicta N , Songca, Sandile P , Oyedeji, Adebola Omowunmi , Mohan, Sneha , Oluwafemi, Oluwatobi S
- Date: 2017
- Subjects: Metal nanoparticles , Acacia mearnsii , Nociceptive pain
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/1528 , vital:37774 , https://doi.org/10.1080/17518253.2017.1287310
- Description: The biosynthesis of silver nanoparticles (Ag-NPs) using the hydrosol extract of the dry stem bark of Acacia mearnsii as reducing and capping agents, and their antinociceptive properties are hereby reported. By varying the temperature and reaction time, the temporal evolution of the optical and morphological properties of the as-synthesized material was investigated. The NPs were characterized by UV–visible absorption spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffractometry (XRD) The optical analyses show that the position of the maximum surface plasmon resonance (SPR) peak is red-shifted as the reaction temperature decreased. The TEM micrographs show that the as-synthesized Ag-NPs are spherical while the X-ray diffraction shows that the material is highly crystalline with face-centered cubic structures. The anti-inflammatory efficacy, analyzed by the formalin model, indicates that the as-synthesized Ag-NPs are very effective, with an inhibition rate of about 76%.
- Full Text:
- Date Issued: 2017
- Authors: Avoseh, Opeyemi N , Oyedeji, Opeoluwa O , Aremu, Olukayode , Nkeh-Chungag, Benedicta N , Songca, Sandile P , Oyedeji, Adebola Omowunmi , Mohan, Sneha , Oluwafemi, Oluwatobi S
- Date: 2017
- Subjects: Metal nanoparticles , Acacia mearnsii , Nociceptive pain
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/1528 , vital:37774 , https://doi.org/10.1080/17518253.2017.1287310
- Description: The biosynthesis of silver nanoparticles (Ag-NPs) using the hydrosol extract of the dry stem bark of Acacia mearnsii as reducing and capping agents, and their antinociceptive properties are hereby reported. By varying the temperature and reaction time, the temporal evolution of the optical and morphological properties of the as-synthesized material was investigated. The NPs were characterized by UV–visible absorption spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffractometry (XRD) The optical analyses show that the position of the maximum surface plasmon resonance (SPR) peak is red-shifted as the reaction temperature decreased. The TEM micrographs show that the as-synthesized Ag-NPs are spherical while the X-ray diffraction shows that the material is highly crystalline with face-centered cubic structures. The anti-inflammatory efficacy, analyzed by the formalin model, indicates that the as-synthesized Ag-NPs are very effective, with an inhibition rate of about 76%.
- Full Text:
- Date Issued: 2017
Book Review: Democratic South Africa's foreign policy
- Authors: Magadla, Siphokazi
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/298617 , vital:57721 , xlink:href="https://doi.org/10.1080/10220461.2017.1361863"
- Description: Suzanne Graham's book reviews South Africa's voting behaviour in the United Nations (UN) over a 20-year period (1994–2014), focusing specifically on four themes that featured predominantly in both the policy and rhetoric of South African policymakers during this period: the promotion of human rights and democracy; disarmament and related non-proliferation issues; advancing African interests; and voting on reform of the UN.
- Full Text:
- Date Issued: 2017
- Authors: Magadla, Siphokazi
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/298617 , vital:57721 , xlink:href="https://doi.org/10.1080/10220461.2017.1361863"
- Description: Suzanne Graham's book reviews South Africa's voting behaviour in the United Nations (UN) over a 20-year period (1994–2014), focusing specifically on four themes that featured predominantly in both the policy and rhetoric of South African policymakers during this period: the promotion of human rights and democracy; disarmament and related non-proliferation issues; advancing African interests; and voting on reform of the UN.
- Full Text:
- Date Issued: 2017
Calcium supplementation commencing before or early in pregnancy, or food fortification with calcium, for preventing hypertensive disorders of pregnancy
- Date: 2017
- Subjects: South Africa Pregnancy Journal article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/6187 , vital:45261 , xlink:href="https://DOI:10.1002/14651858.CD011192.pub2"
- Description: Background Pre-eclampsia is considerably more prevalent in low- than high-income countries. One possible explanation for this discrepancy is dietary diKerences, particularly calcium deficiency. Calcium supplementation in the second half of pregnancy reduces the serious consequences of pre-eclampsia and is recommended by the WorldHealthOrganization (WHO) for women with low dietary calcium intake, but has limited eKect on the overallrisk of pre-eclampsia. It is important to establish whether calcium supplementation before and in early pregnancy has added benefit. Such evidence would be justification for population-level fortification of staple foods with calcium. Objectives To determine the eKect of calcium supplementation or food fortification with calcium, commenced before or early in pregnancy and continued at least until mid-pregnancy, on pre-eclampsia and other hypertensive disorders, maternal morbidity and mortality, as well as fetal and neonatal outcomes. Search methods We searched the Cochrane Pregnancy and Childbirth Trials Register (10 August 2017), PubMed (29 June 2017), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (10 August 2017) and reference lists of retrieved studies. Selection criteria Randomised controlled trials of calcium supplementation orfood fortification which include women of child bearing age not yet pregnant, or in early pregnancy. Cluster-RCTs, quasi-RCTs and trials published in abstract form only would have been eligible for inclusion in this review but none were identified. Cross-over designs are not appropriate for this intervention. The scope of this review is to consider interventions including calcium supplementation with or without additional supplements or treatments, compared with placebo or no intervention. Data collection and analysis Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. Main results This review is based on one RCT (involving 60 women) which looked at calcium plus additional supplements versus control. The women (who had lowantioxidant status)were in the early stages of pregnancy.We did notidentify any studieswhere supplementation commenced pre-pregnancy. Another RCT comparing calcium versus placebo is ongoing but not yet complete. We did not identify any studies looking at any of our other planned comparisons. Calcium plus antioxidants and other supplements versus placebo We included one small study (involving 60 women with low antioxidantlevels) which was conducted in an academic hospital in Indondesia. The study was at low risk of bias for all domains with the exception of selective reporting, for which it was unclear. Women in the intervention group received calcium (800 mg) plus N-acetylcysteine (200 mg), Cu (2 mg), Zn (15 mg), Mn (0.5 mg) and selenium (100 mcg) and vitamins A (1000 IU), B6 (2.2 mg), B12 (2.2 mcg), C (200 mg), and E (400 IU) versus the placebo control group of women who received similar looking tablets containing iron and folic acid. Both groups received iron (30 mg) and folic acid (400 mcg). Tablets were taken twice daily from eight to 12 weeks of gestation and then throughout pregnancy. The included study found that calcium supplementation plus antioxidants and other supplements may slightly reduce pre-eclampsia (gestational hypertension and proteinuria) (risk ratio (RR) 0.24, 95% confidence interval (CI) 0.06 to 1.01; low-quality evidence), but this is uncertain due to wide confidence intervals just crossing the line of no eKect, and small sample size. It appears that earlypregnancy loss before 20 weeks' gestation (RR 0.06, 95% CI 0.00 to 1.04; moderate-quality evidence) may be slightly reduced by calcium plus antioxidants and other supplements, but this outcome also has wide confidence intervals, which just cross the line of no eKect. Very few events were reported under the composite outcome, severe maternal morbidity and mortality index and no clear diKerence was seen between groups (RR 0.36, 95% CI 0.04 to 3.23; low-quality evidence). However, the included study observed a reduction in the composite outcome pre-eclampsia and/or pregnancy loss at any gestational age (RR 0.13, 95% CI 0.03 to 0.50; moderate-quality evidence), and pregnancy loss/stillbirth at any gestational age (RR 0.06, 95% CI 0.00 to 0.92;moderate-quality evidence)in the calcium plus antioxidant/supplement group. Other outcomes reported (placental abruption, severe pre-eclampsia and preterm birth (less than 37 weeks' gestation)) were