Current developments in arbuscular mycorrhizal fungi research and its role in salinity stress alleviation a biotechnological perspective
- Kumar, Ashwani, Dames, Joanna F, Gupta, Aditi, Sharma, Satyawati, Gilbert, Jack A, Ahmad, Parvaiz
- Authors: Kumar, Ashwani , Dames, Joanna F , Gupta, Aditi , Sharma, Satyawati , Gilbert, Jack A , Ahmad, Parvaiz
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443998 , vital:74177 , https://doi.org/10.3109/07388551.2014.899964
- Description: Arbuscular mycorrhizal fungi (AMF) form widespread symbiotic associations with 80% of known land plants. They play a major role in plant nutrition, growth, water absorption, nutrient cycling and protection from pathogens, and as a result, contribute to ecosystem processes. Salinity stress conditions undoubtedly limit plant productivity and, therefore, the role of AMF as a biological tool for improving plant salt stress tolerance, is gaining economic importance worldwide. However, this approach requires a better understanding of how plants and AMF intimately interact with each other in saline environments and how this interaction leads to physiological changes in plants. This knowledge is important to develop sustainable strategies for successful utilization of AMF to improve plant health under a variety of stress conditions. Recent advances in the field of molecular biology, “omics” technology and advanced microscopy can provide new insight about these mechanisms of interaction between AMF and plants, as well as other microbes. This review mainly discusses the effect of salinity on AMF and plants, and role of AMF in alleviation of salinity stress including insight on methods for AMF identification. The focus remains on latest advancements in mycorrhizal research that can potentially offer an integrative understanding of the role of AMF in salinity tolerance and sustainable crop production.
- Full Text:
- Authors: Kumar, Ashwani , Dames, Joanna F , Gupta, Aditi , Sharma, Satyawati , Gilbert, Jack A , Ahmad, Parvaiz
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443998 , vital:74177 , https://doi.org/10.3109/07388551.2014.899964
- Description: Arbuscular mycorrhizal fungi (AMF) form widespread symbiotic associations with 80% of known land plants. They play a major role in plant nutrition, growth, water absorption, nutrient cycling and protection from pathogens, and as a result, contribute to ecosystem processes. Salinity stress conditions undoubtedly limit plant productivity and, therefore, the role of AMF as a biological tool for improving plant salt stress tolerance, is gaining economic importance worldwide. However, this approach requires a better understanding of how plants and AMF intimately interact with each other in saline environments and how this interaction leads to physiological changes in plants. This knowledge is important to develop sustainable strategies for successful utilization of AMF to improve plant health under a variety of stress conditions. Recent advances in the field of molecular biology, “omics” technology and advanced microscopy can provide new insight about these mechanisms of interaction between AMF and plants, as well as other microbes. This review mainly discusses the effect of salinity on AMF and plants, and role of AMF in alleviation of salinity stress including insight on methods for AMF identification. The focus remains on latest advancements in mycorrhizal research that can potentially offer an integrative understanding of the role of AMF in salinity tolerance and sustainable crop production.
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DDoS Attack Mitigation Through Control of Inherent Charge Decay of Memory Implementations
- Herbert, Alan, Irwin, Barry V W, van Heerden, Renier P
- Authors: Herbert, Alan , Irwin, Barry V W , van Heerden, Renier P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430339 , vital:72684 , https://www.academic-bookshop.com/ourshop/prod_3774091-ICCWS-2015-10th-International-Conference-on-Cyber-Warfare-and-Security-Kruger-National-Park-South-Africa-PRINT-ver-ISBN-978191030996.html
- Description: DDoS (Distributed Denial of Service) attacks over recent years have shown to be devastating on the target systems and services made publicly available over the Internet. Furthermore, the backscatter1 caused by DDoS attacks also affects the available bandwidth and responsiveness of many other hosts within the Internet. The unfortunate reality of these attacks is that the targeted party cannot fight back due to the presence of botnets and malware-driven hosts. These hosts that carry out the attack on a target are usually controlled remotely and the owner of the device is unaware of it; for this reason one cannot attack back directly as this will serve little more than to disable an innocent party. A proposed solution to these DDoS attacks is to identify a potential attacking address and ignore communication from that address for a set period of time through time stamping.
