Macroinvertebrate communities associated with duckweed (Lemnaceae) in two Eastern Cape rivers, South Africa
- Muskett, Phillippa C, Hill, Jaclyn M, Weyl, Philip S R
- Authors: Muskett, Phillippa C , Hill, Jaclyn M , Weyl, Philip S R
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444065 , vital:74182 , https://doi.org/10.2989/16085914.2016.1241173
- Description: The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.
- Full Text:
- Date Issued: 2016
- Authors: Muskett, Phillippa C , Hill, Jaclyn M , Weyl, Philip S R
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444065 , vital:74182 , https://doi.org/10.2989/16085914.2016.1241173
- Description: The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.
- Full Text:
- Date Issued: 2016
Mapping epistemic cultures and learning potential of participants in citizen science projects
- Vallabh, Priya, Lotz-Sisitka, Heila, O'Donoghue, Rob B, Schudel, Ingrid J
- Authors: Vallabh, Priya , Lotz-Sisitka, Heila , O'Donoghue, Rob B , Schudel, Ingrid J
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/128939 , vital:36192 , https://doi.org/10.1111/cobi.12701
- Description: The ever-widening scope and range of global change and interconnected systemic risks arising from people–environment relationships (social‐ecological risks) appears to be increasing concern among, and involvement of, citizens in an increasingly diversified number of citizen science projects responding to these risks. We examined the relationship between epistemic cultures in citizen science projects and learning potential related to matters of concern. We then developed a typology of purposes and a citizen science epistemic‐cultures heuristic and mapped 56 projects in southern Africa using this framework. The purpose typology represents the range of knowledge‐production purposes, ranging from laboratory science to social learning, whereas the epistemic‐cultures typology is a relational representation of scientist and citizen participation and their approach to knowledge production. Results showed an iterative relationship between matters of fact and matters of concern across the projects; the nexus of citizens’ engagement in knowledge‐production activities varied. The knowledge‐production purposes informed and shaped the epistemic cultures of all the sampled citizen science projects, which in turn influenced the potential for learning within each project. Through a historical review of 3 phases in a long‐term river health‐monitoring project, we found that it is possible to evolve the learning curve of citizen science projects. This evolution involved the development of scientific water monitoring tools, the parallel development of pedagogic practices supporting monitoring activities, and situated engagement around matters of concern within social activism leading to learning‐led change. We conclude that such evolutionary processes serve to increase potential for learning and are necessary if citizen science is to contribute to wider restructuring of the epistemic culture of science under conditions of expanding social-ecological risk.
- Full Text:
- Date Issued: 2016
- Authors: Vallabh, Priya , Lotz-Sisitka, Heila , O'Donoghue, Rob B , Schudel, Ingrid J
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/128939 , vital:36192 , https://doi.org/10.1111/cobi.12701
- Description: The ever-widening scope and range of global change and interconnected systemic risks arising from people–environment relationships (social‐ecological risks) appears to be increasing concern among, and involvement of, citizens in an increasingly diversified number of citizen science projects responding to these risks. We examined the relationship between epistemic cultures in citizen science projects and learning potential related to matters of concern. We then developed a typology of purposes and a citizen science epistemic‐cultures heuristic and mapped 56 projects in southern Africa using this framework. The purpose typology represents the range of knowledge‐production purposes, ranging from laboratory science to social learning, whereas the epistemic‐cultures typology is a relational representation of scientist and citizen participation and their approach to knowledge production. Results showed an iterative relationship between matters of fact and matters of concern across the projects; the nexus of citizens’ engagement in knowledge‐production activities varied. The knowledge‐production purposes informed and shaped the epistemic cultures of all the sampled citizen science projects, which in turn influenced the potential for learning within each project. Through a historical review of 3 phases in a long‐term river health‐monitoring project, we found that it is possible to evolve the learning curve of citizen science projects. This evolution involved the development of scientific water monitoring tools, the parallel development of pedagogic practices supporting monitoring activities, and situated engagement around matters of concern within social activism leading to learning‐led change. We conclude that such evolutionary processes serve to increase potential for learning and are necessary if citizen science is to contribute to wider restructuring of the epistemic culture of science under conditions of expanding social-ecological risk.
- Full Text:
- Date Issued: 2016
MARS Motif: Assessment and Ranking Suite for transcription factor binding motifs
- Kibet, Cabel K, Machanick, Philip
- Authors: Kibet, Cabel K , Machanick, Philip
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439339 , vital:73568 , https://doi.org/10.1101/065615
- Description: We describe MARS (Motif Assessment and Ranking Suite), a web-based suite of tools used to evaluate and rank PWM-based motifs. The increased number of learned motif models that are spread across databases and in different PWM formats, leading to a choice dilemma among the users, is our motivation. This increase has been driven by the difficulty of modelling transcription factor binding sites and the advance in high-throughput sequencing technologies at a continually reducing cost. Therefore, several experimental techniques have been developed resulting in diverse motif-finding algorithms and databases. We collate a wide variety of available motifs into a benchmark database, including the corresponding experimental ChIP-seq and PBM data obtained from ENCODE and UniPROBE databases, respectively. The implemented tools include: a data-independent consistency-based motif assessment and ranking (CB-MAR), which is based on the idea that ‘correct motifs’ are more similar to each other while incorrect motifs will differ from each other; and a scoring and classification-based algorithms, which rank binding models by their ability to discriminate sequences known to contain binding sites from those without. The CB-MAR and scoring techniques have a 0.86 and 0.73 median rank correlation using ChIP-seq and PBM respectively. Best motifs selected by CB-MAR achieve a mean AUC of 0.75, comparable to those ranked by held out data at 0.76 – this is based on ChIP-seq motif discovery using five algorithms on 110 transcription factors. We have demonstrated the benefit of this web server in motif choice and ranking, as well as in motif discovery.
