Seasonal population dynamics and energy consumption by waterbirds in a small temperate estuary
- Hean, Jeffrey W, Craig, Adrian J F K, Richoux, Nicole B
- Authors: Hean, Jeffrey W , Craig, Adrian J F K , Richoux, Nicole B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/456305 , vital:75501 , xlink:href="https://doi.org/10.2989/00306525.2016.1230897"
- Description: Simple measures of population dynamics and energy consumption can provide baseline information on the role of consumers in food webs, particularly for cryptic or highly-mobile species of waterbirds. We provide estimates of the seasonal population dynamics and energy consumption of waterbirds along the Kowie Estuary, South Africa. Ten census counts were conducted every month along the estuary from June 2013 to May 2014. Energy consumption and fresh-matter intake were calculated based on body-mass equations. Piscivorous birds dominated the waterbird assemblage during summer (up to 289 individuals), whereas non-migratory shorebirds were dominant at other times of the year. The total wet mass of prey items ingested by waterbirds ranged from 2.8 kg ha−1 during winter to 8.5 kg ha−1 during summer. The total energy consumption of waterbirds ranged from 12 543 kJ ha−1 during June to 33 104 kJ ha−1 during December. Shannon–Wiener diversity calculations revealed that the Kowie Estuary had a greater diversity of waterbirds than several other South African estuaries, but less diversity than many large European estuaries. Studies that incorporate census counts and energy consumption measures, although rudimentary, may provide valuable information on resource use by waterbirds in estuaries and may benefit conservation management schemes.
- Full Text:
- Date Issued: 2017
- Authors: Hean, Jeffrey W , Craig, Adrian J F K , Richoux, Nicole B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/456305 , vital:75501 , xlink:href="https://doi.org/10.2989/00306525.2016.1230897"
- Description: Simple measures of population dynamics and energy consumption can provide baseline information on the role of consumers in food webs, particularly for cryptic or highly-mobile species of waterbirds. We provide estimates of the seasonal population dynamics and energy consumption of waterbirds along the Kowie Estuary, South Africa. Ten census counts were conducted every month along the estuary from June 2013 to May 2014. Energy consumption and fresh-matter intake were calculated based on body-mass equations. Piscivorous birds dominated the waterbird assemblage during summer (up to 289 individuals), whereas non-migratory shorebirds were dominant at other times of the year. The total wet mass of prey items ingested by waterbirds ranged from 2.8 kg ha−1 during winter to 8.5 kg ha−1 during summer. The total energy consumption of waterbirds ranged from 12 543 kJ ha−1 during June to 33 104 kJ ha−1 during December. Shannon–Wiener diversity calculations revealed that the Kowie Estuary had a greater diversity of waterbirds than several other South African estuaries, but less diversity than many large European estuaries. Studies that incorporate census counts and energy consumption measures, although rudimentary, may provide valuable information on resource use by waterbirds in estuaries and may benefit conservation management schemes.
- Full Text:
- Date Issued: 2017
The effect of different dietary microalgae on the fatty acid profile, fecundity and population development of the calanoid copepod Pseudodiaptomus hessei (Copepoda: Calanoida)
- Siqwepu, Oyama, Richoux, Nicole B, Vine, Niall G
- Authors: Siqwepu, Oyama , Richoux, Nicole B , Vine, Niall G
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/456318 , vital:75502 , xlink:href="https://doi.org/10.1016/j.aquaculture.2016.10.008"
- Description: We studied the effect of dietary microalgae on the fecundity, population development, and fatty acid profile [with focus on the essential fatty acids docosahexaenoic acid (DHA; 22:6ω3) and eicosapentaenoic acid (EPA; 20:5ω3)] of the calanoid copepod Pseudodiaptomus hessei, a potential live food for finfish larvae in aquaculture. Two mono-algal diets, the Tahitian strain of Isochrysis galbana and Rhodomonas salina, and a 50:50 binary diet of the two were fed to copepods. Wild caught copepods were used as a baseline reference point. Copepods fed I. galbana and the 50:50 binary diet had high DHA:EPA ratios and DHA content relative to those fed R. salina. The EPA content of the copepods was similar for all three diets. Copepods fed R. salina had the highest fecundity relative to those fed I. galbana and the 50:50 binary diet. The largest population was obtained when the copepods were fed I. galbana, which differed from those fed R. salina and the 50:50 binary diet. The results of this study showed that the fatty acid composition of P. hessei can be altered by changing its dietary microalgae, and that the copepod can accumulate fatty acids from its diet, especially DHA and EPA. Diet also affected fecundity and population development of P. hessei, so this species represents a potential live food candidate for marine finfish larvae as its nutritional composition and productivity can be manipulated to suit the needs of marine finfish larvae.
- Full Text:
- Date Issued: 2017
- Authors: Siqwepu, Oyama , Richoux, Nicole B , Vine, Niall G
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/456318 , vital:75502 , xlink:href="https://doi.org/10.1016/j.aquaculture.2016.10.008"
- Description: We studied the effect of dietary microalgae on the fecundity, population development, and fatty acid profile [with focus on the essential fatty acids docosahexaenoic acid (DHA; 22:6ω3) and eicosapentaenoic acid (EPA; 20:5ω3)] of the calanoid copepod Pseudodiaptomus hessei, a potential live food for finfish larvae in aquaculture. Two mono-algal diets, the Tahitian strain of Isochrysis galbana and Rhodomonas salina, and a 50:50 binary diet of the two were fed to copepods. Wild caught copepods were used as a baseline reference point. Copepods fed I. galbana and the 50:50 binary diet had high DHA:EPA ratios and DHA content relative to those fed R. salina. The EPA content of the copepods was similar for all three diets. Copepods fed R. salina had the highest fecundity relative to those fed I. galbana and the 50:50 binary diet. The largest population was obtained when the copepods were fed I. galbana, which differed from those fed R. salina and the 50:50 binary diet. The results of this study showed that the fatty acid composition of P. hessei can be altered by changing its dietary microalgae, and that the copepod can accumulate fatty acids from its diet, especially DHA and EPA. Diet also affected fecundity and population development of P. hessei, so this species represents a potential live food candidate for marine finfish larvae as its nutritional composition and productivity can be manipulated to suit the needs of marine finfish larvae.