- Full Text:
- Authors: Herbert, Alan , Irwin, Barry V W , van Heerden, Renier P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430339 , vital:72684 , https://www.academic-bookshop.com/ourshop/prod_3774091-ICCWS-2015-10th-International-Conference-on-Cyber-Warfare-and-Security-Kruger-National-Park-South-Africa-PRINT-ver-ISBN-978191030996.html
- Description: DDoS (Distributed Denial of Service) attacks over recent years have shown to be devastating on the target systems and services made publicly available over the Internet. Furthermore, the backscatter1 caused by DDoS attacks also affects the available bandwidth and responsiveness of many other hosts within the Internet. The unfortunate reality of these attacks is that the targeted party cannot fight back due to the presence of botnets and malware-driven hosts. These hosts that carry out the attack on a target are usually controlled remotely and the owner of the device is unaware of it; for this reason one cannot attack back directly as this will serve little more than to disable an innocent party. A proposed solution to these DDoS attacks is to identify a potential attacking address and ignore communication from that address for a set period of time through time stamping.
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Deep genetic divergence between geographically isolated populations of the goldie barb (Barbus pallidus) in South Africa: potential taxonomic and conservation implications
- Chakona, Albert, Malherbe, Willem S, Gouws, Gavin, Swartz, Ernst R
- Authors: Chakona, Albert , Malherbe, Willem S , Gouws, Gavin , Swartz, Ernst R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443284 , vital:74105 , https://hdl.handle.net/10520/EJC177698
- Description: Barbus pallidus as it is presently defined has a disjunct distribution that is divided between northern and southern populations in South Africa. Sequence data from the cytochrome b gene region showed two distinct lineages that correspond to these geographically distant areas. Divergence between these two lineages was relatively high (5.5-6.5%) and comparable to typical interspecific divergences found between closely related southern African cyprinid fishes. Based on this deep genetic divergence, we conclude that the northern lineage may represent a previously unrecognised species or may belong to a different, but known species or species complex not associated with 'true' B. pallidus. These findings add to a growing body of evidence that freshwater fish diversity in southern Africa requires major revision.
- Full Text:
- Authors: Chakona, Albert , Malherbe, Willem S , Gouws, Gavin , Swartz, Ernst R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443284 , vital:74105 , https://hdl.handle.net/10520/EJC177698
- Description: Barbus pallidus as it is presently defined has a disjunct distribution that is divided between northern and southern populations in South Africa. Sequence data from the cytochrome b gene region showed two distinct lineages that correspond to these geographically distant areas. Divergence between these two lineages was relatively high (5.5-6.5%) and comparable to typical interspecific divergences found between closely related southern African cyprinid fishes. Based on this deep genetic divergence, we conclude that the northern lineage may represent a previously unrecognised species or may belong to a different, but known species or species complex not associated with 'true' B. pallidus. These findings add to a growing body of evidence that freshwater fish diversity in southern Africa requires major revision.
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Density and regrowth of a forest restio (Ischyrolepis eleocharis) under harvest and non-harvest treatments in dune forests of Eastern Cape Province, South Africa
- Ruwanza, Sheunesu, Shackleton, Charlie M
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180828 , vital:43649 , xlink:href="https://doi.org/10.1007/s12231-015-9306-y"
- Description: Ischyrolepis eleocharis (Mast.) H.P.Linder is a perennial rush or sedge-like herb in the Restionaceae family and has been harvested for various uses from coastal forest dunes of South Africa. Around 2005, a ban on I. eleocharis harvesting in Bathurst coastal forest was instituted by provincial conservation authorities based on their unsubstantiated impression that the species population was decreasing. Here we report on the population density pre and post the harvest ban, as well as further explore the autecology of the species by assessing plant density relative to environmental factors (slope and aspect) and a controlled experiment on regrowth after harvesting at different intensities. The results show that the shoot density of both living and dead I. eleocharis increased significantly over the past eight years. This concurs with results from the harvesting experiment which showed that I. eleocharis recovered rapidly within a year of harvesting. Both aspect and slope play a key role in the distribution of I. eleocharis, with most plants found in open patches in the forest located on the summit and upper slopes of dunes facing the landward side. These results indicate that I. eleocharis is highly abundant and resilient to harvesting.