- Full Text:
- Date Issued: 2016
- Authors: Kibet, Cabel K , Machanick, Philip
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439339 , vital:73568 , https://doi.org/10.1101/065615
- Description: We describe MARS (Motif Assessment and Ranking Suite), a web-based suite of tools used to evaluate and rank PWM-based motifs. The increased number of learned motif models that are spread across databases and in different PWM formats, leading to a choice dilemma among the users, is our motivation. This increase has been driven by the difficulty of modelling transcription factor binding sites and the advance in high-throughput sequencing technologies at a continually reducing cost. Therefore, several experimental techniques have been developed resulting in diverse motif-finding algorithms and databases. We collate a wide variety of available motifs into a benchmark database, including the corresponding experimental ChIP-seq and PBM data obtained from ENCODE and UniPROBE databases, respectively. The implemented tools include: a data-independent consistency-based motif assessment and ranking (CB-MAR), which is based on the idea that ‘correct motifs’ are more similar to each other while incorrect motifs will differ from each other; and a scoring and classification-based algorithms, which rank binding models by their ability to discriminate sequences known to contain binding sites from those without. The CB-MAR and scoring techniques have a 0.86 and 0.73 median rank correlation using ChIP-seq and PBM respectively. Best motifs selected by CB-MAR achieve a mean AUC of 0.75, comparable to those ranked by held out data at 0.76 – this is based on ChIP-seq motif discovery using five algorithms on 110 transcription factors. We have demonstrated the benefit of this web server in motif choice and ranking, as well as in motif discovery.
- Full Text:
- Date Issued: 2016
MARS: Motif Assessment and Ranking Suite for transcription factor binding motifs
- Kibet, Caleb K, Machanick, Philip
- Authors: Kibet, Caleb K , Machanick, Philip
- Date: 2016
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61155 , vital:27985 , http://dx.doi.org/10.1101/065615
- Description: We describe MARS (Motif Assessment and Ranking Suite), a web-based suite of tools used to evaluate and rank PWM-based motifs. The increased number of learned motif models that are spread across databases and in different PWM formats, leading to a choice dilemma among the users, is our motivation. This increase has been driven by the difficulty of modelling transcription factor binding sites and the advance in high-throughput sequencing technologies at a continually reducing cost. Therefore, several experimental techniques have been developed resulting in diverse motif-finding algorithms and databases. We collate a wide variety of available motifs into a benchmark database, including the corresponding experimental ChIP-seq and PBM data obtained from ENCODE and UniPROBE databases, respectively. The implemented tools include: a data-independent consistency-based motif assessment and ranking (CB-MAR), which is based on the idea that `correct motifs' are more similar to each other while incorrect motifs will differ from each other; and a scoring and classification-based algorithms, which rank binding models by their ability to discriminate sequences known to contain binding sites from those without. The CB-MAR and scoring techniques have a 0.86 and 0.73 median rank correlation using ChIP-seq and PBM respectively. Best motifs selected by CB-MAR achieve a mean AUC of 0.75, comparable to those ranked by held out data at 0.76 { this is based on ChIP-seq motif discovery using five algorithms on 110 transcription factors. We have demonstrated the benefit of this web server in motif choice and ranking, as well as in motif.
- Full Text:
- Date Issued: 2016
- Authors: Kibet, Caleb K , Machanick, Philip
- Date: 2016
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/61155 , vital:27985 , http://dx.doi.org/10.1101/065615
- Description: We describe MARS (Motif Assessment and Ranking Suite), a web-based suite of tools used to evaluate and rank PWM-based motifs. The increased number of learned motif models that are spread across databases and in different PWM formats, leading to a choice dilemma among the users, is our motivation. This increase has been driven by the difficulty of modelling transcription factor binding sites and the advance in high-throughput sequencing technologies at a continually reducing cost. Therefore, several experimental techniques have been developed resulting in diverse motif-finding algorithms and databases. We collate a wide variety of available motifs into a benchmark database, including the corresponding experimental ChIP-seq and PBM data obtained from ENCODE and UniPROBE databases, respectively. The implemented tools include: a data-independent consistency-based motif assessment and ranking (CB-MAR), which is based on the idea that `correct motifs' are more similar to each other while incorrect motifs will differ from each other; and a scoring and classification-based algorithms, which rank binding models by their ability to discriminate sequences known to contain binding sites from those without. The CB-MAR and scoring techniques have a 0.86 and 0.73 median rank correlation using ChIP-seq and PBM respectively. Best motifs selected by CB-MAR achieve a mean AUC of 0.75, comparable to those ranked by held out data at 0.76 { this is based on ChIP-seq motif discovery using five algorithms on 110 transcription factors. We have demonstrated the benefit of this web server in motif choice and ranking, as well as in motif.
- Full Text:
- Date Issued: 2016
MCD spectroscopy and TD-DFT calculations of magnesium tetra-(15-crown-5-oxanthreno)-phthalocyanine
- Mack, John, Mkhize, Scebi, Safonoya, Evgeniya A, Gorbunova, Yulia G, Tsivadze, Aslan Yu, Nyokong, Tebello
- Authors: Mack, John , Mkhize, Scebi , Safonoya, Evgeniya A , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240743 , vital:50867 , xlink:href="https://doi.org/10.1142/S1088424616500322"
- Description: An analysis of the MCD spectroscopy and TD-DFT calculations of magnesium tetra-(15-crown-5-oxanthreno)-phthalocyanine is reported. This study provides a reassessment of an earlier study on the nature of the bands in UV-visible absorption spectra of magnesium and zinc tetra-(15-crown-5-oxanthreno)-phthalocyanine that was based on an analysis of TD-DFT calculations for a series of model complexes with the B3LYP functional. A detailed analysis of MCD spectral data and TD-DFT calculations with the CAM-B3LYP functional for the complete Mg(II) complex provides an additional insight into the optical properties and electronic structures of tetra-(15-crown-5-oxanthreno)-phthalocyanines. Thus, the bands in the Q-band region are reassigned as being due exclusively to the Q transition of Gouterman’s 4-orbital model, since intense pseudo-A1𝒜1 terms are observed in the MCD spectrum in a spectral region that had previously been assigned as charge transfer bands.