- Full Text:
- Date Issued: 2017
The relevance of cross-scale connections and spatial interactions for ecosystem service delivery by protected areas: Insights from southern Africa
- de Vos, Alta, Cumming, Graeme S, Roux, Dirk J
- Authors: de Vos, Alta , Cumming, Graeme S , Roux, Dirk J
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416438 , vital:71348 , xlink:href="https://doi.org/10.1016/j.ecoser.2017.11.014"
- Description: The ecosystem services (ES) concept can frame the value of protected areas (PAs) to society and identify management actions that bridge biodiversity conservation and human benefits. In this special issue on ES flows to and from southern African PAs we consider two themes: (1) water as a biophysical and social-ecological connector; and (2) cross-scale interactions and connections as influences on cultural ecosystem service (CES) provision. Freshwater flows have supporting, regulating, and cultural elements, leading to complexities in governance as well as place attachment, intellectual, and recreational services. Scale dependence in CES creates trade-offs that challenge the usefulness of the ES framework for PA management. Ecosystem service production can potentially create political support for PAs and helps to build connections and feedbacks that increase PA resilience. Papers in the feature highlight a need to understand trade-offs in optimising for biodiversity vs. particular bundles of ES; impacts of investment in built infrastructure on ES use; how managers facilitate ES; scale and heterogeneity as influences; the role of adaptive monitoring of PAs as social–ecological systems; and services and benefits from PAs that are not well-articulated in ES classifications. PA research can thus add nuance, depth and substance to broader thinking around CES.
- Full Text:
- Date Issued: 2017
- Authors: de Vos, Alta , Cumming, Graeme S , Roux, Dirk J
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416438 , vital:71348 , xlink:href="https://doi.org/10.1016/j.ecoser.2017.11.014"
- Description: The ecosystem services (ES) concept can frame the value of protected areas (PAs) to society and identify management actions that bridge biodiversity conservation and human benefits. In this special issue on ES flows to and from southern African PAs we consider two themes: (1) water as a biophysical and social-ecological connector; and (2) cross-scale interactions and connections as influences on cultural ecosystem service (CES) provision. Freshwater flows have supporting, regulating, and cultural elements, leading to complexities in governance as well as place attachment, intellectual, and recreational services. Scale dependence in CES creates trade-offs that challenge the usefulness of the ES framework for PA management. Ecosystem service production can potentially create political support for PAs and helps to build connections and feedbacks that increase PA resilience. Papers in the feature highlight a need to understand trade-offs in optimising for biodiversity vs. particular bundles of ES; impacts of investment in built infrastructure on ES use; how managers facilitate ES; scale and heterogeneity as influences; the role of adaptive monitoring of PAs as social–ecological systems; and services and benefits from PAs that are not well-articulated in ES classifications. PA research can thus add nuance, depth and substance to broader thinking around CES.
- Full Text:
- Date Issued: 2017
The use of experimental design for the development of a capillary zone electrophoresis method for the quantitation of captopril
- Mukozhiwa, S Y, Khamanga, Sandile M, Walker, Roderick B
- Authors: Mukozhiwa, S Y , Khamanga, Sandile M , Walker, Roderick B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183828 , vital:44073 , xlink:href="https://doi.org/10.1691/ph.2017.7071"
- Description: A capillary zone electrophoresis (CZE) method for the quantitation of captopril (CPT) using UV detection was developed. Influence of electrolyte concentration and system variables on electrophoretic separation was evaluated and a central composite design (CCD) was used to optimize the method. Variables investigated were pH, molarity, applied voltage and capillary length. The influence of sodium metabisulphite on the stability of test solutions was also investigated. The use of sodium metabisulphite prevented degradation of CPT over 24 hours. A fused uncoated silica capillary of 67.5cm total and 57.5 cm effective length was used for analysis. The applied voltage and capillary length affected the migration time of CPT significantly. A 20 mM phosphate buffer adjusted to pH 7.0 was used as running buffer and an applied voltage of 23.90 kV was suitable to effect a separation. The optimized electrophoretic conditions produced sharp, well-resolved peaks for CPT and sodium metabisulphite. Linear regression analysis of the response for CPT standards revealed the method was linear (R2 = 0.9995) over the range 5-70 μg/mL. The limits of quantitation and detection were 5 and 1.5 μg/mL. A simple, rapid and reliable CZE method has been developed and successfully applied to the analysis of commercially available CPT products.
- Full Text:
- Date Issued: 2017
- Authors: Mukozhiwa, S Y , Khamanga, Sandile M , Walker, Roderick B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183828 , vital:44073 , xlink:href="https://doi.org/10.1691/ph.2017.7071"
- Description: A capillary zone electrophoresis (CZE) method for the quantitation of captopril (CPT) using UV detection was developed. Influence of electrolyte concentration and system variables on electrophoretic separation was evaluated and a central composite design (CCD) was used to optimize the method. Variables investigated were pH, molarity, applied voltage and capillary length. The influence of sodium metabisulphite on the stability of test solutions was also investigated. The use of sodium metabisulphite prevented degradation of CPT over 24 hours. A fused uncoated silica capillary of 67.5cm total and 57.5 cm effective length was used for analysis. The applied voltage and capillary length affected the migration time of CPT significantly. A 20 mM phosphate buffer adjusted to pH 7.0 was used as running buffer and an applied voltage of 23.90 kV was suitable to effect a separation. The optimized electrophoretic conditions produced sharp, well-resolved peaks for CPT and sodium metabisulphite. Linear regression analysis of the response for CPT standards revealed the method was linear (R2 = 0.9995) over the range 5-70 μg/mL. The limits of quantitation and detection were 5 and 1.5 μg/mL. A simple, rapid and reliable CZE method has been developed and successfully applied to the analysis of commercially available CPT products.