- Full Text:
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180828 , vital:43649 , xlink:href="https://doi.org/10.1007/s12231-015-9306-y"
- Description: Ischyrolepis eleocharis (Mast.) H.P.Linder is a perennial rush or sedge-like herb in the Restionaceae family and has been harvested for various uses from coastal forest dunes of South Africa. Around 2005, a ban on I. eleocharis harvesting in Bathurst coastal forest was instituted by provincial conservation authorities based on their unsubstantiated impression that the species population was decreasing. Here we report on the population density pre and post the harvest ban, as well as further explore the autecology of the species by assessing plant density relative to environmental factors (slope and aspect) and a controlled experiment on regrowth after harvesting at different intensities. The results show that the shoot density of both living and dead I. eleocharis increased significantly over the past eight years. This concurs with results from the harvesting experiment which showed that I. eleocharis recovered rapidly within a year of harvesting. Both aspect and slope play a key role in the distribution of I. eleocharis, with most plants found in open patches in the forest located on the summit and upper slopes of dunes facing the landward side. These results indicate that I. eleocharis is highly abundant and resilient to harvesting.
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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:
- 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.
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Editorial. Perspectives on transformations in learning and education
- Authors: Lotz-Sisitka, Heila
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387277 , vital:68221 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137656"
- Description: Perspectives on transformations in learning and education
- Full Text:
- Authors: Lotz-Sisitka, Heila
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387277 , vital:68221 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137656"
- Description: Perspectives on transformations in learning and education
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Effect of conventional and organic orchard floor management practices on arbuscular mycorrhizal fungi in a ‘Cripp’s Pink’/M7 apple orchard soil
- Meyer, André H, Wooldridge, John, Dames, Joanna F
- Authors: Meyer, André H , Wooldridge, John , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444012 , vital:74178 , https://doi.org/10.1016/j.agee.2015.07.026
- Description: Arbuscular mycorrhizal (AM) fungi are key components of agricultural soil–plant systems, which may be affected by agricultural practices. In organically managed (ORG) orchards, nutrients are supplied in the form of compost, and weeds are suppressed with mulches, whereas synthetic fertilizers and herbicides are used for these respective purposes in conventional (CON) orchards. The effects of ORG and CON orchard floor management practices on native AM fungi in apple orchards were investigated in a randomized field trial. AM root colonization, spore abundance, infectivity potentials and soil glomalin contents were determined in the 0–30 cm soil depth interval, in tree rows, over consecutive seasons. Root colonization was higher in the ORG than the CON treatments, but intermediate where straw mulch was substituted for green work-row covers. Glomalin levels were not affected by the treatments. Root colonization by AM fungi increased with increasing soil pH, P, C, K, Zn, and Mn concentrations, but were suppressed by Cu. Colonization correlated positively with leaf P, Ca and Mg, and with stem circumference, but negatively with leaf N and yield. ORG orchard floor management practices therefore, promoted functional AM associations more effectively than CON practices.
- Full Text:
- Authors: Meyer, André H , Wooldridge, John , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444012 , vital:74178 , https://doi.org/10.1016/j.agee.2015.07.026
- Description: Arbuscular mycorrhizal (AM) fungi are key components of agricultural soil–plant systems, which may be affected by agricultural practices. In organically managed (ORG) orchards, nutrients are supplied in the form of compost, and weeds are suppressed with mulches, whereas synthetic fertilizers and herbicides are used for these respective purposes in conventional (CON) orchards. The effects of ORG and CON orchard floor management practices on native AM fungi in apple orchards were investigated in a randomized field trial. AM root colonization, spore abundance, infectivity potentials and soil glomalin contents were determined in the 0–30 cm soil depth interval, in tree rows, over consecutive seasons. Root colonization was higher in the ORG than the CON treatments, but intermediate where straw mulch was substituted for green work-row covers. Glomalin levels were not affected by the treatments. Root colonization by AM fungi increased with increasing soil pH, P, C, K, Zn, and Mn concentrations, but were suppressed by Cu. Colonization correlated positively with leaf P, Ca and Mg, and with stem circumference, but negatively with leaf N and yield. ORG orchard floor management practices therefore, promoted functional AM associations more effectively than CON practices.
