Selective modulation of plasmodial Hsp70s by small molecules with antimalarial activity
- Cockburn, Ingrid, Boshoff, Aileen, Pesce, Eva-Rachele, Blatch, Gregory L
- Authors: Cockburn, Ingrid , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431192 , vital:72752 , xlink:href="https://doi.org/10.1515/hsz-2014-0138"
- Description: Plasmodial heat shock protein 70 (Hsp70) chaperones represent a promising new class of antimalarial drug targets because of the important roles they play in the survival and pathogenesis of the malaria parasite Plasmodium falciparum. This study assessed a set of small molecules (lapachol, bromo-β-lapachona and malonganenones A, B and C) as potential modulators of two biologically important plasmodial Hsp70s, the parasite-resident PfHsp70-1 and the exported PfHsp70-x. Compounds of interest were assessed for modulatory effects on the steady-state basal and heat shock protein 40 (Hsp40)-stimulated ATPase activities of PfHsp70-1, PfHsp70-x and human Hsp70, as well as on the protein aggregation suppression activity of PfHsp70-x. The antimalarial marine alkaloid malonganenone A was of particular interest, as it was found to have limited cytotoxicity to mammalian cell lines and exhibited the desired properties of an effective plasmodial Hsp70 modulator. This compound was found to inhibit plasmodial and not human Hsp70 ATPase activity (Hsp40-stimulated), and hindered the aggregation suppression activity of PfHsp70-x. Furthermore, malonganenone A was shown to disrupt the interaction between PfHsp70-x and Hsp40. This is the first report to show that PfHsp70-x has chaperone activity, is stimulated by Hsp40 and can be specifically modulated by small molecule compounds.
- Full Text:
- Authors: Cockburn, Ingrid , Boshoff, Aileen , Pesce, Eva-Rachele , Blatch, Gregory L
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431192 , vital:72752 , xlink:href="https://doi.org/10.1515/hsz-2014-0138"
- Description: Plasmodial heat shock protein 70 (Hsp70) chaperones represent a promising new class of antimalarial drug targets because of the important roles they play in the survival and pathogenesis of the malaria parasite Plasmodium falciparum. This study assessed a set of small molecules (lapachol, bromo-β-lapachona and malonganenones A, B and C) as potential modulators of two biologically important plasmodial Hsp70s, the parasite-resident PfHsp70-1 and the exported PfHsp70-x. Compounds of interest were assessed for modulatory effects on the steady-state basal and heat shock protein 40 (Hsp40)-stimulated ATPase activities of PfHsp70-1, PfHsp70-x and human Hsp70, as well as on the protein aggregation suppression activity of PfHsp70-x. The antimalarial marine alkaloid malonganenone A was of particular interest, as it was found to have limited cytotoxicity to mammalian cell lines and exhibited the desired properties of an effective plasmodial Hsp70 modulator. This compound was found to inhibit plasmodial and not human Hsp70 ATPase activity (Hsp40-stimulated), and hindered the aggregation suppression activity of PfHsp70-x. Furthermore, malonganenone A was shown to disrupt the interaction between PfHsp70-x and Hsp40. This is the first report to show that PfHsp70-x has chaperone activity, is stimulated by Hsp40 and can be specifically modulated by small molecule compounds.
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Spectral properties and photophysical behaviour of water soluble cationic Mg (II) and Al (III) phthalocyanines
- Idowu, Mopelola A, Arslanoğlu, Yasin, Nyokong, Tebello
- Authors: Idowu, Mopelola A , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241549 , vital:50949 , xlink:href="https://doi.org/10.2478/s11532-013-0388-z"
- Description: Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (FT) and the triplet lifetimes (tT) were found to be higher in DMSO with ΦT ranging from 0.32 to 0.51, while tT ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where ΦT ranged from 0.15 to 0.19 and tT from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).
- Full Text:
- Authors: Idowu, Mopelola A , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241549 , vital:50949 , xlink:href="https://doi.org/10.2478/s11532-013-0388-z"
- Description: Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (FT) and the triplet lifetimes (tT) were found to be higher in DMSO with ΦT ranging from 0.32 to 0.51, while tT ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where ΦT ranged from 0.15 to 0.19 and tT from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).
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Successful identification of the final instar nymph of Quintilia carinata (Thunberg)(Hemiptera: Cicadidae) by DNA extraction from the exuvium
- Bouwer, Nicolette, Midgley, John M, Timm, Alicia E, Villet, Martin H
- Authors: Bouwer, Nicolette , Midgley, John M , Timm, Alicia E , Villet, Martin H
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442347 , vital:73977 , https://doi.org/10.1080/00222933.2013.836759
- Description: Despite being taxonomically and phylogenetically informative, the morphology of the immature stages of cicadas has received comparatively superficial attention. One reason for this is the difficulty of positively identifying immature stages, particularly as these stages are fossorial. We present a method for identifying cicada exuviae using DNA sequence data and describe a set of characters and character states for the final instar nymph of Quintilia carinata (Thunberg). The identification of immature stages using molecular methods will increase our knowledge of African cicadas, allowing for the initiation of future phylogenetic and ecological comparisons.
- Full Text:
- Authors: Bouwer, Nicolette , Midgley, John M , Timm, Alicia E , Villet, Martin H
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442347 , vital:73977 , https://doi.org/10.1080/00222933.2013.836759
- Description: Despite being taxonomically and phylogenetically informative, the morphology of the immature stages of cicadas has received comparatively superficial attention. One reason for this is the difficulty of positively identifying immature stages, particularly as these stages are fossorial. We present a method for identifying cicada exuviae using DNA sequence data and describe a set of characters and character states for the final instar nymph of Quintilia carinata (Thunberg). The identification of immature stages using molecular methods will increase our knowledge of African cicadas, allowing for the initiation of future phylogenetic and ecological comparisons.