- Full Text:
- Date Issued: 2017
Antibacterial effects of Alchornea cordifolia (Schumach. and Thonn.) Müll. Arg extracts and compounds on gastrointestinal, skin, respiratory and urinary tract pathogens
- Siwe-Noundou, Xavier, Krause, Rui W M, van Vuuren, Sandy, Tantoh Ndinteh, Derek, Olivier, Denise K
- Authors: Siwe-Noundou, Xavier , Krause, Rui W M , van Vuuren, Sandy , Tantoh Ndinteh, Derek , Olivier, Denise K
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/195418 , vital:45563 , xlink:href="https://doi.org/10.1016/j.jep.2015.12.043"
- Description: Ethnopharmacological relevance:The leaves, stems and roots ofAlchornea cordifolia(Schumach. andThonn.) Müll. Arg. are used as traditional medicine in many African countries for the management ofgastrointestinal, respiratory and urinary tract infections as well as for the treatment of wounds.Aim of the study:To determine the in vitro antibacterial activity of the crude extracts of leaves and stemsofA. cordifoliaon gastrointestinal, skin, respiratory and urinary tract pathogens and to identify thecompounds in the extracts that may be responsible for this activity.Materials and methods:The antibacterial activities of crude extracts [hexane, chloroform (CHCl3), ethylacetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O)] as well as pure compounds isolatedfrom these extracts were evaluated by means of the micro-dilution assay against four Gram-positivebacteria, i.e.Bacillus cereusATCC 11778,Enterococcus faecalisATCC 29212, Staphylococcus aureusATCC25923 andS. saprophyticusATCC 15305,as well as four Gram-negative bacterial strains, i.e.EscherichiacoliATCC 25922, Klebsiella pneumoniaeATCC 13883, Moraxella catarrhalisATCC 23246 andProteus mir-abilisATCC 43071. The isolation of the active constituents was undertaken by bio-autographic assays inconjunction with chromatographic techniques. The identification and characterisation of the isolatedcompounds were done using mass spectrometry (MS) and Fourier transformed infrared spectrometry(FTIR) as well as 1D- and 2D- nuclear magnetic resonance (NMR) analyses.Results:The leaves and stems ofA. cordifoliaexhibited varied antibacterial activity against all eight pa-thogens. Most of the MIC values ranged between 63 and 2000mg/ml. The highest activities for the crudeextracts (63mg/ml) were observed againstS. saprophyticus[stem (EtOAc, CHCl3and hexane), leaves(MeOH, EtOH, EtOAc and CHCl3)],E. coli[stem (MeOH and EtOH), leaves (MeOH, EtOH, EtOAc andCHCl3)],M. catarrhalis[leaves (EtOAc and CHCl3)],K. pneumoniae[stem (CHCl3), leaves (CHCl3)] andS.aureus[leaves (CHCl3)]. Seven constituents [stigmasterol (1), stigmasta-4,22-dien-3-one (2), friedelin (3),friedelane-3-one-28-al (4), 3-O-acetyl-aleuritolic acid (5), 3-O-acetyl-erythrodiol (6) and methyl-3,4,5-trihydroxybenzoate (methyl gallate) (7)] were isolated from the stem MeOH extract. All these com-pounds displayed some antibacterial activity against the eight pathogens with highest activity againstS.saprophyticus(2mg/ml). Furthermore, this is thefirst report of compounds1,2,3,4,6and7isolated fromA. cordifoliaand where a complete set of 2D-NMR data for fridelane-3-one-28-al (4) is presented.Conclusion:The study demonstrated that the antibacterial activities ofA. cordifoliaextracts may be dueto the presence of the seven isolated compounds, where compounds3–6showed the best activity. Theobserved activity against gastrointestinal, skin, respiratory and urinary tract pathogens supports thetraditional use for the treatment of such ailments.
- Full Text:
- Date Issued: 2016
- Authors: Siwe-Noundou, Xavier , Krause, Rui W M , van Vuuren, Sandy , Tantoh Ndinteh, Derek , Olivier, Denise K
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/195418 , vital:45563 , xlink:href="https://doi.org/10.1016/j.jep.2015.12.043"
- Description: Ethnopharmacological relevance:The leaves, stems and roots ofAlchornea cordifolia(Schumach. andThonn.) Müll. Arg. are used as traditional medicine in many African countries for the management ofgastrointestinal, respiratory and urinary tract infections as well as for the treatment of wounds.Aim of the study:To determine the in vitro antibacterial activity of the crude extracts of leaves and stemsofA. cordifoliaon gastrointestinal, skin, respiratory and urinary tract pathogens and to identify thecompounds in the extracts that may be responsible for this activity.Materials and methods:The antibacterial activities of crude extracts [hexane, chloroform (CHCl3), ethylacetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O)] as well as pure compounds isolatedfrom these extracts were evaluated by means of the micro-dilution assay against four Gram-positivebacteria, i.e.Bacillus cereusATCC 11778,Enterococcus faecalisATCC 29212, Staphylococcus aureusATCC25923 andS. saprophyticusATCC 15305,as well as four Gram-negative bacterial strains, i.e.EscherichiacoliATCC 25922, Klebsiella pneumoniaeATCC 13883, Moraxella catarrhalisATCC 23246 andProteus mir-abilisATCC 43071. The isolation of the active constituents was undertaken by bio-autographic assays inconjunction with chromatographic techniques. The identification and characterisation of the isolatedcompounds were done using mass spectrometry (MS) and Fourier transformed infrared spectrometry(FTIR) as well as 1D- and 2D- nuclear magnetic resonance (NMR) analyses.Results:The leaves and stems ofA. cordifoliaexhibited varied antibacterial activity against all eight pa-thogens. Most of the MIC values ranged between 63 and 2000mg/ml. The highest activities for the crudeextracts (63mg/ml) were observed againstS. saprophyticus[stem (EtOAc, CHCl3and hexane), leaves(MeOH, EtOH, EtOAc and CHCl3)],E. coli[stem (MeOH and EtOH), leaves (MeOH, EtOH, EtOAc andCHCl3)],M. catarrhalis[leaves (EtOAc and CHCl3)],K. pneumoniae[stem (CHCl3), leaves (CHCl3)] andS.aureus[leaves (CHCl3)]. Seven constituents [stigmasterol (1), stigmasta-4,22-dien-3-one (2), friedelin (3),friedelane-3-one-28-al (4), 3-O-acetyl-aleuritolic acid (5), 3-O-acetyl-erythrodiol (6) and methyl-3,4,5-trihydroxybenzoate (methyl gallate) (7)] were isolated from the stem MeOH extract. All these com-pounds displayed some antibacterial activity against the eight pathogens with highest activity againstS.saprophyticus(2mg/ml). Furthermore, this is thefirst report of compounds1,2,3,4,6and7isolated fromA. cordifoliaand where a complete set of 2D-NMR data for fridelane-3-one-28-al (4) is presented.Conclusion:The study demonstrated that the antibacterial activities ofA. cordifoliaextracts may be dueto the presence of the seven isolated compounds, where compounds3–6showed the best activity. Theobserved activity against gastrointestinal, skin, respiratory and urinary tract pathogens supports thetraditional use for the treatment of such ailments.
- Full Text:
- Date Issued: 2016
Efficient energy transfer in ethynyl bridged corrole–BODIPY dyads
- Yan, Yu, Wu, Fan, Qin, Jiawei, Xu, Haijun, Shi, Maohu, Zhou, Jingfeng, Mack, John, Fomo, Gertrude, Nyokong, Tebello, Shen, Zhen
- Authors: Yan, Yu , Wu, Fan , Qin, Jiawei , Xu, Haijun , Shi, Maohu , Zhou, Jingfeng , Mack, John , Fomo, Gertrude , Nyokong, Tebello , Shen, Zhen
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240899 , vital:50883 , xlink:href="https://doi.org/10.1039/C6RA12271J"
- Description: A series of new corrole–BODIPY dyads bridged by ethynyl linker moieties have been synthesized in high yields and fully characterized. The direction of energy transfer upon electronic excitation has been explored, and was found to be dependent on the number of corrole rings and their connection position on the BODIPY core. Intense bands in the absorption spectrum cover most of the visible region, which is potentially advantageous for capturing solar energy. Studies on the excitation spectra and lifetimes suggest that the energy transfer efficiency between the BODIPY and corrole moieties reaches almost 85%, which appears to be efficient in the context of energy transfer within the singlet manifold.