- Full Text:
- Date Issued: 2016
- Authors: Mack, John , Mkhize, Scebi , Safonoya, Evgeniya A , Gorbunova, Yulia G , Tsivadze, Aslan Yu , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240743 , vital:50867 , xlink:href="https://doi.org/10.1142/S1088424616500322"
- Description: An analysis of the MCD spectroscopy and TD-DFT calculations of magnesium tetra-(15-crown-5-oxanthreno)-phthalocyanine is reported. This study provides a reassessment of an earlier study on the nature of the bands in UV-visible absorption spectra of magnesium and zinc tetra-(15-crown-5-oxanthreno)-phthalocyanine that was based on an analysis of TD-DFT calculations for a series of model complexes with the B3LYP functional. A detailed analysis of MCD spectral data and TD-DFT calculations with the CAM-B3LYP functional for the complete Mg(II) complex provides an additional insight into the optical properties and electronic structures of tetra-(15-crown-5-oxanthreno)-phthalocyanines. Thus, the bands in the Q-band region are reassigned as being due exclusively to the Q transition of Gouterman’s 4-orbital model, since intense pseudo-A1𝒜1 terms are observed in the MCD spectrum in a spectral region that had previously been assigned as charge transfer bands.
- Full Text:
- Date Issued: 2016
Miscellaneous provisions
- Arendse, Jacqueline A, Clegg, David, Williams, Robert C
- Authors: Arendse, Jacqueline A , Clegg, David , Williams, Robert C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/131276 , vital:36548 , https://store.lexisnexis.co.za/products/silke-on-tax-administration-skuZASKUPG1440
- Description: Miscellaneous provisions pertaining to tax administration are explained in this chapter.
- Full Text: false
- Date Issued: 2016
- Authors: Arendse, Jacqueline A , Clegg, David , Williams, Robert C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/131276 , vital:36548 , https://store.lexisnexis.co.za/products/silke-on-tax-administration-skuZASKUPG1440
- Description: Miscellaneous provisions pertaining to tax administration are explained in this chapter.
- Full Text: false
- Date Issued: 2016
Modelling transport of inshore and deep-spawned chokka squid (Loligo reynaudi) paralarvae off South Africa: the potential contribution of deep spawning to recruitment
- Downey-Breedt, Nicola, Roberts, Michael J, Sauer, Warwick H H, Chang, N
- Authors: Downey-Breedt, Nicola , Roberts, Michael J , Sauer, Warwick H H , Chang, N
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125183 , vital:35742 , https://doi.10.1111/fog.12132
- Description: The South African chokka squid, Loligo reynaudi, spawns both inshore (≤70 m) and on the mid-shelf (71–130 m) of the Eastern Agulhas Bank. The fate of these deep-spawned hatchlings and their potential contribution to recruitment is as yet unknown. Lagrangian ROMS-IBM (Regional Ocean Modelling System-Individual-Based Model) simulations confirm westward transport of inshore and deep-spawned hatchlings, but also indicate that the potential exists for paralarvae hatched on the Eastern Agulhas Bank deep spawning grounds to be removed from the shelf ecosystem. Using a ROMS-IBM, this study determined the transport and recruitment success of deepspawned hatchlings relative to inshore-hatched paralarvae. A total of 12 release sites were incorporated into the model, six inshore and six deep-spawning sites. Paralarval survival was estimated based on timely transport to nursery grounds, adequate retention within the nursery grounds and retention on the Agulhas Bank shelf. Paralarval transport and survival were dependent on both spawning location and time of hatching. Results suggest the importance of the south coast as a nursery area for inshore-hatched paralarvae, and similarly the cold ridge nursery grounds for deep-hatched paralarvae. Possible relationships between periods of highest recruitment success and spawning peaks were identified for both spawning habitats. Based on the likely autumn increase in deep spawning off the Tsitsikamma coast, and the beneficial currents during this period (as indicated by the model results) it can be concluded that deep spawning may at times contribute significantly to recruitment.
- Full Text:
- Date Issued: 2016
- Authors: Downey-Breedt, Nicola , Roberts, Michael J , Sauer, Warwick H H , Chang, N
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125183 , vital:35742 , https://doi.10.1111/fog.12132
- Description: The South African chokka squid, Loligo reynaudi, spawns both inshore (≤70 m) and on the mid-shelf (71–130 m) of the Eastern Agulhas Bank. The fate of these deep-spawned hatchlings and their potential contribution to recruitment is as yet unknown. Lagrangian ROMS-IBM (Regional Ocean Modelling System-Individual-Based Model) simulations confirm westward transport of inshore and deep-spawned hatchlings, but also indicate that the potential exists for paralarvae hatched on the Eastern Agulhas Bank deep spawning grounds to be removed from the shelf ecosystem. Using a ROMS-IBM, this study determined the transport and recruitment success of deepspawned hatchlings relative to inshore-hatched paralarvae. A total of 12 release sites were incorporated into the model, six inshore and six deep-spawning sites. Paralarval survival was estimated based on timely transport to nursery grounds, adequate retention within the nursery grounds and retention on the Agulhas Bank shelf. Paralarval transport and survival were dependent on both spawning location and time of hatching. Results suggest the importance of the south coast as a nursery area for inshore-hatched paralarvae, and similarly the cold ridge nursery grounds for deep-hatched paralarvae. Possible relationships between periods of highest recruitment success and spawning peaks were identified for both spawning habitats. Based on the likely autumn increase in deep spawning off the Tsitsikamma coast, and the beneficial currents during this period (as indicated by the model results) it can be concluded that deep spawning may at times contribute significantly to recruitment.