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Sustainability Assessment of University of Gondar, Gondar, North-west Ethiopia
- Moges, Haimanot G, Kifle, Desalegn W, Lotz-Sisitka, Heila, Woldyohhanes, Solomon M
- Authors: Moges, Haimanot G , Kifle, Desalegn W , Lotz-Sisitka, Heila , Woldyohhanes, Solomon M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182845 , vital:43885 , xlink:href="https://doi.org/10.1177/0973408214529990"
- Description: The purpose of this article is to provide an overview of the cross-institutional assessment of sustainable development practices in the University of Gondar (UoG). The focus of the assessment was the level of UoG academic departments’ integration of sustainability concerns in teaching, research and community service. Management contributions to sustainable development, student initiatives on sustainability issues and policy statements about sustainable development of UoG were also considered in the assessment. The data collection was based on the Unit-based Sustainability Assessment Tool (USAT); in addition, supplementary information was collected through observations across the four campuses of UoG from January to February 2012.The result of the assessment showed that only a few academic departments have incorporated sustainability concerns in their curricula and teaching approach. The initiation and commitment of academic departments in mainstreaming sustainability concerns in the research and community service delivered were relatively poor. The operation and management of UoG showed inadequate sustainable development practices on waste management, energy utilization and purchasing from environment-friendly companies. In addition, the written policy and statements of UoG did not reflect sustainability in an explicit manner. The university is expected to respond to the key themes defined through sustainability declarations on higher education; there is also a need to establish the relevance of these in relation to the systemic environment. From the study undertaken, we have learnt that sustainability assessment of universities using USAT will be more valuable, if universities have already initiated the embedding of sustainability so that USAT can be used to benchmark the continual improvement.
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- Authors: Moges, Haimanot G , Kifle, Desalegn W , Lotz-Sisitka, Heila , Woldyohhanes, Solomon M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182845 , vital:43885 , xlink:href="https://doi.org/10.1177/0973408214529990"
- Description: The purpose of this article is to provide an overview of the cross-institutional assessment of sustainable development practices in the University of Gondar (UoG). The focus of the assessment was the level of UoG academic departments’ integration of sustainability concerns in teaching, research and community service. Management contributions to sustainable development, student initiatives on sustainability issues and policy statements about sustainable development of UoG were also considered in the assessment. The data collection was based on the Unit-based Sustainability Assessment Tool (USAT); in addition, supplementary information was collected through observations across the four campuses of UoG from January to February 2012.The result of the assessment showed that only a few academic departments have incorporated sustainability concerns in their curricula and teaching approach. The initiation and commitment of academic departments in mainstreaming sustainability concerns in the research and community service delivered were relatively poor. The operation and management of UoG showed inadequate sustainable development practices on waste management, energy utilization and purchasing from environment-friendly companies. In addition, the written policy and statements of UoG did not reflect sustainability in an explicit manner. The university is expected to respond to the key themes defined through sustainability declarations on higher education; there is also a need to establish the relevance of these in relation to the systemic environment. From the study undertaken, we have learnt that sustainability assessment of universities using USAT will be more valuable, if universities have already initiated the embedding of sustainability so that USAT can be used to benchmark the continual improvement.
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Synthesis and characterization of quantum dots designed for biomedical use
- Kuzyniak, Weronika, Adegoke, Oluwasesan, Sekhosana, Kutloana E, D'Souza, Sarah, Tshangana, Sesethu Charmaine, Hoffmann, Björn, Ermilov, Eugeny A, Nyokong, Tebello, Höpfner, Michael
- Authors: Kuzyniak, Weronika , Adegoke, Oluwasesan , Sekhosana, Kutloana E , D'Souza, Sarah , Tshangana, Sesethu Charmaine , Hoffmann, Björn , Ermilov, Eugeny A , Nyokong, Tebello , Höpfner, Michael
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241516 , vital:50946 , xlink:href="https://doi.org/10.1016/j.ijpharm.2014.03.037"
- Description: Semiconductor quantum dots (QDs) have become promising nanoparticles for a wide variety of biomedical applications. However, the major drawback of QDs is their potential toxicity. Here, we determined possible cytotoxic effects of a set of QDs by systematic photophysical evaluation in vitro as well as in vivo. QDs were synthesized by the hydrothermal aqueous route with sizes in the range of 2.0–3.5 nm. Cytotoxic effects of QDs were studied in the human pancreatic carcinoid cell line BON. Cadmium telluride QDs with or without zinc sulfide shell and coated with 3-mercaptopropionic acid (MPA) were highly cytotoxic even at nanomolar concentrations. Capping with L-glutathione (GSH) or thioglycolic acid (TGA) reduced the cytotoxicity of cadmium telluride QDs and cadmium selenide QDs. Determination of the toxicity of QDs revealed IC50 values in the micromolar range. In vivo studies showed good tolerability of CdSe QDs with ZnS shell and GSH capping. We could demonstrate that QDs with ZnS shell and GSH capping exhibit low toxicity and good tolerability in cell models and living organisms. These QDs appear to be promising candidates for biomedical applications such as drug delivery for enhanced chemotherapy or targeted delivery of light sensitive substances for photodynamic therapy.
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- Authors: Kuzyniak, Weronika , Adegoke, Oluwasesan , Sekhosana, Kutloana E , D'Souza, Sarah , Tshangana, Sesethu Charmaine , Hoffmann, Björn , Ermilov, Eugeny A , Nyokong, Tebello , Höpfner, Michael
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241516 , vital:50946 , xlink:href="https://doi.org/10.1016/j.ijpharm.2014.03.037"
- Description: Semiconductor quantum dots (QDs) have become promising nanoparticles for a wide variety of biomedical applications. However, the major drawback of QDs is their potential toxicity. Here, we determined possible cytotoxic effects of a set of QDs by systematic photophysical evaluation in vitro as well as in vivo. QDs were synthesized by the hydrothermal aqueous route with sizes in the range of 2.0–3.5 nm. Cytotoxic effects of QDs were studied in the human pancreatic carcinoid cell line BON. Cadmium telluride QDs with or without zinc sulfide shell and coated with 3-mercaptopropionic acid (MPA) were highly cytotoxic even at nanomolar concentrations. Capping with L-glutathione (GSH) or thioglycolic acid (TGA) reduced the cytotoxicity of cadmium telluride QDs and cadmium selenide QDs. Determination of the toxicity of QDs revealed IC50 values in the micromolar range. In vivo studies showed good tolerability of CdSe QDs with ZnS shell and GSH capping. We could demonstrate that QDs with ZnS shell and GSH capping exhibit low toxicity and good tolerability in cell models and living organisms. These QDs appear to be promising candidates for biomedical applications such as drug delivery for enhanced chemotherapy or targeted delivery of light sensitive substances for photodynamic therapy.