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Effect of temperature on development of the blowfly, Lucilia cuprina (Wiedemann)(Diptera: Calliphoridae)
- Kotzé, Zanthé, Villet, Martin H, Weldon, Christopher W
- Authors: Kotzé, Zanthé , Villet, Martin H , Weldon, Christopher W
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442116 , vital:73960 , https://doi.org/10.1007/s00414-015-1153-y
- Description: The blowfly Lucilia cuprina is a primary colonizer of decaying vertebrate carrion, and its development provides a temperature-dependent clock that may be used to estimate the post-mortem interval of corpses and carcasses in medicolegal forensic investigations. This study uses the development of L. cuprina raised on a substrate of chicken liver at six constant temperatures from 18 to 33 °C to calibrate a thermal accumulation model of development for forensic applications. Development was optimal near 24 °C; above this temperature, survival of post-feeding life stages was increasingly compromised, while below it, development was increasingly retarded. The lower developmental threshold (~12 °C) and thermal summation constants of L. cuprina are distinct from those reported for Lucilia sericata, verifying that it is essential to identify African Lucilia specimens accurately when using them to estimate post-mortem intervals.
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- Authors: Kotzé, Zanthé , Villet, Martin H , Weldon, Christopher W
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442116 , vital:73960 , https://doi.org/10.1007/s00414-015-1153-y
- Description: The blowfly Lucilia cuprina is a primary colonizer of decaying vertebrate carrion, and its development provides a temperature-dependent clock that may be used to estimate the post-mortem interval of corpses and carcasses in medicolegal forensic investigations. This study uses the development of L. cuprina raised on a substrate of chicken liver at six constant temperatures from 18 to 33 °C to calibrate a thermal accumulation model of development for forensic applications. Development was optimal near 24 °C; above this temperature, survival of post-feeding life stages was increasingly compromised, while below it, development was increasingly retarded. The lower developmental threshold (~12 °C) and thermal summation constants of L. cuprina are distinct from those reported for Lucilia sericata, verifying that it is essential to identify African Lucilia specimens accurately when using them to estimate post-mortem intervals.
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Effects of differently shaped silver nanoparticles on the photophysics of pyridylsulfanyl-substituted phthalocyanines
- D'Souza, Sarah, Mashazi, Philani N, Britton, Jonathan, Nyokong, Tebello
- Authors: D'Souza, Sarah , Mashazi, Philani N , Britton, Jonathan , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193564 , vital:45348 , xlink:href="https://doi.org/10.1016/j.poly.2015.06.038"
- Description: This paper reports on the photophysical behavior of (2-pyridylsulfanyl)phthalocyaninato zinc(II) and 2,9(10),16(17),23(24)-tetra-(2-pyridylsulfanyl)phthalocyaninato zinc(II) in the presence of differently shaped silver nanoparticles (nanospheres, nanotriangles and nanoflowers). The presence of shaped nanoparticles increased both triplet quantum yields and lifetimes of the tetra-substituted mercaptopyridine zinc phthalocyanine in DMSO. It is apparent from this work that the shape of the silver nanoparticle used is of little consequence in influencing photophysical behavior of the phthalocyanines.
- Full Text:
- Authors: D'Souza, Sarah , Mashazi, Philani N , Britton, Jonathan , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193564 , vital:45348 , xlink:href="https://doi.org/10.1016/j.poly.2015.06.038"
- Description: This paper reports on the photophysical behavior of (2-pyridylsulfanyl)phthalocyaninato zinc(II) and 2,9(10),16(17),23(24)-tetra-(2-pyridylsulfanyl)phthalocyaninato zinc(II) in the presence of differently shaped silver nanoparticles (nanospheres, nanotriangles and nanoflowers). The presence of shaped nanoparticles increased both triplet quantum yields and lifetimes of the tetra-substituted mercaptopyridine zinc phthalocyanine in DMSO. It is apparent from this work that the shape of the silver nanoparticle used is of little consequence in influencing photophysical behavior of the phthalocyanines.