too infrequent for meaningful analysis. No data were reported for the outcomes caesarean section, birthweight less 2500 g, Apgar score less than seven at five minutes, death or admission to neonatal intensive care unit (ICU), or pregnancy loss, stillbirth or neonatal death before discharge from hospital. Authors' conclusions The results of this review are based on one small study in which the calcium intervention group also received antioxidants and other supplements. Therefore, we are uncertain whether any of the eKects observed in the study were due to calcium supplementation or not. The evidence in this review was graded low to moderate due to imprecision. There is insuKicient evidence on the eKectiveness or otherwise of pre- or early-pregnancy calcium supplementation, or food fortification for preventing hypertensive disorders of pregnancy. Furtherresearch is needed to determine whether pre- or early-pregnancy supplementation, orfood fortification with calcium is associated with a reduction in adverse pregnancy outcomes such as pre-eclampsia and pregnancy loss. Such studies should be adequately powered, limited to calcium supplementation, placebo-controlled, and include relevant outcomes such as those chosen for this review. There is one ongoing study of calcium supplementation alone versus placebo and this may provide additional evidence in future updates
- Full Text:
- Date Issued: 2017
- Date: 2017
- Subjects: South Africa Pregnancy Journal article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/6187 , vital:45261 , xlink:href="https://DOI:10.1002/14651858.CD011192.pub2"
- Description: Background Pre-eclampsia is considerably more prevalent in low- than high-income countries. One possible explanation for this discrepancy is dietary diKerences, particularly calcium deficiency. Calcium supplementation in the second half of pregnancy reduces the serious consequences of pre-eclampsia and is recommended by the WorldHealthOrganization (WHO) for women with low dietary calcium intake, but has limited eKect on the overallrisk of pre-eclampsia. It is important to establish whether calcium supplementation before and in early pregnancy has added benefit. Such evidence would be justification for population-level fortification of staple foods with calcium. Objectives To determine the eKect of calcium supplementation or food fortification with calcium, commenced before or early in pregnancy and continued at least until mid-pregnancy, on pre-eclampsia and other hypertensive disorders, maternal morbidity and mortality, as well as fetal and neonatal outcomes. Search methods We searched the Cochrane Pregnancy and Childbirth Trials Register (10 August 2017), PubMed (29 June 2017), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (10 August 2017) and reference lists of retrieved studies. Selection criteria Randomised controlled trials of calcium supplementation orfood fortification which include women of child bearing age not yet pregnant, or in early pregnancy. Cluster-RCTs, quasi-RCTs and trials published in abstract form only would have been eligible for inclusion in this review but none were identified. Cross-over designs are not appropriate for this intervention. The scope of this review is to consider interventions including calcium supplementation with or without additional supplements or treatments, compared with placebo or no intervention. Data collection and analysis Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. Main results This review is based on one RCT (involving 60 women) which looked at calcium plus additional supplements versus control. The women (who had lowantioxidant status)were in the early stages of pregnancy.We did notidentify any studieswhere supplementation commenced pre-pregnancy. Another RCT comparing calcium versus placebo is ongoing but not yet complete. We did not identify any studies looking at any of our other planned comparisons. Calcium plus antioxidants and other supplements versus placebo We included one small study (involving 60 women with low antioxidantlevels) which was conducted in an academic hospital in Indondesia. The study was at low risk of bias for all domains with the exception of selective reporting, for which it was unclear. Women in the intervention group received calcium (800 mg) plus N-acetylcysteine (200 mg), Cu (2 mg), Zn (15 mg), Mn (0.5 mg) and selenium (100 mcg) and vitamins A (1000 IU), B6 (2.2 mg), B12 (2.2 mcg), C (200 mg), and E (400 IU) versus the placebo control group of women who received similar looking tablets containing iron and folic acid. Both groups received iron (30 mg) and folic acid (400 mcg). Tablets were taken twice daily from eight to 12 weeks of gestation and then throughout pregnancy. The included study found that calcium supplementation plus antioxidants and other supplements may slightly reduce pre-eclampsia (gestational hypertension and proteinuria) (risk ratio (RR) 0.24, 95% confidence interval (CI) 0.06 to 1.01; low-quality evidence), but this is uncertain due to wide confidence intervals just crossing the line of no eKect, and small sample size. It appears that earlypregnancy loss before 20 weeks' gestation (RR 0.06, 95% CI 0.00 to 1.04; moderate-quality evidence) may be slightly reduced by calcium plus antioxidants and other supplements, but this outcome also has wide confidence intervals, which just cross the line of no eKect. Very few events were reported under the composite outcome, severe maternal morbidity and mortality index and no clear diKerence was seen between groups (RR 0.36, 95% CI 0.04 to 3.23; low-quality evidence). However, the included study observed a reduction in the composite outcome pre-eclampsia and/or pregnancy loss at any gestational age (RR 0.13, 95% CI 0.03 to 0.50; moderate-quality evidence), and pregnancy loss/stillbirth at any gestational age (RR 0.06, 95% CI 0.00 to 0.92;moderate-quality evidence)in the calcium plus antioxidant/supplement group. Other outcomes reported (placental abruption, severe pre-eclampsia and preterm birth (less than 37 weeks' gestation)) were too infrequent for meaningful analysis. No data were reported for the outcomes caesarean section, birthweight less 2500 g, Apgar score less than seven at five minutes, death or admission to neonatal intensive care unit (ICU), or pregnancy loss, stillbirth or neonatal death before discharge from hospital. Authors' conclusions The results of this review are based on one small study in which the calcium intervention group also received antioxidants and other supplements. Therefore, we are uncertain whether any of the eKects observed in the study were due to calcium supplementation or not. The evidence in this review was graded low to moderate due to imprecision. There is insuKicient evidence on the eKectiveness or otherwise of pre- or early-pregnancy calcium supplementation, or food fortification for preventing hypertensive disorders of pregnancy. Furtherresearch is needed to determine whether pre- or early-pregnancy supplementation, orfood fortification with calcium is associated with a reduction in adverse pregnancy outcomes such as pre-eclampsia and pregnancy loss. Such studies should be adequately powered, limited to calcium supplementation, placebo-controlled, and include relevant outcomes such as those chosen for this review. There is one ongoing study of calcium supplementation alone versus placebo and this may provide additional evidence in future updates
- Full Text:
- Date Issued: 2017
Challenges of information and communication technology policy implementation in rural South Africa
- Chisango, Grasia, Lesame, Carol
- Authors: Chisango, Grasia , Lesame, Carol
- Date: 2017
- Subjects: Information society , Digital inclusion , Education
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5592 , vital:44611 , https://doi.org/10.18820/24150525/Comm.v22.4
- Description: While the South African government has implemented an information and communication technology (ICT) policy to address issues of universal access and service, questions remain about the effective implementation of this policy in rural areas. This article explores the extent to which ICT policy and regulation were implemented in rural South Africa, with specific reference to the Eastern Cape province. Focus group interviews and in-depth face-to-face interviews were conducted to collect qualitative data from 28 high school learners, two local municipal mayors and two women support group leaders in the Chris Hani District Municipality. A theme analysis indicated that the Universal Service and Access Agency of South Africa (USAASA) is failing to fulfil its mandate of promoting universal access and service. It is recommended that the provincial government in the Eastern Cape design an ICT strategy for its municipalities and that there should be easy access to Thusong Service Centres in rural areas.