- Full Text:
- Date Issued: 2016
Molecular genetic, life-history and morphological variation in a coastal warm-temperate sciaenid fish: evidence for an upwelling-driven speciation event
- Henriques, Romina, Potts, Warren M, Sauer, Warwick H H, Santos, Carmen V D, Kruger, Jerraleigh, Thomas, Jessica A, Shaw, Paul W
- Authors: Henriques, Romina , Potts, Warren M , Sauer, Warwick H H , Santos, Carmen V D , Kruger, Jerraleigh , Thomas, Jessica A , Shaw, Paul W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125252 , vital:35750 , http://dx.doi.10.1111/jbi.12829
- Description: The marine environment is punctuated by biogeographical barriers that limit dispersal and gene flow in otherwise widespread species (Teske et al., 2011a,b; Briggs & Bowen, 2012; Luiz et al., 2012). These barriers may be physical obstacles such as landmasses (e.g. Isthmus of Panama) or less intuitive features such as deep water (Lessios et al., 2003), freshwater outflows (Floeter et al., 2008) or oceanographic features (Shaw et al., 2004; Galarza et al., 2009; von der Heyden et al., 2011). Upwelling cells and sea surface temperature (SSTs) gradients in particular are known to disrupt gene flow, leading to divergence of allopatric populations and species (Waters & Roy, 2004; Teske et al., 2011a; Henriques et al., 2012, 2014, 2015). However, as oceanographic features are seldom permanent and frequently subject to considerable environmental variability, many barriers often permit some level of permeability to dispersal (Floeter et al., 2008). Other processes may influence the persistence of differentiated allopatric taxa across such physical barriers (Bradbury et al., 2008), with ecological divergence (and diversifying selection) being reported as a major evolutionary process influencing the biogeographical distributions of marine species (Pelc et al., 2009; Teske et al., 2011a; Gaither et al., 2015).
- Full Text:
- Date Issued: 2016
- Authors: Henriques, Romina , Potts, Warren M , Sauer, Warwick H H , Santos, Carmen V D , Kruger, Jerraleigh , Thomas, Jessica A , Shaw, Paul W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125252 , vital:35750 , http://dx.doi.10.1111/jbi.12829
- Description: The marine environment is punctuated by biogeographical barriers that limit dispersal and gene flow in otherwise widespread species (Teske et al., 2011a,b; Briggs & Bowen, 2012; Luiz et al., 2012). These barriers may be physical obstacles such as landmasses (e.g. Isthmus of Panama) or less intuitive features such as deep water (Lessios et al., 2003), freshwater outflows (Floeter et al., 2008) or oceanographic features (Shaw et al., 2004; Galarza et al., 2009; von der Heyden et al., 2011). Upwelling cells and sea surface temperature (SSTs) gradients in particular are known to disrupt gene flow, leading to divergence of allopatric populations and species (Waters & Roy, 2004; Teske et al., 2011a; Henriques et al., 2012, 2014, 2015). However, as oceanographic features are seldom permanent and frequently subject to considerable environmental variability, many barriers often permit some level of permeability to dispersal (Floeter et al., 2008). Other processes may influence the persistence of differentiated allopatric taxa across such physical barriers (Bradbury et al., 2008), with ecological divergence (and diversifying selection) being reported as a major evolutionary process influencing the biogeographical distributions of marine species (Pelc et al., 2009; Teske et al., 2011a; Gaither et al., 2015).
- 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
Mongrel: essays, William Dicey
- Authors: Wylie, Dan
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142748 , vital:38113 , https://www.ajol.info/index.php/tvl/article/view/143393
- Description: If I had the liberty to run an introductory course on South African history, I might well start with William Dicey’s Borderline (2004). Borderline recounts Dicey and some friends’ canoe trip down the Orange River, from Orania to the sea. It’s by turns lyrical and funny, and rich with historical perspectives stimulated by people and places Dicey encounters en route.
- Full Text:
- Date Issued: 2016
- Authors: Wylie, Dan
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142748 , vital:38113 , https://www.ajol.info/index.php/tvl/article/view/143393
- Description: If I had the liberty to run an introductory course on South African history, I might well start with William Dicey’s Borderline (2004). Borderline recounts Dicey and some friends’ canoe trip down the Orange River, from Orania to the sea. It’s by turns lyrical and funny, and rich with historical perspectives stimulated by people and places Dicey encounters en route.
- Full Text:
- Date Issued: 2016
Monitoring of invertebrate and fish recovery following river rehabilitation using rotenone in the Rondegat River
- Weyl, Olaf L F, Barrow, S, Bellingan, Terence A, Dalu, Tatenda, Ellender, Bruce R, Esler, K, Impson, D, Gouws, J, Jordaan, M, Villet, Martin H, Wasserman, Ryan J, Woodford, Darragh J
- Authors: Weyl, Olaf L F , Barrow, S , Bellingan, Terence A , Dalu, Tatenda , Ellender, Bruce R , Esler, K , Impson, D , Gouws, J , Jordaan, M , Villet, Martin H , Wasserman, Ryan J , Woodford, Darragh J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442411 , vital:73982 , https://www.wrc.org.za/wp-content/uploads/mdocs/2261.pdf
- Description: Fish invasions have been cited as a primary threat to imperilled South African fishes and other aquatic fauna. As a result, the management and control of alien invasive species is a legislated priority in South Africa. From a river rehabilitation perspective, eradicating alien fish allows for the rehabilitation of several kilometres of river, with very significant benefits for the endangered fish species present and for the associated aquatic biota. In South Africa, the piscicide rotenone is one of the preferred methods for achieving eradication.