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Synthesis and MRSA PK inhibitory activity of thiazole containing deoxytopsentin analogues
- Veale, Clinton G L, Lobb, Kevin A, Zoraghi, Roya, Morrison, James P, Reiner, Neil E, Andersen, Raymond J, Davies-Coleman, Michael T
- Authors: Veale, Clinton G L , Lobb, Kevin A , Zoraghi, Roya , Morrison, James P , Reiner, Neil E , Andersen, Raymond J , Davies-Coleman, Michael T
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448028 , vital:74692 , xlink:href="https://doi.org/10.1016/j.tet.2014.09.007"
- Description: The public health care crisis caused by the emergence of drug resistant bacterial strains, e.g., methicillin resistant Staphylococcus aureus (MRSA) has underlined the urgent need to accelerate the discovery of new chemical entities active against antibiotic resistant bacteria. We report here the synthesis of a series thiazole containing deoxytopsentin analogues, which show moderate activity against a target MRSA pyruvate kinase enzyme: an evolutionary conserved hub protein critical for bacterial survival. A Hantzsch thiazole coupling between a-oxo-1H-indole-3-thioacetamides and 2-bromo-1-(1H-indol-3-yl)-ethanones provided facile access to the thiazole containing deoxytopsentin compounds.
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- Authors: Veale, Clinton G L , Lobb, Kevin A , Zoraghi, Roya , Morrison, James P , Reiner, Neil E , Andersen, Raymond J , Davies-Coleman, Michael T
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448028 , vital:74692 , xlink:href="https://doi.org/10.1016/j.tet.2014.09.007"
- Description: The public health care crisis caused by the emergence of drug resistant bacterial strains, e.g., methicillin resistant Staphylococcus aureus (MRSA) has underlined the urgent need to accelerate the discovery of new chemical entities active against antibiotic resistant bacteria. We report here the synthesis of a series thiazole containing deoxytopsentin analogues, which show moderate activity against a target MRSA pyruvate kinase enzyme: an evolutionary conserved hub protein critical for bacterial survival. A Hantzsch thiazole coupling between a-oxo-1H-indole-3-thioacetamides and 2-bromo-1-(1H-indol-3-yl)-ethanones provided facile access to the thiazole containing deoxytopsentin compounds.
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Synthesis of ytterbium bisphthalocyanines
- Sekhosana, Kutloana E, Nyokong, Tebello
- Authors: Sekhosana, Kutloana E , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189887 , vital:44943 , xlink:href="https://doi.org/10.1016/j.optmat.2014.05.013"
- Description: Herein we report on the syntheses, photophysico-chemical properties and nonlinear absorption parameters of bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-2-yloxy phthalocyaninato)} ytterbium (III) (3) and bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium (III) (4). The fluorescence and singlet oxygen quantum yields obtained for complexes 3 and 4 are low. The triplet quantum yield obtained for complex 3 is high at ΦT = 0.89 whereas for complex 4 ΦT = 0.48. The third order optical susceptibility values are of the order: 10−11 esu (for complex 3), and 10−13 esu (for complex 4) while the hyperpolarizability values are of the order: 10−28 esu (for complex 3) and 10−31 esu (for complex 4). Complexes 3 and 4 show two-photon absorption coefficients of the order of 10−46 cm4 s/photon and 10−48 cm4 s/photon, and threshold intensities as low as 0.3 J cm−2 and 0.0045 J cm−2, respectively.
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- Authors: Sekhosana, Kutloana E , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189887 , vital:44943 , xlink:href="https://doi.org/10.1016/j.optmat.2014.05.013"
- Description: Herein we report on the syntheses, photophysico-chemical properties and nonlinear absorption parameters of bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-2-yloxy phthalocyaninato)} ytterbium (III) (3) and bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium (III) (4). The fluorescence and singlet oxygen quantum yields obtained for complexes 3 and 4 are low. The triplet quantum yield obtained for complex 3 is high at ΦT = 0.89 whereas for complex 4 ΦT = 0.48. The third order optical susceptibility values are of the order: 10−11 esu (for complex 3), and 10−13 esu (for complex 4) while the hyperpolarizability values are of the order: 10−28 esu (for complex 3) and 10−31 esu (for complex 4). Complexes 3 and 4 show two-photon absorption coefficients of the order of 10−46 cm4 s/photon and 10−48 cm4 s/photon, and threshold intensities as low as 0.3 J cm−2 and 0.0045 J cm−2, respectively.
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Synthesis, characterization and photodynamic therapy properties of an octa-4-tert-butylphenoxy-substituted phosphorus (V) triazatetrabenzcorrole
- Shi, Maohu, Tian, Jiangwei, Mkhize, Colin, Kubheka, Gugu, Zhou, Jinfeng, Mack, John, Nyokong, Tebello, Shen, Zhen
- Authors: Shi, Maohu , Tian, Jiangwei , Mkhize, Colin , Kubheka, Gugu , Zhou, Jinfeng , Mack, John , Nyokong, Tebello , Shen, Zhen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241494 , vital:50944 , xlink:href="https://doi.org/10.1142/S1088424614500436"
- Description: A novel octa-4-tert-butylphenoxy-substituted phosphorus(V) triazatetrabenzcorrole (PVTBC), has been synthesized and characterized by MALDI-TOF MS and NMR, FT-IR and MCD spectroscopy. The fluorescence emission spectrum was used to determine the fluorescence quantum yield and the quantum yield for singlet oxygen generation was calculated by using 1,3-diphenylisobenzofuran as a scavenger. The photocytoxicity against U87MG cells was measured. The results indicated that PVTBC is potentially useful as an NIR region photosensitizer for photodynamic therapy (PDT).