- Full Text:
- Date Issued: 2017
- Authors: Chisango, Grasia , Lesame, Carol
- Date: 2017
- Subjects: Information society , Digital inclusion , Education
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/5592 , vital:44611 , https://doi.org/10.18820/24150525/Comm.v22.4
- Description: While the South African government has implemented an information and communication technology (ICT) policy to address issues of universal access and service, questions remain about the effective implementation of this policy in rural areas. This article explores the extent to which ICT policy and regulation were implemented in rural South Africa, with specific reference to the Eastern Cape province. Focus group interviews and in-depth face-to-face interviews were conducted to collect qualitative data from 28 high school learners, two local municipal mayors and two women support group leaders in the Chris Hani District Municipality. A theme analysis indicated that the Universal Service and Access Agency of South Africa (USAASA) is failing to fulfil its mandate of promoting universal access and service. It is recommended that the provincial government in the Eastern Cape design an ICT strategy for its municipalities and that there should be easy access to Thusong Service Centres in rural areas.
- Full Text:
- Date Issued: 2017
Characterization and physicochemical studies of the conjugates of graphene quantum dots with differently charged zinc phthalocyanines
- Matshitse, Refilwe, Sekhosana, Kutloana E, Achadu, Ojodomo John, Nyokong, Tebello
- Authors: Matshitse, Refilwe , Sekhosana, Kutloana E , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189227 , vital:44829 , xlink:href="https://doi.org/10.1080/00958972.2017.1387652"
- Description: Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.
- Full Text:
- Date Issued: 2017
- Authors: Matshitse, Refilwe , Sekhosana, Kutloana E , Achadu, Ojodomo John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189227 , vital:44829 , xlink:href="https://doi.org/10.1080/00958972.2017.1387652"
- Description: Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.
- Full Text:
- Date Issued: 2017
Characterization of conjugates of NaYF4
- Watkins, Zane, Uddin, Imran, Britton, Jonathan, Nyokong, Tebello
- Authors: Watkins, Zane , Uddin, Imran , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238132 , vital:50589 , xlink:href="https://doi.org/10.1016/j.molstruc.2016.10.011"
- Description: NaYF4:Er/Yb/Gd upconversion nanoparticles (UCNP) capped with amino groups were covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). There was a decrease in the intensity of fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to Förster resonance energy transfer (FRET). FRET efficiencies of 18% and 21% for ClAlTSPc and ClAlTCPc, respectively, were obtained. Oxygen generation by ClAlTSPc following FRET was proved.
- Full Text:
- Date Issued: 2017
- Authors: Watkins, Zane , Uddin, Imran , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238132 , vital:50589 , xlink:href="https://doi.org/10.1016/j.molstruc.2016.10.011"
- Description: NaYF4:Er/Yb/Gd upconversion nanoparticles (UCNP) capped with amino groups were covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). There was a decrease in the intensity of fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to Förster resonance energy transfer (FRET). FRET efficiencies of 18% and 21% for ClAlTSPc and ClAlTCPc, respectively, were obtained. Oxygen generation by ClAlTSPc following FRET was proved.
- Full Text:
- Date Issued: 2017
Characterization of phthalocyanine functionalized quantum dots by dynamic light scattering, laser Doppler, and capillary electrophoresis
- Ramírez-García, Gonzalo, Oluwole, David O, Nxele, Siphesihle Robin, d’Orlyé, Fanny, Nyokong, Tebello, Bedioui, Fethi, Varenne, Anne
- Authors: Ramírez-García, Gonzalo , Oluwole, David O , Nxele, Siphesihle Robin , d’Orlyé, Fanny , Nyokong, Tebello , Bedioui, Fethi , Varenne, Anne
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238184 , vital:50595 , xlink:href="https://doi.org/10.1007/s00216-016-0120-x"
- Description: In this work, we characterized different phtalocyanine-capped core/shell/shell quantum dots (QDs) in terms of stability, ζ-potential, and size at various pH and ionic strengths, by means of capillary electrophoresis (CE), and compared these results to the ones obtained by laser Doppler electrophoresis (LDE) and dynamic light scattering (DLS). The effect of the phthalocyanine metallic center (Zn, Al, or In), the number (one or four), and nature of substituents (carboxyphenoxy- or sulfonated-) of functionalization on the phthalocyanine physicochemical properties were evaluated. Whereas QDs capped with zinc mono-carboxyphenoxy-phtalocyanine (ZnMCPPc-QDs) remained aggregated in the whole analyzed pH range, even at low ionic strength, QDs capped with zinc tetracarboxyphenoxy phtalocyanine (ZnTPPc-QDs) were easily dispersed in buffers at pH equal to or higher than 7.4. QDs capped with aluminum tetrasulfonated phthalocyanine (AlTSPPc-QDs) and indium tetracarboxyphenoxy phthalocyanines (InTCPPc-QDs) were stable in aqueous suspension only at pH higher than 9.0 due to the presence of functional groups bound to the metallic center of the phthalocyanine. The ζ-potential values determined by CE for all the samples decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiological relevant solutions and thereby, its usefulness for improving their design and applications for photodynamic therapy.
- Full Text:
- Date Issued: 2017
- Authors: Ramírez-García, Gonzalo , Oluwole, David O , Nxele, Siphesihle Robin , d’Orlyé, Fanny , Nyokong, Tebello , Bedioui, Fethi , Varenne, Anne
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/238184 , vital:50595 , xlink:href="https://doi.org/10.1007/s00216-016-0120-x"
- Description: In this work, we characterized different phtalocyanine-capped core/shell/shell quantum dots (QDs) in terms of stability, ζ-potential, and size at various pH and ionic strengths, by means of capillary electrophoresis (CE), and compared these results to the ones obtained by laser Doppler electrophoresis (LDE) and dynamic light scattering (DLS). The effect of the phthalocyanine metallic center (Zn, Al, or In), the number (one or four), and nature of substituents (carboxyphenoxy- or sulfonated-) of functionalization on the phthalocyanine physicochemical properties were evaluated. Whereas QDs capped with zinc mono-carboxyphenoxy-phtalocyanine (ZnMCPPc-QDs) remained aggregated in the whole analyzed pH range, even at low ionic strength, QDs capped with zinc tetracarboxyphenoxy phtalocyanine (ZnTPPc-QDs) were easily dispersed in buffers at pH equal to or higher than 7.4. QDs capped with aluminum tetrasulfonated phthalocyanine (AlTSPPc-QDs) and indium tetracarboxyphenoxy phthalocyanines (InTCPPc-QDs) were stable in aqueous suspension only at pH higher than 9.0 due to the presence of functional groups bound to the metallic center of the phthalocyanine. The ζ-potential values determined by CE for all the samples decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiological relevant solutions and thereby, its usefulness for improving their design and applications for photodynamic therapy.
- Full Text:
- Date Issued: 2017
Children and wild foods in the context of deforestation in rural Malawi
- Maseko, Heather N, Shackleton, Charlie M, Nagoli, J, Pullanikkatil, Deepa
- Authors: Maseko, Heather N , Shackleton, Charlie M , Nagoli, J , Pullanikkatil, Deepa
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182101 , vital:43800 , xlink:href="https://doi.org/10.1007/s10745-017-9956-8"
- Description: There is growing recognition of the contribution of wild foods to local diets, nutrition, and culture. Yet disaggregation of understanding of wild food use by gender and age is limited. We used a mixed methods approach to determine the types, frequencies, and perceptions of wild foods used and sold by children in four villages in southern Malawi that have different levels of deforestation. Household and individual dietary diversity scores are low at all sites. All households consume one or more wild foods. Across the four sites, children listed 119 wild foods, with a wider variety at the least deforested sites than the most deforested ones. Older children can name more wild foods than younger ones. More children from poor households sell wild foods than from well-off households. Several reasons were provided for the consumption or avoidance of wild foods (most commonly taste, contribution to health, limited alternatives, hunger, availability, local taboos).