- Full Text:
- Date Issued: 2016
- Authors: Weyl, Olaf L F , Barrow, S , Bellingan, Terence A , Dalu, Tatenda , Ellender, Bruce R , Esler, K , Impson, D , Gouws, J , Jordaan, M , Villet, Martin H , Wasserman, Ryan J , Woodford, Darragh J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442411 , vital:73982 , https://www.wrc.org.za/wp-content/uploads/mdocs/2261.pdf
- Description: Fish invasions have been cited as a primary threat to imperilled South African fishes and other aquatic fauna. As a result, the management and control of alien invasive species is a legislated priority in South Africa. From a river rehabilitation perspective, eradicating alien fish allows for the rehabilitation of several kilometres of river, with very significant benefits for the endangered fish species present and for the associated aquatic biota. In South Africa, the piscicide rotenone is one of the preferred methods for achieving eradication.
- Full Text:
- Date Issued: 2016
Morphological variations in southern African populations of Myriophyllum spicatum: Phenotypic plasticity or local adaptation?
- Weyl, Philip S R, Coetzee, Julie A
- Authors: Weyl, Philip S R , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424789 , vital:72184 , xlink:href="https://doi.org/10.1016/j.sajb.2015.07.01"
- Description: Variability in aquatic plant morphology is usually driven by phenotypic plasticity and local adaptations to environmental conditions experienced. This study aimed to elucidate which of these drivers is responsible for the morphological variation exhibited by three populations of Myriophyllum spicatum L. (Haloragaceae), a submerged aquatic plant whose status as native or exotic within southern Africa is uncertain. Individuals from three populations on the Vaal River (Northern Cape), Klipplaat River (Eastern Cape) and Lake Sibaya (KwaZulu-Natal) were grown under two nutrient treatments (high: 30 mg N/kg sediment and low: sediment only), while all other variables were kept the same. Morphological characteristics were measured at the start of the experiment to obtain a baseline morphology, and again eight weeks later. By the end of the experiment, the individuals from each population had responded to the different growing conditions. In most cases, the individuals from each population were significantly larger under the high nutrient treatment (Stem diameter: F(5,86) = 18.435, P is less than 0.001, Internode length: F(5,86) = 5.0747, P is less than 0.001, Leaf length: F(5,86) = 19.692, P is less than 0.001). Despite these differences in nutrient treatments, the growth pattern of each population remained true to the original starting point indicated by the lack of overlap between populations in the PCA groupings. This suggests that local adaptations are responsible for the differences in morphology between populations of M. spicatum, but shows that phenotypic plasticity does play a role as evidenced by individual responses to the different nutrient conditions. The development of these local adaptations within southern Africa suggests that the populations have had a long evolutionary history in the region and are relatively isolated with little reproductive mixing.
- Full Text:
- Date Issued: 2016
- Authors: Weyl, Philip S R , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424789 , vital:72184 , xlink:href="https://doi.org/10.1016/j.sajb.2015.07.01"
- Description: Variability in aquatic plant morphology is usually driven by phenotypic plasticity and local adaptations to environmental conditions experienced. This study aimed to elucidate which of these drivers is responsible for the morphological variation exhibited by three populations of Myriophyllum spicatum L. (Haloragaceae), a submerged aquatic plant whose status as native or exotic within southern Africa is uncertain. Individuals from three populations on the Vaal River (Northern Cape), Klipplaat River (Eastern Cape) and Lake Sibaya (KwaZulu-Natal) were grown under two nutrient treatments (high: 30 mg N/kg sediment and low: sediment only), while all other variables were kept the same. Morphological characteristics were measured at the start of the experiment to obtain a baseline morphology, and again eight weeks later. By the end of the experiment, the individuals from each population had responded to the different growing conditions. In most cases, the individuals from each population were significantly larger under the high nutrient treatment (Stem diameter: F(5,86) = 18.435, P is less than 0.001, Internode length: F(5,86) = 5.0747, P is less than 0.001, Leaf length: F(5,86) = 19.692, P is less than 0.001). Despite these differences in nutrient treatments, the growth pattern of each population remained true to the original starting point indicated by the lack of overlap between populations in the PCA groupings. This suggests that local adaptations are responsible for the differences in morphology between populations of M. spicatum, but shows that phenotypic plasticity does play a role as evidenced by individual responses to the different nutrient conditions. The development of these local adaptations within southern Africa suggests that the populations have had a long evolutionary history in the region and are relatively isolated with little reproductive mixing.
- Full Text:
- Date Issued: 2016
Multilingual education for Africa: Concepts and practices
- Kaschula, Russell H, Wolff, H Ekkehard
- Authors: Kaschula, Russell H , Wolff, H Ekkehard
- Date: 2016
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/174838 , vital:42513 , ISBN 978-0415315760 , https://www.amazon.com/Multilingual-Education-Africa-Practices-Routledge/dp/041531576X
- Description: The common thread in this book is the exploration of innovative pedagogies in language teaching and language use in education. The greatest danger facing educators is one of complacency. Whether set in Zimbabwe, Ethiopia, South Africa or elsewhere in Africa, all the chapters in this book emphasise the imperative for educators to constantly revise curricula and teaching methods in order to find the most appropriate ways of teaching and using language in multilingual settings.
- Full Text:
- Date Issued: 2016
- Authors: Kaschula, Russell H , Wolff, H Ekkehard
- Date: 2016
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/174838 , vital:42513 , ISBN 978-0415315760 , https://www.amazon.com/Multilingual-Education-Africa-Practices-Routledge/dp/041531576X
- Description: The common thread in this book is the exploration of innovative pedagogies in language teaching and language use in education. The greatest danger facing educators is one of complacency. Whether set in Zimbabwe, Ethiopia, South Africa or elsewhere in Africa, all the chapters in this book emphasise the imperative for educators to constantly revise curricula and teaching methods in order to find the most appropriate ways of teaching and using language in multilingual settings.