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- Authors: Shi, Maohu , Tian, Jiangwei , Mkhize, Colin , Kubheka, Gugu , Zhou, Jinfeng , Mack, John , Nyokong, Tebello , Shen, Zhen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241494 , vital:50944 , xlink:href="https://doi.org/10.1142/S1088424614500436"
- Description: A novel octa-4-tert-butylphenoxy-substituted phosphorus(V) triazatetrabenzcorrole (PVTBC), has been synthesized and characterized by MALDI-TOF MS and NMR, FT-IR and MCD spectroscopy. The fluorescence emission spectrum was used to determine the fluorescence quantum yield and the quantum yield for singlet oxygen generation was calculated by using 1,3-diphenylisobenzofuran as a scavenger. The photocytoxicity against U87MG cells was measured. The results indicated that PVTBC is potentially useful as an NIR region photosensitizer for photodynamic therapy (PDT).
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Synthesis, photophysicochemical properties and TD-DFT calculations of tetrakis (2-benzoyl-4-chlorophenoxy) phthalocyanines
- Yilmaz, Yusuf, Mack, John, Sener, M Kasim, Sönmez, Mehmet, Nyokong, Tebello
- Authors: Yilmaz, Yusuf , Mack, John , Sener, M Kasim , Sönmez, Mehmet , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241538 , vital:50948 , xlink:href="https://doi.org/10.1142/S1088424614500047"
- Description: The synthesis of metal free, magnesium and zinc tetrakis(2-benzoyl-4-chlorophenoxy) phthalocyanine derivatives (2–4) is described along with their characterization by elemental analysis, IR, UV-visible absorption, and 1H NMR spectroscopy and mass spectrometry. Trends observed in the fluorescence, triplet state, singlet oxygen and photodegradation quantum yields and the triplet state lifetimes are also analyzed. The compounds exhibit high solubility in a wide range of organic solvents and no evidence of aggregation was observed over a wide concentration range. The Zn(II) complex (4) was found to have a very high singlet oxygen quantum yield (ΦΔ = 0.78) in dimethylsulfoxide (DMSO) and a reasonably large triplet state quantum yield (ΦT = 0.82). The photophysical and photochemical properties clearly demonstrate that these compounds could prove useful in singlet oxygen applications such as photodynamic therapy (PDT). DFT and TD-DFT calculations were used to assess the impact of the positional isomerism of the 2-benzoyl-4-chlorophenoxy substituents on the electronic structures and optical spectroscopy.
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- Authors: Yilmaz, Yusuf , Mack, John , Sener, M Kasim , Sönmez, Mehmet , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241538 , vital:50948 , xlink:href="https://doi.org/10.1142/S1088424614500047"
- Description: The synthesis of metal free, magnesium and zinc tetrakis(2-benzoyl-4-chlorophenoxy) phthalocyanine derivatives (2–4) is described along with their characterization by elemental analysis, IR, UV-visible absorption, and 1H NMR spectroscopy and mass spectrometry. Trends observed in the fluorescence, triplet state, singlet oxygen and photodegradation quantum yields and the triplet state lifetimes are also analyzed. The compounds exhibit high solubility in a wide range of organic solvents and no evidence of aggregation was observed over a wide concentration range. The Zn(II) complex (4) was found to have a very high singlet oxygen quantum yield (ΦΔ = 0.78) in dimethylsulfoxide (DMSO) and a reasonably large triplet state quantum yield (ΦT = 0.82). The photophysical and photochemical properties clearly demonstrate that these compounds could prove useful in singlet oxygen applications such as photodynamic therapy (PDT). DFT and TD-DFT calculations were used to assess the impact of the positional isomerism of the 2-benzoyl-4-chlorophenoxy substituents on the electronic structures and optical spectroscopy.
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Teaching Without Technology
- Authors: Machanick, Philip
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439238 , vital:73558 , https://homes.cs.ru.ac.za/philip/Publications/_SACLA/teachWOtech-2014.pdf
- Description: Technology is touted as a solution to problems in education. But is it? I report here on experiences with dropping use of slides in lectures and returning to working on the board. The apparent result is more interactive, engaged classes. Unfortunately there are too many other variables to make the experiences here definitive. The purpose of this paper is to provoke discussion on whether technology is overused in teaching when the goals of improving student engagement and general effectiveness of learning can be met many ways. Technology is not necessarily bad, but making it the starting point risks locking out nontechnological options.
- Full Text:
- Authors: Machanick, Philip
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439238 , vital:73558 , https://homes.cs.ru.ac.za/philip/Publications/_SACLA/teachWOtech-2014.pdf
- Description: Technology is touted as a solution to problems in education. But is it? I report here on experiences with dropping use of slides in lectures and returning to working on the board. The apparent result is more interactive, engaged classes. Unfortunately there are too many other variables to make the experiences here definitive. The purpose of this paper is to provoke discussion on whether technology is overused in teaching when the goals of improving student engagement and general effectiveness of learning can be met many ways. Technology is not necessarily bad, but making it the starting point risks locking out nontechnological options.
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Testing antivirus engines to determine their effectiveness as a security layer
- Haffejee, Jameel, Irwin, Barry V W
- Authors: Haffejee, Jameel , Irwin, Barry V W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429673 , vital:72631 , 10.1109/ISSA.2014.6950496
- Description: This research has been undertaken to empirically test the assumption that it is trivial to bypass an antivirus application and to gauge the effectiveness of antivirus engines when faced with a number of known evasion techniques. A known malicious binary was combined with evasion techniques and deployed against several antivirus engines to test their detection ability. The research also documents the process of setting up an environment for testing antivirus engines as well as building the evasion techniques used in the tests. This environment facilitated the empirical testing that was needed to determine if the assumption that antivirus security controls could easily be bypassed. The results of the empirical tests are also presented in this research and demonstrate that it is indeed within reason that an attacker can evade multiple antivirus engines without much effort. As such while an antivirus application is useful for protecting against known threats, it does not work as effectively against unknown threats.