- Full Text:
- Date Issued: 2017
- Authors: Maseko, Heather N , Shackleton, Charlie M , Nagoli, J , Pullanikkatil, Deepa
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182101 , vital:43800 , xlink:href="https://doi.org/10.1007/s10745-017-9956-8"
- Description: There is growing recognition of the contribution of wild foods to local diets, nutrition, and culture. Yet disaggregation of understanding of wild food use by gender and age is limited. We used a mixed methods approach to determine the types, frequencies, and perceptions of wild foods used and sold by children in four villages in southern Malawi that have different levels of deforestation. Household and individual dietary diversity scores are low at all sites. All households consume one or more wild foods. Across the four sites, children listed 119 wild foods, with a wider variety at the least deforested sites than the most deforested ones. Older children can name more wild foods than younger ones. More children from poor households sell wild foods than from well-off households. Several reasons were provided for the consumption or avoidance of wild foods (most commonly taste, contribution to health, limited alternatives, hunger, availability, local taboos).
- Full Text:
- Date Issued: 2017
Comparative fish ecology in three periodically connected rivers in the upper Zambezi and Okavango ecoregions
- Authors: Taylor, Geraldine Claire
- Date: 2017
- Subjects: Fishes Ecology Zambia Zambezi District , Floodplain ecology Zambia Zambezi District , Stable isotopes , Fishes Food Zambia Zambezi District , Fishes Mortality Zambia Zambezi District , Fish populations Zambia Zambezi District , Fishes Growth
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/65055 , vital:28660 , DOI https://doi.org/10.21504/10962/65055
- Description: The Upper Zambezi, Kavango and Kwando rivers are three periodically interlinked floodplain rivers which share the same Upper Zambezian floodplain ichthyofauna. The aim of this thesis was to compare the biology and ecology of the fish communities in these three rivers. The objective was to test the hypothesis that fish community composition and assemblage structure, fish diets, food web structure and trophic dynamics, fish growth rates and total mortality are influenced by the differing flood magnitudes of the three rivers, in support of the flood pulse concept. To understand the abiotic characteristics of each river, water temperature, flood regime, total dissolved inorganic nitrogen concentrations and water quality parameters were measured and compared between rivers. Water temperatures varied seasonally, and seven day moving averages peaked above 30 °C in January, and fell to between 16 and 19 °C in June. The Zambezi River had the largest flood (6.14 m), followed by the Kavango River (3.80 m), while the Kwando River had the smallest flood (0.65 m). Total dissolved inorganic nitrogen concentrations were low in the Kavango and Zambezi Rivers (0.2 - 0.6 mg/l), and slightly higher in the Kwando River (<1 mg/l). Conductivity, total dissolved solids and total dissolved inorganic nitrogen concentrations decreased with the flood (dilution effect). Using biomass catch per unit effort data from experimental gillnets, fish community composition and assemblage structure was described, and differed between rivers in all hydrological seasons. In the Zambezi and Kavango rivers, fish assemblages varied with hydrological season as a result of the homogenising influence of the flood pulse, while in the Kwando River fish assemblages did not differ seasonally as flood pulses were small and often irregular. Differences in community composition were attributed to the abundance of Hydrocynus vittatus, a large bodied open water predator, in the Zambezi and Kavango rivers, and its relative absence in the Kwando River. Based on the results of the community composition, six focus species were chosen that were abundant and representative of the various feeding modes and life history strategies of the fish community. These were the striped robber Brycinus lateralis, sharptooth catfish Clarias gariepinus, blunttooth catfish Clarias ngamensis, African pike Hepsetus cuvieri, silver catfish Schilbe intermedius and purpleface largemouth Serranochromis macrocephalus. Stomach contents analysis was then used to compare the feeding ecology of the six example species between rivers. Clarias gariepinus, C. ngamensis and S. intermedius were piscivorous in the Zambezi and Kavango rivers, and preyed upon more invertebrates in the Kwando River, while Hepsetus cuvieri and S. macrocephalus were piscivorous in all three rivers. Differences in diets were attributed to seasonal prey abundance, with prey fishes abundant during falling and low water when the Zambezi and Kavango rivers were sampled, while invertebrates were abundant during rising and high water when the Kwando River was sampled. Prey mastication by B. lateralis made prey identification difficult. For other predators, the usefulness of stomach contents analysis for dietary descriptions was restricted by the high proportion of empty stomachs. As a result, whole ecosystem stable isotope analysis was used to gain a holistic understanding of the food web structure and fish feeding ecology of the three rivers. The Zambezi and Kavango river food webs were supported by C enriched resources such as C4 and C3 riparian vegetation from the floodplain, while the Kwando River food web was based on C depleted resources such as filamentous algae and aquatic macrophytes. The Zambezi River food web had a restricted nitrogen range, with reduced food chain length and the predators in this river did not occupy such elevated trophic positions compared to in the Kavango and Kwando river food webs. This was attributed to the overfishing of the primary and tertiary consumers in the Zambezi River, a phenomenon known to reduce food chain length. Focussing on predator communities, in the Zambezi and Kavango rivers, H. vittatus isotopic niche width was large and overlapped significantly with most other predators, while in the Kwando River predator niches were more distinct. This supported previously proposed hypotheses by describing H. vittatus as a dominant predator which excludes all other fishes by predation or competition. Despite the dominance of H. vittatus, C. gariepinus occupied the position of top predator in all three rivers, and information on the habitat use, feeding habits and trophic niches of the serranochromine cichlids added understanding of their ecology. Lastly, age was determined using sectioned sagittal otoliths for C. gariepinus, C. ngamensis, S. intermedius and S. macrocephalus and using whole asteriscus otoliths for B. lateralis and H. cuvieri, and growth was modelled using the von Bertalanffy growth equation. Growth performance was high in the Zambezi and Kavango rivers, and lower in the Kwando River, most likely in response to the varying flood magnitudes. Total mortality rates, estimated using Hoenig’s maximum-age based equation, were high in the Zambezi River as a result of the high fishing pressure on this river. Overall floodplain fish ecology in the Zambezi, Kavango and Kwando rivers was influenced by the flood pulse, as was predicted by the flood pulse concept. Periodic and equilibrium life history strategists were found to adapt either to the pulsing environments of the Zambezi and Kavango rivers, or to the more stable environment of the Kwando River, and large bodied, long lived periodic strategists such as C. gariepinus tended to be highly plastic and able to thrive in most conditions. Data also suggested that Zambezi River food web structure and fish mortality rates have been impacted by overfishing, for which more information is needed to conserve and manage this system. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2018
- Full Text:
- Date Issued: 2017
- Authors: Taylor, Geraldine Claire
- Date: 2017
- Subjects: Fishes Ecology Zambia Zambezi District , Floodplain ecology Zambia Zambezi District , Stable isotopes , Fishes Food Zambia Zambezi District , Fishes Mortality Zambia Zambezi District , Fish populations Zambia Zambezi District , Fishes Growth
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/65055 , vital:28660 , DOI https://doi.org/10.21504/10962/65055