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Effects of inoculating Lachnum and Cadophora isolates on the growth of Vaccinium corymbosum
- MBizabani, Christine, Dames, Joanna F
- Authors: MBizabani, Christine , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444024 , vital:74179 , https://doi.org/10.1016/j.micres.2015.08.005
- Description: The roots of ericaceous plants harbour a diversity of fungal taxa, which confer eco-physiological benefits to the host. Some of the fungi have been established to form ericoid mycorrhizal (ERM) associations and enhance plant growth in certain ericaceous genera. Although, Lachnum and Cadophora isolates have frequently been identified from the roots of this family, the status of their association and functional roles is still vague. The aims of this study were to identify Lachnum and Cadophora isolates; determine the root-fungal interactive structures formed in associations with Vaccinium corymbosum L. (blueberry) hosts and to examine inoculation effects of the fungal associates using several varieties of the blueberry. Lachnum and Cadophora were isolated and identified from Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth using morphological and molecular techniques. Micropropagated blueberry varieties (Bluecrop, Elliott, Spartan, Chandler and Brightwell) were inoculated with respective fungi and plant growth evaluated. Both fungi colonised the roots and did not have any pathogenic effect.
- Full Text:
- Authors: MBizabani, Christine , Dames, Joanna F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444024 , vital:74179 , https://doi.org/10.1016/j.micres.2015.08.005
- Description: The roots of ericaceous plants harbour a diversity of fungal taxa, which confer eco-physiological benefits to the host. Some of the fungi have been established to form ericoid mycorrhizal (ERM) associations and enhance plant growth in certain ericaceous genera. Although, Lachnum and Cadophora isolates have frequently been identified from the roots of this family, the status of their association and functional roles is still vague. The aims of this study were to identify Lachnum and Cadophora isolates; determine the root-fungal interactive structures formed in associations with Vaccinium corymbosum L. (blueberry) hosts and to examine inoculation effects of the fungal associates using several varieties of the blueberry. Lachnum and Cadophora were isolated and identified from Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth using morphological and molecular techniques. Micropropagated blueberry varieties (Bluecrop, Elliott, Spartan, Chandler and Brightwell) were inoculated with respective fungi and plant growth evaluated. Both fungi colonised the roots and did not have any pathogenic effect.
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Effects of ZnO nanohexagons and nanorods on the fluorescence behavior of metallophthalocyanines
- D'Souza, Sarah, Moeno, Sharon, Nyokong, Tebello
- Authors: D'Souza, Sarah , Moeno, Sharon , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189741 , vital:44927 , xlink:href="https://doi.org/10.1016/j.poly.2014.09.012"
- Description: This paper looks at the fluorescence behavior of zinc phthalocyanines: 2,(3),9(10),16(17),23(24)-tetrakis- (mercaptoacetic acid phthalocyaninato) zinc(II) (ZnTMAAPc), 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptopropanoic acid phthalocyaninato) zinc(II) (ZnTMPAPc) and (OH)AlPcSmix (the latter contains a mixture of the di-, tri- and tetra-sulfonated derivatives with an average of three sulfonated groups per molecule) in the presence of ZnO nanoparticles. Fluorescence lifetimes of Pc complexes generally decreased in the presence of ZnO nanoparticles, with generally longer lifetimes for ZnO nanohexagons compared to ZnO nanorods.
- Full Text:
- Authors: D'Souza, Sarah , Moeno, Sharon , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189741 , vital:44927 , xlink:href="https://doi.org/10.1016/j.poly.2014.09.012"
- Description: This paper looks at the fluorescence behavior of zinc phthalocyanines: 2,(3),9(10),16(17),23(24)-tetrakis- (mercaptoacetic acid phthalocyaninato) zinc(II) (ZnTMAAPc), 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptopropanoic acid phthalocyaninato) zinc(II) (ZnTMPAPc) and (OH)AlPcSmix (the latter contains a mixture of the di-, tri- and tetra-sulfonated derivatives with an average of three sulfonated groups per molecule) in the presence of ZnO nanoparticles. Fluorescence lifetimes of Pc complexes generally decreased in the presence of ZnO nanoparticles, with generally longer lifetimes for ZnO nanohexagons compared to ZnO nanorods.
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Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
- Maringa, Audacity, Mashazi, Philani N, Nyokong, Tebello
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
- Full Text:
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189719 , vital:44925 , xlink:href="https://doi.org/10.1016/j.jcis.2014.10.056"
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 lA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 lA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 lM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.