- Full Text:
- Date Issued: 2016
Multiple drivers of local (non-) compliance in community-cased marine resource management: case studies from the South Pacific
- Rohe, Janne R, Aswani, Shankar, Schlüter, Achim, Ferse, Sebastian C A
- Authors: Rohe, Janne R , Aswani, Shankar , Schlüter, Achim , Ferse, Sebastian C A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70571 , vital:29676 , https://doi.org/10.3389/fmars.2017.00172
- Description: The outcomes of marine conservation and related management interventions depend to a large extent on people's compliance with these rule systems. In the South Pacific, community-based marine resource management (CBMRM) has gained wide recognition as a strategy for the sustainable management of marine resources. In current practice, CBMRM initiatives often build upon customary forms of marine governance, integrating scientific advice and management principles in collaboration with external partners. However, diverse socio-economic developments as well as limited legal mandates can challenge these approaches. Compliance with and effective (legally-backed) enforcement of local management strategies constitute a growing challenge for communities—often resulting in considerable impact on the success or failure of CBMRM. Marine management arrangements are highly dynamic over time, and similarly compliance with rule systems tends to change depending on context. Understanding the factors contributing to (non-) compliance in a given setting is key to the design and function of adaptive management approaches. Yet, few empirical studies have looked in depth into the dynamics around local (non-) compliance with local marine tenure rules under the transforming management arrangements. Using two case studies from Solomon Islands and Fiji, we investigate what drives local (non-) compliance with CBMRM and what hinders or supports its effective enforcement. The case studies reveal that non-compliance is mainly driven by: (1) diminishing perceived legitimacy of local rules and rule-makers; (2) increased incentives to break rules due to market access and/ or lack of alternative income; and (3) relatively weak enforcement of local rules (i.e., low perceptions of risk from sanctions for rule-breaking). These drivers do not stand alone but can act together and add up to impair effective management. We further analyze how enforcement of CBMRM is challenged through a range of institutional; socio-cultural and technical/financial constraints, which are in parts a result of the dynamism and ongoing transformations of management arrangements. Our study underlines the importance of better understanding and contextualizing marine resource management processes under dynamic conditions for an improved understanding of compliance in a particular setting.
- Full Text:
- Date Issued: 2016
- Authors: Rohe, Janne R , Aswani, Shankar , Schlüter, Achim , Ferse, Sebastian C A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70571 , vital:29676 , https://doi.org/10.3389/fmars.2017.00172
- Description: The outcomes of marine conservation and related management interventions depend to a large extent on people's compliance with these rule systems. In the South Pacific, community-based marine resource management (CBMRM) has gained wide recognition as a strategy for the sustainable management of marine resources. In current practice, CBMRM initiatives often build upon customary forms of marine governance, integrating scientific advice and management principles in collaboration with external partners. However, diverse socio-economic developments as well as limited legal mandates can challenge these approaches. Compliance with and effective (legally-backed) enforcement of local management strategies constitute a growing challenge for communities—often resulting in considerable impact on the success or failure of CBMRM. Marine management arrangements are highly dynamic over time, and similarly compliance with rule systems tends to change depending on context. Understanding the factors contributing to (non-) compliance in a given setting is key to the design and function of adaptive management approaches. Yet, few empirical studies have looked in depth into the dynamics around local (non-) compliance with local marine tenure rules under the transforming management arrangements. Using two case studies from Solomon Islands and Fiji, we investigate what drives local (non-) compliance with CBMRM and what hinders or supports its effective enforcement. The case studies reveal that non-compliance is mainly driven by: (1) diminishing perceived legitimacy of local rules and rule-makers; (2) increased incentives to break rules due to market access and/ or lack of alternative income; and (3) relatively weak enforcement of local rules (i.e., low perceptions of risk from sanctions for rule-breaking). These drivers do not stand alone but can act together and add up to impair effective management. We further analyze how enforcement of CBMRM is challenged through a range of institutional; socio-cultural and technical/financial constraints, which are in parts a result of the dynamism and ongoing transformations of management arrangements. Our study underlines the importance of better understanding and contextualizing marine resource management processes under dynamic conditions for an improved understanding of compliance in a particular setting.
- Full Text:
- Date Issued: 2016
Natural resource use, incomes, and poverty along the rural–urban continuum of two medium-sized, South African towns
- Ward, Catherine D, Shackleton, Charlie M
- Authors: Ward, Catherine D , Shackleton, Charlie M
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180790 , vital:43646 , xlink:href="https://doi.org/10.1016/j.worlddev.2015.10.025"
- Description: Urbanization is a significant driver of global change, reshaping livelihoods, productive activities, and incomes. Yet, many elements of what are typically regarded as rural activities can be found in urban places and vice versa. We report on the incomes from land- and cash-based activities along the rural–urban gradient of two South African towns. Although the dominant income strategies varied, all households had more than one income source. Use of wild resources and agriculture were common in urban settings, although variable between and within towns. Poverty levels would be 5–10% higher in the absence of natural resource-based incomes.
- Full Text:
- Date Issued: 2016
- Authors: Ward, Catherine D , Shackleton, Charlie M
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180790 , vital:43646 , xlink:href="https://doi.org/10.1016/j.worlddev.2015.10.025"
- Description: Urbanization is a significant driver of global change, reshaping livelihoods, productive activities, and incomes. Yet, many elements of what are typically regarded as rural activities can be found in urban places and vice versa. We report on the incomes from land- and cash-based activities along the rural–urban gradient of two South African towns. Although the dominant income strategies varied, all households had more than one income source. Use of wild resources and agriculture were common in urban settings, although variable between and within towns. Poverty levels would be 5–10% higher in the absence of natural resource-based incomes.