- Description: The Upper Zambezi, Kavango and Kwando rivers are three periodically interlinked floodplain rivers which share the same Upper Zambezian floodplain ichthyofauna. The aim of this thesis was to compare the biology and ecology of the fish communities in these three rivers. The objective was to test the hypothesis that fish community composition and assemblage structure, fish diets, food web structure and trophic dynamics, fish growth rates and total mortality are influenced by the differing flood magnitudes of the three rivers, in support of the flood pulse concept. To understand the abiotic characteristics of each river, water temperature, flood regime, total dissolved inorganic nitrogen concentrations and water quality parameters were measured and compared between rivers. Water temperatures varied seasonally, and seven day moving averages peaked above 30 °C in January, and fell to between 16 and 19 °C in June. The Zambezi River had the largest flood (6.14 m), followed by the Kavango River (3.80 m), while the Kwando River had the smallest flood (0.65 m). Total dissolved inorganic nitrogen concentrations were low in the Kavango and Zambezi Rivers (0.2 - 0.6 mg/l), and slightly higher in the Kwando River (<1 mg/l). Conductivity, total dissolved solids and total dissolved inorganic nitrogen concentrations decreased with the flood (dilution effect). Using biomass catch per unit effort data from experimental gillnets, fish community composition and assemblage structure was described, and differed between rivers in all hydrological seasons. In the Zambezi and Kavango rivers, fish assemblages varied with hydrological season as a result of the homogenising influence of the flood pulse, while in the Kwando River fish assemblages did not differ seasonally as flood pulses were small and often irregular. Differences in community composition were attributed to the abundance of Hydrocynus vittatus, a large bodied open water predator, in the Zambezi and Kavango rivers, and its relative absence in the Kwando River. Based on the results of the community composition, six focus species were chosen that were abundant and representative of the various feeding modes and life history strategies of the fish community. These were the striped robber Brycinus lateralis, sharptooth catfish Clarias gariepinus, blunttooth catfish Clarias ngamensis, African pike Hepsetus cuvieri, silver catfish Schilbe intermedius and purpleface largemouth Serranochromis macrocephalus. Stomach contents analysis was then used to compare the feeding ecology of the six example species between rivers. Clarias gariepinus, C. ngamensis and S. intermedius were piscivorous in the Zambezi and Kavango rivers, and preyed upon more invertebrates in the Kwando River, while Hepsetus cuvieri and S. macrocephalus were piscivorous in all three rivers. Differences in diets were attributed to seasonal prey abundance, with prey fishes abundant during falling and low water when the Zambezi and Kavango rivers were sampled, while invertebrates were abundant during rising and high water when the Kwando River was sampled. Prey mastication by B. lateralis made prey identification difficult. For other predators, the usefulness of stomach contents analysis for dietary descriptions was restricted by the high proportion of empty stomachs. As a result, whole ecosystem stable isotope analysis was used to gain a holistic understanding of the food web structure and fish feeding ecology of the three rivers. The Zambezi and Kavango river food webs were supported by C enriched resources such as C4 and C3 riparian vegetation from the floodplain, while the Kwando River food web was based on C depleted resources such as filamentous algae and aquatic macrophytes. The Zambezi River food web had a restricted nitrogen range, with reduced food chain length and the predators in this river did not occupy such elevated trophic positions compared to in the Kavango and Kwando river food webs. This was attributed to the overfishing of the primary and tertiary consumers in the Zambezi River, a phenomenon known to reduce food chain length. Focussing on predator communities, in the Zambezi and Kavango rivers, H. vittatus isotopic niche width was large and overlapped significantly with most other predators, while in the Kwando River predator niches were more distinct. This supported previously proposed hypotheses by describing H. vittatus as a dominant predator which excludes all other fishes by predation or competition. Despite the dominance of H. vittatus, C. gariepinus occupied the position of top predator in all three rivers, and information on the habitat use, feeding habits and trophic niches of the serranochromine cichlids added understanding of their ecology. Lastly, age was determined using sectioned sagittal otoliths for C. gariepinus, C. ngamensis, S. intermedius and S. macrocephalus and using whole asteriscus otoliths for B. lateralis and H. cuvieri, and growth was modelled using the von Bertalanffy growth equation. Growth performance was high in the Zambezi and Kavango rivers, and lower in the Kwando River, most likely in response to the varying flood magnitudes. Total mortality rates, estimated using Hoenig’s maximum-age based equation, were high in the Zambezi River as a result of the high fishing pressure on this river. Overall floodplain fish ecology in the Zambezi, Kavango and Kwando rivers was influenced by the flood pulse, as was predicted by the flood pulse concept. Periodic and equilibrium life history strategists were found to adapt either to the pulsing environments of the Zambezi and Kavango rivers, or to the more stable environment of the Kwando River, and large bodied, long lived periodic strategists such as C. gariepinus tended to be highly plastic and able to thrive in most conditions. Data also suggested that Zambezi River food web structure and fish mortality rates have been impacted by overfishing, for which more information is needed to conserve and manage this system. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2018
- Full Text:
- Date Issued: 2017
Composition and fate of triclosan in the sludge from wastewater treatment in Grahamstown, South Africa and Tiaret, Algeria
- Authors: Ncube, Mbonisi
- Date: 2017
- Subjects: Sewage sludge , Sewage Purification South Africa Grahamstown , Sewage Purification Algeria Tiaret , Sewage sludge as fertilizer , Anti-infective agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65156 , vital:28697
- Description: Physicochemical properties such as pH, specific surface area (SSA), cationic exchange capacity (CEC), loss on ignition (LOI), pathogens, plant nutrients (nitrates, ammonium and phosphates), and heavy metals (manganese, copper, lead and cadmium) were determined for sewage sludge from Grahamstown and Tiaret. The values obtained were log transformed thereafter a t-test at 5 % level of significance was used to test for the difference in each parameter for both sludges. The pH of sludge was determined in 1:3 water, 16 water, 1:3 0.01 M calcium chloride and 1:3 1 M potassium chloride. The pH for Grahamstown and Tiaret sludge were in the ranges of 6.66-7.11 and 7.88-8.18 respectively. The SSA values for Grahamstown and Tiaret were 218 ± 108 and 261 ± 99.9 m2/g, and the CEC values were 119 ± 2.09 and 136 ± 6.03 mEq/100, respectively. The LOI values obtained were 1.33 ± 0.03 and 1.48 ± 0.11 % for Grahamstown and Tiaret, respectively. E. coll and heterotrophic bacteria were the pathogens determined, and were extracted from sludge using sterile saline and nutrient broth. The concentration of E. coll in Grahamstown and Tiaret sludge were 468 ± 7.63 and 7769 ± 1268 CFU/g d.w and for heterotrophic bacteria were 1.17x109 ± 7.42x108 and 1.43x109 ± 9.11 x108 CFU/g d.w. For Grahamstown sludge, the concentration of nitrates, ammonium and phosphates were 55.61 ± 55.20 mg/g d.w, 6.60 ± 2.36 mg/g d.w and 1.40 ± 0.30 mg/g d.w, respectively. For Tiaret sludge, the concentration of nitrates, ammonium and phosphates were 2.56 ± 2.90 mg/g d.w, 0.64 ± 0.45 mg/g d.w and 0.24 ± 0.19 mg/g d.w, respectively. The concentration of Mn, Cu, Pb and Cd in Grahamstown sludge were 423 ± 101, 353 ± 92, 40.2 ± 20 and 0.0 mg/kg d.w respectively, and for Tiaret sludge, the corresponding concentrations were 358± 295, 549±50, 1427± 1352 and 1.54 ± 0.61 mg/kg d.w. Sewage sludge was found to contain Triclosan, and solubility studies of the compound were conducted using sodium deoxycholate and sodium lithocholate. The apparent solubilities and rate constants indicated in brackets of TCS at 37 °C were 35.4 ± 1.21 mg/L (1.28 ± 0.36 Hr-) and 14.4 ± 0.34 mg/L (0.99 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. The apparent solubilities and rate