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Electrocatalytic studies of covalently immobilized metal tetra-amino phthalocyanines onto derivatized screen-printed gold electrodes
- Mashazi, Philani N, Nyokong, Tebello
- Authors: Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249059 , vital:51774 , xlink:href="https://doi.org/10.1007/s00604-010-0438-6"
- Description: Metal tetra-amino phthalocyanine complexes (MTAPc; where M is Co or Mn) were immobilized on screen-printed gold electrodes pre-modified with monolayers of benzylamino groups. The functionalized electrodes were then activated using benzene-1,4-dicarbaldehyde as a linker before MTAPc complexes were immobilized. The surface coverages for the modified electrodes confirmed the perpendicular orientation of the MTAPcs. The apparent electron transfer constant (kapp) for the electrodes is 2.2 × 10−5 cm.s−1 for both CoTAPc and MnTAPc modified electrodes as calculated with data from impedance measurements. The kapp values for the bare and benzylamino modified electrodes were found to be 1.2 × 10−4 cm.s−1 and 4.9 × 10−6 cm.s−1, respectively. The electrocatalysis of the modified electrodes towards detection of H2O2 gave significant peak current densities and electrocatalytic potentials at −0.28 V and −0.31 V for the MnTAPc and CoTAPc modified electrodes, respectively.
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- Authors: Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/249059 , vital:51774 , xlink:href="https://doi.org/10.1007/s00604-010-0438-6"
- Description: Metal tetra-amino phthalocyanine complexes (MTAPc; where M is Co or Mn) were immobilized on screen-printed gold electrodes pre-modified with monolayers of benzylamino groups. The functionalized electrodes were then activated using benzene-1,4-dicarbaldehyde as a linker before MTAPc complexes were immobilized. The surface coverages for the modified electrodes confirmed the perpendicular orientation of the MTAPcs. The apparent electron transfer constant (kapp) for the electrodes is 2.2 × 10−5 cm.s−1 for both CoTAPc and MnTAPc modified electrodes as calculated with data from impedance measurements. The kapp values for the bare and benzylamino modified electrodes were found to be 1.2 × 10−4 cm.s−1 and 4.9 × 10−6 cm.s−1, respectively. The electrocatalysis of the modified electrodes towards detection of H2O2 gave significant peak current densities and electrocatalytic potentials at −0.28 V and −0.31 V for the MnTAPc and CoTAPc modified electrodes, respectively.
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Electrode modification using alkynyl substituted Fe (II) phthalocyanine via electrografting and click chemistry for electrocatalysis
- Nxele, Siphesihle R, Mashazi, Philani N, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
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- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189296 , vital:44835 , xlink:href="https://doi.org/10.1002/elan.201500212"
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM.
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Enhanced optical limiting behaviour of indium phthalocyanine derivatives when in solution or embedded in poly (acrylic acid) or poly (methyl methacrylate) polymers
- Sanusi, Kayode, Nyokong, Tebello
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189445 , vital:44847 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.02.003"
- Description: The optical limiting performance of indium phthalocyanine-based polymer thin-films with large nonlinear absorption coefficients (βeff) and low limiting threshold intensity (Ilim) are described. The absorption cross-sections and the population dynamics of the excited states are also reported. The excited state absorption cross-sections (σexc) are shown to depend on the transition moment between the T1 and T2 states. βeff values have been shown to be related to the population density of the molecules in the T1 state. The improved optical limiting performance recorded for the investigated phthalocyanine complexes in the presence of polymer matrices has been attributed to the aggregation effects of the complexes in the polymer thin-films. The optical properties of the indium phthalocyanine moieties were found to possess robust sensitivity to a change of the polymer materials.
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- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189445 , vital:44847 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.02.003"
- Description: The optical limiting performance of indium phthalocyanine-based polymer thin-films with large nonlinear absorption coefficients (βeff) and low limiting threshold intensity (Ilim) are described. The absorption cross-sections and the population dynamics of the excited states are also reported. The excited state absorption cross-sections (σexc) are shown to depend on the transition moment between the T1 and T2 states. βeff values have been shown to be related to the population density of the molecules in the T1 state. The improved optical limiting performance recorded for the investigated phthalocyanine complexes in the presence of polymer matrices has been attributed to the aggregation effects of the complexes in the polymer thin-films. The optical properties of the indium phthalocyanine moieties were found to possess robust sensitivity to a change of the polymer materials.
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Enhanced triplet state parameters for zinc carboxy phenoxy phthalocyanine following conjugation to ascorbic acid
- Ogbodu, Racheal O, Nyokong, Tebello
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189348 , vital:44839 , xlink:href="https://doi.org/10.1016/j.poly.2015.01.032"
- Description: Zinc phthalocyanine bearing four ascorbic acid units (formed via ester bond between zinc carboxy phenoxy phthalocyanines and ascorbic acid) was synthesized and characterized using different spectroscopic methods. The complex (with or without ascorbic acid) was further adsorbed onto single walled carbon nanotubes (SWCNTs) and further characterized using Raman spectroscopy, X-ray diffractometry, transmission electron microscopy and thermogravimetric analysis. The photophysical properties of the complexes were studied. The synthesized complex showed better photophysical properties when compared to the carboxy phenoxy phthalocyanines alone, this is evident in the increase of the triplet quantum yields (ΦT), triplet life-times (τT) and singlet oxygen quantum yields (ΦΔ). The zinc phthalocyanines bearing ascorbic acid showed improved triplet life-times even in the presence of SWCNTs.
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- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189348 , vital:44839 , xlink:href="https://doi.org/10.1016/j.poly.2015.01.032"
- Description: Zinc phthalocyanine bearing four ascorbic acid units (formed via ester bond between zinc carboxy phenoxy phthalocyanines and ascorbic acid) was synthesized and characterized using different spectroscopic methods. The complex (with or without ascorbic acid) was further adsorbed onto single walled carbon nanotubes (SWCNTs) and further characterized using Raman spectroscopy, X-ray diffractometry, transmission electron microscopy and thermogravimetric analysis. The photophysical properties of the complexes were studied. The synthesized complex showed better photophysical properties when compared to the carboxy phenoxy phthalocyanines alone, this is evident in the increase of the triplet quantum yields (ΦT), triplet life-times (τT) and singlet oxygen quantum yields (ΦΔ). The zinc phthalocyanines bearing ascorbic acid showed improved triplet life-times even in the presence of SWCNTs.
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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.
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- 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.
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Enhancing cloud connectivity among NRENs in the SADC region through a novel institution cloud infrastructure framework
- Suresh, Nalina, Mbale, Jameson, Terzoli, Alfredo, Mufeti, Tulimevava K
- Authors: Suresh, Nalina , Mbale, Jameson , Terzoli, Alfredo , Mufeti, Tulimevava K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430592 , vital:72702 , 10.1109/ETNCC.2015.7184830
- Description: It is increasingly being recognized that faster socioeconomic develop-ment in Africa is dependent upon the development of Information and Communication Technology (ICT) Infrastructure for the dissemination of data and educational services. The scalability and flexibility provided by Cloud services in terms of resource management, service provisioning and virtualization makes it an attractive system for use with educational and ICT services. The flexibility of pay-as-you-go models combined with the ability to scale computing, storage and/or networking resources makes Cloud computing an ideal candidate for use with education, re-search and scientific infrastructures. Notwithstanding its benefits, transi-tioning from a traditional IT infrastructure to a Cloud computing para-digm raises security concerns with respect to data storage, data trans-mission and user privacy. This paper presents on-going research for the development of Science, Technology and Innovation (STI) infra-structure for the distribution of Information Communication technologies (ICT) services in the African context. The Inter-Cloud Infrastructure Framework (ICIF) proposed, is conceived as a Cloud computing framework suitable for use with National Research and Education Net-works (NRENs) in the SADC region. The ICIF system is used to create an Inter-Cloud infrastructure, and helps NRENs transition from tradi-tional IT infrastructure systems to the Cloud computing paradigm. It also provides new functional/operational components and Cloud services to support the interconnection and/or interoperability among SADC NRENs through the ICIF infrastructure.
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- Authors: Suresh, Nalina , Mbale, Jameson , Terzoli, Alfredo , Mufeti, Tulimevava K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430592 , vital:72702 , 10.1109/ETNCC.2015.7184830
- Description: It is increasingly being recognized that faster socioeconomic develop-ment in Africa is dependent upon the development of Information and Communication Technology (ICT) Infrastructure for the dissemination of data and educational services. The scalability and flexibility provided by Cloud services in terms of resource management, service provisioning and virtualization makes it an attractive system for use with educational and ICT services. The flexibility of pay-as-you-go models combined with the ability to scale computing, storage and/or networking resources makes Cloud computing an ideal candidate for use with education, re-search and scientific infrastructures. Notwithstanding its benefits, transi-tioning from a traditional IT infrastructure to a Cloud computing para-digm raises security concerns with respect to data storage, data trans-mission and user privacy. This paper presents on-going research for the development of Science, Technology and Innovation (STI) infra-structure for the distribution of Information Communication technologies (ICT) services in the African context. The Inter-Cloud Infrastructure Framework (ICIF) proposed, is conceived as a Cloud computing framework suitable for use with National Research and Education Net-works (NRENs) in the SADC region. The ICIF system is used to create an Inter-Cloud infrastructure, and helps NRENs transition from tradi-tional IT infrastructure systems to the Cloud computing paradigm. It also provides new functional/operational components and Cloud services to support the interconnection and/or interoperability among SADC NRENs through the ICIF infrastructure.
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Evolutionary retention of defensive lateral pedal glands in the smallest siphonariid limpet (Gastropoda: Pulmonata)
- Pinchuck, Shirley C, Allanson, Brian R, Hodgson, Alan N
- Authors: Pinchuck, Shirley C , Allanson, Brian R , Hodgson, Alan N
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443312 , vital:74107 , https://hdl.handle.net/10520/EJC183115
- Description: Despite its cryptic habitat and habits, light and transmission electron microscopy has revealed that like many other siphonariids Siphonaria compressa, the smallest species of this genus, possesses lateral pedal glands. The pear-shaped glands (about 120 µm long Ã? 70 µm maximum diameter) open via a pore, and are multicellular with three types of secretory cell that surround a central lumen. The glands of this minute pulmonate limpet are similar in structure to its larger relatives, suggesting that they are defensive in function.
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- Authors: Pinchuck, Shirley C , Allanson, Brian R , Hodgson, Alan N
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443312 , vital:74107 , https://hdl.handle.net/10520/EJC183115
- Description: Despite its cryptic habitat and habits, light and transmission electron microscopy has revealed that like many other siphonariids Siphonaria compressa, the smallest species of this genus, possesses lateral pedal glands. The pear-shaped glands (about 120 µm long Ã? 70 µm maximum diameter) open via a pore, and are multicellular with three types of secretory cell that surround a central lumen. The glands of this minute pulmonate limpet are similar in structure to its larger relatives, suggesting that they are defensive in function.
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Facile synthesis, spectroscopic and electrochemical properties, and theoretical calculations of porphyrin dimers with a bridging amide-bonded xanthene moiety
- Liang, Xu, Xu, Li, Li, Minzhi, Mack, John, Stone, Justin, Nyokong, Tebello, Jiang, Yu, Kobayashi, Nagao, Zhu, Weihua
- Authors: Liang, Xu , Xu, Li , Li, Minzhi , Mack, John , Stone, Justin , Nyokong, Tebello , Jiang, Yu , Kobayashi, Nagao , Zhu, Weihua
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241390 , vital:50935 , xlink:href="https://doi.org/10.1142/S1088424615500492"
- Description: A free base porphyrin dimer bridged by a flexible amide-bonded xanthene moiety and its binuclear zinc(II) complex zinc(II) complex were synthesized and characterized. Structural characterization by MS and 1H NMR spectroscopy confirmed the bridged porphyrin dimer structure. The properties of the dimers were characterized by IR, UV-visible absorption, fluorescence and magnetic circular dichroism (MCD) spectroscopy, and electrochemistry studies. Theoretical calculations were carried out to analyze the electronic structures of porphyrin dimers with a bridging amide-bonded xanthene moiety.
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- Authors: Liang, Xu , Xu, Li , Li, Minzhi , Mack, John , Stone, Justin , Nyokong, Tebello , Jiang, Yu , Kobayashi, Nagao , Zhu, Weihua
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241390 , vital:50935 , xlink:href="https://doi.org/10.1142/S1088424615500492"
- Description: A free base porphyrin dimer bridged by a flexible amide-bonded xanthene moiety and its binuclear zinc(II) complex zinc(II) complex were synthesized and characterized. Structural characterization by MS and 1H NMR spectroscopy confirmed the bridged porphyrin dimer structure. The properties of the dimers were characterized by IR, UV-visible absorption, fluorescence and magnetic circular dichroism (MCD) spectroscopy, and electrochemistry studies. Theoretical calculations were carried out to analyze the electronic structures of porphyrin dimers with a bridging amide-bonded xanthene moiety.
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