- Full Text:
- Date Issued: 2016
Nature and source of suspended particulate matter and detritus along an austral temperate river–estuary continuum, assessed using stable isotope analysis
- Dalu, Tatenda, Richoux, Nicole B, Froneman, P William
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68012 , vital:29181 , https://doi.org/10.1007/s10750-015-2480-1
- Description: Publisher version , Ecologists are interested in the factors that control, and the variability in, the contributions of different sources to mixed organic materials travelling through lotic systems. We hypothesized that the source matter fuelling mixed organic pools in a river–estuary continuum varies over space and time. Samples of the mixed organic pools were collected along a small temperate river (Kowie River) in southern Africa during early and late spring, summer and winter. The C:N ratios of suspended particulate matter (SPM) collected during summer and winter indicated that the lower reaches of the system had similar organic matter contributions. Stable isotope analysis in R revealed that aquatic macrophytes were significant contributors to SPM in the upper reaches. Bulk detritus had large allochthonous matter components in the lower reaches, and contributions of aquatic macrophytes and benthic algae were high (>50%) in the upper to middle reaches. The evaluation of organic matter contributions to SPM and detritus along the river–estuary continuum provided a baseline assessment of the nature and sources of potential food for consumers inhabiting different locations during different seasons. Incorporating SPM and detritus spatio-temporal variations in food web studies will improve our understanding of carbon flow in aquatic systems.
- Full Text: false
- Date Issued: 2016
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68012 , vital:29181 , https://doi.org/10.1007/s10750-015-2480-1
- Description: Publisher version , Ecologists are interested in the factors that control, and the variability in, the contributions of different sources to mixed organic materials travelling through lotic systems. We hypothesized that the source matter fuelling mixed organic pools in a river–estuary continuum varies over space and time. Samples of the mixed organic pools were collected along a small temperate river (Kowie River) in southern Africa during early and late spring, summer and winter. The C:N ratios of suspended particulate matter (SPM) collected during summer and winter indicated that the lower reaches of the system had similar organic matter contributions. Stable isotope analysis in R revealed that aquatic macrophytes were significant contributors to SPM in the upper reaches. Bulk detritus had large allochthonous matter components in the lower reaches, and contributions of aquatic macrophytes and benthic algae were high (>50%) in the upper to middle reaches. The evaluation of organic matter contributions to SPM and detritus along the river–estuary continuum provided a baseline assessment of the nature and sources of potential food for consumers inhabiting different locations during different seasons. Incorporating SPM and detritus spatio-temporal variations in food web studies will improve our understanding of carbon flow in aquatic systems.
- Full Text: false
- Date Issued: 2016
New evidence for the correlation of basalts of the Suurberg Group with the upper part of the Karoo basalt sequence of Lesotho:
- Authors: Marsh, J S Goonie
- Date: 2016
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/145122 , vital:38410 , ISBN 9783319408590 , https://link.springer.com/chapter/10.1007/978-3-319-40859-0_6
- Description: Tholeiitic basalts build the Mimosa Formation, the uppermost stratigraphic unit of the Suurberg Group in the northern part of the Algoa Basin. Exposures are very poor and the tectonic significance of the Suurberg rocks and the origin of the Mimosa basalts are contentious. Drilling of stratigraphic boreholes at four localities allowed detailed sampling of the basalts from two cores 90 km apart for geochemical, age and palaeomagnetic investigations.
- Full Text:
- Date Issued: 2016
- Authors: Marsh, J S Goonie
- Date: 2016
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/145122 , vital:38410 , ISBN 9783319408590 , https://link.springer.com/chapter/10.1007/978-3-319-40859-0_6
- Description: Tholeiitic basalts build the Mimosa Formation, the uppermost stratigraphic unit of the Suurberg Group in the northern part of the Algoa Basin. Exposures are very poor and the tectonic significance of the Suurberg rocks and the origin of the Mimosa basalts are contentious. Drilling of stratigraphic boreholes at four localities allowed detailed sampling of the basalts from two cores 90 km apart for geochemical, age and palaeomagnetic investigations.
- Full Text:
- Date Issued: 2016
Nitrogen fertilisation improves growth of Chromolaena odorata (Asteraceae) and the performance of the biological control agent, Pareuchaetes insulata (Erebidae)
- Uyi, Osariyekemwen O, Zacharariades, Costas, Hill, Martin P
- Authors: Uyi, Osariyekemwen O , Zacharariades, Costas , Hill, Martin P
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416880 , vital:71393 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: Recent studies have demonstrated, through their contrasting results, that relationships between nitrogen levels in host plants and phytophagous insect performance are not simple. This study examined the effect of varying fertilisation regimes on the invasive alien plant, Chromolaena odorata (L.) (Asteraceae) and the response of a specialist folivore (a biological control agent), Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae). C. odorata plants were treated with 3 different levels of fertilisation and plant characteristics were measured within 2–3 months of fertiliser application. Leaves from each of the three treatments were fed to newly hatched larvae until pupation in order to determine the effect of nitrogen fertilisation on herbivore performance metrics such as survival, development time, fecundity and longevity. High and medium fertilisation significantly increased foliar nitrogen concentrations, basal stem diameter, leaf length, shoot height and above-ground biomass of C. odorata plants relative to low fertilisation. When individuals of P. insulata were fed on leaves from medium- or high-fertilisation treatments, they developed faster, grew to a larger size (by 8%) and achieved higher fecundity (19–22%) than leaves from the low-fertilisation treatment. The results suggest that in mass-rearing, increased production of this biological control agent will occur in high- or medium-fertilised plants.