constants indicated in brackets of TCS at 15 °C were 32.3 ± 0.88 mg/L (2.16 ± 0.80 Hr-) and 14.2 ± 0.39 mg/L (1.02 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. Triclosan was extracted from sludge using 1 g/L sodium deoxycholate and the determined concentration were 142 ± 33.5 gg/g d.w for Grahamstown sludge and 0-12 gg/g d.w for Tiaret sludge. Finally plant growth studies were conducted on radish and garden cress plants using Grahamstown sludge at 0, 20, 40, 80 and 100 % treatments. Statistical analysis (t-test and Kruskal-Wallis) at 5 % level of significance was done to compare growth parameters between control and different sludge treatments. For radish plants, the values for plant height, root length, number of leaves, leaf length and dry mass were 28.4-80-7 mm, 4.3-44.7 mm, 3.3-17.0 mm, 2.3-4.0 leaves and 6.3-15.3 %, respectively. For garden cress, the values for plant height, root length, number of leaves, leaf length and dry mass were 13.7-25.0 mm, 7.7-20.3 mm, 5.7-8.3 leaves, 3.0-8.3 mm and 8.8-15.0 %, respectively. Twenty percent (20 %) sludge treatment gave the best results in radish and garden cress plants with respect to plant height, root length, number of leaves and dry mass. Triclosan concentration in radish and garden cress plants was below the detection limit of 32.4 gg/g d.w. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
- Authors: Ncube, Mbonisi
- Date: 2017
- Subjects: Sewage sludge , Sewage Purification South Africa Grahamstown , Sewage Purification Algeria Tiaret , Sewage sludge as fertilizer , Anti-infective agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65156 , vital:28697
- Description: Physicochemical properties such as pH, specific surface area (SSA), cationic exchange capacity (CEC), loss on ignition (LOI), pathogens, plant nutrients (nitrates, ammonium and phosphates), and heavy metals (manganese, copper, lead and cadmium) were determined for sewage sludge from Grahamstown and Tiaret. The values obtained were log transformed thereafter a t-test at 5 % level of significance was used to test for the difference in each parameter for both sludges. The pH of sludge was determined in 1:3 water, 16 water, 1:3 0.01 M calcium chloride and 1:3 1 M potassium chloride. The pH for Grahamstown and Tiaret sludge were in the ranges of 6.66-7.11 and 7.88-8.18 respectively. The SSA values for Grahamstown and Tiaret were 218 ± 108 and 261 ± 99.9 m2/g, and the CEC values were 119 ± 2.09 and 136 ± 6.03 mEq/100, respectively. The LOI values obtained were 1.33 ± 0.03 and 1.48 ± 0.11 % for Grahamstown and Tiaret, respectively. E. coll and heterotrophic bacteria were the pathogens determined, and were extracted from sludge using sterile saline and nutrient broth. The concentration of E. coll in Grahamstown and Tiaret sludge were 468 ± 7.63 and 7769 ± 1268 CFU/g d.w and for heterotrophic bacteria were 1.17x109 ± 7.42x108 and 1.43x109 ± 9.11 x108 CFU/g d.w. For Grahamstown sludge, the concentration of nitrates, ammonium and phosphates were 55.61 ± 55.20 mg/g d.w, 6.60 ± 2.36 mg/g d.w and 1.40 ± 0.30 mg/g d.w, respectively. For Tiaret sludge, the concentration of nitrates, ammonium and phosphates were 2.56 ± 2.90 mg/g d.w, 0.64 ± 0.45 mg/g d.w and 0.24 ± 0.19 mg/g d.w, respectively. The concentration of Mn, Cu, Pb and Cd in Grahamstown sludge were 423 ± 101, 353 ± 92, 40.2 ± 20 and 0.0 mg/kg d.w respectively, and for Tiaret sludge, the corresponding concentrations were 358± 295, 549±50, 1427± 1352 and 1.54 ± 0.61 mg/kg d.w. Sewage sludge was found to contain Triclosan, and solubility studies of the compound were conducted using sodium deoxycholate and sodium lithocholate. The apparent solubilities and rate constants indicated in brackets of TCS at 37 °C were 35.4 ± 1.21 mg/L (1.28 ± 0.36 Hr-) and 14.4 ± 0.34 mg/L (0.99 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. The apparent solubilities and rate constants indicated in brackets of TCS at 15 °C were 32.3 ± 0.88 mg/L (2.16 ± 0.80 Hr-) and 14.2 ± 0.39 mg/L (1.02 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. Triclosan was extracted from sludge using 1 g/L sodium deoxycholate and the determined concentration were 142 ± 33.5 gg/g d.w for Grahamstown sludge and 0-12 gg/g d.w for Tiaret sludge. Finally plant growth studies were conducted on radish and garden cress plants using Grahamstown sludge at 0, 20, 40, 80 and 100 % treatments. Statistical analysis (t-test and Kruskal-Wallis) at 5 % level of significance was done to compare growth parameters between control and different sludge treatments. For radish plants, the values for plant height, root length, number of leaves, leaf length and dry mass were 28.4-80-7 mm, 4.3-44.7 mm, 3.3-17.0 mm, 2.3-4.0 leaves and 6.3-15.3 %, respectively. For garden cress, the values for plant height, root length, number of leaves, leaf length and dry mass were 13.7-25.0 mm, 7.7-20.3 mm, 5.7-8.3 leaves, 3.0-8.3 mm and 8.8-15.0 %, respectively. Twenty percent (20 %) sludge treatment gave the best results in radish and garden cress plants with respect to plant height, root length, number of leaves and dry mass. Triclosan concentration in radish and garden cress plants was below the detection limit of 32.4 gg/g d.w. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
Contributions to the study of nonholonomic Riemannian manifolds
- Authors: Barrett, Dennis Ian
- Date: 2017
- Subjects: Riemannian manifolds , Curvature , Lie groups , Geometry, Riemannian , Tensor fields
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/7554 , vital:21272 , DOI https://doi.org/10.21504/10962/7554
- Description: In this thesis we consider nonholonomic Riemannian manifolds, and in particular, left- invariant nonholonomic Riemannian structures on Lie groups. These structures are closely related to mechanical systems with (positive definite) quadratic Lagrangians and nonholo- nomic constraints linear in velocities. In the first chapter, we review basic concepts of non- holonomic Riemannian geometry, including the left-invariant structures. We also examine the class of left-invariant structures with so-called Cartan-Schouten connections. The second chapter investigates the curvature of nonholonomic Riemannian manifolds and the Schouten and Wagner curvature tensors. The Schouten tensor is canonically associated to every non- holonomic Riemannian structure (in particular, we use it to define isometric invariants for structures on three-dimensional manifolds). By contrast, the Wagner tensor is not generally intrinsic, but can be used to characterise flat structures (i.e., those whose associated parallel transport is path-independent). The third chapter considers equivalence of nonholonomic Rie- mannian manifolds, particularly up to nonholonomic isometry. We also introduce the notion of a nonholonomic Riemannian submanifold, and investigate the conditions under which such a submanifold inherits its geometry from the enveloping space. The latter problem involves the concept of a geodesically invariant distribution, and we show it is also related to the curvature. In the last chapter we specialise to three-dimensional nonholonomic Riemannian manifolds. We consider the equivalence of such structures up to nonholonomic isometry and rescaling, and classify the left-invariant structures on the (three-dimensional) simply connected Lie groups. We also characterise the flat structures in three dimensions, and then classify the flat structures on the simply connected Lie groups. Lastly, we consider three typical examples of (left-invariant) nonholonomic Riemannian structures on three-dimensional Lie groups, two of which arise from problems in classical mechanics (viz., the Chaplygin problem and the Suslov problem). , Thesis (PhD) -- Faculty of Science, Mathematics (Pure and Applied), 2017
- Full Text:
- Date Issued: 2017
- Authors: Barrett, Dennis Ian
- Date: 2017
- Subjects: Riemannian manifolds , Curvature , Lie groups , Geometry, Riemannian , Tensor fields
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/7554 , vital:21272 , DOI https://doi.org/10.21504/10962/7554