- Full Text:
- Authors: Haffejee, Jameel , Irwin, Barry V W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429673 , vital:72631 , 10.1109/ISSA.2014.6950496
- Description: This research has been undertaken to empirically test the assumption that it is trivial to bypass an antivirus application and to gauge the effectiveness of antivirus engines when faced with a number of known evasion techniques. A known malicious binary was combined with evasion techniques and deployed against several antivirus engines to test their detection ability. The research also documents the process of setting up an environment for testing antivirus engines as well as building the evasion techniques used in the tests. This environment facilitated the empirical testing that was needed to determine if the assumption that antivirus security controls could easily be bypassed. The results of the empirical tests are also presented in this research and demonstrate that it is indeed within reason that an attacker can evade multiple antivirus engines without much effort. As such while an antivirus application is useful for protecting against known threats, it does not work as effectively against unknown threats.
- Full Text:
Thaumatotibia leucotreta and the Navel orange: ovipositional preferences and host susceptibility
- Love, C N, Hill, Martin P, Moore, Sean D
- Authors: Love, C N , Hill, Martin P , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423811 , vital:72095 , xlink:href="https://doi.org/10.1111/jen.12126"
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), presents a significant threat to the South African citrus industry. To limit income loss due to direct larval damage or from fruit rejection due to the phytosanitary status of this pest, additional pre-harvest control techniques are required for Navel oranges, which are known to be susceptible to T.leucotreta damage. A number of Navel orange cultivars have been developed, and differences in female T. leucotretaovi positional preference and susceptibility of cultivars to larval penetration are known to exist. Navel orange cultivars were grouped according to time of maturity (early, mid- and late season). Female T.leucotreta were subjected to choice and no-choice tests with these cultivars, measured by oviposition. Host susceptibility was tested by allowing neonate T. leucotreta larvae to penetrate the different Navel cultivars. In the early maturing group, Fischer Navels were least preferred for oviposition and the least susceptible to larval penetration. The mid- and late season maturing groupings showed limited differences in oviposition preference, although host susceptibility did appear to be an important factor in assessing the vulnerability of fruit to T. leucotreta. Despite being widely planted in South Africa, the mid-season Palmer Navels were highly susceptible to larval penetration, while for the late season cultivars, Cambria and Glen Ora Late were the least susceptible to T. leucotreta. As a result of these laboratory trials, it is recommended that farmers increase cultivation of Fischer Navels as the principal early season cultivar, avoid Palmer Navels in favour of other mid-season maturing cultivars and give preference to the late maturing Cambria and Glen Ora Late cultivars, to limit T. Leucotreta damage.
- Full Text:
- Authors: Love, C N , Hill, Martin P , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423811 , vital:72095 , xlink:href="https://doi.org/10.1111/jen.12126"
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), presents a significant threat to the South African citrus industry. To limit income loss due to direct larval damage or from fruit rejection due to the phytosanitary status of this pest, additional pre-harvest control techniques are required for Navel oranges, which are known to be susceptible to T.leucotreta damage. A number of Navel orange cultivars have been developed, and differences in female T. leucotretaovi positional preference and susceptibility of cultivars to larval penetration are known to exist. Navel orange cultivars were grouped according to time of maturity (early, mid- and late season). Female T.leucotreta were subjected to choice and no-choice tests with these cultivars, measured by oviposition. Host susceptibility was tested by allowing neonate T. leucotreta larvae to penetrate the different Navel cultivars. In the early maturing group, Fischer Navels were least preferred for oviposition and the least susceptible to larval penetration. The mid- and late season maturing groupings showed limited differences in oviposition preference, although host susceptibility did appear to be an important factor in assessing the vulnerability of fruit to T. leucotreta. Despite being widely planted in South Africa, the mid-season Palmer Navels were highly susceptible to larval penetration, while for the late season cultivars, Cambria and Glen Ora Late were the least susceptible to T. leucotreta. As a result of these laboratory trials, it is recommended that farmers increase cultivation of Fischer Navels as the principal early season cultivar, avoid Palmer Navels in favour of other mid-season maturing cultivars and give preference to the late maturing Cambria and Glen Ora Late cultivars, to limit T. Leucotreta damage.
- Full Text:
The comparative growth rates of indigenous street and garden trees in Grahamstown, South Africa
- De Lacy, Peter J G, Shackleton, Charlie M
- Authors: De Lacy, Peter J G , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180943 , vital:43672 , xlink:href="https://doi.org/10.1016/j.sajb.2014.02.007"
- Description: Urban forestry is advocated worldwide as a means of enhancing the liveability of towns and cities, and mitigating some of the anticipated impacts of climate change. Optimisation of the benefits of trees in urban areas is dependent upon knowledge of tree form, growth, and the products and benefits that trees provide. Growth rates are a vital variable for modelling benefits, yet there is a significant gap in knowledge pertaining to growth rates of trees in urban areas, especially indigenous species in developing world countries. Here we report on growth rates of indigenous street and garden trees in Grahamstown, South Africa, using two approaches; tree ring counts on increment cores and mean rates from trees of known planting age. Growth equations for both street and garden trees were derived. There was no significant difference in mean growth rates determined via the two methods. For both methods street trees grew approximately 30% slower than trees in gardens.
- Full Text:
- Authors: De Lacy, Peter J G , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180943 , vital:43672 , xlink:href="https://doi.org/10.1016/j.sajb.2014.02.007"
- Description: Urban forestry is advocated worldwide as a means of enhancing the liveability of towns and cities, and mitigating some of the anticipated impacts of climate change. Optimisation of the benefits of trees in urban areas is dependent upon knowledge of tree form, growth, and the products and benefits that trees provide. Growth rates are a vital variable for modelling benefits, yet there is a significant gap in knowledge pertaining to growth rates of trees in urban areas, especially indigenous species in developing world countries. Here we report on growth rates of indigenous street and garden trees in Grahamstown, South Africa, using two approaches; tree ring counts on increment cores and mean rates from trees of known planting age. Growth equations for both street and garden trees were derived. There was no significant difference in mean growth rates determined via the two methods. For both methods street trees grew approximately 30% slower than trees in gardens.