- Full Text:
- Date Issued: 2016
- Authors: Uyi, Osariyekemwen O , Zacharariades, Costas , Hill, Martin P
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416880 , vital:71393 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: Recent studies have demonstrated, through their contrasting results, that relationships between nitrogen levels in host plants and phytophagous insect performance are not simple. This study examined the effect of varying fertilisation regimes on the invasive alien plant, Chromolaena odorata (L.) (Asteraceae) and the response of a specialist folivore (a biological control agent), Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae). C. odorata plants were treated with 3 different levels of fertilisation and plant characteristics were measured within 2–3 months of fertiliser application. Leaves from each of the three treatments were fed to newly hatched larvae until pupation in order to determine the effect of nitrogen fertilisation on herbivore performance metrics such as survival, development time, fecundity and longevity. High and medium fertilisation significantly increased foliar nitrogen concentrations, basal stem diameter, leaf length, shoot height and above-ground biomass of C. odorata plants relative to low fertilisation. When individuals of P. insulata were fed on leaves from medium- or high-fertilisation treatments, they developed faster, grew to a larger size (by 8%) and achieved higher fecundity (19–22%) than leaves from the low-fertilisation treatment. The results suggest that in mass-rearing, increased production of this biological control agent will occur in high- or medium-fertilised plants.
- Full Text:
- Date Issued: 2016
Nonlinear optical behavior of alkyne terminated phthalocyanines in solution and when embedded in polysulfone as thin films: effects of aggregation
- Bankole, Owolabi M, Yilmaz, Yusuf, Nyokong, Tebello
- Authors: Bankole, Owolabi M , Yilmaz, Yusuf , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189110 , vital:44817 , xlink:href="https://doi.org/10.1016/j.optmat.2015.11.041"
- Description: We report here for the first time, on the comparative studies of the photophysical and optical limiting behavior of our two novel phthalocyanines namely 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyanines 2, and 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyaninato zinc (II) (3) in solution and thin films. Nonlinear optical (NLO) properties of the samples in solution and contained in polysulfone (PSU) thin films were evaluated using Z-scan technique at 532 nm and 10 ns pulsed duration. Effects of aggregation and disaggregation on the NLO performance of metal-free phthalocyanine are reported in detail. Our findings showed that the prepared Pcs show larger nonlinear absorption coefficient and lower limiting thresholds when embedded in polysulfone films compared to in solutions. The values of nonlinear susceptibility and hyperpolarizability recorded for 3-PSU in this work are respectively, ∼2.09 × 10−8 esu and ∼1.02 × 10−26 esu. These values are among the largest values reported for phthalocyanines and other macrocycles doped on polymer matrices.
- Full Text:
- Date Issued: 2016
- Authors: Bankole, Owolabi M , Yilmaz, Yusuf , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189110 , vital:44817 , xlink:href="https://doi.org/10.1016/j.optmat.2015.11.041"
- Description: We report here for the first time, on the comparative studies of the photophysical and optical limiting behavior of our two novel phthalocyanines namely 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyanines 2, and 2(3), 9(10), 16(17), 23(24)-tetrakis-(4-(5-methylhex-1-yn-3-yloxy)) phthalocyaninato zinc (II) (3) in solution and thin films. Nonlinear optical (NLO) properties of the samples in solution and contained in polysulfone (PSU) thin films were evaluated using Z-scan technique at 532 nm and 10 ns pulsed duration. Effects of aggregation and disaggregation on the NLO performance of metal-free phthalocyanine are reported in detail. Our findings showed that the prepared Pcs show larger nonlinear absorption coefficient and lower limiting thresholds when embedded in polysulfone films compared to in solutions. The values of nonlinear susceptibility and hyperpolarizability recorded for 3-PSU in this work are respectively, ∼2.09 × 10−8 esu and ∼1.02 × 10−26 esu. These values are among the largest values reported for phthalocyanines and other macrocycles doped on polymer matrices.
- Full Text:
- Date Issued: 2016
Nonlinear optical behavior of neodymium mono-and bi-nuclear phthalocyanines linked to zinc oxide nanoparticles and incorporated into poly acrylic acid
- Sekhosana, Kutloana E, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sekhosana, Kutloana E , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188766 , vital:44783 , xlink:href="https://doi.org/10.1016/j.poly.2015.12.045"
- Description: Syntheses of bis{23-(3,4-di-yloxybenzoic acid)-(2(3), 9(10), 16(17), 23(24))-(hexakis-pyridin-3-yloxy phthalocyaninato)} dineodymium (III) acetate (3) and 2(3), 9(10), 16(17), 23(24)-(tetrapyridin-3-yloxy phthalocyaninato) neodymium (III) acetate (4) as well as their conjugates with ZnO nanoparticles (conjugates 6, 7 and 8) are presented. Thin films of conjugate 6 (where complex 3 is linked to ZnO nanoparticles via an amide bond) gave the best third-order susceptibility (5.89 × 10−8 esu), second-order hyperpolarizability (2.53 × 10−25 esu) and the lowest limiting threshold values (0.12 J cm−2). The nonlinear behavior is enhanced in solid state when compared to solution.
- Full Text:
- Date Issued: 2016
- Authors: Sekhosana, Kutloana E , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188766 , vital:44783 , xlink:href="https://doi.org/10.1016/j.poly.2015.12.045"
- Description: Syntheses of bis{23-(3,4-di-yloxybenzoic acid)-(2(3), 9(10), 16(17), 23(24))-(hexakis-pyridin-3-yloxy phthalocyaninato)} dineodymium (III) acetate (3) and 2(3), 9(10), 16(17), 23(24)-(tetrapyridin-3-yloxy phthalocyaninato) neodymium (III) acetate (4) as well as their conjugates with ZnO nanoparticles (conjugates 6, 7 and 8) are presented. Thin films of conjugate 6 (where complex 3 is linked to ZnO nanoparticles via an amide bond) gave the best third-order susceptibility (5.89 × 10−8 esu), second-order hyperpolarizability (2.53 × 10−25 esu) and the lowest limiting threshold values (0.12 J cm−2). The nonlinear behavior is enhanced in solid state when compared to solution.
- Full Text:
- Date Issued: 2016