- Description: In this thesis we consider nonholonomic Riemannian manifolds, and in particular, left- invariant nonholonomic Riemannian structures on Lie groups. These structures are closely related to mechanical systems with (positive definite) quadratic Lagrangians and nonholo- nomic constraints linear in velocities. In the first chapter, we review basic concepts of non- holonomic Riemannian geometry, including the left-invariant structures. We also examine the class of left-invariant structures with so-called Cartan-Schouten connections. The second chapter investigates the curvature of nonholonomic Riemannian manifolds and the Schouten and Wagner curvature tensors. The Schouten tensor is canonically associated to every non- holonomic Riemannian structure (in particular, we use it to define isometric invariants for structures on three-dimensional manifolds). By contrast, the Wagner tensor is not generally intrinsic, but can be used to characterise flat structures (i.e., those whose associated parallel transport is path-independent). The third chapter considers equivalence of nonholonomic Rie- mannian manifolds, particularly up to nonholonomic isometry. We also introduce the notion of a nonholonomic Riemannian submanifold, and investigate the conditions under which such a submanifold inherits its geometry from the enveloping space. The latter problem involves the concept of a geodesically invariant distribution, and we show it is also related to the curvature. In the last chapter we specialise to three-dimensional nonholonomic Riemannian manifolds. We consider the equivalence of such structures up to nonholonomic isometry and rescaling, and classify the left-invariant structures on the (three-dimensional) simply connected Lie groups. We also characterise the flat structures in three dimensions, and then classify the flat structures on the simply connected Lie groups. Lastly, we consider three typical examples of (left-invariant) nonholonomic Riemannian structures on three-dimensional Lie groups, two of which arise from problems in classical mechanics (viz., the Chaplygin problem and the Suslov problem). , Thesis (PhD) -- Faculty of Science, Mathematics (Pure and Applied), 2017
- Full Text:
- Date Issued: 2017
Cu (III) triarylcorroles with asymmetric push–pull meso-substitutions
- Liang, Xu, Niu, Yingjie, Zhang, Ojanchong, Mack, John, Yi, Xiaoyi, Hlatshwayo, Zweli, Li, Minzhi, Zhu, Weihua, Nyokong, Tebello
- Authors: Liang, Xu , Niu, Yingjie , Zhang, Ojanchong , Mack, John , Yi, Xiaoyi , Hlatshwayo, Zweli , Li, Minzhi , Zhu, Weihua , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232947 , vital:50040 , xlink:href="https://doi.org/10.1039/C7DT00716G"
- Description: The synthesis of four low symmetry A2B type Cu (III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties is reported, along with their structural characterization by NMR spectroscopy and X-ray crystallography. An analysis of the structure–property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy, electrochemistry, and spectroelectrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type Cu(III)triarylcorroles are highly efficient catalysts for electrocatalyzed hydrogen evolution reactions (HERs) and that their reactivity can be modulated by changing the nature of the B-position meso-substituent.
- Full Text:
- Date Issued: 2017
- Authors: Liang, Xu , Niu, Yingjie , Zhang, Ojanchong , Mack, John , Yi, Xiaoyi , Hlatshwayo, Zweli , Li, Minzhi , Zhu, Weihua , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232947 , vital:50040 , xlink:href="https://doi.org/10.1039/C7DT00716G"
- Description: The synthesis of four low symmetry A2B type Cu (III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties is reported, along with their structural characterization by NMR spectroscopy and X-ray crystallography. An analysis of the structure–property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy, electrochemistry, and spectroelectrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type Cu(III)triarylcorroles are highly efficient catalysts for electrocatalyzed hydrogen evolution reactions (HERs) and that their reactivity can be modulated by changing the nature of the B-position meso-substituent.
- Full Text:
- Date Issued: 2017
Development and assessment of gastric-retentive sustained release metronidazole microcapsules
- Authors: Makan, Anjana
- Date: 2017
- Subjects: Metronidazole , Drug delivery systems , Helicobacter pylori , High performance liquid chromatography , Gas chromatography , Drugs , Drugs Controlled release
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59240 , vital:27491
- Description: Helicobacter pylori is one of the most common pathogenic bacterial infections and is the leading cause of gastritis, gastroduodenal ulcer disease and gastric cancers. Studies have revealed the prevalence of Helicobacter pylori is high in many countries around the globe. Although Helicobacter pylori is highly sensitive to antimicrobial agents in vitro the clinical eradication rate of the disease is still low. The instability of API at gastric pH, low concentration of API in the gastric mucosa and short gastric residence times are the main reasons for poor eradication rates. The high prevalence rate of this disease necessitates the design and development of gastric-retentive site specific oral dosage forms for the optimized delivery of existing therapeutic molecules and may be an approach to improving the eradication rate of Helicobacter pylori. Metronidazole (MTZ) is a 5-nitroimidazole derivative that exhibits antibiotic and antiprotozoal activity. MTZ is used in combination with other compounds for the treatment of Helicobacter pylori in peptic ulcer disease. MTZ is a potential candidate for inclusion in a sustained release gastric-retentive delivery system that acts in the stomach and since it is unstable in the intestinal/colonic environment enhancing gastric residence time would be a therapeutic advantage. MTZ is a cost-effective therapy that exhibits good anti-microbial activity and has a favourable pharmacokinetic profile. A sustained release gastric-retentive formulation is therefore proposed as an approach to enhance the local delivery of MTZ and improve treatment outcomes for patients infected with Helicobacter pylori. A stability indicating Reversed-Phase High Performance Liquid Chromatography (RP- HPLC) method for the quantitation of MTZ in pharmaceutical dosage forms was developed and optimised using a Central Composite Design (CCD) approach. The RP-HPLC method was found to be linear, accurate, precise, sensitive, selective, and was applied to the analysis of MTZ in commercially available medicines. Preformulation studies were conducted as preparative work prior to manufacture gastric- retentive sustained release MTZ microcapsules. The experiments conducted were tailored for the development of sustained release MTZ microcapsules using a solvent evaporation method. The particle size and shape of the microcapsules was investigated using Scanning Electron Microscopy (SEM). MTZ- excipient compatibility studies were performed using Fourier Transform Infra-red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). The results revealed that no definite interaction between MTZ and intended excipients to be used for manufacture of MTZ formulations occurred. A solvent evaporation procedure was used for the manufacture of MTZ microcapsules. Preliminary formulations were manufactured using two different grades of Methocel® at various levels. In addition the impact of processing parameters on performance was also investigated. The formulations were assessed in terms of in vitro release, buoyancy, yield, encapsulation efficiency and microcapsule size. Formulation optimisation was undertaken using a CCD approach and numerical optimisation was used to predict an optimised formulation composition that would produce minimal initial MTZ release, maximum MTZ release at 12 hours and maximum buoyancy, encapsulation efficiency and yield. The kinetics of MTZ release from microcapsules was established by fitting in vitro release data to different mathematical models. Higuchi model and first-order model appeared to best fit the data as majority of the formulation batches had highest R2 values for these models. Short-term stability assessment of the optimised formulation was established by undertaking stability studies at 25°C/60% RH and 40°C/75%RH. No significant changes in any of the CQA were observed over 30 days of stability testing. A gas chromatographic (GC) method was developed and validated for the quantitation of residual acetone and n-hexane. The optimised formulation contained 213.60 ppm/g acetone and 25.23 ppm/g n-hexane which are well below the limits set for residual solvents. In conclusion, gastric-retentive sustained release MTZ microcapsules with potential for further development and optimisation have been successfully developed and assessed in these studies. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