- Full Text:
The effect of sap-sucking by Falconia intermedia (Hemiptera: Miridae) on the emission of volatile organic compounds from the leaves of Lantana camara varieties
- Heshula, Lelethu U P, Hill, Martin P
- Authors: Heshula, Lelethu U P , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406141 , vital:70242 , xlink:href="https://hdl.handle.net/10520/EJC150957"
- Description: Evidence from more than 100 plant species has confirmed that plants emit volatile organic chemicals (VOC) in response to herbivory (Karban and Baldwin 1997; Dicke et al. 2003; Arimura et al. 2005). Feeding-induced plant responses may result in higher levels of volatiles, and different bouquets of compounds being emitted by plants following herbivore damage (Wei et al. 2006). The emission of volatile chemicals may be beneficial to plants in two ways; undamaged plants may interpret the chemical signals from damaged plants and in turn prime themselves for defence (Arimura et al. 2000; Dicke et al. 2003; Agrawal 2005), or volatiles emitted by damaged plants may attract natural enemies of the herbivores, which may reduce further damage to the plants (Tumlinson et al. 1993; De Moraes et al. 1998; Dicke and Vet 1999).
- Full Text:
- Authors: Heshula, Lelethu U P , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406141 , vital:70242 , xlink:href="https://hdl.handle.net/10520/EJC150957"
- Description: Evidence from more than 100 plant species has confirmed that plants emit volatile organic chemicals (VOC) in response to herbivory (Karban and Baldwin 1997; Dicke et al. 2003; Arimura et al. 2005). Feeding-induced plant responses may result in higher levels of volatiles, and different bouquets of compounds being emitted by plants following herbivore damage (Wei et al. 2006). The emission of volatile chemicals may be beneficial to plants in two ways; undamaged plants may interpret the chemical signals from damaged plants and in turn prime themselves for defence (Arimura et al. 2000; Dicke et al. 2003; Agrawal 2005), or volatiles emitted by damaged plants may attract natural enemies of the herbivores, which may reduce further damage to the plants (Tumlinson et al. 1993; De Moraes et al. 1998; Dicke and Vet 1999).
- Full Text:
The ethical function of research and teaching
- Authors: Tabensky, Pedro
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305738 , vital:58608 , xlink:href="https://doi.org/10.1111/j.1469-5812.2011.00813.x"
- Description: It is the epistemic as well as the ethical responsibility of academics to aim to approach their research and teaching with a proper understanding of the ultimate ethical purpose or telos of their defining activities and products,which is the practical aim of promoting human flourishing. Minimally, academics should aim at understanding, and a key component of understanding is to understand the ideal ethical purpose of what is being researched and taught. For instance, sadistic Nazi medical researchers and teachers—Mengeles of sorts—in addition to having reprehensible commitments,would be significantly ignorant about their own intellectual concerns by virtue of their abject (belief-expressing) commitments. I will show that insights drawn from extreme cases such as this one apply across disciplines and in less extreme cases.
- Full Text:
- Authors: Tabensky, Pedro
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305738 , vital:58608 , xlink:href="https://doi.org/10.1111/j.1469-5812.2011.00813.x"
- Description: It is the epistemic as well as the ethical responsibility of academics to aim to approach their research and teaching with a proper understanding of the ultimate ethical purpose or telos of their defining activities and products,which is the practical aim of promoting human flourishing. Minimally, academics should aim at understanding, and a key component of understanding is to understand the ideal ethical purpose of what is being researched and taught. For instance, sadistic Nazi medical researchers and teachers—Mengeles of sorts—in addition to having reprehensible commitments,would be significantly ignorant about their own intellectual concerns by virtue of their abject (belief-expressing) commitments. I will show that insights drawn from extreme cases such as this one apply across disciplines and in less extreme cases.
- Full Text:
The extent and perceptions of vandalism as a cause of street tree damage in small towns in the Eastern Cape, South Africa
- Richardson, Emma, Shackleton, Charlie M
- Authors: Richardson, Emma , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180954 , vital:43676 , xlink:href="https://doi.org/10.1016/j.ufug.2014.04.003"
- Description: Street trees are important foundations of urban sustainability due to the ecosystem services that they provide society and the environment. However, street trees are vulnerable to vandalism and damage, especially when small, which constraints the flow of benefits they provide and also increases the costs of planting programmes. Despite being a common phenomenon, there is limited knowledge regarding the extent of vandalism and the reasons for it. Here we seek to understand the causes and extent of street tree damage in eleven small Eastern Cape (South Africa) towns and to assess the perceptions of residents and officials. The condition of newly planted street trees was assessed in each town and residents were interviewed in the two towns with the highest number of newly planted street trees. Almost half (42%) of recently planted street trees were totally snapped, ranging between 0% and 63% per town. There was no difference in the prevalence of trees being snapped between those with protective structures and those without. Each town used different structures around newly planted street trees, but in only two towns were all the structures intact. The prevalence of damage declined with increasing trunk thickness and increasing town size. According to residents, boredom, misbehaviour, lack of appreciation of trees and collection for wood were the main factors for tree vandalism by people along with damage by livestock. Ward councillors recognised the presence of vandalism, but indicated that it was not a priority topic in their ward meetings. Suggestions by residents to prevent vandalism included: planting in sensible areas, re-designing the protective structures, re-locating livestock and engendering community participation and ownership in all aspects of street tree planting.