- Full Text:
- Date Issued: 2016
- Authors: Yan, Yu , Wu, Fan , Qin, Jiawei , Xu, Haijun , Shi, Maohu , Zhou, Jingfeng , Mack, John , Fomo, Gertrude , Nyokong, Tebello , Shen, Zhen
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240899 , vital:50883 , xlink:href="https://doi.org/10.1039/C6RA12271J"
- Description: A series of new corrole–BODIPY dyads bridged by ethynyl linker moieties have been synthesized in high yields and fully characterized. The direction of energy transfer upon electronic excitation has been explored, and was found to be dependent on the number of corrole rings and their connection position on the BODIPY core. Intense bands in the absorption spectrum cover most of the visible region, which is potentially advantageous for capturing solar energy. Studies on the excitation spectra and lifetimes suggest that the energy transfer efficiency between the BODIPY and corrole moieties reaches almost 85%, which appears to be efficient in the context of energy transfer within the singlet manifold.
- Full Text:
- Date Issued: 2016
Fluorescence properties of alloyed ZnSeS quantum dots overcoated with ZnTe and ZnTe/ZnS shells
- Adegoke, Oluwasesan, Mashazi, Philani N, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Mashazi, Philani N , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240754 , vital:50868 , xlink:href="https://doi.org/10.1016/j.optmat.2016.02.024"
- Description: Fluorescent alloyed ternary ZnSeS quantum dots (QDs) have been synthesized via the pyrolysis of organometallic precursors. The effects of passivation of ZnTe and ZnTe/ZnS shells on the optical properties of the ternary alloyed ZnSeS core have been studied. A ligand exchange reaction using L-cysteine as a capping ligand was used to obtain water-soluble nanocrystals. The nanocrystals were each characterized by UV/vis absorption and fluorescence spectroscopy, transmission electron microscopy, X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) quantum yield (QY) of alloyed ZnSeS QDs was 14% and this value increased to 27% when ZnTe was overcoated around the surface but further coating with a ZnS shell decreased the PL QY slightly to 24%. This implies that ZnTe shell suppressed non-radiative recombination exciton states in the alloyed core while further layering with a ZnS shell offered no further improvement in suppressing the defect states. XPS analysis confirmed the presence of the first shell layering but showed a weakened intensity signal of S (2p) and Se (3d) for the ZnSeS/ZnTe/ZnS QDs. Our work demonstrates for the first time that shell passivation of alloyed Zn-based QDs can offer improved optical properties. We hope the optical information presented in this work will be useful in the selection of alloyed Zn-based QDs appropriate for the intended application.
- Full Text:
- Date Issued: 2016
- Authors: Adegoke, Oluwasesan , Mashazi, Philani N , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240754 , vital:50868 , xlink:href="https://doi.org/10.1016/j.optmat.2016.02.024"
- Description: Fluorescent alloyed ternary ZnSeS quantum dots (QDs) have been synthesized via the pyrolysis of organometallic precursors. The effects of passivation of ZnTe and ZnTe/ZnS shells on the optical properties of the ternary alloyed ZnSeS core have been studied. A ligand exchange reaction using L-cysteine as a capping ligand was used to obtain water-soluble nanocrystals. The nanocrystals were each characterized by UV/vis absorption and fluorescence spectroscopy, transmission electron microscopy, X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) quantum yield (QY) of alloyed ZnSeS QDs was 14% and this value increased to 27% when ZnTe was overcoated around the surface but further coating with a ZnS shell decreased the PL QY slightly to 24%. This implies that ZnTe shell suppressed non-radiative recombination exciton states in the alloyed core while further layering with a ZnS shell offered no further improvement in suppressing the defect states. XPS analysis confirmed the presence of the first shell layering but showed a weakened intensity signal of S (2p) and Se (3d) for the ZnSeS/ZnTe/ZnS QDs. Our work demonstrates for the first time that shell passivation of alloyed Zn-based QDs can offer improved optical properties. We hope the optical information presented in this work will be useful in the selection of alloyed Zn-based QDs appropriate for the intended application.
- Full Text:
- Date Issued: 2016
Molecular identification of Azolla invasions in Africa: The Azolla specialist, Stenopelmus rufinasus proves to be an excellent taxonomist
- Madeira, P T, Dray, F Allen, Coetzee, Julie A, Paterson, Iain D, Tipping, Philip W
- Authors: Madeira, P T , Dray, F Allen , Coetzee, Julie A , Paterson, Iain D , Tipping, Philip W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424765 , vital:72182 , xlink:href="https://doi.org/10.1016/j.sajb.2016.03.007"
- Description: Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla that was not used during host specificity trials. A. pinnata subsp. africana was only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three. What was thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.
- Full Text:
- Date Issued: 2016
- Authors: Madeira, P T , Dray, F Allen , Coetzee, Julie A , Paterson, Iain D , Tipping, Philip W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424765 , vital:72182 , xlink:href="https://doi.org/10.1016/j.sajb.2016.03.007"
- Description: Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla that was not used during host specificity trials. A. pinnata subsp. africana was only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three. What was thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.
- Full Text:
- Date Issued: 2016
DNA-based identification of Lepidoptera associated with citrus in South Africa
- Marsberg, Tamryn, Hill, Martin P, Moore, Sean D, Timm, Alicia E
- Authors: Marsberg, Tamryn , Hill, Martin P , Moore, Sean D , Timm, Alicia E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405782 , vital:70205 , xlink:href="https://hdl.handle.net/10520/EJC167513"
- Description: A number of insects, primarily Lepidoptera, cause damage to citrus in South Africa. A major limitation to the management and control of these pests is their correct identification. The aim of this study was to develop a database of gene sequences to aid in the identification of these Lepidoptera. Multiple specimens of 12 species were sequenced for the ~650 bp of the cytochrome oxidase I gene. These sequence data were supplemented and validated using sequences available in public databases. Results showed that each species could be unambiguously identified, and neighbour-joining analysis based on K2P distances formed highly supported, distinct clusters for each species, i.e. the maximum intraspecific genetic distance was less than that of the minimum interspecific genetic distances. Thus, this data set provides a molecular means to successfully identify the most important Lepidoptera associated with citrus in South Africa.
- Full Text:
- Date Issued: 2015
- Authors: Marsberg, Tamryn , Hill, Martin P , Moore, Sean D , Timm, Alicia E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405782 , vital:70205 , xlink:href="https://hdl.handle.net/10520/EJC167513"
- Description: A number of insects, primarily Lepidoptera, cause damage to citrus in South Africa. A major limitation to the management and control of these pests is their correct identification. The aim of this study was to develop a database of gene sequences to aid in the identification of these Lepidoptera. Multiple specimens of 12 species were sequenced for the ~650 bp of the cytochrome oxidase I gene. These sequence data were supplemented and validated using sequences available in public databases. Results showed that each species could be unambiguously identified, and neighbour-joining analysis based on K2P distances formed highly supported, distinct clusters for each species, i.e. the maximum intraspecific genetic distance was less than that of the minimum interspecific genetic distances. Thus, this data set provides a molecular means to successfully identify the most important Lepidoptera associated with citrus in South Africa.
- Full Text:
- Date Issued: 2015
Enhanced triplet state yields in aqueous media of asymmetric zinc phthalocyanines when conjugated to silver nanoflowers
- D'Souza, Sarah, George, Reama, Göksel, Meltem, Atilla, Devrim, Durmus, Mahmut, Nyokong, Tebello
- Authors: D'Souza, Sarah , George, Reama , Göksel, Meltem , Atilla, Devrim , Durmus, Mahmut , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189099 , vital:44816 , xlink:href="https://doi.org/10.1016/j.poly.2015.08.017"
- Description: Novel low symmetry water-soluble zinc phthalocyanines (ZnPcs, complexes 1 and 2) were synthesized and then mixed with silver nanoflowers. Photophysical and photochemical studies were performed in order to determine the efficiency of complexes 1 and 2 as photosensitizers when alone and when combined with the silver nanoflowers. The Pcs show low fluorescence quantum yields and excellent triplet quantum yields of 0.78 (for 1) and 0.66 (for 2) in aqueous media. The triplet quantum yield values increased to 0.80 and 0.89, respectively, in the presence of silver nanoflowers. Long triplet lifetimes ranging from 180 to 200 μs in DMSO were obtained for complexes 1, 2 and their conjugates with silver nanoflowers.
- Full Text:
- Date Issued: 2015
- Authors: D'Souza, Sarah , George, Reama , Göksel, Meltem , Atilla, Devrim , Durmus, Mahmut , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189099 , vital:44816 , xlink:href="https://doi.org/10.1016/j.poly.2015.08.017"
- Description: Novel low symmetry water-soluble zinc phthalocyanines (ZnPcs, complexes 1 and 2) were synthesized and then mixed with silver nanoflowers. Photophysical and photochemical studies were performed in order to determine the efficiency of complexes 1 and 2 as photosensitizers when alone and when combined with the silver nanoflowers. The Pcs show low fluorescence quantum yields and excellent triplet quantum yields of 0.78 (for 1) and 0.66 (for 2) in aqueous media. The triplet quantum yield values increased to 0.80 and 0.89, respectively, in the presence of silver nanoflowers. Long triplet lifetimes ranging from 180 to 200 μs in DMSO were obtained for complexes 1, 2 and their conjugates with silver nanoflowers.
- Full Text:
- Date Issued: 2015
Food preferences of the estuarine crab Sesarma catenata estimated through laboratory experiments
- Bergamino, Leandro, Richoux, Nicole B
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457256 , vital:75620 , xlink:href="https://doi.org/10.1071/MF14122"
- Description: Feeding by sesarmid crabs on plants represents an important energy pathway within some estuarine ecosystems. We examined the trophic ecology of estuarine sesarmid crabs Sesarma catenata through a series of laboratory feeding-preference experiments. Our experiments considered decomposed and mature leaves of terrestrial riparian trees, marsh plants Chenolea diffusa and Sarcocornia perennis and the marshgrass Spartina maritima as potential food items. S. catenata preferred decomposed leaves of terrestrial riparian trees, followed by decomposed and mature leaves of S. maritima. We suggest that the low carbon:nitrogen (C:N) ratios of S. maritima and high bacterial production associated with decomposed terrestrial leaves may explain the trophic behaviour of S. catenata. The faecal production by S. catenata during these experiments confirmed the preferential assimilation of decomposed material by the crabs. By combining the consumption rates with an estimated density of S. catenata within the local estuary that it inhabits, we suggest that moderate proportions of the leaf material can potentially be consumed by this species (34% of total leaf litter), leaving substantial amounts of unconsumed leaf litter that may represent an important subsidy for adjacent environments. Our results validate previously published trophic data, showing the value of linking feeding experiments with biological tracers to improve food-web models.
- Full Text:
- Date Issued: 2015
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457256 , vital:75620 , xlink:href="https://doi.org/10.1071/MF14122"
- Description: Feeding by sesarmid crabs on plants represents an important energy pathway within some estuarine ecosystems. We examined the trophic ecology of estuarine sesarmid crabs Sesarma catenata through a series of laboratory feeding-preference experiments. Our experiments considered decomposed and mature leaves of terrestrial riparian trees, marsh plants Chenolea diffusa and Sarcocornia perennis and the marshgrass Spartina maritima as potential food items. S. catenata preferred decomposed leaves of terrestrial riparian trees, followed by decomposed and mature leaves of S. maritima. We suggest that the low carbon:nitrogen (C:N) ratios of S. maritima and high bacterial production associated with decomposed terrestrial leaves may explain the trophic behaviour of S. catenata. The faecal production by S. catenata during these experiments confirmed the preferential assimilation of decomposed material by the crabs. By combining the consumption rates with an estimated density of S. catenata within the local estuary that it inhabits, we suggest that moderate proportions of the leaf material can potentially be consumed by this species (34% of total leaf litter), leaving substantial amounts of unconsumed leaf litter that may represent an important subsidy for adjacent environments. Our results validate previously published trophic data, showing the value of linking feeding experiments with biological tracers to improve food-web models.
- Full Text:
- Date Issued: 2015
Optical properties of water-soluble L-cysteine-capped alloyed CdSeS quantum dot passivated with ZnSeTe and ZnSeTe/ZnS shells
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193609 , vital:45352 , xlink:href="https://doi.org/10.1016/j.optmat.2015.05.024"
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing L-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed L-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties.