- Authors: Makan, Anjana
- Date: 2017
- Subjects: Metronidazole , Drug delivery systems , Helicobacter pylori , High performance liquid chromatography , Gas chromatography , Drugs , Drugs Controlled release
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59240 , vital:27491
- Description: Helicobacter pylori is one of the most common pathogenic bacterial infections and is the leading cause of gastritis, gastroduodenal ulcer disease and gastric cancers. Studies have revealed the prevalence of Helicobacter pylori is high in many countries around the globe. Although Helicobacter pylori is highly sensitive to antimicrobial agents in vitro the clinical eradication rate of the disease is still low. The instability of API at gastric pH, low concentration of API in the gastric mucosa and short gastric residence times are the main reasons for poor eradication rates. The high prevalence rate of this disease necessitates the design and development of gastric-retentive site specific oral dosage forms for the optimized delivery of existing therapeutic molecules and may be an approach to improving the eradication rate of Helicobacter pylori. Metronidazole (MTZ) is a 5-nitroimidazole derivative that exhibits antibiotic and antiprotozoal activity. MTZ is used in combination with other compounds for the treatment of Helicobacter pylori in peptic ulcer disease. MTZ is a potential candidate for inclusion in a sustained release gastric-retentive delivery system that acts in the stomach and since it is unstable in the intestinal/colonic environment enhancing gastric residence time would be a therapeutic advantage. MTZ is a cost-effective therapy that exhibits good anti-microbial activity and has a favourable pharmacokinetic profile. A sustained release gastric-retentive formulation is therefore proposed as an approach to enhance the local delivery of MTZ and improve treatment outcomes for patients infected with Helicobacter pylori. A stability indicating Reversed-Phase High Performance Liquid Chromatography (RP- HPLC) method for the quantitation of MTZ in pharmaceutical dosage forms was developed and optimised using a Central Composite Design (CCD) approach. The RP-HPLC method was found to be linear, accurate, precise, sensitive, selective, and was applied to the analysis of MTZ in commercially available medicines. Preformulation studies were conducted as preparative work prior to manufacture gastric- retentive sustained release MTZ microcapsules. The experiments conducted were tailored for the development of sustained release MTZ microcapsules using a solvent evaporation method. The particle size and shape of the microcapsules was investigated using Scanning Electron Microscopy (SEM). MTZ- excipient compatibility studies were performed using Fourier Transform Infra-red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). The results revealed that no definite interaction between MTZ and intended excipients to be used for manufacture of MTZ formulations occurred. A solvent evaporation procedure was used for the manufacture of MTZ microcapsules. Preliminary formulations were manufactured using two different grades of Methocel® at various levels. In addition the impact of processing parameters on performance was also investigated. The formulations were assessed in terms of in vitro release, buoyancy, yield, encapsulation efficiency and microcapsule size. Formulation optimisation was undertaken using a CCD approach and numerical optimisation was used to predict an optimised formulation composition that would produce minimal initial MTZ release, maximum MTZ release at 12 hours and maximum buoyancy, encapsulation efficiency and yield. The kinetics of MTZ release from microcapsules was established by fitting in vitro release data to different mathematical models. Higuchi model and first-order model appeared to best fit the data as majority of the formulation batches had highest R2 values for these models. Short-term stability assessment of the optimised formulation was established by undertaking stability studies at 25°C/60% RH and 40°C/75%RH. No significant changes in any of the CQA were observed over 30 days of stability testing. A gas chromatographic (GC) method was developed and validated for the quantitation of residual acetone and n-hexane. The optimised formulation contained 213.60 ppm/g acetone and 25.23 ppm/g n-hexane which are well below the limits set for residual solvents. In conclusion, gastric-retentive sustained release MTZ microcapsules with potential for further development and optimisation have been successfully developed and assessed in these studies. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
Distributed leadership in South Africa
- Authors: Grant, Carolyn
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281024 , vital:55684 , xlink:href="https://doi.org/10.1080/13632434.2017.1360856"
- Description: Distributed leadership, while an established concept in the international literature on education leadership, is slowly gaining prominence in post-apartheid South Africa. This is primarily due to its normative and representational appeal. However, of concern is that the concept has become a catch-all phrase to describe any form of devolved or shared leadership and is being espoused as ‘the answer’ to the country’s educational leadership woes. Drawing on a South African publications-based doctoral study of distributed teacher leadership (Grant 2010. “Distributed Teacher Leadership: Troubling the Terrain.” Unpublished PhD diss., University of KwaZulu-Natal, Pietermaritzburg) for its evidence, this article argues for a theoretically robust form of distributed leadership conceptualised as socio-cultural practice and framed as a product of the joint interactions of school leaders, followers and aspects of their situation (Gronn 2000. “Distributed Properties: A New Architecture for Leadership.” Educational Management and Administration 28 (3): 317–338; Spillane, Halverson and Diamond 2004. “Towards a Theory of Leadership Practice: A Distributed Perspective.” Journal of Curriculum Studies 36 (1): 3–34; Spillane 2006. Distributed Leadership. San Francisco: Jossey-Bass). It endorses a sequential distributed leadership framing for the South African context and calls for further empirical studies which interrogate the complex practices of distributed school leadership. For without this theoretically robust work, the article argues, distributed leadership is likely to be relegated to the large pile of redundant leadership theories and become a passing fad.
- Full Text:
- Date Issued: 2017
- Authors: Grant, Carolyn
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281024 , vital:55684 , xlink:href="https://doi.org/10.1080/13632434.2017.1360856"
- Description: Distributed leadership, while an established concept in the international literature on education leadership, is slowly gaining prominence in post-apartheid South Africa. This is primarily due to its normative and representational appeal. However, of concern is that the concept has become a catch-all phrase to describe any form of devolved or shared leadership and is being espoused as ‘the answer’ to the country’s educational leadership woes. Drawing on a South African publications-based doctoral study of distributed teacher leadership (Grant 2010. “Distributed Teacher Leadership: Troubling the Terrain.” Unpublished PhD diss., University of KwaZulu-Natal, Pietermaritzburg) for its evidence, this article argues for a theoretically robust form of distributed leadership conceptualised as socio-cultural practice and framed as a product of the joint interactions of school leaders, followers and aspects of their situation (Gronn 2000. “Distributed Properties: A New Architecture for Leadership.” Educational Management and Administration 28 (3): 317–338; Spillane, Halverson and Diamond 2004. “Towards a Theory of Leadership Practice: A Distributed Perspective.” Journal of Curriculum Studies 36 (1): 3–34; Spillane 2006. Distributed Leadership. San Francisco: Jossey-Bass). It endorses a sequential distributed leadership framing for the South African context and calls for further empirical studies which interrogate the complex practices of distributed school leadership. For without this theoretically robust work, the article argues, distributed leadership is likely to be relegated to the large pile of redundant leadership theories and become a passing fad.
- Full Text:
- Date Issued: 2017