- Full Text:
- Authors: Richardson, Emma , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180954 , vital:43676 , xlink:href="https://doi.org/10.1016/j.ufug.2014.04.003"
- Description: Street trees are important foundations of urban sustainability due to the ecosystem services that they provide society and the environment. However, street trees are vulnerable to vandalism and damage, especially when small, which constraints the flow of benefits they provide and also increases the costs of planting programmes. Despite being a common phenomenon, there is limited knowledge regarding the extent of vandalism and the reasons for it. Here we seek to understand the causes and extent of street tree damage in eleven small Eastern Cape (South Africa) towns and to assess the perceptions of residents and officials. The condition of newly planted street trees was assessed in each town and residents were interviewed in the two towns with the highest number of newly planted street trees. Almost half (42%) of recently planted street trees were totally snapped, ranging between 0% and 63% per town. There was no difference in the prevalence of trees being snapped between those with protective structures and those without. Each town used different structures around newly planted street trees, but in only two towns were all the structures intact. The prevalence of damage declined with increasing trunk thickness and increasing town size. According to residents, boredom, misbehaviour, lack of appreciation of trees and collection for wood were the main factors for tree vandalism by people along with damage by livestock. Ward councillors recognised the presence of vandalism, but indicated that it was not a priority topic in their ward meetings. Suggestions by residents to prevent vandalism included: planting in sensible areas, re-designing the protective structures, re-locating livestock and engendering community participation and ownership in all aspects of street tree planting.
- Full Text:
The herbivorous arthropods associated with the invasive alien plant, Arundo donax, and the native analogous plant, Phragmites australis, in the Free State Province, South Africa s
- Canavan, Kim N, Paterson, Iain D, Hill, Martin P
- Authors: Canavan, Kim N , Paterson, Iain D , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406155 , vital:70243 , xlink:href="https://hdl.handle.net/10520/EJC155690"
- Description: The Enemy Release Hypothesis (ERH) predicts that when plant species are introduced outside their native range there is a release from natural enemies resulting in the plants becoming problematic invasive alien species (Lake and Leishman 2004; Puliafico et al. 2008). The release from natural enemies may benefit alien plants more than simply reducing herbivory because, according to the Evolution of Increased Competitive Ability (EICA) hypothesis, without pressure from herbivores more resources that were previously allocated to defence can be allocated to reproduction (Blossey and Notzold 1995). Alien invasive plants are therefore expected to have simpler herbivore communities with fewer specialist herbivores (Frenzel and Brandl 2003; Heleno et al. 2008; Heger and Jeschke 2014).
- Full Text:
- Authors: Canavan, Kim N , Paterson, Iain D , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406155 , vital:70243 , xlink:href="https://hdl.handle.net/10520/EJC155690"
- Description: The Enemy Release Hypothesis (ERH) predicts that when plant species are introduced outside their native range there is a release from natural enemies resulting in the plants becoming problematic invasive alien species (Lake and Leishman 2004; Puliafico et al. 2008). The release from natural enemies may benefit alien plants more than simply reducing herbivory because, according to the Evolution of Increased Competitive Ability (EICA) hypothesis, without pressure from herbivores more resources that were previously allocated to defence can be allocated to reproduction (Blossey and Notzold 1995). Alien invasive plants are therefore expected to have simpler herbivore communities with fewer specialist herbivores (Frenzel and Brandl 2003; Heleno et al. 2008; Heger and Jeschke 2014).
- Full Text:
The impact of manufacturing variables on in vitro release of clobetasol 17-propionate from pilot scale cream formulations
- Fauzee, Ayesha F B, Khamanga, Sandile M, Walker, Roderick B
- Authors: Fauzee, Ayesha F B , Khamanga, Sandile M , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183872 , vital:44077 , xlink:href="https://doi.org/10.3109/03639045.2013.842579"
- Description: The purpose of the study was to evaluate the effect of different homogenization speeds and times, anchor speeds and cooling times on the viscosity and cumulative % clobetasol 17-propionate released per unit area at 72 h from pilot scale cream formulations. A 24 full factorial central composite design for four independent variables were investigated. Thirty pilot scale batches of cream formulations were manufactured using a Wintech® cream/ointment plant. The viscosity and in vitro release of CP were monitored and compared to an innovator product that is commercially available on the South African market, namely, Dermovate® cream. Contour and three-dimensional response surface plots were produced and the viscosity and cumulative % CP released per unit area at 72 h were found to be primarily dependent on the homogenization and anchor speeds. An increase in the homogenization and anchor speeds appeared to exhibit a synergistic effect on the resultant viscosity of the cream whereas an antagonistic effect was observed for the in vitro release of CP from the experimental cream formulations. The in vitro release profiles were best fitted to a Higuchi model and diffusion proved to be the dominant mechanism of drug release that was confirmed by use of the Korsmeyer–Peppas model. The research was further validated and confirmed by the high prognostic ability of response surface methodology (RSM) with a resultant mean percentage error of (±SD) 0.17 ± 0.093 suggesting that RSM may be an efficient tool for the development and optimization of topical formulations.
- Full Text:
- Authors: Fauzee, Ayesha F B , Khamanga, Sandile M , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183872 , vital:44077 , xlink:href="https://doi.org/10.3109/03639045.2013.842579"
- Description: The purpose of the study was to evaluate the effect of different homogenization speeds and times, anchor speeds and cooling times on the viscosity and cumulative % clobetasol 17-propionate released per unit area at 72 h from pilot scale cream formulations. A 24 full factorial central composite design for four independent variables were investigated. Thirty pilot scale batches of cream formulations were manufactured using a Wintech® cream/ointment plant. The viscosity and in vitro release of CP were monitored and compared to an innovator product that is commercially available on the South African market, namely, Dermovate® cream. Contour and three-dimensional response surface plots were produced and the viscosity and cumulative % CP released per unit area at 72 h were found to be primarily dependent on the homogenization and anchor speeds. An increase in the homogenization and anchor speeds appeared to exhibit a synergistic effect on the resultant viscosity of the cream whereas an antagonistic effect was observed for the in vitro release of CP from the experimental cream formulations. The in vitro release profiles were best fitted to a Higuchi model and diffusion proved to be the dominant mechanism of drug release that was confirmed by use of the Korsmeyer–Peppas model. The research was further validated and confirmed by the high prognostic ability of response surface methodology (RSM) with a resultant mean percentage error of (±SD) 0.17 ± 0.093 suggesting that RSM may be an efficient tool for the development and optimization of topical formulations.