- Full Text:
- Date Issued: 2015
PFB0595w is a Plasmodium falciparum J protein that co-localizes with PfHsp70-1 and can stimulate its in vitro ATP hydrolysis activity
- Njunge, James M, Mandal, Pradipta, Przyborski, Jude M, Boshoff, Aileen, Pesce, Eva-Rachele, Blatch, Gregory L
- Authors: Njunge, James M , Mandal, Pradipta , Przyborski, Jude M , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431739 , vital:72800 , xlink:href="https://doi.org/10.1016/j.biocel.2015.02.008"
- Description: Heat shock proteins, many of which function as molecular chaperones, play important roles in the lifecycle and pathogenesis of the malaria parasite, Plasmodium falciparum. The P. falciparum heat shock protein 70 (PfHsp70) family of chaperones is potentially regulated by a large complement of J proteins that localize to various intracellular compartments including the infected erythrocyte cytosol. While PfHsp70-1 has been shown to be an abundant cytosolic chaperone, its regulation by J proteins is poorly understood. In this study, we characterized the J protein PFB0595w, a homologue of the well-studied yeast cytosolic J protein, Sis1. PFB0595w, similarly to PfHsp70-1, was localized to the parasite cytosol and its expression was upregulated by heat shock. Additionally, recombinant PFB0595w was shown to be dimeric and to stimulate the in vitro ATPase activity of PfHsp70-1. Overall, the expression, localization and biochemical data for PFB0595w suggest that it may function as a cochaperone of PfHsp70-1, and advances current knowledge on the chaperone machinery of the parasite.
- Full Text:
- Date Issued: 2015
- Authors: Njunge, James M , Mandal, Pradipta , Przyborski, Jude M , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431739 , vital:72800 , xlink:href="https://doi.org/10.1016/j.biocel.2015.02.008"
- Description: Heat shock proteins, many of which function as molecular chaperones, play important roles in the lifecycle and pathogenesis of the malaria parasite, Plasmodium falciparum. The P. falciparum heat shock protein 70 (PfHsp70) family of chaperones is potentially regulated by a large complement of J proteins that localize to various intracellular compartments including the infected erythrocyte cytosol. While PfHsp70-1 has been shown to be an abundant cytosolic chaperone, its regulation by J proteins is poorly understood. In this study, we characterized the J protein PFB0595w, a homologue of the well-studied yeast cytosolic J protein, Sis1. PFB0595w, similarly to PfHsp70-1, was localized to the parasite cytosol and its expression was upregulated by heat shock. Additionally, recombinant PFB0595w was shown to be dimeric and to stimulate the in vitro ATPase activity of PfHsp70-1. Overall, the expression, localization and biochemical data for PFB0595w suggest that it may function as a cochaperone of PfHsp70-1, and advances current knowledge on the chaperone machinery of the parasite.
- Full Text:
- Date Issued: 2015
Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
Synthesis and Photophysical Investigation of Tetraazaporphyrin Substituted with Aggregation‐Induced Emission (AIE) Active Moieties
- Tasso, Thiago T, Furuyama, Taniyuki, Mack, John, Nyokong, Tebello, Kobayashi, Nagao
- Authors: Tasso, Thiago T , Furuyama, Taniyuki , Mack, John , Nyokong, Tebello , Kobayashi, Nagao
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193553 , vital:45346 , xlink:href="https://doi.org/10.1002/ejic.201500726"
- Description: The synthesis and characterization of free-base and ZnII tetraazaporphyrins with tetraphenylethylene (TPE) or diphenylphenanthrene (DPP) moieties that are known to be aggregation-induced emission (AIE) active is reported. The optical spectra contain the characteristic Q and B absorption bands of Gouterman's four-orbital model and a broad envelope of weaker charge-transfer bands in the 450–600 nm region. The observed fluorescence emission lies beyond 670 nm and originates exclusively from the decay of the S1 state of the macrocycle, regardless of the excitation wavelength used. Theoretical calculations provide further evidence of strong electronic communication between the peripheral TPE or DPP moieties and the central ring. The ZnII complexes were found to have relatively high singlet-oxygen quantum yields.
- Full Text:
- Date Issued: 2015
- Authors: Tasso, Thiago T , Furuyama, Taniyuki , Mack, John , Nyokong, Tebello , Kobayashi, Nagao
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193553 , vital:45346 , xlink:href="https://doi.org/10.1002/ejic.201500726"
- Description: The synthesis and characterization of free-base and ZnII tetraazaporphyrins with tetraphenylethylene (TPE) or diphenylphenanthrene (DPP) moieties that are known to be aggregation-induced emission (AIE) active is reported. The optical spectra contain the characteristic Q and B absorption bands of Gouterman's four-orbital model and a broad envelope of weaker charge-transfer bands in the 450–600 nm region. The observed fluorescence emission lies beyond 670 nm and originates exclusively from the decay of the S1 state of the macrocycle, regardless of the excitation wavelength used. Theoretical calculations provide further evidence of strong electronic communication between the peripheral TPE or DPP moieties and the central ring. The ZnII complexes were found to have relatively high singlet-oxygen quantum yields.
- Full Text:
- Date Issued: 2015
The influence of livelihood dependency, local ecological knowledge and market proximity on the ecological impacts of harvesting non-timber forest products
- Steele, Melita Z, Shackleton, Charlie M, Shaanker, Ramanan U, Ganeshaiah, Kotiganahalli N, Radloff, Sarah E
- Authors: Steele, Melita Z , Shackleton, Charlie M , Shaanker, Ramanan U , Ganeshaiah, Kotiganahalli N , Radloff, Sarah E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180908 , vital:43669 , xlink:href="https://doi.org/10.1016/j.forpol.2014.07.011"
- Description: It is well established that non-timber forest products make significant contributions to rural incomes throughout most of the developing world. NTFP use frequently raises concerns about the sustainability of, or ecological impacts associated with, NTFP harvesting, as well as local contextual factors which may limit or reduce the impacts. Here we test the conceptual model first advanced by Uma Shaanker et al. (2004) relating to the factors that may limit or exacerbate the ecological impacts associated with NTFP harvesting. These were the extent of local dependence on NTFPs, the degree of marketing and the level of local ecological knowledge. Data were collected via household questionnaires and ecological surveys of woody plants from eight villages throughout South Africa. We found no significant relationships between measures of ecological impact with local ecological knowledge or market proximity and engagement. There was a strong positive relationship between ecological impacts and NTFP dependency as indexed through mean annual direct-use value for NTFPs. This indicates that the higher the dependency and demand for NTFPs, the greater is the possibility of high impacts to the local environment. However, other contextual drivers not included in the original Uma Shaanker et al. (2004) model may also play a role, particularly the strength of local resource governance institutions.
- Full Text: false
- Date Issued: 2015
- Authors: Steele, Melita Z , Shackleton, Charlie M , Shaanker, Ramanan U , Ganeshaiah, Kotiganahalli N , Radloff, Sarah E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180908 , vital:43669 , xlink:href="https://doi.org/10.1016/j.forpol.2014.07.011"
- Description: It is well established that non-timber forest products make significant contributions to rural incomes throughout most of the developing world. NTFP use frequently raises concerns about the sustainability of, or ecological impacts associated with, NTFP harvesting, as well as local contextual factors which may limit or reduce the impacts. Here we test the conceptual model first advanced by Uma Shaanker et al. (2004) relating to the factors that may limit or exacerbate the ecological impacts associated with NTFP harvesting. These were the extent of local dependence on NTFPs, the degree of marketing and the level of local ecological knowledge. Data were collected via household questionnaires and ecological surveys of woody plants from eight villages throughout South Africa. We found no significant relationships between measures of ecological impact with local ecological knowledge or market proximity and engagement. There was a strong positive relationship between ecological impacts and NTFP dependency as indexed through mean annual direct-use value for NTFPs. This indicates that the higher the dependency and demand for NTFPs, the greater is the possibility of high impacts to the local environment. However, other contextual drivers not included in the original Uma Shaanker et al. (2004) model may also play a role, particularly the strength of local resource governance institutions.
- Full Text: false
- Date Issued: 2015
The politics of interweaving performance cultures
- Authors: Krueger, Anton
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225719 , vital:49252 , xlink:href="https://doi.org/10.1080/10137548.2015.1014170"
- Description: According to the former president of the International Federation of Theatre Research (IFTR), Brian Singleton, the study of ‘[i]nterculturalism as a practice and a theory gained currency with Richard Schechner’s anthropologically-inspired new discipline of performance studies’ (p. 79). Schechner’s new discipline led to the formation of the annual Performance Studies International (PSI) conferences, and earlier this year I attended the twentieth instalment in Shanghai, which was held under the rubric of ‘Tradition and the Avant-Garde’. One of the things which struck me was the extent to which the (relatively) newly economically empowered Chinese theatre makers were creating grand productions based on Western theatre traditions. For example, many of the presentations for delegates were based on Western texts (such as Hamlet, Miss Julie and even a play by Woody Allen). And yet these productions were performed in Mandarin, using purist Chinese forms, such as Beijing Opera. During the discussions there seemed to be an awkward defensiveness from some of the Chinese hosts who insisted they were not ‘copying’ Western theatre, but that they were using it to express a pure Chinese aesthetic. There were also other performances at the conference, such as a series of parables called Confucius Disciples, which told didactic tales with content very foreign to a Western audience. A visiting troupe from Bulgaria presented their own version of some of these parables, using a strongly East European aesthetic to convey a Chinese message. In this way, experiments with cultural forms and content were clearly foregrounded by the conference presentations.
- Full Text:
- Date Issued: 2015
- Authors: Krueger, Anton
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225719 , vital:49252 , xlink:href="https://doi.org/10.1080/10137548.2015.1014170"
- Description: According to the former president of the International Federation of Theatre Research (IFTR), Brian Singleton, the study of ‘[i]nterculturalism as a practice and a theory gained currency with Richard Schechner’s anthropologically-inspired new discipline of performance studies’ (p. 79). Schechner’s new discipline led to the formation of the annual Performance Studies International (PSI) conferences, and earlier this year I attended the twentieth instalment in Shanghai, which was held under the rubric of ‘Tradition and the Avant-Garde’. One of the things which struck me was the extent to which the (relatively) newly economically empowered Chinese theatre makers were creating grand productions based on Western theatre traditions. For example, many of the presentations for delegates were based on Western texts (such as Hamlet, Miss Julie and even a play by Woody Allen). And yet these productions were performed in Mandarin, using purist Chinese forms, such as Beijing Opera. During the discussions there seemed to be an awkward defensiveness from some of the Chinese hosts who insisted they were not ‘copying’ Western theatre, but that they were using it to express a pure Chinese aesthetic. There were also other performances at the conference, such as a series of parables called Confucius Disciples, which told didactic tales with content very foreign to a Western audience. A visiting troupe from Bulgaria presented their own version of some of these parables, using a strongly East European aesthetic to convey a Chinese message. In this way, experiments with cultural forms and content were clearly foregrounded by the conference presentations.
- Full Text:
- Date Issued: 2015
Trophic relationships of hake (Merluccius capensis and M. paradoxus) and sharks (Centrophorus squamosus, Deania calcea and D. profundorum) in the Northern (Namibia) Benguela Current region
- Iitembu, J A, Richoux, Nicole B
- Authors: Iitembu, J A , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457418 , vital:75636 , xlink:href="https://hdl.handle.net/10520/EJC183122"
- Description: The trophic relationships of two hake species (Merluccius capensis and M. paradoxus) and three shark species (Centrophorus squamosus, Deania calcea and D. profundorum) were investigated using nitrogen and carbon stable isotope signatures (15N and 13C) of their muscle tissues. The sharks were more enriched in 15N than the hake, an indication of the apex predator status of sharks. Among the sharks considered, C. squamosus occupied the highest trophic level and fed primarily on benthic prey. The two species of shark from the genus Deania were not different based on 15N or 13C, so they had similar diets. The 13C signatures indicated that M. capensis and sharks fed on prey derived from similar basal resources. However, there was a significant difference in 13C between M. paradoxus and all other species examined, suggesting that they occupied different feeding niches. Isotope-based populationmetrics showed narrower trophic ranges in sharks than M. capensis. Carbon and nitrogen ranges indicated that hake fed on a more diverse pool of carbon sources and had generally more enhanced trophic diversity in their feeding patterns than sharks. Among the species considered, C. squamosus occupied a unique isotopic space. Our results supported the hypothesis there are trophic overlaps among these species, but some interesting differentiation was revealed.
- Full Text:
- Date Issued: 2015
- Authors: Iitembu, J A , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457418 , vital:75636 , xlink:href="https://hdl.handle.net/10520/EJC183122"
- Description: The trophic relationships of two hake species (Merluccius capensis and M. paradoxus) and three shark species (Centrophorus squamosus, Deania calcea and D. profundorum) were investigated using nitrogen and carbon stable isotope signatures (15N and 13C) of their muscle tissues. The sharks were more enriched in 15N than the hake, an indication of the apex predator status of sharks. Among the sharks considered, C. squamosus occupied the highest trophic level and fed primarily on benthic prey. The two species of shark from the genus Deania were not different based on 15N or 13C, so they had similar diets. The 13C signatures indicated that M. capensis and sharks fed on prey derived from similar basal resources. However, there was a significant difference in 13C between M. paradoxus and all other species examined, suggesting that they occupied different feeding niches. Isotope-based populationmetrics showed narrower trophic ranges in sharks than M. capensis. Carbon and nitrogen ranges indicated that hake fed on a more diverse pool of carbon sources and had generally more enhanced trophic diversity in their feeding patterns than sharks. Among the species considered, C. squamosus occupied a unique isotopic space. Our results supported the hypothesis there are trophic overlaps among these species, but some interesting differentiation was revealed.
- Full Text:
- Date Issued: 2015
Application of carbon black and iron phthalocyanine composites in bioelectricity production at a brewery wastewater fed microbial fuel cell
- Mshoperi, Edith, Fogel, Ronen, Limson, Janice
- Authors: Mshoperi, Edith , Fogel, Ronen , Limson, Janice
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431050 , vital:72740 , xlink:href="https://doi.org/10.1016/j.electacta.2013.11.01"
- Description: Aerobic cathode microbial fuel cells (MFCs) have been widely researched to provide bioremediation of wastewaters, coupled to sustainable energy production. In order to effectively accomplish this aim, suitable catalysts and catalyst supports for oxygen reduction reaction (ORR) are required. While iron phthaloycanine (FePc), supported on multi-walled carbon nanotubes has previously been studied for this function, cost of industrial production may hinder this. Importantly, this study examines the use of several available grades of carbon black for their relative suitability to perform as supports for FePc in MFC formats. Voltammetric studies showed that the different grades of carbon black provided varying lowering of the ORR overpotential, between ∼160 and ∼270 mV relative to unmodified GCEs, and an optimum grade (N326) was selected for further study. Carbon black/FePC composite electrodes exhibited comparable lowering of the ORR overpotential (606 mV) to potentials previously reported to nanotube/FePc composites (620 mV), as well as lowered charge-transfer resistance compared to electrodes solely modified with FePc. When applied as cathode modifiers in dual chambered MFCs utilising Enterobacter cloacae, the combined use of carbon black and FePc provided greater power densities than either alone; composite electrodes obtaining ∼400% power density, compared to unmodified electrodes. Modification of the anode with carbon black further increased power density, generating power densities an order of magnitude larger than those obtained at unmodified electrodes. The ability of beer brewery waste water (BBWW) to generate power at these modified surfaces yielded permissible power densities (∼40% that of reinforced clostridial media). Differences observed, in particular under agitation, are attributed to variations in nutrient content and nutrient complexity, between the two fuel substrates.
- Full Text:
- Date Issued: 2014
- Authors: Mshoperi, Edith , Fogel, Ronen , Limson, Janice
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431050 , vital:72740 , xlink:href="https://doi.org/10.1016/j.electacta.2013.11.01"
- Description: Aerobic cathode microbial fuel cells (MFCs) have been widely researched to provide bioremediation of wastewaters, coupled to sustainable energy production. In order to effectively accomplish this aim, suitable catalysts and catalyst supports for oxygen reduction reaction (ORR) are required. While iron phthaloycanine (FePc), supported on multi-walled carbon nanotubes has previously been studied for this function, cost of industrial production may hinder this. Importantly, this study examines the use of several available grades of carbon black for their relative suitability to perform as supports for FePc in MFC formats. Voltammetric studies showed that the different grades of carbon black provided varying lowering of the ORR overpotential, between ∼160 and ∼270 mV relative to unmodified GCEs, and an optimum grade (N326) was selected for further study. Carbon black/FePC composite electrodes exhibited comparable lowering of the ORR overpotential (606 mV) to potentials previously reported to nanotube/FePc composites (620 mV), as well as lowered charge-transfer resistance compared to electrodes solely modified with FePc. When applied as cathode modifiers in dual chambered MFCs utilising Enterobacter cloacae, the combined use of carbon black and FePc provided greater power densities than either alone; composite electrodes obtaining ∼400% power density, compared to unmodified electrodes. Modification of the anode with carbon black further increased power density, generating power densities an order of magnitude larger than those obtained at unmodified electrodes. The ability of beer brewery waste water (BBWW) to generate power at these modified surfaces yielded permissible power densities (∼40% that of reinforced clostridial media). Differences observed, in particular under agitation, are attributed to variations in nutrient content and nutrient complexity, between the two fuel substrates.
- Full Text:
- Date Issued: 2014
Carbon nanotube-enhanced photoelectrochemical properties of metallo-octacarboxyphthalocyanines
- Mphahlele, Nonhlanhla E, Le Roux, Lukas, Jafta, Charl J, Cele, Leskev, Mathe, Mkhulu K, Nyokong, Tebello, Kobayashi, Nagao, Ozoemena, Kenneth I
- Authors: Mphahlele, Nonhlanhla E , Le Roux, Lukas , Jafta, Charl J , Cele, Leskev , Mathe, Mkhulu K , Nyokong, Tebello , Kobayashi, Nagao , Ozoemena, Kenneth I
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241595 , vital:50953 , xlink:href="https://doi.org/10.1007/s10853-013-7710-1"
- Description: The photoelectrochemistry of metallo-octacarboxyphthalocyanines (MOCPc, where M = Zn or Si(OH)2) integrated with MWCNTs for the development of dye-sensitized solar cells (DSSCs) is reported. The DSSC performance (obtained from the photo-chronoamperometric and photo-impedimetric data) decreased as ZnOCPc > (OH)2SiOCPc. The incorporation of the MWCNTs on the surface of the TiO2 film (MOCPc–MWCNT systems) gave higher photocurrent density than the bare MOCPc complexes. Also, from the EIS results, the MOCPc–MWCNT hybrids gave faster charge transport kinetics (approximately three times faster) compared to the bare MOCPc complexes. The electron lifetime was slightly longer (ca. 6 ms) at the ZnOCPc systems than at the (OH)2SiOCPc system (ca. 4 ms) meaning that the presence of the MWCNTs on the surface of the TiO2 film did not show any significant improvement on preventing charge recombination process.
- Full Text:
- Date Issued: 2014
- Authors: Mphahlele, Nonhlanhla E , Le Roux, Lukas , Jafta, Charl J , Cele, Leskev , Mathe, Mkhulu K , Nyokong, Tebello , Kobayashi, Nagao , Ozoemena, Kenneth I
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241595 , vital:50953 , xlink:href="https://doi.org/10.1007/s10853-013-7710-1"
- Description: The photoelectrochemistry of metallo-octacarboxyphthalocyanines (MOCPc, where M = Zn or Si(OH)2) integrated with MWCNTs for the development of dye-sensitized solar cells (DSSCs) is reported. The DSSC performance (obtained from the photo-chronoamperometric and photo-impedimetric data) decreased as ZnOCPc > (OH)2SiOCPc. The incorporation of the MWCNTs on the surface of the TiO2 film (MOCPc–MWCNT systems) gave higher photocurrent density than the bare MOCPc complexes. Also, from the EIS results, the MOCPc–MWCNT hybrids gave faster charge transport kinetics (approximately three times faster) compared to the bare MOCPc complexes. The electron lifetime was slightly longer (ca. 6 ms) at the ZnOCPc systems than at the (OH)2SiOCPc system (ca. 4 ms) meaning that the presence of the MWCNTs on the surface of the TiO2 film did not show any significant improvement on preventing charge recombination process.
- Full Text:
- Date Issued: 2014