- Full Text:
The influence of gold nanoparticles on the electroactivity of nickel tetrasulfonated phthalocyanine
- Maringa, Audacity, Nyokong, Tebello
- Authors: Maringa, Audacity , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189774 , vital:44930 , xlink:href="https://doi.org/10.1142/S1088424614500333"
- Description: We report on the electrodeposition of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) followed by deposition of nickel tetrasulfonated phthalocyanine (NiTSPc) film by electropolymerization (poly-NiTSPc-GCE) to form Poly-NiTSPc/AuNPs-GCE. The presence of the gold nanoparticles caused a lowering of the anodic and cathodic peak separation (ΔEp) of ferricyanide from 126 mV on poly-NiTSPc to 110 mV on poly-NiTSPc/AuNPs. The electrooxidation of nitrite improved on modified electrodes compared to GCE, with the latter giving Ep = 0.78 V and the modified electrodes gave Ep = 0.62 V or 0.61 V. Poly-NiTSPc/AuNPs-GCE had higher currents compared to poly-NiTSPc-GCE. This indicates the enhancement effect caused by the AuNPs. Electrochemical impedance spectroscopy and chronoamperometric studies also showed that poly-NiTSPc/AuNPs-GCE was a better electrocatalyst than poly-NiTSPc-GCE or AuNPs-GCE.
- Full Text:
- Authors: Maringa, Audacity , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189774 , vital:44930 , xlink:href="https://doi.org/10.1142/S1088424614500333"
- Description: We report on the electrodeposition of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) followed by deposition of nickel tetrasulfonated phthalocyanine (NiTSPc) film by electropolymerization (poly-NiTSPc-GCE) to form Poly-NiTSPc/AuNPs-GCE. The presence of the gold nanoparticles caused a lowering of the anodic and cathodic peak separation (ΔEp) of ferricyanide from 126 mV on poly-NiTSPc to 110 mV on poly-NiTSPc/AuNPs. The electrooxidation of nitrite improved on modified electrodes compared to GCE, with the latter giving Ep = 0.78 V and the modified electrodes gave Ep = 0.62 V or 0.61 V. Poly-NiTSPc/AuNPs-GCE had higher currents compared to poly-NiTSPc-GCE. This indicates the enhancement effect caused by the AuNPs. Electrochemical impedance spectroscopy and chronoamperometric studies also showed that poly-NiTSPc/AuNPs-GCE was a better electrocatalyst than poly-NiTSPc-GCE or AuNPs-GCE.
- Full Text:
The life history traits of the arctiine moth Pareuchaetes insulata, a biological control agent of Chromolaena odorata in South Africa
- Uyi, Osariyekemwen O, Zachariades, Costas, Hill, Martin P
- Authors: Uyi, Osariyekemwen O , Zachariades, Costas , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406170 , vital:70244 , xlink:href="https://hdl.handle.net/10520/EJC160238"
- Description: Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KwaZulu-Natal, South Africa, as a biological control agent against Chromolaena odorata (L.) King and Robinson (Asteraceae) between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. Two closely related biological control agents, P. pseudoinsulata Rego Barros and P. aurata aurata (Butler) had previously failed to establish despite several years of releases. Studies of life history traits of P. insulata (males and females) were conducted to determine whether several aspects of its developmental and reproductive biology can explain its poor performance, and to compare the development and reproductive biology of P. insulata with the two other closely related species. At 25 °C, overall mortality of immature stages was generally low (below 12 %). Although the duration of the larval life stage was statistically longer for females, overall they eclosed as adults before the males (i.e. protogyny). Pupal mass, growth rate and total leaf area consumed were higher in females. Mated females laid 74% of their eggs on the first four nights following eclosion and lived an average of 5.92 ± 0.19 days. The moth also showed good biological attributes such as high fecundity (number of eggs), egg hatchability and female mating success (the number of matings that resulted in fertile eggs). Significant positive correlations were detected between insect performance metrics and leaf consumption and between fecundity and pupal mass. A 23 % greater lifetime reproductive output (387.62 ± 19.50 eggs per female) for P. insulata compared with P. aurata aurata was recorded. We hypothesize that the absence of protandry in P. insulata might have contributed to the low population levels of the moth in the field. The results of this study contribute to our understanding of the life history traits of erebid moths in the subfamily Arctiinae deployed for the biological control of C. odorata.
- Full Text:
- Authors: Uyi, Osariyekemwen O , Zachariades, Costas , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406170 , vital:70244 , xlink:href="https://hdl.handle.net/10520/EJC160238"
- Description: Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KwaZulu-Natal, South Africa, as a biological control agent against Chromolaena odorata (L.) King and Robinson (Asteraceae) between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. Two closely related biological control agents, P. pseudoinsulata Rego Barros and P. aurata aurata (Butler) had previously failed to establish despite several years of releases. Studies of life history traits of P. insulata (males and females) were conducted to determine whether several aspects of its developmental and reproductive biology can explain its poor performance, and to compare the development and reproductive biology of P. insulata with the two other closely related species. At 25 °C, overall mortality of immature stages was generally low (below 12 %). Although the duration of the larval life stage was statistically longer for females, overall they eclosed as adults before the males (i.e. protogyny). Pupal mass, growth rate and total leaf area consumed were higher in females. Mated females laid 74% of their eggs on the first four nights following eclosion and lived an average of 5.92 ± 0.19 days. The moth also showed good biological attributes such as high fecundity (number of eggs), egg hatchability and female mating success (the number of matings that resulted in fertile eggs). Significant positive correlations were detected between insect performance metrics and leaf consumption and between fecundity and pupal mass. A 23 % greater lifetime reproductive output (387.62 ± 19.50 eggs per female) for P. insulata compared with P. aurata aurata was recorded. We hypothesize that the absence of protandry in P. insulata might have contributed to the low population levels of the moth in the field. The results of this study contribute to our understanding of the life history traits of erebid moths in the subfamily Arctiinae deployed for the biological control of C. odorata.
- Full Text: